(677c) Self-Assembly of Peptide Amphiphiles Into Hydrogel Via Multiscale Simulations

Peptide amphiphiles (PA), which are an emerging class of molecules that have been shown to self-assemble into novel nanostructures such as nanofibers or hydrogel, are of significant interest due to their applications in tissue engineering. A representative PA molecule is comprised of a hydrophobic alkyl tail, a short peptide sequence for intermolecular hydrogen bonding, a group of charged amino acids for enhanced solubility, and a region for bioactive signals to be transduced via cells or proteins. Our studies examine the role of peptide sequences and the conditions on the morphology and mechanical properties of PA molecule assemblies by performing molecular dynamics simulations. Using a newly extended intermediate-resolution protein model that can represent twenty different amino acids with adequate details, we focus on the folding of peptides with or without the alkyl segment as a function of the various conditions such as pH, ion concentrations, or temperature and compare our results with those obtained from all-atom simulations using CHARMM. To examine the kinetic mechanisms involved in PA self-assembly, we perform constant-temperature simulations to observe the whole process of PA assembly starting from random configurations of relatively large PA systems. We also perform replica-exchange simulations to delineate a phase diagram characterizing different types of structure exhibited for each sequence as a function of the condition being examined. The findings of this research will guide experimentalists to identify systems of novel biomaterials with advantageous mechanical properties.