title: Comparison of the effects of inserted C40- and C50-terminally dihydroxylated carotenoids on the mechanical properties of various phospholipid vesicles.
abstract: We have measured the extent of incorporation of zeaxanthin (C40) and decaprenozeaxanthin (C50) in unilamellar vesicles of dimyristoylphosphatidylcholine (n-C14) and dipalmitoylphosphatidylcholine (n-C16). The incorporation is larger when the molecular length of the carotenoid corresponds to the thickness of the phospholipid bilayer. Stereochemically pure 2,3-di-O-phytanyl-sn-glycero-1-phosphocholine was prepared by modification of the polar heads of the phospholipids of Halobacterium halobium. Vesicles of this branched-chain ether phospholipid incorporate poorly the carotenoids, whereas egg lecithin vesicles incorporate them better. Osmotic swelling and water permeability of vesicles, with or without carotenoids, were measured in a stopped-flow, light-scattering system. The reinforcing effect (lower permeability and higher rigidity) of carotenoids at 1.5 mol% incorporation into diphytanylphosphatidylcholine vesicles is comparable to that of 5 mol% cholesterol; however, carotenoids have no measurable effect on the egg lecithin vesicles. These results imply that the reinforcement of the membrane depends on a subtle adjustment of the phospholipid-carotenoid system.
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000378:metabolism; D002338:Carotenoids / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology; D002463:Cell Membrane Permeability / Q000187:drug effects; D055598:Chemical Phenomena; D002621:Chemistry; D004134:Dimyristoylphosphatidylcholine / Q000378:metabolism; D005614:Freeze Fracturing; D006217:Halobacterium / Q000032:analysis; D008027:Light; D008051:Lipid Bilayers / Q000378:metabolism; D008081:Liposomes / Q000378:metabolism* / Q000494:pharmacology; D008854:Microscopy, Electron; D009995:Osmosis / Q000187:drug effects; D010713:Phosphatidylcholines / Q000378:metabolism; D012542:Scattering, Radiation; D013329:Structure-Activity Relationship; D024341:Xanthophylls; D065146:Zeaxanthins; D019207:beta Carotene / Q000031:analogs & derivatives*
chemical_list: D008051:Lipid Bilayers; D008081:Liposomes; D010713:Phosphatidylcholines; D024341:Xanthophylls; D065146:Zeaxanthins; D019207:beta Carotene; C053686:2,3-di-O-phytanyl-sn-glycero-1-phosphocholine; D015060:1,2-Dipalmitoylphosphatidylcholine; C011431:decaprenoxanthin; D002338:Carotenoids; D004134:Dimyristoylphosphatidylcholine