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H2O2 Concentration (h2o2 + concentration)
Selected AbstractsComposite Multienzyme Amperometric Biosensors for an Improved Detection of Phenolic CompoundsELECTROANALYSIS, Issue 22 2003B. Serra Abstract A biosensor design, in which glucose oxidase and peroxidase are coimmobilized by simple physical inclusion into the bulk of graphite-Teflon pellets, is reported for the detection of phenolic compounds. This design allows the "in situ" generation of the H2O2 needed for the enzyme reaction with the phenolic compounds, which avoids several problems detected in the performance of single peroxidase biosensors as a consequence of the presence of a high H2O2 concentration. So, a much lower surface fouling was found at the GOD-HRP biosensor in comparison with a graphite-Teflon-HRP electrode, suggesting that the controlled generation of H2O2 makes more difficult the formation of polymers from the enzyme reaction products. The construction of trienzyme biosensors, in which GOD, HRP and tyrosinase were coimmobilized into the graphite-Teflon matrix is also reported, and their performance was compared with that of GOD-HRP bienzyme electrodes. The practical applicability of the composite multienzyme amperometric biosensors was evaluated by the estimation of the phenolic compounds content in waste waters from a refinery, and the results were compared with those obtained by using a colorimetric official method based on the reaction with 4-aminoantipyrine. [source] Mechanism of DNA damage by cadmium and interplay of antioxidant enzymes and agentsENVIRONMENTAL TOXICOLOGY, Issue 2 2007Veera L. D. Badisa Abstract Cadmium is an environmental toxicant, which causes cancer in different organs. It was found that it damages DNA in the various tissues and cultured cell lines. To investigate the mechanism of DNA damage, we have studied the effect of cadmium-induced DNA damage in plasmid pBR322 DNA, and the possible ameliorative effects of antioxidative agents under in vitro conditions. It was observed that cadmium alone did not cause DNA damage. However, it caused DNA damage in the presence of hydrogen peroxide, in a dose dependent manner, because of production of hydroxyl radicals. Findings from this study show the conversion of covalently closed circular double-stranded pBR 322 DNA to the open circular and linear forms of DNA when treated with 10 ,M cadmium and various concentrations of H2O2. The conversion was due to nicking in DNA strands. The observed rate of DNA strand breakage was dependent on H2O2 concentration, temperature, and time. Metallothionein I failed to prevent cadmium-induced DNA nicking in the presence of H2O2. Of the two antioxidant enzymes (catalase and superoxide dismutase) studied, only catalase conferred significant (50,60%) protection. EDTA and DMSO exhibited protection similar to catalase, while mannitol showed only about 20% protection against DNA damage. Ethyl alcohol failed to ameliorate cadmium-induced DNA strands break. From this study, it is plausible to infer that cadmium in the presence of hydrogen peroxide causes DNA damage probably by the formation of hydroxyl ions. These results may indicate that cadmium in vivo could play a major role in the DNA damage induced by oxidative stress. © 2007 Wiley Periodicals, Inc. Environ Toxicol 22: 144,151, 2007. [source] Biodegradable Porous Silicon Barcode Nanowires with Defined Geometry,ADVANCED FUNCTIONAL MATERIALS, Issue 14 2010Ciro Chiappini Abstract Silicon nanowires are of proven importance in such diverse fields as energy production and storage, flexible electronics, and biomedicine due to the unique characteristics that emerge from their 1D semiconducting nature and their mechanical properties. Here, the synthesis of biodegradable porous silicon barcode nanowires by metal-assisted electroless etching of single-crystal silicon with resistivities ranging from 0.0008 to 10,, cm is reported. The geometry of the barcode nanowires is defined by nanolithography and their multicolor reflectance and photoluminescence is characterized. Phase diagrams are developed for the different nanostructures obtained as a function of metal catalyst, H2O2 concentration, ethanol concentration, and silicon resistivity, and a mechanism that explains these observations is proposed. These nanowires are biodegradable, and their degradation time can be modulated by surface treatments. [source] Energy metabolism and lipid peroxidation of human erythrocytes as a function of increased oxidative stressFEBS JOURNAL, Issue 3 2000Barbara Tavazzi To study the influence of oxidative stress on energy metabolism and lipid peroxidation in erythrocytes, cells were incubated with increasing concentrations (0.5,10 mm) of hydrogen peroxide for 1 h at 37 °C and the main substances of energy metabolism (ATP, AMP, GTP and IMP) and one index of lipid peroxidation (malondialdehyde) were determined by HPLC on cell extracts. Using the same incubation conditions, the activity of AMP-deaminase was also determined. Under nonhaemolysing conditions (at up to 4 mm H2O2), oxidative stress produced, starting from 1 mm H2O2, progressive ATP depletion and a net decrease in the intracellular sum of adenine nucleotides (ATP + ADP + AMP), which were not paralleled by AMP formation. Concomitantly, the IMP level increased by up to 20-fold with respect to the value determined in control erythrocytes, when cells were challenged with the highest nonhaemolysing H2O2 concentration (4 mm). Efflux of inosine, hypoxanthine, xanthine and uric acid towards the extracellular medium was observed. The metabolic imbalance of erythrocytes following oxidative stress was due to a dramatic and unexpected activation of AMP-deaminase (a twofold increase of activity with respect to controls) that was already evident at the lowest dose of H2O2 used; this enzymatic activity increased with increasing H2O2 in the medium, and reached its maximum at 4 mm H2O2 -treated erythrocytes (10-fold higher activity than controls). Generation of malondialdehyde was strictly related to the dose of H2O2, being detectable at the lowest H2O2 concentration and increasing without appreciable haemolysis up to 4 mm H2O2. Besides demonstrating a close relationship between lipid peroxidation and haemolysis, these data suggest that glycolytic enzymes are moderately affected by oxygen radical action and strongly indicate, in the change of AMP-deaminase activity, a highly sensitive enzymatic site responsible for a profound modification of erythrocyte energy metabolism during oxidative stress. [source] Bacterial cell death induced by human pro-apoptotic Bax is blocked by an RNase E mutant that functions in an anti-oxidant pathwayGENES TO CELLS, Issue 3 2000Rika Nanbu-Wakao Background Bax is a member of the Bcl-2 family and induces apoptosis of mammalian cells. We have shown that a trace amount of human Bax induces the cell death of Escherichia coli, accompanied by damage to DNA, and that the region of Bax which is lethal to E. coli is also responsible for apoptosis-inducing activity in the mammalian cells. Results We isolated a Bax-resistant mutant from E. coli cells that survive in the presence of paraquat, a generator of superoxide, by screening a library constructed from the random insertion of a transposon. Psb1 (paraquat-resistant, suppressor of Bax-1) mutant had a Tn 10 transposon inserted in the rne gene of E. coli, splitting the RNase E gene (rne) into N- and C-terminal halves. The introduction of the truncated 5, end of rne specifically enhanced resistance to paraquat, prevented cell death induced by Bax and decreased the intracellular H2O2 concentration. The region responsible for the paraquat- and Bax-resistance was not the catalytic site for the endoribonuclease activity of RNase E. Conclusions The N-terminal region of the RNase E protein inhibits bacterial death induced by human Bax as well as paraquat through a unique mechanism that is distinct from RNA digestion. This study implies that the protection of bacterial death induced by Bax is associated with an anti-oxidant pathway and that a mutant RNase E has a novel function as an anti-oxidant. [source] The influence of extracellular H2O2 production on decolorization ability in fungiJOURNAL OF BASIC MICROBIOLOGY, Issue 6 2006Ivana Eichlerová Dr. A set of 50 randomly chosen fungal strains belonging to different basidiomycete species was tested for H2O2 and ligninolytic enzyme production and for decolorization of synthetic dyes Orange G and Remazol Brilliant Blue R. The decolorization capacity of individual strains was influenced by the level of H2O2 and laccase activity. The strains producing H2O2 at a concentration of 1.0,1.5 µM exhibited the most efficient decolorization; higher or lower H2O2 concentration reduced this ability. None of the strains without a detectable laccase activity was able to decolorize the tested dyes. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Hydrogen peroxide concentration measured in cultivation substrates during growth and fruiting of the mushrooms Agaricus bisporus and Pleurotus spp.JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 7 2007Jean-Michel Savoie Abstract Hydrogen peroxide is suspected of being highly implicated in mushroom nutrition and in substrate bleaching during cultivation. The parameters for measuring H2O2 in compost samples were examined and the methodology was applied to samples from both compost colonized by cultivars and wild isolates of Agaricus bisporus, and wheat straw or coffee pulp colonized by Pleurotus spp. Laccase and peroxidase activities were also measured. H2O2 concentration measured after heating at 80 °C for inactivating laccases and peroxidases was probably both H2O2 pre-existing in the compost and H2O2 generated from quinones and active oxygen species. This potential H2O2 concentration increased during the vegetative growth for all the strains, in agreement with a direct relationship between H2O2 concentration and active biomass of A. bisporus or Pleurotus spp. in their cultivation substrates. Correlations were observed between H2O2 concentration and manganese peroxidase activity in cultivation substrates at the stage of primordia formation. At this stage of development, H2O2 generation via biotic or abiotic mechanisms should be an important physiological trait of mushrooms. Copyright © 2007 Society of Chemical Industry [source] Comparative study of the physiological roles of three peroxidases (NADH peroxidase, Alkyl hydroperoxide reductase and Thiol peroxidase) in oxidative stress response, survival inside macrophages and virulence of Enterococcus faecalisMOLECULAR MICROBIOLOGY, Issue 5 2007Stephanie La Carbona Summary The opportunistic pathogen Enterococcus faecalis is well equipped with peroxidatic activities. It harbours three loci encoding a NADH peroxidase, an alkyl hydroperoxide reductase and a protein (EF2932) belonging to the AhpC/TSA family. We present results demonstrating that ef2932 does encode a thiol peroxidase (Tpx) and show that it is part of the regulon of the hydrogen peroxide regulator HypR. Characterization of unmarked deletion mutants showed that all three peroxidases are important for the defence against externally provided H2O2. Exposure to internal generated H2O2 by aerobic growth on glycerol, lactose, galactose or ribose showed that Npr was absolutely required for aerobic growth on glycerol and optimal growth on the other substrates. Growth on glycerol was also dependent on Ahp. Addition of catalase restored growth of the mutants, and therefore, extracellular H2O2 concentrations have been determined. This showed that the time point of growth arrest of the ,npr mutant correlated with the highest H2O2 concentration measured. Analysis of the survival of the different strains inside peritoneal macrophages revealed that Tpx was the most important antioxidant activity for protecting the cells against the hostile phagocyte environment. Finally, the ,tpx and the triple mutant showed attenuated virulence in a mouse peritonitis model. [source] Genistein selectively potentiates arsenic trioxide-induced apoptosis in human leukemia cells via reactive oxygen species generation and activation of reactive oxygen species-inducible protein kinases (p38-MAPK, AMPK)INTERNATIONAL JOURNAL OF CANCER, Issue 5 2008Yolanda Sánchez Abstract The observation that genistein may behave as a pro-oxidant agent lead us to examine the capacity of this isoflavone to modulate the toxicity of the oxidation-sensitive anti-leukemic agent arsenic trioxide (ATO), and for comparison other anti-tumor drugs. Co-treatment with genistein increased ATO-provoked apoptosis and activated apoptosis regulatory events (Bcl-XL down-regulation, cytochrome c and Omi/HtrA2 release from mitochondria, XIAP decrease and caspase-8/Bid and caspase-3 activation) in U937 promonocytes and other human leukemia cell lines (HL60, THP-1, Jurkat, RPMI-8866), but not in phytohemagglutinin-stimulated non-tumor peripheral blood lymphocytes (PBLs). Genistein, alone and with ATO, stimulated reactive oxygen species generation, and apoptosis was attenuated by N -acetyl- L -cysteine and butylated hydroxyanisole. Addition of low H2O2 concentrations mimicked the capacity of genistein to increase ATO-provoked apoptosis in leukemia cells, but not in PBLs. By contrast, co-treatment with genistein or H2O2 failed to potentiate the toxicity of DNA-targeting agent cisplatin, the proteasome inhibitor MG-132 and the histone deacetylase inhibitor MS-275. Within the here used time-period (14 hr) genistein, alone or with ATO, did not significantly affect Akt phosphorylation and NF-,B binding activity, nor decreased intracellular GSH content. However, it elicited N -acetyl- L -cysteine-inhibitable phosphorylation of p38-MAPK and AMPK, and apoptosis was attenuated by pharmacologic inhibitors against these kinases. The pro-oxidant capacity of genistein might be exploited to improve the efficacy of ATO as anti-leukemic agent, and perhaps the efficacy of other oxidation-based therapeutic approaches. © 2008 Wiley-Liss, Inc. [source] Kinetic study of the manganese-based catalytic hydrogen peroxide oxidation of a persistent azo-dyeJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 2 2010Chedly Tizaoui Abstract BACKGROUND: The discharge of synthetic dyes by the textile industry into the environment poses concerns due to their persistence and toxicity. New efficient treatment processes are required to effectively degrade these dyes. The aim of this work was to study the degradation of a persistent dye (Drimarene Brilliant Reactive Red K-4BL, C.I.147) using H2O2 oxidation catalysed by an Mn(III)-saltren catalyst and to develop a kinetic model for this system. RESULTS: Dye oxidation with H2O2 was significantly improved by the addition of the catalyst. As the pH was increased from 3 to 10, the oxidation rates increased significantly. The kinetic model developed in this study was found to adequately explain the experimental results. In particular, dye oxidation can be described at high pH by pseudo-first-order kinetics. A Michaelis,Menton type equation was developed from the model and was found to adequately describe the effect of H2O2 and catalyst concentrations on the apparent pseudo-first-order rate constant. Optimum catalyst and H2O2 concentrations of 500 mg L,1 and 6.3 g L,1, respectively, were found to give maximum reaction rates. CONCLUSION: Catalytic H2O2 oxidation was found to be effective for the removal of persistent dye and the results obtained in this work are of significance for design and scale-up of a treatment process. Copyright © 2009 Society of Chemical Industry [source] Comparative study of the physiological roles of three peroxidases (NADH peroxidase, Alkyl hydroperoxide reductase and Thiol peroxidase) in oxidative stress response, survival inside macrophages and virulence of Enterococcus faecalisMOLECULAR MICROBIOLOGY, Issue 5 2007Stephanie La Carbona Summary The opportunistic pathogen Enterococcus faecalis is well equipped with peroxidatic activities. It harbours three loci encoding a NADH peroxidase, an alkyl hydroperoxide reductase and a protein (EF2932) belonging to the AhpC/TSA family. We present results demonstrating that ef2932 does encode a thiol peroxidase (Tpx) and show that it is part of the regulon of the hydrogen peroxide regulator HypR. Characterization of unmarked deletion mutants showed that all three peroxidases are important for the defence against externally provided H2O2. Exposure to internal generated H2O2 by aerobic growth on glycerol, lactose, galactose or ribose showed that Npr was absolutely required for aerobic growth on glycerol and optimal growth on the other substrates. Growth on glycerol was also dependent on Ahp. Addition of catalase restored growth of the mutants, and therefore, extracellular H2O2 concentrations have been determined. This showed that the time point of growth arrest of the ,npr mutant correlated with the highest H2O2 concentration measured. Analysis of the survival of the different strains inside peritoneal macrophages revealed that Tpx was the most important antioxidant activity for protecting the cells against the hostile phagocyte environment. Finally, the ,tpx and the triple mutant showed attenuated virulence in a mouse peritonitis model. [source] Effects of H2O2 exposure on human sperm motility parameters, reactive oxygen species levels and nitric oxide levelsANDROLOGIA, Issue 3 2010S. S. Du Plessis Summary Research has revealed that reactive oxygen species (ROS) negatively affect sperm function, both in vivo and in vitro. Sperm preparation techniques for assisted reproductive technologies (ART) are potential causes for additional ROS production. This study aimed to correlate the concentration of exogenous H2O2 with sperm motility parameters and intracellular ROS and nitric oxide (NO) levels to reiterate the importance of minimising ROS levels in ART. Human spermatozoa from 10 donors were incubated and exposed to different exogenous H2O2 concentrations (0, 2.5, 7.5 and 15 ,m). Subsequently, motility was determined using computer-aided semen analysis, while ROS (2,7-dichlorofluorescin diacetate) and NO (diaminofluorescein-2/diacetate) were analysed using fluorescence-activated cell sorting. Results showed that H2O2 did affect the sperm parameters. Exogenous H2O2 was detrimental to motility and resulted in a significant increase in overall ROS and NO levels. A significant increase in static cells was seen as well. It is important to elucidate the mechanisms between intracellular ROS levels with sperm motility parameters. While this experiment demonstrated a need to reduce exogenous ROS levels during ART, it did not illustrate the cause and effect relationship of intracellular ROS and NO levels with sperm motility. Further research needs to be conducted to define a pathological level of ROS. [source] | ||||||||||||||||