Large unilamellar vesicle formation

THE FORMATION OF LARGE UNILAMELLAR VESICLES BY EXTRUSION METHODS... 

J. Y. A.Lehtonen, J. M. Holopainen, P. J. K. Kinnunen, Evidence for the formation of microdomains in liquid crystalline large unilamellar vesicles caused by hydrophobic mismatch of the constituent phospholipids, Biophys. J. 70 (1996) 1753. 

Hydration of Phospholipids with Solutions of Very Low Ionic Strength Very large unilamellar and oligolamellar vesicles can be prepared when a thin lipid film is dispersed in a solution of very low ionic strength (Reeves and Dowben, 1969). The formation of vesicles with diameters up to 300 pm enclosing latex beads with a diameter of 20 pm have been reported (Antanavage et al., 1978). 

The ability of the above mentioned substances to self-organize into bilayer membranes is caused by their amphiphility. During the formation of the vesicles the amphiphilic molecules orient themselves in such a way that their polar heads contact aqueous phases outside and inside the vesicle, while their nonpolar tails are directed towards the interior of the bilayer as shown in Fig. 2c. Vesicles can be classified in multilamellar, small unilamellar (d = 200-500 A) and large unilamellar (d = 1000-5000 A) ones. Since these are small unilamellar vesicles that are typically used for studying PET, in further discussion the term vesicle will always refer to the vesicles of this type, unless otherwise specified. 

Introduction - Liposomes are vesicles composed of one or more lipid bilayers completely surrounding an internal aqueous space. They are usually composed of phospholipids either in pure form or In combination with other amphipathic molecules such as sterols, long chain bases or acids, or membrane proteins. The structure of liposomes varies from large (0.5->5y) multllamellar vesicles to small ( 300 A) unilamellar vesicles.2,3 More recently, new methods have been reported describing the formation of unilamellar vesicles of intermediate size. >5.6 xhe general properties of liposomes and their interaction with various macromolecules have been described in several reviews. ... 

Several methods were applied to show the formation of ceramide-enriched membrane platforms For instance, unilamellar vesicles composed of phospha-tidylcholine/sphingomyelin were treated with immobilized sphingomyelinase, which resulted in rapid formation of large ceramide-enriched membrane platforms visualized by fluorescence microscopy of giant vesicles (Holopainen... 

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