共查询到20条相似文献,搜索用时 31 毫秒
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Yong Peng Chengshan Wang Howard H. Xu Feimeng Zhou 《Journal of inorganic biochemistry》2010,104(4):365-675
Parkinson’s disease (PD) is hallmarked by the abnormal intracellular inclusions (Lewy bodies or LBs) in dopaminergic cells. Amyloidogenic protein α-synuclein (α-syn) and iron (including both Fe(III) and Fe(II)) are both found to be present in LBs. The interaction between iron and α-syn might have important biological relevance to PD etiology. Previously, a moderate binding affinity between α-syn and Fe(II) (5.8 × 103 M−1) has been measured, but studies on the binding between α-syn and Fe(III) have not been reported. In this work, electrospray mass spectrometry (ES-MS), cyclic voltammetry (CV), and fluorescence spectroscopy were used to study the binding between α-syn and Fe(II) and the redox property of the resultant α-syn-Fe(II) complex. The complex is of a 1:1 stoichiometry and can be readily oxidized electrochemically and chemically (by O2) to the putative α-syn-Fe(III) complex, with H2O2 as a co-product. The reduction potential was estimated to be 0.025 V vs. Ag/AgCl, which represents a shift by −0.550 V vs. the standard reduction potential of the free Fe(III)/Fe(II) couple. Such a shift allows a binding constant between α-syn and Fe(III), 1.2 × 1013 M−1, to be deduced. Despite the relatively high binding affinity, α-syn-Fe(III) generated from the oxidation of α-syn-Fe(II) still dissociates due to the stronger tendency of Fe(III) to hydrolyze to Fe(OH)3 and/or ferrihydrite gel. The roles of α-syn and its interaction with Fe(III) and/or Fe(II) are discussed in the context of oxidative stress, metal-catalyzed α-syn aggregation, and iron transfer processes. 相似文献
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Kumaraswamy R Kuenen JG Kleerebezem R van Loosdrecht MC Muyzer G 《Applied microbiology and biotechnology》2006,73(4):922-931
BioDeNOx is a combined physicochemical and biological process for the removal of nitrogen oxides (NOx) from flue gas. In the present study, two anaerobic bioreactors performing BioDeNOx were run consecutively (RUN-1 and RUN-2) at a dilution rate of 0.01 h−1 with Fe(II)EDTA.NO2− and Fe(III)EDTA− as electron acceptors and ethanol as electron donor. The measured protein concentration of the reactor biomass of both runs was 120 mg/l. Different molecular methods were used to determine the identity and abundance of the bacterial populations in both bioreactors. Bacillus azotoformans strain KT-1 was recognized as a key player in Fe(II)EDTA.NO2− reduction. PCR-denaturing gradient gel electrophoresis analysis of the reactor biomass showed a greater diversity in RUN-2 than in RUN-1. Enrichments of Fe(II)EDTA.NO2− and Fe(III)EDTA− reducers and activity assays were conducted using the biomass from RUN-2 as an inoculum. The results on substrate turnover, overall microbial diversity, and enrichments and finally activity assays confirmed that ethanol was used as electron donor for Fe(II)EDTA.NO2− reduction. In addition, the Fe(III)EDTA− reduction rate of the microbial community proved to be feasible enough to run the bioreactors, ruling out the chemical reduction of Fe(III)EDTA− with sulfide as was proposed by other researchers. 相似文献
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Milán Farkas Sándor Szoboszlay Tibor Benedek Fruzsina Révész Péter Gábor Veres Balázs Kriszt András Táncsics 《Folia microbiologica》2017,62(1):63-71
Dissimilatory iron-reducing bacteria are commonly found in microbial communities of aromatic hydrocarbon-contaminated subsurface environments where they often play key role in the degradation of the contaminants. The Siklós benzene, toluene, ethylbenzene, and xylene (BTEX)-contaminated area is one of the best characterized petroleum hydrocarbon-contaminated sites of Hungary. Continuous monitoring of the microbial community in the center of the contaminant plume indicated the presence of an emerging Geobacter population and a Rhodoferax phylotype highly associated with aromatic hydrocarbon-contaminated subsurface environments. The aim of the present study was to make an initial effort to enrich Rhodoferax-related and other dissimilatory iron-reducing bacteria from this environment. Accordingly, four slightly different freshwater media were used to enrich Fe(III) reducers, differing only in the form of nitrogen source (organic, inorganic nitrogen or gaseous headspace nitrogen). Although enrichment of the desired Rhodoferax phylotype was not succeeded, Geobacter-related bacteria were readily enriched. Moreover, the different nitrogen sources caused the enrichment of different Geobacter species. Investigation of the diversity of benzylsuccinate synthase gene both in the enrichments and in the initial groundwater sample indicated that the Geobacter population in the center of the contaminant plume may not play a significant role in the anaerobic degradation of toluene. 相似文献
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Thiosemicarbazones such as Triapine (Tp) and Dp44mT are tridentate iron (Fe) chelators that have well-documented antineoplastic activity. Although Fe–thiosemicarbazones can undergo redox cycling to generate reactive species that may have important roles in their cytotoxicity, there is only limited insight into specific cellular agents that can rapidly reduce Fe(III)–thiosemicarbazones and thereby promote their redox activity. Here we report that thioredoxin reductase-1 (TrxR1) and glutathione reductase (GR) have this activity and that there is considerable specificity to the interactions between specific redox centers in these enzymes and various Fe(III) complexes. Site-directed variants of TrxR1 demonstrate that the selenocysteine (Sec) of the enzyme is not required, whereas the C59 residue and the flavin have important roles. Although TrxR1 and GR have analogous C59/flavin motifs, TrxR is considerably faster than GR. For both enzymes, Fe(III)(Tp)2 is reduced faster than Fe(III)(Dp44mT)2. This reduction promotes redox cycling and the generation of hydroxyl radical (HO) in a peroxide-dependent manner, even with low-micromolar levels of Fe(Tp)2. TrxR also reduces Fe(III)–bleomycin and this activity is Sec-dependent. TrxR cannot reduce Fe(III)–EDTA at significant rates. Our findings are the first to demonstrate pro-oxidant reductive activation of Fe(III)-based antitumor thiosemicarbazones by interactions with specific enzyme species. The marked elevation of TrxR1 in many tumors could contribute to the selective tumor toxicity of these drugs by enhancing the redox activation of Fe(III)–thiosemicarbazones and the generation of reactive oxygen species such as HO. 相似文献
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将胶原纤维用三价铁改性后作为载体,通过戊二醛的交联作用将过氧化氢酶固定在该载体上。制备的固定化过氧化氢酶蛋白固载量为16.7 mg/g,酶活收率为35%。研究了固定化酶与自由酶的最适pH、最适温度、热稳定性、贮存稳定性及操作稳定性。结果表明:过氧化氢酶经此法固定化后,最适pH及最适温度与自由酶相同,分别为pH 7.0和25 ℃;但固定化酶的热稳定性显著提高,在75 ℃保存5 h后,仍能保留30%的活力,而自由酶则完全失活;固定化酶在室温下保存12 d后,酶活力仍保持在88%以上,而自由酶在此条件下则完全失 相似文献
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Floriane Malvolti Olivier Cador Jean-François Halet Loic Toupet Stéphane Cordier 《Inorganica chimica acta》2011,374(1):288-301
The new thiocyanato- (5) and azido- (6) complexes were synthesized and studied under their Fe(II) and Fe(III) redox states. For the first time among the various [Fe(η5-C5Me5)(η2-dppe)]-based cationic radicals studied so far, the magnitude and spatial orientation of the g-tensor diagonal values were experimentally determined for 5[PF6]. These data are in good agreement with those issued from a DFT modelization. The changes experienced by the electronic structure of the Fe(II) complexes subsequent to oxidation are reminiscent of these previously observed for the known arylalkynyl analogues, albeit some differences can be pointed out. Thus, the differences observed in the 1H NMR spectra of 5[PF6] and 6[PF6] are attributed to a slower electronic spin relaxation and to the differently oriented magnetic anisotropy. The sizeable spin density evidenced by DFT on the terminal atom of the ligands of the Fe(III) complexes renders these new paramagnetic metallo-ligands quite appealing for accessing larger polynuclear molecular assemblies with magnetically interacting centers. 相似文献
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Yanlong Shi E. M. Eyring Rudi van Eldik Gang Liu Fred W. Bruenger Scott C. Miller 《Journal of biological inorganic chemistry》1997,2(6):728-743
The kinetics of Fe(III) complexation by lipophilic 3-hydroxy-2-methyl-l(γ-stearoamidopropyl)-4-pyridinone (HMSP) were studied
when [Fe(III)] > [HMSP] in MeOH/H2O mixed solvent and [Fe(III)] < [HMSP] in MeOH, respectively. When Fe(III) was in excess, the observed rate constants depend
on [Fe(III)]2
tot and on the reciprocal of [H+] and decrease with increasing pressure. ΔV
‡ values are around +8.0 cm3 mol–1. A mechanism consisting of the complexations of the hydrolyzed monomer Fe(H2O)5OH2+ and dimer species Fe2(H2O)7 (μ-OH)2OH3+ by HMSP is proposed. This mechanism is supported by the solvent effect and the work of other researchers. When HMSP is in
excess, Fe(HMSP)3 is formed and three kinetic steps on different time-scales are observed. An "intermolecular chelate ring-closure" mechanism
is proposed, differing from the "intramolecular chelate ring-closure" complexation reported for the formation of ferrioxamine
B.
Received: 14 February 1997 / Accepted: 1 September 1997 相似文献
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Plutonium (Pu), a key contaminant at sites associated with the manufacture of nuclear weapons and with nuclear-energy wastes,
can be precipitated to “immobilized” plutonium phases in systems that promote bioreduction. Ferric iron (Fe3+) is often present in contaminated sites, and its bioreduction to ferrous iron (Fe2+) may be involved in the reduction of Pu to forms that precipitate. Alternately, Pu can be reduced directly by the bacteria.
Besides Fe, contaminated sites often contain strong complexing ligands, such as nitrilotriacetic acid (NTA). We used biogeochemical
modeling to interpret the experimental fate of Pu in the absence and presence of ferric iron (Fe3+) and NTA under anaerobic conditions. In all cases, Shewanella alga BrY (S. alga) reduced Pu(V)(PuO2
+) to Pu(III), and experimental evidence indicates that Pu(III) precipitated as PuPO4(am). In the absence of Fe3+ and NTA, reduction of PuO2
+ was directly biotic, but modeling simulations support that PuO2
+ reduction in the presence of Fe3+ and NTA was due to an abiotic stepwise reduction of PuO2
+ to Pu4+, followed by reduction of Pu4+ to Pu3+, both through biogenically produced Fe2+. This means that PuO2
+ reduction was slowed by first having Fe3+ reduced to Fe2+. Modeling results also show that the degree of PuPO4(am) precipitation depends on the NTA concentration. While precipitation out-competes complexation when NTA is present at the
same or lower concentration than Pu, excess NTA can prevent precipitation of PuPO4(am). 相似文献
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微生物氧化As(III)和Sb(III)的研究进展 总被引:3,自引:0,他引:3
砷(Arsenic,As)和锑(Antimony,Sb)属于同族元素,具有相似的化学性质,是公认的有毒类金属(metalloid),广泛存在于自然界中。随着人类的发展,环境中砷和锑的污染日益严重,类金属污染环境的修复已经刻不容缓。现已表明,自然界中的微生物在砷和锑的生物地球化学循环中发挥着重要的作用,尤其是微生物的氧化作用,可以将毒性较强的亚砷酸盐[Arsenite,As(III)]和亚锑酸盐[Antimonite,Sb(III)]氧化为毒性较低的砷酸盐[Arsenate,As(V)]和锑酸盐[Antimonate,Sb(V)],被认为是一种潜在的类金属污染环境修复方法。本文就国内外对As(III)氧化菌和Sb(III)氧化菌的多样性、As(III)和Sb(III)微生物氧化调控机制和应用的研究进展进行总结,旨在为深入了解和探索微生物介导的砷和锑生物地球化学循环及污染环境的微生物修复提供参考。 相似文献
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Ross M. Welch Wendell A. Norvell Stephen C. Schaefer Jon E. Shaff Leon V. Kochian 《Planta》1993,190(4):555-561
We investigated the effects of Fe and Cu status of pea (Pisum sativum L.) seedlings on the regulation of the putative root plasma-membrane Fe(III)-chelate reductase that is involved in Fe(III)-chelate reduction and Fe2+ absorption in dicotyledons and nongraminaceous monocotyledons. Additionally, we investigated the ability of this reductase system to reduce Cu(II)-chelates as well as Fe(III)-chelates. Pea seedlings were grown in full nutrient solutions under control, -Fe, and -Cu conditions for up to 18 d. Iron(III) and Cu(II) reductase activity was visualized by placing roots in an agarose gel containing either Fe(III)-EDTA and the Fe(II) chelate, Na2bathophenanthrolinedisulfonic acid (BPDS), for Fe(III) reduction, or CuSO4, Na3citrate, and Na2-2,9-dimethyl-4,7-diphenyl-1, 10-phenanthrolinedisulfonic acid (BCDS) for Cu(II) reduction. Rates of root Fe(III) and Cu(II) reduction were determined via spectrophotometric assay of the Fe(II)-BPDS or the Cu(I)-BCDS chromophore. Reductase activity was induced or stimulated by either Fe deficiency or Cu depletion of the seedlings. Roots from both Fe-deficient and Cu-depleted plants were able to reduce exogenous Cu(II)-chelate as well as Fe(III)-chelate. When this reductase was induced by Fe deficiency, the accumulation of a number of mineral cations (i.e., Cu, Mn, Fe, Mg, and K) in leaves of pea seedlings was significantly increased. We suggest that, in addition to playing a critical role in Fe absorption, this plasma-membrane reductase system also plays a more general role in the regulation of cation absorption by root cells, possibly via the reduction of critical sulfhydryl groups in transport proteins involved in divalent-cation transport (divalent-cation channels?) across the root-cell plasmalemma. 相似文献
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Photophysical studies of hetero-bischelated complexes of rhodium(III) containing 2,2′-dipyridylamine
《Inorganica chimica acta》2006,359(2):401-408
Four mixed-ligand complexes, cis-Rh[(bipy)(HDPA)Cl2]Cl (1), cis-[Rh(phen)(HDPA)Cl2]Cl (2), cis-[Rh(bipy)(DPA)Cl2] (3), and cis-[Rh(phen)(DPA)Cl2] (4) (where bipy = 2,2′-bipyridine, phen = 1,10-phenantroline, HDPA = 2,2′-dipyridylamine, and DPA = the deprotonated form of 2,2′-dipyridylamine) have been synthesized and characterized. In slightly acidic solution and at low temperature (77 K), both complexes 1 and 2 show a broad, symmetric and structureless red emission with microsecond lifetime identified as dd* phosphorescence. In slightly basic solution, the deprotonated complexes (3 and 4) exhibit a broad and asymmetric blue emission, showing no vibrational structure with a lifetime in the order of microseconds. Emission of complex 3 reveals a blue shift of 0.81 μm−1 compared to the emission of complex 1 and that of complex 4 shows a blue shift of 0.77 μm−1 with respect to complex 2. Electrochemical data have also been obtained for the four complexes in CH3CN. There are two reduction peaks observed for both complexes 1 and 2. Each peak is followed by a one-electron reduction at the metal, with an elimination of chloride during each reduction step, which is in consistent with the dd* phosphorescence assignment for the two complexes. For complexes 3 and 4, only a one-electron reduction process occurs at the metal with an elimination of chloride. Based on the luminescence and electrochemical data, the emission of complexes 3 and 4 are assigned as πd* phosphorescence. Results from density functional theory (DFT) calculations provide theoretical evidence in support of this πd* assignments. 相似文献
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We calculate here the Raman frequencies of the lattice modes A(A g ), B(B 2g ) and C(B 1g B 3g ) as a function of pressure at room temperature for the solid phases (II, III and III’) of benzene. This calculation is performed using volume data through the mode Grüneisen parameter. It is found that our calculated frequencies of those lattice modes increase with increasing pressure, as expected. Calculated frequencies are in good agreement with the measurements of the three lattice modes for the solid phases studied in benzene. 相似文献
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《International journal of radiation applications and instrumentation. Part B, Nuclear medicine and biology》1992,19(1):73-78
New tris(β-diketonato) complexes of trivalent 99Tc/99mTc with the ligands hexane-2,4-dione, heptane-2,4-dione, heptane-3,5-dione, and octane-3,5-dione were synthesized by reduction of pertechnetate with dithionite in the presence of excess β-diketone. The complexes were purified by HPLC, identified by elemental analysis and FAB mass spectrometry, and characterized by vis./u.v./i.r. spectrophotometry. The hexane-2,4-dionato complex crystallizes in the monoclinic space group P21/c, isostructurally with pentane-2,4-dionatotechnetium(III). Biodistribution measurements in mice showed the neutral and lipophilic 99mTc-diketonato complexes to penetrate the blood-brain barrier. However, increasing lipophilicity decreased the brain uptake except for the heptane-2,4-dionato complex, which displayed the highest uptake of 0.82% injected dose/g. 相似文献
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M.N. Sokolov N.E. Fyodorova R. Paetow A.G. Ravelo V.E. Fedorov 《Inorganica chimica acta》2007,360(6):2192-2196
The reactions of [ReCl3(CH3CN)(PPh3)2] with benzil PhC(O)C(O)Ph, and with a natural 1,2-naphthoquinone derivative, β-lapachone (Lap), result in oxidative addition with the formation of Re(V) complexes with stilbenediolate, [ReCl3(PhC(O)C(O)Ph)(PPh3)] (1) and with a reduced semiquinonic form of lapachone, [ReIVCl3(Lap−)(PPh3)] (2). The structures of both compounds were established by X-ray crystallography. 相似文献
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Treatment of anhydrous BiCl3, BiBr3 or BiI3 with an equivalent portion of the β-dialdiminatosodium compound Na[{N(Ar)C(H)}2CPh] [≡ Na(L); Ar = C6H3Pri2-2,6] in tetrahydrofuran and crystallisation from diethyl ether afforded the crystalline red [BiCl2(L)(μ-Cl)Bi(Cl)L(thf)]·OEt2 (1), the isomorphous yellow/orange bromide 2 and the yellow/orange [{BiI(L)(μ-I)}2]·0.5OEt2 (3). The X-ray structures of 1-3 are reported. The known pyrazolium salt was obtained by iodination of 3. 相似文献
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Cr(III), which is thought to be relatively non-toxic, was reduced to Cr(II) ion by biological reductants such as L-cysteine and NADH and Cr(II) thus formed could easily react with hydrogen peroxide (H2O2) to yield very reactive active oxygen species, hydroxyl radical (.OH). The formation of hydroxyl radical was detected by water-soluble spin-traps, alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (POBN) and 5,5-dimethyl-1-pyrroline N-oxide (DMPO). This result indicates that non-toxic Cr(III) compounds have the possibility of causing dangerous effects to living organism in the presence of biological reductants. 相似文献