title: Morphometric image analysis of giant vesicles: a new tool for quantitative thermodynamics studies of phase separation in lipid membranes.
abstract: We have developed a strategy to determine lengths and orientations of tie lines in the coexistence region of liquid-ordered and liquid-disordered phases of cholesterol containing ternary lipid mixtures. The method combines confocal-fluorescence-microscopy image stacks of giant unilamellar vesicles (GUVs), a dedicated 3D-image analysis, and a quantitative analysis based in equilibrium thermodynamic considerations. This approach was tested in GUVs composed of 1,2-dioleoyl-sn-glycero-3-phosphocholine/1,2-palmitoyl-sn-glycero-3-phosphocholine/cholesterol. In general, our results show a reasonable agreement with previously reported data obtained by other methods. For example, our computed tie lines were found to be nonhorizontal, indicating a difference in cholesterol content in the coexisting phases. This new, to our knowledge, analytical strategy offers a way to further exploit fluorescence-microscopy experiments in GUVs, particularly retrieving quantitative data for the construction of three lipid-component-phase diagrams containing cholesterol.
authors.affiliation: MEMPHYS Center for Biomembrane Physics, University of Southern Denmark, Odense, Denmark.
authors.forename: Peter
authors.initials: P
authors.lastname: Husen
authors.forename: Laura R
authors.initials: LR
authors.lastname: Arriaga
authors.forename: Francisco
authors.initials: F
authors.lastname: Monroy
authors.forename: John H
authors.initials: JH
authors.lastname: Ipsen
authors.forename: Luis A
authors.initials: LA
authors.lastname: Bagatolli
mesh_terms: D008051:Lipid Bilayers / Q000737:chemistry*; D008560:Membrane Fluidity; D008563:Membrane Lipids / Q000737:chemistry*; D021962:Membrane Microdomains / Q000737:chemistry* / Q000648:ultrastructure*; D018613:Microscopy, Confocal / Q000379:methods*; D008856:Microscopy, Fluorescence / Q000379:methods*; D044367:Phase Transition; D013816:Thermodynamics
chemical_list: D008051:Lipid Bilayers; D008563:Membrane Lipids