| Abstract
| - We study the role of hydration water in the dynamic transition of low-hydrated proteins upon pressurizationfound recently (Meinhold, L.; Smith, J. C. Phys. Rev. E2005, 72, 061908). Clustering and percolation ofwater in the hydration shells of protein molecules in crystalline Staphylococcal nuclease are analyzed atvarious pressures. The number of water molecules in the hydration shell increases and the hydrogen-bondednetwork of hydration water spans with increasing pressure. The dynamic transition of protein occurs whenthe spanning water network exists with the probability of about 50% and hydration water shows large densityfluctuations. Formation of a spanning water network upon pressurization promotes protein dynamics as inthe case of the dynamic transition with increasing hydration. Properties of hydration water in variousthermodynamic states and their influence on biological function are discussed.
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