Water as the natural environment for life plays a substantial role in the solvation and molecular processes of all biological molecules. One of the key advancements in the understanding of aqueous solvation was the discovery of the existence of a hydration crossover lengthscale with large implications for the interpretation of microscopic water hydration structure and macroscopic hydration thermodynamics. While those lengthscale and curvature effects are well understood now for static properties of water, their impact on dynamical features, such as water mobility or fluctuations, has remained essentially unexplored. In this study we present an investigation of the curvature dependence of water dynamics at hydrophobic solutes by using Molecular Dynamics simulations of SPC/E water at differently sized spherical model surfaces.
We determine the crossover lengthscale by means of structural correlations. As collective dynamical properties we present calculations of positional and density fluctuations of the hydrating water interface. These are put into the contextual findings of previous research.
As an important novel insight into the subject we present the dependence of water molecule mobility on surface curvature. We find that the diffusional behavior and the sojourn times of water molecules at hydrophobic surfaces strongly depend on surface curvature. In addition the curvature dependence exhibits a nonmonotonic progression as it is already known for water hydration structure.
Our study demonstrates the existence of an intimate connection between static and dynamic curvature effects of hydrophobic hydration. Large implications arise for the interpretation of dynamical measurements of hydration at heterogeneous biomolecular surfaces with varying surface geometry.