Intramolecular Electron Transfer in Pentaammineruthenium(III)-Modified Cobaltocytochrome <i>c</i>

Sun, Ji; Su, Chang; Wishart, James F.

doi:10.1021/ic960715w

Cited by 12 publications

(20 citation statements)

References 55 publications

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“…These areas, located on both sides of the haem, are found to react preferentially either with anionic or cationic species. Interestingly, the solvent-exposed histidine residues, despite the use of His-33 for the studies of intramolecular electron transfer by covalently bound ruthenium moieties (Isied et al 1982;Winkler et al 1982;Yocom et al 1982;Nocera et al 1984;Sun et al 1996), have not been considered as possible electron-transfer sites in intermolecular reactions. The present study shows that this inner-sphere pathway can effectively compete with the outer-sphere reactions occurring close to the solvent-exposed haem edge, provided the imidazole side chains can act as bridging ligand to the electron-transfer active reagent.…”

Section: Discussionmentioning

confidence: 99%

Electron-transfer‐mediated binding of optically active cobalt(III) complexes to horse heart cytochromec

Scholten

Merchán

Bernauer

2005

J. R. Soc. Interface.

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Optically active cobalt(II) complexes are used as reducing agents in the electron-transfer reaction involving horse heart cytochrome c. Analysis of the circular dichroism (CD) spectra of reaction products indicates that the corresponding cobalt(III) species of both enantiomers of [Co) are partly attached to the protein during electron transfer by coordination to an imidazole unit of one of the histidine residues. His-26 and His-33 are both solvent exposed, and the results suggest that one of these histidine residues acts as a bridge in the electron transfer to and from the haem iron of cytochrome c. The reaction is enantioselective: the ratio of the relative reactivity at 15 8C is 2.9 in favour of the R,R-enantiomer. A small induced CD activity in the haem chromophore reveals that some structural changes in the protein occur consecutively with the binding of the cobalt(III) complex.

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Section: Discussionmentioning

confidence: 99%

Electron-transfer‐mediated binding of optically active cobalt(III) complexes to horse heart cytochromec

Scholten

Merchán

Bernauer

2005

J. R. Soc. Interface.

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“…Tuna heart cyt c (Sigma) was used as received. Zn-and Co-cyt c were prepared according to established procedures (24,25). Zn:Fe-cyt c cocrystals were grown at room temperature in sitting or hanging drops.…”

Section: Methodsmentioning

confidence: 99%

“…As controls, we examined Fe(II):Zn-cyt c and Co(III):Zn-cyt c cocrystals-ET in the former case is disfavored thermodynamically, whereas in the latter case there is a large barrier, owing to a high Co(III͞II) reorganization energy (Ͼ2.4 eV) (25). *Zn-cyt c decay in both cases was slow and monoexponential, with rate constants [68 s Ϫ1 for Fe(II) and 78 s Ϫ1 for Co(III)] that were essentially the same as those observed in pure Zn-cyt c crystals (Fig.…”

mentioning

confidence: 99%

Electron tunneling in protein crystals

Tezcan

Crane²,

Winkler³

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

120

110

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The current understanding of electron tunneling through proteins has come from work on systems where donors and acceptors are held at fixed distances and orientations. The factors that control electron flow between proteins are less well understood, owing to uncertainties in the relative orientations and structures of the reactants during the very short time that tunneling occurs. As we report here, the way around such structural ambiguity is to examine oxidation-reduction reactions in protein crystals. Accordingly, we have measured and analyzed the kinetics of electron transfer between native and Zn-substituted tuna cytochrome c

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“…These versions of the protein were used in the analysis of protein folding and probing of ET mechanisms. 31 Substitution of the central heme atom was useful in studies of myoglobin and functional mimics of heme proteins. 32 Here, we used CytC and its derivatives as model proteins to investigate the emerging question of energy transfer between them and QDs occurring via two coexisting routes, namely, photoinduced ET and (F)RET.…”

Section: ■ Introductionmentioning

confidence: 99%

“…MnCytC and CoCytC are redox-active, with different redox properties from native FeCytC. These versions of the protein were used in the analysis of protein folding and probing of ET mechanisms . Substitution of the central heme atom was useful in studies of myoglobin and functional mimics of heme proteins …”

Section: Introductionmentioning

confidence: 99%

Competition between Photoinduced Electron Transfer and Resonance Energy Transfer in an Example of Substituted Cytochrome c–Quantum Dot Systems

et al. 2021

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Colloidal quantum dots (QDs) are nanoparticles that are able to photoreduce redox proteins by electron transfer (ET). QDs are also able to transfer energy by resonance energy transfer (RET). Here, we address the question of the competition between these two routes of QDs’ excitation quenching, using cadmium telluride QDs and cytochrome c (CytC) or its metal-substituted derivatives. We used both oxidized and reduced versions of native CytC, as well as fluorescent, nonreducible Zn(II)CytC, Sn(II)CytC, and metal-free porphyrin CytC. We found that all of the CytC versions quench QD fluorescence, although the interaction may be described differently in terms of static and dynamic quenching. QDs may be quenchers of fluorescent CytC derivatives, with significant differences in effectiveness depending on QD size. SnCytC and porphyrin CytC increased the rate of Fe(III)CytC photoreduction, and Fe(II)CytC slightly decreased the rate and ZnCytC presence significantly decreased the rate and final level of reduced FeCytC. These might be partially explained by the tendency to form a stable complex between protein and QDs, which promoted RET and collisional quenching. Our findings show that there is a net preference for photoinduced ET over other ways of energy transfer, at least partially, due to a lack of donors, regenerating a hole at QDs and leading to irreversibility of ET events. There may also be a common part of pathways leading to photoinduced ET and RET. The nature of synergistic action observed in some cases allows the hypothesis that RET may be an additional way to power up the ET.

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Intramolecular Electron Transfer in Pentaammineruthenium(III)-Modified Cobaltocytochrome c

Cited by 12 publications

References 55 publications

Electron-transfer‐mediated binding of optically active cobalt(III) complexes to horse heart cytochromec

Electron-transfer‐mediated binding of optically active cobalt(III) complexes to horse heart cytochromec

Electron tunneling in protein crystals

Competition between Photoinduced Electron Transfer and Resonance Energy Transfer in an Example of Substituted Cytochrome c–Quantum Dot Systems

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