Transverse relaxation-optimized NMR experiment (TROSY) for the measurement of three-bond scalar coupling constant between 1 H α i−1 and 15 N i defining the dihedral angle ψ is described. The triple-spin-state-selective experiment allows measurement of 3 JH α N from 13 C α , 15 N, and 1 H N correlation spectra H 2 O with minimum resonance overlap. Transverse relaxation of 13 C α spin is minimized by using spin-state-selective filtering and by acquiring a signal longer in 15 N-dimension in a manner of semi-constant-time TROSY evolution. The 3 JH α N values obtained with the proposed α/β-HN(CO)CA-J TROSY scheme are in good agreement with the values measured earlier from ubiquitin in D 2 O using the HCACO[N] experiment.