Showing papers on "Hydrogen peroxide published in 1989"

Heme oxygenase is the major 32-kDa stress protein induced in human skin fibroblasts by UVA radiation, hydrogen peroxide, and sodium arsenite.

Abstract: We have shown that UVA (320-380 nm) radiation, hydrogen peroxide, and sodium arsenite induce a stress protein of approximately 32 kDa in human skin fibroblasts. The synthesis and cloning of cDNA from arsenite-induced mRNA populations have now allowed us to unequivocally identify the 32-kDa protein as heme oxygenase. By mRNA analysis we have shown that the heme oxygenase gene is also induced in cultured human skin fibroblasts by UVA radiation, hydrogen peroxide, cadmium chloride, iodoacetamide, and menadione. The known antioxidant properties of heme catabolites taken together with the observation of a high level of induction of the enzyme in cells from an organ not involved in hemoglobin breakdown strongly supports the proposal that the induction of heme oxygenase may be a general response to oxidant stress and constitutes an important cellular defense mechanism against oxidative damage.

Polyethylene glycol-conjugated superoxide dismutase and catalase reduce ischemic brain injury

Abstract: Superoxide dismutase and catalase enzymatically scavenge superoxide and hydrogen peroxide, respectively. Conjugation of polyethylene glycol to superoxide dismutase (PEG-SOD) or catalase (PEG-CAT) prolongs the circulatory half-life of the native enzymes and enhances their intracellular access. We studied the protective effect of these free radical scavengers on ischemic brain injury using a rat model of focal cerebral ischemia, which is suitable for therapeutic trials. Intravenous administration of PEG-SOD (10,000 U/kg) and PEG-CAT (10,000 U/kg) before ischemia reduced the infarct volume (treatment, 139 +/- 9 mm3, means +/- SE, N = 38; placebo, 182 +/- 8 mm3, n = 37, P less than 0.002). This finding supports the concept that superoxide and hydrogen peroxide contribute to brain injury following focal cerebral ischemia.

Potassium monopersulfate and a water-soluble manganese porphyrin complex, [Mn(TMPyP)](OAc)5, as an efficient reagent for the oxidative cleavage of DNA.

Abstract: Reported studies indicate that the association of potassium monopersulfate with [Mn(TMPyP)](OAc)5, a water-soluble manganese porphyrin complex, leads to an efficient reagent for the oxidative cleavage of DNA. Single-strand breaks (SSBs) are observed on double-stranded DNA at manganese porphyrin concentrations as low as 0.5 nM with a short incubation time of 1 min. The number of SSBs linearly varies with the concentration of the manganese complex, and potassium monopersulfate is at least 3 orders of magnitude more efficient as oxygen source than hydrogen peroxide. Cleavage efficiency is optimal in the pH range 7.5-9.0 for a NaCl concentration between 80 and 150 mM or for a MgCl2 concentration of 10 mM. At very low manganese porphyrin concentration and by increasing the incubation time a catalytic cleavage activity of the complex is evidenced: up to 5 SSBs per manganese porphyrin are observed. The high cleavage activity of the monopersulfate-manganese porphyrin system makes it a good candidate for DNA-footprinting experiments.

An electrochemical sensor for hydrogen peroxide based on peroxidase adsorbed on a spectrographic graphite electrode

Abstract: Horse-radish peroxidase was found to strongly adsorb on the surface of spectrographic graphite with retained catalytic activity. Efficient electron transfer from the graphite to the oxidized form of adsorbed peroxidase could be achieved without the deliberate addition of a mediator. The peroxidase-modified graphite was used as a sensor for hydrogen peroxide in a flow-injection system. Response currents to hydrogen peroxide start at +600 mV vs. SCE and reach a maximal value at −200 mV. Highest activities were found between pH 4 and 6. Linear calibration curves for hydrogen peroxide were obtained from 0.1 to 500 μM with an injection volume of 50 μL.

A global response induced in Escherichia coli by redox-cycling agents overlaps with that induced by peroxide stress

Abstract: Escherichia coli treated with nontoxic levels of the superoxide-generating redox-cycling agents menadione and paraquat showed dramatic changes in protein composition as monitored by two-dimensional gel analysis. The distribution of proteins synthesized after treatment with these agents overlapped significantly with that seen after hydrogen peroxide treatment, and it included all the proteins in the oxyR regulon. The redox-cycling agents also elicited the synthesis of at least 33 other proteins that were not seen with hydrogen peroxide, including three heat shock proteins, the Mn-containing superoxide dismutase, the DNA repair protein endonuclease IV, and glucose-6-phosphate dehydrogenase. At least some of these redox-inducible proteins appear to be part of a specific response to intracellular superoxide. E. coli is thus equipped with a network of inducible responses against oxidative damage, controlled in multiple regulatory pathways.

Enzyme monolayer- and bilayer-modified tin oxide electrodes for the determination of hydrogen peroxide and glucose

Abstract: An enzyme-based amperometric biosensor for hydrogen peroxide was developed, employing a horseradish peroxidase (HRP) monolayer covalently attached to a tin oxide electrode and a dissolved electron mediator. The sensor can determine hydrogen peroxide at levels down to 10{sup {minus}8} M and can be applied to a flow system. Stability of the electrode, kinetics of the surface process, and the efficiencies of different mediators were studied. As an extension, glucose oxidase (GOx) was chemically bound to the HRP-modified electrode. A GOx/HRP bilayer-modified electrode thus obtained exhibits much better performance in glucose detection limit, sensitivity, and response speed than previously reported GOx monolayer-modified electrodes.

Detection of methyl, hydroxymethyl and hydroxyethyl hydroperoxides in air and precipitation

Abstract: It is well established that organic peroxides are formed by OH-radical-induced oxidation of hydrocarbons under atmospheric conditions1. Peroxyacyl nitrates have been known to be constituents of polluted air since the 1950s2,3. In a recent study we have shown that the gas-phase reaction of ozone with a variety of natural and anthropogenic alkenes can contribute to the formation of hydro-philic organic peroxides4. Indications that such peroxides are actually present in the environment have been obtained previously by measurements of the peroxide content of cloudwater and rain. In the absence of a specific analytical method the peroxide content after selective enzymatic destruction of the hydrogen peroxide was taken to be the organic peroxide fraction5-7. In this letter we report the determination by high-performance liquid chroma-tography of methyl (MHP; CH3OOH), hydroxymethyl (HMP; HOCH2OOH) and 1-hydroxyethyl (HEP; CH3CH(OH)OOH) hydroperoxides, in addition to H2O2, and present some preliminary concentration ranges in air and precipitation. The existence of this class of atmospheric trace constituents raises questions about possible adverse biological effects.

SINGLET OXYGEN INVOLVEMENT IN THE INACTIVATION OF CULTURED HUMAN FIBROBLASTS BY UVA (334 nm, 365 nm) AND NEAR‐VISIBLE (405 nm) RADIATIONS

Abstract: The UVA (320-380 nm) radiation inactivation of mammalian cells is dependent upon the presence of oxygen. In order to examine the intermediates involved, we have irradiated cells in the presence of chemical probes which are able to modify the activity of various oxygen species. We have also examined the possibility that UVA inactivates cultured human fibroblasts via generation of intracellular hydrogen peroxide. An iron scavenger (desferrioxamine) and a hydroxyl radical scavenger (dimethylsulfoxide) protect the cells against hydrogen peroxide. Diethyldithiocarbamate (a superoxide dismutase inhibitor) and aminotriazole (a catalase inhibitor) sensitize the cells to this oxidizing agent. These data support previous reports that hydrogen peroxide inactivates as a result of the iron-catalyzed generation of hydroxyl radical. None of these agents significantly alter the fluence-dependent inactivation of cell populations by radiation at 365 nm. In contrast, the cells are sensitized to radiation at 334, 365 and 405 nm in the presence of deuterium (an enhancer of singlet oxygen lifetime) and are protected against radiation at 365 nm by sodium azide (a quencher of singlet oxygen). These results are consistent with the conclusion that the generation of singlet oxygen, but not hydrogen peroxide or hydroxyl radical, plays an important role in the inactivation of cultured human cells by UVA and near-visible radiations.

Advanced oxidation processes. Test of a kinetic model for the oxidation of organic compounds with ozone and hydrogen peroxide in a semibatch reactor

Abstract: Experimental data are presented to test a kinetic model of the OE/H{sub 2}O{sub 2} process in a semibatch reactor. The effect of bicarbonate and carbonate ions is measured and found to be in concurrence with model predictions. The effect of pH in the ozone mass-transfer-limited region was examined in bicarbonate-spiked distilled water. Since the reaction is mass transfer limited, the primary effect above pH 7 is the result of changes in the distribution of inorganic carbon species which are OH-radical scavengers. Below pH 7, there is a lag period during which ozone and peroxide increase until the chain reaction begins. The effects of chloride ion and the concentration of radical scavengers other than carbonate species in ground waters are also measured. The mass-transfer/reaction rate model has been used to estimate rate constants for the reaction of hydroxyl radicals with trichloroethylene, 1,2-dibromoethane, 1,2-dibromo-3-chloropropane, carbon tetrachloride, and two bicyclic alcohols, 2-methylisoborneol and geosmin. While the model developed for the distilled water system was successful in predicting the rate of tetrachloroethylene (PCE) oxidation and the concentration of residual ozone and peroxide in regions I and III, respectively, there are several features of the model that remain unresolved when the matrix is changed tomore » a real surface or ground water. This and subsequent papers will investigate these effects.« less

Titanium gel made from metallic titanium and hydrogen peroxide

Abstract: Various titanium-peroxo intermediates may be formed in the Ti-H2O2 redox process. In a catalytically decomposed Ti-H2O2 system, an oxidizing transparent yellow-green gel with a final pH between 3 and 4 is typically formed within 48 h without addition of chelating agents. The redox potential of the gel is larger than that of the Fe(II)/Fe(III) system. The total Ti concentration in the studied gel was spectro-photometrically determined to be about 45 mM. The oxidizing component was determined to be about 15 mM with the use of iodometric titration. A model for the catalytic H2O2 decomposition is discussed, and an explanation for the existence of an ESR-active radical component in the gel is suggested. The possible relation of the gel formation to the known biocompatibility of titanium is speculated on.

Calcium chelator Quin 2 prevents hydrogen-peroxide-induced DNA breakage and cytotoxicity

Abstract: Exposure of cultured Chinese hamster ovary (CHO) cells to hydrogen peroxide results in the production of extensive DNA breakage which can be prevented by the intracellular calcium chelator Quin 2. This effect occurs at Quin 2 AM concentrations as low as 0.1 μM and is maximal at 1 μM. Addition of the extracellular calcium chelator, EGTA, does not affect the level of DNA breakage generated by H2O2. Quin 2 also significantly reduces cellular toxicity caused by the oxidant. Experiments with spin-trapping techniques demonstrate that Quin 2 does not affect the formation of hydroxyl radicals generated by the action of Fe2+ on H2O2. Quin 2 at high concentrations, similar to those reached within the cell, actually enhanced generation of hydroxyl radical in the absence of other iron chelators under our experimental conditions. These results suggest that H2O2 or H2O2-derived radicals do not directly induce DNA strand breakage in intact mammalian cells; rather, these radicals may disturb intracellular Ca2+ homeostasis which results in secondary reactions ultimately leading to DNA strand breakage. In addition to strand breakage, membrane and protein oxidation probably contribute to the cytotoxic effect of H2O2.

Destruction of aromatic pollutants by UV light catalyzed oxidation with hydrogen peroxide

Abstract: Toxic and hazardous compounds are often present in water at low concentrations, which can make their removal difficult and costly by conventional treatment processes A promising method for destroying pollutants in water is ultraviolet (UV) catalyzed oxidation by hydrogen peroxide The effectiveness of this process was determined for typical aromatic compounds including benzene, toluene, chlorobenzene, phenol, 2-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, dimethyl phthalate, and diethyl phthalate The reactions were conducted in a quartz annular reactor equipped with a low-pressure mercury lamp Of the aromatics studied, reaction rates were fastest with 2,4,6-trichlorophenol and slowest with the phthalates Analyses of reacted samples by HPLC and GC/MS indicated that the aromatics formed many intermediates that could be destroyed by extending the treatment time An empirical rate expression was developed to correlate the results

Detection of an oxyferryl porphyrin pi-cation-radical intermediate in the reaction between hydrogen peroxide and a mutant yeast cytochrome c peroxidase. Evidence for tryptophan-191 involvement in the radical site of compound I.

Abstract: Peroxide oxidation of a mutant cytochrome c peroxidase, in which Trp-191 has been replaced by Phe through site-directed mutagenesis, produces an oxidized intermediate whose stable UV/visible absorption spectrum is very similar to that of compound I of the native yeast enzyme. This spectrum is characteristic of an oxyferryl, Fe(IV), heme. Stopped-flow studies reveal that the reaction between the mutant enzyme and hydrogen peroxide is biphasic with the transient formation of an intermediate whose absorption spectrum is quite distinct from that of either the native ferric enzyme or the final product. Rapid spectral scanning of the intermediate provides a spectrum characteristic of an oxyferryl porphyrin pi-cation-radical species. At pH 6, 100 mM ionic strength, and 25 degrees C, the rate constant for formation of the oxyferryl pi-cation radical has a lower limit of 6 X 10(7) M-1 s-1 and the rate of conversion of the transient intermediate to the final oxidized product is 51 +/- 4 s-1. Evidence is presented indicating that Trp-191 either is the site of the radical in CcP compound I or is intimately involved in formation of the radical.

Efficient conversion of nitriles to amides with basic hydrogen peroxide in dimethyl sulfoxide

Abstract: Nitriles 1 are efficiently transformed into N-unsubstituted amides 2 at 20 o C in 5-30 mins in good yield and with high selectivity, using basic 30% hydrogen peroxide in dimethyl sulfoxide

Damage to the bases in DNA induced by stimulated human neutrophils.

Abstract: Leukocyte-induced DNA damage may partially account for the known association between chronic inflammation and malignancy. Since elucidation of the chemical nature of leukocyte-induced DNA damage may enhance our understanding of the mechanisms underlying leukocyte-induced DNA damage and the carcinogenesis associated with inflammation, the present study was undertaken to characterize the chemical modifications that occur in DNA exposed to stimulated human neutrophils. Calf thymus DNA was exposed to phorbol myristate acetate (PMA)-stimulated neutrophils in the presence or absence of exogenously added iron ions. DNA samples were subsequently hydrolyzed, derivatized and analyzed by gas chromatography-mass spectrometry with selected-ion monitoring. A variety of base modifications including cytosine glycol, thymine glycol, 4,6-diamino-5-formamidopyrimidine, 8-hydroxyadenine, 2,6-diamino-4-hydroxy-5-formamidopyrimidine, and 8-hydroxyguanine were identified. The yield of these various base products was increased by the addition of iron ions. Specifically, in the presence of physiologic quantities of iron ions, approximately 7 of every 1,000 DNA bases were modified. Addition of the superoxide anion scavenger, superoxide dismutase, the hydrogen peroxide scavenger, catalase, the hydroxyl scavenger, dimethylsulfoxide, or the iron chelator, deferoxamine, to DNA mixtures containing PMA, neutrophils, and iron ions, greatly decreased the yield of the damaged DNA base products. Our results indicate that stimulated human neutrophils can damage each of the four bases in DNA. It is likely that hydroxyl radical, generated via an iron catalyzed Haber-Weiss reaction, mediates neutrophil-induced DNA base damage, since: (a) the chemical structure of neutrophil-induced DNA base damage is consistent with a hydroxyl radical-mediated mechanism, (b) hydroxyl radical generated via ionizing radiation in aqueous solution produces DNA base modifications that are identical to neutrophil-induced DNA base modifications, (c) iron ions increase neutrophil-induced DNA base damage, and (d) iron chelators or scavengers of superoxide anion, hydrogen peroxide or hydroxyl radical decrease neutrophil-induced DNA base damage.

Pretreatment of cane bagasse with alkaline hydrogen peroxide for enzymatic hydrolysis of cellulose and ethanol fermentation

Abstract: Pretreatment of the agrocellulosic waste, cane bagasse with alkaline hydrogen peroxide greatly enhances its susceptibility to enzymatic cellulolysis and thus the ethanol production from it. Various process conditions have been studied to optimize the enzymate effectiveness. These conditions include the contact time, the hydrogen peroxide concentration and the pretreatment temperature. Results obtained show, that about 50% of lignin and most of hemicellulose content of cane bagasse was solubilized, by 2% alkaline hydrogen peroxide at 30°C within 8 h. The cellulose content was consequently increased from 42% in the orginal cane bagasse to 75% in the oxidized pulp. Saccharification of this pulp residue with cellulase from Trichorderma viride at 45°C for 24 h, yielded glucose with 95% efficiency. The efficiency of ethanol production from the insoluble fraction with S. cervisiae was 90% compared to about 50% for untreated cane bagasse.