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71.
A cDNA clone for the cytosolic Cu/Zn superoxide dismutase (Cu/Zn SOD) from Chinese cabbage (Brassica campestris ssp.pekinensis) was isolated and its DNA sequence was determined. The cDNA clone contains a complete coding sequence which encodes a protein
of 152 amino acids and a 3-untranslated region including a poly A signal. The deduced amino acid sequence shows that it is
highly homologous to the Cu/Zn SODs from other plants (60–90%). The lack of a putative chloroplast targeting transit peptide
indicates that the clone represents a cytosolic form of Cu/Zn SOD. Genomic Southern hybridization suggests that cytosolic
Cu/Zn SOD genes are present in 1 or 2 copies per genome. 相似文献
72.
Solar Cells: Large Efficiency Improvement in Cu2ZnSnSe4 Solar Cells by Introducing a Superficial Ge Nanolayer (Adv. Energy Mater. 21/2015)
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73.
The non-selective apoplastic passage of Cu and Cu-citrate complexes into the root stele of monocotyledonous corn and dicotyledonous soybean was investigated using an inorganic-salt-precipitation technique. Either Cu ions or Cu-citrate complexes were drawn into root through the apoplast from the root growth medium, and K4[Fe(CN)6] was subsequently perfused through xylem vessels or the entire root cross section. Based on microscopic identification of the reddish-brown precipitates of copper ferrocyanide in the cell walls of the xylem of corn and soybean roots, Cu2+ passed through the endodermal barrier into the xylem of both species. When the solution containing 200 μM CuSO4 and 400 μM sodium citrate (containing 199.98 μM Cu-citrate, 0.02 μM Cu2+) was drawn via differential pressure gradients into the root xylem while being perfused with K4[Fe(CN)6] through the entire root cross-section, reddish-brown precipitates were observed in the walls of the stele of soybean, but not corn root. However, when a CuSO4 solution containing 0.02 or 0.2 μM free Cu2+ was used, no reddish-brown precipitates were detected in the stele of either of the two plants. Results indicated that endodermis was permeable to Cu-citrate complexes in primary roots of soybean, but not corn. The permeability of the endodermal barrier to the Cu-citrate complex may vary between dicotyledonous and monocotyledonous plants, which has considerable implications for chelant-enhanced phytoextraction. 相似文献
74.
Probing the interactions between carboxylated multi‐walled carbon nanotubes and copper–zinc superoxide dismutase at a molecular level
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In order to evaluate the toxicity of multi‐walled carbon nanotubes (MWCNTs‐COOH) at a molecular level, the effect of MWCNTs‐COOH on antioxidant enzyme copper–zinc superoxide dismutase (Cu/ZnSOD) was investigated using fluorescence spectroscopy, UV/vis absorption spectroscopy, circular dichroism (CD) spectroscopy and isothermal titration calorimetry (ITC). By deducting the inner filter effect (IFE), the fluorescence emission spectra and synchronous fluorescence spectra indicated that there were interactions between MWCNTs‐COOH and Cu/ZnSOD. Moreover, the microenvironment of the amino acid residues in the enzyme was changed slightly. The UV/vis absorption and CD spectroscopic results showed appreciable conformational changes in Cu/ZnSOD. However, the results of a Cu/ZnSOD activity determination did not show any significant difference. In other words, MWCNTs‐COOH has no significant effect on enzyme activity. The ITC results showed that the binding of MWCNTs‐COOH to Cu/ZnSOD was a weak endothermic process, indicating that the predominant force of the binding was hydrophobic interaction. Moreover, it was essential to consider the IFE in fluorescence assays, which might affect the accuracy and precision of the results. The above results are helpful in evaluating the oxidative stress induced by MWCNTs‐COOH in vivo. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
75.
Fish commonly respond to stress, including stress from chemical exposures, with reduced growth. However, the relevance to wild populations of subtle and sometimes transitory growth reductions may not be obvious. At low-level, sustained exposures, Cu is one substance that commonly causes reduced growth but little mortality in laboratory toxicity tests with fish. To explore the relevance of growth reductions under laboratory conditions to wild populations, we (1) estimated growth effects of low-level Cu exposures to juvenile Chinook salmon (Oncorhynchus tshawytscha), (2) related growth effects to reduced survival in downriver Chinook salmon migrations, (3) estimated population demographics, (4) constructed a demographically structured matrix population model, and (5) projected the influence of Cu-reduced growth on population size, extinction risks, and recovery chances. Reduced juvenile growth from Cu in the range of chronic criteria concentrations was projected to cause disproportionate reductions in survival of migrating juveniles, with a 7.5% length reduction predicting about a 23% to 52% reduction in survival from a headwaters trap to the next census point located 640 km downstream. Projecting reduced juvenile growth out through six generations (~30 years) resulted in little increased extinction risk; however, population recovery times were delayed under scenarios where Cu-reduced growth was imposed. 相似文献
76.
El?bieta ?odyga-Chru?cińska El?bieta Sochacka Longin Chru?ciński Daniele Sanna Monika G?siorkiewicz 《Journal of inorganic biochemistry》2010,104(5):570-575
Copper(II) complexes of histamine modified 2′-deoxyriboadenosine (N-[(9-β-D-2′-deoxyribofuranosylpurin-6-yl)-carbamoyl]histamine) ligand were studied by potentiometric, UV-visible and EPR techniques. The imidazole residue of the ligand was described as the main binding site forming mono-, bis-(ligand) and dimer complexes, but the interactions between adenosine nitrogen N(1) and carbamoyl nitrogen atoms and the copper(II) ion also were detected. This is the first report evaluating the coordinating ability of such a modified adenosine ligand towards copper(II) ion. Our findings suggest that histamine modified 2′-deoxyriboadenosine could chelate efficiently copper(II) ions if it were incorporated into DNAzyme sequence. 相似文献
77.
Cu in blood has been believed to transport into cell via albumin and some amino acids. To shed light on the Cu transport process we studied the reaction of the Cu(II)-peptide with the amino acid by absorption and CD spectra. Albumin mimic peptides GlyGly-L-HisGly (GGHG) and penta-Gly(G5) formed stable 4N coordinated Cu(II) complexes, but in the reaction with histidine (His) and penicillamine (Pes) the ternary Cu(II) complex formations were observed different by the kinetic study. Cu(II)-G5 complexes reacted with Pes to form the ternary complex Cu(H(-1)G5)(Pes(-)) which was subsequently transformed to the binary complex Cu(Pes(-))(2). In the system with GGHG the Cu(II) was also transported from GGHG to Pes, but the ternary Cu(H(-1)GGHG)(Pes(-)) complex as the intermediate was detected a trace. The ternary complex would be spontaneously transformed to Cu(Pes(-))(2) upon forming, because the rate constant of the ternary complex formation k(1+)= approximately 2M(-1)s(-1) was less than k(2+)= approximately 5 x 10(2)M(-1)s(-1) for the Cu(Pes(-))(2) formation at physiological pH. In the Cu(II)-GGHG-His system the ternary Cu(H(-1)GGHG)(His) complex was also hardly identified because the formation constant K(1) and k(1+) were very small and the equilibrium existed between Cu(H(-2)GGHG) and Cu(His)(2) and its overall equilibrium constant beta(2) for Cu(His)(2) was very small to be 1.00+/-0.05 M(-1) at pH 9.0. These results indicated that the ternary complex is formed in the Cu transport process from the albumin to the amino acid, but His imidazole nitrogen in the fourth-binding site of Cu(II) strongly resists the replacement by the incoming ligand. 相似文献
78.
Photooxidation of wetland and riverine dissolved organic matter: altered copper complexation and organic composition 总被引:1,自引:0,他引:1
In natural waters, the uptake of transition metals such as copper (Cu) by aquatic biota depends on the activity of the free
cupric ion ({Cu2+}) rather than on total Cu concentration. Thus, an important ecological function of dissolved organic matter (DOM) in aquatic
ecosystems is Cu–DOM complexation, which greatly decreases the {Cu2+}. However, Cu bioavailability is greatly modified by source and environmental history of DOM because DOM affinity for Cu
varies by orders of magnitude among DOM sources; moreover, DOM is photochemically unstable. During 72-h irradiation experiments
at intensities approximating sunlight with DOM from a palustrine wetland and a third-order river, we investigated photooxidative
effects on DOM complexation of Cu as well as spectral and chemical changes in DOM that might explain altered Cu complexation.
Irradiation decreased Cu complexation by riverine DOM, but unexpectedly increased Cu complexation by wetland DOM, resulting
in 150% greater {Cu2+} in riverine DOM at the same dissolved organic carbon concentrations. The specific ultraviolet absorption (SUVa) and humic substances tracked photochemical changes in the conditional stability constants of Cu–DOM complexes, suggesting
that the aromaticity of DOM influences its affinity for Cu. Carbonyl concentration in 13C nuclear magnetic resonance spectra (13C-NMR) covaried directly with Cu binding-site densities in DOM. However, no aspect of Cu–DOM complexation consistently covaried
with fluorophores (i.e., the fluorescence index) or low molecular weight organic acids. Our results suggest that global increases
in UV radiation will affect Cu–DOM complexation and subsequent Cu toxicity depending on light regime as well as DOM source.
Handling editor: K. Martens 相似文献
79.
Pei-Xiu Yin Jian Zhang Jian-Kai Cheng Lei Zhang Yuan-Gen Yao 《Inorganica chimica acta》2007,360(11):3525-3532
Although the 2,2′-biphenyldicarboxylate ligand (2,2′-dpa) has been widely used to construct metal-organic frameworks (MOFs) with helical sub-structure, the effect of the helical arrangement of spin carriers on the magnetic properties remains rarely scarce. In this article, two unique magnetic metal-organic supramolecular frameworks with different structural features, [Cu2(dpa)2(H2O)2(4,4′-dpdo)0.5]n (1) and [Ni(H2O)4(dpa)] · (4,4′-dpdo)(H2O) (2) (dpdo = 4,4′-dipyridine-N,N′-dioxide), have been isolated from the direct reaction of H2dpa with their corresponding salts in the presence of dpdo. In complex 1, the Cu-dpa double-helical chains, which are bridged by long flexible μ2-dpdo ligands to give rise to a regular 63 covalent layer, exhibit strong antiferromagnetic coupling interactions. Whereas the 1D [Ni(dpa)]n helical chains in complex 2 exhibit weak antiferromagnetic coupling interactions. Rich hydrogen bonds between perpendicular 1D [Ni(dpa)]n helical chains and quasi-1D (dpdo)n chains result in an intricate 3D supramolecular network. 相似文献
80.
Andberg M Jäntti J Heilimo S Pihkala P Paananen A Koskinen AM Söderlund H Linder MB 《Protein science : a publication of the Protein Society》2007,16(8):1751-1761
Improved ways to cleave peptide chains at engineered sites easily and specifically would form useful tools for biochemical research. Uses of such methods include the activation or inactivation of enzymes or the removal of tags for enhancement of recombinant protein expression or tags used for purification of recombinant proteins. In this work we show by gel electrophoresis and mass spectroscopy that salts of Co(II) and Cu(II) can be used to cleave fusion proteins specifically at sites where sequences of His residues have been introduced by protein engineering. The His residues could be either consecutive or spaced with other amino acids in between. The cleavage reaction required the presence of low concentrations of ascorbate and in the case of Cu(II) also hydrogen peroxide. The amount of metal ions required for cleavage was very low; in the case of Cu(II) only one to two molar equivalents of Cu(II) to protein was required. In the case of Co(II), 10 molar equivalents gave optimal cleavage. The reaction occurred within minutes, at a wide pH range, and efficiently at temperatures ranging from 0 degrees C to 70 degrees C. The work described here can also have implications for understanding protein stability in vitro and in vivo. 相似文献