title: Thermally-induced aggregation and fusion of protein-free lipid vesicles.
abstract: Membrane fusion is an important phenomenon in cell biology and pathology. This phenomenon can be modeled using vesicles of defined size and lipid composition. Up to now fusion models typically required the use of chemical (polyethyleneglycol, cations) or enzymatic catalysts (phospholipases). We present here a model of lipid vesicle fusion induced by heat. Large unilamellar vesicles consisting of a phospholipid (dioleoylphosphatidylcholine), cholesterol and diacylglycerol in a 43:57:3 mol ratio were employed. In this simple system, fusion was the result of thermal fluctuations, above 60 °C. A similar system containing phospholipid and cholesterol but no diacylglycerol was observed to aggregate at and above 60 °C, in the absence of fusion. Vesicle fusion occurred under our experimental conditions only when (31)P NMR and cryo-transmission electron microscopy of the lipid mixtures used in vesicle preparation showed non-lamellar lipid phase formation (hexagonal and cubic). Non-lamellar structures are probably the result of lipid reassembly of the products of individual fusion events, or of fusion intermediates. A temperature-triggered mechanism of lipid reassembly might have occurred at various stages of protocellular evolution.
authors.affiliation: Unidad de Biofísica (Centro Mixto CSIC, UPV/EHU), and Departamento de Bioquímica, Universidad del País Vasco, Apto. 644, 48080 Bilbao, Spain. Electronic address: maitaneibarguren@hotmail.com.
authors.forename: Maitane
authors.initials: M
authors.lastname: Ibarguren
authors.affiliation: Soft Matter CryoTEM Research Unit, Laboratory for Materials and Interface Chemistry, P.O. Box 513, 5600MB Eindhoven, The Netherlands. Electronic address: p.h.h.bomans@biomat.tue.
authors.forename: Paul H H
authors.initials: PH
authors.lastname: Bomans
authors.affiliation: Unidad de Biofísica (Centro Mixto CSIC, UPV/EHU), and Departamento de Bioquímica, Universidad del País Vasco, Apto. 644, 48080 Bilbao, Spain; Logic and Philosophy of Science Department, University of the Basque Country, Spain. Electronic address: kepa.ruiz-mirazo@ehu.es.
authors.forename: Kepa
authors.initials: K
authors.lastname: Ruiz-Mirazo
authors.affiliation: Soft Matter CryoTEM Research Unit, Laboratory for Materials and Interface Chemistry, P.O. Box 513, 5600MB Eindhoven, The Netherlands. Electronic address: peter.frederik@elmi.unimaas.nl.
authors.forename: Peter M
authors.initials: PM
authors.lastname: Frederik
authors.affiliation: Unidad de Biofísica (Centro Mixto CSIC, UPV/EHU), and Departamento de Bioquímica, Universidad del País Vasco, Apto. 644, 48080 Bilbao, Spain. Electronic address: alicia.alonso@ehu.es.
authors.forename: Alicia
authors.initials: A
authors.lastname: Alonso
authors.affiliation: Unidad de Biofísica (Centro Mixto CSIC, UPV/EHU), and Departamento de Bioquímica, Universidad del País Vasco, Apto. 644, 48080 Bilbao, Spain. Electronic address: felix.goni@ehu.e.
authors.forename: Félix M
authors.initials: FM
authors.lastname: Goñi
mesh_terms: D008055:Lipids / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D046529:Microscopy, Electron, Transmission; D011506:Proteins / Q000737:chemistry
chemical_list: D008055:Lipids; D011506:Proteins
keywords: Cholesterol; Fusion; Non-lamellar phases; Thermal fluctuations