Pulse schemes for the measurement of (3)J(C'C gamma) and (3)J(NC gamma) scalar couplings in N-15,C-13 uniformly labeled proteins

Pulse sequences are presented for the measurement of (3)J(C'C gamma) and (3)J(NC gamma) scalar couplings for all C-gamma containing residues in N-15,C-13 uniformly labeled proteins. The methods described are based on quantitative J correlation spectroscopy pioneered by Bar and co-workers [Bar et al. (1994) Methods Enzymol., 239, 79-105]. The combination of (3)J(C'C gamma) and (3)J(NC gamma) scalar coupling constants allows the assignment of discrete rotameric states about the chi(1) torsion angle in cases where such states exist or, alternatively, facilitates the establishment of noncanonical chi(1) conformations or the presence of rotameric averaging. The methods are applied to a 1.5 mM sample of staphylococcal nuclease.