Zn2+ Ions (zn2+ + ion)

Distribution by Scientific Domains
Distribution within Chemistry


Selected Abstracts


Highly Enhanced Luminescence of GdTaO4:Eu3+ Phosphors by Codoping with Zn2+ Ions.

CHEMINFORM, Issue 9 2007
Mu Gu
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]


Capillary electrophoretic study of the binding of zinc(II) ion to bacitracin A1 in water-2,2,2-trifluoroethanol

ELECTROPHORESIS, Issue 10 2003
Massimo Castagnola
Abstract Binding of Zn2+ to bacitracin A1 was studied by capillary electrophoresis in water/2,2,2-trifluoroethanol (70/30 v/v) at different apparent pH values in order to estimate the association constant of metal, the acidic dissociation constants and the Stokes radii of both free and bounded peptide in apolar environment. The Stokes radii of the free peptide species were compared with those in aqueous solution, as obtained in a recent study performed by our group, indicating that apolar environment stabilizes bacitracin A1 in a conformational structure with the lateral chain of apolar amino acids exposed on the external surface. This conformation of the macrocyclic dodecapeptide is ready to interact with Zn2+ ion, as pointed out by the strong increase of the association constant measured in water/2,2,2-trifluoroethanol with respect to the value obtained in aqueous solution. In addition, whereas Zn2+ ion binding in aqueous solution provides a sensible reduction of peptide Stokes radius, no sensible variations following to ion binding were observed in hydro-organic solution. The present results suggest that the apolar environment, rather than the metal ion binding, could be responsible for the conformational transition that brings bacitracin A1 towards its biologically active structure.* [source]


The Mycobacterium tuberculosis ino1 gene is essential for growth and virulence

MOLECULAR MICROBIOLOGY, Issue 4 2004
Farahnaz Movahedzadeh
Summary Inositol is utilized by Mycobacterium tuberculosis in the production of its major thiol and of essential cell wall lipoglycans. We have constructed a mutant lacking the gene encoding inositol-1-phosphate synthase (ino1), which catalyses the first committed step in inositol synthesis. This mutant is only viable in the presence of extremely high levels of inositol. Mutant bacteria cultured in inositol-free medium for four weeks showed a reduction in levels of mycothiol, but phosphatidylinositol mannoside, lipomannan and lipoarabinomannan levels were not altered. The ino1 mutant was attenuated in resting macrophages and in SCID mice. We used site-directed mutagenesis to alter four putative active site residues; all four alterations resulted in a loss of activity, and we demonstrated that a D310N mutation caused loss of the active site Zn2+ ion and a conformational change in the NAD+ cofactor. [source]


Observation of a calcium-binding site in the ,-class carbonic anhydrase from Pyrococcus horikoshii

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 10 2008
Jeyaraman Jeyakanthan
Carbonic anhydrases are zinc-containing metalloenzymes that catalyze the interconversion of carbon dioxide and bicarbonate. Three crystal structures of ,-class carbonic anhydrase (one of which is bound to a bicarbonate molecule) from the aerobic OT3 strain of the hyperthermophilic archeon Pyrococcus horikoshii have been solved by molecular replacement in space group F4132. The asymmetric unit contains a monomer of 173 amino acids and a catalytic Zn2+ ion. The protein fold is a regular prism formed by a left-handed ,-helix, similar to previously reported structures. The active-site Zn2+ ion located at the interface between the two monomers is bound to three histidyl residues and a water molecule in a tetrahedral fashion. In addition to the 20 ,-strands comprising the ,-helix, there is also a long C-terminal ,-helix. For the first time, Ca2+ ions have been observed in addition to the catalytic Zn2+ ion. It is hypothesized that Tyr159 (which corresponds to the catalytically important Asn202 in previously reported structures) utilizes C,H..., interactions to fulfill its functions. This study may shed light on the catalytic mechanism of the enzyme and throw open new questions on the mechanism of product removal in carbonic anhydrases. [source]


Electrochemical Investigation of Binding of Heavy Metal Ions to Turkish Lignites

ELECTROANALYSIS, Issue 16 2004
Erol Pehlivan
Abstract Adsorption and desorption of Cu2+, Pb2+, Cd2+, Ni2+ and Zn2+ ions on samples of lignites (young brown coal) from three areas in the vicinity of Konya (Anatolia, Turkey) were followed using the polarographic method of analysis. This method enables the determination of free metal ions in suspensions containing both small and colloidal particles of lignite. Effects of pH, nature of the metal ion, and origin of the lignite on its adsorption capacity were followed. Binding is only between 5 and 30% reversible, indicating that ion exchange is not the predominant factor. The role of the size and shape of cavities inside pulverized lignite and of the functional groups inside these cavities was considered. [source]


Self-Assembly, Structure and Solution Dynamics of Tetranuclear Zn2+ Hydrazone [2×2] Grid-Type Complexes

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 4 2006
Mihail Barboiu
Abstract We describe the self-assembly processes as well as the structural and physico-chemical properties of [2×2]Zn2+4 grid complexes involving the bis-tridentate ligands 7,12, based on bis(hydrazone)pyrimidine complexation subunits and octahedrally coordinated Zn2+ ions. The NMR spectroscopic data and the X-ray crystal structure results indicate that in solution and in the solid state the complexes 13,18 adopt a very compact arrangement providing stable [2×2] hydrazone-grid arrays. The ,,, stacking between the phenyl ring and the hydrazone units of the perpendicular ligands in the complexes induces a perfect orthogonal arrangement suitable for applications in self-organized metallosupramolecular systems. Zinc complexes provide an opportunity to study the acid,base chemistry without the added effects due to paramagnetism or redox chemistry. The intermediate protonated grids undergo relatively rapid proton exchange on the NMR timescale, the presence of a sharp pyrimidine proton resonance suggesting that there is significant delocalization of the negative charge along the backbone of the ligand. Rotation of the phenyl ring is observed. It involves probably a mechanism in which one of the ligands partially dissociates allowing the initially intercalated phenyl group to rotate, before recoordination of the terminal pyridine. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]


Metal-Assisted Hybridization of Oligonucleotides, Evaluation of Circular 2,- O -Me RNA as Ligands for the TAR RNA Target

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 6 2003
Laurence Zapata
Abstract Two complementary oligonucleotides were conjugated with terpyridine ligands at their nearby 5,- and 3,-ends. Addition of a stoichiometric amount of a transition metal (Zn2+, Fe2+) resulted in a large increase in the melting temperature of the duplex. The conjugation of TPY to stem-loop oligomers provided an efficient procedure for the cyclisation of the oligomer after the addition of metal ions. Such a short stem-loop oligomer was designed to target the HIV-1 TAR RNA through loop,loop interactions. The addition of Zn2+ ions yielded a good ligand (Kd = 30 nM) for this RNA structural element. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]


Structural insight into the evolutionary and pharmacologic homology of glutamate carboxypeptidases II and III

FEBS JOURNAL, Issue 16 2009
Klara Hlouchova
Glutamate carboxypeptidase III (GCPIII) is a metalloenzyme that belongs to the transferrin receptor/glutamate carboxypeptidase II (GCPII; EC 3.4.17.21) superfamily. GCPIII has been studied mainly because of its evolutionary relationship to GCPII, an enzyme involved in a variety of neuropathologies and malignancies, such as glutamatergic neurotoxicity and prostate cancer. Given the potential functional and pharmacological overlap between GCPIII and GCPII, studies addressing the structural and physiological properties of GCPIII are crucial for obtaining a deeper understanding of the GCPII/GCPIII system. In the present study, we report high-resolution crystal structures of the human GCPIII ectodomain in a ,pseudo-unliganded' state and in a complex with: (a) l -glutamate (a product of hydrolysis); (b) a phosphapeptide transition state mimetic, namely (2S,3,S)-{[(3,-amino-3,-carboxy-propyl)-hydroxyphosphinoyl]methyl}-pentanedioic acid; and (c) quisqualic acid, a glutamate biostere. Our data reveal the overall fold and quaternary arrangement of the GCPIII molecule, define the architecture of the GCPIII substrate-binding cavity, and offer an experimental evidence for the presence of Zn2+ ions in the bimetallic active site. Furthermore, the structures allow us to detail interactions between the enzyme and its ligands and to characterize the functional flexibility of GCPIII, which is essential for substrate recognition. A comparison of these GCPIII structures with the equivalent GCPII complexes reveals differences in the organization of specificity pockets, in surface charge distribution, and in the occupancy of the co-catalytic zinc sites. The data presented here provide information that should prove to be essential for the structurally-aided design of GCPIII-specific inhibitors and might comprise guidelines for future comparative GCPII/GCPIII studies. [source]


The effects of physiologically important nonmetallic ligands in the reactivity of metallothionein towards 5,5,-dithiobis(2-nitrobenzoic acid)

FEBS JOURNAL, Issue 18 2001
A new method for the determination of ligand interactions with metallothionein
The reaction of Cd5Zn2 -metallothionein (MT) with 5,5,-dithiobis(2-nitrobenzoic acid) (Nbs2) has been studied at different reagent stoichiometries, pH and temperature conditions and in the presence of several ligands. At stoichiometries of Nbs2 to MT from 0.5 to 5, the reaction followed first order kinetics. The first order rate constants obtained were independent from the concentration of Nbs2 but were linearly dependent on the concentration of MT. At higher Nbs2/MT stoichiometries, the reaction deviates from first order kinetics and the observed rate constant increases. The reactivity of MT towards Nbs2 has been probed at 4 µm concentration of both reagents where the reaction is monophasic and is characterized by a linear Arrhenius plot (Ea = 45.8 ± 2.7 kJ·mol,1). It has been demonstrated that metal release at low pH or subtraction from MT by EDTA substantially increases the reactivity of MT towards Nbs2. At the same time, a number of nonmetallic ligands moderately accelerate the reaction of MT with Nbs2 and hyperbolic dose,response curves were obtained. The data have been interpreted with the binding of ligands to MT and following MT. Ligand binding constants were calculated as follows: ATP, K = 0.31 ± 0.06 mm; ADP, K = 0.26 ± 0.07 mm. Several compounds such as AMP, S -methylglutathione, and phosphate had no effect on the reaction, but Zn2+ ions showed an inhibitory effect at micromolar concentrations. [source]


Divalent metal cation binding properties of human prothymosin ,

FEBS JOURNAL, Issue 15 2000
Nina V. Chichkova
The divalent cation binding properties of human prothymosin ,, an abundant nuclear protein involved in cell proliferation, were evaluated. By using prothymosin , retardation on a weak cation chelating resin charged with various divalent cations, specific binding of Zn2+ ions by prothymosin , was observed. This finding was further confirmed by the equilibrium dialysis analysis which demonstrated that, within the micromolar range of Zn2+ concentrations, prothymosin , could bind up to three zinc ions in the presence of 100 mm NaCl and up to 13 zinc ions in the absence of NaCl. Equilibrium dialysis analysis also revealed that prothymosin , could bind Ca2+, although the parameters of Ca2+ binding by prothymosin , were less pronounced than those of Zn2+ binding in terms of the number of metal ions bound, the KD values, and the resistance of the bound metal ions to 100 mm NaCl. The effects of Zn2+ and Ca2+ on the interaction of prothymosin , with its putative partners, Rev of HIV type 1 and histone H1, were examined. We demonstrated that Rev binds prothymosin ,, and that prothymosin , binding to Rev but not to histone H1 was significantly enhanced in the presence of zinc and calcium ions. Our data suggest that the modes of prothymosin , interaction with Rev and histone H1 are distinct and that the observed zinc and calcium-binding properties of prothymosin , might be functionally relevant. [source]


Amorphous Infinite Coordination Polymer Microparticles: A New Class of Selective Hydrogen Storage Materials,

ADVANCED MATERIALS, Issue 11 2008
You-Moon Jeon
A new class of micrometer-sized amorphous infinite coordination particles is selectively prepared from the coordination chemistry of a metallo-salen building block and Zn2+ ions. The particles show moderately high H2 uptake and almost no N2 adsorption, even though they are amorphous and do not have the well-defined channels typically used to explain such selectivity in metal,organic framework systems. [source]


Semiconducting Neutral Microstructures Fabricated by Coordinative Self-Assembly of Intramolecular Charge-Transfer Tetrathiafulvalene Derivatives

CHEMISTRY - A EUROPEAN JOURNAL, Issue 20 2009
Yan Geng Dr.
Abstract A new class of tetrathiafulvalene-based microstructures fabricated by coordinative self-assembly has been prepared by a solution process. Upon incorporation of Pb2+ and Zn2+ ions, 1D wirelike microstructures and spherical polymer particles were achieved, respectively (see picture). The neutral coordination polymers are conductive and magnetic at room temperature without external manipulation. A new class of tetrathiafulvalene(TTF)-based microstructures fabricated by coordinative self-assembly has been successfully prepared by a solution process. The morphology of the TTF coordination polymers is readily tuned by the variation of metal ions. Upon incorporation of Pb2+ and Zn2+ ions, one-dimensional (1D) wirelike microstructures and spherical polymer particles were achieved, respectively. These results indicate that the coordinative approach pursued in this work, in which the building blocks of 1 are linked in a coordination polymer chain by association with metal ions, is an efficient and versatile approach to produce more mechanically robust micro- and nanometer-sized coordination polymer materials. More interestingly, the neutral coordination polymers are conductive and magnetic at room temperature without external manipulation. Such conductivity is reminiscent of the behavior of the neutral conductive TTF in single crystals. [source]


Determination of Copper and Zinc Ions by Flame-AAS After Preconcentraction Using Sodium Dodecyl Sulfate Coated Alumina Modified with 3-((1H -Indol-3-yl)-3,4,5-trimethyl)-1H -indole

CHINESE JOURNAL OF CHEMISTRY, Issue 10 2009
Mehrorang Ghaedi
Abstract A sensitive and simple method for the simultaneous preconcentration of trace amount Cu2+ and Zn2+ ions in some real samples has been established, which is based on the sorption of Cu2+ and Zn2+ on 3-((1H -indol-3-yl)-3,4,5-trimethyl)-1H -indole (ITMI) loaded on sodium dodecyl sulfate (SDS) coated alumina. The metal absorbed on the complexes was eluted using 3 mol/L nitric acid. The influences of the analytical parameters including pH and sample volume were investigated. The effects of matrix ions on the retentions of the analytes were also examined. The recoveries of analytes were generally higher than 95% with a low RSD. The method has been successfully applied to content evaluation of these metals in real samples. [source]