title: Emergence of superstructures from a homogeneous lipid sphere.
abstract: The spontaneous generation of a periodic hexagonal superstructure on a giant phospholipid sphere (GPS) with a diameter of 20-200 microm was studied. The GPS was composed of ternary phospholipids consisting of dioleoylphosphatidylethanolamine (DOPE), dioleoylphosphatidylcholine (DOPC), and dioleoylphosphatidylinositol-bisphosphate (DOPIP(2)). GPSs were prepared by natural swelling of a lipid film formed on a glass substrate. A GPS with a homogeneous lipid mixture tends to form a two-layered structure between the surface and inner parts; the surface layer is attributed to a DOPIP(2) rich region (we call this layer SL), and the interior is rich in DOPE and DOPC (we call this layer IL). A hexagonal superstructure develops in the SL, and the topology then changes to form multiple-doughnut structures. Finally, myelin-like tubes are generated through symmetry breaking of the doughnutlike structures. The time-dependent change in the surface-area expansion of a GPS is shown to obey the logistic growth model, and this is attributed to the kinetic process of phase segregation between the surface and bulk phase of the GPS.
authors.forename: Makiko
authors.initials: M
authors.lastname: Negishi
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kitahata
authors.forename: Kenichi
authors.initials: K
authors.lastname: Yoshikawa
mesh_terms: D004926:Escherichia coli / Q000737:chemistry; D007294:Inositol / Q000737:chemistry; D007700:Kinetics; D008055:Lipids / Q000737:chemistry*; D016015:Logistic Models; D008567:Membranes, Artificial; D008855:Microscopy, Electron, Scanning; D008863:Microspheres; D008958:Models, Molecular; D010316:Particle Size; D010713:Phosphatidylcholines / Q000737:chemistry; D010714:Phosphatidylethanolamines / Q000737:chemistry; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000737:chemistry; D010716:Phosphatidylinositols / Q000737:chemistry; D010743:Phospholipids / Q000737:chemistry
chemical_list: C410262:1,2-dioleoyl-glycero-3-phosphatidyl ethanolamine; C532047:1,2-dioleoylphosphatidylinositol 4,5-bisphosphate; D008055:Lipids; D008567:Membranes, Artificial; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols; D010743:Phospholipids; D007294:Inositol; C017251:1,2-oleoylphosphatidylcholine