THE EFFECT OF SELECTIVE DEUTERATION ON MVK-OXIDE AND ITS UNIMOLECULAR DECAY TO HYDROXYL RADICAL PRODUCTS

The release of cytochrome c from mitochondria during apoptosis results in the enhanced production of superoxide radicals, which are converted to H2O2 by Mn-superoxide dismutase. We have been concerned with the role of cytochrome c/H2O2 in the induction of oxidative stress during apoptosis. Our initial studies showed that cytochrome c is a potent catalyst of 2′,7′-dichlorofluorescin oxidation, thereby explaining the increased rate of production of the fluorophore 2′,7′-dichlorofluorescein in apoptotic cells. Although it has been speculated that the oxidizing species may be a ferryl-haem intermediate, no definitive evidence for the formation of such a species has been reported. Alternatively, it is possible that the hydroxyl radical may be generated, as seen in the reaction of certain iron chelates with H2O2. By examining the effects of radical scavengers on 2′,7′-dichlorofluorescin oxidation by cytochrome c/H2O2, together with complementary EPR studies, we have demonstrated that the hydroxyl radical is not generated. Our findings point, instead, to the formation of a peroxidase compound I species, with one oxidizing equivalent present as an oxo-ferryl haem intermediate and the other as the tyrosyl radical identified by Barr and colleagues [Barr, Gunther, Deterding, Tomer and Mason (1996) J. Biol. Chem. 271, 15498-15503]. Studies with spin traps indicated that the oxo-ferryl haem is the active oxidant. These findings provide a physico-chemical basis for the redox changes that occur during apoptosis. Excessive changes (possibly catalysed by cytochrome c) may have implications for the redox regulation of cell death, including the sensitivity of tumour cells to chemotherapeutic agents.

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Activities of antioxidant enzymes and nitric oxide synthase, hydroxyl radical and zinc contents in gastric mucosa cells during the recovery of stress-induced stomach lesions

Annales UMCS Pharmacia ◽

10.2478/v10080-008-0036-7 ◽

2008 ◽

Vol 21 (1) ◽

pp. 215-217

Author(s):

Olena Bogdanova ◽

Larysa Kot ◽

Dmytro Lukashov ◽

Ludmyla Ostapchenko

Keyword(s):

Nitric Oxide ◽

Antioxidant Enzymes ◽

Nitric Oxide Synthase ◽

Gastric Mucosa ◽

Hydroxyl Radical ◽

Oxide Synthase

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A Systematic DFT Study of Two Elementary Steps Involving Hydrogen Peroxide and the Hydroxyl Radical in the Fenton Reaction

10.26434/chemrxiv.6160142 ◽

2018 ◽

Author(s):

Danilo Carmona ◽

David Contreras ◽

Oscar A. Douglas-Gallardo ◽

Stefan Vogt-Geisse ◽

Pablo Jaque ◽

...

Keyword(s):

Hydrogen Peroxide ◽

Hydroxyl Radical ◽

Ab Initio ◽

Fenton Reaction ◽

Basis Set ◽

Basis Sets ◽

Dft Methods ◽

Elementary Steps ◽

Oxygen Oxygen ◽

Complete Basis Set

The Fenton reaction plays a central role in many chemical and biological processes and has various applications as e.g. water remediation. The reaction consists of the iron-catalyzed homolytic cleavage of the oxygen-oxygen bond in the hydrogen peroxide molecule and the reduction of the hydroxyl radical. Here, we study these two elementary steps with high-level ab-initio calculations at the complete basis set limit and address the performance of different DFT methods following a specific classification based on the Jacob´s ladder in combination with various Pople's basis sets. Ab-initio calculations at the complete basis set limit are in agreement to experimental reference data and identified a significant contribution of the electron correlation energy to the bond dissociation energy (BDE) of the oxygen-oxygen bond in hydrogen peroxide and the electron affinity (EA) of the hydroxyl radical. The studied DFT methods were able to reproduce the ab-initio reference values, although no functional was particularly better for both reactions. The inclusion of HF exchange in the DFT functionals lead in most cases to larger deviations, which might be related to the poor description of the two reactions by the HF method. Considering the computational cost, DFT methods provide better BDE and EA values than HF and post--HF methods with an almost MP2 or CCSD level of accuracy. However, no systematic general prediction of the error based on the employed functional could be established and no systematic improvement with increasing the size in the Pople's basis set was found, although for BDE values certain systematic basis set dependence was observed. Moreover, the quality of the hydrogen peroxide, hydroxyl radical and hydroxyl anion structures obtained from these functionals was compared to experimental reference data. In general, bond lengths were well reproduced and the error in the angles were between one and two degrees with some systematic trend with the basis sets. From our results we conclude that DFT methods present a computationally less expensive alternative to describe the two elementary steps of the Fenton reaction. However, choice of approximated functionals and basis sets must be carefully done and the provided benchmark allows a systematic validation of the electronic structure method to be employed

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Faculty Opinions recommendation of The Dps protein of Agrobacterium tumefaciens does not bind to DNA but protects it toward oxidative cleavage: x-ray crystal structure, iron binding, and hydroxyl-radical scavenging properties.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1004064.191655 ◽

2003 ◽

Author(s):

Elizabeth Theil

Keyword(s):

Crystal Structure ◽

Agrobacterium Tumefaciens ◽

Hydroxyl Radical ◽

Radical Scavenging ◽

Oxidative Cleavage ◽

Iron Binding ◽

X Ray ◽

Radical Scavenging Properties ◽

Dps Protein

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An ab Initio Study of the Kinetics of the Reactions of Halomethanes with the Hydroxyl Radical. Part 1: CH2Br2

10.21236/ada382639 ◽

2000 ◽

Author(s):

Florent Lous ◽

Robert E. Huie ◽

Michael J. Kurylo

Keyword(s):

Hydroxyl Radical ◽

Ab Initio ◽

Ab Initio Study ◽

Kinetics Of

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Enhancement of hydroxyl radical generation by phenols and their reaction intermediates during ozonation

Water Science & Technology ◽

10.2166/wst.1998.0247 ◽

1998 ◽

Vol 38 (6) ◽

pp. 147-154 ◽

Cited By ~ 2

Author(s):

Hideo Utsumi ◽

Sang-Kuk Han ◽

Kazuhiro Ichikawa

Keyword(s):

Hydroxyl Radical ◽

Hydroxyl Radicals ◽

Spin Trapping ◽

Active Species ◽

Generation Rate ◽

Peak Height Ratio ◽

Dependent Manner ◽

Concentration Dependent Manner ◽

Phenol Derivatives ◽

Semiquinone Radicals

Generation of hydroxyl radicals, one of the major active species in ozonation of water was directly observed with a spin-trapping/electron spin resonance (ESR) technique using 5,5-dimethyl-1-pyrrolineN-oxide (DMPO) as a spin-trapping reagent. Hydroxyl radical were trapped with DMPO as a stable radical, DMPO-OH. Eighty μM of ozone produced 1.08 X 10-6M of DMPO-OH, indicating that 1.4% of •OH is trapped with DMPO. Generation rate of DMPO-OH was determined by ESR/stopped-flow measurement. Phenol derivatives increased the amount and generation rate of DMPO-OH, indicating that phenol derivatives enhance •OH generation during ozonation of water. Ozonation of 2,3-, 2,5-, 2,6-dichlorophenol gave an ESR spectra of triplet lines whose peak height ratio were 1:2:1. ESR parameters of the triplet lines agreed with those of the corresponding dichloro-psemiquinone radical. Ozonation of 2,4,5- and 2,4,6-trichlorophenol gave the same spectra as those of 2,5- and 2,6-dichlorophenol, respectively, indicating that a chlorine group in p-position is substituted with a hydroxy group during ozonation. Amounts of the radical increased in an ozone-concentration dependent manner and were inhibited by addition of hydroxyl radical scavengers. These results suggest that p-semiquinone radicals are generated from the chlorophenols by hydroxyl radicals during ozonation. The p-semiquinone radicals were at least partly responsible for enhancements of DMPO-OH generation.

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Heterogeneous Fenton Catalytic Removal of Organic Pollutant in Aqueous Solution by using Coal Gangue as a Catalyst

Recent Innovations in Chemical Engineering (Formerly Recent Patents on Chemical Engineering) ◽

10.2174/2405520412666190806120033 ◽

2019 ◽

Vol 12 (4) ◽

pp. 312-325

Author(s):

Jiwei Zhang ◽

Jingjing Xu ◽

Shuaixia Liu ◽

Baoxiang Gu ◽

Feng Chen ◽

...

Keyword(s):

Aqueous Solution ◽

Hydrogen Peroxide ◽

Hydroxyl Radical ◽

Removal Rate ◽

Organic Pollutant ◽

Coal Gangue ◽

Ion Leakage ◽

Heterogeneous Fenton ◽

Solution Ph ◽

X Ray

Background: Coal gangue was used as a catalyst in heterogeneous Fenton process for the degradation of azo dye and phenol. The influencing factors, such as solution pH gangue concentration and hydrogen peroxide dosage were investigated, and the reaction mechanism between coal gangue and hydrogen peroxide was also discussed. Methods: Experimental results showed that coal gangue has the ability to activate hydrogen peroxide to degrade environmental pollutants in aqueous solution. Under optimal conditions, after 60 minutes of treatment, more than 90.57% of reactive red dye was removed, and the removal efficiency of Chemical Oxygen Demand (COD) up to 72.83%. Results: Both hydroxyl radical and superoxide radical anion participated in the degradation of organic pollutant but hydroxyl radical predominated. Stability tests for coal gangue were also carried out via the continuous degradation experiment and ion leakage analysis. After five times continuous degradation, dye removal rate decreased slightly and the leached Fe was still at very low level (2.24-3.02 mg L-1). The results of Scanning Electron Microscope (SEM), energy dispersive X-Ray Spectrometer (EDS) and X-Ray Powder Diffraction (XRD) indicated that coal gangue catalyst is stable after five times continuous reuse. Conclusion: The progress in this research suggested that coal gangue is a potential nature catalyst for the efficient degradation of organic pollutant in water and wastewater via the Fenton reaction.

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Radiolysis studies on the corrosion inhibitors 1 -hexyn-3-ol, cinnamonitrile, and 1,3-diethyl-2-thiourea

Canadian Journal of Chemistry ◽

10.1139/v95-264 ◽

1995 ◽

Vol 73 (12) ◽

pp. 2137-2142 ◽

Cited By ~ 1

Author(s):

A.J. Elliot ◽

M.P. Chenier ◽

D.C. Ouellette

Keyword(s):

Hydrogen Atom ◽

Hydroxyl Radical ◽

Temperature Dependence ◽

Rate Constant ◽

Rate Constants ◽

Corrosion Inhibitors ◽

Hydrated Electron

In this publication we report: (i) the rate constants for reaction of the hydrated electron with 1-hexyn-3-ol ((8.6 ± 0.3) × 108 dm3 mol−1 s−1 at 18 °C), cinnamonitrile ((2.3 ± 0.2) × 1010 dm3 mol−1 s−1 at 20 °C), and 1,3-diethyl-2-thiourea ((3.5 ± 0.3) × 108 dm3 mol−1 s−1 at 22 °C). For cinnamonitrile and diethylthiourea, the temperature dependence up to 200 °C and 150 °C, respectively, is also reported; (ii) the rate constants for the reaction of the hydroxyl radical with 1-hexyn-3-ol ((5.5 ± 0.5) × 109 dm3 mol−1 s−1 at 20 °C), cinnamonitrile ((9.2 ± 0.3) × 109 dm3 mol−1 s−1 at 21 °C), and diethylthiourea ((8.0 ± 0.8) × 108 dm3 mol−1 s−1 at 22 °C). For cinnamonitrile, the temperature dependence up to 200 °C is also reported; (iii) the rate constant for the hydrogen atom reacting with 1-hexyn-3-ol ((4.3 ± 0.4) × 109 dm3 mol−1 s−1 at 20 °C). Keywords: radiolysis, corrosion inhibitors, rate constants.

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