title: Cubic phase is induced by cholesterol in the dispersion of 1-palmitoyl-2-oleoyl-phosphatidylethanolamine.
abstract: The effect of cholesterol, a major constituent of eukaryotic cell membranes, on the structure and thermotropic phase behaviour of 1-palmitoyl-2-oleoyl-phosphatidylethanolamine (POPE) dispersed in excess water was examined by synchrotron X-ray diffraction methods. Temperature scans over the range 10-75 degrees C showed that the gel to liquid-crystalline phase transition decreased from 25 to 10 degrees C in the presence of 20 mol% cholesterol, and no gel phase could be detected in the wide-angle X-ray scattering (WAXS) intensity profile of mixtures containing 35 mol% cholesterol. The small-angle X-ray scattering (SAXS) intensity profiles showed that the lamellar to nonlamellar phase transition temperature was also decreased in mixtures containing up to 30 mol% cholesterol but the trend was reversed in mixtures containing a higher proportion of cholesterol. There was evidence that the transition of the lamellar liquid-crystal phase is to cubic phases in mixtures containing less than 30 mol% cholesterol. The space group of one of these cubic phases was assigned as Pn3m. This effect of cholesterol on non-bilayer-forming phospholipids is considered in the context of the role of cholesterol in membrane organization and function.
authors.affiliation: Division of Life Sciences, King's College London, UK.
authors.forename: Xiaoyuan
authors.initials: X
authors.lastname: Wang
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Quinn
mesh_terms: D002784:Cholesterol / Q000737:chemistry*; D066298:In Vitro Techniques; D008081:Liposomes / Q000737:chemistry; D008563:Membrane Lipids / Q000737:chemistry; D010714:Phosphatidylethanolamines / Q000737:chemistry*; D012542:Scattering, Radiation; D013816:Thermodynamics; D014867:Water; D014961:X-Ray Diffraction; D014965:X-Rays
chemical_list: D008081:Liposomes; D008563:Membrane Lipids; D010714:Phosphatidylethanolamines; D014867:Water; C057561:1-palmitoyl-2-oleoylphosphatidylethanolamine; D002784:Cholesterol