The Effect of Side-Chain Polarity and Solvation Layers on the Interaction of Amino Acids with ZnS Surface: Adsorption Free Energies from Molecular Dynamics Simulations

Interaction of proteins with inorganic surfaces are of high importance in biological events and biotechnological applications [1-3]. However, the underlying interactions are still not well understood. Here, the adsorption of different amino acids as protein building blocks onto a ZnS (110) is investigated. In this study, Molecular dynamics simulations (MD) combined with umbrella sampling technique are carried out to determine potentials of mean force (PMF) for amino acids in aqueous environment near the surface. According to the adsorption profiles of the strongest binding side chains, two regions can be identified. The density profile of water near surface shows undulations which are symmetrical to the pattern of maxima and minima in energy profiles. Depending on the size and polarity of the side chain, amino acid can adsorb to the first or second solvation layer. These observations reveal the strong dependence of adsorption energy and binding conformation on the chemical character of amino acid and its side chain. The simulations also emphasize the key role of solvation layer in adsorption of biomolecules at inorganic surfaces.