Research Seminar

The self-assembly of diphenylalanine (FF) into macroscopic nanostructures has prompted a wide variety of potential applications to be proposed including use as a nanowire scaffold, as a means for drug delivery, and as an antibacterial agent. These applications, among others, are predicated on the rational modification of FF to self-assemble into an optimized structure for a given application. While previous molecular simulations have been utilized to understand the underlying driving forces of FF self-assembly, inconsistencies in models chosen as well as a lack of quantitative analysis has resulted in conflicting conclusions. This presentation examines results from all-atom molecular dynamics simulations at various points in the FF self-assembly process from dimerization to nanotube growth. Using a free energy decomposition analysis in conjunction with order quantification analyses, we suggest initial aggregation of FF is driven by backbone electrostatics, where as solvent-mediated forces drive FF nanotube growth. Since valine-phenylalanine (VF) and phenylalanine-valine (FV) have significantly reduced aggregation, results highlighting sequence dependence will then be presented. Using molecular dynamic simulations of VF and FV monomers, differences in monomer conformation combined with water dynamics are shown to have comparable rates to unassigned experimental rates. These results are further supported by agreement in calculated IR spectra using quantum mechanical techniques to experimental IR spectra.