DETERMINATION OF H(N),H-ALPHA AND H(N), C' COUPLING-CONSTANTS IN C-13,N-15-LABELED PROTEINS

Sensitive three-dimensional NMR experiments, based on the E.COSY principle, are presented for the measurement of the 3J(H(N),H(alpha) and 3J(H(N),C') coupling constants in uniformly C-13- and N-15-labeled proteins. They employ gradient coherence selection in combination with the sensitivity enhancement method in HSQC-type spectra (Cavanagh et al., 1991; Palmer et al., 1991). In most cases, the two measured coupling constants unambiguously define the phi-angle for protein structure determination. The method is applied to uniformly C-13,N-15-labeled ribonuclease T1.