Distribution by Scientific Domains
Distribution within Chemistry

Kinds of Copper

  • dinuclear copper
  • efficient copper
  • nanoporou copper
  • new copper
  • novel copper
  • serum copper
  • tetranuclear copper
  • trace copper
  • trinuclear copper

  • Terms modified by Copper

  • copper Nanoparticle
  • copper accumulation
  • copper age
  • copper atom
  • copper binding
  • copper catalysis
  • copper catalyst
  • copper center
  • copper centre
  • copper chaperone
  • copper chloride
  • copper complex
  • copper concentration
  • copper content
  • copper coordination polymer
  • copper cylinder
  • copper deficiency
  • copper deposit
  • copper deposition
  • copper electrode
  • copper excess
  • copper exposure
  • copper film
  • copper foil
  • copper halide
  • copper hydroxide
  • copper intake
  • copper ion
  • copper level
  • copper metabolism
  • copper metal
  • copper mine
  • copper nanoparticle
  • copper ore
  • copper oxide
  • copper phthalocyanine
  • copper plate
  • copper powder
  • copper protein
  • copper salt
  • copper site
  • copper speciation
  • copper species
  • copper stress
  • copper substrate
  • copper sulphate
  • copper surface
  • copper toxicity

  • Selected Abstracts

    Aerobic Oxidation of Benzylic Alcohols in Water by 2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO)/Copper(II) 2- N -Arylpyrrolecarbaldimino Complexes


    Abstract Novel copper(II) 2- N -arylpyrrolecarbaldimine-based catalysts for the aerobic oxidation of benzylic alcohols mediated by the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical are reported. The catalytic activity for both synthesized and in situ made complexes in alkaline water solutions was studied revealing high efficiency and selectivity (according to GC selectivity always >99%) for both of these catalytic systems. For example, quantitative conversion of benzyl alcohol to benzaldehyde can be achieved with the in situ prepared bis[2- N -(4-fluorophenyl)-pyrrolylcarbaldimide]copper(II) catalysts in 2,h with atmospheric pressure of O2 at 80,°C. Interestingly, these catalysts can utilize dioxygen as well as air or hydrogen peroxide as the end oxidants, producing water as the only by-product. [source]

    Asymmetric Nazarov Reaction Catalyzed by Chiral Tris(oxazoline)/Copper(II),

    ANGEWANDTE CHEMIE, Issue 26 2010
    Peng Cao Dr.
    In Gegenwart eines dreizähnigen Liganden führte die Titelreaktion hoch effizient zu chiralen O-Heterohexahydroindenonen. Die Produkte wurden mit ausgezeichneten Ausbeuten, Enantio- und Diastereoselektivitäten erhalten. HFIP=Hexafluor-2-propanol, BArF= Tetrakis[3,5-bis(trifluormethyl)phenyl]borat. [source]

    ChemInform Abstract: Copper(II)/Copper(I)-Catalyzed Aza-Michael Addition/Click Reaction of in situ Generated ,-Azidohydrazones: Synthesis of Novel Pyrazolone,Triazole Framework.

    CHEMINFORM, Issue 26 2010
    Orazio A. Attanasi
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

    ChemInform Abstract: Aerobic Palladium(II)/Copper(II)-Catalyzed Oxidation of Olefins under Chloride-Free Nonacidic Conditions.

    CHEMINFORM, Issue 39 2009
    Marcelo G. Speziali
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

    Ligand-Accelerated Asymmetric [1,2]-Stevens Rearrangment of Sulfur Ylides via Decomposition of Diazomalonates Catalyzed by Chiral Bisoxazoline/Copper Complex

    Jian-Ping Qu
    Abstract The first example of catalytic asymmetric [1,2]-Stevens rearrangement reaction of 1,3-oxathiolanes with diazomalonates has been developed and up to 90% ee is achieved by the bisoxazoline 4e/copper(II) triflate [Cu(OTf)2] complex. [source]

    Copper-catalyzed ascorbate oxidation results in glyoxal/AGE formation and cytotoxicity

    Nandita Shangari
    Abstract Previously we showed that 10 ,M glyoxal compromised hepatocyte resistance to hydrogen peroxide (H2O2) by increasing glutathione (GSH) and NADPH oxidation and decreasing mitochondrial membrane potential (MMP) before cytotoxicity ensued. Since transition metal-catalyzed oxidation of ascorbate (Asc) has been shown to result in the generation of both glyoxal and H2O2, we hypothesized that glyoxal formation during this process compromises hepatocyte resistance to H2O2. We used isolated rat hepatocytes and incubated them with Asc/copper and measured cytotoxicity, glyoxal levels, H2O2, GSH levels, and MMP. To investigate the role of Asc/copper on glyoxal-BSA adducts, we measured the appearance of advanced glycation end-products (AGE) in the presence and absence of catalase or aminoguanidine (AG). Asc/copper increased glyoxal and H2O2 formation. Hepatocyte GSH levels were decreased and cytotoxicity ensued after a collapse of the hepatocyte MMP. Glyoxal traps protected hepatocytes against Asc/copper-induced cytotoxicity. In cell-free studies with BSA, incubation with Asc and copper resulted in glyoxal-hydroimidazolone formation, which was decreased by both AG and catalase. To the best of our knowledge, this is the first study that illustrates the importance of glyoxal production by transition metal-catalyzed Asc autoxidation. Understanding this mechanism of toxicity could lead to the development of novel copper chelating drug therapies to treat diabetic complications. [source]

    COPPER: Price to Consolidate?

    Article first published online: 4 JUN 2010
    No abstract is available for this article. [source]


    JOURNAL OF PHYCOLOGY, Issue 2 2002
    Helena Guasch
    Two sets of experiments were done to quantify the effects of chronic copper exposure on natural peri- phyton in a nonpolluted calcareous river. The results of short-term (up to 6 h exposure) experiments corroborated the significance of pH on copper toxicity. Copper toxicity increased when pH was reduced from 8.6 to 7.7, and this was related to the effect of pH on copper speciation (free copper concentration increased from 0.2% to 2.3% of total copper). Longer term experiments demonstrated that periphyton communities exposed to copper under pH variation (8.2,8.6) were already affected at 10 ,g·L,1 (20,80 ng·L,1 Cu2+) after 12 days of exposure. Copper exposure caused stronger effects on structural (algal biomass and community structure) than on functional (photosynthetic efficiency) parameters of peri- phyton. Changes in community composition included the enhancement of some taxa (Gomphonema gracile), the inhibition of others (Fragilaria capucina and Phormidium sp.), and the appearance of filament malformations (Mougeotia sp.). The results of our study demonstrated that several weeks of exposure to copper (10,20 ,g·L,1) were sufficient to cause chronic changes in the periphyton of oligotrophic calcareous rivers. This degree of copper pollution can be commonly found in the Mediterranean region as a result of agricultural practices and farming activities. [source]


    JOURNAL OF PHYCOLOGY, Issue 2 2002
    Ana T. Lombardi
    The purpose of the present investigation was to evaluate possible ecological and physiological functions of mucilaginous capsules produced by the freshwater algae Kirchneriella aperta Teiling (Chlorococcales) as related to copper ions. All experiments were performed using synthetic media under laboratory-controlled conditions. Copper interactions were investigated by distinguishing between adsorption onto the mucilaginous material present at the surface of the cells, intracellular uptake, and differentiation between total dissolved copper and free copper ions in the culture medium. Kirchneriella aperta is sensitive to copper, as revealed by a 96-h EC50 value of 10,9.22 M Cu2+. We demonstrated that the mucilaginous capsules were able to sequester copper ions from the medium through a passive mechanism, thus providing the cell with a mechanism able to postpone the toxic effects of copper. The organic material that diffuses into the test medium as well as the mucilaginous capsules produced by K. aperta both effectively complex copper; thus, toxicity must be related to free copper ions and not the total dissolved copper concentration in the medium. [source]


    Andrea M. Dietrich
    ABSTRACT: Inputs of copper-based crop protectants from tomato fields grown under plastic mulch agriculture (plasticulture) to an estuarine creek were investigated. Copper was measured in runoff from diverse land-uses including conventional agriculture, plasticulture, residences, and natural areas. Water column and sediment copper concentrations were measured in plasticulture and control (nonagriculture) watersheds. Copper concentrations in plasticulture-impacted creeks exceeded background levels episodically. High concentrations occurred during or immediately after runoff-producing rains. Concentrations of 263 ,g/L total copper and 126 ,g/L dissolved copper were measured in a tidal creek affected by plasticulture; concentrations exceeded the shellfish LC50 values and the water quality criteria of 2.9 ,g/L dissolved copper. Control watersheds indicated background water column levels of , 4 ,g/L dissolved copper with similar copper levels during periods with and without rain. The copper concentrations in tomato plasticulture field runoff itself contained up to 238 ,g/L dissolved copper. Copper concentrations in runoff from other land-uses were less than 5 ,g/L dissolved copper. Creek sediment samples adjacent to a plasticulture field contained significantly higher copper concentrations than sediments taken from nonplasticulture watersheds. [source]

    Efficient Chiral N-Heterocyclic Carbene/Copper(I)-Catalyzed Asymmetric Allylic Arylation with Aryl Grignard Reagents,

    ANGEWANDTE CHEMIE, Issue 46 2009
    Gamma ist entscheidend: Die Titelreaktion gelang hoch regioselektiv mit Aryl-Grignard-Reagentien und einem Kupfer(I)-Katalysator mit einzähnigem chiralem N-heterocyclischem Carbenliganden und lieferte Diarylvinylmethane mit ausgezeichnetem Enantiomerenüberschuss und in hoher Ausbeute (siehe Schema). [source]

    ChemInform Abstract: Efficient Chiral N-Heterocyclic Carbene/Copper(I)-Catalyzed Asymmetric Allylic Arylation with Aryl Grignard Reagents.

    CHEMINFORM, Issue 10 2010
    Khalid B. Selim
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

    Differential Pulse Anodic Stripping Voltammetric Simultaneous Determination of Copper(II) and Silver(I) with Bis(2-hydroxyacetophenone) Butane-2,3-dihydrazone Modified Carbon Paste Electrodes

    ELECTROANALYSIS, Issue 19 2010
    M. B. Gholivand
    Abstract The behavior of a modified carbon paste electrode (CPE) for simultaneous determination of copper(II) and silver(I) by anodic adsorptive stripping voltammetry (ASV) was studied. The electrode was built incorporating the bis(2-hydroxyacetophenone) butane-2,3-dihydrazone (BHAB) as a complexing agent to a Nujol-graphite base paste. The resulting electrode demonstrated linear responses over the range of Cu(II) and Ag(I) concentrations 0.1,20 and 0.01,2.0,µM respectively. The relative standard deviation (RSD) for the determination of 5.0,µM of both metal ions were 2.9 and 3.1,% for Cu(II) and Ag(I), respectively. The method has been applied to the analysis of copper in wheat and barley seed samples and silver in developed radiological film. [source]

    Simultaneous Determination of Cadmium, Lead, Copper and Mercury Ions Using Organofunctionalized SBA-15 Nanostructured Silica Modified Graphite,Polyurethane Composite Electrode

    ELECTROANALYSIS, Issue 1 2010
    Ivana Cesarino
    Abstract A new sensor has been developed for the simultaneous detection of cadmium, lead, copper and mercury, using differential pulse and square wave anodic stripping voltammetry (DPASV and SWASV) at a graphite,polyurethane composite electrode with SBA-15 silica organofunctionalized with 2-benzothiazolethiol as bulk modifier. The heavy metal ions were preconcentrated on the surface of the modified electrode at ,1.1,V vs. SCE where they complex with 2-benzothiazolethiol and are reduced to the metals, and are then reoxidized. Optimum SWASV conditions lead to nanomolar detection limits and simultaneous determination of Cd2+, Pb2+, Cu2+ and Hg2+ in natural waters was achieved. [source]

    Interference from Trace Copper in Electrochemical Investigations Employing Carboxylic Acid Terminated Thiol Modified Gold Electrodes

    ELECTROANALYSIS, Issue 6 2009
    Xiaohu Qu
    Abstract Unexpectedly, electrochemistry at variable chain length carboxylic acid terminated alkylthiol self-assembled monolayers (SAMs) on gold electrodes gives rise to a Faradaic process in buffered aqueous electrolyte solution. In particular, the three-carbon chain length, 3-mercaptopropionic acid (MPA), exhibits a chemically reversible process with a mid-point potential of 175,mV vs. Ag/AgCl under conditions of cyclic voltammetry. This process is associated with the presence of trace (parts per billion) amounts of copper(II) ions present in the chemical reagents used to prepare the aqueous electrolyte and also from the gold electrode itself. The carboxylic acid moiety on the SAM concentrates Cu2+ ions by coordination and this surface confined layer is then reduced. Methods to minimize the interference of Cu2+ ions at carboxylic acid terminated SAM are discussed and caution with respect to the interpretation of protein electrochemistry is recommended when using carboxylic acid functionalized SAMs to provide biocompatible electrochemical transduction surfaces, unless a metal free environment can be obtained. [source]

    Simultaneous Quantitative Determination of Cadmium, Lead, and Copper on Carbon-Ink Screen-Printed Electrodes by Differential Pulse Anodic Stripping Voltammetry and Partial Least Squares Regression

    ELECTROANALYSIS, Issue 23 2008
    Michael Cauchi
    Abstract Water is a vital commodity for every living entity on the planet. However, water resources are threatened by various sources of contamination from pesticides, hydrocarbons and heavy metals. This has resulted in the development of concepts and technologies to create a basis for provision of safe and high quality drinking water. This paper focuses on the simultaneous quantitative determination of three common contaminants, the heavy metals cadmium, lead and copper. Multivariate calibration was applied to voltammograms acquired on in-house printed carbon-ink screen-printed electrodes by the highly sensitive electrochemical method of differential pulse anodic stripping voltammetry (DPASV). The statistically inspired modification of partial least squares (SIMPLS) algorithm was employed to effect the multivariate calibration. The application of data pretreatment techniques involving range-scaling, mean-centering, weighting of variables and the effects of peak realignment are also investigated. It was found that peak realignment in conjunction with weighting and SIMPLS led to the better overall root mean square error of prediction (RMSEP) value. This work represents significant progress in the development of multivariate calibration tools in conjunction with analytical techniques for water quality determination. It is the first time that multivariate calibration has been performed on DPASV voltammograms acquired on carbon-ink screen-printed electrodes. [source]

    Renewable Copper and Silver Amalgam Film Electrodes of Prolonged Application for the Determination of Elemental Sulfur Using Stripping Voltammetry

    ELECTROANALYSIS, Issue 7 2008
    Robert Piech
    Abstract New, renewable copper (Hg(Cu)FE) and silver (Hg(Ag)FE) based amalgam film electrodes applied for the determination of elemental sulfur using differential pulse cathodic stripping voltammetry are presented. With surface areas adjustable from 1 to 12,mm2, both electrodes are characterized by very good surface reproducibility (,2%) and long-term stability (a few thousand measurement cycles). The mechanical refreshing of the amalgam film takes about 1,2 seconds. The effects of various factors such as instrumental parameters and the supporting electrolyte composition were optimized. Interferences from sulfides are easily removed by the addition of acid, and bubbling with argon, for Hg(Ag)FE. In the case of Hg(Cu)FE, sulfides did not interfere. The calibration graph is linear within the studied range from 16,ng L,1 to 4.8,,g L,1 for Hg(Cu)FE, and up to 6.4,,g L,1 for Hg(Ag)FE (tacc=15,s). The correlation coefficients for the two electrodes were at least 0.997. The detection limits for a low concentration of S(0) and tacc=60,s are as low as 14,ng L,1 for Hg(Cu)FE and 4,ng L,1 for Hg(Ag)FE. The proposed method was successfully applied and validated by studying the recovery of S(0) from spiked river water. [source]

    DNA Determination in the Presence of Copper in Diluted Alkaline Electrolyte by Adsorptive Stripping Voltammetry at the Mercury Film Electrode

    ELECTROANALYSIS, Issue 11 2007
    Augusto, Mardini Farias, Percio
    Abstract A stripping method for the determination of single-stranded DNA in presence of copper at the submicromolar concentration levels is described. The method is based on controlled adsorptive accumulation of adenine (from acid-treated DNA) at thin-film mercury electrode followed by linear scan voltammetry measurement of the surface species. Optimum experimental conditions were found to be the use of a 5.0×10,3,M NaOH solution, an accumulation potential of ,0.40,V and a scan rate of 200,mV s,1. The response of adenine,copper is linear over the concentration range 50,250,ppb. For an accumulation time of 15,minutes, the detection limit was found to be 4,ppb. The more convenient relation to measuring the ssDNA in presence of metals and nitrogenated bases were also investigated. The utility of the method is demonstrated by the presence of adenosine-triphosphate (ATP) and amino acids. [source]

    Determination of Trace Amounts of Copper in Tap Water Samples with a Calix[4]arene Modified Carbon Paste Electrode by Differential Pulse Anodic Stripping Voltammetry

    ELECTROANALYSIS, Issue 10 2007
    Çelik Canpolat
    Abstract A calix[4]arene modified carbon paste electrode was used for trace determination of copper. The study of the preconcentration of copper as well as the other heavy metal ions at the modified electrode, with subsequent measurement by differential pulse anodic stripping voltammetry (DPASV), indicates the efficient open-circuit accumulation of the analytes onto the electrode. Many parameters such as the composition of the paste, pH, preconcentration time and stirring rate influence the response of the measurement. The procedure was optimized for copper determination. For a 10-minute preconcentration time at pH,6.5,7.5, the detection limit (LOD) was 1.1,,g L,1. The optimized method was successfully applied to the determination of copper in tap water sample by means of standard addition procedure. The copper content of the sample was comparable with the result obtained with AAS method. [source]

    Enhanced Resolution of Copper and Bismuth by Addition of Gallium in Anodic Stripping Voltammetry with the Bismuth Film Electrode

    ELECTROANALYSIS, Issue 24 2006
    Chad Prior
    Abstract This paper presents the enhanced analysis of copper on a bismuth electrode upon addition of gallium(III). The presence of gallium alleviates the problems of overlapping stripping signals usually observed between copper and bismuth when using the Bismuth Film Electrode. In addition, it has been found that the presence of gallium improves the reproducibility of the bismuth stripping signal. Simultaneous deposition of copper and bismuth at ,1500,mV for 2,minutes in a supporting electrolyte composed of 0.1,M pH,4.75 acetate buffer with 250,,g L,1 gallium yields well resolved copper and bismuth signals when analyzed with square-wave anodic stripping voltammetry. Simultaneous analysis of copper and lead yielded linear calibration plots in the range 10 to 100,,g L,1 with regression coefficients of 0.997 and 0.994 respectively. The theoretical detection limit for copper was calculated to be 4.98,,g L,1 utilizing a 2,minutes deposition time. The relative standard deviation for a copper concentration of 50,,g L,1 was 1.6% (n=10). [source]

    Simultaneous Determination of Copper and Bismuth by Anodic Stripping Voltammetry Using H-Point Standard Addition Method with Simultaneous Addition of Analytes

    ELECTROANALYSIS, Issue 17 2005
    Esmaeil Shams
    Abstract Simultaneous determination of bismuth and copper by anodic stripping voltammetry using H-point standard addition method (HPSAM) with simultaneous addition of analytes is described. The effect of various parameters including acid concentration, accumulation time, accumulation potential and concentration ratio of analytes in the standard solution on the sensitivity and accuracy of method were investigated. The results of applying the H-point standard addition method showed that Cu2+ and Bi3+ could be determined simultaneously with the concentration ratios of Cu2+ to Bi3+ varying from 1,:,15 to 16,:,1 in the mixed sample. The method was successfully applied to the simultaneous determination of copper and bismuth in some synthetic mixtures. [source]

    Evaluation of Cu,Ethylenediamine Metal Ion Buffers as Calibrants for Ion-Selective Electrode Measurement of Copper in Fresh Water Systems

    ELECTROANALYSIS, Issue 10 2005
    Ling Zeng
    Abstract An investigation was made into the accuracy of cupric ion selective electrode (ISE) measurement of Cu in solutions approximating acidic freshwaters with Cu-ethylenediamine buffers used as the calibrants. This method overestimates the free Cu compared with calibration using Cu(NO3)2 standards, the standard addition method, and speciation modelling calculations. Statistical tests showed a small, but significant, difference between the intercepts of the linear Nernstian regressions of the calibration plots of Cu-en buffer standardisation and direct calibration with Cu(NO3)2 standards in matrix that matches the samples. The difference in the intercepts, which corresponds with Eo values of the electrode, is not well understood, but is possibly caused by potentially interfering cations such as Fe2+. The results of this study showed that down to 10,8,M Cu2+, where a linear Nernstian response is possible, the Cu ISE is probably better calibrated using Cu standards prepared in the same matrix as the sample solutions to avoid potential matrix effects. [source]

    Heavy Metals in Matrices of Food Interest: Sequential Voltammetric Determination at Trace and Ultratrace Level of Copper, Lead, Cadmium, Zinc, Arsenic, Selenium, Manganese and Iron in Meals

    ELECTROANALYSIS, Issue 18 2004
    Clinio Locatelli
    Abstract The voltammetric methods are very suitable and versatile techniques for the simultaneous metal determination in complex matrices. The present work, regarding the sequential determination of Cu(II), Pb(II), Cd(II), Zn(II) by square-wave anodic stripping voltammetry (SWASV), As(III), Se(IV) by square-wave cathodic stripping voltammetry (SWCSV) and Mn(II), Fe(III) by square-wave voltammetry (SWV) in matrices involved in foods and food chain as wholemeal, wheat and maize meal, are an interesting example of the possibility to sequentially determine each single element in real samples. Besides the set up of the analytical method, particular attention is aimed either at the problem of possible signal interference or to show that, using the peak area Ap as instrumental datum, it is possible to achieve lower limits of detection. The analytical procedure was verified by the analysis of the standard reference materials: Wholemeal BCR-CRM 189, Wheat Flour NIST-SRM 1567a and Rice Flour NIST-SRM 1568a. Precision, as repeatability, and accuracy, expressed as relative standard deviation and relative error, respectively, were lower than 6% in all cases. In the presence of reciprocal interference, the standard addition method considerably improved the resolution of the voltammetric technique. Once set up on the standard reference materials, the analytical procedure was transferred and applied to commercial meals sampled on market for sale. A critical comparison with spectroscopic measurements is also discussed. [source]

    Copper impregnated mesoporous activated carbon as a high efficient catalyst for the complete destruction of pathogens in water,

    L. John Kennedy
    Abstract Copper impregnated mesoporous activated carbon catalyst was applied for the elimination of microorganisms in wastewater. The antibacterial activity of the catalyst was determined qualitatively by testing the removal of pathogens in water after contacting with the catalyst. Escherichia coli, Shigella flexneri, Shigella dysenteriae, Shigella sonnei, and Salmonella typhi were taken as the model pathogens in determining the antimicrobial activity of the catalyst. The catalyst developed for this purpose was thoroughly characterized using instrumental techniques such as BET analysis, X-ray diffraction, FTIR spectroscopy, and scanning electron microscope to determine the pore and surface area, structural phases, surface functional groups, and surface morphology respectively. The energy dispersive X-ray analysis carried out confirmed qualitatively the percentage of copper impregnated in the catalyst. The experimental studies revealed that the catalyst was highly efficient and advantageous to be employed for industrial applications because of the nonleacheablity of copper from the catalyst and nonreoccurrence of the pathogens in the treated water. The transmission electron microscopy evidenced the complete cell wall rupture of the microorganisms. All the experimental results revealed that the copper impregnated mesoporous activated carbon exhibited a strong and long term antibacterial activity throughout the studies for repeated cycles. © 2007 American Institute of Chemical Engineers Environ Prog, 2008 [source]

    Development of a daphnia magna DNA microarray for evaluating the toxicity of environmental chemicals

    Hajime Watanabe
    Abstract Toxic chemical contaminants have a variety of detrimental effects on various species, and the impact of pollutants on ecosystems has become an urgent issue. However, the majority of studies regarding the effects of chemical contaminants have focused on vertebrates. Among aquatic organisms, Daphnia magna has been used extensively to evaluate organism- and populationlevel responses of invertebrates to pollutants in acute toxicity or reproductive toxicity tests. Although these types of tests can provide information concerning hazardous concentrations of chemicals, they provide no information about their mode of action. Recent advances in molecular genetic techniques have provided tools to better understand the responses of aquatic organisms to pollutants. In the present study, we adapted some of the techniques of molecular genetics to develop new tools, which form the basis for an ecotoxicogenomic assessment of D. magna. Based on a Daphnia expressed sequence tag database, we developed an oligonucleotide-based DNA microarray with high reproducibility. The DNA microarray was used to evaluate gene expression profiles of neonatal daphnids exposed to several different chemicals: Copper sulfate, hydrogen peroxide, pentachlorophenol, or ,-naphthoflavone. Exposure to these chemicals resulted in characteristic patterns of gene expression that were chemical-specific, indicating that the Daphnia DNA microarray can be used for classification of toxic chemicals and for development of a mechanistic understanding of chemical toxicity on a common freshwater organism. [source]

    Biological significance of metals partitioned to subcellular fractions within earthworms (Aporrectodea caliginosa),

    Martina G. Vijver
    Abstract Metal ions in excess of metabolic requirements are potentially toxic and must be removed from the vicinity of important biological molecules to protect organisms from adverse effects. Correspondingly, metals are sequestrated in various forms, defining the accumulation pattern and the magnitude of steady-state levels reached. To investigate the subcellular fractions over which Ca, Mg, Fe, Cu, Zn, Cd, Pb, Ni, and As are distributed, earthworms (Aporrectodea caliginosa) collected from the field were analyzed by isolating metal-rich granules and tissue fragments from intracellular microsomal and cytosolic fractions (i.e., heat-stable proteins and heat-denatured proteins). The fractions showed metal-specific binding capacity. Cadmium was mainly retrieved from the protein fractions. Copper was equally distributed over the protein fraction and the fraction comprising tissue fragments, cell membranes, and intact cells. Zinc, Ca, Mg, and As were mainly found in this fraction as well. Lead, Fe, and Ni were mainly isolated from the granular fraction. To study accumulation kinetics in the different fractions, three experiments were conducted in which earthworms were exposed to metal-spiked soil and a soil contaminated by anthropogenic inputs and, indigenous earthworms were exposed to field soils. Although kinetics showed variation, linear uptake and steady-state types of accumulation patterns could be understood according to subcellular compartmentalization. For risk assessment purposes, subcellular distribution of metals might allow for a more precise estimate of effects than total body burden. Identification of subcellular partitioning appears useful in determining the biological significance of steady-state levels reached in animals. [source]

    Transfer of Cd, Cu, Ni, Pb, and Zn in a soil-plant-invertebrate food chain: A microcosm study,

    Renaud Scheifler
    Abstract The transfer of Cd, Cu, Ni, Pb, and Zn was evaluated in a soil-plant (lettuce, Lactuca sativa),invertebrate (snail, Helix aspersa) food chain during a microcosm experiment. Two agricultural soils, polluted and unpolluted, were studied. Lettuce was cultivated for eight weeks before introduction of snails into the microcosms (M-snails). In a parallel experiment, snails were exposed to lettuce only (i.e., without soil) in simpler exposure devices called containers (C-snails). Snail exposure duration was eight weeks for both M- and C-snails. No effects on snail survival were found. Both M- and C-snails exposed to polluted soil showed a growth reduction, but only after two weeks of exposure. Time-dependent accumulation in M-snails exposed to the polluted environment showed a regular increase of Cd and Zn concentrations over time and a rapid increase of Pb concentrations within the first two weeks, which then remained stable. Copper and Ni concentrations did not increase during any of the experiments. Concentrations in M- and C-snails were compared to estimate the relative contribution of soil and plant to the total bioaccumulation. The results suggest that the soil contribution may be higher than 80% for Pb, from 30 to 60% for Zn, and from 2 to 40% for Cd. [source]

    Effects of metal and organophosphate mixtures on Ceriodaphnia dubia survival and reproduction

    Amy M. Mahar
    Abstract The toxicity of mixtures of copper, zinc, and diazinon were determined for Ceriodaphnia dubia using 7-d survival and reproduction tests. Fifteen treatments, including combinations of the chemicals at 0, 25, 50, 75, and 100% of their individual median lethal concentrations, adding up to one toxic unit (TU) were tested. The TU was then used to classify each mixture response as additive, greater than additive, or less than additive. For survival, additive responses occurred in the 75% zinc plus 25% diazinon and the 50% copper plus 25% zinc plus 25% diazinon treatments. For reproduction, additive responses occurred in the 75% copper plus 25% zinc, 75% copper plus 25% diazinon, and 75% zinc plus 25% diazinon treatments. Copper and zinc played a greater role in toxicity than diazinon did. Less-than-additive interactions were found in all remaining mixtures, perhaps because of differences in mode of action between diazinon and metals. Consideration of dose-response curves can help to explain inconsistencies regarding toxic response in treatments with different ratios of the same chemicals. As TU percentages changed, mixture components were taken from different locations on differently shaped dose-response curves. Because most responses were less than additive, however, water-quality criteria based on individual concentrations probably are protective for most metal-organophosphate mixtures. [source]

    Association of heavy metals with metallothionein and other proteins in hepatic cytosol of marine mammals and seabirds

    Tokutaka Ikemoto
    Abstract Distribution of Cu, Zn, Cd, Ag, Hg, and Se were determined in hepatocytosol of northern fur seals (Callorhinus ursinus), black-footed albatrosses (Diomedea nigripes), and Dall's porpoises (Phocoenoides dalli). Copper, Zn, and Cd were accumulated preferentially in metallothionein (MT) fraction and their contents in MT fraction increased with the amounts in the hepatocytosol. Silver was bound to both high-molecular-weight substances (HMWS) and MT in the hepatocytosol for all three species, whereas the distribution of Ag in the cytosol was different among the three species. In northern fur seals, Ag mainly was bound to MT, whereas it mainly was associated with HMWS in Dall's porpoises. In contrast, Ag was distributed almost equally in both HMWS and MT for black-footed albatrosses. Mercury content in HMWS and Se content in HMWS and low-molecular-weight substances (LMWS) increased with their contents in hepatocytosol for all the three species. A significant positive correlation was found between Se and Hg contents in high-molecular weight (HMW) fraction in cytosol. The molar ratio of Hg and Se was close to unity in HMW fraction of the specimens with high Hg concentration in cytosol, implying that the Hg,Se complex was bound to the HMWS. Analysis of metals in the hepatocytosol by high-performance liquid chromatography/inductively coupled plasma,mass spectrometry (HPLC/ICP-MS) suggests that multiple isoforms of MT are present in hepatocytosol of the three species and that the metal profiles in hepatocytosols are different among the species. To our knowledge, this is the first report on the association of Ag with HMWS and MT in hepatocytosol of marine mammals and seabirds. Also, distribution and interaction of Hg and Se were investigated for the first time in hepatocytosol of the higher trophic marine animals. [source]

    Use of vegetative furrows to mitigate copper loads and soil loss in runoff from polyethylene (plastic) mulch vegetable production systems

    Pamela J. Rice
    Abstract The transport of runoff with high copper concentrations and sediment loads into adjacent surface waters can have adverse effects on nontarget organisms as a result of increased turbidity and degraded water quality. Runoff from vegetable production utilizing polyethylene mulch can contain up to 35% of applied copper, a widely used fungicide/bactericide that has adverse effects on aquatic organisms. Copper is primarily transported in runoff with suspended particulates; therefore, implementation of management practices that minimize soil erosion will reduce copper loads. Replacing bare-soil furrows with furrows planted in rye (Secale cereale) significantly improved the sustainability of vegetable production with polyethylene mulch and reduced the potential environmental impact of this management practice. Vegetative furrows decreased runoff volume by >40% and soil erosion by >80%. Copper loads with runoff were reduced by 72% in 2001, primarily as a result of reduced soil erosion since more than 88% of the total copper loads were transported in runoff with suspended soil particulates. Tomato yields in both years were similar between the polyethylene mulch plots containing either bare-soil or vegetative furrows. Replacing bare-soil furrows with vegetative furrows greatly reduces the effects of sediments and agrochemicals on sensitive ecosystems while maintaining crop yields. [source]