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Free Radical Biology & Medicine Jul 2022Beta-2-microglobulin (B2M) is synthesized by all nucleated cells and forms part of the major histocompatibility complex (MHC) class-1 present on cell surfaces, which...
Beta-2-microglobulin (B2M) is synthesized by all nucleated cells and forms part of the major histocompatibility complex (MHC) class-1 present on cell surfaces, which presents peptide fragments to cytotoxic CD8 T-lymphocytes, or by association with CD1, antigenic lipids to natural killer T-cells. Knockout of B2M results in loss of these functions and severe combined immunodeficiency. Plasma levels of this protein are low in healthy serum, but are elevated up to 50-fold in some pathologies including chronic kidney disease and multiple myeloma, where it has both diagnostic and prognostic value. High levels of the protein are associated with amyloid formation, with such deposits containing significant levels of modified or truncated protein. In the current study we examine the chemical and structural changes induced of B2M generated by both inflammatory oxidants (HOCl and ONOOH), and photo-oxidation (O) which is linked with immunosuppression. Oxidation results in oligomer formation, with this occurring most readily with HOCl and O, and a loss of native protein conformation. LC-MS analysis provided evidence for nitrated (from ONOOH), chlorinated (from HOCl) and oxidized residues (all oxidants) with damage detected at Tyr, Trp, and Met residues, together with cleavage of the disulfide (cystine) bond. An intermolecular di-tyrosine crosslink is also formed between Tyr10 and Tyr63. The pattern of these modifications is oxidant specific, with ONOOH inducing a greater range of modifications than HOCl. Comparison of the sites of modification with regions identified as amyloidogenic indicate significant co-localization, consistent with the hypothesis that oxidation may contribute, and predispose B2M, to amyloid formation.
Topics: Chromatography, Liquid; Hypochlorous Acid; Oxidants; Oxidation-Reduction; Protein Conformation; Tyrosine
PubMed: 35609861
DOI: 10.1016/j.freeradbiomed.2022.05.012 -
Chemosphere Jul 2019Chemical oxidation is a promising pretreatment step coupled with bioremediation for removal of polycyclic aromatic hydrocarbons (PAHs). The effectiveness of Fenton,...
Chemical oxidation is a promising pretreatment step coupled with bioremediation for removal of polycyclic aromatic hydrocarbons (PAHs). The effectiveness of Fenton, modified Fenton, potassium permanganate and activated persulfate oxidation treatments on the real contaminated soils collected from a coal gas plant (263.6 ± 73.3 mg kg of the Σ16 PAHs) and a coking plant (385.2 ± 39.6 mg kg of the Σ16 PAHs) were evaluated. Microbial analyses showed only a slight impact on indigenous microbial diversity by Fenton treatment, but showed the inhibition of microbial diversity and delayed population recovery by potassium permanganate reagent. After potassium permanganate treatment, the microorganism mainly existed in the soil was Pseudomonas or Pseudomonadaceae. The results showed that total organic carbon (TOC) content in soil was significantly increased by adding modified Fenton reagent (1.4%-2.3%), while decreased by adding potassium permanganate (0.2%-1%), owing to the nonspecific and different oxidative properties of chemical oxidant. The results also demonstrated that the removal efficiency of total PAHs was ordered: permanganate (90.0%-92.4%) > activated persulfate (81.5%-86.54%) > modified Fenton (81.5%-85.4%) > Fenton (54.1%-60.0%). Furthermore, the PAHs removal efficiency was slightly increased on the 7th day after Fenton and modified Fenton treatments, about 14.6%, and 14.4% respectively, and the PAHs removal efficiency only enhanced 4.1% and 1.3% respectively from 1st to 15th day after potassium permanganate and activated persulfate treatments. The oxidants greatly affect the growth of soil indigenous microbes, which cause further influence for PAHs degradation by bioremediation.
Topics: Biodegradation, Environmental; Coke; Hydrogen Peroxide; Iron; Manganese Compounds; Oxidants; Oxidation-Reduction; Oxides; Polycyclic Aromatic Hydrocarbons; Potassium Permanganate; Pseudomonas; Soil; Soil Pollutants
PubMed: 30951943
DOI: 10.1016/j.chemosphere.2019.03.126 -
Chemosphere May 20171,1-Dimethylhydrazine is used as a fuel for carrier rockets in the majority of countries implementing space exploration programs. Being highly reactive,...
1,1-Dimethylhydrazine is used as a fuel for carrier rockets in the majority of countries implementing space exploration programs. Being highly reactive, 1,1-dimethylhydrazine easily undergoes oxidative transformation with the formation of a number of toxic, mutagenic, and teratogenic compounds. The use of high-resolution mass spectrometry for the study of the reaction of 1,1-dimethylhydrazine oxidation with hydrogen peroxide in aqueous solution allowed us to find hundreds of nitrogen-containing products of the CHN and CHNO classes, formed via radical processes. The vast majority of the compounds have not been previously considered as possible products of the transformation of rocket fuel. We have shown that the oxidation of 1,1-dimethylhydrazine proceeds in two stages, with the formation of a great number of complex unstable intermediates that contain up to ten nitrogen atoms. These intermediates are subsequently converted into final reaction products with a concomitant decrease in the average molecular weight. The intermediates and final products of the oxidative transformation of 1,1-dimethylhydrazine were characterised on the basis of their elemental composition using van Krevelen diagrams and possible compounds corresponding to the most intense peaks in the mass spectra were proposed. The data obtained are indicative of the presence of the following classes of heterocyclic nitrogen-containing compounds among the oxidation products: imines, piperidines, pyrrolidines, dihydropyrazoles, dihydroimidazoles, triazoles, aminotriazines, and tetrazines. The results obtained open up possibilities for the targeted search and identification of new toxic products of the degradation of rocket fuel and, as a result, a more adequate assessment of the ecological consequences of space-rocket activity.
Topics: Dimethylhydrazines; Hydrogen Peroxide; Mass Spectrometry; Oxidants; Oxidation-Reduction
PubMed: 28160679
DOI: 10.1016/j.chemosphere.2017.01.118 -
Biochimica Et Biophysica Acta Aug 2009Melatonin is well-established as a powerful reducing agent of oxidant generated in the cell medium. We aimed to investigate how readily melatonin is oxidized by peroxyl...
BACKGROUND
Melatonin is well-established as a powerful reducing agent of oxidant generated in the cell medium. We aimed to investigate how readily melatonin is oxidized by peroxyl radicals ROO generated by the thermolysis of 2,2'-azobis(2-amidinopropane) hydrochloride (AAPH) and the role of glutathione (GSH) during the reaction course.
METHODS
Chromatographic, mass spectroscopy, and UV-visible spectrometric techniques were used to study the oxidation of melatonin by ROO or horseradish peroxidase (HRP)/H2O2. Our focus was the characterization of products and the study of features of the reaction.
RESULTS
We found that N(1)-acetyl-N(2)-formyl-5-methoxykynuramine (AFMK) and a monohydroxylated derivative of melatonin were the main products of the reaction between melatonin and ROO. Higher pH or saturation of the medium with molecular oxygen increased the yield of AFMK but did not affect the reaction rate. Melatonin increased the depletion of intracellular GSH mediated by AAPH. Using the HRP/H2O2 as the oxidant system, the addition of melatonin promoted the oxidation of GSH to GSSG.
CONCLUSIONS
These results show, for the first time, that melatonin radical is able to oxidize GSH.
GENERAL SIGNIFICANCE
We propose that this new property of melatonin could explain or be related to the recently reported pro-oxidant activities of melatonin.
Topics: Amidines; Chromatography, High Pressure Liquid; Glutathione; Hydrogen Peroxide; Hydrogen-Ion Concentration; Intracellular Space; Melatonin; Nitrogen; Oxidants; Oxidation-Reduction; Oxygen; Peroxides; Solubility
PubMed: 19344745
DOI: 10.1016/j.bbagen.2009.03.021 -
Toxins May 2020Oxidation processes can provide an effective barrier to eliminate cyanotoxins by damaging cyanobacteria cell membranes, releasing intracellular cyanotoxins, and...
Oxidation processes can provide an effective barrier to eliminate cyanotoxins by damaging cyanobacteria cell membranes, releasing intracellular cyanotoxins, and subsequently oxidizing these toxins (now in extracellular form) based on published reaction kinetics. In this work, cyanobacteria cells from two natural blooms (from the United States and Canada) and a laboratory-cultured strain were treated with chlorine, monochloramine, chlorine dioxide, ozone, and potassium permanganate. The release of microcystin was measured immediately after oxidation (t ≤ 20 min), and following oxidant residual quenching (stagnation times = 96 or 168 h). Oxidant exposures (CT) were determined resulting in complete release of intracellular microcystin following chlorine (21 mg-min/L), chloramine (72 mg-min/L), chlorine dioxide (58 mg-min/L), ozone (4.1 mg-min/L), and permanganate (391 mg-min/L). Required oxidant exposures using indigenous cells were greater than lab-cultured . Following partial oxidation of cells (oxidant exposures ≤ CT values cited above), additional intracellular microcystin and dissolved organic carbon (DOC) were released while the samples remained stagnant in the absence of an oxidant (>96 h after quenching). The delayed release of microcystin from partially oxidized cells has implications for drinking water treatment as these cells may be retained on a filter surface or in solids and continue to slowly release cyanotoxins and other metabolites into the finished water.
Topics: Cyanobacteria; Drinking Water; Harmful Algal Bloom; Kinetics; Microcystins; Oxidants; Oxidation-Reduction; Water Microbiology; Water Purification
PubMed: 32443714
DOI: 10.3390/toxins12050335 -
Antioxidants & Redox Signaling Feb 2010Heme is an essential molecule in aerobic organisms. Heme consists of protoporphyrin IX and a ferrous (Fe(2+)) iron atom, which has high affinity for oxygen (O(2)).... (Review)
Review
Heme is an essential molecule in aerobic organisms. Heme consists of protoporphyrin IX and a ferrous (Fe(2+)) iron atom, which has high affinity for oxygen (O(2)). Hemoglobin, the major oxygen-carrying protein in blood, is the most abundant heme-protein in animals and humans. Hemoglobin consists of four globin subunits (alpha(2)beta(2)), with each subunit carrying a heme group. Ferrous (Fe(2+)) hemoglobin is easily oxidized in circulation to ferric (Fe(3+)) hemoglobin, which readily releases free hemin. Hemin is hydrophobic and intercalates into cell membranes. Hydrogen peroxide can split the heme ring and release "free" redox-active iron, which catalytically amplifies the production of reactive oxygen species. These oxidants can oxidize lipids, proteins, and DNA; activate cell-signaling pathways and oxidant-sensitive, proinflammatory transcription factors; alter protein expression; perturb membrane channels; and induce apoptosis and cell death. Heme-derived oxidants induce recruitment of leukocytes, platelets, and red blood cells to the vessel wall; oxidize low-density lipoproteins; and consume nitric oxide. Heme metabolism, extracellular and intracellular defenses against heme, and cellular cytoprotective adaptations are emphasized. Sickle cell disease, an archetypal example of hemolysis, heme-induced oxidative stress, and cytoprotective adaptation, is reviewed.
Topics: Anemia, Sickle Cell; Animals; Blood Vessels; Enzyme Activation; Heme; Heme Oxygenase-1; Hemin; Hemoglobins; Humans; Hydrogen Peroxide; Mice; Models, Biological; Oxidants; Oxidation-Reduction; Oxidative Stress
PubMed: 19697995
DOI: 10.1089/ars.2009.2822 -
Journal of Environmental Science and... Sep 2009Polycyclic aromatic hydrocarbons (PAHs) are organic contaminants of concern due to their ubiquity, persistence in the natural environment and adverse health effects....
Polycyclic aromatic hydrocarbons (PAHs) are organic contaminants of concern due to their ubiquity, persistence in the natural environment and adverse health effects. Numerous studies have looked into the removal and treatment of these contaminants, with mixed results. High molecular weight PAHs have been particularly problematic due to their hydrophobicity and high affinity for organics, resulting in mass transfer limitations for even the fastest advanced oxidation processes (AOPs). The peroxy-acid process has been used to successfully treat PAH contaminated matrices. Experiments were conducted on benzo[a]pyrene contaminated glass beads in order to elucidate the reaction mechanisms responsible for the effectiveness of this process. For the first time peracetic acid (PAA) was identified as the important oxidant in this reaction. Different v/v/v ratios of hydrogen peroxide/acetic acid/DI water were studied which illustrated the importance of reaction ratio on oxidant concentration and rate of formation. Approximately 60% degradation of benzo[a]pyrene was achieved in 24 hours with 1.7% PAA. Observations of the reaction kinetics suggest that the slow desorption/dissolution of benzo[a]pyrene limits the efficiency of the peroxy-acid process. Modifications of the reaction setup supported this observation as treatment efficiencies increased with reactive surface area, and an increase in system agitation. These limitations were also overcome by increasing the concentration of PAA delivered to the contaminated matrix. Greater than 80% degradation of benzo[a]pyrene was achieved in 24 hours with approximately 9.2% PAA.
Topics: Benzo(a)pyrene; Glass; Hydrogen Peroxide; Indicators and Reagents; Kinetics; Oxidants; Oxidation-Reduction; Peracetic Acid; Polycyclic Aromatic Hydrocarbons; Soil Pollutants
PubMed: 19847697
DOI: 10.1080/10934520903005053 -
Nature Jul 2013Methods for carbon-hydrogen (C-H) bond oxidation have a fundamental role in synthetic organic chemistry, providing functionality that is required in the final target...
Methods for carbon-hydrogen (C-H) bond oxidation have a fundamental role in synthetic organic chemistry, providing functionality that is required in the final target molecule or facilitating subsequent chemical transformations. Several approaches to oxidizing aliphatic C-H bonds have been described, drastically simplifying the synthesis of complex molecules. However, the selective oxidation of aromatic C-H bonds under mild conditions, especially in the context of substituted arenes with diverse functional groups, remains a challenge. The direct hydroxylation of arenes was initially achieved through the use of strong Brønsted or Lewis acids to mediate electrophilic aromatic substitution reactions with super-stoichiometric equivalents of oxidants, significantly limiting the scope of the reaction. Because the products of these reactions are more reactive than the starting materials, over-oxidation is frequently a competitive process. Transition-metal-catalysed C-H oxidation of arenes with or without directing groups has been developed, improving on the acid-mediated process; however, precious metals are required. Here we demonstrate that phthaloyl peroxide functions as a selective oxidant for the transformation of arenes to phenols under mild conditions. Although the reaction proceeds through a radical mechanism, aromatic C-H bonds are selectively oxidized in preference to activated Csp3-H bonds. Notably, a wide array of functional groups are compatible with this reaction, and this method is therefore well suited for late-stage transformations of advanced synthetic intermediates. Quantum mechanical calculations indicate that this transformation proceeds through a novel addition-abstraction mechanism, a kind of 'reverse-rebound' mechanism as distinct from the common oxygen-rebound mechanism observed for metal-oxo oxidants. These calculations also identify the origins of the experimentally observed aryl selectivity.
Topics: Abietanes; Benzene Derivatives; Carbon; Catalysis; Hydrogen; Hydrogen Bonding; Hydrolysis; Hydroxylation; Metals; Oxidants; Oxidation-Reduction; Oxygen; Peroxides; Phenols; Quantum Theory; Sesquiterpenes; Tocopherols
PubMed: 23846658
DOI: 10.1038/nature12284 -
Water Research Jul 2022Chlorine dioxide (ClO) applications to drinking water are limited by the formation of chlorite (ClO) which is regulated in many countries. However, when ClO is used as a...
Chlorine dioxide (ClO) applications to drinking water are limited by the formation of chlorite (ClO) which is regulated in many countries. However, when ClO is used as a pre-oxidant, ClO can be oxidized by chlorine during subsequent disinfection. In this study, a kinetic model for the reaction of chlorine with ClO was developed to predict the fate of ClO during chlorine disinfection. The reaction of ClO with chlorine was found to be highly pH-dependent with formation of ClO and ClO in ultrapure water. In presence of dissolved organic matter (DOM), 60-70% of the ClO was transformed to ClO during chlorination, while the in situ regenerated ClO was quickly consumed by reaction with DOM. The remaining 30-40% of the ClO first reacted to ClO which then formed chlorine from the DOM-ClO reaction. Since only part of the ClO was transformed to ClO, the sum of the molar concentrations of oxychlorine species (ClO + ClO) decreased during chlorination. By kinetic modelling, the ClO concentration after 24 h of chlorination was accurately predicted in synthetic waters but was largely overestimated in natural waters, possibly due to a ClO decay enhanced by high concentrations of chloride and in situ formed bromine from bromide. Understanding the chlorine-ClO reaction mechanism and the corresponding kinetics allows to potentially apply higher ClO doses during the pre-oxidation step, thus improving disinfection byproduct mitigation while keeping ClO, and if required, ClO below the regulatory limits. In addition, ClO was demonstrated to efficiently degrade haloacetonitrile precursors, either when used as pre-oxidant or when regenerated in situ during chlorination.
Topics: Chlorides; Chlorine; Chlorine Compounds; Disinfectants; Disinfection; Drinking Water; Halogenation; Kinetics; Oxidants; Oxides; Water Purification
PubMed: 35700645
DOI: 10.1016/j.watres.2022.118515 -
General Pharmacology Aug 19981. Peroxynitrite is a short-lived and damaging oxidant that forms rapidly from the reaction of superoxide with nitric oxide. 2. In 1990, Joseph Beckman proposed that... (Review)
Review
1. Peroxynitrite is a short-lived and damaging oxidant that forms rapidly from the reaction of superoxide with nitric oxide. 2. In 1990, Joseph Beckman proposed that peroxynitrite contributed significantly to pathological oxidative stress in living tissues, and subsequent evidence strongly supports this proposal. 3. In this review, we outline the properties of peroxynitrite and discuss how it can affect biological systems and contribute to human pathologies.
Topics: Animals; Humans; Nitrates; Nitric Oxide; Oxidants; Oxidative Stress; Reactive Oxygen Species; Superoxides
PubMed: 9688457
DOI: 10.1016/s0306-3623(97)00418-7