Zinc Compounds

The present study involves the photocatalytic degradation of Methyl Orange (MO) and Rhodamine 6G (R6G), employing heterogeneous photocatalytic process. Photocatalytic activity of various semiconductors such as titanium dioxide (TiO 2 ), zinc oxide (ZnO), stannic oxide (SnO 2 ), zinc sulphide (ZnS) and cadmium sulphide (CdS) has been investigated. An attempt has been made to study the effect of process parameters viz., amount of catalyst, concentration of dye and pH on photocatalytic degradation of MO and R6G. The experiments were carried out by irradiating the aqueous solutions of dyes containing photocatalysts with UV and solar light. The rate of decolorization was estimated from residual concentration spectrophotometrically. Similar experiments were carried out by varying pH (2-10), amount of catalyst (0.25-2.0 g/l) and initial concentration of dye (5-200 mg/l). The experimental results indicated that the maximum decolorization (more than 90%) of dyes occurred with ZnO catalyst and at basic pH and the maximum adsorption of MO was noticed at pH 4 and of R6G at pH 10. The percentage reduction of MO and R6G was estimated under UV/solar system and it was found that COD reduction takes place at a faster rate under solar light as compared to UV light. In case of R6G, highest decolorizing efficiency was achieved with lower dose of catalyst (0.5 g/l) than MO (1 g/l) under similar conditions. The performance of photocatalytic system employing ZnO/solar light was observed to be better than ZnO/UV system.

Oligonucleotide microarrays were employed to quantitate mRNA levels from a large number of genes regulated by the p53 transcription factor. Responses to DNA damage and to zinc-inducible p53 were compared for their transcription patterns in cell culture. A cluster analysis of these data demonstrates that genes induced by ␥ radiation, UV radiation, and the zinc-induced p53 form distinct sets and subsets with a few genes in common to all these treatments. Cell type-or cell line-specific p53 responses were detected. When p53 proteins were induced with zinc, the kinetics of induction or repression of mRNAs from p53-responsive genes fell into eight distinct classes, five different kinetics of induction, and three different kinetics of repression. In addition, low levels of p53 in a cell induced or repressed only a subset of genes observed at higher p53 levels. The results of this study demonstrate that the nature of the p53 response in diverse mRNA species depends on the levels of p53 protein in a cell, the type of inducing agent or event, and the cell type employed. Of 6000 genes examined for p53 regulatory responses, 107 induced and 54 repressed genes fell into categories of apoptosis and growth arrest, cytoskeletal functions, growth factors and their inhibitors, extracellular matrix, and adhesion genes.

The importance of micronutrients in health and nutrition is undisputable, and among them, zinc is an essential element whose significance to health is increasingly appreciated and whose deficiency may play an important role in the appearance of diseases. Zinc is one of the most important trace elements in the organism, with three major biological roles, as catalyst, structural, and regulatory ion. Zinc-binding motifs are found in many proteins encoded by the human genome physiologically, and free zinc is mainly regulated at the single-cell level. Zinc has critical effect in homeostasis, in immune function, in oxidative stress, in apoptosis, and in aging, and significant disorders of great public health interest are associated with zinc deficiency. In many chronic diseases, including atherosclerosis, several malignancies, neurological disorders, autoimmune diseases, aging, age-related degenerative diseases, and Wilson's disease, the concurrent zinc deficiency may complicate the clinical features, affect adversely immunological status, increase oxidative stress, and lead to the generation of inflammatory cytokines. In these diseases, oxidative stress and chronic inflammation may play important causative roles. It is therefore important that status of zinc is assessed in any case and zinc deficiency is corrected, since the unique properties of zinc may have significant therapeutic benefits in these diseases. In the present paper, we review the zinc as a multipurpose trace element, its biological role in homeostasis, proliferation and apoptosis and its role in immunity and in chronic diseases, such as cancer, diabetes, depression, Wilson's disease, Alzheimer's disease, and other age-related diseases.

The ability to covalently functionalize molecules is a long standing practice in organic chemistry that has led to advances in the synthesis of natural products, pharmaceuticals, and polymers. However, the analogous chemistry of crystalline extended solids remains undeveloped because they generally lose their structural integrity under the reaction conditions required to carry out meaningful organic transformations. Recent reports showed the viability of functionalizing the organic links of porous metal-organic frameworks using mild organic reactions. 1 Here, we extend this strategy to zeolitic imidazolate frameworks (ZIFs), which have unusual thermal and chemical stability, and thus are ideal platforms for performing useful organic transformations under strong reaction conditions. 2 Specifically, the imidazolate-2-carboxyaldehyde (ICA) links, which join tetrahedral zinc(II) centers in a new porous ZIF (vide infra), have been reduced by NaBH 4 to the corresponding alcohol derivative, and converted to an imine functionality in refluxing methanol (Scheme 1). Despite these strong reaction conditions, the integrity of the ZIF structure and its crystallinity are maintained throughout the synthesis. The isolated ZIF derivatives indicate that those organic reactions proceeded in high conversions. In essence the success in achieving typical organic reactions in crystals of extended structures like ZIFs makes the idea of using the "crystal as a molecule" 3 a reality and opens many opportunities for employing the arsenal of organic reactions in the covalent functionalization of extended structures.

We demonstrate the use of luminescent QDs conjugated to antibody fragments to develop solution-phase nanoscale sensing assemblies, based on fluorescence resonance energy transfer (FRET) for the specific detection of the explosive 2,4,6-trinitrotoluene (TNT) in aqueous environments. The hybrid sensor consists of anti-TNT specific antibody fragments attached to a hydrophilic QD via metal-affinity coordination. A dye-labeled TNT analogue prebound in the antibody binding site quenches the QD photoluminescence via proximity-induced FRET. Analysis of the data collected at increasing dye-labeled analogue to QD ratios provided an insight into understanding how the antibody fragments self-assemble on the QD. Addition of soluble TNT displaces the dye-labeled analogue, eliminating FRET and resulting in a concentration-dependent recovery of QD photoluminescence. Sensor performance and specificity were evaluated.

Electronic spectra Positron annihilation lifetime spectroscopy a b s t r a c t Molecular charge-transfer complexes of the tetramethylethylenediamine (TMEDA) with picric acid (Pi-OH), benzene-1,4-diol (QL), tin(IV) tetrachloride (SnCl 4 ), iodine, bromine, and zinc chloride (ZnCl 2 ) have been synthesized and investigated by elemental and thermal analysis, electronic, infrared, Raman and proton-NMR, energy-dispersive X-ray spectroscopy, X-ray powder diffraction and positron annihilation lifetime spectroscopy, and scanning electron microscopy. In this work, three types of acceptors p-acceptors (Pi-OH and QL), r-acceptors (iodine and bromine), and vacant orbital acceptors (SnCl 4 and ZnCl 2 ) were covered. The results of elemental analysis indicated that the CT complexes were formed with ratios 1:1 and 1:2 for QL, SnCl 4 , and ZnCl 2 acceptors and iodine, Pi-OH, and Br 2 acceptors, respectively. The type of chelating between the TMEDA donor and the mentioned acceptors depends upon the behavior of both items. The positron annihilation lifetime parameters were found to be dependent on the structure, electronic configuration, and the power of acceptors. The correlation between these parameters and the molecular weight and biological activities of studied complexes was also observed. Regarding the electrical properties, the AC conductivity and the dielectric coefficients were measured as a function of frequency at room temperature. The TMEDA charge-transfer complexes were screened against antibacterial (Escherichia coli, Staphylococcus aureus, Bacillus subtilis, and Pseudomonas aeruginosa) and antifungal (Aspergillus flavus and Candida albicans) activities.

Periwinkle shell, an abundant and inexpensive natural resource, was used to prepare activated carbon by physicochemical activation with potassium hydroxide (KOH) and carbon dioxide (CO2) as the activating agents at 850 °C for 2 h. The adsorption equilibrium and kinetics of methylene blue dye on such carbon were then examined at 25 °C. Adsorption isotherm of the methylene blue (MB) on the activated carbon was determined and correlated with common isotherm equations. The equilibrium data for methylene blue adsorption well fitted to the Langmuir equation, with maximum monolayer adsorption capacity of 500.00 mg/g. Two simplified kinetic models including pseudo-first-order and pseudo-second-order equation were selected to follow the adsorption processes. The adsorption of methylene blue on activated carbon derived from periwinkle shell could best be described by the pseudo-second-order equation. The kinetic parameters of this best-fit model were calculated and discussed.

We report the development of cell-penetrating quantum dots (QDs) based on the use of multivalent and endosome-disrupting (endosomolytic) surface coatings. Hyperbranched copolymer ligands such as polyethylene glycol (PEG) grafted polyethylenimine (PEI-g-PEG) are found to encapsulate and solubilize luminescent quantum dots through direct ligand-exchange reactions. Because of the positive charges and a "proton sponge effect" associated with multivalent amine groups, this class of ligand-exchanged QDs is able to penetrate cell membranes and is also able to disrupt endosomal organelles in living cells. The grafted PEG segment is essential for reducing the cytotoxicity of PEI as well as for improving the overall nanoparticle stability and biocompatibility. In comparison with previous QDs encapsulated with amphiphilic polymers, the cell-penetrating QDs are smaller in size and are considerably more stable in acidic environments. Cellular uptake and imaging studies reveal that the number of PEG grafts per PEI molecule has a pronounced effect on the intracellular pathways of internalized QDs. In particular, QDs coated with PEI-g-PEG 2 are rapidly internalized by endocytosis, and are initially stored in vesicles, followed by slow endosomal escape and release into the cytoplasm. These insights are important toward the design and development of nanoparticle agents for intracellular imaging and therapeutic applications.

The highly organized structure of M13 bacteriophage was used as an evolved biological template for the nucleation and orientation of semiconductor nanowires. To create this organized template, peptides were selected by using a pIII phage display library for their ability to nucleate ZnS or CdS nanocrystals. The successful peptides were expressed as pVIII fusion proteins into the crystalline capsid of the virus. The engineered viruses were exposed to semiconductor precursor solutions, and the resultant nanocrystals that were templated along the viruses to form nanowires were extensively characterized by using high-resolution analytical electron microscopy and photoluminescence. ZnS nanocrystals were well crystallized on the viral capsid in a hexagonal wurtzite or a cubic zinc blende structure, depending on the peptide expressed on the viral capsid. Electron diffraction patterns showed single-crystal type behavior from a polynanocrystalline area of the nanowire formed, suggesting that the nanocrystals on the virus were preferentially oriented with their [001] perpendicular to the viral surface. Peptides that specifically directed CdS nanocrystal growth were also engineered into the viral capsid to create wurtzite CdS virus-based nanowires. Lastly, heterostructured nucleation was achieved with a dual-peptide virus engineered to express two distinct peptides within the same viral capsid. This work represents a genetically controlled biological synthesis route to a semiconductor nanoscale heterostructure. E xploiting the biologically evolved, self-assembling structures of viral capsids is a possible mechanism in the ordering of technologically important materials. A key characteristic of materials synthesized by natural biological systems is the hierarchical organization of structures on many length scales with controlled size, shape, alignment, and orientation (1-8). There has been much interest in using biological templates in vitro to modulate the growth of inorganic, semiconductor, magnetic, and other technologically important materials (9-14). Our previous work, along with that of others, has shown that biological combinatorial approaches can identify amino acid sequences capable of interacting with a variety of materials (11, 15). Here, we present a system that exploits the self-assembling, crystalline structure of the viral coat to nucleate and template II-VI semiconductor nanocrystals into highly oriented quantum dot nanowires. To accomplish this, the pVIII major coat protein was engineered to display evolutionary-selected peptides, enabling directed nanocrystal growth into viral-semiconductor hybrid nanowires that were crystallographically oriented over the micrometer size range.

Materials and Methods: Materials. Zinc stearate (ZnSt 2 , 12.5-14% ZnO), stearic acid (SA, 95%), selenium powder (~200 mesh, 99.999%) tetramethylammonium hydroxide (TMAH), manganese chloride (MnCl 2), dodacanethiol (DDT), and octadecylamine (ODA, 95%) were purchased from Alpha Aesar. 1-octadecene (ODE), mercaptopropionic acid (MPA), and tributyl phosphine (TBP, 95%) were purchased from Aldrich. Zinc undecylenate was purchased from Gelest. undecylenoic acid was purchased from TCI, Rhodamine 3B and Stilbene 420 dyes were purchased from Eastman. All chemicals were used without further purification.

The photocatalytic inactivation of Gram negative Escherichia coli and Gram positive Lactobacillus helveticus by both TiO 2 and ZnO with 365-nm ultraviolet (UV) light was studied in a batch reactor. Almost all the initial E. coli cell (10 8 CFU/ml) were inactivated in 40 min in the presence of 2 g/l ZnO. Photocatalytic inactivation of bacteria was found to follow first order kinetics with the highest rate constants being 4.5 )/10 (1 and 2.2 )/10 (1 /min for E. coli and L. Helveticus , respectively, treated with 2 g/l ZnO. A similar bactericidal tendency was found in the UV Á/TiO 2 system, where the rate constants were 3.7 )/10 (1 and 1.8)/10 (1 / min for E. coli and L. Helveticus , respectively. The use of air as the purging gas, providing a stronger oxidising environment to both strains, gives a higher catalytic effect on bacteria inactivation than that of nitrogen. #

Nanoengineered fluorescent response is reported from semiconductor core−shell (CdSe/ZnS) quantum dots in proximity to the surface plasmon polariton field of periodic Ag nanoparticle arrays. Tuning the surface plasmon polariton resonance to the quantum dot exciton emission band results in an enhancement of up to ∼50-fold in the overall fluorescence efficiency, in a design where each Ag nanoparticle is interconnected by a continuous Ag thin film. Propagating modes of surface plasmon resonances have a direct impact on the fluorescence enhancement.

A self-healing dielectric elastomer is achieved by the incorporation of metal-ligand coordination as crosslinking sites in non-polar polydimethylsiloxane (PDMS) polymers. The ligand is 2,2'-bipyridine-5,5'-dicarboxylic amide while the metal salts investigated here are Fe2+ and Zn2+ with various counter anions. The kinetically labile coordination between Zn2+ and bipyridine endows the polymer fast self-healing ability at ambient condition. When integrated into organic field-effect transistors (OFETs) as gate dielectrics, transistors with FeCl2 and ZnCl2 salts crosslinked PDMS exhibited increased dielectric constants compared to PDMS and demonstrated hysteresis-free transfer characteristics, owing to the low ion conductivity in PDMS and the strong columbic interaction between metal cations and the small Cl- anions which can prevent mobile anions drifting under gate bias. Fully stretchable transistors with FeCl2-PDMS dielectrics were fabricated and exhibited ideal transfer char...

In this study, we investigated the application of sludge waste obtained from a coal mine drainage treatment facility that treats acid mine drainage (designated as AMD) from metal-mine water. The coal mine drainage sludge (designated as CMDS), which contained 70% goethite and 30% calcite, was utilized as a sorption material for Cu(II) and Zn(II) removal from an aqueous solution of metallic mine drainage. The equilibriums and kinetics were investigated during a series of batch adsorption experiments. The Langmuir model was used to fit the equilibrium data, resulting in the best fits. The removal efficiencies were controlled by solution pH, temperature, initial concentration of heavy metal, sorbent amount and contact time. The pseudo-second-order kinetic model was used to fit the kinetic data, providing a good correlation with the experimental data. The results of a thermodynamic study showed that the activation energies (EA) were 3.75 and 1.75 kJ mol-1 for the adsorption of Cu(II) and Zn(II) on to CMDS at pH 5.5. These values of activation energy could correspond to physisorption. The positive values obtained for both the standard enthalpy change, Δ0, and the standard entropy change, ΔS0, suggest that the adsorption of Cu(II) and Zn(II) on to the CMDS was an endothermic reaction and that randomness increased at the solid-liquid interface during the adsorption of Cu(II) and Zn(II) on to the CMDS. The adsorption process also followed a pseudo-second-order kinetic model. © 2010 Taylor & Francis.

http://www.ncbi.nlm.nih.gov/pubmed/21046950
http://www.tandfonline.com/doi/abs/10.1080/09593330903573215

Reactions of ZrCl 4 and single or mixed linear dicarboxylic acids bearing methyl or azide groups lead to highly stable isoreticular metal−organic frameworks (MOFs) with content-tunable, accessible, reactive azide groups inside the large pores. These Zr-based MOFs offer an ideal platform for pore surface engineering by anchoring various functional groups with controlled loadings onto the pore walls via the click reaction, endowing the MOFs with tailor-made interfaces. Significantly, the framework and crystallinity of the functionalized MOFs are well-retained, and the engineered pore surfaces have been demonstrated to be readily accessible, thus providing more opportunities for powerful and broad applications of MOFs.

Gluconacetobacter diazotrophicus an endophytic diazotroph also encountered as rhizosphere bacterium is reported to possess different plant growth promoting characteristics. In this study, we assessed the zinc solubilizing potential of G. diazotrophicus under in vitro conditions with different Zn compounds using glucose or sucrose as carbon sources. G. diazotrophicus showed variations in their solubilization potential with the strains used and the Zn compounds tested. G. diazotrophicus PAl5 efficiently solubilized the Zn compounds tested and ZnO was effectively solubilized than ZnCO 3 or Zn 3 (PO 4) 2. The soluble Zn concentration was determined in the culture supernatant through Atomic Absorption Spectrophotometer. Gas chromatography coupled Mass Spectrometry analysis revealed 5-ketogluconic acid, a derivative of gluconic acid as the major organic acid produced by G. diazotrophicus PAl5 cultured with glucose as carbon source. This organic anion may be an important agent that helped in the solubilization of insoluble Zn compounds.

The contribution of various bacterial surface functional groups to adhesion at hematite and ZnSe surfaces was examined using attenuated total reflectance (ATR) Fourier transform infrared (FTIR) spectroscopy. When live Shewanella oneidensis, Pseudomonas aeruginosa, and Bacillus subtilis cells were introduced to a horizontal hematite (R-Fe 2 O 3 )coated internal reflection element (IRE), FTIR peaks emerged corresponding to bacterial phosphate group binding. These IR peaks were not observed when bacteria were introduced to the uncoated ZnSe IRE. When cells were added to colloidal suspensions of R-Fe 2 O 3 at pH 7, spectra included peaks corresponding to P-OFe and ν(COOH), the latter being attributed to bridging of carboxylate at mineral surface OH groups. Selected model organic compounds with P-containing functionalities (phenylphosphonic acid [PPA], adenosine 5′-monophosphate [AMP], 2′-deoxyadenyl-(3′f5′)-2′-deoxyadenosine [DADA], and deoxyribonucleic acid [DNA]) produce spectra with similar peaks corresponding to P-OFe when adsorbed to R-Fe 2 O 3 . The data indicate that both terminal phosphate/phosphonate and phosphodiester groups, either exuded from the cell or present as surface biomolecules, are involved in bacterial adhesion to Fe-oxides through formation of innersphere Fe-phosphate/phosphonate complexes. Figure 1. Chemical structures of P-containing model compounds used for ATR-FTIR experiments.

In this study, activated carbons were prepared from sugar beet bagasse by chemical activation and the prepared activated carbons were used to remove nitrate from aqueous solutions. In chemical activation, ZnCl 2 was used as chemical agent. The effects of impregnation ratio and activation temperature were investigated. The produced activated carbons were characterized by measuring their porosities and pore size distributions. The microstructure of the activated carbons was examined by scanning electron microscopy (SEM). The maximum specific surface area of the activated carbon was about 1826 m 2 /g at 700°C and at an impregnation ratio of 3:1. The resulting activated carbon was used for removal of nitrate from aqueous solution. The effects of pH, temperature and contact time were investigated. Isotherm studies were carried out and the data were analyzed by Langmuir, Freundlich and Temkin equations. Three simplified kinetic models were tested to investigate the adsorption mechanism.

An electrochemical immunoassay protocol for the simultaneous measurements of proteins, based on the use of different inorganic nanocrystal tracers is described. The multiprotein electrical detection capability is coupled to the amplification feature of electrochemical stripping transduction (to yield fmol detection limits) and with an efficient magnetic separation (to minimize nonspecific adsorption effects). The multianalyte electrical sandwich immunoassay involves a dual binding event, based on antibodies linked to the nanocrystal tags and magnetic beads. Carbamate linkage is used for conjugating the hydroxyl-terminated nanocrystals with the secondary antibodies. Each biorecognition event yields a distinct voltammetric peak, whose position and size reflects the identity and level, respectively, of the corresponding antigen. The concept is demonstrated for a simultaneous immunoassay of 2 -microglobulin, IgG, bovine serum albumin, and C-reactive protein in connection with ZnS, CdS, PbS, and CuS colloidal crystals, respectively. These nanocrystal labels exhibit similar sensitivity. Such electrochemical coding could be readily multiplexed and scaled up in multiwell microtiter plates to allow simultaneous parallel detection of numerous proteins or samples and is expected to open new opportunities for protein diagnostics and biosecurity.

We present a single particle fluorescence resonance energy transfer (spFRET) study of freely diffusing self-assembled quantum dot (QD) bioconjugate sensors, composed of CdSe-ZnS core-shell QD donors surrounded by dye-labeled protein acceptors. We first show that there is direct correlation between single particle and ensemble FRET measurements in terms of derived FRET efficiencies and donor-acceptor separation distances. We also find that, in addition to increased sensitivity, spFRET provides information about FRET efficiency distributions which can be used to resolve distinct sensor subpopulations. We use this capacity to gain information about the distribution in the valence of self-assembled QDprotein conjugates and show that this distribution follows Poisson statistics. We then apply spFRET to characterize heterogeneity in single sensor interactions with the substrate/target and show that such heterogeneity varies with the target concentration. The binding constant derived from spFRET is consistent with ensemble measurements.

High spatial-resolution secondaryion microprobespectrometry, synchrotron radiation Fourier-transform infraredspectroscopy and polyacrylamide gel analysis demonstrate the intimateassociation of proteins with spheroidal aggregates of biogenic zincsulfide nanocrystals, an example of extracellular biomineralization.Experiments involving synthetic ZnS nanoparticles and representativeamino acids indicate a driving role for cysteine in rapid nanoparticleaggregation. These findings suggest that microbially-derivedextracellular proteins can limit dispersal of nanoparticulatemetal-bearing phases, such as the

Background: Zinc deficiency is commonly prevalent in children in developing countries and plays a role in decreased immunity and increased risk of infection. Preventive zinc supplementation in healthy children can reduce mortality due to common causes like diarrhea, pneumonia and malaria. The main objective was to determine all-cause mortality and cause-specific mortality and morbidity in children under five in developing countries for preventive zinc supplementation. Data sources/ review methods: A literature search was carried out on PubMed, the Cochrane Library and the WHO regional databases to identify RCTs on zinc supplementation for greater than 3 months in children less than 5 years of age in developing countries and its effect on mortality was analyzed.

Nanometre-sized inorganic dots, wires and belts have a wide range of electrical and optical properties, and variable mechanical stability and phase-transition mechanisms that show a sensitive dependency on size, shape and structure. The optical properties of the semiconductor ZnS in wurtzite structures are considerably enhanced, but the lack of structural stability limits technological applications. Here, we demonstrate that morphology-tuned wurtzite ZnS nanobelts show a particular low-energy surface structure dominated by the ±{210} surface facets. Experiments and calculations show that the morphology of ZnS nanobelts leads to a very high mechanical stability to ∼6.8 GPa, and also results in an explosive mechanism for the wurtzite-to-sphalerite phase transformation together with in situ fracture of the nanobelts. ZnS wurtzite nanobelts provide a model that is useful not only for understanding the morphology-tuned stability and transformation mechanism, but also for improving synthesis of metastable nanobelts with quantum effects for electronic and optical devices. Z nS has been extensively investigated as an important wideband-gap semiconductor (3.6 eV). It is one of the oldest and probably one of the most important materials in the electronics industry with a wide range of applications including light-emitting diodes and efficient phosphors in flatpanel displays 1 . An assortment of luminescent properties excited by ultraviolet, X-ray, cathode ray or electrical currents have been observed by doping ZnS with various metals 2 . Excellent light transmission with a high index of refraction (2.27 at 1 μm) also makes ZnS useful in photonic crystal devices that operate in the region from visible to near-infrared 3 .

We provide a detailed protocol for designing water-soluble CdSe–ZnS quantum dots (QDs) based on cap exchange of the native hydrophobic shell with dihydrolipoic acid (DHLA) ligands, and the preparation of functional QD bioconjugates for use in immunoassays. Our conjugation strategy is based on non-covalent self-assembly between DHLA-capped QDs and protein appended with either an electrostatic attachment domain (namely, the basic

There is a growing interest in using semiconductor quantum dots (QDs) as optical labels for biosensing events. [1] The sizecontrolled fluorescence properties of QDs, [2] the high fluorescence quantum yields of QDs, [3] and their stability against photobleaching makes QDs superior optical labels for multiplexed analysis of antigen-antibody complexes, nucleic acid-DNA hybrids, [6] and other biorecognition complexes. QDs were also applied to monitor biocatalytic transformations using fluorescence resonance energy transfer (FRET) processes. FRET processes between CdSe/ZnS QDs and dye units incorporated into replicated DNA systems or into telomers were used to probe the activities of polymerase and telomerase, respectively. Similarly, FRET reactions were used to monitor the biocatalytic cleavage of peptides by hydrolytic enzymes. [9] Alternatively, electron-transfer quenching of QDs by quinone-functionalized peptides was used to detect the activity of tyrosinase, and the hydrolytic cleavage of the quinone-modified peptide and the restoration of the fluorescence of the QDs were used to probe the activities of tyrosinase and thrombin, respectively. In all of these QD assays for monitoring enzyme activities, it is mandatory to include a quencher (energy or electron-transfer quencher) in the analyzed samples as a reporter unit. Also, for each of the enzymes, a specific assay needs to be developed.

Recent studies on the speciation of Zn in contaminated soils confirmed the formation of Zn-layered double hydroxide (LDH) and Zn-phyllosilicate phases. However, no information on the kinetics of the formation of those phases under field conditions is currently available. In the present study, the transformation of Zn in a field soil artificially contaminated with ZnO containing filter dust from a brass foundry was monitored during 4 years using extended X-ray absorption fine structure (EXAFS) spectroscopy. Soil sections were studied by µ-X-ray fluorescence (µ-XRF) and µ-EXAFS spectroscopy. EXAFS spectra were analyzed by principal component analysis (PCA) and linear combination fitting (LCF). The results show that ZnO dissolved within 9 months and that half of the total Zn reprecipitated. The precipitate was mainly of the Zn-LDH type (>75%). Only a minor fraction (<25%) may be of Zn-phyllosilicate type. The remaining Zn was adsorbed to soil organic and inorganic particles. No significant changes in Zn speciation occurred from 9 to 47 months after the contamination. Thermodynamic calculations show that both Zn-LDH and Zn-phyllosilicate may form in the presence of ZnO but that the formation of Zn-phyllosilicate would be thermodynamically favored. Thus, the dominance of Zn-LDH found by spectroscopy suggests that the formation of the Zn precipitates was not solely controlled by thermodynamics but also contained a kinetic component. The rate-limiting step could be the supply of Al and Si from soil minerals to the Zn-rich solutions around dissolving ZnO grains.

We report the synthesis, the structural and optical characterization of CdSe/CdS/ZnS "double shell" nanorods and their exploitation in cell labeling experiments. To synthesize such nanorods, first "dotin-a-rod" CdSe(dot)/CdS(rod) core/shell nanocrystals were prepared. Then a ZnS shell was grown epitaxially over these CdSe/CdS nanorods, which led to a fluorescence quantum yield of the final core-shell-shell nanorods that could be as high as 75%. The quantum efficiency was correlated with the aspect ratio of the nanorods and with the thickness of the ZnS shell around the starting CdSe/CdS rods, which varied from 1 to 4 monolayers (as supported by a combination of X-ray diffraction, elemental analysis with inductively coupled plasma atomic emission spectroscopy and high resolution transmission electron microscopy analysis). Pump-probe and time-resolved photoluminescence measurements confirmed the reduction of trapping at CdS surface due to the presence of the ZnS shell, which resulted in more efficient photoluminescence. These double shell nanorods have potential applications as fluorescent biological labels, as we found that they are brighter in cell imaging as compared to the starting CdSe/CdS nanorods and to the CdSe/ZnS quantum dots, therefore a lower amount of material is required to label the cells. Concerning their cytotoxicity, according to the MTT assay, the double shell nanorods were less toxic than the starting core/shell nanorods and than the CdSe/ZnS quantum dots, although the latter still exhibited a lower intracellular toxicity than both nanorod samples.

To study Pseudomonas putida CZ1, having high tolerance to copper and zinc on the removal of toxic metals from aqueous solutions, the biosorption of Cu(II) and Zn(II) by living and nonliving P. putida CZ1 were studied as functions of reaction time, initial pH of the solution and metal concentration. It was found that the optimum pH for Zn(II) removal by living and nonliving cells was 5.0, while it was 5.0 and 4.5, respectively, for Cu(II) removal. At the optimal conditions, metal ion biosorption was increased as the initial metal concentration increased. The adsorption data with respect to both metals provide an excellent fit to the Langmuir isotherm. The binding capacity of living cells is significantly higher than that of nonliving cells at tested conditions. It demonstrated that about 40-50% of the metals were actively taken up by P. putida CZ1, with the remainder being passively bound to the bacterium. Moreover, desorption efficiency of Cu(II) and Zn(II) by living cells was 72.5 and 45.6% under 0.1 M HCl and it was 95.3 and 83.8% by nonliving cells, respectively. It may be due to Cu(II) and Zn(II) uptake by the living cells enhanced by intracellular accumulation.

Zinc deficiency is common in cirrhosis and has been tent is common in patients with advanced cirrhosis, involved in the altered nitrogen metabolism. In this particularly of alcohol origin, 2 but the biochemical basis study, we measured the effects of zinc supplementation for zinc deficiency is still unknown. Several factors, on the dynamics of amino acid-derived urea synthesis such as poor dietary intake, impaired intestinal absorpin cirrhosis with mild or latent encephalopathy. The hetion, and excessive urinary losses may be responsible patic conversion of amino acids into urea was studied in for reduced whole-body zinc content. 3

It has been suggested that ZIP7 (Ke4, Slc39a7) belongs to the ZIP family of zinc transporters. Transient expression of the V5-tagged human ZIP7 fusion protein in CHO cells led to elevation of the cytoplasmic zinc level. However, the precise function of ZIP7 in cellular zinc homeostasis is not clear. Here we report that the ZIP7 gene is ubiquitously expressed in human and mouse tissues. The endogenous ZIP7 was associated with the Golgi apparatus and was capable of transporting zinc from the Golgi apparatus into the cytoplasm of the cell. Moreover, by using the yeast mutant strain ⌬zrt3 that was defective in release of stored zinc from vacuoles, we found that ZIP7 was able to decrease the level of accumulated zinc and in the meantime to increase the nuclear/cytoplasmic labile zinc level in the ZIP7-expressing zrt3 mutant. We showed that the protein expression of ZIP7 was repressed under zinc-rich condition, whereas there were no effects of zinc on ZIP7 gene expression and intracellular localization. Neither did zinc deficiency affect the intracellular distribution of ZIP7 in mammalian cells. Our study demonstrates that ZIP7 is a functional zinc transporter that acts by transporting zinc from the Golgi apparatus to the cytoplasm of the cell.

With controlled nanometre-sized pores and surface areas of thousands of square metres per gram, metal-organic frameworks (MOFs) may have an integral role in future catalysis, filtration and sensing applications. In general, for MOF-based device fabrication, well-organized or patterned MOF growth is required, and thus conventional synthetic routes are not suitable. Moreover, to expand their applicability, the introduction of additional functionality into MOFs is desirable. Here, we explore the use of nanostructured poly-hydrate zinc phosphate (α-hopeite) microparticles as nucleation seeds for MOFs that simultaneously address all these issues. Affording spatial control of nucleation and significantly accelerating MOF growth, these α-hopeite microparticles are found to act as nucleation agents both in solution and on solid surfaces. In addition, the introduction of functional nanoparticles (metallic, semiconducting, polymeric) into these nucleating seeds translates directly to the fabrication of functional MOFs suitable for molecular size-selective applications.

This study investigated the involvement of NMDA receptors and the l-arginine-nitric oxide (NO) pathway in the antidepressant-like effects of zinc in the forced swimming test (FST). The immobility times in the FST and in the tail suspension test (TST) were reduced by zinc chloride (ZnCl 2 , 30 and 10-30 mg/kg intraperitoneal (i.p.), respectively). The doses active in the FST and TST reduced locomotor activity in an open-field. The antidepressant-like effect of ZnCl 2 in the FST was prevented by pre-treatment of animals with guanosine 5 -monophosphate (GMP), ascorbic acid, l-arginine, or S-nitroso-N-acetyl-penicillamine (SNAP), but not with d-arginine, administered at doses that per se produced no anti-immobility effect. The immobility time of mice treated with ZnCl 2 + MK-801 was not different from the result obtained with ZnCl 2 or MK-801 alone, but ZnCl 2 + imipramine had a greater effect in the FST than administration of either drug alone. Pre-treatment of animals with a sub-threshold dose of ZnCl 2 prevented the anti-immobility effect of MK-801, ketamine, GMP, l-arginine or N G -nitro-l-arginine (l-NNA), but did not alter the effect of imipramine or fluoxetine. Taken together, the results demonstrate that zinc produced an antidepressant-like effect that seems to be mediated through its interaction with NMDA receptors and the l-arginine-NO pathway.

In the primary structure of protein kinase C, the presence of a putative metal-binding site has been suggested (Parker, P.J., Coussens, L., Totty, N., Rhee, L., Young, S., Chen, E., Stabel, S., Waterfield, M.D., and Ullrich, A. (1986) Science 233, 853-859). In the present report, we demonstrate that the most abundant intracellular heavy metal, zinc, can increase the activity of cytosolic protein kinase C. Zinc reversibly binds the enzyme to plasma membranes, and it may contribute to the calcium-induced binding as well. The intracellular heavy metal chelator N,N,N&#39;,N&#39;-tetrakis(2-pyridylmethyl) ethylenediamine prevents the phorbol ester- and antigen-induced translocation of protein kinase C. This effect can be totally reversed by the concomitant addition of Zn2+, while Fe2+ and Mn2+ are only partially counteractive. Our results suggest that zinc can activate protein kinase C and contributes to its binding to plasma membranes in T lymphocytes induced by Ca2+, phorbol ester, or ...

Two materials were produced from sewage sludge by: (1) pyrolysis of dried sewage sludge (PS); (2) chemical activation of dried sewage sludge with ZnCl 2 followed by pyrolysis (AS). The aim was to study the application of these materials for metal purification from water and to determine the efficiency of each material. Although AS displayed higher capacity, both PS and AS were able to adsorb these metals and the preferential order was equal: Hg(II) > Pb(II) > Cu(II) > Cr(III). For each metal-adsorbent pair, metal adsorption was highly pH dependent. In all cases the equilibrium was well described both by the Langmuir and the Freundlich isotherms. At the corresponding optimum pH, AS showed the following adsorption capacities: 175.4, 64.1, 30.7 and 15.4 mg/g of Hg(II), Pb(II), Cu(II) and Cr(III), respectively. These results indicate the potential application of these sewage sludge based adsorbents for the treatment of metal polluted effluents.

Protein tyrosine phosphatases (PTPases) are likely to play important roles in insulin action. We recently demonstrated that the nontransmembrane PTPase PTP1B can act as a negative modulator of insulinstimulated translocation of GLUT4. We now examine the role of PTP-␣ and PTP-(two transmembrane PT-Pases) in this metabolic action of insulin. Rat adipose cells were transfected with either PTP-␣ or PTP-and effects of these PTPases on the translocation of a cotransfected epitope-tagged GLUT4 were studied. Cells overexpressing wild-type PTP-␣ had significantly lower levels of cell surface GLUT4 in response to insulin and a threefold decrease in insulin sensitivity when compared with control cells expressing only tagged GLUT4. Co-overexpression of PTP-␣ and PTP1B did not have additive effects, suggesting that these PTPases share common substrates. Cells overexpressing either wild-type PTPor catalytically inactive mutants of PTP-␣ had dose-response curves similar to those of control cells. Since overexpression of PTP-␣, but not PTP-, had effects on translocation of GLUT4, our data suggest that PTP␣ may be a specific negative modulator of insulin-stimulated glucose transport.

The photocatalytic disinfection capability of the natural semiconducting mineral sphalerite is studied here for the first time. Natural sphalerite can completely inactivate 1.5 Â 10 7 cfu/mL E. coli K-12 within 6 h under visible light irradiation. The photocatalytic disinfection mechanism of natural sphalerite is investigated using multiple scavengers. The critical role that electrons play in bactericidal actions is experimentally demonstrated. The involvement of H 2 O 2 in photocatalytic disinfection is also confirmed using a partition system combined with different scavengers. Moreover, the photocatalytic destruction of bacterial cells is observed through transmission electron microscopic analysis. A catalase activity study reveals that antioxidative enzyme activity is high in the initial stage of photocatalytic disinfection but decreases with time due to damage to enzymatic functioning. Natural sphalerite is abundant and easy to obtain and possesses excellent visible-light photocatalytic activity. These superior properties make it a promising solar-driven photocatalyst for large-scale cost-effective wastewater treatment.

RNA-degrading enzymes play an important role in regulating gene expression, and sequence analyses have revealed significant homology among several plant RNA-degrading enzymes. In this study we surveyed crude extracts of the aboveground part of the common wheat (Triticum aestivum L.) and the cultivated barley (Hordeum vulgate L.) for major RNA-degrading enzymes using a substrate-based SDS-PAGE assay. Fifteen wheat and fourteen barley RNAdegrading enzymes, with apparent molecular masses ranging from 16.3 to 40.1 kD, were identified. These RNA-degrading enzymes were characterized by their response to pH changes and addition o fED TA and ZnCl2 to the preincubation or incubation buffers. The 33.2-to 40.1-kD wheat and barley, 31.7-kD wheat, and 32. O-kD barley enzyme activities were inhibited by both zinc and EDTA and were relatively tolerant to alkaline environment. The 22. 7-to 28.2-kD enzymes were inhibited by zinc but stimulated by EDTA. The 18.8-kD enzyme exists in both wheat and barley. It was active in an acid environment, was inhibited by zinc, but was not affected by EDTA. Two enzyme activities (31.0 and 32.0 kD) are unique to the common wheat. KEY WORDS: Ttqticum aestivum L.; Hordeum vulgate L.; RNase; DNase; phylogenesis. INTRODUCTION RNA-degrading enzymes catalyze the editing and decay of RNA molecules and thus have an important role in regulating gene expression (Donovan and