Chelation Of Cu Research Articles

Electrospun hydrophilic PAN/CO/TA composite nanofibrous membrane for adsorbing Cu(II) in water

In this paper, a novel polyacrylonitrile (PAN)/collagen (CO)/tannic acid (TA) composite nanofiber membrane for the adsorption of Cu(II) in water was prepared. The nanofibrous membranes were characterized by Fourier transform infrared (FTIR), scanning electron microscopy (SEM), thermogravimetric (TG), and water contact angle (WCA) techniques, and their adsorption performance on Cu(II) in water was tested. The results showed that incorporating CO improved the hydrophilic performance of the membranes, and the contact angle of PAN/CO decreased from 60.57° to 39.16° with the increase of CO content, which exhibited good hydrophilicity. Moreover, CO effectively crosslinked TA, so that TA was well fixed on the surface of the fiber membrane, and the resulting PAN/CO/TA composite nanofiber membrane had good fiber morphology, uniform fiber diameter distribution, with an average diameter of 292.22 nm, and good adsorption performance for Cu(II), up to 133.26 mg/g. The adsorption kinetics fitting showed that the adsorption mechanism was mainly electrostatic adsorption and chelation of Cu(II) by phenoxy anion. PAN/CO/TA and PAN/CO/TA/Cu nanofiber membranes showed bacteriostatic effects on E. coli and S. aureus, with PAN/CO/TA/Cu nanofiber membranes being particularly effective, with the average inhibition bands for E. coli and S. aureus being 7.50 mm and 10.05 mm, respectively. The distribution of the electric field during the spinning process was also simulated by finite element analysis in this study. Since TA is a natural polymer of plant origin and CO is of animal origin, it provides an environmentally friendly and cost-effective method to remove Cu(II) from water.

Synthesis, Characterization and Antimicrobial Activity of Homonuclear Cu(II) and Ni(II) Schiff Base Complexes

The current study aimed to synthesise, characterise, and investigate the antimicrobial activity of homonuclear Cu(II) and Ni(II) Schiff base complexes. Homonuclear Schiff Base Complexes chelates of Cu(II) and Ni(II) were synthesised. It appears that the complex is a potential metallo-ligand. It forms binuclear complexes when it reacts with two different metal salts, Ni and Cu. Using a Schiff base ligand made from 4-chloro-o-phenylenediamine and 3,5-dichloro-2-hydroxyacetophenone, the homo and hetero binuclear oxygen bridging Cu(II) and Ni(II) complexes were synthesized. Numerous common physicochemical methods, including elemental analysis, spectroscopic, thermal, cyclic voltammetry, and magnetic moment tests, have been used to characterise the synthesised complexes. For the mono- and binuclear compound of Cu(II) & Ni(II), spectral analysis reveals square planer shape. The antibacterial data indicates that the homo-binuclear copper complex is more active than the other mono- and binuclear complexes. Research has been done on the Schiff base and its complexes' anticancer properties.

A CuSO4/Bicinchoninic acid/Reducing sugar based stable and non-ROS catalyst system for the CuAAC reaction in bioanalysis

The limitations of commonly used sodium ascorbate-based catalyst system for copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction include excess production of reactive oxygen species and rapid catalyst deactivation. In this study instead of using a highly active reducing agent, such as, sodium ascorbate, we chose reducing sugar as a mild reducing agent to build up the catalyst system for CuAAC reaction. Interestingly, the bicinchoninic acid (BCA) assay system containing reducing sugar satisfies the essential elements of the catalyst system for CuAAC reaction. We found that CuSO4/BCA/Reducing sugar system can catalyze the CuAAC reaction but with low yield. Rational analyses of various parameters in CuSO4/BCA/Glucose catalyst system suggested storage at room temperature might enhance the catalytic activity, which was proven to be the case. Importantly, the system remains stable at room temperature and minimal H2O2 was detected. Notably, our study showed that the coordination between the slow reduction of Cu(I) by reducing sugar and the selective chelation of Cu(I) by BCA is key to developing this system. The CuSO4/BCA/Reducing sugar catalyst system was successfully applied to various CuAAC reaction based bioanalyses, and it is suitable for the CuAAC reaction based bioanalyses that are sensitive to ROS or request long reaction time.

Performance and mechanism of amphiphilic polymeric chelator for enhanced removal of high concentrations of Cu(II) from wastewater.

An amphiphilic polymeric chelator (APC16-g-SX) grafted with sodium xanthate (SX) groups was successfully prepared for the efficient removal of high concentrations of Cu(II) from wastewater. The ordinary polymeric chelator (PAM-g-SX) based on linear polyacrylamide (PAM) was also prepared for comparative studies. The polymeric chelators were characterized by Fourier transform infrared spectroscopy (FT-IR), solid-state nuclear magnetic resonance (13C-NMR), gel permeation chromatography (GPC), elemental analyzer, and scanning electron microscope (SEM). The chelating performance of these polymeric chelators was investigated, and the mechanism of APC16-g-SX for enhanced removal of Cu(II) from wastewater was proposed based on fluorescence spectroscopy, cryo-scanning electron microscope (Cryo-SEM), energy-dispersive spectrometer (EDS), and X-ray photoelectron spectroscopy (XPS) tests. The results show that as the initial Cu(II) concentration in the wastewater increases, APC16-g-SX shows more excellent chelating performance than ordinary PAM-g-SX. For the wastewater with an initial Cu(II) concentration of 200mg/L, the removal rate of Cu(II) was 99.82% and 89.34% for both 500mg/L APC16-g-SX and PAM-g-SX, respectively. The pH of the system has a very great influence on the chelating performance of the polymeric chelators, and the increase in pH of the system helps to improve the chelating performance. The results of EDS and XPS tests also show that N, O, and S atoms in APC16-g-SX were involved in the chelation of Cu(II). The mechanism of enhanced removal of Cu(II) by APC16-g-SX can be attributed to the spatial network structure constructed by the self-association of hydrophobic groups that enhances the utilization of chelation sites.

Programmable "triple attack" cancer therapy through in situ activation of disulfiram toxification combined with phototherapeutics.

Effectively and completely eliminating residual tumor cells is the key to reducing the risk of tumor metastasis and recurrence. Designing an "ideal" nanoplatform for programmable cancer therapy has great prospects for completely eliminating residual tumor cells. Herein, an intelligent nanoplatform of disulfiram (DSF)-loaded CuS-tannic acid nanohexahedrons (denoted as "DSF-CuS@TA") with thermal- and pH-sensitive degradation, as well as near-infrared (NIR-II) phototherapeutics properties, was constructed. And then, it was employed for in situ DSF toxification activation programmable "triple attack" cancer therapy. After accumulating in the tumor, DSF-CuS@TA first releases the loaded Cu(DTC)2, and simultaneously degrades and releases Cu2+ and DSF under mildly acidic stimulation to trigger instant intratumoral Cu(DTC)2 chelation, thereby achieving the "first strike." Next, under irradiation by a NIR-II laser, light energy is converted into heat to generate NIR-II photothermal therapy, thereby achieving the second strike. Subsequently, under thermal stimulation, DSF-CuS@TA degrades further, triggering the chelation of Cu(DTC)2 for a second time to reach the third strike. As expected, in vitro and in vivo studies showed that the synergistic integration of DSF-based programmed chemotherapy and NIR-II phototherapeutics could achieve effective tumor removal. Therefore, we propose a novel type of programmed therapy against cancer by designing a nanoplatform via "nontoxicity-to-toxicity" chemical chelation transformation.

Bivalent Metal Chelates with Pentadentate Azo-Schiff Base Derived from Nicotinic Hydrazide: Preparation, Structural Elucidation, and Pharmacological Activity.

Azo-Schiff base ligand (N'-((E)-2-hydroxy-5-((E)-(2-hydroxyphenyl)diazenyl)benzylidene)nicotinohydrazide) and its Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Pd(II) chelates were prepared and elucidated. The geometrical structures of the prepared chelates were characterized by several spectroanalytical techniques and thermogravimetric analysis. The obtained data revealed that the chelates have (1M:1L), (1M:2L), (1M:3L), and (1M:4L) molar ratios. The infrared spectra displayed that the H2 L ligand behaves in a pentacoordinate fashion in chelates of Mn(II), Ni(II), and Cu(II) ions. However, in Zn(II) and Pd(II) chelates, the ligand is coordinated as a tetradentate species (NONO) through nitrogen atoms of azomethine and azo groups as well as oxygen atoms of phenolic hydroxy, and carbonyl groups. Besides, it was concluded that the oxygen atoms of carbonyl and hydroxy groups along with the azomethine nitrogen atom of the ligand are bounded with Co(II) ion in metal chelate (2). According to the measured molar conductance values, the chelates of Cu(II), Zn(II), and Pd(II) are weak electrolytes, but Mn(II), Co(II), and Ni(II) chelates are ionic. The azo-Schiff base ligand and its prepared metal chelates were tested for their antioxidant and antibacterial properties. The Ni(II) chelate was found to be considered an effective antioxidant agent. In addition, the available antibacterial data suggest that the Ni(II) and Co(II) chelates may be employed as inhibitor agents against Proteus vulgaris, Escherichia coli, and Bacillus subtilis bacteria. Furthermore, the data showed that, in comparison to the ligand and other metal chelates, copper(II) chelate (4) exhibited higher action against Bacillus subtilis bacteria.

Liposomal DQ in Combination with Copper Inhibits ARID1A Mutant Ovarian Cancer Growth.

Therapeutic strategies for ARID1A-mutant ovarian cancers are limited. Higher basal reactive oxygen species (ROS) and lower basal glutathione (GSH) empower the aggressive proliferation ability and strong metastatic property of OCCCs, indicated by the increased marker of epithelial-mesenchymal transition (EMT) and serving the immunosuppressive microenvironment. However, the aberrant redox homeostasis also empowers the sensitivity of DQ-Lipo/Cu in a mutant cell line. DQ, a carbamodithioic acid derivative, generates dithiocarbamate (DDC) in response to ROS, and the chelation of Cu and DDC further generates ROS and provides a ROS cascade. Besides, quinone methide (QM) released by DQ targets the vulnerability of GSH; this effect, plus the increase of ROS, destroys the redox homeostasis and causes cancer cell death. Also importantly, the formed Cu(DDC)2 is a potent cytotoxic anti-cancer drug that successfully induces immunogenic cell death (ICD). The synergistic effect of EMT regulation and ICD will contribute to managing cancer metastasis and possible drug resistance. In summary, our DQ-Lipo/Cu shows promising inhibitory effects in cancer proliferation, EMT markers, and "heat" the immune response.

Copper and Copper Oxides Nanoparticles Synthesized by Electrochemical Technique in Chitosan Solution

A synthesis of chitosan copper and copper oxides nanoparticles (Cs-Cu, CuO) NPs via electrochemical technique has been reported. Chitosan copper complexes were prepared by electrochemical oxidation technique at duration time followed by reduction using different reducing agents for producing chitosan copper nanoparticles, Cs used as stabilizer and capping agent. The nanocomposites were characterized by using ultraviolet-visible spectroscopy (UV-vis). Transmission electron microscope (TEM) images were investigated emphasized formation the formation of NPs with different shapes. The average size of formed NPs is 28 nm. X-ray diffraction (XRD) is used to investigate the formation of the crystalline structure of prepared samples exhibited presence of copper and copper oxides in the formed complexes and nanocomposites. Analysis of FTIR showed chelation of Cu+2 with chitosan in complex form and electrostatic interaction between chitosan and copper nanoparticles.

Theoretical Insights into the Luminescence and Sensing Mechanisms of N,N′-Bis(salicylidene)-[2-(3′,4′-diaminophenyl)benzthiazole] for Copper(II)

The intramolecular proton transfer (IPT) reaction potential energy surfaces (PESs) of N,N'-bis(salicylidene)-[2-(3',4'-diaminophenyl)benzthiazole] (BTS) in the S0 state and S1 state are constructed. It is found that the IPT reactions in the ground state hardly take place due to the high reaction energy barrier for single-proton (6.3 kcal/mol) and double-proton transfer (14.1 kcal/mol) reactions and low backward reaction energy barriers for single-proton (1.9 kcal/mol) and double-proton transfer (1.2 kcal/mol) reactions. In comparison, an excited-state intramolecular single-proton transfer reaction is a barrierless and exothermic process, and thus, single-proton transfer tautomer T1H contributes most to the fluorescence emission. Based on the analysis of PESs, the experimental absorption and emission spectra are reproduced well by the calculated vertical excitation energies of BTS and its photoisomerization products, and the triple fluorescence emission profile in the experiment is reassigned unequivocally. Furthermore, thermodynamic analysis of the BTS-Cu(II) complex shows that the dinuclear complex (C1) with Cu(II) coordinating with O and N atoms of the hydrogen bonds is the most thermodynamically stable structure, and the intramolecular hydrogen bonding structure in BTS is destroyed due to the chelation of Cu(II) and BTS; as a result, the IPT reaction of C1 in S0 and S1 states is significantly inhibited. The inhibitor of Cu(II) in the IPT reaction plays a major role in fluorescence quenching.

Oxidation of Alcohols into Carbonyl Compounds Using a CuO@GO Nano Catalyst in Oxygen Atmospheres

In this article, the oxidation of alcohols into carbonyl compounds was studied in oxygen atmospheres using a copper oxide on graphene oxide (CuO@GO) nano composites catalyst, synthesized by the wet chemistry method. CuO@GO nano composites were prepared from GO, and CuO NPs by the sol-gel method. The transformation of aromatic alcohols into corresponding carbonyl compounds in good-to-high yields were observed using the CuO@GO catalyst under an oxygen atmosphere. Synthesized CuO@GO was confirmed by FT-IR, XRD, XPS, TEM, FE-SEM, TEM, and SEM analyses, and revealed intercalation of CuO-NPs on/in GO nano sheets through the chelation of Cu+2 ions with CO, COOH, and OH groups presenting on the GO nano sheets. The catalytic activity of CuO@GO nano composites for the conversion of alcohols into carbonyl compounds were evaluated through TOF (2.56 × 10−3 mol g−1 min−1). The use of CuO@GO has shown catalytic activity and recyclability with a high conversion of alcohols to ketones. We assume that the proposed CuO@GO catalyst can be used for other key organic transformations and will be evaluated in the future.

Anchoring of copper sulfide on cellulose fibers with polydopamine for efficient and recyclable photocatalytic degradation of organic dyes

Due to its narrow band gap, Copper sulfide (CuS) exhibits great potential in photocatalytic degradation of organic dyes. However, there are still some drawbacks in the CuS photocatalytic system, such as easy aggregation, poor reusability, high recombination rate of photogenerated electron-hole pair, and photocorrosion damage. In this study, CuS was anchored onto cellulose fibers (CF) with the help of polydopamine (PDA) for constructing composite paper (CF/PDA/CuS paper) with high photocatalytic efficiency and good reusability. After PDA coatings formed on cellulose fibers, the chelation of Cu 2+ by the catechol group of PDA provided uniform and stable growth sites for CuS, resulting in CuS anchoring in the PDA matrix for increasing the loading capacity and stability of CuS on cellulose fibers. In addition, PDA improved the separation efficiency of photogenerated electrons in CuS and inhibited the photocorrosion of CuS. The CF/PDA/CuS paper exhibited prominently enhanced photocatalytic activity and photocatalytic stability for the degradation of Rhodamine B under near infrared light irradiation. The photocatalytic activity of CF/PDA/CuS paper was about 5.8 times higher than that of CF/CuS paper. During 10 cycles, the photocatalytic efficiency of CF/PDA/CuS paper for degrading Rhodamine B was always above 92 % and the PDA/CuS hybrid structure was always stable on cellulose fibers. This work inspires the construction of stable PDA/CuS hybrid structure on cellulose fibers for a composite paper with high photocatalytic efficiency and good reusability. • A novel CuS-based photocatalytic composite paper was prepared. • The PDA coatings formed on the cellulose fibers were used to anchor CuS. • The chelation of Cu 2+ by the catechol group of PDA provided growth sites for CuS. • PDA separated the photogenerated electrons and inhibited the photocorrosion of CuS. • The composite paper exhibited high photocatalytic activity and good reusability.

Novel synthesis of ultrafiltration membranes by crosslinking metal (II)-Alginate hydrogels with hexamethylene 1,6 -Diisocyanate in inert solvent: Application for remediation of wastewater by removal of toxic pollutants

Hexamethylene 1,6- diisocyanate (HDI) crosslinking agent has been used for novel synthesis of ultrafiltration (UF) membranes from polysaccharide derivatives as natural polymers for the first time. This process takes place by crosslinking the soft membranes of Cu (II)-alginate hydrogels (Cu-Alg2)n with 9 % of (HDI) in dryness acetone (DA) for obtaining its corresponding (CCu-Alg2)n as UF membranes. These new crosslinking membranes can be used for uptaking the toxic metal ion contaminants from wastewater in purification of drinking water. The pore size in such membranes can be controlled by varying the pH of the alginate sol using either NaH2PO4 or Na2HPO4 simple salts. The formed crosslinking membranes (CCu-Alg2)n were characterized by the elemental, FTIR and SEM/EDAX analyses. The experimental results of the crosslinking membranes (CCu-Alg2)n in its hydrogen form (CH2-Alg2)n showed high affinity for removal of some divalent metal ions such as Cu2+, Ni2+, Co2+, Cd2+ and Pb2+ ion pollutants at the pH s 2–6. Also, they revealed high selective separation of some tested metal ions such as Ag+ and Cu2+ from electrolyte mixtures involving these metal ions with other divalent metal ions (0.1–0.5 mmole /L) at 25 °C. Again, such crosslinking membranes of (CCu-Alg2)n has proven high capability for isolation the Serratia marcescens Grahams-negative fine bacterium from contaminated media. The nature of geometrical configuration for chelation of Cu (II) ions with the alginate functional groups (–COO– and –OH) in its non-crosslinked (Cu-Alg2)n and crosslinked with HDI membranes (CCu-Alg2)n were suggested and discussed.

Synthesis, Characterization of Cu++, Ni++ Metal Ion Chelates with Newly Synthesized Benzothiazolyl Hydrazone Derivatives

The transition Metal ion chelates of Cu+2 and Ni+2 is synthesized by using 2-(2´-hydroxy-3´-methyl phenyl)-4-bromo-6-ethoxy benzothiazolyl hydrazones and characterized by different analytical procedure and spectral study. These metal ion chelates are insoluble in common organic solvents. Infrared spectrum showed the bonding through azomethizine N and ring N.

Chelating Cu-N within Cu+-incorporated MIL-101 (Cr)-NH2 framework for enhanced CO adsorption and CO/CO2 selectivity

The development of π-complexation adsorbents with Cu(I) having high CO adsorption capacity, high selectivity, large working capacity, and good stability is still very challenging up to now. In this work, π-complexation adsorbent with Cu+ was fabricated by reducing Cu2+ to Cu+ within amino-functionalized MIL-101 (Cr) framework by employing formate (HCOO-) at low temperature. The obtained results indicated that the Cu+ yield was strongly influenced by the chelation of Cu(II) species into amino groups (NH2) of MIL-101 (Cr)-NH2. The produced CuCl@MIL-101(Cr)-NH2 (CuCl@MCrN) was then applied for CO and CO2 adsorption at various conditions. The results revealed that the formed Cu+ species within MIL-101 (Cr)-NH2 not only increased CO adsorption via CO π-complexation but also reduced CO2 adsorption on the adsorbent through interaction with NH2 groups, resulting in a significant increase of CO/CO2 selectivity onto CuCl@MCrN adsorbent. At 25 °C and 100 kPa, the prepared CuCl@MCrN adsorbent with 30% Cu(I) exhibited the maximum CO uptake amount and CO/CO2 selectivity of ~ 2.52 mmol g−1 and ~ 97, respectively, exceeding those of the benchmark Cu+-based π-complexation adsorbents. The breakthrough experiment indicates that this Cu(I)@MIL-101(Cr)-NH2 adsorbent can efficiently separate CO/CO2mixture under dynamic mixture flow conditions. Moreover, the oxygen-resistant ability of the adsorbent tested under atmospheric humidity conditions demonstrated that CuCl@MCrN adsorbent had good stability.

The effect of Luteolin on DNA damage mediated by a copper catalyzed Fenton reaction

Luteolin has been reviewed as a flavonoid possessing potential cardioprotective, anti-inflammatory, anti-cancer activities. Having multiple biological effects, luteolin may act as either an antioxidant or a pro-oxidant. In this work, the protective role of copper(II)-chelation by luteolin on DNA damage via the Cu-Fenton reaction was studied. EPR and UV–vis spectroscopic data demonstrated that the luteolin, lacking 3-OH group, chelates to Cu(II) via the 5-OH and 4-CO groups, respectively. EPR spin trapping experiments using DMPO spin trap confirmed that the coordination of luteolin to Cu(II) significantly suppressed formation of hydroxyl and superoxide radicals (by 80%) in a Cu-Fenton system. Absorption titrations showed that the chelation of Cu(II) by luteolin slightly increased the mild intercalation strength of its interaction with DNA, as compared with free luteolin. Comparison with kaempferol and quercetin revealed, that the strength of the interaction between the free flavonoids/Cu-flavonoid complexes with DNA is only mildly affected by the presence/absence of 3-OH group. Due to the differences in the sensitivities of absorption titrations and viscometry, the latter confirmed weaker DNA intercalating efficiency of Cu-luteolin complex than does free luteolin. A dose dependent protective effect of luteolin against ROS-induced DNA damage was observed using gel electrophoresis. This effect was more pronounced compared to quercetin and kaempferol. In conclusion, the administration of luteolin to patients suffering from oxidative stress-related diseases with disturbed Cu-metabolism such as Alzheimer's diseases (antioxidant effect) and certain cancers (prooxidant effect) may have several health benefits.

A genome-wide screen reveals the involvement of enterobactin-mediated iron acquisition in Escherichia coli survival during copper stress.

Copper (Cu) is a key transition metal that is involved in many important biological processes in a cell. Cu is also utilized by the immune system to hamper pathogen growth during infection. However, genome-level knowledge on the mechanisms involved in adaptation to Cu stress is limited. Here, we report the results of a genome-wide reverse genetic screen for Cu-responsive phenotypes in Escherichia coli. Our screen has identified novel genes involved in adaptation to Cu stress in E. coli. We detected multiple genes involved in the biosynthesis and uptake of enterobactin, a siderophore utilized for high-affinity TonB-dependent acquisition of iron (Fe), as critical players in survival under Cu intoxication. We demonstrated the specificity of Cu-dependent killing by chelation of Cu and by genetic complementation of tonB. Notably, TonB is involved in protection from Cu in both laboratory and uropathogenic strains of E. coli. Cu stress leads to increased expression of the genes involved in Fe uptake, indicating that Fur regulon is derepressed during exposure to excess Cu. Trace element analyses revealed that Fe homeostasis is dysregulated during Cu stress. Taken together, our data supports a model in which lack of enterobactin-dependent Fe uptake leads to exacerbation of Cu toxicity, and elucidates the intricate connection between the homeostasis of Cu and Fe in a bacterial cell.

Anodic Electrodeposition of Chitosan-AgNP Composites Using In Situ Coordination with Copper Ions.

Chitosan is an attractive material for biomedical applications. A novel approach for the anodic electrodeposition of chitosan–AgNP composites using in situ coordination with copper ions is proposed in this work. The surface and cross-section morphology of the obtained coating with varying concentrations of AgNPs were evaluated by SEM, and surface functional groups were analyzed with FT-IR spectroscopy. The mechanism of the formation of the coating based on the chelation of Cu(II) ions with chitosan was discussed. The antibacterial activity of the coatings towards Staphylococcus epidermidis ATCC 35984/RP62A bacteria was analyzed using the live–dead approach. The presented results indicate that the obtained chitosan–AgNP-based films possess some limited anti-biofilm-forming properties and exhibit moderate antibacterial efficiency at high AgNP loads.

The natural compound chrysosplenol-D is a novel, ultrasensitive optical sensor for detection of Cu(II)

Herein, we introduce a novel, ultrasensitive optical sensor for determination of Cu(II) ions over the concentration range of 0 to 1 μM Cu(II). The optical sensor is based on the natural molecule chrysosplenol-D (Chp-D) extracted from the flowering plant Chiliadenus montanus (Vahl.) Brullo. Free Chp-D emits fluorescence at 566 nm when excited at 292 nm. Chp-D chelates Cu(II) ions to form a 1:1 (metal:ligand) complex, which quenches the fluorescence emission peak of the free probe at 566 nm. “Turn-off” luminescence could be easily determined and provided distinct proof of the chelation of Cu(II) ions by Chp-D. This novel optical sensor offers a considerable fluorescence mechanism (charge transfer complex, CTC). Chp-D is an extremely sensitive and selective optical sensor for Cu(II) ions, with distinctive fluorescence properties, a large Stokes shift of ~275 nm and recognition aptitude. Moreover, Chp-D has low limit of detection (LOD) for Cu(II) of 1.2 × 10−8 M in buffered media at physiological pH (pH 7.4), a linear range of 0.04 to 1.0 μM and a relative standard deviation (RSDr) of 1% (n = 3). Furthermore, this natural probe has a high binding affinity for Cu(II), with a binding constant of 3.36 × 108 M−1. Overall, we propose Chp-D represents a novel, natural optical sensor for the detection of Cu(II).

Bacterial Metabolites Produced Under Iron Limitation Kill Pinewood Nematode and Attract Caenorhabditis elegans.

Pine Wilt Disease (PWD) is caused by Bursaphelenchus xylophilus, the pinewood nematode, and affects several species of pine trees worldwide. The ecosystem of the Pinus pinaster trees was investigated as a source of bacteria producing metabolites affecting this ecosystem: P. pinaster trees as target-plant, nematode as disease effector and its insect-vector as shuttle. For example, metals and metal-carrying compounds contribute to the complex tree-ecosystems. This work aimed to detect novel secondary metabolites like metallophores and related molecules produced under iron limitation by PWD-associated bacteria and to test their activity on nematodes. After screening 357 bacterial strains from Portugal and United States, two promising metallophore-producing strains Erwinia sp. A41C3 and Rouxiella sp. Arv20#4.1 were chosen and investigated in more detail. The genomes of these strains were sequenced, analyzed, and used to detect genetic potential for secondary metabolite production. A combinatorial approach of liquid chromatography-coupled tandem mass spectrometry (LC-MS) linked to molecular networking was used to describe these compounds. Two major metabolites were detected by HPLC analyses and described. One HPLC fraction of strain Arv20#4.1 showed to be a hydroxamate-type siderophore with higher affinity for chelation of Cu. The HPLC fraction of strain A41C3 with highest metal affinity showed to be a catecholate-type siderophore with higher affinity for chelation of Fe. LC-MS allowed the identification of several desferrioxamines from strain Arv20#4.1, in special desferrioxamine E, but no hit was obtained in case of strain A41C3 which might indicate that it is something new. Bacteria and their culture supernatants showed ability to attract C. elegans. HPLC fractions of those supernatant-extracts of Erwinia strain A41C3, enriched with secondary metabolites such as siderophores, were able to kill pinewood nematode. These results suggest that metabolites secreted under iron limitation have potential to biocontrol B. xylophilus and for management of Pine Wilt Disease.

Aminomethylene-Phosphonate Analogue as a Cu(II) Chelator: Characterization and Application as an Inhibitor of Oxidation Induced by the Cu(II)-Prion Peptide Complex.

Recently, we reported on a series of aminomethylene-phosphonate (AMP) analogues, bearing one or two heterocyclic groups on the aminomethylene moiety, as promising Zn(II) chelators. Given the strong Zn(II) binding properties of these compounds, they may find useful applications in metal chelation therapy. With a goal of inhibiting the devastating oxidative damage caused by prion protein in prion diseases, we explored the most promising ligand, {bis[(1H-imidazol-4-yl)methyl]amino}methylphosphonic acid, AMP-(Im)2, 4, as an inhibitor of the oxidative reactivity associated with the Cu(II) complex of prion peptide fragment 84-114. Specifically, we first characterized the Cu(II) complex with AMP-(Im)2 by ultraviolet-visible spectroscopy and electrochemical measurements that indicated the high chemical and electrochemical stability of the complex. Potentiometric pH titration provided evidence of the formation of a stable 1:1 [Cu(II)-AMP-(Im)2]+ complex (ML), with successive binding of a second AMP-(Im)2 molecule yielding ML2 complex [Cu(II)-(AMP-(Im)2)2]+ (log K' = 15.55), and log β' = 19.84 for ML2 complex. The CuN3O1 ML complex was demonstrated by X-ray crystallography, indicating the thermodynamically stable square pyramidal complex. Chelation of Cu(II) by 4 significantly reduced the oxidation potential of the former. CuCl2 and the 1:2 Cu:AMP-(Im)2 complex showed one-electron redox of Cu(II)/Cu(I) at 0.13 and -0.35 V, respectively. Indeed, 4 was found to be a potent antioxidant that at a 1:1:1 AMP-(Im)2:Cu(II)-PrP84-114 molar ratio almost totally inhibited the oxidation reaction of 4-methylcatechol. Circular dichroism data suggest that this antioxidant activity is due to formation of a ternary, redox inactive Cu(II)-Prp84-114-[AMP-(Im)2] complex. Future studies in prion disease animal models are warranted to assess the potential of 4 to inhibit the devastating oxidative damage caused by PrP.