1951
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Oh NY, Suh Y, Park MJ, Seo MS, Kim J, Nam W. Mechanistic Insight into Alcohol Oxidation by High-Valent Iron-Oxo Complexes of Heme and Nonheme Ligands. Angew Chem Int Ed Engl 2005. [DOI: 10.1002/ange.200500623] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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1952
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Urich T, Kroke A, Bauer C, Seyfarth K, Reuff M, Kletzin A. Identification of core active site residues of the sulfur oxygenase reductase fromAcidianus ambivalensby site-directed mutagenesis. FEMS Microbiol Lett 2005; 248:171-6. [PMID: 15970399 DOI: 10.1016/j.femsle.2005.05.031] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2005] [Revised: 05/17/2005] [Accepted: 05/18/2005] [Indexed: 11/23/2022] Open
Abstract
The sulfur oxygenase reductase (SOR) is the initial enzyme in the sulfur oxidation pathway of Acidianus ambivalens. The SOR is composed of 308 aa residues, three of which are cysteines, and contains a mononuclear non-heme iron site. Mutations of the suspected iron-binding residues H86, H90 and E114 to alanine resulted in inactive enzyme with no iron incorporated, whereas an E114D mutant showed 1% of wild type activity. The mutation of C31 to alanine and serine caused inactivity of the enzyme, however, the iron content was the same as in the wild type. C101A, C104S/A, and C101/104S/A double mutants caused a decrease in specific activity to 10-43% of the wild type while the C101S mutant showed only 1% activity of the wild type. The drop in activity of the C101S and E114D mutants was accompanied with a proportional decrease in iron content. In all cases the oxygenase and reductase partial reactions were equally affected. It was concluded that the Fe site with H86, H90 and E114 as ligands and C31 constitute the core active site whereas C101 and C104 optimize reaction conditions.
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Affiliation(s)
- Tim Urich
- Institute of Microbiology and Genetics, Darmstadt University of Technology, Schnittspahnstrasse 10, 64287 Darmstadt, Germany
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1953
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Generation of a Nonheme Oxoiron(IV) Intermediate and Its Reactivities in Oxidation Reactions. B KOREAN CHEM SOC 2005. [DOI: 10.5012/bkcs.2005.26.6.971] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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1954
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Klinker EJ, Kaizer J, Brennessel WW, Woodrum NL, Cramer CJ, Que L. Structures of Nonheme Oxoiron(IV) Complexes from X-ray Crystallography, NMR Spectroscopy, and DFT Calculations. Angew Chem Int Ed Engl 2005. [DOI: 10.1002/ange.200500485] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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1955
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Venkataramanan NS, Kuppuraj G, Rajagopal S. Metal–salen complexes as efficient catalysts for the oxygenation of heteroatom containing organic compounds—synthetic and mechanistic aspects. Coord Chem Rev 2005. [DOI: 10.1016/j.ccr.2005.01.023] [Citation(s) in RCA: 233] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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1956
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Cheng HY, Chang S. On the [Fe(H2O)5XO]2+ (XC, N, O) complex ions via density functional theory. ACTA ACUST UNITED AC 2005. [DOI: 10.1016/j.theochem.2005.03.044] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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1957
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McDonough MA, McNeill LA, Tilliet M, Papamicaël CA, Chen QY, Banerji B, Hewitson KS, Schofield CJ. Selective Inhibition of Factor Inhibiting Hypoxia-Inducible Factor. J Am Chem Soc 2005; 127:7680-1. [PMID: 15913349 DOI: 10.1021/ja050841b] [Citation(s) in RCA: 123] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A set of four non-heme iron(II) and 2-oxoglutarate-dependent enzymes catalyze the post-translational modification of a transcription factor, hypoxia inducible factor (HIF), that mediates the hypoxic response in animals. Hydroxylation of HIF both causes its degradation and limits its activity. We describe how the use of structural data coupled to solid-phase synthesis led to the discovery of a selective inhibitor of one of the HIF hydroxylases. The inhibitor N-oxalyl-d-phenylalanine was shown to inhibit the HIF asparaginyl hydroxylase (FIH) but not a HIF prolyl hydroxylase. A crystal structure of the inhibitor complexed to FIH reveals that it binds in the 2OG and, likely, in the dioxygen binding site. The results will help to enable the modulation of the hypoxic response for the up-regulation of specific genes of biomedical importance, such as erythropoietin and vascular endothelial growth factor.
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Affiliation(s)
- Michael A McDonough
- The Department of Chemistry and The Oxford Centre for Molecular Sciences, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford, OX1 3TA, United Kingdom
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1958
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Yin CX, Finke RG. Vanadium-Based, Extended Catalytic Lifetime Catechol Dioxygenases: Evidence for a Common Catalyst. J Am Chem Soc 2005; 127:9003-13. [PMID: 15969577 DOI: 10.1021/ja051594e] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In 1999, a catechol dioxygenase derived from a V-polyoxometalate was reported which was able to perform a record >100 000 total turnovers of 3,5-di-tert-butylcatechol oxygenation using O2 as the oxidant (Weiner, H.; Finke, R. G. J. Am. Chem. Soc. 1999, 121, 9831). An important goal is to better understand this and other vanadium-based catechol dioxygenases. Scrutiny of 11 literature reports of vanadium-based catechol dioxygenases yielded the insight that they all proceed with closely similar selectivities. This, in turn, led to a "common catalyst hypothesis" for the broad range of vanadium based catechol dioxygenase precatalysts presently known. The following three classes of V-based compounds, 10 complexes total, have been explored to test the common catalyst hypothesis: (i) six vanadium-based polyoxometalate precatalysts, (n-Bu4N)4H5PV14O42, (n-Bu4N)7SiW9V3O40, (n-Bu4N)5[(CH3CN)(x)Fe(II).SiW9V3O40], (n-Bu4N)9P2W15V3O62, (n-Bu4N)5Na2[(CH3CN)(x)Fe(II).P2W15V3O62], and (n-Bu4N)4H2-gamma-SiW10V2O40; (ii) three vanadium catecholate complexes, [V(V)O(DBSQ)(DTBC)]2, [Et3NH]2[V(IV)O(DBTC)2].2CH3OH, and [Na(CH3OH)2]2[V(V)(DTBC)3]2.4CH3OH (where DBSQ = 3,5-di-tert-butylsemiquinone anion and DTBC = 3,5-di-tert-butylcatecholate dianion), and (iii) simple VO(acac)2. Product selectivity studies, catalytic lifetime tests, electron paramagnetic resonance spectroscopy (EPR), negative ion mode electrospray ionization-mass spectrometry (negative ion ESI-MS), and kinetic studies provided compelling evidence for a common catalyst or catalyst resting state, namely, Pierpont's structurally characterized vanadyl semiquinone catecholate dimer complex, [VO(DBSQ)(DTBC)]2, formed from V-leaching from the precatalysts. The results provide a considerable simplification and unification of a previously disparate literature of V-based catechol dioxygenases.
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Affiliation(s)
- Cindy-Xing Yin
- Department of Chemistry, Colorado State University, Ft. Collins, Colorado 80523, USA
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1959
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Kryatov SV, Rybak-Akimova EV, Schindler S. Kinetics and Mechanisms of Formation and Reactivity of Non-heme Iron Oxygen Intermediates. Chem Rev 2005; 105:2175-226. [PMID: 15941212 DOI: 10.1021/cr030709z] [Citation(s) in RCA: 313] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Sergey V Kryatov
- Department of Chemistry, Tufts University, Medford, Massachusetts 02155, USA
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1960
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Price JC, Barr EW, Hoffart LM, Krebs C, Bollinger JM. Kinetic Dissection of the Catalytic Mechanism of Taurine:α-Ketoglutarate Dioxygenase (TauD) from Escherichia coli. Biochemistry 2005; 44:8138-47. [PMID: 15924433 DOI: 10.1021/bi050227c] [Citation(s) in RCA: 136] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Recent studies on taurine:alpha-ketoglutarate dioxygenase (TauD) from Escherichia coli have provided evidence for a three-step, minimal kinetic mechanism involving the quaternary TauD.Fe(II).alpha-ketoglutarate.taurine complex, the taurine-hydroxylating Fe(IV)-oxo intermediate (J) that forms upon reaction of the quaternary complex with O(2), and a poorly defined, Fe(II)-containing intermediate state that converts in the rate-limiting step back to the quaternary complex [Price, J. C., Barr, E. W., Tirupati, B., Bollinger, J. M., Jr., and Krebs, C. (2003) Biochemistry 42, 7497-7508]. The mapping of this kinetic mechanism onto the consensus chemical mechanism for the Fe(II)- and alpha-ketoglutarate-dependent engendered several predictions and additional questions that have been experimentally addressed in the present study. The results demonstrate (1) that postulated intermediates between the quaternary complex and J accumulate very little or not at all; (2) that decarboxylation of alpha-ketoglutarate occurs prior to or concomitantly with formation of J; (3) that the second intermediate state comprises one or more product complex with Mossbauer features that are partially resolved from those of the binary TauD.Fe(II), ternary TauD.Fe(II).alpha-ketoglutarate, and quaternary TauD.Fe(II).alpha-ketoglutarate.taurine complexes; and (4) that the rate-determining step in the catalytic cycle is release of product(s) prior to the rapid, ordered binding of alpha-ketoglutarate and then taurine to regenerate the O(2)-reactive quaternary complex. The results thus integrate the previously proposed kinetic and chemical mechanisms and indicate which of the postulated intermediates in the latter will be detectable only upon perturbation of the kinetics by changes in reaction conditions (e.g., temperature), protein mutagenesis, the use of substrate analogues, or some combination of these.
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Affiliation(s)
- John C Price
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
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1961
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Punniyamurthy T, Velusamy S, Iqbal J. Recent Advances in Transition Metal Catalyzed Oxidation of Organic Substrates with Molecular Oxygen. Chem Rev 2005; 105:2329-63. [PMID: 15941216 DOI: 10.1021/cr050523v] [Citation(s) in RCA: 1332] [Impact Index Per Article: 70.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- T Punniyamurthy
- Department of Chemistry, Indian Institute of Technology Guwahati.
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1962
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Bassan A, Blomberg MRA, Siegbahn PEM, Que L. Two Faces of a Biomimetic Non-Heme HOFeVO Oxidant: Olefin Epoxidation versuscis-Dihydroxylation. Angew Chem Int Ed Engl 2005. [DOI: 10.1002/ange.200463072] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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1963
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Aliaga-Alcalde N, DeBeer George S, Mienert B, Bill E, Wieghardt K, Neese F. The Geometric and Electronic Structure of [(cyclam-acetato)Fe(N)]+: A Genuine Iron(V) Species with a Ground-State SpinS=1/2. Angew Chem Int Ed Engl 2005. [DOI: 10.1002/ange.200462368] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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1964
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Bassan A, Blomberg MRA, Siegbahn PEM, Que L. Two Faces of a Biomimetic Non-Heme HOFeVO Oxidant: Olefin Epoxidation versuscis-Dihydroxylation. Angew Chem Int Ed Engl 2005; 44:2939-41. [PMID: 15812868 DOI: 10.1002/anie.200463072] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Arianna Bassan
- Department of Physics, Stockholm University, SE 106 91, Stockholm, Sweden.
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1965
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Velusamy M, Mayilmurugan R, Palaniandavar M. Functional models for catechol dioxygenases: Iron(III) complexes of cis-facially coordinating linear 3N ligands. J Inorg Biochem 2005; 99:1032-42. [PMID: 15833326 DOI: 10.1016/j.jinorgbio.2005.01.008] [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] [Received: 09/29/2004] [Revised: 01/17/2005] [Accepted: 01/18/2005] [Indexed: 11/18/2022]
Abstract
A series of 1:1 iron(III) complexes of simple and sterically hindered tridentate 3N donor ligands have been synthesized and studied as functional models for catechol dioxygenases. All of them are of the type [FeLCl3], where L is bis(pyrid-2-yl-methyl)amine (L1), N,N-bis(benzimidazol-2-ylmethyl)amine (L2), N-methyl-N'-(pyrid-2-ylmethyl)ethylenediamine (L3), N,N-dimethyl-N'-(pyrid-2-ylmethyl)-ethylenediamine (L4) and N-phenyl-N'-(pyrid-2-ylmethyl)ethylenediamine (L5). They have been characterised by spectral and electrochemical methods. The X-ray crystal structure of the complex [Fe(L4)Cl3] has been successfully determined. The complex crystallizes in the triclinic space group P1 with a = 7.250(6), b = 8.284(3), c = 12.409(4) angstroms, alpha = 80.84(3) degrees, beta = 86.76(6) degrees, gamma = 72.09(7) degrees and Z = 2. It possesses a distorted octahedral geometry in which the L4 ligand is cis-facially coordinated to iron(III) and the chloride ions occupy the remaining coordination sites. The systematic variation in the ligand donor atom type significantly influences the Lewis acidity of the iron(III) center and hence the binding interaction of the complexes with simple and substituted catechols. The spectroscopic and electrochemical properties of the catecholate complexes generated in situ have been investigated. All the complexes catalyze mainly the oxidative intradiol cleavage of 3,5-di-tert-butylcatechol (H2DBC) in the presence of dioxygen, which is unexpected of the cis-facial coordination of the ligands. The rate of intradiol catechol cleavage reaction depends upon the Lewis acidity of iron(III) center and steric demand and hydrogen-bonding functionalities of the ligands. Interestingly, the electron-sink property of N-phenyl substituent in [Fe(L5)Cl3] complex leads to enhancement in rate of cleavage. All these observations provide support to the substrate activation mechanism proposed for intradiol-cleaving enzymes.
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Affiliation(s)
- Marappan Velusamy
- Department of Chemistry, Bharathidasan University, Tiruchirappalli 620 024, India
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1966
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Tierney DL, Rocklin AM, Lipscomb JD, Que L, Hoffman BM. ENDOR Studies of the Ligation and Structure of the Non-Heme Iron Site in ACC Oxidase. J Am Chem Soc 2005; 127:7005-13. [PMID: 15884944 DOI: 10.1021/ja0500862] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Ethylene is a plant hormone involved in all stages of growth and development, including regulation of germination, responses to environmental stress, and fruit ripening. The final step in ethylene biosynthesis, oxidation of 1-aminocyclopropane-1-carboxylic acid (ACC) to yield ethylene, is catalyzed by ACC oxidase (ACCO). In a previous EPR and ENDOR study of the EPR-active Fe(II)-nitrosyl, [FeNO],(7) complex of ACCO, we demonstrated that both the amino and the carboxyl moieties of the inhibitor d,l-alanine, and the substrate ACC by analogy, coordinate to the Fe(II) ion in the Fe(II)-NO-ACC ternary complex. In this report, we use 35 GHz pulsed and CW ENDOR spectroscopy to examine the coordination of Fe by ACCO in more detail. ENDOR data for selectively (15)N-labeled derivatives of substrate-free ACCO-NO (E-NO) and substrate/inhibitor-bound ACCO-NO (E-NO-S) have identified two histidines as protein-derived ligands to Fe; (1,2)H and (17)O ENDOR of samples in D(2)O and H(2)(17)O solvent have confirmed the presence of water in the substrate-free Fe(II) coordination sphere (E-NO). Analysis of orientation-selective (14,15)N and (17)O ENDOR data is interpreted in terms of a structural model of the ACCO active site, both in the presence (E-NO-S) and in the absence (E-NO) of substrate. Evidence is also given that substrate binding dictates the orientation of bound O(2).
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Affiliation(s)
- David L Tierney
- Department of Chemistry, University of New Mexico, Albuquerque, NM 87131, USA.
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1967
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Ghosh A, Tiago de Oliveira F, Yano T, Nishioka T, Beach ES, Kinoshita I, Münck E, Ryabov AD, Horwitz CP, Collins TJ. Catalytically active mu-Oxodiiron(IV) oxidants from Iron(III) and dioxygen. J Am Chem Soc 2005; 127:2505-13. [PMID: 15725005 DOI: 10.1021/ja0460458] [Citation(s) in RCA: 139] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The reaction between an Fe(III) complex and O(2) to afford a stable catalytically active diiron(IV)-mu-oxo compound is described. Phosphonium salts of orange five-coordinated Fe(III)-TAML complexes with an axial aqua ligand ([PPh(4)]1-H(2)O, tetraamidato macrocyclic Fe(III) species derived from 3,3,6,6,9,9-hexamethyl-3,4,8,9-tetrahydro-1H-1,4,8,11-benzotetraazacyclotridecine-2,5,7,10(6H,11H)-tetraone) react rapidly with O(2) in CH(2)Cl(2) or other weakly coordinating solvents to produce black mu-oxo-bridged diiron(IV) complexes, 2, in high yields. Complexes 2 have been characterized by X-ray crystallography (2 cases), microanalytical data, mass spectrometry, UV/Vis, Mossbauer, and (1)H NMR spectroscopies. Mossbauer data show that the diamagnetic Fe-O-Fe unit contains antiferromagnetically coupled S = 1 Fe(IV) sites; diamagnetic (1)H NMR spectra are observed. The oxidation of PPh(3) to OPPh(3) by 2 was confirmed by UV/Vis and GC-MS. Labeling experiments with (18)O(2) and H(2)(18)O established that the bridging oxygen atom of 2 derives from O(2). Complexes 2 catalyze the selective oxidation of benzylic alcohols into the corresponding aldehydes and bleach rapidly organic dyes, such as Orange II in MeCN-H(2)O mixtures; reactivity evidence suggests that free radical autoxidation is not involved. This work highlights a promising development for the advancement of green oxidation technology, as O(2) is an abundant, clean, and inexpensive oxidizing agent.
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Affiliation(s)
- Anindya Ghosh
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
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1968
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Denisov IG, Makris TM, Sligar SG, Schlichting I. Structure and Chemistry of Cytochrome P450. Chem Rev 2005; 105:2253-77. [PMID: 15941214 DOI: 10.1021/cr0307143] [Citation(s) in RCA: 1512] [Impact Index Per Article: 79.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Ilia G Denisov
- Department of Biochemistry, Center for Biophysics and Computational Biology, University of Illinois, Urbana-Champaign, 61801, USA
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1969
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Kennepohl P, Neese F, Schweitzer D, Jackson HL, Kovacs JA, Solomon EI. Spectroscopy of non-heme iron thiolate complexes: insight into the electronic structure of the low-spin active site of nitrile hydratase. Inorg Chem 2005; 44:1826-36. [PMID: 15762709 PMCID: PMC4489710 DOI: 10.1021/ic0487068] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Detailed spectroscopic and computational studies of the low-spin iron complexes [Fe(III)(S2(Me2)N3 (Pr,Pr))(N3)] (1) and [Fe(III)(S2(Me2)N3 (Pr,Pr))]1+ (2) were performed to investigate the unique electronic features of these species and their relation to the low-spin ferric active sites of nitrile hydratases. Low-temperature UV/vis/NIR and MCD spectra of 1 and 2 reflect electronic structures that are dominated by antibonding interactions of the Fe 3d manifold and the equatorial thiolate S 3p orbitals. The six-coordinate complex 1 exhibits a low-energy S(pi) --> Fe 3d(xy) (approximately 13,000 cm(-1)) charge-transfer transition that results predominantly from the low energy of the singly occupied Fe 3d(xy) orbital, due to pure pi interactions between this acceptor orbital and both thiolate donor ligands in the equatorial plane. The 3d(pi) --> 3d(sigma) ligand-field transitions in this species occur at higher energies (>15,000 cm(-1)), reflecting its near-octahedral symmetry. The Fe 3d(xz,yz) --> Fe 3d(xy) (d(pi) --> d(pi)) transition occurs in the near-IR and probes the Fe(III)-S pi-donor bond; this transition reveals vibronic structure that reflects the strength of this bond (nu(e) approximately 340 cm(-1)). In contrast, the ligand-field transitions of the five-coordinate complex 2 are generally at low energy, and the S(pi) --> Fe charge-transfer transitions occur at much higher energies relative to those in 1. This reflects changes in thiolate bonding in the equatorial plane involving the Fe 3d(xy) and Fe 3d(x2-y2) orbitals. The spectroscopic data lead to a simple bonding model that focuses on the sigma and pi interactions between the ferric ion and the equatorial thiolate ligands, which depend on the S-Fe-S bond angle in each of the complexes. These electronic descriptions provide insight into the unusual S = 1/2 ground spin state of these complexes: the orientation of the thiolate ligands in these complexes restricts their pi-donor interactions to the equatorial plane and enforces a low-spin state. These anisotropic orbital considerations provide some intriguing insights into the possible electronic interactions at the active site of nitrile hydratases and form the foundation for further studies into these low-spin ferric enzymes.
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Affiliation(s)
- Pierre Kennepohl
- Departments of Chemistry, Stanford University, Stanford, California 94305
| | - Frank Neese
- Departments of Chemistry, Stanford University, Stanford, California 94305
| | | | | | - Julie A. Kovacs
- University of Washington, Seattle, Washington 98195
- Corresponding authors. (J.A.K.), (E.I.S.)
| | - Edward I. Solomon
- Departments of Chemistry, Stanford University, Stanford, California 94305
- Corresponding authors. (J.A.K.), (E.I.S.)
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1970
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Quiñonero D, Morokuma K, Musaev DG, Mas-Ballesté R, Que L. Metal−Peroxo versus Metal−Oxo Oxidants in Non-Heme Iron-Catalyzed Olefin Oxidations: Computational and Experimental Studies on the Effect of Water. J Am Chem Soc 2005; 127:6548-9. [PMID: 15869272 DOI: 10.1021/ja051062y] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Computational and experimental studies show that Fe(BPMEN)-catalyzed olefin oxidation has two (FeIII-OOH and FeV=O) oxidant species, which act with comparable activation barriers. The presence of water favors formation of an HO-FeV=O oxidant via water-assisted O-OH bond cleavage and leads to both epoxide and cis-diol products. In the absence of water, the oxidant is the FeIII-OOH [or (MeCN)FeIII-OOH], and oxidation mainly leads to epoxide. This conclusion differs from that derived from DFT investigations of iron-porphyrin-catalyzed olefin epoxidation, where the FeIII-OOH pathway is deemed too high in energy to be plausible. The difference between these two systems may lie in the more flexible coordination environment of the non-heme iron complex, which has an available adjacent coordination site that contributes to the activation of the peroxide in both wa and nwa pathways.
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Affiliation(s)
- David Quiñonero
- Cherry L. Emerson Center for Scientific Computation and Department of Chemistry, Emory University, 1515 Dickey Drive, Atlanta, GA 30322, USA
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1971
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Hewitson KS, Granatino N, Welford RWD, McDonough MA, Schofield CJ. Oxidation by 2-oxoglutarate oxygenases: non-haem iron systems in catalysis and signalling. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2005; 363:807-28; discussion 1035-40. [PMID: 15901537 DOI: 10.1098/rsta.2004.1540] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
The 2-oxoglutarate (2OG) and ferrous iron dependent oxygenases are a superfamily of enzymes that catalyse a wide range of reactions including hydroxylations, desaturations and oxidative ring closures. Recently, it has been discovered that they act as sensors in the hypoxic response in humans and other animals. Substrate oxidation is coupled to conversion of 2OG to succinate and carbon dioxide. Kinetic, spectroscopic and structural studies are consistent with a consensus mechanism in which ordered binding of (co)substrates enables control of reactive intermediates. Binding of the substrate to the active site triggers the enzyme for ligation of dioxygen to the metal. Oxidative decarboxylation of 2OG then generates the ferryl species thought to mediate substrate oxidation. Structural studies reveal a conserved double-stranded beta-helix core responsible for binding the iron, via a 2His-1carboxylate motif and the 2OG side chain. The rigidity of this core contrasts with the conformational flexibility of surrounding regions that are involved in binding the substrate. Here we discuss the roles of 2OG oxygenases in terms of the generic structural and mechanistic features that render the 2OG oxygenases suited for their functions.
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Affiliation(s)
- K S Hewitson
- The Department of Chemistry and The Oxford Centre for Molecular Sciences, Chemistry Research Laboratory, Mansfield Road, Oxford OX1 3TA, UK
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1972
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Rohde JU, Que L. Axial Coordination of Carboxylate Activates the Non-heme FeIV?O Unit. Angew Chem Int Ed Engl 2005. [DOI: 10.1002/ange.200462631] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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1973
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Hitomi Y, Ando A, Matsui H, Ito T, Tanaka T, Ogo S, Funabiki T. Aerobic Catechol Oxidation Catalyzed by a Bis(μ-oxo)dimanganese(III,III) Complex via a Manganese(II)−Semiquinonate Complex. Inorg Chem 2005; 44:3473-8. [PMID: 15877428 DOI: 10.1021/ic050109d] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A 3,5-di-tert-butyl-1,2-semiquinonato (DTBSQ) adduct of Mn(II) was prepared by a reaction between Mn(II)(TPA)Cl(2) (TPA = tris(pyridin-2-ylmethyl)amine) and DTBSQ anion and was isolated as a tetraphenylborate salt. The X-ray crystal structure revealed that the complex is formulated as a manganese(II)-semiquinonate complex [Mn(II)(TPA)(DTBSQ)](+) (1). The electronic spectra in solution also indicated the semiquinonate coordination to Mn. The exposure of 1 in acetonitrile to dioxygen afforded 3,5-di-tert-butyl-1,2-benzoquione and a bis(mu-oxo)dimanganese(III,III) complex [Mn(III)(2)(mu-oxo)(2)(TPA)(2)](2+) (2). The reaction of 2 with 3,5-di-tert-butylcatechol (DTBCH(2)) quantitatively afforded two equivalents of 1 under anaerobic conditions. The highly efficient catalytic oxidation of DTBCH(2) with dioxygen was achieved by combining the above two reactions, that is, by constructing a catalytic cycle involving both manganese complexes 1 and 2. It was revealed that dioxygen is reduced to water but not to hydrogen peroxide in the catalytic cycle.
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Affiliation(s)
- Yutaka Hitomi
- Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Japan. hitomi@moleng@.kyoto-u.ac.jp
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1974
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Decker A, Solomon EI. Comparison of FeIV?O Heme and Non-heme Species: Electronic Structures, Bonding, and Reactivities. Angew Chem Int Ed Engl 2005. [DOI: 10.1002/ange.200462182] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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1975
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Kersteen EA, Higgin JJ, Raines RT. Production of human prolyl 4-hydroxylase in Escherichia coli. Protein Expr Purif 2005; 38:279-91. [PMID: 15555944 DOI: 10.1016/j.pep.2004.09.008] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2004] [Revised: 09/07/2004] [Indexed: 11/28/2022]
Abstract
Prolyl 4-hydroxylase (P4H) catalyzes the post-translational hydroxylation of proline residues in collagen strands. The enzyme is an alpha2beta2 tetramer in which the alpha subunits contain the catalytic active sites and the beta subunits (protein disulfide isomerase) maintain the alpha subunits in a soluble and active conformation. Heterologous production of the native alpha2beta2 tetramer is challenging and had not been reported previously in a prokaryotic system. Here, we describe the production of active human P4H tetramer in Escherichia coli from a single bicistronic vector. P4H production requires the relatively oxidizing cytosol of Origami B(DE3) cells. Induction of the wild-type alpha(I) cDNA in these cells leads to the production of a truncated alpha subunit (residues 235-534), which assembles with the beta subunit. This truncated P4H is an active enzyme, but has a high Km value for long substrates. Replacing the Met235 codon with one for leucine removes an alternative start codon and enables production of full-length alpha subunit and assembly of the native alpha2beta2 tetramer in E. coli cells to yield 2 mg of purified P4H per liter of culture (0.2 mg/g of cell paste). We also report a direct, automated assay of proline hydroxylation using high-performance liquid chromatography. We anticipate that these advances will facilitate structure-function analyses of P4H.
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Affiliation(s)
- Elizabeth A Kersteen
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
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1976
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Rohde JU, Que L. Axial Coordination of Carboxylate Activates the Non-heme FeIV?O Unit. Angew Chem Int Ed Engl 2005; 44:2255-8. [PMID: 15739239 DOI: 10.1002/anie.200462631] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Jan-Uwe Rohde
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant Street SE, Minneapolis, MN 55455, USA
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1977
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Long AJ, Clifton IJ, Roach PL, Baldwin JE, Rutledge PJ, Schofield CJ. Structural Studies on the Reaction of Isopenicillin N Synthase with the Truncated Substrate Analogues δ-(l-α-aminoadipoyl)-l-cysteinyl-glycine and δ-(l-α-aminoadipoyl)-l-cysteinyl-d-alanine,. Biochemistry 2005; 44:6619-28. [PMID: 15850395 DOI: 10.1021/bi047478q] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Isopenicillin N synthase (IPNS), a non-heme iron(II)-dependent oxidase, catalyzes conversion of the tripeptide delta-(l-alpha-aminoadipoyl)-l-cysteinyl-d-valine (ACV) to bicyclic isopenicillin N (IPN), concomitant with the reduction of dioxygen to two molecules of water. Incubation of the "truncated"substrate analogues delta-(l-alpha-aminoadipoyl)-l-cysteinyl-glycine (ACG) and delta-(l-alpha-aminoadipoyl)-l-cysteinyl-d-alanine (ACA) with IPNS has previously been shown to afford acyclic products, in which the substrate cysteinyl residue has undergone a two-electron oxidation. We report X-ray crystal structures for the anaerobic IPNS/Fe(II)/ACG and IPNS/Fe(II)/ACA complexes, both in the absence and presence of the dioxygen analogue nitric oxide. The overall protein structures are very similar to those of the corresponding IPNS/Fe(II)/ACV complexes; however, significant differences are apparent in the vicinity of the active site iron. The structure of the IPNS/Fe(II)/ACG complex reveals that the C-terminal carboxylate of this substrate is oriented toward the active site iron atom, apparently hydrogen-bonded to an additional water ligand at the metal; this is a different binding mode to that observed in the IPNS/Fe(II)/ACV complex. ACA binds to the metal in a manner that is intermediate between those observed for ACV and ACG. The addition of NO to these complexes initiates conformational changes such that both the IPNS/Fe(II)/ACG/NO and IPNS/Fe(II)/ACA/NO structures closely resemble the IPNS/Fe(II)/ACV/NO complex. These results further demonstrate the feasibility of metal-centered rearrangements in catalysis by non-heme iron enzymes and provide insight into the delicate balance between hydrophilic-hydrophobic interactions and steric effects in the IPNS active site.
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1978
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Schöneboom JC, Neese F, Thiel W. Toward Identification of the Compound I Reactive Intermediate in Cytochrome P450 Chemistry: A QM/MM Study of Its EPR and Mössbauer Parameters. J Am Chem Soc 2005; 127:5840-53. [PMID: 15839682 DOI: 10.1021/ja0424732] [Citation(s) in RCA: 235] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Quantum mechanical/molecular mechanical (QM/MM) methods have been used in conjunction with density functional theory (DFT) and correlated ab initio methods to predict the electron paramagnetic resonance (EPR) and Mossbauer (MB) properties of Compound I in P450(cam). For calibration purposes, a small Fe(IV)-oxo complex [Fe(O)(NH(3))(4)(H(2)O)](2+) was studied. The (3)A(2) and (5)A(1) states (in C(4)(v)() symmetry) are found to be within 0.1-0.2 eV. The large zero-field splitting (ZFS) of the (FeO)(2+) unit in the (3)A(2) state arises from spin-orbit coupling with the low-lying quintet and singlet states. The intrinsic g-anisotropy is very small. The spectroscopic properties of the model complex [Fe(O)(TMC)(CH(3)CN)](2+) (TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane) are well reproduced by theory. In the model complexes [Fe(O)(TMP)(X)](+) (TMP = tetramesitylporphyrin, X = nothing or H(2)O) the computations again account for the observed spectroscopic properties and predict that the coupling of the (5)A(1) state of the (FeO)(2+) unit to the porphyrin radical leads to a low-lying sextet/quartet manifold approximately 12 kcal/mol above the quartet ground state. The calculations on cytochrome P450(cam), with and without the simulation of the protein environment by point charges, predict a small antiferromagnetic coupling (J approximately -13 to -16 cm(-)(1); H(HDvV) = - 2JS(A)S(B)) and a large ZFS > 15 cm(-)(1) (with E/D approximately 1/3) which will compete with the exchange coupling. This leads to three Kramers doublets of mixed multiplicity which are all populated at room temperature and may therefore contribute to the observed reactivity. The MB and ligand hyperfine couplings ((14)N, (1)H) are fairly sensitive to the protein environment which controls the spin density distribution between the porphyrin ring and the axial cysteinate ligand.
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Affiliation(s)
- Jan C Schöneboom
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany
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1979
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Peters L, Hübner E, Burzlaff N. The new facial tripod ligand 3,3-bis(1-methylimidazol-2-yl)propionic acid and carbonyl complexes thereof containing manganese and rhenium. J Organomet Chem 2005. [DOI: 10.1016/j.jorganchem.2004.11.041] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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1980
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1981
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Kujime M, Fujii H. Synthesis of sterically hindered tris(4-imidazolyl)carbinol ligands and their copper(I) complexes related to metalloenzymes. Tetrahedron Lett 2005. [DOI: 10.1016/j.tetlet.2005.02.122] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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1982
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Decker A, Solomon EI. Dioxygen activation by copper, heme and non-heme iron enzymes: comparison of electronic structures and reactivities. Curr Opin Chem Biol 2005; 9:152-63. [PMID: 15811799 DOI: 10.1016/j.cbpa.2005.02.012] [Citation(s) in RCA: 180] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Enzymes containing heme, non-heme iron and copper active sites play important roles in the activation of dioxygen for substrate oxidation. One key reaction step is CH bond cleavage through H-atom abstraction. On the basis of the ligand environment and the redox properties of the metal, these enzymes employ different methods of dioxygen activation. Heme enzymes are able to stabilize the very reactive iron(IV)-oxo porphyrin-radical intermediate. This is generally not accessible for non-heme iron systems, which can instead use low-spin ferric-hydroperoxo and iron(IV)-oxo species as reactive oxidants. Copper enzymes employ still a different strategy and achieve H-atom abstraction potentially through a superoxo intermediate. This review compares and contrasts the electronic structures and reactivities of these various oxygen intermediates.
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Affiliation(s)
- Andrea Decker
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
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1983
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Shan X, Que L. Intermediates in the oxygenation of a nonheme diiron(II) complex, including the first evidence for a bound superoxo species. Proc Natl Acad Sci U S A 2005; 102:5340-5. [PMID: 15802473 PMCID: PMC556236 DOI: 10.1073/pnas.0409640102] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The reaction of [Fe(2)(mu-OH)(2)(6-Me(3)-TPA)(2)](2+) (1) [6-Me(3)-TPA, Tris(6-methyl-2-pyridylmethyl)amine] with O(2) in CH(2)Cl(2) at -80 degrees C gives rise to two new intermediates, 2 and 3, before the formation of previously characterized [Fe(2)(O)(O(2))(6-Me(3)-TPA)(2)](2+) (4) that allow the oxygenation reaction to be monitored one electron-transfer step at a time. Raman evidence assigns 2 and 3 as a diiron-superoxo species and a diiron-peroxo species, respectively. Intermediate 2 exhibits its nu(O-O) at 1,310 cm(-1) with a -71-cm(-1) (18)O isotope shift. A doublet peak pattern for the (16)O(18)O isotopomer of 2 in mixed-isotope Raman experiments strongly suggests that the superoxide ligand of 2 is bound end-on. This first example of a nonheme iron-superoxo intermediate exhibits the highest frequency nu(O-O) yet observed for a biomimetic metal-dioxygen adduct. The bound superoxide of 2, unlike the bound peroxide of 4, is readily reduced by 2,4-di-tert-butylphenol via a proton-coupled electron-transfer mechanism, emphasizing that metal-superoxo species may serve as oxidants in oxygen activation mechanisms of metalloenzymes. The discovery of intermediates 2 and 3 allows us to dissect the initial steps of dioxygen binding at a diiron center leading to its activation for substrate oxidation.
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Affiliation(s)
- Xiaopeng Shan
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant Street Southeast, Minneapolis, MN 55455, USA
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1984
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Bénisvy L, Chottard JC, Marrot J, Li Y. Iron-Assisted Oxidative Radical C-C Bond Cleavage. Eur J Inorg Chem 2005. [DOI: 10.1002/ejic.200400782] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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1985
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Koehntop KD, Emerson JP, Que L. The 2-His-1-carboxylate facial triad: a versatile platform for dioxygen activation by mononuclear non-heme iron(II) enzymes. J Biol Inorg Chem 2005; 10:87-93. [PMID: 15739104 DOI: 10.1007/s00775-005-0624-x] [Citation(s) in RCA: 352] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2004] [Accepted: 01/04/2005] [Indexed: 10/25/2022]
Abstract
General knowledge of dioxygen-activating mononuclear non-heme iron(II) enzymes containing a 2-His-1-carboxylate facial triad has significantly expanded in the last few years, due in large part to the extensive library of crystal structures that is now available. The common structural motif utilized by this enzyme superfamily acts as a platform upon which a wide assortment of substrate transformations are catalyzed. The facial triad binds a divalent metal ion at the active site, which leaves the opposite face of the octahedron available to coordinate a variety of exogenous ligands. The binding of substrate activates the metal center for attack by dioxygen, which is subsequently converted to a high-valent iron intermediate, a formidable oxidizing species. Herein, we summarize crystallographic and mechanistic features of this metalloenzyme superfamily, which has enabled the proposal of a common but flexible pathway for dioxygen activation.
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Affiliation(s)
- Kevin D Koehntop
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, 55455, USA
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1986
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Bou-Abdallah F, Zhao G, Mayne HR, Arosio P, Chasteen ND. Origin of the Unusual Kinetics of Iron Deposition in Human H-Chain Ferritin. J Am Chem Soc 2005; 127:3885-93. [PMID: 15771525 DOI: 10.1021/ja044355k] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
From microorganisms to humans, ferritin plays a central role in the biological management of iron. The ferritins function as iron storage and detoxification proteins by oxidatively depositing iron as a hydrous ferric hydroxide mineral core within their shell-like structures. The mechanism by which the mineral core is formed has been the subject of intense investigation for many years. A diiron ferroxidase site located on the H-chain subunit of vertebrate ferritins catalyzes the oxidation of Fe(II) to Fe(III) by molecular oxygen. A previous stopped-flow kinetics study of a transient mu-peroxodiFe(III) intermediate formed at this site revealed very unusual kinetics curves, the shape of which depended markedly on the amount of iron presented to the protein. In the present work, a mathematical model for catalysis is developed that explains the observed kinetics. The model consists of two sequential mechanisms. In the first mechanism, turnover of iron at the ferroxidase site is rapid, resulting in steady-state production of the peroxo intermediate with continual formation of the mineral core until the available Fe(II) in solution is consumed. At this point, the second mechanism comes into play whereby the peroxo intermediate decays and the ferroxidase site is postulated to vacate its complement of iron. The kinetic data reveal for the first time that Fe(II) in excess of that required to saturate the ferroxidase site promotes rapid turnover of Fe(III) at this site and that the ferroxidase site plays a role in catalysis at all levels of iron loading of the protein (48-800 Fe/protein). The data also provide evidence for a second intermediate, a putative hydroperoxodiFe(III) complex, that is a decay product of the peroxo intermediate.
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Affiliation(s)
- Fadi Bou-Abdallah
- Department of Chemistry, University of New Hampshire, Durham, New Hampshire 03824, USA
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1987
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Kim SO, Sastri CV, Seo MS, Kim J, Nam W. Dioxygen Activation and Catalytic Aerobic Oxidation by a Mononuclear Nonheme Iron(II) Complex. J Am Chem Soc 2005; 127:4178-9. [PMID: 15783193 DOI: 10.1021/ja043083i] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have used dioxygen, not artificial oxidants such as peracids, iodosylarenes, and hydroperoxides, in the generation of a mononuclear nonheme oxoiron(IV) complex, [Fe(IV)(TMC)(O)]2+ (TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane), from its corresponding Fe(II) complex, [Fe(TMC)(CF3SO3)2]. The formation of oxoiron(IV) species by activating dioxygen was markedly dependent on iron(II) complexes and solvents, and this observation was interpreted with the electronic effect of iron(II) complexes on dioxygen activation to form oxoiron(IV) species. A catalytic aerobic oxidation of organic substrates was demonstrated in the presence of the [Fe(TMC)]2+ complex. By carrying out 18O-labeled water experiment, we were able to conclude that the oxidation of organic substrates was mediated by an oxoiron(IV) intermediate, not by a radical type of autoxidation process.
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Affiliation(s)
- Sun Ok Kim
- Department of Chemistry and Center for Biomimetic Systems, Ewha Womans University, Seoul 120-750, Korea
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1988
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Rohde JU, Torelli S, Shan X, Lim MH, Klinker EJ, Kaizer J, Chen K, Nam W, Que L. Structural insights into nonheme alkylperoxoiron(III) and oxoiron(IV) intermediates by X-ray absorption spectroscopy. J Am Chem Soc 2005; 126:16750-61. [PMID: 15612713 DOI: 10.1021/ja047667w] [Citation(s) in RCA: 130] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Transient mononuclear low-spin alkylperoxoiron(III) and oxoiron(IV) complexes that are relevant to the activation of dioxygen by nonheme iron enzymes have been generated from synthetic iron(II) complexes of neutral tetradentate (TPA) and pentadentate (N4Py, Bn-TPEN) ligands and structurally characterized by means of Fe K-edge X-ray absorption spectroscopy (XAS). Notable features obtained from fits of the EXAFS region are Fe-O bond lengths of 1.78 A for the alkylperoxoiron(III) intermediates and 1.65-1.68 A for the oxoiron(IV) intermediates, reflecting different strengths in the Fe-O pi interactions. These differences are also observed in the intensities of the 1s-to-3d transitions in the XANES region, which increase from 4 units for the nearly octahedral iron(II) precursor to 9-15 units for the alkylperoxoiron(III) intermediates to 25-29 units for the oxoiron(IV) species.
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Affiliation(s)
- Jan-Uwe Rohde
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant Street SE, Minneapolis, MN 55455, USA
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1989
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Bruijnincx PCA, Lutz M, Spek, AL, van Faassen EE, Weckhuysen BM, van Koten G, Klein Gebbink RJM. Bis(1-methylimidazol-2-yl)propionates and Bis(1-methylbenzimidazol-2-yl)-propionates: A New Family of BiomimeticN,N,OLigands - Synthesis, Structures and CuII Coordination Complexes. Eur J Inorg Chem 2005. [DOI: 10.1002/ejic.200400830] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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1990
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Abstract
Hypoxia-inducible factor (HIF) is an alpha,beta-heterodimeric transcription factor that mediates cellular responses to low oxygen concentration via the transcriptional activation of specific genes involved in both tumorogenesis and angiogenesis. Manipulation of the HIF pathway has potential use for the treatment of ischemic disease and cancer. Unlike HIF-beta, which is constitutively expressed, the levels and activity of the HIF-alpha subunit are regulated by processes involving posttranslational hydroxylation, catalyzed by Fe(II)- and 2-oxoglutarate-dependent oxygenases. This review focuses on the HIF pathway as a therapeutic target.
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Affiliation(s)
- Kirsty S Hewitson
- Oxford Centre for Molecular Sciences and the Department of Chemistry, Chemistry Research Laboratory, Mansfield Road, Oxford, OX1 3TA, UK.
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1991
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Hetterscheid DGH, Kaiser J, Reijerse E, Peters TPJ, Thewissen S, Blok ANJ, Smits JMM, de Gelder R, de Bruin B. IrII(ethene): Metal or Carbon Radical? J Am Chem Soc 2005; 127:1895-905. [PMID: 15701024 DOI: 10.1021/ja0439470] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
One-electron oxidation of [(Me(n)tpa)Ir(I)(ethene)]+ complexes (Me(3)tpa = N,N,N-tri(6-methyl-2-pyridylmethyl)amine; Me(2)tpa = N-(2-pyridylmethyl)-N,N,-di[(6-methyl-2-pyridyl)methyl]-amine) results in relatively stable, five-coordinate Ir(II)-olefin species [(Me(n)tpa)Ir(II)(ethene)](2+) (1(2+): n = 3; 2(2+): n = 2). These contain a "vacant site" at iridium and a "non-innocent" ethene fragment, allowing radical type addition reactions at both the metal and the ethene ligand. The balance between metal- and ligand-centered radical behavior is influenced by the donor capacity of the solvent. In weakly coordinating solvents, 1(2+) and 2(2+) behave as moderately reactive metallo-radicals. Radical coupling of 1(2+) with NO in acetone occurs at the metal, resulting in dissociation of ethene and formation of the stable nitrosyl complex [(Me(3)tpa)Ir(NO)](2+) (6(2+)). In the coordinating solvent MeCN, 1(2+) generates more reactive radicals; [(Me(3)tpa)Ir(MeCN)(ethene)](2+) (9(2+)) by MeCN coordination, and [(Me(3)tpa)Ir(II)(MeCN)](2+) (10(2+)) by substitution of MeCN for ethene. Complex 10(2+) is a metallo-radical, like 1(2+) but more reactive. DFT calculations indicate that 9(2+) is intermediate between the slipped-olefin Ir(II)(CH(2)=CH(2)) and ethyl radical Ir(III)-CH(2)-CH(2). resonance structures, of which the latter prevails. The ethyl radical character of 9(2+) allows radical type addition reactions at the ethene ligand. Complex 2(2+) behaves similarly in MeCN. In the absence of further reagents, 1(2+) and 2(2+) convert to the ethylene bridged species [(Me(n)tpa)(MeCN)Ir(III)(mu(2)-C(2)H(4))Ir(III)(MeCN)(Me(3)tpa)](4+) (n = 3: 3(4+); n = 2: 4(4+)) in MeCN. In the presence of TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxo), formation of 3(4+) from 1(2+) in MeCN is completely suppressed and only [(Me(3)tpa)Ir(III)(TEMPO(-))(MeCN)](2+) (7(2+)) is formed. This is thought to proceed via radical coupling of TEMPO at the metal center of 10(2+). In the presence of water, hydrolysis of the coordinated acetonitrile fragment of 7(2+) results in the acetamido complex [(Me(3)tpa)Ir(III)(NHC(O)CH(3)))(TEMPOH)](2+) (8(2+)).
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Affiliation(s)
- Dennis G H Hetterscheid
- Radboud University Nijmegen, Institute for Molecules and Materials, Department of Metal-Organic Chemistry, Toernooiveld 1, NL-6525 ED Nijmegen (The Netherlands)
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1992
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Brown SD, Peters JC. Ground-State Singlet L3Fe-(μ-N)-FeL3 and L3Fe(NR) Complexes Featuring Pseudotetrahedral Fe(II) Centers. J Am Chem Soc 2005; 127:1913-23. [PMID: 15701026 DOI: 10.1021/ja0453073] [Citation(s) in RCA: 169] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Pseudotetrahedral iron(II) coordination complexes that contain bridged nitride and terminal imide linkages, and exhibit singlet ground-state electronic configurations, are described. Sodium amalgam reduction of the ferromagnetically coupled dimer, {[PhBP(3)]Fe(mu-1,3-N(3))}(2) (2) ([PhBP(3)] = [PhB(CH(2)PPh(2))(3)](-)), yields the diamagnetic bridging nitride species [{[PhBP(3)]Fe}(2)(mu-N)][Na(THF)(5)] (3). The Fe-N-Fe linkage featured in the anion of 3 exhibits an unusually bent angle of approximately 135 degrees , and the short Fe-N bond distances (Fe-N(av) approximately equal to 1.70 A) suggest substantial Fe-N multiple bond character. The diamagnetic imide complex {[PhBP(3)]Fe(II)(triple bond)N(1-Ad)}{(n)()Bu(4)N} (4) has been prepared by sodium amalgam reduction of its low-spin iron(III) precursor, [PhBP(3)]Fe(III)(triple bond)N(1-Ad) (5). Complexes 4 and 5 have been structurally characterized, and their respective electronic structures are discussed in the context of a supporting DFT calculation. Diamagnetic 4 provides a bona fide example of a pseudotetrahedral iron(II) center in a low-spin ground-state configuration. Comparative optical data strongly suggest that dinuclear 3 is best described as containing two high-spin iron(II) centers that are strongly antiferromagnetically coupled to give rise to a singlet ground-state at room temperature.
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Affiliation(s)
- Steven D Brown
- Division of Chemistry and Chemical Engineering, Arnold and Mabel Beckman Laboratories of Chemical Synthesis, California Institute of Technology, Pasadena, CA 91125, USA
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1993
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Spiering MJ, Moon CD, Wilkinson HH, Schardl CL. Gene clusters for insecticidal loline alkaloids in the grass-endophytic fungus Neotyphodium uncinatum. Genetics 2005; 169:1403-14. [PMID: 15654104 PMCID: PMC1449547 DOI: 10.1534/genetics.104.035972] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Loline alkaloids are produced by mutualistic fungi symbiotic with grasses, and they protect the host plants from insects. Here we identify in the fungal symbiont, Neotyphodium uncinatum, two homologous gene clusters (LOL-1 and LOL-2) associated with loline-alkaloid production. Nine genes were identified in a 25-kb region of LOL-1 and designated (in order) lolF-1, lolC-1, lolD-1, lolO-1, lolA-1, lolU-1, lolP-1, lolT-1, and lolE-1. LOL-2 contained the homologs lolC-2 through lolE-2 in the same order and orientation. Also identified was lolF-2, but its possible linkage with either cluster was undetermined. Most lol genes were regulated in N. uncinatum and N. coenophialum, and all were expressed concomitantly with loline-alkaloid biosynthesis. A lolC-2 RNA-interference (RNAi) construct was introduced into N. uncinatum, and in two independent transformants, RNAi significantly decreased lolC expression (P < 0.01) and loline-alkaloid accumulation in culture (P < 0.001) compared to vector-only controls, indicating involvement of lolC in biosynthesis of lolines. The predicted LolU protein has a DNA-binding site signature, and the relationships of other lol-gene products indicate that the pathway has evolved from various different primary and secondary biosynthesis pathways.
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Affiliation(s)
- Martin J Spiering
- Department of Plant Pathology, University of Kentucky, Lexington, 40546-0312, USA
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1994
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Bassan A, Blomberg MRA, Siegbahn PEM, Que L. A Density Functional Study on a Biomimetic Non-Heme Iron Catalyst: Insights into Alkane Hydroxylation by a Formally HO?FeV?O Oxidant. Chemistry 2005; 11:692-705. [PMID: 15580652 DOI: 10.1002/chem.200400383] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The reactivity of [HO-(tpa)Fe(V)=O] (TPA=tris(2-pyridylmethyl)amine), derived from O-O bond heterolysis of its [H(2)O-(tpa)Fe(III)-OOH] precursor, was explored by means of hybrid density functional theory. The mechanism for alkane hydroxylation by the high-valent iron-oxo species invoked as an intermediate in Fe(tpa)/H(2)O(2) catalysis was investigated. Hydroxylation of methane and propane by HO-Fe(V)=O was studied by following the rebound mechanism associated with the heme center of cytochrome P450, and it is demonstrated that this species is capable of stereospecific alkane hydroxylation. The mechanism proposed for alkane hydroxylation by HO-Fe(V)=O accounts for the experimentally observed incorporation of solvent water into the products. An investigation of the possible hydroxylation of acetonitrile (i.e., the solvent used in the experiments) shows that the activation energy for hydrogen-atom abstraction by HO-Fe(V)=O is rather high and, in fact, rather similar to that of methane, despite the similarity of the H-CH(2)CN bond strength to that of the secondary C-H bond in propane. This result indicates that the kinetics of hydrogen-atom abstraction are strongly affected by the cyano group and rationalizes the lack of experimental evidence for solvent hydroxylation in competition with that of substrates such as cyclohexane.
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1995
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Paine TK, Zheng H, Que L. Iron Coordination Chemistry of Phenylpyruvate: An Unexpected κ3-Bridging Mode That Leads to Oxidative Cleavage of the C2−C3 Bond. Inorg Chem 2005; 44:474-6. [PMID: 15679371 DOI: 10.1021/ic048427k] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
One mononuclear iron(II)-phenylpyruvate complex [Tp(Ph2)Fe(II)(PPH)] (1) of the tridentate face-capping Tp(Ph2) ligand and two dinuclear iron(II)-phenylpyruvate enolate complexes [(6-Me3-TPA)2Fe(II)2(PP)]2+ (2) and [(6-Me3-TPA)2Fe(II)2(2-NO2-PP)]2+ (3) of the tetradentate 6-Me3-TPA ligand are reported to demonstrate two different binding modes of phenylpyruvate to the iron(II) centers. Phenylpyruvate binds in a kappa2-(O,O) manner to the mononuclear Fe(II)(Tp(Ph2)) center of 1 but bridges in a kappa3-(O,O,O) fashion to the two Fe(II)(6-Me3-TPA) centers of 2 and 3. Mononuclear complex 1 reacts with O2 to undergo oxidative decarboxylation and ortho-hydroxylation of one of the aromatic rings of the Tp(Ph2) ligand. In contrast, dinuclear complexes 2 and 3 react with O2 to undergo oxidative cleavage of the C2-C3 bond of phenylpyruvate.
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Affiliation(s)
- Tapan K Paine
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St. S.E., Minneapolis, Minnesota 55455, USA
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1996
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Hitomi Y, Higuchi M, Minami H, Tanaka T, Funabiki T. Tuning of spin crossover equilibrium in catecholatoiron(iii) complexes by supporting ligands. Chem Commun (Camb) 2005:1758-60. [PMID: 15791323 DOI: 10.1039/b418678h] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Introduction of electron-withdrawing groups on co-ligands effectively raises the spin crossover temperature of catecholatoiron(III) complexes and induces a significant amount of the low spin species in solution even at around room temperature.
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Affiliation(s)
- Yutaka Hitomi
- Department of Molecular Engineering, Kyoto University, Kyoto Daigaku Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.
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1997
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Control of the catalytic oxidations mediated by an oxo-bridged non-heme diiron complex: role of additives and reaction conditions. ACTA ACUST UNITED AC 2005. [DOI: 10.1016/j.molcata.2004.09.002] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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1998
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1999
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Hitomi Y, Yoshida M, Higuchi M, Minami H, Tanaka T, Funabiki T. A linear correlation between energy of LMCT band and oxygenation reaction rate of a series of catecholatoiron(III) complexes: initial oxygen binding during intradiol catechol oxygenation. J Inorg Biochem 2005; 99:755-63. [PMID: 15708796 DOI: 10.1016/j.jinorgbio.2004.12.004] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2004] [Revised: 11/29/2004] [Accepted: 12/02/2004] [Indexed: 11/19/2022]
Abstract
The oxygen reactivity of catecholatoiron(III) complexes has been examined using a series of catecholate ligands as the substrate. All the complexes examined here, [Fe(III)(TPA)(R-Cat)]BPh(4) (1-9) (TPA: tris(pyridin-2-ylmethyl)amine; R-Cat: substituted catecholate ligand, R=3,5-(t)Bu(2) (1), 3,6-(t)Bu2 (2), 3,5-Me2 (3), 3,6-Me2 (4), 4-(t)Bu (5), 4-Me (6), H (7), 4-Cl (8) and 3-Cl (9)), exclusively afforded the intradiol cleaving products of the catecholate ligands upon exposure to O2. It was revealed that 1-7 can be categorized into two classes based on their electrochemical properties; i.e., the complexes having the dialkyl-substituted (group A) and the mono- or non-substituted (group B) catecholate ligands. In spite of their classification, these two groups show a linear correlation between the logarithm of the reaction rate constant with O2 and the energy of the catecholate-to-iron(III) LMCT band, although 2 shows a large negative deviation from the correlation line. Based on this LMCT-energy dependent reactivity of 1 and 3-9 as well as the very low reactivity of 2, we have discussed on the mechanisms of the reaction of [Fe(III)(TPA)(R-Cat)]BPh4 with O2.
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Affiliation(s)
- Yutaka Hitomi
- Department of Molecular Engineering, Kyoto University, Kyoto Daigaku Katsura, Nishikyo-ku, Kyoto 6158510, Japan
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2000
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Tajika Y, Tsuge K, Sasaki Y. Mononuclear oxovanadium complexes of tris(2-pyridylmethyl)amine. Dalton Trans 2005:1438-47. [PMID: 15824782 DOI: 10.1039/b414532a] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Mononuclear oxovanadium(IV) and dioxovanadium(V) complexes of tris(2-pyridylmethyl)amine (tpa) have been prepared for the first time. Crystal structure determinations of three oxovanadium(IV) complexes, [VO(SO4)(tpa)], [VOCl(tpa)]PF6, or [VOBr(tpa)]PF6, and a dioxovanadium(v) complex [V(O)2(tpa)]PF6 disclosed that the tertiary nitrogen of the tpa ligand always occupies the trans-to-oxo site. The structures of an oxo-peroxo complex [VO(O2)(tpa)]Cl that was prepared previously and of a mu-oxo vanadium(III) complex [{VCl(tpa)}2(mu-O)](PF6)2 have also been determined. The tertiary nitrogen is located at a trans site to the peroxo and chloride ligands, respectively. The total sums of the four V-N bond lengths from the tpa ligand are remarkably similar among the six complexes, indicating that the vanadium oxidation states become less influential in tpa bonding due primarily to the coordination of electron-donating oxo ligand(s). Absorption spectra of [VOCl(tpa)]+ in acetonitrile showed a significant change upon addition of p-toluenesulfonic acid and HClO4, but not on addition of benzoic acid. Protonation at the oxo ligand by the former two acids is suggested. Cyclic voltammetric studies in acetonitrile verified the proton-coupled redox behavior of the V(III)/V(IV) process involving the oxo ligand for the first time. From the dependence of the added p-toluenesulfonic acid to the CV, redox potentials for the following species have been estimated: [V(IV)OCl(tpa)]+/[V(III)OCl(tpa)](E1/2=-1.59 V vs. Fc+/Fc), [V(IV)(OH)Cl(tpa)]2+/[V(III)(OH)Cl(tpa)]+(Epc=-1.34 V), [V(IV)(OH2)Cl(tpa)]3+/[V(III)(OH2)Cl(tpa)]2+(Epa=-0.49 V), and [V(IV)Cl2(tpa)]2+/[V(III)Cl2(tpa)]+(E1/2=-0.89 V). The reduction of [V(V)(O)2(tpa)]+ in 0.05 M [(n-Bu)4N]PF6 acetonitrile showed a major irreversible reduction wave V(V)/(IV) at -1.48 V. The metal reduction potentials of the oxovanadium(IV) and dioxovanadium(V) species are very close, reinforcing the significant influence of the oxo ligand(s).
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Affiliation(s)
- Yasunobu Tajika
- Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo, 060-0810, Japan
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