Addition of Zinc Sulfide Shells to Semiconducting Nanoparticles and its Effect on the Nanoparticle Fluorescence Emission Properties

The addition of a ZnS shell to CdSe and CdS quantum dot cores was explored using various methods. Spectrophotometry was used to assess the success of ZnS overcoating, which produces both an increase in overall fluorescence and decrease in particle size distribution. A new method was developed, involving preheating of the zinc and sulfide precursor solutions, resulting in CdSe(ZnS) particles with improved fluorescence and a more uniform shell coating from oleylamine-capped CdSe core particles.

Genome sequence of Desulfovibrio sp. A2, a highly copper resistant, sulfate-reducing bacterium isolated from effluents of a zinc smelter at the Urals

Desulfovibrio sp. A2 is an anaerobic gram-negative sulfate-reducing bacterium with remarkable tolerance to copper. It was isolated from wastewater effluents of a zinc smelter at the Urals. Here, we report the 4.2-Mb draft genome sequence of Desulfovibrio sp. A2 and identify potential copper resistance mechanisms.

Effects of flame made zinc oxide particles in human lung cells - a comparison of aerosol and suspension exposures

Background Predominantly, studies of nanoparticle (NPs) toxicology in vitro are based upon the exposure of submerged cell cultures to particle suspensions. Such an approach however, does not reflect particle inhalation. As a more realistic simulation of such a scenario, efforts were made towards direct delivery of aerosols to air-liquid-interface cultivated cell cultures by the use of aerosol exposure systems. This study aims to provide a direct comparison of the effects of zinc oxide (ZnO) NPs when delivered as either an aerosol, or in suspension to a triple cell co-culture model of the epithelial airway barrier. To ensure dose–equivalence, ZnO-deposition was determined in each exposure scenario by atomic absorption spectroscopy. Biological endpoints being investigated after 4 or 24h incubation include cytotoxicity, total reduced glutathione, induction of antioxidative genes such as heme-oxygenase 1 (HO–1) as well as the release of the (pro)-inflammatory cytokine TNFα. Results Off-gases released as by-product of flame ZnO synthesis caused a significant decrease of total reduced GSH and induced further the release of the cytokine TNFα, demonstrating the influence of the gas phase on aerosol toxicology. No direct effects could be attributed to ZnO particles. By performing suspension exposure to avoid the factor “flame-gases”, particle specific effects become apparent. Other parameters such as LDH and HO–1 were not influenced by gaseous compounds: Following aerosol exposure, LDH levels appeared elevated at both timepoints and the HO–1 transcript correlated positively with deposited ZnO-dose. Under submerged conditions, the HO–1 induction scheme deviated for 4 and 24h and increased extracellular LDH was found following 24h exposure. Conclusion In the current study, aerosol and suspension-exposure has been compared by exposing cell cultures to equivalent amounts of ZnO. Both exposure strategies differ fundamentally in their dose–response pattern. Additional differences can be found for the factor time: In the aerosol scenario, parameters tend to their maximum already after 4h of exposure, whereas under submerged conditions, effects appear most pronounced mainly after 24h. Aerosol exposure provides information about the synergistic interplay of gaseous and particulate phase of an aerosol in the context of inhalation toxicology. Exposure to suspensions represents a valuable complementary method and allows investigations on particle-associated toxicity by excluding all gas–derived effects.

Zinc Compounds as Models for Zinc Metalloenzymes

In this study zinc compounds containing coordination spheres similar to those in zinc metalloenzymes were identified as targets for potential investigation by ssNMR. The title compounds, zinc catena-(tetrakis(µ2-Benzoato-O,O’))-di-zinc(II), diaquabis(salicylato) zinc, Zn2PSAP(OAc)2, cis-diaqua-diglycolatozinc (II), hexaaquazinc(II)p-hydroxybenzoate dihydrate, and catena-((µ-3-nitrobenzoato) (µ-3-nitrobenzoic acid)sodium) were synthesized, crystallized and their structures solved using single crystal Xray diffraction

From endoplasmic reticulum to secretory granules: role of zinc in the secretory pathway of growth hormone

Endocrine and neuroendocrine cells differ from cells which rapidly release all their secreted proteins in that they store some secretory proteins in concentrated forms in secretory granules to be rapidly released when cells are stimulated. Protein aggregation is considered as the first step in the secretory granule biosynthesis and, at least in the case of prolactin and growth hormone, greatly depends on zinc ions that facilitate this process. Hence, regulation of cellular zinc transport especially that within the regulated secretory pathway is of importance to understand. Various zinc transporters of Slc30a/ZnT and Slc39a/Zip families have been reported to fulfil this role and to participate in fine tuning of zinc transport in and out of the endoplasmic reticulum, Golgi complex and secretory granules, the main cellular compartments of the regulated secretory pathway. In this review, we will focus on the role of zinc in the formation of hormone-containing secretory granules with special emphasis on conditions required for growth hormone dimerization/aggregation. In addition, we highlight the role of zinc transporters that govern the process of zinc homeostasis in the regulated hormone secretion.

Rapid endocytosis of copper-zinc superoxide dismutase into human endothelial cells: role for its vascular activity

Cytosolic CuZn-SOD (SOD1) is a dimeric, carbohydrate-free enzyme with a molecular weight of about 32 kDa and also circulates in human blood plasma. Due to its molecular mass it has been believed that the enzyme cannot penetrate the cell membrane. Here we report that rapid endocytosis of FITC-CuZn-SOD into human endothelial cells occurs within 5 min. Moreover, relaxation of rat aortic rings in response to CuZn-SOD is associated with a lag time of 45-60 s and only observed in the presence of intact endothelial cells. The results indicate acute and rapid endothelial cell endocytosis of CuZn-SOD, possibly via activation of a receptor-mediated pathway. Intracellular uptake via endocytosis may contribute to the vascular effects of CuZn-SOD, including vasodilation, and is likely to play a role in regulation of vascular tone and diseases such as atherosclerosis.

Two alpha subunits and one beta subunit of meprin zinc-endopeptidases are differentially expressed in the zebrafish Danio rerio

Meprins are members of the astacin family of metalloproteases expressed in epithelial tissues, intestinal leukocytes and certain cancer cells. In mammals, there are two homologous subunits, which form complex glycosylated disulfide-bonded homo- and heterooligomers. Both human meprin alpha and meprin beta cleave several basement membrane components, suggesting a role in epithelial differentiation and cell migration. There is also evidence that meprin beta is involved in immune defence owing to its capability of activating interleukin-1beta and the diminished mobility of intestinal leukocytes in meprin beta-knockout mice. Here we show for the first time by reverse transcription PCR, immunoblotting and immunofluorescence analyses that meprins are expressed not only in mammals, but also in the zebrafish Danio rerio. In contrast to the human, mouse and rat enzymes, zebrafish meprins are encoded by three genes, corresponding to two homologous alpha subunits and one beta subunit. Observations at both the mRNA and protein level indicate a broad distribution of meprins in zebrafish. However, there are strikingly different expression patterns of the three subunits, which is consistent with meprin expression in mammals. Hence, D. rerio appears to be a suitable model to gain insight into the basic physiological functions of meprin metalloproteases.

Lymphocyte transformation by insulin and insulin-zinc suspensions

The lymphocyte transformation response to the mitogen phytohaemagglutinin (PHA) was determined in 15 well controlled insulin-dependent diabetics (IDD) with a history of insulin allergy or an acute insulin allergy. There was no significant difference in the PHA response of IDD and normal subjects matched in respect of age and sex. The response of peripheral blood lymphocytes to insulin (Actrapid) and an insulin zinc suspension (Monotard) was also determined. Fifty-three percent of IDD gave a positive reaction to Actrapid. Monotard produced positive reactions both in IDD and normal subjects. In normal subjects, a close correlation between the stimulation indices of Monotard and PHA was found (r = 0 . 966) suggesting that these stimulations depend on a common parameter namely, the reactivity to mitogens.

BENEFICIATION OF HIGH-MgO SEDIMENTARY PHOSPHATE ORES

Dolomite [CaMg(CO3)2] is an intolerable impurity in phosphate ores due to its MgO content. Traditionally, the Florida phosphate industry has avoided mining high-MgO phosphate reserves due to the lack of an economically viable process for removal of dolomite. However, as the high grade phosphate reserves become depleted, more emphasis is being put on the development of a cost effective method for separating dolomite from high-MgO phosphate ores. In general, the phosphate industry demands a phosphate concentrate containing less than 1%MgO. Dolomite impurities have mineralogical properties that are very similar to the desired phosphate minerals (francolite), making the separation of the two minerals very difficult. Magnesium is primarily found as distinct dolomite-rich pebbles, very fine dolomite inclusions in predominately francolite pebbles, and magnesium substituted into the francolite structure. Jigging is a gravity separation process that attempts to take advantage of the density difference between the dolomite and francolite pebbles. A unique laboratory scale jig was designed and built at Michigan Tech for this study. Through a series of tests it was found that a pulsation rate of 200 pulse/minute, a stroke length of 1 inch, a water addition rate of 0.5gpm, and alumina ragging balls were optimum for this study. To investigate the feasibility of jigging for the removal of dolomite from phosphate ore, two high-MgO phosphate ores were tested using optimized jigging parameters: (1) Plant #1 was sized to 4.00x0.85mm and contained 1.55%MgO; (2) Plant #2 was sized to 3.40mmx0.85mm and contained 3.07% MgO. A sample from each plant was visually separated by hand into dolomite and francolite rich fractions, which were then analyzed to determine the minimum achievable MgO levels. For Plant #1 phosphate ore, a concentrate containing 0.89%MgO was achieved at a recovery of 32.0%BPL. For Plant #2, a phosphate concentrate containing 1.38%MgO was achieved at a recovery of 74.7%BPL. Minimum achievable MgO levels were determined to be 0.53%MgO for Plant #1 and 1.15%MgO for Plant #2.

The Effect of Cobalt Upon Current Efficiency in the Electrolysis of Zinc Sulphate Solutions

The detrimental effect of the presence of cobalt upon the current efficiency, in the commercial production of zinc by electrolysis, has been recognized for some time. Most authorities differ upon the maximum amount of cobalt allowable. This is due to the fact that the presence of other impurities either increases or diminishes the detrimental effects of the cobalt. The following tests were made with the object in view of ascertaining the relation, if any, between the amount of cobalt present and the current efficiency during the electrolysis of an otherwise pure zinc sulfate solution. The results obtained from these observations indicate that there is little apparent relation between the cobalt concentration of a given solution of zinc sulfate and the current efficiency that may be obtained on the electrolysis of that solution. For certain cobalt concentrations, however, it was noted that the time factor played an important part.