Relationship of two electroactive forms of horse heart cytochrome c at gold and glassy carbon electrodes in water and methanol

A voltammetric study of direct electron transfer to cytochrome c using a very large assembly of carbon microelectrodes

“…Assuming the diffusion coefficient D of ferricytochrome c is approximately 6 3 10 27 cm 2 s 21 and given that the radius r of the microdisk is 3.5 3 10 24 cm, this immediately implies that the standard rate constant of electron transfer k 0 > 5 3 10 22 cm s 21 . Because the electron transfer process is electrochemically reversible, the half wave potential at a microdisk electrode can be related to the formal potential by the equation 15…”

“…It is known that cytochrome c can exist in at least five different conformations, 9,10 and several groups have investigated how the conformational equilibria vary with pH. 2,[19][20][21] When the pH is increased above 8, one ligand of the iron atom, Met 80 , is replaced by another ligand, lysine. This replacement changes the 'native form' of cytochrome c to the 'alkaline form' of cytochrome c. At equilibrium, a solution of cytochrome c contains a mixture of the native and alkaline forms.…”

“…4. All voltammograms were recorded at a potential scan rate of 20 mV s 21 . The corresponding plot of the formal potential of 50.3 mM cytochrome c versus pH is shown in Fig.…”

Electrochemical behaviour of cytochrome c at electrically heated microelectrodes

“…This led to much research activity for developing the most effective promoter. However, in the 1980s, there were reports that electrochemistry could be observed at unmodified electrodes [3,4]. This has been more recently confirmed [5][6][7].…”

Direct voltammetry of cytochrome c at trace concentrations with nanoelectrode ensembles

“…It was also shown that adsorption related problems are relevant for the successful observation of electron transfer between cytochrome c and electrodes surface and such an effect arises by a combination of factors [27]. On the one hand the adsorption of cyt c itself could lead to inhibition and complete blocking of the faradaic process [36][37][38]. On the other hand the adsorption of trace impurities present in the lyophilized protein sample can modify the surface [39,40].…”