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Kajita Y, Kubo M, Arii H, Ishikawa S, Saito Y, Wasada-Tsutsui Y, Funahashi Y, Ozawa T, Masuda H. Preparations of trans- and cis- μ-1,2-Peroxodiiron(III) Complexes. Molecules 2023; 29:205. [PMID: 38202788 PMCID: PMC10780643 DOI: 10.3390/molecules29010205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Revised: 12/20/2023] [Accepted: 12/28/2023] [Indexed: 01/12/2024] Open
Abstract
The iron(II) complex with cis,cis-1,3,5-tris(benzylamino)cyclohexane (Bn3CY) (1) has been synthesized and characterized, which reacted with dioxygen to form the peroxo complex 2 in acetone at -60 °C. On the basis of spectroscopic measurements for 2, it was confirmed that the peroxo complex 2 has a trans-μ-1,2 fashion. Additionally, the peroxo complex 2 was reacted with benzoate anion as a bridging agent to give a peroxo complex 3. The results of resonance Raman and 1H-NMR studies supported that the peroxo complex 3 is a cis-μ-1,2-peroxodiiron(III) complex. These spectral features were interpreted by using DFT calculations.
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Affiliation(s)
- Yuji Kajita
- Department of Applied Chemistry, Graduate School of Engineering, Aichi Institute of Technology, 1247 Yachigusa, Yakusa-cho, Toyota 470-0392, Japan;
| | - Masaki Kubo
- Department of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso, Showa, Nagoya 466-8555, Japan; (M.K.); (Y.W.-T.); (T.O.)
| | - Hidekazu Arii
- Department of Education, Graduate School of Education, University of Miyazaki, Gakuenkibanadai-Nishi, Miyazaki 889-2192, Japan;
| | - Shinya Ishikawa
- Department of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso, Showa, Nagoya 466-8555, Japan; (M.K.); (Y.W.-T.); (T.O.)
| | - Yamato Saito
- Department of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso, Showa, Nagoya 466-8555, Japan; (M.K.); (Y.W.-T.); (T.O.)
| | - Yuko Wasada-Tsutsui
- Department of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso, Showa, Nagoya 466-8555, Japan; (M.K.); (Y.W.-T.); (T.O.)
| | - Yasuhiro Funahashi
- Department of Chemistry, Graduate School of Science, Osaka University, Machikaneyama, Toyonaka, Osaka 560-0043, Japan;
| | - Tomohiro Ozawa
- Department of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso, Showa, Nagoya 466-8555, Japan; (M.K.); (Y.W.-T.); (T.O.)
| | - Hideki Masuda
- Department of Applied Chemistry, Graduate School of Engineering, Aichi Institute of Technology, 1247 Yachigusa, Yakusa-cho, Toyota 470-0392, Japan;
- Department of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso, Showa, Nagoya 466-8555, Japan; (M.K.); (Y.W.-T.); (T.O.)
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Manley OM, Tang H, Xue S, Guo Y, Chang WC, Makris TM. BesC Initiates C-C Cleavage through a Substrate-Triggered and Reactive Diferric-Peroxo Intermediate. J Am Chem Soc 2021; 143:21416-21424. [PMID: 34898198 PMCID: PMC8876372 DOI: 10.1021/jacs.1c11109] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
BesC catalyzes the iron- and O2-dependent cleavage of 4-chloro-l-lysine to form 4-chloro-l-allylglycine, formaldehyde, and ammonia. This process is a critical step for a biosynthetic pathway that generates a terminal alkyne amino acid which can be leveraged as a useful bio-orthogonal handle for protein labeling. As a member of an emerging family of diiron enzymes that are typified by their heme oxygenase-like fold and a very similar set of coordinating ligands, recently termed HDOs, BesC performs an unusual type of carbon-carbon cleavage reaction that is a significant departure from reactions catalyzed by canonical dinuclear-iron enzymes. Here, we show that BesC activates O2 in a substrate-gated manner to generate a diferric-peroxo intermediate. Examination of the reactivity of the peroxo intermediate with a series of lysine derivatives demonstrates that BesC initiates this unique reaction trajectory via cleavage of the C4-H bond; this process represents the rate-limiting step in a single turnover reaction. The observed reactivity of BesC represents the first example of a dinuclear-iron enzyme that utilizes a diferric-peroxo intermediate to capably cleave a C-H bond as part of its native function, thus circumventing the formation of a high-valent intermediate more commonly associated with substrate monooxygenations.
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Affiliation(s)
- Olivia M. Manley
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Haoyu Tang
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Shan Xue
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Yisong Guo
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Wei-chen Chang
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Thomas M. Makris
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, North Carolina 27695, United States,Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
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3
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Specht P, Oßberger M, Klüfers P, Schindler S. Kinetic studies on the reaction of NO with iron(ii) complexes using low temperature stopped-flow techniques. Dalton Trans 2020; 49:9480-9486. [PMID: 32608457 DOI: 10.1039/d0dt01764g] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Low temperature stopped-flow techniques were used to investigate the reaction of three different iron(ii) complexes with nitrogen monoxide. The kinetic studies allowed calculation of the activation parameters from the corresponding Eyring plots for all three systems. The reaction of iron(ii) chloride with NO leading to the formation of MNIC (mononitrosyl-iron-complex) and DNIC (dinitrosyl-iron-complex) led to activation parameters of ΔH‡ = 55.4 ± 0.4 kJ mol-1 and ΔS‡ = 13 ± 2 J K-1 mol-1 for MNIC and ΔH‡ = 32 ± 6 kJ mol-1 and ΔS‡ = -193 ± 21 J K-1 mol-1 for DNIC. Formation of MNIC turned out to be much faster in comparison with DNIC. In contrast, activation parameters for the formation of monoculear [Fe(bztpen)(NO)](OTf)2 (bztpen = N-benzyl-N,N',N'-tris(2-pyridylmethyl)-ethylenediamine) ΔH‡ = 17.8 ± 0.8 kJ mol-1 and ΔS‡ = -181 ± 3 J K-1 mol-1 supported an associative mechanism. Interestingly, [Fe(bztpen)(CH3CN)](OTf)2 does not react with dioxygen at all. Furthermore, activation parameters of ΔH‡ = 37.7 ± 0.7 kJ mol-1 and ΔS‡ = -66 ± 3 J K-1 mol-1 were obtained for the reaction of NO with the dinuclear iron(ii) H-HPTB complex (H-HPTB = N,N,N',N'-tetrakis(2-benzimidazolylmethyl)-2-hydroxy-1,3-diaminopropane), [Fe2(H-HPTB)(Cl)3]. The kinetic data allowed postulation of the mechanisms for all of these reactions.
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Affiliation(s)
- Pascal Specht
- Institut für Anorganische und Analytische Chemie, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 17, 35392 Gießen, Germany.
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Will J, Schneider L, Becker J, Becker S, Miska A, Gawlig C, Schindler S. Synthesis and Reactivity of Iron(II) Complexes with a New Tripodal Imine Ligand. Isr J Chem 2020. [DOI: 10.1002/ijch.201900120] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Janine Will
- Institute of Inorganic and Analytic Chemistry Justus-Liebig University of Gießen Heinrich-Buff Ring 17 D-35392 Gießen Germany
| | - Lars Schneider
- Institute of Inorganic and Analytic Chemistry Justus-Liebig University of Gießen Heinrich-Buff Ring 17 D-35392 Gießen Germany
| | - Jonathan Becker
- Institute of Inorganic and Analytic Chemistry Justus-Liebig University of Gießen Heinrich-Buff Ring 17 D-35392 Gießen Germany
| | - Sabine Becker
- Technische Universität Kaiserslautern Fachbereich Chemie Erwin-Schrödinger-Straße Gebäude 54/684 67663 Kaiserslautern Germany
| | - Andreas Miska
- Institute of Inorganic and Analytic Chemistry Justus-Liebig University of Gießen Heinrich-Buff Ring 17 D-35392 Gießen Germany
| | - Christopher Gawlig
- Institute of Inorganic and Analytic Chemistry Justus-Liebig University of Gießen Heinrich-Buff Ring 17 D-35392 Gießen Germany
| | - Siegfried Schindler
- Institute of Inorganic and Analytic Chemistry Justus-Liebig University of Gießen Heinrich-Buff Ring 17 D-35392 Gießen Germany
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Engilberge S, Wagner T, Carpentier P, Girard E, Shima S. Krypton-derivatization highlights O 2-channeling in a four-electron reducing oxidase. Chem Commun (Camb) 2020; 56:10863-10866. [DOI: 10.1039/d0cc04557h] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Kr-derivatization and X-ray structures indicated O2-channel and gating-loop that prevent side-reaction in reduction of O2 to water in F420H2 oxidase.
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Affiliation(s)
| | - Tristan Wagner
- Microbial Metabolism Group
- Max-Planck-Institut für Marine Mikrobiologie
- Celsiusstraße 1
- Bremen
- Germany
| | - Philippe Carpentier
- Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Laboratoire Chimie et Biologie des Métaux (LCBM)
- Université Grenoble Alpes, CNRS, CEA
- Grenoble
- France
- European Synchrotron Radiation Facility (ESRF)
| | - Eric Girard
- Univ. Grenoble Alpes, CEA, CNRS, IBS
- F-38000 Grenoble
- France
| | - Seigo Shima
- Microbial Protein Structure Group
- Max Planck Institute for Terrestrial Microbiology
- Karl-von-Frisch Straße 10
- 35043 Marburg
- Germany
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Muthuramalingam S, Subramaniyan S, Khamrang T, Velusamy M, Mayilmurugan R. Copper(II)-Bioinspired Models for Copper Amine Oxidases: Oxidative Half-Reaction in Water. ChemistrySelect 2017. [DOI: 10.1002/slct.201601786] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Sethuraman Muthuramalingam
- Bioinorganic Chemistry Laboratory/Physical Chemistry; School of Chemistry; Madurai Kamaraj University; Madurai 625 021, Tamil Nadu India
| | - Shanmugam Subramaniyan
- Bioinorganic Chemistry Laboratory/Physical Chemistry; School of Chemistry; Madurai Kamaraj University; Madurai 625 021, Tamil Nadu India
| | - Themmila Khamrang
- Department of Chemistry; North Eastern Hill Universuty; Shillong- 793022 India
| | - Marappan Velusamy
- Department of Chemistry; North Eastern Hill Universuty; Shillong- 793022 India
| | - Ramasamy Mayilmurugan
- Bioinorganic Chemistry Laboratory/Physical Chemistry; School of Chemistry; Madurai Kamaraj University; Madurai 625 021, Tamil Nadu India
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Khatua S, Majumdar A. Flavodiiron nitric oxide reductases: Recent developments in the mechanistic study and model chemistry for the catalytic reduction of NO. J Inorg Biochem 2015; 142:145-53. [DOI: 10.1016/j.jinorgbio.2014.09.018] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Revised: 09/26/2014] [Accepted: 09/29/2014] [Indexed: 11/24/2022]
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8
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Walli A, Dechert S, Bauer M, Demeshko S, Meyer F. BOX Ligands in Biomimetic Copper-Mediated Dioxygen Activation: A Hemocyanin Model. Eur J Inorg Chem 2014. [DOI: 10.1002/ejic.201402378] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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9
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Coggins MK, Sun X, Kwak Y, Solomon EI, Rybak-Akimova E, Kovacs JA. Characterization of metastable intermediates formed in the reaction between a Mn(II) complex and dioxygen, including a crystallographic structure of a binuclear Mn(III)-peroxo species. J Am Chem Soc 2013; 135:5631-40. [PMID: 23470101 PMCID: PMC3709604 DOI: 10.1021/ja311166u] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Transition-metal peroxos have been implicated as key intermediates in a variety of critical biological processes involving O2. Because of their highly reactive nature, very few metal-peroxos have been characterized. The dioxygen chemistry of manganese remains largely unexplored despite the proposed involvement of a Mn-peroxo, either as a precursor to, or derived from, O2, in both photosynthetic H2O oxidation and DNA biosynthesis. These are arguably two of the most fundamental processes of life. Neither of these biological intermediates has been observed. Herein we describe the dioxygen chemistry of coordinatively unsaturated [Mn(II)(S(Me2)N4(6-Me-DPEN))] (+) (1), and the characterization of intermediates formed en route to a binuclear mono-oxo-bridged Mn(III) product {[Mn(III)(S(Me2)N4(6-Me-DPEN)]2(μ-O)}(2+) (2), the oxo atom of which is derived from (18)O2. At low-temperatures, a dioxygen intermediate, [Mn(S(Me2)N4(6-Me-DPEN))(O2)](+) (4), is observed (by stopped-flow) to rapidly and irreversibly form in this reaction (k1(-10 °C) = 3780 ± 180 M(-1) s(-1), ΔH1(++) = 26.4 ± 1.7 kJ mol(-1), ΔS1(++) = -75.6 ± 6.8 J mol(-1) K(-1)) and then convert more slowly (k2(-10 °C) = 417 ± 3.2 M(-1) s(-1), ΔH2(++) = 47.1 ± 1.4 kJ mol(-1), ΔS2(++) = -15.0 ± 5.7 J mol(-1) K(-1)) to a species 3 with isotopically sensitive stretches at νO-O(Δ(18)O) = 819(47) cm(-1), kO-O = 3.02 mdyn/Å, and νMn-O(Δ(18)O) = 611(25) cm(-1) consistent with a peroxo. Intermediate 3 releases approximately 0.5 equiv of H2O2 per Mn ion upon protonation, and the rate of conversion of 4 to 3 is dependent on [Mn(II)] concentration, consistent with a binuclear Mn(O2(2-)) Mn peroxo. This was verified by X-ray crystallography, where the peroxo of {[Mn(III)(S(Me2)N4(6-Me-DPEN)]2(trans-μ-1,2-O2)}(2+) (3) is shown to be bridging between two Mn(III) ions in an end-on trans-μ-1,2-fashion. This represents the first characterized example of a binuclear Mn(III)-peroxo, and a rare case in which more than one intermediate is observed en route to a binuclear μ-oxo-bridged product derived from O2. Vibrational and metrical parameters for binuclear Mn-peroxo 3 are compared with those of related binuclear Fe- and Cu-peroxo compounds.
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Affiliation(s)
- Michael K Coggins
- Department of Chemistry, University of Washington, Campus Box 351700 Seattle, Washington 98195-1700, USA
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10
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Sun X, Kryatov SV, Rybak-Akimova EV. Kinetic insights into the reactivity of the intermediates generated from hydrogen peroxide and diiron(III) complex with tris(picolyl)amine (TPA). Dalton Trans 2013; 42:4427-35. [PMID: 23338901 DOI: 10.1039/c2dt32599c] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Two intermediates (2 and 3) are formed consecutively in the reaction of a diiron(III) complex [Fe(III)(2)(μ-O)(OH)(H(2)O)(TPA)(2)](ClO(4))(3) (TPA = tris(2-pyridylmethyl)amine, tris(picolyl)amine) with H(2)O(2) in CH(3)CN at -40 °C. Low-temperature stopped-flow studies showed that both species are kinetically competent in oxidation of phosphines and phenols. The first intermediate (2) reacts with substrates very rapidly (second-order rate constants reach 10(5)-10(6) M(-1) s(-1) for substituted triarylphosphines and 10(3)-10(5) M(-1) s(-1) for substituted phenols), in keeping with a diiron(IV)-oxo formulation. The second intermediate (3), a mixed-valent Fe(III)Fe(IV) species, is more stable than 2, and reacts with substrates more slowly (second-order rate constants range from 150 to 550 M(-1) s(-1) for triaryl phosphine oxidation, and from 18 to 790 M(-1) s(-1) for phenol oxidation). Reaction rates increase with increasing electron donating abilities of substituents, indicating that both 2 and 3 act as electrophilic oxidants.
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Affiliation(s)
- Xianru Sun
- Department of Chemistry, Tufts University, Medford, MA, USA.
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11
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Berto TC, Speelman AL, Zheng S, Lehnert N. Mono- and dinuclear non-heme iron–nitrosyl complexes: Models for key intermediates in bacterial nitric oxide reductases. Coord Chem Rev 2013. [DOI: 10.1016/j.ccr.2012.05.007] [Citation(s) in RCA: 144] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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12
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Ye S, Riplinger C, Hansen A, Krebs C, Bollinger JM, Neese F. Electronic structure analysis of the oxygen-activation mechanism by Fe(II)- and α-ketoglutarate (αKG)-dependent dioxygenases. Chemistry 2012; 18:6555-67. [PMID: 22511515 PMCID: PMC3955955 DOI: 10.1002/chem.201102829] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Indexed: 11/09/2022]
Abstract
α-Ketoglutarate (αKG)-dependent nonheme iron enzymes utilize a high-spin (HS) ferrous center to couple the activation of oxygen to the decarboxylation of the cosubstrate αKG to yield succinate and CO(2), and to generate a high-valent ferryl species that then acts as an oxidant to functionalize the target C-H bond. Herein a detailed analysis of the electronic-structure changes that occur in the oxygen activation by this enzyme was performed. The rate-limiting step, which is identical on the septet and quintet surfaces, is the nucleophilic attack of the distal O atom of the O(2) adduct on the carbonyl group in αKG through a bicyclic transition state ((5, 7) TS1). Due to the different electronic structures in (5, 7) TS1, the decay of (7)TS1 leads to a ferric oxyl species, which undergoes a rapid intersystem crossing to form the ferryl intermediate. By contrast, a HS ferrous center ligated by a peroxosuccinate is obtained on the quintet surface following (5)TS1. Thus, additional two single-electron transfer steps are required to afford the same Fe(IV)-oxo species. However, the triplet reaction channel is catalytically irrelevant. The biological role of αKG played in the oxygen-activation reaction is dual. The αKG LUMO (C=O π*) serves as an electron acceptor for the nucleophilic attack of the superoxide monoanion. On the other hand, the αKG HOMO (C1-C2 σ) provides the second and third electrons for the further reduction of the superoxide. In addition to density functional theory, high-level ab initio calculations have been used to calculate the accurate energies of the critical points on the alternative potential-energy surfaces. Overall, the results delivered by the ab initio calculations are largely parallel to those obtained with the B3LYP density functional, thus lending credence to our conclusions.
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Affiliation(s)
- Shengfa Ye
- Max-Plank Institute for Bioinorganic Chemistry Stiftstrasse 34–36 45470 Mülheim an der Ruhr (Germany)
| | - Christoph Riplinger
- Max-Plank Institute for Bioinorganic Chemistry Stiftstrasse 34–36 45470 Mülheim an der Ruhr (Germany)
| | - Andreas Hansen
- Max-Plank Institute for Bioinorganic Chemistry Stiftstrasse 34–36 45470 Mülheim an der Ruhr (Germany)
| | - Carsten Krebs
- Department of Chemistry Department of Biochemistry and Molecular Biology The Pennsylvania State University University Park, Pennsylvania 16802 (USA)
| | - J. Martin Bollinger
- Department of Chemistry Department of Biochemistry and Molecular Biology The Pennsylvania State University University Park, Pennsylvania 16802 (USA)
| | - Frank Neese
- Max-Plank Institute for Bioinorganic Chemistry Stiftstrasse 34–36 45470 Mülheim an der Ruhr (Germany)
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van Eldik R, Hubbard CD. Application of low-temperature rapid-scan techniques in the elucidation of inorganic reaction mechanisms. Coord Chem Rev 2010. [DOI: 10.1016/j.ccr.2009.09.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Wane A, Thallaj N, Mandon D. Biomimetic Interaction between FeIIand O2: Effect of the Second Coordination Sphere on O2Binding to FeIIComplexes: Evidence of Coordination at the Metal Centre by a Dissociative Mechanism in the Formation of μ-Oxo Diferric Complexes. Chemistry 2009; 15:10593-602. [DOI: 10.1002/chem.200901350] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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15
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de Visser S. Is the μ-Oxo-μ-Peroxodiiron Intermediate of a Ribonucleotide Reductase Biomimetic a Possible Oxidant of Epoxidation Reactions? Chemistry 2008; 14:4533-41. [DOI: 10.1002/chem.200701802] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Korendovych IV, Kryatov SV, Rybak-Akimova EV. Dioxygen activation at non-heme iron: insights from rapid kinetic studies. Acc Chem Res 2007; 40:510-21. [PMID: 17521158 DOI: 10.1021/ar600041x] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
One of the common biochemical pathways of binding and activation of dioxygen involves non-heme iron centers. The enzyme cycles usually start with an iron(II) or diiron(II) state and traverse via several intermediates (detected or postulated) such as (di)iron(III)-superoxo, (di)iron(III)-(hydro)peroxo, iron(III)iron(IV)-oxo, and (di)iron(IV)-oxo species, some of which are responsible for substrate oxidation. In this Account, we present results of kinetic and mechanistic studies of dioxygen binding and activation reactions of model inorganic iron compounds. The number of iron centers, their coordination number, and the steric and electronic properties of the ligands were varied in several series of well-characterized complexes that provided reactive manifolds modeling the function of native non-heme iron enzymes. Time-resolved cryogenic stopped-flow spectrophotometry permitted the identification of kinetically competent intermediates in these systems. Inner-sphere mechanisms dominated the chemistry of dioxygen binding, intermediate transformations, and substrate oxidation as most of these processes were controlled by the rates of ligand substitution at the iron centers.
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Affiliation(s)
- Ivan V Korendovych
- Department of Chemistry, Tufts University, Medford, Massachusetts 02155, USA
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Seedorf H, Hagemeier CH, Shima S, Thauer RK, Warkentin E, Ermler U. Structure of coenzyme F420H2 oxidase (FprA), a di-iron flavoprotein from methanogenic Archaea catalyzing the reduction of O2 to H2O. FEBS J 2007; 274:1588-99. [PMID: 17480207 DOI: 10.1111/j.1742-4658.2007.05706.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The di-iron flavoprotein F(420)H(2) oxidase found in methanogenic Archaea catalyzes the four-electron reduction of O(2) to 2H(2)O with 2 mol of reduced coenzyme F(420)(7,8-dimethyl-8-hydroxy-5-deazariboflavin). We report here on crystal structures of the homotetrameric F(420)H(2) oxidase from Methanothermobacter marburgensis at resolutions of 2.25 A, 2.25 A and 1.7 A, respectively, from which an active reduced state, an inactive oxidized state and an active oxidized state could be extracted. As found in structurally related A-type flavoproteins, the active site is formed at the dimer interface, where the di-iron center of one monomer is juxtaposed to FMN of the other. In the active reduced state [Fe(II)Fe(II)FMNH(2)], the two irons are surrounded by four histidines, one aspartate, one glutamate and one bridging aspartate. The so-called switch loop is in a closed conformation, thus preventing F(420) binding. In the inactive oxidized state [Fe(III)FMN], the iron nearest to FMN has moved to two remote binding sites, and the switch loop is changed to an open conformation. In the active oxidized state [Fe(III)Fe(III)FMN], both irons are positioned as in the reduced state but the switch loop is found in the open conformation as in the inactive oxidized state. It is proposed that the redox-dependent conformational change of the switch loop ensures alternate complete four-electron O(2) reduction and redox center re-reduction. On the basis of the known Si-Si stereospecific hydride transfer, F(420)H(2) was modeled into the solvent-accessible pocket in front of FMN. The inactive oxidized state might provide the molecular basis for enzyme inactivation by long-term O(2) exposure observed in some members of the FprA family.
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Affiliation(s)
- Henning Seedorf
- Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
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Diiron(II) complexes showing a reversible oxygenation induced by a proton transfer mediated with a water molecule. Biological implication of a water molecule in hemerythrin function. J Organomet Chem 2007. [DOI: 10.1016/j.jorganchem.2006.04.052] [Citation(s) in RCA: 6] [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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19
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Zhao M, Song D, Lippard SJ. Water Induces a Structural Conversion and Accelerates the Oxygenation of Carboxylate-Bridged Non-Heme Diiron Enzyme Synthetic Analogues. Inorg Chem 2006; 45:6323-30. [PMID: 16878942 DOI: 10.1021/ic0602906] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Recently, we reported the synthesis of a carboxylate-rich non-heme diiron enzyme model compound [Fe2(mu-O2CAr(Tol))4(4-CNPy)2] (1), where (-)O(2)CAr(Tol) is 2,6-di-p-tolylbenzoate and 4-CNPy is 4-cyanopyridine (Yoon, S.; Lippard, S. J. J. Am. Chem. Soc. 2005, 127, 8386-8397). A metal-to-ligand charge-transfer band in the visible region of the optical absorption spectrum involving the nitrogen-donor ligand endowed this complex with a distinctive red color that facilitated analysis of its chemistry. Following this strategy, we prepared and characterized two related isomeric complexes, windmill (3) and paddlewheel (4) species having the formula [Fe2(O2CAr(Tol))4(4-AcPy)2], where 4-AcPy is 4-acetylpyridine. In anhydrous solvents, 1 and 4 adopt paddlewheel structures, but upon the addition of water, they convert to aquated forms, windmill structures having the composition [Fe2(mu-O2CAr(Tol))2(O2CAr(Tol))2(4-RPy)2(H2O)2]. This conversion is favored at low temperature and was studied by NMR spectroscopy. A kinetic analysis of the aquation reaction was undertaken by stopped-flow measurements between 198 and 223 K for both 1 and 4, which revealed a first-order dependence on both the diiron compound and water. The oxygenation rates for the water-containing complexes are much faster than those for the corresponding anhydrous complexes, being 20-fold faster for 4 and 10-fold more rapid for 1. The presence or absence of water had little effect on the activation enthalpies, suggesting that the loss of water may not be necessary prior to dioxygen binding in the transition state.
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Affiliation(s)
- Min Zhao
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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Kodera M, Itoh M, Kano K, Funabiki T. Peroxodiiron Complexes of Polypyridine Ligands: Syntheses, Physicochemical Properties, and Thermal Stability Markedly Enhanced by Hexapyridine Dinucleating Ligand. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2006. [DOI: 10.1246/bcsj.79.252] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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21
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Pavlova SV, To HL, Chan ESH, Li HW, Mak TCW, Lee HK, Chan SI. Synthesis, structure and dioxygen reactivity of a bis(µ-iodo)dicopper(i) complex supported by the [N-(3,5-di-tert-butyl-2-hydroxybenzyl)-N,N-di-(2-pyridylmethyl)]amine ligand. Dalton Trans 2006:2232-43. [PMID: 16673038 DOI: 10.1039/b513898a] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The air-sensitive bis(micro-iodo)dicopper(I) complex 1 supported by [N-(3,5-di-tert-butyl-2-hydroxybenzyl)-N,N-di-(2-pyridylmethyl)]amine (L) has been prepared by treating copper(I) iodide with L in anhydrous THF. Compound 1 crystallizes as a dimer in space group C2/c. Each copper(I) center has distorted tetrahedral N2I2 coordination geometry with Cu-N(pyridyl) distances 2.061(3) and 2.063(3) A, Cu-I distances 2.6162(5) and 2.7817(5) and a Cu...Cu distance of 2.9086(8) A. Complex 1 is rapidly oxidized by dioxygen in CH2Cl2 with a 1 : 1 stoichiometry giving the bis(micro-iodo)peroxodicopper(II) complex [Cu(L)(micro-I)]2O2 (2). The reaction of 1 with dioxygen has been characterized by UV-vis, mass spectrometry, EPR and Cu K-edge X-ray absorption spectroscopy at low temperature (193 K) and above. The mass spectrometry and low temperature EPR measurements suggested an equilibrium between the bis(micro-iodo)peroxodicopper(II) complex 2 and its dimer, namely, the tetranuclear (peroxodicopper(II))2 complex [Cu(L)(micro-I)]4O4 (2'). Complex 2 undergoes an effective oxo-transfer reaction converting PPh3 into O=PPh3 under anaerobic conditions. At sufficiently high concentration of PPh3, the oxygen atom transfer from 2 to PPh3 was followed by the formation of [Cu(PPh3)3I]. The dioxygen reactivity of 1 was compared with that known for other halo(amine)copper(I) dimers.
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Wasser IM, Huang HW, Moënne-Loccoz P, Karlin KD. Heme/non-heme diiron(II) complexes and O2, CO, and NO adducts as reduced and substrate-bound models for the active site of bacterial nitric oxide reductase. J Am Chem Soc 2005; 127:3310-20. [PMID: 15755147 DOI: 10.1021/ja0458773] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
As a first generation model for the reactive reduced active-site form of bacterial nitric oxide reductase, a heme/non-heme diiron(II) complex [(6L)Fe(II)...Fe(II)-(Cl)]+ (2) {where 6L = partially fluorinated tetraphenylporphyrin with a tethered tetradentate TMPA chelate; TMPA = tris(2-pyridyl)amine} was generated by reduction of the corresponding mu-oxo diferric compound [(6L)Fe(III)-O-Fe(III)-Cl]+ (1). Coordination chemistry models for reactions of reduced NOR with O2, CO, and NO were also developed. With O2 and CO, adducts are formed, [(6L)Fe(III)(O2-))(thf)...Fe(II)-Cl]B(C6F5)4 (2a x O2) {lambda(max) 418 (Soret), 536 nm; nu(O-O) = 1176 cm(-1), nu(Fe-O) = 574 cm(-1) and [(6L)Fe(II)(CO)(thf)Fe(II)-Cl]B(C6F5)4 (2a x CO) {nu(CO) 1969 cm(-1)}, respectively. Reaction of purified nitric oxide with 2 leads to the dinitrosyl complex [(6L)Fe(NO)Fe(NO)-Cl]B(C6F5)4 (2a x (NO)2) with nu(NO) absorptions at 1798 cm(-1) (non-heme Fe-NO) and 1689 cm(-1) (heme-NO).
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Affiliation(s)
- Ian M Wasser
- Department of Chemistry, Johns Hopkins University, Charles and 34 Streets, Baltimore, Maryland 21218, USA
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Kryatov SV, Rybak-Akimova EV, Schindler S. Kinetics and Mechanisms of Formation and Reactivity of Non-heme Iron Oxygen Intermediates. Chem Rev 2005; 105:2175-226. [PMID: 15941212 DOI: 10.1021/cr030709z] [Citation(s) in RCA: 313] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Sergey V Kryatov
- Department of Chemistry, Tufts University, Medford, Massachusetts 02155, USA
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Yoon S, Lippard SJ. Water Affects the Stereochemistry and Dioxygen Reactivity of Carboxylate-Rich Diiron(II) Models for the Diiron Centers in Dioxygen-Dependent Non-Heme Enzymes. J Am Chem Soc 2005; 127:8386-97. [PMID: 15941272 DOI: 10.1021/ja0512531] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Carboxylate-bridged high-spin diiron(II) complexes with distinctive electronic transitions were prepared by using 4-cyanopyridine (4-NCC(5)H(4)N) ligands to shift the charge-transfer bands to the visible region of the absorption spectrum. This property facilitated quantitation of water-dependent equilibria in the carboxylate-rich diiron(II) complex, [Fe(2)(mu-O(2)CAr(Tol))(4)(4-NCC(5)H(4)N)(2)] (1), where (-)O(2)CAr(Tol) is 2,6-di-(p-tolyl)benzoate. Addition of water to 1 reversibly shifts two of the bridging carboxylate ligands to chelating terminal coordination positions, converting the structure from a paddlewheel to a windmill geometry and generating [Fe(2)(mu-O(2)CAr(Tol))(2)(O(2)CAr(Tol))(2)(4-NCC(5)H(4)N)(2)(H(2)O)(2)] (3). This process is temperature dependent in solution, rendering the system thermochromic. Quantitative treatment of the temperature-dependent spectroscopic changes over the temperature range from 188 to 298 K in CH(2)Cl(2) afforded thermodynamic parameters for the interconversion of 1 and 3. Stopped flow kinetic studies revealed that water reacts with the diiron(II) center ca. 1000 time faster than dioxygen and that the water-containing diiron(II) complex reacts with dioxygen ca. 10 times faster than anhydrous analogue 1. Addition of {H(OEt(2))(2)}{B}, where B(-) is tetrakis(3,5-di(trifluoromethyl)phenyl)borate, to 1 converts it to [Fe(2)(mu-O(2)CAr(Tol))(3)(4-NCC(5)H(4)N)(2)](B) (5), which was also structurally characterized. Mossbauer spectroscopic investigations of solid samples of 1, 3, and 5, in conjunction with several literature values for high-spin iron(II) complexes in an oxygen-rich coordination environment, establish a correlation between isomer shift, coordination number, and N/O composition. The products of oxygenating 1 in CH(2)Cl(2) were identified crystallographically to be [Fe(2)(mu-OH)(2)(mu-O(2)CAr(Tol))(2)(O(2)CAr(Tol))(2)(4-NCC(5)H(4)N)(2)].2(HO(2)CAr(Tol)) (6) and [Fe(6)(mu-O)(2)(mu-OH)(4)(mu-O(2)CAr(Tol))(6)(4-NCC(5)H(4)N)(4)Cl(2)] (7).
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Affiliation(s)
- Sungho Yoon
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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Shan X, Que L. Intermediates in the oxygenation of a nonheme diiron(II) complex, including the first evidence for a bound superoxo species. Proc Natl Acad Sci U S A 2005; 102:5340-5. [PMID: 15802473 PMCID: PMC556236 DOI: 10.1073/pnas.0409640102] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The reaction of [Fe(2)(mu-OH)(2)(6-Me(3)-TPA)(2)](2+) (1) [6-Me(3)-TPA, Tris(6-methyl-2-pyridylmethyl)amine] with O(2) in CH(2)Cl(2) at -80 degrees C gives rise to two new intermediates, 2 and 3, before the formation of previously characterized [Fe(2)(O)(O(2))(6-Me(3)-TPA)(2)](2+) (4) that allow the oxygenation reaction to be monitored one electron-transfer step at a time. Raman evidence assigns 2 and 3 as a diiron-superoxo species and a diiron-peroxo species, respectively. Intermediate 2 exhibits its nu(O-O) at 1,310 cm(-1) with a -71-cm(-1) (18)O isotope shift. A doublet peak pattern for the (16)O(18)O isotopomer of 2 in mixed-isotope Raman experiments strongly suggests that the superoxide ligand of 2 is bound end-on. This first example of a nonheme iron-superoxo intermediate exhibits the highest frequency nu(O-O) yet observed for a biomimetic metal-dioxygen adduct. The bound superoxide of 2, unlike the bound peroxide of 4, is readily reduced by 2,4-di-tert-butylphenol via a proton-coupled electron-transfer mechanism, emphasizing that metal-superoxo species may serve as oxidants in oxygen activation mechanisms of metalloenzymes. The discovery of intermediates 2 and 3 allows us to dissect the initial steps of dioxygen binding at a diiron center leading to its activation for substrate oxidation.
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Affiliation(s)
- Xiaopeng Shan
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant Street Southeast, Minneapolis, MN 55455, USA
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Synthesis and characterization of new synthetic oxygen carriers. A kinetic study of the reaction of the binuclear iron(III)?copper(II) complex with H2O2. TRANSIT METAL CHEM 2005. [DOI: 10.1007/s11243-004-3433-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Kryatov SV, Taktak S, Korendovych IV, Rybak-Akimova EV, Kaizer J, Torelli S, Shan X, Mandal S, MacMurdo VL, Mairata i Payeras A, Que L. Dioxygen Binding to Complexes with FeII2(μ-OH)2 Cores: Steric Control of Activation Barriers and O2-Adduct Formation. Inorg Chem 2004; 44:85-99. [PMID: 15627364 DOI: 10.1021/ic0485312] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A series of complexes with [Fe(II)(2)(mu-OH)(2)] cores has been synthesized with N3 and N4 ligands and structurally characterized to serve as models for nonheme diiron(II) sites in enzymes that bind and activate O(2). These complexes react with O(2) in solution via bimolecular rate-limiting steps that differ in rate by 10(3)-fold, depending on ligand denticity and steric hindrance near the diiron center. Low-temperature trapping of a (mu-oxo)(mu-1,2-peroxo)diiron(III) intermediate after O(2) binding requires sufficient steric hindrance around the diiron center and the loss of a proton (presumably that of a hydroxo bridge or a yet unobserved hydroperoxo intermediate). The relative stability of these and other (mu-1,2-peroxo)diiron(III) intermediates suggests that these species may not be on the direct pathway for dioxygen activation.
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Affiliation(s)
- Sergey V Kryatov
- Department of Chemistry, Tufts University, 62 Talbot Avenue, Medford, Massachusetts 02155, USA
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Aboelella NW, Kryatov SV, Gherman BF, Brennessel WW, Young VG, Sarangi R, Rybak-Akimova EV, Hodgson KO, Hedman B, Solomon EI, Cramer CJ, Tolman WB. Dioxygen Activation at a Single Copper Site: Structure, Bonding, and Mechanism of Formation of 1:1 Cu−O2 Adducts. J Am Chem Soc 2004; 126:16896-911. [PMID: 15612729 DOI: 10.1021/ja045678j] [Citation(s) in RCA: 166] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
To evaluate the fundamental process of O(2) activation at a single copper site that occurs in biological and catalytic systems, a detailed study of O(2) binding to Cu(I) complexes of beta-diketiminate ligands L (L(1) = backbone Me; L(2) = backbone tBu) by X-ray crystallography, X-ray absorption spectroscopy (XAS), cryogenic stopped-flow kinetics, and theoretical calculations was performed. Using synchrotron radiation, an X-ray diffraction data set for L(2)CuO(2) was acquired, which led to structural parameters in close agreement to theoretical predictions. Significant Cu(III)-peroxo character for the complex was corroborated by XAS. On the basis of stopped-flow kinetics data and theoretical calculations for the oxygenation of L(1)Cu(RCN) (R = alkyl, aryl) in THF and THF/RCN mixtures between 193 and 233 K, a dual pathway mechanism is proposed involving (a) rate-determining solvolysis of RCN by THF followed by rapid oxygenation of L(1)Cu(THF) and (b) direct, bimolecular oxygenation of L(1)Cu(RCN) via an associative process.
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Affiliation(s)
- Nermeen W Aboelella
- Department of Chemistry, Center for Metals in Biocatalysis, and Supercomputer Institute, University of Minnesota, 207 Pleasant Street SE, Minneapolis, MN 55455, USA
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Naróg D, Lechowicz U, Pietryga T, Sobkowiak A. Iron(II, III)-catalyzed oxidative N-dealkylation of amines with dioxygen. ACTA ACUST UNITED AC 2004. [DOI: 10.1016/j.molcata.2003.11.018] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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30
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Kryatov SV, Chavez FA, Reynolds AM, Rybak-Akimova EV, Que L, Tolman WB. Mechanistic Studies on the Formation and Reactivity of Dioxygen Adducts of Diiron Complexes Supported by Sterically Hindered Carboxylates. Inorg Chem 2004; 43:2141-50. [PMID: 15018538 DOI: 10.1021/ic049976t] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Dioxygen activation by enzymes such as methane monooxygenase, ribonucleotide reductase, and fatty acid desaturases occurs at a nonheme diiron active site supported by two histidines and four carboxylates, typically involving a (peroxo)diiron(III,III) intermediate in an early step of the catalytic cycle. Biomimetic tetracarboxylatodiiron(II,II) complexes with the familiar "paddlewheel" topology comprising sterically bulky o-dixylylbenzoate ligands with pyridine, 1-methylimidazole, or THF at apical sites readily react with O(2) to afford thermally labile peroxo intermediates that can be trapped and characterized spectroscopically at low temperatures (193 K). Cryogenic stopped-flow kinetic analysis of O(2) adduct formation carried out for the three complexes reveals that dioxygen binds to the diiron(II,II) center with concentration dependences and activation parameters indicative of a direct associative pathway. The pyridine and 1-methylimidazole intermediates decay by self-decomposition. However, the THF intermediate decays much faster by oxygen transfer to added PPh(3), the kinetics of which has been studied with double mixing experiments in a cryogenic stopped-flow apparatus. The results show that the decay of the THF intermediate is kinetically controlled by the dissociation of a THF ligand, a conclusion supported by the observation of saturation kinetic behavior with respect to PPh(3), inhibition by added THF, and invariant saturation rate constants for the oxidation of various phosphines. It is proposed that the proximity of the reducing substrate to the peroxide ligand on the diiron coordination sphere facilitates the oxygen-atom transfer. This unique investigation of the reaction of an O(2) adduct of a biomimetic tetracarboxylatodiiron(II,II) complex provides a synthetic precedent for understanding the electrophilic reactivity of like adducts in the active sties of nonheme diiron enzymes.
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Affiliation(s)
- Sergey V Kryatov
- Department of Chemistry, Tufts University, 62 Talbot Avenue, Medford, MA 02155, USA
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Machkour A, Mandon D, Lachkar M, Welter R. Easy Preparation of the Tris(2-fluoro-6-pyridylmethyl)amine Ligand and Instantaneous Reaction of the Corresponding Dichloroferrous Complex with Molecular Dioxygen: New Access to Dinuclear Species. Inorg Chem 2004; 43:1545-50. [PMID: 14966993 DOI: 10.1021/ic034485e] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The tris(2-fluoro-6-pyridylmethyl)amine ligand, F3TPA, can easily be prepared by reaction of 2-fluoro-6-bromomethylpyridine with NH4Cl in the presence of NaOH. Complexation to FeCl2 affords the high-spin F3TPAFe(II)Cl2 complex, the X-ray structure of which is reported. The three fluorine substituents provide enough steric hindrance to force the tripod to coordinate in the tridentate mode, affording a trigonal bipyramidal iron center. This complex is thermally stable, and it reacts instantaneously with molecular dioxygen to afford the unsymmetrical micro-oxo dimer F3TPAFe(III)ClOFe(III)Cl3 as the major product, together with small amounts of the mixed salt [F3TPAFe(II)Cl]2, [Fe(III)2OCl6]. These two complexes have been isolated and characterized by X-ray diffraction analysis. A mechanism by which they are obtained is suggested and seems to parallel the well-known process of autoxidation of ferrous porphyrins.
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Affiliation(s)
- Ahmed Machkour
- Laboratoire de Chimie Biomimétique des Métaux de Transition, UMR CNRS 7513, Université Louis Pasteur, Institut Le Bel, 4 Rue Blaise Pascal, F-67070 Strasbourg, France
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Tshuva EY, Lippard SJ. Synthetic Models for Non-Heme Carboxylate-Bridged Diiron Metalloproteins: Strategies and Tactics. Chem Rev 2004; 104:987-1012. [PMID: 14871147 DOI: 10.1021/cr020622y] [Citation(s) in RCA: 536] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Edit Y Tshuva
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Pavlova SV, Chen KHC, Chan SI. Spectroscopic characterization of the oxo-transfer reaction from a bis(μ-oxo)dicopper(iii) complex to triphenylphosphine. Dalton Trans 2004:3261-72. [PMID: 15483710 DOI: 10.1039/b406692h] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The oxygen-atom transfer reaction from the bis(mu-oxo)dicopper(III) complex [Cu(III)(2)(mu-O)(2)(L)(2)](2+), where L =N,N,N',N' -tetraethylethylenediamine, to PPh(3) has been studied by UV-vis, EPR, (1)H NMR and Cu K-edge X-ray absorption spectroscopy in parallel at low temperatures (193 K) and above. Under aerobic conditions (excess dioxygen), 1 reacted with PPh(3), giving O=Ph(3) and a diamagnetic species that has been assigned to an oxo-bridged dicopper(II) complex on the basis of EPR and Cu K-edge X-ray absorption spectroscopic data. Isotope-labeling experiments ((18)O(2)) established that the oxygen atom incorporated into the triphenylphosphine oxide came from both complex 1 and exogenous dioxygen. Detailed kinetic studies revealed that the process is a third-order reaction; the rate law is first order in both complex 1 and triphenylphosphine, as well as in dioxygen. At temperatures above 233 K, reaction of 1 with PPh(3) was accompanied by ligand degradation, leading to oxidative N-dealkylation of one of the ethyl groups. By contrast, when the reaction was performed in the absence of excess dioxygen, negligible substrate (PPh(3)) oxidation was observed. Instead, highly symmetrical copper complexes with a characteristic isotropic EPR signal at g= 2.11 were formed. These results are discussed in terms of parallel reaction channels that are activated under various conditions of temperature and dioxygen.
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Costas M, Cady CW, Kryatov SV, Ray M, Ryan MJ, Rybak-Akimova EV, Que L. Role of Carboxylate Bridges in Modulating Nonheme Diiron(II)/O2 Reactivity. Inorg Chem 2003; 42:7519-30. [PMID: 14606847 DOI: 10.1021/ic034359a] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A series of diiron(II) complexes of the dinucleating ligand HPTP (N,N,N',N'-tetrakis(2-pyridylmethyl)-2-hydroxy-1,3-diaminopropane) with one or two supporting carboxylate bridges has been synthesized and characterized. The crystal structure of one member of each subset has been obtained to reveal for subset A a (micro-alkoxo)(micro-carboxylato)diiron(II) center with one five- and one six-coordinate metal ion and for subset B a coordinatively saturated (micro-alkoxo)bis(micro-carboxylato)diiron(II) center. These complexes react with O(2) in second-order processes to form adducts characterized as (micro-1,2-peroxo)diiron(III) complexes. Stopped-flow kinetic studies show that the oxygenation step is sensitive to the availability of an O(2) binding site on the diiron(II) center, as subset B reacts more slowly by an order of magnitude. The lifetimes of the O(2) adducts are also distinct and can be modulated by the addition of oxygen donor ligands. The O(2) adduct of a monocarboxylate complex decays by a fast second-order process that must be monitored by stopped-flow methods, but becomes stabilized in CH(2)Cl(2)/DMSO (9:1 v/v) and decomposes by a much slower first-order process. The O(2) adduct of a dicarboxylate complex is even more stable in pure CH(2)Cl(2) and decays by a first-order process. These differences in adduct stability are reflected in the observation that only the O(2) adducts of monocarboxylate complexes can oxidize substrates, and only those substrates that can bind to the diiron center. Thus, the much greater stability of the O(2) adducts of dicarboxylate complexes can be rationalized by the formation of a (micro-alkoxo)(micro-1,2-peroxo)diiron(III) complex wherein the carboxylate bridges in the diiron(II) complex become terminal ligands in the O(2) adduct, occupy the remaining coordination sites on the diiron center, and prevent binding of potential substrates. Implications for the oxidation mechanisms of nonheme diiron enzymes are discussed.
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Affiliation(s)
- Miquel Costas
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, USA
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Mehn MP, Fujisawa K, Hegg EL, Que L. Oxygen activation by nonheme iron(II) complexes: alpha-keto carboxylate versus carboxylate. J Am Chem Soc 2003; 125:7828-42. [PMID: 12823001 DOI: 10.1021/ja028867f] [Citation(s) in RCA: 137] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Mononuclear iron(II) alpha-keto carboxylate and carboxylate compounds of the sterically hindered tridentate face-capping ligand Tp(Ph2) (Tp(Ph2) = hydrotris(3,5-diphenylpyrazol-1-yl)borate) were prepared as models for the active sites of nonheme iron oxygenases. The structures of an aliphatic alpha-keto carboxylate complex, [Fe(II)(Tp(Ph2))(O(2)CC(O)CH(3))], and the carboxylate complexes [Fe(II)(Tp(Ph2))(OBz)] and [Fe(II)(Tp(Ph2))(OAc)(3,5-Ph(2)pzH)] were determined by single-crystal X-ray diffraction, all of which have five-coordinate iron centers. Both the alpha-keto carboxylate and the carboxylate compounds react with dioxygen resulting in the hydroxylation of a single ortho phenyl position of the Tp(Ph2) ligand. The oxygenation products were characterized spectroscopically, and the structure of the octahedral iron(III) phenolate product [Fe(III)(Tp(Ph2))(OAc)(3,5-Ph(2)pzH)] was established by X-ray diffraction. The reaction of the alpha-keto carboxylate model compounds with oxygen to produce the phenolate product occurs with concomitant oxidative decarboxylation of the alpha-keto acid. Isotope labeling studies show that (18)O(2) ends up in the Tp(Ph2) phenolate oxygen and the carboxylate derived from the alpha-keto acid. The isotope incorporation mirrors the dioxygenase nature of the enzymatic systems. Parallel studies on the carboxylate complexes demonstrate that the oxygen in the hydroxylated ligand is also derived from molecular oxygen. The oxygenation of the benzoylformate complex is demonstrated to be first order in metal complex and dioxygen, with activation parameters DeltaH++ = 25 +/- 2 kJ mol(-1) and DeltaS++ = -179 +/- 6 J mol(-1) K(-1). The rate of appearance of the iron(III) phenolate product is sensitive to the nature of the substituent on the benzoylformate ligand, exhibiting a Hammett rho value of +1.3 indicative of a nucleophilic mechanism. The proposed reaction mechanism involves dioxygen binding to produce an iron(III) superoxide species, nucleophilic attack of the superoxide at the alpha-keto functionality, and oxidative decarboxylation of the adduct to afford the oxidizing species that attacks the Tp(Ph2) phenyl ring. Interestingly, the alpha-keto carboxylate complexes react 2 orders of magnitude faster than the carboxylate complexes, thus emphasizing the key role that the alpha-keto functionality plays in oxygen activation by alpha-keto acid-dependent iron enzymes.
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Affiliation(s)
- Mark P Mehn
- Department of Chemistry and Center for Metals in Biocatalysis, 207 Pleasant Street Southeast, University of Minnesota, Minneapolis, MN 55455, USA
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Pacześniak T, Sobkowiak A. The influence of solvent on the reaction between iron(II), (III) and hydrogen peroxide. ACTA ACUST UNITED AC 2003. [DOI: 10.1016/s1381-1169(02)00455-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Funabiki T. Functional model oxygenations by nonheme iron complexes. ADVANCES IN CATALYTIC ACTIVATION OF DIOXYGEN BY METAL COMPLEXES 2003. [DOI: 10.1007/0-306-47816-1_4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Shrivastava HY, Kanthimathi M, Nair BU. Copper II complex of a tridentate ligand: an artificial metalloprotease for bovine serum albumin. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1573:149-55. [PMID: 12399024 DOI: 10.1016/s0304-4165(02)00417-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
A copper(II) complex of 2, 6-bis(benzimidazo-2-yl) pyridine was synthesized and its binding properties with bovine serum albumin (BSA) has been evaluated. The binding plot obtained from the absorption titration data gives a binding constant of 2.4 (+/-0.3) x10(3) M(-1). It was found that the charge transfer band of the metal complex was perturbed in the presence of BSA. The gel electrophoresis pattern of BSA incubated with copper(II) complex shows the metalloproteolytic activity of the metal complex. In the presence of oxygen, protein undergoes site-specific cleavage by binding to the histidine residues of domain III, with the resultant formation of four fragments of molecular weight 49, 45, 22 and 17 kDa. This indicates the presence of two specific binding sites in the protein molecule. In the absence of molecular oxygen, the metal complex was found unable to cleave the protein. The circular dichroism (CD) spectrum of the isolated fragments shows nearly 38% and 32% of alpha helical content in 49 and 45 kDa fragments, respectively, which shows that the cleavage leads to no changes in the secondary structure of the protein fragments.
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Affiliation(s)
- H Yamini Shrivastava
- Chemical Laboratory, Central Leather Research Institute, Adyar, Chennai 600 020, India
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Mandon D, Machkour A, Goetz S, Welter R. Trigonal bipyramidal geometry and tridentate coordination mode of the tripod in FeCl(2) complexes with tris(2-pyridylmethyl)amine derivatives bis-alpha-substituted with bulky groups. structures and spectroscopic comparative studies. Inorg Chem 2002; 41:5364-72. [PMID: 12377029 DOI: 10.1021/ic011104t] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A series of dichloroferrous complexes with ligands derived from the tris(2-pyridylmethyl)amine tripod has been prepared and characterized. The X-ray crystal structures of the complexes [bis(2-bromo-6-pyridylmethyl)(2-pyridylmethyl)amine]Fe(II)Cl(2) ((Br(2)TPA)Fe(II)Cl(2)) and [bis(2-phenyl-6-pyridylmethyl)(2-pyridylmethyl)amine]Fe(II)Cl(2), ((Ph(2)TPA)Fe(II)Cl(2)) are reported. In these complexes, the tripod coordinates in the tridentate mode, with a substituted pyridyl arm dangling away from the metal. Both complexes have a trigonal bipyramidal iron center with two equatorial chloride ions. Their crystal structures are compared with those of the [tris(2-pyridylmethyl)amine]Fe(II)Cl(2) and [(2-bromo-6-pyridylmethyl)bis(2-pyridylmethyl)amine]Fe(II)Cl(2) complexes ((TPA)Fe(II)Cl(2) and (BrTPA)Fe(II)Cl(2), respectively) in which the ligand coordinates in the tetradentate mode. For all complexes, the metal to ligand distances are systematically above the value of 2.0 A, and (1)H NMR displays paramagnetically shifted resonances with short relaxation times. This indicates that the iron is in a high-spin state. Electric conductivity measurements show that, for all complexes, the measured values lie within the same range, significantly below those expected for ionic complexes. Together with the analysis of the UV-visible and NMR data, this strongly suggests that the coordination mode of the tripod is retained in solution.
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Affiliation(s)
- Dominique Mandon
- Laboratoire de Chimie Organométallique et de Catalyse and Laboratoire DECMET, UMR CNRS No. 7513, Université Louis Pasteur, Institut Le Bel, 4 rue Blaise Pascal, F-67070 Strasbourg Cedex, France.
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Raffard-Pons Y Moll N, Banse F, Miki K, Nierlich M, Girerd JJ. Hydroxylation of Hexane Using Dioxygen and Trimethylhydroquinone: Biomimetic Catalysis by an Unsymmetrical Diiron-μ-Oxo Complex. Eur J Inorg Chem 2002. [DOI: 10.1002/1099-0682(200208)2002:8<1941::aid-ejic1941>3.0.co;2-b] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Lee D, Pierce B, Krebs C, Hendrich MP, Huynh BH, Lippard SJ. Functional mimic of dioxygen-activating centers in non-heme diiron enzymes: mechanistic implications of paramagnetic intermediates in the reactions between diiron(II) complexes and dioxygen. J Am Chem Soc 2002; 124:3993-4007. [PMID: 11942838 DOI: 10.1021/ja012251t] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Two tetracarboxylate diiron(II) complexes, [Fe(2)(mu-O(2)CAr(Tol))(2)(O(2)CAr(Tol))(2)(C(5)H(5)N)(2)] (1a) and [Fe(2)(mu-O(2)CAr(Tol))(4)(4-(t)BuC(5)H(4)N)(2)] (2a), where Ar(Tol)CO(2)(-) = 2,6-di(p-tolyl)benzoate, react with O(2) in CH(2)Cl(2) at -78 degrees C to afford dark green intermediates 1b (lambda(max) congruent with 660 nm; epsilon = 1600 M(-1) cm(-1)) and 2b (lambda(max) congruent with 670 nm; epsilon = 1700 M(-1) cm(-1)), respectively. Upon warming to room temperature, the solutions turn yellow, ultimately converting to isolable diiron(III) compounds [Fe(2)(mu-OH)(2)(mu-O(2)CAr(Tol))(2)(O(2)CAr(Tol))(2)L(2)] (L = C(5)H(5)N (1c), 4-(t)BuC(5)H(4)N (2c)). EPR and Mössbauer spectroscopic studies revealed the presence of equimolar amounts of valence-delocalized Fe(II)Fe(III) and valence-trapped Fe(III)Fe(IV) species as major components of solution 2b. The spectroscopic and reactivity properties of the Fe(III)Fe(IV) species are similar to those of the intermediate X in the RNR-R2 catalytic cycle. EPR kinetic studies revealed that the processes leading to the formation of these two distinctive paramagnetic components are coupled to one another. A mechanism for this reaction is proposed and compared with those of other synthetic and biological systems, in which electron transfer occurs from a low-valent starting material to putative high-valent dioxygen adduct(s).
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Affiliation(s)
- Dongwhan Lee
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Wasser IM, de Vries S, Moënne-Loccoz P, Schröder I, Karlin KD. Nitric oxide in biological denitrification: Fe/Cu metalloenzyme and metal complex NO(x) redox chemistry. Chem Rev 2002; 102:1201-34. [PMID: 11942794 DOI: 10.1021/cr0006627] [Citation(s) in RCA: 361] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ian M Wasser
- Department of Chemistry, The Johns Hopkins University, Charles and 34th Streets, Baltimore, MD 21218, USA
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