Interfacial properties of phosphatidylcholine bilayers containing vitamin E derivatives.
alpha-Tocopherol and alpha-tocopheryl succinate are biologically active lipids. The activity of these lipids may be related to how they affect membrane physical-chemical properties. Utilizing fluorescence methods, we have investigated the effect of alpha-tocopherol, alpha-tocopheryl succinate, and alpha-tocopheryl acetate on the properties of model membranes consisting of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine. In liquid-crystalline phase phospholipid bilayers, alpha-tocopherol decreased acyl chain mobility and decreased the interfacial polarity, but had no effect on the interfacial surface charge. In contrast, alpha-tocopheryl succinate had little effect on acyl chain motion or interfacial hydration, but increased the interfacial surface charge. alpha-Tocopheryl acetate had very little effect on any of the measurements of these bilayer properties. In a gel phase bilayer, alpha-tocopherol decreased acyl chain order, whereas alpha-tocopheryl succinate and alpha-tocopheryl acetate did not. Each alpha-tocopheryl derivative had a different effect on interfacial polarity, however, only alpha-tocopheryl succinate increased the interfacial surface charge. The acylation of alpha-tocopherol abolishes its antioxidant activity and generates molecules with different membrane physical properties. The non-polar acetate group of alpha-tocopheryl acetate locates this compound in a region of the bilayer where it has little effect on bilayer interfacial properties. The free carboxyl group of alpha-tocopheryl succinate is located in the interfacial region of the bilayer where it increases the membrane surface charge.
Department of Medicine, Baylor College of Medicine, 6565 Fannin Street, M.S.A.-601, Houston, TX 77030, USA. jmassey@bcm.tmc.edu
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Massey
D005454:Fluorescence Polarization; D008051:Lipid Bilayers / Q000737:chemistry*; D010713:Phosphatidylcholines / Q000737:chemistry*; D024505:Tocopherols; D014810:Vitamin E / Q000031:analogs & derivatives* / Q000737:chemistry*
D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D014810:Vitamin E; D024505:Tocopherols