Abstract
The effect of α-tocopherol and its acetate on the membrane structure of egg yolk phosphaticdylcholine (egg PC) dispersions was investigated using phosphate-31 nuclear magnetic resonance (31P-NMR) and small-angle X-ray diffraction. The incorporation of α-tocopherol into egg PC dispersions induced a change in the 31P-NNR spectrum from a multilamellar bilayer line shape to a hexagonal HII one. The phase transition by α-tocopherol was also confirmed by small-angle X-ray diffraction analysis. The amount of hexagonal HII phase increased with increase in concentration of α-tocopherol. Egg PC dispersions containing a molar ration of 0.8 of α-tocopherol gave a 31P-NMR spectrum of an approximately hexagonal HII type at 37°C. The amount of hexagonal HII phase increased with increasing temperature, indicating that the α-tocopherol-induced phase transitin is thermotropic and that the transition temperature of egg PC membranes from the lamellar to the hexagonal HII phase is lowered by α-tocopherol. The incorporation of α-tocopherol acetate did not induce any phase transition. This fact indicates that the hydroxyl group of α-tocopherol may play an important role in the hexagonal HII phase formation of egg PC dispersions.
