(3h)J coupling between C-alpha and H-N across hydrogen bonds in proteins

J couplings between C-13(alpha) and H-1(N) across hydrogen bonds in protein s are reported for the first time, and a two- or three-dimensional NMR tech nique for their measurement is presented. The technique exploits the TROSY effect, i.e., the degree of interference between dipolar and chemical shift anisotropy relaxation mechanisms, for sensitivity enhancement. The 2D or 3 D spectra exhibit E.COSY patterns where the splittings in the (CO)-C-13 and H-1(N) dimensions are (1)J(C-13(alpha), (CO)-C-13) and the desired (3h)J(C -13(alpha), H-1(N)), respectively. A demonstration of the new method is sho wn for the N-15, C-13-labeled protein chymotrypsin inhibitor 2 where 17 (3h )J(C-13(alpha), H-1(N)) coupling constants ranging from 0 to 1.4 Hz where i dentified and all of positive sign. (C) 2000 Academic Press.