title: Ripple phases induced by alpha-tocopherol in saturated diacylphosphatidylcholines.
abstract: The effect of alpha-tocopherol on the structure and phase behavior of dilauroyl-, dimyristoyl-, dipalmitoyl-, and distearoyl-phosphatidylcholines was examined using X-ray diffraction and freeze-fracture electron microscopic methods. A ripple phase was observed in all of the mixtures at temperatures well below the pretransition temperature of the corresponding pure phospholipid. Freeze-fracture studies indicated that with proportion of alpha-tocopherol less than 5 mol% a ripple phase with large periodicity (50-150 nm) predominated and with about 10 mol% alpha-tocopherol a ripple phase of periodicity about 16 nm was formed. With more than 10 mol% alpha-tocopherol planar bilayers tended to be formed. Partial phase diagrams of mixed aqueous dispersions of saturated phosphatidylcholines and alpha-tocopherol over temperature ranges about the gel to liquid-crystal phase boundary have been constructed. Alpha-tocopherol-enriched domains form ripple phases that coexist with regions of lamellar gel phase of the pure phospholipid in mixtures containing less than 10 mol% alpha-tocopherol. The presence of increasing amounts of alpha-tocopherol in the phospholipid causes an increase in the proportion of ripple phase at the expense of pure phospholipid bilayer indicating that the alpha-tocopherol-enriched domains might possess a defined stoichiometry of the two constituents.
authors.affiliation: Division of Life Sciences, King's College London, United Kingdom.
authors.forename: X
authors.initials: X
authors.lastname: Wang
authors.forename: K
authors.initials: K
authors.lastname: Semmler
authors.forename: W
authors.initials: W
authors.lastname: Richter
authors.forename: P J
authors.initials: PJ
authors.lastname: Quinn
mesh_terms: D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry / Q000378:metabolism; D005614:Freeze Fracturing; D008854:Microscopy, Electron; D010713:Phosphatidylcholines / Q000737:chemistry / Q000378:metabolism*; D017356:Synchrotrons; D013696:Temperature; D014810:Vitamin E / Q000737:chemistry / Q000378:metabolism*; D014961:X-Ray Diffraction
chemical_list: D010713:Phosphatidylcholines; D014810:Vitamin E; C015153:1,2-dilauroylphosphatidylcholine; C010942:1,2-distearoyllecithin; D004134:Dimyristoylphosphatidylcholine