title: Non-bilayer formation in the DPPE-DPPG vesicle system induced by deep rough mutant of Salmonella minnesota R595 lipopolysaccharide.
abstract: The vesicle system consisting of 80 mol% dipalmitoylphosphatidylethanolamine (DPPE) and 20 mol% dipalmitoylphosphatidylglycerol (DPPG) undergoes to structural changes caused by various concentrations of Salmonella minnesota R595 lipopolysaccharide (LPS). The phenomenon was investigated by methods applying small- and wide-angle X-ray scattering (SAXS and WAXS), calorimetry (DSC) and freeze-fracture. In the low LPS concentration regime (investigated at 0.02 LPS/DPPE-DPPG molar ratio) a phase separation was observed. Two kind of domains are formed which are rich and poor in DPPE and in these domains cubic and lamellar structures are present, respectively. Increasing the LPS concentration up to 0.1 LPS/DPPE-DPPG molar ratio the phase separation is more expressed and the temperature domains of the phase transitions are more different. Increasing the temperature chain melting of the lamellar phase occurs first and destruction of the cubic phase is observed later. At high LPS concentration (equimolar ratio of LPS/DPPE-DPPG), where this amphiphilic molecule cannot be considered any more a guest molecule, the cubic structure dominates the phase behaviour of the LPS molecules.
authors.affiliation: Department of Physical Chemistry, Budapest University of Technology and Economics, H-1521 Budapest, Hungary.
authors.forename: Edit
authors.initials: E
authors.lastname: Urbán
authors.forename: Attila
authors.initials: A
authors.lastname: Bóta
authors.forename: Béla
authors.initials: B
authors.lastname: Kocsis
mesh_terms: D002152:Calorimetry, Differential Scanning; D020285:Cryoelectron Microscopy; D005614:Freeze Fracturing; D008051:Lipid Bilayers / Q000737:chemistry; D008070:Lipopolysaccharides / Q000737:chemistry* / Q000494:pharmacology; D008081:Liposomes / Q000737:chemistry*; D009154:Mutation; D044367:Phase Transition / Q000187:drug effects; D010714:Phosphatidylethanolamines / Q000737:chemistry*; D010715:Phosphatidylglycerols / Q000737:chemistry*; D012475:Salmonella / Q000737:chemistry* / Q000235:genetics; D044366:Transition Temperature; D014961:X-Ray Diffraction
chemical_list: D008051:Lipid Bilayers; D008070:Lipopolysaccharides; D008081:Liposomes; D010714:Phosphatidylethanolamines; D010715:Phosphatidylglycerols; C007510:1,2-dipalmitoyl-3-phosphatidylethanolamine; C030345:1,2-dipalmitoylphosphatidylglycerol