A graphical method for the analysis of anisotropic rotational diffusion in proteins

A graphical method for the analysis of relaxation data is presented. It allows a fast estimation of the range of values of the components of the axially symmetric rotational diffusion tensor that are compatible with the experimental relaxation data. The graphical method clearly shows the contribution of different experimental relaxation parameters to the measured anisotropy. In particular, for proteins with moderate anisotropy, data from at least two N-H bonds forming angles close to 0 degrees and 90 degrees with respect to the principal axis of the rotational diffusional tensor are needed. For very anisotropic systems, combination of different relaxation parameters from a single residue is enough to characterize the local anisotropy.