A Functional Model Related to Cytochrome c Oxidase and Its Electrocatalytic Four-Electron Reduction of O
            <sub>2</sub>

Collman, James P.; Fu, Lei; Herrmann, Paul C.; Zhang, Xumu

doi:10.1126/science.275.5302.949

Cited by 196 publications

(165 citation statements)

References 16 publications

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“…In this case, P R and F are also in the same oxidation state, but there is no need for reversible OOO cleavage. Clearly, this model lacks the ferric peroxy form, in contradiction of previous assignments and observations made using synthetic model compounds in which a peroxy species was detected during the the reduction of oxygen to water (41).…”

Section: ϫcontrasting

confidence: 99%

A Common Mechanism for the Interaction of Nitric Oxide with the Oxidized Binuclear Centre and Oxygen Intermediates of Cytochromec Oxidase

Torres

Cooper

Wilson

1998

Journal of Biological Chemistry

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The reactions of nitric oxide (NO) with fully oxidized cytochrome c oxidase (O) and the intermediates P and F have been investigated by optical spectroscopy, using both static and kinetic methods. The reaction of NO with O leads to a rapid (ϳ100 s ؊1 ) electron ejection from the binuclear center to cytochrome a and Cu A . The reaction with the intermediates P and F leads to the depletion of these species in slower reactions, yielding the fully oxidized enzyme. The fastest optical change, however, takes place within the dead time of the stopped-flow apparatus (ϳ1 ms), and corresponds to the formation of the F intermediate (580 Cytochrome c oxidase (ferrocytochrome c oxidoreductase, EC 1.9.3.1), the terminal enzyme in the mitochondrial respiratory chain, catalyzes the reduction of molecular oxygen to water (1). This process is coupled to proton translocation across the inner membrane. The enzyme contains four redox-active centers. Electron entry from cytochrome c, the natural substrate, occurs via a diatomic copper center, Cu A . After rapid equilibrium with Fe a , 1 the electron is transferred to Cu B and Fe a3 , which together constitute the binuclear center, where oxygen is reduced.Although oxygen binds with low affinity (10 3 M Ϫ1 ) (2) to reduced Fe a3 , rapid electron transfer from the two reduced metals comprising the binuclear center to molecular oxygen ensures that oxygen remains bound as a peroxy species. In this way, oxygen is kinetically trapped and further reduction can take place (3, 4). The successive steps leading to the formation of water have been studied by different spectroscopic techniques (see Ref. 5 for review). The spectral signatures of two of these intermediates, which exhibit bands at 607 and 580 nm in the difference spectrum with respect to the oxidized enzyme, were first reported by Wikström (6), by reversing the electron transfer reaction, and further characterized by Wikström and Morgan (7). These authors assigned the spectral signatures at 607 and 580 nm to a ferric peroxy (P) and ferryl oxo (F) species, respectively. These assignments, however, have been challenged by a number of authors (8 -10). For example, Resonance Raman results obtained by Proshlyakov et al. (10) suggest that the 607 nm band originates from an oxoferryl structure. On the other hand, the same authors have been unable to identify the putative peroxy species in their system in turnover sustained by H 2 O 2 (11). However, irrespective of the assignments, there seems to exist a general agreement that compound F (580 nm) is a ferryl oxo species and that it is one electron more reduced than compound P (607 nm) (11,12).One of the ways to solve the problem of the identity of the P intermediate could perhaps be through the use of a suitable probe. The possibility that nitric oxide (NO), a powerful reversible inhibitor of cytochrome c oxidase (13-15), can be used as a probe for the binuclear center has been suggested by recent results using enzyme in slow turnover (16 -18). In these experiments, an electron was ejected...

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Section: ϫcontrasting

confidence: 99%

A Common Mechanism for the Interaction of Nitric Oxide with the Oxidized Binuclear Centre and Oxygen Intermediates of Cytochromec Oxidase

Torres

Cooper

Wilson

1998

Journal of Biological Chemistry

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“…In particular, it has been known for five decades that heme/porphyrin-based electrocatalysts (both natural and synthetic) catalyze electrochemical O 2 , H + , and CO 2 reduction (14,(16)(17)(18)(19). Several excellent metalloporphyrin-based O 2 reduction electrocatalysts have been reported, some mimicking natural active sites and some inspired by their design (14,20). Of these catalysts, the Fe-based catalysts generally have provided valuable insights into the O 2 reduction mechanism and a deeper understanding of the structure-function correlations of key enzymes such as CcO, the terminal enzyme in the mitochondrial electron transport chain (1,21).…”

mentioning

confidence: 99%

Direct observation of intermediates formed during steady-state electrocatalytic O ₂ reduction by iron porphyrins

Sengupta

Chatterjee

Samanta

et al. 2013

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

158

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Heme/porphyrin-based electrocatalysts (both synthetic and natural) have been known to catalyze electrochemical O 2 , H + , and CO 2 reduction for more than five decades. So far, no direct spectroscopic investigations of intermediates formed on the electrodes during these processes have been reported; and this has limited detailed understanding of the mechanism of these catalysts, which is key to their development. Rotating disk electrochemistry coupled to resonance Raman spectroscopy is reported for iron porphyrin electrocatalysts that reduce O 2 in buffered aqueous solutions. Unlike conventional single-turnover intermediate trapping experiments, these experiments probe the system while it is under steady state. A combination of oxidation and spin-state marker bands and metal ligand vibrations (identified using isotopically enriched substrates) allow in situ identification of O 2 -derived intermediates formed on the electrode surface. This approach, combining dynamic electrochemistry with resonance Raman spectroscopy, may be routinely used to investigate a plethora of metalloporphyrin complexes and heme enzymes used as electrocatalysts for small-molecule activation.lectrocatalysis has taken center stage in contemporary research because of its indisputable relevance in the thriving area of renewable energy. Electrocatalytic O 2 reduction, O 2 evolution, H 2 evolution, and H 2 oxidation thus are areas of great interest and have attracted focused effort across several disciplines of science (1-11). Both natural systems [metalloenzymes such as cytochrome c oxidase (CcO), hydrogenase, and glucose oxidase] and biomimetic systems (i.e., synthetic/biochemical mimics of the natural enzyme) are known to function as electrocatalysts (12-15). In particular, it has been known for five decades that heme/porphyrin-based electrocatalysts (both natural and synthetic) catalyze electrochemical O 2 , H + , and CO 2 reduction (14,(16)(17)(18)(19). Several excellent metalloporphyrin-based O 2 reduction electrocatalysts have been reported, some mimicking natural active sites and some inspired by their design (14,20). Of these catalysts, the Fe-based catalysts generally have provided valuable insights into the O 2 reduction mechanism and a deeper understanding of the structure-function correlations of key enzymes such as CcO, the terminal enzyme in the mitochondrial electron transport chain (1, 21). Similarly, several naturally occurring enzymes have been used as electrocatalysts for O 2 reduction (e.g., CcO, microperoxidase) and substrate oxidation using O 2 (e.g., cytochrome P450) (22-24). Apart from porphyrins, transition metal complexes of corroles, a related macrocycle that lacks one of the four mesocarbons of porphyrins, have been used extensively as electrocatalysts for O 2 reduction and H 2 O oxidation (5, 6). These catalytic systems are efficient in catalyzing selective O 2 activation/reduction reactions when the electrons (i.e., the reducing component) are provided from the electrode and O 2 (the oxidizing component) is obtai...

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“…[9] Previously we reported the first functional CcO model that consisted of a Co II ± porphyrin with a Cu I -coordinated distal superstructure and with a covalently attached imidazole group as the axial ligand. [10] We demonstrated that this complex catalyzes the 4 e À reduction of O 2 under physiological conditions without the release of H 2 O 2 . Our electrocatalytic studies also demonstrate that both the copper ion and the axial imidazole ligand are essential to achieve the reduction.…”

mentioning

confidence: 79%

A Functional Model of Cytochrome c Oxidase: Thermodynamic Implications

Collman¹,

Fu²,

Herrmann³

et al. 1998

Angewandte Chemie International Edition

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The environment of the Cu ion in the distal ligand group decides the fate of the reduction of O by the two analogues 1 and 2 of the heme a Cu center in cytochrome c oxidase. The fourfold coordination by N in 1 favors the Cu oxidation state and leads to a 4 e -4 H reduction and the formation of H O under physiological conditions, while with 2 a 2 e -2 H reduction occurs to form the cytotoxic H O .

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A Functional Model Related to Cytochrome c Oxidase and Its Electrocatalytic Four-Electron Reduction of O ₂

Cited by 196 publications

References 16 publications

A Common Mechanism for the Interaction of Nitric Oxide with the Oxidized Binuclear Centre and Oxygen Intermediates of Cytochromec Oxidase

A Common Mechanism for the Interaction of Nitric Oxide with the Oxidized Binuclear Centre and Oxygen Intermediates of Cytochromec Oxidase

Direct observation of intermediates formed during steady-state electrocatalytic O ₂ reduction by iron porphyrins

A Functional Model of Cytochrome c Oxidase: Thermodynamic Implications

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A Functional Model Related to Cytochrome c Oxidase and Its Electrocatalytic Four-Electron Reduction of O 2

Cited by 196 publications

References 16 publications

A Common Mechanism for the Interaction of Nitric Oxide with the Oxidized Binuclear Centre and Oxygen Intermediates of Cytochromec Oxidase

A Common Mechanism for the Interaction of Nitric Oxide with the Oxidized Binuclear Centre and Oxygen Intermediates of Cytochromec Oxidase

Direct observation of intermediates formed during steady-state electrocatalytic O 2 reduction by iron porphyrins

A Functional Model of Cytochrome c Oxidase: Thermodynamic Implications

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A Functional Model Related to Cytochrome c Oxidase and Its Electrocatalytic Four-Electron Reduction of O ₂

Direct observation of intermediates formed during steady-state electrocatalytic O ₂ reduction by iron porphyrins