Dynamical Transition of Myoglobin and Cu／Zn Superoxide Dismutase Revealed by Molecular Dynamics Simulation

We have carried out parallel moecular dynamics simulations of solvated and non-solvated myoglobin and solvated Cu/Zn superoxide dismutase at different temperatures.By analysis of several methods,the simulati8ons reproduce the quasielastic neutron scattering experimental reults.Below 200K these two proteins behave as harmonic solids with essentially only vibrational motion,while above this temperature,there is a striking dynamic transition into anharmonic motion.Moreover,the simulations further show that water molecules play an important role for this dynamical transition.There is no such sharp dynamical transition in non-solvated proteins and the higher the solvate density is ,the steeper at transition point the curve of mean square displacement versus temperature will be.The simulations also display that the dynamical transition is a general propoerty for globular protein and this transition temperature is a demarcation of enzyme activity.