Interfacial properties of phosphatidylcholine bilayers containing vitamin E derivatives

alpha -Tocopherol and alpha -tocopheryl succinate are biologically active l ipids. The activity of these lipids may be related to how they affect membr ane physical-chemical properties. Utilizing fluorescence methods, we have i nvestigated the effect of alpha -tocopherol. alpha -tocopheryl succinate, a nd alpha -tocopheryl acetate on the properties of model membranes consistin g of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine and 1,2-dipalmitoyl-s n-glycero-3-phosphocholine. In liquid-crystalline phase phospholipid bilaye rs, alpha -tocopherol decreased acyl chain mobility and decreased the inter facial polarity, but had no effect on the interfacial surface charge. In co ntrast, alpha -tocopheryl succinate had little effect on acyl chain motion or interfacial hydration. but increased the interfacial surface charge. alp ha -Tocopheryl acetate had very little effect on any of the measurements of these bilayer properties. In a gel phase bilayer, alpha -tocopherol decrea sed acyl chain order, whereas alpha -tocopheryl succinate and alpha -tocoph eryl acetate did not. Each alpha -tocopheryl derivative had ii different ef fect on interfacial polarity, however, only a-tocopheryl succinate increase d the interfacial surface charge. The acylation of alpha -tocopherol abolis hes its antioxidant activity and generates molecules with different membran e physical properties. The non-polar acetate group of alpha -tocopheryl ace tate locates this compound in a region of the bilayer where it has little e ffect on bilayer interfacial properties. The free carboxyl group of alpha - tocopheryl succinate is located in the interfacial region of the bilayer wh ere it increases the membrane surface charge. (C) 2001 Published by Elsevie r Science Ireland Ltd.