Interactions of vitamin E with free radicals and membranes

Abstract

alpha-Tocopherol performs an antioxidant role in biological membranes by acting as a one-electron reductant. In micellar solutions it has been observed by pulse radiolysis that the micellar charge has a pronounced effect on the rate constant for repair of organic free radicals by alpha-tocopherol. The interactions between alpha-tocopherol and model bilayer lipid membranes have been studied by fluorescence spectroscopy. Quenching of alpha-tocopherol fluorescence by acrylamide and some n-doxyl stearates shows the transverse distribution of alpha-tocopherol in membranes to be affected by the physical state of the membrane lipids and by the salt concentration in the aqueous phase. Time-resolved fluorescence depolarization measurements, with a diphenylhexatriene-phospholipid conjugate as probe, demonstrate an increase in bilayer order parameter on incorporation of alpha-tocopherol into a membrane.