Interactions of neutral and anionic glycosphingolipids with dilauroylphosphatidylcholine and dilauroylphosphatidic acid in mixed monolayers

Abstract

The effect of short hydrocarbon chains of phospholipids on the interactions with glycosphingolipids having different oligosaccharide chains was studied for systems containing dilauroylphosphatidylcholine or dilauroylphosphatidic acid mixed in different proportions with galactosylceramide, sulfatide, or gangliosides G M1, G D1a or G T1b. Lipid monolayers at the air-NaCl interface in the presence or absence of CaCl 2 were studied. The mean molecular area and surface potential per molecule at different surface pressures and the excess free energy of mixing were compared with the corresponding parameters obtained for mixtures of the same glycosphingolipids with dipalmitoylphosphatidylcholine and dipalmitoylphosphatidic acid. In addition to the well-known influence of the polar head group of the glycosphingolipids and phospholipids on the intermolecular interaction, the present work shows that the organization and surface potential of these interfaces are markedly influenced by the type of hydrocarbon chain of the phospholipid. The surface behavior is modified by the presence of Ca 2+ which, in addition, induces immiscibility in some of these mixtures.