LARGE-AMPLITUDE NONLINEAR MOTIONS IN PROTEINS

A molecular-dynamics calculation on a hydrated protein, crambin, demonstrates that (i) neighboring dihedral angles are correlated to local transitions in the protein backbone, and that (ii) the amplitude of collective excitations, representing correlated global motions in the protein, samples multicentered distributions. The time dependence of the multicentered dihedral and collective excitations show rapid transitions from the center of one distribution to another, followed for some time by damped, low-amplitude motions around one center. The global nonlinear collective excitations are responsible for most of the atomic fluctuations of the molecule. An analysis appropriate to multimodal conformations is reported.