Pulse schemes for the measurement of3 JC′Cγ and3 JNCγ scalar couplings in 15N,13C uniformly labeled proteins

Pulse sequences are presented for the measurement of3JC′Cγ and3JNCγ scalar couplings for allCγ containing residues in15N,13C uniformly labeled proteins. The methodsdescribed are based on quantitative J correlation spectroscopy pioneered byBax and co-workers [Bax et al. (1994) Methods Enzymol., 239, 79–105].The combination of 3JC′Cγ and3JNCγ scalar coupling constants allows theassignment of discrete rotameric states about the χ1 torsion angle in cases where such states exist or, alternatively,facilitates the establishment of noncanonical χ1conformations or the presence of rotameric averaging. The methods areapplied to a 1.5 mM sample of staphylococcal nuclease.