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Biophys J. 1998 Dec;75(6):2923-31.

Interaction of alpha-tocopherol with model human high-density lipoproteins.

Author information

  • 1Department of Medicine, Baylor College of Medicine and The Methodist Hospital, Houston, Texas 77030 USA. jmassey@bcm.tmc.edu

Abstract

The effects of alpha-tocopherol on the properties of model high-density lipoproteins (HDLs), composed of human apolipoprotein A-I and dimyristoylphosphatidylcholine, were investigated by physicochemical methods. The intrinsic fluorescence of alpha-tocopherol and its effects on the polarization of fluorescence of 1,6-diphenyl-1,3,5-hexatriene, which probes the hydrocarbon region of the lipids, and 4-heptadecyl-7-hydroxycoumarin, which is a probe of lipid surfaces, suggest that alpha-tocopherol is located at the lipid-water interface. Relative to cholesterol, alpha-tocopherol in lipid surfaces is virtually inert physicochemically. Incorporation of alpha-tocopherol into HDLs induces only a modest increase in particle size, no change in the transition temperature, and little change in lipid polarity and lipid-lipid interactions. Moreover, alpha-tocopherol has only a negligible effect on the kinetic parameters of the lipophilic enzyme lecithin:cholesterol acyltransferase, which binds to phosphatidylcholine surfaces and forms cholesteryl esters. However, alpha-tocopherol has a dramatic inhibitory effect on the rate of association of apolipoprotein A-I with dimyristoylphosphatidylcholine, a process that occurs through the insertion of the protein into preformed defects in the lipid surface. It is proposed that alpha-tocopherol inhibits the rate of association of apolipoprotein A-I with dimyristoylphosphatidylcholine by inserting into defects within the lipid surface, thereby reducing the size and/or number of sites for insertion of apolipoprotein A-I.

PMID:
9826613
PMCID:
PMC1299964
DOI:
10.1016/S0006-3495(98)77734-3
[PubMed - indexed for MEDLINE]
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