Free energy perturbation and molecular dynamics calculations of copper binding to azurin

Free energy perturbation/molecular dynamics simulations have been carried out on copper/azurin systems calculating the binding affinities of copper (II) ion to azurin either in the native or in the unfolded state. In order to test the validity of the strategy adopted for the calculations and to establish what force field is suitable for these kinds of calculations, three different force fields, AMBER, CVFF, and CFF, have been alternatively used for the calculations and the results have been compared with experimental data obtained by spectroscopic titrations of copper (II)/azurin solutions and denaturation experiments. Our findings have pointed out that only CFF gives satisfactory results, thus providing a reliable tool for copper binding simulations in copper protein.     

河水中痕量铜的形态分析研究

采用离子交换树脂分离／分光光度法研究了铜的形态分离分析条件，提出了铜的形态分析方法。用此法测定了珠江水中痕量铜的总量、悬浮态、溶解态、阴离子态、阳离子态、非离子态及其形态分布，结果令人满意。     

Infrared spectroscopic and theoretical studies on the reactions of copper atoms with carbon monoxide and nitric oxide molecules in rare-gas matrices

Reactions of laser-ablated Cu atoms with CO and NO mixtures in solid argon and neon have been investigated using matrix-isolation infrared spectroscopy. Copper carbonyls and copper nitrosyls have been observed, whereas copper carbonyl nitrosyl complexes are absent from the present experiments. New products, (CuCO)2, [NO]Cu[NO], Cu2(mu2-NO), and Cu(NO)2Cu, have been formed in the copper experiments and characterized using infrared spectroscopy on the basis of the results of the isotopic shifts, mixed isotopic splitting patterns, stepwise annealing, the change of reagent concentration and laser energy, and comparison with theoretical predictions. Density functional theory calculations have been performed on these copper carbonyls and copper nitrosyls, which support the identification of these products from the matrix infrared spectrum. A plausible reaction mechanism has been proposed to account for the formation of copper carbonyls and copper nitrosyls. Similar matrix experiments with Ag and Au produce no new species.     

Characterization of formate complexes formed as corrosion products on copper by raman spectroscopy

Different copper formate complexes formed on the surface of metallic copper have been studied by Raman spectroscopy. Their Raman spectra have been correlated with the dehydrated copper formate, the copper formate dihydrate and the copper formate tetrahydrate. Experiments with deuterated formic acid reveal the influence of water molecules coordinated to the copper ion on the position of Raman bands of the formate ion.     

Bifunctional chelators for copper radiopharmaceuticals: the synthesis of [Cu(ATSM)-amino acid] and [Cu(ATSM)-octreotide] conjugates

Two new bifunctional chelators that are derivatives of the bis(thiosemicarbazone) ATSMH(2) proligand have been prepared, one with two phenyl carboxylate substituents on the exocyclic nitrogens (L(1)H(2)) and one with a single phenyl carboxylate (L(2)H(2)). The new ligands have been characterised by NMR spectroscopy, mass spectrometry and in the case of L(1)H(2) by X-ray crystallography. The copper, nickel and zinc complexes of the new ligands have been synthesised and characterised. Electrochemical measurements show that the copper(II) complexes undergo a reversible reduction attributable to a Cu(II)/Cu(I) process. The new proligands have been tethered to the N-alpha-Boc-protected amino acids lysine and ornithine using solution and solid phase methods. The new amino acid conjugates form copper complexes and the complexes have been characterised by mass spectrometry and electronic spectroscopy. The bifunctional chelator L(2)H(2) has been conjugated to the tumour targeting peptide octreotide and the new ATSMH(2)-octreotide conjugate and its copper complex have been characterized by mass spectrometry. These new systems have the potential to be used for new targeted copper radiopharmaceuticals for imaging and therapy.     

Synthesis,Characterization, and Applications of Copper Nanoparticles

Copper nanoparticles with different structural properties and effective biological effects may be fabricated using new green protocols. The control over particle size and in turn size-dependent properties of copper nanoparticles is expected to provide additional applications. Various methods for the synthesis of copper nanoparticles have been reported including chemical methods, physical methods, biological methods, and green synthesis. Biological methods involve the use of plant extracts, bacteria, and fungi. Commendable work has been done regarding the synthesis and stability of copper nanoparticles. There is a need to summarize the behavior of copper nanoparticles in different media under various conditions. Here, a complete list of the literature on the synthesis of copper nanoparticles, their properties, stabilizing agents, factors affecting the morphology, and their applications is presented. The importance of copper nanoparticles compared to other metal nanoparticles are due to high conductivity. Methods for the synthesis of copper nanoparticles, including green protocols using plants and micro-organisms compared chemical methods, have also been reviewed.     

Formation of copper–polymer nanocomposite upon copper electrodeposition in the presence of poly(<Emphasis Type="Italic">N</Emphasis>-vinylpyrrolidone)

The composition and structure of products formed on a cathode upon electrodeposition of copper from copper sulfate–poly(N-vinylpyrrolidone) mixed solutions have been studied. These products have been shown to be nanocomposites consisting of copper nanoparticles and the polymer. It has been suggested that the composite is formed by a pseudotemplate mechanism via noncovalent interaction between macromolecules and copper particles growing on the cathode. The interaction is accompanied by deceleration of subsequent growth of particles because of their screening by the polymer. This decreases the sizes of copper particles in the reaction product and the rate of metal reduction. The sonication of the reaction system yields a nanocomposite sol containing nanoparticles of copper(I) oxide. The oxide results from rapid oxidation of copper metal particles that have passed to the sol with copper(II) ions.     

Kinetic-spectrophotometric determination of Cu(II) and pyridine by use of the aerial oxidation of dimedone bisguanylhydrazone

The synthesis and analytical properties of dimedone bisguanylhydrazone (DIBG) are described for the first time. DIBG is oxidized by aerial oxygen and the reaction is catalysed by copper(II). The catalytic effect of copper(II) is increased by the presence of pyridine. Kinetic methods are described for determining trace amounts of copper(II) and pyridine. The reaction is followed spectrophotometrically by measuring the rate of change of absorbance at 550 nm. The calibration graphs are linear in the range 0.6-9.5 mug for copper(II) and 0.2-8.8 mg for pyridine. The methods have been applied to the determination of copper in galena and of pyridine in piperidine and isoamyl alcohol. The kinetic parameters of the reaction have been determined.     

Preparation and analytical properties of a chelating resin containing phenylalanine groups

A polystyrene-based macroreticular resin containing phenylalanine groups has been prepared and its analytical properties have been investigated and compared with Dowex A-1. The phenylalanine resin shows high selectivity for mercury(II) and copper(II) in the pH region 2-3. The sorption behaviour of copper has been examined in detail, with the intention of using the resin analytically. The important characteristics of the resin are fast equilibration, high selectivity and small volume change between its hydrogen form and metal forms. These enable it to be applied for the rapid concentration of trace amounts of copper in the presence of large amounts of diverse metals. It may be used for the determination of copper in sea-water and the separation of copper/cobalt and copper/nickel.     

铜铁试剂的交流示波极谱滴定法研究

提出了用交流示波极谱滴定法测定铜合金中的铜和测定铜铁试剂的方法。该法快速、准确、终点直观。测定了铜合金中的铜,变动系数0.07％～0.17％。考察了紫外光照射下铜铁试剂的动力学行为。     

Investigations into the electroreduction of copper(II) ions on chalcocite in ammonia solutions using the rotating disc electrode method

Investigations into the electroreduction of copper(II) ions in ammonia solutions on a disc electrode made of synthetic chalcocite having a deficiency of copper atoms have been presented. It has been concluded that within the range of the diffusion controlled process copper(II) ions are the diffusing substance, at the same time in the course of the reaction two electrons are exchanged. The kinetic parameters for the electroactivating process have been estimated. With a higher concentration of copper in solution an inhibition process has been observed, probably caused by a slow transport rate of the species in the material of the electrode. In the system studied the phenomenon of a partially blocked electrode surface does not occur according to the Landsberg model.     

Electrochemical synthesis of copper(II) carboxylates

A number of copper(II) carboxylates have been synthesized by anodic oxidation of copper. The reactions were found to proceed with current efficiencies of 0.95 to 1.00 eq./Faraday. Reaction products have been characterized by infrared spectral studies and analysis of copper.     

The EPR spectra of copper compounds with tetragonal symmetry in glasses

The conditions for the appearance of the additional absorption peak and its position in the EPR spectra of copper compounds with tetragonal symmetry in glasses have been analyzed. It has been found that the constants of the spin hamiltonians A and B should always have negative signs. The resulting theoretical conclusions have been compared with experimental results on the EPR of bis(salicylideneiminato)copper in various solvents and low-temperature glasses.     

Assessing the whole range of CuAAC mechanisms by DFT calculations--on the intermediacy of copper acetylides

The archetypal Cu(I)-catalyzed alkyne-azide click cycloaddition (CuAAC) has been explored thoroughly via density functional calculations, modeling copper nuclei with the LANL2DZ basis set and aqueous environments with CPCM solvation. All the mechanistic proposals, ranging from the intermediacy of copper acetylides to π-complexes and multinuclear clusters have been compared. The known features of the CuAAC reaction such as the observed second order kinetics for the Cu(I) species and the marked regioselectivity have been taken into account. The calculated energy barriers point to the intermediacy of copper(i) acetylides with two metal centers, in agreement with the observed kinetics, which exhibit barriers of 10.1 kcal mol(-1) and 13.7 kcal mol(-1) for the 1,4- and 1,5-regiochemistries, respectively, thus accounting for the marked regioselectivity of the copper catalyzed azide-alkyne cycloaddition. The copper acetylide versus π-complexes dilemma has also been experimentally addressed through the click reaction of benzyl azide and isotopically labeled phenylacetylene. The total proton/deuterium exchange in the afforded triazole demonstrates the formation of a copper acetylide intermediate during the transformation.     

Opportunities in multidimensional trace metal imaging: taking copper-associated disease research to the next level

Copper plays an important role in numerous biological processes across all living systems predominantly because of its versatile redox behavior. Cellular copper homeostasis is tightly regulated and disturbances lead to severe disorders such as Wilson disease and Menkes disease. Age-related changes of copper metabolism have been implicated in other neurodegenerative disorders such as Alzheimer disease. The role of copper in these diseases has been a topic of mostly bioinorganic research efforts for more than a decade, metal–protein interactions have been characterized, and cellular copper pathways have been described. Despite these efforts, crucial aspects of how copper is associated with Alzheimer disease, for example, are still only poorly understood. To take metal-related disease research to the next level, emerging multidimensional imaging techniques are now revealing the copper metallome as the basis to better understand disease mechanisms. This review describes how recent advances in X-ray fluorescence microscopy and fluorescent copper probes have started to contribute to this field, specifically in Wilson disease and Alzheimer disease. It furthermore provides an overview of current developments and future applications in X-ray microscopic methods.

Spectroelectrochemical and computational studies on the mechanism of hypoxia selectivity of copper radiopharmaceuticals

Detailed chemical, spectroelectrochemical and computational studies have been used to investigate the mechanism of hypoxia selectivity of a range of copper radiopharmaceuticals. A revised mechanism involving a delicate balance between cellular uptake, intracellular reduction, reoxidation, protonation and ligand dissociation is proposed. This mechanism accounts for observed differences in the reported cellular uptake and washout of related copper bis(thiosemicarbazonato) complexes. Three copper and zinc complexes have been characterised by X-ray crystallography and the redox chemistry of a series of copper complexes has been investigated by using electronic absorption and EPR spectroelectrochemistry. Time-dependent density functional theory (TD-DFT) calculations have also been used to probe the electronic structures of intermediate species and assign the electronic absorption spectra. DFT calculations also show that one-electron oxidation is ligand-based, leading to the formation of cationic triplet species. In the absence of protons, metal-centred one-electron reduction gives the reduced anionic copper(I) species, [CuIATSM](-), and for the first time it is shown that molecular oxygen can reoxidise this anion to give the neutral, lipophilic parent complexes, which can wash out of cells. The electrochemistry is pH dependent and in the presence of stronger acids both chemical and electrochemical reduction leads to quantitative and rapid dissociation of copper(I) ions from the mono- or diprotonated complexes, [CuIATSMH] and [Cu(I)ATSMH2]+. In addition, a range of protonated intermediate species have been identified at lower acid concentrations. The one-electron reduction potential, rate of reoxidation of the copper(I) anionic species and ease of protonation are dependent on the structure of the ligand, which also governs their observed behaviour in vivo.     

2-烷基苯并咪唑在铜表面所成膜热稳定性能的研究

分别测定了2-烷基苯并咪唑在铜表面所成膜经150,200,250℃热处理后的FTIR谱,对膜的结构和热稳定性能进行了研究.结果表明,2-烷基苯并咪唑与铜发生了络合反应,并在铜表面形成膜,其热稳定性随2位烷基碳链的增长而减弱;由于独特的稠环结构,与2-烷基咪唑相比,热稳定性能增强.     

Thermal and structural studies of the chloro complexes of cobalt and copper with 2-amino-3-methylpyridine

The chloro complexes of 2-amino-3-methylpyridine with cobalt(II) and copper(II) have been prepared in ethanolic solution and solid compounds have been isolated. The compounds have stoichiometry ML₂Cl₂ whereM is Co²⁺ or Cu²⁺ and L is 2-amino-3-methylpyridine. Spectral and magnetic studies have been used to obtain information about the environment of the metal ion in these compounds. The compounds have tetrahedral structures. The thermal decomposition of each compound has been studied using thermogravimetry and differential thermal analysis. Thermogravimetry studies show that the cobalt complex forms an intermediate compound before the metal oxide is produced while the copper compound undergoes decomposition with loss of organic ligand and the formation of copper chloride which then decomposes to give an oxide of copper. The enthalpy of reaction for each of the processes has been calculated from the thermal analysis curves.     

Catalytic reduction currents in the stripping voltammetry of solutions of the system copper(II)-ascorbic acid and their application in analytical chemistry

It has been found that the analytical signal from copper(II), cadmium(II), and zinc(II) in alternating-current stripping voltammetry in the presence of ascorbic acid (AA) increases only for copper(II) ions, which have significant oxidative potential. It is associated with the appearance of a catalytic current of the reducer in stripping voltammetry, where the reducer is AA. A scheme has been proposed for this process. The rate constant has been calculated for the chemical reduction of copper(I) ions, electrochemically produced in the diffusion layer as a result of the electrochemical oxidation of copper atoms, with AA. A procedure has been developed for the determination of copper in model solutions using the catalytic current of AA; the limit of copper detection is 0.01 μg/L, which is one order lower than the one achieved without AA.     

铜及其配合物在生物体系中的作用

自人类有历史记载以来，铜及其配合物即用作药物。铜是人体必需的金属元素。人体的正常代谢过程需要它们，但无法体内合成，因此，需要每天从饮食摄取和吸收。生物药学家和研究者以极大的努力彻底地了解铜及其配合物在生物体系中的作用，希望获得更多地信息以利于人类疾病的预防和治疗。本综述评述了铜在组织中的分配和代谢、铜依赖酶、在病态时铜的非正常代谢、铜配合物的药疗活性和抑制氧自由基的产生。