Local Structure and Dynamics of Hydration Water in Intrinsically Disordered Proteins.

Hydration water around protein surface plays a key role in structure, folding and dynamics of proteins. Intrinsically disordered proteins lack secondary and/or tertiary structure in their native state. Thus, characterizing the local structure and dynamics of hydration water around disordered proteins is challenging for both experimentalists and theoreticians. The local structure, orientation and dynamics of hydration water in the vicinity of intrinsically disordered proteins is investigated through molecular dynamics simulations. The analysis of the hydration capacity reveals that the disordered proteins have much larger binding capacity for hydration water than globular proteins. The surface and radial distribution of water molecules around the disordered proteins depict a similar trend. The local structure of the hydration water evaluated in terms of the tetrahedral order parameter, shows a higher order among the water molecules surrounding disordered proteins/regions. The residence time of water molecules clearly exhibits slow dynamics of hydration water around the surface of disordered proteins/regions as compared to globular proteins. The orientation of water molecules is found to be distinctly different for ordered and disordered proteins/regions. This analysis provides a better insight into the structure and dynamics of hydration water around disordered proteins.