Determination of H(N),H (α) and H (N),C' coupling constants in (13)C, (15)N-labeled proteins.

Sensitive three-dimensional NMR experiments, based on the E.COSY principle, are presented for the measurement of the (3)J(H(N),H(α)) and (3)J(H(N),C') coupling constants in uniformly (13)C- and (15)N-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 ϕ-angle for protein structure determination. The method is applied to uniformly (13)C, (15)N-labeled ribonuclease T(1).