Incorporation Of Copper Ions Research Articles

Incorporation of Copper Ions into T2/T3 Centers of Two-Domain Laccases

Laccase belongs to the family of copper-containing oxidases. A study was made of the mechanism that sustains the incorporation of copper ions into the T2/T3 centers of recombinant two-domain laccase Streptomyces griseoflavus Ac-993. The occupancy of the T3 center by copper ions was found to increase with an increasing copper content in the culture medium and after dialysis of the protein preparation against a copper sulfate-containing buffer. The T2 center was filled only when overproducer strain cells were grown at a higher copper concentration in the medium. Two-domain laccases were assumed to possess a channel that serves to deliver copper ions to the T3 center during the formation of the three-dimensional laccase conformation and dialysis of the protein preparation. A narrower channel leads to the T2 center in two-domain laccases compared with three-domain ones, rendering the center less accessible for copper atoms. The incorporation of copper ions into the T2 center of two-domain laccases is likely to occur in the course of their biosynthesis or the formation of a functional trimer.

Incorporation of Copper Ions into T2/T3 Centers of Two-Domain Laccases

Incorporation of Copper Ions into T2/T3 Centers of Two-Domain Laccases

Doping effect of transition metals (Zr, Mn, Ti and Ni) on well-shaped CuO/CeO2(rods): nano/micro structure and catalytic performance for selective oxidation of CO in excess H2.

A series of CuO/CeM(rod) catalysts doped by transition metals were prepared and systematically characterized. The introduction of Mn and Ti plays a significant role in promoting the catalytic performance of the CuO/CeO2(rod) catalyst for the preferential oxidation of CO in H2-rich gas, while the doping with Zr basically maintains the same catalytic activity and Ni leads to a negative influence. Mn and Ti additives remarkably enrich the formation of defect structures and promote copper ion incorporation into the surface of CeM(rod), which greatly facilitates the generation of strong interfacial copper-ceria interaction in CuO/CeMn(rod) and CuO/CeTi(rod). In addition, CuO/CeMn(rod) possesses excellent surface oxygen mobility at low temperature due to the existence of manganese species with multiple valence states and todorokite species. The Ce-doped perovskite structure (Na0.5Ce0.5TiO3) further adjusts the oxygen vacancy in CuO/CeTi(rod) and anchors copper oxide species with strong interactions. Although a homogeneous solid solution is formed in CeZr(rod) with increased amounts of oxygen vacancies, the interaction between copper and ceria species in the interface of CuO/CeZr(rod) remains the same as with CuO/CeO2(rod). The addition of Ni impairs the dispersion of copper oxide and weakens the copper-ceria interaction, which damages the catalytic performance of CuO/CeNi(rod).

Copper containing nanosilica thioalated dendritic material: A recyclable catalyst for synthesis of benzimidazoles and benzothiazoles

In this paper, the design and characterization of a new heterogeneous catalyst by incorporation of copper ions into the nanosilica modified by thiole–based dendrimer are reported. The prepared catalyst was characterized by FT–IR, TGA, elemental analysis, FE–SEM, TEM, XPS and ICP–OES techniques. This material was used as catalyst in the synthesis benzimidazoles and benzothiazoles by the reaction of substituted benzaldehydes with 1,2–diaminobenzene or 2–aminothiophenol, respectively. The advantages of the present catalytic system are high yields, mild conditions and short reaction times. On the other hand, this new synthesized catalyst was recycled very well and reused several times without significant loss of its catalytic activity.

Catalytic removal of organic template from TEA-β zeolite by copper ions

The simultaneous decomposition of organic template and incorporation of copper ions into the zeolite were investigated during the heating mixture of copper chloride hydroxide and TEA-β zeolite under static air atmosphere. Detailed characterizations of the samples during calcination and subsequent copper removal treatment were performed with the aid of TG/MS, IR, XRD, pyridine-IR, XPS, 27Al and 29Si MAS-NMR. It was evidenced that the zeolite detemplation process facilitated the copper ions reduction and migration, inducing the solid ion exchange of copper species with TEA-β zeolite at lower temperature. These reduced copper ions migrated into the zeolite to occupy BrØnsted acid sites, and acted as catalysts to accelerate the oxidative decomposition of organic molecules significantly. The result showed that the virtually complete removal of organic template and incorporation of copper ions were obtained in one step by calcination at 350 °C for 3 h, and these ingoing copper species could be easily removed by re-exchanging with ammonium solution. After detemplation and copper removal, the purified H-β zeolite could still retain a well-defined structure and BrØnsted acid sites, showing a higher catalytic activity on the alkylation of benzene with ethylene compared with the conventionally prepared H-β zeolite.

Small organic molecule-mediated hydrothermal synthesis of hierarchical porous hydroxyapatite microspheres by the incorporation of copper ions

Hierarchical porous hydroxyapatite microspheres with a pit in the center were prepared under the synergistic effect of inositol hexakisphosphate and copper ions.

Study on the mechanism of copper–ammonia complex decomposition in struvite formation process and enhanced ammonia and copper removal

Heavy metals and ammonia are difficult to remove from wastewater, as they easily combine into refractory complexes. The struvite formation method (SFM) was applied for the complex decomposition and simultaneous removal of heavy metal and ammonia. The results indicated that ammonia deprivation by SFM was the key factor leading to the decomposition of the copper–ammonia complex ion. Ammonia was separated from solution as crystalline struvite, and the copper mainly co-precipitated as copper hydroxide together with struvite. Hydrogen bonding and electrostatic attraction were considered to be the main surface interactions between struvite and copper hydroxide. Hydrogen bonding was concluded to be the key factor leading to the co-precipitation. In addition, incorporation of copper ions into the struvite crystal also occurred during the treatment process.

Au/CuO–CeO2 catalyst for preferential oxidation of CO in hydrogen-rich stream: Effect of CuO content

A series of Au/CuO–CeO2 with various amounts of CuO was prepared. CuO–CeO2 was prepared by co-precipitation and Au was loaded by deposition–precipitation. The aim of this study was to develop a catalyst which is highly active and selective in preferential oxidation of CO in hydrogen stream (PROX). These catalysts were characterized by N2-sorption, XRD, TEM, HR-TEM, and XPS. The PROX reaction was carried out in a fixed bed continuous flow reactor with a feed of CO: O2: H2: He = 1.33: 1.33: 65.33: 32.01 in volume ratios. The incorporation of copper ion into ceria lattice increased the oxygen storage capacity of ceria and enhanced the activity of the catalyst. The excess CuO would present on the surface of CeO2. Au particles were well dispersed well on the support and the particle size of gold was in the range of 2 and 4 nm. Au was the active species and CuO played the promoter role. Those CuO presented on the surface of CeO had negative effect for CO oxidation. The selectivity of oxygen reacting with CO increased with increasing CuO content. Adding suitable amount of CuO in Au/CeO2 is beneficial for CO conversion and suppressing hydrogen oxidation in fuel cell operation condition.

Incorporation of copper ions into crystals of T2 copper-depleted laccase from Botrytis aclada.

Laccases belong to the class of multicopper oxidases catalyzing the oxidation of phenols accompanied by the reduction of molecular oxygen to water without the formation of hydrogen peroxide. The activity of laccases depends on the number of Cu atoms per enzyme molecule. The structure of type 2 copper-depleted laccase from Botrytis aclada has been solved previously. With the aim of obtaining the structure of the native form of the enzyme, crystals of the depleted laccase were soaked in Cu(+)- and Cu(2+)-containing solutions. Copper ions were found to be incorporated into the active site only when Cu(+) was used. A comparative analysis of the native and depleted forms of the enzymes was performed.

Preparation, characterization and application of nanosized copper ferrite photocatalysts for dye degradation under UV irradiation

Nanosized copper ferrite-type materials (CuxFe3–xO4, 0 ≤ x ≤ 1) have been prepared by combination of co-precipitation and mechanochemical activation and/or thermal treatment. The crystalline structure and morphology of the obtained ferrite nanopowders have been characterized by different instrumental methods, such as Powder X-ray diffraction (PXRD), Mössbauer and FT-IR spectroscopies, specific surface area and porosity measurements, thermal analyses (Differential Thermal Analysis and Thermogravimetric Analysis) and Temperature-Programmed Reduction. The average crystallite size of copper ferrites ranged between 7.8 and 14.7 nm and show a superparamagnetic and collective magnetic excitations nature. The photocatalytic decolorization of Malachite green oxalate under different UV illumination intervals was examined using these copper ferrites as photocatalysts. The results indicate that the prepared nanostructured copper ferrites showed enhanced photocatalytic activity and amount adsorbed Malachite Green dye. The co-precipitated nanosized copper ferrite powder with a low content of copper metal ions in a magnetite host structure (Cu0.25Fe2.75O4) showed an apparent pseudo-first-order rate constant 15.4 × 10−3 min−1 and an amount adsorbed Malachite Green as model organic dye pollutant per 1 g catalyst of 33.4 ppm/g after the dark period. The results confirm that the copper ferrites can be suitable for photocatalytic treatment of wastewaters containing organic dyes. The new aspect of presented investigations is to study the influence of different degree of incorporation of copper ions into the magnetite host structure and preparation methods on the photocatalytic properties of nanosized copper ferrite materials and obtaining of potential photocatalyst (Cu0.25Fe2.75O4) with higher photocatalytic activity (15.4 × 10−3 min−1) than that of the standard referent Degussa P25 (12 × 10−3 min−1) for degradation of organic dye Malachite green under UV irradiation.

Characterization of a Green-Emitting Copper-Doped Barium Aluminate Phosphor

ABSTRACT A novel green-emitting phosphor copper-doped barium aluminate was synthesized by the conventional ceramic method. The crystallographic phase and microstructure identification were performed by powder X-ray diffraction and scanning electron microscopy. The X-ray diffraction pattern of the sample confirms the formation of the phosphor, and the scanning electron microscope image was recorded to observe the surface morphology. Differential thermal analysis results show that the initiatory decomposition temperature of barium carbonate starts at about 728°C. Cathodoluminescence studies have been undertaken to ensure the successful incorporation of copper ions in the barium aluminate host lattice. Under the excitation of the electron beam, the phosphor can efficiently display a broad green emission centered at 490 nm, corresponding to the transition from the conduction band edge to the excited state of copper in the barium aluminate host. However, there are no data available on copper luminescence in barium aluminate. New results on 3d activators of copper emission in the barium aluminate host are reported in this article, thus extending the list of copper-activated phosphors. These results strongly indicate that the copper-activated barium aluminate is a potential material used as a new high-brightness green phosphor for ultraviolet light-emitting diode and display devices.

Spectroscopic ellipsometry of Zn1−xCuxO thin films based on a modified sol–gel dip-coating technique

Nanocrystalline Zn1−xCuxO thin films (x=0, 0.01, 0.02, 0.03, 0.04 and 0.05) were synthesized by sol–gel dip-coating technique on a quartz substrate. These films were annealed at 350°C for 2h. The X-ray diffraction showed a hexagonal crystal structure with high intensity peak for the (002) reflection plane indicating preferential growth along the c-axis of the crystal lattice. The peak position related to the (002) peak was shifted as a result of the copper ion incorporation, confirming the interstitial substitution of the zinc ions by the copper ions. This interstitial substitution leads to a decrease of an average crystallite size and lattice constants and an increase of the micro-strain up to 2at.% of the copper amount. The surface morphology was explored by scanning electron microscopy which confirmed the homogenous distribution of nanoparticles in the deposited films along the quartz substrates. The energy dispersion X-ray spectroscopy revealed absence of impurities in the as-deposited films. The high resolution electron microscopy and selected area electron diffraction depicted that the films have polycrystalline nature. The film thickness and optical constants of the Zn1−xCuxO thin films were estimated by fitting the spectroscopic ellipsometric data (ψ and Δ) using three different models. The refractive index was fitted using harmonic oscillator model from which the oscillator and the dispersive energies were found. The dielectric constant, dielectric loss, energy loss functions were also determined.

Mechanism of Copper Incorporation in Subunit II of Cytochrome c Oxidase from Thermus thermophilus: Identification of Intermediate Species

Detailed spectroscopic and kinetic studies of incorporation of copper ion in the wild type (WT) and the D111AA (AA = K, N, or E) mutants of the metal ion binding site of the soluble fragment of subunit II of cytochrome c oxidase from Thermus thermophilus (TtCuA) showed the formation of at least two distinct intermediates. The global analyses of the multiwavelength kinetic results suggested a four-step reaction scheme involving two distinct intermediates in the pathway of incorporation of copper ions into the apoprotein forming the purple dinuclear CuA. An early intermediate similar to the red copper binding proteins was detected in the WT as well as in all the mutants. The second intermediate was a green copper species in the case of WT TtCuA. Mutation of Asp111, however, formed a second intermediate that is distinctly different from that formed in the case of the WT protein, suggesting that mutants follow pathways of copper ion incorporation different from that in the WT protein. The electrostatic interaction between Asp111 and the coordinating His114 possibly plays a subtle role in the mechanism of incorporation of metal ion into the protein. The overall Kd for WT TtCuA was found to be ~8 nM, which changed with mutation of the Asp111 residue. The activation and thermodynamic parameters were also determined from the temperature- and pH-dependent multiwavelength kinetics, and the results are discussed to unravel the role of Asp111 in the mechanism of formation of the dinuclear CuA center in cytochrome c oxidase.

Synthesis and characterisation of copper doped Ca–Li hydroxyapatite

Hydroxyapapites M10(PO4)6(OH)2 (MHAP), where M is an alkaline earth metal, colored by incorporation of copper ions substituting protons, were discovered recently [1]. Now this kind of apatite-type materials can be used as inorganic pigments. Until now blue (BaHAP), violet (SrHAP) and wine-red (CaHAP) colors were achieved by the copper ions introduction [2]. The task of the present work was to study possibility of further M-ion substitution to affect the color and shift it toward the red–orange tint. Polycrystalline hydroxyapatites Ca10−xLix+yCuz(PO4)6O2H2−y−z−σ (Ca–LiHAP) were synthesized by solid state reaction at 1150°C (ceramic method) and studied by X-ray powder diffraction (XRD), infrared absorption and diffuse-reflectance spectroscopy. Refinement of the X-ray diffraction patterns by the Rietveld method shows that CaHAP unit cell parameters are a little bigger, than Ca–LiHAP ones. Small difference between unit cell parameters could be caused by two ways of the Li+ ions introduction: (1) at the Ca2+ sites (Ca–Li substitution); (2) into hexagonal channels (H–Li substitution). The Li ions doping changes the color of the copper doped CaHAP from wine-red to pink and red.

Multi-biofunctional complexes combining antiseptic copper(II) with antibiotic sulfonamide ligands: Structural, redox and antibacterial study

Copper(II) and nickel(II) complexes of sulfadimethoxine, sulfadiazine, sulfamerazine and sulfamethazine were synthesized with a good yield according to an original procedure. These complexes were first characterized by single-crystal X-ray diffraction and electrochemistry. Structural inspections showed that the antibacterial entity of ligands remains non-coordinated to metal ions in the complex high-lighting the fact that in each cluster, antiseptic activity of the metal has been associated to the antibiotic activity of the ligand. In order to confirm this possibility, antibacterial activities of the complexes were studied on several bacteria. The antibacterial activity of the complex is as important as the ligands one with the addition of antiseptic activity via the incorporation of copper ions.

Stabilization of the Thermal Decomposition of Poly(Propylene Carbonate) Through Copper Ion Incorporation and Use in Self-Patterning

Incorporation of copper ions into poly(propylene carbonate) (PPC) films cast from γ-butyrolactone (GBL), trichloroethylene (TCE) or methylene chloride (MeCl) solutions containing a photo-acid generator is shown to stabilize the PPC from thermal decomposition. Copper ions were introduced into the PPC mixtures by bringing the polymer mixture into contact with copper metal. The metal was oxidized and dissolved into the PPC mixture. The dissolved copper interferes with the decomposition mechanism of PPC, raising its decomposition temperature. Thermogravimetric analysis shows that copper ions make PPC more stable by up to 50°C. Spectroscopic analysis indicates that copper ions may stabilize terminal carboxylic acid groups, inhibiting PPC decomposition. The change in thermal stability based on PPC exposure to patterned copper substrates was used to provide a self-aligned patterning method for PPC on copper traces without the need for an additional photopatterning registration step. Thermal decomposition of PPC is then used to create air isolation regions around the copper traces. The spatial resolution of the self-patterning PPC process is limited by the lateral diffusion of the copper ions within the PPC. The concentration profiles of copper within the PPC, patterning resolution, and temperature effects on the PPC decomposition have been studied.

A luminescent gold(i)–copper(i) cluster with unprecedented carbon-centered trigonal prismatic hexagold

An unprecedented trigonal prismatic (μ(6)-C)Au(6) structure has been found in a novel gold(I)-copper(I) cluster with a hypercoordinated carbon, [CAu(6)Cu(2)(dppy)(6)](BF(4))(4); the incorporation of copper ions enhances the rigidity and integrity of the cluster and turns on the bright red solution luminescence.

Enhancement of Laccase Activity through the Construction and Breakdown of a Hydrogen Bond at the Type I Copper Center in Escherichia coli CueO and the Deletion Mutant Δα5−7 CueO

CueO is a multicopper oxidase involved in a copper efflux system of Escherichia coli and has high cuprous oxidase activity but little or no oxidizing activity toward various organic substances. However, its activity toward oxidization of organic substrates was found to be considerably increased by the removal of the methionine-rich helical segment that covers the substrate-binding site (Δα5-7 CueO) [Kataoka, K., et al. (2007) J. Mol. Biol. 373, 141]. In the study presented here, mutations at Pro444 to construct a second NH-S hydrogen bond between the backbone amide and coordinating Cys500 thiolate of the type I copper are shown to result in positive shifts in the redox potential of this copper center and enhanced oxidase activity in CueO. Analogous enhancement of the activity of Δα5-7 CueO has been identified only in the Pro444Gly mutant because Pro444 mutants limit the incorporation of copper ions into the trinuclear copper center. The activities of both CueO and Δα5-7 CueO were also enhanced by mutations to break down the hydrogen bond between the imidazole group of His443 that is coordinated to the type I copper and the β-carboxy group of Asp439 that is located in the outer sphere of the type I copper center. A synergetic effect of the positive shift in the redox potential of the type I copper center and the increase in enzyme activity has been achieved by the double mutation of Pro444 and Asp439 of CueO. Absorption, circular dichroism, and resonance Raman spectra indicate that the characteristics of the Cu(II)-S(Cys) bond were only minimally perturbed by mutations involving formation or disruption of a hydrogen bond from the coordinating groups to the type I copper. This study provides widely applicable strategies for tuning the activities of multicopper oxidases.

Preparation of Hybrid Layers Consisting of Copper Nanoparticles and Polyimide Matrix via Polyol <I>In Situ</I> Reducing Process

Hybrid layers consisting of copper nanoparticles and polyimide have been successfully fabricated using copper nitrate as the copper precursor and pyromellitic dianhydride/oxydianiline-(PMDA/ODA-) based polyimide films as the substrate. The fabrication method relies on the potassium hydroxide-induced chemical modification of the polyimide surface to introduce carboxylic acid groups, the incorporation of copper ions through subsequent ion exchange reaction, and followed by the polyol in situ reduction of copper ions contained polyimide layers in ethylene glycol solution at 197 degrees C. The amount of copper ions in the modified layer strongly depended on the ion exchange time. The copper nanoparticles size changed from 3 nm to 27 nm when the reduction time increased from 5 min to 30 min. These experiments provided an efficient route for copper metallization of polyimide substrate. The detailed reaction progress and resulted films were characterized by Attenuated total reflection-Fourier transform infrared, X-ray photoelectron spectroscopy, inductively coupled plasma atomic emission spectrometer, X-ray diffraction, transmission and scanning electron microscope.

Nanocrystalline Mullite Synthesis at a Low Temperature: Effect of Copper Ions

Nanocrystalline mullite with grain sizes in the range of 13–30 nm has been prepared by the sol–gel route at a temperature as low as 600°C with the incorporation of copper ions as copper sulfate. Characterization of the copper‐doped mullite was performed by DTA–TG, X‐ray diffraction (XRD), FESEM, and FTIR spectroscopy.