title: Atomic force microscopy of nanometric liposome adsorption and nanoscopic membrane domain formation.
abstract: Scanning probe microscopy studies of membrane fusion and nanoscopic structures were performed using hydrated single lipids and lipid mixtures. Extruded vesicles of DMPC and mixtures at various concentrations of DLPC, DPPC and cholesterol were deposited on freshly cleaved mica and studied in a fluid environment by AFM. The nanostructures formed by these extruded liposomes ranged from isolated unilamellar vesicles to flat sheet membranes and were marked influenced by thermodynamic phase behavior. For DMPC membrane, intact bilayers exhibited a phase transition process in agreement with large bilayer patches. In the DLPC, DPPC and cholesterol mixtures, nanoscopic domain diameters ranged from approximately 25 to 48nm with height differences of approximately 1.4nm; all values were lipid composition-dependent. Our data support and extend previous studies of microscopic domains and phase boundaries of the same mixtures in giant unilamellar vesicles determined by confocal light microscopy. Our approach for preparing and utilizing supported membrane structures is potentially relevant to studies of native cell membranes.
authors.affiliation: Biochemical and Biophysical Parasitology Section, Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Fuyuki
authors.initials: F
authors.lastname: Tokumasu
authors.forename: Albert J
authors.initials: AJ
authors.lastname: Jin
authors.forename: Gerald W
authors.initials: GW
authors.lastname: Feigenson
authors.forename: James A
authors.initials: JA
authors.lastname: Dvorak
mesh_terms: D000327:Adsorption; D002784:Cholesterol / Q000737:chemistry; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry; D008051:Lipid Bilayers / Q000737:chemistry; D008081:Liposomes / Q000737:chemistry*; D008561:Membrane Fusion; D021962:Membrane Microdomains / Q000737:chemistry*; D008567:Membranes, Artificial; D018625:Microscopy, Atomic Force / Q000379:methods*; D010743:Phospholipids / Q000737:chemistry
chemical_list: D008051:Lipid Bilayers; D008081:Liposomes; D008567:Membranes, Artificial; D010743:Phospholipids; D002784:Cholesterol; D004134:Dimyristoylphosphatidylcholine