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7631790 
Journal Article 
Formation of a macroscopic membrane structure by liposomes containing cationic lipids and exposed to DC electric fields 
Soderlund, T; Lehtonen, JYA; Sievi, JJ; Kinnunen, PKJ; , 
1997 
Yes 
Chemistry and Physics of Lipids
ISSN: 0009-3084 
ELSEVIER SCI IRELAND LTD 
CLARE 
107-114 
WOS:A1997WM95100003 
Application of DC electric fields (from 20-30.4 kV/m) caused a rapid (within 1-5 s) formation of a large membrane structure in an aqueous solution of unilamellar liposomes composed of egg phosphatidylcholine and a cationic amphiphile, either sphingosine or stearylamine (mole fraction X = 0.25). The formation of this structure could be readily observed by phase contrast microscopy. Maintenance of the membrane required the DC field and it disappeared rapidly (within approximate to 5 s) upon the removal of the field. The formation of the assembly was reversible. Such structures were not formed by vesicles composed of phosphatidylcholine only or containing instead of the cationic amphiphile an anionic lipid, phosphatidic acid. Fusion or a hemifusion of the vesicles is likely to take place as fluorescence microscopy of liposomes labeled with a pyrene-containing phospholipid analog revealed domain formation within the field-induced membrane, evident as a depletion of fluorescence in the region subjected to highest field intensity. (C) 1997 Elsevier Science Ireland Ltd.