A study of the interaction between glycolipids of different hydrophobicities and glucose oxidase by a monolayer technique

Glycolipids with aliphatic chains of increasing length (C12, C14, C16, C18) and polar heads of either glucoside or maltoside have been synthesized. Glucose oxidase(GOD) was used as a representative of a protein. The surface pressure-area (pi-A) isotherms of these glycolipid monolayers spread at the air/water interface were recorded and their morphology after interacting with GOD was investigated using Brewster angle microscopy. The Delta pi-pi(i) relationships were indicative of the extent of GOD penetration into the lipid monolayer. The experimental results showed that glycolipids with short chains formed liquid-expanded monolayers whereas those with long chains formed condensed monolayers. It was also found that even at very low surface pressures Glu(C18)(2) monolayers aggregated in clusters while the monolayers of Glu(C14)(2) appeared to be homogeneous. The Delta pi-pi(i) curves showed that the longer the hydrophobic chain of a glycolipid, the easier was the penetration of GOD. The obtained results clearly demonstrated that GOD penetration into glycolipids is related to the hydrophobic part of glycolipids, i.e. that the predominant force between GOD and glycolipids is the hydrophobic force.