A many-body effect renders universal sub-diffusion of water on the surface of different proteins

Dynamics of interfacial water is critical for the function of the enclosed protein. By combining neutron scattering and molecular dynamics simulation on proteins with different surface structures and chemistries including intrinsically disordered proteins, demonstrated that, although the average mobility of the interfacial water molecules depends on the structure of the underlying proteins, they present a universal sub-diffusive motion with a common power law. Further analysis of the simulation trajectories, and analytical modeling reveal that it is the inter-water volume-exclusion effect that overrides the surface differences among proteins and renders the surface water a universal sub-diffusive power law. The present findings significantly recast existing ideas in molecular biophysics that assumes the water dynamics is strongly regulated by the surface properties of the enclosed protein. Instead, we showed that, the power law of diffusive motion of hydration water is independent of the underlying protein and this independence results from the inter-water interaction, which has been rarely considered in the past when describing the diffusion of interfacial water.