Effect of α-tocopherol on the phase transition of phosphatidylcholine and on water transport through phosphatidylcholine liposome membranes

The interaction between α-tocopherol and phosphatidylcholine was studied in liposomes by differential scanning calorimetry and osmotic water transport studies. Addition of α-tocopherol to phosphatidylcholine resulted in a reduction in enthalpy at the transition temperature, a rise in osmotic water permeability of the liposomes below the phase transition temperature and disappearance of the discontinuity of osmotic water transport at the phase transition. Also the temperature dependence of osmotic water transport was reduced below the transition temperature. A comparison between cholesterol and α-tocopherol in regulation of permeability was made and the physiological relevance of tocopherol in regulation of membrane permeability is discussed.