Showing papers on "Zinc published in 2015"

The Physiological, Biochemical, and Molecular Roles of Zinc Transporters in Zinc Homeostasis and Metabolism.

Abstract: Zinc is involved in a variety of biological processes, as a structural, catalytic, and intracellular and intercellular signaling component. Thus zinc homeostasis is tightly controlled at the whole ...

An Aqueous Zinc‐Ion Battery Based on Copper Hexacyanoferrate

Abstract: A new zinc-ion battery based on copper hexacyanoferrate and zinc foil in a 20 mM solution of zinc sulfate, which is a nontoxic and noncorrosive electrolyte, at pH 6 is reported. The voltage of this novel battery system is as high as 1.73 V. The system shows cyclability, rate capability, and specific energy values near to those of lithium-ion organic batteries based on Li4 Ti5 O12 and LiFePO4 at 10 C. The effects of Zn(2+) intercalation and H2 evolution on the performance of the battery are discussed in detail. In particular, it has been observed that hydrogen evolution can cause a shift in pH near the surface of the zinc electrode, and favor the stabilization of zinc oxide, which decreases the performance of the battery. This mechanism is hindered when the surface of zinc becomes rougher.

Disparate roles of zinc in chemical hypoxia-induced neuronal death

Abstract: Accumulating evidence has provided a causative role of zinc (Zn2+) in neuronal death following ischemic brain injury. Using a hypoxia model of primary cultured cortical neurons with hypoxia-inducing chemicals, cobalt chloride (1 mM CoCl2), deferoxamine (3 mM DFX), and sodium azide (2 mM NaN3), we evaluated whether Zn2+ is involved in hypoxic neuronal death. The hypoxic chemicals rapidly elicited intracellular Zn2+ release/accumulation in viable neurons. The immediate addition of the Zn2+ chelator, CaEDTA or N,N,N’N’-tetrakis-(2-pyridylmethyl) ethylenediamine (TPEN), prevented the intracellular Zn2+ load and CoCl2-induced neuronal death, but neither 3-hour-later Zn2+ chelation nor a non-Zn2+ chelator ZnEDTA (1 mM) demonstrated any effects. However, neither CaEDTA nor TPEN rescued neurons from cell death following DFX- or NaN3-induced hypoxia, whereas ZnEDTA rendered them resistant to the hypoxic injury. Instead, the immediate supplementation of Zn2+ rescued DFX- and NaN3-induced neuronal death. The iron supplementation also afforded neuroprotection against DFX-induced hypoxic injury. Thus, although intracellular Zn2+ release/accumulation is common during chemical hypoxia, Zn2+ might differently influence the subsequent fate of neurons; it appears to play a neurotoxic or neuroprotective role depending on the hypoxic chemical used. These results also suggest that different hypoxic chemicals may induce neuronal death via distinct mechanisms.

Effect of pH on Crystal Size and Photoluminescence Property of ZnO Nanoparticles Prepared by Chemical Precipitation Method

Abstract: The effects of pH value on crystal size and optical property of zinc oxide nanoparticles prepared by chemical precipitation method were investigated. Prepared samples have been characterized by means of X-ray diffraction, scanning electron microscopy, ultraviolet–visible spectrometer and photoluminescence spectrometer. From X-ray diffraction profile, it is found that the particle size of sample increases from 13.8 to 33 nm when the pH value of the solution was increased from 6 to 13. Microstructural study also shows that the particle size increases with pH value. Hexagonal shape of the zinc oxide nanoparticle has been confirmed by the scanning electron microscopy image. The recorded ultraviolet–visible spectrum shows excitonic absorption peaks around 381 nm. The energy gap of the prepared samples has been determined from the ultraviolet–visible absorption spectrum, effective mass model equation and Tauc’s relation. It was found that the energy gap of the prepared samples decreases with increase in pH value. The recorded blue shift confirmed the quantum confinement effect in the prepared zinc oxide samples. Photoluminescence spectrum infers that the increase in pH value shifts the ultraviolet–visible emission but not the violet and green emissions.

Analyzing free zinc(II) ion concentrations in cell biology with fluorescent chelating molecules

Abstract: Essential metal ions are tightly controlled in biological systems. An understanding of metal metabolism and homeostasis is being developed from quantitative information of the sizes, concentrations, and dynamics of cellular and subcellular metal ion pools. In the case of human zinc metabolism, minimally 24 proteins of two zinc transporter families and a dozen metallothioneins participate in cellular uptake, extrusion, and re-distribution among cellular compartments. Significantly, zinc(ii) ions are now considered signaling ions in intra- and intercellular communication. Such functions require transients of free zinc ions. It is experimentally quite challenging to distinguish zinc that is protein-bound from zinc that is not bound to proteins. Measurement of total zinc is relatively straightforward with analytical techniques such as atomic absorption/emission spectroscopy or inductively coupled plasma mass spectrometry. Total zinc concentrations of human cells are 200-300 μM. In contrast, the pool of non-protein bound zinc is mostly examined with fluorescence microscopy/spectroscopy. There are two widely applied fluorescence approaches, one employing low molecular weight chelating agents ("probes") and the other metal-binding proteins ("sensors"). The protein sensors, such as the CALWY, Zap/ZifCY, and carbonic anhydrase-based sensors, can be genetically encoded and have certain advantages in terms of controlling intracellular concentration, localization, and calibration. When employed correctly, both probes and sensors can establish qualitative differences in free zinc ion concentrations. However, when quantitative information is sought, the assumptions underlying the applications of probes and sensors must be carefully examined and even then measured pools of free zinc ions remain methodologically defined. A consensus is building that the steady-state free zinc ion concentrations in the cytosol are in the picomolar range but there is no consensus on their concentrations in subcellular compartments. Applying the extensive toolbox of available probes/sensors in biological systems requires an understanding of the principles of cellular zinc homeostasis and the chemical biology of the probes and sensors. Regardless of limitations in specificity (for a particular metal ion), selectivity (for a particular metal pool), and sensitivity (detection limit), the technology is making remarkable contributions to imaging zinc with high spatiotemporal resolution in single cells and to defining the biochemical functions of zinc ions in cellular regulation.

Quantitative mapping of zinc fluxes in the mammalian egg reveals the origin of fertilization-induced zinc sparks

Abstract: Fertilization of a mammalian egg initiates a series of 'zinc sparks' that are necessary to induce the egg-to-embryo transition. Despite the importance of these zinc-efflux events little is known about their origin. To understand the molecular mechanism of the zinc spark we combined four physical approaches that resolve zinc distributions in single cells: a chemical probe for dynamic live-cell fluorescence imaging and a combination of scanning transmission electron microscopy with energy-dispersive spectroscopy, X-ray fluorescence microscopy and three-dimensional elemental tomography for high-resolution elemental mapping. We show that the zinc spark arises from a system of thousands of zinc-loaded vesicles, each of which contains, on average, 10(6) zinc atoms. These vesicles undergo dynamic movement during oocyte maturation and exocytosis at the time of fertilization. The discovery of these vesicles and the demonstration that zinc sparks originate from them provides a quantitative framework for understanding how zinc fluxes regulate cellular processes.

Enhancement on Cycle Performance of Zn Anodes by Activated Carbon Modification for Neutral Rechargeable Zinc Ion Batteries

Abstract: A novel composite anode is prepared by mixing zinc particles with activated carbon (AC) to improve the cycle performance of the neutral rechargeable zinc ion batteries. Galvanostatic charge/discharge cycling tests indicate that the capacity retention of the cell with adding 12 wt% activated carbon in Zn anode is 85.6% after 80 cycles, which is much higher than that of 56.7% for the cell using unmodified Zn anode. X-ray diffraction analysis indicates that the addition of activated carbon can suppress the formation of inactive basic zinc sulfates (Zn4SO4(OH)6nH20). Morphology, elemental mapping and N2 adsorption and desorption measurements indicate that the pores of activated carbon can accommodate the deposition of Zn dendrites and insoluble anodic products. As a result, the cycle stability of the Zn anode has been greatly enhanced by activated carbon modification.

Chronic Zinc Deficiency Alters Chick Gut Microbiota Composition and Function.

Abstract: Zinc (Zn) deficiency is a prevalent micronutrient insufficiency. Although the gut is a vital organ for Zn utilization, and Zn deficiency is associated with impaired intestinal permeability and a global decrease in gastrointestinal health, alterations in the gut microbial ecology of the host under conditions of Zn deficiency have yet to be studied. Using the broiler chicken (Gallus gallus) model, the aim of this study was to characterize distinct cecal microbiota shifts induced by chronic dietary Zn depletion. We demonstrate that Zn deficiency induces significant taxonomic alterations and decreases overall species richness and diversity, establishing a microbial profile resembling that of various other pathological states. Through metagenomic analysis, we show that predicted Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways responsible for macro- and micronutrient uptake are significantly depleted under Zn deficiency; along with concomitant decreases in beneficial short chain fatty acids, such depletions may further preclude optimal host Zn availability. We also identify several candidate microbes that may play a significant role in modulating the bioavailability and utilization of dietary Zn during prolonged deficiency. Our results are the first to characterize a unique and dysbiotic cecal microbiota during Zn deficiency, and provide evidence for such microbial perturbations as potential effectors of the Zn deficient phenotype.

Relationship between the architecture of zinc coordination and zinc binding affinity in proteins – insights into zinc regulation

Abstract: Zinc proteins are an integral component of the proteome of all domains of life. Zn(II), one of the most widespread transition elements, serves multiple functions in proteins, such as a catalytic co-factor, a structural center and a signaling component. The mechanism by which proteins associate with and dissociate from Zn(II) and the factors that modulate their affinity and stability remain incompletely understood. In this article, we aim to address how zinc binding sites present in proteins differ in their architecture and how their structural arrangement is associated with protein function, thermodynamic and kinetic stability, reactivity, as well as zinc-dependent regulation. Here, we emphasize that the concentration-dependent functionality of the interprotein zinc binding site may serve as another factor regulating the relationship between cellular Zn(II) availability and protein function.

Hyper-dendritic nanoporous zinc foam anodes

Abstract: The low cost, significant reduction potential and relative safety of the zinc electrode is a common hope for a reductant in secondary batteries, but it is limited mainly to primary implementation due to shape change. In this work, we exploit such shape change for the benefit of static electrodes through the electrodeposition of hyper-dendritic nanoporous zinc foam. Electrodeposition of zinc foam resulted in nanoparticles formed on secondary dendrites in a three-dimensional network with a particle size distribution of 54.1–96.0 nm. The nanoporous zinc foam contributed to highly oriented crystals, high surface area and more rapid kinetics in contrast to conventional zinc in alkaline mediums. The anode material presented had a utilization of ~88% at full depth-of-discharge (DOD) at various rates indicating a superb rate capability. The rechargeability of Zn0/Zn2+ showed significant capacity retention over 100 cycles at a 40% DOD to ensure that the dendritic core structure was imperforated. The dendritic architecture was densified upon charge–discharge cycling and presented superior performance compared with bulk zinc electrodes. A synthetic method turns a problem with plate metal batteries into a path for greater stability and may lead to safer, cheaper batteries. Zinc is more abundant and easier to handle than lithium, but electrodes made from it suffer from shape-change effects that prevent stable cycling. Now, by electrodepositing nanoporous zinc foam onto a traditional current collector, Daniel Steingart from Princeton University in the USA and colleagues have exploited a problem with zinc electrodes — the formation of dendritic crystals that can short-circuit batteries. The team broke convention by deliberately conditioning their zinc electrodes at potentials far from equilibrium. This created a hyper-dendritic network foam that forms with 88% current efficiency and remains stable for over 100 recharge cycles — results superior to those of conventional batteries with non-porous zinc electrodes. The low cost, significant reduction potential and relative safety of the zinc electrode is a common hope for a reductant in secondary batteries, but it is limited mainly to primary implementation due to shape change. In this work, we exploit such shape change for the benefit of static electrodes through the electrodeposition of hyper-dendritic nanoporous zinc foam. Electrodeposition of zinc foam resulted in nanoparticles formed on secondary dendrites in a three-dimensional network with a particle size distribution of 54.1–96.0 nm. The nanoporous zinc foam contributed to highly oriented crystals, high surface area and more rapid kinetics in contrast to conventional zinc in alkaline mediums. The anode material presented had a utilization of ~88% at full depth-of-discharge (DOD) at various rates indicating a superb rate capability. The rechargeability of Zn0/Zn2+ showed significant capacity retention over 100 cycles at a 40% DOD to ensure that the dendritic core structure was imperforated. The dendritic architecture was densified upon charge–discharge cycling and presented superior performance compared with bulk zinc electrodes.

Controlled growth of ZnO nanorod arrays via wet chemical route for NO2 gas sensor applications

Abstract: Metal oxide gas sensors are promising devices that are widely used to detect various gases at moderate temperatures. In this study, nitrogen di-oxide (NO 2 ) sensors were fabricated using zinc oxide (ZnO) nanorod arrays. ZnO nanorod arrays (ZNAs) with various rod lengths were deposited using a wet chemical route with zinc acetate as a precursor. The structural and surface morphological properties of the ZNAs were investigated using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM), respectively. The XRD patterns showed ZNAs with wurtzite crystal structures that were preferentially oriented in the (0 0 2) direction. The intensity of the (0 0 2) plane was found to vary with the length of the nanorods. FESEM micrographs show that the ZNAs had a vertical alignment perpendicular to the substrate, and the diameter and length of the nanorods increased as the nanorod deposition time was increased. The gas sensing performance was studied as a function of the nanorod length, operating temperature, time and gas concentration. The length and inter-rod space was observed to play a crucial role in determining the gas sensing performance of the devices. ZNA gas sensors deposited for 9 h and operating at a temperature of 175 °C were able to detect NO 2 at a concentration of 100 ppm with a high sensitivity of 3100%.

Zinc in Early Life: A Key Element in the Fetus and Preterm Neonate

Abstract: Zinc is a key element for growth and development. In this narrative review, we focus on the role of dietary zinc in early life (including embryo, fetus and preterm neonate), analyzing consequences of zinc deficiency and adequacy of current recommendations on dietary zinc. We performed a systematic search of articles on the role of zinc in early life. We selected and analyzed 81 studies. Results of this analysis showed that preservation of zinc balance is of critical importance for the avoidance of possible consequences of low zinc levels on pre- and post-natal life. Insufficient quantities of zinc during embryogenesis may influence the final phenotype of all organs. Maternal zinc restriction during pregnancy influences fetal growth, while adequate zinc supplementation during pregnancy may result in a reduction of the risk of preterm birth. Preterm neonates are at particular risk to develop zinc deficiency due to a combination of different factors: (i) low body stores due to reduced time for placental transfer of zinc; (ii) increased endogenous losses; and (iii) marginal intake. Early diagnosis of zinc deficiency, through the measurement of serum zinc concentrations, may be essential to avoid severe prenatal and postnatal consequences in these patients. Typical clinical manifestations of zinc deficiency are growth impairment and dermatitis. Increasing data suggest that moderate zinc deficiency may have significant subclinical effects, increasing the risk of several complications typical of preterm neonates (i.e., necrotizing enterocolitis, chronic lung disease, and retinopathy), and that current recommended intakes should be revised to meet zinc requirements of extremely preterm neonates. Future studies evaluating the adequacy of current recommendations are advocated.

Selective formation of light olefins from CO2 hydrogenation over Fe–Zn–K catalysts

Abstract: Fe–Zn–K catalysts were prepared in varied Fe/Zn molar ratios using microwave-aided hydrothermal procedure followed by K modification with impregnation method and applied to CO2 hydrogenation reaction via Fischer–Tropsch synthesis for the selective production of C2–C4 olefins. Results showed that the prepared catalysts had uniform particles within about 100 nm. Addition of zinc to iron matrix formed ZnFe2O4 spinel phase and ZnO phase, and caused increase of the surface areas, enhanced the interaction between iron and zinc and altered the reduction and CO2 adsorption behaviors. The catalysts displayed high activity for the CO2 conversion and significant improvement in the product distribution. The proper interactions between Fe and Zn proved to be advantageous to suppress the production of C5+ hydrocarbons and promote the production of C2–C4 olefin. At set reaction conditions of H2/CO2 of 3, GHSV of 1000 h−1, 320 °C, and 0.5 MPa, the 1Fe–1Zn–K catalyst with H2/CO reduction showed the best performance with the CO2 conversion of 51.03%. The selectivity of C2–C4 olefins in overall hydrocarbons and the ratio of olefin to paraffin in the C2–C4 fraction reached 53.58% and 6.86, respectively.

Antibacterial behaviour of Vitex negundo extract assisted ZnO nanoparticles against pathogenic bacteria.

Abstract: The biological routes are advantageous over the chemical and physical ones as unlike. These, the biological synthesis protocol occurs at ambient conditions, are cheap, non-toxic and eco-friendly. This research describes the synthesis of zinc oxide nanoparticles (ZnO NPs) using Vitex negundo plant extract with zinc nitrate hexahydrate as precursor. Biomolecules present in plant extract can be used to hydrolyze metal ions into metal oxide NPs in a single-step green synthesis. The hydrolyzing agents involved the various water soluble plant metabolites such as flavonoid, alkaloids, flavone, phenolic compounds, terpenoids and co-enzymes. Presence of isoorientin (flavone) in V. negundo plant extract is mainly responsible for the formation of ZnO NPs. The prepared ZnO NPs were calcinated at 450°C and were confirmed by XRD, FT-IR, UV-visible, SEM with EDX and DLS analysis. The biological application of antibacterial activity was done by gram positive and gram negative bacteria.

A Zn–NiO rechargeable battery with long lifespan and high energy density

Abstract: A Zn–NiO rechargeable battery comprising a NiO nanosheet anchored to CNTs as the positive electrode, a zinc plate as the negative one and an alkaline solution of 1 M KOH and 10 mM Zn(Ac)2 as the electrolyte is reported. It delivers a voltage of ∼1.75 V and a high energy density of 228 W h kg−1 (based on the mass of the positive electrode composite and zinc) with good cycling. It has great promise for practical energy storage applications.

Green synthesis and characterization of ZnO nanoparticles for photocatalytic degradation of anthracene

Abstract: Zinc oxide nanoparticles were prepared using corriandrum sativum leaf extract and zinc acetate dihydrate. It was utilized as a photocatalyst for the degradation of anthracene. The catalyst was characterized by x-ray diffraction, high-resolution transmission electron microscopy, scanning electron microscopy, dynamic scattering light, Raman spectrometry and UV–vis spectrophotometry. The catalyst was used in a bench-scale design for degradation of anthracene. The factors affecting the photocatalytic degradation efficiency, including irradiation time, loading catalyst doses, and initial concentration of anthracene were investigated. The results obtained showed that the photocatalytic degradation efficiency was increased with both the decrease of the initial anthracene concentration and the increase of the photocatalyst doses. The optimum photocatalytic degradation was obtained at pH 7, irradiation time of 240 min and loading catalyst dose of 1000 μg L−1. Under these conditions, the photocatalytic degradation percentage of anthracene was 96%. The byproduct was the much less toxic (9, 10-anthraquinone) and a small amount of phthalic acid as confirmed by gas mass spectrometry and high-pressure liquid chromatography. The kinetic studies revealed that the photocatalytic degradation process obeyed the Langmuir–Hinshelwood model and followed a pseudo-first-order rate expression.