Anisotropy of rotational diffusion, dipole-dipole cross-correlated NMR relaxation and angles between bond vectors in proteins

Cross correlations between the fluctuations of dipolar C-13(alpha)-H-1(alph a) interactions yield information about the relative orientation of success ive C-13 alpha-H-1(alpha) bond vectors in proteins, in turn providing a dir ect handle on their structure and dynamics in solution. However, overall an isotropic reorientation must be taken into account in the interpretation of cross-correlation rates. The protein shown, human ubiquitin, has amino aci d residues in white where the cross-correlation rates deviate from those pr edicted for a rigid structure.