Structural dynamics of erabutoxin b. A 13C nuclear magnetic resonance relaxation study of methyl groups

A detailed examination has been made of the 13C NMR relaxation times of the assigned methyl groups of erabutoxin b. Anisotropic rotation was analysed using a restricted diffusion model. The results are compared with a previous study of the 1H NMR relation times. There is good agreement on the segments of the molecule which show restricted motion. Our results are compared with those of previous studies on proteins in solution and in crystals and again the general agreement is good. We have attempted to interpret the value of the limited motion seen in the protein to the reactions of the neurotoxin.