Origin of the anomalous diffusion observed by MD simulation at the protein-water interface

Our recent molecular dynamics simulations of water-plastocyanin systems have shown evidence of a sublinear trend in time, for long times, of the mean square displacements of water oxygens. In this Letter, we extensively analyze the role played by the spatial (protein surface roughness) and temporal (distribution of water residence times) disorder intrinsic to the systems investigated in determining the observed anomalous diffusion process. Moreover, the occurrence of a correlated motion of waters, due to the glassy character of the protein-water interface, is explored in the framework of mode coupling theory.