Effects of osmolytes on the helical conformation of model peptide: molecular dynamics simulation.

Co-solvents such as glycerol and sorbitol are small organic molecules solvated in the cellular solutions that can have profound effects on the protein structures. Here, the molecular dynamics simulations and comparative structural analysis of magainin, as a peptide model, in pure water, 2,2,2-trifluoroethanol∕water, glycerol∕water, and sorbitol∕water are reported. Our results show that the peptide NMR structure is largely maintained its native structure in osmolytes-water mixtures. The simulation data indicates that the stabilizing effect of glycerol and sorbitol is induced by preferential accumulation of glycerol and sorbitol molecules around the nonpolar and aromatic residues. Thus, the presence of glycerol and sorbitol molecules decreases the interactions of water molecules with the hydrophobic residues of the peptide, and the alpha helical structure is stabilized.