In order to gain a better understanding of the dynamics of water in protein solvation shells, we carry out a molecular dynamics simulations of aqueous solutions of amphiphilic and hydrophilic peptides at a range of concentrations. The goal of our study is to determine how these dynamics are reflected in the responses measured in these systems by optical Kerr effect (OKE) and extended depolarized light scattering (EDLS). Both responses arise from relaxation of the collective polarizability anisotropy of the solution, but emphasize different dynamic ranges. The specific systems that we investigate are aqueous solutions of N-acetyl-glycine-methylamide (NAGMA) and N-acetyl-leucine-methylamide (NALMA). We analyze the polarizability anisotropy response in terms of contributions from solute, solvent and their interactions and cross-correlations. We relate the solvation-shell polarizability contributions to water population in the solvation shells, its hydrogen bonding to the solute and, in the case of NALMA, its hydrophobic contacts with the solute. The effects of solute clustering and overlap of solvation shells at higher concentrations will be discussed.

Water dynamics in aqueous solutions of hydrophilic and amphiphilic peptides: Molecular simulation study of polarizability anisotropy response

249th National Meeting (2015)

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