title: Freeze-fracture of lipids and model membrane systems.
abstract: Model membrane systems are used extensively in all aspects of membrane research, and freeze-fracture is the preeminent procedure for directly visualizing local structure in these lipid dispersions. Here we describe in detail the formation of liposomes and how freeze-fracture is routinely employed as a complementary technique to biophysical and biochemical procedures in the characterization of multilamellar vesicles (most commonly known as liposomes) and unilamellar vesicles. Many preparative procedures exist for the formation of multi- and unilamellar vesicles. Examples of each system are given and their properties as well as freeze-fracture morphology are discussed. The detection of lipid-phase transitions is considered, in particular, with emphasis on the application of freeze-fracture to the study of lipid polymorphism. We briefly discuss the fracturing of apolar lipids which do not adopt bilayer structures but which can be stabilized into microemulsions by a phospholipid monolayer. Finally, a critical assessment is made of filipin as a morphological marker for cholesterol domains in the plane of the bilayer.
authors.affiliation: Canadian Liposome Co., Ltd., North Vancouver, British Columbia.
authors.forename: M J
authors.initials: MJ
authors.lastname: Hope
authors.forename: K F
authors.initials: KF
authors.lastname: Wong
authors.forename: P R
authors.initials: PR
authors.lastname: Cullis
mesh_terms: D005614:Freeze Fracturing; D008051:Lipid Bilayers; D008081:Liposomes; D008563:Membrane Lipids; D008854:Microscopy, Electron / Q000379:methods; D015394:Molecular Structure
chemical_list: D008051:Lipid Bilayers; D008081:Liposomes; D008563:Membrane Lipids