Applying fundamental and applied chemistry towards sustainable solutions to agricultural issues
Welcome!
I am Jacobs Jordan, and this is my personal page. All views and comments herein are my own and do not represent the US Department of Agriculture.
I received two baccalaureate degrees from the University of New Orleans in biology (2009) and chemistry (2010). I received my doctoral degree from Tulane University (2018) under the guidance of Prof. Bruce C. Gibb. My postdoctoral appointment began in August 2018 at the Southern Regional Research Center in New Orleans under the supervision of Dr. Michael Easson.
For my baccalaureate degrees I studied microbiology, genetics, and molecular biology in the Department of Biological Sciences. Upon completion of my first baccalaureate degree I decided to pursue a second degree and enrolled in the Department of Chemistry, completing my second degree in Dec 2010. During this time I worked in the lab of Dr. Mark Trudell, and investigated the synthesis of novel cannabinoid receptor ligands for biological evaluation.
Following my coursework at UNO I enrolled at Tulane University in August 2011, where I studied physical organic chemistry and organic synthesis under the guidance of Prof. Bruce C. Gibb. While at Tulane, my research focused on the synthesis of water-soluble cavitands that were used to probe the hydrophobic and Hofmeister effect (i.e. ion-ion, ion-hydrocarbon and non-covalent interactions). I prepared several novel resorcinarene and cavitand receptors used for anion recognition, aided in the development of new binding models for buffered solutions and as supramolecular catalysts.
My postdoctoral appointment in August 2018 as a postdoctoral research chemist at the US Department of Agriculture, Agricultural Research Service (ARS) under the supervision of Dr. Michael Easson. In the Cotton Chemistry & Utilization and Cotton Quality & Innovation research units my postdoctoral research involved materials science and developing functional composites utilizing lignocellulose biomass to replace petroleum-based polymers. Specifically, I used nanocellulose from agricultural bi-products (e.g cotton gin trash) to develop functionalized nanomaterials for use as rheology modifiers, ion-responsive nanocomposites, and for biosensor applications. As an example, nanocellulose-peptide conjugates were developed for protease detection in responsive wound dressings. Additional areas of research include solid-supported metallic nanoparticles for use in sensors, as catalysis and for waste remediation.
I began my independent career in April 2024 when I joined the Commodity Utilization Research Unit in New Orleans.
Selected work
Buffer and Salt Effects in Aqueous Host–Guest Systems: Screening, Competitive Binding, or Both?
There are many open questions regarding the supramolecular properties of ions in water, a fact that has ramifications within any field of study involving buffered solutions. Indeed, as Pielak has noted (Buffers, Especially the Good Kind, Biochemistry, 2021, in press. DOI:10.1021/acs.biochem.1c00200) buffers were conceived of with little regard to their supramolecular properties. But there is a difficulty here; the mathematical models supramolecular chemists use for affinity determinations do not account for screening. As a result, there is uncertainty as to the magnitude of any screening effect and how this compares to competitive salt/buffer binding. Here we use a tetra-cation cavitand to compare halide affinities obtained using a traditional unscreened model and a screened (Debye–Hückel) model. The rule of thumb that emerges is that if ionic strength is changed by >1 order of magnitude─either during a titration or if a comparison is sought between two different buffered solutions─screening should be considered. We also build a competitive mathematical model showing that binding attenuation in buffer is largely due to competitive binding to the host by said buffer. For the system at hand, we find that the effect of competition is approximately twice that of the effect of screening (∼RT at 25 °C). Thus, for strong binders it is less important to account for screening than it is to account for competitive complexation, but for weaker binders both effects should be considered. We anticipate these results will help supramolecular chemists unravel the properties of buffers and so help guide studies of biomacromolecules.
Ion–Hydrocarbon and/or Ion–Ion Interactions: Direct and Reverse Hofmeister Effects in a Synthetic Host
A combination of 1H NMR spectroscopy, DLS, and turbidity measurements reveal that polarizable anions engender both the Hofmeister and reverse Hofmeister effects in positand 2. Host 2 possesses two principal and distinctly different binding sites: a “soft” nonpolar pocket and a “hard” crown of ammonium cations. NMR spectroscopy reveals that anion affinity to both sites is comparable, with each site showing characteristic selectivities. NMR spectroscopy also reveals that anions competitively bind to the pocket and induce the Hofmeister effect in host–guest binding at very low concentrations (∼2 mM). Furthermore, the suite of techniques utilized demonstrates that anion binding to both sites leads to charge attenuation, aggregation, and finally precipitation (the reverse Hofmeister effect). Anion-induced precipitation generally correlated with affinity, and comparisons between the free host and its adamantane carboxylate (Ada-CO2–) complex reveals that the reverse Hofmeister effect is attenuated by blocking anion binding/charge attenuation at the nonpolar pocket.
