Asymmetry and phase separation in lipid membranes
S. Hertrich1, J.-F. Moulin2, M. Haese-Seiller2, J. O. Rädler1, B. Nickel1
1Ludwig-Maximilians-Universität, Fakultät für Physik & CeNS, Geschwister-Scholl-Platz 1, 80539 Munich, Germany
2Helmholtz Zentrum Geesthacht at FRM-2, Institut für Werkstoffforschung, Abteilung WPN, Lichtenbergstr. 1, 85747 Garching
Lipid bilayers with controlled content of anionic lipids are a prerequisite for the quantitative study of hydrophobic-electrostatic interactions of proteins with lipid bilayers. Here, the asymmetric distribution of zwitterionic and anionic lipids in supported lipid bilayers is studied by neutron reflectometry at REFSANS. NR reveals the presence of anionic lipids (d31-POPS) in the outer bilayer leaflet only, while no POPS is observed in the leaflet facing the SiO2 substrate [1]. We argue that this asymmetric distribution of POPS is induced by electrostatic repulsion of the phosphatidylserines from the negatively charged hydroxy-surface groups of the silicon block. Such bilayers with controlled and high content of anionic lipids in the outer leaflet are versatile platforms to study anionic lipid protein interactions which are key elements in signal transduction pathways at the cytoplasmic leaflet of eukaryotic cells.
Furthermore, we report GISANS experiments to study phase separation in mixed bilayers.
[1] S.Stanglmaier, S.Hertrich, K.Fritz, J.-F.Moulin, M.Haese-Seiller, J.O.Rädler, B.Nickel, Langmuir (in press, dx.doi.org/10.1021/la3019887)†
