Determination of backbone angle psi in proteins using a TROSY-based alpha/beta-HN(CO)CA-J experiment

Transverse relaxation-optimized NMR experiment (TROSY) for the measurement of three-bond scalar coupling constant between H-1(i-1 alpha) and N-15(i) d efining the dihedral angle psi is described. The triple-spin-state-selectiv e experiment allows measurement of (3)J(H alpha N) from C-13(alpha), N-15, and H-1(N) correlation spectra H2O with minimum resonance overlap. Transver se relaxation of C-13(alpha) spin is minimized by using spin-state-selectiv e filtering and by acquiring a signal longer in N-15-dimension in a manner of semi-constant-time TROSY evolution. The (3)J(H alpha N) values obtained with the proposed alpha/beta-HN(CO)CA-J TROSY scheme are in good agreement with the values measured earlier from ubiquitin in D2O using the HCACO[N] e xperiment. (C) 2000 Academic Press.