Affinity For Copper Ions Research Articles

Investigating the combined effect of copper, zinc, and iron ions on truncated and full-length Aβ peptides: insights from molecular dynamics simulation

The truncated Aβ1 − 16 peptide containing the metal-binding domain is frequently used in in silico and experimental investigations because it is more soluble and thus more suitable for studies in solution and does not form amyloids. Several spectroscopic studies have shown that the metal binding of Aβ1 − 16 is very similar to that of the full-length Aβ1 − 42. However, since small changes can have a significant impact on aggregation, further experimental and theoretical are needed to elucidate the detailed structures of truncated and full-length Aβ. In this research, the binding of copper ion to the Aβ1 − 16 and Aβ1 − 42 has been studied by molecular dynamics simulation method. To investigate the effect of copper ion on beta-amyloid peptide structure, the simulations were repeated in the copper and zinc ions, copper and iron binary system, and the copper, zinc and iron ions ternary system. The conformation factor was calculated to calculate the binding affinity of copper ion to beta-amyloid peptide residues. The results showed that the initial 16 residues of the beta-amyloid peptide have high binding affinity for copper ions, and histidine 13 and histidine 14 have significantly higher binding affinity for copper ions in all studied systems. Zinc and iron ions were found to reduce the conformational factor of peptide residues in binding to copper ions, and the aggregation tendency was lower in the truncated structure. The SASA results suggest that the side chains of peptide residues are more affected by shortening and the presence of ions. Communicated by Ramaswamy H. Sarma

Templated Total Synthesis of Cu(I)-Methanobactin OB3b.

Methanobactin OB3b (Mbn-OB3b) is a unique natural product with stunning affinity for copper ions (Ka ≈Cu(I) 1034 ). Here, we report the first total synthesis of Cu(I)-bound methanobactin OB3b featuring as key transformations a cyclodehydration-thioacylation sequence, to generate the conjugated heterocyclic systems, and a copper-templated cyclization, to complete the caged structure of the very sensitive target compound.

Templated Total Synthesis of Cu(I)‐Methanobactin OB3b**

AbstractMethanobactin OB3b (Mbn‐OB3b) is a unique natural product with stunning affinity for copper ions (Ka≈Cu(I) 1034). Here, we report the first total synthesis of Cu(I)‐bound methanobactin OB3b featuring as key transformations a cyclodehydration‐thioacylation sequence, to generate the conjugated heterocyclic systems, and a copper‐templated cyclization, to complete the caged structure of the very sensitive target compound.

Preparation of Polyacrylonitrile-Based Immobilized Copper-Ion Affinity Membranes for Protein Adsorption.

A polyacrylonitrile (PAN)-based immobilized metal-ion affinity membrane (IMAM) was prepared with a high capacity for protein adsorption. PAN was selected as the substrate due to its excellent thermal and chemical stability. The cyano groups on the PAN membrane were substituted with carboxyl groups, followed by reactions with ethylenediamine (EDA) and ethylene glycol diglycidyl ether (EGDGE) to produce the terminal epoxy groups. The chelating agent iminodiacetic acid (IDA) was then bound to the modified PAN membrane and further chelated with copper ions. The immobilized copper ion amount of membrane was analyzed to obtain the optimal reaction conditions, which were 60 °C/3 h for EDA coupling and 60 °C/4 h for EGDGE grafting. Furthermore, under the use of minor IDA and copper ion concentrations, the immobilized copper ion capacity of the IMAM was 4.8 μmol/cm2 (253.4 µmol/mL, or 1.47 μmol/mg). At a neutral pH, the cationic lysozyme exhibited a large adsorption capacity with the IMAM (1.96 μmol/mL), which was most likely multilayer binding, whereas the adsorption capacity for bovine serum albumin (BSA) and histidine-tagged green fluorescent protein (GFP-His6) was 0.053 μmol/mL and 0.135 μmol/mL, respectively, with a monolayer adsorption arrangement. The protein desorption efficiency was greater than 95%, implying that the prepared IMAM could be reused for protein adsorption.

Adsorption studies of a multi-metal system within acetate media, with a view to sustainable phosphate recovery from sewage sludge

Phosphate shortages and the ensuing pressures on food security have led to an interest in processed sewage sludge as a substitute for commercial fertilisers. The presence of heavy metals in this nutrient source causes concerns around environmental release and pollution. This work builds towards a resin-in-pulp sludge detoxification process. It showcases the kinetic and thermodynamic adsorption capabilities of the ion-exchange resins C107E (carboxylic acid functionality), MTS9301 (iminodiacetic acid) and TP214 (thiourea), with respect to Cu(II), Fe(II), Pb(II) and Zn(II), within a simulated sewage sludge weak acid (acetate) leachate. The isotherms produced in this complex system were quite different to those generated when single metals were investigated in isolation, with desorption of lower affinity species clearly observed at higher equilibrium concentration values. Mixed-metal isotherm data were fitted to common two-parameter isotherm models and also a novel modified Langmuir model, which better accounted for the effects of desorption and competition. Kinetic data were also fit to common two-parameter models; results suggesting the system was likely film diffusion-controlled and followed pseudo-2nd-order kinetics. C107E displayed rapid adsorption of lead (t1/2 = 26 ± 3min), and significant uptake of all metals. MTS9301 showed high affinity for copper ions, with concurrent desorption of all the other metals, and also displayed the fastest kinetics (t1/2 = 14.1 ± 0.9, 130 ± 20, 25 ± 5 and 49 ± 6 min for copper, iron(II), lead and zinc, respectively). C107E and MTS9301 showed far slower adsorption for iron(II) than the other three metals, which invited the possibility of kinetic separations. TP214 had reasonable effectiveness in removal of copper, but poor affinity for all other metals. The greatest difficulty in modelling the multi-metal system was the two-stage trends observed in equilibrium experiments, as metal-proton exchanges become metal-metal exchanges. While not having the highest capacity, MTS9301 was recommended as the most appropriate resin for rapid and efficient removal of Cu, Pb and Zn from the acetate medium.

Functional covalent organic framework illuminate rapid and efficient capture of Cu (II) and reutilization to reduce fire hazards of epoxy resin

A key challenge for decontamination technologies is to study adsorbents possessing abundant approachable binding sites to realize rapid and effective capture of heavy metal ions in contaminated water. Herein, a three-dimensional porous covalent organic framework (COF) was synthesized, which can function as a scaffold for decorative binding sites. Considering the plentiful functional groups such as catechol groups of polydopamine (PDA), the decoration is demonstrated by coating PDA on the surface of COF via self-polymerization of dopamine under alkaline conditions. The obtained PDA-coated COF (COF@PDA) shows high affinity for copper ions (Cu (II)), while its adsorption capacity reaches 109.2 mg g−1 according to the Langmuir fitting. It takes only 10 min to achieve adsorption equilibrium and its equilibrium data follows pseudo-second-order kinetic model. Thermodynamic studies confirmed a spontaneous and exothermic removal process in essence. To achieve cyclic utilization of Cu (II), the adsorbed Cu (II) ions were heat-treated into CuO to obtain CuO-loaded COF@PDA (COF@PDA@CuO). It can serve as flame retardant for reducing fire hazards (heat, smoke and toxic gas) of epoxy resin (EP), thus confirming its dual functionalities towards environmental remediation and application as flame-retardant.

Multi-component adsorption study by using bone char: modelling and removal mechanisms

ABSTRACT Highly efficient simultaneous removal of paracetamol and Cu2+ ions from aqueous solutions was accomplished by using bovine bone char (BC). The adsorption behaviour was determined by kinetic and equilibrium studies of both single and binary system solutions. BC is a predominantly mesoporous material with a surface area of 103 m2 g−1. The influence of the initial pH on Cu2+ removal was tested, suggesting that the optimal pH was 3.0. The removal of paracetamol from single and binary systems was 9.45 and 12.7%, respectively. On the other hand, the Cu2+ removal was 36.2% for a single system, suggesting a higher affinity for BC. Moreover, in the case of binary mixtures, the presence of paracetamol led to an enhanced affinity of Cu2+ due to a synergistic/cooperative mechanism, which led to a copper removal of 97.3%. The cooperative model was successfully adjusted to the equilibrium data of the binary systems. The modelling results indicated the formation of a first adsorption layer where paracetamol and copper are retained, and a second layer with a great affinity for copper ions after the formation of a Cu-paracetamol complex, leading to higher removal of Cu2+.

Interplays between copper and Mycobacterium tuberculosis GroEL1.

The recalcitrance of pathogenic Mycobacterium tuberculosis, the agent of tuberculosis, to eradication is due to various factors allowing bacteria to escape from stress situations. The mycobacterial chaperone GroEL1, overproduced after macrophage entry and under oxidative stress, could be one of these key players. We previously reported that GroEL1 is necessary for the biosynthesis of phthiocerol dimycocerosate, a virulence-associated lipid and for reducing antibiotic susceptibility. In the present study, we showed that GroEL1, bearing a unique C-terminal histidine-rich region, is required for copper tolerance during Mycobacterium bovis BCG biofilm growth. Mass spectrometry analysis demonstrated that GroEL1 displays high affinity for copper ions, especially at its C-terminal histidine-rich region. Furthermore, the binding of copper protects GroEL1 from destabilization and increases GroEL1 ATPase activity. Altogether, these findings suggest that GroEL1 could counteract copper toxicity, notably in the macrophage phagosome, and further emphasizes that M. tuberculosis GroEL1 could be an interesting antitubercular target.

Binding Free Energy and the structural changes determination in hGH protein with different concentrations of copper ions (A molecular dynamics simulation study)

In this study, we estimated the optimum concentration of copper ions that are effective in the stability and the structural changes of human growth hormone (hGH) protein in the combination of different concentrations of these ions at the molecular level using molecular dynamics simulation by Gromacs 4.6.5 software. Moreover, to estimate the binding affinity of copper ions to hGH protein, binding free energies is calculated by the molecular mechanics Poisson–Boltzmann Surface Area (MM-PBSA). The analysis of molecular dynamics (MD) trajectories as dictionary of the secondary structure of protein (DSSP), solvent accessible surface area (SASA) and binding free energy calculations show that hGH protein structure is more stabilized by increasing a limited concentration of copper ions. These findings align with our previous experimental studies.

Selective absorption of heavy metals by soil and humic acids at different pH levels

Studying processes of sorption-desorption of heavy metals from soil and its individual components allow to predict long-term effects under conditions of multielement contamination. Cations of heavy metals are showing competitive relationship due to their specific adsorption by components of the soil absorption complex, in particular humic acids. Interaction of chernozem podzolized heavy loam, isolated preparation of humic acids and soil residue after its removal with the solution which contain sulphates of Zn, Cd, Ni, Co and Cu in equal ratio were simulated at different pH levels. The task of research was to compare selective absorption of some heavy metals in soil and humic acids at pH values from 3 to 9. The experiment was performed by mixing 10 g of soil material or 0.1 g of humic acid with 100 ml of buffer solution, adding 10 ml 0.01 n equal mixture of Cd, Zn, Ni, Co, Cu and 2-hour exposure. Humic acids were extracted from this soil by 0.1 n NaOH after decalcification using 0.05 n H2SO4. Crystalline Copper sulphate, Zinc, Nickel, Cobalt, Cadmium were used to prepare the solution level of heavy metals. Ammonium acetate-buffer solutions with different pH (3.0, 5.0, 7.0, 9.0) were obtained by varying the ratio CH3СOOH and NH4OH. The experiment showed that competitive relationship between heavy metal in soil and humic acids. Copper has the highest specificity adsorption, Cobalt – the smallest. Under acidic and strongly acidic reaction content of Zn, Cd, Ni in equilibrium solution is close enough. The absorption of copper was increased by 50 % from strongly acidic to neutral reaction. Under alkaline conditions Cobalt and Copper were practically absent in the solution. Has been found that the absorption of heavy metals by soil decreases in sequence: Cu, Zn > Cd, Ni > Co. The selectivity of the absorption of heavy metals by humic acids was less marked, but the ability to sorption has the similar sequence: Cu > Zn > Ni > Cd > Co. The residue of soil after removal of humic acids has a high affinity for copper ions, which was absorbed twice from each other metals. Has been proved experimentally that selective adsorption of heavy metals in soil significantly depends on the pH, decreasing under acidic and strongly acidic conditions where hydrogen is successfully competing with them for exchange places in soil absorption complex. Deviation from the equivalent absorption (20 %) of each heavy metal in soil accounted for 15.0–26.0 % in acidic pH and 1.6–45.4 % in alkaline pH. After the interaction of heavy metals with humic acids in the most acidic medium fluctuations content elements in the equilibrium solution was 15.7–25.3 %, while the highest pH 11.0–26.7 %. Overall, the decrease of sorption capacity for humic acids elements can be placed in the following order: Cu > Zn > Ni > Cd > Co. This sequence is saved by a narrow ratio solution: adsorbent. Thus, under condition of polyelement contamination migration of Cobalt in soil may be more intensive than Zink, Cadmium, Nickel and a lot more than Copper, especially in alkaline pH.

Methanobactin and the Link between Copper and Bacterial Methane Oxidation.

Methanobactins (mbs) are low-molecular-mass (<1,200 Da) copper-binding peptides, or chalkophores, produced by many methane-oxidizing bacteria (methanotrophs). These molecules exhibit similarities to certain iron-binding siderophores but are expressed and secreted in response to copper limitation. Structurally, mbs are characterized by a pair of heterocyclic rings with associated thioamide groups that form the copper coordination site. One of the rings is always an oxazolone and the second ring an oxazolone, an imidazolone, or a pyrazinedione moiety. The mb molecule originates from a peptide precursor that undergoes a series of posttranslational modifications, including (i) ring formation, (ii) cleavage of a leader peptide sequence, and (iii) in some cases, addition of a sulfate group. Functionally, mbs represent the extracellular component of a copper acquisition system. Consistent with this role in copper acquisition, mbs have a high affinity for copper ions. Following binding, mbs rapidly reduce Cu(2+) to Cu(1+). In addition to binding copper, mbs will bind most transition metals and near-transition metals and protect the host methanotroph as well as other bacteria from toxic metals. Several other physiological functions have been assigned to mbs, based primarily on their redox and metal-binding properties. In this review, we examine the current state of knowledge of this novel type of metal-binding peptide. We also explore its potential applications, how mbs may alter the bioavailability of multiple metals, and the many roles mbs may play in the physiology of methanotrophs.

Albumin with an affinity for copper ions as a potential biomarker for mild cognitive impairment and Alzheimer's-type dementia

Albumin with an affinity for copper ions as a potential biomarker for mild cognitive impairment and Alzheimer's-type dementia

Purifying sugar beet pectins from non-pectic components by means of metal precipitation

Metal precipitation is an effective method for the purification of pectins. To study the selectivity of copper ions toward binding pectic or non-pectic compounds, two fractions, namely copper-precipitated pectins (CPP) and copper-unprecipitated pectins (CUP) were fractionated from the mother sugar beet pectins by means of copper precipitation. Comparison on chemical feature revealed the isolated fractions were structurally different in that CUP contained markedly higher neutral sugars (NS) and protein contents, but lower galacturonic acid and acetyl ester group contents than CPP. However, no appreciable difference was observed in terms of degree of methylation (DM). Elution profiles on high performance size exclusion chromatograph showed that CPP exhibited a monomodal-like molecular weight distribution (MWD), while CUP demonstrated a multimodal-like MWD pattern composed of three relatively broad peaks, and a narrow peak that was associated with a high intensity of UV signal at 278 nm. Moreover, AFM analysis showed that CPP displayed branched fibrous structures, while CUP showed distinguishable granular-like shapes. Results obtained in this work indicate the employed copper ions selectively bind the anionic regions among pectin chains, thereby separating pectic saccharides from non-uronide compounds, i.e. low molecular weight carbohydrates and free proteins. The poor affinity of copper ions toward CUP might be determined by the absence of typical homogalacturonan (HG) regions.

Biosorption of copper, nickel and cobalt ions from dilute solutions using BSA-coated air bubbles

This study probed the competitive biosorption behavior of a ternary system containing copper, nickel and cobalt ions using a novel material known as air-filled emulsion (AFE). AFE is a stable colloidal suspension in which fine protein-coated bubbles (<10μm) generated by an ultrasonic technique are dispersed through the aqueous solution, introducing a high surface area between protein as an extractant and metal ions. Effect of different experimental conditions including metal solution pH, temperature, biomass dosage and metal ion concentration on metal ion uptake was investigated. It was observed that an increase in pH led to greater metal uptake; although, bovine serum albumin (BSA)-coated bubbles illustrated higher affinity for copper ions than for nickel and cobalt ions. Increasing the temperature up to 65°C increased copper uptake to roughly 98%; however nickel and cobalt removal did not exhibit a significant change. BSAEM also demonstrated very different adsorption behaviors for copper, nickel and cobalt at various biomass and metal ion concentrations. Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) results revealed that amino, carboxylic and thiol groups of BSA-coated microcells are the active sorbing sites for metal ion uptake in the solution.

Development of a novel flow sensor for copper trace analysis by electrochemical reduction of 4-methoxybenzene diazonium salt

Due to the rapidity and the effectiveness of the method, the reduction of diazonium salts has been widely used to functionalize electrodes for sensor applications. However, the resulting organic film usually designed to provide complexing capabilities for the species to be determined could affect the sensor properties. The electrochemical reduction of 4-methoxybenzene diazonium salt on graphite felt that leads to the formation of an organic film with unexpected high affinity for copper ions is presented. This property combined with a flow electrochemical system led us to achieve a sensitive sensor for copper detection, with good selectivity towards some common interferent ions.

The human tripeptide GHK-Cu in prevention of oxidative stress and degenerative conditions of aging: implications for cognitive health.

Oxidative stress, disrupted copper homeostasis, and neuroinflammation due to overproduction of proinflammatory cytokines are considered leading causative factors in development of age-associated neurodegenerative conditions. Recently, a new mechanism of aging—detrimental epigenetic modifications—has emerged. Thus, compounds that possess antioxidant, anti-inflammatory activity as well as compounds capable of restoring copper balance and proper gene functioning may be able to prevent age-associated cognitive decline and ward off many common neurodegenerative conditions. The aim of this paper is to bring attention to a compound with a long history of safe use in wound healing and antiaging skin care. The human tripeptide GHK was discovered in 1973 as an activity in human albumin that caused old human liver tissue to synthesize proteins like younger tissue. It has high affinity for copper ions and easily forms a copper complex or GHK-Cu. In addition, GHK possesses a plethora of other regenerative and protective actions including antioxidant, anti-inflammatory, and wound healing properties. Recent studies revealed its ability to up- and downregulate a large number of human genes including those that are critical for neuronal development and maintenance. We propose GHK tripeptide as a possible therapeutic agent against age-associated neurodegeneration and cognitive decline.

The impact of calculation on the value of thermodynamic parameters of copper adsorption on poplar sawdust

The adsorption of Cu(II) onto poplar sawdust as an adsorbent is analyzed. The experimental data were fitted by the Langmuir isotherm using four linearized forms at the isotherm along with the original one. The least squares regression method was applied. Using the obtained Langmuir constants by each at methods, the enthalpy, entropy and Gibbs free energy at adsoption were calculated. A comparison of the used linear and non-linear regression methods in view at the goodness of the fit is presented. The coefficient of correlation was adopted as a criterionn to select the best method. The impact of the choice at regression model on the resulting estimates of the thermodynamic parameters is discussed. The best fit of the experimental data is obtained by the nonlinear regression. Thus, it is recommended to use the Langmuir parameters calculated by the nonlinear regression for estimating the thermodynamic parameters of adsorptin. The differences in the values obtained by different models are not so large to change the basic conclusion that the adsorption of copper ions on poplar sawdust is a spontaneous endothermic process i.e. that tested adsorbent has an affinity for copper ions.

Immobilized copper-ion affinity adsorbent based on a cross-linked β-cyclodextrin polymer for adsorption of Candida rugosa lipase

Immobilized copper-ion affinity adsorbent based on a cross-linked β-cyclodextrin polymer for adsorption of Candida rugosa lipase

Immobilized copper-ion affinity adsorbent based on a cross-linked β-cyclodextrin polymer for adsorption of Candida rugosa lipase

Lipase from Candida rugosa was immobilized on a β-cyclodextrin-based polymer by adsorption and subsequent cross-linking with epichlorohydrin (EP-CD). The ligand iminodiacetic acid (IDA) was then bonded with the cross-linked β-cyclodextrin (EP-CD-IDA). This affinity adsorbent was further chelated with Cu2 + for the purpose of binding affinity and stability. The properties of the immobilized lipase were assayed and compared with those of the free enzyme. Results showed that 266 µg protein with an activity of 17.85 U was bound per gram of matrix, giving 188% of the specific activity of the free enzyme and a total recovered activity of 79.7% under the optimum conditions. The pH and thermal stabilities of lipase were improved after immobilization on the β-cyclodextrin-based polymer (EP-CD-IDA-Cu2 +). In addition, experimental results indicated that the residual activity of the immobilized lipase was 50% after eight cycles of reuse.

Analysis of papain adsorption on nylon-based immobilized copper ion affinity membrane

Analysis of papain adsorption on nylon-based immobilized copper ion affinity membrane