Polymer-peptide interfacial interactions investigated by molecular dynamics simulations

We investigated the interfacial interactions between polymers and peptides using molecular dynamics (MD) simulations. Poly(methyl methacrylate) (PMMA) and polystyrene (PS) were used as representative polymer materials, and phenylalanine dipeptide (FF), serine dipeptide (SS), and two 15-residue sequences served as model peptides. Well-equilibrated configurations were prepared via high-temperature simulations, followed by cooling. First, bulk-phase MD simulations were conducted to evaluate temperature-dependent volumetric properties. The estimated glass transition temperatures (Tg) of PMMA and PS were significantly higher than 300 K, indicating that they are in a glassy state at room temperature, while peptide aggregate Tg values were close to 300 K. Next, simulations of polymer and peptide slabs with vacuum interfaces were performed to calculate surface energies by analyzing potential energy differences between the bulk and slab configurations. The calculated surface energies of PMMA and PS were consistent with experimental surface free energy values reported in the literature, considering entropic contributions and sampling limitations. Finally, we performed MD simulations of polymer/peptide interfaces to examine cross-interface density profiles, phenyl ring orientations, and specific atomic interactions. Interfacial energies were quantified by comparing potential energies of systems with and without interfaces. Notably, polymer/peptide pairs with similar functional groups (e.g., the hydrophobic PS/FF interface) exhibited lower interfacial energies than chemically dissimilar pairs (e.g., PS/SS). A high separation energy was observed at the PMMA/SS interface, indicating favorable interactions between polar functional groups. Our computational approach introduces an alternative protocol for probing interfacial interactions of peptides and can be applied to aid the design of materials with specific interfacial properties.