Konstantin Ivanov Intercontinental Magnetic Resonance Seminar

Past Talk Details:

1. April 26, 2024, ICONS Anniversary Seminar, Lucio Frydman, Weizmann Institute of Science, Israel, "2023: The year that PISSed me off”, Pulsed Fourier-transform nuclear magnetic resonance (FT-NMR) has reigned supreme in high resolution, high field spectroscopy. This is particularly true when targeting complex liquid-state samples, seeking to separate multiple sharp peaks spread over large spectral bandwidths. It is known, however, that if spectral resolution is not a must, the FT-based approach is not necessarily the optimal route for maximizing NMR sensitivity: if T2≈T1 –as often in organic solutions– Carr’s steady-state free-precession (SSFP) can provide a superior signal-to-noise ratio per √time (SNRt). A rapid train of pulses will then lead to a transverse component that reaches up to 50% of the thermal equilibrium magnetization, provided that pulses are applied at repetition times TR<<T2,T1, and that a single suitable offset is involved. It is known, however, that having to deal with multiple chemical shifts deprives SSFP from its advantages. The present study revisits this assumption, in particular in what concerns SSFP’s ability to resolve multiple sharp peaks spread out over large bandwidths. An approach is introduced whereby trains of arbitrarily short FIDs can still deliver high resolution spectra, without suffering from peak broadenings or phase distortions. To overcome the absence of high spectral resolution arising in these FIDs, discrimination among nearby frequencies is achieved by collecting signals from a series of regularly phase-incremented excitation pulses. Given SSFP’s amplitude and phase sensitivity to the spins’ offset, this phase-incremented steady state (PISS) approach enables the resolution of sites according to their chemical shift position. In addition, the extreme fold-over associated with the use of arbitrarily short TR acquisitions is dealt with by a customized discrete FT of the inter-pulse time-domain signal. By contrast to conventional NMR, peak intensities are then nearly independent of T1 and T2, while spectral resolution in such experiments will depend on the flip angle used. Solution-state 13C NMR spectra arising from such PISS NMR experiment, compare “OK” with FT-NMR data in terms of sensitivity, bandwidth and resolution.  The physical features of this experiment and a stable, linear protocol to process their data, will be described and exemplified. 

2. April 19, 2024, Anne-Laure Rollet, PHENIX, Sorbonne Université, France, "A little journey of NMR relaxometry in the world of tempera paint", Tempera painting is a pictorial technique widely used from antiquity until the advent of oil painting in the 15th century and then more sporadically. Several recipes have been developed over the centuries and in different geographical areas. This technique consists of mixing crushed mineral pigments with a binder which can be egg, hide glue or wax. Other additives can also be used such as vinegar. Understanding this technique from its properties to its artistic purpose requires understanding the dynamic properties of water at different scales and the correlation with the textural properties of tempera paints. We address this question using fast field NMR relaxometry and the modelling of the NMR dispersion profiles. In this presentation, I will present the results we have obtained on egg yolk-based tempera paints.

3. April 12, 2024, No Seminar (ENC)

4. April 5, 2024, Ewen Lescop, ICSN, France, "Probing (bio)molecular conformational landscapes by High-Pressure NMR", High-Pressure NMR has become a useful tool to explore the structural and dynamic properties of complex molecules or their assemblies such as proteins or lipid bilayers. In this talk, I will first show that efficient paramagnetic effects can be measured under pressure to reveal the pressure effects on protein and lanthanide complexes. Then, I will describe the recent method we developed to explore the intimate coupling between lipid and protein dynamics within biomembranes using high-pressure. 

5. March 29, 2024, Christel Gervais, LCMCP, Sorbonne Université, France,"17O ssNMR : a usefull tool for the characterization of structure and dynamics in hybrid systems",  17O NMR spectroscopy is a very interesting characterization technique since oxygen can exhibit a wide variety of bonding in many molecules and materials.  Thanks to selective 17O-enrichment, high-resolution 17O ssNMR spectra can be recorded and interpreted thanks to the use of DFT calculations:  this combined experimental/theoretical approach allows a precise positioning of hydrogens and the nature of the H-bonding network to be established  as well as binding modes of ligands. This will be illustrated in various systems including Mg, Zn and Al-based MOFs. In addition to the validation of structural models, 17O NMR data can also help to probe local dynamics as observed for instance in ibuprofen and calcium oxalates. Motions related to carboxylic groups are investigated with the help of computational modelling. 

6. March 22, 2024, Dan Taylor, University of York, "Having your cake and eating it: high 1H NMR spectral resolution without low sensitivity", 1H NMR spectra contain a wealth of information about molecular structure and conformation, but extracting this information can be challenging where there is signal overlap caused by limited chemical shift dispersion and signal multiplicity. Suppressing multiplet structure using 1H pure shift NMR methods offers a large improvement in spectral resolution, but these methods almost always incur a concomitant reduction in sensitivity. At low sample concentrations, the poor sensitivity (ca. < 20 %) of broadband pure shift methods traditionally requires extensive signal averaging and collection of useful spectra often becomes impractical due to long experiment durations. Hyperpolarisation techniques, which create a large non-Boltzmann population distribution of the nuclear spin states to transiently amplify the measured NMR signal, have gained recent popularity owing to their proven ability to overcome NMR sensitivity limitations, including in 1H pure shift NMR experiments. Parahydrogen (p-H2) induced polarisation methods are particularly attractive for this application because they can generate orders of magnitude signal enhancement within seconds and require relatively simple and inexpensive instrumentation. Here, we describe the use of p-H2 based signal amplification by reversible exchange (SABRE) hyperpolarisation to obtain broadband 1H pure shift NMR spectra of up to 82 % sensitivity in a single shot experiment.[6] We then show how the methodology can be extended to superior pseudo-2D pure shift experiments through scaling the FID recorded in each separate acquisition of the multiple-shot experiment, to correct for irreproducibility associated with sample re-hyperpolarisation.

7. March 15, 2024, Ville-Veikko Telkki, University of Oulu, Finland, "Ultrafast relaxation and diffusion NMR methods for sustainable materials and biochemical research", Relaxation and diffusion NMR experiments allow elucidation molecular dynamics and obtaining chemical information complementary to conventional spectra. Multidimensional experiments enable one to correlate relaxation and diffusion parameters as well as observing molecular exchange through relaxation or diffusion contrast. Standard multidimensional experiments are slow due to incremented evolution delay in separated experiments. This presentation describes how multidimensional T1, T2 and T1r relaxation as well as diffusion experiments can be accelerated by one to three orders of magnitude by spatial encoding. These single-scan ultrafast experiments facilitate also significantly the use of nuclear spin hyperpolarization to enhance sensitivity by several orders of magnitude. Both ultrafast correlation and exchange type experiments are feasible, and contrary to conventional multidimensional experiments relying on spectral information, the experiments are feasible also with low-field, single-sided magnets with inhomogeneous field. Various applications, ranging from sustainable cements and dairy products to cellular metabolism, protein-ligand interactions, and atmospheric surfactant solutions, are described as well.

8. March 8, 2024, Diana Bermin, Chalmers University of Technology, Gothenburg, Sweden, "Production of bio-based carbon fibers characterized with magnetic resonance methods",  In the light of the transition from a fossil-based to a bio-based economy, carbon fibers made from cellulose and lignin have gained interest. To produce the bio-based precursors, cellulose and lignin is dissolved in e.g. ionic liquids before being coagulated in a non-solvent e.g. water during the wet-spinning process. This process is followed by different temperature treatments to stabilize and then carbonize the fibers. Lignin and cellulose are complex biomolecules defined by crystallinity, molecular weights and the number of various of functional groups. Different MRI and solid and liquid-state NMR methods have been employed to understand the mass transport during the coagulation process and the impact of different lignin fractions during the stabilization. Limitations and preliminary results will be discussed. 

9. March 1, 2024, Meghan Halse, University of York, UK, "Process monitoring using parahydrogen-enhanced benchtop NMR spectroscopy", Benchtop NMR spectrometers are a promising technology for process monitoring applications due to their portability, affordability and low maintenance requirements. However, a key limitation is reduced sensitivity due to their moderate magnetic field strengths (1 – 2 T).  Hyperpolarisation can be used for signal amplification of benchtop NMR but poses additional challenges for quantification. Parahydrogen induced polarisation (PHIP) methods are very attractive for use with benchtop NMR spectrometers because they generate polarisation levels independent of the detection field strength and do not require significant additional instrumentation. In this talk we demonstrate the use of hyperpolarised benchtop NMR for monitoring and quantifying reactivity involving parahydrogen. Perspectives for process monitoring more generally using the catalytic signal amplification by reversible exchange (SABRE) method coupled to benchtop NMR detection will also be discussed, with a focus on exploring the limits of detection and strategies for signal quantification. 

10. February 23, 2024, Klaus Lips, Helmholtz-Zentrum Berlin für Materialien und Energie, Germany. "Room temperature quantum sensing with silicon dangling bonds", Paramagnetic point defects in silicon provide qubits that could open up pathways towards silicon-technology based, low-cost, room-temperature (RT) quantum sensing. The silicon dangling bond is a natural candidate, given its sub-nanometer localization and direct involvement in spin-dependent charge-carrier recombination, allowing for electrical spin readout. However, in crystalline silicon, strong dangling bond spin-coherence loss is observed at RT due to rapid free-electron trapping, which strongly limits quantum applications. Combining density-functional theory and multifrequency (100 MHz–263 GHz) pulsed electrically detected magnetic resonance spectroscopy, we show that dangling bonds in a hydrogenated amorphous silicon matrix form metastable spin pairs in a well-defined quasi two-dimensional (2D) configuration upon electron capture. Although highly localized, these entangled spin pairs exhibit nearly vanishing intrinsic dipolar and exchange coupling. The formation of this specific topological configuration involves a > 0.3 eV energy relaxation of a trapped electron, stabilizing the pair. This extends room-temperature spin coherence times into the microsecond range required for spin-based quantum sensing.

11. February 16, 2024, Riddhiman Sarkar, Helmholtz Center Munich, Germany, "Impact of magnetic field strength and MAS frequency on the resolution and sensitivity of 1H detected solid-state NMR spectra in biosolids",  Solid-state NMR has undergone a revolution during the last decade due to significant developments in hardware, as well as to the advent of new NMR methods and sample preparation strategies. With the help of experimental data recorded by employing state-of-the-art experimental conditions, and numerical simulations, we have analyzed the spectral quality of a model protein in terms of sensitivity and resolution. It is predicted that further increase in MAS frequency as well as B0 will be beneficial to enhance the spectral quality. Comparing the results from experiments and simulations, it is possible to predict what type of isotope labelling scheme would be appropriate for which experimental conditions. 

12. February 9, 2024, Michael Vogel, TU Darmstadt, Germany, "NMR Studies of Water Dynamics in Nanoscale Confinements",  Confined water is ubiquitous in nature and technology. Nevertheless, the dependence of water’s structure and dynamics on the properties of the host material is still elusive. Here, it is shown that valuable information about the rates and mechanisms for the dynamics of water in various types of nanoscale confinements are available from 1H and 2H NMR studies. In particular, very broad dynamic and temperature ranges are accessible by combining stimulated-echo experiments, line-shape analysis, and spin-lattice relaxometry, including field-cycling experiments. In addition to these approaches to water reorientation, measurements in static field gradients provide access to self-diffusion coefficients of confined water. A main focus will be 1H and 2H NMR results for the dynamics of confined water at reduced temperatures, which may yield insights into the origin of water’s anomalies. Another major topic will be approaches to the water-ice equilibrium in nanoscale confinement, which provide access to the rate of molecular exchange between both coexisting phases. 

13. February 2, 2024, Millena Logrado, TU Darmstadt, Germany, "Dipolar NMR Spectroscopy Unveiling Structural Origins of Thermal Properties of Glasses with Multiple Network Formers",  In technologically relevant glasses, understanding the structural roles of network formers and modifiers is part of the strategic approach towards designing and fine-tuning glass properties. However, the multiple factors influencing macroscopic properties can make this task very challenging. The presentation aims to provide insights into the non-linear compositional dependence of the characteristic temperatures (strain, annealing and softening) of a series of sodium-aluminophosphosilicate glasses: 70 SiO2 – 7.5 P2O5 – (22.5 - x)Al2O3 - x Na2O, (0 ≤ x ≤ 17.5). In this context, solid-state Nuclear Magnetic Resonance (ssNMR) is ideally suited to investigate amorphous solid structures, owing to its element- and interaction-selectivity as well as its quantitative character. Using multinuclear 1D and 2D and  31P/27Al and 31P/23Na dipolar recoupling experiments, a detailed picture of the short- and medium-range is obtained. Three distinct regimes of behavior are observed upon the systematic replacement of aluminum by sodium into the network. These regimes are directly correlated with the structural role of the sodium ions in this system. (I) For lower sodium concentrations, 0.00 ≤ x ≤ 10.00, these cations act as charge balancers for anionic tetrahedral aluminum units. (II) In the glasses with 11.25 ≤ x < 15.00, sodium adopts the additional role of network modifier, balancing the charges of newly formed non-bridging oxygen units on phosphorus. In both of these regimes, the network shows a strong preference for the formation of P-O-Al linkages. (III) At the highest sodium concentrations, 15.00 ≤ x ≤ 17.50,  the magnitude of the heteronuclear 23Na-31P second moment is clearly increased upon reaching the limit of the glass forming region. Additionally, the formation of P-O-P linkages in a pyrophosphate structure is detected by a J-based double-quantum filter experiment. Based on this detailed picture, we suggest that the non-linear compositional trend observed in the characteristic temperatures describing the thermal behavior of this system is related to the structural role of the network-modifying sodium ions.

14. January 26,  2024, Ashok Ajoy, Univ. of Berkeley, USA, ``Two surprises with hyperpolarized nuclear spins in solidHyperpolarized nuclear spins in solids can present intriguing and sometimes unexpected features. In this talk, I will describe two such surprises, using polarized 13C nuclear spins in diamond as an example. First, the spins exhibit unexpected,  remarkably long transverse spin lifetimes approaching T2’=1000s at 100K, over a factor of >600,000-fold longer than their corresponding FID decay times. At once, this facilitates many interesting phenomena, including exploration of time crystalline phases, and using nuclear spins as ``quantum sensors” for magnetic fields. Here, the spins behave like virtually frictionless magnetic compass needles, exhibiting continuous precession for over >10^10 cycles, while remaining highly sensitive to external time-varying magnetic fields. A second surprise is the ability to create tunable polarization spin textures in these nuclear spins, using an electron as a nanoscale gradient.  Significantly, the generated texture can be rendered immune to spin diffusion and persists for multiple minutes, while spanning multiple nanometers and encompassing hundreds of nuclear spins.

15. January 19, 204, Guinevere Mathies, University of Konstanz, Germany, "How MAS NMR of amorphous calcium carbonate provides proof for the pre-nucleation cluster pathway", Non-crystalline intermediates, such as amorphous calcium carbonate (ACC), play a crucial role in biomineralization. Obtaining insight into their structures is notoriously difficult. There is no such thing as a unit cell. MAS NMR, however, goes a long way. Investigation indicated the presence of two distinct environments in ACC. In the first environment, structural water molecules are embedded in rigid calcium carbonate and can only undergo restricted, anisotropic motion. The second environment consists of water molecules undergoing slow isotropic motion and dissolved hydroxide ions. Parallel investigation by conductive atomic force microscopy (C-AFM) showed that ACC nanoparticles conduct electricity. The mobile water molecules must therefore form a network through the ACC nanoparticles, with the dissolved hydroxide ions carrying the charge. This structure is a remainder of the history of ACC as the suspended phase of a colloid, consistent with the pre-nucleation cluster pathway. 

16. December 22, 2023-January 12, 2024: Christmas/New Year vacation break

17. December 15, 2023, Andrea Simion, National Institute for R&D of Isotopic and Molecular Technologies Cluj, Romania, "Heteronuclear decoupling sequences development for fast MAS NMR", High-spectral resolution and sensitivity in fast MAS NMR (> 60 kHz) are difficult to obtain using current heteronuclear decoupling sequences. The main drawbacks are the achievement of: (i) robustness for a large chemical-shift range under low-power irradiation, (ii) independence with respect to the radio-frequency (RF) power, and (iii) robustness toward radio-frequency field inhomogeneities. Recently, we introduced a new heteronuclear decoupling pulse sequence for fast MAS NMR, that overcomes these issues, dubbed Rotor-Synchronized Phase-Alternated Cycles (ROSPAC). Here, the benefits of the ROSPAC decoupling sequence compared to that of the established ones are presented. These are illustrated by representative solid-state NMR experiments and theoretical results obtained by using a generalized theoretical framework based on Floquet theory. Finally, further developments to enhance the decoupling sequences’ efficiency are exemplified by preliminary experimental results. 

18. Jan Stanek, University of Warsaw, "Resonance assignment with 1H detection and fast MAS: high dimensional spectroscopy and other solutions for large deuterated proteins", Fast (> 60 kHz) magic-angle spinning provides high sensitivity and narrowed 1H linewidths, however, spectral analysis of large proteins is often severely hampered by peak overlap and/or ambiguity, depending on system size and sample quality. I will demonstrate that four-dimensional variants of the triple-correlations (H-N-CA/CB/CO) disambiguate sequential resonance assignment in challenging systems such as SARS-CoV-2 main protease (2x306 aa). I will discuss the capabilities of automated approaches (e.g. FLYA) to facilitate the spectral analysis in such cases. I will present the advantages of 2H decoupling for resolution and coherence lifetime of 13C alpha spins bonded to deuterons. I will show updated RF designs for backbone resonance assignment and evaluation of internal dynamics featuring higher sensitivity and dramatically improved resolution. Additionally, I will explore specific 1H-labelling of Ile, Leu, and Val residues with linear 13C-chains, and otherwise an extensive 2H- and uniform 13C-enrichment, to establish systematic correlations between methyl 1H/13C and backbone amide 1H resonances, specifically using 3D and 4D spectroscopy and a J-mediated 13C-13C mixing. Finally, novel methods for side-chain resonance assignment and determination of protonation & tautomeric states of histidine residues will be presented.

19. December 1, 2023, Boris Naydenov, Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany, "EPR with small spin ensembles for applications in material science and quantum technology",  Electron Paramagnetic Resonance (EPR) is a well established technique with wide applications in various scientific fields, but with limited spin sensitivity. Here two approaches for measuring small ensembles of electron spins will be presented. In the first part of the talk a miniaturized EPR spectrometer based on a single chip (EPRoC) will be introduced, where the sample volume can be reduced down to few nanolitres. Recent results using rapid frequency sweeps for detection will be shown, which improve the signal to noise for samples with long relaxation times. In the second part of the talk Optically Detected Magnetic Resonance (ODMR) on Nitrogen-Vacancy centers (NVs) in diamond nano-structures will be shown. The NVs can be detected and controlled at the single spin level and they are well studied physical systems as they are very promising quantum sensors and qubits. The presented experiments with NV ensembles are the first steps towards the realization of a unforgeable quantum token, which is protected by the quantum non-cloning theorem.

20. November 24, No seminar

21. November 17, 2023, Asif Equbal, NYU Abu Dhabi, "Direct sensing of remote nuclei: Expanding the reach of cross-effect dynamic nuclear polarization", We will delve into the critical role of controlling both intermolecular and intramolecular electron-electron coupling to achieve efficient DNP transfer, especially in high magnetic fields. Our focus extends to a novel biradical design concept characterized by a strong electron-electron coupling magnitude, in the range of 100s of MHz. This spin system enables direct polarization transfer from coupled electron spins to nuclear spins over substantial distances, exceeding 2.0 nm. We explore the potential applications of coupled electron spins, showcasing their efficacy in scenarios where conventional spin diffusion mechanisms prove inefficient. Moreover, we discuss instances where direct nuclear spin sensing through electron spin interactions becomes imperative.  

22. November 10, 2023, Philippe Pelupessy, ENS, Paris, "The dipolar field in total correlation spectroscopy", The nuclear dipolar field - also called the dipolar demagnetizing field or the distant dipolar field – describes the direct contribution of the nuclear magnetization to the magnetic field through dipolar interactions. Although it has been described in the early days of NMR, its effects have long time been considered negligible until Deville and coworkers showed that it can cause multiple echoes in a simple two-pulse experiment in presence of a magnetic field gradient. The dipolar field generated much interest after Warren and coworkers discovered that it can give rise to intermolecular cross-peaks in COSY-like sequences. Typically, the dipolar field was considered during prolonged free precession delays. Recently, we have shown that it also can mediate an intermolecular transfer of phase coherence during TOCSY-like sequences. In this seminar, I will expand upon this work.  The theory describing the transfer during continuous pulse-trains will be developed. Several experiments with different transfer schemes will be described. The effects of  intricate modulation patterns of the magnetization will be investigated.

23. October 27, 2023, Marcel Utz, Univ. of Soutampton, UK, and KIT, Germany, "Microfluidic Magnetic Resonance As A Tool To Study Biological Systems",  Microfluidic lab-on-a-chip (LoC) systems are rapidly gaining ground in the  life sciences. In particular, they provide a convenient platform to  integrate  culture of cells, cell aggregates, tissues, and even small animals with downstream analytics such as immunostaining, proteomics, and  PCR-based readouts. Nuclear magnetic resonance spectroscopy is an ideal tool to quantify metabolic processes in living systems since it is non-invasive, generic, and requires only minimal sample preparation. It is therefore possible to use NMR to obtain detailed and quantitative information on metabolic processes of live systems in operando. At small scale, however, sensitivity is a particular concern and must be carefully managed. Hyperpolarisation techniques are an attractive way to address this. Parahydrogen-induced polarisation (PHIP) in particular lends itself to be integrated into LoC systems, as the necessary chemical steps can be implemented directly in the LoC itself. Recent progress in the design of NMR detector systems and in their integration with LoC devices opens exciting possibilities, for experimental automation and feedback. 

24. November 3, 2023, Aditya Rawal, University of New South Wales, Sydney, Australia, "Silk as an extended phenotype: Convergence and divergence of silk structures across species", Silk fibers, which are a protein aggregate, present remarkable evidence of evolutionary convergence and divergence among the various species. Key to the usage of extended phenotypes by organisms is their adaptive variability to changing environmental conditions. Silks are ideal models to study various aspects of extended phenotypes, with relative ease of measuring key functional properties, and the remarkable utility of accessing detailed insight into the protein structure via biomolecular NMR spectroscopy. Here, we present a structural comparison of silk fibres from various organisms covering a range of insect and arachnid species. While isotopic enrichment is not always readily afforded, and obtaining sufficient sample size can be challenging, none the less, significant insight into the structure of the silk aggregates is gained. For the silkworm moths (insect species) Bombyx mori (the only domesticated insect species in the world after honeybees), Antheraea assamensis and Samia cynthia ricini (both undomesticated silkworms) NMR reveals distinct structural motifs in silk fiber structure with variation in the inter-residue hydrogen bond strength well correlated to overall tensile properties of silk fibers. However intra-fiber variation in properties which was also noted, was found to be due to nanovoid formation in the wild-type silks. Ultra-high strength dragline silk from Latrodectus hasselti, Argiope keyserlingi and Nephila plumipes reveal structural variations, with motifs in N. Plumipes showing remarkable similarity to that of B. Mori, a species separated by more than 500 million years of evolution. Here, the ~1 micron fiber diameter of spider silks make then extremely amenable to DNP-NMR with ~ 60 fold signal enhancement achieved. Recent work on nano-silks a form of dry adhesive prey capture silk formed by the cribellate spider Badumna longinqua is presented.  

25. October 20, 2023, No Seminar.

26. October 13, 2023, Kazuyuki Takeda, Univ. of Kyoto, Japan, "Up-conversion of radio-frequency NMR signals to light via a membrane transducer",  Radio-frequency NMR signals can be up-converted to an optical regime using a nanomembrane transducer, where a mechanical oscillator made of a silicon nitride membrane plays a major role, bridging electrical and optical systems. In this what we call Electro-Mechano-Optical (EMO) NMR approach[1-4], an electrode and a mirror are built on the membrane, so that the former works as a capacitor of the probe circuit, while the latter serves for one of the mirrors of an optical cavity. Here, we report our recent works on EMO NMR and related topics, including 1H-13C double resonance, metasurface mirrors on the membrane, feedback cooling, and narrowband MRI. 

27. October 6, 2023, Arthanari Haribabu, Harvard Univ., USA, "Leveraging TROSY to Enhance the Efficacy of Fluorine as Molecular Beacons in Bio-NMR", Fluorine has long enjoyed the interest of NMR spectroscopists due to its relatively high sensitivity and the sensitivity of its chemical shift in its surroundings. The fact that fluorine is not commonly found in biological systems makes it an excellent probe for in-cell NMR and other applications. approximately 20% of FDA-approved drugs harbor a fluorine atom and these offer themselves as useful probes in NMR. Despite these attractive properties, the large CSA of fluorine, resulting in rapid relaxation rates, has historically limited its application in exploring the structure and dynamics of large biomolecules. TROSY can be used to partly mitigate this problem and the talk delves into the utilization of aromatic TROSY to disperse broad signals of fluorine, gaining resolution.

28. September 29, 2023, Navin Khaneja, IIT Bombay, India, "Methods for broadband control in NMR spectroscopy", Excitation pulse is ubiquitous in Nuclear Magnetic Resonance (NMR) spectroscopy, being the starting point of all experiments. The standard method is to excite the spins on resonance. However due to phenomenon of chemical shifts the resonance frequency of spins are dispersed over a range. The challenge is then to excite the spins with different resonance frequency with same pulse whose amplitude is smaller than spread of frequency of the spins. In this talk we present two methods to address this problem of broadband control. The method of multiple sweep and chirp excitation.

29. September 22, 2023: Huub de Groot, Leiden Univ., The Netherlands, "Function-based nonadiabatic principles for artificial photosynthesis with high yield", With Magic-angle spinning NMR, cryo-Electron microscopy, and accurate computer simulations we resolve universal mechanisms of biological photosynthesis across taxonomies and species, and study how to transfer biological design principles to chiral biomimetic nanomaterials for high yield artificial photosynthesis. Photosynthetic complexes are activated in the ground state by local mismatches that selectively enhance conformational dynamics to perform the biological functions of light harvesting, charge separation and catalysis upon excitation by light. This leads us into a function-based framework of limited complexity for the design of semisynthetic and biomimetic artificial photosynthesis components. I will present the status and provide underpinning with examples from past and ongoing research in our group. In photosynthetic reaction centers, the local stress induced by the protein matrix leads to partial charge transfer between the His and its chlorophyll partner that oscillates back and forth between overlapping macrocycles upon twisting of the His to establish dynamic heterogeneity in a homogeneous chiral structural framework. The twisting promotes energy transfer and mixing of charge transfer character into the excited state coupled to protonation change of the matrix by a quasi-quantum coherent process denoted Non-adiabatic Conversion by Adiabatic Passage (NCAP). In this mechanism, an adiabatic sweep induces nonadiabatic matrix elements between a reactant and a product state with resonant coupling to a vibration that is self-selected from the vibrational background. This process is best described in a doubly rotating interaction frame to reveal the coherent conversion of a reactant into a product with near unity yield. To make the step to artificial photosynthesis we study for many years chlorosome bacteriochlorophyll antenna aggregates. This is a rather unique biological system without protein. Starting from an idealized symmetric model for the structure determined by cryo-EM and MAS NMR, we have added static and dynamic heterogeneity to track how ultrafast energy transfer can be stimulated by NCAP. Very recently, we have prepared chiral semisynthetic peptide-porphyrin antenna constructs, and the data indicate that a chiral packing may be sufficient to activate NCAP processes. For water oxidation catalysis we also project the biological system on a function-based framework to reduce the complexity. Here we study the level crossings between reactant and product intermediate states and the possibility to induce nonadiabatic transitions while conserving electronic spin angular momentum. A first experimental example of vibrationally assisted rapid catalysis was found in copper oxide nanoleaves with induced asymmetry. All in all, our portfolio of experimental and theoretical results leads us to conclude that with the function based framework of the biological paradigms, we can build on principles of coherent rotations in spin space in a magnetic field to establish quantum principles of high yield NCAP by crossing of reactant and product states for a novel class of asymmetric responsive matrix materials that perform semiclassical chemical conversions by twisting, as in chiral biological systems.

30. September 15, 2023: Sam Bayliss, Univ. of Glasgow, UK, "Harnessing optical interfaces to electronic spins in molecules", Optically active electronic spins in molecules offer potential for a range of applications, from quantum sensing, where they can serve as quantum bits, to energy harvesting, where they can facilitate efficient solar-energy capture. In this talk, I will outline examples of molecular spin platforms which offer promise for such applications, and discuss their spin properties. As a first platform, I will describe ground-state molecular spins which can be prepared and detected with light, and controlled with microwaves, and how these systems are attractive as chemically synthesized spin qubits and quantum sensors. Secondly, I will describe the excited-state spin-1 pairs which can be optically generated by a process called singlet fission, and how these systems offer pathways to more effective solar-energy harvesting.

31. July 14, 2023: Daphna Shimon, Hebrew Univ. Jerusalem, Israel, "Using DNP to explore heterogeneity in powder diamond samples", Electron and nuclear spins in diamond have long coherence and relaxation times at room temperature, making them a promising platform for applications such as biomedical and molecular imaging and nanoscale magnetic field sensing. While the optically-active nitrogen-vacancy (NV) defect has received a great deal of attention, the substitutional nitrogen (or P1) center also exhibits long coherence and relaxation times. These P1 centers are typically present at significantly larger concentrations than NVs, allowing us to explore the role of P1-P1 interactions in mediating dynamic nuclear polarization (DNP). DNP is a method of enhancing the nuclear magnetic resonance (NMR) signal, increasing the NMR signal by several orders of magnitude, and allowing NMR to be much more sensitive. Here, we show enhancement of natural abundance 13C nuclei found within the diamond, using the unpaired electron of the P1 center in micro-particles, under static conditions at room temperature. We discuss the DNP spectrum, the active many DNP mechanisms in this sample, what we can learn about the diamond powder from DNP results, and even how some DNP techniques allow us to control which mechanisms are active.

32. July 7, Lucas Siemons, ENS Paris, France, "Revisiting dynamics in DNA by high-resolution relaxometry and molecular dynamics simulations",  Molecular motions in nucleic acids are vital for their biological functions and determine how and when they interact with their surroundings. While CEST, R1ρ and CPMG experiments are exploited to study μs-ms motions, few experiments target motions occurring on the nanosecond time scale. High Resolution Relaxometry (HRR) has emerged as a unique technique to probe motions occurring on this timescale by recording longitudinal relaxation rates at low fields. This study aims to develop methods to apply HRR and high-field spin relaxation experiments to determine the local motions in nucleic acids and interpret them with molecular dynamics trajectories. We will identify the motions occurring on the ns time scale and provide a detailed picture of the motions occurring in the sugar backbone and the nucleobase.  We have measured carbon-13 relaxation in a 12 base pair DNA helix at natural abundance at sites distributed across the sugar backbone and the nucleobases: low-field longitudinal relaxation rates from 2 T to 10 T with a new prototype of sample shuttle, and high-field rates (R1, R2, 13C-{1H} NOE) at fields from 500 MHz to 1 GHz (11 T – 23 T). These relaxation rates are interpreted with ~70 μs molecular dynamics simulations. We have used experimental rates and MD simulations to build models that describe both the modes of motion and the interactions leading to relaxation. By developing these models we can identify the forcefields and water models that most accurately describe the motions occurring within our DNA helix, and in turn describe the motions themselves. We have recorded the most extensive set of relaxation rates to date on a DNA duplex and demonstrated that the combination of low- and high-field relaxation rates could be combined with MD simulations to determine internal motion in nucleic acids. 

33. June 30, 2023: K.V. Ramanathan, IISc Bangalore, India,  "Order, Topology and Organisation in Liquid Crystals from 1- and 2-D NMR", Liquid crystals in addition to their technological importance continue to be a fascinating field of study in view of the intriguing organisation of the molecules. NMR provides a deep insight into the order and topology of these materials. LC molecules usually consist of a rigid core with a flexible aliphatic chain on one or both ends. The core of the LC molecule can have a variable number of phenyl rings attached to each other rigidly and is responsible majorly for intermolecular interaction that promotes long range order leading to the formation of the liquid crystalline phase. The aliphatic chain too contributes – the length and position of the chain being a critical factor in the formation of a variety of liquid crystalline phases.  In this talk, methods to obtain the orientational order of topologically variant liquid crystalline molecules using solid-state 13C NMR spectroscopy are described.  The 13C-1H dipolar couplings measured from the 2D-separated local field (SLF) technique have been used for computing the local order parameters of a variety of mesogens, which are then utilized for mapping the topology of the mesogens. The chemical shift in the LC phase is also different from the one in the isotropic (solution) phase and can be used to follow the changing dynamics of the LC molecule as a function of temperature. Examples of use of the methods with results on systems of recent interest will be presented in the talk. 

34. June 23, 2023: Bogdan Rodin, ENS Paris, France, “On the analysis of cross-talk in DNP”,  Dynamical nuclear polarization (DNP) is a powerful method that allows one to polarize virtually any spin-bearing nucleus by transferring electron polarization by microwave irradiation of the electron Zeeman transitions. Under certain conditions, the DNP process can be described in thermodynamical terms using the thermal mixing (TM) model. Different nuclear species can exchange energy indirectly through their interactions with the electron spins and reach a common spin temperature. Such ‘‘cross-talk’’ effects can occur between proton (H) and deuterium (D) nuclei in de- and re-polarization experiments. We have recently investigated such effects experimentally for various sample preparations containing proton and deuterium nuclei, and performed analyses based on Provotorov’s equations. This allows one to extract various kinetic parameters, such as the rates of energy transfer between the different reservoirs, and the heat capacity of the non-Zeeman (NZ) electron reservoir. Based on these analyses, predictions of the behaviour of heteronuclei such as 13C or 31P can also be made.  Finally, we present an experimental study of the dependence of Provotorov’s kinetic parameters on the TEMPOL concentration and on the H/D ratio, thus providing insight into the nature of ‘‘hidden’’ spins that are not observable directly because of their proximity to the radicals. 

35. June 16, 2023, Lukas Kaltschnee, MPI for Interdisciplinary sciences, Göttingen, “Hydrogen catalysis of the [Fe]-hydrogenase studied by parahydrogen enhanced NMR", Hydrogenases are nature’s ingenious tools for efficient hydrogen catalysis. These enzymes are capable of catalyzing H2 splitting or production at high turnover frequencies, using nickel and iron complexes as catalytically active centers. For many microorganisms living in anaerobic environments, hydrogenases are essential to perform their metabolism. One example are methanogenic archaea, which gain their energy by reducing CO2 to methane, using H2 as source of energy. To exploit or mimic hydrogenase activity is an attractive research aim, with potential applications of H2 production or conversion. Hydrogenases have extensively been studied to elucidate their H2 catalysis mechanism, with major contributions from X-ray crystallography, FT-IR, XAS, Mössbauer spectroscopy and EPR. In this seminar, I will demonstrate that NMR using parahydrogen offers a different route to study the H2 catalysis mechanism of hydrogenases. In recent work, we show that splitting of parahydrogen by the [Fe]-hydrogenase produces PHIP signals. These signals are observed for the wild-type enzyme under turnover conditions. We used these signals to characterize intermediates of the [Fe]-hydrogenase catalytic cycle, which could previously not be studied experimentally. The readout of these PHIP via CEST enabled the measurement of chemical shifts of bound hydrogen species in the active site. This work illustrates the potential of PHIP experiments for the mechanistic investigation of hydrogenases. 

36. June 9, 2023, Sören Lehmkuhl, Karlsruhe Institute of Technology, Germany, “The parahydrogen fueled RASER - From continuous NMR signals for precision sensing to background-free MRI”,  In my talk, I will focus on the NMR RASER (RASER =radiowave amplification by stimulated emission of radiation). The RASER is a brother of the LASER, but with spontaneous emission of radiowaves instead of light. Just like for a LASER, the RASER requires pumping, which is achieved by parahydrogen hyperpolarization. In this lecture, I will introduce the basic operating principles of a RASER, the parahydrogen-based pumping mechanism and applications of a RASER in NMR. The applications range from high-precision NMR spectroscopy with sub-mHz linewidth to the study of nonlinear phenomena such as period doubling, collapse, and chaos. Finally, RASER MRI is introduced, where magnetic resonance images are generated without rf-irradiation but relying on self-organization instead. 

37. June 2, 2023,  Manuel Etzkorn, Heinrich Heine University, Düsseldorf, Germany,  "Tailored NMR methods for challenging biological systems", NMR spectroscopy has a unique potential to provide high spatial and temporal resolution of target molecules in complex environments. However, often sample preparation, low sensitivity, and ensemble averaging pose clear limitations in increasingly complex biological systems. The presentation will summarize our recent contributions to overcome central restrictions via the development and application of novel methods. This will include optimized isotope-labelling, and polarization-usage strategies as well as selective hyperpolarization via functionalized ligands. Furthermore, it will be discussed how the application of the developed methods can provide new insights into: membrane systems and DNA-mediated biocatalysis.    

38. May 26, 2023, Ralf Wunderlich, Leipzig University, Germany, "Hyperpolarized NMR field cycle experiments on the nitrogen vacancy center in diamond", The nitrogen-vacancy (NV) center in diamond is one of the most promising spin qubit systems for quantum information processing and nuclear hyperpolarization. The spin of this defect can be optically initialized at room temperature, manipulated with microwaves, and read out optically or electrically. Many applications of NV centers require not only deterministic generation and precise positioning at the nanoscale, but also an understanding of the spin environment. For the latter, hyperpolarized NMR measurements using field-cycling experiments can provide useful information. By fabricating diamonds with a high NV density, sub-ensembles of NV pairs or NV centers interacting with other spin defects can be generated. Under certain conditions, a transfer of the electronic hyperpolarization of the NV center to neighboring 13-C spins may occur, which can be detected by a strong nonthermal NMR signal. 

39. May 19, 2023, Quentin Stern,  Université de Lyon, France, "Rapid dynamic nuclear polarization with conductive polymers", Dissolution dynamic nuclear polarization (dDNP) uses the high polarization of electron spins at low temperatures to polarize nuclear spins to near-unity levels on a broad variety of compounds. After dissolving the sample, this hyperpolarization translates into sensitivity gains for liquid-state NMR and MRI of up to five orders of magnitude. Here, we show that DNP is feasible on polyaniline polymers (PANI) at 1.6 K and 7 T and find a surprising variety of DNP mechanisms as a function of radical concentration. DNP on PANI opens the perspective of efficient DNP at moderate temperatures and hence, without the need for liquid helium since electrons in chiral PANI can be hyperpolarized by chirality-induced spin selectivity. 

40. May 12, 2023, Gil Goobes, Bar-Ilan University,"Protein-mineral interfaces – order, disorder, and what’s in-between". We often consider order and crystallinity in materials as the focus of our characterization efforts. Not always do we realize that in disorder, aka amorphism, there are levels or shades that have important bearings for biomaterials and probably for materials, in general. The disorder in solid phases needs to be defined well to better understand regulation of biomaterial formation in Nature and not many techniques can be employed for such as task. I will review work on non-collagenous bone proteins employed in bone mimetic minerals, and how they impact the arrangements of mineral material layers coating the hydroxyapatite crystals that constitute the bulk of bone material in many organisms. Using simple filtered CP, filtered relaxation, and similarly SEDRA recoupling measurements, we distinguished and characterized different mineral layers on the apatitic core crystal. We also inferred the location of the proteins within these layers.

41. May 5, 2023, Dominik Kubicki, University of Birmingham, Atomic-Level Picture of Stabilized Halide Perovskites" Efforts to stabilize photoactive formamidinium (FA) and cesium–based halide perovskites for optoelectronics have been the focus of the materials community over the past few years. I will discuss the role solid-state NMR and NQR have played in understanding the local structure of the stabilized α-FAPbI3 (1), CsPbX3 (X=I, Br) (2) and other materials pertinent to today's optoelectronics research (3). I will highlight the complementarity of NMR and electron diffraction, which is currently emerging as one of the most powerful ways to study microcrystalline materials. References (1) Science 2021, 374 (6575), 1598–1605; (2) Nature, 2023, in press; (3) Nat. Rev. Chem. 2021, 5 (9), 624–645

42. April 28, 2023, Thierry Azaïs, Sorbonne Université,  "MAS DNP approaches for the comprehension of non-classical nucleation and crystallization pathways". Nowadays MAS DNP is a well-established hyperpolarization method used to improve NMR sensitivity. It finds applications in various fields from biochemistry to materials science. This presentation aims at showing that MAS DNP can be a decisive technique to understand non-classical nucleation and crystallization pathways of biominerals formation. Biogenic minerals such as calcium phosphates or calcium carbonates are found in many biological tissues or structures such as bones, teeth, sea shells, coral skeletons... Understanding their formation is crucial both on a biological and on an environmental point-of-view. However, their crystallization mechanisms are still largely debated especially in biological conditions. The main reason is due to the fact that they follow so called non-classical nucleation and crystallization pathways, far distinct from the classical nucleation theory for which nuclei of critical size are growing by monomeric of attachment up to the final crystal. In the former case, prenucleation clusters, distinct from the free ions, exist in solution before the nucleation of the first solid. These clusters are described as soluble, in equilibrium with the free ions, of nanometric size and short lifetime. Their composition and structure are still largely unknown nowadays and MAS DNP is a promising technique combining two main advantages: (1) the freezing of the solution and the trapping of the transient intermediates thanks to low temperature. (2) sensitivity enhancement provided by DNP (particularly useful in physiological conditions). In this communication I will present applications of 13C and 31P MAS DNP to the initial steps of calcium carbonates or calcium phosphates nucleation and how it brings information about the structure and composition of prenucleation species. Finally, I will show that this approach can be extended to 43Ca, an unreceptive quadripolar nucleus of low gamma and low natural abundance.

    References: [1] Weber et al. Anal. Chem. 2019; [2] Epasto et al. Anal. Chem. 2021; [3] Ramnarain et al. JACS 2022

43. April 14, 2023, Geoffrey Bodenhausen, ENS Paris, “Delocalized long-lived states for drug screening”. The identification of putative drug molecules that have an affinity for macromolecular targets such as proteins can be greatly improved if parameters like chemical shifts, diffusion constants, Overhauser effects, intermolecular spin-diffusion rates, or relaxation times feature a marked contrast between free and bound forms of putative drug molecules. Our recent discovery that one can excite and observe delocalized long-lived states that encompass several protons of neighbouring CH2 groups in aliphatic chains of common achiral molecules opens the way to greatly improved contrast between free and bound forms, and hence to improved methods for drug screening. 

44. March 31, 2023,  Frédérique Pourpoint, Universté de Lille, “The use of solid-state NMR to understand the structure of MOF ”. Metal-organic frameworks (MOFs) are tunable microporous materials promising for numerous applications, including the capture of gas or catalysis. These compounds are built from the three-dimensional association of metal clusters and organic ligands. Thanks to this hybrid framework, their porosity and functionalities can be tuned to optimize their properties for the desired application. Better understanding the stability of these materials in the presence of water is critical for their use in industrial processes, including the purification of flue gases or wastewater. We show how solid-state NMR as a local characterization method can probe either the metal environment, the organic part of the MOF or the hosted molecules. 

45. March 24, 2023, Vineeth Thalakottoor, ENS Paris, “Nonlinear magnetization dynamics and dipolar field effects in static solid-state proton NMR-DNP experiments at 1.2K”. Nonlinear magnetization dynamics arising from the interaction between the magnetization and the rf field produced by the NMR coil due to the coupling between highly polarized nuclear spins and the detection circuit, commonly known as radiation damping, is a well-studied phenomenon. In some hyperpolarization experiments, when the nuclear spins are hyperpolarized negatively this nonlinear dynamics can give rise to sustained NMR masers and very long coherent radio frequency signals with amplitude modulation. We recently reported NMR masers in dynamic nuclear polarization (DNP) experiments at cryogenic temperature with distinct behaviors, depending on the experimental conditions, in particular sample composition and the use of deuterated on non-deuterated samples (1,2). The appearance of such sustained maser pulses can be ascribed to the combination of two competing mechanisms, namely the loss of nuclear proton magnetization by radiation damping and the repolarization of the proton spins from either the deuterium spins (via electron spins) or from the electron spins alone. These observations were qualitatively interpreted (2) in a classical picture of dipolar coupled network of nuclear spins, using the Bloch-Maxwell equations for radiation damping, coupled to the Provotrov equation for the thermal mixing model of DNP. References: 1) Weber, et. al, Phys. Chem. Chem. Phys,21, 21278-21286., 2019. 2) Thalakottoor, et. al., Phys. Chem. Chem. Phys, 2023 

46. March 17, 2023, Michael Tayler, The Institute of Photonic Sciences (Barcelona, Spain), “Experimental NMR for all”. Many students, researchers and hobbyists will be familiar with the open-source-electronics ecosystem “Arduino”, which provides an extraordinarily simple way to interface sensors (or other input) and actuators (output) with logic programs, e.g. C code, to create a wide variety of standalone control devices termed embedded systems.  An NMR spectrometer can be regarded as one specific type of embedded system: the output is a magnetic field produced by a coil, the input is a magnetic field (detected and recorded by a digitizer), and a pulse programmer keeps timing and data in order. “NMRduino” is an open magnetic resonance spectrometer based on (but we must stress, not endorsed or supported by) Arduino that we have developed over recent years to study hyperpolarized NMR systems, NMR relaxation, high-resolution spectroscopy, and coherent control at low magnetic fields, as well as teach basic principles of magnetic resonance to student beginners.  In this seminar, I will explain some of its capabilities and how you can take part.

Main features are:

(1) Compact, plug-and-play hardware. A credit-card-sized circuit board contains all electronic components and connects to any laptop, desktop or raspberry Pi computer via USB. Includes pulse programmer and analog sampling up to 100 kHz, suitable for mT-field NMR.

(2) Transparent, intuitive control interface. User-specific pulse sequences (2 us time resolution) can be written to control both DC and AC magnetic fields up to several hundred kHz. Open access to low-level programming interface for advanced users.

(3) Flexible. Can be connected to conventional rf-inductive pickup coils, or alternative sensors such as atomic magnetometers. 

47. March 10, 2023, John Griffin, Lancaster University, “Investigating Structure and Dynamics in Photoresponsive Materials by Solid-State NMR” Solar thermal fuels (STFs) are an emerging class of materials that store light energy in strained bonding configurations of photoresponsive molecules and release it on demand as heat. For some applications solid-state STFs would be desirable, although these are challenging to design owing to the lack of steric freedom in dense phases. In this work, we have been developing solid-state STFs based on molecular photoswitches such as azobenzene confined within metal-organic frameworks (MOFs). Using a combination of X-ray diffraction and solid-state NMR we are able to monitor guest-induced breathing upon loading the well-known framework DMOF-1 with azobenzene. Although this causes the MOF structure to contract, 13C CPMAS and 2H NMR measurements reveal the trans-azobenzene exhibits pedal motion and ring-flipping dynamics within the pores. The observed dynamics suggest that the azobenzene molecules have increased free volume as compared to bulk crystalline azobenzene, and indeed when the composite is exposed to 365 nm light we observe isomerisation to the cis isomer which is also highly mobile. In addition to the guest dynamics, 2H NMR has been used to study ring flipping dynamics in the framework linkers. We find that the activation energy for ring flipping shows a complex dependence on both the nature of guest species within the pores and the degree of guest-induced contraction. These results provide insight into mechanism of energy storage in MOF-based STFs, as well as into host-guest interactions in the wider context of breathable MOFs.

K. Griffiths, N. R. Halcovitch, J. M. Griffin, Chem. Mater. 2020, 32, 9925-9936.

K. Griffiths, N. R. Halcovitch, J. M. Griffin, Chem. Sci. 2022, 13, 3014-3019. 

48. March 3, 2023, Chris Waudby, UCL, “Analysis of Sidechain Dynamics using Slow-Relaxing Methyl Quadruple-Quantum Coherences”. Transverse nuclear spin relaxation is a sensitive probe of chemical exchange on timescales on the order of microseconds to milliseconds. Here we present an experiment for the simultaneous measurement of the relaxation rates of two quadruple- quantum transitions in 13CH3-labelled methyl groups. These coherences are protected against relaxation by intra-methyl dipolar interactions and so have unexpectedly long lifetimes within perdeuterated biomacromolecules. However, these coherences also have an order of magnitude higher sensitivity to chemical exchange broadening than lower order coherences and therefore provide ideal probes of dynamic processes. We show that analysis of the static magnetic field dependence of zero-, double- and quadruple-quantum Hahn echo relaxation rates provides a robust indication of chemical exchange and can determine the signed relative magnitudes of proton and carbon chemical shift differences between ground and excited states. 

49. February, 24, 2023, Perttu Lantto, Oulu University, “Modelling of thermal and environmental effects on 129Xe NMR shift in molecular and material cavities”. NMR spectroscopy of ¹²⁹Xe guest atom in molecular and materials cavities is increasingly used to obtain detailed, local information about the atomic and electronic structure of the host material. ¹²⁹Xe NMR spectral features are very sensitive to physical conditions-dependent dynamical processes and understanding them at the microscopic level requires theoretical first-principles modelling. In this presentation, I will show how modelling increases the amount of information obtained from simple ¹²⁹Xe NMR spectra as well as resolves and predicts new spectral features. Our approach combines state-of-the-art relativistic quantum-chemical (QC) calculations of the electronic structure and Xe NMR parameters with statistical Monte Carlo (MC) and molecular dynamics (MD) simulations of the whole host-guest system in solid or solvent environments. I will discuss few applications, in which we were able to 1) predict unknown crystal structures of fluorophenol clathrates, 2) give quantitative finite temperature estimates of Xe chemical shift inside the cavities of solid porous organic cage (POC) material, 3) provide evidence of endohedral Xe in metal organic polyhedral (MOP) supramolecular complex as well as its hidden diastereomers, 4) predict and explain features of unexpected CEST signals in new shift regions for bridged resorcinarene cage (BRCs) biosensor candidates, and 5) confirm ¹²⁹Xe chemical shifts for two-site model of porous liquid of POC. In these studies, the state-of-the-art modelling combined with modern experimental methods and analysis provides valuable, otherwise unattainable, information on, e.g., the occupancies of the cavities, binding constants, thermodynamic parameters, exchange rates, as well as relaxation and diffusion parameters.

50. February 17, 2023, Davy Sinnaeve, Integrative Structural Biology, Lille, “Resolving individual couplings from overlapping and strongly coupled multiplets using selective 2DJ methods”. 1H-1H couplings, either as scalar (J) or as residual dipolar couplings (RDCs), are abundant in organic molecules and their measurement contributes greatly to constitutional, configurational and conformational structure elucidation studies. The downside of their abundance is that it results in complex and broad multiplets that may overlap, obstructing extraction of individual couplings or other spectral information. Pure shift experiments alleviate the overlap problem by delivering fully homodecoupled 1H spectra, boosting spectral resolution by an order of magnitude. They can elegantly be combined with selective 2D J-resolved experiments, such as SERF, G-SERF or PSYCHEDELIC, allowing individual coupling measurement at pure shift resolution. In this presentation, I will give an overview of our recent developments in this class of experiments. This includes some challenging applications, such as the sign-sensitive extraction of long-range 1H-1H RDCs. I will pay special attention to the situation where coupled protons have very small chemical shift differences (strong coupling), where pure shift and 2DJ methods often break down and line splittings may not accurately represent the actual coupling value. New experiments that are designed to mitigate these issues will be presented.

51. February 10, 2023, Rodrigo Cortinas, Yale, “Experimental discovery of a new quantum regime of Arrhenius' law using superconducting quantum circuits”. We have engineered a double-well system (a bifurcated parametric oscillator) over which we have complete control of the Hamiltonian parameters.  This system allowed for two observations that I will share in this talk. 

     -First, we measured the spectrum of this double-well system as a function of its barrier high. We see the quantum energy levels kissing (coalescing) in pairs, while they tunnel-degenerate as they sink under the barrier. This is the first observation of this physics-textbook example, to the best of our knowledge.

-The second observation is the measurement of the incoherent thermal-induced reaction-rate in between the wells as a function of the barrier height. One may naively expect an exponential reduction of the well-switching rate, but what we find is that the rate decreases in steps instead. This is due to the discrete capture of the quantum states by the wells: effectively, the depth of the well can be measured by the number of states that fit within, and only as a new state sinks under the barrier the wells become "deeper". This makes the reaction-rate a stepped function of the barrier height. This new quantum regime of Kramers's theory was neither predicted nor observed before, to the best of our knowledge. In this talk, I will give a friendly introduction to superconducting quantum circuits making the talk transparent to anyone having elementary training in quantum mechanics.

52. February 3, 2023, Amrit Venkatesh, EPFL, “Rational design of better DNP”. To enable the widespread and routine use of Dynamic Nuclear Polarization (DNP) in a broader range of applications, more efficient strategies of polarization must be developed. We tackle this grand challenge by designing improved polarizing agents and novel approaches for DNP-enhanced NMR. Specifically, we establish the relationship between deuteration and cross effect DNP efficiency using TEKPol biradicals, validate a model for improved Gd(III) polarizing agents,1 and finally demonstrate 1H hyperpolarization at room temperatures using liquid state Overhauser DNP.2

References:

1. Y. Rao, et al. J. Phys. Chem. C 2022, 126, 27, 11310-11317.

2. Y. Rao, et al. J. Phys. Chem. Lett. 2022, 13, 7749-7755.

53.  January 20, 2023, Mohamed Sabba University of Southampton, Symmetry-based Sequences from Solids to Liquids: Applications to Polarization Transfer and Singlet Order Excitation.  At its core, NMR is the application of radiofrequency pulse sequences designed to investigate and observe molecular systems. In an ideal scenario, pulse sequences perform their desired transformations in a robust and time-efficient manner. The reality, however, is quite different. Experimental limitations such as hardware imperfections, environmental noise, and relaxation compromise this goal. To address this issue, many successful strategies have been developed for the design of pulse sequences that perform well even in the presence of imperfections. In solid-state NMR, symmetry-based recoupling is a popular framework for the design of such sequences. In stark contrast, symmetry-based sequence design has been relatively overlooked in liquids.
    Consider a pair of strongly coupled spin-1/2 nuclei supporting a singlet state |S0⟩ and three triplet states. A common task in the context of singlet NMR is the transformation of magnetization into nuclear singlet order and vice versa. Nuclear singlet order - the population difference between |S0⟩ and the triplet manifold - may display exceptionally long solution-state lifetimes that are many multiples of T1. The field of singlet NMR has evolved to a high degree of sophistication since its inception in 2004, with several pulse sequences described for nuclear singlet order excitation.
    We now consider the following question: can we harness solid-state NMR symmetry principles for the design of robust singlet NMR pulse sequences, and perhaps solution-state NMR sequences in general? In our seminar, we will answer this question affirmatively. We will show that symmetry-based sequence design produces highly efficient pulse sequences that outperform existing ones in robustness, speed, and simplicity. To our surprise, some of these sequences are already known in the field of diamond magnetometry under the name of “PulsePol”. We further show preliminary results for the application of symmetry-based sequences for heteronuclear polarization transfer. These sequences enable rapid observation of the elusive low-gamma spin-1/2 nucleus rhodium-103, with an advantage over the standard INEPT sequence. We believe that our demonstrations of symmetry-based sequences in solution may have significant implications to a broader class of problems.

54.  January 13, 2023, Mor Mishkovsky, EPFL, Title: New insights to interrogate cerebral metabolism – what hyperpolarized MRS can add? Molecular imaging enables visualization and quantification of the function of biological processes, bringing new and essential perspectives for disease assessment. Dissolution Dynamic Nuclear Polarization (dDNP) of metabolites dramatically enhances Magnetic Resonance Imaging (MRI) sensitivity, allowing real-time intermediary metabolism monitoring. The huge increase in sensitivity paves the way for a new class of non-invasive, non-radioactive in vivo metabolic imaging that can be applied in preclinical and clinical studies. Most studies have mainly focused on the potential of hyperpolarized [1- 13C]pyruvate, due to its excellent properties as dDNP molecular imaging contrast agent. However, dDNP is a versatile technique that can be employed to polarize a large variety of metabolically relevant molecules. In this seminar, we will look beyond 13C pyruvate, examining other 13C labeled molecules and their implementation in the context of hyperpolarized MR for monitoring real-time cerebral function and metabolism. Technical challenges will be discussed along with the experimental solutions adopted to enable detecting their real-time brain metabolism. We will demonstrate their application in the naïve brain as well as pre-clinical animal models and show the metabolic information they can add.

55. December 16, 2022, Zhenfeng Pang, ENS Paris, "A Unified Description for Polarization-transfer Mechanisms in Magnetic Resonance: Cross polarization and DNP" Polarization transfers are crucial building blocks in magnetic resonance experiments, i.e., they can be used to polarize insensitive nuclei and correlate nuclear spins in multidimensional NMR spectroscopy. The polarization can be transferred either across different nuclear spin species or from electron spins to the relatively low-polarized nuclear spins. The former route occurring in solid-state NMR (ssNMR) can be performed via cross polarization (CP), while the latter route is known as dynamic nuclear polarization (DNP). Despite having different operating conditions, we opinionate that both mechanisms are theoretically similar processes in ideal conditions, i.e., the electron is merely another spin-1/2 particle with a much higher gyromagnetic ratio. We show that the CP and DNP processes can be described using a unified theory based on average Hamiltonian theory (AHT) combined with fictitious operators. We explore the possibility of exploiting theoretically predicted DNP transients for electron-nucleus distance measurements—like routine dipolar-recoupling experiments in solid-state NMR. The intuitive and unified approach has also allowed new insights on the cross effect (CE) DNP mechanism and experiments, leading to better design of DNP polarizing agents and extending the applications beyond just hyperpolarization. 

56. December 9, 2022, Mathilde Lerche, DTU, "Signatures of Metabolic activity obtained by 13C dDNP NMR mixture analysis". NMR spectroscopy is an essential analytical tool for characterization of chemical and biochemical processes. NMR is highly versatile in terms of analyte selection and its ability to provide quantitative information with a high level of confidence. At the same time NMR is non-destructive for the system under investigation. As an analytical method it is, however, inherently, and relative to other methods insensitive. With hardware development, smart acquisition design and in tandem with other methodologies, this sensitivity drawback has been circumvented for numerous but specific applications. The potential of quantitative NMR is, however, far greater than currently exploited. Particularly, for applications where quantitative analysis of compounds in complex mixtures are needed on limited sample amounts.
    Hyperpolarization by dissolution dynamic nuclear polarization (dDNP)1 has recently been applied to enhance the resolution and sensitivity of NMR to detect compounds in complex mixtures2. We have further to this work developed a stable isotope tracer-based hyperpolarized NMR method aiming to quantitatively measure metabolic flux with high sensitivity and high contrast to noise. With this method metabolic pathways and networks can be mapped. The method encompasses three distinct steps; Firstly, incubation of living cells in culture or tissue infusion with stable isotope labelled substrate at targeted conditions (e.g. choice of substrate and time) followed by quenching metabolic activity and extraction of produced metabolites. In a second step stable lyophilized metabolite samples are signal enhanced with dDNP and lastly NMR spectra of the hyperpolarized metabolite samples are acquired and interpreted, and metabolites are quantified.
    [1] Ardenkjaer-Larsen, J. H.; Fridlund, B.; Gram, A.; Hansson, G.; Hansson, L.; Lerche, M. H.; Servin, R.; Thaning, M.; Golman, K. Proc. Natl. Acad. Sci. U. S. A. 2003, 100 (18), 10158−63.
    [2] Bornet, A.; Maucourt, M.; Deborde, C.; Jacob, D.; Milani, J.; Vuichoud, B.; Ji, X.; Dumez, J. N.; Moing, A.; Bodenhausen, G.; Jannin, S.; Giraudeau, P. Anal. Chem. 2016, 88 (12), 6179−83. p

57. December 2, 2022, Patrick Giraudeau , CEISAM, Université de Nantes, "Dissolution DNP opens new perspectives for metabolomics".  NMR spectroscopy is a major analytical tool in metabolomics, owing to its ability to provide highly reliable structural and quantitative information. Over the last decade, we have explored how NMR metabolomics can build upon recent methodological developments to become more sensitive and better resolved. Developments include the integration of fast 2D spectroscopy in NMR metabolomics workflows, and approaches to make NMR metabolomics more accessible with benchtop NMR. During this presentation, we will mainly focus on discussing the potential of dissolution dynamic nuclear polarization (D-DNP) for 13C NMR metabolomics at natural abundance. Such exploration opens many application perspectives but also raises a number of methodological and analytical challenges. After preliminary studies that showed the potential of D-DNP for such samples, we recently developed a complete untargeted NMR-based metabolomics workflow based on D-DNP. Using a D-DNP prototype dedicated to analytical chemistry applications, we showed the ability of this approach to statistically distinguish two group of plant sample extracts, and to highlight relevant biomarkers. We have also explored the potential of D-DNP to analyze biofluids at natural abundance, making it possible to detect and identify several tens of relevant metabolites from 13C hyperpolarized spectra of freeze-dried urine samples. In parallel with these promising metabolomics applications, we are constantly improving the performance of the D-DNP analytical workflow to increase its applicability for the analysis of complex metabolic mixtures. Thanks to a fine optimization of the many parameters involved in the D-DNP experiment, we have been able to significantly increase the sensitivity, the precision and the robustness of our experimental setting. In addition, we are exploring the potential of ultrafast 2D NMR methods to provide single-scan homo- and hetero-nuclear correlations following D-DNP, in order to improve the separation of overlapped metabolite signals. We will describe these recent developments and applications, highlighting the potential of D-DNP for metabolomics, as well as the questions raised by the development of this new analytical approach.

58. November 25, 2022, Stephan Appelt, RWTH, Aachen, "The RASER: From Photon Spin to cooperative Magnetic Resonance Imaging". This presentation discusses the physics of the parahydrogen pumped RASER (Radio-frequency Amplification by Stimulated Emission of Radiation) [1,2]. RASER activity can be observed if the photons of a high Q resonator interact with a negatively polarized nuclear spin ensemble. The theory of multi-mode RASER action in the presence of a magnetic field gradient is based on the slaving principle and on synchronization, which both constitute two basic order principles in nature. These two principles are involved in the image formation process of RASER MRI, where the image is build in a self-organized and cooperative way in the absense of external radio-frequency irradiation [3]. Compared to conventional imaging RASER MRI is more sensitive to local variations in the spin density profile. Recent experiments using RASER active protons pumped by SABRE (Signal Amplification By Reversible Exchange) agree well with the theoretical predictions. All insights might open new applications in science, quantum technology and medical diagnostics.

[1] M. Suefke, S. Lehmkuhl, A. Liebisch, B. Bluemich, S. Appelt, Nat. Phys. 13, 568 (2017).

[2] S. Appelt, A. Kentner, S. Lehmkuhl, B. Blümich, Prog. Nucl. Magn. Reson. Spectrosc. 114-115, 1 (2019).

[3] S. Lehmkuhl, S. Fleischer, L. Lohmann, M. S. Rosen, E. Y. Chekmenev, A. Adams, T. Theis, S. Appelt, RASER MRI: Magnetic Resonance Images formed Spontaneously exploiting Cooperative Nonlinear Interaction, Sci. Adv. 8, eabp8483 (2022) .

59. November 18, 2022, Kirill Sheberstov, ENS, Paris, "Delocalized long-lived proton spin states in aliphatic chains"  In nuclear magnetic resonance (NMR), the memory of spin systems is normally limited by longitudinal relaxation. However, long-lived states (LLSs) have lifetimes that can be significantly longer. In the talk, we will discuss that LLSs are found in various compounds containing aliphatic chains. One can create LLSs involving two chemically equivalent methylene protons (i.e., have identical chemical shifts), provided they are magnetically inequivalent, i.e., have distinct scalar couplings to other nuclei, such as the protons of nearby CH2 groups. The accessed LLS are delocalized throughout the aliphatic chains. They can be excited by the simultaneous application of weak selective radio-frequency fields at several chemical shifts by polychromatic spin-lock induced crossing (poly-SLIC). LLSs in magnetically inequivalent CH2 groups do not require any external manipulations to be sustained, this property may be further exploited to perform the transport of hyperpolarized samples. LLSs are insensitive to the application of pulsed field gradients and therefore can be used to generate contrast in magnetic resonance imaging. LLS can reveal a contrast upon a non-covalent binding of ligands to macromolecules. This suggests new perspectives to achieve high-throughput parallel drug screening by NMR. 

60. November 11, 2022, Kerstin Münnemann, University of Kaiserslautern, "Perspectives for Quantitative ODNP in process monitoring applications".  NMR spectroscopy is an attractive analytical technique for reaction and process monitoring. The robust benchtop NMR spectrometers that have become available recently have extended the applicability of the method to industrial processes. Process monitoring is often carried out on-line: the mixture that is to be analysed is pumped through the analytic instrument, which is operated in flow mode. In these setups, the volume of the line between process and analysis should be small and flow rates should be high to enable a fast transport to the analytic instrument. In NMR spectroscopy, this is in conflict with the time needed for sufficient polarization build-up, which is particularly problematic for benchtop NMR spectrometers because of their compact design. However, hyperpolarization methods like Overhauser Dynamic Nuclear Polarization (ODNP) are well suited to overcome this problem because hyperpolarization build-up happens on very short timescales and can be performed under continuous flow [1]. However, a challenge in combining online NMR with ODNP is quantitative analysis, because the efficiency of polarisation transfer of electron spins to nuclear spins varies greatly depending on the solvent, receptor molecule, type of radical, sample temperature, measured nucleus, and polarization field. To take these effects into account and to understand the underlying physical effects in detail, Molecular Dynamics (MD) simulations combined with quantum mechanical calculations can be performed [2]. However, these simulations are tedious and were demonstrated so far only for a radical dissolved in a pure solvent. For more complex and temporarily changing systems, as being present in chemical reactions, simulations would be extremely time-consuming if possible at all. A better strategy could be to enable quantitative analysis by means of calibration which is the topic of this lecture. We demonstrate continuous-flow ODNP enhanced measurements with immobilized TEMPO radicals in two binary solvent mixtures (acetonitrile + water, acetonitrile + 1,4-dioxane) with varying compositions. Quantitative analysis of the hyperpolarized mixtures is enabled by means of calibration and the benefits and drawbacks of the method are discussed.

References

[1] R. Kircher, H. Hasse, K. Münnemann, Analytical Chemistry 93, 25, 8897–8905 (2021).

[2] D. Sezer, M.J. Prandolini, T.F. Prisner, Physical chemistry chemical physics 11 (31), 6626-6637 (2009).

61. November 4, 2022, Monika Schönhoff, University of Münster, " Diffusion and electrophoretic NMR: Tracking ions in battery electrolytes".  Pulsed-Field-Gradient (PFG)-NMR methods provide detailed and specific information about molecular transport processes. In concentrated electrolyte materials, e.g. for Li ion batteries, a detailed characterization of all constituent species is feasible by multinuclear (e.g. 1H, 7Li, 19F) PFG-NMR. While diffusion coefficients of all species are easily accessible, they are often not sufficient to identify the conductivity contributions of specific ion species, since ion correlations complicate the transport behavior. Electrophoretic NMR (eNMR), however, allows to directly measure the electrophoretic mobility of ions with NMR-active nuclei and allows conclusions on distinct ion correlations. The lecture presents the possibilities and limits of its application to various concentrated electrolyte systems, identifying the mechanisms governing transport, such as vehicular motion or the role of ion-ion anticorrelations.

62. October 28, 2022, Ulrich Scheler, Leibniz Institute für polymerforschung, Dresden, " Electrophoresis NMR – Counterion condensation and complex formation”. Pulsed-field-gradient (PFG) NMR is applied to study translational motion of molecules in solution. Incoherent motion like diffusion and coherent motion like flow can be distinguished by data processing or the design of the experiment. Charged macromolecules like polyelectrolytes or proteins often exhibit a charge density that it so high that counterions do not have sufficient thermal energy to escape that field. As result fraction of counterions condenses on the macromolecules and thus lowers the effective charge and thus electric field of the macromolecule enabling the remaining counterions to escape. The steady-state velocity during electrophoresis reflects the force balance between the force in the electric field and the hydrodynamic friction. The experiment gives direct access to the effective charge. It is applied to study counterion condensation and the formation of complexes.

63. October 21, 2022, Siegfried Stapf, TU Ilmenau, "DNP and field cycling: an unholy alliance? Improving the study of molecular dynamics at low fields”. Low-field and variable-field NMR carry the natural disadvantage of low signal intensity; in particular, fast field-cycling relaxometry cannot benefit from homogeneous fields and narrow lines that are found in modern desktop spectrometers. Throughout the years, all possible types of hyperpolarization techniques have been combined to alleviate these shortcomings at low fields, but DNP alone appears to be suitable for variable-field studies. At first sight, the transfer of electron magnetization to nuclei is very promising in fields below 1 Tesla; on the other hand, it typically requires the addition of radical species which affect the nuclear relaxation time, the very quantity that has to be measured. This presentation gives an overview of the different DNP mechanisms at work in room temperature measurements at low fields, describes the hardware and theoretical approaches that have been used, and finds a way to eliminate the additional relaxation contribution of the unpaired electrons for a number of applications in everyday life.

64. October 14, 2022, Jozef Lewandowski, University of Warwick, “Enabling characterisation of protein dynamics by relaxation measurements in large sensitivity-limited systems in the solid state”. Molecular motions are an important ingredient in understanding how proteins and other biomolecules work. Solid-state NMR can potentially provide a detailed view of protein dynamics spanning several orders of magnitude in very large systems, such as protein complexes or membrane proteins, inaccessible with other methods. From several types of parameters, which we can measure to characterise dynamics, relaxation rates are attractive alternative as they depend on both amplitude and time scale of motions. However, relaxation measurements are very time consuming and sometimes simply not feasible, especially in large sensitivity limited systems. In this presentation I will discuss some of the efforts in our laboratory to make relaxation measurements on such systems more practical and widely applicable. I will talk about various solutions based on multiple acquisitions to speed up the measurements and quantification of dynamics in the presence of paramagnetic dopants. 

65. October 7, 2022, Sonja Egert, University of St Andrews, "Disorder and local structure-property relations in functional oxides: Tracking the effects of electric fields and chemical modification." The sensitivity of solid-state NMR spectroscopy to octahedral tilting, distortions, and disorder makes it a powerful technique for the characterization of the local structure in perovskite oxides. Antiferroelectric oxides in particular constitute a promising class of high-performance materials in energy storage applications. As such, they offer new solutions for the power electronics required in electric vehicles or the integration of renewable energies into the grid. An electric-field-induced structural phase transition between two closely related phases, accompanied by a reorganisation of the lattice polarization configuration, is key to their unique functional properties.  In this work, 207Pb and 23Na are used as local probes to elucidate relationships between compositional modification, local structure, and phase stability based on the analysis of two-dimensional line shapes and ex-situ studies on the effects of electric fields. This approach contributes to an advanced understanding of antiferroelectric ordering in perovskite oxides and, ultimately, to the design of next-generation materials based thereon.

66. September 30, 2022, Amir Goldbourt, Tel Aviv University, "Structural snapshots into the life cycle of filamentous phage viruses" Filamentous phage infect bacterial cells that possess the F-pili organelle. They are one-micron long viruses containing a single-stranded DNA wrapped by several thousand copies of a mostly-helical coat protein at ratios of 1-2.5 nucleotides per coat protein. Infection occurs when a virus attaches to the pilus bacterial filament and the DNA is transferred into the cell. During replication, the non-structural gene V protein (gVp) attaches to a ssDNA creating a pre-mature phage and signaling the assembly of a new particle. In recent years we managed to solve the atomic-resolution structures of two intact viruses, M13 (with solid-state NMR) and IKe (with cryoEM), and detect common structural assembly motifs. Dynamic properties studied by chemical-shift-anisotropy recoupling methods suggest a highly rigid helical coat with a mobile DNA interface. The pre-mature virus made of ssDNA wrapped by gVp is of equivalent length however with very different properties. The coating protein gVp is composed mostly of beta strands and a high percentage of loop and disordered regimes, it is significantly more dynamic then the structural coat protein, and structure determination by solid-state NMR of the entire gVp-ssDNA complex shows that it undergoes a very large conformational change upon binding to the DNA, while losing several additional secondary structure motifs. These modifications facilitate the binding mechanism and promote cooperative binding in the assembly of the gVp-ssDNA complex.

67. September 23, 2022, Mattia Negroni, University of Vienna, "Unexpected Inversion of Hyperpolarized 13C NMR Signals Through Cross-Correlated Cross Relaxation in Dissolution DNP Experiments" During the exploration of new possibilities for the use of Dissolution Dynamic Nuclear Polarization (DDNP) we stumble across an unusual phenomenon: after polarization and subsequent dissolution, protonated carbon groups have a signal that is opposite compared to 1H while the deuterated ones have a sign concordant to it. The explanation is an accelerated cross-correlated cross relaxation (CCR) that induce a selective inversion during sample transfer. Parallel-detection of 1H and 13C allows the monitoring of the signals evolution and the results were confirmed by relaxation simulations. The ubiquitous presence of CH spin systems made this phenomenon quite common and might be exploited for selective spectroscopic labelling. 

68. September 16, 2022, Carlos Meriles, CUNY, "The electronic-nuclear spin cluster under energy matching: A platform for fundamental physics and novel applications" Nuclear spins and paramagnetic centers in a solid randomly group to form clusters featuring nearly-degenerate, hybrid states whose dynamics are central to processes involving nuclear spin-lattice relaxation and diffusion. Their characterization, however, has proven notoriously difficult mostly due to their relative isolation and comparatively low concentration. In this talk, I will discuss recent field-cycling experiments combining optical spin pumping, and variable radiofrequency (RF) excitation to probe transitions between hybrid multi-spin states formed by strongly-coupled electronic and nuclear spins in diamond. Leveraging bulk nuclei as a collective time-integrating sensor, we probe the response of these spin clusters as we simultaneously vary the applied magnetic field and RF excitation conditions to reconstruct multi-dimensional spectra that we qualitatively capture through analytical and numerical modeling. I will then build on these observations to discuss some of the potential applications including alternate thermal-jump-assisted, microwave-free DNP protocols as well as the generation of protected states for use as quantum memories and/or nanoscale sensing.

69. July 29, 2022 Rangeet Bhattacharyya, IISER, Kolkata, " Applications of a Fluctuation-regulated Quantum Master Equation in Magnetic Resonance: quantum computing to solid-state NMR"  Quantum systems are said to be “open” if they are coupled with an environment, and one employs a quantum master equation to describe the dynamics of such systems. Now, all physical systems experience thermal fluctuations even when they are in equilibrium. For example, consider individual solvent molecules of a solution in thermal equilibrium; they undergo thermal kicks in the form of forces and torques, resulting in diffusive motions of these molecules. Traditional approaches to understanding the dynamics of open quantum systems do not take into account these thermal kicks in the environment. In recent years, we developed a new approach to deriving a quantum master equation of a general open quantum system (e.g., nuclear spins) by explicitly incorporating a model of thermal fluctuations that act on the local environment (e.g., spin-bearing molecules). This fluctuation-regulated quantum master equation (FRQME), also helps estimate the higher-order effects of all external drives or coupling terms on the system dynamics, in addition to the regular relaxation terms. In this talk, we will briefly show the construction of FRQME and will discuss in detail its applications in quantum computing and in the spin-locking and related problems in the solid-state NMR.

70. July 22, 2022, Sinha Neeraj, Centre of Biomedical Research, Lucknow, India, " Solid – state nuclear magnetic resonance spectroscopy of bones and cartilage in its native state " Probing high – resolution structural details of extra – cellular mineralized tissue such as bone and cartilage has always been challenging to conventional spectroscopic tools. In recent years, developments in solid – state NMR spectroscopy (ssNMR) has led to interesting structural details of these important classes of biomaterials. In this talk, we will present the recent developments in our laboratory to probe such systems in its native state. The results of 1H detected ssNMR experiments, sensitivity enhancements methods such as BioSolids CryoProbe and DNP will be presented.

71. July 15, 2022, Jacqueline Tognetti, Warwick University, " 1H-Detected Solid-State NMR Experiments at ≥ 60 kHz MAS: Advances and Opportunities " This seminar will focus on two aspects that can significantly impact the acquisition of proton detected experiments in solid-state NMR at fast MAS. The first concerns the improvement of resolution and sensitivity in proton detected spectra, still affected by strong 1H homonuclear dipolar couplings at 60-100 kHz MAS, using windowed PMLG 1H homonuclear decoupling at 60 kHz MAS for a 1H nutation frequency of 100 kHz and less. The second aspect will highlight the development of interleaved and nested methods for accelerating the acquisition of 1H-detected relaxation measurements on multiple nuclei of the protein backbone (15N, 13CO and 13Cα) at 100 kHz MAS.

72. July 8, 2022, Xueqian Kong, Zhejiang University, "Probing Defects in Metal-organic Frameworks by Multidimensional Solid-state Nuclear Magnetic Resonance" It has been demonstrated that structural defects in metal-organic frameworks (MOFs) could have significant impact on their properties. However, the chemical structure and distribution of defects are difficult to characterize due to the nature of complexity and disorder. We recently performed multidimensional solid-state NMR to elucidate the molecular picture of defects in MOFs. Through direct methods, we revealed the dynamic interplay of various defect-associated species including water, formate, acetate, etc. Through indirect methods, we probed the geometry and distribution of defects and provided molecular-level quantifications. In addition, we uncovered the unusual 1D arrangement of correlated defects in specific MOFs. Furthermore, we investigated the docking conformations of bioactive molecules at the defects to assist the design of defect-engineered MOF nanomedicines.

73. July 1st, 2022, Luis Mafra, University of Aveiro, "Understanding CO2 capture mechanisms in porous adsorbents via ssNMR" The nature of CO2 species interacting with porous surfaces determines the gas sorption capacity/kinetics, selectivity and cyclic stability of a given adsorbent material. However, an atomic-level understanding of the CO2 sorption process remains elusive, hindering our ability to design improved sorbents. The lack of advanced spectroscopic studies, tailored to elucidate the structure of adsorbed gas species, has also been a major bottleneck for further progresses in understanding the physical chemistry of gas-solid interfaces. Adapting spectroscopic tools to the study of confined gas species, interacting with porous surfaces, is also not trivial. This presentation highlights the most recent advances from our team showing that solid-state (ss) NMR spectroscopy is a unique site-selective technique to study the structure and the dynamics of CO2 species adsorbed at amorphous silica porous CO2-adsorbents. Strategies combining ssNMR and computational methods to study CO2 speciation, under dry and wet conditions, are showcased. Measurements of T1 and T1ρ relaxation times confirm the presence of physi and chemisorbed CO2 molecular dynamics on very different timescales enabling the quantitative discrimination of distinct confined CO2 species.

74. June 24, 2022, Gabriele Stevanato, Göttingen, "A journey on hyperpolarisation: from design criteria for MAS DNP at 100 K to tracking cellular metabolism in real–time by PHIP"  The rapid progress of MAS DNP has been largely enabled through the understanding of rational design concepts for more efficient polarizing agents (PAs). In the first part, I will talk about the importance of the local geometry in designing nitroxide probes and how Gd complexes could find an important role for the future of MAS DNP at 100 K and high magnetic field. In the second part, I will show how neurodegenerative pathologies can be addressed at a cellular level via an effective an inexpensive way while bridging the current gap between DNP and parahydrogen–based techniques in signal enhancement.

75. June 17 ,2022 Svetlana Pylaeva, Utrecht,  "Structural Anomaly in Glasses: Molecular Dynamics Study of TEMPO in Dibutylphthalate and BMIM-BF4" Understanding heterogeneous nano/microscopic structures of various organic glasses is fundamental and necessary for many applications. Recently, unusual structural phenomena have been observed experimentally in various organic glasses near their glass transition temperatures, including ionic liquids and dibutyl phthalate (DBP). In this talk we report in-depth molecular dynamics studies of structural anomalies in such glasses on an example of DPB and butyl-methyl-imidazole (BMIM) BF4. We revealed insights into the general mechanism of these phenomena. In particular, we have evidenced that the two types of solvation within alkyl chains coexist, allowing only small-angle wobbling of the solute molecule (TEMPO radical), and another favouring large-angle rotations. Remarkably, excellent qualitative and quantitative agreement with previous experimental results were obtained. As such we believe that the above mentioned dynamic phenomena explain the intriguing structural anomalies observed in such glasses in the vicinity of their glass transition temperatures.

76. June 10, 2022 Benesh Joseph, Johann Wolfgang Goethe University, Frankfurt, " Pulsed dipolar ESR spectroscopy of membrane transport protein complexes " Pulsed dipolar electron spin resonance spectroscopy techniques enable the determination of electron-electron dipolar coupling and the interspin distances within a range of materials. Nowadays, these techniques are widely used for characterizing the structure and dynamics of proteins and nucleic acids. I will introduce the application of pulsed electron double resonance (PELDOR or DEER) spectroscopy using different spin centers (nitroxide, gadolinium, and or trityl labels) for the characterization of membrane protein complexes under in vitro and in situ conditions. Further, the application of a five-pulse PELDOR sequence at Q-Band (34 GHz) frequency employing shaped pulses produced from an arbitrary waveform generator (AWG) significantly enhances the sensitivity and the range for such distance measurements. Our results on the elucidation of conformational heterogeneity, equilibrium dynamics, kinetics, and thermodynamics aspects of membrane protein complexes using PELDOR spectroscopy and the ongoing attempts to perform similar investigations directly in the native membrane environment will be discussed.

77. June 3, 2022, William Price, Western Sydney University,  "NMR Diffusion Measurements of Reacting Systems" Most chemical reactions involve the reactants coming together and the reaction products dispersing via translational diffusion. Changes in molecular size and solvent viscosity can also be correlated with diffusion. Thus, diffusion is an obvious probe for studying reacting systems. The pulsed gradient spin-echo (PGSE) NMR technique is especially suited for studying reacting chemical systems since it is non-invasive and thus doesn’t affect the thermodynamics of such systems. Further, it affords the possibility of simultaneous measurement of the kinetics of a reaction and the diffusion of each species. Thus, NMR diffusion measurements can provide deep insight into reaction processes. Traditionally NMR diffusion measurements have been performed on effectively time-invariant systems. However, obtaining accurate diffusion coefficients is greatly complicated when the reaction timescale is of the order of the NMR diffusion measurement. These challenges include the changing populations of the species, reaction-induced temperature changes, and reaction products may alter NMR relaxation behaviour. Numerous strategies and examples will be discussed.

78. May 27, 2022, Moreno Lelli, CERM, Firenze, "Strategies for DNP at High temperature and Fast MAS." One major limit of MAS DNP is in the low temperature, typically around 100 K, which is required to achieve high enhancements. Although a DNP below 100 K has interesting potential, developing strategies to have an efficient DNP at temperatures above 100 K or even 200 K would be useful for studying dynamics in solids. Notably, high-temperature DNP would also open new perspectives in solid-state biological NMR which suffers from a significant loss of resolution at 100 K. Here we show how hybrid biradicals such as HyTEK2, based on the Cross-Effect mechanism and designed by coupling BDPA with a nitroxide unit, as well as BDPA radical dissolved in rigid matrices (OTP, polystyrene, …) can provide an interesting trend with temperature with enhancements of up to 20 also at room temperature. This temperature trend depends on a combination of several factors, from the magnetic properties of the polarizing agent to the role played by spin diffusion and electron relaxation times at different temperatures. Several strategies based on the radical formulation will be discussed presenting our recent results in the study of systems above 200 K.

79. May 20, 2022 Claudia Schmidt, University of Paderborn, "Probing porous materials  by NMR spectroscopy of guest molecules" Porous materials are used in many fields, such as  catalysis, energy and environmental applications, and have been investigated by a variety of  NMR methods. The chemical structure of the material itself can be studied by solid state NMR  spectroscopy, while the pore system may be probed by relaxometry, cryoporometry, or  diffusion of guest molecules. Furthermore, the chemical shifts of guest molecules in  microporous materials are strongly influenced by the chemistry of the interface (causing a  nucleus-independent chemical shift) and by the pore size. In this talk, the spectra of water in  different porous materials, including carbon-based materials obtained by hydrothermal  carbonization of sugars and C 1 N 1 (carbon-nitrogen) materials, will be discussed.

80.  May 13, 2022, Elodie Salager, CEMHTI, Orléans, "Operando NMR spectroscopy of lithium deposition of batteries at low temperature" NMR of functioning lithium-ion batteries (operando) is now a relatively widespread method. Still, there are challenges regarding sensitivity. Sensitivity is necessary to detect parasitic reactions at an early stage and to enhance time resolution, essential for fast charge studies or low temperature.  This talk will present our setup for measuring NMR 7Li spectra , the challenges related to lithium deposition and the efforts we made to improve sensitivity in the context of measurements under 0°C.

81. May 6, 2022, Andrea Capozzi, EPFL, "A 320 km hyperpolarization journey: Performing [U-13C, d7]glucose DNP in Copenhagen and hyperpolarized 13C-MR in Aarhus"  "Since its invention in 2003, dissolution Dynamic Nuclear Polarization (d-DNP) has become the most powerful and versatile method to enhance Nuclear Magnetic Resonance (NMR) sensitivity in the liquid state. Without a doubt, the most important success is the unique opportunity to perform Magnetic Resonance Imaging (MRI) for staging of cancer and early treatment monitoring by means of injection of metabolically relevant hyperpolarized substrates. Despite its undisputed potential, hyperpolarization via d-DNP struggles to enter the clinic on a daily base because the method relies on expensive and technically demanding hardware: the so-called d-DNP polarizer. The technique builds on a method known since the 50s' under the name of simply DNP: if sufficiently low temperature (1 - 4 K) and high magnetic field (3.5 - 7 T) are provided, microwave irradiation at the right frequency can enhance the substrate NMR signal in the solid state by transferring polarization from few unpaired electron spins (e.g. organic free radicals) duly added to the sample. Unfortunately, the same electron spins, in absence of microwave irradiation, represent the main source of NMR signal loss. When extracting the sample from the polarizer, the only way to shelter its hyperpolarization is to create enough distance between the substrate and the unpaired electrons, hence the dissolution step. But, once in the liquid-state, the lifetime of the hyperpolarized substrate is limited to few tens of seconds. As a consequence, each MR facility willing to perform hyperpolarized studies has to be equipped with a d-DNP polarizer on-site. From some years, I am working on making hyperpolarization transportable. In this talk I will discribe one possible approach based on labile radicals."

82. April 29, 2022 Ralf Ludwig, Rostock University, "Noncovalent interactions, structural changes and like-charge attraction in ionic liquids probed by deuterium NMR spectroscopy"  The unique properties of tailored ionic liquids (ILs) result from the delicate balance of Coulomb interactions, hydrogen bonding and dispersion forces. Better understanding of IL behavior at the microscopic scale helps to elucidate macroscopic fluid phenomena, and thus promote specific applications. Here, we show that deuterium NMR in the liquid and solid states of this promising material is suitable for characterizing hydrogen bonding, structural changes, rotational dynamics and phase transition behavior. Deuteron line shape and spin relaxation time analysis provide a description of the structural and dynamical heterogeneity in the supercooled and solid ionic liquids. Deuterium NMR is even capable to distinguish hydrogen bonds between ions of opposite and ions of like charge.

83. Friday, April 22, Marcos de Oliveira, University of Sao Paulo "Modern magnetic resonance approaches for characterizing rare-earth species in inorganic solids" Rare-earth containing inorganic solids are important materials with technologically relevant properties for a variety of applications. For developing the functional potential of these materials, it is important to understand the local environment and spatial distribution of the rare-earth ions and their influence upon the structural organization of the host matrix. Nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) can furnish crucial information about these aspects. In this talk, I will discuss relevant spectroscopic characteristics of several rare-earths which serves as NMR and EPR probes.

84. April 15, 2022, Dimitris Sakellariou, Leuven University "Custom-made Magnetic Resonance: An application-driven instrumentation approach" Low-field NMR is as old as Magnetic Resonance. Recent advances in magnet design have allowed us to bring this technology on the laboratory bench for routine high-resolution NMR spectroscopy. In parallel to this extrapolation from high-field NMR, many new options become available bringing magnetic resonance closer to the chemical and medical analysis. Miniaturization, low-cost and hyphenation are some of the most straightforward attributes of such technology. I will be presenting recent developments from our laboratory in custom-made magnetic resonance as an application-driven tool to answer specific questions. In this talk they will be concerning the structure and function of porous materials in petrophysics, in civil and in materials engineering. 

85. April 8, 2022, Beat Meier, ETHZ, "Biological solid-state: some observations at high field and fast spinning" We discuss theoretical and practical limitations for the spectral resolution in proton-detected spectroscopy of protein in high magnetic fields. In addition, technical advances for compensating field instabilities (a “digital lock”) are described. Samples characterized at 1200 MHz include fibrils, protein complexes, viral capsids and fibrils.

86. April 1, 2022, Clare Grey, University of Cambridge "New NMR Approaches to Study Electrochemical Systems: From Conventional to Redox Flow Batteries to Gated Electronics" The first part of this talk will focus on our work to develop NMR, MRI and ESR methods that allow devices to be probed while they are operating (i.e., operando). This allows transformations of the various cell components to be followed under realistic conditions without having to disassemble and take apart the cell. We can detect side reactions involving the electrolyte and the electrode materials, sorption processes at the electrolyte-electrode interface, and processes that occur during extremely fast charging and discharging. Many of the battery electrode materials are paramagnetic and their study has involved the development of new experimental (NMR) and theoretical approaches to acquire and interpret spectra. Recent studies to correlate lithium hyperfine shifts with local structure and to probe dynamics will be described, focussing on studies aimed to understand degradation in NMC-811 (Li[Ni0.8Co0.1Mn0.1]O2) – graphite full cells. New results on redox flow batteries, using both NMR and MRI,1 extremely high-rate batteries and novel NMR approaches to study interfaces and interphases such as the SEI will be described, using for example Overhauser DNP of Li metal. Finally, the methods have been extended to gated electronics to explore correlations between local structure, cation insertion and dynamics and electronic properties (e.g., metal-to-insulator transitions and hole doping).

87. March 25, 2022, Kaustubh Mote, TIFR, Hyderabad "Multiple-acquisition strategies to boost throughput in biomolecular solid-state NMR" Solid-state NMR, although powerful, is a technique that requires long experimental time for collecting data. This is especially evident in biomolecular applications, as not only are individual experiments time-intensive, but a number of such experiments (often on different samples) are required to perform tasks such as assign resonances and measure distances and dynamics. Over the past decade, multiple-acquisiton strategies have gained prominence as a way to circumvent the above problems. These strategies take advantages of several aspects of experiments such as the inefficiency of pulse-sequence blocks that transfer magnetization, relatively long T1 relaxation times for nuclei, as well as, in some case, the use of multiple receivers for detection on several nuclei. These have allowed the parallelization of most of the experiments that are required for assigning resonances. In this talk, the implementation of these sequences at slow-moderate MAS frequencies (< 20 kHz) with 13C/15N detection, as well as at fast (> 60 kHz) MAS frequencies with 1H detection will be discussed. New techniques that allow the experiments that are used determination of internuclear distances and dynamics to be parallelized in both the MAS regimes will also be demonstrated. Finally, a new strategy that allows a subset of these experiments to be performed at slow-moderate MAS frequencies without increasing the radio-frequency duty-cycle for the experiment will be discussed

88. Friday, March 18, 2022, Anna Zawadzka-Kazimierczuk,  Warsaw University, "High-dimensional NMR experiments for studying intrinsically disordered proteins" Since early 1980’s many examples of functional proteins have been found, that under physiological conditions reveal partial or full structural disorder. Moreover, it has been shown, that in some cases this flexibility is crucial for the protein functionality. The intrinsically disordered proteins (IDPs) were found to be especially abundant in eukaryotic organisms. The connections of IDPs with cancer or neurodegenerative diseases attracted even more attention of researchers. NMR allows to get information on both residual structure of IDPs and their dynamics. Nonetheless, while studying IDPs  with NMR  one comes upon some difficulties, not known from the folded proteins studies. Due to the backbone flexibility, the range of chemical shifts is here especially narrow. It means, that IDPs’ NMR spectra feature high level of peak overlap, in difficult cases even precluding the analysis with standard methods. Acquisition of high-dimensional spectra (4D, 5D) can solve this problem. In the talk, the high-dimensional methods for efficient studying of IDPs will be presented, together with some real-life examples. Methods for IDPs resonance assignment, as well as studying their interactions and residual structure will be shown.

89. March 11, 2022, Markus Weingarth, Utrecht University "The mechanisms of Lipid-targeting Antibiotics" Antimicrobial resistance is a major threat to global health. To combat this threat, new antibiotics are urgently needed. Ideal candidates could be antibiotics that target special lipids that only exist in bacterial, but not in human cell membranes. These drugs kill refractory pathogens without detectable resistance. This has generated huge interest. So far, the molecular mechanisms of lipid-targeting antibiotics have proven elusive due to technical challenges. Here, we determine the killing mechanism of teixobactin1, considered the first new antibiotic in 30 years, on several length- (Å to mm) and time-scales (min to hr). We show that teixobactin kills bacteria by the formation of amyloid-like fibres that disrupt the bacterial membrane, which is a new type of antimicrobial action.

90. Friday March 4 2022, Henrike Heise, Düsseldorf University, "MAS-NMR and DNP – mobility, protein(misfolding) and more"  Protein misfolding is a complex process involving partial unfolding , oligomerization and aggregation. In this talk I demonstrate how MAS-NMR-spectroscopy with and without DNP enhancement can contribute to the structural elucidation of these processes at various stages. In particular, we use DNP-enhanced MAS-NMR-specroscopy to gain insight into conformational ensembles in (partly) undfolded proteins, and real-time MAS NMR spectroscopy to study the process of protein aggregation in situ.

91. Friday, February 25, 2022, Loren Andreas, MPI for Multidisciplinary sciences, Göttingen, "Modest Offset Difference Internuclear Selective Transfer via Homonuclear Dipolar Coupling", Homonuclear dipolar recoupling is routinely used for magic-angle spinning NMR-based structure determination. In fully protonated samples, only short proton-proton distances are accessible to broadband recoupling approaches because of high proton density. Selective methods, in principle, allow detection of longer distances. Here we introduce the selective pulse sequence, MODIST, which recouples spins that have a modest chemical shift offset difference, and demonstrate it to selectively record correlations between amide protons. The sequence was selected for good retention of total signal, leading to up to twice the intensity for proton-proton correlations compared with other selective methods. The sequence is effective across a range of spinning conditions and magnetic fields, here tested at 55.555 and 100 kHz magic-angle spinning, and at proton Larmor frequencies from 600 MHz to 1200 MHz. 

92. Friday February 18, 2022,  Ivan Zhukov, ITC, Novosibirsk, "Elucidation of electron and nuclear spin dynamics in the course of chemical reactions by field cycling photo-CIDNP",  NMR is a powerful tool for studying molecular structures and processes at the atomic level for diamagnetic substances, i.e. those not containing free radicals. However, the observation of paramagnetic species is usually impossible in NMR both due to a large shift of nuclei resonance frequencies and unfavorable relaxation properties of these nuclei. Nevertheless, the CIDNP (Chemically Induced Dynamic Nuclear Polarization) effect allows indirect observation of the processes involving short-lived paramagnetic intermediates of chemical reactions by NMR. The analytical description and numerical simulation of electron and nuclear spin dynamics are necessary to obtain information about the structure and magnetic resonance parameters of these short-lived paramagnetic intermediates. Practical aspects of measuring and numerical modeling of CIDNP field dependences will be considered. An automated iterative search for the best values of simulation parameters considerably reduces the efforts necessary to draw chemically relevant conclusions based on CIDNP data.

93. Friday February 4, 2022, Christian Bonhomme, Sorbonne University, Paris, France, "Recent experimental and theoretical NMR developments in the study of biomaterials" Natural biomaterials usually exhibit a high level of structural complexity. This is inherent to their hybrid nature combining organic (O) and inorganic (I) components at different levels (from nm to cm). Multinuclear and multidimensional solid state NMR is probably the most pertinent spectroscopic tool of investigation to decipher the structure of O/I components and their interfaces. Such interfaces play a specific role in the final properties of the materials. In the first part of the talk, we will focus on a particular family of natural biomaterials, namely the pathological calcifications and their synthetic counterparts. Solid state NMR methodology gives original insight on both structure and local dynamics. Most importantly, interesting phase transformations can be monitored in situ. These transformations can be related to clinical observations. Moreover, NMR observations orient the chemist towards new synthetic pathways mimicking the structure of natural calcifications. In the second part of the talk, we will focus on a particular nucleus, namely 43Ca. It is of fundamental importance in biomaterials (either natural or synthetic). 43Ca nucleus is of quadrupolar nature and is characterized by severe drawbacks in terms of sensitivity (low gamma and very small natural abundance). We will present a complete methodology allowing to bypass these drawbacks including: 1D and 2D 43Ca (MQ)MAS NMR experiments on labeled samples, natural abundance 43Ca MAS experiments at very‑high field and ultra-high magnetic field (35.2 T), and 2D 1H-43Ca DNP MAS experiments in natural abundance. Finally, we will discuss on the importance of 43Ca in the refinement of structures based on NMR crystallography.

94. Friday January 28 2022, Daniel Lee, Manchester University, "Controlling nanoparticle properties: scratching more than just the surface with solid-state (DNP-)NMR" The quest for designer nanoparticles (NPs) with tailored functions ranges from the fields of medicine and health (e.g. for drug delivery) to energy applications (e.g. in solar cells). Therefore, understanding how to control their properties through synthetic routes is crucial. Among various nanosystems, semiconducting ZnO NPs are of large importance owing to their versatility and unique optoelectronic performance. In this presentation, it will be shown how (dynamic nuclear polarization enhanced) solid-state NMR spectroscopy can be used to provide a detailed picture of surface features through probing inter-nuclear distances. This enables the distinction of differences between ligand-capped ZnO NPs produced via two routes: a traditional sol-gel synthesis and an organometallic approach. The discovered differences can then be directly related to contrasting properties of a priori similar NPs. The cause of the distinct surface features is then investigated further, highlighting the unexpected role of “spectator” ions in and around the NPs produced via a sol-gel methodology. Finally, the gained atomic insight is employed to produce stable nanoplatelets of controlled thickness using a ligand that undergoes facet-specific bimodal coordination. The key contributions of multi-nuclear NMR spectroscopy in guiding NP synthesis protocols will pervade the talk.

95. Friday January 21, 2022, Leo van Wuellen, Augsburg University, "Modern Solid State NMR strategies in Materials Science or NMR is wunderbar" For a controlled fine-tuning of materials’ key properties, a detailed knowledge of the structural and dynamic features of the materials poses a prerequisite. To this end we develop and utilize modern Solid State NMR strategies which not only provide information about the structural motifs on short and intermediate length scales but also offer a handle to study the microscopic dynamics within these materials. Especially for materials, which are characterized by a lack of translatorial periodicity, considerable disorder or high dynamics, these approaches offer unprecedented insight into the structure and dynamics. We will show how these novel approaches may be successfully employed to study the structure of amorphous materials at ambient conditions and to obtain information about its evolution with temperature. Further, new solid state electrolytes for next generation’s Li batteries will be presented with the focus here being on the local Li coordination and the mechanism of ion transport. Along the way, a variety of novel NMR (hardware) solutions will be presented, even widening the range of possible applications of NMR spectroscopy in materials science. Examples include MAS NMR at high spinning speeds and ultra high temperature and approaches for high resolution dipolar based NMR spectroscopy without fast MAS. 

96. Friday January 14, 2022, Thomas Wiegand, MPI & RWTH Aachen University, "Spying on proton spins by fast magic-angle spinning NMR" Proton nuclear spins serve as sensitive reporters for noncovalent interactions, particularly hydrogen bondings. Only recently, the technically achievable magic-angle spinning (MAS) frequencies have become high enough to efficiently average out the dipole couplings in the dense proton dipolar network which otherwise lead to rather broad and unresolved 1 H resonances blurring the information on noncovalent interactions. I will discuss the benefit of fast MAS experiments at high magnetic field strengths in chemical and biological applications emphasizing effects of weak interactions. Hydrogen bonding in proteins is probed by measuring temperature-dependent proton chemical-shift gradients, previously only performed in solution.

A special focus of my talk will lie on a large oligomeric bacterial DnaB helicase involved in unwinding double-stranded DNA during DNA replication, which we trap for NMR and EPR studies in its “transition state” of ATP hydrolysis using ADP:AlF 4- . 31 P, 1 H correlation experiments at fast MAS allow distinguishing in an interaction-specific manner between different protein-DNA binding modes. Introducing phosphorus-31 in proton-detected fast MAS experiments has also allowed us to investigate phosphane and phosphonium compounds related to the still emerging field of Frustrated Lewis Pair chemistry.

97. Friday, December 17, 2021, Ingolf Sack, Department of Radiology, Charité - Universitätsmedizin Berlin, "Magnetic resonance elastography: phase contrast MRI for the detection of harmonic waves in soft tissues" Magnetic resonance elastography (MRE) generates a contrast of viscoelastic properties of soft organs for clinical diagnosis. In MRE, external shear waves are excited, which are then encoded into the MRI phase signal and converted into maps of stiffness and viscosity. These key elements of elastography provide insights into the biophysics of soft organs and tissues under normal and diseased conditions in vivo. Many fundamental pathological processes such as inflammation, fibrosis, tumor growth, or malignant transformation are influenced or triggered by altered mechanical properties of cells or the extracellular matrix. After an introduction to the key concepts of MRE, this talk will focus on current challenges such as inverse problem solutions, compression sensitive MRE and viscoelastic model identification. In addition, clinical applications highlighting the detection of biomechanical tissue changes for clinical diagnoses will be discussed. 

98. Friday, December 10, 2021, Paul Hodgkinson, Univ. of Durham, UK, "Understanding disordered materials using solid-state NMR" Disorder is generally perceived as a problem. The pharmaceutical industry, for example, would worry that a solid form containing disorder was metastable with respect to an ordered form, while in terms of characterisation by diffraction, disorder blurs the boundaries between space groups and introduces ambiguities into structure solutions. As NMR spectroscopists, we know that NMR is well-suited to studying dynamics, but we perhaps underestimate the uniquely powerful set of tools at our disposal. In this talk, I will discuss how we have used NMR to characterise disorder in a range of systems from disordered pharmaceuticals to organic and MOF-based materials exhibiting unusual ferroelectric behaviour. NMR's ability to provide strong signatures of dynamics at multiple motional timescales provides much clearer insight into the molecular behaviour than other techniques, such as quasi-elastic neutron scattering or dielectric spectroscopy. The atomic-level insight provided often helps us understand why disordered structures are adopted, and hence how it may be exploited in “functional materials”.

99. Friday December 3, 2021, Phil Williamson, Univ. of Southampton, "Unravelling the role of the Neuroinflammatory Protein S100A9 in Neurodegenerative Disease" Neurodegenerative diseases such as Alzheimer’s or Parkinson’s Disease are typically associated with the deposition of amyloid plaques within the patient brain, less well known however. Neuroinflammation is a common hallmark of many neurodegenerative diseases with patients exhibiting elevated levels of a number of neuroinflammatory markers. Amongst these is the protein S100A9 which has previously been shown to be intrinsically amyloidogenic. Interestingly however, its presence also serves to enhance the deposition of amyloid-beta peptide and alpha-synuclein key proteins in Alzheimer’s and Parkinson’s Disease, respectively. In this presentation I will discuss how we have been able to use a range of both liquid and solid-state NMR methods to characterise the structure of S100A9 fibrils and understand how cellular factors may influence the aggregation process and the role this may play on influencing the deposition of other amyloidogenic proteins.  In the second part of the presentation, I will discuss the potential of proton detected MAS-DNP methods that we have been developing for the analysis of conformational properties of patient derived amyloid deposits.

100. Friday, November 26, 2021, Danila Barski, Johannes Gutenberg University Mainz, "Parahydrogen-based Nuclear Spin Chemistry at Near-Zero Magnetic Fields" In this talk, I will describe our recent results utilizing hyperpolarization method SABRE-relay pioneered by Prof. Simon Duckett. I will show how SABRE-relay-enhanced signals from small molecules methanol and ethanol (including ones extracted from real-world samples) can be detected by optically pumped magnetometers. Combination of affordable and easy-to-scale hyperpolarization technology with non-inductive signal detection shows promise in applications beyond research laboratories.

101. Friday, November 26, 2021, Mattias Eden from Stockholm University, " Solid-State NMR Studies of Phosphoserine-Doped Calcium Phosphate Cements with Bone-Adhesive Properties" When α-tricalcium phosphate (α-TCP) is mixed with water and injected into a bone/tooth void, a calcium phosphate cement (CPC) forms that consists of disordered calcium hydroxyapatite (HA). We recently reported a remarkable increase in the bone-adhesive properties of such cements when O-phospho-L-Serine (Pser) is incorporated [1]. Pser is an ester of serine and phosphoric acid, and is abundant in many non-collagenous proteins that are believed to initiate and regulate bone growth. The organization of CPCs prepared from either α-TCP or tetracalcium phosphate (TTCP) with progressively increased Pser contents (up to ~80 wt%) were characterized by magic-angle-spinning (MAS) NMR experiments. The various crystalline and amorphous constituents of the complex CPC matrices were identified and quantified by 31P, 13C, and 1H MAS NMR, encompassing experiments on cements incorporating 13C-enriched Pser. For growing Pser content, the cement reactions alter markedly: only minute amounts of HA form when the Pser content of the CPC exceeds ~5 wt%, whereas the inorganic phosphate portions involve amorphous calcium phosphate (ACP) and unreacted α-TCP or TTCP. Except for a minor formation of the Ca salt of phosphoserine, the Pser molecules form an amorphous organic network which integrates intimately with ACP [2]: we demonstrate that the amount of the disordered ACP-Pser component may be used for predicting the bone adhesive properties of the cement. An array of advanced MAS NMR experimentation was utilized to probe each organic and inorganic CPC component, as well as the chemical/structural nature of their interface. We will present results from various heteronuclear and homonuclear correlation experiments involving 1H, 13C, and 31P for probing the ACP-Pser interactions. To assist the NMR spectra analysis, we also investigated model systems of ACP and nanocrystalline HA grown in the presence of Pser. We will also discuss a new NMR crystallography method that yields rapid assessments of internuclear distances of a given model structure. The technique offers significant advantages compared to existing (similar) NMR protocols, which are more effort-demanding in terms of experimental as well as computational time.

References:

[1] M. Pujari-Palmer, H. Guo, D. Wenner, H. Autefage, C. D. Spicer, M. M. Stevens, O. Omar, P. Thomsen, M. Edén, G. Insley, P. Procter, H. Engqvist, Materials 11, 2492 (2018).

[2] R. Mathew M. Pujari-Palmer, H. Guo, Y. Yu, B. Stevensson, H. Engqvist, M. Edén, J. Phys. Chem. C, 124, 21512 (2020)

102. Friday, November 12, 2021 Guinevere Mathies, University of Konstanz, "Efficient pulsed dynamic nuclear polarization" Pulsed dynamic nuclear polarization (DNP) is a promising new approach to enhance the sensitivity of high-resolution magic-angle spinning (MAS) NMR. With pulsed DNP, enhancement factors are expected to be independent of the magnetic field and sample heating by absorption of mm-waves will be strongly reduced. The development of DNP pulse sequences is in its infancy, but we have recently added two new sequences to the small repertoire. Both these sequences, XiX and TPPM DNP, are named after analogous heteronuclear decoupling sequences. In this seminar, I will discuss the results of pulsed DNP experiments and provide the theoretical description. I will point out opportunities and challenges of the approach and will try to answer the question "What makes a DNP pulse sequence efficient?".

103. Friday, November 5 2021, Kirill Sheberstov, ENS, Paris, "Reference deconvolution and total lineshape analysis of 2D NMR spectra" The spin–spin J‐coupling constants provide information on molecular structure, stereochemistry, and conformation, but determination of their values can be complicated. This is especially true for spin systems containing multiple coupled spins and also for mixtures of molecules. Strongly coupled systems require total lineshape analysis of the NMR spectra, as the distances between lines do not correspond to the values of J-couplings. We are going to introduce classical 1D approaches of reference deconvolution and total lineshape analysis and then present how they can be adapted for 2D NMR. Examples will be given where usage of 2D instead of 1D spectra is preferable.

First, we are going to explore how B0 field inhomogeneity affects highly resolved 2D correlation NMR spectra and how the reference deconvolution method can be implemented to improve the lineshape. Second, we will present the possibility to use the total lineshape analysis for the multiplets extracted from 2D spectra. This possibility will be illustrated for an androstene molecule containing 20 coupled 1H spins. All the signals coming from these 20 spins fall in the spectral region with a bandwidth of ca. 1 ppm and the total lineshape analysis of 1D 1H NMR spectrum is therefore challenging. The problem of signal overlap is solved using 2D spectroscopy. Here we used a “pure shift method” where a broadband homonuclear decoupling was performed along the F1-axis, and the multiplet structure was conserved along the F2-axis. The extracted 1D crossections with multiplets from this 2D spectrum allowed us to find all the J-couplings in the system using the total lineshape analysis.

104. Friday, October 29, 2021, Steven Brown, Univ. of Warwick, UK, "Magic-Angle Spinning Solid-State NMR of Organic Molecules" Applications of 1H-based fast magic-angle spinning two-dimensional solid-state NMR experiments to organic molecules at natural isotopic abundance, notably pharmaceuticals, are presented. Specifically, the homonuclear 1H double-quantum (DQ) MAS NMR experiment probes proton-proton proximities, typically up to ~3.5 A. Heteronuclear 1H-13C MAS NMR spectra identify one-bond CH correlations, while 14N-1H spectra for the spin I = 1 14N nucleus are invaluable for probing hydrogen-bonding interactions. Results are presented for "rigid" crystalline solids as well as a highly mobile system, CAGE-Oct, where a low MAS frequency is sufficient to observe temperature dependent changes in the 1H chemical shift for a hydrogen-bonded resonance as well as to measure order parameters from motionally averaged 13C-1H and 1H-1H dipolar couplings. 

105. Friday, October 22, 2021, Ilya Shenderovich, University of Regensburg, "Study of Noncovalent interactions in condensed matter using a combination of NMR, DFT, and the Adduct under Field approach" Modern theoretical methods make it possible to significantly facilitate the interpretation of experimentally obtained spectral data from the point of view of the energy and geometric parameters of molecular aggregates. In the gas phase, this can often be done with good accuracy and precision. Problems appear in condensed matter. In all cases, the molecular system under question needs to be large enough to explicitly include the strongest noncovalent interactions that are relevant for the property under study, and at the same time be small enough to use a reliable level of approximation. In addition, it should be possible to implicitly take into account the effect of a matrix or a solvent. The latter effect is the most difficult to consider. In this talk, I will give a few examples to demonstrate the influence of the environment: (i) Solvent effect on the geometry of hydrogen bonded complexes using the example of experimental 1 H and 15 N NMR spectra in CDClF 2 /CDF 3 at 120-130 K. (ii) Matrix effect on NMR chemical shifts using the example of experimental 31 P NMR spectra of polycrystalline samples. (iii) Modeling of these effects using the Adduct under Field approach. Then I will show how the ability to gauge the magnitude of these effects can be put into practice: (iv) The absolute chemical shielding of 31 P and its margin of errors for various DFT functionals and basis sets. (v) Verification of the structure of organometallic transition metal complexes in solution. (vi) Using the Adduct under Field approach to facilitate the analysis of spectra

106. Friday, October 15, 2021, Patrick Berthault, CEA Saclay, France, "Overview - necessarily incomplete - of 129Xe NMR-based biosensors" Xenon is a powerful NMR probe for several reasons. Despite a slightly hydrophobic character, this non-toxic species is soluble in most biological media, and its physical properties make that it can be easily handled. But the most interesting feature lies in the great deformability of its electronic cloud, which leads to a large modularity of its NMR properties according to its close environment. 129Xe nuclear spin can be quickly hyperpolarized via optical pumping. Thus, 129Xe NMR combines a high detection sensitivity and a high selectivity due to this spectral discrimination ability. In particular, in the field of life science, xenon can be vectorized toward biological targets of interest by using functionalized molecular hosts, which enables their detection at nanomolar concentrations. In association with a new generation of detection methods, this gives rise to a powerful molecular imaging approach, whereby xenon can be delivered and detected systematically several times after the introduction of a functionalized host system. My talk will give an overview of some facets of this approach both for in vitro and in vivo studies.

107. Friday October 8, 2021 Jean-Nicolas Dumez, Univ. of Nantes, France, "Ultrafast 2D NMR for the analysis of out-of-equilibrium mixtures"  NMR spectroscopy is a powerful tool for the analysis of mixtures, and the complexity of mixtures often calls for the use of multidimensional experiments. For samples that evolve in time, the duration of these experiments can be a limitation. Ultrafast 2D NMR based on spatial encoding is the fastest approach to collect 2D NMR data. Over the past few years, we have developed an array of ultrafast 2D NMR methods for the analysis of out-of-equilibrium mixtures. I will present several examples of 2D correlation and diffusion-ordered spectroscopy (DOSY) methods. These involved the development of schemes for the spatial encoding of multiple-quantum coherences, and an analysis of diffusion and flow effects during spatial parallelisation.  The methods were used for the monitoring of chemical reactions, and the analysis of hyperpolarised substrates. 

108. Friday October 1, 2021, Sheetal Jain, IISc, Bangalore, India, "Probing structural diversity and evolution of acidic sites in P-modified all silica zeolites using magnetic resonance methods"A precise characterization of the active sites in heterogenous catalysts and the interactions of these sites with the support, reactants and products is crucial for designing catalysts with optimal properties. In this study, the P-sites in an all-silica self-pillared pentasil (P-SPP) with a low P-loading (Si/P = 27) were identified by solid-state 31 P NMR. The P-O-Si and P-O-P linkages in the P-sites were confirmed by 29 Si-filtered 31 P detection and 31 P- 31 P correlation experiments using dynamic nuclear polarization for sensitivity enhancement. 31 P and 1 H MAS-NMR spectra as a function of water content in two types of zeosil frameworks (SPP and dealuminated zeolite BEA) were used to gain insight into the hydrolytic stability of the P-sites. It will be discussed that the variation in the P-site stability can be ascribed to the difference in the distribution and water accessibility of the P-sites in the two frameworks.

109. Friday September 24, Daniel Topgaard, Lund University, Sweden, "Model-free approach to the interpretation of restricted and anisotropic self-diffusion in magnetic resonance of biological tissues" Magnetic resonance imaging conveys information about micrometer-scale structures in biological tissues via their effects on water self-diffusion, which may be investigated in detail using motion-encoding field gradients with tensor-valued spectral content. Data analysis is conventionally performed by invoking simple geometrical models, such as distributions of cylinders or spheres, that often give satisfactory fits to the acquired data without corresponding to the underlying structures—notably for tissues with multiple distinct water populations separated by convoluted biomembranes. Building on the Lipari-Szabo "model-free approach" and the recent "dynamics detectors" for interpreting frequency-dependent magnetic resonance relaxation of macromolecules, we propose a formalism to jointly analyze frequency-dependent (“restricted”) and anisotropic self-diffusion in terms of model-independent metrics reporting on relevant microstructural properties without tempting the user to overinterpretation. Preparing for combined studies of restriction and anisotropy in vivo, the method is here demonstrated on liquid crystal, yeast cells, ex vivo rat brain, and excised tumor. 

110. Friday September 17, 2021, Ann-Christin Poeppler, Univ. of Wuerzburg, Germany, "Taking up the chase with NMR spectroscopy - from structural insights into solid drug-polymer formulations to their fate in biorelevant media" Despite the large number of publications related to drug delivery, recent (critical) comments identified a gap between academic research and benefit to the patient requiring multidisciplinary joint efforts. Through solid-state NMR spectroscopy complemented by quantum chemical calculations, insight into the conformation of guests within copolymer micelles and key intermolecular interactions can be gained. For curcumin loaded poly(2-oxazoline) based polymer micelles, this information enables to hypothesize a loading mechanism, explain pharmaceutically relevant dissolution rates, and derive ideas for improved polymeric carrier materials. For large guest molecules, heteronuclear correlations such as 14N-1H HMQC experiments can disperse the signals over a sufficiently broad shift range and yield valuable information on intermolecular interactions as well as the symmetry of the nitrogen environments. Following a drug molecule through the body, drug absorption occurs from biorelevant media. Working in fed state simulating intestinal fluids, NMR spectroscopy complemented by cryo-TEM enables fascinating insights into the rich concentration and composition dependent colloidal assembly of polymer-drug formulations in the presence of bile.

111. Friday September 10, 2021, Leo van Wuellen, Univ. of Augsburg, Germany,  "Modern Solid State NMR strategies in Materials Science - or NMR is wunderbar" For a controlled fine-tuning of materials’ key properties, a detailed knowledge of the structural and dynamic features of the materials poses a prerequisite. To this end we develop and utilize modern Solid State NMR strategies which not only provide information about the structural motifs on short and intermediate length scales but also offer a handle to study the microscopic dynamics within these materials. Especially for materials, which are characterized by a lack of translatorial periodicity, considerable disorder or high dynamics, these approaches offer unprecedented insight into the structure and dynamics. We will show how these novel approaches may be successfully employed to study the structure of amorphous materials at ambient conditions and to obtain information about its evolution with temperature. Further, new solid state electrolytes for next generation’s Li batteries will be presented with the focus here being on the local Li coordination and the mechanism of ion transport. Along the way, a variety of novel NMR (hardware) solutions will be presented, even widening the range of possible applications of NMR spectroscopy in materials science. Examples include MAS NMR at high spinning speeds and ultra high temperature and approaches for high resolution dipolar based NMR spectroscopy without fast MAS.

112. Friday August 6, 2021, Vinayak Rane, BARC, Mumbai, India, "Designing radical-chromophore (R-C) spin probes with a large electron spin hyperpolarization (ESH)", Generation of a large hyperpolarization in electron spin energy levels of stable radicals is highly desirable due to its potential applications in areas such as photo induced dynamic nuclear polarization (DNP). The radical triplet pair mechanism (RTPM) provides a feasible route to hyperpolarize stable radicals via optical excitation of suitable chromophores. In this talk, I will present our rationale behind designing covalently linked R-C dyads which have a potential for generating a large ESH at room temperature (RT). Then I will demonstrate how our work contributed to improved understanding of the optical ESH mechanisms, which has now resulted in an electron spin polarization (ESP) of about 500 times the thermal equilibrium polarization at RT. Given that the equilibrium ESP at RT is ~1000 times smaller than the extreme polarization value of 1 (where exclusively a single energy level is populated), an enhancement of 550 times in the ESP clearly indicates that the ultimate polarization value is being approached for the electron spins at RT. 

113. Friday July 30, 2021, Björn Corzilius, Univ. of Rostock, Germany, "Heteronuclear cross relaxation under MAS DNP for localized enhancement in biomolecules", With increasing complexity of biomolecular assembly, sensitivity as well as specificity play a major role in NMR-based structural biology. Dynamic nuclear polarization (DNP) has shown tremendous potential to increase sensitivity in numerous applications. Even though in conventional DNP experiments uniform signal enhancements are typically obtained, DNP itself can act as a source of specificity as well. In this presentation, a method allowing to introduce a large degree of specificity to DNP-enhanced MAS NMR spectra will be presented. The method introduces methyl groups as localized polarization transfer pathways between 1H and 13C. The introduction of specifically 13C-labeled methyl groups via different biomolecular methods enables the discrete placement of antennas for hyperpolarization within the carbon network. Based on heteronuclear cross-relaxation, SCREAM-DNP (specific cross-relaxation enhancement by active motions under DNP) can thus probe the local environment around these highly dynamic functions. This is especially interesting in the context of biomolecular complexes and specific contacts between binding partners. Examples and applications on proteins, RNA, and ribonucleoproteins (RNPs) will be presented and future implications discussed.

114. Friday July 23, 2021, Juan Miguel Lopez del Amo, CIC energiGUNE, Spain, "Solid-state NMR characterization of battery materials" In this presentation, some of the recent solid state NMR results obtained in our laboratory in the research of new and advanced battery materials will be briefly reviewed. Examples will be shown that include sodium and lithium-based cathodes, anodes and solid electrolytes (polymeric, ceramic and composites). It will be shown how these solid-state NMR results were used to obtain crucial information about the structure and the dynamics in these materials, as well as in the identification of degradation products and the structural and dynamic changes taking place during electrochemical cycling. We will also show that the observations made by solid state NMR were successfully used to understand and predict the performance of many of these materials. In particular, the covered topics will include:

-  Cathodes: We will illustrate how paramagnetic solid-state NMR can be successfully implemented using a combination of fast MAS (>50 kHz) and low field magnets (200 MHz), allowing the accurate analysis of even very strong paramagnetic cathode materials. In particular, the topics presented will illustrate how this technique was applied in our laboratory to the characterization of: ion dynamics 1 , dopants 2,3 , structural defects 4 , cathode decomposition 5 and the presence of irreversible phases 6 .

-  Anodes: The solid-state NMR analysis of Li containing alloys will be briefly described. It will be illustrated how the Knight shifts governing the NMR spectra of metals can be used in the structural and dynamic analysis of these compounds and how solid-state NMR can accurately detect the presence of Li dendrites 7 .

-  Solid electrolytes: The NMR research carried out in several ultrafast ceramic ionic conductors will be briefly presented. 8,9 In these cases, solid state NMR was used in the structural characterization of the solid materials and to understand and follow the mechanism of material degradation. These results were used to design processes that significantly improved the Li + conductivity. Solid state NMR was also used to detect the Li + exchange process between the ceramic and polymer phases in a solid composite material 10 .

References:

1 E Gonzalo, M Zarrabeitia, N Drewett, J M López del Amo, T Rojo Energy Storage Materials 2021, 34, 682-707

2 L Yang, J M López del Amo, Z Shadike, S Bak, F Bonilla, M Galceran, P Kumar Nayak, J Buchheim, X Yang, T Rojo, P Adelhelm Advanced Functional Materials 2020, 30 (42), 2003364

3 L Yang, L‐Y Kuo, J M López del Amo, P Kumar Nayak, K A Mazzio, S Maletti, D Mikhailova, L Giebeler, P Kaghazchi, T Rojo, P Adelhelm Advanced Functional Materials 2021, https://doi.org/10.1002/adfm.202102939

     4 J Sevillano, D Carlier, A Saracibar, J M Lopez del Amo and M Casas Inorg. Chem. 2019, 58, 13, 8347–8356.

5 M Huon Han, E Gonzalo, N Sharma, J M López del Amo, M Armand, M Avdeev, J Saiz Garitaonandia, T Rojo Chemistry of Materials 2016, 28, 106.

6 N Ortiz-Vitoriano, I Monterrubio, L Garcia-Quintana, J M Lopez del Amo, F Chen, T Rojo, P C Howlett, M Forsyth, C Pozo-Gonzalo ACS Energy Letters 2020, 5, 3, 903–909

7 F Aguesse, W Manalastas, L Buannic, J M Lopez del Amo, G Singh, A Llordés, J Kilner ACS Applied Materials & Interfaces 2017, 9(4), 3808-3816.

8 P López-Aranguren, M Reynaud, P Głuchowski, A Bustinza, M Galceran, J M López del Amo, M Armand, M Casas-Cabanas ACS Energy Letters 2021, 6, 2, 445–450

9 L Buannic, B Orayech, J M Lopez Del Amo, J Carrasco, N A Katcho, F Aguesse, W Manalastas, W Zhang, J Kilner, A Llordés Chemistry of Materials 2017, 29(4), 1769-1778.

10 J Zagórski, J M López del Amo, M J Cordill, F Aguesse, L Buannic, A Llordés ACS Applied Energy Materials 2019, 2(3), 1734-1746

115. Friday July 16, 2021, Tairan Yuwen, Peking University, China, "1H CEST experiment for biomolecular dynamics study", CEST experiment has recently become popular for studying biomolecular dynamics in ~ms timescale, which are closely related to biomolecular functions in many cases.[1] Spin probes such as 15N and 13C are commonly used for biomolecular CEST study, while abundant 1H probes are much less utilized due to potential artifacts caused by 1H-1H cross relaxation effects. In order to overcome 1H-1H cross relaxation effects, spin-state-selective 1H CEST strategy has been developed which allows obtaining clean 1H CEST profiles that only reflect chemical exchange but without any 1H-1H cross relaxation effects.[2] Besides, based on product operator analysis, spin-state-selective 1H CEST scheme can be further optimized with even simpler setup and higher intrinsic sensitivity.[3] It is also possible to combine 1H CEST with other excitation schemes such as DANTE-CEST or COS-CEST, which offers significant time saving without losing information content in CEST profiles.[4]

[1] P. Vallurupalli, A. Sekhar, T. Yuwen, L. E. Kay, Probing conformational dynamics in biomolecules via chemical exchange saturation transfer: a primer. J. Biomol. NMR 67 (2017) 243-271.

[2] T. Yuwen, A. Sekhar, L. E. Kay, Separating dipolar and chemical exchange magnetization transfer processes in 1H-CEST. Angew. Chem. Int. Ed. 56 (2017) 6122-6125.

[3] T. Yuwen, L. E. Kay, A new class of CEST experiment based on selecting different magnetization components at the start and end of the CEST relaxation element: an application to 1H CEST. J. Biomol. NMR 70 (2018) 93-102.

[4] T. Yuwen, G. Bouvignies, L. E. Kay, Exploring methods to expedite the recording of CEST datasets using selective pulse excitation. J Magn. Reson. 292 (2018) 1-7.

116. Friday July 9, 2021, Michael Hope, EPFL, Switzerland, "Solid-State NMR of Hybrid Perovskites", Hybrid perovskites have shown great promise for photovoltaic applications, but improving stability and performance requires structural and dynamic information that is challenging to acquire with conventional techniques. Here I will present three examples of how solid-state NMR can be used to study hybrid perovskite systems. Firstly, I will show how 19F and 13C NMR crystallography can be used to solve the supramolecular structure of the mixed organic spacer layer in a layered hybrid perovskite. Secondly, I will use 1H, 13C and 207Pb NMR to reveal the mechanism whereby a crown ether passivates defects on perovskite surfaces. Finally, I will use 1H relaxometry and quadrupolar 14N NMR to show how the crystallographically-silent phase transitions in FAPbBr3 relate to the cation dynamics and the effect of caesiation.

117. Friday July 2, 2021, Mathias Nilsson, Univ. of Manchester, UK, "Mixture Analysis by NMR" Nuclear magnetic resonance (NMR) spectroscopy is the single tool most widely used by chemists for determining the molecular structures of unknown compounds. It is a wonderfully versatile and sensitive tool, but it has one major drawback: it often struggles to analyze mixtures. Many of the most challenging problems are presented to us as mixtures, so a great deal of effort goes into separating the individual components so that they can be identified and characterized. Fortunately, powerful NMR methods for the analysis of intact mixtures are making its way into the standard set of experiments available to the spectroscopists. One of the most potent is diffusion-ordered spectroscopy (DOSY) in which the signals from different components can be separated by their different diffusion properties. The information available from the basic DOSY experiment can be enhanced by advanced, e.g. multivariate, processing and extended by incorporating information from other sources such as relaxation. NMR spectra of mixtures are often very crowded due to the abundance of signals with multiplet structure caused by scalar coupling. In 1H NMR, multiplets caused by homonuclear scalar coupling are often many times the width of a single line, making it very difficult to distinguish individual chemical shifts in crowded spectra. An efficient method to collapse the multiplet structure has long been sought, but only recently have experimental methods for such homonuclear broadband decoupling become practical. These “pure shift” or “chemical-shift resolved” methods give resolution improvements approaching an order of magnitude, far in excess of any gains realistically to be expected from increases in static magnetic field.

118. Friday, June 25 2021, Martin Wilkening, TU-Graz, Austria, "Probing local and long-range ion dynamics in ceramic electrolytes by NMR", NMR provides many different tools to analyze ionic jump processes in crystalline and amorphous solids taking place on different length scales. In particular, time-domain 1H(2H), 6,7Li, 19F, 23Na NMR helps throw light on the origins of rapid self-diffusion in materials being relevant for energy storage. The talk will give a short overview how simple NMR spin-lattice relaxation measurements, carried out in both the rotating and laboratory frame of reference, can be used to describe local Li hopping processes as well as long-range ion transport in ceramics for energy storage, thereby identifying the origins of fast ion transport in such materials. It is well accepted that in materials with strong site preferences, such as LiAlO2, the Li+ ions are subjected to extremely slow exchange processes. The loss of this site preference, as it is well known for glasses, may, however, lead to rapid (bulk) cation diffusion. Examples that benefit from this effect include cation-mixed, high-entropy fluorides ((Ba,Ca)F2) and LiTi2(PS4)3. In general, in non-equilibrium phases site disorder, polyhedra distortions, strain and the various types of local defects will affect both the migration activation energy and the corresponding Arrhenius pre-factor. Whereas in (Me,Ca)F2 (Me = Ba, Pb) cation mixing influences F anion dynamics, in Li6PS5X (X = Br, Cl, I) the potential landscape can be manipulated by both anion and cation site disorder. On the other hand, in the mixed conductor Li4+xTi5O12, effective cation-cation repulsions immediately lead to a boost in Li+ diffusivity at the early stages of chemical lithiation. Finally, rapid diffusion is also expected for materials that are able to guide the ions along (macroscopic) pathways with confined dimensions, as it is the case in layer-structured fluorides such as RbSn2F5 or BaSnF4 with their buried interfaces. As an example, the 19F NMR spin-lattice relaxation response can only be understood in terms of Richards’ spectral density developed for 2D ion transport.

119. Friday June 18, 2021, Philipp Neudecker, Forschungszentrum Jülich, Germany, " Integrated NMR, Fluorescence, and Molecular Dynamics Benchmark Study of Protein Dynamics and Hydrodynamics"  Understanding the function of a protein requires not only knowledge of its tertiary structure but also an understanding of its conformational dynamics. Nuclear magnetic resonance (NMR) spectroscopy, polarization-resolved fluorescence spectroscopy and molecular dynamics (MD) simulations are powerful methods to provide detailed insight into protein dynamics on multiple timescales by monitoring global rotational diffusion and local flexibility (order parameters) that are sensitive to inter- and intramolecular interactions, respectively. We present an integrated approach where data from these techniques are analyzed and interpreted within a joint theoretical description of depolarization and diffusion, demonstrating their conceptual similarities.

This integrated approach is then applied to the autophagy-related protein GABARAP in its cytosolic form, elucidating its dynamics on the pico- to nanosecond timescale and its rotational and translational diffusion for protein concentrations spanning nine orders of magnitude. We compare the dynamics of GABARAP as monitored by 15N spin relaxation of the backbone amide groups, fluorescence anisotropy decays and fluorescence correlation spectroscopy of side chains labeled with BODIPY FL, and molecular movies of the protein from MD simulations. The recovered parameters agree very well between the distinct techniques if the different measurement conditions (probe localization, sample concentration) are taken into account. Order parameters lower than the average value identify residues 27/28 at the interface between the two sub-domains of GABARAP as a potential hinge for functionally relevant intra-domain motions. In conclusion, the integrated concept of cross-fertilizing techniques is fundamental to obtaining a comprehensive quantitative picture of multi-scale protein dynamics and solvation. The possibility to employ these validated techniques under cellular conditions and combine them with fluorescence imaging opens up the perspective of studying the functional dynamics of proteins in live cells.

120. Friday, June 11, 2021 Danielle Laurencin, CNRS-Montpellier, France " Fatty acids & more : from 17O labeling to high resolution NMR analyses"  Fatty acids are a key family of biomolecules, which find many applications both in life sciences and (nano)materials chemistry. Yet, in may cases, the structural and functional roles of these molecules still need to be elucidated. In this presentation, our recent work on high-resolution oxygen-17 solid state NMR of fatty-acid based (nano)materials will be presented. First, details of the 17O-enrichment schemes we have been developing using mechanochemistry will be exposed. Then, we will show how thanks to this isotopic labeling, high resolution 17O NMR analyses now become accessible, yielding yet-unavailable structural information. This will be illustrated in the case of a crystalline metal soap (Zn-oleate), and oleate-grafted ZnO nanoparticles.

121. Friday, June 4, 2021 Michaël Deschamps, CNRS-Orléans , France, "1D MRI, High Resolution 2D and Spin Counting NMR for Batteries" In batteries and supercapacitors, the variation of concentration profiles can be probed with 1D magnetic resonance imaging of spin bearing atoms, while limiting the signal losses stemming from short relaxation times. In such cases, one can observe interesting effects pertaining to the electrode porosity in batteries or interactions between carbon pores and anions in supercapacitors. Moreover, in favourable systems such as lithium titanates, it has been shown that surface fluorination with XeF2 greatly improves the electrochemical properties. In such systems, high resolution MAS-NMR can help quantify the amount of fluorine in the structure, and the 19F chemical shift analysis yields information on the fluorine environment. Moreover, spin counting strategies based on HMQC experiments can provide the number of fluorine atoms which are coordinated to lithium ions and help understand what kind of structures are created locally upon fluorination.

122. Friday, May 28, 2021, Frederic Mentink-Vigier, NHMFL, Florida, USA, " How well do we understand Cross-Effect MAS-DNP nine years later? " Magic Angle Spinning – Dynamic Nuclear Polarization (MAS-DNP) is a powerful method to obtain atomic scale information when the isotope of interest is in low concentration. Often MAS-DNP is carried out by doping samples with biradicals and irradiating it with an appropriate microwave frequency at low temperature. In routine application this leads to the hyperpolarization of protons via the Cross-Effect mechanism, one of the most efficient continuous wave DNP mechanism. Since 2012, numerical methods have been developed to explain how Cross-Effect works under MAS conditions. First, I will explain this DNP mechanism when accounting for the time dependence induced by the sample’s rotation. The step-by-step analysis enables disentangling the effect of magnetic and experimental parameters and allows the development of more sophisticated models. The numerical simulations revealed the crucial role of the electron-electron coupling, but also the algebraic distance between the g-tensors. In the second part, the applications of the numerical methods, in combination with DFT, MD and high field EPR to understand quantitatively the performance of biradicals such as AMUPol, bcTol and bcTol-M. The performance of these biradicals on a 600 MHz / 395 GHz / 14.1 T MAS-DNP setup is completely quantified and rationalized, the numerical simulations enabling the prediction of both the enhancements but also the nuclear polarization build-up times. Surprisingly the method approach can be further extended to recently introduced biradicals, notably AsymPolPOK where it also accurately predicts all the experimental results on model compounds. This body of work shows that, nine years later, we finally are reaching a point where Cross-Effect and MAS-DNP is understandable and predictable paving the way to more efficient biradical design.

123. Friday May 21, 2021 Pinelopi Moutzouri, EPFL, Switzerland, "Novel methods for achieving high-resolution in 1H NMR of solids" Resolution is still the key limit to wide-spread use of 1H in solid-state NMR, and the possibility to acquire 1H spectra with higher resolution would significantly strengthen its role in the field of structural characterization. However, resolution in proton solid state MAS NMR is usually limited by the intrinsically imperfect nature of coherent averaging induced either by MAS or multiple pulse sequence methods. Here, we suggest two novel approaches to line narrowing in 1H MAS NMR.

First, we show how narrower 1H spectra can be obtained from a simple 2D scheme that generates correlations exclusively in which the coupling partners have all flipped their spin states, i.e., correlations between so-called remote transitions. Specifically, we show that the residual broadening under MAS in a multi-spin system with different chemical shifts is due to a combination of second order shifts and splittings, and that these splittings will be removed in a 45° projection of an anti-z-COSY spectrum. Results obtained with the anti-z-COSY sequence at 100 kHz show an improvement in resolution of up to a factor of two compared to conventional spectra acquired at the same spinning rate.

Secondly, we suggest that instead of optimizing and perfecting a coherent averaging scheme, we could approach the problem by parametrically mapping the error terms due to imperfect averaging in a k-space representation, in such a way that they can be removed in a multi-dimensional correlation leaving only the desired pure isotropic signal. Here we illustrate the approach by determining pure isotropic 1H spectra from a series of MAS spectra acquired at different spinning rates. For six different organic solids we observe on average a 5-fold increase in resolution, and up to a factor of 12, as compared with spectra acquired at 100 kHz MAS.

The approaches presented here are directly applicable to a range of solids and we anticipate that they can be widely applied in the future.

124. Friday May 14 2021, Andrew Pell, from ENS-Lyon, France, " Paramagnetic solid-state NMR: spectroscopy and interpretation"  Paramagnetic systems are of particular interest to materials chemistry, since they have many unique properties due to their unpaired electrons. The characterization of the structural environments of the corresponding ‘paramagnetic centres’ is key to understanding the functions and limitations of these materials. Solid-state paramagnetic nuclear magnetic resonance (pNMR) is a key method for understanding this atomic-level structure, but the unpaired electrons result in broad, low intensity signals that are very difficult to excite, resolve, and interpret using standard NMR methods. Here, we discuss the problems of exciting and resolving broadband NMR spectra of paramagnetic materials, and understanding the nature of the paramagnetic shift. Firstly, we highlight the known fact that the hyperfine interaction results in a shift of the NMR resonance and not a splitting, due to fast electronic relaxation, but go on to show that a shift is only predicted if we employ a model for electronic relaxation incorporating proper thermalization and detailed balance. We show that in the Redfield limit, this can only be done by employing the recently-introduced Lindbladian formalism. Secondly, we describe how short high-powered adiabatic pulses (SHAPs) produce more broadband solid-state NMR of paramagnetically broadened spectra, and how these pulses are incorporated into more complex experiments for resolving overlapping resonances, such as the adiabatic magic-angle turning (aMAT) sequence. Finally, we apply these ideas to the deuterated oxyhydride material BaTiO3-xHy to extract the shift and quadrupolar interaction parameters, and obtain information about the local structure and dynamics of the hydride ions.

125. Friday, May 7, 2021, Ruth Gschwind, Univ. Regensburg, Germany, "NMR in Catalysis and Photocatalysis - Pushing the Frontiers" NMR spectroscopy is a very valuable and versatile tool to get insights into structures of intermediates or reaction mechanisms in the broad field of chemistry and catalysis. However, the classical weak points of NMR such as low time resolution and sensitivity restrict its application and therefore experimental studies are scarce in many fields of catalysis. In this talk I will present tech­niques and methods to extend the application of NMR in catalysis and photocatalysis and explain their impact on examples. Our LED based NMR illumination device, the triple combination of illumination/NMR/UV and an NMR access to intermediates below the detection limit will be introduced. These methods allow for new insights into one- versus two-electron processes usually inacces­sible to UV/Vis, the inclusion of radical species into NMR reaction profiles, the structure elucida­tion of thermally labile photoswitches, the sequencing of tiny intermediates and even the assignment of mechanistic effects to photoreactions. Last, the extension of the NMR time scale to ms is demonstrated using relaxation dispersion methods. In a catalyst substrate complex taken from Brønsted acid catalysis even the switching of a single hydrogen bond can be detected experimentally.

126. Friday, April 30, 2021, Stefan Gloeggler, MPG, Germany, "Giving it the right spin - advancements using nuclear spin singlet states" Singlet states are NMR silent states, yet have attracted a lot of attention in recent years. The most prominent example is para-hydrogen, a singlet spin isomer of hydrogen gas that can be used to
     enhance magnetic resonance signals by over four orders of magnitude. Additionally, such singlet states can be found in a variety of other molecules that contain two spin 1/2-nuclei coupling to each other via electron-mediated couplings. One special feature of singlet states is that their lifetime can exceed multiple times the typically investigated longitudinal relaxation. As a result, singlet states offer new opportunities to store hyperpolarization over extended periods of time or probe dynamic processes. I this presentation, I will show the most recent research from my group with respect to singlet states and signal-enhanced magnetic resonance using para-hydrogen pursuing
     the overarching goal to study biological systems.

127. Friday April 23, 2021, Michael Jaroszewicz, Weizmann Inst. of Science, Israel "Indirect Detection of Solid-State NMR Spectra by PROgressive Saturation of the Proton Resonance (PROSPR) via Zeeman- and Dipolar-Ordered States" Chemical Exchange Saturation Transfer (CEST) is a routinely used technique for enhancing the solution NMR spectra of lowly populated spin pools (e.g., dissolved solutes at low concentration), which are often comprised of NMR-insensitive nuclei by encoding and detecting the latter’s NMR response in a more populated and receptive spin pool of much easier detection; e.g., H2O protons. Based on this principle, our group has developed a family of sensitivity-enhanced solution-state NMR experiments that use a combination of coherent radio-frequency-driven J-based polarization transfers and solvent chemical exchanges in order to encode and read-out the NMR spectra of dilute heteronuclei on the 1H resonance of water. Herein, we introduce a methodology for enhancing the signal-to-noise ratio (SNR) of solid-state NMR spectra that is inspired by this principle, which identifies and seeks to exploit the large and underused spin polarization residing in the protons of the sample as a water-like abundant spin pool. We discuss how a typical organic solid at natural abundance can be formalized in terms of dilute and abundant spin pools and then demonstrate how dipolar-based polarization transfers can be used to impart the former’s shift and coupling information onto the latter. Using numerical simulations and experimental validations, we show how multi-contact cross-polarization interleaved with periods of proton spin diffusion leads to CEST-like heteronuclear-dependent depletion of abundant 1H Zeeman- and dipolar-order, which can be monitored and discerned using either incremented t1 time-domain encodings or point-by-point frequency-domain selective saturations, respectively. For samples having lengthy relaxation times, frequency-domain PROgressive Saturation of the Proton Resonance (PROSPR) or time-domain Nuclear Enhancement by eXchange Transfers (NEXT) NMR approaches give signal enhancements of one to two orders of magnitude over optimized comparisons. A foray of the broad application of these techniques applied under magic-angle spinning and stationary conditions is provided along with a discussion highlighting their current limitations.

128. Friday April 16, 2021, Muslim Dvoyaskin, Univ. Leipzig, Germany "The High-Gradient NMR and Counterintuitive Observations in Nanoconfined Electrolytes" This presentation focuses on basic aspects of high-gradient NMR as a tool for direct probing of molecular and ionic diffusion in a variety of nanostructured materials designed, e.g., for catalysis and energy storage. For a demonstration of its potential, one selected example of diffusion of ions in carbons used as electrodes in a supercapacitor will be presented. Unexpectedly, it was observed that the presence of a network of mesopores in addition to smaller micropores—building up the so-called hierarchical pore system—may lead to ultra-slow ion diffusion. This diffusion pattern is unique and results from the confinement-induced ion-solvent separation taking place in the organic electrolyte at a nanoscale. However, in combination with electrochemical analysis by impedance spectroscopy, it became possible to determine conditions minimizing its negative impact on the dis(charging) rate of a supercapacitor.

129. Friday April 9, 2021 Fabien Ferrage, ENS-Paris, "Detecting metabolite-protein interactions in complex biological samples by high-resolution relaxometry " The magnetic-field dependence of relaxation rates is exquisitely sensitive to the correlation times of molecular motions. This property can be exploited to investigate the interaction of small molecules with macromolecules and supramolecular assemblies. Here, I will introduce high-resolution relaxometry as a method to investigate weak interactions between metabolites and macromolecules in biological fluids. Similarly to metabolomics by NMR, this approach does not require any invasive procedure or separation step. We can detect interactions between small and large molecules in human blood serum, quantify the size of the complexES, and quantify competitive binding in a complex environment. This work is a promising proof of concept with potential for the investigations of metabolite- (or other small molecules) protein interactions in biological fluids for interactomics or pharmaceutical applications.

130. Friday April 2, 2021  G. Rajalakshmi, TIFR Hyderabad, India, "Zero to Ultra low field NMR of solid samples" Zero- to ultralow-field nuclear magnetic resonance (ZULF NMR) provides an alternative to standard high-field NMR to study spin systems in a regime dominated by inter-/intra-nuclear spin-spin interactions. Some of the early experiments in this regime by Pines and coworkers tried to  employ zero field experiments for studying  dipole coupling in powdered solid samples by overcoming the line broadening caused by the random orientation of the dipoles with respect to the applied magnetic field. In these experiments the nuclear spins were prepared in specific Zeeman states at high field, but allowed to evolve in close to zero field. The high resolution of high field detection is then used to detect the sample magnetisation at the end of the low field evolution. Even with such long, multi-step experiments, the advantages of the low field studies for certain class of problems has kept them in use. For liquid samples, low field experiments that use non-inductive detection techniques are becoming popular in recent years. Atomic magnetometers are the preferred choice to study the magnetisation evolution directly at zero field. The fT sensitivity and few 100 Hz bandwidth of atomic magnetometers make them ideally suited for j-spectroscopy. In solid samples, however, the dominant dipole interactions are in the 1-30 KHz regime. We present a proposal to measure these dipole interactions in zero-field using an atomic magnetometer that has pT sensitivity but a bandwidth of about 30 KHz. Our attempts to implement such a scheme will be discussed in this talk.

131. Friday, March 26, 2021  Christina Thiele, TU Darmstadt, Germany, "Recent advances in thermoresponsive alignment media for the residual dipolar coupling approach in organic structure determination" Anisotropic NMR parameters become increasingly important in organic structure determination. For their measurement suitable alignment media are necessary. The use of lyotropic liquid crystalline helically chiral polymers is intriguing in that respect as they additionally allow for enantiodiscrimination. We have recently synthesized several homopolypeptides, which form lyotropic liquid crystals, are suitable for the measurement of anisotropic NMR observables and furthermore induce different orientations at different temperatures. They are thus considered thermoresponsive. The intriguing properties of these new media and their potential use in structure elucidation will be discussed in this presentation.

132. Friday , March 19, 2021  Benno Meier, KIT, Germany, "Towards bullet-DNP around the clock" Dissolution-Dynamic Nuclear Polarization (D-DNP) can offer tremendous sensitivity gains for magnetic resonance, with signal enhancements of 10,000 or more. When the permissibile concentration of analyte is limited by external factors, as is often the case in MRI, these signal enhancements readily translate into otherwise impossible applications. However, dissolution-DNP has so far not become a tool that is used routinely for signal enhancement in NMR spectroscopy. This is because, with the exception of rapid-melt DNP, the price for the large signal enhancement is a substantial reduction in concentration and duty cycle. The duty cycle, or the number of possible experiments per unit time, is limited by a slow polarization time, but also because the D-DNP experiment has so far not been fully automated - it is run only during office hours. MAS-DNP, by comparison, requires no dilution and can increase the duty cycle. It has consequentially become a transformative tool, although - on paper- the signal enhancement is much smaller than in D-DNP. Bullet-DNP is a variant of dissolution-DNP that can provide hyperpolarized solutions with relatively low dilution. In this presentation, I describe the method and current limitations, and report on our progress in setting up a fully automated bullet-DNP system at Karlsruhe Insitute of Technology.

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135. January 22 2021, Nicola Salvi, IBS, Grenoble, "Synergistic Relationship Between Water Dynamics and Functional Motions in Intrinsically Disordered Proteins Revealed by Spin Relaxation and Molecular Dynamics Simulations" The activity of proteins depends on both their structure and dynamics, and one of the fundamental goals of biophysics is understanding the crucial relationship between protein motion and function. The relationship is even tighter in the case of intrinsically disordered proteins (IDPs) that lack a well-defined three-dimensional structure and access a diverse ensemble of conformations in their functional state. The function of IDPs is encoded both in their conformational heterogeneity and dynamics of interconversion between conformers. Solvent plays a fundamental role in determining the dynamic features of proteins. This consideration is particularly relevant for IDPs, whose olvent accessible surfaces are several times larger than those of folded proteins of similar molecular weight. Therefore, our understanding of IDP dynamics and function cannot ignore the crucial role of the molecular environment. We combine temperature-dependent molecular dynamics (MD) simulations with extensive 15N spin relaxation measurements to derive a unified description of IDP dynamics under near-physiological conditions. We develop analytical expressions to analyse protein motions and NMR relaxation properties as a function of temperature and solvent friction. This model not only allows for accurate analysis and prediction of  relaxation rates measured in different crowded environments in vitro but also is applied to experimental 15N relaxation rates measured in cellulo, suggesting a promising method for assessing functionally important IDP dynamics in complex physiological environments.

136. Friday, January 15, 2021, Kasturi Saha, ITT Bombay, India, "Development of a quantum diamond microscope" A diamond quantum microscope is a versatile tool for measuring and imaging extremely small magnetic fields emanating from a variety of samples, from magnetic materials to biological samples. While the diamond quantum microscope is routinely used for the measurement of static magnetic fields in a wide field of view with diffraction limited spatial resolution, dynamic widefield magnetometry for the measurement of temporally varying magnetic fields has been very challenging. In this talk, I will give an overview of our efforts towards the development of a dynamic widefield imager for biological as well as condensed matter applications.

137. Friday, December 18, 2020, Fleming Hansen, UCL, UK, "Pulse Sequences and Deep Learning: From 13C-detected NMR to virtual homonuclear decoupling" In the first part of the presentation a set of 13C-detected NMR methods to characterise functional side-chains in proteins will be presented. These methods allow, amongst others, to elucidate the interactions and dynamics of the guanidinium group of arginine side chains. Specifically, a multi-quantum chemical exchange saturation transfer (MQ-CEST) method will be shown. This method allows a quantification of the interactions formed by arginine side chains in proteins, such as salt-bridges. Subsequently some new applications of Deep Learning within biomolecular NMR will be presented. Over the last ~18 months it has become clear that Deep Learning and Artificial Intelligence have an impressive potential for transforming, analysing and interpreting biomolecular NMR data. A versitile deep neural network architecture, FID-Net, will be presented. FID-Net can easily be trained to perform a variety of tasks on time-domain NMR data, including reconstruction of non-uniformly sampled data, homonuclear virtual decouplings etc.

138. December 11, 2020, Vitali Tugarinov, NIH, USA, "Separating Degenerate Transitions in Methyl Groups of Proteins Using Acute Angle RF Pulses: A Physico-Chemical Perspective" Utility of acute (< 90°) angle 1H RF pulses in several classes of NMR experiments targeting selectively 13CH3-labeled methyl sites of proteins in a highly deuterated environment, is demonstrated focusing on pulse-scheme design optimization from the perspective of both sensitivity and simplicity. We show that efficient and sensitive selection of 1H and 13C transitions belonging to the I = 1/2 manifolds of 13CH3 groups, effectively reducing the complexity of a 13CH3 spin-system to the simpler case of its AX(13C-1H) counterpart, can be achieved using 1H pulses with optimized flip angles. A special case of acute angle RF pulses, the magic-angle (54.7°) 1H pulse, is shown to simplify pulse schemes and improve sensitivity of NMR experiments that quantify the amplitudes of methyl three-fold symmetry axis motions in small-to-intermediate sized proteins. Efficient selection and isolation of sub-classes of 13C transitions in 13CH3 methyl groups using acute angle 1H pulses is described with applications to methyl 13C single-quantum CPMG experiments for quantification of chemical exchange as well as a quantitative description of fast (sub-nanosecond) dynamics of methyl sites in protein structures.

139. Friday, December 4, 2020, Joern Schmedt auf der Guenne, Siegen University, Germany "Probing the Distribution of Paramagnetic Dopants by NMR Visibility " Paramagnetic doping of diamagnetic inorganic lattices is relevant for example for luminescent materials, catalytically active materials and also in dynamic nuclear polarization NMR. Paramagnetic centers can virtually make signals in NMR become invisible. The remaining visible NMR signal in case of a statistical doping scenario can be described by a simple functional dependence which allows to determine the blind volume or radius. The latter corresponds to the length scale at which NMR can be used to study the distribution of paramagnetic centers. It is shown how the basic formula can be related to mono- and co-doping scenarios and also to familiar NMR techniques which for example relate to the full-width half-maximum of the signal. It is shown that NMR is fairly sensitive to the distribution of dopants and shows potential to help with the development of inorganic phosphors.

140. Friday, November 27, 2020, Maria Makrinich, from Tel Aviv University, Israel,  "The use of phase-modulated pulses to study quadrupolar nuclei by solid-state NMR: development and methodology of distance and relaxation measurements" Many common ssNMR experiments that were originally developed for spin – ½ nuclei tend to fail or give low efficiencies when applied to quadrupolar nuclei. This happens because the quadrupolar interaction, when exists, is anisotropic, and tends to be very large (~MHz), while the available power levels for irradiation are much smaller (~kHz). This "broad-band" excitation problem compromises the application of distance measurement experiments to quadrupolar nuclei and quadrupolar spin-lattice relaxation experiments as well.

In this talk, the applicability of a phase-modulated (PM) pulse to quadrupolar nuclei is discussed in two cases – distance determination and relaxation measurements. In the first part, the distance measurement PM-RESPDOR experiment will be demonstrated, and the significant efficiency improvement in relation to other methods will be discussed. Distance measurements between spin pairs with small (<25 MHz) differences in their LARMOR frequency will be addressed as well, showing the split PM-RESPDOR applicability to a 13C-81Br system where 81Br has a quadrupolar coupling of 10.6 MHz. Carbon-bromine bonds are prevalent in pharmaceuticals, organo-catalysts and other compounds, and the usage potential is great. Additional spin-pairs that can benefit from the split-PM RESPDOR experiment are 13C-51V, 13C-27Al, 13C-45Sc, 117Sn-11B, especially for large (>5 MHz) quadrupolar frequencies. In the second part of the talk, the PM pulse will be suggested as the saturation pulse of choice for measuring quadrupolar spin-lattice relaxation times. Its applicability will be demonstrated on 11B, where the quadrupolar frequency is 1.55 MHz, and then the PM pulse will be combined with an indirect (1H) detection approach and relaxation measurements of 14N (nQ=1.9 MHz) and 81Br (nQ=5.3 MHz) will be shown for cases when ‘direct’ quadrupolar spectra couldn’t be acquired at all under spinning conditions.

References:

1. M. Makrinich, R. Gupta, T. Polenova, and A. Goldbourt, Solid State Nucl. Magn. Reson., vol. 84, pp. 196–203, 2017.

2. M. Makrinich, E. Nimerovsky, and A. Goldbourt, Solid State Nucl. Magn. Reson., vol. 92, pp. 19–24, 2018.

3. M. Makrinich, A. Goldbourt, Chem. Commun., 55, 5643-5646 (2019).

4. M. Makrinich, M. Sambol, A. Goldbourt, Phys. Chem. Chem. Phys.,22, 21022-21030, (2020)

141. Friday, November 20, 2020, Juergen Senker, Univ. of Bayreuth, Germany, "Disorder and Function of Side Chains in flexible MOFs – an NMR Crystallographic Study" Porous materials, like metal-organic frameworks (MOFs), offer potential for applications like drug delivery, gas storage and separation as well as sensor design. Such applications rely crucially on interactions between framework and incorporated guests. The latter may also interact with framework flexibility, linker disorder and functionalization. Here, we will show for the flexible MOF topologies MIL-53 [1] and fu-MILPs [2], how the functionalization and side chain disorder influences the breathing behavior and changes the adsorption properties for guest molecules. For MIL-53 the incorporated amide side chains remain almost rigid and order locally. Nevertheless, substantial disorder occurs on the mesoscale due to selective interactions between several side chains and single guest molecules. In the case of fu-MLP the alkoxy side chains express a pronounced dynamical disorder and entropic effects drive the gate opening. To elucidate structural and dynamic properties of the flexible MOFs, we make use of NMR crystallographic strategies. They combine scattering experiments with computational chemistry and solid-state NMR spectroscopy (ssNMR) to overcome the loss of information coming along with the disorder. While scattering provides topologic information, ssNMR probes local and intermediate length scales by determining connectivities, distances, orientation correlations and dynamical properties based on various homo- and heteronuclear correlation and relaxation experiments [3]. For this, we developed a comprehensive software toolkit that is able to handle, create and modify a large number of structure models to simulate the effect of disorder and carries out ssNMR spectroscopic, diffraction and quantum mechanical calculations.

[1]  J. Wack, R. Siegel, T. Ahnfeldt, N. Stock, L. Mafra, J. Senker, J. Phys. Chem. C 117 (2013), 19991.

[2]  S. Henke, A. Schneemann, R. A. Fischer, Adv. Funct. Mater. 23 (2013), 5990.

[3]  C. S. Zehe, R. Siegel, J. Senker, In Handbook of Solid State Chemistry; Wiley-VCH, 3 (2017), pp 245–277.

142. Friday, November 13, 2020, Frans Mulder, Aarhus University, Denmark, "High-pressure NMR investigation of protein folding and stability" The addressability of individual atoms makes it possible to study a large variety of features in proteins with atom- or residue specificity, including dynamics, electrostatics and energetics. For example, protium/deuterium (H/D) hydrogen exchange (HX) allows the quantitative study of protein stability and folding at the level of each amino acid in the sequence, and addresses questions about folding cooperativity and pathways. Transverse relaxation dispersion (RD) NMR, on the other hand, allows us to probe the free energy landscape involving different folded states, and to determine their energies (populations), kinetics (rates) and structural parameters (e.g. chemical shifts). Hydrostatic pressure can be used to modulate the free energy landscape, by driving the system to occupy states with the lowest volume. Its combination with HX and RD NMR thereby opens up the study of many interesting thermodynamic aspects of proteins. Examples to be shown: (i) the cost of cavity formation by mutation, and (ii) the discovery of a hierarchy of partially unfolded states at thermal equilibrium.

143. Friday, November 6, 2020, James Ellis, Johannes Gutenberg University, Mainz, Zero- to ultralow-field (ZULF) NMR is a modality of NMR experiment performed in the absence of a strong magnetic field. In this regime, Larmor precession is suppressed, and other interactions such as J-couplings dominate. This grants three important advantages: the low-frequency signals readily penetrate metals and conductive materials, magnetic susceptibility-induced line broadening from sample inhomogeneity is suppressed, and no NMR magnet is needed. Since no magnetic field is present to polarize the spins, an alternative source of polarization is required. Often this is an external, or transiently applied magnetic field, but an attractive alternative which allows for significantly higher nuclear spin polarization is parahydrogen-induced polarization (PHIP). In recent experiments we have shown that it is possible to form the biomolecule [1-13C]fumarate via parahydrogen-induced polarization in concentrations of ~120 mM, at up to 45% 13C polarization in aqueous solution. In this talk I will discuss applications of PHIP in ZULF NMR for chemical reaction monitoring of heterogeneous samples in metal containers, and present our latest results, showing that ZULF NMR can be used to study metabolism by observing the enzyme-catalyzed biochemical transformation of fumarate to malate.

144. Friday October 30, 2020 Samuel Cousin Université de Lyon, "Hyperpolarization with HYPOP (Hyperpolarizing Porous Polymers) Polarization and transport"  Dissolution Dynamics Nuclear Polarization (dDNP) method remains restricted to few research groups as it needs in principle to be performed at the point of use, with specialized equipment and personnel. However, a series of recent advances have successfully demonstrated that dDNP could potentially be performed remotely, i.e. without the need of a polarizer on-site. In this work, we present a new generation of polarizing matrices termed HYperPolarizing Polymers (HYPOP). These matrices offer the possibility of physically separating the molecules of interest from the polarizing agents on hundreds of nanometer scales by immobilizing the polarizing agents inside the protonated porous polymer walls. This porous material can be hyperpolarized and impregnated with solutions of interest. Polarization is transferred to the target nuclear spin through 1H-1H spin diffusion followed by 1H-13C cross polarization. In these conditions, 13C lifetime is extended at cryogenics temperature and allow the transport of the solution.
     
     

145. Friday October 23, 2020, Dennis Kurzbach, Uni Vienna, Austria, "Dissolution DNP for protein NMR" Mutations of the breast-cancer susceptibility protein 1 (BRCA1) are a major reason for hereditary breast and ovarian cancer. However, structural information still remain scarce not least due to the strong disordered character of the protein. We here propose to study the interactions between the BRCA1 and the EBOX DNA-MYC/MAX transcription factor network by means of dissolution dynamic nuclear polarization (d-DNP)-boosted high-resolution NMR. With d-DNP one can achieve substantial signal enhancements in NMR of proteins providing access to physiological concentrations and buffer conditions, whereas conventional approaches typically rely on NMR-optimized pH, concentration and temperature, which yet have been shown to significantly bias the interactions under study. The dissolution DNP setup built at the university of Vienna will thus be introduced together with first results on the BRCA1-EBOX DNA-MYC/MAX interaction. In particular, it will be demonstrated how one can use hyperpolarized water to study proteins with high-resolution NMR at DNP-boosted signal intensities. 

146. Friday October 16, 2020, Guillaume Bouvignies, ENS Paris, France, "Accelerated CEST experiments using multi-site excitation to study sparsely populated protein states" Chemical exchange saturation transfer (CEST) has recently evolved into a powerful approach for studying sparsely populated, “invisible” protein states in slow exchange with a major, visible conformer. Central to the technique is the use of a weak, highly selective radio‐frequency field that is applied at different frequency offsets in successive experiments, searching for minor state resonances. The recording of CEST profiles with enough points to ensure coverage of the entire spectrum at sufficient resolution can be time‐consuming, especially for applications that require high static magnetic fields or when small chemical shift differences between exchanging states must be quantified. In this presentation, I will show how the process can be significantly accelerated by using a multi‐frequency irradiation scheme, such as the DANTE pulse-train, leading in some applications to an order of magnitude savings in measurement time [ChemPhysChem (2018) 19, 1707-1710; J. Mag. Res. (2018) 292, 1-7]. Building on these recent CEST developments, I will also present a new approach for measuring solvent hydrogen exchange rates in proteins that exploits the one-bond nitrogen-15 deuterium isotope shift [J. Phys. Chem. B (2018) 122, 11206-11217]. The merits of the CEST experiment in relation to the popular CLEANEX-PM scheme will be discussed.

147. Friday October 9, 2020, Rodrigo Cortinas, Yale University, "Spectroscopic techniques used to control and manipulate laser trapped circular Rydberg atoms for quantum information" The techniques used for coherent quantum control are oftentimes adaptations of old tools developed for spectroscopy and in particular for NMR. In this talk, I will discuss -in the context of quantum information- the many spectroscopic tools (Laser, MW, RF-polarization, light-shifts, Hahn-Echoes, etc.) used to calibrate, manipulate and trap cold circular Rydberg atoms in a cryostat. The long term perspective of these experimental efforts is to use the trapped circular atomic states as the building blocks of a many-spin quantum simulator that may be useful to engineering new magnetic materials.

148. Friday October 2, 2020, Pramodh Vallurupalli from TIFR Hyderabad, India, "A methyl 1H SQ-CPMG experiment to study conformational exchange in large systems: Lessons from a methyl 1H DQ-CPMG experiment" CPMG experiments are now routinely used to study protein conformational exchange occurring on the millisecond timescale between a visible major state and sparsely populated invisible minor states. However, until recently there was no methyl 1H CPMG experiment to study conformational exchange in the 13CH3 methyl groups of large systems because methyl 1H CPMG experiments that attempt to exploit the methyl TROSY principle are plagued by artifacts due to ‘pulse imperfections’. In this talk I will describe how we used the lessons that we learnt while developing a methyl 1H double quantum (DQ) CPMG experiment [J. Biomol. NMR., 72, 79–91, (2018)] to design a methyl TROSY based 1H single quantum (SQ) CPMG experiment [Angew. Chem. Int. Ed., 58, 6250 –6254, (2019)] that is sensitive enough to be applied to systems as large as a few 100 kDa. 

149. Friday September 25, 2020, Gottfried Otting, from ANU, Canberra, Australia, "Lanthanide tags for structural biology by NMR and EPR" Many of the lanthanide ions are strongly paramagnetic, generating large effects in NMR spectra. Among them are pseudocontact shifts (PCS), which can be harnessed to obtain detailed structural information on biological macromolecules such as proteins. In fact, it is possible to determine the 3D structure of a protein solely from PCSs. PCSs are measured simply as chemical shifts in the paramagnetic state minus the corresponding chemical shifts in the diamagnetic state. First, pseudocontact shifts (PCS) of the protein are measured by NMR to determine the coordinate frame of the magnetic susceptibility anisotropy (Δχ) tensor associated with the lanthanide ion. Next, the PCSs of the nuclear spins of interest are used to position them relative to the Δχ tensor. With lanthanide tags at four different sites, the position of the nuclear spin can be restricted in a way analogous to the global positioning system (GPS) of a mobile phone. An example of this approach is shown for a protein tagged at different sites. The capability of attaching lanthanide tags to proteins also enables the measurement of nanometre distances between two gadolinium atoms by EPR spectroscopy, which provides a powerful method for monitoring domain motions. Examples are shown for a range of amino-acid binding proteins. The development of chemistries for site-specific attachment of lanthanide tags is a lively contemporary topic of research. Different approaches and requirements are discussed.

150. Friday September 18 , 2020,  Mihajlo Novakovic, the Weizmann Institute of Science, Israel, "Chemical exchange: A foe or a friend" Dipole-dipole cross-relaxation phenomena leading to homonuclear Nuclear Overhauser Effects (NOEs), lie at the center of structural determinations by NMR. One of NOESY’s known drawbacks is its relatively low sensitivity, as off-diagonal cross-peaks carrying the structurally relevant information only involve a small fraction of the total magnetization. The sensitivity of these experiments is additionally compromised when involving labile proton sites, owing to the presence of chemical exchanges with the water. Another important tool in the structural elucidation of biomolecules is the TOCSY experiment, yet this also presents inefficient correlations within systems whose protons exchange fast with the solvent. Something similar happens with Cross-Polarization (CP) –another important tool in heteronuclear signal enhancement. Exchange-challenged examples of these phenomena are furnished by hydroxyl protons in polysaccharides, glycans or nucleic acids; by amides in IDPs; by side-chain amines in proteins: in all these cases, the retrieval of cross-peaks involving these sites is complicated by fast chemical exchanges between these protons and water. Here we will present methods to alleviate this, based on repeated anti-Zeno-like projective measurements.[1,2] Ensuing methods utilize constant water exchange-driven repolarization of the labile protons transforming them into “valves” acting in a solvent→labile→non-labile 1H polarization conveyor. When carefuly associated with Hadamard encoding, these principles can significantly accelerate conventional NOESY and TOCSY experiments by >500-fold.[3] Successful examples of harnessing this idea in homonuclear and heteronuclear transfers in a variety of systems will be presented, and limitations as well as further extensions in other systems will be discussed.

References

[1] C. O. Bretschneider, G. A. Alvarez, G. Kurizki, L. Frydman, Phys. Rev. Lett. 2012, 108, 1–5.

[2] M. Novakovic, S. F. Cousin, M. J. Jaroszewicz, R. Rosenzweig, L. Frydman, J. Magn. Reson. 2018, 294, 169–180.

[3] M. Novakovic, Ē. Kupče, A. Oxenfarth, M. D. Battistel, I. Darón, H. Schwalbe, L. Frydman, 2020, arXiv:2004.13063.

151. Friday September 11, 2020,  Hellmut Eckert, University of Saõ Paulo, Brazil,"New Magnetic Resonance Strategies for Studying Structure/property Correlations in Laser Glasses"  Rare-earth ion (RE) doped glasses and glass-ceramics are luminescent photonic materials with promise for laser applications. To optimize the luminescent properties of these materials, detailed structural information regarding the local environment of the rare-earth species is essential. While solid state nuclear magnetic resonance (NMR) is in general a useful tool for such purposes; unfortunately, the rare-earth ions themselves cannot be studied by NMR due to their paramagnetism. To overcome this difficulty, a three-fold examination strategy has been developed including (1) NMR studies of diamagnetic mimics, (2) NMR studies of framework nuclei affected by paramagnetic interactions, and (3) pulsed-EPR studies sensitive to the magnetic dipolar interactions of the unpaired electrons with nearby nuclear spins, using electron spin echo envelope modulation (ESEEM) and hyperfine sublevel correlation (HYSCORE) spectroscopy. These approaches are complementary in terms of the relevant length scale of the interactions studied and their combination has turned out very successful in eludicating the short- and medium-range order details of the rare-earth ion local environments, allowing a rationalization of the luminescent properties of these glasses on a structural basis. Recent applications of this experimental strategy to fluoride phosphate laser glasses will be discussed.

152. Friday July 31, 2020, Norbert Müller, Johannes Kepler University at Linz, "Nuclear Spin Noise Imaging in 3 Dimensions" Our group first succeeded to use spin-noise-detected NMR for two dimensional imaging in 2005. Over the following years we focused on many different aspects of spin noise mostly targeted at spin noise spectroscopy. These efforts resulted in a number of unexpected insights concerning (non-)linearity and probe properties leading to applications to different sub-fields of NMR spectroscopy including ultra-low temperature NMR and hyperpolarisation. Recently we took up the topic of imaging again. Taking advantage of the accumulated knowledge, we have recently been able to demonstrate three dimensional nuclear spin-noise-detected imaging, which also includes a new processing approach relying on SART (simultaneous algebraic reconstruction technique) on a conventional NMR spectrometer equipped with a cryoprobe. The potential and prospective applications of spin noise in NMR will be discussed.

153. Friday July 24, 2020, Kaustubh Mote, from the Tata Institute of Fundamental Research, Hyderabad, "Adapting REDOR for the increasingly higher magic-angle spinning frequencies and the measurement of strong dipole-dipole couplings" Rotational-echo double resonance (REDOR) is a widely used technique for the measurement of heteronuclear dipole-dipole couplings under magic-angle spinning. When the distance between spins is known, it can also be used to determine order parameters, which contain information on the amplitude of motion present in the system being studied. The popularity of this technique is due to its straightforward implementation, robustness to experimental imperfections, and a one-parameter fit to the experimental curve. However, there are two cases where the use of REDOR is not straightforward: (i) Fast MAS frequencies: REDOR requires two &#960; pulses per rotor period, and smallest radiofrequency amplitude that can be used is the one that generates a nutation frequency equal to MAS frequency. Its implementation at the currently available fast MAS frequencies (> 100 kHz) is impractical, especially for nuclei with a low gyromagnetic ratio, where such high nutation frequencies cannot be generated. (ii) Measuring strong dipolar couplings (> 10 kHz) using REDOR is also problematic due to the stroboscopic nature of this sequence. In this talk, I will present our work on the implementation of modified versions of REDOR which circumvent both of these problems. These modifications will additionally be shown to be directly applicable to the closely related DIPSHIFT (Dipolar chemical shift correlation) and TEDOR (Transferred-echo double resonance) sequences as well. 

154. Friday July 17, 2020,  Giuseppe Pileio, University of Southampton, "Singlet Assisted Diffusion NMR (SAD-NMR)" Singlet order is the population difference between the singlet and triplet states in a system of two coupled spin-1/2 nuclei. This form of order is long-lived, silent and accessible on demand. It is long-lived because it is affected by relaxation mechanism to a lesser extent than longitudinal or transverse order; it is silent because proportional to the rank-zero irreducible spherical spin operator; and it is accessible on demand because it is generally unaffected by rf pulses and pulsed field gradients unless these are cleverly arranged to satisfy very precise conditions. For the past few years, part of the activities of my research group were focused at exploiting these three main properties of singlet order in order to develop applications in NMR and MRI. The possibility granted by singlet order to store information in a spin system for significantly longer time (tens of minutes rather than seconds as in conventional NMR/MRI) has interesting applications in many fields: the long-term storage of hyperpolarisation can allow, in the near future, hyperpolarised substrates to be distributed to hospitals for enhanced MRI scans; the measurements of slow diffusion and flow has relevance in material science and many industrial sectors; the determination of structural features of porous media such as tortuosity and structural anisotropy has relevance across many fields from material science to medicine; and so on. In this talk I will briefly introduce the concept and main features of singlet order as well as the tools we are developing in order to manipulate it. I will then show how we used this form of order to enhance the capabilities of diffusion-based NMR (and MRI) techniques.

155. July 10, 2020, Gabriel Hétet, Ecole Normale Supérieure, Paris " Spin mechanics with electronic spins inside levitating particles", A recently proposed route for observing quantum effects with macro-scale objects is to work with levitating particles and to control the motional state via embedded spins. Our approach in this direction consists in using a non-invasive electrodynamical trap (a Paul trap) to levitate diamond particles containing nitrogen-vacancy defects (so called NV centers). Unlike many defects in solids, NV centers can be polarized and read-out optically at room-temperature and manipulated coherently using microwave signals. We have shown that the electronic spin resonance signals can give information about the particle motion. I will also report our experimental demonstrations of optically-detected magnetic resonance of spins in a levitating diamond under vacuum, and our recent observations of the torque and the cooling applied by the spins to the diamond orientation.

156. Friday, July 3, 2020, Kazuyuki Takeda, Kyoto University, "Mechanical rotation with modulation can align microcrystals and, possibly, tip spins" 

1. We report in-situ solid-state NMR measurements of a magnetically oriented microcrystal suspension (MOMS).　Under modulated rotation of a static field, or nearly equivalently, of the sample tube in the static field fixed in the laboratory, randomly oriented microcrystals in a viscous liquid medium feel a torque arising from the anisotropic bulk susceptibility in such a way that the individual microcrystals are eventually aligned in the same direction. A three-dimensional MOMS (3D-MOMS) obtained in this way gives NMR spectra corresponding to single-crystal (SC) rotation patterns when the pulse excitation is triggered in synchronous with the sample-tube rotation with varuous delay times. Unlike the traditional SC method, the 3D-MOMS approach presented here does not require elaborate and often impossible crystal growth. We discuss potential applications as well as limitation of MOMS NMR.

2. A particle with a spin angular momentum in an inertial frame of reference acquires an extra energy in a non-inertial frame rotating with respect to the former due to the spin-rotation coupling. As a consequence, the spin system is magnetized as if it were exposed to a magnetic field. Development of the magnetization by rotation was first observed by Barnett in 1915 in a rotating ferromagnetic body. Very recently, the Barnett effect was also reported for paramagnetic electron spins as well as for nuclear spins. Here, we explore the possibility of exciting/detecting NMR through the alternating Barnett field in the presence of a polarizing static field.

157. Friday June 26, 2020, Giulia Mollica, Université Aix-Marseille, " Time-resolved investigation of nucleation and crystallisation of polymorphic solids via solid-state DNP NMR" Crystallization plays an important role in many areas of biology, chemistry and materials science, but the underlying mechanisms that govern crystallization are still poorly understood because of experimental limitations in the analysis of such complex, evolving systems. To derive a fundamental understanding of crystallization processes, it is essential to access the sequence of solid phases produced as a function of time, with atomic-level resolution. Rationalization of crystallization processes is particularly relevant for polymorphic materials, i.e. solids that can exist as distinct crystalline forms. Despite being chemically identical, different polymorphs display different physicochemical properties, offering great opportunities for tuning the performance of the material. However, manufacture or storage-induced, unexpected, polymorph transitions can compromise the end-use of the solid product. Interestingly, these transformations often imply the formation of metastable forms, which are receiving growing attention because they can offer new crystal forms with improved properties. Today, detection and accurate structural analysis of these – generally transient – forms remain challenging, essentially because of the present limitations in temporal and spatial resolution of the analysis, which prevents rationalization (and hence control) of crystallization processes. In our laboratory, we develop dynamic nuclear polarization (DNP) solid-state NMR approaches to overcome these limitations. In this contribution, I will present some of our latest results showing that cryogenic MAS NMR [1] combined with the sensitivity enhancement provided by DNP [2] can be an efficient way of monitoring the structural evolution of crystallizing solutions with atomic-scale resolution on a time scale of a few minutes. This work opens up the prospect of studying the very early stages of crystallization, such as nucleation and pre-nucleation phenomena, at which the amount of solid phase present is intrinsically low.

[1] P. Cerreia-Vioglio, G. Mollica, M. Juramy, C.E. Hughes, P.A. Williams, F. Ziarelli, S. Viel, P. Thureau, K.D.M. Harris, Angew. Chem. Int. Ed. 2018, 57, 6619.

[2] P. Cerreia-Vioglio, P. Thureau, M. Juramy, F. Ziarelli, S. Viel, P.A. Williams, C.E. Hughes, K.D.M. Harris, G. Mollica J. Phys. Chem. Lett. 2019, 10, 1505

158. Friday June 19, 2020,  Michael Tayler, The Institute of Photonics Sciences, Barcelona, " Zero-to-earth-field NMR, and beyond: spectroscopy and relaxometry via atomic sensing" Insights into molecular structure and dynamics may be obtained by probing spin resonance behavior of nuclei at magnetic fields anywhere from a few nanotesla to several tens of tesla.  Very often, nuclear spin systems behave interestingly as a function of magnetic field and a detailed study of these field-dependent effects demands switchable magnet apparatus and/or shuttling of samples from one magnetic location to another.  The choice of apparatus is based primarily upon available field range, spectroscopic resolution and sensitivity depending on timing, power consumption, cost and size constraints.This seminar will discuss principles, merits and challenges of field-cycling NMR experiments performed at magnetic fields below earth’s field, inside magnetically shielded enclosures.  Experimental demonstrations focus on liquid-state systems where chemical shifts do not need to be resolved: (1) ultralow-field homonuclear T1 and T2 relaxation times to characterize surface motion effects in pore-confined liquids, including an example of T1/T2 convergence below 100 Hz Larmor frequency; (2) heteronuclear-J-coupled systems.  I will discuss fast-field-cycling NMR across the Hz to MHz 1H Larmor frequency range, coupled with NMR detection at arbitrary Larmor frequency from Hz to several kHz using a DC-field-tunable atomic magnetometer. Pre-polarization fields supplied inside the shield obviates sample shuttling or hyperpolarization approaches.

159. Friday June 12, 2020, Ivan Zhukov, ITC, Novosibirsk, " Two-dimensional NMR experiments exploiting spin mixing under ZULF conditions" Multi-dimentional correlation spectroscopy in liquid-state NMR provides invaluable information about properties of complex molecular systems. For example, the 2D TOCSY experiment is a useful tool for identification of substances in complex mixtures, notably, metabolites in biological samples, and further assignment of the signals. However, even when state-of-the-art high-resolution NMR methods are used, the problem of overlapping spectral peaks imposes limitations on analytical capabilities of 2D-NMR. Utilizing heteronuclear correlation methods improves the situation and provides additional information on molecular properties. In this talk, a new heteronuclear 2D experiment is presented, which exploits spin mixing at Zero or Ultra-Low Field (ZULF) and detection at high field. We propose to name this experiment ZULF-TOCSY. The method allows one to achieve correlation across all NMR-active nuclei also taking advantage of high-resolution NMR detection. The features of the ZULF-TOCSY technique are demonstrated using solutions of 13C,15N labeled amino acids and ISOGRO growth media - a mixture of 13C,15N uniformly labeled small biological molecules. We also discuss experimental approaches, which allow one to experiments run with fast switching of the external magnetic field between two field positions: an ultralow field used for spin mixing and a high field used for NMR detection.

160. Friday June 5, 2020, Daniel Jardon-Alvarez, WIS, "DNP without Spin Diffusion – Helping Spins in Need" Dynamic nuclear polarization (DNP) significantly enhances the sensitivity of NMR. Efficient spin diffusion among the nuclear spins is considered to be essential for spreading the hyperpolarization throughout the sample enabling large DNP enhancements. This scenario mostly limits the polarization enhancement of low sensitivity nuclei in inorganic materials to the surface sites when the polarization source is an exogenous radical. In metal ions based DNP, the polarization agents are distributed in the bulk sample and act as both source of relaxation and of polarization enhancement. We have found that as long as the polarization agent is the main source of relaxation, the enhancement does not depend on the distance between the nucleus and dopant. As a consequence, the requirement of efficient spin diffusion is lifted and the entire sample can be directly polarized. In this talk I will present a theoretical description of the involved hyperpolarization and relaxation mechanisms in ion based DNP using a simplified model and show how this can be exploited to measure high quality NMR spectra of 17O in inorganic materials, specifically looking at the electrode material Li4Ti5O12 doped with Fe(III).

161. Friday May 29, 2020, Christian Bengs, University of Southampton, "Rotational-permutational dual-pairing and long-lived spin order" Quantum systems in contact with a thermal environment experience coherent and incoherent dynamics. These drive the system back towards thermal equilibrium after an initial perturbation. The relaxation process involves the reorganisation of spin state populations and the decay of spin state coherences. Individual populations and coherences may exhibit different relaxation time constants. Particular spin configurations may exhibit exceptionally long relaxation time constants. Such spin configurations are known as long-lived spin order. The existence of long-lived spin order is a direct consequence of the symmetries of the system. For nuclear spin systems rotational and permutational symmetries are of fundamental importance. Based on the Schur-Weyl duality theorem we describe a theoretical framework for the study of rotational and permutational dual-symmetries in the context of long-lived spin order. The proposed formalism is applied to derive bounds on the number on long-lived spin populations and coherences for such systems. 

162. Friday May 22, 2020,  Torsten Gutmann, TU-Darmstadt "Identification of surface sites of technical catalysts by advanced solid-state NMR techniques." Technical catalysts play an important role in industrial scale oxidation processes for the production of platform chemicals as well as in the exhaust gas cleaning. Examples are the oxidation of methane to formaldehyde, the oxidation of acrolein to acrylic acid or the oxidation of carbon monoxide to carbon dioxide. In these reactions transition metal oxides or molecular sieve catalysts containing vanadium, or supported metallic nanoparticles are often utilized. While for many years, such catalysts are known and studies concerning their reactivity have been presented, there is still a lack of knowledge of their surface chemistry. Especially, surface sites that are formed during the synthesis or catalysis have to be identified to understand catalytic data. In the past, many of these catalysts have been investigated by vibrational spectroscopy, XRD or EPR. However, in many cases the resolution of these techniques is too low to obtain details when a variety of surface sites is present. This requires an analytical tool sensitive to local environments as provided by solid-state NMR. [1] The presentation will show how line-shape analysis combined with spectral simulation can be used as a powerful approach to identify vanadium containing surface species in technical catalyst systems. As example, vanadium catalysts on mesoporous silica materials prepared via different synthesis routes are studied and the results from 51V MAS NMR data are correlated with catalytic activity tests. [2] In case of low surface area catalysts, however, solid state NMR is limited due its low intrinsic sensitivity. Combination with Dynamic nuclear polarization (DNP) can overcome this issue. [3] The second part of the presentation will show how this approach is applied to identify surface sites on mixed oxide catalysts as well as on supported metallic nanoparticles . [4,5]

Literature:

[1] O.B. Lapina et al., Catal. Today. 2003, 78, 91-104.

[2] M. de Oliveira Jr. et al., Catal. Sci. Technol. 2019, 9, 6180-6190.

[3] A. Lesage et al., J. Amer. Chem. Soc. 2010, 132, 15459-15461.

[4] A. S. L. Thankamony et al., J. Phys. Chem. C 2017, 121, 20857-20864.

[5] V. Klimavicius et al., Catal. Sci. Technol. 2019,9, 3743-3752.

163. Friday May 15, 2020,  Yonghong Ding, U. Leipzig, "Field-dependence of photo-CIDNP effect generated by designed flavoproteins" The solid-state photo-chemically induced dynamic nuclear polarization (photo-CIDNP) effect generates non-Boltzmann magnetization detected by NMR spectroscopy as significant modification of signal intensity. The effect was well known to occur in reaction centers of photo-synthetic systems and in a light-oxygen-voltage (LOV) domain of a biological blue-light receptor called phototropin, in which the conserved cysteine was removed to avoid the natural photo-chemical reactions with the cofactor, flavin mononucleotide (FMN). Thereby under illumination the FMN abstracts instead an electron from a remote tryptophan residue to form transient spin-correlated radical pairs and results in photo-CIDNP. Here I report the successful design of further two LOV proteins able to show solid-state photo-CIDNP effect: a LOV domain of aureochrome from Phaeodactylum tricornutum as well as an unusual LOV domain named 4511 from Methylobacterium radiotolerans (Mr4511) which lacks an otherwise conserved tryptophan in its wild-type. Mutating the tryptophan at canonical and novel positions in Mr4511 enables occurrence of 15N and 1H photo-CIDNP effect with characteristic field-dependence. And for the first time we observed an non-tryptophan derived photo-CIDNP effect generated by a cysteine-devoid Mr4511 protein where no tryptophan is present. Our experiments demonstrate possibilities to explore conditions that allows for solid-state photo-CIDNP and design molecular spin-machines which produces light-induced nuclear spin-hyperpolarization.

164. Friday May 8, 2020, Asif Equbal from U.C. Santa Barbara,"DNP: Melting boundaries between NMR and EPR"  Dynamic Nuclear Polarization or DNP is well-recognized for dramatically enhancing the sensitivity of Nuclear Magnetic Resonance spectroscopy. However, the DNP efficiency drastically goes down at higher magnetic field and faster sample spinning. A major bottle-neck is lack of knowledge about electron spin dynamics under DNP conditions. My talk will focus on strategies to improve DNP efficiency using: (1) pulse shaped microwave irradiation, and (2) EPR detection under DNP conditions.

165. Friday May 1, 2020, Bogdan Rodin, ITC, Novosibirsk, "Algorithmic cooling of nuclear spins using long-lived singlet order" Algorithmic cooling is the method consisting of the deterministic sequence of events to diminish the entropy of the whole ensemble of quibits (or spins ). It exploits two kinds of spins. The first one is the fast relaxing spins which contact with the environment and exchange the energy and entropy. The second one is the slow relaxing spins which store the initial spin order. To proceed with this algorithm the spins should be addressed selectively. In the case of a strongly coupled spin pair this procedure fails. It is almost impossible to address spins selectively and they also have almost identical relaxation properties. Here we propose a new method which utilizes long-lived spin order and enables the algorithmic cooling procedure for the strongly coupled spin pair. By using this sequence we managed to pump the long-lived nuclear singlet order well beyond the unitary limit. The pumped singlet order was converted into nuclear magnetization which was enhanced by 21% relative to its thermal equilibrium value.

166. Friday April 24, 2020, Bharti Kumari, TU Darmstadt "Surface Studies of Porous Materials using Solid-state NMR and DNP-NMR" Porous materials are known for applications in industrial use, for example in catalysis, filtration processes, gas and heat storage, ion exchange, oil recovery and drug delivery. Porous materials have also been utilized as model systems to investigate the effect of confinement on small molecules. Solid-state NMR techniques partially combined with DNP are extensively used to study surface interactions and the surface functionalization of such porous materials. In the presentation, three types of materials are discussed: (i) mesoporous silica SBA­15, (ii) etched ion-track polycarbonate membranes and (iii) complex cellulose paper substrates. For mesoporous silica, the detailed investigation of interactions of water and octanol-1 molecules with the pore surface of silica SBA-15 is presented. For this, conventional room temperature 1D and 2D solid-state NMR techniques were utilized. The 1D experiments provided valuable information on the 1H chemical shift dependency of SBA-15 while 2D 1H-29Si FSLG CPMAS HETCOR projects local interactions between surface and guest molecules (octanol-1 and water). With these observations, the assembling of the octanol-1 and water molecules under the confinement was derived [1]. In addition, a new referencing approach is developed using the 2D 1H-1H MAS FSLG pulse sequence to refernce the indirect 1H dimension of 2D 1H-X FSLG CPMAS HETCOR experiment [2]. Apart from this, materials comprising low surface areas, e.g., etched ion-track polycarbonate foils and cellulose paper substrate were studied using solid-state NMR employing DNP. The characterization of pore surface of silica coated ion etched PC membrane was investigated by DNP-SENS [3]. Following this approach, functionalized paper substrates were investigated with DNP-SENS, and various kinds of radical matrices were tested in these experiments to obtain a correlation between polarization matrix and reachable signal enhancement in the spectra [4].

References:

[1] B. Kumari et al., The Journal of Physical Chemistry C, 2018, 122, 19540-19550

[2] B. Kumari et al., Applied Magnetic Resonance, 2019, 50, 1399-1407

[3] B. Kumari et al., Z. Phys. Chem, 2018, Vol. 232, p 1173

[4] T. Gutmann et al., The Journal of Physical Chemistry C, 2017, 121 (7), 3896-3903.

167. Friday April 17, 2020, Diego Carnevale, ENS Paris, "Surges of Dynamic Nuclear Polarization resulting from Cross-Relaxation between Protons and Quadrupolar Nuclei."

168. Friday April 8, 2020, Kirill Sheberstov, Johannes Gutenberg Universität, Mainz