Oxygen species

The objective of this work is to experimentally investigate the effect of the oxygen potential on the fuel and FP chemical behaviour in conditions representative of a severe accident. More specifically, the speciation of Cs, Mo and Ba is investigated.

10p christabelhuynh 29-05-2020 11 3   Download

Recovering useful hydrocarbons from sewage sludge using zirconia-supporting iron oxide catalysts was investigated. Zirconia has activity for decomposing water molecules to generate active oxygen and hydrogen species.

6p tuananhhumg 04-11-2013 37 2   Download

The Na+-translocating NADH:quinone oxidoreductase (Na+-NQR) from Vibrio alginolyticus was inactivated by reactive oxygen species. Highest Na+-NQR activity was observed in anaerobically prepared membranes that exhibited 1 : 1 coupling of NADH oxidation and Q reduction activities (1.6 UÆmg)1). Optical and EPR spectroscopy documented the presence of b-type cytochromes, a [2Fe)2S] cluster and an organic radical signal in anaerobically pre- pared membranes from V. alginolyticus.

6p research12 01-06-2013 48 4   Download

Chlorite dismutase (EC 1.13.11.49), an enzyme capable of reducing chlorite to chloride while producing molecular oxygen, has been characterized using EPR and optical spectroscopy. The EPR spectrum of GR-1 chlorite dis-mutase shows two different high-spin ferric heme species, whichwe have designated
narrow(gx,y,z¼6.24, 5.42, 2.00) and
broad(gz,y,x ¼6.70, 5.02, 2.00).

7p research12 29-04-2013 37 3   Download

Flavonols are produced by the desaturation of flavanols catalyzed by flavonol synthase. The enzyme belongs to the class of intermolecular dioxygenases which depend on molecular oxygen and Fe II /2-oxoglutarate for activity, and have been in focus of structural studies recently. Flavonol synthase cDNAs were cloned from six plant species, but none of the enzymes had been studied in detail.

9p research12 23-04-2013 51 4   Download

Human hepatitis delta (HDV) ribozyme is one of small ribozymes, such as hammerhead and hairpin ribozymes, etc. Its secondary structure shows pseudoknot structure com-posed of four stems (I to IV) and three single-stranded regions (SSrA, -B and -C). The 3D structure of 3¢-cleaved product of genomic HDV ribozyme provided extensive information about tertiary hydrogen bonding interactions between nucleotide bases, phosphate oxygens and 2¢OHs including new stem structure P1.1.

12p tumor12 22-04-2013 38 3   Download

Self-regulation of the 2-oxo acid dehydrogenase complexes during catalysiswas studied.Radical species as sideproducts of catalysis were detected by spin trapping, lucigenin fluor-escence and ferricytochromec reduction. Studies of the complexes after converting the bound lipoate or FAD cofactors tononfunctional derivatives indicated that radicals are generated viaFAD. In the presence of oxygen, the 2-oxo acid, CoA-dependent production of the superoxide anion radical was detected.

12p tumor12 22-04-2013 38 3   Download

Reactive oxygen species (ROS) are products of normal metabolic activities and are thought to be the cause of many diseases. A selenium-containing single-chain abzyme 2F3 (Se-2F3-scFv) that imitates glutathione peroxidase has been produced which has the capacity to remove ROS. To evaluate the antioxidant ability of Se-2F3-scFv, we con-structeda ferrous sulfate/ascorbate (Vc/Fe 2+ )-inducedmito-chondrial damage model system and investigated the capacity of Se-2F3-scFv to protect mitochondria from oxi-dative damage.

6p tumor12 20-04-2013 33 4   Download

Exposure of mammalian cells to oxidant stress causes early (iron catalysed) lysosomal rupture followed by apoptosis or necrosis. Enhanced intracellular production of reactive oxygen species (ROS), presumably of mitochondrial origin, is also observed when cells are exposed to nonoxidant pro-apoptotic agonists of cell death. We hypothesized that ROS generation in this latter case might promote the apoptotic cascade and could arise from effects of released lysosomal materials on mitochondria.

9p tumor12 20-04-2013 33 1   Download

The transport of oxygen in the hemolymph of many arth-ropod and mollusc species is mediated by large copper-proteins that are referred to as hemocyanins. Arthropod hemocyanins are composed of hexamers and oligomers of hexamers. Arachnid hemocyanins usually form 4·6-mers consisting of seven distinct subunit types (termed a–g), although in some spider taxa deviations from this standard scheme have been observed.

8p tumor12 20-04-2013 36 4   Download

Ascorbic acid is often regarded as an antioxidantin vivo, where it protects against cancer by scavenging DNA-dam-aging reactive oxygen species. However, the detailed mech-anism of the action of ascorbic acid on genetic DNA is still unclear. We examined the effect of ascorbic acid on the higher-order structure of DNA through real-time observa-tion by fluorescence microscopy. We found that ascorbic acid generates a pearling structure in single giant DNA molecules, with elongated and compact regions coexisting along a molecular chain. ...

6p tumor12 20-04-2013 32 5   Download

Hemocyanins are large oligomeric copper-containing pro-teins that serve for the transport of oxygen in many arth-ropod species. While studied in detail in the Chelicerata and Crustacea, hemocyanins had long been considered unnec-essary in the Myriapoda. Here we report the complete molecular structure of the hemocyanin from the common house centipedeScutigera coleoptrata(Myriapoda: Chilo-poda), as deduced from 2D-gel electrophoresis, MALDI-TOF mass spectrometry, protein and cDNA sequencing, and homology modeling....

9p fptmusic 16-04-2013 37 3   Download

The peroxidase–oxidase reaction is known to involve react-ive oxygen species as intermediates. These intermediates inactivatemany types of biomolecules, including peroxidase itself. Previously,wehave shown that oscillatorydynamics in the peroxidase–oxidase reaction seem to protect the enzyme frominactivation. It was suggested that this is due to a lower average concentration of reactive oxygen species in the oscillatory state compared to the steady state. Here, we studied the peroxidase–oxidase reaction with either 4-hydroxybenzoic acid or melatonin as cofactors. ...

9p fptmusic 16-04-2013 45 4   Download

Photodynamic treatment (PDT) is an emerging therapeutic procedure for the management of cancer, based on the use of photosensitizers, compounds that generate highly reactive oxygen species (ROS) on irradiation with visible light. The ROS generated may oxidize a variety of bio-molecules within the cell, loaded with a photosensitizer. The high reactivity of these ROS restricts their radius of action to 5–20 nm from the site of their generation.

7p fptmusic 12-04-2013 45 3   Download

Oxidative stress and imbalance between free radical generation and detoxi-fication may play a pivotal role in the pathogenesis of Leber’s hereditary optic neuropathy (LHON). Mitochondria, carrying the homoplasmic 11778⁄ND4, 3460⁄ND1 and 14484⁄ND6 mtDNA point mutations associ-ated with LHON, were used to generate osteosarcoma-derived cybrids. Enhanced mitochondrial production of reactive oxygen species has recently been demonstrated in these cybrids [Beretta S, Mattavelli L, Sala G, Trem-olizzo L, Schapira AHV, Martinuzzi A, Carelli V & Ferrarese C (2004) Brain127, 2183–2192]. ...

0p awards 05-04-2013 45 4   Download

Metformin (1,1-dimethylbiguanide) is an antihyperglycae-mic drug used to normalize glucose concentrations in type 2 diabetes. Furthermore, antioxidant benefits have been reported in diabetic patients treated with metformin. This work was aimed at studying the scavenging capacity of this drug against reactive oxygen species (ROS) like Æ OH and O Æ
2 -free radicals. ROS were produced by gamma radio-lysis of water. The irradiated solutions of metformin were analyzed by UV/visible absorption spectrophotometry.

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Cytochrome P450 enzymes promote a number of oxidative biotransformations including the hydroxylation of unacti-vated hydrocarbons.

26p awards 05-04-2013 44 7   Download

This paper reports the results obtained using the osmotic stress method applied to the purified cathodic and anodic hemoglobins (Hbs) from the catfishHoplosternum littorale, a species that displays facultative accessorial air oxygen-ation. We demonstrate that water potential affects the oxy-gen affinity ofH. littoraleHbs in the presence of an inert solute (sucrose). Oxygen affinity increases when water activity increases, indicating that water molecules stabilize thehigh-affinitystateof theHb.

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Three pairs of parental (q + ) and established mitochondrial DNAdepleted (q 0 ) cells, derived frombone, lungandmuscle were used to verify the influence of the nuclear background and the lack of efficient mitochondrial respiratory chain on antioxidant defences and homeostasis of intracellular reactive oxygen species (ROS).

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The retinal pigment epithelium (RPE) is essential for main-tenance of photoreceptors and normally functions under conditions enriched with reactive oxygen species. RPE therefore expresses various defense enzymes against oxida-tive stress, including heme oxygenase-1 (HO-1). HO-1 catalyzes heme breakdown to release iron, carbon monox-ide, and biliverdin, which is reduced to bilirubin, a potent radical scavenger. HO-1 expression is induced by various environmental factors, which has been established as a def-ense mechanism....

9p awards 05-04-2013 42 4   Download