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PubMed2004

Assessment of menstrual blood loss in Brazilian users of the frameless copper-releasing IUD with copper surface area of 330 mm2 and the frameless levonorgestrel-releasing intrauterine system.

OBJECTIVE: This study was conducted to evaluate the effect of two types of IUDs on the amount of menstrual blood loss (MBL): the frameless copper-releasing intrauterine device (IUD) with copper surface area of 330 mm2 (GyneFix; Contrel Research, Ghent, Belgium) and the frameless levonorgestrel (LNG)-releasing intrauterine system (IUS) releasing 14 microg per day (FibroPlant-LNG; Contrel Research). Heavy and abnormal MBL is the main reason for discontinuation of intrauterine devices. METHODS: In 20 Brazilian women using GyneFix 330 and 32 using FibroPlant-LNG, respectively, MBL was measured by the quantitative alkaline hematin technique. In addition, ferritin levels were measured in GyneFix 330 and FibroPlant-LNG users. RESULTS: MBL with GyneFix 330, measured over a 24-month period, increased but was less when compared with TCu380A. Ferritin levels with GyneFix 330 were not affected in contrast with TCu380A. In FibroPlant-LNG users, mean MBL decreased by about 90% and ferritin levels increased significantly. CONCLUSIONS: The authors confirm earlier reports that, especially for women with low body iron stores and heavy menstrual bleeding, there is an order of preference for IUD use to minimize MBL. The choice should first be a progestin-releasing IUS, then a copper IUD, which has the least effect on menstrual bleeding, such as the frameless GyneFix IUD.

Brazil↗

PubMed2004

The structure of Rigidoporus lignosus Laccase containing a full complement of copper ions, reveals an asymmetrical arrangement for the T3 copper pair.

Laccase is a multicopper blue oxidase that couples the four-electron reduction of oxygen with the oxidation of a broad range of organic substrates, including phenols and arylamines. The enzyme is the object of intense biotechnological research, due to its employment in bioremediation of soils and water as well as in other biotechnological applications. We report here the cDNA and protein sequences, the post-translational modifications, the crystallization and X-ray structure determination of a laccase from the white-rot fungus Rigidoporus lignosus. The amino acid residues sequence deduced from cDNA clearly identified a pre-sequence of 21 residues representing the signal for extra-cellular localization. Mass spectrometry analysis performed on the salvage enzyme, confirmed the deduced sequence and precisely mapped two glycosylation sites at Asn337 and Asn435, determining the nature of the bound glycosidic moieties. The crystal structure was determined at 1.7A resolution from perfectly hemihedrally twinned crystals, by molecular replacement technique. While the overall structure closely resembled those reported for other fungal laccases, the analysis of the T2/T3 trinuclear cluster revealed an unprecedented coordination sphere for the T3 copper pair. No bridging oxygen ligand was present between the two T3 copper ions, which were no longer symmetrically coordinated. The observed structure could represent an intermediate along the process of four-electron reduction of oxygen to water taking place at the trinuclear copper cluster.

Amino Acid Sequence↗

PubMed1977

Ligand-exchange separations of amino acids. I. Distribution equilibria of some amino acids between ammoniacal copper(II) nitrate solutions and phosphonic, carboxylic and iminodiacetic ion exchangers in the copper(II) form.

The ligand-exchange process for the distribution of glycine, alanine and leucine between a copper(II) phosphonate resin and ammoniacal solutions of copper nitrate has been studied. The formation in both resin and solution phases of mixed CuA(NH3)+i complexes (i = 1-3) was demonstrated. A theoretical expression for the distribution coefficient, taking into account the various parameters upon which it depends, has been established and verified experimentally. Some experiments carried out with carboxylic and iminodiacetic resin in the Cu(II) form confirmed the validity of the theoretical model. The distribution of an amino acid by ligand exchange occurs as a complex phenomenon that brings many equilibria into play. However, by simplifying the theory with some approximations, it is possible to describe the distribution by means of two equilibria, one of ion exchange and the other of the formation in solution of mixed complexes. This simplified theory clearly displays how the ammonia and copper(II) concentrations affect the amino acid fixation. Some experimental graphs illustrate the variation of the distribution coefficients for different amino acids with each of these parameters. Finally, some observations on the selectivity that may be expected from this process are made. In particular, it is shown how the optimal conditions for the separation of two amino acids can be determined.

Acetates↗

PubMed1990

Comparison of three histochemical staining methods for the detection of copper in white perch (Morone americana) with abnormal hepatic copper storage.

A comparison of orcein, rubeanic acid and rhodanine histochemical stains in serial sections of liver from white perch (Morone americana) with abnormal hepatic copper storage is described. Staining reactions correlated well with hepatic copper concentrations although the threshold was the most problematic for rhodanine and rubeanic acid. Orcein was positive at a lower concentration than the two other stains. Hepatocellular granules and macrophage centres increased in size and number with copper concentration and could be related to increased lysosomes, as described for other species.

Animals↗

PubMed1998

Copper toxicity and copper-zinc interactions in amphibian embryos.

The copper hazard was evaluated by means of a 7-day toxicity test with Bufo arenarum embryos. The LC50 and LC10 values from 24 to 168 h of exposure were approx. 0.085 and 0.05 mg Cu2+/1, respectively, while the LC90 resulted in 0.155 mg Cu2+/1 but in this case from 96 h onwards the LC90 diminished up to approx. 0.105 mg Cu2+/1. These data plotted as Toxicity Profiles (TOP) provide a better understanding of concentration and time-dependent thresholds. For instance, exposure threshold occurs within the first 24 h of treatment while for concentration thresholds LC10 and LC90 seem to be more meaningful than LC50 because the S.D. of this last value is overlapping those of LC10 and LC90 for most of the exposure period evaluated. Toxicity data corresponds to a pH of 6.8 which is normal for the maintaining media. Combined treatments of copper and zinc point out a beneficial effect of zinc proportional to the zinc concentration in the maintaining media, e.g. 100% of protection was achieved with 30 mg Zn2+/1 for a copper concentration exerting 90% of mortality. The presence of Cu2+ did not enhance Zn2+ toxicity. The results are discussed in terms of water quality criteria for wildlife and human health protection purposes.

Animals↗

PubMed2000

Concentrations of mercury, cadmium, lead and copper in fruiting bodies of edible mushrooms in an emission area of a copper smelter and a mercury smelter.

Four metals were determined by AAS techniques in 56 samples of 23 wild mushroom species collected in a heavily polluted area in eastern Slovakia in 1997 and 1998. The area has been contaminated from historical polymetallic ores mining and smelting and by emissions from a mercury smelter between 1969 and 1993 and from a copper smelter since 1951. No significant differences in metal concentrations (P < 0.05) were found in four species when comparing the periods 1992-1993 and 1997-1998. Considerable contamination of most species was observed mainly for mercury and cadmium. The highest levels of mercury, up to 50 mg kg-1 dry matter, were found in Boletus reticulatus, Lycoperdon perlatum and Marasmius oreades, and of cadmium up to 20 mg kg-1 dry matter in Xerocomus chrysenteron and Lycoperdon perlatum. The latter species also had extremely high lead and copper concentrations in hundreds of milligrams per kilogram dry matter. Concentrations of mercury and copper in caps of four Boletaceae species were significantly (P < 0.05) higher than those in stipes.

Agaricales↗

PubMed2003

Structural and functional models for the dinuclear copper active site in catechol oxidases. Synthesis, X-ray crystal structures, magnetic and spectroscopic properties of mu-methoxo-bridged dinuclear copper(II) complexes with N-substituted sulfonamide ligands.

Two new mu-methoxo-bridged dinuclear copper(II) complexes with a N-substituted sulfonamide, [Cu(mu-OMe)(L)(NH(3))](2) (1) and [Cu(mu-OMe)(L)(DMSO)](2) (2) [HL, N-2-(4-methylbenzothiazole)benzenesulfonamide], have been prepared and characterized by single-crystal X-ray difraction analyses. Compound 1 crystallizes in the monoclinic space group C(2)/c with a=22.0678(18), b=7.9134(7), c=21.1186(18)A, beta=113.788(4) degrees and Z=8. Compound 2 crystallizes in the monoclinic space group C(2)/c with a=18.0900(10), b=9.5720(10), c=24.2620(10) A, beta=98.7120(10) degrees and Z=8. In both complexes the copper atoms have square-planar environments bridged by two oxygen atoms from methoxide groups. Magnetic susceptibility measurements indicate a very strong antiferromagnetic coupling between the copper(II) ions in both complexes (2J<-1000 cm(-1)). Electronic Paramagnetic Resonance (EPR) spectra of the two complexes both in solid and in solution are silent. 13C NMR spectra of the complexes in solid state have been studied. The complexes have been evaluated as model systems for the catechol oxidase enzyme using 3,5-di-tert-butylcatechol as the test substrate. Complex 2 is slightly more active than complex 1.

Binding Sites↗

PubMed2002

Thermodynamics of ligand exchange reactions between bis(dithiocarbamato)copper(II) and copper(II) salts. An EPR study.

EPR spectroscopy was chosen to investigate the ligand exchange reactions between copper(II) bis(dithiocarbamate), Cu(dtc)2, and copper(II) salts which proceeds with the formation of mixed-ligand complexes of the type Cu(dtc)X, where X = Cl, NO3, ClO4. Large concentrations of 1:1 mixed-ligand complexes of this type are obtained as indicated by the EPR spectra of acetone, CHCl3/EtOH, CHCl3/i-PrOH, CCl4/EtOH and CCl4/i-PrOH, solutions of Cu(dtc)2 and the appropriate copper(II) salt CuCl2, Cu(NO3)2 or Cu(ClO4)2. Double integration of Cu(dtc)2 EPR signals obtained at temperatures between 240 and 310 K affords the calculation of the equilibrium constant (K) of the reaction: Cu(dtc)2 + CuX2 <==> 2 Cu(dtc)X in all solvents as a function of T. From the values of K the stability constant beta of the mixed-ligand complexes has been derived. The error associated with the calculated stability constant is +/- 10%. Thermodynamic parameters (deltaH0, deltaG0 and deltaS0) are determined from the temperature dependence of K as measured by EPR spectroscopy.

Chemistry, Physical↗

PubMed2006

Copper complexes of thiosemicarbazone-pyridylhydrazine (THYNIC) hybrid ligands: a new versatile potential bifunctional chelator for copper radiopharmaceuticals.

Two new thiosemicarbazone-pyridylhydrazine (THYNIC) hybrid ligands have been synthesized. Copper(II) and copper(I) complexes of the ligands have been prepared and characterized by X-ray crystallography. Cyclic voltammetry measurements show that the copper(II) complexes undergo quasi-reversible reductions at biologically accessible potentials. One of the ligands, bearing a pendant carboxylate arm, has been conjugated to N-alpha-(tert-butoxycarbonyl)-L-lysine.

Chelating Agents↗

PubMed2006

Crystal structure and thermochemical reactivity of an unusual copper complex that contains copper in four different coordination geometries.

According to X-ray single-crystal structure analysis, {[Cu(II)(en)2]2[Cu(I)2(CN)6]}[Cu(II)(en)2]2[Cu(I)(CN)3]2.2H2O contains copper in four different coordination environments: trigonal planar, square planar, square pyramidal and tetrahedral. The different coordination geometries of copper were investigated by quantum chemical calculations of model compounds, thus allowing to tentatively assign the different CN-bands in the IR spectrum. The thermolysis led to sub-microm sized rod-like copper(II) oxide particles.

Copper↗

PubMed1980

Optical properties of japanese-lacquer-tree (Rhus vernicifera) laccase depleted of type 2 copper(II). Involvement of type-2 copper(II) in the 330nm chromophore.

1. Spectroscopic and functional properties of Japanese-lacquer-tree (Rhus vernicifera) laccase were re-investigated, with special emphasis on the relationships between the different types of copper centres (Types 1, 2, and 3). 2. On removal of the Type 2 Cu(II), a decrease of absorbance occurred in the wavelength region above 650 nm (delta epsilon 750 = 300 M-1 . cm-1) and around 330 nm (delta episom 330 up to 2200 M-1 . cm-1). 3. Reductive titrations with ascorbic acid or ferrocyanide showed that the electron-accepting capacity of the partial apoprotein is one electron-equivalent lower than that of the native protein, i.e. the protein two-electron acceptor is present in the oxidized state in spite of absorbance loss at 330 nm. 4. The 330 nm chromophore apparently depends on the presence of both the Type 2 and the Type 3 copper in the oxidized state. 5. This finding may have implications in the relative location of Type 2 and 3 copper centres and on the redox behaviour of laccase.

Circular Dichroism↗

PubMed1983

Low-temperature resonance-Raman spectra of Japanese-lacquer-tree (Rhus vernicifera) laccase, type-2-copper-depleted laccase and H2O2-treated type-2-copper-depleted laccase.

Resonance-Raman spectra of Japanese-lacquer-tree (Rhus vernicifera) laccase, type-2-copper-depleted laccase and the latter form treated with H2O2 were measured in liquid and frozen solution, on excitation into the 600 nm absorption band. Significant changes in intensity and/or frequency of the bands lying in the 370-430 cm-1 region were observed on freezing, indicating local structural rearrangements taking place at the blue copper site. These findings corroborate previous suggestions based on e.p.r. measurements and redox data [Morpurgo, Calabrese, Desideri & Rotilio (1981) Biochem. J. 193, 639-642]. They show the strong dependence of the physical properties of blue copper centres on local symmetry. Some conclusions on the origin of the Raman bands are also drawn.

Cold Temperature↗

PubMed1984

Copper-phenanthroline-induced site-specific oxygen-radical damage to DNA. Detection of loosely bound trace copper in biological fluids.

Copper(II) ions, in the presence of 1,10-phenanthroline, O2 and a reducing agent, degrade DNA with the release of thiobarbituric-acid-reactive material. This reaction, dependent on the formation of oxygen radicals, was made the basis of a sensitive and specific assay for loosely bound copper in body fluids. When applied to certain extracellular fluids, trace amounts of copper could be detected in the lower micromolar range.

Binding Sites↗

PubMed2001

The Candida glabrata Amt1 copper-sensing transcription factor requires Swi/Snf and Gcn5 at a critical step in copper detoxification.

The yeast Candida glabrata rapidly autoactivates transcription of the AMT1 gene in response to potentially toxic copper levels through the copper-inducible binding of the Amt1 transcription factor to a metal response element (MRE) within a positioned nucleosome. Our previous studies have characterized the role of a 16 bp homopolymeric dA:dT DNA structural element in facilitating rapid Amt1 access to the AMT1 promoter nucleosomal MRE. In this study, we have used the genetically more facile yeast Saccharomyces cerevisiae to identify additional cellular factors that are important for promoting rapid autoactivation of the AMT1 gene in response to toxic copper levels. We demonstrate that the Swi/Snf nucleosome remodelling complex and the histone acetyltransferase Gcn5 are both essential for AMT1 gene autoregulation, and that the requirement for these chromatin remodelling factors is target gene specific. Chromatin accessibility measurements performed in vitro and in vivo indicate that part of the absolute requirement for these factors is derived from their involvement in facilitating nucleosomal access to the AMT1 promoter MRE. Additionally, these data implicate the involvement of Swi/Snf and Gcn5 at multiple levels of AMT1 gene autoregulation.

Acetylation↗

PubMed2001

Copper neurotoxicity is dependent on dopamine-mediated copper uptake and one-electron reduction of aminochrome in a rat substantia nigra neuronal cell line.

The mechanism of copper (Cu) neurotoxicity was studied in the RCSN-3 neuronal dopaminergic cell line, derived from substantia nigra of an adult rat. The formation of a Cu-dopamine complex was accompanied by oxidation of dopamine to aminochrome. We found that the Cu-dopamine complex mediates the uptake of (64)CuSO(4) into the Raúl Caviedes substantia nigra-clone 3 (RCSN3) cells, and it is inhibited by the addition of excess dopamine (2 m M) (63%, p < 0.001) and nomifensine (2 microM) (77%, p < 0.001). Copper sulfate (1 m M) alone was not toxic to RCSN-3 cells, but was when combined with dopamine or with dicoumarol (95% toxicity; p < 0.001) which inhibits DPNH and TPNH (DT)-diaphorase. Electron spin resonance (ESR) spectrum of the 5,5-dimethylpyrroline-N-oxide (DMPO) spin trap adducts showed the presence of a C-centered radical when incubating cells with dopamine, CuSO(4) and dicoumarol. A decrease in the expression of CuZn-superoxide dismutase and glutathione peroxidase mRNA was observed when RCSN-3 cells were treated with CuSO(4), dopamine, or CuSO(4) and dopamine. However, the mRNA expression of glutathione peroxidase remained at control levels when the cells were treated with CuSO(4), dopamine and dicoumarol. The regulation of catalase was different since all the treatments with CuSO(4) increased the expression of catalase mRNA. Our results suggest that copper neurotoxicity is dependent on: (i) the formation of Cu-dopamine complexes with concomitant dopamine oxidation to aminochrome; (ii) dopamine-dependent Cu uptake; and (iii) one-electron reduction of aminochrome.

Animals↗

PubMed2005

BACE1 cytoplasmic domain interacts with the copper chaperone for superoxide dismutase-1 and binds copper.

The amyloidogenic pathway leading to the production and deposition of Abeta peptides, major constituents of Alzheimer disease senile plaques, is linked to neuronal metal homeostasis. The amyloid precursor protein binds copper and zinc in its extracellular domain, and the Abeta peptides also bind copper, zinc, and iron. The first step in the generation of Abeta is cleavage of amyloid precursor protein by the aspartic protease BACE1. Here we show that BACE1 interacts with CCS (the copper chaperone for superoxide dismutase-1 (SOD1)) through domain I and the proteins co-immunoprecipitate from rat brain extracts. We have also been able to visualize the co-transport of membranous BACE1 and soluble CCS through axons. BACE1 expression reduces the activity of SOD1 in cells consistent with direct competition for available CCS as overexpression of CCS restores SOD1 activity. Finally, we demonstrate that the twenty-four residue C-terminal domain of BACE1 binds a single Cu(I) atom with high affinity through cysteine residues.

Amyloid Precursor Protein Secretases↗

PubMed2005

Removal of copper and copper-binding organic ligands during potable water treatment.

The concentrations and chemical speciation of copper before and after potable water treatment have been examined using 3 techniques: a copper ion-selective electrode (Cu-ISE), chemiluminescence (CL) and anodic stripping voltammetry (ASV), together with water quality parameters colour, turbidity and dissolved organic carbon (DOC). As expected, only a small fraction of colour (6.6-11%), turbidity (6.7-14%) and DOC (20%) remained after treatment. The removal of Cu and Cu-binding natural organic matter (NOM) was more variable but still significant: 17-64% of total dissolved Cu and 19-61% of Cu-binding NOM (as determined by ASV) remained after treatment. Labile Cu levels, as measured by CL, were 0-23% after treatment. The Cu-ISE titrations showed significant Cu-binding in raw water in the concentration range 10(-7) to 10(-6) mol l(-1) Cu2+, but very little binding after treatment. The results indicate that conventional water treatment has a significant effect on both total Cu levels and Cu-binding NOM, with implications for Cu2+ speciation and bio-availability, particularly in reticulation systems containing copper pipes.

Copper↗

PubMed1982

A randomized trial of copper therapy in rats with electrocardiographic abnormalities due to copper deficiency.

Abnormalities of the ECG were induced in rats by a diet deficient in copper. Abnormalities of the ST segment, bundle branch block, supraventricular beats, ventricular beats, and wandering pacemaker were found. Ventricular aneurysm, hemothorax, pleural effusion, cardiac rupture, and hemopericardium also occurred. Gross pathology and abnormal electrophysiology were not closely associated. Electrocardiograms of 12 rats were found to have abnormal ST segments. Rats with similar electrocardiographic abnormalities were assigned to pairs, one member of each pair was selected for treatment with copper by coin toss. Gross pathological findings of treated and untreated rats were similar. Treatment improved the survival of the group and the ECGs of four of the six. These findings were related to certain aspects of ischemic heart disease and to dietary copper in the industrialized part of the world.

Animals↗