Chemical shift anisotropy tensors of carbonyl, nitrogen, and amide proton nuclei in proteins through cross-correlated relaxation in NMR spectroscopy

The principal components and orientations of the chem. shift anisotropy (CSA) tensors of the carbonyl (C'), nitrogen (N), and amide proton (HN) nuclei of 64 distinct amide bonds in human ubiquitin have been detd. in isotropic soln. by a set of 14 complementary auto- and cross-correlated relaxation rates involving the CSA interactions of the nuclei of interest and several dipole-dipole (DD) interactions. The CSA parameters thus obtained depend to some degree on the models used for local motions. Three cases have been considered: restricted isotropic diffusion, three-dimensional Gaussian axial fluctuations (3D-GAF), and independent out-of-plane motions of the NHN vectors with respect to the peptide planes. [on SciFinder (R)]