Cytochrome electrochemical reactivity

E.I. Iwuoha, S. Joseph, Z. Zhang, M.R. Smyth, U. Fuhr, and P.R. Ortiz de Montellano, Drug metabolism biosensors electrochemical reactivities of cytochrome CYP101 immobilised in synthetic vesicular systems. J. Pharm. Biom. Anal. 17, 1101-1110 (1998). 

Cyclic voltammetry has been also used for estimation of the rate constants for oxidation of water-soluble ferrocenes in the presence of HRP (131). There is a perfect match between the data obtained spectrophotometrically and electrochemically (Table IV), which proves that the cyclic voltammetry reveals information on the oxidation of ferrocenes by Compound II. It is interesting to note that an enzyme similar to HRP, viz. cytochrome c peroxidase, which catalyzes the reduction of H202 to water using two equivalents of ferrocytochrome c (133-136), is ca. 100 times more reactive than HRP (131,137). The second-order rate constant equals 1.4 x 106 M-1 s 1 for HOOCFc at pH 6.5 (131). There is no such rate difference in oxidation of [Fe(CN)e]4- by cytochrome c peroxidase and HRP (8). These comparisons should not however create an impression that the enzymatic oxidation of ferrocenes is always fast. The active-R2 subunit of Escherichia coli ribonucleotide reductase, which has dinuclear nonheme iron center in the active site, oxidizes ferrocene carboxylic acid and other water-soluble ferrocenes with a rate constant of... 

Reduction of horse cytochrome C with [Colsepll ", [Co(diAMsar)]2+, and [Co(NOcapten)]2+ cations was reported in Refs. 316-320. The intrinsic reactivity of these complexes with proteins make it possible the use of clathrochelates as potential protein redox titrants, electrochemical mediators, and electrode modifiers. 

IwuohaEl, Kane S, Ania CO, Smyth MR, Ortiz de Montellano PR, Fuhr U (2000) Reactivities of (H-ganic phase biosensors 3 electrochemical study of cytochrome P450 cam immobiUsed in a methyltriethoxysilane sol-gel. Electroanalysis 12 980-986... 

In this report we address cytochrome c, which is the most well-understood electron transfer protein. It has occupied a prominent role in interfacial electrochemical investigations due to its high degree of structural and reactivity characterization and its ready availability and purification. Cytochrome c has been found to react in a reproducible, quasi-reversible manner at a number of solid electrode surfaces. Electrode surfaces which have been most successful in this regard are metal oxides and chemically modified metal electrodes . Cytochrome c also has the potential to react readily at unmodified metal electrodes, as exemplified by the recent report of a stable, quasi-reversible reaction at bare silver . 

The results of a recent investigational of model systems provide compelling evidence that stabilized atomic oxygen is present in Compound I and Compound II of horseradish peroxidase and the reactive form of cytochrome P-450. Thus, the combination of tetrakis(2,6-dichlorophenyl)-porphinato iron(III) perchlorate (1, Scheme 1) with pentafluoro-iodoso-benzene, m-chloroperbenzoic acid, or ozone in acetonitrile at -35 C yields a green porphyrin-oxene adduct (2). This species, which has been characterized by spectroscopic, magnetic and electrochemical methods, cleanly and stereospecifically epoxidizes olefins (>99% exo-norbornene-oxide), oxidizes alcohols to aldehydes, oxidatively cleaves diols, and demethylates dimethyl aniline (Scheme 1). 

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