Role of coke-bounded environmentally persistent free radicals in phenanthrene degradation by hydrogen peroxide

This study puts particular emphasis on the role of copper ions in the performance of hydrogen peroxide bleaching (P-stage). Owing to their variable levels across the bleaching line due to washing filtrates, bleaching reagents, and equipment corrosion, these ions can play a major role in hydrogen peroxide decomposition and be detrimental to polysaccharide integrity. In this study, a Cu-contaminated D0(EOP)D1 prebleached pulp was subjected to an acidic washing (A-stage) or chelation (Q-stage) before the alkaline P-stage. The objective was to understand the isolated and combined role of copper ions in peroxide bleaching performance. By applying an experimental design, it was possible to identify the main effects of the pretreatment variables on the extent of metals removal and performance of the P-stage. The acid treatment was unsuccessful in terms of complete copper removal, magnesium preservation, and control of hydrogen peroxide consumption in the following P-stage. Increasing reaction temperature and time of the acidic A-stage improved the brightness stability of the D0(EOP)D1AP bleached pulp. The optimum conditions for chelation pretreatment to maximize the brightness gains obtained in the subsequent P-stage with the lowest peroxide consumption were 0.4% diethylenetriaminepentaacetic acid (DTPA), 80ºC, and 4.5 pH.

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The Role of free radicals in female unexplained subfertility

10.36295/asro.2020.2311 ◽

2020 ◽

Vol 23 (01) ◽

pp. 01-08

Author(s):

Ban Jaber Edan ◽

Huda Mahmood Shakir ◽

Naseer Jwaad Almukhtar

Keyword(s):

Free Radicals

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Role Of Taurine In Male Reproductive System Performance In Adult Male Rats Exposed To Oxiative Stress By Hydrogen Peroxide

Journal of Applied Veterinary Sciences ◽

10.21608/javs.2019.62661 ◽

2019 ◽

Vol 4 (2) ◽

pp. 71-79

Author(s):

Nadhem Al-kassim

Keyword(s):

Hydrogen Peroxide ◽

Adult Male ◽

Reproductive System ◽

System Performance ◽

Male Reproductive System ◽

Male Rats

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Study of antioxidant potential in leaves, stems, nuts of Juglans regia L.

International Journal of Bioassays ◽

10.21746/ijbio.2012.10.003 ◽

2012 ◽

Vol 1 (10) ◽

pp. 79 ◽

Cited By ~ 2

Author(s):

G. Raja* ◽

Ivvala Anand Shaker ◽

Inampudi Sailaja ◽

R. Swaminathan ◽

S. Saleem Basha ◽

...

Keyword(s):

Free Radicals ◽

Free Radical ◽

Antioxidant Activities ◽

Radical Scavenging Activity ◽

Juglans Regia ◽

Radical Scavenging ◽

Antioxidant Compounds ◽

Free Radical Damage ◽

Radical Damage

Natural antioxidants can protect the human body from free radicals and retard the progress of many chronic diseases as well as lipid oxidative rancidity in foods. The role of antioxidants has protected effect against free radical damage that may cause many diseases including cancer. Primary sources of naturally occurring antioxidants are known as whole grains, fruits, and vegetables. Several studies suggest that regular consumption of nuts, mostly walnuts, may have beneficial effects against oxidative stress mediated diseases such as cardiovascular disease and cancer. The role of antioxidants has attracted much interest with respect to their protective effect against free radical damage that may cause many diseases including cancer. Juglans regia L. (walnut) contains antioxidant compounds, which are thought to contribute to their biological properties. Polyphenols, flavonoids and flavonols concentrations and antioxidant activity of Leaves, Stems and Nuts extract of Juglans regia L. as evaluated using DPPH, ABTS, Nitric acid, hydroxyl and superoxide radical scavenging activity, lipid peroxidation and total oxidation activity were determined. The antioxidant activities of Leaves, Stems and Nuts extract of Juglans regia L. were concentration dependent in different experimental models and it was observed that free radicals were scavenged by the test compounds in all the models.

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An ESR study of the peroxidase reaction catalyzed by human methaemoglobin and methaemoglobin-haptoglobin complex

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19910923 ◽

1991 ◽

Vol 56 (4) ◽

pp. 923-932

Author(s):

Jana Stejskalová ◽

Pavel Stopka ◽

Zdeněk Pavlíček

Keyword(s):

Hydrogen Peroxide ◽

Ascorbic Acid ◽

Amino Acid ◽

Peroxidase Activity ◽

Amino Acid Analysis ◽

Superoxide Radical ◽

Esr Spectra ◽

The Other ◽

Delocalized Electron

The ESR spectra of peroxidase systems of methaemoglobin-ascorbic acid-hydrogen peroxide and methaemoglobin-haptoglobin complex-ascorbic acid-hydrogen peroxide have been measured in the acetate buffer of pH 4.5. For the system with methaemoglobin an asymmetrical signal with g ~ 2 has been observed which is interpreted as the perpendicular region of anisotropic spectrum of superoxide radical. On the other hand, for the system with methaemoglobin-haptoglobin complex the observed signal with g ~ 2 is symmetrical and is interpreted as a signal of delocalized electron. After realization of three repeatedly induced peroxidase processes the ESR signal of the perpendicular part of anisotropic spectrum of superoxide radical is distinctly diminished, whereas the signal of delocalized electron remains practically unchanged. An amino acid analysis of methaemoglobin along with results of the ESR measurements make it possible to derive a hypothesis about the role of haptoglobin in increasing of the peroxidase activity of methaemoglobin.

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The effect of cation concentration on the nitrogen splitting constant of nitroxide free radicals

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19902377 ◽

1990 ◽

Vol 55 (10) ◽

pp. 2377-2380

Author(s):

Hamza A. Hussain

Keyword(s):

Hydrogen Peroxide ◽

Hydrogen Bonding ◽

Free Radicals ◽

Esr Spectroscopy ◽

The Other ◽

Tetraethylammonium Bromide ◽

Splitting Constant ◽

The One ◽

Positively Charged ◽

Two Equilibria

Nitroxide free radicals prepared from diethylamine, piperidine and pyrrolidine by oxidation with hydrogen peroxide were studied by ESR spectroscopy. The changes in the 14N splitting constant (aN) caused by the addition of KBr or tetraethylammonium bromide were measured in dependence on the concentration of the ions. For diethylamine nitroxide and piperidine nitroxide, the results are discussed in terms of two equilibria: the one, involving the anion, is associated with a gain or loss of hydrogen bonds to the nitroxide oxygen atom, the other is associated with the formation of solvent shared units involving the cation, which results in changes in the hydrogen bonding strenght. The large increase in the aN value in the case of pyrrolidine nitroxide is explained in terms of an interaction from one side of the positively charged N atom; the increase in aN in the case of diethylamine and piperidine nitroxides is explained in terms of interactions with both sides of the positively charged N atom.

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Inhibition of the water channel aquaporin-1 prevents myocardial remodeling by blocking the transmembrane transport of hydrogen peroxide

European Heart Journal ◽

10.1093/ehjci/ehaa946.3665 ◽

2020 ◽

Vol 41 (Supplement_2) ◽

Author(s):

V Montiel ◽

R Bella ◽

L Michel ◽

E Robinson ◽

J.C Jonas ◽

...

Keyword(s):

Hydrogen Peroxide ◽

Cardiac Hypertrophy ◽

Cardiac Myocytes ◽

Cardiac Remodeling ◽

Cardiac Myocyte ◽

Water Channel ◽

Transmembrane Transport ◽

Funding Source ◽

Water Pore

Abstract Background Pathological remodeling of the myocardium has long been known to involve oxidant signaling, but so far, strategies using systemic anti-oxidants have generally failed to prevent it. Aquaporins are a family of transmembrane water channels with thirteen isoforms currently known. Some isoforms have been implicated in oxidant signaling. AQP1 is the most abundant aquaporin in cardiovascular tissues but its specific role in cardiac remodeling remains unknown. Purpose We tested the role of AQP1 as a key regulator of oxidant-mediated cardiac remodeling amenable to targeted pharmacological therapy. Methods We used mice with genetic deletion of Aqp1 (and wild-type littermate), as well as primary isolates from the same mice and human iPSC/Engineered Heart Tissue to test the role of AQP1 in pro-hypertrophic signaling. Human cardiac myocyte-specific (PCM1+) expression of AQP's and genes involved in hypertrophic remodeling was studied by RNAseq and bioinformatic GO pathway analysis. Results RNA sequencing from human cardiac myocytes revealed that the archetypal AQP1 is a major isoform. AQP1 expression correlates with the severity of hypertrophic remodeling in patients with aortic stenosis. The AQP1 channel was detected at the plasma membrane of human and mouse cardiac myocytes from hypertrophic hearts, where it colocalizes with the NADPH oxidase-2 (NOX2) and caveolin-3. We show that hydrogen peroxide (H2O2), produced extracellularly, is necessary for the hypertrophic response of isolated cardiac myocytes and that AQP1 facilitates the transmembrane transport of H2O2 through its water pore, resulting in activation of oxidant-sensitive kinases in cardiac myocytes. Structural analysis of the amino acid residues lining the water pore of AQP1 supports its permeation by H2O2. Deletion of Aqp1 or selective blockade of AQP1 intra-subunit pore (with Bacopaside II) inhibits H2O2 transport in mouse and human cells and rescues the myocyte hypertrophy in human induced pluripotent stem cell-derived engineered heart muscle. This protective effect is due to loss of transmembrane transport of H2O2, but not water, through the intra-subunit pore of AQP1. Treatment of mice with clinically-approved Bacopaside extract (CDRI08) inhibitor of AQP1 attenuates cardiac hypertrophy and fibrosis. Conclusion We provide the first demonstration that AQP1 functions as an aqua-peroxiporin in primary rodent and human cardiac parenchymal cells. We show that cardiac hypertrophy is mediated by the transmembrane transport of H2O2 through the AQP1 water channel. Our studies open the way to complement the therapeutic armamentarium with specific blockers of AQP1 for the prevention of adverse remodeling in many cardiovascular diseases leading to heart failure. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): FRS-FNRS, Welbio

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