Interaction between the bio-surfactant surfactin and lipid membranes.

Abstract

The bio-surfactant Surfactin possesses antifungal, antiviral and antitumural properties. We investigated the interaction of Surfactin with lipid monolayers and vesicles applying differential scanning calorimetry (DSC), static light scattering, cryo-transmission electron microscopy (TEM) fluorescence microscopy and small angle neutron scattering (SANS). Our target was to clarify how lipid membranes are influenced by the insertion of different amounts of Surfactin: This should lead to a better understanding of the biological function of Surfactin. Low concentrations of Surfactin were solubilized in monolayers or vesibles of L-a-Di-myristoylphosphatidylcholine (DMPC) or L-a-Dipalmitoylphosphatidylcholine (DPPC) and normal phase transition behavior was observed. In the range from 4–20 % of Surfactin to lipid increasing heysteresis was characteristic for the phase behavior. At higher concentrations of Surfactin the vesicles disintegrated into mixed micelles. In addition to the thermodynamic and structural investigations we also performed temperature-jump experiments to learn about the dynamics of the lipid-Surfactin system