Protein adsorption mechanisms on solid surfaces: lysozyme-on-mica

A methodology for discovering the mechanisms and dynamics of protein clustering on solid surfaces is reviewed and complemented by atomistic molecular dynamics (MD) simulations. In situ atomic force microscopy images of the early stages of protein film formation are quantitatively compared with Monte Carlo simulations, using cluster statistics to differentiate various growth models. We have studied lysozyme adsorption on mica as a model system, finding that all surface-supported clusters are mobile with diffusion constant inversely related to cluster size. Furthermore, our results suggest that protein monomers diffusing to the surface from solution only adhere to the bare surface with a finite probability. Fully atomistic MD simulations reveal that the lysozyme does indeed have a preferred orientation for binding to the surface, so that proteins with incorrect orientations move away from the surface rather than towards it. Agreement with experimental studies in the literature for the residues involved in the surface adsorption is found.