Pulse radiolytic studies of the reaction of perhydroxyl/superoxide O2- with iron(II)/iron(III) ions. The reactivity of HO2/O2- with ferric ions and its implication on the occurrence of the Haber-Weiss reaction

Rush, J. D.; Bielski, Benon H. J.

doi:10.1021/j100269a035

Cited by 327 publications

(203 citation statements)

References 4 publications

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“…• -above pH 6, which is 1.50 ¥ 10 8 M -1 s -1 (Rush and Bielski, 1985). Even with a re-optimization of all other parameters, fp2 could not be increased to above 10 4 M -1 s -1 (LMW DOM sample from site P3) and above 10 3 M -1 s -1 (LMW DOM sample from site M4) without a significant increase of the sum of squared residuals.…”

Section: Kinetics Of Fe(ii) and H 2 O 2 Formation And Decaymentioning

confidence: 91%

Effects of size and origin of natural dissolved organic matter compounds on the redox cycling of iron in sunlit surface waters

et al. 2005

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Abstract. The effects of size and origin of natural dissolved organic matter compounds (DOM) on the redox cycling of iron were investigated in water samples from a marine system (Strait of Gibraltar), from a freshwater system (Lake of Murten, i.e., Murtensee, Switzerland), and from a "river-to-ocean" system (Rivers Scheldt and Rhine and corresponding estuaries). In the irradiated seawater samples, Fe(II) steady-state concentrations ([Fe(II)] ss ), both as percentage of total dissolved iron and normalized to 1 mg C L -1 , were higher in the low-molecular-weight (LMW) than in the high-molecular-weight (HMW) DOM fractions, despite higher net rates of H 2 O 2 formation in the HMW DOM fractions. Also in the samples from Murtensee, [Fe(II)] ss , both as percentage of total dissolved iron and normalized to the decadic absorption coefficient at 350 nm (a 350 , unit m -1 ), were higher in the LMW than in the HMW DOM fractions. Unlike in the seawater samAquatic Sciences ples, however, net rates of H 2 O 2 production, normalized to a 350 , were higher in the LMW DOM fractions, as compared to the HMW DOM fractions, indicating a higher efficiency of O 2• -formation with these LMW compounds from Murtensee. Based on the simulation of experimental data with mathematical kinetic modeling, we hypothesize that Fe(II) is formed through photolysis of Fe(III) complexes in the LMW DOM fractions from the Strait of Gibraltar and from Murtensee and that Fe(II) is stabilized by a ligand in the water samples from Murtensee. In the irradiated HMW DOM fractions from the "river-toocean" system, [Fe(II)] ss , normalized to a 350 , were generally higher in the water samples from the Rivers Scheldt and Rhine than in the water samples from their estuaries, suggesting that terrestrially derived DOM has a higher photochemical reactivity towards Fe(II) formation than autochthonous DOM.

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Section: Kinetics Of Fe(ii) and H 2 O 2 Formation And Decaymentioning

confidence: 91%

Effects of size and origin of natural dissolved organic matter compounds on the redox cycling of iron in sunlit surface waters

et al. 2005

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“…Pulse Radiolysis Assays-Pulse radiolysis experiments were carried out using the 2 MeV Van de Graaff accelerator as described previously (16). Dosimetry was measured using the (SCN) 2 Ϫ dosimeter (16).…”

Section: Neelaredoxin Reactivity Toward Superoxidementioning

confidence: 99%

“…Dosimetry was measured using the (SCN) 2 Ϫ dosimeter (16). The radiolysis of water, either by electrons or ␥-rays, yields the species described in Reaction 1, where the numbers in parentheses are G values, that is the number of molecules/100 eV of energy absorbed by the medium (17).…”

Section: Neelaredoxin Reactivity Toward Superoxidementioning

confidence: 99%

The Mechanism of Superoxide Scavenging byArchaeoglobus fulgidus Neelaredoxin

Abreu

Saraiva

Soares

et al. 2001

Journal of Biological Chemistry

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Neelaredoxin is a mononuclear iron protein widespread among prokaryotic anaerobes and facultative aerobes, including human pathogens. It has superoxide scavenging activity, but the exact mechanism by which this process occurs has been controversial. In this report, we present the study of the reaction of superoxide with the reduced form of neelaredoxin from the hyperthermophilic archaeon Archaeoglobus fulgidus by pulse radiolysis. This protein reduces superoxide very efficiently (k ‫؍‬ 1.5 ؋ 10 9 M ؊1 s ؊1 ), and the dismutation activity is rate-limited, in steady-state conditions, by the much slower superoxide oxidation step. These data show unambiguously that the superfamily of neelaredoxin-like proteins (including desulfoferrodoxin) presents a novel type of reactivity toward superoxide, a result of particular relevance for the understanding of both oxygen stress response mechanisms and, in particular, how pathogens may respond to the oxidative burst produced by the defense cells in eukaryotes. The actual in vivo functioning of these enzymes will depend strongly on the cell redox status. Further insight on the catalytic mechanism was obtained by the detection of a transient intermediate ferric species upon oxidation of neelaredoxin by superoxide, detectable by visible spectroscopy with an absorption maximum at 610 nm, blueshifted ϳ50 nm from the absorption of the resting ferric state. The role of the iron sixth ligand, glutamate-12, in the reactivity of neelaredoxin toward superoxide was assessed by studying two site-directed mutants: E12Q and E12V.

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“…Pulse radiolysis experiments were carried out using the 2 MeV Van de Graaff accelerator, as described previously (Rush and Bielski, 1985). Dosimetry was measured using the (SCN) 2 2 dosimeter (Rush and Bielski, 1985). The radiolysis of water yields the species described in eqn 1, where the numbers in parentheses are G-values, i.e.…”

Section: Expression and Purification Of Recombinant Neelaredoxinmentioning

confidence: 99%

Oxygen detoxification in the strict anaerobic archaeon Archaeoglobus fulgidus: superoxide scavenging by Neelaredoxin

Abreu

Saraiva

Carita

et al. 2000

Molecular Microbiology

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Archaeoglobus fulgidus is a hyperthermophilic sulphate‐reducing archaeon. It has an optimum growth temperature of 83°C and is described as a strict anaerobe. Its genome lacks any homologue of canonical superoxide (O2·−) dismutases. In this work, we show that neelaredoxin (Nlr) is the main O2·− scavenger in A. fulgidus, by studying both the wild‐type and recombinant proteins. Nlr is a 125‐amino‐acid blue‐coloured protein containing a single iron atom/molecule, which in the oxidized state is high spin ferric. This iron centre has a reduction potential of +230 mV at pH 7.0. Nitroblue tetrazolium‐stained gel assays of cell‐soluble extracts show that Nlr is the main protein from A. fulgidus which is reactive towards O2·−. Furthermore, it is shown that Nlr is able to both reduce and dismutate O2·−, thus having a bifunctional reactivity towards O2·−. Kinetic and spectroscopic studies indicate that Nlr's superoxide reductase activity may allow the cell to eliminate O2·− quickly in a NAD(P)H‐dependent pathway. On the other hand, Nlr's superoxide dismutation activity will allow the cell to detoxify O2·− independently of the cell redox status. Its superoxide dismutase activity was estimated to be 59 U mg−1 by the xanthine/xanthine oxidase assay at 25°C. Pulse radiolysis studies with the isolated and reduced Nlr proved unambiguously that it has superoxide dismutase activity; at pH 7.1 and 83°C, the rate constant is 5 × 106 M−1 s−1. Besides the superoxide dismutase activity, soluble cell extracts of A. fulgidus also exhibit catalase and NAD(P)H/oxygen oxidoreductase activities. By putting these findings together with the entire genomic data available, a possible oxygen detoxification mechanism in A. fulgidus is discussed.

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Pulse radiolytic studies of the reaction of perhydroxyl/superoxide O2- with iron(II)/iron(III) ions. The reactivity of HO2/O2- with ferric ions and its implication on the occurrence of the Haber-Weiss reaction

Cited by 327 publications

References 4 publications

Effects of size and origin of natural dissolved organic matter compounds on the redox cycling of iron in sunlit surface waters

Effects of size and origin of natural dissolved organic matter compounds on the redox cycling of iron in sunlit surface waters

The Mechanism of Superoxide Scavenging byArchaeoglobus fulgidus Neelaredoxin

Oxygen detoxification in the strict anaerobic archaeon Archaeoglobus fulgidus: superoxide scavenging by Neelaredoxin

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