Self-Assembly of Diphenylalanine Peptides on Graphene via Detailed Atomistic Simulations

The self-assembly of diphenylalanine peptides (FF) on a graphene layer, in aqueous solution, is investigated, through all atom Molecular Dynamics simulations. Two interfacial systems are studied, with different concentration of dipeptides and results are compared with an aqueous solution of FF at room temperature. Length and time scales of the formed structures are quantified providing important insight into the adsorption mechanism of FF onto the graphene surface. A hierarchical formation of FF structures is observed involving two sequential processes: first, a stabilized interfacial layer of dipeptides onto the graphene surface is formulated, followed by the development of a structure of self-aggregated dipeptides on top of this layer. The whole procedure is completed in almost 200ns, whereas self-assembly in the system without graphene is accomplished much faster; in less than 50ns cylindrical structures, signal of the macroscopic fibrilliar ones, are formed. Strong π – π* interactions between FF and the graphene lead to a parallel to the graphene layer orientation of the phenyl rings. Reduction in the number of hydrogen bonds between FF peptides is observed because of the graphene layer, since it disturbs their self-assembly propensity.