Interaction of GM(1) glycolipid in phospholipid monolayers with wheat germagglutinin: effect of phospholipidic environment and subphase

Mixed monolayers of GM(1) glycolipid and stearoyl-oleoyl-phosphatidylcholin e (SOPC) or dipalmitoyl-phosphatidycholine (DPPC) phospholipids were studie d by surface pressure measurements. The effects induced by GM(1) on the mea n molecular areas of mixtures and DPPC phase transition were followed for G M(1) concentrations ranging from 1 to 20 mol.%. Under our experimental cond itions, one main parameter influencing the behavior of phospholipid-GM(1) m onolayers is the ionic strength of the subphase. Mixed monolayers are in a more expanded state on buffer than on pure water. This could be due to a ch ange of GM(1) orientation at the interface. The interaction of wheat germ a gglutinin (WGA), a lectin recognizing specifically GM(1) with these monolay ers was quantified in terms of the Gibbs equation. Specific WGA-GM(1) inter actions are clearly reduced in the presence of DPPC as compared with SOPC, probably because of the higher packing density of these monolayers. Phospho lipid-GM(1) monolayers could also undergo some rearrangements induced by WG A binding. (C) 2001 Published by Elsevier Science Ireland Ltd.