scholarly journals Generation of *OH initiated by interaction of Fe2+ and Cu+ with dioxygen; comparison with the Fenton chemistry.

2000 ◽  
Vol 47 (4) ◽  
pp. 951-962 ◽  
Author(s):  
N K Urbański ◽  
A Beresewicz
Keyword(s):  
Superoxide Dismutase ◽  
Hydroxyl Radical ◽  
Fenton Reaction ◽  
Copper Toxicity ◽  
Reducing Agents ◽  
H2o2 Concentration ◽  
Fenton Chemistry ◽  
Fenton System ◽  
Krebs Henseleit Buffer

Iron and copper toxicity has been presumed to involve the formation of hydroxyl radical (*OH) from H2O2 in the Fenton reaction. The aim of this study was to verify that Fe2+-O2 and Cu+-O2 chemistry is capable of generating *OH in the quasi physiological environment of Krebs-Henseleit buffer (KH), and to compare the ability of the Fe2+-O2 system and of the Fenton system (Fe2+ + H2O2) to produce *OH. The addition of Fe2+ and Cu+ (0-20 microM) to KH resulted in a concentration-dependent increase in *OH formation, as measured by the salicylate method. While Fe3+ and Cu2+ (0-20 microM) did not result in *OH formation, these ions mediated significant *OH production in the presence of a number of reducing agents. The *OH yield from the reaction mediated by Fe2+ was increased by exogenous Fe3+ and Cu2+ and was prevented by the deoxygenation of the buffer and reduced by superoxide dismutase, catalase, and desferrioxamine. Addition of 1 microM, 5 microM or 10 microM Fe2+ to a range of H2O2 concentrations (the Fenton system) resulted in a H2O2-concentration-dependent rise in *OH formation. For each Fe2+ concentration tested, the *OH yield doubled when the ratio [H2O2]:[Fe2+] was raised from zero to one. (i) Fe2+-O2 and Cu+-O2 chemistry is capable of promoting *OH generation in the environment of oxygenated KH, in the absence of pre-existing superoxide and/or H2O2, and possibly through a mechanism initiated by the metal autoxidation; (ii) The process is enhanced by contaminating Fe3+ and Cu2+; (iii) In the presence of reducing agents also Fe3+ and Cu2+ promote the *OH formation; (iv) Depending on the actual [H2O2]:[Fe2+] ratio, the efficiency of the Fe2+-O2 chemistry to generate *OH is greater than or, at best, equal to that of the Fe2+-driven Fenton reaction.

Fenton chemistry in biology and medicine

2007 ◽  
Vol 79 (12) ◽  
pp. 2325-2338 ◽  
Author(s):  
Josef Prousek
Keyword(s):  
Hydroxyl Radical ◽  
Fenton Reaction ◽  
Brown Rot ◽  
White Rot ◽  
Practical Utilization ◽  
Fenton Chemistry ◽  
Radical Production

Various aspects of the participation of Fenton chemistry in biology and medicine are reviewed. Accumulated evidence shows that both hydroxyl radical and ferryl [Fe(IV)=O]2+ can be formed under a variety of Fenton and Fenton-like reactions. Some examples of metal-independent hydroxyl radical production are included. Extracellular Fenton reaction is illustrated by the white rot and brown rot wood-decaying fungi. The natural and practical utilization of catechol-driven Fenton reaction is also presented.

scholarly journals Free hydroxyl radical is not involved in an important reaction of lignin degradation by Phanerochaete chrysosporium Burds

1985 ◽  
Vol 226 (2) ◽  
pp. 455-460 ◽  
Author(s):  
T K Kirk ◽  
M D Mozuch ◽  
M Tien
Keyword(s):  
Hydroxyl Radical ◽  
Phanerochaete Chrysosporium ◽  
Fenton Reaction ◽  
Lignin Degradation ◽  
Mechanism Of Formation ◽  
Mass Spectral ◽  
Free Hydroxyl ◽  
Lignin Model ◽  
Trapping Agent ◽  
Fenton System

Hydroxyl radical (HO.) has been implicated in the degradation of lignin by Phanerochaete chrysosporium. This study assessed the possible involvement of HO. in degradation of lignin substructural models by intact cultures and by an extracellular ligninase isolated from the cultures. Two non-phenolic lignin model compounds [aryl-C(alpha)HOH-C(beta)HR-C(gamma)H2OH, in which R = aryl (beta-1) or R = O-aryl (beta-O-4)] were degraded by cultures, by the purified ligninase, and by Fenton's reagent (H2O2 + Fe2+), which generates HO. The ligninase and the cultures formed similar products, derived via an initial cleavage between C(alpha) and C(beta) (known to be an important biodegradative reaction), indicating that the ligninase is responsible for model degradation in cultures. Products from the Fenton degradation were mainly polar phenolics that exhibited little similarity to those from the biological systems. Mass-spectral analysis, however, revealed traces of the same products in the Fenton reaction as seen in the biological reactions; even so, an 18O2-incorporation study showed that the mechanism of formation differed. E.s.r. spectroscopy with a spin-trapping agent readily detected HO. in the Fenton system, but indicated that no HO. is formed during ligninase catalysis. We conclude, therefore that HO. is not involved in fungal C(alpha)-C(beta) cleavage in the beta-1 and beta-O-4 models and, by extension, in the same reaction in lignin.

scholarly journals Superoxide dismutase enhances the formation of hydroxyl radicals in the reaction of 3-hydroxyanthranilic acid with molecular oxygen

1988 ◽  
Vol 251 (3) ◽  
pp. 893-899 ◽  
Author(s):  
H Iwahashi ◽  
T Ishii ◽  
R Sugata ◽  
R Kido
Keyword(s):  
Hydrogen Peroxide ◽  
Superoxide Dismutase ◽  
Hydroxyl Radical ◽  
Molecular Oxygen ◽  
Hydroxyl Radicals ◽  
Fenton Reaction ◽  
Potassium Phosphate ◽  
Radical Formation ◽  
Superoxide Anions ◽  
Hydroxyanthranilic Acid

Superoxide dismutase (SOD) enhanced the formation of hydroxyl radicals, which were detected by using the e.s.r. spin-trapping technique, in a reaction mixture containing 3-hydroxyanthranilic acid (or p-aminophenol), Fe3+ ions, EDTA and potassium phosphate buffer, pH 7.4. The hydroxyl-radical formation enhanced by SOD was inhibited by catalase and desferrioxamine, and stimulated by EDTA and diethylenetriaminepenta-acetic acid, suggesting that both hydrogen peroxide and iron ions participate in the reaction. The hydroxyl-radical formation enhanced by SOD may be considered to proceed via the following steps. First, 3-hydroxyanthranilic acid is spontaneously auto-oxidized in a process that requires molecular oxygen and yields superoxide anions and anthranilyl radicals. This reaction seems to be reversible. Secondly, the superoxide anions formed in the first step are dismuted by SOD to generate hydrogen peroxide and molecular oxygen, and hence the equilibrium in the first step is displaced in favour of the formation of superoxide anions. Thirdly, hydroxyl radicals are generated from hydrogen peroxide through the Fenton reaction. In this Fenton reaction Fe2+ ions are available since Fe3+ ions are readily reduced by 3-hydroxyanthranilic acid. The superoxide anions do not seem to participate in the reduction of Fe3+ ions, since superoxide anions are rapidly dismuted by SOD present in the reaction mixture.

scholarly journals Endogenous Superoxide Dismutase Levels Regulate Iron-Dependent Hydroxyl Radical Formation in Escherichia coli Exposed to Hydrogen Peroxide

1998 ◽  
Vol 180 (3) ◽  
pp. 622-625 ◽  
Author(s):  
Michael L. McCormick ◽  
Garry R. Buettner ◽  
Bradley E. Britigan
Keyword(s):  
Escherichia Coli ◽  
Dna Damage ◽  
Superoxide Dismutase ◽  
Hydroxyl Radical ◽  
Iron Chelator ◽  
Spin Adduct ◽  
Control Strain ◽  
Paramagnetic Resonance ◽  
Fenton Chemistry ◽  
E Coli

ABSTRACT Aerobic organisms contain antioxidant enzymes, such as superoxide dismutase (SOD) and catalase, to protect them from both direct and indirect effects of reactive oxygen species, such as O2 ·− and H2O2. Previous work by others has shown that Escherichia colimutants lacking SOD not only are more susceptible to DNA damage and killing by H2O2 but also contain larger pools of intracellular free iron. The present study investigated if SOD-deficient E. coli cells are exposed to increased levels of hydroxyl radical (·OH) as a consequence of the reaction of H2O2 with this increased iron pool. When the parental E. coli strain AB1157 was exposed to H2O2 in the presence of an α-(4-pyridyl-1-oxide)-N-tert-butyl-nitrone (4-POBN)–ethanol spin-trapping system, the 4-POBN–·CH(CH3)OH spin adduct was detectable by electron paramagnetic resonance (EPR) spectroscopy, indicating ·OH production. When the isogenic E. coli mutant JI132, lacking both Fe- and Mn-containing SODs, was exposed to H2O2 in a similar manner, the magnitude of ·OH spin trapped was significantly greater than with the control strain. Preincubation of the bacteria with the iron chelator deferoxamine markedly inhibited the magnitude of·OH spin trapped. Exogenous SOD failed to inhibit·OH formation, indicating the need for intracellular SOD. Redox-active iron, defined as EPR-detectable ascorbyl radical, was greater in the SOD-deficient strain than in the control strain. These studies (i) extend recent data from others demonstrating increased levels of iron in E. coli SOD mutants and (ii) support the hypothesis that a resulting increase in ·OH formation generated by Fenton chemistry is responsible for the observed enhancement of DNA damage and the increased susceptibility to H2O2-mediated killing seen in these mutants lacking SOD.

scholarly journals 2′,7′-dichlorofluorescin-based analysis of Fenton chemistry reveals auto-amplification of probe fluorescence and albumin as catalyst for the detection of hydrogen peroxide

2020 ◽  
Vol 477 (24) ◽  
pp. 4689-4710
Author(s):  
Teresa Gonzalez ◽  
Franck Peiretti ◽  
Catherine Defoort ◽  
Patrick Borel ◽  
Roland Govers
Keyword(s):  
Hydrogen Peroxide ◽  
Hydroxyl Radical ◽  
Hydroxyl Radicals ◽  
Ferrous Iron ◽  
Fenton Reaction ◽  
Iron Chelation ◽  
Intact Cells ◽  
Free System ◽  
Fenton Chemistry ◽  
In Cells

Fluorophore 2′,7′-dichlorofluorescin (DCF) is the most frequently used probe for measuring oxidative stress in cells, but many aspects of DCF remain to be revealed. Here, DCF was used to study the Fenton reaction in detail, which confirmed that in a cell-free system, the hydroxyl radical was easily measured by DCF, accompanied by the consumption of H2O2 and the conversion of ferrous iron into ferric iron. DCF fluorescence was more specific for hydroxyl radicals than the measurement of thiobarbituric acid (TBA)-reactive 2-deoxy-D-ribose degradation products, which also detected H2O2. As expected, hydroxyl radical-induced DCF fluorescence was inhibited by iron chelation, anti-oxidants, and hydroxyl radical scavengers and enhanced by low concentrations of ascorbate. Remarkably, due to DCF fluorescence auto-amplification, Fenton reaction-induced DCF fluorescence steadily increased in time even when all ferrous iron was oxidized. Surprisingly, the addition of bovine serum albumin rendered DCF sensitive to H2O2 as well. Within cells, DCF appeared not to react directly with H2O2 but indirect via the formation of hydroxyl radicals, since H2O2-induced cellular DCF fluorescence was fully abolished by iron chelation and hydroxyl radical scavenging. Iron chelation in H2O2-stimulated cells in which DCF fluorescence was already increasing did not abrogate further increases in fluorescence, suggesting DCF fluorescence auto-amplification in cells. Collectively, these data demonstrate that DCF is a very useful probe to detect hydroxyl radicals and hydrogen peroxide and to study Fenton chemistry, both in test tubes as well as in intact cells, and that fluorescence auto-amplification is an intrinsic property of DCF.

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

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

A Novel pH-responsive Fe-MOF System for Enhanced Cancer Treatment Mediated by Fenton Reaction

2021 ◽  
Author(s):  
Senlin Wang ◽  
Hong-Shuai Wu ◽  
Kai Sun ◽  
Jinzhong Hu ◽  
Fanghui Chen ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Hydroxyl Radical ◽  
Cancer Treatment ◽  
Cell Apoptosis ◽  
Fenton Reaction ◽  
Reactive Oxygen ◽  
Cationic Polymer ◽  
Intracellular Reactive Oxygen Species ◽  
Oxygen Species ◽  
Ph Responsive

Recently, the toxic hydroxyl radical (·OH) has received wide interest in inducing cell apoptosis by increasing the intracellular reactive oxygen species (ROS) levels. Herein, a cationic polymer (MV-PAH) was rationally...

scholarly journals Enhancement of Iron-Based Photo-Driven Processes by the Presence of Catechol Moieties

Catalysts ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 372
Author(s):  
Javier Moreno-Andrés ◽  
Iván Vallés ◽  
Paula García-Negueroles ◽  
Lucas Santos-Juanes ◽  
Antonio Arques
Keyword(s):  
Fenton Reaction ◽  
Advanced Oxidation Processes ◽  
Salt Water ◽  
Degradation Process ◽  
Contaminants Of Emerging Concern ◽  
Low Salt ◽  
Aquaculture Industry ◽  
Iron Based ◽  
Ph Range ◽  
Fenton System

Photo-induced Advanced Oxidation Processes (AOPs) using H2O2 or S2O82− as radical precursors were assessed for the abatement of six different contaminants of emerging concern (CECs). In order to increase the efficiency of these AOPs at a wider pH range, the catechol organic functional compound was studied as a potential assistant in photo-driven iron-based processes. Different salinity regimes were also studied (in terms of Cl− concentration), namely low salt water (1 g·L−1) or a salt–water (30 g·L−1) matrix. Results obtained revealed that the presence of catechol could efficiently assist the photo-Fenton system and partly promote the photo-induced S2O82− system, which was highly dependent on salinity. Regarding the behavior of individual CECs, the photo-Fenton reaction was able to enhance the degradation of all six CECs, meanwhile the S2O82−-based process showed a moderate enhancement for acetaminophen, amoxicillin or clofibric acid. Finally, a response-surface methodology was employed to determine the effect of pH and catechol concentration on the different photo-driven processes. Catechol was removed during the degradation process. According to the results obtained, the presence of catechol in organic macromolecules can bring some advantages in water treatment for either freshwater (wastewater) or seawater (maritime or aquaculture industry).

scholarly journals Secretion of Iron(III)-Reducing Metabolites during Protein Acquisition by the Ectomycorrhizal Fungus Paxillus involutus

2020 ◽  
Vol 9 (1) ◽  
pp. 35
Author(s):  
Firoz Shah ◽  
Markus Gressler ◽  
Susan Nehzati ◽  
Michiel Op De Beeck ◽  
Luigi Gentile ◽  
...  
Keyword(s):  
Fenton Reaction ◽  
Ectomycorrhizal Fungus ◽  
Paxillus Involutus ◽  
Environmental Cues ◽  
Rapid Reduction ◽  
Fenton Chemistry ◽  
X Ray ◽  
Solid Iron ◽  
X Ray Absorption ◽  
Step Mechanism

The ectomycorrhizal fungus Paxillus involutus decomposes proteins using a two-step mechanism, including oxidation and proteolysis. Oxidation involves the action of extracellular hydroxyl radicals (•OH) generated by the Fenton reaction. This reaction requires the presence of iron(II). Here, we monitored the speciation of extracellular iron and the secretion of iron(III)-reducing metabolites during the decomposition of proteins by P. involutus. X-ray absorption spectroscopy showed that extracellular iron was mainly present as solid iron(III) phosphates and oxides. Within 1 to 2 days, these compounds were reductively dissolved, and iron(II) complexes were formed, which remained in the medium throughout the incubation. HPLC and mass spectrometry detected five extracellular iron(III)-reducing metabolites. Four of them were also secreted when the fungus grew on a medium containing ammonium as the sole nitrogen source. NMR identified the unique iron(III)-reductant as the diarylcyclopentenone involutin. Involutin was produced from day 2, just before the elevated •OH production, preceding the oxidation of BSA. The other, not yet fully characterized iron(III)-reductants likely participate in the rapid reduction and dissolution of solid iron(III) complexes observed on day one. The production of these metabolites is induced by other environmental cues than for involutin, suggesting that they play a role beyond the Fenton chemistry associated with protein oxidation.

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