GRADIENT-ENHANCED TRIPLE-RESONANCE 3-DIMENSIONAL NMR EXPERIMENTS WITH IMPROVED SENSITIVITY

The sensitivities of a number of gradient and nongradient versions of triple-resonance experiments are compared by quantitating the signal-to-noise ratios in spectra recorded on Cellulomonas fimi cellulose binding domain (110 amino acids), Xenopus laevis calmodulin (148 amino acids), Mycococcus xanthus protein S (173 amino acids), and a 93-amino acid fragment of protein S. It is shown that it is possible to construct sensitivity-enhanced gradient experiments, with N-15 selection achieved via pulsed field gradients, that are as sensitive as their sensitivity-enhanced nongradient counterparts and significantly more sensitive than other gradient approaches. These sequences are very closely related to the family of improved-sensitivity sequences proposed by Rance and co-workers (A. G. Palmer, J. Cavanagh, P. E. Wright, and M. Rance, J. Magn. Reson. 93, 151, 1991). The use of gradients greatly improves the quality of water suppression and reduces both the number of artifacts and the phase-cycling requirements at no cost in sensitivity for the proteins considered in this study. (C) 1994 Academic Press, Inc,