Effect Of Cu Research Articles

The effects of copper ions on the catalytical degradation of azo dye acid chrome blue K

Abstract The effects of Cu2+ on the catalytical degradation of acid chrome blue K (ACBK) in UV-TiO2 and H2O2 processes were studied. In these two processes, Cu2+ markedly depressed the catalytical degradation of ACBK by its interaction with ACBK. Through this interaction, the new complex Cu(ACBK)2 formed. The formation of this new complex was favorable to protect some groups in ACBK from the oxidation of reactive oxygen generated in UV-TiO2 and H2O2 processes, and consequently had suppressing effects on degradation of ACBK. In addition, Cu2+ also inhibited the degradation of ACBK in UV-TiO2 process by influencing the adsorption of ACBK on the surface of TiO2 particles.

Regulation of Heme Synthesis and Proteasomal Activity by Copper: Possible Implications for Wilson's Disease

Wilson's disease (Wd) is a genetic disorder resulting in Cu2+ accumulation, and is caused by mutations in the ATP7B gene, the copper transporter. In vivo studies show a correlation between Cu2+ accumulation and malfunction of the heme biosynthesis pathway. In this study, we describe multiple effects of Cu2+ accumulation on heme synthesis, which, in turn, affect proteasomal activity. Cu2+ toxicity was examined in two hepatocellular carcinoma cell lines, HepG2 and Hep3B, with Hep3B cells containing an integrated hepatitis B virus genome. Exposure of HepG2 and Hep3B cells to Cu2+ inhibited the enzymes PBGD and ALAD of the heme synthesis pathway and, in parallel, upregulated heme oxygenase-1 (HO-1). Proto-porphyrin IX (PpIX) and the heme pool were reduced as a result of these processes. PpIX synthesis was found to be lower in cells expressing the mutant ATP7B (P1134P), compared to those expressing the WT enzyme. Proteasomal activity was inhibited under Cu2+ treatment in HepG2 cells; however, Cu2+ induced marked proteosomal acceleration in Hep3B cells. Under these conditions, Ub-conjugated proteins were gradually accumulated, whereas treatment with bathocuproine disulfonic acid (BCS), a Cu2+ chelator, reversed this effect. In conclusion, our data suggest that copper downregulates the heme synthesis pathway in hepatocellular cells and further reduces it in the presence of mutated ATP7B.

Copper and the structural biology of the prion protein

PrP (prion-related protein) is a cell-surface Cu(2+)-binding glycoprotein which, when misfolded, is responsible for a number of transmissible spongiform encephalopathies. The co-ordination geometry, stoichiometry and affinity of Cu(2+) for PrP are the subject of much debate. In the present paper, we review the recent progress we have made in these areas. As many as six Cu(2+) ions bind to PrP with submicromolar affinity. Initially, two Cu(2+) ions bind to full-length PrP in the amyloidogenic region, between the octarepeats and the structured domain, at His(95) and His(110). Only subsequent Cu(2+) ions bind to single histidine residues within the octarepeat region. Competitive chelators have been used to determine the affinity of the first molar equivalent of Cu(2+) bound to full-length PrP; this approach places the affinity in the nanomolar range. The affinity and number of Cu(2+)-binding sites support the suggestion that PrP could act as an antioxidant by binding potentially harmful Cu(2+) ions and sacrificially quenching of free radicals generated as a result of copper redox cycling. Finally, the effect of Cu(2+) on the prion structure and misassembly into oligomers and fibres is discussed.

Effect of Cu2+ on the Oxidative Folding of Synthetic Maurotoxin In Vitro

Maurotoxin (MTX) is a 34-mer scorpion toxin cross-linked by four disulphide bridges that acts on various K+ channel types. It folds according to an α/β scaffold, i.e., a helix connected to a two stranded β-sheet by two disulphide bridges. In a former study, various parameters that affect the oxidation and folding of the reduced form of synthetic MTX were investigated in vitro. It was found that MTX achieves its final 3-D structure by evolving over time through a series of oxidation intermediates, from the least to the most oxidized species. MTX oxidative intermediates can be studied by iodoacetamide alkylation of free cysteine residues followed by mass spectrometry analysis. Here, we have analysed the effect of Cu2+ (0.1 to 50 mM) on the kinetics of MTX oxidative folding and found that it dramatically speeds up the formation of the four-disulphide bridged, native-like, MTX (maximal production within 30 minutes instead of > 60 hours). This catalysing effect of Cu2+ was found to be concentration-dependent, reaching a plateau at 10 mM copper ions. Cu2+ was also found to prevent the slow transition of a three disulphide-bridged MTX intermediate towards the final four disulphide-bridged product (12% of total MTX). The data are discussed in light of the potential effects of Cu2+ on MTX secondary structure formation, disulphide bridging and peptidyl prolyl cis-trans isomerization.

Preparation of CuMgAl Hydrotalcite-Like Compounds at Low M<sup>II</sup>/M<sup>III</sup> Molar Ratios

CuMgAl hydrotalcite-like compounds with MII/MIII=1 and Cu/Mg molar ratios 3:1, 1:1, 1:3 and 1:19 were synthesized by coprecipitation and characterized by elemental analyses, XRD, SEM, FT-IR, TG-DTA and BET surface area test. XRD of all samples showed that Cu/Mg/Al hydrotalcites without any detectable impurity phase could be obtained at Cu/Mg molar ratios 1:3 and 1:19, however, at high Cu/Mg molar ratios 3:1 and 1:1, Al(OH)3 and copper hydroxides or oxides were obtained in the products besides the hydrotalcites, owing to the strong Jahn-Teller effect of Cu2+. It was also found that the crystallinity of the solids increased with an increase in copper content. IR results showed that the symmetry of carbonate was reduced from D3h to lower symmetry at high copper content. The thermal stability of the compounds decreased with increasing copper content, as indicated by TG-DTA measurements. Further thermal decomposition analyses showed that the surface area reached the maximum at calcination temperature of 500 ° C and mixed metal oxides with crystalline MgO, amorphous Al2O3 and highly dispersed CuO were obtained.

Effect of heavy metals on samples and model population of rotifers Brachionus plicatilis muller at different salinity

Effect of Cu2+ and Cr6+ on samples and on model populations of rotifers Brachionus plicatilis Muller in chronic conditions at different salinity was investigated. The LC50 (48 h) at salinities 10, 20, and 30‰ were 53.9, 0.25, and 0.1 mg Cr/l, respectively. The concentrations of 0.3 mg Cu/l and more led to the death of 100% of rotifers in 48 h in salinities 10 and 20‰, but at 30‰ the concentration 0.1 mg Cu/l was lethal. LC50 (48 h) at salinities 10, 20, and 30‰ were 7.06, 0.07, and 0.01 mg Cu/l, respectively. The toxicity of Cr and Cu for samples became higher with increasing salinity. For the model populations, the salinity influenced toxicity only at high concentrations of Cr (20 mg/l). The effect of Cr was higher on samples than on model populations.

A sensitive nonenzymatic hydrogen peroxide sensor based on DNA–Cu2+ complex electrodeposition onto glassy carbon electrode

In this paper, DNA–Cu2+ complex was electrodeposited onto the surface of glassy carbon (GC) electrode, which fabricated a DNA–Cu2+/GC electrode sensor to detect H2O2 with nonenzyme. Cyclic voltammogram of DNA–Cu2+/GC electrode showed a pair of well-defined redox peaks for Cu2+/Cu+. Moreover, the electrodeposited DNA–Cu2+ complex exhibited excellent electrocatalytic behavior and good stability for the detection of H2O2. The effects of Cu2+ concentration, electrodeposition time and determination conditions such as pH value, applied potential on the current response of the DNA–Cu2+/GC electrode toward H2O2 were optimized to obtain the maximal sensitivity. The linear range for the detection of H2O2 is 8.0 × 10−7 M to 4.5 × 10−3 M with a high sensitivity of −40.25 μA mM−1, a low detection limit of 2.5 × 10−7 M and a fast response time of within 4 s. In addition, the sensor has good reproducibility and long-term stability and is interference free.

Intestinal morphology, brush border and digesta enzyme activities of broilers fed on a diet containing Cu2+-loaded montmorillonite

1. A total of 320 1-d-old Arbor Acres broiler chicks were used to investigate the effect of Cu2+-loaded montmorillonite (CM) on the growth performance, intestinal morphology and activities of brush border enzyme in the intestinal mucosa and digestive enzyme in the intestinal digesta of broilers. 2. The chicks were assigned randomly into 4 groups with 80 chicks per treatment. The 4 dietary treatments were: basal diet only (control group), basal diet + 2 g montmorillonite/kg, basal diet + 1 g CM/kg, and basal diet + 2 g CM/kg. The chicks were raised in cages and feed and water were provided ad libitum for a period of 42 d. 3. The addition of CM to the diet of broilers significantly increased body weight and feed efficiency. Similarly, birds receiving montmorillonite had higher feed efficiency than the control after 42 d of feeding. 4. Data on villus height and crypt depth for duodenum, jejunum and ileum indicated that treating the diet of broilers with either CM or montmorillonite improved the mucosal morphology of the small intestine. 5. The presence of CM in the diet of broilers significantly increased the activities of maltase, aminopeptidase N and alkaline phosphatase in small intestinal mucosa. However, the activities of protease, trypsin, chymotrypsin, amylase and lipase in small intestinal digesta of broilers fed on the CM-supplemented diet were slightly higher than control values.

In vitroeffects of alloxan/copper combinations on lipid peroxidation, protein oxidation and antioxidant enzymes

The in vitro effects of alloxan and the product of its reduction dialuric acid (alone or in combination with copper ions) on lipid peroxidation, carbonyl content, GSH level and antioxidant enzyme activities in rat liver and kidney have been studied. The effects of Cu2+/alloxan and Cu2+/dialuric acid were compared with those of Fe3+/alloxan and Fe3+/dialuric acid. Unlike alloxan, dialuric acid increased liver and kidney lipid peroxidation; similar effects were registered in the presence of Fe3+. In the presence of Cu2+/dialuric acid, the lipid peroxidation was strongly inhibited and vice versa--the liver protein oxidation was increased. Alloxan and dialuric acid, as well as their combinations with Fe3+ had no effect on the total GSH level. Both substances did not affect the Cu2+-induced changes in GSH level, glucose-6-phosphate dehydrogenase and gluthatione reductase activities. In contrast, Cu2+ had no effect on dialuric-acid induced changes in gluthatione peroxidase and superoxide dismutase activities. The present in vitro results, concerning the metal dependence of the effects of alloxan and dialuric acid, are a premise for in vivo study of alloxan effects in metal-loaded animals.

Copper Ions InhibitS-Adenosylhomocysteine Hydrolase by Causing Dissociation of NAD+Cofactor

S-Adenosylhomocysteine hydrolase (SAHH) regulates biomethylation and homocysteine metabolism and thus is an attractive target in drug design studies. SAHH has been shown to be a copper binding protein in vivo; however, the structure and catalytic mechanism of SAHH exclude a role for Cu2+. In the present work, we studied the mechanism of inhibition of SAHH activity by Cu2+. The experimental results showed that Cu2+ inhibited SAHH activity in a noncompetitive manner. Binding of Cu2+ to SAHH resulted in the release of NAD+ cofactors, explaining the loss of the enzymatic activity of SAHH. Further investigation by an ESR probe and computational simulation suggested that Cu2+ could bind at the central channel and interrupt the subunit interactions of SAHH, resulting in a large decrease in affinity to the NAD+ cofactor. This effect of Cu2+ resembled that of enzyme mutations at the C-terminal domain or Asp244 [Komoto, J., Huang, Y., Gomi, T., Ogawa, H., Takata, Y., Fujioka, M., and Takusagawa, F. (2000) Effects of site-directed mutagenesis on structure and function of recombinant rat liver S-adenosylhomocysteine hydrolase. Crystal structure of D244E mutant enzyme, J. Biol. Chem. 275, 32147-32156]. The mechanism of action of Cu2+ on SAHH suggested a possible regulative role for Cu2+ on the intracellular activity of SAHH. This could be helpful in understanding the biological effects of copper compounds and suggest a potential coupling mechanism between biomethylation and the redox states of cells.

Effect of Cu2+ on the magnetic properties and reducibility of Fe2TiO5

Abstract Ferrites have been studied for several years due to their wide use as magnetic materials for telecommunications, audio and video, power transformers and many other applications. Equimolar mixtures of Fe2O3 and TiO2 were fired in a muffle furnace at 1200 °C for 4 h. Mixed samples were prepared by replacing TiO2 with calculated amounts of CuO (x = 0.2, 0.4, 0.6, 0.8 and 1 mol). The synthesized samples were characterized with X-ray diffraction and their magnetic properties were measured using vibrating-sample magnetometer. The microstructure of the sample was examined using reflected light microscope and scanning electron microscope. The formation of Fe2TiO5, Fe5CuO8, Cu2TiO3 and CuFeO2 phases were detected whereas their magnetic properties increased with increasing the added mole ratio of Cu2+ ions. The isothermal reduction kinetics of synthesized nanocrystallites Ti–Cu mixed ferrite compacts were studied at 500 °C using hydrogen gas. It was found that the reduction rate and the reduction extent increased with increasing the extent of Cu2+ (0.2–1) whereas the maximum reduction extent (100%) was detected for pure Cu ferrite (Cu2+) while the minimum reduction extent (12%) was detected for pure iron titanate (Cu2+ = 0). The magnetic properties showed a drastic improvement upon reduction with hydrogen gas.

Influence of Cu2+‐organic montmorillonites on thermal decomposition and smoke emission of poly(vinyl chloride) by cone calorimetric study

AbstractCu2+‐Organic montmorillonites were prepared by modifying Na+ montmorillonite (Na+‐MMT) with silane coupling agents and cupric sulfate. PVC/organic montmorillonite composites were prepared by the melt intercalation method. Morphological structure of modified MMT and PVC/MMT was obtained by using XRD and SEM. The XRD results showed that silanes and Cu2+ were intercalated among interlayers and that modified MMT may have exfoliated dispersion in PVC. Effects of Cu2+‐organic montmorillonites on decomposition and smoke emission of poly(vinyl chloride) (PVC) in the flaming mode were investigated by using a cone calorimeter at an incident heat flux of 25 kW·m−2. Cone experimental data demonstrated that the Cu2+‐organic montmorillonites prepared were new effective smoke suppressants. They clearly promoted an early HCl elimination, crosslinking reactions, and char residue formation, based upon the decomposition parameters of mass loss, mass loss rate, and time of initial decomposition (tinitial). Cu2+‐Organic montmorillonites decreased peak heat release rate, total heat release, peak smoke production rate, total smoke production, and smoke extinction area during the flaming process. The smoke‐reducing efficiency of Cu2+‐organic montmorillonites (Cu2+‐OMMTs) was the best. However, the content of cupric ion was only 0.6–0.8% in Cu2+‐OMMTs and 0.03–0.04% in PVC composites. They may make the smoke‐reducing efficiency reach 45–50%. This result further demonstrates that Cu2+ ion is a very effective smoke suppressant for PVC. J. VINYL ADDIT. TECHNOL., 13:31–39, 2007. © 2007 Society of Plastics Engineers.

Growth, photosynthetic and respiratory responses to sub-lethal copper concentrations in Scenedesmus incrassatulus (Chlorophyceae)

In the present paper we investigated the effects of sub-lethal concentrations of Cu2+ in the growth and metabolism of Scenedesmus incrassatulus. We found that the effect of Cu2+ on growth, photosynthetic pigments (chlorophylls and carotenoids) and metabolism do not follow the same pattern. Photosynthesis was more sensitive than respiration. The analysis of chlorophyll a fluorescence transient shows that the effect of sub-lethal Cu2+ concentration in vivo, causes a reduction of the active PSII reaction centers and the primary charge separation, decreasing the quantum yield of PSII, the electron transport rate and the photosynthetic O2 evolution. The order of sensitivity found was: Growth>photosynthetic pigments content=photosynthetic O2 evolution>photosynthetic electron transport>respiration. The uncoupled relationship between growth and metabolism is discussed.

Effects of Cu2+ on characteristic of SV currents

Applying the patch-clamp technique to vacuoles from Radish we studied the effects of Cu 2+ on Slow Vacuolar (SV) current’s characteristic. Our results show that Cu 2+ in bath solution at higher concentration inhibits SV currents and the percentage of inhibition increases with increasing concentration and changes with different voltage. When at lower concentration, Cu 2+ significantly promotes the SV currents and the promotion ratio decrease with increasing voltage. At the same time, the time constants of activation become lesser after adding Cu 2+ . These results show that there may be some Cu 2+ binding sites on SV channels and binding to which can change SV current’s characteristic.

Functional expression of the particulate methane mono-oxygenase gene in recombinantRhodococcus erythropolis

In order to construct an expression system for the particulate methane mono-oxygenase (pMMO) gene (pmo), the structural gene cluster pmoCAB amplified from Methylosinus trichosporium OB3b was inserted into a shuttle vector pBS305 under the control of a dsz promoter and transformed into Rhodococcus erythropolis LSSE8-1. A stable transformant was successfully obtained using ethane as the sole carbon source. Fluorescence in situ hybridization results showed that the dsz promoter allowed the pmo genes to be transcribed in the recombinant strain. The effects of Cu2+ and Zn2+ concentrations on cell growth and pMMO activity in ethane-containing medium were examined. It was discovered that 7.5 microM Cu2+ and 1.8 microM Zn2+ were suitable to achieve high cell concentration and pMMO activity, but the amount of methanol accumulated during methane oxidation by the recombinant strain was still low.

Temperature dependent Mössbauer and neutron diffraction studies of Cu x Fe1−x Cr2S4 compounds

The cation distribution and magnetic structure of Cu x Fe1−x Cr2S4 (x=0.1, 0.2, 0.3, 0.4, and 0.5) has been studied by X-ray and neutron diffraction, vibrating sample magnetometer (VSM), and Mossbauer spectroscopy. The charge state of Fe is found to be ferrous (Fe2+) for the x=0.1 sample; ferric (Fe3+) for the x=0.5 sample; mixed state (Fe2+, Fe3+) for the x=0.2, 0.3, and 0.4 samples. The Mossbauer spectra of the x=0.1 sample show asymmetric line broadening, which is considered to be due to the Jahn-Teller effect of Cu2+ ions, and a symmetrical six-line pattern is shown for the x=0.5 sample. The valence state of the Cu ions for the x=0.1 and 0.5 samples is found to be divalent and monovalent, respectively. The magnetic structure of the samples was determined to be a ferrimagnetic structure with antiparallel alignment of the Fe and Cr ion magnetic moments.

Copper and Zinc Mediated Oligomerisation of Aβ Peptides

The accumulation of senile plaques composed primarily of aggregated amyloid β-peptide (Aβ), is the major characteristic of Alzheimer’s disease. Many studies correlate plaque accumulation and the presence of metal ions, particularly copper and zinc. The metal binding sites of the amyloid Aβ peptide of Alzheimer’s disease are located in the N-terminal region of the full-length peptide. In this work, the interactions with metals of a model peptide comprising the first 16 amino acid residues of the amyloid Aβ peptide, Aβ(1–16), were studied. The effect of Cu2+ and Zn2+ binding to Aβ(1–16) on peptide structure and oligomerisation are reported. The results of ESI-MS, gel filtration chromatography and NMR spectroscopy demonstrated formation of oligomeric complexes of the peptide in the presence of the metal ions and revealed the stoichiometry of Cu2+ and Zn2+ binding to Aβ(1–16), with Cu2+ showing a higher affinity for binding the peptide than Zn2+.

Effect of Cu2+ on K+ Current in Acutely Isolated Rat Hippocampal Neurons by Whole Cell Patch Clamp Technique

Using the whole cell patch clamp technique, the effect of Cu2+ on transient outward K+ current (Ito) and delayed rectifier K+ current (Idr) was studied in acutely isolated rat hippocampal neurons. Ito and Idr were increased when the concentration of Cu2+was lower than 2×10−5 and 10−5 mol/L, respectively, and increased ratio was decreased with increasing Cu2+concentration in the bath solutions. When the concentration continued to increase to 5×10−5 and2×10−5 mol/L, the currents were hardly changed, while the concentration was more than 10−4 and 5×10−5 mol/L, the currents were inhibited remarkably. Cu2+ (10−5 mol/L) did not affect the activation and inactivation process of Ito. The activation curve of Idr was shifted toward positive potential, but 10−5 mol/L Cu2+ did not affect slope factor. According to these results, it was considered that Cu2+ at low concentration in the bath solution could promote Ito and Idr while at high concentration could inhibit them, and change of amplitude was different with different membrane voltage. Conclusion was drawn: Cu2+ may be involved in the pathophysiologic mechanism of diseases with neuropathological components.

PH-Dependent Association of Factor VIII Chains: Enhancement of Affinity at Physiological pH by Cu2+.

Factor VIII circulates as a heterodimer composed of a heavy chain (HC) and light chain (LC). The structural integrity of the heterodimer is crucial for factor VIII function. In this study we found that the reconstitution of factor VIII from isolated HC and LC was pH-dependent. In the presence of Ca2+, up to 80% of native factor VIII activity was recovered over a wide range of pH values. The affinity of HC and LC was maximal at pH 6.5-6.75 (Kd ~ 4 nM), whereas a Kd of ~20 nM was observed at physiological pH (7.25) (Figure). The effect of Cu2+ (0.5 μM total Cu2+) on maximal activity regenerated was negligible at pH 6.25–8.0. However, this level of Cu2+ increased the inter-chain affinity by ~5 fold at pH 7.25 (Figure). This effect resulted from an ~1.5-fold increased association rate constant (kon) and an ~3-fold reduced dissociation rate constant (koff). Addition of Cu2+ to a mixture of HC and LC at equilibrium resulted in an increase in cofactor activity that followed a single exponential, suggesting that association was defined by a simple reaction model. High affinity (Kd = 5.3 fM) of the factor VIII chains for Cu2+, as estimated by increases in cofactor activity, suggested a rapid association rate for the metal ion. Together, these results suggest that the protonation state of specific residues, His in particular, modulate inter-chain affinity. Furthermore, copper ion contributes to the maintenance of the heterodimer at physiologic pH by a mechanism consistent with bridging the two chains. [Display omitted]

Copper induction of phosphorus deficiency in Ulva fasciata (Ulvales, Chlorophyta)

T.-M. Lee, Y.-L. Huang and M.-H. Chen. 2005. Copper induction of phosphorus deficiency in Ulva fasciata (Ulvales, Chlorophyta). Phycologia 44: 620–628.The effects of Cu2+ on phosphorus (P) availability in Ulva fasciata Delile were studied by exposure to CuSO4 (0–100 µM) added in the nutrient-enriched artificial seawater media for 8 days. The growth rate decreased as medium Cu2+ contents increased, 50% growth inhibition was achieved at 9.8 µM Cu2+ (850 µg l−1). Tissue total Cu contents as well as cell wall–bound and intracellular Cu contents increased as medium Cu2+ contents increased. Normally, cell wall–bound Cu contents in Cu2+-treated thalli consisted of approximately 60% of total tissue Cu contents. When Cu2+ contents in the media were ≥ 50 µM, tissue P contents decreased in conjunction to tissue C : P and N : P molar ratio increased, but tissue C and N contents and tissue C : N molar ratio remained unchanged. Tissue soluble reactive phosphorus, soluble nonreactive phosphorus and total soluble phosphorus contents decreased, whereas Cu2+ contents in the medium were ≥ 50 µM. After 4 days of treatment, the inorganic oxyanion phosphate (Pi) uptake rate in 50 µM Cu2+-treated thalli (0.69 µmol h−1 g−1 d. wt. (dry weight)) decreased as compared with the control (2.25 to 0.69 µmol h−1 g−1 d. wt.). The apparent Km and Vmax values for Pi uptake in the control were 20.54 µM Pi and 2.79 µmol h−1 g−1 d. wt., respectively, and those in 50 µM Cu2+-treated thalli were 15.13 µM Pi and 0.81 µmol h−1 g−1 d. wt., respectively. There was an increase of medium Pi contents after 8 days of pre-exposure to 100 µM Cu2+, reflecting a leakage in response to extraordinarily high Cu2+ contents. The activities of extracellular alkaline phosphatase and intracellular acid phosphatase increased in both 50 and 100 µM Cu2+ treatments. Overall, Cu results in P deficiency in U. fasciata via a depression of Pi uptake, and a leakage of cellular P under exposure to excess high Cu contents. The role of Cu-adsorptive ability of cell walls in relation to Cu tolerance in U. fasciata is discussed.