Simulation of adhesion forces and energies of peptides on titanium dioxide surfaces

Force field molecular dynamics simulations on a decapeptide in contact with a rutile (100) surface in aqueous solution are reported. The peptide sequence is part of α(1)-collagen. Force-distance curves yield discrete peaks to the rupture of charged lysine and glutamate side chains from the surface according to the model of contact points. The rupture forces are 0.2-2.2 nN, and the values strongly depend on the charges of surface hydroxyl groups. Adhesion energies are evaluated from the areas of the rupture peaks. For proton charges of 0.4 and 1, adhesion energies between 40 and 190 kJ/mol were found being comparable to recent ab initio molecular dynamics results. Flips in the torsional angles of the peptide are observed during restrained desorption. The partial charges of hydroxyproline are revised, and the polarization of the C(β)-C(γ) bond as well as the ring pucker conformations are taken into account. It is shown that transition from collagen to helix fold is more likely for hydroxyproline than for proline and might be relevant for differences in the properties of POG (proline, hydroxyproline, glycine) and PPG collagen sequences.