title: Differential membrane packing of stereoisomers of bis(monoacylglycero)phosphate.
abstract: Bis(monoacylglycero)phosphate (BMP) reveals an unusual sn-1,sn-1' stereoconfiguration of glycerophosphate. We synthesized sn-(3-myristoyl-2-hydroxy)glycerol-1-phospho-sn-1'-(3'-myristoyl-2'-hydroxy)glycerol (1,1'-DMBMP) and characterized the thermotropic phase behavior and membrane structure, in comparison with those of the corresponding sn-3:sn-1' stereoisomer (3,1'-DMBMP), by means of differential scanning calorimetry (DSC), small- and wide-angle X-ray scattering (SAXS and WAXS, respectively), pressure-area (pi-A) isotherms, epifluorescence microscopy of monolayers, and molecular dynamics (MD) simulations. In DSC, these lipids exhibited weakly energetic broad peaks with an onset temperature of 9 degrees C for 1,1'-DMBMP and 18 degrees C for 3,1'-DMBMP. In addition, a highly cooperative, strongly energetic transition peak was observed at approximately 40 degrees C for 1,1'-DMBMP and approximately 42 degrees C for 3,1'-DMBMP. These results are supported by the observation that 1,1'-DMBMP exhibited a larger phase transition pressure (pi(c)) than 3,1'-DMBMP. Small- and wide-angle X-ray scattering measurements identified these small and large energetic transitions as a quasi-crystalline (L(c1))-quasi-crystalline with different tilt angle (L(c2)) phase transition and an L(c2)-L(alpha) main phase transition, respectively. X-ray measurements also revealed that these DMBMPs undergo an unbinding at the main phase transition temperature. The MD simulations estimated stronger hydrogen bonding formation in the 3,1'-DMBMP membrane than in 1,1'-DMBMP, supporting the experimental data.
authors.affiliation: Lipid Biology Laboratory, RIKEN (Institute of Physical and Chemical Research), 2-1, Hirosawa, Wako-shi, Saitama 351-0198, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Hayakawa
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Hirano
authors.forename: Asami
authors.initials: A
authors.lastname: Makino
authors.forename: Sabine
authors.initials: S
authors.lastname: Michaud
authors.forename: Michel
authors.initials: M
authors.lastname: Lagarde
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Pageaux
authors.forename: Alain
authors.initials: A
authors.lastname: Doutheau
authors.forename: Kazuki
authors.initials: K
authors.lastname: Ito
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Fujisawa
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Takahashi
authors.forename: Toshihide
authors.initials: T
authors.lastname: Kobayashi
mesh_terms: D002152:Calorimetry, Differential Scanning; D006860:Hydrogen Bonding; D008246:Lysophospholipids / Q000737:chemistry*; D008567:Membranes, Artificial; D050178:Monoglycerides / Q000737:chemistry*; D012542:Scattering, Radiation; D013237:Stereoisomerism; D013816:Thermodynamics; D014965:X-Rays
chemical_list: D008246:Lysophospholipids; D008567:Membranes, Artificial; D050178:Monoglycerides; C012786:bis(monoacylglyceryl)phosphate