Ganglioside GM1 and asialo-GM1 at low concentration are preferentially incorporated into the gel phase in two-component, two-phase phosphatidylcholine bilayers.
Multilamellar liposomes composed of 1:1 dielaidoylphosphatidylcholine: dipalmitoylphosphatidylcholine at 20 degrees C contain laterally separated gel and liquid-crystalline phases that can be identified by electron microscopy in freeze-etch replicas on the basis of their distinctive morphology. Visualization of marker proteins that specifically bind to glycosphingolipids included in these liposomes has revealed that, at 1 mol % or less, the ganglioside GM1 and the neutral asialo-GM1 derived from it are localized within the gel-phase regions exclusively. Increasing the mole fraction of the glycosphingolipids results in the appearance of marker in the fluid-phase regions. Another neutral glycosphingolipid, Forssman, does not display a phase preference and is found in both phases at a low mole percent. The phase preference of these three glycosphingolipids depends primarily upon interactions between the hydrophobic moieties of these molecules and the matrix phosphatidylcholines.
Rock
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P
Department of Pathology, University of Virginia Health Sciences Center, Charlottesville 22908.
Allietta
M
M
Young
W W
WW
Thompson
T E
TE
Tillack
T W
TW
D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry; D002772:Cholera Toxin; D005613:Freeze Etching; D005677:G(M1) Ganglioside / Q000737:chemistry*; D005782:Gels; D006028:Glycosphingolipids / Q000737:chemistry*; D007700:Kinetics; D008051:Lipid Bilayers / Q000737:chemistry*; D008854:Microscopy, Electron; D010713:Phosphatidylcholines / Q000737:chemistry*
D005782:Gels; D006028:Glycosphingolipids; D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D015060:1,2-Dipalmitoylphosphatidylcholine; D005677:G(M1) Ganglioside; C018835:asialo GM1 ganglioside; D002772:Cholera Toxin; C017251:1,2-oleoylphosphatidylcholine