Small Amounts Of H2O2 Research Articles

Doping vs. heterojunction: A comparative study of the approaches for improving the photocatalytic activity of flower-like Bi2WO6 for water treatment with domestic LED light

In this work, Bi2WxMo1–xO6 solid solutions and Bi2WO6/g-C3N4 composites were synthesized by a simple hydrothermal method, characterized by a complex of physicochemical methods and used in the decomposition of organic pollutants under visible light to comprehensively compare different modulating techniques. The highest efficiency was detected for Bi2W0.5Mo0.5O6 in the degradation of methylene blue (conversion of 52.9%, TON = 0.022), indicating the attractiveness of the doping strategy. Excellent results were achieved with small amounts of H2O2 in the photodegradation of methylene blue (conversion of 97.9%, TON = 0.040) and phenol (conversion of 81.2%, TON = 0.056).

H2 O2 feeding enables LPMO-assisted cellulose saccharification during simultaneous fermentative production of lactic acid.

Simultaneous saccharification and fermentation (SSF) is a well-known strategy for valorization of lignocellulosic biomass. Because the fermentation process typically is anaerobic, oxidative enzymes found in modern commercial cellulase cocktails, such as lytic polysaccharide monooxygenases (LPMOs), may be inhibited, limiting the overall efficiency of the enzymatic saccharification. Recent discoveries, however, have shown that LPMOs are active under anoxic conditions if they are provided with H2 O2 at low concentrations. In this study, we build on this concept and investigate the potential of using externally added H2 O2 to sustain oxidative cellulose depolymerization by LPMOs during an SSF process for lactic acid production. The results of bioreactor experiments with 100 g/L cellulose clearly show that continuous addition of small amounts of H2 O2 (at a rate of 80 µM/h) during SSF enables LPMO activity and improves lactic acid production. While further process optimization is needed, the present proof-of-concept results show that modern LPMO-containing cellulase cocktails such as Cellic CTec2 can be used in SSF setups, without sacrificing the LPMO activity in these cocktails.

A Polyimide-Based Photocatalyst for Continuous Hydrogen Peroxide Production Using Air and Water under Solar Light

A Polyimide-Based Photocatalyst for Continuous Hydrogen Peroxide Production Using Air and Water under Solar Light

Comparative study of discharge schemes for production rates and ratios of reactive oxygen and nitrogen species in plasma activated water

Plasma activated water (PAW) containing reactive oxygen and nitrogen species (RONS) is of great interest for applications in the agricultural and food industries, where processing methods with large capacities and high energy-yields are required. In this work, we studied the differences between seven types of discharge schemes in terms of the production rates and concentration ratios of RONS using deionized water and tap water in comparison. We used N2 and air as the feed gas with a variable admixture of water vapour. When O2 was incorporated into the reaction system, the major products in the PAW became and , while small amounts of H2O2 and were detected only in O2 poor situations with water vapour. Of the major products, the condition of whether or becomes predominant is dependent on the extent of successive oxidation reactions from NO to NO2 and NO3 and the competing rates between gas phase reactions and dissolutions into water. In our tested discharge schemes, those with volumetric glow-like discharge structures produced rich PAW, while those with spark discharge structures over the water surface or in water were favourable for the production of rich PAW. In particular, a discharge scheme with a wire-in-nozzle structure operated in a spark-mode with a bubbling gas flow yielded PAW with the highest concentration, more than 70%, at a high energy-yield of 2 g kWh−1. In the storage period, was converted into due to ionic reactions in aqueous solution, but the buffer action of tap water was observed to suppress the conversion for a fairly long period.

When a Semiconductor Utilized as an NIR Laser-Responsive Photodynamic/Photothermal Theranostic Agent Integrates with Upconversion Nanoparticles.

Photoactive theranostics including photodynamic therapy (PDT) hace aroused an intensive interest that combines medical diagnostics with treatment under a single irradiation laser. However, the conventional organic PDT agents usually suffer from aggregation caused by the quenching effect. In this research, we designed a core-shell-shell (CSS) UCNPs with NaGdF4 as the host, and the UCNPs could emit higher blue/green light by the energy transfer processes among Nd/Yb/Tm/Gd/Tb under 808 nm laser. When the CSS UCNPs were combined with the MnO2 semiconductor as the energy acceptor, CSS@Mn could be utilized as an effective PDT agent under a NIR laser. The temperature also increased more than 12.2 °C under the 808 nm laser, indicating the potential of synergistic photothermal therapy (PTT) and PDT. Interestingly, cells with small amounts of H2O2 could be responsive to the CSS@Mn platform. The antitumor effect was proved by the in vitro and in vivo experiments. Also, the biocompatibility, biodistribution, and excretion pathway were detected and revealed by the H&E stained pathological section and photoacoustic (PA) images. That means this platform could be potentially used as antitumor PDT/PTT agents.

A Carbon Electrode Functionalized by a Tricopper Cluster Complex: Overcoming Overpotential and Production of Hydrogen Peroxide in the Oxygen Reduction Reaction.

A study of the oxygen reduction reaction (ORR) on a screen printed carbon electrode surface mediated by the tricopper cluster complex Cu3 (7-N-Etppz(CH2 OH)) dispersed on electrochemically reduced carbon black, where 7-N-Etppz(CH2 OH) is the ligand 3,3'-(6-(hydroxymethyl)-1,4-diazepane-1,4-diyl)bis(1-(4-ethyl piperazin-1-yl)propan-2-ol), is described. Onset oxygen reduction potentials of about 0.92 V and about 0.77 V are observed at pH 13 and pH 7 vs. the reversible hydrogen electrode, which are comparable to the best values reported for any synthetic copper complex. Based on half-wave potentials (E1/2 ), the corresponding overpotentials are about 0.42 V and about 0.68 V, respectively. Kinetic studies indicate that the trinuclear copper catalyst can accomplish the 4 e- reduction of O2 efficiently and the ORR is accompanied by the production of only small amounts of H2 O2 . The involvement of the copper triad in the O2 activation process is also verified.

Degradation of Reactive Dyes Using Advanced Oxidation Method

In this study, the photo‐Fenton process was used to identify degradation conditions of Reactive Blue 19 (RB19) and Reactive Red 21 (RR21). The effects of pH, initial H2O2 and FeSO4 concentrations, time, and UV light intensity in determining the degradation rate were studied. The optimal conditions for the degradation of 0.156 mmol L−1 RB19 and 0.036 mmol L−1 RR21 in water were found to be: pH 4, 0.1 mL 30% H2O2 for RB19 and RR21, 0.2 mL 0.5% FeSO4 for RB19 and 0.1 mL 0.5% FeSO4 for RR21, 20 mL volume, and a temperature of 20°C. Optimal conditions were applied to synthetic dye wastewater using small amounts of H2O2 in 1 L for degradation. The degree of degradation efficiency of synthetic wastewater by the photo‐Fenton process was found to be >95% within 10 min.

Drinking Water Purification by Electrosynthesis of Hydrogen Peroxide in a Power‐Producing PEM Fuel Cell

The industrial anthraquinone auto-oxidation process produces most of the world's supply of hydrogen peroxide. For applications that require small amounts of H2 O2 or have economically difficult transportation means, an alternate, on-site H2 O2 production method is needed. Advanced drinking water purification technologies use neutral-pH H2 O2 in combination with UV treatment to reach the desired water purity targets. To produce neutral H2 O2 on-site and on-demand for drinking water purification, the electroreduction of oxygen at the cathode of a proton exchange membrane (PEM) fuel cell operated in either electrolysis (power consuming) or fuel cell (power generating) mode could be a possible solution. The work presented here focuses on the H2 /O2 fuel cell mode to produce H2 O2 . The fuel cell reactor is operated with a continuous flow of carrier water through the cathode to remove the product H2 O2 . The impact of the cobalt-carbon composite cathode catalyst loading, Teflon content in the cathode gas diffusion layer, and cathode carrier water flowrate on the production of H2 O2 are examined. H2 O2 production rates of up to 200 μmol h(-1) cmgeometric (-2) are achieved using a continuous flow of carrier water operating at 30 % current efficiency. Operation times of more than 24 h have shown consistent H2 O2 and power production, with no degradation of the cobalt catalyst.

Suppression of Early Stages of Fungus Development by Hydrogen Peroxide at Low Concentrations

Hydrogen peroxide mediates some anti-infectional responses of plants. It is toxic to pathogenous bacteria and fungi. To evaluate its minimal fungitoxic amounts, it was applied to spores of the causal agents of cucurbit scab (Cladosporium cucumerinum) and rice blast (Magnaporthe grisea, formerly Pyricularia oryzae) over the broad concentration range (10(-2) to 10(-14) M). Spore germination and appressorium formation were examined. The dose-response dependence was found multimodal for both fungi. The inhibition of spore germination was maximal at 10(-2) M and practically disappeared at 10(-5) - 10(-6) M H2O2. However, weaker peroxide solutions had increased fungitoxicity. The inhibition of C. cucumerinum spore germination at 10(-11)- 10(-12) M was almost the same extent as at 10(-2) M H2O2. For M. grisea, two maxima of germination inhibition near 10(-7) M and 10-10 M H2O2 were found. Here, the toxicity was higher than at its millimolar concentration. M. grisea appressoria formation repeated the aforementioned pattern generally. Therefore, hydrogen peroxide can have an antifungal action at very low concentrations. Such small amounts of H2O2 might be sufficient for plant defense responses as well.

Characterization of Superoxide-producing Sites in Isolated Brain Mitochondria

Mitochondrial respiratory chain complexes I and III have been shown to produce superoxide but the exact contribution and localization of individual sites have remained unclear. We approached this question investigating the effects of oxygen, substrates, inhibitors, and of the NAD+/NADH redox couple on H2O2 and superoxide production of isolated mitochondria from rat and human brain. Although rat brain mitochondria in the presence of glutamate+malate alone do generate only small amounts of H2O2 (0.04 +/- 0.02 nmol H2O2/min/mg), a substantial production is observed after the addition of the complex I inhibitor rotenone (0.68 +/- 0.25 nmol H2O2/min/mg) or in the presence of the respiratory substrate succinate alone (0.80 +/- 0.27 nmol H2O2/min/mg). The maximal rate of H2O2 generation by respiratory chain complex III observed in the presence of antimycin A was considerably lower (0.14 +/- 0.07 nmol H2O2/min/mg). Similar observations were made for mitochondria isolated from human parahippocampal gyrus. This is an indication that most of the superoxide radicals are produced at complex I and that high rates of production of reactive oxygen species are features of respiratory chain-inhibited mitochondria and of reversed electron flow, respectively. We determined the redox potential of the superoxide production site at complex I to be equal to -295 mV. This and the sensitivity to inhibitors suggest that the site of superoxide generation at complex I is most likely the flavine mononucleotide moiety. Because short-term incubation of rat brain mitochondria with H2O2 induced increased H2O2 production at this site we propose that reactive oxygen species can activate a self-accelerating vicious cycle causing mitochondrial damage and neuronal cell death.

Thiopentone and propofol, but not methohexitone nor midazolam, inhibit neutrophil oxidative responses to the bacterial peptide FMLP.

The effects of different anaesthetics on the neutrophil oxidative response in vitro are compared. Neutrophils were stimulated with small amounts of the bacterial peptide N-formyl-L-methionyl-L-leucyl-phenylalanine as a physiological, receptor-dependent stimulus. A new flow cytometry-based method capable of detecting the small amounts of H2O2 generated by neutrophils in a heterogeneous all-or-none response following submaximal stimulation with N-formyl-L-methionyl-L-leucyl-phenylalanine was used. Propofol and thiopentone suppressed the respiratory burst significantly (P < 0.05 and P < 0.01) in therapeutic concentrations, while midazolam and methohexitone inhibited significantly (P < 0.01) only at concentrations greater than the therapeutic range. Impairment of the neutrophil response was primarily because of a reduction in the number of neutrophils participating in the respiratory burst and not of a proportional decrease of the fluorescence of all neutrophils.

Effects of low-dose hydrogen peroxide in the isolated perfused rat lung.

Isolated perfused rat lungs (IPRL) were used to determine if treatment with hydrogen peroxide would result in measurable changes in exhaled ethane during the early stages of capillary leak. Pulmonary capillary filtration coefficient, pulmonary vascular resistance, and dynamic pulmonary compliance were measured at two time points in an IPRL. Additionally, exhaled ethane was determined before and after the addition of 0.25 mM H2O2 to the perfusate in a second group of lungs. Lung wet/dry weight ratios were measured at the termination of the experiments. The ethane in the exhaled alveolar gas from IPRLs ventilated with 5%CO2/20%O2/balance N2 was quantitated using gas chromatography before and after the addition of 0.25 mM H2O2 to Krebs Ringer's 5% albumin perfusate. H2O2 (0.25 mM) caused a small but significant increase in capillary filtration coefficient from 0.0122 (+/- 0.0008) to 0.0173 (+/- 0.0013) mL/min/cm H2O/g dry lung weight (p < .05). Wet/dry lung weight ratios were increased in the H2O2-treated lungs (6.0654 +/- 0.1024 versus 5.4149 +/- 0.1143; p < .05). Exhaled ethane did not increase over the period of time hydrogen peroxide was present in the perfusate. In other experiments in closed-chested rats, 0.25 mM peroxide did not cause increased exhaled ethane, whereas 1 mM H2O2 did. This latter increase in ethane was not noted in similarly perfused open-chested rats. These data indicate that small amounts of H2O2 may increase pulmonary capillary permeability without affecting exhaled ethane measurements.

Rapid inactivation of plant aconitase by hydrogen peroxide.

Preincubation of potato (Solanum tuberosum) tuber mitochondria with 300 microM-H2O2 for 10 min nearly stopped the State 3 rate of citrate oxidation. Addition of isocitrate resulted in resumption of O2 uptake. The State 3 rates of succinate, external NADH and 2-oxoglutarate oxidation were unaffected by H2O2 over the dose range 50-500 microM. Preincubation of mitochondria with 300 microM-H2O2 for 5 min unmasked in the matrix space a paramagnetic signal with a peak at a g value of approx. 2.03. Aconitase was purified over 135-fold to a specific activity of 32 mumol/min per mg (with isocitrate as substrate) from the matrix of potato tuber mitochondria. The native enzyme was composed of a single polypeptide chain (molecular mass 90 kDa). Incubation of purified aconitase with small amounts of H2O2 caused the build up of a paramagnetic 3Fe cluster with a low-field maximum of g = 2.03 leading to a progressive inhibition of aconitase activity. The results show that aconitase present in the matrix space was the major intramitochondrial target for inactivation by H2O2.

Enhanced light microscopic visualization of oxidase activity with the cerium capture method

Visualization methods for the light microscopic detection of the activity of oxidases after being localized with cerium ions as reported by Angermüller and Fahimi (1988a, b) are not suitable for the demonstration of H2O2-genrating oxidases at sites with low activity. Therefore, the cerium-diaminobenzidine (DAB) visualization procedure of these authors was modified. Nickel or cobalt ions were added to the DAB solution together with small amounts of H2O2. Visualization was performed in a one-step-method. This modified visualization technique enables light microscopic detection of amino acid oxidase activity in kidney and liver cells where it was found with the original method but the amounts of final reaction product were considerably higher. Moreover, the DAB-nickel-H2O2 and DAB-cobalt-H2O2 procedures were more sensitive than the cerium-lead method of Angermüller and Fahimi (1988a, b). The method appeared to be specific, because final reaction product was not found after control incubation. Especially the DAB-nickel-H2O2 procedure can also be used for immunohistochemistry when glucose oxidase serves as the enzyme label.

Non-deleterious inhibition of endogenous peroxidase activity (EPA) by cyclopropanone hydrate: a definitive approach.

Endogenous peroxidase activity (EPA) poses a serious problem in immunoperoxidase localization of antigens unable to withstand deleterious effects of aldehyde fixatives, alcohols, and various oxidative reagents. This has forced the development of more selective inhibition methods. Of these, phenylhydrazine or azide combined with small amounts of H2O2 have proved quite effective. However, the precise mechanism of the action of these compounds on EPA generating proteins is not understood. Cyclopropanone hydrate is a compound whose inhibitory action on the heme moiety of horseradish peroxidase is well understood. The aim of this study was to investigate the effect of this compound on EPA and to compare its efficiency with that of optimal phenylhydrazine and sodium azide regimens. In addition, any gross deleteriousness of cyclopropanone hydrate towards immunoperoxidase immunolocalization of three of the most delicate lymphocyte surface antigens was investigated. Cyclopropanone hydrate was found to inhibit EPA with progressing strength between 0.15-15 mM. Over this range, H2O2 was found necessary for inhibition only for cyclopropanone hydrate concentrations up to 0.15 mM. Beyond this amount, the compound inhibited EPA equally strongly in the presence or absence of H2O2, reaching near-maximum inhibition at 15 mM. This and the H2O2-requiring regimens were found to cause no gross diminution in immunoperoxidase staining of CD4, CD6, and CD8 antigens in snap-frozen, acetone-fixed human tonsil sections. Cyclopropanone hydrate therefore provides a definitive non-deleterious mode of inhibiting EPA for immunoperoxidase staining of delicate antigens.

Myeloperoxidase oxidation states involved in myeloperoxidase-oxidase oxidation of thiols.

The changes in the oxidation state of the leucocyte enzyme myeloperoxidase, induced by buffer and thiols, were studied with visible-light-absorption spectroscopy. It was concluded that phosphate buffer contains small amounts of H2O2 and that thiols, when added to buffer, induce the generation of minute amounts of superoxide radical anion. These minute amounts of reduced oxygen species are suggested to account for the initiation of myeloperoxidase-oxidase oxidation of thiols. Myeloperoxidase was found to be in its Compound III oxidation state during myeloperoxidase-oxidase oxidation of thiols. However, myeloperoxidase-mediated oxidation of thiols with concomitant O2 consumption can also occur with myeloperoxidase in its Compound II oxidation state. These studies indicate that the ferro and Compound III oxidation states may not be essential intermediates in myeloperoxidase-oxidase oxidation of thiols, but rather that the formation of the Compound III oxidation state retards the reaction.

Azide-binding studies reveal type 3 copper heterogeneity in ascorbate oxidase from the green zucchini squash (Cucurbita pepo).

Titration of native ascorbate oxidase from green zucchini squash (Cucurbita pepo) with azide in 0.1 M-phosphate buffer, pH 6.8, exhibits a biphasic spectral behaviour. Binding of the anion with 'high affinity' (K greater than 5000 M-1) produces a broad increase of absorption in the 400-500 nm region (delta epsilon approximately 1000 M-1.cm-1) and c.d. activity in the 300-450 nm region, whereas azide binding with 'low affinity' (K approximately 100 M-1) is characterized by an intense absorption band at 420 nm (delta epsilon = 6000 M-1.cm-1), corresponding to negative c.d. activity and a decrease of absorption at 330 nm (delta epsilon = -2000 M-1.cm-1). The high-affinity binding involves a minor fraction of the protein containing Type 3 copper in the reduced state, and the spectral features of this azide adduct can be eliminated by treatment of the native enzyme with small amounts of H2O2, followed by dialysis before azide addition. As shown by e.s.r. spectroscopy, Type 2 copper is involved in both types of binding, its signal being converted into that of a species with small hyperfine splitting constant [12 mT (approximately 120 G)] in the case of the low-affinity azide adduct. The spectral similarities of the two types of azide adducts with the corresponding adducts formed by native laccase, which also exhibits Type 3 copper heterogeneity, are discussed.

ChemInform Abstract: Mechanism of Formation of Oxygen Difluoride.

AbstractPassage of F2 over ice at temp. around ‐50 °C produces a mixture of O2, HOF, OF2 and small amounts of H2O2.

Inhibition of Streptococcus mutans by the lactoperoxidase antimicrobial system.

Inhibition of bacterial metabolism by the lactoperoxidase (LP)-hydrogen peroxide (H2O2)-thiocyanate system was studied with representatives of serotypes a through g of Streptococcus mutans. The aims were to determine whether the amount of H2O2 released from these catalase-negative bacteria is sufficient to activate the LP system and whether these oral bacteria are resistant to inhibition by the LP system, which is active in human saliva. When the washed, stationary-phase cells were incubated aerobically with LP, thiocyanate, and glucose (Glc), greater than 90% inhibition of Glc utilization and lactate production was obtained with strains that released large amounts of H2O2 (BHT, FA-1, OMZ-176); 20 to 50% inhibition was obtained with strains that released about half as much H2O2 (B-13, Ingbritt); and no inhibition was obtained with strains that released only small amounts of H2O2 (AHT, HS-6, GS-5, LM-7, OMZ-175, 6715-15). Inhibition was most effective at pH 5, whereas release of H2O2 and accumulation of the inhibitor (hypothiocyanite ion) were highest at pH 8. With H2O2-releasing cells from early stationary phase, preincubation with Glc abolished inhibition, though it did not influence H2O2 release. Cells harvested 24 h later were depleted of sulfhydryl compounds. Inhibition of these cells was abolished by preincubation with Glc and certain sulfhydryl or disulfide compounds (reduced or oxidized glutathione, cysteine or cystine). This preincubation increased cell sulfhydryl content but had no effect on H2O2 release. All strains were inhibited when incubated with LP, thiocyanate, and added (exogenous) H2O2. Smaller amounts of H2O2 were required to inhibit at pH 5, and larger amounts were required to inhibit cells preincubated with Glc or with Glc and the sulfhydryl or disulfide compounds. The results indicate that pH, amount of H2O2, cell sulfhydryl content, and stored-carbohydrate content determine susceptibility to inhibition.

Mechanistic aspects of cathodic oxygen reduction

An investigation of cathodic oxygen reduction in pure and contaminated solutions using the ring-disc technique showed:o(1)On Pt and Ag under clean conditions the four-electron reduction of O2 is operative, only small amounts of H2O2 are produced. In contaminated solution, a decrease of the catalytically active surface of Pt is observed, but on Ag the H2O2 formation significantly increases.(2)The two-electron reduction of O2 to H2O2 takes place only on Au and C. On Pt and Ag under clean conditions the four-electron reduction of O2 is operative, only small amounts of H2O2 are produced. In contaminated solution, a decrease of the catalytically active surface of Pt is observed, but on Ag the H2O2 formation significantly increases. The two-electron reduction of O2 to H2O2 takes place only on Au and C. The results are interpreted considering different models of the O2 adsorption. The different behaviour of Au and Ag, both having almost identical electronic and crystallographic structures, is explained on the basis of simple MO calculations. An influence of the metal ionization potential on the type of the reaction is postulated which might be generalized for sp-materials.