Showing papers on "Zinc published in 1996"
TL;DR: The ability of zinc to be bound specifically within a range of tetrahedral sites appears to be responsible for the evolution of the wide range of zinc-stabilized structural domains now known to exist.
Abstract: Zinc ions are key structural components of a large number of proteins. The binding of zinc stabilizes the folded conformations of domains so that they may facilitate interactions between the proteins and other macromolecules such as DNA. The modular nature of some of these zinc-containing proteins has allowed the rational design of site-specific DNA binding proteins. The ability of zinc to be bound specifically within a range of tetrahedral sites appears to be responsible for the evolution of the side range of zinc-stabilized structural domains now known to exist. The lack of redox activity for the zinc ion and its binding and exchange kinetics also may be important in the use of zinc for specific functional roles.
1,801 citations
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01 Jan 1996
TL;DR: In this article, the authors present properties, products, and processes of corrosion in water and aqueous solutions, such as surface film formation, under paint and concrete, as well as in other environments.
Abstract: Properties, Products, and Processes. Electrochemical Thermodynamics and Elemental Reactions. Passivation and Surface Film Formation. Semiconductor Electrochemistry of Zinc Oxide. Corrosion Potential and Corrosion Current. Corrosion Products. Corrosion Forms. Atmospheric Corrosion. Corrosion in Water and Aqueous Solutions. Corrosion in Soil. Under Paint Corrosion. Zinc Rich Coating. Corrosion in Concrete. Corrosion in Batteries. Corrosion in other Environments. Index.
684 citations
TL;DR: In this article, transparent zinc oxide (ZnO) films were cathodically deposited on conductive glasses from a simple aqueous zinc nitrate electrolyte kept at 335 K. ZnO films prepared had a wurtzite structure and exhibited an optical band gap energy of 3.3 eV.
Abstract: Transparent zinc oxide (ZnO) films has been cathodically deposited on conductive glasses from a simple aqueous zinc nitrate electrolyte kept at 335 K. ZnO films prepared had a wurtzite structure and exhibited an optical band gap energy of 3.3 eV which is characteristic of ZnO. A 2‐μm‐thick ZnO film with an optical transmittance of 72% has been deposited by electrolysis only for approximately 20 minutes at the cathodic potential of −1.0 V compared with the Ag/AgCl reference electrode.
597 citations
TL;DR: Results suggest that ZRT1 is regulated at the transcriptional level by the intracellular concentration of zinc, and is an additional member of a growing family of metal transport proteins.
Abstract: The yeast Saccharomyces cerevisiae has two separate systems for zinc uptake. One system has high affinity for substrate and is induced in zinc-deficient cells. The second system has lower affinity and is not highly regulated by zinc status. The ZRT1 gene encodes the transporter for the high-affinity system, called Zrt1p. The predicted amino acid sequence of Zrt1p is similar to that of Irt1p, a probable Fe(II) transporter from Arabidopsis thaliana. Like Irt1p, Zrt1p contains eight potential transmembrane domains and a possible metal-binding domain. Consistent with the proposed role of ZRT1 in zinc uptake, overexpressing this gene increased high-affinity uptake activity, whereas disrupting it eliminated that activity and resulted in poor growth of the mutant in zinc-limited media. Furthermore, ZRT1 mRNA levels and uptake activity were closely correlated, as was zinc-limited induction of a ZRT1-lacZ fusion. These results suggest that ZRT1 is regulated at the transcriptional level by the intracellular concentration of zinc. ZRT1 is an additional member of a growing family of metal transport proteins.
545 citations
TL;DR: In this paper, an asymmetry in Zn 2 p 3 2 photoelectron peaks has been observed for aluminum-doped transparent conducting films, which has been attributed to the presence of excess zinc in the films.
535 citations
506 citations
TL;DR: It is suggested that ZnT‐2 protects zinc‐sensitive BHK cells from zinc toxicity by facilitating zinc transport into an endosomal/lysosomal compartment.
Abstract: A cDNA encoding a second zinc transporter (ZnT-2) was isolated from a rat kidney cDNA expression library by complementation of a zinc-sensitive BHK cell line. The protein predicted from the open reading frame of ZnT-2 cDNA has 359 amino acids and initiates with a CTG codon. It resembles ZnT-1 (a plasma membrane protein that stimulates zinc efflux) in overall topology in that it has six membrane-spanning domains, a histidine-rich intracellular loop and a long C-terminal tail; however, the overall amino acid identity is only 26%. Unlike ZnT-1, which is in the plasma membrane and lowers cellular zinc by stimulating zinc efflux, ZnT-2 is localized on vesicles and allows the zinc-sensitive BHK cells to accumulate zinc to levels that are much higher than non-transformed cells can tolerate. Zinc was visualized within these vesicles with zinquin, a zinc-specific fluorescent probe. The intracellular compartment that accumulates zinc is acidic as revealed by staining with acridine orange or LysoTracker. Prolonged exposure of cells expressing ZnT-2 to zinc causes an accretion of intracellular vesicles. We suggest that ZnT-2 protects these cells from zinc toxicity by facilitating zinc transport into an endosomal/lysosomal compartment.
451 citations
TL;DR: Analysis of the zinc levels required for growth of zrt2 mutant strains as well as the effects of the zRT2 mutation on the regulation of the high affinity system demonstrated that the low affinity system is a biologically relevant mechanism of zinc accumulation.
391 citations
TL;DR: It is concluded that binding of zinc to the HHCC motif stabilizes the folded state of the N-terminal domain of integrase and bound zinc is required for optimal enzymatic activity.
Abstract: The N-terminal domain of HIV-1 integrase contains a pair of His and Cys residues (the HHCC motif) that are conserved among retroviral integrases. Although His and Cys residues are often involved in binding zinc, the HHCC motif does not correspond to any recognized class of zinc binding domain. We have investigated the binding of zinc to HIV-1 integrase protein and find that it binds zinc with a stoichiometry of one zinc per integrase monomer. Analysis of zinc binding to deletion derivatives of integrase locates the binding site to the N-terminal domain. Integrase with a mutation in the HHCC motif does not bind zinc, consistent with coordination of zinc by these residues. The isolated N-terminal domain is disordered in the absence of zinc but, in the presence of zinc, it adopts a secondary structure with a high alpha helical content. Integrase bound by zinc tetramerizes more readily than the apoenzyme and is also more active than the apoenzyme in in vitro integration assays. We conclude that binding of zinc to the HHCC motif stabilizes the folded state of the N-terminal domain of integrase and bound zinc is required for optimal enzymatic activity.
349 citations
TL;DR: Structural analysis indicates that affinity for the penta-coordinated zinc can be modulated by neighboring residues, perhaps explaining the absence of the second zinc in the B. cereus structure.
329 citations
TL;DR: In this article, a comparison of the spectra of in vitro (3-hydroxymethyl-131-oxometallochlorin) and in vivo chlorosomal (bacterio-chlorophyll-c) aggregates suggests a similar supramolecular structure for the artificial oligomers and the bacte-riochlorophyll c aggregates in the extramembranous antenna complexes (chlorosomes) of green photosynthetic bacteria.
Abstract: — A comparison of the spectra of in vitro (3-hydroxymethyl-131-oxometallochlorin) and in vivo chlorosomal (bacterio-chlorophyll-c) aggregates suggests a similar supramolecular structure for the artificial oligomers and the bacte-riochlorophyll-c aggregates in the extramembranous antenna complexes (chlorosomes) of green photosynthetic bacteria. Synthetic zinc and magnesium chlorins have been found to aggregate in 1 % (vol/vol) tetrahydrofuran and hexane solutions and in thin films to form oligomers with the Qy absorption bands shifted to longer wavelengths by about 1900 (Zn chlorins) and 2100 cm−1 (Mg) relative to the corresponding monomer bands. Visible absorption and circular dichroism spectra of various zinc chlorins establish that a central metal, a 31-hydroxy and a 131-keto group are functional prerequisites for the aggregation. Vibrational bands measured by IR spectroscopy of solid films reveal two characteristic structural features of the oligomers: (1) a five-coordinated metallochlorin macrocycle with an axial ligand (bands at 1500-1630 cm−1), and (2) a hydrogen bond between the keto oxygen of one chlorin and the hydroxy group of a second chlorin, the oxygen of which is chelated to the metal atom of a third molecule, i.e. C=O…H-O…M (=Zn or Mg).
TL;DR: In this article, the role of metal oxides such as Ga 2 O 3, Al 2 O 4, ZrO 2 and Cr 2 O 5, contained in Cu/ZnO-based ternary catalysts for methanol synthesis from CO 2 and H 2 was classified into two categories: to improve the Cu dispersion and to increase the specific activity.
Abstract: The role of metal oxides such as Ga 2 O 3 , Al 2 O 3 , ZrO 2 and Cr 2 O 3 contained in Cu/ZnO-based ternary catalysts for methanol synthesis from CO 2 and H 2 was classified into two categories: to improve the Cu dispersion and to increase the specific activity The Cu/ZnO-based multicomponent catalysts developed on the basis of the role of metal oxides were highly active and stable for a long period in a continuous methanol synthesis operation
TL;DR: In this article, the extent of copper precipitation, higher than that of zinc, depends on the initial concentration of both copper and phenolic compounds and on the control of acidification which results from complexation.
Abstract: Precipitation of copper(II) and zinc(II) by low molecular weight phenols, penta-O-galloyl-β-d-glucose, and commercial tannins is studied at pH 5. The extent of copper precipitation, higher than that of zinc, depends on the initial concentration of both copper and phenolic compounds and on the control of acidification which results from complexation. The copper/phenol ratio in the precipitate, determined by elemental analysis, is independent of the initial concentration of catechol. However, it increases with chestnut tannin when the metal concentration is increased to a value corresponding to complexation with all o-dihydroxyphenyl chelating groups in the molecule. Stability of the precipitates obtained with coppper(II) and various polyphenols in water, acetic acid, and ethylenediaminetetraacetic acid solutions is determined. Models for metal/polyphenol precipitation are proposed. Keywords: Polyphenols; tannins; metal ions; copper; zinc; complexation; precipitation
TL;DR: In this paper, a transparent ZnO film with optical bandgap energy of 3.3 eV was obtained by electrodeposition from an aqueous, 0.1 mol/liter zinc nitrate electrolyte.
Abstract: Zinc oxide is of considerable interest to the optical and electronic industries, because of its electrical, optical, and acoustic characteristics. ZnO films can be prepared by several techniques, such as radio frequency (RF) magnetron sputtering, chemical vapor deposition, and molecular beam epitaxy. Preparation of oxide films by electrodeposition from aqueous solutions has several potential advantages over the other techniques. However, the formation of oxide films through electrochemical reactions have been demonstrated only on thallic oxide by Switzer and zirconium oxide by Gal-Or. In this work, the authors have prepared transparent ZnO films with optical bandgap energy of 3.3 eV by electrodeposition from an aqueous, 0.1 mol/liter zinc nitrate electrolyte. The deposition technology is still being developed. This paper reports the effects of the electrolyte concentration on the electrodeposition and properties of the ZnO films.
TL;DR: The position of the inhibitor within the active site suggests that the nucleophile for the hydrolysis reaction is the metal-bound hydroxide, and this most likely explains the broad substrate specificity exhibited by phosphotriesterase.
Abstract: Phosphotriesterase from Pseudomonas diminuta catalyzes the hydrolysis of paraoxon and related acetylcholinesterase inhibitors with rate enhancements that approach 1012. The enzyme requires a binuclear metal center for activity and as isolated contains 2 equiv of zinc per subunit. Here we describe the three-dimensional structure of the Zn2+/Zn2+-substituted enzyme complexed with the substrate analog diethyl 4-methylbenzylphosphonate. Crystals employed in the investigation belonged to the space group C2 with unit cell dimensions of a = 129.6 A, b = 91.4 A, c = 69.4 A, β = 91.9°, and two subunits in the asymmetric unit. The model was refined by least-squares analysis to a nominal resolution of 2.1 A and a crystallographic R-factor of 15.4% for all measured X-ray data. As in the previously reported structure of the cadmium-containing enzyme, the bridging ligands are a carbamylated lysine residue (Lys 169) and a hydroxide. The zinc ions are separated by 3.3 A. The more buried zinc ion is surrounded by His 55, ...
TL;DR: In this paper, a dansylamidoethyl−pendant cyclen (1-(2-(5-(dimethylamino)-1-naphthalenesulfonamido)ethyl)-1,4,7,10-tetraazacyclododecane, HL) has been synthesized as a novel type of zinc(II)−fluorophore.
Abstract: On the basis of the chemical principle of carbonic anhydrase (CA)−aromatic sulfonamide inhibitor interaction, a dansylamidoethyl−pendant cyclen (1-(2-(5-(dimethylamino)-1-naphthalenesulfonamido)ethyl)-1,4,7,10-tetraazacyclododecane, HL) has been synthesized as a novel type of zinc(II)−fluorophore. The new ligand HL forms very stable complexes (ML) with zinc(II), cadmium(II), and copper(II) at physiological pH. The potentiometric and spectrophotometric pH-titration study disclosed the 1:1 metal(II) complexes stability constants log K(ML) (= log([ML]/[M][L])) to be 20.8 ± 0.1 for ZnL, 19.1 ± 0.1 for CdL, and >30 for CuL. The crystalline zinc(II) complex ZnL was isolated from aqueous solution at pH 7. The X-ray crystal study of ZnL disclosed a five-coordinate, distorted square-pyramidal structure with the deprotonated dansylamide N- coordinating at the apical site. Crystals of the monoperchlorate salt of ZnL (C22H35N6O6SClZn) are orthorhombic, space group Pna21 (no. 33) with a = 23.777(3) A, b = 12.744(5) A,...
TL;DR: In this article, two novel lumophores based on aluminum and zinc metallo-8-hydroxyquinolates have been prepared as electroluminescent materials, and their absorbance, photoluminescence, and electrolUMinescence properties compared with unsubstituted versions of these same complexes.
Abstract: Two novel lumophores based on aluminum and zinc metallo-8-hydroxyquinolates have been prepared as electroluminescent materials, and their absorbance, photoluminescence, and electroluminescence properties compared with unsubstituted versions of these same complexes. 8-Hydroxy-5-piperidinylquinolinesulfonamide (1) was synthesized in order to add an electron-withdrawing substituent at the 5-position in 8-hydroxyquinoline, increasing the solubility of the corresponding metal quinolate complexes in nonpolar solvents, and producing a blue-shift in the emission wavelength maximum, relative to complexes formed from the unsubstituted compound. The aluminum complex (Al(QS)3) and the zinc complex (Zn(QS)2) of 1 were compared with the aluminum and zinc complexes of unsubstituted 8-hydroxyquinoline (AlQ3 and ZnQ2), both as solutions and as pure thin films, or as poly(N-vinylcarbazole) (PVK) thin films doped with the metal quinolates. Ultraviolet photoelectron spectroscopy data are presented to assist in estimating the...
TL;DR: It is suggested that the lack of a hepatic reservoir of zinc jeopardizes the developing kidney in the MT-null mice, which are more sensitive to dietary zinc restriction, and MT I and MT II can protect against both zinc deficiency and zinc toxicity.
Abstract: Metallothionein (MT)-bound zinc accumulates when animals are exposed to excess zinc and is depleted under conditions of zinc deficiency, suggesting that MT serves as a means of sequestering excess zinc as well as a zinc reservoir that can be utilized when zinc is deficient. To examine the importance of MT for these processes, mice with null alleles of both MT I and MT II genes were created and the zinc concentration and histological appearance of multiple organs assessed. At birth, the hepatic zinc concentration of these MT-null mice was lower than that of wild-type controls (0.27 +/- 0.02 vs. 0.65 +/- 0.11 micromol zinc/g tissue, P < 0.05). During the next 3 wk of suckling zinc-replete (95 micrograms zinc/g diet) dams, the hepatic zinc concentration of controls fell to 0.42 +/- 0.04 micromol/g but was unchanged in the MT-null mice (0.28 +/- 0.04 micromol/g). The most prominent histological anomaly observed at 3 wk of age was the presence of swollen Bowman's capsules in the kidneys of MT-null mice. When nursing MT-null dams were fed a severely zinc-deficient (1.5 microg/g) diet, kidney development in the MT-null pups was retarded as indicated by the retention of the nephrogenic zone and incomplete tubule development. We suggest that the lack of a hepatic reservoir of zinc jeopardizes the developing kidney in the MT-null mice. In addition to being more sensitive to dietary zinc restriction, MT-null mice are more sensitive to zinc toxicity. When adult mice were challenged with a ramping dose of zinc up to a total of 3700 micromol zinc/kg body weight, MT-null mice had a greater incidence of pancreatic acinar cell degeneration compared with control mice despite accumulating less zinc (2.72 +/- 0.46 vs. 1.23 +/- 0.52 micromol zinc/g pancreas, control and MT-null, respectively, P < 0.05). The results of these experiments suggest that MT I and MT II can protect against both zinc deficiency and zinc toxicity.
TL;DR: The clinical manifestations of zinc deficiency include growth retardation, hypogonadism in males, neurosensory disorders, cell-mediated immunological dysfunctions, and skin changes.
Abstract: Zinc deficiency in humans is widespread and is more prevalent in areas where the population subsists on cereal proteins. Conditioned deficiency of zinc is seen in many diseased states. A mild deficiency of zinc in pregnancy is associated with increased maternal morbidity, abnormal taste sensation, prolonged gestation, inefficient labor, atonic bleeding, and increased risks to the fetus. Among the urban poor in the US, a marginal zinc intake during pregnancy was associated with increased risk of preterm and very preterm delivery. Factors responsible for zinc deficiency in premature infants include high fecal losses of zinc, low body stores of zinc at birth, and increased zinc requirement during rapid growth. Zinc supplemented infants demonstrated improved linear growth velocity and maximum motor development scores. Marginal and moderate growth impairment in children as a consequence of inadequate zinc intake has been reported from many developed and developing countries. In one study from Japan, 21 prepube...
TL;DR: The data indicate that long‐term oral zinc speeds up the kinetics of urea formation from amino acids and ammonia, whereas the beneficial effects on encephalopathy might stem from decreased ammonia.
TL;DR: It is concluded that similar alterations in the properties of the zinc binding site can be caused by mutations scattered throughout the protein structure, which may help to explain what is perhaps the most perplexing question in copper-zinc superoxide dismutase-associated familial ALS-i.e., how such a diverse set of mutations can result in the same gain of function that causes the disease.
Abstract: A series of mutant human and yeast copper-zinc superoxide dismutases has been prepared, with mutations corresponding to those found in familial amyotrophic lateral sclerosis (ALS; also known as Lou Gehrig's disease) These proteins have been characterized with respect to their metal-binding characteristics and their redox reactivities Replacement of Zn2+ ion in the zinc sites of several of these proteins with either Cu2+ or Co2+ gave metal-substituted derivatives with spectroscopic properties different from those of the analogous derivative of the wild-type proteins, indicating that the geometries of binding of these metal ions to the zinc site were affected by the mutations Several of the ALS-associated mutant copper-zinc superoxide dismutases were also found to be reduced by ascorbate at significantly greater rate than the wild-type proteins We conclude that similar alterations in the properties of the zinc binding site can be caused by mutations scattered throughout the protein structure This finding may help to explain what is perhaps the most perplexing question in copper-zinc superoxide dismutase-associated familial ALS-ie, how such a diverse set of mutations can result in the same gain of function that causes the disease
TL;DR: The results do not support proposals attributing an important role to five-coordinate zinc complexes in the catalytic mechanism of alcohol dehydrogenase, and the strain induced by the enzyme onto the zinc ion and its ligands is quantified.
Abstract: The coordination number of the catalytic zinc ion in alcohol dehydrogenase has been studied by integrated ab initio quantum-chemical and molecular mechanics geometry optimisations involving the whole enzyme. A four-coordinate active-site zinc ion is 100-200 kJ/mol more stable than a five-coordinate one, depending on the ligands. The only stable binding site for a fifth ligand at the zinc ion is opposite to the normal substrate site, in a small cavity buried behind the zinc ion. The zinc coordination sphere has to be strongly distorted to accommodate a ligand in this site, and the ligand makes awkward contacts with surrounding atoms. Thus, the results do not support proposals attributing an important role to five-coordinate zinc complexes in the catalytic mechanism of alcohol dehydrogenase. The present approach makes it possible also to quantify the strain induced by the enzyme onto the zinc ion and its ligands; it amounts to 42-87 kJ/mol for four-coordinate active-site zinc ion complexes and 131-172 kJ/mol for five-coordinate ones. The four-coordinate structure with a water molecule bound to the zinc ion is about 20 kJ/mol less strained than the corresponding structure with a hydroxide ion, indicating that the enzyme does not speed up the reaction by forcing the zinc coordination sphere into a structure similar to the reaction intermediates.
TL;DR: Calculations, based on the metal binding data and the pH-dependent charging behavior, reveal that the cell wall becomes positively charged at high coverage with bivalent ions.
Abstract: Metal ion binding to the bacterial cell wall is the first step in the interactions of a metal with a bacterium. Cadmium and zinc ion binding to isolated cell walls of Rhodococcus erythropolis A177 has been studied for a wide range of proton and calcium concentrations. The release of calcium ions and protons during metal ion binding is an indication of the competitive nature of the binding. Calculations, based on the metal binding data and the pH-dependent charging behavior, reveal that the cell wall becomes positively charged at high coverage with bivalent ions. A cooperative effect of the presence of calcium on metal ion binding was observed. Apparently, the cell wall structure is altered in the presence of bivalent ions. Since calcium is a dominant bivalent cation in most natural systems, one may regard the calcium as a “structure determining ion”. On the basis of a qualitative interpretation of the data, the NICA model was selected for a quantitative description of the data.
TL;DR: In this article, the EIS results obtained at the open-circuit corrosion potential have been interpreted using a model involving the impedance of particle to particle contact to account for the increasing resistance between zinc particles with immersion period, in addition to the impedance due to the zinc surface oxide layer and the electrical resistivity of the binder.
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TL;DR: The interrelationships among zinc, growth, gonadal function, and GH-IGF-I axis appears to be complex.
Abstract: Zinc is an essential nutrients and plays an important role in growth and sexual function. Zinc deficiency has been known to cause growth retardation and hypogonadism. Several mechanisms of growth retardation and hypogonadism due to zinc deficiency have been suggested. Zinc affects growth hormone (GH) metabolism. Conversely, GH affects zinc metabolism. Zinc deficiency may result in reduced GH production and/or insulin-like growth factor-I (IGF-I). Zinc deficiency may also affect bone metabolism and gonadal function. The interrelationships among zinc, growth, gonadal function, and GH-IGF-I axis appears to be complex.
TL;DR: In this paper, the bridging-to-non-bridging oxygen ratio in a series of x ZnO · (1 − x )P 2 O 5 (0.50 ≤ x ≤ 0.67) glasses was measured using X-ray photoelectron spectroscopy.
Abstract: X-ray photoelectron spectroscopy has been used to determine oxygen bonding in a series of x ZnO · (1 − x )P 2 O 5 (0.50 ≤ x ≤ 0.67) glasses. Curve fitting of the O 1s spectra leads to a quantitative measure of the bridging-to-non-bridging oxygen ratio which is shown to depend on composition according to a simple structural depolymerization model. A third peak, present in the O 1s spectra collected from y B 2 O 3 · (1 − y )Zn(PO 3 ) 2 (0.00 ≤ y ≤ 0.40) glasses, is due to oxygens which link borate and phosphate tetrahedra. The relative concentrations of POP, POZn and POB bonds are shown to be in good agreement with a structural model which assumes that borophosphate units (BPO 4 ) form when B 2 O 3 is added to Zn metaphosphate glass.
TL;DR: In this paper, a propanol-bridged octaazacryptand (26-hydroxy-1,4,7,10,13,16,19,22-octaazabicyclo[11.11.3]heptacosane, HL) has been synthesized from diethylenetriamine and [2-oxo-6-(aminomethyl)morpholyl]-N,N‘,N
Abstract: A propanol-bridged octaazacryptand (26-hydroxy-1,4,7,10,13,16,19,22-octaazabicyclo[11.11.3]heptacosane, HL) has been synthesized from diethylenetriamine and [2-oxo-6-(aminomethyl)morpholyl]-N,N‘,N‘-triacetic acid triethyl ester by refluxing in MeOH followed by BH3·THF reduction. This octaazacryptand forms a novel dinuclear zinc(II) cryptate (Zn2L) (L = alkoxide form of HL) in aqueous solution. The X-ray crystal structure of the cryptate showed each zinc(II) ion in a distorted trigonal-bipyramidal environment involving two NH's and an alkoxide O- anion as equatorial donors, with tertiary amine and an NH stand in apical positions. Crystals of the triperchlorate salt of Zn2L (C19H43N8O13Cl3Zn2) are monoclinic, space group P21/n (No. 14) with a = 15.037(5) A, b = 13.862(5) A, c = 15.780(4) A, β = 90.29(2)°, Z = 4, and R = 0.109. Although the two zinc(II) ions (separated with a distance of 3.42 A) in the cryptate appeared to be coordinately saturated and hence were assumed unreactive, they work together to sel...
TL;DR: In this paper, a Schiff-base ligand based on condensation of diaminomaleonitrile and 4-(diethylamino)salicylaldehyde is reported with its copper, nickel, and zinc complexes.
Abstract: A new Schiff-base ligand based on the condensation of diaminomaleonitrile and 4-(diethylamino)salicylaldehyde is reported with its copper, nickel, and zinc complexes. Their second-order nonlinear optical properties are investigated by electric field induced second harmonic (EFISH) and ZINDO quantum-chemical calculations to probe the role of the metal center in the nonlinearity. All the complexes exhibit a second-order nonlinear response that is larger than that of the ligand with an hyperpolarizability (β) value of 400 (±100) 10-30 cm5 esu-1 for the zinc derivative at 1.34 μm. Theoretical calculations indicate that the two-level model is inadequate to describe the nonlinearity in such systems.
TL;DR: It is concluded that zinc may play an important role in modulating serum testosterone levels in normal men and zinc supplementation of marginally zinc-deficient normal elderly men for six months resulted in an increase in serum testosterone.
TL;DR: The antioxidant efficacy of various oxidation inhibitors in low erucic acid rapeseed oil has been studied in a screening test at 130°C by an induction period method as discussed by the authors, and the results showed that these additives were distinctly superior to commercially recommended formulations.
Abstract: The antioxidant efficacy of various oxidation inhibitors in low erucic acid rapeseed oil has been studied in a screening test at 130°C by an induction period method. Hindered monophenols, sulphides, phosphites, aromatic amines and zinc dithiophosphates yielded no or only marginal stabilising effects. Remarkably increased oxidation stabilities were observed with certain hindered bisphenols, polyhydroxybenzenes, zinc and bismuth dithiocarbamates. In high oleic sunflower oil with a lesser portion of multiple unsaturation, these additives induced relatively longer induction periods. Mixtures of zinc dithiocarbamates and 4,4′-methylenebis-(2, 6-di-tert-butylphenol) or octylated di-phenylamine, as well as compositions of all three compounds, exhibited synergistic effects. Under the conditions employed these additives were distinctly superior to commercially recommended formulations. A mechanistic concept of the antioxidant action of zinc dithiocarbamate is briefly discussed.