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.

Direct Catalytic Conversion of Methane to Methanol in an Aqueous Medium by using Copper‐Promoted Fe‐ZSM‐5

Abstract: Iron copper zeolite (Fe-Cu-ZSM-5) with aqueous hydrogen peroxide is active for the selective oxidation of methane to methanol. Iron is involved in the activation of the carbon–hydrogen bond, while copper allows methanol to form as the major product. The catalyst is stable, re-usable and activates methane giving >90 % methanol selectivity and 10 % conversion in a closed catalytic cycle (see scheme).

Thylakoid-Bound Ascorbate Peroxidase in Spinach Chloroplasts and Photoreduction of Its Primary Oxidation Product Monodehydroascorbate Radicals in Thylakoids

Abstract: Ascorbate peroxidase, a key enzyme for the scavenging of hydrogen peroxide in chloroplasts, was found in a thylakoid-bound form in spinach chloroplasts at comparable activity to that in the stroma. The activity of peroxidase was detectable in the thylakoids only when prepared by an ascorbate-containing medium, and enriched in the stroma thylakoids. The thylakoid enzyme was not released from the membranes by either 2 mM EDTA, 1 M KC1, 2 M NaBr or 2 M NaSCN, but was solubilized by detergents. Enzymatic properties of the thylakoid-bound ascorbate peroxidase were very similar to those of the stromal ascorbate peroxidase. Thylakoid-bound ascorbate peroxidase could scavenge the hydrogen peroxide either added or photoproduced by the thylakoids. No photoreductio n of hydrogen peroxide was observed, however, in the thylakoids whose ascorbate peroxidase was inhibited by KCN and thiol reagents or inactivated by the treatment with ascorbate-depletion. The primary oxidation product of ascorbate in a reaction of ascorbate peroxidase, monodehydroascorbate (MDA) radical, was photoreduced in the thylakoids, as detected by the quenching of chlorophyll fluorescence, disappearance of EPR signals of the MDA radicals and the MDA radical-induced oxygen evolution. Thus, ascorbate is photoregenerated in the thylakoids from the MDA radicals produced in a reaction of ascorbate peroxidase for the scavenging of hydrogen peroxide.

Superoxide-dependent formation of hydroxyl radicals in the presence of iron salts. Detection of ‘free’ iron in biological systems by using bleomycin-dependent degradation of DNA

Abstract: Bleomycin in the presence of iron(II) degrades DNA to form a thiobarbituric acid-reactive product. This has been made the basis of a specific assay method for 'free' iron in biological fluids. Human synovial fluid, human cerebrospinal fluid and rat pleural-exudate fluid were found to contain micromolar concentrations of 'free' iron, which would be sufficient to allow formation of the hydroxyl radical from superoxide and hydrogen peroxide generated in vivo. This assay method does not detect iron bound to transport proteins or to enzymes.

Bipolar Electrochemical Mechanism for the Propulsion of Catalytic Nanomotors in Hydrogen Peroxide Solutions

Abstract: Bimetallic nanorods are propelled in aqueous solutions by the catalytic decomposition of hydrogen peroxide to oxygen and water. Several mechanisms (interfacial tension gradients, bubble recoil, viscous Brownian ratchet, self-electrophoresis) have been proposed for the transduction of chemical to mechanical energy in this system. From Tafel plots of anodic and cathodic hydrogen peroxide reactions at various metal (Au, Pt, Rh, Ni, Ru, and Pd) ultramicroelectrodes, we determine the potential at which the anodic and cathodic reaction rates are equal for each metal. These measurements allow one to predict the direction of motion of all possible bimetallic combinations according to the bipolar electrochemical (or self-electrophoretic) mechanism. These predictions are consistent with the observed direction of motion in all cases studied, providing strong support for the mechanism. We also find that segmented nanorods with one Au end and one poly(pyrrole) end containing catalase, an enzyme that decomposes hydroge...