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Sample records for active metal ions

  1. Metal interactions with voltage- and receptor-activated ion channels.

    PubMed Central

    Vijverberg, H P; Oortgiesen, M; Leinders, T; van Kleef, R G

    1994-01-01

    Effects of Pb and several other metal ions on various distinct types of voltage-, receptor- and Ca-activated ion channels have been investigated in cultured N1E-115 mouse neuroblastoma cells. Experiments were performed using the whole-cell voltage clamp and single-channel patch clamp techniques. External superfusion of nanomolar to submillimolar concentrations of Pb causes multiple effects on ion channels. Barium current through voltage-activated Ca channels is blocked by micromolar concentrations of Pb, whereas voltage-activated Na current appears insensitive. Neuronal type nicotinic acetylcholine receptor-activated ion current is blocked by nanomolar concentrations of Pb and this block is reversed at micromolar concentrations. Serotonin 5-HT3 receptor-activated ion current is much less sensitive to Pb. In addition, external superfusion with micromolar concentrations of Pb as well as of Cd and aluminum induces inward current, associated with the direct activation of nonselective cation channels by these metal ions. In excised inside-out membrane patches of neuroblastoma cells, micromolar concentrations of Ca activate small (SK) and big (BK) Ca-activated K channels. Internally applied Pb activates SK and BK channels more potently than Ca, whereas Cd is approximately equipotent to Pb with respect to SK channel activation, but fails to activate BK channels. The results show that metal ions cause distinct, selective effects on the various types of ion channels and that metal ion interaction sites of ion channels may be highly selective for particular metal ions. PMID:7531139

  2. Breast milk metal ion levels in a young and active patient with a metal-on-metal hip prosthesis.

    PubMed

    Nelis, Raymond; de Waal Malefijt, Jan; Gosens, Taco

    2013-01-01

    Metal-on-metal resurfacing arthroplasty of the hip has been used increasingly over the last 10 years in younger active patients. The dissolution of the metal wear particles results in measurable increases in cobalt and chromium ions in the serum and urine of patients with a metal-on-metal bearing. We measured the cobalt, chromium, and molybdenum ion levels in urine; serum; and breast milk in a young and active patient with a metal-on-metal hip prosthesis after a pathologic fracture of the femoral neck. Metal-on-metal hip prosthesis leads to increasing levels of molybdenum in breast milk in the short-term follow-up. There are no increasing levels of chromium and cobalt ions in breast milk. Besides the already known elevated concentrations in serum of chromium and cobalt after implantation of a metal-on-metal hip prosthesis, we found no increasing levels of chromium and cobalt in urine.

  3. Adsorption of metal ions by pecan shell-based granular activated carbons.

    PubMed

    Bansode, R R; Losso, J N; Marshall, W E; Rao, R M; Portier, R J

    2003-09-01

    The present investigation was undertaken to evaluate the adsorption effectiveness of pecan shell-based granular activated carbons (GACs) in removing metal ions (Cu(2+), Pb(2+), Zn(2+)) commonly found in municipal and industrial wastewater. Pecan shells were activated by phosphoric acid, steam or carbon dioxide activation methods. Metal ion adsorption of shell-based GACs was compared to the metal ion adsorption of a commercial carbon, namely, Calgon's Filtrasorb 200. Adsorption experiments were conducted using solutions containing all three metal ions in order to investigate the competitive effects of the metal ions as would occur in contaminated wastewater. The results obtained from this study showed that acid-activated pecan shell carbon adsorbed more lead ion and zinc ion than any of the other carbons, especially at carbon doses of 0.2-1.0%. However, steam-activated pecan shell carbon adsorbed more copper ion than the other carbons, particularly using carbon doses above 0.2%. In general, Filtrasorb 200 and carbon dioxide-activated pecan shell carbons were poor metal ion adsorbents. The results indicate that acid- and steam-activated pecan shell-based GACs are effective metal ion adsorbents and can potentially replace typical coal-based GACs in treatment of metal contaminated wastewater.

  4. Ligational behavior of Schiff bases towards transition metal ion and metalation effect on their antibacterial activity

    NASA Astrophysics Data System (ADS)

    Devi, Jai; Batra, Nisha; Malhotra, Rajesh

    2012-11-01

    New Schiff bases pyrazine-2-carboxylicacid (phenyl-pyridin-2-yl-methylene)-hydrazide (Hpch-bp) HL1 and pyrazine-2-carboxylicacid (pyridin-2-ylmethylene)-hydrazide (Hpch-pc) HL2 derived from condensation of pyrazine carboxylic hydrazide (Hpch) with 2-benzoyl pyridine (bp) or pyridine 2-carbaldehyde (pc) and their transition metal complexes of type ML(1-2)2 have been synthesized, where M = Mn(II), Co(II), Ni(II), Cu(II) and Zn(II). Characterization of ligands and their metal complexes was carried out by elemental analysis, conductimetric studies, magnetic susceptibility, spectroscopic techniques (IR, UV-VIS, NMR, ESR, Mass) and thermogravimetric analysis. The physico-chemical studies revealed octahedral geometry or distorted octahedral geometry around metal ion. These azomethine Schiff base ligands acted as tridentate ? coordinating through carbonyl, azomethine and pyridine nitrogen present in the ligand. The thermodynamic and thermal properties of the complexes have been investigated and it was observed on the basis of these studies that thermal stability of complexes follows the order Mn < Zn < Cu < Co < Ni. The ligands and their complexes were tested for in vitro antibacterial activity at different concentrations against bacteria viz. Gram positive Bacillus subtilis, Micrococcus luteus and Gram negative Pseudomonas aeruginosa, Pseudomonas mendocina. A marked enhancement in biocidal activity of the ligands under similar experimental conditions was observed as a consequence of coordination with metal ions. The trend of growth inhibition in the complexes was found to be in the order: Cu > Mn > Ni > Co > Zn.

  5. Metal Ions, Not Metal-Catalyzed Oxidative Stress, Cause Clay Leachate Antibacterial Activity

    PubMed Central

    Otto, Caitlin C.; Koehl, Jennifer L.; Solanky, Dipesh; Haydel, Shelley E.

    2014-01-01

    Aqueous leachates prepared from natural antibacterial clays, arbitrarily designated CB-L, release metal ions into suspension, have a low pH (3.4–5), generate reactive oxygen species (ROS) and H2O2, and have a high oxidation-reduction potential. To isolate the role of pH in the antibacterial activity of CB clay mixtures, we exposed three different strains of Escherichia coli O157:H7 to 10% clay suspensions. The clay suspension completely killed acid-sensitive and acid-tolerant E. coli O157:H7 strains, whereas incubation in a low-pH buffer resulted in a minimal decrease in viability, demonstrating that low pH alone does not mediate antibacterial activity. The prevailing hypothesis is that metal ions participate in redox cycling and produce ROS, leading to oxidative damage to macromolecules and resulting in cellular death. However, E. coli cells showed no increase in DNA or protein oxidative lesions and a slight increase in lipid peroxidation following exposure to the antibacterial leachate. Further, supplementation with numerous ROS scavengers eliminated lipid peroxidation, but did not rescue the cells from CB-L-mediated killing. In contrast, supplementing CB-L with EDTA, a broad-spectrum metal chelator, reduced killing. Finally, CB-L was equally lethal to cells in an anoxic environment as compared to the aerobic environment. Thus, ROS were not required for lethal activity and did not contribute to toxicity of CB-L. We conclude that clay-mediated killing was not due to oxidative damage, but rather, was due to toxicity associated directly with released metal ions. PMID:25502790

  6. Ligational behavior of Schiff bases towards transition metal ion and metalation effect on their antibacterial activity.

    PubMed

    Devi, Jai; Batra, Nisha; Malhotra, Rajesh

    2012-11-01

    New Schiff bases pyrazine-2-carboxylicacid (phenyl-pyridin-2-yl-methylene)-hydrazide (Hpch-bp) HL(1) and pyrazine-2-carboxylicacid (pyridin-2-ylmethylene)-hydrazide (Hpch-pc) HL(2) derived from condensation of pyrazine carboxylic hydrazide (Hpch) with 2-benzoyl pyridine (bp) or pyridine 2-carbaldehyde (pc) and their transition metal complexes of type ML((1-2)2) have been synthesized, where M=Mn(II), Co(II), Ni(II), Cu(II) and Zn(II). Characterization of ligands and their metal complexes was carried out by elemental analysis, conductimetric studies, magnetic susceptibility, spectroscopic techniques (IR, UV-VIS, NMR, ESR, Mass) and thermogravimetric analysis. The physico-chemical studies revealed octahedral geometry or distorted octahedral geometry around metal ion. These azomethine Schiff base ligands acted as tridentate coordinating through carbonyl, azomethine and pyridine nitrogen present in the ligand. The thermodynamic and thermal properties of the complexes have been investigated and it was observed on the basis of these studies that thermal stability of complexes follows the order Mnactivity at different concentrations against bacteria viz. Gram positive Bacillus subtilis, Micrococcus luteus and Gram negative Pseudomonas aeruginosa, Pseudomonas mendocina. A marked enhancement in biocidal activity of the ligands under similar experimental conditions was observed as a consequence of coordination with metal ions. The trend of growth inhibition in the complexes was found to be in the order: Cu>Mn>Ni>Co>Zn.

  7. Metal ion specificities for folding and cleavage activity in the Schistosoma hammerhead ribozyme

    PubMed Central

    Boots, Jennifer L.; Canny, Marella D.; Azimi, Ehsan; Pardi, Arthur

    2008-01-01

    The effects of various metal ions on cleavage activity and global folding have been studied in the extended Schistosoma hammerhead ribozyme. Fluorescence resonance energy transfer was used to probe global folding as a function of various monovalent and divalent metal ions in this ribozyme. The divalent metals ions Ca2+, Mg2+, Mn2+, and Sr2+ have a relatively small variation (less than sixfold) in their ability to globally fold the hammerhead ribozyme, which contrasts with the very large difference (>10,000-fold) in apparent rate constants for cleavage for these divalent metal ions in single-turnover kinetic experiments. There is still a very large range (>4600-fold) in the apparent rate constants for cleavage for these divalent metal ions measured in high salt (2 M NaCl) conditions where the ribozyme is globally folded. These results demonstrate that the identity of the divalent metal ion has little effect on global folding of the Schistosoma hammerhead ribozyme, whereas it has a very large effect on the cleavage kinetics. Mechanisms by which the identity of the divalent metal ion can have such a large effect on cleavage activity in the Schistosoma hammerhead ribozyme are discussed. PMID:18755844

  8. Poultry litter-based activated carbon for removing heavy metal ions in water.

    PubMed

    Guo, Mingxin; Qiu, Guannan; Song, Weiping

    2010-02-01

    Utilization of poultry litter as a precursor material to manufacture activated carbon for treating heavy metal-contaminated water is a value-added strategy for recycling the organic waste. Batch adsorption experiments were conducted to investigate kinetics, isotherms, and capacity of poultry litter-based activated carbon for removing heavy metal ions in water. It was revealed that poultry litter-based activated carbon possessed significantly higher adsorption affinity and capacity for heavy metals than commercial activated carbons derived from bituminous coal and coconut shell. Adsorption of metal ions onto poultry litter-based carbon was rapid and followed Sigmoidal Chapman patterns as a function of contact time. Adsorption isotherms could be described by different models such as Langmuir and Freundlich equations, depending on the metal species and the coexistence of other metal ions. Potentially 404 mmol of Cu2+, 945 mmol of Pb2+, 236 mmol of Zn2+, and 250-300 mmol of Cd2+ would be adsorbed per kg of poultry litter-derived activated carbon. Releases of nutrients and metal ions from litter-derived carbon did not pose secondary water contamination risks. The study suggests that poultry litter can be utilized as a precursor material for economically manufacturing granular activated carbon that is to be used in wastewater treatment for removing heavy metals.

  9. Influence of several metal ions on the gelation activation energy of silicon tetraethoxide

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.

    1988-01-01

    The effects of nine metal cations (Li(+), Na(+), Mg(2+), Ca(2+), Sr(2+), Cu(2+), Al(3+), La(3+), and Y(3+) on silica gel formation has been investigated by studying the hydrolysis and polycondensation of silicon tetraethoxide (TEOS) in the presence of metal nitrates. The influence of water: TEOS mole ratio, metal ion concentration, and the reaction temperature has been investigated. The overall activation energy for gel formation has been determined from the temperature dependence of the time of gelation for each system. The activation energy for -Si-O-Si- network formation is found to be 54.5 kJ/mol. The gel formation time as well as the activation energy sharply increase in the presence of Cu(2+), Al(3+), La(3+) and Y(3+). In contrast, the presence of Li(+), Na(+), Mg(2+), Ca(2+), or, Sr(2+) lowers the gelation time, but has no appreciable effect on the activation energy. This difference may be attributed to the participation or nonparticipation of the metal ions in the formation of the three-dimensional polymeric network during the polycondensation step. The concentration of metal ion (Mg(2+), Ca(2+), Y(3+) or the water: TEOS mole ratio had no appreciable effect on the gelation activation energy. A simple test has been proposed to determine whether a metal ion would act as a network intermediate or modifier in silica and other glassy networks.

  10. Influence of several metal ions on the gelation activation energy of silicon tetraethoxide

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.

    1990-01-01

    The effects of nine metal cations Li(+), Na(+), Mg(2+), Ca(2+), Sr(2+), Cu(2+), Al(3+), La(3+), and Y(3+) on silica gel formation has been investigated by studying the hydrolysis and polycondensation of silicon tetraethoxide (TEOS) in the presence of metal nitrates. The influence of water:TEOS mole ratio, metal ion concentration, and the reaction temperature has been investigated. The overall activation energy for gel formation has been determined from the temperature dependence of the time of gelation for each system. The activation energy for -Si-O-Si- network formation is found to be 54.5 kJ/mol. The gel formation time as well as the activation energy sharply increase in the presence of Cu(2+), Al(3+), La(3+) and Y(3+). In contrast, the presence of Li(+), Na(+), Mg(2+), Ca(2+), or Sr(2+) lowers the gelation time, but has no appreciable effect on the activation energy. This difference may be attributed to the participation or nonparticipation of the metal ions in the formation of the three-dimensional polymeric network during the polycondensation step. The concentration of metal ion Mg(2+), Ca(2+), Y(3+) or the water:TEOS mole ratio had no appreaciable effect on the gelation activation energy. A simple test has been proposed to determine whether a metal ion would act as a network intermediate or modifier in silica and other glassy networks.

  11. Metal Ion Activation of Clostridium sordellii Lethal Toxin and Clostridium difficile Toxin B

    PubMed Central

    Genth, Harald; Schelle, Ilona; Just, Ingo

    2016-01-01

    Lethal Toxin from Clostridium sordellii (TcsL) and Toxin B from Clostridium difficile (TcdB) belong to the family of the “Large clostridial glycosylating toxins.” These toxins mono-O-glucosylate low molecular weight GTPases of the Rho and Ras families by exploiting UDP-glucose as a hexose donor. TcsL is casually involved in the toxic shock syndrome and the gas gangrene. TcdB—together with Toxin A (TcdA)—is causative for the pseudomembranous colitis (PMC). Here, we present evidence for the in vitro metal ion activation of the glucosyltransferase and the UDP-glucose hydrolysis activity of TcsL and TcdB. The following rating is found for activation by divalent metal ions: Mn2+ > Co2+ > Mg2+ >> Ca2+, Cu2+, Zn2+. TcsL and TcdB thus require divalent metal ions providing an octahedral coordination sphere. The EC50 values for TcsL were estimated at about 28 µM for Mn2+ and 180 µM for Mg2+. TcsL and TcdB further require co-stimulation by monovalent K+ (not by Na+). Finally, prebound divalent metal ions were dispensible for the cytopathic effects of TcsL and TcdB, leading to the conclusion that TcsL and TcdB recruit intracellular metal ions for activation of the glucosyltransferase activity. With regard to the intracellular metal ion concentrations, TcsL and TcdB are most likely activated by K+ and Mg2+ (rather than Mn2+) in mammalian target cells. PMID:27089365

  12. Study on preparation of Luffa activated carbon and its adsorption of metal ions

    NASA Astrophysics Data System (ADS)

    Zhai, Kuilu; Li, Zichao; Li, Qun

    2017-03-01

    In this paper, loofah was used as raw material and alkali and hydrogen peroxide were used to pre-oxidize. The activated carbon was activated by zinc chloride, and the activated carbon was used to desorb the heavy metal ions nickel and copper. The removal efficiency of heavy metal ions was studied under different conditions. The effects of retinervus Luffae Fructus active carbon adsorption of metal ions on process conditions, including metal ion concentration, reaction temperature, loofah activated carbon types and activated carbon dosage. In the present study, in different strain rate on the loofah sponge material compression tests in a wide range of density from 24 to 64 kg cubic meters. Luffa fibers and followed by carbonization to prepare MCAC KOH activation. MCAC has dense in parallel channels 10 mm in diameter and 4 - 0.3 - 1 mm wall thickness, which is inherited from the native structure of Luffa. Micro and middle holes are formed on the inner surface of the channel wall to form a hierarchical porous structure.

  13. The inhibitory effect of metals and other ions on acid phosphatase activity from Vigna aconitifolia seeds.

    PubMed

    Srivastava, Pramod Kumar; Anand, Asha

    2015-01-01

    Sensitivity of acid phosphatase from Vigna aconitifolia seeds to metal ions, fluoride, and phosphate was examined. All the effectors had different degree of inhibitory effect on the enzyme. Among metal ions, molybdate and ferric ion were observed to be most potent inhibitors and both exhibited mixed type of inhibition. Acid phosphatase activity was inhibited by Cu2+ in a noncompetitive manner. Zn and Mn showed mild inhibition on the enzyme activity. Inhibition kinetics analysis explored molybdate as a potent inhibitor for acid phosphatase in comparison with other effectors used in this study. Fluoride was the next most strong inhibitor for the enzyme activity, and caused a mixed type of inhibition. Phosphate inhibited the enzyme competitively, which demonstrates that inhibition due to phosphate is one of the regulatory factors for enzyme activity.

  14. Adsorption of aqueous metal ions on oxygen and nitrogen functionalized nanoporous activated carbons.

    PubMed

    Xiao, B; Thomas, K M

    2005-04-26

    In this study, the adsorption characteristics of two series of oxygen and nitrogen functionalized activated carbons were investigated. These series were a low nitrogen content (approximately 1 wt % daf) carbon series derived from coconut shell and a high nitrogen content (approximately 8 wt % daf) carbon series derived from polyacrylonitrile. In both series, the oxygen contents were varied over the range approximately 2-22 wt % daf. The porous structures of the functionalized activated carbons were characterized using N(2) (77 K) and CO(2) (273 K) adsorption. Only minor changes in the porous structure were observed in both series. This allowed the effect of changes in functional group concentrations on metal ion adsorption to be studied without major influences due to differences in porous structure characteristics. The surface group characteristics were examined by Fourier transform infrared (FTIR) spectroscopy, acid/base titrations, and measurement of the point of zero charge (pH(PZC)). The adsorption of aqueous metal ion species, M(2+)(aq), on acidic oxygen functional group sites mainly involves an ion exchange mechanism. The ratios of protons displaced to the amount of M(2+)(aq) metal species adsorbed have a linear relationship for the carbons with pH(PZC) < or = 4.15. Hydrolysis of metal species in solution may affect the adsorption of metal ion species and displacement of protons. In the case of basic carbons, both protons and metal ions are adsorbed on the carbons. The complex nature of competitive adsorption between the proton and metal ion species and the amphoteric character of carbon surfaces are discussed in relation to the mechanism of adsorption.

  15. Effect of heavy metals ions on enzyme activity in the Mediterranean mussel, Donax trunculus

    SciTech Connect

    Mizrahi, L.; Achituv, Y. )

    1989-06-01

    Heavy metal ions strongly are bound by sulfhydryl groups of proteins. Sulfhydryl binding changes the structure and enzymatic activities of proteins and causes toxic effects evident at the whole organism level. Heavy metal ions like Cd, Cu, Hg, Zn, and Pb in sufficiently high concentrations might kill organisms or cause other adverse effects that changing aquatic community structures. Bivalves are known to be heavy metal accumulators. The aim of the present study was to examine the effects of different concentrations of each of five heavy metal ions on the activity of four enzymes in D. trunculus. As it is known that heavy metals inhibit the activity of a wide range of enzymes, the authors chose representative examples of dehydrogenases (lactate and malate dehydrogenases), respiratory enzyme (cytochrome oxidase) and digestive enzyme ({alpha}-amylase). The acute effects of different concentrations of selected metals were examined. These concentrations were higher than those found usually in the locality where the animals occur, but might be encountered during a given event of pollution.

  16. Sorption of metal ions from multicomponent aqueous solutions by activated carbons produced from waste

    SciTech Connect

    Tikhonova, L.P.; Goba, V.E.; Kovtun, M.F.; Tarasenko, Y.A.; Khavryuchenko, V.D.; Lyubchik, S.B.; Boiko, A.N.

    2008-08-15

    Activated carbons produced by thermal treatment of a mixture of sunflower husks, low-grade coal, and refinery waste were studied as adsorbents of transition ion metals from aqueous solutions of various compositions. The optimal conditions and the mechanism of sorption, as well as the structure of the sorbents, were studied.

  17. pH-Dependent Metal Ion Toxicity Influences the Antibacterial Activity of Two Natural Mineral Mixtures

    PubMed Central

    Cunningham, Tanya M.; Koehl, Jennifer L.; Summers, Jack S.; Haydel, Shelley E.

    2010-01-01

    Background Recent studies have demonstrated that several mineral products sold for medicinal purposes demonstrate antimicrobial activity, but little is known about the physicochemical properties involved in antibacterial activity. Methodology/Principal Findings Using in vitro mineral suspension testing, we have identified two natural mineral mixtures, arbitrarily designated BY07 and CB07, with antibacterial activity against a broad-spectrum of bacterial pathogens. Mineral-derived aqueous leachates also exhibited antibacterial activity, revealing that chemical, not physical, mineral characteristics were responsible for the observed activity. The chemical properties essential for bactericidal activity against Escherichia coli were probed by testing antibacterial activity in the presence of metal chelators, the hydroxyl radical scavenger, thiourea, and varying pH levels. Chelation of the BY07 minerals with EDTA or desferrioxamine eliminated or reduced BY07 toxicity, respectively, suggesting a role of an acid-soluble metal species, particularly Fe3+ or other sequestered metal cations, in mineral toxicity. This conclusion was supported by NMR relaxation data, which indicated that BY07 and CB07 leachates contained higher concentrations of chemically accessible metal ions than leachates from non-bactericidal mineral samples. Conclusions/Significance We conclude that the acidic environment of the hydrated minerals significantly contributes to antibacterial activity by increasing the availability and toxicity of metal ions. These findings provide impetus for further investigation of the physiological effects of mineral products and their applications in complementary antibacterial therapies. PMID:20209160

  18. Synthesis and Characterization of Layered Double Hydroxides Containing Optically Active Transition Metal Ion

    NASA Astrophysics Data System (ADS)

    Tyagi, S. B.; Kharkwal, Aneeta; Nitu; Kharkwal, Mamta; Sharma, Raghunandan

    2017-01-01

    The acetate intercalated layered double hydroxides of Zn and Mn, have been synthesized by chimie douce method. The materials were characterized by XRD, TGA, CHN, IR, XPS, SEM-EDX and UV-visible spectroscopy. The photoluminescence properties was also studied. The optical properties of layered hydroxides are active transition metal ion dependent, particularly d1-10 system plays an important role. Simultaneously the role of host - guest orientation has been considered the basis of photoluminescence. Acetate ion can be exchanged with iodide and sulphate ions. The decomposed product resulted the pure phase Mn doped zinc oxide are also reported.

  19. Role of Metal Ions on the Activity of Mycobacterium tuberculosis Pyrazinamidase

    PubMed Central

    Sheen, Patricia; Ferrer, Patricia; Gilman, Robert H.; Christiansen, Gina; Moreno-Román, Paola; Gutiérrez, Andrés H.; Sotelo, Jun; Evangelista, Wilfredo; Fuentes, Patricia; Rueda, Daniel; Flores, Myra; Olivera, Paula; Solis, José; Pesaresi, Alessandro; Lamba, Doriano; Zimic, Mirko

    2012-01-01

    Pyrazinamidase of Mycobacterium tuberculosis catalyzes the conversion of pyrazinamide to the active molecule pyrazinoic acid. Reduction of pyrazinamidase activity results in a level of pyrazinamide resistance. Previous studies have suggested that pyrazinamidase has a metal-binding site and that a divalent metal cofactor is required for activity. To determine the effect of divalent metals on the pyrazinamidase, the recombinant wild-type pyrazinamidase corresponding to the H37Rv pyrazinamide-susceptible reference strain was expressed in Escherichia coli with and without a carboxy terminal. His-tagged pyrazinamidase was inactivated by metal depletion and reactivated by titration with divalent metals. Although Co2+, Mn2+, and Zn2+ restored pyrazinamidase activity, only Co2+ enhanced the enzymatic activity to levels higher than the wild-type pyrazinamidase. Cu2+, Fe2+, Fe3+, and Mg2+ did not restore the activity under the conditions tested. Various recombinant mutated pyrazinamidases with appropriate folding but different enzymatic activities showed a differential pattern of recovered activity. X-ray fluorescence and atomic absorbance spectroscopy showed that recombinant wild-type pyrazinamidase expressed in E. coli most likely contained Zn. In conclusion, this study suggests that M. tuberculosis pyrazinamidase is a metalloenzyme that is able to coordinate several ions, but in vivo, it is more likely to coordinate Zn2+. However, in vitro, the metal-depleted enzyme could be reactivated by several divalent metals with higher efficiency than Zn. PMID:22764307

  20. The biological effect of metal ions on the granulation of aerobic granular activated sludge.

    PubMed

    Hao, Wen; Li, Yaochen; Lv, Junping; Chen, Lisha; Zhu, Jianrong

    2016-06-01

    As a special biofilm structure, microbial attachment is believed to play an important role in the granulation of aerobic granular activated sludge (AGAS). This experiment was to investigate the biological effect of Ca(2+), Mg(2+), Cu(2+), Fe(2+), Zn(2+), and K(+) which are the most common ions present in biological wastewater treatment systems, on the microbial attachment of AGAS and flocculent activated sludge (FAS), from which AGAS is always derived, in order to provide a new strategy for the rapid cultivation and stability control of AGAS. The result showed that attachment biomass of AGAS was about 300% higher than that of FAS without the addition of metal ions. Different metal ions had different effects on the process of microbial attachment. FAS and AGAS reacted differently to the metal ions as well, and in fact, AGAS was more sensitive to the metal ions. Specifically, Ca(2+), Mg(2+), and K(+) could increase the microbial attachment ability of both AGAS and FAS under appropriate concentrations, Cu(2+), Fe(2+), and Zn(2+) were also beneficial to the microbial attachment of FAS at low concentrations, but Cu(2+), Fe(2+), and Zn(2+) greatly inhibited the attachment process of AGAS even at extremely low concentrations. In addition, the acylated homoserine lactone (AHL)-based quorum sensing system, the content of extracellular polymeric substances and the relative hydrophobicity of the sludges were greatly influenced by metal ions. As all these parameters had close relationships with the microbial attachment process, the microbial attachment may be affected by changes of these parameters.

  1. Logical regulation of the enzyme-like activity of gold nanoparticles by using heavy metal ions

    NASA Astrophysics Data System (ADS)

    Lien, Chia-Wen; Chen, Ying-Chieh; Chang, Huan-Tsung; Huang, Chih-Ching

    2013-08-01

    In this study we employed self-deposition and competitive or synergistic interactions between metal ions and gold nanoparticles (Au NPs) to develop OR, AND, INHIBIT, and XOR logic gates through regulation of the enzyme-like activity of Au NPs. In the presence of various metal ions (Ag+, Bi3+, Pb2+, Pt4+, and Hg2+), we found that Au NPs (13 nm) exhibited peroxidase-, oxidase-, or catalase-like activity. After Ag+, Bi3+, or Pb2+ ions had been deposited on the Au NPs, the particles displayed strong peroxidase-like activity; on the other hand, they exhibited strong oxidase- and catalase-like activities after reactions with Ag+/Hg2+ and Hg2+/Bi3+ ions, respectively. The catalytic activities of these Au NPs arose mainly from the various oxidation states of the surface metal atoms/ions. Taking advantage of this behavior, we constructed multiplex logic operations--OR, AND, INHIBIT, and XOR logic gates--through regulation of the enzyme-like activity after the introduction of metal ions into the Au NP solution. When we deposited Hg2+ and/or Bi3+ ions onto the Au NPs, the catalase-like activities of the Au NPs were strongly enhanced (>100-fold). Therefore, we could construct an OR logic gate by using Hg2+/Bi3+ as inputs and the catalase-like activity of the Au NPs as the output. Likewise, we constructed an AND logic gate by using Pt4+ and Hg2+ as inputs and the oxidase-like activity of the Au NPs as the output; the co-deposition of Pt and Hg atoms/ions on the Au NPs was responsible for this oxidase-like activity. Competition between Pb2+ and Hg2+ ions for the Au NPs allowed us to develop an INHIBIT logic gate--using Pb2+ and Hg2+ as inputs and the peroxidase-like activity of the Au NPs as the output. Finally, regulation of the peroxidase-like activity of the Au NPs through the two inputs Ag+ and Bi3+ enabled us to construct an XOR logic gate.In this study we employed self-deposition and competitive or synergistic interactions between metal ions and gold nanoparticles (Au NPs

  2. Biologically activated noble metal alloys at the nanoscale: for lithium ion battery anodes.

    PubMed

    Lee, Yun Jung; Lee, Youjin; Oh, Dahyun; Chen, Tiffany; Ceder, Gerbrand; Belcher, Angela M

    2010-07-14

    We report the synthesis and electrochemical activity of gold and silver noble metals and their alloy nanowires using multiple virus clones as anode materials for lithium ion batteries. Using two clones, one for specificity (p8#9 virus) and one versatility (E4 virus), noble metal nanowires of high-aspect ratio with diameters below 50 nm were successfully synthesized with control over particle sizes, morphologies, and compositions. The biologically derived noble metal alloy nanowires showed electrochemical activities toward lithium even when the electrodes were prepared from bulk powder forms. The improvement in capacity retention was accomplished by alloy formation and surface stabilization. Although the cost of noble metals renders them a less ideal choice for lithium ion batteries, these noble metal/alloy nanowires serve as great model systems to study electrochemically induced transformation at the nanoscale. Given the demonstration of the electrochemical activity of noble metal alloy nanowires with various compositions, the M13 biological toolkit extended its utility for the study on the basic electrochemical property of materials.

  3. Ion activity and distribution of heavy metals in acid mine drainage polluted subtropical soils.

    PubMed

    Li, Yong-Tao; Becquer, Thierry; Dai, Jun; Quantin, Cécile; Benedetti, Marc F

    2009-04-01

    The oxidative dissolution of mine wastes gives rise to acidic, metal-enriched mine drainage (AMD) and has typically posed an additional risk to the environment. The poly-metallic mine Dabaoshan in South China is an excellent test site to understand the processes affecting the surrounding polluted agricultural fields. Our objectives were firstly to investigate metal ion activity in soil solution, distribution in solid constituents, and spatial distribution in samples, secondly to determine dominant environment factors controlling metal activity in the long-term AMD-polluted subtropical soils. Soil Column Donnan Membrane Technology (SC-DMT) combined with sequential extraction shows that unusually large proportion of the metal ions are present as free ion in the soil solutions. The narrow range of low pH values prevents any pH effects during the binding onto oxides or organic matter. The differences in speciation of the soil solutions may explain the different soil degradation observed between paddy and non-paddy soils.

  4. A Two-Metal-Ion-Mediated Conformational Switching Pathway for HDV Ribozyme Activation

    PubMed Central

    Lee, Tai-Sung; Radak, Brian K.; Harris, Michael E.; York, Darrin M.

    2016-01-01

    RNA enzymes serve as a potentially powerful platform from which to design catalysts and engineer new biotechnology. A fundamental understanding of these systems provides insight to guide design. The hepatitis delta virus ribozyme (HDVr) is a small, self-cleaving RNA motif widely distributed in nature, that has served as a paradigm for understanding basic principles of RNA catalysis. Nevertheless, questions remain regarding the precise roles of divalent metal ions and key nucleotides in catalysis. In an effort to establish a reaction mechanism model consistent with available experimental data, we utilize molecular dynamics simulations to explore different conformations and metal ion binding modes along the HDVr reaction path. Building upon recent crystallographic data, our results provide a dynamic model of the HDVr reaction mechanism involving a conformational switch between multiple non-canonical G25:U20 base pair conformations in the active site. These local nucleobase dynamics play an important role in catalysis by modulating the metal binding environments of two Mg2+ ions that support catalysis at different steps of the reaction pathway. The first ion plays a structural role by inducing a base pair flip necessary to obtain the catalytic fold in which C75 moves towards to the scissile phosphate in the active site. Ejection of this ion then permits a second ion to bind elsewhere in the active site and facilitate nucleophile activation. The simulations collectively describe a mechanistic scenario that is consistent with currently available experimental data from crystallography, phosphorothioate substitutions, and chemical probing studies. Avenues for further experimental verification are suggested. PMID:27774349

  5. Effect of detergents, trypsin, and bivalent metal ions on interfacial activation and functioning of phospholipase D.

    PubMed

    Madyarov, Sh R

    2014-07-01

    The effects of detergents, trypsin, and bivalent metal ions on production of phosphatidic and lysophosphatidic acids by the action of phospholipase D (PLD) on lecithin and lysolecithin were studied. It was found that these reaction products and dodecyl sulfate ions activate PLD, whereas other anionic detergents are less effective. A protective effect of the functioning enzyme against its hydrolytic inactivation by trypsin was found. Bivalent metal ions can be arranged in the following sequence by their ability to activate PLD in the hydrolysis of lecithin and lysolecithin: Ca2+>Sr2+>Ba2+>Mg2+. These results are considered in relation to a proposed mechanism of activation and functioning of PLD with the participation of clusters of phosphatidates and lysophosphatidates. Such Me2+-induced formation of rafts or microdomains from the products of hydrolysis of phospholipids can rationalize not only PLD activation and self-regulation, but also the action of this mechanism on other components and properties of biomembranes. PLD and other lipolytic enzymes can be classified as lateral vector enzymes.

  6. Metal Ions in Unusual Valency States.

    ERIC Educational Resources Information Center

    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)

  7. Ectoenzyme activity in coastal marine waters: response to temperature and metal ion availability

    NASA Astrophysics Data System (ADS)

    Wiedenbeck, J. K.; Neino, V.; Allison, S. D.; Martiny, A.

    2009-12-01

    Ectoenzymes in the ocean are vital for the breakdown of complex organic substrates and for the uptake of nutrients by marine organisms. The activity levels of these enzymes affect the turnover rate of nutrient pools within the ocean, and thus have a significant impact on global biogeochemical nutrient cycles. This study measured the activity of extracellular enzymes from seawater samples under different environmental conditions. Samples were collected daily from coastal waters in the subtropical North Pacific (Lat.: 33°). Ambient seawater temperatures were between 18° and 20° C for the duration of the study. The activity response of four enzymes (alkaline phosphatase, β-glucosidase, β-N-acetyl glucosaminidase, and leucine aminopeptidase) was measured over a range of temperatures (4° to 40° C). The optimal temperatures of all four enzymes were above the ambient seawater temperature of the samples: optimal temperatures of β-glucosidase, β-N-acetyl glucosaminidase, and leucine aminopeptidase in the seawater samples were between 28° and 34° C, while alkaline phosphatase activity increased with the temperature over the range tested. Enzymatic activity of alkaline phosphatase was further investigated under several metal ion conditions. Activity was highest in the presence of Co2+ ions, while the availability of other ions (Ca2+ and Mg2+/Zn2+) had a lesser effect. The influence of Co2+ on alkaline phosphatase activity indicates the presence of a Co2+-dependent alkaline phosphatase in coastal marine waters. These results suggest that variations in environmental conditions (such as temperature and ion concentration) have discernable effects on enzyme activity, and thus affect turnover rates of nutrient pools in the ocean.

  8. In Vitro Antioxidant versus Metal Ion Chelating Properties of Flavonoids: A Structure-Activity Investigation

    PubMed Central

    Cherrak, Sabri Ahmed; Mokhtari-Soulimane, Nassima; Berroukeche, Farid; Bensenane, Bachir; Cherbonnel, Angéline; Merzouk, Hafida; Elhabiri, Mourad

    2016-01-01

    Natural flavonoids such as quercetin, (+)catechin and rutin as well as four methoxylated derivatives of quercetin used as models were investigated to elucidate their impact on the oxidant and antioxidant status of human red blood cells (RBCs). The impact of these compounds against metal toxicity was studied as well as their antiradical activities with DPPH assay. Antihemolytic experiments were conducted on quercetin, (+)catechin and rutin with excess of Fe, Cu and Zn (400 μM), and the oxidant (malondialdehyde, carbonyl proteins) and antioxidant (reduced glutathione, catalase activity) markers were evaluated. The results showed that Fe and Zn have the highest prooxidant effect (37 and 33% of hemolysis, respectively). Quercetin, rutin and (+)catechin exhibited strong antioxidant properties toward Fe, but this effect was decreased with respect to Zn ions. However, the Cu showed a weak antioxidant effect at the highest flavonoid concentration (200 μM), while a prooxidant effect was observed at the lowest flavonoid concentration (100 μM). These results are in agreement with the physico-chemical and antiradical data which demonstrated that binding of the metal ions (for FeNTA: (+)Catechin, KLFeNTA = 1.6(1) × 106 M-1 > Rutin, KLFeNTA = 2.0(9) × 105 M-1 > Quercetin, KLFeNTA = 1.0(7) × 105 M-1 > Q35OH, KLFeNTA = 6.3(8.7) × 104 M-1 > Quercetin3’4’OH and Quercetin 3OH, KLFeNTA ~ 2 × 104 M-1) reflects the (anti)oxidant status of the RBCs. This study reveals that flavonoids have both prooxidant and antioxidant activity depending on the nature and concentration of the flavonoids and metal ions. PMID:27788249

  9. In Vitro Antioxidant versus Metal Ion Chelating Properties of Flavonoids: A Structure-Activity Investigation.

    PubMed

    Cherrak, Sabri Ahmed; Mokhtari-Soulimane, Nassima; Berroukeche, Farid; Bensenane, Bachir; Cherbonnel, Angéline; Merzouk, Hafida; Elhabiri, Mourad

    2016-01-01

    Natural flavonoids such as quercetin, (+)catechin and rutin as well as four methoxylated derivatives of quercetin used as models were investigated to elucidate their impact on the oxidant and antioxidant status of human red blood cells (RBCs). The impact of these compounds against metal toxicity was studied as well as their antiradical activities with DPPH assay. Antihemolytic experiments were conducted on quercetin, (+)catechin and rutin with excess of Fe, Cu and Zn (400 μM), and the oxidant (malondialdehyde, carbonyl proteins) and antioxidant (reduced glutathione, catalase activity) markers were evaluated. The results showed that Fe and Zn have the highest prooxidant effect (37 and 33% of hemolysis, respectively). Quercetin, rutin and (+)catechin exhibited strong antioxidant properties toward Fe, but this effect was decreased with respect to Zn ions. However, the Cu showed a weak antioxidant effect at the highest flavonoid concentration (200 μM), while a prooxidant effect was observed at the lowest flavonoid concentration (100 μM). These results are in agreement with the physico-chemical and antiradical data which demonstrated that binding of the metal ions (for FeNTA: (+)Catechin, KLFeNTA = 1.6(1) × 106 M-1 > Rutin, KLFeNTA = 2.0(9) × 105 M-1 > Quercetin, KLFeNTA = 1.0(7) × 105 M-1 > Q35OH, KLFeNTA = 6.3(8.7) × 104 M-1 > Quercetin3'4'OH and Quercetin 3OH, KLFeNTA ~ 2 × 104 M-1) reflects the (anti)oxidant status of the RBCs. This study reveals that flavonoids have both prooxidant and antioxidant activity depending on the nature and concentration of the flavonoids and metal ions.

  10. Physicochemical characteristics and sorption capacities of heavy metal ions of activated carbons derived by activation with different alkyl phosphate triesters

    NASA Astrophysics Data System (ADS)

    Wang, Jing; Liu, Hai; Yang, Shaokun; Zhang, Jian; Zhang, Chenglu; Wu, Haiming

    2014-10-01

    Five alkyl phosphate triesters (APTEs), including trimethyl phosphate (TMP), triethyl phosphate (TEP), triisopropyl phosphate (TPP), tributyl phosphate (TBP) and trioctyl phosphate (TOP), were used as activating agents for preparing activated carbons (AC-APTEs) with high surface acidity and metal ion sorption capacity. N2 adsorption/desorption isotherms, surface morphologies, elemental compositions, results of Boehm's titration and sorption capacities of heavy metal ions of the carbons were investigated. AC-APTEs contained much more acidic groups and exhibited much less surface area (<500 m2/g) in comparison with activated carbon (AC-PPA, 1145 m2/g) obtained from phosphoric acid activation. For the AC-APTEs, AC-TOP had the highest surface area (488 m2/g), AC-TMP showed the highest yield (41.1%), and AC-TBP possessed the highest acidic groups (2.695 mmol/g), oxygen content (47.0%) and metal ion sorption capacities (40.1 mg/g for Ni(II) and 53.5 mg/g for Cd(II)). For the carbons, AC-APTEs showed much larger Ni(II) and Cd(II) sorption capacities than AC-PPA, except AC-TPP. The differences of the carbons in the physicochemical and sorption properties suggested surface chemistry of the carbons was the main factor influencing their sorption capacities whereas the pore structure played a secondary role.

  11. The effect of metal ions on the microbial attachment ability of flocculent activate sludge.

    PubMed

    Hao, Wen; Lv, Junping; Li, Yaochen; Chen, Lisha; Zhu, Jianrong

    2016-01-01

    As a kind of biofilm structure, microbial attachment was believed to play an important role in the aggregation and stability of flocculent activated sludge (FAS), and also its translation to aerobic granular activated sludge (AGAS). The aim of this study was to investigate the effect of Ca2+, Mg2+, Cu2+, Fe2+, Zn2+, K+, and Na+, which were frequently found in the biological wastewater-treatment systems on the microbial attachment of FAS, in order to provide a new strategy for the cultivation of FAS and AGAS. The results showed that different metal ions had different effects on the process of microbial attachment of FAS; in particular, Cu2+, Fe2+, and Zn2+ could increase the microbial attachment ability of FAS at appropriate concentrations, and disrupted the process at higher concentrations. Mg2+ would greatly enhance the microbial attachment of FAS at lower concentrations but then the biomass of attachment was fallen down to a level close to that of the control. However, Ca2+), K+, and Na+ always exhibited a positive impact on the microbial attachment of FAS. Besides, the concentration of FAS suspension and the culture time both had an effect on the microbial attachment of FAS. Moreover, the acyl-homoserine-lactones-based quorum-sensing system, the content of EPS, and the relative hydrophobicity of FAS had been greatly influenced by metal ions. As all these parameters had close relationships with microbial attachment process, changes in these parameters may affect the microbial attachment of FAS.

  12. Mechanistic insights into metal ion activation and operator recognition by the ferric uptake regulator

    NASA Astrophysics Data System (ADS)

    Deng, Zengqin; Wang, Qing; Liu, Zhao; Zhang, Manfeng; Machado, Ana Carolina Dantas; Chiu, Tsu-Pei; Feng, Chong; Zhang, Qi; Yu, Lin; Qi, Lei; Zheng, Jiangge; Wang, Xu; Huo, Xinmei; Qi, Xiaoxuan; Li, Xiaorong; Wu, Wei; Rohs, Remo; Li, Ying; Chen, Zhongzhou

    2015-07-01

    Ferric uptake regulator (Fur) plays a key role in the iron homeostasis of prokaryotes, such as bacterial pathogens, but the molecular mechanisms and structural basis of Fur-DNA binding remain incompletely understood. Here, we report high-resolution structures of Magnetospirillum gryphiswaldense MSR-1 Fur in four different states: apo-Fur, holo-Fur, the Fur-feoAB1 operator complex and the Fur-Pseudomonas aeruginosa Fur box complex. Apo-Fur is a transition metal ion-independent dimer whose binding induces profound conformational changes and confers DNA-binding ability. Structural characterization, mutagenesis, biochemistry and in vivo data reveal that Fur recognizes DNA by using a combination of base readout through direct contacts in the major groove and shape readout through recognition of the minor-groove electrostatic potential by lysine. The resulting conformational plasticity enables Fur binding to diverse substrates. Our results provide insights into metal ion activation and substrate recognition by Fur that suggest pathways to engineer magnetotactic bacteria and antipathogenic drugs.

  13. Activated boron nitride as an effective adsorbent for metal ions and organic pollutants

    PubMed Central

    Li, Jie; Xiao, Xing; Xu, Xuewen; Lin, Jing; Huang, Yang; Xue, Yanming; Jin, Peng; Zou, Jin; Tang, Chengchun

    2013-01-01

    Novel activated boron nitride (BN) as an effective adsorbent for pollutants in water and air has been reported in the present work. The activated BN was synthesized by a simple structure-directed method that enabled us to control the surface area, pore volume, crystal defects and surface groups. The obtained BN exhibits an super high surface area of 2078 m2/g, a large pore volume of 1.66 cm3/g and a special multimodal microporous/mesoporous structure located at ~ 1.3, ~ 2.7, and ~ 3.9 nm, respectively. More importantly, the novel activated BN exhibits an excellent adsorption performance for various metal ions (Cr3+, Co2+, Ni2+, Ce3+, Pb2+) and organic pollutants (tetracycline, methyl orange and congo red) in water, as well as volatile organic compounds (benzene) in air. The excellent reusability of the activated BN has also been confirmed. All the features render the activated BN a promising material suitable for environmental remediation. PMID:24220570

  14. Activated boron nitride as an effective adsorbent for metal ions and organic pollutants

    NASA Astrophysics Data System (ADS)

    Li, Jie; Xiao, Xing; Xu, Xuewen; Lin, Jing; Huang, Yang; Xue, Yanming; Jin, Peng; Zou, Jin; Tang, Chengchun

    2013-11-01

    Novel activated boron nitride (BN) as an effective adsorbent for pollutants in water and air has been reported in the present work. The activated BN was synthesized by a simple structure-directed method that enabled us to control the surface area, pore volume, crystal defects and surface groups. The obtained BN exhibits an super high surface area of 2078 m2/g, a large pore volume of 1.66 cm3/g and a special multimodal microporous/mesoporous structure located at ~ 1.3, ~ 2.7, and ~ 3.9 nm, respectively. More importantly, the novel activated BN exhibits an excellent adsorption performance for various metal ions (Cr3+, Co2+, Ni2+, Ce3+, Pb2+) and organic pollutants (tetracycline, methyl orange and congo red) in water, as well as volatile organic compounds (benzene) in air. The excellent reusability of the activated BN has also been confirmed. All the features render the activated BN a promising material suitable for environmental remediation.

  15. C-H functionalization: thoroughly tuning ligands at a metal ion, a chemist can greatly enhance catalyst's activity and selectivity.

    PubMed

    Shul'pin, Georgiy B

    2013-09-28

    This brief essay consists of a few "exciting stories" devoted to relations within a metal-complex catalyst between a metal ion and a coordinated ligand. When, as in the case of a human couple, the rapport of the partners is cordial and a love cements these relations, a chemist finds an ideal married couple, in other words he obtains a catalyst of choice which allows him to functionalize C-H bonds very efficiently and selectively. Examples of such lucky marriages in the catalytic world of ions and ligands are discussed here. Activity of the catalyst is characterized by turnover number (TON) or turnover frequency (TOF) as well as by yield of a target product. Introducing a chelating N,N- or N,O-ligand to the catalyst molecule (this can be an iron or manganese derivative) sharply enhances its activity. However, the activity of vanadium derivatives (with additionally added to the solution pyrazinecarboxylic acid, PCA) as well as of various osmium complexes does not dramatically depend on the nature of ligands surrounding metal ions. Complexes of these metals are very efficient catalysts in oxidations with H2O2. Osmium derivatives are record-holders exhibiting extremely high TONs whereas vanadium complexes are on the second position. Finally, elegant examples of alkane functionalization on the ions of non-transition metals (aluminium, gallium etc.) are described when one ligand within the metal complex (namely, hydroperoxyl ligand HOO(-)) helps other ligand of this complex (H2O2 molecule coordinated to the metal) to disintegrate into two species, generating very reactive hydroxyl radical. Hydrogen peroxide molecule, even ligated to the metal ion, is perfectly stable without the assistance of the neighboring HOO(-) ligand. This ligand can be easily oxidized donating an electron to its partner ligand (H2O2). In an analogous case, when the central ion in the catalyst is a transition metal, this ion changing its oxidation state can donate an electron to the coordinated H2O2

  16. Using metal-ligand binding characteristics to predict metal toxicity: quantitative ion character-activity relationships (QICARs).

    PubMed Central

    Newman, M C; McCloskey, J T; Tatara, C P

    1998-01-01

    Ecological risk assessment can be enhanced with predictive models for metal toxicity. Modelings of published data were done under the simplifying assumption that intermetal trends in toxicity reflect relative metal-ligand complex stabilities. This idea has been invoked successfully since 1904 but has yet to be applied widely in quantitative ecotoxicology. Intermetal trends in toxicity were successfully modeled with ion characteristics reflecting metal binding to ligands for a wide range of effects. Most models were useful for predictive purposes based on an F-ratio criterion and cross-validation, but anomalous predictions did occur if speciation was ignored. In general, models for metals with the same valence (i.e., divalent metals) were better than those combining mono-, di-, and trivalent metals. The softness parameter (sigma p) and the absolute value of the log of the first hydrolysis constant ([symbol: see text] log KOH [symbol: see text]) were especially useful in model construction. Also, delta E0 contributed substantially to several of the two-variable models. In contrast, quantitative attempts to predict metal interactions in binary mixtures based on metal-ligand complex stabilities were not successful. PMID:9860900

  17. Copper toxicity to bioluminescent Nitrosomonas europaea in soil is explained by the free metal ion activity in pore water.

    PubMed

    Ore, S; Mertens, J; Brandt, K K; Smolders, E

    2010-12-01

    The terrestrial biotic ligand model (BLM) for metal toxicity in soil postulates that metal toxicity depends on the free metal ion activity in solution and on ions competing for metal sorption to the biotic ligand. Unequivocal evidence for the BLM assumptions is most difficult to obtain for native soil microorganisms because the abiotic and biotic compartments cannot be experimentally separated. Here, we report copper (Cu) toxicity to a bioluminescent Nitrosomonas europaea reporter strain that was used in a solid phase-contact assay and in corresponding soil extracts and artificial soil solutions. The Cu(2+) ion activities that halve bioluminescence (EC50) in artificial solutions ranged 10(-5) to 10(-7) M and increased with increasing activities of H(+), Ca(2+) and Mg(2+) according to the BLM concept. The solution based Cu(2+) EC50 values of N. europaea in six contaminated soils ranged 2 × 10(-6) to 2 × 10(-9) M and these thresholds for both solid phase or soil extract based assays were well predicted by the ion competition model fitted to artificial solution data. In addition, solution based Cu(2+) EC50 of the solid phase-contact assay were never smaller than corresponding values in soil extracts suggesting no additional solid phase toxic route. By restricting the analysis to the same added species, we show that the Cu(2+) in solution represents the toxic species to this bacterium.

  18. Transition Metal Ions in Zeolites: Coordination and activation of O2

    PubMed Central

    Smeets, Pieter J.; Woertink, Julia S.; Sels, Bert F.; Solomon, Edward I.; Schoonheydt, Robert A.

    2010-01-01

    Zeolites containing transition metal ions (TMI) often show promising activity as heterogeneous catalysts in pollution abatement and selective oxidation reactions. In this paper, two aspects of research on the TMI Cu, Co and Fe in zeolites are discussed: (i) coordination to the lattice and (ii) activated oxygen species. At low loading, TMI preferably occupy exchange sites in six-membered oxygen rings (6MR) where the TMI preferentially coordinate with the oxygen atoms of Al tetrahedra. High TMI loadings result in a variety of TMI species formed at the zeolite surface. Removal of the extra-lattice oxygens during high temperature pretreatments can result in auto-reduction. Oxidation of reduced TMI sites often results in the formation of highly reactive oxygen species. In Cu-ZSM-5, calcination with O2 results in the formation of a species, which was found to be a crucial intermediate in both the direct decomposition of NO and N2O and the selective oxidation of methane into methanol. An activated oxygen species, called α-oxygen, is formed in Fe-ZSM5 and reported to be the active site in the partial oxidation of methane and benzene into methanol and phenol, respectively. However, this reactive α-oxygen can only be formed with N2O, not with O2. O2 activated Co intermediates in Faujasite (FAU) zeolites can selectively oxidize α-pinene and epoxidize styrene. In Co-FAU, CoIII superoxo and peroxo complexes are suggested to be the active cores, whereas in Cu and Fe-ZSM-5 various monomeric and dimeric sites have been proposed, but no consensus has been obtained. Very recently, the active site in Cu-ZSM-5 was identified as a bent [Cu-O-Cu]2+ core (Proc. Natl. Acad. Sci. USA 2009, 106, 18908-18913). Overall, O2 activation depends on the interplay of structural factors such as type of zeolite, size of the channels and cages and chemical factors such as Si/Al ratio and the nature, charge and distribution of the charge balancing cations. The presence of several different TMI sites

  19. New transition metal ion complexes with benzimidazole-5-carboxylic acid hydrazides with antitumor activity.

    PubMed

    Galal, Shadia A; Hegab, Khaled H; Kassab, Ahmed S; Rodriguez, Mireya L; Kerwin, Sean M; el-Khamry, Abdel-Mo'men A; el-Diwani, Hoda I

    2009-04-01

    Metal complexes of 2-methyl-1H-benzimidazole-5-carboxylic acid hydrazide (4a; L(1)) and its Schiff base 2-methyl-N-(propan-2-ylidene)-1H-benzimidazole-5-carbohydrazide (5a; L(2)) with transition metal ions e.g., copper, silver, nickel, iron and manganese were prepared. The complexes formed were 1:1 or 1:2 M:L complexes and have the structural formulae [Cu(L(1))Cl(H(2)O)]Cl x 3 H(2)O (6), [Ag(L(1))NO(3)(H(2)O)] (7), [Ni(L(1))Cl(2)(H(2)O)(2)] x H(2)O (8), [Fe(L(1))Cl(3)(H(2)O)] x 3 H(2)O (9) and [Mn(L(1))(2)Cl(H(2)O)]Cl x 3 H(2)O (10) for ligand L(1), and [Cu(L(2))Cl(2)(H(2)O)(2)] x H(2)O (11), [Ag(L(2))(2)]NO(3) x H(2)O (12), [Ni(L(2))(2)Cl(2)] x 5 H(2)O (13), [Fe(L(2))(2)Cl(2)]Cl x 2 H(2)O (14) and [Mn(L(2))Cl(2)(H(2)O)(2)] x H(2)O (15) for ligand L(2). The antitumor activity of the synthesized compounds has been studied. The silver complex 7 was found to display cytotoxicity (IC(50)=2 microM) against both human lung cancer cell line A549 and human breast cancer cell line MCF-7.

  20. Metal Ion Interactions in the DNA Cleavage/Ligation Active Site of Human Topoisomerase IIα†

    PubMed Central

    Deweese, Joseph E.; Guengerich, F. Peter; Burgin, Alex B.; Osheroff, Neil

    2009-01-01

    Human topoisomerase IIα utilizes a two-metal-ion mechanism for DNA cleavage. One of the metal ions (M12+) is believed to make a critical interaction with the 3′-bridging atom of the scissile phosphate, while the other (M22+) is believed to interact with a non-bridging oxygen of the scissile phosphate. Based on structural and mutagenesis studies of prokaryotic nucleic acid enzymes, it has been proposed that the active site divalent metal ions interact with type II topoisomerases through a series of conserved acidic amino acid residues. The homologous residues in human topoisomerase IIα are E461, D541, D543, and D545. To address the validity of these assignments and to delineate interactions between individual amino acids and M12+ and M22+, we individually mutated each of these acidic amino acid residues in topoisomerase IIα to either cysteine or alanine. Mutant enzymes displayed a marked loss of catalytic and DNA cleavage activity as well as a reduced affinity for divalent metal ions. Additional experiments determined the ability of wild-type and mutant topoisomerase IIα enzymes to cleave an oligonucleotide substrate that contained a sulfur atom in place of the 3′-bridging oxygen of the scissile phosphate in the presence of Mg2+, Mn2+, or Ca2+. Based on the results of these studies, we conclude that the four acidic amino acid residues interact with metal ions in the DNA cleavage/ligation active site of topoisomerase IIα. Furthermore, we propose that M12+ interacts with E461, D543, and D545 and M22+ interacts with E461 and D541. PMID:19697956

  1. Enhancement of antibiotic-activity through complexation with metal ions - Combined ITC, NMR, enzymatic and biological studies.

    PubMed

    Möhler, Jasper S; Kolmar, Theresa; Synnatschke, Kevin; Hergert, Marcel; Wilson, Liam A; Ramu, Soumya; Elliott, Alysha G; Blaskovich, Mark A T; Sidjabat, Hanna E; Paterson, David L; Schenk, Gerhard; Cooper, Matthew A; Ziora, Zyta M

    2017-02-01

    Alternative solutions need to be developed to overcome the growing problem of multi-drug resistant bacteria. This study explored the possibility of creating complexes of antibiotics with metal ions, thereby increasing their activity. Analytical techniques such as isothermal titration calorimetry and nuclear magnetic resonance were used to examine the structure and interactions between Cu(II), Ag(I) or Zn(II) and β-lactam antibiotics. The metal-β-lactam complexes were also tested for antimicrobial activity, by micro-broth dilution and disk diffusion methods, showing a synergistic increase in the activity of the drugs, and enzymatic inhibition assays confirming inhibition of β-lactamases responsible for resistance. The metal-antibiotic complex concept was proven to be successful with the activity of the drugs enhanced against β-lactamase-producing bacteria. The highest synergistic effects were observed for complexes formed with Ag(I).

  2. Metal Ion Removal from Wastewaters by Sorption on Activated Carbon, Cement Kiln Dust, and Sawdust.

    PubMed

    Shaheen, Sabry M; Eissa, Fawzy I; Ghanem, Khaled M; El-Din, Hala M Gamal; Al Anany, Fathia S

    2015-06-01

    This study assessed the efficiency of activated carbon, cement kiln dust (CKD), and sawdust for the removal of cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn) from aqueous solutions under mono-metal and competitive sorption systems and the removal of Cd, Cu, and Zn from different industrial wastewaters. Batch equilibrium experiments were conducted in a mono-metal and competitive sorption system. The efficiency of the sorbents in the removal of Cd, Cu, and Zn from industrial wastewaters was also investigated. Cement kiln dust expressed the highest affinity for the metals followed by activated carbon and sawdust. Competition among the metals changed their distribution coefficient (Kd) with the sorbents. Sorption of Pb and Cu was higher than Cd and Zn. The average metal removal from the wastewaters varied from 74, 61, and 60% for Cd, Cu, and Zn, respectively, to nearly 100%. The efficiencies of CKD and activated carbon in removing metals were higher than sawdust, suggesting their potential as low-cost sorbents for the removal of toxic metals from wastewaters.

  3. Photocatalytic activity of transition-metal-ion-doped coordination polymer (CP): photoresponse region extension and quantum yields enhancement via doping of transition metal ions into the framework of CPs.

    PubMed

    Xu, Xin-Xin; Cui, Zhong-Ping; Gao, Xin; Liu, Xiao-Xia

    2014-06-21

    To improve photocatalytic activity of a coordination polymer (CP) in the visible light region, five different transition metal ions (Fe(3+), Cr(3+), Ru(3+), Co(2+) and Ni(2+)) were introduced into its framework through an ion-exchange process. Among all the resulting transition metal ion doped coordination polymers (TMI/CPs), the one doped with Fe(3+) took on the most excellent photocatalytic activity and the highest quantum yields in the visible light region, decomposing 94% Rhodamine B (RhB) in 8 hours. It can be attributed to the doping of Fe(3+), which reduced the band gap (Eg) of the original CP, facilitating photocatalysis of the obtained polymer. Compared with the coordination polymer with Fe(3+) as a dopant, products doped with other metal ions presented weaker photocatalytic activities in the visible light region, while under the irradiation of ultraviolet light, they showed favorable photocatalytic properties. The results suggest that to dope transition metal ions into the framework of CPs would be an ideal option for enhancing the photocatalytic activity of coordination polymers.

  4. "JCE" Classroom Activity #106. Sequestration of Divalent Metal Ion by Superabsorbent Polymer in Diapers

    ERIC Educational Resources Information Center

    Chen, Yueh-Huey; Lin, Jia-Ying; Lin, Li-Pin; Liang, Han; Yaung, Jing-Fun

    2010-01-01

    This activity explores an alternative use of a superabsorbent polymer known as a water absorbing material. A dilute solution of CuCl[subscript 2] is treated with a small piece of unused disposable diaper containing superabsorbent sodium polyacrylates. The polymer is used for the removal of Cu[superscript 2+] ions from the solution. The…

  5. Metal Ion Adsorption by Activated Carbons Made from Pecan Shells: Effect of Oxygen Level During Activation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Agricultural by-products represent a considerable quantity of harvested commodity crops. The use of by-products as precursors for the production of widely used adsorbents, such as activated carbons, may impart a value-added component of the overall biomass harvested. Our objective in this presenta...

  6. Recovery of valuable metals from cathodic active material of spent lithium ion batteries: Leaching and kinetic aspects.

    PubMed

    Meshram, Pratima; Pandey, B D; Mankhand, T R

    2015-11-01

    This work is focussed on the processing of cathodic active material of spent lithium ion batteries (LIBs) to ensure resource recovery and minimize environmental degradation. The sulfuric acid leaching of metals was carried out for the recovery of all the valuable metals including nickel and manganese along with the frequently targeted metals like lithium and cobalt. The process parameters such as acid concentration, pulp density, time and temperature for the leaching of metals from the cathode powder containing 35.8% Co, 6.5% Li, 11.6% Mn and 10.06% Ni, were optimized. Results show the optimized leach recovery of 93.4% Li, 66.2% Co, 96.3% Ni and 50.2% Mn when the material was leached in 1M H2SO4 at 368 K and 50 g/L pulp density for 240 min. The need of a reductant for improved recovery of cobalt and manganese has been explained by the thermodynamic analysis (Eh-pH diagram) for these metals. Leaching of the valuable metals was found to follow the logarithmic rate law controlled by surface layer diffusion of the lixiviant reacting with the particles. The mode of leaching of the metals from the spent LIBs was further examined by chemical analysis of the samples at various stage of processing which was further corroborated by characterizing the untreated sample and the leach residues by XRD phase identification and the SEM-EDS studies.

  7. The effect of metal ions on the activity and thermostability of the extracellular proteinase from a thermophilic Bacillus, strain EA.1.

    PubMed Central

    Coolbear, T; Whittaker, J M; Daniel, R M

    1992-01-01

    The proteinase from the extremely thermophilic Bacillus strain EA.1 exhibits maximum stability at a pH of approx. 6.5. In the presence of calcium ions the half-life at 95 degrees C of the enzyme at this pH was 17 min, and loss of activity followed first-order decay kinetics. The role of metal ions in the activity and stability of the enzyme was studied using the holoenzyme, the metal-depleted apoenzyme, and a zinc-enriched apoenzyme preparation. Zinc and calcium ions were the preferred bivalent cations for the active site and stabilization site(s) respectively. Stabilization by metal ions was not in itself a highly stringent process, but ions other than calcium which stabilized the enzyme generally had a concomitant inhibitory effect on activity. Inhibition and stabilization of the enzyme by cations were concentration-dependent effects and certain ions activated the apoenzyme but not the holoenzyme. Manganese(II) ions conferred some stability and also activated the enzyme, but in the latter case were not as effective as zinc ions. The results are discussed with reference to the ionic radii, co-ordination number and preferred ligand donors of the ions. Mercury(II) ions severely compromised enzyme activity and stability, and the effects of thiol-reactive agents suggest that thiol groups also have a role in enzyme integrity. PMID:1445196

  8. The M17 leucine aminopeptidase of the malaria parasite Plasmodium falciparum: importance of active site metal ions in the binding of substrates and inhibitors.

    PubMed

    Maric, Selma; Donnelly, Sheila M; Robinson, Mark W; Skinner-Adams, Tina; Trenholme, Katharine R; Gardiner, Donald L; Dalton, John P; Stack, Colin M; Lowther, Jonathan

    2009-06-16

    The M17 leucine aminopeptidase of the intraerythrocytic stages of the malaria parasite Plasmodium falciparum (PfLAP) plays a role in releasing amino acids from host hemoglobin that are used for parasite protein synthesis, growth, and development. This enzyme represents a target at which new antimalarials could be designed since metalloaminopeptidase inhibitors prevent the growth of the parasites in vitro and in vivo. A study on the metal ion binding characteristics of recombinant P. falciparum M17 leucine aminopeptidase (rPfLAP) shows that the active site of this exopeptidase contains two metal-binding sites, a readily exchangeable site (site 1) and a tight binding site (site 2). The enzyme retains activity when the metal ion is removed from site 1, while removal of metal ions from both sites results in an inactive apoenzyme that cannot be reactivated by the addition of divalent metal cations. The metal ion at site 1 is readily exchangeable with several divalent metal ions and displays a preference in the order of preference Zn(2+) > Mn(2+) > Co(2+) > Mg(2+). While it is likely that native PfLAP contains a Zn(2+) in site 2, the metal ion located in site 1 may be dependent on the type and concentration of metal ions in the cytosolic compartment of the parasite. Importantly, the type of metal ion present at site 1 influences not only the catalytic efficiency of the enzyme for peptide substrates but also the mode of binding by bestatin, a metal-chelating inhibitor of M17 aminopeptidases with antimalarial activity.

  9. Group III alcohol dehydrogenase from Pectobacterium atrosepticum: insights into enzymatic activity and organization of the metal ion-containing region.

    PubMed

    Elleuche, Skander; Fodor, Krisztian; von der Heyde, Amélie; Klippel, Barbara; Wilmanns, Matthias; Antranikian, Garabed

    2014-05-01

    NAD(P)(+)-dependent alcohol dehydrogenases (ADH) are widely distributed in all phyla. These proteins can be assigned to three nonhomologous groups of isozymes, with group III being highly diverse with regards to catalytic activity and primary structure. Members of group III ADHs share a conserved stretch of amino acid residues important for cofactor binding and metal ion coordination, while sequence identities for complete proteins are highly diverse (<20 to >90 %). A putative group III ADH PaYqhD has been identified in BLAST analysis from the plant pathogenic enterobacterium Pectobacterium atrosepticum. The PaYqhD gene was expressed in the heterologous host Escherichia coli, and the recombinant protein was purified in a two-step purification procedure to homogeneity indicating an obligate dimerization of monomers. Four conserved amino acid residues involved in metal ion coordination were substituted with alanine, and their importance for catalytic activity was confirmed by circular dichroism spectrum determination, in vitro, and growth experiments. PaYqhD exhibits optimal activity at 40 °C with short carbon chain aldehyde compounds and NADPH as cofactor indicating the enzyme to be an aldehyde reductase. No oxidative activities towards alcoholic compounds were detectable. EDTA completely inhibited catalytic activity and was fully restored by the addition of Co(2+). Activity measurements together with sequence alignments and structure analysis confirmed that PaYqhD belongs to the butanol dehydrogenase-like enzymes within group III of ADHs.

  10. Influence of Humic Acid Complexation with Metal Ions on Extracellular Electron Transfer Activity

    NASA Astrophysics Data System (ADS)

    Zhou, Shungui; Chen, Shanshan; Yuan, Yong; Lu, Qin

    2015-11-01

    Humic acids (HAs) can act as electron shuttles and mediate biogeochemical cycles, thereby influencing the transformation of nutrients and environmental pollutants. HAs commonly complex with metals in the environment, but few studies have focused on how these metals affect the roles of HAs in extracellular electron transfer (EET). In this study, HA-metal (HA-M) complexes (HA-Fe, HA-Cu, and HA-Al) were prepared and characterized. The electron shuttle capacities of HA-M complexes were experimentally evaluated through microbial Fe(III) reduction, biocurrent generation, and microbial azoreduction. The results show that the electron shuttle capacities of HAs were enhanced after complexation with Fe but were weakened when using Cu or Al. Density functional theory calculations were performed to explore the structural geometry of the HA-M complexes and revealed the best binding sites of the HAs to metals and the varied charge transfer rate constants (k). The EET activity of the HA-M complexes were in the order HA-Fe > HA-Cu > HA-Al. These findings have important implications for biogeochemical redox processes given the ubiquitous nature of both HAs and various metals in the environment.

  11. Synthesis, characterization, biological activity and equilibrium studies of metal(II) ion complexes with tridentate hydrazone ligand derived from hydralazine

    NASA Astrophysics Data System (ADS)

    El-Sherif, Ahmed A.; Shoukry, Mohamed M.; Abd-Elgawad, Mohamed M. A.

    2012-12-01

    In the present study, a new hydrazone ligand (2-((2-phthalazin-1-yl)hydrazono)methyl)phenol) prepared by condensation of hydralazine (1-Hydralazinophthalazine) with salicylaldehyde (SAH). The synthesized SAH-hydrazone and its metal complexes have been characterized by elemental analyses, IR, 1H NMR, solid reflectance, magnetic moment, molar conductance, mass spectra, UV-vis and thermal analysis (TGA). The analytical data of the complexes show the formation of 1:1 [M:L] ratio, where M represents Ni(II), Co(II) and Cu(II) ions, while L represents the deprotonated hydrazone ligand. IR spectra show that SAH is coordinated to the metal ions in a tridentate manner through phthalazine-N, azomethine-N and phenolic-oxygen groups. The ligand and their metal chelates have been screened for their antimicrobial activities using the disc diffusion method against the selected bacteria and fungi. Proton-ligand association constants of (SAH) and the stepwise stability constants of its metal complexes are determined potentiometrically in 0.1 M NaNO3 at different temperatures and the corresponding thermodynamic parameters were derived and discussed. The order of -ΔG° and -ΔH° were found to obey Mn2+ < Co2+ < Ni2+ < Cu2+, in accordance with the Irving-Williams order. The complexes were stabilized by enthalpy changes and the results suggest that the complexation is an enthalpy-driven process. The concentration distribution diagrams of the complexes are evaluated.

  12. Efficient continuous biosynthesis of silver nanoparticles by activated sludge micromycetes with enhanced tolerance to metal ion toxicity.

    PubMed

    Tyupa, Dmitry V; Kalenov, Sergei V; Baurina, Marina M; Yakubovich, Liubov M; Morozov, Alexander N; Zakalyukin, Ruslan M; Sorokin, Vladimir V; Skladnev, Dmitry A

    2016-12-01

    The method for producing AgNPs by granules of activated sludge micromycetes with enhanced tolerance to metal ion toxicity - Penicillium glabrum, Fusarium nivale and Fusarium oxysporum has been developed; the optimum conditions for AgNP biosynthesis being found: the Ag(+) ion concentration, duration of the contact of microbial cells with silver ions, a growth phase of microorganisms, medium composition, a рН value, mixing conditions, and also lighting intensity. The effect of Cl(-), SO4(2-) and HPO4(2-) ions binding Ag(+) ions was eliminated, that brought to significant increase of the yield of NPs. Under batch conditions, silver particles of 60-110 nanometers in size were formed with a 65% yield. It was established that the nanoparticles were covered with microbial cell membrane proteins composed up to 70% by weight of the NPs that prevented their aggregation. In addition, it was the first time stable AgNPs had been formed by continuous AgNP biosynthesis by living cells of F. oxysporum with an 80% yield for a long time.

  13. An economically viable method for the removal of selected divalent metal ions from aqueous solutions using activated rice husk.

    PubMed

    Akhtar, Mubeena; Iqbal, Shahid; Kausar, Abida; Bhanger, M I; Shaheen, Muhammad Ashraf

    2010-01-01

    Biosorption of divalent metal ions, i.e. Pb(II), Cd(II), Zn(II) and Cu(II) onto rice husk activated (RHA) is investigated over pH range (1-10) via batch adsorption technique. The chemical and thermal activation of rice husk with 0.1M HNO(3) and 1M K(2)CO(3) at 473 K enhanced the removal efficiency of RHA (35+/-2.1-99+/-0.5%, 33+/-1.2-97+/-0.6%, 32+/-1.3-96+/-0.8% and 28+/-1.8-95+/-0.9% before and after treatment, respectively). The surface area analysis of RHA by BET (Brunauer, Emmett and Teller) nitrogen adsorption method provided pore area and average pore diameter to be 542+/-2.3m(2)g(-1) and 1076+/-5.6 nm respectively. SEM and FTIR analyses of RHA were carried out to determine the surface morphology and functional groups involved in metal binding mechanism, respectively. The adsorption equilibrium was well described by Freundlich, Langmuir and Dubinin-Radushkevish (D-R) isotherm models by employing (4.8-48, 8.9-89, 15.3-153 and 15.7-157)x10(-5)M solution concentrations of sorbates, respectively, at equilibrium time of 20 min at pH 6 and onto 0.2g of sorbent. The kinetics of mass transfer and intra-particle diffusion for metal ions sorption onto RHA were studied with Lagergren and Morris-Weber kinetic models. The numerical values of thermodynamic parameters indicated the exothermic nature, spontaneity and feasibility of the sorption process. The desorption study of metal components from RHA surface was carried out with 0.1M HCl. The sorption mechanism developed illustrates the strong interactions of sorbates with the active sites of the sorbent coupled with efficient and environmentally clean exploitation of rice waste product.

  14. Voltage clustering in redox-active ligand complexes: mitigating electronic communication through choice of metal ion

    SciTech Connect

    Zarkesh, Ryan A.; Ichimura, Andrew S.; Monson, Todd C.; Tomson, Neil C.; Anstey, Mitchell R.

    2016-02-01

    We used the redox-active bis(imino)acenapthene (BIAN) ligand to synthesize homoleptic aluminum, chromium, and gallium complexes of the general formula (BIAN)3M. The resulting compounds were characterized using X-ray crystallography, NMR, EPR, magnetic susceptibility and cyclic voltammetry measurements and modeled using both DFT and ab initio wavefunction calculations to compare the orbital contributions of main group elements and transition metals in ligand-based redox events. Ultimately, complexes of this type have the potential to improve the energy density and electrolyte stability of grid-scale energy storage technologies, such as redox flow batteries, through thermodynamically-clustered redox events.

  15. Divalent metal ion triggered activity of a synthetic antimicrobial in cardiolipin membranes.

    PubMed

    Som, Abhigyan; Yang, Lihua; Wong, Gerard C L; Tew, Gregory N

    2009-10-28

    One member of a prototypical class of antimicrobial oligomers was used to study pore formation in cardiolipin-rich membranes. Both vesicle dye-leakage assays and small-angle X-ray scattering were used to study bilayer remodeling. The results indicate that the presence of negative intrinsic curvature lipids is essential for pore formation by this class of molecules: In Gram-positive bacteria, cardiolipin and divalent metal cations like Ca(2+) and Mg(2+) are needed. This is consistent with the role of phosphatidylethanolamine (PE) lipid in Gram-negative bacteria, where antimicrobial activity is dependent on the negative intrinsic curvature of PE rather than a specific interaction with PE.

  16. Voltage clustering in redox-active ligand complexes: mitigating electronic communication through choice of metal ion

    DOE PAGES

    Zarkesh, Ryan A.; Ichimura, Andrew S.; Monson, Todd C.; ...

    2016-02-01

    We used the redox-active bis(imino)acenapthene (BIAN) ligand to synthesize homoleptic aluminum, chromium, and gallium complexes of the general formula (BIAN)3M. The resulting compounds were characterized using X-ray crystallography, NMR, EPR, magnetic susceptibility and cyclic voltammetry measurements and modeled using both DFT and ab initio wavefunction calculations to compare the orbital contributions of main group elements and transition metals in ligand-based redox events. Ultimately, complexes of this type have the potential to improve the energy density and electrolyte stability of grid-scale energy storage technologies, such as redox flow batteries, through thermodynamically-clustered redox events.

  17. Activation of the EGF receptor tyrosine kinase by divalent metal ions: comparison of holoreceptor and isolated kinase domain properties.

    PubMed

    Koland, J G; Cerione, R A

    1990-05-22

    The activation of the epidermal growth factor (EGF) receptor tyrosine kinase activity is thought to represent a key initial step in EGF-mediated mitogenesis. The mechanisms underlying the regulation of the EGF receptor tyrosine kinase activity were examined through comparisons of the holoreceptor, purified from human placenta, and a soluble 42 kDa tyrosine kinase domain (TKD), generated by the limited trypsin proteolysis of the holoreceptor. The results of these studies highlight the importance of divalent metal ions (Me2+), i.e., Mn2+ and Mg2+, as activators of the tyrosine kinase activity. Manganese is an extremely effective activator of the holoreceptor tyrosine kinase, and under some conditions (low ionic strength) it completely alleviates the need for EGF to stimulate activity. In contrast, Mg2+ only weakly stimulates the holoreceptor tyrosine kinase activity in the absence of EGF, but promotes essentially full activity in the presence of the growth factor. Like the holoreceptor, the soluble TKD is highly active in the presence of Mn2+. However, the isolated TKD is completely inactive in the presence of Mg2+, and, in fact, Mg2+ inhibits the Mn2(+)-stimulated tyrosine kinase activity. The differences in the effects of Mn2+ and Mg2+ on the isolated TKD were further demonstrated by monitoring the effects of Me2+ on the modification of a reactive cysteine residue(s) on the TKD. While Mn2+ potentiates the inhibition by cysteine-directed reagents of the tyrosine kinase activity, Mg2+ has no effect on either the rate or the extent of the inhibition. Both the regulation by Mn2+ of the kinase activity of the TKD and the potentiation by Mn2+ of the cysteine reactivity of the TKD occur over a millimolar concentration range, which implicates a direct binding interaction by the metal ion. Overall, these results demonstrate that there are two key activator sites on the EGF receptor, i.e., the EGF binding site on the extracellular domain and a Me2+ binding site on the

  18. The effects of metal ions in Euphorbia cf. lactea latex on the fibrinogenolytic activity of a plant protease.

    PubMed

    Siritapetawee, Jaruwan; Limphirat, Wanwisa; Kantachot, Chortip; Kongmark, Chanapa

    2015-01-01

    Two synchrotron-based techniques, synchrotron X-ray fluorescence (SXRF) and X-ray absorption spectroscopy (XAS), have demonstrated that Ca(2+) and Zn(2+) were the major metal ions distributed in the natural latex of Euphorbia cf. lactea. Both metal ions were found to affect the fibrinogenolytic activity of a homodimeric protease purified from the latex of this plant. The dimeric protein had an estimated molecular mass of about 82 kDa analyzed by SDS-PAGE. Therefore this protein was called as EuP-82. Based on the results of circular dichroism (CD) spectroscopy and the fibrinolytic activity measurement, it was found that Ca(2+) could activate the proteolytic activity of the enzyme by stabilizing its backbone structure. The intact conformation of EuP-82 was predicted from CD spectrum, which consisted of 51 % α-helix and 9 % β-sheet. Zn(2+) (10 mM) could decrease the fibrinolytic activity of EuP-82 to 30 ± 1 %. CD spectrum also supported that the inhibitory effect of Zn(2+) on the enzyme activity occurred by the drastic change of the enzyme structure with increasing the random coil conformation and by switching between α-helix and β-sheet structure. These results could be of first importance for further application to use EuP-82, the natural source protease as a potential drug for the thrombosis treatment. The fibrinolytic activity of EuP-82 may be enhanced by plasma Ca(2+) which generally involves in human hemostasis system.

  19. Study on the interaction of ions of transient metals with ascorbic acid in the presence of different scavengers of active oxygen species in SOS chromotest.

    PubMed

    Marczewska, Jadwiga; Koziorowska, Jadwiga H

    2002-03-01

    SOS chromotest was employed to study the interaction of ascorbic acid with free ions of transient metals in the presence of added catalase, superoxide dismutase or D-mannitol. Catalase diminished the genotoxic activity of the mixture of ascorbic acid with copper ions in E. coli strains PQ37 and PQ 300, but genotoxicity of this mixture was not suppressed by superoxide dismutase and D-mannitol. The results suggest that copper ions diminished the content of peroxide generated by ascorbic acid.

  20. Redox inactive metal ion triggered N-dealkylation by an iron catalyst with dioxygen activation: a lesson from lipoxygenases.

    PubMed

    Zhang, Jisheng; Wang, Yujuan; Luo, Nengchao; Chen, Zhuqi; Wu, Kangbing; Yin, Guochuan

    2015-06-07

    Utilization of dioxygen as the terminal oxidant at ambient temperature is always a challenge in redox chemistry, because it is hard to oxidize a stable redox metal ion like iron(III) to its high oxidation state to initialize the catalytic cycle. Inspired by the dioxygenation and co-oxidase activity of lipoxygenases, herein, we introduce an alternative protocol to activate the sluggish iron(III) species with non-redox metal ions, which can promote its oxidizing power to facilitate substrate oxidation with dioxygen, thus initializing the catalytic cycle. In oxidations of N,N-dimethylaniline and its analogues, adding Zn(OTf)2 to the [Fe(TPA)Cl2]Cl catalyst can trigger the amine oxidation with dioxygen, whereas [Fe(TPA)Cl2]Cl alone is very sluggish. In stoichiometric oxidations, it has also been confirmed that the presence of Zn(OTf)2 can apparently improve the electron transfer capability of the [Fe(TPA)Cl2]Cl complex. Experiments using different types of substrates as trapping reagents disclosed that the iron(IV) species does not occur in the catalytic cycle, suggesting that oxidation of amines is initialized by electron transfer rather than hydrogen abstraction. Combined experiments from UV-Vis, high resolution mass spectrometry, electrochemistry, EPR and oxidation kinetics support that the improved electron transfer ability of iron(III) species originates from its interaction with added Lewis acids like Zn(2+) through a plausible chloride or OTf(-) bridge, which has promoted the redox potential of iron(III) species. The amine oxidation mechanism was also discussed based on the available data, which resembles the co-oxidase activity of lipoxygenases in oxidative dealkylation of xenobiotic metabolisms where an external electron donor is not essential for dioxygen activation.

  1. Metal ion-containing epoxies

    NASA Technical Reports Server (NTRS)

    Stoakley, D. M.; St.clair, A. K.

    1982-01-01

    A variety of metallic and organometallic complexes to be used as potential additives for an epoxy used by the aerospace industry as a composite matrix resin were investigated. A total of 9 complexes were screened for compatibility and for their ability to accelerate or inhibit the cure of a highly crosslinkable epoxy resin. Methods for combining the metallic complexes with the resin were investigated, gel times recorded, and cure exotherms studied by differential scanning calorimetry. Glass transition temperatures of cured metal ion containing epoxy castings were determined by thermomechanical analysis. Thermal stabilities of the castings were determined by thermogravimetric analysis. Mechanical strength and stiffness of these doped epoxies were also measured.

  2. Structure of the endonuclease IV homologue from Thermotoga maritima in the presence of active-site divalent metal ions

    SciTech Connect

    Tomanicek, Stephen J.; Hughes, Ronny C.; Ng, Joseph D.; Coates, Leighton

    2010-10-05

    The most frequent lesion in DNA is at apurinic/apyrimidinic (AP) sites resulting from DNA-base losses. These AP-site lesions can stall DNA replication and lead to genome instability if left unrepaired. The AP endonucleases are an important class of enzymes that are involved in the repair of AP-site intermediates during damage-general DNA base-excision repair pathways. These enzymes hydrolytically cleave the 5{prime}-phosphodiester bond at an AP site to generate a free 3{prime}-hydroxyl group and a 5{prime}-terminal sugar phosphate using their AP nuclease activity. Specifically, Thermotoga maritima endonuclease IV is a member of the second conserved AP endonuclease family that includes Escherichia coli endonuclease IV, which is the archetype of the AP endonuclease superfamily. In order to more fully characterize the AP endonuclease family of enzymes, two X-ray crystal structures of the T. maritima endonuclease IV homologue were determined in the presence of divalent metal ions bound in the active-site region. These structures of the T. maritima endonuclease IV homologue further revealed the use of the TIM-barrel fold and the trinuclear metal binding site as important highly conserved structural elements that are involved in DNA-binding and AP-site repair processes in the AP endonuclease superfamily.

  3. Preconcentration and separation of trace amount of heavy metal ions on bis(2-hydroxy acetophenone)ethylendiimine loaded on activated carbon.

    PubMed

    Ghaedi, M; Shokrollahi, A; Kianfar, A H; Pourfarokhi, A; Khanjari, N; Mirsadeghi, A S; Soylak, M

    2009-03-15

    A sensitive and simple method for simultaneous preconcentration of trace heavy metal ions in some food samples has been reported. The method is based on the adsorption of Cr(3+), Fe(3+), Cu(2+), Ni(2+), Co(2+) and Zn(2+) on bis(2-hydroxy acetophenone)ethylendiimine (BHAPED) loaded on activated carbon (AC). The adsorbed metals on activated carbon were eluted using 2 mol L(-1) nitric acid in acetone. The influences of the analytical parameters including pH and sample volume were investigated. The effects of matrix ions on the recoveries of analyte ions were also investigated. The recoveries of analytes were generally higher than 94%. The method has been successfully applied for analysis of the metal contents in real samples including natural water samples.

  4. Mechanistic Enzyme Models: Pyridoxal and Metal Ions.

    ERIC Educational Resources Information Center

    Hamilton, S. E.; And Others

    1984-01-01

    Background information, procedures, and results are presented for experiments on the pyridoxal/metal ion model system. These experiments illustrate catalysis through Schiff's base formation between aldehydes/ketones and primary amines, catalysis by metal ions, and the predictable manner in which metal ions inhibit or catalyze reactions. (JN)

  5. Reversible photodeposition and dissolution of metal ions

    DOEpatents

    Foster, Nancy S.; Koval, Carl A.; Noble, Richard D.

    1994-01-01

    A cyclic photocatalytic process for treating waste water containing metal and organic contaminants. In one embodiment of the method, metal ions are photoreduced onto the photocatalyst and the metal concentrated by resolubilization in a smaller volume. In another embodiment of the method, contaminant organics are first oxidized, then metal ions removed by photoreductive deposition. The present invention allows the photocatalyst to be recycled until nearly complete removal of metal ions and organic contaminants is achieved.

  6. NMR Localization of Divalent Cations at the Active Site of the Neurospora VS Ribozyme Provides Insights into RNA–Metal-Ion Interactions

    PubMed Central

    2013-01-01

    Metal cations represent key elements of RNA structure and function. In the Neurospora VS ribozyme, metal cations play diverse roles; they are important for substrate recognition, formation of the active site, and shifting the pKa’s of two key nucleobases that contribute to the general acid–base mechanism. Recently, we determined the NMR structure of the A730 loop of the VS ribozyme active site (SLVI) that contributes the general acid (A756) in the enzymatic mechanism of the cleavage reaction. Our studies showed that magnesium (Mg2+) ions are essential to stabilize the formation of the S-turn motif within the A730 loop that exposes the A756 nucleobase for catalysis. In this article, we extend these NMR investigations by precisely mapping the Mg2+-ion binding sites using manganese-induced paramagnetic relaxation enhancement and cadmium-induced chemical-shift perturbation of phosphorothioate RNAs. These experiments identify five Mg2+-ion binding sites within SLVI. Four Mg2+ ions in SLVI are associated with known RNA structural motifs, including the G–U wobble pair and the GNRA tetraloop, and our studies reveal novel insights about Mg2+ ion binding to these RNA motifs. Interestingly, one Mg2+ ion is specifically associated with the S-turn motif, confirming its structural role in the folding of the A730 loop. This Mg2+ ion is likely important for formation of the active site and may play an indirect role in catalysis. PMID:24364590

  7. Behavior of metal ions in bioelectrochemical systems: A review

    NASA Astrophysics Data System (ADS)

    Lu, Zhihao; Chang, Dingming; Ma, Jingxing; Huang, Guangtuan; Cai, Lankun; Zhang, Lehua

    2015-02-01

    Bioelectrochemical systems (BESs) have been focused on by many researchers to treat wastewater and recover energy or valuable chemicals from wastes. In BESs, metal ions play an important role in the conductivity of solution, reactors' internal resistance, power generation, chemical production and activity of microorganisms. Additionally, the metal ions are also involved in anodic or cathodic reaction processes directly or indirectly in BESs. This paper reviews the behavior of metal ions in BESs, including (1) increase of the conductivity of electrolyte and decrease of internal resistance, (2) transfer for desalination, (3) enhancement or inhibition of the biocatalysis in anode, (4) improvement of cathodic performance by metal ions through electron acceptance or catalysis in cathodic process and (5) behavior of metal ions on membranes. Moreover, the perspectives of BESs removing heavy metal ions in wastewater or solid waste are discussed to realize recovery, reduction and detoxification simultaneously.

  8. Metal-ion rescue revisited: biochemical detection of site-bound metal ions important for RNA folding.

    PubMed

    Frederiksen, John K; Li, Nan-Sheng; Das, Rhiju; Herschlag, Daniel; Piccirilli, Joseph A

    2012-06-01

    Within the three-dimensional architectures of RNA molecules, divalent metal ions populate specific locations, shedding their water molecules to form chelates. These interactions help the RNA adopt and maintain specific conformations and frequently make essential contributions to function. Defining the locations of these site-bound metal ions remains challenging despite the growing database of RNA structures. Metal-ion rescue experiments have provided a powerful approach to identify and distinguish catalytic metal ions within RNA active sites, but the ability of such experiments to identify metal ions that contribute to tertiary structure acquisition and structural stability is less developed and has been challenged. Herein, we use the well-defined P4-P6 RNA domain of the Tetrahymena group I intron to reevaluate prior evidence against the discriminatory power of metal-ion rescue experiments and to advance thermodynamic descriptions necessary for interpreting these experiments. The approach successfully identifies ligands within the RNA that occupy the inner coordination sphere of divalent metal ions and distinguishes them from ligands that occupy the outer coordination sphere. Our results underscore the importance of obtaining complete folding isotherms and establishing and evaluating thermodynamic models in order to draw conclusions from metal-ion rescue experiments. These results establish metal-ion rescue as a rigorous tool for identifying and dissecting energetically important metal-ion interactions in RNAs that are noncatalytic but critical for RNA tertiary structure.

  9. Novel Glucose-1-Phosphatase with High Phytase Activity and Unusual Metal Ion Activation from Soil Bacterium Pantoea sp. Strain 3.5.1.

    PubMed

    Suleimanova, Aliya D; Beinhauer, Astrid; Valeeva, Liia R; Chastukhina, Inna B; Balaban, Nelly P; Shakirov, Eugene V; Greiner, Ralf; Sharipova, Margarita R

    2015-10-01

    Phosphorus is an important macronutrient, but its availability in soil is limited. Many soil microorganisms improve the bioavailability of phosphate by releasing it from various organic compounds, including phytate. To investigate the diversity of phytate-hydrolyzing bacteria in soil, we sampled soils of various ecological habitats, including forest, private homesteads, large agricultural complexes, and urban landscapes. Bacterial isolate Pantoea sp. strain 3.5.1 with the highest level of phytase activity was isolated from forest soil and investigated further. The Pantoea sp. 3.5.1 agpP gene encoding a novel glucose-1-phosphatase with high phytase activity was identified, and the corresponding protein was purified to apparent homogeneity, sequenced by mass spectroscopy, and biochemically characterized. The AgpP enzyme exhibits maximum activity and stability at pH 4.5 and at 37°C. The enzyme belongs to a group of histidine acid phosphatases and has the lowest Km values toward phytate, glucose-6-phosphate, and glucose-1-phosphate. Unexpectedly, stimulation of enzymatic activity by several divalent metal ions was observed for the AgpP enzyme. High-performance liquid chromatography (HPLC) and high-performance ion chromatography (HPIC) analyses of phytate hydrolysis products identify dl-myo-inositol 1,2,4,5,6-pentakisphosphate as the final product of the reaction, indicating that the Pantoea sp. AgpP glucose-1-phosphatase can be classified as a 3-phytase. The identification of the Pantoea sp. AgpP phytase and its unusual regulation by metal ions highlight the remarkable diversity of phosphorus metabolism regulation in soil bacteria. Furthermore, our data indicate that natural forest soils harbor rich reservoirs of novel phytate-hydrolyzing enzymes with unique biochemical features.

  10. Novel Glucose-1-Phosphatase with High Phytase Activity and Unusual Metal Ion Activation from Soil Bacterium Pantoea sp. Strain 3.5.1

    PubMed Central

    Suleimanova, Aliya D.; Beinhauer, Astrid; Valeeva, Liia R.; Chastukhina, Inna B.; Balaban, Nelly P.; Greiner, Ralf

    2015-01-01

    Phosphorus is an important macronutrient, but its availability in soil is limited. Many soil microorganisms improve the bioavailability of phosphate by releasing it from various organic compounds, including phytate. To investigate the diversity of phytate-hydrolyzing bacteria in soil, we sampled soils of various ecological habitats, including forest, private homesteads, large agricultural complexes, and urban landscapes. Bacterial isolate Pantoea sp. strain 3.5.1 with the highest level of phytase activity was isolated from forest soil and investigated further. The Pantoea sp. 3.5.1 agpP gene encoding a novel glucose-1-phosphatase with high phytase activity was identified, and the corresponding protein was purified to apparent homogeneity, sequenced by mass spectroscopy, and biochemically characterized. The AgpP enzyme exhibits maximum activity and stability at pH 4.5 and at 37°C. The enzyme belongs to a group of histidine acid phosphatases and has the lowest Km values toward phytate, glucose-6-phosphate, and glucose-1-phosphate. Unexpectedly, stimulation of enzymatic activity by several divalent metal ions was observed for the AgpP enzyme. High-performance liquid chromatography (HPLC) and high-performance ion chromatography (HPIC) analyses of phytate hydrolysis products identify dl-myo-inositol 1,2,4,5,6-pentakisphosphate as the final product of the reaction, indicating that the Pantoea sp. AgpP glucose-1-phosphatase can be classified as a 3-phytase. The identification of the Pantoea sp. AgpP phytase and its unusual regulation by metal ions highlight the remarkable diversity of phosphorus metabolism regulation in soil bacteria. Furthermore, our data indicate that natural forest soils harbor rich reservoirs of novel phytate-hydrolyzing enzymes with unique biochemical features. PMID:26209662

  11. Interplay of metal ions and urease

    PubMed Central

    Carter, Eric L.; Flugga, Nicholas; Boer, Jodi L.; Mulrooney, Scott B.; Hausinger, Robert P.

    2009-01-01

    Summary Urease, the first enzyme to be crystallized, contains a dinuclear nickel metallocenter that catalyzes the decomposition of urea to produce ammonia, a reaction of great agricultural and medical importance. Several mechanisms of urease catalysis have been proposed on the basis of enzyme crystal structures, model complexes, and computational efforts, but the precise steps in catalysis and the requirement of nickel versus other metals remain unclear. Purified bacterial urease is partially activated via incubation with carbon dioxide plus nickel ions; however, in vitro activation also has been achieved with manganese and cobalt. In vivo activation of most ureases requires accessory proteins that function as nickel metallochaperones and GTP-dependent molecular chaperones or play other roles in the maturation process. In addition, some microorganisms control their levels of urease by metal ion-dependent regulatory mechanisms. PMID:20046957

  12. Removal of Heavy Metal Ions and Diethylenetriamine Species from Solutions by Magnetic Activated Carbon

    NASA Astrophysics Data System (ADS)

    Liu, Kaiwen

    Even though activated carbon is widely used in the removal of contaminants from effluents, it is difficult to be completely recovered by screening or classification. In this project, we prepared a magnetic form of activated carbon (M-AC) by co-precipitation of iron oxides onto activated carbon surface. M-AC can be separated from solutions by applying an external magnetic field and regenerated for reuse. The synthesized M-AC was characterized by X-ray diffraction, specific surface area measurement, and scanning electron microscope. Characterization results show that the major phase of coated iron oxides is magnetite (Fe 3O4). Batch adsorption experiments were carried out for single-component and multi-component solutions. M-AC shows a better adsorption capacity for singlecomponent of Cu (II), Ni (II), or diethylenetriamine (DETA) and for multiple-components of Cu-DETA and Ni-DETA complexes in deionized water than activated carbon. M-AC also shows the potential application in carbon-in-pulp process for gold recovery.

  13. Spectroscopic and structural studies of the Schiff base 3-methoxy-N-salicylidene-o-amino phenol complexes with some transition metal ions and their antibacterial, antifungal activities

    NASA Astrophysics Data System (ADS)

    Abo-Aly, M. M.; Salem, A. M.; Sayed, M. A.; Abdel Aziz, A. A.

    2015-02-01

    Spectroscopic (IR, Raman, NMR, UV-visible, and ESR), and structural studies of the ligand 3-methoxy-N-salicylidene-o-amino phenol (H2L) and its synthesized complexes with some transition metal ions (Mn(II), Co(II), Ni(II)), Cu(II) and Zn(II)) were recorded and analyzed. The magnetic properties and thermal gravimetric analysis (TGA and DTA) were also measured for the complexes. The metal complexes were found to have The structural formula MLṡH2O and the metal ions Mn(II), Co(II), Ni(II)) and Zn(II) were found to form tetrahedral complexes with the ligand whereas Cu(II) formed a square planar one. Antimicrobial activity of the ligand and its complexes were also investigated and discussed.

  14. Spectroscopic and structural studies of the Schiff base 3-methoxy-N-salicylidene-o-amino phenol complexes with some transition metal ions and their antibacterial, antifungal activities.

    PubMed

    Abo-Aly, M M; Salem, A M; Sayed, M A; Abdel Aziz, A A

    2015-02-05

    Spectroscopic (IR, Raman, NMR, UV-visible, and ESR), and structural studies of the ligand 3-methoxy-N-salicylidene-o-amino phenol (H2L) and its synthesized complexes with some transition metal ions (Mn(II), Co(II), Ni(II)), Cu(II) and Zn(II)) were recorded and analyzed. The magnetic properties and thermal gravimetric analysis (TGA and DTA) were also measured for the complexes. The metal complexes were found to have The structural formula ML⋅H2O and the metal ions Mn(II), Co(II), Ni(II)) and Zn(II) were found to form tetrahedral complexes with the ligand whereas Cu(II) formed a square planar one. Antimicrobial activity of the ligand and its complexes were also investigated and discussed.

  15. Synthesis and characterization of ligational behavior of curcumin drug towards some transition metal ions: Chelation effect on their thermal stability and biological activity

    NASA Astrophysics Data System (ADS)

    Refat, Moamen S.

    2013-03-01

    Complexes of Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) with curcumin ligand as antitumor activity were synthesized and characterized by elemental analysis, conductometry, magnetic susceptibility, UV-Vis, IR, Raman, ESR, 1H-NMR spectroscopy, X-ray diffraction analysis of powdered samples and thermal analysis, and screened for antimicrobial activity. The IR spectral data suggested that the ligand behaves as a monobasic bidentate ligand towards the central metal ion with an oxygen's donor atoms sequence of both sbnd OH and Cdbnd O groups under keto-enol structure. From the microanalytical data, the stoichiometry of the complexes 1:2 (metal:ligand) was found. The ligand and their metal complexes were screened for antibacterial activity against Escherichia Coli, Staphylococcus aureus, Bacillus subtilis and Pseudomonas aeruginosa and fungicidal activity against Aspergillus flavus and Candida albicans.

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

    SciTech Connect

    Taha, Mohd F. Shaharun, Maizatul S.; Shuib, Anis Suhaila Borhan, Azry

    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.

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

    NASA Astrophysics Data System (ADS)

    Taha, Mohd F.; Shuib, Anis Suhaila; Shaharun, Maizatul S.; Borhan, Azry

    2014-10-01

    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 m2/g and 0.17 cm2/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.

  18. How do metal ions direct ribozyme folding?

    NASA Astrophysics Data System (ADS)

    Denesyuk, Natalia A.; Thirumalai, D.

    2015-10-01

    Ribozymes, which carry out phosphoryl-transfer reactions, often require Mg2+ ions for catalytic activity. The correct folding of the active site and ribozyme tertiary structure is also regulated by metal ions in a manner that is not fully understood. Here we employ coarse-grained molecular simulations to show that individual structural elements of the group I ribozyme from the bacterium Azoarcus form spontaneously in the unfolded ribozyme even at very low Mg2+ concentrations, and are transiently stabilized by the coordination of Mg2+ ions to specific nucleotides. However, competition for scarce Mg2+ and topological constraints that arise from chain connectivity prevent the complete folding of the ribozyme. A much higher Mg2+ concentration is required for complete folding of the ribozyme and stabilization of the active site. When Mg2+ is replaced by Ca2+ the ribozyme folds, but the active site remains unstable. Our results suggest that group I ribozymes utilize the same interactions with specific metal ligands for both structural stability and chemical activity.

  19. Liquid metal ion source and alloy

    DOEpatents

    Clark, Jr., William M.; Utlaut, Mark W.; Behrens, Robert G.; Szklarz, Eugene G.; Storms, Edmund K.; Santandrea, Robert P.; Swanson, Lynwood W.

    1988-10-04

    A liquid metal ion source and alloy, wherein the species to be emitted from the ion source is contained in a congruently vaporizing alloy. In one embodiment, the liquid metal ion source acts as a source of arsenic, and in a source alloy the arsenic is combined with palladium, preferably in a liquid alloy having a range of compositions from about 24 to about 33 atomic percent arsenic. Such an alloy may be readily prepared by a combustion synthesis technique. Liquid metal ion sources thus prepared produce arsenic ions for implantation, have long lifetimes, and are highly stable in operation.

  20. Polyethylene separator activated by hybrid coating improving Li+ ion transference number and ionic conductivity for Li-metal battery

    NASA Astrophysics Data System (ADS)

    Mao, Xufeng; Shi, Liyi; Zhang, Haijiao; Wang, Zhuyi; Zhu, Jiefang; Qiu, Zhengfu; Zhao, Yin; Zhang, Meihong; Yuan, Shuai

    2017-02-01

    Low Li+ ion transference number is one fatal defect of the liquid LiPF6 electrolyte for Li-metal anode based batteries. This work aims to improve Li+ ion transference number and ionic conductivity polyethylene (PE) separators. By a simple dip-coating method, the water-borne nanosized molecular sieve with 3D porous structure (ZSM-5) can be coated on PE separators. Especially, the Li+ ion transference number is greatly enhanced from 0.28 to 0.44, which should be attributed to the specific pore structure and channel environment of ZSM-5 as well as the interaction between ZSM-5 and electrolyte. Compared with the pristine PE separator, the ionic conductivity of modified separators is remarkably improved from 0.30 to 0.54 mS cm-1. As results, the C-rate capability and cycling stability are both improved. The Li-metal battery using the ZSM-5-modified PE separator keeps 94.2% capacity after 100 cycles. In contrast, the discharge capacity retention of the battery using pristine PE is only 74.7%.

  1. Hydrated metal ions in the gas phase.

    PubMed

    Beyer, Martin K

    2007-01-01

    Studying metal ion solvation, especially hydration, in the gas phase has developed into a field that is dominated by a tight interaction between experiment and theory. Since the studied species carry charge, mass spectrometry is an indispensable tool in all experiments. Whereas gas-phase coordination chemistry and reactions of bare metal ions are reasonably well understood, systems containing a larger number of solvent molecules are still difficult to understand. This review focuses on the rich chemistry of hydrated metal ions in the gas phase, covering coordination chemistry, charge separation in multiply charged systems, as well as intracluster and ion-molecule reactions. Key ideas of metal ion solvation in the gas phase are illustrated with rare-gas solvated metal ions.

  2. Metal hydrides for lithium-ion batteries.

    PubMed

    Oumellal, Y; Rougier, A; Nazri, G A; Tarascon, J-M; Aymard, L

    2008-11-01

    Classical electrodes for Li-ion technology operate via an insertion/de-insertion process. Recently, conversion electrodes have shown the capability of greater capacity, but have so far suffered from a marked hysteresis in voltage between charge and discharge, leading to poor energy efficiency and voltages. Here, we present the electrochemical reactivity of MgH(2) with Li that constitutes the first use of a metal-hydride electrode for Li-ion batteries. The MgH(2) electrode shows a large, reversible capacity of 1,480 mAh g(-1) at an average voltage of 0.5 V versus Li(+)/Li(o) which is suitable for the negative electrode. In addition, it shows the lowest polarization for conversion electrodes. The electrochemical reaction results in formation of a composite containing Mg embedded in a LiH matrix, which on charging converts back to MgH(2). Furthermore, the reaction is not specific to MgH(2), as other metal or intermetallic hydrides show similar reactivity towards Li. Equally promising, the reaction produces nanosized Mg and MgH(2), which show enhanced hydrogen sorption/desorption kinetics. We hope that such findings can pave the way for designing nanoscale active metal elements with applications in hydrogen storage and lithium-ion batteries.

  3. Metal ions and RNA folding: a highly charged topic with a dynamic future.

    PubMed

    Woodson, Sarah A

    2005-04-01

    Metal ions are required to stabilize RNA tertiary structure and to begin the folding process. How different metal ions enable RNAs to fold depends on the electrostatic potential of the RNA and correlated fluctuations in the positions of the ions themselves. Theoretical models, fluorescence spectroscopy, small angle scattering and structural biology reveal that metal ions alter the RNA dynamics and folding transition states. Specifically coordinated divalent metal ions mediate conformational rearrangements within ribozyme active sites.

  4. Pseudo ribbon metal ion beam source

    SciTech Connect

    Stepanov, Igor B. Ryabchikov, Alexander I.; Sivin, Denis O.; Verigin, Dan A.

    2014-02-15

    The paper describes high broad metal ion source based on dc macroparticle filtered vacuum arc plasma generation with the dc ion-beam extraction. The possibility of formation of pseudo ribbon beam of metal ions with the parameters: ion beam length 0.6 m, ion current up to 0.2 A, accelerating voltage 40 kV, and ion energy up to 160 kV has been demonstrated. The pseudo ribbon ion beam is formed from dc vacuum arc plasma. The results of investigation of the vacuum arc evaporator ion-emission properties are presented. The influence of magnetic field strength near the cathode surface on the arc spot movement and ion-emission properties of vacuum-arc discharge for different cathode materials are determined. It was shown that vacuum-arc discharge stability can be reached when the magnetic field strength ranges from 40 to 70 G on the cathode surface.

  5. Predicting criteria continuous concentrations of metals or metalloids for protecting marine life by use of quantitative ion characteristic-activity relationships-species sensitivity distributions (QICAR-SSD).

    PubMed

    Qie, Yu; Chen, Cheng; Guo, Fei; Mu, Yunsong; Sun, Fuhong; Wang, Hao; Wang, Ying; Wang, Huanhua; Wu, Fengchang; Hu, Qing; Dang, Zhi; Giesy, John P

    2017-02-26

    Marine pollution by metals has been a major challenge for ecological systems; however, water quality criteria (WQC) for metals in saltwater is still lacking. Especially from a regulatory perspective, chronic effects of metals on marine organisms should receive more attention. A quantitative ion characteristic-activity relationships-species sensitivity distributions (QICAR-SSD) model, based on chronic toxicities for eight marine organisms, was established to predict the criteria continuous concentrations (CCCs) of 21 metals. The results showed that the chronic toxicities of various metals had good relationships with their physicochemical properties. Predicted CCCs of six metals (Hg(2+), Cu(2+), Pb(2+), Cd(2+), Ni(2+) and Zn(2+)) were in accordance with the values recommended by the U.S. EPA, with prediction errors being less than an order of magnitude. The QICAR-SSD approach provides an alternative tool to empirical methods and can be useful for deriving scientifically defensible WQC for metals for marine organisms and conducting ecological risk assessments.

  6. Separation of metal ions from aqueous solutions

    DOEpatents

    Almon, Amy C.

    1994-01-01

    A process and apparatus for quantitatively and selectively separating metal ions from mixtures thereof in aqueous solution. The apparatus includes, in combination, a horizontal electrochemical flow cell containing flow bulk electrolyte solution and an aqueous, metal ion-containing solution, the cell containing a metal mesh working electrode, a counter electrode positioned downstream from the working electrode, an independent variable power supply/potentiostat positioned outside of the flow cell and connected to the electrodes, and optionally a detector such as a chromatographic detector, positioned outside the flow cell. This apparatus and its operation has significant application where trace amounts of metal ions are to be separated.

  7. Activated parthenium carbon as an adsorbent for the removal of dyes and heavy metal ions from aqueous solution.

    PubMed

    Rajeshwarisivaraj; Subburam, V

    2002-11-01

    Parthenium hysterophorous (L) is a perennial weed distributed all over the country. Carbonized parthenium activated with conc. H2SO4 and ammonium persulphate was effective in the removal of dyes, heavy metals and phenols. Variation in the percentage removal of adsorbates was observed with increase in the contact time. Among the adsorbates tested, the affinity of the activated parthenium carbon was highest for Hg2+, Methylene Blue and Malachite Green.

  8. Mechanically Activated Ion Channels

    PubMed Central

    Ranade, Sanjeev S.; Syeda, Ruhma; Patapoutian, Ardem

    2015-01-01

    Mechanotransduction, the conversion of physical forces into biochemical signals, is an essential component of numerous physiological processes including not only conscious senses of touch and hearing, but also unconscious senses such as blood pressure regulation. Mechanically activated (MA) ion channels have been proposed as sensors of physical force, but the identity of these channels and an understanding of how mechanical force is transduced has remained elusive. A number of recent studies on previously known ion channels along with the identification of novel MA ion channels have greatly transformed our understanding of touch and hearing in both vertebrates and invertebrates. Here, we present an updated review of eukaryotic ion channel families that have been implicated in mechanotransduction processes and evaluate the qualifications of the candidate genes according to specified criteria. We then discuss the proposed gating models for MA ion channels and highlight recent structural studies of mechanosensitive potassium channels. PMID:26402601

  9. Mechanically Activated Ion Channels.

    PubMed

    Ranade, Sanjeev S; Syeda, Ruhma; Patapoutian, Ardem

    2015-09-23

    Mechanotransduction, the conversion of physical forces into biochemical signals, is essential for various physiological processes such as the conscious sensations of touch and hearing, and the unconscious sensation of blood flow. Mechanically activated (MA) ion channels have been proposed as sensors of physical force, but the identity of these channels and an understanding of how mechanical force is transduced has remained elusive. A number of recent studies on previously known ion channels along with the identification of novel MA ion channels have greatly transformed our understanding of touch and hearing in both vertebrates and invertebrates. Here, we present an updated review of eukaryotic ion channel families that have been implicated in mechanotransduction processes and evaluate the qualifications of the candidate genes according to specified criteria. We then discuss the proposed gating models for MA ion channels and highlight recent structural studies of mechanosensitive potassium channels.

  10. Ascorbate does not act as a pro-oxidant towards lipids and proteins in human plasma exposed to redox-active transition metal ions and hydrogen peroxide.

    PubMed

    Suh, Jung; Zhu, Ben-Zhan; Frei, Balz

    2003-05-15

    The combination of ascorbate, transition metal ions, and hydrogen peroxide (H(2)O(2)) is an efficient hydroxyl radical generating system called "the Udenfriend system." Although the pro-oxidant role of ascorbate in this system has been well characterized in vitro, it is uncertain whether ascorbate also acts as a pro-oxidant under physiological conditions. To address this question, human plasma, used as a representative biological fluid, was either depleted of endogenous ascorbate with ascorbate oxidase, left untreated, or supplemented with 25 microM-1 mM ascorbate. Subsequently, the plasma samples were incubated at 37 degrees C with 50 microM-1 mM iron (from ferrous ammonium sulfate), 60 or 100 microM copper (from cupric sulfate), and/or 200 microM or 1 mM H(2)O(2). Although endogenous and added ascorbate was depleted rapidly in the presence of transition metal ions and H(2)O(2), no cholesterol ester hydroperoxides or malondialdehyde were formed, i.e., ascorbate protected against, rather than promoted, lipid peroxidation. Conversely, depletion of endogenous ascorbate was sufficient to cause lipid peroxidation, the rate and extent of which were enhanced by the addition of metal ions but not H(2)O(2). Ascorbate also did not enhance protein oxidation in plasma exposed to metal ions and H(2)O(2), as assessed by protein carbonyl formation and depletion of reduced thiols. Interestingly, neither the rate nor the extent of endogenous alpha-tocopherol oxidation in plasma was affected by any of the treatments. Our data show that even in the presence of redox-active iron or copper and H(2)O(2), ascorbate acts as an antioxidant that prevents lipid peroxidation and does not promote protein oxidation in human plasma in vitro.

  11. Antileishmanial Activity of Disulfiram and Thiuram Disulfide Analogs in an Ex Vivo Model System Is Selectively Enhanced by the Addition of Divalent Metal Ions

    PubMed Central

    Peniche, Alex G.; Renslo, Adam R.; Melby, Peter C.

    2015-01-01

    Current treatments for cutaneous and visceral leishmaniasis are toxic, expensive, difficult to administer, and limited in efficacy and availability. Disulfiram has primarily been used to treat alcoholism. More recently, it has shown some efficacy as therapy against protozoan pathogens and certain cancers, suggesting a wide range of biological activities. We used an ex vivo system to screen several thiuram disulfide compounds for antileishmanial activity. We found five compounds (compound identifier [CID] 7188, 5455, 95876, 12892, and 3117 [disulfiram]) with anti-Leishmania activity at nanomolar concentrations. We further evaluated these compounds with the addition of divalent metal salts based on studies that indicated these salts could potentiate the action of disulfiram. In addition, clinical studies suggested that zinc has some efficacy in treating cutaneous leishmaniasis. Several divalent metal salts were evaluated at 1 μM, which is lower than the normal levels of copper and zinc in plasma of healthy individuals. The leishmanicidal activity of disulfiram and CID 7188 were enhanced by several divalent metal salts at 1 μM. The in vitro therapeutic index (IVTI) of disulfiram and CID 7188 increased 12- and 2.3-fold, respectively, against L. major when combined with ZnCl2. The combination of disulfiram with ZnSO4 resulted in a 1.8-fold increase in IVTI against L. donovani. This novel combination of thiuram disulfides and divalent metal ions salts could have application as topical and/or oral therapies for treatment of cutaneous and visceral leishmaniasis. PMID:26239994

  12. Metal Ion-dependent Heavy Chain Transfer Activity of TSG-6 Mediates Assembly of the Cumulus-Oocyte Matrix*

    PubMed Central

    Briggs, David C.; Birchenough, Holly L.; Ali, Tariq; Rugg, Marilyn S.; Waltho, Jon P.; Ievoli, Elena; Jowitt, Thomas A.; Enghild, Jan J.; Richter, Ralf P.; Salustri, Antonietta; Milner, Caroline M.; Day, Anthony J.

    2015-01-01

    The matrix polysaccharide hyaluronan (HA) has a critical role in the expansion of the cumulus cell-oocyte complex (COC), a process that is necessary for ovulation and fertilization in most mammals. Hyaluronan is organized into a cross-linked network by the cooperative action of three proteins, inter-α-inhibitor (IαI), pentraxin-3, and TNF-stimulated gene-6 (TSG-6), driving the expansion of the COC and providing the cumulus matrix with its required viscoelastic properties. Although it is known that matrix stabilization involves the TSG-6-mediated transfer of IαI heavy chains (HCs) onto hyaluronan (to form covalent HC·HA complexes that are cross-linked by pentraxin-3) and that this occurs via the formation of covalent HC·TSG-6 intermediates, the underlying molecular mechanisms are not well understood. Here, we have determined the tertiary structure of the CUB module from human TSG-6, identifying a calcium ion-binding site and chelating glutamic acid residue that mediate the formation of HC·TSG-6. This occurs via an initial metal ion-dependent, non-covalent, interaction between TSG-6 and HCs that also requires the presence of an HC-associated magnesium ion. In addition, we have found that the well characterized hyaluronan-binding site in the TSG-6 Link module is not used for recognition during transfer of HCs onto HA. Analysis of TSG-6 mutants (with impaired transferase and/or hyaluronan-binding functions) revealed that although the TSG-6-mediated formation of HC·HA complexes is essential for the expansion of mouse COCs in vitro, the hyaluronan-binding function of TSG-6 does not play a major role in the stabilization of the murine cumulus matrix. PMID:26468290

  13. Catalysis using hydrous metal oxide ion exchangers

    DOEpatents

    Dosch, R.G.; Stephens, H.P.; Stohl, F.V.

    1983-07-21

    In a process which is catalyzed by a catalyst comprising an active metal on a carrier, said metal being active as a catalyst for the process, an improvement is provided wherein the catalyst is a hydrous, alkali metal or alkaline earth metal titanate, zirconate, niobate or tantalate wherein alkali or alkaline earth metal cations have been exchanged with a catalytically effective amount of cations of said metal.

  14. Catalysis using hydrous metal oxide ion exchanges

    DOEpatents

    Dosch, Robert G.; Stephens, Howard P.; Stohl, Frances V.

    1985-01-01

    In a process which is catalyzed by a catalyst comprising an active metal on a carrier, said metal being active as a catalyst for the process, an improvement is provided wherein the catalyst is a hydrous, alkali metal or alkaline earth metal titanate, zirconate, niobate or tantalate wherein alkali or alkaline earth metal cations have been exchanged with a catalytically effective amount of cations of said metal.

  15. Metal ion substrate inhibition of ferrochelatase.

    PubMed

    Hunter, Gregory A; Sampson, Matthew P; Ferreira, Gloria C

    2008-08-29

    Ferrochelatase catalyzes the insertion of ferrous iron into protoporphyrin IX to form heme. Robust kinetic analyses of the reaction mechanism are complicated by the instability of ferrous iron in aqueous solution, particularly at alkaline pH values. At pH 7.00 the half-life for spontaneous oxidation of ferrous ion is approximately 2 min in the absence of metal complexing additives, which is sufficient for direct comparisons of alternative metal ion substrates with iron. These analyses reveal that purified recombinant ferrochelatase from both murine and yeast sources inserts not only ferrous iron but also divalent cobalt, zinc, nickel, and copper into protoporphyrin IX to form the corresponding metalloporphyrins but with considerable mechanistic variability. Ferrous iron is the preferred metal ion substrate in terms of apparent k(cat) and is also the only metal ion substrate not subject to severe substrate inhibition. Substrate inhibition occurs in the order Cu(2+) > Zn(2+) > Co(2+) > Ni(2+) and can be alleviated by the addition of metal complexing agents such as beta-mercaptoethanol or imidazole to the reaction buffer. These data indicate the presence of two catalytically significant metal ion binding sites that may coordinately regulate a selective processivity for the various potential metal ion substrates.

  16. Predicting the relative toxicity of metal ions using ion characteristics: Microtox{reg_sign} bioluminescence assay

    SciTech Connect

    McCloskey, J.T.; Newman, M.C.; Clark, S.B.

    1996-10-01

    Quantitative structure-activity relationships have been used to predict the relative toxicity of organic compounds. Although not as common, ion characteristics have also proven useful for predicting the relative toxicity of metal ions. The purpose of this study was to determine if the relative toxicity of metal ions using the Microtox{reg_sign} bioassay was predictable using ion characteristics. Median effect concentrations (EC50s) were determined for 20 metals in a NaNO{sub 3} medium, which reflected freshwater speciation conditions, using the Microtox bacterial assay. The log of EC50 values was modeled using several ion characteristics, and Akaike`s Information Criterion was calculated to determine which ion characteristics provided the best fit. Whether modeling total ion or free ion EC50 values, the one variable which best modeled EC50s was the softness index, while a combination of {chi}{sub m}{sup 2}r ({chi}{sub m} = electronegativity, r = Pauling ionic radius) and {vert_bar}log K{sub OH}{vert_bar} was the best two-variable model. Other variables, including {Delta}E{sub 0} and {chi}{sub m}{sup 2}r (one-variable models) and (AN/{Delta}IP, {Delta}E{sub 0}) and ({chi}{sub m}{sup 2}r, Z{sup 2}/r) (two-variable models), also gave adequate fits. Modeling with speciated (free ion) versus unspeciated (total ion) EC50 values did not improve fits. Modeling mono-, di-, and trivalent metal ions separately improved the models. The authors conclude that ion characteristics can be used to predict the relative toxicity of metal ions whether in freshwater (NaNO{sub 3} medium) or saltwater (NaCl medium) speciation conditions and that this approach can be applied to metal ions varying widely in both valence and binding tendencies.

  17. [THE EFFECT OF METAL IONES AND SPECIFIC CHEMICAL REAGENTS ON THE ACTIVITY OF ASPERGILLUS FLAVUS VAR. ORYZAE AND BACILLUS SUBTILIS α-AMYLASES].

    PubMed

    Avdiyuk, K V; Varbanets, L D

    2015-01-01

    The effect of cations and anions on the activity of Aspergillus flavus var. oryzae and Bacillus subtilis α-amylases showed that the tested enzymes are sensitive to most of cations and resistant to anions. The most significant inhibitory effects on the activity of A. flavus var. oryzae α-amylase have been demonstrated by Al3+ and Fe3+ ions, while on the activity of B. subtilis α-amylase - Hg2+, Cu2+ and Fe3+ ions. Inactivation of A. flavus var. oryzae and B. subtilis α-amylases in the presence of EGTA is indicated on the presence within their structure of metal ions. An important role in the enzymatic catalysis of both enzymes play carboxyl groups as evidenced by their inhibition of 1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide methiodide. Inhibition of B. subtilis α-amylase by p-chloromercuribenzoate, N-ethylmaleimide and sodium sulfite is indicated on the probable involvement of the sulfhydryl groups in the functioning of the enzyme. Unlike most studied glycosidases the tested enzymes do not contain histidine imidazole group in the active center.

  18. Nucleic acid-metal ion interactions in the solid state.

    PubMed

    Aoki, Katsuyuki; Murayama, Kazutaka

    2012-01-01

    Metal ions play a key role in nucleic acid structure and activity. Elucidation of the rules that govern the binding of metal ions is therefore an essential step for better understanding of the nucleic acid functions. This review is as an update to a preceding one (Metal Ions Biol. Syst., 1996, 32, 91-134), in which we offered a general view of metal ion interactions with mono-, di-, tri-, and oligonucleotides in the solid state, based on their crystal structures reported before 1994. In this chapter, we survey all the crystal structures of metal ion complexes with nucleotides involving oligonucleotides reported after 1994 and we have tried to uncover new characteristic metal bonding patterns for mononucleotides and oligonucleotides with A-RNA and A/B/Z-DNA fragments that form duplexes. We do not cover quadruplexes, duplexes with metal-mediated base-pairs, tRNAs, rRNAs in ribosome, ribozymes, and nucleic acid-drug and -protein complexes. Factors that affect metal binding to mononucleotides and oligonucleotide duplexes are also dealt with.

  19. Comparison of activated carbon and oxidized multiwalled carbon nanotubes modified with bis(3-nitrobenzylidene)-1,2-ethanediamine for enrichment of trace amounts of some metal ions.

    PubMed

    Ghaedi, Mehrorang; Montazerozohori, Mortaza; Tabatabie, Maryam; Noormohamadi, Hamid; Haghighi, Alireza Borhan

    2012-01-01

    The efficiency of modified activated carbon (AC) and multiwalled carbon nanotubes (MWCNTs) for the separation/preconcentration and determination of Co, Cd, Pb, Zn, and Cu following their complexation by bis(3-nitrobenzylidene)-1,2-ethanediamine has been described and compared. A one-at-a-time optimization method investigated the influence of various parameters that significantly influence the recoveries of the studied metal ions. At the optimum values of all variables, the response was linear over the range of 0.01-0.3 microg/mL, and detection limit (3 SDb/m, n = 10) was between 1.41-2.05 ng/mL for both sorbents while the preconcentration factor was 100 for AC and 500 for MWCNTs. The method was successfully applied for preconcentration and determination of trace amount of the aforementioned ions in various real samples such as orange, lettuce, bread, and pear.

  20. Transition metal ions effect on the properties and photocatalytic activity of nanocrystalline TiO2 prepared in an ionic liquid.

    PubMed

    Ghasemi, S; Rahimnejad, S; Setayesh, S Rahman; Rohani, S; Gholami, M R

    2009-12-30

    TiO(2) and transition metal (Cr, Mn, Fe, Co, Ni, Cu, and Zn) doped TiO(2) nanoparticles were synthesized by the sol-gel method using 2-hydroxylethylammonium formate as an ionic liquid. All the prepared samples were calcined at 500 degrees C and characterized by X-ray diffraction (XRD), BET surface area determination, energy dispersive X-ray (EDX) analysis, diffuse reflectance spectroscopy (DRS), and Fourier transformed infrared (FT-IR) techniques. The studies revealed that transition metal (TM) doped nanoparticles have smaller crystalline size and higher surface area than pure TiO(2). Dopant ions in the TiO(2) structure caused significant absorption shift into the visible region. The results of photodegradation of Acid Blue92 (AB92) in aqueous medium under UV light showed that photocatalytic activity of TiO(2) nanoparticles was significantly enhanced by the presence of some transition metal ions. Chemical Oxygen Demand (COD) of dye solutions were done at regular intervals gave a good idea about mineralization of dye.

  1. Metal Ion Modeling Using Classical Mechanics.

    PubMed

    Li, Pengfei; Merz, Kenneth M

    2017-02-08

    Metal ions play significant roles in numerous fields including chemistry, geochemistry, biochemistry, and materials science. With computational tools increasingly becoming important in chemical research, methods have emerged to effectively face the challenge of modeling metal ions in the gas, aqueous, and solid phases. Herein, we review both quantum and classical modeling strategies for metal ion-containing systems that have been developed over the past few decades. This Review focuses on classical metal ion modeling based on unpolarized models (including the nonbonded, bonded, cationic dummy atom, and combined models), polarizable models (e.g., the fluctuating charge, Drude oscillator, and the induced dipole models), the angular overlap model, and valence bond-based models. Quantum mechanical studies of metal ion-containing systems at the semiempirical, ab initio, and density functional levels of theory are reviewed as well with a particular focus on how these methods inform classical modeling efforts. Finally, conclusions and future prospects and directions are offered that will further enhance the classical modeling of metal ion-containing systems.

  2. Metal Ion Modeling Using Classical Mechanics

    PubMed Central

    2017-01-01

    Metal ions play significant roles in numerous fields including chemistry, geochemistry, biochemistry, and materials science. With computational tools increasingly becoming important in chemical research, methods have emerged to effectively face the challenge of modeling metal ions in the gas, aqueous, and solid phases. Herein, we review both quantum and classical modeling strategies for metal ion-containing systems that have been developed over the past few decades. This Review focuses on classical metal ion modeling based on unpolarized models (including the nonbonded, bonded, cationic dummy atom, and combined models), polarizable models (e.g., the fluctuating charge, Drude oscillator, and the induced dipole models), the angular overlap model, and valence bond-based models. Quantum mechanical studies of metal ion-containing systems at the semiempirical, ab initio, and density functional levels of theory are reviewed as well with a particular focus on how these methods inform classical modeling efforts. Finally, conclusions and future prospects and directions are offered that will further enhance the classical modeling of metal ion-containing systems. PMID:28045509

  3. Three-dimensional activated graphene network-sulfonate-terminated polymer nanocomposite as a new electrode material for the sensitive determination of dopamine and heavy metal ions.

    PubMed

    Yuan, Xiaoyan; Zhang, Yijia; Yang, Lu; Deng, Wenfang; Tan, Yueming; Ma, Ming; Xie, Qingji

    2015-03-07

    We report here that three-dimensional activated graphene networks (3DAGNs) are a better matrix to prepare graphene-polymer nanocomposites for sensitive electroanalysis than two-dimensional graphene nanosheets (2DGNs). 3DAGNs were synthesized in advance by the direct carbonization and simultaneous chemical activation of a cobalt ion-impregnated D113-type ion exchange resin, which showed an interconnected network structure and a large specific surface area. Then, the 3DAGN-sulfonate-terminated polymer (STP) nanocomposite was prepared via the in situ chemical co-polymerization of m-aminobenzene sulfonic acid and aniline in the presence of 3DAGNs. The 3DAGN-STP nanocomposite can adsorb dopamine (DA) and heavy metal ions, which was confirmed by quartz crystal microbalance studies. The 3DAGN-STP modified glassy carbon electrode (GCE) was used for the electrochemical detection of DA in the presence of ascorbic acid and uric acid, with a linear response range of 0.1-32 μM and a limit of detection of 10 nM. In addition, differential pulse voltammetry was used for the simultaneous determination of Cd(2+) and Pb(2+) at the 3DAGN-STP/GCE further modified with a bismuth film, exhibiting linear response ranges of 1-70 μg L(-1) for Cd(2+) and 1-80 μg L(-1) for Pb(2+) with limits of detection of 0.1 μg L(-1) for Cd(2+) and 0.2 μg L(-1) for Pb(2+). Because the 3DAGN-STP can integrate the advantages of 3DAGNs with STPs, the 3DAGN-STP/GCE was more sensitive than the bare GCE, 3DAGN/GCE, and 2DGN-STP/GCE for the determination of DA and heavy metal ions.

  4. ION EXCHANGE SOFTENING: EFFECTS ON METAL CONCENTRATIONS

    EPA Science Inventory

    A corrosion control pipe loop study to evaluate the effect of ion exchange water softening on metal leaching from household plumbing materials was conducted on two different water qualities having different pH's and hardness levels. The results showed that removing hardness ions ...

  5. Metal-ion recycle technology for metal electroplating waste waters

    SciTech Connect

    Sauer, N.N.; Smith, B.F.

    1993-06-01

    As a result of a collaboration with Boeing Aerospace, the authors have begun a program to identify suitable treatments or to develop new treatments for electroplating baths. The target baths are mixed-metal or alloy baths that are being integrated into the Boeing electroplating complex. These baths, which are designed to replace highly toxic chromium and cadmium baths, contain mixtures of two metals, either nickel-tungsten, nickel-zinc, or zinc-tin. This report reviews the literature and details currently available on emerging technologies that could affect recovery of metals from electroplating baths under development by Boeing Aerospace. This literature survey summarizes technologies relevant to the recovery of metals from electroplating processes. The authors expanded the scope to investigate single metal ion recovery technologies that could be applied to metal ion recovery from alloy baths. This review clearly showed that the electroplating industry has traditionally relied on precipitation and more recently on electrowinning as its waste treatment methods. Despite the almost ubiquitous use of precipitation to remove contaminant metal ions from waste electroplating baths and rinse waters, this technology is clearly no longer feasible for the electroplating industry for several reasons. First, disposal of unstabilized sludge is no longer allowed by law. Second, these methods are no longer adequate as metal-removal techniques because they cannot meet stringent new metal discharge limits. Third, precious resources are being wasted or discarded because these methods do not readily permit recovery of the target metal ions. As a result, emerging technologies for metal recovery are beginning to see application to electroplating waste recycle. This report summarizes current research in these areas. Included are descriptions of various membrane technologies, such as reverse osmosis and ultrafiltration, ion exchange and chelating polymer technology, and electrodialysis.

  6. Metal vapor arc ion plating

    DOEpatents

    Bertram, L.A.; Fisher, R.W.; Mattox, D.M.; Zanner, F.J.

    1986-09-09

    A method and apparatus for ion plating are described. The apparatus uses more negative than a first electrode voltage in a vacuum arc remelt system to attract low energy ions from the anode electrode to the article to be plated. 2 figs.

  7. Comparative studies on adsorptive removal of heavy metal ions by biosorbent, bio-char and activated carbon obtained from low cost agro-residue.

    PubMed

    Kırbıyık, Çisem; Pütün, Ayşe Eren; Pütün, Ersan

    2016-01-01

    In this study, Fe(III) and Cr(III) metal ion adsorption processes were carried out with three adsorbents in batch experiments and their adsorption performance was compared. These adsorbents were sesame stalk without pretreatment, bio-char derived from thermal decomposition of biomass, and activated carbon which was obtained from chemical activation of biomass. Scanning electron microscopy and Fourier transform-infrared techniques were used for characterization of adsorbents. The optimum conditions for the adsorption process were obtained by observing the influences of solution pH, adsorbent dosage, initial solution concentration, contact time and temperature. The optimum adsorption efficiencies were determined at pH 2.8 and pH 4.0 for Fe(III) and Cr(III) metal ion solutions, respectively. The experimental data were modelled by different isotherm models and the equilibriums were well described by the Langmuir adsorption isotherm model. The pseudo-first-order, pseudo-second-order kinetic, intra-particle diffusion and Elovich models were applied to analyze the kinetic data and to evaluate rate constants. The pseudo-second-order kinetic model gave a better fit than the others. The thermodynamic parameters, such as Gibbs free energy change ΔG°, standard enthalpy change ΔH° and standard entropy change ΔS° were evaluated. The thermodynamic study showed the adsorption was a spontaneous endothermic process.

  8. Bioavailability of Metal Ions and Evolutionary Adaptation

    PubMed Central

    Hong Enriquez, Rolando P.; Do, Trang N.

    2012-01-01

    The evolution of life on earth has been a long process that began nearly 3.5 × 109 years ago. In their initial moments, evolution was mainly influenced by anaerobic environments; with the rise of O2 and the corresponding change in bioavailability of metal ions, new mechanisms of survival were created. Here we review the relationships between ancient atmospheric conditions, metal ion bioavailability and adaptation of metals homeostasis during early evolution. A general picture linking geochemistry, biochemistry and homeostasis is supported by the reviewed literature and is further illustrated in this report using simple database searches. PMID:25371266

  9. The domain of unknown function DUF1521 exhibits metal ion-inducible autocleavage activity - a novel example from a putative effector protein of Vibrio coralliilyticus ATCC BAA-450.

    PubMed

    Schirrmeister, Jana; Zocher, Sara; Flor, Liane; Göttfert, Michael; Zehner, Susanne

    2013-06-01

    Vibrio coralliilyticus ATCC BAA-450 is a pathogen causing coral bleaching at elevated seawater temperatures. Based on the available genome sequence, the strain has a type III secretion system. Within the corresponding gene cluster, VIC_001052 is encoded, which contains a conserved domain of unknown function DUF1521. In this study, we show that the purified domain exhibits autocleavage activity in the presence of several divalent metal ions, for example, calcium and manganese but not with magnesium or zinc. Autocleavage is not affected by temperatures between 0 and 30 °C, indicating that seawater temperature is not a critical factor for this activity. The DUF1521 domain and the cleavage site are conserved in several proteins from proteobacteria, suggesting a similar cleavage activity for these proteins.

  10. Computational Design of Metal Ion Sequestering Agents

    SciTech Connect

    Hay, Benjamin P.; Rapko, Brian M.

    2006-06-01

    Organic ligands that exhibit a high degree of metal ion recognition are essential precursors for developing separation processes and sensors for metal ions. Since the beginning of the nuclear era, much research has focused on discovering ligands that target specific radionuclides. Members of the Group 1A and 2A cations (e.g., Cs, Sr, Ra) and the f-block metals (actinides and lanthanides) are of primary concern to DOE. Although there has been some success in identifying ligand architectures that exhibit a degree of metal ion recognition, the ability to control binding affinity and selectivity remains a significant challenge. The traditional approach for discovering such ligands has involved lengthy programs of organic synthesis and testing that, in the absence of reliable methods for screening compounds before synthesis, have resulted in much wasted research effort.

  11. Computational Design of Metal Ion Sequestering Agents

    SciTech Connect

    Hay, Benjamin P.; Rapko, Brian M.

    2005-06-15

    Organic ligands that exhibit a high degree of metal ion recognition are essential precursors for developing separation processes and sensors for metal ions. Since the beginning of the nuclear era, much research has focused on discovering ligands that target specific radionuclides. Members of the Group 1A and 2A cations (e.g., Cs, Sr, Ra) and the f-block metals (actinides and lanthanides) are of primary concern to DOE. Although there has been some success in identifying ligand architectures that exhibit a degree of metal ion recognition, the ability to control binding affinity and selectivity remains a significant challenge. The traditional approach for discovering such ligands has involved lengthy programs of organic synthesis and testing that, in the absence of reliable methods for screening compounds before synthesis, have resulted in much wasted research effort.

  12. Purification and characterization of the carbonic anhydrase enzyme from Black Sea trout (Salmo trutta Labrax Coruhensis) kidney and inhibition effects of some metal ions on enzyme activity.

    PubMed

    Kucuk, Murat; Gulcin, İlhami

    2016-06-01

    In this study, the carbonic anhydrase (CA) enzyme was purified from Black Sea trout (Salmo trutta Labrax Coruhensis) kidney with a specific activity of 603.77EU/mg and a yield of 35.5% using Sepharose-4B-l-tyrosine- sulphanilamide affinity column chromatography. For determining the enzyme purity and subunit molecular mass, sodiumdodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) was performed and single band was observed. The molecular mass of subunit was found approximately 29.71kDa. The optimum temperature, activation energy (Ea), activation enthalpy (ΔH) and Q10 values were obtained from Arrhenius plot. Km and Vmax values for p-nitrophenyl acetate of the purified enzyme were calculated from Lineweaver-Burk graphs. In addition, the inhibitory effects of different heavy metal ions (Fe(2+), Pb(2+), Co(2+), Ag(+) and Cu(2+)) on Black Sea trout kidney tissue CA enzyme activities were investigated by using esterase method under in vitro conditions. The heavy metal concentrations inhibiting 50% of enzyme activity (IC50) were obtained. Finally Ki values and inhibition types were calculated from Lineweaver-Burk graphs.

  13. Separation of metal ions in nitrate solution by ultrasonic atomization

    NASA Astrophysics Data System (ADS)

    Sato, Masanori; Ikeno, Masayuki; Fujii, Toshitaka

    2004-11-01

    In the ultrasonic atomization of metal nitrate solutions, the molar ratio of metal ions is changed between solution and mist. Small molar metal ions tend to be transferred to mist by ultrasonic wave acceleration, while large molar ions tend to remain in solution. As a result, metal ions can be separated by ultrasonic atomization. We show experimental data and propose a conceptual mechanism for the ultrasonic separation of metal ions.

  14. Separation of metal ions in nitrate solution by ultrasonic atomization.

    PubMed

    Sato, Masanori; Ikeno, Masayuki; Fujii, Toshitaka

    2004-11-15

    In the ultrasonic atomization of metal nitrate solutions, the molar ratio of metal ions is changed between solution and mist. Small molar metal ions tend to be transferred to mist by ultrasonic wave acceleration, while large molar ions tend to remain in solution. As a result, metal ions can be separated by ultrasonic atomization. We show experimental data and propose a conceptual mechanism for the ultrasonic separation of metal ions.

  15. Coordination modes of bidentate lornoxicam drug with some transition metal ions. Synthesis, characterization and in vitro antimicrobial and antibreastic cancer activity studies.

    PubMed

    Mahmoud, Walaa H; Mohamed, Gehad G; El-Dessouky, Maher M I

    2014-03-25

    The NSAID lornoxicam (LOR) drug was used for complex formation reactions with different metal salts like Cr(III), Mn(II), Fe(III) and Ni(II) chlorides and Fe(II), Co(II), Cu(II) and Zn(II) borates. Mononuclear complexes of these metals are obtained that coordinated to NO sites of LOR ligand molecule. The nature of bonding and the stereochemistry of the complexes have been deduced from elemental analyses, IR, UV-Vis, (1)H NMR, mass, electronic spectra, magnetic susceptibility and ESR spectral studies, conductivity measurements, thermogravimetric analyses (TG-DTG) and further confirmed by X-ray powder diffraction. The activation thermodynamic parameters are calculated using Coats-Redfern and Horowitz-Metzger methods. The data show that the complexes have composition of ML2 type except for Fe(II) where the type is [ML3]. The electronic absorption spectral data of the complexes suggest an octahedral geometry around the central metal ion for all the complexes. The antimicrobial data reveals that LOR ligand in solution show inhibition capacity less or sometimes more than the corresponding complexes against all the species under study. In order to establish their future potential in biomedical applications, anticancer evaluation studies against standard breast cancer cell lines (MCF7) was performed using different concentrations. The obtained results indicate high inhibition activity for Cr(III), Fe(II) and Cu(II) complexes against breast cancer cell line (MCF7) and recommends them for testing as antitumor agents.

  16. Coordination modes of bidentate lornoxicam drug with some transition metal ions. Synthesis, characterization and in vitro antimicrobial and antibreastic cancer activity studies

    NASA Astrophysics Data System (ADS)

    Mahmoud, Walaa H.; Mohamed, Gehad G.; El-Dessouky, Maher M. I.

    2014-03-01

    The NSAID lornoxicam (LOR) drug was used for complex formation reactions with different metal salts like Cr(III), Mn(II), Fe(III) and Ni(II) chlorides and Fe(II), Co(II), Cu(II) and Zn(II) borates. Mononuclear complexes of these metals are obtained that coordinated to NO sites of LOR ligand molecule. The nature of bonding and the stereochemistry of the complexes have been deduced from elemental analyses, IR, UV-Vis, 1H NMR, mass, electronic spectra, magnetic susceptibility and ESR spectral studies, conductivity measurements, thermogravimetric analyses (TG-DTG) and further confirmed by X-ray powder diffraction. The activation thermodynamic parameters are calculated using Coats-Redfern and Horowitz-Metzger methods. The data show that the complexes have composition of ML2 type except for Fe(II) where the type is [ML3]. The electronic absorption spectral data of the complexes suggest an octahedral geometry around the central metal ion for all the complexes. The antimicrobial data reveals that LOR ligand in solution show inhibition capacity less or sometimes more than the corresponding complexes against all the species under study. In order to establish their future potential in biomedical applications, anticancer evaluation studies against standard breast cancer cell lines (MCF7) was performed using different concentrations. The obtained results indicate high inhibition activity for Cr(III), Fe(II) and Cu(II) complexes against breast cancer cell line (MCF7) and recommends them for testing as antitumor agents.

  17. Computational Design of Metal Ion Sequestering Agents

    SciTech Connect

    Hay, Benjamin P.; Rapko, Brian M.

    2004-06-15

    Organic ligands that exhibit a high degree of metal ion recognition are essential precursors for developing separation processes and sensors for metal ions. Since the beginning of the nuclear era, much research has focused on discovering ligands that target specific radionuclides. Members of the Group 1A and 2A cations (e.g., Cs, Sr, Ra) and the f-block metals (actinides and lanthanides) are of primary concern to DOE. Although there has been some success in identifying ligand architectures that exhibit a degree of metal ion recognition, the ability to control binding affinity and selectivity remains a significant challenge. The traditional approach for discovering such ligands has involved lengthy programs of organic synthesis and testing that, in the absence of reliable methods for screening compounds before synthesis, have resulted in much wasted research effort. This project seeks to enhance and strengthen the traditional approach through computer-aided design of new and improved host molecules. Accurate electronic structure calculations are coupled with experimental data to provide fundamental information about ligand structure and the nature of metal-donor group interactions (design criteria). This fundamental information then is used in a molecular mechanics model (MM) that helps us rapidly screen proposed ligand architectures and select the best members from a set of potential candidates. By using combinatorial methods, molecule building software has been developed that generates large numbers of candidate architectures for a given set of donor groups. The specific goals of this project are: further understand the structural and energetic aspects of individual donor group- metal ion interactions and incorporate this information within the MM framework; further develop and evaluate approaches for correlating ligand structure with reactivity toward metal ions, in other words, screening capability; use molecule structure building software to generate large

  18. Computational Design of Metal Ion Sequestering Agents

    SciTech Connect

    Hay, Benjamin P.; Dixon, David A.; Rapko, Brian M.

    2003-06-01

    Organic ligands that exhibit a high degree of metal ion recognition are essential precursors for developing separation processes and sensors for metal ions. Since the beginning of the nuclear era, much research has focused on discovering ligands that target specific radionuclides. Members of the Group 1A and 2A cations (e.g., Cs, Sr, Ra) and the f-block metals (actinides and lanthanides) are of primary concern to DOE. Although there has been some success in identifying ligand architectures that exhibit a degree of metal ion recognition, the ability to control binding affinity and selectivity remains a significant challenge. The traditional approach for discovering such ligands has involved lengthy programs of organic synthesis and testing that, in the absence of reliable methods for screening compounds before synthesis, have resulted in much wasted research effort. This project seeks to enhance and strengthen the traditional approach through computer-aided design of new and improved host molecules. Accurate electronic structure calculations are coupled with experimental data to provide fundamental information about ligand structure and the nature of metal-donor group interactions (design criteria). This fundamental information then is used in a molecular mechanics model (MM3) that helps us rapidly screen proposed ligand architectures and select the best members from a set of potential candidates. By using combinatorial methods, molecule building software has been developed that generates large numbers of candidate architectures for a given set of donor groups. The specific goals of this project are: (1) further understand the structural and energetic aspects of individual donor group-metal ion interactions and incorporate this information within the MM3 framework; (2) further develop and evaluate approaches for correlating ligand structure with reactivity toward metal ions, in other words, screening capability; (3) use molecule structure building software to

  19. Computational Design of Metal Ion Sequestering Agents

    SciTech Connect

    Hay, Benjamin P.; Dixon, David A.; Rapko, Brian M.

    2002-06-01

    Organic ligands that exhibit a high degree of metal ion recognition are essential precursors for developing separation processes and sensors for metal ions. Since the beginning of the nuclear era, much research has focused on discovering ligands that target specific radionuclides. Members of the Group 1A and 2A cations (e.g., Cs, Sr, Ra) and the f-block metals (actinides and lanthanides) are of primary concern to the U.S. Department of Energy (DOE). Although there has been some success in identifying ligand architectures that exhibit a degree of metal ion recognition, the ability to control binding affinity and selectivity remains a significant challenge. The traditional approach for discovering such ligands has involved lengthy programs of organic synthesis and testing that, in the absence of reliable methods for screening compounds before synthesis, have resulted in much wasted research effort. This project seeks to enhance and strengthen the traditional approach through computer-aided design of new and improved host molecules. Accurate electronic structure calculations are coupled with experimental data to provide fundamental information about ligand structure and the nature of metal-donor group interactions (design criteria). This fundamental information then is used in a molecular mechanics model (MM3) that helps us rapidly screen proposed ligand architectures and select the best members from a set of potential candidates. By using combinatorial methods, molecule building software has been developed that generates large numbers of candidate architectures for a given set of donor groups. The specific objectives of this project are as follows: (1) Further understand the structural and energetic aspects of individual donor group- metal ion interactions and incorporate this information within the framework of MM3. (2) Further develop and evaluate approaches for correlating ligand structure with reactivity toward metal ions, in other words, screening capability. (3

  20. Computational Design of Metal Ion Sequestering Agents

    SciTech Connect

    Hay, Benjamin P.; Rapko, Brian M.

    2005-06-15

    Organic ligands that exhibit a high degree of metal ion recognition are essential precursors for developing separation processes and sensors for metal ions. Since the beginning of the nuclear era, much research has focused on discovering ligands that target specific radionuclides. Members of the Group 1A and 2A cations (e.g., Cs, Sr, Ra) and the f-block metals (actinides and lanthanides) are of primary concern to DOE. Although there has been some success in identifying ligand architectures that exhibit a degree of metal ion recognition, the ability to control binding affinity and selectivity remains a significant challenge. The traditional approach for discovering such ligands has involved lengthy programs of organic synthesis and testing that, in the absence of reliable methods for screening compounds before synthesis, have resulted in much wasted research effort. This project seeks to enhance and strengthen the traditional approach through computer-aided design of new and improved host molecules. Accurate electronic structure calculations are coupled with experimental data to provide fundamental information about ligand structure and the nature of metal-donor group interactions (design criteria). This fundamental information then is used in a molecular mechanics model (MM) that helps us rapidly screen proposed ligand architectures and select the best members from a set of potential candidates. By using combinatorial methods, molecule building software has been developed that generates large numbers of candidate architectures for a given set of donor groups. The specific goals of this project are: • further understand the structural and energetic aspects of individual donor group- metal ion interactions and incorporate this information within the MM framework • further develop and evaluate approaches for correlating ligand structure with reactivity toward metal ions, in other words, screening capability • use molecule structure building software to generate

  1. Metal ion separations by supported liquid membranes

    SciTech Connect

    Gyves, J. de; San Miguel, E.R. de

    1999-06-01

    Carrier-mediated transport through supported liquid membranes is currently recognized as a potentially valuable technology for selective separation and concentration of toxic and valuable metal ions. In this paper, a review of the fundamental aspects concerning metal ion transport and the influencing factors are surveyed in terms of data modeling, membrane efficiency (permeability, selectivity, stability), and data acquisition and evaluation. An account of the information reviewed demonstrates the need for critical reflection on system performances in order to accomplish scaling up operations. On the same basis, an attempt to outline some future trends in the field is presented.

  2. Solvent effects and alkali metal ion catalysis in phosphodiester hydrolysis.

    PubMed

    Gomez-Tagle, Paola; Vargas-Zúñiga, Idania; Taran, Olga; Yatsimirsky, Anatoly K

    2006-12-22

    The kinetics of the alkaline hydrolysis of bis(p-nitrophenyl) phosphate (BNPP) have been studied in aqueous DMSO, dioxane, and MeCN. In all solvent mixtures the reaction rate steadily decreases to half of its value in pure water in the range of 0-70 vol % of organic cosolvent and sharply increases in mixtures with lower water content. Correlations based on different scales of solvent empirical parameters failed to describe the solvent effect in this system, but it can be satisfactorily treated in terms of a simplified stepwise solvent-exchange model. Alkali metal ions catalyze the BNPP hydrolysis but do not affect the rate of hydrolysis of neutral phosphotriester p-nitrophenyl diphenyl phosphate in DMSO-rich mixtures. The catalytic activity decreases in the order Li+ > Na+ > K+ > Rb+ > Cs+. For all cations except Na+, the reaction rate is first-order in metal ion. With Na+, both first- and second-order kinetics in metal ions are observed. Binding constants of cations to the dianionic transition state of BNPP alkaline hydrolysis are of the same order of magnitude and show a similar trend as their binding constants to p-nitrophenyl phosphate dianion employed as a transition-state model. The appearance of alkali metal ion catalysis in a medium, which solvates metal ions stronger than water, is attributed to the increased affinity of cations to dianions, which undergo a strong destabilization in the presence of an aprotic dipolar cosolvent.

  3. Adsorbent for metal ions and method of making and using

    DOEpatents

    White, Lloyd R.; Lundquist, Susan H.

    2000-01-01

    A method comprises the step of spray-drying a solution or slurry comprising (alkali metal or ammonium) (metal) hexacyanoferrate particles in a liquid, to provide monodisperse, substantially spherical particles in a yield of at least 70 percent of theoretical yield and having a particle size in the range of 1 to 500 micrometers, said particles being active towards Cs ions. The particles, which can be of a single salt or a combination of salts, can be used free flowing, in columns or beds, or entrapped in a nonwoven, fibrous web or matrix or a cast porous membrane, to selectively remove Cs ions from aqueous solutions.

  4. Adsorbent for metal ions and method of making and using

    DOEpatents

    White, Lloyd R.; Lundquist, Susan H.

    1999-01-01

    A method comprises the step of spray-drying a solution or slurry comprising (alkali metal or ammonium) (metal) hexacyanoferrate particles in a liquid, to provide monodisperse, substantially spherical particles in a yield of at least 70 percent of theoretical yield and having a particle size in the range of 1 to 500 micrometers, said particles being active towards Cs ions. The particles, which can be of a single salt or a combination of salts, can be used free flowing, in columns or beds, or entrapped in a nonwoven, fibrous web or matrix or a cast porous membrane, to selectively remove Cs ions from aqueous solutions.

  5. Adsorbent for metal ions and method of making and using

    DOEpatents

    White, L.R.; Lundquist, S.H.

    1999-08-10

    A method comprises the step of spray-drying a solution or slurry comprising (alkali metal or ammonium) (metal) hexacyanoferrate particles in a liquid, to provide monodisperse, substantially spherical particles in a yield of at least 70 percent of theoretical yield and having a particle size in the range of 1 to 500 micrometers, said particles being active towards Cs ions. The particles, which can be of a single salt or a combination of salts, can be used free flowing, in columns or beds, or entrapped in a nonwoven, fibrous web or matrix or a cast porous membrane, to selectively remove Cs ions from aqueous solutions. 2 figs.

  6. Determination of metal ions in biological purification of waste waters

    SciTech Connect

    Tikhomirova, L.N.; Spiridonova, N.N.; Mandzhgaladze, I.D.

    1994-12-01

    Chromium, nickel, copper, zinc, and manganese were determined in active sludge extracted for utilization from sewage purification works in biological purification of waste waters. The measurements were carried out by the atomic absorption method and with Merck colorimetric kits for rapid determination of metal ions. The results obtained by the rapid colorimetric method agree fairly well with those obtained by the atomic absorption method, which makes it possible to recommend rapid colorimetric methods for routine analysis of biological objects for the content of ions of heavy metals.

  7. Effect of metal ions on positron annihilation characteristics in metal ion containing epoxies

    NASA Technical Reports Server (NTRS)

    Singh, J. J.; St. Clair, A. K.; Stoakley, D. M.; Holt, W. H.; Mock, W., Jr.

    1984-01-01

    In the course of developing improved moisture-resistant epoxy resins, two different types of epoxy resins containing variable mole ratios of chromium ions per polymer repeat unit were developed. Positron annihilation characteristics have been investigated in these resins as a function of their metal ion content. In both cases, the presence of metal ions reduces the lifetime as well as the intensity of the long life component. The long life component intensity reduction is considerably more pronounced than the lifetime reduction. These results have been discussed in terms of increased unpaired electron density at Ps formation sites due to the presence of chromium ions in the matrix.

  8. Mutation of the aspartic acid residues of the GDD sequence motif of poliovirus RNA-dependent RNA polymerase results in enzymes with altered metal ion requirements for activity.

    PubMed Central

    Jablonski, S A; Morrow, C D

    1995-01-01

    The poliovirus RNA-dependent RNA polymerase, 3Dpol, is known to share a region of sequence homology with all RNA polymerases centered at the GDD amino acid motif. The two aspartic acids have been postulated to be involved in the catalytic activity and metal ion coordination of the enzyme. To test this hypothesis, we have utilized oligonucleotide site-directed mutagenesis to generate defined mutations in the aspartic acids of the GDD motif of the 3Dpol gene. The codon for the first aspartate (3D-D-328 [D refers to the single amino acid change, and the number refers to its position in the polymerase]) was changed to that for glutamic acid, histidine, asparagine, or glutamine; the codons for both aspartic acids were simultaneously changed to those for glutamic acids; and the codon for the second aspartic acid (3D-D-329) was changed to that for glutamic acid or asparagine. The mutant enzymes were expressed in Escherichia coli, and the in vitro poly(U) polymerase activity was characterized. All of the mutant 3Dpol enzymes were enzymatically inactive in vitro when tested over a range of Mg2+ concentrations. However, when Mn2+ was substituted for Mg2+ in the in vitro assays, the mutant that substituted the second aspartic acid for asparagine (3D-N-329) was active. To further substantiate this finding, a series of different transition metal ions were substituted for Mg2+ in the poly(U) polymerase assay. The wild-type enzyme was active with all metals except Ca2+, while the 3D-N-329 mutant was active only when FeC6H7O5 was used in the reaction. To determine the effects of the mutations on poliovirus replication, the mutant 3Dpol genes were subcloned into an infectious cDNA of poliovirus. The cDNAs containing the mutant 3Dpol genes did not produce infectious virus when transfected into tissue culture cells under standard conditions. Because of the activity of the 3D-N-329 mutant in the presence of Fe2+ and Mn2+, transfections were also performed in the presence of the

  9. Chitosan Hydrogel Structure Modulated by Metal Ions

    PubMed Central

    Nie, Jingyi; Wang, Zhengke; Hu, Qiaoling

    2016-01-01

    As one of the most important polysaccharide, chitosan (CS) has generated a great deal of interest for its desirable properties and wide applications. In the utilization of CS materials, hydrogel is a major and vital branch. CS has the ability to coordinate with many metal ions by a chelation mechanism. While most researchers focused on the applications of complexes between CS and metal ions, the complexes can also influence gelation process and structure of CS hydrogel. In the present work, such influence was studied with different metal ions, revealing two different kinds of mechanisms. Strong affinity between CS and metal ions leads to structural transition from orientation to multi-layers, while weak affinity leads to composite gel with in-situ formed inorganic particles. The study gave a better understanding of the gelation mechanism and provided strategies for the modulation of hydrogel morphology, which benefited the design of new CS-based materials with hierarchical structure and facilitated the utilization of polysaccharide resources. PMID:27777398

  10. Chitosan Hydrogel Structure Modulated by Metal Ions

    NASA Astrophysics Data System (ADS)

    Nie, Jingyi; Wang, Zhengke; Hu, Qiaoling

    2016-10-01

    As one of the most important polysaccharide, chitosan (CS) has generated a great deal of interest for its desirable properties and wide applications. In the utilization of CS materials, hydrogel is a major and vital branch. CS has the ability to coordinate with many metal ions by a chelation mechanism. While most researchers focused on the applications of complexes between CS and metal ions, the complexes can also influence gelation process and structure of CS hydrogel. In the present work, such influence was studied with different metal ions, revealing two different kinds of mechanisms. Strong affinity between CS and metal ions leads to structural transition from orientation to multi-layers, while weak affinity leads to composite gel with in-situ formed inorganic particles. The study gave a better understanding of the gelation mechanism and provided strategies for the modulation of hydrogel morphology, which benefited the design of new CS-based materials with hierarchical structure and facilitated the utilization of polysaccharide resources.

  11. IMMUNOASSAYS FOR METAL IONS. (R824029)

    EPA Science Inventory

    Abstract

    Antibodies that recognize chelated forms of metal ions have been used to construct immunoassays for Cd(II), Hg(II), Pb(II), and Ni(II). In this paper, the format of these immunoassays is described and the binding properties of three monoclonal antibodies direc...

  12. Material Removes Heavy Metal Ions From Water

    NASA Technical Reports Server (NTRS)

    Philipp, Warren H., Jr.; Street, Kenneth W.; Hill, Carol; Savino, Joseph M.

    1995-01-01

    New high capacity ion-exchange polymer material removes toxic metal cations from contaminated water. Offers several advantages. High sensitivities for such heavy metals as lead, cadmium, and copper and capable of reducing concentrations in aqueous solutions to parts-per-billion range. Removes cations even when calcium present. Material made into variety of forms, such as thin films, coatings, pellets, and fibers. As result, adapted to many applications to purify contaminated water, usually hard wherever found, whether in wastewater-treatment systems, lakes, ponds, industrial plants, or homes. Another important feature that adsorbed metals easily reclaimed by either destructive or nondestructive process. Other tests show ion-exchange polymer made inexpensively; easy to use; strong, flexible, not easily torn; and chemically stable in storage, in aqueous solutions, and in acidic or basic solution.

  13. DNA breakage induced by 1,2,4-benzenetriol: relative contributions of oxygen-derived active species and transition metal ions.

    PubMed

    Li, A S; Bandy, B; Tsang, S; Davison, A J

    2001-05-01

    We report here the relative roles of metals and selected reactive oxygen species in DNA damage by the genotoxic benzene metabolite 1,2,4-benzenetriol, and the interactions of antioxidants in affording protection. 1,2,4-Benzenetriol induces scission in supercoiled phage DNA in neutral aqueous solution with an effective dose (ED(50)) of 6.7 microM for 50% cleavage of 2.05 microg/ml supercoiled PM2 DNA. In decreasing order of effectiveness: catalase (20 U/ml), formate (25 mM), superoxide dismutase (20 U/ml), and mannitol (50 mM) protected, from 85 to 28%. Evidently, H(2)O(2) is the dominant active species, with O(2)(*)(-) and *OH playing subordinate roles. Desferrioxamine or EDTA inhibited DNA breakage by 81-85%, despite accelerating 1,2,4-benzenetriol autoxidation. Consistent with this suggestion of a crucial role for metals, addition of cupric, cuprous, ferric, or ferrous ions enhanced DNA breakage, with copper being more active than iron. Combinations of scavengers protected more effectively than any single scavenger alone, with implications for antioxidants acting in concert in living cells. Synergistic combinations were superoxide dismutase with *OH scavengers, superoxide dismutase with desferrioxamine, and catalase with desferrioxamine. Antagonistic (preemptive) combinations were catalase with superoxide dismutase, desferrioxamine with *OH scavengers, and catalase with *OH scavengers. The most striking aspect of synergism was the extent to which metal chelation (desferrioxamine) acted synergistically with either catalase or superoxide dismutase to provide virtually complete protection. Concluding, 1,2,4-benzenetriol-induced DNA damage occurs mainly by site-specific, Fenton-type mechanisms, involving synergism between several reactive intermediates. Multiple antioxidant actions are needed for effective protection.

  14. The Crystal Structure of a Quercetin 2,3-Dioxygenase from Bacillus subtilis Suggests Modulation of Enzyme Activity by a Change in the Metal Ion at the Active Site(s)

    SciTech Connect

    Gopal, B.; Madan, Lalima L.; Betz, Stephen F.; Kossiakoff, Anthony A.

    2010-11-10

    Common structural motifs, such as the cupin domains, are found in enzymes performing different biochemical functions while retaining a similar active site configuration and structural scaffold. The soil bacterium Bacillus subtilis has 20 cupin genes (0.5% of the total genome) with up to 14% of its genes in the form of doublets, thus making it an attractive system for studying the effects of gene duplication. There are four bicupins in B. subtilis encoded by the genes yvrK, yoaN, yxaG, and ywfC. The gene products of yvrK and yoaN function as oxalate decarboxylases with a manganese ion at the active site(s), whereas YwfC is a bacitracin synthetase. Here we present the crystal structure of YxaG, a novel iron-containing quercetin 2,3-dioxygenase with one active site in each cupin domain. Yxag is a dimer, both in solution and in the crystal. The crystal structure shows that the coordination geometry of the Fe ion is different in the two active sites of YxaG. Replacement of the iron at the active site with other metal ions suggests modulation of enzymatic activity in accordance with the Irving-Williams observation on the stability of metal ion complexes. This observation, along with a comparison with the crystal structure of YvrK determined recently, has allowed for a detailed structure-function analysis of the active site, providing clues to the diversification of function in the bicupin family of proteins.

  15. The role of metal ion-ligand interactions during divalent metal ion adsorption.

    PubMed

    Eldridge, Daniel S; Crawford, Russell J; Harding, Ian H

    2015-09-15

    A suite of seven different divalent metal ions (Ca(II), Cd(II), Cu(II), Mg(II), Ni(II), Pb(II), Zn(II)) was adsorbed from solution onto two Fe2O3 samples, quartz SiO2 and three different amphoteric polystyrene latices (containing amine and carboxyl functional groups). For the metal oxides, a high correlation was observed between the pH at which 50% of the metal was removed from solution (pH50) and the first hydrolysis constant for the metal ion (pK1). For the polystyrene latices, a much higher correlation was observed between the pH50 and pKc (equilibrium constant describing metal-carboxyl affinity) as opposed to pK1. These observations provide evidence of a strong relationship that exists between a metal's affinity for a particular ligand in solution and for that metal ion's affinity for the same ligand present as part of an adsorbing surface. The isoelectric point of the amphoteric latex surface can be increased by decreasing the carboxyl content of the latex surface. For all 7 metal ions, this resulted in a substantial decrease, for any given pH, in adsorption. We suggest that this may be partly due to the decreased carboxyl content, but is dominantly attributable to the presence of less favorable electrostatic conditions. This, in turn, demonstrates that electrostatics play a controlling role in metal ion adsorption onto amphoteric latex surfaces and, in addition to the nature of the metal ion, also controls the pH at which adsorption takes place.

  16. Ion irradiation effects on metallic nanocrystals

    SciTech Connect

    Kluth, P.; Johannessen, B.; Giulian, R.; Schnohr, C.S.; Foran, G.J.; Cookson, D.J.; Byrne, A.P.; Ridgway, M.C.

    2008-04-02

    We have investigated structural and morphological properties of metallic nanocrystals (NCs) exposed to ion irradiation. NCs were characterized by transmission electron microscopy in combination with advanced synchrotron-based analytical techniques, in particular X-ray absorption spectroscopy and small-angle X-ray scattering. A number of different effects were observed depending on the irradiation conditions. At energies where nuclear stopping is predominant, structural disorder/amorphization followed by inverse Ostwald ripening/dissolution due to ion beam mixing was observed for Au and Cu NCs embedded in SiO{sub 2}. The ion-irradiation-induced crystalline to amorphous transition in the NCs, which cannot be achieved in the corresponding bulk metals, was attributed to their initially higher structural energy as compared to bulk material and possibly preferential nucleation of the amorphous phase at the NC/SiO{sub 2} interface. At very high irradiation energies (swift heavy ion irradiation), where the energy loss is nearly entirely due to electronic stopping, a size-dependent shape transformation of the NCs from spheres to rod like shapes was apparent in Au NCs. Our preliminary results are in good agreement with considerations on melting of the NCs in the ion track as one mechanism involved in the shape transformation.

  17. AlOOH-reduced graphene oxide nanocomposites: one-pot hydrothermal synthesis and their enhanced electrochemical activity for heavy metal ions.

    PubMed

    Gao, Chao; Yu, Xin-Yao; Xu, Ren-Xia; Liu, Jin-Huai; Huang, Xing-Jiu

    2012-09-26

    This work described the preparation, characterization, and electrochemical behavior toward heavy metal ions of the AlOOH-reduced graphene oxide nanocomposites. This new material was synthesized through a green one-pot hydrothermal method. The morphologic and structure of the nanocomposites were characterized using atomic force microscopy, X-ray diffraction, Raman spectroscopy, X-ray photoemission spectroscopy, Fourier transform-infrared spectroscopy, and transmission electron microscopy. Electrochemical properties were characterized by cyclic voltammetry and electrochemical impedance spectroscopy. The chemical and electrochemical parameters that have influence on deposition and stripping of metal ions, such as pH value, deposition potential, and deposition time, were also studied. Due to the strong affinity of AlOOH to heavy metal ions and the fast electron-transfer kinetics of graphene, the combination of solid-phase extraction and stripping voltammetric analysis allowed fast and sensitive determination of Cd(II) and Pb(II) in drinking water, making these new nanocomposites promising candidates for practical applications in the fields of detecting heavy metal ions. Most importantly, these new nanocomposites may possess many unknown properties waiting to be explored.

  18. Fluorescence enhancement of photoswitchable metal ion sensors

    NASA Astrophysics Data System (ADS)

    Sylvia, Georgina; Heng, Sabrina; Abell, Andrew D.

    2016-12-01

    Spiropyran-based fluorescence sensors are an ideal target for intracellular metal ion sensing, due to their biocompatibility, red emission frequency and photo-controlled reversible analyte binding for continuous signal monitoring. However, increasing the brightness of spiropyran-based sensors would extend their sensing capability for live-cell imaging. In this work we look to enhance the fluorescence of spiropyran-based sensors, by incorporating an additional fluorophore into the sensor design. We report a 5-membered monoazacrown bearing spiropyran with metal ion specificity, modified to incorporate the pyrene fluorophore. The effect of N-indole pyrene modification on the behavior of the spiropyran molecule is explored, with absorbance and fluorescence emission characterization. This first generation sensor provides an insight into fluorescence-enhancement of spiropyran molecules.

  19. [Near-infrared photoluminescence properties of natural sodalite activated with Mn and Fe transition metal ions doping].

    PubMed

    Aidilibike, Tuerxun; Asilibieke, Bahetiguli; Sidike, Aierken

    2013-11-01

    Na8Al6Si6O24Cl2 : Mn and Na8Al6Si6O24Cl2 : Fe NIR phosphors were prepared by a solid-solid reaction at high temperature. Their crystal structures of fluorescent powder were investigated by using X-ray powder diffraction (XRD), and their NIR emission spectrum and excitation spectrum were measured at room temperature. The main emission peak of Mn5+ in the Na8Al6Si6O24Cl2 : Mn phosphor was observed at 1 200 nm in the NIR spectral region under 400 or 602 nm excitation, attributing to the 3A2-3T2 and 3A2-1E transitions of Mn5+ ions. The characteristic NIR luminescence of Mn5+ in sodalite is greatly enhanced by co-doping manganese and sulfur. A mechanism of the energy transfer between S2(-) and Mn5+ was also proposed here. The main emission peak of Fe2+ ions in the Na8Al6Si6O24Cl2 : Fe phosphor was recorded at 1 000 nm in the NIR region under the excitation of 334 or 500 nm. This photoluminescence originated from the 3T1-5 E transition of Fe2+. Such an emission in the NIR region suggests a potential application in improving solar spectrum to enhance the efficiency of silicon solar cells.

  20. Effects of metal ion adduction on the gas-phase conformations of protein ions.

    PubMed

    Flick, Tawnya G; Merenbloom, Samuel I; Williams, Evan R

    2013-11-01

    Changes in protein ion conformation as a result of nonspecific adduction of metal ions to the protein during electrospray ionization (ESI) from aqueous solutions were investigated using traveling wave ion mobility spectrometry (TWIMS). For all proteins examined, protein cations (and in most cases anions) with nonspecific metal ion adducts are more compact than the fully protonated (or deprotonated) ions with the same charge state. Compaction of protein cations upon nonspecific metal ion binding is most significant for intermediate charge state ions, and there is a greater reduction in collisional cross section with increasing number of metal ion adducts and increasing ion valency, consistent with an electrostatic interaction between the ions and the protein. Protein cations with the greatest number of adducted metal ions are no more compact than the lowest protonated ions formed from aqueous solutions. These results show that smaller collisional cross sections for metal-attached protein ions are not a good indicator of a specific metal-protein interaction in solution because nonspecific metal ion adduction also results in smaller gaseous protein cation cross sections. In contrast, the collisional cross section of α-lactalbumin, which specifically binds one Ca(2+), is larger for the holo-form compared with the apo-form, in agreement with solution-phase measurements. Because compaction of protein cations occurs when metal ion adduction is nonspecific, elongation of a protein cation may be a more reliable indicator that a specific metal ion-protein interaction occurs in solution.

  1. Photochemical Activity of Uranyl Ion in Acetone Irradiated by Light in the Presence of Metal Cations and Anions

    NASA Astrophysics Data System (ADS)

    Umreiko, D. S.; Vileishikova, N. P.; Zajogin, A. P.; Komyak, A. I.

    2015-11-01

    The effects of several metal cations and anions on complexation of tetra- and pentavalent uranium in an acetone solution of UO2(ClO4)2·5H2O irradiated by an LED (420-440 nm) were studied using electronic absorption. It was shown that addition of background components to the solution had an insignificant effect on complexation of the lowest-valent uranium. The composition of the UO 2 2 + coordination sphere could change at a certain irradiation time (>90 min) but the system as a whole was maintained.

  2. Metal assisted focused-ion beam nanopatterning

    NASA Astrophysics Data System (ADS)

    Kannegulla, Akash; Cheng, Li-Jing

    2016-09-01

    Focused-ion beam milling is a versatile technique for maskless nanofabrication. However, the nonuniform ion beam profile and material redeposition tend to disfigure the surface morphology near the milling areas and degrade the fidelity of nanoscale pattern transfer, limiting the applicability of the technique. The ion-beam induced damage can deteriorate the performance of photonic devices and hinders the precision of template fabrication for nanoimprint lithography. To solve the issue, we present a metal assisted focused-ion beam (MAFIB) process in which a removable sacrificial aluminum layer is utilized to protect the working material. The new technique ensures smooth surfaces and fine milling edges; in addition, it permits direct formation of v-shaped grooves with tunable angles on dielectric substrates or metal films, silver for instance, which are rarely achieved by using traditional nanolithography followed by anisotropic etching processes. MAFIB was successfully demonstrated to directly create nanopatterns on different types of substrates with high fidelity and reproducibility. The technique provides the capability and flexibility necessary to fabricate nanophotonic devices and nanoimprint templates.

  3. Method for removing metal ions from solution with titanate sorbents

    DOEpatents

    Lundquist, Susan H.; White, Lloyd R.

    1999-01-01

    A method for removing metal ions from solution comprises the steps of providing titanate particles by spray-drying a solution or slurry comprising sorbent titanates having a particle size up to 20 micrometers, optionally in the presence of polymer free of cellulose functionality as binder, said sorbent being active towards heavy metals from Periodic Table (CAS version) Groups IA, IIA, IB, IIB, IIIB, and VIII, to provide monodisperse, substantially spherical particles in a yield of at least 70 percent of theoretical yield and having a particle size distribution in the range of 1 to 500 micrometers. The particles can be used free flowing in columns or beds, or entrapped in a nonwoven, fibrous web or matrix or a cast porous membrane, to selectively remove metal ions from aqueous or organic liquid.

  4. On the Metal Ion Selectivity of Oxoacid Extractants

    SciTech Connect

    Hay, Benjamin; Chagnes, Alexandre; Cote, Gerard

    2013-01-01

    Relationships between metal chelate stability, ligand basicity, and metal ion acidity are reviewed and the general applicability is illustrated by linear correlations between aqueous stability constants and ligand pKa values for 35 metals with 26 ligands. The results confirm that most individual ligands of this type exhibit a stability ordering that correlates with the Lewis acidity of the metal ion. It is concluded that the general metal ion selectivity exhibited by liquid-liquid oxoacid extractants such as carboxylic acids, -diketones, and alkylphosphoric acids reflects the intrinsic affinity of the metal ion for the negative oxygen donor ligand.

  5. Liquid metal ion source assembly for external ion injection into an electron string ion source (ESIS)

    NASA Astrophysics Data System (ADS)

    Segal, M. J.; Bark, R. A.; Thomae, R.; Donets, E. E.; Donets, E. D.; Boytsov, A.; Ponkin, D.; Ramsdorf, A.

    2016-02-01

    An assembly for a commercial Ga+ liquid metal ion source in combination with an ion transportation and focusing system, a pulse high-voltage quadrupole deflector, and a beam diagnostics system has been constructed in the framework of the iThemba LABS (Cape Town, South Africa)—JINR (Dubna, Russia) collaboration. First, results on Ga+ ion beam commissioning will be presented. Outlook of further experiments for measurements of charge breeding efficiency in the electron string ion source with the use of external injection of Ga+ and Au+ ion beams will be reported as well.

  6. Liquid metal ion source assembly for external ion injection into an electron string ion source (ESIS)

    SciTech Connect

    Segal, M. J.; Bark, R. A.; Thomae, R.; Donets, E. E.; Donets, E. D.; Boytsov, A.; Ponkin, D.; Ramsdorf, A.

    2016-02-15

    An assembly for a commercial Ga{sup +} liquid metal ion source in combination with an ion transportation and focusing system, a pulse high-voltage quadrupole deflector, and a beam diagnostics system has been constructed in the framework of the iThemba LABS (Cape Town, South Africa)—JINR (Dubna, Russia) collaboration. First, results on Ga{sup +} ion beam commissioning will be presented. Outlook of further experiments for measurements of charge breeding efficiency in the electron string ion source with the use of external injection of Ga{sup +} and Au{sup +} ion beams will be reported as well.

  7. Transparent monolithic metal ion containing nanophase aerogels

    SciTech Connect

    Risen, W. M., Jr.; Hu, X.; Ji, S.; Littrell, K.

    1999-12-01

    The formation of monolithic and transparent transition metal containing aerogels has been achieved through cooperative interactions of high molecular weight functionalized carbohydrates and silica precursors, which strongly influence the kinetics of gelation. After initial gelation, subsequent modification of the ligating character of the system, coordination of the group VIII metal ions, and supercritical extraction afford the aerogels. The structures at the nanophase level have been probed by photon and electron transmission and neutron scattering techniques to help elucidate the basis for structural integrity together with the small entity sizes that permit transparency in the visible range. They also help with understanding the chemical reactivities of the metal-containing sites in these very high surface area materials. These results are discussed in connection with new reaction studies.

  8. Ion-exchange behavior of alkali metals on treated carbons

    SciTech Connect

    Mohiuddin, G.; Hata, W.Y.; Tolan, J.S.

    1983-01-01

    The ion-exchange behavior of trace quantities of the alkali-metal ions sodium and cesium, on activated carbon impregnated with zirconium phosphate (referred to here as ZrP), was studied. Impregnated carbon had twice as much ion-exchange activity as unimpregnated, oxidized carbon, and 10 times as much as commercial activated carbons. The distribution coefficient of sodium increased with increasing pH; the distribution coefficient of cesium decreased with increasing pH. Sodium and cesium were separated with an electrolytic solution of 0.1 M HCl. Preliminary studies indicated that 0.2 M potassium and cesium can also be separated. Distribution coefficients of the supported ZrP were determined by the elution technique and agreed within 20% of the values for pure ZrP calculated from the literature.

  9. Metal ion binding to iron oxides

    NASA Astrophysics Data System (ADS)

    Ponthieu, M.; Juillot, F.; Hiemstra, T.; van Riemsdijk, W. H.; Benedetti, M. F.

    2006-06-01

    The biogeochemistry of trace elements (TE) is largely dependent upon their interaction with heterogeneous ligands including metal oxides and hydrous oxides of iron. The modeling of TE interactions with iron oxides has been pursued using a variety of chemical models. The objective of this work is to show that it is possible to model the adsorption of protons and TE on a crystallized oxide (i.e., goethite) and on an amorphous oxide (HFO) in an identical way. Here, we use the CD-MUSIC approach in combination with valuable and reliable surface spectroscopy information about the nature of surface complexes of the TE. The other objective of this work is to obtain generic parameters to describe the binding of the following elements (Cd, Co, Cu, Ni, Pb, and Zn) onto both iron oxides for the CD-MUSIC approach. The results show that a consistent description of proton and metal ion binding is possible for goethite and HFO with the same set of model parameters. In general a good prediction of almost all the collected experimental data sets corresponding to metal ion binding to HFO is obtained. Moreover, dominant surface species are in agreement with the recently published surface complexes derived from X-ray absorption spectroscopy (XAS) data. Until more detailed information on the structure of the two iron oxides is available, the present option seems a reasonable approximation and can be used to describe complex geochemical systems. To improve our understanding and modeling of multi-component systems we need more data obtained at much lower metal ion to iron oxide ratios in order to be able to account eventually for sites that are not always characterized in spectroscopic studies.

  10. Peptide immobilisation on porous silicon surface for metal ions detection

    NASA Astrophysics Data System (ADS)

    Sam, Sabrina S.; Chazalviel, Jean-Noël Jn; Gouget-Laemmel, Anne Chantal Ac; Ozanam, François F.; Etcheberry, Arnaud A.; Gabouze, Nour-Eddine N.

    2011-06-01

    In this work, a Glycyl-Histidyl-Glycyl-Histidine (GlyHisGlyHis) peptide is covalently anchored to the porous silicon PSi surface using a multi-step reaction scheme compatible with the mild conditions required for preserving the probe activity. In a first step, alkene precursors are grafted onto the hydrogenated PSi surface using the hydrosilylation route, allowing for the formation of a carboxyl-terminated monolayer which is activated by reaction with N-hydroxysuccinimide in the presence of a peptide-coupling carbodiimide N-ethyl- N'-(3-dimethylaminopropyl)-carbodiimide and subsequently reacted with the amino linker of the peptide to form a covalent amide bond. Infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy are used to investigate the different steps of functionalization. The property of peptides to form stable complexes with metal ions is exploited to achieve metal-ion recognition by the peptide-modified PSi-based biosensor. An electrochemical study of the GlyHisGlyHis-modified PSi electrode is achieved in the presence of copper ions. The recorded cyclic voltammograms show a quasi-irreversible process corresponding to the Cu(II)/Cu(I) couple. The kinetic factors (the heterogeneous rate constant and the transfer coefficient) and the stability constant of the complex formed on the porous silicon surface are determined. These results demonstrate the potential role of peptides grafted on porous silicon in developing strategies for simple and fast detection of metal ions in solution.

  11. Peptide immobilisation on porous silicon surface for metal ions detection.

    PubMed

    Sam, Sabrina S; Chazalviel, Jean-Noël Jn; Gouget-Laemmel, Anne Chantal Ac; Ozanam, François F; Etcheberry, Arnaud A; Gabouze, Nour-Eddine N

    2011-06-06

    In this work, a Glycyl-Histidyl-Glycyl-Histidine (GlyHisGlyHis) peptide is covalently anchored to the porous silicon PSi surface using a multi-step reaction scheme compatible with the mild conditions required for preserving the probe activity. In a first step, alkene precursors are grafted onto the hydrogenated PSi surface using the hydrosilylation route, allowing for the formation of a carboxyl-terminated monolayer which is activated by reaction with N-hydroxysuccinimide in the presence of a peptide-coupling carbodiimide N-ethyl-N'-(3-dimethylaminopropyl)-carbodiimide and subsequently reacted with the amino linker of the peptide to form a covalent amide bond. Infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy are used to investigate the different steps of functionalization.The property of peptides to form stable complexes with metal ions is exploited to achieve metal-ion recognition by the peptide-modified PSi-based biosensor. An electrochemical study of the GlyHisGlyHis-modified PSi electrode is achieved in the presence of copper ions. The recorded cyclic voltammograms show a quasi-irreversible process corresponding to the Cu(II)/Cu(I) couple. The kinetic factors (the heterogeneous rate constant and the transfer coefficient) and the stability constant of the complex formed on the porous silicon surface are determined. These results demonstrate the potential role of peptides grafted on porous silicon in developing strategies for simple and fast detection of metal ions in solution.

  12. Peptide immobilisation on porous silicon surface for metal ions detection

    PubMed Central

    2011-01-01

    In this work, a Glycyl-Histidyl-Glycyl-Histidine (GlyHisGlyHis) peptide is covalently anchored to the porous silicon PSi surface using a multi-step reaction scheme compatible with the mild conditions required for preserving the probe activity. In a first step, alkene precursors are grafted onto the hydrogenated PSi surface using the hydrosilylation route, allowing for the formation of a carboxyl-terminated monolayer which is activated by reaction with N-hydroxysuccinimide in the presence of a peptide-coupling carbodiimide N-ethyl-N'-(3-dimethylaminopropyl)-carbodiimide and subsequently reacted with the amino linker of the peptide to form a covalent amide bond. Infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy are used to investigate the different steps of functionalization. The property of peptides to form stable complexes with metal ions is exploited to achieve metal-ion recognition by the peptide-modified PSi-based biosensor. An electrochemical study of the GlyHisGlyHis-modified PSi electrode is achieved in the presence of copper ions. The recorded cyclic voltammograms show a quasi-irreversible process corresponding to the Cu(II)/Cu(I) couple. The kinetic factors (the heterogeneous rate constant and the transfer coefficient) and the stability constant of the complex formed on the porous silicon surface are determined. These results demonstrate the potential role of peptides grafted on porous silicon in developing strategies for simple and fast detection of metal ions in solution. PMID:21711937

  13. Heterogeneous behavior of metalloproteins toward metal ion binding and selectivity: insights from molecular dynamics studies.

    PubMed

    Gogoi, Prerana; Chandravanshi, Monika; Mandal, Suraj Kumar; Srivastava, Ambuj; Kanaujia, Shankar Prasad

    2016-07-01

    About one-third of the existing proteins require metal ions as cofactors for their catalytic activities and structural complexities. While many of them bind only to a specific metal, others bind to multiple (different) metal ions. However, the exact mechanism of their metal preference has not been deduced to clarity. In this study, we used molecular dynamics (MD) simulations to investigate whether a cognate metal (bound to the structure) can be replaced with other similar metal ions. We have chosen seven different proteins (phospholipase A2, sucrose phosphatase, pyrazinamidase, cysteine dioxygenase (CDO), plastocyanin, monoclonal anti-CD4 antibody Q425, and synaptotagmin 1 C2B domain) bound to seven different divalent metal ions (Ca(2+), Mg(2+), Zn(2+), Fe(2+), Cu(2+), Ba(2+), and Sr(2+), respectively). In total, 49 MD simulations each of 50 ns were performed and each trajectory was analyzed independently. Results demonstrate that in some cases, cognate metal ions can be exchanged with similar metal ions. On the contrary, some proteins show binding affinity specifically to their cognate metal ions. Surprisingly, two proteins CDO and plastocyanin which are known to bind Fe(2+) and Cu(2+), respectively, do not exhibit binding affinity to any metal ion. Furthermore, the study reveals that in some cases, the active site topology remains rigid even without cognate metals, whereas, some require them for their active site stability. Thus, it will be interesting to experimentally verify the accuracy of these observations obtained computationally. Moreover, the study can help in designing novel active sites for proteins to sequester metal ions particularly of toxic nature.

  14. Rational Design of Metal Ion Sequestering Agents

    SciTech Connect

    Raymond, Kenneth N.

    2000-09-30

    The discriminate bonding of metal ions is a challenge to the synthetic chemist and a phenomenon of considerable practical importance.1 An important feature of many technical applications is the specific or preferential binding of a single metal ion in the presence of many metals. Examples range from large-volume uses (e.g. ferric EDTA as a plant food, calcium complexing agents as water softeners or anticaking formulations) to very high technology applications (technetium complexation in radiopharmaceuticals, synthetic metalloenzymes). We are interested in efficient and discriminate binding of actinides for waste stream remediation. Actinides represent a major and long-lived contaminant in nuclear waste. While the separation of actinides from other radioactive components of waste, such as Sr and Cs, is relatively well established, the separation of actinides from each other and in complex solutions (e.g. those found in tank wastes) is not as well resolved. The challenge of designing metal-specific (actinide) ligands is facilitated by examples from nature. Bacteria synthesize Fe(III)-specific ligands, called siderophores, to sequester Fe(III) from the environment and return it to the cell. The similarities between Fe(III) and Pu(IV) (their charge-to-size ratios and acidity), make the siderophores prototypical for designing actinide-specific ligands. The chelating groups present in siderophores are usually hydroxamic acids and catecholamides. We have developed derivatives of these natural products which have improved properties. The catechol derivatives are the 2,3-dihydroxyterephthalamides (TAMs), and 3,4-dihydroxysulfonamides (SFAMs), and the hydroxamic acid derivatives are three isomers of hydroxypyridinones, 1,2- HOPO, 3,2-HOPO, and 3,4-HOPO. All of these ligands are attached to molecular backbones by amides and a very important feature of HOPO and CAM ligands is a strong hydrogen bonds formed between the amide proton and the adjacent phenolic oxygen in the metal

  15. Laser materials based on transition metal ions

    NASA Astrophysics Data System (ADS)

    Moncorgé, Richard

    2017-01-01

    The purpose of this presentation is to review the spectroscopic properties of the main laser materials based on transition metal ions which lead to noticeable laser performance at room temperature and, for very few cases, because of unique properties, when they are operated at cryogenic temperatures. The description also includes the materials which are currently being used as saturable absorbers for passive-Q-switching of a variety of other near- and mid-infrared solid state lasers. A substantial part of the article is devoted first to the description of the energy levels and of the absorption and emission transitions of the transition metal ions in various types of environments by using the well-known Tanabe-Sugano diagrams. It is shown in particular how these diagrams can be used along with other theoretical considerations to understand and describe the spectroscopic properties of ions sitting in crystal field environments of near-octahedral or near-tetrahedral symmetry. The second part is then dedicated to the description (positions and intensities) of the main absorption and emission features which characterize the different types of materials.

  16. Accumulation of metal ions by pectinates

    NASA Astrophysics Data System (ADS)

    Deiana, S.; Deiana, L.; Palma, A.; Premoli, A.; Senette, C.

    2009-04-01

    The knowledge of the mechanisms which regulate the interactions of metal ions with partially methyl esterified linear polymers of α-1,4 linked D-galacturonic acid units (pectinates), well represented in the root inner and outer apoplasm, is of great relevance to understand the processes which control their accumulation at the soil-root interface as well as their mobilization by plant metabolites. Accumulation of a metal by pectinates can be affected by the presence of other metals so that competition or distribution could be expected depending on the similar or different affinity of the metal ions towards the binding sites, mainly represented by the carboxylate groups. In order to better understand the mechanism of accumulation in the apoplasm of several metal ions, the sorption of Cd(II), Zn(II), Cu(II), Pb(II) and Cr(III) by a Ca-polygalacturonate gel, used as model of the soil-root interface, with a degree of esterification of 18% (PGAE1) and 65% (PGAE2) was studied at pH 3.0, 4.0, 5.0 and 6.0 in the presence of CaCl2 2.5 mM.. The results show that sorption increases with increasing both the initial metal concentration and pH. A similar sorption trend was evidenced for Cu(II) and Pb(II) and for Zn(II) and Cd(II), indicating that the mechanism of sorption for these two ionic couples is quite different. As an example, at pH 6.0 and an initial metal concentration equal to 2.0 mM, the amount of Cu(II) and Pb(II) sorbed was about 1.98 mg-1 of PGAE1 while that of Cd(II) and Zn(II) was about 1.2 mg-1. Cr(III) showed a rather different sorption trend and a much higher amount (2.8 mg-1of PGAE1 at pH 6.0) was recorded. The higher affinity of Cr(III) for the polysaccharidic matrix is attributable to the formation of Cr(III) polynuclear species in solution, as shown by the distribution diagrams obtained through the MEDUSA software. On the basis of these findings, the following affinity towards the PGAE1 can be assessed: Cr(III) > Cu(II) ? Pb(II) > Zn (II) ? Cd

  17. Activation of mammalian tyrosinase by ferrous ions.

    PubMed

    Palumbo, A; d'Ischia, M; Misuraca, G; Carratú, L; Prota, G

    1990-03-26

    Kinetic experiments are reported showing that mammalian tyrosinase from B16 mouse melanoma is significantly activated by catalytic amounts of ferrous ions. Monitoring of tyrosine oxidation by both dopachrome formation and oxygen consumption showed that ferrous ions at micromolar concentrations induce a marked enzymatic activity with 0.01 U/ml of highly purified tyrosinase, whereas no detectable reaction occurs in the absence of metal over a sufficiently prolonged period of time. The extent of the activating effect, which is specific for the reduced form of iron, is proportional to the concentration of the added metal with a typical saturation profile, no further effect being observed beyond a threshold value. Changing the buffer system from phosphate to hepes or tris results in a marked decrease of the Fe2(+)-induced activation. Scavengers of active oxygen species, such as superoxide dismutase, catalase, formate and mannitol have no detectable effect on the tyrosinase activity. These results are accounted for in terms of an activation mechanism involving reduction of the cupric ions at the active site of the resting enzyme.

  18. Substrate Profile and Metal-ion Selectivity of Human Divalent Metal-ion Transporter-1*

    PubMed Central

    Illing, Anthony C.; Shawki, Ali; Cunningham, Christopher L.; Mackenzie, Bryan

    2012-01-01

    Divalent metal-ion transporter-1 (DMT1) is a H+-coupled metal-ion transporter that plays essential roles in iron homeostasis. DMT1 exhibits reactivity (based on evoked currents) with a broad range of metal ions; however, direct measurement of transport is lacking for many of its potential substrates. We performed a comprehensive substrate-profile analysis for human DMT1 expressed in RNA-injected Xenopus oocytes by using radiotracer assays and the continuous measurement of transport by fluorescence with the metal-sensitive PhenGreen SK fluorophore. We provide validation for the use of PhenGreen SK fluorescence quenching as a reporter of cellular metal-ion uptake. We determined metal-ion selectivity under fixed conditions using the voltage clamp. Radiotracer and continuous measurement of transport by fluorescence assays revealed that DMT1 mediates the transport of several metal ions that were ranked in selectivity by using the ratio Imax/K0.5 (determined from evoked currents at −70 mV): Cd2+ > Fe2+ > Co2+, Mn2+ ≫ Zn2+, Ni2+, VO2+. DMT1 expression did not stimulate the transport of Cr2+, Cr3+, Cu+, Cu2+, Fe3+, Ga3+, Hg2+, or VO+. 55Fe2+ transport was competitively inhibited by Co2+ and Mn2+. Zn2+ only weakly inhibited 55Fe2+ transport. Our data reveal that DMT1 selects Fe2+ over its other physiological substrates and provides a basis for predicting the contribution of DMT1 to intestinal, nasal, and pulmonary absorption of metal ions and their cellular uptake in other tissues. Whereas DMT1 is a likely route of entry for the toxic heavy metal cadmium, and may serve the metabolism of cobalt, manganese, and vanadium, we predict that DMT1 should contribute little if at all to the absorption or uptake of zinc. The conclusion in previous reports that copper is a substrate of DMT1 is not supported. PMID:22736759

  19. The effect of group IIIA metal ion dopants on the photocatalytic activities of nanocrystalline Sr0.25H1.5Ta2O6·H2O.

    PubMed

    Liang, Shijing; Zhu, Shuying; Zhu, Jia; Chen, Yan; Zhang, Yongfan; Wu, Ling

    2012-01-21

    A series of group IIIA metal ion electron acceptors doped into Sr(0.25)H(1.5)Ta(2)O(6)·H(2)O (HST) samples have been prepared by an impregnation and calcination method for the first time. The samples are characterized by XRD, TEM, DRS and XPS. The variations in the electronic structure and photoelectric response after metal ion doping are investigated by theoretical calculations and photocurrent experiments, respectively. Results show that the metal ions can be efficiently incorporated into the HST crystal structure, which is reflected in the lattice contraction. Meanwhile, the photoabsorption edges of the metal-doped HST samples are red shifted to a longer wavelength. Taking into account the ionic radii and electronegativities of the dopants, as well as the XRD and XPS results, it is concluded that Ta(5+) ions may be partially substituted by the Al(3+) and Ga(3+) ions in the framework, while In(3+) ions are the favourable substitutes for Sr(2+) sites in the cavity. The first-principles DFT calculations confirm that the variation of the band structure is sensitive to the type of group IIIA metal ion. Introducing the dopant only at the Ta site induces an obvious variation in the band structure and the band gap becomes narrow. Meanwhile, an ''extra step'' appeared in the band gap, which can trap photogenerated electrons from the valance band (VB) and could enhance the charge mobility and the photocurrent. For the photocatalytic degradation of methyl orange in an aqueous solution and in benzene in the gas phase, the doped samples show superior photocatalytic activities compared with both undoped samples and TiO(2). The enhanced photocatalytic activities can be well explained by their electronic structure, photoabsorption performance, photoelectric response, and the concentration of the active species. Due to the fact that Ga ion doping can create an acceptor impurity level and change the electronic band, efficiently narrowing the band gap, the Ga-doped sample shows

  20. Metal Ion Toxins and Brain Aquaporin-4 Expression: An Overview

    PubMed Central

    Ximenes-da-Silva, Adriana

    2016-01-01

    Metal ions such as iron, zinc, and manganese are essential to metabolic functions, protein synthesis, neurotransmission, and antioxidant neuroprotective mechanisms. Conversely, non-essential metals such as mercury and lead are sources of human intoxication due to occupational activities or environmental contamination. Essential or non-essential metal accumulation in the central nervous system (CNS) results in changes in blood-brain barrier (BBB) permeability, as well as triggering microglia activation and astrocyte reactivity and changing water transport through the cells, which could result in brain swelling. Aquaporin-4 is the main water channel in the CNS, is expressed in astrocyte foot processes in brain capillaries and along the circumventricular epithelium in the ventricles, and has important physiological functions in maintaining brain osmotic homeostasis and supporting brain excitability through regulation of the extracellular space. Some evidence has pointed to a role of AQP4 during metal intoxication in the brain, where it may act in a dual form as a neuroprotector or a mediator of the development of oxidative stress in neurons and astrocytes, resulting in brain swelling and neuronal damage. This mini-review presents the way some metal ions affect changes in AQP4 expression in the CNS and discuss the ways in which water transport in brain cells can be involved in brain damage. PMID:27313504

  1. Antifungal Properties of Electrically Generated Metallic Ions

    PubMed Central

    Berger, T. J.; Spadaro, J. A.; Bierman, Richard; Chapin, S. E.; Becker, R. O.

    1976-01-01

    A qualitative and quantitative investigation was undertaken to study the susceptibility of unicellular eucaryotic organisms (yeasts) to metallic cations generated by low levels of direct current. Results were characteristic of effects obtained previously using clinical and standard bacteria test organisms. The present study demonstrated that anodic silver (Ag+) at low direct currents had inhibitory and fungicidal properties. Broth dilution susceptibility tests were made on several species of Candida and one species of Torulopsis. Growth in all isolates was inhibited by concentrations of electrically generated silver ions between 0.5 and 4.7 μg/ml, and silver exhibited fungicidal properties at concentrations as low as 1.9 μg/ml. The inhibitory and fungicidal concentrations of electrically generated silver ions are lower than those reported for other silver compounds. Images PMID:1034467

  2. Metal nanocrystal/metal-organic framework core/shell nanostructure from selective self-assembly induced by localization of metal ion precursors on nanocrystal surface.

    PubMed

    Ohhashi, Takashi; Tsuruoka, Takaaki; Matsuyama, Tetsuhiro; Takashima, Yohei; Nawafune, Hidemi; Minami, Hideto; Akamatsu, Kensuke

    2015-08-01

    Metal nanocrystal/metal-organic framework core/shell nanostructures have been constructed using metal ion-trapped nanocrystals as scaffolds through a selective self-assembly of framework components on the nanocrystal surfaces. The resulting nanostructures exhibit unique catalytic activity toward nitrophenol analogs.

  3. Systems and methods for producing metal clusters; functionalized surfaces; and droplets including solvated metal ions

    DOEpatents

    Cooks, Robert Graham; Li, Anyin; Luo, Qingjie

    2017-01-24

    The invention generally relates to systems and methods for producing metal clusters; functionalized surfaces; and droplets including solvated metal ions. In certain aspects, the invention provides methods that involve providing a metal and a solvent. The methods additionally involve applying voltage to the solvated metal to thereby produce solvent droplets including ions of the metal containing compound, and directing the solvent droplets including the metal ions to a target. In certain embodiments, once at the target, the metal ions can react directly or catalyze reactions.

  4. Lanthanide Metal-Organic Frameworks with Six-Coordinated Ln(III) Ions and Free Functional Organic Sites for Adsorptions and Extensive Catalytic Activities

    PubMed Central

    Zhu, Yu; Zhu, Min; Xia, Li; Wu, Yunlong; Hua, Hui; Xie, Jimin

    2016-01-01

    Three chelating-amino-functionalized lanthanide metal-organic frameworks, Y-DDQ, Dy-DDQ and Eu-DDQ, were synthesized with a flexible dicarboxylate ligand based on quinoxaline (H2DDQ = N, N′-dibenzoic acid-2,3-diaminoquinoxaline). The three-dimensional framework is constructed by the H2DDQ linkers connecting the zigzag ladders, showing a net of sra topology. In the structures, one kind of Ln(III) ions metal centers are six-coordinated and thus can potentially behave as open metal sites (OMSs), while the free chelating amino groups can act as free functional organic sites (FOSs). The N2 and Ar adsorption behaviors indicate that these Ln-DDQ exhibits stable microporous frameworks with high surface area after remove of the solvents. Owing to presence of OMSs and FOSs, these MOFs show good ability of CO2, dyes captures and Lewis acid catalyst for cyanosilylation reaction. In view of the existing FOSs in the framework, Pd NPs were immobilized onto the MOFs through graft interactions between free chelating amino groups and metal ions precursor using postsynthetic modification. The well dispersed Pd@Ln-DDQs exhibit efficient and recyclable catalytic reduction of 4-nitrophenol to 4-aminophenol, and they can also act as an excellent catalyst for Suzuki-Miyaura cross-coupling reactions with the exposed Pd NPs. PMID:27431731

  5. Lanthanide Metal-Organic Frameworks with Six-Coordinated Ln(III) Ions and Free Functional Organic Sites for Adsorptions and Extensive Catalytic Activities

    NASA Astrophysics Data System (ADS)

    Zhu, Yu; Zhu, Min; Xia, Li; Wu, Yunlong; Hua, Hui; Xie, Jimin

    2016-07-01

    Three chelating-amino-functionalized lanthanide metal-organic frameworks, Y-DDQ, Dy-DDQ and Eu-DDQ, were synthesized with a flexible dicarboxylate ligand based on quinoxaline (H2DDQ = N, N‧-dibenzoic acid-2,3-diaminoquinoxaline). The three-dimensional framework is constructed by the H2DDQ linkers connecting the zigzag ladders, showing a net of sra topology. In the structures, one kind of Ln(III) ions metal centers are six-coordinated and thus can potentially behave as open metal sites (OMSs), while the free chelating amino groups can act as free functional organic sites (FOSs). The N2 and Ar adsorption behaviors indicate that these Ln-DDQ exhibits stable microporous frameworks with high surface area after remove of the solvents. Owing to presence of OMSs and FOSs, these MOFs show good ability of CO2, dyes captures and Lewis acid catalyst for cyanosilylation reaction. In view of the existing FOSs in the framework, Pd NPs were immobilized onto the MOFs through graft interactions between free chelating amino groups and metal ions precursor using postsynthetic modification. The well dispersed Pd@Ln-DDQs exhibit efficient and recyclable catalytic reduction of 4-nitrophenol to 4-aminophenol, and they can also act as an excellent catalyst for Suzuki-Miyaura cross-coupling reactions with the exposed Pd NPs.

  6. Virulence modulation of Candida albicans biofilms by metal ions commonly released from orthodontic devices.

    PubMed

    Ronsani, Maiara Medeiros; Mores Rymovicz, Alinne Ulbrich; Meira, Thiago Martins; Trindade Grégio, Ana Maria; Guariza Filho, Odilon; Tanaka, Orlando Motohiro; Ribeiro Rosa, Edvaldo Antonio

    2011-12-01

    The installation of metal devices leads to an increase in the salivary concentration of metal ions and in the growth of salivary Candida spp. However, the relationship between released metal ions and Candida virulence has not been previously examined. The objective of this study was to evaluate whether metal ions affect fungal virulence. We prepared culture media containing Ni(2+), Fe(3+), Cr(3+), Co(2+) or a mixture of these metal ions at concentrations similar to those released in saliva of orthodontic patients. Biofilms of Candida albicans SC5314 were grown for 72 h and their biomasses were determined. The supernatants were analyzed for secretory aspartyl protease (SAP) and hemolysin activities. To verify changes in virulence following treatment with metals, proteolytic and hemolytic activities were converted into specific activities. The results revealed that all ions, except Co(2+), caused increases in biofilm biomass. In addition, Ni(2+) caused an increase in SAP activity and Fe(3+) reduced hemolytic activity. However, the SAP and hemolysin activities in the presence of the mixture of ions did not differ from those of control. These results indicate that metal ions released during the degradation of orthodontic appliances can modulate virulence factors in C. albicans biofilms.

  7. Yeast metallothionein function in metal ion detoxification.

    PubMed

    Ecker, D J; Butt, T R; Sternberg, E J; Neeper, M P; Debouck, C; Gorman, J A; Crooke, S T

    1986-12-25

    A genetic approach was taken to test the function of yeast metallothionein in metal ion detoxification. A yeast strain was constructed in which the metallothionein locus was deleted (cup1 delta). The cup1 delta strain was complemented with normal or mutant metallothionein genes under normal or constitutive regulatory control on high copy episomal plasmids. Metal resistance of the cup1 delta strain with and without the metallothionein-expressing vectors was analyzed. The normally regulated metallothionein gene conferred resistance only to copper (1000-fold); constitutively expressed metallothionein conferred resistance to both copper (500-fold) and cadmium (1000-fold), but not to mercury, zinc, silver, cobalt, nickel, gold, platinum, lanthanum, uranium, or tin. Two mutant versions of the metallothionein gene were constructed and tested for their ability to confer metal resistance in the cup1 delta background. The first had a deletion of a highly conserved amino acid sequence (Lys-Lys-Ser-Cys-Cys-Ser). The second was a hybrid gene consisting of the sequences coding for the first 20 amino acids of the yeast protein fused to the monkey metallothionein gene. Expression of these genes under the CUP1 promoter provided significant protection from copper, but none of the other metals tested. These results demonstrate that there is significant flexibility in the structural requirements for metallothionein to function in copper detoxification and that yeast metallothionein is also capable of detoxifying cadmium under conditions of constitutive expression.

  8. Metal Ions: Supporting Actors in the Playbook of Small Ribozymes

    PubMed Central

    Johnson-Buck, Alexander E.; McDowell, Sarah E.; Walter, Nils G.

    2012-01-01

    Since the 1980s, several small RNA motifs capable of chemical catalysis have been discovered. These small ribozymes, composed of between approximately 40 and 200 nucleotides, have been found to play vital roles in the replication of subviral and viral pathogens, gene regulation in prokaryotes, and have recently been discovered in noncoding eukaryotic RNAs. All of the known natural small ribozymes – the hairpin, hammerhead, hepatitis delta virus, Varkud satellite, and glmS ribozymes – catalyze the same self-cleavage reaction as RNAse A, resulting in two products, one bearing a 2′–3′ cyclic phosphate and the other a 5′-hydroxyl group. Although originally thought to be obligate metalloenzymes like the group I and II self-splicing introns, the small ribozymes are now known to support catalysis in a wide variety of cations that appear to be only indirectly involved in catalysis. Nevertheless, under physiologic conditions, metal ions are essential for the proper folding and function of the small ribozymes, the most effective of these being magnesium. Metal ions contribute to catalysis in the small ribozymes primarily by stabilizing the catalytically active conformation, but in some cases also by activating RNA functional groups for catalysis, directly participating in catalytic acid-base chemistry, and perhaps by neutralizing the developing negative charge of the transition state. Although interactions between the small ribozymes and cations are relatively nonspecific, ribozyme activity is quite sensitive to the types and concentrations of metal ions present in solution, suggesting a close evolutionary relationship between cellular metal ion homeostasis and cation requirements of catalytic RNAs, and perhaps RNA in general. PMID:22010272

  9. Predicting relative toxicity of metal ions to bacteria (Microtox{reg_sign}) using ion characteristics

    SciTech Connect

    McCloskey, J.T.; Newman, M.C.; Clark, S.B.

    1995-12-31

    The use of predictive effects models with metals has received little attention in toxicology. The purpose of this study was to predict the relative toxicity of individual metal ions and metal mixtures using ion characteristics. The concentration of metal resulting in a 50% reduction in light output (EC50) in marine bacteria (Vibrio fischeri) was determined for several metals using the Microtox{reg_sign} Toxicity Analyzer. Trends in metal toxicity were predicted by combining metal speciation calculations with empirical models based on metal ion characteristics. These trends were consistent for nine divalent metals (Ca{prime} Cd, Cu, Hg, Mg, Mn, Ni, Pb and Zn) whether the media mimicked salt water (NaC, medium) or freshwater (NaNO{sub 3} medium). When expanding the study to include an additional 14 mono-, di-, and trivalent metal ions, ion characteristics were still useful for predicting the relative toxicity of metal ions to bacteria. The prediction of nonadditive toxic effects using metal mixtures was also possible based on ion characteristics. Overall, models based on ion characteristics show much promise for predicting the relative toxicity of metal ions using the Microtox{reg_sign} assay.

  10. Photoelectric properties in metal ion modified DNA nanostructure.

    PubMed

    Kulkarni, Atul; Dugasani, Sreekantha Reddy; Jang Ah Kim; Kim; Sung Ha Park; Taesung Kim

    2015-08-01

    Due to specific or as designed self-assembly, DNA nanostructures gaining popularity in various nanoscale electronic applications. Herein, a novel divalent metal ion-DNA complex known as M-DNA have been investigated for its photoelectric characteristics. The increased conductivity of M-DNA thin films is attributed to the metal ion electrical and optical properties. The gate voltage effect along with illumination on the conductivity of M-DNA demonstrates that M-DNA can be used as an active element of a field-effect transistor. The Zn DNA shows maximum conductivity of 300μS/cm at 480 nm light illumination suggest that M-DNA can be utilized in nano-opto-electronics and bio-sensing applications.

  11. The spliceosome and its metal ions.

    PubMed

    Butcher, Samuel E

    2011-01-01

    The spliceosome is a massive complex of 5 RNAs and many proteins that associate to catalyze precursor messenger RNA splicing. The process of splicing involves two phosphoryl transfer reactions that result in intron excision and ligation of the flanking exons. Since it is required for normal protein production in eukaryotic cells, pre-mRNA splicing is an essential step in gene expression. Although high resolution structural views of the spliceosome do not yet exist, a growing body of evidence indicates that the spliceosome is a magnesium-dependent enzyme that utilizes catalytic metal ions to stabilize both transition states during the two phosphoryl transfer steps of splicing. A wealth of data also indicate that the core of the spliceosome is comprised of RNA, and suggest that the spliceosome may be a ribozyme. This chapter presents the evidence for metal ion catalysis by the spliceosome, draws comparisons to similar RNA enzymes, and discusses the future directions for research into the mechanism of pre-mRNA splicing.

  12. Separation of traces of metal ions from sodium matrices

    NASA Technical Reports Server (NTRS)

    Korkisch, J.; Orlandini, K. A.

    1969-01-01

    Method for isolating metal ion traces from sodium matrices consists of two extractions and an ion exchange step. Extraction is accomplished by using 2-thenoyltrifluoracetone and dithizone followed by cation exchange.

  13. Optical methods for the detection of heavy metal ions

    NASA Astrophysics Data System (ADS)

    Uglov, A. N.; Bessmertnykh-Lemeune, A.; Guilard, R.; Averin, A. D.; Beletskaya, I. P.

    2014-03-01

    The review covers an important area of the modern chemistry, namely, the detection of heavy metal ions using optical molecular detectors. The role of this method in metal ion detection and the physicochemical grounds of operation of chemosensors are discussed, and examples of detection of most abundant heavy metal ions and synthetic approaches to molecular detectors are presented. The immobilization of molecular detectors on solid substrates for the design of analytical sensor devices is described. The bibliography includes 178 references.

  14. MeRNA: a Database of Metal Ion Binding Sites in RNAStructures

    SciTech Connect

    Stefan, Liliana R.; Zhang, Rui; Levitan, Aaron G.; Hendrix, DonnaF.; Brenner, Steven E.; Holbrook, Stephen R.

    2005-10-05

    Metal ions are essential for the folding of RNA into stable tertiary structures and for the catalytic activity of some RNA enzymes. To aid in the study of the roles of metal ions in RNA structural biology, we have created MeRNA (Metals in RNA), a comprehensive compilation of all metal binding sites identified in RNA three-dimensional structures available from the Protein Data Bank (PDB) and Nucleic Acid Database (NDB). Currently, our database contains information relating to binding of 9764 metal ions corresponding to 23 distinct elements; in 256 RNA structures. The metal ion locations were confirmed and ligands characterized using original literature references. MeRNA includes eight manually identified metal-ion binding motifs, which are described in the literature. MeRNA is searchable by PDB identifier, metal ion, method of structure determination, resolution and R-values for X-ray structure, and distance from metal to any RNA atom or to water. New structures with their respective binding motifs will be added to the database as they become available. The MeRNA database will further our understanding of the roles of metal ions in RNA folding and catalysis and have applications in structural and functional analysis, RNA design and engineering.

  15. Plasma immersion ion implantation for reducing metal ion release

    SciTech Connect

    Diaz, C.; Garcia, J. A.; Maendl, S.; Pereiro, R.; Fernandez, B.; Rodriguez, R. J.

    2012-11-06

    Plasma immersion ion implantation of Nitrogen and Oxygen on CoCrMo alloys was carried out to improve the tribological and corrosion behaviors of these biomedical alloys. In order to optimize the implantation results we were carried experiments at different temperatures. Tribocorrosion tests in bovine serum were used to measure Co, Cr and Mo releasing by using Inductively Coupled Plasma Mass Spectrometry analysis after tests. Also, X-ray Diffraction analysis were employed in order to explain any obtained difference in wear rate and corrosion tests. Wear tests reveals important decreases in rate of more than one order of magnitude for the best treatment. Moreover decreases in metal release were found for all the implanted samples, preserving the same corrosion resistance of the unimplanted samples. Finally this paper gathers an analysis, in terms of implantation parameters and achieved properties for industrial implementation of these treatments.

  16. Plasma immersion ion implantation for reducing metal ion release

    NASA Astrophysics Data System (ADS)

    Díaz, C.; García, J. A.; Mändl, S.; Pereiro, R.; Fernández, B.; Rodríguez, R. J.

    2012-11-01

    Plasma immersion ion implantation of Nitrogen and Oxygen on CoCrMo alloys was carried out to improve the tribological and corrosion behaviors of these biomedical alloys. In order to optimize the implantation results we were carried experiments at different temperatures. Tribocorrosion tests in bovine serum were used to measure Co, Cr and Mo releasing by using Inductively Coupled Plasma Mass Spectrometry analysis after tests. Also, X-ray Diffraction analysis were employed in order to explain any obtained difference in wear rate and corrosion tests. Wear tests reveals important decreases in rate of more than one order of magnitude for the best treatment. Moreover decreases in metal release were found for all the implanted samples, preserving the same corrosion resistance of the unimplanted samples. Finally this paper gathers an analysis, in terms of implantation parameters and achieved properties for industrial implementation of these treatments.

  17. Structures and physical properties of gaseous metal cationized biological ions.

    PubMed

    Burt, Michael B; Fridgen, Travis D

    2012-01-01

    Metal chelation can alter the activity of free biomolecules by modifying their structures or stabilizing higher energy tautomers. In recent years, mass spectrometric techniques have been used to investigate the effects of metal complexation with proteins, nucleobases and nucleotides, where small conformational changes can have significant physiological consequences. In particular, infrared multiple photon dissociation spectroscopy has emerged as an important tool for determining the structure and reactivity of gas-phase ions. Unlike other mass spectrometric approaches, this method is able to directly resolve structural isomers using characteristic vibrational signatures. Other activation and dissociation methods, such as blackbody infrared radiative dissociation or collision-induced dissociation can also reveal information about the thermochemistry and dissociative pathways of these biological ions. This information can then be used to provide information about the structures of the ionic complexes under study. In this article, we review the use of gas-phase techniques in characterizing metal-bound biomolecules. Particular attention will be given to our own contributions, which detail the ability of metal cations to disrupt nucleobase pairs, direct the self-assembly of nucleobase clusters and stabilize non-canonical isomers of amino acids.

  18. Antibacterial, Antifungal and Nematicidal Activities of Rare Earth Ions.

    PubMed

    Wakabayashi, Tokumitsu; Ymamoto, Ayumi; Kazaana, Akira; Nakano, Yuta; Nojiri, Yui; Kashiwazaki, Moeko

    2016-12-01

    Despite the name, rare earth elements are relatively abundant in soil. Therefore, these elements might interact with biosphere during the history of life. In this study, we have examined the effect of rare earth ions on the growth of bacteria, fungi and soil nematode. All rare earth ions, except radioactive promethium that we have not tested, showed antibacterial and antifungal activities comparable to that of copper ions, which is widely used as antibacterial metals in our daily life. Rare earth ions also have nematicidal activities as they strongly perturb the embryonic development of the nematode, Caenorhabditis elegans. Interestingly, the nematicidal activity increased with increasing atomic number of lanthanide ions. Since the rare earth ions did not show high toxicity to the human lymphoblastoid cell line or even stimulate the growth of the cultured cells at 1 mM, it raised the possibility that we can substitute rare earth elements for the antibacterial metals usually used because of their safety.

  19. A biosystem for removal of metal ions from water

    SciTech Connect

    Kilbane, J.J. II.

    1990-01-01

    The presence of heavy metal ions in ground and surface waters constitutes a potential health risk and is an environmental concern. Moreover, processes for the recovery of valuable metal ions are of interest. Bioaccumulation or biosorption is not only a factor in assessing the environmental risk posed by metal ions; it can also be used as a means of decontamination. A biological system for the removal and recovery of metal ions from contaminated water is reported here. Exopolysaccharide-producing microorganisms, including a methanotrophic culture, are demonstrated to have superior metal binding ability, compared with other microbial cultures. This paper describes a biosorption process in which dried biomass obtained from exopolysaccharide-producing microorganisms is encapsulated in porous plastic beads and is used for metal ion binding and recovery. 22 refs., 13 figs.

  20. Metal ions in biological catalysis: from enzyme databases to general principles.

    PubMed

    Andreini, Claudia; Bertini, Ivano; Cavallaro, Gabriele; Holliday, Gemma L; Thornton, Janet M

    2008-11-01

    We analysed the roles and distribution of metal ions in enzymatic catalysis using available public databases and our new resource Metal-MACiE (http://www.ebi.ac.uk/thornton-srv/databases/Metal_MACiE/home.html). In Metal-MACiE, a database of metal-based reaction mechanisms, 116 entries covering 21% of the metal-dependent enzymes and 70% of the types of enzyme-catalysed chemical transformations are annotated according to metal function. We used Metal-MACiE to assess the functions performed by metals in biological catalysis and the relative frequencies of different metals in different roles, which can be related to their individual chemical properties and availability in the environment. The overall picture emerging from the overview of Metal-MACiE is that redox-inert metal ions are used in enzymes to stabilize negative charges and to activate substrates by virtue of their Lewis acid properties, whereas redox-active metal ions can be used both as Lewis acids and as redox centres. Magnesium and zinc are by far the most common ions of the first type, while calcium is relatively less used. Magnesium, however, is most often bound to phosphate groups of substrates and interacts with the enzyme only transiently, whereas the other metals are stably bound to the enzyme. The most common metal of the second type is iron, which is prevalent in the catalysis of redox reactions, followed by manganese, cobalt, molybdenum, copper and nickel. The control of the reactivity of redox-active metal ions may involve their association with organic cofactors to form stable units. This occurs sometimes for iron and nickel, and quite often for cobalt and molybdenum.

  1. Molecular designs for controlling the local environments around metal ions.

    PubMed

    Cook, Sarah A; Borovik, A S

    2015-08-18

    The functions of metal complexes are directly linked to the local environment in which they are housed; modifications to the local environment (or secondary coordination sphere) are known to produce changes in key properties of the metal centers that can affect reactivity. Noncovalent interactions are the most common and influential forces that regulate the properties of secondary coordination spheres, which leads to complexities in structure that are often difficult to achieve in synthetic systems. Using key architectural features from the active sites of metalloproteins as inspiration, we have developed molecular systems that enforce intramolecular hydrogen bonds (H-bonds) around a metal center via incorporation of H-bond donors and acceptors into rigid ligand scaffolds. We have utilized these molecular species to probe mechanistic aspects of biological dioxygen activation and water oxidation. This Account describes the stabilization and characterization of unusual M-oxo and heterobimetallic complexes. These types of species have been implicated in a range of oxidative processes in biology but are often difficult to study because of their inherent reactivity. Our H-bonding ligand systems allowed us to prepare an Fe(III)-oxo species directly from the activation of O2 that was subsequently oxidized to form a monomeric Fe(IV)-oxo species with an S = 2 spin state, similar to those species proposed as key intermediates in non-heme monooxygenases. We also demonstrated that a single Mn(III)-oxo center that was prepared from water could be converted to a high-spin Mn(V)-oxo species via stepwise oxidation, a process that mimics the oxidative charging of the oxygen-evolving complex (OEC) of photosystem II. Current mechanisms for photosynthetic O-O bond formation invoke a Mn(IV)-oxyl species rather than the isoelectronic Mn(V)-oxo system as the key oxidant based on computational studies. However, there is no experimental information to support the existence of a Mn

  2. Effect of Mg(2+), Ca(2+), Sr(2+) and Ba(2+) metal ions on the antifungal activity of ZnO nanoparticles tested against Candida albicans.

    PubMed

    Haja Hameed, Abdulrahman Syedahamed; Karthikeyan, Chandrasekaran; Senthil Kumar, Venugopal; Kumaresan, Subramanian; Sasikumar, Seemaisamy

    2015-01-01

    The antifungal ability of pure and alkaline metal ion (Mg(2+), Ca(2+), Sr(2+) and Ba(2+)) doped ZnO nanoparticles (NPs) prepared by the co-precipitation method was tested against the pathogenic yeast, Candida albicans (C. albicans), and the results showed that the Mg-doped ZnO NPs possessed greater effect than the other alkaline metal ion doped ZnO NPs. The impact of the concentration of Mg doped ZnO sample on the growth of C. albicans was also studied. The Minimal Fungicidal Concentration (MFC) of the Mg doped ZnO NPs was found to be 2000 μg/ml for which the growth of C. albicans was completely inhibited. The ZnO:Mg sample (1.5mg/ml) with various concentrations of histidine reduced the fungicidal effect of the nanoparticles against C. albicans, which was deliberately explained by the role of ROS. The ZnO:Mg sample added with 5mM of histidine scavenged the ample amount of generated ROS effectively. The binding of the NPs with fungi was observed by their FESEM images and their electrostatic attraction is confirmed by the zeta potential measurement.

  3. Spectroscopic detection of metals ions using a novel selective sensor

    NASA Astrophysics Data System (ADS)

    Peralta-Domínguez, D.; Ramos-Ortiz, G.; Maldonado, J. L.; Rodriguez, M.; Meneses-Nava, M. A.; Barbosa-Garcia, O.; Santillan, R.; Farfan, N.

    2011-09-01

    Colorimetric chemosensors are simple, economical and practical optical approach for detecting toxic metal ions (Hg2+, Pb2+, Ni2+, etc.) in the environment. In this work, we present a simple but highly specific organic compound 4-chloro-2-((E)-((E)-3-(4-(dimethylamino)phenyl)allylidene)amino)phenol (L1) that acts as a colorimetric sensor for divalent metal ions in H2O. The mechanism of the interaction between L1 and various metal-ions has been established by UV-vis absorption and emission spectroscopic experiments that indicate favorable coordination of metal ions with L1 in different solvents. Experimental results indicate that the shape of the electronic transition band of L1 (receptor compound) changed after the interaction with divalent metal-ions, such as Hg2+, Pb2+, Mn2+, Co2+, Cu2+, and Ni2+ in aqueous solution. We found that L1 have a considerable selectivity for Ni2+ ions, even in presence of other metals ions when mixtures of DMSO/H2O as are used as solvents. L1, which has been targeted for sensing transition metal ions, exhibits binding-induced color changes from yellow to pink observed even by the naked eye in presence of Ni2+ ions.

  4. A divalent cation stabilizes the active conformation of the B. subtilis RNase P x pre-tRNA complex: a role for an inner-sphere metal ion in RNase P.

    PubMed

    Hsieh, John; Koutmou, Kristin S; Rueda, David; Koutmos, Markos; Walter, Nils G; Fierke, Carol A

    2010-07-02

    Metal ions interact with RNA to enhance folding, stabilize structure, and, in some cases, facilitate catalysis. Assigning functional roles to specifically bound metal ions presents a major challenge in analyzing the catalytic mechanisms of ribozymes. Bacillus subtilis ribonuclease P (RNase P), composed of a catalytically active RNA subunit (PRNA) and a small protein subunit (P protein), catalyzes the 5'-end maturation of precursor tRNAs (pre-tRNAs). Inner-sphere coordination of divalent metal ions to PRNA is essential for catalytic activity but not for the formation of the RNase P x pre-tRNA (enzyme-substrate, ES) complex. Previous studies have demonstrated that this ES complex undergoes an essential conformational change (to the ES* conformer) before the cleavage step. Here, we show that the ES* conformer is stabilized by a high-affinity divalent cation capable of inner-sphere coordination, such as Ca(II) or Mg(II). Additionally, a second, lower-affinity Mg(II) activates cleavage catalyzed by RNase P. Structural changes that occur upon binding Ca(II) to the ES complex were determined by time-resolved Förster resonance energy transfer measurements of the distances between donor-acceptor fluorophores introduced at specific locations on the P protein and pre-tRNA 5' leader. These data demonstrate that the 5' leader of pre-tRNA moves 4 to 6 A closer to the PRNA x P protein interface during the ES-to-ES* transition and suggest that the metal-dependent conformational change reorganizes the bound substrate in the active site to form a catalytically competent ES* complex.

  5. Multiple metal ions drive DNA association by PvuII endonuclease.

    PubMed

    Conlan, Lori H; Dupureur, Cynthia M

    2002-12-17

    Restriction enzymes serve as important model systems for understanding the role of metal ions in phosphodiester hydrolysis. To this end, a number of laboratories have reported dramatic differences between the metal ion-dependent and metal ion-independent DNA binding behaviors of these systems. In an effort to illuminate the underlying mechanistic details which give rise to these differences, we have quantitatively dissected these equilibrium behaviors into component association and dissociation rates for the representative PvuII endonuclease and use these data to assess the stoichiometry of metal ion involvement in the binding process. The dependence of PvuII cognate DNA on Ca(II) concentration binding appears to be cooperative, exhibiting half-saturation at 0.6 mM metal ion and yielding an n(H) of 3.5 +/- 0.2 per enzyme homodimer. Using both nitrocellulose filter binding and fluorescence assays, we observe that the cognate DNA dissociation rate (k(-)(1) or k(off)) is very slow (10(-)(3) s(-)(1)) and exhibits a shallow dependence on metal ion concentration. DNA trap cleavage experiments with Mg(II) confirm the general irreversibility of DNA binding relative to cleavage, even at low metal ion concentrations. More dramatically, the association rate (k(1) or k(on)) also appears to be cooperative, increasing more than 100-fold between 0.2 and 10 mM Ca(II), with an optimum value of 2.7 x 10(7) M(-)(1) s (-)(1). Hill analysis of the metal ion dependence of k(on) indicates an n(H) of 3.6 +/- 0.2 per enzyme dimer. This value is consistent with the involvement in DNA association of two metal ions per subunit active site, a result which lends new strength to arguments for two-metal ion mechanisms in restriction enzymes.

  6. Fluorescent carbon nanoparticles for the fluorescent detection of metal ions.

    PubMed

    Guo, Yongming; Zhang, Lianfeng; Zhang, Shushen; Yang, Yan; Chen, Xihan; Zhang, Mingchao

    2015-01-15

    Fluorescent carbon nanoparticles (F-CNPs) as a new kind of fluorescent nanoparticles, have recently attracted considerable research interest in a wide range of applications due to their low-cost and good biocompatibility. The fluorescent detection of metal ions is one of the most important applications. In this review, we first present the general detection mechanism of F-CNPs for the fluorescent detection of metal ions, including fluorescence turn-off, fluorescence turn-on, fluorescence resonance energy transfer (FRET) and ratiometric response. We then focus on the recent advances of F-CNPs in the fluorescent detection of metal ions, including Hg(2+), Cu(2+), Fe(3+), and other metal ions. Further, we discuss the research trends and future prospects of F-CNPs. We envision that more novel F-CNPs-based nanosensors with more accuracy and robustness will be widely used to assay and remove various metal ions, and there will be more practical applications in coming years.

  7. Molecular Designs for Controlling the Local Environments around Metal Ions

    PubMed Central

    Cook, Sarah A.; Borovik, A.S.

    2015-01-01

    CONSPECTUS The functions of metal complexes are directly linked to the local environment in which they are housed; modifications to the local environment (or secondary coordination sphere) are known to produce changes in key properties of the metal centers that can affect reactivity. Non-covalent interactions are the most common and influential forces that regulate the properties of secondary coordination spheres, which leads to complexities in structure that are often difficult to achieve in synthetic systems. Using key architectural features from the active sites of metalloproteins as inspiration, we have developed molecular systems that enforce intramolecular hydrogen bonds (H-bonds) around a metal center via incorporation of H-bond donors and acceptors into rigid ligand scaffolds. We have utilized these molecular species to probe mechanistic aspects of biological dioxygen activation and water oxidation. This Account describes the stabilization and characterization of unusual M–oxo and heterobimetallic complexes. These types of species have been implicated in a range of oxidative processes in biology but are often difficult to study because of their inherent reactivity. Our H-bonding ligand systems allowed us to prepare an FeIII–oxo species directly from the activation of O2 that was subsequently oxidized to form a monomeric FeIV–oxo species with an S = 2 spin state, similar to those species proposed as key intermediates in non-heme monooxygenases. We also demonstrated that a single MnIII–oxo center that was prepared from water could be converted to a high spin MnV–oxo species via stepwise oxidation—a process that mimics the oxidative charging of the oxygen-evolving complex (OEC) of photosystem II. Current mechanisms for photosynthetic O–O bond formation invoke a MnIV–oxyl species rather than the isoelectronic MnV–oxo system as the key oxidant based on computational studies. However, there is no experimental information to support the existence

  8. Mixed ligand complexation of some transition metal ions in solution and solid state: Spectral characterization, antimicrobial, antioxidant, DNA cleavage activities and molecular modeling

    NASA Astrophysics Data System (ADS)

    Shobana, Sutha; Dharmaraja, Jeyaprakash; Selvaraj, Shanmugaperumal

    2013-04-01

    Equilibrium studies of Ni(II), Cu(II) and Zn(II) mixed ligand complexes involving a primary ligand 5-fluorouracil (5-FU; A) and imidazoles viz., imidazole (him), benzimidazole (bim), histamine (hist) and L-histidine (his) as co-ligands(B) were carried out pH-metrically in aqueous medium at 310 ± 0.1 K with I = 0.15 M (NaClO4). In solution state, the stoichiometry of MABH, MAB and MAB2 species have been detected. The primary ligand(A) binds the central M(II) ions in a monodentate manner whereas him, bim, hist and his co-ligands(B) bind in mono, mono, bi and tridentate modes respectively. The calculated Δ log K, log X and log X' values indicate higher stability of the mixed ligand complexes in comparison to binary species. Stability of the mixed ligand complex equilibria follows the Irving-Williams order of stability. In vitro biological evaluations of the free ligand(A) and their metal complexes by well diffusion technique show moderate activities against common bacterial and fungal strains. Oxidative cleavage interaction of ligand(A) and their copper complexes with CT DNA is also studied by gel electrophoresis method in the presence of oxidant. In vitro antioxidant evaluations of the primary ligand(A), CuA and CuAB complexes by DPPH free radical scavenging model were carried out. In solid, the MAB type of M(II)sbnd 5-FU(A)sbnd his(B) complexes were isolated and characterized by various physico-chemical and spectral techniques. Both the magnetic susceptibility and electronic spectral analysis suggest distorted octahedral geometry. Thermal studies on the synthesized mixed ligand complexes show loss of coordinated water molecule in the first step followed by decomposition of the organic residues subsequently. XRD and SEM analysis suggest that the microcrystalline nature and homogeneous morphology of MAB complexes. Further, the 3D molecular modeling and analysis for the mixed ligand MAB complexes have also been carried out.

  9. A self-sputtering ion source: A new approach to quiescent metal ion beams

    SciTech Connect

    Oks, Efim M.; Anders, Andre

    2009-09-03

    A new metal ion source is presented based on sustained self-sputtering plasma in a magnetron discharge. Metals exhibiting high self-sputtering yield like Cu, Ag, Zn, and Bi can be used in a high-power impulse magnetron sputtering (HIPIMS) discharge such that the plasma almost exclusively contains singly charged metal ions of the target material. The plasma and extracted ion beam are quiescent. The ion beams consist mostly of singly charged ions with a space-charge limited current density which reached about 10 mA/cm2 at an extraction voltage of 45 kV and a first gap spacing of 12 mm.

  10. DNA as sensors and imaging agents for metal ions.

    PubMed

    Xiang, Yu; Lu, Yi

    2014-02-17

    Increasing interest in detecting metal ions in many chemical and biomedical fields has created demands for developing sensors and imaging agents for metal ions with high sensitivity and selectivity. This review covers recent progress in DNA-based sensors and imaging agents for metal ions. Through both combinatorial selection and rational design, a number of metal-ion-dependent DNAzymes and metal-ion-binding DNA structures that can selectively recognize specific metal ions have been obtained. By attachment of these DNA molecules with signal reporters such as fluorophores, chromophores, electrochemical tags, and Raman tags, a number of DNA-based sensors for both diamagnetic and paramagnetic metal ions have been developed for fluorescent, colorimetric, electrochemical, and surface Raman detection. These sensors are highly sensitive (with a detection limit down to 11 ppt) and selective (with selectivity up to millions-fold) toward specific metal ions. In addition, through further development to simplify the operation, such as the use of "dipstick tests", portable fluorometers, computer-readable disks, and widely available glucose meters, these sensors have been applied for on-site and real-time environmental monitoring and point-of-care medical diagnostics. The use of these sensors for in situ cellular imaging has also been reported. The generality of the combinatorial selection to obtain DNAzymes for almost any metal ion in any oxidation state and the ease of modification of the DNA with different signal reporters make DNA an emerging and promising class of molecules for metal-ion sensing and imaging in many fields of applications.

  11. Alkali metal ion battery with bimetallic electrode

    DOEpatents

    Boysen, Dane A; Bradwell, David J; Jiang, Kai; Kim, Hojong; Ortiz, Luis A; Sadoway, Donald R; Tomaszowska, Alina A; Wei, Weifeng; Wang, Kangli

    2015-04-07

    Electrochemical cells having molten electrodes having an alkali metal provide receipt and delivery of power by transporting atoms of the alkali metal between electrode environments of disparate chemical potentials through an electrochemical pathway comprising a salt of the alkali metal. The chemical potential of the alkali metal is decreased when combined with one or more non-alkali metals, thus producing a voltage between an electrode comprising the molten the alkali metal and the electrode comprising the combined alkali/non-alkali metals.

  12. Heavy metals testing in active pharmaceutical ingredients: an alternate approach.

    PubMed

    Raghuram, P; Soma Raju, I V; Sriramulu, J

    2010-01-01

    The principle of the pharmacopoeial heavy metals test is detection and estimation of the metallic impurities colored by sulfide ion by comparison against lead standard. The test suffers from a loss of analytes upon ashing and from having varied responses for various metals. An inductively coupled plasma-optical emission spectroscopy (ICP-OES) for estimating 23 metals in active pharmaceutical ingredients is being proposed. The method covers the metals listed in USP, Ph. Eur and EMEA guidance on "Residues of Metal Catalysts or Metal Reagents".

  13. How do energetic ions damage metallic surfaces?

    DOE PAGES

    Osetskiy, Yury N.; Calder, Andrew F.; Stoller, Roger E.

    2015-02-20

    Surface modification under bombardment by energetic ions observed under different conditions in structural and functional materials and can be either unavoidable effect of the conditions or targeted modification to enhance materials properties. Understanding basic mechanisms is necessary for predicting properties changes. The mechanisms activated during ion irradiation are of atomic scale and atomic scale modeling is the most suitable tool to study these processes. In this paper we present results of an extensive simulation program aimed at developing an understanding of primary surface damage in iron by energetic particles. We simulated 25 keV self-ion bombardment of Fe thin films withmore » (100) and (110) surfaces at room temperature. A large number of simulations, ~400, were carried out allow a statistically significant treatment of the results. The particular mechanism of surface damage depends on how the destructive supersonic shock wave generated by the displacement cascade interacts with the free surface. Three basic scenarios were observed, with the limiting cases being damage created far below the surface with little or no impact on the surface itself, and extensive direct surface damage on the timescale of a few picoseconds. In some instances, formation of large <100> vacancy loops beneath the free surface was observed, which may explain some earlier experimental observations.« less

  14. How do energetic ions damage metallic surfaces?

    SciTech Connect

    Osetskiy, Yury N.; Calder, Andrew F.; Stoller, Roger E.

    2015-02-20

    Surface modification under bombardment by energetic ions observed under different conditions in structural and functional materials and can be either unavoidable effect of the conditions or targeted modification to enhance materials properties. Understanding basic mechanisms is necessary for predicting properties changes. The mechanisms activated during ion irradiation are of atomic scale and atomic scale modeling is the most suitable tool to study these processes. In this paper we present results of an extensive simulation program aimed at developing an understanding of primary surface damage in iron by energetic particles. We simulated 25 keV self-ion bombardment of Fe thin films with (100) and (110) surfaces at room temperature. A large number of simulations, ~400, were carried out allow a statistically significant treatment of the results. The particular mechanism of surface damage depends on how the destructive supersonic shock wave generated by the displacement cascade interacts with the free surface. Three basic scenarios were observed, with the limiting cases being damage created far below the surface with little or no impact on the surface itself, and extensive direct surface damage on the timescale of a few picoseconds. In some instances, formation of large <100> vacancy loops beneath the free surface was observed, which may explain some earlier experimental observations.

  15. Structural resolution of 4-substituted proline diastereomers with ion mobility spectrometry via alkali metal ion cationization.

    PubMed

    Flick, Tawnya G; Campuzano, Iain D G; Bartberger, Michael D

    2015-03-17

    The chirality of substituents on an amino acid can significantly change its mode of binding to a metal ion, as shown here experimentally by traveling wave ion mobility spectrometry-mass spectrometry (TWIMS-MS) of different proline isomeric molecules complexed with alkali metal ions. Baseline separation of the cis- and trans- forms of both hydroxyproline and fluoroproline was achieved using TWIMS-MS via metal ion cationization (Li(+), Na(+), K(+), and Cs(+)). Density functional theory calculations indicate that differentiation of these diastereomers is a result of the stabilization of differing metal-complexed forms adopted by the diastereomers when cationized by an alkali metal cation, [M + X](+) where X = Li, Na, K, and Cs, versus the topologically similar structures of the protonated molecules, [M + H](+). Metal-cationized trans-proline variants exist in a linear salt-bridge form where the metal ion interacts with a deprotonated carboxylic acid and the proton is displaced onto the nitrogen atom of the pyrrolidine ring. In contrast, metal-cationized cis-proline variants adopt a compact structure where the carbonyl of the carboxylic acid, nitrogen atom, and if available, the hydroxyl and fluorine substituent solvate the metal ion. Experimentally, it was observed that the resolution between alkali metal-cationized cis- and trans-proline variants decreases as the size of the metal ion increases. Density functional theory demonstrates that this is due to the decreasing stability of the compact charge-solvated cis-proline structure with increased metal ion radius, likely a result of steric hindrance and/or weaker binding to the larger metal ion. Furthermore, the unique structures adopted by the alkali metal-cationized cis- and trans-proline variants results in these molecules having significantly different quantum mechanically calculated dipole moments, a factor that can be further exploited to improve the diastereomeric resolution when utilizing a drift gas with a

  16. Impregnated-electrode-type liquid metal ion source

    NASA Astrophysics Data System (ADS)

    Ishikawa, J.; Gotoh, Y.; Tsuji, H.; Takagi, T.

    We have developed an impregnated-electrode-type liquid metal ion source whose tip is a sintered-porous structure made of a refractory metal such as tungsten. By this structure the ratio of the liquid metal surface area facing the vacuum to the volume is low, which decreases useless metal evaporation from the surface. The maximum vapour pressure of the metal in operation for this ion source is 10 -1-10 0 Torr, which is 2-3 orders of magnitude higher than that for the needle type. Therefore, useful metal ions such as Ga +, Au +, Ag +, In +, Si 2+, Ge 2+, and Sb 2+ can be extracted from single element metals or alloys. The porous structure of the tip has also an effect on the positive control of the liquid metal flow rate to the tip head. Thus, a stable operation with a high current of a few hundreds of μA can be obtained together with a low current high brightness ion beam. Therefore, this ion source is suitable not only for microfocusing but also for a general use as a metal ion source.

  17. Reusable chelating resins concentrate metal ions from highly dilute solutions

    NASA Technical Reports Server (NTRS)

    Bauman, A. J.; Weetal, H. H.; Weliky, N.

    1966-01-01

    Column chromatographic method uses new metal chelating resins for recovering heavy-metal ions from highly dilute solutions. The absorbed heavy-metal cations may be removed from the chelating resins by acid or base washes. The resins are reusable after the washes are completed.

  18. Universal collisional activation ion trap mass spectrometry

    DOEpatents

    McLuckey, S.A.; Goeringer, D.E.; Glish, G.L.

    1993-04-27

    A universal collisional activation ion trap comprises an ion trapping means containing a bath gas and having connected thereto a noise signal generator. A method of operating a universal collisional activation ion trap comprises the steps of: providing an ion trapping means; introducing into the ion trapping means a bath gas; and, generating a noise signal within the ion trapping means; introducing into the ion trapping means a substance that, when acted upon by the noise signal, undergoes collisional activation to form product ions.

  19. Universal collisional activation ion trap mass spectrometry

    DOEpatents

    McLuckey, Scott A.; Goeringer, Douglas E.; Glish, Gary L.

    1993-01-01

    A universal collisional activation ion trap comprises an ion trapping means containing a bath gas and having connected thereto a noise signal generator. A method of operating a universal collisional activation ion trap comprises the steps of: providing an ion trapping means; introducing into the ion trapping means a bath gas; and, generating a noise signal within the ion trapping means; introducing into the ion trapping means a substance that, when acted upon by the noise signal, undergoes collisional activation to form product ions.

  20. Selected metal ions protect Bacillus subtilis biofilms from erosion.

    PubMed

    Grumbein, S; Opitz, M; Lieleg, O

    2014-08-01

    Many problems caused by bacterial biofilms can be traced back to their high resilience towards chemical perturbations and their extraordinary sturdiness towards mechanical forces. However, the molecular mechanisms that link the mechanical properties of a biofilm with the ability of bacteria to survive in different chemical environments remain enigmatic. Here, we study the erosion stability of Bacillus subtilis (B. subtilis) biofilms in the presence of different chemical environments. We find that these biofilms can utilize the absorption of certain metal ions such as Cu(2+), Zn(2+), Fe(2+), Fe(3+) and Al(3+) into the biofilm matrix to avoid erosion by shear forces. Interestingly, many of these metal ions are toxic for planktonic B. subtilis bacteria. However, their toxic activity is suppressed when the ions are absorbed into the biofilm matrix. Our experiments clearly demonstrate that the biofilm matrix has to fulfill a dual function, i.e. regulating both the mechanical properties of the biofilm and providing a selective barrier towards toxic chemicals.

  1. Removal of some heavy metals ions from wastewater by copolymer of iron and aluminum impregnated with active silica derived from rice husk ash.

    PubMed

    Abo-El-Enein, S A; Eissa, M A; Diafullah, A A; Rizk, M A; Mohamed, F M

    2009-12-30

    Recently because of increasing of the environmental awareness and demands, several attempts were carried out for the conversion of by-products of natural materials, especially agricultural wastes, to highly sorption capacity materials. In recent years, attention has been focused on the utilization of unmodified or modified agro-residues as sorbents for removal of pollutants. Various modifications have been reported to enhance sorption capacities for heavy metals. The present study deals with the adsorption equilibrium of iron, manganese, lead and arsenic ions from aqueous solutions on copolymer of Al(+3), Si(+4) and Fe(+3) using batch techniques. The influence of various parameters, such as agitation time, sorbent mass and pH of sorbate solution were investigated. Under this study the maximum adsorption capacity of iron and aluminum copolymer impregnated with silica (PAlFeClSi) for lead, iron, manganese and arsenic are found to be 416, 222, 158, 146 mg/g, respectively.

  2. New Catalytic DNA Biosensors for Radionuclides and Metal ions

    SciTech Connect

    Lu, Yi

    2003-06-01

    The goals of the project are to develop new catalytic DNA biosensors for simultaneous detection and quantification of bioavailable radionuclides and metal ions, and apply the sensors for on-site, real-time assessment of concentration, speciation and stability of the individual contaminants during and after bioremediation. A negative selection strategy was tested and validated. In vitro selection was shown to yield highly active and specific transition metal ion-dependent catalytic DNA/RNA. A fluorescence resonance energy transfer (FRET) study of in vitro selected DNA demonstrated that the trifluorophore labeled system is a simple and powerful tool in studying complex biomolecules structure and dynamics, and is capable of revealing new sophisticated structural changes. New fluorophore/quenchers in a single fluorosensor yielded improved signal to noise ratio in detection, identification and quantification of metal contaminants. Catalytic DNA fluorescent and colorimetric sensors were shown useful in sensing lead in lake water and in leaded paint. Project results were described in two papers and two patents, and won an international prize.

  3. New Catalytic DNA Biosensors for Radionuclides and Metal ions

    SciTech Connect

    Lu, Yi

    2002-06-01

    The goals of the project are to develop new catalytic DNA biosensors for simultaneous detection and quantification of bioavailable radionuclides and metal ions, and apply the sensors for on-site, real-time assessment of concentration, speciation and stability of the individual contaminants during and after bioremediation. A negative selection strategy was tested and validated. In vitro selection was shown to yield highly active and specific transition metal ion-dependent catalytic DNA/RNA. A fluorescence resonance energy transfer (FRET) study of in vitro selected DNA demonstrated that the trifluorophore labeled system is a simple and powerful tool in studying complex biomolecules structure and dynamics, and is capable of revealing new sophisticated structural changes. New fluorophore/quenchers in a single fluorosensor yielded improved signal to noise ratio in detection, identification and quantification of metal contaminants. Catalytic DNA fluorescent and colorimetric sensors were shown useful in sensing lead in lake water and in leaded paint. Project results were described in two papers and two patents, and won an international prize.

  4. Ion Beam Synthesis Of Metal - Silicon Carbide - Si Multilayer Structures

    NASA Astrophysics Data System (ADS)

    Lindner, J. K. N.; Tsang, W. M.; Stritzker, B.; Wong, S. P.

    2003-08-01

    High doses of Ti, Ni, Mo, or W ions were implanted at elevated temperatures either conventionally or using a MEVVA ion source into ion beam synthesized Si/SiC/Si or SiC/Si layer structures in order to create metallic layers contacting the SiC. The depth distribution of metal atoms and the formation of silicide and carbide phases as well as the formation of cavities at the lower SiC/Si interface are studied by Rutherford backscattering spectroscopy (RBS) and cross-sectional transmission electron microscopy (XTEM). A brief survey of the effects ocurring in the ion beam metallization of SiC films is given and the benefit of using ion beams for metallization of thin films is elucidated.

  5. Metal ion sensing solution containing double crossover DNA

    NASA Astrophysics Data System (ADS)

    Park, Byeongho; Dugasani, Sreekantha R.; Cho, Youngho; Oh, Juyeong; Kim, Chulki; Seo, Min Ah; Lee, Taikjin; Jhon, Young Miin; Woo, Deok Ha; Lee, Seok; Jun, Seong Chan; Park, Sung Ha; Kim, Jae Hun

    2015-07-01

    The current study describes metal ion sensing with double crossover DNAs (DX1 and DX2), artificially designed as a platform of doping. The sample for sensing is prepared by a facile annealing method to grow the DXs lattice on a silicon/silicon oxide. Adding and incubating metal ion solution with the sensor substrate into the micro-tube lead the optical property change. Photoluminescence (PL) is employed for detecting the concentration of metal ion in the specimen. We investigated PL emission for sensor application with the divalent copper. In the range from 400 to 650 nm, the PL features of samples provide significantly different peak positions with excitation and emission detection. Metal ions contribute to modify the optical characteristics of DX with structural and functional change, which results from the intercalation of them into hydrogen bonding positioned at the center of double helix. The PL intensity is decreased gradually after doping copper ion in the DX tile on the substrate.

  6. Metal-ion mutagenesis: conversion of a purple acid phosphatase from sweet potato to a neutral phosphatase with the formation of an unprecedented catalytically competent Mn(II)Mn(II) active site.

    PubMed

    Mitić, Natasa; Noble, Christopher J; Gahan, Lawrence R; Hanson, Graeme R; Schenk, Gerhard

    2009-06-17

    The currently accepted paradigm is that the purple acid phosphatases (PAPs) require a heterovalent, dinuclear metal-ion center for catalysis. It is believed that this is an essential feature for these enzymes in order for them to operate under acidic conditions. A PAP from sweet potato is unusual in that it appears to have a specific requirement for manganese, forming a unique Fe(III)-mu-(O)-Mn(II) center under catalytically optimal conditions (Schenk et al. Proc. Natl. Acad. Sci. U.S.A. 2005, 102, 273). Herein, we demonstrate, with detailed electron paramagnetic resonance (EPR) spectroscopic and kinetic studies, that in this enzyme the chromophoric Fe(III) can be replaced by Mn(II), forming a catalytically active, unprecedented antiferromagnetically coupled homodivalent Mn(II)-mu-(H)OH-mu-carboxylato-Mn(II) center in a PAP. However, although the enzyme is still active, it no longer functions as an acid phosphatase, having optimal activity at neutral pH. Thus, PAPs may have evolved from distantly related divalent dinuclear metallohydrolases that operate under pH neutral conditions by stabilization of a trivalent-divalent metal-ion core. The present Mn(II)-Mn(II) system models these distant relatives, and the results herein make a significant contribution to our understanding of the role of the chromophoric metal ion as an activator of the nucleophile. In addition, the detailed analysis of strain broadened EPR spectra from exchange-coupled dinuclear Mn(II)-Mn(II) centers described herein provides the basis for the full interpretation of the EPR spectra from other dinuclear Mn metalloenzymes.

  7. Synthesis of modified gum tragacanth/graphene oxide composite hydrogel for heavy metal ions removal and preparation of silver nanocomposite for antibacterial activity.

    PubMed

    Sahraei, Razieh; Ghaemy, Mousa

    2017-02-10

    New composite hydrogels were synthesized based on gum tragacanth (GT) carbohydrate and graphene oxide (GO). GT was sulfonic acid-functionalized and cross-linked by using 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and N,N'-methylenebisacrylamide (MBA) monomers and ceric ammonium nitrate (CAN) as an initiator. The prepared hydrogels were characterized by Fourier transform infrared spectrum (FT-IR), field emission scanning electron microscope (FE-SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). Adsorption process for removal of heavy metal ions has followed the pseudo-first-order kinetic model and fitted well with the Langmuir model. The maximum adsorption capacity (Qm) was 142.50, 112.50 and 132.12mgg(-1) for Pb(II), Cd(II), and Ag(I), respectively. The removal percentage decreased slightly after several adsorption/desorption cycles. The adsorbed Ag(I) ions in hydrogel were transformed to Ag(0) nanoparticles (with a narrow distribution and mean size of 13.0nm) by using Achillea millefolium flower extract. The antibacterial performance of the Ag(0) nanocomposite hydrogel was also investigated.

  8. Adhesive bonding of ion beam textured metals and fluoropolymers

    NASA Technical Reports Server (NTRS)

    Mirtich, M. J.; Sovey, J. S.

    1978-01-01

    An electron bombardment argon ion source was used to ion etch various metals and fluoropolymers. The metal and fluoropolymers were exposed to (0.5 to 1.0) keV Ar ions at ion current densities of (0.2 to 1.5) mA/sq cm for various exposure times. The resulting surface texture is in the form of needles or spires whose vertical dimensions may range from tenths to hundreds of micrometers, depending on the selection of beam energy, ion current density, and etch time. The bonding of textured surfaces is accomplished by ion beam texturing mating pieces of either metals or fluoropolymers and applying a bonding agent which wets in and around the microscopic cone-like structures. After bonding, both tensile and shear strength measurements were made on the samples. Also tested, for comparison's sake, were untextured and chemically etched fluoropolymers. The results of these measurements are presented.

  9. Bioinorganic Chemistry of the Alkali Metal Ions.

    PubMed

    Kim, Youngsam; Nguyen, Thuy-Tien T; Churchill, David G

    2016-01-01

    The common Group 1 alkali metals are indeed ubiquitous on earth, in the oceans and in biological systems. In this introductory chapter, concepts involving aqueous chemistry and aspects of general coordination chemistry and oxygen atom donor chemistry are introduced. Also, there are nuclear isotopes of importance. A general discussion of Group 1 begins from the prevalence of the ions, and from a comparison of their ionic radii and ionization energies. While oxygen and water molecule binding have the most relevance to biology and in forming a detailed understanding between the elements, there is a wide range of basic chemistry that is potentially important, especially with respect to biological chelation and synthetic multi-dentate ligand design. The elements are widely distributed in life forms, in the terrestrial environment and in the oceans. The details about the workings in animal, as well as plant life are presented in this volume. Important biometallic aspects of human health and medicine are introduced as well. Seeing as the elements are widely present in biology, various particular endogenous molecules and enzymatic systems can be studied. Sodium and potassium are by far the most important and central elements for consideration. Aspects of lithium, rubidium, cesium and francium chemistry are also included; they help in making important comparisons related to the coordination chemistry of Na(+) and K(+). Physical methods are also introduced.

  10. Progress in metal ion separation and preconcentration : an overview.

    SciTech Connect

    Bond, A. H.

    1998-05-19

    A brief historical perspective covering the most mature chemically-based metal ion separation methods is presented, as is a summary of the recommendations made in the 1987 National Research Council (NRC) report entitled ''Separation and Purification: Critical Needs and Opportunities''. A review of Progress in Metal Ion Separation and Preconcentration shows that advances are occurring in each area of need cited by the NRC. Following an explanation of the objectives and general organization of this book, the contents of each chapter are briefly summarized and some future research opportunities in metal ion separations are presented.

  11. An Animal Model Using Metallic Ions to Produce Autoimmune Nephritis.

    PubMed

    Ramírez-Sandoval, Roxana; Luévano-Rodríguez, Nayeli; Rodríguez-Rodríguez, Mayra; Pérez-Pérez, María Elena; Saldívar-Elias, Sergio; Gurrola-Carlos, Reinaldo; Avalos-Díaz, Esperanza; Bollain-y-Goytia, Juan José; Herrera-Esparza, Rafael

    2015-01-01

    Autoimmune nephritis triggered by metallic ions was assessed in a Long-Evans rat model. The parameters evaluated included antinuclear autoantibody production, kidney damage mediated by immune complexes detected by immunofluorescence, and renal function tested by retention of nitrogen waste products and proteinuria. To accomplish our goal, the animals were treated with the following ionic metals: HgCl2, CuSO4, AgNO3, and Pb(NO3)2. A group without ionic metals was used as the control. The results of the present investigation demonstrated that metallic ions triggered antinuclear antibody production in 60% of animals, some of them with anti-DNA specificity. Furthermore, all animals treated with heavy metals developed toxic glomerulonephritis with immune complex deposition along the mesangium and membranes. These phenomena were accompanied by proteinuria and increased concentrations of urea. Based on these results, we conclude that metallic ions may induce experimental autoimmune nephritis.

  12. Does bearing size influence metal ion levels in large-head metal-on-metal total hip arthroplasty? A comparison of three total hip systems

    PubMed Central

    2014-01-01

    Background The purpose of the study was twofold: first, to determine whether there is a statistically significant difference in the metal ion levels among three different large-head metal-on-metal (MOM) total hip systems. The second objective was to assess whether position of the implanted prostheses, patient demographics or factors such as activity levels influence overall blood metal ion levels and whether there is a difference in the functional outcomes between the systems. Methods In a cross-sectional cohort study, three different metal-on-metal total hip systems were assessed: two monoblock heads, the Durom socket (Zimmer, Warsaw, IN, USA) and the Birmingham socket (Smith and Nephew, Memphis, TN, USA), and one modular metal-on-metal total hip system (Pinnacle, Depuy Orthopedics, Warsaw, IN, USA). Fifty-four patients were recruited, with a mean age of 59.7 years and a mean follow-up time of 41 months (12 to 60). Patients were evaluated clinically, radiologically and biochemically. Statistical analysis was performed on all collected data to assess any differences between the three groups in terms of overall blood metal ion levels and also to identify whether there was any other factor within the group demographics and outcomes that could influence the mean levels of Co and Cr. Results Although the functional outcome scores were similar in all three groups, the blood metal ion levels in the larger monoblock large heads (Durom, Birmingham sockets) were significantly raised compared with those of the Pinnacle group. In addition, the metal ion levels were not found to have a statistically significant relationship to the anteversion or abduction angles as measured on the radiographs. Conclusions When considering a MOM THR, the use of a monoblock large-head system leads to higher elevations in whole blood metal ions and offers no advantage over a smaller head modular system. PMID:24472283

  13. Rechargeable dual-metal-ion batteries for advanced energy storage.

    PubMed

    Yao, Hu-Rong; You, Ya; Yin, Ya-Xia; Wan, Li-Jun; Guo, Yu-Guo

    2016-04-14

    Energy storage devices are more important today than any time before in human history due to the increasing demand for clean and sustainable energy. Rechargeable batteries are emerging as the most efficient energy storage technology for a wide range of portable devices, grids and electronic vehicles. Future generations of batteries are required to have high gravimetric and volumetric energy, high power density, low price, long cycle life, high safety and low self-discharge properties. However, it is quite challenging to achieve the above properties simultaneously in state-of-the-art single metal ion batteries (e.g. Li-ion batteries, Na-ion batteries and Mg-ion batteries). In this contribution, hybrid-ion batteries in which various metal ions simultaneously engage to store energy are shown to provide a new perspective towards advanced energy storage: by connecting the respective advantages of different metal ion batteries they have recently attracted widespread attention due to their novel performances. The properties of hybrid-ion batteries are not simply the superposition of the performances of single ion batteries. To enable a distinct description, we only focus on dual-metal-ion batteries in this article, for which the design and the benefits are briefly discussed. We enumerate some new results about dual-metal-ion batteries and demonstrate the mechanism for improving performance based on knowledge from the literature and experiments. Although the search for hybrid-ion batteries is still at an early age, we believe that this strategy would be an excellent choice for breaking the inherent disadvantages of single ion batteries in the near future.

  14. Metal ion levels: how can they help us?

    PubMed

    Griffin, William L

    2014-04-01

    Ion levels have been shown to reliably predict abnormal function of the bearing surface with increased wear, but ion levels should not be used alone as a trigger for when to proceed with revision surgery with metal-metal articulations. Risk stratification strategies help determine which patients should be monitored more closely with serial ion levels, cross-sectional imaging with a MARS MRI, or proceed on to revision. Based on the current data available, an ion level greater than 4.5 ppb (Cr or Co) may serve as a threshold for when abnormal wear is occurring, and is suggested as a trigger for a MARS MRI scan.

  15. The catalytic role of the M2 metal ion in PP2Cα.

    PubMed

    Pan, Chang; Tang, Jun-yi; Xu, Yun-fei; Xiao, Peng; Liu, Hong-da; Wang, Hao-an; Wang, Wen-bo; Meng, Fan-guo; Yu, Xiao; Sun, Jin-peng

    2015-02-24

    PP2C family phosphatases (the type 2C family of protein phosphatases; or metal-dependent phosphatase, PPM) constitute an important class of signaling enzymes that regulate many fundamental life activities. All PP2C family members have a conserved binuclear metal ion active center that is essential for their catalysis. However, the catalytic role of each metal ion during catalysis remains elusive. In this study, we discovered that mutations in the structurally buried D38 residue of PP2Cα (PPM1A) redefined the water-mediated hydrogen network in the active site and selectively disrupted M2 metal ion binding. Using the D38A and D38K mutations of PP2Cα as specific tools in combination with enzymology analysis, our results demonstrated that the M2 metal ion determines the rate-limiting step of substrate hydrolysis, participates in dianion substrate binding and stabilizes the leaving group after P-O bond cleavage. The newly characterized catalytic role of the M2 metal ion in this family not only provides insight into how the binuclear metal centers of the PP2C phosphatases are organized for efficient catalysis but also helps increase our understanding of the function and substrate specificity of PP2C family members.

  16. The catalytic role of the M2 metal ion in PP2Cα

    NASA Astrophysics Data System (ADS)

    Pan, Chang; Tang, Jun-Yi; Xu, Yun-Fei; Xiao, Peng; Liu, Hong-Da; Wang, Hao-An; Wang, Wen-Bo; Meng, Fan-Guo; Yu, Xiao; Sun, Jin-Peng

    2015-02-01

    PP2C family phosphatases (the type 2C family of protein phosphatases; or metal-dependent phosphatase, PPM) constitute an important class of signaling enzymes that regulate many fundamental life activities. All PP2C family members have a conserved binuclear metal ion active center that is essential for their catalysis. However, the catalytic role of each metal ion during catalysis remains elusive. In this study, we discovered that mutations in the structurally buried D38 residue of PP2Cα (PPM1A) redefined the water-mediated hydrogen network in the active site and selectively disrupted M2 metal ion binding. Using the D38A and D38K mutations of PP2Cα as specific tools in combination with enzymology analysis, our results demonstrated that the M2 metal ion determines the rate-limiting step of substrate hydrolysis, participates in dianion substrate binding and stabilizes the leaving group after P-O bond cleavage. The newly characterized catalytic role of the M2 metal ion in this family not only provides insight into how the binuclear metal centers of the PP2C phosphatases are organized for efficient catalysis but also helps increase our understanding of the function and substrate specificity of PP2C family members.

  17. Pharmacological activity of metal binding agents that alter copper bioavailability

    PubMed Central

    Helsel, Marian E.

    2015-01-01

    Iron, copper and zinc are required nutrients for many organisms but also potent toxins if misappropriated. An overload of any of these metals can be cytotoxic and ultimately lead to organ failure, whereas deficiencies can result in anemia, weakened immune system function, and other medical conditions. Cellular metal imbalances have been implicated in neurodegenerative diseases, cancer and infection. It is therefore critical for living organisms to maintain careful control of both the total levels and subcellular distributions of these metals to maintain healthy function. This perspective explores several strategies envisioned to alter the bioavailability of metal ions by using synthetic metal-binding agents targeted for diseases where misappropriated metal ions are suspected of exacerbating cellular damage. Specifically, we discuss chemical properties that influence the pharmacological outcome of a subset of metal-binding agents known as ionophores, and review several examples that have shown multiple pharmacological activities in metal-related diseases, with a specific focus on copper. PMID:25797044

  18. Silica-polyamine composite materials for heavy metal ion removal, recovery, and recycling. 2. Metal ion separations from mine wastewater and soft metal ion extraction efficiency

    SciTech Connect

    Fischer, R.J.; Pang, D.; Beatty, S.T.; Rosenberg, E.

    1999-12-01

    Silica-polyamine composites have been synthesized which have metal ion capacities as high as 0.84 mmol/g for copper ions removed from aqueous solutions. In previous reports it has been demonstrated that these materials survive more than 3,000 cycles of metal ion extraction, elution, and regeneration with almost no loss of capacity (less than 10%). This paper describes two modified silica-polyamine composite materials and reveals the results of tests designed to determine the effectiveness of these materials for extracting and separating metal ions from actual mining wastewater samples. Using these materials, the concentration of copper, aluminum, and zinc in Berkeley Pit mine wastewater is reduced to below allowable discharge limits. The recovered copper and zinc solutions were greater than 90% pure, and metal ion concentration factors of over 20 for copper were realized. Further, the ability of one of these materials to decrease low levels of the soft metals cadmium, mercury, and lead from National Sanitation Foundation recommended challenge levels to below Environmental Protection Agency allowable limits is also reported.

  19. Metal ion removal from aqueous solution using physic seed hull.

    PubMed

    Mohammad, Masita; Maitra, Saikat; Ahmad, Naveed; Bustam, Azmi; Sen, T K; Dutta, Binay K

    2010-07-15

    The potential of physic seed hull (PSH), Jantropha curcas L. as an adsorbent for the removal of Cd(2+) and Zn(2+) metal ions from aqueous solution has been investigated. It has been found that the amount of adsorption for both Cd(2+) and Zn(2+) increased with the increase in initial metal ions concentration, contact time, temperature, adsorbent dosage and the solution pH (in acidic range), but decreased with the increase in the particle size of the adsorbent. The adsorption process for both metal ions on PSH consists of three stages-a rapid initial adsorption followed by a period of slower uptake of metal ions and virtually no uptake at the final stage. The kinetics of metal ions adsorption on PSH followed a pseudo-second-order model. The adsorption equilibrium data were fitted in the three adsorption isotherms-Freundlich, Langmuir and Dubinin-Radushkevich isotherms. The data best fit in the Langmuir isotherm indication monolayer chemisorption of the metal ions. The adsorption capacity of PSH for both Zn(2+) and Cd(2+) was found to be comparable with other available adsorbents. About 36-47% of the adsorbed metal could be leached out of the loaded PSH using 0.1M HCl as the eluting medium.

  20. Merging Visible Light Photoredox Catalysis with Metal Catalyzed C–H Activations: On the Role of Oxygen and Superoxide Ions as Oxidants

    PubMed Central

    2016-01-01

    Conspectus The development of efficient catalytic systems for direct aromatic C–H bond functionalization is a long-desired goal of chemists, because these protocols provide environmental friendly and waste-reducing alternatives to classical methodologies for C–C and C–heteroatom bond formation. A key challenge for these transformations is the reoxidation of the in situ generated metal hydride or low-valent metal complexes of the primary catalytic bond forming cycle. To complete the catalytic cycle and to regenerate the C–H activation catalyst, (super)stoichiometric amounts of Cu(II) or Ag(I) salts have often been applied. Recently, “greener” approaches have been developed by applying molecular oxygen in combination with Cu(II) salts, internal oxidants that are cleaved during the reaction, or solvents or additives enabling the metal hydride reoxidation. All these approaches improved the environmental friendliness but have not overcome the obstacles associated with the overall limited functional group and substrate tolerance. Hence, catalytic processes that do not feature the unfavorable aspects described above and provide products in a streamlined as well as economically and ecologically advantageous manner would be desirable. In this context, we decided to examine visible light photoredox catalysis as a new alternative to conventionally applied regeneration/oxidation procedures. This Account summarizes our recent advances in this expanding area and will highlight the new concept of merging distinct redox catalytic processes for C–H functionalizations through the application of visible light photoredox catalysis. Photoredox catalysis can be considered as catalytic electron-donating or -accepting processes, making use of visible-light absorbing homogeneous and heterogeneous metal-based catalysts, as well as organic dye sensitizers or polymers. As a consequence, photoredox catalysis is, in principle, an ideal tool for the recycling of any given metal

  1. Characterization of detergent compatible protease of a halophilic Bacillus sp. EMB9: differential role of metal ions in stability and activity.

    PubMed

    Sinha, Rajeshwari; Khare, S K

    2013-10-01

    A moderately halophilic protease producer, Bacillus sp. strain isolated from sea water is described. The protease is purified to homogeneity by ammonium sulphate precipitation and CM cellulose chromatography. The serine protease has a molecular mass of 29 kDa. Enzymatic characterization of protease revealed K(m) 2.22 mg mL(-1), Vmax 1111.11 U mL(-1), pH optimum 9.0, t1/2 190 min at 60°C and salt optima 1% (w/v) NaCl. The protease is remarkably stable in hydrophilic and hydrophobic solvents at high concentrations. The purified preparation is unstable at room temperature. Ca(2+) ions are required for preventing this loss of activity. Interestingly, the activity and stability are modulated differentially. Whereas, divalent cation Ca(2+) are involved in maintaining stability in solution at room temperature by preventing unfolding, monovalent Na(+) and K(+) ions participate in regulating the activity and assist in refolding of the enzyme. Application of the protease is shown in efficient removal of blood stain.

  2. Alternative binding modes of l-histidine guided by metal ions for the activation of the antiterminator protein HutP of Bacillus subtilis.

    PubMed

    Dhakshnamoorthy, Balasundaresan; Mizuno, Hiroshi; Kumar, Penmetcha K R

    2013-09-01

    Anti-terminator proteins control gene expression by recognizing control signals within cognate transcripts and then preventing transcription termination. HutP is such a regulatory protein that regulates the expression of the histidine utilization (hut) operon in Bacillus subtilis by binding to cis-acting regulatory sequences in hut mRNAs. During the anti-termination process, l-histidine and a divalent ion are required for hutP to bind to the specific sequence within the hut mRNA. Our previous crystal structure of the HutP-l-histidine-Mg(2+)-RNA ternary complex demonstrated that the l-histidine ligand and Mg(2+) bind together such that the backbone nitrogen and carboxyl oxygen of l-histidine coordinate with Mg(2+). In addition to the Mg(2+), other divalent ions are also known to efficiently support the l-histidine-dependent anti-termination of the hut operon, and the best divalent ion is Zn(2+). In this study, we determined the crystal structure of the HutP-l-histidine-Zn(2+) complex and found that the orientation of l-histidine coordinated to Zn(2+) is reversed relative to that of l-histidine coordinated to Mg(2+), i.e., the imidazole side chain nitrogen of l-histidine coordinates to Zn(2+). This alternative binding mode of the l-histidine ligand to a divalent ion provides further insight into the mechanisms responsible for the activation of RNA binding during the hut anti-termination process.

  3. Effects of Alkali Metal Ion Cationization on Fragmentation Pathways of Triazole-Epothilone

    NASA Astrophysics Data System (ADS)

    Duan, Xiyan; Luo, Guoan; Chen, Yue; Kong, Xianglei

    2012-06-01

    The collisionally activated dissociation mass spectra of the protonated and alkali metal cationized ions of a triazole-epothilone analogue were studied in a Fourier transform ion cyclotron resonance mass spectrometer. The fragmentation pathway of the protonated ion was characterized by the loss of the unit of C3H4O3. However, another fragmentation pathway with the loss of C3H2O2 was identified for the complex ions with Na+, K+, Rb+, and Cs+. The branching ratio of the second pathway increases with the increment of the size of alkali metal ions. Theoretical calculations based on density functional theory (DFT) method show the difference in the binding position of the proton and the metal ions. With the increase of the radii of the metal ions, progressive changes in the macrocycle of the compound are induced, which cause the corresponding change in their fragmentation pathways. It has also been found that the interaction energy between the compound and the metal ion decreases with increase in the size of the latter. This is consistent with the experimental results, which show that cesiated complexes readily eject Cs+ when subject to collisions.

  4. Ion plating seals microcracks or porous metal components

    NASA Technical Reports Server (NTRS)

    Spalvins, T.; Buckley, D. H.; Brainard, W. A.

    1972-01-01

    Description of ion plating process is given. Advantage of this process is that any plating metal or alloy can be selected, whereas, for conventional welding, material selection is limited by compatability.

  5. Extracting metal ions with diphosphonic acid, or derivative thereof

    DOEpatents

    Horwitz, Earl P.; Gatrone, Ralph C.; Nash, Kenneth L.

    1994-01-01

    Thermodynamically-unstable complexing agents which are diphosphonic acids and diphosphonic acid derivatives (or sulphur containing analogs), like carboxyhydroxymethanediphosphonic acid and vinylidene-1,1-diphosphonic acid, are capable of complexing with metal ions, and especially metal ions in the II, III, IV, V and VI oxidation states, to form stable, water-soluble metal ion complexes in moderately alkaline to highly-acidic media. However, the complexing agents can be decomposed, under mild conditions, into non-organic compounds which, for many purposes are environmentally-nondamaging compounds thereby degrading the complex and releasing the metal ion for disposal or recovery. Uses for such complexing agents as well as methods for their manufacture are also described.

  6. Extracting metal ions with diphosphonic acid, or derivative thereof

    DOEpatents

    Horwitz, E.P.; Gatrone, R.C.; Nash, K.L.

    1994-07-26

    Thermodynamically-unstable complexing agents which are diphosphonic acids and diphosphonic acid derivatives (or sulfur containing analogs), like carboxyhydroxymethanediphosphonic acid and vinylidene-1,1-diphosphonic acid, are capable of complexing with metal ions, and especially metal ions in the II, III, IV, V and VI oxidation states, to form stable, water-soluble metal ion complexes in moderately alkaline to highly-acidic media. However, the complexing agents can be decomposed, under mild conditions, into non-organic compounds which, for many purposes are environmentally-nondamaging compounds thereby degrading the complex and releasing the metal ion for disposal or recovery. Uses for such complexing agents as well as methods for their manufacture are also described. 1 fig.

  7. Ion exchange extraction of heavy metals from wastewater sludges.

    PubMed

    Al-Enezi, G; Hamoda, M F; Fawzi, N

    2004-01-01

    Heavy metals are common contaminants of some industrial wastewater. They find their way to municipal wastewaters due to industrial discharges into the sewerage system or through household chemicals. The most common heavy metals found in wastewaters are lead, copper, nickel, cadmium, zinc, mercury, arsenic, and chromium. Such metals are toxic and pose serious threats to the environment and public health. In recent years, the ion exchange process has been increasingly used for the removal of heavy metals or the recovery of precious metals. It is a versatile separation process with the potential for broad applications in the water and wastewater treatment field. This article summarizes the results obtained from a laboratory study on the removal of heavy metals from municipal wastewater sludges obtained from Ardhiya plant in Kuwait. Data on heavy metal content of the wastewater and sludge samples collected from the plant are presented. The results obtained from laboratory experiments using a commercially available ion exchange resin to remove heavy metals from sludge were discussed. A technique was developed to solubilize such heavy metals from the sludge for subsequent treatment by the ion exchange process. The results showed high efficiency of extraction, almost 99.9%, of heavy metals in the concentration range bound in wastewater effluents and sludges. Selective removal of heavy metals from a contaminated wastewater/sludge combines the benefits of being economically prudent and providing the possibility of reuse/recycle of the treated wastewater effluents and sludges.

  8. Metallic glass as a temperature sensor during ion plating

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Spalvins, T.; Buckley, D. H.

    1985-01-01

    The temperature of the interface and/or a superficial layer of a substrate during ion plating was investigated using a metallic glass of the composition Fe67Co18B14Si1 as the substrate and as the temperature sensor. Transmission electron microscopy and diffraction studies determined the microstructure of the ion-plated gold film and the substrate. Results indicate that crystallization occurs not only in the film, but also in the substrate. The grain size of crystals formed during ion plating was 6 to 60 nm in the gold film and 8 to 100 nm in the substrate at a depth of 10 to 15 micrometers from the ion-plated interface. The temperature rise of the substrate during ion plating was approximately 500 C. Discontinuous changes in metallurgical microstructure, and physical, chemical, and mechanical properties during the amorphous to crystalline transition in metallic glasses make metallic glasses extremely useful materials for temperature sensor applications in coating processes.

  9. Metallic glass as a temperature sensor during ion plating

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Spalvins, T.; Buckley, D. H.

    1984-01-01

    The temperature of the interface and/or a superficial layer of a substrate during ion plating was investigated using a metallic glass of the composition Fe67Co18B14Si1 as the substrate and as the temperature sensor. Transmission electron microscopy and diffraction studies determined the microstructure of the ion-plated gold film and the substrate. Results indicate that crystallization occurs not only in the film, but also in the substrate. The grain size of crystals formed during ion plating was 6 to 60 nm in the gold film and 8 to 100 nm in the substrate at a depth of 10 to 15 micrometers from the ion-plated interface. The temperature rise of the substrate during ion plating was approximately 500 C. Discontinuous changes in metallurgical microstructure, and physical, chemical, and mechanical properties during the amorphous to crystalline transition in metallic glasses make metallic glasses extremely useful materials for temperature sensor applications in coating processes.

  10. Effects of metal ions on the catalytic degradation of dicofol by cellulase.

    PubMed

    Zhai, Zihan; Yang, Ting; Zhang, Boya; Zhang, Jianbo

    2015-07-01

    A new technique whereby cellulase immobilized on aminated silica was applied to catalyze the degradation of dicofol, an organochlorine pesticide. In order to evaluate the performance of free and immobilized cellulase, experiments were carried out to measure the degradation efficiency. The Michaelis constant, Km, of the reaction catalyzed by immobilized cellulase was 9.16 mg/L, and the maximum reaction rate, Vmax, was 0.40 mg/L/min, while that of free cellulase was Km=8.18 mg/L, and Vmax=0.79 mg/L/min, respectively. The kinetic constants of catalytic degradation were calculated to estimate substrate affinity. Considering that metal ions may affect enzyme activity, the effects of different metal ions on the catalytic degradation efficiency were explored. The results showed that the substrate affinity decreased after immobilization. Monovalent metal ions had no effect on the reaction, while divalent metal ions had either positive or inhibitory effects, including activation by Mn2+, reversible competition with Cd2+, and irreversible inhibition by Pb2+. Ca2+ promoted the catalytic degradation of dicofol at low concentrations, but inhibited it at high concentrations. Compared with free cellulase, immobilized cellulase was affected less by metal ions. This work provided a basis for further studies on the co-occurrence of endocrine-disrupting chemicals and heavy metal ions in the environment.

  11. An Engineered Palette of Metal Ion Quenchable Fluorescent Proteins

    PubMed Central

    Yu, Xiaozhen; Strub, Marie-Paule; Barnard, Travis J.; Noinaj, Nicholas; Piszczek, Grzegorz; Buchanan, Susan K.; Taraska, Justin W.

    2014-01-01

    Many fluorescent proteins have been created to act as genetically encoded biosensors. With these sensors, changes in fluorescence report on chemical states in living cells. Transition metal ions such as copper, nickel, and zinc are crucial in many physiological and pathophysiological pathways. Here, we engineered a spectral series of optimized transition metal ion-binding fluorescent proteins that respond to metals with large changes in fluorescence intensity. These proteins can act as metal biosensors or imaging probes whose fluorescence can be tuned by metals. Each protein is uniquely modulated by four different metals (Cu2+, Ni2+, Co2+, and Zn2+). Crystallography revealed the geometry and location of metal binding to the engineered sites. When attached to the extracellular terminal of a membrane protein VAMP2, dimeric pairs of the sensors could be used in cells as ratiometric probes for transition metal ions. Thus, these engineered fluorescent proteins act as sensitive transition metal ion-responsive genetically encoded probes that span the visible spectrum. PMID:24752441

  12. Smart textile device using ion polymer metal compound.

    PubMed

    Nakamura, Taro; Ihara, Tadashi

    2013-01-01

    We have developed a smart textile device that detects angular displacement of attached surface using ion polymer metal compound. The device was composed of ion polymer metal compound (IPMC) which was fabricated from Nafion resin by heat-press and chemical gold plating. The generated voltage from IPMC was measured as a function of bending angle. Fabricated IPMC device was weaved into a cotton cloth and multidirectional movements were detected.

  13. An optical dosimeter for monitoring heavy metal ions in water

    NASA Astrophysics Data System (ADS)

    Mignani, Anna G.; Regan, Fiona; Leamy, D.; Mencaglia, A. A.; Ciaccheri, L.

    2005-05-01

    This work presents an optochemical dosimeter for determining and discriminating nickel, copper, and cobalt ions in water that can be used as an early warning system for water pollution. An inexpensive fiber optic spectrophotometer monitors the sensor's spectral behavior under exposure to water solutions of heavy metal ions in the 1-10 mg/l concentration range. The Principal Component Analysis (PCA) method quantitatively determines the heavy metals and discriminates their type and combination.

  14. Frictional and morphological characteristics of ion plated soft, metallic films

    NASA Technical Reports Server (NTRS)

    Spalvins, T.; Buzek, B.

    1981-01-01

    Ion plated metallic films in contrast to films applied by other deposition techniques offer a lower friction coefficient, longer endurance lives and exhibit a gradual increase in friction coefficient after the film has been worn off. The friction coefficients of metallic films are affected by the degree of adherence, thickness and nucleation and growth characteristics during ion plating lead to a fine, continuous crystalline structure, which contributes to a lower friction coefficient.

  15. Isothermal Titration Calorimetry Measurements of Metal Ions Binding to Proteins.

    PubMed

    Quinn, Colette F; Carpenter, Margaret C; Croteau, Molly L; Wilcox, Dean E

    2016-01-01

    ITC measurements involving metal ions are susceptible to a number of competing reactions (oxidation, precipitation, and hydrolysis) and coupled reactions involving the buffer and protons. Stabilization and delivery of the metal ion as a well-defined and well-characterized complex with the buffer, or a specific ligand, can suppress undesired solution chemistry and, depending on the stability of the metal complex, allow accurate measurements of higher affinity protein-binding sites. This requires, however, knowledge of the thermodynamics of formation of the metal complex and accounting for its contribution to the experimentally measured values (KITC and ΔHITC) through a post hoc analysis that provides the condition-independent binding thermodynamics (K, ΔG(o), ΔH, ΔS, and ΔCP). This analysis also quantifies the number of protons that are displaced when the metal ion binds to the protein.

  16. Metal ion implantation for large scale surface modification

    SciTech Connect

    Brown, I.G.

    1992-10-01

    Intense energetic beams of metal ions can be produced by using a metal vapor vacuum arc as the plasma discharge from which the ion beam is formed. We have developed a number of ion sources of this kind and have built a metal ion implantation facility which can produce repetitively pulsed ion beams with mean ion energy up to several hundred key, pulsed beam current of more than an ampere, and time averaged current of several tens of milliamperes delivered onto a downstream target. We've also done some preliminary work on scaling up this technology to very large size. For example, a 50-cm diameter (2000 cm[sup 2]) set of beam formation electrodes was used to produce a pulsed titanium beam with ion current over 7 amperes at a mean ion energy of 100 key. Separately, a dc embodiment has been used to produce a dc titanium ion beam with current over 600 mA, power supply limited in this work, and up to 6 amperes of dc plasma ion current was maintained for over an hour. In a related program we've developed a plasma immersion method for applying thin metallic and compound films in which the added species is atomically mixed to the substrate. By adding a gas flow to the process, well-bonded compound films can also be formed; metallic films and multilayers as well as oxides and nitrides with mixed transition zones some hundreds of angstroms thick have been synthesized. Here we outline these parallel metal-plasma-based research programs and describe the hardware that we've developed and some of the surface modification research that we've done with it.

  17. Production of negative hydrogen ions on metal grids

    SciTech Connect

    Oohara, W.; Maetani, Y.; Takeda, Takashi; Takeda, Toshiaki; Yokoyama, H.; Kawata, K.

    2015-03-15

    Negative hydrogen ions are produced on a nickel grid with positive-ion irradiation. In order to investigate the production mechanism, a copper grid without the chemisorption of hydrogen atoms and positive helium ions without negative ionization are used for comparison. Positive hydrogen ions reflected on the metal surface obtain two electrons from the surface and become negatively ionized. It is found that the production yield of negative ions by desorption ionization of chemisorbed hydrogen atoms seems to be small, and the production is a minor mechanism.

  18. Hematein chelates of unusual metal ions for tinctorial histochemistry.

    PubMed

    Smith, A A

    2010-02-01

    Hematoxylin is oxidized easily to hematein, an excellent stain for metal ions. If it already is bound to a substrate, the metal ion becomes a mordant linking the dye to the substrate. Metal ions added to hematein in solution are chelated by the hematein to form a lake. Most of these chelates stain animal tissues. They usually are bound to the tissue by a combination of hydrogen bonding of the hematein and ionic bonding of the metal ion. When binding of the lake to the tissue occurs by way of the metal ion, the metal ion is a mordant. Mordant staining often is specific. Chromium hematoxylin binds to strong acids; it can be made selective for protein-bound sulfonic acids. Zirconyl hematoxylin is selective for acidic mucins. Mucihematein can be made selective for all acidic mucins or for sulfomucins alone. Bismuth hematoxylin appears to be selective for the guanido group of arginine and there is some evidence that the bonding is covalent. Although it is not a histochemical stain, copper-chrome hematoxylin is an excellent stain for organelles with double membranes, i.e., mitochondria and nuclei.

  19. Heterogeneous processes affecting metal ion transport in the presence of organic ligands: Reactive transport modeling

    NASA Astrophysics Data System (ADS)

    Kantar, Cetin

    2007-04-01

    The development of models to accurately simulate metal ion transport through saturated systems under variable chemical conditions, e.g., in systems containing organic ligands (L) such as natural organic matter (NOM), has two essential aspects: (1) establishing the ability to simulate metal ion sorption to aquifer solids over a range of metal/ligand ratios; and (2) to incorporate this ability to simulate metal speciation over a range in chemical conditions (e.g., pH, ligand activity) into mass transport models. Modeling approaches to evaluate metal ion sorption and transport in the presence of NOM include: (1) isotherm-based transport models, and (2) multicomponent (MC) transport models. The accuracy of transport models depends on how well the chemical interactions affecting metal ion transport in the presence of organic ligands (e.g., metal/ligand complexation) are described in transport equations. The isotherm-based transport models often fail to accurately describe metal ion transport in the presence of NOM since these models treat NOM as a single solute despite the fact that NOM is a multicomponent mixture of subcomponents with different chemical and polyfunctional behavior. On the other hand, the calculations presented in this study suggest that a multicomponent reactive transport model, in conjunction with a mechanistic modeling approach for the description of metal ion binding by NOM in a manner conducive to the application of surface complexation modeling (SCM), can effectively be used as an important predictive tool in simulating metal ion sorption and transport under variable chemical conditions in the presence of NOM.

  20. Implantation of nitrogen, carbon, and phosphorus ions into metals

    SciTech Connect

    Guseva, M.I.; Gordeeva, G.V.

    1987-01-01

    The application of ion implantation for alloying offers a unique opportunity to modify the chemical composition, phase constitution, and microstructure of the surface layers of metals. The authors studied ion implantation of nitrogen and carbon into the surface layers of metallic targets. The phase composition of the implanted layers obtained on the Kh18N10T stainless steel, the refractory molybdenum alloy TsM-6, niobium, and nickel was determined according to the conventional method of recording the x-ray diffraction pattern of the specimens using monochromatic FeK/sub alpha/-radiation on a DRON-2,0 diffractometer. The targets were bombarded at room temperature in an ILU-3 ion accelerator. The implantation of metalloid ions was also conducted with the targets being bombarded with 100-keV phosphorus ions and 40-keV carbon ions.

  1. Crystal structures of Bacillus alkaline phytase in complex with divalent metal ions and inositol hexasulfate.

    PubMed

    Zeng, Yi-Fang; Ko, Tzu-Ping; Lai, Hui-Lin; Cheng, Ya-Shan; Wu, Tzu-Hui; Ma, Yanhe; Chen, Chun-Chi; Yang, Chii-Shen; Cheng, Kuo-Joan; Huang, Chun-Hsiang; Guo, Rey-Ting; Liu, Je-Ruei

    2011-06-03

    Alkaline phytases from Bacillus species, which hydrolyze phytate to less phosphorylated myo-inositols and inorganic phosphate, have great potential as additives to animal feed. The thermostability and neutral optimum pH of Bacillus phytase are attributed largely to the presence of calcium ions. Nonetheless, no report has demonstrated directly how the metal ions coordinate phytase and its substrate to facilitate the catalytic reaction. In this study, the interactions between a phytate analog (myo-inositol hexasulfate) and divalent metal ions in Bacillus subtilis phytase were revealed by the crystal structure at 1.25 Å resolution. We found all, except the first, sulfates on the substrate analog have direct or indirect interactions with amino acid residues in the enzyme active site. The structures also unraveled two active site-associated metal ions that were not explored in earlier studies. Significantly, one metal ion could be crucial to substrate binding. In addition, binding of the fourth sulfate of the substrate analog to the active site appears to be stronger than that of the others. These results indicate that alkaline phytase starts by cleaving the fourth phosphate, instead of the third or the sixth that were proposed earlier. Our high-resolution, structural representation of Bacillus phytase in complex with a substrate analog and divalent metal ions provides new insight into the catalytic mechanism of alkaline phytases in general.

  2. Quantum ion-acoustic wave oscillations in metallic nanowires

    SciTech Connect

    Moradi, Afshin

    2015-05-15

    The low-frequency electrostatic waves in metallic nanowires are studied using the quantum hydrodynamic model, in which the electron and ion components of the system are regarded as a two-species quantum plasma system. The Poisson equation as well as appropriate quantum boundary conditions give the analytical expressions of dispersion relations of the surface and bulk quantum ion-acoustic wave oscillations.

  3. ION EXCHANGE IN FUSED SALTS. II. THE DISTRIBUTION OF ALKALI METAL AND ALKALINE EARTH IONS BETWEEN CHABAZITE AND FUSED LINO3, NANO3, AND KNO3,

    DTIC Science & Technology

    ION EXCHANGE, SALTS ), (*ALKALI METALS, ION EXCHANGE), (*ALKALINE EARTH METALS, ION EXCHANGE), (*NITRATES, ION EXCHANGE), SODIUM , CALCIUM, POTASSIUM...BARIUM, RUBIDIUM, CESIUM, LITHIUM COMPOUNDS, SODIUM COMPOUNDS, POTASSIUM COMPOUNDS, DISTRIBUTION, MINERALS, IONS

  4. Generation of reactive oxygen species by interaction between antioxidants used as food additive and metal ions.

    PubMed

    Iwasaki, Yusuke; Oda, Momoko; Tsukuda, Yuri; Nagamori, Yuki; Nakazawa, Hiroyuki; Ito, Rie; Saito, Koichi

    2014-01-01

    Food additives, such as preservatives, sweeteners, coloring agents, and flavoring agents, are widely used in food manufacturing. However, their combined effects on the human body are not known. The purpose of this study was to examine whether combinations of antioxidants and metal ions generate reactive oxygen species (ROS) under in vitro conditions using electron spin resonance (ESR). Among the metal ions examined, only iron and copper generated ROS in the presence of antioxidants. Moreover, certain phenolic antioxidants having pro-oxidant activity induced DNA oxidation and degradation via the generation of high levels of ROS in the presence of copper ion, resulting in complete degradation of DNA in vitro.

  5. Structural Metals in the Group I Intron: A Ribozyme with a Multiple Metal Ion Core

    SciTech Connect

    Stahley,M.; Adams, P.; Wang, J.; Strobel, S.

    2007-01-01

    Metal ions play key roles in the folding and function for many structured RNAs, including group I introns. We determined the X-ray crystal structure of the Azoarcus bacterial group I intron in complex with its 5' and 3' exons. In addition to 222 nucleotides of RNA, the model includes 18 Mg2+ and K+ ions. Five of the metals bind within 12 Angstroms of the scissile phosphate and coordinate the majority of the oxygen atoms biochemically implicated in conserved metal-RNA interactions. The metals are buried deep within the structure and form a multiple metal ion core that is critical to group I intron structure and function. Eight metal ions bind in other conserved regions of the intron structure, and the remaining five interact with peripheral structural elements. Each of the 18 metals mediates tertiary interactions, facilitates local bends in the sugar-phosphate backbone or binds in the major groove of helices. The group I intron has a rich history of biochemical efforts aimed to identify RNA-metal ion interactions. The structural data are correlated to the biochemical results to further understand the role of metal ions in group I intron structure and function.

  6. Immobilized metal ion affinity partitioning, a method combining metal-protein interaction and partitioning of proteins in aqueous two-phase systems.

    PubMed

    Birkenmeier, G; Vijayalakshmi, M A; Stigbrand, T; Kopperschläger, G

    1991-02-22

    Immobilized metal ions were used for the affinity extraction of proteins in aqueous two-phase systems composed of polyethylene glycol (PEG) and dextran or PEG and salt. Soluble chelating polymers were prepared by covalent attachment of metal-chelating groups to PEG. The effect on the partitioning of proteins of such chelating PEG derivatives coordinated with different metal ions is demonstrated. The proteins studied were alpha 2-macroglobulin, tissue plasminogen activator, superoxide dismutase and monoclonal antibodies. The results indicate that immobilized metal ion affinity partitioning provides excellent potential for the extraction of proteins.

  7. Control of redox reactivity of flavin and pterin coenzymes by metal ion coordination and hydrogen bonding.

    PubMed

    Fukuzumi, Shunichi; Kojima, Takahiko

    2008-03-01

    The electron-transfer activities of flavin and pterin coenzymes can be fine-tuned by coordination of metal ions, protonation and hydrogen bonding. Formation of hydrogen bonds with a hydrogen-bond receptor in metal-flavin complexes is made possible depending on the type of coordination bond that can leave the hydrogen-bonding sites. The electron-transfer catalytic functions of flavin and pterin coenzymes are described by showing a number of examples of both thermal and photochemical redox reactions, which proceed by controlling the electron-transfer reactivity of coenzymes with metal ion binding, protonation and hydrogen bonding.

  8. Removal of metal ions from aqueous solution

    DOEpatents

    Jackson, Paul J.; Delhaize, Emmanuel; Robinson, Nigel J.; Unkefer, Clifford J.; Furlong, Clement

    1990-11-13

    A method of removing heavy metals from aqueous solution, a composition of matter used in effecting said removal, and apparatus used in effecting said removal. One or more of the polypeptides, poly (.gamma.-glutamylcysteinyl)glycines, is immobilized on an inert material in particulate form. Upon contact with an aqueous solution containing heavy metals, the polypeptides sequester the metals, removing them from the solution. There is selectivity of poly (.gamma.-glutamylcysteinyl)glycines having a particular number of monomer repeat unit for particular metals. The polypeptides are easily regenerated by contact with a small amount of an organic acid, so that they can be used again to remove heayv metals from solution. This also results in the removal of the metals from the column in a concentrated form.

  9. Removal of metal ions from aqueous solution

    DOEpatents

    Jackson, Paul J.; Delhaize, Emmanuel; Robinson, Nigel J.; Unkefer, Clifford J.; Furlong, Clement

    1990-01-01

    A method of removing heavy metals from aqueous solution, a composition of matter used in effecting said removal, and apparatus used in effecting said removal. One or more of the polypeptides, poly (.gamma.-glutamylcysteinyl)glycines, is immobilized on an inert material in particulate form. Upon contact with an aqueous solution containing heavy metals, the polypeptides sequester the metals, removing them from the solution. There is selectivity of poly (.gamma.-glutamylcysteinyl)glycines having a particular number of monomer repeat units for particular metals. The polypeptides are easily regenerated by contact with a small amount of an organic acid, so that they can be used again to remove heavy metals from solution. This also results in the removal of the metals from the column in a concentrated form.

  10. Self-propelled droplets for extracting rare-earth metal ions.

    PubMed

    Ban, Takahiko; Tani, Kentaro; Nakata, Hiroki; Okano, Yasunori

    2014-09-07

    We have developed self-propelled droplets having the abilities to detect a chemical gradient, to move toward a higher concentration of a specific metal ion (particularly the dysprosium ion), and to extract it. Such abilities rely on the high surface activity of di(2-ethylhexyl) phosphoric acid (DEHPA) in response to pH and the affinity of DEHPA for the dysprosium ion. We used two external stimuli as chemical signals to control droplet motion: a pH signal to induce motility and metal ions to induce directional sensing. The oil droplets loaded with DEHPA spontaneously move around beyond the threshold of pH even in a homogeneous pH field. In the presence of a gel block containing metal ions, the droplets show directional sensing and their motility is biased toward higher concentrations. The metal ions investigated can be arranged in decreasing order of directional sensing as Dy(3+)≫ Nd(3+) > Y(3+) > Gd(3+). Furthermore, the analysis of components by using an atomic absorption spectrophotometer reveals that the metal ions can be extracted from the environmental media to the interiors of the droplets. This system may offer alternative self-propelled nano/microscale machines to bubble thrust engines powered by asymmetrical catalysts.

  11. Comparative study of metal and non-metal ion implantation in polymers: Optical and electrical properties

    NASA Astrophysics Data System (ADS)

    Resta, V.; Quarta, G.; Farella, I.; Maruccio, L.; Cola, A.; Calcagnile, L.

    2014-07-01

    The implantation of 1 MeV metal (63Cu+, 107Ag+, 197Au+) and non-metal (4He+, 12C+) ions in a polycarbonate (PC) matrix has been studied in order to evaluate the role of ion species in the modification of optical and electrical properties of the polymer. When the ion fluence is above ∼1 × 1013 ions cm-2, the threshold for latent tracks overlapping is overcome and π-bonded carbon clusters grow and aggregate forming a network of conjugated Cdbnd C bonds. For fluences around 1 × 1017 ions cm-2, the aggregation phenomena induce the formation of amorphous carbon and/or graphite like structures. At the same time, nucleation of metal nanoparticles (NPs) from implanted species can take place when the supersaturation threshold is overcome. The optical absorption of the samples increases in the visible range and the optical band gap redshifts from 3.40 eV up to 0.70 eV mostly due to the carbonization process and the formation of C0x clusters and cluster aggregates. Specific structures in the extinction spectra are observed when metal ions are selected in contrast to the non-metal ion implanted PC, thus revealing the possible presence of noble metal based NPs interstitial to the C0x cluster network. The corresponding electrical resistance decreases much more when metal ions are implanted with at least a factor of 2 orders of magnitude difference than the non-metal ions based samples. An absolute value of ∼107 Ω/sq has been measured for implantation with metals at doses higher than 5 × 1016 ions cm-2, being 1017 Ω/sq the corresponding sheet resistance for pristine PC.

  12. Means for obtaining a metal ion beam from a heavy-ion cyclotron source

    DOEpatents

    Hudson, E.D.; Mallory, M.L.

    1975-08-01

    A description is given of a modification to a cyclotron ion source used in producing a high intensity metal ion beam. A small amount of an inert support gas maintains the usual plasma arc, except that it is necessary for the support gas to have a heavy mass, e.g., xenon or krypton as opposed to neon. A plate, fabricated from the metal (or anything that can be sputtered) to be ionized, is mounted on the back wall of the ion source arc chamber and is bombarded by returning energetic low-charged gas ions that fail to cross the initial accelerating gap between the ion source and the accelerating electrode. Some of the atoms that are dislodged from the plate by the returning gas ions become ionized and are extracted as a useful beam of heavy ions. (auth)

  13. Neutralization by Metal Ions of the Toxicity of Sodium Selenide

    PubMed Central

    Dauplais, Marc; Lazard, Myriam; Blanquet, Sylvain; Plateau, Pierre

    2013-01-01

    Inert metal-selenide colloids are found in animals. They are believed to afford cross-protection against the toxicities of both metals and selenocompounds. Here, the toxicities of metal salt and sodium selenide mixtures were systematically studied using the death rate of Saccharomyces cerevisiae cells as an indicator. In parallel, the abilities of these mixtures to produce colloids were assessed. Studied metal cations could be classified in three groups: (i) metal ions that protect cells against selenium toxicity and form insoluble colloids with selenide (Ag+, Cd2+, Cu2+, Hg2+, Pb2+ and Zn2+), (ii) metal ions which protect cells by producing insoluble metal-selenide complexes and by catalyzing hydrogen selenide oxidation in the presence of dioxygen (Co2+ and Ni2+) and, finally, (iii) metal ions which do not afford protection and do not interact (Ca2+, Mg2+, Mn2+) or weakly interact (Fe2+) with selenide under the assayed conditions. When occurring, the insoluble complexes formed from divalent metal ions and selenide contained equimolar amounts of metal and selenium atoms. With the monovalent silver ion, the complex contained two silver atoms per selenium atom. Next, because selenides are compounds prone to oxidation, the stabilities of the above colloids were evaluated under oxidizing conditions. 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB), the reduction of which can be optically followed, was used to promote selenide oxidation. Complexes with cadmium, copper, lead, mercury or silver resisted dissolution by DTNB treatment over several hours. With nickel and cobalt, partial oxidation by DTNB occurred. On the other hand, when starting from ZnSe or FeSe complexes, full decompositions were obtained within a few tens of minutes. The above properties possibly explain why ZnSe and FeSe nanoparticles were not detected in animals exposed to selenocompounds. PMID:23342137

  14. Optical studies of ion-beam synthesized metal alloy nanoparticles

    NASA Astrophysics Data System (ADS)

    Magudapathy, P.; Srivatsava, S. K.; Gangopadhyay, P.; Amirthapandian, S.; Sairam, T. N.; Panigrahi, B. K.

    2015-06-01

    AuxAg1-x alloy nanoparticles with tunable surface plasmon resonance (SPR) have been synthesized on a silica glass substrate. A small Au foil on an Ag foil is irradiated as target substrates such that ion beam falls on both Ag foil and Au foils. Silica slides are kept at an angle ˜45° with respect to the metallic foils. While irradiating the metallic foils with 100 keV Ar+ ions, sputtered Au and Ag atoms get deposited on the silica-glass. In this configuration the foils have been irradiated by Ar+ ions to various fluences at room temperature and the sputtered species are collected on silica slides. Formation of AuxAg1-x nanoparticles has been confirmed from the optical absorption measurements. With respect to the exposure area of Au and Ag foils to the ion beam, the SPR peak position varies from 450 to 500 nm. Green photoluminescence has been observed from these alloy metal nanoparticles.

  15. Hall transport of divalent metal ion modified DNA lattices

    SciTech Connect

    Dugasani, Sreekantha Reddy; Lee, Keun Woo; Yoo, Sanghyun; Gnapareddy, Bramaramba; Bashar, Saima; Park, Sung Ha; Kim, Si Joon; Jung, Joohye; Jung, Tae Soo; Kim, Hyun Jae

    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.

  16. A vacuum spark ion source: High charge state metal ion beams

    SciTech Connect

    Yushkov, G. Yu. Nikolaev, A. G.; Frolova, V. P.; Oks, E. M.

    2016-02-15

    High ion charge state is often important in ion beam physics, among other reasons for the very practical purpose that it leads to proportionately higher ion beam energy for fixed accelerating voltage. The ion charge state of metal ion beams can be increased by replacing a vacuum arc ion source by a vacuum spark ion source. Since the voltage between anode and cathode remains high in a spark discharge compared to the vacuum arc, higher metal ion charge states are generated which can then be extracted as an ion beam. The use of a spark of pulse duration less than 10 μs and with current up to 10 kA allows the production of ion beams with current of several amperes at a pulse repetition rate of up to 5 pps. We have demonstrated the formation of high charge state heavy ions (bismuth) of up to 15 + and a mean ion charge state of more than 10 +. The physics and techniques of our vacuum spark ion source are described.

  17. A vacuum spark ion source: High charge state metal ion beams

    NASA Astrophysics Data System (ADS)

    Yushkov, G. Yu.; Nikolaev, A. G.; Oks, E. M.; Frolova, V. P.

    2016-02-01

    High ion charge state is often important in ion beam physics, among other reasons for the very practical purpose that it leads to proportionately higher ion beam energy for fixed accelerating voltage. The ion charge state of metal ion beams can be increased by replacing a vacuum arc ion source by a vacuum spark ion source. Since the voltage between anode and cathode remains high in a spark discharge compared to the vacuum arc, higher metal ion charge states are generated which can then be extracted as an ion beam. The use of a spark of pulse duration less than 10 μs and with current up to 10 kA allows the production of ion beams with current of several amperes at a pulse repetition rate of up to 5 pps. We have demonstrated the formation of high charge state heavy ions (bismuth) of up to 15 + and a mean ion charge state of more than 10 +. The physics and techniques of our vacuum spark ion source are described.

  18. The Role of Metals in the Reaction Catalyzed by Metal-Ion-Independent Bacillary RNase

    PubMed Central

    Ulyanova, Vera; Zelenikhin, Pavel; Kolpakov, Alexey; Blokhin, Dmitriy; Müller, Dieter; Klochkov, Vladimir; Ilinskaya, Olga

    2016-01-01

    Extracellular enzymes of intestinal microbiota are the key agents that affect functional activity of the body as they directly interact with epithelial and immune cells. Several species of the Bacillus genus, like Bacillus pumilus, a common producer of extracellular RNase binase, can populate the intestinal microbiome as a colonizing organism. Without involving metal ions as cofactors, binase depolymerizes RNA by cleaving the 3′,5′-phosphodiester bond and generates 2′,3′-cyclic guanosine phosphates in the first stage of a catalytic reaction. Maintained in the reaction mixture for more than one hour, such messengers can affect the human intestinal microflora and the human body. In the present study, we found that the rate of 2′,3′-cGMP was growing in the presence of transition metals that stabilized the RNA structure. At the same time, transition metal ions only marginally reduced the amount of 2′,3′-cGMP, blocking binase recognition sites of guanine at N7 of nucleophilic purine bases. PMID:28096759

  19. Selective removal of heavy metal ions by disulfide linked polymer networks.

    PubMed

    Ko, Dongah; Lee, Joo Sung; Patel, Hasmukh A; Jakobsen, Mogens H; Hwang, Yuhoon; Yavuz, Cafer T; Hansen, Hans Chr Bruun; Andersen, Henrik R

    2017-03-06

    Heavy metal contaminated surface water is one of the oldest pollution problems, which is critical to ecosystems and human health. We devised disulfide linked polymer networks and employed as a sorbent for removing heavy metal ions from contaminated water. Although the polymer network material has a moderate surface area, it demonstrated cadmium removal efficiency equivalent to highly porous activated carbon while it showed 16 times faster sorption kinetics compared to activated carbon, owing to the high affinity of cadmium towards disulfide and thiol functionality in the polymer network. The metal sorption mechanism on polymer network was studied by sorption kinetics, effect of pH, and metal complexation. We observed that the metal ions-copper, cadmium, and zinc showed high binding affinity in polymer network, even in the presence of competing cations like calcium in water.

  20. Actively convected liquid metal divertor

    NASA Astrophysics Data System (ADS)

    Shimada, Michiya; Hirooka, Yoshi

    2014-12-01

    The use of actively convected liquid metals with j × B force is proposed to facilitate heat handling by the divertor, a challenging issue associated with magnetic fusion experiments such as ITER. This issue will be aggravated even more for DEMO and power reactors because the divertor heat load will be significantly higher and yet the use of copper would not be allowed as the heat sink material. Instead, reduced activation ferritic/martensitic steel alloys with heat conductivities substantially lower than that of copper, will be used as the structural materials. The present proposal is to fill the lower part of the vacuum vessel with liquid metals with relatively low melting points and low chemical activities including Ga and Sn. The divertor modules, equipped with electrodes and cooling tubes, are immersed in the liquid metal. The electrode, placed in the middle of the liquid metal, can be biased positively or negatively with respect to the module. The j × B force due to the current between the electrode and the module provides a rotating motion for the liquid metal around the electrodes. The rise in liquid temperature at the separatrix hit point can be maintained at acceptable levels from the operation point of view. As the rotation speed increases, the current in the liquid metal is expected to decrease due to the v × B electromotive force. This rotating motion in the poloidal plane will reduce the divertor heat load significantly. Another important benefit of the convected liquid metal divertor is the fast recovery from unmitigated disruptions. Also, the liquid metal divertor concept eliminates the erosion problem.

  1. Ion-Plated Soft Metallic Films Reduce Friction and Wear

    NASA Technical Reports Server (NTRS)

    Spalvins, T.

    1986-01-01

    Ion plating is ion-assisted or glow-discharge surface-deposition technique. In this process, ions or energetic atoms transfer energy, momentum, and charge to substrate and deposited surface film. Process controlled to modify physical characteristics of surface, subsurface chemical conditions, and surface and subsurface microstructures as well. Ion plating with such soft, thin metallic films as gold, silver, or lead has great potential for producing self-contained lubricating surfaces. Such films reduce friction, wear, and corrosion on sliding or rotating mechanical surfaces used in wide range of environments.

  2. Adaptation of intertidal biofilm communities is driven by metal ion and oxidative stresses

    PubMed Central

    Zhang, Weipeng; Wang, Yong; Lee, On On; Tian, Renmao; Cao, Huiluo; Gao, Zhaoming; Li, Yongxin; Yu, Li; Xu, Ying; Qian, Pei-Yuan

    2013-01-01

    Marine organisms in intertidal zones are subjected to periodical fluctuations and wave activities. To understand how microbes in intertidal biofilms adapt to the stresses, the microbial metagenomes of biofilms from intertidal and subtidal zones were compared. The genes responsible for resistance to metal ion and oxidative stresses were enriched in both 6-day and 12-day intertidal biofilms, including genes associated with secondary metabolism, inorganic ion transport and metabolism, signal transduction and extracellular polymeric substance metabolism. In addition, these genes were more enriched in 12-day than 6-day intertidal biofilms. We hypothesize that a complex signaling network is used for stress tolerance and propose a model illustrating the relationships between these functions and environmental metal ion concentrations and oxidative stresses. These findings show that bacteria use diverse mechanisms to adapt to intertidal zones and indicate that the community structures of intertidal biofilms are modulated by metal ion and oxidative stresses. PMID:24212283

  3. Adaptation of intertidal biofilm communities is driven by metal ion and oxidative stresses.

    PubMed

    Zhang, Weipeng; Wang, Yong; Lee, On On; Tian, Renmao; Cao, Huiluo; Gao, Zhaoming; Li, Yongxin; Yu, Li; Xu, Ying; Qian, Pei-Yuan

    2013-11-11

    Marine organisms in intertidal zones are subjected to periodical fluctuations and wave activities. To understand how microbes in intertidal biofilms adapt to the stresses, the microbial metagenomes of biofilms from intertidal and subtidal zones were compared. The genes responsible for resistance to metal ion and oxidative stresses were enriched in both 6-day and 12-day intertidal biofilms, including genes associated with secondary metabolism, inorganic ion transport and metabolism, signal transduction and extracellular polymeric substance metabolism. In addition, these genes were more enriched in 12-day than 6-day intertidal biofilms. We hypothesize that a complex signaling network is used for stress tolerance and propose a model illustrating the relationships between these functions and environmental metal ion concentrations and oxidative stresses. These findings show that bacteria use diverse mechanisms to adapt to intertidal zones and indicate that the community structures of intertidal biofilms are modulated by metal ion and oxidative stresses.

  4. Removal of heavy metal ions from wastewaters: a review.

    PubMed

    Fu, Fenglian; Wang, Qi

    2011-03-01

    Heavy metal pollution has become one of the most serious environmental problems today. The treatment of heavy metals is of special concern due to their recalcitrance and persistence in the environment. In recent years, various methods for heavy metal removal from wastewater have been extensively studied. This paper reviews the current methods that have been used to treat heavy metal wastewater and evaluates these techniques. These technologies include chemical precipitation, ion-exchange, adsorption, membrane filtration, coagulation-flocculation, flotation and electrochemical methods. About 185 published studies (1988-2010) are reviewed in this paper. It is evident from the literature survey articles that ion-exchange, adsorption and membrane filtration are the most frequently studied for the treatment of heavy metal wastewater.

  5. Acylpyrazolones: Synthesis, self-assembly and lanthanide metal ion separation

    NASA Astrophysics Data System (ADS)

    Yang, Jun

    The central hypothesis that nanoscale self-assemblies can provide excellent metal ion recognition has been substantiated by employing acylpyrazolones and trivalent lanthanide metal ions as model systems. Several novel acylpyrazolones and their amphiphilic analogs have been designed, synthesized, and characterized. Their lanthanide metal ion recognition efficacies have been demonstrated through baseline separations of a mixture of light, middle, and heavy lanthanide metal ions by employing them in the aqueous mobile phase of high performance liquid chromatography (HPLC) with octadecylsilanized silica (ODS) as the stationary phase. The complex separation mechanism is influenced by the structures of acylpyrazolone and amphiphilic moieties, and spontaneous self-assembly of the ligand in the aqueous and on the stationary phases. Transmission electron microscopy (TEM) studies of the ligand self-assemblies in the aqueous phase in the absence and presence of lanthanide metal ions reveal spherical, dendritic, and linear (nanofibers, nanorods, and nanotubes) nanoscale structures. Such structures have also been observed when chloromethylated acylpyrazolones are stimulated to self-assemble by a base in nonaqueous solvents and when silica nanoparticles derivatized with them spontaneously self-assemble in aqueous and nonaqueous solvents.

  6. Process for modifying the metal ion sorption capacity of a medium

    DOEpatents

    Lundquist, Susan H.

    2002-01-01

    A process for modifying a medium is disclosed that includes treating a medium having a metal ion sorption capacity with a solution that includes: A) an agent capable of forming a complex with metal ions; and B) ions selected from the group consisting of sodium ions, potassium ions, magnesium ions, and combinations thereof, to create a medium having an increased capacity to sorb metal ions relative to the untreated medium.

  7. Two Divalent Metal Ions and Conformational Changes Play Roles in the Hammerhead Ribozyme Cleavage Reaction

    PubMed Central

    Mir, Aamir; Chen, Ji; Robinson, Kyle; Lendy, Emma; Goodman, Jaclyn; Neau, David; Golden, Barbara L.

    2016-01-01

    The hammerhead ribozyme is a self-cleaving RNA broadly dispersed across all kingdoms of life. Although it was the first of the small, nucleolytic ribozymes discovered, the mechanism by which it catalyzes its reaction remains elusive. The nucleobase of G12 is well positioned to be a general base, but it is unclear if or how this guanine base becomes activated for proton transfer. Metal ions have been implicated in the chemical mechanism, but no interactions between divalent metal ions and the cleavage site have been observed crystallographically. To better understand how this ribozyme functions, we have solved crystal structures of wild-type and G12A mutant ribozymes. We observe a pH-dependent conformational change centered around G12, consistent with this nucleotide becoming deprotonated. Crystallographic and kinetic analysis of the G12A mutant reveals a Zn2+ specificity switch suggesting a direct interaction between a divalent metal ion and the purine at position 12. The metal ion specificity switch and the pH–rate profile of the G12A mutant suggest that the minor imino tautomer of A12 serves as the general base in the mutant ribozyme. We propose a model in which the hammerhead ribozyme rearranges prior to the cleavage reaction, positioning two divalent metal ions in the process. The first metal ion, positioned near G12, becomes directly coordinated to the O6 keto oxygen, to lower the pKa of the general base and organize the active site. The second metal ion, positioned near G10.1, bridges the N7 of G10.1 and the scissile phosphate and may participate directly in the cleavage reaction. PMID:26398724

  8. Two Divalent Metal Ions and Conformational Changes Play Roles in the Hammerhead Ribozyme Cleavage Reaction.

    PubMed

    Mir, Aamir; Chen, Ji; Robinson, Kyle; Lendy, Emma; Goodman, Jaclyn; Neau, David; Golden, Barbara L

    2015-10-20

    The hammerhead ribozyme is a self-cleaving RNA broadly dispersed across all kingdoms of life. Although it was the first of the small, nucleolytic ribozymes discovered, the mechanism by which it catalyzes its reaction remains elusive. The nucleobase of G12 is well positioned to be a general base, but it is unclear if or how this guanine base becomes activated for proton transfer. Metal ions have been implicated in the chemical mechanism, but no interactions between divalent metal ions and the cleavage site have been observed crystallographically. To better understand how this ribozyme functions, we have solved crystal structures of wild-type and G12A mutant ribozymes. We observe a pH-dependent conformational change centered around G12, consistent with this nucleotide becoming deprotonated. Crystallographic and kinetic analysis of the G12A mutant reveals a Zn(2+) specificity switch suggesting a direct interaction between a divalent metal ion and the purine at position 12. The metal ion specificity switch and the pH-rate profile of the G12A mutant suggest that the minor imino tautomer of A12 serves as the general base in the mutant ribozyme. We propose a model in which the hammerhead ribozyme rearranges prior to the cleavage reaction, positioning two divalent metal ions in the process. The first metal ion, positioned near G12, becomes directly coordinated to the O6 keto oxygen, to lower the pKa of the general base and organize the active site. The second metal ion, positioned near G10.1, bridges the N7 of G10.1 and the scissile phosphate and may participate directly in the cleavage reaction.

  9. Membranes Remove Metal Ions Fron Industrial Liquids

    NASA Technical Reports Server (NTRS)

    Hsu, W. P. L.; May, C.

    1983-01-01

    Use of membrane films affords convenient and economical alternative for removing and recovering metal cations present in low concentrations from large quantities of liquid solutions. Possible applications of membrane films include use in analytical chemistry for determination of small amounts of toxic metallic impurities in lakes, streams, and municipal effluents. Also suitable for use as absorber of certain pollutant gases and odors present in confined areas.

  10. Immunologic mechanisms in hypersensitivity reactions to metal ions: an overview.

    PubMed

    Büdinger, L; Hertl, M

    2000-02-01

    Metal ions such as Ni2+, Co2+, Cu2+, or Cr3+ are haptens with a high immunogenic potential, as contact dermatitis caused by ionic metals occurs in about 10-15% of the human population. Since alloys containing Ni2+, Co2+, and Cr3+ are components of implants in replacement surgery, dentures, orthodontic wires, and various other devices, adverse reactions to metal ions create serious problems in practical medicine as incompatibility reactions to metal-containing biomaterials. On the other hand, contact dermatitis to metal ions such as Ni2+ is a well-established model for studying the molecular mechanisms involved in the recognition of haptens by the immune system. Although many investigations have been performed to elucidate the molecular interactions causing contact hypersensitivity in man, many aspects remain to be clarified. This review will focus on the experimental data accumulated so far on the immunologic mechanisms responsible for the recognition of metal ions by T cells and eliciting adverse immune reactions causing contact dermatitis.

  11. Reducing hazardous heavy metal ions using mangium bark waste.

    PubMed

    Khabibi, Jauhar; Syafii, Wasrin; Sari, Rita Kartika

    2016-08-01

    The objective of this study was to evaluate the characteristics of mangium bark and its biosorbent ability to reduce heavy metal ions in standard solutions and wastewater and to assess changes in bark characteristics after heavy metal absorption. The experiments were conducted to determine heavy metal absorption from solutions of heavy metals alone and in mixtures as well as from wastewater. The results show that mangium bark can absorb heavy metals. Absorption percentages and capacities from single heavy metal solutions showed that Cu(2+) > Ni(2+) > Pb(2+) > Hg(2+), while those from mixture solutions showed that Hg(2+) > Cu(2+) > Pb(2+) > Ni(2+). Wastewater from gold mining only contained Cu, with an absorption percentage and capacity of 42.87 % and 0.75 mg/g, respectively. The highest absorption percentage and capacity of 92.77 % and 5.18 mg/g, respectively, were found for Hg(2+) in a mixture solution and Cu(2+) in single-metal solution. The Cu(2+) absorption process in a single-metal solution changed the biosorbent characteristics of the mangium bark, yielding a decreased crystalline fraction; changed transmittance on hydroxyl, carboxyl, and carbonyl groups; and increased the presence of Cu. In conclusion, mangium bark biosorbent can reduce hazardous heavy metal ions in both standard solutions and wastewater.

  12. Low coefficient of thermal expansion polyimides containing metal ion additives

    NASA Technical Reports Server (NTRS)

    Stoakley, D. M.; St. Clair, A. K.

    1992-01-01

    Polyimides have become widely used as high performance polymers as a result of their excellent thermal stability and toughness. However, lowering their coefficient of thermal expansion (CTE) would increase their usefulness for aerospace and electronic applications where dimensional stability is a requirement. The incorporation of metal ion-containing additives into polyimides, resulting in significantly lowered CTE's, has been studied. Various metal ion additives have been added to both polyamic acid resins and soluble polyimide solutions in the concentration range of 4-23 weight percent. The incorporation of these metal ions has resulted in reductions in the CTE's of the control polyimides of 12 percent to over 100 percent depending on the choice of additive and its concentration.

  13. Metal ion modulated electron transfer in photosynthetic proteins.

    SciTech Connect

    Utschig, L. M.; Thurnauer, M. C.; Chemistry

    2004-07-01

    Photosynthetic purple bacterial reaction center (RC) proteins are ideal native systems for addressing basic questions regarding the nature of biological electron transfer because both the protein structure and the electron-transfer reactions are well-characterized. Metal ion binding to the RC can affect primary photochemistry and provides a probe for understanding the involvement of local protein environments in electron transfer. The RC has two distinct transition metal ion binding sites, the well-known non-heme Fe{sup 2+} site buried in the protein interior and a recently discovered Zn{sup 2+} site located on the surface of the protein. Fe{sup 2+} removal and Zn{sup 2+} binding systematically affect different electron-transfer steps in the RC. Factors involved in the metal ion alteration of RC electron transfer may provide a paradigm for other biological systems involved in electron transfer.

  14. Ion exchange properties of novel hydrous metal oxide materials

    SciTech Connect

    Gardner, T.J.; McLaughlin, L.I.

    1996-12-31

    Hydrous metal oxide (HMO) materials are inorganic ion exchangers which have many desirable characteristics for catalyst support applications, including high cation exchange capacity, anion exchange capability, high surface area, ease of adjustment of acidity and basicity, bulk or thin film preparation, and similar chemistry for preparation of various transition metal oxides. Cation exchange capacity is engineered into these materials through the uniform incorporation of alkali cations via manipulation of alkoxide chemistry. Specific examples of the effects of Na stoichiometry and the addition of SiO{sub 2} to hydrous titanium oxide (HTO) on ion exchange behavior will be given. Acid titration and cationic metal precursor complex exchange will be used to characterize the ion exchange behavior of these novel materials.

  15. Studying Activity Series of Metals.

    ERIC Educational Resources Information Center

    Hoon, Tien-Ghun; And Others

    1995-01-01

    Presents teaching strategies that illustrate the linking together of numerous chemical concepts involving the activity of metals (quantitative analysis, corrosion, and electrolysis) through the use of deep-level processing strategies. Concludes that making explicit links in the process of teaching chemistry can lead effectively to meaningful…

  16. Reactions of fourth-period metal ions (Ca + - Zn + ) with O2: Metal-oxide ion bond energies

    NASA Astrophysics Data System (ADS)

    Fisher, Ellen R.; Elkind, J. L.; Clemmer, D. E.; Georgiadis, R.; Loh, S. K.; Aristov, N.; Sunderlin, L. S.; Armentrout, P. B.

    1990-08-01

    Reactions of Ca+, Zn+ and all first-row atomic transition metal ions with O2 are studied using guided ion beam techniques. While reactions of the ground states of Sc+, Ti+, and V+ are exothermic, the remaining metal ions react with O2 in endothermic processes. Analyses of these endothermic reactions provide new determinations of the M+-O bond energies for these eight elements. Source conditions are varied such that the contributions of excited states of the metal ions can be explicitly considered for Mn+, Co+, Ni+, and Cu+. Results (in eV) at 0 K are D0(Ca+-O)= 3.57±0.05, D0(Cr+-O)=3.72±0.12, D0(Mn+-O)=2.95±0.13, D0(Fe+-O)=3.53±0.06 (reported previously), D0(Co+-O)=3.32±0.06, D0(Ni+-O) =2.74±0.07, D0(Cu+-O)=1.62±0.15, and D0(Zn+-O)=1.65±0.12. These values along with literature data for neutral metal oxide bond energies and ionization energies are critically evaluated. Periodic trends in the ionic metal oxide bond energies are compared with those of the neutral metal oxides and those of other related molecules.

  17. Synthesis, characterization, molecular modeling and antioxidant activity of Girard‧s T thiosemicarbazide and its complexes with some transition metal ions

    NASA Astrophysics Data System (ADS)

    El-Gammal, O. A.; Mostafa, M. M.

    2014-06-01

    The chelation behavior of N-{[(allylamino) thiomethyl] hydrazinocarbonylmethyl} trimethylammonium chloride (H3ATHC) towards VO2+, Co2+, Ni2+, Cu2+, Zn2+ and UO22+ ions have been studied. The structures of the complexes were elucidated using elemental analyses, spectral (IR, UV-visible, 1H NMR and ESR and mass) as well as magnetic and thermal measurements. The ligand acted as ON bidentate, ONS tridentate donor forming mononuclear complexes. A tetrahedral geometry for Co2+, square-planar for Ni2+ and Cu2+, an octahedral for Zn2+ and a square-pyramidal arrangement for VO2+ complexes were proposed, respectively. The EPR spectra of Cu2+ and VO2+ complexes confirmed the suggested geometries with values of α2 and β2 indicating that the in-plane σ-bonding and in-plane π-bonding are appreciably covalent, and were consistent with very strong in-plane σ bonding in the complexes. Also, the bond length, bond angle, HOMO, LUMO, dipole moment and charges on the atoms have been calculated. Also, the thermal behavior and kinetic parameters were determined using Coats-Redfern and Horowitz-Metzger methods. Furthermore, the synthesized compounds were screened for their superoxide-scavenging activity in the PMS/NADH-NBT system as well as their scavenging effect on ABTS (2,2‧-azino-bis(3-ethyl benzthiazoline-6-sulfonic acid) and 2,2-diphenyl-1-picrylhydrazyl(DPPH) radicals. Among these compounds, the ligand and Zn2+ complex, exhibited the potent ABTS (2,2‧-azino-bis(3-ethyl benzthiazoline-6-sulfonic acid) radical scavenging activity, comparable to that of vitamin C.

  18. Comet encke: meteor metallic ion identification by mass spectrometer.

    PubMed

    Goldberg, R A; Aikin, A C

    1973-04-20

    Metal ions including 23(+) (Na(+)), 24(+) (Mg(+)) 28(+) (Si(+)), 39(+) (K(+)), 40(+) (Ca(+)), 45(+) (Sc(+)), 52(+) Cr(+)). 56(+) (Fe(+)), and 58(+) (Ni(+)) have been detected in the upper atmosphere during the period of the Beta Taurids meteor shower. The abundances of these ions relative to Si(+) show, agreement in most instances with abundances in chondrites. A notable exception is 45(+), which, if it is Sc(+), is 100 times more abundant than neutral scandium found in chondrites.

  19. Comet Encke: Meteor metallic ion identification by mass spectrometer

    NASA Technical Reports Server (NTRS)

    Goldberg, R. A.; Aikin, A. C.

    1972-01-01

    Metal ions including Na-40(+), Mg-24(+), Si-28(+), K-39(+), Ca-40(+), Sc-45(+), Cr-52(+), Fe-56(+), and Ni-58(+) were detected in the upper atmosphere during the beta Taurids meteor shower. Abundances of these ions relative to Si(+) show agreement in most instances with chondrites. A notable exception is 45(+), which is Sc(+), is 100 times more abundant than neutral scandium found in chondrites.

  20. Smart responsive microcapsules capable of recognizing heavy metal ions.

    PubMed

    Pi, Shuo-Wei; Ju, Xiao-Jie; Wu, Han-Guang; Xie, Rui; Chu, Liang-Yin

    2010-09-15

    Smart responsive microcapsules capable of recognizing heavy metal ions are successfully prepared with oil-in-water-in-oil double emulsions as templates for polymerization in this study. The microcapsules are featured with thin poly(N-isopropylacrylamide-co-benzo-18-crown-6-acrylamide) (P(NIPAM-co-BCAm)) membranes, and they can selectively recognize special heavy metal ions such as barium(II) or lead(II) ions very well due to the "host-guest" complexation between the BCAm receptors and barium(II) or lead(II) ions. The stable BCAm/Ba(2+) or BCAm/Pb(2+) complexes in the P(NIPAM-co-BCAm) membrane cause a positive shift of the volume phase transition temperature of the crosslinked P(NIPAM-co-BCAm) hydrogel to a higher temperature, and the repulsion among the charged BCAm/Ba(2+) or BCAm/Pb(2+) complexes and the osmotic pressure within the P(NIPAM-co-BCAm) membranes result in the swelling of microcapsules. Induced by recognizing barium(II) or lead(II) ions, the prepared microcapsules with P(NIPAM-co-BCAm) membranes exhibit isothermal and significant swelling not only in outer and inner diameters but also in the membrane thickness. The proposed microcapsules in this study are highly attractive for developing smart sensors and/or carriers for detection and/or elimination of heavy metal ions.

  1. Existence of efficient divalent metal ion-catalyzed and inefficient divalent metal ion-independent channels in reactions catalyzed by a hammerhead ribozyme

    PubMed Central

    Zhou, Jing-Min; Zhou, De-Min; Takagi, Yasuomi; Kasai, Yasuhiro; Inoue, Atsushi; Baba, Tadashi; Taira, Kazunari

    2002-01-01

    The hammerhead ribozyme is generally accepted as a well characterized metalloenzyme. However, the precise nature of the interactions of the RNA with metal ions remains to be fully defined. Examination of metal ion-catalyzed hammerhead reactions at limited concentrations of metal ions is useful for evaluation of the role of metal ions, as demonstrated in this study. At concentrations of Mn2+ ions from 0.3 to 3 mM, addition of the ribozyme to the reaction mixture under single-turnover conditions enhances the reaction with the product reaching a fixed maximum level. Further addition of the ribozyme inhibits the reaction, demonstrating that a certain number of divalent metal ions is required for proper folding and also for catalysis. At extremely high concentrations, monovalent ions, such as Na+ ions, can also serve as cofactors in hammerhead ribozyme-catalyzed reactions. However, the catalytic efficiency of monovalent ions is extremely low and, thus, high concentrations are required. Furthermore, addition of monovalent ions to divalent metal ion-catalyzed hammerhead reactions inhibits the divalent metal ion-catalyzed reactions, suggesting that the more desirable divalent metal ion–ribozyme complexes are converted to less desirable monovalent metal ion–ribozyme complexes via removal of divalent metal ions, which serve as a structural support in the ribozyme complex. Even though two channels appear to exist, namely an efficient divalent metal ion-catalyzed channel and an inefficient monovalent metal ion-catalyzed channel, it is clear that, under physiological conditions, hammerhead ribozymes are metalloenzymes that act via the significantly more efficient divalent metal ion-dependent channel. Moreover, the observed kinetic data are consistent with Lilley’s and DeRose’s two-phase folding model that was based on ground state structure analyses. PMID:12034824

  2. DUHOCAMIS: a dual hollow cathode ion source for metal ion beams.

    PubMed

    Zhao, W J; Müller, M W O; Janik, J; Liu, K X; Ren, X T

    2008-02-01

    In this paper we describe a novel ion source named DUHOCAMIS for multiply charged metal ion beams. This ion source is derived from the hot cathode Penning ion gauge ion source (JINR, Dubna, 1957). A notable characteristic is the modified Penning geometry in the form of a hollow sputter electrode, coaxially positioned in a compact bottle-magnetic field along the central magnetic line of force. The interaction of the discharge geometry with the inhomogeneous but symmetrical magnetic field enables this device to be operated as hollow cathode discharge and Penning discharge as well. The main features of the ion source are the very high metal ion efficiency (up to 25%), good operational reproducibility, flexible and efficient operations for low charged as well as highly charged ions, compact setup, and easy maintenance. For light ions, e.g., up to titanium, well-collimated beams in the range of several tens of milliamperes of pulsed ion current (1 ms, 10/s) have been reliably performed in long time runs.

  3. Metal-Ion Additives Reduce Thermal Expansion Of Polyimides

    NASA Technical Reports Server (NTRS)

    Stoakley, Diane M.; St. Clair, Anne K.; Emerson, Burt R., Jr.; Willis, George L.

    1994-01-01

    Polyimides widely used as high-performance polymers because of their excellent thermal stability and toughness. However, their coefficients of thermal expansion (CTE's) greater than those of metals, ceramics, and glasses. Decreasing CTE's of polyimides increase usefulness for aerospace and electronics applications in which dimensional stability required. Additives containing metal ions reduce coefficients of thermal expansion of polyimides. Reductions range from 11 to over 100 percent.

  4. Comparison between the electrocatalytic properties of different metal ion phthalocyanines and porphyrins towards the oxidation of hydroxide.

    PubMed

    De Wael, Karolien; Adriaens, Annemie

    2008-02-15

    This work reports on the electrocatalytic oxidation of hydroxide using different central metal ion phthalocyanines and porphyrins immobilized on gold electrodes. The apparent electrocatalytic activity of cobalt phthalocyanine or porphyrin modified electrodes was found to be the greatest among the present series of metal ion macrocycles investigated. Copper and unmetallated phthalocyanine or porphyrin modified electrodes show no electrocatalytic behaviour towards hydroxide, such as bare gold. A possible mechanism for the enhanced reactivity of cobalt ion macrocycles towards the oxygen evolution is given. It is also stated that the electrocatalytic activity towards an adsorbate involves several aspects, such as the coordination state of the central metal ion, the nature of the ligand, the stability of the complexes, the number of d electrons, the energy of orbitals and the strength of the bonding between the central metal ion and the axial ligand.

  5. Removal and recovery of toxic metal ions from aqueous waste sites using polymer pendant ligands

    SciTech Connect

    Fish, D.

    1996-10-01

    The purpose of this project is to investigate the use of polymer pendant ligand technology to remove and recover toxic metal ions from DOE aqueous waste sites. Polymer pendant lgiands are organic ligands, anchored to crosslinked, modified divinylbenzene-polystyrene beads, that can selectively complex metal ions. The metal ion removal step usually occurs through a complexation or ion exchange phenomena, thus recovery of the metal ions and reuse of the beads is readily accomplished.

  6. Heavy metal ions are potent inhibitors of protein folding

    SciTech Connect

    Sharma, Sandeep K.; Goloubinoff, Pierre; Christen, Philipp

    2008-07-25

    Environmental and occupational exposure to heavy metals such as cadmium, mercury and lead results in severe health hazards including prenatal and developmental defects. The deleterious effects of heavy metal ions have hitherto been attributed to their interactions with specific, particularly susceptible native proteins. Here, we report an as yet undescribed mode of heavy metal toxicity. Cd{sup 2+}, Hg{sup 2+} and Pb{sup 2+} proved to inhibit very efficiently the spontaneous refolding of chemically denatured proteins by forming high-affinity multidentate complexes with thiol and other functional groups (IC{sub 50} in the nanomolar range). With similar efficacy, the heavy metal ions inhibited the chaperone-assisted refolding of chemically denatured and heat-denatured proteins. Thus, the toxic effects of heavy metal ions may result as well from their interaction with the more readily accessible functional groups of proteins in nascent and other non-native form. The toxic scope of heavy metals seems to be substantially larger than assumed so far.

  7. Adsorption characteristics of metal ions on chitosan chemically modified by D-galactose

    SciTech Connect

    Kondo, Kazuo; Sumi, Hisaharu; Matsumoto, Michiaki

    1996-07-01

    The adsorption characteristics of metal ions on chitosan chemically modified by D-galactose were examined. The pH dependency on the distribution ratio was found to be affected by the valency of the metal ion, and the apparent adsorption equilibrium constants of the metal ions were determined. The order of adsorption of the metal ions is Ga > In > Nd > Eu for the trivalent metal ions and Cu > Ni > Co for the divalent metal ions. It is believed that amino and hydroxyl groups in the chitosan act as a chelating ligand.

  8. Bidentate and tridentate metal-ion coordination states within ternary complexes of RB69 DNA polymerase

    SciTech Connect

    Xia, Shuangluo; Eom, Soo Hyun; Konigsberg, William H.; Wang, Jimin

    2012-02-21

    Two divalent metal ions are required for primer-extension catalyzed by DNA polymerases. One metal ion brings the 3'-hydroxyl of the primer terminus and the {alpha}-phosphorus atom of incoming dNTP together for bond formation so that the catalytically relevant conformation of the triphosphate tail of the dNTP is in an {alpha},{beta},{gamma}-tridentate coordination complex with the second metal ion required for proper substrate alignment. A probable base selectivity mechanism derived from structural studies on Dpo4 suggests that the inability of mispaired dNTPs to form a substrate-aligned, tridentate coordination complex could effectively cause the mispaired dNTPs to be rejected before catalysis. Nevertheless, we found that mispaired dNTPs can actually form a properly aligned tridentate coordination complex. However, complementary dNTPs occasionally form misaligned complexes with mutant RB69 DNA polymerases (RB69pols) that are not in a tridentate coordination state. Here, we report finding a {beta},{gamma}-bidentate coordination complex that contained the complementary dUpNpp opposite dA in the structure of a ternary complex formed by the wild type RB69pol at 1.88 {angstrom} resolution. Our observations suggest that several distinct metal-ion coordination states can exist at the ground state in the polymerase active site and that base selectivity is unlikely to be based on metal-ion coordination alone.

  9. Metal ion bombardment of onion skin cell wall

    NASA Astrophysics Data System (ADS)

    Sangyuenyongpipat, S.; Vilaithong, T.; Yu, L. D.; Verdaguer, A.; Ratera, I.; Ogletree, D. F.; Monteiro, O. R.; Brown, I. G.

    2005-01-01

    Ion bombardment of living cellular material is a novel subfield of ion beam surface modification that is receiving growing attention from the ion beam and biological communities. Although it has been demonstrated that the technique is sound, in that an adequate fraction of the living cells can survive both the vacuum environment and energetic ion bombardment, there remains much uncertainty about the process details. Here we report on our observations of onion skin cells that were subjected to ion implantation, and propose some possible physical models that tend to support the experimental results. The ion beams used were metallic (Mg, Ti, Fe, Ni, Cu), mean ion energy was typically 30 keV, and the implantation fluence was in the range 1014-1016 ions/cm2. The cells were viewed using Atomic Force Microscopy, revealing the formation of microcrater-like structures due to ion bombardment. The implantation depth profile was measured with Rutherford backscattering spectrometry and compared to the results of the TRIM, T-DYN and PROFILE computer codes.

  10. Metal ion bombardment of onion skin cell wall

    SciTech Connect

    Sangyuenyongpipat, S.; Vilaithong, T.; Yu, L.D.; Verdaguer, A.; Ratera, I.; Ogletree, D.F.; Monteiro, O.R.; Brown, I.G.

    2004-05-10

    Ion bombardment of living cellular material is a novel subfield of ion beam surface modification that is receiving growing attention from the ion beam and biological communities. Although it has been demonstrated that the technique is sound, in that an adequate fraction of the living cells can survive both the vacuum environment and energetic ion bombardment, there remains much uncertainty about the process details. Here we report on our observations of onion skin cells that were subjected to ion implantation, and propose some possible physical models that tend to support the experimental results. The ion beams used were metallic (Mg, Ti, Fe, Ni, Cu), mean ion energy was typically 30keV, and the implantation fluence was in the range 1014 1016 ions/cm2. The cells were viewed using Atomic Force Microscopy, revealing the formation of microcrater-like structures due to ion bombardment. The implantation depth profile was measured with Rutherford backscattering spectrometry and compared to the results of the TRIM, T-DYN and PROFILE computer codes.

  11. Piezoelectric sensor for sensitive determination of metal ions based on the phosphate-modified dendrimer

    NASA Astrophysics Data System (ADS)

    Wang, S. H.; Shen, C. Y.; Lin, Y. M.; Du, J. C.

    2016-08-01

    Heavy metal ions arising from human activities are retained strongly in water; therefore public water supplies must be monitored regularly to ensure the timely detection of potential problems. A phosphate-modified dendrimer film was investigated on a quartz crystal microbalance (QCM) for sensing metal ions in water at room temperature in this study. The chemical structures and sensing properties were characterized by Fourier transform infrared spectroscopy and QCM measurement, respectively. This phosphate-modified dendrimer sensor can directly detect metal ions in aqueous solutions. This novel sensor was evaluated for its capacity to sense various metal ions. The sensor exhibited a higher sensitivity level and shorter response time to copper(II) ions than other sensors. The linear detection range of the prepared QCM based on the phosphate-modified dendrimer was 0.0001 ∼ 1 μM Cu(II) ions (R2 = 0.98). The detection properties, including sensitivity, response time, selectivity, reusability, maximum adsorption capacity, and adsorption equilibrium constants, were also investigated.

  12. Current and prospective applications of metal ion-protein binding.

    PubMed

    Ueda, E K M; Gout, P W; Morganti, L

    2003-02-21

    Since immobilized metal ion affinity chromatography (IMAC) was first introduced, several variants of this method and many other metal affinity-based techniques have been devised. IMAC quickly established itself as a highly reliable purification procedure, showing rapid expansion in the number of preparative and analytical applications while not remaining confined to protein separation. It was soon applied to protein refolding (matrix-assisted refolding), evaluation of protein folding status, protein surface topography studies and biosensor development. In this review, applications in protein processing are described of IMAC as well as other metal affinity-based technologies.

  13. Uptake of Metal Ions by Rhizopus arrhizus Biomass

    PubMed Central

    Tobin, J. M.; Cooper, D. G.; Neufeld, R. J.

    1984-01-01

    Rhizopus arrhizus biomass was found to absorb a variety of different metal cations and anions but did not absorb alkali metal ions. The amount of uptake of the cations was directly related to ionic radii of La3+, Mn2+, Cu2+, Zn2+, Cd2+, Ba2+, Hg2+, Pb2+, UO22+, and Ag+. The uptake of all the cations is consistent with absorption of the metals by sites in the biomass containing phosphate, carboxylate, and other functional groups. The uptake of the molybdate and vanadate anions was strongly pH dependent, and it is proposed that the uptake mechanism involves electrostatic attraction to positively charged functional groups. PMID:16346521

  14. Principles Governing Metal Ion Selectivity in Ion Channel Proteins

    NASA Astrophysics Data System (ADS)

    Lim, Carmay

    2014-03-01

    Our research interests are to (i) unravel the principles governing biological processes and use them to identify novel drug targets and guide drug design, and (ii) develop new methods for studying macromolecular interactions. This talk will provide an overview of our work in these two areas and an example of how our studies have helped to unravel the principles underlying the conversion of Ca2+-selective to Na+-selective channels. Ion selectivity of four-domain voltage-gated Ca2+(Cav) and sodium (Nav) channels, which is controlled by the selectivity filter (SF, the narrowest region of an open pore), is crucial for electrical signaling. Over billions of years of evolution, mutation of the Glu from domain II/III in the EEEE/DEEA SF of Ca2+-selective Cav channels to Lys made these channels Na+-selective. This talk will delineate the physical principles why Lys is sufficient for Na+/Ca2+selectivity and why the DEKA SF is more Na+-selective than the DKEA one.

  15. Quadrupole ion trap studies of the structure and reactivity of transition metal ion pair complexes

    PubMed

    Vachet; Callahan

    2000-03-01

    Ion pairs are common species observed in the electrospray mass spectra of transition metal coordination complexes. To understand the nature of these ion pairs, a systematic study of the gas-phase chemistry of these species using ion-molecule reactions and collision-induced dissociation (CID) was carried out. Ion pair complexes of the type MLnX+ (where M is Mn(II), Fe(II), Co(II), Ni(II), Cu(II) or Zn(II), L is 1,10-phenanthroline, 2,2'-bipyridine, ethylenediamine, diethylenetriamine or 1,4,8,11-tetraazacyclotetradecane and X is Cl-, NO3-, acetylacetonate, ClO4-, acetate or SCN-) were studied. Ion-molecule reactions can distinguish whether the counterion in an ion pair is an inner- or outer-sphere ligand and can determine the coordination mode of the counterion. In addition, CID and ion-molecule reactions reveal some interesting chemistry of these complexes and unique coordination modes for some of the anions studied here were inferred from the ion-molecule reactions. For example, the thiocyanate ion is found to coordinate in a bidentate fashion in Zn(II) and Ni(II) complexes, contrasting behavior typically observed in solution. Also, certain Co(II) and Fe(II) ion pair complexes undergo oxidation reactions in which species such as dioxygen and nitric oxide from the counterions ClO4- and NO3- are transferred to the Co(II) and Fe(II) complexes, showing the inherent affinity of these metals for these molecules. These complexes were also studied by ion-molecule reactions and CID. Dioxygen in complexes formed by CID is demonstrated to be bidentate, suggesting the formation of a peroxo ligand with concurrent oxidation of the metal.

  16. Host Materials for Transition-Metal Ions

    DTIC Science & Technology

    1989-09-01

    BeA1204 (Chrysoberyl, Cr:BeA204 - Alexandrite ) ..................... 90 15.1 Crystallographic Data on BeA 204 ............................ 9 0 15.2 X...Chrysoberyl, Cr:BeA1 2 04 = Alexandrite ) 15.1 Crystallographic Data on BeA204 Orthorhombic D 16 (Pnma), 62, Z = 4 Orthorhomb__ D2h Ion Site Symmetry x...Stimulated Emission from Alexandrite (BeAl 1204 :Cr 3 +) Sov. J. Quantum Electron. 8 (1978), 671. 2. C. F. Cline, R. C. Morris, M. Dutoit, and P. J

  17. Precipitation of alkylbenzene sulfonates with metal ions

    SciTech Connect

    Peacock, J.M.; Matijevic, E.

    1980-10-01

    The precipitation domains of P-(1-methylnonyl)benzene sulfonate ions with Li/sup +/, Na/sup +/, K/sup +/, Ca/sup 2 +/, Mg/sup 2 +/, Al/sup 3 +/, and La/sup 3 +/ and of Ca/sup 2 +/-P-(hexyloctyl)benzene sulfonate have been determined at constant pH and 25 C. The linear solubility boundaries reverse their slope at the critical micellar concentration of the surfactant. A semiquantitative interpretation of the data is offered. The properties of the solids formed also are described. 18 references.

  18. Neutralization by metal ions of the toxicity of sodium selenide.

    PubMed

    Dauplais, Marc; Lazard, Myriam; Blanquet, Sylvain; Plateau, Pierre

    2013-01-01

    Inert metal-selenide colloids are found in animals. They are believed to afford cross-protection against the toxicities of both metals and selenocompounds. Here, the toxicities of metal salt and sodium selenide mixtures were systematically studied using the death rate of Saccharomyces cerevisiae cells as an indicator. In parallel, the abilities of these mixtures to produce colloids were assessed. Studied metal cations could be classified in three groups: (i) metal ions that protect cells against selenium toxicity and form insoluble colloids with selenide (Ag⁺, Cd²⁺, Cu²⁺, Hg²⁺, Pb²⁺ and Zn²⁺), (ii) metal ions which protect cells by producing insoluble metal-selenide complexes and by catalyzing hydrogen selenide oxidation in the presence of dioxygen (Co²⁺ and Ni²⁺) and, finally, (iii) metal ions which do not afford protection and do not interact (Ca²⁺, Mg²⁺, Mn²⁺) or weakly interact (Fe²⁺) with selenide under the assayed conditions. When occurring, the insoluble complexes formed from divalent metal ions and selenide contained equimolar amounts of metal and selenium atoms. With the monovalent silver ion, the complex contained two silver atoms per selenium atom. Next, because selenides are compounds prone to oxidation, the stabilities of the above colloids were evaluated under oxidizing conditions. 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB), the reduction of which can be optically followed, was used to promote selenide oxidation. Complexes with cadmium, copper, lead, mercury or silver resisted dissolution by DTNB treatment over several hours. With nickel and cobalt, partial oxidation by DTNB occurred. On the other hand, when starting from ZnSe or FeSe complexes, full decompositions were obtained within a few tens of minutes. The above properties possibly explain why ZnSe and FeSe nanoparticles were not detected in animals exposed to selenocompounds.

  19. Electropositive bivalent metallic ion unsaturated polyester complexed polymer concrete

    DOEpatents

    Sugama, T.; Kukacka, L.E.; Horn, W.H.

    1981-11-04

    Quick setting polymer concrete compositions which are mixtures of unsaturated polyesters and crosslinking monomers together with appropriate initiators and promoters in association with aggregate which may be wet and a source of bivalent metallic ions which will set to polymer concrete with excellent structural properties.

  20. Electropositive bivalent metallic ion unsaturated polyester complexed polymer concrete

    DOEpatents

    Sugama, T.; Kukacka, L.E.; Horn, W.H.

    1983-05-13

    Quick setting polymer concrete compositions are described which are mixtures of unsaturated polyesters and crosslinking monomers together with appropriate initiators and promoters in association with aggregate which may be wet and a source of bivalent metallic ions which will set to polymer concrete with excellent structural properties.

  1. Electropositive bivalent metallic ion unsaturated polyester complexed polymer concrete

    DOEpatents

    Sugama, Toshifumi; Kukacka, Lawrence E.; Horn, William H.

    1985-01-01

    Quick setting polymer concrete compositions with excellent structural properties are disclosed; these polymer concrete compositions are mixtures of unsaturated polyesters and crosslinking monomers together with appropriate initiators and promoters in association with aggregate, which may be wet, and with a source of bivalent metallic ions.

  2. Broad-beam, high current, metal ion implantation facility

    SciTech Connect

    Brown, I.G.; Dickinson, M.R.; Galvin, J.E.; Godechot, X.; MacGill, R.A.

    1990-07-01

    We have developed a high current metal ion implantation facility with which high current beams of virtually all the solid metals of the Periodic Table can be produced. The facility makes use of a metal vapor vacuum arc ion source which is operated in a pulsed mode, with pulse width 0.25 ms and repetition rate up to 100 pps. Beam extraction voltage is up to 100 kV, corresponding to an ion energy of up to several hundred keV because of the ion charge state multiplicity; beam current is up to several Amperes peak and around 10 mA time averaged delivered onto target. Implantation is done in a broad-beam mode, with a direct line-of-sight from ion source to target. Here we describe the facility and some of the implants that have been carried out using it, including the seeding' of silicon wafers prior to CVD with titanium, palladium or tungsten, the formation of buried iridium silicide layers, and actinide (uranium and thorium) doping of III-V compounds. 16 refs., 6 figs.

  3. New Catalytic DNA Biosensors for Radionuclides and Metal ions

    SciTech Connect

    Lu, Yi

    2005-06-01

    In vitro selection for DNAzymes that are catalytically active with UO22+ ions as the metal cofactor has been completed. The 10th generation pool of DNA was cloned and sequenced. A total of 84 clones were sequenced and placed into families based on sequence alignments. Selected members of each family were 5-labeled with 32P and amplified using PCR. Activity assays were conducted using the isotopically labeled DNAzymes in order to determine which sequences were the most active. The secondary structures of the two most active sequences, called Clone 13 and Clone 39, were determined using the computer program Mfold. A cleavage rate of approximately 1 min-1 in the presence of 10 uM UO22+ was observed for both clones. Clone 39 was determined to be the best candidate for truncation to create a trans-cleaving DNAzyme, based on its secondary structure. An enzyme strand, called 39E, and a substrate strand, called 39DS, were designed by truncating the cis-cleaving DNAzyme. An alternative enzyme strand, called 39Ec, was also assayed with the 39DS substrate. This strand was designed so that the two binding arms were perfectly complimentary, unlike 39E, which formed three mismatched base pairs with 39DS. Both 39E and 39Ec were found to be active, with a rate of approximately 1 min-1 in the presence of 10 uM UO22+. A preliminary UO22+ binding curve was obtained for the 39Ec/39DS trans-cleaving system. The enzyme is active with UO22+ concentrations as low as 1 nM. Based on the preliminary binding curve data, the apparent UO22+ binding constant is approximately 330 nM, and kmax is approximately 1 min-1.

  4. Selective quenching of benzimidazole derivatives by Cu2+ metal ion

    NASA Astrophysics Data System (ADS)

    Jayabharathi, J.; Thanikachalam, V.; Jayamoorthy, K.; Sathishkumar, R.

    2012-11-01

    It is a very big challenge to develop a Cu2+ selective fluorescent sensor with the ability to exclude the interference of some metal ions such as Fe3+, Mg2+, Ag+, K+ and Na+. Herein, we report a fluorescence quenching of some benzimidazole derivatives (1-6) with Cu2+ metal ion. These benzimidazole derivatives have been shown to bind copper ions resulting in quenching of its fluorescence. The response to Cu2+ is rapid, selective and reversible upon addition of a copper chelator. These benzimidazole derivatives were characterized by 1H, 13C NMR mass and elemental analysis. XRD analysis was carried out for 1-(4-methylbenzyl)-2-p-tolyl-1H-benzo[d]imidazole.

  5. [Spectroscopic studies on transition metal ions in colored diamonds].

    PubMed

    Meng, Yu-Fei; Peng, Ming-Sheng

    2004-07-01

    Transition metals like nickel, cobalt and iron have been often used as solvent catalysts in high pressure high temperature (HPHT) synthesis of diamond, and nickel and cobalt ions have been found in diamond lattice. Available studies indicated that nickel and cobalt ions could enter the lattice as interstitial or substitutional impurities and form complexes with nitrogen. Polarized microscopy, SEM-EDS, EPR, PL and FTIR have been used in this study to investigate six fancy color natural and synthetic diamonds in order to determine the spectroscopic characteristics and the existing forms of transition metal ions in colored diamond lattice. Cobalt-related optical centers were first found in natural chameleon diamonds, and some new nickel and cobalt-related optical and EPR centers have also been detected in these diamond samples.

  6. [Biological activity of selenorganic compounds at heavy metal salts intoxication].

    PubMed

    Rusetskaya, N Y; Borodulin, V B

    2015-01-01

    Possible mechanisms of the antitoxic action of organoselenium compounds in heavy metal poisoning have been considered. Heavy metal toxicity associated with intensification of free radical oxidation, suppression of the antioxidant system, damage to macromolecules, mitochondria and the genetic material can cause apoptotic cell death or the development of carcinogenesis. Organic selenium compounds are effective antioxidants during heavy metal poisoning; they exhibit higher bioavailability in mammals than inorganic ones and they are able to activate antioxidant defense, bind heavy metal ions and reactive oxygen species formed during metal-induced oxidative stress. One of promising organoselenium compounds is diacetophenonyl selenide (DAPS-25), which is characterized by antioxidant and antitoxic activity, under conditions including heavy metal intoxication.

  7. Liquid metal ion source and alloy for ion emission of multiple ionic species

    DOEpatents

    Clark, Jr., William M.; Utlaut, Mark W.; Wysocki, Joseph A.; Storms, Edmund K.; Szklarz, Eugene G.; Behrens, Robert G.; Swanson, Lynwood W.; Bell, Anthony E.

    1987-06-02

    A liquid metal ion source and alloy for the simultaneous ion evaporation of arsenic and boron, arsenic and phosphorus, or arsenic, boron and phosphorus. The ionic species to be evaporated are contained in palladium-arsenic-boron and palladium-arsenic-boron-phosphorus alloys. The ion source, including an emitter means such as a needle emitter and a source means such as U-shaped heater element, is preferably constructed of rhenium and tungsten, both of which are readily fabricated. The ion sources emit continuous beams of ions having sufficiently high currents of the desired species to be useful in ion implantation of semiconductor wafers for preparing integrated circuit devices. The sources are stable in operation, experience little corrosion during operation, and have long operating lifetimes.

  8. Metal negative ion beam extraction from a radio frequency ion source

    SciTech Connect

    Kanda, S.; Yamada, N.; Kasuya, T.; Romero, C. F. P.; Wada, M.

    2015-04-08

    A metal ion source of magnetron magnetic field geometry has been designed and operated with a Cu hollow target. Radio frequency power at 13.56 MHz is directly supplied to the hollow target to maintain plasma discharge and induce self-bias to the target for sputtering. The extraction of positive and negative Cu ion beams have been tested. The ion beam current ratio of Cu{sup +} to Ar{sup +} has reached up to 140% when Ar was used as the discharge support gas. Cu{sup −} ion beam was observed at 50 W RF discharge power and at a higher Ar gas pressure in the ion source. Improvement of poor RF power matching and suppression of electron current is indispensable for a stable Cu{sup −} ion beam production from the source.

  9. Comparative Photoluminescence Properties and Judd-Ofelt Analysis of Eu3+ Ion-Activated Metal Molybdate Phosphors A2MoO6:Eu3+ (A = La, Y, Gd and Bi)

    NASA Astrophysics Data System (ADS)

    Han, Bing; Liu, Bingkun; Zhang, Jie; Li, Pengju; Shi, Hengzhen

    2017-03-01

    A class of red-emitting Eu3+ ion-activated metal molybdate A2MoO6:Eu3+ (A = La, Y, Gd and Bi) phosphors were synthesized by a conventional high-temperature solid-state reaction method. The x-ray diffraction patterns, scanning electron microscope images, Fourier transform infrared spectra, ultraviolet-visible diffuse reflection spectra as well as photoluminescence properties were measured to characterize the as-prepared samples. The photoluminescence properties including excitation/emission spectra, decay curves, Commission Internationale de L'Eclairage chromaticity coordinates and quantum efficiency were comparatively investigated in detail. The Judd-Ofelt theory was also applied to understand the radiative properties of f-f transitions of Eu3+ ions in this system for the first time. The as-prepared phosphors can be effectively excited with near-ultraviolet and/or blue light, and exhibit red emission belonging to the prevailing 5D0 → 7F2 transitions of Eu3+ with short decay time (millisecond level). The results demonstrated that A2MoO6:Eu3+ (A = La, Y, Gd and Bi) phosphors could have potential application as red-emitting phosphors in white light-emitting diodes based on near-ultraviolet and/or blue light-emitting diode chips.

  10. Stable alkali metal ion intercalation compounds as optimized metal oxide nanowire cathodes for lithium batteries.

    PubMed

    Zhao, Yunlong; Han, Chunhua; Yang, Junwei; Su, Jie; Xu, Xiaoming; Li, Shuo; Xu, Lin; Fang, Ruopian; Jiang, Hong; Zou, Xiaodong; Song, Bo; Mai, Liqiang; Zhang, Qingjie

    2015-03-11

    Intercalation of ions in electrode materials has been explored to improve the rate capability in lithium batteries and supercapacitors, due to the enhanced diffusion of Li(+) or electrolyte cations. Here, we describe a synergistic effect between crystal structure and intercalated ion by experimental characterization and ab initio calculations, based on more than 20 nanomaterials: five typical cathode materials together with their alkali metal ion intercalation compounds A-M-O (A = Li, Na, K, Rb; M = V, Mo, Co, Mn, Fe-P). Our focus on nanowires is motivated by general enhancements afforded by nanoscale structures that better sustain lattice distortions associated with charge/discharge cycles. We show that preintercalation of alkali metal ions in V-O and Mo-O yields substantial improvement in the Li ion charge/discharge cycling and rate, compared to A-Co-O, A-Mn-O, and A-Fe-P-O. Diffraction and modeling studies reveal that preintercalation with K and Rb ions yields a more stable interlayer expansion, which prevents destructive collapse of layers and allow Li ions to diffuse more freely. This study demonstrates that appropriate alkali metal ion intercalation in admissible structure can overcome the limitation of cyclability as well as rate capability of cathode materials, besides, the preintercalation strategy provides an effective method to enlarge diffusion channel at the technical level, and more generally, it suggests that the optimized design of stable intercalation compounds could lead to substantial improvements for applications in energy storage.

  11. Chitosan removes toxic heavy metal ions from cigarette mainstream smoke

    NASA Astrophysics Data System (ADS)

    Zhou, Wen; Xu, Ying; Wang, Dongfeng; Zhou, Shilu

    2013-09-01

    This study investigated the removal of heavy metal ions from cigarette mainstream smoke using chitosan. Chitosan of various deacetylation degrees and molecular weights were manually added to cigarette filters in different dosages. The mainstream smoke particulate matter was collected by a Cambridge filter pad, digested by a microwave digestor, and then analyzed for contents of heavy metal ions, including As(III/V), Pb(II), Cd(II), Cr(III/VI) and Ni(II), by graphite furnace atomic absorption spectrometry (GFAAS). The results showed that chitosan had a removal effect on Pb(II), Cd(II), Cr(III/VI) and Ni(II). Of these, the percent removal of Ni(II) was elevated with an increasing dosage of chitosan. Chitosan of a high deace tylation degree exhibited good binding performance toward Cd(II), Cr(III/VI) and Ni(II), though with poor efficiency for Pb(II). Except As(III/V), all the tested metal ions showed similar tendencies in the growing contents with an increasing chitosan molecular weight. Nonetheless, the percent removal of Cr(III/VI) peaked with a chitosan molecular weight of 200 kDa, followed by a dramatic decrease with an increasing chitosan molecular weight. Generally, chitosan had different removal effects on four out of five tested metal ions, and the percent removal of Cd(II), Pb(II), Cr(III/VI) and Ni(II) was approximately 55%, 45%, 50%, and 16%, respectively. In a word, chitosan used in cigarette filter can remove toxic heavy metal ions in the mainstream smoke, improve cigarette safety, and reduce the harm to smokers.

  12. Metal ion influence on eumelanin fluorescence and structure

    NASA Astrophysics Data System (ADS)

    Sutter, Jens-Uwe; Birch, David J. S.

    2014-06-01

    Melanin has long been thought to have an unworkably weak and complex fluorescence, but here we study its intrinsic fluorescence in order to demonstrate how metal ions can be used to control the rate of formation, constituents and structure of eumelanin formed from the well-known laboratory auto-oxidation of 3,4-dihydroxy-L-phenylalanine (L-DOPA). The effect on eumelanin absorption and fluorescence of a range of solvated metal ions is reported including Cu, Zn, Ni, Na and K. Monovalent cations and Zn have little effect, but the effect of transition metal cations can be considerable. For example, at pH 10, copper ions are shown to accelerate the onset of eumelanin formation, but not the rate of formation once it commences, and simplify the usual complex structure and intrinsic fluorescence of eumelanin in a way that is consistent with an increased abundance of 5,5-dihydroxyindole-2-carboxylic acid (DHICA). The presence of a dominant 6 ns fluorescence decay time at 480 nm, when excited at 450 nm describes a distinct photophysical species, which we tentatively assign to small oligomers. Copper is well-known to normally quench fluorescence, but increasing amounts of copper surprisingly leads to an increase in the fluorescence decay time of eumelanin, while reducing the fluorescence intensity, suggesting copper modification of the excited state. Such results have bearing on diverse areas. The most accepted morphology for melanin is that of a graphite-like sheet structure, and one which readily binds metal ions, an interaction that is thought to have an important, though as yet unclear bearing on several areas of medicine including neurology. There is also increasing interest in bio-mimicry by preparing and labelling sheet structures with metal ions for new electronic and photonic materials.

  13. Cardiovascular Outcomes and the Physical and Chemical Properties of Metal Ions Found in Particulate Matter Air Pollution: A QICAR Study

    PubMed Central

    Meng, Qingyu; Lu, Shou-En; Buckley, Barbara; Welsh, William J.; Whitsel, Eric A.; Hanna, Adel; Yeatts, Karin B.; Warren, Joshua; Herring, Amy H.; Xiu, Aijun

    2013-01-01

    Background: This paper presents an application of quantitative ion character–activity relationships (QICAR) to estimate associations of human cardiovascular (CV) diseases (CVDs) with a set of metal ion properties commonly observed in ambient air pollutants. QICAR has previously been used to predict ecotoxicity of inorganic metal ions based on ion properties. Objectives: The objective of this work was to examine potential associations of biological end points with a set of physical and chemical properties describing inorganic metal ions present in exposures using QICAR. Methods: Chemical and physical properties of 17 metal ions were obtained from peer-reviewed publications. Associations of cardiac arrhythmia, myocardial ischemia, myocardial infarction, stroke, and thrombosis with exposures to metal ions (measured as inference scores) were obtained from the Comparative Toxicogenomics Database (CTD). Robust regressions were applied to estimate the associations of CVDs with ion properties. Results: CVD was statistically significantly associated (Bonferroni-adjusted significance level of 0.003) with many ion properties reflecting ion size, solubility, oxidation potential, and abilities to form covalent and ionic bonds. The properties are relevant for reactive oxygen species (ROS) generation, which has been identified as a possible mechanism leading to CVDs. Conclusion: QICAR has the potential to complement existing epidemiologic methods for estimating associations between CVDs and air pollutant exposures by providing clues about the underlying mechanisms that may explain these associations. PMID:23462649

  14. Protective activity of plicatin B against human LDL oxidation induced in metal ion-dependent and -independent processes. Experimental and theoretical studies.

    PubMed

    Turchi, G; Alagona, G; Lubrano, V

    2009-11-01

    Oxidation of low-density lipoproteins (LDL) is thought to be a major factor in the pathophysiology of atherosclerosis. Natural antioxidants have been shown to protect LDL from oxidation and to inhibit atherogenic developments in animals. Structurally related prenylated pterocarpans, erybraedin C and bitucarpin A, and the prenylchalcone plicatin B were examined for their ability to inhibit LDL oxidation in vitro. The kinetic profile of peroxidation is characterized by the lag time of oxidation (t(lag)), the maximal rate of oxidation (V(max)) and the maximal accumulation of oxidation products (OD(max)). Specific variation of the set of kinetic parameters by antioxidants may provide important information about the mechanism of inhibitory action of a given compound. At equimolar concentrations (1 microM) the prenylated derivatives tested were found to inhibit 1 microM copper sulphate-induced oxidation of LDL (50 microg protein/ml) in accordance with the following order of activity: plicatin B>erybraedin Cbitucarpin A. Structural aspects, such as hydrogen-donating substituents, their number and arrangement in the aromatic ring moieties, and the prenyl and methoxy substituents, were investigated in order to explain the findings obtained. It is well known that the antioxidant activity of flavonoids is believed to be caused by a combination of transition metal chelation and free-radical-scavenging activities. To investigate these differences we comparatively studied the protective mechanism of plicatin B in copper-dependent or -independent LDL oxidation. The latter was mediated by 2,2'-azo-bis-(2-amidinopropane) dihydrochloride (ABAP). We measured the formation of conjugated dienes (OD(234 nm)). Plicatin B (0.2-1.5 microM) delayed the Cu(2+) (1 microM) promoted oxidation as conjugate diene formation (t(lag)) of the LDL by 45.2-123.5 min and reduced V(max) by 0.46-0.29 microM/min. In the ABAP (0.2mM) promoted LDL oxidation t(lag) increased by 67.2-110.2 min through plicatin

  15. ‘Pseudotumour’ invading the proximal femur with normal metal ions following metal on metal hip resurfacing

    PubMed Central

    Krishnan, Harry; Sugand, Kapil; Ali, Ibrahim; Smith, Jay

    2015-01-01

    A 75-year-old woman who had undergone hybrid metal-on-metal hip resurfacing 8 years earlier underwent revision arthroplasty because of hip, groin and lateral thigh pain. The main differential was aseptic loosening; however, serum cobalt and chromium levels were normal. Multiple imaging modalities revealed a periprosthetic, cystic soft tissue mass adjacent to the proximal femur. A large ‘pseudotumour’ with proximal femoral invasion was found at revision arthroplasty. We report the first finding of a ‘pseudotumour’ invading the proximal femur with normal metal ions following metal on metal hip resurfacing. PMID:25670783

  16. Toxicity of metallic ions and oxides to rabbit alveolar macrophages

    SciTech Connect

    Labedzka, M.; Gulyas, H.; Schmidt, N.; Gercken, G. )

    1989-04-01

    The effects of soluble compounds and oxides of As, Cd, Cu, Hg, Ni, Pb, Sb, Sn, V, and Zn on oxidative metabolism and membrane integrity of rabbit alveolar macrophages were studied by 24-hr in vitro exposure. Oxidative metabolism induced by phagocytosis of opsonized zymosan was measured by H{sub 2}O{sub 2} and O{sub 2}{sup {minus}} release and by chemiluminescence in the presence of luminol. Membrane integrity was estimated by extracellular LDH activity. Metallic ions and oxides inhibited the release of active oxygen species. Cd(II), As(III), and V(V) were the most toxic elements as measured by all investigated parameters. Cu(II) decreased O{sub 2}{sup {minus}} release and chemiluminescence effectively but H{sub 2}O{sub 2} release and membrane integrity less. Chemiluminescence was decreased strongly by Hg(II) while O{sub 2}{sup {minus}} and H{sub 2}O{sub 2} release were depressed moderately. Zn(II) and Sb(III) compounds caused medium toxicity and the tested Sn, Ni, and Pb compounds showed only faint toxic effects.

  17. Solution NMR refinement of a metal ion bound protein using metal ion inclusive restrained molecular dynamics methods.

    PubMed

    Chakravorty, Dhruva K; Wang, Bing; Lee, Chul Won; Guerra, Alfredo J; Giedroc, David P; Merz, Kenneth M

    2013-06-01

    Correctly calculating the structure of metal coordination sites in a protein during the process of nuclear magnetic resonance (NMR) structure determination and refinement continues to be a challenging task. In this study, we present an accurate and convenient means by which to include metal ions in the NMR structure determination process using molecular dynamics (MD) simulations constrained by NMR-derived data to obtain a realistic and physically viable description of the metal binding site(s). This method provides the framework to accurately portray the metal ions and its binding residues in a pseudo-bond or dummy-cation like approach, and is validated by quantum mechanical/molecular mechanical (QM/MM) MD calculations constrained by NMR-derived data. To illustrate this approach, we refine the zinc coordination complex structure of the zinc sensing transcriptional repressor protein Staphylococcus aureus CzrA, generating over 130 ns of MD and QM/MM MD NMR-data compliant sampling. In addition to refining the first coordination shell structure of the Zn(II) ion, this protocol benefits from being performed in a periodically replicated solvation environment including long-range electrostatics. We determine that unrestrained (not based on NMR data) MD simulations correlated to the NMR data in a time-averaged ensemble. The accurate solution structure ensemble of the metal-bound protein accurately describes the role of conformational sampling in allosteric regulation of DNA binding by zinc and serves to validate our previous unrestrained MD simulations of CzrA. This methodology has potentially broad applicability in the structure determination of metal ion bound proteins, protein folding and metal template protein-design studies.

  18. Agonist-activated ion channels

    PubMed Central

    Colquhoun, David

    2006-01-01

    This paper looks at ion channels as an example of the pharmacologist's stock in trade, the action of an agonist on a receptor to produce a response. Looked at in this way, ion channels have been helpful because they are still the only system which is simple enough for quantitative investigation of transduction mechanisms. A short history is given of attempts to elucidate what happens between the time when agonist first binds, and the time when the channel opens. PMID:16402101

  19. Development of a four-zone carousel process packed with metal ion-imprinted polymer for continuous separation of copper ions from manganese ions, cobalt ions, and the constituent metal ions of the buffer solution used as eluent.

    PubMed

    Jo, Se-Hee; Park, Chanhun; Yi, Sung Chul; Kim, Dukjoon; Mun, Sungyong

    2011-08-19

    A three-zone carousel process, in which Cu(II)-imprinted polymer (Cu-MIP) and a buffer solution were employed as adsorbent and eluent respectively, has been developed previously for continuous separation of Cu²⁺ (product) from Mn²⁺ and Co²⁺ (impurities). Although this process was reported to be successful in the aforementioned separation task, the way of using a buffer solution as eluent made it inevitable that the product stream included the buffer-related metal ions (i.e., the constituent metal ions of the buffer solution) as well as copper ions. For a more perfect recovery of copper ions, it would be necessary to improve the previous carousel process such that it can remove the buffer-related metal ions from copper ions while maintaining the previous function of separating copper ions from the other 2 impure heavy-metal ions. This improvement was made in this study by proposing a four-zone carousel process based on the following strategy: (1) the addition of one more zone for performing the two-step re-equilibration tasks and (2) the use of water as the eluent of the washing step in the separation zone. The operating conditions of such a proposed process were determined on the basis of the data from a series of single-column experiments. Under the determined operating conditions, 3 runs of carousel experiments were carried out. The results of these experiments revealed that the feed-loading time was a key parameter affecting the performance of the proposed process. Consequently, the continuous separation of copper ions from both the impure heavy-metal ions and the buffer-related metal ions could be achieved with a purity of 91.9% and a yield of 92.8% by using the proposed carousel process based on a properly chosen feed-loading time.

  20. Liquid metal alloy ion sources—An alternative for focussed ion beam technology

    NASA Astrophysics Data System (ADS)

    Bischoff, Lothar; Mazarov, Paul; Bruchhaus, Lars; Gierak, Jacques

    2016-06-01

    Today, Focused Ion Beam (FIB) processing is nearly exclusively based on gallium Liquid Metal Ion Sources (LMIS). But, many applications in the μm- or nm range could benefit from ion species other than gallium: local ion implantation, ion beam mixing, ion beam synthesis, or Focused Ion Beam Lithography (IBL). Therefore, Liquid Metal Alloy Ion Sources (LMAIS) represent a promising alternative to expand the remarkable application fields for FIB. Especially, the IBL process shows potential advantages over, e.g., electron beam or other lithography techniques: direct, resistless, and three-dimensional patterning, enabling a simultaneous in-situ process control by cross-sectioning and inspection. Taking additionally into account that the used ion species influences significantly the physical and chemical nature of the resulting nanostructures—in particular, the electrical, optical, magnetic, and mechanic properties leading to a large potential application area which can be tuned by choosing a well suited LMAIS. Nearly half of the elements of the periodic table are recently available in the FIB technology as a result of continuous research in this area during the last forty years. Key features of a LMAIS are long life-time, high brightness, and stable ion current. Recent developments could make these sources feasible for nano patterning issues as an alternative technology more in research than in industry. The authors will review existing LMAIS, LMIS other than Ga, and binary and ternary alloys. These physical properties as well as the fabrication technology and prospective domains for modern FIB applications will similarly be reviewed. Other emerging ion sources will be also presented and their performances discussed.

  1. Optical studies of ion-beam synthesized metal alloy nanoparticles

    SciTech Connect

    Magudapathy, P. Srivatsava, S. K.; Gangopadhyay, P.; Amirthapandian, S.; Sairam, T. N.; Panigrahi, B. K.

    2015-06-24

    Au{sub x}Ag{sub 1-x} alloy nanoparticles with tunable surface plasmon resonance (SPR) have been synthesized on a silica glass substrate. A small Au foil on an Ag foil is irradiated as target substrates such that ion beam falls on both Ag foil and Au foils. Silica slides are kept at an angle ∼45° with respect to the metallic foils. While irradiating the metallic foils with 100 keV Ar{sup +} ions, sputtered Au and Ag atoms get deposited on the silica-glass. In this configuration the foils have been irradiated by Ar{sup +} ions to various fluences at room temperature and the sputtered species are collected on silica slides. Formation of Au{sub x}Ag{sub 1-x} nanoparticles has been confirmed from the optical absorption measurements. With respect to the exposure area of Au and Ag foils to the ion beam, the SPR peak position varies from 450 to 500 nm. Green photoluminescence has been observed from these alloy metal nanoparticles.

  2. Low energy ion beam assisted growth of metal multilayers

    NASA Astrophysics Data System (ADS)

    Quan, Junjie

    Vapor deposited metal multilayers have attracted a great deal of interest in recent years because they offer extraordinary strength, hardness, heat resistance, and unexpected new properties like high reflectivity and spin-dependent conductivity. The giant magnetoresistance effects discovered in Fe/Cr artificial superstructures in 1988 stimulated a large number of studies on the electronic transport properties of spintronic materials because of their important applications in highly sensitive magnetic sensors, nonvolatile random access memories, and the data storage industry in general. Magnetic multilayers allow exploitation of unique micromagnetic, magnetooptic, and magnetoelectronic phenomena that cannot be realized using conventional materials. For example, if ferromagnetic layers (such as CoFe) with a thicknesses of 5-7 nm are separated by a non-magnetic spacer (such as Cu or AlOx) of an appropriate thickness (1-3 nm), they can exhibit large changes in their electrical resistance when a magnetic field is applied. These changes are caused mainly by spin-dependent conduction electron scattering at magnetic multilayer interfaces. Many experimental and theoretical works have sought to promote a basic understanding of the effect of atomic structure in thin film multilayers upon spin dependent transport. It has been found that interfacial imperfections, such as interfacial roughness and interlayer mixing, dramatically reduce the properties exploited for spintronic applications. A combination of computer modeling and experiments has been used to discover more effective ways to control the interfacial structures of metal multilayers. Earlier atomic simulations had indicated that it is very important to control adatom energy during deposition in order to improve interface properties. Based on these ideas, this dissertation has investigated the effects of low energy ion assistance during metal multilayer deposition. Using molecular dynamics modeling, the effects of ion

  3. Ion Implantation Effects on the Metal-Semiconductor Interfaces.

    NASA Astrophysics Data System (ADS)

    Yapsir, Andrie Setiawan

    1988-12-01

    In this thesis, the effects of ion implantation on metal-semiconductor interfaces are studied. Hydrogen ions have been used as the implanted species. The implantation is carried out on Al/n-Si Schottky contacts. Electrical characterizations, deep level transient spectroscopy measurements, and the ^{15}N hydrogen profiling technique have been used to study the effects of ion implantation. It is demonstrated that the defect centers in the depletion region created by hydrogen implantation have more likely negative or possibly neutral signatures, rather than a positive signature as has been previously speculated. These negatively charged centers compensate for the positive donor resulting in a widening of the depletion region and reduction in the capacitance of the metal-semiconductor contacts. The tendency of hydrogen to passivate its own damage which results in the recovery of electronic transport across the metal-semiconductor junction upon low temperature heat treatment is also demonstrated. In connection with the behavior of hydrogen in silicon, in the second part of this thesis, detailed theoretical calculations on the hydrogen passivation of defects in silicon are carried out. A particular type of defect, namely, a substitutional sulfur in silicon, is chosen and is studied using the modified intermediate neglect of differential overlap (MINDO/3) molecular orbital method. It is found that the sulfur center can be passivated using one or two hydrogen atoms. The calculations indicate that the most stable positions of the hydrogen atoms are between the sulfur and its silicon neighbors. The hydrogens bond to the nearest silicon atoms and only weakly interact with the sulfur. Thermochemistry considerations predict that a single hydrogen passivates the sulfur center, provided these centers are in abundance in the silicon. Hydrogen ion implantation has also been carried out on Schottky contacts having a large difference in metal work function, Ti/p-Si and Pt

  4. Polymer filtration systems for dilute metal ion recovery

    SciTech Connect

    Smith, B.F.; Robison, T.W.; Jarvinen, G.D.

    1998-12-01

    Scientists at Los Alamos National Laboratory have developed a metal recovery system that meets the global treatment demands for all kinds of industrial and metal-processing streams. The Polymer Filtration (PF) System--a process that is easily operated and robust--offers metal-finishing businesses a convenient and inexpensive way to recover and recycle metal ions in-house, thus reducing materials costs, waste removal costs, and industrial liability. As a valuable economic and environmental asset, the PF System has been named a winner of a 1995 R and D 100 Award. These awards are presented annually by R and D Magazine to the one hundred most significant technical innovations of the year. The PF System is based on the use of water-soluble metal-binding polymers and on advanced ultrafiltration membranes. Customers for this technology will receive new soluble polymers, especially formulated for their waste stream, and the complete PF processing unit: a reaction reservoir, pumps, plumbing, controls, and the advanced ultrafiltration membranes, all in a skid mounted frame. Metal-bearing waste water is treated in the reaction reservoir, where the polymer binds with the metal ions under balanced acid/base conditions. The reservoir fluid is then pumped through the ultrafiltration system--a cartridge packed with ultrafiltration membranes shaped in hollow fibers. As the fluid travels inside the fiber, water and other small molecules--simple salts such as calcium and sodium, for example--pass through the porous membrane walls of the fibers and are discharged through the outlet as permeate. The polymer-bound metal, which is too large to pass through the pores, is both purified and concentrated inside the hollow fibers and is returned to the fluid reservoir for further waste water treatment.

  5. Biochemical and structural characterization of Salmonella typhimurium glyoxalase II: new insights into metal ion selectivity.

    PubMed

    Campos-Bermudez, Valeria A; Leite, Ney Ribeiro; Krog, Renata; Costa-Filho, Antonio J; Soncini, Fernando C; Oliva, Glaucius; Vila, Alejandro J

    2007-10-02

    Glyoxalase II is a hydrolytic enzyme part of the glyoxalase system, responsible for detoxifying several cytotoxic compounds employing glutathione. Glyoxalase II belongs to the superfamily of metallo-beta-lactamases, with a conserved motif able to bind up to two metal ions in their active sites, generally zinc. Instead, several eukaryotic glyoxalases II have been characterized with different ratios of iron, zinc, and manganese ions. We have expressed a gene coding for a putative member of this enzyme superfamily from Salmonella typhimurium that we demonstrate, on the basis of its activity, to be a glyoxalase II, named GloB. Recombinant GloB expressed in Escherichia coli was purified with variable amounts of iron, zinc, and manganese. All forms display similar activities, as can be shown from protein expression in minimal medium supplemented with specific metal ions. The crystal structure of GloB solved at 1.4 A shows a protein fold and active site similar to those of its eukaryotic homologues. NMR and EPR experiments also reveal a conserved electronic structure at the metal site. GloB is therefore able to accommodate these different metal ions and to carry out the hydrolytic reaction with similar efficiencies in all cases. The metal promiscuity of this enzyme (in contrast to other members of the same superfamily) can be accounted for by the presence of a conserved Asp residue acting as a second-shell ligand that is expected to increase the hardness of the metal binding site, therefore favoring iron uptake in glyoxalases II.

  6. Ion beam mixing of metal/fluoropolymer interfaces

    NASA Astrophysics Data System (ADS)

    Dennis, D. L.; Giedd, R. E.; Wang, Y. Q.; Glass, G. A.

    1999-06-01

    Ion beam mixing of metals and polymers with very low dielectric constants such as Teflon can provide many applications in the area of electronic materials. This work is a study of the "mixing" effect of 50 keV nitrogen implanted thin metal layers on Teflon PTFE (polytetrafluoroethylene) substrates. RBS analysis shows that the distribution of thin layers of copper and chromium (approximately 300-400 Å thick) through the implant layer of the Teflon depends on the reactivity of the metal. As the implant fluence is increased, the distribution of metal atoms in the polymer matrix becomes concentrated over smaller ranges near the bottom of the implant layer. In situ RGA analysis during the implantation shows the liberation of an abundance of fluorine in many different forms. This is supported by results from a NRA experiment that shows the non-uniform concentration profile of fluorine throughout the implant layer. During the implantation process, the fluorine is released through the incident ion track leaving a carbon and metal rich region near the surface of the implant layer. The fluorine density increases with depth through the implant layer making a smooth transition to the undamaged bulk Teflon below. Low dielectric materials with highly conductive surfaces, such as this one, may provide an opportunity for a broad range of new microelectronic applications.

  7. Effect of ion implantation on the tribology of metal-on-metal hip prostheses.

    PubMed

    Bowsher, John G; Hussain, Azad; Williams, Paul; Nevelos, Jim; Shelton, Julia C

    2004-12-01

    Nitrogen ion implantation (which considerably hardens the surface of the bearing) may represent one possible method of reducing the wear of metal-on-metal (MOM) hip bearings. Currently there are no ion-implanted MOM bearings used clinically. Therefore a physiological hip simulator test was undertaken using standard test conditions, and the results compared to previous studies using the same methods. N2-ion implantation of high carbon cast Co-Cr-Mo-on-Co-Cr-Mo hip prostheses increased wear by 2-fold during the aggressive running-in phase compared to untreated bearing surfaces, plus showing no wear reductions during steady-state conditions. Although 2 specimens were considered in the current study, it would appear that ion implantation has no clinical benefit for MOM.

  8. Interaction of metal ions with biomolecular ligands: how accurate are calculated free energies associated with metal ion complexation?

    PubMed

    Gutten, Ondrej; Beššeová, Ivana; Rulíšek, Lubomír

    2011-10-20

    To address fundamental questions in bioinorganic chemistry, such as metal ion selectivity, accurate computational protocols for both the gas-phase association of metal-ligand complexes and solvation/desolvation energies of the species involved are needed. In this work, we attempt to critically evaluate the performance of the ab initio and DFT electronic structure methods available and recent solvation models in calculations of the energetics associated with metal ion complexation. On the example of five model complexes ([M(II)(CH(3)S)(H(2)O)](+), [M(II)(H(2)O)(2)(H(2)S)(NH(3))](2+), [M(II)(CH(3)S)(NH(3))(H(2)O)(CH(3)COO)], [M(II)(H(2)O)(3)(SH)(CH(3)COO)(Im)], [M(II)(H(2)S)(H(2)O)(CH(3)COO)(PhOH)(Im)](+) in typical coordination geometries) and four metal ions (Fe(2+), Cu(2+), Zn(2+), and Cd(2+); representing open- and closed-shell and the first- and second-row transition metal elements), we provide reference values for the gas-phase complexation energies, as presumably obtained using the CCSD(T)/aug-cc-pVTZ method, and compare them with cheaper methods, such as DFT and RI-MP2, that can be used for large-scale calculations. We also discuss two possible definitions of interaction energies underlying the theoretically predicted metal-ion selectivity and the effect of geometry optimization on these values. Finally, popular solvation models, such as COSMO-RS and SMD, are used to demonstrate whether quantum chemical calculations can provide the overall free enthalpy (ΔG) changes in the range of the expected experimental values for the model complexes or match the experimental stability constants in the case of three complexes for which the experimental data exist. The data presented highlight several intricacies in the theoretical predictions of the experimental stability constants: the covalent character of some metal-ligand bonds (e.g., Cu(II)-thiolate) causing larger errors in the gas-phase complexation energies, inaccuracies in the treatment of solvation of the

  9. Statistical evaluation of biogeochemical variables affecting spatiotemporal distributions of multiple free metal ion concentrationsin an urban estuary

    EPA Science Inventory

    Free metal ion concentrations have been recognized as a better indicator of metal bioavailability in aquatic environments than total dissolved metal concentrations. However, our understanding of the determinants of free ion concentrations, especially in a metal mixture, is limite...

  10. The Corrosion Protection of Metals by Ion Vapor Deposited Aluminum

    NASA Technical Reports Server (NTRS)

    Danford, M. D.

    1993-01-01

    A study of the corrosion protection of substrate metals by ion vapor deposited aluminum (IVD Al) coats has been carried out. Corrosion protection by both anodized and unanodized IVD Al coats has been investigated. Base metals included in the study were 2219-T87 Al, 7075-T6 Al, Titanium-6 Al-4 Vanadium (Ti-6Al-4V), 4130 steel, D6AC steel, and 4340 steel. Results reveal that the anodized IVD Al coats provide excellent corrosion protection, but good protection is also achieved by IVD Al coats that have not been anodized.

  11. Ab Initio Calculations Applied to Problems in Metal Ion Chemistry

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.; Partridge, Harry; Arnold, James O. (Technical Monitor)

    1994-01-01

    Electronic structure calculations can provide accurate spectroscopic data (such as molecular structures) vibrational frequencies, binding energies, etc.) that have been very useful in explaining trends in experimental data and in identifying incorrect experimental measurements. In addition, ab initio calculations. have given considerable insight into the many interactions that make the chemistry of transition metal systems so diverse. In this review we focus on cases where calculations and experiment have been used to solve interesting chemical problems involving metal ions. The examples include cases where theory was used to differentiate between disparate experimental values and cases where theory was used to explain unexpected experimental results.

  12. The corrosion protection of metals by ion vapor deposited aluminum

    SciTech Connect

    Danford, M.D.

    1993-10-01

    A study of the corrosion protection of substrate metals by ion vapor deposited aluminum (IVD Al) coats has been carried out. Corrosion protection by both anodized and unanodized IVD Al coats has been investigated. Base metals included in the study were 2219-T87 Al, 7075-T6 Al, Titanium-6 Al-4 Vanadium (Ti-6Al-4V), 4130 steel, D6AC steel, and 4340 steel. Results reveal that the anodized IVD Al coats provide excellent corrosion protection, but good protection is also achieved by IVD Al coats that have not been anodized.

  13. Selective extraction of metal ions with polymeric extractants by ion exchange/redox

    DOEpatents

    Alexandratos, Spiro D.

    1987-01-01

    The specification discloses a method for the extraction of metal ions having a reduction potential of above about +0.3 from an aqueous solution. The method includes contacting the aqueous solution with a polymeric extractant having primary phosphinic acid groups, secondary phosphine oxide groups, or both phosphinic acid and phosphine oxide groups.

  14. Is there a difference in metal ion-based inhibition between members of thionin family: Molecular dynamics simulation study.

    PubMed

    Oard, Svetlana; Karki, Bijaya; Enright, Frederick

    2007-10-01

    Thionins have a considerable potential as antimicrobial compounds although their application may be restricted by metal ion-based inhibition of membrane permeabilizing activity. We previously reported the properties associated with the proposed mechanism of metal ion-based inhibition of beta-purothionin. In this study, we investigated the effects of metal ions on alpha-hordothionin which differs from beta-purothionin by eight out of 45 residues. Three of the differing residues are thought to be involved in the mechanism of metal ion-based inhibition in beta-purothionin. The structure and dynamics of alpha-hordothionin were explored using unconstrained molecular dynamics (MD) simulations in explicit water as a function of metal ions. Although the global fold is almost identical to that of beta-purothionin, alpha-hordothionin displays reduced fluctuating motions. Moreover, alpha-hordothionin is more resistant to the presence of metal ions than beta-purothionin. Mg(+2) ions do not affect alpha-hordothionin, whereas K(+) ions induce perturbations in the alpha2 helix, modify dynamics and electrostatic properties. Nevertheless, these changes are considerably smaller than those in beta-purothionin. The proposed mechanism of metal ion-based inhibition involves the hydrogen bonding network of Arg5-Arg30-Gly27, which regulates dynamic unfolding of the alpha2 C-end which is similar to beta-purothionin response. The key residues responsible for the increased resistance for alpha-hordothionin are Gly27 and Gly42 which replace Asn27 and Asp42 involved into the mechanism of metal ion-based inhibition in beta-purothionin. Comparison of MD simulations of alpha-hordothionin with beta-purothionin reveals dynamic properties which we believe are intrinsic properties of thionins with four disulphide bonds.

  15. Application of Freeze-Dried Powders of Genetically Engineered Microbial Strains as Adsorbents for Rare Earth Metal Ions.

    PubMed

    Moriwaki, Hiroshi; Masuda, Reiko; Yamazaki, Yuki; Horiuchi, Kaoru; Miyashita, Mari; Kasahara, Jun; Tanaka, Tatsuhito; Yamamoto, Hiroki

    2016-10-12

    The adsorption behaviors of the rare earth metal ions onto freeze-dried powders of genetically engineered microbial strains were compared. Cell powders obtained from four kinds of strains, Bacillus subtilis 168 wild type (WT), lipoteichoic acid-defective (ΔLTA), wall teichoic acid-defective (ΔWTA), and cell wall hydrolases-defective (EFKYOJLp) strains, were used as an adsorbent of the rare earth metal ions at pH 3. The adsorption ability of the rare earth metal ions was in the order of EFKYOJLp > WT > ΔLTA > ΔWTA. The order was the same as the order of the phosphorus quantity of the strains. This result indicates that the main adsorption sites for the ions are the phosphate groups and the teichoic acids, LTA and WTA, that contribute to the adsorption of the rare earth metal ions onto the cell walls. The contribution of WTA was clearly greater than that of LTA. Each microbial powder was added to a solution containing 16 kinds of rare earth metal ions, and the removals (%) of each rare earth metal ion were obtained. The scandium ion showed the highest removal (%), while that of the lanthanum ion was the lowest for all the microbial powders. Differences in the distribution coefficients between the kinds of lanthanide ions by the EFKYOJLp and ΔWTA powders were greater than those of the other strains. Therefore, the EFKYOJLp and ΔWTA powders could be applicable for the selective extraction of the lanthanide ions. The ΔLTA powder coagulated by mixing with a rare earth metal ion, although no sedimentation of the WT or ΔWTA powder with a rare earth metal ion was observed under the same conditions. The EFKYOJLp powder was also coagulated, but its flocculating activity was lower than that of ΔLTA. The ΔLTA and EFKYOJLp powders have a long shape compared to those of the WT or ΔWTA strain. The shapes of the cells will play an important role in the sedimentation of the microbial powders with rare earth metal ions. As the results, three kinds of the genetically

  16. Thermodynamic analysis of metal ion-induced protein assembly.

    PubMed

    Herr, Andrew B; Conrady, Deborah G

    2011-01-01

    A large number of biological systems are regulated by metal ion-induced protein assembly. This phenomenon can play a critical role in governing protein function and triggering downstream biological responses. We discuss the basic thermodynamic principles of linked equilibria that pertain to metal ion-induced dimerization and describe experimental approaches useful for studying such systems. The most informative techniques for studying these systems are sedimentation velocity and sedimentation equilibrium analytical ultracentrifugation, although a wide range of other spectroscopic, chromatographic, or qualitative approaches can provide a wealth of useful information. These experimental procedures are illustrated with examples from two systems currently under study: zinc-induced assembly of a staphylococcal protein responsible for intercellular adhesion in bacterial biofilms and calcium-induced dimerization of a human nucleotidase.

  17. Aqueous batteries based on mixed monovalence metal ions: a new battery family.

    PubMed

    Chen, Liang; Zhang, Leyuan; Zhou, Xufeng; Liu, Zhaoping

    2014-08-01

    As existing battery technologies struggle to meet the requirements for widespread use in the field of large-scale energy storage, new concepts are urgently needed to build batteries with high energy density, low cost, and good safety. Here, we demonstrate two new aqueous batteries based on two monovalence metal ions (Li(+) /K(+) and Na(+) /K(+) ) as charge-transfer ions, Ni1 Zn1 HCF/TiP2 O7 and Ni1 Zn1 HCF/NaTi2 (PO4 )3 . These new batteries are unlike the conventional "rocking-chair" aqueous metal-ion batteries based on the migration of one type of shuttle ion between cathode and anode. They can deliver specific energy of 46 Wh kg(-1) and 53 Wh kg(-1) based on the total mass of active materials; this is superior to current aqueous battery systems based on sodium-ion and/or potassium-ion technologies. These two new batteries together with the previously developed Li(+) /Na(+) mixed-ion battery not only constitute a new battery family for energy storage, but also greatly broaden our horizons for battery research.

  18. Metals in proteins: correlation between the metal-ion type, coordination number and the amino-acid residues involved in the coordination.

    PubMed

    Dokmanić, Ivan; Sikić, Mile; Tomić, Sanja

    2008-03-01

    Metal ions are constituents of many metalloproteins, in which they have either catalytic (metalloenzymes) or structural functions. In this work, the characteristics of various metals were studied (Cu, Zn, Mg, Mn, Fe, Co, Ni, Cd and Ca in proteins with known crystal structure) as well as the specificity of their environments. The analysis was performed on two data sets: the set of protein structures in the Protein Data Bank (PDB) determined with resolution <1.5 A and the set of nonredundant protein structures from the PDB. The former was used to determine the distances between each metal ion and its electron donors and the latter was used to assess the preferred coordination numbers and common combinations of amino-acid residues in the neighbourhood of each metal. Although the metal ions considered predominantly had a valence of two, their preferred coordination number and the type of amino-acid residues that participate in the coordination differed significantly from one metal ion to the next. This study concentrates on finding the specificities of a metal-ion environment, namely the distribution of coordination numbers and the amino-acid residue types that frequently take part in coordination. Furthermore, the correlation between the coordination number and the occurrence of certain amino-acid residues (quartets and triplets) in a metal-ion coordination sphere was analysed. The results obtained are of particular value for the identification and modelling of metal-binding sites in protein structures derived by homology modelling. Knowledge of the geometry and characteristics of the metal-binding sites in metalloproteins of known function can help to more closely determine the biological activity of proteins of unknown function and to aid in design of proteins with specific affinity for certain metals.

  19. Lithium metal doped electrodes for lithium-ion rechargeable chemistry

    DOEpatents

    Liu, Gao; Battaglia, Vince; Wang, Lei

    2016-09-13

    An embodiment of the invention combines the superior performance of a polyvinylidene difluoride (PVDF) or polyethyleneoxide (POE) binder, the strong binding force of a styrene-butadiene (SBR) binder, and a source of lithium ions in the form of solid lithium metal powder (SLMP) to form an electrode system that has improved performance as compared to PVDF/SBR binder based electrodes. This invention will provide a new way to achieve improved results at a much reduced cost.

  20. Superhydrogels of nanotubes capable of capturing heavy-metal ions.

    PubMed

    Song, Shasha; Wang, Haiqiao; Song, Aixin; Hao, Jingcheng

    2014-01-01

    Self-assembly regulated by hydrogen bonds was successfully achieved in the system of lithocholic acid (LCA) mixed with three organic amines, ethanolamine (EA), diethanolamine (DEA), and triethanolamine (TEA), in aqueous solutions. The mixtures of DEA/LCA exhibit supergelation capability and the hydrogels consist of plenty of network nanotubes with uniform diameters of about 60 nm determined by cryogenic TEM. Interestingly, the sample with the same concentration in a system of EA and LCA is a birefringent solution, in which spherical vesicles and can be transformed into nanotubes as the amount of LCA increases. The formation of hydrogels could be driven by the delicate balance of diverse noncovalent interactions, including electrostatic interactions, hydrophobic interactions, steric effects, van der Waals forces, and mainly hydrogen bonds. The mechanism of self-assembly from spherical bilayer vesicles into nanotubes was proposed. The dried hydrogels with nanotubes were explored to exhibit the excellent capability for capturing heavy-metal ions, for example, Cu(2+), Co(2+), Ni(2+), Pb(2+), and Hg(2+). The superhydrogels of nanotubes from the self-assembly of low-molecular-weight gelators mainly regulated by hydrogen bonds used for the removal of heavy-metal ions is simple, green, and high efficiency, and provide a strategic approach to removing heavy-metal ions from industrial sewage.

  1. The role of transition metal ions chemistry on multiphase chemistry

    NASA Astrophysics Data System (ADS)

    Deguillaume, L.; Leriche, M.; Monod, A.; Chaumerliac, N.

    2003-04-01

    A modelling study of the role of transition metal ions chemistry on cloud chemistry is presented. First, new developments of the Model of Multiphase Cloud Chemistry (M2C2) are described: the transition metal ions reactivity and variable photolysis in the aqueous phase. Secondly, three summertime scenarios describing urban, remote and marine conditions are simulated. First, comparisons between results from M2C2 and from CAPRAM2.3 models for the same scenarios (Herrmann et al., 2000) show a good agreement between the two models with respect to their different chemical mechanisms. Secondly, chemical regimes in cloud are analysed to understand the role of transition metal ions chemistry on cloud chemistry. This study focuses on HOx chemistry, which afterwards influences the sulphur and the VOCs chemistry in droplets. The ratio of Fe(II)/Fe(III) exhibits a diurnal variation with values in agreement with the few measurements of Fe speciation available. In the polluted case, sensitivity tests with and without TMI chemistry, show an enhancement of OH concentration in the aqueous phase when TMI chemistry is considered. This implies a more important oxidation of VOCs in droplets, which produces the HO2 radical, the hydrogen peroxide precursor. In fact, the HO2 radical is mainly converted into hydrogen peroxide by reactions between HO2/O2- radicals with Fe(II). This production of hydrogen peroxide leads to a rapid conversion of S(IV) into S(VI) at the beginning of the simulation.

  2. Measuring and Imaging Metal Ions With Fluorescence-Based Biosensors: Speciation, Selectivity, Kinetics, and Other Issues.

    PubMed

    Thompson, Richard B; Fierke, Carol A

    2017-01-01

    Fluorescence-based biosensors have shown themselves to be a powerful tool for the study of a variety of chemical species in biological systems, notably including metal ions. This chapter provides an overview of several important issues in using such sensors to study metallobiochemistry. These issues include selectivity for the analyte over potential interferents, including those that do not themselves induce a signal, the different forms in which metal ions are found (speciation), the utility of metal ion buffers, and the importance of kinetics in studying metal ion binding reactions. Finally, the chapter briefly discusses some of the issues in understanding whole-organism distribution of metal ions and its control.

  3. Template-directed synthesis of oligoguanylic acids - Metal ion catalysis

    NASA Technical Reports Server (NTRS)

    Bridson, P. K.; Fakhrai, H.; Lohrmann, R.; Orgel, L. E.; Van Roode, M.

    1981-01-01

    The effects of Zn(2+), Pb(2+) and other metal ions on the efficiency and stereo-selectivity of the template-directed oligomerization of guanosine 5'-phosphorimidazolide are investigated. Reactions were run in the presence of a polyC template in a 2,6-lutidine buffer, and products analyzed by high-performance liquid chromatography on an RPC-5 column. The presence of the Pb(2+) ion is found to lead to the formation of 2'-5' linked oligomers up to the 40-mer, while Zn(2+) favors the formation of predominantly 3'-5' linked oligomers up to the 35-mer. When amounts of uracil, cytidine or adenosine 5'-phosphorimidazole equal to those of the guanosine derivative are included in the reaction mixture, the incorrect base is incorporated into the oligomer about 10% of the time with a Pb(2+) catalyst, but less than 0.5% of the time with Zn(2+). The Sn(2+), Sb(3+) and Bi(3+) ions are also found to promote the formation of 2'-5' oligomers, although not as effectively as Pb(2+), while no metal ions other than Zn(2+) promote the formation of the 3'-5' oligomers. The results may be important for the understanding of the evolution of nucleic acid replication in the absence of enzymes.

  4. Plasmonics for the study of metal ion-protein interactions.

    PubMed

    Grasso, Giuseppe; Spoto, Giuseppe

    2013-02-01

    The study of metal-protein interactions is an expanding field of research investigated by bioinorganic chemists as it has wide applications in biological systems. Very recently, it has been reported that it is possible to study metal-protein interactions by immobilizing biomolecules on metal surfaces and applying experimental approaches based on plasmonics which have usually been used to investigate protein-protein interactions. This is possible because the electronic structure of metals generates plasmons whose properties can be exploited to obtain information from biomolecules that interact not only with other molecules but also with ions in solution. One major challenge of such approaches is to immobilize the protein to be studied on a metal surface with preserved native structure. This review reports and discusses all the works that deal with such an expanding new field of application of plasmonics with specific attention to surface plasmon resonance, highlighting the advantages and drawbacks of such approaches in comparison with other experimental techniques traditionally used to study metal-protein interactions.

  5. Note: An ion source for alkali metal implantation beneath graphene and hexagonal boron nitride monolayers on transition metals

    SciTech Connect

    Lima, L. H. de; Cun, H. Y.; Hemmi, A.; Kälin, T.; Greber, T.

    2013-12-15

    The construction of an alkali-metal ion source is presented. It allows the acceleration of rubidium ions to an energy that enables the penetration through monolayers of graphene and hexagonal boron nitride. Rb atoms are sublimated from an alkali-metal dispenser. The ionization is obtained by surface ionization and desorption from a hot high work function surface. The ion current is easily controlled by the temperature of ionizer. Scanning Tunneling Microscopy measurements confirm ion implantation.

  6. Electrospray Ionization Mass Spectrometry: From Cluster Ions to Toxic metal Ions in Biology

    SciTech Connect

    Lentz, Nicholas B.

    2007-01-01

    This dissertation focused on using electrospray ionization mass spectrometry to study cluster ions and toxic metal ions in biology. In Chapter 2, it was shown that primary, secondary and quarternary amines exhibit different clustering characteristics under identical instrument conditions. Carbon chain length also played a role in cluster ion formation. In Chapters 3 and 4, the effects of solvent types/ratios and various instrumental parameters on cluster ion formation were examined. It was found that instrument interface design also plays a critical role in the cluster ion distribution seen in the mass spectrum. In Chapter 5, ESI-MS was used to investigate toxic metal binding to the [Gln11]-amyloid β-protein fragment (1-16). Pb and Cd bound stronger than Zn, even in the presence of excess Zn. Hg bound weaker than Zn. There are endless options for future work on cluster ions. Any molecule that is poorly ionized in positive ion mode can potentially show an increase in ionization efficiency if an appropriate anion is used to produce a net negative charge. It is possible that drug protein or drug/DNA complexes can also be stabilized by adding counter-ions. This would preserve the solution characteristics of the complex in the gas phase. Once in the gas phase, CID could determine the drug binding location on the biomolecule. There are many research projects regarding toxic metals in biology that have yet to be investigated or even discovered. This is an area of research with an almost endless future because of the changing dynamics of biological systems. What is deemed safe today may show toxic effects in the future. Evolutionary changes in protein structures may render them more susceptible to toxic metal binding. As the understanding of toxicity evolves, so does the demand for new toxic metal research. New instrumentation designs and software make it possible to perform research that could not be done in the past. What was undetectable yesterday will

  7. Nickel and vanadium metal ions induce apoptosis of T-lymphocyte Jurkat cells.

    PubMed

    Au, Angela; Ha, Jinny; Hernandez, Mauro; Polotsky, Anna; Hungerford, David S; Frondoza, Carmelita G

    2006-12-01

    Metal alloys are used as prosthetic components in the orthopaedic and dental field. However, there is growing concern over the reported leaching of metal ions from implants. Ions released from metals have been thought to be associated with local immune dysfunction, inflammation, and tissue cell death. The objective of our study was to investigate whether nickel(II) and vanadium(V), present at a smaller percentage in most alloys, are cytotoxic to T-lymphocyte cell models. Jurkat T cells possess characteristics similar to human T-lymphocytes and proliferate at a faster rate. Jurkat T cells were incubated with control media alone or with concentrations of 1, 10, and 100 microg/mL of Ni(II) or V(V) for 24 h. Both types of metal ions reduced cell viability and proliferation in a dose-dependent manner. Ni(II) at 10 microg/mL and V(V) at 100 microg/mL activated Caspase-3 expression. Hoechst 33258 staining and transmission electron microscopy revealed chromatin condensation, as well as nuclear blebbing and fragmentation. Induction of DNA fragmentation by Ni(II) at 100 microg/mL was also indicated by agarose electrophoresis. Our observations indicate that Ni and V ions kill T cells via apoptotic and nonapoptotic pathways.

  8. Inhibition of proton-transfer steps in transhydrogenase by transition metal ions.

    PubMed

    Whitehead, Simon J; Iwaki, Masayo; Cotton, Nick P J; Rich, Peter R; Jackson, J Baz

    2009-10-01

    Transhydrogenase couples proton translocation across a bacterial or mitochondrial membrane to the redox reaction between NAD(H) and NADP(H). Purified intact transhydrogenase from Escherichia coli was prepared, and its His tag removed. The forward and reverse transhydrogenation reactions catalysed by the enzyme were inhibited by certain metal ions but a "cyclic reaction" was stimulated. Of metal ions tested they were effective in the order Pb(2+)>Cu(2+)>Zn(2+)=Cd(2+)>Ni(2+)>Co(2+). The results suggest that the metal ions affect transhydrogenase by binding to a site in the proton-transfer pathway. Attenuated total-reflectance Fourier-transform infrared difference spectroscopy indicated the involvement of His and Asp/Glu residues in the Zn(2+)-binding site(s). A mutant in which betaHis91 in the membrane-spanning domain of transhydrogenase was replaced by Lys had enzyme activities resembling those of wild-type enzyme treated with Zn(2+). Effects of the metal ion on the mutant were much diminished but still evident. Signals in Zn(2+)-induced FTIR difference spectra of the betaHis91Lys mutant were also attributable to changes in His and Asp/Glu residues but were much smaller than those in wild-type spectra. The results support the view that betaHis91 and nearby Asp or Glu residues participate in the proton-transfer pathway of transhydrogenase.

  9. Measurement of binding constants of poly(ethylenimine) with metal ions and metal chelates in aqueous media by ultrafiltration

    SciTech Connect

    Juang, R.S.; Chen, M.N.

    1996-06-01

    Equilibrium constants for the binding of poly(ethylenimine) (PEI) with metal ions and metal chelates of ethylenediaminetetraacetic acid and nitrilotriacetic acid in the aqueous sulfate solutions were determined by batch ultrafiltration (UF) in the pH range of 3.0--3.8. The average coordination number of PEI groups interacting with one metal ion and metal chelate was also obtained by varying the initial concentration ratio of PEI to metal ion. A simple chemical equilibrium model proposed in this work enabled the authors to satisfactorily predict the rejection coefficient of UF of metal ions and metal chelates in the presence of PEI. Also, the effect of the formation of soluble hydroxy complexes of metal chelates on their retention was emphasized.

  10. Polymer metallization: Low energy ion beam surface modification to improve adhesion

    NASA Astrophysics Data System (ADS)

    Bertrand, P.; Lambert, P.; Travaly, Y.

    1997-08-01

    The interface formation between copper and poly(ethylene terephthalate) (PET) and poly(methyl methacrylate) (PMMA) films is studied in situ by Ion Scattering Spectrometry (ISS). Very low metal fluxes (˜ 10 13 atoms/cm 2 s) and hence low deposition rates are obtained by using a Knudsen's effusion cell. This allows to reach very low metal coverages down to the sub-monolayer regime. The results indicate that without surface activation, Cu atoms interact only very weakly with both polymer surfaces. Indeed, the oxygen/carbon ISS intensity ratio remains nearly unaffected by the metal deposition, showing no preferential shadowing effect. Moreover, the ISS polymer signals are still detected after exposure to Cu atom fluences corresponding to several monolayers coverage. Cu diffusion below the polymer surface is evidenced by the presence of an inelastic multiple collision contribution in the ISS spectra. It is observed that 2 keV 3He + ion beam irradiation prior to metallization induces a drastic modification in the interface formation. Ion beam irradiation prevents the metal diffusion into the polymer bulk and leads to an increase of the metal concentration at the surface. In order to explain these results, the surface modifications produced by the ion beam on pristine polymers are studied by ISS and ToF-SIMS. Dehydrogenation and preferential loss of O containing fragments are found. These modifications are associated with the production of radicals leading to the creation of new adsorption sites for the Cu atoms. It is proposed that the reaction between radicals of different macrochains induces a surface crosslinking, that can prevent the diffusion for the deposited metal atoms into the polymer bulk.

  11. A Mononuclear Non-Heme Manganese(IV)-Oxo Complex Binding Redox-Inactive Metal Ions

    SciTech Connect

    Chen, Junying; Lee, Yong-Min; Davis, Katherine M.; Wu, Xiujuan; Seo, Mi Sook; Cho, Kyung-Bin; Yoon, Heejung; Park, Young Jun; Fukuzumi, Shunichi; Pushkar, Yulia N.; Nam, Wonwoo

    2013-05-29

    Redox-inactive metal ions play pivotal roles in regulating the reactivities of high-valent metal–oxo species in a variety of enzymatic and chemical reactions. A mononuclear non-heme Mn(IV)–oxo complex bearing a pentadentate N5 ligand has been synthesized and used in the synthesis of a Mn(IV)–oxo complex binding scandium ions. The Mn(IV)–oxo complexes were characterized with various spectroscopic methods. The reactivities of the Mn(IV)–oxo complex are markedly influenced by binding of Sc3+ ions in oxidation reactions, such as a ~2200-fold increase in the rate of oxidation of thioanisole (i.e., oxygen atom transfer) but a ~180-fold decrease in the rate of C–H bond activation of 1,4-cyclohexadiene (i.e., hydrogen atom transfer). The present results provide the first example of a non-heme Mn(IV)–oxo complex binding redox-inactive metal ions that shows a contrasting effect of the redox-inactive metal ions on the reactivities of metal–oxo species in the oxygen atom transfer and hydrogen atom transfer reactions.

  12. MRI findings following metal on metal hip arthroplasty and their relationship with metal ion levels and acetabular inclination angles.

    PubMed

    Fox, Ciara M; Bergin, Karen M; Kelly, Gabrielle E; McCoy, Gerry F; Ryan, Anthony G; Quinlan, John F

    2014-08-01

    Following the global recall of all ASR metal on metal hip products, our aim was to correlate MRI findings with acetabular inclination angles and metal ion levels in patients with these implants. Both cobalt and chromium levels were significantly higher in the presence of a periprosthetic fluid collection. There was no association between the presence of a periprosthetic mass, bone marrow oedema, trochanteric bursitis or greater levels of abductor muscle destruction for cobalt or chromium. There was no association between the level of periprosthetic tissue reaction and the acetabular inclination angle with any of the pathologies identified on MRI. The relationship between MRI pathology, metal ion levels and acetabular inclination angles in patients with ASR implants remains unclear adding to the complexity of managing patients.

  13. Sputtering of metals at ion-electron irradiation

    NASA Astrophysics Data System (ADS)

    Martynenko, Yu. V.; Korshunov, S. N.; Skorlupkin, I. D.

    2014-02-01

    It has been found that, in contrast to the commonly accepted opinion, simultaneous irradiation by 15-keV Ar+ ions and 2.5-keV electrons at temperatures above 0.5 T m ( T m is the melting temperature) induces much larger sputtering of metallic copper, nickel, and steel than irradiation only by Ar+ ions. The effect increases with the temperature. At T = 0.7 T m, the sputtering coefficients in the case of ion-electron irradiation are more than twice as large as the sputtering coefficients in the case of irradiation by Ar+ ions. The experiments on the sublimation of copper show that the sublimation rate in the case of the heating of a sample by an electron beam is higher than that in the case of heating in an electric vacuum oven. The revealed effects are explained by the electron-induced excitation of adatoms (atoms stuck over the surface, which appear owing to ion bombardment). Excited adatoms have a smaller binding energy with the surface and are sputtered more easily.

  14. Radiation damage from single heavy ion impacts on metal surfaces

    SciTech Connect

    Donnelly, S.E.; Birtcher, R.C.

    1998-06-01

    The effects of single ion impacts on the surfaces of films of Au, Ag, In and Pb have been studied using in-situ transmission electron microscopy. On all of these materials, individual ion impacts produce surface craters, in some cases, with associated expelled material. The cratering efficiency scales with the density of the irradiated metal. For very thin Au foils ({approx} 20--50 nm), in some cases individual ions are seen to punch small holes completely through the foil. Continued irradiation results in a thickening of the foil. The process giving rise to crater and hole formation and other changes observed in the thin foils has been found to be due to pulsed localized flow--i.e. melting and flow due to the thermal spikes arising from individual ion impacts. Experiments carried out on thin films of silver sandwiched between SiO{sub 2} layers have indicated that pulsed localized flow also occurs in this system and contributes to the formation of Ag nanoclusters in SiO{sub 2}--a system of interest for its non-linear optical properties. Calculation indicates that, when ion-induced, collision cascades occur near surfaces (within {approx} 5 nm) with energy densities sufficient to cause melting, craters are formed. Crater formation occurs as a result of the explosive outflow of material from the hot molten core of the cascade. Processes occurring in the sandwiched layer are less well understood.

  15. Optical metal-organic framework sensor for selective discrimination of some toxic metal ions in water.

    PubMed

    Shahat, Ahmed; Hassan, Hassan M A; Azzazy, Hassan M E

    2013-09-02

    This paper reports the development of a facile and effective approach, based on the use of Zr-based metal-organic frameworks (UiO-66) sensor with micropores geometry, shape and particle morphology for the visual detection and removal of ultra-traces of some toxic metal ions such as Bi(III), Zn(II), Pb(II), Hg(II) and Cd(II). UiO-66 was used as selective carriers for accommodating hydrophobic chromophore probes such as dithizone (DZ) without coupling agent for sensitive and selective discrimination of trace level of toxic analytes. The developed UiO-66 sensor was utilized for the detection of ultra-traces of some toxic metal ions with the naked eye. The new sensor displays high sensitivity and selectivity of a wide range of detectable metals analytes up to 10(-10) mol dm(-3) in solution, in a rapid analyte uptake response (seconds). The developed sensor is stable, cost effective, easy to prepare, and would be useful for rapid detection and removal of ultra-traces of toxic metal ions in water samples.

  16. New Insight into Metal Ion-Driven Catalysis of Nucleic Acids by Influenza PA-Nter

    PubMed Central

    Kotlarek, Daria; Worch, Remigiusz

    2016-01-01

    PA subunit of influenza RNA-dependent RNA polymerase deserves constantly increasing attention due to its essential role in influenza life cycle. N-terminal domain of PA (PA-Nter) harbors endonuclease activity, which is indispensable in viral transcription and replication. Interestingly, existing literature reports on in vitro ion preferences of the enzyme are contradictory. Some show PA-Nter activity exclusively with Mn2+, whereas others report Mg2+ as a natural cofactor. To clarify it, we performed a series of experiments with varied ion concentrations and substrate type. We observed cleavage in the presence of both ions, with a slight preference for manganese, however PA-Nter activity highly depended on the amount of residual, co-purified ions. Furthermore, to quantify cleavage reaction rate, we applied fluorescence cross-correlation spectroscopy (FCCS), providing highly sensitive and real-time monitoring of single molecules. Using nanomolar ssDNA in the regime of enzyme excess, we estimated the maximum reaction rate at 0.81± 0.38 and 1.38± 0.34 nM/min for Mg2+ and Mn2+, respectively. However, our calculations of PA-Nter ion occupancy, based on thermodynamic data, suggest Mg2+ to be a canonical metal in PA-Nter processing of RNA in vivo. Presented studies constitute a step toward better understanding of PA-Nter ion-dependent activity, which will possibly contribute to new successful inhibitor design in the future. PMID:27300442

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

    PubMed

    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.

  18. Study on the interaction between cyanobacteria FBP/SBPase and metal ions.

    PubMed

    Sun, Yao; Liao, Xun; Li, Ding; Feng, Lingling; Li, Jun; Wang, Xiaofeng; Jin, Jing; Yi, Fan; Zhou, Li; Wan, Jian

    2012-04-01

    Fructose-1,6-/sedoheptulose-1,7-bisphosphatase (FBP/SBPase) is a potential important target enzyme for finding inhibitors to solve harmful algal bloom. In this paper, the interactions between FBP/SBPase and metal ions were studied by enzyme activity analysis, fluorescence and molecular modeling method. The enzyme activity analysis showed that FBP/SBPase can be activated by Mg2+ or Mn2+ but cannot be activated by Ca2+ or Zn2+. Spectroscopic analysis of emission quenching showed that quenching mechanism of FBP/SBPase with Mg2+ or Mn2+ was static quenching mechanism while that of Ca2+ or Zn2+ was dynamic quenching process. Hydrogen bonds and van der Waals interaction might be the predominant intermolecular forces in stabilizing FBP/SBPase-Mg2+ while hydrophobic forces were the predominant intermolecular forces in stabilizing FBP/SBPase-Mn2+. Microenvironment and conformation of FBP/SBPase were changed in binding reaction. The effect of metal ions and important amino acid residues on FBP/SBPase-metal ion complex was also discussed by molecular modeling study.

  19. Barcoded materials based on photoluminescent hybrid system of lanthanide ions-doped metal organic framework and silica via ion exchange.

    PubMed

    Shen, Xiang; Yan, Bing

    2016-04-15

    A multicolored photoluminescent hybrid system based on lanthanide ions-doped metal organic frameworks/silica composite host has potential in display and barcode applications. By controlling the stoichiometry of the lanthanides via cation exchange, proportional various lanthanide ions are successfully introduced into metal organic frameworks, whose emission intensity is correspondingly proportional to its amount. The resulting luminescent barcodes depend on the lanthanide ions ratios and compositions. Subsequently, the lanthanide ions located in the channels of metal organic frameworks are protected from any interaction with the environment after the modification of silica on the surface. The optical and thermal stability of the hybrid materials are improved for technological application.

  20. The electron-transfer based interaction between transition metal ions and photoluminescent graphene quantum dots (GQDs): a platform for metal ion sensing.

    PubMed

    Huang, Hongduan; Liao, Lei; Xu, Xiao; Zou, Mingjian; Liu, Feng; Li, Na

    2013-12-15

    The electron-transfer based quenching effect of commonly encountered transition metal ions on the photoluminescence of grapheme quantum dots (GQDs) was for the first time investigated, and was found to be associated with electron configuration of the individual metal ion. Ethylene diamine tetraacetic acid (EDTA), the metal ion chelator, can competitively interact with metal ions to recover the quenched photoluminescence of GQDs. Basically, metal ions with empty or completely filled d orbits could not quench the photoluminescence of GQDs, but this quenching effect was observed for the metal ions with partly filled d orbits. Based on the quenching-recovering strategy, a simple optical metal sensing platform was established by taking Ni(2+) as an example. Using the nickel ion-specific chelating reagent, dimethylglyoxime (DMG), to replace EDTA, a detection limit of 4.1 μM was obtained in standard solution. This proposed strategy does not need further functionalization of GQDs, facilitating the application for simple, fast and cost-effective screening of metal ions.

  1. [Metal ions restrain the elimination of 4-tert-octylphenol by delta-MnO2].

    PubMed

    Li, Fei-Li; Mou, Hua-Qian

    2013-06-01

    The effect of metal ions on elimination of 4-t-OP by synthetic delta-MnO2 suspension at pH 4.0 was studied. Experiments indicated that the removal of 4-t-OP by delta-MnO2 achieved 100% at reaction time of 150 min. However, the removal of 4-t-OP by delta-MnO2 was restrained when metal ions were added, and the higher concentration of metal ion was, the stronger the inhibition produced. Additionally, there were apparent differences among the inhibitory effect of the tested metal ions. Firstly, Pb2+ and Mn2+ had the strongest effect at pH 4.0, followed by the transition metal ions, then the alkaline earth ions, while the alkali metal ions had little influence on the removal of 4-t-OP by delta-MnO2. Also comparing the adsorption results of metal ions by delta-MnO2, Pb2+ showed the greatest attraction with delta-MnO2, and among the other metal ions, transition metal ions were adsorbed a little more strongly on delta-MnO2 than alkaline earth metal ions. Consequences showed that the inhibitory effects of metal ions were due to their occupying reactive sites on delta-MnO2 surface, which competed with 4-t-OP. Moreover, the dissimilar suppressions were contributed by the different adsorption capacities, surface structure change of MnO2 and the difference of free metal ion percentage in solution as well as metal ions radii.

  2. Metal ion catalyzed hydrolysis of ethyl p-nitrophenyl phosphate.

    PubMed

    Rawlings, J; Cleland, W W; Hengge, A C

    2003-01-01

    15N isotope effects in the nitro group and 18O isotope effects in the phenolic oxygen have been measured for the hydrolysis of ethyl p-nitrophenyl phosphate catalyzed by several metal ions. Co(III)-cyclen at pH 7, 50 degrees C, gave an 15N isotope effect of 0.12% and an 18O one of 2.23%, showing that P-O cleavage is rate limiting and the bond is approximately 50% broken in the transition state. The active catalyst is a dimer and the substrate is presumably coordinated to the open site of one Co(III), and is attacked by hydroxide coordinated to the other Co(III). Co(III)-tacn under the same conditions shows a similar 15N isotope effect (0.13%), but a smaller 18O one (0.8%). Zn(II)-cyclen at pH 8.5, 80 degrees C, gave an 15N isotope effect of 0.05% and an 18O one of 0.95%, suggesting an earlier transition state. The catalyst in this case is monomeric, and thus the substrate is coordinated to one position and attacked by a cis-coordinated hydroxide. Eu(III) at pH 6.5, 50 degrees C, shows a very large 15N isotope effect of 0.34% and a 1.6% 18O isotope effect. The large 15N isotope effect argues for a late transition state or Eu(III) interaction with the nitro group, and was also seen in Eu(III)-catalyzed hydrolysis of p-nitrophenyl phosphate.

  3. Antimicrobial activity of the metals and metal oxide nanoparticles.

    PubMed

    Dizaj, Solmaz Maleki; Lotfipour, Farzaneh; Barzegar-Jalali, Mohammad; Zarrintan, Mohammad Hossein; Adibkia, Khosro

    2014-11-01

    The ever increasing resistance of pathogens towards antibiotics has caused serious health problems in the recent years. It has been shown that by combining modern technologies such as nanotechnology and material science with intrinsic antimicrobial activity of the metals, novel applications for these substances could be identified. According to the reports, metal and metal oxide nanoparticles represent a group of materials which were investigated in respect to their antimicrobial effects. In the present review, we focused on the recent research works concerning antimicrobial activity of metal and metal oxide nanoparticles together with their mechanism of action. Reviewed literature indicated that the particle size was the essential parameter which determined the antimicrobial effectiveness of the metal nanoparticles. Combination therapy with the metal nanoparticles might be one of the possible strategies to overcome the current bacterial resistance to the antibacterial agents. However, further studies should be performed to minimize the toxicity of metal and metal oxide nanoparticles to apply as proper alternatives for antibiotics and disinfectants especially in biomedical applications.

  4. Antibacterial activity of nanosilver ions and particles.

    PubMed

    Sotiriou, Georgios A; Pratsinis, Sotiris E

    2010-07-15

    The antibacterial activity of nanosilver against Gram negative Escherichia coli bacteria is investigated by immobilizing nanosilver on nanostructured silica particles and closely controlling Ag content and size. These Ag/SiO(2) nanoparticles were characterized by S/TEM, EDX spectroscopy, X-ray diffraction the exposed Ag surface area was measured qualitatively by O(2) chemisorption. Furthermore, the fraction of dissolved nanosilver was determined by measuring the released (leached) Ag(+) ion concentration in aqueous suspensions of such Ag/SiO(2) particles. The antibacterial effect of Ag(+) ions was distinguished from that of nanosilver particles by monitoring the growth of E. coli populations in the presence and absence of Ag/SiO(2) particles. The antibacterial activity of nanosilver was dominated by Ag(+) ions when fine Ag nanoparticles (less than about 10 nm in average diameter) were employed that release high concentrations of Ag(+) ions. In contrast, when relatively larger Ag nanoparticles were used, the concentration of the released Ag(+) ions was lower. Then the antibacterial activity of the released Ag(+) ions and nanosilver particles was comparable.

  5. What Ion Flow along Ion Channels Can Tell us about Their Functional Activity

    PubMed Central

    Becucci, Lucia; Guidelli, Rolando

    2016-01-01

    The functional activity of channel-forming peptides and proteins is most directly verified by monitoring the flow of physiologically relevant inorganic ions, such as Na+, K+ and Cl−, along the ion channels. Electrical current measurements across bilayer lipid membranes (BLMs) interposed between two aqueous solutions have been widely employed to this end and are still extensively used. However, a major drawback of BLMs is their fragility, high sensitivity toward vibrations and mechanical shocks, and low resistance to electric fields. To overcome this problem, metal-supported tethered BLMs (tBLMs) have been devised, where the BLM is anchored to the metal via a hydrophilic spacer that replaces and mimics the water phase on the metal side. However, only mercury-supported tBLMs can measure and regulate the flow of the above inorganic ions, thanks to mercury liquid state and high hydrogen overpotential. This review summarizes the main results achieved by BLMs incorporating voltage-gated channel-forming peptides, interpreting them on the basis of a kinetic mechanism of nucleation and growth. Hg-supported tBLMs are then described, and their potential for the investigation of voltage-gated and ohmic channels is illustrated by the use of different electrochemical techniques. PMID:27983579

  6. Heavy Metal Ion Regulation of Gene Expression: MECHANISMS BY WHICH LEAD INHIBITS OSTEOBLASTIC BONE-FORMING ACTIVITY THROUGH MODULATION OF THE Wnt/β-CATENIN SIGNALING PATHWAY.

    PubMed

    Beier, Eric E; Sheu, Tzong-Jen; Dang, Deborah; Holz, Jonathan D; Ubayawardena, Resika; Babij, Philip; Puzas, J Edward

    2015-07-17

    Exposure to lead (Pb) from environmental sources remains an overlooked and serious public health risk. Starting in childhood, Pb in the skeleton can disrupt epiphyseal plate function, constrain the growth of long bones, and prevent attainment of a high peak bone mass, all of which will increase susceptibility to osteoporosis later in life. We hypothesize that the effects of Pb on bone mass, in part, come from depression of Wnt/β-catenin signaling, a critical anabolic pathway for osteoblastic bone formation. In this study, we show that depression of Wnt signaling by Pb is due to increased sclerostin levels in vitro and in vivo. Downstream activation of the β-catenin pathway using a pharmacological inhibitor of GSK-3β ameliorates the Pb inhibition of Wnt signaling activity in the TOPGAL reporter mouse. The effect of Pb was determined to be dependent on sclerostin expression through use of the SOST gene knock-out mice, which are resistant to Pb-induced trabecular bone loss and maintain their mechanical bone strength. Moreover, isolated bone marrow cells from the sclerostin null mice show improved bone formation potential even after exposure to Pb. Also, our data suggest that the TGFβ canonical signaling pathway is the mechanism by which Pb controls sclerostin production. Taken together these results support our hypothesis that the osteoporotic-like phenotype observed after Pb exposure is, in part, regulated through modulation of the Wnt/β-catenin pathway.

  7. Extraordinary rates of transition metal ion-mediated ribozyme catalysis

    PubMed Central

    Roychowdhury-Saha, Manami; Burke, Donald H.

    2006-01-01

    In pre-steady-state, fast-quench kinetic analysis, the tertiary-stabilized hammerhead ribozyme “RzB” cleaves its substrate RNA with maximal measured k obs values of ∼3000 min−1 in 1 mM Mn2+ and ∼780 min−1 in 1 mM Mg2+ at 37°C (pH 7.4). Apparent pKa for the catalytic general base is ∼7.8–8.5, independent of the corresponding metal hydrate pKa, suggesting potential involvement of a nucleobase as general base as suggested previously from nucleobase substitution studies. The pH-rate profile is bell-shaped for Cd2+, for which the general catalytic acid has a pKa of 7.3 ± 0.1. Simulations of the pH-rate relation suggest a pKa for the general catalytic acid to be ∼9.5 in Mn2+ and >9.5 in Mg2+. The acid pKa's follow the trend in the pKa of the hydrated metal ions but are displaced by ∼1–2 pH units in the presence of Cd2+ and Mn2+. One possible explanation for this trend is direct metal ion coordination with a nucleobase, which then acts as general acid. PMID:16912216

  8. No association between serum metal ions and implant fixation in large-head metal-on-metal total hip arthroplasty

    PubMed Central

    Søballe, Kjeld; Jakobsen, Stig Storgaard; Lorenzen, Nina Dyrberg; Mechlenburg, Inger; Stilling, Maiken

    2014-01-01

    Background The mechanism of failure of metal-on-metal (MoM) total hip arthroplasty (THA) has been related to a high rate of metal wear debris, which is partly generated from the head-trunnion interface. However, it is not known whether implant fixation is affected by metal wear debris. Patients and methods 49 cases of MoM THA in 41 patients (10 women) with a mean age of 52 (28–68) years were followed with stereoradiographs after surgery and at 1, 2, and 5 years to analyze implant migration by radiostereometric analysis (RSA). Patients also participated in a 5- to 7-year follow-up with measurement of serum metal ions, questionnaires (Oxford hip score (OHS) and Harris hip score (HHS)), and measurement of cup and stem positions and systemic bone mineral density. Results At 1–2 years, mean total translation (TT) was 0.04 mm (95% CI: –0.07 to 0.14; p = 0.5) for the stems; at 2–5 years, mean TT was 0.13 mm (95% CI: –0.25 to –0.01; p = 0.03), but within the precision limit of the method. For the cups, there was no statistically significant TT or total rotation (TR) at 1–2 and 2–5 years. At 2–5 years, we found 4 cups and 5 stems with TT migrations exceeding the precision limit of the method. There was an association between cup migration and total OHS < 40 (4 patients, 4 hips; p = 0.04), but there were no statistically significant associations between cup or stem migration and T-scores < –1 (n = 10), cup and stem positions, or elevated serum metal ion levels (> 7µg/L (4 patients, 6 hips)). Interpretation Most cups and stems were well-fixed at 1–5 years. However, at 2–5 years, 4 cups and 5 stems had TT migrations above the precision limits, but these patients had serum metal ion levels similar to those of patients without measurable migrations, and they were pain-free. Patients with serum metal ion levels > 7 µg/L had migrations similar to those in patients with serum metal ion levels < 7 µg/L. Metal wear debris does not appear to influence the

  9. Adsorption of Heavy Metal Ions from Aqueous Solutions by Bentonite Nanocomposites.

    PubMed

    Ma, Jing; Su, Guojun; Zhang, Xueping; Huang, Wen

    2016-08-01

    A series of bentonite nanocomposites have been synthesized by modifying bentonite with hexadecyltrimethylammonium bromide (CTMAB) and the common complexing agents, complexone (ethylene diamine tetraacetic acid, EDTA) or mercaptocomplexant (2-Mercaptobenzothiazole, MBT). These adsorbents are used to remove heavy metal ions (Cu(2+), Zn(2+), Mn(2+),Co(2+)). The Bent-CTMAB-MBT adsorbed metal ions are higher than Bent-CTMAB-EDTA under the same ion concentration in AAS. Compared with the single ion system, the adsorption of the mixed ion system of Cu(2+), Zn(2+), Mn(2+), Co(2+) had decreased differently. In the mixed system, the adsorption of Mn(2+) is significantly lower, but the adsorption of Cu(2+) was highest. The adsorption sequence of these four metal ions was Cu(2+) > Zn(2+) > Co(2+) > Mn(2+), and the selective adsorption was closely related to the hydration energy of heavy metal ions. We could remove more metal ions in different stages with the adsorption sequence.

  10. Strategic feeding of ammonium and metal ions for enhanced GLA-rich lipid accumulation in Cunninghamella bainieri 2A1.

    PubMed

    Shuib, Shuwahida; Nawi, Wan Nazatul Naziah Wan; Taha, Ekhlass M; Omar, Othman; Kader, Abdul Jalil Abdul; Kalil, Mohd Sahaid; Hamid, Aidil Abdul

    2014-01-01

    Strategic feeding of ammonium and metal ions (Mg(2+), Mn(2+), Fe(3+), Cu(2+), Ca(2+), Co(2+), and Zn(2+)) for enhanced GLA-rich lipid accumulation in C. bainieri 2A1 was established. When cultivated in nitrogen-limited medium, the fungus produced up to 30% lipid (g/g biomass) with 12.9% (g/g lipid) GLA. However, the accumulation of lipid stopped at 48 hours of cultivation although glucose was abundant. This event occurred in parallel to the diminishing activity of malic enzyme (ME), fatty acid synthase (FAS), and ATP citrate lyase (ACL) as well as the depletion of metal ions in the medium. Reinstatement of the enzymes activities was achieved by feeding of ammonium tartrate, but no increment in the lipid content was observed. However, increment in lipid content from 32% to 50% (g/g biomass) with 13.2% GLA was achieved when simultaneous feeding of ammonium, glucose, and metal ions was carried out. This showed that the cessation of lipid accumulation was caused by diminishing activities of the enzymes as well as depletion of the metal ions in the medium. Therefore, strategic feeding of ammonium and metal ions successfully reinstated enzymes activities and enhanced GLA-rich lipid accumulation in C. bainieri 2A1.

  11. Strategic Feeding of Ammonium and Metal Ions for Enhanced GLA-Rich Lipid Accumulation in Cunninghamella bainieri 2A1

    PubMed Central

    Wan Nawi, Wan Nazatul Naziah; Taha, Ekhlass M.; Omar, Othman; Abdul Kader, Abdul Jalil; Kalil, Mohd Sahaid; Abdul Hamid, Aidil

    2014-01-01

    Strategic feeding of ammonium and metal ions (Mg2+, Mn2+, Fe3+, Cu2+, Ca2+, Co2+, and Zn2+) for enhanced GLA-rich lipid accumulation in C. bainieri 2A1 was established. When cultivated in nitrogen-limited medium, the fungus produced up to 30% lipid (g/g biomass) with 12.9% (g/g lipid) GLA. However, the accumulation of lipid stopped at 48 hours of cultivation although glucose was abundant. This event occurred in parallel to the diminishing activity of malic enzyme (ME), fatty acid synthase (FAS), and ATP citrate lyase (ACL) as well as the depletion of metal ions in the medium. Reinstatement of the enzymes activities was achieved by feeding of ammonium tartrate, but no increment in the lipid content was observed. However, increment in lipid content from 32% to 50% (g/g biomass) with 13.2% GLA was achieved when simultaneous feeding of ammonium, glucose, and metal ions was carried out. This showed that the cessation of lipid accumulation was caused by diminishing activities of the enzymes as well as depletion of the metal ions in the medium. Therefore, strategic feeding of ammonium and metal ions successfully reinstated enzymes activities and enhanced GLA-rich lipid accumulation in C. bainieri 2A1. PMID:24991637

  12. Delineating ion-ion interactions by electrostatic modeling for predicting rhizotoxicity of metal mixtures to lettuce Lactuca sativa.

    PubMed

    Le, T T Yen; Wang, Peng; Vijver, Martina G; Kinraide, Thomas B; Hendriks, A Jan; Peijnenburg, Willie J G M

    2014-09-01

    Effects of ion-ion interactions on metal toxicity to lettuce Lactuca sativa were studied based on the electrical potential at the plasma membrane surface (ψ0 ). Surface interactions at the proximate outside of the membrane influenced ion activities at the plasma membrane surface ({M(n+)}0). At a given free Cu(2+) activity in the bulk medium ({Cu(2+)}b), additions of Na(+), K(+), Ca(2+), and Mg(2+) resulted in substantial decreases in {Cu(2+)}0. Additions of Zn(2+) led to declines in {Cu(2+)}0, but Cu(2+) and Ag(+) at the exposure levels tested had negligible effects on the plasma membrane surface activity of each other. Metal toxicity was expressed by the {M(n+)}0 -based strength coefficient, indicating a decrease of toxicity in the order: Ag(+)  > Cu(2+)  > Zn(2+). Adsorbed Na(+), K(+), Ca(2+), and Mg(2+) had significant and dose-dependent effects on Cu(2+) toxicity in terms of osmolarity. Internal interactions between Cu(2+) and Zn(2+) and between Cu(2+) and Ag(+) were modeled by expanding the strength coefficients in concentration addition and response multiplication models. These extended models consistently indicated that Zn(2+) significantly alleviated Cu(2+) toxicity. According to the extended concentration addition model, Ag(+) significantly enhanced Cu(2+) toxicity whereas Cu(2+) reduced Ag(+) toxicity. By contrast, the response multiplication model predicted insignificant effects of adsorbed Cu(2+) and Ag(+) on the toxicity of each other. These interactions were interpreted using ψ0, demonstrating its influence on metal toxicity.

  13. Select metal adsorption by activated carbon made from peanut shells.

    PubMed

    Wilson, Kermit; Yang, Hong; Seo, Chung W; Marshall, Wayne E

    2006-12-01

    Agricultural by-products, such as peanut shells, contribute large quantities of lignocellulosic waste to the environment each growing season; but few, if any, value-added uses exist for their disposal. The objective of this study was to convert peanut shells to activated carbons for use in adsorption of select metal ions, namely, cadmium (Cd2+), copper (Cu2+), lead (Pb2+), nickel (Ni2+) and zinc (Zn2+). Milled peanut shells were pyrolyzed in an inert atmosphere of nitrogen gas, and then activated with steam at different activation times. Following pyrolysis and activation, the carbons underwent air oxidation. The prepared carbons were evaluated either for adsorption efficiency or adsorption capacity; and these parameters were compared to the same parameters obtained from three commercial carbons, namely, DARCO 12x20, NORIT C GRAN and MINOTAUR. One of the peanut shell-based carbons had metal ion adsorption efficiencies greater than two of the three commercial carbons but somewhat less than but close to Minotaur. This study demonstrates that peanut shells can serve as a source for activated carbons with metal ion-removing potential and may serve as a replacement for coal-based commercial carbons in applications that warrant their use.

  14. The Effect of Complex Formation upon the Redox Potentials of Metallic Ions. Cyclic Voltammetry Experiments.

    ERIC Educational Resources Information Center

    Ibanez, Jorge G.; And Others

    1988-01-01

    Describes experiments in which students prepare in situ soluble complexes of metal ions with different ligands and observe and estimate the change in formal potential that the ion undergoes upon complexation. Discusses student formation and analysis of soluble complexes of two different metal ions with the same ligand. (CW)

  15. Transition metal dissolution, ion migration, electrocatalytic reduction and capacity loss in Lithium-ion full cells

    DOE PAGES

    Gilbert, James A.; Shkrob, Ilya A.; Abraham, Daniel P.

    2017-01-05

    Continuous operation of full cells with layered transition metal (TM) oxide positive electrodes (NCM523) leads to dissolution of TM ions and their migration and incorporation into the solid electrolyte interphase (SEI) of the graphite-based negative electrode. These processes correlate with cell capacity fade and accelerate markedly as the upper cutoff voltage (UCV) exceeds 4.30 V. At voltages ≥ 4.4 V there is enhanced fracture of the oxide during cycling that creates new surfaces and causes increased solvent oxidation and TM dissolution. Despite this deterioration, cell capacity fade still mainly results from lithium loss in the negative electrode SEI. Among TMs,more » Mn content in the SEI shows a better correlation with cell capacity loss than Co and Ni contents. As Mn ions become incorporated into the SEI, the kinetics of lithium trapping change from power to linear at the higher UCVs, indicating a large effect of these ions on SEI growth and implicating (electro)catalytic reactions. Lastly, we estimate that each MnII ion deposited in the SEI causes trapping of ~102 additional Li+ ions thereby hastening the depletion of cyclable lithium ions. Using these results, we sketch a mechanism for cell capacity fade, emphasizing the conceptual picture over the chemical detail.« less

  16. Effect of electro-activated brine solution on the migration of metallic ions from the cans to the product in sterilized canned sweet corn.

    PubMed

    Liato, Viacheslav; Labrie, Steve; Benali, Marzouk; Aider, Mohammed

    2016-11-01

    Tinplate cans were used to study if electro-activated brine solution (EAS) is more corrosive than conventional one by ICP analysis. The results showed different effects of EAS on cans, alone or filled with product. Acidic EAS (pH 2-3) and Redox +900 to +1200 mV highly reacted with the cans. The concentrations of Zn, Fe, and Cu in the solution were 0.028, 28.81, and 0.022 ppm, respectively. No Sn migration was observed in this case. When neutral or acidic chlorine-free EAS was used, no significant difference was observed in comparison with the corrosivity of standard NaCl brine. Alkaline EAS with pH>10 and negative E (≤-966 mV) did not affect Zn, Fe, and Cu migration. However, it affected tin migration. Nevertheless, it is important to mention that even if some corrosion was observed, it was in the limit of the permitted level of concentration when the cans were filled with a product.

  17. High current metal ion implantation to synthesize some conducting metal-silicides

    SciTech Connect

    Liu, B. X.; Gao, K. Y.

    1999-06-10

    High current metal-ion implantation by a metal vapor vacuum arc ion source was conducted to synthesize some conducting metal-silicides. It was found that C54-TiSi{sub 2}, ZrSi{sub 2}, NiSi{sub 2}, CoSi{sub 2}, {beta}-FeSi{sub 2}, NbSi{sub 2} and TaSi{sub 2} layers on Si wafers with good electric properties could be obtained directly after implantation. In comparison, the formation of some other silicides like {alpha}-FeSi{sub 2}, NbSi{sub 2}, TaSi{sub 2}, tetragonal-WSi{sub 2} and tetragonal-MoSi{sub 2} required an additional post-annealing to improve their crystallinity and thus their electric properties. Interestingly, the NiSi{sub 2} layers of superior electric properties were obtained at a selected Ni-ion current density of 35 {mu}A/cm{sup 2}. At this current, a beam heating raised the Si wafer to a specific temperature of 380 deg. C, at which the size difference between NiSi{sub 2} and Si lattices was nil. The resistivity of the NiSi{sub 2} layers so obtained was much lower than that of the Ni-disilicide formed by solid-state reaction at >750 deg. C. The formation mechanism of the above metal-silicides and the associated electric properties will also be discussed.

  18. Metal-organic frameworks for lithium ion batteries and supercapacitors

    SciTech Connect

    Ke, Fu-Sheng; Wu, Yu-Shan; Deng, Hexiang

    2015-03-15

    Porous materials have been widely used in batteries and supercapacitors attribute to their large internal surface area (usually 100–1000 m{sup 2} g{sup −1}) and porosity that can favor the electrochemical reaction, interfacial charge transport, and provide short diffusion paths for ions. As a new type of porous crystalline materials, metal-organic frameworks (MOFs) have received huge attention in the past decade due to their unique properties, i.e. huge surface area (up to 7000 m{sup 2} g{sup −1}), high porosity, low density, controllable structure and tunable pore size. A wide range of applications including gas separation, storage, catalysis, and drug delivery benefit from the recent fast development of MOFs. However, their potential in electrochemical energy storage has not been fully revealed. Herein, the present mini review appraises recent and significant development of MOFs and MOF-derived materials for rechargeable lithium ion batteries and supercapacitors, to give a glimpse into these potential applications of MOFs. - Graphical abstract: MOFs with large surface area and high porosity can offer more reaction sites and charge carriers diffusion path. Thus MOFs are used as cathode, anode, electrolyte, matrix and precursor materials for lithium ion battery, and also as electrode and precursor materials for supercapacitors. - Highlights: • MOFs have potential in electrochemical area due to their high porosity and diversity. • We summarized and compared works on MOFs for lithium ion battery and supercapacitor. • We pointed out critical challenges and provided possible solutions for future study.

  19. Metallic atoms and ions in comets: Comet Halley 1986 3

    NASA Technical Reports Server (NTRS)

    Ibadov, S.

    1992-01-01

    The origin of metallic atoms and ions in the cometary comae is investigated theoretically. Two effects are revealed in the comas of bright comets: (1) the Na anomalous type effect is possible within the gas-dust jets of comet P/Halley 1986 3 due to cooling cometary dust by cryogenic gas flow from the nucleus; and (2) the production of ions of refractory elements (Fe(+), Si(+), etc.) at large heliocentric distances is possible in the comas of the Halley type dusty comets due to high-velocity impacts between cometary and zodiacal dust particles. Spectral observations of comets with high sensitivity and spatial resolution are important for studying both comets and interplanetary dust.

  20. Alloying of metal nanoparticles by ion-beam induced sputtering

    NASA Astrophysics Data System (ADS)

    Magudapathy, P.; Srivastava, S. K.; Gangopadhyay, P.; Amirthapandian, S.; Saravanan, K.; Das, A.; Panigrahi, B. K.

    2017-01-01

    Ion-beam sputtering technique has been utilized for controlled synthesis of metal alloy nanoparticles of compositions that can be tuned. Analysis of various experimental results reveals the formation of Ag-Cu alloy nanoparticles on a silica substrate. Surface-plasmon optical resonance positions and observed shifts of Ag Bragg angles in X-ray diffraction pattern particularly confirm formation of alloy nanoparticles on glass samples. Sputtering induced nano-alloying mechanism has been discussed and compared with thermal mixing of Ag and Cu thin films on glass substrates. Compositions and sizes of alloy nanoparticles formed during ion-beam induced sputtering are found to exceed far from the values of thermal mixing.

  1. Characterization and activity of cephalosporin metal complexes.

    PubMed

    Auda, S H; Mrestani, Y; Fetouh, M I; Neubert, R H H

    2008-08-01

    Semi-synthetic cephalosporin antibiotics have structures similar to that of penicillins, and both groups of compounds are characterized by similar properties and determined by the same methods. Most antibiotics, including cephalosporins and their decomposition products, contain electron donor groups that can bind naturally occurring metal ions in vivo. Cephalosporin antibiotics exhibit a change in their toxicological properties and biological performance when they were tested as metal complexes. The proposed reason for such a behavior is the capability of chelate binding of the cephalosporins to the metals. In an attempt to understand the coordination mode of metals with cephalosporins, different spectroscopic techniques such as IR, UV-visible, NMR spectroscopy and voltammetric measurements were carried out to elucidate the structure of the metal-cephalosporin complexes. Synthesis, characterization and biological screening of the cephalosporins and of the cephalosporin-metal complexes are discussed in this review. However, little information is available on the influence of the metal ions on the pharmacokinetics of the cephalosporin derivatives.

  2. Negative interference of metal (II) ions with nucleotide excision repair in human cell-free extracts.

    PubMed

    Calsou, P; Frit, P; Bozzato, C; Salles, B

    1996-12-01

    Inhibition of the nucleotide excision repair (NER) process is believed to cause the potentiation of the genotoxic and mutagenic effects of DNA damaging agents like UV-light or cisplatin by metal ions. However, the precise underlying molecular mechanism of this phenomenon is still unknown. Using in vitro assays, we have determined the potential interference of several metal (II) ions with the lesion recognition and strand incision/displacement steps of the NER mechanism, independently from the DNA polymerization step. When combinations of an optimal Mg2+ concentration and concentrations of various metal ions in a range from 0.1 to 1 mM were tested, all combinations, with Mn2+ and Ni2+ excepted, inhibited specifically the incision repair activity by human protein extracts. There was a good correlation for Cd2+, Co2+, Fe2+, Cu2+, Hg2+, Pb2+ and Zn2+ between an inhibiting effect on the incision activity and a reduced protein binding activity to a damaged DNA probe as assessed by gel mobility shift assay.

  3. Correlation between the limiting pH of metal ion solubility and total metal concentration

    SciTech Connect

    Apak, R.; Hizal, J.; Ustaer, C.

    1999-03-15

    As an alternative to species distribution diagrams (pM vs pH curves in aqueous solution) drawn for a fixed total metal concentration, this work has developed simple linear models for correlating the limiting pH of metal ion solubility -- in equilibrium with the least soluble amorphous metal hydroxide solid phase -- to the total metal concentration. Thus adsorptive metal removal processes in complex systems can be better designed once the limiting pH of heavy metal solubility (i.e., pH{sup *}) in such a complex environment can be envisaged by simple linear equations. pH{sup *} vs pM{sub t} (M{sub t} = total metal concentration that can exist in aqueous solution in equilibrium with M(OH){sub 2(s)}) linear curves for uranyl-hydroxide, uranyl-carbonate-hydroxide, and mercuric-chloride-hydroxide simple and mixed-ligand systems and cupric-carbonate-hydroxide complexes in equilibrium with mixed hydroxide solid phases may enable the experimental chemist to distinguish true adsorption (e.g., onto hydrous oxide sorbents) from bulk precipitation removal of the metal and to interpret some anomalous metal fixation data -- usually attributed to pure adsorption in the literature -- with precipitation if the pM{sub t} at the studied pH is lower than that tolerated by pH{sup *} vs pM{sub t} curves. This easily predictable pH{sup *} corresponding to a given pM{sub t} may aid the design of desorptive mobilization experiments for certain metals as well as their adsorptive removal with the purpose of simulating metal adsorption and desorption cycles in real complex environments with changing groundwater pH.

  4. Electrolyte materials containing highly dissociated metal ion salts

    DOEpatents

    Lee, H.S.; Geng, L.; Skotheim, T.A.

    1996-07-23

    The present invention relates to metal ion salts which can be used in electrolytes for producing electrochemical devices, including both primary and secondary batteries, photoelectrochemical cells and electrochromic displays. The salts have a low energy of dissociation and may be dissolved in a suitable polymer to produce a polymer solid electrolyte or in a polar aprotic liquid solvent to produce a liquid electrolyte. The anion of the salts may be covalently attached to polymer backbones to produce polymer solid electrolytes with exclusive cation conductivity. 2 figs.

  5. Electrolyte materials containing highly dissociated metal ion salts

    DOEpatents

    Lee, Hung-Sui; Geng, Lin; Skotheim, Terje A.

    1996-07-23

    The present invention relates to metal ion salts which can be used in electrolytes for producing electrochemical devices, including both primary and secondary batteries, photoelectrochemical cells and electrochromic displays. The salts have a low energy of dissociation and may be dissolved in a suitable polymer to produce a polymer solid electrolyte or in a polar aprotic liquid solvent to produce a liquid electrolyte. The anion of the salts may be covalently attached to polymer backbones to produce polymer solid electrolytes with exclusive cation conductivity.

  6. Theoretical study of transition-metal ions bound to benzene

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Partridge, Harry; Langhoff, Stephen R.

    1992-01-01

    Theoretical binding energies are reported for all first-row and selected second-row transition metal ions (M+) bound to benzene. The calculations employ basis sets of at least double-zeta plus polarization quality and account for electron correlation using the modified coupled-pair functional method. While the bending is predominantly electrostatic, the binding energies are significantly increased by electron correlation, because the donation from the metal d orbitals to the benzene pi* orbitals is not well described at the self-consistent-field level. The uncertainties in the computed binding energies are estimated to be about 5 kcal/mol. Although the calculated and experimental binding energies generally agree to within their combined uncertainties, it is likely that the true binding energies lie in the lower portion of the experimental range. This is supported by the very good agreement between the theoretical and recent experimental binding energies for AgC6H6(+).

  7. Influence of phytic acid and its metal complexes on the activity of pectin degrading polygalacturonase.

    PubMed

    Asghar, Uzma; Rehman, Haneef Ur; Qader, Shah Ali Ul; Maqsood, Zahida Tasneem

    2013-06-05

    Polygalacturonase is one of the important requirements of different microorganism to cause pathogenicity and spoilage of fruits and vegetables that involved in degradation of pectin during plant tissue infections. In current study, 20 mM phytic acid inhibited 70% activity of polygalacturonase. The effect of different concentration of metal ions such as Cu(+2), Al(+3) and V(+4) were studied separately and it was found that the 20 mM of these metal ions inhibited 37.2%, 79%, and 53% activity of polygalacturonase, respectively. Finally, the complexes of phytic acid and these metals ions were prepared and 1:1 ratio of phytic acid and metal ions complexes showed maximum inhibitory activity of enzyme as compared to complexes having 1:2 and 1:3 ratio except phytate-copper complexes which showed no inhibitory effect on the activity of polygalacturonase.

  8. Metals distributions in activated sludge systems

    SciTech Connect

    Patterson, J.W.; Kodukula, P.S.

    1984-05-01

    Despite extensive laboratory and field studies over the past 25 years, little advance has been made in prediction of metals distribution and removal in activated sludge treatment systems. This paper reports the results of carefully controlled pilot studies, from which empirical metals distribution models were developed. The models accurately predict the distribution of process stream metals at each point in the activated sludge process between the soluble and solids phases. The distribution models together with data on primary and secondary clarifier suspended solids removal efficiencies, are easily applied to predict the removals of influent metals in activated sludge systems. 36 references, 2 figures.

  9. Trifunctional metal ion-catalyzed solvolysis: Cu(II)-promoted methanolysis of N,N-bis(2-picolyl) benzamides involves unusual Lewis acid activation of substrate, delivery of coordinated nucleophile, powerful assistance of the leaving group departure.

    PubMed

    Raycroft, Mark A R; Maxwell, Christopher I; Oldham, Robyn A A; Andrea, Areen Saffouri; Neverov, Alexei A; Brown, R Stan

    2012-10-01

    The methanolyses of Cu(II) complexes of a series of N,N-bis(2-picolyl) benzamides (4a-g) bearing substituents X on the aromatic ring were studied under (s)(s)pH-controlled conditions at 25 °C. The active form of the complexes at neutral (s)(s)pH has a stoichiometry of 4:Cu(II):((-)OCH(3))(HOCH(3)) and decomposes unimolecularly with a rate constant k(x). A Hammett plot of log(k(x)) vs σ(x) values has a ρ(x) of 0.80 ± 0.05. Solvent deuterium kinetic isotope effects of 1.12 and 1.20 were determined for decomposition of the 4-nitro and 4-methoxy derivatives, 4b:Cu(II):((-)OCH(3))(HOCH(3)) and 4g:Cu(II):((-)OCH(3))(HOCH(3)), in the plateau region of the (s)(s)pH/log(k(x)) profiles in both CH(3)OH and CH(3)OD. Activation parameters for decomposition of these complexes are ΔH(++) = 19.1 and 21.3 kcal mol(-1) respectively and ΔS(++) = -5.1 and -2 cal K(-1) mol(-1). Density functional theory (DFT) calculations for the reactions of the Cu(II):((-)OCH(3))(HOCH(3)) complexes of 4a,b and g (4a, X = 3,5-dinitro) were conducted to probe the relative transition state energies and geometries of the different states. The experimental and computational data support a mechanism where the metal ion is coordinated to the N,N-bis(2-picolyl) amide unit and positioned so that it permits delivery of a coordinated Cu(II):((-)OCH(3)) nucleophile to the C═O in the rate-limiting transition state (TS) of the reaction. This proceeds to a tetrahedral intermediate INT, occupying a shallow minimum on the free energy surface with the Cu(II) coordinated to both the methoxide and the amidic N. Breakdown of INT is a virtually barrierless process, involving a Cu(II)-assisted departure of the bis(2-picolyl)amide anion. The analysis of the data points to a trifunctional role for the metal ion in the solvolysis mechanism where it activates intramolecular nucleophilic attack on the C═O group by coordination to an amidic N in the first step of the reaction and subsequently assists leaving group

  10. Transition metal ion capture using functional mesoporous carbon made with 1,10-phenanthroline☆

    PubMed Central

    Chouyyok, Wilaiwan; Yantasee, Wassana; Shin, Yongsoon; Grudzien, Rafal M.; Fryxell, Glen E.

    2012-01-01

    Functional mesoporous carbon has been built using 1,10-phenanthroline as the fundamental building block, resulting in a nanoporous, high surface area sorbent capable of selectively binding transition metal ions. This material had a specific surface area of 870 m2/g, an average pore size of about 30 Å, and contained as much as 8.2 wt% N. Under acidic conditions, where the 1,10-phenanthroline ligand is protonated, this material was found to be an effective anion exchange material for transition metal anions like PdCl42- and H2VO41-. 1,10-Phenanthroline functionalized mesoporous carbon (“Phen-FMC”) was found to have a high affinity for Cu(II), even down to a pH of 1. At pHs above 5, Phen-FMC was found to bind a variety of transition metal cations (e.g. Co(II), Ni(II), Zn(II), etc.) from filtered ground water, river water and seawater. Phen-FMC displayed rapid sorption kinetics with Co(II) in filtered river water, reaching equilibrium in less than an hour, and easily lowering the [Co(II)] to sub-ppb levels. Phen-FMC was found to be more effective for transition metal ion capture than ion-exchange resin or activated carbon. PMID:23762013

  11. Engineering Metal Ion Coordination to Regulate Amyloid Fibril Assembly And Toxicity

    SciTech Connect

    Dong, J.; Canfield, J.M.; Mehta, A.K.; Shokes, J.E.; Tian, B.; Childers, W.S.; Simmons, J.A.; Mao, Z.; Scott, R.A.; Warncke, K.; Lynn, D.G.

    2009-06-02

    Protein and peptide assembly into amyloid has been implicated in functions that range from beneficial epigenetic controls to pathological etiologies. However, the exact structures of the assemblies that regulate biological activity remain poorly defined. We have previously used Zn{sup 2+} to modulate the assembly kinetics and morphology of congeners of the amyloid {beta} peptide (A{beta}) associated with Alzheimer's disease. We now reveal a correlation among A{beta}-Cu{sup 2+} coordination, peptide self-assembly, and neuronal viability. By using the central segment of A{beta}, HHQKLVFFA or A{beta}(13-21), which contains residues H13 and H14 implicated in A{beta}-metal ion binding, we show that Cu{sup 2+} forms complexes with A{beta}(13-21) and its K16A mutant and that the complexes, which do not self-assemble into fibrils, have structures similar to those found for the human prion protein, PrP. N-terminal acetylation and H14A substitution, Ac-A{beta}(13-21)H14A, alters metal coordination, allowing Cu{sup 2+} to accelerate assembly into neurotoxic fibrils. These results establish that the N-terminal region of A{beta} can access different metal-ion-coordination environments and that different complexes can lead to profound changes in A{beta} self-assembly kinetics, morphology, and toxicity. Related metal-ion coordination may be critical to the etiology of other neurodegenerative diseases.

  12. Stability and isomerization of complexes formed by metal ions and cytosine isomers in aqueous phase.

    PubMed

    Ai, Hongqi; Liu, Jingjing; Chan, Kwaichow

    2013-08-01

    We present a systematic study of the stability of the formation of complexes produced by four metal ions (M(+/2+)) and 14 cytosine isomers (Cn). This work predicts theoretically that predominant product complexes are associated with higher-energy C4M(+/2+) and C5M(+/2+) rather than the most stable C1M(+/2+). The prediction resolves successfully several experimental facts puzzling two research groups. Meanwhile, in-depth studies further reveal that direct isomerization of C1↔C4 is almost impossible, and also that the isomerization induced by either metalation or hydration, or by a combination of the two unfavorable. It is the single water molecule locating between the H1(-N1) and O2 of the cytosine that plays the dual roles of being a bridge and an activator that consequently improves the isomerization greatly. Moreover, the cooperation of divalent metal ion and such a monohydration actually leads to an energy-free C1←C4 isomerization in the gas phase. Henceforth, we are able to propose schemes inhibiting the free C1←C4 isomerization, based purely on extended hydration at the divalent metal ion.

  13. The New Role for an Old Kinase: Protein Kinase CK2 Regulates Metal Ion Transport

    PubMed Central

    Johnson, Adam J.; Wu, Ming J.

    2016-01-01

    The pleiotropic serine/threonine protein kinase CK2 was the first kinase discovered. It is renowned for its role in cell proliferation and anti-apoptosis. The complexity of this kinase is well reflected by the findings of past decades in terms of its heterotetrameric structure, subcellular location, constitutive activity and the extensive catalogue of substrates. With the advent of non-biased high-throughput functional genomics such as genome-wide deletion mutant screening, novel aspects of CK2 functionality have been revealed. Our recent discoveries using the model organism Saccharomyces cerevisiae and mammalian cells demonstrate that CK2 regulates metal toxicity. Extensive literature search reveals that there are few but elegant works on the role of CK2 in regulating the sodium and zinc channels. As both CK2 and metal ions are key players in cell biology and oncogenesis, understanding the details of CK2’s regulation of metal ion homeostasis has a direct bearing on cancer research. In this review, we aim to garner the recent data and gain insights into the role of CK2 in metal ion transport. PMID:28009816

  14. The two faces of metal ions: From implants rejection to tissue repair/regeneration.

    PubMed

    Vasconcelos, Daniel M; Santos, Susana G; Lamghari, Meriem; Barbosa, Mário A

    2016-04-01

    The paradigm of metallic ions as exclusive toxic agents is changing. During the last 60 years, knowledge about toxicological and immunological reactions to metal particles and ions has advanced considerably. Hip prostheses, namely metal-on-metal bearings, have prompted studies about excessive and prolonged exposure to prosthetic debris. In that context, the interactions of metal particles and ions with cells and tissues are mostly harmful, inducing immune responses that lead to osteolysis and implant failure. However, in the last decade, new strategies to promote immunomodulation and healing have emerged based on the unique properties of metallic ions. The atom-size and charge enable ions to interact with key macromolecules (e.g. proteins, nucleic acids) that affect cellular function. Moreover, these agents are inexpensive, stable and can be integrated in biomaterials, which may open new avenues for a novel generation of medical devices. Herein, orthopedic devices are discussed as models for adverse responses to metal ions, and debated together with the potential to use metal ions-based therapies, thus bridging the gap between unmet clinical needs and cutting-edge research. In summary, this review addresses the two "faces" of metallic ions, from pathological responses to innovative research strategies that use metal ions for regenerative medicine.

  15. Mechanism of beta-purothionin antimicrobial peptide inhibition by metal ions: molecular dynamics simulation study.

    PubMed

    Oard, Svetlana; Karki, Bijaya

    2006-04-20

    Wheat beta-purothionin is a highly potent antimicrobial peptide which, however, is inactivated by metal ions. The key structural properties and mechanisms of inhibition of beta-purothionin were investigated for the first time using unconstrained molecular dynamics simulations in explicit water. A series of simulations were performed to determine effects of temperature and the metal ions. Analyses of the unconstrained simulations allowed the experimentally unavailable structural and dynamic details to be unambiguously examined. The global fold and the alpha1 helix of beta-purothionin are thermally stable and not affected by metal ions. In contrast, the alpha2 helix unfolds with shift of temperature from 300 K and in the presence of metal ions. The network of conserved residues including Arg30 and Lys5 is sensitive to environmental changes and triggers unfolding. Loop regions display high flexibility and elevated dynamics, but are affected by metal ions. Our study provides insights into the mechanism of metal ion-based inhibition.

  16. Structure of the alkali-metal-atom + strontium molecular ions: Towards photoassociation and formation of cold molecular ions

    SciTech Connect

    Aymar, M.; Dulieu, O.; Guerout, R.

    2011-08-14

    The potential energy curves, permanent and transition dipole moments, and the static dipolar polarizability, of molecular ions composed of one alkali-metal atom and a strontium ion are determined with a quantum chemistry approach. The molecular ions are treated as effective two-electron systems and are treated using effective core potentials including core polarization, large gaussian basis sets, and full configuration interaction. In the perspective of upcoming experiments aiming at merging cold atom and cold ion traps, possible paths for radiative charge exchange, photoassociation of a cold lithium or rubidium atom and a strontium ion are discussed, as well as the formation of stable molecular ions.

  17. Moving metal ions through ferritin-protein nanocages from three-fold pores to catalytic sites.

    PubMed

    Tosha, Takehiko; Ng, Ho-Leung; Bhattasali, Onita; Alber, Tom; Theil, Elizabeth C

    2010-10-20

    Ferritin nanocages synthesize ferric oxide minerals, containing hundreds to thousands of Fe(III) diferric oxo/hydroxo complexes, by reactions of Fe(II) ions with O(2) at multiple di-iron catalytic centers. Ferric-oxy multimers, tetramers, and/or larger mineral nuclei form during postcatalytic transit through the protein cage, and mineral accretion occurs in the central cavity. We determined how Fe(II) substrates can access catalytic sites using frog M ferritins, active and inactivated by ligand substitution, crystallized with 2.0 M Mg(II) ± 0.1 M Co(II) for Co(II)-selective sites. Co(II) inhibited Fe(II) oxidation. High-resolution (<1.5 Å) crystal structures show (1) a line of metal ions, 15 Å long, which penetrates the cage and defines ion channels and internal pores to the nanocavity that link external pores to the cage interior, (2) metal ions near negatively charged residues at the channel exits and along the inner cavity surface that model Fe(II) transit to active sites, and (3) alternate side-chain conformations, absent in ferritins with catalysis eliminated by amino acid substitution, which support current models of protein dynamics and explain changes in Fe-Fe distances observed during catalysis. The new structural data identify a ∼27-Å path Fe(II) ions can follow through ferritin entry channels between external pores and the central cavity and along the cavity surface to the active sites where mineral synthesis begins. This "bucket brigade" for Fe(II) ion access to the ferritin catalytic sites not only increases understanding of biological nanomineral synthesis but also reveals unexpected design principles for protein cage-based catalysts and nanomaterials.

  18. Triboelectrification-Enabled Self-Powered Detection and Removal of Heavy Metal Ions in Wastewater.

    PubMed

    Li, Zhaoling; Chen, Jun; Guo, Hengyu; Fan, Xing; Wen, Zhen; Yeh, Min-Hsin; Yu, Chongwen; Cao, Xia; Wang, Zhong Lin

    2016-04-20

    A fundamentally new working principle into the field of self-powered heavy-metal-ion detection and removal using the triboelectrification effect is introduced. The as-developed tribo-nanosensors can selectively detect common heavy metal ions. The water-driven triboelectric nanogenerator is taken as a sustainable power source for heavy-metal-ion removal by recycling the kinetic energy from flowing wastewater.

  19. State promotion and neutralization оf ions near metal surface

    NASA Astrophysics Data System (ADS)

    Zinoviev, A. N.

    2011-05-01

    When a multiply charged ion with charge Z approaches the metal surface, a dipole is formed by the multiply charged ion and the charge induced in the metal. The states for such a dipole are promoted into continuum with decreasing ion-surface distance and cross the states formed from metal atom. The model proposed explains the dominant population of deep bound states in collisions considered.

  20. Polaronic Transport in Phosphate Glasses Containing Transition Metal Ions

    NASA Astrophysics Data System (ADS)

    Henderson, Mark

    The goal of this dissertation is to characterize the basic transport properties of phosphate glasses containing various amounts of TIs and to identify and explain any electronic phase transitions which may occur. The P2 O5-V2O5-WO3 (PVW) glass system will be analyzed to find the effect of TI concentration on conduction. In addition, the effect of the relative concentrations of network forming ions (SiO2 and P2O5) on transport will be studied in the P2O5-SiO2-Fe2O 3 (PSF) system. Also presented is a numerical study on a tight-binding model adapted for the purposes of modelling Gaussian traps, mimicking TI's, which are arranged in an extended network. The results of this project will contribute to the development of fundamental theories on the electronic transport in glasses containing mixtures of transition oxides as well as those containing multiple network formers without discernible phase separation. The present study on the PVW follows up on previous investigation into the effect on mixed transition ions in oxide glasses. Past research has focused on glasses containing transition metal ions from the 3d row. The inclusion of tungsten, a 5d transition metal, adds a layer of complexity through the mismatch of the energies of the orbitals contributing to localized states. The data have indicated that a transition reminiscent of a metal-insulator transition (MIT) occurs in this system as the concentration of tungsten increases. As opposed to some other MIT-like transitions found in phosphate glass systems, there seems to be no polaron to bipolaron conversion. Instead, the individual localization parameter for tungsten noticeably decreases dramatically at the transition point as well as the adiabaticity. Another distinctive feature of this project is the study of the PSF system, which contains two true network formers, phosphorous pentoxide (P2O 5) and silicon dioxide (SiO2). It is not usually possible to do a reliable investigation of the conduction properties of

  1. Metal ion sorption by untreated and chemically treated biomass

    SciTech Connect

    Kilbane, J.J.; Xie, J.

    1992-12-31

    The metal-binding ability of biosorbents is well known; however, in comparison with commercial ion-exchange resins the capacity of biosorbents is low. The purpose of this research was to examine chemically modified biosorbents and biosorbents prepared from microorganisms isolated from extreme environments to determine if significant improvements in metal-binding capacity or biosorbents with unique capabilities could be produced. Chemical treatments examined included acid, alkali, carbon disulfide, phosphorus oxychloride, anhydrous formamide, sodium thiosulfate, sodium chloroacetic acid, and phenylsulfonate. Biosorbents were prepared from microorganisms isolated from pristine and acid mine drainage impacted sites and included heterotrophs, methanotrophs, algae, and sulfate reducers. Chemical modification with carbon disulfide, phosphorous oxychloride, and sodium thiosulfate yielded biosorbents with such as much as 74%, 133%, and 155% improvements, respectively, in metal-binding capacity, but the performance of these chemically modified biosorbents deteriorated upon repeated use. A culture isolated from an acid mine drainage impacted site, IGTM17, exhibits about 3-fold higher metal-binding capacity in comparison with other biosorbents examined in this study. IGTM17 also exhibits superior metal-binding ability at decreased pH or in the presence of interfering common cations in comparison with other biosorbents or some commercially available cation exchange resins. Some biosorbents, such as IGTM5, can bind anions. To our knowledge this is the first demonstration of the ability of biosorbents to bind anions. Moreover, preliminary data indicate that the chemical modification of biosorbents may be capable of imparting the ability to selectively bind certain anions. Further research is needed to optimize conditions for the chemical modification and stabilization of biosorbents.

  2. Electrospray droplet exposure to organic vapors: metal ion removal from proteins and protein complexes.

    PubMed

    DeMuth, J Corinne; McLuckey, Scott A

    2015-01-20

    The exposure of aqueous nanoelectrospray droplets to various organic vapors can dramatically reduce sodium adduction on protein ions in positive ion mass spectra. Volatile alcohols, such as methanol, ethanol, and isopropanol lead to a significant reduction in sodium ion adduction but are not as effective as acetonitrile, acetone, and ethyl acetate. Organic vapor exposure in the negative ion mode, on the other hand, has essentially no effect on alkali ion adduction. Evidence is presented to suggest that the mechanism by which organic vapor exposure reduces alkali ion adduction in the positive mode involves the depletion of alkali metal ions via ion evaporation of metal ions solvated with organic molecules. The early generation of metal/organic cluster ions during the droplet desolvation process results in fewer metal ions available to condense on the protein ions formed via the charged residue mechanism. These effects are demonstrated with holomyoglobin ions to illustrate that the metal ion reduction takes place without detectable protein denaturation, which might be revealed by heme loss or an increase in charge state distribution. No evidence is observed for denaturation with exposure to any of the organic vapors evaluated in this work.

  3. Ion-beam-assisted deposition of metal nanocluster thin films with nonlinear optical properties

    SciTech Connect

    Cotell, C.M.; Carosella, C.A.; Flom, S.R.; Schiestel, S.; Haralampus, N.; Barnett, T.W.; Bartoli, F.J.

    1996-12-31

    Metal nanocluster thin films ({approximately} 200 nm thickness) consisting of noble metal (Au) clusters (5--30 nm) in an active metal oxide (Nb{sub 2}O{sub 5}) matrix were deposited by evaporation or ion beam assisted deposition (IBAD). In some cases the films were given a post-deposition anneal. The microstructure of the films was examined by plan view and cross sectional transmission electron microscopy (TEM). The size of the metal nanoclusters was found to depend upon the temperature of the post-deposition anneal as well as the conditions of ion bombardment. Ion bombardment was found to stabilize smaller size particles. The linear optical properties of the films, as measured by VIS/UV spectroscopy, show particle size-dependent surface plasmon resonance effects. The nonlinear optical (NLO) properties of the nanoclusters in oxidized niobium were probed experimentally using degenerate four wave mixing (DFWM) and nonlinear transmission (NLT). The DFWM measurements yielded signals that showed strong evidence of saturation and give large values of {vert_bar}{chi}{sup (3)}{sub xxxx}{vert_bar}. NLT measurements demonstrated that the nonlinear absorption coefficient and, hence, I{sub m}{chi}{sup (3)}{sub xxxx} was negative. Time resolved DFWM measurements exhibited dynamics that decayed on a several picosecond time scale. The magnitude and the picosecond dynamics of the NLO response were compared to those observed in gold nanoclusters formed by ion implantation in other media. The advantages of the IBAD method for fabricating third order NLO films include the ability to deposit films of arbitrary active region thickness and, more importantly, high cluster densities.

  4. Nanoparticles reduce nickel allergy by capturing metal ions

    NASA Astrophysics Data System (ADS)

    Vemula, Praveen Kumar; Anderson, R. Rox; Karp, Jeffrey M.

    2011-05-01

    Approximately 10% of the population in the USA suffer from nickel allergy, and many are unable to wear jewellery or handle coins and other objects that contain nickel. Many agents have been developed to reduce the penetration of nickel through skin, but few formulations are safe and effective. Here, we show that applying a thin layer of glycerine emollient containing nanoparticles of either calcium carbonate or calcium phosphate on an isolated piece of pig skin (in vitro) and on the skin of mice (in vivo) prevents the penetration of nickel ions into the skin. The nanoparticles capture nickel ions by cation exchange, and remain on the surface of the skin, allowing them to be removed by simple washing with water. Approximately 11-fold fewer nanoparticles by mass are required to achieve the same efficacy as the chelating agent ethylenediamine tetraacetic acid. Using nanoparticles with diameters smaller than 500 nm in topical creams may be an effective way to limit the exposure to metal ions that can cause skin irritation.

  5. Surface oxidation of metals by oxygen ion bombardment

    NASA Astrophysics Data System (ADS)

    Alov, Nikolai V.

    2007-03-01

    Surface oxidation of molybdenum, tungsten, niobium and tantalum by low-energy oxygen ion beams is investigated using X-ray photoelectron spectroscopy (XPS). Oxygen ion bombardment of molybdenum and tungsten surfaces leads to the formation of thin oxide films containing metals in oxidation states 4+, 5+ and 6+. At the initial stage of irradiation, rapid surface oxidation of molybdenum and tungsten was observed. At higher fluences the oxidation reaches saturation and the surface composition remains almost unchanged with increasing fluence. Oxygen ion bombardment of niobium and tantalum surfaces leads to the formation of thin oxide films containing niobium and tantalum in oxidation states 2+, 4+ and 5+. At the initial stage of irradiation, again rapid surface oxidation of niobium and tantalum was observed. At higher fluences the population of Nb2+ and Nb4+, Ta2+ and Ta4+ reaches a maximum and then begins to decrease. The population of Nb5+ and Ta5+ continues to increase and finally the entire oxide films consists of only Nb5+ and Ta5+, respectively.

  6. Use of Divalent Metal Ions in the DNA Cleavage Reaction of Human Type II Topoisomerases†

    PubMed Central

    Deweese, Joseph E.; Burch, Amber M.; Burgin, Alex B.; Osheroff, Neil

    2009-01-01

    All type II topoisomerases require divalent metal ions in order to cleave and ligate DNA. In order to further elucidate the mechanistic basis for these critical enzyme-mediated events, the role of the metal ion in the DNA cleavage reaction of human topoisomerase IIβ was characterized and compared to that of topoisomerase IIα. The present study utilized divalent metal ions with varying thiophilicities in conjunction with DNA cleavage substrates that substituted a sulfur atom for the 3′-bridging oxygen or the non-bridging oxygens of the scissile phosphate. Based on time courses of DNA cleavage, cation titrations, and metal ion mixing experiments, we propose the following model for the use of divalent metal ions by human type II topoisomerases. First, both enzymes employ a two-metal-ion mechanism to support DNA cleavage. Second, an interaction between one divalent metal ion and the 3′-bridging atom of the scissile phosphate greatly enhances enzyme-mediated DNA cleavage, most likely by stabilizing the leaving 3′-oxygen. Third, there is an important interaction between a divalent second metal ion and a non-bridging atom of the scissile phosphate that stimulates DNA cleavage mediated by topoisomerase IIβ. If this interaction exists in topoisomerase IIα, its effects on DNA cleavage are equivocal. This last aspect of the model highlights a difference in metal ion utilization during DNA cleavage mediated by human topoisomerase IIα and IIβ. PMID:19222228

  7. Prostate cancer outcome and tissue levels of metal ions

    USGS Publications Warehouse

    Sarafanov, A.G.; Todorov, T.I.; Centeno, J.A.; MacIas, V.; Gao, W.; Liang, W.-M.; Beam, C.; Gray, Michael A.; Kajdacsy-Balla, A.

    2011-01-01

    BACKGROUND There are several studies examining prostate cancer and exposure to cadmium, iron, selenium, and zinc. Less data are available on the possible influence of these metal ions on prostate cancer outcome. This study measured levels of these ions in prostatectomy samples in order to examine possible associations between metal concentrations and disease outcome. METHODS We obtained formalin fixed paraffin embedded tissue blocks of prostatectomy samples of 40 patients with PSA recurrence, matched 1:1 (for year of surgery, race, age, Gleason grading, and pathology TNM classification) with tissue blocks from 40 patients without recurrence (n = 80). Case-control pairs were compared for the levels of metals in areas adjacent to tumors. Inductively coupled plasma-mass spectrometry (ICP-MS) was used for quantification of Cd, Fe, Zn, and Se. RESULTS Patients with biochemical (PSA) recurrence of disease had 12% lower median iron (95 ??g/g vs. 111 ??g/g; P = 0.04) and 21% lower zinc (279 ??g/g vs. 346 ??g/g; P = 0.04) concentrations in the normal-appearing tissue immediately adjacent to cancer areas. Differences in cadmium (0.489 ??g/g vs. 0.439 ??g/g; 4% higher) and selenium (1.68 ??g/g vs. 1.58 ??g/g; 5% higher) levels were not statistically significant in recurrence cases, when compared to non-recurrences (P = 0.40 and 0.21, respectively). CONCLUSIONS There is an association between low zinc and low iron prostate tissue levels and biochemical recurrence in prostate cancer. Whether these novel findings are a cause or effect of more aggressive tumors, or whether low zinc and iron prostatic levels raise implications for therapy, remains to be investigated. Copyright ?? 2011 Wiley-Liss, Inc.

  8. New Proton-Ionizable, Calixarene-Based Ligands for Selective Metal Ion Separations

    SciTech Connect

    Bartsch, Richard A.

    2012-06-04

    The project objective was the discovery of new ligands for performing metal ion separations. The research effort entailed the preparation of new metal ion complexing agents and polymers and their evaluation in metal ion separation processes of solvent extraction, synthetic liquid membrane transport, and sorption. Structural variations in acyclic, cyclic, and bicyclic organic ligands were used to probe their influence upon the efficiency and selectivity with which metal ion separations can be performed. A unifying feature of the ligand structures is the presence of one (or more) side arm with a pendent acidic function. When a metal ion is complexed within the central cavity of the ligand, ionization of the side arm(s) produces the requisite anion(s) for formation of an overall electroneutral complex. This markedly enhances extraction/transport efficiency for separations in which movement of aqueous phase anions of chloride, nitrate, or sulfate into an organic medium would be required. Through systematic structural variations, new ligands have been developed for efficient and selective separations of monovalent metal ions (e.g., alkali metal, silver, and thallium cations) and of divalent metal ion species (e.g., alkaline earth metal, lead, and mercury cations). Research results obtained in these fundamental investigations provide important insight for the design and development of ligands suitable for practical metal ion separation applications.

  9. Gas-phase catalysis by atomic and cluster metal ions: the ultimate single-site catalysts.

    PubMed

    Böhme, Diethard K; Schwarz, Helmut

    2005-04-15

    Gas-phase experiments with state-of-the-art techniques of mass spectrometry provide detailed insights into numerous elementary processes. The focus of this Review is on elementary reactions of ions that achieve complete catalytic cycles under thermal conditions. The examples chosen cover aspects of catalysis pertinent to areas as diverse as atmospheric chemistry and surface chemistry. We describe how transfer of oxygen atoms, bond activation, and coupling of fragments can be mediated by atomic or cluster metal ions. In some cases truly unexpected analogies of the idealized gas-phase ion catalysis can be drawn with related chemical transformations in solution or the solid state, and so improve our understanding of the intrinsic operation of a practical catalyst at a strictly molecular level.

  10. Towards metals analysis using corona discharge ionization ion mobility spectrometry.

    PubMed

    Jafari, Mohammad T; Saraji, Mohammad; Sherafatmand, Hossein

    2016-02-25

    For the first time, the capability of corona discharge ionization ion mobility spectrometry (CD-IMS) in the determination of metal complex was evaluated. The extreme simplicity of dispersive liquid-liquid microextraction (DLLME) coupled to the high sensitivity of CD-IMS measurement could make this combination really useful for simple, rapid, and sensitive determination of metals in different samples. In this regard, mercury, as a model metal, was complexed with diethyldithiocarbamate (DEDTC), and then extracted into the carbon tetrachloride using DLLME. Some parameters affecting the extraction efficiency, including the type and volume of the extraction solvent, the type and volume of the disperser solvent, the concentration of the chelating agent, salt addition and, pH were exhaustively investigated. Under the optimized condition, the enrichment factor was obtained to be 142. The linear range of 0.035-10.0 μg mL(-1) with r(2) = 0.997 and the detection limit of 0.010 μg mL(-1) were obtained. The relative standard deviation values were calculated to be lower than 4% and 8% for intra-day and inter-day, respectively. Finally, the developed method was successfully applied for the extraction and determination of mercury in various real samples. The satisfactory results revealed the capability of the proposed method in trace analysis without tedious derivatization or hydride generation.

  11. NEW INSTRUMENTS AND METHODS OF MEASUREMENTS: Liquid-metal ion emitters

    NASA Astrophysics Data System (ADS)

    Gabovich, M. D.

    1983-05-01

    This article describes and discusses the fundamental laws of ion emission from liquid-metal tips in a strong electric field. The widespread views of a liquid-metal emitter as being the smoothed tip of a Taylor cone are examined critically. The instability of a liquid metal in an electric field is discussed, and in line with this, an alternative concept is given of a sharp-tipped electrohydrodynamic emitter. The prospects for applying liquid-metal ion emitters are noted.

  12. The effect of platform switching on the levels of metal ion release from different implant–abutment couples

    PubMed Central

    Alrabeah, Ghada O; Knowles, Jonathan C; Petridis, Haralampos

    2016-01-01

    The improved peri-implant bone response demonstrated by platform switching may be the result of reduced amounts of metal ions released to the surrounding tissues. The aim of this study was to compare the levels of metal ions released from platform-matched and platform-switched implant–abutment couples as a result of accelerated corrosion. Thirty-six titanium alloy (Ti-6Al-4V) and cobalt–chrome alloy abutments were coupled with titanium cylinders forming either platform-switched or platform-matched groups (n=6). In addition, 18 unconnected samples served as controls. The specimens were subjected to accelerated corrosion by static immersion in 1% lactic acid for 1 week. The amount of metal ions ion of each test tube was measured using inductively coupled plasma mass spectrometry. Scanning electron microscope (SEM) images and energy dispersive spectroscopy X-ray analyses were performed pre- and post-immersion to assess corrosion at the interface. The platform-matched groups demonstrated higher ion release for vanadium, aluminium, cobalt, chrome, and molybdenum compared with the platform-switched groups (P<0.05). Titanium was the highest element to be released regardless of abutment size or connection (P<0.05). SEM images showed pitting corrosion prominent on the outer borders of the implant and abutment platform surfaces. In conclusion, implant–abutment couples underwent an active corrosion process resulting in metal ions release into the surrounding environment. The highest amount of metal ions released was recorded for the platform-matched groups, suggesting that platform-switching concept has a positive effect in reducing the levels of metal ion release from the implant–abutment couples. PMID:27357323

  13. Negative ion photoelectron spectroscopic studies of transition metal cluster

    NASA Astrophysics Data System (ADS)

    Marcy, Timothy Paul

    The studies reported in this thesis were performed using a negative ion photoelectron spectrometer consisting of a cold cathode DC discharge ion source, a flowing afterglow ion-molecule reactor, a magnetic sector mass analyzer, an argon ion laser for photodetachment and a hemispherical electron kinetic energy analyzer and microchannel plate detector for photoelectron spectrum generation. The 476.5 nm (2.601 eV), 488.0 nm (2.540 eV) and 514.5 nm (2.410 eV) negative ion photoelectron spectra of VMn are reported and compared to the previously studied spectra of isoelectronic Cr2.1 The photoelectron spectra are remarkably similar to those of Cr2 in electron affinity and vibrational frequencies. The 488.0 nm photoelectron spectra and electron affinities of Nb n- (n = 1 - 9) are reported with discussion of observed vibrational structure. There are transitions to several electronic states of Nb2 in the reported spectra with overlapping vibrational progressions. The spectra of Nb3, Nb4 and Nb6 show partially resolved vibrational structure in the transitions to the lowest observed electronic state of each cluster. There is a single distinct active vibrational mode in the transition to the ground state of Nb8. Spin-orbit energies of Nb- are also reported. The 488.0 nm negative ion photoelectron spectra of Nb3H(D) are reported and compared to those of Nb3. There is a single vibrational mode active in the spectra of Nb3H(D) which is very similar to the most distinct mode active in the spectrum of Nb3. The 488.0 nm photoelectron spectra of the NbxCyH(D) y- (x = 1, 2, 3, y = 2, 4, 6) dehydrogenated products of the reactions of ethylene with niobium cluster anions are reported. Temperature studies of some of these species give evidence for the presence of multiple isomers of each molecule in the ion beam. The spectra of NbC6H(D) 6 are identical to those obtained from the reactions of benzene with niobium clusters and indicate that benzene is being formed from ethylene in the flow

  14. Measurement of Two-Photon Absorption Cross Section of Metal Ions by a Mass Sedimentation Approach

    PubMed Central

    Ma, Zhuo-Chen; Chen, Qi-Dai; Han, Bing; Liu, Xue-Qing; Song, Jun-Feng; Sun, Hong-Bo

    2015-01-01

    The photo-reduction of metal ions in solution induced by femtosecond laser is an important and novel method for fabricating three-dimensional metal microstructures. However, the nonlinear absorption cross section of metal ions remains unknown because its measurement is difficult. In the present study, a method based on Two-Photon Excited Sedimentation (TPES) is proposed to measure the two-photon absorption cross section (TPACS) of metal ions in solution. The power-squared dependence of the amount of sediment on the excitation intensity was confirmed, revealing that 800 nm femtosecond laser induced reduction of metal ions was a two photon absorption process. We believe that the proposed method may be applied to measure the TPACS of several metal ions, thereby opening a new avenue towards future analysis of two-photon absorption materials. PMID:26657990

  15. Rational design of metal ion sequestering agents. 1998 annual progress report

    SciTech Connect

    Raymond, K.N.

    1998-06-01

    'This project addresses fundamental issues and requirements in developing hazardous metal ion separation technologies needed in the treatment and disposal of radioactive and chemical toxic waste. It encompasses the synthesis of new agents, followed by their characterization and evaluation, with the aim to optimize their metal ion sequestering properties for use in applied technologies. This research is focused on the following key areas: (1) basic design and synthesis of new metal ion specific sequestering ligands; (2) structural and thermodynamic investigations of these ligands and their complexes formed with the targeted metal ions; and (3) development of sequestering agents and their incorporation into systems designed to be prototypes of inexpensive and highly effective materials for hazardous metal ion decontamination. Basic studies of the sequestration of relevant toxic metals are required in order to develop processes that will treat effluents sufficiently well to allow direct release into the environment and minimize the production of secondary wastes.'

  16. Some aspects of metallic ion chemistry and dynamics in the mesosphere and thermosphere

    NASA Technical Reports Server (NTRS)

    Mathews, J. D.

    1987-01-01

    The relationship between the formation of sporadic layers of metallic ion and the dumping of these ions into the upper mesosphere is discussed in terms of the tidal wind, classical (i.e., windshear) and other more complex, perhaps highly nonlinear layer formation mechanisms, and a possible circulation mechanism for these ions. Optical, incoherent scatter radar, rocket, and satellite derived evidence for various layer formation mechanisms and for the metallic ion circulation system is reviewed. The results of simple one dimensional numerical model calculations of sporadic E and intermediate layer formation are presented along with suggestions for more advanced models of intense or blanketing sporadic E. The flux of metallic ions dumped by the tidal wind system into the mesosphere is estimated and compared with estimates of total particle flux of meteoric origin. Possible effects of the metallic ion flux and of meteoric dust on D region ion chemistry are discussed.

  17. Metal cation/anion adsorption on calcium carbonate: Implications to metal ion concentrations in groundwater

    SciTech Connect

    Zachara, J.M.; Cowan, C.E.; Resch, C.T.

    1990-05-01

    This chapter evaluates the sorption behavior of metallic ions on specimen calcite as a basis for determining the importance of calcite relative to other subsurface sorbents, such as layer silicates and oxides, in controlling metal ion concentration in calcareous groundwaters. A review of the literature shows the sorption of both metallic cations and anions on calcite over ranges in pH and CO{sub 2} partial pressure to be consistent with a surface-exchange process where cations exchange with surface Ca and anions exchange with surface CO{sub 3}. A general surface-exchange model was developed to account for the effects of Ca and CO{sub 3} concentrations, pH, and calcite surface area on cation and anion sorption onto calcite. The model was applied to recently developed experimental sorption data of Zn and SeO{sub 3} on specimen calcite in equilibrium CaCO{sub 3}(aq) suspensions. The surface-exchange model was able to describe the effects of pH on both cation and anion sorption, and provided good predictions of the effects of variable CO{sub 2}(g) pressure on Zn sorption and of PO{sub 4} on SeO{sub 3} sorption. The surface-exchange model, combined with sorption constants for other phases, was used to calculate Cd sorption to a hypothetical aquifer material containing a mixture of sorbents. The sorbent concentrations were fixed to those expected in groundwater zones. The multi-sorbent calculation documented the importance of calcite as a sorbent for metallic ions in groundwater.93 refs., 18 figs., 5 tabs.

  18. Metallation of ethylenediamine based Schiff base with biologically active Cu(II), Ni(II) and Zn(II) ions: synthesis, spectroscopic characterization, electrochemical behaviour, DNA binding, photonuclease activity and in vitro antimicrobial efficacy.

    PubMed

    Raman, N; Selvan, A; Sudharsan, S

    2011-09-01

    A new ligand [C28H20N6O8] (L2) has been synthesized by the condensation reaction of 3-hydroxy-4-nitrobenzaldehydenephenylhydrazine (L1) with diethyloxalate. This ligand L2 is allowed to react with bis(ethylenediamine)Cu(II)/Ni(II)/Zn(II) complexes. It affords [(L2)Cu(en)2]Cl2(1)/[(L2)Ni(en)2]Cl2(2)/[(L2)Zn(en)2]Cl2(3) complexes, respectively. These complexes (1-3) have been characterized by the spectral and analytical techniques. The interaction of these complexes with calf thymus (CT) DNA is characterized by the absorption spectra which exhibit a slight red shift with hypochromic effect. Electrochemical analyses and viscosity measurements have also been carried out to determine the mode of binding. The shift in ΔEp, E1/2 and Ipc values explores the interaction of CT DNA with the above metal complexes. The slight increase in the viscosity of CT DNA indicates that these complexes bind to CT DNA through a partial non-classical intercalative mode. Cleavage experiments using pBR322 DNA in presence of H2O2 indicate that these complexes behave as efficient artificial chemical nucleases in the order of 1>2>3. Moreover, the antibacterial and antifungal studies reveal that complex 1 is highly active against the bacterial and fungal growth.

  19. A corpora allata farnesyl diphosphate synthase in mosquitoes displaying a metal ion dependent substrate specificity

    PubMed Central

    Rivera-Perez, Crisalejandra; Nyati, Pratik; Noriega, Fernando G.

    2015-01-01

    Farnesyl diphosphate synthase (FPPS) is a key enzyme in isoprenoid biosynthesis, it catalyzes the head-to-tail condensation of dimethylallyl diphosphate (DMAPP) with two molecules of isopentenyl diphosphate (IPP) to generate farnesyl diphosphate (FPP), a precursor of juvenile hormone (JH). In this study, we functionally characterized an Aedes aegypti FPPS (AaFPPS) expressed in the corpora allata. AaFPPS is the only FPPS gene present in the genome of the yellow fever mosquito, it encodes a 49.6 kDa protein exhibiting all the characteristic conserved sequence domains on prenyltransferases. AaFPPS displays its activity in the presence of metal cofactors; and the product condensation is dependent of the divalent cation. Mg2+ ions lead to the production of FPP, while the presence of Co2+ ions lead to geranyl diphosphate (GPP) production. In the presence of Mg2+ the AaFPPS affinity for allylic substrates is GPP>DMAPP>IPP. These results suggest that AaFPPS displays “catalytic promiscuity”, changing the type and ratio of products released (GPP or FPP) depending on allylic substrate concentrations and the presence of different metal cofactors. This metal ion-dependent regulatory mechanism allows a single enzyme to selectively control the metabolites it produces, thus potentially altering the flow of carbon into separate metabolic pathways. PMID:26188328

  20. A corpora allata farnesyl diphosphate synthase in mosquitoes displaying a metal ion dependent substrate specificity.

    PubMed

    Rivera-Perez, Crisalejandra; Nyati, Pratik; Noriega, Fernando G

    2015-09-01

    Farnesyl diphosphate synthase (FPPS) is a key enzyme in isoprenoid biosynthesis, it catalyzes the head-to-tail condensation of dimethylallyl diphosphate (DMAPP) with two molecules of isopentenyl diphosphate (IPP) to generate farnesyl diphosphate (FPP), a precursor of juvenile hormone (JH). In this study, we functionally characterized an Aedes aegypti FPPS (AaFPPS) expressed in the corpora allata. AaFPPS is the only FPPS gene present in the genome of the yellow fever mosquito, it encodes a 49.6 kDa protein exhibiting all the characteristic conserved sequence domains on prenyltransferases. AaFPPS displays its activity in the presence of metal cofactors; and the product condensation is dependent of the divalent cation. Mg(2+) ions lead to the production of FPP, while the presence of Co(2+) ions lead to geranyl diphosphate (GPP) production. In the presence of Mg(2+) the AaFPPS affinity for allylic substrates is GPP > DMAPP > IPP. These results suggest that AaFPPS displays "catalytic promiscuity", changing the type and ratio of products released (GPP or FPP) depending on allylic substrate concentrations and the presence of different metal cofactors. This metal ion-dependent regulatory mechanism allows a single enzyme to selectively control the metabolites it produces, thus potentially altering the flow of carbon into separate metabolic pathways.

  1. Lithium-free transition metal monoxides for positive electrodes in lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Jung, Sung-Kyun; Kim, Hyunchul; Cho, Min Gee; Cho, Sung-Pyo; Lee, Byungju; Kim, Hyungsub; Park, Young-Uk; Hong, Jihyun; Park, Kyu-Young; Yoon, Gabin; Seong, Won Mo; Cho, Yongbeom; Oh, Myoung Hwan; Kim, Haegyeom; Gwon, Hyeokjo; Hwang, Insang; Hyeon, Taeghwan; Yoon, Won-Sub; Kang, Kisuk

    2017-01-01

    Lithium-ion batteries based on intercalation compounds have dominated the advanced portable energy storage market. The positive electrode materials in these batteries belong to a material group of lithium-conducting crystals that contain redox-active transition metal and lithium. Materials without lithium-conducting paths or lithium-free compounds could be rarely used as positive electrodes due to the incapability of reversible lithium intercalation or the necessity of using metallic lithium as negative electrodes. These constraints have significantly limited the choice of materials and retarded the development of new positive electrodes in lithium-ion batteries. Here, we demonstrate that lithium-free transition metal monoxides that do not contain lithium-conducting paths in their crystal structure can be converted into high-capacity positive electrodes in the electrochemical cell by initially decorating the monoxide surface with nanosized lithium fluoride. This unusual electrochemical behaviour is attributed to a surface conversion reaction mechanism in contrast with the classic lithium intercalation reaction. Our findings will offer a potential new path in the design of positive electrode materials in lithium-ion batteries.

  2. Process for the displacement of cyanide ions from metal-cyanide complexes

    DOEpatents

    Smith, Barbara F.; Robinson, Thomas W.

    1997-01-01

    The present invention relates to water-soluble polymers and the use of such water-soluble polymers in a process for the displacement of the cyanide ions from the metal ions within metal-cyanide complexes. The process waste streams can include metal-cyanide containing electroplating waste streams, mining leach waste streams, mineral processing waste streams, and related metal-cyanide containing waste streams. The metal ions of interest are metals that give very strong complexes with cyanide, mostly iron, nickel, and copper. The physical separation of the water-soluble polymer-metal complex from the cyanide ions can be accomplished through the use of ultrafiltration. Once the metal-cyanide complex is disrupted, the freed cyanide ions can be recovered for reuse or destroyed using available oxidative processes rendering the cyanide nonhazardous. The metal ions are released from the polymer, using dilute acid, metal ion oxidation state adjustment, or competing chelating agents, and collected and recovered or disposed of by appropriate waste management techniques. The water-soluble polymer can then be recycled. Preferred water-soluble polymers include polyethyleneimine and polyethyleneimine having a catechol or hydroxamate group.

  3. Controlled Segmentation of Metal Nanowire Array by Block Copolymer Lithography and Reversible Ion Loading.

    PubMed

    Mun, Jeong Ho; Cha, Seung Keun; Kim, Ye Chan; Yun, Taeyeong; Choi, Young Joo; Jin, Hyeong Min; Lee, Jae Eun; Jeon, Hyun Uk; Kim, So Youn; Kim, Sang Ouk

    2017-02-20

    Spatial arrangement of 1D nanomaterials may offer enormous opportunities for advanced electronics and photonics. Moreover, morphological complexity and chemical diversity in the nanoscale components may lead to unique properties that are hardly anticipated in randomly distributed homogeneous nanostructures. Here, controlled chemical segmentation of metal nanowire arrays using block copolymer lithography and subsequent reversible metal ion loading are demonstrated. To impose chemical heterogeneity in the nanowires generated by block copolymer lithography, reversible ion loading method highly specific for one particular polymer block is introduced. Reversibility of the metal ion loading enables area-selective localized replacement of metal ions in the self-assembled patterns and creates segmented metal nanowire arrays with different metallic components. Further integration of this method with shear aligning process produces high aligned segmented metal nanowire array with desired local chemical compositions.

  4. Highly charged Ar{sup q+} ions interacting with metals

    SciTech Connect

    Wang Jijin; Zhang Jian; Gu Jiangang; Luo Xianwen; Hu Bitao

    2009-12-15

    Using computer simulation, alternative methods of the interaction of highly charged ions Ar{sup q+} with metals (Au, Ag) are used and verified in the present work. Based on the classical over-barrier model, we discussed the promotion loss and peeling off processes. The simulated total potential electron yields agree well with the experiment data in incident energy ranging from 100 eV to 5 keV and all charge states of Ar{sup q+}. Based on the TRIM code, we obtain the side-feeding rate as well as the motion and charge transfer of HCI below the surface. Some results, including the array of KL{sup x} x-ray satellite lines, the respective contribution of autoionization, and side-feeding to inner shells, and the filling rates and lifetime of inner shells for Ar agree well with experiment or theory.

  5. Highly Emissive Transition Metal Ion Doped Semiconducting Nanocrystals

    NASA Astrophysics Data System (ADS)

    Jana, Santanu; Srivastava, Bhupendra B.; Sarma, D. D.; Pradhan, Narayan

    2011-07-01

    Doped semiconductor nanocrystals (d-dots), specifically ones not containing heavy metal ions, have the potential to become a class of mainstream emissive materials. Mn- and Cu-doped ZnSe or ZnS d-dots can cover an emission window similar to that of the current workhorse of intrinsic quantum dot (q-dots) emitters, CdSe nanocrystals. We synthesized high quality stable Cu doped ZnSe in nonpolar as well as polar solvent. The emission intensity of these doped nanocrystals is found stable for months under UV irradiation, after different multifunctional ligand which is important for any biological detection. We have also synthesized the stable Mn doped ZnS in nonpolar solvent more than 50% QY.. The doped nanocrystals are characterized by TEM, XRD, EPR and ICP analysis.

  6. Metal ion dependence of cooperative collapse transitions in RNA.

    PubMed

    Moghaddam, Sarvin; Caliskan, Gokhan; Chauhan, Seema; Hyeon, Changbong; Briber, R M; Thirumalai, D; Woodson, Sarah A

    2009-10-30

    Positively charged counterions drive RNA molecules into compact configurations that lead to their biologically active structures. To understand how the valence and size of the cations influences the collapse transition in RNA, small-angle X-ray scattering was used to follow the decrease in the radius of gyration (R(g)) of the Azoarcus and Tetrahymena ribozymes in different cations. Small, multivalent cations induced the collapse of both ribozymes more efficiently than did monovalent ions. Thus, the cooperativity of the collapse transition depends on the counterion charge density. Singular value decomposition of the scattering curves showed that folding of the smaller and more thermostable Azoarcus ribozyme is well described by two components, whereas collapse of the larger Tetrahymena ribozyme involves at least one intermediate. The ion-dependent persistence length, extracted from the distance distribution of the scattering vectors, shows that the Azoarcus ribozyme is less flexible at the midpoint of transition in low-charge-density ions than in high-charge-density ions. We conclude that the formation of sequence-specific tertiary interactions in the Azoarcus ribozyme overlaps with neutralization of the phosphate charge, while tertiary folding of the Tetrahymena ribozyme requires additional counterions. Thus, the stability of the RNA structure determines its sensitivity to the valence and size of the counterions.

  7. Photoluminescence properties of Jahn-Teller transition-metal ions

    NASA Astrophysics Data System (ADS)

    Sanz-Ortiz, Marta N.; Rodríguez, Fernando

    2009-09-01

    This work investigates the influence of electron-phonon coupling associated with E ⊗e and T ⊗e Jahn-Teller (JT) effect in different transition-metal (TM) ions on de-excitation phenomena through nonradiative multiphonon relaxation, i.e., photoluminescence (PL) quenching. We developed a configurational curve model which is able to predict from the absorption spectrum whether a given JT-TM ion is PL or quenched. The prediction is made on the basis of an adapted Dexter-Klick-Russell parameter for JT systems, defined in terms of spectroscopic parameters through ΛJT=αΔeabs/Eabs, where Δeabs refers to the splitting of the parent octahedral Eg states by the JT distortion in E ⊗e (α =3/4) or T ⊗e (α =1/4), and Eabs is the energy of the first absorption band involving electronic transition between Eg and T2g. We show that PL in any JT-TM ion occurs whenever ΛJT<0.1 or is quenched if ΛJT>0.2. This result is noteworthy since it allows us to establish structural requirements for the JT-TM ion and the host crystal to be PL. Although PL properties of materials containing TM ions depend on a variety of structural factors such as the electronic configuration, the site symmetry, and the crystal field produced by neighboring atoms, the present model achieves this goal through a simple spectroscopic parameter: ΛJT. In this work we correlated the PL properties of different sixfold-coordinated JT systems such as Ti3+, Cu2+, Mn3+, Cr2+, Fe2+, Co3+, and Ni3+ in halides and oxides with ΛJT obtained from their respective absorption spectra. From this analysis we conclude that depending on the nature of the JT coupling and its strength, PL is either strongly favored or quenched in T ⊗e while it is mostly quenched in E ⊗e systems due to the larger JT distortion.

  8. Removal of the metal ions from aqueous solutions by nanoscaled low molecular pectin isolated from seagrass Phyllospadix iwatensis.

    PubMed

    Khozhaenko, Elena; Kovalev, Valeri; Podkorytova, Elena; Khotimchenko, Maksim

    2016-09-15

    Pectins from sea grasses are considered as promising substances with pronounced metal-binding activity. Due to the high molecular weight and heterogeneous structure, the use of pectins for removal of metal ions is difficult. Technology of directed pectin degradation was developed and homogenous degraded nanoscaled pectin polymers were synthesized. Experimental samples of degraded pectin isolated from Phyllospadix iwatensis were tested for their metal binding activity in comparison with native pectin from this seagrass and commercial citrus pectin. The metal uptake of all pectin compounds was highest within the pH range from 4.0 to 6.0. The Langmuir, Freundlich and BET sorption models were applied to describe the isotherms and constants. Results showed that depolymerized pectin exerts highest lead and cadmium binding activity with pronounced affinity. All pectin compounds were suggested to be favorable sorbents. Therefore, it can be concluded that degraded pectin is a prospective material for creation of metal-removing water treatment systems.

  9. Topoisomerase IV-quinolone interactions are mediated through a water-metal ion bridge: mechanistic basis of quinolone resistance.

    PubMed

    Aldred, Katie J; McPherson, Sylvia A; Turnbough, Charles L; Kerns, Robert J; Osheroff, Neil

    2013-04-01

    Although quinolones are the most commonly prescribed antibacterials, their use is threatened by an increasing prevalence of resistance. The most common causes of quinolone resistance are mutations of a specific serine or acidic residue in the A subunit of gyrase or topoisomerase IV. These amino acids are proposed to serve as a critical enzyme-quinolone interaction site by anchoring a water-metal ion bridge that coordinates drug binding. To probe the role of the proposed water-metal ion bridge, we characterized wild-type, GrlA(E85K), GrlA(S81F/E85K), GrlA(E85A), GrlA(S81F/E85A) and GrlA(S81F) Bacillus anthracis topoisomerase IV, their sensitivity to quinolones and related drugs and their use of metal ions. Mutations increased the Mg(2+) concentration required to produce maximal quinolone-induced DNA cleavage and restricted the divalent metal ions that could support quinolone activity. Individual mutation of Ser81 or Glu85 partially disrupted bridge function, whereas simultaneous mutation of both residues abrogated protein-quinolone interactions. Results provide functional evidence for the existence of the water-metal ion bridge, confirm that the serine and glutamic acid residues anchor the bridge, demonstrate that the bridge is the primary conduit for interactions between clinically relevant quinolones and topoisomerase IV and provide a likely mechanism for the most common causes of quinolone resistance.

  10. Metal ion-assisted self-assembly of complexes for controlled and sustained release of minocycline for biomedical applications.

    PubMed

    Zhang, Zhiling; Wang, Zhicheng; Nong, Jia; Nix, Camilla A; Ji, Hai-Feng; Zhong, Yinghui

    2015-01-20

    This study reports the development of novel drug delivery complexes self-assembled by divalent metal ion-assisted coacervation for controlled and sustained release of a hydrophilic small drug molecule minocycline hydrochloride (MH). MH is a multifaceted agent that has demonstrated therapeutic effects in infection, inflammation, tumor, as well as cardiovascular, renal, and neurological disorders due to its anti-microbial, anti-inflammatory, and cytoprotective properties. However, the inability to translate the high doses used in experimental animals to tolerable doses in human patients limits its clinical application. Localized delivery can potentially expose the diseased tissue to high concentrations of MH that systemic delivery cannot achieve, while minimizing the side effects from systemic exposure. The strong metal ion binding-assisted interaction enabled high drug entrapment and loading efficiency, and stable long term release for more than 71 d. Released MH demonstrated potent anti-biofilm, anti-inflammatory, and neuroprotective activities. Furthermore, MH release from the complexes is pH-sensitive as the chelation between minocycline and metal ions decreases with pH, allowing 'smart' drug release in response to the severity of pathology-induced tissue acidosis. This novel metal ion binding-mediated drug delivery mechanism can potentially be applied to other drugs that have high binding affinity for metal ions and may lead to the development of new delivery systems for a variety of drugs.

  11. Ion mobility studies of carbohydrates as group I adducts: isomer specific collisional cross section dependence on metal ion radius.

    PubMed

    Huang, Yuting; Dodds, Eric D

    2013-10-15

    Carbohydrates play numerous critical roles in biological systems. Characterization of oligosaccharide structures is essential to a complete understanding of their functions in biological processes; nevertheless, their structural determination remains challenging in part due to isomerism. Ion mobility spectrometry provides the means to resolve gas phase ions on the basis of their shape-to-charge ratios, thus providing significant potential for separation and differentiation of carbohydrate isomers. Here, we report on the determination of collisional cross sections for four groups of isomeric carbohydrates (including five isomeric disaccharides, four isomeric trisaccharides, two isomeric pentasaccharides, and two isomeric hexasaccharides) as their group I metal ion adducts (i.e., [M + Li](+), [M + Na](+), [M + K](+), [M + Rb](+), and [M + Cs](+)). In all, 65 collisional cross sections were measured, the great majority of which have not been previously reported. As anticipated, the collisional cross sections of the carbohydrate metal ion adducts generally increase with increasing metal ion radius; however, the collisional cross sections were found to scale with the group I cation size in isomer specific manners. Such measurements are of substantial analytical value, as they illustrate how the selection of charge carrier influences carbohydrate ion mobility determinations. For example, certain pairs of isomeric carbohydrates assume unique collisional cross sections upon binding one metal ion, but not another. On the whole, these data suggest a role for the charge carrier as a probe of carbohydrate structure and thus have significant implications for the continued development and application of ion mobility spectrometry for the distinction and resolution of isomeric carbohydrates.

  12. Kinetic and equilibrium metal-ion-binding behaviour reflected in a metal-ion-dependent antigenic determinant in bovine prothrombin. Comparison with bovine prothrombin fragment 1.

    PubMed Central

    Madar, D A; Hall, T J; Hiskey, R G; Koehler, K A

    1981-01-01

    Rabbit anti-(bovine prothrombin fragment 1) antibodies were fractionated by using fragment-1 affinity chromatography in the absence of metal ions, and showed an absolute requirement for the presence of metal ions in their interactions with bovine fragment 1 or prothrombin. These antibodies were employed to evaluate both the rate constants for a protein conformation change and the equilibrium metal-ion binding to isolated bovine fragment 1 and intact prothrombin. The close similarity of the rates obtained for the conformation change in fragment 1 and those observed in prothrombin indicated that the same process is involved in both proteins and that the non-fragment-1 region of the prothrombin has essentially no effect on this process in the fragment-1 region. Equilibrium metal-ion-binding studies indicate that the details of the metal-ion-binding process in fragment 1 and prothrombin are essentially the same. We conclude that the metal-ion-binding behaviour of the fragment-1 domain of intact prothrombin is identical with that of isolated fragment 1. PMID:6171251

  13. Metal ion binding and function in natural and artificial small RNA enzymes from a structural perspective.

    PubMed

    Wedekind, Joseph E

    2011-01-01

    Ribozymes are often perceived as part of an antiquated catalytic arsenal hearkening back to a pre-biotic RNA World that was eventually supplanted by proteins. However, recent genome-wide searches have revealed a plethora of new catalytic RNA motifs that appear to be variations on well-known themes. This suggests that ribozymes have continued to evolve in order to fulfill specific, RNA-essential biological niches. Although such ribozymes are small and catalyze one-step phosphodiester-bond scission reactions, ongoing structure and function analyses at the lab bench have demonstrated that RNA has the capacity for a diverse number of reactions such as carbon-carbon bond formation, and tRNA aminoacylation. Here we describe the fundamental structure and metal binding properties of four naturally occurring RNA enzymes: the hammerhead, hairpin, hepatitis delta virus, and glmS metabolite sensing ribozyme. In addition, we discuss the fold and ion coordination of three artificial ribozymes developed to probe the boundaries of RNA catalysis; these include the leadzyme, the flexizyme, and the Diels-Alder ribozyme. Our approach is to relate structure to function with the knowledge of ideal metal-ion coordination geometry that we have derived herein from surveys of high-resolution small molecule structures. An emergent theme is that natural and artificial ribozymes that catalyze single-step reactions often possess a pre-formed active site. Multivalent ions facilitate RNA active site formation, but can also provide Lewis acid functionality that is necessary for catalysis. When metal ion binding isn't possible, ribozymes make due by ionizing their bases, or by recruiting cofactors that augment their chemical functionality.

  14. Metal Ions Removal Using Nano Oxide Pyrolox™ Material

    NASA Astrophysics Data System (ADS)

    Gładysz-Płaska, A.; Skwarek, E.; Budnyak, T. M.; Kołodyńska, D.

    2017-02-01

    The paper presents the use of Pyrolox™ containing manganese nano oxides used for the removal of Cu(II), Zn(II), Cd(II), and Pb(II) as well as U(VI) ions. Their concentrations were analyzed using the atomic absorption spectrometer SpectrAA 240 FS (Varian) as well as UV-vis method. For this purpose the static kinetic and equilibrium studies were carried out using the batch technique. The effect of solution pH, shaking time, initial metal ion concentrations, sorbent dosage, and temperature was investigated. The equilibrium data were analyzed using the sorption isotherm models proposed by Freundlich, Langmuir-Freundlich, Temkin, and Dubinin-Radushkevich. The kinetic results showed that the pseudo second order kinetic model was found to correlate the experimental data well. The results indicate that adsorption of Cu(II), Zn(II), Cd(II), and Pb(II) as well as U(VI) ions is strongly dependent on pH. The value of pH 4-7 was optimal adsorption. The time to reach the equilibrium was found to be 24 h, and after this time, the sorption percentage reached about 70%. Kinetics of Cu(II), Zn(II), Cd(II), Pb(II), and U(VI) adsorption on the adsorbent can be described by the pseudo second order rate equation. Nitrogen adsorption/desorption, infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) measurements for adsorbent characterization were performed. Characteristic points of the double layer determined for the studied Pyrolox™ sample in 0.001 mol/dm3 NaCl solution are pHPZC = 4 and pHIEP < 2.

  15. Metal Ions Removal Using Nano Oxide Pyrolox™ Material.

    PubMed

    Gładysz-Płaska, A; Skwarek, E; Budnyak, T M; Kołodyńska, D

    2017-12-01

    The paper presents the use of Pyrolox™ containing manganese nano oxides used for the removal of Cu(II), Zn(II), Cd(II), and Pb(II) as well as U(VI) ions. Their concentrations were analyzed using the atomic absorption spectrometer SpectrAA 240 FS (Varian) as well as UV-vis method. For this purpose the static kinetic and equilibrium studies were carried out using the batch technique. The effect of solution pH, shaking time, initial metal ion concentrations, sorbent dosage, and temperature was investigated. The equilibrium data were analyzed using the sorption isotherm models proposed by Freundlich, Langmuir-Freundlich, Temkin, and Dubinin-Radushkevich. The kinetic results showed that the pseudo second order kinetic model was found to correlate the experimental data well. The results indicate that adsorption of Cu(II), Zn(II), Cd(II), and Pb(II) as well as U(VI) ions is strongly dependent on pH. The value of pH 4-7 was optimal adsorption. The time to reach the equilibrium was found to be 24 h, and after this time, the sorption percentage reached about 70%. Kinetics of Cu(II), Zn(II), Cd(II), Pb(II), and U(VI) adsorption on the adsorbent can be described by the pseudo second order rate equation. Nitrogen adsorption/desorption, infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) measurements for adsorbent characterization were performed. Characteristic points of the double layer determined for the studied Pyrolox™ sample in 0.001 mol/dm(3) NaCl solution are pHPZC = 4 and pHIEP < 2.

  16. Influence of metal ion complexation on the metastable fragmentation of DNA hexamers

    NASA Astrophysics Data System (ADS)

    Piekarczyk, Andreas; Bald, Ilko; Flosadóttir, Helga D.; Ómarsson, Benedikt; Lafosse, Anne; Ingólfsson, Oddur

    2014-06-01

    Here, we study the metastable decay of 5'-d(TTGCTT) in the presence of 0-6 alkaline metal ions (Li+, Na+, K+, Rb+) and 0-3 alkaline earth metal ions (Mg2+ and Ca2 +), which replace the corresponding number of protons in the oligonucleotide. We find that all ions studied here stabilize the oligonucleotide with respect to simple 3'-C-O backbone cleavage, but at the same time these metal ions promote a central oligonucleotide deletion accompanied by a concomitant recombination of the terminal d(TT) groups. We find that the quenching of the 3'-C-O backbone cleavage is not ion specific, since it is due to the removal of the phosphate protons upon replacement with the respective metal ions. The central nucleotide deletion competes with the 3'-C-O backbone cleavage channels and is thus promoted through the replacement of the exchangeable protons against metal ions. However, with increasing positive charge density of the metal ions the yield of the central nucleotide deletion further increases. We attribute this effect to the necessity of sufficient proximity of the terminal d(TT) group to allow for their recombination on this reaction path. Hence, the formation of a reactive conformer is mediated by the metal ions.

  17. Structural and mechanistic basis of proton-coupled metal ion transport in the SLC11/NRAMP family

    PubMed Central

    Ehrnstorfer, Ines A.; Manatschal, Cristina; Arnold, Fabian M.; Laederach, Juerg; Dutzler, Raimund

    2017-01-01

    Secondary active transporters of the SLC11/NRAMP family catalyse the uptake of iron and manganese into cells. These proteins are highly conserved across all kingdoms of life and thus likely share a common transport mechanism. Here we describe the structural and functional properties of the prokaryotic SLC11 transporter EcoDMT. Its crystal structure reveals a previously unknown outward-facing state of the protein family. In proteoliposomes EcoDMT mediates proton-coupled uptake of manganese at low micromolar concentrations. Mutants of residues in the transition-metal ion-binding site severely affect transport, whereas a mutation of a conserved histidine located near this site results in metal ion transport that appears uncoupled to proton transport. Combined with previous results, our study defines the conformational changes underlying transition-metal ion transport in the SLC11 family and it provides molecular insight to its coupling to protons. PMID:28059071

  18. Structural and mechanistic basis of proton-coupled metal ion transport in the SLC11/NRAMP family.

    PubMed

    Ehrnstorfer, Ines A; Manatschal, Cristina; Arnold, Fabian M; Laederach, Juerg; Dutzler, Raimund

    2017-01-06

    Secondary active transporters of the SLC11/NRAMP family catalyse the uptake of iron and manganese into cells. These proteins are highly conserved across all kingdoms of life and thus likely share a common transport mechanism. Here we describe the structural and functional properties of the prokaryotic SLC11 transporter EcoDMT. Its crystal structure reveals a previously unknown outward-facing state of the protein family. In proteoliposomes EcoDMT mediates proton-coupled uptake of manganese at low micromolar concentrations. Mutants of residues in the transition-metal ion-binding site severely affect transport, whereas a mutation of a conserved histidine located near this site results in metal ion transport that appears uncoupled to proton transport. Combined with previous results, our study defines the conformational changes underlying transition-metal ion transport in the SLC11 family and it provides molecular insight to its coupling to protons.

  19. Porous metal oxide microspheres from ion exchange resin

    NASA Astrophysics Data System (ADS)

    Picart, S.; Parant, P.; Caisso, M.; Remy, E.; Mokhtari, H.; Jobelin, I.; Bayle, J. P.; Martin, C. L.; Blanchart, P.; Ayral, A.; Delahaye, T.

    2015-07-01

    This study is devoted to the synthesis and the characterization of porous metal oxide microsphere from metal loaded ion exchange resin. Their application concerns the fabrication of uranium-americium oxide pellets using the powder-free process called Calcined Resin Microsphere Pelletization (CRMP). Those mixed oxide ceramics are one of the materials envisaged for americium transmutation in sodium fast neutron reactors. The advantage of such microsphere precursor compared to classical oxide powder is the diminution of the risk of fine dissemination which can be critical for the handling of highly radioactive powders such as americium based oxides and the improvement of flowability for the filling of compaction chamber. Those millimetric oxide microspheres incorporating uranium and americium were synthesized and characterizations showed a very porous microstructure very brittle in nature which occurred to be adapted to shaping by compaction. Studies allowed to determine an optimal heat treatment with calcination temperature comprised between 700-800 °C and temperature rate lower than 2 °C/min. Oxide Precursors were die-pressed into pellets and then sintered under air to form regular ceramic pellets of 95% of theoretical density (TD) and of homogeneous microstructure. This study validated thus the scientific feasibility of the CRMP process to prepare bearing americium target in a powder free manner.

  20. Reactions of metal ions at surfaces of hydrous iron oxide

    USGS Publications Warehouse

    Hem, J.D.

    1977-01-01

    Cu, Ag and Cr concentrations in natural water may be lowered by mild chemical reduction involving ferric hydroxide-ferrous ion redox processes. V and Mo solubilities may be controlled by precipitation of ferrous vanadate or molybdate. Concentrations as low as 10-8.00 or 10-9.00 M are readily attainable for all these metals in oxygen-depleted systems that are relatively rich in Fe. Deposition of manganese oxides such as Mn3O4 can be catalyzed in oxygenated water by coupling to ferrous-ferric redox reactions. Once formed, these oxides may disproportionate, giving Mn4+ oxides. This reaction produces strongly oxidizing conditions at manganese oxide surfaces. The solubility of As is significantly influenced by ferric iron only at low pH. Spinel structures such as chromite or ferrites of Cu, Ni, and Zn, are very stable and if locally developed on ferric hydroxide surfaces could bring about solubilities much below 10-9.00 M for divalent metals near neutral pH. Solubilities calculated from thermodynamic data are shown graphically and compared with observed concentrations in some natural systems. ?? 1977.

  1. Analysis of Supercritical-Extracted Chelated Metal Ions From Mixed Organic-Inorganic Samples

    NASA Technical Reports Server (NTRS)

    Sinha, Mahadeva P. (Inventor)

    1996-01-01

    Organic and inorganic contaminants of an environmental sample are analyzed by the same GC-MS instrument by adding an oxidizing agent to the sample to oxidize metal or metal compounds to form metal ions. The metal ions are converted to chelate complexes and the chelate complexes are extracted into a supercritical fluid such as CO2. The metal chelate extract after flowing through a restrictor tube is directly injected into the ionization chamber of a mass spectrometer, preferably containing a refractory metal filament such as rhenium to fragment the complex to release metal ions which are detected. This provides a fast, economical method for the analysis of metal contaminants in a sample and can be automated. An organic extract of the sample in conventional or supercritical fluid solvents can be detected in the same mass spectrometer, preferably after separation in a supercritical fluid chromatograph.

  2. Fe(III)-based metal-organic framework-derived core-shell nanostructure: Sensitive electrochemical platform for high trace determination of heavy metal ions.

    PubMed

    Zhang, Zhihong; Ji, Hongfei; Song, Yingpan; Zhang, Shuai; Wang, Minghua; Jia, Changchang; Tian, Jia-Yue; He, Linghao; Zhang, Xiaojing; Liu, Chun-Sen

    2017-03-07

    A new core-shell nanostructured composite composed of Fe(III)-based metal-organic framework (Fe-MOF) and mesoporous Fe3O4@C nanocapsules (denoted as Fe-MOF@mFe3O4@mC) was synthesized and developed as a platform for determining trace heavy metal ions in aqueous solution. Herein, the mFe3O4@mC nanocapsules were prepared by calcining the hollow Fe3O4@C that was obtained using the SiO2 nanoparticles as the template, followed by composing the Fe-MOF. The Fe-MOF@mFe3O4@mC nanocomposite demonstrated excellent electrochemical activity, water stability and high specific surface area, consequently resulting in the strong biobinding with heavy-metal-ion-targeted aptamer strands. Furthermore, by combining the conformational transition interaction, which is caused by the formation of the G-quadruplex between a single-stranded aptamer and high adsorbed amounts of heavy metal ions, the developed aptasensor exhibited a good linear relationship with the logarithm of heavy metal ion (Pb(2+) and As(3+)) concentration over the broad range from 0.01 to 10.0nM. The detection limits were estimated to be 2.27 and 6.73 pM toward detecting Pb(2+) and As(3+), respectively. The proposed aptasensor showed good regenerability, excellent selectivity, and acceptable reproducibility, suggesting promising applications in environment monitoring and biomedical fields.

  3. Formulation and Evaluation of Antibacterial Creams and Gels Containing Metal Ions for Topical Application

    PubMed Central

    Chen, Mei X.; Alexander, Kenneth S.

    2016-01-01

    Background. Skin infections occur commonly and often present therapeutic challenges to practitioners due to the growing concerns regarding multidrug-resistant bacterial, viral, and fungal strains. The antimicrobial properties of zinc sulfate and copper sulfate are well known and have been investigated for many years. However, the synergistic activity between these two metal ions as antimicrobial ingredients has not been evaluated in topical formulations. Objective. The aims of the present study were to (1) formulate topical creams and gels containing zinc and copper alone or in combination and (2) evaluate the in vitro antibacterial activity of these metal ions in the formulations. Method. Formulation of the gels and creams was followed by evaluating their organoleptic characteristics, physicochemical properties, and in vitro antibacterial activity against Escherichia coli and Staphylococcus aureus. Results. Zinc sulfate and copper sulfate had a strong synergistic antibacterial activity in the creams and gels. The minimum effective concentration was found to be 3 w/w% for both active ingredients against the two tested microorganisms. Conclusions. This study evaluated and confirmed the synergistic in vitro antibacterial effect of copper sulfate and zinc sulfate in a cream and two gels. PMID:27885352

  4. Post-synthesis addition of transition metal ions and lanthanide ions to the surface of anatase titanium (IV) dioxide nanorods

    NASA Astrophysics Data System (ADS)

    Balasanthiran, Choumini

    Solar energy utilization is an attractive option for new energy technology and economic development. Our research is the formulation of catalyst materials for solar production of hydrogen from water. Titanium(IV) oxide has been explored for water splitting; however, a major challenge is that titanium(IV) oxide can only absorb UV light. Visible light absorption can be increased by metal ion or anion doping by creating interband states. Most dopant protocols lead to deposition of dopant ions throughout the solid, and interfacial deposition has received very little attention. We have developed a method to selectively attach transition metal ions and lanthanide ions on the surface of titanium(IV) oxide nanorods using metal chlorides as precursors. The present study demonstrates that Cr(III), Mn(II), Fe(II), Co(II), Ni(II), Cu (II), Eu(III), Ce(III), Pr(III) and Er(III) were coordinated to the surface of oleic acid capped TiO2 nanorods (NRs) by post-synthesis method without any phase or morphology transformation. Metal ion loading could be carefully controlled, and we show a titration curve for addition of transition metal ions and Eu(III) to the nanorod surface. The materials were characterized with UV-visible spectroscopy, transmission electron microscopy, elemental analysis, XPS and powder X-ray diffraction. X-ray photoelectron spectra were obtained for a series of M-TiO2 samples in which transition metal (M = Cr, Mn, Fe, Co, Ni, Cu) ions are directly attached to the surface of anatase TiO2 nanocrystals. Further, we report sequential, quantitative loading of transition metal ions (Cr, Mn, Fe, Co, Ni, Cu) to the surface of rod-shape anatase TiO2 nanocrystals in bimetallic combinations (6C2 = 15). TEM, PXRD, UV-Vis, XPS and elemental analysis characterization show that bimetallic combinations were synthesized successfully.

  5. Highly active oxygen reduction non-platinum group metal electrocatalyst without direct metal-nitrogen coordination.

    PubMed

    Strickland, Kara; Miner, Elise; Jia, Qingying; Tylus, Urszula; Ramaswamy, Nagappan; Liang, Wentao; Sougrati, Moulay-Tahar; Jaouen, Frédéric; Mukerjee, Sanjeev

    2015-06-10

    Replacement of noble metals in catalysts for cathodic oxygen reduction reaction with transition metals mostly create active sites based on a composite of nitrogen-coordinated transition metal in close concert with non-nitrogen-coordinated carbon-embedded metal atom clusters. Here we report a non-platinum group metal electrocatalyst with an active site devoid of any direct nitrogen coordination to iron that outperforms the benchmark platinum-based catalyst in alkaline media and is comparable to its best contemporaries in acidic media. In situ X-ray absorption spectroscopy in conjunction with ex situ microscopy clearly shows nitrided carbon fibres with embedded iron particles that are not directly involved in the oxygen reduction pathway. Instead, the reaction occurs primarily on the carbon-nitrogen structure in the outer skin of the nitrided carbon fibres. Implications include the potential of creating greater active site density and the potential elimination of any Fenton-type process involving exposed iron ions culminating in peroxide initiated free-radical formation.

  6. Calcium-independent metal-ion catalytic mechanism of anthrax edema factor

    SciTech Connect

    Shen, Yuequan; Zhukovskaya, Natalia L.; Guo, Qing; Florián, Jan; Tang, Wei-Jen

    2009-11-18

    Edema factor (EF), a key anthrax exotoxin, has an anthrax protective antigen-binding domain (PABD) and a calmodulin (CaM)-activated adenylyl cyclase domain. Here, we report the crystal structures of CaM-bound EF, revealing the architecture of EF PABD. CaM has N- and C-terminal domains and each domain can bind two calcium ions. Calcium binding induces the conformational change of CaM from closed to open. Structures of the EF-CaM complex show how EF locks the N-terminal domain of CaM into a closed conformation regardless of its calcium-loading state. This represents a mechanism of how CaM effector alters the calcium affinity of CaM and uncouples the conformational change of CaM from calcium loading. Furthermore, structures of EF-CaM complexed with nucleotides show that EF uses two-metal-ion catalysis, a prevalent mechanism in DNA and RNA polymerases. A histidine (H351) further facilitates the catalysis of EF by activating a water to deprotonate 3'OH of ATP. Mammalian adenylyl cyclases share no structural similarity with EF and they also use two-metal-ion catalysis, suggesting the catalytic mechanism-driven convergent evolution of two structurally diverse adenylyl cyclases.

  7. Metal-clad optical waveguide fluorescence device for the detection of heavy metal ions

    NASA Astrophysics Data System (ADS)

    Margheri, Giancarlo; Giorgetti, Emilia; Marsili, Paolo; Zoppi, Angela; Lascialfari, Luisa; Cicchi, Stefano

    2014-07-01

    We developed Hg-sensing chips by decorating the external surface of metal-clad optical waveguides with a monolayer of Hg-sensitive fluorescent molecular probes. The emission properties of the original water-soluble form of the molecule were previously found to be selectively quenched in the presence of Hg ions. The fabricated samples were tested with optical waveguide fluorescence spectroscopy by putting them in contact with a 5-μM water solution of Hg ions and recording the emission spectra versus incubation time. The estimate of the limit of detection was 150 nM. A preliminary evaluation of the selectivity of the structure was also performed by using Cd as possible interfering analytes.

  8. Probing oxidative stress: Small molecule fluorescent sensors of metal ions, reactive oxygen species, and thiols

    PubMed Central

    Hyman, Lynne M.; Franz, Katherine J.

    2013-01-01

    Oxidative stress is a common feature shared by many diseases, including neurodegenerative diseases. Factors that contribute to cellular oxidative stress include elevated levels of reactive oxygen species, diminished availability of detoxifying thiols, and the misregulation of metal ions (both redox-active iron and copper as well as non-redox active calcium and zinc). Deciphering how each of these components interacts to contribute to oxidative stress presents an interesting challenge. Fluorescent sensors can be powerful tools for detecting specific analytes within a complicated cellular environment. Reviewed here are several classes of small molecule fluorescent sensors designed to detect several molecular participants of oxidative stress. We focus our review on describing the design, function and application of probes to detect metal cations, reactive oxygen species, and intracellular thiol-containing compounds. In addition, we highlight the intricacies and complications that are often faced in sensor design and implementation. PMID:23440254

  9. Tuned by metals: the TET peptidase activity is controlled by 3 metal binding sites.

    PubMed

    Colombo, Matteo; Girard, Eric; Franzetti, Bruno

    2016-02-08

    TET aminopeptidases are dodecameric particles shared in the three life domains involved in various biological processes, from carbon source provider in archaea to eye-pressure regulation in humans. Each subunit contains a dinuclear metal site (M1 and M2) responsible for the enzyme catalytic activity. However, the role of each metal ion is still uncharacterized. Noteworthy, while mesophilic TETs are activated by Mn(2+), hyperthermophilic TETs prefers Co(2+). Here, by means of anomalous x-ray crystallography and enzyme kinetics measurements of the TET3 aminopeptidase from the hyperthermophilic organism Pyrococcus furiosus (PfTET3), we show that M2 hosts the catalytic activity of the enzyme, while M1 stabilizes the TET3 quaternary structure and controls the active site flexibility in a temperature dependent manner. A new third metal site (M3) was found in the substrate binding pocket, modulating the PfTET3 substrate preferences. These data show that TET activity is tuned by the molecular interplay among three metal sites.

  10. Multiheteromacrocycles that Complex Metal Ions. Sixth Progress Report, 1 May 1979-30 April 1980

    DOE R&D Accomplishments Database

    Cram, D. J.

    1980-01-15

    Objective is to design synthesize, and evaluate cyclic and polycyclic host organic compounds for their abilities to complex and lipophilize guest metal ions, their complexes, and their clusters. Host organic compounds consist of strategically placed solvating, coordinating, and ion-pairing sites tied together by covalent bonds through hydrocarbon units around cavities shaped to be occupied by guest metal ions or by metal ions plus their ligands. Specificity in complexation is sought by matching the following properties of host and guest: cavity and metal ion sizes; geometric arrangements of binding sites; number of binding sites; character of binding sites; and valences. During this period, hemispherands based on an aryloxy or cyclic urea unit, spherands based on aryloxyl units only, and their complexes with alkali metals and alkaline earths were investigated. An attempt to separate {sup 6}Li and {sup 7}Li by gel permeation chromatography of lithiospherium chloride failed. (DLC)

  11. A fluorometric paper-based sensor array for the discrimination of heavy-metal ions.

    PubMed

    Feng, Liang; Li, Hui; Niu, Li-Ya; Guan, Ying-Shi; Duan, Chun-Feng; Guan, Ya-Feng; Tung, Chen-Ho; Yang, Qing-Zheng

    2013-04-15

    A fluorometric paper-based sensor array has been developed for the sensitive and convenient determination of seven heavy-metal ions at their wastewater discharge standard concentrations. Combining with nine cross-reactive BODIPY fluorescent indicators and array technologies-based pattern-recognition, we have obtained the discrimination capability of seven different heavy-metal ions at their wastewater discharge standard concentrations. After the immobilization of indicators and the enrichment of analytes, identification of the heavy-metal ions was readily acquired using a standard chemometric approach. Clear differentiation among heavy-metal ions as a function of concentration was also achieved, even down to 10(-7)M. A semi-quantitative estimation of the heavy-metal ion concentration was obtained by comparing color changes with a set of known concentrations. The sensor array was tentatively investigated in spiked tap water and sea water, and showed possible feasibility for real sample testing.

  12. An artificial tongue fluorescent sensor array for identification and quantitation of various heavy metal ions.

    PubMed

    Xu, Wang; Ren, Changliang; Teoh, Chai Lean; Peng, Juanjuan; Gadre, Shubhankar Haribhau; Rhee, Hyun-Woo; Lee, Chi-Lik Ken; Chang, Young-Tae

    2014-09-02

    Herein, a small-molecule fluorescent sensor array for rapid identification of seven heavy metal ions was designed and synthesized, with its sensing mechanism mimicking that of a tongue. The photoinduced electron transfer and intramolecular charge transfer mechanism result in combinatorial interactions between sensor array and heavy metal ions, which lead to diversified fluorescence wavelength shifts and emission intensity changes. Upon principle component analysis (PCA), this result renders clear identification of each heavy metal ion on a 3D spatial dispersion graph. Further exploration provides a concentration-dependent pattern, allowing both qualitative and quantitative measurements of heavy metal ions. On the basis of this information, a "safe-zone" concept was proposed, which provides rapid exclusion of versatile hazardous species from clean water samples based on toxicity characteristic leaching procedure standards. This type of small-molecule fluorescent sensor array could open a new avenue for multiple heavy metal ion detection and simplified water quality analysis.

  13. Protein-responsive assemblies from catechol-metal ion supramolecular coordination.

    PubMed

    Yuan, C; Chen, J; Yu, S; Chang, Y; Mao, J; Xu, Y; Luo, W; Zeng, B; Dai, L

    2015-03-21

    Supramolecular self-assembly driven by catechol-metal ion coordination has gained great success in the fabrication of functional materials including adhesives, capsules, coatings and hydrogels. However, this route has encountered a great challenge in the construction of nanoarchitectures in the absence of removable templates, because of the uncontrollable crosslinking of catechol-metal ion coordination. Herein, we show that a supramolecular approach, combining both catechol-metal ion coordination and polymer self-assembly together, can organize polymers into hybrid nanoassemblies ranging from solid particles, homogeneous vesicles to Janus vesicles. Without the introduction of a specific binding ligand or complicated molecular design, these assemblies can totally disassemble in response to proteins. UV/vis absorption, fluorescence quenching and recovery investigations have confirmed that proteins can seize metal ions from the hybrid nanoassemblies, thus causing the degradation of catechol-metal ion coordination networks.

  14. Bioleaching of valuable metals from spent lithium-ion mobile phone batteries using Aspergillus niger

    NASA Astrophysics Data System (ADS)

    Horeh, N. Bahaloo; Mousavi, S. M.; Shojaosadati, S. A.

    2016-07-01

    In this paper, a bio-hydrometallurgical route based on fungal activity of Aspergillus niger was evaluated for the detoxification and recovery of Cu, Li, Mn, Al, Co and Ni metals from spent lithium-ion phone mobile batteries under various conditions (one-step, two-step and spent medium bioleaching). The maximum recovery efficiency of 100% for Cu, 95% for Li, 70% for Mn, 65% for Al, 45% for Co, and 38% for Ni was obtained at a pulp density of 1% in spent medium bioleaching. The HPLC results indicated that citric acid in comparison with other detected organic acids (gluconic, oxalic and malic acid) had an important role in the effectiveness of bioleaching using A. niger. The results of FTIR, XRD and FE-SEM analysis of battery powder before and after bioleaching process confirmed that the fungal activities were quite effective. In addition, bioleaching achieved higher removal efficiency for heavy metals than the chemical leaching. This research demonstrated the great potential of bio-hydrometallurgical route to recover heavy metals from spent lithium-ion mobile phone batteries.

  15. Sunflower stalks as adsorbents for the removal of metal ions from wastewater

    SciTech Connect

    Sun, G.; Shi, W.

    1998-04-01

    Sunflower stalks as adsorbents for the removal of metal ions such as copper, cadmium, zinc, and chromium ions in aqueous solutions were studied with equilibrium isotherms and kinetic adsorptions. The maximum adsorptions of four heavy metals are 29.3 mg/g (Cu{sup 2+}), 30.73 mg/g (Zn{sup 2+}), 42.18 mg/g (Cd{sup 2+}), and 25.07 mg/g (Cr{sup 3+}), respectively. Particle sizes of sunflower stalks affected the adsorption of metal ions; the finer size of particles showed better adsorption to the ions. Temperature also plays an interesting role in the adsorption of different metal ions. Copper, zinc, and cadmium exhibited lower adsorption on sunflower stalks at higher temperature, while chromium showed the opposite phenomenon. The adsorption rates of copper, cadmium, and chromium are quite rapid. Within 60 min of operation about 60--80% of these ions were removed from the solutions.

  16. Metal ion transport quantified by ICP-MS in intact cells.

    PubMed

    Figueroa, Julio A Landero; Stiner, Cory A; Radzyukevich, Tatiana L; Heiny, Judith A

    2016-02-03

    The use of ICP-MS to measure metal ion content in biological tissues offers a highly sensitive means to study metal-dependent physiological processes. Here we describe the application of ICP-MS to measure membrane transport of Rb and K ions by the Na,K-ATPase in mouse skeletal muscles and human red blood cells. The ICP-MS method provides greater precision and statistical power than possible with conventional tracer flux methods. The method is widely applicable to studies of other metal ion transporters and metal-dependent processes in a range of cell types and conditions.

  17. Metal ion transport quantified by ICP-MS in intact cells

    PubMed Central

    Figueroa, Julio A. Landero; Stiner, Cory A.; Radzyukevich, Tatiana L.; Heiny, Judith A.

    2016-01-01

    The use of ICP-MS to measure metal ion content in biological tissues offers a highly sensitive means to study metal-dependent physiological processes. Here we describe the application of ICP-MS to measure membrane transport of Rb and K ions by the Na,K-ATPase in mouse skeletal muscles and human red blood cells. The ICP-MS method provides greater precision and statistical power than possible with conventional tracer flux methods. The method is widely applicable to studies of other metal ion transporters and metal-dependent processes in a range of cell types and conditions. PMID:26838181

  18. Method for forming metallic silicide films on silicon substrates by ion beam deposition

    DOEpatents

    Zuhr, Raymond A.; Holland, Orin W.

    1990-01-01

    Metallic silicide films are formed on silicon substrates by contacting the substrates with a low-energy ion beam of metal ions while moderately heating the substrate. The heating of the substrate provides for the diffusion of silicon atoms through the film as it is being formed to the surface of the film for interaction with the metal ions as they contact the diffused silicon. The metallic silicide films provided by the present invention are contaminant free, of uniform stoichiometry, large grain size, and exhibit low resistivity values which are of particular usefulness for integrated circuit production.

  19. The involvement of transition metal ions on iron-dependent lipid peroxidation.

    PubMed

    Repetto, Marisa G; Ferrarotti, Nidia F; Boveris, Alberto

    2010-04-01

    The metals iron (Fe) and copper (Cu) are considered trace elements, and the metals cobalt (Co) and nickel (Ni) are known as ultra-trace elements, considering their presence in low to very low quantity in humans. The biologic activity of these transition metals is associated with the presence of unpaired electrons that favor their participation in redox reactions. They are part of important enzymes involved in vital biologic processes. However, these transition metals become toxic to cells when they reach elevated tissue concentrations and produce cellular oxidative damage. Phospholipid liposomes (0.5 mg/ml, phosphatidylcholine (PC)/phosphatidylserine (PS), 60/40) were incubated for 60 min at 37 degrees C with 25 microM of Fe2+ in the absence and in the presence of Cu2+, Co2+, and Ni2+ (0-100 microM) with and without the addition of hydrogen peroxide (H2O2, 5-50 microM). Iron-dependent lipid peroxidation in PC/PS liposomes was assessed by thiobarbituric acid-reactive substances (TBARS) production. Metal transition ions promoted lipid peroxidation by H2O2 decomposition and direct homolysis of endogenous hydroperoxides. The Fe2+-H2O2-mediated lipid peroxidation takes place by a pseudo-second order process, and the Cu2+-mediated process by a pseudo-first order reaction. Co2+ and Ni2+ alone do not induce lipid peroxidation. Nevertheless, when they are combined with Fe2+, Fe2+-H2O2-mediated lipid peroxidation was stimulated in the presence of Ni2+ and was inhibited in the presence of Co2+. The understanding of the effects of transition metal ions on phospholipids is relevant to the prevention of oxidative damage in biologic systems.

  20. Ion conductivity and transport by porous coordination polymers and metal-organic frameworks.

    PubMed

    Horike, Satoshi; Umeyama, Daiki; Kitagawa, Susumu

    2013-11-19

    Ion conduction and transport in solids are both interesting and useful and are found in widely distinct materials, from those in battery-related technologies to those in biological systems. Scientists have approached the synthesis of ion-conductive compounds in a variety of ways, in the areas of organic and inorganic chemistry. Recently, based on their ion-conducting behavior, porous coordination polymers (PCPs) and metal-organic frameworks (MOFs) have been recognized for their easy design and the dynamic behavior of the ionic components in the structures. These PCP/MOFs consist of metal ions (or clusters) and organic ligands structured via coordination bonds. They could have highly concentrated mobile ions with dynamic behavior, and their characteristics have inspired the design of a new class of ion conductors and transporters. In this Account, we describe the state-of-the-art of studies of ion conductivity by PCP/MOFs and nonporous coordination polymers (CPs) and offer future perspectives. PCP/MOF structures tend to have high hydrophilicity and guest-accessible voids, and scientists have reported many water-mediated proton (H(+)) conductivities. Chemical modification of organic ligands can change the hydrated H(+) conductivity over a wide range. On the other hand, the designable structures also permit water-free (anhydrous) H(+) conductivity. The incorporation of protic guests such as imidazole and 1,2,4-triazole into the microchannels of PCP/MOFs promotes the dynamic motion of guest molecules, resulting in high H(+) conduction without water. Not only the host-guest systems, but the embedding of protic organic groups on CPs also results in inherent H(+) conductivity. We have observed high H(+) conductivities under anhydrous conditions and in the intermediate temperature region of organic and inorganic conductors. The keys to successful construction are highly mobile ionic species and appropriate intervals of ion-hopping sites in the structures. Lithium (Li

  1. Thio Effects and an Unconventional Metal Ion Rescue in the Genomic HDV Ribozyme§

    PubMed Central

    Thaplyal, Pallavi; Ganguly, Abir; Golden, Barbara L.; Hammes-Schiffer, Sharon; Bevilacqua, Philip C.

    2013-01-01

    Metal ion and nucleobase catalysis are important for ribozyme mechanism, but the extent to which they cooperate is unclear. A crystal structure of the hepatitis delta virus (HDV) ribozyme suggested that the pro-RP oxygen at the scissile phosphate directly coordinates a catalytic Mg2+ ion and is within hydrogen bonding distance of the amine of the general acid C75. Prior studies on the genomic HDV ribozyme, however, showed neither a thio effect nor metal ion rescue using Mn2+. Here, we combine experiment and theory to explore phosphorothioate substitutions at the scissile phosphate. We report significant thio effects at the scissile phosphate and metal ion rescue with Cd2+. Reaction profiles with an SP-phosphorothioate substitution are indistinguishable from those of the unmodified substrate in the presence of Mg2+ or Cd2+, supporting that the pro-SP oxygen does not coordinate metal ions. The RP-phosphorothioate substitution, however, exhibits biphasic kinetics, with the fast-reacting phase displaying a thio effect of up to 5-fold effect and the slow-reacting phase displaying a thio effect of ~1,000-fold. Moreover, the fast- and slow-reacting phases give metal ion rescues in Cd2+ of up to 10- and 330-fold, respectively. The metal ion rescues are unconventional in that they arise from Cd2+ inhibiting the oxo substrate but not the RP substrate. This metal ion rescue suggests a direct interaction of the catalytic metal ion with the pro-RP oxygen, in line with experiments on the antigenomic HDV ribozyme. Experiments without divalent ions, with mutants that interfere with Mg2+ binding, or with C75 deleted suggest that the pro-RP oxygen plays at most a redundant role in positioning C75. Quantum mechanical/molecular mechanical (QM/MM) studies indicate that the metal ion contributes to catalysis by interacting with both the pro-RP oxygen and the nucleophilic 2’- hydroxyl, supporting the experimental findings. PMID:24001219

  2. Multidiagnostics analysis of ion dynamics in ultrafast laser ablation of metals over a large fluence range

    SciTech Connect

    Anoop, K. K.; Polek, M. P.; Bruzzese, R.; Amoruso, S.; Harilal, Sivanandan S.

    2015-02-28

    The ions dynamics in ultrafast laser ablation of metals is studied over a fluence range spanning from the ablation threshold up to ~75 J/cm2 by means of three established diagnostic techniques. Langmuir probe, Faraday cup and spectrally resolved ICCD imaging simultaneously monitor the laser-produced plasma ions produced during ultrafast laser ablation of a copper target. The fluence dependence of ion yield is analyzed observing the occurrence of three different regimes. Moreover, the specific ion yield shows a maximum at about 4-5 J/cm2, followed by a gradual reduction and a transition to a high-fluence regime above ~50 J/cm2. The fluence variation of the copper ions angular distribution is also analyzed, observing a gradual increase of forward peaking of Cu ions for fluences up to ~10 J/cm2. Then, a broader ion component is observed at larger angles for fluences larger than ~10 J/cm2. Finally, an experimental characterization of the ions angular distribution for several metallic targets (Mg, Al, Cr, Fe, Cu, and W) is carried out at a relatively high fluence of ~66 J/cm2. Interestingly, the ion emission from the volatile metals show a narrow forward peaked distribution and a high peak ion yield compared to the refractory metals. Moreover, the width of ion angular distributions presents a striking correlation with the peak ion yield.

  3. Thermal Hazard Evaluation of Cumene Hydroperoxide-Metal Ion Mixture Using DSC, TAM III, and GC/MS.

    PubMed

    You, Mei-Li

    2016-04-28

    Cumene hydroperoxide (CHP) is widely used in chemical processes, mainly as an initiator for the polymerization of acrylonitrile-butadiene-styrene. It is a typical organic peroxide and an explosive substance. It is susceptible to thermal decomposition and is readily affected by contamination; moreover, it has high thermal sensitivity. The reactor tank, transit storage vessel, and pipeline used for manufacturing and transporting this substance are made of metal. Metal containers used in chemical processes can be damaged through aging, wear, erosion, and corrosion; furthermore, the containers might release metal ions. In a metal pipeline, CHP may cause incompatibility reactions because of catalyzed exothermic reactions. This paper discusses and elucidates the potential thermal hazard of a mixture of CHP and an incompatible material's metal ions. Differential scanning calorimetry (DSC) and thermal activity monitor III (TAM III) were employed to preliminarily explore and narrate the thermal hazard at the constant temperature environment. The substance was diluted and analyzed by using a gas chromatography spectrometer (GC) and gas chromatography/mass spectrometer (GC/MS) to determine the effect of thermal cracking and metal ions of CHP. The thermokinetic parameter values obtained from the experiments are discussed; the results can be used for designing an inherently safer process. As a result, the paper finds that the most hazards are in the reaction of CHP with Fe(2+). When the metal release is exothermic in advance, the system temperature increases, even leading to uncontrollable levels, and the process may slip out of control.

  4. Importance of diffuse metal ion binding to RNA.

    PubMed

    Tan, Zhi-Jie; Chen, Shi-Jie

    2011-01-01

    RNAs are highly charged polyanionic molecules. RNA structure and function are strongly correlated with the ionic condition of the solution. The primary focus of this article is on the role of diffusive ions in RNA folding. Due to the long-range nature of electrostatic interactions, the diffuse ions can contribute significantly to RNA structural stability and folding kinetics. We present an overview of the experimental findings as well as the theoretical developments on the diffuse ion effects in RNA folding. This review places heavy emphasis on the effect of magnesium ions. Magnesium ions play a highly efficient role in stabilizing RNA tertiary structures and promoting tertiary structural folding. The highly efficient role goes beyond the mean-field effect such as the ionic strength. In addition to the effects of specific ion binding and ion dehydration, ion-ion correlation for the diffuse ions can contribute to the efficient role of the multivalent ions such as the magnesium ions in RNA folding.

  5. Catalytic activity of rhodium complex immobilized on AN-31 ion exchanger

    SciTech Connect

    Parshikova, G.N.; Korneva, L.I.; Kononov, Yu.S.

    1995-08-10

    Immobilized platinum-metal complexes are of interest as heterogeneous catalysts. Ion-exchange resins may be used as supports for catalytically active complexes. However, immobilized metal complexes are often unstable, are washed out from supports, and are lost with reaction products. Secure immobilization of metal complexes on supports is possible, for example, via coordination of the central metal by electron-donor groups of the support. This is the case when platinum metals are sorbed from solutions by nitrogen-containing ion exchangers. Complexes thus immobilized have high catalytic activity. Previously the authors demonstrated that rhodium(III) is sorbed from solutions containing rhodium aqua-chloro complexes as stable complexes with AN-31. These complexes were not desorbed with 10 M hydrochloric acid. Stable amino complexes of transition metals sorbed on ion exchangers are known to be active in decomposition of hydrogen peroxide. In this work, the authors have studied catalytic properties of rhodium complex with the ion exchanger under atmospheric pressure at 25-80{degrees}C.

  6. [Hydrogen ion activity in the cell].

    PubMed

    Sorokin, Z A

    1976-07-01

    Literature data and results of our experiments evidence for a heterogenous hydrogen distribution in cells. Intracellular pH should be regarded as a mean activity of hydrogen ions which is the sum of activities in different phases of a cell. Intracellular pH value does not depend on the transmembrane action potential difference, and is resistant to respiratory and metabolic disorders of acid-base equilibrium in the body. It also slightly changes with changing the electrolyte composition and pH of the medium and is not influenced by metabolic inhibitors. A low hydrogen activity in the cell has a certain functional significance. The pH stability is ensured by a number of regulatory mechanism: the buffer properties of the protoplasm itself, and the active hydrogen transport into the medium. Hydrogen released from cells is supposed to be connected with functioning of a specific respiratory chain of superficial protoplasmic membranes.

  7. A crystallographic study of the binding of 13 metal ions to two related RNA duplexes

    PubMed Central

    Ennifar, Eric; Walter, Philippe; Dumas, Philippe

    2003-01-01

    Metal ions, and magnesium in particular, are known to be involved in RNA folding by stabilizing secondary and tertiary structures, and, as cofactors, in RNA enzymatic activity. We have conducted a systematic crystallographic analysis of cation binding to the duplex form of the HIV-1 RNA dimerization initiation site for the subtype-A and -B natural sequences. Eleven ions (K+, Pb2+, Mn2+, Ba2+, Ca2+, Cd2+, Sr2+, Zn2+, Co2+, Au3+ and Pt4+) and two hexammines [Co (NH3)6]3+ and [Ru (NH3)6]3+ were found to bind to the DIS duplex structure. Although the two sequences are very similar, strong differences were found in their cation binding properties. Divalent cations bind almost exclusively, as Mg2+, at ‘Hoogsteen’ sites of guanine residues, with a cation-dependent affinity for each site. Notably, a given cation can have very different affinities for a priori equivalent sites within the same molecule. Surprisingly, none of the two hexammines used were able to efficiently replace hexahydrated magnesium. Instead, [Co (NH3)4]3+ was seen bound by inner-sphere coordination to the RNA. This raises some questions about the practical use of [Co (NH3)6]3+ as a [Mg (H2O)6]2+ mimetic. Also very unexpected was the binding of the small Au3+ cation exactly between the Watson–Crick sites of a G-C base pair after an obligatory deprotonation of N1 of the guanine base. This extensive study of metal ion binding using X-ray crystallography significantly enriches our knowledge on the binding of middleweight or heavy metal ions to RNA, particularly compared with magnesium. PMID:12736317

  8. Anticancer Activity of Metal Complexes: Involvement of Redox Processes

    PubMed Central

    Jungwirth, Ute; Kowol, Christian R.; Keppler, Bernhard K.; Hartinger, Christian G.; Berger, Walter; Heffeter, Petra

    2012-01-01

    Cells require tight regulation of the intracellular redox balance and consequently of reactive oxygen species for proper redox signaling and maintenance of metal (e.g., of iron and copper) homeostasis. In several diseases, including cancer, this balance is disturbed. Therefore, anticancer drugs targeting the redox systems, for example, glutathione and thioredoxin, have entered focus of interest. Anticancer metal complexes (platinum, gold, arsenic, ruthenium, rhodium, copper, vanadium, cobalt, manganese, gadolinium, and molybdenum) have been shown to strongly interact with or even disturb cellular redox homeostasis. In this context, especially the hypothesis of “activation by reduction” as well as the “hard and soft acids and bases” theory with respect to coordination of metal ions to cellular ligands represent important concepts to understand the molecular modes of action of anticancer metal drugs. The aim of this review is to highlight specific interactions of metal-based anticancer drugs with the cellular redox homeostasis and to explain this behavior by considering chemical properties of the respective anticancer metal complexes currently either in (pre)clinical development or in daily clinical routine in oncology. PMID:21275772

  9. Oxidative degradation of propachlor by ferrous and copper ion activated persulfate.

    PubMed

    Liu, C S; Shih, K; Sun, C X; Wang, F

    2012-02-01

    The process of in situ chemical oxidation (ISCO) by persulfate (S(2)O(8)(2-)) can be accelerated by metal ion activation, which more effectively degrades subsurface pollutants by enhancing sulfate radical (SO(4)(-)) generation. This study compared the results of propachlor degradation by Cu(2+) and Fe(2+) activated persulfate and revealed differing degradation kinetics and mechanisms between the two types of activation system. The activation of persulfate by Fe(2+) ions generally resulted in rapid degradation in the early stage, but was accompanied by a dramatic decrease in efficiency due to the rapid depletion of Fe(2+) by the sulfate radicals generated. In contrast, the Cu(2+) activated persulfate had a longer lasting degradation effect and a proportionally greater degradation enhancement at elevated Cu(2+) concentrations. An optimal Fe(2+) concentration should be sought to activate the persulfate, as a high Fe(2+) concentration of 2.5mM or above, as was used in this study, may inhibit propachlor degradation due to the competitive consumption of sulfate radicals by the excess Fe(2+) ions. Higher temperatures (55°C compared with 30°C) resulted in enhanced metal activation, particularly with the Cu(2+) activated system. Furthermore, acidic conditions were found to be more favorable for propachlor degradation by metal activated persulfate. The ecotoxicity of degraded propachlor samples, which was indicated by average well color development (AWCD) for its microbial community activity, was confirmed to be decreased during the degradation processes with these two ions activated persulfate.

  10. Activation of Autophagy by Metals in Chlamydomonas reinhardtii.

    PubMed

    Pérez-Martín, Marta; Blaby-Haas, Crysten E; Pérez-Pérez, María Esther; Andrés-Garrido, Ascensión; Blaby, Ian K; Merchant, Sabeeha S; Crespo, José L

    2015-09-01

    Autophagy is an intracellular self-degradation pathway by which eukaryotic cells recycle their own material in response to specific stress conditions. Exposure to high concentrations of metals causes cell damage, although the effect of metal stress on autophagy has not been explored in photosynthetic organisms. In this study, we investigated the effect of metal excess on autophagy in the model unicellular green alga Chlamydomonas reinhardtii. We show in cells treated with nickel an upregulation of ATG8 that is independent of CRR1, a global regulator of copper signaling in Chlamydomonas. A similar effect on ATG8 was observed with copper and cobalt but not with cadmium or mercury ions. Transcriptome sequencing data revealed an increase in the abundance of the protein degradation machinery, including that responsible for autophagy, and a substantial overlap of that increased abundance with the hydrogen peroxide response in cells treated with nickel ions. Thus, our results indicate that metal stress triggers autophagy in Chlamydomonas and suggest that excess nickel may cause oxidative damage, which in turn activates degradative pathways, including autophagy, to clear impaired components and recover cellular homeostasis.

  11. Characteristics of the brown hagfish Paramyxine atami transthyretin: metal ion-dependent thyroid hormone binding.

    PubMed

    Suzuki, Shunsuke; Kasai, Kentaro; Nishiyama, Norihito; Ishihara, Akinori; Yamauchi, Kiyoshi

    2017-02-24

    Transthyretin (TTR) is a vertebrate-specific protein involved in thyroid hormone distribution in plasma, and its gene is thought to have emerged by gene duplication from the gene for the ancient TTR-related protein, 5-hydroxyisourate hydrolase, at some early stage of chordate evolution. We investigated the molecular and hormone-binding properties of the brown hagfish Paramyxine atami TTR. The amino acid sequence deduced from the cloned hagfish TTR cDNA shared 33-50% identities with those of other vertebrate TTRs but less than 24% identities with those of vertebrate and deuterostome invertebrate 5-hydroxyisourate hydrolases. Hagfish TTR, as well as lamprey and little skate TTRs, had an N-terminal histidine-rich segment, allowing purification by metal-affinity chromatography. The affinity of hagfish TTR for 3,3',5-triiodo-L-thyronine (T3) was 190 times higher than that for L-thyroxine, with a dissociation constant of 1.5‒3.9 nM at 4°C. The high-affinity binding sites were strongly sensitive to metal ions. Zn(2+) and Cu(2+) decreased the dissociation constant to one-order of magnitude, whereas a chelator, o-phenanthroline, increased it four times. The number of metal ions (mainly Zn(2+) and Cu(2+)) was approximately 12/TTR (mol/mol). TTR was also a major T3-binding protein in adult hagfish sera and its serum concentration was approximately 8 μM. These results suggest that metal ions and the acquisition of N-terminal histidine-rich segment may cooperatively contribute to the evolution toward an ancient TTR with high T3 binding activity from either 5-hydroxyisourate hydrolase after gene duplication.

  12. Interactions of Some Divalent Metal Ions with Thymine and Uracil Thiosemicarbazide Derivatives.

    PubMed

    Hammud, Hassan H; El-Dakdouki, Mohammad H; Sonji, Nada; Sonji, Ghassan; Bouhadir, Kamal H

    2016-05-03

    The study of interactions between metal ions and nucleobases, nucleosides, nucleotides, or nucleic acids has become an active research area in chemical, biological, and therapeutic fields. In this respect, the coordination behavior of nucleobase derivatives to transition metals was studied in order to get a better understanding about DNA-metal interactions in in vitro and in vivo systems. Two nucleobase derivatives, 3-benzoyl-1-[3-(thymine-1-yl)propamido]thiourea and 3-benzoyl-1-[3-(uracil-1-yl)propamido]thiourea, were synthesized and their dissociation constants were determined at different temperatures and 0.3 ionic strength. Potentiometric studies were carried out on the interaction of the derivatives towards some divalent metals in 50% v/v ethanol-water containing 0.3 mol.dm(-3) KCl, at five different temperatures. The formation constants of the metal complexes for both ligands follow the order: Cu(2+) > Ni(2+) > Co(2+) > Zn(2+) > Pb(2+) > Cd(2+) > Mn(2+). The thermodynamic parameters were estimated; the complexation process has been found to be spontaneous, exothermic, and entropically favorable.

  13. The effect of metal ions on the photophysical and photochemical property of phenylthio bromo metal phthalocyanines

    NASA Astrophysics Data System (ADS)

    Pan, Sujuan; Shen, Pingping; Ma, Dongdong; Wang, Yuhua; Zhang, Tiantian; Chen, Kuizhi; Yang, Hongqin; Xie, Shusen; Peng, Yiru

    2016-10-01

    Phthalocyanines have attracted great attention because of their applications in material science including electro-optical devices, electrochromic display, and photodynamic therapy (PDT) of cancer. In addition, the Pcs exhibit great flexibility of chemical structure modification enabled by either peripheral substituents or metal ions co-ordination to central cavity of highly conjugated tetrapyrrolic macrocycles. However, because of the hydrophobic nature of the phthalocyanine ring, Pcs have strong tendency to aggregate in solution, which limited their applications. To overcome this problem, the introduction of dendritic wedge to peripheral positions of phthalocyanines can prevent the formation of aggregation to some extent. The preparation procedure involved the modification of the zinc (II) and magnesium (II) phthalocyanines with peripherally dendritic substitutions. The photophysical and photochemical properties of dendritic phthalocyanines were studied by UV/Vis and fluorescence spectroscopic methods. Compared with the magnesium (II) phthalocyanine, the intensity of Q band of zinc (II) phthalocyanine was increased but no obviously position changes was observed. Furthermore, the zinc (II) phthalocyanine exhibited relatively higher fluorescence intensity than the magnesium (II) phthalocyanine. The fluorescence quantum yield and lifetimes of magnesium (II) phthalocyanine was clearly longer than that of zinc (II) phthalocyanine. As the better photosensitizer, the zinc (II) phthalocyanine has higher singlet oxygen quantum yield owning superior performance. This results indicated that the singlet oxygen quantum yield would be effected by the nature of metal ions.

  14. The Interchangeability of Plasma and Whole Blood Metal Ion Measurement in the Monitoring of Metal on Metal Hips

    PubMed Central

    Malek, Ibrahim A.; Rogers, Joanne; King, Amanda Christina; Clutton, Juliet; Winson, Daniel; John, Alun

    2015-01-01

    One hundred and twenty six paired samples of plasma and whole blood were measured with inductively coupled plasma mass spectrometry technique for metal ions analysis to determine a relationship between them. There was a significant difference between the mean plasma and whole blood concentrations of both cobalt (Co) and chromium (Cr) (p < 0.0001 for both Co and Cr). The mean ratio between plasma and whole blood Cr and Co was 1.56 (range: 0.39–3.85) and 1.54 (range: 0.64–18.26), respectively, but Bland and Altman analysis illustrated that this relationship was not universal throughout the range of concentrations. There was higher variability at high concentrations for both ions. We conclude that both these concentrations should not be used interchangeably and conversion factors are unreliable due to concentration dependent variability. PMID:26798516

  15. Humic colloid-borne natural polyvalent metal ions: dissociation experiment.

    PubMed

    Geckeis, H; Rabung, Th; Ngo Manh, T; Kim, J I; Beck, H P

    2002-07-01

    The natural association nature of the humic colloid-borne trace elements is investigated. Rare earth elements (REE) Th and U are chosen as naturally occurring representatives and chemical homologues for actinides of different oxidation states present in nuclear waste. Tri- and tetravalent elements in two investigated Gorleben groundwaters (Gohy-532 and -2227) almost exclusively occur as humic or fulvic colloid-borne species. Their desorption behavior from colloids is examined in the unperturbed groundwater (pH approximately 8) under anaerobic conditions (Ar/1% CO2) by addition of a chelating cation exchanger resin. Particularly, the dissociation process of naturally occurring Eu(III) in the groundwater is compared with the Eu(III) desorption from its humate complex prepared with purified Aldrich humic acid in a buffered aqueous solution at pH approximately 8. The Eu(III) dissociation from the groundwater colloids is found to be considerably slower than found for the humate complex synthesized in the laboratory. This suggests that under natural aquatic conditions the Eu(III) binding in colloids is chemically different from the simple humate complexation as observed in the laboratory experiment. The colloid characterization bythe size exclusion chromatography (SEC) and the flow field-flow fractionation (FFFF) indicates that natural colloid-borne trace elements are found predominantly in colloids of larger size (>15 nm in size), while Eu(III) in its humate complex is found mainly in colloids of hydrodynamic diameters <5 nm. The slower desorption kinetics and the larger colloid size suggest that the polyvalent metal ion binding in natural humic colloids is associated to polynucleation with other co-present trace metal ions. Radiotracer experiments reveal that isotopic equilibria with the naturally colloid-borne trace elements are not attained within a period of more than 100 days, indicating irreversible binding of at least a part of colloid-borne polyvalent trace

  16. Antioxidant action of eugenol compounds: role of metal ion in the inhibition of lipid peroxidation.

    PubMed

    Ito, Masae; Murakami, Keiko; Yoshino, Masataka

    2005-03-01

    Antioxidant action of eugenol compounds was analyzed in relation to the role of transition metal. Iron-mediated lipid peroxidation and autooxidation of Fe2+ ion were inhibited markedly by isoeugenol, and less effectively by eugenol. Copper-dependent oxidation of low density lipoprotein (LDL) was potently inhibited by eugenol and isoeugenol to the same extent: eugenol compounds showed protective effects by prolonging lag phase and by suppressing propagation rate in the absence and presence of alpha-tocopherol. Inhibition of LDL oxidation by eugenol compounds was closely related to activities reducing copper and scavenging a stable radical, 1,1'-diphenyl-2-picrylhydrazyl (DPPH). Antioxidant properties of eugenol compounds can be explained by forming complexes with reduced metals. Potent inhibitory effect of isoeugenol on lipid peroxidation may be related to the decreased formation of perferryl ion or the iron-oxygen chelate complex as the initiating factor of lipid peroxidation by keeping iron at a reduced state. Inhibition of LDL oxidation by eugenol compounds is due to the suppression of free radical cascade of lipid peroxidation in LDL by reducing copper ion.

  17. Fe(2+) substrate transport through ferritin protein cage ion channels influences enzyme activity and biomineralization.

    PubMed

    Behera, Rabindra K; Torres, Rodrigo; Tosha, Takehiko; Bradley, Justin M; Goulding, Celia W; Theil, Elizabeth C

    2015-09-01

    Ferritins, complex protein nanocages, form internal iron-oxy minerals (Fe2O3·H2O), by moving cytoplasmic Fe(2+) through intracage ion channels to cage-embedded enzyme (2Fe(2+)/O2 oxidoreductase) sites where ferritin biomineralization is initiated. The products of ferritin enzyme activity are diferric oxy complexes that are mineral precursors. Conserved, carboxylate amino acid side chains of D127 from each of three cage subunits project into ferritin ion channels near the interior ion channel exits and, thus, could direct Fe(2+) movement to the internal enzyme sites. Ferritin D127E was designed and analyzed to probe properties of ion channel size and carboxylate crowding near the internal ion channel opening. Glu side chains are chemically equivalent to, but longer by one -CH2 than Asp, side chains. Ferritin D127E assembled into normal protein cages, but diferric peroxo formation (enzyme activity) was not observed, when measured at 650 nm (DFP λ max). The caged biomineral formation, measured at 350 nm in the middle of the broad, nonspecific Fe(3+)-O absorption band, was slower. Structural differences (protein X-ray crystallography), between ion channels in wild type and ferritin D127E, which correlate with the inhibition of ferritin D127E enzyme activity include: (1) narrower interior ion channel openings/pores; (2) increased numbers of ion channel protein-metal binding sites, and (3) a change in ion channel electrostatics due to carboxylate crowding. The contributions of ion channel size and structure to ferritin activity reflect metal ion transport in ion channels are precisely regulated both in ferritin protein nanocages and membranes of living cells.

  18. Redox-inactive metal ions promoted the catalytic reactivity of non-heme manganese complexes towards oxygen atom transfer.

    PubMed

    Choe, Cholho; Yang, Ling; Lv, Zhanao; Mo, Wanling; Chen, Zhuqi; Li, Guangxin; Yin, Guochuan

    2015-05-21

    Redox-inactive metal ions can modulate the reactivity of redox-active metal ions in a variety of biological and chemical oxidations. Many synthetic models have been developed to help address the elusive roles of these redox-inactive metal ions. Using a non-heme manganese(II) complex as the model, the influence of redox-inactive metal ions as a Lewis acid on its catalytic efficiency in oxygen atom transfer was investigated. In the absence of redox-inactive metal ions, the manganese(II) catalyst is very sluggish, for example, in cyclooctene epoxidation, providing only 9.9% conversion with 4.1% yield of epoxide. However, addition of 2 equiv. of Al(3+) to the manganese(II) catalyst sharply improves the epoxidation, providing up to 97.8% conversion with 91.4% yield of epoxide. EPR studies of the manganese(II) catalyst in the presence of an oxidant reveal a 16-line hyperfine structure centered at g = 2.0, clearly indicating the formation of a mixed valent di-μ-oxo-bridged diamond core, Mn(III)-(μ-O)2-Mn(IV). The presence of a Lewis acid like Al(3+) causes the dissociation of this diamond Mn(III)-(μ-O)2-Mn(IV) core to form monomeric manganese(iv) species which is responsible for improved epoxidation efficiency. This promotional effect has also been observed in other manganese complexes bearing various non-heme ligands. The findings presented here have provided a promising strategy to explore the catalytic reactivity of some di-μ-oxo-bridged complexes by adding non-redox metal ions to in situ dissociate those dimeric cores and may also provide clues to understand the mechanism of methane monooxygenase which has a similar diiron diamond core as the intermediate.

  19. Photocaged DNAzymes as a general method for sensing metal ions in living cells

    DOE PAGES

    Hwang, Kevin; Wu, Peiwen; Kim, Taejin; ...

    2014-10-14

    DNAzymes, which are sequences of DNA with catalytic activity, have been demonstrated as a potential platform for sensing a wide range of metal ions. Despite their significant promise, cellular sensing using DNAzymes has however been difficult, mainly because of the “always-on” mode of first-generation DNAzyme sensors. In this paper, to overcome this limitation, a photoactivatable (or photocaged) DNAzyme was designed and synthesized, and its application in sensing ZnlI in living cells was demonstrated. In this design, the adenosine ribonucleotide at the scissile position of the 8–17 DNAzyme was replaced by 2'-O-nitrobenzyl adenosine, rendering the DNAzyme inactive and thus allowing itsmore » delivery into cells intact, protected from nonspecific degradation within cells. Irradiation at 365 nm restored DNAzyme activity, thus allowing the temporal control over the sensing activity of the DNAzyme for metal ions. Finally, the same strategy was also applied to the GR-5 DNAzyme for the detection of PbII, thus demonstrating the possible scope of the method.« less

  20. Photocaged DNAzymes as a general method for sensing metal ions in living cells

    SciTech Connect

    Hwang, Kevin; Wu, Peiwe