Molecular organization of surfactin-phospholipid monolayers: Effect of phospholipid chain length and polar head |
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Authors: | O Bouffioux A Berquand M Eeman M Paquot R Brasseur |
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Institution: | a Centre de Biophysique Moléculaire Numérique, Faculté Universitaire des Sciences Agronomiques de Gembloux, Passage des Déportés, 2, B-5030 Gembloux, Belgium b Unité de Chimie Biologique Industrielle, Faculté Universitaire des Sciences Agronomiques de Gembloux, Passage des Déportés, 2, B-5030 Gembloux, Belgium c Unité de Chimie des Interfaces, Université Catholique de Louvain, Croix du Sud 2/18, B-1348 Louvain-la-Neuve, Belgium |
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Abstract: | Mixed monolayers of the surface-active lipopeptide surfactin-C15 and various lipids differing by their chain length (DMPC, DPPC, DSPC) and polar headgroup (DPPC, DPPE, DPPS) were investigated by atomic force microscopy (AFM) in combination with molecular modeling (Hypermatrix procedure) and surface pressure-area isotherms. In the presence of surfactin, AFM topographic images showed phase separation for each surfactin-phospholipid system except for surfactin-DMPC, which was in good agreement with compression isotherms. On the basis of domain shape and line tension theory, we conclude that the miscibility between surfactin and phospholipids is higher for shorter chain lengths (DMPC > DPPC > DSPC) and that the polar headgroup of phospholipids influences the miscibility of surfactin in the order DPPC > DPPE > DPPS. Molecular modeling data show that mixing surfactin and DPPC has a destabilizing effect on DPPC monolayer while it has a stabilizing effect towards DPPE and DPPS molecular interactions. Our results provide valuable information on the activity mechanism of surfactin and may be useful for the design of surfactin delivery systems. |
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Keywords: | Langmuir film Atomic force microscopy Molecular modeling Miscibility Stabilizing effect Nanoscale resolution |
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