(193q) Hydrophobic Surface Significantly Alters the Conformational Equilibria of Polyglycine

Polyglycine a poly-secondary amide is a useful model to study generic polypeptide backbones. Previous results using Molecular dynamics simulations show that polyglycine forms disordered globules in water. In this, study we have performed extensive Replica Exchange Molecular Dynamics simulations of sixteen residue polyglycine sequences in bulk, and near Hydrophobic Self-Assembled monolayer surfaces. The simulations have been performed using the Amber03w forcefield for the protein and the Tip4p/2005 model of water molecules. The Self-Assembled monolayer (SAM) surface has been modeled using two surfactant chains each comprising C10 alkane chains with -CH3 head group at one end attached to sulfur atoms whose positions are fixed in space. The SAM surface has been modeled using the Amber03 Parm-94 forcefield. We observe that at 300K, polyglycine remains adsorbed near the surface of the SAM. Interestingly we observe significant propensity of beta-sheets stabilized by intra-peptide hydrogen bonds near the SAM surface. These results highlight the modulation of the conformational equilibria of polyglycine by hydrophobic surfaces suggesting modulation of intrinsic preferences of peptide backbones near hydrophobic surfaces.