Showing papers on "Zinc published in 2001"
TL;DR: In this paper, the capacitance matrix was calculated for different chain lengths using the software package FastCap MIT (1992) and a ligand shell dielectric constant of 3.14 aF.
Abstract: nanoparticles in dimethylsulfoxide onto the PLL film for about 20 min, after which it was rinsed in dimethylsulfoxide and then dichloromethane. From the molecular weight, the average length of the PLL is about 30 nm. Therefore, each polymer can accommodate about seven or eight nanoparticles. [20] L. Clarke, M. N. Wybourne, M. Yan, S. X. Cai, J. F. W. Keana, Appl. Phys. Lett. 1997, 71, 617. [21] A. A. Middleton, N. S. Wingreen, Phys. Rev. Lett. 1993, 71, 3198. [22] G. Y. Hu, R. F. O'Connell, Phys. Rev. B 1994, 49, 16 773. [23] A. J. Rimberg, T. R. Ho, J. Clarke, Phys. Rev. Lett. 1995, 74, 4714. [24] L. Clarke, M. N. Wybourne, M. Yan, S. X. Cai, L. O. Brown, J. Hutchison, J. F. W. Keana, J. Vac. Sci. Technol. B 1997, 15, 2925. [25] The capacitance matrix was calculated for different chain lengths using the software package FastCap MIT (1992). We used the nanoparticle dimensions given in the text and a ligand shell dielectric constant of 3. For nanoclusters away from the end of the chains we obtain Cdd » 0.04 aF and Cg » 0.17 aF. As expected, the value of Cg is slightly larger than the value calculated for an isolated metal sphere of radius a coated with a dielectric shell, Cg» (4pee0a)/(1 + (a/d)(e±1)) = 0.14 aF, where d is the total radius of the core plus ligand shell. [26] Simulations were carried out using both MOSES (Monte-Carlo SingleElectronics Simulator, R. H. Chen) and SIMON (Simulation of Nano Structures, C. Wasshuber). [27] S. Chen, R. S. Ingram, M. J. Hostetler, J. J. Pietron, R. W. Murray, T. G. Schaaff, J. T. Khoury, M. M. Alvarez, R. L. Whetton, Science 1998, 280, 2098. [28] L. Y. Gorelik, A. Isacsson, M. V. Voinova, B. Kasemo, R. I. Shekhter, M. Jonson, Phys. Rev. Lett. 1998, 80, 4526. [29] O. D. Häberlen, S. C. Chung, M. Stener, N. Rösch, J. Chem. Phys. 1997, 106, 5189. [30] Y. Awakuni, J. H. Calderwood, J. Phys. D: Appl. Phys. 1972, 5, 1038. [31] G. Markovich, C. P. Collier, J. R. Heath, Phys. Rev. Lett. 1998, 80, 3807. [32] C. P. Collier, R. J. Saykally, J. J. Shiang, S. E. Hendrichs, J. R. Heath, Science 1997, 277, 1978. [33] N. Mott, Metal Insulator Transitions, Taylor and Francis, London 1990.
2,726 citations
TL;DR: The photoluminescence (PL) spectra of undoped ZnO films deposited on Si substrates by dc reactive sputtering have been studied in this paper, where two emission peaks, centered at 3.18 eV and 2.38 eV, were found to correspond to oxide antisite defect OZn rather than oxygen vacancy VO, zinc vacancy VZn, interstitial zinc Zni, and interstitial oxygen Oi.
Abstract: The photoluminescence (PL) spectra of the undoped ZnO films deposited on Si substrates by dc reactive sputtering have been studied. There are two emission peaks, centered at 3.18 eV (UV) and 2.38 eV (green). The variation of these peak intensities and that of the I–V properties of the ZnO/Si heterojunctions were investigated at different annealing temperatures and atmospheres. The defect levels in ZnO films were also calculated using the method of full-potential linear muffin-tin orbital. It is concluded that the green emission corresponds to the local level composed by oxide antisite defect OZn rather than oxygen vacancy VO, zinc vacancy VZn, interstitial zinc Zni, and interstitial oxygen Oi.
1,923 citations
TL;DR: The mechanism of zinc sensors that control metal uptake or export in Escherichia coli are determined and their response against the thermodynamically defined free zinc concentration suggests an extraordinary intracellular zinc-binding capacity.
Abstract: Intracellular zinc is thought to be available in a cytosolic pool of free or loosely bound Zn(II) ions in the micromolar to picomolar range To test this, we determined the mechanism of zinc sensors that control metal uptake or export in Escherichia coli and calibrated their response against the thermodynamically defined free zinc concentration Whereas the cellular zinc quota is millimolar, free Zn(II) concentrations that trigger transcription of zinc uptake or efflux machinery are femtomolar, or six orders of magnitude less than one atom per cell This is not consistent with a cytosolic pool of free Zn(II) and suggests an extraordinary intracellular zinc-binding capacity Thus, cells exert tight control over cytosolic metal concentrations, even for relatively low-toxicity metals such as zinc
1,389 citations
TL;DR: The substituents on the beta-diiminate ligand exert a significant influence upon the course of the polymerizations, affecting both the degree of stereoselectivity and the rate of polymerization.
Abstract: A series of zinc(II) and magnesium(II) alkoxides based upon a β-diiminate ligand framework has been prepared. [(BDI-1)ZnOiPr]2 [(BDI-1) = 2-((2,6-diisopropylphenyl)amido)-4-((2,6-diisopropylphenyl)...
1,088 citations
TL;DR: In this article, the authors present a review of the charge carrier transport in zinc oxide and show that a physical limit due to ionized impurity scattering is reached for homogeneously doped layers, which can be attributed to the clustering of charge carriers connected with increased scattering due to the Z-2 dependence of the scattering cross section on the charge Z.
Abstract: Heavily doped zinc oxide films are used as transparent and conductive electrodes, especially in thin film solar cells. Despite decades of research on zinc oxide it is not yet clear what the lower limit of the resistivity of such films is. Therefore, the electrical parameters of zinc oxide films deposited by magnetron sputtering, metal organic chemical vapour deposition and pulsed laser ablation are reviewed and related to the deposition parameters. It is found that the lowest resistivities are in the range of 1.4 to 2×10-4 Ω cm, independently of the deposition method. The highest reported Hall mobilities are about 60 cm2 V-1 s-1. The thin film electrical data are compared with the corresponding values of single crystalline zinc oxide and with that of boron and phosphorous doped crystalline silicon. From this comparison it can be seen that the dependence of the Hall mobilities on the carrier concentration n are quite similar for silicon and zinc oxide. In the region n>5×1020 cm-3, which is most important for the application of zinc oxide as a transparent and conductive electrode, phosphorous doped silicon has a mobility only slightly higher than zinc oxide. The experimental data on the electron and hole mobilities in silicon as a function of the impurity concentration have been described by a fit function (Masetti et al 1983), which can also be applied with different fitting parameters to the available zinc oxide mobility data. A comparison of the experimental data with the well known ionized impurity scattering theories of Conwell-Weisskopf (1946) and Brooks-Herring-Dingle (1955) shows that these theories are not able to describe the data very well, even if the non-parabolic band structure is taken into account. As in the case of silicon, an additional reduction of the mobility also occurs for zinc oxide for concentrations n>5×1020 cm-3, which can be ascribed qualitatively to the clustering of charge carriers connected with increased scattering due to the Z-2 dependence of the scattering cross section on the charge Z of the scattering centre. The presented review of the charge carrier transport in zinc oxide indicates that a physical limit due to ionized impurity scattering is reached for homogeneously doped layers. Due to the universal nature of this limitation it is suggested that it also applies to the other important materials indium-tin (ITO) and tin oxide. Experiments are proposed to overcome this limit.
735 citations
TL;DR: The influence of zinc on quaternary protein structure has led to the identification of a fourth type of zinc binding site, protein interface, which is formed from ligands supplied from amino acid residues residing in the binding surface of two proteins.
Abstract: Zinc is known to be indispensable to growth and development and transmission of the genetic message. It does this through a remarkable mosaic of zinc binding motifs that orchestrate all aspects of metabolism. There are now nearly 200 three dimensional structures for zinc proteins, representing all six classes of enzymes and covering a wide range of phyla and species. These structures provide standards of reference for the identity and nature of zinc ligands in other proteins for which only the primary structure is known. Three primary types of zinc sites are apparent from examination of these structures: structural, catalytic and cocatalytic. The most common amino acids that supply ligands to these sites are His, Glu, Asp and Cys. In catalytic sites zinc generally forms complexes with water and any three nitrogen, oxygen and sulfur donors with His being the predominant amino acid chosen. Water is always a ligand to such sites. Structural zinc sites have four protein ligands and no bound water molecule. Cys is the preferred ligand in such sites. Cocatalytic sites contain two or three metals in close proximity with two of the metals bridged by a side chain moiety of a single amino acid residue, such as Asp, Glu or His and sometimes a water molecule. Asp and His are the preferred amino acids for these sites. No Cys ligands are found in such sites. The scaffolding of the zinc sites is also important to the function and reactivity of the bound metal. The influence of zinc on quaternary protein structure has led to the identification of a fourth type of zinc binding site, protein interface. In this case zinc sites are formed from ligands supplied from amino acid residues residing in the binding surface of two proteins. The resulting zinc site usually has the coordination properties of a catalytic or structural zinc binding site.
699 citations
TL;DR: New hypotheses regarding regulatory functions of zinc ions in cellular signaling pathways are proposed as a conclusion of observations on zinc homeostasis in eukaryotic cells.
Abstract: Zinc is essential for cell proliferation and differentiation, especially for the regulation of DNA synthesis and mitosis. On the molecular level, it is a structural constituent of a great number of proteins, including enzymes of cellular signaling pathways and transcription factors. Zinc homeostasis in eukaryotic cells is controlled on the levels of uptake, intracellular sequestration in zinc storing vesicles ('zincosomes'), nucleocytoplasmic distribution and elimination. These processes involve the major zinc binding protein metallothionein as a tool for the regulation of the cellular zinc level and the nuclear translocation of zinc in the course of the cell cycle and differentiation. In addition, there is also increasing evidence for a direct signaling function for zinc on all levels of signal transduction. Zinc can modulate cellular signal recognition, second messenger metabolism, protein kinase and protein phosphatase activities, and it may stimulate or inhibit activities of transcription factors, depending on the experimental systems studied. Zinc has been shown to modify specifically the metabolism of cGMP, the activities of protein kinase C and mitogen activated protein kinases, and the activity of transcription factor MTF-1 which controls the transcription of the genes for metallothionein and the zinc transporter ZnT-1. As a conclusion of these observations new hypotheses regarding regulatory functions of zinc ions in cellular signaling pathways are proposed.
586 citations
TL;DR: This work has found that at least one member of the ZIP family transporters transports stored zinc out of an intracellular compartment during adaptation to zinc deficiency, and this remarkable conservation of function suggests that other, as yet uncharacterized members of the family, will also be involved in metal ion transport.
Abstract: The last ten years have witnessed major advances in our understanding of zinc transporters and their regulation in eukaryotic organisms. Two families of transporters, the ZIP (Zrt-, Irt-like Protein) and CDF (Cation Diffusion Facilitator) families, have been found to play a number of important roles in zinc transport. These are ancient gene families that span all phylogenetic levels. The characterized members of each group have been implicated in the transport of metal ions, frequently zinc, across lipid bilayer membranes. This remarkable conservation of function suggests that other, as yet uncharacterized members of the family, will also be involved in metal ion transport. Many of the ZIP family transporters are involved in cellular zinc uptake and at least one member, the Zrt3 transporter of S. cerevisiae, transports stored zinc out of an intracellular compartment during adaptation to zinc deficiency. In contrast, CDF family members mediate zinc efflux out of cells or facilitate zinc transport into intracellular compartments for detoxification and/or storage. The activity of many of these transporters is regulated in response to zinc through transcriptional and post-transcriptional mechanisms to maintain zinc homeostasis at both the cellular and organismal levels.
525 citations
TL;DR: In this article, the hydrometallurgical processes have been described for the recovery of zinc from the secondaries using sulphuric acid, hydrochloric acid and ammoniacal solution as lixiviants.
Abstract: Zinc containing wastes/secondaries viz. zinc ash, dross, flue dusts, sludge, residue etc. are generated in various chemical and metallurgical industries. The materials contain different level of impurities depending on the source. The hydrometallurgical processing is effective and flexible for treating such materials as it can control the different level of impurities. Depending on the nature and composition of the secondaries, a suitable lixiviant could be selected to dissolve the desired metals leaving gangue in the residue. In the present paper, the hydrometallurgical processes have been described for the recovery of zinc from the secondaries using sulphuric acid, hydrochloric acid, ammoniacal solution and sodium hydroxide etc. as lixiviants. The leach solution thus obtained has been purified with respect to dissolved impurities using precipitation, ion exchange or solvent extraction method. The metal or salt is produced from the purified solution by electrolysis or crystallization.
446 citations
TL;DR: In this paper, blue luminescent complexes of aluminum, boron, beryllium, and zinc using ligands that contain only nitrogen donor atoms are presented, and the ligands in these complexes are based on di-2-pyridylamine and 7-azaindole.
437 citations
TL;DR: Analysis of available methods of evaluating zinc status in individuals and populations indicates that nearly half of the world's population is at risk for inadequate zinc intake, suggesting that public health programs are urgently needed to control zinc deficiency.
Abstract: This paper summarizes recent research on the importance of zinc for human health, and reviews available methods of evaluating zinc status in individuals and populations. The lack of generally accepted biomarkers of zinc status has impeded estimation of the global prevalence of zinc deficiency. Although measurement of zinc consumption and/or plasma zinc concentration can be used to assess population zinc status, few countries have collected adequate data to permit estimation of the prevalence of zinc deficiency. An alternative method, described herein, is to estimate the zinc content of national food supplies, using FAO food balance sheets; the assumed bioavailability of that zinc based on phytate: zinc molar ratios; and the relation between absorbable zinc and theoretical requirements according to country-specific demographics. The results of these analyses indicate that nearly half of the world's population is at risk for inadequate zinc intake, suggesting that public health programs are urgently needed ...
TL;DR: It is confirmed that interstitial protium may act as a shallow donor in zinc oxide, by direct spectroscopic observation of its muonium counterpart, and results for the cadmium chalcogenides suggest that such shallow donor states are generic to the II-VI compounds.
Abstract: We confirm the recent prediction that interstitial protium may act as a shallow donor in zinc oxide, by direct spectroscopic observation of its muonium counterpart. On implantation into ZnO, positive muons---chemically analogous to protons in this context---form paramagnetic centers below about 40 K. The muon-electron contact hyperfine interaction, as well as the temperature and activation energy for ionization, imply a shallow level. Similar results for the cadmium chalcogenides suggest that such shallow donor states are generic to the II-VI compounds. The donor level depths should serve as a guide for the electrical activity of interstitial hydrogen.
TL;DR: In this paper, the feasibility of using biosurfactants for the removal of heavy metals from sediments was evaluated using batch washing experiments, and it was shown that the metal removal process occurs through sorption of the surfactant on to the soil surface and complexation with the metal, detachment of the metal from the soil into the soil solution and hence association with surfactants micelles.
TL;DR: The physiological and pathological effects of the release of zinc from these zinc-containing synaptic terminals are reviewed and it is hypothesize that zinc signals may loosely mimic phosphate `signals' in the sense that signal zinc ions may commonly bind to proteins in a lasting manner with consequential changes in protein structure and function.
Abstract: In addition to its familiar role as a component of metalloproteins, zinc is also sequestered in the presynaptic vesicles of a specialized type of neurons called ‘zinc-containing’ neurons. Here we review the physiological and pathological effects of the release of zinc from these zinc-containing synaptic terminals. The best-established physiological role of synaptically released zinc is the tonic modulation of brain excitability through modulation of amino acid receptors; prominent pathological effects include acceleration of plaque deposition in Alzheimer’s disease and exacerbation of excitotoxic neuron injury. Synaptically released zinc functions as a conventional synaptic neurotransmitter or neuromodulator, being released into the cleft, then recycled into the presynaptic terminal. Beyond this, zinc also has the highly unconventional property that it passes into postsynaptic neurons during synaptic events, functioning analogously to calcium in this regard, as a transmembrane neural signal. To stimulate comparisons of zinc signals with calcium signals, we have compiled a list of the important parameters of calcium signals and zinc signals. More speculatively, we hypothesize that zinc signals may loosely mimic phosphate ‘signals’ in the sense that signal zinc ions may commonly bind to proteins in a lasting manner (i.e., ‘zincylating’ the proteins) with consequential changes in protein structure and function.
TL;DR: In this paper, the formation energies and electronic structure of native defects in ZnO were investigated by a first-principles plane-wave pseudopotential method, and the effect of self-compensation by the donor-type defects should be significant in p-type doping.
Abstract: We have investigated the formation energies and electronic structure of native defects in ZnO by a first-principles plane-wave pseudopotential method. When p-type conditions are assumed, the formation energies of donor-type defects can be quite low. The effect of self-compensation by the donor-type defects should be significant in p-type doping. Under n-type conditions, the oxygen vacancy exhibits the lowest formation energy among the donor-type defects. The electronic structure, however, implies that only the zinc interstitial or the zinc antisite can explain the n-type conductivity of undoped ZnO.
TL;DR: Zinc homeostasis in the brain is closely related to neuronal activity and adequate zinc supply is important for brain functions and prevention of neurological diseases.
Abstract: The brain barrier system, i.e., the blood-brain and blood-cerebrospinal fluid barriers, is important for zinc homeostasis in the brain. Zinc is supplied to the brain via both barriers. A large portion of zinc serves as zinc metalloproteins in neurons and glial cells. Approximately 10% of the total zinc in the brain, probably ionic zinc, exists in the synaptic vesicles, and may serve as an endogenous neuromodulator in synaptic neurotransmission. The turnover of zinc in the brain is much slower than in peripheral tissues such as the liver. However, dietary zinc deprivation affects zinc homeostasis in the brain. Vesicular zinc-enriched regions, e.g., the hippocampus, are responsive to dietary zinc deprivation, which causes brain dysfunctions such as learning impairment and olfactory dysfunction. Olfactory recognition is reversibly disturbed by the chelation of zinc released from amygdalar neuron terminals. On the other hand, the susceptibility to epileptic seizures, which may decrease vesicular zinc, is also enhanced by zinc deficiency. Therefore, zinc homeostasis in the brain is closely related to neuronal activity. Even in adult animals and probably adult humans, adequate zinc supply is important for brain functions and prevention of neurological diseases.
TL;DR: Results show that zinc can protect membranes from iron-initiated lipid oxidation by occupying negatively charged sites with potential iron binding capacity, and suggests that zinc is a pivotal component of the antioxidant defense network that protects membranes from oxidation.
TL;DR: In this paper, a cloud point extraction (CPE) was used for the simultaneous pre-concentration of cadmium, copper, lead and zinc after the formation of a complex with 1-(2-thiazolylazo)-2-naphthol (TAN), and later analysis by flame atomic absorption spectrometry (FAAS) using octylphenoxypolyethoxyethanol (Triton X-114) as surfactant.
TL;DR: The data suggest the potential beneficial antioxidant effects of the individual and combined supplementation of Zn and Cr in people with type 2 DM, and are particularly important in light of the deleterious consequences of oxidative stress inPeople with diabetes.
Abstract: Objective: To determine the effects of combined zinc (Zn) and chromium (Cr) supplementation on oxidative stress and glucose homeostasis of people with type 2 diabetes.Design: Tunisian adult subjects with HbA1C >7.5% were supplemented for 6 months with 30 mg/d of Zn as Zn gluconate or 400 μg/d of Cr as Cr pidolate or combined Zn/Cr supplementation or placebo. The effects of supplementation on plasma zinc (Zn), copper (Cu), selenium (Se), urinary Zn, Cr, plasma thiobarbituric acid reactive substances (TBARS), Cu-Zn superoxide dismutase (SOD) and Se glutathione peroxidase (GPx) in red blood cells, blood lipids and lipoproteins, HbA1C and fasting glucose were measured at the beginning of the study and after six months.Results: At the beginning of the study, more than 30% of the subjects may have been Zn deficient with plasma Zn values less than 10.7 μmol/L, whereas levels of plasma Cu, Se and antioxidant RBC enzyme activities were in the normal ranges. Following supplementation, there were significant decreas...
TL;DR: The current model suggests that the zinc-finger domain of MTF-1 directly (and reversibly) binds to zinc, and this metalloregulatory protein then adopts a DNA-binding conformation and translocates to the nucleus, where it binds to metal-response elements in these gene promoters leading to increased transcription.
Abstract: Zinc metabolism in higher eukaryotes is complex, being controlled by uptake, efflux, and storage in individual cells, as well as in peripheral tissues and organs. Recently there have been advances in the understanding of the genes involved in these processes and their regulation. Metal-response element-binding transcription factor-1 (MTF-1) functions as a cellular zinc sensor which coordinates the expression of genes involved in zinc homeostasis, as well as protection against metal toxicity and oxidative stresses. In mice, these are known to include the metallothionein (MT), the zinc-transporter-1 (ZnT1) and the γ-glutamylcysteine synthetase heavy chain (γGCShc) genes. The cysteine-rich MTs function as an intracellular metal-chelators that bind zinc with high affinity, whereas the transmembrane protein ZnT1 exports zinc from the cell. γ-Glutamylcysteine synthetase controls the rate limiting step in glutathione (GSH) biosynthesis. GSH, which is present in mM concentrations in cells, effectively chelates large amounts of zinc in vitro. Both MT and GSH also function as antioxidants. The current model suggests that the zinc-finger domain of MTF-1 directly (and reversibly) binds to zinc. This metalloregulatory protein then adopts a DNA-binding conformation and translocates to the nucleus, where it binds to metal-response elements in these gene promoters leading to increased transcription. The six zinc-finger domain of this factor is highly conserved from insects to mammals, and biochemical studies confirm that the zinc-fingers are heterogeneous in function and in zinc-binding. Furthermore, the mouse MTF-1 gene is essential for development of the embryo, thus underscoring the importance of this transcription factor.
TL;DR: Thirty strains of algae were examined for their biosorption abilities in the uptake of cadmium, lead, nickel, and zinc from aqueous solution and the cyanophyceae Lyngbya taylorii exhibited high uptake capacities for the four metals.
Abstract: Thirty strains of algae were examined for their biosorption abilities in the uptake of cadmium, lead, nickel, and zinc from aqueous solution. A wide range of adsorption capacities between the different strains of algae and between the four metals can be observed. The cyanophyceae Lyngbya taylorii exhibited high uptake capacities for the four metals. The algae showed maximum capacities according to the Langmuir Adsorption Model of 1.47 mmol lead, 0.37 mmol cadmium, 0.65 mmol nickel, and 0.49 mmol zinc per gram of dry biomass. The optimum pH for L. taylorii was between pH 3 and 7 for lead, cadmium, and zinc and between pH 4 and 7 for nickel. Studies with the algae indicated a preference for the uptake of lead over cadmium, nickel, and zinc in a four metal solution. The metal binding abilities of L. taylorii could be improved by phosphorylation of the biomass. The modified biosorbent demonstrated maximum capacities of 2.52 mmol cadmium, 3.08 mmol lead, 2.79 mmol nickel, and 2.60 mmol zinc per gram of dry biomass. Investigations with phosphated L. taylorii indicated high capacities for the four metals also at low pH. The selectivity remained quite similar to the unmodified algae.
TL;DR: The observation that hZIP1 is the major zinc transporter in K562 cells, coupled with its expression in many normal cell types, indicates that h ZIP1 plays an important role in zinc uptake in human tissues.
TL;DR: In this article, the luminescence properties of BaZnSiO4 activated by Eu3+ and Mn2+ ions were reported, and a solid-state reaction starting from ox...
Abstract: The aim of this work is to report on the luminescence properties of BaZnSiO4 activated by Eu3+ and Mn2+ ions. Doped and undoped powder samples were prepared by solid-state reaction starting from ox...
TL;DR: It appears that zinc can induce an increase in glucose transport into cells and potentiate insulin-induced glucose transport, likely acting through the insulin-signaling pathway.
Abstract: Zinc has insulin-like effects on cells, including promotion of both lipogenesis and glucose transport. The relationship between zinc and the stimulation of glucose transport is unclear. We hypothesize that zinc affects the insulin-signaling pathway. In this study, the effect of zinc on glucose transport and insulin signaling was examined in 3T3-L1-preadipocytes and -adipocytes. Treatment of cells with up to 200 micromol/L zinc significantly increased glucose transport (P < 0.05). The effect of zinc on adipocytes was greater than on preadipocytes, and the effect of zinc plus insulin was greater than that of either insulin or zinc alone. Cytochalasin D, which disrupts actin filaments, attenuated the increase of glucose transport induced by zinc or insulin (P < 0.05). At 100 nmol/L, wortmannin, the phosphoinositide (PI) 3-kinase inhibitor, decreased basal glucose transport and blocked zinc-stimulated glucose transport in both cell types (P < 0.05). H7, an inhibitor of protein kinase C, did not reduce basal glucose transport but decreased zinc-induced glucose transport (P < 0.05). Zinc increased tyrosine phosphorylation of the insulin receptor beta subunit of both preadipocytes and adipocytes after 5-10 min of treatment (P < 0.05). Zinc at 200 micromol/L did not affect tyrosine phosphorylation of insulin receptor substrate (IRS)-1 or -2; further, there was no effect of zinc on the association of the p85 subunit of PI 3-kinase and IRS-1. Zinc significantly increased serine-473 phosphorylation of Akt in both preadipocytes and adipocytes (P < 0.05). The PI 3-kinase inhibitor, wortmannin, totally blocked the effect of zinc on Akt activation. Hence, it appears that zinc can induce an increase in glucose transport into cells and potentiate insulin-induced glucose transport, likely acting through the insulin-signaling pathway.
TL;DR: Disruption of zinc finger structures may result in interference with manifold cellular processes involved in gene expression, growth regulation, and maintenance of the genomic integrity.
Abstract: Zinc finger structures are frequently found in transcription factors and DNA repair proteins, mediating DNA-protein and protein-protein binding. As low concentrations of transition metal compounds, including those of cadmium, nickel, and cobalt, have been shown to interfere with DNA transcription and repair, several studies have been conducted to elucidate potential interactions of toxic metal ions with zinc-binding protein domains. Various effects have been identified, including the displacement of zinc, e.g., by cadmium or cobalt, the formation of mixed complexes, incomplete coordination of toxic metal ions, as well as the oxidation of cysteine residues within the metal-binding domain. Besides the number of cysteine and/or histidine ligands, unique structural features of the respective protein under investigation determine whether or not zinc finger structures are disrupted by one or more transition metals. As improper folding of zinc finger domains is mostly associated with the loss of correct protein function, disruption of zinc finger structures may result in interference with manifold cellular processes involved in gene expression, growth regulation, and maintenance of the genomic integrity.
TL;DR: In this article, stable colloidal aqueous suspensions of magnetic nanostructures made of copper, nickel, and zinc ferrites are reported, which could represent a new alternative for biological applications.
Abstract: We report on stable colloidal aqueous suspensions of magnetic nanostructures made of copper, nickel, and zinc ferrites. These magnetic fluids could represent a new alternative for biological applications. The basic steps of the nanoparticles synthesis, their chemical surface treatment, and their peptization in a stable colloidal sol are given. Their chemical composition is carefully checked, and X-ray diffraction patterns provide both their mean size and a structural characterization. Magnetization results obtained at 300 K are presented and discussed.
TL;DR: In this article, the authors used X-ray diffraction line profile analysis to estimate the size and strain of the reduced Cu and ZnO phases after reduction in 2 vol% H2 at 513 K.
Abstract: Binary Cu/ZnO catalysts with varying molar ratios (90/10 through 10/90) were studied under methanol synthesis conditions at 493 K and at atmospheric pressure. The methanol synthesis activity of the catalysts was correlated to their specific Cu surface area (N2O reactive frontal chromatography, N2O RFC) after reduction in 2 vol% H2 at 513 K. Activity data were supplemented with a detailed analysis of the microstructure, i.e., crystallite size and strain of the reduced Cu and the ZnO phases after reduction using X-ray diffraction line profile analysis. The estimated copper surface area based on a spherical shape of the copper crystallites is in good agreement with data determined by N2O RFC. A positive correlation of the turnover frequency for methanol production with the observed microstrain of copper in the Cu/ZnO system was found. The results indicate a mutual structural interaction of both components (copper and zinc oxide) in the sense that strained copper particles are stabilized by the unstrained state of the zinc oxide microcrystallites. The observed structural deformation of ZnO in samples with higher Cu loading can originate, for instance, from epitaxial bonding of the oxide lattice to the copper metal, insufficient reduction or residual carbonate due to incomplete thermal decomposition during reduction. Additional EXAFS measurements at the Cu K and the Zn K edge show that about 5% ZnO are dissolved in the CuO matrix of the calcined precursors. Furthermore, it is shown that the microstructural changes (e.g., size and strain) of copper can be traced back to the phase composition of the corresponding hydroxycarbonate precursors.
TL;DR: Cadmium was the most easily exchangeable element in case of variations in the physical and chemical conditions but the quantities involved remained small and lead and copper did not appear to be highly mobile.
Abstract: The concentrations of lead, copper, cadmium, zinc, nickel and chromium were measured in road dust and roadside soils from a French major highway. The profiles of total levels in the soil as a function of distance from the road edge and as a function of depth were investigated. Lead, zinc, copper and, to a lesser extent, cadmium contamination were found in samples taken on the surface and in the immediate vicinity of the road. The observed concentrations decreased rapidly with distance and depth. Soil samples appeared to exhibit little nickel and chromium pollution. The geochemical phases on which heavy metals (lead, copper, zinc, cadmium and chromium) were fixed preferentially, as well as the potential mobility of the different metals under certain physical and chemical conditions were evaluated. Sequential extractions and single extractions with different reagents were performed. Chromium, which was present mostly in residual form, was mainly of natural origin in the studied samples and was not highly mo...
TL;DR: In this article, a correlation among luminescence properties of ZnO, obtained from zinc hydroxycarbonate, and crystalline lattice defects, microstrain, as function of thermal treatment is reported.