[1H, 15N]-NOESY-HSQC

The pulse sequence from the HSQC portion is a sensitivity enhanced and gradient selected version and consists of two defocusing gradients while the coherences of interest are along the Z-axis. The proton pulses phases are selected to realign the water magnetization to the +z axis while the gradient selection helps to suppress the solvent signal.

The flow of magnetization is as such:

1Hi (t1) -> 1Hj ->15Nj (t2) -> 1Hj (t3)

NOE is used for the exchange of magnetization between all hydrogens and is transferred to neighboring 15N nuclei and back to 1H for detection.

1H protons are excited and their chemical shifts are labeled in T1 evolution during which there is a NOESY-transfer from protons to protons. Magnetization transfer occurs from the proton attached to 15N to the nitrogen via a process called Insensitive Nuclei Enhanced by Polarization Transfer (INEPT) due to the low gyromagnetic ratio of the 15N Nuclei. The 15N chemical shifts are labeled in T2 evolution and there is a reverse INEPT back to HN protons and a detection at T3 of the HN protons.

Pulse program from paper:

Pulse program from Bruker:

Magnetisation transfer in a 15N-NOESY HSQC experiment:

References:

E.R.P. Zuiderweg and S.W. Fesik (1989) Heteronuclear three-dimensional NMR spectroscopy of the inflammatory protein C5aBiochemistry 28 2387-2391.

D. Marion, P.C. Driscoll, L.E. Kay, P.T. Wingfield, A. Bax, A.M. Gronenborn and G.M. Clore (1989) Overcoming the overlap problem in the assignment of proton NMR spectra of larger proteins by use of three-dimensional heteronuclear proton-nitrogen-15 Hartmann-Hahn-multiple quantum coherence and nuclear Overhauser-multiple quantum coherence spectroscopy: application to interleukin 1beta. Biochemistry 28 6150-6156.

D. Marion, L.E. Kay, S.W. Sparks, D.A. Torchia and A. Bax (1989) Three-dimensional heteronuclear NMR of nitrogen-15 labeled proteins. J. Am. Chem. Soc. 111 1515-1517.

Helena Kovacs (2003). Avance 3D/Triple Resonance Manual.