Zinc Precipitation Research Articles

A new method for the isolation of histatins 1, 3, and 5 from parotid secretion using zinc precipitation.

Histatins, a family of small-molecular-weight, histidine-rich cationic salivary proteins, have been difficult to isolate in an efficient way by conventional procedures due to their anomalous interactions with chromatographic resins. In the present study we explored the possibility of developing a new isolation procedure based on recent observations that histatins associate with various metal ions, including zinc. Since solubility studies showed that histatin 5 forms precipitates with zinc under alkaline conditions, we investigated whether this characteristic could be exploited for the preparative isolation of histatins from salivary secretions. A fast and efficient two-step procedure was developed using zinc precipitation of histatins from human parotid secretion followed by final purification using reversed-phase high-performance liquid chromatography (HPLC). Analysis of zinc precipitates by Tricine-SDS-PAGE, cationic PAGE, HPLC, and mass spectrometry revealed the presence of the three major histatins, 1, 3, and 5, as well as statherin. The histatin yield obtained by the precipitation step was approximately 90%. Therefore, zinc precipitation of histatins from glandular salivary secretions is a novel, rapid, and effective means for the isolation of these proteins.

ZnGep2 : Optical Transparency and Melt Composition

AbstractThe paper presents the results of TEM and optical transparency measurements on ZnGeP2 crystals grown by the vertical Bridgman technique from melts of differing compositions. The TEM study reveals the presence of nano-dimensional precipitates of second phases: zinc and ZnxPy precipitation occurs in material grown from Zn-rich melts and GeP from the deficient melts. The precipitation is associated with cooling through the retrograde solidus at a temperature below the melting point. Elastic stress fields are also observed. The relationships between the precipitates and elastic stresses and between precipitation and optical losses are investigated

Tratamiento metalúrgico de los óxidos Waelz mediante lixiviación alcalina utilizando carbonato amónico

A method to carry out the treatment of the Waelz oxides is proposed, and the principal stages implicated are studied laboratory-scale. The process consists of the oxides leaching with an ammonium carbonate/ammonia solution, followed the recovery of the zinc leached by means of its precipitation as zinc basic carbonate. The process stages that have been studied are: Waelz oxides leaching, loaded leach purification, zinc precipitation, zinc basic carbonate washing and zinc basic carbonate transformation. The designed treatment presents a null environmental impact, and more than 90 % of the zinc contained in the Waelz oxides, as well as 80 % of the copper and cadmium contents could be recovered. Also, the process presents great flexibility as soon as zinc could be recovered in the most convenient form (zinc metal, oxide or salt).

Precipitation of Metal Ions by Plant Polyphenols: Optimal Conditions and Origin of Precipitation

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

Negative staining with zinc-imidazole of gel electrophoresis-separated nucleic acids.

Zinc and imidazole salts were applied for the detection of nucleic acids on either polyacrylamide of agarose gels. After electrophoresis, polyacrylamide gels are washed in distilled water to remove most of the residual electrophoresis reagents, then incubated in 10 mM zinc sulfate for 10 min, and subsequently immersed in 0.2 M imidazole for 3 min. As a result, zinc salts precipitate on the gel surface, except in the positions occupied by nucleic acids, which appear as transparent, colorless bands. Staining of nucleic acids on agarose gels can be performed by incubation in 40 mM zinc sulfate for 10 min, followed by immersion in 0.2 M imidazole for 5 min to form a deep white-stained background. On soaking in 2 M imidazole for 45 min, the imidazole-induced zinc precipitate is removed from the positions were nucleic acids are located resulting in a negative image of colorless and transparent nucleic acid bands against a white background. The sensitivity of this stain ranges from 5 to 7 ng/band for small (from 1 to 0.2 kbp) DNA, from 7.8 to 13 ng/band for different 22-base oligonucleotides, from 62 to 125 ng/band for large (from 20 to 2 kbp) DNA, and is 1 microgram/band for human peripheral-blood monocyte RNA. After chelation of zinc with EDTA, the nucleic acids can be quantitatively recovered from the gel. The principal advantage of this technique over ethidium bromide staining is evident for preparative purposes. Using zinc-imidazole in the detection of purified pBACIB.1 (2.8 kbp) plasmid DNA and anti-HBsAg single chain Fv antibody fragment (0.7 kbp) DNA, followed by elution from gel slices, ligation and transformation of competent E. coli XL-1 Blue cells, the number of transformants notably increased from 280 (obtained with conventional ethidium bromide staining plus UV-irradiation at 312 nm) to 10,000.

Complex formation between transition metal ions and salicylglycine, a metabolite of aspirin

Ionization constant and complex formation constants of salicylglycine (1) in aqueous solution at 25°C and ionic strength 0.2 mol dm −3 KCl have been determined. The p K a values for the ligand are 3.44(1) and 8.24(4) and 1H NMR studies show that there is no further ionization at higher pH as was previously suggested. In the case of copper(II) there is no evidence for complex formation below pH 4 and the main species in solution at pH5 according to pH-metric and UV-vis spectrophotometric evidence in MLH − in which the ligand is bonded to the metal through the phenolate and carboxylate oxygen atoms and the deprotonated peptide nitrogen. The species ML also exists albeit in low concentrations. At pH10 the formation of MLH −2 resulting from ionization of an equatorial aquo ligand is observed. In the case of nickel(II) and zinc(II) no complex formation occurs below pH 6 but above this pH the species ML and MLH −1, the latter involving deprotonation of an aquo ligand, are observed although at pH ca 8 in the case of nickel(II) and pH ∼ 7.5 in the case of zinc(II) precipitation occurs.

Pyrite flotation from gold leach residues

GENMIN Process Research has been investigating the possibility of a low cost pyrite flotation process suitable for cyanidation leach residue. The flotation of auriferous pyrite in gold leach residues through traditional techniques is only possible after conditioning with sulphuric acid to overcome depression by cyanide and hydroxide. Recent testwork at both GENMIN Process Research and on site at Buffelsfontein Gold Mine suggested that the auriferous pyrite contained in the cyanide residues could be floated by using an amine as a collector. The amine float, although slow, gave 83% S (tot) recovery during rougher flotation. It was then found that washing and repulping the leach residue with fresh water results in pyrite which can be readily floated under alkaline conditions. Investigating further showed that it is in washing the cyanide residue filter cake prior to repulping that the depression of the pyrite is determined. In this way 95.3% S (tot) was recovered with the addition of fresh water, CuSO 4, SIBX and frother. Washing and repulping in plant water containing ±100 ppm cyanide, as is plant practice using barren cycle water from the zinc precipitation circuit (PPT) results in the effective depression of the pyrite. In the laboratory, only 2.9% S (tot) was recovered using this procedure.

Identification by microsequencing of lipopolysaccharide-induced proteins secreted by mouse macrophages.

The conditioned medium of the murine macrophage PU5.1.8 was analyzed by two-dimensional gel electrophoresis in order to detect LPS-induced proteins. Spots of interest were identified by microsequencing of internal peptides generated by limited in situ acid hydrolysis. In total conditioned medium, several monokines (TNF-alpha and macrophage inflammatory protein-1 alpha and 1 beta) were identified as LPS-induced spots. Because minor spots could be masked by the complexity of the 2-D pattern, conditioned medium was successively fractionated by zinc precipitation and affinity chromatography (Procion red and Con A agarose). Zinc supernatant fraction, Procion red flow-through, and Con A eluate fractions were further analyzed by 2-D gel electrophoresis for the presence of LPS-induced spots. In these fractions serum amyloid A3, lipocalin 24p3, cathepsin B, and plasminogen activator inhibitor-I were characterized as LPS-induced proteins secreted by macrophages. Lipocalin 24p3 protein was retrieved for the first time. In addition to these proteins that follow a classical secretory pathway, several cellular proteins (mainly ribosomal proteins) were retrieved as LPS-induced proteins in the conditioned medium. Control experiments argue against the obvious explanation that the latter observation is caused solely by cellular leakage.

Neurons of origin of zinc-containing pathways and the distribution of zinc-containing boutons in the hippocampal region of the rat

Recent methods allow the study of neurons that contain zinc in synaptic vesicles of their boutons (Timm-stainable boutons) by the intravital precipitation (local or throughout the CNS) of the vesicular zinc with selenium compounds and its subsequent retrograde transport to the parent neurons, where the precipitate can be silver enhanced. The present study is a description of the distribution of zinc-containing neurons, their possible connections and their terminal fields within the hippocampal region of the rat. Problems inherent to the methods are addressed. Finally, based on the results and a review of literature, the possible function of zinc in the hippocampal region is considered. Neurons which contain silver-enhanced precipitates were observed in layers II, V and VI of the lateral entorhinal area and in layers V and VI of the medial entorhinal area. In the parasubiculum, labeled cells were seen in layer II/III of the parasubiculum a and in layer V. Labeled cells in the presubiculum were concentrated in layers III and V, in the hippocampal pyramidal cell layer and the dentate granule cell layer, but neurons containing precipitates were largely absent from the subiculum. Zinc-containing axonal boutons defined subpopulations within principal hippocampal neuron populations. Within layer II of the lateral entorhinal cortex and the pyramidal cell layer for regio inferior deeply situated neurons were labeled, whereas superficially placed pyramidal cells were labeled in regio superior. The neuropil staining described in the present study corresponded to that found in earlier studies. However, glial and vascular staining or unspecific background were largely absent, and the neuropil staining could unequivocally be identified light microscopically. Methodological problems are most prominently reflected in unstained mossy fibers in some animals. Based on series from animals treated with decreasing doses of sodium selenite and increased survival times, this problem can be related to small amounts of circulating reactive selenium and a competition of zinc compartments (vesicles) for the selenium. Staining will fail where the competition prevents individual compartments from reaching a threshold amount of zinc precipitate for silver amplification. A guide to evaluate histological material is provided. The distribution of zinc-containing boutons and their cells of origin indicate that zinc-containing and zinc-negative projections are not organized as parallel pathways. The mossy fibers provide an example of a pure zinc-containing pathway. Projections from regio superior to the dorsal presubiculum are likely to be zinc-negative while projections from the same area to the subiculum are zinc-containing. Intrinsic projections originating in septal parts of regio inferior are zinc-negative and septal terminal staining in regio inferior must be derived from contralateral or temporal ipsilateral sources. Subicular efferent pathways appear pure zinc-negative. It is argued that the release of zinc may lend stability to synapses in areas where the density of N-methyl- d-aspartate receptors indicates a high potential for the modification of synaptic strength. Such synapses may provide basic processing capabilities to the hippocampal region, the alteration of which is not desirable once they have been established during development. Also, zinc may provide a transient protection against the progression of seizure-induced pathology.

Organic reagents for removing heavy metals from a 10-34-0 (N-P2O5-K2O) grade fertilizer solution and wet-process phosphoric acid

Fertilizer solutions and wet-process phosphoric acid (WPA) contain heavy metal impurities such as cadmium, zinc, lead, copper, manganese, and chromium. Trisodium trithiocyanuric acid (TMT-15), sodium trithiocarbonate (5% Na2CS3), and sodium polythiocarbonate (Thio-Red II) were evaluated as precipitating agents for heavy metals in a 10-34-0 (N-P2O5-K2O) grade fertilizer solution and WPA. A water-insoluble starch xanthate was also evaluated as an adsorbent for the heavy metals in 10-34-0 (N-P2O5-K2O) and WPA. Arsenic (24−99+%), cadmium (36−97+%), copper (98+%), mercury (96+%), lead (83−88+%), and zinc (8−83+%) precipitated from 10-34-0 (N-P2O5-K2O) upon the addition of each organic reagent, while levels of manganese and chromium were unaffected. Mercury (97+%), lead (75+%), cadmium (11−38%), copper (99+%), and chromium (3−35%) precipitated from WPA upon the addition of 5% Na2CS3 and Thio-Red II, while precipitation of manganese and zinc was negligible. The water-insoluble starch xanthate adsorbed mercury (96+%), copper (38−98+%), and lead (24−75%) from 10-34-0 (N-P2O5-K2O) and WPA while adsorption of arsenic, cadmium, manganese, chromium, and zinc was negligible.

Rapid thermal diffusion of zinc into GaAs

Rapid thermal diffusion of zinc into semi-insulating GaAs from spin-on Zn doped silica film was performed. Spin-on films act both as Zn diffusion sources and GaAs surface encapsulant layer against decomposition during the rapid thermal diffusion. The very shallowp + layers were obtained at a diffusion temperature of 900° C for 5 sec. Non-alloyed ohmic contacts to thesep + layers were achieved with an average contact resistivity of 2.4 × 10−6 Ω cm2. The interface is very smooth. The zinc diffusion coefficient for rapid thermal diffusion with effective diffusion time of 6 sec at 900° C was numerically calculated from SIMS profiles. In contrast to the common Longini-Weisberg-Blanc model, the rapid thermal diffusion is under nonequilibrium condition. Complications due to interstitial-substitutional nonequilibrium, vacancy supply resulted from the interface stress field, and zinc precipitation are briefly discussed.

Selective Separation of Cu, Zn, and As from Solution by Flotation Techniques

Abstract The selective precipitation and flotation of copper, zinc, and arsenic ions from dilute aqueous solutions were investigated. Phase separation was accomplished effectively by the dissolved-air technique for the production of fine gas bubbles, and a short-chain xanthate was applied as the collector for copper ions, dialkyldithiocarbamate for zinc, and ferric sulfate for the pentavalent arsenic. The procedures followed were ion flotation for copper and zinc, and adsorbing colloid flotation for arsenic (without a surfactant).

Algal mats, load structures, and synsedimentary sulfides in Revett quartzites of Montana and Idaho

Carbonate-rich patches in quartzites of the Revett Formation are due to algal mats in marine arenites of about a 1.3-b.y. age; some occur in growth positions on bedding planes, some on slumped foresets, but mostly they were disrupted by faster currents depositing heavy minerals as lag sediments. Discovery of stromatolites in the Revett Formation confirms the algal growths.Algal debris provided the food source for anaerobes which produced H 2 S for sulfide precipitation of copper (silver), lead, zinc, and iron in the zonal sequence typical of stratiform syngenetic sulfides. At the Troy mine, these sulfide zones cross the strata.Sulfides vary in grain size and aggregation and are classified into original fine disseminations, reworked aggregates formed during dewatering, and infilling of fractures and vein openings by lateral secretion. The relationship of fine sulfide disseminations to heavy minerals and to algal carbonate indicates deposition of minute sulfide grains with the sediment.A quartzite pillow which contained 24 sagged and folded layers, each layer with three sublayers of, first, heavy minerals, and then clean quartzite, both overlain by sulfide-rich quartzite, was examined and revealed the previously poorly understood mechanism of pillow growth contemporaneous with sedimentation-and in this example--also with sulfide precipitation.Better mineralization in arenites is ascribed, not to permeability, but to stronger currents depositing sand and causing increased mixing of the upper metal-bearing waters with the lower anoxic water, in which hydrogen sulfide precipitates selectively, first, copper and silver as minute sulfide grains. The sulfides are incorporated into the suspended sediment, which is then sorted by waxing and waning currents according to grain size and specific gravity into the varying proportions especially observed in the tripartite laminae of the 24 layers of the quartzite pillow described in detail.

The Precipitation and Dissolution of Zinc during Leaching of Cu‐Al‐Zn Alloys in Alkali Solutions

The leaching kinetics of a Cu‐39 weight percent (w/o) Al‐17.8 w/o Zn alloy over a range of leachant temperatures and concentrations were found to be liquid‐phase diffusion controlled within the porous reaction product layer of Raney copper. High concentrations in the leached grains at the product alloy interface result in deposition of significant amounts of . Further from this interface, the kinetics of secondary dissolution of from the porous copper are shown to be first order with respect to hydroxyl ion concentration. Because the coverage of copper by is frequently less than a monolayer, the secondary dissolution process is also dependent on residual zinc concentration. A Langmuir‐Hinshelwood adsorption model for the dissolution process, coupled with liquid‐phase diffusion of both and , is shown to describe accurately the zinc concentration profiles and to yield reasonable estimates of the diffusion coefficients.

The interaction of zinc(II) and phytic acid with soya bean glycinin

AbstractBinding of phytic acid to Zn(II) free glycinin was not observed in 0.5 M KCl at pH 6.2. The addition of varying quantities of phytic acid to a Zn(II)‐ glycinin system at pH 6.2 ([KCl]=0.5 M) initially resulted in binding of phytate and increased binding of Zn(II) to glycinin probably as a phytate‐Zn(II)‐glycinin complex. Further addition of phytate resulted in precipitation of zinc and protein. Bovine serum albumin also showed increased affinity for Zn(II) owing to the presence of phytic acid.Phytic acid‐Zn(II) precipitates have a capacity of removing glycinin from solution, presumably by surface adsorption. The presence of soluble Zn(II) inhibits this adsorption. Bovine serum albumin is removed from solution by phytic acid‐Zn(II) precipitates only when soluble zinc is present.

The effect of weak chelating agents on the removal of heavy metals by precipitation processes

AbstractParticle size distributions and heavy metal removals are presented for hydroxide precipitations and heavy metal removals are presented for hydroxide precipitation and sulfide precipitation of zinc and cadmium in the presence of several weak complexing agents, namely citrate, tartrate, and ammonia. The pH was held constant at pH 10.0 in these experiments. The presence of these weak complexing agents had little effect on the chemical equilibrium for both the hydroxide and sulfide systems due to their weak complexing ability with metal ions. The presence of the complexing agents does affect the particle size distribution, generally forming smaller particles. Particle size distributions are presented for the Zn(OH)2, ZnS, Cd(OH)2, and CdS systems (at pH 10.0) in the presence of the chelating agents citrate, tartrate, and ammonia. Sulfide precipitation exhibits a better particle size distribution and settling characteristics than the corresponding metal hydroxide precipitation for both zinc and cadmium.

The precipitation of sparingly‐soluble metal chromates from aqueous solution in the presence of chelating organic anions: Induction periods and nucleation rates

AbstractThe precipitation of barium, zinc, lead, copper and silver chromates was studied in the presence of the chelating organic anions gluconate, tartrate, citrate, aspartate, glutamate and E.D.T. Aate. Generally, these chelators complex the metal cation and reduce the free metal cation and mean metal chromate concentrations in solution. The rates of nucleation with microcrystallite formation were then markedly reduced and the induction periods increased from below 1 sec to well above 100,000 sec with increasing chelator/cation concentration ratio; the experimental results were expressed by the relations;magnified image The coefficients F at any metal chromate concentration were related in turn to the stability constants of the metal‐chelator complexes.

The Influence of pH, Water Hardness, and Alkalinity on the Acute Lethality of Zinc to Rainbow Trout (Salmo gairdneri)

The acute lethality of dissolved zinc to rainbow trout (Salmo gairdneri) was significantly increased at higher pH and lower hardness levels. Changes in pH from 5.5 to 7.0 increased zinc toxicity by factors of 2 to 5, depending on total hardness levels. A decrease in hardness from 386 to 31 mg CaCO3/L increased zinc toxicity by more than an order of magnitude at both pH levels. These effects of pH and hardness were not caused by changes in the chemical speciation of zinc. An increase in carbonate alkalinity from 8.4 to 24 mg CaCO3/L at pH 7.0 did not significantly alter zinc toxicity at either hardness level. Thus, carbonate alkalinity is not an important factor at or below pH 7.0. At low hardness, dissolved zinc was more than 10 times as toxic at pH 9.0 as at pH 5.5. Two competing mechanisms appear to operate: as the pH rises, dissolved zinc becomes increasingly toxic, but at higher pH levels it is increasingly replaced by zinc precipitate, which is of very low toxicity to fish.

Regeneration of zinc from the plasticization bath by a reagent method

Precipitation of zinc with sodium carbonate and filtration of the suspension formed is very efficient, if the precipitation is carried out in the presence of part of the preceding precipitate, that is, by the method of “precipitate recycling.”

The compatability of four trace elements in total parenteral nutrition infusions

Injection MTE-4 contains zinc (10 mg), copper (4 mg), manganese (1 mg) and chromium (40 μg). After addition to Synthamin-containing TPN regimens in 3 litre bags, there was no evidence for precipitation of any of the four elements after storage at 2–6°C for periods up to 4 months. The concentration of zinc, manganese and copper were measured after 24 h storage. Only zinc showed a lower than expected result, although the differences were small (about 6%) and probably due to inherent dilution and other errors difficult to control in the experimental design. This assessment is supported by the lack of evidence for precipitation of zinc. Elements in MTE-4 were not precipitated in Synthamin 17 for at least 2 days, although after longer periods copper residues were evident. Zinc precipitates were also recovered after long-term storage.