Simulation of Gold Functionalization with Cysteine by Reactive Molecular Dynamics

The anchoring mechanism of cysteine to gold in water solution is characterized in detail by means of a combination of quantum chemistry (QC) and reactive classical molecular dynamics (RC-MD) calculations. A possible adsorption reaction route is proposed, through RC-MD simulations based on a modified version of the protein reactive force field (ReaxFF), in which gold protein interactions have been included after accurate parametrization at the QC level. The computational results confirm recent experimental findings regarding the mechanism as a two-step binding, namely, a slow physisorption followed by a fast chemisorption. The reaction barriers are estimated through the nudged elastic band approach and checked by QC calculations. Surface reconstructions, induced by the strong adsorption of the molecule, are identified, and their role, as further adsorbate stabilizers, is properly disclosed. The satisfactory agreement with QC data and experiments confirm the reliability of the simulations and the unique opportunity they provide to follow locally molecule adsorption on selected materials.