51
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Suzuki T, Tanaka H, Shiota Y, Sajith PK, Arikawa Y, Yoshizawa K. Proton-Assisted Mechanism of NO Reduction on a Dinuclear Ruthenium Complex. Inorg Chem 2015; 54:7181-91. [PMID: 26186365 DOI: 10.1021/acs.inorgchem.5b00394] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Density-functional-theory (DFT) calculations are performed for the proposal of a plausible mechanism on the reduction of NO to N2O by a dinuclear ruthenium complex, reported by Arikawa and co-workers [J. Am. Chem. Soc. 2007, 129, 14160]. On the basis of the experimental fact that the reduction proceeds under strongly acidic conditions, the role of protons in the mechanistic pathways is investigated with model complexes, where one or two NO ligands are protonated. The reaction mechanism of the NO reduction is partitioned into three steps: reorientation of N2O2 (cis-NO dimer), O-N bond cleavage, and N2O elimination. A key finding is that the protonation of the NO ligand(s) significantly reduces the activation barrier in the rate-determining reorientation step. The activation energy of 43.1 kcal/mol calculated for the proton-free model is reduced to 30.2 and 17.6 kcal/mol for the mono- and diprotonated models, respectively. The protonation induces the electron transfer from the Ru(II)Ru(II) core to the O═N-N═O moiety to give a Ru(III)Ru(III) core and a hyponitrite (O-N═N-O)(2-) species. The formation of the hyponitrite species provides an alternative pathway for the N2O2 reorientation, resulting in the lower activation energies in the presence of proton(s). The protonation also has a marginal effect on the O-N bond cleavage and the N2O elimination steps. Our calculations reveal a remarkable role of protons in the NO reduction via N2O formation and provide new insights into the mechanism of NO reduction catalyzed by metalloenzymes such as nitric oxide reductase (NOR) that contains a diiron active site.
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Affiliation(s)
- Tatsuya Suzuki
- †Institute for Materials Chemistry and Engineering and International Research Center for Molecular System, Kyushu University, Nishi-ku, Fukuoka 819-0395, Japan
| | - Hiromasa Tanaka
- ‡Elements Strategy Initiative for Catalysts and Batteries, Kyoto University, Nishikyo-ku, Kyoto 615-8245, Japan
| | - Yoshihito Shiota
- †Institute for Materials Chemistry and Engineering and International Research Center for Molecular System, Kyushu University, Nishi-ku, Fukuoka 819-0395, Japan
| | - P K Sajith
- †Institute for Materials Chemistry and Engineering and International Research Center for Molecular System, Kyushu University, Nishi-ku, Fukuoka 819-0395, Japan
| | - Yasuhiro Arikawa
- §Division of Chemistry and Materials Science, Graduate School of Engineering, Nagasaki University, Bunkyo-machi 1-14, Nagasaki 852-8521, Japan
| | - Kazunari Yoshizawa
- †Institute for Materials Chemistry and Engineering and International Research Center for Molecular System, Kyushu University, Nishi-ku, Fukuoka 819-0395, Japan.,‡Elements Strategy Initiative for Catalysts and Batteries, Kyoto University, Nishikyo-ku, Kyoto 615-8245, Japan
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52
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Orzeł Ł, Polaczek J, Procner M. Review: Recent advances in the investigations of NO activation on cobalt and manganese porphyrins: a brief review. J COORD CHEM 2015. [DOI: 10.1080/00958972.2015.1068303] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Łukasz Orzeł
- Faculty of Chemistry, Jagiellonian University, Kraków, Poland
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53
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Affiliation(s)
- Ashley M. Wright
- Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, California 93106, United States
| | - Trevor W. Hayton
- Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, California 93106, United States
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54
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Kumar P, Lee YM, Park YJ, Siegler MA, Karlin KD, Nam W. Reactions of Co(III)-nitrosyl complexes with superoxide and their mechanistic insights. J Am Chem Soc 2015; 137:4284-7. [PMID: 25793706 DOI: 10.1021/ja513234b] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
New Co(III)-nitrosyl complexes bearing N-tetramethylated cyclam (TMC) ligands, [(12-TMC)Co(III)(NO)](2+) (1) and [(13-TMC)Co(III)(NO)](2+) (2), were synthesized via [(TMC)Co(II)(CH3CN)](2+) + NO(g) reactions. Spectroscopic and structural characterization showed that these compounds bind the nitrosyl moiety in a bent end-on fashion. Complexes 1 and 2 reacted with KO2/2.2.2-cryptand to produce [(12-TMC)Co(II)(NO2)](+) (3) and [(13-TMC)Co(II)(NO2)](+) (4), respectively; these possess O,O'-chelated nitrito ligands. Mechanistic studies using (18)O-labeled superoxide ((18)O2(•-)) showed that one O atom in the nitrito ligand is derived from superoxide and the O2 produced comes from the other superoxide O atom. Evidence supporting the formation of a Co-peroxynitrite intermediate is also presented.
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Affiliation(s)
- Pankaj Kumar
- †Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea
| | - Yong-Min Lee
- †Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea
| | - Young Jun Park
- †Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea
| | - Maxime A Siegler
- ‡Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Kenneth D Karlin
- ‡Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Wonwoo Nam
- †Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea
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55
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Kurtikyan TS, Hayrapetyan VA, Mehrabyan MM, Ford PC. Six-coordinate nitrito and nitrato complexes of manganese porphyrin. Inorg Chem 2014; 53:11948-59. [PMID: 25369232 DOI: 10.1021/ic5014329] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Reaction of small increments of NO2 gas with sublimed amorphous layers of Mn(II)(TPP) (TPP = meso-tetra-phenylporphyrinato dianion) in a vacuum cryostat leads to formation of the 5-coordinate monodentate nitrato complex Mn(III)(TPP)(η(1)-ONO2) (II). This transformation proceeds through the two distinct steps with initial formation of the five coordinate O-nitrito complex Mn(III)(TPP)(η(1)-ONO) (I) as demonstrated by the electronic absorption spectra and by FTIR spectra using differently labeled nitrogen dioxide. A plausible mechanism for the second stage of reaction is offered based on the spectral changes observed upon subsequent interaction of (15)NO2 and NO2 with the layered Mn(TPP). Low-temperature interaction of I and II with the vapors of various ligands L (L = O-, S-, and N-donors) leads to formation of the 6-coordinate O-nitrito Mn(III)(TPP)(L)(η(1)-ONO) and monodentate nitrato Mn(III)(TPP)(L)(η(1)-ONO2) complexes, respectively. Formation of the 6-coordinate O-nitrito complex is accompanied by the shifts of the ν(N═O) band to lower frequency and of the ν(N-O) band to higher frequency. The frequency difference between these bands Δν = ν(N═O) - ν(N-O) is a function of L and is smaller for the stronger bases. Reaction of excess NH3 with I leads to formation of Mn(TPP)(NH3)(η(1)-ONO) and of the cation [Mn(TPP)(NH3)2](+) plus ionic nitrite. The nitrito complexes are relatively unstable, but several of the nitrato species can be observed in the solid state at room temperature. For example, the tetrahydrofuran complex Mn(TPP)(THF)(η(1)-ONO2) is stable in the presence of THF vapors (∼5 mm), but it loses this ligand upon high vacuum pumping at RT. When L = dimethylsulfide (DMS), the nitrato complex is stable only to ∼-30 °C. Reactions of II with the N-donor ligands NH3, pyridine, or 1-methylimidazole are more complex. With these ligands, the nitrato complexes Mn(III)(TPP)(L)(η(1)-ONO2) and the cationic complexes [Mn(TPP)(L)2](+) coexist in the layer at room temperature, the latter formed as a result of NO3(-) displacement when L is in excess.
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Affiliation(s)
- T S Kurtikyan
- Molecule Structure Research Centre (MSRC) of the Scientific and Technological Centre of Organic and Pharmaceutical Chemistry NAS , 375014, Yerevan, Armenia
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56
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Yokoyama A, Han JE, Karlin KD, Nam W. An isoelectronic NO dioxygenase reaction using a nonheme iron(III)-peroxo complex and nitrosonium ion. Chem Commun (Camb) 2014; 50:1742-4. [PMID: 24394960 DOI: 10.1039/c3cc48782b] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Reaction of a nonheme iron(III)-peroxo complex, [Fe(III)(14-TMC)(O2)](+), with NO(+), a transformation which is essentially isoelectronic with that for nitric oxide dioxygenases [Fe(III)(O2˙(-)) + NO], affords an iron(IV)-oxo complex, [Fe(IV)(14-TMC)(O)](2+), and nitrogen dioxide (NO2), followed by conversion to an iron(III)-nitrato complex, [Fe(III)(14-TMC)(NO3)(F)](+).
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Affiliation(s)
- Atsutoshi Yokoyama
- Department of Chemistry and Nano Science, Department of Bioinspired Science, Ewha Womans University, Seoul 120-750, Korea.
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57
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Kumar V, Kalita A, Mondal B. Phenol ring nitration induced by the unprecedented reduction of the Cu(II) centre by nitrogen dioxide. Dalton Trans 2014; 42:16264-7. [PMID: 24100925 DOI: 10.1039/c3dt51642c] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Nitrogen dioxide (˙NO2) induces tyrosine nitration through a radical mechanism in biological systems. Two copper(II) complexes, 1 and 2, with ligands L₁ and L₂ [L₁ = 2,4-di-tert-butyl-6-(((2-(dimethylamino)ethyl)(isopropyl)amino)methyl)phenol; L₂ = 6,6'-(((2-(dimethylamino)ethyl)azanediyl)bis(methylene))bis(2,4-di-tert-butylphenol)], respectively, have been made to react with ˙NO2. In both cases, the reduction of the copper(II) center was observed in the presence of ˙NO2 which induces phenol ring nitration through nitronium ion (NO2(+)) formation.
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58
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Kim S, Siegler MA, Karlin KD. Peroxynitrite chemistry derived from nitric oxide reaction with a Cu(II)-OOH species and a copper mediated NO reductive coupling reaction. Chem Commun (Camb) 2014; 50:2844-6. [PMID: 24322625 PMCID: PMC3931255 DOI: 10.1039/c3cc47942k] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
New peroxynitrite-copper chemistry ensues via addition of nitric oxide (˙NO(g)) to a Cu(II)-hydroperoxo species. In characterizing the system, the ligand-Cu(i) complex was shown to effect a seldom observed ˙NO(g) reductive coupling reaction. Biological implications are discussed.
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Affiliation(s)
- Sunghee Kim
- Department of Chemistry, The Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA. ; Fax: +1 410-516-8420; Tel: +1 410-516-8027
| | - Maxime A. Siegler
- Department of Chemistry, The Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA. ; Fax: +1 410-516-8420; Tel: +1 410-516-8027
| | - Kenneth D. Karlin
- Department of Chemistry, The Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA. ; Fax: +1 410-516-8420; Tel: +1 410-516-8027
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59
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Wright AM, Zaman HT, Wu G, Hayton TW. Mechanistic Insights into the Formation of N2O by a Nickel Nitrosyl Complex. Inorg Chem 2014; 53:3108-16. [DOI: 10.1021/ic403038e] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- Ashley M. Wright
- Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, California 93106, United States
| | - Homaira T. Zaman
- Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, California 93106, United States
| | - Guang Wu
- Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, California 93106, United States
| | - Trevor W. Hayton
- Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, California 93106, United States
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60
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Chakraborty S, Reed J, Ross M, Nilges MJ, Petrik ID, Ghosh S, Hammes-Schiffer S, Sage JT, Zhang Y, Schulz CE, Lu Y. Spectroscopic and Computational Study of a Nonheme Iron Nitrosyl Center in a Biosynthetic Model of Nitric Oxide Reductase. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201308431] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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61
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Chakraborty S, Reed J, Ross M, Nilges MJ, Petrik ID, Ghosh S, Hammes-Schiffer S, Sage JT, Zhang Y, Schulz CE, Lu Y. Spectroscopic and computational study of a nonheme iron nitrosyl center in a biosynthetic model of nitric oxide reductase. Angew Chem Int Ed Engl 2014; 53:2417-21. [PMID: 24481708 DOI: 10.1002/anie.201308431] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Revised: 11/27/2013] [Indexed: 11/07/2022]
Abstract
A major barrier to understanding the mechanism of nitric oxide reductases (NORs) is the lack of a selective probe of NO binding to the nonheme FeB center. By replacing the heme in a biosynthetic model of NORs, which structurally and functionally mimics NORs, with isostructural ZnPP, the electronic structure and functional properties of the FeB nitrosyl complex was probed. This approach allowed observation of the first S=3/2 nonheme {FeNO}(7) complex in a protein-based model system of NOR. Detailed spectroscopic and computational studies show that the electronic state of the {FeNO}(7) complex is best described as a high spin ferrous iron (S=2) antiferromagnetically coupled to an NO radical (S=1/2) [Fe(2+)-NO(.)]. The radical nature of the FeB -bound NO would facilitate N-N bond formation by radical coupling with the heme-bound NO. This finding, therefore, supports the proposed trans mechanism of NO reduction by NORs.
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Affiliation(s)
- Saumen Chakraborty
- Department of Chemistry and Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL (USA)
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62
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Nitric oxide generation from heme/copper assembly mediated nitrite reductase activity. J Biol Inorg Chem 2014; 19:515-28. [PMID: 24430198 DOI: 10.1007/s00775-013-1081-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2013] [Accepted: 12/18/2013] [Indexed: 01/03/2023]
Abstract
Nitric oxide (NO) as a cellular signaling molecule and vasodilator regulates a range of physiological and pathological processes. Nitrite (NO2 (-)) is recycled in vivo to generate nitric oxide, particularly in physiologic hypoxia and ischemia. The cytochrome c oxidase binuclear heme a 3/CuB active site is one entity known to be responsible for conversion of cellular nitrite to nitric oxide. We recently reported that a partially reduced heme/copper assembly reduces nitrite ion, producing nitric oxide; the heme serves as the reductant and the cupric ion provides a Lewis acid interaction with nitrite, facilitating nitrite (N-O) bond cleavage (Hematian et al., J. Am. Chem. Soc. 134:18912-18915, 2012). To further investigate this nitrite reductase chemistry, copper(II)-nitrito complexes with tridentate and tetradentate ligands were used in this study, where either O,O'-bidentate or O-unidentate modes of nitrite binding to the cupric center are present. To study the role of the reducing ability of the ferrous heme center, two different tetraarylporphyrinate-iron(II) complexes, one with electron-donating para-methoxy peripheral substituents and the other with electron-withdrawing 2,6-difluorophenyl substituents, were used. The results show that differing modes of nitrite coordination to the copper(II) ion lead to differing kinetic behavior. Here, also, the ferrous heme is in all cases the source of the reducing equivalent required to convert nitrite to nitric oxide, but the reduction ability of the heme center does not play a key role in the observed overall reaction rate. On the basis of our observations, reaction mechanisms are proposed and discussed in terms of heme/copper heterobinuclear structures.
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63
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Qiao L, Liu B, Girault HH. Antioxidant promotion of tyrosine nitration in the presence of copper(II). Metallomics 2013; 5:686-92. [PMID: 23689680 DOI: 10.1039/c3mt00048f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Copper(II) is known to catalyze the generation of reactive nitrogen species in the presence of hydrogen peroxide, nitrite or nitric oxide, leading to tyrosine nitration, a biomarker for free radical species associated diseases. Here, we find that biological antioxidants such as ascorbic acid can promote tyrosine nitration in the presence of copper(II) and nitrite under aerobic and weak acidic conditions. Tyrosine nitration is demonstrated on both the β-amyloid peptide and angiotensin I. These studies show that (i) ascorbic acid works as a pro-oxidant in the presence of copper(II) to induce oxidation and nitration on peptides, (ii) both free and coordinated copper(II) can catalyze peptide oxidation and nitration, (iii) nitration occurs under mild acidic conditions (pH = 6.0-6.5).
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Affiliation(s)
- Liang Qiao
- Laboratoire d'Electrochimie Physique et Analytique, Ecole Polytechnique Fédérale de Lausanne, Station 6, CH-1015, Lausanne, Switzerland
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64
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Kurtikyan TS, Eksuzyan SR, Goodwin JA, Hovhannisyan GS. Nitric oxide interaction with oxy-coboglobin models containing trans-pyridine ligand: two reaction pathways. Inorg Chem 2013; 52:12046-56. [PMID: 24090349 DOI: 10.1021/ic4018689] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The oxy-cobolglobin models of the general formula (Py)Co(Por)(O2) (Por = meso-tetraphenyl- and meso-tetra-p-tolylporphyrinato dianions) were constructed by sequential low-temperature interaction of Py and dioxygen with microporous layers of Co-porphyrins. At cryogenic temperatures small increments of NO were introduced into the cryostat and the following reactions were monitored by the FTIR and UV-visible spectroscopy during slow warming. Similar to the recently studied (NH3)Co(Por)(O2) system (Kurtikyan et al. J. Am. Chem. Soc., 2012, 134, 13671-13680), this interaction leads to the nitric oxide dioxygenation reaction with the formation of thermally unstable nitrato complexes (Py)Co(Por)(η(1)-ONO2). The reaction proceeds through the formation of the six-coordinate peroxynitrite adducts (Py)Co(Por)(OONO), as was demonstrated by FTIR measurements with the use of isotopically labeled (18)O2, (15)NO, N(18)O, and (15)N(18)O species and DFT calculations. In contrast to the ammonia system, however, the binding of dioxygen in (Py)Co(Por)(O2) is weaker and the second reaction pathway takes place due to autoxidation of NO by rebound O2 that in NO excess gives N2O3 and N2O4 species adsorbed in the layer. This leads eventually to partial formation of (Py)Co(Por)(NO) and (Py)Co(Por)(NO2) as a result of NO and NO2 reactions with five-coordinate Co(Por)(Py) complexes that are present in the layer after the O2 has been released. The former is thermally unstable and at room temperature passes to the five-coordinate nitrosyl complex, while the latter is a stable compound. In these experiments at 210 K, the layer consists mostly of six-coordinate nitrato complexes and some minor quantities of six-coordinate nitro and nitrosyl species. Their relative quantities depend on the experimental conditions, and the yield of nitrato species is proportional to the relative quantity of peroxynitrite intermediate. Using differently labeled nitrogen oxide isotopomers in different stages of the process the formation of the caged radical pair after homolytic disruption of the O-O bond in peroxynitrite moiety is clearly shown. The composition of the layers upon farther warming to room temperature depends on the experimental conditions. In vacuo the six-coordinate nitrato complexes decompose to give nitrate anion and oxidized cationic complex Co(III)(Por)(Py)2. In the presence of NO excess, however, the nitro-pyridine complexes (Py)Co(Por)(NO2) are predominantly formed formally indicating the oxo-transfer reactivity of (Py)Co(Por)(η(1)-ONO2) with regard to NO. Using differently labeled nitrogen in nitric oxide and coordinated nitrate a plausible mechanism of this reaction is suggested based on the isotope distribution in the nitro complexes formed.
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Affiliation(s)
- Tigran S Kurtikyan
- Molecule Structure Research Centre (MSRC), Scientific and Technological Centre of Organic and Pharmaceutical Chemistry NAS , 0014, Yerevan, Armenia
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65
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Yokoyama A, Cho KB, Karlin KD, Nam W. Reactions of a chromium(III)-superoxo complex and nitric oxide that lead to the formation of chromium(IV)-oxo and chromium(III)-nitrito complexes. J Am Chem Soc 2013; 135:14900-3. [PMID: 24066924 DOI: 10.1021/ja405891n] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The reaction of an end-on Cr(III)-superoxo complex bearing a 14-membered tetraazamacrocyclic TMC ligand, [Cr(III)(14-TMC)(O2)(Cl)](+), with nitric oxide (NO) resulted in the generation of a stable Cr(IV)-oxo species, [Cr(IV)(14-TMC)(O)(Cl)](+), via the formation of a Cr(III)-peroxynitrite intermediate and homolytic O-O bond cleavage of the peroxynitrite ligand. Evidence for the latter comes from electron paramagnetic resonance spectroscopy, computational chemistry and the observation of phenol nitration chemistry. The Cr(IV)-oxo complex does not react with nitrogen dioxide (NO2), but reacts with NO to afford a Cr(III)-nitrito complex, [Cr(III)(14-TMC)(NO2)(Cl)](+). The Cr(IV)-oxo and Cr(III)-nitrito complexes were also characterized spectroscopically and/or structurally.
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Affiliation(s)
- Atsutoshi Yokoyama
- Department of Bioinspired Science and Department of Chemistry and Nano Science, Ewha Womans University , Seoul 120-750, Korea
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66
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Kalita A, Deka RC, Mondal B. Reaction of a Copper(II)–Nitrosyl Complex with Hydrogen Peroxide: Phenol Ring Nitration through a Putative Peroxynitrite Intermediate. Inorg Chem 2013; 52:10897-903. [DOI: 10.1021/ic400890f] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Apurba Kalita
- Department
of Chemistry, Indian Institute of Technology, Guwahati, Assam 781039, India
| | - Ramesh C. Deka
- Department
of Chemical Sciences, Tezpur University, Napaam, Tezpur, Assam 784028, India
| | - Biplab Mondal
- Department
of Chemistry, Indian Institute of Technology, Guwahati, Assam 781039, India
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67
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Arikawa Y, Ikeda A, Matsumoto N, Umakoshi K. Reactivity of a nitrosyl ligand on dinuclear ruthenium hydrotris(pyrazolyl)borato complexes toward a NO molecule. Dalton Trans 2013; 42:11626-31. [PMID: 23828251 DOI: 10.1039/c3dt51319j] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
A cationic mononitrosyl dinuclear ruthenium complex was prepared by removing one NO ligand of a dicationic dinitrosyl ruthenium complex using NaN3. Reduction and oxidation reactions of the mononitrosyl complex led to the isolation of a neutral nitrosyl-bridged complex and a dicationic mononitrosyl complex, respectively, as expected from the cyclic voltammogram. According to the electron count, their reactions with a second NO molecule resulted in an N-N coupling complex from the nitrosyl-bridged complex and the dicationic dinitrosyl complex from the dicationic mononitrosyl complex.
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Affiliation(s)
- Yasuhiro Arikawa
- Division of Chemistry and Materials Science, Graduate School of Engineering, Nagasaki University, Nagasaki, Japan.
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68
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Santolini J, Maréchal A, Boussac A, Dorlet P. EPR characterisation of the ferrous nitrosyl complex formed within the oxygenase domain of NO synthase. Chembiochem 2013; 14:1852-7. [PMID: 23943262 PMCID: PMC4159581 DOI: 10.1002/cbic.201300233] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2013] [Indexed: 11/10/2022]
Abstract
Nitric oxide is produced in mammals by a class of enzymes called NO synthases (NOSs). It plays a central role in cellular signalling but also has deleterious effects, as it leads to the production of reactive oxygen and nitrogen species. NO forms a relatively stable adduct with ferrous haem proteins, which, in the case of NOS, is also a key catalytic intermediate. Despite extensive studies on the ferrous nitrosyl complex of other haem proteins (in particular myoglobin), little characterisation has been performed in the case of NOS. We report here a temperature-dependent EPR study of the ferrous nitrosyl complex of the inducible mammalian NOS and the bacterial NOS-like protein from Bacillus subtilis. The results show that the overall behaviours are similar to those observed for other haem proteins, but with distinct ratios between axial and rhombic forms in the case of the two NOS proteins. The distal environment appears to control the existence of the axial form and the evolution of the rhombic form.
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Affiliation(s)
- Jérôme Santolini
- CNRS, UMR 8221, CEA/iBiTec-S/SB2SM, Bât. 532, CEA Saclay, 91191 Gif-sur-Yvette Cedex (France).
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69
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Pluth MD, Lippard SJ. Reversible binding of nitric oxide to an Fe(III) complex of a tetra-amido macrocycle. Chem Commun (Camb) 2013; 48:11981-3. [PMID: 23133836 DOI: 10.1039/c2cc37221e] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Nitric oxide binds reversibly to the Fe(III) complex of a well-developed tetra-amido macrocyclic ligand. Reaction with NO results in formation of a species consistent with an S = 1 {Fe-NO}(6) ground state as characterized by UV-vis, IR, EPR, and Mössbauer spectroscopy. The resultant nitrosyl is labile and dissociates readily upon purging with N(2), thus providing a rare example of reversible NO binding to non-heme iron.
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Affiliation(s)
- Michael D Pluth
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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70
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Hetterscheid DGH, Chikkali SH, de Bruin B, Reek JNH. Binuclear Cooperative Catalysts for the Hydrogenation and Hydroformylation of Olefins. ChemCatChem 2013. [DOI: 10.1002/cctc.201300092] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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71
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Sanders BC, Patra AK, Harrop TC. Synthesis, properties, and reactivity of a series of non-heme {FeNO}7/8 complexes: Implications for Fe-nitroxyl coordination. J Inorg Biochem 2013; 118:115-27. [DOI: 10.1016/j.jinorgbio.2012.08.026] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2012] [Revised: 08/17/2012] [Accepted: 08/18/2012] [Indexed: 10/27/2022]
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72
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Wong JL, Sánchez RH, Logan JG, Zarkesh RA, Ziller JW, Heyduk AF. Disulfide reductive elimination from an iron(iii) complex. Chem Sci 2013. [DOI: 10.1039/c3sc22335c] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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73
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Hematian S, Siegler MA, Karlin KD. Heme/copper assembly mediated nitrite and nitric oxide interconversion. J Am Chem Soc 2012; 134:18912-5. [PMID: 23130610 DOI: 10.1021/ja3083818] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The heme(a3)/Cu(B) active site of cytochrome c oxidase is responsible for cellular nitrite reduction to nitric oxide; the same center can return NO to the nitrite pool via oxidative chemistry. Here, we show that a partially reduced heme/Cu assembly reduces NO(2)(-) ion, producing nitric oxide. The heme serves as the reductant, but the Cu(II) ion is also required. In turn, a μ-oxo heme-Fe(III)-O-Cu(II) complex facilitates NO oxidation to nitrite; the final products are the reduced heme and Cu(II)-nitrito complexes.
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Affiliation(s)
- Shabnam Hematian
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA
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74
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Shaw WJ. The Outer-Coordination Sphere: Incorporating Amino Acids and Peptides as Ligands for Homogeneous Catalysts to Mimic Enzyme Function. CATALYSIS REVIEWS-SCIENCE AND ENGINEERING 2012. [DOI: 10.1080/01614940.2012.679453] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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75
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Yokoyama A, Han JE, Cho J, Kubo M, Ogura T, Siegler MA, Karlin KD, Nam W. Chromium(IV)-peroxo complex formation and its nitric oxide dioxygenase reactivity. J Am Chem Soc 2012; 134:15269-72. [PMID: 22950528 DOI: 10.1021/ja307384e] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The O(2) and NO reactivity of a Cr(II) complex bearing a 12-membered tetraazamacrocyclic N-tetramethylated cyclam (TMC) ligand, [Cr(II)(12-TMC)(Cl)](+) (1), and the NO reactivity of its peroxo derivative, [Cr(IV)(12-TMC)(O(2))(Cl)](+) (2), are described. By contrast to the previously reported Cr(III)-superoxo complex, [Cr(III)(14-TMC)(O(2))(Cl)](+), the Cr(IV)-peroxo complex 2 is formed in the reaction of 1 and O(2). Full spectroscopic and X-ray analysis revealed that 2 possesses side-on η(2)-peroxo ligation. The quantitative reaction of 2 with NO affords a reduction in Cr oxidation state, producing a Cr(III)-nitrato complex, [Cr(III)(12-TMC)(NO(3))(Cl)](+) (3). The latter is suggested to form via a Cr(III)-peroxynitrite intermediate. [Cr(II)(12-TMC)(NO)(Cl)](+) (4), a Cr(II)-nitrosyl complex derived from 1 and NO, could also be synthesized; however, it does not react with O(2).
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Affiliation(s)
- Atsutoshi Yokoyama
- Department of Bioinspired Science, Ewha Womans University, Seoul 120-750, Korea
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76
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Kurtikyan TS, Eksuzyan SR, Hayrapetyan VA, Martirosyan GG, Hovhannisyan GS, Goodwin JA. Nitric oxide dioxygenation reaction by oxy-coboglobin models: in-situ low-temperature FTIR characterization of coordinated peroxynitrite. J Am Chem Soc 2012; 134:13861-70. [PMID: 22881578 DOI: 10.1021/ja305774v] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The oxy-cobolglobin models of the general formula (NH(3))Co(Por)(O(2)) (Por = meso-tetra-phenyl and meso-tetra-p-tolylporphyrinato dianions) were constructed by sequential low temperature interaction of NH(3) and dioxygen with microporous layers of Co-porphyrins. At cryogenic temperatures small increments of NO were introduced into the cryostat and the following reactions were monitored by the FTIR and UV-visible spectroscopy during slow warming. Upon warming the layers from 80 to 120 K a set of new IR bands grows with correlating intensities along with the consumption of the ν(O(2)) band. Isotope labeling experiments with (18)O(2), (15)NO and N(18)O along with DFT calculations provides a basis for assigning them to the six-coordinate peroxynitrite complexes (NH(3))Co(Por)(OONO). Over the course of warming the layers from 140 to 170 K these complexes decompose and there are spectral features suggesting the formation of nitrogen dioxide NO(2). Upon keeping the layers at 180-210 K the bands of NO(2) gradually decrease in intensity and the set of new bands grows in the range of 1480, 1270, and 980 cm(-1). These bands have their isotopic counterparts when (15)NO, (18)O(2) and N(18)O are used in the experiments and certainly belong to the 6-coordinate nitrato complexes (NH(3))Co(Por)(η(1)-ONO(2)) demonstrating the ability of oxy coboglobin models to promote the nitric oxide dioxygenation (NOD) reaction similar to oxy-hemes. As in the case of Hb, Mb and model iron-porphyrins, the six-coordinate nitrato complexes are not stable at room temperature and dissociate to give nitrate anion and oxidized cationic complex Co(III)(Por)(NH(3))(1,2).
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Affiliation(s)
- Tigran S Kurtikyan
- Molecule Structure Research Centre (MSRC) of the Scientific and Technological Centre of Organic and Pharmaceutical Chemistry NAS, 0014, Yerevan, Armenia.
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78
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Wright AM, Wu G, Hayton TW. Formation of N2O from a Nickel Nitrosyl: Isolation of the cis-[N2O2]2– Intermediate. J Am Chem Soc 2012; 134:9930-3. [DOI: 10.1021/ja304204q] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ashley M. Wright
- Department of Chemistry and Biochemistry, University of California—Santa Barbara, Santa
Barbara, California 93106, United States
| | - Guang Wu
- Department of Chemistry and Biochemistry, University of California—Santa Barbara, Santa
Barbara, California 93106, United States
| | - Trevor W. Hayton
- Department of Chemistry and Biochemistry, University of California—Santa Barbara, Santa
Barbara, California 93106, United States
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79
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Kristian KE, Bakac A. Reduction of nitrous acid with a macrocyclic rhodium complex that acts as a functional model of nitrite reductase. Inorg Chem 2012; 51:4877-82. [PMID: 22480334 DOI: 10.1021/ic300597n] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Nitrous acid reacts with L(2)(H(2)O)Rh(2+) (L(2) = meso-hexamethylcyclam) in acidic aqueous solutions to generate a strongly absorbing intermediate Int-1 (λ(max) 400 nm, ε = 1200 M(-1) cm(-1)). The reaction follows a mixed second order rate law with k = (6.9 ± 0.3) × 10(4) M(-1) s(-1), independent of [H(+)]. The lack of acid dependence shows that Int-1 is a rhodium(II) complex of HNO(2), most reasonably assigned as L(2)(H(2)O)Rh(HNO(2))(2+). This species is analogous to the early iron and copper intermediates in the reduction of nitrite by nitrite reductases and by deoxyhemoglobin. In the presence of excess L(2)(H(2)O)Rh(2+), the lifetime of Int-1 is about 1 min. It decays to a 1:1 mixture of L(2)(H(2)O)RhNO(2+) and L(2)Rh(H(2)O)(2)(3+) with kinetics that are largely independent of the concentration of excess L(2)(H(2)O)Rh(2+) and of [H(+)] at [H(+)] < 0.03 M. At [H(+)] > 0.03 M, an acid-catalyzed pathway becomes effective, suggesting protonation and dehydration of Int-1 to generate L(2)(H(2)O)RhNO(3+) (Int-2) followed by rapid reduction of Int-2 by excess L(2)(H(2)O)Rh(2+). Int-2, which was generated and characterized independently, is an analog of the electrophilic intermediates in the mechanism of biological reduction of nitrite to (•)NO. Excess nitrite greatly reduces the lifetime of Int-1, which under such conditions decomposes on a millisecond time scale by nitrite-catalyzed disproportionation to yield L(2)(H(2)O)RhNO(2+) and L(2)Rh(III). This reaction provides additional support for the designation of Int-1 as a Rh(II) species. The complex reaction mechanism and the detection of Int-1 demonstrate the ability of inorganic complexes to perform the fundamental chemistry believed to take place in the biological reduction of HNO(2) to NO catalyzed by nitrite reductases or deoxyhemoglobin.
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80
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Arikawa Y, Onishi M. Reductive N–N coupling of NO molecules on transition metal complexes leading to N2O. Coord Chem Rev 2012. [DOI: 10.1016/j.ccr.2011.10.023] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
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81
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Reductive NO dimerization to trans-hyponitrite in diruthenium complexes: Intramolecular attack of hyponitrite on a CO ligand. J Organomet Chem 2012. [DOI: 10.1016/j.jorganchem.2011.11.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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82
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Samanta S, Sengupta K, Mittra K, Bandyopadhyay S, Dey A. Selective four electron reduction of O2 by an iron porphyrin electrocatalyst under fast and slow electron fluxes. Chem Commun (Camb) 2012; 48:7631-3. [DOI: 10.1039/c2cc32832a] [Citation(s) in RCA: 88] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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83
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A detailed investigation into the electronic structures of macrocyclic iron(II)-nitrosyl compounds and their similarities to ferrous heme-nitrosyls. Inorganica Chim Acta 2012. [DOI: 10.1016/j.ica.2011.09.039] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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84
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Doctorovich F, Bikiel D, Pellegrino J, Suárez SA, Larsen A, Martí MA. Nitroxyl (azanone) trapping by metalloporphyrins. Coord Chem Rev 2011. [DOI: 10.1016/j.ccr.2011.04.012] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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85
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Affiliation(s)
- Liang Qiao
- Laboratoire d’Electrochimie Physique et Analytique, Ecole Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne, Switzerland
| | - Yu Lu
- Laboratoire d’Electrochimie Physique et Analytique, Ecole Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne, Switzerland
| | - Baohong Liu
- Department of Chemistry, Institute of Biomedical Sciences, Fudan University, Shanghai 200433, People’s Republic of China
| | - Hubert H. Girault
- Laboratoire d’Electrochimie Physique et Analytique, Ecole Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne, Switzerland
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Schwartz KR, Mann KR. Optical Response of a Cyclometalated Iridium(III) Hydrazino Complex to Carbon Dioxide: Generation of a Strongly Luminescent Iridium(III) Carbazate. Inorg Chem 2011; 50:12477-85. [DOI: 10.1021/ic201286k] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Kyle R. Schwartz
- Department of Chemistry, University of Minnesota, Minneapolis,
Minnesota 55455,
United States
| | - Kent R. Mann
- Department of Chemistry, University of Minnesota, Minneapolis,
Minnesota 55455,
United States
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87
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Dynamic gut microbiome across life history of the malaria mosquito Anopheles gambiae in Kenya. PLoS One 2011; 6:e24767. [PMID: 21957459 PMCID: PMC3177825 DOI: 10.1371/journal.pone.0024767] [Citation(s) in RCA: 362] [Impact Index Per Article: 27.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2011] [Accepted: 08/17/2011] [Indexed: 11/19/2022] Open
Abstract
The mosquito gut represents an ecosystem that accommodates a complex, intimately associated microbiome. It is increasingly clear that the gut microbiome influences a wide variety of host traits, such as fitness and immunity. Understanding the microbial community structure and its dynamics across mosquito life is a prerequisite for comprehending the symbiotic relationship between the mosquito and its gut microbial residents. Here we characterized gut bacterial communities across larvae, pupae and adults of Anopheles gambiae reared in semi-natural habitats in Kenya by pyrosequencing bacterial 16S rRNA fragments. Immatures and adults showed distinctive gut community structures. Photosynthetic Cyanobacteria were predominant in the larval and pupal guts while Proteobacteria and Bacteroidetes dominated the adult guts, with core taxa of Enterobacteriaceae and Flavobacteriaceae. At the adult stage, diet regime (sugar meal and blood meal) significantly affects the microbial structure. Intriguingly, blood meals drastically reduced the community diversity and favored enteric bacteria. Comparative genomic analysis revealed that the enriched enteric bacteria possess large genetic redox capacity of coping with oxidative and nitrosative stresses that are associated with the catabolism of blood meal, suggesting a beneficial role in maintaining gut redox homeostasis. Interestingly, gut community structure was similar in the adult stage between the field and laboratory mosquitoes, indicating that mosquito gut is a selective eco-environment for its microbiome. This comprehensive gut metatgenomic profile suggests a concerted symbiotic genetic association between gut inhabitants and host.
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Berto TC, Hoffman MB, Murata Y, Landenberger KB, Alp EE, Zhao J, Lehnert N. Structural and electronic characterization of non-heme Fe(II)-nitrosyls as biomimetic models of the Fe(B) center of bacterial nitric oxide reductase. J Am Chem Soc 2011; 133:16714-7. [PMID: 21630658 DOI: 10.1021/ja111693f] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The detoxification of nitric oxide (NO) by bacterial NO reductase (NorBC) has gained much attention as this reaction provides a paradigm as to how NO can be detoxified anaerobically in cells. However, a clear mechanistic picture of how the heme/non-heme active site of NorBC activates NO is lacking, mostly as a result of insufficient knowledge about the properties of the non-heme iron(II)-NO adduct. Here we report the first biomimetic model complexes for this species that closely resemble the coordination environment found in the protein, using the ligands BMPA-Pr and TPA. The systematic investigation of these compounds allowed us to gain key insight into the electronic structure and geometric properties of high-spin non-heme iron(II)-NO adducts. In particular, we show how small changes in the ligand environment of iron could be used by NorBC to greatly modulate the properties, and hence, the reactivity of this species.
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Affiliation(s)
- Timothy C Berto
- Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, USA
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Annamaria H, Manno D, Strand SE, Bruce NC, Hawari J. Biodegradation of RDX and MNX with Rhodococcus sp. strain DN22: new insights into the degradation pathway. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2010; 44:9330-9336. [PMID: 21105645 DOI: 10.1021/es1023724] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Previously we demonstrated that Rhodococcus sp. strain DN22 can degrade RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) aerobically via initial denitration. The present study describes the role of oxygen and water in the key denitration step leading to RDX decomposition using (18)O(2) and H(2)(18)O labeling experiments. We also investigated degradation of MNX (hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine) with DN22 under similar conditions. DN22 degraded RDX and MNX giving NO(2)(-), NO(3)(-), NDAB (4-nitro-diazabutanal), NH(3), N(2)O, and HCHO with NO(2)(-)/NO(3)(-) molar ratio reaching 17 and ca. 2, respectively. In the presence of (18)O(2), DN22 degraded RDX and produced NO(2)(-) with m/z at 46 Da that subsequently oxidized to NO(3)(-) containing one (18)O atom, but in the presence of H(2)(18)O we detected NO(3)(-) without (18)O. A control containing NO(2)(-), DN22, and (18)O(2) gave NO(3)(-) with one (18)O, confirming biotic oxidation of NO(2)(-) to NO(3)(-). Treatment of MNX with DN22 and (18)O(2) produced NO(3)(-) with two mass ions, one (66 Da) incorporating two (18)O atoms and another (64 Da) incorporating only one (18)O atom and we attributed their formation to bio-oxidation of the initially formed NO and NO(2)(-), respectively. In the presence of H(2)(18)O we detected NO(2)(-) with two different masses, one representing NO(2)(-) (46 Da) and another representing NO(2)(-) (48 Da) with the inclusion of one (18)O atom suggesting auto-oxidation of NO to NO(2)(-). Results indicated that denitration of either RDX or MNX and denitrosation of MNX by DN22 did not involve direct participation of either oxygen or water, but both played major roles in subsequent secondary chemical and biochemical reactions of NO and NO(2)(-).
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Affiliation(s)
- Halasz Annamaria
- Biotechnology Research Institute, National Research Council Canada, 6100 Royalmount Ave. Montreal (PQ), Canada, H4P 2R2
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