Phase transitions, lateral phase separation and microstructure of model membranes composed of a polymerizable two-chain lipid and dimyristoylphosphatidylcholine

摘要: The structural and dynamic properties of aqueous dispersions a cationic two-chain lipid containing one dienoyl group per chain for polymerization as well mixtures this with dimyristoylphosphatidylcholine (DMPC) were studied. A variety techniques such calorimetry, densitometry, fluorescence depolarization spectroscopy, light scattering, freeze fracture electron diffraction, the photobleaching technique applied. In pure water forms large thin-walled vesicles above 40°C. These exhibit two phase transitions: melting transition at Tm =35°C solid-solid change which occurs Ts+ = 28°C increasing Ts− 21°C decreasing temperature. This hysteresis is ionic strength dependent. Evidence provided that latter accompanied by chains from tilted to non-tilted configuration. At low strengths remain stable after repetitive heating cooling through both transitions. high salt concentrations (≳0.1 M NaCl) crystallization bilayers their aggregation into spherulites or platelets these multilayers shifted temperatures (about 50°C). first diagram mixture established microscopy 90°-light-scattering characterized miscibility gap in solid state. domain like lateral organization components may be exploited order prepare composed patches cross-linked monomeric lipid. Photochemical abolishes while chain-melting preserved slightly higher (Tm∗ ≈ 38°C). form hexagonal lattice T < Tm. degree polymerization, N, has been estimated N ⩽ 100 on basis results. rather small also suggested reduction diffusion coefficients probes penetrate bilayer either partially completely.