Interfacial behavior of surfactin at the decane/water interface: a molecular dynamics simulation.

The structural and dynamical properties of protonated surfactin molecules at the decane/water interface have been studied by molecular dynamics simulation. The rigidity of the surfactin hydration layer and the dynamics of surfactin-water and water-water hydrogen bonds have been evaluated. The simulation shows that the peptide rings slightly tilt at the interface and the aliphatic chains exhibit more extended conformation protruding into decane phase, and thus a smaller interfacial molecular area is obtained. Dynamical motions of surfactin at the interface are largely restricted by the strong polar interaction between surfactin and water molecule. Motion activities of the water molecules are decreased in the vicinity of surfactin and lead to longer lifetimes of water-water hydrogen bonds and a higher rigidity of the hydration layer. The lifetimes and the structural relaxation behaviors of surfactin-water hydrogen bonds are consistent with those of the corresponding water-water hydrogen bonds as well as the dynamics of the hydration layer water.