GRADIENT-ENHANCED PROTON-DETECTED HETERONUCLEAR NMR AT IMPROVED RESOLUTION

The two-dimensional gradient-enhanced heteronuclear multiple-quantum e xperiment, ge-HMQC, can be modified to produce spectra that are unaffe cted by magnetic field inhomogeneity broadening along the evolution di mension. Two sequences are proposed. In the first one, ge-SHARP1-HMQC, refocusing is accomplished by asymmetric partitioning of the evolutio n time. In the second, ge-SHARP-HMQC, an additional heteronuclear 180 degrees pulse is applied during the evolution time. The two sequences differ in their response to the evolution of heteronuclear scalar coup lings and chemical shifts. Results on model solutions demonstrate the expected immunity of the C-13 spectral resolution to poor shimming and the concomitant higher detection sensitivity of the narrowed signals. (C) 1994 Academic Press, Inc.