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Li Y, Wu Y, Li T, Yao Y, Cai H, Gao J, Qian G. Amorphous Engineering of Scalable Metal-Organic Framework-Derived Electrocatalyst for Highly Efficient Oxygen Evolution Reaction. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024; 20:e2311356. [PMID: 38295058 DOI: 10.1002/smll.202311356] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Revised: 01/17/2024] [Indexed: 02/02/2024]
Abstract
The engineering of amorphous metal-organic frameworks (MOFs) offers potential opportunities for the construction of electrocatalysts for efficient oxygen evolution reaction (OER). Herein, highly efficient OER performance and durability in alkaline electrolyte are discovered for MOF-derived amorphous and porous electrocatalysts, which are synthesized in a brief procedure and can be facilely produced in scalable quantities. The structural inheritance of MOF amorphous catalysts is significant for the retention of catalytic sites and the diffusion of electrolytes, and the presence of Fe sites can change the electronic structure and effectively control the adsorption behavior of important intermediates, accelerating reaction kinetics. The obtained amorphous A-FeNi can be transformed from FeNi-MOF effortlessly and instantly, and it only needs low overpotentials of 152 and 232 mV at 10 and 100 mA cm-2 with a Tafel slope of 17 mV dec-1 in 1 m KOH for OER. Moreover, A-FeNi possesses high corrosion resistance and durability, therefore A-FeNi can work continually for at least 400 h at 100 mA cm-2. This work may pave a new avenue for the design of MOFs-related amorphous electrocatalyst.
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Affiliation(s)
- Yuwen Li
- State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Yuhang Wu
- Institute of Functional Porous Materials, School of Materials Science and Engineering, Zhejiang Sci-Tech University, Hangzhou, Zhejiang, 310018, China
| | - Tongtong Li
- Institute of Functional Porous Materials, School of Materials Science and Engineering, Zhejiang Sci-Tech University, Hangzhou, Zhejiang, 310018, China
| | - Yue Yao
- State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Haotian Cai
- State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Junkuo Gao
- Institute of Functional Porous Materials, School of Materials Science and Engineering, Zhejiang Sci-Tech University, Hangzhou, Zhejiang, 310018, China
| | - Guodong Qian
- State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang, 310058, China
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Chen J, Xie P, Huang Y, Gao H. Complex Interplay of Heme-Copper Oxidases with Nitrite and Nitric Oxide. Int J Mol Sci 2022; 23:979. [PMID: 35055165 PMCID: PMC8780969 DOI: 10.3390/ijms23020979] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 01/13/2022] [Accepted: 01/15/2022] [Indexed: 12/19/2022] Open
Abstract
Nitrite and nitric oxide (NO), two active and critical nitrogen oxides linking nitrate to dinitrogen gas in the broad nitrogen biogeochemical cycle, are capable of interacting with redox-sensitive proteins. The interactions of both with heme-copper oxidases (HCOs) serve as the foundation not only for the enzymatic interconversion of nitrogen oxides but also for the inhibitory activity. From extensive studies, we now know that NO interacts with HCOs in a rapid and reversible manner, either competing with oxygen or not. During interconversion, a partially reduced heme/copper center reduces the nitrite ion, producing NO with the heme serving as the reductant and the cupric ion providing a Lewis acid interaction with nitrite. The interaction may lead to the formation of either a relatively stable nitrosyl-derivative of the enzyme reduced or a more labile nitrite-derivative of the enzyme oxidized through two different pathways, resulting in enzyme inhibition. Although nitrite and NO show similar biochemical properties, a growing body of evidence suggests that they are largely treated as distinct molecules by bacterial cells. NO seemingly interacts with all hemoproteins indiscriminately, whereas nitrite shows high specificity to HCOs. Moreover, as biologically active molecules and signal molecules, nitrite and NO directly affect the activity of different enzymes and are perceived by completely different sensing systems, respectively, through which they are linked to different biological processes. Further attempts to reconcile this apparent contradiction could open up possible avenues for the application of these nitrogen oxides in a variety of fields, the pharmaceutical industry in particular.
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Affiliation(s)
| | | | | | - Haichun Gao
- Institute of Microbiology, College of Life Sciences, Zhejiang University, Hangzhou 310058, China; (J.C.); (P.X.); (Y.H.)
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Ding B, Xu B, Ding Z, Zhang T, Wang Y, Qiu H, He J, An P, Yao Y, Hou Z. Catalytic selective oxidation of aromatic amines to azoxy derivatives with an ultralow loading of peroxoniobate salts. Catal Sci Technol 2022. [DOI: 10.1039/d2cy01137a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Tartaric acid-coordinated peroxoniobate salts demonstrate an exceptionally high TOF value (up to 4435 h−1) even at an ultralow catalyst loading for the oxidation of aromatic amines to azoxy compounds under green and very mild conditions.
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Affiliation(s)
- Bingjie Ding
- Key Laboratory for Advanced Materials, Research Institute of Industrial Catalysis, School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Beibei Xu
- Physics Department and Shanghai Key Laboratory of Magnetic Resonance, East China Normal University, Shanghai 200062, China
| | - Zuoji Ding
- Key Laboratory for Advanced Materials, Research Institute of Industrial Catalysis, School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Tong Zhang
- Key Laboratory for Advanced Materials, Research Institute of Industrial Catalysis, School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Yajun Wang
- Key Laboratory for Advanced Materials, Research Institute of Industrial Catalysis, School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Hewen Qiu
- Key Laboratory for Advanced Materials, Research Institute of Industrial Catalysis, School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Jingjing He
- Key Laboratory for Advanced Materials, Research Institute of Industrial Catalysis, School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Pengfei An
- Institute of High Energy Physics, Chinese Academy of Sciences, Beijing Synchrotron Radiation Facility (BSRF), Beijing 100049, China
| | - Yefeng Yao
- Physics Department and Shanghai Key Laboratory of Magnetic Resonance, East China Normal University, Shanghai 200062, China
| | - Zhenshan Hou
- Key Laboratory for Advanced Materials, Research Institute of Industrial Catalysis, School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai 200237, China
- Shanghai Key Laboratory of Green Chemistry and Chemical Processes, East China Normal University, School of Chemistry and Molecular Engineering, Shanghai 200062, China
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Silveira CM, Zuccarello L, Barbosa C, Caserta G, Zebger I, Hildebrandt P, Todorovic S. Molecular Details on Multiple Cofactor Containing Redox Metalloproteins Revealed by Infrared and Resonance Raman Spectroscopies. Molecules 2021; 26:4852. [PMID: 34443440 PMCID: PMC8398457 DOI: 10.3390/molecules26164852] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Revised: 08/06/2021] [Accepted: 08/07/2021] [Indexed: 12/12/2022] Open
Abstract
Vibrational spectroscopy and in particular, resonance Raman (RR) spectroscopy, can provide molecular details on metalloproteins containing multiple cofactors, which are often challenging for other spectroscopies. Due to distinct spectroscopic fingerprints, RR spectroscopy has a unique capacity to monitor simultaneously and independently different metal cofactors that can have particular roles in metalloproteins. These include e.g., (i) different types of hemes, for instance hemes c, a and a3 in caa3-type oxygen reductases, (ii) distinct spin populations, such as electron transfer (ET) low-spin (LS) and catalytic high-spin (HS) hemes in nitrite reductases, (iii) different types of Fe-S clusters, such as 3Fe-4S and 4Fe-4S centers in di-cluster ferredoxins, and (iv) bi-metallic center and ET Fe-S clusters in hydrogenases. IR spectroscopy can provide unmatched molecular details on specific enzymes like hydrogenases that possess catalytic centers coordinated by CO and CN- ligands, which exhibit spectrally well separated IR bands. This article reviews the work on metalloproteins for which vibrational spectroscopy has ensured advances in understanding structural and mechanistic properties, including multiple heme-containing proteins, such as nitrite reductases that house a notable total of 28 hemes in a functional unit, respiratory chain complexes, and hydrogenases that carry out the most fundamental functions in cells.
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Affiliation(s)
- Célia M. Silveira
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade NOVA de Lisboa, Av. da República, 2780-157 Oeiras, Portugal; (C.M.S.); (L.Z.); (C.B.)
| | - Lidia Zuccarello
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade NOVA de Lisboa, Av. da República, 2780-157 Oeiras, Portugal; (C.M.S.); (L.Z.); (C.B.)
| | - Catarina Barbosa
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade NOVA de Lisboa, Av. da República, 2780-157 Oeiras, Portugal; (C.M.S.); (L.Z.); (C.B.)
| | - Giorgio Caserta
- Institut fur Chemie, Sekr. PC14, Technische Universitat Berlin, Strasse des 17. Juni 135, D-10623 Berlin, Germany; (G.C.); (I.Z.); (P.H.)
| | - Ingo Zebger
- Institut fur Chemie, Sekr. PC14, Technische Universitat Berlin, Strasse des 17. Juni 135, D-10623 Berlin, Germany; (G.C.); (I.Z.); (P.H.)
| | - Peter Hildebrandt
- Institut fur Chemie, Sekr. PC14, Technische Universitat Berlin, Strasse des 17. Juni 135, D-10623 Berlin, Germany; (G.C.); (I.Z.); (P.H.)
| | - Smilja Todorovic
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade NOVA de Lisboa, Av. da República, 2780-157 Oeiras, Portugal; (C.M.S.); (L.Z.); (C.B.)
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Kruse F, Nguyen AD, Dragelj J, Schlesinger R, Heberle J, Mroginski MA, Weidinger IM. Characterisation of the Cyanate Inhibited State of Cytochrome c Oxidase. Sci Rep 2020; 10:3863. [PMID: 32123230 PMCID: PMC7052191 DOI: 10.1038/s41598-020-60801-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Accepted: 02/17/2020] [Indexed: 12/22/2022] Open
Abstract
Heme-copper oxygen reductases are terminal respiratory enzymes, catalyzing the reduction of dioxygen to water and the translocation of protons across the membrane. Oxygen consumption is inhibited by various substances. Here we tested the relatively unknown inhibition of cytochrome c oxidase (CcO) with isocyanate. In contrast to other more common inhibitors like cyanide, inhibition with cyanate was accompanied with the rise of a metal to ligand charge transfer (MLCT) band around 638 nm. Increasing the cyanate concentration furthermore caused selective reduction of heme a. The presence of the CT band allowed for the first time to directly monitor the nature of the ligand via surface-enhanced resonance Raman (SERR) spectroscopy. Analysis of isotope sensitive SERR spectra in comparison with Density Functional Theory (DFT) calculations identified not only the cyanate monomer as an inhibiting ligand but suggested also presence of an uretdion ligand formed upon dimerization of two cyanate ions. It is therefore proposed that under high cyanate concentrations the catalytic site of CcO promotes cyanate dimerization. The two excess electrons that are supplied from the uretdion ligand lead to the observed physiologically inverse electron transfer from heme a3 to heme a.
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Affiliation(s)
- Fabian Kruse
- Technische Universität Dresden, Department of Chemistry and Food Chemistry, 01069, Dresden, Germany
| | - Anh Duc Nguyen
- Technische Universität Berlin, Department of Chemistry, Strasse des 17. Juni 135, 10623, Berlin, Germany
| | - Jovan Dragelj
- Technische Universität Berlin, Department of Chemistry, Strasse des 17. Juni 135, 10623, Berlin, Germany
| | - Ramona Schlesinger
- Freie Universität Berlin, Department of Physics, Arnimallee 14, 14195, Berlin, Germany
| | - Joachim Heberle
- Freie Universität Berlin, Department of Physics, Arnimallee 14, 14195, Berlin, Germany
| | - Maria Andrea Mroginski
- Technische Universität Berlin, Department of Chemistry, Strasse des 17. Juni 135, 10623, Berlin, Germany
| | - Inez M Weidinger
- Technische Universität Dresden, Department of Chemistry and Food Chemistry, 01069, Dresden, Germany.
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Huang X, Groves JT. Oxygen Activation and Radical Transformations in Heme Proteins and Metalloporphyrins. Chem Rev 2018; 118:2491-2553. [PMID: 29286645 PMCID: PMC5855008 DOI: 10.1021/acs.chemrev.7b00373] [Citation(s) in RCA: 591] [Impact Index Per Article: 98.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Indexed: 12/20/2022]
Abstract
As a result of the adaptation of life to an aerobic environment, nature has evolved a panoply of metalloproteins for oxidative metabolism and protection against reactive oxygen species. Despite the diverse structures and functions of these proteins, they share common mechanistic grounds. An open-shell transition metal like iron or copper is employed to interact with O2 and its derived intermediates such as hydrogen peroxide to afford a variety of metal-oxygen intermediates. These reactive intermediates, including metal-superoxo, -(hydro)peroxo, and high-valent metal-oxo species, are the basis for the various biological functions of O2-utilizing metalloproteins. Collectively, these processes are called oxygen activation. Much of our understanding of the reactivity of these reactive intermediates has come from the study of heme-containing proteins and related metalloporphyrin compounds. These studies not only have deepened our understanding of various functions of heme proteins, such as O2 storage and transport, degradation of reactive oxygen species, redox signaling, and biological oxygenation, etc., but also have driven the development of bioinorganic chemistry and biomimetic catalysis. In this review, we survey the range of O2 activation processes mediated by heme proteins and model compounds with a focus on recent progress in the characterization and reactivity of important iron-oxygen intermediates. Representative reactions initiated by these reactive intermediates as well as some context from prior decades will also be presented. We will discuss the fundamental mechanistic features of these transformations and delineate the underlying structural and electronic factors that contribute to the spectrum of reactivities that has been observed in nature as well as those that have been invented using these paradigms. Given the recent developments in biocatalysis for non-natural chemistries and the renaissance of radical chemistry in organic synthesis, we envision that new enzymatic and synthetic transformations will emerge based on the radical processes mediated by metalloproteins and their synthetic analogs.
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Affiliation(s)
- Xiongyi Huang
- Department
of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
- Department
of Chemistry, California Institute of Technology, Pasadena, California 91125, United States
| | - John T. Groves
- Department
of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
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Hanif S, Liu H, Chen M, Muhammad P, Zhou Y, Cao J, Ahmed SA, Xu J, Xia X, Chen H, Wang K. Organic Cyanide Decorated SERS Active Nanopipettes for Quantitative Detection of Hemeproteins and Fe3+ in Single Cells. Anal Chem 2017; 89:2522-2530. [DOI: 10.1021/acs.analchem.6b04689] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- Sumaira Hanif
- State Key Laboratory of Analytical
Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Hailing Liu
- State Key Laboratory of Analytical
Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Ming Chen
- State Key Laboratory of Analytical
Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Pir Muhammad
- State Key Laboratory of Analytical
Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Yue Zhou
- State Key Laboratory of Analytical
Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Jiao Cao
- State Key Laboratory of Analytical
Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Saud Asif Ahmed
- State Key Laboratory of Analytical
Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Jingjuan Xu
- State Key Laboratory of Analytical
Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Xinghua Xia
- State Key Laboratory of Analytical
Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Hongyuan Chen
- State Key Laboratory of Analytical
Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Kang Wang
- State Key Laboratory of Analytical
Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
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Abstract
Like most bacteria, Escherichia coli has a flexible and branched respiratory chain that enables the prokaryote to live under a variety of environmental conditions, from highly aerobic to completely anaerobic. In general, the bacterial respiratory chain is composed of dehydrogenases, a quinone pool, and reductases. Substrate-specific dehydrogenases transfer reducing equivalents from various donor substrates (NADH, succinate, glycerophosphate, formate, hydrogen, pyruvate, and lactate) to a quinone pool (menaquinone, ubiquinone, and dimethylmenoquinone). Then electrons from reduced quinones (quinols) are transferred by terminal reductases to different electron acceptors. Under aerobic growth conditions, the terminal electron acceptor is molecular oxygen. A transfer of electrons from quinol to O₂ is served by two major oxidoreductases (oxidases), cytochrome bo₃ encoded by cyoABCDE and cytochrome bd encoded by cydABX. Terminal oxidases of aerobic respiratory chains of bacteria, which use O₂ as the final electron acceptor, can oxidize one of two alternative electron donors, either cytochrome c or quinol. This review compares the effects of different inhibitors on the respiratory activities of cytochrome bo₃ and cytochrome bd in E. coli. It also presents a discussion on the genetics and the prosthetic groups of cytochrome bo₃ and cytochrome bd. The E. coli membrane contains three types of quinones that all have an octaprenyl side chain (C₄₀). It has been proposed that the bo₃ oxidase can have two ubiquinone-binding sites with different affinities. "WHAT'S NEW" IN THE REVISED ARTICLE: The revised article comprises additional information about subunit composition of cytochrome bd and its role in bacterial resistance to nitrosative and oxidative stresses. Also, we present the novel data on the electrogenic function of appBCX-encoded cytochrome bd-II, a second bd-type oxidase that had been thought not to contribute to generation of a proton motive force in E. coli, although its spectral properties closely resemble those of cydABX-encoded cytochrome bd.
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Loullis A, Noor MR, Soulimane T, Pinakoulaki E. Observation of ligand transfer in ba3 oxidase from Thermus thermophilus: simultaneous FTIR detection of photolabile heme a3(2+)-CN and transient Cu(B)(2+)-CN complexes. J Phys Chem B 2012; 116:8955-60. [PMID: 22765881 DOI: 10.1021/jp305096y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
FTIR and light-minus-dark FTIR spectroscopy have been employed to investigate the reaction of oxidized and fully reduced ba(3) oxidase with cyanide. The characterization of the structures of the bound CN(-) in the binuclear heme Fe-Cu(B) center is essential, given that a central issue in the function of ba(3) oxidase is the extent to which the partially reduced substrates interact with the two metals. In the reaction of oxidized ba(3) oxidase with cyanide the initially formed heme a(3)(3+)-C≡N-Cu(B)(2+) species with ν(CN) frequency at 2152 cm(-1) was replaced by a photolabile complex with a frequency at 2075 cm(-1) characteristic of heme a(3)(2+)-CN(-). Photolysis of the heme a(3)(2+)-CN(-) adduct produced a band at 2146 cm(-1) attributed to the formation of a transient Cu(B)(2+)-CN(-) complex. All forms are pH independent between pH 5.5-9.5 and at pD 7.5 indicating the absence of ionizable groups that influence the properties of the cyanide complexes. In contrast to previous reports, our results show that CN(-) does not bind simultaneously to both heme a(3)(2+) and Cu(B)(2+) to form the mixed valence a(3)(2+)-CN·Cu(B)(2+)CN species. The photolysis products of the heme a(3)(2+)-CN(-)/Cu(B)(2+) and heme a(3)(2+)-CN(-)/Cu(B)(1+) species are different suggesting that relaxation dynamics in the binuclear center following ligand photodissociation are dependent on the oxidation state of Cu(B).
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Affiliation(s)
- Andreas Loullis
- Department of Chemistry, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus
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Pavlou A, Soulimane T, Pinakoulaki E. Evidence for the Presence of Two Conformations of the Heme a3-CuB Pocket of Cytochrome caa3 from Thermus thermophilus. J Phys Chem B 2011; 115:11455-61. [DOI: 10.1021/jp2033356] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Andrea Pavlou
- Department of Chemistry, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus
| | - Tewfik Soulimane
- Chemical and Environmental Sciences Department and Materials & Surface Science Institute, University of Limerick, Limerick, Ireland
| | - Eftychia Pinakoulaki
- Department of Chemistry, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus
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Abstract
Like most bacteria, Escherichia coli has a flexible and branched respiratory chain that enables the prokaryote to live under a variety of environmental conditions, from highly aerobic to completely anaerobic. In general, the bacterial respiratory chain is composed of dehydrogenases, a quinone pool, and reductases. Substrate specific dehydrogenases transfer reducing equivalents from various donor substrates (NADH, succinate, glycerophoshate, formate, hydrogen, pyruvate, and lactate) to a quinone pool (menaquinone, ubiquinone, and demethylmenoquinone). Then electrons from reduced quinones (quinols) are transferred by terminal reductases to different electron acceptors. Under aerobic growth conditions, the terminal electron acceptor is molecular oxygen. A transfer of electrons from quinol to O2 is served by two major oxidoreductases (oxidases), cytochrome bo3 and cytochrome bd. Terminal oxidases of aerobic respiratory chains of bacteria, which use O2 as the final electron acceptor, can oxidize one of two alternative electron donors, either cytochrome c or quinol. This review compares the effects of different inhibitors on the respiratory activities of cytochrome bo3 and cytochrome bd in E. coli. It also presents a discussion on the genetics and the prosthetic groups of cytochrome bo3 and cytochrome bd. The E. coli membrane contains three types of quinones which all have an octaprenyl side chain (C40). It has been proposed that the bo3 oxidase can have two ubiquinone-binding sites with different affinities. The spectral properties of cytochrome bd-II closely resemble those of cydAB-encoded cytochrome bd.
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Hrabakova J, Ataka K, Heberle J, Hildebrandt P, Murgida DH. Long distance electron transfer in cytochrome c oxidase immobilised on electrodes. A surface enhanced resonance Raman spectroscopic study. Phys Chem Chem Phys 2006; 8:759-66. [PMID: 16482317 DOI: 10.1039/b513379n] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cytochrome c oxidase was tethered to a functionalised Ag electrode via a histidine-tag on the C-terminus of subunit I or II and embedded in a phospholipid bilayer. The uniformly oriented membrane-bound proteins were studied by surface enhanced resonance Raman spectroscopy (SERRS) that reveals preservation of the native structures of the heme a and heme a(3) sites. On the basis of time-dependent SERRS measurements, the rate constant for the heterogeneous electron transfer to heme a was determined to be 0.002 s(-1) independent of the enzyme orientation and the overpotential. Taking into account that the electrode-to-heme a distance is larger than 50 A, these findings suggest an electron hopping mechanism in which the Cu(A) center is not involved. Electrochemical reduction is restricted to heme a whereas electron transfer from heme a to heme a(3), which in solution occurs on the nanosecond time scale, is drastically slowed down. It may be that the network of cooperativities that links intramolecular electron transfer and proton translocation is perturbed in the immobilised enzyme, possibly due to the effect of the interfacial electric field.
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Affiliation(s)
- Jana Hrabakova
- Technische Universität Berlin, Institut für Chemie, D-10623 Berlin, Germany
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