Alpha-tocopherol-induced hexagonal HII phase formation in egg yolk phosphatidylcholine membranes.
The effect of alpha-tocopherol and its acetate on the membrane structure of egg yolk phosphatidylcholine (egg PC) dispersions was investigated using phosphate-31 nuclear magnetic resonance (31P-NMR) and small-angle X-ray diffraction. The incorporation of alpha-tocopherol into egg PC dispersions induced a change in the 31P-NMR spectrum from a multilamellar bilayer line shape to a hexagonal HII one. The phase transition by alpha-tocopherol was also confirmed by small-angle X-ray diffraction analysis. The amount of hexagonal HII phase increased with increase in concentration of alpha-tocopherol. Egg PC dispersions containing a molar ratio of 0.8 of alpha-tocopherol gave a 31P-NMR spectrum of an approximately hexagonal HII type at 37 degrees C. The amount of hexagonal HII phase increased with increasing temperature, indicating that the alpha-tocopherol-induced phase transition is thermotropic and that the transition temperature of egg PC membranes from the lamellar to the hexagonal HII phase is lowered by alpha-tocopherol. The incorporation of alpha-tocopherol acetate did not induce any phase transition. This fact indicates that the hydroxyl group of alpha-tocopherol may play an important role in the hexagonal HII phase formation of egg PC dispersions.
Nakajima
K
K
Tokyo Metropolitan Research Laboratory of Public Health, Japan.
Utsumi
H
H
Kazama
M
M
Hamada
A
A
D004530:Egg Yolk / Q000032:analysis*; D009682:Magnetic Resonance Spectroscopy; D008566:Membranes / Q000032:analysis; D010713:Phosphatidylcholines / Q000032:analysis*; D014810:Vitamin E / Q000494:pharmacology*; D014961:X-Ray Diffraction
D010713:Phosphatidylcholines; D014810:Vitamin E