Absence Of Copper Ions Research Articles

Effects of copper on hydroxyapatite thin films by pulsed laser deposition on silicon

AbstractThis study deals with the effect of Cu on hydroxyapatite (HAp) thin films on silicon substrates prepared by pulsed laser deposition (PLD) technique for Cu concentrations ranging from 0 to 0.8 wt.%. Fourier transform infrared spectroscopy and Raman spectroscopy provide additional evidence of HAp in the films, which exhibit characteristic HAp bands such as the 960 cm−1 phosphate ion band. The X‐ray diffraction patterns confirm the presence of HAp, without copper‐related peaks, suggesting that it is not incorporated into the HAp lattice, which is present as an amorphous phase. X‐ray photoelectron spectroscopy confirms the presence of Cu on the HAp thin films, possibly related to the adsorption of Cu2+ on HAp surfaces through electrostatic or interactions with (PO4)3− groups. Atomic force microscopy shows that the roughness of the films varies depending on the presence or absence of copper ions. Finally, density functional theory and kinetic Monte Carlo simulations explain the effects of atomic diffusion on roughness and HAp clustering. These changes correlate with the contact angle values, indicating the formation of hydrophobic films due to copper inclusions.

The Copper Efflux Regulator (CueR).

The copper efflux regulator (CueR) is a classical member of the MerR family of metalloregulators and is common in gram-negative bacteria. Through its C-terminal effector-binding domain, CueR senses cytoplasmic copper ions to regulate the transcription of genes contributing to copper homeostasis, an essential process for survival of all cells. In this chapter, we review the regulatory roles of CueR in the model organism Escherichia coli and the mechanisms for CueR in copper binding, DNA recognition, and interplay with RNA polymerase in regulating transcription. In light of biochemical and structural analyses, we provide molecular details for how CueR represses transcription in the absence of copper ions, how copper ions mediate CueR conformational change to form holo CueR, and how CueR bends and twists promoter DNA to activate transcription. We also characterize the functional domains and key residues involved in these processes. Since CueR is a representative member of the MerR family, elucidating its regulatory mechanisms could help to understand the CueR-like regulators in other organisms and facilitate the understanding of other metalloregulators in the same family.

Decontamination of water co-polluted by copper, toluene and tetrahydrofuran using lauric acid

Co-contamination by organic solvents (e.g., toluene and tetrahydrofuran) and metal ions (e.g., Cu2+) is common in industrial wastewater and in industrial sites. This manuscript describes the separation of THF from water in the absence of copper ions, as well as the treatment of water co-polluted with either THF and copper, or toluene and copper. Tetrahydrofuran (THF) and water are freely miscible in the absence of lauric acid. Lauric acid separates the two solvents, as demonstrated by proton nuclear magnetic resonance (1H NMR) and Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy (ATR-FTIR). The purity of the water phase separated from 3:7 (v/v) THF:water mixtures using 1 M lauric acid is ≈87%v/v. Synchrotron small angle X-Ray scattering (SAXS) indicates that lauric acid forms reverse micelles in THF, which swell in the presence of water (to host water in their interior) and ultimately lead to two free phases: 1) THF-rich and 2) water-rich. Deprotonated lauric acid (laurate ions) also induces the migration of Cu2+ ions in either THF (following separation from water) or in toluene (immiscible in water), enabling their removal from water. Laurate ions and copper ions likely interact through physical interactions (e.g., electrostatic interactions) rather than chemical bonds, as shown by ATR-FTIR. Inductively coupled plasma—optical emission spectrometry (ICP-OES) demonstrates up to 60% removal of Cu2+ ions from water co-polluted by CuSO4 or CuCl2 and toluene. While lauric acid emulsifies water and toluene in the absence of copper ions, copper salts destabilize emulsions. This is beneficial, to avoid that copper ions are re-entrained in the water phase alongside with toluene, following their migration in the toluene phase. The effect of copper ions on emulsion stability is explained based on the decreased interfacial activity and compressional rigidity of interfacial films, probed using a Langmuir trough. In wastewater treatment, lauric acid (a powder) can be mixed directly in the polluted water. In the context of groundwater remediation, lauric acid can be solubilized in canola oil to enable its injection to treat aquifers co-polluted by organic solvents and Cu2+. In this application, injectable filters obtained by injecting cationic hydroxyethylcellulose (HEC +) would impede the flow of toluene and copper ions partitioned in it, protecting downstream receptors. Co-contaminants can be subsequently extracted upstream of the filters (using pumping wells), to enable their simultaneous removal from aquifers.

Proteomic analysis of a copper mine isolated fungus Rhizopus microspores IOC 4686 when exposed to copper sulfate

The fungus Rhizopus microsporus, known for its absorption capacity for toxic metals was used to understand the green metal recovery via analysis of its physiology under metal stress conditions through proteomic methods. To investigate the effects of copper stress on fungus, R. microsporus IOC 4686, isolated from the mine environment, was exposed to copper ions (50mgL-1) for 48 h. This study was performed only on copper exposure. Tryptic and chymotryptic extracts of proteins were analyzed by nano- liquid chromatography-tandem mass spectrometry, identification was performed by PEAKS Studio 8.5. Proteins were classified according to their molecular function and biological process. Enzymes, such as catalase, superoxide dismutase, and cytochrome c peroxidase were found in the presence and absence of copper ions. However, only in presence of copper ions, was observed the presence of heat shock proteins (HPS 20, HPS 70, and HPS 78) and metalloproteins (GrpE protein homolog and cytochrome P450). These classes of proteins have been produced by cells in response to stress conditions. The control group (absence of copper ions) also presented antioxidant enzymes suggesting that the fungus isolated from the mine environment already has adapted to the copper. The presence of these proteins suggested a physiological response of R. microsporus IOC 4686 to oxidative stress induced by copper.

СОРБЦИЯ СУЛЬФАНИЛОВОЙ КИСЛОТЫ И ИОНОВ МЕДИ АКТИВИРОВАННЫМ УГЛЕМ, МОДИФИЦИРОВАННЫМ ОКСИДАМИ МЕТАЛЛОВ

The possibility of using activated carbon brand Filtrasorb 300 modified with metal oxides (F300 M) in comparison with unmodified (F300 H) for the simultaneous extraction of organic com-pounds and copper ions from water has been established. A solution of metal chloride obtained by acid-thermal activation of waste from alumina production "red mud" is used as a modifier. The process of sulfanilic acid and copper ions sorption by modified and unmodified activated carbon Filtrasorb 300 (AC F300) is investigated. The structural-sorption characteristics of the studied materials, such as: static exchange cationic and anionic capacities and the number of surface groups (carboxyl, lactone, phenolic), are determined. Positive effect of activated carbon modification by metal oxides that has been obtained as a result of acid-thermal treatment of “red mud” is shown. The presence of negatively charged active centers on modified activated carbon surface makes it possible to increase by 59 % the value of sulfanilic acid adsorption due to the interaction of the ma-terial surface with –NH2 group of the acid with the absence of copper ions in the solution, which is 24 % more than AB F300. Simultaneous presence of copper ions and sulfanilic acid reduces their adsorption on the modified sorbent as a result of blocking the active groups and reducing the electrostatic interaction. Taking into account the complex nature of physical-chemical interactions in a system that contains sulfanilic acid with acidic and basic groups, and the competing effect under certain conditions, it can be expected that the modification of activated carbon with a metal chloride solution (obtained by acidic activation of alumina production wastes with their subsequent conversion to oxide form), is a promising direction in water treatment in case of containing both organic compounds and non-ferrous metal ions.

Isoferulic acid prevents methylglyoxal-induced protein glycation and DNA damage by free radical scavenging activity.

BackgroundIsoferulic acid (IFA), a naturally occurring cinnamic acid derivative, is a main active ingredient of the rhizoma of Cimicifuga dahurica. It has been shown various pharmacological activities. The aim of the study was to investigate the effect of IFA against MG-induced protein glycation and oxidative DNA damage. Free radical scavenging activity and the MGO-trapping abilities of IFA were also investigated.MethodsThe fluorescent MG-derived AGEs and non-fluorescent Nε-(carboxymethyl) lysine (Nε-CML) was measured using a spectrofluorometer and an enzyme linked immunosorbant assay (ELISA). Protein carbonyl content was used to detect protein oxidation. Gel electrophoresis was used to determine DNA damage. Superoxide anion radicals and hydroxyl radicals were determined using cytochrome c reduction assay and thiobarbituric acid reactive 2-deoxy-D-ribose oxidation products, respectively. The MG-trapping capacity was performed by HPLC.ResultsIFA (1.25–5 mM) inhibited the formation of fluorescent MG-derived AGEs, and Nε-CML, and protein carbonyl in bovine serum albumin. In addition, IFA (0.1–1 mM) also prevented MG/lysine-mediated oxidative DNA damage in the presence and absence of copper ion. The protective ability of IFA was directly correlated to inhibition of hydroxyl and superoxide anion radical generation during the reaction of MG and lysine. Most notably, IFA had no the directly trapping ability to MG.ConclusionsThe present results highlighted that free radical scavenging activity, but not the MG-trapping ability, is the mechanism of IFA for preventing MG-induced protein glycation and DNA damage.

Oxidation of Methionine-35 in Alzheimer’s amyloid-beta peptide and the aggregation of the oxidized peptide

Alzheimer’s disease (AD) is a neurodegenerative disease characterized by progressive loss of brain tissue and accumulation of amyloid-β(Aβ) and tau. Aggregation of Aβ peptides into amyloid plaques is considered to be a causative factor in AD, however the precise mechanism behind the AD onset has remained elusive. Oxidative stress (OS) is also characteristic to AD, but it is not known whether OS is a risk factor or a consequence of AD. It is assumed that Aβ aggregates generate free radicals in the presence of copper ions by participation of the Met35 residue, which can increase the OS levels. The aim of our study was to establish the role of Met35 residue in the oxidation of Aβ and peptide aggregation processes. Oxidation of Aβ was studied in the presence of two redox-active compounds: H2O2 and copper ions. In the absence of copper ions the Met35 residue was readily oxidized by H2O2 in a two electron process. The fibrillization of Aβ with Met35 oxidized to sulfoxide was threefold slower compared to that of the native peptide. TEM analysis showed that the fibrils of native and oxidized peptides are similar. The relatively small inhibitory effect of Met35 oxidation on the fibrillization suggests that the possible variation in the Met oxidation state should not affect the in vivo plaque formation. In the presence of copper ions (one-electron process) the oxidation was more complex: addition of the first oxygen was still the fastest process, however, it was accompanied by multiple unspecific modifications of several amino acid residues. Addition of copper ions to the already oxidized Aβ Met35 by H2O2, resulted in a similar pattern of nonspecific modifications, suggesting that the one-electron oxidation processes in Aβ do not depend on the oxidation state of Met35. Thus, it can be concluded that Met35 residue is not a part of the radical generating mechanism of Aβ-Cu(II) complex.

Electrochemical Comparison of the Interaction of 5-Nitrouracil with Single- or Double-Stranded DNA at mercury and glassy carbon electrodes

The interaction of the 5-Nitrouracil (5NU), with ss-, and ds-DNA was investigated electrochemically in absence and presence of copper ions by using cyclic voltammetry (CV) and differential pulse stripping voltammetry (DPSV) at hanging mercury drop electrode (HMDE) and glassy carbon electrode (GCE) surfaces. It was found that, in absence of copper ions, the addition of ss- or ds-DNA to a buffered solution of 5NU results in a decrease on the 5NU redox peak current with a remarkable change in the peak potential (ca. 150 mV vs. Ag/AgCl) at both electrodes. This means that, an interaction of 5NU molecules with both ss- and ds-DNA was observed. The results also demonstrate that a distinguish between ss-, and ds-DNA can be achieved in presence of copper ion through their interaction with 5NU. The binding constants of 5NU with ds-DNA at HMDE and GCE were determined through the changes on the 5NU redox peak currents (at HMDE, 1.45x10^5 and at GCE, 2.65x10^5). The calibration plot for the DNA determination was obtained through the corresponding decreases on the DPSV peak current of 5NU to different additions of DNA (ss- or ds-DNA) concentration levels at the optimum conditions.

CdSe/ZnS core/shell quantum dots as luminescence lifetime sensors for Cu2+

We report the use of CdSe/ZnS core/shell quantum dots QDot800 (Invitrogen) as luminescence lifetime sensors for copper ions Cu2+(H2O)8 in solution with a sensitivity of <1 ppb that is relevant to intracellular copper concentrations. Excitation of QDot800 at 485 nm was found to be optimum in that it did not cause any change in the level of luminescence intensity or luminescence lifetime in the absence of copper ions. When excited at 485 nm a bi-exponential luminescence decay of QDot800 was observed suggesting the presence of two distinct emitting states, both capable of undergoing metal ion quenching that facilitates Cu2+ detection. Selectivity for copper, as against other transition metal ions, as well as other evidence, suggests the primary origin of the quenching is luminescence resonance energy transfer to both free and bound copper ions. The luminescence kinetics of quantum dots and their optimization and applicability for resonance energy transfer-based lifetime sensing in general is discussed.

Structural and functional characterization of the transcriptional repressor CsoR from Thermus thermophilus HB8

The TTHA1719 gene from Thermus thermophilus HB8 encodes an orthologue of the copper-sensing transcriptional repressor CsoR. X-ray crystal structure analysis of T. thermophilus CsoR indicated that it forms a homotetramer. The structures of the CsoR monomer and dimer are similar to those of Mycobacterium tuberculosis CsoR. In the absence of copper ions, T. thermophilus CsoR bound to the promoter region of the copper-sensitive operon copZ-csoR-copA, which encodes the copper chaperone CopZ, CsoR and the copper efflux P-type ATPase CopA, to repress their expression, while in the presence of approximately an equal amount of copper ion, CsoR was released from the DNA, to allow expression of the downstream genes. Both Cu(II) and Cu(I) ions could bind CsoR, and were effective for transcriptional derepression. Additionally, CsoR could also sense various other metal ions, such as Zn(II), Ag(I), Cd(II) and Ni(II), which led to transcriptional derepression. The copper-binding motif of T. thermophilus CsoR contains C-H-H, while those of most orthologues contain C-H-C. The X-ray crystal structure of T. thermophilus CsoR suggests that a histidine residue in the N-terminal domain is also involved in metal-ion binding; that is, the binding motif could be H-C-H-H, like that of Escherichia coli RcnR, which binds Ni(II)/Co(II). The non-conserved H70 residue in the metal-binding motif of T. thermophilus CsoR is important for its DNA-binding affinity and metal-ion responsiveness.

A copper-activated magnetic resonance imaging contrast agent with improved turn-on relaxivity response and anion compatibility

We present the synthesis and characterization of Copper-Gad-7 (CG7), a new copper-activated magnetic resonance imaging (MRI) contrast agent that possesses a Gd(3+)-DO3A scaffold with an appended thioether-rich receptor for copper recognition. Installation of additional carboxylate groups on the periphery of the CG scaffold affords a practical strategy to increase the absolute relaxivity of these types of copper-responsive MRI sensors as well as reduce their sensitivity to biologically abundant anions. Due in large part to restricted access of inner-sphere water molecules to the paramagnetic Gd(3+) core, in the absence of copper ions, CG7 exhibits a relatively low relaxivity value of r(1) = 2.6 mM(-1) s(-1); addition of Cu(+) triggers a 340% enhancement in relaxivity to r(1) = 11.4 mM(-1) s(-1). For comparison, the relaxivity of the analogous CG2 sensor without peripheral carboxylates increases from r(1) = 1.5 to 6.9 mM(-1) s(-1) upon Cu(+) binding. CG7 features high selectivity for Cu(+) over a range of biologically relevant metal ions, including the cellular abundant alkali and alkaline earth cations and d-block ions Zn(2+) and Cu(2+). Moreover, the Cu(+)-response of the CG7 sensor is not significantly affected by bicarbonate, phosphate, citrate, and lactate anions at cellular levels. (17)O NMR dysprosium-induced shift (DIS) and nuclear magnetic relaxation dispersion (NMRD) experiments suggest that the origin of the improved anion compatibility of CG7 is a reduced q modulation compared to previous members of the CG family, and T(1)-weighted phantom images confirm that CG7 can monitor changes in copper levels by MRI at clinically relevant field strengths.

Copper-Responsive Magnetic Resonance Imaging Contrast Agents

The design, synthesis, and evaluation of the Copper-Gad (CG) family, a new class of copper-activated magnetic resonance imaging (MRI) contrast agents, are presented. These indicators comprise a Gd(3+)-DO3A core coupled to various thioether-rich receptors for copper-induced relaxivity switching. In the absence of copper ions, inner-sphere water binding to the Gd(3+) chelate is restricted, resulting in low longitudinal relaxivity values (r(1) = 1.2-2.2 mM(-1) s(-1) measured at 60 MHz). Addition of Cu(+) to CG2, CG3, CG4, and CG5 and either Cu(+) or Cu(2+) to CG6 triggers marked enhancements in relaxivity (r(1) = 2.3-6.9 mM(-1) s(-1)). CG2 and CG3 exhibit the greatest turn-on responses, going from r(1) = 1.5 mM(-1) s(-1) in the absence of Cu(+) to r(1) = 6.9 mM(-1) s(-1) upon Cu(+) binding (a 360% increase). The CG sensors are highly selective for Cu(+) and/or Cu(2+) over competing metal ions at cellular concentrations, including Zn(2+) at 10-fold higher concentrations. (17)O NMR dysprosium-induced shift and nuclear magnetic relaxation dispersion measurements support a mechanism in which copper-induced changes in the coordination environment of the Gd(3+) core result in increases in q and r(1). T(1)-weighted phantom images establish that the CG sensors are capable of visualizing changes in copper levels by MRI at clinical field strengths.

The role of copper in cysteine oxidation: study of intra- and inter-molecular reactions in mass spectrometry

Cysteine-containing peptide oxidation was studied both by using an inert platinum electrode and a sacrificial electrode (copper or zinc) generating metallic ions in electrospray ionization mass spectrometry (ESI-MS). Using peptides containing one, two and three cysteines, we have compared the different chemical and electrochemical oxidation pathways of cysteine (RS(-II)H) to cystine (RS(-I)S(-I)R) and to sulfenic, sulfinic and sulfonic acid (RS(0)OH, RS(II)O(2)H and RS(IV)O(3)H, respectively). In the absence of copper ions, intra-molecular reactions were the most abundant, whereas inter-molecular reactions were found to be enhanced by the presence of copper ions. These cations favor the formation of 2 : 1 (peptide : copper) complexes compared to 1 : 1 complexes, thus enhancing the formation of inter-molecular bridges. This study highlights the importance of the position of cysteine inside a peptide during disulfide bridge formation.

Determination of trace selenium on hanging copper amalgam drop electrode

Hanging copper amalgam drop electrode has been applied for trace determination of selenium by cathodic stripping analysis. Detection limit for Se(IV) as low as 0.25 nM (0.02 μg L −1) at deposition time (120 s) could be obtained. For seven successive determinations of Se(IV) at concentration of 5 nM relative standard deviation was 2.3% ( n = 7). Interferences from selected metals and surfactant substances were examined. Absence of copper ions in sample solution causes easier optimization and makes method less vulnerable on contamination. The developed method was validated by analysis of certified reference materials (BCRs) and applied to selenium determinations in natural water samples, snow, mushrooms and ox liver.

Determination of trace arsenic on hanging copper amalgam drop electrode

Hanging copper amalgam drop electrode has been applied for trace determination of arsenic by cathodic stripping analysis. Detection limit for As(III) as low as 0.33 nM (0.02 μg/L) at deposition time (240 s) could be obtained. For seven successive determinations of As(III) at concentration of 5 nM relative standard deviation was 2.5% ( n = 7). Interferences from selected metals and surfactant substances were examined. Absence of copper ions in sample solution causes easier optimization and makes method less vulnerable on contamination. The developed method was validated by analysis of certified reference materials (CRMs) and applied to arsenic determinations in natural water samples.

Palladium-catalysed alkynylation of 2- or 3-bromopyridine

2- or 3-Alkynylpyridines were prepared using a palladium complex, in the absence of copper ions or amines. The mild procedure tolerated a range of 1-alkynes giving 2- or 3-alkynylpyridine in moderate to good yield.

Protective Effects of Extra Virgin Olive Oil Phenolics on Oxidative Stability in the Presence or Absence of Copper Ions

The antioxidant activity of the phenolic fraction of extra virgin olive oil was assessed in samples that had a decreasing content of antioxidants in the presence and absence of copper ions as a catalyst of autoxidation. The oxidation process was evaluated by measuring primary and secondary oxidation products. Changes in phenols and tocopherols were investigated by high-performance liquid chromatography. Both the total phenol content and their antioxidant activity were monitored by spectrophotometric assays (with Folin-Ciocalteu and ABTS*+ reagents). The important role of phenolic compounds (particularly the o-diphenols) in protection from autoxidation was confirmed. However, the tocopherols were more quickly consumed in oils that had the lowest content of o-diphenols, which also showed evidence of an ability to chelate copper. In particular, a dramatic decrease was observed in the isomeric form of decarboxymethyl-oleuropein aglycone after addition of the metal, despite its significant increase in samples stored in the absence of copper.

Copper excess triggers phospholipase D activity in wheat roots

Wheat seedlings ( Triticum durum Desf.) were incubated in 100 μM Cu 2+ for different periods of time ranging from 1 min up to 16 h. Following metal addition a rapid intake of copper ions into the roots was observed. Cu 2+ induced an accumulation of both phosphatidic acid and phosphatidylbutanol within 1 min of incubation, the latter indicating a very rapid induction of phospholipase D (PLD) activity. The highest PLD stimulation was detected after 2 h from copper addition and decreased almost to the initial value at increasing times. Cycloheximide treatment of roots lowered phosphatidylbutanol accumulation because of a reduced PLD activity. The expression profile of a T. durum putative PLD-encoding gene showed a peak after 1 h of treatment as well, indicating that enhanced gene expression contributed to the increase in PLD activity. In the absence of copper ions, roots treated with the G protein activator mastoparan showed increases in phosphatidic acid and phosphatidylbutanol similar to those detected with the metal. PLD activity was also stimulated by cholera toxin. Two putatively G protein α subunit encoding sequences were isolated and no significant differences in transcription activity following Cu 2+ addition were observed. In copper-treated roots an early production of superoxide generated both by total and membrane-bound NADPH oxidase occurred. The G protein inhibitor suramin as well as the PLD antagonist 1-butanol abolished copper-induced superoxide production.

EQCM Study of the Influence of Copper Ions on the Adsorption of Polyethylene Glycol and Bis(sodium sulfopropyl) Disulfide at a Copper Cathode

An electrochemical quartz crystal microbalance (EQCM) has been used to examine the role of polyethylene glycol (PEG) and bis (sodiumsulfopropyl) disulfide (SPS) in the deposition of copper from acidified aqueous sulfate solutions containing chloride ions. Neither PEG nor SPS was observed to adsorb on copper at cathodic potentials in the absence of copper ions in solution. When a small amount of copper (principally Cu (II)) was introduced into solution by a double potential step, the adsorption of PEG was observed, as was the inhibition of that adsorption by SPS.

Electrochemical characterization of chemical species formed during the electrochemical treatment of chalcopyrite in sulfuric acid

The dissolution mechanism of chalcopyrite, and the potential range in which its passivation phenomenon takes place, were studied on carbon paste electrodes with chalcopyrite (99.46% purity, +300 mesh, 53 μm size) (CPE–CP) in 1.7 mol/dm 3 H 2SO 4. A sequence of anodic potential pulses was applied to the CPE–CP to characterize its electrochemical behavior. Copper ions, dissolved by the potential pulses, were determined using a mercury film electrode (MFE) and the anodic stripping voltammetry (ASV) on a vitreous carbon disk. In addition, the modified surface of CPE–CP was characterized, before and after the potential pulses, by cyclic voltammetry (CV). The characterization of the final surface state of each electrochemically modified CPE–CP and the amount of dissolved copper showed five potential regions where the chalcopyrite dissolution mechanism changed. The initial dissolution occurs at 0.615 V ≤ E anod < 1.015 V versus SHE forming a non-stoichiometric polysulfide (Cu 1− r Fe 1− s S 2− t ). The absence of copper ions in the solution indicates a passive sulfide. However, at 1.015 V ≤ E anod < 1.085 V versus SHE, the passive product decomposes forming porous layers of non-stoichiometric polysulfide (Cu 1− x Fe 1− y S 2− z ) that allow the diffusional transport of charged species and the dissolution of the mineral. In the region of 1.085 V ≤ E anod < 1.165 V versus SHE, formation covellite (CuS) was identified. At E > 1.165 V versus SHE, CuS is unstable and gives rise to complete dissolution of the chalcopyrite. Due to the experimental conditions, the mineral dissolution is inhibited by possible jarosite precipitation.