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1.
Heme catalases are considered to degrade two molecules of H 2O 2 to two molecules of H 2O and one molecule of O 2 employing the catalatic cycle. We here studied the catalytic behaviour of bovine liver catalase at low fluxes of H 2O 2 (relative to catalase concentration), adjusted by H 2O 2-generating systems. At a ratio of a H 2O 2 flux (given in μM/min - 1) to catalase concentration (given in μM) of 10 min - 1 and above, H 2O 2 degradation occurred via the catalatic cycle. At lower ratios, however, H 2O 2 degradation proceeded with increasingly diminished production of O 2. At a ratio of 1 min - 1, O 2 formation could no longer be observed, although the enzyme still degraded H 2O 2. These results strongly suggest that at low physiological H 2O 2 fluxes H 2O 2 is preferentially metabolised reductively to H 2O, without release of O 2. The pathways involved in the reductive metabolism of H 2O 2 are presumably those previously reported as inactivation and reactivation pathways. They start from compound I and are operative at low and high H 2O 2 fluxes but kinetically outcompete the reaction of compound I with H 2O 2 at low H 2O 2 production rates. In the absence of NADPH, the reducing equivalents for the reductive metabolism of H 2O 2 are most likely provided by the protein moiety of the enzyme. In the presence of NADPH, they are at least in part provided by the coenzyme. 相似文献
2.
Hydrogen peroxide, produced by inflammatory and vascular cells, induces oxidative stress that may contribute to endothelial dysfunction. In smooth muscle cells, H 2O 2 induces production of O 2− by activating NADPH oxidase. However, the mechanisms whereby H 2O 2 induces oxidative stress in endothelial cells are poorly understood. We examined the effects of H 2O 2 on O 2− levels on porcine aortic endothelial cells (PAEC). Treatment with 60 μmol/L H 2O 2 markedly increased intracellular O 2− levels (determined by conversion of dihydroethidium to hydroxyethidium) and produced cytotoxicity (determined by propidium iodide staining) in PAEC. Overexpression of human manganese superoxide dismutase in PAEC reduced O 2− levels and attenuated cytotoxicity resulting from treatment with H 2O 2. L-NAME, an inhibitor of nitric oxide synthase (NOS), and apocynin, an inhibitor of NADPH oxidase, reduced O 2− levels in PAEC treated with H 2O 2, suggesting that both NOS and NADPH oxidase contribute to H 2O 2-induced O 2− in PAEC. Inhibition of NADPH oxidase using apocynin and NOS rescue with L-sepiapterin together reduced O 2− levels in PAEC treated with H 2O 2 to control levels. This suggests interaction-distinct NOS and NADPH oxidase pathways to superoxide. We conclude that H 2O 2 produces oxidative stress in endothelial cells by increasing intracellular O 2− levels through NOS and NADPH oxidase. These findings suggest a complex interaction between H 2O 2 and oxidant-generating enzymes that may contribute to endothelial dysfunction. 相似文献
3.
Studies were conducted using a 10-chamber Micro-Oxymax (Columbus, OH, USA) respirometer to determine the effect of bioaugmentation and biostimulation (by diverse ways of O 2 supply) on enhancing biodegradation of oil hydrocarbons to reduce risk at a former military airport in Kluczewo, Poland. Indigenous or exogenous bacteria bioaugmentation was used to degrade hydrocarbons. Aerated water and/or aqueous solutions of H 2O 2 or KMnO 4 were used to supply O 2. The intrinsic and enhanced biodegradation was evaluated by the O 2 uptake and CO 2 production rates obtained using a linear regression of the cumulative O 2 uptake and CO 2 production curves. Generally, in all cases biodegradation rates enhanced by bioaugmentation were two to four times higher than the rates of intrinsic biodegradation. Moreover, application of indigenous bacteria was more efficient in comparison to the exogenous consortia. The highest CO 2 production rates were achieved when aqueous solution of KMnO 4 was applied, as the increase of CO 2 production rates were about 71% to 97% higher compared to a control. The aqueous solution of H 2O 2 did not cause any significant improvement of the biodegradation rates. Compared to a control, the addition of aerated water resulted in a decrease of CO 2 production rates. Most probably the excessive soil moisture could reduce the air-filled porosity and, consequently, the oxygen contents in soil. 相似文献
4.
Ferritins are ubiquitous iron storage and detoxification proteins distributed throughout the plant and animal kingdoms. Mammalian ferritins oxidize and accumulate iron as a ferrihydrite mineral within a shell-like protein cavity. Iron deposition utilizes both O 2 and H 2O 2 as oxidants for Fe 2+ where oxidation can occur either at protein ferroxidase centers or directly on the surface of the growing mineral core. The present study was undertaken to determine whether the nature of the mineral core formed depends on the protein ferroxidase center versus mineral surface mechanism and on H 2O 2 versus O 2 as the oxidant. The data reveal that similar cores are produced in all instances, suggesting that the structure of the core is thermodynamically, not kinetically controlled. Cores averaging 500 Fe/protein shell and diameter 2.6 nm were prepared and exhibited superparamagnetic blocking temperatures of 19 and 22 K for the H 2O 2 and O 2 oxidized samples, respectively. The observed blocking temperatures are consistent with the unexpectedly large effective anisotropy constant Keff = 312 kJ/m 3 recently reported for ferrihydrite nanoparticles formed in reverse micelles [E.L. Duarte, R. Itri, E. Lima Jr., M.S. Batista, T.S. Berquó and G.F. Goya, Large Magnetic Anisotropy in ferrihydrite nanoparticles synthesized from reverse micelles, Nanotechnology 17 (2006) 5549–5555.]. All ferritin samples exhibited two magnetic phases present in nearly equal amounts and ascribed to iron spins at the surface and in the interior of the nanoparticle. At 4.2 K, the surface spins exhibit hyperfine fields, Hhf, of 436 and 445 kOe for the H 2O 2 and O 2 samples, respectively. As expected, the spins in the interior of the core exhibit larger Hhf values, i.e. 478 and 486 kOe for the H 2O 2 and O 2 samples, respectively. The slightly smaller hyperfine field distribution DH hf for both surface (78 kOe vs. 92 kOe) and interior spins (45 kOe vs. 54 kOe) of the O 2 sample compared to the H 2O 2 samples implies that the former is somewhat more crystalline. 相似文献
5.
1. 1. The mechanism of the photooxidation of ascorbate and of Mn2+ by isolated chloroplasts was reinvestigated. 2. 2. Our results suggest that ascorbate or Mn2+ oxidation is the result of the Photosystem I-mediated production of the radical superoxide, and that neither ascorbate nor Mn2+ compete with water as electron donors to Photosystem II nor affect the rate of electron transport through the two photosystems: The radical superoxide is formed as a result of the autooxidation of the reduced forms of low potential electron acceptors, such as methylviologen, diquat, napthaquinone, or ferredoxin. 3. 3. In the absence of ascorbate or Mn2+ the superoxide formed dismutases either spontaneously or enzymatically producing O2 and H2O2. In the presence of ascorbate or Mn2+, however, the superoxide is reduced to H2O2 with no formation of O2. Consequently, in the absence of reducing compounds, in the reaction H2O to low potential acceptor one O2 (net) is taken up per four electrons transported where as in the presence of ascorbate, Mn2+ or other suitable reductants up to three molecules O2 can be taken up per four electrons transported. 4. 4. This interpretation is supported by the following observations: (a) in a chloroplast-free model system containing NADPH and ferredoxin-NADP reductase, methylviologen can be reduced to a free radical which is autooxidizable in the presence of O2; the addition of ascorbate or Mn2+ to this system results in a two fold stimulation of O2 uptake, with no stimulation of NADPH oxidation. The stimulation of O2 uptake is inhibited by the enzyme superoxide dismutase; (b) the stimulation of light-dependent O2 uptake in the system H2O → methylviologen in chloroplasts is likewise inhibited by the enzyme superoxide dismutase. 5. 5. In Class II chloroplasts in the system H2O → NADP upon the addition of ascorbate or Mn2+ an apparent inhibition of O2 evolution is observed. This is explained by the interaction of these reductants with the superoxide formed by the autooxidation of ferredoxin, a reaction which proceeds simultaneously with the photoreduction of NADP. Such an effect usually does not occur in Class I chloroplasts in which the enzyme superoxide dismutase is presumably more active than in Class II chloroplasts. 6. 6. It is proposed that since in the Photosystem I-mediated reaction from reduced 2,4-dichlorophenolindophenol to such low potential electron acceptor as methylviologen, superoxide is formed and results in the oxidation of the ascorbate present in the system, the ratio ATP/2e in this system (when the rate of electron flow is based on the rate of O2 uptake) should be revised in the upward direction.
Abbreviations: DCMU, 3-(3′,4′-dichlorophenyl)-1,1-dimethylurea; HEPES, hydroxyethyl-piperazineethanesulfonic acid; MES, (N-morpholino)ethanesulfonic acid; DCIP, 2,4-dichlorophenol-indophenol 相似文献
6.
将水稻(Oryza sativa L.)幼苗悬浮培养于含有羧基化多壁碳纳米管MWCNTs-COOH(0、2.5、5.0、10.0 mg/L)、50 mmol/L混合盐(1NaCl:9Na 2SO 4:9NaHCO 3:1Na 2CO 3),以及MWCNTs-COOH+混合盐的复合溶液中,10 d后检测叶片生理生化指标变化,研究MWCNTs-COOH复合盐碱胁迫对水稻幼苗的毒性及生态风险。结果显示,与对照组相比,MWCNTs-COOH单一组诱导下水稻叶片O 2·-和H 2O 2的产生不明显,而混合盐组和混合盐+MWCNTs-COOH复合组均诱导了O 2·-和H 2O 2产物的大量累积。MWCNTs-COOH与混合盐复合后,加剧了O 2·-和H 2O 2的累积,并有明显的浓度效应。活性氧(ROS)作为信号分子在一定程度上诱导了各处理组部分抗氧化酶(SOD、CAT、POD、APX)活性的升高;与混合盐组相比,低浓度混合盐+MWCNTs-COOH复合组中叶绿素a和胡萝卜素含量呈一定程度的升高;MWCNTs-COOH与混合盐复合后,抑制了叶片中可溶性糖(SS)和脯氨酸(Pro)的合成,致使相对电导率(REC)和丙二醛(MDA)含量显著升高。上述抗氧化酶活性及叶绿素a和胡萝卜素含量的升高对缓解水稻叶片氧化损伤、维持正常的光合电子传递及对过剩光能的热耗散是有益的,是水稻幼苗重要的防御机制。本研究表明MWCNTs-COOH单一处理在一定程度上诱导了水稻叶片的氧化胁迫和应激响应,与混合盐复合后加剧了叶片的氧化胁迫和应激损伤。 相似文献
7.
通过开顶箱(OTCs)模拟,以环境臭氧(O 3)浓度约40 nmol·mol -1为对照,研究大气O 3浓度升高(80和160 nmol·mol -1O 3)对冷季型草坪草高羊茅生长、亚细胞结构及其活性氧代谢的影响.结果表明: 14 d的80 nmol·mol -1O 3熏蒸使高羊茅株高和叶宽降低,总生物量降低43.7%,老叶变黄,而160 nmol·mol -1O 3处理高羊茅叶出现大量枯死褐斑,叶尖坏死,新叶卷曲,总生物量降低46.2%,叶肉细胞膜卷曲,叶绿体和线粒体受损严重.与对照相比,80和160 nmol·mol -1O 3熏蒸下高羊茅叶片超氧阴离子(O 2-·)产生速率、过氧化氢(H 2O 2)和丙二醛(MDA)含量显著增加,抗氧化酶活性显著升高,但叶片总酚含量和抗氧化能力随O 3浓度升高而先升高后降低.在明显O 3伤害症状出现之前,O 3已对高羊茅的生长和抗氧化代谢产生不利影响;高羊茅抗氧化系统虽对O 3浓度的升高存在一定的适应性反应,但其不能抵御过高浓度的长期胁迫和伤害. 相似文献
8.
Human neutrophils (PMN) activated by N-formyl-methionyl-leucyl-phenylalanine (fMLP) simultaneously release nitric oxide (.NO), superoxide anion (O 2-) and its dismutation product, hydrogen peroxide (H 2O 2). To assess whether NO production shares common steps with the activation of the NADPH oxidase, PMN were treated with inhibitors and antagonists of intracellular signaling pathways and subsequently stimulated either with fMLP or with a phorbol ester (PMA). The G-protein inhibitor, pertussis toxin (1-10 μg/ml) decreased H 2O 2 yield without significantly changing. NO production in fMLP-stimulated neutrophils; no effects were observed in PMA-activated cells. The inhibition of tyrosine kinases by genistein (1-25 μg/ml) completely abolished H 2O 2 release by fMLP-activated neutrophils; conversely, NO production increased about 1.5- and 3-fold with fMLP and PMA, respectively. Accordingly, orthovanadate, an inhibitor of phosphotyrosine phosphatase, markedly decreased -NO production and increased O 2;- release. On the other hand, inhibition of protein kinase C with staurosporine and the use of burst antagonists like adenosine, cholera toxin or dibutyryl-cAMP diminished both H 2O 2 and NO production. The results suggest that the activation of the tyrosine kinase pathway in stimulated human neutrophils controls positively O 2- and H 2O 2 generation and simultaneously maintains -NO production in low levels. In contrast, activation of protein kinase C is a positive modulator for O 2;-and *NO production. 相似文献
9.
1. For comparison with flavoprotein oxidases, a study has been made of free flavins in the reduced form with respect to the specificity and stoichiometry of their oxidation by a series of acceptors. 2. Reduced flavins uncombined with proteins show very little acceptor specificity and react very rapidly with nearly all the commonly used acceptors. Their behaviour resembles that of dithionite very closely indeed, and it differs considerably from that of flavoproteins. Like dithionite, free reduced flavins reduce O2 quantitatively to H2O2; this oxidizes a further molecule of flavin. 3. H2O2 and cytochrome c react more slowly than most acceptors with reduced flavins. Nitrate and NDA+ do not act at all and require special activation. 4. Catalase can act as a catalyst for the aerobic oxidation of flavins by converting slowly-reacting H2O2 into rapidly-reacting O2. 5. In the absence of catalytic metals ascorbate reacts with acceptors much more slowly than reduced flavins do. 相似文献
10.
采用开顶式气室熏蒸法,设置自然条件下臭氧(O 3)浓度(对照,约40 nmol·mol -1)、80、160及200 nmol·mol -14个臭氧浓度,观测了不同浓度臭氧条件下银杏叶片可见伤害、活性氧生成量、抗氧化酶活性及相关基因表达变化情况,分析大气臭氧浓度升高对植物活性氧代谢的影响.结果表明: 160和200 nmol·mol -1 O 3熏蒸明显伤害银杏叶片,80 nmol·mol -1与对照无差异,无可见伤害.O 3处理20 d后,160和200 nmol·mol -1条件下银杏叶片的超氧自由基(O 2-·)产生速率显著高于80 nmol·mol -1和对照,而80 nmol·mol -1与对照无差异;O 3处理40 d后,160和200 nmol·mol -1熏蒸下叶片过氧化氢(H 2O 2)含量显著高于80 nmol·mol -1和对照,而过氧化氢酶(CAT)活性显著高于80 nmol·mol -1和对照,各臭氧处理抗坏血酸过氧化物酶(APX)活性均低于对照.熏蒸40 d后,CAT、APX基因的转录表达持续加强;防御素(GbD)的表达强度则随着臭氧浓度的增加及熏蒸时间的延长而呈显著加强.高浓度臭氧胁迫可使银杏叶片活性氧生成量增加、抗氧化酶活性下降、相关基因表达水平上调,有明显可见叶片伤害. 相似文献
11.
Photosynthetic lamellae from Anabaena variabilis catalyze a vigorous photoreduction of O 2 to H 2O 2. The electrons come to O 2 from an artificial donor, reduced 2,3′,6-trichlorophenolindophenol, and the reaction does not require an exogenous autoxidizable substance. Evidence is presented to show that reduced 2,3′,6-trichlorophenolindophenol can donate electrons at two distinct sites. Photoreduction of O 2 is inhibited by antibodies which block the function of the ferredoxin-reducing substance. The O 2-reducing system may result from the formation of a reduced photoproduct which is more accessible to autoxidation than is the analogous product formed in higher plant chloroplasts. 相似文献
12.
Trehalose is known to protect membranes and macromolecules. Its accumulation has been implicated in allowing plants to tolerate stress, including heat-shock. However, under heat-shock, it is not clear whether trehalose eliminates reactive oxygen species (ROS) directly or indirectly by protecting antioxidant enzymes. In this study, we initially examined the effects of trehalose on the activities of key antioxidant enzymes, including superoxide dismutases (SODs), ascorbate catalases (CATs), and ascorbate peroxidases (APX) from wheat ( Triticum aestivum L.), and then measured the ability of trehalose to scavenge hydrogen peroxide (H 2O 2) and superoxide anions (O 2−). Our results indicated that trehalose protected SOD activity slightly. However, it inhibited CAT and APX activities under heat stress, with a little protection of CAT activity (only about 7% promotion) at 22 °C. Moreover, trehalose scavenged H 2O 2 and O 2− greatly in a concentration-dependent manner, reaching the maximal scavenging H 2O 2 rate of 95% and O 2− rate of 78%, respectively, at 50 mM trehalose. These results suggest that trehalose plays a direct role in eliminating H 2O 2 and O 2− in wheat under heat stress. 相似文献
13.
β-Amyloid peptide (Aβ) 1–42, involved in the pathogenesis of Alzheimer’s disease, binds copper ions to form Aβ · Cu n complexes that are able to generate H 2O 2 in the presence of a reductant and O 2. The production of H 2O 2 can be stopped with chelators. More reactive than H 2O 2 itself, hydroxyl radicals HO (generated when a reduced redox active metal complex interacts with H 2O 2) are also probably involved in the oxidative stress that creates brain damage during the disease. We report in the present work a method to monitor the effect of chelating agents on the production of hydrogen peroxide by metallo-amyloid peptides. The addition of H 2O 2 associated to a pre-incubation step between ascorbate and Aβ · Cu n allows to study the formation of H 2O 2 but also, at the same time, its transformation by the copper complexes. Aβ · Cu n peptides produce but do not efficiently degrade H 2O 2. The reported analytic method, associated to precipitation experiments of copper-containing amyloid peptides, allows to study the inhibition of H 2O 2 production by chelators. The action of a ligand such as EDTA is probably due to the removal of the copper ions from Aβ · Cu n, whereas bidentate ligands such as 8-hydroxyquinolines probably act via the formation of ternary complexes with Aβ · Cu n. The redox activity of these bidentate ligands can be modulated by the incorporation or the modification of substituents on the quinoline heterocycle. 相似文献
14.
Specimens of brain or spinal cord fixed in formalin, Cajal's formol-bromide, or Koenig, Groat and Windle's formalin-acacia can be used to stain oligodendrocytes in frozen, in paraffin, or in celloidin sections. The sections are soaked 3-5 min in 0.02% acetic acid, pH 3.4, then rinsed 2-3 sec in 3% H 2O 2 and transferred to a silver bath prepared as follows: Mix equal parts of 10% AgNO 3 and 10% Na 2WO 4, and dissolve the precipitate with concentrated NH 4OH; avoid an excess of ammonia. Silver at room temperature for 15-20 sec, develop in 1% formalin, dehydrate, and mount. For embedded material, prepare a mixture consisting of 1 part of 10% aqueous Aerosol MA and 4 parts of 10% Aerosol OT in 95% alcohol. Add 5 drops of this mixture to each 50 ml of dilute acetic acid and 3% H 2O 2; 5 drops to each 20 ml of the silver bath. 相似文献
15.
1. Easily constructed apparatus is described for spectrophotometry under strictly anaerobic conditions without requiring special cuvettes. It permits the addition of several reagents successively without opening the system to the air. 2. The absorption spectrum of dithionite shows a strong peak at 314 nm, the molar absorbance of which has been determined. This gives a convenient method for the titration of acceptors with dithionite. 3. One molecule of dithionite reacts very rapidly with one molecule of O2 in solution. The O2 is reduced quantitatively to H2O2. With excess of dithionite another, much slower, reaction follows, in which a second molecule of dithionite is oxidized by the peroxide. 4. A study has been made of the reduction by dithionite of a variety of acceptors commonly used in the study of flavoproteins. The majority react very rapidly, but a few are reduced relatively slowly or not at all. 5. The majority of acceptors do not react significantly with sulphite, the oxidation product of dithionite. One molecule of dithionite then provides two reduction equivalents. A few acceptors, however, react with the sulphite formed, giving a second reaction involving two more equivalents. 相似文献
16.
The toxicity of H 2O 2 in Escherichia coli wild type and superoxide dismutase mutants was investigated under different experimental conditions. Cells were either grown aerobically, and then treated in M9 salts or K medium, or grown anoxically, and then treated in K medium. Results have demonstrated that the wild type and superoxide dismutase mutants display a markedly different sensitivity to both modes of lethality produced by H 2O 2 (i.e. mode one killing, which is produced by concentrations of H 2O 2 lower than 5 mM, and mode two killing which results from the insult generated by concentrations of H 2O 2 higher than 10 mM). Although the data obtained do not clarify the molecular basis of H 2O 2 toxicity and/or do not explain the specific function of superoxide ions in H 2O 2-induced bacterial inactivation, they certainly demonstrate that the latter species plays a key role in both modes of H 2O 2 lethality. A mechanism of H 2O 2 toxicity in E. coli is proposed, involving the action of a hypothetical enzyme which should work as an O 2-• generating system. This enzyme should be active at low concentrations of H 2O 2 (<5 mM) and high concentrations of the oxidant (>5 mM) should inactivate the same enzyme. Superoxide ions would then be produced and result in mode one lethality. The resistance at intermediate H 2O 2 concentrations may be dependent on the inactivation of such enzyme with no superoxide ions being produced at levels of H 2O 2 in the range 5–10 mM. Mode two killing could be produced by the hydroxyl radical in concert with superoxide ions, chemically produced via the reaction of high concentrations of H 2O 2 (>10 mM) with hydroxyl radicals. The rate of hydroxyl radical production may be increased by the higher availability of Fe 2+ since superoxide ions may also reduce trivalent iron to the divalent form. 相似文献
17.
The aqueous chemistry of vanadium with physiologically relevant ligands constitutes a subject of burgeoning research, extending from bacterial metalloenzymic functions to human-health physiology. Vanadium, in the form of VCl 3 and V 2O 5, reacted expediently with citric acid, in a 1:2 molar ratio in water at pH4, and, in the presence of various cations, afforded crystalline materials bearing the general formula (Cat) 2[V 2O 4(C 6H 6O 7) 2]· nH 2O (A) (Cat +=Na +, NH 4 +, n=2; Me 4N +, K +, n=4). Exploration of the reactivity of A toward H 2O 2 yielded the peroxo-containing complexes (Cat) 2[V 2O 2(O 2) 2(C 6H 6O 7) 2]·2H 2O (B) (Cat +=K +, NH 4 +). Both classes of compounds were characterized analytically and spectroscopically. The X-ray structures of complexes A and B emphasize the exceptional stability of the dimeric rhombic unit V V 2O 2, which is retained upon H 2O 2 reaction, and the preserved mode of coordination of the citrate ligand as a doubly deprotonated moiety. In these complexes, typical six and eight coordination numbers were observed for the Na + and K + counter-ions, respectively. The variety of synthetic approaches leading to A, along with the stepwise and direct assembly and isolation of peroxo-compounds (B), denotes the significance of reaction pathways and intermediates in vanadium(III–V)–citrate synthetic chemistry. Hence, a systematic investigation of reactivity modes in aqueous vanadium–citrate systems emerges as a crucial tool for the establishment of chemical interconnectivity among low MW complex species, potentially participating in the intricate biodistribution of that metal ion in biological fluids. 相似文献
18.
The polymorphonuclear leukocyte secretes both O 2-and H 2O 2 when stimulated by various soluble or particulate stimuli. Since a rcaction involving iron, O 2-, and H 2O 2 could generate the hydroxyl radical (HO.) there has been speculation that the HO-may participate in the bactericidal activity of the neutroph-il. A variety of water-soluble HO. scavengers have been used to test for the participation of HO. and the results imply that HO. might participate. However, other workers have not been able to detect the formation of significant amounts of HO-by the activated neutrophil. We have examined the effect of several commonly used HO. radical scavengers on the ability of the neutrophil to secrete O 2-and H 2O 2. Several of these compounds actively inhibit secretion without affecting the viability of the neutrophil. After considering the various complications inherent in using water soluble radical scavengers, we suggest that they only be used with well defined experimental systems. 相似文献
19.
Electron spin resonance spin trapping was utilized to investigate free radical generation from cobalt (Co) mediated reactions using 5,5-dimethyl-l-pyrroline (DMPO) as a spin trap. A mixture of Co with water in the presence of DMPO generated 5,5-dimethylpyrroline-(2)-oxy(1) DMPOX, indicating the production of strong oxidants. Addition of superoxide dismutase (SOD) to the mixture produced hydroxyl radical ( OH). Catalase eliminated the generation of this radical and metal chelators, such as desferoxamine, diethylenetriaminepentaacetic acid or 1,10-phenanthroline, decreased it. Addition of Fe(II) resulted in a several fold increase in the OH generation. UV and O 2 consumption measurements showed that the reaction of Co with water consumed molecular oxygen and generated Co(II). Since reaction of Co(II) with H 2O 2 did not generate any significant amount of OH radicals, a Co(I) mediated Fenton-like reaction [Co(I) + H 2O 2 → Co(II) + OH + OH −] seems responsible for OH generation. H 2O 2 is produced from O 2− via dismutation. O 2− is produced by one-electron reduction of molecular oxygen catalyzed by Co. Chelation of Co(II) by biological chelators, such as glutathione or β-ananyl-3-methyl-
-histidine alters, its oxidation–reduction potential and makes Co(II) capable of generating OH via a Co(II)-mediated Fenton-like reaction [Co(II) + H 2O 2 → Co(III) + OH + OH −]. Thus, the reaction of Co with water, especially in the presence of biological chelators, glutathione, glycylglycylhistidine and β-ananyl-3-methyl-
-histidine, is capable of generating a whole spectrum of reactive oxygen species, which may be responsible for Co-induced cell injury. 相似文献
20.
以大豆栽培品种铁丰29为试验材料,利用开顶式气室研究O 3浓度升高和UV B辐射增强复合胁迫对大豆叶片叶绿素(Chl)含量、膜脂过氧化程度、活性氧产生速率、抗氧化酶活性和籽粒产量的影响.结果表明: 在大豆整个生育期内,与对照相比,O 3和UV-B单一胁迫及其复合胁迫下的大豆叶片Chl(a+b)、Chl a和Chl b含量均呈下降趋势;相对电导率、丙二醛含量增大,活性氧产生速率和H 2O 2含量增加,超氧化物歧化酶、过氧化物酶和过氧化氢酶活性下降,产量降低.O 3和UV-B复合胁迫加剧了大豆叶片膜脂过氧化程度,促进大豆体内活性氧自由基的产生,使大豆抗氧化能力减弱,叶绿素含量降低,对大豆表现为协同效应.O 3胁迫对大豆叶片的影响与复合胁迫更相近,其原因可能是在复合胁迫中臭氧起主要作用. 相似文献
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