Physical/Chemical Studies of Vitamin E in Membranes

Summary

Interaction of α-tocopherol and its analogue vitamin E acetate in model membranes has been studied using ¹H, ³¹P and ¹³C NMR. α-tocopherol binds strongly with the lipid molecule through intermolecular hydrogen bond. The possibility of such a hydrogen bond is excluded in Vitamin E acetate which binds loosely to the membrane through normal hydrophobic interactions. ESR spin labeling experiments indicate that whereas α-tocopherol broadens gel to liquid crystalline phase transition, vitamin E acetate lowers the phase transition temperature. Profile of permeation of small molecules through liposomes has been found to alter on incorporation of these drugs. However, no alteration in the mode of packing has been revealed by ³¹P NMR and Electron Microscopy. The membrane retains normal lamellar bilayer arrangement. A model for α-tocopherol-lipid interaction has been constructed using computer aided graphics. Protection offered to intact cells (spermatozoa) by α-tocopherol against peroxidation caused by UV treatment has been studied using biochemical methods and spin labeling ESR technique.