title: Physical properties of the hybrid lipid POPC on micrometer-sized domains in mixed lipid membranes.
abstract: Macro-phase separation in mixed lipid membranes containing the hybrid lipid palmitoyloleoylphosphatidylcholine (POPC) was observed by fluorescent and confocal laser scanning microscopy. In a binary system consisting of the saturated lipid dipalmitoylphosphatidylcholine (DPPC) and the hybrid lipid POPC, the hybrid lipid forms a liquid-disordered (Ld) phase. In a ternary system consisting of this binary system and an unsaturated lipid dioleoylphosphatidylcholine (DOPC), three-phase coexistence is observed. The POPC-rich phase appears around DPPC-rich domains, and the hybrid lipid is expected to behave like a line-active agent (linactant). Finally, phase separation in a four-component system, composed of this ternary system and cholesterol, was examined. Domains with a size that is smaller than 1 μm are found, and domain-induced budding is also observed. To explain small domain formation and domain-induced budding, chain ordering was evaluated based on Laurdan generalized polarization measurements. Our observations revealed that the hybrid lipid acted like a linactant to solid domains and disturbed chain ordering in liquid-ordered (Lo) domains. In both cases, the hybrid lipid reduced line tension at the domain boundary.
authors.affiliation: School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi City, Ishikawa 923-1292, Japan. takagi@jaist.ac.jp.
authors.forename: Naofumi
authors.initials: N
authors.lastname: Shimokawa
authors.forename: Mariko
authors.initials: M
authors.lastname: Nagata
authors.forename: Masahiro
authors.initials: M
authors.lastname: Takagi
mesh_terms: D002627:Chemistry, Physical; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D010316:Particle Size; D010713:Phosphatidylcholines / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D010713:Phosphatidylcholines; C017251:1,2-oleoylphosphatidylcholine; C028694:1-palmitoyl-2-oleoylphosphatidylcholine