Lateral Diffusion in the Hydrophobic Region of Phospholipid Liposomes Containing Tocopheryl Acetates

Abstract

The lateral diffusion coefficient in phosphatidylcholine membranes was determined using pyrene as a fluorescence probe and the effect of .alpha.-, .gamma.- and .delta.-tocopheryl acetates on the liposomes and the interaction between tocopheryl acetates and cholesterol in the liposomes were studied. .alpha.-, .gamma.- and .delta.-Tocopheryl acetates reduced the diffusion of pyrene in the liposomes of dipalmitoyl, egg yolk and soybean phosphatidylcholines. .alpha.-Tocopheryl acetate was the most effective compound among the 3 tocopheryl acetates in reducing the diffusion coefficient of pyrene; the degree of reduction of pyrene diffusion by each tocopheryl acetate correlated well with its vitamin E activity. Tocopheryl acetates and cholesterol independently reduced the diffusion of pyrene in the membranes. Tocopherols may physically stabilize biological membranes.