The effect of sterols on the rates of nonelectrolyte movement in multilayered liposomal membranes formed from various phosphatidylcholine (PC) analogues was studied. We measured the temperature dependence of the permeation of small, polar solutes through lipid bilayers in the liquidcrystalline state of the following saturated phosphatidylcholines: diesters containing 14, 16, or 18 carbon atoms in each acyl chain; the corresponding diethers, which lack the carbonyl groups; and alkyl analogues, such as 2-octadecyleicosylphosphorylcholine (OEPC), which have no diacylglycerol or glycerol diether moiety. In addition, a diether-PC having one saturated and one unsaturated chain was used, and analogues of OEPC were synthesized in which the choline group is modified. At temperatures above the gel to liquid-crystalline phase transition of these diester, diether, and alkyl analogues of PC, the 30-hydroxysteroids cholesterol and ergosterol decreased the permeability of glycerol, urea, acetamide, and glucose, whereas epicholesterol and lanosterol exerted little effect on the reflection coefficient for acetamide penetration. Cholesterol reduced solute permeability in liposomes from OEPC analogues having increased separation

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Gangliosides were compared with glycoproteins as potential receptors for Sendai virus by incorporating measured amounts of the glycoconjugates into lecithin-cholesterol liposomes and measuring binding by a hemagglutination assay with sheep erythrocytes. HeLa cell gangliosides showed no binding activity toward the virus up to 15 jig of sialic acid per 5 ,umol of lecithin-cholesterol, whereas HeLa cell glycoproteins incorporated into similar liposomes caused avid virus binding below 1 ,ug of sialic acid. These sialoglycoproteins could be separated from the bulk of cell proteins by multiple chloroform-methanol extractions. Purified rat brain gangliosides at a level of 120 ,ug of sialic acid in liposomes did not bind virus, whereas chloroform-methanol-extracted rat brain proteins caused only marginal binding. Bovine brain gangliosides differed slightly from the rat brain mixture in showing weak binding properties. Our results thus indicate that glycoproteins, rather than gangliosides, are the natural receptors for Sendai virus and that tissues differ as to the quantity of such protein receptors.

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