Metal Ions Zn Research Articles

Detailed investigation of effects of Zn2 +, Fe2 + and Cu2 + metal ions on the binding interaction between eletriptan hydrochloride an anti-migraine headache drug and bovine serum albumin by various spectrometric techniques and molecular docking studies

Bovine serum albumin acts as storage and a transport of endogenous and exogenous compounds with protein in the blood. Eletriptan hydrochloride is an anti-migraine headache drug and binding of this drug to albumin is necessary in pharmacokinetic and pharmacodynamics. Many metal ions are present in blood plasma, therefore, the study on the effects of metal ions on the interaction between drugs and plasma proteins are essential. In this study, the effects of metal ions Zn2+, Fe2+ and Cu2+ on the interaction between bovine serum albumin (BSA) and eletriptan hydrochloride (ELT) were investigated by employing emission fluorescence, synchronous fluorescence, ultraviolet–visible (UV–Vis) absorption, Fourier transform infrared (FT-IR) spectroscopic and molecular docking studies at physiological buffer conditions (pH7.4). Results show that static quenching, spontaneous process, hydrogen bonds and vander Waals interactions and the values of Ka, n,Kb, R0,r and thermodynamic parameters were obtained at different temperatures; then the binding sites for ELT in BSA present in sub-domains IIA, IIIA and IB. The entire outcome indicates that the metal ions decrease the binding efficacy of ELT on BSA. The study of binding phenomena is important in providing basic information on the pharmacological actions, biotransformation and bio-distribution, and this would be useful in pharmaceutical industry, life sciences and clinical medicine.

Adhesion profile and differentiation capacity of human adipose tissue derived mesenchymal stem cells grown on metal ion (Zn, Ag and Cu) doped hydroxyapatite nano-coated surfaces

Accelerated Mesenchymal Stem Cells (MSCs) condensation and robust MSC-matrix and MSC-MSC interactions on nano-surfaces may provide critical factors contributing to such events, likely through the orchestrated signal cascades and cellular events modulated by the extracellular matrix. In this study, human adipose tissue derived mesenchymal stem cells (hMSC)', were grown on metal ion (Zn, Ag and Cu) doped hydroxyapatite (HAP) nano-coated surfaces. These metal ions are known to have different chemical and surface properties; therefore we investigated their respective contributions to cell viability, cellular behavior, osteogenic differentiation capacity and substrate-cell interaction. Nano-powders were produced using a wet chemical process. Air spray deposition was used to accumulate the metal ion doped HAP films on a glass substrate. Cell viability was determined by MTT, LDH and DNA quantitation methods Osteogenic differentiation capacity of hMSCs was analyzed with Alizarin Red Staining and Alkaline Phosphatase Specific Activity. Adhesion of the hMSCs and the effect of cell adhesion on biomaterial biocompatibility were explored through cell adhesion assay, immunofluorescence staining for vinculin and f-actin cytoskeleton components, SEM and microarray including 84 known extracellular matrix proteins and cell adhesion pathway genes, since, adhesion is the first step for good biocompability. The results demonstrate that the viability and osteogenic differentiation of the hMSCs (in growth media without osteogenic stimulation) and cell adhesion capability are higher on nanocoated surfaces that include Zn, Ag and/or Cu metal ions than commercial HAP. These results reveal that Zn, Ag and Cu metal ions contribute to the biocompatibility of exogenous material.

Estimation of heavy metal-contaminated soils’ mechanical characteristics using electrical resistivity

Under the process of urbanization in China, more and more attention has been paid to the reuse of heavy metal-contaminated sites. The shear characteristics of heavy metal-contaminated soils are investigated by electrical detection in this paper. Three metal ions (Zn2+, Cd2+, and Pb2+) were used, the metal concentrations of which are 50, 166.67, 500, 1666.67, and 5000mg/kg, respectively. Direct shear tests were used to investigate the influence of heavy metal ions on the shear characters of soil samples. It is found that with the addition of heavy metal ions, the shear strength, cohesion, and friction angle of contaminated soils are higher than the control samples. The higher concentration of heavy metal ions penetrated in soils, the higher these engineering characteristics of contaminated soils observed. In addition, an electrical resistivity detection machine is used to evaluate the shear characteristics of contaminated soils. The electrical resistivity test results show that there is a decreasing tendency of resistivity with the increase of heavy metal ion concentrations in soils. Compared with the electrical resistivity and the shear characteristics of metal-contaminated soils, it is found that, under fixed compactness and saturation, shear strength of metal-contaminated soils decreased with the increase of resistivity. A basic linear relationship between C/log(N+10) and resistivity can be observed, and there is a basic linear relationship between φ/log(N+10) and resistivity. Besides, a comparison of the measured and predicted shear characteristics shows a high accuracy, indicating that the resistivity can be used to evaluate the shear characteristics of heavy metal contaminated soils.

Effect of donor atom identity on metal-binding pharmacophore coordination.

The inhibition and binding of three metal-binding pharmacophores (MBPs), 2-hydroxycyclohepta-2,4,6-trien-1-one (tropolone), 2-mercaptopyridine-N-oxide (1,2-HOPTO), and 2-hydroxycyclohepta-2,4,6-triene-1-thione (thiotropolone) to human carbonic anhydrase II (hCAII) and a mutant protein hCAII L198G were investigated. These MBPs displayed bidentate coordination to the active site Zn(II) metal ion, but the MBPs respond to the mutation of L198G differently, as characterized by inhibition activity assays and X-ray crystallography. The L198G mutation increases the active site volume thereby decreasing the steric pressure exerted on MBPs upon binding, allowing changes in MBP coordination to be observed. When comparing the binding mode of tropolone to thiotropolone or 1,2-HOPTO (O,O versus O,S donor sets), structural modifications of the hCAII active site were shown to have a stronger effect on MBPs with an O,O versus O,S donor set. These findings were corroborated with density functional theory (DFT) calculations of model coordination complexes. These results suggest that the MBP binding geometry is a malleable interaction, particularly for certain ligands, and that the identity of the donor atoms influences the response of the ligand to changes in the protein active site environment. Understanding underlying interactions between a MBP and a metalloenzyme active site may aid in the design and development of potent metalloenzyme inhibitors.

New Delhi Metallo‐Beta‐Lactamase Variants NDM‐4 and NDM‐12 from E. coli Clinical Isolates Exhibit Increased Activity and Stability

Metallo‐Beta‐Lactamases (MBLs) confer resistance to carbapenems, cephalosporins, and penicillins in several clinically relevant Gram‐negative bacteria including Acinetobacter, Pseudomonas aeruginosa, and many Enterobacteriaceae. New Delhi Metallo‐Beta‐Lactamases (NDMs) are amongst some of the most worrisome and prevalent MBLs. This family of MBLs is capable of hydrolyzing all generations of bicyclic beta‐lactams. Two new NDM variants, NDM‐4 and ‐12, have recently been identified in E. coli clinical isolates. NDM‐4 contains an M154L substitution while NDM‐12 bears both M154L and G222D mutations. Considering the clinical significance of Gram‐negative species possessing these enzymes, there is a need to characterize the structures and activities of these variants in order to provide a better basis for drug discovery efforts. We have found that NDM‐4 and NDM‐12 possess higher hydrolytic activity compared to NDM‐1. Our differential scanning fluorimetry studies suggest that the M154L mutation confers increased thermal stability and improved affinity for active site catalytic Zn metal ions. The additional G222D mutation of NDM‐12 further improves stability and Zn affinity. M154L, found in the secondary coordination sphere, accounts for changes in stability by acting as a buttress to the loop containing His122, a direct Zn coordinating residue. G222D, on the other hand, is a mutation located in a loop just above the active site approximately 10 Å from the active site zinc ions. Together, our crystal structures of these NDM variants, including the first known structure of NDM‐12, biochemical analyses, and biophysical analyses provide a basis for understanding the roles of key residues surrounding the active site within NDM variants. A better understanding of clinically relevant NDM variants is essential in the fight against MBL‐mediated antibiotic resistance. Our structural, biochemical, and biophysical studies will help to inform drug design efforts to develop new MBL inhibitors.Support or Funding InformationThe authors acknowledge financial support from the US National Institutes of Health (Award No. R01 GM111926 to RCP, DLT, MWC, and WF) and institutional support from Miami University through the Robert H. and Nancy J. Blayney Professorship (to RCP). The Advanced Light Source is supported by the US Department of Energy under contract number DE‐AC03‐76SF00098 at Lawrence Berkeley National Laboratory.

New Luminescent Three-Dimensional Zn(II)/Cd(II)-Based Metal–Organic Frameworks Showing High H2 Uptake and CO2 Selectivity Capacity

Three new three-dimensional (3D) luminescent metal–organic frameworks (MOFs), namely, [Zn2(L)2]·2DMA·3H2O (1), [Zn2(L)2]·H2O (2), and [Cd2(L)2]·H2O (3) [H2L = 2-(imidazol-1-yl)terephthalic acid], have been solvothermally synthesized by using d10 metal ions Zn(II)/Cd(II) and H2L in different solvent systems, which have been well characterized by elemental analysis, Fourier transform infrared spectroscopy, powder X-ray diffraction, and thermogravimetric analysis. As influenced by the different solvents and metal ions, single-crystal X-ray diffraction shows that 1 is a three-dimensional (3D) microporous framework with one-dimensional (1D) pores (10.85 × 8.79 A2) based on the [Zn2(μ2-COO)4] secondary building units, and 2 and 3 are two 3D isostructural networks composed by 1D zigzag chains, which are further connected by L2– ligands into dense packing structures. Topology analyses reveal that 1 can be simplified as a binodal (6,3)-connected ant topological net with a point symbol of (44·63·83)(48·62), and 2 a...

Utilizing Phosphating Sludge to Synthesize Lithium Iron Phosphate with a Hybrid Coating of Metal Oxides and Carbon

In order to utilize the hazardous phosphating sludge, a novel approach including FeCl3 solution replacement leaching and MeO (metal oxides) coprecipitation coating is proposed to prepare LiFePO4 coated with metal oxides and carbon, where FePO4 is recycled from phosphating sludge and its valuable impurities are utilized as coating materials. The FeCl3 solution replacement leaching is a process for PO43+ enrichment and FePO4 purifying. The metal ions (Zn2+, Ca2+, Mn2+, etc.) of the impurity phosphates can be leached into the solution, meanwhile their corresponding PO43– are reprecipitated as FePO4, whose Fe3+ come from the FeCl3 leaching solution. Taking the obtained FePO4 as the core material, the MeO can be coprecipitated from the leached solution and coated onto the FePO4 particle uniformly under the critical pH and appropriate concentration. This uniform hybrid coating is helpful to avoid the asymmetrical conductivity both for electron and lithium ion on the surface of the LiFePO4 particle, and hence im...

Adsorption of heavy-metal ions from aqueous solution onto chitosan-modified polyethylene terephthalate (PET)

A novel chitosan-modified polyethylene terephthalate (PET) composite (CCP) adsorbent was specifically fabricated using a dip-padding method for removal of toxic metal ions (Zn2+, Cu2+, and Pb2+) from aqueous solution, especially during emergency treatment of river pollution. The fabricated CCP sample was investigated by scanning electron microscopy, static contact angle measurement, and X-ray photoelectron spectroscopy to confirm successful coating of chitosan onto PET fibers. Adsorption experiments demonstrated that the adsorption process of metal ions onto the surface of CCP was well fit by the Langmuir isotherm model and pseudo-second-order kinetic model. Maximum adsorption values (q max) of 18.69, 23.70, and 31.25 mg g−1 were obtained from the Langmuir isotherm model for Zn(II), Cu(II), and Pb(II), respectively.

Formation of sol-gel based Cu2ZnSnS4 thin films using ppm-level hydrogen sulfide

This study reports the preparation of copper zinc tin sulfide (Cu2ZnSnS4 or CZTS) thin films using parts-per-million (ppm) level of hydrogen sulfide (H2S) gas as opposed to high percentage level of H2S (e.g., ≥5%) in many other studies. Sol-gel technique was adopted for the preparation of metal oxide films from precursor solutions with different ratios of Cu, Zn, and Sn metal ions. Sulfurization process was carried out in tube furnace using 100ppm H2S balanced by hydrogen at different temperatures. Generally, it was observed that the sulfur content of the thin films obtained showed strong dependence on the sulfurization temperature. Samples sulfurized at higher temperatures (e.g., ~450 and 550°C) in ppm-level H2S experienced significant sulfur loss as confirmed by EDS, which was accompanied by the formation of metal alloys such as Cu3Sn as identified by XRD. On the other hand, samples sulfurized at lower temperatures of ~350°C and even 125°C revealed the formation of CZTS phase as confirmed by XRD, Raman micro-spectroscopy, and sheet resistance measurement. Moreover, local EDS analysis indicates that CZTS films prepared at those low temperatures have near-stoichiometric composition and are sometimes accompanied by the formation of Cu2−xS phase(s). In addition, stoichiometric and Cu-rich precursor solutions tend to yield CZTS samples with better crystallinity and superior optical properties compared with the Cu-deficient solution. These results are discussed from thermodynamics perspective and the directions for future research for safer and more economical processing of CZTS solar cells are pointed out.

Preparation of activated carbons from pecan nutshell and their application in the antagonistic adsorption of heavy metal ions

Abstract Activated carbons have been synthetized using the pecan nutshell (Carya illinoinensis) biomass for the adsorption of heavy metal ions. Adsorbents with different surface and ion exchange properties were obtained using physical and chemical activation routes with different reagents. These activated carbons have been assessed and compared in the removal of heavy metal ions Zn2+, Cd2+, Ni2+ and Cu2+ given a special emphasis on the analysis of competitive adsorption of these pollutants in binary systems. Adsorption behavior of tested adsorbents was correlated with some of their physicochemical properties and a removal mechanism has been proposed. Results showed that a synthesis route combining physical and chemical activation improved substantially the adsorption properties of these adsorbents. The chemical activation may improve the metal adsorption using these adsorbents up to 1214 % where adsorption capacities ranged from 0.011 to 0.368 mmol/g. However, the tailoring of activated carbons for the effective multi-component adsorption of heavy metals is still a challenge. This study highlights the impact and relevance of surface chemistry and ion exchange capacity of pecan nutshell – based adsorbents in the antagonistic adsorption of heavy metal ions.

Synthesis of several novel coordination complexes: ion exchange, magnetic and photocatalytic studies

Eight different novel polymers by the reactions of H2L and metal ions (Zn2+, Cu2+, Co2+) in the presence or absence of auxiliary ligands were constructed. The Zn2+ in complexes 1–3 could be partially exchanged with Cu2+ ions.

Efficiency of Rice Husk for Removal of Cu(II) and Zn(II) Ions from Aqueous Solution

In the present study the adsorption of Cu(II) and Zn(II) ions on rice husk from artificially prepared aqueous solutions of these metal ions was investigated following the batch mode adsorption procedure. Accordingly, the effects of operating parameters such as pH, contact time, and initial concentration of metal ion solution were evaluated. The results so obtained in this study indicated that the optimum conditions for the Cu(II) and Zn(II) ions adsorption were found to be as follows: pH of 6 and 7; contact times of 100 and 125 minutes; and these values were actually determined by setting the initial concentration of 50mg/L for each metal ion solution. Upon measurements of the residual metal ion concentration using FAAS method, the percent adsorption of both Cu(II) and Zn(II) ions showed significant increase with an increase in each case of the contact time. Furthermore, it was evidently implicated that the binding process of the metal ions on the adsorbent (rice husk) could be affected by change in the pH of both metal ion solutions. In addition the experimental data were analyzed against both Langmuir and Freundlich isotherm for determining the maximum adsorption capacity of the title biosorbent with respect to each of the tested metal ions. The adsorption maxima were calculated on the basis the Langmuir isotherm and found to be 1.93 and 12.98 mg/g for Cu(II) and Zn(II) metal ions respectively. These values were suggested that the rice husk investigated in this study can have a good application potential for the removal of both metal ions (Cu(II) and Zn(II)) from aqueous solutions. In fact, the goal of this work was to develop an inexpensive, highly available, effective metal ion adsorbent from natural waste as alternative to existing commercial adsorbents.

The amyloid architecture provides a scaffold for enzyme-like catalysts.

Natural biological enzymes possess catalytic sites that are generally surrounded by a large three-dimensional scaffold. However, the proportion of the protein molecule that participates in the catalytic reaction is relatively small. The generation of artificial or miniature enzymes has long been a focus of research because enzyme mimetics can be produced with high activity at low cost. These enzymes aim to mimic the active sites without the additional architecture contributed by the protein chain. Previous work has shown that amyloidogenic peptides are able to self-assemble to create an active site that is capable of binding zinc and catalysing an esterase reaction. Here, we describe the structural characterisation of a set of designed peptides that form an amyloid-like architecture and reveal that their capability to mimic carbonic anhydrase and serve as enzyme-like catalysts is related to their ability to self-assemble. These amyloid fibril structures can bind the metal ion Zn2+via a three-dimensional arrangement of His residues created by the amyloid architecture. Our results suggest that the catalytic efficiency of amyloid-like assembly is not only zinc-dependent but also depends on an active centre created by the peptides which is, in turn, dependent on the ordered architecture. These fibrils have good esterase activity, and they may serve as good models for the evolution of modern-day enzymes. Furthermore, they may be useful in designing self-assembling fibrils for applications as metal ion catalysts. This study also demonstrates that the ligands surrounding the catalytic site affect the affinity of the zinc-binding site to bind the substrate contributing to the enzymatic activity of the assembled peptides.

Nano-Silica Modified by Hematoporphyrin for Determination Some of Traces Metals Ions (Cu(II), Zn(II) and Mn(II)) in Environmental and Pharmaceutical Formula

Recovering of heavy metal ions Zn(II), Cu(II) and Mn(II) in aqueous solution has been investigated using a novel nano silica modified by hemtaprophyrin. Nano sorbent was prepared by sol gel method. Transmission electron microscope and EDAX analysis showed the nano scale with porosity of a new sorbent. The proposed structure of modified silica with HP was predicted according to FTIR and elemental analysis. The new sorbent have good thermal stability. The phenomena of the sorbent sorption included the static studies such as pH and the Langmuir and Freundlish models were applied at equilibrium state. The linear regression analysis was Langmuir isotherm according to the values of relation coefficient (R2). The limit of detection (LOD) for Zn, Cu and Mn were 0.01, 0.12 and 0.03 μg L-1 respectively, within the analytical range 0.1-10 μgL-1. This method achieved highly precision for the samples of environmental and pharmaceutical formulations of % RSD less than 10%.

Molecular Mechanism of Action for Allosteric Modulators and Agonists in CC-chemokine Receptor 5 (CCR5)

The small molecule metal ion chelators bipyridine and terpyridine complexed with Zn2+ (ZnBip and ZnTerp) act as CCR5 agonists and strong positive allosteric modulators of CCL3 binding to CCR5, weak modulators of CCL4 binding, and competitors for CCL5 binding. Here we describe their binding site using computational modeling, binding, and functional studies on WT and mutated CCR5. The metal ion Zn2+ is anchored to the chemokine receptor-conserved Glu-283VII:06/7.39 Both chelators interact with aromatic residues in the transmembrane receptor domain. The additional pyridine ring of ZnTerp binds deeply in the major binding pocket and, in contrast to ZnBip, interacts directly with the Trp-248VI:13/6.48 microswitch, contributing to its 8-fold higher potency. The impact of Trp-248 was further confirmed by ZnClTerp, a chloro-substituted version of ZnTerp that showed no inherent agonism but maintained positive allosteric modulation of CCL3 binding. Despite a similar overall binding mode of all three metal ion chelator complexes, the pyridine ring of ZnClTerp blocks the conformational switch of Trp-248 required for receptor activation, thereby explaining its lack of activity. Importantly, ZnClTerp becomes agonist to the same extent as ZnTerp upon Ala mutation of Ile-116III:16/3.40, a residue that constrains the Trp-248 microswitch in its inactive conformation. Binding studies with 125I-CCL3 revealed an allosteric interface between the chemokine and the small molecule binding site, including residues Tyr-37I:07/1.39, Trp-86II:20/2.60, and Phe-109III:09/3.33 The small molecules and CCL3 approach this interface from opposite directions, with some residues being mutually exploited. This study provides new insight into the molecular mechanism of CCR5 activation and paves the way for future allosteric drugs for chemokine receptors.

Structural and Functional Influence of the Glycine-Rich Loop G302GGGY on the Catalytic Tyrosine of Histone Deacetylase 8.

Histone deacetylase 8 (HDAC8) catalyzes the hydrolysis of acetyl-l-lysine to yield products l-lysine and acetate through a mechanism in which a nucleophilic water molecule is activated by a histidine general base and a catalytic metal ion (Zn2+ or Fe2+). Acetyl-l-lysine also requires activation by metal coordination and a hydrogen bond with catalytic tyrosine Y306, which also functions in transition state stabilization. Interestingly, Y306 is located in the conserved glycine-rich loop G302GGGY. The potential flexibility afforded by the tetraglycine segment may facilitate induced-fit conformational changes in Y306 between "in" and "out" positions, as observed in related deacetylases. To probe the catalytic importance of the glycine-rich loop in HDAC8, we rigidified this loop by preparing the G302A, G303A, G304A, and G305A mutants and measured their steady state kinetics and determined their X-ray crystal structures. Substantial losses of catalytic efficiency are observed (10-500-fold based on kcat/KM), particularly for G304A HDAC8 and G305A HDAC8. These mutants also exhibit the greatest structural changes for catalytic tyrosine Y306 (1.3-1.7 Å shifts of the phenolic hydroxyl group). Molecular dynamics simulations further indicate that G304 and G305 undergo pronounced structural changes as residue 306 undergoes a transition between "in" and "out" conformations. Thus, the G304A and G305A substitutions likely compromise the position and conformational changes of Y306 required for substrate activation and transition state stabilization. The G302A and G303A substitutions have less severe catalytic consequences, and these substitutions may influence an internal channel through which product acetate is believed to exit.

Study on the interactional behaviour of transition metal ions with myoglobin: A detailed calorimetric, spectroscopic and light scattering analysis

The energetics and the impact on the conformation of heme containing protein myoglobin (Mb) due to the binding of three transition metal ions (Zn2+, Ni2+, and Mn2+) have been investigated using isothermal titration calorimetry (ITC), dynamic light scattering (DLS), UV–vis, and circular dichroism (CD) spectroscopy under physiological conditions. The binding affinity of the order of 104M−1 has been observed for all metal ions from calorimetry as well as from absorption spectroscopy. The binding of these metal ions with Mb is a spontaneous process that exposes the hydrophobic groups away from the protein core as exhibited by the negative Gibbs free energy change (ΔG) and positive heat capacity change (ΔCp) values. Both light scattering and CD results demonstrates that the binding of Zn2+ and Mn2+ ions with Mb results in the folding whereas Ni2+ ion results in the unfolding of the protein. No direct interactions among the transition metal ions and heme moiety of Mb has been observed from absorption study. The results of these studies reveals that Mn2+ ion influences the biological functions of Mb to a larger extent in spite of its lowest affinity followed by Zn2+ and Ni2+ ions.

On-line micro-solid phase preconcentration of Cd2 + coupled to TS-FF-AAS using a novel ion-selective bifunctional hybrid imprinted adsorbent

A novel hybrid ion imprinted polymer (HIIP) is proposed aiming at the development of an online micro-solid phase preconcentration system of Cd2+ coupled to TS-FF-AAS. To evaluate the selective and adsorptive performance of HIIP towards Cd2+, hybrid non-imprinted polymer (HNIP), organic ion imprinted polymer (OIIP), and the inorganic ion imprinted polymer (IIIP) were synthesized and compared with each other. Adsorption capacity of HIIP was 53% higher than HNIP, and dual-site Langmuir–Freundlich isotherm model showed the best fit for data of both polymers. The preconcentration system coupled to TS-FF-AAS was performed by loading 10.0mL of Cd2+ solution at pH7.5 through 80.0mg of HIIP packed into a micro-column with posterior online elution using 1.0molL−1 HCl/ethanol 1:1 (v/v) mixture. The developed method was highly tolerant for other metal ions Zn2+, Pb2+, Cu2+, Co2+, Fe2+, and Hg2+ at analyte:interferent (1:50, m/m) ratio and Ca2+ and Mg2+ at 1:500 (m/m) ratio. Analytical curve ranging from 0.5 to 7.0μgL−1, limit of detection of 30ngL−1 and preconcentration factor of 14-fold were obtained. Intra-day and inter-day (3days) experiment precision (n=10) was, respectively, 3.9 and 0.6% (relative standard deviation, RSD), and 4.4 and 2.4% for concentrations of 0.7 and 6.5μgL−1. Sensitivity of method (Abs Lμg−1) was about 3.3, 2.2 and 1.9-fold higher when compared to preconcentration method using HNIP, OIIP and IIIP, respectively, thus clearly showing that hybrid polymer and imprinting process enhance Cd2+ adsorption. Addition and recovery experiments ranging from 94 to 106% in mineral, lake water and tap water, urine and cigarette samples attested the feasibility of method for analysis of matrices containing different components. Moreover, the accuracy of method was checked from analysis of certified reference material (DOLT-4, fish liver), being the obtained value of 23.9±0.6mgkg−1 (n=3) statistically equal to the certified value of 24.3±0.8mgkg−1, by applying Student t-test at 95% confidence level.

Metagenomics analysis reveals a new metallothionein family: Sequence and metal-binding features of new environmental cysteine-rich proteins

Metallothioneins are cysteine-rich proteins, which function as (i) metal carriers in basal cell metabolism and (ii) protective metal chelators in conditions of metal excess. Metallothioneins have been characterized from different eukaryotic model and cultivable species. Presently, they are categorized in 15 families but evolutionary relationships between these metallothionein families remain unresolved. Several cysteine-rich protein encoding genes that conferred Cd-tolerance in Cd-sensitive yeast mutants have previously been isolated from soil eukaryotic metatranscriptomes. They were called CRPs for “cysteine-rich proteins”. These proteins, of unknown taxonomic origins, share conserved cysteine motifs and could be considered as metallothioneins. In the present work, we analyzed these CRPs with respect to their amino acid sequence features and their metal-binding abilities towards Cd, Zn and Cu metal ions. Sequence analysis revealed that they share common features with different known metallothionein families, but also exhibit unique specific features. Noticeably, CRPs display two separate cysteine-rich domains which, when expressed separately in yeast, confer Cd-tolerance. The N-terminal domain contains some conserved atypical Cys motifs, such as one CCC and two CXCC ones. Five CRPs were expressed and purified as recombinant proteins and their metal-binding characteristics were studied. All these CRPs chelated Cd(II), Zn(II) and Cu(I), although displaying a better capacity for Zn(II) coordination. All CRPs are able to confer Cd-tolerance, and four of them confer Zn-tolerance in the Zn-sensitive zrc1Δ yeast mutant. We designated these CRPs as environmental metallothioneins belonging to a new formerly undescribed metallothionein family.

Optical biosensing using newly synthesized metal salphen complexes: A potential DNA diagnostic tool

A solid-state DNA optode sensor has been developed based on the employment of glutaraldehyde (GD)-activated aminated silica nanoparticles (SiO2NPs-NH2) DNA carrier matrix, and the newly synthesized yellowish N,N’-bis-5-(hydroxysalicylidene)phenylene-diamine-zinc(II) (i.e. the Zn salphen complex) oligonucleotide label. Some three Schiff base complexes with three different transition metal ions (Zn2+, Ni2+, Cu2+) were synthesized through a simple one-pot reaction (5h), and characterized by their physical and chemical properties based on FTIR, NMR and ESI–MS analyses. Due to the square planar geometry and aromatic ring structured characteristics of the metal complex intercalators, they could intercalate between DNA bases via π-π stacking interaction, and rendered a yellowish pink hue on the DNA biosensor surface. Reflectometric optimization revealed high selectivity of the nanosilica-based DNA biosensor in the detection of dengue serotype 2 DNA, which capable of discriminating even a single nucleotide mismatch. The optical DNA biosensor demonstrated a linear reflectance response between 1.0×10−15M and 1.0×10−11M cDNA (R2=0.9975) with a fast DNA hybridization time of 30min and a limit of detectable (LOD) DNA concentration as low as 1zM. In addition, this biosensor showed high shelf life stability with a 20-day operational duration and reusable for five consecutive DNA testings. The proposed optical DNA biosensor offers biosensing performance far superior to that of previously reported electrochemical DNA biosensor for early diagnosis of dengue infection with respect to dynamic linear range, LOD and response time.