Cupric Ion Complexes Research Articles

Complexes of cupric ion and tartaric acid enhanced calcium peroxide Fenton-like reaction for metronidazole degradation

To surmount the obstacles of traditional Fenton method and synchronously utilize Cu2+ and polyphenol in water, an improved Fenton-like reaction applying calcium peroxide (CaO2) as H2O2 source and regulating by the complex of Cu2+-tartaric acid (TA, a representative of polyphenol) was constructed. A typical antibiotic, metronidazole (MTZ) could be effectively eliminated by the Cu2+/TA/CaO2 system, and the optimized parameters were as follows: 0.1 mmol/L Cu2+, 2 mmol/L TA, 2 mmol/L CaO2, and initial pH 5. UV spectrum confirmed the formation of Cu2+-TA complex, which promoted the Cu2+/Cu+ circulation through decreasing the Cu2+/Cu+ couple redox potential, which further enhanced the H2O2 decomposition and the formation of reactive species. Hydroxyl radical was dominant for MTZ degradation, followed by oxygen and superoxide radical. The degradation intermediates of MTZ were detected and their evolution way was speculated. Furthermore, the ternary process showed a wide pH tolerance (3–8) for removing MTZ and broad applicability for eliminating other dyes and antibiotics. This work provided a reference for Cu-based Fenton-like strategy for organic wastewater settlement.

A phenomenological study of the silver sulfide passivation and oxidative degradation of thiosulfate in the thiosulfate-ammonia‑copper-citrate leaching system

The oxidative decomposition of thiosulfate is one the main problems found in the thiosulfate leaching of precious metals. This work presents a detailed analysis of the effect of different dissolved components on the silver sulfide dissolution kinetics and efficiency faced by the thiosulfate-citrate‑copper-ammonia system. The analysis comprises the quantification of thiosulfate concentration; furthermore, it is discussed the effect of copper sulfides and copper hydroxides -formed in the leaching system- on the thiosulfate decomposition and silver dissolution efficiency. The results revealed that citrate promotes the complexation of cupric ions decreasing the thiosulfate consumption in the leaching system. The individual and combined effects of copper solid species (Cu(OH)2, CuS, Cu2S and solid residues obtained from silver sulfide leaching) on the thiosulfate stability and silver extraction efficiency, showed that the thiosulfate decomposition that occurs in the system is not significantly related to these copper species, while the silver extraction (~80%) does not show any substantial change. However, the presence of Cu2S and a small amount of dissolved silver have certain effect on the the partial in-situ regeneration of thiosulfate in the leaching system. Finally, it was also found that the silver sulfide dissolution is passivated obtaining an 80% of silver extraction. Such passivation is mainly attributed to: a) the precipitation of copper-sulfide and copper-hydroxide species on the unreacted silver sulfide sites; these copper phases act as a physical barrier which inhibits the direct contact of fluid reactants with the silver sulfide, and b) the silver sulfide dissolution reaches an equilibrium state.

Tyrosine nitration catalyzed by copper (II)

Tyrosine nitration is often observed during neurodegenerative disorders under nitrative stress. This protein posttranslational modification can be induced by peroxynitrite or nitrogen dioxide (NO2). In this study, the role of cupric ions on catalyzing tyrosine nitration was investigated by development of a microfluidic chip working as a microreactor [1] . The microfluidic chip acted also as an emitter for electrospray ionization mass spectrometry to online detect the nitration products. We found that cupric ions can efficiently catalyze tyrosine nitration in the presence of nitric oxide (NO), oxygen and H2O2, or in the presence of nitrite and H2O2. With mechanism study, we showed that cupric ions and peptide-cupric ion complexes are excellent Fenton-catalysts, even better than Fe (III) or heme, for the formation of hydroxyl radicals (OH) and/or copper (II)-bound OH from hydrogen peroxide. These radicals were efficiently scavenged by tyrosine to form tyrosine radicals and by nitrite to form NO2, leading to tyrosine nitration in polypeptides. This study shows that copper has a polyvalent role in the processes of tyrosine nitration.

Complexation of Ferrous and Cupric Ions by Phenanthroline and Terpyridine Langmuir Films

The complexation of Fe(II) and Cu(II) ions by phenanthroline and terpyridine-based Langmuir films was studied by the effect the added ions in the subphase on the isotherms. We found that Cu(II) had a pronounced effect on the isotherm consisting of phenanthroline moieties forming a square-planar 1:2 (Cu(II)/phenanthroline) complex. However, Fe(II) affected the isotherm made of 1:1 phenanthroline/terpyridine amphiphiles as a result of forming a pentacoordinate complex.

Copper ion redox state is critical for its effects on ion transport pathways and methaemoglobin formation in trout erythrocytes

We have studied the mechanism of copper uptake by the cells, its oxidative action and effects on ion transport systems using rainbow trout erythrocytes. Cupric ions enter trout erythrocytes as negatively charged complexes with chloride and hydroxyl anions via the band 3-mediated Cl −/HCO 3 − exchanger. Replacement of Cl − by gluconate, and complexation of cupric ions with histidine abolish rapid Cu 2+ uptake. Within the cell cupric ions interact with haemoglobin, causing methaemoglobin formation by direct electron transfer from heme Fe 2+ to Cu 2+, and consecutive proton release. Ascorbate-mediated reduction of cupric ions to cuprous decreases copper-induced metHb formation and proton release. Moreover, cuprous ions stimulate Na +/H + exchange and residual Na + transport causing net Na + accumulation in the cells. The effect requires copper binding to an externally facing thiol group. Copper-induced Na + accumulation is accompanied by K + loss occurring mainly via K +–Cl − cotransporter. Taurine efflux is also stimulated by copper exposure. However, net loss of osmolytes is not as pronounced as Na + uptake and modest swelling of the cells occurs after 5 min of copper exposure. Taken together the results indicate that copper toxicity, including copper transport into the cells and its interactions with ion transport processes, depend on the valency and complex formation of copper ions.

The Effect of the Synthetic Conditions on the Deposition and Distribution of Copper Complexes on Polymer Supports

The influence of conditions (e.g., ratios of components, temperature etc.) on the reaction of Cu(OCOCH3)2·2H2O with polyethylene grafted-polyacrylic on the amount of the metal and the composition of the immobilized Cu(II) complexes was studied. The concentration dependence obeys the Langmuir law. Analysis of the data leads to an evaluation of the stability constant for the Cu(II) complexes (K=300 l/mole at 333 K). The constant corresponds to a Cu(II) fixation value, k=0.35 mole/l (22.22 mg Cu(II)/g). The multistage fixation mechanism for Cu(II) complex formation was demonstrated by the marked atom technique. Cu(II) is fixed by one carboxylate group (to 16 mol% of the supported Cu(II), K 1=16×10−2 mole/g) and by two carboxylate groups (K 2=2.54×10−3 mole/g) of the grafted ligands. The PE-gr-PAA–Cu(II) system mimics the situation-insoluble support-soluble functional polymer covering and realizes the advantages of both the soluble and the three-dimensional crosslinked polymer. Steady-state magnetic susceptibility measurements and ESR spectroscopy were used to study the distribution of cupric ion attached to a polyethylene-grafted poly(acrylic acid) support. The existence of three types of cupric ion complexes was demonstrated: (1) isolated complexes, (2) complexes bonded by dipole–dipole interactions, and (3) clusters with strong exchange interactions. The mean distances between the isolated ions (¯r≥22–15 A) and between the dipole–bound complexes (¯r agreg≤7 A) were estimated. The results obtained were compared to the data for other immobilized catalysts. Preliminary results on the fixation of bimetallic Cu(II) and Pd(II) complexes to the polymers as well as on their distributions were obtained.

Reactivity of glycidyl‐methacrylate‐grafted cellulose prepared by means of photografting

AbstractPhotografting was applied to functionalize cellulose, that is, epoxy groups were introduced into the cellulose substrate by photografting of glycidyl methacrylate (GMA) using hydrogen peroxide as a photoinitiator. Dissolving pulp from softwoods was used as the cellulose sample. The GMA‐grafted cellulose (G‐Cell) was subjected to the following examinations in comparision with epoxy‐activated cellulose (E‐Cell) prepared by reaction with epichlorohydrin: (1) reactivity of G‐Cell towards amines such as ethylenediamine, tetramethylenediamine, hexamethylenediamine, diethylenetriamine, and triethylenetetramine; (2) ability of the aminated celluloses obtained by examination (1) to adsorb cupric ion; and (3) catalytic activity of the aminated cellulose–cupric ion complexes prepared by examination (2) for decomposition of hydrogen peroxide. The amount of amine residue introduced into the substrate was higher for E‐Cell than G‐Cell, showing the existence of epoxy groups in G‐Cell which cannot contribute to the reaction. The ability of the aminated celluloses to adsorb cupric ion was nearly equal for G‐Cell and E‐Cell though tetramethylenediamine and hexamethylenediamine‐introduced samples did not show the ability. It was found that all complexes prepared by reaction of the aminated cellulose with cupric ion exhibited catalytic activity for decomposition of hydrogen peroxide. © 1995 John Wiley & Sons, Inc.

Relationship of Free Ionic Copper and Toxicity to Bacteria in Solutions of Organic Compounds

The complexation of cupric ions added to solutions of different organic compounds and to culture media was determined using an ion-specific electrode to ascertain the toxic forms of copper. Toxicity of Cu 2+ to copper-sensitive and copper-tolerant strains of Pseudomonas syringae was reduced in the presence of all organic compounds tested, including 100 mM solutions of glucose, fructose, sucrose, succinate, and particularly citrate. The apparent toxicity of copper solutions was reduced 30× or more in the presence of organic solute (...)

Modeling of additive effects on the electroplating of a through‐hole

AbstractA mathematical model of copper plating of a through‐hole is developed which relates uniformity of deposition to bulk electrolyte composition, applied potential difference, aspect ratio, through‐hole diameter, and deposition kinetics. The electrochemical transport equations governing plating in a through‐hole are solved assuming that the fluid within the through‐hole is stagnant. Conditions for uniform plating are determined both for Butler‐Volmer kinetics considering the effects of dissociation of bisulfate ions in the electrolytic solution and for kinetics limited by complexation of cupric ions with an adsorbed neutral additive species.

Minor lamin polypeptides from rat liver nuclei can be cross-linked into heteropolymers by disulfide bridges.

The peripheral lamina of rat liver nuclei is characterized by the presence of three major polypeptides called lamins A, B, and C. Recent studies have identified in rat liver lamina two quantitatively minor polypeptides that have some of the biochemical and immunological properties of the lamins and were tentatively called minor lamin species. We have further characterized these minor lamin polypeptides. Both minor lamin species copurified quantitatively with the major lamins in dissociation-reassociation experiments and shared epitopes with all three major lamins as well as with intermediate filament proteins, including an epitope involved in coiled-coil interactions in lamina and filaments. Minor lamins generated partial peptide maps very similar to each other but completely different from those of lamins A, B, and C. The two minor lamin species could be cross-linked into heteropolymers containing a constant ratio of both polypeptides by exposure to O-phenanthroline - cupric ion complexes, although they did not appear to be cross-linked by disulfide bonds in the native envelope. Preliminary results suggest that the cross-linked minor lamins could be preferentially associated with lamin B. It therefore appears that in addition to the network of lamins A, B, and C, the peripheral lamina is characterized by the presence of two closely juxtaposed minor lamin polypeptides. The molecular interactions between these various polypeptides and their respective roles remain to be identified.

Assessment of the spherical-averaging approximation for the interpretation of electron spin-echo modulation for cupric ion complexes

A comparison is made between three methods for the simulation of deuterated ligand modulation from cupric ion complexes as powders using electron spin-echo modulation (ESEM) spectroscopy: (a) the spherical-averaging approximation which assumes both isotropic g and a random distribution of deuterium nuclei about the paramagnetic center, (b) an average which is performed over specific orientations of the field H0 with respect to g∥ using analytical expressions for the spin-echo intensity for an axially symmetric g tensor, and (c) a similar approach to (b) but with full geometrical correlation between the deuterium nuclei. Approach (c) is found to be unnecessary because of the degree of freedom of the ligand molecules to rotate about the ligand axis before freezing locks them into a particular configuration. This, in effect, removes any strict correlation between the deuterium nuclei. Approaches (a) and (b) are found to be equivalent when (i) the electron–nuclear distance r is greater than 0.35 nm, (ii) r is less than 0.35 nm but the number of interacting nuclei, N, is 6 or greater, and (iii) r is less than 0.35 nm, N is less than 6, and the angle θI between g∥ and r is greater than 45°. In all cases microwave irradiation must be near g⊥. When the situation is none of the above, then parameters defined by the spherical-averaging approximation should be interpreted with caution.

Phosphate ester hydrolysis catalyzed by metallomicelles

Two long-chained cupric ion complexes were synthesized and found to possess remarkable catalytic activity toward phosphate triesters, diesters, and other phosphorus(V) compounds (including some particularly toxic and persistent materials). The complexes form metallomicelles which bind substrates with enzyme-like efficiency (K/sub assoc/ > 10/sup 5/ M). Rate accelerations approach the 10/sup 5/-fold level with turnover behavior. Possible reasons for the huge rate accelerations include enhanced electrophilicity of the micellized metal (demonstrated by polarography) and enhanced acidity of copper-bound water (demonstrated by rate vs pH studies).

Mechanism of the reaction of cuprous dialkylthiophosphates with haloacetylenes

The ethynylation of cuprous salts of dialkylthiophosphoric acids by substituted ethynyl bromides proceeds through the formation of paramagnetic cupric ion complexes. These complexes are unstable and, under ordinary conditions, decompose with the formation of substituted S-ethynylthiophosphates and cuprous ions.

Complexation of ferric and cupric ions with pyridoxal

1. Mathematical modelling was used to demonstrate the formation of mono and hydroxo complexes of ferric and cupric ions with pyridoxal in physiological solution and their stability constants were calculated. 2. Ferric ions form more stable complexes than cupric ions.

Copper (II) metformin hydrochloride complexes and its utility for spectrophotometric determination of copper (II)

A systematie spectrophotometric study is carried on the complexation of cupric ions with metformin hydrochloride. Physicochemical studies on the chelate in both solution and solid Sta¬te are performed. The optimum conditions for formation of the chelate are reported. Spectroph¬otometric measurements are applied to deduce the composition, structure and mode of chela- tion. Chelate formation has been utilised for the determination of copper (II).

Heteropolymer filaments of vimentin and desmin in vascular smooth muscle tissue and cultured baby hamster kidney cells demonstrated by chemical crosslinking.

Certain smooth muscle cells of blood vessel walls as well as cultured baby hamster kidney cells contain simultaneously two different intermediate-sized filament (IF) proteins, desmin and vimentin. We have examined the question of the occurrence of both proteins in the same IF by chemically crosslinking the single cysteine group present in each of them. Oxidative crosslinking of filaments present in cytoskeletal preparations with cupric ion complexes of 1,10-phenanthroline resulted in formation of three types of dimers: vimentin-vimentin, desmin-desmin, and vimentin-desmin. These dimers were separated by NaDodSO4/polyacrylamide gel electrophoresis and characterized by binding of specific antibodies, by one- and two-dimensional gel electrophoresis of monomers obtained after cleavage of the disulfide bond by thiol agents, and by mapping of radioiodinated tryptic peptides. The demonstration of heterodimers of vimentin and desmin in vascular smooth muscle tissue of cow and chicken and in baby hamster kidney cells shows that the two proteins can be integrated in the same IF and can be nearest neighbors, oriented with their cysteine residues in a mirror-image symmetry. The possible existence of heteropolymer IF in other cell types is discussed.

Structural characterization and biological activity of cupric complexes of leu- and met-enkephalins

Abstract The formation of cupric ion complexes with leucine-enkephalin and methionine-enkephalin was analysed by 1H NMR, EPR and visible spectroscopy. The biological activity of the complexes was measured by the guinea pig ileum assay and the opiate binding test to rat brain homogenates. Small changes in biological activities are reported in spite of strong binding of the copper ions to the pentapeptides.

Copper complexation by isatin β-thiosemicarbazones in aqueous solution

The reactions in aqueous solution between cupric ion and water-soluble derivatives of the antiviral drug methisazone (1-methylisatin β-thiosemicarbazone, mibt) have been investigated. Alkalimetric titrations and n.m.r. experiments showed that 5-sulfonatoisatin β-thiosemicarbazone, sibt (3), its 1-methyl derivative, msibt (4), and also p-sulfonatobenzaldehyde thiosemicarbazone, sbat (5), reduce cupric ion and form copper(I) complexes. Stability constants were obtained from measurements of pH and pCu+ on solutions of copper(II) nitrate and excess ligand (I = 0.15 M KNO3, at 37�). The pCu+ values were obtained with an ORION solid state copper electrode. At pH 6-7.5 and moderate excess of ligand, polymeric complexes with an approximate 1 : 1 copper(1)-to-ligand ratio are formed: CunLn or CunLn+,H with n > 6. Monomeric complexes CuL23- predominate at higher pH and in the presence of a more than twentyfold excess of ligand. The stability constants log β2 are 17.9 for sibt, 18.5 for msibt and 19.8 for sbat. At physiological pH (7.4), the order of stability is msibt > sibt & sbat, with conditional stability constants log β2 = 16.2, 15.7 and 13.4, respectively. Comparison with penicillamine shows that some in vivo complexation of copper(I) by methisazone may be possible. On the other hand, a histidinato-copper(II) complex is formed in the presence of histidine.

Potentiometric investigation of simple and mixed complexes of cupric ion in aqueous solution

Simple and mixed complexes of copper(II) with 2,2′-dipyridyl and oxydiacetic or thiodiacetic acid have been tnvestigated at 25 δC in 0.1 M (NaClO 4) by potentiometric measurements Stabiliy constants for the systems CuL, CuL 2, CuHL, Cu(dip)L, Cu- (dip)HL (where L is oxydiacetic or thiodiacetic acid and dip is 2,2′-dipyridyl) have been determined. Some considerations about the stability of these complexes are reported.

Inhibition of [formula omitted] DNA polymerase I by 1,10-phenanthroline

A 1,10-phenanthroline-cuprous ion complex is a potent reversible inhibitor of E. coli DNA polymerase I yielding 50% inhibition in the micromolar concentration range. The 2:1 1,10-phenanthroline-cuprous ion complex is most probably the inhibitory species. Complexes of cupric ion and 1,10-phenanthroline have no apparent kinetic effect. The previously reported inhibition of the enzyme by 1,10-phenanthroline (1,2) is most likely due to the formation of this complex from thiols normally added to the assay mixtures and trace amounts of cupric ion invariably present notwithstanding reasonable precaution. The reversible and instantaneous 1,10-phenanthroline inhibition observed for other polymerases may be due to this unique inhibitory species and not coordination of a catalytically important zinc ion at the active site by the chelating agent.