title: Budding and fission of vesicles.
abstract: We report on budding and fission of protein-free vesicles swollen from a natural lipid mixture of bovine brain sphingomyelins. Budding was induced by increasing the area-to-volume ratio through heating. Morphological changes were monitored by phase contrast microscopy and correlated with the thermal behavior of the bilayer by differential scanning calorimetry. Freeze fracture electron microscopy revealed that budding and fission are not restricted to giant vesicles but also occur on length scales relevant for cellular processes. We also observed osmotically induced budding and fission in mixtures of dimyristoyl phosphatidylcholine with cholesterol. We find that these shape transitions are driven by liquid/gel domain formation and/or coupling of the spontaneous curvature of the membrane to the local lipid composition. Our results provide evidence that coat proteins are not necessary for budding and fission of vesicles. The physics of the lipid bilayer is rich enough to explain the observed behavior.
authors.affiliation: Department of Physics, Simon Fraser University, Burnaby, British Columbia, Canada.
authors.forename: H G
authors.initials: HG
authors.lastname: Döbereiner
authors.forename: J
authors.initials: J
authors.lastname: Käs
authors.forename: D
authors.initials: D
authors.lastname: Noppl
authors.forename: I
authors.initials: I
authors.lastname: Sprenger
authors.forename: E
authors.initials: E
authors.lastname: Sackmann
mesh_terms: D000818:Animals; D055592:Biophysical Phenomena; D001703:Biophysics; D001923:Brain Chemistry; D002417:Cattle; D005614:Freeze Fracturing; D066298:In Vitro Techniques; D008051:Lipid Bilayers / Q000737:chemistry*; D008563:Membrane Lipids / Q000737:chemistry; D008565:Membrane Proteins / Q000737:chemistry; D008854:Microscopy, Electron; D008968:Molecular Conformation; D013109:Sphingomyelins / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D008051:Lipid Bilayers; D008563:Membrane Lipids; D008565:Membrane Proteins; D013109:Sphingomyelins