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1.
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
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.
The abilities of 15 flavonoids as a scavenger of active oxygens (hydroxyl radical and superoxide anion) were studied. Hydroxyl radical ( .OH) was generated by the Fenton system, and assayed by the determination of methanesulfinic acid (MSA) formed from the reaction of dimethyl sulfoxide (DMSO) with .OH. (+)-Catechin, (−)-epicatechin, 7,8-dihydroxy flavone, and rutin showed the .OH scavenging effect 100–300 times superior to that of mannitol, a typical .OH scavenger. The other flavonoids showed no .OH scavenging effect at their concentrations up to 50 μM. Baicalein, quercetin, morin, and myricetin unexpectedly increased the .OH production in the Fenton system. The flavonoids tested now, except monohydroxy flavones, were more or less inhibitive to the superoxide anion (O 2) generation in the hypoxanthine-xanthine oxidase system. A great part of this inhibitory effect was likely owing to suppression of xanthine oxidase activity by the flavonoids. The flavonoids, which scavenged .OH or O 2−, were necessarily antioxidants to the peroxidation of methyl linoleate. However, there was a type of flavonoid such as morin, which have neither .OH nor O 2− scavenging effect, but was a strong antioxidant. 相似文献
4.
The embryo of oviparous species is confronted by a highly oxidative stress generating as it grows and must rely on effective antioxidant system for protection. Proteins of avian egg albumin have been suggested to play the major redox-modulatory role during embryo development. Recently, we found that ovotransferrin (OTf) undergoes distinct thiol-linked self-cleavage in a redox-dependent process. In this study, we explore that OTf is SOD mimic protein with a potent superoxide anion (O 2−) scavenging activity. The O 2− scavenging activity was investigated using the natural xanthine/xanthine oxidase (X/XOD) coupling system. OTf exhibited O 2− scavenging activity in a dose-dependent manner and showed remarkably higher scavenging activity than the known antioxidants, ascorbate or serum albumin. The isolated half-molecules of OTf exhibited higher scavenging activity than the intact molecule, whereas the N-lobe showed much greater activity. OTf dramatically quenched the O 2− flux but had no effect on the urate production in the X/XOD system, indicating its unique specificity to scavenge O 2− but not oxidase inhibition. Strikingly, metal-bound OTf exhibited greater O 2− dismutation capacity than the apo-protein, ranging from moderate (Zn 2+-OTf and Fe 2+-OTf) to high (Mn 2+-OTf and Cu 2+-OTf) activity with the Cu 2+-OTf being the most potent scavenger. In a highly sensitive fluorogenic assay, the metal-bound OTf exhibited significant increase in the rate of H 2O 2 production in the X/XOD reaction than the apo-OTf, providing evidence that Zn 2+-, Mn 2+- and Cu 2+-OTf possess SOD mimic activity. This finding is the first to describe that OTf is an O 2− scavenging molecule, providing insight into its novel SOD-like biological function, and heralding a fascinating opportunity for its potential candidacy as antioxidant drug. 相似文献
5.
In the present study, using the technique of EPR spin trapping with DMPO a spin trap, we demonstrated formation of thiyl radicals from thiol-containing angiotensin converting enzyme (ACE) inhibitor captopril (CAP) and from its stereoisomer epicaptopril (EPICAP), a non-ACE inhibitor, in the process of .OH radical scavenging. Splitting constants of DMPO/thiyl radical adducts were identical for both thiols and were a N = 15.3 G, and a H = 16.2 G. Bimolecular rate constants for the reaction of CAP and EPICAP with .OH radicals were close to a diffusion-controlled rate (≈ 2 × 10 10 M −1s −1). Our data also show that both CAP and EPICAP reduce Fe(III) ions and that their respective thiyl radicals are formed in this reaction. In the presence of Fe(III), H 2O 2, and CAP, or EPICAP, .OH radicals were produced by a thiol-driven Fenton mechanism. Copper(II) ions were also reduced by these thiols, but no thiyl radicals could be detected in these reactions, and no .OH or other Fenton oxidants were observed in the presence of H 2O 2. Our data show direct evidence that thiol groups of CAP and EPICAP are involved in scavenging of .OH radicals. The direct .OH radical scavenging, together with the reductive “repair” of other sites of .OH radical attack, may contribute to the known protective effect of CAP against ischemia/reperfusion-induced arrhythmias. The formation of reactive thiyl radicals in the reactions of the studied compounds with .OH radicals and with Fe(III) ions may play a role in some of the known adverse effects of CAP. 相似文献
6.
The past two decades have witnessed an explosion in our understanding of oxygen toxicity. The discovery of superoxide dismutases (SODs) (EC.1.15.1.1), which specifically catalyze the dismutation of superoxide radicals (O 2−) to hydrogen peroxide (H 2O 2) and oxygen, has indicated that O 2− is a normal and common byproduct of oxygen metabolism. There is an increasing evidence to support the conclusion that superoxide radicals play a major role in cellular injury, mutagenesis, and many diseases. In all cases SODs have been shown to protect the cells against these deleterious effects. Recent advances in molecular biology and the isolation of different SOD genes and SOD c-DNAs have been useful in proving beyond doubt the physiological function of the enzyme. The biosynthesis of SODs, in most biological systems, is under rigorous controls. In general, exposure to increased pO 2, increased intracellular fluxes of O 2−, metal ions perturbation, and exposures to several environmental oxidants have been shown to influence the rate of SOD synthesis in both prokaryotic and eukaryotic organisms. Recent developments in the mechanism of regulation of the manganese-containing superoxide dismutase of Escherichia coli will certainly open new research avenues to better understand the regulation of SODs in other organisms. 相似文献
7.
The effect of lactic acid (lactate) on Fenton based hydroxyl radical ( ·OH) production was studied by spin trapping, ESR, and fluorescence methods using DMPO and coumarin-3-carboxylic acid (3-CCA) as the ·OH traps respectively. The ·OH adduct formation was inhibited by lactate up to 0.4mM (lactate/iron stoichiometry = 2) in both experiments, but markedly enhanced with increasing concentrations of lactate above this critical concentration. When the H 2O 2 dependence was examined, the DMPO-OH signal was increased linearly with H 2O 2 concentration up to 1 mM and then saturated in the absence of lactate. In the presence of lactate, however, the DMPO-OH signal was increased further with higher H 2O 2 concentration than 1 mM, and the saturation level was also increased dependent on lactate concentration. Spectroscopic studies revealed that lactate forms a stable colored complex with Fe 3+ at lactate/Fe 3+ stoichiometry of 2, and the complex formation was strictly related to the DMPO-OH formation. The complex formation did not promote the H 2O 2 mediated Fe 3+ reduction. When the Fe 3+-lactate (1:2) complex was reacted with H 2O 2, the initial rate of hydroxylated 3-CCA formation was linearly increased with H 2O 2 concentrations. All the data obtained in the present experiments suggested that the Fe 3+-lactate (1:2) complex formed in the Fenton reaction system reacts directly with H 2O 2 to produce additional ·OH in the Fenton reaction by other mechanisms than lactate or lactate/Fe 3+ mediated promotion of Fe 3+/Fe 2+ redox cycling. 相似文献
8.
1. Single reduced methyl viologen (MV .+) acts as an electron donor in a number of enzyme systems. The large changes in extinction coefficient upon oxidation (λ max 600 nm; MV .+, = 1.3 · 10 4 M −1 · cm −1; oxidised form of methyl viologen (MV 2+), = 0.0) make it ideally suited to kinetic studies of electron transfer reactions using stopped-flow and standard spectrophotometric techniques. 2. A convenient electrochemical preparation of large amounts of MV.+ has been developed. 3. A commercial stopped-flow apparatus was modified in order to obtain a high degree of anaerobicity. 4. The reaction of MV.+ with O2 produced H2O2 (k > 5 · 106 M−1 · s−1, pH 7.5, 25 °C). H2O2 subsequently reacted with excess MV.+ (k = 2.3 · 103 M−1 · s−1, pH 7.5, 25 °C) to produce water. The kinetics of this reaction were complex and have only been interpreted over a limited range of concentrations. 5. The results support the theory that the herbicidal action of methyl viologen (Paraquat, Gramoxone) is due to H2O2 (or radicals derived from H2O2) induced damage of plant cell membrane. 相似文献
9.
Two new multi-cobalt-containing polyoxotungstates K 4Na 6Co 2(H 2O) 12{Co(H 2O) 4[Co 2(H 2O) 10Co 4(H 2O) 2( B--SiW 9O 34) 2] 2} · 40H 2O (1) and K 10Na 2[Co 4(H 2O) 2(GeW 9O 34) 2] · 20H 2O (2) have been obtained by the routine synthetic reactions in aqueous solution. The polyoxoanion framework of 1 consists of two sandwich-type polyoxoanions [Co 4(H 2O) 2( B--SiW 9O 34) 2] 12− connected together by a [CoO 2(H 2O) 4] cluster to constitute the sandwich dimer, and then, four isolated Co(H 2O) 5 cations coordinate to the dimer through four μ2-O atoms. The polyoxoanion 2 is isomorphic to the sandwich-type polyoxoanion [Co 4(H 2O) 2( B--SiW 9O 34) 2] 12− in 1. The magnetic property of compound 1 has been studied by measuring its magnetic susceptibility in the temperature range 2.0–300.0 K, indicating the existence of intramolecular ferromagnetic Co–Co interactions, and, the electrochemical properties of 1 and 2 are detected in the pH 4 buffer solution. 相似文献
10.
1. Rate constants for reduction of paraquat ion (1,1′-dimethyl-4,4′-bipyridy-lium, PQ 2+) to paraquat radical (PQ +·) by e−aq and CO 2−· have been measured by pulse radiolysis. Reduction by e−aq is diffusion controlled ( k = 8.4·10 10 M −1·s −1) and reduction by CO 2−· is also very fast k = 1.5·10 10 M −1·s −1). 2. The reaction of paraquat radical with oxygen has been analysed to give rate constants of 7.7·108 M−1·s−1 and 6.5·108 M−1·s−1 for the reactions of paraquat radical with O2 and O2−·, respectively. The similarity in these rate constants is in marked contrast to the difference in redox potentials of O2 and O2−· (− 0.59 V and + 1.12 V, respectively). 3. These rate constants, together with that for the self-reaction of O2−·, have been used to calculate the steady-state concentration of O2−· under conditions thought to apply at the site of reduction of paraquat in the plant cell. On the basis of these calculations the decay of O2−· appears to be governed almost entirely by its self-reaction, and the concentration 5 μm away from the thylakoid is still 90% of that at the thylakoid itself. Thus, O2−· persists long enough to diffuse as far as the chloroplast envelope and tonoplast, which are the first structures to be damaged by paraquat treatment. O2−· is therefore sufficiently long-lived to be a candidate for the phytotoxic product formed by paraquat in plants. 相似文献
11.
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
12.
Om wild-type Escherichia coli, near-ultraviolet radiation (NUV) was only weakly mutagenic. However, in an allelic mutant strain ( sodA sodB) that lacks both Mn- and Fe-superoxide dismutase (SOD) and assumed to have excess superoxide anion (O 2−), NUV induced a 9-fold increase in mutation above the level that normally occurs in this double mutant. When a sodA sodB double mutant contained a plasmid carrying katG+ HP-I catalase), mutation by NUV was reduced to wild-type ( sodA+ sodB+) levels. Also, in the sodA sodB xthA triple mutant, which lacks exonuclease III (exoIII) in addition to SOD, the mutations frequency by NUV was reduced to wild-type levels. This synergistic action of NUV and O 2− suggested that pre-mutational lesions occur, with exoIII converting these lesions to stable mutants. Exposure to H 2O 2 induced a 2.8 fold increase in mutations in sodA sodB double mutants, but was reduced to control levels when a plasmid carrying katG+ was introduced. These results suggest that NUV, in addition to its other effects on cells, increases mutations indirectly by increasing the flux of OH . radicals, possibly by generating excess H 2O 2. 相似文献
13.
[MnL](ClO 4) 2 (L = N, N′, N″-tris(2-hydroxypropyl)-1,4,7-triazacyclononane) has been tested for catalyzing sulfide oxidation. In the presence of this complex, ethyl phenyl sulfide, butyl sulfide and phenyl sulfide are completely oxidized to the corresponding sulfoxides and sulfones with H 2O 2 as the oxidant. 2-Chloroethyl phenyl sulfide oxidation yield 2-chloroethyl phenyl sulfone and phenyl vinyl sulfone. In ethyl phenyl sulfide oxidation, effects of complex and H 2O 2 concentration and temperature on the reaction rate have been discussed. Through controlling reaction conditions, ethyl phenyl sulfoxide and ethyl phenyl sulfone may be produced selectively. The UV–Vis and electron paramagnetic resonance (EPR) studies on catalyst solution indicate that metal centre of the complex is transformed from Mn(II) to Mn(IV) after the addition of H 2O 2. At 25 °C, rate constant for ethyl phenyl sulfide oxidation is 4.38 × 10 −3 min −1. 相似文献
14.
The reduction of ferricytochrome c by O 2− and CO 2− was studied in the pH range 6.6–9.2 and Arrhenius as well as Eyring parameters were derived from the rate constants and their temperature dependence. Ionic effects on the rate indicate that the redox process proceeds through a multiply-positively charged interaction site on cytochrome c. It is shown that the reaction with O 2− and correspondingly with O 2 of ferrocytochrome c) is by a factor of approx. 10 3 slower than warranted by factors such as redox potential. Evidence is adduced to support the view that this slowness is connected with the role of water in the interaction between O 2−/O 2 and ferri-ferrocytochrome c in the positively charged interaction site on cytochrome c in which water molecules are specifically involved in maintaining the local structure of cytochrome c and participate in the process of electron equivalent transfer. 相似文献
15.
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
16.
We examined the effects of the recombinant human colony stimulating factors GM-CSF and G-CSF, cycloheximide (a protein synthesis inhibitor) and dihydrocytochalasin B (a microfilament disrupting agent) upon FMLP (N-formyl-methionyl-leucylphenylalanine)-stimulated O 2 − production by neutrophils. We confirmed a time dependent augmentation of O 2 − production following preincubation of neutrophils either alone or with colony stimulating factors. Furthermore, we found that GM-CSF, but not G-CSF, increased O 2 − production at some concentrations of the stimulus. Preincubation of neutrophils with cycloheximide in the absence of CSF caused a marked fall in O 2−-production that was first evident at 2 hours. The fall in O 2−-forming capacity caused by cycloheximide was much less pronounced if dihydrocytochalasin B was also included in the preincubation buffer. These findings suggest a previously unrecognized role for de novo protein synthesis in maintaining the ability of neutrophils to manufacture O 2−, and support earlier studies indicating that the cycling of FMLP receptors between the cell membrane and an intracellular compartment is important in determining the magnitude of the respiratory burst in FMLP-stimulated neutrophils. 相似文献
17.
Three-dimensionally (3D) ordered macroporous active carbon has been fabricated and used as electrode substrate for the direct electrochemistry of horse heart cytochrome c (Cyt c). The Cyt c immobilized on the surface of the ordered macroporous active carbon shows a pair of well-defined and nearly reversible redox waves at the formal potential of −0.033 V in pH 6.8 phosphate buffer solution. The interaction between Cyt c and the 3D macroporous active carbon makes the formal potential shift negatively compared to that of Cyt c in solution. Spectrophotometric and electrochemical methods have been used to investigate the interaction between Cyt c and the porous active carbon. The immobilized Cyt c maintains its biological activity, and shows a surface controlled electrode process with the electron-transfer rate constant ( ks) of 17.6 s −1 and the charge-transfer coefficient ( a) of 0.52, and displays the features of a peroxidase in the electrocatalytic reduction of hydrogen peroxide (H 2O 2). A potential application of the Cyt c-immobilized porous carbon electrode as a biosensor to monitor H 2O 2 has been investigated. The steady-state current response increases linearly with H 2O 2 concentration from 2.0 × 10 −5 to 2.4 × 10 −4 mol l −1. The detection limit (3 σ) for determination of H 2O 2 has been found to be 1.46 × 10 −5 mol l −1. 相似文献
18.
The oxidation of melatonin (MEL) using the Cu(II) + H 2O 2 + HO − (the Fenton-like reaction) system was investigated by chemiluminescence (CL), fluorescence, spectrophotometric, and EPR spin trapping techniques. The reaction exhibits CL in the 400–730 nm region. The light emission from the Fenton-like reaction was greatly enhanced in the presence of MEL and was strongly dependent on its concentration. The spectrum measured with cut-off filters revealed maxima at around 460, 500, 580–590, 640–650, and 690–700 nm. The band at 460 nm may be due to the excited cleavage product, N 1-acetyl-N 2-formyl-5-methoxykynuramine, whereas the bands at 500, 580–590, 640–650, and 700 nm were similar to those observed for singlet molecular oxygen ( 1O 2). The effect of reactive oxygen species (ROS) scavengers on the light emission was studied. The CL was strongly inhibited by the 1O 2 scavengers in a dose-dependent manner; at concentration 1 mM the potency of 1O 2 scavenging was 5,5-dimethylcyclohexandione-1,3 > methionine > histidine > hydroquinone. The potency of HO • scavenging by thiourea, tryptophan, cysteine at concentration 5 mM was 79–94%, by 1 mM glutathione and trolox 75 and 94%, respectively, and by 10 mM cimetidine 18%. Specific acceptors of O 2•− such as p-nitroblue tetrazolium chloride and 4,5-dihydroxy-1,3-benzene disulfonic acid (tiron) at concentration 5 mM decreased the CL by 51 and 95%, respectively, whereas superoxide dismutase (SOD) does not reduce the emission at concentration 2.8 U/ml. At higher concentration SOD substantially enhanced the light emission. Addition of 1360 U/ml catalase and 100 μM desferrioxamine strongly inhibited CL (96 and 90%, respectively). The increased generation of 1O 2 from the Cu/H 2O 2 system in the presence of MEL was confirmed using the spectrophotometric method based on the bleaching of p-nitrosodimethylaniline and by trapping experiments with 2,2,6,6-tetramethylpiperidine (TEMP) and subsequent electron paramagnetic (EPR) spectroscopy. These findings suggest the increased production of reactive oxygen species (O 2•−, HO •, 1O 2) from the Fenton-like reaction in the presence of MEL. This means that the hormone is not able to act as classical chain-breaking antioxidant even at low concentration, and may show clear prooxidant activity at higher concentrations. In addition, long-lived carbonyl product of the MEL transformation in the triplet state can also be toxic by transferring its energy to organelles and causing a photochemical process. 相似文献
19.
The effect of photoexcited riboflavin (RF) on the viscosity of hyaluronic acid (HA) solutions has been investigated. UV irradiation of RF causes under aerobic conditions fragmentation of HA and a decrease in the viscosity of its solutions. A decrease of HA viscosity occurs in PO 4-buffered solutions and is accelerated by high pH, Fe 2+ (but much less so by Fe 3+), certain metal chelators, and horseradish peroxidase (HRP); it is partially inhibited by catalase and less so by superoxide dismutase (SOD). The reactivity of the system was completely blocked by Tris, ethanol, aspirin, d-manitol, dimethylthiourea (DMTU), dimethylsulfoxide (DMSO), and sodium azide. These results indicate that the most likely chemical species involved in the reaction is the hydroxyl radical. Singlet oxygen ( 10 2) generation is suggested by the ability of NaN 3 and DMSO to completely inhibit the reactivity of the system. These two agents, however, may also interact with OH √ radical, as well and suppress the reactivity of the system. H 2O 2 and
seem also to be produced in significant amounts, because catalase and SOD partially block the reactivity of the system. The effect of HRP may be due to hydrogen subtraction from HA and H 2O 2 reduction to water. Photoexcitation of RF may potentially occur in vitro and in vivo in the organs and tissues that are permeable to light, such as the eye or skin, and damage HA and other cell-matrix components causing inflammation and accelerating aging. © 1997 Elsevier Science Inc. 相似文献
20.
N-acetylcysteine has been widely used as an antioxidant in vivo and in vitro. Its reaction with four oxidant species has therefore been examined. N-acetylcysteine is a powerful scavenger of hypochlorous acid (H---OCl); low concentrations are able to protect 1-antiproteinase against inactivation by HOCl. N-acetylcysteine also reacts with hydroxyl radical with a rate constant of 1.36 × 10 10 M −1s −1, as determined by pulse radiolysis. It also reacts slowly with H 2O 2, but no reaction of N-acetylcysteine with superoxide (O 2−) could be detected within the limits of our assay procedures. 相似文献
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