Effect of cholesterol on vesicle bilayer geometry of choline plasmalogen and comparison with dialkyl-, alkylacyl- and diacyl-glycerophosphocholines.
Small unilamellar vesicles containing alkenylacyl-, alkylacyl-, dialkyl- or diacyl-glycerophosphocholine were prepared by sonication. Their size was determined from the average internal volume after chromatography on Sepharose 2B and from 31P-NMR linewidths. Alkenylacyl glycerophosphocholine (choline plasmalogen) was found to form the largest vesicles. By addition of 30 mol% cholesterol, the size of plasmalogen vesicles, but not of those containing the alkyl and acyl analogue lipids, was significantly increased. The presence of 50 mol% sterol led to highly increased vesicle sizes of alkylacyl, dialkyl and diacyl-glycerophosphocholine. Mixtures of plasmalogens with 50 mol% cholesterol did not form unilamellar vesicles upon sonication. Bilayer thickness and surface area per phospholipid molecule were determined by small angle X-ray scattering and measurement of partial specific volumes. There is little difference between alkenylacyl glycerophosphocholine and the corresponding diacyl-analog, whereas bilayers consisting of dioleoyl glycerophosphocholine are significantly thinner. Correspondingly their molecular surface area is by about 8% larger than that of the mixed-chain diradyl glycerophosphocholine, since the partial molar volumes are similar for all vesicles tested.
D002784:Cholesterol / Q000032:analysis*; D002850:Chromatography, Gel; D005997:Glycerylphosphorylcholine / Q000031:analogs & derivatives* / Q000032:analysis; D008051:Lipid Bilayers / Q000032:analysis*; D009682:Magnetic Resonance Spectroscopy; D010955:Plasmalogens / Q000032:analysis*; D014961:X-Ray Diffraction
D008051:Lipid Bilayers; D010955:Plasmalogens; C032459:choline plasmalogens; D005997:Glycerylphosphorylcholine; D002784:Cholesterol