title: Fluid domain patterns in free-standing membranes captured on a solid support.
abstract: We devise a methodology to fixate and image dynamic fluid domain patterns of giant unilamellar vesicles (GUVs) at sub-optical length scales. Individual GUVs are rapidly transferred to a solid support forming planar bilayer patches. These are taken to represent a fixated state of the free standing membrane, where lateral domain structures are kinetically trapped. High-resolution images of domain patterns in the liquid-ordered (lo) and liquid-disordered (ld) co-existence region in the phase-diagram of ternary lipid mixtures are revealed by atomic force microscopy (AFM) scans of the patches. Macroscopic phase separation as known from fluorescence images is found, but with superimposed fluctuations in the form of nanoscale domains of the lo and ld phases. The size of the fluctuating domains increases as the composition approaches the critical point, but with the enhanced spatial resolution, such fluctuations are detected even deep in the coexistence region. Agreement between the area-fraction of domains in GUVs and the patches respectively, supports the assumption that the thermodynamic state of the membrane remains stable. The approach is not limited to specific lipid compositions, but could potentially help uncover lateral structures in highly complex membranes.
authors.affiliation: MEMPHYS - Center for Biomembrane Physics, University of Southern Denmark (SDU), 5230 Odense M, Denmark; Department of Physics Chemistry and Pharmacy, SDU.
authors.forename: Tripta
authors.initials: T
authors.lastname: Bhatia
authors.affiliation: MEMPHYS - Center for Biomembrane Physics, University of Southern Denmark (SDU), 5230 Odense M, Denmark.
authors.forename: Peter
authors.initials: P
authors.lastname: Husen
authors.affiliation: MEMPHYS - Center for Biomembrane Physics, University of Southern Denmark (SDU), 5230 Odense M, Denmark; Department of Physics Chemistry and Pharmacy, SDU.
authors.forename: John H
authors.initials: JH
authors.lastname: Ipsen
authors.affiliation: MEMPHYS - Center for Biomembrane Physics, University of Southern Denmark (SDU), 5230 Odense M, Denmark; Department of Biochemistry and Molecular Biology, SDU.
authors.forename: Luis A
authors.initials: LA
authors.lastname: Bagatolli
authors.affiliation: MEMPHYS - Center for Biomembrane Physics, University of Southern Denmark (SDU), 5230 Odense M, Denmark; Department of Physics Chemistry and Pharmacy, SDU. Electronic address: adam@memphys.sdu.dk.
authors.forename: Adam Cohen
authors.initials: AC
authors.lastname: Simonsen
mesh_terms: D008563:Membrane Lipids / Q000737:chemistry*; D021962:Membrane Microdomains / Q000737:chemistry* / Q000000981:diagnostic imaging; D008567:Membranes, Artificial; D018625:Microscopy, Atomic Force; D014463:Ultrasonography
chemical_list: D008563:Membrane Lipids; D008567:Membranes, Artificial
keywords: AFM; Domains; Giant unilamellar vesicles; Membranes; Rafts