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Deng Y, Weaver ML, Hoke KR, Pletneva EV. A Heme Propionate Staples the Structure of Cytochrome c for Methionine Ligation to the Heme Iron. Inorg Chem 2019; 58:14085-14106. [PMID: 31589413 DOI: 10.1021/acs.inorgchem.9b02111] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Ligand-switch reactions at the heme iron are common in biological systems, but their mechanisms and the features of the polypeptide fold that support dual ligation are not well understood. In cytochrome c (cyt c), two low-stability loops (Ω-loop C and Ω-loop D) are connected by the heme propionate HP6. At alkaline pH, the native Met80 ligand from Ω-loop D switches to a Lys residue from the same loop. Deprotonation of an as yet unknown group triggers the alkaline transition. We have created the two cyt c variants T49V/K79G and T78V/K79G with altered connections of these two loops to HP6. Electronic absorption, NMR, and EPR studies demonstrate that at pH 7.4 ferric forms of these variants are Lys-ligated, whereas ferrous forms maintain the native Met80 ligation. Measurements of protein stability, cyclic voltammetry, pH-jump and gated electron-transfer kinetics have revealed that these Thr to Val substitutions greatly affect the alkaline transition in both ferric and ferrous proteins. The substitutions modify the stability of the Met-ligated species and reduction potentials of the heme iron. The kinetics of ligand-switch processes are also altered, and analyses of these effects implicate redox-dependent differences in metal-ligand interactions and the role of the protein dynamics, including cross-talk between the two Ω-loops. With the two destabilized variants, it is possible to map energy levels for the Met- and Lys-ligated species in both ferric and ferrous proteins and assess the role of the protein scaffold in redox-dependent preferences for these two ligands. The estimated shift in the heme iron reduction potential upon deprotonation of the "trigger" group is consistent with those associated with deprotonation of an HP, suggesting that HP6, on its own or as a part of a hydrogen-bonded cluster, is a likely "trigger" for the Met to Lys ligand switch.
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Affiliation(s)
- Yunling Deng
- Department of Chemistry , Dartmouth College , Hanover , New Hampshire 03755 , United States
| | - Madeline L Weaver
- Department of Chemistry and Biochemistry , Berry College , Mount Berry , Georgia 30149 , United States
| | - Kevin R Hoke
- Department of Chemistry and Biochemistry , Berry College , Mount Berry , Georgia 30149 , United States
| | - Ekaterina V Pletneva
- Department of Chemistry , Dartmouth College , Hanover , New Hampshire 03755 , United States
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Direct voltammetry of cytochrome c at trace concentrations with nanoelectrode ensembles. J Electroanal Chem (Lausanne) 2003. [DOI: 10.1016/j.jelechem.2003.06.007] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Battistuzzi G, Borsari M, Ranieri A, Sola M. Conservation of the free energy change of the alkaline isomerization in mitochondrial and bacterial cytochromes c. Arch Biochem Biophys 2002; 404:227-33. [PMID: 12147260 DOI: 10.1016/s0003-9861(02)00283-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The thermodynamic parameters of the alkaline transition for oxidized native yeast iso-1 cytochrome c and Rhodopseudomonas palustris cytochrome c(2) (cytc(2)) have been determined through direct electrochemistry experiments carried out at variable pH and temperature and compared to those for horse and beef heart cytochromes c. We have found that both transition enthalpy and entropy are remarkably species dependent, following the order R. palustris cytc(2) >> beef (horse) heart cytc>yeast iso-1 cytc. Considering the high homology at the heme-protein interface in the native species, this variability is likely to be mainly determined by differences in the structural and solvation properties and the relative abundance of the various alkaline conformers. Notably, changes in transition enthalpy and entropy among these cytochromes c are compensative and result in small variations in the free energy change of the process (which amounts approximately to +50 kJ mol(-1)) and consequently in the apparent pK(a) value. This compensation indicates that solvent reorganization effects play an important role in the thermodynamics of the transition. This mechanism is functional to ensure a relatively high pK(a) value for the alkaline transition, which is needed to preserve His,Met ligation to the heme iron in cytochrome c at physiological pH and temperature, hence the E(o) value required for the biological function.
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Affiliation(s)
- Gianantonio Battistuzzi
- Department of Chemistry, University of Modena and Reggio Emilia, Via Campi 183, 41100, Modena, Italy
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Battistuzzi G, Borsari M, Ranieri A, Sola M. Effects of Specific Anion-Protein Binding on the Alkaline Transition of Cytochrome c. Arch Biochem Biophys 2001; 386:117-22. [PMID: 11360995 DOI: 10.1006/abbi.2000.2183] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The thermodynamic parameters of the alkaline transition of beef heart ferricytochrome c have been measured through direct electrochemistry experiments carried out at variable pH and temperature in the presence of different sulfate concentrations. Sulfate is known to bind specifically to cytochrome c in a sequential manner at two surface sites. The effects of such a specific binding reflect on the thermodynamics of the transition and can be satisfactorily interpreted within the frame of the Debye-Hückel theory with simple electrostatic considerations. In particular, the increase in the thermodynamic pKa values (extrapolated to I = 0) upon sulfate binding turns out to be a fully enthalpic effect which can be accounted for by considering the coulombic effects of the formation of ionic couple(s) on the protein surface. This study also shows that the apparent pKa values at finite ionic strength are only moderately affected by the nature of the anion in solution, and differences tend to vanish at high ionic strength.
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Affiliation(s)
- G Battistuzzi
- Department of Chemistry, University of Modena and Reggio Emilia, Italy
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Sivakolundu SG, Mabrouk PA. Cytochrome c Structure and Redox Function in Mixed Solvents Are Determined by the Dielectric Constant. J Am Chem Soc 2000. [DOI: 10.1021/ja993225m] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - Patricia Ann Mabrouk
- Contribution from the Department of Chemistry, Northeastern University, Boston, Massachusetts 02115
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Battistuzzi G, Borsari M, Loschi L, Martinelli A, Sola M. Thermodynamics of the alkaline transition of cytochrome c. Biochemistry 1999; 38:7900-7. [PMID: 10387031 DOI: 10.1021/bi983060e] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The apparent equilibrium constant (Kapp) of the alkaline transition (AT) of beef heart cytochrome c, obtained from pH titrations of the current intensities in cyclic voltammetry experiments, has been measured as a function of the temperature from 5 to 65 degrees C, at different ionic strength (I = 0.01-0.2 M). The temperature profile of the pKapp values is biphasic and yields two distinct sets of DeltaH degrees 'AT and DeltaS degrees 'AT values below and above approximately 40 degrees C. In the low-temperature range, the process is endothermic and is accompanied by a small positive entropy change, while at higher temperatures it becomes less endothermic and involves a pronounced entropy loss. The temperature dependence of the transition thermodynamics is most likely the result of the thermal transition of native ferricytochrome c from a low-T to an high-T conformer which occurs at alkaline pH values at a temperature comparable with above (Ikeshoji, T., Taniguchi, I., and Hawkridge, F. M. (1989) J. Electroanal. Chem. 270, 297-308; Battistuzzi, G., Borsari, M., Sola, M., and Francia, F. (1997) Biochemistry 36, 16247-16258). Thus, it is apparent that the transitions of the two native conformers to the corresponding alkaline form(s) are thermodynamically distinct processes. It is suggested that this difference arises from either peculiar transition-induced changes in the hydration sphere of the protein or to the preferential binding of different lysines to the heme iron in the two temperature ranges. Extrapolation of the Kapp values at null ionic strength allowed the determination of the thermodynamic equilibrium constants (Ka) at each temperature, hence of the "true" standard thermodynamic parameters of the transition. The pKa value at 25 degrees C was found to be 8.0. A pKapp value of 14.4 was calculated for the alkaline transition of ferrocytochrome c at 25 degrees C and I = 0.1 M. The much greater relative stabilization of the native state in the reduced as compared to the oxidized form turns out to be almost entirely enthalpic in origin, and is most likely due to the greater affinity of the methionine sulfur for the Fe(II) ion. Finally, it is found that the Debye-Hückel theory fits the ionic strength dependence of the pKapp values, at least qualitatively, as observed previously for the ionic strength dependence of the reduction potential of this protein class. It is apparent that the increase in the pKapp values with increasing ionic strength is for the most part an entropic effect.
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Affiliation(s)
- G Battistuzzi
- Department of Chemistry, University of Modena and Reggio Emilia, Italy
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Voss T, Gründler P, Brett CM, Brett AM. Electrochemical behaviour of cytochrome c at electrically heated microelectrodes. J Pharm Biomed Anal 1999; 19:127-33. [PMID: 10698574 DOI: 10.1016/s0731-7085(98)00189-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The structural changes in cytochrome c with temperature have been been followed using a recently developed electrically-heated microelectrode sensor. Differential pulse voltammetry was used to perform electrochemical measurements of cytochrome c oxidation at different temperatures at heated bare gold electrodes contained in phosphate-buffered cytochrome c solution at room temperature. The voltammetric response shows the onset of unfolding and a marked dependence of the signal on electrode temperature. This augurs well for applications of heated electrodes as local probes in the study of the temperature dependence of electron transfer processes of other redox proteins, avoiding problems of bulk deterioration.
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Affiliation(s)
- T Voss
- Department of Chemistry, University of Rostock, Germany
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Bond AM, Colton R, D'Agostino A, Traeger JC, Downard AJ, Canty AJ. An electrospray mass spectrometric and voltammetric study of horse heart cytochrome c in the presence of metal ions. Inorganica Chim Acta 1998. [DOI: 10.1016/s0020-1693(97)05775-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Battistuzzi G, Borsari M, Sola M, Francia F. Redox thermodynamics of the native and alkaline forms of eukaryotic and bacterial class I cytochromes c. Biochemistry 1997; 36:16247-58. [PMID: 9405059 DOI: 10.1021/bi971535g] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The reduction potentials of beef heart cytochrome c and cytochromes c2 from Rhodopseudomonas palustris, Rhodobacter sphaeroides, and Rhodobacter capsulatus were measured through direct electrochemistry at a surface-modified gold electrode as a function of temperature in nonisothermal experiments carried out at neutral and alkaline pH values. The thermodynamic parameters for protein reduction (DeltaS degrees rc and DeltaH degrees rc) were determined for the native and alkaline conformers. Enthalpy and entropy terms underlying species-dependent differences in E degrees and pH- and temperature-induced E degrees changes for a given cytochrome were analyzed. The difference of about +0.1 V in E degrees between cytochromes c2 and the eukaryotic species can be separated into an enthalpic term (-DeltaDeltaH degrees rc/F) of +0.130 V and an entropic term (TDeltaDeltaS degrees rc/F) of -0.040 V. Hence, the higher potential of the bacterial species appears to be determined entirely by a greater enthalpic stabilization of the reduced state. Analogously, the much lower potential of the alkaline conformer(s) as compared to the native species is by far enthalpic in origin for both protein families, and is largely determined by the substitution of Met for Lys in axial heme ligation. Instead, the biphasic E degrees /temperature profile for the native cytochromes is due to a difference in reduction entropy between the conformers at low and high temperatures. Temperature-dependent 1H NMR experiments suggest that the temperature-induced transition also involves a change in orientation of the axial methionine ligand with respect to the heme plane.
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Affiliation(s)
- G Battistuzzi
- Department of Chemistry, University of Modena, Via Campi 183, 41100 Modena, Italy
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Allen H, Hill O, Hunt NI, Bond AM. The transient nature of the diffusion controlled component of the electrochemistry of cytochrome c at ‘bare’ gold electrodes: an explanation based on a self-blocking mechanism. J Electroanal Chem (Lausanne) 1997. [DOI: 10.1016/s0022-0728(97)00307-0] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Hill HAO, Nakagawa Y, Marken F, Compton RG. Voltammetry in the Presence of Ultrasound: Sonovoltammetric Detection of Cytochrome c under Very Fast Mass Transport Conditions. ACTA ACUST UNITED AC 1996. [DOI: 10.1021/jp961347k] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Ting Chen, Yizhu Guo, Shaojun Dong. Voltammetry of cytochrome c entrapped in hydrogel membrane on graphite electrode. ACTA ACUST UNITED AC 1995. [DOI: 10.1016/0302-4598(95)01811-r] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Mabrouk PA. First direct interfacial electron transfer between a biomolecule and a solid electrode in non-aqueous media: Direct electrochemistry of microperoxidase-11 at glassy carbon in dimethyl sulfoxide solution. Anal Chim Acta 1995. [DOI: 10.1016/0003-2670(94)00559-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Szűcs Á, Novák M. Stable and reversible electrochemistry of cytochrome c on bare electrodes Part II: Effects of experimental conditions. J Electroanal Chem (Lausanne) 1995. [DOI: 10.1016/0022-0728(94)03741-k] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Bond A. Chemical and electrochemical approaches to the investigation of redox reactions of simple electron transfer metalloproteins. Inorganica Chim Acta 1994. [DOI: 10.1016/0020-1693(94)04082-6] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Effect of pH on the electron transfer of cytochrome c on a gold electrode modified with bis(4-pyridyl)disulphide. ACTA ACUST UNITED AC 1992. [DOI: 10.1016/0302-4598(92)80054-k] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Bond AM. Robert Boyle anniversary lecture. New aspects of the electrochemistry of redox active metalloproteins and enzymes based on a microscopic model of electron transfer at the electrode–solution interface. ACTA ACUST UNITED AC 1992. [DOI: 10.1039/ap9922900132] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Salamon Z, Tollin G. Interfacial electrochemistry of cytochrome c at a lipid bilayer modified electrode: effect of incorporation of negative charges into the bilayer on cyclic voltammetric parameters. ACTA ACUST UNITED AC 1991. [DOI: 10.1016/0022-0728(91)85605-o] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Salamon Z, Tollin G. Interfacial electrochemistry of cytochrome c at a lipid bilayer modified electrode: Effect of incorporation of negative charges into the bilayer on cyclic voltammetric parameters. ACTA ACUST UNITED AC 1991. [DOI: 10.1016/0302-4598(91)80033-y] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Interpretation of the electrochemistry of cytochrome c at macro and micro sized carbon electrodes using a microscopic model based on a partially blocke. ACTA ACUST UNITED AC 1991. [DOI: 10.1016/0022-0728(91)85437-t] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Haladjian J, Draqui K, Bianco P. Electron transfer reaction of cytochrome C3 at pyrolytic graphite electrodes. Electrochim Acta 1991. [DOI: 10.1016/0013-4686(91)85328-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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Rafferty SP, Pearce LL, Barker PD, Guillemette JG, Kay CM, Smith M, Mauk AG. Electrochemical, kinetic, and circular dichroic consequences of mutations at position 82 of yeast iso-1-cytochrome c. Biochemistry 1990; 29:9365-9. [PMID: 2174257 DOI: 10.1021/bi00492a009] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Replacement of Phe-82 in yeast iso-1-cytochrome c with Tyr, Leu, Ile, Ser, Ala, and Gly produces a gradation of effects on (1) the reduction potential of the protein, (2) the rate of reaction with Fe(EDTA)2-, and (3) the CD spectra of the ferricytochromes in the Soret region under conditions where contributions from the alkaline forms of these proteins are absent. The reduction potential of cytochrome c is lowered by as little as 10 mV (Tyr-82) or by as much as 43 mV (Gly-82; pH 6.0) as the result of these substitutions. The second-order rate constants for reduction of these cytochromes range from a low of 6.20 (2) x 10(4) for the Tyr-82 variant to a high of 14.8 x 10(4) M-1 s-1 for the Ser-82 variant [pH 6.0, 25 degrees C, mu = 0.1 M (sodium phosphate)]. Analysis of these rates by use of relative Marcus theory produces values of k11corr that range from 10.9 M-1 s-1 for the wild-type protein to 190 M-1 s-1 for the Gly-82 mutant [25 degrees C, mu = 0.1 M, pH 6.0 (sodium phosphate)]. Reinvestigation of the effect of substituting Phe-82 by a Tyr residue on the CD spectrum of the protein now reveals little alteration of the intense, negative Cotton effect in the Soret CD spectrum of ferricytochrome c. On the other hand, substitution of nonaromatic residues of various sizes at this position results in loss of this spectroscopic feature, consistent with previous findings.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- S P Rafferty
- Department of Biochemistry, University of British Columbia, Vancouver, Canada
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Bond AM, Hill HA, Page DJ, Psalti IS, Walton NJ. Evidence for fast and discriminatory electron transfer of proteins at modified gold electrodes. EUROPEAN JOURNAL OF BIOCHEMISTRY 1990; 191:737-42. [PMID: 2167852 DOI: 10.1111/j.1432-1033.1990.tb19182.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The electrochemistry of the redox proteins, cytochrome c, cytochrome b5, plastocyanin and ferredoxin at modified gold electrodes has been examined on the basis that electron transfer takes place at electroactive sites which are microscopic in size. Using this model, it is now proposed that electrochemistry of these proteins occurs at suitably modified sites with fast rates at potentials near the standard redox potential. The microscopic model implies that redox proteins and enzymes take part in fast electron transfer at specific sites on the electrode, other sites being completely ineffective. This form of molecular recognition, i.e. the ability to discriminate between the different sites on an electrode surface, mimics homogeneous redox reactions wherein redox active proteins 'recognize' their biological partners in a very specific sense. Previously, protein electrochemistry has been interpreted via use of a macroscopic model in which the proteins are transported to the electrode surface by linear diffusion followed by quasi-reversible or irreversible electron transfer to the electrode surface. The microscopic model, which assumes that the movement of the protein occurs predominantly by radial diffusion to very small sites, would appear to explain the data more satisfactorily and be consistent with biologically important, homogeneous redox reactions which are known to be fast.
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Affiliation(s)
- A M Bond
- Division of Chemical and Physical Sciences, Deakin University, Geelong, Victoria, Australia
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