Improved spin-echo-edited NMR diffusion measurements.
The need for simple and robust schemes for the analysis of ligand-protein binding has resulted in the development of diffusion-based NMR techniques that can be used to assay binding in protein solutions containing a mixture of several ligands. As a means of gaining spectral selectivity in NMR diffusion measurements, a simple experiment, the gradient modified spin-echo (GOSE), has been developed to reject the resonances of coupled spins and detect only the singlets in the (1)H NMR spectrum. This is accomplished by first using a spin echo to null the resonances of the coupled spins. Following the spin echo, the singlet magnetization is flipped out of the transverse plane and a dephasing gradient is applied to reduce the spectral artifacts resulting from incomplete cancellation of the J-coupled resonances. The resulting modular sequence is combined here with the BPPSTE pulse sequence; however, it could be easily incorporated into any pulse sequence where additional spectral selectivity is desired. Results obtained with the GOSE-BPPSTE pulse sequence are compared with those obtained with the BPPSTE and CPMG-BPPSTE experiments for a mixture containing the ligands resorcinol and tryptophan in a solution of human serum albumin.
Otto
W H
WH
Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, USA.
Larive
C K
CK
D000418:Albumins / Q000737:chemistry*; D004058:Diffusion; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D012118:Resorcinols / Q000737:chemistry; D014364:Tryptophan / Q000737:chemistry*
D000418:Albumins; D012118:Resorcinols; D014364:Tryptophan; C031389:resorcinol