Coincidence of dynamical transitions in a soluble protein and its hydration water: direct measurements by neutron scattering and MD simulations.

The coupling between protein dynamics and hydration-water dynamics was assessed by perdeuteration, temperature-dependent neutron scattering, and molecular dynamics simulations. Mean square displacements of water and protein motions both show a broad transition at 220 K and are thus coupled. In particular, the protein dynamical transition appears to be driven by the onset of hydration-water translational motion.