scholarly journals Reversible Metal-Centered Reduction Empowers a Ni-Corrin to Mimic F430

2021 ◽  
Author(s):  
Christopher Brenig ◽  
Leila Mosberger ◽  
Olivier Blacque ◽  
Reinhard Kissner ◽  
Felix Zelder
Keyword(s):  
Catalytically Active ◽  
Electron Reduction ◽  
Cofactor F430

This communication presents a novel truncated NiII-containing metbalamin and describes its reversible one electron reduction to a catalytically active NiI species, that features cofactor F430 model character. Our results strikingly...

Electrochemical behaviour of molybdenum-nitrosyl complexes of the type Mo(NO)2Cl2L2 and Mo(NO)Cl3L2

1982 ◽  
Vol 47 (6) ◽  
pp. 1721-1732 ◽  
Author(s):  
Jiří Mašek ◽  
Jan Fiedler ◽  
Jiří Klíma ◽  
Karl Seyferth ◽  
Rudolph Taube
Keyword(s):  
Esr Spectroscopy ◽  
Electrochemical Behaviour ◽  
Active Species ◽  
Redox Properties ◽  
Electron Localization ◽  
Potential Region ◽  
Nitrosyl Complexes ◽  
Catalytically Active ◽  
Electron Reduction ◽  
Dinitrosyl Complexes

Electrochemical behaviour of 22 molybdenum-nitrosyl complexes of the title types serving as catalyst precursors of olefin metathesis reactions was investigated and the odd-electron localization in the 1-electron reduction products was determined by ESR spectroscopy. It was found that the mononitrosyl complexes containing the fragment {Mo(NO)}4 are reduced in a potential region more positive and distinctly separated from that of the dinitrosyl complexes containing the fragment {Mo(NO)2}6. In the reduction of the former complexes the electrons are accepted into a MO having prevailingly metal d-character while with the latter class of complexes the electrons accepted in the reduction are accommodated in a π-NO based MO. The comparison of the electrochemical results with the catalytic activity of the corresponding systems shows that the ability of the precursor complexes to form the catalytically active species depends on their substitution lability rather than on their redox properties.

scholarly journals Electrochemical evidence that pyranopterin redox chemistry controls the catalysis of YedY, a mononuclear Mo enzyme

2015 ◽  
Vol 112 (47) ◽  
pp. 14506-14511 ◽  
Author(s):  
Hope Adamson ◽  
Alexandr N. Simonov ◽  
Michelina Kierzek ◽  
Richard A. Rothery ◽  
Joel H. Weiner ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Catalytic Reduction ◽  
Reduction Process ◽  
Electron Transition ◽  
Hydrogen Electrode ◽  
Redox Titration ◽  
Catalytically Active ◽  
Alternating Current Voltammetry ◽  
Titration Data ◽  
Electron Reduction

A long-standing contradiction in the field of mononuclear Mo enzyme research is that small-molecule chemistry on active-site mimic compounds predicts ligand participation in the electron transfer reactions, but biochemical measurements only suggest metal-centered catalytic electron transfer. With the simultaneous measurement of substrate turnover and reversible electron transfer that is provided by Fourier-transformed alternating-current voltammetry, we show that Escherichia coli YedY is a mononuclear Mo enzyme that reconciles this conflict. In YedY, addition of three protons and three electrons to the well-characterized “as-isolated” Mo(V) oxidation state is needed to initiate the catalytic reduction of either dimethyl sulfoxide or trimethylamine N-oxide. Based on comparison with earlier studies and our UV-vis redox titration data, we assign the reversible one-proton and one-electron reduction process centered around +174 mV vs. standard hydrogen electrode at pH 7 to a Mo(V)-to-Mo(IV) conversion but ascribe the two-proton and two-electron transition occurring at negative potential to the organic pyranopterin ligand system. We predict that a dihydro-to-tetrahydro transition is needed to generate the catalytically active state of the enzyme. This is a previously unidentified mechanism, suggested by the structural simplicity of YedY, a protein in which Mo is the only metal site.

scholarly journals Nitrogenase of Azotobacter chroococcum. Kinetics of the reduction of oxidized iron-protein by sodium dithionite

1976 ◽  
Vol 155 (1) ◽  
pp. 137-144 ◽  
Author(s):  
R N F Thorneley ◽  
M G Yates ◽  
D J Lowe
Keyword(s):  
Electron Paramagnetic Resonance Spectroscopy ◽  
Sodium Dithionite ◽  
Azotobacter Chroococcum ◽  
High Rate ◽  
Resonance Spectroscopy ◽  
Paramagnetic Resonance ◽  
Fe Protein ◽  
Catalytically Active ◽  
Electron Reduction ◽  
Kinetics Of

The kinetics of the reduction of oxidized Fe-protein of nitrogenase from Azotobacter chroococcum by sodium dithionite were studied by stopped-flow and rapid-freezing e.p.r. (electron-paramagnetic-resonance) spectroscopy. The appearance of the gav. = 1.94 e.p.r. signal (0.24 electron integrated intensity/mol) was associated with a one-electron reduction by SO2- with k greater than 10(8)M-.S-1 at 23 degrees C. A value of k = 1.75s-1 was obtained for the rate of dissociation of S2O42- into 2SO2- at 23 degrees C. Further reductions by SO2- occurred in three slower phases with rate constants in the range 10(4) −10(6)M-1-S-1. These latter phases have no corresponding e.p.r. signal changes and are probably associated with enzymically inactive protein. The high rate of reduction by SO2-of the Fe-protein alone (k greater than 108M1.S-1) relative to the rate of oxidation of the Fe-protein in the catalytically active Fe:Mo-Fe protein complex (k = 2.2 } 102s-1) and the observation that in the steady state the Fe-protein is substantially oxidized means that at normal assay concentrations another reaction must limit the rate of reduction of Fe-protein during turnover.

Growth of Catalytically Active Nanostructures in the Nonequilibrium Epitaxy Regime

2015 ◽  
Vol 60 (6) ◽  
pp. 546-552
Author(s):  
V.M. Gorshkov ◽  
◽  
V.V. Kuzmenko
Keyword(s):  
Catalytically Active

Room Temperature Alkali Metal Reduction of Carbon Dioxide

2020 ◽  
Author(s):  
Lucas A. Freeman ◽  
Akachukwu D. Obi ◽  
Haleigh R. Machost ◽  
Andrew Molino ◽  
Asa W. Nichols ◽  
...  
Keyword(s):  
Alkali Metal ◽  
Alkali Metals ◽  
Room Temperature ◽  
Chemical Reduction ◽  
Bond Cleavage ◽  
Open Shell ◽  
Metal Reduction ◽  
One Pot ◽  
Earth Abundant ◽  
Electron Reduction

The reduction of the relatively inert carbon–oxygen bonds of CO<sub>2</sub> to access useful CO<sub>2</sub>-derived organic products is one of the most important fundamental challenges in synthetic chemistry. Facilitating this bond-cleavage using earth-abundant, non-toxic main group elements (MGEs) is especially arduous because of the difficulty in achieving strong inner-sphere interactions between CO<sub>2</sub> and the MGE. Herein we report the first successful chemical reduction of CO<sub>2</sub> at room temperature by alkali metals, promoted by a cyclic(alkyl)(amino) carbene (CAAC). One-electron reduction of CAAC-CO<sub>2</sub> adduct (<b>1</b>) with lithium, sodium or potassium metal yields stable monoanionic radicals clusters [M(CAAC–CO<sub>2</sub>)]<sub>n</sub>(M = Li, Na, K, <b> 2</b>-<b>4</b>) and two-electron alkali metal reduction affords open-shell, dianionic clusters of the general formula [M<sub>2</sub>(CAAC–CO<sub>2</sub>)]<sub>n </sub>(<b>5</b>-<b>8</b>). It is notable that these crystalline clusters of reduced CO<sub>2</sub> may also be isolated via the “one-pot” reaction of free CO<sub>2</sub> with free CAAC followed by the addition of alkali metals – a reductive process which does not occur in the absence of carbene. Each of the products <b>2</b>-<b>8</b> were investigated using a combination of experimental and theoretical methods.<br>

Sewage sludge as a precursor of adsorbents/catalysts for environmental applications

2007 ◽  
Vol 2 (1) ◽  
Author(s):  
A. Ros ◽  
C. Canals-Batlle ◽  
M.A. Lillo-Ródenas ◽  
E. Fuente ◽  
M. A. Montes-Morán ◽  
...  
Keyword(s):  
Sewage Sludge ◽  
Room Temperature ◽  
Waste Water Treatment ◽  
Textural Properties ◽  
Active Species ◽  
Elemental Sulphur ◽  
Gaseous Emissions ◽  
Removal Experiments ◽  
Catalytically Active

This paper focuses on the valorisation of solid residues obtained from the thermal treatment of sewage sludge. In particular, sewage sludge samples were collected from two waste water treatment plants (WWTPs) with different sludge line basic operations. After drying, sludges were heated up to 700 °C in appropriate ovens under diluted air (gasification) and inert (pyrolysis) atmospheres. The solids obtained, as well as the dried (raw) sludges, were characterised to determine their textural properties and chemical composition, including the speciation of their inorganic fraction. All the materials under study were employed as adsorbents/catalysts in H2S removal experiments at room temperature. It was found that, depending on the particular sludge characteristics, outstanding results can be achieved both in terms of retention capacities and selectivity. Some of the solids outperform commercially available sorbents specially designed for gaseous emissions control. In these adsorbents/catalysts, H2S is selectively oxidised to elemental sulphur most likely due to the presence of inorganic, catalytically active species. The role of the carbon-enriched part on these solids is also remarked.

Antimyotoxic Activity of Synthetic Peptides Derived from Bothrops atrox Snake Gamma Phospholipase A2 Inhibitor Selected by Virtual Screening

2019 ◽  
Vol 19 (22) ◽  
pp. 1952-1961 ◽  
Author(s):  
J.C. Sobrinho ◽  
A.F. Francisco ◽  
R. Simões-Silva ◽  
A.M. Kayano ◽  
J.J. Alfonso Ruiz Diaz ◽  
...  
Keyword(s):  
Amino Acids ◽  
Molecular Docking ◽  
Synthetic Peptides ◽  
Cell Damage ◽  
Neutralization Assay ◽  
Phospholipase Activity ◽  
Phospholipases A2 ◽  
Catalytically Active ◽  
Bothrops Atrox

Background: Several studies have aimed to identify molecules that inhibit the toxic actions of snake venom phospholipases A2 (PLA2s). Studies carried out with PLA2 inhibitors (PLIs) have been shown to be efficient in this assignment. Objective: This work aimed to analyze the interaction of peptides derived from Bothrops atrox PLIγ (atPLIγ) with a PLA2 and to evaluate the ability of these peptides to reduce phospholipase and myotoxic activities. Methods: Peptides were subjected to molecular docking with a homologous Lys49 PLA2 from B. atrox venom modeled by homology. Phospholipase activity neutralization assay was performed with BthTX-II and different ratios of the peptides. A catalytically active and an inactive PLA2 were purified from the B. atrox venom and used together in the in vitro myotoxic activity neutralization experiments with the peptides. Results: The peptides interacted with amino acids near the PLA2 hydrophobic channel and the loop that would be bound to calcium in Asp49 PLA2. They were able to reduce phospholipase activity and peptides DFCHNV and ATHEE reached the highest reduction levels, being these two peptides the best that also interacted in the in silico experiments. The peptides reduced the myotubes cell damage with a highlight for the DFCHNV peptide, which reduced by about 65%. It has been suggested that myotoxic activity reduction is related to the sites occupied in the PLA2 structure, which could corroborate the results observed in molecular docking. Conclusion: This study should contribute to the investigation of the potential of PLIs to inhibit the toxic effects of PLA2s.

Catalytically active coatings for steam reforming systems: synthesis and catalytic properties

2019 ◽  
pp. 96-105
Author(s):  
M. L. Shishkova ◽  
N. V. Yakovleva
Keyword(s):  
Catalytic Properties ◽  
Raw Materials ◽  
Cold Gas Dynamic Spraying ◽  
Hydrogen Fuel ◽  
Functional Coatings ◽  
Science And Engineering ◽  
Powder Mixtures ◽  
Conversion Of Methane ◽  
Catalytically Active ◽  
Metal Support

The paper considers science and engineering aspects of catalytically active compositions creation as regards immobilized catalysts for reforming hydrocarbon raw materials into hydrogen fuel. The authors investigate synthesis of catalytic powder mixtures and manufacturing of functional coatings by supersonic cold gas dynamic spraying. Research results in the field of creation of catalysts for steam conversion of methane to hydrogenous fuel on the metal support (Cr15Al15 tape support) are given. Composite powder mixtures (Ni–Al–Al(OH)3– Ca(OH)2–Mg(OH)2) were used as starting materials.

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