Showing papers on "Hydrogen peroxide published in 1998"
TL;DR: Cyclohexene can now be oxidized directly to colorless crystalline adipic acid with aqueous 30 percent hydrogen peroxide under organic solvent- and halide-free conditions, which could provide an ideal solution to this serious problem.
Abstract: Currently, the industrial production of adipic acid uses nitric acid oxidation of cyclohexanol or a cyclohexanol/cyclohexanone mixture. The nitrous oxide emission from this process measurably contributes to global warming and ozone depletion. Therefore, the development of an adipic acid production process that is less damaging to the environment is an important subject in chemical research. Cyclohexene can now be oxidized directly to colorless crystalline adipic acid with aqueous 30 percent hydrogen peroxide under organic solvent- and halide-free conditions, which could provide an ideal solution to this serious problem.
671 citations
01 Jan 1998
TL;DR: Ozonation is widely and successfully applied for many types of oxidative water treatments and its chemical effects can be described by considering the sequences of highly selective direct reactions of molecular ozone and the reactions of more reactive but less selective OH radicals which are always produced from decomposed ozone in aqueous systems as mentioned in this paper.
Abstract: Ozonation is widely and successfully applied for many types of oxidative water treatments. Its chemical effects can be described by considering the sequences of highly selective direct reactions of molecular ozone and the reactions of the more reactive but less selective OH radicals which are always produced from decomposed ozone in aqueous systems. These radicals also control the ozone based AOPs (Advanced Oxidation Processes). In some cases even formation and reactions of additional secondary oxidants, such as carbonate radicals, hypobromite, and hydrogen peroxide have to be accounted for.
379 citations
TL;DR: Hydrogen peroxide is produced in blood plasma and elevation of its level could constitute a pathogenic factor in vascular organ damage attendant upon systemic hypertension.
Abstract: BackgroundOxygen free radicals may play roles in hypertension both in arteriolar constriction and in formation of lesions.ObjectiveTo quantify free radical production in blood plasma of genetic hypertensives.DesignHydrogen peroxide levels were measured, because it is one of the most stable reactive
351 citations
TL;DR: In this paper, solid materials such as iron powder, graphite and activated carbon were tested for their catalytic properties for the oxidation of 4-chlorophenol in aqueous solution with hydrogen peroxide.
290 citations
TL;DR: Chloramine formation and nitrogen-centred radicals are therefore key species in HOCl-induced protein fragmentation, and treatment with excess methionine or antioxidants protects against fragmentation; urate and bilirubin do not.
Abstract: Stimulated monocytes and neutrophils generate hypochlorite (HOCl) via the release of the enzyme myeloperoxidase and hydrogen peroxide. HOCl damages proteins by reaction with amino acid side-chains or backbone cleavage. Little information is available about the mechanisms and intermediates involved in these reactions. EPR spin trapping has been employed to identify radicals on proteins, peptides and amino acids after treatment with HOCl. Reaction with HOCl gives both high- and low-molecular-mass nitrogen-centred, protein-derived radicals; the yield of the latter increases with both higher HOCl:protein ratios and enzymic digestion. These radicals, which arise from lysine side-chain amino groups, react with ascorbate, glutathione and Trolox. Reaction of HOCl-treated proteins with excess methionine eliminates radical formation, which is consistent with lysine-derived chloramines (via homolysis of N-Cl bonds) being the radical source. Incubation of HOCl-treated proteins, after removal of excess oxidant, gives rise to both nitrogen-centred radicals, over a period of hours, and time-dependent fragmentation of the protein. Treatment with excess methionine or antioxidants (Trolox, ascorbate, glutathione) protects against fragmentation; urate and bilirubin do not. Chloramine formation and nitrogen-centred radicals are therefore key species in HOCl-induced protein fragmentation.
283 citations
TL;DR: The proposition that the msrA gene is involved in the resistance of yeast and mammalian cells to oxidative stress is supported.
Abstract: The yeast peptide-methionine sulfoxide reductase (MsrA) was overexpressed in a Saccharomyces cerevisiae null mutant of msrA by using a high-copy plasmid harboring the msrA gene and its promoter. The resulting strain had about 25-fold higher MsrA activity than its parent strain. When exposed to either hydrogen peroxide, paraquat, or 2,2′-azobis-(2-amidinopropane) dihydrochloride treatment, the MsrA overexpressed strain grew better, had lower free and protein-bound methionine sulfoxide and had a better survival rate under these conditions than did the msrA mutant and its parent strain. Substitution of methionine with methionine sulfoxide in a medium lacking hydrogen peroxide had little effect on the growth pattern, which suggests that the oxidation of free methionine in the growth medium was not the main cause of growth inhibition of the msrA mutant. Ultraviolet A radiation did not result in obvious differences in survival rates among the three strains. An enhanced resistance to hydrogen peroxide treatment was shown in human T lymphocyte cells (Molt-4) that were stably transfected with the bovine msrA and exposed to hydrogen peroxide. The survival rate of the transfected strain was much better than its parent strain when grown in the presence of hydrogen peroxide. These results support the proposition that the msrA gene is involved in the resistance of yeast and mammalian cells to oxidative stress.
280 citations
TL;DR: Data is provided about the in vivo effects of oxidative stress on protein oxidation and insights are given into understanding how such modifications can affect cellular functions.
272 citations
TL;DR: The results show that thiocyanate is an important substrate of myeloperoxidase in most environments and that hypothiocianate is likely to contribute to leukocyte antimicrobial activity.
Abstract: Myeloperoxidase plays a fundamental role in oxidant production by neutrophils. The enzyme uses hydrogen peroxide to oxidize chloride (Cl-), bromide (Br-), iodide (I-), and the pseudohalide thiocyanate (SCN-) to their respective hypohalous acids. This study for the first time presents transient kinetic measurements of the oxidation of these halides and thiocyanate by the myeloperoxidase intermediate compound I, using the sequential mixing stopped-flow technique. At pH 7 and 15 degrees C, the two-electron reduction of compound I to the native enzyme by Cl- has a second-order rate constant of (2.5 +/- 0.3) x 10(4) M(-1) s(-1), whereas reduction of compound I by SCN- has a second-order rate constant of (9.6 +/- 0.5) x 10(6) M(-1) s(-1). Iodide [(7.2 +/- 0.7) x 10(6) M(-1) s(-1)] is shown to be a better electron donor for compound I than Br- [(1.1 +/- 0.1) x 10(6) M(-1) s(-1)]. The pH dependence studies suggest that compound I reduction by (pseudo-)halides is controlled by a residue with a pKa of about 4.6. The protonation of this group is necessary for optimum (pseudo-)halide anion oxidation. These transient kinetic results are underlined by steady-state spectral and kinetic investigations. SCN- is shown to be most effective in shifting the system myeloperoxidase/hydrogen peroxide from the peroxidatic cycle to the halogenation cycle, whereas iodide is shown to be more effective than bromide which in turn is much more effective than chloride. Decreasing pH increases the rate of this transition. Our results show that thiocyanate is an important substrate of myeloperoxidase in most environments and that hypothiocyanate is likely to contribute to leukocyte antimicrobial activity.
259 citations
TL;DR: In this article, naturallyoccurring iron minerals, goethite and magnetite, were used to catalyze hydrogen peroxide and initiate Fenton-like reaction of silica sand contaminated with diesel and/or kerosene in batch system.
254 citations
TL;DR: In this paper, the steady-state current response as a function of both rotation rate and [H2O2 was studied at pH 7.26 for the [H 2O2] range 0-80 mM and for rotation rates 630-10,000 rp.m.
243 citations
TL;DR: In this paper, the degradation mechanism of 1,4-dioxane and its byproducts in dilute aqueous solution toward complete mineralization was investigated by using the UV/H2O2 process in a UV semibatch reactor.
Abstract: 1,4-Dioxane is an EPA priority pollutant often found in contaminated groundwaters and industrial effluents. The common techniques used for water purification are not applicable to 1,4-dioxane, and the currently used method (distillation) is laborious and expensive. This study aims to understand the degradation mechanism of 1,4-dioxane and its byproducts in dilute aqueous solution toward complete mineralization, by using the UV/H2O2 process in a UV semibatch reactor. The decay of 1,4-dioxane generated several intermediates identified and quantified as aldehydes (formaldehyde, acetaldehyde, and glyoxal), organic acids (formic, methoxyacetic, acetic, glycolic, glyoxylic, and oxalic) and the mono- and diformate esters of 1,2-ethanediol. Measurement of the total organic carbon (TOC) during the treatment indicated a good agreement between the experimentally determined TOC values and those calculated from the quantified reaction intermediates, ending in complete mineralization. A reaction mechanism, which accoun...
TL;DR: It is observed that two iron chelators, deferoxamine and hydroxybenzyl ethylenediamine (HBED), both inhibited spontaneous and accelerated apoptosis, suggesting that HO may mediate neutrophil apoptosis.
TL;DR: Hydrogen peroxide and various substances known to interfere with oxidative metabolism were shown to either inhibit or enhance the uptake of iodide, confirming that apoplastic oxidations play a key role in iodide uptake in Laminaria.
Abstract: Sporophytes of Laminaria digitata (L.) Lamour. were assayed for their content of accumulated iodine, which ranged from 0.4% of dry weight in adult plants up to 4.7% for young plantlets. Sporophyte tissue from Laminaria saccharina (L.) Lamour. and L. digitata took up iodide according to Michaelis-Menten kinetics. Hydrogen peroxide and various substances known to interfere with oxidative metabolism were shown to either inhibit or enhance the uptake of iodide, confirming that apoplastic oxidations play a key role in iodide uptake in Laminaria. Consistently, iodide uptake was triggered in L. saccharina protoplasts by incubation in the presence of hydrogen peroxide. Similarly, the uptake of iodide was enhanced in L. digitata gametophytes by addition of haloperoxidase, suggesting that this enzyme catalyses the oxidation of iodide by hydrogen peroxide and plays a key role in iodine uptake. Oxidative stress resulted in a marked efflux of the intracellular iodine. In both influx and efflux experiments, a marked proportion (10–30%) of the tracer was not accounted for, indicating volatilisation of iodine. The mechanism and possible functions of the accumulation of iodine by kelps are discussed.
TL;DR: In this paper, a series of manganese(II)-substituted polyoxometalates were synthesized and characterized by X-ray structure analyses, and the use of these oxidatively and solvolytically stable heteropolyanions as homogeneous catalysts for the epoxidation of dienes was investigated.
Abstract: A series of novel manganese(II)-substituted polyoxometalates, [(MnII(H2O)3)2(WO2)2(BiW9O33)2]10- (1), [(MnII(H2O))3(SbW9O33)2]12- (2), and [(MnII(H2O)3)2(MnII(H2O)2)2(TeW9O33)2]8- (3), were synthesized and characterized by X-ray structure analyses. The use of these oxidatively and solvolytically stable heteropolyanions as homogeneous catalysts for the epoxidation of dienes was investigated by gas chromatography/mass spectrometry, IR spectroscopy, UV−visible studies, and cyclic voltammetric measurements. The catalytic performance is exemplified by the model substrate (R)-(+)-limonene, at ambient temperatures in a biphasic system, with excellent regioselectivities, >99%, and very high turnovers even with only a small molar excess of hydrogen peroxide.
TL;DR: Data indicate that oxidation of ascorbic acid by hydrogen peroxide primarily proceeds through three major six-carbon intermediates, each with distinctive redox properties, which indicate that the stable metabolite diketogulonic may be a critical antioxidant in asCorbic-acid-containing systems.
TL;DR: A catalytic amount of an oxalate/oxalic acid buffer strongly enhances the catalytic properties of Mn-tmtacn complexes for epoxidation reactions with H 2 O 2.
TL;DR: In this article, surface catalyzed loss of quinoline, a model pollutant, in the presence of three iron oxides: ferrihydrite, goethite, and a semicrystalline iron oxide was examined and compared.
Abstract: The objective of this research was to examine and compare the surface catalyzed loss of quinoline, a model pollutant, in the presence of three iron oxides: ferrihydrite, goethite, and a semicrystalline iron oxide. These are ubiquitous in the subsurface environment and have been implicated in the possible abiotic loss of contaminants when hydrogen peroxide is injected for augmenting bioremediation. This suggests the possible use of hydrogen peroxide specifically as an oxidant of some compounds in the subsurface. A comparison also reveals the best candidate for use in a supported oxide fixed bed treatment system utilizing hydrogen peroxide as an oxidant. The catalytic activity toward quinoline oxidation was highest for goethite, much less for the semicrystalline material, and negligible in the presence of ferrihydrite. Several water constituents affected reaction rates and stoichiometry by adsorption or through effects on solution chemistry. The stoichiometric efficiency relating quinoline loss to hydrogen peroxide decomposition was not a function of oxide concentration, nor was it affected by the presence of carbonate or phosphate that reduced the rate of hydrogen peroxide decomposition. The effect of humic acid on quinoline loss and hydrogen peroxide decomposition rate depended on its concentration, suggesting that it may act as a radicalmore » scavenger, radical chain promoter, and catalytic site inhibitor.« less
TL;DR: It is shown that cells undergoing apoptosis from exposure to H2O2 display a significant decrease in intracellular concentration of superoxide (O− 2) which is associated with a reduction of the intrACEllular milieu, as measured by an increase in the GSH/GSSG ratio and a decrease in intrusion pH.
TL;DR: There are two lines of evidence that indicate catalases are required in the absence of GSH; firstly, strains that lack both catalase A and T accumulate increased levels of oxidized glutathione following treatment with hydrogen peroxide; and secondly, deletion ofCatalase genes exacerbates the hydrogen perox sensitivity of glr1 and gsh1 mutants.
Patent•
21 Jul 1998
TL;DR: In this paper, the standard electrode potential in the solution of this oxidizing substance is set at 1.23-2.00V, and preferably set at 0.3-1.8V.
Abstract: PROBLEM TO BE SOLVED: To provide a lithium secondary battery having excellent charge and discharge cycle characteristics by treating lithium manganese oxide with a solution having a specified standard electrode potential, which includes an oxidizing substance, and lowering or eliminating the oxygen defectiveness, and thereafter, using it as a positive electrode active material. SOLUTION: Lithium compound powder and manganese compound powder are evenly mixed, and heated so that each solid reacts with each other to obtain lithium manganese oxide. This lithium manganese oxide is treated by a solution containing oxidizing substance. At this stage, standard electrode potential in the solution of this oxidizing substance is set at 1.23-2.00V, and preferably set at 1.3-1.8V. As the oxidizing substance, an inorganic oxide such as potassium permanganate and lithium permanganate and peroxide such as hydrogen peroxide is used. A lithium secondary battery, in which capacity change accompanying charge and discharge cycles is small, is obtained by using this lithium manganese oxide after the treatment as the positive electrode active material.
Journal Article•
TL;DR: The results of this investigation indicate that the heme moiety of Fe(II) hemoglobin undergoes degradation in presence of H2O2, a sensitive marker in order to asses hemoglobin and RBC oxidative stress under pathological conditions.
TL;DR: The Photo-Fenton-Process as discussed by the authors was employed to degrade biorefractory organic pollutants in landfill leachate, and the results showed that the photo-fenton-process gave a higher COD degradation and a reduced energy consumption of at least 30% compared to the H 2 O 2 /UVC process.
Abstract: The Photo-Fenton-Process utilizing the combinations Fe(II)/H 2 O 2 /UVA and Fe(III) oxalate/H 2 O 2 /UVA was employed with success to degrade biorefractory organic pollutants in landfill leachate. The rate of degradation of the organic pollutants depends on the concentrations of hydrogen peroxide and the iron catalyst, the pH value and the concentration of dissolved oxygen. A comparison of the Photo-Fenton-Process with the H 2 O 2 /Fe(II) process and the H 2 O 2 /UVC process shows that the Photo-Fenton-Process gives a higher COD degradation and a reduced energy consumption of at least 30% compared to the H 2 O 2 /UVC process. By using photogenerated Fe(II) the amount of the iron catalyst required and the volume of sludge produced are strongly reduced.
TL;DR: In the intact heart, finely adjusted NO concentrations regulate mitochondrial O2uptake and superoxide anion production (reflected by H2O2), which in turn contributes to the physiological clearance of NO through peroxynitrite formation.
Abstract: Isolated rat heart perfused with 1.5–7.5 μM NO solutions or bradykinin, which activates endothelial NO synthase, showed a dose-dependent decrease in myocardial O2uptake from 3.2 ± 0.3 to 1.6 ± 0.1 ...
TL;DR: The chemical mechanism and reaction intermediates generated during conversion of amino acids into aldehydes by myeloperoxidase-generated HOCl are detailed.
TL;DR: The key role of the proteasome in the degradation of oxidized proteins in fibroblasts could be demonstrated and it was demonstrated for the first time, that the increased protein turnover was accompanied by a removal of protein‐bound carbonyl groups.
TL;DR: Overexpression of SOD1 in the presence of developmentally low activities of the catalytic enzymes glutathione peroxidase and catalase leads to an increased production of H2O2, and may explain the increased brain injury observed after hypoxia–ischemia in neonatal S OD1 mice.
Abstract: Unlike the mature animal, immature mice transgenic for copper/zinc superoxide dismutase (SODI) have greater brain injury after hypoxia-ischemia than their wild-type nontransgenic littermates. To assess the role of oxidative stress in the pathogenesis of this injury, we measured histopathological damage, lipid peroxidation products, enzymatic activities of catalase and glutathione peroxidase, and hydrogen peroxide (H 2 O 2 ) concentration in these animals before and after hypoxic-ischemic injury. Lipid peroxidation products were significantly increased 2 hours after the insult in both transgenic and nontransgenic brains in hippocampus, the most damaged brain region. Catalase activity did not increase in response to SOD1 overexpression or injury in either group. However, glutathione peroxidase activity, unchanged in response to overexpression, decreased significantly 24 hours after injury in both groups. At 24 hours after injury, greater H 2 O 2 accumulation was observed in transgenic brains. Because SOD1 dismutates superoxide to H 2 O 2 , overexpression of SOD1 in the presence of developmentally low activities of the catalytic enzymes glutathione peroxidase and catalase leads to an increased production of H 2 O 2 , and may explain the increased brain injury observed after hypoxia-ischemia in neonatal SOD1 mice.
Journal Article•
TL;DR: Doxorubicin participates in a wide range of free radical reactions and the resultant iron-drug complex is an efficient catalyst of the conversion of hydrogen peroxide to the highly reactive hydroxyl radical.
TL;DR: The peroxide assay originally described for the determination of hydrogen peroxide production during experimental protein glycation was adapted to microtiter plates and allows the determined of the rapid detoxification of various peroxides by cultured cells.
TL;DR: The potential of the comet assay to detect DNA strand breakage at subcytotoxic concentrations of a range of agents, some of which require metabolic activation, may provide a sensitive, but nonspecific, molecular biomarker of genotoxicity.