title: Impact of Lipid Oxidization on Vertical Structures and Electrostatics of Phospholipid Monolayers Revealed by Combination of Specular X-ray Reflectivity and Grazing-Incidence X-ray Fluorescence.
abstract: The influence of phospholipid oxidization of floating monolayers on the structure perpendicular to the global plane and on the density profiles of ions near the lipid monolayer has been investigated by a combination of grazing incidence X-ray fluorescence (GIXF) and specular X-ray reflectivity (XRR). Systematic variation of the composition of the floating monolayers unravels changes in the thickness, roughness and electron density of the lipid monolayers as a function of molar fraction of oxidized phospholipids. Simultaneous GIXF measurements enable one to qualitatively determine the element-specific density profiles of monovalent (K(+) or Cs(+)) and divalent ions (Ca(2+)) in the vicinity of the interface in the presence and absence of two types of oxidized phospholipids (PazePC and PoxnoPC) with high spatial accuracy (±5 Å). We found the condensation of Ca(2+) near carboxylated PazePC was more pronounced compared to PoxnoPC with an aldehyde group. In contrast, the condensation of monovalent ions could hardly be detected even for pure oxidized phospholipid monolayers. Moreover, pure phospholipid monolayers exhibited almost no ion specific condensation near the interface. The quantitative studies with well-defined floating monolayers revealed how the elevation of lipid oxidization level alters the structures and functions of cell membranes.
authors.affiliation: †Physical Chemistry of Biosystems, Physical Chemistry Institute, University of Heidelberg, 69120 Heidelberg, Germany.
authors.forename: Agatha
authors.initials: A
authors.lastname: Korytowski
authors.affiliation: †Physical Chemistry of Biosystems, Physical Chemistry Institute, University of Heidelberg, 69120 Heidelberg, Germany.
authors.forename: Wasim
authors.initials: W
authors.lastname: Abuillan
authors.affiliation: †Physical Chemistry of Biosystems, Physical Chemistry Institute, University of Heidelberg, 69120 Heidelberg, Germany.|‡Institut Galien Paris Sud, Faculté de Pharmacie-Université Paris-Sud, 5 rue Jean-Baptiste Clément, 92296 Châtenay-Malabry, France.
authors.forename: Ali
authors.initials: A
authors.lastname: Makky
authors.affiliation: §European Synchrotron Radiation Facility (ESRF), Grenoble Cedex 9 38053, France.
authors.forename: Oleg
authors.initials: O
authors.lastname: Konovalov
authors.affiliation: †Physical Chemistry of Biosystems, Physical Chemistry Institute, University of Heidelberg, 69120 Heidelberg, Germany.|∥Institute for Integrated Cell-Material Sciences (iCeMS), Kyoto University, 606-8501 Kyoto, Japan.
authors.forename: Motomu
authors.initials: M
authors.lastname: Tanaka
mesh_terms: D002118:Calcium / Q000737:chemistry; D002586:Cesium / Q000737:chemistry; D004583:Electrons; D010084:Oxidation-Reduction; D010743:Phospholipids / Q000737:chemistry*; D011188:Potassium / Q000737:chemistry; D013050:Spectrometry, Fluorescence; D055672:Static Electricity; D014961:X-Ray Diffraction
chemical_list: D010743:Phospholipids; D002586:Cesium; D011188:Potassium; D002118:Calcium