Freeze-fracture of lipids and model membrane systems.
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.
Hope
M J
MJ
Canadian Liposome Co., Ltd., North Vancouver, British Columbia.
Wong
K F
KF
Cullis
P R
PR
D005614:Freeze Fracturing; D008051:Lipid Bilayers; D008081:Liposomes; D008563:Membrane Lipids; D008854:Microscopy, Electron / Q000379:methods; D015394:Molecular Structure
D008051:Lipid Bilayers; D008081:Liposomes; D008563:Membrane Lipids