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  • Title: Effect of phospholipid oxidation products on transbilayer movement of phospholipids in single lamellar vesicles.
    Author: Shaw JM, Thompson TE.
    Journal: Biochemistry; 1982 Mar 02; 21(5):920-7. PubMed ID: 7074060.
    Abstract:
    Single lamellar phosphatidyl[methyl-2H]choline vesicles were incubated with an excess of unlabeled phosphatidylcholine vesicles or phosphatidylcholine-cholesterol vesicles containing 8 mol % glucuronosyldiglyceride. Incubation of the two vesicle populations was performed in the presence or absence of a purified phosphatidylcholine exchange protein. The negatively charged glycolipid donor vesicles could be completely removed by column chromatography on DEAE-Sephacel. Following incubation with exchange protein and subsequent fractionation, the -N(CD3)3 phosphatidylcholine acceptor vesicles exhibited a 61-73% enrichment of the unlabeled phosphatidylcholine in the outer monolayer. Upon incubation in an air atmosphere, no appreciable transbilayer movement of the outer monolayer -N(CH3)3 phosphatidylcholine was observed for at least 5 days. Between days 5 and 7, however, extensive transbilayer movement occurred, leading to an outer monolayer/inner monolayer phosphatidylcholine ratio of 2.1 on day 7. In phosphatidylcholine-6 mol % cholesterol vesicles treated similarly, the outside/inside ratio of the unlabeled phospholipid was 6.7, suggesting a much smaller percentage of transbilayer movement. The loss of transbilayer asymmetry which occurred during a 36-h period after day 5 could be estimated at the upper limit, t 1/2 approximately 7.3 h for phosphatidylcholine vesicles and t 1/2 approximately 53 h for phosphatidylcholine-cholesterol vesicles. The actual rates for transbilayer movement, however, were likely more rapid. Transbilayer movement occurred at a time period when oxidized phospholipid breakdown products had reached critical levels.
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