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Reed CJ, Lam QN, Mirts EN, Lu Y. Molecular understanding of heteronuclear active sites in heme-copper oxidases, nitric oxide reductases, and sulfite reductases through biomimetic modelling. Chem Soc Rev 2021; 50:2486-2539. [PMID: 33475096 PMCID: PMC7920998 DOI: 10.1039/d0cs01297a] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Heme-copper oxidases (HCO), nitric oxide reductases (NOR), and sulfite reductases (SiR) catalyze the multi-electron and multi-proton reductions of O2, NO, and SO32-, respectively. Each of these reactions is important to drive cellular energy production through respiratory metabolism and HCO, NOR, and SiR evolved to contain heteronuclear active sites containing heme/copper, heme/nonheme iron, and heme-[4Fe-4S] centers, respectively. The complexity of the structures and reactions of these native enzymes, along with their large sizes and/or membrane associations, make it challenging to fully understand the crucial structural features responsible for the catalytic properties of these active sites. In this review, we summarize progress that has been made to better understand these heteronuclear metalloenzymes at the molecular level though study of the native enzymes along with insights gained from biomimetic models comprising either small molecules or proteins. Further understanding the reaction selectivity of these enzymes is discussed through comparisons of their similar heteronuclear active sites, and we offer outlook for further investigations.
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Affiliation(s)
- Christopher J Reed
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urban, IL 61801, USA.
| | - Quan N Lam
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urban, IL 61801, USA
| | - Evan N Mirts
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA and Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Yi Lu
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urban, IL 61801, USA. and Department of Biochemistry, University of Illinois at Urbana-Champaign, Urban, IL 61801, USA and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA and Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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2
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Marquardt M, Cula B, Budhija V, Dallmann A, Schwalbe M. Structural Determination of an Unusual Cu I -Porphyrin-π-Bond in a Hetero-Pacman Cu-Zn-Complex. Chemistry 2021; 27:3991-3996. [PMID: 33405305 PMCID: PMC7986761 DOI: 10.1002/chem.202004945] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Revised: 12/17/2020] [Indexed: 12/02/2022]
Abstract
The synthesis and characterization of a hetero‐dinuclear compound is presented, in which a copper(I) trishistidine type coordination unit is positioned directly above a zinc porphyrin unit. The close distance between the two coordination fragments is secured by a rigid xanthene backbone, and a unique (intramolecular) copper porphyrin‐π‐bond was determined for the first time in the molecular structure. This structural motif was further analyzed by temperature‐dependent NMR studies: In solution at room temperature the coordinative bond fluctuates, while it can be frozen at low temperatures. Preliminary reactivity studies revealed a reduced reactivity of the copper(I) moiety towards dioxygen. The results adumbrate why nature is avoiding metal porphyrin‐π‐bonds by fixing reactive metal centers in a predetermined distance to each other within multimetallic enzymatic reaction centers.
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Affiliation(s)
- Michael Marquardt
- Institute of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Strasse 2, 12489, Berlin, Germany
| | - Beatrice Cula
- Institute of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Strasse 2, 12489, Berlin, Germany
| | - Vishal Budhija
- Institute of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Strasse 2, 12489, Berlin, Germany
| | - André Dallmann
- Institute of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Strasse 2, 12489, Berlin, Germany
| | - Matthias Schwalbe
- Institute of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Strasse 2, 12489, Berlin, Germany
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Ferousi C, Majer SH, DiMucci IM, Lancaster KM. Biological and Bioinspired Inorganic N-N Bond-Forming Reactions. Chem Rev 2020; 120:5252-5307. [PMID: 32108471 PMCID: PMC7339862 DOI: 10.1021/acs.chemrev.9b00629] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The metallobiochemistry underlying the formation of the inorganic N-N-bond-containing molecules nitrous oxide (N2O), dinitrogen (N2), and hydrazine (N2H4) is essential to the lifestyles of diverse organisms. Similar reactions hold promise as means to use N-based fuels as alternative carbon-free energy sources. This review discusses research efforts to understand the mechanisms underlying biological N-N bond formation in primary metabolism and how the associated reactions are tied to energy transduction and organismal survival. These efforts comprise studies of both natural and engineered metalloenzymes as well as synthetic model complexes.
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Affiliation(s)
- Christina Ferousi
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, United States
| | - Sean H Majer
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, United States
| | - Ida M DiMucci
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, United States
| | - Kyle M Lancaster
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, United States
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Naveen P, Vijaya Pandiyan B, Anu D, Dallemer F, Kolandaivel P, Prabhakaran R. A pseudo trinuclear nickel–sodium complex containing tris(8‐methyl‐2‐oxo‐quinolidineamino ethylamine): Synthesis, spectral characterization, X‐ray crystallography and in vitrobiological evaluations. Appl Organomet Chem 2020. [DOI: 10.1002/aoc.5605] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- P. Naveen
- Department of ChemistryBharathiar University Coimbatore 641 046 India
| | | | - D. Anu
- Department of ChemistryBharathiar University Coimbatore 641 046 India
| | - F. Dallemer
- LaboratoireChimie Provence‐CNRS, UMR7246Université of Aix‐Marseille, Campus Scientifique de Saint‐Jérôme, Avenue Escadrille Normandie‐Niemen F‐13397 Marseille Cedex 20 France
| | - P. Kolandaivel
- Department of PhysicsBharathiar University Coimbatore 641046 India
| | - R. Prabhakaran
- Department of ChemistryBharathiar University Coimbatore 641 046 India
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5
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6
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Kim H, Sharma SK, Schaefer AW, Solomon EI, Karlin KD. Heme-Cu Binucleating Ligand Supports Heme/O 2 and Fe II-Cu I/O 2 Reactivity Providing High- and Low-Spin Fe III-Peroxo-Cu II Complexes. Inorg Chem 2019; 58:15423-15432. [PMID: 31657921 DOI: 10.1021/acs.inorgchem.9b02521] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The focus of this study is in the description of synthetic heme/copper/O2 chemistry employing a heme-containing binucleating ligand which provides a tridentate chelate for copper ion binding. The addition of O2 (-80 °C, tetrahydrofuran (THF) solvent) to the reduced heme compound (PImH)FeII (1), gives the oxy-heme adduct, formally a heme-superoxide complex FeIII-(O2•-) (2) (resonance Raman spectroscopy (rR): νO-O, 1171 cm-1 (Δ18O2, -61 cm-1); νFe-O, 575 cm-1 (Δ18O2, -24 cm-1)). Simple warming of 2 to room temperature regenerates reduced complex 1; this reaction is reversible, as followed by UV-vis spectroscopy. Complex 2 is electron paramagnetic resonance (EPR)-silent and exhibits upfield-shifted pyrrole resonances (δ 9.12 ppm) in 2H NMR spectroscopy, indicative of a six-coordinate low-spin heme. The coordination of the tethered imidazolyl arm to the heme-superoxide complex as an axial base ligand is suggested. We also report the new fully reduced heme-copper complex [(PImH)FeIICuI]+ (3), where the copper ion is bound to the tethered tridentate portion of PImH. This reacts with O2 to give a distinctive low-temperature-stable, high-spin (S = 2, overall) peroxo-bridged complex [(PImH)FeIII-(O22-)-CuII]+ (3a): λmax, 420 (Soret), 545, 565 nm; δpyrr, 93 ppm; νO-O, 799 cm-1 (Δ18O2, -48 cm-1); νFe-O, 524 cm-1 (Δ18O2, -23 cm-1). To 3a, the addition of dicyclohexylimidazole (DCHIm), which serves as a heme axial base, leads to low-spin (S = 0 overall) species complex [(DCHIm)(PImH)FeIII-(O22-)-CuII]+ (3b): λmax, 425 (Soret), 538 nm; δpyrr, 10.2 ppm; νO-O, 817 cm-1 (Δ18O2, -55 cm-1); νFe-O, 610 cm-1 (Δ18O2, -26 cm-1). These investigations into the characterization of the O2-adducts from (PImH)FeII (1) with/without additional copper chelation advance our understanding of the dioxygen reactivity of heme-only and heme/Cu-ligand heterobinuclear system, thus potentially relevant to O2 reduction in heme-copper oxidases or fuel-cell chemistry.
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Affiliation(s)
- Hyun Kim
- Department of Chemistry , Johns Hopkins University , Baltimore , Maryland 21218 , United States
| | - Savita K Sharma
- Department of Chemistry , Johns Hopkins University , Baltimore , Maryland 21218 , United States
| | - Andrew W Schaefer
- Department of Chemistry , Stanford University , Stanford , California 94305 , United States
| | - Edward I Solomon
- Department of Chemistry , Stanford University , Stanford , California 94305 , United States
| | - Kenneth D Karlin
- Department of Chemistry , Johns Hopkins University , Baltimore , Maryland 21218 , United States
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Schaefer AW, Ehudin MA, Quist DA, Tang JA, Karlin KD, Solomon EI. Spin Interconversion of Heme-Peroxo-Copper Complexes Facilitated by Intramolecular Hydrogen-Bonding Interactions. J Am Chem Soc 2019; 141:4936-4951. [PMID: 30836005 PMCID: PMC6457345 DOI: 10.1021/jacs.9b00118] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Synthetic peroxo-bridged high-spin (HS) heme-(μ-η2:η1-O22-)-Cu(L) complexes incorporating (as part of the copper ligand) intramolecular hydrogen-bond (H-bond) capabilities and/or steric effects are herein demonstrated to affect the complex's electronic and geometric structure, notably impacting the spin state. An H-bonding interaction with the peroxo core favors a low-spin (LS) heme-(μ-η1:η1-O22-)-Cu(L) structure, resulting in a reversible temperature-dependent interconversion of spin state (5 coordinate HS to 6 coordinate LS). The LS state dominates at low temperatures, even in the absence of a strong trans-axial heme ligand. Lewis base addition inhibits the H-bond facilitated spin interconversion by competition for the H-bond donor, illustrating the precise H-bonding interaction required to induce spin-crossover (SCO). Resonance Raman spectroscopy (rR) shows that the H-bonding pendant interacts with the bridging peroxide ligand to stabilize the LS but not the HS state. The H-bond (to the Cu-bound O atom) acts to weaken the O-O bond and strengthen the Fe-O bond, exhibiting ν(M-O) and ν(O-O) values comparable to analogous known LS complexes with a strong donating trans-axial ligand, 1,5-dicyclohexylimidazole, (DCHIm)heme-(μ-η1:η1-O22-)-Cu(L). Variable-temperature (-90 to -130 °C) UV-vis and 2H NMR spectroscopies confirm the SCO process and implicate the involvement of solvent binding. Examining a case of solvent binding without SCO, thermodynamic parameters were obtained from a van't Hoff analysis, accounting for its contribution in SCO. Taken together, these data provide evidence for the H-bond group facilitating a core geometry change and allowing solvent to bind, stabilizing a LS state. The rR data, complemented by DFT analysis, reveal a stronger H-bonding interaction with the peroxo core in the LS compared to the HS complexes, which enthalpically favors the LS state. These insights enhance our fundamental understanding of secondary coordination sphere influences in metalloenzymes.
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Affiliation(s)
- Andrew W. Schaefer
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Melanie A. Ehudin
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - David A. Quist
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Joel A. Tang
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Kenneth D. Karlin
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Edward I. Solomon
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
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8
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Ehudin MA, Schaefer AW, Adam SM, Quist DA, Diaz DE, Tang JA, Solomon EI, Karlin KD. Influence of intramolecular secondary sphere hydrogen-bonding interactions on cytochrome c oxidase inspired low-spin heme-peroxo-copper complexes. Chem Sci 2019; 10:2893-2905. [PMID: 30996867 PMCID: PMC6431958 DOI: 10.1039/c8sc05165h] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Accepted: 01/03/2019] [Indexed: 11/21/2022] Open
Abstract
Dioxygen reduction by heme-copper oxidases is a critical biochemical process, wherein hydrogen bonding is hypothesized to participate in the critical step involving the active-site reductive cleavage of the O-O bond. Sixteen novel synthetic heme-(μ-O2 2-)-Cu(XTMPA) complexes, whose design is inspired by the cytochrome c oxidase active site structure, were generated in an attempt to form the first intramolecular H-bonded complexes. Derivatives of the "parent" ligand (XTMPA, TMPA = (tris((2-pyridyl)methyl)amine)) possessing one or two amine pendants preferentially form an H-bond with the copper-bound O-atom of the peroxide bridge. This is evidenced by a characteristic blue shift in the ligand-to-metal charge transfer (LMCT) bands observed in UV-vis spectroscopy (consistent with lowering of the peroxo π* relative to the iron orbitals) and a weakening of the O-O bond determined by resonance Raman spectroscopy (rR), with support from Density Functional Theory (DFT) calculations. Remarkably, with the TMPA-based infrastructure (versus similar heme-peroxo-copper complexes with different copper ligands), the typically undetected Cu-O stretch for these complexes was observed via rR, affording critical insights into the nature of the O-O peroxo core for the complexes studied. While amido functionalities have been shown to have greater H-bonding capabilities than their amino counterparts, in these heme-peroxo-copper complexes amido substituents distort the local geometry such that H-bonding with the peroxo core only imparts a weak electronic effect; optimal H-bonding interactions are observed by employing two amino groups on the copper ligand. The amino-substituted systems presented in this work reveal a key orientational anisotropy in H-bonding to the peroxo core for activating the O-O bond, offering critical insights into effective O-O cleavage chemistry. These findings indirectly support computational and protein structural studies suggesting the presence of an interstitial H-bonding water molecule in the CcO active site, which is critical for the desired reactivity. The results are evaluated with appropriate controls and discussed with respect to potential O2-reduction capabilities.
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Affiliation(s)
- Melanie A Ehudin
- Department of Chemistry , Johns Hopkins University , Baltimore , Maryland 21218 , USA .
| | - Andrew W Schaefer
- Department of Chemistry , Stanford University , Stanford , California 94305 , USA .
| | - Suzanne M Adam
- Department of Chemistry , Johns Hopkins University , Baltimore , Maryland 21218 , USA .
| | - David A Quist
- Department of Chemistry , Johns Hopkins University , Baltimore , Maryland 21218 , USA .
| | - Daniel E Diaz
- Department of Chemistry , Johns Hopkins University , Baltimore , Maryland 21218 , USA .
| | - Joel A Tang
- Department of Chemistry , Johns Hopkins University , Baltimore , Maryland 21218 , USA .
| | - Edward I Solomon
- Department of Chemistry , Stanford University , Stanford , California 94305 , USA .
| | - Kenneth D Karlin
- Department of Chemistry , Johns Hopkins University , Baltimore , Maryland 21218 , USA .
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Adam SM, Wijeratne GB, Rogler PJ, Diaz DE, Quist DA, Liu JJ, Karlin KD. Synthetic Fe/Cu Complexes: Toward Understanding Heme-Copper Oxidase Structure and Function. Chem Rev 2018; 118:10840-11022. [PMID: 30372042 PMCID: PMC6360144 DOI: 10.1021/acs.chemrev.8b00074] [Citation(s) in RCA: 132] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Heme-copper oxidases (HCOs) are terminal enzymes on the mitochondrial or bacterial respiratory electron transport chain, which utilize a unique heterobinuclear active site to catalyze the 4H+/4e- reduction of dioxygen to water. This process involves a proton-coupled electron transfer (PCET) from a tyrosine (phenolic) residue and additional redox events coupled to transmembrane proton pumping and ATP synthesis. Given that HCOs are large, complex, membrane-bound enzymes, bioinspired synthetic model chemistry is a promising approach to better understand heme-Cu-mediated dioxygen reduction, including the details of proton and electron movements. This review encompasses important aspects of heme-O2 and copper-O2 (bio)chemistries as they relate to the design and interpretation of small molecule model systems and provides perspectives from fundamental coordination chemistry, which can be applied to the understanding of HCO activity. We focus on recent advancements from studies of heme-Cu models, evaluating experimental and computational results, which highlight important fundamental structure-function relationships. Finally, we provide an outlook for future potential contributions from synthetic inorganic chemistry and discuss their implications with relevance to biological O2-reduction.
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Affiliation(s)
- Suzanne M. Adam
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Gayan B. Wijeratne
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Patrick J. Rogler
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Daniel E. Diaz
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - David A. Quist
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Jeffrey J. Liu
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Kenneth D. Karlin
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
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11
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Huang X, Groves JT. Oxygen Activation and Radical Transformations in Heme Proteins and Metalloporphyrins. Chem Rev 2018; 118:2491-2553. [PMID: 29286645 PMCID: PMC5855008 DOI: 10.1021/acs.chemrev.7b00373] [Citation(s) in RCA: 579] [Impact Index Per Article: 96.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Indexed: 12/20/2022]
Abstract
As a result of the adaptation of life to an aerobic environment, nature has evolved a panoply of metalloproteins for oxidative metabolism and protection against reactive oxygen species. Despite the diverse structures and functions of these proteins, they share common mechanistic grounds. An open-shell transition metal like iron or copper is employed to interact with O2 and its derived intermediates such as hydrogen peroxide to afford a variety of metal-oxygen intermediates. These reactive intermediates, including metal-superoxo, -(hydro)peroxo, and high-valent metal-oxo species, are the basis for the various biological functions of O2-utilizing metalloproteins. Collectively, these processes are called oxygen activation. Much of our understanding of the reactivity of these reactive intermediates has come from the study of heme-containing proteins and related metalloporphyrin compounds. These studies not only have deepened our understanding of various functions of heme proteins, such as O2 storage and transport, degradation of reactive oxygen species, redox signaling, and biological oxygenation, etc., but also have driven the development of bioinorganic chemistry and biomimetic catalysis. In this review, we survey the range of O2 activation processes mediated by heme proteins and model compounds with a focus on recent progress in the characterization and reactivity of important iron-oxygen intermediates. Representative reactions initiated by these reactive intermediates as well as some context from prior decades will also be presented. We will discuss the fundamental mechanistic features of these transformations and delineate the underlying structural and electronic factors that contribute to the spectrum of reactivities that has been observed in nature as well as those that have been invented using these paradigms. Given the recent developments in biocatalysis for non-natural chemistries and the renaissance of radical chemistry in organic synthesis, we envision that new enzymatic and synthetic transformations will emerge based on the radical processes mediated by metalloproteins and their synthetic analogs.
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Affiliation(s)
- Xiongyi Huang
- Department
of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
- Department
of Chemistry, California Institute of Technology, Pasadena, California 91125, United States
| | - John T. Groves
- Department
of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
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12
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Naveen P, Dallemer F, Butcher R, Prabhakaran R. New Ru(II) complexes containing tris(2-pyridylmethyl)amine. Synthesis, structural, CT-DNA/albumin interaction, anti-oxidant and cytotoxicity studies. Inorganica Chim Acta 2018. [DOI: 10.1016/j.ica.2017.12.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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13
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Lang P, Schwalbe M. Pacman Compounds: From Energy Transfer to Cooperative Catalysis. Chemistry 2017; 23:17398-17412. [DOI: 10.1002/chem.201703675] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2017] [Indexed: 01/08/2023]
Affiliation(s)
- Philipp Lang
- Institut für Chemie; Humboldt-Universität zu Berlin; Brook-Taylor-St. 2 12489 Berlin Germany
| | - Matthias Schwalbe
- Institut für Chemie; Humboldt-Universität zu Berlin; Brook-Taylor-St. 2 12489 Berlin Germany
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Adam SM, Garcia-Bosch I, Schaefer AW, Sharma SK, Siegler MA, Solomon EI, Karlin KD. Critical Aspects of Heme-Peroxo-Cu Complex Structure and Nature of Proton Source Dictate Metal-O(peroxo) Breakage versus Reductive O-O Cleavage Chemistry. J Am Chem Soc 2017; 139:472-481. [PMID: 28029788 PMCID: PMC5274545 DOI: 10.1021/jacs.6b11322] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The 4H+/4e- reduction of O2 to water, a key fuel-cell reaction also carried out in biology by oxidase enzymes, includes the critical O-O bond reductive cleavage step. Mechanistic investigations on active-site model compounds, which are synthesized by rational design to incorporate systematic variations, can focus on and resolve answers to fundamental questions, including protonation and/or H-bonding aspects, which accompany electron transfer. Here, we describe the nature and comparative reactivity of two low-spin heme-peroxo-Cu complexes, LS-4DCHIm, [(DCHIm)F8FeIII-(O22-)-CuII(DCHIm)4]+, and LS-3DCHIm, [(DCHIm)F8FeIII-(O22-)-CuII(DCHIm)3]+ (F8 = tetrakis(2,6-difluorophenyl)-porphyrinate; DCHIm = 1,5-dicyclohexylimidazole), toward different proton (4-nitrophenol and [DMF·H+](CF3SO3-)) (DMF = dimethyl-formamide) or electron (decamethylferrocene (Fc*)) sources. Spectroscopic reactivity studies show that differences in structure and electronic properties of LS-3DCHIm and LS-4DCHIm lead to significant differences in behavior. LS-3DCHIm is resistant to reduction, is unreactive toward weakly acidic 4-NO2-phenol, and stronger acids cleave the metal-O bonds, releasing H2O2. By contrast, LS-4DCHIm forms an adduct with 4-NO2-phenol, which includes an H-bond to the peroxo O-atom distal to Fe (resonance Raman (rR) spectroscopy and DFT). With addition of Fc* (2 equiv overall required), O-O reductive cleavage occurs, giving water, Fe(III), and Cu(II) products; however, a kinetic study reveals a one-electron rate-determining process, ket = 1.6 M-1 s-1 (-90 °C). The intermediacy of a high-valent [(DCHIm)F8FeIV═O] species is thus implied, and separate experiments show that one-electron reduction-protonation of [(DCHIm)F8FeIV═O] occurs faster (ket2 = 5.0 M-1 s-1), consistent with the overall postulated mechanism. The importance of the H-bonding interaction as a prerequisite for reductive cleavage is highlighted.
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Affiliation(s)
- Suzanne M. Adam
- Johns Hopkins University, Baltimore, Maryland 21218, United States
| | | | - Andrew W. Schaefer
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Savita K. Sharma
- Johns Hopkins University, Baltimore, Maryland 21218, United States
| | | | - Edward I. Solomon
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
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15
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Hg(II) coordination complexes containing the tris(2-pyridylmethyl)amine ligand: Synthesis, characterization and crystal structure analysis. Polyhedron 2016. [DOI: 10.1016/j.poly.2016.09.015] [Citation(s) in RCA: 5] [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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16
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Hematian S, Garcia-Bosch I, Karlin KD. Synthetic heme/copper assemblies: toward an understanding of cytochrome c oxidase interactions with dioxygen and nitrogen oxides. Acc Chem Res 2015; 48:2462-74. [PMID: 26244814 DOI: 10.1021/acs.accounts.5b00265] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Our long-time niche in synthetic biological inorganic chemistry has been to design ligands and generate coordination complexes of copper or iron ions or both, those reacting with dioxygen (O2) or nitrogen oxides (e.g., nitric oxide (NO(g)) and nitrite (NO2(-))) or both. As inspiration for this work, we turn to mitochondrial cytochrome c oxidase, which is responsible for dioxygen consumption and is also the predominant target for NO(g) and nitrite within mitochondria. In this Account, we highlight recent advances in studying synthetic heme/Cu complexes in two respects. First, there is the design, synthesis, and characterization of new O2 adducts whose further study will add insights into O2 reductive cleavage chemistry. Second, we describe how related heme/Cu constructs reduce nitrite ion to NO(g) or the reverse, oxidize NO(g) to nitrite. The reactions of nitrogen oxides occur as part of CcO's function, which is intimately tied to cellular O2 balance. We had first discovered that reduced heme/Cu compounds react with O2 giving μ-oxo heme-Fe(III)-O-Cu(II)(L) products; their properties are discussed. The O-atom is derived from dioxygen, and interrogations of these systems led to the construction and characterization of three distinctive classes of heme-peroxo complexes, two high-spin and one low-spin species. Recent investigations include a new approach to the synthesis of low-spin heme-peroxo-Cu complexes, employing a "naked" synthon, where the copper ligand denticity and geometric types can be varied. The result is a collection of such complexes; spectroscopic and structural features (by DFT calculations) are described. Some of these compounds are reactive toward reductants/protons effecting subsequent O-O cleavage. This points to how subtle improvements in ligand environment lead to a desired local structure and resulting optimized reactivity, as known to occur at enzyme active sites. The other sector of research is focused on heme/Cu assemblies mediating the redox interplay between nitrite and NO(g). In the nitrite reductase chemistry, the cupric center serves as a Lewis acid, while the heme is the redox active center providing the electron. The orientation of nitrite in approaching the ferrous heme center and N-atom binding are important. Also, detailed spectroscopic and kinetic studies of the NO(g) oxidase chemistry, in excellent agreement with theoretical calculations, reveal the intermediates and key mechanistic steps. Thus, we suggest that both chemical and biochemical heme/Cu-mediated nitrite reductase and NO(g) oxidase chemistry require N-atom binding to a ferrous heme along with cupric ion O-atom coordination, proceeding via a three-membered O-Fe-N chelate ring transition state. These important mechanistic features of heme/Cu systems interconverting NO(g) and nitrite are discussed for the first time.
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Affiliation(s)
- Shabnam Hematian
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21211, United States
| | - Isaac Garcia-Bosch
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21211, United States
| | - Kenneth D. Karlin
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21211, United States
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Garcia-Bosch I, Adam SM, Schaefer AW, Sharma SK, Peterson RL, Solomon EI, Karlin KD. A "naked" Fe(III)-(O₂²⁻)-Cu(II) species allows for structural and spectroscopic tuning of low-spin heme-peroxo-Cu complexes. J Am Chem Soc 2015; 137:1032-5. [PMID: 25594533 PMCID: PMC4311974 DOI: 10.1021/ja5115198] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
![]()
Here
we describe a new approach for the generation of heme-peroxo-Cu
compounds, using a “naked” complex synthon, [(F8)FeIII-(O22–)-CuII(MeTHF)3]+ (MeTHF = 2-methyltetrahydrofuran;
F8 = tetrakis(2,6-difluorophenyl)porphyrinate).
Addition of varying ligands (L) for Cu allows the generation and spectroscopic
characterization of a family of high- and low-spin FeIII-(O22–)-CuII(L) complexes.
These possess markedly varying CuII coordination geometries,
leading to tunable Fe-O, O-O, and Cu-O bond strengths. DFT calculations
accompanied by vibrational data correlations give detailed structural
insights.
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Sharma SK, Rogler PJ, Karlin KD. Reactions of a heme-superoxo complex toward a cuprous chelate and •NO (g): C cO and NOD chemistry. J PORPHYR PHTHALOCYA 2015; 19:352-360. [PMID: 26056423 PMCID: PMC4457333 DOI: 10.1142/s108842461550025x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Following up on the characterization of a new (heme)FeIII-superoxide species formed from the cryogenic oxygenation of a ferrous-heme (PPy)FeII (1) (PPy = a tetraarylporphyrinate with a covalently tethered pyridine group as a potential axial base), giving (PPy)FeIII-O2•- (2) (Li Y et al., Polyhedron 2013; 58: 60-64), we report here on (i) its use in forming a cytochrome c oxidase (CcO) model compound, or (ii) in a reaction with nitrogen monoxide (•NO; nitric oxide) to mimic nitric oxide dioxygenase (NOD) chemistry. Reaction of (2) with the cuprous chelate [CuI(AN)][B(C6F5)4] (AN = bis[3-(dimethylamino) propyl]amine) gives a meta-stable product [(PPy)FeIII-([Formula: see text])-CuII(AN)][B(C6F5)4] (3a), possessing a high-spin iron(III) and Cu(II) side-on bridged peroxo moiety with a μ-η2:η2-binding motif. This complex thermally decays to a corresponding μ-oxo complex [(PPy)FeIII-(O2-)-CuII(AN)][B(C6F5)4] (3). Both (3) and (3a) have been characterized by UV-vis, 2H NMR and EPR spectroscopies. When (2) is exposed to •NO(g), a ferric heme nitrato compound forms; if 2,4-di-tert-butylphenol is added prior to •NO(g) exposure, phenol ortho-nitration occurs with the iron product being the ferric hydroxide complex (PPy) FeIII(OH) (5). The latter reactions mimic the action of NOD's.
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Affiliation(s)
- Savita K. Sharma
- Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Patrick J. Rogler
- Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218, USA
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Weidinger IM. Analysis of structure-function relationships in cytochrome c oxidase and its biomimetic analogs via resonance Raman and surface enhanced resonance Raman spectroscopies. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1847:119-25. [PMID: 25223590 DOI: 10.1016/j.bbabio.2014.09.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2014] [Revised: 08/27/2014] [Accepted: 09/05/2014] [Indexed: 01/08/2023]
Abstract
Cytochrome c oxidase (CcO) catalyzes the four electron reduction of molecular oxygen to water while avoiding the formation of toxic peroxide; a quality that is of high relevance for the development of oxygen-reducing catalysts. Resonance Raman spectroscopy has been used since many years as a technique to identify electron transfer pathways in cytochrome c oxidase and to identify the key intermediates in the catalytic cycle. This information can be compared to artificial systems such as modified heme-copper enzymes, molecular heme-copper catalysts or CcO/electrode complexes in order to shed light into the reaction mechanism of these non-natural systems. Understanding the structural commonalities and differences of CcO with its non-natural analogs is of great value for designing efficient oxygen-reducing catalysts. In this review therefore Raman spectroscopic measurements on artificial heme-copper enzymes and model complexes are summarized and compared to the natural enzyme cytochrome c oxidase. This article is part of a Special Issue entitled: Vibrational spectroscopies and bioenergetic systems.
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Affiliation(s)
- Inez M Weidinger
- Department of Chemistry PC 14, Technische Universitaet Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany.
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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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Li Y, Sharma SK, Karlin KD. New heme-dioxygen and carbon monoxide adducts using pyridyl or imidazolyl tailed porphyrins. Polyhedron 2013; 58. [PMID: 24223452 DOI: 10.1016/j.poly.2012.11.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Inspired by the chemistry relevant to dioxygen storage, transport and activation by metalloproteins, in particular for heme/copper oxidases, and carbon monoxide binding to metal-containing active sites as a probe or surrogate for dioxygen binding, a series of heme derived dioxygen and CO complexes have been designed, synthesized, and characterized with respect to their physical properties and reactivity. The focus of this study is in the description and comparison of three types heme-superoxo and heme-CO adducts. The starting point is in the characterization of the reduced heme complexes, [(F8)FeII], [(PPy)FeII] and [(PIm)FeII], where F8, PPy and PIm are iron(II)-porphyrinates and where PPy and PIm possess a covalently tethered axial base pyridyl or imidazolyl group, respectively. The spin-state properties of these complexes vary with solvent. The low temperature reaction between O2 and these reduced porphyrin FeII complex yield distinctive low spin heme-superoxo adducts. The dioxygen binding properties for all three complexes are shown to be reversible, via alternate argon or O2 bubbling. Carbon monoxide binds to the reduced heme-FeII precursors to form low spin heme-CO adducts. The implications for future investigations of these heme O2 and CO adducts are discussed.
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Affiliation(s)
- Yuqi Li
- Department of Chemistry, The Johns Hopkins University, Baltimore, MD 21218
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Kieber-Emmons MT, Li Y, Halime Z, Karlin KD, Solomon EI. Electronic structure of a low-spin heme/Cu peroxide complex: spin-state and spin-topology contributions to reactivity. Inorg Chem 2011; 50:11777-86. [PMID: 22007669 PMCID: PMC3226806 DOI: 10.1021/ic2018727] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
This study details the electronic structure of the heme–peroxo–copper adduct {[(F8)Fe(DCHIm)]-O2-[Cu(AN)]}+ (LS(AN)) in which O2(2–) bridges the metals in a μ-1,2 or “end-on” configuration. LS(AN) is generated by addition of coordinating base to the parent complex {[(F8)Fe]-O2-[Cu(AN)]}+ (HS(AN)) in which the O2(2–) bridges the metals in an μ-η2:η2 or “side-on” mode. In addition to the structural change of the O2(2–) bridging geometry, coordination of the base changes the spin state of the heme fragment (from S = 5/2 in HS(AN) to S = 1/2 in LS(AN)) that results in an antiferromagnetically coupled diamagnetic ground state in LS(AN). The strong ligand field of the porphyrin modulates the high-spin to low-spin effect on Fe–peroxo bonding relative to nonheme complexes, which is important in the O–O bond cleavage process. On the basis of DFT calculations, the ground state of LS(AN) is dependent on the Fe–O–O–Cu dihedral angle, wherein acute angles (<~150°) yield an antiferromagnetically coupled electronic structure while more obtuse angles yield a ferromagnetic ground state. LS(AN) is diamagnetic and thus has an antiferromagnetically coupled ground state with a calculated Fe–O–O–Cu dihedral angle of 137°. The nature of the bonding in LS(AN) and the frontier molecular orbitals which lead to this magneto-structural correlation provide insight into possible spin topology contributions to O–O bond cleavage by cytochrome c oxidase.
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Affiliation(s)
| | - Yuqi Li
- Department of Chemistry, The Johns Hopkins University, Baltimore, MD 21218
| | - Zakaria Halime
- Department of Chemistry, The Johns Hopkins University, Baltimore, MD 21218
| | - Kenneth D. Karlin
- Department of Chemistry, The Johns Hopkins University, Baltimore, MD 21218
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Kieber-Emmons MT, Qayyum MF, Li Y, Halime Z, Hodgson KO, Hedman B, Karlin KD, Solomon EI. Spectroscopic elucidation of a new heme/copper dioxygen structure type: implications for O···O bond rupture in cytochrome c oxidase. Angew Chem Int Ed Engl 2011; 51:168-72. [PMID: 22095556 DOI: 10.1002/anie.201104080] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2011] [Revised: 08/24/2011] [Indexed: 11/11/2022]
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Kieber-Emmons MT, Qayyum MF, Li Y, Halime Z, Hodgson KO, Hedman B, Karlin KD, Solomon EI. Spectroscopic Elucidation of a New Heme/Copper Dioxygen Structure Type: Implications for O⋅⋅⋅O Bond Rupture in Cytochrome c Oxidase. Angew Chem Int Ed Engl 2011. [DOI: 10.1002/ange.201104080] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Schopfer MP, Wang J, Karlin KD. Bioinspired heme, heme/nonheme diiron, heme/copper, and inorganic NOx chemistry: *NO((g)) oxidation, peroxynitrite-metal chemistry, and *NO((g)) reductive coupling. Inorg Chem 2010; 49:6267-82. [PMID: 20666386 DOI: 10.1021/ic100033y] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The focus of this Forum Article highlights work from our own laboratories and those of others in the area of biochemical and biologically inspired inorganic chemistry dealing with nitric oxide [nitrogen monoxide, *NO((g))] and its biological roles and reactions. The latter focus is on (i) oxidation of *NO((g)) to nitrate by nitric oxide dioxygenases (NODs) and (ii) reductive coupling of two molecules of *NO((g)) to give N(2)O(g). In the former case, NODs are described, and the highlighting of possible peroxynitrite/heme intermediates and the consequences of this are given by a discussion of recent works with myoglobin and a synthetic heme model system for NOD action. Summaries of recent copper complex chemistries with *NO((g)) and O(2)(g), leading to peroxynitrite species, are given. The coverage of biological reductive coupling of *NO((g)) deals with bacterial nitric oxide reductases (NORs) with heme/nonheme diiron active sites and on heme/copper oxidases such as cytochrome c oxidase, which can mediate the same chemistry. Recently designed protein and synthetic model compounds (heme/nonheme/diiron or heme/copper) as functional mimics are discussed in some detail. We also highlight examples from the chemical literature, not necessarily involving biologically relevant metal ions, that describe the oxidation of *NO((g)) to nitrate (or nitrite) and possible peroxynitrite intermediates or reductive coupling of *NO((g)) to give nitrous oxide.
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Affiliation(s)
- Mark P Schopfer
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA
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Wang J, Schopfer MP, Puiu SC, Sarjeant AAN, Karlin KD. Reductive coupling of nitrogen monoxide (*NO) facilitated by heme/copper complexes. Inorg Chem 2010; 49:1404-19. [PMID: 20030370 DOI: 10.1021/ic901431r] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The interactions of nitrogen monoxide (*NO; nitric oxide) with transition metal centers continue to be of great interest, in part due to their importance in biochemical processes. Here, we describe *NO((g)) reductive coupling chemistry of possible relevance to that process (i.e., nitric oxide reductase (NOR) biochemistry), which occurs at the heme/Cu active site of cytochrome c oxidases (CcOs). In this report, heme/Cu/*NO((g)) activity is studied using 1:1 ratios of heme and copper complex components, (F(8))Fe (F(8) = tetrakis(2,6-difluorophenyl)porphyrinate(2-)) and [(tmpa)Cu(I)(MeCN)](+) (TMPA = tris(2-pyridylmethyl)amine). The starting point for heme chemistry is the mononitrosyl complex (F(8))Fe(NO) (lambda(max) = 399 (Soret), 541 nm in acetone). Variable-temperature (1)H and (2)H NMR spectra reveal a broad peak at delta = 6.05 ppm (pyrrole) at room temperature (RT), which gives rise to asymmetrically split pyrrole peaks at 9.12 and 8.54 ppm at -80 degrees C. A new heme dinitrosyl species, (F(8))Fe(NO)(2), obtained by bubbling (F(8))Fe(NO) with *NO((g)) at -80 degrees C, could be reversibly formed, as monitored by UV-vis (lambda(max) = 426 (Soret), 538 nm in acetone), EPR (silent), and NMR spectroscopies; that is, the mono-NO complex was regenerated upon warming to RT. (F(8))Fe(NO)(2) reacts with [(tmpa)Cu(I)(MeCN)](+) and 2 equiv of acid to give [(F(8))Fe(III)](+), [(tmpa)Cu(II)(solvent)](2+), and N(2)O((g)), fitting the stoichiometric *NO((g)) reductive coupling reaction: 2*NO((g)) + Fe(II) + Cu(I) + 2H(+) --> N(2)O((g)) + Fe(III) + Cu(II) + H(2)O, equivalent to one enzyme turnover. Control reaction chemistry shows that both iron and copper centers are required for the NOR-type chemistry observed and that, if acid is not present, half the *NO is trapped as a (F(8))Fe(NO) complex, while the remaining nitrogen monoxide undergoes copper complex promoted disproportionation chemistry. As part of this study, [(F(8))Fe(III)]SbF(6) was synthesized and characterized by X-ray crystallography, along with EPR (77 K: g = 5.84 and 6.12 in CH(2)Cl(2) and THF, respectively) and variable-temperature NMR spectroscopies. These structural and physical properties suggest that at RT this complex consists of an admixture of high and intermediate spin states.
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Affiliation(s)
- Jun Wang
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA
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Halime Z, Kieber-Emmons MT, Qayyum MF, Mondal B, Gandhi T, Puiu SC, Chufán EE, Sarjeant AAN, Hodgson KO, Hedman B, Solomon EI, Karlin KD. Heme-copper-dioxygen complexes: toward understanding ligand-environmental effects on the coordination geometry, electronic structure, and reactivity. Inorg Chem 2010; 49:3629-45. [PMID: 20380465 PMCID: PMC2893725 DOI: 10.1021/ic9020993] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The nature of the ligand is an important aspect of controlling the structure and reactivity in coordination chemistry. In connection with our study of heme-copper-oxygen reactivity relevant to cytochrome c oxidase dioxygen-reduction chemistry, we compare the molecular and electronic structures of two high-spin heme-peroxo-copper [Fe(III)O(2)(2-)Cu(II)](+) complexes containing N(4) tetradentate (1) or N(3) tridentate (2) copper ligands. Combining previously reported and new resonance Raman and EXAFS data coupled to density functional theory calculations, we report a geometric structure and more complete electronic description of the high-spin heme-peroxo-copper complexes 1 and 2, which establish mu-(O(2)(2-)) side-on to the Fe(III) and end-on to Cu(II) (mu-eta(2):eta(1)) binding for the complex 1 but side-on/side-on (mu-eta(2):eta(2)) mu-peroxo coordination for the complex 2. We also compare and summarize the differences and similarities of these two complexes in their reactivity toward CO, PPh(3), acid, and phenols. The comparison of a new X-ray structure of mu-oxo complex 2a with the previously reported 1a X-ray structure, two thermal decomposition products respectively of 2 and 1, reveals a considerable difference in the Fe-O-Cu angle between the two mu-oxo complexes ( angleFe-O-Cu = 178.2 degrees in 1a and angleFe-O-Cu = 149.5 degrees in 2a). The reaction of 2 with 1 equiv of an exogenous nitrogen-donor axial base leads to the formation of a distinctive low-temperature-stable, low-spin heme-dioxygen-copper complex (2b), but under the same conditions, the addition of an axial base to 1 leads to the dissociation of the heme-peroxo-copper assembly and the release of O(2). 2b reacts with phenols performing H-atom (e(-) + H(+)) abstraction resulting in O-O bond cleavage and the formation of high-valent ferryl [Fe(IV)=O] complex (2c). The nature of 2c was confirmed by a comparison of its spectroscopic features and reactivity with those of an independently prepared ferryl complex. The phenoxyl radical generated by the H-atom abstraction was either (1) directly detected by electron paramagnetic resonance spectroscopy using phenols that produce stable radicals or (2) indirectly detected by the coupling product of two phenoxyl radicals.
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Affiliation(s)
- Zakaria Halime
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA
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Lu C, Zhao X, Lu Y, Rousseau DL, Yeh SR. Role of copper ion in regulating ligand binding in a myoglobin-based cytochrome C oxidase model. J Am Chem Soc 2010; 132:1598-605. [PMID: 20070118 DOI: 10.1021/ja907777f] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Cytochrome c oxidase (CcO), the terminal enzyme in the mitochondrial respiratory chain, catalyzes the four-electron reduction of dioxygen to water in a binuclear center comprised of a high-spin heme (heme a(3)) and a copper atom (Cu(B)) coordinated by three histidine residues. As a minimum model for CcO, a mutant of sperm whale myoglobin, named Cu(B)Mb, has been engineered, in which a copper atom is held in the distal heme pocket by the native E7 histidine and two nonnative histidine residues. In this work, the role of the copper in regulating ligand binding in Cu(B)Mb was investigated. Resonance Raman studies show that the presence of copper in CO-bound Cu(B)Mb leads to a CcO-like distal heme pocket. Stopped-flow data show that, upon the initiation of the CO binding reaction, the ligand first binds to the Cu(+); it subsequently transfers from Cu(+) to Fe(2+) in an intramolecular process, similar to that reported for CcO. The high CO affinity toward Cu(+) and the slow intramolecular CO transfer rate between Cu(+) and Fe(2+) in the Cu(B)Mb/Cu(+) complex are analogous to those in Thermus thermophilus CcO (TtCcO) but distinct from those in bovine CcO (bCcO). Additional kinetic studies show that, upon photolysis of the NO-bound Cu(B)Mb/Cu(+) complex, the photolyzed ligand transiently binds to Cu(+) and subsequently rebinds to Fe(2+), accounting for the 100% geminate recombination yield, similar to that found in TtCcO. The data demonstrate that the Cu(B)Mb/Cu(+) complex reproduces essential structural and kinetic features of CcO and that the complex is more akin to TtCcO than to bCcO.
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Affiliation(s)
- Changyuan Lu
- Department of Physiology and Biophysics, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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Liang J, Canary JW. A stereodynamic tripodal ligand with three different coordinating arms: synthesis and zinc(II), copper(I) complexation study. Chirality 2010; 23:24-33. [PMID: 20222142 DOI: 10.1002/chir.20833] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
A tetradentate tripodal ligand containing a chiral center and three different coordinating arms was designed and synthesized. Its complexation properties with Zn(II) and Cu(I) were studied by NMR and optical spectroscopy. NMR experiments demonstrated the formation of two diastereomers, indicating the stabilization of the central tertiary amine configuration by metal coordination. The inversion of pyramidalization of the central tertiary amine of the ligand was found to be highly dependent upon metal ion, solvent, and temperature. Dynamic NMR measurements were used to estimate the energy of activation required for nitrogen atom inversion. Finally, absorption and circular dichroism measurements confirmed the expectation that metal complexes of the ligand gave rise to circular dichroism but that such spectra were not characterized by exciton-coupling, in contrast to previously described ligands containing two identical arms with strong chromophores.
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Affiliation(s)
- Jian Liang
- Department of Chemistry, New York University, New York 10003, USA
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30
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Toma HE, Araki K. Exploring the Supramolecular Coordination Chemistry-Based Approach for Nanotechnology. ACTA ACUST UNITED AC 2009. [DOI: 10.1002/9780470440124.ch5] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
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31
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Fukuzumi S. Roles of Metal Ions in Controlling Bioinspired Electron-Transfer Systems. Metal Ion-Coupled Electron Transfer. PROGRESS IN INORGANIC CHEMISTRY 2009. [DOI: 10.1002/9780470440124.ch2] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
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32
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Topolski A, Lipińska M, Kita P, Wiśniewska J. Kinetic studies on promazine oxidation by FeIII/CuII in acidic aqueous bromide solutions. Spectroscopic and kinetic non-additivity as evidence for the CuII–Br–FeIII-type heterobimetallic complex formation. TRANSIT METAL CHEM 2008. [DOI: 10.1007/s11243-008-9120-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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33
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Blackman AG. Tripodal Tetraamine Ligands Containing Three Pyridine Units: The
other
Polypyridyl Ligands. Eur J Inorg Chem 2008. [DOI: 10.1002/ejic.200800115] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Allan G. Blackman
- Department of Chemistry, University of Otago, P. O. Box 56, Dunedin, New Zealand, Fax: +64‐3‐479‐7906
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Maiti D, Woertink JS, Narducci Sarjeant AA, Solomon EI, Karlin KD. Copper Dioxygen Adducts: Formation of Bis(μ-oxo)dicopper(III) versus (μ-1,2)Peroxodicopper(II) Complexes with Small Changes in One Pyridyl-Ligand Substituent. Inorg Chem 2008; 47:3787-800. [DOI: 10.1021/ic702437c] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Debabrata Maiti
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, and Department of Chemistry, Stanford University, Stanford, California 94305
| | - Julia S. Woertink
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, and Department of Chemistry, Stanford University, Stanford, California 94305
| | - Amy A. Narducci Sarjeant
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, and Department of Chemistry, Stanford University, Stanford, California 94305
| | - Edward I. Solomon
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, and Department of Chemistry, Stanford University, Stanford, California 94305
| | - Kenneth D. Karlin
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, and Department of Chemistry, Stanford University, Stanford, California 94305
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