ROLE OF INTERFACIAL WATER IN THE MOLECULAR DYNAMICS-SIMULATED DYNAMICAL TRANSITION OF PLASTOCYANIN

Molecular dynamics simulations of dry and partially hydrated plastocya nin have been performed at 13 temperatures, in the 20-350 K range, for 600 ps to investigate the role of hydration water on the thermal acti vation of protein dynamics. The analysis of results points out that a sharp dynamical transition occurs in the hydrated protein at about 220 K; such a transition appearing to be smeared out in the dry protein. The dynamical transition, which is much more marked for the solvent-ex posed side chains than for the C-alpha atoms, is strongly coupled to t he hydrogen bond network restructuring dynamics involving the interfac ial water. (C) 1998. Published by Elsevier Science B.V. All rights res erved.