Structure of a New Tetranuclear Iron(III) Complex with an Oxo-Bridge; Factors to Govern Formation and Stability of Oxo-Bridged Iron(III) Species in the L-Subunit of Ferritin

2006 ◽  
Vol 61 (1-2) ◽  
pp. 149-154 ◽  
Author(s):  
Yuichi Sutoh ◽  
Yuko Okawamukai ◽  
Satoshi Nishino ◽  
Yuzo Nishida
Keyword(s):  
Hydrogen Peroxide ◽  
Oxygen Atom ◽  
Electron Donor ◽  
Carboxyl Groups ◽  
Cavity Surface ◽  
Reaction Products ◽  
Ferroxidase Activity ◽  
Oxo Bridge

Abstract We have investigated the reaction products of several iron(III) compounds with hydrogen peroxide, and have found that hydrogen peroxide promotes the formation of an oxo-bridged iron(III) species in the presence of methanol (electron donor), and carboxyl groups of the ligand systems play a role to give the tetranuclear iron(III) compound containing a bent Fe- O-Fe unit (O: oxo oxygen atom). Based on the present results and the facts that L-chains of human ferritins lack ferroxidase activity, but are richer in carboxyl groups (glutamates) exposed on the cavity surface, it seems reasonable to conclude that (i) the hydrogen peroxide released in the H-subunit may contribute to the formation of a diferric oxo-hydrate in the L-subunit, (ii) the formation of a bent oxo-bridged iron(III) species is essentially important in the L-subunit, and (iii) rich carboxyl groups in L-subunits contribute to facilitate iron nucleation and mineralization through the capture and activation of the peroxide ion, and formation of a stable bent oxo-bridged iron(III) species

scholarly journals Manganese and iron tetraphenylporphyrin-catalyzed oxidation of a cardanol derivative (hydrogenated tert-butylcardanol)

2002 ◽  
Vol 06 (01) ◽  
pp. 12-16 ◽  
Author(s):  
Pietro Tagliatesta ◽  
Claudia Crestini ◽  
Raffaele Saladino ◽  
Veronica Neri ◽  
Paolino Filippone ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Oxygen Atom ◽  
Reaction Products ◽  
Catalyst Structure ◽  
Halogen Atoms ◽  
Catalyzed Oxidation

Manganese and iron 2,6-disubstituted meso-tetraphenylporphyrins, bearing halogen atoms on the β-positions, have been used as catalysts for the oxidation of a cardanol derivative (hydrogenated tert-butylcardanol), using iodosilbenzene or hydrogen peroxide as oxygen atom donors. The reaction products can be correlated to the catalyst structure and to the nature of the oxidants.

scholarly journals Evidence of H- and L-chains have co-operative roles in the iron-uptake mechanism of human ferritin

1992 ◽  
Vol 288 (2) ◽  
pp. 591-596 ◽  
Author(s):  
S Levi ◽  
S J Yewdall ◽  
P M Harrison ◽  
P Santambrogio ◽  
A Cozzi ◽  
...  
Keyword(s):  
Iron Uptake ◽  
Cavity Surface ◽  
Iron Core ◽  
Reaction Products ◽  
Uptake Mechanism ◽  
Iron Incorporation ◽  
Surface Iron ◽  
Ferroxidase Activity ◽  
Human Ferritin

The ability to incorporate iron in vitro was studied in homopolymers of human ferritin L-chain, human ferritin H-chain and its variants and in homopolymer mixtures. The H-chain variants carried amino acid substitutions in the ferroxidase centre and/or in carboxy residues on the cavity surface. Iron incorporation was examined by gel electrophoresis of the reaction products by staining for iron and protein. It was found that inactivation of the ferroxidase centre combined with the substitution of four carboxy groups on the cavity abolished the ability of H-chain ferritin to incorporate iron. Competition experiments with limited amounts of iron showed that, at neutral pH, L-chain ferritin is more efficient in forming iron cores than the H-chain variants altered at the ferroxidase activity or in the cavity. Competition experiments at pH 5.5 demonstrated that L-chain apoferritin is able to incorporate iron only when in the presence of H-chain variants with ferroxidase activity. The results indicate that L-chain apoferritin has a higher capacity than the H-chain apoferritin to induce iron-core nucleation, whereas H-chain ferritin is superior in promoting Fe(II) oxidation. The finding of cooperative roles of the H- and L-chains in ferritin iron uptake provides a clue to understanding the biological function of isoferritins.

Ionic liquids: green solvents and reactive compounds? Reaction of tri-n-butylmethylphosphonium dimethylphosphate with elemental sulfur

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Natalia Tarasova ◽  
Efrem Krivoborodov ◽  
Alexey Zanin ◽  
Yaroslav Mezhuev
Keyword(s):  
Ionic Liquids ◽  
Nmr Spectroscopy ◽  
Oxygen Atom ◽  
Elemental Sulfur ◽  
Green Solvents ◽  
Reaction Products ◽  
Mechanism Of Interaction

AbstractThe opening of the S8 ring with the formation of linear sulfur oligomers in the presence of tri-n-butylmethylphosphonium dimethylphosphate is shown. The reaction products are separated and characterized with 1H, 13C, 31P, 17O NMR spectroscopy, HD-MS, MALDI spectroscopy and XRD. It is shown that dimethylphosphate-anion is active in the reaction, and the addition of sulfur atoms occurs via the oxygen atom of dimethylphosphate-anion. It is found that a mixture of products is formed, which differ in the number of sulfur atoms in the chain. The assumptions were made about the mechanism of interaction of sulfur with tri-n-butylmethylphosphonium dimethylphosphate.

scholarly journals Equilibrium constants and protonation site for N-methylbenzenesulfonamides

2011 ◽  
Vol 7 ◽  
pp. 1732-1738 ◽  
Author(s):  
José A Moreira ◽  
Ana M Rosa da Costa ◽  
Luis García-Río ◽  
Márcia Pessêgo
Keyword(s):  
Sulfuric Acid ◽  
Oxygen Atom ◽  
Electron Donor ◽  
Equilibrium Constants ◽  
Acidity Constants ◽  
Protonation Site ◽  
Protonation Equilibria ◽  
Vis Spectroscopy ◽  
Donor Character ◽  
Solvation Parameter

The protonation equilibria of four substituted N-methylbenzenesulfonamides, X-MBS: X = 4-MeO (3a), 4-Me (3b), 4-Cl (3c) and 4-NO2 (3d), in aqueous sulfuric acid were studied at 25 °C by UV–vis spectroscopy. As expected, the values for the acidity constants are highly dependent on the electron-donor character of the substituent (the pK BH+ values are −3.5 ± 0.2, −4.2 ± 0.2, −5.2 ± 0.3 and −6.0 ± 0.3 for 3a, 3b, 3c and 3d, respectively). The solvation parameter m* is always higher than 0.5 and points to a decrease in the importance of solvation on the cation stabilization as the electron-donor character of the substituent increases. Hammett plots of the equilibrium constants showed a better correlation with the σ+ substituent parameter than with σ, which indicates that the initial protonation site is the oxygen atom of the sulfonyl group.

scholarly journals Novel homogeneous photocatalyst for oxygen to hydrogen peroxide reduction in aqueous media

2019 ◽  
Vol 18 (8) ◽  
pp. 1982-1989
Author(s):  
Daniil A. Lukyanov ◽  
Liya D. Funt ◽  
Alexander S. Konev ◽  
Alexey V. Povolotskiy ◽  
Anatoliy A. Vereshchagin ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Electron Donor ◽  
Aqueous Media ◽  
Peroxide Reduction ◽  
Hydrogen Peroxide Reduction

Novel pyrrolo-isoquinoline dyad was shown to be a promising photocatalyst for O2 to H2O reduction using oxalate as a sacrificial electron donor.

scholarly journals Characterization, Antimicrobial Properties and Coatings Application of Gellan Gum Oxidized with Hydrogen Peroxide

Foods ◽  
2019 ◽  
Vol 8 (1) ◽  
pp. 31 ◽  
Author(s):  
Yushuang Lu ◽  
Xiaojian Zhao ◽  
Sheng Fang
Keyword(s):  
Hydrogen Peroxide ◽  
1H Nmr Spectroscopy ◽  
Antimicrobial Properties ◽  
Antimicrobial Activities ◽  
Gellan Gum ◽  
Proton Nuclear Magnetic Resonance ◽  
Carboxyl Groups ◽  
Gram Negative Bacteria ◽  
Gram Positive Bacteria ◽  
H2o2 Oxidation

The effect of hydrogen peroxide (H2O2) oxidation on the physicochemical, gelation and antimicrobial properties of gellan gum was studied. The oxidized gellan gum (OGG) was characterized by measuring the carboxyl/carbonyl group contents, Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1H-NMR) spectroscopy. The H2O2 oxidation resulted in a large increase in the carboxyl groups in gellan gum. The OGG lost gelation ability by oxidation even in the presence of metal ions. The antimicrobial activities of the OGG against Gram-positive bacteria (Staphylococcus aureus), Gram-negative bacteria (Escherichia coli), and fungal (Aspergillus niger) were tested. The OGG could inhibit the growth of both bacteria and fungal, and the activity was improved with an increase in the oxidation level. Finally, the application of the OGG as an active coatings material to extend the storage of apples was tested.

Darstellung von o-Phenylen-bis(dibromphosphan) — Reaktionsprodukte von o-Phenylen-bis(dichlorphosphan) / Synthesis of o-Phenylene-bis(dibromophosphane) — Reaction Products of o-Phenylene-bis(dichlorophosphane)

1984 ◽  
Vol 39 (12) ◽  
pp. 1706-1710 ◽  
Author(s):  
H.-J. Wörz ◽  
E. Quien ◽  
H. P. Latscha
Keyword(s):  
Hydrogen Peroxide ◽  
Hydrogen Bromide ◽  
Equimolar Amount ◽  
Reaction Products ◽  
Large Excess ◽  
Cyclic Anhydride ◽  
Complete Hydrolysis ◽  
Hydrolysis Of

o-Phenylene-bis(dibromophosphane) (1) is prepared by reaction of P ,P,P′,P′-tetrakis(dim ethylamino)-o-phenylenediphosphane with hydrogen bromide in ether. The reaction of o-phenylene- bis(dichlorophosphane) (2) with CH3OH in ether yields o-phenylene-bis(phosphonousacid- dimethylester) (3). The Michaelis-Arbuzov conversion of 3, either by heat or by catalytic amounts of CH3I in toluene, yields ophenylene-bis(methylphosphinic-acid-methylester) (4). The reduction of 2 must be carried out with a large excess of LiAlH4 (1:4) in ether to give o-phenylenediphosphane (5). The cyclic anhydride (6) of P.P′-dichloro-o-phenylenediphosphonous acid is formed when 2 is hydrolyzed in ether with an equimolar amount of water. Complete hydrolysis of 2 with an excess of water gives o-phenylenediphosphonous acid (7). With hydrogen peroxide o-phenylenediphosphonic acid (8) can be isolated.

scholarly journals Localization of cerium-based reaction products by scanning laser reflectance confocal microscopy.

1990 ◽  
Vol 38 (3) ◽  
pp. 315-318 ◽  
Author(s):  
J M Robinson ◽  
B E Batten
Keyword(s):  
Hydrogen Peroxide ◽  
Confocal Microscopy ◽  
Scanning Laser ◽  
Reaction Products ◽  
Laser Confocal Microscopy ◽  
Light Microscope Level ◽  
New Approach ◽  
Detection Systems ◽  
Laser Reflectance ◽  
Hydrogen Peroxide Release

Scanning laser confocal microscopy was utilized to visualize sites of hydrogen peroxide release from stimulated neutrophils and lysosomal acid phosphatase in these and other cells using cerium in the detection systems. Imaging of the cerium-containing reactions was achieved by employing the reflectance mode of this instrument. Localization of these products at the light microscope level was direct and did not require other reactions to generate a visible product. This new approach to cerium cytochemistry should prove useful for many applications.

Evaluation of Horseradish Peroxidase for the Treatment of Estrogenic Alkylphenols

2005 ◽  
Vol 40 (2) ◽  
pp. 145-154 ◽  
Author(s):  
Monika Wagner ◽  
James A. Nicell
Keyword(s):  
Hydrogen Peroxide ◽  
Reaction Time ◽  
Horseradish Peroxidase ◽  
Estrogenic Activity ◽  
Complete Disappearance ◽  
Reaction Products ◽  
Compound A ◽  
New Approach ◽  
Microtox Toxicity ◽  
High Degree

Abstract The xenoestrogen alkylphenols 4-nonylphenol (3.4 mg/L) and octylphenol (6.0 mg/L) were oxidized by hydrogen peroxide using horseradish peroxidase (HRP) as a biocatalyst. Substrate transformation required about one mole of peroxide per mole of phenolic compound. A high degree of conversion of alkylphenol was achieved within a 3-h reaction time. In the case of 4-nonylphenol, HRP treatment led to complete disappearance of Microtox toxicity. Results of the yeast estrogen screen (YES) assay demonstrated that the reaction products of HRP-catalyzed 4-nonylphenol conversion lacked estrogenic activity. A new approach to the YES assay has been suggested based on observations made during this study.

Anchimeric assistance in hexosaminidases

2002 ◽  
Vol 80 (8) ◽  
pp. 1064-1074 ◽  
Author(s):  
Brian L Mark ◽  
Michael NG James
Keyword(s):  
Oxygen Atom ◽  
Active Site ◽  
Sequence Similarity ◽  
Carbonyl Oxygen ◽  
Carbonyl Oxygen Atom ◽  
Carboxyl Groups ◽  
Displacement Mechanism ◽  
Glycosidic Bonds ◽  
Anchimeric Assistance ◽  
Hydrolysis Of

Configuration retaining glycosidases catalyse the hydrolysis of glycosidic bonds via a double displacement mechanism, typically involving two key active site carboxyl groups (Glu or Asp). One of the enzymic carboxyl groups functions as a general acid–base catalyst, the other acts as a nucleophile. Alternatively, configuration-retaining hexosaminidases from the sequence-related glycosidase families 18, 20, and 56 lack a suitably positioned enzymic nucleophile; instead, they use the carbonyl oxygen atom of the neighbouring C2-acetamido group of the substrate. The carbonyl oxygen atom of the 2-acetamido group provides anchimeric assistance to the enzyme catalyzed reaction by acting as an intramolecular nucleophile, attacking the anomeric center and forming a cyclized oxazolinium ion intermediate that is stereochemically equivalent to the glycosyl–enzyme intermediate formed in the "normal" double displacement mechanism. Although there is little sequence similarity between families 18, 20, and 56 hexosaminidases, X-ray crystallographic studies demonstrate that they have evolved similar catalytic domains and active site architectures that are designed to distort the bound substrate so that the C2-acetamido group can become appropriately positioned to participate in catalysis. The substrate distortion allows for a substrate-assisted catalytic reaction that displays all the general characteristics of the classic double-displacement mechanism including the formation of a covalent intermediate.Key words: glycoside hydrolase, hexosaminidase, glycosidase, substrate-assisted catalysis, anchimeric assistance.

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