Home About us Contact
|
Home About us Contact | ||
|
|
||
Different Metal Ions (different + metal_ion)
Selected AbstractsProgramming Heteropolymetallic Lanthanide Helicates: Thermodynamic Recognition of Different Metal Ions Along the StrandsCHEMISTRY - A EUROPEAN JOURNAL, Issue 5 2004Sébastien Floquet Dr. Abstract Under stoichiometric conditions, the segmental tris-tridentate ligand L9 assembles with two different lanthanide metal ions Ln1 and Ln2 (Ln1, Ln2=La, Nd, Sm, Eu, Yb, Lu, Y) to give mixtures of the heterotrimetallic triple-stranded helicates [(Ln1)x(Ln2)3,x(L9)3]9+ (x=0,3) in acetonitrile. The combination of qualitative (ESI-MS) and quantitative (1H NMR) speciations provides a set of thermodynamic data that were analysed with various statistical chemical models. A satisfying description requires the consideration of different affinities for the terminal N6O3 sites (k) and for the central N9 site (k) for each specific lanthanide. The nontrivial dependence of these parameters on the ionic radius provides size-discriminating effects that favour the formation of heterotrimetallic helicates in which the central site is occupied by the larger metal of the pair. Combining the latter enthalpic driving forces with entropic contributions due to specific stoichiometric conditions allows partial selection (i.e., programming) of a specific heterotrimetallic species in solution, which can be isolated by crystallisation, as demonstrated for [Eu2.04La0.96(L9)3](CF3SO3)9(CH3NO2)9 (1, Eu2.04La0.96C207H222N48O51S9F27, monoclinic, P21/c, Z=4) in which the cation [EuLaEu(L9)3]9+ is the major component in the crystal. The scope and limitation of this approach is discussed together with the conditions for explicitly considering intermetallic interaction parameters uLn1Ln2 in more sophisticated chemical models. [source] Effect of different metal ions on structural, thermal, spectroscopic and optical properties of ATCC and ATMC single crystalsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 8 2007R. Perumal Abstract A novel metal-organic coordination complex nonlinear optical crystals, tri-allylthiourea cadmium chloride [(CdCl2(AT)3] and tri-allylthiourea mercury chloride [(HgCl2(AT)3] abbreviated as ATCC, ATMC (AT is Allylthiourea i.e.,CH2=CHCH2NHCSNH2) has been synthesized and grown as single crystals. It was synthesized in deionised water and further recrystallized to improve its purity. Single crystals of the allylthiourea co-ordination complex nonlinear optical crystals tri allylthiourea cadmium chloride (ATCC) with dimensions of 14x14x10 mm3 and tri allylthiourea mercury chloride (ATMC) with dimensions of 15x15x12 mm3 were grown successfully from aqueous solution by solvent evaporation as well as by temperature lowering method. It exhibits powder SHG efficiencies higher than that of a well known organic NLO crystal Urea. The solubility of the as grown crystals was estimated from the aqueous solution and the effect of different metal ions on the grown crystals, structural, thermal, spectral and optical properties were analyzed. XRD studies the reveals the same structure of both materials. Influence of the different central metal (Cd and Hg) atoms, changing the thermal properties of the materials when NLO complexes formed with the common ligand allylthiourea. The metal co-ordination was confirmed form the spectroscopic analysis. From the UV transmittance studies, red shift was from the transparency cut-off wavelengths. The value is 285nm for ATCC is and is 335nm ATMC, Non-linear an optical study confirms the suitabilities of the as grown crystals for the non linear optical applications. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Improved ,-Glucanase Production by a Recombinant Escherichia coli Strain using Zinc-Ion Supplemented MediumENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 3 2007U. Beshay Abstract In order to investigate the suitability of different metal chelates for affinity chromatography, an expression vector was constructed. It contained a hybrid ,-glucanase as a model protein fused with a His6 -tag and a secretion cassette providing the ability to secrete ,-glucanase into the culture medium. Supplementation of zinc to the medium led to a rapidly increased expression and release of the target protein into the cultivation medium. Results in respect to the supplementation of the commonly used Terrific Broth "TB-medium" with different metal ions are reported with special emphasis on the influence of zinc ions. A concentration of zinc ions in the order of about 0.175 mM led to optimal results. Batch cultivation under well-controlled conditions showed that the growth behavior did not change significantly by adding zinc ions. Growth in a stirred tank bioreactor was much faster in unsupplemented TB-medium compared to shake flask experiments leading to a much higher biomass concentration (15,g/L instead of 3,g/L). The secretion of ,-glucanase under theses conditions started at the transition into the stationary phase and increased to yield an extracellular activity of 1350,U/mL at the end of the fermentation process. An even higher yield of extracellular ,-glucanase (2800,U/mL) was reached when the fermentation was carried out with TB-medium supplemented with 0.175,mM ZnSO4. [source] Chromosomal antioxidant genes have metal ion-specific roles as determinants of bacterial metal toleranceENVIRONMENTAL MICROBIOLOGY, Issue 10 2009Joe J. Harrison Summary Microbiological metal toxicity involves redox reactions between metal species and cellular molecules, and therefore, we hypothesized that antioxidant systems might be chromosomal determinants affecting the susceptibility of bacteria to metal toxicity. Here, survival was quantified in metal ion-exposed planktonic cultures of several Escherichia coli strains, each bearing a mutation in a gene important for redox homeostasis. This characterized ,250 gene,metal combinations and identified that sodA, sodB, gor, trxA, gshA, grxA and marR have distinct roles in safeguarding or sensitizing cells to different toxic metal ions (Cr2O72,, Co2+, Cu2+, Ag+, Zn2+, AsO2,, SeO32, or TeO32,). To shed light on these observations, fluorescent sensors for reactive oxygen species (ROS) and reduced thiol (RSH) quantification were used to ascertain that different metal ions exert oxidative toxicity through disparate modes-of-action. These oxidative mechanisms of metal toxicity were categorized as involving ROS and thiol-disulfide chemistry together (AsO2,, SeO32,), ROS predominantly (Cu2+, Cr2O72,) or thiol-disulfide chemistry predominantly (Ag+, Co2+, Zn2+, TeO32,). Corresponding to this, promoter- luxCDABE fusions showed that toxic doses of different metal ions up- or downregulate the transcription of gene sets marking distinct pathways of cellular oxidative stress. Altogether, our findings suggest that different metal ions are lethal to cells through discrete pathways of oxidative biochemistry, and moreover, indicate that chromosomally encoded antioxidant systems may have metal ion-specific physiological roles as determinants of bacterial metal tolerance. [source] Pseudomonas fluorescens' view of the periodic tableENVIRONMENTAL MICROBIOLOGY, Issue 1 2008Matthew L. Workentine Summary Growth in a biofilm modulates microbial metal susceptibility, sometimes increasing the ability of microorganisms to withstand toxic metal species by several orders of magnitude. In this study, a high-throughput metal toxicity screen was initiated with the aim of correlating biological toxicity data in planktonic and biofilm cells to the physiochemical properties of metal ions. To this end, Pseudomonas fluorescens ATCC 13525 was grown in the Calgary Biofilm Device (CBD) and biofilms and planktonic cells of this microorganism were exposed to gradient arrays of different metal ions. These arrays included 44 different metals with representative compounds that spanned every group of the periodic table (except for the halogens and noble gases). The minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and minimum biofilm eradication concentration (MBEC) values were obtained after exposing the biofilms to metal ions for 4 h. Using these values, metal ion toxicity was correlated to the following ion-specific physicochemical parameters: standard reduction-oxidation potential, electronegativity, the solubility product of the corresponding metal,sulfide complex, the Pearson softness index, electron density and the covalent index. When the ions were grouped according to outer shell electron structure, we found that heavy metal ions gave the strongest correlations to these parameters and were more toxic on average than the other classes of the ions. Correlations were different for biofilms than for planktonic cells, indicating that chemical mechanisms of metal ion toxicity differ between the two modes of growth. We suggest that biofilms can specifically counter the toxic effects of certain physicochemical parameters, which may contribute to the increased ability of biofilms to withstand metal toxicity. [source] Systematic Hydrothermal Investigation of Metal Phosphonatobenzenesulfonates by High-Throughput MethodsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2010Palanikumar Maniam Abstract A high-throughput (HT) investigation using the rigid bifunctional ligand 4-phosphonobenzenesulfonic acid, H2O3P-C6H4 -SO3H (H3L), generated five new phosphonatobenzenesulfonates with copper(II) or lead(II) ions. A comprehensive HT study comprising the screenings of different metal ions, metal salt types and the synthesis optimization were conducted whereby the influence of pH and molar ratios M2+/H3L were investigated. The HT-study led to five new compounds Pb2[(O3P-C6H4 -SO3)(OH)] (1), Cu1.5[(O3P-C6H4 -SO3)(H2O)] (2), NaCu(O3P-C6H4 -SO3)(H2O)3 (3), Cu2[(O3P-C6H4 -SO3)(OH)(H2O)] (4) and Cu3[(O3P-C6H4 -SO3)2(H2O)2] (5). Metal ion screening showed lead(II) and copper(II) to be suitable metal ions. The utilization of discovery and focused arrays allowed to determine the optimal formation fields of the respective compounds. The crystal structures were determined from single-crystal X-ray diffraction and revealed the presence of various MOx polyhedra that form clusters, chains or layers which are connected through the organic linker. IR spectra, thermogravimetric studies, magnetic susceptibility measurements and elemental analyses were conducted to further characterize the compounds 1, 3, 4 and 5. [source] A New Carrier for Selective Removal of Heavy Metal Ions from Aqueous Solutions through Bulk Liquid MembranesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 18 2004Nicoletta Spreti Abstract The carrier-mediated transport of heavy metal ions through bulk liquid membranes has been examined: toxic Hg2+, Cd2+ and Pb2+ ions were studied, along with Cu2+ ions for comparative purposes. The ability of a new carrier, 2,2,-bis(p -octyloxybenzyl)diethylenetriamine (bis- pODET), to complex and transport all the selected metal ions is reported. Differing affinities of the carrier for the different metal ions and the different experimental conditions required for their release into the receiving phase allowed the selective separation of equimolar binary mixtures. For Hg2+/Cd2+ and Hg2+/Pb2+ mixtures, two different separation methods were performed, while the inefficacy of the separation of Cd2+/Pb2+ and Hg2+/Cu2+ mixtures was for two different reasons: (i) the carrier is able to extract the metal ions with similar levels of ability, and (ii) the carrier metal ion complexes require the same acidity of the receiving phase to release the metal ions. The capability of the carrier to transport Hg2+ efficiently in consecutive cycles is also reported: over 90% of the metal ions were transferred into the receiving phase for three consecutive processes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Transition metal complexes of a cyclic pseudo hexapeptide: synthesis, complex formation and catalytic activities,,JOURNAL OF PEPTIDE SCIENCE, Issue 9 2008Huong Ngyen Abstract To contribute to a better understanding of metalloenzymes, we studied ion selectivity, complex formation tendencies and catalytic activities of linear and cyclic pseudopeptides. In this contribution, a linear and cyclic pseudo hexapeptide is described. The complex with transition metal ions and the sequence were designed using the programme COSMOS. Different routes of solid-phase synthesis were performed and compared using anchoring by C -terminus or a His side chain, using preformed pseudodipeptide building units or formation of N -functionalized peptide bond during stepwise assembly. The different strategies were compared regarding cyclization tendency, yield and purity. Side-chain anchoring to solid support favours the cyclization but leads to the formation of difficult to separate dioxopiperazine. Both routes require preformed building units. Complex-formation tendencies and selectivity for certain bivalent transition metal ions were experimentally estimated and compared to ones predicted theoretically. CD measurements indicate conformational changes by complex formation with different metal ions. Catalytic activities on oxidation of catechol and hydrolysis of bis-phosphate esters by some metal complexes of linear and cyclic peptide show only low catalytic activities compared to other model peptides and related metalloenzymes. The preference of the cyclic peptide for complexation of Ni2+ corresponds well to the predictions of COSMOS-NMR force field calculations. Copyright © 2008 European Peptide Society and John Wiley & Sons, Ltd. [source] Metallosupramolecular approach toward functional coordination polymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2005Rainer Dobrawa Abstract An appropriate definition of metallosupramolecular coordination polymer is offered, and the relationship between the polymer length, binding constant, and concentration is clarified. The possibility of influencing the binding constant with chelating ligands is discussed on the basis of examples of different Zn2+ complexes and their respective binding constants. In the main part, coordination polymers constructed by a supramolecular approach from different metal ions and pyridine,ligand systems are highlighted, and their applications as functional materials for artificial membrane and enzyme models, responsive gels, light-harvesting systems, and organic light-emitting diodes are discussed on the basis of individual examples. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4981,4995, 2005 [source] Low-oxidation-potential conducting polymers derived from 3,4-ethylenedioxythiophene and dialkoxybenzenesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2001Jennifer A. Irvin Abstract Monomers derived from 3,4-ethylenedioxythiophene and phenylenes with branched or oligomeric ether dialkoxy substituents were prepared with the Negishi coupling technique. Electrooxidative polymerization led to the corresponding dialkoxy-substituted 3,4-ethylenedioxythiophene,phenylene polymers, with extremely low oxidation potentials (E1/2,p = ,0.16 to ,0.50 V vs Ag/Ag+) due to the highly electron-rich nature of these materials. The polymers were electrochromic, reversibly switching from red to blue upon oxidation, with bandgaps at about 2 eV. The electrochemical behavior of the oligomeric ether-substituted polymer was investigated in the presence of different metal ions. Films of the polymer exhibited electrochemical recognition for several alkali and alkaline-earth cations with selectivity in the order Li+ > Ba2+ > Na+ > Mg2+. Cyclic voltammetry showed a decrease in the oxidation potential and an improvement in the definition of the voltammetric response, as well as an increase in the overall electroactivity of the polymer films when the concentration of the cations in the medium was increased. These results are discussed in terms of the electrostatic interactions between the complexed cation and the redox center, as well as the diffusion of the ionic species into the polymer matrix. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2164,2178, 2001 [source] Metal ion permeation properties of silk fibroin/chitosan blend membranesPOLYMER INTERNATIONAL, Issue 4 2006Chun-Hui Du Abstract Silk fibroin/chitosan (SF/CS) blend membranes were prepared and characterized by infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy. It was found that SF and CS were compatible in the blend membranes and that the membranes were dense without microscopic phase separation. Swelling experiments showed that the swelling ratio of the blend membranes increased with CS content and reached the highest value when CS content was 70 wt%. Experiments indicated that the permeability coefficient of K+ through the blend membrane was 2,4 times higher than that of pure CS membrane, and 10 times higher than that of pure SF membrane. The permeation rate of K+ increased linearly with CS content in the blend membrane for the lower concentration feeding solution. For different metal ions, the permeability through SF/CS blend membranes was in the sequence K+ > Ca2+ > Cd2+ > Pb2+ > Cu2+ > Ni2+. Copyright © 2006 Society of Chemical Industry [source] Metal-Ion-Dependent Gas Sorptivity of Elastic Layer-Structured MOFsCHEMISTRY - A EUROPEAN JOURNAL, Issue 31 2009Atsushi Kondo Dr. Elastic layers: By comparing the gas adsorptivities of N2, O2, CO2, and H2 on two elastic layer-structured metal,organic frameworks (MOFs) with different metal ions, definite differences could be observed in O2, CO2, and H2 despite their structural similarity. In most cases of MOFs, the metal ion has been considered as a connector. However, the metal ion clearly has the potential to regulate gas adsorptivity especially in flexible MOFs. [source] Precursors of Biological Cofactors from Ultraviolet Irradiation of Circumstellar/Interstellar Ice AnaloguesCHEMISTRY - A EUROPEAN JOURNAL, Issue 17 2005Uwe J. Meierhenrich Priv.-Doz. Abstract Biological cofactors include functionalized derivatives of cyclic tetrapyrrole structures that incorporate different metal ions. They build up structural partnerships with proteins, which play a crucial role in biochemical reactions. Porphyrin, chlorin, bacteriochlorin, and corrin are the basic structures of cofactors (heme, chlorophyll, bacteriochlorophyll, siroheme, F 430, and vitamin B12). Laboratory and theoretical work suggest that the molecular building blocks of proteins (,-amino acids) and nucleic acids (carbohydrates, purines, and pyrimidines) were generated under prebiotic conditions. On the other hand, experimental data on the prebiotic chemistry of cofactors are rare. We propose to search directly for the pathways of the formation of cofactors in the laboratory. Herein we report on the detection of N-heterocycles and amines in the room-temperature residue obtained after photo- and thermal processing of an interstellar ice analogue under high vacuum at 12 K. Among them, hexahydro-1,3,5-triazine and its derivatives, together with monopyrrolic molecules, are precursors of porphinoid cofactors. Hexahydropyrimidine was also detected. This is the first detection of these compounds in experiments simulating circumstellar/interstellar conditions. Except for 2-aminopyrrole and 2,4-diaminofuran, which were only found in 13C-labeled experiments, all the reported species were detected in both 12C- and 13C-labeled experiments, excluding contamination. The molecules reported here might be present in circumstellar/interstellar grains and cometary dust and could be detected by the Stardust and Rosetta missions. [source] Catalytic Kinetics of the Schiff Base Metal Complexes Bearing Side Chain of Cyclic morpholine in Carboxylic Ester HydrolysisCHINESE JOURNAL OF CHEMISTRY, Issue 6 2007Shu-Lin Zhang Abstract It has been reported that two Schiff base transition metal complexes bearing the side chain of the morpholine ring were synthesized and characterized, and two complexes with the same base agent but different metal ions were used as a simulant hydrolase in the catalytic hydrolysis of p -nitrophenyl picolinate in this paper. The mechanism of PNPP catalytic hydrolysis is proposed and supported by the results of the spectral analysis and the kinetic calculation. A kinetic mathematical model, applied to the calculation of the kinetic and thermodynamics parameters of PNPP catalytic hydrolysis, has been established on the foundation of the mechanism proposed. The result of the study shows that the two complexes have a good catalytic activity in PNPP catalytic hydrolysis, and the rate of the PNPP catalytic hydrolysis was increased with the increase of the pH values in the buffer solution and affected by the polarization effect of metal ion of the complexes. [source] Cupric ion enhanced molecular imprinting of bovine serum albumin in hydrogelJOURNAL OF SEPARATION SCIENCE, JSS, Issue 19 2009Sheng-Hua Li Abstract A novel molecularly imprinted hydrogel for bovine serum albumin (BSA) was prepared using cupric ion as the bridge between the template BSA and the functional monomer 4-vinylpyridine. N-Isopropylacrylamide (NIPA) was used as an assistant monomer to provide the stimuli-responsibility of the polymer. The adsorption conditions of BSA on the BSA-Cu(II)-imprinted hydrogel were optimized considering the influences of pH, temperature, and salt concentration. The proteins bound on the imprinted hydrogel can be easily recovered under mild conditions by using 10 mmol/L ethylene diamine tetraacetic acid (EDTA) (pH 7.0) containing 150 mmol/L NaCl as the eluting solution. The imprinting effect and adsorption capacity of the polymer were found to be significantly improved compared to the hydrogel prepared in the absence of cupric ion. The results demonstrated the advantages of using a template-metal ion-monomer coordination system to strengthen the interaction between the protein and monomer. The effects of different metals ions including Zn(II), Ni(II), Co(II), Cd(II), and Al(III) on the recognition ability of the BSA-Cu(II)-imprinted hydrogel were also investigated. The polymer showed high selectivity toward both the template protein and the cupric ion. [source] | ||||||||||||||||