Influence of the surface pressure on the organization of mixed Langmuir films of behenic acid and glucose oxidase

Abstract

The mechanism of adsorption of glucose oxidase at the air-water interface and under a behenic acid film has been studied. Fluorescence microscopy shows that glucose oxidase molecules adsorb at the air-water interface to form circular domains. At the equilibrium state, coalescence of the glucose oxidase domains occurs leading to a homogeneous Gibbs film of enzyme. When behenic acid is present at the air-water interface, the increase in surface pressure due to the glucose oxidase adsorption is faster than with a behenic acid free air-water interface. Isothermal compression expansion cycles of the mixed glucose oxidase behenic acid film were performed. This study shows that glucose oxidase molecules are adsorbed under the behenic acid film and at the air-water interface. Insertion of glucose oxidase molecules at the air-water interface occurs when the surface pressure of the film is below 25 mN/m. When the surface pressure is above 35 mN/m, the inserted glucose oxidase molecules are expelled from the air-water interface.