Showing papers on "Hydrogen peroxide published in 2009"
TL;DR: This work reveals a sustained rise in H2O2 concentration at the wound margin, and shows that this gradient is created by dual oxidase (Duox), and that it is required for rapid recruitment of leukocytes to the wound.
Abstract: Barrier structures (for example, epithelia around tissues and plasma membranes around cells) are required for internal homeostasis and protection from pathogens. Wound detection and healing represent a dormant morphogenetic program that can be rapidly executed to restore barrier integrity and tissue homeostasis. In animals, initial steps include recruitment of leukocytes to the site of injury across distances of hundreds of micrometres within minutes of wounding. The spatial signals that direct this immediate tissue response are unknown. Owing to their fast diffusion and versatile biological activities, reactive oxygen species, including hydrogen peroxide (H(2)O(2)), are interesting candidates for wound-to-leukocyte signalling. Here we probe the role of H(2)O(2) during the early events of wound responses in zebrafish larvae expressing a genetically encoded H(2)O(2) sensor. This reporter revealed a sustained rise in H(2)O(2) concentration at the wound margin, starting approximately 3 min after wounding and peaking at approximately 20 min, which extended approximately 100-200 microm into the tail-fin epithelium as a decreasing concentration gradient. Using pharmacological and genetic inhibition, we show that this gradient is created by dual oxidase (Duox), and that it is required for rapid recruitment of leukocytes to the wound. This is the first observation, to our knowledge, of a tissue-scale H(2)O(2) pattern, and the first evidence that H(2)O(2) signals to leukocytes in tissues, in addition to its known antiseptic role.
1,317 citations
TL;DR: Various purification techniques for higher recovery of glucose oxidase are described here, and issues of enzyme kinetics, stability studies and characterization are addressed.
976 citations
TL;DR: A bioinspired iron-based catalyst with semiconductor photocatalytic functions in combination with a high surface area holds promise for synthetic chemistry via combining photocatalysis with organosynthesis through using g-C(3)N(4) nanoparticles.
Abstract: A bioinspired iron-based catalyst with semiconductor photocatalytic functions in combination with a high surface area holds promise for synthetic chemistry via combining photocatalysis with organosynthesis. Here exemplified for phenol synthesis, Fe-g-C3N4/SBA-15 is able to oxidize benzene to phenol with H2O2 even without the aid of strong acids or alkaline promoters. By taking advantage of both catalysis and photocatalyisis functions of g-C3N4 nanoparticles, the yield of the phenol can be markedly promoted.
946 citations
TL;DR: It is shown that acid pretreatment of a carbon support for gold-palladium alloy catalysts switches off the decomposition of H2O2, and the acid-pretreated catalysts give high yields of H 2O2 with hydrogen selectivities greater than 95%.
Abstract: Hydrogen peroxide (H2O2) is an important disinfectant and bleach and is currently manufactured from an indirect process involving sequential hydrogenation/oxidation of anthaquinones. However, a direct process in which H2 and O2 are reacted would be preferable. Unfortunately, catalysts for the direct synthesis of H2O2 are also effective for its subsequent decomposition, and this has limited their development. We show that acid pretreatment of a carbon support for gold-palladium alloy catalysts switches off the decomposition of H2O2. This treatment decreases the size of the alloy nanoparticles, and these smaller nanoparticles presumably decorate and inhibit the sites for the decomposition reaction. Hence, when used in the direct synthesis of H2O2, the acid-pretreated catalysts give high yields of H2O2 with hydrogen selectivities greater than 95%.
730 citations
TL;DR: In this article, the use of HNO3, H2SO4 and H2O2 at relatively low concentrations, short treatment times and low sonication power, in an attempt to achieve experimental conditions which efficiently functionalize the surface of multiwalled CNTs minimizing nanotube damage.
540 citations
TL;DR: This review summarizes recent progress in understanding of the catalytic and regulatory mechanisms of ‘typical 2‐Cys’ peroxiredoxins and of the biological roles played by these important enzymes in oxidative stress and nonstress‐related cellular signaling.
Abstract: Peroxiredoxins are abundant cellular antioxidant proteins that help to control intracellular peroxide levels. These proteins may also function, in part, through an evolved sensitivity of some peroxiredoxins towards peroxide-mediated inactivation in hydrogen peroxide signaling in eukaryotes. This review summarizes recent progress in our understanding of the catalytic and regulatory mechanisms of 'typical 2-Cys' peroxiredoxins and of the biological roles played by these important enzymes in oxidative stress and nonstress-related cellular signaling. New evidence suggests localized peroxide buildup plays a role in nonstress-related signaling.
416 citations
TL;DR: In this paper, pyridinic and graphitic (quaternary) nitrogens may act as active sites of catalysts for oxygen reduction reaction, which facilitates the reductive oxygen adsorption.
412 citations
TL;DR: In this paper, the authors presented a novel process for the production of H2O2 based on the bioelectrochemical oxidation of wastewater organics at an anode coupled to the cathodic reduction of oxygen to H 2O2.
377 citations
TL;DR: It is shown that alizarin red and its products may be effectively degraded by the OH radicals produced by the reaction between the Fe(2+) ions and the electrogenerated H(2)O(2).
336 citations
TL;DR: A better approach, which is based on biomimetric research on oxidative halogenation in nature, consists of generating the halogenating reagent in situ under acidic conditions from a halide salt and the result of such a reaction has been Halogenation with 100 % halogen atom economy.
Abstract: It is difficult to imagine organic chemistry without organo-halogen compounds and the molecular halogens needed for their preparation. The halogens have very different reactivity, with iodine usually requiring some form of activation, while others are reactive and hazardous chemicals. To avoid their use, various modified reagents have been discovered (N-bromo- and N-chlorosuccinimide, Selectfluor..), but halogens are used to prepare these reagents and when they are used the atom economy is poor. A better approach, which is based on biomimetric research on oxidative halogenation in nature, consists of generating the halogenating reagent in situ under acidic conditions from a halide salt. The result of such a reaction has been halogenation with 100 % halogen atom economy. Suitable oxidants for the oxidation of halides are hydrogen peroxide and oxygen.
326 citations
TL;DR: A significant enhancement in oxidant production is attributable to the interaction of Fe with Al and Si in the mixed oxides, which alters the surface redox processes, favoring the production of strong oxidants during H( 2)O(2) decomposition.
Abstract: Iron oxides catalyze the conversion of hydrogen peroxide (H2O2) into oxidants capable of transforming recalcitrant contaminants. Unfortunately, the process is relatively inefficient at circumneutral pH values because of competing reactions that decompose H2O2 without producing oxidants. Silica- and alumina-containing iron oxides prepared by sol−gel processing of aqueous solutions containing Fe(ClO4)3, AlCl3, and tetraethyl orthosilicate efficiently catalyzed the decomposition of H2O2 into oxidants capable of transforming phenol at circumneutral pH values. Relative to hematite, goethite, and amorphous FeOOH, the silica−iron oxide catalyst exhibited a stoichiometric efficiency, defined as the number of moles of phenol transformed per mole of H2O2 consumed, which was 10−40 times higher than that of the iron oxides. The silica−alumina−iron oxide catalyst had a stoichiometric efficiency that was 50−80 times higher than that of the iron oxides. The significant enhancement in oxidant production is attributable t...
TL;DR: Enzyme-linked immunosorbent assay (ELISA) tests, in which peroxidase enzyme is the most common enzyme used for labelling an antibody, are a simple and reliable way of detecting toxins, pathogens, cancer risk in bladder and prostate, and many other analytes.
TL;DR: It is found that manganese does not protect peroxide‐stressed cells by scavenging peroxide, and the beneficial effects ofManganese correlate with its ability to metallate mononuclear enzymes, which may prevent protein damage.
Abstract: Very little manganese is imported into Escherichia coli under routine growth conditions: the import system is weakly expressed, the manganese content is low, and a manganese-dependent enzyme is not correctly metallated. Mutants that lack MntH, the importer, grow at wild-type rates, indicating that manganese plays no critical role. However, MntH supports the growth of iron-deficient cells, suggesting that manganese can substitute for iron in activating at least some metalloenzymes. MntH is also strongly induced when cells are stressed by hydrogen peroxide. This adaptation is essential, as E. coli cannot tolerate peroxide stress if mntH is deleted. Other workers have observed that manganese improves the ability of a variety of microbes to tolerate oxidative stress, and the prevailing hypothesis is that manganese does so by chemically scavenging hydrogen peroxide and/or superoxide. We found that manganese does not protect peroxide-stressed cells by scavenging peroxide. Instead, the beneficial effects of manganese correlate with its ability to metallate mononuclear enzymes. Because iron-loaded enzymes are vulnerable to the Fenton reaction, the substitution of manganese may prevent protein damage. Accordingly, during H2O2 stress, mutants that cannot import manganese and/or are unable to sequester iron suffer high rates of protein oxidation.
TL;DR: The current consensus view of sites, rates, mechanisms, and topology of superoxide production by mitochondria is described and a brief overview of the methods for measuring reactive oxygen species production in isolated mitochondria and cells is presented.
Abstract: Oxidative damage to cellular macromolecules is believed to underlie the development of many pathological states and aging. The agents responsible for this damage are generally thought to be reactive oxygen species, such as superoxide, hydrogen peroxide, and hydroxyl radical. The main source of reactive species production within most cells is the mitochondria. Within the mitochondria the primary reactive oxygen species produced is superoxide, most of which is converted to hydrogen peroxide by the action of superoxide dismutase. The production of superoxide by mitochondria has been localized to several enzymes of the electron transport chain, including Complexes I and III and glycerol-3-phosphate dehydrogenase. In this chapter the current consensus view of sites, rates, mechanisms, and topology of superoxide production by mitochondria is described. A brief overview of the methods for measuring reactive oxygen species production in isolated mitochondria and cells is also presented.
TL;DR: By means of hybrid QM/MM Car-Parrinello metadynamics simulations, the mechanism of the reduction of Compound I by H( 2)O(2) in Helicobacter pylori catalase (HPC) and Penicillium vitale catalases (PVC) is investigated and it is found that the Cpd I-H(2).
Abstract: Catalases are ubiquitous enzymes that prevent cell oxidative damage by degrading hydrogen peroxide to water and oxygen (2H2O2 → 2 H2O + O2) with high efficiency. The enzyme is first oxidized to a high-valent iron intermediate, known as Compound I (Cpd I) which, in contrast to other hydroperoxidases, is reduced back to the resting state by further reacting with H2O2. By means of hybrid QM/MM Car−Parrinello metadynamics simulations, we have investigated the mechanism of the reduction of Compound I by H2O2 in Helicobacter pylori catalase (HPC) and Penicillium vitale catalase (PVC). We found that the Cpd I−H2O2 complex evolves to a Cpd II-like species through the transfer of a hydrogen atom from the peroxide to the oxoferryl unit. To complete the reaction, two mechanisms may be operative: a His-mediated (Fita-Rossmann) mechanism, which involves the distal His as an acid−base catalyst mediating the transfer of a proton (associated with an electron transfer), and a direct mechanism, in which a hydrogen atom tra...
TL;DR: A 90% removal efficiency could be accomplished in 39 pharmaceuticals at UV dose of 923 mJ/cm(2), indicating that it will be possible to reduce UV energy required for the effective pharmaceuticals removal by the combination of H( 2)O(2) with UV process.
TL;DR: In this paper, the peak-current potential-differences obtained from cyclic voltammetry and charge transfer resistance obtained from electrochemical impedance spectroscopy were used to characterize surface cleanliness.
TL;DR: The removal of azo dye Acid Orange 7 from water was investigated by the electro-Fenton technology using electrogenerated hydroxyl radicals (OH) which leads to the oxidative degradation of AO7 up to its complete mineralization.
TL;DR: Results showed great potential of BDD anode system in engineering application as a final treatment of coking wastewater, and organic pollutants were mainly degraded by reaction with free hydroxyl radicals and electrogenerated oxidants.
TL;DR: Radical species other than hydroxyl radicals were suggested to occur at acidic pH which can explain fast ciprofloxacin ozonation at pH 3.5.
TL;DR: The effect of reaction conditions including the initial pH value, and the dosages of ferrous ions and hydrogen peroxide on 2,6-dimethylaniline and COD removal were investigated and an oxidation pathway of the target organic was proposed.
Abstract: 2,6-Dimethylaniline degradation by Fenton process has been studied in depth for the purpose of learning more about the reactions involved in the oxidation of 2,6-dimethylaniline under various reaction conditions. The effect of reaction conditions including the initial pH value, and the dosages of ferrous ions and hydrogen peroxide on 2,6-dimethylaniline and COD removal were investigated. 2,6-Dimethylaniline removal efficiency of 70% was achieved under optimal reaction conditions of pH value of 2, dosage of 2 mM of ferrous ion, and 20 mM of hydrogen peroxide after 3 h. A series of intermediates were identified, corresponding to ring compounds and short-chain organic acids. The intermediates were 2,6-dimethylphenol, 2,6-dimethylnitrobenzene, 2,6-dimethylbenzoquinone, 3-hexanone, maleic acid, acetic acid, formic acid, and oxalic acid. An oxidation pathway of the target organic was also proposed in this study.
TL;DR: The results have shown that the almost complete conversion of phenol was possible, after only 5 min, under the following operating conditions: UV-C radiation; a pH of the aqueous solution of 3; a dose of 1 g(catalyst)/L, and a hydrogen peroxide concentration of 50 mmol/L for a solution containing 1 ml/L of Phenol.
TL;DR: A new luminescent assay using 11-mercaptoundecanoic acid-bound Au nanodots (11-MUA-Au NDs) for the highly selective and sensitive detection of hydrogen peroxide and glucose, based on luminescence quenching is unveiled.
TL;DR: Hydroxyl radicals then enhance antimicrobial lethality, as suggested by earlier work, and findings indicate that oxidative stress networks may provide targets for antimicrobial potentiation.
Abstract: A potential pathway linking hydroxyl radicals to antimicrobial lethality was examined by using mutational and chemical perturbations of Escherichia coli. Deficiencies of sodA or sodB had no effect on norfloxacin lethality; however, the absence of both genes together reduced lethal activity, consistent with rapid conversion of excessive superoxide to hydrogen peroxide contributing to quinolone lethality. Norfloxacin was more lethal with a mutant deficient in katG than with its isogenic parent, suggesting that detoxification of peroxide to water normally reduces quinolone lethality. An iron chelator (bipyridyl) and a hydroxyl radical scavenger (thiourea) reduced the lethal activity of norfloxacin, indicating that norfloxacin-stimulated accumulation of peroxide affects lethal activity via hydroxyl radicals generated through the Fenton reaction. Ampicillin and kanamycin, antibacterials unrelated to fluoroquinolones, displayed behavior similar to that of norfloxacin except that these two agents showed hyperlethality with an ahpC (alkyl hydroperoxide reductase) mutant rather than with a katG mutant. Collectively, these data are consistent with antimicrobial stress increasing the production of superoxide, which then undergoes dismutation to peroxide, from which a highly toxic hydroxyl radical is generated. Hydroxyl radicals then enhance antimicrobial lethality, as suggested by earlier work. Such findings indicate that oxidative stress networks may provide targets for antimicrobial potentiation.
TL;DR: In this article, a pre-treatment of olive mill wastewater by Fenton Oxidation with zero-valent iron and hydrogen peroxide was investigated to improve phenolic compounds degradation and the chemical oxygen demand (COD) removal.
TL;DR: A review of authors' researches regarding homogenous oxidation with hydrogen peroxide applied for different types of textile dyes in order to perform high textile dye removals considering some relevant factors: pH, agitation regime, temperature, H2O2 concentration, textile dye concentration, oxidation time, ferrous or metallic ions concentration, etc as discussed by the authors.
Abstract: The textile wastewaters have a diverse composition depending both on the used raw materials and applied manufacturing technologies. These wastewaters may contain various pollutants such as organic compounds (e.g. residual dyes), suspended solids, metal ions etc. Most of dyes are synthetic compounds with aromatic molecular structures and non-biodegradable. The oxidative destruction via homogenous oxidation processes with hydrogen peroxide (simple chemical oxidation with H2O2 or advanced oxidation processes (AOPs) as Fenton oxidation, ozonation, photo-oxidation and photo-Fenton oxidation etc.) are attractive alternatives to conventional treatments, easy to be applied and not so expensive. The use of H2O2 in AOPs has the advantage that the decomposition products of organic pollutants are common harmless compounds. Moreover, H2O2 decomposes itself in water and oxygen. This paper is a review of authors’ researches regarding homogenous oxidation with hydrogen peroxide applied for different types of textile dyes in order to perform high textile dye removals considering some relevant factors: pH, agitation regime, temperature, H2O2 concentration, textile dye concentration, oxidation time, ferrous or metallic ions concentration, etc.
TL;DR: The results indicate that OH is not the only oxidant produced by the photo-Fenton reaction in circum-neutral natural waters; however the photo's reaction could still be significant for contaminant degradation.
Abstract: The photo-Fenton reaction, oxidation of photoproduced ferrous iron by hydrogen peroxide, produces reactive oxidants that may be important to degradation of biologically and chemically recalcitrant organic compounds in surface waters at circum-neutral pH. Sufficient Fe(II) for the photo-Fenton reaction was produced in situ at two field sites (pH 6.1−7.1) and during irradiations of model systems at pH 7.0 with Suwannee River fulvic acid (SRFA). Amorphous iron oxyhydroxide preparations were much more easily photoreduced than ferrihydrite (Ferr-90). The rate of the photo-Fenton reaction was measured as the difference in the H2O2 accumulation rate in irradiations without and with iron in model systems. Use of benzene as a probe for hydroxyl radical (OH) and nitrate photolysis as the OH source indicated that the yield of phenol from the reaction of benzene with OH is reduced in the presence of iron and SRFA. Even when this reduction in yield was accounted for, the rate of OH production from the Fenton reaction ...
TL;DR: The present study proposes the ZVAl/O2 process as a viable method of oxidative water treatment because of the stability of aquo-complexed Al3+ ions over a wider pH range.
Abstract: Oxidative degradation of aquatic organic contaminants using zero-valent aluminum (ZVAl) in the presence of dissolved oxygen (O2) was investigated. The metal corrosion process in acidic conditions (pH <4) was accompanied by electron transfer from ZVAl to O2, which led to the simultaneous generation of Al3+ and hydrogen peroxide (H2O2). The oxidation of 4-chlorophenol (4-CP), a model substrate, was initiated by the generation of hydroxyl radicals (HO•) via electron transfer from Al0 to H2O2. Degradation was initiated after an induction period of about 2 h, during which the native oxide layer was dissoluted. The HO•-mediated oxidation reaction was completely quenched by adding methanol as a radical scavenger. Systematic studies on the effects of ZVAl loading, pH, and surface oxide content revealed that the oxide layer dissolution controlled the Al0-mediated oxidation of 4-CP. The proposed process is similarly compared with the zero-valent iron (ZVI) system, but the ZVAl/O2 system showed a higher oxidation ca...
TL;DR: It is demonstrated that the covered porous PLGA microspheres could be successfully fabricated using hydrogen peroxide and that thecovered skin layer on the PLGAmicrosphere played an important role in determining the characteristic release profiles of Dex.
TL;DR: With inocula of 6 to 7 log 10 CFU, most vegetative bacteria and spores tested survived on surfaces for more than 5 weeks, but all were inactivated within 90 min of exposure to hydrogen peroxide vapor in a 100m3 test room even in the presence of 0.3% bovine serum albumin to simulate biological soiling as mentioned in this paper.
Abstract: With inocula of 6 to 7 log10 CFU, most vegetative bacteria and spores tested survived on surfaces for more than 5 weeks, but all were inactivated within 90 min of exposure to hydrogen peroxide vapor in a 100-m3 test room even in the presence of 0.3% bovine serum albumin to simulate biological soiling.