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 ii different effect on interfacial polarity, however, only a-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. (C) 2001 Published by Elsevier Science Ireland Ltd.