Molecular dynamics study of a protein-water interface: the role of bound water

Abstract

We have calculated the reorientational time correlation function Cμ(t) of water dipoles in the aqueous protein (1ETN) solutions for various protein concentrations at two different temperatures (300 K and 350 K) using atomistic molecular dynamics simulation studies. The reorientational time correlation function follows an exponentially decaying function of the form Cμ(t)=Aexp(-t/τ) , where A represents the percentage of water dipoles reorienting with an average time constant τ. We find that, with increasing protein concentration, the parameter A or the number of freely reorienting dipoles decreases considerably for both temperatures studied and more so at the higher temperature. We infer that this decrease in the number of freely reorientating water molecules may be related to some of the water molecules bound to the protein back bone.