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Hydrogen Peroxide Concentration (hydrogen + peroxide_concentration)
Selected AbstractsHydrogen 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] Kinetic modeling of aqueous phenol degradation by UV/H2O2 processINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 1 2008Maryam Edalatmanesh A dynamic kinetic model for the oxidation of phenol in water by an UV/H2O2 process is developed. The model is based on the elementary chemical and photochemical reactions, initiated by the photolysis of hydrogen peroxide into hydroxyl radicals. The model is validated by using experimental data obtained from the open literature for an actual UV/H2O2 process. Using those data and the developed kinetic model, kinetic rate constants for phenol intermediates, catechol and hydroquinone, are estimated. Moreover, the optimum initial hydrogen peroxide concentration is estimated by means of the validated model. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 40: 34,43, 2008 [source] Proline Analogue of Nitrosourea as a New Cytotoxic ProdrugARCHIV DER PHARMAZIE, Issue 11 2009Anna Stankiewicz-Kranc Abstract Carmustine is frequently used as anticancer drug. High toxicity and low selectivity reduces the application of this drug. Though, there is a necessity to find new compounds characterized by similar therapeutic effects but a higher selectivity and safety. As a result, the proline analogue of nitrosourea, N -[N,-(2-bromophenyl)- N,-nitrosocarbamoyl]proline (AC), has been synthesized. The aim of this study was to compare the influence of carmustine and the proline analogue of nitrosourea on the antioxidant abilities of fibroblasts and leukemia cells, MOLT4. It was shown that carmustine as well as AC cause an increase in hydrogen peroxide concentration in normal and neoplastic cells. Incubation with both compounds led to a diminution of the activity of antioxidant enzymes such as superoxide dismutase, glutathione peroxidase, and reductase. Changes in activity / level of antioxidant parameters were accompanied by augmentation of lipid and oxidative protein modifications. In conclusion, carmustine and AC cause changes in the antioxidative system of normal and MOLT4 cells and are a reason of oxidative stress formation. [source] Production, localisation and possible roles of nitric oxide in drought-stressed grapevinesAUSTRALIAN JOURNAL OF GRAPE AND WINE RESEARCH, Issue 1 2010A.A. PATAKAS Abstract Background and Aims:, The aim of this study was to monitor nitric oxide (NO) production in response to progressive soil drying as well as to evaluate its possible role as an intermolecular signalling molecule mediating drought-stress responses in grapevines. Methods and Results:, NO production in response to water stress was examined in potted grapevine plants (Vitis vinifera L. cv. Mavrodafni). The cellular sites of NO production and localisation in stressed plants were monitored by fluorometric techniques. Results indicated that both abscisic acid and NO concentrations increased significantly in leaves of stressed plants. The stomatal guard cells seemed to be the sites of earlier NO accumulation. The changes in stomatal conductance seemed to be closely related to both abscisic acid and NO increase, while there was no significant correlation between stomatal conductance and hydrogen peroxide concentration. Conclusions:, The close relationships between stomatal conductance and NO concentrations indicate a potential role of this molecule in drought-signalling pathway in grapevines. Significance of the Study:, Results suggest a contribution of hydrogen peroxide to triggering NO production as well as a possible role of NO on both stomatal closure and antioxidant defence in drought-stressed grapevines. [source] Treatment of paper and pulp wastewater and removal of odorous compounds by a Fenton-like process at the pilot scaleJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 8 2006José L Tambosi Abstract A Fenton-like process, involving oxidation and coagulation, was evaluated for the removal of odorous compounds and treatment of a pulp and paper wastewater. The main parameters that govern the complex reactive system [pH and Fe(III) and hydrogen peroxide concentrations] were studied. Concentrations of Fe(III) between 100 and 1000 mg L,1 and of H2O2 between 0 and 2000 mg L,1 were chosen. The main mechanism for color removal was coagulation. The maximum COD, color and aromatic compound removals were 75, 98 and 95%, respectively, under optimal operating conditions ([Fe(III)] = 400 mg L,1; [H2O2] = 500,1000 mg L,1; pH = 2.5; followed by coagulation at pH 5.0). The biodegradability of the wastewater treated increased from 0.4 to 0.7 under optimal conditions and no residual hydrogen peroxide was found after treatment. However, partially or non-oxidized compounds present in the treated wastewater presented higher acute toxicity to Artemia salina than the untreated wastewater. Based on the optimum conditions, pilot-scale experiments were conducted and revealed a high efficiency in relation to the mineralization of organic compounds. Terpenes [(1S)-,-pinene, ,-pinene, (1R)-,-pinene and limonene] were identified in the wastewater and were completely eliminated by the Fenton-like treatment. Copyright © 2006 Society of Chemical Industry [source] Activation of the redox sensor Pap1 by hydrogen peroxide requires modulation of the intracellular oxidant concentrationMOLECULAR MICROBIOLOGY, Issue 5 2004Ana P. Vivancos Summary The transcription factor Pap1 and the MAP kinase Sty1 are key regulators of hydrogen peroxide-induced responses in Schizosaccharomyces pombe. Pap1 can be activated quickly at low, but not high, hydrogen peroxide concentrations. The MAP kinase Sty1 has been reported to participate in Pap1 activation by the oxidant. Here, we provide biochemical and genetic evidence for the in vivo formation of a hydrogen peroxide-induced disulphide bond in Pap1, which precedes the rapid and reversible nuclear accumulation of the transcription factor. We show that activation of the Sty1 cascade before the oxidative insult, or overexpression of the Sty1-regulated genes ctt1 (encoding catalase) or gpx1 (encoding glutathione peroxidase), can accelerate Pap1 entry even at high doses of hydrogen peroxide. In fact, the lack of Sty1 impedes Pap1 nuclear localization, but only at high doses of the oxidant. We propose that, whereas low doses of hydrogen peroxide lead directly to Pap1 oxidation-activation, high concentrations of the oxidant initially activate the Sty1 pathway, with the consequent increase in scavenging enzymes, which in turn helps to decompose the excess of hydrogen peroxide and achieve an appropriate concentration for the subsequent activation of Pap1. Our results also suggest that activation of Sty1 at high doses of hydrogen peroxide may also be required to trigger other antioxidant activities such as those reverting the overoxidation of cysteine residues at the Pap1 pathway. [source] | ||||||||||