Figure 6 Background-subtracted cyclic voltammetry of metmyoglobin: (A) 86 µM met-myoglobin, pH 7.0; (B) 67 mM metmyoglobin, pH 7.0, with excess cyanide to give [Mb(III)H O]:[CN] of 1:300. Scan

The goal was to immobilize cytochrome c oxidase in an electrode-supported lipid bilayer membrane so that it would undergo direct electron transfer with the electrode and mediate electron transfer from cytochrome c in solution to the electrode. This system was envisioned to better mimic the in vivo conditions of the reaction between cytochrome c and the oxidase compared to experiments with detergent-solubilized oxidase [62, 63] as described above. Also, this system was designed to provide a more direct means of probing this reaction couple compared to experiments with the oxidase inserted into the bilayer membrane of vesicles in solution [64]. In other experiments probing this reaction couple, the electrons involved in the catalytic oxidation of reduced cytochrome c by cytochrome c oxidase ultimately reduce another species also present in solution (e.g., molecular oxygen). Direct electron transfer between the electrode and the cytochrome c oxidase would make it possible to probe the kinetics of the reaction between cytochrome c in solution and the immobilized cytochrome c oxidase. The current generated by enzyme-mediated electron transfer from cytochrome c in solution, through the cytochrome c oxidase to the electrode, could then be controlled by the applied electrode potential.