title: In situ determination of structure and fluctuations of coexisting fluid membrane domains.
abstract: Biophysical understanding of membrane domains requires accurate knowledge of their structural details and elasticity. We report on a global small angle x-ray scattering data analysis technique for coexisting liquid-ordered (Lo) and liquid-disordered (Ld) domains in fully hydrated multilamellar vesicles. This enabled their detailed analysis for differences in membrane thickness, area per lipid, hydrocarbon chain length, and bending fluctuation as demonstrated for two ternary mixtures (DOPC/DSPC/CHOL and DOPC/DPPC/CHOL) at different cholesterol concentrations. Lo domains were found to be ~10 Å thicker, and laterally up to 20 Å(2)/lipid more condensed than Ld domains. Their bending fluctuations were also reduced by ~65%. Increase of cholesterol concentration caused significant changes in structural properties of Ld, while its influence on Lo properties was marginal. We further observed that temperature-induced melting of Lo domains is associated with a diffusion of cholesterol to Ld domains and controlled by Lo/Ld thickness differences.
authors.affiliation: Biophysics Division, Institute of Molecular Biosciences, University of Graz, NAWI Graz, Graz, Austria; BioTechMed-Graz, Graz, Austria.
authors.forename: Peter
authors.initials: P
authors.lastname: Heftberger
authors.affiliation: Biophysics Division, Institute of Molecular Biosciences, University of Graz, NAWI Graz, Graz, Austria; BioTechMed-Graz, Graz, Austria.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Kollmitzer
authors.affiliation: Biophysics Division, Institute of Molecular Biosciences, University of Graz, NAWI Graz, Graz, Austria; BioTechMed-Graz, Graz, Austria.
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Rieder
authors.affiliation: Institute of Inorganic Chemistry, Graz University of Technology, Graz, Austria.
authors.forename: Heinz
authors.initials: H
authors.lastname: Amenitsch
authors.affiliation: Biophysics Division, Institute of Molecular Biosciences, University of Graz, NAWI Graz, Graz, Austria; BioTechMed-Graz, Graz, Austria. Electronic address: georg.pabst@uni-graz.at.
authors.forename: Georg
authors.initials: G
authors.lastname: Pabst
mesh_terms: D008560:Membrane Fluidity; D008563:Membrane Lipids / Q000737:chemistry*; D021962:Membrane Microdomains / Q000737:chemistry*; D056004:Molecular Dynamics Simulation
chemical_list: D008563:Membrane Lipids