A sensitive pulse scheme for measuring the backbone dihedral angle ψ based on cross-correlation between 13Cα-1Hα dipolar and carbonyl chemical shift anisotropy relaxation interactions

A pulse scheme for measuring cross-correlation between C-13(alpha)-H-1(alpha) dipolar and carbonyl chemical shift anisotropy relaxation mechanisms is presented from which the protein backbone dihedral angle psi is measured. The method offers significant sensitivity gains relative to our recently published scheme for measuring psi based on this cross-correlation effect [Yang et al. (1997) J. Am. Chem. Sec., 119, 11938-11940]. The utility of the method is demonstrated with an application to a 42 kDa complex of N-15,C-13-labeled maltose binding protein and beta-cyclodextrin.