A computational study of the properties of water near a stable peptide surface

The properties of water near a stable peptide are not well understood. An understanding of these properties and how to manipulate them could lead to novel ideas in peptide preservation. The objective of our research was to study the properties of water near a small, stable peptide. In this study we have chosen a pentapeptide that predominantly remains in a stable secondary structure, the alpha-helix. We examine this peptide at 250, 275, and 300 K through an analysis of the structure and dynamics of water near the peptide surface. The presence of a peptide molecule disrupts the tetrahedral arrangement of nearby water molecules and restricts their translational and rotational ability. These destructuring effects are a direct result of steric constraints imposed by the peptide molecule and are further influenced by the peptide's ability to form intramolecular hydrogen bonds. The ability of the peptide to form stable hydrogen bonds with water is at the root of the slow dynamics of water near the peptide surface. The peptide's presence also induces an evident decoupling between the translational and rotational motions of nearby water molecules. The formation of intramolecular hydrogen bonds results in an increase in translational order around the atoms involved lowering the translational diffusion.