Combining a Commercial Mixer with a Wall-Tube Electrode Allows the Arbitrary Control of Concentrations in Protein Film Electrochemistry
Résumé
Protein Film Electrochemistry is a technique in which an enzyme is immobilized on an electrode in a configuration which allows following the changes in turnover frequency as a response to changes in the experimental conditions. Insights on the reactivity of the enzyme can be obtained by quantitatively modeling such responses. As a consequence, the more the technique allows flexibility in changing conditions, the more useful it becomes. The most commonly used setup, based on the rotating disc electrode, allows easy stepwise increases in the concentration of non-gaseous substrates, or exposure to constant concentration of dissolved gas, but does not permit to easily decrease the concentration of non-gaseous substrates, or to change the concentration of dissolved gas in a stepwise fashion. To overcome the limitation by mass-transport of the substrate towards the electrode when working with fast enzymes, we have designed another kind of electrochemical cell based on the wall-tube electrode. We demonstrate here that by using a system combining two syringe pumps, a commercial mixer and the wall-tube electrode, it is possible to change the concentration of species in a stepwise fashion in all directions, opening new possibilities to study redox enzymes. As a proof-of-concept, this device was applied to the study of the electrochemical response of the cytochrome c nitrite reductase of Desulfovibrio desulfuricans.