GANGLIOSIDE GM1 AND ASIALO-GM1 AT LOW CONCENTRATION ARE PREFERENTIALLY INCORPORATED INTO THE GEL PHASE IN 2-COMPONENT, 2-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 G(M1) and the neutral asialo-G(M1) 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.