共查询到20条相似文献,搜索用时 15 毫秒
1.
Ye J Ding M Leonard SS Robinson VA Millecchia L Zhang X Castranova V Vallyathan V Shi X 《Molecular and cellular biochemistry》1999,202(1-2):9-17
Apoptosis is a physiological mechanism for the control of DNA integrity in mammalian cells. Vanadium induces both DNA damage and apoptosis. It is suggested that vanadium-induced apoptosis serves to eliminate DNA-damaged cells. This study is designed to clarify a role of reactive oxygen species in the mechanism of apoptosis induced by vanadium. We established apoptosis model with murine epidermal JB6 P+ cells in the response to vanadium stimulation. Apoptosis was detected by a cell death ELISA assay and morphological analysis. The result shows that apoptosis induced by vanadate is dose-dependent, reaching its saturation level at a concentration of 100 M vanadate. Vanadyl (IV) can also induce apoptosis albeit with lesser potency. A role of reactive oxygen species was analyzed by multiple reagents including specific scavengers of different reactive oxygen species. The result shows that vanadate-induced apoptosis is enhanced by NADPH, superoxide dismutase and sodium formate, but was inhibited by catalase and deferoxamine. Cells exposed to vanadium consume more molecular oxygen and at the same time, produce more H2O2 as measured by the change in fluorescence of scopoletin in the presence of horseradish peroxidase. This change in oxygen consumption and H2O2 production is enhanced by NADPH. Taken together, these results show that vanadate induces apoptosis in epidermal cells and H2O2 induced by vanadate plays a major role in this process. 相似文献
2.
Georg Süss-Fink Laura Gonzalez Cuervo Helen Stoeckli-Evans 《Inorganica chimica acta》2004,357(2):475-484
A series of mono- and oligonuclear vanadium(V) and vanadium(IV) complexes containing various chelating N,O-, N3-, and O2-ligands have been prepared. The biphasic reaction of an aqueous solution of ammonium vanadate and a dichloromethane solution of hexamethylphosphoramide (hmpa) and pyrazine-2-carboxylic acid (pcaH) or pyrazine-2,5-dicarboxylic acid (pdcaH2) or pyridine-2,5-dicarboxylic acid (pycaH2) yields yellow crystals of [VO2(pca)(hmpa)] (1), [(VO2)2(pdca)(hmpa)2] (2), and [VO2(pycaH)(hmpa)] (3), respectively. The single-crystal X-ray structure analyses reveal 1 and 3 to be mononuclear vanadium(V) complexes, in which a VO2 unit coordinates to one nitrogen and one oxygen atom of a pca or pycaH chelating ligand, and 2 to be a dinuclear vanadium(V) complex, in which two VO2 units are coordinated through one nitrogen and one oxygen atom of a pdca bridging ligand; in the three complexes the vanadium atoms also coordinate to the oxygen atom of a hmpa ligand. The reaction of N,N,N′,N′-tetrakis(2-benzimidazolylmethyl)-2-hydroxo-1,3-diaminopropane (hptbH) and VOSO4 in methanol gives the cationic complex [(VO)4(hptb)2(μ-O)]4+ (4), which can be crystallized as the perchlorate salt. In this tetranuclear complex, two dinuclear vanadium(IV) units are held together by a μ-oxo bridge. The known complex [VOCl2(tmtacn)] (5) was synthesized from the reaction of 1,4,7-trimethyl-1,4,7-triazacyclononane (tmtacn) and VCl3 in acetonitrile; the reaction of tetrabutylammonium vanadate with pyro-cathecol (catH2) in acetonitrile gives the known anionic complex [V(cat)3]− (6), in which the vanadium(V) center is bonded to three cat chelating ligands through the oxygen atoms, obtained as the tetrabutylammonium salt. All compounds synthesized are highly efficient oxidation catalysts for the reaction of cyclohexane with air and hydrogen peroxide in the presence of four equivalents of pcaH per vanadium, although the catalytic activity of the complexes containing bulky chelating ligands 4 and 5 is somewhat lower in the initial period of the reaction. During this period the active species are formed from the complexes and final turnover numbers are high. The catecholate ligands of complex 6 may reduce from V(V) to V(IV) in the beginning of the process, thus providing very high initial oxidation rates. 相似文献
3.
Dieter Rehder 《Molecular Engineering》1993,3(1-3):121-130
Polyoxovanadates are inhibitors to various phosphate-metabolizing enzymes. The question arises of how the cluster is bound to the protein matrix. This paper describes oxovanadates with carboxylate and hydroxide ligands in the periphery of the cluster, which may be considered to model oxovanadate binding to carboxylic and alcoholic side-chain functions of the protein. Examples for complexes carrying alkoxo ligands dealt with in this article are dinuclear vanadate(V) esters, and hexa-, octa- and decanuclear, mixed-valence (VV/VIV) clusters, the latter related to decavanadate. The possible role of dimeric vanadate esters as transition state anologues in enzymatic phosphoester cleavage is addressed. Examples for carboxylate complexes are the mononuclear, seven-coordinate mixed anhydride between orthovanadic acid and pivalic acid, containing the carboxylate in the bidentate mode, tetra-, penta- and hexanuclear VIV/VV clusters with bridging carboxylate, and trinuclear VIV and VII/VIII clusters, bridged by carboxylates and trebly bridged by O2–. Special attention is given to a comparison of the bowls containing a V4(-O)3(-OH)(O2CR)4 and V4(-O4(O2CR)4 core, respectively, which can accomodate a K+ or a NO
3
–
.51V NMR spectroscopy is shown to be a useful tool, in many cases, for the vanadium speciation of complex systems. 相似文献
4.
Jacqueline van Marwijk Diederik J. Opperman Lizelle A. Piater Esta van Heerden 《Biotechnology letters》2009,31(6):845-849
Dissimilatory reduction of vanadium(V) by Enterobacter cloacae EV-SA01, isolated from a gold mine at 1.6 km below surface, is shown to occur anaerobically as well as aerobically. Growth
rates were unaffected by up to 2 mM V2O5. Reduction of vanadium(V) was growth phase-dependent and resulted in cell deformities and precipitation of the vanadium in
its lower oxidation states. The vanadate reductase activity was membrane-associated and coupled the oxidation of NADH to the
reduction of vanadate. 相似文献
5.
A new insulin-enhancing oxovanadium complex 5-chloro-salicylaldhyde ethylenediamine oxovanadium (V) ([V2O2(μ-O)2L2]) has been synthesized. The complex was characterized by a variety of physical methods, including X-ray crystallography. The X-ray diffraction analysis show a dinuclear complex of two six-coordinate vanadium centers doubly bridged by the oxygen atoms of the Schiff base ligand with a V2O2 diamond core. The complex was administered intragastrically to STZ-diabetic rats for 2 weeks. The biological activity results show that the complex at the dose of 10.0 and 20.0 mg V kg− 1, could significantly decrease the blood glucose level and ameliorate impaired glucose tolerance in STZ-diabetic rats. That results suggested that the complex exerts an antidiabetic effect in STZ-diabetic rats. Furthermore, the complex ([V2O2(μ-O)2L2]) had permeability above 10− 5 cm/s. The experimental results suggested that the vanadium complex permeates via a passive diffusion mechanism. It was also suggested the complex with salen-type ligands has good lipophilic properties and better oral administration. The cytotoxicity of the complex ([V2O2(μ-O)2L2]) on Caco-2 cells was measured by a decrease of cell viability using the MTT assay suggesting that the chlorine atom at C4 of complex [V2O2(μ-O)2L2] increased cytotoxicity for vanadium complexes. 相似文献
6.
Dithiothreitol (CH2SHCHOHCHOHCH2SH), under neutral conditions in aqueous medium, reacts readily and reversibly with vanadate to form longlived complexes.
The ligand, vanadium and proton stoichiometries were established from concentration and pH studies. The two predominant products
each contained two vanadium(V) nuclei and one dithiothreitol and carried an overall doubly negative charge. The equilibrium
shifted toward a triply negative charge with increase in pH through the pK
a range of the products. The 51V NMR spectra clearly showed two resonances for each product (–352 and –362 ppm for one and –399 and –526 ppm for the other),
thus establishing there are chemical differences in the coordination about each vanadium. A coordination scheme was proposed
for each product. The common motif proposed was the presence of a cyclic [VO]2 core as the source of a strong stabilizing interaction leading to the very favourable formation constants (overall about
107 at pH 7). The coordination shell about the individual vanadiums each contained one sulfur in the one product and one sulfur
about one vanadium and only oxygen about the other vanadium in the second product. Under neutral conditions the reduction
of V(V) to V(IV) requires in the order of 90 min. However, if hydrogen peroxide, in greater than a 2 : 1 molar ratio over
dithiothreitol, is included in the reaction medium, all the dithiothreitol is rapidly oxidized, and peroxovanadium(V) complexes
are observed. Addition of excess dithiothreitol regenerates the dithiothreitol/vanadate complexes.
Received: 2 May 1997 / Accepted: 2 July 1997 相似文献
7.
In the present focused review, vanadate-dependent haloperoxidases and vanadate-inhibited enzymes which catalyze the hydrolysis of phosphoester bonds are addressed. In these systems, vanadate [HxVO4](3−x)− is covalently coordinated to the imidazolyl moiety of an active site histidine, with a geometrical arrangement close to a trigonal bipyramid. The resulting ligand set, NO4, and ligand arrangement provide peroxidase activity to the haloperoxidases and, to a certain extent, also to vanadate-inhibited phosphatases. The haloperoxidases are responsible for the oxidative halogenation of a variety of organic substrates. They are also active in other oxidation reactions relying on peroxide as the oxidant, such as the oxidative cyclizations of terpenes and, specifically, the oxygenation of (prochiral) sulfides to (chiral) sulfoxides. These functions can be modeled by vanadium complexes. Attracted interest is paid to {V(NO4)} complexes that are functional and structural models of the peroxidases. In the vanadate-inhibited phosphatases – structural analogs of the transition state in phosphoester hydrolysis by the native enzymes – the position of the axial histidine can also be taken by cysteinate or serinate, a fact which has implications for the insulin-mimetic potential of vanadate. 相似文献
8.
An underinvestigated aspect of the mitogenic and cell regulatory actions of vanadium is the regulation of gene expression. Among the fifteen cellular genes studied in cultured mouse C127 cells, vanadium (as 10 M sodium vanadate) increased levels of mRNA of the actin and c-Ha-ras to four times control values. These increases represented de novo synthesis of mRNA, since they were inhibited by actinomycin D. Vanadate did not increase mRNA corresponding to c-src, c-mos, c-myc, p53, HSP70, pODC or RB genes, and expression of c-erb A, c-erb B, c-sis and c-fes genes was undetectable whether vanadium was present or not. Expression of a third gene affected by vanadium, c-jun, was augmented by addition of a reductant or oxidant together with the vanadate. Addition of NADH (marginally effective on its own) or H2O2 (effective alone) dramatically enhanced the effect of vanadate on c-jun gene expression. Catalase inhibited the effect of NADH partly. The vanadate-stimulated expression of actin and c-Ha-ras mRNA were unaffected by oxidants, reductants, metal chelators, or anti-oxidant enzymes. Evidently vanadate acts by two separate mechanisms on these two categories of genes. The alternate hypothesis that the actions of vanadate on actin and c-Ha-ras were mediated by a protein kinase cascade was inconsistent with the following observations. Neither insulin nor epidermal growth factor increased mRNA levels of c-Ha-ras or actin gene. Neither genistein (a tyrosine kinase inhibitor) nor pretreatment with 12-O-tetradecanoylphorbol-13-acetate blocked the actions of vanadate on these genes. Clearly the biological actions of vanadium depend in part on altered expression of genes. Since two of the genes are proto-oncogenes, this mechanism is potentially relevant to the mitogenic responses of cells to vanadium.Abbreviations TPA
(12-O-tetradecanoylphorbol-13-acetate) 相似文献
9.
Oxidation of NADH by decavanadate, a polymeric form vanadate with a cage-like structure, in presence of rat liver microsomes followed a biphasic pattern. An initial slow phase involved a small rate of oxygen uptake and reduction of 3 of the 10 vanadium atoms. This was followed by a second rapid phase in which the rates of NADH oxidation and oxygen uptake increased several-fold with a stoichiometry of NADH: O2 of 11. The burst of NADH oxidation and oxygen uptake which occurs in phosphate, but not in Tris buffer, was prevented by SOD, catalase, histidine, EDTA, MnCl2 and CuSO4, but not by the hydroxyl radical quenchers, ethanol, methanol, formate and mannitol. The burst reaction is of a novel type that requires the polymeric structure of decavanadate for reduction of vanadium which, in presence of traces of H2O2, provides a reactive intermediate that promotes transfer of electrons from NADH to oxygen. 相似文献
10.
11.
《Free radical research》2013,47(5):317-323
Vanadyl (V(IV)) was found to induce rapidly developing lipid peroxidation in intact and sonicated mitochondria as well as in phosphatidylcholine suspension. The ability of vanadate (V(V)) to induce lipid peroxidation was much less pronounced compared to that of vanadyl. The peroxidative action of vanadate on phosphatidylcholine much increased in the presence of NADH and ascorbate. Preincubation of vanadate with glucose had the same effect.Vanadyl-induced lipid peroxidation was not essentially influenced by SOD, catalase and ethanol but was completely inhibited by butylated hydroxytoluene.All these effects of vanadyl and vanadate are thought to participate in the insulin-like and other biological actions of vanadium. 相似文献
12.
Mechanisms of hydrogen peroxide generation in Escherichia coli were investigated using a strain lacking scavenging enzymes. Surprisingly, the deletion of many abundant flavoenzymes that are known to autoxidize in vitro did not substantially lessen overall H2O2 formation. However, H2O2 production diminished by 25–30% when NadB turnover was eliminated. The flavin‐dependent desaturating dehydrogenase, NadB uses fumarate as an electron acceptor in anaerobic cells. Experiments showed that aerobic NadB turnover depends upon its oxidation by molecular oxygen, with H2O2 as a product. This reaction appears to be mechanistically adventitious. In contrast, most desaturating dehydrogenases are associated with the respiratory chain and deliver electrons to fumarate anaerobically or oxygen aerobically without the formation of toxic by‐products. Presumably, NadB can persist as an H2O2‐generating enzyme because its flux is limited. The anaerobic respiratory enzyme fumarate reductase uses a flavoprotein subunit that is homologous to NadB and accordingly forms substantial H2O2 upon aeration. This tendency is substantially suppressed by cytochrome oxidase. Thus cytochrome d oxidase, which is prevalent among anaerobes, may diminish intracellular H2O2 formation by the anaerobic respiratory chain, whenever these organisms encounter oxygen. These two examples reveal biochemical and physiological arrangements through which evolution has minimized the rate of intracellular oxidant formation. 相似文献
13.
M. W. Ahmed S. Choi K. Lyakhov U. Shaislamov R. K. Mongre D. K. Jeong R. Suresh H. J. Lee 《Plasma Physics Reports》2017,43(3):381-392
Plasma discharge is a novel disinfection and effectual inactivation approach to treat microorganisms in aqueous systems. Inactivation of Gram-negative Escherichia coli (E. coli) by generating high-frequency, high-voltage, oxygen (O2) injected and hydrogen peroxide (H2O2) added discharge in water was achieved. The effect of H2O2 dose and oxygen injection rate on electrical characteristics of discharge and E. coli disinfection has been reported. Microbial log reduction dependent on H2O2 addition with O2 injection was observed. The time variation of the inactivation efficiency quantified by the log reduction of the initial E. coli population on the basis of optical density measurement was reported. The analysis of emission spectrum recorded after discharge occurrence illustrated the formation of oxidant species (OH?, H, and O). Interestingly, the results demonstrated that O2 injected and H2O2 added, underwater plasma discharge had fabulous impact on the E. coli sterilization. The oxygen injection notably reduced the voltage needed for generating breakdown in flowing water and escalated the power of discharge pulses. No impact of hydrogen peroxide addition on breakdown voltage was observed. A significant role of oxidant species in bacterial inactivation also has been identified. Furthermore the E. coli survivability in plasma treated water with oxygen injection and hydrogen peroxide addition drastically reduced to zero. The time course study also showed that the retardant effect on E. coli colony multiplication in plasma treated water was favorable, observed after long time. High-frequency underwater plasma discharge based biological applications is technically relevant and would act as baseline data for the development of novel antibacterial processing strategies. 相似文献
14.
Aqueous solutions of vanadium(V) have been prepared at different OH− vs. vanadium concentrations from both decavanadic acid and metavanadate solutions. These solutions have been extracted with an excess of tetraheptylammonium bromide in benzene. The bromide displaced has been determined in order to gain information on the average charge of the extracting species already known to be variously protonated decavanadate anions. The addition of a constant excess of supporting electrolytes has been avoided, as it is known it could affect the position of equilibria.Besides the already well known H2V10O284−, HV10 O285− and V10O286− species, strong evidence has also been obtained for the existence of H3V10O283−.Moreover, a slow disproportionation of V10O286− into HV10O285− and V2O74− (or HVO42−) during a first stage, and then into metavanadate, resulted.Therefore, H6V10O28 proves a strong acid as triprotic instead of tetraprotic, as reported in the literature. Inconsistent results are almost certainly due to the high ionic media usually employed. 相似文献
15.
Helmut Sies 《The Journal of biological chemistry》2014,289(13):8735-8741
Hydrogen peroxide, the nonradical 2-electron reduction product of oxygen, is a normal aerobic metabolite occurring at about 10 nm intracellular concentration. In liver, it is produced at 50 nmol/min/g of tissue, which is about 2% of total oxygen uptake at steady state. Metabolically generated H2O2 emerged from recent research as a central hub in redox signaling and oxidative stress. Upon generation by major sources, the NADPH oxidases or Complex III of the mitochondrial respiratory chain, H2O2 is under sophisticated fine control of peroxiredoxins and glutathione peroxidases with their backup systems as well as by catalase. Of note, H2O2 is a second messenger in insulin signaling and in several growth factor-induced signaling cascades. H2O2 transport across membranes is facilitated by aquaporins, denoted as peroxiporins. Specialized protein cysteines operate as redox switches using H2O2 as thiol oxidant, making this reactive oxygen species essential for poising the set point of the redox proteome. Major processes including proliferation, differentiation, tissue repair, inflammation, circadian rhythm, and aging use this low molecular weight oxygen metabolite as signaling compound. 相似文献
16.
《Archives of biochemistry and biophysics》1987,255(2):274-278
Vanadyl (V(IV)) salts autoxidize in neutral aqueous solution yielding O2− plus vanadate (V(V)) and these, in turn, cause the oxidation of NADH, by a free radical chain reaction. This oxidation of NADH was inhibited by superoxide dismutase, but not by a scavenger of HO.. When H2O2 was present V(IV)) caused rapid oxidation of NADH by a process which was unaffected by superoxide dismutase but was inhibited by a scavenger of HO.. This appeared to be dependent upon reduction of H2O2 to OH− plus HO., by V(IV)), followed by oxidation of NADH by HO.. Since there are reductants, within cells, capable of reducing V(V)) to V(IV), these reactions are likely to contribute to the toxicity of vanadate. 相似文献
17.
Meera Rau Milind S. Patole S. Vijaya C. K. Ramakrishna Kurup T. Ramasarmal 《Molecular and cellular biochemistry》1987,75(2):151-159
Addition of vanadate, stimulated oxidation of NADH by rat liver microsomes. The products were NAD+ and H2O2. High rates of this reaction were obtained in the presence of phosphate buffer and at low pH values. The yellow-orange colored polymeric form of vanadate appears to be the active species and both ortho- and meta-vanadate gave poor activities even at mM concentrations.The activity as measured by oxygen uptake was inhibited by cyanide, EDTA, mannitol, histidine, ascorbate, noradrenaline, adriamycin, cytochrome c, Mn2+, superoxide dismutase, horseradish peroxidase and catalase. Mitochondrial outer membranes possess a similar activity of vanadate-stimulated NADH oxidation. But addition of mitochondria and some of its derivative particles abolished the microsomal activity. In the absence of oxygen, disappearance of NADH measured by decrease in absorbance at 340 nm continued at nearly the same rate since vanadate served as an electron acceptor in the microsomal system. Addition of excess catalase or SOD abolished the oxygen uptake while retaining significant rates of NADH disappearance indicating that the two activities are delinked. A mechanism is proposed wherein oxygen receives the first electron from NAD radical generated by oxidation of NADH by phosphovanadate and the consequent reduced species of vanadate (Viv) gives the second electron to superoxide to reduce it H2O2. This is applicable to all membranes whereas microsomes have the additional capability of reducing vanadate. 相似文献
18.
Debbie C. Crans Mohammed Mahroof-Tahir Anastasios D. Keramidas 《Molecular and cellular biochemistry》1995,153(1-2):17-24
The stability of 11 vanadium compounds is tested under physiological conditions and in administration fluids. Several compounds including those currently used as insulin-mimetic agents in animal and human studies are stable upon dissolution in distilled water but lack such stability in distilled water at pH7. Complex lability may result in decomposition at neutral pH and thus may compromise the effectiveness of these compounds as therapeutic agents; Even well characterized vanadium compounds are surprisingly labile. Sufficiently stable complexes such as the VEDTA complex will only slowly reduce, however, none of the vanadium compounds currently used as insulin-mimetic agents show the high stability of the VEDTA complex. Both the bis(maltolato)oxovanadium(IV) and peroxovanadium complexes extend the insulin-mimetic action of vanadate in reducing cellular environments probably by increased lifetimes under physiological conditions and/or by decomposing to other insulin mimetic compounds. For example, treatment with two equivalents of glutathione or other thiols the (dipicolinato)peroxovanadate(V) forms 9dipicolinato)oxovanadate(V) and vanadate, which are both insulin-mimetic vanadium(V) compounds and can continue to act. The reactivity of vanadate under physiological conditions effects a multitude of biological responses. Other vanadium complexes may mimic insulin but not induce similar responses if the vanadate formation is blocked or reduced. We conclude that three properties, stability, lability and redox chemistry are critical to prolong the half-life of the insulin-mimetic form of vanadium compounds under physiological conditions and should all be considered in development of vanadium-based oral insulin-mimetic agents.Abbreviations ADP
adenosine 5-diphosphate
- ATP
adenosine 5-triphosphate
- ADP-V
adenosine 5-diphosphate-vanadate
- bpV
bis(peroxo)oxovanadium(V)
- (bpV)2
bis(peroxo)oxovanadium(V) dimer
- bpVpic
bis(peroxo)picolinatooxovanadate(V)
-
13C
carbon-13
- EDTA
ethylenediaminetetraacetic acid
- EPR
electron paramagnetic resonance
- EXSY
exchange spectroscopy
-
1H
proton
- HSG
glutathione
- NAD
-nicotinamide adenine dinucleotide
- NADP
-nicotinamide adenine dinucleotide phosphate
- NADV
-nicotinamide adenine dinucleotide vanadate
- NMR
nuclear magnetic resonance (also referred to as magnetic resonance imaging)
- pVdipic
(dipicolinato)peroxovanadate(V)
- Vcit
(citrato)dioxovanadate(V)
- VEDTA
(ethylenediaminetetraacetato)dioxovanadate(V)
- Vmalto
bis(maltolato)-oxovanadium(IV)
- Voxal
bis(oxalato)dioxovanadate(V)
-
51V
vanadium-51
- V1
vanadate monomer
- V2
vanadate dimer
- V4
vanadate tetramer
- V5
vanadate pentamer
- UV-vis spectroscopy
ultraviolet-visible spectroscopy 相似文献
19.
Ines Lippold 《Journal of inorganic biochemistry》2009,103(4):480-486
Reaction of potassium vanadate with the hydrazone ligand derived from Schiff-base condensation of salicylaldehyde and biphenyl-4-carboxylic acid hydrazide (H2salhybiph) in the presence of two equivalents α-cyclodextrin (α-CD) in water yields the 1:2 inclusion compound K[VO2(salhybiph)@(α-CD)2]. Characterization in solution confirmed the integrity of the inclusion compound in the polar solvent water. The inclusion compound crystallizes together with additional water molecules as K[VO2(salhybiph)@(α-CD)2] · 18H2O in the monoclinic space group P2(1). Two α-CD rings forming a hydrogen bonded head to head dimer are hosting the hydrophobic biphenyl side chain of the complex K[VO2(salhybiph)]. The supramolecular aggregation of the inclusion compound in the solid state is established through hydrogen bonding interactions among adjacent α-CD hosts and with vanadate moieties of the guest complexes as well as ionic interactions with the potassium counterions. In contrast the supramolecular structure of the guest complex K[VO2(salhybiph)] without the presence of CD host molecules is governed by π-π-stacking interactions and additional CH/π interactions. The new inclusion complex K[VO2(salhybiph)@(α-CD)2] and the analogous 1:1 inclusion compound with β-CD were tested as catalyst in the oxidation of methyl phenyl sulfide (thioanisol) using hydrogen peroxide as oxidant in a water/ethanol mixture, under neutral as well as acidic conditions. 相似文献
20.
Vanadate in the polymeric form of decavanadate, but not other forms, stimulated oxidation of NADH to NAD+ NADPH was also oxidized with comparable rates. This oxidation of NADH was accompanied by uptake of oxygen and generated hydrogen peroxide with the following stoichiometry: NADH + H+ + O2 → NAD+ + H2O2. The reaction followed second-order kinetics. The rate was dependent on the concentration of both NADH and vanadate and increased with decreasing pH. The reaction had an obligatory requirement for phosphate ions. Esr studies in the presence of the spin trap dimethyl pyrroline N oxide indicated the involvement of Superoxide anion as an intermediate. The reaction was sensitive to Superoxide dismutase and other scavengers of superoxide anions. 相似文献