Addition Of Cupric Ions Research Articles

Eco-friendly ink formulation of column purified carbon dots from GABA for anticounterfeiting applications

Forgery of valuable products causes a negative impact on the society as well as the economy of the country. There is a growing demand to not only differentiate or authenticate genuine documents/products but also to protect their integrity. Carbon dots (CDs) are a class of fluorescent nanomaterials that are well-known for their facile synthesis, good photostability and less toxicity profile. The current research work focuses on the preparation of CDs via hydrothermal method using γ-aminobutyric acid (GABA) that contains amino and carboxylic groups. Column chromatography technique is adopted to purify the GABA-derived CDs from the reactants and by-products. The fourth fraction obtained after column purification containing CDs with fluorescence emission in the visible region is chosen for further studies. The presence of spherical CDs confirmed through TEM imaging are chemically characterised using SAED, EDS, DLS, FTIR, XPS, Raman and XRD spectroscopy. The blue (λem = 490 nm) and green (λem = 538 nm) emitting CDs present in the fourth fraction displayed a fluorescence lifetime of 1.90 ns and 2.02 ns. Theoretical studies are performed using B3LYP/6-31G(d,p) theory level on different plausible structures. The HOMO-LUMO band gap of 2.3 eV deduced using DFT calculation is in close agreement with the optical band gap of 2.6 eV derived from Tauc plot. A complex forming mechanism is proposed for the fluorescence quenching of CDs upon examining the EDS data of the precipitate obtained upon addition of cupric ions. Further, the CDs are used as pigments to formulate a water-based ink for flexographic printing on UV-dull paper substrate. The printed samples exhibited good colorimetric values, lightfastness, and rub resistance. The security features of the ink film include an UV-induced yellow fluorescence, which will be known to the forger and a secondary quenching of fluorescence when exposed to cupric ions, which can be used by the user to validate document/product authenticity. This stimulus responsive optical property is also explored in the design of ionochromic security paper based on cupric ion induced fluorescence quenching of CDs for data storage and decryption. Moreover, the lesser surface roughness and electrical parameter values obtained for the print proofs could be further explored for the potential application of CD-derived ink in electronic anticounterfeiting.

A Preliminary Study on the Newly Isolated High Laccase-producing Fungi: Screening, Strain Characteristics and Induction of Laccase Production.

A simple separation method was used in this study to directly separate laccase-producing fungi from withered plant materials. A laccase-producing filamentous fungus was isolated and purified. The strain was highly similar to the species in genus Trametes by ITS sequence analysis, and therefore named Trametes sp. MA-X01. The addition of cupric ions and aromatic compounds to the liquid medium could induce the laccase synthesis in Trametes sp. MA-X01. Copper-induced laccase activity increased in a dose-dependent manner. The highest laccase activity (2138.9 ± 340.2 U/L) was obtained by adding 2.5 mM Cu2+ to the culture medium, which was about 7 times higher than that of the control group. The induction degree of aromatic compounds was different. For the present study, the highest laccase activities were obtained by adding vanillic acid (1007.9±59.5 U/L) or vanillin (981.6±77.2 U/L) to the medium, which were 3.5 and 3.4 times higher than the laccase activity of the control group, respectively.

Ammoniacal Dissolution of Polymetallic Alloy Produced from Waste Electroscrap

The paper reports spontaneous and electrochemical dissolution of polymetallic alloy obtained from electrowaste. Effectiveness of chloride, carbonate and sulfate ammoniacal solutions was compared. Leaching process was conducted with and without addition of cupric ions. It resulted in the transfer of primarily copper (over 90%) and negligible amounts of zinc, lead, nickel and iron to the electrolyte, but the rate of the spontaneous dissolution was low. The best condition of the alloy leaching was obtained in the presence of Cu2+ ions in ammonium-carbonate solution. Anodic dissolution of the alloy led to unfavorable distribution of metals among the slime, electrolyte and cathodic deposit, but the highest dissolution rate in the chloride bath was found. Copper can be selectively recovered on the cathode from all electrolytes.

Effects of metal ions on disinfection byproduct formation during chlorination of natural organic matter and surrogates.

The effects of calcium, cupric, ferrous and ferric ions on the formation of trihalomethanes (THMs) and haloacetic acids (HAAs) were investigated using natural organic matter (NOM), small molecular weight NOM surrogates and natural water samples. The results showed that the effects were greatly dependent on the disinfection byproduct (DBP) precursor structure and molecular weight, and metal ions species. While using NOM as precursors, addition of 4.00 mM calcium ions increased the formation of THMs, dihaloacetic acids (DHAAs) and trihaloacetic acids (THAAs) by 24-47%, 51-61% and 15-25%, respectively. Addition of cupric ions at 0.02 mM increased the formation of THMs and DHAAs by 74-83% and 90-100%, respectively, but decreased the formation of THAAs by 26-27%. Similar effect was not observed when 0.04 mM ferrous or ferric ions were added. The effects of calcium and cupric ions on DBP formation were generally more evident for the NOM surrogates than that for NOM. The primary catalytic effect of calcium ions was due to complexation and less sensitive to molecular structure or weight, while that of cupric ions was attributed to redox reactions and greatly dependent on molecular structure. Both ferric and ferrous iron had substantial effects on the DBP formation of surrogates (citric acid and catechol in particular), which implied that the catalytic effects of ferric and ferrous iron mainly depended on molecular weight. The catalytic effect of cupric ions was also observed on natural water samples, while the effects of calcium, ferrous and ferric ions on natural water samples were not evident.

A Citrate-Based Coating System for AZ31 Magnesium Alloys

The effect of sulfate and cupric ion on citrate conversion coating for AZ31 magnesium alloys is investigated in this study. Microstructure characterization shows that the existence of sulfate in aqueous citrate conversion system inhibits the formation of citrate conversion coating, which leads to a deterioration in corrosion property. With the addition of cupric ion, cupric/cuprous oxide is found to precipitates on the citrate conversion coating formed in aqueous solution, which results in a high corrosion current density in potentiodynamic polarization test. A post treatment using poly(hexamethylene succinimide-co-citramide), abbreviated as PSICA, is also proposed in this study. It was found that the total impedance of the AZ31 in EIS increases from around 5,000 to 10,000 Ωcm2 after citrate-based conversion coating, and can be further elevated to near 20,000 Ωcm2 with the PSICA post treatment.

Spectroscopic studies of alpha tocopherol interaction with a model liposome and its influence on oxidation dynamics

The influence of α-tocopherol on the surface conformation of liposome, as a model component of lipoproteins, and its role in oxidation process were studied. FT-IR spectra from suspensions of neat liposome, mixtures of liposome and α-tocopherol and liposome with incorporated α-tocopherol were analyzed. When α-tocopherol was incorporated into liposome, intensities of some bands were decreased or increased in comparison with the spectra of liposome and α-tocopherol mixture. These changes reflect the different localization of α-tocopherol in two types of liposome suspensions. The oxidation of liposome suspensions was initiated by addition of cupric ions. After prolonged oxidation, the differences in FT-IR spectra of oxidized samples were recorded. Differences were observed in comparison with spectra of native and oxidized liposomes were analyzed. The rate of oxidation was measured by EPR oximetry. Oxidation was generally very slow, but faster in liposome without α-tocopherol, indicating the protective role of α-tocopherol against liposome oxidation. On the other hand, liposome suspensions with EDTA in the buffer were not oxidized at all, while those with α-tocopherol and liposome mixture were only slightly oxidized. In this case the consumption of oxygen was the result of liposome oxidation supported by α-tocopherol. These results reflect the ambivalent role of α-tocopherol in liposome oxidation, similarly to findings in studies of lipoprotein oxidation.

Electrochemical Characteristics of Natural Mineral Covellite

Electrochemical characteristics of covellite (CuS) are of importance from flotation and metallurgical point of view, as well as due to its potential application in solid state solar cells and in photocatalytic reactions. Also, the compound CuS appears as an intermediary product or a final product in electrochemical oxidation reactions of chalcocite (Cu2S) which exhibits supercapacitor characteristics. Natural copper mineral covellite has been investigated in inorganic sulfate acid electrolytes, as well as in strong alkaline electrolyte. Physical properties of covellite were characterized by X-ray diffraction (XRD) and the active surface was examined by optical and electron microscopy (EM) before and after oxidation in galvanostatic regime. Different electrochemical methods (galvanostatic, potentiostatic, cyclic voltammetry and electrochemical impedance spectroscopy - EIS) have been used. The capacitance of around 21 Fcm-2 (geometric area), serial resistance of about 90 Ωcm2 and leakage resistance of about 1200 Ωcm2 have been measured in 1 M H2SO4. The addition of cupric ions in sulfate electrolyte leads to the significant increasing of the capacitance, but having the increase of self-discharge as a negative side phenomenon. The capacitance of around 6.7 Fcm-2 (geometric area), serial resistance of about 80 Ωcm2 and leakage resistance of about 380 Ωcm2 have been measured in 6 M KOH.

Effects of the Functional Groups of Complexing Agents and Cu Oxide Formation on Cu Dissolution Behaviors in Cu CMP Process

Cu dissolution behaviors with select reagents (malonic acid, glycine, malic acid, citric acid) were investigated in terms of the functional groups of complexing agents. Based on the results of Cu dissolution rate testing at various values, as well as UV–visible analysis with the addition of cupric ions, reaction mechanisms and effects of each functional group are proposed. The effect of Cu oxide formation on the Cu dissolution rate was also investigated by monitoring Cu dissolution rates with various concentrations and complexing agent concentrations. Additionally, the effect of the addition of corrosion inhibitor (5-aminotretrazole) on Cu dissolution was investigated. By combining the experimental results, we interpreted the Cu dissolution behaviors based on a competitive contribution from Cu oxide formation and complex formation between Cu (Cu oxide) and the complexing agent.

The metal-binding motif of dipeptidyl peptidase III directly influences the enzyme activity in the copper derivative of dipeptidyl peptidase III

The zinc-binding motif (HELLGH) of dipeptidyl peptidase III (DPP III) is different from the common zinc-binding motif (HExxH) of metallopeptidases. To clarify the importance of the zinc-binding motif part of DPP III for enzymatic activity, we measured the recovery of the enzyme activity of apo-Leu 453-deleted dipeptidyl peptidase III (apo-Leu 453-del-DPP III), which has a motif (HELGH) like that of the common peptidase (HExxH), in the presence of various metal ions. The enzyme activity of apo-Leu 453-deleted DPP III could not be recovered by the addition of cupric ions, while apo-DPP III could be easily reactivated by the addition of cupric ions. The visible and electron paramagnetic resonance spectra of the isolated Cu(II)-Leu 453-del DPP III clearly show that the cupric ions of Cu(II)-Leu 453-del-DPP III bound to the motif part (HELGH) but did not exhibit any enzyme activity. The motif part of DPP III directly influences the expression of the enzyme activity in the copper derivative of DPP III. The competitive inhibitor that is not at all digested by DPP III, Hisprophen (His-Pro-Phe-His-Leu-d-Leu-Val-Tyr), has been determined. The inhibition constant ( K i) of Hisprophen for DPP III or Cu(II)-DPP III was 4.1 × 10 −5 or 3.8 × 10 −5 M, respectively. In the presence of the competitive peptide inhibitor, Hisprophen, the EPR spectra of Cu(II)-DPP III were completely different from that of Cu(II)-DPP III itself. This result clearly indicates that the metal ions of DPP III are located in the active site and directly interact with the substrate.

Whence topa? Models for the biogenesis of topa quinone in copper amine oxidases

Copper amine oxidases are dual function enzymes that first make their own cofactor, and then use this cofactor to catalyze amine oxidation. The cofactor, oxidized 2,4,5-trihydroxyphenylalanine (TPQ), is formed by the addition of cupric ion and dioxygen to precursor protein. Drawing on the mechanism of the oxidative half reaction in the copper amine oxidases, together with knowledge from other metal-containing enzyme systems, a new model is put forth for TPQ biogenesis.

Interaction modes in sol–gel transition of alginate solutions by the addition of cupric ions

Interaction modes in sol–gel transition of alginate solutions by the addition of cupric ions

Interaction modes in sol-gel transition of alginate solutions by the addition of cupric ions

The interaction mode between cupric ions and alginate in aqueous solutions during sol–gel transition has been experimentally examined at different temperatures. Some clusters were found to pass through a conformational transformation as the temperature increased, i.e. clusters formed by intramolecular crosslinks turned into intermolecular crosslinking clusters. This transformation of the interaction mode is not reversible as the temperature decreases. The interaction mode between cupric ions and alginate was re-examined by optical absorption techniques, and results suggest that the coordination of cupric ions mainly occurs to carboxyl groups and that the stoichiometric ratio f is proportional to the fraction of crosslinks formed. © 1997 John Wiley & Sons, Ltd.

Alterations in the structure of apolipoprotein B-100 determine the behaviour of LDL towards thromboplastin

Apolipoprotein B-100 acts as an inhibitor of thromboplastin activity independently of the tissue factor pathway inhibitor (TFPI) associated with plasma lipoproteins. Analysis of the primary structure of Apo B-100 showed a higher than expected occurrence of lysine groups in the receptor-binding region. In order to demonstrate the participation of lysine groups of Apo B-100 in the inhibition of thromboplastin, thromboplastin and Apo B-100 were incubated together in the presence of poly- l-lysine, poly- l-arginine, lysine and arginine monomers. The inhibition of thromboplastin by Apo B-100 was completely suppressed in the presence of poly- l-lysine. Poly- l-arginine was found to be less effective and neither lysine or arginine monomers had any significant effect on the inhibitory effect of Apo B-100. Alterations in the structure of Apo B-100 reconstituted in lipid vesicles resembling LDL, brought about by lipid peroxidation and lipid loading were examined by means of Fourier transform infra-red spectroscopy. It was found that, upon oxidation without the addition of cupric ions, the apolipoprotein attains a more exposed conformation with an increase in α-helical structure. This increase occurred at the expense of β-structure. On lipid loading, an increase in β-structure at the expense of the α-helix, was demonstrated. It is therefore proposed that the variable action of LDL towards thromboplastin derives from alterations in the secondary structure of the Apo B-100, particularly the receptor-binding region.

The Copper-containing Dissimilatory Nitrite Reductase Involved in the Denitrifying System of the Fungus Fusarium oxysporum

A copper-containing nitrite reductase (Cu-NiR) was purified to homogeneity from the denitrifying fungus Fusarium oxysporum. The enzyme seemed to consist of two subunits with almost the same M(r) value of 41,800 and contains two atoms of copper per subunit. The electron paramagnetic resonance spectrum showed that both type 1 and type 2 copper centers are present in the protein, whereas the visible absorption spectrum exhibited a sole and strong absorption maximum at 595 nm, causing a blue but not green color. The reaction product due to the Cu-NiR was mainly nitric oxide (NO), whereas a stoichiometric amount of nitrous oxide (N2O) was formed when cytochrome P-450nor was further added to the assay system. Therefore, the denitrifying (N2O forming) nitrite reductase activity that we had detected in the cell-free extract of the denitrifying cells (Shoun, H., and Tanimoto, T. (1991) J. Biol. Chem. 266, 11078-11082) could be reconstituted upon combination of the purified Cu-NiR and P-450nor. The Km for nitrite and specific activity at pH 7.0 were estimated as 49 microM and 447 mumol NO.min-1.mg protein-1, respectively. Its activity was strongly inhibited by cyanide, carbon monoxide, and diethyldithiocarbamate, whereas enormously restored by the addition of cupric ions. An azurin-like blue copper protein (M(r) = 15,000) and a cytochrome c were also isolated from the same fungus, both of which together with cytochrome c of the yeast Saccharomyces cerevisiae were effective in donating electrons to the fungal Cu-NiR. The result suggested that the physiological electron donor of the Cu-NiR is the respiratory electron transport system. The intracellular localization of Cu-NiR was investigated, and it was suggested that the Cu-NiR localizes in an organelle such as mitochondrion. These findings showed the identity in many aspects between the fungal nitrite reductase and bacterial dissimilatory Cu-NiRs. This is the first isolation of dissimilatory NiR from a eukaryote.

Diphenylhexatriene as a fluorescent probe for monitoring low density lipoprotein peroxidation.

The use of the fluorescent probe diphenylhexatriene (DPH) for monitoring low density lipoprotein (LDL) peroxidation has been investigated. The DPH incorporation into LDL results in a high fluorescence signal which decreases with time after addition of cupric ions. A strong correlation was found between the decay of the DPH fluorescence signal and the appearance of the thiobarbituric reactive substances (TBARS). HPLC and spectrofluorometric analyses demonstrated that DPH is destroyed during the time course of the copper-induced LDL peroxidation. The decrease in DPH fluorescent signal is prevented by addition of EDTA, vitamin E and drugs which protect LDL against peroxidation such as probucol or calcium antagonists. The high fluorescence of DPH allows the use of very small quantities of LDL (less than 5 micrograms/ml LDL protein). We thus suggest that DPH could be of use for continuous monitoring of LDL autooxidation, especially for the in vitro testing of the protective effect of antioxidant compounds.

Chemical conversion of a DNA-binding protein into a site-specific nuclease.

The tryptophan gene (trp) repressor of Escherichia coli has been converted into a site-specific nuclease by covalently attaching it to the 1,10-phenanthroline-copper complex. In its cuprous form, the coordination complex with hydrogen peroxide as a coreactant cleaves DNA by oxidatively attacking the deoxyribose moiety. The chemistry for the attachment of 1,10-phenanthroline to the trp repressor involves modification of lysyl residues with iminothiolane followed by alkylation of the resulting sulfhydryl groups with 5-iodoacetamido-1,10-phenanthroline. The modified trp repressor cleaves the operators of aroH and trpEDCBA upon the addition of cupric ion and thiol in a reaction dependent on the corepressor L-tryptophan. Scission was restricted to the binding site for the repressor, defined by deoxyribonuclease I footprinting. Since DNA-binding proteins have recognition sequences approximately 20 base pairs long, the nucleolytic activities derived from them could be used to isolate long DNA fragments for sequencing or chromosomal mapping.

Kinetics and mechanism of captopril oxidation in aqueous solution under controlled oxygen partial pressure.

The stability of captopril in aqueous solution at 32 degrees C was studied in the pH range 6.6 to 8.0 under controlled oxygen partial pressure (90-760 mm Hg) with and without the addition of cupric ion. The oxidation product, captopril disulfide, was found to be the sole degradation product. A change in reaction rate from first order to zero order occurs as the captopril concentration decreases. The concentration at which this transition takes place is a function of the pH, oxygen partial pressure, and cupric ion concentration. The apparent first-order rate constants show a first-order dependency on both the oxygen partial pressure and the cupric ion concentration. However, the apparent zero-order rate constants show a first-order dependency on oxygen partial pressure and a second-order dependency on cupric ion concentration. As the pH increases from 6.6 to 8.0, the first-order process becomes more predominant. A mechanism which consists of cupric ion- and molecular oxygen-catalyzed oxidation is proposed to explain those observations.

Nuclease activity of 1,10-phenanthroline-copper: sequence-specific targeting.

The nuclease activity of 1,10-phenanthroline-copper ion can be targeted to specific DNA sequences by attachment of the ligand to the 5' end of complementary deoxyoligonucleotides via a phosphoramidate linkage. To synthesize the adduct, the phosphorimidazolide of the deoxyoligonucleotide is prepared using a water-soluble carbodiimide and is then coupled to 5-glycylamido-1,10-phenanthroline. After hybridization to the target DNA, sequence-specific cleavage is observed upon the addition of cupric ion and 3-mercaptopropionic acid. Two methods of assaying the cutting of the operator sequence of the lac operon have been employed using the oligonucleotide 5'-AATTGTTATCCGCTCACAATT-3' representing sequence positions 21-1 of the template strand. In the first, the single-stranded DNA of the phage M13mp8 was the target, and cuts were detected using a primer-extension assay. In the second, the substrate was an EcoRI fragment 3' labeled in the nontemplate strand. After denaturation and reannealing to the oligonucleotide-1,10-phenanthroline adduct, cupric ion and 3-mercaptopropionic acid were added, and the products were analyzed directly on a sequencing gel. With the phenanthroline moiety attached to position 21 of the oligonucleotide carrier, cutting was observed at positions 20-25 using both assays.

Iodide Ion‐Selective Electrode and Its Application to the Determination of Organic Compounds

AbstractThe mixture of silver iodide and ferrocene is used to prepare the membrane of iodide ion‐selective electrode. The interference of sulfide can be reduced by the addition of cupric ion in the test solution. Ethylene glycol is determined by potentiometric titration using iodine ion‐selective electrode as an indicator electrode.

Linoleic Acid Oxidation Catalysed by Various Amino Acids and Cupric Ions in Aqueous Media

AbstractModel systems were designed to study the linoleic acid oxidation in the presence and absence of various amino acids and with or without cupric ions. The tested amino acids have shown to possess potential pro‐oxidant capacity in linoleic acid dispersed in aqueous media. The effectiveness of various amino acids on linoleic acid oxidation decreased in the following order: cysteine > serine > tryptophan > phenylalanine > histidine > alanine. The addition of alanine, serine, phenylalanine, histidine or tryptophan to linoleic acid have shown features of an autocatalytic oxidation chain reaction. With cysteine, there was a linear relation between concentration of hydroperoxides and time during the early stages of oxidation. The pro‐oxidative activity of the tested amino acids in general could be attributed to the presence of the α‐amino group in the form H3‐N‐R. The apparent difference in the pro‐oxidative activity is mainly due to the functional groups attached to β‐carbon in the amino acid molecules. The addition of cupric ions at concentration of 10–5 M to linoleic acid catalysed with various α‐amino acids have shown that these amino acids had no significant effect. The increasing copper concentration from 10–5 to 10–1 M shortened the induction period of linoleic acid catalysed by amino acids having aromatic side chain, had no effect on the induction period but increased the oxidation rate during the propagation step in the model systems catalysed by alanine and serine and in the model system containing cysteine increased the linoleic acid oxidation linearly from the start of the reaction.