Interactions of mono- and di-sialogangliosides with phospholipids in mixed monolayers at air-water interface

The interactions among five different gangliosides (three monosialogangliosides GM1, GM2. GM3 and two disialogangliosides GD1a and GD1b) in mixed monolayers with dipalmitoylphosphatidylcholine [DPPC] were investigated at the air-water interface by means of surface pressure measurements. The surface pressure-area isotherms have been obtained on aqueous substrates at an ionic strength 0.145 M NaCl, pH = 7.2, at a temperature of 20 degrees C. Excess Gibbs energies of mixing in the monolayers have been calculated as a function of composition and surface pressure. Deviation from ideality denotes a different molecular organization of monosialogangliosides and disialogangliosides, indicating changes in their molecular arrangement in phospholipid monolayers due to different polar head group interactions. The possible significance of these observations is discussed in relation to ganglioside organization in biological cell membranes. (C) 1999 Elsevier Science B.V. All rights reserved.