1
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Tang Y, Li Y, Feng Tao F. Activation and catalytic transformation of methane under mild conditions. Chem Soc Rev 2021; 51:376-423. [PMID: 34904592 DOI: 10.1039/d1cs00783a] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
In the last few decades, worldwide scientists have been motivated by the promising production of chemicals from the widely existing methane (CH4) under mild conditions for both chemical synthesis with low energy consumption and climate remediation. To achieve this goal, a whole library of catalytic chemistries of transforming CH4 to various products under mild conditions is required to be developed. Worldwide scientists have made significant efforts to reach this goal. These significant efforts have demonstrated the feasibility of oxidation of CH4 to value-added intermediate compounds including but not limited to CH3OH, HCHO, HCOOH, and CH3COOH under mild conditions. The fundamental understanding of these chemical and catalytic transformations of CH4 under mild conditions have been achieved to some extent, although currently neither a catalyst nor a catalytic process can be used for chemical production under mild conditions at a large scale. In the academic community, over ten different reactions have been developed for converting CH4 to different types of oxygenates under mild conditions in terms of a relatively low activation or catalysis temperature. However, there is still a lack of a molecular-level understanding of the activation and catalysis processes performed in extremely complex reaction environments under mild conditions. This article reviewed the fundamental understanding of these activation and catalysis achieved so far. Different oxidative activations of CH4 or catalytic transformations toward chemical production under mild conditions were reviewed in parallel, by which the trend of developing catalysts for a specific reaction was identified and insights into the design of these catalysts were gained. As a whole, this review focused on discussing profound insights gained through endeavors of scientists in this field. It aimed to present a relatively complete picture for the activation and catalytic transformations of CH4 to chemicals under mild conditions. Finally, suggestions of potential explorations for the production of chemicals from CH4 under mild conditions were made. The facing challenges to achieve high yield of ideal products were highlighted and possible solutions to tackle them were briefly proposed.
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Affiliation(s)
- Yu Tang
- Institute of Molecular Catalysis and In situ/operando Studies, College of Chemistry, Fuzhou University, Fujian, 350000, China.
| | - Yuting Li
- Department of Chemical and Petroleum Engineering, University of Kansas, KS 66045, USA.
| | - Franklin Feng Tao
- Department of Chemical and Petroleum Engineering, University of Kansas, KS 66045, USA.
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2
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Boudalis AK. Half-Integer Spin Triangles: Old Dogs, New Tricks. Chemistry 2021; 27:7022-7042. [PMID: 33336864 DOI: 10.1002/chem.202004919] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Revised: 12/14/2020] [Indexed: 11/06/2022]
Abstract
Spin triangles, that is, triangular complexes of half-integer spins, are the oldest molecular nanomagnets (MNMs). Their magnetic properties have been studied long before molecular magnetism was delineated as a research field. This Review presents the history of their study, with references to the parallel development of new experimental investigations and new theoretical ideas used for their interpretation. It then presents an indicative list of spin-triangle families to illustrate their chemical diversity. Finally, it makes reference to recent developments in terms of theoretical ideas and new phenomena, as well as to the relevance of spin triangles to spintronic devices and new physics.
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Affiliation(s)
- Athanassios K Boudalis
- Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), UMR 7504, Université de Strasbourg, CNRS, 67000, Strasbourg, France.,Institut de Chimie de Strasbourg (UMR 7177, CNRS-Unistra), Université de Strasbourg, 4 rue Blaise Pascal, CS 90032, 67081, Strasbourg, France
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3
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Mathivathanan L, Rogez G, Ben Amor N, Robert V, Raptis RG, Boudalis AK. Origin of Ferromagnetism and Magnetic Anisotropy in a Family of Copper(II) Triangles. Chemistry 2020; 26:12769-12784. [DOI: 10.1002/chem.202001028] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Indexed: 11/11/2022]
Affiliation(s)
- Logesh Mathivathanan
- Department of Chemistry and Biochemistry and the Biomolecular Sciences Institute Florida International University Miami FL 33199 USA
| | - Guillaume Rogez
- Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS) CNRS/Université de Strasbourg UMR 7504 67000 Strasbourg France
| | - Nadia Ben Amor
- Laboratoire de Chimie et Physique Quantiques UMR 5626 CNRS/Université Paul Sabatier—Bat. 3R1B4 118 route de Narbonne 31062, Cedex 09 Toulouse France
| | - Vincent Robert
- Institut de Chimie de Strasbourg (UMR 7177, CNRS-Unistra) Université de Strasbourg 4 rue Blaise Pascal, CS 90032 67081 Strasbourg France
| | - Raphael G. Raptis
- Department of Chemistry and Biochemistry and the Biomolecular Sciences Institute Florida International University Miami FL 33199 USA
| | - Athanassios K. Boudalis
- Institut de Chimie de Strasbourg (UMR 7177, CNRS-Unistra) Université de Strasbourg 4 rue Blaise Pascal, CS 90032 67081 Strasbourg France
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4
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Wanna WH, Ramu R, Janmanchi D, Tsai YF, Thiyagarajan N, Yu SSF. An efficient and recyclable copper nano-catalyst for the selective oxidation of benzene to p-benzoquinone (p-BQ) using H2O2(aq) in CH3CN. J Catal 2019. [DOI: 10.1016/j.jcat.2019.01.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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5
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Yeh C, Yu SS, Chan SI, Jiang J. Quantum Chemical Studies of Methane Oxidation to Methanol on a Biomimetic Tricopper Complex: Mechanistic Insights. ChemistrySelect 2018. [DOI: 10.1002/slct.201800550] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Chen‐Hao Yeh
- Department of Chemical EngineeringNational Taiwan University of Science and Technology Taipei 10607 Taiwan
| | - Steve S.‐F. Yu
- Institute of ChemistryAcademia Sinica Nankang Taipei 11529 Taiwan
| | - Sunney I. Chan
- Department of Chemical EngineeringNational Taiwan University of Science and Technology Taipei 10607 Taiwan
- Institute of ChemistryAcademia Sinica Nankang Taipei 11529 Taiwan
| | - Jyh‐Chiang Jiang
- Department of Chemical EngineeringNational Taiwan University of Science and Technology Taipei 10607 Taiwan
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6
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Liu YF, Du L. Theoretical Study of the Oxidation of Methane to Methanol by the [CuIICuII(μ-O)2CuIII(7-N-Etppz)]1+ Complex. Inorg Chem 2018; 57:3261-3271. [DOI: 10.1021/acs.inorgchem.8b00054] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- Yan Fang Liu
- The Key Laboratory of Biobased Materials, The Qingdao Key Lab of Solar Energy Utilization and Energy Storage Technology, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, Shandong 266101, People’s Republic of China
| | - Likai Du
- Hubei Key Laboratory of Agricultural Bioinformatics, College of Informatics, Huazhong Agricultural University, Wuhan, 430070, People’s Republic of China
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7
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Wang VCC, Maji S, Chen PPY, Lee HK, Yu SSF, Chan SI. Alkane Oxidation: Methane Monooxygenases, Related Enzymes, and Their Biomimetics. Chem Rev 2017; 117:8574-8621. [PMID: 28206744 DOI: 10.1021/acs.chemrev.6b00624] [Citation(s) in RCA: 244] [Impact Index Per Article: 34.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Methane monooxygenases (MMOs) mediate the facile conversion of methane into methanol in methanotrophic bacteria with high efficiency under ambient conditions. Because the selective oxidation of methane is extremely challenging, there is considerable interest in understanding how these enzymes carry out this difficult chemistry. The impetus of these efforts is to learn from the microbes to develop a biomimetic catalyst to accomplish the same chemical transformation. Here, we review the progress made over the past two to three decades toward delineating the structures and functions of the catalytic sites in two MMOs: soluble methane monooxygenase (sMMO) and particulate methane monooxygenase (pMMO). sMMO is a water-soluble three-component protein complex consisting of a hydroxylase with a nonheme diiron catalytic site; pMMO is a membrane-bound metalloenzyme with a unique tricopper cluster as the site of hydroxylation. The metal cluster in each of these MMOs harnesses O2 to functionalize the C-H bond using different chemistry. We highlight some of the common basic principles that they share. Finally, the development of functional models of the catalytic sites of MMOs is described. These efforts have culminated in the first successful biomimetic catalyst capable of efficient methane oxidation without overoxidation at room temperature.
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Affiliation(s)
- Vincent C-C Wang
- Institute of Chemistry, Academia Sinica , 128, Section 2, Academia Road, Nankang, Taipei 11529, Taiwan
| | - Suman Maji
- School of Chemical Engineering and Physical Sciences, Lovely Professional University , Jalandhar-Delhi G. T. Road (NH-1), Phagwara, Punjab India 144411
| | - Peter P-Y Chen
- Department of Chemistry, National Chung Hsing University , 250 Kuo Kuang Road, Taichung 402, Taiwan
| | - Hung Kay Lee
- Department of Chemistry, The Chinese University of Hong Kong , Shatin, New Territories, Hong Kong
| | - Steve S-F Yu
- Institute of Chemistry, Academia Sinica , 128, Section 2, Academia Road, Nankang, Taipei 11529, Taiwan
| | - Sunney I Chan
- Institute of Chemistry, Academia Sinica , 128, Section 2, Academia Road, Nankang, Taipei 11529, Taiwan.,Department of Chemistry, National Taiwan University , No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan.,Noyes Laboratory, 127-72, California Institute of Technology , 1200 East California Boulevard, Pasadena, California 91125, United States
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8
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Culpepper MA, Cutsail GE, Gunderson WA, Hoffman BM, Rosenzweig AC. Identification of the valence and coordination environment of the particulate methane monooxygenase copper centers by advanced EPR characterization. J Am Chem Soc 2014; 136:11767-75. [PMID: 25059917 PMCID: PMC4140498 DOI: 10.1021/ja5053126] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
Particulate methane monooxygenase (pMMO) catalyzes the oxidation of methane to methanol in methanotrophic bacteria. As a copper-containing enzyme, pMMO has been investigated extensively by electron paramagnetic resonance (EPR) spectroscopy, but the presence of multiple copper centers has precluded correlation of EPR signals with the crystallographically identified monocopper and dicopper centers. A soluble recombinant fragment of the pmoB subunit of pMMO, spmoB, like pMMO itself, contains two distinct copper centers and exhibits methane oxidation activity. The spmoB protein, spmoB variants designed to disrupt one or the other or both copper centers, as well as native pMMO have been investigated by EPR, ENDOR, and ESEEM spectroscopies in combination with metal content analysis. The data are remarkably similar for spmoB and pMMO, validating the use of spmoB as a model system. The results indicate that one EPR-active Cu(II) ion is present per pMMO and that it is associated with the active-site dicopper center in the form of a valence localized Cu(I)Cu(II) pair; the Cu(II), however, is scrambled between the two locations within the dicopper site. The monocopper site observed in the crystal structures of pMMO can be assigned as Cu(I). (14)N ENDOR and ESEEM data are most consistent with one of these dicopper-site signals involving coordination of the Cu(II) ion by residues His137 and His139, the other with Cu(II) coordinated by His33 and the N-terminal amino group. (1)H ENDOR measurements indicate there is no aqua (HxO) ligand bound to the Cu(II), either terminally or as a bridge to Cu(I).
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Affiliation(s)
- Megen A Culpepper
- Departments of ‡Molecular Biosciences and of §Chemistry, Northwestern University , Evanston, Illinois 60208, United States
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9
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Solomon EI, Heppner DE, Johnston EM, Ginsbach JW, Cirera J, Qayyum M, Kieber-Emmons MT, Kjaergaard CH, Hadt RG, Tian L. Copper active sites in biology. Chem Rev 2014; 114:3659-853. [PMID: 24588098 PMCID: PMC4040215 DOI: 10.1021/cr400327t] [Citation(s) in RCA: 1112] [Impact Index Per Article: 111.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
| | - David E. Heppner
- Department of Chemistry, Stanford University, Stanford, CA, 94305
| | | | - Jake W. Ginsbach
- Department of Chemistry, Stanford University, Stanford, CA, 94305
| | - Jordi Cirera
- Department of Chemistry, Stanford University, Stanford, CA, 94305
| | - Munzarin Qayyum
- Department of Chemistry, Stanford University, Stanford, CA, 94305
| | | | | | - Ryan G. Hadt
- Department of Chemistry, Stanford University, Stanford, CA, 94305
| | - Li Tian
- Department of Chemistry, Stanford University, Stanford, CA, 94305
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10
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Synthesis and properties of hyperbranched polyester polyacrylic acids and their metal complexes. Russ Chem Bull 2014. [DOI: 10.1007/s11172-014-0419-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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11
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Yoshizawa K. Quantum Chemical Studies on Dioxygen Activation and Methane Hydroxylation by Diiron and Dicopper Species as well as Related Metal–Oxo Species. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2013. [DOI: 10.1246/bcsj.20130127] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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12
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Chen KHC, Chen CL, Tseng CF, Yu SSF, Ke SC, Lee JF, Nguyen HT, Elliott SJ, Alben JO, Chan SI. The Copper Clusters in the Particulate Methane Monooxygenase (pMMO) fromMethylococcus Capsulatus(Bath). J CHIN CHEM SOC-TAIP 2013. [DOI: 10.1002/jccs.200400162] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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13
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Chen PPY, Nagababu P, Yu SSF, Chan SI. Development of the Tricopper Cluster as a Catalyst for the Efficient Conversion of Methane into MeOH. ChemCatChem 2013. [DOI: 10.1002/cctc.201300473] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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14
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Shiota Y, Juhász G, Yoshizawa K. Role of Tyrosine Residue in Methane Activation at the Dicopper Site of Particulate Methane Monooxygenase: A Density Functional Theory Study. Inorg Chem 2013; 52:7907-17. [DOI: 10.1021/ic400417d] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yoshihito Shiota
- Institute for Materials
Chemistry and Engineering and International Research Center for Molecular
System, Kyushu University, Fukuoka 819-0395,
Japan
| | - Gergely Juhász
- Institute for Materials
Chemistry and Engineering and International Research Center for Molecular
System, Kyushu University, Fukuoka 819-0395,
Japan
| | - Kazunari Yoshizawa
- Institute for Materials
Chemistry and Engineering and International Research Center for Molecular
System, Kyushu University, Fukuoka 819-0395,
Japan
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15
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Hammond C, Conrad S, Hermans I. Oxidative methane upgrading. CHEMSUSCHEM 2012; 5:1668-1686. [PMID: 22848012 DOI: 10.1002/cssc.201200299] [Citation(s) in RCA: 171] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2012] [Indexed: 06/01/2023]
Abstract
The economically viable oxidative upgrading of methane presents one of the most difficult but rewarding challenges within catalysis research. Its potential to revolutionalise the chemical value chain, coupled with the associated supremely challenging scientific aspects, has ensured this topic's high popularity over the preceeding decades. Herein, we report a non-exhaustive account of the current developments within the field of oxidative methane upgrading and summarise the pertaining challenges that have yet to be solved.
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Affiliation(s)
- Ceri Hammond
- Department of Chemistry and Applied Biosciences, ETH Zurich, Switzerland
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16
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Maji S, Lee JCM, Lu YJ, Chen CL, Hung MC, Chen PPY, Yu SSF, Chan SI. Dioxygen Activation of a Trinuclear CuICuICuI Cluster Capable of Mediating Facile Oxidation of Organic Substrates: Competition between O-Atom Transfer and Abortive Intercomplex Reduction. Chemistry 2012; 18:3955-68. [DOI: 10.1002/chem.201103075] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2011] [Indexed: 11/09/2022]
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17
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Models for the trinuclear copper(II) cluster in the particulate methane monooxygenase from methanotrophic bacteria: Synthesis, spectroscopic and theoretical characterization of trinuclear copper(II) complexes. CR CHIM 2012. [DOI: 10.1016/j.crci.2011.11.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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18
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Smith SM, Rawat S, Telser J, Hoffman BM, Stemmler TL, Rosenzweig AC. Crystal structure and characterization of particulate methane monooxygenase from Methylocystis species strain M. Biochemistry 2011; 50:10231-40. [PMID: 22013879 PMCID: PMC3364217 DOI: 10.1021/bi200801z] [Citation(s) in RCA: 111] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Particulate methane monooxygenase (pMMO) is an integral membrane metalloenzyme that oxidizes methane to methanol in methanotrophic bacteria. Previous biochemical and structural studies of pMMO have focused on preparations from Methylococcus capsulatus (Bath) and Methylosinus trichosporium OB3b. A pMMO from a third organism, Methylocystis species strain M, has been isolated and characterized. Both membrane-bound and solubilized Methylocystis sp. strain M pMMO contain ~2 copper ions per 100 kDa protomer and exhibit copper-dependent propylene epoxidation activity. Spectroscopic data indicate that Methylocystis sp. strain M pMMO contains a mixture of Cu(I) and Cu(II), of which the latter exhibits two distinct type 2 Cu(II) electron paramagnetic resonance (EPR) signals. Extended X-ray absorption fine structure (EXAFS) data are best fit with a mixture of Cu-O/N and Cu-Cu ligand environments with a Cu-Cu interaction at 2.52-2.64 Å. The crystal structure of Methylocystis sp. strain M pMMO was determined to 2.68 Å resolution and is the best quality pMMO structure obtained to date. It provides a revised model for the pmoA and pmoC subunits and has led to an improved model of M. capsulatus (Bath) pMMO. In these new structures, the intramembrane zinc/copper binding site has a different coordination environment from that in previous models.
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Affiliation(s)
- Stephen M. Smith
- Departments of Molecular Biosciences and of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Swati Rawat
- Department of Biochemistry and Molecular Biology, Wayne State University, School of Medicine, Detroit, Michigan 48201, United States
| | - Joshua Telser
- Departments of Molecular Biosciences and of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Brian M. Hoffman
- Departments of Molecular Biosciences and of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Timothy L. Stemmler
- Department of Biochemistry and Molecular Biology, Wayne State University, School of Medicine, Detroit, Michigan 48201, United States
| | - Amy C. Rosenzweig
- Departments of Molecular Biosciences and of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
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Tumanova LV, Tukhvatullin IA, Burbaev DS, Gvozdev RI, Andersson KK. The binuclear iron site of membrane-bound methane hydroxylase from Methylococcus capsulatus (Strain M). RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2011; 34:194-203. [DOI: 10.1134/s1068162008020064] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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20
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Abstract
pMMO (particulate methane mono-oxygenase) is an integral membrane metalloenzyme that catalyses the oxidation of methane to methanol. The pMMO metal active site has not been identified, precluding detailed investigation of the reaction mechanism. Models for the metal centres proposed by various research groups have evolved as crystallographic and spectroscopic data have become available. The present review traces the evolution of these active-site models before and after the 2005 Methylococcus capsulatus (Bath) pMMO crystal structure determination.
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21
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Shiota Y, Yoshizawa K. Comparison of the Reactivity of Bis(μ-oxo)CuIICuIII and CuIIICuIII Species to Methane. Inorg Chem 2008; 48:838-45. [DOI: 10.1021/ic8003933] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yoshihito Shiota
- Institute for Materials Chemistry and Engineering, Kyushu University, Fukuoka 819-0395, Japan
| | - Kazunari Yoshizawa
- Institute for Materials Chemistry and Engineering, Kyushu University, Fukuoka 819-0395, Japan
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22
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Chan SI, Yu SSF. Controlled oxidation of hydrocarbons by the membrane-bound methane monooxygenase: the case for a tricopper cluster. Acc Chem Res 2008; 41:969-79. [PMID: 18605740 DOI: 10.1021/ar700277n] [Citation(s) in RCA: 172] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
[Figure: see text]. The growing need for inexpensive methods to convert methane to methanol has sparked considerable interest in methods that catalyze this process. The integral membrane protein particulate methane monooxygenase (pMMO) mediates the facile conversion of methane to methanol in methanotrophic bacteria. Most evidence indicates that pMMO is a multicopper enzyme, and these copper ions support redox, dioxygen, and oxo-transfer chemistry. However, the exact identity of the copper species that mediates the oxo-transfer chemistry remains an area of intense debate. This highly complex enzyme is notoriously difficult to purify because of its instability outside the lipid bilayer and tendency to lose its essential metal cofactors. For this reason, pMMO has resisted both initial identification and subsequent isolation and purification for biochemical and biophysical characterization. In this Account, we describe evidence that pMMO is a multicopper protein. Its unique trinuclear copper cluster mediates dioxygen chemistry and O-atom transfer during alkane hydroxylation. Although a recent crystal structure did not show this tricopper cluster, we provide compelling evidence for such a cluster through redox potentiometry and EPR experiments on the "holo" enzyme in pMMO-enriched membranes. We also identify a site in the structure of pMMO that could accommodate this cluster. A hydrophobic pocket capable of harboring pentane, the enzyme's largest known substrate, lies adjacent to this site. In addition, we have designed and synthesized model tricopper clusters to provide further chemical evidence that a tricopper cluster mediates the enzyme's oxo-transfer chemistry. These biomimetic models exhibit similar spectroscopic properties and chemical reactivity to the putative tricopper cluster in pMMO. Based on computational analysis using density functional theory (DFT), triangular tricopper clusters are capable of harnessing a "singlet oxene" upon activation by dioxygen. An oxygen atom is then inserted via a concerted process into the C-H bond of an alkane in the transition state during hydroxylation. The turnover frequency and kinetic isotope effect predicted by DFT show excellent agreement with experimental data.
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Affiliation(s)
- Sunney I. Chan
- Institute of Chemistry, Academia Sinica, Nankang, Taipei 11509, Taiwan
- A. A. Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, CA 91125
| | - Steve S.-F. Yu
- Institute of Chemistry, Academia Sinica, Nankang, Taipei 11509, Taiwan
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23
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Hakemian AS, Kondapalli KC, Telser J, Hoffman BM, Stemmler TL, Rosenzweig AC. The metal centers of particulate methane monooxygenase from Methylosinus trichosporium OB3b. Biochemistry 2008; 47:6793-801. [PMID: 18540635 PMCID: PMC2664655 DOI: 10.1021/bi800598h] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Particulate methane monooxygenase (pMMO) is a membrane-bound metalloenzyme that oxidizes methane to methanol in methanotrophic bacteria. The nature of the pMMO active site and the overall metal content are controversial, with spectroscopic and crystallographic data suggesting the presence of a mononuclear copper center, a dinuclear copper center, a trinuclear center, and a diiron center or combinations thereof. Most studies have focused on pMMO from Methylococcus capsulatus (Bath). pMMO from a second organism, Methylosinus trichosporium OB3b, has been purified and characterized by spectroscopic and crystallographic methods. Purified M. trichosporium OB3b pMMO contains approximately 2 copper ions per 100 kDa protomer. Electron paramagnetic resonance (EPR) spectroscopic parameters indicate that type 2 Cu(II) is present as two distinct species. Extended X-ray absorption fine structure (EXAFS) data are best fit with oxygen/nitrogen ligands and reveal a Cu-Cu interaction at 2.52 A. Correspondingly, X-ray crystallography of M. trichosporium OB3b pMMO shows a dinuclear copper center, similar to that observed previously in the crystal structure of M. capsulatus (Bath) pMMO. There are, however, significant differences between the pMMO structures from the two organisms. A mononuclear copper center present in M. capsulatus (Bath) pMMO is absent in M. trichosporium OB3b pMMO, whereas a metal center occupied by zinc in the M. capsulatus (Bath) pMMO structure is occupied by copper in M. trichosporium OB3b pMMO. These findings extend previous work on pMMO from M. capsulatus (Bath) and provide new insight into the functional importance of the different metal centers.
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Affiliation(s)
| | | | | | | | - Timothy L. Stemmler
- To whom correspondence may be addressed. A.C.R.: tel, 847-467-5301; fax, 847-467-6489; e-mail, . T.L.S.: tel, 313-577-5712; fax, 313-577-2765; e-mail,
| | - Amy C. Rosenzweig
- To whom correspondence may be addressed. A.C.R.: tel, 847-467-5301; fax, 847-467-6489; e-mail, . T.L.S.: tel, 313-577-5712; fax, 313-577-2765; e-mail,
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Abstract
Methanotrophic bacteria oxidize methane to methanol in the first step of their metabolic pathway. Two forms of methane monooxygenase (MMO) enzymes catalyze this reaction: soluble MMO (sMMO) and membrane-bound or particulate MMO (pMMO). pMMO is expressed when copper is available, and its active site is believed to contain copper. Whereas sMMO is well characterized, most aspects of pMMO biochemistry remain unknown and somewhat controversial. This review emphasizes advances in the past two to three years related to pMMO and to copper uptake and copper-dependent regulation in methanotrophs. The pMMO metal centers have been characterized spectroscopically, and the first pMMO crystal structure has been determined. Significant effort has been devoted to improving in vitro pMMO activity. Proteins involved in sMMO regulation and additional copper-regulated proteins have been identified, and the Methylococcus capsulatus (Bath) genome has been sequenced. Finally, methanobactin (mb), a small copper chelator proposed to facilitate copper uptake, has been characterized.
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Affiliation(s)
- Amanda S Hakemian
- Department of Biochemistry, Northwestern University, Evanston, Illinois 60208, USA.
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Balasubramanian R, Rosenzweig AC. Structural and mechanistic insights into methane oxidation by particulate methane monooxygenase. Acc Chem Res 2007; 40:573-80. [PMID: 17444606 DOI: 10.1021/ar700004s] [Citation(s) in RCA: 160] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Particulate methane monooxygense (pMMO) is an integral membrane copper-containing enzyme that converts methane to methanol. Knowledge of how pMMO selectively oxidizes methane under ambient conditions could impact the development of new catalysts. The crystal structure of Methylococcus capsulatus (Bath) pMMO reveals the composition and location of three metal centers. Spectroscopic data provide insight into the coordination environments and oxidation states of these metal centers. These results, combined with computational studies and comparisons to relevant systems, are discussed in the context of identifying the most likely site for O 2 activation.
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Chan S, Wang VC, Lai JH, Yu SF, Chen PY, Chen KC, Chen CL, Chan M. Redox Potentiometry Studies of Particulate Methane Monooxygenase: Support for a Trinuclear Copper Cluster Active Site. Angew Chem Int Ed Engl 2007. [DOI: 10.1002/ange.200604647] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Chan SI, Wang VCC, Lai JCH, Yu SSF, Chen PPY, Chen KHC, Chen CL, Chan MK. Redox Potentiometry Studies of Particulate Methane Monooxygenase: Support for a Trinuclear Copper Cluster Active Site. Angew Chem Int Ed Engl 2007; 46:1992-4. [PMID: 17274089 DOI: 10.1002/anie.200604647] [Citation(s) in RCA: 118] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Sunney I Chan
- Institute of Chemistry, Academia Sinica, Nankang, Taipei, Taiwan 11529, Republic of China.
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Chen PPY, Chan SI. Theoretical modeling of the hydroxylation of methane as mediated by the particulate methane monooxygenase. J Inorg Biochem 2006; 100:801-9. [PMID: 16494948 DOI: 10.1016/j.jinorgbio.2005.12.014] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2005] [Accepted: 12/13/2005] [Indexed: 11/22/2022]
Abstract
We present here the results of density functional theory (DFT) calculations directed toward elucidation of the CH bond activation mechanism that might be adopted by the particulate methane monooxygenase (pMMO) in the hydroxylation of methane and related small alkanes. In these calculations, we considered three of the most probable models for the transition metal active site mediating the "oxo-transfer": (i) the trinuclear copper cluster bis(mu(3)-oxo)trinuclear copper(II, II, III) complex 1, recently proposed by Chan et al. [S.I. Chan, K.H.-C. Chen, S.S.-F. Yu, C.-L. Chen, S.S.-J. Kuo, Biochemistry 43 (2004) 4421-4430.]; (ii) the most frequently used model complex, bis(mu-oxo)Cu(III)(2) complex 2; and (iii) the mixed-valence bis(mu-oxo)Cu(II)Cu(III) complex 3. The results obtained indicate that the methane hydroxylation chemistry mediated by the trinuclear copper cluster bis(mu(3)-oxo)trinuclear copper(II, II, III) complex 1 offers the most facile pathway for methane hydroxylation, and this model yields KIE values that are in good agreement with experiment. In this mechanism, the reaction proceeds along a "singlet" potential surface and a "singlet oxene" is directly inserted across a CH bond in a concerted manner. Kinetic isotope effects (k(H)/k(D) or KIE) associated with the concerted oxene insertion process mediated by complex 1 are calculated to be 5.2 at 300K when tunneling effects are included. Overall rate constants for the methane hydroxylation by the three models have been calculated as a function of temperature, and the rates are at least 5-6 orders of magnitude more facile when the chemistry is mediated by complex 1 compared to complex 2 or complex 3.
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Affiliation(s)
- Peter P-Y Chen
- Institute of Chemistry, Academia Sinica, 128 Section 2, Academia Road, Nankang, Taipei 115, Taiwan, ROC
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Lieberman RL, Rosenzweig AC. The quest for the particulate methane monooxygenase active site. Dalton Trans 2005:3390-6. [PMID: 16234916 DOI: 10.1039/b506651d] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Particulate methane monooxygenase is a copper-containing, membrane-bound metalloenzyme that converts methane to methanol in Nature. How pMMO accomplishes this difficult reaction under ambient conditions is one of the major unsolved problems in bioinorganic chemistry. Despite considerable research efforts in the past 20 years, the active site of the enzyme remains unknown. We recently solved the first crystal structure of pMMO to 2.8 è resolution, revealing the overall structure, oligomerization state, subunit ratio, and composition and location of the metal centers. Almost none of the key structural features were predicted. In this Perspective, we review the state of knowledge before and after the structure determination, emphasizing elucidation of the pMMO active site.
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Affiliation(s)
- Raquel L Lieberman
- Department of Biochemistry, Northwestern University, Evanston, Illinois 60208, USA
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