Flexible loops of thread-like micelles are formed upon interaction of L-alpha-dimyristoyl-phosphatidylcholine with the biosurfactant surfactin as revealed by cryo-electron tomography.
Vesicles of L-alpha-dimyristoyl-phosphatidylcholine (DMPC) are known to disintegrate upon treatment with surfactin, a lipoheptapeptide biosurfactant from Bacillus subtilis OKB 105, as was observed by static light scattering (SLS) and cryo-transmission electron microscopy (cryo-TEM) recently. The lysis of DMPC bilayers occurs strongly dependent on the surfactin concentration according to a three-stage model. Unilamellar DMPC vesicles are disrupted to form sheet-like lamellar intermediates at a moderate surfactant concentration, but undergo a transition towards smaller particles of unknown structure at a higher surfactant concentration according to earlier neutron scattering experiments. Here we present direct structural evidence from cryo-electron tomography data that thread-like micelles with a uniform diameter of 6.5 nm are organized into loops of different sizes at a surfactin concentration of > 15 mol%.
Boettcher
Christoph
C
Forschungszentrum für Elektronenmikroskopie, Institut für Chemie und Biochemie, Freie Universität Berlin, Fabeckstr. 36a, D-14195 Berlin, Germany. christoph.boettcher@fzem.fu-berlin.de
Kell
Henny
H
Holzwarth
Josef F
JF
Vater
Joachim
J
D003198:Computer Simulation; D020285:Cryoelectron Microscopy; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry*; D055666:Lipopeptides / Q000737:chemistry*; D008823:Micelles; D010456:Peptides, Cyclic / Q000737:chemistry*; D017434:Protein Structure, Tertiary; D013501:Surface-Active Agents / Q000737:chemistry*; D053835:Unilamellar Liposomes / Q000737:chemistry
D055666:Lipopeptides; D008823:Micelles; D010456:Peptides, Cyclic; D013501:Surface-Active Agents; D053835:Unilamellar Liposomes; C009365:surfactin peptide; D004134:Dimyristoylphosphatidylcholine