A Functional Model of Cytochrome c Oxidase: Thermodynamic Implications

Collman, James P.; Fu, Lei; Herrmann, Paul C.; Wang, Zhong; Rapta, Miroslav; Bröring, Martin; Schwenninger, Reinhold; Boitrel, Bernard

doi:10.1002/(sici)1521-3773(19981231)37:24<3397::aid-anie3397>3.3.co;2-e

Cited by 35 publications

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“…Reaction of two equivalents of CoCp 2 does effect O-O cleavage and the formation of the corresponding previously structurally characterized μ -oxo-bridged compounds [(F 8 )Fe III -(O 2- )-Cu II (TMPA)] + ( 1a ) and [(F 8 )Fe III -(O 2- )-Cu II (AN)] + ( 2a ) 37. This result differs from an earlier work of Collman and coworkers where they showed that the addition of CoCp 2 to heme–dioxygen-copper complexes containing appended imidazole axial base for iron lead to fully reduced Fe II /Cu I and the reduction of O 2 to H 2 O 2 69-72…”

Section: Resultsmentioning

confidence: 63%

Heme−Copper−Dioxygen Complexes: Toward Understanding Ligand-Environmental Effects on the Coordination Geometry, Electronic Structure, and Reactivity

et al. 2010

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The nature of the ligand is an important aspect of controlling structure and reactivity in coordination chemistry. In connection with our study of heme/copper/oxygen reactivity relevant to cytochrome c oxidase O 2 -reduction chemistry, we compare the molecular and electronic structure of two highspin heme-peroxo-copper [Fe III -O 2 2--Cu II ] + complexes containing N 4 -tetradentate (1) or N 3 -tridentate (2) copper ligands. Combining previously reported and new resonance Raman and EXAFS data coupled to DFT calculations we report a geometric structure and more complete electronic description of the high-spin heme-peroxo-copper complexes 1 and 2, which establish μ-(O 2 2-) sideon to the Fe III and end-on to Cu II (μ-η 2 :η 1 ) binding for the complex 1 but side-on/side-on (μ-η 2 :η 2 ) μ-peroxo coordination for the complex 2. We also compare and summarize the differences and similarities of these two complexes in their reactivity toward CO, PPh 3 , acid and phenols. The comparison of a new X-ray structure of μ-oxo complex 2a with the previously reported 1a X-ray structure, two thermal decomposition products respectively of 2 and 1, reveals a considerable difference in the Fe-O-Cu angle between the two μ-oxo complexes (∠Fe-O-Cu = 178.2° in 1a, ∠Fe-O-Cu = 149.5° in 2a). The reaction of 2 with one equivalent of exogenous N-donor axial base leads to the formation of a distinctive low-temperature stable, low-spin heme-O 2 -Cu complex (2b), but under the same conditions the addition of an axial base to 1 leads to the dissociation of the hemeperoxo-Cu assembly and the release of O 2 . 2b reacts with phenols performing hydrogen-atom (e -+ H + ) abstraction resulting in O-O bond cleavage and the formation of high-valent ferryl [Fe IV =O] complex (2c). The nature of 2c was confirmed by comparison of its spectroscopic features and reactivity with those of an independently prepared ferryl complex. The phenoxyl radical generated by the hydrogen-atom abstraction was either 1) directly detected by EPR spectroscopy using phenols that produce stable radicals or 2) indirectly by detection of the coupling product of two phenoxyl radicals.karlin@jhu.edu, edward.solomon@stanford.edu. Supporting Information Available. UV-visible spectra of the reaction of (2b) with 1 equiv. of 2,4-di-tertbutylphenol ( Figure S1), UVvis spectra of the reaction of [(F 8 )Fe III -(O 2 2-)-Cu II (TMPA)] + (1) with DMAP ( Figure S2), EPR spectra of (2b) reaction with 1 equiv.of 2,4-di-tert-butylphenol ( Figure S3), GC-MS trace of the oxidative coupling of 2,4-di-tert-butylphenol in presence of (2b) ( Figure S4), ORTEP diagram ( Figure S5) and crystal data and structure refinement for [(F 8 )Fe III -(O 2-)-Cu II (AN)] + (2a) X-ray structure (Table S1), XAS spectra and computational data.NIH Public Access

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Section: Resultsmentioning

confidence: 63%

Heme−Copper−Dioxygen Complexes: Toward Understanding Ligand-Environmental Effects on the Coordination Geometry, Electronic Structure, and Reactivity

et al. 2010

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“…This difference was explained to come about as a result of the relative reduction potentials of the Fe III and Cu II centers. 925,1012,1013…”

Section: Small Molecule Synthetic Models Of Heme-copper Oxidasesmentioning

confidence: 99%

Synthetic Fe/Cu Complexes: Toward Understanding Heme-Copper Oxidase Structure and Function

et al. 2018

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Heme-copper oxidases (HCOs) are terminal enzymes on the mitochondrial or bacterial respiratory electron transport chain, which utilize a unique heterobinuclear active site to catalyze the 4H+/4e− reduction of dioxygen to water. This process involves a proton-coupled electron transfer (PCET) from a tyrosine (phenolic) residue and additional redox events coupled to transmembrane proton pumping and ATP synthesis. Given that HCOs are large, complex, membrane-bound enzymes, bioinspired synthetic model chemistry is a promising approach to better understand heme-Cu-mediated dioxygen reduction, including the details of proton and electron movements. This review encompasses important aspects of heme-O2 and copper–O2 (bio)chemistries as they relate to the design and interpretation of small molecule model systems and provides perspectives from fundamental coordination chemistry, which can be applied to the understanding of HCO activity. We focus on recent advancements from studies of heme–Cu models, evaluating experimental and computational results, which highlight important fundamental structure–function relationships. Finally, we provide an outlook for future potential contributions from synthetic inorganic chemistry and discuss their implications with relevance to biological O2-reduction.

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“…Accordingly, biological processes coupled to O 2 reduction (i.e., respiration) are highly selective for the complete 4e À þ 4H þ pathway in order to maximize the energy available for adenosine triphosphate (ATP) synthesis. The pursuit of structural and functional models for O 2 activation and its complete reduction has emphasized bimetallic reaction centers positioned within well-defined rigid pockets (117)(118)(119)(120)(121). Dicobalt(II) cofacial bisporphyrins are among the few molecular catalysts capable of mediating the selective four-electron, four-proton reduction of oxygen to water.…”

Section: Oxygen Activation Chemistry Of Pacman and Hangmanmentioning

confidence: 99%

Oxygen Activation Chemistry of Pacman and Hangman Porphyrin Architectures Based on Xanthene and Dibenzofuran Spacers

Rosenthal¹,

Nocera²

2007

Progress in Inorganic Chemistry

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A Functional Model of Cytochrome c Oxidase: Thermodynamic Implications

Cited by 35 publications

References 0 publications

Heme−Copper−Dioxygen Complexes: Toward Understanding Ligand-Environmental Effects on the Coordination Geometry, Electronic Structure, and Reactivity

Heme−Copper−Dioxygen Complexes: Toward Understanding Ligand-Environmental Effects on the Coordination Geometry, Electronic Structure, and Reactivity

Synthetic Fe/Cu Complexes: Toward Understanding Heme-Copper Oxidase Structure and Function

Oxygen Activation Chemistry of Pacman and Hangman Porphyrin Architectures Based on Xanthene and Dibenzofuran Spacers

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