Immobilisation of redox proteins and enzymes on electrode surfaces forms the basis for the development of bionanotechnological systems and the use of electrochemical techniques provides opportunities to study their function in great detail. Membrane proteins and enzymes functioning as ion-channels or pumps regulate ion transport across cell membranes, a vital process for signal transduction and energetics of the cell. In particular redox enzymes, involved in cellular respiration utilise the free energy generated by electron transfer reactions to transport protons across membranes, generating a transmembrane proton electrochemical gradient used in cells for ATP synthesis. Although, such biomolecules can be difficult to manipulate, a membrane-friendly interface has been developed that allows the immobilisation of model membranes in the form of vesicles on Au electrodes. The pH-sensitive-fluorescent probe loaded vesicles remain intact on the SAM functionalised electrodes; and the incorporation of an ubiquinol oxidase, cytochrome bo₃ from Escherichia coli, allows studying the mechanism (proton pumping activity) of the enzyme, by monitoring the fluorescence response of the probe in real time. The activity of cytochrome bo₃ can be regulated by electrochemically tuning the redox state of ubiquinone that serves as an electron shuttle to the enzyme.

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1. Electrodes for integral membrane enzymes
2. Nitrite Reductase, an enzyme for which kinetics are different at rest than during turn over.