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Sample records for divalent metal ii

  1. Mutational analysis of divalent metal ion binding in the active site of class II α-mannosidase from sulfolobus solfataricus

    DEFF Research Database (Denmark)

    Hansen, Dennis K.; Webb, Helen; Nielsen, Jonas Willum;

    2015-01-01

    Mutational analysis of Sulfolobus solfataricus class II α-mannosidase was focused on side chains that interact with the hydroxyls of the-1 mannosyl of the substrate (Asp-534) or form ligands to the active site divalent metal ion (His-228 and His-533) judged from crystal structures of homologous...... enzymes. D534A and D534N appeared to be completely inactive. When compared to the wild-type enzyme, the mutant enzymes in general showed only small changes in KM for the substrate, p-nitrophenyl-α-mannoside, but elevated activation constants, KA, for the divalent metal ion (Co2+, Zn2+, Mn2+, or Cd2......+). Some mutant enzyme forms displayed an altered preference for the metal ion compared to that of the wild type-enzyme. Furthermore, the H228Q, H533E, and H533Q enzymes were inhibited at increasing Zn2+ concentrations. The catalytic rate was reduced for all enzymes compared to that of the wild-type enzyme...

  2. Multiple Metal Binding Domains Enhance the Zn(II) Selectivity of the Divalent Metal Ion Transporter AztA

    Energy Technology Data Exchange (ETDEWEB)

    Liu, T.; Reyes-Caballero, H.; Li, C.; Scott, R.A.; Giedroc, D.P.

    2009-06-03

    Transition metal-transporting P{sub 1B}-type CPx ATPases play crucial roles in mediating metal homeostasis and resistance in all cells. The degree to which N-terminal metal binding domains (MBDs) confer metal specificity to the transporter is unclear. We show that the two MBDs of the Zn/Cd/Pb effluxing pump Anabaena AztA are functionally nonequivalent, but only with respect to zinc resistance. Inactivation of the a-MBD largely abrogates resistance to high intracellular Zn(II) levels, whereas inactivation of the b-MBD is not as deleterious. In contrast, inactivation of either the a- or b-MBD has little measurable impact on Cd(II) and Pb(II) resistance. The membrane proximal b-MBD binds Zn(II) with a higher affinity than the distal N-terminal a-MBD. Facile Zn(II)-specific intermolecular transfer from the a-MBD to the higher-affinity b-MBD is readily observed by {sup 1}H-{sup 15}N HSQC spectroscopy. Unlike Zn(II), Cd(II) and Pb(II) form saturated 1:1 S{sub 4} or S{sub 3}(O/N) complexes with AztA{sup aHbH}, where a single metal ion bridges the two MBDs. We propose that the tandem MBDs enhance Zn(II)-specific transport, while stabilizing a non-native inter-MBD Cd/Pb cross-linked structure that is a poor substrate and/or regulator for the transporter.

  3. Synthesis, characterization and properties of some divalent metal(II) complexes: Their electrochemical, catalytic, thermal and antimicrobial activity studies

    Science.gov (United States)

    Tümer, Mehmet; Ekinci, Duygu; Tümer, Ferhan; Bulut, Akif

    2007-07-01

    In this study, we synthesized the amine compound 2-(2-aminoethyliminomethyl)phenol (H 3A) as the starting material, and then we prepared the polydentate Schiff base ligands from the reactions of the amine compound (H 3A) with phtaldialdehyde (H 2L), 4-methyl-2,6-di-formlyphenol (H 3L 1) and 4- t-butyl-2,6-di-formylphenol (H 3L 2) in the ethanol solution. Moreover, the complexes Cd(II), Cu(II), Co(II), Ni(II), Zn(II) and Sn(II) of the ligands H 2L, H 3L 1 and H 3L 2 have been prepared. All compounds have been characterized by the analytical and spectroscopic methods. In addition, the magnetic susceptibility and molar conductance measurements have been made. The catalytic properties of the mono- and binuclear Co(II) and Cu(II) complexes have been studied on the 3,5-di- tert-butylcatechol (3,5-DTBC) and ascorbic acid (aa) as a substrate. The oxidative C-C coupling properties of the Co(II) and Cu(II) complexes have been investigated on the sterically hindered 2,6-di- tert-butylphenol (dtbp). The antimicrobial activity properties of the ligands and their mono- and binuclear complexes have been studied against the bacteria and fungi. The results have been compared to the antibacterial and fungi drugs. The TGA curves show that the decomposition takes place in three steps for all complexes. Electrochemical properties of the complexes Cu(II) and Ni(II) have been investigated for the first time in acetonitrile by cyclic voltammetry.

  4. Influence of divalent metal on the decomposition products of hydrotalcite-like ternary systems M{sup II}-Al-Cr (M{sup II} = Zn, Cd)

    Energy Technology Data Exchange (ETDEWEB)

    Perez, M.R.; Crespo, I.; Ulibarri, M.A.; Barriga, C. [Departamento de Quimica Inorganica e Ingenieria Quimica, Campus de Rabanales, Universidad de Cordoba, Cordoba (Spain); Rives, V. [GIR-QUESCAT, Departamento de Quimica Inorganica, Universidad de Salamanca, Salamanca (Spain); Fernandez, J.M., E-mail: um1feroj@uco.es [Departamento de Quimica Inorganica e Ingenieria Quimica, Campus de Rabanales, Universidad de Cordoba, Cordoba (Spain)

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer LDHs M{sup II}-Al-Cr (M = Zn, Cd) with Cr in the layer or interlayer have been prepared. Black-Right-Pointing-Pointer LDHs Zn-Al or Zn-Cr decompose by heating forming ZnO and ZnAl{sub 2}O{sub 4} or ZnO and ZnCr{sub 2}O{sub 4}. Black-Right-Pointing-Pointer LDHs Zn-Al-Cr give rise to the formation of ZnO and the mixed spinel ZnAl{sub 2-x}Cr{sub x}O{sub 4}. Black-Right-Pointing-Pointer LDH Cd-Al-Cr shows the formation of CdO, CdCr{sub 2-x}Al{sub x}O{sub 4}, and (Al, Cr){sub 2}O{sub 3} mixed oxide. Black-Right-Pointing-Pointer Calcination of the CdAl-CrO{sub 4} give rise to (Al, Cr){sub 2}O{sub 3} as the majority phase. - Abstract: Layered double hydroxides (LDHs) containing M{sup II}, Al{sup III}, and Cr{sup III} in the brucite-like layers (M = Cd, Zn) with different starting Al/Cr molar ratios and nitrate/carbonate as the interlayer anion have been prepared following the coprecipitation method at a constant pH: Zn{sup II}-Al{sup III}-Cr{sup III}-CO{sub 3}{sup 2-} at pH = 10, and Cd{sup II}-Al{sup III}-Cr{sup III}-NO{sub 3}{sup -} at pH = 8. Two additional M{sup II},Al{sup III}-LDH samples (M = Cd, Zn) with chromate ions (CrO{sub 4}{sup 2-}) in the interlayer have been prepared by ionic exchange at pH = 9 and 8, respectively, starting from M{sup II}-Al{sup III}-NO{sub 3}{sup -}. The samples have been characterised by absorption atomic spectrometry, powder X-ray diffraction (PXRD), FT-IR spectroscopy and transmission electron microscopy (TEM). Their thermal stability has been assessed by DTA-TG and mass spectrometric analysis of the evolved gases. The PXRD patterns of the solids calcined at 800 Degree-Sign C show diffraction lines corresponding to ZnO and ZnAl{sub 2-x}Cr{sub x}O{sub 4} for the Zn-containing samples, and diffraction lines attributed to CdO and CdCr{sub 2}O{sub 4} and (Al,Cr){sub 2}O{sub 3} for the Cd-containing ones. Additionally a minority oxide, Cd{sub 2}CrO{sub 5}, is observed to Cd{sup II}-Al{sup III

  5. Histone Deacetylase 8: Characterization of Physiological Divalent Metal Catalysis.

    Science.gov (United States)

    Nechay, Michael R; Gallup, Nathan M; Morgenstern, Amanda; Smith, Quentin A; Eberhart, Mark E; Alexandrova, Anastassia N

    2016-07-07

    Histone deacetylases (HDACs) are responsible for the removal of acetyl groups from histones, resulting in gene silencing. Overexpression of HDACs is associated with cancer, and their inhibitors are of particular interest as chemotherapeutics. However, HDACs remain a target of mechanistic debate. HDAC class 8 is the most studied HDAC, and of particular importance due to its human oncological relevance. HDAC8 has traditionally been considered to be a Zn-dependent enzyme. However, recent experimental assays have challenged this assumption and shown that HDAC8 is catalytically active with a variety of different metals, and that it may be a Fe-dependent enzyme in vivo. We studied two opposing mechanisms utilizing a series of divalent metal ions in physiological abundance (Zn(2+), Fe(2+), Co(2+), Mn(2+), Ni(2+), and Mg(2+)). Extensive sampling of the entire protein with different bound metals was done with the mixed quantum-classical QM/DMD method. Density functional theory (DFT) on an unusually large cluster model was used to describe the active site and reaction mechanism. We have found that the reaction profile of HDAC8 is similar among all metals tested, and follows one of the previously published mechanisms, but the rate-determining step is different from the one previously claimed. We further provide a scheme for estimating the metal binding affinities to the protein. We use the quantum theory of atoms in molecules (QTAIM) to understand the different binding affinities for each metal in HDAC8 as well as the ability of each metal to bind and properly orient the substrate for deacetylation. The combination of this data with the catalytic rate constants is required to reproduce the experimentally observed trend in metal-depending performance. We predict Co(2+) and Zn(2+) to be the most active metals in HDAC8, followed by Fe(2+), and Mn(2+) and Mg(2+) to be the least active.

  6. Dispersion relations of the acoustic modes in divalent liquid metals

    Directory of Open Access Journals (Sweden)

    Inui Masanori

    2017-01-01

    Full Text Available Collective dynamics in liquid Ca and liquid Cd was studied by inelastic x-ray scattering (IXS. Using our experimental technique to prepare proper sample cells and high performance of an IXS beamline (BL35XU at SPring-8 in Japan, the dynamic structure factor with reasonable statistics was obtained for these divalent liquid metals. For both liquids, the dynamic structure factor at low Q exhibits a central peak with a shoulder or small hump clearly visible on each side, and the inelastic excitation energy determined using the model function composed of Lorentzian and the damped harmonic oscillator function disperses with increasing Q. The dispersion curves of these liquids were compared with that of the longitudinal acoustic phonon in each crystalline phase. From these results, clear difference in the interatomic interaction be- tween liquid Ca and liquid Cd was inferred.

  7. Hall transport of divalent metal ion modified DNA lattices

    Energy Technology Data Exchange (ETDEWEB)

    Dugasani, Sreekantha Reddy; Lee, Keun Woo; Yoo, Sanghyun; Gnapareddy, Bramaramba; Bashar, Saima; Park, Sung Ha, E-mail: sunghapark@skku.edu [Department of Physics and Sungkyunkwan Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Kim, Si Joon; Jung, Joohye; Jung, Tae Soo; Kim, Hyun Jae, E-mail: hjk3@yonsei.ac.kr [School of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of)

    2015-06-29

    We investigate the Hall transport characteristics of double-crossover divalent metal ion (Cu{sup 2+}, Ni{sup 2+}, Zn{sup 2+}, and Co{sup 2+})-modified DNA (M-DNA) lattices grown on silica via substrate-assisted growth. The electronic characteristics of the M-DNA lattices are investigated by varying the concentration of the metal ions and then conducting Hall measurements, including resistivity, Hall mobility, carrier concentration, and magneto resistance. The tendency of the resistivity and Hall mobility was to initially decrease as the ion concentration increased, until reaching the saturation concentration (C{sub s}) of each metal ion, and then to increase as the ion concentration increased further. On the other hand, the carrier concentration revealed the opposite tendency as the resistivity and Hall mobility. The specific binding (≤C{sub s}) and the nonspecific aggregates (>C{sub s}) of the ions into the DNA lattices were significantly affected by the Hall characteristics. The numerical ranges of the Hall parameters revealed that the M-DNA lattices with metal ions had semiconductor-like characteristics. Consequently, the distinct characteristics of the electrical transport through M-DNA lattices will provide useful information on the practical use of such structures in physical devices and chemical sensors.

  8. Complexation and Antimicrobial Studies of Some Divalent Metal Chelates

    Directory of Open Access Journals (Sweden)

    Suparna Ghosh

    2010-01-01

    Full Text Available Metal chelates of Ni(II and Cu(II with the ligand 5-acetamido-1,3,4-thiadiazole-2-sulphonamide have been synthesized. The isolated compounds have been characterized by elemental analysis, molar conductivity, magnetic moment, electronic and IR spectral studies. The analytical data reflects the metal to ligand stoichiometry to be 1: 2. The conductivity data of the complexes also suggests their non-electrolytic nature. The stability constants and free energy change for the complexes have been calculated.. Ligand and their complexes have been screened for their biological activity and the data show good activity of these complexes and ligands.

  9. New 14-membered octaazamacrocyclic complexes of divalent transition metal ions with their antimicrobial and spectral studies

    Science.gov (United States)

    Singh, D. P.; Kumar, Krishan; Sharma, Chetan

    2010-01-01

    A novel series of macrocyclic complexes of the type [M(C 18H 14N 10S 2)X 2]; where M = Co(II), Ni(II), Cu(II), Zn(II) and Cd(II); X = Cl -, NO 3-, CH 3COO - has been synthesized by [2+2] condensation of thiocarbohydrazide and isatin in the presence of divalent metal salts in methanolic medium. The complexes have been characterized with the help of elemental analyses, conductance measurements, magnetic measurements, electronic, NMR and infrared spectral studies. The low value of molar conductance indicates them to be non-electrolytes. On the basis of various studies a distorted octahedral geometry may be proposed for all of these complexes. These metal complexes were also tested for their in vitro antimicrobial activities against some Gram-positive bacteria viz. Staphylococcus aureus, Bacillus subtilis, and some Gram-negative bacteria Escherichia coli, Pseudomonas aeruginosa and some fungal strains Aspergillus niger, Aspergillus flavus (molds), Candida albicans, Saccharomyces cerevisiae (yeasts). The results obtained were compared with standard antibiotic: Ciprofloxacin and the standard antifungal drug: Amphotericin-B.

  10. X-ray crystal structure of divalent metal-activated ß-xyloisdase, RS223BX

    Science.gov (United States)

    We report the first X-ray structure of a glycoside hydrolase family 43 ß-xylosidase, RS223BX, which is strongly activated by the addition of divalent metal cations. The 2.69 Å structure reveals that the Ca2+ cation is located at the back of the active site pocket. The Ca2+ coordinates to H274 to sta...

  11. Cloning and divalent-metal activation of a ß-xylosidase, RUM630-BX

    Science.gov (United States)

    The gene encoding RUM630-BX, a ß-xylosidase/arabinofuranosidase, was identified from activity-based screening of a cow rumen metagenomic library. The recombinant enzyme is activated as much as 14-fold (kcat) by divalent metals Mg2+, Mn2+ and Co2+ but not by Ca2+, Ni2+, and Zn2+. Activation of RUM6...

  12. Synthesis, Characterization, and Biological Activity of N1-Methyl-2-(1H-1,2,3-Benzotriazol-1-y1-3-Oxobutan-ethioamide Complexes with Some Divalent Metal (II Ions

    Directory of Open Access Journals (Sweden)

    Nouria A. Al-Awadi

    2008-01-01

    Full Text Available A new series of Zn2+, Cu2+, Ni2+, and Co2+ complexes of N1-methyl-2-(1H-1,2,3-benzotriazol-1-yl-3-oxobutanethioamide (MBOBT, HL, has been synthesized and characterized by different spectral and magnetic measurements and elemental analysis. IR spectral data indicates that (MBOBT exists only in the thione form in the solid state while 13C NMR spectrum indicates its existence in thione and thiole tautomeric forms. The IR spectra of all complexes indicate that (MBOBT acts as a monobasic bidentate ligand coordinating to the metal(II ions via the keto-oxygen and thiolato-sulphur atoms. The electronic spectral studies showed that (MBOBT bonded to all metal ions through sulphur and nitrogen atoms based on the positions and intensity of their charge transfer bands. Furthermore, the spectra reflect four coordinate tetrahedral zinc(II, tetragonally distorted copper(II, square planar nickel(II, and cobalt(II complexes. Thermal decomposition study of the complexes was monitored by TG and DTG analyses under N2 atmosphere. The decomposition course and steps were analyzed and the activation parameters of the nonisothermal decomposition are determined. The isolated metal chelates have been screened for their antimicrobial activities and the findings have been reported and discussed in relation to their structures.

  13. Novel kinetic model of the removal of divalent heavy metal ions from aqueous solutions by natural clinoptilolite.

    Science.gov (United States)

    Jovanovic, Mina; Rajic, Nevenka; Obradovic, Bojana

    2012-09-30

    Removal of heavy metal ions from aqueous solutions using zeolites is widely described by pseudo-second order kinetics although this model may not be valid under all conditions. In this work, we have extended approaches used for derivation of this model in order to develop a novel kinetic model that is related to the ion exchange mechanism underlying sorption of metal ions in zeolites. The novel model assumed two reversible steps, i.e. release of sodium ions from the zeolite lattice followed by bonding of the metal ion. The model was applied to experimental results of Cu(II) sorption by natural clinoptilolite-rich zeolitic tuff at different initial concentrations and temperatures and then validated by predictions of ion exchange kinetics of other divalent heavy metal ions (i.e. Mn(II), Zn(II) and Pb(II)). Model predictions were in excellent agreements with experimental data for all investigated systems. In regard to the proposed mechanism, modeling results implied that the sodium ion release rate was constant for all investigated metals while the overall rate was mainly determined by the rate of heavy metal ion bonding to the lattice. In addition, prediction capabilities of the novel model were demonstrated requiring one experimentally determined parameter, only.

  14. Synthesis of some novel divalent transition metal complexes as antimicrobials

    Institute of Scientific and Technical Information of China (English)

    Kaushal K. Oza; Paresh N. Patel; Hasmukh S. Patel

    2011-01-01

    A novel series of transition metal complexes have been synthesized from the reaction of 5-((3-(methylthio)-5-(pyridin-4-yl)-4H-1,2,4-triazol-4-ylamino)methyl)quinolin-8-ol with transition metal salts. The structures of these compounds have been elucidated by elemental and spectral analysis. Furthermore, compounds were screened for in vitro antimicrobial activity against the representative panel of two Gram-positive and two Gram-negative bacteria and two strains of fungus. The various compounds show potent inhibitory action against test organisms.

  15. Aspartate buffer and divalent metal ions affect oxytocin in aqueous solution and protect it from degradation

    DEFF Research Database (Denmark)

    Avanti, Christina; Oktaviani, Nur Alia; Hinrichs, Wouther L.J.

    2013-01-01

    is improved by the addition of divalent metal ions (unpublished results). The stabilizing effect of Zn2+ was by far superior compared to that of Mg2+. In addition, it was found that stabilization correlated well with the ability of the divalent metal ions to interact with oxytocin in aspartate buffer...... favorable. These interactions may explain the protection of the disulfide bridge against intermolecular reactions that lead to dimerization.Mg or Zn, using 2D NOESY, TOCSY, H-C HSQC and H- N HSQC NMR spectroscopy. Almost all H, C and N resonances of oxytocin could be assigned using HSQC spectroscopy...... that the carboxylate group of aspartate neutralizes the positive charge of the N-terminus of Cys, allowing the interactions with Zn to become more favorable. These interactions may explain the protection of the disulfide bridge against intermolecular reactions that lead to dimerization....

  16. Electrochemical Studies of Eight New Divalent Transition Metal Benzenesulphonate Ternary Complexes with 1,10-Phenanthroline

    Institute of Scientific and Technical Information of China (English)

    LU Yao; GUO Li-ping; MA Jian-fang; YANG Jin; WU Dongmei

    2004-01-01

    The electrochemical properties of eight new divalent transition metal benzenesulphonate complexes with 1,10-phenanthroline in different solvents and supporting electrolytes were investigated by means of cyclic voltammetry(CV). Based on the CV data the influences of various coordination modes on the electrochemical behavior of the complexes were discussed. The diffusion coefficient Dc and rate constant ks of those complexes in DMF systems were estimated according to CV and the results show that these processes were all quasi-reversible.

  17. Effects of composition and structure of alginates on adsorption of divalent metals

    Science.gov (United States)

    Zheng, Nai-Yu; Zhang, Yan-Xia; Fan, Xiao; Han, Li-Jun

    1994-03-01

    Results of a series of experiments (on the adsorption of divalent metal ions by dried alginic acid, Na and Ca alginates of different composition and block structure) conducted in this systematic study of the effects of the composition and structure of alginates on the static adsorption equilibrium of divalent metal ions indicate that the properties of alginate adsorption to divalent metal ions are highly different, depending not only on the cations used, but also on the form and structure of the alginates. There is close correlation between the adsorption properties and the structure of the alginates. The selectivity coefficient of Na alginate for Cd-Sr ion exchange tends to increase with the increase of the M/G ratio in alginate, whereas the adsorption capacity of Ca alginate for Cu2+ ion decrease with the increase of the G-block or the average length of the G-block(bar N_G ) and the total adsorption capacity of alginic acid is found to vary in the same order as the F MM(diad frequency) in alginate in the mixed solution of Sr2+, Ba2+ and Cd2+.

  18. Use of MgO doped with a divalent or trivalent metal cation for removing arsenic from water

    Science.gov (United States)

    Moore, Robert C; Holt-Larese, Kathleen C; Bontchev, Ranko

    2013-08-13

    Systems and methods for use of magnesium hydroxide, either directly or through one or more precursors, doped with a divalent or trivalent metal cation, for removing arsenic from drinking water, including water distribution systems. In one embodiment, magnesium hydroxide, Mg(OH).sub.2 (a strong adsorbent for arsenic) doped with a divalent or trivalent metal cation is used to adsorb arsenic. The complex consisting of arsenic adsorbed on Mg(OH).sub.2 doped with a divalent or trivalent metal cation is subsequently removed from the water by conventional means, including filtration, settling, skimming, vortexing, centrifugation, magnetic separation, or other well-known separation systems. In another embodiment, magnesium oxide, MgO, is employed, which reacts with water to form Mg(OH).sub.2. The resulting Mg(OH).sub.2 doped with a divalent or trivalent metal cation, then adsorbs arsenic, as set forth above. The method can also be used to treat human or animal poisoning with arsenic.

  19. Use of MgO doped with a divalent or trivalent metal cation for removing arsenic from water

    Energy Technology Data Exchange (ETDEWEB)

    Moore, Robert C; Holt-Larese, Kathleen C; Bontchev, Ranko

    2013-08-13

    Systems and methods for use of magnesium hydroxide, either directly or through one or more precursors, doped with a divalent or trivalent metal cation, for removing arsenic from drinking water, including water distribution systems. In one embodiment, magnesium hydroxide, Mg(OH).sub.2 (a strong adsorbent for arsenic) doped with a divalent or trivalent metal cation is used to adsorb arsenic. The complex consisting of arsenic adsorbed on Mg(OH).sub.2 doped with a divalent or trivalent metal cation is subsequently removed from the water by conventional means, including filtration, settling, skimming, vortexing, centrifugation, magnetic separation, or other well-known separation systems. In another embodiment, magnesium oxide, MgO, is employed, which reacts with water to form Mg(OH).sub.2. The resulting Mg(OH).sub.2 doped with a divalent or trivalent metal cation, then adsorbs arsenic, as set forth above. The method can also be used to treat human or animal poisoning with arsenic.

  20. Use of MgO doped with a divalent or trivalent metal cation for removing arsenic from water

    Energy Technology Data Exchange (ETDEWEB)

    Moore, Robert C.; Larese, Kathleen Caroline; Bontchev, Ranko Panayotov

    2017-05-30

    Systems and methods for use of magnesium hydroxide, either directly or through one or more precursors, doped with a divalent or trivalent metal cation, for removing arsenic from drinking water, including water distribution systems. In one embodiment, magnesium hydroxide, Mg(OH).sub.2 (a strong adsorbent for arsenic) doped with a divalent or trivalent metal cation is used to adsorb arsenic. The complex consisting of arsenic adsorbed on Mg(OH).sub.2 doped with a divalent or trivalent metal cation is subsequently removed from the water by conventional means, including filtration, settling, skimming, vortexing, centrifugation, magnetic separation, or other well-known separation systems. In another embodiment, magnesium oxide, MgO, is employed, which reacts with water to form Mg(OH).sub.2. The resulting Mg(OH).sub.2 doped with a divalent or trivalent metal cation, then adsorbs arsenic, as set forth above. The method can also be used to treat human or animal poisoning with arsenic.

  1. A new strategy to stabilize oxytocin in aqueous solutions : I. The effects of divalent metal ions and citrate buffer

    NARCIS (Netherlands)

    Avanti, Christina; Amorij, Jean-Pierre; Setyaningsih, Dewi; Hawe, Andrea; Jiskoot, Wim; Visser, Jan; Kedrov, Alexej; Driessen, Arnold J. M.; Hinrichs, Wouter L. J.; Frijlink, Henderik W.

    In the current study, the effect of metal ions in combination with buffers (citrate, acetate, pH 4.5) on the stability of aqueous solutions of oxytocin was investigated. Both monovalent metal ions (Na+and K+) and divalent metal ions (Ca2+, Mg2+, and Zn2+) were tested all as chloride salts. The

  2. A new strategy to stabilize oxytocin in aqueous solutions : I. The effects of divalent metal ions and citrate buffer

    NARCIS (Netherlands)

    Avanti, Christina; Amorij, Jean-Pierre; Setyaningsih, Dewi; Hawe, Andrea; Jiskoot, Wim; Visser, Jan; Kedrov, Alexej; Driessen, Arnold J. M.; Hinrichs, Wouter L. J.; Frijlink, Henderik W.

    2011-01-01

    In the current study, the effect of metal ions in combination with buffers (citrate, acetate, pH 4.5) on the stability of aqueous solutions of oxytocin was investigated. Both monovalent metal ions (Na+and K+) and divalent metal ions (Ca2+, Mg2+, and Zn2+) were tested all as chloride salts. The effec

  3. DIVALENT METAL TRANSPORTER-1 REGULATION BY IRON AND VANADIUM MODULATES HYDROGEN PEROXIDE-INDUCED DNA DAMAGE IN LUNG CELLS

    Science.gov (United States)

    The divalent metal transporter-1 (DMT1) participates in the detoxification of metals that can damage lung epithelium. Elevated iron levels increase the expression of DMT1 in bronchial epithelial cells stimulating its uptake and storage in ferritin, thus making iron unavailable t...

  4. A new strategy to stabilize oxytocin in aqueous solutions: I. The effects of divalent metal ions and citrate buffer.

    Science.gov (United States)

    Avanti, Christina; Amorij, Jean-Pierre; Setyaningsih, Dewi; Hawe, Andrea; Jiskoot, Wim; Visser, Jan; Kedrov, Alexej; Driessen, Arnold J M; Hinrichs, Wouter L J; Frijlink, Henderik W

    2011-06-01

    In the current study, the effect of metal ions in combination with buffers (citrate, acetate, pH 4.5) on the stability of aqueous solutions of oxytocin was investigated. Both monovalent metal ions (Na(+) and K(+)) and divalent metal ions (Ca(2+), Mg(2+), and Zn(2+)) were tested all as chloride salts. The effect of combinations of buffers and metal ions on the stability of aqueous oxytocin solutions was determined by RP-HPLC and HP-SEC after 4 weeks of storage at either 4°C or 55°C. Addition of sodium or potassium ions to acetate- or citrate-buffered solutions did not increase stability, nor did the addition of divalent metal ions to acetate buffer. However, the stability of aqueous oxytocin in aqueous formulations was improved in the presence of 5 and 10 mM citrate buffer in combination with at least 2 mM CaCl(2), MgCl(2), or ZnCl(2) and depended on the divalent metal ion concentration. Isothermal titration calorimetric measurements were predictive for the stabilization effects observed during the stability study. Formulations in citrate buffer that had an improved stability displayed a strong interaction between oxytocin and Ca(2+), Mg(2+), or Zn(2+), while formulations in acetate buffer did not. In conclusion, our study shows that divalent metal ions in combination with citrate buffer strongly improved the stability of oxytocin in aqueous solutions.

  5. Modeling the sorption kinetics of divalent metal ions onto mineral adsorbent using integral method.

    Science.gov (United States)

    Singhal, Nidhi; Prasad, Murari; Gupta, Neelmani; Kumar, Vineet

    2007-09-15

    A mathematical model has been developed that could predict kinetic parameters for the adsorption of divalent cations (lead, copper and zinc) onto low-grade rock phosphate using experimental data. The experiments were conducted with the initial concentrations of metal ions ranging from 10 to 100 mg/L. The mathematical model is based on application of Freundlich isotherm to mass transfer across the film surrounding the adsorbent. A code in C programming is used to numerically integrate the model equation, and to obtain the best simulated values of Freundlich constants K, N, order of reaction n, and film transfer coefficient, alpha. It is observed that the adsorption of metal ions on rock phosphate is more sensitive to N,n, and alpha in comparison to K, and lead is adsorbed more favorably than copper and zinc.

  6. Interaction of Divalent Metal Ions with the Adenosine Triphosphate Measured Using Nuclear Magnetic Resonance

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The interaction of adenosine triphosphate with divalent metal ions is important in biochemical functions. The effects of pH and metal ions Mg2+, Ca2+, Zn2+, Mn2+, and Co2+ on the chemical shift of the phosphate group of ATP have been studied using Nuclear Magnetic Resonance. The chemical shift of the β-phosphate of ATP is the most sensitive to pH. Ca2+ and Mg2+ bind with the α- and β-phosphate groups of ATP. Zn2+ binds to the adenosine ring hydrogen as well as to phosphate. The paramagnetic ions Mn2+ and Co2+ do not cause chemical shifts of the phosphate or proton peak. Mn2+ and Co2+ broaden the resonance peak only.

  7. Synthesis, characterization, and ligand exchange reactivity of a series of first row divalent metal 3-hydroxyflavonolate complexes.

    Science.gov (United States)

    Grubel, Katarzyna; Rudzka, Katarzyna; Arif, Atta M; Klotz, Katie L; Halfen, Jason A; Berreau, Lisa M

    2010-01-01

    A series of divalent metal flavonolate complexes of the general formula [(6-Ph(2)TPA)M(3-Hfl)]X (1-5-X; X = OTf(-) or ClO(4)(-); 6-Ph(2)TPA = N,N-bis((6-phenyl-2-pyridyl)methyl)-N-((2-pyridyl)methyl)amine; M = Mn(II), Co(II), Ni(II), Cu(II), Zn(II); 3-Hfl = 3-hydroxyflavonolate) were prepared and characterized by X-ray crystallography, elemental analysis, FTIR, UV-vis, (1)H NMR or EPR, and cyclic voltammetry. All of the complexes have a bidentate coordinated flavonolate ligand. The difference in M-O distances (Delta(M-O)) involving this ligand varies through the series, with the asymmetry of flavonolate coordination increasing in the order Mn(II) approximately Ni(II) pi*) of the coordinated flavonolate ligand in 1-5-OTf (relative to that in free anion) increases in the order Ni(II) metals fit well with this ordering. (1)H NMR studies indicate that the 3-Hfl complexes of Co(II), Ni(II), and Zn(II) exhibit a pseudo-octahedral geometry in solution. EPR studies suggest that the Mn(II) complex 1-OTf may form binuclear structures in solution. The mononuclear Cu(II) complex 4-OTf has a distorted square pyramidal geometry. The oxidation potential of the flavonolate ligand depends on the metal ion present and/or the solution structure of the complex, with the Mn(II) complex 1-OTf exhibiting the lowest potential, followed by the pseudo-octahedral Ni(II) and Zn(II) 3-Hfl complexes, and the distorted square pyramidal Cu(II) complex 4-OTf. The Mn(II) complex [(6-Ph(2)TPA)Mn(3-Hfl)]OTf (1-OTf) is unique in the series in undergoing ligand exchange reactions in the presence of M(ClO(4))(2).6H(2)O (M = Co, Ni, Zn) in CD(3)CN to produce [(6-Ph(2)TPA)M(CD(3)CN)(n)](X)(2), [Mn(3-Hfl)(2).0.5H(2)O], and MnX(2) (X = OTf(-) or ClO(4)(-)). Under similar conditions, the 3-Hfl complexes of Co(II), Ni(II), and Cu(II) undergo flavonolate ligand exchange to produce [(6-Ph(2)TPA)M(CD(3)CN)(n)](X)(2) (M = Co, Ni, Cu; n = 1 or 2) and [Zn(3-Hfl)(2).2H(2)O]. An Fe(II) complex of 3-Hfl, [(6-Ph(2)TPA

  8. Crystal Structure and Conformational Change Mechanism of a Bacterial Nramp-Family Divalent Metal Transporter.

    Science.gov (United States)

    Bozzi, Aaron T; Bane, Lukas B; Weihofen, Wilhelm A; Singharoy, Abhishek; Guillen, Eduardo R; Ploegh, Hidde L; Schulten, Klaus; Gaudet, Rachelle

    2016-12-06

    The widely conserved natural resistance-associated macrophage protein (Nramp) family of divalent metal transporters enables manganese import in bacteria and dietary iron uptake in mammals. We determined the crystal structure of the Deinococcus radiodurans Nramp homolog (DraNramp) in an inward-facing apo state, including the complete transmembrane (TM) segment 1a (absent from a previous Nramp structure). Mapping our cysteine accessibility scanning results onto this structure, we identified the metal-permeation pathway in the alternate outward-open conformation. We investigated the functional impact of two natural anemia-causing glycine-to-arginine mutations that impaired transition metal transport in both human Nramp2 and DraNramp. The TM4 G153R mutation perturbs the closing of the outward metal-permeation pathway and alters the selectivity of the conserved metal-binding site. In contrast, the TM1a G45R mutation prevents conformational change by sterically blocking the essential movement of that helix, thus locking the transporter in an inward-facing state.

  9. Effect of EDTA on divalent metal adsorption onto grape stalk and exhausted coffee wastes.

    Science.gov (United States)

    Escudero, Carlos; Gabaldón, Carmen; Marzal, Paula; Villaescusa, Isabel

    2008-04-01

    In the present work, two industrial vegetable wastes, grape stalk, coming from a wine producer, and exhausted coffee, coming from a soluble coffee manufacturer, have been investigated for the removal of Cu(II) and Ni(II) from aqueous solutions in presence and in absence of the strongly complexing agent EDTA. Effects of pH and metal-EDTA molar ratio, kinetics as a function of sorbent concentration, and sorption equilibrium for both metals onto both sorbents were evaluated in batch experiments. Metal uptake was dependent of pH, reaching a maximum from pH around 5.5. EDTA was found to dramatically reduce metal adsorption, reaching total uptake inhibition for both metals onto both sorbents at equimolar metal:ligand concentrations. Kinetic results were successfully modelled by means of the pseudo second order model. Langmuir and Freundlich models were used to describe the sorption equilibrium data. Grape stalk showed the best performance for Cu(II) and Ni(II) removal in presence and in absence of EDTA, despite exhausted coffee appears as less sensitive to the presence of complexing agent. The performance of Cu(II) and Ni(II) sorption onto grape stalk in a continuous flow process was evaluated. In solutions containing EDTA, an initial metal concentration in the outlet flow corresponding to the complexed metal fraction was observed from the beginning of the process. A high metal recovery yield (>97%) was achieved by feeding the metal-loaded column with 0.05 M HCl.

  10. Removal of divalent heavy metals (Cd, Cu, Pb, and Zn) and arsenic(III) from aqueous solutions using scoria: kinetics and equilibria of sorption.

    Science.gov (United States)

    Kwon, Jang-Soon; Yun, Seong-Taek; Lee, Jong-Hwa; Kim, Soon-Oh; Jo, Ho Young

    2010-02-15

    Kinetic and equilibrium sorption experiments were conducted on removal of divalent heavy metals (Pb(II), Cu(II), Zn(II), Cd(II)) and trivalent arsenic (As(III)) from aqueous solutions by scoria (a vesicular pyroclastic rock with basaltic composition) from Jeju Island, Korea, in order to examine its potential use as an efficient sorbent. The removal efficiencies of Pb, Cu, Zn, Cd, and As by the scoria (size=0.1-0.2mm, dose=60gL(-1)) were 94, 70, 63, 59, and 14%, respectively, after a reaction time of 24h under a sorbate concentration of 1mM and the solution pH of 5.0. A careful examination on ionic concentrations in sorption batches suggested that sorption behaviors of heavy metals onto scoria are mainly controlled by cation exchange. On the other hand, arsenic appeared to be sensitive to specific sorption onto hematite (a minor constituent of scoria). Equilibrium sorption tests indicated that the removal efficiency for heavy metals increases with increasing pH of aqueous solutions, which is resulted from precipitation as hydroxides. Similarly, multi-component systems containing heavy metals and arsenic showed that the arsenic removal increases with increasing pH of aqueous solutions, which can be attributed to coprecipitation with metal hydroxides. The empirically determined sorption kinetics were well fitted to a pseudo-second order model, while equilibrium sorption data for heavy metals and arsenic onto scoria were consistent with the Langmuir and Freundlich isotherms, respectively. Natural scoria studied in this work is an efficient sorbent for concurrent removal of divalent heavy metals and arsenic.

  11. H(+)-coupled divalent metal-ion transporter-1: functional properties, physiological roles and therapeutics.

    Science.gov (United States)

    Shawki, Ali; Knight, Patrick B; Maliken, Bryan D; Niespodzany, Eric J; Mackenzie, Bryan

    2012-01-01

    Divalent metal-ion transporter-1 (DMT1) is a widely expressed, iron-preferring membrane transport protein. Animal models establish that DMT1 plays indispensable roles in intestinal nonheme-iron absorption and iron acquisition by erythroid precursor cells. Rare mutations in human DMT1 result in severe microcytic-hypochromic anemia. When we express DMT1 in RNA-injected Xenopus oocytes, we observe rheogenic Fe(2+) transport that is driven by the proton electrochemical potential gradient. In that same preparation, DMT1 also transports cadmium and manganese but not copper. Whether manganese metabolism relies upon DMT1 remains unclear but DMT1 contributes to the effects of overexposure to cadmium and manganese in some tissues. There exist at least four DMT1 isoforms that arise from variant transcription of the SLC11A2 gene. Whereas these isoforms display identical functional properties, N- and C-terminal variations contain cues that direct the cell-specific targeting of DMT1 isoforms to discrete subcellular compartments (plasma membrane, endosomes, and lysosomes). An iron-responsive element (IRE) in the mRNA 3'-untranslated region permits the regulation of some isoforms by iron status, and additional mechanisms by which DMT1 is regulated are emerging. Natural-resistance-associated macrophage protein-1 (NRAMP1)-the only other member of the mammalian SLC11 gene family-contributes to antimicrobial function by extruding from the phagolysosome divalent metal ions (e.g. Mn(2+)) that may be essential cofactors for bacteria-derived enzymes or required for bacterial growth. The principal or only intestinal nonheme-iron transporter, DMT1 is a validated therapeutic target in hereditary hemochromatosis (HHC) and other iron-overload disorders.

  12. Divalent metal ion differentially regulates the sequential nicking reactions of the GIY-YIG homing endonuclease I-BmoI.

    Directory of Open Access Journals (Sweden)

    Benjamin P Kleinstiver

    Full Text Available Homing endonucleases are site-specific DNA endonucleases that function as mobile genetic elements by introducing double-strand breaks or nicks at defined locations. Of the major families of homing endonucleases, the modular GIY-YIG endonucleases are least understood in terms of mechanism. The GIY-YIG homing endonuclease I-BmoI generates a double-strand break by sequential nicking reactions during which the single active site of the GIY-YIG nuclease domain must undergo a substantial reorganization. Here, we show that divalent metal ion plays a significant role in regulating the two independent nicking reactions by I-BmoI. Rate constant determination for each nicking reaction revealed that limiting divalent metal ion has a greater impact on the second strand than the first strand nicking reaction. We also show that substrate mutations within the I-BmoI cleavage site can modulate the first strand nicking reaction over a 314-fold range. Additionally, in-gel DNA footprinting with mutant substrates and modeling of an I-BmoI-substrate complex suggest that amino acid contacts to a critical GC-2 base pair are required to induce a bottom-strand distortion that likely directs conformational changes for reaction progress. Collectively, our data implies mechanistic roles for divalent metal ion and substrate bases, suggesting that divalent metal ion facilitates the re-positioning of the GIY-YIG nuclease domain between sequential nicking reactions.

  13. Characterization and application of tourmaline and beryl from Brazilian pegmatite in adsorption process with divalent metals

    Institute of Scientific and Technical Information of China (English)

    Denis L.Guerra; Silze P.Oliveira; Ricardo A.R.Silva; Victor Leidens; Adriano C.Batista

    2012-01-01

    In this study,the original tourmaline and beryl mineral samples have been collected from a Brazilian pegmatite.The objective of this study was to examine the adsorption behavior of Brazilian ciclosilicate sampies,towards divalent metals (Pb2+,Mn2+,and Zn2+) in ethanol solution has been studies by a batch technique.The ciclosilicate samples were characterized by elemental analysis,Fourier transform infrared spectroscopy,helium picnometry,mercury porosity,and nitrogen adsorption-desorption.The Langmuir expression for adsorption isotherm was applied in order to determine the adsorption capacity to form a monolayer and the constant related to the adsorption intensity.In aqueous solution there was a significant adsorption increase with the temperature and pronounced synergistic effects were observed.The maximum number of moles adsorbed was determined to be 12.48 and 11.49 mmol/g for systems Pb2+/beryl and Pb2+/tourmaline,respectively.The energetic effects caused by metal cations adsorption were determined through calorimetric titrations.Thermodynamics indicated the existence of favorable conditions for such Pb2+-,Mn2+-,and Zn2+-OH interactions.

  14. Crystal structure of a divalent metal ion transporter CorA at 2.9 angstrom resolution.

    Science.gov (United States)

    Eshaghi, Said; Niegowski, Damian; Kohl, Andreas; Martinez Molina, Daniel; Lesley, Scott A; Nordlund, Pär

    2006-07-21

    CorA family members are ubiquitously distributed transporters of divalent metal cations and are considered to be the primary Mg2+ transporter of Bacteria and Archaea. We have determined a 2.9 angstrom resolution structure of CorA from Thermotoga maritima that reveals a pentameric cone-shaped protein. Two potential regulatory metal binding sites are found in the N-terminal domain that bind both Mg2+ and Co2+. The structure of CorA supports an efflux system involving dehydration and rehydration of divalent metal ions potentially mediated by a ring of conserved aspartate residues at the cytoplasmic entrance and a carbonyl funnel at the periplasmic side of the pore.

  15. Synthesis, structural characterization and biological studies of some nalidixic acid-metal complexes: Metalloantibiotic complexes of some divalent and trivalent metal ions

    Science.gov (United States)

    Al-Khodir, Fatima A. I.; Refat, Moamen S.

    2015-08-01

    This article describes the synthesis, characterization, computational and biological assessments of some divalent and trivalent metal (Ca(II), Fe(III), Pd(II) and Au(III)) complexes of nalidixic acid (nixH). The structures of these complexes were assigned using elemental analyses and spectral measurements e.g., IR, Raman, 1H NMR, 13C NMR and electronic techniques. These results indicated that, nalidixic acid reacts as a bidentate ligand bound to the metal ion through the oxygen atoms of carbonyl and carboxylate groups. The molar conductance measurements of the complexes in DMSO correspond to be non-electrolyte nature. Thus, these complexes may be formulated as [Ca(nix)(Cl)(H2O)3]. H2O, [Fe(nix)(Cl)2(H2O)2]·3H2O, [Pd(nix)(Cl)(H2O)] and [Au(nix)(Cl)2]. Base on the Coats-Redfern and Horowitz-Metzeger methods, the kinetic thermodynamic parameters (E∗, ΔS∗, ΔH∗ and ΔG∗) of the thermal decomposition reactions have been calculated from thermogravimetric curves of TG and DTG. The nano-scale range of the nalidixic acid complexes have been discussed using X-ray powder diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM) analyzer. The computational studies for the synthesized complexes have been estimated.

  16. Solid-State Properties of One-Dimensional Metals Based on bis(oxalato)platinate Anions with Divalent Cations

    DEFF Research Database (Denmark)

    Braude, A.; Carneiro, K.; Jacobsen, Claus Schelde

    1987-01-01

    The crystal structures, superstructures, dc conductivity, optical properties, and thermopower of six linear-chain conductors of the type M0.8[Pt(C2O4)2]⋅(M=Ni,Co,Zn,Fe,Mg,Mn), where M is a divalent metal (M=Ni,Co,Zn,Fe,Mg,Mn), have been studied. At high temperatures they form a common orthorhombi...

  17. Characterization of divalent metal metavanadates by 51V magic-angle spinning NMR spectroscopy of the central and satellite transitions.

    Science.gov (United States)

    Nielsen, U G; Jakobsen, H J; Skibsted, J

    2000-05-15

    51V quadrupole coupling and chemical shielding tensors have been determined from 51V magic-angle spinning (MAS) NMR spectra at a magnetic field of 14.1 T for nine divalent metal metavanadates: Mg(VO3)2, Ca(VO3)2, Ca(VO3)(2).4H2O, alpha-Sr(VO3)2, Zn(VO3)2, alpha- and beta-Cd(VO3)2. The manifold of spinning sidebands (ssbs) from the central and satellite transitions, observed in the 15V MAS NMR spectra, have been analyzed using least-squares fitting and numerical error analysis. This has led to a precise determination of the eight NMR parameters characterizing the magnitudes and relative orientations of the quadrupole coupling and chemical shielding tensors. The optimized data show strong similarities between the NMR parameters for the isostructural groups of divalent metal metavanadates. This demonstrates that different types of metavanadates can easily be distinguished by their anisotropic NMR parameters. The brannerite type of divalent metal metavanadates exhibits very strong 51V quadrupole couplings (i.e., CQ = 6.46-7.50 MHz), which reflect the highly distorted octahedral environments for the V5+ ion in these phases. Linear correlations between the principal tensor elements for the 51V quadrupole coupling tensors and electric field gradient tensor elements, estimated from point-monopole calculations, are reported for the divalent metal metavanadates. These correlations are used in the assignment of the NMR parameters for the different crystallographic 51V sites of Ca(VO3)(2).4H2O, Pb(VO3)2, and Ba(VO3)2. For alpha-Sr(VO3)2, with an unknown crystal structure, the 51V NMR data strongly suggest that this metavanadate is isostructural with Ba(VO3)2, for which the crystal structure has been reported. Finally, the chemical shielding parameters for orthovanadates and mono- and divalent metal metavanadates are compared.

  18. Viscometric studies of divalent transition metal sulphates in mixtures of water-diethylene glycol at 298.15-318.15 K

    Science.gov (United States)

    Thakur, Ramesh C.; Sharma, Ravi

    2017-09-01

    Relative viscosities of divalent transition metal sulphates solutions, viz. manganese, cobalt, nickel, copper, zinc and magnesium sulphate has been determined in water-diethylene glycol mixtures. Effect of temperature on the viscosities at 298.15-318.15 K has been studied and B coefficients of Jones-Dole equation are determined for these solutions. The obtained parameters have been interpreted in terms of ion-ion and ion-solvent interactions. Magnesium sulphate is taken as the reference electrolyte to see the change in the behavior of divalent ions when we shift from divalent transition metal ions to some other divalent ions in these solutions. Here these transition metal and magnesium sulphates behave in the same manner i.e structure makers in both water and in DEG + water mixtures.

  19. Reversible CO binding enables tunable CO/H₂ and CO/N₂ separations in metal-organic frameworks with exposed divalent metal cations.

    Science.gov (United States)

    Bloch, Eric D; Hudson, Matthew R; Mason, Jarad A; Chavan, Sachin; Crocellà, Valentina; Howe, Joshua D; Lee, Kyuho; Dzubak, Allison L; Queen, Wendy L; Zadrozny, Joseph M; Geier, Stephen J; Lin, Li-Chiang; Gagliardi, Laura; Smit, Berend; Neaton, Jeffrey B; Bordiga, Silvia; Brown, Craig M; Long, Jeffrey R

    2014-07-30

    Six metal-organic frameworks of the M2(dobdc) (M = Mg, Mn, Fe, Co, Ni, Zn; dobdc(4-) = 2,5-dioxido-1,4-benzenedicarboxylate) structure type are demonstrated to bind carbon monoxide reversibly and at high capacity. Infrared spectra indicate that, upon coordination of CO to the divalent metal cations lining the pores within these frameworks, the C-O stretching frequency is blue-shifted, consistent with nonclassical metal-CO interactions. Structure determinations reveal M-CO distances ranging from 2.09(2) Å for M = Ni to 2.49(1) Å for M = Zn and M-C-O angles ranging from 161.2(7)° for M = Mg to 176.9(6)° for M = Fe. Electronic structure calculations employing density functional theory (DFT) resulted in good agreement with the trends apparent in the infrared spectra and crystal structures. These results represent the first crystallographically characterized magnesium and zinc carbonyl compounds and the first high-spin manganese(II), iron(II), cobalt(II), and nickel(II) carbonyl species. Adsorption isotherms indicate reversible adsorption, with capacities for the Fe, Co, and Ni frameworks approaching one CO per metal cation site at 1 bar, corresponding to loadings as high as 6.0 mmol/g and 157 cm(3)/cm(3). The six frameworks display (negative) isosteric heats of CO adsorption ranging from 52.7 to 27.2 kJ/mol along the series Ni > Co > Fe > Mg > Mn > Zn, following the Irving-Williams stability order. The reversible CO binding suggests that these frameworks may be of utility for the separation of CO from various industrial gas mixtures, including CO/H2 and CO/N2. Selectivities determined from gas adsorption isotherm data using ideal adsorbed solution theory (IAST) over a range of gas compositions at 1 bar and 298 K indicate that all six M2(dobdc) frameworks could potentially be used as solid adsorbents to replace current cryogenic distillation technologies, with the choice of M dictating adsorbent regeneration energy and the level of purity of the resulting gases.

  20. Divalent Metal Ion Transport across Large Biological Ion Channels and Their Effect on Conductance and Selectivity

    Directory of Open Access Journals (Sweden)

    Elena García-Giménez

    2012-01-01

    Full Text Available Electrophysiological characterization of large protein channels, usually displaying multi-ionic transport and weak ion selectivity, is commonly performed at physiological conditions (moderate gradients of KCl solutions at decimolar concentrations buffered at neutral pH. We extend here the characterization of the OmpF porin, a wide channel of the outer membrane of E. coli, by studying the effect of salts of divalent cations on the transport properties of the channel. The regulation of divalent cations concentration is essential in cell metabolism and understanding their effects is of key importance, not only in the channels specifically designed to control their passage but also in other multiionic channels. In particular, in porin channels like OmpF, divalent cations modulate the efficiency of molecules having antimicrobial activity. Taking advantage of the fact that the OmpF channel atomic structure has been resolved both in water and in MgCl2 aqueous solutions, we analyze the single channel conductance and the channel selectivity inversion aiming to separate the role of the electrolyte itself, and the counterion accumulation induced by the protein channel charges and other factors (binding, steric effects, etc. that being of minor importance in salts of monovalent cations become crucial in the case of divalent cations.

  1. Cyclopiazonic Acid Is Complexed to a Divalent Metal Ion When Bound to the Sarcoplasmic Reticulum Ca2+-ATPase

    DEFF Research Database (Denmark)

    Laursen, Mette; Bublitz, Maike; Moncoq, Karine

    2009-01-01

    .5 angstrom resolution leads to a significantly revised model of CPA binding when compared with earlier reports. It shows that a divalent metal ion is required for CPA binding through coordination of the tetramic acid moiety at a characteristic kink of the M1 helix found in all P-type ATPase structures, which...... is expected to be part of the cytoplasmic cation access pathway. Our model is consistent with the biochemical data on CPA function and provides new measures in structure-based drug design targeting Ca2+-ATPases, e. g. from pathogens. We also present an extended structural basis of ATP modulation pinpointing...

  2. Unexpectedly Enhanced Solubility of Aromatic Amino Acids and Peptides in an Aqueous Solution of Divalent Transition-Metal Cations

    Science.gov (United States)

    Shi, Guosheng; Dang, Yaru; Pan, Tingting; Liu, Xing; Liu, Hui; Li, Shaoxian; Zhang, Lijuan; Zhao, Hongwei; Li, Shaoping; Han, Jiaguang; Tai, Renzhong; Zhu, Yiming; Li, Jichen; Ji, Qing; Mole, R. A.; Yu, Dehong; Fang, Haiping

    2016-12-01

    We experimentally observed considerable solubility of tryptophan (Trp) in a CuCl2 aqueous solution, which could reach 2-5 times the solubility of Trp in pure water. Theoretical studies show that the strong cation-π interaction between Cu2 + and the aromatic ring in Trp modifies the electronic distribution of the aromatic ring to enhance significantly the water affinity of Trp. Similar solubility enhancement has also been observed for other divalent transition-metal cations (e.g., Zn2 + and Ni2 + ), another aromatic amino acid (phenylalanine), and three aromatic peptides (Trp-Phe, Phe-Phe, and Trp-Ala-Phe).

  3. Divalent metal transporter 1 regulates iron-mediated ROS and pancreatic ß cell fate in response to cytokines

    DEFF Research Database (Denmark)

    Hansen, Jakob Bondo; Tonnesen, Morten Fog; Madsen, Andreas Nygaard

    2012-01-01

    divalent metal transporter 1 (DMT1) expression correlating with increased ß cell iron content and ROS production. Iron chelation and siRNA and genetic knockdown of DMT1 expression reduce cytokine-induced ROS formation and cell death. Glucose-stimulated insulin secretion in the absence of cytokines in Dmt1...... knockout islets is defective, highlighting a physiological role of iron and ROS in the regulation of insulin secretion. Dmt1 knockout mice are protected against multiple low-dose streptozotocin and high-fat diet-induced glucose intolerance, models of type 1 and type 2 diabetes, respectively. Thus, ß cells...

  4. Structural mapping and framework interconversions in 1D, 2D, and 3D divalent metal R,S-hydroxyphosphonoacetate hybrids.

    Science.gov (United States)

    Colodrero, Rosario M P; Olivera-Pastor, Pascual; Cabeza, Aurelio; Papadaki, Maria; Demadis, Konstantinos D; Aranda, Miguel A G

    2010-01-18

    Reactions of divalent cations (Mg(2+), Co(2+), Ni(2+), and Zn(2+)) with R,S-hydroxyphosphonoacetic acid (HPAA) in aqueous solutions (pH values ranging 1.0-4.0) yielded a range of crystalline hydrated M-HPAA hybrids. One-dimensional (1D) chain compounds were formed at room temperature whereas reactions conducted under hydrothermal conditions resulted in two-dimensional (2D) layered frameworks or, in some cases, three-dimensional (3D) networks incorporating various alkaline cations. 1D phases with compositions [M{HO(3)PCH(OH)CO(2)}(H(2)O)(2)].2H(2)O (M = Mg, Co, and Zn) were isolated. These compounds were dehydrated in liquid water to yield the corresponding [M{HO(3)PCH(OH)CO(2)}(H(2)O)(2)] compounds lacking the lattice water between the 1D chains. [M{HO(3)PCH(OH)CO(2)}(H(2)O)(2)] (M = Mg, Ni, Co, Zn) compounds were formed by crystallization at room temperature (at higher pH values) or also by partial dehydration of 1D compounds with higher hydration degrees. Complete dehydration of these 1D solids at 240-270 degrees C led to 3D phases, [M{HO3PCH(OH)CO(2)}]. The 2D layered compound [Mg{HO(3)PCH(OH)CO(2)}(H(2)O)(2)] was obtained under hydrothermal conditions. For both synthesis methods, addition of alkali metal hydroxides to adjust the pH usually led to mixed phase materials, whereas direct reactions between the metal oxides and the hydroxyphosphonoacetic acid gave single phase materials. On the other hand, adjusting the pH with acetate salts and increasing the ratio M(2+)/HPAA and/or the A(+)/M(2+) ratio (A = Na, K) resulted in 3D networks, where the alkali cations were incorporated within the frameworks for charge compensation. The crystal structures of eight new M(II)-HPAA hybrids are reported herein and the thermal behavior related to dehydration/rehydration of some compounds are studied in detail.

  5. Adsorption performances and mechanisms of the newly synthesized N,N'-di (carboxymethyl) dithiocarbamate chelating resin toward divalent heavy metal ions from aqueous media

    Energy Technology Data Exchange (ETDEWEB)

    Jing Xiaosheng [State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210093 (China); Liu Fuqiang, E-mail: jogia@163.com [State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210093 (China) and Engineering Technology Research Center of Organic Toxic Substance Control and Resource Reuse of Jiangsu Province, Nanjing 210046 (China); Yang Xin; Ling Panpan; Li Lanjuan [State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210093 (China); Long Chao; Li Aimin [State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210093 (China); Engineering Technology Research Center of Organic Toxic Substance Control and Resource Reuse of Jiangsu Province, Nanjing 210046 (China)

    2009-08-15

    N,N'-di (carboxymethyl) dithiocarbamate chelating resin (PSDC) was synthesized by anchoring the chelating agent of N,N'-di (carboxymethyl) dithiocarbamate to the chloromethylated PS-DVB (Cl-PS-DVB) matrix, as a new adsorbent for removing divalent heavy metal ions from waste-stream. The physicochemical structures of Cl-PS-DVB and PSDC were elaborately characterized using Fourier transform infrared spectroscopy (FT-IR), elemental analysis (EA), and were further morphologically characterized using BET and BJH methods. The adsorption performances of PSDC towards heavy metals such as Cu(II), Pb(II) and Ni(II) were systematically investigated, based upon which the adsorption mechanisms were deeply exploited. For the above target, the classic batch adsorption experiments were conducted to explore the kinetics and isotherms of the removal processes with pH-value, initial concentration, temperature, and contact time as the controlling parameters. The kinetic and isotherm data could be well elucidated with Lagergren-second-order equation and Langmuir model respectively. The strong affinity of PSDC toward these target soft acids could be well demonstrated with the electrostatic attraction and chelating interaction caused by IDA moiety and sulphur which were namely soft bases on the concept of hard and soft acids and bases (HASB). Thermodynamic parameters, involving {Delta}H{sup o}, {Delta}S{sup o} and {Delta}G{sup o} were also calculated from graphical interpretation of the experimental data. The standard heats of adsorption ({Delta}H{sup o}) were found to be endothermic and the entropy change values ({Delta}S{sup o}) were calculated to be positive for the adsorption of Cu(II), Pb(II) and Ni(II) ions onto the tested adsorbents. Negative values of {Delta}G{sup o} indicated that adsorption processes for all tested metal ions onto PSDC were spontaneous.

  6. Headgroup interactions and ion flotation efficiency in mixtures of a chelating surfactant, different foaming agents, and divalent metal ions.

    Science.gov (United States)

    Svanedal, Ida; Boija, Susanne; Norgren, Magnus; Edlund, Håkan

    2014-06-10

    The correlation between interaction parameters and ion flotation efficiency in mixtures of chelating surfactant metal complexes and different foaming agents was investigated. We have recently shown that chelating surfactant 2-dodecyldiethylenetriaminepentaacetic acid (4-C12-DTPA) forms strong coordination complexes with divalent metal ions, and this can be utilized in ion flotation. Interaction parameters for mixed micelles and mixed monolayer formation for Mg(2+) and Ni(2+) complexes with the chelating surfactant 4-C12-DTPA and different foaming agents were calculated by Rubingh's regular solution theory. Parameters for the calculations were extracted from surface tension measurements and NMR diffusometry. The effects of metal ion coordination on the interactions between 4-C12-DTPA and the foaming agents could be linked to a previously established difference in coordination chemistry between the examined metal ions. As can be expected from mixtures of amphoteric surfactants, the interactions were strongly pH-dependent. Strong correlation was found between interaction parameter β(σ) for mixed monolayer formation and the phase-transfer efficiency of Ni(2+) complexes with 4-C12-DTPA during flotation in a customized flotation cell. In a mixture of Cu(2+) and Zn(2+), the significant difference in conditional stability constants (log K) between the metal complexes was utilized to selectively recover the metal complex with the highest log K (Cu(2+)) by ion flotation. Flotation experiments in an excess concentration of metal ions confirmed the coordination of more than one metal ion to the headgroup of 4-C12-DTPA.

  7. Characterization of the interactions between the active site of a protein tyrosine kinase and a divalent metal activator

    Directory of Open Access Journals (Sweden)

    Ayrapetov Marina K

    2005-11-01

    Full Text Available Abstract Background Protein tyrosine kinases are important enzymes for cell signalling and key targets for anticancer drug discovery. The catalytic mechanisms of protein tyrosine kinase-catalysed phosphorylation are not fully understood. Protein tyrosine kinase Csk requires two Mg2+ cations for activity: one (M1 binds to ATP, and the other (M2 acts as an essential activator. Results Experiments in this communication characterize the interaction between M2 and Csk. Csk activity is sensitive to pH in the range of 6 to 7. Kinetic characterization indicates that the sensitivity is not due to altered substrate binding, but caused by the sensitivity of M2 binding to pH. Several residues in the active site with potential of binding M2 are mutated and the effect on metal activation studied. An active mutant of Asn319 is generated, and this mutation does not alter the metal binding characteristics. Mutations of Glu236 or Asp332 abolish the kinase activity, precluding a positive or negative conclusion on their role in M2 coordination. Finally, the ability of divalent metal cations to activate Csk correlates to a combination of ionic radius and the coordination number. Conclusion These studies demonstrate that M2 binding to Csk is sensitive to pH, which is mainly responsible for Csk activity change in the acidic arm of the pH response curve. They also demonstrate critical differences in the metal activator coordination sphere in protein tyrosine kinase Csk and a protein Ser/Thr kinase, the cAMP-dependent protein kinase. They shed light on the physical interactions between a protein tyrosine kinase and a divalent metal activator.

  8. Evaluation of the effect of divalent metal transporter 1 gene polymorphism on blood iron, lead and cadmium levels

    Energy Technology Data Exchange (ETDEWEB)

    Kayaaltı, Zeliha, E-mail: kayaalti@ankara.edu.tr; Akyüzlü, Dilek Kaya; Söylemezoğlu, Tülin

    2015-02-15

    Divalent metal transporter 1 (DMT1), a member of the proton-coupled metal ion transporter family, mediates transport of ferrous iron from the lumen of the intestine into the enterocyte and export of iron from endocytic vesicles. It has an affinity not only for iron but also for other divalent cations including manganese, cobalt, nickel, cadmium, lead, copper, and zinc. DMT1 is encoded by the SLC11a2 gene that is located on chromosome 12q13 in humans and express four major mammalian isoforms (1A/+IRE, 1A/-IRE, 2/+IRE and 2/-IRE). Mutations or polymorphisms of DMT1 gene may have an impact on human health by disturbing metal trafficking. To study the possible association of DMT1 gene with the blood levels of some divalent cations such as iron, lead and cadmium, a single nucleotide polymorphism (SNP) (IVS4+44C/A) in DMT1 gene was investigated in 486 unrelated and healthy individuals in a Turkish population by method of polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP). The genotype frequencies were found as 49.8% homozygote typical (CC), 38.3% heterozygote (CA) and 11.9% homozygote atypical (AA). Metal levels were analyzed by dual atomic absorption spectrometer system and the average levels of iron, lead and cadmium in the blood samples were 446.01±81.87 ppm, 35.59±17.72 ppb and 1.25±0.87 ppb, respectively. Individuals with the CC genotype had higher blood iron, lead and cadmium levels than those with AA and CA genotypes. Highly statistically significant associations were detected between IVS4+44 C/A polymorphism in the DMT1 gene and iron and lead levels (p=0.001 and p=0.036, respectively), but no association was found with cadmium level (p=0.344). This study suggested that DMT1 IVS4+44 C/A polymorphism is associated with inter-individual variations in blood iron, lead and cadmium levels. - Highlights: • DMT1 IVS4+44 C/A polymorphism is associated with inter-individual variations in blood iron, cadmium and lead levels.

  9. Polymerization of a divalent/tetravalent metal-storing atom-mimicking dendrimer.

    Science.gov (United States)

    Albrecht, Ken; Hirabayashi, Yuki; Otake, Masaya; Mendori, Shin; Tobari, Yuta; Azuma, Yasuo; Majima, Yutaka; Yamamoto, Kimihisa

    2016-12-01

    The phenylazomethine dendrimer (DPA) has a layer-by-layer electron density gradient that is an analog of the Bohr atom (atom mimicry). In combination with electron pair mimicry, the polymerization of this atom-mimicking dendrimer was achieved. The valency of the mimicked atom was controlled by changing the chemical structure of the dendrimer. By mimicking a divalent atom, a one-dimensional (1D) polymer was obtained, and by using a planar tetravalent atom mimic, a 2D polymer was obtained. These poly(dendrimer) polymers could store Lewis acids (SnCl2) in their unoccupied orbitals, thus indicating that these poly(dendrimer) polymers consist of a series of nanocontainers.

  10. Cyclopiazonic Acid Is Complexed to a Divalent Metal Ion When Bound to the Sarcoplasmic Reticulum Ca2+-ATPase

    DEFF Research Database (Denmark)

    Laursen, Mette; Bublitz, Maike; Moncoq, Karine;

    2009-01-01

    Abstract: We have determined the structure of the sarco(endo) plasmic reticulum Ca2+-ATPase (SERCA) in an E2.P-i-like form stabilized as a complex with MgF42-, an ATP analog, adenosine 5'-(beta,gamma-methylene) triphosphate (AMPPCP), and cyclopiazonic acid (CPA). The structure determined at 2.......5 angstrom resolution leads to a significantly revised model of CPA binding when compared with earlier reports. It shows that a divalent metal ion is required for CPA binding through coordination of the tetramic acid moiety at a characteristic kink of the M1 helix found in all P-type ATPase structures, which...... is expected to be part of the cytoplasmic cation access pathway. Our model is consistent with the biochemical data on CPA function and provides new measures in structure-based drug design targeting Ca2+-ATPases, e. g. from pathogens. We also present an extended structural basis of ATP modulation pinpointing...

  11. Studies on the effect of divalent metal ions on exfoliative toxins from Staphylococcus hyicus: indications of ExhA and ExhB being metalloproteins

    DEFF Research Database (Denmark)

    Andresen, Lars Ole

    1999-01-01

    The exfoliative toxins ExhA and ExhB produced by Staphylococcus hyicus strains NCTC10350 and 1289D-88, respectively, were investigated with regard to the effect of divalent metal ions on toxin production as measured in indirect enzyme-linked immunosorbent assay (ELISA) using monoclonal antibodies...

  12. Radical bonding: structure and stability of bis(phenalenyl) complexes of divalent metals from across the periodic table.

    Science.gov (United States)

    Craciun, Smaranda; Donald, Kelling J

    2009-07-06

    We examine the bonding possibilities of the bis(phenalenyl) MP(2) sandwich complexes of the divalent metals M = Be, Mg, Ca, Sr, Ba, Zn, Cd, and Hg, at the B3LYP level of theory. The outcome is an extraordinarily diverse class of low symmetry bis(phenalenyl)metal complexes in which bonding preferences and binding enthalpies differ dramatically. The lowest energy group 2 metal MP(2) complexes include an intriguing eta(1),eta(3) BeP(2) structure, and bent eta(6),eta(6) systems for M = Ca, Sr, and Ba. The group 12 bis(phenalenyl) complexes are thermodynamically unstable eta(1),eta(1) slip-sandwich structures. To better understand changes in the structural preferences going from the (eta(6),eta(6)) group 2 to the (eta(1),eta(1)) group 12 complexes, we explored the bonding in the bis(phenalenyl) complexes of transition metals with stable +2 oxidations states between Ca and Zn in period 4. The computed binding enthalpies are large and negative for nearly all of the minimum energy bis(phenalenyl) complexes of the group 2 and the transition metals; they are tiny for MgP(2), and are quite positive for the group 12 systems. The structural preferences and stability of the complexes is a subtle negotiation of several influences: the (un)availability of (n - 1)d and np, orbitals for bonding, the cost of the rehybridization at carbon sites in the phenalenyl rings in preparation for bonding to the metals, and the (P---P) interaction between the phenalenyl radicals.

  13. Speciation study on the interaction of some divalent transition metal ions with succinic acid dihydrazide in aqueous medium.

    Science.gov (United States)

    Satyanarayana, Atreyapurapu; Kenie, Dunkana Negussa; Shyamala, Pulipaka

    2013-01-01

    The interaction of succinic acid dihydrazide with Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) was investigated in aqueous medium at 303K and ionic strength of 0.1 mol dm-3. The speciation and stability constants of the metal complexes formed were determined by pH-metric method. Mononuclear and homo binuclear species in different protonation and deprotonation states were identified, the corresponding formation constants calculated using MINIQUAD-75 computer program, and species distribution diagrams produced using the HYSS computer program. Selection of the best-fit chemical models was based on statistical parameters.

  14. divalent metal complexes of 4-amino-n-pyrimidin-2-ylbenzene ...

    African Journals Online (AJOL)

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    use of metal complexes as chemotherapeutic drugs has become a vibrant and growing area of ..... through the pyrimidine nitrogen atom [17]. ... binding can take place by the acceptance of a one pair of electron from the donor nitrogen atom.

  15. Dissolved Divalent Metal and pH Effects on Amino Acid Polymerization: A Thermodynamic Evaluation

    Science.gov (United States)

    Kitadai, Norio

    2016-06-01

    Polymerization of amino acids is a fundamentally important step for the chemical evolution of life. Nevertheless, its response to changing environmental conditions has not yet been well understood because of the lack of reliable quantitative information. For thermodynamics, detailed prediction over diverse combinations of temperature and pH has been made only for a few amino acid-peptide systems. This study used recently reported thermodynamic dataset for the polymerization of the simplest amino acid "glycine (Gly)" to its short peptides (di-glycine and tri-glycine) to examine chemical and structural characteristics of amino acids and peptides that control the temperature and pH dependence of polymerization. Results showed that the dependency is strongly controlled by the intramolecular distance between the amino and carboxyl groups in an amino acid structure, although the side-chain group role is minor. The polymerization behavior of Gly reported earlier in the literature is therefore expected to be a typical feature for those of α-amino acids. Equilibrium calculations were conducted to examine effects of dissolved metals as a function of pH on the monomer-polymer equilibria of Gly. Results showed that metals shift the equilibria toward the monomer side, particularly at neutral and alkaline pH. Metals that form weak interaction with Gly (e.g., Mg2+) have no noticeable influence on the polymerization, although strong interaction engenders significant decrease of the equilibrium concentrations of Gly peptides. Considering chemical and structural characteristics of Gly and Gly peptides that control their interactions with metals, it can be expected that similar responses to the addition of metals are applicable in the polymerization of neutral α-amino acids. Neutral and alkaline aqueous environments with dissolved metals having high affinity with neutral α-amino acids (e.g., Cu2+) are therefore not beneficial places for peptide bond formation on the primitive

  16. Dissolved Divalent Metal and pH Effects on Amino Acid Polymerization: A Thermodynamic Evaluation.

    Science.gov (United States)

    Kitadai, Norio

    2017-03-01

    Polymerization of amino acids is a fundamentally important step for the chemical evolution of life. Nevertheless, its response to changing environmental conditions has not yet been well understood because of the lack of reliable quantitative information. For thermodynamics, detailed prediction over diverse combinations of temperature and pH has been made only for a few amino acid-peptide systems. This study used recently reported thermodynamic dataset for the polymerization of the simplest amino acid "glycine (Gly)" to its short peptides (di-glycine and tri-glycine) to examine chemical and structural characteristics of amino acids and peptides that control the temperature and pH dependence of polymerization. Results showed that the dependency is strongly controlled by the intramolecular distance between the amino and carboxyl groups in an amino acid structure, although the side-chain group role is minor. The polymerization behavior of Gly reported earlier in the literature is therefore expected to be a typical feature for those of α-amino acids. Equilibrium calculations were conducted to examine effects of dissolved metals as a function of pH on the monomer-polymer equilibria of Gly. Results showed that metals shift the equilibria toward the monomer side, particularly at neutral and alkaline pH. Metals that form weak interaction with Gly (e.g., Mg(2+)) have no noticeable influence on the polymerization, although strong interaction engenders significant decrease of the equilibrium concentrations of Gly peptides. Considering chemical and structural characteristics of Gly and Gly peptides that control their interactions with metals, it can be expected that similar responses to the addition of metals are applicable in the polymerization of neutral α-amino acids. Neutral and alkaline aqueous environments with dissolved metals having high affinity with neutral α-amino acids (e.g., Cu(2+)) are therefore not beneficial places for peptide bond formation on the primitive

  17. Dissolved Divalent Metal and pH Effects on Amino Acid Polymerization: A Thermodynamic Evaluation

    Science.gov (United States)

    Kitadai, Norio

    2017-03-01

    Polymerization of amino acids is a fundamentally important step for the chemical evolution of life. Nevertheless, its response to changing environmental conditions has not yet been well understood because of the lack of reliable quantitative information. For thermodynamics, detailed prediction over diverse combinations of temperature and pH has been made only for a few amino acid-peptide systems. This study used recently reported thermodynamic dataset for the polymerization of the simplest amino acid "glycine (Gly)" to its short peptides (di-glycine and tri-glycine) to examine chemical and structural characteristics of amino acids and peptides that control the temperature and pH dependence of polymerization. Results showed that the dependency is strongly controlled by the intramolecular distance between the amino and carboxyl groups in an amino acid structure, although the side-chain group role is minor. The polymerization behavior of Gly reported earlier in the literature is therefore expected to be a typical feature for those of α-amino acids. Equilibrium calculations were conducted to examine effects of dissolved metals as a function of pH on the monomer-polymer equilibria of Gly. Results showed that metals shift the equilibria toward the monomer side, particularly at neutral and alkaline pH. Metals that form weak interaction with Gly (e.g., Mg2+) have no noticeable influence on the polymerization, although strong interaction engenders significant decrease of the equilibrium concentrations of Gly peptides. Considering chemical and structural characteristics of Gly and Gly peptides that control their interactions with metals, it can be expected that similar responses to the addition of metals are applicable in the polymerization of neutral α-amino acids. Neutral and alkaline aqueous environments with dissolved metals having high affinity with neutral α-amino acids (e.g., Cu2+) are therefore not beneficial places for peptide bond formation on the primitive

  18. SYNTHESIS AND CHARACTERIZATION OF SALICYLALDAZINE AND ITS METAL (II) COMPLEXES DERIVED FROM METAL (II) CHLORIDES

    OpenAIRE

    Jamila wazir

    2016-01-01

    The salicylaldazine (ligand) and its metal (II) complexes like copper (II), nickel (II), zinc (II), cobalt (II) and manganese (II) complexes has been synthesized and characterized by different techniques using FTIR, UV-VIS spectroscopy. The ligand (salicylaldazine) is synthesized by the condensation reaction of salicylaldehyde and hydrazine sulfate. The salicylaldazine metal (II) complexes like Cu (II) , Ni(II), Zn (II), Co(II), Mn(II) were prepared by using metal (II) chloride in dioxane. Th...

  19. Metal Cation Binding to Gas-Phase Pentaalanine: Divalent Ions Restructure the Complex

    NARCIS (Netherlands)

    Dunbar, R. C.; Steill, J. D.; Polfer, N. C.; Oomens, J.

    2013-01-01

    Ion-neutral complexes of pentaalalanine with several singly- and doubly charged metal ions are examined using conformation analysis by infrared multiple photon dissociation (IRMPD) spectroscopy and density functional theory (DFT) computations. The infrared spectroscopy in the 1500-1800 cm(-1) region

  20. Metal Cation Binding to Gas-Phase Pentaalanine: Divalent Ions Restructure the Complex

    NARCIS (Netherlands)

    Dunbar, R.C.; Steill, J.D.; Polfer, N.C.; Oomens, J.

    2013-01-01

    Ion-neutral complexes of pentaalalanine with several singly- and doubly charged metal ions are examined using conformation analysis by infrared multiple photon dissociation (IRMPD) spectroscopy and density functional theory (DFT) computations. The infrared spectroscopy in the 1500-1800 cm(-1) region

  1. Divalent metal transporter 1 regulates iron-mediated ROS and pancreatic β cell fate in response to cytokines.

    Science.gov (United States)

    Hansen, Jakob Bondo; Tonnesen, Morten Fog; Madsen, Andreas Nygaard; Hagedorn, Peter H; Friberg, Josefine; Grunnet, Lars Groth; Heller, R Scott; Nielsen, Anja Østergren; Størling, Joachim; Baeyens, Luc; Anker-Kitai, Leeat; Qvortrup, Klaus; Bouwens, Luc; Efrat, Shimon; Aalund, Mogens; Andrews, Nancy C; Billestrup, Nils; Karlsen, Allan E; Holst, Birgitte; Pociot, Flemming; Mandrup-Poulsen, Thomas

    2012-10-03

    Reactive oxygen species (ROS) contribute to target-cell damage in inflammatory and iron-overload diseases. Little is known about iron transport regulation during inflammatory attack. Through a combination of in vitro and in vivo studies, we show that the proinflammatory cytokine IL-1β induces divalent metal transporter 1 (DMT1) expression correlating with increased β cell iron content and ROS production. Iron chelation and siRNA and genetic knockdown of DMT1 expression reduce cytokine-induced ROS formation and cell death. Glucose-stimulated insulin secretion in the absence of cytokines in Dmt1 knockout islets is defective, highlighting a physiological role of iron and ROS in the regulation of insulin secretion. Dmt1 knockout mice are protected against multiple low-dose streptozotocin and high-fat diet-induced glucose intolerance, models of type 1 and type 2 diabetes, respectively. Thus, β cells become prone to ROS-mediated inflammatory damage via aberrant cellular iron metabolism, a finding with potential general cellular implications. Copyright © 2012 Elsevier Inc. All rights reserved.

  2. TOLERANCE OF AGAVE TEQUILANA TO HIGH LEVELS OF DIVALENT METAL CATIONS

    Directory of Open Access Journals (Sweden)

    Elmi Roseida Cen-Cen

    2015-11-01

    Full Text Available Los agaves son plantas que pertenecen a un género constituido por numerosas especies, adaptadas para crecer en muy diversos hábitats, algunos con condiciones ambientales extremas. Distintas especies de agave crecen sobre distintos tipos de suelos, algunas en suelos con muy bajo contenido de nutrientes minerales y otras en suelos salinos o en suelos contaminados con iones metálicos. La relación planta-suelo ha sido escasamente estudiada en este género por lo que se desconoce, entre otras cuestiones, cuál es la capacidad de los agaves para absorber, transportar y almacenar nutrientes minerales, cuáles son los mecanismos celulares y bioquímicos que utilizan, o si poseen especial sensibilidad o tolerancia a los iones metálicos. Este estudio reporta el efecto de diversas concentraciones de sulfato de cadmio, cobalto, cobre, zinc o de manganeso sobre plántulas deAgave tequilana, bajo condiciones controladas de laboratorio; la concentración mínima de esos iones metálicos requerida para inducir un efecto tóxico visualmente detectable en tiempos cortos (ocho días; describimos los efectos tóxicos que estos metales generan sobre las plántulas de agave; y reportamos la cantidad de Cu2+, Cd2+ y Co2+ que se acumula en las hojas de plántulas de agave tratadas con altas concentraciones (milimolares de esos metales. Nuestros resultados muestran que, en experimentos de toxicidad aguda y bajo las condiciones aquí establecidas, elA. tequilanaposee una notable tolerancia a altas concentraciones de los distintos metales iónicos probados, incluyendo tanto micronutrientes como metales tóxicos, así como la capacidad de transportar en altas cantidades estos metales a tejido aéreo.

  3. Divalent metal transporter, iron, and Parkinson's disease:A pathological relationship

    Institute of Scientific and Technical Information of China (English)

    Hyun-pil Lee; Xiongwei Zhu; Gang Liu; Shu G Chen; George Perry; Mark A Smith; Hyoung-gon Lee

    2010-01-01

    @@ Iron is an essential component of oxidative metabolism and a cofactor for a variety of enzymes. Because of its chemical properties as a transition metal, iron can serve both as an electron donor and acceptor and, as such, excess levels of free iron are toxic. Given this potential for toxicity, a number of pro-teins, including transferrin, transferrin receptor, and ferritin, tightly control iron transport, uptake, and storage in the central nervous system.

  4. Interaction of selected divalent metal ions with human ataxin-3 Q36.

    Science.gov (United States)

    Stawoska, Iwona; Wesełucha-Birczyńska, Aleksandra; Regonesi, Maria Elena; Riva, Matteo; Tortora, Paolo; Stochel, Grazyna

    2009-11-01

    The mode of interaction of ataxin-3 Q36 (AT-3 Q36) with selected endogenous and exogenous metal ions, namely, Zn(2+), Cu(2+), Ni(2+), and Cd(2+), was examined. Metal-ion-induced structural changes of the protein were monitored by fluorescence as well as Fourier transform Raman spectroscopy. We found that the cations tested lead to a decrease in alpha-helical content and a concurrent increase in beta-sheet as well as undefined (beta-turn and random-coil) structures. The most evident effect was observed for copper and nickel cations. After titration with these cations, the AT3 Q36 secondary structure content (27% alpha-helices in the presence of either ion, 31 and 27% beta-sheets for Cu(2+) and Ni(2+), respectively) was similar to that observed for the aggregated form of the protein (27% alpha-helices, 36% beta-sheets). Using the 1-anilinonaphthalene-8-sulfonate hydrophobic fluorescence probe, we showed that the presence of the metal ions tested led to the formation of solvent-exposed hydrophobic patches of AT-3 Q36, and that such an effect decreased with increasing ionic radius.

  5. Study the effects of divalent metallic ions on the combination of DNA and histones with fluorescence anisotropy assays

    Institute of Scientific and Technical Information of China (English)

    LIU YuYing; WANG PengYe; DOU ShuoXing; XIE Ping; XI XuGuang

    2007-01-01

    The effects of divalent ions (Mn2+, Mg2+, Ca2+) on the interaction between DNA and histone are studied using a fluorescence anisotropy assay. Fluorescence anisotropies of DNA and DNA-histone in the presence of divalent ions (Mn2+, Mg2+, Ca2+) are measured. The results indicate that histone reduces the fluorescence anisotropy of lambda DNA while the divalent ions (Mn2+, Mg2+, Ca2+) significantly enhance the fluorescence anisotropy. Compared to the case of DNA incubated with histone alone, there are more histones binding to DNA when divalent ion, histone and DNA are incubated together. We also find that Mn2+ makes the DNA-histone complexes more condensed than the other ions do.

  6. Metal-ion dependent catalytic properties of Sulfolobus solfataricus class II α-mannosidase

    DEFF Research Database (Denmark)

    Nielsen, Jonas Willum; Poulsen, Nina Rødtness; Johnsson, Anna Margit Susanne;

    2012-01-01

    The active site for the family GH38 class II α-mannosidase is constituted in part by a divalent metal ion, mostly Zn(2+), as revealed in the crystal structures of enzymes from both animal and bacterial sources. The metal ion coordinates to the bound substrate and side chains of conserved amino acid...... residues. Recently, evidence has accumulated that class II α-mannosidase is active in complex with a range of divalent metal ions. In the present work, with employment of the class II α-mannosidase, ManA, from the hyperthermophilic archaeon Sulfolobus solfataricus, we explored the influence of the divalent...... metal ion on the associated steady-state kinetic parameters, K(M) and k(cat), for various substrates. With p-nitrophenyl-α-d-mannoside as a substrate, the enzyme showed activity in the presence of Co(2+), Cd(2+), Mn(2+), and Zn(2+), whereas Ni(2+) and Cu(2+) were inhibitory and nonactivating. Co(2...

  7. Enhanced Retention of Chelating Reagents in Octadecylsilyl Silica Phase by Interaction with Residual Silanol Groups in Solid Phase Extraction of Divalent Metal Ions.

    Science.gov (United States)

    Ohmuro, Satoshi; Fujii, Kan; Yasui, Takashi; Takada, Kazutake; Yuchi, Akio; Kokusen, Hisao

    2016-01-01

    Solid-phase extraction (SPE) of divalent metal ions with a lipophilic and potentially divalent hexadentate chelating reagent (H2L), with which octadecylsilyl silica (ODS), was impregnated with was studied to gain more insight into and develop the potential of this methodology. This is the first time to demonstrate that this reagent as well as other common nitrogen-containing reagents were retained both by adsorption due to hydrogen bonding between nitrogen atoms of the reagent and residual silanol groups in the ODS phase and by simple distribution into the hydrophobic space. An appreciably large amount of this reagent could be retained by the adsorption mechanism even with a relatively thin loading solution. The divalent metal ions of Mn(2+), Co(2+) and Zn(2+) were extracted as 1:1 neutral complexes ([ML]), while Ni(2+) and Cu(2+) as ion-pairs of 1:1 cationic complex ([MHL](+)) with anion in SPE with H2L. The extractability and selectivity were substantially the same as that in liquid-liquid extraction.

  8. Tuning of the magnetostrictive properties of cobalt ferrite by forced distribution of substituted divalent metal ions at different crystallographic sites

    Science.gov (United States)

    Anantharamaiah, P. N.; Joy, P. A.

    2017-03-01

    Comparative studies have been made to understand the role of different crystallographic site preferences of the substituted non-magnetic divalent metal ions in the magnetostrictive properties of cobalt ferrite, by substitution of Zn2+ and/or Mg2+ for Fe3+ in CoMgxFe2-xO4, CoZnxFe2-xO4, and CoMgx/2Znx/2Fe2-xO4 (0.0 ≤ x ≤ 0.2). Detailed Raman spectral and magnetic characterizations are made to extract the information on the tetrahedral/octahedral site preferences of Zn and Mg in the spinel lattice of cobalt ferrite. The structural, microstructural, magnetic, Raman spectral, and magnetostrictive parameters of the studied compositions show distinguishable variations for x < 0.1 and x ≥ 0.1. Co-substitution of a small amount of Mg and Zn for Fe in CoMgx/2Znx/2Fe2-xO4 (x < 0.1) showed relatively larger strain sensitivity, [dλ/dH]max (-2.6 × 10-9 mA-1 for x = 0.05), higher than that for the Mg-substituted samples (-2.05 × 10-9 mA-1 for x = 0.05) and comparable to that for the Zn-substituted samples (-2.47 × 10-9 mA-1 for x = 0.05), without much drop in the maximum value of magnetostriction, λmax (-189 ppm for x = 0.05) compared to that for the unsubstituted counterpart (-221 ppm). The results show that it is possible to obtain high strain sensitivity (at fields <50 kA/m), along with high magnetostriction strain at low magnetic fields (˜250 kA/m), by tuning the distribution of the substituted cations in the tetrahedral and octahedral sites of the cobalt ferrite lattice.

  9. A Versatile Strategy for Production of Membrane Proteins with Diverse Topologies: Application to Investigation of Bacterial Homologues of Human Divalent Metal Ion and Nucleoside Transporters.

    Directory of Open Access Journals (Sweden)

    Cheng Ma

    Full Text Available Membrane proteins play key roles in many biological processes, from acquisition of nutrients to neurotransmission, and are targets for more than 50% of current therapeutic drugs. However, their investigation is hampered by difficulties in their production and purification on a scale suitable for structural studies. In particular, the nature and location of affinity tags introduced for the purification of recombinant membrane proteins can greatly influence their expression levels by affecting their membrane insertion. The extent of such effects typically depends on the transmembrane topologies of the proteins, which for proteins of unknown structure are usually uncertain. For example, attachment of oligohistidine tags to the periplasmic termini of membrane proteins often interferes with folding and drastically impairs expression in Escherichia coli. To circumvent this problem we have employed a novel strategy to enable the rapid production of constructs bearing a range of different affinity tags compatible with either cytoplasmic or periplasmic attachment. Tags include conventional oligohistidine tags compatible with cytoplasmic attachment and, for attachment to proteins with a periplasmic terminus, either tandem Strep-tag II sequences or oligohistidine tags fused to maltose binding protein and a signal sequence. Inclusion of cleavage sites for TEV or HRV-3C protease enables tag removal prior to crystallisation trials or a second step of purification. Together with the use of bioinformatic approaches to identify members of membrane protein families with topologies favourable to cytoplasmic tagging, this has enabled us to express and purify multiple bacterial membrane transporters. To illustrate this strategy, we describe here its use to purify bacterial homologues of human membrane proteins from the Nramp and ZIP families of divalent metal cation transporters and from the concentrative nucleoside transporter family. The proteins are expressed in

  10. Divalent metals stabilize cellular prion proteins and alter the rate of proteinase-K dependent limited proteolysis

    Science.gov (United States)

    Background: The key biochemical event in the pathogenesis of prion diseases is the conversion of normal cellular prion proteins (PrP**c) to the proteinase K (PK) resistant, abnormal form (PrP**sc); however, the cellular mechanisms underlying the conversion remain enigmatic. Binding of divalent ca...

  11. Trace Metals in Groundwater & Vadose Zone Calcite: In Situ Containment & Stabilization of Stronthium-90 & Other Divalent Metals & Radionuclides at Arid West DOE

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Robert W

    2003-06-01

    microbial calcite precipitation on the partitioning and retention of strontium and other naturally occurring divalent metals in groundwater. * Identification of specific microbial characteristics that signify subsurface geochemical conditions conducive to ureolytically-driven calcite precipitation.

  12. Affinity of Smectite and Divalent Metal Ions (Mg2+, Ca2+, Cu2+) with L-leucine: An Experimental and Theoretical Approach Relevant to Astrobiology

    Science.gov (United States)

    Pandey, Pramod; Pant, Chandra Kala; Gururani, Kavita; Arora, Priyanka; Pandey, Neetu; Bhatt, Preeti; Sharma, Yogesh; Negi, Jagmohan Singh; Mehata, Mohan Singh

    2015-12-01

    Earth is the only known planet bestowed with life. Several attempts have been made to explore the pathways of the origin of life on planet Earth. The search for the chemistry which gave rise to life has given answers related to the formation of biomonomers, and their adsorption on solid surfaces has gained much attention for the catalysis and stabilization processes related to the abiotic chemical evolution of the complex molecules of life. In this communication, surface interactions of L-leucine (Leu) on smectite (SMT) group of clay (viz. bentonite and montmorillonite) and their divalent metal ion (Mg2+, Ca2+ and Cu2+) incorporated on SMT has been studied to find the optimal conditions of time, pH, and concentration at ambient temperature (298 K). The progress of adsorption was followed spectrophotometrically and further characterized by FTIR, SEM/EDS and XRD. Leu, a neutral/non polar amino acid, was found to have more affinity in its zwitterionic form towards Cu2+- exchanged SMT and minimal affinity for Mg2+- exchanged SMT. The vibrational frequency shifts of —NH3 + and —COO- favor Van der Waal's forces during the course of surface interaction. Quantum calculations using density functional theory (DFT) have been applied to investigate the absolute value of metal ion affinities of Leu (Leu—M2+ complex, M = Mg2+, Ca2+, Cu2+) with the help of their physico-chemical parameters. The hydration effect on the relative stability and geometry of the individual species of Leu—M2+ × (H2O)n, ( n =2 and 4) has also been evaluated within the supermolecule approach. Evidence gathered from investigations of surface interactions, divalent metal ions affinities and hydration effects with biomolecules may be important for better understanding of chemical evolution, the stabilization of biomolecules on solid surfaces and biomolecular-metal interactions. These results may have implications for understanding the origin of life and the preservation of biomarkers.

  13. Affinity of Smectite and Divalent Metal Ions (Mg(2+), Ca(2+), Cu(2+)) with L-leucine: An Experimental and Theoretical Approach Relevant to Astrobiology.

    Science.gov (United States)

    Pandey, Pramod; Pant, Chandra Kala; Gururani, Kavita; Arora, Priyanka; Pandey, Neetu; Bhatt, Preeti; Sharma, Yogesh; Negi, Jagmohan Singh; Mehata, Mohan Singh

    2015-12-01

    Earth is the only known planet bestowed with life. Several attempts have been made to explore the pathways of the origin of life on planet Earth. The search for the chemistry which gave rise to life has given answers related to the formation of biomonomers, and their adsorption on solid surfaces has gained much attention for the catalysis and stabilization processes related to the abiotic chemical evolution of the complex molecules of life. In this communication, surface interactions of L-leucine (Leu) on smectite (SMT) group of clay (viz. bentonite and montmorillonite) and their divalent metal ion (Mg(2+), Ca(2+) and Cu(2+)) incorporated on SMT has been studied to find the optimal conditions of time, pH, and concentration at ambient temperature (298 K). The progress of adsorption was followed spectrophotometrically and further characterized by FTIR, SEM/EDS and XRD. Leu, a neutral/non polar amino acid, was found to have more affinity in its zwitterionic form towards Cu(2+)- exchanged SMT and minimal affinity for Mg(2+)- exchanged SMT. The vibrational frequency shifts of -NH3 (+) and -COO(-) favor Van der Waal's forces during the course of surface interaction. Quantum calculations using density functional theory (DFT) have been applied to investigate the absolute value of metal ion affinities of Leu (Leu-M(2+) complex, M = Mg(2+), Ca(2+), Cu(2+)) with the help of their physico-chemical parameters. The hydration effect on the relative stability and geometry of the individual species of Leu-M(2+) × (H2O)n, (n =2 and 4) has also been evaluated within the supermolecule approach. Evidence gathered from investigations of surface interactions, divalent metal ions affinities and hydration effects with biomolecules may be important for better understanding of chemical evolution, the stabilization of biomolecules on solid surfaces and biomolecular-metal interactions. These results may have implications for understanding the origin of life and the preservation of

  14. Synthesis and characterization of divalent metal complexes with ligand derived from the reaction of 3-aminopyridine and biacetyl

    Directory of Open Access Journals (Sweden)

    RAMESH KUMAR

    2006-09-01

    Full Text Available Divalent cobalt, nickel and copper salts reacted in situ with 3-aminopyridine and biacetyl to form complexes of the type: [M(Ap2biac2X2], where Ap2biac is the ligand and X=Cl, Br, NO3 or NCS. The complexes were analysed and characterized as distorted octahedral by conductance, molecular weight, magnetic, electronic and IR spectral studies. The electronic spectra were interpreted and tentative aassignments made. The infrared spectral studies revealed that two molecules of 3-aminopyridine were joined by molecules of biacetyl through a two carbon atom bridge and that the ligand coordinated through azomethine nitrogen atoms, whereas the pyridine nitrogen does not participate in the coordination. In the far infrared spectra, various metal–ligand vibrations were observed and are discussed.

  15. Synthesis, structural elucidation, microbial, antioxidant and nuclease activities of some novel divalent M(II complexes derived from 5-fluorouracil and l-tyrosine

    Directory of Open Access Journals (Sweden)

    Jeyaprakash Dharmaraja

    2017-01-01

    Full Text Available Novel N2O2 sequence of mononuclear amino acid metal(II complexes (1a–1e was synthesized from 5-fluorouracil (5-FU: A and l-tyrosine (tyr: B with Mn(II, Co(II, Ni(II, Cu(II and Zn(II ions. The synthesized complexes were structurally characterized by analytical, spectral (FT-IR, UV–vis, 1H NMR, FAB-Mass, TGA/DTA and EPR as well as molar conductance and magnetic studies. From spectral studies, both the ligands act as bidentate and they bind metal(II ions through deprotonated-N3 and C4O atoms and amino-N and deprotonated carboxylato-O atoms, respectively, to form a stable metal chelate. The observed low molar conductance values suggest a non-electrolytic nature. Calculated g tensor values of Cu(II complex (1d at 77 and 300 K confirm their geometry. Thermal behavior of metal(II complexes (1a–1c shows loss of coordinated water molecules in the first step followed by decomposition of ligand moieties in a respective manner and leads to form air stable metal oxide as final residues. Powder X-ray diffraction and SEM studies illustrate that all the complexes have uniform microcrystalline with homogenous morphology. Mn(II, Ni(II and Cu(II complexes show significant in vitro antimicrobial and antioxidant activities than 5-fluorouracil(A. Moreover, the nuclease studies of Ni(II and Cu(II complexes (1c and 1d show considerable DNA binding and oxidative DNA cleavage activities than other complexes.

  16. Macrocyclic receptor showing extremely high Sr(II)/Ca(II) and Pb(II)/Ca(II) selectivities with potential application in chelation treatment of metal intoxication.

    Science.gov (United States)

    Ferreirós-Martínez, Raquel; Esteban-Gómez, David; Tóth, Éva; de Blas, Andrés; Platas-Iglesias, Carlos; Rodríguez-Blas, Teresa

    2011-04-18

    Herein we report a detailed investigation of the complexation properties of the macrocyclic decadentate receptor N,N'-Bis[(6-carboxy-2-pyridil)methyl]-4,13-diaza-18-crown-6 (H(2)bp18c6) toward different divalent metal ions [Zn(II), Cd(II), Pb(II), Sr(II), and Ca(II)] in aqueous solution. We have found that this ligand is especially suited for the complexation of large metal ions such as Sr(II) and Pb(II), which results in very high Pb(II)/Ca(II) and Pb(II)/Zn(II) selectivities (in fact, higher than those found for ligands widely used for the treatment of lead poisoning such as ethylenediaminetetraacetic acid (edta)), as well as in the highest Sr(II)/Ca(II) selectivity reported so far. These results have been rationalized on the basis of the structure of the complexes. X-ray crystal diffraction, (1)H and (13)C NMR spectroscopy, as well as theoretical calculations at the density functional theory (B3LYP) level have been performed. Our results indicate that for large metal ions such as Pb(II) and Sr(II) the most stable conformation is Δ(δλδ)(δλδ), while for Ca(II) our calculations predict the Δ(λδλ)(λδλ) form being the most stable one. The selectivity that bp18c6(2-) shows for Sr(II) over Ca(II) can be attributed to a better fit between the large Sr(II) ions and the relatively large crown fragment of the ligand. The X-ray crystal structure of the Pb(II) complex shows that the Δ(δλδ)(δλδ) conformation observed in solution is also maintained in the solid state. The Pb(II) ion is endocyclically coordinated, being directly bound to the 10 donor atoms of the ligand. The bond distances to the donor atoms of the pendant arms (2.55-2.60 Å) are substantially shorter than those between the metal ion and the donor atoms of the crown moiety (2.92-3.04 Å). This is a typical situation observed for the so-called hemidirected compounds, in which the Pb(II) lone pair is stereochemically active. The X-ray structures of the Zn(II) and Cd(II) complexes show that

  17. Sorption of his-tagged Protein G and Protein G onto chitosan/divalent metal ion sorbent used for detection of microcystin-LR.

    Science.gov (United States)

    Demey, Hary; Tria, Scherrine A; Soleri, Romain; Guiseppi-Elie, Anthony; Bazin, Ingrid

    2017-01-01

    A highly sensitive, specific, simple, and rapid chemiluminescence enzyme immunoassay (CLEIA) was developed for the determination of microcystin-LR (MC-LR) by using strategies for oriented immobilization of functionally intact polyclonal antibodies on chitosan surface. Several physicochemical parameters such as metal ion adsorption, hexahistidine-tagged Protein G sorption, the dilution ratio polyclonal antibody concentration, and peroxidase-labeled MC-LR concentration were studied and optimized. The sorption in batch system of G-histidine and G-proteins was studied on a novel sorbent consisting of chitosan/divalent metal ions. Transition metals as Ni(++) and Zn(++) were immobilized through interaction with -NH2 groups of chitosan in order to supply a material capable to efficiently remove the proteins from aqueous solutions. The maximum uptake of divalent metals onto the chitosan material was found to be 230 mg g(-1) for Zn(++) and 62 mg g(-1) for Ni(++). Experimental data were evaluated using the Langmuir and Freundlich models; the results were well fitted with the Langmuir model; chitosan/Ni(++) foam was found to be the best sorbent for G-protein, maximum sorption capacity obtained was 17 mg g(-1), and chitosan/Zn(++) was found to be the best for G-histidine with a maximum sorption capacity of 44 mg g(-1). Kinetic data was evaluated with pseudo-first- and pseudo-second-order models; the sorption kinetics were in all cases better represented by a pseudo-second-order model. Under optimum conditions, the calibration curve obtained for MC-LR gave detection limits of 0.5 ± 0.06 μg L(-1), the 50 % inhibition concentration (IC50) was 2.75 ± 0.03 μg L(-1), and the quantitative detection range was 0.5-25 μg L(-1). The limit of detection (LOD) attained from the calibration curves and the results obtained demonstrate the potential use of CLEIA with chitosan support as a screening tool for the analysis of pollutants in environmental samples.

  18. Metal complexes of triazine - Schiff bases: Spectroscopic and thermodynamic studies of complexation of some divalent metal ions with 3-(a-acetylethylidenehydrazino-5,6-diphenyl-1,2,4-triazine

    Directory of Open Access Journals (Sweden)

    A. TAHA

    1999-10-01

    Full Text Available Metal complexes of some divalent metal ions (Co, Ni, Cu and Zn with 3-(a-acetylethylidenehydrazino-5,6-diphenyl-1,2,4-triazine (AHDT as a Schiff-base have been investigated potentiometrically and spectrophotometrically and found to have the stoichiometric formulae 1:1 and 1:2 (M:L. The formation constants of the proton-ligand and metal-ligand complexes have been determined potentiometrically at different temperatures (10, 20, 30, 40 and 50°C at an ionic strength of 0.1 M KNO3 in 75% (v/v dioxane-water solution. The standard thermodynamic parameters, viz. DG°, DH°, and DS°, for the proton-ligand and the stepwise metal-ligand complexes have been evaluated.

  19. Synthesis and characterization of new complexes of some divalent transition metals with N-isonicotinamido-4-chlorobenzalaldimine

    Directory of Open Access Journals (Sweden)

    ADINA MAGDALENA MUSUC

    2011-08-01

    Full Text Available New complexes of N-isonicotinamido-4-chlorobenzalaldimine (INHCBA with Cu(II, Co(II and Cd(II, having formula of the type [M(INHCBA(ac2]·xH2O (M = Cu2+, x = 1, M = Co2+, x = 2, M = Cd2+, x = 0, ac = CH3COO-, and with Cu(II, Mn(II and Zn(II, having formula of the type [M(INHCBA2(H2O2]SO4·xH2O (M = Cu2+, Mn2+, x = 2 and Zn2+ x = 2.5 were synthesized and characterized by analytical and physico-chemical techniques, i.e., elemental analyses, IR, UV–Vis–NIR and EPR spectroscopy as well as thermal analysis and the determination of the molar conductivity and magnetic moments. The thermal behaviour of complexes was studied by ther­mogravimetry (TG, differential thermal analysis (DTA and differential scan­ning calorimetry (DSC. The ligand behaves as bidentate NO, being coordi­nated through the azomethine nitrogen and carbonylic oxygen. The heats of decomposition, ΔH, associated with the exothermal effects, were also deter­mined.

  20. A new strategy to stabilize oxytocin in aqueous solutions: I. The effects of divalent metal ions and citrate buffer

    National Research Council Canada - National Science Library

    Avanti, Christina; Amorij, Jean-Pierre; Setyaningsih, Dewi; Hawe, Anea; Jiskoot, Wim; Visser, Jan; Keov, Alexej; essen, Arnold J. M; Hinrichs, Wouter L. J; Frijlink, Henderik W

    2011-01-01

    ... (Ca2+, Mg2+, and Zn2+) were tested all as chloride salts. The effect of combinations of buffers and metal ions on the stability of aqueous oxytocin solutions was determined by RP-HPLC and HP-SEC after 4 weeks of storage at either 4°C or 55°C...

  1. Divalent metal-ion transporter 1 is decreased in intestinal epithelial cells and contributes to the anemia in inflammatory bowel disease.

    Science.gov (United States)

    Wu, Wei; Song, Yang; He, Chong; Liu, Changqin; Wu, Ruijin; Fang, Leilei; Cong, Yingzi; Miao, Yinglei; Liu, Zhanju

    2015-11-17

    Divalent metal-ion transporter 1 (DMT1) has been found to play an important role in the iron metabolism and hemogenesis. However, little is known about the potential role of DMT1 in the pathogenesis of anemia from patients with inflammatory bowel disease (IBD). Herein, we investigated expression of DMT1 in the intestinal mucosa by quantitative real-time polymerase chain reaction (qRT-PCR) and immunohistochemistry, and found that DMT1 was significantly decreased in the inflamed mucosa of active IBD patients compared with that in those patients at remission stage and healthy controls. To further study the mechanism, we cultured HCT 116 cell line in vitro. Expression of DMT1 in HCT116 was demonstrated to be markedly decreased under stimulation with TNF for 24 and 48 h, while JNK inhibitor (JNK-IN-7) could significantly reverse the decrease. Interestingly, anti-TNF therapy successfully improved anemia in clinical responsive Crohn's disease patients, and DMT1 was found to be markedly up-regulated in intestinal mucosa. Taken together, our studies demonstrate that decreased expression of DMT1 in intestinal mucosa leads to compromised absorption and transportation of iron and that blockade of TNF could rescue anemia and promote DMT1 expression in gut mucosa. This work provides a therapeutic approach in the management of anemia in IBD.

  2. Potentiometric studies on ternary complexes involving some divalent transition metal ions, gallic acid and biologically abundant aliphatic dicarboxylic acids in aqueous solutions

    Directory of Open Access Journals (Sweden)

    Abdelatty Mohamed Radalla

    2015-06-01

    Full Text Available Formation of binary and ternary complexes of the divalent transition metal ions, Cu2+, Ni2+, Co2+ and Zn2+ with gallic acid and the biologically important aliphatic dicarboxylic acids (adipic, succinic, malic, malonic, maleic, tartaric and oxalic acids were investigated by means of the potentiometric technique at 25 °C and I = 0.10 mol dm−3 NaNO3. The acid-base properties of the ligands were investigated and discussed. The acidity constants of gallic acid and aliphatic dicarboxylic acids were determined and used for determining the stability constants of the binary and ternary complexes formed in the aqueous medium under the above experimental conditions. The formation of the different 1:1 and 1:2 binary complexes and 1:1:1 ternary complexes are inferred from the corresponding potentiometric pH-metric titration curves. The ternary complex formation was found to occur in a stepwise manner. The stability constants of these binary and ternary systems were calculated. The values of Δ log K, percentage of relative stabilization (%R.S. and log X were evaluated and discussed. The concentration distribution of the various complex species formed in solution was evaluated and discussed. The mode of chelation of ternary complexes formed was ascertained by conductivity measurements.

  3. Transition Metal(II Complexes with Cefotaxime-Derived Schiff Base: Synthesis, Characterization, and Antimicrobial Studies

    Directory of Open Access Journals (Sweden)

    Aurora Reiss

    2014-01-01

    Full Text Available New [ML2(H2O2] complexes, where M = Co(II, Ni(II, Cu(II, and Zn(II while L corresponds to the Schiff base ligand, were synthesized by condensation of cefotaxime with salicylaldehyde in situ in the presence of divalent metal salts in ethanolic medium. The complexes were characterized by elemental analyses, conductance, and magnetic measurements, as well as by IR and UV-Vis spectroscopy. The low values of the molar conductance indicate nonelectrolyte type of complexes. Based on spectral data and magnetic moments, an octahedral geometry may be proposed for Co(II, Ni(II, and Zn(II complexes while a tetragonal geometry for Cu(II complex. Molecular structure of the Schiff base ligand and its complexes were studied using programs dedicated to chemical modeling and quantomolecular calculation of chemical properties. All the synthesized complexes were tested for in vitro antibacterial activity against some pathogenic bacterial strains, namely Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Bacillus subtilis, and Staphylococcus aureus. The MIC values shown by the complexes against these bacterial strains revealed that the metal complexes possess superior antibacterial activity than the Schiff base.

  4. Physicochemical impact studies of gamma rays on "aspirin" analgesics drug and its metal complexes in solid form: Synthesis, spectroscopic and biological assessment of Ca(II), Mg(II), Sr(II) and Ba(II) aspirinate complexes

    Science.gov (United States)

    Refat, Moamen S.; Sharshar, T.; Elsabawy, Khaled M.; Heiba, Zein K.

    2013-09-01

    Metal aspirinate complexes, M2(Asp)4, where M is Mg(II), Ca(II), Sr(II) or Ba(II) are formed by refluxed of aspirin (Asp) with divalent non-transition metal ions of group (II) and characterized by elemental analysis and spectroscopic measurements (infrared, electronic, 1H NMR, Raman, X-ray powder diffraction and scanning electron microscopy). Elemental analysis of the chelates suggests the stoichiometry is 1:2 (metal:ligand). Infrared spectra of the complexes agree with the coordination to the central metal atom through three donation sites of two oxygen atoms of bridge bidentate carboxylate group and oxygen atom of sbnd Cdbnd O of acetyl group. Infrared spectra coupled with the results of elemental analyzes suggested a distorted octahedral structure for the M(II) aspirinate complexes. Gamma irradiation was tested as a method for stabilization of aspirin as well as their complexes. The effect of gamma irradiation, with dose of 80 Gy, on the properties of aspirinate complexes was studied. The aspirinate chelates have been screened for their in vitro antibacterial activity against four bacteria, gram-positive (Bacillus subtilis and Staphylococcus aureus) and gram-negative (Escherichia coli and Pseudomonas aeruginosa) and two strains of fungus (Aspergillus flavus and Candida albicans). The metal chelates were shown to possess more antibacterial activity than the free aspirin chelate.

  5. Synthesis and characterization of divalent metal complexes of the macrocyclic ligand derived from isatin and 1,2-diaminobenzene

    Directory of Open Access Journals (Sweden)

    DHARAM PAL SINGH

    2011-03-01

    Full Text Available A novel series of complexes of the type [M(C28H18N6X2], where M=Co(II, Ni(II, Cu(II or Zn(II and X = Cl-, NO3- or CH3COO-, were synthesized by template condensation of isatin and 1,2-diaminobenzene in methanolic medium. The complexes were characterized with the help of various physico–chemical techniques, such as elemental analyses, molar conductance measurements, magnetic measurements, and NMR, infrared and far infrared spectral studies. The low value of molar conductance indicates them to be non-electrolytes. Based on various studies, a distorted octahedral geometry may be proposed for all the complexes. All the synthesized macrocyclic complexes were also tested for their in vitro antibacterial activity against some pathogenic bacterial strains. The MIC values shown by the complexes against these bacterial strains were compared with those of the standard antibiotics linezolid and cefaclor. Some of the complexes showed good antibacterial activities.

  6. Cross-sectional study of expression of divalent metal transporter-1, transferrin, and hepcidin in blood of smelters who are occupationally exposed to manganese

    Directory of Open Access Journals (Sweden)

    Qiyuan Fan

    2016-09-01

    Full Text Available Background Manganese (Mn is widely used in industries including the manufacture of Mn-iron (Fe alloy. Occupational Mn overexposure causes manganism. Mn is known to affect Fe metabolism; this study was designed to test the hypothesis that workers exposed to Mn may have an altered expression of mRNAs encoding proteins in Fe metabolism. Methods Workers occupationally exposed to Mn (n = 71 from a Mn–Fe alloy factory and control workers without Mn-exposure (n = 48 from a pig-iron plant from Zunyi, China, were recruited for this study. Blood samples were collected into Trizol-containing tubes. Total RNA was isolated, purified, and subjected to real-time RT-PCR analysis. Metal concentrations were quantified by atomic absorption spectrophotometry. Results Working environment and genetic background of both groups were similar except for marked differences in airborne Mn concentrations (0.18 mg/m3 in Mn–Fe alloy factory vs. 0.0022 mg/m3 in pig-Fe plant, and in blood Mn levels (34.3 µg/L vs. 10.4 µg/L. Mn exposure caused a significant decrease in the expression of divalent metal transporter-1 (DMT1, transferrin (Tf and hepcidin by 58.2%, 68.5% and 61.5%, respectively, as compared to controls, while the expression of transferrin receptor (TfR was unaltered. Linear regression analysis revealed that expressions of DMT1, Tf and hepcidin were inversely correlated with the accumulative Mn exposure; the correlation coefficients (r are −0.47, −0.54, and −0.49, respectively (p < 0.01. Conclusion The data suggest that occupational Mn exposure causes decreased expressions of DMT1, Tf and hepcidin in blood cells; the finding will help understand the mechanism underlying Mn exposure-associated alteration in Fe homeostasis among workers.

  7. Functional Analysis of the Citrate Activator CitO from Enterococcus faecalis Implicates a Divalent Metal in Ligand Binding

    Science.gov (United States)

    Blancato, Víctor S.; Pagliai, Fernando A.; Magni, Christian; Gonzalez, Claudio F.; Lorca, Graciela L.

    2016-01-01

    The regulator of citrate metabolism, CitO, from Enterococcus faecalis belongs to the FCD family within the GntR superfamily. In the presence of citrate, CitO binds to cis-acting sequences located upstream of the cit promoters inducing the expression of genes involved in citrate utilization. The quantification of the molecular binding affinities, performed by isothermal titration calorimetry (ITC), indicated that CitO has a high affinity for citrate (KD = 1.2 ± 0.2 μM), while it did not recognize other metabolic intermediates. Based on a structural model of CitO where a putative small molecule and a metal binding site were identified, it was hypothesized that the metal ion is required for citrate binding. In agreement with this model, citrate binding to CitO sharply decreased when the protein was incubated with EDTA. This effect was reverted by the addition of Ni2+, and Zn2+ to a lesser extent. Structure-based site-directed mutagenesis was conducted and it was found that changes to alanine in residues Arg97 and His191 resulted in decreased binding affinities for citrate, as determined by EMSA and ITC. Further assays using lacZ fusions confirmed that these residues in CitO are involved in sensing citrate in vivo. These results indicate that the molecular modifications induced by a ligand and a metal binding in the C-terminal domain of CitO are required for optimal DNA binding activity, and consequently, transcriptional activation. PMID:26903980

  8. Functional analysis of the citrate activator CitO from Enterococcus faecalis implicates a divalent metal in ligand binding

    Directory of Open Access Journals (Sweden)

    Victor S. Blancato

    2016-02-01

    Full Text Available The regulator of citrate metabolism, CitO, from Enterococcus faecalis belongs to the FCD family within the GntR superfamily. In the presence of citrate, CitO binds to cis-acting sequences located upstream of the cit promoters inducing the expression of genes involved in citrate utilization. The quantification of the molecular binding affinities, performed by isothermal titration calorimetry (ITC, indicated that CitO has a high affinity for citrate (KD= 1.2±0.2 µM, while it did not recognize other metabolic intermediates. Based on a structural model of CitO where a putative small molecule and a metal binding site were identified, it was hypothesized that the metal ion is required for citrate binding. In agreement with this model, citrate binding to CitO sharply decreased when the protein was incubated with EDTA. This effect was reverted by the addition of Ni2+, and Zn2+ to a lesser extent. Structure-based site-directed mutagenesis was conducted and it was found that changes to alanine in residues Arg97 and His191 resulted in decreased binding affinities for citrate, as determined by EMSA and ITC. Further assays using lacZ fusions confirmed that these residues in CitO are involved in sensing citrate in vivo. These results indicate that the molecular modifications induced by a ligand and a metal binding in the C-terminal domain of CitO are required for optimal DNA binding activity, and consequently, transcriptional activation.

  9. Differentiation of cyclosporin A from isocyclosporin A by liquid chromatography/electrospray ionization mass spectrometry with post-column addition of divalent metal salt.

    Science.gov (United States)

    Cirigliano, Adriana M; Cabrera, Gabriela M

    2014-03-15

    Cyclosporin A (CsA) rearranges to its isomer isocyclosporin A (isoCsA) upon acid hydrolysis and also during ionization in the ion source of the mass spectrometer. It has been reported that both compounds could not be differentiated by tandem mass spectrometry (MS/MS) using atmospheric pressure ionization (API) sources and ambiguously differentiated by using other sources. In order to analyze these compounds which are common fungal metabolites, it is relevant to develop a simple method for their differentiation. CsA and isoCsA were analyzed by liquid chromatography/mass spectrometry (LC/MS) with post-column addition of metal ion solutions in a quadrupole time-of-flight instrument equipped with an electrospray ionization (ESI) source. Mass spectra of CsA obtained upon post-column addition of solutions of Ca(II), Cu(II) and Zn(II) showed complexes between cyclosporin and the metal, including [2CsA + Me](2+) and [CsA-H + Me](+). These complexes were not observed in the spectra of isoCsA. The same results were observed at different metal concentrations. Differentiation via metal complexation in positive ion mode LC/ESI-MS was performed to simultaneously distinguish CsA and its isomer isoCsA. Copyright © 2014 John Wiley & Sons, Ltd.

  10. Ca(II) Binding Regulates and Dominates the Reactivity of a Transition-Metal-Ion-Dependent Diesterase from Mycobacterium tuberculosis.

    Science.gov (United States)

    Pedroso, Marcelo M; Larrabee, James A; Ely, Fernanda; Gwee, Shuhui E; Mitić, Nataša; Ollis, David L; Gahan, Lawrence R; Schenk, Gerhard

    2016-01-18

    The diesterase Rv0805 from Mycobacterium tuberculosis is a dinuclear metallohydrolase that plays an important role in signal transduction by controlling the intracellular levels of cyclic nucleotides. As Rv0805 is essential for mycobacterial growth it is a promising new target for the development of chemotherapeutics to treat tuberculosis. The in vivo metal-ion composition of Rv0805 is subject to debate. Here, we demonstrate that the active site accommodates two divalent transition metal ions with binding affinities ranging from approximately 50 nm for Mn(II) to about 600 nm for Zn(II) . In contrast, the enzyme GpdQ from Enterobacter aerogenes, despite having a coordination sphere identical to that of Rv0805, binds only one metal ion in the absence of substrate, thus demonstrating the significance of the outer sphere to modulate metal-ion binding and enzymatic reactivity. Ca(II) also binds tightly to Rv0805 (Kd ≈40 nm), but kinetic, calorimetric, and spectroscopic data indicate that two Ca(II) ions bind at a site different from the dinuclear transition-metal-ion binding site. Ca(II) acts as an activator of the enzymatic activity but is able to promote the hydrolysis of substrates even in the absence of transition-metal ions, thus providing an effective strategy for the regulation of the enzymatic activity.

  11. Role of ATP-bound divalent metal ion in the conformation and function of actin. Comparison of Mg-ATP, Ca-ATP, and metal ion-free ATP-actin.

    Science.gov (United States)

    Valentin-Ranc, C; Carlier, M F

    1991-04-25

    The fluorescence of N-acetyl-N'-(sulfo-1-naphthyl)ethylenediamine (AEDANS) covalently bound to Cys-374 of actin is used as a probe for different conformational states of G-actin according to whether Ca-ATP, Mg-ATP, or unchelated ATP is bound to the nucleotide site. Upon addition of large amounts (greater than 10(2)-fold molar excess) of EDTA to G-actin, metal ion-free ATP-G-actin is obtained with EDTA bound. Metal ion free ATP-G-actin is characterized by a higher AEDANS fluorescence than Mg-ATP-G-actin, which itself has a higher fluorescence than Ca-ATP-G-actin. Evidence for EDTA binding to G-actin is shown using difference spectrophotometry. Upon binding of EDTA, the rate of dissociation of the divalent metal ion from G-actin is increased (2-fold for Ca2+, 10-fold for Mg2+) in a range of pH from 7.0 to 8.0. A model is proposed that quantitatively accounts for the kinetic data. The affinity of ATP is weakened 10(6)-fold upon removal of the metal ion. Metal ion-free ATP-G-actin is in a partially open conformation, as indicated by the greater accessibility of -SH residues, yet it retains functional properties of polymerization and ATP hydrolysis that appear almost identical to those of Ca-ATP-actin, therefore different from those of Mg-ATP-actin. These results are discussed in terms of the role of the ATP-bound metal ion in actin structure and function.

  12. Trace Metals in Groundwater & Vadose Zone Calcite: In Situ Containment & Stabilization of 90Strontium & Other Divalent Metals & Radionuclides at Arid West DOE Sites

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Robert W.; Fujita, Yoshiko; Ferris, F. Grant; Cosgrove, Donna M.; Colwell, Rick S.

    2004-06-01

    Radionuclide and metal contaminants such as 90Sr are present beneath U.S. Department of Energy (DOE) lands in both the groundwater (e.g., 100-N area at Hanford, WA) and vadose zone (e.g., Idaho Nuclear Technology and Engineering Center (INTEC) at the Idaho National Engineering and Environmental Laboratory). In situ containment and stabilization of these contaminants is a cost-effective treatment strategy. However, implementing in situ containment and stabilization approaches requires definition of the mechanisms that control contaminant sequestration. We are investigating the in situ immobilization of radionuclides or contaminant metals (e.g., 90Sr) by their facilitated co-precipitation with calcium carbonate in groundwater and vadose zone systems. Our facilitated approach, shown schematically in Figure 1, relies upon the hydrolysis of introduced urea to cause the acceleration of calcium carbonate precipitation (and trace metal co-precipitation) by increasing pH and alkalinity. Subsurface urea hydrolysis is catalyzed by the urease enzyme, which may be either introduced with the urea or produced in situ by ubiquitous subsurface urea hydrolyzing microorganisms. Because the precipitation process tends to be irreversible and many western aquifers are saturated with respect to calcite, the co-precipitated metals and radionuclides will be effectively removed from the aqueous phase over the long-term. Another advantage of the ureolysis approach is that the ammonium ions produced by the reaction can exchange with radionuclides sorbed to subsurface minerals, thereby enhancing the availability of the radionuclides for re-capture in a more stable solid phase (co-precipitation rather than adsorption).

  13. Trace Metals in Groundwater & the Vadose Zone Calcite: In Situ Containment & Stabilization of Strontium-90 & Other Divalent Metals & Radionuclides at Arid West DOE

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Robert W.

    2004-12-01

    Radionuclide and metal contaminants such as strontium-90 are present beneath U.S. Department of Energy (DOE) lands in both the groundwater (e.g., 100-N area at Hanford, WA) and vadose zone (e.g., Idaho Nuclear Technology and Engineering Center at the Idaho National Engineering and Environmental Laboratory). In situ containment and stabilization of these contaminants is a cost-effective treatment strategy. However, implementing in situ containment and stabilization approaches requires definition of the mechanisms that control contaminant sequestration. We are investigating the in situ immobilization of radionuclides or contaminant metals (e.g., strontium-90) by their facilitated co-precipitation with calcium carbonate in groundwater and vadose zone systems. Our facilitated approach, shown schematically in Figure 1, relies upon the hydrolysis of introduced urea to cause the acceleration of calcium carbonate precipitation (and trace metal co-precipitation) by increasing pH and alkalinity. Subsurface urea hydrolysis is catalyzed by the urease enzyme, which may be either introduced with the urea or produced in situ by ubiquitous subsurface urea hydrolyzing microorganisms. Because the precipitation process tends to be irreversible and many western aquifers are saturated with respect to calcite, the co-precipitated metals and radionuclides will be effectively removed from the aqueous phase over the long-term. Another advantage of the ureolysis approach is that the ammonium ions produced by the reaction can exchange with radionuclides sorbed to subsurface minerals, thereby enhancing the availability of the radionuclides for re-capture in a more stable solid phase (co-precipitation rather than adsorption).

  14. Trace Metals in Groundwater & Vadose Zone Calcite: In Situ Containment & Stabilization of Stronthium-90 & Other Divalent Metals & Radionuclides at Arid West DOE

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Robert W.

    2005-06-01

    Radionuclide and metal contaminants such as strontium-90 are present beneath U.S. Department of Energy (DOE) lands in both the groundwater (e.g., 100-N area at Hanford, WA) and vadose zone (e.g., Idaho Nuclear Technology and Engineering Center [INTEC] at the Idaho National Laboratory [INL]). In situ containment and stabilization of these contaminants is a cost-effective treatment strategy. However, implementing in situ containment and stabilization approaches requires definition of the mechanisms that control contaminant sequestration. We are investigating the in situ immobilization of radionuclides or contaminant metals (e.g., strontium-90) by their facilitated co-precipitation with calcium carbonate (primarily calcite) in groundwater and vadose zone systems. Our facilitated approach relies upon the hydrolysis of introduced urea to cause the acceleration of calcium carbonate precipitation (and trace metal co-precipitation) by (a) increasing pH and alkalinity and (b) liberating cations from the aquifer matrix by cation exchange reactions. Subsurface urea hydrolysis is catalyzed by the urease enzyme, which is produced in situ by native urea hydrolyzing microorganisms. Because the precipitation process tends to be irreversible and many western aquifers are saturated with respect to calcite, the co-precipitated metals and radionuclides will be effectively removed from the aqueous phase over the long term. We are currently conducting field based activities at both the INL Vadose Zone Research Park (VZRP), an uncontaminated surrogate site for the strontium-90 contaminated vadose zone at INTEC and at the strontium-90 contaminated aquifer of 100-N area of the Hanford site.

  15. Reductive spectrophotometry of divalent tin sensitization on soda lime glass

    Science.gov (United States)

    Bejugam, Vinith; Wei, Xingfei; Roper, D. Keith

    2016-07-01

    Rapid and facile evaluation of tin (II) sensitization could lead to improved understanding of metal deposition in electroless (EL) plating. This report used a balanced redox reaction between 3,3‧,5,5‧-tetramethylbenzidine dihydrochloride (TMB-HCL) and N-bromosuccinimide (NBS) to evaluate effects of sensitization conditions (i.e., sensitization time, analyte concentration, aqueous immersion, and acid content) on the accumulated mass of surface-associated divalent tin ion. The accumulated mass of tin (II) increased as the sensitization time increased up to 30 s in proportion to aqueous tin (II) chloride concentrations between 2.6 and 26 mM at a trifluoroacetic acid (TFA) content of 68 mM. The average mass peaked at 7.3 nanomoles (nmol) per cm2 after a 5 s aqueous immersion post-sensitization, and then decreased with increasing aqueous immersion post-sensitization. The total average tin (II) + tin (IV) accumulated on soda lime glass measured by inductively coupled plasma optical emission spectrometry (ICP-OES) was 17% higher at 30 s sensitization, suggesting a fraction of the tin (II) present may have oxidized to tin (IV). These results indicated that in situ spectrophotometric evaluation of tin (II) could support development of EL plating for electronics, catalysis, and solar cells.

  16. Reduction of aqueous transition metal species on the surfaces of Fe(II)-containing oxides

    Science.gov (United States)

    White, A.F.; Peterson, M.L.

    1996-01-01

    Experimental studies demonstrate that structural Fe(II) in magnetite and ilmenite heterogeneously reduce aqueous ferric, cupric, vanadate, and chromate ions at the oxide surfaces over a pH range of 1-7 at 25??C. For an aqueous transition metal m, such reactions are 3[Fe2+Fe3+2]O4(magnetite) + 2/nmz ??? 4[Fe3+2]O3(maghemite) + Fe2+ + 2/nmz-n and 3[Fe2+Ti]O3(ilmenite) + 2/nmz ??? Fe3+2Ti3O9(pseudorutile) + Fe2+ + 2/nmz-n, where z is the valance state and n is the charge transfer number. The half cell potential range for solid state oxidation [Fe(II)] ??? [Fe(III)] is -0.34 to -0.65 V, making structural Fe(II) a stronger reducing agent than aqueous Fe2+ (-0.77 V). Reduction rates for aqueous metal species are linear with time (up to 36 h), decrease with pH, and have rate constants between 0.1 and 3.3 ?? 10-10 mol m-2 s-1. Iron is released to solution both from the above reactions and from dissolution of the oxide surface. In the presence of chromate, Fe2+ is oxidized homogeneously in solution to Fe3+. X-ray photoelectron spectroscopy (XPS) denotes a Fe(III) oxide surface containing reduced Cr(III) and V(IV) species. Magnetite and ilmenite electrode potentials are insensitive to increases in divalent transition metals including Zn(II), Co(II), Mn(II), and Ni(II) and reduced V(IV) and Cr(III) but exhibit a log-linear concentration-potential response to Fe(III) and Cu(II). Complex positive electrode responses occur with increasing Cr(VI) and V(V) concentrations. Potential dynamic scans indicate that the high oxidation potential of dichromate is capable of suppressing the cathodic reductive dissolution of magnetite. Oxide electrode potentials are determined by the Fe(II)/Fe(III) composition of the oxide surface and respond to aqueous ion potentials which accelerate this oxidation process. Natural magnetite sands weathered under anoxic conditions are electrochemically reactive as demonstrated by rapid chromate reduction and the release of aqueous Fe(III) to experimental

  17. Structural Studies of Divalent Transition Metal Cobalt With Bis-(2,6-Diacetyl Pyridine Monoxime 1,2-Di-Iminobenzene.

    Directory of Open Access Journals (Sweden)

    Shamshad Ahmad Khan

    2015-12-01

    Full Text Available The complexes of divalent Cobalt with bis(2,6-diacetyl pyridine monoxime1,2-di-iminobenzene have been prepared separately in presence of respective salts. The general molecular formula of the complexes have been found to be [Co(L]X2 where L=Bis(2,6-diacetyl pyridine monoxime1,2-di-iminobenzene, X=chloride, bromide, sulphate, perchlorate, nitrate, acetate ions, On the characterisation of the complexes by usual physico-chemical method, all the complexes have been found to be monomeric and octahedral in geometry.

  18. Divalent Cu, Cd, and Pb Biosorption in Mixed Solvents

    Directory of Open Access Journals (Sweden)

    M. H. Al-Qunaibit

    2009-01-01

    Full Text Available Dead dried Chlorella vulgaris was studied in terms of its performance in binding divalent copper, cadmium, and lead ions from their aqueous or 50% v/v methanol, ethanol, and acetone solutions. The percentage uptake of cadmium ions exhibited a general decrease with decrease in dielectric constant values, while that of copper and lead ions showed a general decrease with increase in donor numbers. Uptake percentage becomes less sensitive to solvent properties the larger the atomic radius of the biosorbed ion, and uptake of copper was the most affected. FT-IR analyses revealed stability of the biomass in mixed solvents and a shift in vibrations of amide(I and (II, carboxylate, glucose ring, and metal oxygen upon metal binding in all media. ΔνCOO values (59–69 cm−1 confirmed bidentate metal coordination to carboxylate ligands. The value of νasCOO increased slightly upon Cu, Cd, and Pb biosorption from aqueous solutions indicating lowering of symmetry, while a general decrease was noticed in mixed solvents pointing to the opposite. M–O stretching frequencies increased unexpectedly with increase in atomic mass as a result of solvent effect on the nature of binding sites. Lowering polarity of the solvent permits variations in metal-alga bonds strengths; the smaller the metal ion, the more affected.

  19. Energy-resolved collision-induced dissociation studies of 1,10-phenanthroline complexes of the late first-row divalent transition metal cations: determination of the third sequential binding energies.

    Science.gov (United States)

    Nose, Holliness; Chen, Yu; Rodgers, M T

    2013-05-23

    The third sequential binding energies of the late first-row divalent transition metal cations to 1,10-phenanthroline (Phen) are determined by energy-resolved collision-induced dissociation (CID) techniques using a guided ion beam tandem mass spectrometer. Five late first-row transition metal cations in their +2 oxidation states are examined including: Fe(2+), Co(2+), Ni(2+), Cu(2+), and Zn(2+). The kinetic energy dependent CID cross sections for loss of an intact Phen ligand from the M(2+)(Phen)3 complexes are modeled to obtain 0 and 298 K bond dissociation energies (BDEs) after accounting for the effects of the internal energy of the complexes, multiple ion-neutral collisions, and unimolecular decay rates. Electronic structure theory calculations at the B3LYP, BHandHLYP, and M06 levels of theory are employed to determine the structures and theoretical estimates for the first, second, and third sequential BDEs of the M(2+)(Phen)x complexes. B3LYP was found to deliver results that are most consistent with the measured values. Periodic trends in the binding of these complexes are examined and compared to the analogous complexes to the late first-row monovalent transition metal cations, Co(+), Ni(+), Cu(+), and Zn(+), previously investigated.

  20. studies on transition metal complexes of herbicidal compounds. ii

    African Journals Online (AJOL)

    a

    II: TRANSITION METAL COMPLEXES OF DERIVATIZED 2-CHLORO-4- ... Several compounds of this class like atrazine, simazine, prometryn, aziprotryn, etc. .... dissolve in water and most of the common polar organic solvents. ... coordination.

  1. Structural analysis of inter-genus complexes of V-antigen and its regulator and their stabilization by divalent metal ions.

    Science.gov (United States)

    Basu, Abhishek; Das, Atanu; Mondal, Abhisek; Datta, Saumen

    2016-03-01

    Gram-negative bacteria like Yersinia, Pseudomonas, and Aeromonas need type III secretion system (T3SS) for their pathogenicity. V-antigen and its regulator are essential for functioning of T3SS. There is significant functional conservation amongst V-antigen and its regulator belonging to the Ysc family. In this study, we have structurally characterized the inter-genus complexes of V-antigen and its regulator. ConSurf analysis demonstrates that V-antigens belonging to the Ysc family show high structural identity predominantly confined to the two long helical regions. The regulator of V-antigen shows high conservation in its first intramolecular coiled-coil domain, responsible for interaction with V-antigen. ∆LcrG(1-70) localizes within the groove formed by long helices of LcrV, as observed in PcrV-∆PcrG(13-72) interaction. Inter-genus complexes of LcrV-PcrG and PcrV-LcrG exhibited elongated conformation and 1:1 heterodimeric state like the native complex of PcrV-PcrG and LcrV-LcrG. Both native and inter-genus complexes showed rigid tertiary structure, solvent-exposed hydrophobic patches, and cooperative melting behavior with high melting temperature. LcrV-PcrG and PcrV-LcrG showed nanomolar affinity of interaction, identical to PcrV-PcrG interaction, but stronger than LcrV-LcrG interaction. Calcium (a secretion blocker of T3SS) propels all the complexes towards a highly monodisperse form. Calcium and magnesium increase the helicity of the native and inter-genus complexes, and causes helix-helix stabilization. Stabilization of helices leads to a slight increase in the melting temperature by 1.5-2.0 °C. However, calcium does not alter the affinity of interaction of V-antigen and its regulator, emphasizing the effect of divalent of cations at the structural level without any regulatory implications. Therefore, the structural conservation of these inter-genus complexes could be the basis for their functional complementation.

  2. Redox-active on-surface polymerization of single-site divalent cations from pure metals by a ketone-functionalized phenanthroline

    Energy Technology Data Exchange (ETDEWEB)

    Skomski, Daniel; Tempas, Christopher D.; Bukowski, Gregory S.; Smith, Kevin A.; Tait, Steven L., E-mail: tait@indiana.edu [Department of Chemistry, Indiana University, 800 E. Kirkwood Ave., Bloomington, Indiana 47405 (United States)

    2015-03-14

    Metallic iron, chromium, or platinum mixing with a ketone-functionalized phenanthroline ligand on a single crystal gold surface demonstrates redox activity to a well-defined oxidation state and assembly into thermally stable, one dimensional, polymeric chains. The diverging ligand geometry incorporates redox-active sub-units and bi-dentate binding sites. The gold surface provides a stable adsorption environment and directs growth of the polymeric chains, but is inert with regard to the redox chemistry. These systems are characterized by scanning tunnelling microscopy, non-contact atomic force microscopy, and X-ray photoelectron spectroscopy under ultra-high vacuum conditions. The relative propensity of the metals to interact with the ketone group is examined, and it is found that Fe and Cr more readily complex the ligand than Pt. The formation and stabilization of well-defined transition metal single-sites at surfaces may open new routes to achieve higher selectivity in heterogeneous catalysts.

  3. metal complexes of copper(ii)

    African Journals Online (AJOL)

    ABSTRACT. Thermally stable metal complexes based on oligomers were prepared by the reaction ... Besides, coordination compounds of salicylaldehyde Schiff base have proven to be an excellent .... They were insoluble in common organic.

  4. METAL MONITORING .~\\;'\\iI) GEOCHEM ISTRY

    African Journals Online (AJOL)

    _c_oe1'-Ecient between metal pairs of river watera rid ground water samples are ea-lcul-ated and ... The present study is significant in that water. and land. the vital resources of life are ... River Osun bears its origin from Igede Ekiti. flows.

  5. Synthesis and Characterization of Divalent Manganese, Iron, and Cobalt Complexes in Tripodal Phenolate/N-Heterocyclic Carbene Ligand Environments

    DEFF Research Database (Denmark)

    Käß, Martina; Hohenberger, Johannes; Adelhardt, Mario

    2014-01-01

    . The complete ligand series offers a convenient way of tuning the electronic and steric environment around the metal center, thus, allowing for control of the complex’s reactivity. This series of divalent complexes of Mn, Fe, and Co was synthesized and characterized by 1H NMR, IR, and UV/vis spectroscopy....... Zero-field 57Fe Mössbauer spectroscopy of the Fe(II) complexes 3, 4, 8, and 11 shows isomer shifts δ that increase gradually as carbenes are substituted for phenolates in the series of ligands. From the single-crystal structure determinations of the complexes, the different steric demand...

  6. Metallic fuels: The EBR-II legacy and recent advances

    Energy Technology Data Exchange (ETDEWEB)

    Douglas L. Porter; Steven L. Hayes; J. Rory Kennedy

    2012-09-01

    Experimental Breeder Reactor – II (EBR-II) metallic fuel was qualified for high burnup to approximately 10 atomic per cent. Subsequently, the electrometallurgical treatment of this fuel was demonstrated. Advanced metallic fuels are now investigated for increased performance, including ultra-high burnup and actinide burning. Advances include additives to mitigate the fuel/cladding chemical interaction and uranium alloys that combine Mo, Ti and Zr to improve alloy performance. The impacts of the advances—on fabrication, waste streams, electrorefining, etc.—are found to be minimal and beneficial. Owing to extensive research literature and computational methods, only a modest effort is required to complete their development.

  7. The Infrared Ca II triplet as metallicity indicator

    CERN Document Server

    Carrera, Ricardo; Pancino, Elena; Zinn, Robert

    2007-01-01

    From observations of almost 500 RGB stars in 29 Galactic open and globular clusters, we have investigated the behaviour of the infrared Ca II triplet (8498, 8542 and 8662 \\AA) in the age range 13$\\leq$Age/Gyr$\\leq$0.25 and the metallicity range $-2.2\\leq$ [Fe/H] $\\leq$+0.47. These are the widest ranges of ages and metallicities in which the behaviour of the Ca II triplet lines has been investigated in a homogeneous way. We report the first empirical study of the variation of the CaII triplet lines strength, for given metallicities, with respect to luminosity. We find that the sequence defined by each cluster in the Luminosity-$\\Sigma$Ca plane is not exactly linear. However, when only stars in a small magnitude interval are observed, the sequences can be considered as linear. We have studied the the Ca II triplet lines on three metallicities scales. While a linear correlation between the reduced equivalent width ($W'_V$ or $W'_I$) versus metallicity is found in the \\citet{cg97} and \\citet{ki03} scales, a secon...

  8. Adsorption and preconcentration of divalent metal ions in fossil fuels and biofuels: gasoline, diesel, biodiesel, diesel-like and ethanol by using chitosan microspheres and thermodynamic approach.

    Science.gov (United States)

    Prado, Alexandre G S; Pescara, Igor C; Evangelista, Sheila M; Holanda, Matheus S; Andrade, Romulo D; Suarez, Paulo A Z; Zara, Luiz F

    2011-05-15

    Biodiesel and diesel-like have been obtained from soybean oil by transesterification and thermal cracking process, respectively. These biofuels were characterized as according to ANP standards by using specific ASTM methods. Ethanol, gasoline, and diesel were purchased from a gas station. Deacetylation degree of chitosan was determined by three distinct methods (conductimetry, FTIR and NMR), and the average degree was 78.95%. The chitosan microspheres were prepared from chitosan by split-coating and these spheres were crosslinked using glutaraldehyde. The surface area of microspheres was determined by BET method, and the surface area of crosslinked microspheres was 9.2m(2)g(-1). The adsorption isotherms of cooper, nickel and zinc on microspheres of chitosan were determined in petroleum derivatives (gasoline and diesel oil), as well as in biofuels (alcohol, biodiesel and diesel-like). The adsorption order in all fuels was: Cu>Ni>Zn. The elution tests presented the following preconcentration degrees: >4.5 to ethanol, >4.4 to gasoline, >4.0 to diesel, >3.8 to biodiesel and >3.6 to diesel-like. The application of chitosan microspheres in the metal ions preconcentration showed the potential of this biopolymer to enrich fuel sample in order to be analyzed by flame atomic absorption spectrometry.

  9. Complexation of divalent metal ions with diols in the presence of anion auxiliary ligands: zinc-induced oxidation of ethylene glycol to glycolaldehyde by consecutive hydride ion and proton shifts.

    Science.gov (United States)

    Ruttink, Paul J A; Dekker, Lennard J M; Luider, Theo M; Burgers, Peter C

    2012-07-01

    Ternary complexes of the type AH•••M(2+)•••L(-) (AH = diol, including diethylene and triethylene glycol, M = Ca, Mn, Fe, Co, Ni, Cu and Zn and auxiliary anion ligand L(-)  = CH(3)COO(-), HCOO(-) and Cl(-)) have been generated in the gas phase by MALDI and ESI, and their dissociation characteristics have been obtained. Use of the auxiliary ligands enables the complexation of AH with the divalent metal ion without AH becoming deprotonated, although A(-)•••M(2+) is often also generated in the ion source or after MS/MS. For M = Ca, dissociation occurs to AH + M(2+)•••L(-) and/or to A(-)•••M(2+) + LH, the latter being produced from the H-shifted isomer A(-) •••M(2+)•••LH. For a given ligand L(-), the intensity ratio of these processes can be interpreted (barring reverse energy barriers) in terms of the quantity PA(A(-)) - Ca(aff) (A(-)), where PA is the proton affinity and Ca(aff) is the calcium ion affinity. Deuterium labeling shows that the complex ion HOCH(2)CH(2) OH•••Zn(2+)•••(-)OOCCH(3), in addition to losing acetic acid (60 Da), also eliminates glycolaldehyde (HOCH(2)CH=O, also 60 Da); it is proposed that these reactions commence with a hydride ion shift to produce the ion-dipole complex HOCH(2)CHOH(+)••• HZnOOCCH(3), which then undergoes proton transfer and dissociation to HOCH(2)CH=O + HZn(+)•••O = C(OH)CH(3). In this reaction, ethylene glycol is oxidized by consecutive hydride ion and proton shifts. A minor process leads to loss of the isomeric species HOCH=CHOH.

  10. Adsorption of divalent copper, zinc, cadmium and lead ions from aqueous solution by waste tea and coffee adsorbents.

    Science.gov (United States)

    Djati Utomo, H; Hunter, K A

    2006-01-01

    The adsorption of the divalent cations of Cu, Zn, Cd and Pb by tea leaves and coffee grounds from aqueous solutions is described. Both adsorbents exhibited strong affinity for these ions which could be described by a simple single-site equilibrium model. For coffee, the order of increasing adsorption equilibrium constant K was Cu 10, probably because of anion formation in the case of Zn2+ and also increased leaching of metal-binding soluble materials. The effect of metal ion concentration on the adsorptive equilibria indicated a threshold concentration above which overall adsorption became limited by saturation of the adsorption sites. Competition between two metal ions for the same sites was not observed with Cu(II) and Pb(II), however Zn(II) reacted competitively with Cd(II) binding sites on both tea and coffee. If fresh coffee or tea adsorbents were used, the fraction of metal ion taken up by the adsorbent was diminished by the competitive effects of soluble metal-binding ligands released by the tea or coffee. Experiments with coffee showed that roasting temperature controls the formation of metal ion adsorption sites for this adsorbent.

  11. Alkaline-earth metal hydrides as novel host lattices for Eu(II) luminescence.

    Science.gov (United States)

    Kunkel, Nathalie; Kohlmann, Holger; Sayede, Adlane; Springborg, Michael

    2011-07-04

    Luminescence of divalent europium has been investigated for the first time in metal hydrides. A complete solid-solution series was found for the pseudobinary system Eu(x)Sr(1-x)H(2) [a = 637.6(1) pm -12.1(3)x pm, b = 387.0(1)-6.5(2)x pm, c = 732.2(2)-10.1(4)x pm]. Europium-doped alkaline-earth hydrides Eu(x)M(1-x)H(2) (M = Ca, Sr, Ba) with a small europium concentration (x = 0.005) exhibit luminescence with maximum emission wavelengths of 764 nm (M = Ca), 728 nm (M = Sr), and 750 nm (M = Ba); i.e., the emission energy of divalent europium shows an extremely large red shift compared to the emission energies of fluorides or oxides. Theoretical calculations (LDA+U) confirm decreasing band gaps with increasing europium content of the solid solutions.

  12. Synthesis, structure, spectroscopic properties and DFT studies on some 7-hydroxy-4-methyl-8-(arylazo)-2H-1-benzopyran-2-one and their complexes with some divalent transition metal ions

    Science.gov (United States)

    Abdel-Latif, Samir A.; Mohamed, Adel A.

    2017-04-01

    A novel 7-hydroxy-4-methyl-8-(p-tolylazo)-2H-1-benzopyran-2-one (coumarin) (L1) and 7-hydroxy-4-methyl-8-(p-anisylazo)-2H-1-benzopyran-2-one (coumarin) (L2) and their metal complexes with Mn(II), Co(II), Ni(II) Cu(II) and Zn(II) have been prepared and characterized by elemental analysis, infrared (IR), proton nuclear magnetic resonance (1H NMR) and mass spectra. The solid complexes have been also characterized by thermal analyses (TG and DTA), magnetic measurements, electronic transition, molar conductance; mass spectra, and electron spin resonance (ESR). The molecular orbital calculations of the complexes have been performed using the density functional theory (DFT) method and the basis sets 6-31G* and 6-311G**. The computational results revealed that the proposed geometrical structures for the investigated metal complexes suggest trigonal bipyramid for 1:1 and tetrahedral geometry for 1:2 complexes. The 1:1 complexes contain coordinated and lattice held water molecules whereas 1:2 complexes contain only lattice water molecules. The complexes behave as non-electrolytes in dimethyl formamide (DMF).

  13. Mixed metal copper(II)-nickel(II) and copper(II)-zinc(II) complexes of multihistidine peptide fragments of human prion protein.

    Science.gov (United States)

    Jószai, Viktória; Turi, Ildikó; Kállay, Csilla; Pappalardo, Giuseppe; Di Natale, Giuseppe; Rizzarelli, Enrico; Sóvágó, Imre

    2012-07-01

    Mixed metal copper(II)-nickel(II) and copper(II)-zinc(II) complexes of four peptide fragments of human prion protein have been studied by potentiometric, UV-vis and circular dichroism spectroscopic techniques. One peptide contained three histidyl residues: HuPrP(84-114) with H85 inside and H96, H111 outside the octarepeat domain. The other three peptides contained two histidyl residues; H96 and H111 for HuPrP(91-115) and HuPrP(84-114)H85A while HuPrP(84-114)H96A contained the histidyl residues at positions 85 and 111. It was found that both histidines of the latter peptides can simultaneously bind copper(II) and nickel(II) ions and dinuclear mixed metal complexes can exist in slightly alkaline solution. One molecule of the peptide with three histidyl residues can bind two copper(II) and one nickel(II) ions. H85 and H111 were identified as the major copper(II) and H96 as the preferred nickel(II) binding sites in mixed metal species. The studies on the zinc(II)-PrP peptide binary systems revealed that zinc(II) ions can coordinate to the 31-mer PrP peptide fragments in the form of macrochelates with two or three coordinated imidazol-nitrogens but the low stability of these complexes cannot prevent the hydrolysis of the metal ion in slightly alkaline solution. These data provide further support for the outstanding affinity of copper(II) ions towards the peptide fragments of prion protein but the binding of nickel(II) can significantly modify the distribution of copper(II) among the available metal binding sites.

  14. Preparation and Characterization of Bi-metallic and Tri-metallic Metal Organic Frameworks Based on Trimesic Acid and Co(II), Ni(II), and Cu(II) Ions

    Science.gov (United States)

    Sahiner, Nurettin; Demirci, Sahin; Yildiz, Mustafa

    2016-10-01

    Trimesic acid-M1(II):M2(II) (M1,2(II)=M(II)=Co(II), Ni(II) and Cu(II)) bi-metallic or tri-metallic organic frameworks (MOFs) were synthesized by the reaction of trimesic acid (H3BTC) ligand with the corresponding MCl2nH2O aqueous solutions. Here, bi- and tri-metallic MOF preparations were demonstrated by using H3BTC as an organic linker, with dual metal ion mixtures at different mole ratios such as Co(II):Ni(II), Ni(II):Cu(II), and Cu(II):Co(II) as metal ion sources in the synthesis of bi-metallic MOFs, and the triple metal ion mixture of Co(II):Ni(II):Cu(II) as the metal ion source in the synthesis of tri-metallic MOFs. The bi- or tri-metallic MOFs were characterized via the Brunauer-Emmett-Teller method, thermogravimetric analyzer (TGA), and magnetic susceptibility measurements with the Gouy method, FT-IR spectroscopy, and electronic spectral studies. The results revealed that the H3BTC MOFs have octahedral and distorted octahedral arrangement around the metal ions, and the d-d transition was not observed in the complex. It was further found that all the prepared MOFs contain water molecules confirmed by Fourier transform infrared (FT-IR) and TGA analyses. The FT-IR spectra of the MOF complexes were characterized by the appearance of a broad band in the region of 3454-3300 cm-1 due to the ν(-OH) of the coordinated water; therefore, the location of the two water molecules was assumed to be inside the complex structure. Remarkably, the synthesized bi-metallic MOFs had unique and distinct colors depending on the amounts of metal ions used in the feed, implying that these bi-metallic MOFs with tunable M1(II) and M2(II) ratios offer great potential in the design of color-coded materials for use as sensors.

  15. Preparation and Characterization of Bi-metallic and Tri-metallic Metal Organic Frameworks Based on Trimesic Acid and Co(II), Ni(II), and Cu(II) Ions

    Science.gov (United States)

    Sahiner, Nurettin; Demirci, Sahin; Yildiz, Mustafa

    2017-02-01

    Trimesic acid-M1(II):M2(II) (M1,2(II)=M(II)=Co(II), Ni(II) and Cu(II)) bi-metallic or tri-metallic organic frameworks (MOFs) were synthesized by the reaction of trimesic acid (H3BTC) ligand with the corresponding MCl2nH2O aqueous solutions. Here, bi- and tri-metallic MOF preparations were demonstrated by using H3BTC as an organic linker, with dual metal ion mixtures at different mole ratios such as Co(II):Ni(II), Ni(II):Cu(II), and Cu(II):Co(II) as metal ion sources in the synthesis of bi-metallic MOFs, and the triple metal ion mixture of Co(II):Ni(II):Cu(II) as the metal ion source in the synthesis of tri-metallic MOFs. The bi- or tri-metallic MOFs were characterized via the Brunauer-Emmett-Teller method, thermogravimetric analyzer (TGA), and magnetic susceptibility measurements with the Gouy method, FT-IR spectroscopy, and electronic spectral studies. The results revealed that the H3BTC MOFs have octahedral and distorted octahedral arrangement around the metal ions, and the d-d transition was not observed in the complex. It was further found that all the prepared MOFs contain water molecules confirmed by Fourier transform infrared (FT-IR) and TGA analyses. The FT-IR spectra of the MOF complexes were characterized by the appearance of a broad band in the region of 3454-3300 cm-1 due to the ν(-OH) of the coordinated water; therefore, the location of the two water molecules was assumed to be inside the complex structure. Remarkably, the synthesized bi-metallic MOFs had unique and distinct colors depending on the amounts of metal ions used in the feed, implying that these bi-metallic MOFs with tunable M1(II) and M2(II) ratios offer great potential in the design of color-coded materials for use as sensors.

  16. Copper (II) and zinc (ii) metal-based salicyl-, furanyl-, thienyl- and pyrrolyl-derived ONNO, NNNO, ONNS & NNNS donor asymmetrically mixed schiff-bases with antibacterial and antifungal potentials.

    Science.gov (United States)

    Chohan, Zahid H; Arif, M; Rashid, A

    2008-12-01

    A new series of asymmetric salicyl-, furanyl-, thienyl- and pyrrolyl-derived ONNO, NNNO, ONNS & NNNS donor antibacterial and antifungal Schiff-bases and their copper(II) and zinc(II) metal complexes have been synthesized and characterized. IR spectra indicated the ligands to act as quartdentate towards divalent metal ions via two azomethine-N, deprotonated-O of salicyl, furanyl-O, thienyl-S and/or pyrrolyl-N. The magnetic moments and electronic spectral data suggest octahedral geometry for Cu(II) and Zn(II) complexes. NMR spectral data of the ligands and their diamagnetic zinc(II) complexes well-define their proposed structures/geometries. Elemental analyses data of the ligands and metal complexes agree with their proposed structures/geometries. The synthesized ligands, along with their metal complexes were screened for their antibacterial activity against B. cereus, C. diphtheriae, E. coli, K. pneumoniae, P. mirabilis, P. aeruginosa, S. typhi, S. dysenteriae and S. aureus strains and for in-vitro antifungal activity against T. schoenleinii, C. glabrata, P. boydii, C. albicans, A. niger, M. canis and T. mentagrophytes. The results of these studies show the metal complexes to be more antibacterial/antifungal against one or more species as compared to the uncomplexed ligands. The brine shrimp bioassay was also carried out to study their in-vitro cytotoxic properties. Eight compounds, L(4), (1), (7), (8), (11), (17), (19) and (23) displayed potent cytotoxic activity with LD(50) = 1.445 x 10(- 3), 1.021 x 10(- 3), 7.478 x 10(- 4), 8.566 x 10(- 4), 1.028 x 10(- 3), 9.943 x 10(- 4), 8.730 x 10(- 4) and 1.124 x 10(- 3) M respectively, against Artemia salina.

  17. Synthesis and Characterization of 2-(Hydroxyimino-1-(phenylpropylidenethiocarbonohydrazide and its Metal Complexes with Co(II, Ni(II and Cu(II Ions

    Directory of Open Access Journals (Sweden)

    A. Venkatchallam

    2009-01-01

    Full Text Available Synthesis and characterization of 2-(hydroxyimino-1-(phenyl propylidene thiocarbonohydrazide (called ‘HPTCHOPD’ was studied. The synthesized compound having the molecular formula C10H13N5OS, where in isonitrosopropiophenone is reacted with thiocarbonohydrazide in presence of sodium acetate in ethanol-water mixture. The yield which is comprises effecting the reaction in the presence of sodium acetate. Also the present work report a process for producing metal complexes having the formula ML2 and (ML2 Cl, wherein M is the divalent metal cation, like cobalt (Co+2, nickel (Ni+2 and copper (Cu+2. The compound HPTCHOPD is admixed with a basic divalent compound that is halide, mainly chloride of Co+2, Ni+2 and Cu+2 in presence of methanol-water mixture. The metal complexes so produced are characterized on the basis of spectral, elemental and magnetic analysis; reveal interesting geometries and bonding features. The data suggested square planar geometry for Co+2 complex, a distorted tetrahedral/square planar-octahedral geometry for Ni+2 complex and a bridged structure for Cu+2 complex.

  18. Metallicity from Type II Supernovae from the (i)PTF

    CERN Document Server

    Taddia, F; Sollerman, J; Rubin, A; Leloudas, G; Gal-Yam, A; Arcavi, I; Cao, Y; Filippenko, A V; Graham, M L; Mazzali, P A; Nugent, P E; Pan, Y -C; Silverman, J M; Xu, D; Yaron, O

    2016-01-01

    Type IIP supernovae (SNe IIP) have recently been proposed as metallicity ($Z$) probes. The spectral models of Dessart et al. (2014) showed that the pseudo-equivalent width of Fe II $\\lambda$5018 (pEW$_{5018}$) during the plateau phase depends on the primordial $Z$, but there was a paucity of SNe IIP exhibiting pEW$_{5018}$ compatible with $Z < 0.4 {\\rm Z}_{\\odot}$. This lack might be due to some physical property of the SN II population, or to the fact that those SNe were discovered in luminous, metal-rich targeted galaxies. Here we use SN II observations from the untargeted (intermediate) Palomar Transient Factory [(i)PTF] survey, aiming to investigate the pEW$_{5018}$ distribution of this SN population and in particular to look for the presence of SNe II at lower $Z$. We perform pEW$_{5018}$ measurements on the spectra of a sample of 39 (i)PTF SNe II, selected to have well-constrained explosion epochs and light-curve properties (Rubin et al. 2015). Based on the comparison with the pEW$_{5018}$ spectral m...

  19. Magnetic circular dichroism spectroscopy of weakly exchange coupled transition metal dimers: A model study

    DEFF Research Database (Denmark)

    Piligkos, S.; Slep, L.D.; Weyhermuller, T.

    2009-01-01

    A- is the monoanion of pyridine-2-aldoxime. The trivalent metal ion M(III) is either diamagnetic Ga(III) or paramagnetic Cr(III) (S-Cr = 3/2). The divalent metal ion M(II) is either diamagnetic Zn(II) or paramagnetic Ni(II) (S-Ni = 1). The three systems 1 (CrZn), 2 (GaNi) and 3 (CrNi) have been structurally...

  20. Structural and Spectroscopic Aspects of Schiff Base Metal Complexes of Cobalt(II, Nickel(II and Copper(II

    Directory of Open Access Journals (Sweden)

    B.K. Rai

    2014-09-01

    Full Text Available The complexes of Co(II, Ni(II and Cu(II with Schiff base 2-butyl thioquinazoline 4(3H thiosemicarbazone were synthesized. The general formulae of the complexes are of the type {M(L2X2], L=2 – butyl thioquinazoline 4(3H thiosemicarbazone; x = Cl-, Br-, I- and NO3-. Elemental analyses and spectral (IR, electronic studies of the synthesized complexes suggest the presence of octahedral, environment around the central metal ion. These complexes were also subjected to study their antimicrobial screening against, Gram positive bacteria Candida albicans and gram negative bacteria Escherichia coli by disc diffusion technique.

  1. Influence of the ADP/ATP ratio, 2-oxoglutarate and divalent ions on Azospirillum brasilense PII protein signalling.

    Science.gov (United States)

    Gerhardt, Edileusa C M; Araújo, Luíza M; Ribeiro, Ronny R; Chubatsu, Leda S; Scarduelli, Marcelo; Rodrigues, Thiago E; Monteiro, Rose A; Pedrosa, Fábio O; Souza, Emanuel M; Huergo, Luciano F

    2012-06-01

    Proteins belonging to the P(II) family coordinate cellular nitrogen metabolism by direct interaction with a variety of enzymes, transcriptional regulators and transporters. The sensing function of P(II) relies on its ability to bind the nitrogen/carbon signalling molecule 2-oxoglutarate (2-OG). In Proteobacteria, P(II) is further subject to reversible uridylylation according to the intracellular levels of glutamine, which reflect the cellular nitrogen status. A number of P(II) proteins have been shown to bind ADP and ATP in a competitive manner, suggesting that P(II) might act as an energy sensor. Here, we analyse the influence of the ADP/ATP ratio, 2-OG levels and divalent metal ions on in vitro uridylylation of the Azospirillum brasilense P(II) proteins GlnB and GlnZ, and on interaction with their targets AmtB, DraG and DraT. The results support the notion that the cellular concentration of 2-OG is a key factor governing occupation of the GlnB and GlnZ nucleotide binding sites by ATP or ADP, with high 2-OG levels favouring the occupation of P(II) by ATP. Both P(II) uridylylation and interaction with target proteins responded to the ADP/ATP ratio within the expected physiological range, supporting the concept that P(II) proteins might act as cellular energy sensors.

  2. ENVIRONMENTAL MANAGEMENT SCIENCE PROGRAM PROJECT NUMBER 87016 CO-PRECIPITATION OF TRACE METALS IN GROUNDWATER AND VADOSE ZONE CALCITE: IN SITU CONTAINMENT AND STABILIZATION OF STRONTIUM-90 AND OTHER DIVALENT METALS AND RADIONUCLIDES AT ARID WESTERN DOE SITES

    Energy Technology Data Exchange (ETDEWEB)

    Ferris, F. Grant; Fujita, Yoshiko; Smith, Robert W.

    2004-06-15

    Radionuclide and metal contaminants are present in the vadose zone and groundwater throughout the U.S. Department of Energy (DOE) weapons complex. In situ containment and stabilization of these contaminants in vadose zones or groundwater is a cost-effective treatment strategy. Our facilitated approach relies upon the hydrolysis of introduced urea to cause the acceleration of calcium carbonate precipitation (and trace metal coprecipitation) by increasing groundwater pH and alkalinity (Fujita et al., 2000; Warren et al., 2001). Subsurface urea hydrolysis is catalyzed by the urease enzyme, which may be either introduced with the urea or produced in situ by ubiquitous subsurface urea hydrolyzing microorganisms. Because the precipitation processes are irreversible and many western aquifers are saturated with respect to calcite, the co-precipitated metals and radionuclides will be effectively removed from groundwater. The rate at which trace metals are incorporated into calcite is a function of calcite precipitation kinetics, adsorption interactions between the calcite surface and the trace metal in solution (Zachara et al., 1991), solid solution properties of the trace metal in calcite (Tesoriero and Pankow, 1996), and also the surfaces upon which the calcite is precipitating. A fundamental understanding of the coupling of calcite precipitation and trace metal partitioning, and how this occurs in aquifers and vadose environments is lacking. This report summarizes work undertaken during the second year of this project.

  3. Trace Metals in Groundwater and Vadose Zone Calcite: In Situ Containment and Stabilization of Stronthium-90 and Other Divalent Metals and Radionuclides at Arid Western DOE Sites: Final Report for Award Number DE-FG07-02ER63486 to the University of Idaho (RW Smith) Environmental Management Science Program Project Number 87016

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Robert W.; Fujita, Yoshiko

    2007-11-07

    Radionuclide and metal contaminants are present in the vadose zone and groundwater throughout the U.S. Department of Energy (DOE) energy research and weapons complex. In situ containment and stabilization of these contaminants represents a cost-effective treatment strategy that minimizes workers’ exposure to hazardous substances, does not require removal or transport of contaminants, and generally does not generate a secondary waste stream. We have investigated an in situ bioremediation approach that immobilizes radionuclides or contaminant metals (e.g., strontium-90) by their microbially facilitated co-precipitation with calcium carbonate in groundwater and vadose zone systems. Calcite, a common mineral in many aquifers and vadose zones in the arid west, can incorporate divalent metals such as strontium, cadmium, lead, and cobalt into its crystal structure by the formation of a solid solution. Collaborative research undertaken by the Idaho National Laboratory (INL), University of Idaho, and University of Toronto as part of this Environmental Management Science Program project has focused on in situ microbially-catalyzed urea hydrolysis, which results in an increase in pH, carbonate alkalinity, ammonium, calcite precipitation, and co-precipitation of divalent cations. In calcite-saturated aquifers, microbially facilitated co-precipitation with calcium carbonate represents a potential long-term contaminant sequestration mechanism. Key results of the project include: **Demonstrating the linkage between urea hydrolysis and calcite precipitation in field and laboratory experiments **Observing strontium incorporation into calcite precipitate by urea hydrolyzers with higher distribution coefficient than in abiotic **Developing and applying molecular methods for characterizing microbial urease activity in groundwater including a quantitative PCR method for enumerating ureolytic bacteria **Applying the suite of developed molecular methods to assess the feasibility of the

  4. Synthesis and characterization of divalent manganese, iron, and cobalt complexes in tripodal phenolate/N-heterocyclic carbene ligand environments.

    Science.gov (United States)

    Käß, Martina; Hohenberger, Johannes; Adelhardt, Mario; Zolnhofer, Eva M; Mossin, Susanne; Heinemann, Frank W; Sutter, Jörg; Meyer, Karsten

    2014-03-03

    Two novel tripodal ligands, (BIMPN(Mes,Ad,Me))(-) and (MIMPN(Mes,Ad,Me))(2-), combining two types of donor atoms, namely, NHC and phenolate donors, were synthesized to complete the series of N-anchored ligands, ranging from chelating species with tris(carbene) to tris(phenolate) chelating arms. The complete ligand series offers a convenient way of tuning the electronic and steric environment around the metal center, thus, allowing for control of the complex's reactivity. This series of divalent complexes of Mn, Fe, and Co was synthesized and characterized by (1)H NMR, IR, and UV/vis spectroscopy as well as by single-crystal X-ray diffraction studies. Variable-temperature SQUID magnetization measurements in the range from 2 to 300 K confirmed high-spin ground states for all divalent complexes and revealed a trend of increasing zero-field splitting |D| from Mn(II), to Fe(II), to Co(II) complexes. Zero-field (57)Fe Mössbauer spectroscopy of the Fe(II) complexes 3, 4, 8, and 11 shows isomer shifts δ that increase gradually as carbenes are substituted for phenolates in the series of ligands. From the single-crystal structure determinations of the complexes, the different steric demand of the ligands is evident. Particularly, the molecular structure of 1-in which a pyridine molecule is situated next to the Mn-Cl bond-and those of azide complexes 2, 4, and 6 demonstrate the flexibility of these mixed-ligand derivatives, which, in contrast to the corresponding symmetrical TIMEN(R) ligands, allow for side access of, e.g., organic substrates, to the reactive metal center.

  5. 二价金属离子对含铜水滑石结构稳定性的影响%Effect of Divalent Metal Ions on the Stability of Cu-Containing Layered Double Hydroxides

    Institute of Scientific and Technical Information of China (English)

    倪哲明; 刘娇; 薛继龙; 李远; 施炜

    2012-01-01

    通过构建不同的二价金属离子(M2+=Mg2+,Ca2+,Zn2+,Cd2+,Ni2+,Co2+)部分取代铜离子形成CuMAl水滑石(CuM2Al-LDHs)的周期性模型,基于密度泛函理论(DFT),用CASTEP程序模块对周期性模型进行几何全优化和性质计算,通过分析各体系的结构参数、电子排布、Mulliken电荷布居、氢键、结合能,总结出含铜水滑石体系结构的稳定性规律.计算结果表明:在CuM2Al-LDHs体系中,主客体间作用力对层板厚度的影响占主要因素:M离子对中心三价铝离子的影响较小,对二价铜离子的影响较大,其中价电子均匀排布的M离子对铜的畸变影响小于价电子不均匀排布的M离子.另外在价电子均匀排布的CuM2Al-LDHs体系中,主客体间的静电作用力和氢键强度逐渐增强.总体上,随着M离子周期数的增加,体系的畸变角增大,结合能绝对值逐渐减小,体系的稳定性下降.价电子不均匀排布的CuCo2Al-LDHs体系的稳定性最差,这有助于从理论上更好地认识含铜水滑石的合成规律.%We proposed a periodic interaction model for the CuM2AI-layered double hydroxides (CuM2AI-LDHs), where M represents the different divalent metal ions (Mg2+, Ca2+, Zn2+, Cd2+, Ni2*, Co2+) that might partially replace the copper ion. Based on density functional theory, the geometry of CuM;AI-LDHs was optimized using the CASTEP program. The stabilities of Cu-containing LDHs were investigated by analyzing the geometric parameters, electronic distribution, charge populations, hydrogen-bonding, and binding energies. The results showed that the electrostatic interactions between the host layer and the guest played a major role in the laminate thickness of the CuMzAI-LDHs. M ions had only a minor effect on the central Al3+, whereas they had a major effect on the Cu2+. Furthermore, M ions with a uniform distribution of valence electrons had only a negligible impact. In addition, in the CuM2AI-LDHs, where the valance electrons of the M

  6. Red Giants in the Small Magellanic Cloud. II. Metallicity Gradient and Age-Metallicity Relation

    CERN Document Server

    Dobbie, P D; Subramaniam, A; Keller, S

    2015-01-01

    We present results from the largest CaII triplet line metallicity study of Small Magellanic Cloud (SMC) field red giant stars to date, involving 3037 objects spread across approximately 37.5 sq. deg., centred on this galaxy. We find a median metallicity of [Fe/H]=-0.99+/-0.01, with clear evidence for an abundance gradient of -0.075+/-0.011 dex / deg. over the inner 5 deg. We interpret the abundance gradient to be the result of an increasing fraction of young stars with decreasing galacto-centric radius, coupled with a uniform global age-metallicity relation. We also demonstrate that the age-metallicity relation for an intermediate age population located 10kpc in front of the NE of the Cloud is indistinguishable from that of the main body of the galaxy, supporting a prior conjecture that this is a stellar analogue of the Magellanic Bridge. The metal poor and metal rich quartiles of our RGB star sample (with complementary optical photometry from the Magellanic Clouds Photometric Survey) are predominantly older ...

  7. Cubane-type Cu(II)4 and Mn(II)2Mn(III)2 complexes based on pyridoxine: a versatile ligand for metal assembling.

    Science.gov (United States)

    Marino, Nadia; Armentano, Donatella; Mastropietro, Teresa F; Julve, Miguel; De Munno, Giovanni; Martínez-Lillo, José

    2013-10-21

    By using Vitamin B6 in its monodeprotonated pyridoxine form (PN-H) [PN = 3-hydroxy-4,5-bis(hydroxymethyl)-2-methylpyridine], two tetranuclear compounds of formula [Mn4(PN-H)4(CH3CO2)3Cl2]Cl·2CH3OH·2H2O (1) and [Cu4(PN-H)4Cl2(H2O)2]Cl2 (2) have been synthesized and magneto-structurally characterized. 1 crystallizes in the triclinic system with space group P1 whereas 2 crystallizes in the orthorhombic system with Fdd2 as space group. They exhibit Mn(II)2Mn(III)2 (1) and Cu(II)4 (2) cubane cores containing four monodeprotonated pyridoxine groups simultaneously acting as chelating and bridging ligands (1 and 2), three bridging acetate ligands in the syn-syn conformation (1), and two terminally bound chloride anions (1 and 2) plus two coordinated water molecules (2). The electroneutrality is achieved by the presence of chloride counterions in both compounds. Tri- [Mn(1) and Mn(3)] and divalent [Mn(2) and Mn(4)] manganese centers coexist in 1, all being six-coordinate with distorted Mn(1/3)O6 and Mn(2/4)O5Cl octahedral surroundings, respectively, the equatorial Mn-O bonds being about 0.2 Å shorter at the former ones. The two crystallographically independent copper(II) ions in 2 are five-coordinate in somewhat distorted CuO5 [Cu(1)] and CuO4Cl [Cu(2)] square pyramidal geometries. The values of the intracore metal-metal separation cover the ranges 3.144(1)-3.535(1) (1) and 2.922(6)-3.376(1) Å (2). The magnetic properties of 1 and 2 were investigated in the temperature range 1.9-300 K, and they correspond to an overall antiferromagnetic behavior with susceptibility maxima at 5.0 (1) and 65.0 K (2). The analysis of the magnetic susceptibility data showed the coexistence of intracore antiferro- and ferromagnetic interactions in the two compounds. Their values compare well with those existing in the literature for the parent systems.

  8. Metal ion controlled self-assembly of a chemically reengineered protein drug studied by small-angle X-ray scattering

    DEFF Research Database (Denmark)

    Jesper, Nygaard; Munch, Henrik K.; Thulstrup, Peter W.;

    2012-01-01

    Precise control of the oligomeric state of proteins is of central importance for biological function and for the properties of biopharmaceutical drugs. Here, the self-assembly of 2,2′-bipyridine conjugated monomeric insulin analogues, induced through coordination to divalent metal ions, was studied....... This protein drug system was designed to form non-native homo-oligomers through selective coordination of two divalent metal ions, Fe(II) and Zn(II), respectively. The insulin type chosen for this study is a variant designed for a reduced tendency toward native dimer formation at physiological concentrations...

  9. Synthesis and characterization of transition metal(II) complexes with tridentate schiff base in DMF solution

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Jeong Geun [Seonam Univ., Namwon (Korea, Republic of); Choi, Yong Kook [Cheonnam National Univ., Kwangju (Korea, Republic of)

    1999-10-01

    Shiff Base ligand such as (NOIPH) have been synthesized from 2-hydroxy-1naph-thaldehyde and arometic amine, Co(II), Ni(II), and Cu(II) complexes from the reaction metal salts with Tridentate Schiff Base (NOIPH) were synthesized. The ligand and metal(II) complexes were characterized by the elementary analysis, IR, UV-Vis, NMR spectra, and thermogravimetric analysis. Metal(II) complexes in solid state have been shown that the mole ratio of Schiff base (NOIPH) as N{sub 2}O type to Metal(II) is 2:1 and the metal(II) complexes of N{sub 2}O ligand type were four-coordinated configurations.

  10. Immobilization of heavy metal ions (CuII, CdII, NiII, and PbII) by broiler litter-derived biochars in water and soil.

    Science.gov (United States)

    Uchimiya, Minori; Lima, Isabel M; Thomas Klasson, K; Chang, SeChin; Wartelle, Lynda H; Rodgers, James E

    2010-05-12

    Chars, a form of environmental black carbon resulting from incomplete burning of biomass, can immobilize organic contaminants by both surface adsorption and partitioning mechanisms. The predominance of each sorption mechanism depends upon the proportion of organic to carbonized fractions comprising the sorbent. Information is currently lacking in the effectiveness of char amendment for heavy metal immobilization in contaminated (e.g., urban and arms range) soils where several metal contaminants coexist. The present study employed sorbents of a common biomass origin (broiler litter manure) that underwent various degrees of carbonization (chars formed by pyrolysis at 350 and 700 degrees C and steam-activated analogues) for heavy metal (Cd(II), Cu(II), Ni(II), and Pb(II)) immobilization in water and soil. ATR-FTIR, (1)H NMR, and Boehm titration results suggested that higher pyrolysis temperature and activation lead to the disappearance (e.g., aliphatic -CH(2) and -CH(3)) and the formation (e.g., C-O) of certain surface functional groups, portions of which are leachable. Both in water and in soil, pH increase by the addition of basic char enhanced the immobilization of heavy metals. Heavy metal immobilization resulted in nonstoichiometric release of protons, that is, several orders of magnitude greater total metal concentration immobilized than protons released. The results suggest that with higher carbonized fractions and loading of chars, heavy metal immobilization by cation exchange becomes increasingly outweighed by other controlling factors such as the coordination by pi electrons (C=C) of carbon and precipitation.

  11. Adsorptive removal of Cu(II) and Ni(II) from single-metal, binary-metal, and industrial wastewater systems by surfactant-modified alumina.

    Science.gov (United States)

    Khobragade, Moni U; Pal, Anjali

    2015-01-01

    Batch adsorption was carried out to investigate the possibility of utilizing surfactant-modified alumina (SMA) as an adsorbent for the removal of Cu(II) and Ni(II) from single-metal and binary-metal solutions. Scanning electron microscopic (SEM) images of SMA before and after metal removal from single-metal matrix, showed no significant changes, whereas energy dispersive X-ray (EDX) studies confirmed the incorporation of Cu(II) (∼ 0.74 atomic%) and Ni(II) (∼ 0.64 atomic%) on the adsorbent surface. The removal of Cu(II) and Ni(II), using SMA depends on contact time, adsorbent dose and medium pH. The sorption kinetics followed pseudo-second-order model for Cu(II). However, for Ni(II), either pseudo-first-order or pseudo-second-order model is applicable. The batch experimental data were fitted to Langmuir and Freundlich isotherm, and based on the correlation coefficient value (R(2)), the adsorption could be described more precisely by the Freundlich isotherm. The maximum adsorption capacity from Langmuir isotherm of Cu(II) was 9.34 mg g(-1) and for Ni(II) 6.87 mg g(-1). In a synthetic binary mixture of Cu(II) and Ni(II), having a concentration of 10 mg L(-1) each, removal of Cu(II) was better. The treatment method was further applied to real wastewater from an electroplating industry. The batch experiment results showed that SMA was effective in the simultaneous removal of Cu(II) and Ni(II) to a significant extent, with additional improvement of water quality of the industrial effluent considered.

  12. Biological Role of Cobalt(II), Copper(II) and Nickel(II) Metal Ions on the Antibacterial Properties of Some Nicotinoyl-Hydrazine Derived Compounds

    OpenAIRE

    Chohan, Zahid H.; Sherazi, Syed K. A.

    1997-01-01

    Several cobalt(II), copper(II) and nickel(II) complexes of nicotinoylhydrazine-derived compounds were prepared and characterised by physical, spectral and analytical data. These compounds and their complexes have proven to be antibacterial. The screening data show the metal complexes to be more potential/bactericidal than the uncomplexed compounds against one or more bacterial species.

  13. Co (II and Zn (II Metal Complexes of Heterocyclic Schiff Bases: A Synthesis, Spectral and Antimicrobial Study

    Directory of Open Access Journals (Sweden)

    Sachin R. Joshi

    2014-09-01

    Full Text Available The Schiff bases have been synthesised by the reaction of Benzoinoxime primary ligand with heterocyclic compounds such as 2-aminothiazole (SL1 and 8-hydroxyquinoline (SL2 to form the secondary ligand, which than react with the metal halides to form complexes of Co (II and Zn (II. The elemental analysis data shows that the metal to ligand ratio in all Co (II simple is 1:2 for simple complexes and 1:2:2 for metal complex with oxime as a primary ligand and SL1 as a secondary ligand while it is 1:2:1 for metal complex with oxime as a primary ligand and SL3 as a secondary ligand whereas Zn (II complexes of mixed ligand exhibit the stoichiometry 1:2:2. The structural features have been determined from IR, UV-Vis, and XRD data. All the complex shows a distorted octahedral geometry to mononuclear Co (II complexes of mixed ligands, while square planner geometry to mononuclear Co (II complexes of oximes. Zn (II complexes of mixed ligands shows a distorted octahedral geometry, while square planner geometry to mononuclear Zn (II complexes of oximes. All the synthesised compounds were screened for antimicrobial activity.

  14. Metal Ions in Unusual Valency States.

    Science.gov (United States)

    Sellers, Robin M.

    1981-01-01

    Discusses reactivity of metal ions with the primary products of water radiolysis, hyper-reduced metal ions, zero-valent metal ions, unstable divalent ions from the reduction of bivalent ions, hyper-oxidized metal ions, and metal complexes. (CS)

  15. Synthesis and Spectroscopic Characterization of New Ligand and Its Pd(II, Cu(II Metal Complexes

    Directory of Open Access Journals (Sweden)

    Isam Hussain Al-Karkhi

    2013-08-01

    Full Text Available A novel Schiff base ligand containing nitrogen and sulfur donor atoms was synthesized by condensing thioamide (TA with imidothioic acid (IT to form 1, 4 dithiane-2, 3-diamine (TAIT. Metal complexes of this ligand were prepared using Cu (II chloride dihydrates and Pd (III chloride. These complexes have been characterized using various physico-chemical and spectroscopic techniques. Based on physico-chemical and spectroscopic analyses, the structure of Cu (II complex is expected to be octahedral, while Pd (II complex is proposed to be square planner geometry. Schiff base and its metal complexes were expected to show strong bioactivity against microbes and cancer cells.

  16. A RhIII-N-heterocyclic carbene complex from metal-metal singly bonded [RhII−RhII] precursor

    Indian Academy of Sciences (India)

    Arup Sinha; Abir Sarbajna; Shrabani dinda; Jitendra K Bera

    2011-11-01

    Metal-metal singly bonded [Rh2(CO)4(acac)2][OTf]2 (1) has been synthesized and characterized by spectroscopic and analytical techniques. A density functional theory (DFT) optimized structure has been computed for the unbridged centro-symmetric structure. Reaction of 1 with PIN.HBr results in the [Rh(PIN)2(H2O)Br][OTf]2 (2) in high yield. The reaction involves metal-oxidation from RhII to RhIII accompanied by the metal-metal bond cleavage. The X-ray structure of 2 has been determined which reveals the incorporation of two N-heterocyclic carbene (NHC) ligands to each rhodium. This work demonstrates the general utility of the metal-metal bonded compounds for the easy synthesis of metal-NHC compounds.

  17. Theoretical calculation of the NMR spin-spin coupling constants and the NMR shifts allow distinguishability between the specific direct and the water-mediated binding of a divalent metal cation to guanine.

    Science.gov (United States)

    Sychrovský, Vladimír; Sponer, Jirí; Hobza, Pavel

    2004-01-21

    The calculated intermolecular and intramolecular indirect NMR spin-spin coupling constants and NMR shifts were used for the discrimination between the inner-shell and the outer-shell binding motif of hydrated divalent cations Mg(2+) or Zn(2+) with a guanine base. The intermolecular coupling constants (1)J(X,O6) and (1)J(X,N7) (X = Mg(2+), Zn(2+)) can be unambiguously assigned to the specific inner-shell binding motif of the hydrated cation either with oxygen O6 or with nitrogen N7 of guanine. The calculated coupling constants (1)J(Mg,O6) and (1)J(Zn,O6) were 6.2 and -17.5 Hz, respectively, for the inner-shell complex of cation directly interacting with oxygen O6 of guanine. For the inner-shell coordination of the cation at nitrogen N7, the calculated coupling constants (1)J(Mg,N7) and (1)J(Zn,N7) were 5.6 and -36.5 Hz, respectively. When the binding of the cation is water-mediated, the coupling constant is zero. To obtain reliable shifts in NMR parameters, hydrated guanine was utilized as the reference state. The calculated change of NMR spin-spin coupling constants due to the hydration and coordination of the cation with guanine is caused mainly by the variation of Fermi-contact coupling contribution while the variation of diamagnetic spin-orbit, paramagnetic spin-orbit, and spin-dipolar coupling contributions is small. The change of s-character of guanine sigma bonding, sigma antibonding, and lone pair orbitals upon the hydration and cation coordination (calculated using the Natural Bond Orbital analysis) correlates with the variation of the Fermi-contact term. The calculated NMR shifts delta(N7) of -15.3 and -12.2 ppm upon the coordination of Mg(2+) and Zn(2+) ion are similar to the NMR shift of 19.6 ppm toward the high field measured by Tanaka for N7 of guanine upon the coordination of the Cd(2+) cation (Tanaka, Y.; Kojima, C.; Morita, E. H.; Kasai. Y.; Yamasaki, K.; Ono, A.; Kainosho, M.; Taira, K. J. Am. Chem. Soc. 2002, 124, 4595-4601). The present data

  18. Synthesis, spectral characterization thermal stability, antimicrobial studies and biodegradation of starch–thiourea based biodegradable polymeric ligand and its coordination complexes with [Mn(II, Co(II, Ni(II, Cu(II, and Zn(II] metals

    Directory of Open Access Journals (Sweden)

    Nahid Nishat

    2016-09-01

    Full Text Available A biodegradable polymer was synthesized by the modification reaction of polymeric starch with thiourea which is further modified by transition metals, Mn(II, Co(II, Ni(II, Cu(II and Zn(II. All the polymeric compounds were characterized by (FT-IR spectroscopy, 1H NMR spectroscopy, 13C NMR spectroscopy, UV–visible spectra, magnetic moment measurements, thermogravimetric analysis (TGA and antibacterial activities. Polymer complexes of Mn(II, Co(II and Ni(II show octahedral geometry, while polymer complexes of Cu(II and Zn(II show square planar and tetrahedral geometry, respectively. The TGA revealed that all the polymer metal complexes are more thermally stable than their parental ligand. In addition, biodegradable studies of all the polymeric compounds were also carried out through ASTM-D-5338-93 standards of biodegradable polymers by CO2 evolution method which says that coordination decreases biodegradability. The antibacterial activity was screened with the agar well diffusion method against some selected microorganisms. Among all the complexes, the antibacterial activity of the Cu(II polymer–metal complex showed the highest zone of inhibition because of its higher stability constant.

  19. Effects of metal cations and fulvic acid on the adsorption of ciprofloxacin onto goethite.

    Science.gov (United States)

    Tan, Yinyue; Guo, Yong; Gu, Xueyuan; Gu, Cheng

    2015-01-01

    Ciprofloxacin (CIP) can be strongly adsorbed by ferric oxides, but some influencing factors, such as multivalent cations and soil organic matter, have not been evaluated extensively. In this study, the interaction between CIP and four divalent metals (Ca, Cd, Cu, and Pb) was investigated using potentiometric titration and the results indicated that CIP can bind to the divalent metals in the following affinity order: Cu(II) > Pb(II) > Cd(II) > Ca(II). The effects of metals and fulvic acid (FA) on the adsorption behavior of CIP onto goethite surfaces were also examined using batch experiments. It was found that metal cations enhanced the CIP retention on goethite surfaces in the same order as the affinity order with CIP, indicating that metals likely increased CIP retention through cation bridging. FA was found to promote CIP sorption rather than compete with it, and the coexistence of FA and Cu(II) in the system exhibited an addictive effect with CIP sorption, indicating that they might influence the sorption separately under the studied loading condition. Taken together, our results suggested that the coexistence of divalent cations or soil organic matter will enhance CIP sorption on goethite surfaces, hence reducing its mobility and bioavailability in the environment.

  20. Divalent thulium triflate. A structural and spectroscopic study

    Energy Technology Data Exchange (ETDEWEB)

    Xemard, Mathieu; Jaoul, Arnaud; Cordier, Marie; Nocton, Gregory [Univ. Paris-Saclay, Palaiseau (France). LCM, Ecole polytechnique, CNRS; Molton, Florian; Duboc, Carole [Grenoble Univ., Saint Martin d' Heres (France). Dept. de Chimie Moleculaire; Cador, Olivier; Le Guennic, Boris [Univ. de Rennes 1 (France). Inst. des Sciences Chimique de Rennes, UMR 6226 CNRS; Maury, Olivier [Univ. Claude Bernard Lyon 1 (France). Lab. de Chimie; Clavaguera, Carine [Univ. Paris-Saclay, Palaiseau (France). LCM, Ecole polytechnique, CNRS; Univ. Paris Sud, Univ. Paris-Saclay, Orsay (France). Lab. de Chimie Physique, CNRS

    2017-04-03

    The first molecular Tm{sup II} luminescence measurements are reported along with rare magnetic, X and Q bands EPR studies. Access to simple and soluble molecular divalent lanthanide complexes is highly sought for small-molecule activation studies and organic transformations using single-electron transfer processes. However, owing to their low stability and propensity to disproportionate, these complexes are hard to synthetize and their electronic properties are therefore almost unexplored. Herein we present the synthesis of [Tm(μ-OTf){sub 2}(dme){sub 2}]{sub n}, a rare and simple coordination compound of divalent thulium that can be seen as a promising starting material for the synthesis of more elaborated complexes. This reactive complex was structurally characterized by X-ray diffraction analysis and its electronic structure has been compared with that of its halide cousin TmI{sub 2}(dme){sub 3}. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Heavy metal/polyacid interaction. An electrochemical study of the binding of Cd(II), Pb(II) and Zn(II) to polycarboxylic and humic acids

    NARCIS (Netherlands)

    Cleven, R.F.M.J.

    1984-01-01

    Polyelectrolyte effects in the interaction of heavy metal ions with model polycarboxylic acids have been described, in order to establish the relevance of these effects in the interaction of heavy metal ions with naturally occurring humic and fulvic acids. The model systems consisted of Cd(II), Pb(I

  2. Metal ions removal from polluted waters by sorption onto exhausted coffee waste. Application to metal finishing industries wastewater treatment

    OpenAIRE

    Liu, Chang

    2014-01-01

    A new technology for Cr(VI) and divalent metal ions removal based on metal sorption onto exhausted coffee waste has been developed. Physical and chemical characterization of exhausted coffee waste was explored as well as the role of structural and non structural compounds of the waste in metal ions sorption. Kinetics of Cr(VI) sorption from binary mixtures containing different Cr(VI) and Cu(II) molar ratios were carried out in a batch reactor. A synergistic effect of Cu(II) in Cr(VI) reductio...

  3. Molecular cloning, sequencing, and expression analysis of cDNA encoding metalloprotein II (MP II) induced by single and combined metals (Cu(II), Cd(II)) in polychaeta Perinereis aibuhitensis.

    Science.gov (United States)

    Yang, Dazuo; Zhou, Yibing; Zhao, Huan; Zhou, Xiaoxiao; Sun, Na; Wang, Bin; Yuan, Xiutang

    2012-11-01

    We amplified and analyzed the complete cDNA of metalloprotein II (MP II) from the somatic muscle of the polychaete Perinereis aibuhitensis, the full length cDNA is 904 bp encoding 119 amino acids. The MP II cDNA sequence was subjected to BLAST searching in NCBI and was found to share high homology with hemerythrin of other worms. MP II expression of P. aibuhitensis exposed to single and combined metals (Cu(II), Cd(II)) was analyzed using real time-PCR. MP II mRNA expression increased at the start of Cu(II) exposure, then decreased and finally return to the normal level. Expression pattern of MP II under Cd(II) exposure was time- and dose-dependent. MP II expression induced by a combination of Cd(II) and Cu(II) was similar to that induced by Cd(II) alone.

  4. Tungsten and other refractory metals for VLSI applications II

    Energy Technology Data Exchange (ETDEWEB)

    Broadbent, E.K.

    1987-01-01

    This book presents papers on tungsten and other refractory metals for VLSI applications. Topics include the following: Selectivity loss and nucleation on insulators, fundamental reaction and growth studies, chemical vapor deposition of tungsten, chemical vapor deposition of molybdenum, reactive ion etching of refractory metal films; and properties of refractory metals deposited by sputtering.

  5. Manufacturing processes of cellular metals. Part II. Solid route, metals deposition, other processes; Procesos de fabricacion de metales celulares. Parte II: Via solida, deposicion de metales otros procesos

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, P.; Cruz, L. J.; Coleto, J.

    2009-07-01

    At the first part of this paper review a description about cellular metal processes by liquid route, was made. In this second part, solid processes and metals deposition are described. In similar way, the different kind of processes in each case are reviewed; making a short description about the main parameters involved and the advantages and drawbacks in each of them. (Author) 147 refs.

  6. Integral field spectroscopy of supernova explosion sites: constraining mass and metallicity of the progenitors -- II. Type II-P and II-L supernovae

    CERN Document Server

    Kuncarayakti, Hanindyo; Aldering, Greg; Arimoto, Nobuo; Maeda, Keiichi; Morokuma, Tomoki; Pereira, Rui; Usuda, Tomonori; Hashiba, Yasuhito

    2013-01-01

    Thirteen explosion sites of type II-P and II-L supernovae in nearby galaxies have been observed using integral field spectroscopy, enabling both spatial and spectral study of the explosion sites. We used the properties of the parent stellar population of the coeval supernova progenitor star to derive its metallicity and initial mass (c.f. Paper I). The spectrum of the parent stellar population yields the estimates of metallicity via strong-line method, and age via comparison with simple stellar population (SSP) models. These metallicity and age parameters are adopted for the progenitor star. Age, or lifetime of the star, was used to derive initial (ZAMS) mass of the star by comparing with stellar evolution models. With this technique, we were able to determine metallicity and initial mass of the SN progenitors in our sample. Our result indicates that some type-II supernova progenitors may have been stars with mass comparable to SN Ib/c progenitors.

  7. 8-aminoquinoline functionalized silica nanoparticles: a fluorescent nanosensor for detection of divalent zinc in aqueous and in yeast cell suspension.

    Science.gov (United States)

    Rastogi, Shiva K; Pal, Parul; Aston, D Eric; Bitterwolf, Thomas E; Branen, A Larry

    2011-05-01

    Zinc is one of the most important transition metal of physiological importance, existing primarily as a divalent cation. A number of sensors have been developed for Zn(II) detection. Here, we present a novel fluorescent nanosensor for Zn(II) detection using a derivative of 8-aminoquinoline (N-(quinolin-8-yl)-2-(3 (triethoxysilyl)propylamino)acetamide (QTEPA) grafted on silica nanoparticles (SiNPs). These functionalized SiNPs were used to demonstrate specific detection of Zn(II) in tris-HCl buffer (pH 7.22), in yeast cell (Saccharomyces cerevisiae) suspension, and in tap water. The silane QTEPA, SiNPs and final product were characterized using solution and solid state nuclear magnetic resonance, Fourier transform infrared, ultraviolet-visible absorption spectroscopy, transmission electron microscopy, elemental analysis, thermogravimetric techniques, and fluorescence spectroscopy. The nanosensor shows almost 2.8-fold fluorescence emission enhancement and about 55 nm red-shift upon excitation with 330 ± 5 nm wavelength in presence of 1 μM Zn(II) ions in tris-HCl (pH 7.22). The presence of other metal ions has no observable effect on the sensitivity and selectivity of nanosensor. This sensor selectively detects Zn(II) ions with submicromolar detection to a limit of 0.1 μM. The sensor shows good applicability in the determination of Zn(II) in tris-HCl buffer and yeast cell environment. Further, it shows enhancement in fluorescence intensity in tap water samples.

  8. Synthetic and structural studies of linear bis-catechol amide, N,N{prime}-bis(2,3-dihydroxybenzoyl)-1,7-diazaheptane (5-LICAM), and its complexes with Ni{sup 2+} and Co{sup 2+}: Utilization of a polymer-supported, sulfonated analog, 5-LICAMS, as a biomimetic ligand for divalent metal ion removal from aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Song-Ping, Franz, K.J.; Fish, R.H. [Lawrence Berkeley Lab., CA (United States); Olmstead, M.M. [Univ. of California, Davis, CA (United States)

    1995-05-24

    The synthesis and structural characterization of the linear bis(catechol) amide ligand, N,N{prime}-bis(2,3-dihydroxy-benzoyl)-1.7-diazaheptane (5-LICAM, 1), was studied along with several metal complexes, namely, Ni{sup 2+} and Co{sup 2+}. In order to test the utilization of 1 in removing Ni{sup 2+} from aqueous solution for environmental inorganic applications, the authors synthesized the polymer pendant ligand version, PS-5-LICAM, bonded to modified 6% macroporous divinylbenzene-polystyrene beads (0.55 mmol/g), with an important modification of a sulfonate group on the catechol ring, PS-5-LICAMS, to impart hydrophilicity to the ligand site. Indeed, it was found that the PS-5-LICAMS ligand removed 0.35 mmol of Ni/g of polymer beads from aqueous solution at pH 2.5, but unfortunately, was not selective to Ni{sup 2+} in competition with other divalent metal ions. An in depth discussion of the X-ray structure of ligand 2 and that of the Ni complex, 3, will be presented.

  9. Transition metal catalysed Grignard-like allylic activation across tetragonal tin(II) oxide

    Indian Academy of Sciences (India)

    Pradipta Sinha; Moloy Banerjee; Abhijit Kundu; Sujit Roy

    2002-08-01

    The reaction of allyl halide and a carbonyl compound under the aegis of tetragonal tin(II) oxide and catalytic 8, 10 metal complexes provides the corresponding homoallylic alcohol, via a novel allyl tin intermediate.

  10. ENVIRONMENTALMANAGEMENT SCIENCE PROGRAM PROJECT NUMBER 87016 CO-PRECIPITATION OF TRACEMETALS INGROUNDWATER AND VADOSE ZONE CALCITE: IN SITU CONTAINMENT AND STABILIZATION OF STRONTIUM-90 ANDOTHER DIVALENT METALS AND RADIONUCLIDES AT ARIDWESTERN DOE SITES

    Energy Technology Data Exchange (ETDEWEB)

    Ferris, F. Grant; Fujita, Yoshiko; Smith, Robert W.; Cosgrove, Donna M.; Colwell, F. S.

    2004-06-15

    Radionuclide and metal contaminants are present in the vadose zone and groundwater throughout the U.S. Department of Energy (DOE) weapons complex. In situ containment and stabilization of these contaminants in vadose zones or groundwater is a cost-effective treatment strategy. Our facilitated approach relies upon the hydrolysis of introduced urea to cause the acceleration of calcium carbonate precipitation (and trace metal coprecipitation) by increasing groundwater pH and alkalinity (Fujita et al., 2000; Warren et al., 2001). Subsurface urea hydrolysis is catalyzed by the urease enzyme, which may be either introduced with the urea or produced in situ by ubiquitous subsurface urea hydrolyzing microorganisms. Because the precipitation processes are irreversible and many western aquifers are saturated with respect to calcite, the co-precipitated metals and radionuclides will be effectively removed from groundwater. The rate at which trace metals are incorporated into calcite is a function of calcite precipitation kinetics, adsorption interactions between the calcite surface and the trace metal in solution (Zachara et al., 1991), solid solution properties of the trace metal in calcite (Tesoriero and Pankow, 1996), and also the surfaces upon which the calcite is precipitating. A fundamental understanding of the coupling of calcite precipitation and trace metal partitioning, and how this occurs in aquifers and vadose environments is lacking. This report summarizes work undertaken during the second year of this project.

  11. Type II-Plateau supernovae as metallicity probes of the Universe

    CERN Document Server

    Dessart, L; Hamuy, M; Hillier, D J; Lanz, T; Anderson, J P; Folatelli, G; Freedman, W L; Ley, F; Morrell, N; Persson, S E; Phillips, M M; Stritzinger, M; Suntzeff, N B

    2014-01-01

    We explore a method for metallicity determinations based on quantitative spectroscopy of type II-Plateau (II-P) supernovae (SNe). For consistency, we first evolve a set of 15Msun main sequence stars at 0.1, 0.4, 1, and 2 x the solar metallicity. At the onset of core collapse, we trigger a piston-driven explosion and model the resulting ejecta and radiation. Our theoretical models of such red-supergiant-star explosions at different metallicity show that synthetic spectra of SNe II-P possess optical signatures during the recombination phase that are sensitive to metallicity variations. This sensitivity can be quantified and the metallicity inferred from the strength of metal-line absorptions. Furthermore, these signatures are not limited to O, but also include Na, Ca, Sc, Ti, or Fe. When compared to a sample of SNe II-P from the Carnegie SN Project and previous SN followup programs, we find that most events lie at a metallicity between 0.4 and 2 x solar, with a marked scarcity of SN II-P events at SMC metallici...

  12. Coordination Modes of a Schiff Base Derived from Substituted 2-Aminothiazole with Chromium(III, Manganese(II, Iron(II, Cobalt(II, Nickel(II and Copper(II Metal Ions: Synthesis, Spectroscopic and Antimicrobial Studies

    Directory of Open Access Journals (Sweden)

    Ambit Thakar

    2011-01-01

    Full Text Available Transition metal complexes of Cr(III, Mn(II, Fe(II, Co(II, Ni(II and Cu(II metal ions with general stoichiometry [ML2.2H2O] and [ML3], where M= Mn(II, Cr(III, Fe(II, Co(II, Ni(II and Cu(II, L= Schiff base derived from the condensation of 2-amino-4(4’-phenyl/methylphenyl-5-methyl-thiazole with 4-acetyl-1(3-chloro phenyl-3-methyl-2-pyrazoline-5-ones, have been synthesized and structurally characterized by elemental analysis, molar conductance measurements, magnetic susceptibility measurements and spectral techniques like IR, UV, 1H NMR, 13C NMR and Mass Spectra. All the complexes were found to be octahedral geometry. The ligand and its complexes have been screened for their antifungal and antibacterial activities against three fungi, i.e. Alternaria brassicae, Aspergillus niger and Fesarium oxysporum and two bacteria, i.e. Xanthomonas compestris and Pseudomonas aeruginosa.

  13. Micellar effect on metal-ligand complexes of Co(II, Ni(II, Cu(II and Zn(II with citric acid

    Directory of Open Access Journals (Sweden)

    Nageswara Rao Gollapalli

    2009-12-01

    Full Text Available Chemical speciation of citric acid complexes of Co(II, Ni(II, Cu(II and Zn(II was investigated pH-metrically in 0.0-2.5% anionic, cationic and neutral micellar media. The primary alkalimetric data were pruned with SCPHD program. The existence of different binary species was established from modeling studies using the computer program MINIQUAD75. Alkalimetric titrations were carried out in different relative concentrations (M:L:X = 1:2:5, 1:3:5, 1:5:3 of metal (M to citric acid. The selection of best chemical models was based on statistical parameters and residual analysis. The species detected were MLH, ML2, ML2H and ML2H2. The trend in variation of stability constants with change in mole fraction of the medium is explained on the basis of electrostatic and non-electrostatic forces. Distributions of the species with pH at different compositions of micellar media are also presented.

  14. Design, synthesis and characterization of macrocyclic ligand based transition metal complexes of Ni(II), Cu(II) and Co(II) with their antimicrobial and antioxidant evaluation

    Science.gov (United States)

    Gull, Parveez; Malik, Manzoor Ahmad; Dar, Ovas Ahmad; Hashmi, Athar Adil

    2017-04-01

    Three new complexes Ni(II), Cu(II) and Co(II) were synthesized of macrocyclic ligand derived from 1, 4-dicarbonyl-phenyl-dihydrazide and O-phthalaldehyde in the ratio of 2:2. The synthesized compounds were characterized by elemental analyses, molar conductance, magnetic susceptibility measurements, FTIR, UV-Vis., Mass and 1H NMR spectral studies. The electronic spectra of the metal complexes indicate a six coordinate octahedral geometry of the central metal ion. These metal complexes and the ligand were evaluated for antimicrobial activity against bacteria (E. coli, B. subtilis, S. aureus) and fungi (A. niger, A. flavus, C. albicans) and compared against standard drugs chloramphenicol and nystatin respectively. In addition, the antioxidant activity of the compounds was also investigated through scavenging effect on DPPH radicals.

  15. The NIR Ca II triplet at low metallicity : Searching for extremely low-metallicity stars in classical dwarf galaxies

    NARCIS (Netherlands)

    Starkenburg, E.; Hill, V.; Tolstoy, E.; Gonzalez Hernandez, J.I.; Irwin, M.; Helmi, A.; Battaglia, G.; Jablonka, P.; Tafelmeyer, M.; Shetrone, M.; Venn, K.; de Boer, T.

    2010-01-01

    The NIR Ca II triplet absorption lines have proven to be an important tool for quantitative spectroscopy of individual red giant branch stars in the Local Group, providing a better understanding of metallicities of stars in the Milky Way and dwarf galaxies and thereby an opportunity to constrain the

  16. Metal Abundance Calibration of the Ca II Triplet Lines in RR Lyrae Stars

    CERN Document Server

    Wallerstein, George; Huang, Wenjin

    2011-01-01

    The GAIA satellite is likely to observe thousands of RR Lyrae stars within a small spectral window, between 8470A and 8750A, at a resolution of 11,500. In order to derive the metallicity of RR Lyrae stars from Gaia, we have obtained numerous spectra of RR Lyrae stars at a resolution of 35,000 with the Apache Point Observatory 3.5 m echelle spectrograph. We have correlated the Ca II triplet line strengths with metallicity as derived from Fe II abundances, analogous to Preston's (1959) use of the Ca II K line to estimate the metallicity of RR Lyrae stars. The Ca II line at 8498A is the least blended with neighboring Paschen lines and thus provides the best correlation.

  17. Transition metal M(II complexes with isonicotinoylhydrazone-9-anthraldehyde

    Directory of Open Access Journals (Sweden)

    Dianu M.L.

    2010-01-01

    Full Text Available New complexes of isonicotinoylhydrazone-9-anthraldehyde with Cu(II, Co(II and Ni(II have been prepared and characterized by analytical and physico-chemical techniques, such as elemental and thermal analyses, magnetic susceptibility and conductivity measurements, and electronic, EPR and IR spectral studies. The infrared spectral studies revealed the bidentate or monodentate nature of the Schiff base in the complexes; the pyridine nitrogen does not participate in the coordination. A tetrahedral geometry is suggested for the nitrate-complexes and an octahedral geometry for the others. Thermal studies support the chemical formulation of these complexes.

  18. Tidal Downsizing model. II. Planet-metallicity correlations

    CERN Document Server

    Nayakshin, Sergei

    2015-01-01

    Core Accretion (CA), the de-facto accepted theory of planet formation, requires formation of massive solid cores as a prerequisite for assembly of gas giant planets. The observed metallicity correlations of exoplanets are puzzling in the context of CA. While gas giant planets are found preferentially around metal-rich host stars, planets smaller than Neptune orbit hosts with a wide range of metallicities. We propose an alternative interpretation of these observations in the framework of a recently developed planet formation hypothesis called Tidal Downsizing (TD). We perform population synthesis calculations based on TD, and find that the connection between the populations of the gas giant and the smaller solid-core dominated planets is non linear and not even monotonic. While gas giant planets formed in the simulations in the inner few AU region follow a strong positive correlation with the host star metallicity, the smaller planets do not. The simulated population of these smaller planets shows a shallow pe...

  19. Pb(II) Distributions at Biofilm-Metal Oxide Interfaces

    National Research Council Canada - National Science Library

    Alexis S. Templeton; Thomas P. Trainor; Samuel J. Traina; Alfred M. Spormann; Gordon E. Brown

    2001-01-01

    .... Attached bacteria and adsorbed organic matter may interfere with sorption processes on metal oxide surfaces by changing the characteristics of the electrical double layer at the solid-solution...

  20. Organic and inorganic mercurials have distinct effects on cellular thiols, metal homeostasis, and Fe-binding proteins in Escherichia coli

    OpenAIRE

    LaVoie, Stephen P.; Mapolelo, Daphne T.; Cowart, Darin M.; Polacco, Benjamin J.; Johnson, Michael K.; Scott, Robert A.; Miller, Susan M.; Summers, Anne O.

    2015-01-01

    The protean chemical properties of the toxic metal mercury (Hg) have made it attractive in diverse applications since antiquity. However, growing public concern has led to an international agreement to decrease its impact on health and the environment. During a recent proteomics study of acute Hg exposure in E. coli, we also examined the effects of inorganic and organic Hg compounds on thiol- and metal- homeostases. On brief exposure, lower concentrations of divalent inorganic mercury Hg(II) ...

  1. Beryllium metal II. a review of the available toxicity data.

    Science.gov (United States)

    Strupp, Christian

    2011-01-01

    Beryllium metal was classified in Europe collectively with beryllium compounds, e.g. soluble salts. Toxicological equivalence was assumed despite greatly differing physicochemical properties. Following introduction of the Registration, Evaluation, Authorization and Restriction of Chemicals (REACH) regulation, beryllium metal was classified as individual substance and more investigational efforts to appropriately characterize beryllium metal as a specific substance apart from soluble beryllium compounds was required. A literature search on toxicity of beryllium metal was conducted, and the resulting literature compiled together with the results of a recently performed study package into a comprehensive data set. Testing performed under Organisation for Economic Co-Operation and Development guidelines and Good Laboratory Practice concluded that beryllium metal was neither a skin irritant, an eye irritant, a skin sensitizer nor evoked any clinical signs of acute oral toxicity; discrepancies between the current legal classification of beryllium metal in the European Union (EU) and the experimental results were identified. Furthermore, genotoxicity and carcinogenicity were discussed in the context of the literature data and the new experimental data. It was concluded that beryllium metal is unlikely to be a classical nonthreshold mutagen. Effects on DNA repair and morphological cell transformation were observed but need further investigation to evaluate their relevance in vivo. Animal carcinogenicity studies deliver evidence of carcinogenicity in the rat; however, lung overload may be a species-specific confounding factor in the existing studies, and studies in other species do not give convincing evidence of carcinogenicity. Epidemiology has been intensively discussed over the last years and has the problem that the studies base on the same US beryllium production population and do not distinguish between metal and soluble compounds. It is noted that the correlation

  2. The Milky Way Tomography with SDSS: II. Stellar Metallicity

    CERN Document Server

    Ivezic, Zeljko; Juric, Mario; Bond, Nicholas; Dalcanton, Julianne; Rockosi, Constance M; Yanny, Brian; Newberg, Heidi J; Beers, Timothy C; Prieto, Carlos Allende; Wilhelm, Ron; Lee, Young Sun; Sivarani, Thirupathi; Norris, John E; Bailer-Jones, Coryn A L; Fiorentin, Paola Re; Schlegel, David; Uomoto, Alan; Lupton, Robert H; Knapp, Gillian R; Gunn, James E; Covey, Kevin R; Smith, J Allyn; Miknaitis, Gajus; Doi, Mamoru; Tanaka, Masayuki; Fukugita, Masataka; Kent, Steve; Finkbeiner, Douglas; Munn, Jeffrey A; Pier, Jeffrey R; Quinn, Tom; Hawley, Suzanne; Anderson, Scott; Kiuchi, Furea; Chen, Alex; Bushong, James; Sohi, Harkirat; Haggard, Daryl; Kimball, Amy; Barentine, John; Brewington, Howard; Harvanek, Mike; Kleinman, Scott; Krzesinski, Jurek; Long, Dan; Nitta, Atsuko; Snedden, Stephanie; Lee, Brian; Harris, Hugh; Brinkmann, Jonathan; Schneider, Donald P; York, Donald G

    2008-01-01

    Using effective temperature and metallicity derived from SDSS spectra for ~60,000 F and G type main sequence stars (0.2metallicity distribution for a complete volume-limited sample of stars at distances between 500 pc and 8 kpc. The metallicity distribution can be exquisitely modeled using two components with a spatially varying number ratio, that correspond to disk and halo. The two components also possess the kinematics expected for disk and halo stars. The metallicity of the halo component is spatially invariant, while the median disk metallicity smoothly decreases with distance from the Galactic plane from -0.6 at 500 pc to -0.8 beyond several kpc. The absence of a correlation between metallicity and kinematics for disk stars is in a conflict with the traditional decomposition in terms of thin an...

  3. Removal of Ni(II), Zn(II) and Pb(II) ions from single metal aqueous solution using rice husk-based activated carbon

    Energy Technology Data Exchange (ETDEWEB)

    Taha, Mohd F., E-mail: faisalt@petronas.com.my; Shaharun, Maizatul S. [Fundamental and Applied Sciences Department, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750, Perak Darul Ridzuan (Malaysia); Shuib, Anis Suhaila, E-mail: anisuha@petronas.com.my; Borhan, Azry [Chemical Engineering Department, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750, Perak Darul Ridzuan (Malaysia)

    2014-10-24

    An attempt was made to investigate the potential of rice husk-based activated carbon as an alternative low-cost adsorbent for the removal of Ni(II), Zn(II) and Pb(II) ions from single aqueous solution. Rice husk-based activated carbon was prepared via treatment of rice husk with NaOH followed by the carbonization process at 400°C for 2 hours. Three samples, i.e. raw rice husk, rice husk treated with NaOH and rice husk-based activated carbon, were analyzed for their morphological characteristics using field-emission scanning electron microscope/energy dispersive X-ray (FESEM/EDX). These samples were also analyzed for their carbon, hydrogen, nitrogen, oxygen and silica contents using CHN elemental analyzer and FESEM/EDX. The porous properties of rice husk-based activated carbon were determined by Brunauer-Emmett-Teller (BET) surface area analyzer, and its surface area and pore volume were 255 m{sup 2}/g and 0.17 cm{sup 2}/g, respectively. The adsorption studies for the removal of Ni(II), Zn(II) and Pb(II) ions from single metal aqueous solution were carried out at a fixed initial concentration of metal ion (150 ppm) with variation amount of adsorbent (rice husk-based activated carbon) as a function of varied contact time at room temperature. The concentration of each metal ion was analyzed using atomic absorption spectrophotometer (AAS). The results obtained from adsorption studies indicate the potential of rice husk as an economically promising precursor for the preparation of activated carbon for removal of Ni(II), Zn(II) and Pb(II) ions from single aqueous solution. Isotherm and kinetic model analyses suggested that the experimental data of adsorption studies fitted well with Langmuir, Freundlich and second-order kinetic models.

  4. Stable divalent germanium, tin and lead amino(ether)-phenolate monomeric complexes: structural features, inclusion heterobimetallic complexes, and ROP catalysis.

    Science.gov (United States)

    Wang, Lingfang; Roşca, Sorin-Claudiu; Poirier, Valentin; Sinbandhit, Sourisak; Dorcet, Vincent; Roisnel, Thierry; Carpentier, Jean-François; Sarazin, Yann

    2014-03-21

    Stable germanium(II) and lead(II) amido complexes {LO(i)}M(N(SiMe3)2) (M = Ge(II), Pb(II)) bearing amino(ether)phenolate ligands are readily available using the proteo-ligands {LO(i)}H of general formula 2-CH2NR2-4,6-tBu2-C6H2OH (i = 1, NR2 = N((CH2)2OCH3)2; i = 2, NR2 = NEt2; i = 3, NR2 = aza-15-crown-5) and M(N(SiMe3)2)2 precursors. The molecular structures of these germylenes and plumbylenes, as well as those of {LO(3)}GeCl, {LO(3)}SnCl and of the congeneric {LO(4)}Sn(II)(N(SiMe3)2) where NR2 = aza-12-crown-4, have been determined crystallographically. All complexes are monomeric, with 3-coordinate metal centres. The phenolate systematically acts as a N^O(phenolate) bidentate ligand, with no interactions between the metal and the O(side-arm) atoms in these cases (for {LO(1)}(-), {LO(3)}(-) and {LO(4)}(-)) where they could potentially arise. For each family, the lone pair of electrons essentially features ns(2) character, and there is little, if any, hybridization of the valence orbitals. Heterobimetallic complexes {LO(3)}M(N(SiMe3)2)·LiOTf, where the Li(+) cation sits inside the tethered crown-ether, were prepared by reaction of {LO(3)}M(N(SiMe3)2) and LiOTf (M = Ge(II), Sn(II)). The inclusion of Li(+) (featuring a close contact with the triflate anion) in the macrocycle bears no influence on the coordination sphere of the divalent tetrel element. In association with iPrOH, the amido germylenes, stannylenes and plumbylenes catalyse the controlled polymerisation of L- and racemic lactide. The activity increases linearly according to Ge(II) ≪ Sn(II) ≪ Pb(II). The simple germylenes generate very sluggish catalysts, but the activity is significantly boosted if the heterobimetallic complex {LO(3)}Ge(N(SiMe3)2)·LiOTf is used instead. On the other hand, with 10-25 equiv. of iPrOH, the plumbylenes afford highly active binary catalysts, converting 1000 or 5000 equiv. of monomer at 60 °C within 3 or 45 min, respectively, in a controlled fashion.

  5. Chromium(II) Metal-Organic Polyhedra as Highly Porous Materials.

    Science.gov (United States)

    Park, Jinhee; Perry, Zachary; Chen, Ying-Pin; Bae, Jaeyeon; Zhou, Hong-Cai

    2017-08-23

    Herein we report for the first time the synthesis of Cr(II)-based metal-organic polyhedra (MOPs) and the characterization of their porosities. Unlike the isostructural Cu(II)- or Mo(II)-based MOPs, Cr(II)-based MOPs show unusually high gas uptakes and surface areas. The combination of comparatively robust dichromium paddlewheel units (Cr2 units), cage symmetries, and packing motifs enable these materials to achieve Brunauer-Emmett-Teller surface areas of up to 1000 m(2)/g. Reducing the aggregation of the Cr(II)-based MOPs upon activation makes their pores more accessible than their Cu(II) or Mo(II) counterparts. Further comparisons of surface areas on a molar (m(2)/mol cage) rather than gravimetric (m(2)/g) basis is proposed as a rational method of comparing members of a family of related molecular materials.

  6. Creation of a putative third metal binding site in type II dihydroorotases significantly enhances enzyme activity.

    Science.gov (United States)

    Huang, Yen-Hua; Huang, Cheng-Yang

    2015-01-01

    Dihydroorotase (DHOase) is the third enzyme in the de novo biosynthesis pathway of pyrimidine nucleotides. DHOase is divided into two types (I and II). Type II DHOase generally contains a binuclear metal center in its active site. Recently, the crystal structure of DHOase domain in human CAD protein (huDHOase) has revealed three metal ions in the protein's active site. However, whether type II DHOase can have the critical third metal ion, as observed in huDHOase, remains unknown. In the present study, the putative third metal binding site in type II enzymes, such as the prokaryotic Salmonella enterica serovar Typhimurium LT2 DHOase (StDHOase) and the eukaryotic Saccharomyces cerevisiae DHOase (ScDHOase), was created and identified. StDHOase T198E and ScDHOase T208E mutants had higher activities compared with their wild-type enzymes. The need for a higher DHOase stability and activity may drive creation of the third metal ion binding site in huDHOase, which can be achieved by mutating a highly conserved position T in type II dihydroorotases to E, similar to that in huDHOase.

  7. MIXED-METAL COMPLEXES OF MIXED-VALENT DINUCLEAR RUTHENIUM(II,III CARBOXYLATE AND TETRACYANIDONICKELATE(II

    Directory of Open Access Journals (Sweden)

    Masahiro Mikuriya

    2014-06-01

    Full Text Available Mixed-metal chain complexes constructed from lantern-type dinuclear ruthenium(II,III carboxylate unit and tetracyanidonickelate(II, (PPh4n[Ru2(O2CCH34Ni(CN4]n•nH2O (1 and (PPh4n[Ru2{O2CC(CH33}4]3n[Ni(CN4]2n•2nH2O (2, where very weak antiferromagnetic interaction is operating, were synthesized and characterized by elemental analysis and IR and UV-vis spectroscopies and temperature dependence of magnetic susceptibilities (4.5—300K.

  8. Design, spectral characterization and biological studies of transition metal(II) complexes with triazole Schiff bases

    Science.gov (United States)

    Hanif, Muhammad; Chohan, Zahid H.

    2013-03-01

    A new series of three biologically active triazole derived Schiff base ligands L1-L3 have been synthesized in equimolar reaction of 3-amino-1H-1,2,4-triazole with pyrrol-2-carboxaldehyde, 4-bromo-thiophene-2-carboxaldehyde, and 5-iodo-2-hydroxy benzaldehyde. The prepared Schiff bases were used for further complex formation reaction with different metal elements like Co(II), Ni(II), Cu(II) and Zn(II) as chlorides by using a molar ratio of ligand:metal as 2:1. The structure and bonding nature of all the compounds were identified by their physical, spectral and analytical data. All the metal(II) complexes possessed an octahedral geometry except the Cu(II) complexes which showed a distorted octahedral geometry. All the synthesized compounds, were studied for their in vitro antibacterial, and antifungal activities, against four Gram-negative (Escherichia coli, Shigella sonnei, Pseudomonas aeruginosa and Salmonella typhi) and two Gram-positive (Bacillus subtilis and Staphylococcus aureus) bacterial strains and against six fungal strains (Trichophyton longifusus, Candida albicans, Aspergillus flavus, Microsporum canis, Fusarium solani and Candida glabrata) by using agar-well diffusion method. It has been shown that all the synthesized compounds showed moderate to significant antibacterial activity against one or more bacterial strains. In vitro Brine Shrimp bioassay was also carried out to investigate the cytotoxic properties of these compounds. The data also revealed that the metal complexes showed better activity than the ligands due to chelation/coordination.

  9. Design, spectral characterization and biological studies of transition metal(II) complexes with triazole Schiff bases.

    Science.gov (United States)

    Hanif, Muhammad; Chohan, Zahid H

    2013-03-01

    A new series of three biologically active triazole derived Schiff base ligands L(1)-L(3) have been synthesized in equimolar reaction of 3-amino-1H-1,2,4-triazole with pyrrol-2-carboxaldehyde, 4-bromo-thiophene-2-carboxaldehyde, and 5-iodo-2-hydroxy benzaldehyde. The prepared Schiff bases were used for further complex formation reaction with different metal elements like Co(II), Ni(II), Cu(II) and Zn(II) as chlorides by using a molar ratio of ligand:metal as 2:1. The structure and bonding nature of all the compounds were identified by their physical, spectral and analytical data. All the metal(II) complexes possessed an octahedral geometry except the Cu(II) complexes which showed a distorted octahedral geometry. All the synthesized compounds, were studied for their in vitro antibacterial, and antifungal activities, against four Gram-negative (Escherichia coli, Shigella sonnei, Pseudomonas aeruginosa and Salmonella typhi) and two Gram-positive (Bacillus subtilis and Staphylococcus aureus) bacterial strains and against six fungal strains (Trichophyton longifusus, Candida albicans, Aspergillus flavus, Microsporum canis, Fusarium solani and Candida glabrata) by using agar-well diffusion method. It has been shown that all the synthesized compounds showed moderate to significant antibacterial activity against one or more bacterial strains. In vitro Brine Shrimp bioassay was also carried out to investigate the cytotoxic properties of these compounds. The data also revealed that the metal complexes showed better activity than the ligands due to chelation/coordination.

  10. Stellar Kinematics and Metallicities in the Ultra-faint Dwarf Galaxy Reticulum II

    Science.gov (United States)

    Simon, J. D.; Drlica-Wagner, A.; Li, T. S.; Nord, B.; Geha, M.; Bechtol, K.; Balbinot, E.; Buckley-Geer, E.; Lin, H.; Marshall, J.; Santiago, B.; Strigari, L.; Wang, M.; Wechsler, R. H.; Yanny, B.; Abbott, T.; Bauer, A. H.; Bernstein, G. M.; Bertin, E.; Brooks, D.; Burke, D. L.; Capozzi, D.; Carnero Rosell, A.; Carrasco Kind, M.; D'Andrea, C. B.; da Costa, L. N.; DePoy, D. L.; Desai, S.; Diehl, H. T.; Dodelson, S.; Cunha, C. E.; Estrada, J.; Evrard, A. E.; Fausti Neto, A.; Fernandez, E.; Finley, D. A.; Flaugher, B.; Frieman, J.; Gaztanaga, E.; Gerdes, D.; Gruen, D.; Gruendl, R. A.; Honscheid, K.; James, D.; Kent, S.; Kuehn, K.; Kuropatkin, N.; Lahav, O.; Maia, M. A. G.; March, M.; Martini, P.; Miller, C. J.; Miquel, R.; Ogando, R.; Romer, A. K.; Roodman, A.; Rykoff, E. S.; Sako, M.; Sanchez, E.; Schubnell, M.; Sevilla, I.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thaler, J.; Tucker, D.; Vikram, V.; Walker, A. R.; Wester, W.; DES Collaboration

    2015-07-01

    We present Magellan/M2FS, Very Large Telescope/GIRAFFE, and Gemini South/GMOS spectroscopy of the newly discovered Milky Way satellite Reticulum II. Based on the spectra of 25 Ret II member stars selected from Dark Energy Survey imaging, we measure a mean heliocentric velocity of 62.8+/- 0.5 {km} {{{s}}}-1 and a velocity dispersion of 3.3+/- 0.7 {km} {{{s}}}-1. The mass-to-light ratio of Ret II within its half-light radius is 470+/- 210 {M}⊙ /{L}⊙ , demonstrating that it is a strongly dark matter-dominated system. Despite its spatial proximity to the Magellanic Clouds, the radial velocity of Ret II differs from that of the LMC and SMC by 199 and 83 {km} {{{s}}}-1, respectively, suggesting that it is not gravitationally bound to the Magellanic system. The likely member stars of Ret II span 1.3 dex in metallicity, with a dispersion of 0.28 ± 0.09 dex, and we identify several extremely metal-poor stars with {{[Fe/H]}}\\lt -3. In combination with its luminosity, size, and ellipticity, these results confirm that Ret II is an ultra-faint dwarf galaxy. With a mean metallicity of {{[Fe/H]}}=-2.65+/- 0.07, Ret II matches Segue 1 as the most metal-poor galaxy known. Although Ret II is the third-closest dwarf galaxy to the Milky Way, the line-of-sight integral of the dark matter density squared is {{log}}10(J)=18.8+/- 0.6 {GeV}{ }2 {{cm}}-5 within 0.°2, indicating that the predicted gamma-ray flux from dark matter annihilation in Ret II is lower than that of several other dwarf galaxies. Based on data obtained from the ESO Science Archive Facility under request number 157689.

  11. Adsorption of Cu(II), Zn(II), Cd(II) and Pb(II) by dead Avena fatua biomass and the effect of these metals on their growth.

    Science.gov (United States)

    Areco, María Mar; Saleh-Medina, Leila; Trinelli, María Alcira; Marco-Brown, Jose Luis; Dos Santos Afonso, María

    2013-10-01

    The biosorption of copper(II), zinc(II), cadmium(II) and lead(II) from aqueous solutions by dead Avena fatua biomass and the effect of these metals on the growth of this wild oat were investigated. Pseudo-first- and second-order and intra-particle diffusion models were applied to describe the kinetic data and to evaluate the rate constants. The adsorption kinetics of all the metals follows a pseudo-second-order model. The adsorption capacity was determined, and the Freundlich and Langmuir models were applied. The experimental data obtained for all the metals are best described by the Langmuir model. A. fatua was characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and zeta potential. The results obtained evidence the presence of Zn(II), Cu(II), Cd(II) or Pb(II) on the surface of the weed. The growth of A. fatua was affected by the presence of all metals. The decrease in the growth rate with increasing metal concentration was more noticeable for zinc.

  12. The metallomics approach: use of Fe(II) and Cu(II) footprinting to examine metal binding sites on serum albumins.

    Science.gov (United States)

    Duff, Michael R; Kumar, Challa V

    2009-11-01

    Metal binding to serum albumins is examined by oxidative protein-cleavage chemistry, and relative affinities of multiple metal ions to particular sites on these proteins were identified using a fast and reliable chemical footprinting approach. Fe(ii) and Cu(ii), for example, mediate protein cleavage at their respective binding sites on serum albumins, in the presence of hydrogen peroxide and ascorbate. This metal-mediated protein-cleavge reaction is used to evaluate the binding of metal ions, Na(+), Mg(2+), Ca(2+), Al(3+), Cr(3+), Mn(2+), Co(2+), Ni(2+), Zn(2+), Cd(2+), Hg(2+), Pb(2+), and Ce(3+) to albumins, and the relative affinities (selectivities) of the metal ions are rapidly evaluated by examining the extent of inhibition of protein cleavage. Four distinct systems Fe(II)/BSA, Cu(II)/BSA, Fe(II)/HSA and Cu(II)/HSA are examined using the above strategy. This metallomics approach is novel, even though the cleavage of serum albumins by Fe(II)/Cu(II) has been reported previously by this laboratory and many others. The protein cleavage products were analyzed by SDS PAGE, and the intensities of the product bands quantified to evaluate the extent of inhibition of the cleavage and thereby evaluate the relative binding affinities of specific metal ions to particular sites on albumins. The data show that Co(II) and Cr(III) showed the highest degree of inhibition, across the table, followed by Mn(II) and Ce(III). Alakali metal ions and alkaline earth metal ions showed very poor affinity for these metal sites on albumins. Thus, metal binding profiles for particular sites on proteins can be obtained quickly and accurately, using the metallomics approach.

  13. Removal of divalent nickel from aqueous solutions using Carissa carandas and Syzygium aromaticum: isothermal studies and kinetic modelling

    Science.gov (United States)

    Sharma, Sanjay K.; Mahiya, Suresh; Lofrano, Giusy

    2015-11-01

    Biosorptive removal of divalent nickel from aqueous solution using Carissa Carandas and Syzygium aromaticum was investigated in batch mode and the observations were correlated with the pH variation, agitation time, dose of the adsorbent and initial metal ion concentration in the solution. In the course of this study Sorption efficiency of C. carandas leaf powder found higher than that of S. aromaticum under identical experimental conditions. The maximum adsorption capacities estimated for Ni(II) through Freundlich isotherm model were 3.76 and 2.96 mg/g for C. carandas and S. aromaticum, respectively. In kinetic studies the correlation coefficient (R 2 = 0.99) for the pseudo-second order kinetics modal was higher than that of pseudo-first order kinetics model and the calculated value of q e for the pseudo-second order kinetic model resulted very close to the experimental value, which indicates that it fits well with the equilibrium data for Ni(II) sorption from aqueous solutions on biosorbents.

  14. Removal of divalent nickel from aqueous solutions using Carissa carandas and Syzygium aromaticum: isothermal studies and kinetic modelling

    Science.gov (United States)

    Sharma, Sanjay K.; Mahiya, Suresh; Lofrano, Giusy

    2017-07-01

    Biosorptive removal of divalent nickel from aqueous solution using Carissa Carandas and Syzygium aromaticum was investigated in batch mode and the observations were correlated with the pH variation, agitation time, dose of the adsorbent and initial metal ion concentration in the solution. In the course of this study Sorption efficiency of C. carandas leaf powder found higher than that of S. aromaticum under identical experimental conditions. The maximum adsorption capacities estimated for Ni(II) through Freundlich isotherm model were 3.76 and 2.96 mg/g for C. carandas and S. aromaticum, respectively. In kinetic studies the correlation coefficient ( R 2 = 0.99) for the pseudo-second order kinetics modal was higher than that of pseudo-first order kinetics model and the calculated value of q e for the pseudo-second order kinetic model resulted very close to the experimental value, which indicates that it fits well with the equilibrium data for Ni(II) sorption from aqueous solutions on biosorbents.

  15. Metal-Based Antibacterial and Antifungal Agents: Synthesis, Characterization, and In Vitro Biological Evaluation of Co(II, Cu(II, Ni(II, and Zn(II Complexes with Amino Acid-Derived Compounds

    Directory of Open Access Journals (Sweden)

    Zahid H. Chohan

    2006-01-01

    Full Text Available A series of antibacterial and antifungal amino acid-derived compounds and their cobalt(II, copper(II, nickel(II, and zinc(II metal complexes have been synthesized and characterized by their elemental analyses, molar conductances, magnetic moments, and IR, and electronic spectral measurements. Ligands (L1–(L5 were derived by condensation of β-diketones with glycine, phenylalanine, valine, and histidine and act as bidentate towards metal ions (cobalt, copper, nickel, and zinc via the azomethine-N and deprotonated-O of the respective amino acid. The stoichiometric reaction between the metal(II ion and synthesized ligands in molar ratio of M: L (1: 1 resulted in the formation of the metal complexes of type [M(L(H2O4]Cl (where M = Co(II, Cu(II, and Zn(II and of M: L (1: 2 of type [M(L2(H2O2] (where M = Co(II, Cu(II, Ni(II, and Zn(II. The magnetic moment data suggested for the complexes to have an octahedral geometry around the central metal atom. The electronic spectral data also supported the same octahedral geometry of the complexes. Elemental analyses and NMR spectral data of the ligands and their metal(II complexes agree with their proposed structures. The synthesized ligands, along with their metal(II complexes, were screened for their in vitro antibacterial activity against four Gram-negative (Escherichia coli, Shigella flexeneri, Pseudomonas aeruginosa, and Salmonella typhi and two Gram-positive (Bacillus subtilis and Staphylococcus aureus bacterial strains and for in vitro antifungal activity against Trichophyton longifusus, Candida albicans, Aspergillus flavus, Microsporum canis, Fusarium solani, and Candida glaberata. The results of these studies show the metal(II complexes to be more antibacterial/antifungal against one or more species as compared to the uncomplexed ligands. The brine shrimp bioassay was also carried out to study their in vitro cytotoxic properties. Five compounds, (3, (7, (10, (11, and (22, displayed potent cytotoxic

  16. Biodegradable coordination polymer: Polycondensation of glutaraldehyde and starch in complex formation with transition metals Mn(II, Co(II, Ni(II, Cu(II and Zn(II

    Directory of Open Access Journals (Sweden)

    Nahid Nishat

    2016-11-01

    Full Text Available Starch a biopolymer, possesses many unique characteristics features accompanied with some shortcoming simultaneously. Some synthetic compounds are of great help to these demerits of starch and so by an addition of all these alternatively may acquire the tailor made features of starch-based compounds. By combining the individual advantages of starch and some other compounds and elements, starch-based biodegradable polymers were prepared for potential applications in biomedical and environmental fields. In this research, the structural analysis and characterization studies of starch glutaraldehyde polycondensed polymer were undertaken, and then the formation of polymer metal complexes with transition metal in coordinated form are carried out. FT-IR spectroscopy and 1H NMR and 13C NMR spectroscopy were used to analyze the functionality of the synthesized compound. CHN of the synthesized compound was supported by FT-IR and NMR which again proved helpful for structural analysis. Electronic spectroscopy confirmed the geometry of the synthesized compounds. Thermal studies were carried out by thermogravimetric analysis (TGA and differential scanning calorimetry (DSC. Besides this the biodegradable studies were carried out by ASTM standards of biodegradable materials by CO2 evolution in respirometric titration method. All the polymers showed good thermal strength and reduced biodegradation on attachment of transition metals, Mn(II, Co(II, Ni(II, Cu(II and Zn(II.

  17. Electronic Structure of Rare-Earth Metals. II. Positron Annihilation

    DEFF Research Database (Denmark)

    Williams, R. W.; Mackintosh, Allan

    1968-01-01

    The angular correlation of the photons emitted when positrons annihilate with electrons has been studied in single crystals of the rare-earth metals Y, Gd, Tb, Dy, Ho, and Er, and in a single crystal of an equiatomic alloy of Ho and Er. A comparison of the results for Y with the calculations...... of Loucks shows that the independent-particle model gives a good first approximation to the angular distribution, although correlation effects probably smear out some of the structure. The angular distributions from the heavy rare-earth metals are very similar to that from Y and can be understood...... qualitatively in terms of the relativistic augmented-plane-wave calculations by Keeton and Loucks. The angular distributions in the c direction in the paramagnetic phases are characterized by a rapid drop at low angles followed by a hump, and these features are associated with rather flat regions of Fermi...

  18. Speciation of metals in natural waters

    Directory of Open Access Journals (Sweden)

    Millero Frank

    2001-09-01

    Full Text Available The form or speciation of a metal in natural waters can change its kinetic and thermodynamic properties. For example, Cu(II in the free ionic form is toxic to phytoplankton, while copper complexed to organic ligands is not toxic. The form of a metal in solution can also change its solubility. For example, Fe(II is soluble in aqueous solutions while Fe(III is nearly insoluble. Natural organic ligands interactions with Fe(III can increase the solubility by 20-fold in seawater. Ionic interaction models that can be used to determine the activity and speciation of divalent and trivalent metals in seawater and other natural elements will be discussed. The model is able to consider the interactions of metals with the major (Cl-, SO42-, HCO3-, CO32-, Br-, F- and minor (OH-, H2PO4-, HPO42-, PO43-, HS- anions as a function of temperature (0 to 50 °C, ionic strength [0 to 6 m (m = mol kg-1] and pH (1 to 13. Recently, it has been shown that many divalent metals are complexed with organic ligands. Although the composition of these ligands is not known, a number of workers have used voltammetry to determine the concentration of the ligand [Ln] and the stability constant (KML for the formation of the complex M2+ + Ln → MLn+2 KML= [MLn+2]/[M2+] [Ln] We have added the experimental values of KML for the formation of complexes of natural organics in seawater of known concentration ([Ln] with Cu2+, Zn2+, Cd2+, Co2+, and Fe3+ . The model can be used to examine the competition of inorganic and organic ligands for divalent metals as a function of ionic strength. The importance of organic ligands in controlling the solubility of Fe(III in seawater will be discussed. New experimental studies are needed to extend the model to higher temperatures and ionic strength.

  19. Efficient polymerization of acrylonitrile catalyzed by diValent lanthanide complex/sodium phenolate systems

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Four divalent lanthanide complexes Sm(ArO)2(THF)4, Yb(ArO)2(THF)3, Eu(ArO)2(THF)3 (ArO = 2,6-ditert-butyl-4-methylphenolate) and (ButCp)2Sm(THF)2 were synthesized. Their catalytic activities on the polymerization of acrylonitrile were studied. The catalytic activities were influenced by the central metal ions involved. The catalytic activities of these divalent lanthanide complexes can be greatly increased by adding NaOC~H2-2,6-But2-4-Me,NaOC6H4-4-But, or NaOC10H6-2-Me. The amount of additive has apparent effect on the catalytic activity, but the additive has no effect on the tacticity of the resulting polyacrylonitrile

  20. Selective divalent cobalt ions detection using Ag2O3-ZnO nanocones by ICP-OES method for environmental remediation.

    Directory of Open Access Journals (Sweden)

    Mohammed M Rahman

    Full Text Available Here, we have synthesized Ag2O3-ZnO nanocones (NCs by a wet-chemical route using reducing agents at low temperature. The structural, optical and morphological properties of Ag2O3-ZnO NCs were investigated by several conventional techniques such as powder XRD, XPS, FESEM, XEDS, FTIR and UV/vis. spectroscopy. The analytical parameters of prepared NCs were also calculated for a selective detection of divalent cobalt [Co(II] prior to its determination by inductively coupled plasma-optical emission spectrometry (ICP-OES. The selectivity of NCs toward various metal ions, including Cd(II, Co(II, Cr(III, Cu(II, Fe(III, Ni(II, and Zn(II was studied. Results of the selectivity study demonstrated that Ag2O3-ZnO NC phase was the most selective towards Co(II ion. The uptake capacity for Co(II ion was experimentally calculated to be ∼76.69 mgg-1. Moreover, adsorption isotherm data provided that the adsorption process was mainly monolayer on homogeneous adsorbent surfaces of Ag2O3-ZnO NCs. Kinetic study revealed that the adsorption of Co(II on Ag2O3-ZnO NCs phase followed the pseudo-second-order kinetic model. In addition, thermodynamic results provided that the adsorption mechanism of Co(II ions on Ag2O3-ZnO NCs was a spontaneous process and thermodynamically favorable. Finally, the proposed method was validated by applying it to real environmental water samples with reasonable results.

  1. Effect of biofilm coatings at metal-oxide/water interfaces II: Competitive sorption between Pb(II) and Zn(II) at Shewanella oneidensis/metal-oxide/water interfaces

    Science.gov (United States)

    Wang, Yingge; Gélabert, Alexandre; Michel, F. Marc; Choi, Yongseong; Eng, Peter J.; Spormann, Alfred M.; Brown, Gordon E.

    2016-09-01

    Competitive sorption of Pb(II) and Zn(II) on Shewanella oneidensis MR-1 biofilm-coated single-crystal α-Al2O3 (1 -1 0 2) and α-Fe2O3 (0 0 0 1) surfaces was investigated using long-period X-ray standing wave-florescence yield (LP-XSW-FY) spectroscopy. In situ partitioning of aqueous Pb(II) and Zn(II) between the biofilms and underlying metal-oxide substrates was probed following exposure of these complex interfaces to equi-molar Pb and Zn solutions (0.01 M NaNO3 as background electrolyte, pH = 6.0, and 3-h equilibration time). At higher Pb and Zn concentrations (⩾10-5 M), more than 99% of these ions partitioned into the biofilms at S. oneidensis/α-Al2O3 (1 -1 0 2)/water interfaces, which is consistent with the partitioning behavior of both Pb(II) or Zn(II) in single-metal-ion experiments. Thus, no apparent competitive effects were found in this system at these relatively high metal-ion concentrations. However, at lower equi-molar concentrations (⩽10-6 M), Pb(II) and Zn(II) partitioning in the same system changed significantly compared to the single-metal-ion systems. The presence of Zn(II) decreased Pb(II) partitioning onto α-Al2O3 (1 -1 0 2) substantially (∼52% to ∼13% at 10-7 M, and ∼23% to ∼5% at 10-6 M), whereas the presence of Pb(II) caused more Zn(II) to partition onto α-Al2O3 (1 -1 0 2) surfaces (∼15% to ∼28% at 10-7 M, and ∼1% to ∼7% at 10-6 M). The higher observed partitioning of Zn(II) (∼28%) at the α-Al2O3 (1 -1 0 2) surfaces compared to Pb(II) (∼13%) in the mixed-metal-ion systems at the lowest concentration (10-7 M) suggests that Zn(II) is slightly favored over Pb(II) for sorption sites on α-Al2O3 (1 -1 0 2) surfaces under our experimental conditions. Competitive sorption of Pb(II) and Zn(II) at S. oneidensis/α-Fe2O3 (0 0 0 1)/water interfaces at equi-molar metal-ion concentrations of ⩽10-6 M showed that the presence of Pb(II) ions decreased Zn(II) partitioning onto α-Fe2O3 (0 0 0 1) significantly (∼45% to biofilm

  2. Influences of Mn(II) and V(IV) on Bacterial Surface Chemistry and Metal Reactivity

    Science.gov (United States)

    French, S.; Fakra, S.; Glasauer, S.

    2009-05-01

    Microorganisms in terrestrial and marine environments are typically bathed in solutions that contain a range of metal ions, toxic and beneficial. Bacteria such as Shewanella putrefaciens CN32 are metabolically versatile in their respiration, and the reductive dissolution of widely dispersed metals such as Fe(III), Mn(IV), or V(V) can present unique challenges if nearby bodies of water are used for irrigation or drinking. In redox transition zones, dissimilatory metal reduction (DMR) by bacteria can lead to generation of high concentrations of soluble metals. It has been shown that metals will associate with negatively charged bacterial membranes, and the mechanisms of metal reduction are well defined for many species of bacteria. The interaction of metals with the cell wall during DMR is, however, not well documented; very little is known about the interaction of respired transition metals with membrane lipids. Furthermore, bacterial surfaces tend to change in response to their immediate environments. Variations in conditions such as oxygen or metal presence may affect surface component composition, including availability of metal reactive sites. Our research seeks to characterize the biochemical nature of metal-membrane interactions, as well as identify the unique changes at the cell surface that arise as a result of metal presence in their environments. We have utilized scanning transmission X-ray microscopy (STXM) to examine the dynamics of soluble Mn(II) and V(IV) interactions with purified bacterial membranes rather than whole cells. This prevents intracellular interferences, and allows for near edge X-ray absorption fine structure (NEXAFS) spectroscopic analyses of cell surface and surface-associated components. NEXAFS spectra for carbon, nitrogen, and oxygen edges indicate that Mn(II) and V(IV) induce biological modifications of the cell membrane in both aerobic and anaerobic conditions. These changes depend not only on the metal, but also on the presence of

  3. Nearby supernova host galaxies from the CALIFA Survey: II. SN environmental metallicity

    CERN Document Server

    Galbany, L; Mourão, A M; Rodrigues, M; Flores, H; Walcher, C J; Sánchez, S F; García-Benito, R; Mast, D; Badenes, C; Delgado, R M González; Kehrig, C; Lyubenova, M; Marino, R A; Mollá, M; Meidt, S; Pérez, E; van de Ven, G; Vílchez, J M

    2016-01-01

    The metallicity of a supernova (SN) progenitor, together with its mass, is one of the main parameters that rules their outcome. We present a metallicity study of 115 nearby SN host galaxies (0.00510 dex) by targeted searches. We also found no evidence that the metallicity at the SN location differs from the average metallicity at the GCD of the SNe. By extending our SN sample with published metallicities at the SN location, we studied the metallicity distributions for all SN subtypes split into SN discovered in targeted and untargeted searches. We confirm a bias toward higher host masses and metallicities in the targeted searches. Combining data from targeted and untargeted searches we found a sequence from higher to lower local metallicity: SN Ia, Ic, and II show the highest metallicity, which is significantly higher than SN Ib, IIb, and Ic-BL. Our results support the picture of SN Ib resulting from binary progenitors and, at least part of, SN Ic being the result of single massive stars stripped of their out...

  4. Instability of some divalent rare earth ions and photochromic effect

    Science.gov (United States)

    Egranov, A. V.; Sizova, T. Yu.; Shendrik, R. Yu.; Smirnova, N. A.

    2016-03-01

    It was shown that the divalent rare earth ions (La, Ce, Gd, Tb, Lu, and Y) in cubic sites in alkaline earth fluorides are unstable with respect to electron autodetachment since its d1(eg) ground state is located in the conduction band which is consistent with the general tendency of these ions in various compounds. The localization of doubly degenerate d1(eg) level in the conduction band creates a configuration instability around the divalent rare earth ion that leading to the formation of anion vacancy in the nearest neighborhood, as was reported in the previous paper [A. Egranov, T. Sizova, Configurational instability at the excited impurity ions in alkaline earth fluorites, J. Phys. Chem. Solids 74 (2013) 530-534]. Thus, the formation of the stable divalent ions as La, Ce, Gd, Tb, Lu, and Y (PC+ centers) in CaF2 and SrF2 crystals during x-ray irradiation occurs via the formation of charged anion vacancies near divalent ions (Re2+va), which lower the ground state of the divalent ion relative to the conductivity band. Photochromic effect occurs under thermally or optically stimulated electron transition from the divalent rare earth ion to the neighboring anion vacancy and reverse under ultraviolet light irradiation. It is shown that the optical absorption of the PC+ centers due to d → d and d → f transitions of the divalent rare-earth ion.

  5. Mechanical, thermal and laser damage threshold analyses of II group metal complexes of thiourea

    Energy Technology Data Exchange (ETDEWEB)

    Dhanuskodi, S., E-mail: dhanus2k3@yahoo.com [School of Physics, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu (India); Sabari Girisun, T.C. [School of Physics, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu (India); Department of Physics, Bishop Heber College, Tiruchirappalli 620 017, Tamil Nadu (India); Bhagavannarayana, G. [Material Characterization Division, National Physical laboratory, New Delhi 110 012 (India); Uma, S.; Phillip, J. [Sophisticated Test and Instrumentation Center, Cochin University of Science and Technology, Cochin 682 022 (India)

    2011-04-15

    Research highlights: {yields} The role of the Group II metal ions in improving the stability is discussed. {yields} BTCC has a higher heat capacity than BTZC. {yields} Elastic stiffness is found to be higher for BTCC than BTZC. {yields} Microscopy studies confirm the damage is due to thermo-chemical ablation. {yields} BTCC has a higher laser damage threshold than BTZC. - Abstract: Single crystals of thiourea metal complexes with selected Group II metal ions, Zinc and Cadmium, have been grown by solvent evaporation technique. The crystals grown are bisthiourea zinc chloride (BTZC) and bisthiourea cadmium chloride (BTCC). Following an improved photopyroelectric technique, the thermal transport properties have been determined. It is found that BTCC has a higher heat capacity (304.09 J kg{sup -1} K{sup -1}) than BTZC (255.24 J kg{sup -1} K{sup -1}), and hence BTCC has better thermal stability. Vicker's microhardness measurements reveal that these materials have reverse indentation size effect and belong to the category of soft materials. Elastic stiffness is found to be higher for BTCC (1.57 GPa) than BTZC (0.76 GPa). The roles of the Group II metal ions in improving the mechanical and thermal stability of the metal complexes are discussed. Multi-shot laser damage studies on these materials reveal that BTCC has a higher laser damage threshold (15 GW cm{sup -2}) than BTZC (6 GW cm{sup -2}).

  6. SERS and DFT investigation of 1-(2-pyridylazo)-2-naphthol and its metal complexes with Al(III), Mn(II), Fe(III), Cu(II), Zn(II) and Pb(II)

    Science.gov (United States)

    Szabó, László; Herman, Krisztian; Mircescu, Nicoleta E.; Fălămaş, Alexandra; Leopold, Loredana F.; Leopold, Nicolae; Buzumurgă, Claudia; Chiş, Vasile

    The development of surface-enhanced Raman scattering (SERS) as a prospective analytical methodology for detection of metal ions was shown in recent years by several studies on metal complexes. In this work, 1-(2-pyridylazo)-2-naphthol (PAN) and its Al(III), Mn(II), Fe(III), Cu(II), Zn(II) and Pb(II) complexes were studied by FTIR, FT-Raman and surface enhanced Raman spectroscopies. Molecular geometry optimization, molecular electrostatic potential (MEP) distribution and vibrational frequencies calculations were performed using the hybrid B3LYP exchange-correlation functional for the PAN molecule and its bidentate complexes. The calculated MEP distributions indicated the atoms with highest electronegativity, the adsorption to the silver surface occurring through these atoms. Based on experimental and theoretical data we were able to identify unique and representative features, useful for the identification of each PAN-metal complex.

  7. Extremely bulky amido first row transition metal(II) halide complexes: potential precursors to low coordinate metal-metal bonded systems.

    Science.gov (United States)

    Hicks, Jamie; Jones, Cameron

    2013-04-01

    Reactions of the extremely bulky potassium amide complexes, [KL'(η(6)-toluene)] or [KL"] (L'/L" = N(Ar*)(SiR3), Ar* = C6H2{C(H)Ph2}2Me-2,6,4; R = Me (L') or Ph (L")), with a series of first row transition metal(II) halides have yielded 10 rare examples of monodentate amido first row transition metal(II) halide complexes, all of which were crystallographically characterized. They encompass the dimeric, square-planar chromium complexes, [{CrL'(THF)(μ-Cl)}2] and [{CrL"(μ-Cl)}2], the latter of which displays intramolecular η(2)-Ph···Cr interactions; the dimeric tetrahedral complexes, [{ML'(THF)(μ-Br)}2] (M = Mn or Fe), [{ML"(THF)(μ-X)}2] (M = Mn, Fe or Co; X = Cl or Br) and [{CoL"(μ-Cl)}2] (which displays intramolecular η(2)-Ph···Co interactions); and the monomeric zinc amides, [L'ZnBr(THF)] (three-coordinate) and [L"ZnBr] (two-coordinate). Solution state magnetic moment determinations on all but one of the paramagnetic compounds show them to be high-spin systems. Throughout, comparisons are made with related bulky terphenyl transition metal(II) halide complexes, and the potential for the use of the prepared complexes as precursors to low-valent transition metal systems is discussed.

  8. Structural and spectroscopic characterization of iron(II), cobalt(II), and nickel(II) ortho-dihalophenolate complexes: insights into metal-halogen secondary bonding.

    Science.gov (United States)

    Machonkin, Timothy E; Boshart, Monica D; Schofield, Jeremy A; Rodriguez, Meghan M; Grubel, Katarzyna; Rokhsana, Dalia; Brennessel, William W; Holland, Patrick L

    2014-09-15

    Metal complexes incorporating the tris(3,5-diphenylpyrazolyl)borate ligand (Tp(Ph2)) and ortho-dihalophenolates were synthesized and characterized in order to explore metal-halogen secondary bonding in biorelevant model complexes. The complexes Tp(Ph2)ML were synthesized and structurally characterized, where M was Fe(II), Co(II), or Ni(II) and L was either 2,6-dichloro- or 2,6-dibromophenolate. All six complexes exhibited metal-halogen secondary bonds in the solid state, with distances ranging from 2.56 Å for the Tp(Ph2)Ni(2,6-dichlorophenolate) complex to 2.88 Å for the Tp(Ph2)Fe(2,6-dibromophenolate) complex. Variable temperature NMR spectra of the Tp(Ph2)Co(2,6-dichlorophenolate) and Tp(Ph2)Ni(2,6-dichlorophenolate) complexes showed that rotation of the phenolate, which requires loss of the secondary bond, has an activation barrier of ~30 and ~37 kJ/mol, respectively. Density functional theory calculations support the presence of a barrier for disruption of the metal-halogen interaction during rotation of the phenolate. On the other hand, calculations using the spectroscopically calibrated angular overlap method suggest essentially no contribution of the halogen to the ligand-field splitting. Overall, these results provide the first quantitative measure of the strength of a metal-halogen secondary bond and demonstrate that it is a weak noncovalent interaction comparable in strength to a hydrogen bond. These results provide insight into the origin of the specificity of the enzyme 2,6-dichlorohydroquinone 1,2-dioxygenase (PcpA), which is specific for ortho-dihalohydroquinone substrates and phenol inhibitors.

  9. Characterization of Irradiated Metal Waste from the Pyrometallurgical Treatment of Used EBR-II Fuel

    Energy Technology Data Exchange (ETDEWEB)

    B.R. Westphal; K.C. Marsden; W.M. McCartin; S.M. Frank; D.D. Keiser, Jr.; T.S. Yoo; D. Vaden; D.G. Cummings; K.J. Bateman; J. J. Giglio; T. P. O' Holleran; P. A. Hahn; M. N. Patterson

    2013-03-01

    As part of the pyrometallurgical treatment of used Experimental Breeder Reactor-II fuel, a metal waste stream is generated consisting primarily of cladding hulls laden with fission products noble to the electrorefining process. Consolidation by melting at high temperature [1873 K (1600 degrees C)] has been developed to sequester the noble metal fission products (Zr, Mo, Tc, Ru, Rh, Te, and Pd) which remain in the iron-based cladding hulls. Zirconium from the uranium fuel alloy (U-10Zr) is also deposited on the hulls and forms Fe-Zr intermetallics which incorporate the noble metals as well as residual actinides during processing. Hence, Zr has been chosen as the primary indicator for consistency of the metal waste. Recently, the first production-scale metal waste ingot was generated and sampled to monitor Zr content for Fe-Zr intermetallic phase formation and validation of processing conditions. Chemical assay of the metal waste ingot revealed a homogeneous distribution of the noble metal fission products as well as the primary fuel constituents U and Zr. Microstructural characterization of the ingot confirmed the immobilization of the noble metals in the Fe-Zr intermetallic phase.

  10. Sorption behavior of Pb(II) and Cd(II) on iron ore slime and characterization of metal ion loaded sorbent.

    Science.gov (United States)

    Mohapatra, M; Rout, K; Mohapatra, B K; Anand, S

    2009-07-30

    The present investigation evaluates the sorption effectiveness of Pb(II) and Cd(II) ions on iron ore slime (IOS) obtained from Jindal Steel Ltd., Vijayanagaram, India. The sorption followed pseudo-second-order kinetics for both the cations. Pb(II) and Cd(II) sorption increased with the increase in pH from 2 to 4.5. The sorption data fitted well to Freundlich model as compared to Langmuir model. Synergistic effect of Pb(II) and Cd(II) on their sorption on IOS sample showed that Pb(II) sorption increases in presence of Cd(II) whereas Cd(II) sorption decreases. Presence of chloride or sulphate resulted in increased Pb(II) sorption but adversely affected Cd(II) sorption. The XRD patterns of Pb(II) adsorbed on IOS sample showed disappearance of some silica peaks and shifting of hematite peaks corresponding to 104 and 110 plane. For Cd(II) sorbed IOS sample, only peak shift for hematite of 104 and 110 plane was observed. Shifting of IR bands indicated that the Pb(II) sorption occurred through an inner sphere mechanism where as Cd(II) sorption occurred through outer sphere mechanism. EPMA studies showed that Pb(II) form a uniform thin layer and Cd(II) concentrate only on iron oxide phase. Regeneration and stability data on metal ion loaded IOS sample has been included.

  11. Stellar Kinematics and Metallicities in the Ultra-Faint Dwarf Galaxy Reticulum II

    CERN Document Server

    Simon, J D; Li, T S; Nord, B; Geha, M; Bechtol, K; Balbinot, E; Buckley-Geer, E; Lin, H; Marshall, J; Santiago, B; Strigari, L; Wang, M; Wechsler, R H; Yanny, B; Abbott, T; Bauer, A H; Bernstein, G M; Bertin, E; Brooks, D; Burke, D L; Capozzi, D; Rosell, A Carnero; Kind, M Carrasco; D'Andrea, C B; da Costa, L N; DePoy, D L; Desai, S; Diehl, H T; Dodelson, S; Cunha, C E; Estrada, J; Evrard, A E; Neto, A Fausti; Fernandez, E; Finley, D A; Flaugher, B; Frieman, J; Gaztanaga, E; Gerdes, D; Gruen, D; Gruendl, R A; Honscheid, K; James, D; Kuehn, K; Kuropatkin, N; Lahav, O; Maia, M A G; March, M; Martini, P; Miller, C J; Miquel, R; Ogando, R; Romer, A K; Roodman, A; Rykoff, E S; Sako, M; Sanchez, E; Schubnell, M; Sevilla, I; Smith, R C; Soares-Santos, M; Sobreira, F; Suchyta, E; Swanson, M E C; Tarle, G; Thaler, J; Tucker, D; Vikram, V; Walker, A R; Wester, W

    2015-01-01

    We present Magellan/M2FS, VLT/GIRAFFE, and Gemini South/GMOS spectroscopy of the newly discovered Milky Way satellite Reticulum II. Based on the spectra of 25 Ret II member stars selected from Dark Energy Survey imaging, we measure a mean heliocentric velocity of 62.8 +/- 0.5 km/s and a velocity dispersion of 3.3 +/- 0.7 km/s. The mass-to-light ratio of Ret II within its half-light radius is 470 +/- 210 Msun/Lsun, demonstrating that it is a strongly dark matter-dominated system. Despite its spatial proximity to the Magellanic Clouds, the radial velocity of Ret II differs from that of the LMC and SMC by 199 and 83 km/s, respectively, suggesting that it is not gravitationally bound to the Magellanic system. The likely member stars of Ret II span 1.3 dex in metallicity, with a dispersion of 0.28 +/- 0.09 dex, and we identify several extremely metal-poor stars with [Fe/H] < -3. In combination with its luminosity, size, and ellipticity, these results confirm that Ret II is an ultra-faint dwarf galaxy. With a me...

  12. Hydride reactivity of Ni(II)-X-Ni(II) entities: mixed-valent hydrido complexes and reversible metal reduction.

    Science.gov (United States)

    Gehring, Henrike; Metzinger, Ramona; Herwig, Christian; Intemann, Julia; Harder, Sjoerd; Limberg, Christian

    2013-01-28

    After the lithiation of PYR-H(2) (PYR(2-) =[{NC(Me)C(H)C(Me)NC(6)H(3)(iPr)(2)}(2)(C(5)H(3)N)](2-)), which is the precursor of an expanded β-diketiminato ligand system with two binding pockets, its reaction with [NiBr(2) (dme)] led to a dinuclear nickel(II)-bromide complex, [(PYR)Ni(μ-Br)NiBr] (1). The bridging bromide ligand could be selectively exchanged for a thiolate ligand to yield [(PYR)Ni(μ-SEt)NiBr] (3). In an attempt to introduce hydride ligands, both compounds were treated with KHBEt(3). This treatment afforded [(PYR)Ni(μ-H)Ni] (2), which is a mixed valent Ni(I)-μ-H-Ni(II) complex, and [(PYR-H)Ni(μ-SEt)Ni] (4), in which two tricoordinated Ni(I) moieties are strongly antiferromagnetically coupled. Compound 4 is the product of an initial salt metathesis, followed by an intramolecular redox process that separates the original hydride ligand into two electrons, which reduce the metal centres, and a proton, which is trapped by one of the binding pockets, thereby converting it into an olefin ligand on one of the Ni(I) centres. The addition of a mild acid to complex 4 leads to the elimination of H(2) and the formation of a Ni(II)Ni(II) compound, [(PYR)Ni(μ-SEt)NiOTf] (5), so that the original Ni(II) (μ-SEt)Ni(II) X core of compound 3 is restored. All of these compounds were fully characterized, including by X-ray diffraction, and their molecular structures, as well as their formation processes, are discussed.

  13. Condensation of nonstochiometric DNA/polycation complexes by divalent cations.

    Science.gov (United States)

    Budker, Vladimir; Trubetskoy, Vladimir; Wolff, Jon A

    2006-12-15

    This study found that divalent cations induced the further condensation of partially condensed DNA within nonstochiometric polycation complexes. The addition of a few mmol of a divalent cation such as calcium reduced by half the inflection point at which DNA became fully condensed by poly-L-lysine (PLL) and a variety of other polycations. The effect on DNA condensation was initially observed using a new method, which is based on the concentration-dependent self-quenching of fluorescent moieties (e.g., rhodamine) covalently linked to the DNA backbone at relatively high densities. Additional analyses, which employed ultracentrifugation, dynamic light scattering, agarose gel electrophoresis, and atomic force microscopy, confirmed the effect of divalent cations. These results provide an additional accounting of the process by which divalent cations induce greater chromatin compaction that is based on the representation of chromatin fibers as a nonstoichiometric polyelectrolyte complex. They also offer a new approach to assemble nonviral vectors for gene therapy.

  14. Synthesis, Crystal Structure and Luminescent Property of a Novel Pt(II) Complex with Weak Metal-metal Interaction

    Institute of Scientific and Technical Information of China (English)

    YUE Cheng-Yang; JIANG Fei-Long; FENG Rui; HONG Mao-Chun

    2008-01-01

    The title complex cis-bis(tetrahydrothiophene)-bis(nitrate) platinum(II), (tht)2Pt(NO3)2, was the reducing product from potassium hexachloroplatinate(IV) K2PtCl6 where the platinum is tetra-valenced. Crystal data for C8H16N2O6PtS2: monoclinic, space group P21/c, a = 9.8833(5), b = 8.6744(4), c = 18.6407(9) (A), β = 114.401(3)°, V = 1455.35(12) (A)3, Z = 4, Mr = 495.44, Dc = 2.261 g/cm3, F(000) = 944, μ = 9.950 mm-1, λ(MoKα) = 0.71073 (A), T = 293(2) K, 2θmax = 54.96o, GOOF = 1.033, R = 0.0350 and wR = 0.0785 for 2572 observed reflections with I > 2σ(I). X-ray diffraction studies reveal that the title complex has interesting weak metal-metal interactions and two molecules linked by metal-metal interaction exist as a group. Luminescent spectrum illuminates red emission of the complex at room temperature.

  15. Synthesis, spectral characterization of biologically active compounds derived from oxalyldihydrazide and 5-tert-Butyl-2-hydroxy-3-(3-phenylpent-3-yl benzaldehyde and their Cu(II, Ni(II and Co(II Complexes

    Directory of Open Access Journals (Sweden)

    Rajeev Johari

    2011-02-01

    Full Text Available A series of Schiff base M(II complexes of the type [HLMClH2O] and [HLMOAcH2O], where M =Cu(II, Ni(II and Co(II have been synthesized by condensation of 3-tert-butl-2-hydroxy-3-(3-phenylpent-3-ylbenzaldehyde and oxalyldihydrazide (2:1 in the presence of divalent metal salt in methanolic medium. Thecomplexes have been characterized with the help of elemental analysis, conductance measurements, magneticmeasurements and their structural configuration have been determined by various spectroscopic (electronic, IR,1H NMR, 13C NMR, GCMS techniques. Electronic and magnetic moments of the complexes indicate that thegeometries of the metal centers were octahedral. These metal complexes were also tested for their antimicrobialactivities to assess their inhibiting potential.

  16. Influence of divalent metal ions on degradation of dimethylsulphide ...

    African Journals Online (AJOL)

    SERVER

    2007-06-04

    Jun 4, 2007 ... ide (H2S) are malodorous compounds which exceed the odour threshold at low ... They are produced by the wood-pulping industry, manure and ... ional Institute of Bioscience and Human-Technology, Tsukuba,. Japan) and ...

  17. Incorporation of sulfide ions into the cadmium(II) thiolate cluster of Cicer arietinum metallothionein2.

    Science.gov (United States)

    Wan, Xiaoqiong; Freisinger, Eva

    2013-01-18

    The plant metallothionein2 from Cicer arietinum (chickpea), cic-MT2, is known to coordinate five divalent metal ions such as Zn(II) or Cd(II), which are arranged in a single metal thiolate cluster. When the Zn(II) form of the protein is titrated with Cd(II) ions in the presence of sulfide ions, an increased Cd(II) binding capacity and concomitant incorporation of sulfide ions into the cluster are observed. The exact stoichiometry of this novel cluster, its spectroscopic properties, and the significantly increased pH stability are analyzed with different techniques, including UV and circular dichroism spectroscopy and colorimetric assays. Limited proteolytic digestion provides information about the spacial arrangement of the cluster within the protein. Increasing the Cd(II) scavenging properties of a metallothionein by additionally recruiting sulfide ions might be an economic and very efficient detoxification strategy for plants.

  18. Potentiometric study of atenolol as hypertension drug with Co(II, Ni(II, Cu(II and Zn(II transition metal ions in aqueous solution

    Directory of Open Access Journals (Sweden)

    Abdulbaset A. Zaid

    2015-01-01

    Full Text Available Binary and ternary complexes of Co(II, Ni(II, Cu(II and Zn(II with atenolol as hypertension drug and glycine have been determined pH metrically at room temperature and 0.01 M ionic strength (NaClO4 in aqueous solution. The formation of various possible species has been evaluated by computer program and discussed in terms of various relative stability parameters.

  19. New dinuclear copper(II) and zinc(II) complexes for the investigation of sugar-metal ion interactions.

    Science.gov (United States)

    Bera, Manindranath; Patra, Ayan

    2011-10-18

    We have studied the binding interactions of biologically important carbohydrates (D-glucose, D-xylose and D-mannose) with the newly synthesized five-coordinate dinuclear copper(II) complex, [Cu(2)(hpnbpda)(μ-OAc)] (1) and zinc(II) complex, [Zn(2)(hpnbpda)(μ-OAc)] (2) [H(3)hpnbpda=N,N'-bis(2-pyridylmethyl)-2-hydroxy-1,3-propanediamine-N,N'-diacetic acid] in aqueous alkaline solution. The complexes 1 and 2 are fully characterized both in solid and solution using different analytical techniques. A geometrical optimization was made of the ligand H(3)hpnbpda and the complexes 1 and 2 by molecular mechanics (MM+) method in order to establish the stable conformations. All carbohydrates bind to the metal complexes in a 1:1 molar ratio. The binding events have been investigated by a combined approach of FTIR, UV-vis and (13)C NMR spectroscopic techniques. UV-vis spectra indicate a significant blue shift of the absorption maximum of complex 1 during carbohydrate coordination highlighting the sugar binding ability of complex 1. The apparent binding constants of the substrate-bound copper(II) complexes have been determined from the UV-vis titration experiments. The binding ability and mode of binding of these sugar substrates with complex 2 are indicated by their characteristic coordination induced shift (CIS) values in (13)C NMR spectra for carbon atoms C1, C2, and C3 of sugar substrates.

  20. Ca II triplet spectroscopy of RGB stars in NGC 6822: kinematics and metallicities

    Science.gov (United States)

    Swan, J.; Cole, A. A.; Tolstoy, E.; Irwin, M. J.

    2016-03-01

    We present a detailed analysis of the chemistry and kinematics of red giants in the dwarf irregular galaxy NGC 6822. Spectroscopy at ≈8500 Å was acquired for 72 red giant stars across two fields using FORS2 at the VLT. Line-of-sight extinction was individually estimated for each target star to accommodate the variable reddening across NGC 6822. The mean radial velocity was found to be = -52.8 ± 2.2 km s-1 with dispersion σv = 24.1 km s-1, in agreement with other studies. Ca II triplet equivalent widths were converted into [Fe/H] metallicities using a V magnitude proxy for surface gravity. The average metallicity was = -0.84 ± 0.04 with dispersion σ = 0.31 dex and interquartile range 0.48. Our assignment of individual reddening values makes our analysis more sensitive to spatial variations in metallicity than previous studies. We divide our sample into metal-rich and metal-poor stars; the former were found to cluster towards small radii with the metal-poor stars more evenly distributed across the galaxy. The velocity dispersion of the metal-poor stars was found to be higher than that of the metal-rich stars (σ _{v_MP}=27.4 km s-1; σ _{v_MR}=21.1 km s-1); combined with the age-metallicity relation this indicates that the older populations have either been dynamically heated during their lifetimes or were born in a less disc-like distribution than the younger stars.. The low ratio vrot/σv suggests that within the inner 10 arcmin, NGC 6822's stars are dynamically decoupled from the H I gas, and possibly distributed in a thick disc or spheroid structure.

  1. A study on the use of nano/micro structured goethite and hematite as adsorbents for the removal of Cr(III, Co(II, Cu(II, Ni(II, and Zn(II metal ions from aqueous solutions.

    Directory of Open Access Journals (Sweden)

    Hala Hafez

    2012-06-01

    Full Text Available Numerous adsorbents for the removal of heavy metals from aqueous solutions are in various stages of research. The main goal for most of this research is to develop low-cost and environmentally friendly materials for the removal of heavy metals from contaminated groundwater, surface water, and drinking water. Materials that have ion exchange sites are expected to be able to efficiently remove heavy metals from water. Iron oxides, especially in the micro/nano structured forms, are good candidates for the removal of toxic heavymetal ions from water due to their structural properties. In the present work the efficiency of synthesized micro/nano particles of goethite and hematite for the removal of Cr(III, Co(II , Cu(II, Ni(II and Zn(II ions from water was compared. The absorbent capability of goethite as a function of pH, contact time, and initialmetal ion concentration was studied. The results showed that maximum absorption for all metal ions using goethite occurred at a pH=5.3, which was a common trend for all metal ions. At this pH and after one hour contact time goethite was able to adsorb about 100% of the Cu ions (50mg/g, 85% (42.5 mg/g of the Ni ions, 70% (35mg/g of the Cr and Co ions and 60% (30 mg/g of Zn ions from the solutions. Whereas and under the same conditions hematite was able to adsorb 20% (10mg/g of the Cu ions, 85% (42.5mg/g of the Ni ions, 95% (47.5mg/g of the Cr ions, 80% (40mg/g of the Zn ions, and 70% (35mg/g of the Co ions. Both oxides are equally efficient for the removal of Co(II and Ni(II from water. However, goethite is a much more efficient candidate than hematite for the removal of Cu(II,while hematite is more efficient adsorbent for Zn(II and Cr(III. The adsorption affinity of the five metallic cations to goethite is Cu > Ni > Co ~ Cr > Zn, whereas the adsorption affinity of the cations to hematite is Cr > Ni > Zn > Co > Cu. Under the conditions used in the batch experiments (mass of goethite 2g/l maximumadsorption of

  2. Modelling how incorporation of divalent cations affects calcite wettability–implications for biomineralisation and oil recovery

    Science.gov (United States)

    Andersson, M. P.; Dideriksen, K.; Sakuma, H.; Stipp, S. L. S.

    2016-06-01

    Using density functional theory and geochemical speciation modelling, we predicted how solid-fluid interfacial energy is changed, when divalent cations substitute into a calcite surface. The effect on wettability can be dramatic. Trace metal uptake can impact organic compound adsorption, with effects for example, on the ability of organisms to control crystal growth and our ability to predict the wettability of pore surfaces. Wettability influences how easily an organic phase can be removed from a surface, either organic compounds from contaminated soil or crude oil from a reservoir. In our simulations, transition metals substituted exothermically into calcite and more favourably into sites at the surface than in the bulk, meaning that surface properties are more strongly affected than results from bulk experiments imply. As a result of divalent cation substitution, calcite-fluid interfacial energy is significantly altered, enough to change macroscopic contact angle by tens of degrees. Substitution of Sr, Ba and Pb makes surfaces more hydrophobic. With substitution of Mg and the transition metals, calcite becomes more hydrophilic, weakening organic compound adsorption. For biomineralisation, this provides a switch for turning on and off the activity of organic crystal growth inhibitors, thereby controlling the shape of the associated mineral phase.

  3. Ca II triplet spectroscopy of RGB stars in NGC 6822: kinematics and metallicities

    CERN Document Server

    Swan, Jesse; Tolstoy, Eline; Irwin, Mike J

    2016-01-01

    We present a detailed analysis of the chemistry and kinematics of red giants in the dwarf irregular galaxy NGC 6822. Spectroscopy at 8500 Angstroms was acquired for 72 red giant stars across two fields using FORS2 at the VLT. Line of sight extinction was individually estimated for each target star to accommodate the variable reddening across NGC 6822. The mean radial velocity was found to be v_helio = (52.8 +/- 2.2) km/s with dispersion rms = 24.1 km/s, in agreement with other studies. Ca II triplet equivalent widths were converted into [Fe/H] metallicities using a V magnitude proxy for surface gravity. The average metallicity was [Fe/H] = (-0.84 +/- 0.04) with dispersion rms = 0.31 dex and interquartile range 0.48. Our assignment of individual reddening values makes our analysis more sensitive to spatial variations in metallicity than previous studies. We divide our sample into metal-rich and metal-poor stars; the former are found to cluster towards small radii with the metal-poor stars more evenly distribut...

  4. Adsorption of strontium (II) metal ions using phosphonate-functionalized polymer

    Indian Academy of Sciences (India)

    S M BHOSLE; S PONRATHNAM; S S TAMBE; N N CHAVAN

    2016-10-01

    Diethyl[3-(methoxydimethylsilyl)propyl]phosphonate (DMPP) polymer was synthesized for the strontium (II) metal ion recovery using diethylallylphosphonate as staring material. Diethylallylphosphonate was reactedwith poly(methylhydro)siloxane (MW 1900–2000 g mol$^{−1}$) in the presence of Speier’s catalyst. The synthesized monomer was characterized by IR, ${}^1$H NMR, ${}^{13}$C NMR and FT-IR spectroscopy techniques, and the synthesizedpolymers were characterized by IR and NMR spectroscopy, differential scanning calorimetry, thermogravimetric analysis and solubility. The synthesized polymer was used for sequestering strontium metal from the aqueous solution. The metal binding was examined by the energy dispersive spectroscopy and scanning electron microscopy for the adsorbed Sr(II). Batch adsorption studies were performed by varying three parameters, namely initial pH, adsorbentdose and the contact time. The reaction kinetics was determined by the Langmuir, Freundlich, and pseudo-firstand second-order models. Results of this study indicate that the synthesized polymer DMPP has been effective inremoving Sr(II) from the aqueous solution.

  5. Synthesis, characterization and biological evaluation of Rutin-zinc(II) flavonoid -metal complex.

    Science.gov (United States)

    Ikeda, Norma Estefania Andrades; Novak, Estela Maria; Maria, Durvanei Augusto; Velosa, Adélia Segin; Pereira, Regina Mara Silva

    2015-09-01

    Synthesis of compounds analogous to natural products from secondary metabolites, such as flavonoids, is a promising source of novel drugs. Rutin (quercetin-3-O-rutinoside) is a natural flavone, which has, in its chemical structure, different sites for coordination with transition metals and the complexation with these metals enhances its biological properties. Rutin-zinc(II), a flavonoid-metal complex, was synthesized and characterized by UV-VIS, FT-IR, elemental analysis and (1)H NMR. The antioxidant and antitumor activities, as well as the cytotoxicity and in vivo toxicity of this complex were evaluated and compared with the free rutin. Rutin-zinc(II) has not shown any cytotoxicity against normal cells (fibroblasts and HUVECs) or toxicity in BALB/c mice, but has shown antioxidant activity in vitro and cytotoxicity against leukemia (KG1, K562 and Jurkat), multiple myeloma (RPMI8226) and melanoma (B16F10 and SK-Mel-28) cell lines in vitro. In Ehrlich ascites carcinoma model, Rutin-zinc(II) modulated the mitochondrial membrane potential and the expression of genes related to cell cycle progression, angiogenesis and apoptosis.

  6. Kinetics of metal exchange in Cd(II) octa(4-bromophenyl)porphyrinate with d-metal salts in organic solvents

    Science.gov (United States)

    Zvezdina, S. V.; Chizhova, N. V.; Mamardashvili, N. Zh.

    2017-03-01

    The reaction of metal exchange between Cd(II) octa(4-bromophenyl)porphyrinate with CuCl2 and ZnCl2 in DMFA and DMSO is studied by means of spectrophotometry. The kinetic parameters of the metal exchange reaction are calculated, a stoichiometric reaction mechanism is proposed. The effect the natures of the solvent, salt solvate, and the chemical modification of tetrapyrrole macrocycle have on the kinetic parameters of the metal exchange reaction are revealed.

  7. Synthesis, Spectroscopic, Anticancer, and Antimicrobial Properties of Some Metal(II Complexes of (Substituted Nitrophenol Schiff Base

    Directory of Open Access Journals (Sweden)

    Aderoju A. Osowole

    2012-01-01

    Full Text Available The Schiff base, 2-[(2,3-dihydro-1H-inden-4-yliminomethyl]-5-nitrophenol coordinates to Mn(II, Cu(II, Zn(II, and Pd(II ions through the phenolic O and imine N atoms. The complexes are characterized by physicochemical and spectroscopic methods. The metal complexes formed as [ML2]xH2O with exception of the Cu(II complex which is anhydrous. Spectroscopic data corroborate the adoption of a four-coordinate, tetrahedral geometry for the Mn(II, and Zn(II complexes, and a four-coordinate, square planar geometry for the Cu(II and Pd(II complexes. None is an electrolyte in DMSO. The in vitro anticancer activities of the metal free ligand, Cu(II, Zn(II, and Pd(II complexes against MCF-7 (human breast adenocarcinoma and HT-29 (colon carcinoma cells reveal that the Pd(II complex has the best cytotoxic activity against MCF-7 cells with an IC50 of 5.94 μM, which is within the same order of activity as cisplatin. Furthermore, the ligand and the Zn(II complex exhibit broad-spectrum activity against two gram-positive bacteria, three gram-negative bacteria, and a fungus with inhibitory zones range of 10.0–20.0 and 10.0–17.0 mm, respectively.

  8. Type-II Dirac fermions in the PtSe2 class of transition metal dichalcogenides

    Science.gov (United States)

    Huang, Huaqing; Zhou, Shuyun; Duan, Wenhui

    2016-09-01

    Recently, a new "type-II" Weyl fermion, which exhibits exotic phenomena, such as an angle-dependent chiral anomaly, was discovered in a new phase of matter where electron and hole pockets contact at isolated Weyl points [Nature (London) 527, 495 (2015), 10.1038/nature15768]. This raises an interesting question about whether its counterpart, i.e., a type-II Dirac fermion, exists in real materials. Here, we predict the existence of symmetry-protected type-II Dirac fermions in a class of transition metal dichalcogenide materials. Our first-principles calculations on PtSe2 reveal its bulk type-II Dirac fermions which are characterized by strongly tilted Dirac cones, novel surface states, and exotic doping-driven Lifshitz transition. Our results show that the existence of type-II Dirac fermions in PtSe2-type materials is closely related to its structural P 3 ¯m 1 symmetry, which provides useful guidance for the experimental realization of type-II Dirac fermions and intriguing physical properties distinct from those of the standard Dirac fermions known before.

  9. Metal-ion exchange induced structural transformation as a way of forming novel Ni(II)- and Cu(II)-salicylaldimine structures

    Science.gov (United States)

    Wu, Jing-Yun; Tsai, Chi-Jou; Chang, Ching-Yun; Wu, Yung-Yuan

    2017-02-01

    A Zn(II)-salicylaldimine complex [Zn(Lsalpyca)(H2O)]n (1, where H2Lsalpyca=4-hydroxy-3-(((pyridin-2-yl)methylimino)methyl)benzoic acid), with a one-dimensional (1D) chain structure, has been successfully converted to a discrete Ni(II)-salicylaldimine complex [Ni(Lsalpyca)(H2O)3] (2) and an infinite Cu(II)-salicylaldimine complex {[Cu(Lsalpyca)]·3H2O}n (3) through a metal-ion exchange induced structural transformation process. However, such processes do not worked by Mn(II) and Co(II) ions. Solid-state structure analyses reveal that complexes 1-3 form comparable coordinative or supramolecular zigzag chains running along the crystallographic [201] direction. In addition, replacing Zn(II) ion by Ni(II) and Cu(II) ions caused changes in coordination environment and sphere of metal centers, from a 5-coordinate intermediate geometry of square pyramidal and trigonal bipyramidal in 1 to a 6-coordinate octahedral geometry in 2, and to a 4-coordiante square planar geometry in 3. This study shows that metal-ion exchange serves as a very efficient way of forming new coordination complexes that may not be obtained through direct synthesis.

  10. Oxidative addition of disulfide/diselenide to group 10 metal(0) and in situ functionalization to form neutral thiasalen/selenasalen group 10 metal(II) complexes.

    Science.gov (United States)

    Dutta, Pradip Kr; Asatkar, Ashish K; Zade, Sanjio S; Panda, Snigdha

    2014-01-28

    Three components, one pot synthesis of thiasalen/selenasalen Ni(II), Pd(II) and Pt(II) complexes, 14-19, by the oxidative addition of S-S/Se-Se bond of bis(o-formylphenyl)disulfide/-diselenide to Ni(0), Pd(0) and Pt(0) followed by in situ Schiff base formation with ethylenediamine is reported. S-S or Se-Se bonds were cleaved and coordinated to the metal center as thiolate (ArS(-)) or selenolate (ArSe(-)) while the formal oxidation state of metal centers was changed from '0' to '+2'. The disulfide/diselenide reacted with zero-valent metals at room temperature to give only the monometallic complexes. All complexes (except Pd-thiolate complex 15) were studied by single crystal X-ray crystallography and revealed the square planar geometry around metal centers.

  11. Spectral, NLO, Fluorescence, and Biological Activity of Knoevenagel Condensate of β-Diketone Ligands and Their Metal(II Complexes

    Directory of Open Access Journals (Sweden)

    S. Sumathi

    2011-01-01

    Full Text Available Transition metal complexes of various acetylacetone-based ligands of the type ML (where M=  Cu(II, Ni(II, Co(II; L=  3-(aryl-pentane-2,4-dione have been synthesized. The structural features have been derived from their elemental analysis, magnetic susceptibility, molar conductance, IR, UV-Vis, H1NMR, mass and ESR spectral studies. Conductivity measurements reveal that all the complexes are nonelectrolytic in nature. Spectroscopic and other analytical data of the complexes suggest square planar geometry for copper(II, cobalt(II, and nickel(II complexes of 3-(3-phenylallylidenepentane-2,4-dione and octahedral geometry for other metal(II complexes. The redox behaviors of the copper(II complexes have been studied by cyclic voltammetry. The free ligands and their metal complexes have been screened for their in vitro biological activities against bacteria and fungus. The metal(II complexes are found to possess increased activities compared to those of the free ligands. All synthesized compounds may serve as potential photoactive materials as indicated from their characteristic fluorescence properties. The second harmonic generation (SHG efficiency of the ligands was found to have considerable effect compared to that of urea and KDP.

  12. Synthesis, characterization and extraction studies of some metal (II) complexes containing (hydrazoneoxime and bis-acylhydrazone) moieties

    Science.gov (United States)

    Al-Ne'aimi, Mohammed Mahmmod; Al-Khuder, Mohammed Moudar

    2013-03-01

    In this study, diacetylmonoximebenzoylhydrazone (L1H2) and 1,4-diacetylbenzene bis(benzoyl hydrazone) (L2H2) were synthesized by the condensation of benzohydrazide with diacetyl monoxime and 1,4-diacetylbenzene, respectively. Complexes of these ligands with Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) inos were prepared with a metal:ligand ratio of 1:2 for L1H2 ligand, and 1:1 for L2H2 ligand. The ligands and their complexes were elucidated on the basis of elemental analyses CHN, AAS, FT-IR, 1H- and 13C NMR spectra, UV-vis spectra and magnetic susceptibility measurements. Results show the L1H2 ligand act as monoanionic O,N,N-tridentate and coordination takes place in the enol form through the oxime nitrogen, the imine nitrogen and the enolate oxygen atoms with a N4O2 donor environment, while the L2H2 ligand act as a dianionic O,N,N,O-tetradentate and coordination takes place in the enol form through the enolate oxygen and the azomethine nitrogen atoms with a N2O2 donor environment. These results are consistent with the formation of mononuclear metal (II) complexes [M(L1H)2], and binuclear polymeric metal (II) complexes [{M2(L2)}n]. The extraction ability of both ligands were examined in chloroform by the liquid-liquid extraction of selected transition metal [Co2+, Ni2+, Cu2+, Zn2+ and Pb2+] cations. The effects of pH and contact time on the percentage extraction of metal (II) ions were studied under the optimum extraction conditions. The (L1H2) ligand shows strong binding ability toward copper(II) and lead(II) ions, while the (L2H2) ligand shows strong binding ability toward nickel(II) and zinc(II) ions.

  13. Type II supernovae as probes of environment metallicity: observations of host HII regions

    CERN Document Server

    Anderson, J P; Dessart, L; Hamuy, M; Galbany, L; Morrell, N I; Stritzinger, M D; Phillips, M M; Folatelli, G; Boffin, H M J; de Jaeger, T; Kuncarayakti, H; Prieto, J L

    2016-01-01

    Spectral modelling of SNII atmospheres indicates a clear dependence of metal line strengths on progenitor metallicity. This motivates further work to evaluate the accuracy with which these SNe can be used as metallicity indicators. To assess this accuracy we present a sample of SNII HII-region spectroscopy, from which environment abundances are derived. These environment abundances are compared to the observed strength of metal lines in SN spectra. Combining our sample with measurements from the literature, we present oxygen abundances of 119 host HII regions, by extracting emission line fluxes and using abundance diagnostics. Then, following Dessart et al., these abundances are compared to equivalent widths of Fe 5018 A at various time and colour epochs. Our distribution of inferred SNII host HII-region abundances has a range of ~0.6 dex. We confirm the dearth of SNeII exploding at metallicities lower than those found (on average) in the Large Magellanic Cloud. The equivalent width of Fe 5018 A at 50 days po...

  14. Removal of heavy metal Cu(II) in simulated aquaculture wastewater by modified palygorskite.

    Science.gov (United States)

    Cao, Jia-Shun; Wang, Cheng; Fang, Fang; Lin, Jun-Xiong

    2016-12-01

    Palygorskite (PAL) is a good heavy metal adsorbent due to its high surface area, low cost, and environmentally compatibility. But the natural PAL has limited its adsorption capacity and selectivity. In this study, a cost-effective and readily-generated absorbent, l-threonine-modified palygorskite (L-PAL), was used and its performance for Cu(II) removal in simulated aquaculture wastewater was evaluated. After preparation, L-PAL was characterized by using Fourier transform infrared spectroscopy, scanning electron microscope, energy dispersive X-ray spectroscopy, X-ray diffractometer, X-ray photoelectron spectroscopy, transmission electron microscopy and thermogravimetric analysis. The impacts of pH, adsorbent dosage, contact time, and initial Cu(II) concentration on the adsorption capacity of L-PAL were examined. The Cu(II) adsorption capacity on L-PAL was enhanced almost 10 times than that of raw PAL. The adsorption isotherms of Cu(II) fit the Langmuir isotherms, and the adsorption kinetics was dominated by the pseudo-second-order model. The thermodynamic parameters at four temperatures were calculated, which indicated that the adsorption was spontaneous and endothermic. The adsorption mechanism involves complexation, chelation, electrostatic attraction, and micro-precipitation. Furthermore, L-PAL is shown to have a high regeneration capacity. These results indicate that L-PAL is a cheap and promising absorbent for Cu(II) removal and hold potential to be used for aquaculture wastewater treatment.

  15. Lifetime of combustion-generated environmentally persistent free radicals on Zn(II)O and other transition metal oxides.

    Science.gov (United States)

    Vejerano, Eric; Lomnicki, Slawo; Dellinger, Barry

    2012-10-26

    Previous studies indicated that Environmentally Persistent Free Radicals (EPFRs) are formed in the post-flame, cool zone of combustion. They result from the chemisorption of gas-phase products of incomplete combustion (particularly hydroxyl- and chlorine-substituted aromatics) on Cu(II)O, Fe(III)(2)O(3), and Ni(II)O domains of particulate matter (fly ash or soot particles). This study reports our detailed laboratory investigation on the lifetime of EPFRs on Zn(II)O/silica surface. Similarly, as in the case of other transition metals, chemisorption of the adsorbate on the Zn(II)O surface and subsequent transfer of electron from the adsorbate to the metal forms a surface-bound EPFR and a reduced metal ion center. The EPFRs are stabilized by their interaction with the metal oxide domain surface. The half-lives of EPFRs formed on Zn(II)O domains were the longest observed among the transition metal oxides studied and ranged from 3 to 73 days. These half-lives were an order of magnitude longer than those formed on nickel and iron oxides, and were 2 orders of magnitude longer compared to the EPFRs on copper oxide which have half-lives only on the order of hours. The longest-lived radicals on Zn(II)O correspond to the persistency in ambient air particles of almost a year. The half-life of EPFRs was found to correlate with the standard reduction potential of the associated metal.

  16. Anti-oxidant, in vitro, in vivo anti-inflammatory activity and antiproliferative activity of mefenamic acid and its metal complexes with manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II).

    Science.gov (United States)

    Kovala-Demertzi, Dimitra; Hadjipavlou-Litina, Dimitra; Staninska, Malgorzata; Primikiri, Alexandra; Kotoglou, Chronis; Demertzis, Mavroudis A

    2009-06-01

    Some new complexes of mefenamic acid with potentially interesting biological activity are described. The complexes of mefenamic acid [Mn(mef)(2)(H(2)O)(2)], 1, [Co(mef)(2)(H(2)O)(2)], 2, [Ni(mef)(2)(H(2)O)(2)], 3, [Cu(mef)(2)(H(2)O)](2), 4 and [Zn(mef)(2)], 5, were prepared by the reaction of mefenamic acid, a potent anti-inflammatory drug with metal salts. Optical and infrared spectral data of these new complexes are reported. Monomeric six-coordinated species were isolated in the solid state for Mn(II), Ni(II) and Co(II), dimeric five-coordinated for Cu(II) and monomeric four-coordinated for Zn(II). In DMF or CHCl(3) solution the coordination number is retained and the coordinated molecules of water are replaced by solvent molecules. The anti-oxidant properties of the complexes were evaluated using the 1,1-diphenyl-2-picrylhydrazyl, DPPH, free radical scavenging assay. The scavenging activities of the complexes were measured and compared with those of the free drug and vitamin C. We have explored their ability to inhibit soybean lipoxygenase, beta-glucuronidase and trypsin- induced proteolysis. The complex [Mn(mef)(2)(H(2)O)(2)] exhibits the highest antioxidant activity and the highest inhibitory effect against the soybean lipogygenase (LOX), properties that are not demonstrated by mefenamic acid. Their inhibitory effects on rat paw edema induced by Carrageenan was studied and compared with those of mefenamic acid. The complex [Zn(mef)(2)] exhibited a strong inhibitory effect at 0.1 mmol/Kg B.W. (81.5 +/- 1.3% inhibition), superior to the inhibition induced by mefenamic acid at the same dose (61.5 +/- 2.3% inhibition). Mefenamic acid and its metal complexes have been evaluated for antiproliferative activity in vitro against the cells of three human cancer cell lines: MCF-7 (human breast cancer cell line), T24 (bladder cancer cell line), A-549 (non-small cell lung carcinoma) and a mouse fibroblast L-929 cell line. The copper(II) complex displays against T24, MCF-7

  17. Cluster-Continuum Calculations of Hydration Free Energies of Anions and Group 12 Divalent Cations.

    Science.gov (United States)

    Riccardi, Demian; Guo, Hao-Bo; Parks, Jerry M; Gu, Baohua; Liang, Liyuan; Smith, Jeremy C

    2013-01-08

    Understanding aqueous phase processes involving group 12 metal cations is relevant to both environmental and biological sciences. Here, quantum chemical methods and polarizable continuum models are used to compute the hydration free energies of a series of divalent group 12 metal cations (Zn(2+), Cd(2+), and Hg(2+)) together with Cu(2+) and the anions OH(-), SH(-), Cl(-), and F(-). A cluster-continuum method is employed, in which gas-phase clusters of the ion and explicit solvent molecules are immersed in a dielectric continuum. Two approaches to define the size of the solute-water cluster are compared, in which the number of explicit waters used is either held constant or determined variationally as that of the most favorable hydration free energy. Results obtained with various polarizable continuum models are also presented. Each leg of the relevant thermodynamic cycle is analyzed in detail to determine how different terms contribute to the observed mean signed error (MSE) and the standard deviation of the error (STDEV) between theory and experiment. The use of a constant number of water molecules for each set of ions is found to lead to predicted relative trends that benefit from error cancellation. Overall, the best results are obtained with MP2 and the Solvent Model D polarizable continuum model (SMD), with eight explicit water molecules for anions and 10 for the metal cations, yielding a STDEV of 2.3 kcal mol(-1) and MSE of 0.9 kcal mol(-1) between theoretical and experimental hydration free energies, which range from -72.4 kcal mol(-1) for SH(-) to -505.9 kcal mol(-1) for Cu(2+). Using B3PW91 with DFT-D3 dispersion corrections (B3PW91-D) and SMD yields a STDEV of 3.3 kcal mol(-1) and MSE of 1.6 kcal mol(-1), to which adding MP2 corrections from smaller divalent metal cation water molecule clusters yields very good agreement with the full MP2 results. Using B3PW91-D and SMD, with two explicit water molecules for anions and six for divalent metal cations, also

  18. Cluster-Continuum Calculations of Hydration Free Energies of Anions and Group 12 Divalent Cations

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Hao-Bo [ORNL; Liang, Liyuan [ORNL; Parks, Jerry M [ORNL; Smith, Jeremy C [ORNL; Riccardi, Demian M [ORNL; Gu, Baohua [ORNL

    2013-01-01

    Understanding aqueous phase processes involving group 12 metal cations is relevant to both environmental and biological sciences. Here, quantum chemical methods and polarizable continuum models are used to compute the hydration free energies of a series of divalent group 12 metal cations (Zn2+, Cd2+, and Hg2+) together with Cu2+ and the anions OH , SH , Cl , and F . A cluster-continuum method is employed, in which gas-phase clusters of the ion and explicit solvent molecules are immersed in a dielectric continuum. Two approaches to define the size of the solute-water cluster are compared, in which the number of explicit waters used is either held constant or determined variationally as that of the most favorable hydration free energy. Results obtained with various polarizable continuum models are also presented. Each leg of the relevant thermodynamic cycle is analyzed in detail to determine how different contributions yield the observed mean signed error (MSE) and the standard deviation of the error (STDEV) between theory and experiment. The use of a constant number of water molecules for each set of ions is found to lead to predicted relative trends that benefit from error cancellation. Overall, the best results are obtained with MP2 and the Solvent Model D polarizable continuum model (SMD), with eight explicit water molecules for anions and ten for the metal cations, yielding a STDEV of 2.3 kcal/mol and MSE of 0.9 kcal/mol between theoretical to experimental hydration free energies, which range from -72.4 kcal/mol for SH to -505.9 kcal/mol for Cu2+. Using B3PW91 with DFT-D3 dispersion corrections (B3PW91-D) and SMD yields a STDEV of 3.3 kcal mol 1 and MSE of 1.6 kcal/mol, to which adding MP2 corrections from smaller divalent metal ion water molecule clusters yields very good agreement with the full MP2 results. Using B3PW91-D and SMD, with two explicit water molecules for anions and six for divalent metal cations also yields reasonable agreement with experiment

  19. Adsorptive behaviour of mercury on algal biomass: Competition with divalent cations and organic compounds

    Energy Technology Data Exchange (ETDEWEB)

    Carro, Leticia; Barriada, Jose L. [Departamento de Quimica Fisica e Ingenieria Quimica I, Universidad de A Coruna, c/Rua da Fraga 10, 15008 A Coruna (Spain); Herrero, Roberto, E-mail: r.herrero@udc.es [Departamento de Quimica Fisica e Ingenieria Quimica I, Universidad de A Coruna, c/Rua da Fraga 10, 15008 A Coruna (Spain); Sastre de Vicente, Manuel E. [Departamento de Quimica Fisica e Ingenieria Quimica I, Universidad de A Coruna, c/Rua da Fraga 10, 15008 A Coruna (Spain)

    2011-08-15

    Highlights: {yields} Native and protonated macroalga S. muticum are good materials for mercury removal. {yields} Fast kinetic process and high mercury uptakes have been found for those materials. {yields} Diffusion control is the rate limiting step of the process. {yields} Competition effects by organic compounds, inorganic salts and divalent cations were analyzed. {yields} Continuous flow experiments allowed identification of mercury reduction during metal removal. - Abstract: Biosorption processes constitute an effective technique for mercury elimination. Sorption properties of native and acid-treated Sargassum muticum have been studied. Effect of pH, initial mercury concentration and contact time studies provided fundamental information about the sorption process. This information was used as the reference values to analyse mercury sorption under competition conditions. Saline effect has shown little influence in sorption, when only electrostatic modifications took place upon salt addition. On the contrary, if mercury speciation dramatically changed owing to the addition of an electrolyte, such as in the case of chloride salt, very large modifications in mercury sorption were observed. Competition with other divalent cations or organic compounds has shown little or none effect on mercury, indicating that a different mechanism is taking place during the removal of these pollutants. Finally, continuous flow experiments have clearly shown that a reduction process is also taking place during mercury removal. This fact is not obvious to elucidate under batch sorption experiments. Scanning Electron Microscopy analysis of the surface of the materials show deposits of mercury(I) and metallic mercury which is indicative of the reduction process proposed.

  20. Effect of biofilm coatings at metal-oxide/water interfaces I: Pb(II) and Zn(II) partitioning and speciation at Shewanella oneidensis/metal-oxide/water interfaces

    Science.gov (United States)

    Wang, Yingge; Gélabert, Alexandre; Michel, F. Marc; Choi, Yongseong; Gescher, Johannes; Ona-Nguema, Georges; Eng, Peter J.; Bargar, John R.; Farges, Francois; Spormann, Alfred M.; Brown, Gordon E.

    2016-09-01

    Microbial biofilms are often present as coatings on metal-oxide surfaces in natural and industrial environments and may induce significant changes in the partitioning behavior and speciation of aqueous metal ions, which in turn can impact their transport and fate. In this study, long-period X-ray standing wave-fluorescence yield (LP-XSW-FY) spectroscopy was used to measure under in situ conditions the partitioning of aqueous Pb(II) and Zn(II) between multilayer Shewanella oneidensis MR-1 biofilms and highly polished, oriented single-crystal surfaces of α-Al2O3 and α-Fe2O3 as a function of metal-ion concentration and time at pH 6.0. We show that after 3-h exposure time, Pb(II) binds preferentially to the α-Al2O3 (1-102) and α-Fe2O3 (0 0 0 1) surfaces at low Pb concentration ([Pb] = 10-7 M) and then increasingly partitions into the biofilm coatings at higher concentrations (10-6 to 10-4 M). In contrast, Zn(II) partitions preferentially into the biofilm coating for both surfaces at all Zn concentrations studied (10-7 to 10-4 M). In comparison, the α-Al2O3 (0 0 0 1) surface has a low affinity for both Pb(II) and Zn(II), and the biofilm coatings are the dominant sink for both ions. These findings suggest that in the presence of S. oneidensis biofilm coatings, α-Al2O3 (0 0 0 1) is the least reactive surface for Pb(II) and Zn(II) compared to α-Al2O3 (1-102) and α-Fe2O3 (0 0 0 1). They also show that Zn(II) has a lower affinity than Pb(II) for reactive sites on α-Al2O3 (1-102) and α-Fe2O3 (0 0 0 1) at [Me(II)] of 10-7 M; at 10-5 M, the bulk of the metal ions partition into the biofilm coatings. At longer exposure times (20-24 h), both Pb(II) and Zn(II) increasingly partition to the metal-oxide surfaces at [Me(II)] = 10-5 M and pH 6.0, indicating possible reaction/diffusion-controlled sorption processes. Pb LIII-edge and Zn K-edge grazing-incidence extended X-ray absorption fine structure (GI-EXAFS) measurements suggest that both Pb(II) and Zn(II) ions may be

  1. Instability of some divalent rare earth ions and photochromic effect

    OpenAIRE

    Egranov, A. V.; Sizova, T. Yu.; Shendrik, R. Yu.; Smirnova, N. A.

    2015-01-01

    It was shown that the divalent rare earth ions (La, Ce, Gd, Tb, Lu, and Y) in cubic sites in alkaline earth fluorides are unstable with respect to electron autodetachment since its d1(eg) ground state is located in the conduction band which is consistent with the general tendency of these ions in various compounds. The localization of doubly degenerate d1(eg) level in the conduction band creates a configuration instability around the divalent rare earth ion that leading to the formation of an...

  2. Inhibition of Aβ42 peptide aggregation by a binuclear ruthenium(II)-platinum(II) complex: Potential for multi-metal organometallics as anti-amyloid agents.

    Science.gov (United States)

    Kumar, Amit; Moody, Lamaryet; Olaivar, Jason F; Lewis, Nerissa A; Khade, Rahul L; Holder, Alvin A; Zhang, Yong; Rangachari, Vijayaraghavan

    2010-08-23

    Design of inhibitors for amyloid-β (Aβ) peptide aggregation has been widely investigated over the years towards developing viable therapeutic agents for Alzheimer's disease (AD). The biggest challenge seems to be inhibiting Aβ aggregation at the early stages of aggregation possibly at the monomeric level, as oligomers are known to be neurotoxic. In this regard, exploiting the metal chelating property of Aβ to generate molecules that can overcome this impediment presents some promise. Recently, one such metal complex containing Pt(II) ([Pt(BPS)Cl(2)]) was reported to effectively inhibit Aβ42 aggregation and toxicity (1). This complex was able bind to Aβ42 at the N-terminal part of the peptide and triggered a conformational change resulting in effective inhibition. In the current report, we have generated a mixed-binuclear metal complex containing Pt(II) and Ru(II) that inhibited Aβ42 aggregation at an early stage of aggregation and seemed to have different modes of interaction than the previously reported Pt(II) complex, suggesting an important role of the second metal center. This 'proof-of-concept' compound will help in developing more effective molecules against Aβ aggregation by modifying the two metal centers as well as their ligands, which will open doors to new rationale for Aβ inhibition.

  3. The Reduction of Aqueous Metal Species on the Surfaces of Fe(II)-Containing Oxides: The Role of Surface Passivation

    Science.gov (United States)

    White, A.F.; Peterson, M.L.

    1998-01-01

    The reduction of aqueous transition metal species at the surfaces of Fe(II)- containing oxides has important ramifications in predicting the transport behavior in ground water aquifers. Experimental studies using mineral suspensions and electrodes demonstrate that structural Fe(II) heterogeneously reduces aqueous ferric, cupric, vanadate and chromate ions on magnetite and ilmenite surfaces. The rates of metal reduction on natural oxides is strongly dependent on the extent of surface passivation and redox conditions in the weathering environment. Synchrotron studies show that surface oxidation of Fe(II)-containing oxide minerals decreases their capacity for Cr(VI) reduction at hazardous waste disposal sites.

  4. Synthesis, Characterization and Biological Properties of Tridentate NNO, NNS and NNN Donor Thiazole-Derived Furanyl, Thiophenyl and Pyrrolyl Schiff Bases and Their Co(II), Cu(II), Ni(II) and Zn(II) Metal Chelates.

    Science.gov (United States)

    Chohan, Z H; Kausar, S

    2000-01-01

    2-Aminothiazole undergoes condensation reactions with furane-, thiophene- and pyrrole-2-carboxylaldehyde to give tridentate NNO, NNS and NNN Schiff bases respectively. These tridentate Schiff bases formed complexes of the type [M (L)(2)]X(2) where [M=Co(II), Cu(II), Ni(II) or Zn(II), L=N-(2-furanylmethylene)-2-aminothiazole (L(1)), N-(2-thiophenylmethylene)-2-aminothiazole (L(2), N-(2-pyrrolylmethylene)-2-aminothiazole (L(3)) and X=Cl. The structures of these Schiff bases and of their complexes have been determined on the basis of their physical, analytical and spectral data. The screening results of these compounds indicated them to possess excellent antibacterial activity against tested pathogenic bacterial organisms e.g., Escherichia coli, Staphylococcus aureous and Pseudomonas aeruginosa. However, in comparison, their metal chelates have been shown to possess more antibacterial activity than the uncomplexed Schiff bases.

  5. Studies on the complex formed between bacitracin A and divalent cations.

    Science.gov (United States)

    Scogin, D A; Baldwin, T O; Gennis, R B

    1983-01-12

    Bacitracin A is a peptide antibiotic which forms stoichiometric complexes with divalent cations, including Ni2+ and Zn2+. In this paper it is shown that the metal-bacitracin complex contains a group which has a pKa near pH 5.5. Deprotonation of the group is concomitant with the aggregation and precipitation of the metal-bacitracin complex. Bacitracin A, in the absence of metals, does not contain any group which has a pKa in this range. It is postulated that this group is the N-terminal amino of isoleucine, which was previously postulated not to be directly involved in metal coordination based on proton release measurements. An attempt was made to demonstrate directly that the N-terminal amino group is not coordinated to the metal by examining the reactivity of this group with 2,4,6-trinitrobenzene sulfonate. It was clearly shown that bound metals protect the N-terminal amino group from reacting with this reagent. It is speculated that this metal-protection results from a combination of factors, including steric hindrance.

  6. Variable primary coordination environments of Cd(II) binding to three helix bundles provide a pathway for rapid metal exchange.

    Science.gov (United States)

    Tebo, Alison G; Hemmingsen, Lars; Pecoraro, Vincent L

    2015-12-01

    Members of the ArsR/SmtB family of transcriptional repressors, such as CadC, regulate the intracellular levels of heavy metals like Cd(II), Hg(II), and Pb(II). These metal sensing proteins bind their target metals with high specificity and affinity, however, a lack of structural information about these proteins makes defining the coordination sphere of the target metal difficult. Lingering questions as to the identity of Cd(II) coordination in CadC are addressed via protein design techniques. Two designed peptides with tetrathiolate metal binding sites were prepared and characterized, revealing fast exchange between CdS3O and CdS4 coordination spheres. Correlation of (111m)Cd PAC spectroscopy and (113)Cd NMR spectroscopy suggests that Cd(II) coordinated to CadC is in fast exchange between CdS3O and CdS4 forms, which may provide a mechanism for rapid sensing of heavy metal contaminants by this regulatory protein.

  7. A porous Cu(II) metal-organic framework: Synthesis, crystal structure and gas adsorption properties

    Science.gov (United States)

    Li, Wu-Wu; Guo, Ying; Zhang, Wei-Hong

    2017-09-01

    Presented here is a new porous Cu(II) metal-organic framework, namely [Cu(tdc)(H2O)]n·n(DMA) (1 H2tdc = thiophene-2,5-dicarboxylic acid, DMA = N,N‧-dimethylacetamide), which was obtained by the self-assembly reaction of CuCl2 and H2tdc under solvothermal conditions. Single crystal X-ray diffraction analysis revealed that compound 1 features a 3D porous framework based on 1D chain structure subunits, and the 1D rhombohedral channels are occupied by the lattice DMA molecules. Gas adsorption studies reveal that this desolvated sample exhibit high uptake capacity for light hydrocarbons.

  8. Type Ia and II supernovae contributions to the metal enrichment in intra-cluster medium observed with Suzaku

    CERN Document Server

    Sato, Kosuke; Matsushita, Kyoko; Ishisaki, Yoshitaka; Yamasaki, Noriko Y; Ishida, Manabu; Ohashi, Takaya

    2007-01-01

    We studied the properties of the intra-cluster medium (ICM) in two clusters of galaxies (AWM 7 and Abell 1060) and two groups (HCG 62 and NGC 507) with the X-ray Observatory Suzaku. Based on spatially resolved energy spectra, we measured for the first time precise cumulative ICM metal masses within 0.1 and ~0.3 r_{180}. Comparing our results with supernova nucleosynthesis models, the number ratio of type II (SNe II) to type Ia (SNe Ia) is estimated to be ~3.5, assuming the metal mass in the ICM is represented by the sum of products synthesized in SNe Ia and SNe II. Normalized by the K-band luminosities of present galaxies, and including the metals in stars, the integrated number of past SNe II explosions is estimated to be close to or somewhat higher than the star formation rate determined from Hubble Deep Field observations.

  9. Structural studies of transition metal complexes with 4,5-bis(2-pyridylmethylsulfanyl)-4',5'-ethylenedithiotetrathiafulvalene: probing their potential for the construction of multifunctional molecular assemblies.

    Science.gov (United States)

    Liu, Shi-Xia; Dolder, Stefan; Franz, Patrick; Neels, Antonia; Stoeckli-Evans, Helen; Decurtins, Silvio

    2003-08-11

    Three divalent transition metal complexes of 4,5-bis(2-pyridylmethylsulfanyl)-4',5'-ethylenedithiotetrathiafulvalene have been prepared and crystallographically characterized. The isostructural Co(II) and the Ni(II) complexes show octahedral geometries around the metal ions with the coordination sites occupied by the pyridyl nitrogen atoms and the thioether sulfur atoms of the ligand and cis coordination of the halide ions. Cyclic voltammetry reveals that the complexation leads to a small anodic shift in the first oxidation potential of the TTF system.

  10. Characterization of parvalbumin and polcalcin divalent ion binding by isothermal titration calorimetry.

    Science.gov (United States)

    Henzl, Michael T

    2009-01-01

    The elucidation of structure-affinity relationships in EF-hand proteins requires a reliable assay of divalent ion affinity. In principle, isothermal titration calorimetry (ITC) should be capable of furnishing estimates for Ca2+- and Mg2+-binding constants in these systems. And because the method yields the binding enthalpy directly, ITC can provide a more detailed view of binding energetics than methods that rely on 45Ca2+ or fluorescent indicators. For several reasons, however, it is generally not possible to extract reliable binding parameters from single ITC experiments. Ca2+ affinity is often too high, and Mg2+ affinity is invariably too low. Moreover, least-squares minimization of multisite systems may not afford a unique fit because of strong parameter correlations. This chapter outlines a strategy for analyzing two-site systems that overcomes these obstacles. The method--which involves simultaneous, or global, least-squares analysis of direct and competitive ITC data--yields binding parameters for both Ca2+ and Mg2+. Application of the method is demonstrated for two systems. The S55D/E59D variant of rat alpha-parvalbumin, noteworthy for its elevated metal ion affinity, binds divalent ions noncooperatively and is amenable to analysis using an independent two-site model. On the other hand, Phl p 7, a pollen-specific EF-hand protein from timothy grass, binds Ca2+ with positive cooperativity. Divalent ion-binding data for the protein must be analyzed using a two-site Adair model.

  11. Thermodynamics of binding of divalent magnesium and manganese to uridine phosphates: implications for diabetes-related hypomagnesaemia and carbohydrate biocatalysis

    Directory of Open Access Journals (Sweden)

    Pohl Nicola L

    2008-07-01

    Full Text Available Abstract Background Although the necessity of divalent magnesium and manganese for full activity of sugar nucleotidyltransferases and glycosyltransferases is well known, the role of these metal cations in binding the substrates (uridine 5'-triphosphate, glucose-1-phosphate, N-acetylglucosamine-1-phosphate, and uridine 5'-diphosphate glucose, products (uridine 5'-diphosphate glucose, uridine 5'-diphosphate N-acetylglucosamine, pyrophosphate, and uridine 5'-diphosphate, and/or enzyme is not clearly understood. Results Using isothermal titration calorimetry we have studied the binding relationship between the divalent metals, magnesium and manganese, and uridine 5'-phosphates to determine the role these metals play in carbohydrate biosynthesis. It was determined from the isothermal titration calorimetry (ITC data that Mg+2 and Mn+2 are most tightly bound to PPi, Kb = 41,000 ± 2000 M-1 and 28,000 ± 50,000 M-1 respectively, and UTP, Kb = 14,300 ± 700 M-1 and 13,000 ± 2,000 M-1 respectively. Conclusion Our results indicate that the formal charge state of the phosphate containing substrates determine the binding strength. Divalent metal cations magnesium and manganese showed similar trends in binding to the sugar substrates. Enthalpy of binding values were all determined to be endothermic except for the PPi case. In addition, entropy of binding values were all found to be positive. From this data, we discuss the role of magnesium and manganese in both sugar nucleotidyltransferase and glycosyltransferase reactions, the differences in metal-bound substrates expected under normal physiological metal concentrations and those of hypomagnesaemia, and the implications for drug design.

  12. Metals from the ritual site of Shaitanskoye Ozero II (Sverdlovsk Oblast, Russia

    Directory of Open Access Journals (Sweden)

    Nikolaevna Korochkova, Olga

    2010-12-01

    Full Text Available The present article describes materials from the ritual site of Shaitanskoye Ozero II, Sverdlovsk Oblast. Few excavations carried out at the site measuring less than 240 sq. m in size, yielded more than 160 bronze artifacts: utensils, weapons, rolled copper ornaments, and abundant smelting and casting waste. Apart from Seima-Turbino (celts and laminar knives and Eurasian types (daggers with cast hilts, truncated knives with guards, fluted bracelets and rings, several metal artifacts were revealed manufactured in the style of the Samus-Kizhirovo tradition. Bronze artifacts, stone knives and scrapers, and numerous arrowheads are accompanied by ceramics of the Koptyaki type. Metals use mainly a copper-tin alloy. This assemblage is shown to be relevant to the local tradition of metalworking, which, in this particular region, was comparatively ancient having been left uninterrupted by the rapid migrations of the Seima-Turbino people. In addition, the assemblage indicates the sources from which post-Seima artifacts reached the Alakul people. These artifacts may also have been linked with a large metalworking center located in the Middle Urals.

    Este artículo describe los materiales del sitio ritual de Shaitanskoye Ozero II, Provincia de Sverdlovsk. Las reducidas excavaciones emprendidas en el lugar con superficie inferior a los 240 m2 han entregado más de 160 objetos de bronce: utensilios, armas, adornos en espiral de cobre y abundantes residuos de la fusión y el trabajo del metal. Además de tipos Seima-Turbino (hachas tubulares y cuchillos planos y Euroasiáticos (puñales de mango fundido, cuchillos con empuñadura de lengüeta, brazaletes y anillos acanalados, varios artefactos metálicos resultaron manufacturados según el estilo de la tradición Samus-Kizhirovo. Los artefactos de bronce, los líticos (cuchillos, raspadores y numerosas puntas de flecha están acompañados por cerámicos de tipo Koptyaki. El metal es

  13. Role of direct reactivity with metals in chemoprotection by N-acetylcysteine against chromium(VI), cadmium(II), and cobalt(II).

    Science.gov (United States)

    Luczak, Michal W; Zhitkovich, Anatoly

    2013-12-01

    The antioxidant N-acetylcysteine (NAC) is widely used for the assessment of the role of reactive oxygen species (ROS) in various biological processes and adverse drug reactions. NAC has been found to effectively inhibit the toxicity of carcinogenic metals, which was attributed to its potent ROS-suppressive properties. However, the absence of redox activity among some metals and findings from genetic models suggested a more diverse, smaller role of oxidative stress in metal toxicity. Here, we examined mechanisms of chemoprotection by NAC against Cd(II), Co(II), and Cr(VI) in human cells. We found that NAC displayed a broad-spectrum chemoprotective activity against all three metals, including suppression of cytotoxicity, apoptosis, p53 activation, and HSP72 and HIF-1α upregulation. Cytoprotection by NAC was independent of cellular glutathione. NAC strongly inhibited the uptake of all three metals in histologically different types of human cells, explaining its high chemoprotective potential. A loss of Cr(VI) accumulation by cells was caused by NAC-mediated extracellular reduction of chromate to membrane-impermeative Cr(III). Suppression of Co(II) uptake resulted from a rapid formation of Co(II)-NAC conjugates that were unable to enter cells. Our results demonstrate that NAC acts through more than one mechanism in preventing metal toxicity and its chemoprotective activity can be completely ROS-independent. Good clinical safety and effectiveness in Co(II) sequestration suggest that NAC could be useful in the prevention of tissue accumulation and toxic effects of Co ions released by cobalt-chromium hip prostheses.

  14. Metal Ion Selectivity of Kojate Complexes: A Theoretical Study

    Directory of Open Access Journals (Sweden)

    Sarita Singh

    2013-01-01

    Full Text Available Density functional calculations have been performed on four-coordinate kojate complexes of selected divalent metal ions in order to determine the affinity of the metal ions for the kojate ion. The complexation reactions are characterized by high energies, showing that they are highly exothermic. It is found that Ni(II exhibits the highest affinity for the kojate ion, and this is attributed to the largest amount of charge transfer from the ligand to the metal ion. The Ni(II complex has distorted square planar structure. The HOMOs and LUMOs of the complexes are also discussed. All complexes display a strong band at ~1500 cm−1 corresponding to the stretching frequency of the weakened carbonyl bond. Comparison of the complexation energies for the two steps shows that most of the complexation energy is realized in the first step. The energy released in the second step is about one-third that of the first step.

  15. IrII(ethene): metal or carbon radical? Part II: oxygenation via iridium or direct oxygenation at ethene?

    Science.gov (United States)

    Hetterscheid, Dennis G H; Bens, Mariska; de Bruin, Bas

    2005-03-07

    Treatment of [(Me3tpa)IrII(ethene)]2+ (Me(3)tpa =N,N,N-tri(6-methyl-2-pyridylmethyl)amine)(1(2+)) with dioxygen in weakly coordinating solvents results in formation of [(Me3tpa)IrIII(ethene)(superoxo)]2+ (4a2+). In the presence of DMPO (DMPO = 5,5-dimethyl-2-pyrrolidine-1-oxide) DMPO is substituted for ethene, and subsequently oxidized to DMPOX by the superoxo fragment to give [(Me3tpa)IrIII(DMPOX)]2+ (7(2+); DMPOX = 5,5-dimethyl-2-pyrrolidone-1-oxide). In acetonitrile, in the absence of DMPO, oxygenation of 1(2+) to [(Me3tpa)IrIII(formylmethyl)(MeCN)]2+ (2(2+)) is observed. In the presence of DMPO the formation of 2(2+) and 7(2+) is competing. Oxygenation of 1(2+) to 2(2+) may proceed via 4a(2+), involving an insertion mechanism at the metal. However, a mechanism based on olefin ligand non-innocence seems a reasonable alternative. This involves formation of acetonitrile adduct [(Me3tpa)Ir(ethene)(MeCN)]2+ (3(2+)), which has a significant metalla-ethyl radical (IrIII-CH2CH2*) character, allowing attack of 3O2 directly at the ethene ligand. Both pathways are discussed on the basis of experimental observations and DFT geometry optimizations.

  16. Synthesis, spectroscopic characterization, DFT optimization and biological activities of Schiff bases and their metal (II) complexes

    Science.gov (United States)

    Rauf, Abdur; Shah, Afzal; Munawar, Khurram Shahzad; Khan, Abdul Aziz; Abbasi, Rashda; Yameen, Muhammad Arfat; Khan, Asad Muhammad; Khan, Abdur Rahman; Qureshi, Irfan Zia; Kraatz, Heinz-Bernhard; Zia-ur-Rehman

    2017-10-01

    A Novel Schiff base, 3-(((4-chlorophenyl)imino)methyl)benzene-1,2-diol (HL1) was successfully synthesized along with a structurally similar Schiff base 3-(((4-bromophenyl)imino)methyl)benzene-1,2-diol (HL2). Both the Schiff bases were used to synthesize their zinc (II) and cobalt (II) complexes. These compounds were characterized by FTIR, 1H NMR, 13C NMR and elemental analysis. Metal complexes were confirmed by TGA. Crystals of Schiff bases were also characterized by X-ray analysis and experimental parameters were found in line with the theoretical parameters. Quantum mechanical approach was also used to fine useful structural parameters and to ensure the geometry of metal complexes. The photometric behaviors of all the synthesized compounds were investigated in a wide pH range using BR buffers. The appearance of isosbestic points indicated the existence of Schiff bases in more than one isomeric form. Moreover, these compounds were screened for enzyme inhibition; antibacterial, cytotoxic and in vivo antidiabetic activities and compounds were found active against one or other activity. Results indicate that ZnL22 is a good inhibitor of alkaline phosphatase enzyme and possess highest potential against diabetes, blood cholesterol level and cancer cells. This effort just provides preliminary data for some biological properties. Further investigations are required to precisely determine mechanistic pathways of their use towards drug development.

  17. Structural Insights into Divalent Cation Modulations of ATP-Gated P2X Receptor Channels

    Directory of Open Access Journals (Sweden)

    Go Kasuya

    2016-02-01

    Full Text Available P2X receptors are trimeric ATP-gated cation channels involved in physiological processes ranging widely from neurotransmission to pain and taste signal transduction. The modulation of the channel gating, including that by divalent cations, contributes to these diverse physiological functions of P2X receptors. Here, we report the crystal structure of an invertebrate P2X receptor from the Gulf Coast tick Amblyomma maculatum in the presence of ATP and Zn2+ ion, together with electrophysiological and computational analyses. The structure revealed two distinct metal binding sites, M1 and M2, in the extracellular region. The M1 site, located at the trimer interface, is responsible for Zn2+ potentiation by facilitating the structural change of the extracellular domain for pore opening. In contrast, the M2 site, coupled with the ATP binding site, might contribute to regulation by Mg2+. Overall, our work provides structural insights into the divalent cation modulations of P2X receptors.

  18. Evaluación del poder biosorbente de cáscara de naranja para la eliminación de metales pesados, Pb (II) y Zn (II)

    OpenAIRE

    Anahí Fernanda Cardona Gutiérrez; Dulce Diana Cabañas Vargas; Alejando Zepeda Pedreguera

    2013-01-01

    En el presente trabajo se investigó la biosorción de Pb (II) y Zn (II) por biomasa de cáscara de naranjas secas, trituradas, con y sin tratamiento de reticulación (con CaCl2). El objetivo general fue evaluar la capacidad de biosorción de la cáscara de naranja para la eliminación de metales pesados y el porcentaje de remoción de dichos metales. Se variaron 7 parámetros fisicoquímicos (pH, tamaño de partícula de la biomasa, concentración del contaminante -metal-, cantidad de la biomasa, tempera...

  19. Microbial reduction of chromium from the hexavalent to divalent state

    Science.gov (United States)

    Daulton, Tyrone L.; Little, Brenda J.; Jones-Meehan, Joanne; Blom, Douglas A.; Allard, Lawrence F.

    2007-02-01

    We demonstrate that Shewanella oneidensis, a metal-reducing bacteria species with cytoplasmic-membrane-bound reductases and remarkably diverse respiratory capabilities, reduced Cr(VI) to Cr(II) in anaerobic cultures where chromate was the sole terminal electron acceptor. Individual cell microanalysis by transmission electron microscopy (TEM) using electron energy-loss spectroscopy (EELS) and energy dispersive X-ray spectroscopy (EDXS) demonstrates Cr(II) concentrated near the cytoplasmic membrane, suggesting the terminal reduction pathway is intracellularly localized. Further, estimated cellular Cr(II) concentrations are relatively high at upwards of 0.03-0.09 g Cr/g bacterium. Accumulation of Cr(II) is observed in S. oneidensis cells prior to the formation of submicron-sized precipitates of insoluble Cr(III) on their surfaces. Furthermore, under anaerobic conditions, Cr(III) precipitates that encrust cells are shown to contain Cr(II) that is likely bound in the net negatively charged extracellular biopolymers which can permeate the surfaces of the precipitates. In otherwise nearly identical incubations, Cr(III) precipitate formation was observed in cultures maintained anaerobic with bubbled nitrogen but not in three replicate cultures in an anaerobic chamber.

  20. Spectroscopic, thermal and biological studies of coordination compounds of sulfasalazine drug: Mn(II), Hg(II), Cr(III), ZrO(II), VO(II) and Y(III) transition metal complexes

    Indian Academy of Sciences (India)

    M G Abd El-Wahed; M S Refat; S M El-Megharbel

    2009-04-01

    The complexations of sulfasalazine (H3Suz) with some of transition metals have been investigated. Three types of complexes, [Mn(HSuz)-2(H2O)4].2H2O, [M(HSuz)-2(H2O)2].H2O (M = Hg(II), ZrO(II) and VO(II), = 4, 8 and 6, respectively) and [M(HSuz)-2(Cl)(H2O)3].H2O (M = Cr(III) and Y(III), = 5 and 6, respectively) were obtained and characterized by physicochemical and spectroscopic methods. The IR spectra of the complexes suggest that the sulfasalazine behaves as a monoanionic bidentate ligand. The thermal decomposition of the complexes as well as thermodynamic parameters ( *}, *, * and *) were estimated using Coats–Redfern and Horowitz–Metzger equations. In vitro antimicrobial activities of the H3Suz and the complexes were tested.

  1. Studies on metal-organic frameworks of Cu(II) with isophthalate linkers for hydrogen storage.

    Science.gov (United States)

    Yan, Yong; Yang, Sihai; Blake, Alexander J; Schröder, Martin

    2014-02-18

    Hydrogen (H2) is a promising alternative energy carrier because of its environmental benefits, high energy density, and abundance. However, development of a practical storage system to enable the "Hydrogen Economy" remains a huge challenge. Metal-organic frameworks (MOFs) are an important class of crystalline coordination polymers constructed by bridging metal centers with organic linkers. MOFs show promise for H2 storage owing to their high surface area and tuneable properties. In this Account, we summarize our research on novel porous materials with enhanced H2 storage properties and describe frameworks derived from 3,5-substituted dicarboxylates (isophthalates) that serve as versatile molecular building blocks for the construction of a range of interesting coordination polymers with Cu(II) ions. We synthesized a series of materials by connecting linear tetracarboxylate linkers to {Cu(II)2} paddlewheel moieties. These materials exhibit high structural stability and permanent porosity. Varying the organic linker modulates the pore size, geometry, and functionality to control the overall H2 adsorption. Our top-performing material in this series has a H2 storage capacity of 77.8 mg g(-1) at 77 K, 60 bar. H2 adsorption at low, medium, and high pressures correlates with the isosteric heat of adsorption, surface area, and pore volume, respectively. Another series, using tribranched C3-symmetric hexacarboxylate ligands with Cu(II), gives highly porous (3,24)-connected frameworks incorporating {Cu(II)2} paddlewheels. Increasing the length of the hexacarboxylate struts directly tunes the porosity of the resultant material from micro- to mesoporosity. These materials show exceptionally high H2 uptakes owing to their high surface area and pore volume. The first member of this family reported adsorbs 111 mg g(-1) of H2, or 55.9 g L(-1), at 77 K, 77 bar, while at 77 K, 1 bar, the material adsorbs 2.3 wt % H2. We and others have since achieved enhanced H2 adsorption in these

  2. Synthesis, characterization and biological activity of ferrocene-based Schiff base ligands and their metal (II) complexes

    Science.gov (United States)

    Liu, Yu-Ting; Lian, Gui-Dan; Yin, Da-Wei; Su, Bao-Jun

    Metal (II) complexes derived from S-benzyl-N-(1-ferrocenyl-3-(4-methylbenzene)acrylketone) dithiocarbazate; HL1, S-benzyl-N-(1-ferrocenyl-3-(4-chlorobenzene)acrylketone)dithiocarbazate; HL2, all the compounds were characterized using various spectroscopic techniques. The molar conductance data revealed that the chelates were non-electrolytes. IR spectra showed that the Schiff bases were coordinated to the metal ions in a bidentate manner with N, S donor sites. The ligands and their metal complexes have been screened for in vitro antibacterial, antifungal properties. The result of these studies have revealed that zinc (II) complexes 6 and 13 of both the ligands and copper (II) complexes 9 of the HL2 were observed to be the most active against all bacterial strains, antifungal activity was overall enhanced after complexation of the ligands.

  3. A plasmid containing the human metallothionein II gene can function as an antibody-assisted electrophoretic biosensor for heavy metals.

    Science.gov (United States)

    Wooten, Dennis C; Starr, Clarise R; Lyon, Wanda J

    2016-01-01

    Different forms of heavy metals affect biochemical systems in characteristic ways that cannot be detected with typical metal analysis methods like atomic absorption spectrometry. Further, using living systems to analyze interaction of heavy metals with biochemical systems can be laborious and unreliable. To generate a reliable easy-to-use biologically-based biosensor system, the entire human metallothionein-II (MT-II) gene was incorporated into a plasmid (pUC57-MT) easily replicated in Escherichia coli. In this system, a commercial polyclonal antibody raised against human metal-responsive transcription factor-1 protein (MTF-1 protein) could modify the electrophoretic migration patterns (i.e. cause specific decreases in agarose gel electrophoretic mobility) of the plasmid in the presence or absence of heavy metals other than zinc (Zn). In the study here, heavy metals, MTF-1 protein, and polyclonal anti-MTF-1 antibody were used to assess pUC57-MT plasmid antibody-assisted electrophoretic mobility. Anti-MTF-1 antibody bound both MTF-1 protein and pUC57-MT plasmid in a non-competitive fashion such that it could be used to differentiate specific heavy metal binding. The results showed that antibody-inhibited plasmid migration was heavy metal level-dependent. Zinc caused a unique mobility shift pattern opposite to that of other metals tested, i.e. Zn blocked the antibody ability to inhibit plasmid migration, despite a greatly increased affinity for DNA by the antibody when Zn was present. The Zn effect was reversed/modified by adding MTF-1 protein. Additionally, antibody inhibition of plasmid mobility was resistant to heat pre-treatment and trypsinization, indicating absence of residual DNA extraction-resistant bacterial DNA binding proteins. DNA binding by anti-DNA antibodies may be commonly enhanced by xenobiotic heavy metals and elevated levels of Zn, thus making them potentially effective tools for assessment of heavy metal bioavailability in aqueous solutions and

  4. Metal-pyrazolyl diazine interaction: synthesis, structure and electrochemistry of binuclear transition metal(II) complexes derived from an 'end-off' compartmental Schiff base ligand.

    Science.gov (United States)

    Budagumpi, Srinivasa; Revankar, Vidyanand K

    2010-09-15

    Pyrazolyl diazine (mu-NN) bridged late first row transition metal(II) complexes have been prepared by the interaction of metal(II) chlorides with an 'end-off' compartmental Schiff base ligand. The ligand system has a strong diazine bridging component and obtained as a condensation product between 1H-pyrazole-3,5-dicarbohydrazide and 3-acetylcoumarin in absolute ethanol. All synthesized compounds are characterized on the basis of various spectral and analytical techniques. Complexes are found to be non-electrolytes and monomeric in nature. The magnetic exchange interactions are very weak because of the more electronegative exogenous chloride, though diazine bridging group bring metal centers in a close proximity.

  5. Synthesis, characterization, electrochemical and biological studies on some metal(II) Schiff base complexes containing quinoxaline moiety

    Science.gov (United States)

    Justin Dhanaraj, Chellaian; Johnson, Jijo

    2014-01-01

    Novel Co(II), Ni(II), Cu(II) and Zn(II) complexes of Schiff base derived from quinoxaline-2,3-(1,4H)-dione and 4-aminoantipyrine (QDAAP) were synthesized. The ligand and its complexes were characterized by elemental analyses, molar conductance, magnetic susceptibility measurements, FTIR, UV-Vis., mass and 1H NMR spectral studies. The X band ESR spectrum of the Cu(II) complex at 300 and 77 K were also recorded. Thermal studies of the ligand and its complexes show the presence of coordinated water in the Ni(II) and Zn(II) complexes. The coordination behavior of QDAAP is also discussed. All the complexes are mono nuclear and tetrahedral geometry was found for Co(II) complex. For the Ni(II) and Zn(II) complexes, octahedral geometry was assigned and for the Cu(II) complex, square planar geometry has been suggested. The grain size of the complexes was estimated using powder XRD. The surface morphology of the compounds was studied using SEM analysis. Electrochemical behavior of the synthesized complexes in DMF at room temperature was investigated by cyclic voltammetry. The in vitro biological screening of QDAAP and its metal complexes were tested against bacterial species Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. The fungal species include Aspergillus niger, Aspergillus flavus and Candida albicans. The DNA cleavage activity of QDAAP and its complexes were also discussed.

  6. An unprecedented Co(II) cuboctahedron as the secondary building unit in a Co-based metal-organic framework.

    Science.gov (United States)

    Holmberg, Rebecca J; Kay, Marika; Korobkov, Ilia; Kadantsev, Eugene; Boyd, Peter G; Aharen, Tomoko; Desgreniers, Serge; Woo, Tom K; Murugesu, Muralee

    2014-05-25

    A cubic metal-organic framework with an unprecedented octanuclear secondary building unit (SBU) was isolated. The obtained SBU is composed of 8 Co(II) ions at each vertex, 6 μ4-OH groups at each face, and 12 cpt(-) ligands framing the metal core. The cuboctahedra arrange in a ubt framework topology, eliciting a highly symmetrical MOF structure. Magnetic measurements as well as DFT calculations on this crystalline MOF reveal intramolecular antiferromagnetic coupling between Co(II) ions in the octanuclear SBU.

  7. MODIFICATION OF KELUD VOLCANIC ASH 2014 AS SELECTIVE ADSORBENT MATERIAL FOR COPPER(II METAL ION

    Directory of Open Access Journals (Sweden)

    Susila Kristianingrum

    2017-01-01

      This research aims to prepare an adsorbent from Kelud volcanic ash for better Cu(II adsorption efficiency than Kiesel gel 60G E'Merck. Adsorbent synthesis was done by dissolving 6 grams of volcanic ash activated 700oC 4 hours and washed with HCl 0.1 M into 200 ml of 3M sodium hydroxide with stirring and heating of 100 °C for 1 hour. The filtrate sodium silicate was then neutralized using sulfuric acid. The mixture was allowed to stand for 24 hours then filtered and washed with aquaDM, then dried and crushed. The procedure is repeated for nitric acid, acetic acid and formic acid with a contact time of 24 hours. The products were then characterized using FTIR and XRD, subsequently determined acidity, moisture content, and tested for its adsorption of the ion Cu (II with AAS. The results showed that the type of acid that produced highest rendemen is AK-H2SO4-3M ie 36.93%, acidity of the adsorbent silica gel synthesized similar to Kiesel gel 60G E'Merck ie adsorbent AK-CH3COOH-3M and the water content of the silica gel adsorbent synthesized similar to Kiesel gel 60G E'Merck ie adsorbent AK-H2SO4-2 M. The character of the functional groups of silica gel synthesized all have similarities with Kiesel gel 60G E'Merck as a comparison. Qualitative analysis by XRD for all modified adsorbent showed a dominant peak of SiO2 except adsorbent AK-H2SO4 amorphous and chemical bonds with FTIR indicates that it has formed a bond of Si-O-Si and Si-OH. The optimum adsorption efficiency of the metal ions Cu(II obtained from AK-H2SO4-5M adsorbent that is equal to 93.2617% and the optimum adsorption capacity of the Cu(II metal ions was obtained from the adsorbent AK-CH3COOH-3M is equal to 2.4919 mg/ g.   Keywords: adsorbents, silica gel, adsorption, kelud volcanic ash

  8. Stabilization of polymer gels against divalent ion-induced syneresis

    Energy Technology Data Exchange (ETDEWEB)

    Albonico, Paola; Lockhart, Thomas P. [Eniricerche SpA, San Donato, Milan (Italy)

    1997-07-15

    Polymer solutions and polymer gels are unstable to extended ageing in divalent cation-rich brines at elevated temperature. This paper shows that low-molecular-weight compounds that complex strongly with Ca{sup 2+} and Mg{sup 2+} are capable of neutralizing their destabilizing influence on polymer solubility and of inhibiting the syneresis of crosslinked acrylamide polymer gels in hard brines. The solubility of the inhibitor-divalent ion complexes formed in hard brine at elevated temperature have also been examined. The results obtained offer the possibility to extend significantly the upper temperature limit for the use of polyacrylamides and acrylamide copolymers in brines in both polymer flooding and polymer gel treatments

  9. Bioremediation of heavy metals by growing hyperaccumulaor endophytic bacterium Bacillus sp. L14.

    Science.gov (United States)

    Guo, Hanjun; Luo, Shenglian; Chen, Liang; Xiao, Xiao; Xi, Qiang; Wei, Wanzhi; Zeng, Guangming; Liu, Chengbin; Wan, Yong; Chen, Jueliang; He, Yejuan

    2010-11-01

    Heavy metal bioremediation by a multi-metal resistant endophytic bacteria L14 (EB L14) isolated from the cadmium hyperaccumulator Solanum nigrum L. was characterized for its potential application in metal treatment. 16S rDNA analysis revealed that this endophyte belonged to Bacillus sp. The hormesis of EB L14 were observed in presence of divalent heavy metals (Cu (II), Cd (II) and Pb (II)) at a relatively lower concentration (10mg/L). Such hormesis was the side effect of abnormal activities increases of ATPase which was planned to provide energy to help EB L14 reduce the toxicity of heavy metals by exporting the cations. Within 24h incubation, EB L14 could specifically uptake 75.78%, 80.48%, 21.25% of Cd (II), Pb (II) and Cu (II) under the initial concentration of 10mg/L. However, nearly no chromium uptake was observed. The mechanism study indicated that its remediation efficiencies may be greatly promoted through inhibiting the activities of ATPase. The excellent adaptation abilities and promising remediation efficiencies strongly indicated the superiority of this endophyte in heavy metal bioremediation at low concentrations, which could be useful for developing efficient metal removal system.

  10. Simulation of the influence of EDTA on the sorption of heavy metals by humic acids

    Science.gov (United States)

    Kropacheva, T. N.; Didik, M. V.; Kornev, V. I.

    2015-04-01

    The results of mathematical simulation of sorption equilibria with the participation of divalent cations of heavy metals (HMs), chelant (EDTA), and insoluble forms of humic acids (HAs) are discussed. It is shown that the formation of chelates of metals with EDTA in solutions results in the decreasing sorption of the metals by humic acids. We also analyzed the effect of the acidity of the medium and the HM: EDTA: HA ratio (in a wide range) on the desorption of metals. The desorbing effect of EDTA on the metals is the highest at pH 3-5 and increases with an increase in the concentration of EDTA and a decrease in the concentration of HAs. With respect to the remobilization of metals under the impact of EDTA, the metal cations can be arranged into the following sequence: Cu(II) > Ni(II) > Pb(II) ≫ Cd(II) > Co(II) > Zn(II). The obtained data have been used to analyze the remobilization / extraction of HMs from soils with a high content of humic substances.

  11. Coordination modes of a schiff base pentadentate derivative of 4-aminoantipyrine with cobalt(II), nickel(II) and copper(II) metal ions: synthesis, spectroscopic and antimicrobial studies.

    Science.gov (United States)

    Chandra, Sulekh; Jain, Deepali; Sharma, Amit Kumar; Sharma, Pratibha

    2009-01-01

    Transition metal complexes of Co(II), Ni(II) and Cu(II) metal ions with general stoichiometry [M(L)X]X and [M(L)SO(4)], where M = Co(II), Ni(II) and Cu(II), L = 3,3'-thiodipropionic acid bis(4-amino-5-ethylimino-2,3-dimethyl-1-phenyl-3-pyrazoline) and X = NO(3)(-), Cl(-) and OAc(-), have been synthesized and structurally characterized by elemental analyses, molar conductance measurements, magnetic susceptibility measurements and spectral techniques like IR, UV and EPR. The nickel(II) complexes were found to have octahedral geometry, whereas cobalt(II) and copper(II) complexes were of tetragonal geometry. The covalency factor (beta) and orbital reduction factor (k) suggest the covalent nature of the complexes. The ligand and its complexes have been screened for their antifungal and antibacterial activities against three fungi, i.e. Alternaria brassicae, Aspergillus niger and Fusarium oxysporum and two bacteria, i.e. Xanthomonas compestris and Pseudomonas aeruginosa.

  12. Nickel(II) oxide nanostructure derived from metal-organic frameworks and its adsorption capability

    Science.gov (United States)

    Ru, Shuai; Xu, Lina; Xiao, Hongping; Li, Xinhua

    2016-11-01

    Nanosized nickel(II) oxide (NiO) was obtained by oxidation of ([(Ni2(nic)4(H2O)] n , nic = nicotinic acid), a metal-organic framework (MOF), at 350 °C. Nanosized NiO assembled to form block NiO having a mesoporous structure similar to the porous structure of activated carbon block. This bulk NiO exhibits excellent adsorbing capability, with 100% higher adsorption capacities than the [(Ni2(nic)4(H2O)] n MOF towards toluene and water steam; therefore, it can find potential application in gas adsorption. Moreover, this bulk NiO can be synthesized using a facile, environment-friendly, and cost-effective method, and exhibits excellent hydrothermal stability, which is not commonly observed for MOFs.

  13. A microporous Zn(II)-MOF with open metal sites: structure and selective adsorption properties.

    Science.gov (United States)

    Zheng, Xiaofang; Huang, Yumei; Duan, Jingui; Wang, Chenggang; Wen, Lili; Zhao, Jinbo; Li, Dongfeng

    2014-06-14

    A three-dimensional microporous framework, Zn(II)-MOF [Zn(HPyImDC)(DMA)]n (1) (H3PyImDC = 2-(pyridine-4-yl)-1H-4,5-imidazoledicarboxylic, DMA = N,N'-dimethylacetamide), with open metal sites and small-sized pores, exhibits excellent selective capture of CO2 over N2 and CH4 at 273 K, as well as alcohols from water. The excellent CO2 adsorption selectivity of 1 allows its potential use in the capture of CO2 from industrial flue gas or the removal of CO2 from natural gas. More interestingly, compound represents the rare case of porous materials separating propanol isomers, which may be caused by the relative flexibility of the linear n-propanol considering that both n-propanol and i-propanol have similar kinetic diameters.

  14. Surface complexation of heavy metal cations on clay edges: insights from first principles molecular dynamics simulation of Ni(II)

    Science.gov (United States)

    Zhang, Chi; Liu, Xiandong; Lu, Xiancai; He, Mengjia; Jan Meijer, Evert; Wang, Rucheng

    2017-04-01

    Aiming at an atomistic mechanism of heavy metal cation complexing on clay surfaces, we carried out systematic first principles molecular dynamics (FPMD) simulations to investigate the structures, free energies and acidity constants of Ni(II) complexes formed on edge surfaces of 2:1 phyllosilicates. Three representative complexes were studied, including monodentate complex on the tbnd SiO site, bidentate complex on the tbnd Al(OH)2 site, and tetradentate complex on the octahedral vacancy where Ni(II) fits well into the lattice. The complexes structures were characterized in detail. Computed free energy values indicate that the tetradentate complex is significantly more stable than the other two. The calculated acidity constants indicate that the tetradentate complex can get deprotonated (pKa = 8.4) at the ambient conditions whereas the other two hardly deprotonate due to extremely high pKa values. By comparing with the 2 Site Protolysis Non Electrostatic Surface Complexation and Cation Exchange (2SPNE SC/CE) model, the vacant site has been assigned to the strong site and the other two to the weak site, respectively. Thus a link has been built between atomistic simulations and macroscopic experiments and it is deduced that this should also apply to other heavy metal cations based on additional simulations of Co(II) and Cu(II) and previous simulations of Fe(II) and Cd(II)). This study forms a physical basis for understanding the transport and fixation of heavy metal elements in many geologic environments.

  15. HIGH-RESOLUTION SPECTROSCOPY OF EXTREMELY METAL-POOR STARS IN THE LEAST EVOLVED GALAXIES: BOÖTES II

    Energy Technology Data Exchange (ETDEWEB)

    Ji, Alexander P.; Frebel, Anna [Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Simon, Joshua D. [Observatories of the Carnegie Institution of Washington, 813 Santa Barbara St., Pasadena, CA 91101 (United States); Geha, Marla, E-mail: alexji@mit.edu [Astronomy Department, Yale University, New Haven, CT 06520 (United States)

    2016-01-20

    We present high-resolution Magellan/MIKE spectra of the four brightest confirmed red giant stars in the ultra-faint dwarf galaxy Boötes II (Boo II). These stars all inhabit the metal-poor tail of the Boo II metallicity distribution function. The chemical abundance pattern of all detectable elements in these stars is consistent with that of the Galactic halo. However, all four stars have undetectable amounts of neutron-capture elements Sr and Ba, with upper limits comparable to the lowest ever detected in the halo or in other dwarf galaxies. One star exhibits significant radial velocity variations over time, suggesting it to be in a binary system. Its variable velocity has likely increased past determinations of the Boo II velocity dispersion. Our four stars span a limited metallicity range, but their enhanced α-abundances and low neutron-capture abundances are consistent with the interpretation that Boo II has been enriched by very few generations of stars. The chemical abundance pattern in Boo II confirms the emerging trend that the faintest dwarf galaxies have neutron-capture abundances distinct from the halo, suggesting the dominant source of neutron-capture elements in halo stars may be different than in ultra-faint dwarfs.

  16. Synthesis, structural characterization, thermal and electrochemical studies of the N,N'-bis[(3,4-dichlorophenyl)methylidene]cyclohexane-1,4-diamine and its Cu(II), Co(II) and Ni(II) metal complexes.

    Science.gov (United States)

    Dolaz, Mustafa; McKee, Vickie; Gölcü, Ayşegül; Tümer, Mehmet

    2009-01-01

    In this study, N,N'-bis[(3,4-dichlorophenyl)methylidene]cyclohexane-1,4-diamine (L) and its Cu(II), Co(II) and Ni(II) complexes were prepared and characterized by the analytical and spectroscopic methods. The analytical data show the composition of the metal complex to be [M(2)L(Cl)(4)(H(2)O)(2)], where L is the Schiff base ligand. The conductance data indicate that all the complexes are non-electrolytes. The compound (L) behaves as a monodentate ligand. But, obtained complexes have binuclear nature. The electrochemical properties of the metal complexes are dependent on reversible, irreversible and quasi-reversible redox waves in the anodic and cathodic regions due to oxidation and reduction of the metal ions. The single crystal of the ligand (L) was obtained from CH(3)CN solution. Space group and crystal system of the ligand are P2(1)/C and monoclinic, respectively.

  17. Recovery of high-purity metallic Pd from Pd(II)-sorbed biosorbents by incineration.

    Science.gov (United States)

    Won, Sung Wook; Lim, Areum; Yun, Yeoung-Sang

    2013-06-01

    This work reports a direct way to recover metallic palladium with high purity from Pd(II)-sorbed polyethylenimine-modified Corynebacterium glutamicum biosorbent using a combined method of biosorption and incineration. This study is focused on the incineration part which affects the purity of recovered Pd. The incineration temperature and the amount of Pd loaded on the biosorbent were considered as major factors in the incineration process, and their effects were examined. The results showed that both factors significantly affected the enhancement of the recovery efficiency and purity of the recovered Pd. SEM-EDX and XRD analyses were used to confirm that Pd phase existed in the ash. As a result, the recovered Pd was changed from PdO to zero-valent Pd as the incineration temperature was increased from 600 to 900°C. Almost 100% pure metallic Pd was recovered with recovery efficiency above 99.0% under the conditions of 900°C and 136.9 mg/g.

  18. Reaction dynamics and photochemistry of divalent systems

    Energy Technology Data Exchange (ETDEWEB)

    Davis, H. Floyd [Univ. of California, Berkeley, CA (United States)

    1992-05-01

    Results are presented of molecular beam studies of bimolecular and unimolecular reactions of Ba. Chapter 1 discusses the reaction Ba + NO2. Formation of the dominant BaO(1Σ) + NO products resulted primarily from decay of long-lived Ba+NO2- collision complexes. Secondary mechanisms led to formation of forward scattered, internally excited BaO, and BaNO + O. Do(Ba-NO) = 65±20 kcal/mol. Reactions of ground state and electronically excited Ba with water and alcohols are examined in Chapter 2. Reaction of Ba(1S) + H2O led to BaO + H2, whereas excited state Ba(1D) + H2O reacted to form BaOH + H. Collisions between Ba and CH3OH led to BaOCH3 + H. Radical channels involve H-atom migration and are promoted by excitation of the incident Ba atom. In Chapter 3, reactions of Ba(1S) with ClO22 and O3 are discussed. Again, direct and complex mechanisms were observed. Formation of BaCl + O2 from decomposition of Ba+ClO2- accounted for 10% of total reaction crass section. Although Ba + O3 → BaO + 02 occurs primarily by direct reaction mechanisms, the secondary channel Ba + 03 → BaO2 + 0 involved decay of long lived Ba1+O3- intermediates. Do(Ba-O2) = 120 ±20 kcal/mol. Photodissociation dynamics of NO3 is explored in chapter 4. Visible excitation leads to formation of NO + 02 and NO2 + O. Wavelength dependence of branching ratios is investigated. Do(O-NO2) = 48.55 kcal/mole ;and calculate ΔHf(NO3) = 17.75 kcal/mole (298K). Chapter 5 discusses the photodissociation of OClO in a molecular beam. Although ClO(2II) + O(3P) is dominant, Cl(2P) + O2

  19. ANNUAL REPORT FOR ENVIRONMENTAL MANAGEMENT SCIENCE PROGRAM PROJECT NUMBER 87016 CO-PRECIPITATION OF TRACE METALS IN GROUNDWATER AND VADOSE ZONE CALCITE: IN SITU CONTAINMENT AND STABILIZATION OF STRONTIUM-90 AND OTHER DIVALENT METALS AND RADIONUCLIDES AT ARID WESTERN DOE SITES

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Robert W.; Fujita, Yoshiko; Ferris, F. Grant; Cosgrove, Donna M.; Colwell, F. S.

    2003-06-15

    Radionuclide and metal contaminants such as 90Sr are present beneath U.S. Department of Energy (DOE) lands in both the groundwater (e.g., 100-N area at Hanford, WA) and vadose zone (e.g., Idaho Nuclear Technology and Engineering Center at the Idaho National Engineering and Environmental Laboratory). In situ containment and stabilization of these contaminants is a cost-effective treatment strategy. However, implementing in situ containment and stabilization approaches requires definition of the mechanisms that control contaminant sequestration. We are investigating the in situ immobilization of radionuclides or contaminant metals (e.g., 90Sr) by their facilitated co-precipitation with calcium carbonate in groundwater and vadose zone systems. Our facilitated approach, shown schematically in Figure 1, relies upon the hydrolysis of introduced urea to cause the acceleration of calcium carbonate precipitation (and trace metal co-precipitation) by increasing pH and alkalinity. Subsurface urea hydrolysis is catalyzed by the urease enzyme, which may be either introduced with the urea or produced in situ by ubiquitous subsurface urea hydrolyzing microorganisms. Because the precipitation process tends to be irreversible and many western aquifers are saturated with respect to calcite, the coprecipitated metals and radionuclides will be effectively removed from the aqueous phase over the long-term. Another advantage of the ureolysis approach is that the ammonium ions produced by the reaction can exchange with radionuclides sorbed to subsurface minerals, thereby enhancing the availability of the radionuclides for re-capture in a more stable solid phase (co-precipitation rather than adsorption).

  20. Magnetic and Photochromic Properties of a Manganese(II) Metal-Zwitterionic Coordination Polymer.

    Science.gov (United States)

    Gong, Teng; Yang, Xiao; Sui, Qi; Qi, Yan; Xi, Fu-Gui; Gao, En-Qing

    2016-01-04

    The solvothermal reaction of Mn(ClO4)2, NaN3, and a rigid viologen-tethered tetracarboxylic acid (1,1'-bis(3,5-dicarboxyphenyl)-4,4'-bipyridinium chloride, [H4L]Cl2) led to a coordination polymer of formula [Mn4(L)(N3)6(H2O)2]n. X-ray analysis revealed a 3D coordination structure. The Mn(II) ions are connected by mixed azide and carboxylate bridges to give 2D layers, which are pillared by the viologen tether of the zwitterionic ligand. Magnetic analyses suggested that the compound features antiferromagnetism and field-induced metamagnetism. The compound also shows photochromic and photomagnetic properties. The long-range magnetic ordering is owed to the spin-canting structure of the Mn(II)-azide-carboxylate layer; the photochromism involves the formation of viologen radicals via photoinduced electron transfer, and the photomagnetism is related to the interactions between the metal ion and the photogenerated radicals. The study demonstrates a strategy for the design of new multifunctional materials with photoresponsive properties.

  1. Assembly of three novel metal (II) complexes based on polycarboxylate and 1,10-phenanthroline ligands

    Science.gov (United States)

    Chen, Xiaoli; Qiao, Yali; Gao, Loujun; Cui, Huali; Zhang, Meili; Lv, Junfang

    2013-04-01

    With the principles of crystal engineering, three novel metal(II) complexes, [Cu2(betd)(phen)4].15H2O (1), [Cd4(betd)2(phen)8]ṡ28H2O (2) and {[Co2(betd)(phen)2(H2O)2]·2H2O}n (3) (H4betd = bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid, phen = 1,10-phenanthroline) were synthesized and structurally characterized by elemental analyses, IR spectroscopy, single-crystal X-ray diffraction analyses, TGA, powder XRD and fluorescent measurements. Complex 1 is a binuclear structure, novel water tapes are observed to be encapsulated in the 3D open supramolecular architecture by hydrogen bond interactions. In 2, two pairs of CdII ions joined with two (betd)4- ions to form a cyclic tetranuclear structure. The neighboring tetranuclear units are linked into 2D network through π⋯π stacking interactions. Interestingly, the lattice H2O molecules are joined by strong hydrogen bond interactions generating a wavy water layer, which contacts the 2D network to form 3D supramolecular structure. 3 shows a 2D (4, 4) grid network, which are assembled in an ABAB sequence to 3D supramolecular structures via π⋯π stacking interactions between two central phen ligands from two adjacent sheets and hydrogen bond interactions.

  2. Multiobjective Optimization for Fixture Locating Layout of Sheet Metal Part Using SVR and NSGA-II

    Directory of Open Access Journals (Sweden)

    Yuan Yang

    2017-01-01

    Full Text Available Fixture plays a significant role in determining the sheet metal part (SMP spatial position and restraining its excessive deformation in many manufacturing operations. However, it is still a difficult task to design and optimize SMP fixture locating layout at present because there exist multiple conflicting objectives and excessive computational cost of finite element analysis (FEA during the optimization process. To this end, a new multiobjective optimization method for SMP fixture locating layout is proposed in this paper based on the support vector regression (SVR surrogate model and the elitist nondominated sorting genetic algorithm (NSGA-II. By using ABAQUS™ Python script interface, a parametric FEA model is established. And the fixture locating layout is treated as design variables, while the overall deformation and maximum deformation of SMP under external forces are as the multiple objective functions. First, a limited number of training and testing samples are generated by combining Latin hypercube design (LHD with FEA. Second, two SVR prediction models corresponding to the multiple objectives are established by learning from the limited training samples and are integrated as the multiobjective optimization surrogate model. Third, NSGA-II is applied to determine the Pareto optimal solutions of SMP fixture locating layout. Finally, a multiobjective optimization for fixture locating layout of an aircraft fuselage skin case is conducted to illustrate and verify the proposed method.

  3. Theoretical study of heavy metal Cd, Cu, Hg, and Ni(II) adsorption on the kaolinite(0 0 1) surface

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Jian, E-mail: zhaojian0209@aliyun.com [Institute of Applied Physics and Computational Mathematics, PO Box 8009, Beijing 100088 (China); State Key Laboratory of Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Beijing 100083 (China); He, Man-Chao [State Key Laboratory of Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Beijing 100083 (China)

    2014-10-30

    Highlights: • We investigated the adsorption of Cd, Cu, Hg, and Ni(II) on kaolinite(0 0 1) surface. • The adsorption capabilities of the kaolinite for HM atoms were Ni > Cu > Cd > Hg(II). • The adsorption energy increases with the coverage for Cd, Cu, and Hg(II) atoms. • The adsorption energy decreases with the coverage for Ni(II) atoms. - Abstract: Heavy metal pollution is currently of great concern because it has been recognized as a potential threat to air, water, and soil. Adsorption was one of the most popular methods for the removal of heavy metal. The adsorption of heavy metal Cd, Cu, Hg, and Ni(II) atoms on the hydroxylated (0 0 1) surface of kaolinite was investigated using density-functional theory within the generalized gradient approximation and a supercell approach. The coverage dependence of the adsorption structures and energetics were systematically studied for a wide range of coverage Θ [from 0.11 to 1.0 monolayers (ML)] and adsorption sites. The most stable among all possible adsorption sites for Cd(II) atom was the two-fold bridge site followed by the one-fold top site, and the top site was the most favorite adsorption site for Cu and Ni(II) atoms, while the three-fold hollow site was the most stable adsorption site for Hg(II) atom followed by the two-fold bridge site. The adsorption energy increases with the coverage for Cd, Cu, and Hg(II) atoms, thus indicating the higher stability of surface adsorption and a tendency to the formation of adsorbate islands (clusters) with increasing the coverage. However, the adsorption energy of Ni(II) atoms decreases when increasing the coverage. The adsorption capabilities of the kaolinite clay for the heavy metal atoms were in the order of Ni > Cu > Cd > Hg(II). The other properties of the Cd, Cu, Hg, and Ni(II)/kaolinite(0 0 1) system including the different charge distribution, the lattice relaxation, and the electronic density of states were also studied and discussed in detail.

  4. Nonlinear Color--Metallicity Relations of Globular Clusters. VI. On Calcium II Triplet Based Metallicities of Globular Clusters in Early-type Galaxies

    CERN Document Server

    Chung, Chul; Lee, Sang-Yoon; Lee, Young-Wook

    2016-01-01

    The metallicity distribution function of globular clusters (GCs) in galaxies is a key to understanding galactic formation and evolution. The calcium II triplet (CaT) index has recently become a popular metal abundance indicator thanks to its sensitivity to GC metallicity. Here we revisit and assess the reliability of CaT as a metallicity indicator using our new stellar population synthesis simulations based on empirical, high-resolution fluxes. The model shows that the CaT strength of old ($>$ 10 Gyr) GCs is proportional to ${\\rm [Fe/H]}$ below $-0.5$. In the modest metal-rich regime, however, CaT does not increase anymore with ${\\rm [Fe/H]}$ due to the little contribution from coolest red giant stars to the CaT absorption. The nonlinear nature of the color--$CaT$ relation is confirmed by the observations of GCs in nearby early-type galaxies. This indicates that the CaT should be used carefully when deriving metallicities of metal-rich stellar populations. Our results offer an explanation for the observed sha...

  5. Coordination behaviour and two-dimensional-network formation in poly[[mu-aqua-diaqua(mu5-propane-1,3-diyldinitrilotetraacetato)dilithium(I)cobalt(II)] dihydrate]: the first example of an M(II)-1,3-pdta complex with a monovalent metal counter-ion.

    Science.gov (United States)

    Rychlewska, Urszula; Warzajtis, Beata; Djuran, Milos I; Radanović, Dusanka D; Dimitrijević, Mirjana Dj; Rajković, Sneaeana

    2008-06-01

    The title compound, {[CoLi2(C11H14N2O8)(H2O)3].2H2O}n, constitutes the first example of a salt of the [M(II)(1,3-pdta)](2-) complex (1,3-pdta is propane-1,3-diyldinitrilotetraacetate) with a monopositive cation as counter-ion. Insertion of the Li+ cation could only be achieved through application of the ion-exchange column technique which, however, appeared unsuccessful with other alkali metals and the ammonium cation. The structure contains two tetrahedrally coordinated Li+ cations, an octahedral [Co(1,3-pdta)](2-) anion and five water molecules, two of which are uncoordinated, and is built of two-dimensional layers extending parallel to the (010) lattice plane, the constituents of which are connected by the coordinate bonds. O-H(water)...O hydrogen bonds operate both within and between these layers. The crystal investigated belongs to the enantiomeric space group P2(1) with only one (Lambda) of two possible optical isomers of the [Co(1,3-pdta)](2-) complex. A possible cause of enantiomer separation during crystallization might be the rigidification and polarization of the [M(1,3-pdta)](2-) core, resulting from direct coordination of Li+ cations to three out of four carboxylate groups constituting the 1,3-pdta ligand. The structure of (I) differs considerably from those of the other [M(II)(1,3-pdta)](2-) complexes, in which the charge compensation is realized by means of divalent hexaaqua complex cations. This finding demonstrates a significant structure-determining role of the counter-ions.

  6. Octaammine Eu{sup II} and Yb{sup II} azides and their thermal decompositions to the nitrides

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, Thomas G.; Mogk, Jochen; Conrad, Matthias; Kraus, Florian [Anorganische Chemie, Fluorchemie, Fachbereich Chemie, Philipps-Universitaet Marburg, 35032, Marburg (Germany)

    2016-09-15

    The common preparation for many nitrides is the synthesis from the corresponding metals and nitrogen at quite high temperatures and/or high pressures. Here we present a route to metal nitrides by the use of ammine metal azides under relatively mild conditions. Europium(II) and ytterbium(II) azides are prepared in liquid ammonia at -36 C in form of their temperature-sensitive octaammine complexes. These were investigated by single-crystal X-ray diffraction at low temperatures, and their structures seem to be the first evidence for the existence of homoleptic ammine Eu{sup II} and Yb{sup II} complexes, as well as that the coordination number of these divalent cations can go beyond six with NH{sub 3} ligands. In one of the cases presented here the observed coordination polyhedron is better described as a bicapped trigonal prism (C{sub 2v}), in one case better as square-antiprismatic (D{sub 4d}). Warming of these compounds to room temperature leads to the lanthanoid metal azides still containing approximately 1 equiv. of ammonia. The behaviour of these azides towards further heating was investigated: By very careful and slow decomposition, the nitrides of europium(III) and ytterbium(III) are obtained at only 230 C at ambient pressure. This method may be suitable to obtain other metal nitrides at remarkably low temperatures and pressures. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  7. Outliers from the Mass--Metallicity Relation II: A Sample of Massive Metal-Poor Galaxies from SDSS

    CERN Document Server

    Peeples, Molly S; Stanek, K Z

    2008-01-01

    We present a sample of 42 high-mass low-metallicity outliers from the mass--metallicity relation of star-forming galaxies. These galaxies have stellar masses that span log(M_*/M_sun) ~9.4 to 11.1 and are offset from the mass--metallicity relation by -0.3 to -0.85 dex in 12+log(O/H). In general, they are extremely blue, have high star formation rates for their masses, and are morphologically disturbed. Tidal interactions are expected to induce large-scale gas inflow to the galaxies' central regions, and we find that these galaxies' gas-phase oxygen abundances are consistent with large quantities of low-metallicity gas from large galactocentric radii diluting the central metal-rich gas. We conclude with implications for deducing gas-phase metallicities of individual galaxies based solely on their luminosities, specifically in the case of long gamma-ray burst host galaxies.

  8. A Study of Thermal Aging Effects on Microstructures of Type-II Boundary in Dissimilar Metal Weld Joint

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Seung Chang; Choi, Kyung Joon; Kim, Ji Hyun [Ulsan National Institute of Science and Technology, Ulsan (Korea, Republic of)

    2013-10-15

    Fusion boundary region has complex microstructure because of welding heat and latter heat treatment that cause changes of mechanical property and corrosion resistance of material. Due to this reason, this region has very different characteristic with base metal or filler metal. Therefore, it needs to be more studied. Nelson et al. found type-II boundary which is parallel to fusion boundary in the filler metal within 100μm in dilution zone is a potential crack path for SCC. Mechanism of formation of type-II boundary is not clearly turned out. Nelson et al. suggest that the type-II boundary is created by changing process of solidification from body centered cubic structure of ferrite to face centered cubic structure of austenite at welding process. But further research is required on this region. As nuclear power plant operation time increased, concerns occur about decreased integrity of dissimilar metal weld about SCC due to thermal aging. This study purposes to analyze the detailed microstructure of type-II boundary of Alloy 152 . A533 Gr. B weld joint, applying thermal aging effect simulation of nuclear power plant environment to evaluating integrity of this region about SCC. The microstructure of type-II boundary region of Alloy 152 . A533 Gr. B weld joint had been analyzed with optical microscope (OM), energy dispersive x-ray spectroscope attached to scanning electron microscope (SEM-EDX), Vickers micro-hardness tester. In order to characterize the thermal aging effect on microstructures in the fusion boundary and type-II boundary, the DMWs consisting of Alloy 690-Alloy 152-A533 Gr. B were analyzed with several instruments. Hardness was maximized at narrow zone near type-II boundary. Reason for this phenomenon may include residual stress, precipitate and stiff composition gradient. There are studies which report that SCC is easily propagates at the region with higher hardness, so integrity to SCC at this region must be considered. After heat treatment, nickel

  9. The removal of toxic metals from liquid effluents by ion exchange resins. Part II: cadmium(II/ sulphate/Lewatit TP260

    Directory of Open Access Journals (Sweden)

    Alguacil, F. J.

    2002-10-01

    Full Text Available The adsorption of cadmium (II, from aqueous sulphate solutions, on Lewatit TP260 resin has been investigated in batch equilibrium experiments. The influence of pH and temperature on metal adsorption capacity have also been examined. The kinetic performance of the resin has been assesed and the results have been correlated by the pore diffusion model. The resin has been used in mini-columns to study its performance under dynamics conditions. The desorption of metal ion is achieved using sulphuric acid (0.25M and 0.5M.

    Se estudia la adsorción de cadmio(II, de disoluciones en medio sulfato, sobre la resina Lewatit TP260. La adsorción del metal se ha investigado en función del pH, la temperatura y el tiempo de contacto con la resina. Los estudios cinéticos permiten correlacionar el proceso de intercambio iónico con el modelo de difusión en poro. Se ha empleado el sistema en mini columnas para evaluar el comportamiento de la resina bajo condiciones dinámicas. La desorción del metal se lleva a cabo con disoluciones de ácido sulfúrico (0,25M y 0,5M.

  10. Phenotypic plasticity in Scenedesmus incrassatulus (Chlorophyceae) in response to heavy metals stress.

    Science.gov (United States)

    Peña-Castro, Julián Mario; Martínez-Jerónimo, Fernando; Esparza-García, Fernando; Cañizares-Villanueva, Rosa Olivia

    2004-12-01

    The microalgae genus Scenedesmus is commonly found in freshwater bodies, wastewater facilities and water polluted with heavy metals. Phenotypic plasticity in Scenedesmus has been documented in response to a wide variety of conditions; however, heavy metals have not been comprehensively documented as phenotypic plasticity inducers. In this study, we report the phenotypic plasticity of Scenedesmus incrassatulus (a non-spiny, four-cell coenobium forming species) in response to EC(50) value of copper, cadmium and hexavalent chromium. S. incrassatulus was grown in batch cultures in the presence of each metal. Chlorophyll-a content, cell size, parameters derived from the schematic energy-flux model for photosystem II, and morphotype expressions were recorded. Divalent cation metals induced unicellular forms, and hexavalent chromium produced out-of-shape coenobia corresponding to various stages of autospore formation. The changes induced by divalent metals were interpreted as phenotypic plasticity, because they were always associated to population doublings and were reversible when toxicant pressure was removed (only for Cu). Copper was the best inductor of unicellular forms and also affected significantly all the photosynthetic parameters measured. The developed morphotypes could confer ecological advantages to S. incrassatulus in metal stressed environments.

  11. Peripherally and non-peripherally tetra-benzothiazole substituted metal-free zinc (II) and lead (II) phthalocyanines: Synthesis, characterization, and investigation of photophysical and photochemical properties

    Science.gov (United States)

    Demirbaş, Ümit; Göl, Cem; Barut, Burak; Bayrak, Rıza; Durmuş, Mahmut; Kantekin, Halit; Değirmencioğlu, İsmail

    2017-02-01

    In this study, novel phthalonitrile compounds bearing 2-methylbenzo[d]thiazol-5-yloxy groups (4 and 5) and their peripherally and non-peripherally tetra-substituted metal-free (6 and 7), zinc (II) (8 and 9), and lead (II) (10 and 11) phthalocyanine derivatives were synthesized and characterized for the first time. These novel compounds showed extremely good solubility in most common organic solvents. The novel phthalocyanine compounds presented excellent results from photophysical and photochemical examinations in DMF solution. Especially, the singlet oxygen quantum yield (ΦΔ) values of the substituted zinc (II) phthalocyanines indicate that these compounds have significant potential as photosensitizers in cancer treatment by the photodynamic therapy (PDT) technique. The fluorescence quenching behaviour of these novel phthalocyanine compounds by 1,4-benzoquinone (BQ) was also examined in DMF solution.

  12. Transition metal complexes of neocryptolepine analogues. Part I: Synthesis, spectroscopic characterization, and invitro anticancer activity of copper(II) complexes

    Science.gov (United States)

    Emam, Sanaa Moustafa; El Sayed, Ibrahim El Tantawy; Nassar, Nagla

    2015-03-01

    New generation of copper(II) complexes with aminoalkylaminoneocryptolepine as bidentate ligands has been synthesized and it is characterized by elemental analyses, magnetic moment, spectra (IR, UV-Vis, 1H NMR and ESR) and thermal studies. The IR data suggest the coordination modes for ligands which behave as a bidentate with copper(II) ion. Based on the elemental analysis, magnetic studies, electronic and ESR data, binuclear square planar geometry was proposed for complexes 7a, 7b, square pyramidal for 9a, 9b and octahedral for 8a, 8b, 10a, 10b. The molar conductance in DMF solution indicates that all complexes are electrolyte except 7a and 7b. The ESR spectra of solid copper(II) complexes in powder form showed an axial symmetry with 2B1g as a ground state and hyperfine structure. The thermal stability and degradation of the ligands and their metal complexes were studied employing DTA and TG methods. The metal-free ligands and their copper(II) complexes were tested for their in vitro anticancer activity against human colon carcinoma (HT-29). The results showed that the synthesized copper(II) complexes exhibited higher anticancer activity than their free ligands. Of all the studied copper(II) complexes, the bromo-substituted complex 9b exhibited high anticancer activity at low micromolar inhibitory concentrations (IC50 = 0.58 μM), compared to the other complexes and the free ligands.

  13. Interpretation with a Donnan-based concept of the influence of simple salt concentration on the apparent binding of divalent ions to the polyelectrolytes polystyrenesulfonate and dextran sulfate

    Science.gov (United States)

    Marinsky, J.A.; Baldwin, Robert F.; Reddy, M.M.

    1985-01-01

    It has been shown that the apparent enhancement of divalent metal ion binding to polyions such as polystyrenesulfonate (PSS) and dextran sulfate (DS) by decreasing the ionic strength of these mixed counterion systems (M2+, M+, X-, polyion) can be anticipated with the Donnan-based model developed by one of us (J.A.M.). Ion-exchange distribution methods have been employed to measure the removal by the polyion of trace divalent metal ion from simple salt (NaClO4)-polyion (NaPSS) mixtures. These data and polyion interaction data published earlier by Mattai and Kwak for the mixed counterion systems MgCl2-LiCl-DS and MgCl2-CsCl-DS have been shown to be amenable to rather precise analysis by this model. ?? 1985 American Chemical Society.

  14. Syntheses, structural characterization and spectroscopic studies of cadmium(II)-metal(II) cyanide complexes with 4-(2-aminoethyl)pyridine

    Science.gov (United States)

    Karaağaç, Dursun; Kürkçüoğlu, Güneş Süheyla; Şenyel, Mustafa; Hökelek, Tuncer

    2017-02-01

    Three new cadmium(II)-metal(II) cyanide complexes, [Cd(4aepy)2(H2O)2][Ni(CN)4] (1), [Cd(4aepy)2(H2O)2][Pd(CN)4] (2) and [Cd(4aepy)2(H2O)2][Pt(CN)4] (3) [4aepy = 4-(2-aminoethyl)pyridine], have been synthesized and characterized by elemental, thermal, FT-IR and Raman spectral analyses. The crystal structures of 1 and 2 have been determined by single crystal X-ray diffraction technique, in which they crystallize in the monoclinic system and C2/c space group. The M(II) [M(II) = Ni(II), Pd(II) and Pt(II)] ions are coordinated with the carbon atoms of the four cyanide groups in the square planar geometries and the [M(CN)4]2- ions act as counter ions. The Cd(II) ions display an N4O2 coordination sphere with a distorted octahedral geometry, the nitrogen donors belonging to four molecules of the organic 4aepy that act as unidentate ligands and two oxygen atoms from aqua ligands. 3D supramolecular structures of 1 and 2 were occurred by M⋯π and hydrogen bonding (Nsbnd H⋯N and Osbnd H⋯N) interactions. Vibrational assignments of all the observed bands were given and the spectral properties were also supported the crystal structures of the complexes. A possible decompositions of the complexes were investigated in the temperature range 30-800 °C in the static atmosphere.

  15. Two ligand-functionalized Pb(II) metal-organic frameworks: structures and catalytic performances.

    Science.gov (United States)

    Lin, Xiao-Ming; Li, Ting-Ting; Chen, Lian-Fen; Zhang, Li; Su, Cheng-Yong

    2012-09-14

    A microporous Pb(II) metal-organic framework (MOF) [PbL(2)]·2DMF·6H(2)O (1) has been assembled from a N-oxide and amide doubly functionalized ligand HL (= N-(4-carboxyphenyl)isonicotinamide 1-oxide). Complex 1 features a three-dimensional (3D) framework possessing one-dimensional (1D) rhombic channels with dimensions of 13 × 13 Å(2). The 3D framework is built up from 1D PbO(2) chains that link ligands in parallel fashion to construct single-wall channels. When recrystallizing 1 in a DMSO-DMF mixture (3 : 5 v/v), a new coordination polymer, [PbL(2)]·DMF·2H(2)O (2), was obtained. Complex 2 is also a 3D framework containing 1D rectangular channels, but the channel dimensions become reduced in size to 13 × 8 Å(2) due to reorganization of the Pb(ii) coordination environment. The PbO(2) chains in 2 are reformed to link ligands in a double-wall fashion, significantly reducing the channel size. Even though, the guest exchange study indicates that the DMF molecules in 2 could be replaced with benzene molecules when immersing in benzene solvent, showing single-crystal-to-single-crystal (SC-SC) guest exchange in the solid state and leading to a daughter crystal [PbL(2)]·0.5C(6)H(6)·2H(2)O (2'). Desolvated 1 and 2 display preferential adsorption behaviors of water vapour over CO(2) due to the hydrophilic nature of the channels and the strong host-guest interactions. Catalytic tests indicate that desolvated 1 and 2 have size-selective catalytic activity towards the Knoevenagel condensation reaction.

  16. Liquid Metallic Hydrogen II. A Critical Assessment of Current and Primordial Helium Levels in the Sun

    Directory of Open Access Journals (Sweden)

    Robitaille P.-M.

    2013-04-01

    lar winds which, though highly variable, provide a wealth of data. Evaluations of pr imordial helium levels based on 1 the spectroscopic study of H-II regions and 2 microwav e anisotropy data, re- main highly questionable. Current helium levels, both with in the stars (Robitaille J. C. and Robitaille P.-M. Liquid Metallic Hydrogen III. Interca lation and Lattice Exclusion versus Gravitational Settling, and Their Consequences Rel ative to Internal Structure, Surface Activity, and Solar Winds in the Sun. Progr. Phys. , 2013, v. 2, in press and the universe at large, appear to be overstated. A careful con sideration of available ob- servational data suggests that helium abundances are consi derably lower than currently believed.

  17. Synthesis, characterization, DNA interaction and pharmacological studies of substituted benzophenone derived Schiff base metal(II complexes

    Directory of Open Access Journals (Sweden)

    P. Subbaraj

    2015-03-01

    Full Text Available A new bidentate NO type Schiff base ligand (HL, derived from 2-hydroxy-4-methoxyphenylphenylmethanone with aniline and its metal(II [M = Mn, Co, Ni, Cu and Zn] complexes has been synthesized. The synthesized ligand and the metal(II complexes were structurally characterized by analytical, spectral (FT-IR, UV–vis., 1H NMR, FAB-Mass, TGA/DTA and EPR as well as molar conductance and magnetic studies. All the complexes are non-electrolytes having 1:2 stoichiometry. They adopt tetrahedral and octahedral geometry. Thermal behavior of metal(II complexes (1a–1c shows loss of coordinated water molecules in the first step followed by the decomposition of ligand moieties in a respective manner and leads to form an air stable metal oxide as the final residue. Micro crystalline nature and the presence of coordinated water molecules have been confirmed by powder XRD, SEM and thermal analyses. The ligand and its complexes have efficient bio-efficacy, DNA binding and cleavage ability.

  18. The Wilson-Bappu effect of the MgII k line - dependence on stellar temperature, activity and metallicity

    DEFF Research Database (Denmark)

    Elgaroy, O.; Engvold, O.; Lund, Niels

    1999-01-01

    The Wilson-Bappu effect is investigated using accurate absolute magnitudes of 65 stars obtained through early release of data from the Hipparcos satellite together with MgII k fine widths determined from high resolution spectra observed with the International Ultraviolet Explorer (IUE) observatory....... Stars of spectral classes F, G, K and M and luminosity classes I-V are represented in the sample. Wilson-Bappu relations for the Mg II k line for stars of different temperatures i.e. spectral classes are determined. The relation varies with spectral class and there is a significant scatter of the line...... to be present. Magnetic activity affects the width of the Mg II k line in dwarfs. Metallicity is found to influence the Mg II k line width in giants and supergiants. Possible interpretations of the new results are briefly discussed....

  19. Robust Type-II Weyl Semimetal Phase in Transition Metal Diphosphides X P2 (X =Mo , W)

    Science.gov (United States)

    Autès, G.; Gresch, D.; Troyer, M.; Soluyanov, A. A.; Yazyev, O. V.

    2016-08-01

    The recently discovered type-II Weyl points appear at the boundary between electron and hole pockets. Type-II Weyl semimetals that host such points are predicted to exhibit a new type of chiral anomaly and possess thermodynamic properties very different from their type-I counterparts. In this Letter, we describe the prediction of a type-II Weyl semimetal phase in the transition metal diphosphides MoP2 and WP2 . These materials are characterized by relatively simple band structures with four pairs of type-II Weyl points. Neighboring Weyl points have the same chirality, which makes the predicted topological phase robust with respect to small perturbations of the crystalline lattice. In addition, this peculiar arrangement of the Weyl points results in long topological Fermi arcs, thus making them readily accessible in angle-resolved photoemission spectroscopy.

  20. Cu(II), Co(II), Ni(II), Mn(II), and Fe(II) metal complexes containing N,N'-(3,4-diaminobenzophenon)-3,5-Bu(t)(2)-salicylaldimine ligand: Synthesis, structural characterization, thermal properties, electrochemistry, and spectroelectrochemistry.

    Science.gov (United States)

    Tas, E; Kilic, A; Durgun, M; Küpecik, L; Yilmaz, I; Arslan, S

    2010-02-01

    The synthesis, structure, spectroscopic and electro-spectrochemical properties of steric hindered Schiff-base ligand [N,N'-(3,4-benzophenon)-3,5-Bu(t)(2)-salicylaldimine (LH(2))] and its mononuclear Cu(II), Co(II), Ni(II), Mn(II) and Fe(II) complexes are described in this work. The new dissymmetric steric hindered Schiff-base ligand containing a donor set of NONO was prepared through reaction of 3,4-diaminobenzophenon with 3,5-Bu(t)(2)-salicylaldehyde. Certain metal complexes of this ligand were synthesized by treating an ethanolic solution of the ligand with an equimolar amount of metal salts. The ligand and its complexes were characterized by FT-IR, UV-vis, (1)H NMR, elemental analysis, molar conductivity and thermal analysis methods in addition to magnetic susceptibility, electrochemistry and spectroelectrochemistry techniques. The tetradentate and mononuclear metal complexes were obtained by reacting N,N'-(3,4-benzophenon)-3,5-Bu(t)(2)-salicylaldimine (LH(2)) with some metal acetate in a 1:1 mole ratio. The molar conductance data suggest metal complexes to be non-electrolytes.

  1. Divalent samarium compounds with heavier chalcogenolate (EPh; E = Se, Te) ligands.

    Science.gov (United States)

    Freedman, D; Kornienko, A; Emge, T J; Brennan, J G

    2000-05-15

    Crystalline coordination complexes of Sm(EPh)2 (E = Se, Te) are described. The selenolate compound Sm(SePh)2 is unstable in solution, but a divalent selenolate can be prepared and isolated when precisely 1 equiv of Zn(SePh)2 is present to form heterometallic [(THF)3Sm(mu 2-SePh)3Zn(mu 2-SePh)]n (1). This compound is a 1D coordination polymer with alternating Sm(II) and Zn(II) ions connected by an alternating (1,3) number of bridging selenolate ligands and three THF ligands bound to each Sm(II) ion. The tellurolate Sm(TePh)2 forms a stable pyridine coordination compound (py)5Sm(TePh)2 (2) that is isostructural with known Eu and Yb benzenetellurolates. Both compounds were characterized by conventional spectroscopic methods. Polymer 1 was characterized by low-temperature single-crystal X-ray diffraction, and the unit cell of the tellurolate was determined. Crystal data (Mo K alpha, 153(5) (K) are as follows. 1: monoclinic space group P21, a = 10.666(2) A, b = 16.270(3) A, c = 12.002(3) A, beta = 114.81(2) degrees, Z = 2.2: orthorhombic space group Pbca, with a = 13.865(3) A, b = 16.453(5) A, c = 31.952(7) A, Z = 8.

  2. Synthesis, antimicrobial activity, structural and spectral characterization and DFT calculations of Co(II), Ni(II), Cu(II) and Pd(II) complexes of 4-amino-5-pyrimidinecarbonitrile.

    Science.gov (United States)

    Mohamed, Tarek A; Shaaban, Ibrahim A; Farag, Rabei S; Zoghaib, Wajdi M; Afifi, Mahmoud S

    2015-01-25

    Co(II), Ni(II), Cu(II) and Pd(II) complexes of 4-amino-5-pyrimidinecarbonitrile (APC) have been synthesized and characterized using elemental analysis, magnetic susceptibility, mass spectrometry, infrared (4000-200 cm(-1)), UV-Visible (200-1100 nm), (1)H NMR and ESR spectroscopy as well as TGA analysis. The molar conductance measurements in DMSO imply non-electrolytic complexes, formulated as [M(APC)2Cl2] where M=Co(II), Ni(II), Cu(II) and Pd(II). The infrared spectra of Co(II), Ni(II) and Cu(II) complexes indicate a bidentate type of bonding for APC through the exocyclic amino and adjacent pyrimidine nitrogen as donors whereas APC coordinated to Pd(II) ion as a monodentated ligand via a pyrimidine nitrogen donor. The magnetic measurements and the electronic absorption spectra support distorted octahedral geometries for Co(II), Ni(II) and Cu(II) complexes however a square planar complex was favored for the Pd(II) complex (C2h skeleton symmetry). In addition, we carried out B3LYP and ω-B97XD geometry optimization at 6-31G(d) basis set except for Pd(II) where we implemented LanL2DZ/6-31G(d) combined basis set. The computational results favor all trans geometrical isomers where amino N, pyrimidine N and Cl are trans to each other (structure 1). Finally, APC and its divalent metal ion complexes were screened for their antibacterial activity, and the synthesized complexes were found to be more potent antimicrobial agents than APC against one or more microbial species.

  3. Structural characterization of a metal-based perfusion tracer: copper(II) pyruvaldehyde bis(N4-methylthiosemicarbazone).

    Science.gov (United States)

    John, E; Fanwick, P E; McKenzie, A T; Stowell, J G; Green, M A

    1989-01-01

    Copper(II) pyruvaldehyde bis(N4-methylthiosemicarbazone), Cu(PTSM), has been obtained as a dark red crystalline solid from EtOH-DMSO solvent mixture and structurally characterized by x-ray crystallography. The molecule possesses the expected pseudo-square planar N2S2 metal coordination sphere; however, the copper center also interacts through its axial coordination site with the sulfur atom of an adjacent Cu(PTSM) molecule in the crystal lattice. The structure of this compound is compared with the structures of other metal complexes that have been proposed in the nuclear medicine literature as perfusion tracers.

  4. Radial velocities and metallicities from infrared Ca II triplet spectroscopy of open clusters II. Berkeley 23, King 1, NGC 559, NGC 6603 and NGC 7245

    CERN Document Server

    Carrera, R; Ospina, N; Balaguer-Nuñez, L; Jordi, C; Monteagudo, L

    2015-01-01

    Context: Open clusters are key to studying the formation and evolution of the Galactic disc. However, there is a deficiency of radial velocity and chemical abundance determinations for open clusters in the literature. Aims: We intend to increase the number of determinations of radial velocities and metallicities from spectroscopy for open clusters. Methods: We acquired medium-resolution spectra (R~8000) in the infrared region Ca II triplet lines (~8500 AA) for several stars in five open clusters with the long-slit IDS spectrograph on the 2.5~m Isaac Newton Telescope (Roque de los Muchachos Observatory, Spain). Radial velocities were obtained by cross-correlation fitting techniques. The relationships available in the literature between the strength of infrared Ca II lines and metallicity were also used to derive the metallicity for each cluster. Results: We obtain = 48.6+/-3.4, -58.4+/-6.8, 26.0+/-4.3 and -65.3+/-3.2 km s-1 for Berkeley 23, NGC 559, NGC 6603 and NGC 7245, respectively. We found [Fe/H] =-0.25+...

  5. Metalloantibiotics: synthesis, characterization and in-vitro antibacterial studies on cobalt (II), copper (II), nickel (II) and zinc (II) complexes with cloxacillin.

    Science.gov (United States)

    Chohan, Zahid H; Supuran, Claudiu T

    2006-08-01

    The synthesis and characterization of cloxacillin (clox) complexes with divalent metal ions [Co (II), Cu (II), Ni (II) and Zn (II)] is described. The nature of bonding of the chelated cloxacillin and the structures of the metal complexes have been elucidated on the basis of their physical and spectroscopic data. In all the complexes, the cloxacillin acts as a uninegatively charged bidentate ligand with coordination involving the carboxylate-O and endocyclic-N of the beta-lactam ring. The new compounds have been screened for in-vitro antibacterial activity against Escherichia coli (a), Klebsiella pneumonae (b), Proteus mirabilis (c), Pseudomonas aeruginosa (d), Salmonella typhi (e), Shigella dysentriae (f), Bacillus cereus (g), Corynebacterium diphtheriae (h), Staphylococcus aureus (j) and Streptococcus pyogenes (k) bacterial strains. The brine shrimp bioassay was also carried out to study their in-vitro cytotoxic properties. All compounds, respectively, showed a promising activity (90%) against five bacterial species at 10 microg/ml concentration and a significant activity (52%) against the same test bacteria at 25 microg/ml concentration.

  6. Photophysical Studies of Ru(II)tris(2,2`-bipyridine) Confined within a Zn(II)-Trimesic Acid Polyhedral Metal-Organic Framework

    Energy Technology Data Exchange (ETDEWEB)

    Larsen, Randy W; Wojtas, Lukasz [USF

    2012-10-25

    The ability to confine photoactive catalysts within metal-organic framework (MOF) materials affords the opportunity to expand the functional diversity of these materials into solar based applications. Here, the confinement of Ru(II)tris(2,2'-bipyridine) (RuBpy) by a MOF material derived from Zn(II) ions and trimesic acid (hereafter, USF2) is examined. Although the encapsulated RuBpy could not be crystallographically resolved within the MOF framework, the photophysical properties of the complex are characteristic of confinement including extended triplet metal-to-ligand (3MLCT) lifetime (τethanol = 614 ns and {τUSF2 = 1.2 μs at 25 °C) and a slight hypsochromic shift in the steady-state emission spectrum relative to RuBpy in ethanol. The extended lifetime is attributed to a deactivation of a nonradiative 3dd that is antibonding with respect to the Ru(II)-bipyridine due to a confined molecular environment. These results represent one of the first examples of RuBpy encapsulation and photophysical characterization within a polyhedral MOF material.

  7. Energy levels scheme simulation of divalent cobalt doped bismuth germanate

    Energy Technology Data Exchange (ETDEWEB)

    Andreici, Emiliana-Laura, E-mail: andreicilaura@yahoo.com [Department of Physics, West University of Timisoara, Bd. V. Parvan 4,300223 Timisoara (Romania); Petkova, Petya [Shumen University “Konstantin Preslavsky”, 115 Universitetska street, 9712 Shumen (Bulgaria); Avram, Nicolae M. [Department of Physics, West University of Timisoara, Bd. V. Parvan 4,300223 Timisoara (Romania); Academy of Romanian Scientists, Independentei 54, 050094-Bucharest (Romania)

    2015-12-07

    The aim of this paper is to simulate the energy levels scheme for Bismuth Germanate (BGO) doped with divalent cobalt, in order to give a reliable explanation for spectral experimental data. In the semiempirical crystal field theory we first modeled the Crystal Field Parameters (CFPs) of BGO:Cr{sup 2+} system, in the frame of Exchange Charge Model (ECM), with actually site symmetry of the impurity ions after doping. The values of CFPs depend on the geometry of doped host matrix and by parameter G of ECM. First, we optimized the geometry of undoped BGO host matrix and afterwards, that of doped BGO with divalent cobalt. The charges effect of ligands and covalence bonding between cobalt cations and oxygen anions, in the cluster approach, also were taken into account. With the obtained values of the CFPs we simulate the energy levels scheme of cobalt ions, by diagonalizing the matrix of the doped crystal Hamiltonian. Obviously, energy levels and estimated Racah parameters B and C were compared with the experimental spectroscopic data and discussed. Comparison of obtained results with experimental data shows quite satisfactory, which justify the model and simulation schemes used for the title system.

  8. Preparation, structural characterization and biological evaluation of L-tyrosinate metal ion complexes

    Science.gov (United States)

    Refat, Moamen S.; El-Korashy, Sabry A.; Ahmed, Ahmed S.

    2008-06-01

    The complexes formed between different metal ions and biological molecules like amino acids play an important role in human life. Sn(II), Sn(IV), Zn(II), Cd(II), Hg(II), Cr(III), Fe(III), La(III), ZrO(II) and UO 2(II) complexes are synthesized with L-tyrosine (tyr). These complexes are characterized by elemental analysis, molar conductance, magnetic measurements, mass, IR, UV-vis and 1H NMR spectra as well as thermogravimetric analysis (TGA/DTG). It has been found from the elemental analysis and the thermal studies that the ligand behaves as bidentate ligand forming chelates with 1:3 (metal:ligand) stoichiometry for trivalent metals and 1:2 for divalent and tetravalent metals. The molar conductance measurements of the complexes in DMSO indicate that the complexes are non-electrolyte. The activation energies and other kinetic parameters were calculated from the Coats-Redfern and Horowitz-Metzger equations. The biological activities of the metal complexes have also been studied against different bacteria and fungi.

  9. Efficiency of Aluminum and Iron Electrodes for the Removal of Heavy Metals [(Ni (II), Pb (II), Cd (II)] by Electrocoagulation Method

    Energy Technology Data Exchange (ETDEWEB)

    Khosa, Muhammad Kaleem; Jamal, Muhammad Asghar; Hussain, Amira; Muneer, Majid; Zia, Khalid Mahmood [Government College Univ., Faisalabad (Pakistan); Hafeez, Samia [Bahaud-din-Zakariya Univ., Multan (Pakistan)

    2013-06-15

    Electrocoagulation (EC) technique is applied for the treatment of wastewater containing heavy metals ions such as nickel (Ni), lead (Pb) and cadmium (Cd) by using sacrificial anodes corrode to release active coagulant flocs usually aluminium or iron cations into the solution. During electrolytic reactions hydrogen gas evolve at the cathode. All the experiments were carried out in Batch mode. The tank was filled with synthetic wastewater containing heavy metals and efficiency of electrocoagulation in combination with aluminum and iron electrodes were investigated for removal of such metals. Several parameters, such as contact time, pH, electro-coagulant concentration, and current density were optimized to achieve maximum removal efficiency (%). The concentrations of heavy metals were determined by using Atomic Absorption Spectroscopy (AAS). It is found that the electro-coagulation process has potential to be utilized for the cost-effective removal of heavy metals from wastewater specially using iron electrodes in terms of high removal efficiencies and operating cost.

  10. Biological low pH Mn(II) oxidation in a manganese deposit influenced by metal-rich groundwater

    Science.gov (United States)

    Bohu, Tsing; Akob, Denise M.; Abratis, Michael; Lazar, Cassandre S.; Küsel, Kirsten

    2016-01-01

    The mechanisms, key organisms, and geochemical significance of biological low-pH Mn(II) oxidation are largely unexplored. Here, we investigated the structure of indigenous Mn(II)-oxidizing microbial communities in a secondary subsurface Mn oxide deposit influenced by acidic (pH 4.8) metal-rich groundwater in a former uranium mining area. Microbial diversity was highest in the Mn deposit compared to the adjacent soil layers and included the majority of known Mn(II)-oxidizing bacteria (MOB) and two genera of known Mn(II)-oxidizing fungi (MOF). Electron X-ray microanalysis showed that romanechite [(Ba,H2O)2(Mn4+,Mn3+)5O10] was conspicuously enriched in the deposit. Canonical correspondence analysis revealed that certain fungal, bacterial, and archaeal groups were firmly associated with the autochthonous Mn oxides. Eight MOB within the Proteobacteria, Actinobacteria, and Bacteroidetes and one MOF strain belonging to Ascomycota were isolated at pH 5.5 or 7.2 from the acidic Mn deposit. Soil-groundwater microcosms demonstrated 2.5-fold-faster Mn(II) depletion in the Mn deposit than adjacent soil layers. No depletion was observed in the abiotic controls, suggesting that biological contribution is the main driver for Mn(II) oxidation at low pH. The composition and species specificity of the native low-pH Mn(II) oxidizers were highly adapted to in situ conditions, and these organisms may play a central role in the fundamental biogeochemical processes (e.g., metal natural attenuation) occurring in the acidic, oligotrophic, and metalliferous subsoil ecosystems.

  11. Synthesis and characterization of bis (acetylacetonato κ-O, O') [zinc(ii)/copper(ii)] hybrid organic-inorganic complexes as solid metal organic precursors.

    Science.gov (United States)

    Rooydell, Reza; Wang, Ruey-Chi; Brahma, Sanjaya; Ebrahimzadeh, Farzaneh; Liu, Chuan-Pu

    2015-05-07

    We have synthesized novel metal organic hybrid mixed compounds of bis (acetylacetonato κ-O, O') [zinc(ii)/copper(ii)]. Taking C10H14O4Zn0.7Cu0.3 (Z0.7C0.3AA) as an example, the crystals are composed of Z0.7C0.3AA units and uncoordinated water molecules. Single-crystal X-ray diffraction results show that the complex Z0.7C0.3AA crystallizes in the monoclinic system, space group P21/n. The unit cell dimensions are a = 10.329(4) Å, b = 4.6947(18) Å, and c = 11.369(4) Å; the angles are α = 90°, β = 91.881(6)°, and γ = 90°, the volume is 551.0(4) Å(3), and Z = 2. In this process, the M(ii) ions of Zn and Cu mix and occupy the centers of symmetrical structural units, which are coordinated to two ligands. The measured bond lengths and angles of O-M-O vary with the ratio of metal species over the entire series of the complexes synthesized. The chemistry of the as-synthesized compounds has been characterized using infrared spectroscopy, mass spectroscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy analysis, and the morphology of the products has been characterized using scanning electron microscopy. The thermal decomposition of the Z0.7C0.3AA composites measured by thermogravimetric analysis suggests that these complexes are volatile. The thermal characteristics of these complexes make them attractive precursors for metal organic chemical vapor deposition.

  12. Some new nano-sized Fe(II), Cd(II) and Zn(II) Schiff base complexes as precursor for metal oxides: Sonochemical synthesis, characterization, DNA interaction, in vitro antimicrobial and anticancer activities.

    Science.gov (United States)

    Abdel-Rahman, Laila H; Abu-Dief, Ahmed M; El-Khatib, Rafat M; Abdel-Fatah, Shimaa Mahdy

    2016-12-01

    The complexes of Fe(II), Cd(II) and Zn(II) with Schiff base derived from 2-amino-3-hydroxypyridine and 3-methoxysalicylaldehyde have been prepared. Melting points, decomposition temperatures, Elemental analyses, TGA, conductance measurements, infrared (IR) and UV-Visible spectrophotometric studies were utilized in characterizing the compounds. The UV-Visible spectrophotometric analysis revealed 1:1 (metal-ligand) stoichiometry for the three complexes. In addition to, the prepared complexes have been used as precursors for preparing their corresponding metal oxides nanoparticles via thermal decomposition. The structures of the nano-sized complexes and their metal oxides were characterized by X-ray powder diffraction and transmittance electron microscopy. Moreover, the prepared Schiff base ligand, its complexes and their corresponding nano-sized metal oxides have been screened in vitro for their antibacterial activity against three bacteria, gram-positive (Microccus luteus) and gram-negative (Escherichia coli, Serratia marcescence) and three strains of fungus. The metal chelates were shown to possess more antimicrobial activity than the free Schiff-base chelate and their nano-sized metal oxides have the highest activity. The binding behaviors of the complexes to calf thymus DNA have been investigated by absorption spectra, viscosity mensuration and gel electrophoresis. The DNA binding constants reveal that all these complexes interact with DNA through intercalative binding mode. Furthermore, the cytotoxic activity of the prepared Schiff base complexes on human colon carcinoma cells, (HCT-116 cell line) and hepatic cellular carcinoma cells, (HepG-2) showed potent cytotoxicity effect against growth of carcinoma cells compared to the clinically used Vinblastine standard. Copyright © 2016 Elsevier Inc. All rights reserved.

  13. Flame atomic absorption spectrometric determination of heavy metals in aqueous solution and surface water preceded by co-precipitation procedure with copper(II) 8-hydroxyquinoline

    Science.gov (United States)

    Ipeaiyeda, Ayodele Rotimi; Ayoade, Abisayo Ruth

    2017-07-01

    Co-precipitation procedure has widely been employed for preconcentration and separation of metal ions from the matrices of environmental samples. This is simply due to its simplicity, low consumption of separating solvent and short duration for analysis. Various organic ligands have been used for this purpose. However, there is dearth of information on the application of 8-hydroxyquinoline (8-HQ) as ligand and Cu(II) as carrier element. The use of Cu(II) is desirable because there is no contamination and background adsorption interference. Therefore, the objective of this study was to use 8-HQ in the presence of Cu(II) for coprecipitation of Cd(II), Co(II), Cr(III), Ni(II) and Pb(II) from standard solutions and surface water prior to their determinations by flame atomic absorption spectrometry (FAAS). The effects of pH, sample volume, amount of 8-HQ and Cu(II) and interfering ions on the recoveries of metal ions from standard solutions were monitored using FAAS. The water samples were treated with 8-HQ under the optimum experimental conditions and metal concentrations were determined by FAAS. The metal concentrations in water samples not treated with 8-HQ were also determined. The optimum recovery values for metal ions were higher than 85.0%. The concentrations (mg/L) of Co(II), Ni(II), Cr(III), and Pb(II) in water samples treated with 8-HQ were 0.014 ± 0.002, 0.03 ± 0.01, 0.04 ± 0.02 and 0.05 ± 0.02, respectively. These concentrations and those obtained without coprecipitation technique were significantly different. Coprecipitation procedure using 8-HQ as ligand and Cu(II) as carrier element enhanced the preconcentration and separation of metal ions from the matrix of water sample.

  14. Effects of thermal aging on the microstructure of Type-II boundaries in dissimilar metal weld joints

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Seung Chang; Choi, Kyoung Joon [School of Mechanical and Nuclear Engineering, Ulsan National Institute of Science and Technology (UNIST), 100 Banyeon-ri, Eonyang-eup, Ulju-gun, Ulsan 689-798 (Korea, Republic of); Bahn, Chi Bum [School of Mechanical Engineering, Pusan National University, 63-gil, Geumjeong-Gu, Pusan 609-735 (Korea, Republic of); Kim, Si Hoon; Kim, Ju Young [School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), 100 Banyeon-ri, Eonyang-eup, Ulju-gun, Ulsan 689-798 (Korea, Republic of); Kim, Ji Hyun, E-mail: kimjh@unist.ac.kr [School of Mechanical and Nuclear Engineering, Ulsan National Institute of Science and Technology (UNIST), 100 Banyeon-ri, Eonyang-eup, Ulju-gun, Ulsan 689-798 (Korea, Republic of)

    2015-04-15

    In order to investigate the effects of long-term thermal aging on the microstructural evolution of Type-II boundary regions in the weld metal of Alloy 152, a representative dissimilar metal weld was fabricated from Alloy 690, Alloy 152, and A533 Gr.B. This mock-up was thermally aged at 450 °C to accelerate the effects of thermal aging in a nuclear power plant operation condition (320 °C). The microstructure of the Type-II boundary region of the weld root, which is parallel to and within 100 μm of the fusion boundary and known to be more susceptible to material degradation, was then characterized after different aging times using a scanning electron microscope equipped with an energy dispersive X-ray spectroscope for micro-compositional analysis, electron backscattered diffraction detector for grain and grain boundary orientation analysis, and a nanoindenter for measurement of mechanical properties. Through this, it was found that a steep compositional gradient and high grain average misorientation is created in the narrow zone between the Type-II and fusion boundaries, while the concentration of chromium and number of low-angle grain boundaries increases with aging time. A high average hardness was also observed in the same region of the dissimilar metal welds, with hardness peaking with thermal aging simulating an operational time of 15 years.

  15. Effects of thermal aging on the microstructure of Type-II boundaries in dissimilar metal weld joints

    Science.gov (United States)

    Yoo, Seung Chang; Choi, Kyoung Joon; Bahn, Chi Bum; Kim, Si Hoon; Kim, Ju Young; Kim, Ji Hyun

    2015-04-01

    In order to investigate the effects of long-term thermal aging on the microstructural evolution of Type-II boundary regions in the weld metal of Alloy 152, a representative dissimilar metal weld was fabricated from Alloy 690, Alloy 152, and A533 Gr.B. This mock-up was thermally aged at 450 °C to accelerate the effects of thermal aging in a nuclear power plant operation condition (320 °C). The microstructure of the Type-II boundary region of the weld root, which is parallel to and within 100 μm of the fusion boundary and known to be more susceptible to material degradation, was then characterized after different aging times using a scanning electron microscope equipped with an energy dispersive X-ray spectroscope for micro-compositional analysis, electron backscattered diffraction detector for grain and grain boundary orientation analysis, and a nanoindenter for measurement of mechanical properties. Through this, it was found that a steep compositional gradient and high grain average misorientation is created in the narrow zone between the Type-II and fusion boundaries, while the concentration of chromium and number of low-angle grain boundaries increases with aging time. A high average hardness was also observed in the same region of the dissimilar metal welds, with hardness peaking with thermal aging simulating an operational time of 15 years.

  16. Synthesis, spectroscopic, thermal and anticancer studies of metal-antibiotic chelations: Ca(II), Fe(III), Pd(II) and Au(III) chloramphenicol complexes

    Science.gov (United States)

    Al-Khodir, Fatima A. I.; Refat, Moamen S.

    2016-09-01

    Four Ca(II), Fe(III), Pd(II) and Au(III) complexes of chloramphenicol drug have been synthesized and well characterized using elemental analyses, (infrared, electronic, and 1H-NMR) spectra, magnetic susceptibility measurement, and thermal analyses. Infrared spectral data show that the chloramphenicol drug coordinated to Ca(II), Pd(II) and Au(III) metal ions through two hydroxyl groups with 1:1 or 1:2 M ratios, but Fe(III) ions chelated towards chloramphenicol drug via the oxygen and nitrogen atoms of amide group with 1:2 ratio based on presence of keto↔enol form. The X-ray powder diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM) techniques were used to identify the nano-size particles of both iron(III) and gold(III) chloramphenicol complexes. The antimicrobial assessments of the chloramphenicol complexes were scanned and collected the results against of some kind of bacteria and fungi. The cytotoxic activity of the gold(III) complex was tested against the human colon carcinoma (HCT-116) and human hepatocellular carcinoma (HepG-2) tumor cell lines.

  17. Preliminary screening of Ni(II) metal tolerance and dye-decolorizing byNocardiopsis sp. SD8

    Institute of Scientific and Technical Information of China (English)

    Ramasamy Thangaraj; Saha Subhasish; Dharumadurai Dhanasekaran; Nooruddin Thajuddin

    2016-01-01

    Objective:To reveal the screening of metal tolerance and dye-decolorizing ofNocardiopsis sp. Methods: NiSO4 and Congo red dye were used for evaluating the metal tolerance and dye-decolorizing of the randomly selected actinobacterial isolates. Results:Nocardiopsis sp.SD8 showed a better efficiency in Ni(II) tolerance, though a longer lag phase was observed for this microorganism grown for 7 days in integrated mismatch negativity. Interestingly, we also found thatNocardiopsis sp.SD8 had dye-decolorizing, hemolytic, lipase and protease activity. Conclusions:The present results revealed the bioremediation of metal resistant and diverse properties ofNocardiopsis sp.SD8 and further investigations are needed to extract and identify the potent molecule.

  18. Preliminary screening of Ni(II metal tolerance and dye-decolorizing by Nocardiopsis sp. SD8

    Directory of Open Access Journals (Sweden)

    Ramasamy Thangaraj

    2016-04-01

    Full Text Available Objective: To reveal the screening of metal tolerance and dye-decolorizing of Nocardiopsis sp. Methods: NiSO4 and Congo red dye were used for evaluating the metal tolerance and dyedecolorizing of the randomly selected actinobacterial isolates. Results: Nocardiopsis sp. SD8 showed a better efficiency in Ni(II tolerance, though a longer lag phase was observed for this microorganism grown for 7 days in integrated mismatch negativity. Interestingly, we also found that Nocardiopsis sp. SD8 had dye-decolorizing, hemolytic, lipase and protease activity. Conclusions: The present results revealed the bioremediation of metal resistant and diverse properties of Nocardiopsis sp. SD8 and further investigations are needed to extract and identify the potent molecule.

  19. Binding selectivity of vitamin K3 based chemosensors towards nickel(II) and copper(II) metal ions

    Science.gov (United States)

    Patil, Amit; Lande, Dipali N.; Nalkar, Archana; Gejji, Shridhar P.; Chakrovorty, Debamitra; Gonnade, Rajesh; Moniz, Tânia; Rangel, Maria; Pereira, Eulália; Salunke-Gawali, Sunita

    2017-09-01

    The vitamin K3 derivatives 2-methyl-3-[(pyridin-2-ylmethyl)-amino]-1,4-naphthoquinone (M-1), 2-methyl-3-[(pyridin-2-ylethyl)-amino]-1,4-naphthoquinone (M-2), 2-methyl-3-((2-(thiophen-2-yl)methyl)amino)naphthalene-1,4-dione (M-3) and 2-methyl-3-((2-(thiophen-2-yl)ethyl)amino)naphthalene-1,4-dione (M-4) have been synthesized, characterized and studied for their chemosensor abilities towards transition metal ions. Crystal structures of M-1 to M-4 revealed a variety of Nsbnd H⋯O, Csbnd H⋯O, Csbnd H⋯π and π⋯π interactions. Minor variations in such interactions by chemical stimuli such as metal ions, results in change in color that can be visualized by naked eyes. It has been shown that electronic structure and 1H NMR, vibrational as well as electronic spectra from the density functional theory agree well with the experiments. The metal ion binding in ethanol, ethanol-water and in mild base triethylamine brings forth recognizing ability of M-1 toward Ni2+ whereas M-2 exhibits large sensing ability for Cu2+ ion. Interestingly M-1 display varying metal ion binding specificity in different solvents with the association constant in ethanol being 11,786 M-1 for Ni2+ compared to 9462 M-1 for the Cu2+. A reversal in preferential binding of M-2 with the respective association constants being 4190 M-1 and 6370 M-1 is discernible.

  20. Donnan membrane speciation of Al, Fe, trace metals and REEs in coastal lowland acid sulfate soil-impacted drainage waters.

    Science.gov (United States)

    Jones, Adele M; Xue, Youjia; Kinsela, Andrew S; Wilcken, Klaus M; Collins, Richard N

    2016-03-15

    Donnan dialysis has been applied to forty filtered drainage waters collected from five coastal lowland acid sulfate soil (CLASS) catchments across north-eastern NSW, Australia. Despite having average pH values70%) as negatively-charged complexes. In contrast, the speciation of the divalent trace metals Co, Mn, Ni and Zn was dominated by positively-charged complexes and was strongly correlated with the alkaline earth metals Ca and Mg. Thermodynamic equilibrium speciation calculations indicated that natural organic matter (NOM) complexes dominated Fe(III) speciation in agreement with that obtained by Donnan dialysis. In the case of Fe(II), however, the free cation was predicted to dominate under thermodynamic equilibrium, whilst our results indicated that Fe(II) was mainly present as neutral or negatively-charged complexes (most likely with sulfate). For all other divalent metals thermodynamic equilibrium speciation calculations agreed well with the Donnan dialysis results. The proportion of Al and REEs predicted to be negatively-charged was also grossly underestimated, relative to the experimental results, highlighting possible inaccuracies in the stability constants developed for these trivalent Me(SO4)2(-) and/or Me-NOM complexes and difficulties in modeling complex environmental samples. These results will help improve metal mobility and toxicity models developed for CLASS-affected environments, and also demonstrate that Australian CLASS environments can discharge REEs at concentrations an order of magnitude greater than previously reported.

  1. I. New Techniques for the Synthesis of Metals and Alloys. II. The Properties of Rare Earth Metals and Alloys

    Science.gov (United States)

    1974-11-01

    Evaporation Apparatus Gas Scattering Evaporation High Rate Physical Vapor Deposition Process Hafnium Carbide *** 20. ABSTRACT (Conttnu» on r...2,500 Aluminium oxide 2 100 Tungsten carbide 1,700 Quartz 820 Metals < 800 34 ^^M ■ ’ ■ The microstructure of the deposit shows a fine

  2. Investigation of Explosively Driven Fragmentation of Metals - Two Dimensional Fracture and Fragmentation of Metal Shells: Progress Report II

    Energy Technology Data Exchange (ETDEWEB)

    Grady, D

    2003-02-01

    High explosive enclosed by a metal case qualitatively describes an essential component of high energy systems of importance to the Department of Energy. Detonation of the high explosive causes intense transient pressure loading of the metal following arrival of normal or obliquely incident explosive detonation wave. Subsequent expansion and deformation of the metal case leads to eventual rupture and the opening of fractures and fissures. Details of the rupture process are critical to performance of the system. Consequently, it is essential that the material and kinematic issues governing the processes of dynamic loading and subsequent failure of an explosive-metal case component within a functioning system be adequately understood. Among the reasons are to quantify existing performance, characterize potential degradation of performance resulting from system aging, and optimizing or maintaining system performance through implementation of structural or material changes. The physical and engineering issues underlying this dynamic response and failure phenomena are not adequately understood. The purpose of the present program is to identify the key issues and develop theoretical, computational and experimental models needed to achieve a satisfactory theoretical and analysis framework for analysis of metal case failure in the explosive environment. Specific tasks within the present program include: (1) Models and theories currently being pursued based on physical principles of both the statistical fragmentation concepts of Mott and the energy-based concept of others show promise of providing the analytic and computational methodology capable of predicting explosion-induced fracture and fragmentation of metal components. Experimental studies initiated in the earlier effort offer promise to provide critical test data for validation. The present task shall involve the further refinement and development of the dynamic failure and fragmentation models and theories, and the

  3. Equilibrium modeling of mono and binary sorption of Cu(II and Zn(II onto chitosan gel beads

    Directory of Open Access Journals (Sweden)

    Nastaj Józef

    2016-12-01

    Full Text Available The objective of the work are in-depth experimental studies of Cu(II and Zn(II ion removal on chitosan gel beads from both one- and two-component water solutions at the temperature of 303 K. The optimal process conditions such as: pH value, dose of sorbent and contact time were determined. Based on the optimal process conditions, equilibrium and kinetic studies were carried out. The maximum sorption capacities equaled: 191.25 mg/g and 142.88 mg/g for Cu(II and Zn(II ions respectively, when the sorbent dose was 10 g/L and the pH of a solution was 5.0 for both heavy metal ions. One-component sorption equilibrium data were successfully presented for six of the most useful three-parameter equilibrium models: Langmuir-Freundlich, Redlich-Peterson, Sips, Koble-Corrigan, Hill and Toth. Extended forms of Langmuir-Freundlich, Koble-Corrigan and Sips models were also well fitted to the two-component equilibrium data obtained for different ratios of concentrations of Cu(II and Zn(II ions (1:1, 1:2, 2:1. Experimental sorption data were described by two kinetic models of the pseudo-first and pseudo-second order. Furthermore, an attempt to explain the mechanisms of the divalent metal ion sorption process on chitosan gel beads was undertaken.

  4. Synthesis, Characterization and Antibacterial Activity of Novel Schiff Bases Derived from 4-Phenyl-2-aminothiazole and their Mn(II, Fe(II, Co(II, Ni(II and Cu(II Metal complexes

    Directory of Open Access Journals (Sweden)

    A. S. Thakar

    2011-01-01

    Full Text Available Novel Schiff bases and their metal complexes were derived from some hetero cyclic β-diketones with 4-phenyl-2-aminothiazole. All the synthesized compounds were confirmed their structure by Elemental analysis, FT-IR, 1H NMR, 13C NMR, Mass spectra, TGA analysis and UV spectra. All the compounds were tested for their antibacterial activity. Spectroscopic measurements suggest that all Schiff base metal complexes are of type ML2.(H2O2 (M=Mn, Fe, Co, Ni and Cu and all the metal complexes shows moderate antibacterial activity in the agar cup assay method.

  5. Electron Capture Dissociation of Trivalent Metal Ion-Peptide Complexes

    National Research Council Canada - National Science Library

    Flick, Tawnya G; Donald, William A; Williams, Evan R

    2013-01-01

    .... ECD of these doubly charged complexes containing MT results in significantly higher electron capture efficiency and sequence coverage than peptide-divalent metal ion complexes that have the same net charge...

  6. New fluorescent azo-Schiff base Cu(II) and Zn(II) metal chelates; spectral, structural, electrochemical, photoluminescence and computational studies

    Science.gov (United States)

    Purtas, Fatih; Sayin, Koray; Ceyhan, Gokhan; Kose, Muhammet; Kurtoglu, Mukerrem

    2017-06-01

    A new Schiff base containing azo chromophore group obtained by condensation of 2-hydroxy-4-[(E)-phenyldiazenyl]benzaldehyde with 3,4-dimethylaniline (HL) are used for the syntheses of new copper(II) and zinc(II) chelates, [Cu(L)2], and [Zn(L)2], and characterized by physico-chemical and spectroscopic methods such as 1H and 13C NMR, IR, UV.-Vis. and elemental analyses. The solid state structure of the ligand was characterized by single crystal X-ray diffraction study. X-ray diffraction data was then used to calculate the harmonic oscillator model of aromaticity (HOMA) indexes for the rings so as to investigate of enol-imine and keto-amine tautomeric forms in the solid state. The phenol ring C10-C15 shows a considerable deviation from the aromaticity with HOMA value of 0.837 suggesting the shift towards the keto-amine tautomeric form in the solid state. The analytical data show that the metal to ligand ratio in the chelates was found to be 1:2. Theoretical calculations of the possible isomers of the ligand and two metal complexes are performed by using B3LYP method. Electrochemical and photoluminescence properties of the synthesized azo-Schiff bases were also investigated.

  7. Synthesis, Crystal Structure, and Luminescent Properties of New Zinc(II and Cadmium(II Metal-Organic Frameworks Based on Flexible Bis(imidazol-1-ylalkane Ligands

    Directory of Open Access Journals (Sweden)

    Marina Barsukova

    2016-10-01

    Full Text Available New metal-organic frameworks (MOFs based on zinc and cadmium ions, terephthalic acid, and flexible ligands 1,5-bis(imidazol-1-ylpentane or 1,6-bis(imidazol-1-ylhexane were prepared and characterized by X-ray diffraction, thermorgavimetric analysis and IR spectroscopy. The imidazolyl ligands were prepared by a new robust procedure involving the reaction between imidazole and 1,5-dibromopentane or 1,6-dibromohexane in a superbasic medium (KOH in DMSO. MOFs based on 1,5-bis(imidazol-1-ylpentane had diamond topology (dia and are triply interpenetrated. Ligands with longer spacer 1,6-bis(imidazol-1-ylhexane, terephthalate ions and zinc(II ions formed five-fold interpenetrated metal-organic framework also with dia topology, while cadmium(II ions with the same ligands formed eight-connected uninodal net with a very rare self-penetrated topological type ilc and a point symbol 424.5.63. The influence of the chemical composition of MOFs on their photoluminescent properties is investigated and discussed in detail.

  8. Sulfitos duplos contendo cobre (I e um metal de transição M(II tipo Cu2SO3.M(IISO3.2H 2O [M(II = Cu(II, Fe(II, Mn(II e Cd(II]: preparação e seletividade na incorporação de M(II Double sulfite containing copper (I and a metal transition M(II like Cu2SO3.M(IISO3.2H 2O [M(II = Cu(II, Fe(II, Mn(II and Cd(II]: synthesis and selectivity in M(II incorporation

    Directory of Open Access Journals (Sweden)

    Luciana Almeida Silva

    1998-04-01

    Full Text Available The metal-catalyzed autooxidation of S(IV has been studied for more than a century without a consensus being obtained as to reaction rates, rate laws or mechanisms. The main objective in this work was to explore the reaction between Cu(II and SO2 in the presence of M(II, paying special attention to the formation of double sulfites like Cu2SO3.M(IISO3.2H 2O. The two principal aspects studied were: i a new way to prepare double sulfites with high purity degree and the selectivity in the M(II incorporation during the salt formation.

  9. Protonation of a hydroxide anion bridging two divalent magnesium cations in water probed by first-principles metadynamics simulation.

    Science.gov (United States)

    Park, Jung Mee; Boero, Mauro

    2010-09-01

    The protonation of a hydroxide anion (OH(-)) located between two magnesium cations (Mg(2+)) in aqueous solution has been investigated by first-principles metadynamics simulation. We observe that the complex Mg(2+)-OH(-)-Mg(2+) is stabilized by the coparticipation of the hydroxide anion to the first hydration shells of both the Mg(2+) cations. Contrary to the cases of OH(-) in pure water, the transfer of protons in the presence of the divalent metal ions turns out to be a slow chemical event. This can be ascribed to the decreased proton affinity of the bridging OH(-). Metadynamics simulation, used to overcome the difficulty of the long time scale required by the protonation of the bridging OH(-), has shown that the system possesses a great stability on the reactant state, characterized by a bioctahedral (6,6) solvation structure around the two Mg(2+) cations. The exploration of the free energy landscape shows that this stable bioctahedral configuration converts into a lower coordinated (5,6) structure, leading to a proton transfer from a water molecule belonging to the first solvation shell of the Mg(2+) ion having the lower coordination to the bridging OH(-); the free energy barrier for the protonation reaction is 11 kcal/mol, meaning that the bridging hydroxide is a weak base. During the proton transfer, the bridging OH(-) reverts to an H(2)O molecule, and this breaks the electrostatic coupling of the two Mg(2+) ions, which depart independently with their own hydration shells, one of which is entirely formed by water molecules. The second one carries the newly created OH(-). Our results show that the flexibility in the metal coordination plays a crucial role in both the protonation process of the bridging OH(-) and the separation of the metal cations, providing useful insight into the nature of proton transfer in binuclear divalent metal ions, with several biological implications, such as, for instance, transesterification of catalytic RNA.

  10. Synthesis of ethylenediamine modified chitosan microspheres for removal of divalent and hexavalent ions.

    Science.gov (United States)

    Chethan, P D; Vishalakshi, B

    2015-04-01

    Ethylenediamine modified chitosan was obtained in the form of microspheres by chemical crosslinking with gluteraldehyde and evaluated for the effective removal of metal ions. The present modification results in additional nitrogen centers which function as potential binding sites and the microsphere form enhances the specific surface area during adsorption of metal ions. The adsorbent was used in batch experiments to evaluate the adsorption of Cu(II), Zn(II), Pb(II) and Cr(VI) in a individual metal salt solutions. The samples exhibited highest affinity for Cu(II) and least for Cr(VI) ions. The adsorption data were interpreted based on Langmuir and Freundlich isotherm models. The maximum adsorption capacity obtained from Langmuir model is 60.9 mg g(-1). The modified microspheres can be regenerated with high efficiency, suggesting that this adsorbent is satisfactory to reuse. Copyright © 2015 Elsevier B.V. All rights reserved.

  11. Using Mössbauer spectroscopy to choose the sites that can be occupied by divalent tin

    Science.gov (United States)

    Dénès, Georges; Merazig, Hocine; Muntasar, Abdualhafed

    2014-04-01

    Mössbauer spectroscopy can be a useful structural tool to assist crystallographic methods for site assignment when the compound under investigation contains divalent tin. The goal of this work was to show that the structure of tin(II) fluoride, also know as stannous fluoride, SnF2, could have been solved 14 years earlier if Mössbauer spectroscopic results, already known, had been used. A first attempt to solve the crystal structure, carried out by Bergerhoff in 1962 seemed to find the tin positions, however, it failed to find the positions of fluorine. Further extensive studies by Dénès et al. in the mid 1970s yielded the same results as those of Bergerhoff, despite the use of a Nonius CAD-4 automatic diffractometer, in contrast with Bergerhoff's film work. The tin positions yielded a residual of 0.23, and Fourier difference maps showed significant electron density that could be fluorine atoms, however, their number did not match the number of fluorine atoms expected and several F-F distances were way too short. In addition, refinement using these possible fluorine positions led to no improvement of the residual factor. Finally, the crystal structure was published by McDonald et al. in 1976. It was found that the tin sublattice determined by Bergerhoff was basically correct, except that half of the tin atoms found by Bergerhoff to be on the (4b) and (4e) special Wyckoff sites were actually on the (8f) general site. A translation of the origin of the unit-cell by the [1/8, 0, 3/16] vector allows to change the tin Wyckoff sites from (4b), (4e) and (8f) to two (8f) sites, while keeping the basic spatial distribution of tin. A method has now been designed, using 119Sn Mössbauer spectroscopy, to test the suitability of some Wyckoff sites for divalent tin, using the Mössbauer spectrum. The tin(II) doublet ( δ = 3.430(3) mm/s, Δ = 1.532(3) mm/s) shows that the lone pair is on a hybrid orbital, therefore, it is stereoactive, and it results that tin cannot be on

  12. Ni(II, Cu(II, AND Zn(II COMPLEXES DERIVED FROM A NEW SCHIFF BASE 2-((Z-(3-METHYLPYRIDIN-2- YLEIMINOMETHYLPHENOL AND SYNTHESIS OF NANO SIZED METAL OXIDE PARTICLES FROM THESE COMPOUNDS

    Directory of Open Access Journals (Sweden)

    Masoumeh Orojloo

    2015-11-01

    Full Text Available Synthesis, spectral identification, and magnetic properties of three complexes of Ni(II, Cu(II, and Zn(II are described. All three compounds have the general formula [M(L2(H2O2], where L = deprotonated phenol in the Schiff base 2-((z-(3-methylpyridin-2-yleiminomethylphenol. The three complexes were synthesized in a one-step synthesis and characterized by elemental analysis, Fourier transform infrared spectroscopy, electronic spectra, X-ray diffraction (XRD, and room temperature magnetic moments. The Cu(II and Ni(II complexes exhibited room temperature magnetic moments of 1.85 B.M. per copper atom and 2.96 B.M. per nickel atom. The X-band electron spin resonance spectra of a Cu(II sample in dimethylformamide frozen at 77 K (liquid nitrogen temperature showed a typical ΔMS = ± 1 transition. The complexes ([M(L2(H2O2] were investigated by the cyclic voltammetry technique, which provided information regarding the electrochemical mechanism of redox behavior of the compounds. Thermal decomposition of the complexes at 750 ºC resulted in the formation of metal oxide nanoparticles. XRD analyses indicated that the nanoparticles had a high degree of crystallinity. The average sizes of the nanoparticles were found to be approximately 54.3, 30.1, and 44.4 nm for NiO, CuO, and ZnO, respectively.

  13. Relationship between breakthrough curve and adsorption isotherm of Ca(II) imprinted chitosan microspheres for metal adsorption

    Institute of Scientific and Technical Information of China (English)

    Yangcheng Lu; Jing He; Longwen Wu; Guangsheng Luo

    2016-01-01

    In this work, an equilibrium-dispersion model was successfully established to describe the breakthrough performance of Ca(II) imprinted chitosan (Ca(II)-CS) microspheres packed column for metal adsorption, and the assumptions of Langmuir isotherms and axial dispersion controlled mass transfer process were confirmed. The axial dispersion coefficient in Ca(II)-CS microspheres packed column was found to be almost proportional to the linear velocity and fit for prediction through single breakthrough test. Sensitivity analysis for breakthrough curve indicated the axial dispersion coefficient as well as Langmuir coefficient was sensitive variable for deep removal requirement. The retrieval of the adsorption isotherms of Ca(II)-CS microspheres from breakthrough curve was fulfilled by model ing calibration. A strategy based on the correlation between adsorption isotherms and breakthrough performance was further proposed to simplify the column adsorption design using absorbents with smal/uniform size and fast adsorption kinetics like Ca(II)-CS microspheres to cut down the gap between lab and industry.

  14. Adsorption of Azo-Dye Orange II from Aqueous Solutions Using a Metal-Organic Framework Material: Iron- Benzenetricarboxylate

    Directory of Open Access Journals (Sweden)

    Elizabeth Rojas García

    2014-12-01

    Full Text Available A Metal-Organic Framework (MOF, iron-benzenetricarboxylate (Fe(BTC, has been studied for the adsorptive removal of azo-dye Orange II from aqueous solutions, where the effect of various parameters was tested and isotherm and kinetic models were suggested. The adsorption capacities of Fe(BTC were much higher than those of an activated carbon. The experimental data can be best described by the Langmuir isotherm model (R2 > 0.997 and revealed the ability of Fe(BTC to adsorb 435 mg of Orange II per gram of adsorbent at the optimal conditions. The kinetics of Orange II adsorption followed a pseudo-second-order kinetic model, indicating the coexistence of physisorption and chemisorption, with intra-particle diffusion being the rate controlling step. The thermodynamic study revealed that the adsorption of Orange II was feasible, spontaneous and exothermic process (−25.53 kJ·mol−1. The high recovery of the dye showed that Fe(BTC can be employed as an effective and reusable adsorbent for the removal of Orange II from aqueous solutions and showed the economic interest of this adsorbent material for environmental purposes.

  15. Adsorption of Azo-Dye Orange II from Aqueous Solutions Using a Metal-Organic Framework Material: Iron- Benzenetricarboxylate

    Science.gov (United States)

    Rojas García, Elizabeth; López Medina, Ricardo; May Lozano, Marcos; Hernández Pérez, Isaías; Valero, Maria J.; Maubert Franco, Ana M.

    2014-01-01

    A Metal-Organic Framework (MOF), iron-benzenetricarboxylate (Fe(BTC)), has been studied for the adsorptive removal of azo-dye Orange II from aqueous solutions, where the effect of various parameters was tested and isotherm and kinetic models were suggested. The adsorption capacities of Fe(BTC) were much higher than those of an activated carbon. The experimental data can be best described by the Langmuir isotherm model (R2 > 0.997) and revealed the ability of Fe(BTC) to adsorb 435 mg of Orange II per gram of adsorbent at the optimal conditions. The kinetics of Orange II adsorption followed a pseudo-second-order kinetic model, indicating the coexistence of physisorption and chemisorption, with intra-particle diffusion being the rate controlling step. The thermodynamic study revealed that the adsorption of Orange II was feasible, spontaneous and exothermic process (−25.53 kJ·mol−1). The high recovery of the dye showed that Fe(BTC) can be employed as an effective and reusable adsorbent for the removal of Orange II from aqueous solutions and showed the economic interest of this adsorbent material for environmental purposes. PMID:28788289

  16. Highly Efficient Adsorption of Aqueous Pb(II with Mesoporous Metal-Organic Framework-5: An Equilibrium and Kinetic Study

    Directory of Open Access Journals (Sweden)

    José María Rivera

    2016-01-01

    Full Text Available Mesoporous metal-organic framework-5 (MOF-5, with the composition Zn4O(BDC3, showed a high capacity for the adsorptive removal of Pb(II from 100% aqueous media. After the adsorption process, changes in both morphology and composition were detected using a scanning electron microscope (SEM equipped with an energy dispersive X-ray (EDX system, Fourier transform infrared spectroscopy (FTIR, and X-ray photoelectron spectroscopy (XPS analysis. The experimental evidence showed that Zn(II liberation from MOF-5 structure was provoked by the water effect demonstrating that Pb(II removal is not due to ionic exchange with Zn. A kinetic study showed that Pb(II removal was carried out in 30 min with a behavior of pseudo-second-order kinetic model. The experimental data on Pb(II adsorption were adequately fit by both the Langmuir and BET isotherm models with maximum adsorption capacities of 658.5 and 412.7 mg/g, respectively, at pH 5 and 45°C. The results of this work demonstrate that the use of MOF-5 has great potential for applications in environmental protection, especially regarding the removal of the lead present in industrial wastewaters and tap waters.

  17. Direct measurement of the Mn(II) hydration state in metal complexes and metalloproteins through 17O NMR line widths.

    Science.gov (United States)

    Gale, Eric M; Zhu, Jiang; Caravan, Peter

    2013-12-11

    Here we describe a simple method to estimate the inner-sphere hydration state of the Mn(II) ion in coordination complexes and metalloproteins. The line width of bulk H2(17)O is measured in the presence and absence of Mn(II) as a function of temperature, and transverse (17)O relaxivities are calculated. It is demonstrated that the maximum (17)O relaxivity is directly proportional to the number of inner-sphere water ligands (q). Using a combination of literature data and experimental data for 12 Mn(II) complexes, we show that this method provides accurate estimates of q with an uncertainty of ±0.2 water molecules. The method can be implemented on commercial NMR spectrometers working at fields of 7 T and higher. The hydration number can be obtained for micromolar Mn(II) concentrations. We show that the technique can be extended to metalloproteins or complex:protein interactions. For example, Mn(II) binds to the multimetal binding site A on human serum albumin with two inner-sphere water ligands that undergo rapid exchange (1.06 × 10(8) s(-1) at 37 °C). The possibility of extending this technique to other metal ions such as Gd(III) is discussed.

  18. The preparation of polyelectrolyte complexes carboxymethyl chitosan(CMC)-pectin by reflux method as a Pb (II) metal ion adsorbent

    Science.gov (United States)

    Hastuti, Budi; Mudasir, Siswanta, Dwi; Triyono

    2016-02-01

    Aim of this research is to synthesized a chemically stable polyelectrolyte complexs carboxymetyl chitosan CMC-pectin as Pb(II) ion adsorbent by reflux method. During synthesis process, the optimum mass ratio of CMC and pectin was pre-determined and the active groups of the CMC-pectin complex was characterized by using IR spectrofotometer. Finally, adsorption capacity of the adsorbent material for Pb (II) ions was studied under optimum condition, i.e. adsorbent mass, contact time, and pH. Result shows that CMC could be succesfully combined with pectin to produce CMC-pectin complex. The optimum mass ratio CMC: pectin to form the polyelectrolyte complexs CMC-pectin was 70% : 30%. The active groups identified in the CMC-pectin complex was a hydroxyl (OH) and carboxylate (-COOH) groups. The optimum conditions for Pb (II) ion absoprtion was 10 mg of the adsorbent mass, 75 min of contact time, and pH 5. This material can be effectively used as adsorbents for Pb (II) ions, where up to 91% Pb (II) metal ions was adsorbed from aqueous solution and the adsorption capacity of the adsorbent was 41.63 mg/g.

  19. Effect of metal oxides on the reactivity of persulfate/Fe(II) in the remediation of diesel-contaminated soil and sand.

    Science.gov (United States)

    Do, Si-Hyun; Kwon, Yong-Jae; Kong, Sung-Ho

    2010-10-15

    The effect of metal oxides on the ability of persulfate (PS) with Fe(II) to remediate diesel-contaminated soil was investigated. In both natural soil and purchased sand, the highest diesel degradation occurred at pH 3 and the optimum molar ratio of PS/Fe(II) was 100:1 (i.e. 500 mM PS to 5 mM Fe(II)). Moreover, adding Fe(II) increased PS reactivity more in soil than it did in sand, indicating the involvement of metal oxides in the soil matrix. Evaluating the effects of metal oxides (i.e. goethite, hematite, magnetite, and manganese oxide) on the reactivity of PS with/without Fe(II) in a system containing diesel-contaminated sand revealed that manganese oxide increased PS activity the most and that the highest diesel degradation by PS occurred when both manganese oxide and Fe(II) were used as activators. XRD did not show the transformation of manganese oxide in the presence of Fe(II). SEM-EDS showed the association of Fe(II) on the surface of manganese oxide, and ICP analysis revealed that almost all the added Fe(II) adsorbed to manganese oxide but almost none adsorbed to iron oxides under acidic conditions. Therefore, the high reactivity of PS could be due to the high density of Fe(II) over the surface of manganese oxide. 2010 Elsevier B.V. All rights reserved.

  20. Binding of kinetically inert metal ions to RNA: the case of platinum(II).

    Science.gov (United States)

    Chapman, Erich G; Hostetter, Alethia A; Osborn, Maire F; Miller, Amanda L; DeRose, Victoria J

    2011-01-01

    In this chapter several aspects of Pt(II) are highlighted that focus on the properties of Pt(II)-RNA adducts and the possibility that they influence RNA-based processes in cells. Cellular distribution of Pt(II) complexes results in significant platination of RNA, and localization studies find Pt(II) in the nucleus, nucleolus, and a distribution of other sites in cells. Treatment with Pt(II) compounds disrupts RNA-based processes including enzymatic processing, splicing, and translation, and this disruption may be indicative of structural changes to RNA or RNA-protein complexes. Several RNA-Pt(II) adducts have been characterized in vitro by biochemical and other methods. Evidence for Pt(II) binding in non-helical regions and for Pt(II) cross-linking of internal loops has been found. Although platinated sites have been identified, there currently exists very little in the way of detailed structural characterization of RNA-Pt(II) adducts. Some insight into the details of Pt(II) coordination to RNA, especially RNA helices, can be gained from DNA model systems. Many RNA structures, however, contain complex tertiary folds and common, purine-rich structural elements that present suitable Pt(II) nucleophiles in unique arrangements which may hold the potential for novel types of platinum-RNA adducts. Future research aimed at structural characterization of platinum-RNA adducts may provide further insights into platinum-nucleic acid binding motifs, and perhaps provide a rationale for the observed inhibition by Pt(II) complexes of splicing, translation, and enzymatic processing.

  1. Pb(II) and Hg(II) binding to $\\textit{de novo}$ designed proteins studied by $^{204m}$Pb- and $^{199m}$Hg-Perturbed Angular Correlation of $\\gamma$-rays (PAC) spectroscopy : Clues to heavy metal toxicity

    CERN Multimedia

    2002-01-01

    $\\textit{De novo}$ design of proteins combined with PAC spectroscopy offers a unique and powerful approach to the study of fundamental chemistry of heavy metal-protein interactions, and thus of the mechanisms underlying heavy metal toxicity. In this project we focus on Pb(II) and Hg(II) binding to designed three stranded coiled coil proteins with one or two binding sites, mimicking a variety of naturally occurring thiolate-rich metal ion binding sites in proteins. The $^{204m}$Pb- and $^{199m}$Hg-PAC experiments will complement data already recorded with EXAFS, NMR, UV-Vis and CD spectroscopies.

  2. Microbial Mineral Transformations at the Fe(II)/Fe(III) Redox Boundary for Solid Phase Capture of Strontium and Other Metal/Radionuclide Contaminants

    Energy Technology Data Exchange (ETDEWEB)

    F. G. Ferris; E. E. Roden

    2000-01-31

    The migration of {sup 90}Sr in groundwater is a significant environmental concern at former nuclear weapons production sites in the US and abroad. Although retardation of {sup 90}Sr transport relative to mean groundwater velocity is known to occur in contaminated aquifers, Sr{sup 2+} does not sorb as strongly to iron oxides and other mineral phases as do other metal-radionuclides contaminants. Thus, some potential exists for extensive {sup 90}Sr migration from sources of contamination. Chemical or biological processes capable of retarding or immobilizing Sr{sup 2+} in groundwater environments are of interest from the standpoint of understanding controls on subsurface Sr{sup 2+} migration. In addition, it may be possible to exploit such processes for remediation of subsurface Sr contamination. In this study the authors examined the potential for the solid phase sorption and incorporation of Sr{sup 2+} into carbonate minerals formed during microbial Fe(III) oxide reduction as a first step toward evaluating whether this process could be used to promote retardation of {sup 90}Sr migrations in anaerobic subsurface environments. The demonstration of Sr{sup 2+} capture in carbonate mineral phases formed during bacterial HFO reduction and urea hydrolysis suggests that microbial carbonate mineral formation could contribute to Sr{sup 2+} retardation in groundwater environments. This process may also provide a mechanism for subsurface remediation of Sr{sup 2+} and other divalent metal contaminants that form insoluble carbonate precipitates.

  3. Synthesis, characterization and anti-microbial activity of phenylurea-formaldehyde resin (PUF) and its polymer metal complexes (PUF-Mn(II).

    Science.gov (United States)

    Ahamad, Tansir; Alshehri, Saad M

    2012-10-01

    Phenylurea-formaldehyde polymer (PUF) was synthesized via polycondensation of phenylurea and formaldehyde in basic medium, its polymer-metal complexes [PUF-M(II)] were prepared with Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) ions. PUF and PUF-M(II) were characterized with magnetic moment measurements, elemental and spectral (UV-visible, FTIR, 1H-NMR, 13C-NMR and ESR) analysis. The thermal behaviors of all the synthesized polymers were carried out using thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The thermal data revealed that all of the PUF-M(II) showed higher thermal stabilities than the PUF and also ascribed that the PUF-Cu(II) showed better thermal stability than the other PUF-M(II). The kinetic parameters such as activation energy, pre-exponential factor etc., were evaluated for these polymer metal complexes using Coats-Redfern equation. In addition, the antimicrobial activity of the synthesized polymers was tested against several microorganisms using agar well diffusion methods. Among all of the PUF-M(II), the antimicrobial activity of the PUF-Cu(II) showed the highest zone of inhibition because of its higher stability constant and may be used in biomedical applications.

  4. Synthesis, characterization and anti-microbial activity of phenylurea-formaldehyde resin (PUF) and its polymer metal complexes (PUF-Mn(II)

    Science.gov (United States)

    Ahamad, Tansir; Alshehri, Saad M.

    2012-10-01

    Phenylurea-formaldehyde polymer (PUF) was synthesized via polycondensation of phenylurea and formaldehyde in basic medium, its polymer-metal complexes [PUF-M(II)] were prepared with Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) ions. PUF and PUF-M(II) were characterized with magnetic moment measurements, elemental and spectral (UV-visible, FTIR, 1H-NMR, 13C-NMR and ESR) analysis. The thermal behaviors of all the synthesized polymers were carried out using thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The thermal data revealed that all of the PUF-M(II) showed higher thermal stabilities than the PUF and also ascribed that the PUF-Cu(II) showed better thermal stability than the other PUF-M(II). The kinetic parameters such as activation energy, pre-exponential factor etc., were evaluated for these polymer metal complexes using Coats-Redfern equation. In addition, the antimicrobial activity of the synthesized polymers was tested against several microorganisms using agar well diffusion methods. Among all of the PUF-M(II), the antimicrobial activity of the PUF-Cu(II) showed the highest zone of inhibition because of its higher stability constant and may be used in biomedical applications.

  5. Recovery of Pd(II) from hydrochloric solution using polyallylamine hydrochloride-modified Escherichia coli biomass.

    Science.gov (United States)

    Park, Jiyeong; Won, Sung Wook; Mao, Juan; Kwak, In Seob; Yun, Yeoung-Sang

    2010-09-15

    A new type of biosorbent able to bind anionic metals was developed by cross-linking of waste biomass Escherichia coli with polyallylamine hydrochloride (PAH). The PAH-modified biomass was investigated for the removal and recovery of Pd(II), in the chloro-complex form, from aqueous solution. The performance of the PAH-modified biomass was evaluated in terms of the following parameters: the solution pH, contact time and initial metal concentration. In the pH edge experiments, the uptake of Pd(II) increased with increasing pH. Pd(II) biosorption proceeded rapidly in the first 10 min, with almost complete equilibrium being achieved within 60 min. Moreover, the isotherm data showed that the maximum uptakes of Pd(II) were 265.3mg/g at pH 3 and 212.9 mg/g at pH 2, respectively. After incineration of the Pd-loaded PAH-modified biomass, metallic palladium was recovered in the ash. X-ray photoelectron spectroscopy (XPS) results confirmed that the palladium was recovered in two valency states: zero-valent and divalent palladium (as PdO). Therefore, we concluded that PAH-modified biomass is a useful and cost-effective biosorbent for the recovery of anionic precious metals as chloro-complex solutions containing hydrochloric acid produced from metal refining processes.

  6. RHAPSODY-G simulations - II. Baryonic growth and metal enrichment in massive galaxy clusters

    Science.gov (United States)

    Martizzi, Davide; Hahn, Oliver; Wu, Hao-Yi; Evrard, August E.; Teyssier, Romain; Wechsler, Risa H.

    2016-07-01

    We study the evolution of the stellar component and the metallicity of both the intracluster medium and of stars in massive (Mvir ≈ 6 × 1014 M⊙ h-1) simulated galaxy clusters from the RHAPSODY-G suite in detail and compare them to observational results. The simulations were performed with the AMR code RAMSES and include the effect of active galactic nucleus (AGN) feedback at the subgrid level. AGN feedback is required to produce realistic galaxy and cluster properties and plays a role in mixing material in the central regions and regulating star formation in the central galaxy. In both our low- and high-resolution runs with fiducial stellar yields, we find that stellar and ICM metallicities are a factor of 2 lower than in observations. We find that cool core clusters exhibit steeper metallicity gradients than non-cool core clusters, in qualitative agreement with observations. We verify that the ICM metallicities measured in the simulation can be explained by a simple `regulator' model in which the metallicity is set by a balance of stellar yield and gas accretion. It is plausible that a combination of higher resolution and higher metal yield in AMR simulation would allow the metallicity of simulated clusters to match observed values; however, this hypothesis needs to be tested with future simulations. Comparison to recent literature highlights that results concerning the metallicity of clusters and cluster galaxies might depend sensitively on the scheme chosen to solve the hydrodynamics.

  7. 7. Trace Metal Levels in Water and Sediment from the Sakumo II and ...

    African Journals Online (AJOL)

    User

    sediment in the Muni lagoon had trace metal concentrations with upper mean values as Cd (< 0.002 mg/l, 0.325. ± 0.01 mg/kg), Pb ... which physico-chemical measurements are made are ... pH are two important factors that govern ... status of coastal lagoons (Biney et al.,. 1998). .... detection of the analyzed metals were.

  8. Synthesis, crystal structure and photo luminescent property of a 3D metal-organic hybrid of Cd(II) constructed by two different bridging carboxylate

    Indian Academy of Sciences (India)

    Biswajit Bhattacharya; Rajdip Dey; Debajyoti Ghoshal

    2013-05-01

    A solvothermal reaction of cadmium (II) nitrate with succinic acid and isonicotinic acid creates a novel 3D metal-organic framework, [Cd3(isonicotinate)2(suc)2] (1). Single crystal X-ray structure determination reveals that complex 1 posses two crystallographically independent Cd(II) centres. The succinate anion acts here as a heptadented ligand and binds five Cd(II) centre simultaneously. The heptacoordinated Cd(II) centres are oxo-bridged by succinate moiety and the hexacoordinated metal centres are terminally connected through four different succinate moiety to make the overall 2D sheet arrangement. In unit cell, the ratio of hexadented Cd(II) and heptadented Cd(II) is 1:2. The new compound was also characterized by luminescence spectra and compared with the luminescence spectra of the pure isonicotinic acid.

  9. Competition between kaolinite flocculation and stabilization in divalent cation solutions dosed with anionic polyacrylamides.

    Science.gov (United States)

    Lee, Byung Joon; Schlautman, Mark A; Toorman, Erik; Fettweis, Michael

    2012-11-01

    Divalent cations have been reported to develop bridges between anionic polyelectrolytes and negatively-charged colloidal particles, thereby enhancing particle flocculation. However, results from this study of kaolinite suspensions dosed with various anionic polyacrylamides (PAMs) reveal that Ca(2+) and Mg(2+) can lead to colloid stabilization under some conditions. To explain the opposite but coexisting processes of flocculation and stabilization with divalent cations, a conceptual flocculation model with (1) particle-binding divalent cationic bridges between PAM molecules and kaolinite particles and (2) polymer-binding divalent cationic bridges between PAM molecules is proposed. The particle-binding bridges enhanced flocculation and aggregated kaolinite particles in large, easily-settleable flocs whereas the polymer-binding bridges increased steric stabilization by developing polymer layers covering the kaolinite surface. Both the particle-binding and polymer-binding divalent cationic bridges coexist in anionic PAM- and kaolinite-containing suspensions and thus induce the counteracting processes of particle flocculation and stabilization. Therefore, anionic polyelectrolytes in divalent cation-enriched aqueous solutions can sometimes lead to the stabilization of colloidal particles due to the polymer-binding divalent cationic bridges.

  10. Effect of divalent anions on photodegradation kinetics and pathways of riboflavin in aqueous solution.

    Science.gov (United States)

    Ahmad, Iqbal; Ahmed, Sofia; Sheraz, Muhammad Ali; Vaid, Faiyaz H M; Ansari, Izhar A

    2010-05-10

    The present investigation is based on a study of the effect of buffer and non-buffer divalent anions (phosphate, sulphate, tartrate, succinate, malonate) on the kinetics, product distribution and photodegradation pathways of riboflavin (RF) at pH 6.0-8.0. RF solutions (5x10(-5)M) were photodegraded in the presence of divalent anions (0.2-1.0M) using a visible light source and the photoproducts, cyclodehydroriboflavin (CDRF), formylmethylflavin (FMF), lumichrome (LC) and lumiflavin (LF) were assayed by a specific multicomponent spectrophotometric method. RF degradation in the presence of divalent anions follows parallel first-order kinetics to give CDRF and LC as the final products through photoaddition and photoreduction reactions, respectively. The divalent anion-catalysed CDRF formation is affected in the order: phosphate>sulphate>tartrate>succinate>malonate, showing maximum activity of the anions around pH 7. The divalent anions cause deviation of the photoreduction pathway in favour of the photoaddition pathway to form CDRF. The first- and second-order rate constants for the reactions involved in the photodegradation of RF have been determined and the rate-pH profiles and pathway relationships discussed. The catalytic activity of the divalent anions appears to be a function of the relative strength and chemical reactivity of the RF-divalent anion complex acting as a mediator in the photoaddition reaction.

  11. Polyplex Formation Influences Release Mechanism of Mono- and Di-Valent Ions from Phosphorylcholine Group Bearing Hydrogels

    Directory of Open Access Journals (Sweden)

    A. Nolan Wilson

    2014-09-01

    Full Text Available The release of monovalent potassium and divalent calcium ions from zwitterionic phosphorylcholine containing poly(2-hydroxyethyl methacrylate (pHEMA-based hydrogels was studied and the effects of polymer swelling, ion valence and temperature were investigated. For comparison, ions were loaded during hydrogel formulation or loaded by partitioning following construct synthesis. Using the Koshmeyer-Peppas release model, the apparent diffusion coefficient, Dapp, and diffusional exponents, n, were Dapp (pre-K+ = 2.03 × 10−5, n = 0.4 and Dapp (post-K+ = 1.86 × 10−5, n = 0.33 respectively, indicative of Fickian transport. The Dapp (pre-Ca2+ = 3.90 × 10−6, n = 0.60 and Dapp (post-Ca2+ = 2.85 × 10−6, n = 0.85, respectively, indicative of case II and anomalous transport. Results indicate that divalent cations form cation-polyelectrolyte anion polymer complexes while monovalent ions do not. Temperature dependence of potassium ion release was shown to follow an Arrhenius-type relation with negative apparent activation energy of −19 ± 15 while calcium ion release was temperature independent over the physiologically relevant range (25–45 °C studied. The negative apparent activation energy may be due to temperature dependent polymer swelling. No effect of polymer swelling on the diffusional exponent or rate constant was found suggesting polymer relaxation occurs independent of polymer swelling.

  12. Synthesis, characterisation and catalytic activity of 4, 5-imidazoledicarboxylate ligated Co(II) and Cd(II) metal-organic coordination complexes

    Science.gov (United States)

    Gangu, Kranthi Kumar; Maddila, Suresh; Mukkamala, Saratchandra Babu; Jonnalagadda, Sreekantha B.

    2017-09-01

    Two mono nuclear coordination complexes, namely, [Co(4,5-Imdc)2 (H2O)2] (1) and [Cd(4,5-Imdc)2(H2O)3]·H2O (2) were constructed using Co(II) and Cd(II) metal salts with 4,5-Imidazoledicarboxylic acid (4,5-Imdc) as organic ligand. Both 1, 2 were structurally characterized by single crystal XRD and the results reveal that 1 belongs to P21/n space group with unit cell parameters [a = 5.0514(3) Å, b = 22.5786(9) Å, c = 6.5377(3) Å, β = 111.5°] whereas, 2 belongs to P21/c space group with unit cell parameters [a = 6.9116(1) Å, b = 17.4579(2) Å, c = 13.8941(2) Å, β = 97.7°]. While Co(II) in 1 exhibited a six coordination geometry with 4,5-Imdc and water molecules, Cd(II) ion in 2 showed a seven coordination with the same ligand and solvent. In both 1 and 2, the hydrogen bond interactions with mononuclear unit generated 3D-supramolecular structures. Both complexes exhibit solid state fluorescent emission at room temperature. The efficacy of both the complexes as heterogeneous catalysts was examined in the green synthesis of six pyrano[2,3,c]pyrazole derivatives with ethanol as solvent via one-pot reaction between four components, a mixture of aromatic aldehyde, malononitrile, hydrazine hydrate and dimethyl acetylenedicarboxylate. Both 1 and 2 have produced pyrano [2,3,c]pyrazoles in impressive yields (92-98%) at room temperature in short interval of times (<20 min), with no need for any chromatographic separations. With good stability, ease of preparation and recovery plus reusability up to six cycles, both 1 and 2 prove to be excellent environmental friendly catalysts for the value-added organic transformations using green principles.

  13. Divalent lead cations induce cyclooxygenase-2 gene expression by epidermal growth factor receptor/nuclear factor-kappa B signaling in A431carcinoma cells.

    Science.gov (United States)

    Chou, Yii-Her; Woon, Peng-Yeong; Huang, Wan-Chen; Shiurba, Robert; Tsai, Yao-Ting; Wang, Yu-Shiuan; Hsieh, Tusty-Jiuan; Chang, Wen-Chang; Chuang, Hung-Yi; Chang, Wei-Chiao

    2011-06-10

    Divalent lead cations (Pb²+) are toxic metal pollutants that may contribute to inflammatory diseases in people and animals. Human vascular smooth muscle cells in culture respond to low concentrations of Pb²+ ions by activating mediators of inflammation via the plasma membrane epidermal growth factor receptor (EGFR). These include cyclooxygenase-2 (COX-2) and cytosolic phospholipase A₂ as well as the hormone-like lipid compound prostaglandin E₂. To further clarify the mechanism by which Pb²+ induces such mediators of inflammation, we tested human epidermoid carcinoma cell line A431 that expresses high levels of EGFR. Reverse transcription PCR and western blots confirmed A431 cells treated with a low concentration (1 μM) of Pb²+ in the form of lead (II) nitrate increased expression of COX-2 mRNA and its encoded protein in a time-dependent manner. Promoter deletion analysis revealed the transcription factor known as nuclear factor-kappa B (NF-κB) was a necessary component of the COX-2 gene response. NF-κB inhibitor BAY 11-7082 suppressed Pb²+-induced COX-2 mRNA expression, and EGFR inhibitors AG1478 and PD153035 as well as EGFR small interfering RNA reduced the coincident nuclear translocation of NF-κB. Our findings support the hypothesis that low concentrations of Pb²+ ions incite inflammation by inducing COX-2 gene expression via the EGFR/NF-κB signal transduction pathway. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

  14. Synthesis, spectroscopic and redox properties of the mononuclear NiII, NiII(BPh2)2 containing (B-C) bond and trinuclear CuII-NiII-CuII type-metal complexes of ,'-(4-amino-1-benzyl piperidine)-glyoxime

    Indian Academy of Sciences (India)

    Ahmet Kilic; Esref Tas; Ismail Yilmaz

    2009-01-01

    The novel vic-dioxime ligand containing the 4-amino-1-benzyl piperidine group, ,'-(4-amino-1-benzyl piperidine)-glyoxime, (LH2) has been prepared from 4-amino-1-benzyl piperidine with anti-dichloroglyoxime at -15°C in absolute THF. Mononuclear NiII metal complex has been obtained with 1 : 2 metal/ligand ratio. The NiII complex of this ligand is proposed to be square planar geometry. IR spectra show that the ligand acts in a tetradentate manner and coordinates N4 donor groups of LH2 to NiII ion. The detection of H-bonding (O-H$\\cdots$O) in the [Ni(LH))2] (${\\rm 1}$) metal complex by IR spectra supported the square-planar MN4 coordination of mononuclear complex. The disappereance of H-bonding (O-H$\\cdots$O) in the [Ni(L)2(BPh2)2] (2) complex shows that the BPh$^{+}_{2}$-capped groups (BPh$^{+}_{2}$ cation formed BPh4 anion) attaches to the main oxime core. MN4 coordination of the [Ni(LH)2] (1) and [Ni(L)2(BPh2)2] (2) metal complexes were also determined by 1H-NMR spectroscopy. In the trinuclear CuII-NiII-CuII metal complexes, the NiII ion centered into the main oxime core by the coordination of the imino groups while the two CuII ions coordinate dianionic oxygen donors of the oxime groups and linked to the ligands of 1,10-phenanthroline, 2,2'-bipyridine, and 4,4'-bipyridine. The ligand and their mono and trinuclear metal complexes were characterized by elemental analyses, FT-IR, UV-Vis, 1H and 13C-NMR spectra, magnetic susceptibility measurements, molar conductivity, cyclic voltammetry, mass spectra and X-ray powder techniques. The cyclic voltammetric results show that the cathodic peak potential of [Ni(L)2(BPh2)2] shifted toward more negative value compared to that of [Ni(LH)2], probably due to a decreasing effect of back donation of metal-oxime moieties as a result of the BPh$^{+}_{2}$-bridged complex formation. Also, the formation of the trinuclear CuII-NiII-CuII metal complexes caused considerable changes on the CV behaviour of mononuclear [Ni(LH)2] (1

  15. Adsorption and surface oxidation of Fe(II) on metal (hydr)oxides.

    NARCIS (Netherlands)

    Hiemstra, T.; Riemsdijk, van W.H.

    2007-01-01

    The Fe(II) adsorption by non-ferric and ferric (hydr)oxides has been analyzed with surface complexation modeling. The CD model has been used to derive the interfacial distribution of charge. The fitted CD coefficients have been linked to the mechanism of adsorption. The Fe(II) adsorption is

  16. A new Mannich base and its transition metal (II) complexes - Synthesis, structural characterization and electrochemical study

    Indian Academy of Sciences (India)

    N Raman; S Esthar; C Thangaraja

    2004-06-01

    new Mannich base, N-(1-morpholinobenzyl) semicarbazide (MBS), formed by the condensation of morpholine, semicarbazide and benzaldehyde, and its Cu(II), Ni(II), Co(II) and Zn(II) complexes have been synthesized. Their structures have been elucidated on the basis of analytical, magnetic, electrical conductivity and spectral study as well as elemental analyses. The complexes exhibit square-planar geometry. The monomeric and non-electrolytic nature of the complexes is evidenced by their magnetic susceptibility and low conductance data. The electrochemical property of the ligand and its complexes in acetonitrile solution was studied by cyclic voltammetry. The X-band ESR spectra of the Cu(II) complex in DMSO at 300 and 77 K were recorded and their salient features are reported.

  17. How metal substitution affects the enzymatic activity of catechol-o-methyltransferase.

    Directory of Open Access Journals (Sweden)

    Manuel Sparta

    Full Text Available Catechol-O-methyltransferase (COMT degrades catecholamines, such as dopamine and epinephrine, by methylating them in the presence of a divalent metal cation (usually Mg(II, and S-adenosyl-L-methionine. The enzymatic activity of COMT is known to be vitally dependent on the nature of the bound metal: replacement of Mg(II with Ca(II leads to a complete deactivation of COMT; Fe(II is slightly less than potent Mg(II, and Fe(III is again an inhibitor. Considering the fairly modest role that the metal plays in the catalyzed reaction, this dependence is puzzling, and to date remains an enigma. Using a quantum mechanical / molecular mechanical dynamics method for extensive sampling of protein structure, and first principle quantum mechanical calculations for the subsequent mechanistic study, we explicate the effect of metal substitution on the rate determining step in the catalytic cycle of COMT, the methyl transfer. In full accord with experimental data, Mg(II bound to COMT is the most potent of the studied cations and it is closely followed by Fe(II, whereas Fe(III is unable to promote catalysis. In the case of Ca(II, a repacking of the protein binding site is observed, leading to a significant increase in the activation barrier and higher energy of reaction. Importantly, the origin of the effect of metal substitution is different for different metals: for Fe(III it is the electronic effect, whereas in the case of Ca(II it is instead the effect of suboptimal protein structure.

  18. Clustered Conserved Cysteines in Hyaluronan Synthase Mediate Cooperative Activation by Mg(2+) Ions and Severe Inhibitory Effects of Divalent Cations.

    Science.gov (United States)

    Tlapak-Simmons, Valarie L; Medina, Andria P; Baggenstoss, Bruce A; Nguyen, Long; Baron, Christina A; Weigel, Paul H

    2011-11-15

    Hyaluronan synthase (HAS) uses UDP-GlcUA and UDP-GlcNAc to make hyaluronan (HA). Streptococcus equisimilis HAS (SeHAS) contains four conserved cysteines clustered near the membrane, and requires phospholipids and Mg(2+) for activity. Activity of membrane-bound or purified enzyme displayed a sigmoidal saturation profile for Mg(2+) with a Hill coefficient of 2. To assess if Cys residues are important for cooperativity we examined the Mg(2+) dependence of mutants with various combinations of Cys-to-Ala mutations. All Cys-mutants lost the cooperative response to Mg(2+). In the presence of Mg(2+), other divalent cations inhibited SeHAS with different potencies (Cu(2+)~Zn(2+) >Co(2+) >Ni(2+) >Mn(2+) >Ba(2+) Sr(2+) Ca(2+)). Some divalent metal ions likely inhibit by displacement of Mg(2+)-UDP-Sugar complexes (e.g. Ca(2+), Sr(2+) and Ba(2+) had apparent Ki values of 2-5 mM). In contrast, Zn(2+) and Cu(2+) inhibited more potently (apparent Ki ≤ 0.2 mM). Inhibition of Cys-null SeHAS by Cu(2+), but not Zn(2+), was greatly attenuated compared to wildtype. Double and triple Cys-mutants showed differing sensitivities to Zn(2+) or Cu(2+). Wildtype SeHAS allowed to make HA prior to exposure to Zn(2+) or Cu(2+) was protected from inhibition, indicating that access of metal ions to sensitive functional groups was hindered in processively acting HA•HAS complexes. We conclude that clustered Cys residues mediate cooperative interactions with Mg(2+) and that transition metal ions inhibit SeHAS very potently by interacting with one or more of these -SH groups.

  19. Alginate and Algal-Based Beads for the Sorption of Metal Cations: Cu(II) and Pb(II)

    Science.gov (United States)

    Wang, Shengye; Vincent, Thierry; Faur, Catherine; Guibal, Eric

    2016-01-01

    Alginate and algal-biomass (Laminaria digitata) beads were prepared by homogeneous Ca ionotropic gelation. In addition, glutaraldehyde-crosslinked poly (ethyleneimine) (PEI) was incorporated into algal beads. The three sorbents were characterized by scanning electron microscopy (SEM) coupled with energy dispersive X-ray analysis (EDX): the sorption occurs in the whole mass of the sorbents. Sorption experiments were conducted to evaluate the impact of pH, sorption isotherms, and uptake kinetics. A special attention was paid to the effect of drying (air-drying vs. freeze-drying) on the mass transfer properties. For alginate, freeze drying is required for maintaining the porosity of the hydrogel, while for algal-based sorbents the swelling of the material minimizes the impact of the drying procedure. The maximum sorption capacities observed from experiments were 415, 296 and 218 mg Pb g−1 and 112, 77 and 67 mg Cu g−1 for alginate, algal and algal/PEI beads respectively. Though the sorption capacities of algal-beads decreased slightly (compared to alginate beads), the greener and cheaper one-pot synthesis of algal beads makes this sorbent more competitive for environmental applications. PEI in algal beads decreases the sorption properties in the case of the sorption of metal cations under selected experimental conditions. PMID:27598128

  20. Modification and characterization of PET fibers for fast removal of Hg(II), Cu(II) and Co(II) metal ions from aqueous solutions.

    Science.gov (United States)

    Monier, M; Abdel-Latif, D A

    2013-04-15

    A new chelating fiber (PET-TSC) was prepared with PET for fast removal of Hg(2+), Cu(2+) and Co(2+) from water. Elemental analysis, SEM, BET surface area, (13)C NMR, FTIR and X-ray diffraction spectra were used to characterize PET-TSC. The higher uptake capacity of the studied metal ions was observed at higher pH values. Kinetic study indicated that the adsorption of Hg(2+), Cu(2+) and Co(2+) followed the pseudo-second-order equation, suggesting chemical sorption as the rate-limiting step of the adsorption process. The best interpretation for the equilibrium data was given by Langmuir isotherm, and the maximum adsorption capacities were 120.02, 96.81 and 78.08 mg/g for Hg(2+), Cu(2+) and Co(2+) ions, respectively. 1M HCl or 0.1M EDTA could be used as effective eluant to desorb the Hg(2+), Cu(2+) and Co(2+) adsorbed by PET-TSC, and the adsorption capacity of PET-TSC for the three heavy metal ions could still be maintained at about 90% level at the 5th cycle. Accordingly, it is expected that PET-TSC could be used as a promising adsorbent for fast removal of heavy metal ions from water, and the present work also might provide a simple and effective method to reuse the waste PET fibers.

  1. Star Formation in the First Galaxies - II: Clustered Star Formation and the Influence of Metal Line Cooling

    CERN Document Server

    Safranek-Shrader, Chalence; Bromm, Volker

    2013-01-01

    Population III stars are believed to have been more massive than typical stars today and to have formed in relative isolation. The thermodynamic impact of metals is expected to induce a transition leading to clustered, low-mass Population II star formation. In this work, we present results from three cosmological simulations, only differing in gas metallicity, that focus on the impact of metal fine-structure line cooling on the formation of stellar clusters in a high-redshift atomic cooling halo. Introduction of sink particles allows us to follow the process of gas hydrodynamics and accretion onto cluster stars for 4 Myr corresponding to multiple local free-fall times. At metallicities at least 10^-3 Zsun, gas is able to reach the CMB temperature floor and fragment pervasively resulting in a stellar cluster of size ~1 pc and total mass ~1000 Msun. The masses of individual sink particles vary, but are typically ~100 Msun, consistent with the Jeans mass when gas cools to the CMB temperature, though some solar m...

  2. High-Resolution Spectroscopy of Extremely Metal-Poor Stars from SDSS/SEGUE: II. Binary Fraction

    CERN Document Server

    Aoki, Wako; Beers, Timothy C; Honda, Satoshi

    2014-01-01

    The fraction of binary systems in various stellar populations of the Galaxy and the distribution of their orbital parameters are important but not well-determined factors in studies of star formation, stellar evolution, and Galactic chemical evolution. While observational studies have been carried out for a large sample of nearby stars, including some metal-poor, Population II stars, almost no constraints on the binary nature for extremely metal-poor (EMP; [Fe/H] < -3.0) stars have yet been obtained. Here we investigate the fraction of double-lined spectroscopic binaries and carbon-enhanced metal-poor (CEMP) stars, many of which could have formed as pairs of low-mass and intermediate-mass stars, to estimate the lower limit of the fraction of binary systems having short periods. The estimate is based on a sample of very metal-poor stars selected from the Sloan Digital Sky Survey, and observed at high spectral resolution in a previous study by Aoki et al. That survey reported three double-lined spectroscopic...

  3. Interfacial binding of divalent cations to calixarene-based Langmuir monolayers.

    Science.gov (United States)

    Tulli, Ludovico G; Wang, Wenjie; Lindemann, William R; Kuzmenko, Ivan; Meier, Wolfgang; Vaknin, David; Shahgaldian, Patrick

    2015-03-03

    The interactions of Langmuir monolayers produced through the self-assembly of an amphiphilic p-carboxycalix[4]arene (1) with a series of divalent, fourth-period transition metals, at the air-water interface, were investigated. Changes in the interfacial behavior of 1 in response to the presence of CuCl2, CoCl2, MnCl2, and NiCl2 were studied by means of Langmuir compression isotherms and Brewster angle microscopy (BAM). The measurements revealed that the self-assembly properties of 1 are significantly affected by Cu(2+) ions. The interactions of 1-based monolayers with Co(2+) and Cu(2+) ions were further investigated by means of synchrotron radiation-based X-ray reflectivity (XRR), X-ray near-total-reflection fluorescence (XNTRF), and grazing incidence X-ray diffraction (GIXD). XNTRF and XRR analyses revealed that the monolayer of 1 binds more strongly to Cu(2+) than Co(2+) ions. In the presence of relatively high concentrations of Cu(2+) ions in the subphase (1.4 × 10(-3) M), XNTRF exhibited anomalous depth profile behavior and GIXD measurements showed considerably strong diffuse scattering. Both measurements suggest the formation of Cu(2+) clusters contiguous to the monolayer of 1.

  4. A porous Cd(II) metal-organic framework with high adsorption selectivity for CO2 over CH4

    Science.gov (United States)

    Zhu, Chunlan

    2017-05-01

    Metal-organic frameworks (MOFs) have attracted a lot of attention in recent decades. We applied a semi-rigid four-carboxylic acid linker to assemble with Cd(II) ions to generate a novel microporous Cd(II) MOF material. Single crystal X-ray diffraction study reveals the different two dimension (2D) layers can be further packed together with an AB fashion by hydrogen bonds (O4sbnd H4⋯O7 = 1.863 Å) to construct a three dimension (3D) supermolecular architecture. The resulting sample can be synthesized under solvothermal reactions successfully, which exhibits high selectivity adsorption of CO2 over CH4 at room temperature. In addition, the obtained sample was characterized by thermal gravimetric analyses (TGA), Fourier-transform infrared spectra (FT-IR), elemental analysis (CHN) and powder X-ray diffraction (PXRD).

  5. Theoretical study of the Pb(II)-catechol system in dilute aqueous solution: Complex structure and metal coordination sphere determination

    Science.gov (United States)

    Lapouge, Christine; Cornard, Jean-Paul

    2010-04-01

    We investigated the unknown interaction of Pb(II) with catechol ligand in diluted aqueous solution by electronic spectroscopies combined with quantum chemical calculations. The aim of this work is the determination of the complete structure of the complex formed and particularly the metal coordination sphere. Three successive steps have been necessary to reach this goal: (i) the comparison of the experimental electronic absorption spectrum with theoretical spectra calculated from various hypothetical structures, (ii) complexation reaction pathways calculations in vacuum and with taking into account the solvent effects and finally (iii) the fluorescence emission wavelength calculations. All these investigations led to identify a monodentate complex with the monodeprotonated ligand, in which the Pb atom presents a coordination number of five. The formula of the complex is [Pb(Hcat)(HO)4]mono+.

  6. Synthesis, Characterization, and Magnetic and Thermal Studies on Some Metal(II Thiophenyl Schiff Base Complexes

    Directory of Open Access Journals (Sweden)

    Aderoju Amoke Osowole

    2011-01-01

    Full Text Available 4-(Thiophen-3-yl-aniline undergoes condensation with o-vanillin to form an ONS donor Schiff base, 2-methoxy-6-[(4-thiophene-3-yl-phenylimino-methyl]-phenol, which forms complexes of the type [ML2]xH2O (where M = Mn, Co, Ni, Cu, Zn, Pd. These complexes are characterized by elemental analysis, 1H nmr, electronic, mass, and IR spectroscopies and conductance measurements. The electronic, IR and CHN data are supportive of a 4-coordinate tetrahedral geometry for Mn(II, Co(II, Ni(II, and Zn(II complexes and square-planar geometry for Cu(II and Pd(II complexes, with the chromophores N2O2. The magnetic data reveals that the complexes are magnetically dilute and mononuclear with exception of the Cu(II complex, which exhibits some anti-ferromagnetisms. The complexes are air-stable solids, and none is an electrolyte in nitro methane.

  7. A curious interplay in the films of N-heterocyclic carbene PtII complexes upon deposition of alkali metals

    Science.gov (United States)

    Makarova, Anna A.; Grachova, Elena V.; Niedzialek, Dorota; Solomatina, Anastasia I.; Sonntag, Simon; Fedorov, Alexander V.; Vilkov, Oleg Yu.; Neudachina, Vera S.; Laubschat, Clemens; Tunik, Sergey P.; Vyalikh, Denis V.

    2016-05-01

    The recently synthesized series of PtII complexes containing cyclometallating (phenylpyridine or benzoquinoline) and N-heterocyclic carbene ligands possess intriguing structures, topologies, and light emitting properties. Here, we report curious physicochemical interactions between in situ PVD-grown films of a typical representative of the aforementioned PtII complex compounds and Li, Na, K and Cs atoms. Based on a combination of detailed core-level photoelectron spectroscopy and quantum-chemical calculations at the density functional theory level, we found that the deposition of alkali atoms onto the molecular film leads to unusual redistribution of electron density: essential modification of nitrogen sites, reduction of the coordination PtII centre to Pt0 and decrease of electron density on the bromine atoms. A possible explanation for this is formation of a supramolecular system “Pt complex-alkali metal ion” the latter is supported by restoration of the system to the initial state upon subsequent oxygen treatment. The discovered properties highlight a considerable potential of the PtII complexes for a variety of biomedical, sensing, chemical, and electronic applications.

  8. Spectral characterization, electrochemical and anticancer studies on some metal(II) complexes containing tridentate quinoxaline Schiff base

    Science.gov (United States)

    Chellaian, Justin Dhanaraj; Johnson, Jijo

    2014-06-01

    Co(II), Ni(II), Cu(II) and Zn(II) complexes of a tridentate ONO donor Schiff base ligand derived from 3-(2-aminoethylamino)quinoxalin-2(1H)-one were synthesized. The ligand and its metal complexes were characterized using elemental analysis, molar conductance, IR, 1H NMR, mass, magnetic susceptibility, electronic spectra and ESR spectral studies. Electrochemical behavior of the synthesized compounds was studied using cyclic voltammetry. The grain size of the synthesized compounds was determined by powder XRD. The Schiff base and its complexes have been screened for their antimicrobial activities against the bacterial species E. coli, K. pneumoniae, P. aeruginosa and S. aureus; fungal species include, A. niger, and C. albicans by disc diffusion method. The results show that the complexes have higher activity than the free ligand. The interaction of the complexes with calf thymus DNA (CT DNA) has been investigated by electronic absorption method. Furthermore, the DNA cleavage activity of the complexes was studied using agarose gel electrophoresis. In vitro anticancer studies of the ligand and its complexes using MTT assay was also done.

  9. Half-sandwich iron(ii) complexes with protic acyclic diaminocarbene ligands: synthesis, deprotonation and metalation reactions.

    Science.gov (United States)

    Ruiz, Javier; García, Lucía; Vivanco, Marilín; Sol, Daniel; García-Granda, Santiago

    2017-08-08

    A variety of half-sandwich iron(ii) complexes with diprotic acyclic diaminocarbene ligands (pADCs) have been obtained by reaction of the cationic complexes [Fe(Cp)(CO)2(CNR)](+) and [Fe(Cp)(CO)(CNR)2](+) with methylamine, and their acid-base behaviour was studied, revealing an easy reversible deprotonation reaction of both N-H moieties of the carbene ligands. The deprotonation process is frequently followed by a nucleophilic attack of the nitrogen atom on a vicinal carbonyl or isocyanide ligand, affording the corresponding metallacycles. Metalation of one or two N-H groups of the pADC ligands can be accomplished by reaction of the carbene complexes with either [AuCl(PPh3)] or [Ru(p-cym)Cl2]2 in the presence of KOH or LiHMDS as deprotonating agents. A number of Fe(ii)/Au(i) and Fe(ii)/Ru(ii) heterometallic complexes have been prepared in this way, some of them formally containing unique metalla-N-heterocyclic carbene ligands.

  10. A curious interplay in the films of N-heterocyclic carbene Pt(II) complexes upon deposition of alkali metals.

    Science.gov (United States)

    Makarova, Anna A; Grachova, Elena V; Niedzialek, Dorota; Solomatina, Anastasia I; Sonntag, Simon; Fedorov, Alexander V; Vilkov, Oleg Yu; Neudachina, Vera S; Laubschat, Clemens; Tunik, Sergey P; Vyalikh, Denis V

    2016-05-06

    The recently synthesized series of Pt(II) complexes containing cyclometallating (phenylpyridine or benzoquinoline) and N-heterocyclic carbene ligands possess intriguing structures, topologies, and light emitting properties. Here, we report curious physicochemical interactions between in situ PVD-grown films of a typical representative of the aforementioned Pt(II) complex compounds and Li, Na, K and Cs atoms. Based on a combination of detailed core-level photoelectron spectroscopy and quantum-chemical calculations at the density functional theory level, we found that the deposition of alkali atoms onto the molecular film leads to unusual redistribution of electron density: essential modification of nitrogen sites, reduction of the coordination Pt(II) centre to Pt(0) and decrease of electron density on the bromine atoms. A possible explanation for this is formation of a supramolecular system "Pt complex-alkali metal ion"; the latter is supported by restoration of the system to the initial state upon subsequent oxygen treatment. The discovered properties highlight a considerable potential of the Pt(II) complexes for a variety of biomedical, sensing, chemical, and electronic applications.

  11. The Metal Abundances across Cosmic Time (MACT) Survey. II. Evolution of the Mass-metallicity Relation over 8 Billion Years, Using [OIII]4363AA-based Metallicities

    Science.gov (United States)

    Ly, Chun; Malkan, Matthew A.; Rigby, Jane R.; Nagao, Tohru

    2016-09-01

    We present the first results from MMT and Keck spectroscopy for a large sample of 0.1≤slant z≤slant 1 emission-line galaxies selected from our narrowband imaging in the Subaru Deep Field. We measured the weak [O iii] λ4363 emission line for 164 galaxies (66 with at least 3σ detections, and 98 with significant upper limits). The strength of this line is set by the electron temperature for the ionized gas. Because the gas temperature is regulated by the metal content, the gas-phase oxygen abundance is inversely correlated with [O iii] λ4363 line strength. Our temperature-based metallicity study is the first to span ≈ 8 Gyr of cosmic time and ≈ 3 dex in stellar mass for low-mass galaxies, {log}({M}\\star /{M}⊙ )≈ 6.0-9.0. Using extensive multi-wavelength photometry, we measure the evolution of the stellar mass-gas metallicity relation and its dependence on dust-corrected star formation rate (SFR). The latter is obtained from high signal-to-noise Balmer emission-line measurements. Our mass-metallicity relation is consistent with Andrews & Martini at z≤slant 0.3, and evolves toward lower abundances at a given stellar mass, {log}{({{O/H}})\\propto (1+z)}-{2.32-0.26+0.52}. We find that galaxies with lower metallicities have higher SFRs at a given stellar mass and redshift, although the scatter is large (≈ 0.3 dex) and the trend is weaker than seen in local studies. We also compare our mass-metallicity relation against predictions from high-resolution galaxy formation simulations, and find good agreement with models that adopt energy- and momentum-driven stellar feedback. We identified 16 extremely metal-poor galaxies with abundances of less than a tenth of solar; our most metal-poor galaxy at z≈ 0.84 is similar to I Zw 18.

  12. Amending the anisotropy barrier and luminescence behavior of heterometallic trinuclear linear [M(II) -Ln(III) -M(II) ] (Ln(III) =Gd, Tb, Dy; M(II) =Mg/Zn) complexes by change from divalent paramagnetic to diamagnetic metal ions.

    Science.gov (United States)

    Das, Sourav; Bejoymohandas, K S; Dey, Atanu; Biswas, Sourav; Reddy, M L P; Morales, Roser; Ruiz, Eliseo; Titos-Padilla, Silvia; Colacio, Enrique; Chandrasekhar, Vadapalli

    2015-04-20

    The sequential reaction of a multisite coordinating compartmental ligand [2-(2-hydroxy-3-(hydroxymethyl)-5-methylbenzylideneamino)-2-methylpropane-1,3-diol] (LH4 ) with appropriate lanthanide salts followed by the addition of [Mg(NO3 )2 ]⋅6 H2 O or [Zn(NO3 )2 ]⋅6 H2 O in a 4:1:2 stoichiometric ratio in the presence of triethylamine affords a series of isostructural heterometallic trinuclear complexes containing [Mg2 Ln](3+) (Ln=Dy, Gd, and Tb) and [Zn2 Ln](3+) (Ln=Dy, Gd, and Tb) cores. The formation of these complexes is demonstrated by X-ray crystallography as well as ESI-MS spectra. All complexes are isostructural possessing a linear trimetallic core with a central lanthanide ion. The comprehensive studies discussed involve the synthesis, structure, magnetism, and photophysical properties on this family of trinuclear [Mg2 Ln](3+) and [Zn2 Ln](3+) heterometallic complexes. [Mg2 Dy](3+) and [Zn2 Dy](3+) show slow relaxation of the magnetization below 12 K under zero applied direct current (dc) field, but without reaching a neat maximum, which is due to the overlapping with a faster quantum tunneling relaxation mediated through dipole-dipole and hyperfine interactions. Under a small applied dc field of 1000 Oe, the quantum tunneling is almost suppressed and temperature and frequency dependent peaks are observed, thus confirming the single-molecule magnet behavior of complexes [Mg2 Dy](3+) and [Zn2 Dy](3+) .

  13. Physico – Chemical Study of Transition Metal Complexes with Schiff’s Base derived from Naphthaldehyde and Substituted Aromatic Amines

    Directory of Open Access Journals (Sweden)

    Prem Mohan Mishra

    2016-10-01

    Full Text Available In continuation of the previous work here we are going to report stability constant values of transition metals like Cu(II , Ni(II, Co(II and Zn (II with Schiff;s base ligand. Schiff’s base ligands were synthesized by the condensation reaction of Naphthaldehyde with 7- Hydroxy naphthalene – 2 – amine .Nitrate salts of divalent cobalt, nickel, copper and zinc were estimated by usual methods. Ligand was analysed for elements by standard method. pH metric titrations were carried out with the help of digital pH meter and stability constant of complexes of these metals with the ligands synthesized were computed by Irving- Rossotti technique modified by Calvin-Bjerrum. The stability constant values of metals for the given ligand were found to be in the order Cu(II > Ni(II, Co(II > Zn (II. This result is in agreement with the natural order proposed by Irving-William.

  14. Galaxy evolution in cosmological simulations with outflows - II. Metallicities and gas fractions

    Science.gov (United States)

    Davé, Romeel; Finlator, Kristian; Oppenheimer, Benjamin D.

    2011-09-01

    We use cosmological hydrodynamic simulations to investigate how inflows, star formation and outflows govern the gaseous and metal content of galaxies within a hierarchical structure formation context. In our simulations, galaxy metallicities are established by a balance between inflows and outflows as governed by the mass outflow rate, implying that the mass-metallicity relation reflects how the outflow rate varies with stellar mass. Gas content, meanwhile, is set by a competition between inflow into and gas consumption within the interstellar medium, the latter being governed by the star formation law, while the former is impacted by both wind recycling and preventive feedback. Stochastic variations in the inflow rate move galaxies off the equilibrium mass-metallicity and mass-gas fraction relations in a manner correlated with the star formation rate, and the scatter is set by the time-scale to re-equilibrate. The evolution of both relations from z= 3 → 0 is slow, as individual galaxies tend to evolve mostly along the relations. Gas fractions at a given stellar mass slowly decrease with time because the cosmic inflow rate diminishes faster than the consumption rate, while metallicities slowly increase as infalling gas becomes more enriched. Observations from z˜ 3 → 0 are better matched by simulations employing momentum-driven wind scalings rather than constant wind speeds, but all models predict too low gas fractions at low masses and too high metallicities at high masses. All our models reproduce observed second-parameter trends of the mass-metallicity relation with the star formation rate and environment, indicating that these are a consequence of equilibrium and not feedback. Overall, the analytical framework of our equilibrium scenario broadly captures the relevant physics establishing the galaxy gas and metal content in simulations, which suggests that the cycle of baryonic inflows and outflows centrally governs the cosmic evolution of these properties

  15. Heavy metals in urban soils of East St. Louis, IL. Part II: Leaching characteristics and modeling.

    Science.gov (United States)

    Kaminski, M D; Landsberger, S

    2000-09-01

    The city of East St. Louis, IL, has a history of abundant industrial activities including smelters of ferrous and non-ferrous metals, a coal-fired power plant, companies that produced organic and inorganic chemicals, and petroleum refineries. Following a gross assessment of heavy metals in the community soils (see Part I of this two-part series), leaching tests were performed on specific soils to elucidate heavy metal-associated mineral fractions and general leachability. Leaching experiments, including the Toxicity Characteristic Leaching Procedure (TLCP) and column tests, and sequential extractions, illustrated the low leachability of metals in East St. Louis soils. The column leachate results were modeled using a formulation developed for fly ash leaching. The importance of instantaneous dissolution was evident from the model. By incorporating desorption/adsorption terms into the source term, the model was adapted very well to the time-dependent heavy metal leachate concentrations. The results demonstrate the utility of a simple model to describe heavy metal leaching from contaminated soils.

  16. Bivalent transition metal complexes of cetirizine: Spectroscopic, equilibrium studies and biological activity

    Science.gov (United States)

    El-Sherif, Ahmed A.; Shoukry, Mohamed M.; Abobakr, Lamis O.

    2013-08-01

    Metal complexes of cetirizineṡ2HCl (CTZ = 2-[2-[4-[(4-chlorophenyl)phenyl methyl]piperazine-1-yl]-ethoxy]acetic acid, dihydrochloride have been prepared and characterized by elemental analyses, IR, solid reflectance, magnetic moment, molar conductance, and UV-Vis spectra. The analytical data of the complexes show the formation of 1:2 [M:L] ratio, where M represents Ni(II), Co(II) and Cu(II) ions, while L represents the deprotonated CTZ ligand. IR spectra show that CTZ is coordinated to the metal ions in a monodentate manner through carboxylate-O atom. Protonation equilibria of CTZ and its metal complexation by some divalent metal ions were determined in aqueous solution at constant ionic strength (0.1 M NaCl) using an automatic potentiometric technique. Thermodynamic parameters for the protonation equilibria of CTZ were calculated and discussed. The stability order of M(II)-CTZ complexes were found to obey Mn2+ Bacillus subtillis RCMB 010067, Staphylococcus aureus RCMB 010028, Pseudomonas aeuroginosa RCMB 010043, and Escherichia coli RCMB 010052) and fungi as (Aspergillus flavus RCMB 02568, Pencicillium italicum RCMB 03924, Candida albicans RCMB 05031 and Geotricum candidum RCMB 05097). The activity data show that the metal complexes have antibacterial and antifungal activity more than the parent CTZ ligand against one or more bacterial or fungi species. MIC was evaluated for the isolated complexes.

  17. Studies in transition metal chemistry ; VI. Soluble Ziegler-type catalysts based on vanadium, part II

    NARCIS (Netherlands)

    Liefde Meijer, H.J. de; Hurk, J.W.G. van den; Kerk, G.J.M. van der

    1966-01-01

    Spectrophotometric measurements in the visible region on soluble catalyst systems prepared from (i) vanadium tetrachloride, aluminium bromide and tetraphenyltin and (ii) vanadium tetrachloride or vanadium oxytrichloride and ethylaluminium dihalides are reported. The formation of hydrocarbonsoluble i

  18. Modification and characterization of PET fibers for fast removal of Hg(II), Cu(II) and Co(II) metal ions from aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Monier, M., E-mail: monierchem@yahoo.com [Chemistry Department, Faculty of Science, Mansoura University, Mansoura (Egypt); Abdel-Latif, D.A. [Chemistry Department, Faculty of Science, Mansoura University, Mansoura (Egypt)

    2013-04-15

    Highlights: ► PET fibers were graft copolymerized with acrylonitrile. ► Further modification was carried out through the reaction with hydrazine hydrate and then potassium thiocyanate. ► The resulted chelating fibers were characterized by various instrumental methods. ► The fibers were applied to remove Hg{sup 2+}, Cu{sup 2+} and Co{sup 2+} from aqueous solutions. -- Abstract: A new chelating fiber (PET-TSC) was prepared with PET for fast removal of Hg{sup 2+}, Cu{sup 2+} and Co{sup 2+} from water. Elemental analysis, SEM, BET surface area, {sup 13}C NMR, FTIR and X-ray diffraction spectra were used to characterize PET-TSC. The higher uptake capacity of the studied metal ions was observed at higher pH values. Kinetic study indicated that the adsorption of Hg{sup 2+}, Cu{sup 2+} and Co{sup 2+} followed the pseudo-second-order equation, suggesting chemical sorption as the rate-limiting step of the adsorption process. The best interpretation for the equilibrium data was given by Langmuir isotherm, and the maximum adsorption capacities were 120.02, 96.81 and 78.08 mg/g for Hg{sup 2+}, Cu{sup 2+} and Co{sup 2+} ions, respectively. 1 M HCl or 0.1 M EDTA could be used as effective eluant to desorb the Hg{sup 2+}, Cu{sup 2+} and Co{sup 2+} adsorbed by PET-TSC, and the adsorption capacity of PET-TSC for the three heavy metal ions could still be maintained at about 90% level at the 5th cycle. Accordingly, it is expected that PET-TSC could be used as a promising adsorbent for fast removal of heavy metal ions from water, and the present work also might provide a simple and effective method to reuse the waste PET fibers.

  19. Multi-component synthesis of 2-amino-6-(alkyllthio)pyridine-3,5-dicarbonitriles using Zn(II) and Cd(II) metal-organic frameworks (MOFs) under solvent-free conditions.

    Science.gov (United States)

    Thimmaiah, Muralidhara; Li, Peng; Regati, Sridhar; Chen, Banglin; Zhao, John Cong-Gui

    2012-09-05

    Multi-component synthesis 2-amino-3,5-dicarbonitrile-6-thio-pyridines has been developed by using the reaction of aldehydes, malononitrile, and thiophenols in the presence of a Zn (II) or a Cd(II) metal-organic framework (MOF) as the heterogeneous catalyst. This protocol tolerates different functional groups on the substrates and does not require the use of any organic solvent. Moreover, the Zn(II) and Cd (II) MOF catalysts can be recovered and reused for a number of runs without loss of activity.

  20. Structural Insights into Mitochondrial Calcium Uniporter Regulation by Divalent Cations.

    Science.gov (United States)

    Lee, Samuel K; Shanmughapriya, Santhanam; Mok, Mac C Y; Dong, Zhiwei; Tomar, Dhanendra; Carvalho, Edmund; Rajan, Sudarsan; Junop, Murray S; Madesh, Muniswamy; Stathopulos, Peter B

    2016-09-22

    Calcium (Ca(2+)) flux into the matrix is tightly controlled by the mitochondrial Ca(2+) uniporter (MCU) due to vital roles in cell death and bioenergetics. However, the precise atomic mechanisms of MCU regulation remain unclear. Here, we solved the crystal structure of the N-terminal matrix domain of human MCU, revealing a β-grasp-like fold with a cluster of negatively charged residues that interacts with divalent cations. Binding of Ca(2+) or Mg(2+) destabilizes and shifts the self-association equilibrium of the domain toward monomer. Mutational disruption of the acidic face weakens oligomerization of the isolated matrix domain and full-length human protein similar to cation binding and markedly decreases MCU activity. Moreover, mitochondrial Mg(2+) loading or blockade of mitochondrial Ca(2+) extrusion suppresses MCU Ca(2+)-uptake rates. Collectively, our data reveal that the β-grasp-like matrix region harbors an MCU-regulating acidic patch that inhibits human MCU activity in response to Mg(2+) and Ca(2+) binding.

  1. Divalent counterion-induced condensation of triple-strand DNA.

    Science.gov (United States)

    Qiu, Xiangyun; Parsegian, V Adrian; Rau, Donald C

    2010-12-14

    Understanding and manipulation of the forces assembling DNA/RNA helices have broad implications for biology, medicine, and physics. One subject of significance is the attractive force between dsDNA mediated by polycations of valence ≥ 3. Despite extensive studies, the physical origin of the "like-charge attraction" remains unsettled among competing theories. Here we show that triple-strand DNA (tsDNA), a more highly charged helix than dsDNA, is precipitated by alkaline-earth divalent cations that are unable to condense dsDNA. We further show that our observation is general by examining several cations (Mg(2+), Ba(2+), and Ca(2+)) and two distinct tsDNA constructs. Cation-condensed tsDNA forms ordered hexagonal arrays that redissolve upon adding monovalent salts. Forces between tsDNA helices, measured by osmotic stress, follow the form of hydration forces observed with condensed dsDNA. Probing a well-defined system of point-like cations and tsDNAs with more evenly spaced helical charges, the counterintuitive observation that the more highly charged tsDNA (vs. dsDNA) is condensed by cations of lower valence provides new insights into theories of polyelectrolytes and the biological and pathological roles of tsDNA. Cations and tsDNAs also hold promise as a model system for future studies of DNA-DNA interactions and electrostatic interactions in general.

  2. Role of Reverse Divalent Cation Diffusion in Forward Osmosis Biofouling.

    Science.gov (United States)

    Xie, Ming; Bar-Zeev, Edo; Hashmi, Sara M; Nghiem, Long D; Elimelech, Menachem

    2015-11-17

    We investigated the role of reverse divalent cation diffusion in forward osmosis (FO) biofouling. FO biofouling by Pseudomonas aeruginosa was simulated using pristine and chlorine-treated thin-film composite polyamide membranes with either MgCl2 or CaCl2 draw solution. We related FO biofouling behavior-water flux decline, biofilm architecture, and biofilm composition-to reverse cation diffusion. Experimental results demonstrated that reverse calcium diffusion led to significantly more severe water flux decline in comparison with reverse magnesium permeation. Unlike magnesium, reverse calcium permeation dramatically altered the biofilm architecture and composition, where extracellular polymeric substances (EPS) formed a thicker, denser, and more stable biofilm. We propose that FO biofouling was enhanced by complexation of calcium ions to bacterial EPS. This hypothesis was confirmed by dynamic and static light scattering measurements using extracted bacterial EPS with the addition of either MgCl2 or CaCl2 solution. We observed a dramatic increase in the hydrodynamic radius of bacterial EPS with the addition of CaCl2, but no change was observed after addition of MgCl2. Static light scattering revealed that the radius of gyration of bacterial EPS with addition of CaCl2 was 20 times larger than that with the addition of MgCl2. These observations were further confirmed by transmission electron microscopy imaging, where bacterial EPS in the presence of calcium ions was globular, while that with magnesium ions was rod-shaped.

  3. Gastrointestinal transit of undigestible solids measured by metal detector EAS II.

    Science.gov (United States)

    Ewe, K; Press, A G; Dederer, W

    1989-06-01

    A new method was developed to measure gastrointestinal transit: a metal particle is followed on its way through the gastrointestinal tract by means of a portable metal detector. Deviation of measured localization of the metal particle from the exact site was 0.5-1.0 cm depending on its size and distance from the search probe. A metal sphere of 6 mm diameter can be located accurately in the body at a distance of 2-12 cm from the abdominal surface. Emptying of a metal particle from the stomach, its arrival at the caecal area and its passage through the colon into the rectum can be registered and hence, gastric residence time, small intestinal transit and transit through different parts of the colon were determined. Gastric residence time at the interdigestive phase was (mean +/- SD) 67 +/- 52 min in 20 persons with a range of 9-185 min. When gastric emptying was recorded by pH sensitive radiotelemetering capsule in 10 persons, correlation of both methods was r = 0.99. Small intestinal transit averaged 110 +/- 56 min in six healthy volunteers when breakfast was eaten after the marker had left the stomach. It was delayed to 218 +/- 34 min (P less than 0.01) when fasting was continued. Large intestinal transit of the metal marker was compared to whole body transit of radio-opaque ('Hinton') markers. In nine normal persons, 70% of the Hinton markers were excreted together with the metal particle. It is concluded that this new method is suitable for studying a large variety of physiological, pathophysiological and pharmacological questions concerning gastrointestinal transit.(ABSTRACT TRUNCATED AT 250 WORDS)

  4. Gas adsorption and structural diversity in a family of Cu(II) pyridyl-isophthalate metal-organic framework materials

    Science.gov (United States)

    Gould, Jamie A.; Athwal, Harprit Singh; Blake, Alexander J.; Lewis, William; Hubberstey, Peter; Champness, Neil R.; Schröder, Martin

    2017-01-01

    A family of Cu(II)-based metal-organic frameworks (MOFs) has been synthesized using three pyridyl-isophthalate ligands, H2L1 (4'-(pyridin-4-yl)biphenyl-3,5-dicarboxylic acid), H2L2 (4''-(pyridin-4-yl)-1,1':4',1''-terphenyl-3,5-dicarboxylic acid) and H2L3 (5-[4-(pyridin-4-yl)naphthalen-1-yl]benzene-1,3-dicarboxylic acid). Although in each case the pyridyl-isophthalate ligands adopt the same pseudo-octahedral [Cu2(O2CR)4N2] paddlewheel coordination modes, the resulting frameworks are structurally diverse, particularly in the case of the complex of Cu(II) with H2L3, which leads to three distinct supramolecular isomers, each derived from Kagomé and square nets. In contrast to [Cu(L2)] and the isomers of [Cu(L3)], [Cu(L1)] exhibits permanent porosity. Thus, the gas adsorption properties of [Cu(L1)] were investigated with N2, CO2 and H2, and the material exhibits an isosteric heat of adsorption competitive with leading MOF sorbents for CO2. [Cu(L1)] displays high H2 adsorption, with the density in the pores approaching that of liquid H2. This article is part of the themed issue 'Coordination polymers and metal-organic frameworks: materials by design'.

  5. Confinement of a bioinspired nonheme Fe(II) complex in 2D hexagonal mesoporous silica with metal site isolation.

    Science.gov (United States)

    Jollet, Véronique; Albela, Belén; Sénéchal-David, Katell; Jégou, Pascale; Kolodziej, Emilie; Sainton, Joëlle; Bonneviot, Laurent; Banse, Frédéric

    2013-08-28

    A mixed amine pyridine polydentate Fe(II) complex was covalently tethered in hexagonal mesoporous silica of the MCM-41 type. Metal site isolation was generated using adsorbed tetramethylammonium cations acting as a patterned silanol protecting mask and trimethylsilylazane as a capping agent. Then, the amine/pyridine ligand bearing a tethering triethoxysilane group was either grafted to such a pretreated silica surface prior to or after complexation to Fe(II). These two synthetic routes, denoted as two-step and one-step, respectively, were also applied to fumed silica for comparison, except that the silanol groups were capped after tethering the metal unit. The coordination of the targeted complex was monitored using UV-visible spectrophotometry and, according to XPS, the best control was achieved inside the channels of the mesoporous silica for the two-step route. For the solid prepared according to the one-step route, tethering of the complex occurred mainly at the entrance of the channel.

  6. KMOS view of the Galactic Centre - II. Metallicity distribution of late-type stars

    Science.gov (United States)

    Feldmeier-Krause, A.; Kerzendorf, W.; Neumayer, N.; Schödel, R.; Nogueras-Lara, F.; Do, T.; de Zeeuw, P. T.; Kuntschner, H.

    2017-01-01

    Knowing the metallicity distribution of stars in the Galactic Centre has important implications for the formation history of the Milky Way nuclear star cluster. However, this distribution is not well known, and is currently based on a small sample of fewer than 100 stars. We obtained near-infrared K-band spectra of more than 700 late-type stars in the central 4 pc2 of the Milky Way nuclear star cluster with the integral-field spectrograph KMOS (VLT). We analyse the medium-resolution spectra using a full-spectral fitting method employing the Göttingen spectral library of synthetic PHOENIX spectra. The derived stellar metallicities range from metal-rich [M/H] > +0.3 dex to metal-poor [M/H] 0 dex), a globular cluster origin can be ruled out. As there is only a very low fraction of metal-poor stars in the central 4 pc2 of the Galactic Centre, we believe that our data can discard a scenario in which the Milky Way nuclear star cluster is purely formed from infalling globular clusters.

  7. VizieR Online Data Catalog: On the metallicity of open clusters. II. (Heiter+, 2014)

    Science.gov (United States)

    Heiter, U.; Soubiran, C.; Netopil, M.; Paunzen, E.

    2013-11-01

    In Table 1 we list the basic information for each star and each metallicity determination in the starting sample, which should be sufficient to extract the corresponding atmospheric parameters from the PASTEL catalogue. Table 4 lists the weighted mean metallicities for each OC and each paper, which were computed using the metallicities from the references in Table 1. For the weights we used the inverse square of the individual errors quoted by the authors. Table 4 also gives the ranges of effective temperature (Teff) and surface gravity (logg) of the stars corresponding to each paper. After removing all determinations with Teff outside the range 4400 to 6500K and with logg<2.0, we constructed a list of recommended cluster metallicities, which we call the final high-resolution sample. The weighted mean metallicities for each cluster in the final sample are given in Table 11, and the individual determinations included in the final sample are identified in Table 1 (first column). (3 data files).

  8. KMOS view of the Galactic Centre - II. Metallicity distribution of late-type stars

    CERN Document Server

    Feldmeier-Krause, A; Neumayer, N; Schödel, R; Nogueras-Lara, F; Do, T; de Zeeuw, P T; Kuntschner, H

    2016-01-01

    Knowing the metallicity distribution of stars in the Galactic Centre has important implications for the formation history of the Milky Way nuclear star cluster. However, this distribution is not well known, and is currently based on a small sample of fewer than 100 stars. We obtained near-infrared K-band spectra of more than 700 late-type stars in the central 4 pc^2 of the Milky Way nuclear star cluster with the integral-field spectrograph KMOS (VLT). We analyse the medium-resolution spectra using a full-spectral fitting method employing the G\\"ottingen Spectral library of synthetic PHOENIX spectra. The derived stellar metallicities range from metal-rich [M/H]>+0.3 dex to metal-poor [M/H]0 dex) a globular cluster origin can be ruled out. As there is only a very low fraction of metal-poor stars in the central 4 pc^2 of the Galactic Centre, we believe that our data can discard a scenario in which the Milky Way nuclear star cluster is purely formed from infalling globular clusters.

  9. Interactions between microbial iron reduction and metal geochemistry: effect of redox cycling on transition metal speciation in iron bearing sediments.

    Science.gov (United States)

    Cooper, D Craig; Picardal, Flynn F; Coby, Aaron J

    2006-03-15

    Microbial iron reduction is an important biogeochemical process that can affect metal geochemistry in sediments through direct and indirect mechanisms. With respectto Fe(III) (hydr)oxides bearing sorbed divalent metals, recent reports have indicated that (1) microbial reduction of goethite/ferrihydrite mixtures preferentially removes ferrihydrite, (2) this process can incorporate previously sorbed Zn(II) into an authigenic crystalline phase that is insoluble in 0.5 M HCl, (3) this new phase is probably goethite, and (4) the presence of nonreducible minerals can inhibit this transformation. This study demonstrates that a range of sorbed transition metals can be selectively sequestered into a 0.5 M HCl insoluble phase and that the process can be stimulated through sequential steps of microbial iron reduction and air oxidation. Microbial reduction experiments with divalent Cd, Co, Mn, Ni, Pb, and Zn indicate that all metals save Mn experienced some sequestration, with the degree of metal incorporation into the 0.5 M HCl insoluble phase correlating positively with crystalline ionic radius at coordination number = 6. Redox cycling experiments with Zn adsorbed to synthetic goethite/ferrihydrite or iron-bearing natural sediments indicate that redox cycling from iron reducing to iron oxidizing conditions sequesters more Zn within authigenic minerals than microbial iron reduction alone. In addition, the process is more effective in goethite/ferrihydrite mixtures than in iron-bearing natural sediments. Microbial reduction alone resulted in a -3x increase in 0.5 M HCl insoluble Zn and increased aqueous Zn (Zn-aq) in goethite/ferrihydrite, but did not significantly affect Zn speciation in natural sediments. Redox cycling enhanced the Zn sequestration by approximately 12% in both goethite/ferrihydrite and natural sediments and reduced Zn-aq to levels equal to the uninoculated control in goethite/ferrihydrite and less than the uninoculated control in natural sediments. These

  10. Exhaled metallic mercury in acatalasemic, hypocatalasemic and normal mice injected with mercury (II chloride.

    Directory of Open Access Journals (Sweden)

    Meguro,Tadamichi

    1990-10-01

    Full Text Available To clarify the relationship between the catalase activity in mouse organs and the amounts of metallic mercury exhaled, normal, homozygous hypocatalasemic and acatalasemic mice were injected with mercuric chloride. The cumulative amount of metallic mercury exhaled by mice was evidently expressed in the descending order of acatalasemic, hypocatalasemic, and normal mice. Statistically significant differences in the cumulative exhaled metallic mercury levels were observed between acatalasemic and hypocatalasemic mice, between normal and hypocatalasemic mice, and between acatalasemic and normal mice using the method of one way analysis of variance (ANOVA. A linear relationship was obtained through logarithm of catalase activity in the lungs or the blood, and logarithm of the cumulative amount of the exhaled mercury.

  11. DFT/TD-DFT study on spectroscopic properties of zinc(II, nickel(II, and palladium(II metal complexes with a thiourea derivative

    Directory of Open Access Journals (Sweden)

    Wang Xin

    2016-01-01

    Full Text Available The geometries, electronic structures, and spectral properties of three metal complexes Zn(C10H12N3OS2 (1, Ni(C10H12N3OS2 (2, and Pd(C10H12N3OS2 (3 with N-(2-pyridinylmorpholine-4-carbothioamide as a ligand are investigated by means of DFT (density functional theory and TD-DFT (time-dependent density functional theory methods. Complex 1 is a distorted tetrahedral geometry, while complexes 2 and 3 present a distorted square-planar coordination environment. In the simulated range, the spectrum of complex 1 has five obvious absorption peaks and one of them has the strongest intensity. The latter two complexes have one more absorption peak and shoulder peak with the similar intensity. Moreover, the strongest peaks of complexes 2.

  12. Preparation and characterization of chelating fibers based on natural wool for removal of Hg(II), Cu(II) and Co(II) metal ions from aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Monier, M., E-mail: monierchem@yahoo.com [Chemistry Department, Faculty of Science, Mansoura University, 35516 (Egypt); Nawar, N., E-mail: nnawar@mans.edu.eg [Chemistry Department, Faculty of Science, Mansoura University, 35516 (Egypt); Abdel-Latif, D.A. [Chemistry Department, Faculty of Science, Mansoura University, 35516 (Egypt)

    2010-12-15

    The graft copolymerization of acrylonitrile (AN) onto natural wool fibers initiated by KMnO{sub 4} and oxalic acid combined redox initiator system in limited aqueous medium was carried out in heterogeneous media. Moreover, modification of the grafted wool fibers was done by changing the nitrile group (-CN) into cyano-acetic acid {alpha}-amino-acrylic-hydrazide through the reaction with hydrazine hydrate followed by ethylcyanoacetate which eventually produce wool-grafted-poly(cyano-acetic acid {alpha}-amino-acrylic-hydrazide) (wool-g-PCAH) chelating fibers. The application of the modified fibers for metal ion uptake was studied using Hg{sup 2+}, Cu{sup 2+} and Co{sup 2+}. The modified chelating fibers were characterized using FTIR spectroscopy, SEM and X-ray diffraction.

  13. Phonon dispersion relation of liquid metals

    Indian Academy of Sciences (India)

    P B Thakor; P N Gajjar; A R Jani

    2009-06-01

    The phonon dispersion curves of some liquid metals, viz. Na ( = 1), Mg ( = 2), Al ( = 3) and Pb ( = 4), have been computed using our model potential. The charged hard sphere (CHS) reference system is applied to describe the structural information. Our model potential along with CHS reference system is capable of explaining the phonon dispersion relation for monovalent, divalent, trivalent and tetravalent liquid metals.

  14. A quasi-stationary numerical model of atomized metal droplets, II: Prediction and assessment

    DEFF Research Database (Denmark)

    Pryds, Nini H.; Hattel, Jesper Henri; Thorborg, Jesper

    1999-01-01

    by comparing experimental and calculated results for the powder particles of 12Cr-Mo-V steel. The study is also focusing on some aspects of the process which are not available experimentally, e.g. the effect of undercooling and gas/metal ratio on the solidification. The important effect of these parameters has......A new model which extends previous studies and includes the interaction between enveloping gas and an array of droplets has been developed and presented in a previous paper. The model incorporates the probability density function of atomized metallic droplets into the heat transfer equations...

  15. Engineering Short Preorganized Peptide Sequences for Metal Ion Coordination: Copper(II) a Case Study.

    Science.gov (United States)

    Lima, L M P; Iranzo, O

    2016-01-01

    Peptides are multidentate chiral ligands capable of coordinating different metal ions. Nowadays, they can be obtained with high yield and purity, thanks to the advances on peptide/protein chemistry as well as in equipment (peptide synthesizers). Based on the identity and length of their amino acid sequences, peptides can present different degrees of flexibility and folding. Although short peptide sequences (ion coordination. Based on our experience, we present a general scheme for the design, synthesis, and characterization of these peptidic scaffolds and provide protocols for the study of their metal ion coordination properties.

  16. Interactions Between Microbial Iron Reduction and Metal Geochemistry: Effect of Redox Cycling on Transition Metal Speciation in Iron Bearing Sediments

    Energy Technology Data Exchange (ETDEWEB)

    D. Craig Cooper; Flynn W. Picardal; Aaron J. Coby

    2006-02-01

    Microbial iron reduction is an important biogeochemical process that can affect metal geochemistry in sediments through direct and indirect mechanisms. With respect to Fe(III) (hydr)oxides bearing sorbed divalent metals, recent reports have indicated that (1) microbial reduction of goethite/ferrihydrite mixtures preferentially removes ferrihydrite, (2) this process can incorporate previously sorbed Zn(II) into an authigenic crystalline phase that is insoluble in 0.5 M HCl, (3) this new phase is probably goethite, and (4) the presence of nonreducible minerals can inhibit this transformation. This study demonstrates that a range of sorbed transition metals can be selectively sequestered into a 0.5 M HCl insoluble phase and that the process can be stimulated through sequential steps of microbial iron reduction and air oxidation. Microbial reduction experiments with divalent Cd, Co, Mn, Ni, Pb, and Zn indicate that all metals save Mn experienced some sequestration, with the degree of metal incorporation into the 0.5 M HCl insoluble phase correlating positively with crystalline ionic radius at coordination number = 6. Redox cycling experiments with Zn adsorbed to synthetic goethite/ferrihydrite or iron-bearing natural sediments indicate that redox cycling from iron reducing to iron oxidizing conditions sequesters more Zn within authigenic minerals than microbial iron reduction alone. In addition, the process is more effective in goethite/ferrihydrite mixtures than in iron-bearing natural sediments. Microbial reduction alone resulted in a ~3× increase in 0.5 M HCl insoluble Zn and increased aqueous Zn (Zn-aq) in goethite/ferrihydrite, but did not significantly affect Zn speciation in natural sediments. Redox cycling enhanced the Zn sequestration by ~12% in both goethite/ferrihydrite and natural sediments and reduced Zn-aq to levels equal to the uninoculated control in goethite/ferrihydrite and less than the uninoculated control in natural sediments. These data suggest

  17. Synthesis and Structural Studies on Transition Metal Complexes Derived from 4-Hydroxy-4-methyl–2-pentanone-1H-benzimidazol-2-yl-hydrazone

    Directory of Open Access Journals (Sweden)

    M. Neelamma

    2011-01-01

    Full Text Available Transition metal complexes of Cr(III, Fe(III, Mn(II, Co(II, Ni(II, Cu(II and Zn(II with a tridentate ligand, 4-hydroxy-4-methyl-2-pentanone-1H-benzimidazole-2yl-hydrazone (H-HPBH derived from the condensation of 2-hydrazinobenzimidazole and diacetone alcohol was synthesized. Characterization has been done on the basis of analytical, conductance, thermal and magnetic data, infrared, 1H NMR, electronic, mass and ESR spectral data. From analytical and thermal data, the stoichiometry of the complexes has been found to be 1:1 (metal: ligand. Divalent complexes have the general formula [M(HPBHCl(H2O2] in octahedral geometry, [M(HPBHCl] in tetrahedral and square planar stereochemistries and trivalent complexes [M(HPBHCl2(H2O] in octahedral disposition. Infrared spectral data suggest that the ligand HPBH behaves as a monobasic tridentate ligand with N: N: O donor sequence towards the metal ions. On the basis of the above physicochemical data, octahedral, tetrahedral and square planar geometries were assigned for the complexes. The ligand and metal complexes were screened for their physiological activities against E. coli and S. aureus. The order of physiological activity has been found to be Cu(II > Ni(II > Zn(II > Co(II > Cr(III > Mn(II > Fe (III > ligand against E.coli and Ni(II > Cu(II > Zn(II > Mn(II > Cr(III > Fe(III > Co(II > ligand against S. aureus.

  18. Local impacts of coal mines and power plants across Canada. II. Metals, organics and toxicity in sediments

    Energy Technology Data Exchange (ETDEWEB)

    Cheam, V.; Reynoldson, T.; Garbai, G.; Rajkumar, J.; Milani, D. [Environment of Canada, Burlington, ON (Canada). National Water Research Institute

    2000-07-01

    A Canada-wide survey was undertaken to study local impacts of coal mines and coal-fired electrical generating stations. The first part dealt with thallium in waters and sediments. This, Part II, deals with metals and organics in sediments as well as sediment toxicity to four different organisms. Several elevated metal and PAH concentrations as well as high toxicity (based on biological sediment guidelines) were observed compared to uncontaminated sites. Based on Ontario's sediment guidelines, most of the studied sediments fell in the 'marginally to significantly polluted' category of sediment quality, although two belonged to the 'grossly polluted' class due to the extremely high concentrations of some metals. The observed diversity of PAHs and near-unity carbon preference indices indicate non-biological origins of the studied sediments. In this initial study, four different organisms, Chironomus riparius, Hyalella azteca, Hexagenia spp. (Hexagenia limbata) and Tubifex tubifex were used to determine sediment toxicity, which showed 50% of the tested sites were highly stressed.

  19. Reversible structural transformations in a Co(II)-based 2D dynamic metal-organic framework showing selective solvent uptake

    Indian Academy of Sciences (India)

    Sanjog S Nagarkar; Sujit K Ghosh

    2015-04-01

    A Co(II)-based two-dimensional (2D) metal-organic framework (MOF) [Co(pca)(bdc)0.5(H2O)2] (1) {pca = pyrazine carboxylic acid, and bdc = 1,4-benzene dicarboxylic acid} was synthesized solvothermally. The compound loses the coordinated lattice water molecules on heating which is accompanied by solidstate structural transformation to yield dehydrated phase [Co(pca)(bdc)0.5] (1′). The hydrated structure can be regained by exposing 1′ to water vapour (1′′). These reversible solid-state structural transformations are accompanied by a visible colour change in the material. The dehydrated compound also shows highly selective water uptake over other solvents like MeOH, EtOH, THF. This selective water uptake can be ascribed to the high affinity of polar water molecule towards the open metal site created on heating. The present report provides important insights into the reversible structural transformations observed due to variable coordination number of the central metal ion and transformability of the framework. The selective water uptake over alcohols along with visible colour change demonstrates the potential of the present compound in bio-alcohol purification.

  20. Role of the metal in the bonding and properties of bimetallic complexes involving manganese, iron, and cobalt.

    Science.gov (United States)

    Tereniak, Stephen J; Carlson, Rebecca K; Clouston, Laura J; Young, Victor G; Bill, Eckhard; Maurice, Rémi; Chen, Yu-Sheng; Kim, Hyun Jung; Gagliardi, Laura; Lu, Connie C

    2014-02-05

    A multidentate ligand platform is introduced that enables the isolation of both homo- and heterobimetallic complexes of divalent first-row transition metal ions such as Mn(II), Fe(II), and Co(II). By means of a two-step metalation strategy, five bimetallic coordination complexes were synthesized with the general formula M1M2Cl(py3tren), where py3tren is the triply deprotonated form of N,N,N-tris(2-(2-pyridylamino)ethyl)amine. The metal-metal pairings include dicobalt (1), cobalt-iron (2), cobalt-manganese (3), diiron (4), and iron-manganese (5). The bimetallic complexes have been investigated by X-ray diffraction and X-ray anomalous scattering studies, cyclic voltammetry, magnetometry, Mössbauer spectroscopy, UV-vis-NIR spectroscopy, NMR spectroscopy, combustion analyses, inductively coupled plasma optical emission spectrometry, and ab initio quantum chemical methods. Only the diiron chloride complex in this series contains a metal-metal single bond (2.29 Å). The others show weak metal-metal interactions (2.49 to 2.53 Å). The diiron complex is also distinct with a septet ground state, while the other bimetallic species have much lower spin states from S = 0 to S = 1. We propose that the diiron system has delocalized metal-metal bonding electrons, which seems to correlate with a short metal-metal bond and a higher spin state. Multiconfigurational wave function calculations revealed that, indeed, the metal-metal bonding orbitals in the diiron complex are much more delocalized than those of the dicobalt analogue.

  1. Synthesis, structure and electrochemical behavior of a 3D crystalline copper(II) metal-organic framework

    Science.gov (United States)

    Bai, Hong-Ye; Fan, Wei-Qiang; Liu, Chun-Bo; Shi, Wei-Dong; Yan, Yong-Sheng

    2014-05-01

    Using an flexible amide-type tripodal ligand N,N‧,N″-tris(3-pyridyl)-1,3,5-benzenetricarboxamide (L) and 1,4-benzenedicarboxylic acid (H2bdc), a three-dimensional copper(II) metal-organic framework (MOF) formulated as [Cu(bdc)(L)]n has been hydrothermally synthesized and structurally characterized by IR, elemental, X-ray single-crystal diffraction and thermal analysis. The complex crystallizes in the triclinic, space group P - 1, a = 8.891(2) Å, b = 11.760(2) Å, c = 15.348(3) Å, α = 96.73(3)°, β = 105.96(3)°, γ = 106.47(3)°, V = 1446.2(5) Å3, Mr = 666.10, Dc = 1.530 g/cm3, Z = 2, F(000) = 682, GOOF = 1.0560, μ(MoKα) = 0.817 mm-1, R = 0.0366 and wR = 0.0885. The structural analyses reveal that the title compound consists of one Cu(II) atom, two halves of bdc, and one L ligand. Each Cu(II) atom is linked by two bdc ligands and three L ligands to form a three-dimensional network. In addition, the electrochemical behavior of title compound has been studied. CCDC No. 990526.

  2. Azadipyrromethene dye derivatives in coordination chemistry: the structure-property relationship in homoleptic metal(II) complexes.

    Science.gov (United States)

    Bessette, André; Ferreira, Janaina G; Giguère, Martin; Bélanger, Francis; Désilets, Denis; Hanan, Garry S

    2012-11-19

    As a chromophore closely related to dipyrromethene (DPM), the azadipyrromethene (ADPM) family has attracted much interest in the life sciences and optoelectronic fields. A high-yielding microwave-assisted synthesis is reported for new homoleptic complexes of cobalt(II), nickel(II), copper(II) and zinc(II) based on the tetrakis(p-methoxyphenyl)azadipyrromethene ligand 1b. These complexes are compared with other homoleptic complexes of the same metal(II) series based on the tetraphenylazadipyrromethene 1a and also with related BF2(+) chelates (Aza-BODIPYs 6a and 6b) for a better understanding of trends arising from substitution of the chelate and/or the electron-donating effect of the p-methoxy substituents. The electrochemical behavior of the new compounds 2b, 3b, and 5b in dichloromethane revealed two pseudoreversible reductions (2b, -1.09 and -1.25 V vs SCE; 3b, -1.05 and -1.29 V; 5b, -1.13 and -1.25 V) followed by a third irreversible process (2b, -1.78 V; 3b, -1.80 V; 5b, -1.77 V) along with two pseudoreversible oxidations (2b, 0.55 and 0.80 V; 3b, 0.56 and 0.80 V; 5b, 0.55 and 0.80 V) followed by two closely spaced irreversible processes (2b, 1.21 and 1.27 V; 3b, 1.21 and 1.28 V; 5b, 1.22 and 1.25 V). On its side, copper(II) homoleptic complex 4b revealed only one pseudoreversible reduction at -0.59 V followed by three irreversible processes at -0.95, -1.54, and -1.74 V, respectively. The oxidation behavior of this complex exhibited two pseudoreversible processes (0.55 and 0.82 V) and two irreversible processes (1.19 and 1.25 V). The redox processes are assigned and discussed in relation to their photophysical properties. X-ray structures for 1b and related copper(II) complex 2b are also discussed.

  3. Statistical properties of exoplanets II. Metallicity, orbital parameters, and space velocities

    CERN Document Server

    Santos, N C; Mayor, M; Rebolo, R; Udry, S

    2003-01-01

    In this article we present a detailed spectroscopic analysis of more than 50 extra-solar planet host stars. Stellar atmospheric parameters and metallicities are derived using high resolution and high S/N spectra. The spectroscopy results, added to the previous studies, imply that we have access to a large and uniform sample of metallicities for about 80 planet hosts stars. We make use of this sample to confirm the metal-rich nature of stars with planets, and to show that the planetary frequency is rising as a function of the [Fe/H]. Furthermore, the source of this high metallicity is shown to have most probably an ``primordial'' source, confirming previous results. The comparison of the orbital properties (period and eccentricity) and minimum masses of the planets with the stellar properties also reveal some emerging but still not significant trends. These are discussed and some explanations are proposed. Finally, we show that the planet host stars included in the CORALIE survey have similar kinematical prope...

  4. Synthesis and antimicrobial activity of polysaccharide alginate derived cationic surfactant-metal(II) complexes.

    Science.gov (United States)

    Tawfik, Salah M; Hefni, Hassan H

    2016-01-01

    New natural polysaccharide carbohydrate derivatives of sodium alginate surfactant and its cobalt, copper and zinc complexes were synthesized. Structures of the synthesized compounds are reported using FTIR, (1)H NMR and UV-vis. The critical micelle concentration (CMC) value of the alginate surfactant and its metal complexes in aqueous solution was found out from surface tension measurements. Surface tension data at different temperatures served for the evaluation of the temperature-dependent CMC and the thermodynamics of micellization (ΔGmic, ΔHmic, ΔSmic) and adsorption (ΔGads, ΔGads, ΔSads). The surface activities of the synthesized polymeric surfactant and its metal complexes were influenced by their chemical structures and the type of the transition metals. These compounds were evaluated against Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus), Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) and fungi (Candida albicans and Asperigllus niger). The antibacterial and antifungal screening tests of the alginate surfactant metal complexes have shown good results compared to its precursor alginate surfactant.

  5. RHAPSODY-G simulations II - Baryonic growth and metal enrichment in massive galaxy clusters

    CERN Document Server

    Martizzi, Davide; Wu, Hao-Yi; Evrard, August E; Teyssier, Romain; Wechsler, Risa H

    2015-01-01

    We study the evolution of the stellar component and the metallicity of both the intracluster medium and of stars in massive ($M_{\\rm vir}\\approx 6\\times 10^{14}$ M$_{\\odot}$) simulated galaxy clusters from the RHAPSODY-G suite in detail and compare them to observational results. The simulations were performed with the AMR code RAMSES and include the effect of AGN feedback at the sub-grid level. AGN feedback is required to produce realistic galaxy and cluster properties and plays a role in mixing material in the central regions and regulating star formation in the central galaxy. In our low resolution runs with fiducial stellar yields, we find that stellar and ICM metallicities are a factor of two lower than in observations, however they tend to converge to the observed values $\\sim 0.3$ Z$_{\\odot}$ as the resolution is increased. We find that cool core clusters exhibit steeper metallicity gradients than non-cool core clusters, in qualitative agreement with observations. We verify that the ICM metallicities me...

  6. Galaxy Evolution in Cosmological Simulations with Outflows II: Metallicities and Gas Fractions

    CERN Document Server

    Davé, Romeel; Oppenheimer, Benjamin D

    2011-01-01

    We use cosmological hydrodynamic simulations to investigate how inflows, star formation, and outflows govern the the gaseous and metal content of galaxies. In our simulations, galaxy metallicities are established by a balance between inflows and outflows as governed by the mass outflow rate, implying that the mass-metallicity relation reflects how the outflow rate varies with stellar mass. Gas content is set by a competition between inflow into and gas consumption within the ISM, the latter being governed by the star formation law, while the former is impacted by both wind recycling and preventive feedback. Stochasticity in the inflow rate moves galaxies off the equilibrium mass-metallicity and mass-gas fraction relations in a manner correlated with the SFR, and the scatter is set by the timescale to re-equilibrate. The evolution of both relations from z=3-0 is slow, as individual galaxies tend to evolve mostly along the relations. Gas fractions at a given stellar mass slowly decrease with time because the co...

  7. Dark Matter Halos in Galaxies and Globular Cluster Populations. II: Metallicity and Morphology

    CERN Document Server

    Harris, William; Hudson, Michael

    2015-01-01

    An increasing body of data reveals a one-to-one linear correlation between galaxy halo mass and the total mass in its globular cluster (GC) population, M_{GCS} ~ M_h^{1.03 \\pm 0.03}, valid over 5 orders of magnitude. We explore the nature of this correlation for galaxies of different morphological types, and for the subpopulations of metal-poor (blue) and metal-rich (red) GCs. For the subpopulations of different metallicity we find M_{GCS}(blue) ~ M_h^{0.96 \\pm 0.03} and M_{GCS}(red) ~ M_h^{1.21 \\pm 0.03} with similar scatter. The numerical values of these exponents can be derived from the detailed behavior of the red and blue GC fractions with galaxy mass and provide a self-consistent set of relations. In addition, all morphological types (E, S0, S/Irr) follow the same relation, but with a second-order trend for spiral galaxies to have a slightly higher fraction of metal-rich GCs for a given mass. These results suggest that the amount of gas available for GC formation at high redshift was in nearly direct pr...

  8. Thermolysis synthesis of pure phase NiO from novel sonochemical synthesized Ni(II) nano metal-organic supramolecular architecture.

    Science.gov (United States)

    Hanifehpour, Younes; Morsali, Ali; Mirtamizdoust, Babak; Joo, Sang Woo; Soltani, Behzad

    2017-07-01

    Nano-structures of a new supramolecular coordination compound of divalent nickel with the pyrazol (pzH) containing the terminal azide anions, [Ni(pzH)2(N3)2] (1), with discrete molecular architecture (DMA) in solid state was synthesized via sonochemical method. The new nanostructure was characterized by scanning electron microscopy, X-ray powder diffraction, IR, and elemental analysis. Compound 1 was structurally characterized by single crystal X-ray diffraction and the single-crystal X-ray data shows that the coordination number of Ni (II) ions is six, (NiN6), with four N-donor atoms from neutral "pzH" ligands and two N-donors from two terminal azide anions. The supramolecular features in these complexes are guided and controlled by weak directional intermolecular interactions. The structure of the title complex was optimized by density functional theory calculations. Calculated structural parameters and IR spectra for the title complex are consistent with the crystal structure. The NiO nanoparticles were obtained by thermolysis of 1 at 180°C with oleic acid as a surfactant. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Stability Constants of Mixed Ligand Complexes of Transition Metal(II Ions with Salicylidene-4-methoxyaniline as Primary Ligand and 5-Bromosalicylidene-4-nitroaniline as Secondary Ligand

    Directory of Open Access Journals (Sweden)

    N. G. Nadkarni

    2011-01-01

    Full Text Available Binary and ternary complexes of the type M-Y and M-X-Y [M = Mn(II, Ni(II, Cu(II and Zn(II; X = salicylidene-4-methoxyaniline and Y=5-bromosalicylidene-4-nitroaniline] have been examined pH-metrically at 27±0.5 °C and at constant ionic strength, μ= 0.1 M (KCl in 75 : 25(v/v 1,4-dioxne-water medium. The stability constants for binary (M-Y and ternary (M-X-Y systems were calculated. The relative stability (Δ log KT values of the ternary complexes with corresponding binary complexes for all the metal(II ions in the present study found to be negative indicating that ternary 1:1:1 (M-X-Y complexes are less stable than binary 1:1 (M-Y complexes. In the ternary system studied, the order of stability constants of mixed ligand complexes with respect to the metal ions was found to be Cu(II > NI(II > Mn(II > Zn(II; which is same as in the corresponding binary (M-Y systems.

  10. Synthesis and Characterization of a New Bidentate Ligand 5-Substituted-(2-methyl-5-nitro-1-imidazomethyl-1,3,4-oxadiazole-2-thione and its Metal Complexes of Ag(I, Cu(II and Zn(II

    Directory of Open Access Journals (Sweden)

    Shabbir A. A. Kazi

    2011-01-01

    Full Text Available A new ligand (2-methyl-5-nitro-1-imidazomethyl-1,3,4-oxadiazole-2-thione (L and its Ag(I,Cu(II and Zn(II complexes were synthesized. The authenticity of the ligand and its transition metal complexes were established by elemental analyses, conductance and magnetic susceptibility measurements, as well as spectroscopic (IR, 1H NMR, electronic, mass and ESR and thermal studies. The IR spectral studies revealed the existence thiol-thione tautamerism in the ligand molecule. The magnetic and electronic spectral studies suggest an octahedral geometry for Cu(II and Zn(II complexes. The ligand acts as a bidentate coordinating through the N-3 nitrogen and the exocyclic sulfur atoms of oxadiazole rings. Antimicrobial screening of the ligand and its metal complexes were determined against the bacteria Escherichia coli and Salmonella paratyphiA.

  11. Globular Cluster Abundances from High-Resolution, Integrated-Light Spectroscopy. II. Expanding the Metallicity Range for Old Clusters and Updated Analysis Techniques

    CERN Document Server

    Colucci, J E; McWilliam, A

    2016-01-01

    We present abundances of globular clusters in the Milky Way and Fornax from integrated light spectra. Our goal is to evaluate the consistency of the integrated light analysis relative to standard abundance analysis for individual stars in those same clusters. This sample includes an updated analysis of 7 clusters from our previous publications and results for 5 new clusters that expand the metallicity range over which our technique has been tested. We find that the [Fe/H] measured from integrated light spectra agrees to $\\sim$0.1 dex for globular clusters with metallicities as high as [Fe/H]=$-0.3$, but the abundances measured for more metal rich clusters may be underestimated. In addition we systematically evaluate the accuracy of abundance ratios, [X/Fe], for Na I, Mg I, Al I, Si I, Ca I, Ti I, Ti II, Sc II, V I, Cr I, Mn I, Co I, Ni I, Cu I, Y II, Zr I, Ba II, La II, Nd II, and Eu II. The elements for which the integrated light analysis gives results that are most similar to analysis of individual stellar ...

  12. Donnan membrane speciation of Al, Fe, trace metals and REEs in coastal lowland acid sulfate soil-impacted drainage waters

    Energy Technology Data Exchange (ETDEWEB)

    Jones, Adele M.; Xue, Youjia [School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW 2052 (Australia); Kinsela, Andrew S. [School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW 2052 (Australia); Institute for Environmental Research (IER), Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, NSW 2234 (Australia); Wilcken, Klaus M. [Institute for Environmental Research (IER), Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, NSW 2234 (Australia); Collins, Richard N., E-mail: richard.collins@unsw.edu.au [School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW 2052 (Australia)

    2016-03-15

    Donnan dialysis has been applied to forty filtered drainage waters collected from five coastal lowland acid sulfate soil (CLASS) catchments across north-eastern NSW, Australia. Despite having average pH values < 3.9, 78 and 58% of Al and total Fe, respectively, were present as neutral or negatively-charged species. Complementary isotope dilution experiments with {sup 55}Fe and {sup 26}Al demonstrated that only soluble (i.e. no colloidal) species were present. Trivalent rare earth elements (REEs) were also mainly present (> 70%) as negatively-charged complexes. In contrast, the speciation of the divalent trace metals Co, Mn, Ni and Zn was dominated by positively-charged complexes and was strongly correlated with the alkaline earth metals Ca and Mg. Thermodynamic equilibrium speciation calculations indicated that natural organic matter (NOM) complexes dominated Fe(III) speciation in agreement with that obtained by Donnan dialysis. In the case of Fe(II), however, the free cation was predicted to dominate under thermodynamic equilibrium, whilst our results indicated that Fe(II) was mainly present as neutral or negatively-charged complexes (most likely with sulfate). For all other divalent metals thermodynamic equilibrium speciation calculations agreed well with the Donnan dialysis results. The proportion of Al and REEs predicted to be negatively-charged was also grossly underestimated, relative to the experimental results, highlighting possible inaccuracies in the stability constants developed for these trivalent Me(SO{sub 4}){sub 2}{sup −} and/or Me–NOM complexes and difficulties in modeling complex environmental samples. These results will help improve metal mobility and toxicity models developed for CLASS-affected environments, and also demonstrate that Australian CLASS environments can discharge REEs at concentrations an order of magnitude greater than previously reported. - Highlights: • CLASS discharge large amounts of metals and their speciation is poorly

  13. Chemodynamics of metal complexation by natural soft colloids: Cu(II) binding by humic acid

    NARCIS (Netherlands)

    Town, R.M.; Duval, J.F.L.; Buffle, J.; Leeuwen, van H.P.

    2012-01-01

    The chemodynamics of Cu(II) complexation by humic acid is interpreted in terms of recently developed theory for permeable charged nanoparticles. Two opposing electric effects are operational with respect to the overall rate of association, namely, (i) the conductive enhancement of the diffusion of

  14. Heavy Metals (Mg, Mn, Ni and Sn contamination in Soil Samples of Ahvaz II Industrial Estate of Iran in 2013

    Directory of Open Access Journals (Sweden)

    Soheil l Sobhanardakani

    2016-04-01

    Full Text Available Background & Aims of the Study: Due to the rapid industrial development in Khuzestan province of Iran during recent years, this study was performed to analyze the variation of metals concentrations (Mg, Mn, Ni, and Sn in soil samples of Ahvaz II Industrial estate during the spring season of 2013. Materials & Methods: In this experimental study, 27 topsoil samples were collected from nine stations. The intensity of the soil contamination was evaluated, using a contamination factor (Cf and geo-accumulation index (I-geo. Results:  The mean soil concentrations (in mg kg-1 (dry weight were in ranged within 870-1144 (Mg, 188-300 (Mn, 93-199 (Ni and 9-15 (Sn. The data indicated that the I-geo value for all metals falls in class ‘1’. Also the Cf value for Mg and Mn falls in class ‘0’, the Cf value for Sn falls in class ‘1’ and the Cf value for Ni falls in the classes of ‘1’ and ‘2’. The result of the Pearson correlation showed that there were significant positive associations between all metals. Conclusions: According to the results which were achieved by a cluster analysis, there were significant positive associations among all metals based on Pearson correlation coefficient, especially between Ni and Sn; also both of them with Mn. Because the Ni originates from oil sources it can be resulted that Mn and Sn originate from oil sources, too. Therefore, industrial activities and exploitation of oil reservoirs are the main cause of pollution in that area. Also, it can be concluded that, with increasing the distance from the source of pollution, the accumulation of contaminants in the soil samples decreased.

  15. High-resolution spectroscopy of extremely metal-poor stars from SDSS/Segue. II. Binary fraction

    Energy Technology Data Exchange (ETDEWEB)

    Aoki, Wako; Suda, Takuma [National Astronomical Observatory, Mitaka, Tokyo 181-8588 (Japan); Beers, Timothy C. [Department of Physics and JINA Center for the Evolution of the Elements, University of Notre Dame,225 Nieuwland Science Hall, Notre Dame, IN 46656 (United States); Honda, Satoshi, E-mail: aoki.wako@nao.ac.jp, E-mail: takuma.suda@nao.ac.jp, E-mail: tbeers@nd.edu, E-mail: honda@nhao.jp [Center for Astronomy, University of Hyogo, 407-2, Nishigaichi, Sayo-cho, Sayo, Hyogo 679-5313 (Japan)

    2015-02-01

    The fraction of binary systems in various stellar populations of the Galaxy and the distribution of their orbital parameters are important but not well-determined factors in studies of star formation, stellar evolution, and Galactic chemical evolution. While observational studies have been carried out for a large sample of nearby stars, including some metal-poor Population II stars, almost no constraints on the binary nature for extremely metal-poor (EMP; [Fe/H] <−3.0) stars have yet been obtained. Here we investigate the fraction of double-lined spectroscopic binaries and carbon-enhanced metal-poor (CEMP) stars, many of which could have formed as pairs of low-mass and intermediate-mass stars, to estimate the lower limit of the fraction of binary systems having short periods. The estimate is based on a sample of very metal-poor stars selected from the Sloan Digital Sky Survey and observed at high spectral resolution in a previous study by Aoki et al. That survey reported 3 double-lined spectroscopic binaries and 11 CEMP stars, which we consider along with a sample of EMP stars from the literature compiled in the SAGA database. We have conducted measurements of the velocity components for stacked absorption features of different spectral lines for each double-lined spectroscopic binary. Our estimate indicates that the fraction of binary stars having orbital periods shorter than 1000 days is at least 10%, and possibly as high as 20% if the majority of CEMP stars are formed in such short-period binaries. This result suggests that the period distribution of EMP binary systems is biased toward short periods, unless the binary fraction of low-mass EMP stars is significantly higher than that of other nearby stars.

  16. Pareto-Lognormal Modeling of Known and Unknown Metal Resources. II. Method Refinement and Further Applications

    Energy Technology Data Exchange (ETDEWEB)

    Agterberg, Frits, E-mail: agterber@nrcan.gc.ca [Geological Survey of Canada (Canada)

    2017-07-01

    Pareto-lognormal modeling of worldwide metal deposit size–frequency distributions was proposed in an earlier paper (Agterberg in Nat Resour 26:3–20, 2017). In the current paper, the approach is applied to four metals (Cu, Zn, Au and Ag) and a number of model improvements are described and illustrated in detail for copper and gold. The new approach has become possible because of the very large inventory of worldwide metal deposit data recently published by Patiño Douce (Nat Resour 25:97–124, 2016c). Worldwide metal deposits for Cu, Zn and Ag follow basic lognormal size–frequency distributions that form straight lines on lognormal Q–Q plots. Au deposits show a departure from the straight-line model in the vicinity of their median size. Both largest and smallest deposits for the four metals taken as examples exhibit hyperbolic size–frequency relations and their Pareto coefficients are determined by fitting straight lines on log rank–log size plots. As originally pointed out by Patiño Douce (Nat Resour Res 25:365–387, 2016d), the upper Pareto tail cannot be distinguished clearly from the tail of what would be a secondary lognormal distribution. The method previously used in Agterberg (2017) for fitting the bridge function separating the largest deposit size–frequency Pareto tail from the basic lognormal is significantly improved in this paper. A new method is presented for estimating the approximate deposit size value at which the upper tail Pareto comes into effect. Although a theoretical explanation of the proposed Pareto-lognormal distribution model is not a required condition for its applicability, it is shown that existing double Pareto-lognormal models based on Brownian motion generalizations of the multiplicative central limit theorem are not applicable to worldwide metal deposits. Neither are various upper tail frequency amplification models in their present form. Although a physicochemical explanation remains possible, it is argued that

  17. Effect of heavy metals on the stabilization of mercury(II) by DTCR in desulfurization solutions

    Energy Technology Data Exchange (ETDEWEB)

    Hou, Jiaai; Lu, Rongjie; Sun, Mingyang; Baig, Shams Ali; Tang, Tingmei; Cheng, Lihua [Department of Environmental Engineering, Zhejiang University, Hangzhou 310058 (China); Xu, Xinhua, E-mail: xuxinhua@zju.edu.cn [Department of Environmental Engineering, Zhejiang University, Hangzhou 310058 (China)

    2012-05-30

    Highlights: Black-Right-Pointing-Pointer The interference of heavy metals on Hg{sup 2+} removal by DTCR was first investigated. Black-Right-Pointing-Pointer Mechanism of the decrease in the participating performance over Hg{sup 2+} was analyzed. Black-Right-Pointing-Pointer Optimal DTCR dosage was determined in the coexistence of Cu{sup 2+} or Pb{sup 2+} with Hg{sup 2+}. Black-Right-Pointing-Pointer Effect of pH value on the interference of Hg{sup 2+} removal rate was studied. Black-Right-Pointing-Pointer The equilibrium constant of Cu{sup 2+} and Hg{sup 2+} with DTCR was obtained. - Abstract: Several heavy metals, including Cu{sup 2+}, Ni{sup 2+}, Pb{sup 2+}, and Zn{sup 2+}, were investigated in simulated desulfurization solutions to evaluate their interferences with Hg{sup 2+} during the reaction with dithiocarbamate type chelating resin (DTCR). Appropriate DTCR dosage and the effect of pH were also explored with respect to restoration of high Hg{sup 2+} precipitation efficiency and reduction of mercury concentrations. The experimental results suggested that increasing heavy metal concentration inhibited Hg{sup 2+} precipitation efficiency to a considerable extent and the inhibition order of the four heavy metals was Cu{sup 2+} > Ni{sup 2+} > Pb{sup 2+} > Zn{sup 2+}. However, the coordination ability was closely related to the configuration and the orbital hybridization of each metal. In the cases of Cu{sup 2+} and Pb{sup 2+}, increased DTCR dosage was beneficial to Hg{sup 2+} precipitation, which could lay the foundation of practical applications of DTCR dosage for industrial wastewater treatment. The enhanced Hg{sup 2+} precipitation performance seen for increasing pH might have come from the deprotonation of sulfur atoms on the DTCR functional groups and the formation of metal hydroxides (M(OH){sub 2}, M = Cu, Pb, Hg).

  18. Spectral, mechanical, thermal, optical and solid state parameters, of metal-organic bis(hydrogenmaleate)-CO(II) tetrahydrate crystal

    Energy Technology Data Exchange (ETDEWEB)

    Chandran, Senthilkumar [Centre for Crystal Growth, Department of Physics, SSN College of Engineering, Kalavakkam 603110 (India); Jagan, R. [Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036 (India); Paulraj, Rajesh, E-mail: rajeshp@ssn.edu.in [Centre for Crystal Growth, Department of Physics, SSN College of Engineering, Kalavakkam 603110 (India); Ramasamy, P. [Centre for Crystal Growth, Department of Physics, SSN College of Engineering, Kalavakkam 603110 (India)

    2015-10-15

    Metal-organic bis(hydrogenmaleate)-Co(II) tetrahydrate single crystals have been grown by slow evaporation solution growth technique at room temperature. The crystal structure and the unit cell parameters were analyzed from the X-ray diffraction studies. Single-crystal X-ray diffraction analyses reveal that the grown crystal belongs to triclinic system with the space group P-1. Functional groups in bis(hydrogenmaleate)-Co(II) tetrahydrate were identified by Fourier transform infrared spectral analysis. The peak observed at 663 cm{sup −1} is assigned to the (Co–O) stretching vibrations. The optical transmission of the crystal was studied by UV–vis–NIR spectral analysis. The photoluminescence emission studies were carried out for the title compound in a wide wavelength range between 350 nm and 550 nm at 303 K. Mechanical strength was tested by Vickers microhardness test. The laser damage threshold value has been determined using Nd:YAG laser operating at 1064 nm. At various frequencies and temperatures the dielectric behavior of the material was investigated. Solid state parameters such as plasma energy, Penn gap, Fermi energy and electronic polarizability were evaluated. Photoconductivity measurements were carried out for the grown crystal in the presence of DC electric field at room temperature. Thermal stability and decomposition of the crystal were studied by TG–DTA. The weight loss of the title compound occurs in different steps. - Graphical abstract: Molecular structure of the bis(hydrogenmaleate)-Co(II) tetrahydrate drawn at 40% ellipsoid probability level. - Highlights: • Bis(hydrogenmaleate)-Co(II) tetrahydrate single crystal is grown by slow evaporation method. • Structural and optical properties were discussed. • The title complex crystal is thermally stable up to 91 °C. • Plasma energy, Fermi energy and electronic polarizability are evaluated. • It exhibits positive photoconductivity.

  19. Synthesis and photodynamic activity of unsymmetrical A3B tetraarylporphyrins functionalized with l-glutamate and their Zn(II) and Cu(II) metal complex derivatives.

    Science.gov (United States)

    Arredondo-Espinoza, Eder U; López-Cortina, Susana T; Ramírez-Cabrera, Mónica A; Balderas-Rentería, Isaías

    2016-08-01

    Four novel unsymmetrical A3B porphyrins 1, 2, 3 and 4 were synthesized following Lindsey procedure. Porphyrins 3 and 4 include one and three l-glutamate groups, respectively, and all porphyrins were metallated with Zn(II) (1a-4a) or Cu(II) (1b-4b). Porphyrins and metalloporphyrins presented values of singlet oxygen quantum yields (ΦD) ranging from 0.21 to 0.67. The tetraaryl derivatives in this study showed phototoxicity in SiHa cells with IC50 values ranging from IC50 value. Comparing the phototoxic activity between all porphyrins, functionalization of porphyrins with glutamate increased 100 times phototoxic activity (1 (IC50 4.81±0.34μM) vs. 3 (IC50 0.04±0.02μM) and 2 (IC50 5.19±0.42μM) vs. 4 (IC50 0.05±0.01μM)). This increased activity could be attributed to reduced hydrophobicity and increased ΦΔ, given by functionalization with l-glutamate. Metalloporphyrins 3a (IC50 0.04±0.01μM) and 4a (IC50<0.01μM) presented the best values ​​of phototoxic activity. Therefore, functionalization and zinc metalation increased the phototoxic activity. SiHa cells treated with porphyrins 3, 4, 3a and 4a at a final concentration of 10μM, showed increased activity of caspase-3 enzyme compared to the negative control; indicating the induction of apoptosis. Differential gene expression pattern in SiHa cells was determined; treatments with metalloporphyrins 4a and 4b were performed, respectively, comparing the expression with untreated control. Treatments in both cases showed similar gene expression pattern in upregulated genes, since they share about 25 biological pathways and a large number of genes. According to the new photophysical properties related to the structural improvement and phototoxic activity, these molecules may have the potential application as photosensitizers in the photodynamic therapy.

  20. Metal-line emission from the warm-hot intergalactic medium: II. Ultraviolet

    CERN Document Server

    Bertone, Serena; Booth, C M; Vecchia, Claudio Dalla; Theuns, Tom; Wiersma, Robert P C

    2010-01-01

    Approximately half the baryons in the local Universe are thought to reside in the warm-hot intergalactic medium (WHIM). Emission lines from metals in the UV band are excellent tracers of the cooler fraction of this gas. We present predictions for the surface brightness of a sample of UV lines that could potentially be observed by the next generation of UV telescopes at z10^3 photon/s/cm^2/sr), comes from relatively dense (rho>10^2 rho_mean) and metal rich (Z>0.1 Z_sun) gas. As such, emission lines are highly biased tracers of the missing baryons and are not an optimal tool to close the baryon budget. However, they do provide a powerful means to detect the gas cooling onto or flowing out of galaxies and groups. (Abridged)

  1. Analysis of metal-matrix composite structures. I - Micromechanics constitutive theory. II - Laminate analyses

    Science.gov (United States)

    Arenburg, R. T.; Reddy, J. N.

    1991-01-01

    The micromechanical constitutive theory is used to examine the nonlinear behavior of continuous-fiber-reinforced metal-matrix composite structures. Effective lamina constitutive relations based on the Abouli micromechanics theory are presented. The inelastic matrix behavior is modeled by the unified viscoplasticity theory of Bodner and Partom. The laminate constitutive relations are incorporated into a first-order deformation plate theory. The resulting boundary value problem is solved by utilizing the finite element method. Attention is also given to computational aspects of the numerical solution, including the temporal integration of the inelastic strains and the spatial integration of bending moments. Numerical results the nonlinear response of metal matrix composites subjected to extensional and bending loads are presented.

  2. Perylenetetracarboxylic-metal assemblies and anisotropic charge transport in a CuII assembly

    Science.gov (United States)

    Bai, Linyi; Xia, Youyi; Jana, Avijit; Ang, Chung Yen; Zhao, Lingzhi; Fan, Zhi; Zhao, Yanli

    2016-04-01

    Structural diversity and uniformity of nanomaterials are usually prerequisites for many practical applications involving the oriented fabrication of various devices with full control over their desired physiochemical properties. Particularly in the optoelectronic field, ordered assembly inside cells is required not only for obtaining attractive configurations but also for playing an important role in the characteristics of photoconduction and conductivity. Here, we present a synergetic self-assembly driven by coordination and intermolecular interactions for the construction of organic-inorganic hybrids with multi-morphologies and tunable physical properties. 3,4,9,10-Perylenetetracarboxylic dianhydride was treated with base to produce various assemblies by coordination with metal ions, showing morphologies of nanowires, nanosheets, nanoribbons and nanorods. The organic π-spacer affords an extension in different directions through the suitable incorporation of metal ions with different coordination modes for the formation of metal-ligand complexes. Interestingly, the obtained nanorods were twisted rods with obvious screw threads on the rod wall, supporting the synergetic self-assembly. Then, anisotropic mobility measurements of the obtained Cu2+-ligand assembly were carried out to show the importance of the size- and shape-confined synthesis of the hybrids. By presenting a series of ordered metal-ligand complex superstructures driven by synergetic self-assembly, this work is expected to pave the way for future anisotropic measurements of complex assemblies.Structural diversity and uniformity of nanomaterials are usually prerequisites for many practical applications involving the oriented fabrication of various devices with full control over their desired physiochemical properties. Particularly in the optoelectronic field, ordered assembly inside cells is required not only for obtaining attractive configurations but also for playing an important role in the

  3. Palladium(II)-catalyzed direct alkoxylation of arenes: evidence for solvent-assisted concerted metalation deprotonation.

    Science.gov (United States)

    Anand, Megha; Sunoj, Raghavan B

    2011-09-16

    Density functional theory investigations on the mechanism of palladium acetate catalyzed direct alkoxylation of N-methoxybenzamide in methanol reveal that the key steps involve solvent-assisted N-H as well as C-H bond activations. The transition state for the critical palladium-carbon bond formation through a concerted metalation deprotonation (CMD) process leading to a palladacycle intermediate has been found to be more stable in the methanol-assisted pathway as compared to an unassisted route.

  4. Metallic nanoparticles and their medicinal potential. Part II: aluminosilicates, nanobiomagnets, quantum dots and cochleates.

    Science.gov (United States)

    Loomba, Leena; Scarabelli, Tiziano

    2013-09-01

    Metallic miniaturization techniques have taken metals to nanoscale size where they can display fascinating properties and their potential applications in medicine. In recent years, metal nanoparticles such as aluminium, silicon, iron, cadmium, selenium, indium and calcium, which find their presence in aluminosilicates, nanobiomagnets, quantum dots (Q-dots) and cochleates, have caught attention of medical industries. The increasing impact of metallic nanoparticles in life sciences has significantly advanced the production techniques for these nanoparticles. In this Review, the various methods for the synthesis of nanoparticles are outlined, followed by their physicochemical properties, some recent applications in wound healing, diagnostic imaging, biosensing, assay labeling, antimicrobial activity, cancer therapy and drug delivery are listed, and finally their toxicological impacts are revised. The first half of this article describes the medicinal uses of two noble nanoparticles - gold and silver. This Review provides further information on the ability of aluminum, silicon, iron, selenium, indium, calcium and zinc to be used as nanoparticles in biomedical sciences. Aluminosilicates find their utility in wound healing and antibacterial growth. Iron-oxide nanoparticles enhance the properties of MRI contrast agents and are also used as biomagnets. Cadmium, selenium, tellurium and indium form the core nanostructures of tiny Q-dots used in cellular assay labeling, high-resolution cell imaging and biosensing. Cochleates have the bivalent nano ions calcium, magnesium or zinc imbedded in their structures and are considered to be highly effective agents for drug and gene delivery. The aluminosilicates, nanobiomagnets, Q-dots and cochleates are discussed in the light of their properties, synthesis and utility.

  5. The study on recycle scheme of the metallic radioactive wastes (II)

    Energy Technology Data Exchange (ETDEWEB)

    Shin, J. I.; Park, J. H.; Jung, K. J. [and others

    2003-01-01

    It was understood that regulation criteria for material release varied with countries and that international standards were not setup. But, most advanced countries are continuously studying on the recycling of metallic wastes for the purpose of the reuse of resources and disposal cost reduction. Practically, the advanced countries make a lot of cost profits compared with disposal as their metallic wastes are recycled and reused through technology like melting. The reasonable international standards are also expected to be set in the near future because of the aggressive cooperation between international agencies such as IAEA and NEA toward recycling these wastes. In our case, the recycle criteria for radioactive waste containing radioactive nuclide with long half-life such as Cs-137(half-life: 30y) and Co-60(half-life: 5.26y) including others, which are generated from the nuclear fission or dismantling of nuclear facilities, are not yet established. Therefore, it is required that the recommendation and legalization of the regulatory criteria be carried out for the recycle and reuse of metallic wastes to be generated from the dismantling of domestic nuclear facilities in the future.

  6. The LAMOST spectroscopic survey of star clusters in M31. II. Metallicities, ages and masses

    CERN Document Server

    Bingqiu, Chen; Maosheng, Xiang; Haibo, Yuan; Yang, Huang; Jianrong, Shi; Zhou, Fan; Zhiying, Huo; Chun, Wang; Juanjuan, Ren; Zhijia, Tian; Huawei, Zhang; Gaochao, Liu; Zihuang, Cao; Yong, Zhang; Yonghui, Hou; Yuefei, Wang

    2016-01-01

    We select from Paper I a sample of 306 massive star clusters observed with the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) in the vicinity fields of M31 and M33 and determine their metallicities, ages and masses. Metallicities and ages are estimated by fitting the observed integrated spectra with stellar synthesis population (SSP) models with a pixel-to-pixel spectral fitting technique. Ages for most young clusters are also derived by fitting the multi-band photometric measurements with model spectral energy distributions (SEDs). The estimated cluster ages span a wide range, from several million years to the age of the universe. The numbers of clusters younger and older than 1 Gyr are respectively 46 and 260. With ages and metallicities determined, cluster masses are then estimated by comparing the multi-band photometric measurements with SSP model SEDs. The derived masses range from $\\sim 10^{3}$ to $\\sim 10^7$ $M_{\\odot}$, peaking at $\\sim 10^{4.3}$ and $\\sim 10^{5.7}$ $M_{\\odot}$ for...

  7. Tetra- and octa-[4-(2-hydroxyethyl)phenoxy bearing novel metal-free and zinc(II) phthalocyanines: Synthesis, characterization and investigation of photophysicochemical properties

    Energy Technology Data Exchange (ETDEWEB)

    Köksoy, Baybars [Marmara University, Department of Chemistry, 34722 Kadıköy, Istanbul (Turkey); Durmuş, Mahmut [Gebze Technical University, Department of Chemistry, 41400 Gebze, Kocaeli (Turkey); Bulut, Mustafa, E-mail: mbulut@marmara.edu.tr [Marmara University, Department of Chemistry, 34722 Kadıköy, Istanbul (Turkey)

    2015-05-15

    In this study, four novel phthalonitriles (1–4) and their corresponding metal-free (5–8) and zinc(II) phthalocyanine derivatives (9–12) bearing 4-(hydroxyethyl)phenoxy groups were synthesized. These novel compounds were characterized by IR, elemental analyses, {sup 1}H-NMR, UV–vis, and MALDI-TOF spectral data. Furthermore, photophysical (fluorescence quantum yields and lifetimes) and photochemical properties (singlet oxygen generation and photodegradation quantum yields) of these phthalocyanines were investigated in dimethylsulfoxide. The studied zinc(II) phthalocyanines generated highly singlet oxygen which is very important for the photodynamic therapy (PDT) of cancer. The fluorescence quenching behaviour of the newly synthesized phthalocyanine compounds were also investigated using 1,4-benzoquinone. - Highlights: • Octa and tetra 4-(hydroxyethyl)phenoxy substituted metal-free and zinc(II) phthalocyanines. • Study of photophysicochemical properties of eight new phthalocyanines. • Highly singlet oxygen generation for novel zinc(II) phthalocyanine photosensitizers.

  8. Determination of Ni(II) in metal alloys by spectrophotometry UV-Vis using dopasemiquinone

    OpenAIRE

    2010-01-01

    A spectrophotometric method was proposed for Ni(II) determination in alloys using a dopa-semiquinone (L-1) to form [Ni(II)(L1-)3]1-, ε = 9.3 x 10³ L mol-1 cm-1. The optimal conditions for the determination were: wavelength 590 nm, temperature 25 °C, reaction time 45 min and pH 7.5. The Beer's law was obeyed for nickel from 3.33 x 10-5 to 1.78 x 10-4 mol L-1. The method was applied to complex samples, such as inox, nickel-titanium and cobalt-chromium alloys. A study of the potential inter...

  9. Determination of Ni(II in metal alloys by spectrophotometry UV-Vis using dopasemiquinone

    Directory of Open Access Journals (Sweden)

    Wagner José Barreto

    2010-01-01

    Full Text Available A spectrophotometric method was proposed for Ni(II determination in alloys using a dopa-semiquinone (L-1 to form [Ni(II(L1-3]1-, ε = 9.3 x 10³ L mol-1 cm-1. The optimal conditions for the determination were: wavelength 590 nm, temperature 25 °C, reaction time 45 min and pH 7.5. The Beer's law was obeyed for nickel from 3.33 x 10-5 to 1.78 x 10-4 mol L-1. The method was applied to complex samples, such as inox, nickel-titanium and cobalt-chromium alloys. A study of the potential interferents revealed that Mn was the major interferent. The limit of detection and quantification were 2.88 x 10-5 mol L-1 and 3.06 x 10-5 mol L-1, respectively.

  10. Acomprehensive study of high metallicity giant extragalactic h ii regions: chemical abundances

    Directory of Open Access Journals (Sweden)

    Marcelo Castellanos

    2002-01-01

    Full Text Available Hemos realizado observaciones espectrofotom etricas en el optico e infrarrojo cercano de 15 regiones H II en las galaxias espirales NGC 628, NGC 925, NGC 1232 y NGC 1637. Dichas observaciones han sido realizadas con una amplia cobertura espectral y con una resoluci on su ciente para detectar y medir tanto las d ebiles l neas aurorales como las caracter sticas de estrellas Wolf-Rayet (WR. Hemos derivado la temperatura electr onica en las regiones observadas con el n de investigar la estructura de ionizaci on de las mismas y la composici on qu mica del gas. De esta manera, hemos seleccionado de la muestra de Van Zee et al. (1998, aquellas regiones H II gigantes cuya metalicidad, obtenida a partir de calibraciones emp ricas basadas en las l neas prohibidas del ox geno, es solar o sobresolar.

  11. Unexpected metal ion-assisted transformations leading to unexplored bridging ligands in Ni(II) coordination chemistry: the case of PO3F(2-) group.

    Science.gov (United States)

    Dermitzaki, Despina; Raptopoulou, Catherine P; Psycharis, Vassilis; Escuer, Albert; Perlepes, Spyros P; Stamatatos, Theocharis C

    2014-10-21

    The initial 'accidental', metal ion-assisted hydrolysis of PF6(-) to PO3F(2-) has been evolved in a systematic investigation of the bridging affinity of the latter group in Ni(II)/oximate chemistry; mono-, di- and trinuclear complexes have been prepared and confirmed both the rich reactivity of PO3F(2-) and its potential for further use as bridging ligand in high-nuclearity 3d-metal cluster chemistry.

  12. Manganese Abundances In Three Metal-poor Stars Using Improved log(gf) Data For Mn I And Mn II Lines

    Science.gov (United States)

    Lawler, James E.; Sobeck, J. S.; Den Hartog, E. A.; Sneden, C.; Cowan, J. J.; Truran, J. W.

    2012-01-01

    We present accurate Mn abundances for three very metal-poor stars using new log(gf) measurements [Den Hartog et al. 2011] for transitions of Mn I and Mn II spanning a wavelength range from 2300 to 6050 Å. The three metal-poor ([Fe/H] Hartog, E A, Lawler J E, Sobeck J S, Sneden C, and Cowan J J 2011, ApJS 194, 35

  13. [Implant placement with metal ceramic restorations in a patient with type II diabetes and asthma].

    Science.gov (United States)

    Kuznetsov, S V; Markina, M S

    2013-01-01

    In out-patient dental care a history of somatic pathology is of vital importance. Unfortunately patients are not always compliant enough not understanding the impact of somatic pathology on dental treatment. The current paper presents a case of dental implant placement and splint bridge fixation in a patient with type II diabetes and asthma. The authors summarize the most useful recommendations for treatment and follow-up of such patients.

  14. Phototoxicity of strained Ru(ii) complexes: is it the metal complex or the dissociating ligand?

    Science.gov (United States)

    Azar, Daniel F; Audi, Hassib; Farhat, Stephanie; El-Sibai, Mirvat; Abi-Habib, Ralph J; Khnayzer, Rony S

    2017-07-27

    A photochemically dissociating ligand in Ru(bpy)2(dmphen)Cl2 [bpy = 2,2'-bipyridine; dmphen = 2,9-dimethyl-1,10-phenanthroline] was found to be more cytotoxic on the ML-2 Acute Myeloid Leukemia cell line than Ru(bpy)2(H2O)2(2+) and prototypical cisplatin. Our findings illustrate the potential potency of diimine ligands in photoactivatable Ru(ii) complexes.

  15. Acomprehensive study of high metallicity giant extragalactic h ii regions: chemical abundances

    OpenAIRE

    Marcelo Castellanos; Díaz, Angeles I.; Elena Terlevich

    2002-01-01

    Hemos realizado observaciones espectrofotom etricas en el optico e infrarrojo cercano de 15 regiones H II en las galaxias espirales NGC 628, NGC 925, NGC 1232 y NGC 1637. Dichas observaciones han sido realizadas con una amplia cobertura espectral y con una resoluci on su ciente para detectar y medir tanto las d ebiles l neas aurorales como las caracter sticas de estrellas Wolf-Rayet (WR). Hemos derivado la temperatura electr onica en las regiones observadas con el n de investi...

  16. Oxoaporphine Metal Complexes (CoII, NiII, ZnII) with High Antitumor Activity by Inducing Mitochondria-Mediated Apoptosis and S-phase Arrest in HepG2

    Science.gov (United States)

    Qin, Jiao-Lan; Shen, Wen-Ying; Chen, Zhen-Feng; Zhao, Li-Fang; Qin, Qi-Pin; Yu, Yan-Cheng; Liang, Hong

    2017-01-01

    Three new oxoaporphine Co(II), Ni(II) and Zn(II) complexes 1–3 have been synthesized and fully characterized. 1–3 have similar mononuclear structures with the metal and ligand ratio of 1:2. 1–3 exhibited higher cytotoxicity than the OD ligand and cisplatin against HepG2, T-24, BEL-7404, MGC80–3 and SK-OV-3/DDP cells, with IC50 value of 0.23−4.31 μM. Interestingly, 0.5 μM 1–3 significantly caused HepG2 arrest at S-phase, which was associated with the up-regulation of p53, p21, p27, Chk1 and Chk2 proteins, and decrease in cyclin A, CDK2, Cdc25A, PCNA proteins. In addition, 1–3 induced HepG2 apoptosis via a caspase-dependent mitochondrion pathway as evidenced by p53 activation, ROS production, Bax up-regulation and Bcl-2 down-regulation, mitochondrial dysfunction, cytochrome c release, caspase activation and PARP cleavage. Furthermore, 3 inhibited tumor growth in HepG2 xenograft model, and displayed more safety profile in vivo than cisplatin. PMID:28436418

  17. Crystal structure of nonadentate tricompartmental ligand derived from pyridine-2,6-dicarboxylic acid: Spectroscopic, electrochemical and thermal investigations of its transition metal(II) complexes

    Science.gov (United States)

    Vadavi, Ramesh S.; Shenoy, Rashmi V.; Badiger, Dayananda S.; Gudasi, Kalagouda B.; Devi, L. Gomathi; Nethaji, Munirathinam

    2011-07-01

    The coordinating behavior of a new dihydrazone ligand, 2,6-bis[(3-methoxysalicylidene)hydrazinocarbonyl]pyridine towards manganese(II), cobalt(II), nickel(II), copper(II), zinc(II) and cadmium(II) has been described. The metal complexes were characterized by magnetic moments, conductivity measurements, spectral (IR, NMR, UV-Vis, FAB-Mass and EPR) and thermal studies. The ligand crystallizes in triclinic system, space group P-1, with α = 98.491(10)°, β = 110.820(10)° and γ = 92.228(10)°. The cell dimensions are a = 10.196(7) Å, b = 10.814(7) Å, c = 10.017(7) Å, Z = 2 and V = 1117.4(12). IR spectral studies reveal the nonadentate behavior of the ligand. All the complexes are neutral in nature and possess six-coordinate geometry around each metal center. The X-band EPR spectra of copper(II) complex at both room temperature and liquid nitrogen temperature showed unresolved broad signals with giso = 2.106. Cyclic voltametric studies of copper(II) complex at different scan rates reveal that all the reaction occurring are irreversible.

  18. Synthesis, characterization and biological relevance of some metal (II) complexes with oxygen, nitrogen and oxygen (ONO) donor Schiff base ligand derived from thiazole and 2-hydroxy-1-naphthaldehyde

    Science.gov (United States)

    Nagesh, G. Y.; Mruthyunjayaswamy, B. H. M.

    2015-04-01

    The novel Schiff base ligand 2-((2-hydroxynaphthalen-1-yl)methylene)-N-(4-phenylthiazol-2-yl)hydrazinecarboxamide (L) obtained by the condensation of N-(4-phenylthiazol-2-yl)hydrazinecarboxamide with 2-hydroxy-1-naphthaldehyde and its newly synthesized Cu(II), Co(II), Ni(II), Zn(II) and Cd(II) complexes have been characterized by microanalysis, molar conductance, IR, 1H NMR, ESI-mass, UV-Visible, TGA/DTA, ESR and powder X-ray diffraction data to explicate their structures. The IR results confirmed the tridentate binding of the ligand involving oxygen atom of amide carbonyl, azomethine nitrogen and naphthol oxygen. 1H NMR spectral data of the ligand (L) and its Zn(II) complex agreed well with the proposed structures. Thermogravimetric studies for Cu(II) and Ni(II) complexes indicated the presence of coordinated water molecules and the final product is the metal oxide. In order to appraise the effect of antimicrobial activity of metal ions upon chelation, the newly synthesized ligand and its metal complexes were screened for their antimicrobial activity by minimum inhibitory concentration (MIC) method. The DNA cleavage activities were studied using plasmid DNA pBR322 (Bangal re Genei, Bengaluru, Cat. No 105850) as a target molecule by agarose gel electrophoresis method. The brine shrimp bioassay was also carried out to study the in vitro cytotoxicity properties against Artemia salina. Furthermore, the antioxidant activity were determined in vitro by reduction of 1,1-diphenyl-2-picryl hydrazyl (DPPH). The ligand exhibited better in vitro-antioxidant activity than its metal complexes.

  19. Globular Cluster Abundances from High-resolution, Integrated-light Spectroscopy. II. Expanding the Metallicity Range for Old Clusters and Updated Analysis Techniques

    Science.gov (United States)

    Colucci, Janet E.; Bernstein, Rebecca A.; McWilliam, Andrew

    2017-01-01

    We present abundances of globular clusters (GCs) in the Milky Way and Fornax from integrated-light (IL) spectra. Our goal is to evaluate the consistency of the IL analysis relative to standard abundance analysis for individual stars in those same clusters. This sample includes an updated analysis of seven clusters from our previous publications and results for five new clusters that expand the metallicity range over which our technique has been tested. We find that the [Fe/H] measured from IL spectra agrees to ∼0.1 dex for GCs with metallicities as high as [Fe/H] = ‑0.3, but the abundances measured for more metal-rich clusters may be underestimated. In addition we systematically evaluate the accuracy of abundance ratios, [X/Fe], for Na i, Mg i, Al i, Si i, Ca i, Ti i, Ti ii, Sc ii, V i, Cr i, Mn i, Co i, Ni i, Cu i, Y ii, Zr i, Ba ii, La ii, Nd ii, and Eu ii. The elements for which the IL analysis gives results that are most similar to analysis of individual stellar spectra are Fe i, Ca i, Si i, Ni i, and Ba ii. The elements that show the greatest differences include Mg i and Zr i. Some elements show good agreement only over a limited range in metallicity. More stellar abundance data in these clusters would enable more complete evaluation of the IL results for other important elements. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

  20. Impact of Lewis base on chemical reactivity and separation efficiency for hydrated fourth-row transition metal (II) complexes: an ONIOM DFT/MM study.

    Science.gov (United States)

    He, Dingsheng; Ma, Ming

    2014-04-24

    In this paper, two-layer ONIOM combinations of high-level quantum mechanics (QM) and inexpensive molecular mechanics (MM) are successfully used to investigate the structural characters of metal (M, all the transition metals in the fourth period)-H2O-Lewis base (A(-)) complexes. Global and local descriptors of chemical reactivity and selectivity from conceptual density functional theory are employed to show the properties of the active complexes of M(H2O)2A2 and to study the effect of the Lewis base for the separation of transition metal ions. It is shown that chemical potential, hardness, electrophilicity, as well as the dual and multiphilic descriptors are adequate for characterizing the global and local reactivity trends of the M(H2O)2A2 complex. It is found that the reactivity is well localized at the metallic center in M(H2O)2A2 and the dual descriptor (ΔfM(r)) can also be used to characterize the directional attack of the electrophile and nucleophile except for the selectivity of the reaction. On the basis of the values of ωM and Δsk, and the sign of ΔfM(r), the selectivity of the nucleophilic reagent (R(-)) for M(II) in M(H2O)2A2 (from high to low) follows this order: Cu(II) > Ni(II) > Co(II) > Fe(II) ≫ Mn(II) > Zn(II) > Cr(II). The Lewis base (A(-)) improves chemical reactivity and selectivity because of changing the reaction path and forming an intermediate, which possesses the higher antibonding character and the larger HOMO/LUMO gap. NBO or AIMALL analysis and Frontier orbital theory results presented here provided more theoretical support for the above reactivity and selectivity studies.

  1. A Dynamic Zn Site in Helicobacter pylori HypA: A Potential Mechanism for Metal-Specific Protein Activity

    Energy Technology Data Exchange (ETDEWEB)

    Kennedy,D.; Herbst, R.; Iwig, J.; Chivers, P.; Maroney, M.

    2007-01-01

    HypA is an accessory protein and putative metallochaperone that is critical for supplying nickel to the active site of NiFe hydrogenases. In addition to binding Ni(II), HypA is known to contain a Zn site that has been suggested to play a structural role. X-ray absorption spectroscopy has been used to show that the Zn site changes structure upon binding nickel, from a S{sub 3}(O/N)-donor ligand environment to an S{sub 4}-donor ligand environment. This provides a potential mechanism for discriminating Ni(II) from other divalent metal ions. The Ni(II) site is shown to be a six-coordinate complex composed of O/N-donors including two histidines. As such, it resembles the nickel site in UreE, a nickel metallochaperone involved in nickel incorporation into urease.

  2. Galaxy counterparts of metal-rich damped Lyman-alpha absorbers - II. A solar-metallicity, molecular-rich, and dusty DLA at z_abs=2.58

    CERN Document Server

    Fynbo, J P U; Noterdaeme, P; Christensen, L; Moller, P; Durgapal, A K; Goldoni, P; Kaper, L; Krogager, J -K; Laursen, P; Maund, J R; Milvang-Jensen, B; Okoshi, K; Rasmussen, P K; Thorsen, T J; Toft, S; Zafar, T

    2010-01-01

    [Abridged]. Here, we report on the discovery of the galaxy counterpart of the z_abs=2.58 DLA on the line-of-sight to the z=3.07 quasar SDSS J091826.16+163609.0. The galaxy counterpart of the DLA is detected in the OIII 5007 and OII 3726,3729 emission lines redshifted into the NIR at an impact parameter of 16 kpc. Ly-alpha emission is not detected. The upper limit implies that Ly-alpha emission from this galaxy is suppressed by more than an order of magnitude. The DLA is amongst the most metal-rich DLAs studied so far at comparable redshifts. We find evidence for substantial depletion of refractory elements onto dust grains. Fitting the main metal line component of the DLA, which is located at z_abs=2.5832 and accounts for at least 85% of the total column density of low-ionisation species, we measure metal abundances from ZnII, SII, SiII, CrII, MnII, FeII and NiII of -0.12, -0.26, -0.46, -0.88, -0.92, -1.03 and -0.78, respectively. In addition, we detect absorption in the Lyman and Werner bands of hydrogen, wh...

  3. Promiscuity comes at a price: catalytic versatility vs efficiency in different metal ion derivatives of the potential bioremediator GpdQ.

    Science.gov (United States)

    Daumann, Lena J; McCarthy, Bianca Y; Hadler, Kieran S; Murray, Tracy P; Gahan, Lawrence R; Larrabee, James A; Ollis, David L; Schenk, Gerhard

    2013-01-01

    The glycerophosphodiesterase from Enterobacter aerogenes (GpdQ) is a highly promiscuous dinuclear metallohydrolase with respect to both substrate specificity and metal ion composition. While this promiscuity may adversely affect the enzyme's catalytic efficiency its ability to hydrolyse some organophosphates (OPs) and by-products of OP degradation have turned GpdQ into a promising candidate for bioremedial applications. Here, we investigated both metal ion binding and the effect of the metal ion composition on catalysis. The prevalent in vivo metal ion composition for GpdQ is proposed to be of the type Fe(II)Zn(II), a reflection of natural abundance rather than catalytic optimisation. The Fe(II) appears to have lower binding affinity than other divalent metal ions, and the catalytic efficiency of this mixed metal center is considerably smaller than that of Mn(II), Co(II) or Cd(II)-containing derivatives of GpdQ. Interestingly, metal ion replacements do not only affect catalytic efficiency but also the optimal pH range for the reaction, suggesting that different metal ion combinations may employ different mechanistic strategies. These metal ion-triggered modulations are likely to be mediated via an extensive hydrogen bond network that links the two metal ion binding sites via residues in the substrate binding pocket. The observed functional diversity may be the cause for the modest catalytic efficiency of wild-type GpdQ but may also be essential to enable the enzyme to evolve rapidly to alter substrate specificity and enhance k(cat) values, as has recently been demonstrated in a directed evolution experiment. This article is part of a Special Issue entitled: Chemistry and mechanism of phosphatases, diesterases and triesterases.

  4. Bright Metal-Poor Stars from the Hamburg/ESO Survey. II. A Chemodynamical Analysis

    Science.gov (United States)

    Beers, Timothy C.; Placco, Vinicius M.; Carollo, Daniela; Rossi, Silvia; Lee, Young Sun; Frebel, Anna; Norris, John E.; Dietz, Sarah; Masseron, Thomas

    2017-01-01

    We obtain estimates of stellar atmospheric parameters for a previously published sample of 1777 relatively bright (9Survey. The original Frebel et al. analysis of these stars was able to derive estimates of [Fe/H] and [C/Fe] only for a subset of the sample, due to limitations in the methodology then available. A new spectroscopic analysis pipeline has been used to obtain estimates of {T}{eff}, {log} g, [Fe/H], and [C/Fe] for almost the entire data set. This sample is very local—about 90% of the stars are located within 0.5 kpc of the Sun. We consider the chemodynamical properties of these stars in concert with a similarly local sample of stars from a recent analysis of the Bidelman and MacConnell “weak metal” candidates by Beers et al. We use this combined sample to identify possible members of the halo stream of stars suggested by Helmi et al. and Chiba & Beers, as well as stars that may be associated with stripped debris from the putative parent dwarf of the globular cluster Omega Centauri, suggested to exist by previous authors. We identify a clear increase in the cumulative frequency of carbon-enhanced metal-poor (CEMP) stars with declining metallicity, as well as an increase in the fraction of CEMP stars with distance from the Galactic plane, consistent with previous results. We also identify a relatively large number of CEMP stars with kinematics consistent with the metal-weak thick-disk population, with possible implications for its origin.

  5. New force field parameters for metalloproteins I: Divalent copper ion centers including three histidine residues and an oxygen-ligated amino acid residue.

    Science.gov (United States)

    Wise, Olivia; Coskuner, Orkid

    2014-06-30

    Transition metal ion complexation with proteins is ubiquitous across such diverse fields as neurodegenerative and cardiovascular diseases and cancer. In this study, the structures of divalent copper ion centers including three histidine and one oxygen-ligated amino acid residues and the relative binding affinities of the oxygen-ligated amino acid residues with these metal ion centers, which are debated in the literature, are presented. Furthermore, new force field parameters, which are currently lacking for the full-length metal-ligand moieties, are developed for metalloproteins that have these centers. These new force field parameters enable investigations of metalloproteins possessing these binding sites using molecular simulations. In addition, the impact of using the atom equivalence and inequivalence atomic partial charge calculation procedures on the simulated structures of these metallopeptides, including hydration properties, is described.

  6. Unusual composition dependence of magnetic relaxation for Co(II)(1-x)Ni(II)(x) chain-based metal-organic frameworks.

    Science.gov (United States)

    Wang, Yan-Qin; Cheng, Ai-Ling; Liu, Pei-Pei; Gao, En-Qing

    2013-08-11

    A series of isomorphous 3D Co(II)(1-x)Ni(II)(x) MOFs based on ferromagnetic chains show SCM-type slow relaxation and the Co-rich system can exhibit a higher blocking temperature than both Co(II) and Ni(II) parent materials.

  7. Paving the way for the synthesis of a series of divalent actinide complexes: a theoretical perspective.

    Science.gov (United States)

    Wu, Q-Y; Lan, J-H; Wang, C-Z; Cheng, Z-P; Chai, Z-F; Gibson, J K; Shi, W-Q

    2016-02-21

    Recently, the +2 formal oxidation state in soluble molecular complexes for lanthanides (La-Nd, Sm-Lu) and actinides (Th and U) has been discovered [W. J. Evans, et al., J. Am. Chem. Soc., 2011, 133, 15914; J. Am. Chem. Soc., 2012, 134, 8420; J. Am. Chem. Soc., 2013, 135, 13310; Chem. Sci., 2015, 6, 517]. To explore the nature of the bonding and stabilities of the low-valent actinide complexes, a series of divalent actinide species, [AnCp'3](-) (An[double bond, length as m-dash]Th-Am, Cp' = [η(5)-C5H4(SiMe3)](-)) have been investigated in THF solution using scalar relativistic density functional theory. The electronic structures and electron affinity properties were systematically studied to identify the interactions between the +2 actinide ions and Cp' ligands. The ground state electron configurations for the [AnCp'3](-) species are [ThCp'3](-) 6d(2), [PaCp'3](-) 5f(2)6d(1), [UCp'3](-) 5f(3)6d(1), [NpCp'3](-) 5f(5), [PuCp'3](-) 5f(6), and [AmCp'3](-) 5f(7), respectively, according to the MO analysis. The total bonding energy decreases from the Th- to the Am-complex and the electrostatic interactions mainly dominate the bonding between the actinide atom and ligands. The electron affinity analysis suggests that the reduction reaction of AnCp'3→ [AnCp'3](-) should become increasingly facile across the actinide series from Th to Am, in accord with the known An(iii/ii) reduction potentials. This work expands the knowledge on the low oxidation state chemistry of actinides, and further motivates and guides the synthesis of related low oxidation state compounds of 5f elements.

  8. Magnetic interactions in a copper(II) trimer encapsulated in a molecular metal oxide cluster

    Energy Technology Data Exchange (ETDEWEB)

    Kokoszka, G.F.; Padula, F.; Goldstein, A.S.; Venturini, E.L.; Azevedo, L.; Siedle, A.R.

    1988-01-13

    This paper presents EPR and magnetic susceptibility data on the trimeric Cu(II) complex (W/sub 9/AsO/sub 33/)/sub 2/Cu/sub 3/(H/sub 2/O)/sub 2//sup 12/minus//, with emphasis on the intramolecular spin-exchange coupling processes. The exchange interaction arises from the coupling of one unpaired electron centered on each of the three Cu(II) ions, which are arranged in an isosceles triangle (Cu-Cu distances = 4.669 and 4.707 /angstrom/). An isotropic antiferromagnetic interaction means that the highest spin state (S = 3/2) is above the two S = 1/2 states. The observed quartet state is quite normal in its EPR behavior and shows the allowed transitions centered at about 3000 G (g/sub 11/ = 2.075, g/sub 1/ = 2.243, D = 1.9 /times/ 10/sup /minus/2/ cm/sup /minus/1/, and E < 30 g) as well as the two sets of forbidden lines at about one-half and one-third of that field value over the range 10-300 K. The quartet spectrum was observed, with some changes in shape and intensity, down to 2 K. Additional EPR lines are found both below and above the S = 3/2 EPR absorptions and have a pronounced temperature dependence with a maximum intensity at about 40 K. The most prominent of these lines is at g /approximately/ 10 at both 9 and 53 GHz. The magnetic susceptibility data in the 10-300 K range can be fit with an equation of the form C/(T + T/sub c/) + A with T/sub c/ = 3.3 K, C = 2.54 /times/ 10/sup /minus/4/ cm/sup 3/K/g and A = /minus/8.7 /times/ 10/sup /minus/8/. This value of C yields a typical Cu(II) g value based on the value of S = 1/2 for each of the unpaired electrons centered on three Cu(II) ions. Below 10 K, the magnetic susceptibility deviates from a Curie temperature dependence and can be interpreted with an intramolecular antiferromagnetic coupling with J = /minus/7.5 K; intermolecular effects may play a role at the lowest temperature (2 K). 17 refs., 8 figs.

  9. Erosive Effects of Various Pure and Combustion-Generated Gases on Metals. Part II.

    Science.gov (United States)

    1977-10-01

    ii«M)iiii«< -———• --——- ~• —"•—- VMH -11- solid carbon. The interest in the carbonyl formation and in particular to the iron...Di TD ~ c c m u a do o 0 m ««* n o CH41 o «a a •H M 3 • < A O c n c o w o u Z 2 o o M M H to vo o on CM •H UQ i

  10. Changes of Multiple Metal Accumulation (MMA in New Orleans Soil: Preliminary Evaluation of Differences between Survey I (1992 and Survey II (2000

    Directory of Open Access Journals (Sweden)

    Paul W. Mielke

    2005-08-01

    Full Text Available Soil metal surveys were conducted in Baltimore, MD (1976-1979, Minnesota (1981-1988 and most recently, New Orleans, LA (1989-present. The unique characteristic of New Orleans is that it has two surveys; Survey I was completed in 1992 and Survey II was completed in 2000. This paper seeks to determine if there is a perceptible change in the amount of metals during less than a decade that separated these surveys. The Survey I collection was 4,026 samples stratified by 283 census tracts. All samples were collected in residential neighborhoods at least one block from a busy street. The Survey II collection was 5,467 samples stratified by 286 census tracts (plus City Park. The Survey II collection included busy streets as a category of samples. For comparison, the busy street category of 1,078 samples was excluded from Survey II for a total of 4,388 samples. The extraction methods of the two surveys used the same protocol for strength of acid (1 M HNO3, shaker-time (2 hours, and room temperature (~22ºC. However, Survey II differed in amount of sample used in extraction. For Surveys I and II, 4.0g and 0.4g were used respectively. The same ICP-AES was used to measure 8 metals in both surveys. To evaluate the analytical results of the two methods, reference soil samples (n=36 from the Wageningen Evaluating Programs for Analytical Laboratories, International Soil-analytical Exchange (WEPAL; ISE were used. The relationship between the 4.0 and 0.4 g results were linear and the Survey I results were adjusted for sample:acid ratio. Further evaluation was done by creating interpolated Multiple Metal Accumulation (MMA maps based on the median MMA for each census tract. A new map was created by dividing Survey II MMA by Survey I MMA. The ratio indicates increases of soil metals in the inner city and decreases of soil metals in the outlying areas of Metropolitan New Orleans. Comparing fresh parent alluvium from the Mississippi River with urban soil metal

  11. Enhancement of chitosan-graphene oxide SPR sensor with a multi-metallic layers of Au–Ag–Au nanostructure for lead(II) ion detection

    Energy Technology Data Exchange (ETDEWEB)

    Kamaruddin, Nur Hasiba [Department of Electric, Electronic and Systems Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor (Malaysia); Bakar, Ahmad Ashrif A., E-mail: ashrif@ukm.edu.my [Department of Electric, Electronic and Systems Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor (Malaysia); Yaacob, Mohd Hanif; Mahdi, Mohd Adzir [Wireless and Photonic Network Research Centre, Faculty of Engineering, Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Zan, Mohd Saiful Dzulkefly [Department of Electric, Electronic and Systems Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor (Malaysia); Shaari, Sahbudin [Institute of Microengineering and Nanoelectronics, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor (Malaysia)

    2016-01-15

    Highlights: • Tri-metallic Au–Ag–Au CS-GO SPR sensor was fabricated for the first time. • The tri-metallic nanostructure provided an enhanced evanescent field. • Successful functionalization of the CS-GO sensing layer. • Superior performance for lead(II) ion detection. - Abstract: We demonstrate the enhancement of surface plasmon resonance (SPR) technique by implementing a multi-metallic layers of Au–Ag–Au nanostructure in the chitosan-graphene oxide (CS-GO) SPR sensor for lead(II) ion detection. The performance of the sensor is analyzed via SPR measurements, from which the sensitivity, signal-to-noise ratio and repeatability are determined. The nanostructure layers are characterized using field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). We showed that the proposed structure has increased the shift in the SPR angle up to 3.5° within the range of 0.1–1 ppm due to the enhanced evanescent field at the sensing layer-analyte interface. This sensor also exhibits great repeatability which benefits from the stable multi-metallic nanostructure. The SNR value of 0.92 for 5 ppm lead(II) ion solution and reasonable linearity range up to that concentration shows that the tri-metallic CS-GO SPR sensor gives a good response towards the lead(II) ion solution. The CS-GO SPR sensor is also sensitive to at least a 10{sup −5} change in the refractive index. The results prove that our proposed tri-metallic CS-GO SPR sensor demonstrates a strong performance and reliability for lead(II) ion detection in accordance with the standardized lead safety level for wastewater.

  12. Bright Metal-Poor Stars from the Hamburg/ESO Survey. II. A Chemodynamical Analysis

    CERN Document Server

    Beers, Timothy C; Carollo, Daniela; Rossi, Silvia; Frebel, Anna; Norris, John E; Dietz, Sarah; Masseron, Thomas

    2016-01-01

    We obtain estimates of stellar atmospheric parameters for a previously published sample of 1777 relatively bright (9 < B < 14) metal-poor candidates from the Hamburg/ESO Survey. The original Frebel et al. analysis of these stars was only able to derive estimates of [Fe/H] and [C/Fe] for a subset of the sample, due to limitations in the methodology then available. A new spectroscopic analysis pipeline has been used to obtain estimates of Teff, log g, [Fe/H], and [C/Fe] for almost the entire dataset. This sample is very local - about 90% of the stars are located within 0.5 kpc of the Sun. We consider the chemodynamical properties of these stars in concert with a similarly local sample of stars from a recent analysis of the Bidelman & MacConnell 'weak-metal' candidates by Beers et al. We use this combined sample to identify possible members of the suggested halo stream of stars by Helmi et al. and Chiba & Beers, as well as stars that may be associated with stripped debris from the putative parent d...

  13. A novel route for the removal of bodily heavy metal lead (II)

    Science.gov (United States)

    Huang, Weirong; Zhang, Penghua; Xu, Hui; Chang, Shengli; He, Yongju; Wang, Fei; Liang, Gaowei

    2015-09-01

    The lead ion concentration in bile is considerably higher than in blood, and bile is released into the alimentary tract. Thiol-modified SBA-15 administered orally can combine with lead ions in the alimentary tract. In this paper, the in vitro lead absorption of bile was investigated. This thiol-modified SBA-15 material was used in pharmacodynamics studies on rabbits. The result that the lead content in faeces was notably higher indicates that thiol-modified SBA-15 can efficiently remove lead. The mechanism could include the following: thiol-modified SBA-15 material cuts off the heavy metal lead recirculation in the process of bile enterohepatic circulation by chelating the lead in the alimentary tract, causing a certain proportion of lead to be removed by the thiol mesoporous material, and the lead is subsequently egested out of the body in faeces. The results indicate that this material might be a potential non-injection material for the removal bodily heavy metal lead in the alimentary tract. This material may also be a useful means of lead removal, especially for non-acute sub-poisoning symptoms.

  14. Absolute dimensions of detached eclipsing binaries. II. The metallic-lined system XY Ceti

    CERN Document Server

    Southworth, John; Tamajo, E; Smalley, B; West, R G; Anderson, D R

    2011-01-01

    We present phase-resolved spectroscopy and extensive survey photometry of the detached eclipsing binary system XY Cet, which is composed of two metallic-lined stars. We measure their masses to be 1.773 +/- 0.016 and 1.615 +/- 0.014 Msun and their radii to be 1.873 +/- 0.035 and 1.773 +/- 0.029 Rsun, resulting in logarithmic surface gravities of 4.142 +/- 0.016 and 4.149 +/- 0.014 (cgs). We determine effective temperatures of 7870 +/- 115 and 7620 +/- 125 K. The projected rotational velocities are 34.4 +/- 0.4 and 34.1 +/- 0.4 km/s, which are close to synchronous. Theoretical models cannot match all of these properties, but come closest for a solar helium and metal abundance and an age in the region of 850 Myr. We obtain the individual spectra of the two stars by the spectral disentangling method, and compare them to synthetic spectra calculated for the measured effective temperatures and a solar chemical composition. Both stars show enhanced abundances of iron-group elements and clear deficiencies of Ca I and...

  15. Nanosheets of Two-Dimensional Magnetic and Conducting Fe(II)/Fe(III) Mixed-Valence Metal-Organic Frameworks.

    Science.gov (United States)

    Benmansour, Samia; Abhervé, Alexandre; Gómez-Claramunt, Patricia; Vallés-García, Cristina; Gómez-García, Carlos J

    2017-08-09

    We report the synthesis, magnetic properties, electrical conductivity, and delamination into thin nanosheets of two anilato-based Fe(II)/Fe(III) mixed-valence two-dimensional metal-organic frameworks (MOFs). Compounds [(H3O)(H2O)(phenazine)3][Fe(II)Fe(III)(C6O4X2)3]·12H2O [X = Cl (1) and Br (2)] present a honeycomb layered structure with an eclipsed packing that generates hexagonal channels containing the water molecules. Both compounds show ferrimagnetic ordering at ca. 2 K coexisting with electrical conductivity (with room temperature conductivities of 0.03 and 0.003 S/cm). Changing the X group from Cl to Br leads to a decrease in the ordering temperature and room temperature conductivity that is correlated with the decrease of the electronegativity of X. Despite the ionic charge of the anilato-based layers, these MOFs can be easily delaminated in thin nanosheets with the thickness of a few monolayers.

  16. Unbound position II in MXCXXC metallochaperone model peptides impacts metal binding mode and reactivity: Distinct similarities to whole proteins.

    Science.gov (United States)

    Shoshan, Michal S; Dekel, Noa; Goch, Wojciech; Shalev, Deborah E; Danieli, Tsafi; Lebendiker, Mario; Bal, Wojciech; Tshuva, Edit Y

    2016-06-01

    The effect of position II in the binding sequence of copper metallochaperones, which varies between Thr and His, was investigated through structural analysis and affinity and oxidation kinetic studies of model peptides. A first Cys-Cu(I)-Cys model obtained for the His peptide at acidic and neutral pH, correlated with higher affinity and more rapid oxidation of its complex; in contrast, the Thr peptide with the Cys-Cu(I)-Met coordination under neutral conditions demonstrated weaker and pH dependent binding. Studies with human antioxidant protein 1 (Atox1) and three of its mutants where S residues were replaced with Ala suggested that (a) the binding affinity is influenced more by the binding sequence than by the protein fold (b) pH may play a role in binding reactivity, and (c) mutating the Met impacted the affinity and oxidation rate more drastically than did mutating one of the Cys, supporting its important role in protein function. Position II thus plays a dominant role in metal binding and transport.

  17. Spectral, mechanical, thermal, optical and solid state parameters, of metal-organic bis(hydrogenmaleate)-CO(II) tetrahydrate crystal

    Science.gov (United States)

    Chandran, Senthilkumar; Jagan, R.; Paulraj, Rajesh; Ramasamy, P.

    2015-10-01

    Metal-organic bis(hydrogenmaleate)-Co(II) tetrahydrate single crystals have been grown by slow evaporation solution growth technique at room temperature. The crystal structure and the unit cell parameters were analyzed from the X-ray diffraction studies. Single-crystal X-ray diffraction analyses reveal that the grown crystal belongs to triclinic system with the space group P-1. Functional groups in bis(hydrogenmaleate)-Co(II) tetrahydrate were identified by Fourier transform infrared spectral analysis. The peak observed at 663 cm-1 is assigned to the (Co-O) stretching vibrations. The optical transmission of the crystal was studied by UV-vis-NIR spectral analysis. The photoluminescence emission studies were carried out for the title compound in a wide wavelength range between 350 nm and 550 nm at 303 K. Mechanical strength was tested by Vickers microhardness test. The laser damage threshold value has been determined using Nd:YAG laser operating at 1064 nm. At various frequencies and temperatures the dielectric behavior of the material was investigated. Solid state parameters such as plasma energy, Penn gap, Fermi energy and electronic polarizability were evaluated. Photoconductivity measurements were carried out for the grown crystal in the presence of DC electric field at room temperature. Thermal stability and decomposition of the crystal were studied by TG-DTA. The weight loss of the title compound occurs in different steps.

  18. Proton conduction and long-range ferrimagnetic ordering in two isostructural Copper(II) mesoxalate metal-organic frameworks.

    Science.gov (United States)

    Gil-Hernández, Beatriz; Savvin, Stanislav; Makhloufi, Gamall; Núñez, Pedro; Janiak, Christoph; Sanchiz, Joaquín

    2015-02-16

    Two compounds of formula {(H3O)[Cu7(Hmesox)5(H2O)7]·9H2O}n (1a) and {(NH4)0.6(H3O)0.4[Cu7(Hmesox)5(H2O)7]·11H2O}n (1b) were prepared and structurally characterized by single-crystal X-ray diffraction (H4mesox = mesoxalic acid, 2-dihydroxymalonic acid). The compounds are crystalline functional metal-organic frameworks exhibiting proton conduction and magnetic ordering. Variable-temperature magnetic susceptibility measurements reveal that the copper(II) ions are strongly ferro- and antiferromagnetically coupled by the alkoxide and carboxylate bridges of the mesoxalate linker to yield long-range magnetic ordering with a Tc of 17.6 K, which is reached by a rare mechanism known as topologic ferrimagnetism. Electric conductivity, measured by impedance methods, shows values as high as 6.5 × 10(-5) S cm(-1) and occurs by proton exchange among the hydronium/ammonium and water molecules of crystallization, which fill the voids left by the three-dimensional copper(II) mesoxalate anionic network.

  19. Mn(II)-based porous metal-organic framework showing metamagnetic properties and high hydrogen adsorption at low pressure.

    Science.gov (United States)

    Han, Zheng-Bo; Lu, Rui-Yun; Liang, Yan-Fang; Zhou, Yan-Ling; Chen, Qing; Zeng, Ming-Hua

    2012-01-02

    A Mn(II)-based homometallic porous metal-organic framework, Mn(5)(btac)(4)(μ(3)-OH)(2)(EtOH)(2)·DMF·3EtOH·3H(2)O (1, btac = benzotriazole-5-carboxylate), has been solvothermally synthesized and structurally characterized by elemental analysis, thermogravimetric analysis, and X-ray crystallographic study. 1 is a 3D neutral framework featuring 1D porous channels constructed by {Mn-OH-Mn}(n) chains and btac linkers. Magnetic studies show that 1 is a 3D metamagnet containing 1D {Mn-OH-Mn}(n) ferrimagnetic chains. High-pressure H(2) adsorption measurement at 77 K reveals that activated 1 can absorb 0.99 wt % H(2) at 0.5 atm and reaches a maximum of 1.03 wt % at 5.5 atm. The steep H(2) absorption at lower pressure (98.2% of the storage capacity at 0.5 atm) is higher than the corresponding values of some MOFs (MIL-100 (16.1%), MOF-177 (57.1%), and MOF-5 (22.2%)). Furthermore, activated 1 can adsorb CO(2) at room temperature and 275 K. The adsorption enthalpy is 22.0 kJ mol(-1), which reveals the high binding ability for CO(2). Detailed gas sorption implies that the exposed Mn(II) coordination sites in the activated 1 play an important role to improve its adsorption capacities.

  20. Mercury (II) reduction and co-precipitation of metallic mercury on hydrous ferric oxide in contaminated groundwater.

    Science.gov (United States)

    Richard, Jan-Helge; Bischoff, Cornelia; Ahrens, Christian G M; Biester, Harald

    2016-01-01

    Mercury (Hg) speciation and sorption analyses in contaminated aquifers are useful for understanding transformation, retention, and mobility of Hg in groundwater. In most aquifers hydrous ferric oxides (HFOs) are among the most important sorbents for trace metals; however, their role in sorption or mobilization of Hg in aquifers has been rarely analyzed. In this study, we investigated Hg chemistry and Hg sorption to HFO under changing redox conditions in a highly HgCl2-contaminated aquifer (up to 870μgL(-1) Hg). Results from aqueous and solid phase Hg measurements were compared to modeled (PHREEQC) data. Speciation analyses of dissolved mercury indicated that Hg(II) forms were reduced to Hg(0) under anoxic conditions, and adsorbed to or co-precipitated with HFO. Solid phase Hg thermo-desorption measurements revealed that between 55 and 93% of Hg bound to HFO was elemental Hg (Hg(0)). Hg concentrations in precipitates reached more than 4 weight %, up to 7000 times higher than predicted by geochemical models that do not consider unspecific sorption to and co-precipitation of elemental Hg with HFO. The observed process of Hg(II) reduction and Hg(0) formation, and its retention and co-precipitation by HFO is thought to be crucial in HgCl2-contaminated aquifers with variable redox-conditions regarding the related decrease in Hg solubility (factor of ~10(6)), and retention of Hg in the aquifer.

  1. A GMOS-N IFU study of the central H ii region in the blue compact dwarf galaxy NGC 4449: kinematics, nebular metallicity and star formation

    Science.gov (United States)

    Kumari, Nimisha; James, Bethan L.; Irwin, Mike J.

    2017-10-01

    We use integral field spectroscopic (IFS) observations from the Gemini Multi-Object Spectrograph North (GMOS-N) to study the central H ii region in a nearby blue compact dwarf (BCD) galaxy NGC 4449. The IFS data enable us to explore the variation of physical and chemical conditions of the star-forming region and the surrounding gas on spatial scales as small as 5.5 pc. Our kinematical analysis shows possible signatures of shock ionization and shell structures in the surroundings of the star-forming region. The metallicity maps of the region, created using direct Te and indirect strong line methods (R23, O3N2 and N2), do not show any chemical variation. From the integrated spectrum of the central H ii region, we find a metallicity of 12 + log(O/H) = 7.88 ± 0.14 ({˜ }0.15^{+0.06}_{-0.04} Z⊙) using the direct method. Comparing the central H ii region metallicity derived here with those of H ii regions throughout this galaxy from previous studies, we find evidence of increasing metallicity with distance from the central nucleus. Such chemical inhomogeneities can be due to several mechanisms, including gas loss via supernova blowout, galactic winds or metal-poor gas accretion. However, we find that the localized area of decreased metallicity aligns spatially with the peak of star-forming activity in the galaxy, suggesting that gas accretion may be at play here. Spatially resolved IFS data for the entire galaxy are required to confirm the metallicity inhomogeneity found in this study and determine its possible cause.

  2. Ternary complexes metal [Co(II), Ni(II), Cu(II) and Zn(II)]--ortho-iodohippurate (I-hip)--acyclovir. X-ray characterization of isostructural [(Co, Ni or Zn)(I-hip)(2)(ACV)(H(2)O)(3)] with stacking as a recognition factor.

    Science.gov (United States)

    Barceló-Oliver, M; Terrón, A; García-Raso, A; Fiol, J J; Molins, E; Miravitlles, C

    2004-11-01

    Four ternary metal--ortho-iodohippurate (I-hip)--acyclovir (ACV) complexes, [M(I-hip)(2)(ACV)(H(2)O)(3)] where M is Co(II) (1), Ni(II) (2), Cu (3) and Zn(II) have been obtained by reaction between the corresponding binary complexes M(II)(I-hip)(2)xnH(2)O and ACV. Three ternary complexes (M=Co, Ni and Zn) and the corresponding Zn(II)--ortho-iodohippurate binary derivative have been structurally characterized by X-ray diffraction: The studies show these three ternary complexes are isostructural and present, in solid state, an interesting stacking between the nucleobase and the aryl ring of the hippurate moiety, which probably promotes the formation of ternary complexes. Moreover, the two different ligands interact between them by means of ancillary hydrogen bonds with water molecules coordinated to the metal ion. It must be mentioned that these two recognition factors, hydrogen bonds plus stacking, could explain the reason for the isostructurality of these ternary derivatives with so different three metal ions, with diverses trends in coordination numbers and geometries. In solid state, there are two enantiomeric molecules that are related by an inversion center as the crystal-building unit (as a translational motif) for the ternary complexes.

  3. Structures and Spectroscopy Studies of Two M(II-Phosphonate Coordination Polymers Based on Alkaline Earth Metals (M = Ba, Mg

    Directory of Open Access Journals (Sweden)

    Kui-Rong Ma

    2013-01-01

    Full Text Available The two examples of alkaline-earth M(II-phosphonate coordination polymers, [Ba2(L(H2O9]·3H2O (1 and [Mg1.5(H2O9]·(L-H21.5·6H2O (2 (H4L = H2O3PCH2N(C4H8NCH2PO3H2, N,N′-piperazinebis(methylenephosphonic acid, (L-H2 = O3PH2CHN(C4H8NHCH2PO3 have been hydrothermally synthesized and characterized by elemental analysis, FT-IR, PXRD, TG-DSC, and single-crystal X-ray diffraction. Compound 1 possesses a 2D inorganic-organic alternate arrangement layer structure built from 1D inorganic chains through the piperazine bridge, in which the ligand L−4 shows two types of coordination modes reported rarely at the same time. In 1, both crystallographic distinct Ba(1 and Ba(2 ions adopt 8-coordination two caps and 9-coordination three caps triangular prism geometry structures, respectively. Compound 2 possesses a zero-dimensional mononuclear structure with two crystallographic distinct Mg(II ions. Free metal cations   [MgO6]n2+ and uncoordinated anions (L-H2n2- are joined together by static electric force. Results of photoluminescent measurement indicate three main emission bands centered at 300 nm, 378.5 nm, and 433 nm for 1 and 302 nm, 378 nm, and 434.5 nm for 2 (λex=235 nm, respectively. The high energy emissions could be derived from the intraligand π∗-n transition stations of H4L (310 nm and 382 nm, λex=235 nm, while the low energy emission (>400 nm of 1-2 may be due to the coordination effect with metal(II ions.

  4. New approach in modeling Cr(VI) sorption onto biomass from metal binary mixtures solutions

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Chang [College of Environmental Science and Engineering, Anhui Normal University, South Jiuhua Road, 189, 241002 Wuhu (China); Chemical Engineering Department, Escola Politècnica Superior, Universitat de Girona, Ma Aurèlia Capmany, 61, 17071 Girona (Spain); Fiol, Núria [Chemical Engineering Department, Escola Politècnica Superior, Universitat de Girona, Ma Aurèlia Capmany, 61, 17071 Girona (Spain); Villaescusa, Isabel, E-mail: Isabel.Villaescusa@udg.edu [Chemical Engineering Department, Escola Politècnica Superior, Universitat de Girona, Ma Aurèlia Capmany, 61, 17071 Girona (Spain); Poch, Jordi [Applied Mathematics Department, Escola Politècnica Superior, Universitat de Girona, Ma Aurèlia Capmany, 61, 17071 Girona (Spain)

    2016-01-15

    In the last decades Cr(VI) sorption equilibrium and kinetic studies have been carried out using several types of biomasses. However there are few researchers that consider all the simultaneous processes that take place during Cr(VI) sorption (i.e., sorption/reduction of Cr(VI) and simultaneous formation and binding of reduced Cr(III)) when formulating a model that describes the overall sorption process. On the other hand Cr(VI) scarcely exists alone in wastewaters, it is usually found in mixtures with divalent metals. Therefore, the simultaneous removal of Cr(VI) and divalent metals in binary mixtures and the interactive mechanism governing Cr(VI) elimination have gained more and more attention. In the present work, kinetics of Cr(VI) sorption onto exhausted coffee from Cr(VI)–Cu(II) binary mixtures has been studied in a stirred batch reactor. A model including Cr(VI) sorption and reduction, Cr(III) sorption and the effect of the presence of Cu(II) in these processes has been developed and validated. This study constitutes an important advance in modeling Cr(VI) sorption kinetics especially when chromium sorption is in part based on the sorbent capacity of reducing hexavalent chromium and a metal cation is present in the binary mixture. - Highlights: • A kinetic model including Cr(VI) reduction, Cr(VI) and Cr(III) sorption/desorption • Synergistic effect of Cu(II) on Cr(VI) elimination included in the model • Model validation by checking it against independent sets of data.

  5. Enhancement of chitosan-graphene oxide SPR sensor with a multi-metallic layers of Au-Ag-Au nanostructure for lead(II) ion detection

    Science.gov (United States)

    Kamaruddin, Nur Hasiba; Bakar, Ahmad Ashrif A.; Yaacob, Mohd Hanif; Mahdi, Mohd Adzir; Zan, Mohd Saiful Dzulkefly; Shaari, Sahbudin

    2016-01-01

    We demonstrate the enhancement of surface plasmon resonance (SPR) technique by implementing a multi-metallic layers of Au-Ag-Au nanostructure in the chitosan-graphene oxide (CS-GO) SPR sensor for lead(II) ion detection. The performance of the sensor is analyzed via SPR measurements, from which the sensitivity, signal-to-noise ratio and repeatability are determined. The nanostructure layers are characterized using field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). We showed that the proposed structure has increased the shift in the SPR angle up to 3.5° within the range of 0.1-1 ppm due to the enhanced evanescent field at the sensing layer-analyte interface. This sensor also exhibits great repeatability which benefits from the stable multi-metallic nanostructure. The SNR value of 0.92 for 5 ppm lead(II) ion solution and reasonable linearity range up to that concentration shows that the tri-metallic CS-GO SPR sensor gives a good response towards the lead(II) ion solution. The CS-GO SPR sensor is also sensitive to at least a 10-5 change in the refractive index. The results prove that our proposed tri-metallic CS-GO SPR sensor demonstrates a strong performance and reliability for lead(II) ion detection in accordance with the standardized lead safety level for wastewater.

  6. Covalent attachment of diphosphine ligands to glassy carbon electrodes via Cu-catalyzed alkyne-azide cycloaddition. Metallation with Ni( ii )

    Energy Technology Data Exchange (ETDEWEB)

    Das, Atanu K. [Center for Molecular Electrocatalysis; Physical Sciences Division; Pacific Northwest National Laboratory; Richland, USA; Engelhard, Mark H. [Environmental Molecular Sciences Laboratory; Pacific Northwest National Laboratory; Richland, USA; Lense, Sheri [Center for Molecular Electrocatalysis; Physical Sciences Division; Pacific Northwest National Laboratory; Richland, USA; Roberts, John A. S. [Center for Molecular Electrocatalysis; Physical Sciences Division; Pacific Northwest National Laboratory; Richland, USA; Bullock, R. Morris [Center for Molecular Electrocatalysis; Physical Sciences Division; Pacific Northwest National Laboratory; Richland, USA

    2015-01-01

    Covalent tethering of a P2N2ligand to a planar, azide-terminated glassy carbon electrode surface was accomplished using a CuI-catalyzed “click” reaction, followed by metallation with NiII.

  7. MoTe2 : A Type-II Weyl Topological Metal

    Science.gov (United States)

    Wang, Zhijun; Gresch, Dominik; Soluyanov, Alexey A.; Xie, Weiwei; Kushwaha, S.; Dai, Xi; Troyer, Matthias; Cava, Robert J.; Bernevig, B. Andrei

    2016-07-01

    Based on the ab initio calculations, we show that MoTe2 , in its low-temperature orthorhombic structure characterized by an x-ray diffraction study at 100 K, realizes 4 type-II Weyl points between the N th and (N +1 )th bands, where N is the total number of valence electrons per unit cell. Other WPs and nodal lines between different other bands also appear close to the Fermi level due to a complex topological band structure. We predict a series of strain-driven topological phase transitions in this compound, opening a wide range of possible experimental realizations of different topological semimetal phases. Crucially, with no strain, the number of observable surface Fermi arcs in this material is 2—the smallest number of arcs consistent with time-reversal symmetry.

  8. Predicting 3D Structure, Flexibility, and Stability of RNA Hairpins in Monovalent and Divalent Ion Solutions

    Science.gov (United States)

    Shi, Ya-Zhou; Jin, Lei; Wang, Feng-Hua; Zhu, Xiao-Long; Tan, Zhi-Jie

    2015-01-01

    A full understanding of RNA-mediated biology would require the knowledge of three-dimensional (3D) structures, structural flexibility, and stability of RNAs. To predict RNA 3D structures and stability, we have previously proposed a three-bead coarse-grained predictive model with implicit salt/solvent potentials. In this study, we further develop the model by improving the implicit-salt electrostatic potential and including a sequence-dependent coaxial stacking potential to enable the model to simulate RNA 3D structure folding in divalent/monovalent ion solutions. The model presented here can predict 3D structures of RNA hairpins with bulges/internal loops (RNA hairpins with bulge loops of different lengths at several divalent/monovalent ion conditions. In addition, the model successfully predicts the stability of RNA hairpins with various loops/stems in divalent/monovalent ion solutions. PMID:26682822

  9. Synthesis and characterization of a series of transition metal complexes with a new symmetrical polyoxaaza macroacyclic Schiff base ligand: X-ray crystal structure of cobalt(II) and nickel(II) complexes and their antibacterial properties.

    Science.gov (United States)

    Keypour, Hassan; Shayesteh, Maryam; Rezaeivala, Majid; Chalabian, Firoozeh; Valencia, Laura

    2013-01-15

    A new symmetrical [N4O2] hexadentate Schiff base ligand, (E)-N-(pyridin-2-ylmethylene)-2-(3-(2-((E)-pyridin-2-lmethyleneamino)phenoxy)naphthalen-2-yloxy)benzenamine, abbreviated to L, and its complexes of Ni(II), Cu(II), Zn(II), Co(II), Cd(II) and Mn(II) have been synthesized in the presence of metal ions. The complexes were structurally characterized by elemental analyses, IR, UV-Vis, NMR and molar conductivity. The crystal structures of two complexes, [NiL(ONO2)2]·2H2O and [CoLCl2]CH3OH·0.5H2O, have been determined by a single crystal X-ray diffraction study. In these complexes, the ligand is coordinated in a neutral form via pyridine and azomethine nitrogen atoms. The metal ions complete their six coordination with two coordinated nitrate or chloride ions, forming a distorted octahedral geometry. The synthesized compounds have antibacterial activity against the three Gram-positive bacteria: Enterococcus faecalis, Bacillus cereus and Staphylococcus epid and also against the three Gram-negative bacteria: Citrobacter freundii, Enterobacter aerogenes and Salmonella typhi. The activity data show that the complexes are more potent antibacterials than the parent Schiff base.

  10. Synthesis and characterization of a series of transition metal complexes with a new symmetrical polyoxaaza macroacyclic Schiff base ligand: X-ray crystal structure of cobalt(II) and nickel(II) complexes and their antibacterial properties

    Science.gov (United States)

    Keypour, Hassan; Shayesteh, Maryam; Rezaeivala, Majid; Chalabian, Firoozeh; Valencia, Laura

    2013-01-01

    A new symmetrical [N4O2] hexadentate Schiff base ligand, (E)-N-(pyridin-2-ylmethylene)-2-(3-(2-((E)-pyridin-2-lmethyleneamino)phenoxy)naphthalen-2-yloxy)benzenamine, abbreviated to L, and its complexes of Ni(II), Cu(II), Zn(II), Co(II), Cd(II) and Mn(II) have been synthesized in the presence of metal ions. The complexes were structurally characterized by elemental analyses, IR, UV-Vis, NMR and molar conductivity. The crystal structures of two complexes, [NiL(ONO2)2]·2H2O and [CoLCl2]CH3OH·0.5H2O, have been determined by a single crystal X-ray diffraction study. In these complexes, the ligand is coordinated in a neutral form via pyridine and azomethine nitrogen atoms. The metal ions complete their six coordination with two coordinated nitrate or chloride ions, forming a distorted octahedral geometry. The synthesized compounds have antibacterial activity against the three Gram-positive bacteria: Enterococcus faecalis, Bacillus cereus and Staphylococcus epid and also against the three Gram-negative bacteria: Citrobacter freundii, Enterobacter aerogenes and Salmonella typhi. The activity data show that the complexes are more potent antibacterials than the parent Schiff base.

  11. Characterization of Cu(II) and Cd(II) resistance mechanisms in Sphingobium sp. PHE-SPH and Ochrobactrum sp. PHE-OCH and their potential application in the bioremediation of heavy metal-phenanthrene co-contaminated sites.

    Science.gov (United States)

    Chen, Chen; Lei, Wenrui; Lu, Min; Zhang, Jianan; Zhang, Zhou; Luo, Chunling; Chen, Yahua; Hong, Qing; Shen, Zhenguo

    2016-04-01

    Soil that is co-contaminated with heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) is difficult to bioremediate due to the ability of toxic metals to inhibit PAH degradation by bacteria. We demonstrated the resistance mechanisms to Cu(II) and Cd(II) of two newly isolated strains of Sphingobium sp. PHE-SPH and Ochrobactrum sp. PHE-OCH and further tested their potential application in the bioremediation of HM-phenanthrene (PhA) co-contaminated sites. The PHE-SPH and PHE-OCH strains tolerated 4.63 and 4.34 mM Cu(II) and also showed tolerance to 0.48 and 1.52 mM Cd(II), respectively. Diverse resistance patterns were detected between the two strains. In PHE-OCH cells, the maximum accumulation of Cu(II) occurred in the cell wall, while the maximum accumulation was in the cytoplasm of PHE-SPH cells. This resulted in a sudden suppression of growth in PHE-OCH and a gradual inhibition in PHE-SPH as the concentration of Cu(II) increased. Organic acid production was markedly higher in PHE-OCH than in PHE-SPH, which may also have a role in the resistance mechanisms, and contributes to the higher Cd(II) tolerance of PHE-OCH. The factors involved in the absorption of Cu(II) or Cd(II) in PHE-SPH and PHE-OCH were identified as proteins and carbohydrates by Fourier transform infrared (FT-IR) spectroscopy. Furthermore, both strains showed the ability to efficiently degrade PhA and maintained this high degradation efficiency under HM stress. The high tolerance to HMs and the PhA degradation capacity make Sphingobium sp. PHE-SPH and Ochrobactrum sp. PHE-OCH excellent candidate organisms for the bioremediation of HM-PhA co-contaminated sites.

  12. COMPARING METAL AND TRANSPARENT MATRICES IN PREVENTING GINGIVAL OVERHANG WITH DIFFERENT RESIN MATERIAL IN CLASS II RESTORATIONS – AN SEM STUDY

    Directory of Open Access Journals (Sweden)

    Dr Dinesh Shetty

    2010-06-01

    Full Text Available Transparent matrices and reflective wedges are difficult to adapt, thus their ability to prevent gingival overhang was compared in this study with metal matrices and wooden wedges.Class II MOD cavitieswere prepared and randomly divided into six groups. Group I microhybrid composite, Group II flowable composite liner and Group III compomer. In above 3 groups metal matrices and wooden wedges were used. Group IV microhybrid composite, Group V flowable composite liner and GroupVI compomer. In above 3 groups transparent matrices and light reflecting wedges were used.Specimens were filled with respective resin composite material, using corresponding matrix andwedge.Percentage of gingival overhang was determined under SEM.The result showed greateroverhang formation in transparent matrix group compared to metal matrix group as transparentmatrices are difficult to adapt to the teeth

  13. Metalloprotein-inhibitor binding: human carbonic anhydrase II as a model for probing metal-ligand interactions in a metalloprotein active site.

    Science.gov (United States)

    Martin, David P; Hann, Zachary S; Cohen, Seth M

    2013-11-01

    An ever-increasing number of metalloproteins are being discovered that play essential roles in physiological processes. Inhibitors of these proteins have significant potential for the treatment of human disease, but clinical success of these compounds has been limited. Herein, zinc(II)-dependent metalloprotein inhibitors in clinical use are reviewed, and the potential for using novel metal-binding groups (MBGs) in the design of these inhibitors is discussed. By using human carbonic anhydrase II as a model system, the nuances of MBG-metal interactions in the context of a protein environment can be probed. Understanding how metal coordination influences inhibitor binding may help in the design of new therapeutics targeting metalloproteins.

  14. Influence of Divalent Cations on Deformation and Rupture of Adsorbed Lipid Vesicles.

    Science.gov (United States)

    Dacic, Marija; Jackman, Joshua A; Yorulmaz, Saziye; Zhdanov, Vladimir P; Kasemo, Bengt; Cho, Nam-Joon

    2016-06-28

    The fate of adsorbed lipid vesicles on solid supports depends on numerous experimental parameters and typically results in the formation of a supported lipid bilayer (SLB) or an adsorbed vesicle layer. One of the poorly understood questions relates to how divalent cations appear to promote SLB formation in some cases. The complexity arises from the multiple ways in which divalent cations affect vesicle-substrate and vesicle-vesicle interactions as well as vesicle properties. These interactions are reflected, e.g., in the degree of deformation of adsorbed vesicles (if they do not rupture). It is, however, experimentally challenging to measure the extent of vesicle deformation in real-time. Herein, we investigated the effect of divalent cations (Mg(2+), Ca(2+), Sr(2+)) on the adsorption of zwitterionic 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) lipid vesicles onto silicon oxide- and titanium oxide-coated substrates. The vesicle adsorption process was tracked using the quartz crystal microbalance-dissipation (QCM-D) and localized surface plasmon resonance (LSPR) measurement techniques. On silicon oxide, vesicle adsorption led to SLB formation in all cases, while vesicles adsorbed but did not rupture on titanium oxide. It was identified that divalent cations promote increased deformation of adsorbed vesicles on both substrates and enhanced rupture on silicon oxide in the order Ca(2+) > Mg(2+) > Sr(2+). The influence of divalent cations on different factors in these systems is discussed, clarifying experimental observations on both substrates. Taken together, the findings in this work offer insight into how divalent cations modulate the interfacial science of supported membrane systems.

  15. Next Generation Metallic Iron Nodule Technology in Electric Arc Steelmaking - Phase II

    Energy Technology Data Exchange (ETDEWEB)

    Donald R. Fosnacht; Iwao Iwasaki; Richard F. Kiesel; David J. Englund; David W. Hendrickson; Rodney L. Bleifuss

    2010-12-22

    The current trend in the steel industry is a gradual decline in conventional steelmaking from taconite pellets in blast furnaces, and an increasing number of alternative processes using metallic scrap iron, pig iron and metallized iron ore products. Currently, iron ores from Minnesota and Michigan are pelletized and shipped to the lower Great Lakes ports as blast furnace feed. The existing transportation system and infrastructure is geared to handling these bulk materials. In order to expand the opportunities for the existing iron ore mines beyond their blast furnace customer base, a new material is needed to satisfy the needs of the emerging steel industry while utilizing the existing infrastructure and materials handling. A recent commercial installation employing Kobe Steel’s ITmk3 process, was installed in Northeastern Minnesota. The basic process uses a moving hearth furnace to directly reduce iron oxides to metallic iron from a mixture of iron ore, coals and additives. The resulting products can be shipped using the existing infrastructure for use in various steelmaking processes. The technology reportedly saves energy by 30% over the current integrated steelmaking process and reduces emissions by more than 40%. A similar large-scale pilot plant campaign is also currently in progress using JFE Steel’s Hi-QIP process in Japan. The objective of this proposal is to build upon and improve the technology demonstrated by Kobe Steel and JFE, by further reducing cost, improving quality and creating added incentive for commercial development. This project expands previous research conducted at the University of Minnesota Duluth’s Natural Resources Research Institute and that reported by Kobe and JFE Steel. Three major issues have been identified and are addressed in this project for producing high-quality nodular reduced iron (NRI) at low cost: (1) reduce the processing temperature, (2) control the furnace gas atmosphere over the NRI, and (3) effectively use sub

  16. Evolution of thermally pulsing asymptotic giant branch stars - II. Dust production at varying metallicity

    Science.gov (United States)

    Nanni, Ambra; Bressan, Alessandro; Marigo, Paola; Girardi, Léo

    2013-09-01

    We present the dust ejecta of the new stellar models for the thermally pulsing asymptotic giant branch (TP-AGB) phase computed with the COLIBRI code. We use a formalism of dust growth coupled with a stationary wind for both M- and C-stars. In the original version of this formalism, the most efficient destruction process of silicate dust in M-giants is chemisputtering by H2 molecules. For these stars, we find that dust grains can only form at relatively large radial distances (r ˜ 5R*), where they cannot be efficiently accelerated, in agreement with other investigations. In the light of recent laboratory results, we also consider the alternative case that the condensation temperature of silicates is determined only by the competition between growth and free evaporation processes (i.e. no chemisputtering). With this latter approach we obtain dust condensation temperatures that are significantly higher (up to Tcond ˜ 1400 K) than those found when chemisputtering is included (Tcond ˜ 900 K), and in better agreement with condensation experiments. As a consequence, silicate grains can remain stable in inner regions of the circumstellar envelopes (r ˜ 2 R*), where they can rapidly grow and can be efficiently accelerated. With this modification, our models nicely reproduce the observed trend between terminal velocities and mass-loss rates of Galactic M-giants. For C-stars the formalism is based on the homogeneous growth scheme where the key role is played by the carbon over oxygen excess. The models reproduce fairly well the terminal velocities of Galactic stars and there is no need to invoke changes in the standard assumptions. At decreasing metallicity the carbon excess becomes more pronounced and the efficiency of dust formation increases. This trend could be in tension with recent observational evidence in favour of a decreasing efficiency, at decreasing metallicity. If confirmed by more observational data, it would indicate that either the amount of the carbon

  17. General synthetic approach to heterostructured nanocrystals based on noble metals and I-VI, II-VI, and I-III-VI metal chalcogenides.

    Science.gov (United States)

    Liu, Minghui; Zeng, Hua Chun

    2014-08-19

    Solid metal precursors (alloys or monometals) can serve both as a starting template and as a source material for chemical transformation to metal chalcogenides. Herein, we develop a simple solution-based strategy to obtain highly monodisperse noble-metal-based heterostructured nanocrystals from such precursor seeds. By utilizing chemical and structural inhomogeneity of these metal seeds, in this work, we have synthesized a total of five I-VI (Ag2S, Ag2Se, Ag3AuS2, Ag3AuSe2, and Cu9S5), three II-VI (CdS, CdSe, and CuSe), and four I-III-VI (AgInS2, AgInSe2, CuInS2, and CuInSe2) chalcogenides, together with their fifteen associated heterodimers (Au-Ag2S, Au-Ag2Se, Au-Ag3AuS2, Au-Ag3AuSe2, Au-AgInS2, Au-AgInSe2, Au-CdS, Au-CdSe, Ag-Ag2S, Ag-AgInS2, Au-Cu9S5, Au-CuInS2, Au-CuSe, Au-CuInSe2, and Pt-AgInS2) to affirm the process generality. Briefly, by adding elemental sulfur or selenium to AuAg alloy seeds and tuning the reaction conditions, we can readily obtain phase-pure Au-Ag2S, Au-Ag2Se, Au-Ag3AuS2, and Au-Ag3AuSe2 heterostructures. Similarly, we can also fabricate Au-AgInS2 and Au-AgInSe2 heterostructures from the AuAg seeds by adding sulfur/selenium and indium precursors. Furthermore, by partial or full conversion of Ag seeds, we can prepare both single-phase Ag chalcogenide nanocrystals and Ag-based heterostructures. To demonstrate wide applicability of this strategy, we have also synthesized Au-based binary and ternary Cu chalcogenide (Au-Cu9S5, Au-CuSe, Au-CuInS2, and Au-CuInSe2) heterostructures from alloy seeds of AuCu and Pt chalcogenides (e.g., Pt-AgInS2) from alloy seeds of PtAg. The structure and composition of the above products have been confirmed with X-ray diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and energy-dispersive X-ray spectroscopy methods. A kinetic investigation of the formation mechanism of these heterostructures is brought forward using Au-AgInS2 and Ag-CuInS2 as model examples.

  18. Application of Local Adsorbant From Southeast Sulawesi Clay Immobilized Saccharomyces Cerevisiae Bread’s Yeast Biomass for Adsorption Of Mn(Ii) Metal Ion

    Science.gov (United States)

    R, Halimahtussaddiyah; Mashuni; Budiarni

    2017-05-01

    Southeast Sulawesi has a great stock of clay. It is probably to use as a source of adsorbent. The adsorbent capacity of clay can be largered with teratment using bread’s yeast as biomass. At this research, study of analysis adsorption of Mn(II) metal ion on clay immobilized Saccharomyces cerevisiae bread’s yeast biomass adsorbent has been conducted. The aims of this research were to determine the effects of contact time, pH and concentration of Mn(II) metal ion and to determine the adsorption capacity of clay immobilized S. cerevisiae biomass for adsorbtion of Mn(II) metal ion. Activated clay was synthesized by reaction of clay with KMnO4, H2SO4 and HCl. S. cerevisiae biomass was result by bread’s yeast mashed. Immobilization of S. cerevisiae biomass into clay was done by mixing of ratio of S. cerevisiae bread’s yeast biomass and clay equal to 1:3 (mass of biomassa : mass of clay). The adsorption capacity was determined by using Freundlich and Langmuir adsorption isoterms. The results of FTIR spectrums showed that the functional groups of clay immobilized S. cerevisiae biomass were Si-OH (wave number 1643 cm-1), Si-O-Si (wave number 1033 cm-1), N-H (wave number 2337 cm-1), O-H (wave number 3441cm-1), and C-H (wave number 2931 cm-1). The result of adsorption capacity from Mn(II) metal ion of contact time optimum 120 minutes, pH optimun at 7 and concentration optimum 50 mg/L were 1,816 mg/g; 0,509 mg/g and 2,624mg/g respectively. The adsorption capacity of Mn(II) metal ion with ratio 1:3 (biomass : clay) was 0,1045 mg/g. Type of isothermal adsorption followed the Freunlich adsorption.

  19. Coordination mode of pentadentate ligand derivative of 5-amino-1,3,4-thiadiazole-2-thiol with nickel(II) and copper(II) metal ions: synthesis, spectroscopic characterization, molecular modeling and fungicidal study.

    Science.gov (United States)

    Chandra, Sulekh; Gautam, Seema; Kumar, Amit; Madan, Molly

    2015-02-01

    Complexes of nickel(II), and copper(II) were synthesized with pantadentate ligand i.e. 3,3'-thiodipropionicacid-bis(5-amino-1,3,4-thiadiazole-2-thiol) (L). The ligand was synthesized by the condensation of thiodipropionic acid and 5-amino-1,3,4-thiadiazole-2-thiol in 1:2 ratio, respectively. Synthesized ligand was characterized by elemental analysis, mass, (1)H NMR, IR, and molecular modeling. All the complexes were characterized by elemental analysis, molar conductance, magnetic moment, IR, electronic spectra, ESR, and molecular modeling. The newly synthesized complexes possessed general composition [M(L)X2] where M = Ni(II), Cu(II), L = pantadentate ligand and X = Cl(-), CH3COO(-). The IR spectral data indicated that the ligand behaved as a pantadentate ligand and coordinated to the metal ion through N2S3 donor atoms. The molar conductance value of Ni(II), and Cu(II) complexes in DMSO corresponded to their electrolytic behavior. On the basis of spectral study, octahedral and tetragonal geometry was assigned for Ni(II) and Cu(II) complexes, respectively. In vitro fungicidal study of ligand and its complexes was investigated against fungi Candida albicans, Candida parapsilosis, Candidia krusei, and Candida tropicalis by means of well diffusion method.

  20. Iron, hepcidin and the metal connection.

    Directory of Open Access Journals (Sweden)

    Olivier eLoréal

    2014-06-01

    Full Text Available Identification of new players in iron metabolism, such as hepcidin, which regulates ferroportin and divalent metal transporter 1 expression, has improved our knowledge of iron metabolism and iron-related diseases. However, from both experimental data and clinical findings, iron-related proteins appear to also be involved in the metabolism of other metals, especially divalent cations. Reports have demonstrated that some metals may affect, directly or indirectly, the expression of proteins involved in iron metabolism. Throughout their lives, individuals are exposed to various metals during personal and/or occupational activities. Therefore, better knowledge of the connections between iron and other metals could improve our understanding of iron-related diseases, especially the variability in phenotypic expression, as well as a variety of diseases in which iron metabolism is secondarily affected. Controlling the metabolism of other metals could represent a promising innovative therapeutic approach.

  1. Tunable anisotropic thermal expansion of a porous zinc(II) metal-organic framework.

    Science.gov (United States)

    Grobler, Ilne; Smith, Vincent J; Bhatt, Prashant M; Herbert, Simon A; Barbour, Leonard J

    2013-05-01

    A novel three-dimensional metal-organic framework (MOF) that displays anisotropic thermal expansion has been prepared and characterized by single-crystal X-ray diffraction (SCD) and thermal analysis. The as-prepared MOF has one-dimensional channels containing guest molecules that can be removed and/or exchanged for other guest molecules in a single-crystal to single-crystal fashion. When the original guest molecules are replaced there is a noticeable effect on the host mechanics, altering the thermal expansion properties of the material. This study of the thermal expansion coefficients of different inclusion complexes of the host MOF involved systematic alteration of guest size, i.e., methanol, ethanol, n-propanol, and isopropanol, showing that fine control over the thermal expansion coefficients can be achieved and that the coefficients can be correlated with the size of the guest. As a proof of concept, this study demonstrates the realizable principle that a single-crystal material with an exchangeable guest component (as opposed to a composite) may be used to achieve a tunable thermal expansion coefficient. In addition, this study demonstrates that greater variance in the absolute dimensions of a crystal can be achieved when one has two variables that affect it, i.e., the host-guest interactions and temperature.

  2. Density functional perturbational orbital theory of spin polarization in electronic systems. II. Transition metal dimer complexes.

    Science.gov (United States)

    Seo, Dong-Kyun

    2007-11-14

    We present a theoretical scheme for a semiquantitative analysis of electronic structures of magnetic transition metal dimer complexes within spin density functional theory (DFT). Based on the spin polarization perturbational orbital theory [D.-K. Seo, J. Chem. Phys. 125, 154105 (2006)], explicit spin-dependent expressions of the spin orbital energies and coefficients are derived, which allows to understand how spin orbitals form and change their energies and shapes when two magnetic sites are coupled either ferromagnetically or antiferromagnetically. Upon employment of the concept of magnetic orbitals in the active-electron approximation, a general mathematical formula is obtained for the magnetic coupling constant J from the analytical expression for the electronic energy difference between low-spin broken-symmetry and high-spin states. The origin of the potential exchange and kinetic exchange terms based on the one-electron picture is also elucidated. In addition, we provide a general account of the DFT analysis of the magnetic exchange interactions in compounds for which the active-electron approximation is not appropriate.

  3. Complexes of bis(cyclopentadienyl)hydridorhenium with group-II metal halides

    Energy Technology Data Exchange (ETDEWEB)

    Ishchenko, V.M.; Arkhireeva, T.M.; Bulychev, B.M.; Soloveichik, G.L.; Nikolaeva, S.N.

    1986-11-01

    It has been shown that the interaction of bis(cyclopentadienyl)hydridorhenium (Cp/sub 2/ReH, where Cp = eta/sup 5 -/C/sub 5/H/sub 5/) with the halides of zinc, cadmium, beryllium, and magnesium in diethyl ether results in the formation of complex compounds with the general formula Cp/sub 2/ReH MHal/sub 2/. The replacement of ether by tetrahydrofuran in the case of zinc derivatives gives monosolvates with the formula Cp/sub 2/ReH x ZnHal/sub 2/ x THF (Hal = Br, I). On the basis of data from IR and PMR spectroscopy it has been concluded that the bonding of the metal-containing fragments in these complexes is realized either as a result of an Re :..-->.. M donor-acceptor interaction (the complexes with ZnHal/sub 2/ and CdI/sub 2/) or as a result of the formation of a mixed bond (the complexes with BeCl/sub 2/ and MgHal/sub 2/).

  4. Evolution, nucleosynthesis and yields of low mass AGB stars at different metallicities (II): the FRUITY database

    CERN Document Server

    Cristallo, Sergio; Straniero, Oscar; Gallino, Roberto; Dominguez, Inma; Abia, Carlos; DiRico, Gianluca; Quintini, Massimo; Bisterzo, Sara

    2011-01-01

    By using updated stellar low mass stars models, we can systematically investigate the nucleosynthesis processes occurring in AGB stars, when these objects experience recurrent thermal pulses and third dredge-up episodes. In this paper we present the database dedicated to the nucleosynthesis of AGB stars: the FRUITY (FRANEC Repository of Updated Isotopic Tables & Yields) database. An interactive web-based interface allows users to freely download the full (from H to Bi) isotopic composition, as it changes after each third dredge-up episode and the stellar yields the models produce. A first set of AGB models, having masses in the range 1.5 < M/Msun < 3.0 and metallicities 1e-3 < Z < 2e-2, is discussed here. For each model, a detailed description of the physical and the chemical evolution is provided. In particular, we illustrate the details of the s-process and we evaluate the theoretical uncertainties due to the parametrization adopted to model convection and mass loss. The resulting nucleosynt...

  5. Spectral and thermal studies of solid-phase thermochromism of Co(II) double metal complexes

    Science.gov (United States)

    AL-Sha'alan, Noura H.

    2007-09-01

    Tetrahedral solid state structures of the blue potassium tris(aryloxo)cobaltate(II)-tetrahydrofurane complexes of the formula KCo(OAr) 3·2thf (OAr = o-chloro-, o-bromo-, m-chloro-, p-bromo, 2,6-dichloro-, 2,4-dichloro- or 2,4-dimethylphenoxide) undergo solid-phase thermal tetrahedral to octahedral transformation accompanied by change in their colours from blue to rose (one-step thermochromism). Magnetic moments, electronic and infrared spectral studies supported these results. Thermal treatment of theses complexes leads to the loss of the crystallized thf molecule yielding also blue tetrahedral complexes. However, further heating leads to the loss of the coordinated thf molecule and the formation of rose octahedral trimeric products. TG-DTA results showed that the, two solvated thf molecules were eliminated in two steps. Mass spectral studies and IR intensity measurements confirmed the trimeric behaviour of the rose octahedral geometry of thermal products. Conductance measurements of solutions of these complexes in thf indicated that they behave as non-electrolytes.

  6. Cooperative metal-ligand assisted E/Z isomerization and cyano activation at Cu(II) and Co(II) complexes of arylhydrazones of active methylene nitriles.

    Science.gov (United States)

    Mahmudov, Kamran T; Kopylovich, Maximilian N; Sabbatini, Alessandra; Drew, Michael G B; Martins, Luísa M D R S; Pettinari, Claudio; Pombeiro, Armando J L

    2014-09-15

    New (E/Z)-2-(2-(1-cyano-2-methoxy-2-oxoethylidene)hydrazinyl)benzoic acid (H2L(4)) and known sodium 2-(2-(dicyanomethylene)hydrazinyl)benzenesulfonate (NaHL(1)), 2-(2-(dicyano-methylene)hydrazinyl)benzoic acid (H2L(2)), and sodium (E/Z)-2-(2-(1-cyano-2-methoxy-2-oxoethylidene)hydrazinyl)benzenesulfonate (NaHL(3)) were used in the template synthesis of a series of Cu(II) and Co(II) complexes [Cu(H2O)2L(1a)]·H2O (1), [Cu(H2O)(3-pyon)L(1b)]·H2O (2), [Cu(H2O)(4-pyon)L(1b)] (3), [Co(H2O)((CH3)2NCHO)(μ-L(2a))]2·(CH3)2NCHO (4), [Cu3(μ3-OH)(NO3)(CH3OH)(μ2-X)3(μ2-HL(3))] (5), [Cu(H2O)(py)L(3)]·H2O (6), [Cu(H2O)2(μ-L(4))]6·6H2O (7), [Cu(2-cnpy(b))2(L(1b))2]·2H2O (8), [Cu(2-cnpy(a))2(L(1a))2]·2H2O (9), and [Cu(H2O)(4-cnpy)(L(1a))2] (10), where 3-pyon = 1-(pyridin-3-yl)ethanone, 4-pyon = 1-(pyridin-4-yl)ethanone, py = pyridine, HX = syn-2-pyridinealdoxime, 4-cnpy = 4-cyanopyridine; 2-cnpy(a), 2-cnpy(b), L(1a), L(1b), L(2a) are the ligands derived from nucleophilic attack of methanol (a) or water (b) on a cyano group of 2-cyanopyridine (2-cnpy), L(1) or L(2), respectively, giving the corresponding iminoesters (2-cnpy(a), L(1a) or L(2a)) or carboxamides (2-cnpy(b) or L(1b)). An auxiliary ligand, namely syn-2-pyridinealdoxime or pyridine, acting cooperatively with the metal ion (Cu(II) in this case), induced an E/Z isomerization of the H2L(4) ligand; the E- and Z-isomers were isolated separately and fully characterized (compounds 9 and 10, respectively). A one-pot activation of nitrile groups in different molecules was achieved in the syntheses of 8 and 9. Complexes 1-10 are catalyst precursors for the solvent-free microwave (MW)-assisted selective oxidation of secondary alcohols to the corresponding ketones, with typical yields in the 29-99% range (TOFs up to 4.94 × 10(3) h(-1)) after 30 min of MW irradiation.

  7. Synthesis, characterization and in vitro inhibition of metal complexes of pyrazole based sulfonamide on human erythrocyte carbonic anhydrase isozymes I and II.

    Science.gov (United States)

    Büyükkıdan, Nurgün; Büyükkıdan, Bülent; Bülbül, Metin; Kasımoğulları, Rahmi; Mert, Samet

    2017-12-01

    Sulfonamides represent an important class of biologically active compounds. A sulfonamide possessing carbonic anhydrase (CA) inhibitory properties obtained from a pyrazole based sulfonamide, ethyl 1-(3-nitrophenyl)-5-phenyl-3-((5-sulfamoyl-1,3,4-thiadiazol-2-yl)carbamoyl)-1H-pyrazole-4-carboxylate (1), and its metal complexes with the Ni(II) for (2), Cu(II) for (3) and Zn(II) for (4) have been synthesized. The structures of metal complexes (2-4) were established on the basis of their elemental analysis, (1)H NMR, IR, UV-Vis and MS spectral data. The inhibition of two human carbonic anhydrase (hCA, EC 4.2.1.1) isoenzymes I and II, with 1 and synthesized complexes (2-4) and acetazolamide (AAZ) as a control compound was investigated in vitro by using the hydratase and esterase assays. The complexes 2, 3 and 4 showed inhibition constant in the range 0.1460-0.3930 µM for hCA-I and 0.0740-0.0980 µM for hCA-II, and they had effective more inhibitory activity on hCA-I and hCA-II than corresponding free ligand 1 and than AAZ.

  8. A novel three-dimensional CdII metal-organic framework based on [Cd6(malonate)6] metallomacrocycles with zeolite SOD (sodalite) topology: poly[ammine-μ3-malonato-cadmium(II)].

    Science.gov (United States)

    Yuan, Shuai; Liu, Mei-Jiao; Xie, Han-Yi; Xu, Meng-Zhen; Sun, Di

    2012-03-01

    A novel Cd(II) metal-organic framework, [Cd(C(3)H(2)O(4))(NH(3))](n), was synthesized by liquid diffusion conducted in the presence of ammonia. The Cd(II) atom has seven-coordinate O(6)N pentagonal-bipyramidal geometry. Six Cd(II) centers are joined by six malonate ligands to form an S(6)-symmetric [Cd(6)(malonate)(6)] metallomacrocycle, which is further extended through a side-on chelating malonate ligand to form a three-dimensional network. Topologically, each Cd(II) center is connected to four others to yield an infinite three-periodic four-coordinated SOD (sodalite) network with point symbol {4(2)·6(4)}. The overall network structure in the crystal is maintained and stabilized by the presence of N-H...O hydrogen bonds.

  9. A liquid metal-based structurally embedded vascular antenna: II. Multiobjective and parameterized design exploration

    Science.gov (United States)

    Hartl, D. J.; Frank, G. J.; Malak, R. J.; Baur, J. W.

    2017-02-01

    Research on the structurally embedded vascular antenna concept leverages past efforts on liquid metal (LM) reconfigurable electronics, microvascular composites, and structurally integrated and reconfigurable antennas. Such a concept has potential for reducing system weight or volume while simultaneously allowing in situ adjustment of resonant frequencies and/or changes in antenna directivity. This work considers a microvascular pattern embedded in a laminated composite and filled with LM. The conductive liquid provides radio frequency (RF) functionality while also allowing self-cooling. Models describing RF propagation and heat transfer, in addition to the structural effects of both the inclusion of channels and changes in temperature, were described in part 1 of this two-part work. In this part 2, the engineering models developed and demonstrated in part 1 toward the initial exploration of design trends are implemented into multiple optimization frameworks for more detailed design studies, one of which being novel and particularly applicable to this class of problem. The computational expense associated with the coupled multiphysical analysis of the structurally embedded LM transmitting antenna motivates the consideration of surrogate-based optimization methods. Both static and adaptive approaches are explored; it is shown that iteratively correcting the surrogate leads to more accurate optimized design predictions. The expected strong dependence of antenna performance on thermal environment motivates the consideration of a novel ‘parameterized’ optimization approach that simultaneously calculates whole families of optimal designs based on changes in design or operational variables generally beyond the control of the designer. The change in Pareto-optimal response with evolution in operating conditions is clearly demonstrated.

  10. Metal-biradical chains from a high-spin ligand and bis(hexafluoroacetylacetonato)copper(II).

    Science.gov (United States)

    Rajadurai, Chandrasekar; Enkelmann, Volker; Ikorskii, Vladimir; Ovcharenko, Victor I; Baumgarten, Martin

    2006-11-27

    The synthesis, X-ray crystal structure, and magnetic studies of a rare example of organic/inorganic spin hybrid clusters extended in infinite ladder-type chain [Cu(C5F6HO2)2]7(C35H35N5O4)2 ([Cu(hfac)2]7(pyacbisNN)2, 2) formed by the reaction of a high spin nitronylnitroxide biradical C35H35N5O4 (pyacbisNN, 1) and bis(hexafluroacetylacetonate)copper(II) = Cu(hfac)2 are described. Single-crystal X-ray structure analysis revealed the triclinic P1 space group of 2 with the following parameters: a = 10.6191(4) A, b = 19.6384(7) A, c = 21.941(9) A, alpha = 107.111(7) degrees, beta = 95.107(8) degrees, gamma = 94.208(0) degrees , Z = 2. Each repeating unit in 2 carries a centrosymmetric cyclic six spin and a linear five spin cluster with four different copper coordination environments having octahedral and square planar geometries. These clusters are interconnected to form infinite chains which are running along the crystallographic b axis. The magnetic measurements show nearly paramagnetic behavior with very small variations over a large temperature range. The magnetic properties are thus result of complex competitions of many weak ferro- and antiferromagnetic interactions, which appear as small deviations from quite linear mu(eff) vs T dependence at low temperature. At high temperature (300-14 K), antiferromagnetic behavior dominates a little, while at very low temperature (14-2 K), a small increase of mu(eff) was observed. The magnetic susceptibility data are described by the Curie-Weiss law [chi = C/(T - theta)] with the optimal parameters C = 4.32 +/- 0.01 emuK/mol and theta = - 0.6 +/- 0.3 K, where C is the Curie constant and theta is the Weiss temperature.

  11. Spin Forming Aluminum Crew Module (CM) Metallic Aft Pressure Vessel Bulkhead (APVBH) - Phase II

    Science.gov (United States)

    Hoffman, Eric K.; Domack, Marcia S.; Torres, Pablo D.; McGill, Preston B.; Tayon, Wesley A.; Bennett, Jay E.; Murphy, Joseph T.

    2015-01-01

    The principal focus of this project was to assist the Multi-Purpose Crew Vehicle (MPCV) Program in developing a spin forming fabrication process for manufacture of the Orion crew module (CM) aft pressure vessel bulkhead. The spin forming process will enable a single piece aluminum (Al) alloy 2219 aft bulkhead resulting in the elimination of the current multiple piece welded construction, simplify CM fabrication, and lead to an enhanced design. Phase I (NASA TM-2014-218163 (1)) of this assessment explored spin forming the single-piece CM forward pressure vessel bulkhead. The Orion MPCV Program and Lockheed Martin (LM) recently made two critical decisions relative to the NESC Phase I work scope: (1) LM selected the spin forming process to manufacture a single-piece aft bulkhead for the Orion CM, and (2) the aft bulkhead will be manufactured from Al 2219. Based on the Program's new emphasis related to the spin forming process, the NESC was asked to conduct a Phase II assessment to assist in the LM manufacture of the aft bulkhead and to conduct a feasibility study into spin forming the Orion CM cone. This activity was approved on June 19, 2013. Dr. Robert Piascik, NASA Technical Fellow for Materials at the Langley Research Center (LaRC), was selected to lead this assessment. The project plan was approved by the NASA Engineering and Safety Center (NESC) Review Board (NRB) on July 18, 2013. The primary stakeholders for this assessment were the NASA and LM MPCV Program offices. Additional benefactors are commercial launch providers developing CM concepts.

  12. Photocatalytic Reduction of Ni (II Ions Using Low Amounts of Titania Nanoparticles: RSM Modelling, Kinetic

    Directory of Open Access Journals (Sweden)

    Javad Saien

    2014-09-01

    Full Text Available Background: Heavy metals in aquatic systems usually interfere with many beneficial uses of water. Divalent nickel is a commonly occurring toxic metal in natural ecosystems due to the effluent of refineries, electroplating, and casting industries. In aquatic environments, nickel appears as Ni (II and Ni0. Despite the high reported toxicity for Ni (II, Ni0 is only slightly toxic. Various methods have been proposed for the treatment of aqueous solutions containing Ni (II. Photocatalytic reduction is an important process; titanium dioxide has been mostly used as a very efficient photocatalyst. Methods: In this study, the removal of divalent nickel ions in aqueous solutions was studied in the presence of remarkably low dosages of nano-titania photocatalyst. Direct imposed irradiation was utilized for treatment of solutions. Accordingly, the influence of four operational parameters, including temperature within the conventional range of 20 to 40 °C, was investigated. Design of experiments, modeling and process optimization were accomplished using central composite design of response surface methodology. Results: Reduced quadratic expression was developed for the reduction efficiency (RE, and the analysis of variance showed its capability in reproducing the data. The effectiveness of each parameter was determined. At the best found conditions of [TiO2] = 42 mg/L, pH = 9.2, T = 34 °C and after 90 minutes of treatment, about 85% removal was achieved for initial 5 mg/L nickel solutions. Pseudo first order reactions proceeded. Conclusion: Based on CCD method, the influence of individual operating parameters and their interactions were obtained. A quadratic equation predicted the variations quite well.

  13. Bio-sensitive activities of coordination compounds containing 1,10-phenanthroline as co-ligand: Synthesis, structural elucidation and DNA binding properties of metal(II) complexes

    Science.gov (United States)

    Raman, Natarajan; Mahalakshmi, Rajkumar; Mitu, Liviu

    2014-10-01

    Present work reports the DNA binding and cleavage characteristics of a series of mixed-ligand complexes having the composition [M(L)(phen)2]Cl2 (where M = Cu(II), Ni(II), Co(II) and Zn(II) and phen as co-ligand) in detail. Their structural features and other properties have been deduced from their elemental analyses, magnetic susceptibility and molar conductivity as well as from IR, UV-Vis, 1H NMR and EPR spectral studies. The UV-Vis, magnetic susceptibility and EPR spectral data of metal complexes suggest an octahedral geometry. The binding properties of these complexes with calf thymus DNA (CT-DNA) have been explored using electronic absorption spectroscopy, viscosity measurement, cyclic voltammetry and differential pulse voltammetry. The DNA-binding constants for Cu(II), Ni(II), Co(II), and Zn(II) complexes are 6.14 × 105 M-1, 1.8 × 105 M-1, 6.7 × 104 M-1 and 2.5 × 104 M-1 respectively. Detailed analysis reveals that these complexes interact with DNA through intercalation binding. Nuclease activity has also been investigated by gel electrophoresis. Moreover, the synthesized Schiff base and its mixed-ligand complexes have been screened for antibacterial and antifungal activities. The data reveal that the complexes exhibit higher activity than the parent ligand.

  14. Effects of background electrolytes and ionic strength on enrichment of Cd(II) ions with magnetic graphene oxide-supported sulfanilic acid.

    Science.gov (United States)

    Hu, Xin-jiang; Liu, Yun-guo; Zeng, Guang-ming; You, Shao-hong; Wang, Hui; Hu, Xi; Guo, Yi-ming; Tan, Xiao-fei; Guo, Fang-ying

    2014-12-01

    To elucidate the influence mechanisms of background electrolytes and ionic strength on Cd(II) removal, the adsorption of Cd(II) onto magnetic graphene oxide-supported sulfanilic acid (MGO-SA) in aqueous solutions containing different types and concentrations of background electrolytes was studied. The results indicate that Cd(II) adsorption was strongly dependent on pH and could be strongly affected by background electrolytes and ionic strength. The Cd(II) removal was decreased with the presence of background electrolyte cations (Na(+), K(+), Ca(2+), Mg(2+), Mn(2+), Zn(2+), and Ni(2+)), and the divalent cations exerted more obvious influences on the Cd(II) uptake than the monovalent cations at pH 6. Both Cl(-) and NO3(-) had negative effects on Cd(II) adsorption because they can form water-soluble metal-anion complexes with Cd(II) ions. The presence of 0.01molL(-1) Na3PO4 reduced the removal percentage of Cd(II) at pH5. The Cd(II) adsorption was sensitive to changes in the concentration of NaCl, NaNO3, NaClO4, and Na3PO4. Besides, the adsorption isotherm of Cd(II) onto MGO-SA could be well described by the Freundlich model and was also influenced by the type of background electrolyte ions and the ionic strength.

  15. Study of the heavy metal phytoextraction capacity of two forage species growing in an hydroponic environment

    Energy Technology Data Exchange (ETDEWEB)

    Bonfranceschi, Barros A. [Centro de Investigacion y Desarrollo en Fermentaciones Industriales (CINDEFI, UNLP-CC