Search results for "COPP"
showing 10 items of 3147 documents
Selective recognition of fluoride anion in water by a copper(II) center embedded in a hydrophobic cavity
2014
The ability of a water-soluble pentacationic calix[6]arene-based CuII complex to bind anions in water has been explored. Quite remarkably, the complex exhibits strong and selective fluoride binding in the pH range of 6–7. The binding constant at pH 5.9 was evaluated to be 85 000 M−1, which is one of the highest values ever reported for a fluoride probe in water and at this pH. The complex also binds chloride ions, but 1000 times less efficiently. The combination of the calix[6]arene hydrophobic cavity with the CuII complex, presenting its labile site in the endo position, is the reason for the selective recognition process. The single crystal X-ray structure of the organo-soluble parent com…
Catalytic reduction of nitrates and nitrites in water solution on pumice-supported Pd–Cu catalysts
2000
Abstract Two series of pumice-supported palladium and palladium–copper catalysts, prepared by impregnation with different palladium and copper precursors, were tested for the hydrogenation of aqueous nitrate and nitrite solutions. Measurements were performed in a stirred tank reactor, operating in batch conditions, in buffered water solution at atmospheric pressure and at 293 K. The activities of the catalysts were calculated in terms of nitrate and/or nitrite removal. With the monometallic Pd/pumice, the reduction of nitrite is highly selective; only 0.2% of the initial nitrite content is converted to ammonium ions. The activity in terms of turn over frequency (TOF) is higher as compared t…
ChemInform Abstract: Synthesis and Magnetic Properties of Bis(μ-hydroxo)bis((2,2′-bipyridyl)copper(II)) Squarate. Crystal Structure of Bis(μ-hydroxo)…
1990
Abstract The compound [Cu2(bipy)2(OH)2](C4O4)·5.5H2O, where bipy and C4O42− correspond to 2,2′-bipyridyl and squarate (dianion of 3,4-dihydroxy-3-cyclo- butene-1,3-dione) respectively, has been synthesized. Its magnetic properties have been investigated in the 2–300 K temperature range. The ground state is a spin-triplet state, with a singlet-triplet separation of 145 cm−1. The EPR powder spectrum confirms the nature of the ground state. Well-formed single crystals of the tetrahydrate, [Cu2(bipy)2(OH)2](C4O4)·4H2O, were grown from aqueous solutions and characterized by X-ray diffraction. The system is triclinic, space group P 1 , with a = 9.022(2), b = 9.040(2), c = 8.409(2) A, α = 103.51(2…
Temporal aspects of copper homeostasis and its crosstalk with hormones
2015
To cope with the dual nature of copper as being essential and toxic for cells, plants temporarily adapt the expression of copper homeostasis components to assure its delivery to cuproproteins while avoiding the interference of potential oxidative damage derived from both copper uptake and photosynthetic reactions during light hours. The circadian clock participates in the temporal organization of coordination of plant nutrition adapting metabolic responses to the daily oscillations. This timely control improves plant fitness and reproduction and holds biotechnological potential to drive increased crop yields. Hormonal pathways, including those of abscisic acid, gibberellins, ethylene, auxin…
The role of post-transcriptional modulators of metalloproteins in response to metal deficiencies
2021
Copper and iron proteins play a wide range of functions in living organisms. Metal assembly into metalloproteins is a complex process, where mismetalation is detrimental and energy-consuming to cells. Under metal deficiency, metal distribution is expected to reach a metalation ranking, prioritizing essential versus dispensable metalloproteins, while avoiding interferences with other metals and protecting metal-sensitive processes. In this review, we propose that posttranscriptional Modulators of Metalloprotein messenger RNA (ModMeR) are good candidates in metal prioritization under metal-limited conditions. ModMeR target high quota or redundant metalloproteins and, by adjusting their synthe…
Comparison of global responses to mild deficiency and excess copper levels in Arabidopsis seedlings
2013
[EN] Copper is an essential micronutrient in higher plants, but it is toxic in excess. The fine adjustments required to fit copper nutritional demands for optimal growth are illustrated by the diverse, severe symptoms resulting from copper deficiency and excess. Here, a differential transcriptomic analysis was done between Arabidopsis thaliana plants suffering from mild copper deficiency and those with a slight copper excess. The effects on the genes encoding cuproproteins or copper homeostasis factors were included in a CuAt database, which was organised to collect additional information and connections to other databases. The categories overrepresented under copper deficiency and copper e…
Enterramientos prehistóricos en fosa en el entorno megalítico de Los Molares (margen izquierda de la cuenca del Bajo Guadalquivir)
2020
El artículo presenta nuevos datos procedentes de excavaciones recientes en Los Molares (provincia de Sevilla), en el entorno próximo de los dólmenes de El Palomar y Cañada Real. Los datos fueron obtenidos durante los trabajos arqueológicos previos a la urbanización de la finca de El Palomar, localizándose varias fosas rellenas con materiales prehistóricos, tres de ellas con restos humanos. Se presentan sus contextos arqueológicos y restos recuperados, así como los resultados de los análisis radiocarbónicos efectuados. Se realiza una discusión sobre las implicaciones de estos nuevos hallazgos en relación con el entorno megalítico conocido y con el registro funerario del IV milenio cal BC en …
Instability of cuboctahedral copper clusters.
1992
Equilibrium structures of copper clusters up to 10 000 atoms are studied using molecular-dynamics and effective-medium theory. Icosahedral closed-shell clusters are most stable up to \ensuremath{\sim}2500 atoms and the Wulff polyhedra are favored for larger clusters. Cuboctahedral closed-shell clusters up to \ensuremath{\sim}2000 atoms are unstable. They undergo a nondiffusive transition to an icosahedral structure at low temperatures and melt directly above the fcc-cluster-melting temperature. The melting temperature decreases with decreasing cluster size but not as deeply as has been reported for pure metals.
A theoretical investigation on the Cd doping of Cu-depleted CuInSe<inf>2</inf> materials
2011
Because of their outstanding characteristics and affordable price, polycrystalline thin film solar cells based on CuIn 1−x Ga x Se 2 (CIGS) absorber layer have emerged to be one of the most promising materials for photovoltaic applications [1–2]. To further enhance the efficiency of these solar cells much effort is spent on the in-depth investigation of the production methods. However, the effect of structural defects and dopants upon the macroscopic properties and morphology of epitaxially grown CIGS films is not yet fully understood [3]. More importantly, it is well established that the best cells can be prepared by growing the CIGS absorber layer under Cu-poor conditions [4]. Thus, it is…
Oscillatory Changes of the Heterogeneous Reactive Layer Detected with the Motional Resistance during the Galvanostatic Deposition of Copper in Sulfur…
2015
Metallic copper was galvanostatically deposited on quartz|gold resonant electrodes by applying a constant current in a 0.5 M CuSO4/0.1 M H2SO4 aqueous solution. Galvanostatic copper deposition is one of the best methodologies to calibrate the electrochemical quartz crystal microbalances (EQCM), a gravimetric sensor to evaluate changes in mass during the electrochemical reactions through the Sauerbrey equation. The simultaneous measurement of mass, current density, and motional resistance by an EQCM with motional resistance monitoring allows us to characterize the processes occurring on the electrode surface and at the interfacial regions with unprecedented detail. During the galvanostatic c…