A protein backbone psi and phi angle dependence of 2J(N(i),C alpha(i-1)): the new NMR experiment and quantum chemical calculations.

A new pulse sequence exploiting double- and zero-quantum evolution of two-spin 15N-13C' coherence is proposed for the accurate measurements of 2J(N(i),C alpha(i-1)) coupling constants. Application of the new experiment is presented for 13C,15N-labeled ubiquitin sample. The density functional theory calculations of 2J(N(i),C alpha(i-1)) coupling constants have been performed to study their dependence on both psi(i - 1) and phi(i - 1) angle in model peptides, and the results exhibit a good correlation with experimental data.