title: Effects of surfactin on membrane models displaying lipid phase separation.
abstract: Surfactin, a bacterial amphiphilic lipopeptide is attracting more and more attention in view of its bioactive properties which are in relation with its ability to interact with lipids of biological membranes. In this work, we investigated the effect of surfactin on membrane structure using model of membranes, vesicles as well as supported bilayers, presenting coexistence of fluid-disordered (DOPC) and gel (DPPC) phases. A range of complementary methods was used including AFM, ellipsometry, dynamic light scattering, fluorescence measurements of Laurdan, DPH, calcein release, and octadecylrhodamine B dequenching. Our findings demonstrated that surfactin concentration is critical for its effect on the membrane. The results suggest that the presence of rigid domains can play an essential role in the first step of surfactin insertion and that surfactin interacts both with the membrane polar heads and the acyl chain region. A mechanism for the surfactin lipid membrane interaction, consisting of three sequential structural and morphological changes, is proposed. At concentrations below the CMC, surfactin inserted at the boundary between gel and fluid lipid domains, inhibited phase separation and stiffened the bilayer without global morphological change of liposomes. At concentrations close to CMC, surfactin solubilized the fluid phospholipid phase and increased order in the remainder of the lipid bilayer. At higher surfactin concentrations, both the fluid and the rigid bilayer structures were dissolved into mixed micelles and other structures presenting a wide size distribution.
authors.affiliation: Université de Liège, Gembloux Agro-Bio Tech, Unité de Chimie Biologique Industrielle, Passage des Déportés, 2, B-5030 Gembloux, Belgium. magali.deleu@ulg.ac.be
authors.forename: Magali
authors.initials: M
authors.lastname: Deleu
authors.forename: Joseph
authors.initials: J
authors.lastname: Lorent
authors.forename: Laurence
authors.initials: L
authors.lastname: Lins
authors.forename: Robert
authors.initials: R
authors.lastname: Brasseur
authors.forename: Nathalie
authors.initials: N
authors.lastname: Braun
authors.forename: Karim
authors.initials: K
authors.lastname: El Kirat
authors.forename: Tommy
authors.initials: T
authors.lastname: Nylander
authors.forename: Yves F
authors.initials: YF
authors.lastname: Dufrêne
authors.forename: Marie-Paule
authors.initials: MP
authors.lastname: Mingeot-Leclercq
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry; D015081:2-Naphthylamine / Q000031:analogs & derivatives / Q000737:chemistry; D018407:Bacterial Physiological Phenomena; D002151:Calorimetry / Q000379:methods; D002462:Cell Membrane / Q000378:metabolism*; D004161:Diphenylhexatriene / Q000737:chemistry; D005452:Fluoresceins / Q000737:chemistry; D007848:Laurates / Q000737:chemistry; D008027:Light; D008051:Lipid Bilayers / Q000737:chemistry; D008055:Lipids / Q000737:chemistry*; D055666:Lipopeptides / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry; D008823:Micelles; D018625:Microscopy, Atomic Force / Q000379:methods; D008856:Microscopy, Fluorescence / Q000379:methods; D010456:Peptides, Cyclic / Q000737:chemistry*; D010713:Phosphatidylcholines / Q000737:chemistry; D010743:Phospholipids / Q000737:chemistry; D012235:Rhodamines / Q000737:chemistry; D012542:Scattering, Radiation; D013050:Spectrometry, Fluorescence / Q000379:methods
chemical_list: D005452:Fluoresceins; D007848:Laurates; D008051:Lipid Bilayers; D008055:Lipids; D055666:Lipopeptides; D008081:Liposomes; D008823:Micelles; D010456:Peptides, Cyclic; D010713:Phosphatidylcholines; D010743:Phospholipids; D012235:Rhodamines; C425723:octadecylrhodamine B; D004161:Diphenylhexatriene; C009365:surfactin peptide; D015060:1,2-Dipalmitoylphosphatidylcholine; D015081:2-Naphthylamine; C017251:1,2-oleoylphosphatidylcholine; C007740:fluorexon; C065580:laurdan