Showing papers on "Hydrogen peroxide published in 1971"

The autoxidation of human red cell lipids induced by hydrogen peroxide.

Abstract: Summary. Malonyldialdehyde (MDA) formation, a measure of polyunsaturated fat autoxidation, was estimated in normal human red cells incubated in vitro. Exposure to oxygen under a variety of conditions did not induce autoxidation. Exposure to hydrogen peroxide was either by the addition of a hydrogen peroxide solution or by incubation in an atmosphere saturated with hydrogen peroxide vapour. A pattern of MDA formation was established with both methods. Lack of reproducibility, a feature of previous methods of measuring the susceptibility of red cells to exogenous peroxide, could be overcome by (i) catalase inhibition, (ii) attention to the non-linear relation between packed-cell volume and MDA formation, and (iii) elimination of potentially misleading coloured complexes on spectroscopy. A number of recognized antioxidants inhibited peroxide-induced MDA formation. Inhibition was proportional to the logarithm of the antioxidant concentration. Under certain conditions pre-incubation with nucleosides and with lecithin protected the cells against autoxidation on subsequent exposure to peroxide. Peroxide-induced cell autoxidation was also influenced by plasma, bovine albumin, and ascorbic acid. Haemolysis was an invariable consequence of autoxidation. Similarities and dissimilarities between autoxidation and antioxidation in free lipid emulsions and in organized biological structures were examined and discussed in the light of the experimental findings.

Inhibition of biogenic amine uptake by hydrogen peroxide: a mechanism for toxic effects of 6-hydroxydopamine.

Abstract: Hydrogen peroxide, dialuric acid, or 6-hydroxydopamine inhibited the uptake of dopamine, norepinephrine, and serotonin into rat brain synaptosomal preparations. The addition of catalase protected all systems, but catalase was only partially protective for 6-hydroxydopamine acting upon catecholamine uptake. The data show that 6-hydroxydopamine generates hydrogen peroxide and that hydrogen peroxide can damage the biogenic amine uptake systems. Part of the damage caused by the 6-hydroxydopamine that accumulates in the catecholamine nerve terminals in vivo may be attributed to the hydrogen peroxide.

Kinetics and mechanisms of catalase in peroxisomes of the mitochondrial fraction.

Abstract: 1. The primary intermediate of catalase and hydrogen peroxide was identified and investigated in peroxisome-rich mitochondrial fractions of rat liver. On the basis of kinetic constants determined in vitro, it is possible to calculate with reasonable precision the molecular statistics of catalase action in the peroxisomes. 2. The endogenous hydrogen peroxide generation is adequate to sustain a concentration of the catalase intermediate (p(m)/e) of 60-70% of the hydrogen peroxide saturation value. Total amount of catalase corresponds to 0.12-0.15nmol of haem iron/mg of protein. In State 1 the rate of hydrogen peroxide generation corresponds to 0.9nmol/min per mg of protein or 5% of the mitochondrial respiratory rate in State 4. 3. Partial saturation of the catalase intermediate with hydrogen peroxide (p(m)/e) in the mitochondrial fraction suggests its significant peroxidatic activity towards its endogenous hydrogen donor. A variation of this value (p(m)/e) from 0.3 in State 4 to 0 under anaerobic conditions is observed. 4. For a particular preparation the hydrogen peroxide generation rate in the substrate-supplemented State 4 corresponds to 0.17s(-1) (eqn. 6), the hydrogen peroxide concentration to 2.5nm and the hydrogen-donor concentration (in terms of ethanol) to 0.12mm. The reaction is 70% peroxidatic and 30% catalatic. 5. A co-ordinated production of both oxidizing and reducing substrates for catalase in the mitochondrial fraction is suggested by a 2.2-fold increase of hydrogen peroxide generation and a threefold increase in hydrogen-donor generation in the State 1 to State 4 transition. 6. Additional hydrogen peroxide generation provided by the urate oxidase system of peroxisomes (8-12nmol of uric acid oxidized/min per mg of protein) permits saturation of the catalase with hydrogen peroxide to haem occupancy of 40% compared with values of 36% for a purified rat liver catalase ofk(1)=1.7x10(7)m(-1).s(-1) and k'(4)=2.6x10(7)m(-1). s(-1)(Chance, Greenstein & Roughton, 1952). 7. The turnover of the catalase ethyl hydrogen peroxide intermediate (k'(3)) in the peroxisomes is initially very rapid since endogenous hydrogen peroxide acts as a hydrogen donor. k'(3) decreases fivefold in the uncoupled state of the mitochondria.

Metabolic and bactericidal activities of human eosinophils.

Abstract: Summary. Eosinophils obtained from three patients with transient eosinophilia and polymorphonuclear neutrophils(PMN) obtained from young adults with acute suppurative infections were compared with regard to their metabolic and bactericidal responses to phagocytosis. Eosinophils ingested zymosan particles and staphylococci more slowly and to a lesser extent than did PMN, and displayed a more potent oxidative response during phagocytosis which led to a greater production of intracellular hydrogen peroxide. This enhanced oxidative response was primarily due to increased activity of TPNH oxidase, a granule enzyme, rather than the soluble DPNH oxidase which mediates hydrogen peroxide production in neutrophils. Despite the enhanced peroxide production, eosinophils were less bactericidal than PMN.

Reaction of bleomycin with DNA. Strand scission of DNA in the absence of sulfhydryl or peroxide compounds.

Abstract: The effect of bleomycin on the infectivity and the molecular integrity of bacteriophage ΦX174 DNA was examined by means of the spheroplast assay and sucrose density gradient centrifugation. Bleomycins caused degradation of the DNA, both in the single and double stranded forms even in the absence of 2-mercaptoethanol or hydrogen peroxide, although the reaction was accelerated by the addition of either of the compounds.All the bleomycin compounds examined, A2, A5 and B2, were effective for the reaction but copper-chelated A2 was not. The reaction was inhibited by the addition of EDTA*.

Solutions for chemical dissolution treatment of metallic materials

Abstract: The present invention relates to solutions used for chemical dissolution treatment such as, pickling, etching, chemical polishing, etc., of metallic materials. In such a treatment, however, where hydrogen peroxide is used as an oxidizing agent, a considerable excess of the agent is required due to low efficiency. On the other hand, when chloride ions are contained in the solution, the dissolution rate of metallic materials is remarkably decreased. The present invention has overcome the above difficulties by using a solution for chemical dissolution treatment of metallic materials containing hydrogen peroxide, an acid and at least one of an alcohol polyoxyethylene ether, an alkylsulfonic acid, an alkyl hydrogen phosphate, an alkyl hydrogen phosphite, an alkyl hydrogen sulfate and their salts.

Inhibition of Glycolipid Biosynthesis in Chloroplasts by Ozone and Sulfhydryl Reagents

Abstract: The metabolism of uridine 5′-pyrophosphate-galactose by spinach ( Spinacia oleracea ) chloroplast preparations was inhibited by ozone The formation of digalactosyl diglyceride and trigalactosyl diglyceride was inhibited much more than the formation of monogalactosyl diglyceride, steryl glycoside, and acylated steryl glycoside Essentially identical results were obtained when glycolipid synthesis was inhibited by N-ethyl maleimide, p -hydroxymercuribenzoate, and CdCl 2 Iodoacetate and iodoacetamide affected neither the total incorporation of sugar from uridine 5′-pyrophosphate-galactose nor distribution of the incorporated sugar in the various glycolipids Ozone reacted with model membrane systems prepared with egg lecithin In the absence of reduced glutathione, products included malonaldehyde and hydrogen peroxide In the presence of glutathione, malonaldehyde was still produced, but the glutathione was oxidized and no peroxide was detected When these studies were extended to chloroplast preparations, it was also found that malonaldehyde was produced and glutathione was oxidized It was concluded that ozone inhibits glycolipid biosynthesis in chloroplast preparations by way of oxidation of enzyme sulfhydryl groups but that this reaction may be a secondary effect of oxidation of unsaturated fatty acids

Complex-formation between cytochrome c and cytochrome c peroxidase. Equilibrium and titration studies.

Abstract: 1. Physical studies of complex-formation between cytochrome c and yeast peroxidase are consistent with kinetic predictions that these complexes participate in the catalytic activity of yeast peroxidase towards ferrocytochrome c. Enzyme–ferricytochrome c complexes have been detected both by the analytical ultracentrifuge and by column chromatography, whereas an enzyme–ferrocytochrome c complex was demonstrated by column chromatography. Estimated binding constants obtained from chromatographic experiments were similar to the measured kinetic values. 2. The physicochemical study of the enzyme–ferricytochrome c complex, and an analysis of its spectrum and reactivity, suggest that the conformation and reactivity of neither cytochrome c nor yeast peroxidase are grossly modified in the complex. 3. The peroxide compound of yeast cytochrome c peroxidase was found to have two oxidizing equivalents accessible to cytochrome c but only one readily accessible to ferrocyanide. Several types of peroxide compound, differing in available oxidizing equivalents and in reactivity with cytochrome c, seem to be formed by stoicheiometric amounts of hydrogen peroxide. 4. Fluoride combines not only with free yeast peroxidase but also with peroxidase–peroxide and accelerates the decomposition of the latter compound. The ligand-catalysed decomposition provides evidence for one-electron reduction pathways in yeast peroxidase, and the reversible binding of fluoride casts doubt upon the concept that the peroxidase–peroxide intermediate is any form of peroxide complex. 5. A mechanism for cytochrome c oxidation is proposed involving the successive reaction of two reversibly bound molecules of cytochrome c with oxidizing equivalents associated with the enzyme protein.

The Interaction of Fungal Laccase with Hydrogen Peroxide and the Removal of Fluoride from the Inhibited Enzyme

Abstract: 1 Electron paramagnetic resonance analysis shows that H2O2 added to native fungal laccase binds to one specific Cu2+ of the four copper atoms in the enzyme (the so-called Type 2 or “nonblue” Cu2+). 2 This binding of H2O2 is associated with a new absorption band in the visible and nearultraviolet spectrum of the enzyme with its maximum absorbance at 400 nm. 3 Fluoride bound to Type 2 Cu2+ of the enzyme, as commonly prepared, can easily be removed by dialysis of the reduced enzyme. Presence of H2O2 in this dialysis makes the removal of fluoride faster.

The peroxidase activity of deuterohemin.

Abstract: The reaction of hydrogen peroxide with deuterohemin and the reaction of the products with peroxidase substrates in neutral aqueous solution have been investigated. Qualitative observations indicate that, prior to oxidative degradation of the porphyrin ring system, a peroxidatic hemeperoxide complex is formed which can react with hydrogen donors to regenerate free deuterohemin. Quantitative data support this conclusion and show that this complex formation can account for the peroxidase activity of deuterohemin. The kinetics of formation of this complex and its reaction with peroxidase substrates have been studied and indicate that the principal difference between the catalytic mechanisms of deuterohemin and peroxidase is the very much more rapid rate of formation of the primary active complex in peroxidase. The overall rate of conversion of the primary active complex to the free catalyst is approximately the same in both enzyme and model systems, although in the latter case no intermediate analogous to compound II of peroxidase is formed. The mechanism of action of peroxidases and the nature of their active peroxide complexes is discussed in the light of these findings.

The Photochemistry of Dyes. IV—The Role of Singlet Oxygen and Hydrogen Peroxide in Photosensitised Degradation of Polymers

Abstract: The effect of sensitising dyes on the photochemical degradation of textile fibres is discussed. The degradation is dependent upon the presence of oxygen, and is accelerated by water vapour and rise in temperature. The study of simple model photochemical systems intended to simulate the dyed fibre system indicates that there are significant differences between the two systems. The sensitising effect of dyes in the textile systems seems to be due to the formation of excited singlet oxygen and hydrogen peroxide. The latter is not formed in the absence of water vapour.

Pulse- and X-radiolysis of 2-mercaptoethanol in Aqueous Solution

Abstract: SummaryAqueous solutions of 2-mercaptoethanol have been irradiated with pulses of 4 MeV electrons and with 240 kVp x-rays. The specific rate-constants for reactions of hydroxyl radicals, hydrated electrons and hydrogen atoms with the thiol were found to be 6·5 × 109, 1·2 × 1010 and 2 × 109 M−1 sec−1, respectively. Reaction products have been identified by gas chromatography and functional group analysis as hydrogen peroxide, hydrogen sulphide, acetaldehyde, ethanol and dithiodiglycol. Yields were determined quantitatively by spectrophotometric means after the addition, where necessary, of suitable reagents. Radical scavengers such as acetone have been used to isolate effects due to the various primary species. In the absence of oxygen, dithiodiglycol was formed with G up to 5 while hydrogen peroxide was formed in very small yield. In oxygenated solutions, dithiodiglycol and hydrogen peroxide were formed in equal yields with G values up to about 30, while hydrogen sulphide and ethanol had yields up to G ∼ ...

Stabilized acidic hydrogen peroxide solutions

Abstract: STABILIZERS ARE PROVIDED FOR HYDROGEN PEROXIDE IN AQUEOUS SOLUTION OF UP TO 80 PERCENT HYDROGEN PEROXIDE BY WEIGHT AND IN ACIDIC SOLUTION CONTAINING UP TO ABOUT 5 PERCENT HYDROGEN PEROXIDE BY WEIGHT, UP TO 85 PERCENT INORGANIC ACID BY WEIGHT, UP TO 5 PERCENT METAL IONS BY WEIGHT, AND AT TEMPERATURES UP TO 90* C. SUCH STABILIZERS ARE INCLUDED IN CONCENTRATIONS UP TO ABOUT 5 PERCENT, PREFERABLY UP TO ABOUT 1 PERCENT, BY WEIGHT, AS REQUIRED, DEPENDING ON THE CONCENTRATIONS OF HYDROGEN PEROXIDE, ACID, AND METAL IONS PRESENT. THE STABILIZERS INCLUDE CERTAIN SUBSITUTED ANILINES, AROMATIC SULFONIC ACIDS, SULFAMIC ACID, SULFOLENES, SULFOALNES, SULFOXIDES AND SULFONES, AND MIXTURES THEREOF.

The kinetics of the formation of the primary lactoperoxidase-hydrogen peroxide compound.

Abstract: The kinetics of the formation of the primary lactoperoxidase – hydrogen peroxide compound (compound I) at 25 °C have been studied over the pH range 3.0–10.8 by steady state methods. The second-order rate constant k1 is pH-independent over the pH region investigated, having a value of (9.2 ± 0.9) × 106M−1s−1. An anomalous effect of formate buffer on the kinetics of the formation of compound I is reported.

Carboalkoxy substituted bis-phenyl oxalates as superior chemiluminescent materials

Abstract: NEW COMPOUNDS WHICH ARE ESTER SUBSTITUTED BIS(ARYL) OXALATE ESTERS. THE COMPOUNDS ARE REACTIVE WITH HYDROGEN PEROXIDE IN THE PRESENCE OF A SOLVENT AND A FLUORESCER TO GIVE VISIBLE CHEMILUMINESCENT LIGHT.