Hydrogen peroxide

About: Hydrogen peroxide is a research topic. Over the lifetime, 42583 publications have been published within this topic receiving 1043732 citations. The topic is also known as: H2O2 & dioxidane.

Nitric oxide protects against cellular damage and cytotoxicity from reactive oxygen species

Abstract: Nitric oxide, NO, which is generated by various components of the immune system, has been presumed to be cytotoxic. However, NO has been proposed to be protective against cellular damage resulting during ischemia reperfusion. Along with NO there is often concomitant formation of superoxide/hydrogen peroxide, and hence a synergistic relationship between the cytotoxic effects of nitric oxide and these active oxygen species is frequently assumed. To study more carefully the potential synergy between NO and active oxygen species in mammalian cell cytotoxicity, we utilized either hypoxanthine/xanthine cell cytotoxicity, we utilized either hypoxanthine/xanthine oxidase (a system that generates superoxide/hydrogen peroxide) or hydrogen peroxide itself. NO generation was accomplished by the use of a class of compounds known as "NONOates," which release NO at ambient temperatures without the requirement of enzyme activation or biotransformation. When Chinese hamster lung fibroblasts (V79 cells) were exposed to hypoxanthine/xanthine oxidase for various times or increasing amounts of hydrogen peroxide, there was a dose-dependent decrease in survival of V79 cells as measured by clonogenic assays. However, in the presence of NO released from (C2H5)2N[N(O)NO]-Na+ (DEA/NO), the cytotoxicity resulting from superoxide or hydrogen peroxide was markedly abrogated. Similarly, primary cultures of rat mesencephalic dopaminergic cells exposed either to hydrogen peroxide or to hypoxanthine/xanthine oxidase resulted in the degradation of the dopamine uptake and release mechanism. As was observed in the case of the V79 cells, the presence of NO essentially abrogated this peroxide-mediated cytotoxic effect on mesencephalic cells.

The interaction of bovine erythrocyte superoxide dismutase with hydrogen peroxide: inactivation of the enzyme.

Abstract: Bovine erythrocyte superoxide dismutase was slowly and irreversibly inactivated by hydrogen peroxide. The rate of this inactivation was directly dependent upon the concentrations of both H2O2 and of enzyme, and its second-order rate constant at pH 10.0 and 25 degrees was 6.7 M-1 sec-1. Inactivation was preceded by a bleaching due to rapid reduction of Cu2+ on the enzyme, and following this there was a gradual reappearance of a new absorption in the visible region, which was coincident with the loss of catalytic activity. Inactivation of the enzyme was pH-dependent and indicated an essential ionization whose pKa was approximately 10.2. Replacement of H2O by D2O raised this pKa but did not diminish the catalytic activity of superoxide dismutase, measured at pH 10.0. Several compounds, including xanthine, urate, formate, and azide, protected the enzyme against inactivation by H2O2. Alcohols and benzoate, which scavenge hydroxyl radical, did not protect. Compounds with special affinity for singlet oxygen were similarly ineffective. The data were interpreted in terms of the reduction of the enzyme-bound Cu2+ to Cu+, by H2O2, followed by a Fenton's type reaction of the Cu+ with additional H2O2. This would generate Cu2+-OH- or its ionized equivalent, Cu2+-O--, which could then oxidatively attack an adjacent histidine and thus inactivate the enzyme. Compounds which protected the enzyme could have done so by reacting with the bound oxidant, in competition with the adjacent histidine.

Catalytic Oxidation of Organic Substrates by Molecular Oxygen and Hydrogen Peroxide by Multistep Electron Transfer : A Biomimetic Approach

Abstract: Oxidation reactions are of fundamental importance in nature, and are key transformations in organic synthesis. The development of new processes that employ transition metals as substrate-selective catalysts and stoichiometric environmentally friendly oxidants, such as molecular oxygen or hydrogen peroxide, is one of the most important goals in oxidation chemistry. Direct oxidation of the catalyst by molecular oxygen or hydrogen peroxide is often kinetically unfavored. The use of coupled catalytic systems with electron-transfer mediators (ETMs) usually facilitates the procedures by transporting the electrons from the catalyst to the oxidant along a low-energy pathway, thereby increasing the efficiency of the oxidation and thus complementing the direct oxidation reactions. As a result of the similarities with biological systems, this can be dubbed a biomimetic approach.

Formation of hydrogen peroxide and depletion of oxalic acid in atmospheric water by photolysis of iron(III)-oxalato complexes

Abstract: The generation of hydrogen peroxide (H 2 O 2 ,) and the depletion of oxalic acid by photochemical/chemical cycling of Fe(III)/Fe(II)-oxalato complexes in sunlight has been studied under the conditions typical for acidified atmospheric water. H 2 O 2 is produced though the reduction of oxygen by intermediates formed from photoreactions of Fe(III)-oxalato complexes. The rate of H 2 O 2 formation increases with sunlight intensity, and with oxalate and Fe(III) concentration within the concentration range used

Iron-catalyzed oxidation of arsenic(III) by oxygen and by hydrogen peroxide: pH-dependent formation of oxidants in the Fenton reaction.

Abstract: The oxidation kinetics of As(III) with natural and technical oxidants is still not well understood, despite its importance in understanding the behavior of arsenic in the environment and in arsenic removal procedures. We have studied the oxidation of 6.6 μM As(III) by dissolved oxygen and hydrogen peroxide in the presence of Fe(II,III) at pH 3.5−7.5, on a time scale of hours. As(III) was not measurably oxidized by O2, 20−100 μM H2O2, dissolved Fe(III), or iron(III) (hydr)oxides as single oxidants, respectively. In contrast, As(III) was partially or completely oxidized in parallel to the oxidation of 20−90 μM Fe(II) by oxygen and by 20 μM H2O2 in aerated solutions. Addition of 2-propanol as an •OH-radical scavenger quenched the As(III) oxidation at low pH but had little effect at neutral pH. High bicarbonate concentrations (100 mM) lead to increased oxidation of As(III). On the basis of these results, a reaction scheme is proposed in which H2O2 and Fe(II) form •OH radicals at low pH but a different oxidant...