title: Nanoscale membrane activity of surfactins: influence of geometry, charge and hydrophobicity.
abstract: We used real-time atomic force microscopy (AFM) to visualize the interactions between supported lipid membranes and well-defined surfactin analogs, with the aim to understand the influence of geometry, charge and hydrophobicity. AFM images of mixed dioleoylphosphatidylcholine/dipalmitoylphosphatidylcholine (DOPC/DPPC) bilayers recorded after injection of cyclic surfactin at 1 mM, i.e. well-above the critical micelle concentration, revealed a complete solubilization of the bilayers within 30 min. A linear analog having the same charge and acyl chains was able to solubilize DOPC, but not DPPC, and to promote redeposition leading eventually to a new bilayer. Increasing the charge of the polar head or the length of the acyl chains of the analogs lead to the complete solubilization of both DOPC and DPPC, thus to a stronger membrane activity. Lastly, we found that at low surfactin concentrations (40 microM), DPPC domains were always resistant to solubilization. These data demonstrate the crucial role played by geometry, charge and hydrophobicity in modulating the membrane activity (solubilization, redeposition) of surfactin. Also, this study suggests that synthetic analogs are excellent candidates for developing new surfactants with tunable, well-defined properties for medical and biotechnological applications.
authors.affiliation: Unité de chimie des interfaces, Université catholique de Louvain, Croix du Sud 2/18, B-1348 Louvain-la-Neuve, Belgique.
authors.forename: Grégory
authors.initials: G
authors.lastname: Francius
authors.forename: Samuel
authors.initials: S
authors.lastname: Dufour
authors.forename: Magali
authors.initials: M
authors.lastname: Deleu
authors.forename: Michel
authors.initials: M
authors.lastname: Paquot
authors.forename: Marie-Paule
authors.initials: MP
authors.lastname: Mingeot-Leclercq
authors.forename: Yves F
authors.initials: YF
authors.lastname: Dufrêne
mesh_terms: D000595:Amino Acid Sequence; D008051:Lipid Bilayers / Q000737:chemistry*; D055666:Lipopeptides / Q000737:chemistry* / Q000235:genetics; D008563:Membrane Lipids / Q000737:chemistry; D018625:Microscopy, Atomic Force; D010456:Peptides, Cyclic / Q000737:chemistry* / Q000235:genetics; D010713:Phosphatidylcholines / Q000737:chemistry; D013499:Surface Properties
chemical_list: D008051:Lipid Bilayers; D055666:Lipopeptides; D008563:Membrane Lipids; D010456:Peptides, Cyclic; D010713:Phosphatidylcholines; C480658:didecanoylphosphatidylcholine; C009365:surfactin peptide; C017251:1,2-oleoylphosphatidylcholine