Peptide-TiO₂ interaction in aqueous solution: Conformational dynamics of RGD using different water models

Adsorption behavior and dynamics of Arg-Gly-Asp (RGD) tripeptides with different orientations onto the rutile TiO₂ (110) surface in water solution were systematically investigated by molecular dynamics (MD) simulations, using two different water models, TIP3P (transferable intermolecular potential 3P) and SPC/E (extended simple point charge). Possible RGD-TiO₂ binding modes in the form of hydrogen-bonding interactions, involving the amide groups (NH₃⁺ or NH₂ ⁺, NH₂) and surface oxygen atoms were identified. The behavior of RGD in contact with the TiO₂ layer was elucidated in detail by the analysis of atom-atom distances, backbone dihedral angles and hydration layers distributed over the interface. The simulation results suggest that, the attachment modes of tripeptides with the same starting arrangement are similar when solvated in TIP3P and SPC/E water, but the conformational stability of the amino sequence is somewhat sensitive to the adopted solvent model. Moreover, the intensity of peptide-surface interaction varies widely depending on the initial arrangement of the RGD sequence.