Self-Assembly of Peptides on Montmorillonite Nanoparticles
Short peptides (8 to 12 amino acids) in aqueous solution bind selectively to various nanoparticles such as montmorillonite depending on the sequence of amino acids. Of several million peptides automatically screened by phage display techniques, adsorption of the two most strongly binding peptides has been studied by molecular dynamics simulation with an accurate force field for clay minerals to elucidate details of the mechanism as well as adsorption energies. The peptides typically are surrounded by a swollen layer of alkali cations on the surface, and major factors for binding appear to be the interaction between the alkali cations and polar groups in the peptide as well as the exchange of lysine side groups against alkali ions on the surface, which is nicely seen in the simulation. A quantitative analysis of the adsorption energies and changes in backbone conformation relative to solution, including Ramachandran plots, average mobility of peptide groups and orientational correlation parameters, provide further details on the mechanism of self-assembly of peptides on sheet silicates. The results are evaluated in the context of available experimental data.