Role of Surface Coordination and Thiol–Amine Cooperative Interactions in Cysteine Adsorption on Nanostructured Gold

The interaction of cysteine and related amino acid thiols with metal substrates has applications in several fields of science, technology and health. Despite widespread interest in these systems, the relationship between thiol adsorption and surface coarsening, including the effects of surface adatoms and other defect sites, has not been systematically addressed. Here, the effect of binding site unsaturation on the adsorption strength of l-cysteine on gold substrates is examined using density functional theory. Adsorption sites with a full range of in-surface coordination numbers are generated using surface adatoms or pitting structures. The configurational space of the adsorbate on the nanostructured surface is sampled extensively using Born–Oppenheimer molecular dynamics simulation. Our results indicate that binding strength is primarily determined by a combination of surface site reactivity to the mercapto group and the availability of additional sites for amino group coordination. The study aims to further our understanding of amino acid binding to substrates with defects and low-coordinated nanoparticle sites, and to provide a basis for the development of coordination-dependent force fields that may be used in classical simulations of these systems.