Showing papers on "Hydrogen peroxide published in 2011"

Glutathione Peroxidase-1 in Health and Disease: From Molecular Mechanisms to Therapeutic Opportunities

Abstract: Reactive oxygen species, such as superoxide and hydrogen peroxide, are generated in all cells by mitochondrial and enzymatic sources. Left unchecked, these reactive species can cause oxidative damage to DNA, proteins, and membrane lipids. Glutathione peroxidase-1 (GPx-1) is an intracellular antioxidant enzyme that enzymatically reduces hydrogen peroxide to water to limit its harmful effects. Certain reactive oxygen species, such as hydrogen peroxide, are also essential for growth factor-mediated signal transduction, mitochondrial function, and maintenance of normal thiol redox-balance. Thus, by limiting hydrogen peroxide accumulation, GPx-1 also modulates these processes. This review explores the molecular mechanisms involved in regulating the expression and function of GPx-1, with an emphasis on the role of GPx-1 in modulating cellular oxidant stress and redox-mediated responses. As a selenocysteine-containing enzyme, GPx-1 expression is subject to unique forms of regulation involving the trace ...

Review of the methods to form hydrogen peroxide in electrical discharge plasma with liquid water

Abstract: This paper presents a review of the literature dealing with the formation of hydrogen peroxide from plasma processes. Energy yields for hydrogen peroxide generation by plasma from water span approximately three orders of magnitude from 4 ? 10?2 to 80?g?kWh?1. A wide range of plasma processes from rf to pulsed, ac, and dc discharges directly in the liquid phase have similar energy yields and may thus be limited by radical quenching processes at the plasma?liquid interface. Reactor modification using discharges in bubbles and discharges over the liquid phase can provide modest improvements in energy yield over direct discharge in the liquid, but the interpretation is complicated by additional chemical reactions of gas phase components such as ozone and nitrogen oxides. The highest efficiency plasma process utilizes liquid water droplets that may enhance efficiency by sequestering hydrogen peroxide in the liquid and by suppressing decomposition reactions by radicals from the gas and at the interface. Kinetic simulations of water vapor reported in the literature suggest that plasma generation of hydrogen peroxide should approach 45% of the thermodynamics limit, and this fact coupled with experimental studies demonstrating improvements with the presence of the condensed liquid phase suggest that further improvements in energy yield may be possible. Plasma generation of hydrogen peroxide directly from water compares favorably with a number of other methods including electron beam, ultrasound, electrochemical and photochemical methods, and other chemical processes.

Long-term antibacterial efficacy of air plasma-activated water

Abstract: Indirect air dielectric barrier discharge in close proximity to water creates an acidified, nitrogen-oxide containing solution known as plasma-activated water (PAW), which remains antibacterial for several days. Suspensions of E. coli were exposed to PAW for either 15 min or 3 h over a 7-day period after PAW generation. Both exposure times yielded initial antibacterial activity corresponding to a ~5-log reduction in cell viability, which decreased at differing rates over 7 days to negligible activity and a 2.4-log reduction for 15 min and 3 h exposures, respectively. The solution remained at pH ~2.7 for this period and initially included hydrogen peroxide, nitrate and nitrite anions. The solution composition varied significantly over this time, with hydrogen peroxide and nitrite diminishing within a few days, during which the antibacterial efficacy of 15 min exposures decreased significantly, while that of 3 h exposures produced a 5-log reduction or more. These results highlight the complexity of PAW solutions where multiple chemical components exert varying biological effects on differing time scales.

Development of a highly sensitive fluorescence probe for hydrogen peroxide.

Abstract: Hydrogen peroxide is believed to play a role in cellular signal transduction by reversible oxidation of proteins. Here, we report the design and synthesis of a novel fluorescence probe for hydrogen peroxide, utilizing a photoinduced electron transfer strategy based on benzil chemistry to control the fluorescence. The practical value of this highly sensitive and selective fluorescence probe, NBzF, was confirmed by its application to imaging of hydrogen peroxide generation in live RAW 264.7 macrophages. NBzF was also employed for live cell imaging of hydrogen peroxide generated as a signaling molecule in A431 human epidermoid carcinoma cells.

In situ generated (hypo)iodite catalysts for the direct α-oxyacylation of carbonyl compounds with carboxylic acids.

Abstract: The introduction of an O-acyl group at the α-position of carbonyl compounds is smoothly achieved using tetrabutylammonium iodide catalyst in the presence of hydrogen peroxide or tert-butyl hydroperoxide.

Functionalized graphene oxide as a nanocarrier in a multienzyme labeling amplification strategy for ultrasensitive electrochemical immunoassay of phosphorylated p53 (S392).

Abstract: P53 phosphorylation plays an important role in many biological processes and might be used as a potential biomarker in clinical diagnoses. We report a new electrochemical immunosensor for ultrasensitive detection of phosphorylated p53 at Ser392 (phospho-p53392) based on graphene oxide (GO) as a nanocarrier in a multienzyme amplification strategy. Greatly enhanced sensitivity was achieved by using the bioconjugates featuring horseradish peroxidase (HRP) and p53392 signal antibody (p53392Ab2) linked to functionalized GO (HRP−p53392Ab2−GO) at a high ratio of HRP/p53392Ab2. After a sandwich immunoreaction, the HRP−p53392Ab2−GO captured onto the electrode surface produced an amplified electrocatalytic response by the reduction of enzymatically oxidized thionine in the presence of hydrogen peroxide. The increase of response current was proportional to the phospho-p53392 concentration in the range of 0.02−2 nM with the detection limit of 0.01 nM, which was 10-fold lower than that of the traditional sandwich elec...

Recent advances in catalytic asymmetric epoxidation using the environmentally benign oxidant hydrogen peroxide and its derivatives.

Abstract: There has been a recent drive to develop asymmetric catalytic methods to produce epoxides using environmentally benign oxidants, especially hydrogen peroxide. This critical review discusses the advances that have been made using both metal-based and organocatalytic homogeneous catalysts (142 references).

Superoxide Dismutase in Redox Biology: The roles of superoxide and hydrogen peroxide

Abstract: Superoxide dismutases (SOD) are considered to be antioxidant enzymes. This view came about because its substrate, superoxide, is a free radical; in the era of their discovery, 1960’s – 1970’s, the general mindset was that free radicals in biology must be damaging. Indeed SOD blunts the cascade of oxidations initiated by superoxide. However in the late 1970’s it was observed that cancer cells that have low activity of the mitochondrial form of SOD, MnSOD, grow faster than those with higher activities of MnSOD. These observations indicated that SOD, superoxide, and hydrogen peroxide affected the basic biology of cells and tissues, not just via damaging oxidation reactions. It is now realized that superoxide and hydrogen peroxide are essential for normal cellular and organism function. MnSOD appears to be a central player in the redox biology of cells and tissues.

Hydrogen peroxide inducible DNA cross-linking agents: targeted anticancer prodrugs.

Abstract: The major concern for anticancer chemotherapeutic agents is the host toxicity. The development of anticancer prodrugs targeting the unique biochemical alterations in cancer cells is an attractive approach to achieve therapeutic activity and selectivity. We designed and synthesized a new type of nitrogen mustard prodrug that can be activated by high level of reactive oxygen species (ROS) found in cancer cells to release the active chemotherapy agent. The activation mechanism was determined by NMR analysis. The activity and selectivity of these prodrugs toward ROS was determined by measuring DNA interstrand cross-links and/or DNA alkylations. These compounds showed 60–90% inhibition toward various cancer cells, while normal lymphocytes were not affected. To the best of our knowledge, this is the first example of H2O2-activated anticancer prodrugs.

p-Nitrophenol degradation by a heterogeneous Fenton-like reaction on nano-magnetite: Process optimization, kinetics, and degradation pathways

Abstract: Heterogeneous Fenton-like reactions on nano-magnetite (Fe 3 O 4 ) were investigated for the degradation of p-Nitrophenol (p-NP). A four factor central composite design (CCD) coupled with response surface methodology (RSM) was applied to evaluate and optimize the important variables. A significant quadratic model ( P -value R 2 = 0.9442) was derived using analysis of variance (ANOVA), which was adequate to perform the process variables optimization. Optimum conditions were determined to be 1.5 g L −1 Fe 3 O 4 , 620 mM H 2 O 2 , pH 7.0 and 25–45 mg L −1 p-NP. More than 90% of p-NP was experimentally degraded after 10 h of reaction time under the optimum conditions, which agreed well with the model predictions. The results demonstrated that the degradation of p-NP was due to the attack of hydroxyl radicals ( OH) generated by the surface-catalyzed decomposition of hydrogen peroxide on the nano-Fe 3 O 4 , i.e. heterogeneous Fenton-like reactions. Possible mechanisms of p-NP degradation in this system were proposed, based on intermediates identified by LC–MS and GC–MS and included benzoquinone, hydroquinone, 1,2,4-trihydroxybenzene and p-nitrocatechol. The kinetic analysis implied that the generation rate of OH ( V OH ) was increased along with the degradation of p-NP. This was attributed to the formation of acidic products, which decreased the solution pH and enhanced the decomposition of absorbed hydrogen peroxide via a radical producing pathway on the nano-Fe 3 O 4 surface.

Estimation of Possible Mechanisms of Escherichia coli Inactivation by Plasma Treated Sodium Chloride Solution

Abstract: Treatment of aqueous liquids by surface-DBD in atmospheric air resulted in bactericidal activity of the liquid itself. A 7 min treatment of sodium chloride (NaCl) solution and its immediate addition to Escherichia coli resulted in a complete bacteria inactivation (≥7 log) after 15 min exposure time. With a 30 min delay between plasma treatment of liquid and its addition to the bacteria, bactericidal effect was reduced but still detectable. Nitrate (), nitrite (), and hydrogen peroxide (H2O2), respectively, as well as strong acidification are detected in plasma treated liquids and can explain this bactericidal activity partially. Combination of 1.5 mg · L−1 and 2.5 mg · L−1 H2O2 at pH 3 results in maximum 3.5 log E. coli reduction within 60 min. Plasma diagnostics and liquid analytics are combined with theoretical considerations to focus possible reaction channels of plasma–water interactions. Using FT-IR, stable molecules like nitrous oxide (N2O), ozone (O3), carbon dioxide (CO2), and traces of nitric acid (HNO3) and/or peroxynitrous acid (ONOOH) were measured. Reactions of these molecules from the plasma/gas phase with the aqueous liquid can result in acidification and generation of H2O2, , and or peroxynitrite (ONOO−), respectively, via reactions which are associated with the occurrence of several more or less stable but biologically active chemical intermediates like or nitrogen dioxide (). On the other hand, H2O2, , and /ONOO− could serve as starting reaction partners to generate , , , or hydroxyl radicals () in the liquid.

Environmentally Persistent Free Radicals (EPFRs). 1. Generation of Reactive Oxygen Species in Aqueous Solutions

Abstract: Reactive oxygen species (ROS) generated by environmentally persistent free radicals (EPFRs) of 2-monochlorophenol, associated with CuO/silica particles, were detected using the chemical spin trap, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), in conjunction with electron paramagnetic resonance (EPR) spectroscopy. Yields of hydroxyl radical (•OH), superoxide anion radical (O2•–), and hydrogen peroxide (H2O2) generated by EPFR–particle systems were reported. Failure to trap superoxide radicals in aqueous solvent, formed from reaction of EPFRs with molecular oxygen, results from fast transformation of the superoxide to hydrogen peroxide. However, formation of superoxide as an intermediate product in hydroxyl radical formation in aprotic solutions of dimethyl sulfoxide (DMSO) and acetonitrile (AcN) was observed. Experiments with superoxide dismutase (SOD) and catalase (CAT) confirmed formation of superoxide and hydrogen peroxide, respectively, in the presence of EPFRs. The large number of hydroxyl radicals formed ...

Hydrogen Peroxide as a Signaling Molecule

Abstract: Increases in hydrogen peroxide can initiate protective responses to limit or repair oxidative damage. However, hydrogen peroxide signals also fine-tune responses to growth factors and cytokines to control cell division, differentiation, and migration. Here we discuss some of the mechanisms by which hydrogen peroxide is sensed and utilized as a signaling molecule to regulate diverse biological processes. We also discuss how the localization and levels of hydrogen peroxide, antioxidants, and the cellular metal composition together influence the nature of the response. Antioxid. Redox Signal. 15, 147–151.

Hydrogen peroxide fuels aging, inflammation, cancer metabolism and metastasis: the seed and soil also needs "fertilizer".

Abstract: In 1889, Dr. Stephen Paget proposed the "seed and soil" hypothesis, which states that cancer cells (the seeds) need the proper microenvironment (the soil) for them to grow, spread and metastasize systemically. In this hypothesis, Dr. Paget rightfully recognized that the tumor microenvironment has an important role to play in cancer progression and metastasis. In this regard, a series of recent studies have elegantly shown that the production of hydrogen peroxide, by both cancer cells and cancer-associated fibroblasts, may provide the necessary "fertilizer," by driving accelerated aging, DNA damage, inflammation and cancer metabolism, in the tumor microenvironment. By secreting hydrogen peroxide, cancer cells and fibroblasts are mimicking the behavior of immune cells (macrophages/neutrophils), driving local and systemic inflammation, via the innate immune response (NFκB). Thus, we should consider using various therapeutic strategies (such as catalase and/or other anti-oxidants) to neutralize the production of cancer-associated hydrogen peroxide, thereby preventing tumor-stroma co-evolution and metastasis. The implications of these findings for overcoming chemo-resistance in cancer cells are also discussed in the context of hydrogen peroxide production and cancer metabolism.

Silver Nanoparticle−Reactive Oxygen Species Interactions: Application of a Charging−Discharging Model

Abstract: The silver-nanoparticle-catalyzed decomposition of hydrogen peroxide (H2O2) in pH 9.5 bicarbonate buffer is investigated here with attention given to (i) the mechanism of decomposition, (ii) the role of superoxide in mediating silver nanoparticle re-formation, and (iii) the effect of nanoparticle size on decomposition rate. Silver nanoparticles (AgNPs) of average size between 25.0 and 69.4 nm were synthesized via the reduction of Ag+ [the dominant Ag(I) species present] by photochemically produced superoxide at pH 9.5 and characterized by UV−visible spectroscopy and dynamic light scattering. The ability of these particles to catalytically decompose H2O2 was examined by measuring the decay of H2O2 and the approach to steady state in AgNP and Ag+ concentrations. Additionally, the generation of superoxide on reaction of AgNPs with H2O2 was monitored using a chemiluminescence-based method. The second-order rate constants for reaction between AgNPs and H2O2 correlated linearly with their average particle size ...

Hydrogen Peroxide Probes Directed to Different Cellular Compartments

Abstract: Background Controlled generation and removal of hydrogen peroxide play important roles in cellular redox homeostasis and signaling. We used a hydrogen peroxide biosensor HyPer, targeted to different compartments, to examine these processes in mammalian cells.

Alkaline peroxide pretreatment of corn stover: effects of biomass, peroxide, and enzyme loading and composition on yields of glucose and xylose

Abstract: Background: Pretreatment is a critical step in the conversion of lignocellulose to fermentable sugars. Although many pretreatment processes are currently under investigation, none of them are entirely satisfactory in regard to effectiveness, cost, or environmental impact. The use of hydrogen peroxide at pH 11.5 (alkaline hydrogen peroxide (AHP)) was shown by Gould and coworkers to be an effective pretreatment of grass stovers and other plant materials in the context of animal nutrition and ethanol production. Our earlier experiments indicated that AHP performed well when compared against two other alkaline pretreatments. Here, we explored several key parameters to test the potential of AHP for further improvement relevant to lignocellulosic ethanol production. Results: The effects of biomass loading, hydrogen peroxide loading, residence time, and pH control were tested in combination with subsequent digestion with a commercial enzyme preparation, optimized mixtures of four commercial enzymes, or optimized synthetic mixtures of pure enzymes. AHP pretreatment was performed at room temperature (23°C) and atmospheric pressure, and after AHP pretreatment the biomass was neutralized with HCl but not washed before enzyme digestion. Standard enzyme digestion conditions were 0.2% glucan loading, 15 mg protein/g glucan, and 48 h digestion at 50°C. Higher pretreatment biomass loadings (10% to 20%) gave higher monomeric glucose (Glc) and xylose (Xyl) yields than the 2% loading used in earlier studies. An H2O2 loading of 0.25 g/g biomass was almost as effective as 0.5 g/g, but 0.125 g/g was significantly less effective. Optimized mixtures of four commercial enzymes substantially increased post-AHP-pretreatment enzymatic hydrolysis yields at all H2O2 concentrations compared to any single commercial enzyme. At a pretreatment biomass loading of 10% and an H2O2 loading of 0.5 g/g biomass, an optimized commercial mixture at total protein loadings of 8 or 15 mg/g glucan gave monomeric Glc yields of 83% or 95%, respectively. Yields of Glc and Xyl after pretreatment at a low hydrogen peroxide loading (0.125 g H2O2/g biomass) could be improved by extending the pretreatment residence time to 48 h and readjusting the pH to 11.5 every 6 h during the pretreatment. A Glc yield of 77% was obtained using a pretreatment of 15% biomass loading, 0.125 g H2O2/g biomass, and 48 h with pH adjustment, followed by digestion with an optimized commercial enzyme mixture at an enzyme loading of 15 mg protein/g glucan. Conclusions: Alkaline peroxide is an effective pretreatment for corn stover. Particular advantages are the use of reagents with low environmental impact and avoidance of special reaction chambers. Reasonable yields of monomeric Glc can be obtained at an H2O2 concentration one-quarter of that used in previous AHP research. Additional improvements in the AHP process, such as peroxide stabilization, peroxide recycling, and improved pH control, could lead to further improvements in AHP pretreatment.

The Antibacterial Activity of Honey Derived from Australian Flora

Abstract: Chronic wound infections and antibiotic resistance are driving interest in antimicrobial treatments that have generally been considered complementary, including antimicrobially active honey. Australia has unique native flora and produces honey with a wide range of different physicochemical properties. In this study we surveyed 477 honey samples, derived from native and exotic plants from various regions of Australia, for their antibacterial activity using an established screening protocol. A level of activity considered potentially therapeutically useful was found in 274 (57%) of the honey samples, with exceptional activity seen in samples derived from marri (Corymbia calophylla), jarrah (Eucalyptus marginata) and jellybush (Leptospermum polygalifolium). In most cases the antibacterial activity was attributable to hydrogen peroxide produced by the bee-derived enzyme glucose oxidase. Non-hydrogen peroxide activity was detected in 80 (16.8%) samples, and was most consistently seen in honey produced from Leptospermum spp. Testing over time found the hydrogen peroxide-dependent activity in honey decreased, in some cases by 100%, and this activity was more stable at 4°C than at 25°C. In contrast, the non-hydrogen peroxide activity of Leptospermum honey samples increased, and this was greatest in samples stored at 25°C. The stability of non-peroxide activity from other honeys was more variable, suggesting this activity may have a different cause. We conclude that many Australian honeys have clinical potential, and that further studies into the composition and stability of their active constituents are warranted.