Anisotropy of Rotational Diffusion, Dipole-Dipole Cross-Correlated NMR Relaxation and Angles between Bond Vectors in Proteins

Cross correlations between the fluctuations of dipolar (13)C(α)-(1)H(α) interactions yield information about the relative orientation of successive (13)C(α)-(1)H(α) bond vectors in proteins, in turn providing a direct handle on their structure and dynamics in solution. However, overall anisotropic reorientation must be taken into account in the interpretation of cross-correlation rates. The protein shown, human ubiquitin, has amino acid residues in white where the cross-correlation rates deviate from those predicted for a rigid structure.