Computer simulation of surfactin conformation at a hydrophobic/hydrophilicinterface

Using a molecular modeling method, different conformations of surfactin at a hydrophobic/hydrophilic interface are established. Two conformations of t he peptide ring (S1 and S2) provided by NMR experiments built with three di fferent aliphatic chains in folded or extended configurations were studied. For the structures including the S2 peptide ring conformation, the theoret ical interfacial molecular area corresponds to the experimental limiting ar ea A(0) value obtained with a Langmuir film balance. The peptide ring is po sitioned in the plane of the interface with the two acidic chains close to each other and protruding in the aqueous phase, and the beta-hydroxy fatty acid chain, folded to interact mainly with the Leu2 side chain and also wit h the Val4 side chain. This design has the largest calculated molecular are a and would correspond to the most stable amphipathic structure representin g the surfactin experimental behavior in weak compression.