title: Cubic phases in hydrated 1:1 and 1:2 dipalmitoylphosphatidylcholine-dipalmitoylglycerol mixtures.
abstract: The structures of fully hydrated 1:1 and 1:2 (mol/mol) dipalmitoylphosphatidylcholine (DPPC)-dipalmitoylglycerol (DPG) mixtures were studied by means of small-angle x-ray diffraction. The x-ray diffraction pattern of the 1:1 (mol/mol) DPPC-DPG mixture at 65 degrees C contains three reflections with spacings in the ratio of 1:1/ square root of 2:1/ square root of 3 in addition to reflections of an inverted hexagonal (H11) phase. A possible interpretation of this result is that a cubic phase of the body-centered space group lm3m, with a lattice constant of 23.1 +/- 0.6 nm, is formed. This cubic phase appears at intermediate temperatures between the lamellar and the H11 phases. The 1:2 (mol/mol) DPPC-DPG mixture gives an x-ray diffraction pattern at temperatures higher than the lamellar-to-H11 transition containing a number of reflections that index a cubic phase structure. The space group of the cubic phase was assigned a face-centered group Fd3m with a lattice constant of 16.3 +/- 0.1 nm at 82 degrees C. The possible role of cubic phases in membrane phenomena such as transmembrane signal transduction and fusion is discussed.
authors.affiliation: Department of Applied Physics, Nagoya University, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Takahashi
authors.forename: I
authors.initials: I
authors.lastname: Hatta
authors.forename: P J
authors.initials: PJ
authors.lastname: Quinn
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry*; D055592:Biophysical Phenomena; D001703:Biophysics; D004075:Diglycerides / Q000737:chemistry*; D066298:In Vitro Techniques; D046911:Macromolecular Substances; D008561:Membrane Fusion; D015394:Molecular Structure; D015398:Signal Transduction; D013816:Thermodynamics; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D004075:Diglycerides; D046911:Macromolecular Substances; D014867:Water; D015060:1,2-Dipalmitoylphosphatidylcholine; C005071:dipalmitin