Absence Of Cu Research Articles

Multifunctional Logic Operations Based Upon Congruent Ion Sensing Appended with a Strategic Molecular Device: Spectroscopic Approach

AbstractA multi‐responsive smart molecular system is constructed using a newly synthesized Salen molecule, 1,3‐bis((E)‐2,3,4‐trimethoxy benzylideneamino) propan‐2‐ol (TMBP), to selectively recognize the presence and absence of Cu2+ ions aided by another selective metal ion, Zn2+. The emission efficiency of the non‐emissive probe is selectively and significantly enhanced in presence of Zn2+, while the improved emission of probe‐Zn2+ complex is completely quenched upon interaction with Cu2+. Thus, the probe acts as a reporter molecule for the selective detection of Cu2+ in the co‐presence of Zn2+. Comprehensive spectroscopic studies indicate that Zn2+ ion‐coordination significantly reduces the flexibility of the Schiff base unit and the extent of photoinduced electron transfer which in turn enhance the fluorescence intensity. While Cu2+, a d9 system, induces paramagnetic quenching over the enhanced emission through stable ground‐state complexation and metal‐ligand charge transfer. The spectroscopic results are translated into the designing of a multifunctional smart‐molecular system that could function as YES, NOT, INHIBIT, PASS 0, TRANSFER and NOT TRANSFER logic gates. Finally, a blueprint of a smart molecular device is proposed to present the relay sensing of Zn2+ and Cu2+ through logical outputs that would work in‐sync with the spectroscopic results.

Interface engineering of BiVO4/Zn3V2O8 heterocatalysts for escalating the synergism: Impact of Cu electron mediator for overall water splitting

The risk of global warming is increasing due to excessive consumption of fossil fuels. To fill the gap between production and consumption of conventional energy sources, modern societies are searching green and renewable alternatives. In this work, BiVO4/Zn3V2O8 heterocatalysts were synthesized and interfacially engineered for overall water splitting reactions. To obtain the structural and interfacial morphologies, catalysts were characterized by XRD, FTIR, Raman spectroscopy, SEM and AFM techniques. The optical and chemical characteristics of as-synthesized catalysts were evaluated using UV–Vis/DRS, PL, EIS, EDX, XPS and BET analysis. The role of Cu metal, synergism between BiVO4/Zn3V2O8 and mechanistic approaches were further revealed. The results depict that Cu metal exceptionally compete to sustain the synergism as an electron mediator source. The synergistic effect and electron mediator were found as key factors to boost the overall water splitting efficiencies. Due to interfacial engineering of BiVO4/Zn3V2O8 system, charge transfer becomes more feasible for the redox reactions (i.e. water splitting). It was examined that due to presence of Cu metal, rate of overall water splitting reaction was higher than the catalysts having no mediator (i.e. absence of Cu). During photoreaction, two successive rates for H2 and O2 evolution were speculated 17.66 and 8.96 mmol g−1 h−1, respectively which delivers approximately 5.04 kJ g−1 h−1 energy. On the basis of results and activities, it could be concluded that, this research will exhibit exceptional potential and hold promise of an ultimate transition to the water splitting and green energy technologies.

Effects of Cu(II)-DOM complexation on DOM degradation: Insights from spectroscopic evidence

The fate of dissolved organic matter (DOM) is primarily governed by its sources, degradation, and transformation processes within the environment. However, the influence of metal-DOM complexation on DOM degradation remains ambiguous. In this study, controlled laboratory experiments were conducted using Cu(II) and natural water from the Duliujian River and the Beidagang Wetland to examine the effects of metal-DOM binding on the degradation pathway of DOM. Our results showed that Cu(II)-DOM complexation affected the distribution of DOM molecular weight with elevated Mw after complexed with Cu(II). Nevertheless, the concentration of DOM decreased over the incubation period due to degradation. In the absence of Cu(II) binding, both wetland and river DOM followed similar degradation pathways, transforming from high to low molecular weight with changes predominantly in the 1–10 kDa size-fraction during DOM degradation. In contrast, in the presence of Cu(II) and thus Cu(II)-DOM binding, the degradation of DOM was enhanced, resulting in higher kinetic rate constants for both wetland and river DOM. The results of differential spectra further confirmed the degradation of DOM with a decrease in bulk spectroscopic properties and an increase in the degree of DOM-Cu(II) complexation. These findings imply a mutually reinforcing relationship between metal-DOM complexation and the degradation of DOM in aquatic environments, providing new insights into the biogeochemical behavior and environmental fate of DOM.

Copper binding alters the core structure of amyloid fibrils formed by Y145Stop human prion protein.

Transmissible spongiform encephalopathies (or prion diseases) such as Creutzfeldt-Jacob disease, mad cow disease, and scrapie are characterized by accumulation in the brain of misfolded prion protein aggregates (PrPSc) that have properties of amyloid fibrils. Given that transition metal ions, such as copper and zinc, appear to be important for physiological functions of cellular PrP (PrPC) as well as for prion disease pathogenesis, exploring their role in the protein aggregation process is of considerable interest. Copper(II) in particular is well-known to bind to the four tandem octapeptide repeats (PHGGGWGQ) located in the N-terminal region of PrP (human PrP amino acids 60-91), as well as to additional histidine binding sites outside the octarepeat region with distinct binding modes depending on Cu2+ concentration. Here, using the Y145Stop human prion protein variant (huPrP23-144) as a model and a combination of multidimensional solution and solid-state NMR spectroscopy, atomic force microscopy and thioflavin T fluorescence assays we probed the binding of Cu2+ to monomeric huPrP23-144 and the impact of this binding on fibril assembly kinetics and their structural properties. Remarkably, we found that fibrils formed by huPrP23-144 containing one molar equivalent of bound Cu2+ adopt a core structure that is distinct from that found for huPrP23-144 in the absence of Cu2+ but, instead, corresponds to a conformational strain formed by huPrP23-144 containing the A117V mutation. A similar huPrP23-144 A117V-like amyloid core structure was adopted by a Cu2+-bound Δ51-91 huPrP23-144 deletion variant lacking the entire octarepeat region, suggesting that Cu2+ binding to His residues 96, 111 and 140 located near the C-terminus of huPrP23-144 is primarily responsible for the observed change in fibril conformation, potentially due to partial structuring of the intrinsically disordered huPrP23-144 by the bound Cu2+ during the fibril assembly process. We also found that fibrils formed by Cu2+-bound huPrP23-144 adopt the native huPrP23-144-like rather than A117V-like structure when the fibrillization reaction is seeded with pre-formed huPrP23-144 amyloid.

Revealing the DNA Binding Modes of CsoR by EPR Spectroscopy.

In pathogens, a unique class of metalloregulator proteins, called gene regulatory proteins, sense specific metal ions that initiate gene transcription of proteins that export metal ions from the cell, thereby preventing toxicity and cell death. CsoR is a metalloregulator protein found in various bacterial systems that "sense" Cu(I) ions with high affinity. Upon copper binding, CsoR dissociates from the DNA promoter region, resulting in initiation of gene transcription. Crystal structures of CsoR in the presence and absence of Cu(I) from various bacterial systems have been reported, suggesting either a dimeric or tetrameric structure of these helical proteins. However, structural information about the CsoR-DNA complex is missing. Here, we applied electron paramagnetic resonance (EPR) spectroscopy to follow the conformational and dynamical changes that Mycobacterium tuberculosis CsoR undergoes upon DNA binding in solution. We showed that the quaternary structure is predominantly dimeric in solution, and only minor conformational and dynamical changes occur in the DNA bound state. Also, labeling of the unresolved C- terminus revealed no significant change in dynamics upon DNA binding. These observations are unique, since for other bacterial copper metalloregulators, such as the MerR and CopY families, major conformational changes were observed upon DNA binding, indicating a different mode of action for this protein family.

New Hybrid Compounds Incorporating Natural Products as Multifunctional Agents against Alzheimer's Disease.

A series of new hybrid derivatives 1a-c, 2a-c, 3a-c, 4a-c, 5a-c, inspired by nature, were synthesized and studied as multifunctional agents for the treatment of Alzheimer's disease (AD). These compounds were designed to merge together the trifluoromethyl benzyloxyaminic bioactive moiety, previously identified, with different acids available in nature. The ability of the synthesized compounds to chelate biometals, such as Cu2+, Zn2+ and Fe2+, was studied by UV-Vis spectrometer, and through a preliminary screening their antioxidant activity was evaluated by DPPH. Then, selected compounds were tested by in vitro ABTS free radical method and ex vivo rat brain TBARS assay. Compounds 2a-c, combining the strongest antioxidant and biometal chelators activities, were studied for their ability to contrast Aβ1-40 fibrillization process. Finally, starting from the promising profile obtained for compound 2a, we evaluated if it could be able to induce a positive cross-interaction between transthyretin (TTR) and Aβ in presence and in absence of Cu2+.

Antiglycation and antioxidant activity of herbal medicines used in the treatment of climacteric symptoms

ObjectivesThis work had the objective to evaluate the antiglycation and antioxidant potential of Cimicifuga racemosa L., Trifolium pratense L., Humulus lupulus L. and Morus nigra L., commonly used in traditional medicine for the treatment of climacteric symptoms. MethodsAntioxidant activity was evaluated by 2,2-Diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging, ferric reducing antioxidant power, inhibition of lipid peroxidation thiobarbituric acid reactive substances (TBARS), nitric oxide (NO) radical scavenging and inhibition of oxidative haemolysis test. The evaluation of antiglycation activity was performed by the determination of relative electrophoretic mobility of bovine serum albumin (BSA) with ribose and BSA with methylglyoxa in the presence and absence of Cu2+ ion. Total polyphenol and flavonoid contents were determined by spectrophotometric methods. ResultsThe highest antioxidant activity for DPPH and ferric reducing antioxidant power test was detected in Humulus lupulus (83.56% and 46.95 µM TE/g dry extract, respectively). For the inhibition of lipid peroxidation, the lowest percentages of TBARS were found in M. nigra (4.82%) and H. lupulus (18.26%). C. racemosa presented the lowest nitrite formation (34.57 µmol/mL nitrite formed) in nitric oxide test. T. pratense presented the highest polyphenol (24.61 mg GAE/g dry extract) and flavonoid (22.79 mg RE/g dry extract) contents. For the oxidative haemolysis assay, the extracts showed concentration-dependent inhibitory capacity, while for the antiglycation activity all extracts showed antiglycation potential against glycation of BSA promoted by Ribose evaluated by the electrophoretic profile. ConclusionsIn view of the results obtained in this study, it was possible to verify that the dry extracts of herbal medicines used for climacteric symptoms present antioxidant and antiglycation activities, mainly due to the presence of phenols compounds in their composition.

A comparative study of fluid characteristics of W and Cu mineralization in the Shiweidong deposit, giant Dahutang ore field, South China: Evidence from LA-ICP-MS analysis of fluid inclusion

The Shiweidong W-Cu deposit, located within the giant Dahutang W-Cu ore field, contains quartz vein type W-Cu and veinlet-disseminated type W mineralization. These ore veins are mainly hosted in the Jinningian biotite granodiorite. Two distinct mineralization stages were identified in association with quartz, namely wolframite-quartz veins and chalcopyrite-scheelite-quartz association. The deposit represents an example of a complex of economically valuable W and Cu, with resources of 0.3 Mt WO3 and 0.24 Mt Cu. The characteristic and origin of the W and Cu mineralizing fluids remain debated. In our study, homogenization temperature (Th) and salinity were determined for fluid inclusions (FIs) in ore or associated gangue minerals. Additionally, we use the trace element compositions of fluid inclusions obtained by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to clarify fluid characteristics responsible for W and Cu mineralization. Primary fluid inclusions (FIs) trapped in wolframite display high Th ranging from 305 to 352 °C and have moderate salinity from 3.2 to 5.0 wt% NaCl equiv., quartz associated with chalcopyrite exhibit a close syngenetic relationship, and a significant low-temperature (248 ∼ 271 °C) fluid was recorded by FIs in quartz. Wolframite-hosted FIs were characterized by high concentrations of incompatible lithophile element Cs and volatile elements including Li and B, indicating that W mineralization fluid was derived from highly fractionated granitic systems. All FIs in wolframite display the absence of Cu. In contrast, FIs hosted in quartz coexisting with chalcopyrite have the high Cu concentrations with average value of 1033 ppm. Giving the lower Cs content in FIs from quartz coexisting with chalcopyrite, we suggest that the Cu-rich ore-forming fluid released from a less fractionated magma. These results indicate that W and Cu mineralization at Shiweidong was introduced by distinct fluids. Fluid simple cooling is likely a major driving factor in wolframite formation, while fluid boiling accompanied chalcopyrite deposition. Our new findings illuminate that the existence of independent Cu mineralization events in the W deposit in northern Jiangxi.

Ligand-Mediated Control of the Surface Oxidation States of Copper Nanoparticles Produced by Laser Ablation

We report on studies that demonstrate how the chemical composition of the surface of copper nanoparticles (CuNPs) - in terms of percentage copper(I/II) oxides - can be varied by the presence of N-donor ligands during their formation via laser ablation. Changing the chemical composition thus allows systematic tuning of the surface plasmon resonance (SPR) transition. The trialed ligands include pyridines, tetrazoles, and alkylated tetrazoles. CuNPs formed in the presence of pyridines, and alkylated tetrazoles exhibit a SPR transition only slightly blue shifted with respect to CuNPs formed in the absence of any ligand. On the other hand, the presence of tetrazoles results in CuNPs characterized by a significant blue shift of the order of 50-70 nm. By comparing these data also with the SPR of CuNPs formed in the presence of carboxylic acids and hydrazine, this work demonstrates that the blue shift in the SPR is due to tetrazolate anions providing a reducing environment to the nascent CuNPs, thus preventing the formation of copper(II) oxides. This conclusion is further supported by the fact that both AFM and TEM data indicate only small variations in the size of the nanoparticles, which is not enough to justify a 50-70 nm blue-shift of the SPR transition. High-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) studies further confirm the absence of Cu(II)-containing CuNPs when prepared in the presence of tetrazolate anions.

Exploring particulate methane monooxygenase (pMMO) proteins using experimentation and computational molecular docking

Researchers had difficulty studying pure full-length pMMO due to the solubility problem and loss of enzymatic activity after its elimination from the native membrane. To study pMMO, we performed several bioinformatics tools to analyze the entire structure of it available in the PDB database. We also carried out molecular docking studies to prove that quinone and duroquinone can bind to several sites of eight pMMO proteins. However, some sites in the orientation are not required by the catalysis process. Furthermore, molecular docking was done for predicting the binding affinity of P450 with target enzymes. Interestingly, our analysis illustrated that pMMO can produce methanol in the presence of quinone and duroquinone and the absence of Cu. Moreover, pmoB1 can interact with P450. Consequently, our findings highlight, for the first time, the significance of studying the membrane of pMMO to provide valuable insights into its functions.

Cell volume maintenance capacity of the sea anemone Bunodosoma cangicum: the effect of copper.

Cell volume regulation is an essential strategy for the maintenance of life under unfavorable osmotic conditions. Mechanisms aimed at minimizing the physiological challenges caused by environmental changes are crucial in anisosmotic environments. However, aquatic ecosystems experience multiple stressors, including variations in salinity and heavy metal pollution. The accumulation of heavy metals in aquatic ecosystems has a significant effect on the biota, leading to impaired function. The aim of this study was to investigate the capacity of volume regulation in isolated cells of the sea anemone Bunodosoma cangicum exposed to nominal copper (Cu) concentrations of 5 and 50µg L-1, associated or not with hypoosmotic (15‰) or hyperosmotic (45‰) shock for 15min. In the absence of the metal, our results showed volume maintenance in all osmotic conditions. Our results showed that cell volume was maintained under all osmotic conditions in the absence of Cu. Similarly, no significant differences were observed in cell volumes under isosmotic and hyperosmotic conditions in the presence of both Cu concentrations. A similar homeostatic response was observed under the hypoosmotic condition with 5µg L-1 Cu. Our results showed an increase in cell volume with exposure of the cells to the hypoosmotic condition and 50µg L-1 Cu. The response could be associated with the increased bioavailability of Cu, reduced ability to resist multixenobiotics and their efflux pathways, and the impairment of water efflux in specialized transmembrane proteins. Therefore, B. cangicum pedal disk cells can tolerate osmotic variations in aquatic ecosystems. However, the capacity to regulate cell volume under hypoosmotic conditions can be affected by the presence of a metal contaminant (50µg L-1 Cu), which could be due to the inhibition of water channels.

Addition of jabuticaba peel extract with antioxidant properties in biodiesel

The unsaturated esters present in biodiesel as well as the presence of metallic ions traces from its production, storage, and transport are factors responsible for its susceptibility to the oxidation reaction. The oxidative stability of samples with jabuticaba peel extract was analyzed in the presence and absence of Cu2+, Fe2+, and Fe3+. The oxidative stability assays on the samples were carried out at 110, 115, 120, and 125 °C. It was obtained the induction periods and the kinetic and thermodynamic parameters of the oxidation reaction. The addition of jabuticaba peel extract increased the biodiesel induction period compared to the control sample and decreased the rate constants at each evaluated temperature. The oxidation process was non-spontaneous and endothermic in all assays: ∆G‡ > 0, ∆H‡ > 0, and ∆S‡ < 0.

Influence of Fe2O3 and bacterial biofilms on Cu(II) distribution in a simulated aqueous solution: A feasibility study to sediments in the Pearl River Estuary (PR China)

This study investigated physico-chemical interactions among Cu(II), biogenic materials, and Fe2O3 in a continuous-flow biofilm reactor system under a well-controlled environment. The effects of Fe2O3 and bacterial biofilms on the distribution of Cu(II) in a simulated aquatic environment were studied. To control biological and abiotic elements in the marine environment, a biofilm reactor was designed to understand the metal speciation of Cu(II) and its distribution. The reactor consisted of a biofilm chamber equipped with glass slides for biofilms attachment. Due to its ability to grow as biofilm in the medium, Pseudomonas atlantica was cultivated to adsorb trace Cu(II) to attached and suspended cells. It was found that biofilms with 170–285 mequiv chemical oxygen demand (COD) concentration/m2 of total oxidizable materials accelerated the Cu(II) adsorption to the surface of the reactor significantly by a factor of five. A significant inhibition to the bacterial growth took place (p ≤ 0.05; t-test) when Cu(II) concentration was higher than 0.5 mg/L. In the absence of Cu(II), bacterial cells grew normally to 0.075 of optical density (OD). However, at the Cu(II) concentration of 0.2 mg/L, the cells grew to a lower OD of 0.58. The presence of glycine and EDTA substantially reduced the toxicity of Cu(II) on bacterial growth (p ≤ 0.05; paired t-test). Their complexation with Cu(II) rendered the metal ions less available to bacterial cells. This implies that the Fe2O3 and bacterial biofilm affected Cu(II) distribution and speciation in the aquatic environment.

Physicochemical Investigation of Some Oil Emulsions Oxidized by UV-B Radiation

In this study, the effects of UV B (50 µW/cm2) radiation at 306 nm on oil-in-water emulsions (O/W) using canola oil, soybean oil and linoleic acid were investigated. The oxidation rates of emulsions incubated at pH 7.0 and 37°C in the presence and absence of Cu (II) ions were determined by using iron (III) thiocyanate and thiobarbituric acid methods for the determination of primary and secondary products, respectively. The UV B-induced oxidation rates followed the order LA / Cu (II) &gt; LA &gt; Canola Oil / Cu (II) &gt; Canola Oil &gt; Soybean Oil / Cu (II) &gt; Soybean Oil for both crops. Simultaneously, structural studies were performed using gas chromatography mass spectrometry (GC-MS). It was found that 18-carbon polyunsaturated fatty acid (PUFA) and monounsaturated fatty acid (MUFA) contents have an important role in canola and soybean oil oxidation. The unsaturated fatty acid contents of small carbon numbers increased for each emulsion sample, while the oxidation of fatty acid changes did not follow a regular order.

Dual-palindrome chained assembly regulates the formation of palindromic DNAzyme wire transducers empowering sensitized and one-step copper ion- dependent assay

The accurate and rapid analysis of heavy metal ions is significant for food safety and human health. In this work, a dual-palindrome chained assembly (dual-PCA) was rationally designed to form copper ion (Cu2+)-responsive palindromic DNAzyme wire (P-DNAzyme-W) transducers based on the inverted reading of palindromes. Structurally, P-DNAzyme-W is composed of numerous intermolecular paired dual-palindrome DNAzyme monomers. In the absence of Cu2+, the background fluorescence of the P-DNAzyme-W transducer was strongly quenched because of palindrome-induced co-quenching effects. Upon introduction of Cu2+ to form catalytic cores for the cleavage of the substrate strand into two parts, the sensing system exhibits strong fluorescence recovery within 25 min. These features allow the sensing system to exhibit a high signal-to-noise ratio to sensitized detect Cu2+ in one step but maximally maintain the simplicity of common DNAzyme monomers. Moreover, the sensing system possesses a good anti-matrix effect for sensitized detection of Cu2+ from lake water and tap water, suggesting promising potential in determining the level of Cu2+ in aquatic environments. We expect our research to provide an avenue to customize functional nucleic acids for heavy metal ion detection in the fields of food safety analysis, clinical diagnosis, and environmental monitoring.

To what extent can soil moisture and soil Cu contamination stresses affect nitrous species emissions? Estimation through calibration of a nitrification–denitrification model

Abstract. Continental biogeochemical models are commonly used to predict the effect of land use, exogenous organic matter input or climate change on soil greenhouse gas emission. However, they cannot be used for this purpose to investigate the effect of soil contamination, while contamination affects several soil processes and concerns a large fraction of land surface. For that, in this study we implemented a commonly used model estimating soil nitrogen (N) emissions, the DeNitrification DeCompostion (DNDC) model, with a function taking into account soil copper (Cu) contamination in nitrate production control. Then, we aimed at using this model to predict N2O-N, NO2-N, NO-N and NH4-N emissions in the presence of contamination and in the context of changes in precipitations. Initial incubations of soils were performed at different soil moisture levels in order to mimic expected rainfall patterns during the next decades and in particular drought and excess of water. Then, a bioassay was used in the absence or presence of Cu to assess the effect of the single (moisture) or double stress (moisture and Cu) on soil nitrate production. Data of nitrate production obtained through a gradient of Cu under each initial moisture incubation were used to parameterise the DNDC model and to estimate soil N emission considering the various effects of Cu. Whatever the initial moisture incubation, experimental results showed a NO3-N decreasing production when Cu was added but depending on soil moisture. The DNDC-Cu version we proposed was able to reproduce these observed Cu effects on soil nitrate concentration with r2 &gt; 0.99 and RMSE &lt; 10 % for all treatments in the DNDC-Cu calibration range (&gt; 40 % of the water holding capacity) but showed poor performances for the dry treatments. We modelled a Cu effect inducing an increase in NH4-N soil concentration and emissions due to a reduced nitrification activity and therefore a decrease in NO3-N, N2O-N and NOx-N concentrations and emissions. The effect of added Cu predicted by the model was larger on N2-N and N2O-N emissions than on the other N species and larger for the soils incubated under constant than variable moisture. Our work shows that soil contamination can be considered in continental biogeochemical models to better predict soil greenhouse gas emissions.

Copper-mediated DNA damage caused by purpurin, a natural anthraquinone

BackgroundPurpurin (1,2,4-trihydroxy-9,10-anthraquinone), a natural red anthraquinone pigment, has historically been used as a textile dye. However, purpurin induced urinary bladder tumors in rats, and displayed a mutagenic activity in assay using bacteria and mammalian cells. Many carcinogenic dyes are known to induce bladder cancers via DNA adduct formation, but carcinogenic mechanisms of purpurin remain unknown. In this study, to clarify the mechanism underlying carcinogenicity of purpurin, copper-mediated DNA damage induced by purpurin was examined using 32P-labeled DNA fragments of human genes relevant to cancer. Furthermore, we also measured 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodG), an indicator of oxidative DNA damage, in calf thymus DNA.ResultsPurpurin plus Cu(II) cleaved 32P-labeled DNA fragments only under piperidine treatment, indicating that purpurin caused base modification, but not breakage of the DNA backbone. In the absence of Cu(II), purpurin did not induce DNA cleavage even with piperidine treatment. Purpurin plus Cu(II) caused piperidine-labile sites predominantly at G and some T residues. Bathocuproine, a Cu(I) chelator, completely prevented the occurrence of piperidine-labile sites, indicating a critical role of Cu(I) in piperidine-labile sites induced by purpurin plus Cu(II). On the other hand, methional, a scavenger of a variety of reactive oxygen species (ROS) and catalase showed limited inhibitory effects on the induction of piperidine-labile sites, suggesting that ROS could not be major mediators of the purpurin-induced DNA damage. Considering reported DNA adduct formation by quinone metabolites of several carcinogenic agents, quinone form of purpurin, which is possibly generated via purpurin autoxidation accompanied by Cu(I)/Cu(II) redox cycle, might lead to DNA adducts and piperidine-labile sites. In addition, we measured contents of 8-oxodG. Purpurin moderately but significantly increased 8-oxodG in calf thymus DNA in the presence of Cu(II). The 8-oxodG formation was inhibited by catalase, methional and bathocuproine, suggesting that Cu(I)-hydroperoxide, which was generated via Cu(I) and H2O2, caused oxidative DNA base damage.ConclusionsWe demonstrated that purpurin induces DNA base damage possibly mediated by Cu(I)/Cu(II) redox cycle both with and without ROS generation, which are likely to play an important role in its carcinogenicity.

Electrochemical codeposition of copper‑antimony and interactions with electrolyte additives: Towards the use of electronic waste for sustainable copper electrometallurgy

The use of electronic waste or low grade materials as feedstock for the electrolytic production of copper is challenging because impurity metals such as Sb(III) are introduced in the electrolyte. In this work, the mechanisms that lead to antimony contamination in electrolytic copper are studied. Linear sweep voltammetry experiments indicate that the reduction of Sb(III) is kinetically slow in the absence of Cu(II). In the presence of Cu(II), however, reduction of Sb(III) can occur readily by the codeposition of Cu(II) and Sb(III) as demonstrated by chronoamperometry. The ToF-SIMS analyses confirmed the codeposition of antimony in the very first micrometer of the copper deposit, enabled by the nucleation overpotential for galvanostatic copper electrodeposition under conditions relevant for the commercial production of copper. Based on potentiostatic electrodeposition experiments, we suggest that a copper concentration of ≥40 g L−1 Cu(II) in Sb(III) containing electrolytes is beneficial to obtain high purity copper. Codeposition reactions were impacted by the presence of additives (thiourea, glue and chloride ions). In particular, the addition of 0.02 g L−1 chloride mitigated the codeposition of antimony (0.02 g L−1 Sb(III)) to produce grade A copper. For optimal removal of Sb(III) from bleed electrolytes, a molar ratio of ~3 Cu(II)/Sb(III) should be maintained (e.g. 0.3 g L−1 Cu(II) for a typical concentration of 0.2 g L−1 Sb(III)).

Single-Particle Resolution of Copper-Associated Annular α-Synuclein Oligomers Reveals Potential Therapeutic Targets of Neurodegeneration.

Metal ions stabilize protein–protein interactions and can modulate protein aggregation. Here, using liquid-based atomic force microscopy and molecular dynamics simulations, we study the concentration-dependent effect of Cu2+ ions on the aggregation pathway of α-synuclein (α-Syn) proteins, which play a key role in the pathology of Parkinson’s disease. The full spectrum of α-Syn aggregates in the presence and absence of Cu2+ ions from monomers to mature fibrils was resolved and quantified at the gold–water interface. Raman spectroscopy confirmed the atomic force microscopy (AFM) findings on the heterogeneity in aggregated states of α-Syn. The formation of annular oligomers was exclusively detected upon incubating α-Syn with Cu2+ ions. Our findings emphasize the importance of targeting annular α-Syn protein oligomers for therapeutic intervention and their potential role as biomarkers for early detection and monitoring progression of neurodegeneration.

Pre-Steady-State Reactivity of Peptidylglycine Monooxygenase Implicates Ascorbate in Substrate Triggering of the Active Conformer.

Peptidylglycine monooxygenase (PHM) is essential for the posttranslational amidation of neuroendocrine peptides. An important aspect of the PHM mechanism is the complete coupling of oxygen reduction to substrate hydroxylation, which implies no oxygen reactivity of the fully reduced enzyme in the absence of peptidyl substrates. As part of studies aimed at investigating this feature of the PHM mechanism, we explored pre-steady-state kinetics using chemical quench (CQ) and rapid freeze-quench (RFQ) studies of the fully reduced ascorbate-free PHM enzyme. First, we confirmed the absence of Cu(I)-enzyme oxidation by O2 at catalytic rates in the absence of peptidyl substrate. Next, we investigated reactivity in the presence of the substrate dansyl-YVG. Surprisingly, when ascorbate-free di-Cu(I) PHM was shot against oxygenated buffer containing the dansyl-YVG substrate, <15% of the expected product was formed. Substoichiometric reactivity was confirmed by stopped-flow and RFQ EPR spectroscopy. Product generation reached a maximum of 70% by the addition of increasing amounts of the ascorbate cosubstrate in a process that was not the result of multiple turnovers. FTIR spectroscopy of the Cu(I)-CO reaction chemistry was then used to show that increasing ascorbate concentrations correlated with a substrate-induced Cu(I)M-CO species characteristic of an altered conformation. We conclude that ascorbate and peptidyl substrate work together to induce a transition from an inactive to an active conformation and suggest that the latter may represent the "closed" conformation (Cu-Cu of ∼4 Å) recently observed for both PHM and its sister enzyme DBM by crystallography.