1: Langmuir. 2007 Sep 11;23(19):9769-72. Epub 2007 Aug 14. The biologically important surfactin lipopeptide induces nanoripples in supported lipid bilayers. Brasseur R, Braun N, El Kirat K, Deleu M, Mingeot-Leclercq MP, Dufrêne YF. Centre de Biophysique Moléculaire Numérique, Faculté Universitaire des Sciences Agronomiques de Gembloux, Passage des Déportés 2, B-5030 Gembloux, Belgium. Under specific conditions, lipid membranes form ripple phases with intriguing nanoscale undulations. Here, we show using in situ atomic force microscopy (AFM) that the biologically important surfactin lipopeptide induces nanoripples of 30 nm periodicity in dipalmitoyl phosphatidylcholine (DPPC) bilayers at 25 degrees (i.e. well below the pretransition temperature of DPPC). Whereas most undulations formed the classical straight orientation with characteristic angle changes of 120 degrees , some of them also displayed unusual circular orientations. Strikingly, ripple structures were formed at 15% surfactin but were rarely or never observed at 5 and 30% surfactin, emphasizing the important role played by the surfactin concentration. Theoretical simulations corroborated the AFM data by revealing the formation of stable surfactin/lipid assemblies with positive curvature. PMID: 17696376 [PubMed - in process] Related Links Temperature-controlled structure and kinetics of ripple phases in one- and two-component supported lipid bilayers. [Biophys J. 2003] PMID:12829489 Nanometer scale organization of mixed surfactin/phosphatidylcholine monolayers. [Biophys J. 1999] PMID:10512848 Penetration of surfactin into phospholipid monolayers: nanoscale interfacial organization. [Langmuir. 2006] PMID:17154623 Phase behavior and nanoscale structure of phospholipid membranes incorporated with acylated C14-peptides. [Biophys J. 2005] PMID:16100273 Molecular mechanism of membrane permeabilization by the peptide antibiotic surfactin. [Biochim Biophys Acta. 2003] PMID:12659949