Home About us Contact
|
Home About us Contact | ||
|
|
||
Ni2+ Ions (ni2+ + ion)
Selected AbstractsStudies on Nickel(II) Complexes with Amide-Based Ligands: Syntheses, Structures, Electrochemistry and Oxidation ChemistryEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 12 2008Jyoti Singh Abstract The present work discusses the nickel chemistry in a set of amide-based open-chain ligands with subtle differences in the backbone or terminal amine substituents. The ligands coordinate to the Ni2+ ion through the Namide and Namine atoms maintaining a square-planar geometry. Absorption spectra and NMR studies reveal that the solid-state square-planar geometry is retained in solution. The electrochemical results suggest that the NiIII/NiII redox couple primarily depends on the N4 donors, which is composed of two Namide and twoNamine atoms and not on the peripheral substituents. All four ligands with variable backbone and substituents are equally competent in stabilizing the NiIII state. On the basis of electrochemical findings, chemical oxidations were carried out, and they reveal generation of the NiIII state in two cases, whereas decomposition was observed in others. Preliminary alkene epoxidation reactions suggest that the present nickel complexes transiently stabilize the higher oxidation state of the nickel ion that possibly participates in the oxidation of the substrates.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Configuration of Octahedral Metal Compounds , Equilibrium, Crystal and Molecular Structure of Nickel(II) Complexes of Linear N2O4, N4S2 or N6 Donors Set Atoms LigandsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2004Aminou Mohamadou Abstract Two new nickel(II) complexes of symmetric hexadentate mixed-ligand N,O [1,12-bis(2-pyridyl)-5,8-dioxa-2,11-diazadodecane (pydado)] and N,S [1,12-bis(2-pyridyl)-5,8-dithia-2,11-diazadodecane (pydadt)] donor atoms have been synthesised as perchlorate salts and characterised by X-ray crystallography and ligand-field spectroscopy. In both complexes the Ni2+ ion is hexacoordinate. The cation [Ni(pydado)]2+ is pseudo-octahedral with the two pyridyl groups in trans position; all Ni,N and Ni,O bond lengths are practically equivalent. In [Ni(pydadt)]2+ complex, however, the size of the thioether sulfur atoms imposes a C2v symmetry; the pyridyl groups and the sulfur atoms are in trans positions and all Ni,N bond lengths are equivalent. The comparison of these structures with those of octahedral cobalt, copper and zinc complexes with the same ligands shows that their configurations depend not only on the nature of the two central donor atoms of the ligand, but also on the nature of the metallic ion. In aqueous solution, the stability constants of the NiII chelates with these two ligands, determined by potentiometry, show the formation of [Ni(LH)]3+ and [NiL]2+ species in all cases. The chelating power of the pydadt ligand is slightly greater than that of pydado. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Fully relativistic analysis of the absorption spectra of Ca3Sc2Ge3O12:Ni2+PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 12 2006M. G. Brik Abstract Systematic analysis of the energy level schemes, ground state absorption (GSA) and covalency effects for the Ni2+ ion in Ca3Sc2Ge3O12 was performed. The recently developed first-principles approach to the analysis of the absorption spectra of impurity ions in crystals based on the discrete variational multi-electron method (DV-ME) [K. Ogasawara et al., Phys. Rev. B 64, 115413 (2001)] was used in the calculations. As a result, complete energy level schemes of Ni2+ and its absorption spectra at both possible crystallographic positions (distorted octahedral Sc3+ and tetrahedral Ge4+ positions) were calculated, assigned and compared with experimental data. Energies of the charge transfer (CT) transitions for both positions are estimated. Numerical contributions of all possible electron configurations into the calculated energy states were determined. By performing analysis of the molecular orbitals (MO) population, it was shown that the covalency of the chemical bonds between the Ni2+ and O2, ions increases in passing from the hexa- to the tetra-coordinated complex. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Ni2+ removal from aqueous solutions using conditioned clinoptilolites: Kinetic and isotherm studiesENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 1 2009Semra Çoruh Abstract The aim of this study is to investigate the effects of conditioning with NaCl and HCl solutions on removal of Ni2+ ions from aqueous solutions using natural clinoptilolite. Batch studies were performed to evaluate the effects of various parameters such as chemically conditioning, adsorbent amount, contact time, initial pH of the solution, mixing temperature, and initial metal ions. The results clearly showed that the conditioning improved both the exchange capacity and the removal efficiency. Langmuir, Freundlich, Temkin, and Dubinin-Kaganer-Radushkevich (DKR) isotherm models were adopted to describe the adsorption isotherms. Adsorption isotherms of Ni2+ ions could be best modeled by Langmuir equation. Three simplified models including pseudo-second-order, intraparticle diffusion and Elovich were used to test the adsorption kinetics. These results indicate a significant potential for the natural and conditioned clinoptilolites as an adsorbent/ion-exchange material for heavy metal removal. © 2008 American Institute of Chemical Engineers Environ Prog, 2009 [source] Insertion of light-harvesting chlorophyll a/b protein into the thylakoidFEBS JOURNAL, Issue 4 2000Topographical studies The major light-harvesting chlorophyll a/b -binding protein (Lhcb1,2) of photosystem II is inserted into the thylakoid via the signal recognition particle dependent pathway. However, the mechanism by which the protein enters the membrane is at this time unknown. In order to define some topographical restrictions for this process, we constructed several recombinant derivatives of Lhcb1 carrying hexahistidine tags at either protein terminus or in the stromal loop domain. Additionally, green fluorescent protein (GFP) was fused to either terminus. None of the modifications significantly impair the pigment-binding properties of the protein in the in vitro reconstitution of LHCII. With the exception of the C-terminal GFP fusion, all mutants stably insert into isolated thylakoids in the absence of Ni2+ ions. The addition of low concentrations of Ni2+ ions abolishes the thylakoid insertion of C-terminally His-tagged mutants whereas the other His-tagged proteins fail to insert only at higher Ni2+ concentrations. The C-terminus of Lhcb1 must cross the membrane during protein insertion whereas the other sites of Lhcb1 modification are positioned on the stromal side of LHCII. We conclude that a Ni2+ -complexed His tag and fusion to GFP inhibit translocation of the protein C-terminus across the thylakoid. Our observations indicate that the N-terminal and stromal domain of Lhcb1 need not traverse the thylakoid during protein insertion and are consistent with a loop mechanism in which only the C-terminus and the lumenal loop of Lhcb1 are translocated across the thylakoid. [source] Decorating Liquid Crystal Surfaces with Proteins for Real-Time Detection of Specific Protein,Protein BindingADVANCED FUNCTIONAL MATERIALS, Issue 22 2009Deny Hartono Abstract Here, a novel method of immobilizing proteins with well-defined orientation directly on liquid crystal surfaces that allow subsequent real-time imaging of specific protein,protein binding events on these surfaces is reported. Self-assembly of nitrilotriacetic acid terminated amphiphiles loaded with Ni2+ ions at aqueous-liquid crystal interface creates a surface capable of immobilizing histidine-tagged ubiquitin through complex formation between Ni2+ and histidine. When these surfaces containing immobilized histidine-tagged ubiquitin are exposed to anti-ubiquitin antibody, the spatial and temporal of specific protein,protein binding events trigger orientational transitions of liquid crystals. As a result, sharp liquid crystal optical switching from dark to bright can readily be observed under polarized lighting. The protein,protein binding can be observed within seconds and only requires nanogram quantities of proteins. This work demonstrates a simple strategy to immobilize proteins with well-defined orientation on liquid crystal surfaces for real-time and label-free detection of specific protein,protein binding events, which may find use in biomedical diagnostics. [source] Electrokinetic Properties of Nanosized SiC Particles in Highly Concentrated Electrolyte SolutionsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2001Sheng-Chang Wang In this research, the electrokinetic behavior and stability of nanosized SiC particles suspended in various electroplating solutions were studied. Analyses were performed using electrophoretic mobility photometry and streaming current (SC) techniques. The electrolytes included NiCl2, Ni(SO3NH2)2, and Na3Co(NO2)6, which are currently used in composite plating solutions with concentrations as high as 0.5M. The results showed that the adsorption of dissolved Ni2+ ions onto the surface of the SiC in the pH range 4,8 changed the sign and magnitude of the surface potential. Moreover, trivalent complex species Co(NO2)63, replaced nickel species on the SiC surface and decreased the surface charge of SiC to between pH 3 and pH 5. Even in a highly concentrated electrolyte solution, the SiC particles still maintained a positive charge in a Ni(SO3NH2)2 suspension with nickel coplating on the cathode. The difference between the SC reading and the zeta potential, as well as the surface adsorption of various species onto the SiC, are discussed here. [source] Synthesis and photophysical behavior of a water-soluble coumarin-bearing polymer for proton and Ni2+ ion sensingPOLYMER INTERNATIONAL, Issue 6 2009Bao-Yan Wang Abstract BACKGROUND: In recent years, many fluorescent chemosensors with various macromolecular structures have been prepared for the detection of protons or metal cations in the environment. Most of this research is focused on polymer sensors with fluorescent recognition sites in the main chain. In this case, the fluorescent recognition sites are covalently bonded to the polymer chain, and thus the polymer shows photophysical properties as a chemosensor for protons and metal ions. RESULTS: An acrylic monomer bearing coumarin moieties, 7-hydroxy-4-methyl-8-(4,-acryloylpiperazin-1,-yl)methylcoumarin, was synthesized. This was then copolymerized with N -vinylpyrrolidone to obtain a blue fluorescent material. The fluorescent copolymer has good solubility in aqueous solution. Its main photophysical properties were determined in relation to its use as a sensor for protons and metal cations. It is an efficient ,off-on' switcher for pH between 3.02 and 12.08. Additionally, the polymer sensor is selective to Ni2+ ions, with the increase in the fluorescence intensity depending on Ni2+ ion concentrations in the range 0.33 × 10,5,7.67 × 10,5 mol L,1. CONCLUSION: The results suggest that this copolymer may offer potential as a reusable polymer sensor for protons and Ni2+ ions in aqueous solution. Copyright © 2009 Society of Chemical Industry [source] A benzene-rich pseudopolymorph of bis[,-1,3-bis(pentafluorophenyl)propane-1,3-dionato]-,3O,O,:O,;,3O:O,O,-bis{aqua[1,3-bis(pentafluorophenyl)propane-1,3-dionato-,2O,O,]nickel(II)} benzene tetrasolvateACTA CRYSTALLOGRAPHICA SECTION C, Issue 11 2009Akiko Hori The title complex comprises two Ni2+ ions, four fluorinated ligands and two water molecules in a centrosymmetric dinuclear complex. This compound was crystallized from benzene,CH2Cl2, and two types of crystals, viz. the title benzene tetrasolvate, [Ni2(C15HF10O2)4(H2O)2]·4C6H6, (I), and the previously reported benzene disolvate, [Ni2(C15HF10O2)4(H2O)2]·2C6H6, (II) [Hori et al. (2009). Bull. Chem. Soc. Jpn, 82, 96,98], were obtained as pseudopolymorphs. In the crystal structure of (I), the four benzene solvent molecules interact closely with all the pentafluorophenyl groups of the complex through arene,perfluoroarene interactions. The molecular structures of the two compounds show essentially the same conformation, although the benzene molecules are accommodated in a columnar packing in (I), while they are isolated from each other in (II). [source] Structure of Thermotoga maritima TM0439: implications for the mechanism of bacterial GntR transcription regulators with Zn2+ -binding FCD domainsACTA CRYSTALLOGRAPHICA SECTION D, Issue 4 2009Meiying Zheng The GntR superfamily of dimeric transcription factors, with more than 6200 members encoded in bacterial genomes, are characterized by N-terminal winged-helix DNA-binding domains and diverse C-terminal regulatory domains which provide a basis for the classification of the constituent families. The largest of these families, FadR, contains nearly 3000 proteins with all-,-helical regulatory domains classified into two related Pfam families: FadR_C and FCD. Only two crystal structures of FadR-family members, those of Escherichia coli FadR protein and LldR from Corynebacterium glutamicum, have been described to date in the literature. Here, the crystal structure of TM0439, a GntR regulator with an FCD domain found in the Thermotoga maritima genome, is described. The FCD domain is similar to that of the LldR regulator and contains a buried metal-binding site. Using atomic absorption spectroscopy and Trp fluorescence, it is shown that the recombinant protein contains bound Ni2+ ions but that it is able to bind Zn2+ with Kd < 70,nM. It is concluded that Zn2+ is the likely physiological metal and that it may perform either structural or regulatory roles or both. Finally, the TM0439 structure is compared with two other FadR-family structures recently deposited by structural genomics consortia. The results call for a revision in the classification of the FadR family of transcription factors. [source] His-tagged protein purification by metal-chelate affinity extraction with nickel-chelate reverse micellesBIOTECHNOLOGY PROGRESS, Issue 4 2010Xiao-Yan Dong Abstract Di(2-ethylhexyl) phosphoric acid (HDEHP) was used as a transition metal ion chelator and introduced to the nonionic reverse micellar system composed of equimolar Triton X-45 and Span 80 at a total concentration of 30 mmol/L. Ni(II) ions were chelated to the HDEHP dimers in the reverse micelles, forming a complex denoted as Ni(II)R2. The Ni(II)-chelate reverse micelles were characterized for the purification of recombinant hexahistidine-tagged enhanced green fluorescent protein (EGFP) expressed in Escherichia coli. The affinity binding of EGFP to Ni(II)R2 was proved by investigation of the forward and back extraction behaviors of purified EGFP. Then, EGFP was purified with the affinity reverse micelles. It was found that the impurities in the feedstock impeded EGFP transfer to the reverse micelles, though they were little solubilized in the organic phase. The high specificity of the chelated Ni2+ ions toward the histidine tag led to the production of electrophoretically pure EGFP, which was similar to that purified by immobilized metal affinity chromatography. A two-stage purification by the metal-chelate affinity extraction gave rise to 87% recovery of EGFP. Fluorescence spectrum analysis suggests the preservation of native protein structure after the separation process, indicating the system was promising for protein purification. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source] A Metal-Chelating Piezoelectric Sensor Chip for Direct Detection and Oriented Immobilization of PolyHis-Tagged ProteinsBIOTECHNOLOGY PROGRESS, Issue 4 2004Hsiu-Mei Chen A metal-chelating piezoelectric (PZ) chip for direct detection and controlled immobilization of polyHis-tagged proteins has been demonstrated. The chip was prepared by covalently binding a hydrogel matrix complex of oxidized dextran and nitrilotriacetic acid (NTA) ligand onto an activated alkanethiol-modified PZ crystal. The resulting chip effectively captured Ni2+ ions onto its NTA surface, as disclosed by the resonant frequency shift of the crystal and an X-ray photoelectron spectroscopy analysis. The real-time frequency analysis revealed that the bare NTA chip was nonfouling, regenerable, and highly reusable during continuous repetitive injections of ion solutions and binding proteins. In addition, the chip displayed good long-term reusability and storage stability. The individual binding studies of a polyHis-tagged glutathione- S -transferase and its native untagged form on various metal-charged chips revealed that Co2+, Cu2+, and Ni2+ ions each had different immobilization ability on the NTA surface, as well as their binding ability and selectivity with the tagged protein. As a result, the tagged protein immobilized on the Ni2+ -charged chip can actively be bound with its antibody and substrate. Further, the quantitative analyses of the tagged protein in crude cell lysate with a single Ni2+ -charged chip and of its substrate with a protein-coated chip were also successfully demonstrated. Therefore, this study initiates the possibilities of oriented, reversible, and universal immobilization of any polyHis-tagged protein and its functional study using a real-time PZ biosensor. [source] | |||||||||||||