Computer Simulation of Surfactin Conformation at a Hydrophobic/Hydrophilic Interface

Abstract

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

Surface behavior of a model surfactant: A theoretical simulation study

“…In recent years, molecular dynamics (MD) simulations also have been widely used to investigate the molecular structures of surfactants at various interfaces or in aqueous solution [31][32][33][34][35]. Some structures and molecular orientations at the air/liquid interface predicted by these methods are in good agreement with many experimental observations [36,37].…”

Fengycin interaction with lipid monolayers at the air–aqueous interface—implications for the effect of fengycin on biological membranes

“…This gives a large area per molecule of the peptide ring. In addition, the fatty acid chain is expected to orient in such a way that it interacts intramolecularly with the hydrophobic amino acids, as shown for surfactin [21]. The hydrophobic intermolecular interactions between the fatty acid chains of adjacent molecules, and consequently, the formation of ordered aggregates are therefore unlikely.…”

Monolayer Behavior of Cyclic and Linear Forms of Surfactins: Thermodynamic Analysis of Langmuir Monolayers and AFM Study of Langmuir-Blodgett Monolayers

“…The π-A isotherm of the pure CSF monolayer indicates that CSF forms a stable Le phase at the air/water interface, probably due to the less effective van der Waals interactions between the long alkyl chains. Gallet et al calculated that the hydrophobic chains of CSF folded back to interact mainly with the Leu2 and Val4 side chains at the air/water interface 25 . In the case of LSF, such a linear molecular could adopt extended conformations to minimize steric interactions and surface area, so that LSF could adopt a dense molecular packing to form an Lc phase.…”