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 princ iple, 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 prote ins. 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 c onstants unambiguously define the phi-angle for protein structure dete rmination. The method is applied to uniformly C-13,N-15-labeled ribonu clease T1.