Effect of cholesterol on vesicle bilayer geometry of choline plasmalogen and comparison with dialkyl-, alkylacyl- and diacyl-glycerophosphocholines
✍ Scribed by A. Hermetter; K. Lohner; G. Degovics; P. Laggner; F. Paltauf
- Publisher
- Elsevier Science
- Year
- 1985
- Tongue
- English
- Weight
- 593 KB
- Volume
- 38
- Category
- Article
- ISSN
- 0009-3084
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✦ Synopsis
Small unilamellar vesicles containing alkenylacyl-, alkylacyi-, 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 measdrement 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.