title: Polymorphic phase behavior of unsaturated lysophosphatidylethanolamines: a 31P NMR and X-ray diffraction study.
abstract: The polymorphic phase behavior of aqueous dispersions of 1-oleoyl-, 1-linoleoyl-, and 1-linolenoyl-sn-3-glycerophosphoethanolamine (1-C18:1c-PE, 1-C18:2c-PE, and 1-C18:3c-PE, respectively) has been investigated by 31P NMR, small-angle and wide-angle X-ray diffraction, and freeze-fracture techniques in response to changes in temperature and pH. Between -20 and 0 degrees C at pH 7, NMR and X-ray data indicate that 1-C18:1c-PE adopts a lamellar phase. Above 20 degrees C, the X-ray diffraction from 1-C18:1c-PE reveals no long-range lattice order, whereas the NMR data indicate lamellar structure to 90 degrees C. Freeze-fracture electron microscopy shows that 1-C18:1c-PE at pH 8.2 forms closed multilamellar vesicles upon dispersion and also that large unilamellar vesicles produced by extrusion techniques (LUVETs) can be made from 1-C18:1c-PE at pH 7. Such LUVETs can trap [3H]inulin and support a K+ diffusion potential for up to 4 h. At pH 8.5 and above, 1-C18:1c-PE forms optically clear, fluid dispersions with NMR and X-ray characteristics consistent with a micellar (noninverted) phase structure. Attempts to prepare LUVETs from 1-C18:1c-PE at pH 9 result in structures that can neither trap [3H]inulin nor support a membrane potential.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D005231:Fatty Acids, Unsaturated; D005614:Freeze Fracturing; D007700:Kinetics; D008081:Liposomes; D008246:Lysophospholipids; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008564:Membrane Potentials; D008854:Microscopy, Electron; D008954:Models, Biological; D008968:Molecular Conformation; D010714:Phosphatidylethanolamines; D013329:Structure-Activity Relationship; D014961:X-Ray Diffraction / Q000379:methods
chemical_list: D005231:Fatty Acids, Unsaturated; D008081:Liposomes; D008246:Lysophospholipids; D010714:Phosphatidylethanolamines; C008301:lysophosphatidylethanolamine