Artificial enzyme membranes: ion-exchange, electrochemical, kinetic and electron microscopic studies of immobilized acetylcholinesterase

• Published in: Colloids and surfaces 1984, Vol.10, p.359-369
• Main Authors: Barbotin, Jean-Noel, Friboulet, Alain, Malpiece, Yves, Thomas, Daniel
• Format: Article
• Language: English
• ISSN: 0166-6622; 1873-4340
• DOI: 10.1016/0166-6622(84)80037-2

Artificial enzyme membranes can be produced with different protein molecules which offer amphoteric sites with weakly ionizable groups. The adsorption of phosphate and sodium ions in such membranes is studied as a function of both pH and concentration of the external solution. Potential differences are measured under steady-state conditions as a function of the amount of injected acetylcholine, with and without acetylcholinesterase activity in the membrane. Electron microscopic observations indicate the homogeneous repartition of active sites inside the membranes. Computer simulation based on experimental kinetic parameters is performed in order to discuss precipitate product repartition observed by electron microscopy using an histochemical reaction. By changing diffusion limitations some profiles of the insoluble product can be visualized inside the membrane. The study of our model system leads to the conclusions that firstly, there is no geometrical similarity between the distribution of active sites and the precipitate repartition, and secondly, the diffusion reaction is able to “create” a focalised precipitation line.