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Gera R, De P, Singh KK, Jannuzzi SAV, Mohanty A, Velasco L, Kulbir, Kumar P, Marco JF, Nagarajan K, Pecharromán C, Rodríguez-Pascual PM, DeBeer S, Moonshiram D, Gupta SS, Dasgupta J. Trapping an Elusive Fe(IV)-Superoxo Intermediate Inside a Self-Assembled Nanocage in Water at Room Temperature. J Am Chem Soc 2024; 146:21729-21741. [PMID: 39078020 DOI: 10.1021/jacs.4c05849] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/31/2024]
Abstract
Molecular cavities that mimic natural metalloenzymes have shown the potential to trap elusive reaction intermediates. Here, we demonstrate the formation of a rare yet stable Fe(IV)-superoxo intermediate at room temperature subsequent to dioxygen binding at the Fe(III) site of a (Et4N)2[FeIII(Cl)(bTAML)] complex confined inside the hydrophobic interior of a water-soluble Pd6L412+ nanocage. Using a combination of electron paramagnetic resonance, Mössbauer, Raman/IR vibrational, X-ray absorption, and emission spectroscopies, we demonstrate that the cage-encapsulated complex has a Fe(IV) oxidation state characterized by a stable S = 1/2 spin state and a short Fe-O bond distance of ∼1.70 Å. We find that the O2 reaction in confinement is reversible, while the formed Fe(IV)-superoxo complex readily reacts when presented with substrates having weak C-H bonds, highlighting the lability of the O-O bond. We envision that such optimally trapped high-valent superoxos can show new classes of reactivities catalyzing both oxygen atom transfer and C-H bond activation reactions.
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Affiliation(s)
- Rahul Gera
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Mumbai 400005, India
- Department of Education in Science and Mathematics, Regional Institute of Education - Mysuru, NCERT, Mysuru 570006, India
| | - Puja De
- Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal 741246, India
| | - Kundan K Singh
- Chemical Engineering Division, CSIR-National Chemical Laboratory, Pune, Maharashtra 411008, India
- Chemistry Department, Indian Institute of Technology, Dharwad 580007, India
| | - Sergio A V Jannuzzi
- Department of Inorganic Spectroscopy, Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, Mülheim an der Ruhr 45470, Germany
| | - Aisworika Mohanty
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Mumbai 400005, India
| | - Lucia Velasco
- Instituto de Ciencia de Materiales de Madrid Consejo Superior de Investigaciones Científicas Sor Juana Inés de la Cruz, 3, Madrid 28049, Spain
| | - Kulbir
- Department of Chemistry, Indian Institute of Science Education and Research (IISER), Tirupati 517507, India
| | - Pankaj Kumar
- Department of Chemistry, Indian Institute of Science Education and Research (IISER), Tirupati 517507, India
| | - J F Marco
- Instituto de Quimica Fisica Blas Cabrera, Consejo Superior de Investigaciones Científicas, Serrano 119, Madrid 28006, Spain
| | - Kalaivanan Nagarajan
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Mumbai 400005, India
| | - Carlos Pecharromán
- Instituto de Ciencia de Materiales de Madrid Consejo Superior de Investigaciones Científicas Sor Juana Inés de la Cruz, 3, Madrid 28049, Spain
| | - P M Rodríguez-Pascual
- Instituto de Ciencia de Materiales de Madrid Consejo Superior de Investigaciones Científicas Sor Juana Inés de la Cruz, 3, Madrid 28049, Spain
| | - Serena DeBeer
- Department of Inorganic Spectroscopy, Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, Mülheim an der Ruhr 45470, Germany
| | - Dooshaye Moonshiram
- Instituto de Ciencia de Materiales de Madrid Consejo Superior de Investigaciones Científicas Sor Juana Inés de la Cruz, 3, Madrid 28049, Spain
| | - Sayam Sen Gupta
- Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal 741246, India
| | - Jyotishman Dasgupta
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Mumbai 400005, India
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2
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Jeong D, Selverstone Valentine J, Cho J. Bio-inspired mononuclear nonheme metal peroxo complexes: Synthesis, structures and mechanistic studies toward understanding enzymatic reactions. Coord Chem Rev 2023. [DOI: 10.1016/j.ccr.2023.215021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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3
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Sarkar S, Shah Tuglak Khan F, Guchhait T, Rath SP. Binuclear complexes with single M-F-M bridge (M: Fe, Mn, and Cu): A critical analysis of the impact of fluoride for isoelectronic hydroxide substitution. Coord Chem Rev 2023. [DOI: 10.1016/j.ccr.2022.215003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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4
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Kisgeropoulos EC, Gan YJ, Greer SM, Hazel JM, Shafaat HS. Pulsed Multifrequency Electron Paramagnetic Resonance Spectroscopy Reveals Key Branch Points for One- vs Two-Electron Reactivity in Mn/Fe Proteins. J Am Chem Soc 2022; 144:11991-12006. [PMID: 35786920 DOI: 10.1021/jacs.1c13738] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Traditionally, the ferritin-like superfamily of proteins was thought to exclusively use a diiron active site in catalyzing a diverse array of oxygen-dependent reactions. In recent years, novel redox-active cofactors featuring heterobimetallic Mn/Fe active sites have been discovered in both the radical-generating R2 subunit of class Ic (R2c) ribonucleotide reductases (RNRs) and the related R2-like ligand-binding oxidases (R2lox). However, the protein-specific factors that differentiate the radical reactivity of R2c from the C-H activation reactions of R2lox remain unknown. In this work, multifrequency pulsed electron paramagnetic resonance (EPR) spectroscopy and ligand hyperfine techniques in conjunction with broken-symmetry density functional theory calculations are used to characterize the molecular and electronic structures of two EPR-active intermediates trapped during aerobic assembly of the R2lox Mn/Fe cofactor. A MnIII(μ-O)(μ-OH)FeIII species is identified as the first EPR-active species and represents a common state between the two classes of redox-active Mn/Fe proteins. The species downstream from the MnIII(μ-O)(μ-OH)FeIII state exhibits unique EPR properties, including unprecedented spectral breadth and isotope-dependent g-tensors, which are attributed to a weakly coupled, hydrogen-bonded MnIII(μ-OH)FeIII species. This final intermediate precedes formation of the MnIII/FeIII resting state and is suggested to be relevant to understanding the endogenous reactivity of R2lox.
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Affiliation(s)
- Effie C Kisgeropoulos
- The Ohio State Biochemistry Program, The Ohio State University, 100 W 18th Avenue, Columbus, Ohio 43210, United States
| | - Yunqiao J Gan
- Department of Chemistry and Biochemistry, The Ohio State University, 100 W 18th Avenue, Columbus, Ohio 43210, United States
| | - Samuel M Greer
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, United States.,Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, United States
| | - Joseph M Hazel
- Department of Chemistry and Biochemistry, The Ohio State University, 100 W 18th Avenue, Columbus, Ohio 43210, United States
| | - Hannah S Shafaat
- The Ohio State Biochemistry Program, The Ohio State University, 100 W 18th Avenue, Columbus, Ohio 43210, United States.,Department of Chemistry and Biochemistry, The Ohio State University, 100 W 18th Avenue, Columbus, Ohio 43210, United States
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5
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Lee C, Hwang Y, Kang HG, Lee SJ. Electron Transfer to Hydroxylase through Component Interactions in Soluble Methane Monooxygenase. J Microbiol Biotechnol 2022; 32:287-293. [PMID: 35131957 PMCID: PMC9628860 DOI: 10.4014/jmb.2201.01029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 02/02/2022] [Accepted: 02/03/2022] [Indexed: 12/15/2022]
Abstract
The hydroxylation of methane (CH4) is crucial to the field of environmental microbiology, owing to the heat capacity of methane, which is much higher than that of carbon dioxide (CO2). Soluble methane monooxygenase (sMMO), a member of the bacterial multicomponent monooxygenase (BMM) superfamily, is essential for the hydroxylation of specific substrates, including hydroxylase (MMOH), regulatory component (MMOB), and reductase (MMOR). The diiron active site positioned in the MMOH α-subunit is reduced through the interaction of MMOR in the catalytic cycle. The electron transfer pathway, however, is not yet fully understood due to the absence of complex structures with reductases. A type II methanotroph, Methylosinus sporium 5, successfully expressed sMMO and hydroxylase, which were purified for the study of the mechanisms. Studies on the MMOH-MMOB interaction have demonstrated that Tyr76 and Trp78 induce hydrophobic interactions through π-π stacking. Structural analysis and sequencing of the ferredoxin domain in MMOR (MMOR-Fd) suggested that Tyr93 and Tyr95 could be key residues for electron transfer. Mutational studies of these residues have shown that the concentrations of flavin adenine dinucleotide (FAD) and iron ions are changed. The measurements of dissociation constants (Kds) between hydroxylase and mutated reductases confirmed that the binding affinities were not significantly changed, although the specific enzyme activities were significantly reduced by MMOR-Y93A. This result shows that Tyr93 could be a crucial residue for the electron transfer route at the interface between hydroxylase and reductase.
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Affiliation(s)
- Chaemin Lee
- Department of Chemistry, Jeonbuk National University, Jeonju 54896, Republic of Korea
| | - Yunha Hwang
- Department of Chemistry, Jeonbuk National University, Jeonju 54896, Republic of Korea
| | - Hyun Goo Kang
- Department of Neurology, Research Institute of Clinical Medicine of Jeonbuk National University and Biomedical Research Institute of Jeonbuk National University Hospital, Jeonju 54907, Republic of Korea,Corresponding authors H.G. Kang Phone: +82-63-250-1590 Fax: +82-63-251-9363 E-mail:
| | - Seung Jae Lee
- Department of Chemistry, Jeonbuk National University, Jeonju 54896, Republic of Korea,Institute for Molecular Biology and Genetics, Jeonbuk National University, Jeonju 54896, Republic of Korea,
S.J. Lee Phone: +82-63-270-3412 Fax: +82-63-270-3407 E-mail:
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6
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Guan H, Tung CH, Liu L. Methane Monooxygenase Mimic Asymmetric Oxidation: Self-Assembling μ-Hydroxo, Carboxylate-Bridged Diiron(III)-Catalyzed Enantioselective Dehydrogenation. J Am Chem Soc 2022; 144:5976-5984. [PMID: 35324200 DOI: 10.1021/jacs.2c00638] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Mimicking naturally occurring metalloenzymes to enrich the diversity of catalytic asymmetric oxidation reactions is a long-standing goal for modern chemistry. Toward this end, a range of methane monooxygenase (MMO) mimic chiral carboxylate-bridged (μ-hydroxo) diiron(III) dimer complexes using salan as basal ligand and sodium aryl carboxylate as additive have been designed and synthesized. The chiral diiron complexes exhibit efficient catalytic reactivity in dehydrogenative kinetic resolution of indolines using environmentally benign hydrogen peroxide as oxidant. In particular, complex C9 bearing sterically encumbered salan ligands and a 2-naphthoate bridge is identified as the optimal catalyst in terms of chiral recognition. Further investigation reveals that this MMO mimic chiral catalyst can be readily generated by self-assembly under the dehydrogenation conditions. The self-assembling catalytic system is applicable to a series of indolines with multiple stereocenters and diverse substituent patterns in high efficiency with a high level of chiral recognition (selectivity factor up to 153). Late-stage dehydrogenative kinetic resolution of bioactive molecules is further examined.
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Affiliation(s)
- Honghao Guan
- School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China
| | - Chen-Ho Tung
- School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China
| | - Lei Liu
- School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China
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7
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Shteinman AA, Mitra M. Nonheme mono- and dinuclear iron complexes in bio-inspired C H and C C bond hydroxylation reactions: Mechanistic insight. Inorganica Chim Acta 2021. [DOI: 10.1016/j.ica.2021.120388] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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8
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A three-component monooxygenase from Rhodococcus wratislaviensis may expand industrial applications of bacterial enzymes. Commun Biol 2021; 4:16. [PMID: 33398074 PMCID: PMC7782822 DOI: 10.1038/s42003-020-01555-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 12/03/2020] [Indexed: 12/14/2022] Open
Abstract
The high-valent iron-oxo species formed in the non-heme diiron enzymes have high oxidative reactivity and catalyze difficult chemical reactions. Although the hydroxylation of inert methyl groups is an industrially promising reaction, utilizing non-heme diiron enzymes as such a biocatalyst has been difficult. Here we show a three-component monooxygenase system for the selective terminal hydroxylation of α-aminoisobutyric acid (Aib) into α-methyl-D-serine. It consists of the hydroxylase component, AibH1H2, and the electron transfer component. Aib hydroxylation is the initial step of Aib catabolism in Rhodococcus wratislaviensis C31-06, which has been fully elucidated through a proteome analysis. The crystal structure analysis revealed that AibH1H2 forms a heterotetramer of two amidohydrolase superfamily proteins, of which AibHm2 is a non-heme diiron protein and functions as a catalytic subunit. The Aib monooxygenase was demonstrated to be a promising biocatalyst that is suitable for bioprocesses in which the inert C–H bond in methyl groups need to be activated. Makoto Hibi et al. report a novel three-component monooxygenase system in Rhodococcus wratislaviensis. This enzyme catalyzes the activation of an inert C–H bond and may be potentially important as a biocatalyst for industrial applications.
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Ansari M, Senthilnathan D, Rajaraman G. Deciphering the origin of million-fold reactivity observed for the open core diiron [HO-Fe III-O-Fe IV[double bond, length as m-dash]O] 2+ species towards C-H bond activation: role of spin-states, spin-coupling, and spin-cooperation. Chem Sci 2020; 11:10669-10687. [PMID: 33209248 PMCID: PMC7654192 DOI: 10.1039/d0sc02624g] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Accepted: 06/16/2020] [Indexed: 01/26/2023] Open
Abstract
High-valent metal-oxo species have been characterised as key intermediates in both heme and non-heme enzymes that are found to perform efficient aliphatic hydroxylation, epoxidation, halogenation, and dehydrogenation reactions. Several biomimetic model complexes have been synthesised over the years to mimic both the structure and function of metalloenzymes. The diamond-core [Fe2(μ-O)2] is one of the celebrated models in this context as this has been proposed as the catalytically active species in soluble methane monooxygenase enzymes (sMMO), which perform the challenging chemical conversion of methane to methanol at ease. In this context, a report of open core [HO(L)FeIII-O-FeIV(O)(L)]2+ (1) gains attention as this activates C-H bonds a million-fold faster compared to the diamond-core structure and has the dual catalytic ability to perform hydroxylation as well as desaturation with organic substrates. In this study, we have employed density functional methods to probe the origin of the very high reactivity observed for this complex and also to shed light on how this complex performs efficient hydroxylation and desaturation of alkanes. By modelling fifteen possible spin-states for 1 that could potentially participate in the reaction mechanism, our calculations reveal a doublet ground state for 1 arising from antiferromagnetic coupling between the quartet FeIV centre and the sextet FeIII centre, which regulates the reactivity of this species. The unusual stabilisation of the high-spin ground state for FeIV[double bond, length as m-dash]O is due to the strong overlap of with the orbital, reducing the antibonding interactions via spin-cooperation. The electronic structure features computed for 1 are consistent with experiments offering confidence in the methodology chosen. Further, we have probed various mechanistic pathways for the C-H bond activation as well as -OH rebound/desaturation of alkanes. An extremely small barrier height computed for the first hydrogen atom abstraction by the terminal FeIV[double bond, length as m-dash]O unit was found to be responsible for the million-fold activation observed in the experiments. The barrier height computed for -OH rebound by the FeIII-OH unit is also smaller suggesting a facile hydroxylation of organic substrates by 1. A strong spin-cooperation between the two iron centres also reduces the barrier for second hydrogen atom abstraction, thus making the desaturation pathway competitive. Both the spin-state as well as spin-coupling between the two metal centres play a crucial role in dictating the reactivity for species 1. By exploring various mechanistic pathways, our study unveils the fact that the bridged μ-oxo group is a poor electrophile for both C-H activation as well for -OH rebound. As more and more evidence is gathered in recent years for the open core geometry of sMMO enzymes, the idea of enhancing the reactivity via an open-core motif has far-reaching consequences.
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Affiliation(s)
- Mursaleem Ansari
- Department of Chemistry , Indian Institute of Technology Bombay , Mumbai 400076 , India .
| | - Dhurairajan Senthilnathan
- Center for Computational Chemistry , CRD , PRIST University , Vallam , Thanjavur , Tamilnadu 613403 , India
| | - Gopalan Rajaraman
- Department of Chemistry , Indian Institute of Technology Bombay , Mumbai 400076 , India .
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11
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Jasniewski AJ, Que L. Dioxygen Activation by Nonheme Diiron Enzymes: Diverse Dioxygen Adducts, High-Valent Intermediates, and Related Model Complexes. Chem Rev 2018; 118:2554-2592. [PMID: 29400961 PMCID: PMC5920527 DOI: 10.1021/acs.chemrev.7b00457] [Citation(s) in RCA: 304] [Impact Index Per Article: 50.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
A growing subset of metalloenzymes activates dioxygen with nonheme diiron active sites to effect substrate oxidations that range from the hydroxylation of methane and the desaturation of fatty acids to the deformylation of fatty aldehydes to produce alkanes and the six-electron oxidation of aminoarenes to nitroarenes in the biosynthesis of antibiotics. A common feature of their reaction mechanisms is the formation of O2 adducts that evolve into more reactive derivatives such as diiron(II,III)-superoxo, diiron(III)-peroxo, diiron(III,IV)-oxo, and diiron(IV)-oxo species, which carry out particular substrate oxidation tasks. In this review, we survey the various enzymes belonging to this unique subset and the mechanisms by which substrate oxidation is carried out. We examine the nature of the reactive intermediates, as revealed by X-ray crystallography and the application of various spectroscopic methods and their associated reactivity. We also discuss the structural and electronic properties of the model complexes that have been found to mimic salient aspects of these enzyme active sites. Much has been learned in the past 25 years, but key questions remain to be answered.
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Affiliation(s)
- Andrew J. Jasniewski
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Lawrence Que
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
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12
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Sekino M, Furutachi H, Tojo R, Hishi A, Kajikawa H, Suzuki T, Suzuki K, Fujinami S, Akine S, Sakata Y, Ohta T, Hayami S, Suzuki M. New mechanistic insights into intramolecular aromatic ligand hydroxylation and benzyl alcohol oxidation initiated by the well-defined (μ-peroxo)diiron(iii) complex. Chem Commun (Camb) 2018; 53:8838-8841. [PMID: 28726874 DOI: 10.1039/c7cc04382a] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
A (μ-peroxo)diiron(iii) complex [Fe2(LPh4)(O2)(Ph3CCO2)]2+ (1-O2) with a dinucleating ligand (LPh4), generated from the reaction of a carboxylate bridged diiron(ii) complex [Fe2(LPh4)(Ph3CCO2)]2+ (1) with dioxygen in CH2Cl2, provides a diiron(iv)-oxo species as an active oxidant which is involved in either aromatic ligand hydroxylation or benzyl alcohol oxidation.
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Affiliation(s)
- Mio Sekino
- Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
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13
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Wang CH, Das A, Gao WY, Powers DC. Probing Substrate Diffusion in Interstitial MOF Chemistry with Kinetic Isotope Effects. Angew Chem Int Ed Engl 2018; 57:3676-3681. [DOI: 10.1002/anie.201713244] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2017] [Revised: 02/08/2018] [Indexed: 11/12/2022]
Affiliation(s)
- Chen-Hao Wang
- Department of Chemistry; Texas A&M University; 3255 TAMU College Station TX USA
| | - Anuvab Das
- Department of Chemistry; Texas A&M University; 3255 TAMU College Station TX USA
| | - Wen-Yang Gao
- Department of Chemistry; Texas A&M University; 3255 TAMU College Station TX USA
| | - David C. Powers
- Department of Chemistry; Texas A&M University; 3255 TAMU College Station TX USA
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14
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Wang CH, Das A, Gao WY, Powers DC. Probing Substrate Diffusion in Interstitial MOF Chemistry with Kinetic Isotope Effects. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201713244] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Chen-Hao Wang
- Department of Chemistry; Texas A&M University; 3255 TAMU College Station TX USA
| | - Anuvab Das
- Department of Chemistry; Texas A&M University; 3255 TAMU College Station TX USA
| | - Wen-Yang Gao
- Department of Chemistry; Texas A&M University; 3255 TAMU College Station TX USA
| | - David C. Powers
- Department of Chemistry; Texas A&M University; 3255 TAMU College Station TX USA
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15
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Khenkin AM, Vedichi M, Shimon LJW, Cranswick MA, Klein JEMN, Que L, Neumann R. Hydrogen-Atom Transfer Oxidation with H 2O 2 Catalyzed by [FeII(1,2-bis(2,2'-bipyridyl-6-yl)ethane(H 2O) 2] 2+: Likely Involvement of a (μ-Hydroxo)(μ-1,2-peroxo)diiron(III) Intermediate. Isr J Chem 2018; 57:990-998. [PMID: 29335656 DOI: 10.1002/ijch.201700059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The iron(II) triflate complex (1) of 1,2-bis(2,2'-bipyridyl-6-yl)ethane, with two bipyridine moieties connected by an ethane bridge, was prepared. Addition of aqueous 30% H2O2 to an acetonitrile solution of 1 yielded 2, a green compound with λmax=710 nm. Moessbauer measurements on 2 showed a doublet with an isomer shift (δ) of 0.35 mm/s and a quadrupole splitting (ΔEQ) of 0.86 mm/s, indicative of an antiferromagnetically coupled diferric complex. Resonance Raman spectra showed peaks at 883, 556 and 451 cm-1 that downshifted to 832, 540 and 441 cm-1 when 1 was treated with H218O2. All the spectroscopic data support the initial formation of a (μ-hydroxo)(μ-1,2-peroxo)diiron(III) complex that oxidizes carbon-hydrogen bonds. At 0°C 2 reacted with cyclohexene to yield allylic oxidation products but not epoxide. Weak benzylic C-H bonds of alkylarenes were also oxidized. A plot of the logarithms of the second order rate constants versus the bond dissociation energies of the cleaved C-H bond showed an excellent linear correlation. Along with the observation that oxidation of the probe substrate 2,2-dimethyl-1-phenylpropan-1-ol yielded the corresponding ketone but no benzaldehyde, and the kinetic isotope effect, kH/kD , of 2.8 found for the oxidation of xanthene, the results support the hypothesis for a metal-based H-atom abstraction mechanism. Complex 2 is a rare example of a (μ-hydroxo)(μ-1,2-peroxo)diiron(III) complex that can elicit the oxidation of carbon-hydrogen bonds.
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Affiliation(s)
- Alexander M Khenkin
- Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel 76100, phone: +972-8-9343354
| | - Madhu Vedichi
- Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel 76100, phone: +972-8-9343354
| | - Linda J W Shimon
- Department of Chemical Research Support, Weizmann Institute of Science, Rehovot, Israel 76100
| | - Matthew A Cranswick
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, USA
| | - Johannes E M N Klein
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, USA
| | - Lawrence Que
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, USA
| | - Ronny Neumann
- Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel 76100, phone: +972-8-9343354
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Mondal D, Bhattacharya K. Synthesis and structural characterization of a hemiacetal and aldehyde bound diiron(III) complex with two different coordination numbers: A product by oxidative cleavage of carbon nitrogen single bond. INORG CHEM COMMUN 2017. [DOI: 10.1016/j.inoche.2017.08.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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17
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Kynadi AS, Suchithra TV. Bacterial Degradation of Phenol to Control Environmental Pollution. Microb Biotechnol 2017. [DOI: 10.1007/978-981-10-6847-8_11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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Khan FST, Pandey AK, Rath SP. Remarkable Anion-Dependent Spin-State Switching in Diiron(III) μ-Hydroxo Bisporphyrins: What Role do Counterions Play? Chemistry 2016; 22:16124-16137. [PMID: 27682429 DOI: 10.1002/chem.201603163] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Indexed: 12/20/2022]
Abstract
Addition of 2,4,6-trinitrophenol (HTNP) to an ethene-bridged diiron(III) μ-oxo bisporphyrin (1) in CH2 Cl2 initially leads to the formation of diiron(III) μ-hydroxo bisporphyrin (2⋅TNP) with a phenolate counterion that, after further addition of HTNP or dissolution in a nonpolar solvent, converts to a diiron(III) complex with axial phenoxide coordination (3⋅(TNP)2 ). The progress of the reaction from μ-oxo to μ-hydroxo to axially ligated complex has been monitored in solution by using 1 H NMR spectroscopy because their signals appear in three different and distinct spectral regions. The X-ray structure of 2⋅TNP revealed that the nearly planar TNP counterion fits perfectly within the bisporphyrin cavity to form a strong hydrogen bond with the μ-hydroxo group, which thus stabilizes the two equivalent iron centers. In contrast, such counterions as I5 , I3 , BF4 , SbF6 , and PF6 are found to be tightly associated with one of the porphyrin rings and, therefore, stabilize two different spin states of iron in one molecule. A spectroscopic investigation of 2⋅TNP has revealed the presence of two equivalent iron centers with a high-spin state (S=5/2) in the solid state that converts to intermediate spin (S=3/2) in solution. An extensive computational study by using a range of DFT methods was performed on 2⋅TNP and 2+ , and clearly supports the experimentally observed spin flip triggered by hydrogen-bonding interactions. The counterion is shown to perturb the spin-state ordering through, for example, hydrogen-bonding interactions, switched positions between counterion and axial ligand, ion-pair interactions, and charge polarization. The present investigation thus provides a clear rationalization of the unusual counterion-specific spin states observed in the μ-hydroxo bisporphyrins that have so far remained the most outstanding issue.
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Affiliation(s)
| | - Anjani Kumar Pandey
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India
| | - Sankar Prasad Rath
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India.
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Sil D, Khan FST, Rath SP. Effect of Inter-Porphyrin Distance on Spin-State in Diiron(III) μ-Hydroxo Bisporphyrins. Chemistry 2016; 22:14585-97. [DOI: 10.1002/chem.201602018] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Indexed: 12/16/2022]
Affiliation(s)
- Debangsu Sil
- Department of Chemistry; Indian Institute of Technology Kanpur; Kanpur- 208016 India
| | | | - Sankar Prasad Rath
- Department of Chemistry; Indian Institute of Technology Kanpur; Kanpur- 208016 India
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20
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Kurt C, Sönmez B, Vardar N, Yanık-Yıldırım KC, Vardar-Schara G. Cavity residue leucine 95 and channel residues glutamine 204, aspartic acid 211, and phenylalanine 269 of toluene o-xylene monooxygenase influence catalysis. Appl Microbiol Biotechnol 2016; 100:7599-609. [PMID: 27311562 DOI: 10.1007/s00253-016-7658-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Revised: 05/27/2016] [Accepted: 05/31/2016] [Indexed: 10/21/2022]
Abstract
Structural analysis of toluene-o-xylene monooxygenase (ToMO) hydroxylase revealed the presence of three hydrophobic cavities, a channel, and a pore leading from the protein surface to the active site. Here, saturation mutagenesis was used to investigate the catalytic roles of alpha-subunit (TouA) second cavity residue L95 and TouA channel residues Q204, D211, and F269. By testing the substrates toluene, phenol, nitrobenzene, and/or naphthalene, these positions were found to influence the catalytic activity of ToMO. Several regiospecific variants were identified from TouA positions Q204, F269, and L95. For example, TouA variant Q204H had the regiospecificity of nitrobenzene changed significantly from 30 to 61 % p-nitrophenol. Interestingly, a combination of mutations at Q204H and A106V altered the regiospecificity of nitrobenzene back to 27 % p-nitrophenol. TouA variants F269Y, F269P, Q204E, and L95D improved the meta-hydroxylating capability of nitrobenzene by producing 87, 85, 82, and 77 % m-nitrophenol, respectively. For naphthalene oxidation, TouA variants F269V, Q204A, Q204S/S222N, and F269T had the regiospecificity changed from 16 to 9, 10, 23, and 25 % 2-naphthol, respectively. Here, two additional TouA residues, S222 and A106, were also identified that may have important roles in catalysis. Most of the isolated variants from D211 remained active, whereas having a hydrophobic residue at this position appeared to diminish the catalytic activity toward naphthalene. The mutational effects on the ToMO regiospecificity described here suggest that it is possible to further fine tune and engineer the reactivity of multicomponent diiron monooxygenases toward different substrates at positions that are relatively distant from the active site.
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Affiliation(s)
- Cansu Kurt
- Department of Genetics and Biongineering, Fatih University, Buyukcekmece, 34500, Istanbul, Turkey
| | - Burcu Sönmez
- Department of Genetics and Biongineering, Fatih University, Buyukcekmece, 34500, Istanbul, Turkey
| | - Nurcan Vardar
- Department of Genetics and Biongineering, Fatih University, Buyukcekmece, 34500, Istanbul, Turkey
| | - K Cansu Yanık-Yıldırım
- Department of Genetics and Biongineering, Fatih University, Buyukcekmece, 34500, Istanbul, Turkey
| | - Gönül Vardar-Schara
- Department of Genetics and Biongineering, Fatih University, Buyukcekmece, 34500, Istanbul, Turkey.
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21
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Sil D, Kumar A, Rath SP. Diiron(III)-μ-Fluoro Bisporphyrins: Effect of Bridging Ligand on the Metal Spin State. Chemistry 2016; 22:11214-23. [DOI: 10.1002/chem.201600786] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Indexed: 11/08/2022]
Affiliation(s)
- Debangsu Sil
- Department of Chemistry; Indian Institute of Technology Kanpur; Kanpur- 208016 India
| | - Amit Kumar
- Department of Chemistry; Indian Institute of Technology Kanpur; Kanpur- 208016 India
| | - Sankar Prasad Rath
- Department of Chemistry; Indian Institute of Technology Kanpur; Kanpur- 208016 India
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22
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Lee SJ. Hydroxylation of methane through component interactions in soluble methane monooxygenases. J Microbiol 2016; 54:277-82. [DOI: 10.1007/s12275-016-5642-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2015] [Revised: 02/25/2016] [Accepted: 02/26/2016] [Indexed: 10/22/2022]
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23
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Sil D, Bhowmik S, Khan FST, Rath SP. Experimental and Theoretical Investigation of a Series of Novel Dimanganese(III) μ-Hydroxo Bisporphyrins: Magneto–Structural Correlation and Effect of Metal Spin on Porphyrin Core Deformation. Inorg Chem 2016; 55:3239-51. [DOI: 10.1021/acs.inorgchem.5b02226] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Debangsu Sil
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India
| | - Susovan Bhowmik
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India
| | | | - Sankar Prasad Rath
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India
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Zhang J, Wang Y, Luo N, Chen Z, Wu K, Yin G. Redox inactive metal ion triggered N-dealkylation by an iron catalyst with dioxygen activation: a lesson from lipoxygenases. Dalton Trans 2016; 44:9847-59. [PMID: 25939391 DOI: 10.1039/c5dt00804b] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Utilization of dioxygen as the terminal oxidant at ambient temperature is always a challenge in redox chemistry, because it is hard to oxidize a stable redox metal ion like iron(III) to its high oxidation state to initialize the catalytic cycle. Inspired by the dioxygenation and co-oxidase activity of lipoxygenases, herein, we introduce an alternative protocol to activate the sluggish iron(III) species with non-redox metal ions, which can promote its oxidizing power to facilitate substrate oxidation with dioxygen, thus initializing the catalytic cycle. In oxidations of N,N-dimethylaniline and its analogues, adding Zn(OTf)2 to the [Fe(TPA)Cl2]Cl catalyst can trigger the amine oxidation with dioxygen, whereas [Fe(TPA)Cl2]Cl alone is very sluggish. In stoichiometric oxidations, it has also been confirmed that the presence of Zn(OTf)2 can apparently improve the electron transfer capability of the [Fe(TPA)Cl2]Cl complex. Experiments using different types of substrates as trapping reagents disclosed that the iron(IV) species does not occur in the catalytic cycle, suggesting that oxidation of amines is initialized by electron transfer rather than hydrogen abstraction. Combined experiments from UV-Vis, high resolution mass spectrometry, electrochemistry, EPR and oxidation kinetics support that the improved electron transfer ability of iron(III) species originates from its interaction with added Lewis acids like Zn(2+) through a plausible chloride or OTf(-) bridge, which has promoted the redox potential of iron(III) species. The amine oxidation mechanism was also discussed based on the available data, which resembles the co-oxidase activity of lipoxygenases in oxidative dealkylation of xenobiotic metabolisms where an external electron donor is not essential for dioxygen activation.
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Affiliation(s)
- Jisheng Zhang
- School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Key Laboratory for Large-Format Battery Materials and System, Ministry of Education, Luoyu Road 1037, Wuhan 430074, PR China.
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25
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Cummins DC, Yap GPA, Theopold KH. Scorpionates of the “Tetrahedral Enforcer” Variety as Ancillary Ligands for Dinitrogen Complexes of First Row Transition Metals (Cr–Co). Eur J Inorg Chem 2016. [DOI: 10.1002/ejic.201501326] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Daniel C. Cummins
- Department of Chemistry and BiochemistryUniversity of Delaware19716NewarkDEUSA
| | - Glenn P. A. Yap
- Department of Chemistry and BiochemistryUniversity of Delaware19716NewarkDEUSA
| | - Klaus H. Theopold
- Department of Chemistry and BiochemistryUniversity of Delaware19716NewarkDEUSA
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26
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Wang W, Liang AD, Lippard SJ. Coupling Oxygen Consumption with Hydrocarbon Oxidation in Bacterial Multicomponent Monooxygenases. Acc Chem Res 2015; 48:2632-9. [PMID: 26293615 PMCID: PMC4624108 DOI: 10.1021/acs.accounts.5b00312] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
A fundamental goal in catalysis is the coupling of multiple reactions to yield a desired product. Enzymes have evolved elegant approaches to address this grand challenge. A salient example is the biological conversion of methane to methanol catalyzed by soluble methane monooxygenase (sMMO), a member of the bacterial multicomponent monooxygenase (BMM) superfamily. sMMO is a dynamic protein complex of three components: a hydroxylase, a reductase, and a regulatory protein. The active site, a carboxylate-rich non-heme diiron center, is buried inside the 251 kDa hydroxylase component. The enzyme processes four substrates: O2, protons, electrons, and methane. To couple O2 activation to methane oxidation, timely control of substrate access to the active site is critical. Recent studies of sMMO, as well as its homologues in the BMM superfamily, have begun to unravel the mechanism. The emerging and unifying picture reveals that each substrate gains access to the active site along a specific pathway through the hydroxylase. Electrons and protons are delivered via a three-amino-acid pore located adjacent to the diiron center; O2 migrates via a series of hydrophobic cavities; and hydrocarbon substrates reach the active site through a channel or linked set of cavities. The gating of these pathways mediates entry of each substrate to the diiron active site in a timed sequence and is coordinated by dynamic interactions with the other component proteins. The result is coupling of dioxygen consumption with hydrocarbon oxidation, avoiding unproductive oxidation of the reductant rather than the desired hydrocarbon. To initiate catalysis, the reductase delivers two electrons to the diiron(III) center by binding over the pore of the hydroxylase. The regulatory component then displaces the reductase, docking onto the same surface of the hydroxylase. Formation of the hydroxylase-regulatory component complex (i) induces conformational changes of pore residues that may bring protons to the active site; (ii) connects hydrophobic cavities in the hydroxylase leading from the exterior to the diiron active site, providing a pathway for O2 and methane, in the case of sMMO, to the reduced diiron center for O2 activation and substrate hydroxylation; (iii) closes the pore, as well as a channel in the case of four-component BMM enzymes, restricting proton access to the diiron center during formation of "Fe2O2" intermediates required for hydrocarbon oxidation; and (iv) inhibits undesired electron transfer to the Fe2O2 intermediates by blocking reductase binding during O2 activation. This mechanism is quite different from that adopted by cytochromes P450, a large class of heme-containing monooxygenases that catalyze reactions very similar to those catalyzed by the BMM enzymes. Understanding the timed enzyme control of substrate access has implications for designing artificial catalysts. To achieve multiple turnovers and tight coupling, synthetic models must also control substrate access, a major challenge considering that nature requires large, multimeric, dynamic protein complexes to accomplish this feat.
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Affiliation(s)
- Weixue Wang
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Alexandria D. Liang
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Stephen J. Lippard
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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27
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Nešvera J, Rucká L, Pátek M. Catabolism of Phenol and Its Derivatives in Bacteria: Genes, Their Regulation, and Use in the Biodegradation of Toxic Pollutants. ADVANCES IN APPLIED MICROBIOLOGY 2015; 93:107-60. [PMID: 26505690 DOI: 10.1016/bs.aambs.2015.06.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Phenol and its derivatives (alkylphenols, halogenated phenols, nitrophenols) are natural or man-made aromatic compounds that are ubiquitous in nature and in human-polluted environments. Many of these substances are toxic and/or suspected of mutagenic, carcinogenic, and teratogenic effects. Bioremediation of the polluted soil and water using various bacteria has proved to be a promising option for the removal of these compounds. In this review, we describe a number of peripheral pathways of aerobic and anaerobic catabolism of various natural and xenobiotic phenolic compounds, which funnel these substances into a smaller number of central catabolic pathways. Finally, the metabolites are used as carbon and energy sources in the citric acid cycle. We provide here the characteristics of the enzymes that convert the phenolic compounds and their catabolites, show their genes, and describe regulatory features. The genes, which encode these enzymes, are organized on chromosomes and plasmids of the natural bacterial degraders in various patterns. The accumulated data on similarities and the differences of the genes, their varied organization, and particularly, an astonishingly broad range of intricate regulatory mechanism may be read as an exciting adventurous book on divergent evolutionary processes and horizontal gene transfer events inscribed in the bacterial genomes. In the end, the use of this wealth of bacterial biodegradation potential and the manipulation of its genetic basis for purposes of bioremediation is exemplified. It is envisioned that the integrated high-throughput techniques and genome-level approaches will enable us to manipulate systems rather than separated genes, which will give birth to systems biotechnology.
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Affiliation(s)
- Jan Nešvera
- Institute of Microbiology CAS, v. v. i., Prague, Czech Republic
| | - Lenka Rucká
- Institute of Microbiology CAS, v. v. i., Prague, Czech Republic
| | - Miroslav Pátek
- Institute of Microbiology CAS, v. v. i., Prague, Czech Republic
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Ansari A, Rajaraman G. ortho-Hydroxylation of aromatic acids by a non-heme Fe(V)=O species: how important is the ligand design? Phys Chem Chem Phys 2015; 16:14601-13. [PMID: 24812659 DOI: 10.1039/c3cp55430a] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
There is a growing interest in probing the mechanism of catalytic transformations effected by non-heme iron-oxo complexes as these reactions set a platform for understanding the relevant enzymatic reactions. The ortho-hydroxylation of aromatic compounds is one such reaction catalysed by iron-oxo complexes. Experimentally [Fe(II)(BPMEN)(CH3CN)2](2+) (1) and [Fe(II)(TPA)(CH3CN)2](2+) (2) (where TPA = tris(2-pyridylmethyl)amine and BPMEN = N,N′-dimethyl-N,N′-bis(2-pyridylmethyl)ethane-1,2-diamine) complexes containing amino pyridine ligands along with H2O2 are employed to carry out these transformations where complex 1 is found to be more reactive than complex 2. Herein, using density functional methods employing B3LYP and dispersion corrected B3LYP (B3LYP-D) functionals, we have explored the mechanism of this reaction to reason out the importance of ligand design in fine-tuning the reactivity of such catalytic transformations. Dispersion corrected B3LYP is found to be superior to B3LYP in predicting the correct ground state of these species and also yields lower barrier heights than the B3LYP functional. Starting the reaction from the Fe(III)–OOH species, both homolytic and heterolytic cleavage of the O···O bond is explored leading to the formation of the transient Fe(IV)=O and Fe(V)=O species. For both the ligand systems, heterolytic cleavage was energetically preferable and our calculations suggest that both the reactions are catalyzed by an elusive high-valent Fe(V)=O species. The Fe(V)=O species undergoes the reaction via an electrophilic attack of the benzene ring to effect the ortho-hydroxylation reaction. The reactivity pattern observed for 1 and 2 are reflected in the computed barrier heights for the ortho-hydroxylation reaction. Electronic structure analysis reveals that the difference in reactivity between the ligand architectures described in complex 1 and 2 arise due to orientation of the pyridine ring(s) parallel or perpendicular to the Fe(V)=O bond. The parallel orientation of the pyridine ring is found to mix with the (πFe(dyz)–O(py))* orbital of the Fe-oxo bond leading to a reduction in the electrophilicity of the ferryl oxygen atom. Our calculations highlight the importance of ligand design in this chemistry and suggest that this concept can be used to (i) stabilize high-valent intermediates which can be trapped and thoroughly characterized (ii) enhance the reactivity and efficiency of the oxidants by increasing the electrophilicity of the ferryl oxygen containing FeVO species. Our computed results are in general agreement with the experimental results.
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Affiliation(s)
- Azaj Ansari
- Department of Chemistry, Indian Institute of Technology-Bombay, Powai, Mumbai, India.
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29
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Ye S, Xue G, Krivokapic I, Petrenko T, Bill E, Que Jr L, Neese F. Magnetic circular dichroism and computational study of mononuclear and dinuclear iron(IV) complexes. Chem Sci 2015; 6:2909-2921. [PMID: 26417426 PMCID: PMC4583211 DOI: 10.1039/c4sc03268c] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Accepted: 02/26/2015] [Indexed: 12/13/2022] Open
Abstract
High-valent iron(IV)-oxo species are key intermediates in the catalytic cycles of a range of O2-activating iron enzymes. This work presents a detailed study of the electronic structures of mononuclear ([FeIV(O)(L)(NCMe)]2+, 1, L = tris(3,5-dimethyl-4-methoxylpyridyl-2-methyl)amine) and dinuclear ([(L)FeIV(O)(μ-O)FeIV(OH)(L)]3+, 2) iron(IV) complexes using absorption (ABS), magnetic circular dichroism (MCD) spectroscopy and wave-function-based quantum chemical calculations. For complex 1, the experimental MCD spectra at 2-10 K are dominated by a broad positive C-term band between 12000 and 18000 cm-1. As the temperature increases up to ~20 K, this feature is gradually replaced by a derivative-shaped signal. The computed MCD spectra are in excellent agreement with experiment, which reproduce not only the excitation energies and the MCD signs of key transitions but also their temperature-dependent intensity variations. To further corroborate the assignments suggested by the calculations, the individual MCD sign for each transition is independently determined from the corresponding electron donating and accepting orbitals. Thus, unambiguous assignments can be made for the observed transitions in 1. The ABS/MCD data of complex 2 exhibit ten features that are assigned as ligand-field transitions or oxo- or hydroxo-to-metal charge transfer bands, based on MCD/ABS intensity ratios, calculated excitation energies, polarizations, and MCD signs. In comparison with complex 1, the electronic structure of the FeIV=O site is not significantly perturbed by the binding to another iron(IV) center. This may explain the experimental finding that complexes 1 and 2 have similar reactivities toward C-H bond activation and O-atom transfer.
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Affiliation(s)
- Shengfa Ye
- Max-Planck Institut für Chemische Energiekonversion , Stiftstraße 34-36 , D-45470 Mülheim an der Ruhr , Germany . ; ;
| | - Genqiang Xue
- Department of Chemistry , Center for Metals in Biocatalysis , University of Minnesota , 207 Pleasant St. SE , Minneapolis , Minnesota 55455 , USA .
| | - Itana Krivokapic
- Max-Planck Institut für Chemische Energiekonversion , Stiftstraße 34-36 , D-45470 Mülheim an der Ruhr , Germany . ; ;
| | - Taras Petrenko
- Max-Planck Institut für Chemische Energiekonversion , Stiftstraße 34-36 , D-45470 Mülheim an der Ruhr , Germany . ; ;
| | - Eckhard Bill
- Max-Planck Institut für Chemische Energiekonversion , Stiftstraße 34-36 , D-45470 Mülheim an der Ruhr , Germany . ; ;
| | - Lawrence Que Jr
- Department of Chemistry , Center for Metals in Biocatalysis , University of Minnesota , 207 Pleasant St. SE , Minneapolis , Minnesota 55455 , USA .
| | - Frank Neese
- Max-Planck Institut für Chemische Energiekonversion , Stiftstraße 34-36 , D-45470 Mülheim an der Ruhr , Germany . ; ;
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30
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The Toluene o-Xylene Monooxygenase Enzymatic Activity for the Biosynthesis of Aromatic Antioxidants. PLoS One 2015; 10:e0124427. [PMID: 25915063 PMCID: PMC4411060 DOI: 10.1371/journal.pone.0124427] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Accepted: 03/13/2015] [Indexed: 01/06/2023] Open
Abstract
Monocyclic phenols and catechols are important antioxidant compounds for the food and pharmaceutic industries; their production through biotransformation of low-added value starting compounds is of major biotechnological interest. The toluene o-xylene monooxygenase (ToMO) from Pseudomonas sp. OX1 is a bacterial multicomponent monooxygenase (BMM) that is able to hydroxylate a wide array of aromatic compounds and has already proven to be a versatile biochemical tool to produce mono- and dihydroxylated derivatives of aromatic compounds. The molecular determinants of its regioselectivity and substrate specificity have been thoroughly investigated, and a computational strategy has been developed which allows designing mutants able to hydroxylate non-natural substrates of this enzyme to obtain high-added value compounds of commercial interest. In this work, we have investigated the use of recombinant ToMO, expressed in cells of Escherichia coli strain JM109, for the biotransformation of non-natural substrates of this enzyme such as 2-phenoxyethanol, phthalan and 2-indanol to produce six hydroxylated derivatives. The hydroxylated products obtained were identified, isolated and their antioxidant potential was assessed both in vitro, using the DPPH assay, and on the rat cardiomyoblast cell line H9c2. Incubation of H9c2 cells with the hydroxylated compounds obtained from ToMO-catalyzed biotransformation induced a differential protective effect towards a mild oxidative stress induced by the presence of sodium arsenite. The results obtained confirm once again the versatility of the ToMO system for oxyfunctionalization reactions of biotechnological importance. Moreover, the hydroxylated derivatives obtained possess an interesting antioxidant potential that encourages the use of the enzyme for further functionalization reactions and their possible use as scaffolds to design novel bioactive molecules.
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31
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Guillet GL, Gordon JB, Di Francesco GN, Calkins MW, Čižmár E, Abboud KA, Meisel MW, García-Serres R, Murray LJ. A Family of Tri- and Dimetallic Pyridine Dicarboxamide Cryptates: Unusual O,N,O-Coordination and Facile Access to Secondary Coordination Sphere Hydrogen Bonding Interactions. Inorg Chem 2015; 54:2691-704. [DOI: 10.1021/ic502873d] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Gary L. Guillet
- Center for Catalysis, Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200, United States
| | - Jesse B. Gordon
- Center for Catalysis, Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200, United States
| | - Gianna N. Di Francesco
- Center for Catalysis, Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200, United States
| | - Matthew W. Calkins
- Department
of Physics and the National High Magnetic Field Laboratory, University of Florida, Gainesville, Florida 32611-8440, United States
| | - Erik Čižmár
- Institute
of Physics, Faculty of Science, P.J. Šafárik University, 04154 Košice, Slovakia
| | - Khalil A. Abboud
- Center for Catalysis, Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200, United States
| | - Mark W. Meisel
- Department
of Physics and the National High Magnetic Field Laboratory, University of Florida, Gainesville, Florida 32611-8440, United States
| | - Ricardo García-Serres
- Laboratoire
de Chimie de Biologie des Métaux, UMR 5249, Université Joseph Fourier, Grenoble-1, CNRS-CEA, 17 Rue des Martyrs, 38054 Grenoble Cedex 9, France
| | - Leslie J. Murray
- Center for Catalysis, Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200, United States
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32
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Tsuruta T, Yamazaki T, Watanabe K, Chiba Y, Yoshida A, Naito S, Nakazawa J, Hikichi S. Mimicking the Active Sites of Non-heme Iron Oxygenases on the Solid Supports of Catalysts: Formation of Immobilized Iron Complexes with Imidazolyl and Carboxylate Ligands. CHEM LETT 2015. [DOI: 10.1246/cl.140937] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
| | | | - Kazuki Watanabe
- Department of Material and Life Chemistry, Kanagawa University
| | - Yosuke Chiba
- Department of Material and Life Chemistry, Kanagawa University
| | - Akihiro Yoshida
- Department of Material and Life Chemistry, Kanagawa University
| | - Shuichi Naito
- Department of Material and Life Chemistry, Kanagawa University
| | - Jun Nakazawa
- Department of Material and Life Chemistry, Kanagawa University
| | - Shiro Hikichi
- Department of Material and Life Chemistry, Kanagawa University
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33
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Sainna MA, Sil D, Sahoo D, Martin B, Rath SP, Comba P, de Visser SP. Spin-State Ordering in Hydroxo-Bridged Diiron(III)bisporphyrin Complexes. Inorg Chem 2015; 54:1919-30. [DOI: 10.1021/ic502803b] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Mala A. Sainna
- Manchester Institute
of Biotechnology and School of Chemical Engineering and Analytical
Science, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - Debangsu Sil
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India
| | - Dipankar Sahoo
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India
| | - Bodo Martin
- Anorganisch-Chemisches Institüt and Interdisciplinary
Center for Scientific Computing (IWR), University of Heidelberg, Im Neuenheimer
Feld 270, 69120 Heidelberg, Germany
| | - Sankar Prasad Rath
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India
| | - Peter Comba
- Anorganisch-Chemisches Institüt and Interdisciplinary
Center for Scientific Computing (IWR), University of Heidelberg, Im Neuenheimer
Feld 270, 69120 Heidelberg, Germany
| | - Sam P. de Visser
- Manchester Institute
of Biotechnology and School of Chemical Engineering and Analytical
Science, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
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34
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Sazinsky MH, Lippard SJ. Methane Monooxygenase: Functionalizing Methane at Iron and Copper. Met Ions Life Sci 2015; 15:205-56. [DOI: 10.1007/978-3-319-12415-5_6] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Abstract
In order to address how diverse metalloprotein active sites, in particular those containing iron and copper, guide O₂binding and activation processes to perform diverse functions, studies of synthetic models of the active sites have been performed. These studies have led to deep, fundamental chemical insights into how O₂coordinates to mono- and multinuclear Fe and Cu centers and is reduced to superoxo, peroxo, hydroperoxo, and, after O-O bond scission, oxo species relevant to proposed intermediates in catalysis. Recent advances in understanding the various factors that influence the course of O₂activation by Fe and Cu complexes are surveyed, with an emphasis on evaluating the structure, bonding, and reactivity of intermediates involved. The discussion is guided by an overarching mechanistic paradigm, with differences in detail due to the involvement of disparate metal ions, nuclearities, geometries, and supporting ligands providing a rich tapestry of reaction pathways by which O₂is activated at Fe and Cu sites.
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36
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Subedi BP, Corder AL, Zhang S, Foss FW, Pierce BS. Steady-state kinetics and spectroscopic characterization of enzyme-tRNA interactions for the non-heme diiron tRNA-monooxygenase, MiaE. Biochemistry 2014; 54:363-76. [PMID: 25453905 DOI: 10.1021/bi5012207] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
MiaE [2-methylthio-N(6)-isopentenyl-adenosine(37)-tRNA monooxygenase] isolated from Salmonella typhimurium is a unique non-heme diiron enzyme that catalyzes the O2-dependent post-transcriptional allylic hydroxylation of a hypermodified nucleotide (ms(2)i(6)A37) at position 37 of selected tRNA molecules to produce 2-methylthio-N(6)-(4-hydroxyisopentenyl)-adenosine(37). In this work, isopentenylated tRNA substrates for MiaE were produced from small RNA oligomers corresponding to the anticodon stem loop (ACSL) region of tRNA(Trp) using recombinant MiaA and dimethylallyl pyrophosphate. Steady-state rates for MiaE-catalyzed substrate hydroxylation were determined using recombinant ferredoxin (Fd) and ferredoxin reductase (FdR) to provide a catalytic electron transport chain (ETC) using NADPH as the sole electron source. As with previously reported peroxide-shunt assays, steady-state product formation retains nearly stoichiometric (>98%) E stereoselectivity. MiaE-catalyzed i(6)A-ACSL(Trp) hydroxylation follows Michaelis-Menten saturation kinetics with kcat, KM, and V/K determined to be 0.10 ± 0.01 s(-1), 9.1 ± 1.5 μM, and ∼11000 M(-1) s(-1), respectively. While vastly slower, MiaE-catalyzed hydroxylation of free i(6)A nucleoside could also be observed using the (Fd/FdR)-ETC assay. By comparison to the V/K determined for i(6)A-ACSL substrates, an ∼6000-fold increase in enzymatic efficiency is imparted by ACSL(Trp)-MiaE interactions. The impact of substrate tRNA-MiaE interactions on protein secondary structure and active site electronic configuration was investigated using circular dichroism, dual-mode X-band electron paramagnetic resonance, and Mössbauer spectroscopies. These studies demonstrate that binding of tRNA to MiaE induces a protein conformational change that influences the electronic structure of the diiron site analogous to what has been observed for various bacterial multicomponent diiron monooxygenases upon titration with their corresponding effector proteins. These observations suggest that substrate-enzyme interactions may play a pivotal role in modulating the reactivity of the MiaE diiron active site. Moreover, the simplified monomeric (α) protein configuration exhibited by MiaE provide an unparalleled opportunity to study the impact of protein-effector interactions on non-heme diiron site geometry and reactivity.
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Affiliation(s)
- Bishnu P Subedi
- Department of Chemistry and Biochemistry, College of Sciences, The University of Texas at Arlington , Arlington, Texas 76019, United States
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37
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Bagchi V, Paraskevopoulou P, Das P, Chi L, Wang Q, Choudhury A, Mathieson JS, Cronin L, Pardue DB, Cundari TR, Mitrikas G, Sanakis Y, Stavropoulos P. A Versatile Tripodal Cu(I) Reagent for C–N Bond Construction via Nitrene-Transfer Chemistry: Catalytic Perspectives and Mechanistic Insights on C–H Aminations/Amidinations and Olefin Aziridinations. J Am Chem Soc 2014; 136:11362-81. [DOI: 10.1021/ja503869j] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Vivek Bagchi
- Department
of Chemistry, Missouri University of Science and Technology, Rolla, Missouri 65409, United States
| | - Patrina Paraskevopoulou
- Inorganic
Chemistry Laboratory, Department of Chemistry, University of Athens, Panepistimiopolis Zografou 15771, Athens, Greece
| | - Purak Das
- Department
of Chemistry, Missouri University of Science and Technology, Rolla, Missouri 65409, United States
| | - Lingyu Chi
- Department
of Chemistry, Missouri University of Science and Technology, Rolla, Missouri 65409, United States
| | - Qiuwen Wang
- Department
of Chemistry, Missouri University of Science and Technology, Rolla, Missouri 65409, United States
| | - Amitava Choudhury
- Department
of Chemistry, Missouri University of Science and Technology, Rolla, Missouri 65409, United States
| | - Jennifer S. Mathieson
- School of Chemistry, University of Glasgow, University Avenue, Glasgow, G12 8QQ, U.K
| | - Leroy Cronin
- School of Chemistry, University of Glasgow, University Avenue, Glasgow, G12 8QQ, U.K
| | - Daniel B. Pardue
- Department
of Chemistry, Center for Advanced Scientific Computing and Modeling (CASCaM), Denton, Texas 76203, United States
| | - Thomas R. Cundari
- Department
of Chemistry, Center for Advanced Scientific Computing and Modeling (CASCaM), Denton, Texas 76203, United States
| | - George Mitrikas
- Institute
of Advanced Materials, Physicochemical Processes, Nanotechnology and
Microsystems, NCSR “Demokritos”, Ag. Paraskevi 15310, Athens, Greece
| | - Yiannis Sanakis
- Institute
of Advanced Materials, Physicochemical Processes, Nanotechnology and
Microsystems, NCSR “Demokritos”, Ag. Paraskevi 15310, Athens, Greece
| | - Pericles Stavropoulos
- Department
of Chemistry, Missouri University of Science and Technology, Rolla, Missouri 65409, United States
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38
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Wang W, Iacob RE, Luoh RP, Engen JR, Lippard SJ. Electron transfer control in soluble methane monooxygenase. J Am Chem Soc 2014; 136:9754-62. [PMID: 24937475 PMCID: PMC4105053 DOI: 10.1021/ja504688z] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
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The
hydroxylation or epoxidation of hydrocarbons by bacterial multicomponent
monooxygenases (BMMs) requires the interplay of three or four protein
components. How component protein interactions control catalysis,
however, is not well understood. In particular, the binding sites
of the reductase components on the surface of their cognate hydroxylases
and the role(s) that the regulatory proteins play during intermolecular
electron transfer leading to the hydroxylase reduction have been enigmatic.
Here we determine the reductase binding site on the hydroxylase of
a BMM enzyme, soluble methane monooxygenase (sMMO) from Methylococcus
capsulatus (Bath). We present evidence that the ferredoxin
domain of the reductase binds to the canyon region of the hydroxylase,
previously determined to be the regulatory protein binding site as
well. The latter thus inhibits reductase binding to the hydroxylase
and, consequently, intermolecular electron transfer from the reductase
to the hydroxylase diiron active site. The binding competition between
the regulatory protein and the reductase may serve as a control mechanism
for regulating electron transfer, and other BMM enzymes are likely
to adopt the same mechanism.
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Affiliation(s)
- Weixue Wang
- Departments of †Chemistry and §Biological Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
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39
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Liang AD, Wrobel AT, Lippard SJ. A flexible glutamine regulates the catalytic activity of toluene o-xylene monooxygenase. Biochemistry 2014; 53:3585-92. [PMID: 24873259 PMCID: PMC4059525 DOI: 10.1021/bi500387y] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
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Toluene/o-xylene
monooxygenase (ToMO) is a bacterial
multicomponent monooxygenase capable of oxidizing aromatic substrates.
The carboxylate-rich diiron active site is located in the hydroxylase
component of ToMO (ToMOH), buried 12 Å from the surface of the
protein. A small, hydrophilic pore is the shortest pathway between
the diiron active site and the protein exterior. In this study of
ToMOH from Pseudomonas sp. OX1, the
functions of two residues lining this pore, N202 and Q228, were investigated
using site-directed mutagenesis. Steady-state characterization of
WT and the three mutant enzymes demonstrates that residues N202 and
Q228 are critical for turnover. Kinetic isotope effects and pH profiles
reveal that these residues govern the kinetics of water egress and
prevent quenching of activated oxygen intermediates formed at the
diiron active site. We propose that this activity arises from movement
of these residues, opening and closing the pore during catalysis,
as seen in previous X-ray crystallographic studies. In addition, N202
and Q228 are important for the interactions of the reductase and regulatory
components to ToMOH, suggesting that they bind competitively to the
hydroxylase. The role of the pore in the hydroxylase components of
other bacterial multicomponent monooxygenases within the superfamily
is discussed in light of these conclusions.
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Affiliation(s)
- Alexandria Deliz Liang
- Department of Chemistry, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
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40
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Keltjens JT, Pol A, Reimann J, Op den Camp HJM. PQQ-dependent methanol dehydrogenases: rare-earth elements make a difference. Appl Microbiol Biotechnol 2014; 98:6163-83. [PMID: 24816778 DOI: 10.1007/s00253-014-5766-8] [Citation(s) in RCA: 244] [Impact Index Per Article: 24.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2014] [Revised: 04/07/2014] [Accepted: 04/08/2014] [Indexed: 01/06/2023]
Abstract
Methanol dehydrogenase (MDH) catalyzes the first step in methanol use by methylotrophic bacteria and the second step in methane conversion by methanotrophs. Gram-negative bacteria possess an MDH with pyrroloquinoline quinone (PQQ) as its catalytic center. This MDH belongs to the broad class of eight-bladed β propeller quinoproteins, which comprise a range of other alcohol and aldehyde dehydrogenases. A well-investigated MDH is the heterotetrameric MxaFI-MDH, which is composed of two large catalytic subunits (MxaF) and two small subunits (MxaI). MxaFI-MDHs bind calcium as a cofactor that assists PQQ in catalysis. Genomic analyses indicated the existence of another MDH distantly related to the MxaFI-MDHs. Recently, several of these so-called XoxF-MDHs have been isolated. XoxF-MDHs described thus far are homodimeric proteins lacking the small subunit and possess a rare-earth element (REE) instead of calcium. The presence of such REE may confer XoxF-MDHs a superior catalytic efficiency. Moreover, XoxF-MDHs are able to oxidize methanol to formate, rather than to formaldehyde as MxaFI-MDHs do. While structures of MxaFI- and XoxF-MDH are conserved, also regarding the binding of PQQ, the accommodation of a REE requires the presence of a specific aspartate residue near the catalytic site. XoxF-MDHs containing such REE-binding motif are abundantly present in genomes of methylotrophic and methanotrophic microorganisms and also in organisms that hitherto are not known for such lifestyle. Moreover, sequence analyses suggest that XoxF-MDHs represent only a small part of putative REE-containing quinoproteins, together covering an unexploited potential of metabolic functions.
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Affiliation(s)
- Jan T Keltjens
- Department of Microbiology, Institute of Wetland and Water Research, Radboud University Nijmegen, Heyendaalseweg 135, 6525AJ, Nijmegen, The Netherlands
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41
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Poater A, Chaitanya Vummaleti SV, Cavallo L. The "innocent" role of Sc(3+) on a non-heme Fe catalyst in an O2 environment. Dalton Trans 2014; 43:11190-4. [PMID: 24740434 DOI: 10.1039/c4dt00321g] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Density functional theory calculations have been used to investigate the reaction mechanism proposed for the formation of an oxoiron(iv) complex [Fe(IV)(TMC)O](2+) (P) (TMC = 1,4,8,11-tetramethylcyclam) starting from a non-heme reactant complex [Fe(II)(TMC)](2+) (R) and O2 in the presence of acid H(+) and reductant BPh4(-). We also addressed the possible role of redox-inactive Sc(3+) as a replacement for H(+) acid in this reaction to trigger the formation of P. Our computational results substantially confirm the proposed mechanism and, more importantly, support that Sc(3+) could trigger the O2 activation, mainly dictated by the availability of two electrons from BPh4(-), by forming a thermodynamically stable Sc(3+)-peroxo-Fe(3+) core that facilitates O-O bond cleavage to generate P by reducing the energy barrier. These insights may pave the way to improve the catalytic reactivity of metal-oxo complexes in O2 activation at non-heme centers.
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Affiliation(s)
- Albert Poater
- Institut de Química Computacional i Catàlisi, Departament de Química, Universitat de Girona, Campus de Montilivi, E-17071 Girona, Catalonia, Spain.
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42
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Corder AL, Subedi BP, Zhang S, Dark AM, Foss FW, Pierce BS. Peroxide-shunt substrate-specificity for the Salmonella typhimurium O2-dependent tRNA modifying monooxygenase (MiaE). Biochemistry 2013; 52:6182-96. [PMID: 23906247 DOI: 10.1021/bi4000832] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Post-transcriptional modifications of tRNA are made to structurally diversify tRNA. These modifications alter noncovalent interactions within the ribosomal machinery, resulting in phenotypic changes related to cell metabolism, growth, and virulence. MiaE is a carboxylate bridged, nonheme diiron monooxygenase, which catalyzes the O2-dependent hydroxylation of a hypermodified-tRNA nucleoside at position 37 (2-methylthio-N(6)-isopentenyl-adenosine(37)-tRNA) [designated ms(2)i(6)A37]. In this work, recombinant MiaE was cloned from Salmonella typhimurium , purified to homogeneity, and characterized by UV-visible and dual-mode X-band EPR spectroscopy for comparison to other nonheme diiron enzymes. Additionally, three nucleoside substrate-surrogates (i(6)A, Cl(2)i(6)A, and ms(2)i(6)A) and their corresponding hydroxylated products (io(6)A, Cl(2)io(6)A, and ms(2)io(6)A) were synthesized to investigate the chemo- and stereospecificity of this enzyme. In the absence of the native electron transport chain, the peroxide-shunt was utilized to monitor the rate of substrate hydroxylation. Remarkably, regardless of the substrate (i(6)A, Cl(2)i(6)A, and ms(2)i(6)A) used in peroxide-shunt assays, hydroxylation of the terminal isopentenyl-C4-position was observed with >97% E-stereoselectivity. No other nonspecific hydroxylation products were observed in enzymatic assays. Steady-state kinetic experiments also demonstrate that the initial rate of MiaE hydroxylation is highly influenced by the substituent at the C2-position of the nucleoside base (v0/[E] for ms(2)i(6)A > i(6)A > Cl(2)i(6)A). Indeed, the >3-fold rate enhancement exhibited by MiaE for the hydroxylation of the free ms(2)i(6)A nucleoside relative to i(6)A is consistent with previous whole cell assays reporting the ms(2)io(6)A and io(6)A product distribution within native tRNA-substrates. This observation suggests that the nucleoside C2-substituent is a key point of interaction regulating MiaE substrate specificity.
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Affiliation(s)
- Andra L Corder
- Biophysical/Bioinorganic Group and ‡Synthetic Organic Group, Department of Chemistry and Biochemistry, College of Science, The University of Texas at Arlington , Arlington, Texas 76019, United States
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43
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Affiliation(s)
- Artur Gora
- Loschmidt Laboratories,
Department
of Experimental Biology and Research Centre for Toxic Compounds in
the Environment, Faculty of Science, Masaryk University, Kamenice 5/A13, 625 00 Brno, Czech Republic
| | - Jan Brezovsky
- Loschmidt Laboratories,
Department
of Experimental Biology and Research Centre for Toxic Compounds in
the Environment, Faculty of Science, Masaryk University, Kamenice 5/A13, 625 00 Brno, Czech Republic
| | - Jiri Damborsky
- Loschmidt Laboratories,
Department
of Experimental Biology and Research Centre for Toxic Compounds in
the Environment, Faculty of Science, Masaryk University, Kamenice 5/A13, 625 00 Brno, Czech Republic
- International Centre for Clinical
Research, St. Anne’s University Hospital Brno, Pekarska 53, 656 91 Brno, Czech Republic
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44
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Nitschke W, Russell MJ. Beating the acetyl coenzyme A-pathway to the origin of life. Philos Trans R Soc Lond B Biol Sci 2013; 368:20120258. [PMID: 23754811 DOI: 10.1098/rstb.2012.0258] [Citation(s) in RCA: 93] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Attempts to draft plausible scenarios for the origin of life have in the past mainly built upon palaeogeochemical boundary conditions while, as detailed in a companion article in this issue, frequently neglecting to comply with fundamental thermodynamic laws. Even if demands from both palaeogeochemistry and thermodynamics are respected, then a plethora of strongly differing models are still conceivable. Although we have no guarantee that life at its origin necessarily resembled biology in extant organisms, we consider that the only empirical way to deduce how life may have emerged is by taking the stance of assuming continuity of biology from its inception to the present day. Building upon this conviction, we have assessed extant types of energy and carbon metabolism for their appropriateness to conditions probably pertaining in those settings of the Hadean planet that fulfil the thermodynamic requirements for life to come into being. Wood-Ljungdahl (WL) pathways leading to acetyl CoA formation are excellent candidates for such primordial metabolism. Based on a review of our present understanding of the biochemistry and biophysics of acetogenic, methanogenic and methanotrophic pathways and on a phylogenetic analysis of involved enzymes, we propose that a variant of modern methanotrophy is more likely than traditional WL systems to date back to the origin of life. The proposed model furthermore better fits basic thermodynamic demands and palaeogeochemical conditions suggested by recent results from extant alkaline hydrothermal seeps.
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Affiliation(s)
- Wolfgang Nitschke
- Bioénergétique et Ingénierie des Protéines UMR7281, CNRS/AMU, FR3479 Marseille, France.
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45
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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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46
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Xue G, Geng C, Ye S, Fiedler AT, Neese F, Que L. Hydrogen-bonding effects on the reactivity of [X-Fe(III)-O-Fe(IV)═O] (X = OH, F) complexes toward C-H bond cleavage. Inorg Chem 2013; 52:3976-84. [PMID: 23496330 DOI: 10.1021/ic3027896] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Complexes 1-OH and 1-F are related complexes that share similar [X-Fe(III)-O-Fe(IV)═O](3+) core structures with a total spin S of ½, which arises from antiferromagnetic coupling of an S = 5/2 Fe(III)-X site and an S = 2 Fe(IV)═O site. EXAFS analysis shows that 1-F has a nearly linear Fe(III)-O-Fe(IV) core compared to that of 1-OH, which has an Fe-O-Fe angle of ~130° due to the presence of a hydrogen bond between the hydroxo and oxo groups. Both complexes are at least 1000-fold more reactive at C-H bond cleavage than 2, a related complex with a [OH-Fe(IV)-O-Fe(IV)═O](4+) core having individual S = 1 Fe(IV) units. Interestingly, 1-F is 10-fold more reactive than 1-OH. This raises an interesting question about what gives rise to the reactivity difference. DFT calculations comparing 1-OH and 1-F strongly suggest that the H-bond in 1-OH does not significantly change the electrophilicity of the reactive Fe(IV)═O unit and that the lower reactivity of 1-OH arises from the additional activation barrier required to break its H-bond in the course of H-atom transfer by the oxoiron(IV) moiety.
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Affiliation(s)
- Genqiang Xue
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota 55455, USA
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47
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Ansari A, Kaushik A, Rajaraman G. Mechanistic Insights on the ortho-Hydroxylation of Aromatic Compounds by Non-heme Iron Complex: A Computational Case Study on the Comparative Oxidative Ability of Ferric-Hydroperoxo and High-Valent FeIV═O and FeV═O Intermediates. J Am Chem Soc 2013; 135:4235-49. [DOI: 10.1021/ja307077f] [Citation(s) in RCA: 105] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Azaj Ansari
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Abhishek Kaushik
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, India
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48
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Frisch JR, McDonnell R, Rybak-Akimova EV, Que L. Factors affecting the carboxylate shift upon formation of nonheme diiron-O2 adducts. Inorg Chem 2013; 52:2627-36. [PMID: 23432330 DOI: 10.1021/ic302543n] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Several [Fe(II)2(N-EtHPTB)(μ-O2X)](2+) complexes (1·O2X) have been synthesized, where N-EtHPTB is the anion of N,N,N'N'-tetrakis(2-benzimidazolylmethyl)-2-hydroxy-1,3-diaminopropane and O2X is an oxyanion bridge. Crystal structures reveal five-coordinate (μ-alkoxo)diiron(II) cores. These diiron(II) complexes react with O2 at low temperatures in CH2Cl2 (-90 °C) to form blue-green O2 adducts that are best described as triply bridged (μ-η(1):η(1)-peroxo)diiron(III) species (2·O2X). With one exception, all 2·O2X intermediates convert irreversibly to doubly bridged, blue (μ-η(1):η(1)-peroxo)diiron(III) species (3·O2X). Where possible, 2·O2X and 3·O2X intermediates were characterized using resonance Raman spectroscopy, showing respective νO-O values of ∼850 and ∼900 cm(-1). How the steric and electronic properties of O2X affect conversion of 2·O2X to 3·O2X was examined. Stopped-flow analysis reveals that oxygenation kinetics of 1·O2X is unaffected by the nature of O2X, and for the first time, the benzoate analog of 2·O2X (2·O2CPh) is observed.
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Affiliation(s)
- Jonathan R Frisch
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St. S.E., Minneapolis, Minnesota 55455, United States
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49
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Latifi R, Sainna MA, Rybak-Akimova EV, de Visser SP. Does Hydrogen-Bonding Donation to Manganese(IV)-Oxo and Iron(IV)-Oxo Oxidants Affect the Oxygen-Atom Transfer Ability? A Computational Study. Chemistry 2013; 19:4058-68. [DOI: 10.1002/chem.201202811] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2012] [Revised: 11/16/2012] [Indexed: 12/21/2022]
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50
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Zhu S, Qiu Z, Ni T, Zhao X, Yan S, Xing F, Zhao Y, Bai Y, Li M. Dinuclear complexes of copper and zinc with m-xylene/cyclohexane-linked bis-aspartic acids: Synthesis, characterization, dioxygen activation, and catalytic oxidation of nitrobenzene in pure aqueous solution. Dalton Trans 2013; 42:10898-911. [DOI: 10.1039/c3dt50923k] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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