The interaction of alpha-tocopherol with bilayers of 1-palmitoyl-2-oleoyl-phosphatidylcholine.
The effect of alpha-tocopherol on the structure and phase behaviour of 1-palmitoyl-2-oleoyl-phosphatidylcholine was examined by real-time synchrotron X-ray diffraction and freeze-fracture electron microscopic methods. X-ray scattering intensity was recorded from mixed aqueous dispersions of phospholipid with 2.5, 5, 10 and 20 mol% alpha-tocopherol during temperature scans at 3 degrees /min between -25 and 10 degrees C. A ripple structure is induced by the presence of alpha-tocopherol that coexists with the ripple phase characteristic of the pure phospholipid in mixtures containing 2.5 mol% alpha-tocopherol but completely replaces it in mixtures containing greater proportions of alpha-tocopherol. Freeze-fracture replicas of dispersions containing 5 mol% alpha-tocopherol indicate a ripple phase with a periodicity of about 9 nm. Increasing amounts of alpha-tocopherol result in a progressive reduction in temperature of the gel to liquid-crystal phase transition and broadening of the transition. Two lamellar phases coexist in the liquid-crystal state, one with a spacing of 6.4 nm assigned to an alpha-tocopherol-enriched lamellar structure and the other with a lamellar repeat of 6.1 nm corresponding to bilayers of pure phospholipid.
Wang
Xiaoyuan
X
Division of Life Sciences, King's College London, 150 Stamford Street, London SE1 9NN, United Kingdom.
Quinn
Peter J
PJ
D008051:Lipid Bilayers; D008854:Microscopy, Electron; D010713:Phosphatidylcholines / Q000737:chemistry*; D014961:X-Ray Diffraction; D024502:alpha-Tocopherol / Q000737:chemistry*
D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D024502:alpha-Tocopherol; C028694:1-palmitoyl-2-oleoylphosphatidylcholine