Showing papers on "Zinc published in 2004"
TL;DR: Five porous metal-organic frameworks based on linking zinc oxide clusters with benzene-1,4-dicarboxylate, naphthalene-2,6-dICarboxyate, 4,5,9,10-tetrahydropyrene- 2,7-divellyate, 2,3,5-6-Tetramethylbenzene-3,3-tris(4-benzoate) or benzene
Abstract: Five porous metal−organic frameworks based on linking zinc oxide clusters with benzene-1,4-dicarboxylate, naphthalene-2,6-dicarboxylate, 4,5,9,10-tetrahydropyrene-2,7-dicarboxylate, 2,3,5,6-tetramethylbenzene-1,4-dicarboxylate, or benzene-1,3,5-tris(4-benzoate) were synthesized in gram-scale quantities to measure their hydrogen uptake properties. Hydrogen adsorption isotherms measured at 77 K show a distinct dependence of uptake on the nature of the link. At 1 atm, the materials sorb between 4.2 and 9.3 molecules of H2 per formula unit. The results imply a trend in hydrogen uptake with the number of rings in the organic moiety.
1,240 citations
01 Jul 2004
TL;DR: It was confirmed that carboxyl, ether, alcoholic, and amino groups are responsible for the binding of the metal ions, with higher pH favoring higher metal-ion removal.
Abstract: The marine algae Sargassum sp, Padina sp, Ulva sp, and Gracillaria sp, harvested locally, were investigated for their biosorption performance in the removal of lead, copper, cadmium, zinc, and nickel from dilute aqueous solutions It was found that the biosorption capacities were significantly affected by solution pH, with higher pH favoring higher metal-ion removal Kinetic and isotherm experiments were carried out at the optimal pH: at pH 50 for lead and copper, and at pH 55 for cadmium, zinc, and nickel The metal removal rates were rapid, with 90% of the total adsorption taking place within 60 min Sargassum sp and Padina sp showed the highest potential for the sorption of the metal ions, with the maximum uptake capacities ranging from 061 to 116 mmol/g for Sargassum sp and 063 to 125 mmol/g for Padina sp The general affinity sequence for Padina sp was Pb>Cu>Cd>Zn>Ni, while that for Sargassum sp was Pb>Zn>Cd>Cu>Ni XPS and FTIR analysis of Sargassum sp and Padina sp revealed the chelating character of the ion coordination to carboxyl groups It was confirmed that carboxyl, ether, alcoholic, and amino groups are responsible for the binding of the metal ions
1,044 citations
813 citations
01 Jan 2004
TL;DR: This chapter discusses dietary sources of zinc and factors affecting the proportion of zinc available for absorption in the diet, as well as causes of zinc deficiency and groups at high risk.
Abstract: Chapter 1: Overview of Zinc Nutrition S99 1.1 Biological functions of zinc S99 1.2 Tissue zinc distribution and reserves S99 1.3 Zinc metabolism S100 1.4 Importance of zinc for human health S101 1.5 Human zinc requirements S105 1.5.1 Adult men S106 1.5.2 Adult women S109 1.5.3 Children S110 1.5.4 Pregnancy S111 1.5.5 Lactation S112 1.6 Dietary sources of zinc and suggested revisions of Recommended Daily Intakes S112 1.6.1 Dietary sources of zinc and factors affecting the proportion of zinc available for absorption ........ S112 1.6.2 Revised estimates of dietary requirements and recommended intakes for zinc S114 1.7 Zinc toxicity S118 1.8 Causes of zinc deficiency and groups at high risk S121 1.9 Summary S123
768 citations
TL;DR: The effects of substituents and solvents on the photophysical and photochemical parameters of zinc(II) phthalocyanines are reported in this paper, where it was found that the presence of peripheral substituent on the macrocycle enhances the yield of the triplet state.
Abstract: The effects of substituents and solvents on the photophysical and photochemical parameters of zinc(II) phthalocyanines are reported. The complexes studied are zinc phthalocyanine (ZnPc), zinc tetra(tert-butylphenoxy)phthalocyanine [ZnPc(TBPh)4], zinc octa(methylphenoxy)phthalocyanine [ZnPc(MPh)8], zinc tetranitrophthalocyanine [ZnPc(NO2)4], zinc octachlorophthalocyanine (ZnPcCl8), zinc tetrasulfophthalocyanine [ZnPc(SO3−)4], a mixture of zinc mono-, di-, tri- and tetrasulfophthalocyanine [ZnPc(SO3−)mix] and zinc naphthalocyanine (ZnNPc). It was found that the presence of peripheral substituents on the macrocycle enhances the yield of the triplet state. Among the different substituents, the sulfonated derivative, ZnPc(SO3−)mix, has the longest triplet lifetime (τT) and the highest singlet oxygen quantum yield (ϕΔ). The near infra-red absorptions of the solvents reveal that solvents that absorb around 1100 nm (triplet energy level) and around 1270 nm (singlet oxygen energy level), quench the triplet state of the ZnPc derivative as well as singlet oxygen. Although water has a high singlet oxygen quenching effect, the ϕΔ value for ZnPc(SO3−)mix in water is still reasonably high at 0.48, which may provide an explanation for the efficient photosensitization by this molecule in photodynamic studies.
662 citations
TL;DR: Based on first-principles calculations, a model for large-size-mismatched group-V dopants in ZnO agrees with the recent observations that both As and Sb have low acceptor-ionization energies and that to obtain p-type Zn O requires O-rich growth or annealing conditions.
Abstract: Based on first-principles calculations, a model for large-size-mismatched group-V dopants in ZnO is proposed. The dopants do not occupy the O sites as is widely perceived, but rather the Zn sites: each forms a complex with two spontaneously induced Zn vacancies in a process that involves fivefold As coordination. Moreover, an As(Zn)-2V(Zn) complex may have lower formation energy than any of the parent defects. Our model agrees with the recent observations that both As and Sb have low acceptor-ionization energies and that to obtain p-type ZnO requires O-rich growth or annealing conditions.
600 citations
TL;DR: The best fitting of experimental results to the proposed isotherms was observed in models that assume that ionic species bind first at energetically most favorable sites, with multi-layer adsorption taking place subsequently.
531 citations
TL;DR: ZnT transporters reduce intracellular zinc availability by promoting extracellular zinc uptake and, perhaps, vesicular zinc release into the cytoplasm.
Abstract: New insights into mammalian zinc metabolism have been acquired through the identification and characterization of zinc transporters. These proteins all have transmembrane domains, and are encoded by two solute-linked carrier (SLC) gene families: ZnT (SLC30) and Zip (SLC39). There are at least 9 ZnT and 15 Zip transporters in human cells. They appear to have opposite roles in cellular zinc homeostasis. ZnT transporters reduce intracellular zinc availability by promoting zinc efflux from cells or into intracellular vesicles, while Zip transporters increase intracellular zinc availability by promoting extracellular zinc uptake and, perhaps, vesicular zinc release into the cytoplasm. Both the ZnT and Zip transporter families exhibit unique tissue-specific expression, differential responsiveness to dietary zinc deficiency and excess, and differential responsiveness to physiologic stimuli via hormones and cytokines.
524 citations
TL;DR: It is demonstrated that AtHMA4 is localized at the plasma membrane and expressed in tissues surrounding the root vascular vessels and plays a role in metal loading in the xylem.
505 citations
TL;DR: The results suggest that zinc supplementation may lead to down regulation of the inflammatory cytokines through upregulation of the negative feedback loop A20 to inhibit induced NF-kappaB activation.
488 citations
TL;DR: The design, synthesis, and properties of the benzoxazole-based, ratiometric zinc probe, Zinbo-5 are described, which is well suited for two-photon excitation microscopy ratio imaging and can readily reveal changes in intracellular zinc concentration within optical planes of single cells.
Abstract: Zinc and calcium are ubiquitous intracellular metals, and while a variety of quantitative probes have been developed for measuring intracellular changes in calcium concentration, the same is not true of zinc. We describe here the design, synthesis, and properties of the benzoxazole-based, ratiometric zinc probe, Zinbo-5. This bright fluorescent reporter has a quantum yield of 0.1 in the zinc-form, exhibits a Kd for Zn2+ in the nanomolar range, and shows significant changes in both excitation and emission maxima upon zinc binding. The utility of this cell permeable probe is demonstrated in fluorescence microscopy emission ratio imaging experiments on mammalian cells. We further show that Zinbo-5 is well suited for two-photon excitation microscopy ratio imaging and can readily reveal changes in intracellular zinc concentration within optical planes of single cells. To the best of our knowledge, this is the first example of two-photon excitation microscopy applied to ratio imaging of zinc. These methods can be applied to real-time emission or excitation ratio imaging studies of zinc physiology in living cells.
TL;DR: Zinc clearly has an important role in infant and childhood infectious diseases; programs to increase the intake of zinc among deficient populations are needed.
Abstract: Zinc is an essential micronutrient for human growth, development, and immune function. Zinc deficiency impairs overall immune function and resistance to infection. Mild to moderate zinc deficiency can be best detected through a positive response to supplementation trials. Zinc supplementation has been shown to have a positive effect on the incidence of diarrhea (18% reduction, 95% CI: 7-28%) and pneumonia (41% reduction, 95% CI: 17-59%), and might lead to a decrease in the incidence of malaria. Zinc has also proven to decrease the duration of diarrhea by 15% (95% CI: 5-24%). Maternal zinc supplementation may lead to a decrease in infant infections. Studies assessing the role of zinc supplementation among persons with HIV, tuberculosis, and the common cold have not been conclusive. Two studies have shown zinc supplementation to decrease child mortality by more than 50%. Zinc clearly has an important role in infant and childhood infectious diseases; programs to increase the intake of zinc among deficient populations are needed.
TL;DR: Decamethyldizincocene, Zn2(η5-C5Me5)2, an organometallic compound of Zn(I) formally derived from the dimetallic [Zn–Zn]2+ unit, has been isolated from the low-temperature (–10°C) reaction
Abstract: Unlike mercury, which has an extensive +1 oxidation state chemistry, zinc usually adopts the +2 oxidation state. Decamethyldizincocene, Zn2(eta5-C5Me5)2, an organometallic compound of Zn(I) formally derived from the dimetallic [Zn-Zn]2+ unit, has been isolated from the low-temperature (-10 degrees C) reaction of Zn(C5Me5)2 and Zn(C2H5)2 in diethyl ether. X-ray studies show that it contains two eclipsed Zn(eta5-C5Me5) fragments with a Zn-Zn distance (+/- standard deviation) of 2.305(+/-3) angstroms, indicative of a metal-metal bonding interaction.
TL;DR: This review will focus on potential mechanisms by which zinc deficiency impairs host protective mechanisms designed to protect against DNA damage, enhances susceptibility to DNA-damaging agents and ultimately increases risk for cancer.
Abstract: A large body of evidence suggests that a significant percentage of deaths resulting from cancer in the United States could be avoided through greater attention to proper and adequate nutrition. Although many dietary compounds have been suggested to contribute to the prevention of cancer, there is strong evidence to support the fact that zinc, a key constituent or cofactor of over 300 mammalian proteins, may be of particular importance in host defense against the initiation and progression of cancer. Remarkably, 10% of the U.S. population consumes less than half the recommended dietary allowance for zinc and are at increased risk for zinc deficiency. Zinc is known to be an essential component of DNA-binding proteins with zinc fingers, as well as copper/zinc superoxide dismutase and several proteins involved in DNA repair. Thus, zinc plays an important role in transcription factor function, antioxidant defense and DNA repair. Dietary deficiencies in zinc can contribute to single- and double-strand DNA breaks and oxidative modifications to DNA that increase risk for cancer development. This review will focus on potential mechanisms by which zinc deficiency impairs host protective mechanisms designed to protect against DNA damage, enhances susceptibility to DNA-damaging agents and ultimately increases risk for cancer.
TL;DR: In this paper, a copolymerization of CO2 and epoxide with a quaternary ammominum or phosphonium salt is described. And the copolymers obtained by this system are shown to have very narrow molecular weight distribution.
Abstract: Alternating copolymerization of CO2 and epoxide to give aliphatic polycarbonate with high molecular weight proceeds under mild conditions by organometallic catalyst systems. The reaction product of diethylzinc with a polyhydric compound, such as water or polyhydric phenol, exhibits high catalytic activity. Elementary reactions for the copolymerization of CO2 and epoxide with an organozinc catalyst system is considered to be the reaction of a zinc alkoxide with CO2 to form a zinc alkyl carbonate, and the reaction of the zinc alkyl carbonate with epoxide to regenerate zinc alkoxide. The system of aluminum porphyrin such as (tetraphenylporphinato)aluminum chloride, coupled with a quaternary ammominum or phosphonium salt, such as ethyltriphenylphosphonium bromide, is a good catalyst for this copolymerization. Of much interest is the very narrow molecular weight distribution of the copolymer obtained by this system. Aluminum porphyrin and the quaternary salt forms a hexa-coordinate complex, and the copolymerization reaction is considered to proceed on both sides of the porphyrin ring. Some properties of the copolymer for possible application are described.
TL;DR: An effective solvothermal procedure has been developed to synthesize the new three-dimensional metal-organic framework, [ZnF(AmTAZ], suggesting a possible route for preparing one-dimensional crystalline nanomaterials.
Abstract: An effective solvothermal procedure has been developed to synthesize the new three-dimensional metal−organic framework, [ZnF(AmTAZ)]·solvents, using either 3-amino-1,2,4-triazole (AmTAZ) or 3-amino-1,2,4-triazole-5-carboxylic acid (AmTAZAc) and a choice of several Zn(II) salts as starting materials. The three-dimensional structure displays open-ended, hollow nanotubular channels that are formed by hexanuclear metallamacrocyclic Zn6F6(AmTAZ)6 rings. The framework integrity is maintained to 350 °C, at which point most of the guest solvent molecules have been removed, as evidenced by single-crystal X-ray analyses, 1H solid-state NMR, and TGA measurements. At higher temperatures, the framework is converted either to zinc oxide (ZnO) when heated in air or to zinc cyanamide (ZnCN2) when heated in an inert atmosphere. In both cases, the as-grown, rodlike crystal shape is maintained during the solid-state transformation, suggesting a possible route for preparing one-dimensional crystalline nanomaterials.
TL;DR: The alternating copolymerization of (R)- or (S)-limonene oxide and CO2 using beta-diiminate zinc acetate catalysts is reported, which exhibits a high selectivity for the trans isomer and produces regioregular polycarbonate.
Abstract: The alternating copolymerization of (R)- or (S)-limonene oxide and CO2 using beta-diiminate zinc acetate catalysts is reported. At 100 psi CO2 and 25 degrees C, the catalyst exhibits a high selectivity for the trans isomer and produces regioregular polycarbonate. The copolymer contains >99% carbonate linkages, a narrow molecular weight distribution, and an Mn value consistent with the [epoxide]/[Zn] ratio.
TL;DR: In this article, five chitosan-zinc complexes with different zinc content were prepared and characterized by FT-IR, XRD, AAS and elemental analysis, and three possible structures corresponding to different chelate ratios were proposed and preliminarily complexation mechanisms were discussed.
TL;DR: Results indicate that NS5A is a zinc metalloprotein and that zinc coordination is likely required for NS 5A function in the hepatitis C replicase.
TL;DR: Parrot feather showed greater tolerance to toxicity followed by water mint and creeping primrose, and the growth of creeps primrose was significantly affected by heavy metal toxicity.
TL;DR: It is concluded that the long sought role of MT lies in the control of the cellular zinc distribution as a function of the energy state of the cell and not in the widely held belief that MT primarily scavenges radicals or detoxifies metals.
Abstract: Metallothioneins (MTs) define a superfamily of ubiquitous cysteine-rich low molecular weight proteins or polypeptides that contain polynuclear metalsulfur coordination sites formed by metal ions with d10 configuration. The most prominent characteristics of these biomolecules, which have been discovered as a cadmium and zinc containing protein in horse kidney by Margoshes and Vallee in 1957,1 are their extremely high metal and sulfur contents (up to 10% w/w). Although MTs have been known as long as about half a century, their precise physiological function is still under debate. According to Kägi and Schäffer, they are thought to play roles both in the intracellular fixation of the essential trace elements zinc and copper, in controlling the concentrations of the free ions of these elements, in regulating their flow to their cellular destinations, in neutralizing the harmful influences of exposure to toxic elements such as cadmium and mercury, and in the protection from a variety of stress conditions.2 More recently, it was concluded by Maret and Vallee that the long sought role of MT lies in the control of the cellular zinc distribution as a function of the energy state of the cell and not in the widely held belief that MT primarily scavenges radicals or detoxifies metals.3 As can be learned by these speculations, investigations directed to explore the structure and chemistry of metallothioneins in greater detail are extremely important taking into account that nature makes use of them as multipurpose proteins. Several reviews covering this issue are available in the literature.4 Today, MTs are known to occur in all animal phyla examined so far as well as in certain fungi, plants, and cyanobacteria. Characterized by a low molecular mass of 6.000-7.000 amu, by 20 totally conserved cysteines out of a total of 61 or 62 amino acid residues (according to ca. 30% by number), without aromatic amino acids such as tyrosine or histidine, the apoprotein from rat liver (thionein) is able to bind a total of seven equivalents of divalent metal ions with d10 configuration such as Zn2+ or Cd2+ in two noninteracting domains. After demetalation, these proteins can be loaded with up to six Cu1+ ions in each domain.5 * To whom correspondence should be addressed. (G.H.) Tel +495251-60-2494. Fax +49-5251-60-3423. E-mail biohenkel@ uni-paderborn.de. (B.K.) Tel +49-251-833-3131. Fax +49-251-8338366. E-mail krebs@uni-muenster.de. † Universität Paderborn. ‡ Universität Münster. 801 Chem. Rev. 2004, 104, 801−824
TL;DR: The photoluminescence (PL) quantum yield of ZnSe nanocrystals reached as high as 50% with a full width of half-maximum (fwhm) as narrow as 14 nm as mentioned in this paper.
Abstract: Nearly monodisperse ZnSe and ZnS nanocrystals were formed in noncoordinating solvents using alternative precursors. The parameter window for the growth of high quality zinc chalcogenide nanocrystals was found to be much narrower than that of the corresponding cadmium chalcogenide nanocrystals. In contrast to syntheses performed in coordinating solvents, generic oxygen containing ligands, such as fatty acids, were found to be reasonable ligands for the formation of ZnSe and ZnS nanocrystals. Activation of the zinc precursor (zinc fatty acid salts) by alkylamines was found to be critical for the formation of high quality ZnSe nanocrystals. The photoluminescence (PL) quantum yield (QY) of ZnSe nanocrystals reached as high as 50% with a full width of half-maximum (fwhm) as narrow as 14 nm. The band gap PL of ZnS nanocrystals was always mixed with a deep-trap tail. The PL fwhm of the band gap emission of the ZnS nanocrystals was typically between 10 and 12 nm.
TL;DR: Solution pH reduction during metal retention and flow calorimetry analysis both supported the hypothesis of retention of Pb, Cu, and Zn by surface adsorption or complexation, demonstrating that PR can effectively remove Pb from solutions, even in the presence of other heavy metals.
TL;DR: It is demonstrated that the nanocrystal nucleation and growth stages can be automatically separated in a homogeneous system with the presence of nucleation initiators.
Abstract: This paper reports a one-pot synthetic method for producing CdS nanocrystals. We have demonstrated that the nanocrystal nucleation and growth stages can be automatically separated in a homogeneous system with the presence of nucleation initiators. Accelerators used for more than 70 years in rubber vulcanization (i.e., tetraethylthiuram disulfides, and 2,2‘-dithiobisbenzothiazole) were found to be effective nucleation initiators for CdS nanocrystal synthesis. The as-prepared CdS nanocrystals are highly monodisperse and possess a zinc blende crystal structure. The quantum yield of the band-gap photoluminescence is up to 12% when the surface-trap emission was totally eliminated after a gentle oxidation under laboratory fluorescent light.
TL;DR: Investigation of lead, zinc, and copper adsorption properties of Ceratophyllum demersum (Coontail or hornwort) showed that it can be successfully used for heavy metal removal under dilute metal concentration.
TL;DR: In this paper, a review of microwave-assisted leaching of copper, gold, nickel, cobalt, and manganese, lead and zinc and also coal desulphurization is presented.
TL;DR: In this paper, annealing to 800°C, the implanted Mn remains in the ZnO nanobelts and the matrix recovers both in structure and luminescence.
Abstract: Zinc oxide (ZnO) nanobelts synthesized by thermal evaporation have been ion implanted with 30 keV Mn+ ions. Both transmission electron microscopy and photoluminescence investigations show highly defective material directly after the implantation process. Upon annealing to 800 °C, the implanted Mn remains in the ZnO nanobelts and the matrix recovers both in structure and luminescence. The produced high-quality ZnO:Mn nanobelts are potentially useful for spintronics.
TL;DR: The phase behavior of a variety of quaternary ammonium halides/ZnCl(2) mixtures is characterized and it is shown that the depression of freezing point is related to the increase in size of the component ions.
Abstract: The synthesis of ionic liquids based upon functionalized quaternary ammonium salts and metal salts of zinc, tin, or iron is demonstrated. The freezing point of these ionic liquids was studied as a function of the quaternary ammonium cation. The complex anions were identified and quantified using mass spectrometry and potentiometry. It is shown that the primary zinc anion is Zn2Cl5- with Zn3Cl7- becoming more abundant in more Lewis basic solutions. Similar results were observed for ionic liquids containing SnCl2. The surface tension was also measured and was used to explain the high viscosity of the ionic liquids in terms of the large ion:hole size ratio and the small probability of finding a hole of suitable dimensions adjacent to a given ion to permit movement. The phase behavior of a variety of quaternary ammonium halides/ZnCl2 mixtures is characterized and it is shown that the depression of freezing point is related to the increase in size of the component ions.
TL;DR: Using a thin film of metallic tin as catalyst, ultrasmall single-crystalline zinc oxide nanobelts have been synthesized in large quantity using a simple solid-vapor technique as discussed by the authors.
Abstract: Using a thin film of metallic tin as catalyst, ultrasmall single-crystalline zinc oxide nanobelts have been synthesized in large quantity using a simple solid-vapor technique. The nanobelts have an average width of 5.5 nm and a narrow size distribution of (1.5 nm. The nanobelts grew along the [0001] direction, with (21 h10) top/bottom surfaces and (011 h0) side surfaces. Photoluminescence measurement showed a blue shift in the emission spectrum compared to that acquired from ZnO nanobelts of 200 nm in width. These ultrafine nanobelts should be good candidates for investigating size-induced electrical and optical properties of functional oxides.
TL;DR: Extended x-ray absorption fine structure measurements were performed on frozen hydrated samples of the cadmium (Cd)/zinc (Zn) hyperaccumulator Thlaspi caerulescens (Ganges ecotype) after 6 months of Zn2+ treatment with and without addition of Cd2+.
Abstract: Extended x-ray absorption fine structure measurements were performed on frozen hydrated samples of the cadmium (Cd)/zinc (Zn) hyperaccumulator Thlaspi caerulescens (Ganges ecotype) after 6 months of Zn2+ treatment with and without addition of Cd2+. Ligands depended on the metal and the function and age of the plant tissue. In mature and senescent leaves, oxygen ligands dominated. This result combined with earlier knowledge about metal compartmentation indicates that the plants prefer to detoxify hyperaccumulated metals by pumping them into vacuoles rather than to synthesize metal specific ligands. In young and mature tissues (leaves, petioles, and stems), a higher percentage of Cd was bound by sulfur (S) ligands (e.g. phytochelatins) than in senescent tissues. This may indicate that young tissues require strong ligands for metal detoxification in addition to the detoxification by sequestration in the epidermal vacuoles. Alternatively, it may reflect the known smaller proportion of epidermal metal sequestration in younger tissues, combined with a constant and high proportion of S ligands in the mesophyll. In stems, a higher proportion of Cd was coordinated by S ligands and of Zn by histidine, compared with leaves of the same age. This may suggest that metals are transported as stable complexes or that the vacuolar oxygen coordination of the metals is, like in leaves, mainly found in the epidermis. The epidermis constitutes a larger percentage of the total volume in leaves than in stems and petioles. Zn-S interaction was never observed, confirming earlier results that S ligands are not involved in Zn resistance of hyperaccumulator plants.