Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Zinc Compounds”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15Linked to original sources
PubMed2005

Changes in zinc speciation in field soil after contamination with zinc oxide.

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 micro-X-ray fluorescence (micro-XRF) and micro-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 bythermodynamics 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.

Absorption↗
PubMed2002

Reactions of hydroxymesitylboranes with metal alkyls: an approach to new sterically hindered (metaloxy)mesitylboranes.

Reactions of mesitylboronic acid with alkyl derivatives of aluminum R(3)Al (R = Me, Et, Bu(i)), gallium (Me(3)Ga), and zinc (Et(2)Zn) were investigated. The treatment of mesitylboronic acid, MesB(OH)(2), with trimethylgallium afforded the discrete dimer [mu-(MesB(OH)O)GaMe(2)](2) (1), which is the simple example of a O-metalated boronic acid with no hydrogen bonding in the crystal lattice. In addition, the reaction of dimesitylborinic acid, Mes(2)BOH, with diethylzinc produced the low-valent zinc compound [(mu-Mes(2)BO)ZnEt](2) (2), which was also characterized by X-ray diffraction.

Journal Article↗
PubMed2004

Palladium-catalyzed arylation of trimethylsilyl enolates of esters and imides. High functional group tolerance and stereoselective synthesis of alpha-aryl carboxylic acid derivatives.

A general procedure for the palladium-catalyzed arylation of trimethylsilyl enolates of esters and imides is reported. In the presence of ZnF2 or Zn(O-t-Bu)2 as an additive, the trimethylsilyl enolates of esters, including those bearing alpha-alkoxy derivatives, underwent arylation in high yield with high functional group tolerance. This arylation chemistry was extended to ester derivatives bearing chiral auxiliaries to form new tertiary stereocenters. The arylation of imides bearing the Evans auxiliary proceeded with selectivities up to 90% de. Further, the arylation of the ketal developed by Ley provided alpha-aryl glycolates with excellent diastereoselectivities (90 to >98% de). This reaction provides a convenient route to the synthesis of enantiopure alpha-aryl-alpha-hydroxy esters. Reactions conducted with Zn(O-t-Bu)2 as an additive occurred at room temperature to give enhanced diastereoselectivities with both chiral reagents. Mechanistic studies showed that the reaction conditions are neutral enough that the observed diastereomeric ratios reflect kinetic selectivities.

Acetals↗
PubMed2005

Bioaffinity sensing using biologically functionalized conducting-polymer nanowire.

A simple, one-step method for fabricating single biologically functionalized conducting-polymer (polypyrrole) nanowire on prepatterned electrodes and its application to biosensing was demonstrated. The biologically functionalized polypyrrole was formed by the electropolymerization of an aqueous solution of pyrrole monomer and the model biomolecule, avidin- or streptavidin-conjugated ZnSe/CdSe quantum dots, within 100 or 200 nm wide by 3 mum long channels between gold electrodes on prefabricated silicon substrate. When challenged with biotin-DNA, the avidin- and streptavidin-polypyrrole nanowires generated a rapid change in resistance to as low as 1 nM, demonstrating the utility of the biomolecule-functionalized nanowire as biosensor. The method offers advantages of direct incorporation of functional biological molecules into the conducting-polymer nanowire during its synthesis, site-specific positioning, built-in electrical contacts, and scalability to high-density nanoarrays over the reported silicon nanowire and carbon nanotube biosensors.

Biosensing Techniques↗
PubMed2005

Room-temperature Wurtzite ZnS nanocrystal growth on Zn finger-like peptide nanotubes by controlling their unfolding peptide structures.

ZnS nanocrystal, a class of wide-gap semiconductors, has shown interesting optical, electrical, and optoelectric properties via quantum confinement. For those applications, phase controls of ZnS nanocrystals and nanowires were critical to tune their physical properties to the appropriate ones. The wurtzite ZnS nanocrystal growth at room temperature is the useful fabrication; however, the most stable ZnS structure in nanoscale is the zinc blende (cubic) structure, and scientists have just begun exploring the room-temperature synthesis of the wurtzite (hexagonal) structure of ZnS nanocrystals. In this report, we applied the Zn finger-like peptides as templates to control the phase of ZnS nanocrystals to the wurtzite structure at room temperature. The peptide nanotubes, consisting of a 20 amino acids (VAL-CYS-ALA-THR-CYS-GLU-GLN-ILE-ALA-ASP-SER-GLN-HIS-ARG-SER-HIS-ARG-GLN-MET-VAL, M1 peptide) synthesized based on the peptide motif of the Influenza Virus Matrix Protein M1, could grow the wurtzite ZnS nanocrystals on the nanotube templates in solution. In the M1 protein, the unfolding process of the helical peptide motif via pH change creates a linker region between N- and C-terminated helical domains that contains a Zn finger-like Cys2His2 motif. Because the higher pH increases the uptake of Zn ions in the Cys2His2 motif of the M1 peptide by unfolding more helical domains, the pH change can essentially control the size and the number of the nucleation sites in the M1 peptides to grow ZnS nanocrystals with desired phases. Here we optimized the nucleation sites in the M1 peptides by unfolding them via pH change to obtain highly monodisperse and crystalline wurtzite ZnS nanocrystals on the template nanotubes at room temperature. This type of peptide-induced biomineralization technique will provide a clean and reproducible method to produce semiconductor nanotubes due to its efficient nanocrystal formation, and the band gaps of resulting nanotubes can also be tuned simply by phase control of ZnS nanocrystal coatings via the optimization of the unfolding peptide structures.

Crystallization↗
PubMed1986

Metal complexes of mitomycins.

The preparation of stable complexes between the N7-[2-(2-pyridyl)ethyl] and N7-(2-piperazinylethyl) derivatives of mitomycin C and metal ions such as Cu(II), Zn(II), and Pt(II) was accomplished. Mitomycin C did not form stable complexes, but it rearranged to a mitosene capable of complex formation. Some of these complexes had antitumor activity in mice. However, they were less active than mitomycin C. Weak associations between mitomycin C and metal ions were demonstrated by 13C and 15N NMR spectrometry.

Animals↗
PubMed2006

Bio-friendly synthesis of ZnO nanoparticles in aqueous solution at near-neutral pH and low temperature.

ZnO nanoparticles are synthesized using a new bio-friendly method. The experimental conditions are very mild: aqueous solution at near-neutral pH and 37 degrees C. The as-obtained nanoparticles show the stable wurtzite structure without the need of annealing. The two reagents used are aqueous solutions of zinc nitrate and buffer tris(hydroxymethyl)aminomethane. This is a standard nontoxic buffer and inert to a wide variety of chemicals and biomolecules, therefore extremely satisfactory for biochemical reactions. Furthermore, this is a polydentade ligand which adsorbs strongly on one or more surfaces of ZnO inhibiting its crystal growth and yielding nearly spherical ZnO nanoparticles. Our objective is to use the crystallization method described here for further incorporation of biomolecules as additives in the reaction solution, aiming at the formation of ZnO with new physical properties.

Cold Temperature↗
PubMed2004

Elimination of zinc-65 from the brain under kainate-induced seizures.

On the basis of the previous evidence that 65Zn concentrations in the brain of EL (epilepsy) mice was affected by induction of seizures, 65Zn movement in the brain was quantitatively evaluated in ddY mice treated with kainate. Six days after intravenous injection of 65ZnCl2, mice were intraperitoneally injected with kainate (10 mg/kg x 6 times in 2 weeks). Myoclonic jerks were observed during treatment with kainate. Twenty days after 65Zn injection, 65Zn distribution in the brain was compared between the kainite-treated and control mice. 65Zn distribution in the brain of the kainate-treated mice was overall lower than in the control mice. 65Zn concentration was significantly decreased in the frontal cortex, hippocampal CA1, thalamus and hypothalamus by treatment with kainate. These results demonstrate that kainate-induced seizures are linked to decreased zinc concentrations in the brain.

Animals↗
PubMed1996

Determination of trace levels of niguldipine in urine and blood by adsorptive stripping voltammetry at the hanging mercury drop electrode.

A relatively simple electroanalytical procedure for the determination of niguldipine in biological samples is described. The technique involves adsorptive accumulation of the drug at the hanging mercury drop electrode (HMDE) followed by a differential-pulse polarographic determination of the preconcentrated species. The adsorptive stripping response is evaluated with respect to various experimental conditions, such as solvent composition and pH of the supporting electrolyte, accumulation potential and accumulation time. After a simple sample preparation, the method can be used for the determination of niguldipine in blood and urine. Interfering substances are simply removed by precipitation, adding a small amount of 5% ZnSO4 solution and ethanol to the urine or blood sample and centrifuging the mixture. A limit of detection of 6.7 ng per ml of urine and 41 ng per ml of blood is found with a mean recovery of 96% in urine and 71% in blood. The mean relative errors are 8.4% and 2.2%, respectively.

Adsorption↗
PubMed2004

Rotor-like ZnO by epitaxial growth under hydrothermal conditions.

Rotor-like ZnO was grown from a mixture of rod-like ZnO powder and a saturated Zn(OH)(4)(2-) solution under moderate hydrothermal conditions at 100 degree C, in which the precursor rod-like ZnO crystal plane acts as a matrix core, and the branched nanorods showed fast epitaxial growth on the six directions around the prism core.

Crystallization↗
PubMed1995

Partial sequence of the purified protein confirms the identity of cDNA coding for human lysosomal alpha-mannosidase B.

Human lysosomal alpha-mannosidase has been purified by a simple and rapid method in sufficient quantities for the analysis of its subunit composition and partial protein sequencing. Analysis of the N-terminal residues of the 30 kDa polypeptide has enabled us to confirm the identity of the recently cloned cDNA that was tentatively identified as that of lysosomal alpha-mannosidase [Nebes and Schmidt (1994) Biochem. Biophys. Res. Commun. 200, 239-245] and to locate the position of this polypeptide within the total deduced amino acid sequence. This finding will therefore provide a firm foundation for the characterization of alpha-mannosidosis mutations.

Amino Acid Sequence↗
PubMed2001

Zinc salts precipitate unconjugated bilirubin in vitro and inhibit enterohepatic cycling of bilirubin in hamsters.

BACKGROUND: We have evidence for enterohepatic cycling of bilirubin experimentally and in vivo in humans. This study was designed to investigate whether Zn salts might inhibit such cycling of bilirubin. MATERIALS AND METHODS: Micellar bile salt solutions with unconjugated bilirubin were prepared, appropriate concentrations of Zn salts were added, and unconjugated bilirubin precipitation was measured. Hamsters and Wistar rats were fed a chow diet or a chow diet enriched with 1% ZnSO4, and bilirubin secretion rates were monitored. RESULTS: Unconjugated bilirubin was precipitated maximally (90%) after a 10-min incubation with 5 mM Zn salts in the pH range of 6.8-9.0. In control hamsters, total bilirubin secretion rates into bile were 36.0 +/- 2.8 nmol h(-1) 100g(-1) body weight, whereas they were 25.0 +/- 3.3 nmol h-1 100(-1) g in the ZnSO4 group (P < 0.05). CONCLUSIONS: Zn salts that flocculate at physiological pH adsorb unconjugated bilirubin almost completely from unsaturated micellar BS solutions. In addition, Zn salts administered orally suppress biliary bilirubin secretion rates in hamsters. These findings suggest that the administration of Zn salts may inhibit the enterohepatic cycling of unconjugated bilirubin in humans who are predisposed to pigment gallstone formation due to diet, disease or drugs.

Animals↗
PubMed1996

Dengue virus-induced cytotoxin releases nitrite by spleen cells.

Dengue type-2 virus (DV) infection in mice induces T cells to produce a cytokine, the cytotoxic factor (CF), which induces H2-A positive macrophages to produce another cytokine, cyototoxic (CF2), which amplifies its cytotoxic effects on target cells. The present study was undertaken to investigate the production of nitrite (NO2-) by the spleen cells of mice in vitro and in vivo following inoculation of CF2. Maximum NO2- production occurred at 1 hour after inoculation of 100 micrograms CF2. Pretreatment of CF2 with anti-CF2-antisera (CF2-As) inhibited the production of NO2-. Pretreatment of the spleen cells with NG-monomethyl-L-arginine (NMA) or with arginase inhibited NO2- production. The NO2- production was diminished in a dose dependent manner by treatment of spleen cells with the Ca2+ channel blocking drug, nifedipine and Zn2+ as ZnSO4. The findings of the present study thus demonstrate that CF2 induces production of NO2- in the spleen cells in a CA(2+)-dependent manner which may be a mechanism of target cell killing.

Animals↗
PubMed1996

Zinc supplementation and amino acid-nitrogen metabolism in patients with advanced cirrhosis.

Zinc deficiency is common in cirrhosis and has been involved in the altered nitrogen metabolism. In this study, we measured the effects of zinc supplementation on the dynamics of amino acid-derived urea synthesis in cirrhosis with mild or latent encephalopathy. The hepatic conversion of amino acids into urea was studied in eight patients with advanced cirrhosis under controlled conditions of substrate availability (continuous alanine infusion), before and after 3-month oral zinc sulfate supplementation (600 mg/d). Eight more patients, matched for hepatocellular failure and encephalopathy, served as controls. Plasma zinc levels were reduced in all patients and returned to normal after oral zinc. The alanine-stimulated urea nitrogen synthesis rate in relation to alpha-amino-N concentration--the functional hepatic nitrogen clearance--increased by 25% after zinc supplementation, i.e., more urea was produced at any alpha-amino-N concentration. Basal and alanine-induced glucagon decreased by 50%, and the ammonia response to alanine decreased by 30%. Psychometric tests improved, as did routine and dynamic liver function tests and the Child-Pugh score. Also, the plasma concentration of lipid peroxides was reduced by zinc. No significant changes were observed in the control group. Our data indicate that long-term oral zinc speeds up the kinetics of urea formation from amino acids and ammonia. Changes in the hormonal drive and/or the antioxidant activity of zinc might be involved in the general improvement in liver function, whereas the beneficial effects on encephalopathy might stem from decreased ammonia.

Administration, Oral↗
PubMed1996

Antisense RNA to the type I insulin-like growth factor receptor suppresses tumor growth and prevents invasion by rat prostate cancer cells in vivo.

Prostate carcinoma is the second leading cause of death from malignancy in men in the United States. Prostate cancer cells express type I insulin-like growth factor receptor (IGF-IR) and prostate cancer selectively metastazises to bone, which is an environment rich in insulin-like growth factors (IGFs), thereby supporting a paracrine action for cancer cell proliferation. We asked whether the IGF-IR is coupled to tumorigenicity and invasion of prostate cancer. When rat prostate adenocarcinoma cells (PA-III) were stably transfected with an antisense IGF-IR expression construct containing the ZnSO4-inducible metallothionein-1 transcriptional promoter, the transfectants expressed high levels of IGF-IR antisense RNA after induction with ZnSO4, which resulted in dramatically reduced levels of endogenous IGF-IR mRNA. A significant reduction in expression both of tissue-type plasminogen activator and of urokinase-type plasminogen activator occurred in PA-III cells accompanying inhibition of IGF-IR. Subcutaneous injection of either nontransfected PA-III or PA-III cells transfected with vector minus the IGF-IR insert into nude mice resulted in large tumors after 4 weeks. However, mice injected with IGF-IR antisense-transfected PA-III cells either developed tumors 90% smaller than controls or remained tumor-free after 60 days of observation. When control-transfected PA-III cells were inoculated over the abraded calvaria of nude mice, large tumors formed with invasion of tumor cells into the brain parenchyma. In contrast, IGF-IR antisense transfectants formed significantly smaller tumors with no infiltration into brain. These results indicate an important role for the IGF/IGF-IR pathway in metastasis and provide a basis for targeting IGF-IR as a potential treatment for prostate cancer.

Adenocarcinoma↗
PubMed1995

C-jun and Egr-1 participate in DNA synthesis and cell survival in response to ionizing radiation exposure.

Exposure of mammalian cells to ionizing radiation results in the induction of the immediate early genes, c-jun and Egr-1, which encode transcription factors implicated in cell growth as well as the cellular response to oxidative stress. We studied the role of these immediate early genes in cell cycle kinetics and cell survival following x-irradiation of clones containing inducible dominant negatives to c-jun and Egr-1. The dominant negative constructs to c-jun (delta 9) and Egr-1 (WT/Egr) prevented x-ray induction of transcription through the AP-1 and Egr binding sites, respectively. Twenty percent of confluent, serum-deprived SQ20B human tumor cells, normal fibroblasts, and fibroblasts from patients with ataxia telangiectasia entered S phase within 5 h of irradiation. Clones containing inducible delta 9 and WT/Egr dominant negative constructs demonstrated attenuation of the percentage of cells exiting G1 phase and reduced survival following irradiation. These data indicate that the dominant negatives to the stress-inducible immediate early genes Egr-1 and c-jun prevent the onset of S phase and reduce the survival of human cells exposed to ionizing radiation.

Cell Cycle↗