The role of polarization and charge transfer in the solvation of biomolecules

Herein we demonstrate that charge transfer from the protein to the first solvation layer is a significant contributor to the total solvation interaction energy between water and major cold shock protein A (CspA). Interestingly, we find that polarization and electrostatic interactions are predicted to be less important in protein-water interactions than charge transfer. Charge transfer is most prominent for charged residues, but also occurs between water molecules and the hydrophilic side chains and the carbonyl and amide groups of the main chain. The route of charge transfer is via hydrogen bonds between protein and solvent. These results an consistent with recent NMR and X-ray observations, which show that hydrogen bonding interactions have a significant covalent character as opposed to the traditional purely electrostatic view.