New techniques for the measurement of C ' N and C ' H-N J coupling constants across hydrogen bonds in proteins

Two new two- or three-dimensional NMR methods for measuring (3h)J(C'N), and (2h)J(C'H), coupling constants across hydrogen bonds in proteins are prese nted, They are tailored to suit the size of the TROSY effect, i.e., the deg ree of interference between dipolar and chemical shift anisotropy relaxatio n mechanisms. The methods edit 2D or 3D spectra into two separate subspectr a corresponding to the two possible spin states of the H-1(N) Spin during e volution of (CO)-C-13 coherences, This allows (2h)J(C'H) to be measured in an E.COSY-type way while (3h)J(C'N) can be measured in the so-called quanti tative way provided a reference spectrum is also recorded, A demonstration of the new methods is shown for the N-15,C-13-labeled protein chymotrypsin inhibitor 2. (C) 2000 Academic Press.