Direct electrochemistry of proteins

The first reports on direct electrochemistry of a redox active protein were published in 1977 by Hill [49] and Kuwana [50], They independently reported that cytochrome c (cyt c) exhibited virtually reversible electrochemistry on gold and tin doped indium oxide (ITO) electrodes as revealed by cyclic voltammetry, respectively. Unlike using specific promoters to realize direct electrochemistry of protein in the earlier studies, recently a novel approach that only employed specific modifications of the electrode surface without promoters was developed. From then on, achieving reversible, direct electron transfer between redox proteins and electrodes without using any mediators and promoters had made great accomplishments. 

The term direct electrochemistry of proteins means the possibility to detect the direct exchange of electrons between the active site(s) of a protein and a (metallic or inert material) electrode without the help of redox mediators, which might favour an indirect interaction between the electrode and the protein (see the discussion on Electrocatalysis in Chapter 2, Section 1.4.4). This aspect of electrochemistry is not yet as widely explored as it deserves, but the relevant results are now analysed in a rather comprehensive fashion.1 ... 

An obvious application of direct electrochemistry of proteins is the determination of redox potentials. In cases of thermodynamically inaccessible or kinetically reactive species for which traditional potentio-metric methods are inappropriate, direct electrochemistry offers an alternative approach. A good example is the 7Fe ferredoxin from Azo-tobacter chroococcum, which contains one [4Fe-4S] and one [3Fe-4S] cluster. The [4Fe-4S] + potential obtained (7i) by cyclic voltamme-... 

There now is no difficulty in achieving the electrochemistry of small redox proteins (see, for example, Armstrong et al., 1987, 1988, Frew and Hill, 1987, 1988) whether, e.g., cytochrome c, (Figure 1) ferredoxin, azurin, rubredoxin or flavodoxin (Figure 2), A variety of electrode surfaces exist at which the direct electrochemistry of proteins proceeds without the need for mediators. At some metal electrodes, what is required is the presence of some compound, called a promoter (Eddowes and Hill, 1977), which binds to the surface yet allows electron transfer to proceed (Figure 3). Over the years, many promoters have been reported (Taniguchi et al., 1982 Allen et al., 1984) and they are all bifunctional molecules, one part of which causes... 

Bagby, S., Barker, P.D., Guo, L.-H. and Hill, H.A.O. (1990) "The Direct Electrochemistry of Protein-Protein Complexes Involving Cytochrome c. Cytochrome b- and Plastocyanin, Biochemistry, 29, 3213-9. 

Ferapontova EE, Shleev S, Ruzgas T, Stoica L, Christenson A, Tkac J, Yaropolov AI, Graton L (2005) Direct electrochemistry of proteins and enzymes. Perspectives in bioanalysis 1 517-... 

Leger C (2012) Direct electrochemistry of proteins and enzymes an introduction... 

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