QUANTITATIVE MEASUREMENTS OF THE INTERACTION BETWEEN MONOSIALOGANGLIOSIDE MONOLAYERS AND WHEAT-GERM-AGGLUTININ (WGA) BY A QUARTZ-CRYSTAL MICROBALANCE

Monosialogangliosides (GM1, GM2, GM3 and GM4) were reconstituted in li pid monolayers at the air-water interface, The binding amounts and the initial binding rates of wheat germ agglutinin (WGA) to the monosialo ganglioside monolayers were quantitatively studied by use of a quartz- crystal microbalance (QCM). A QCM was horizontally attached to the mon olayer from the air phase, and the binding behavior (mass, increase) w as followed by the frequency decrease of the QCM. WGA binding affiniti es for the ganglioside monolayers were influenced by hydrophilic head groups OF lipid matrices, densities of gangliosides, and sequences of oligosaccharide in gangliosides. Binding of WGA to the gangliosides re constituted in a phosphatidylcholine (sphingomyelin and distearoylphos phatidylcholine) matrix was strongly suppressed. but not in a neutral glycolipids (GlcCer, GalCer, and LacCer, dipalmitoylphosphatidylethano lamine, and dipalmitoylphosphatidylethanolamine matrix. WGA showed hig h affinity for monolayers containing 20mol% gangliosides, but only low affinity for 100% ganglioside monolayers. WGA preferably binds to gan gliosides in the following sequence: GM3 > GM4 much greater than GM2 = GM1. No affinities of WGA for GM2 and GM1 were observed. The combined techniques of monolayer and QCM have the advantages of investigating recognition properties of gangliosides. (C) 1998 Elsevier Science B.V.