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Sample records for biological metal cations

  1. Recognition of metal cations by biological systems.

    PubMed

    Truter, M R

    1975-11-01

    Recognition of metal cations by biological systems can be compared with the geochemical criteria for isomorphous replacement. Biological systems are more highly selective and much more rapid. Methods of maintaining an optimum concentration, including storage and transfer for the essential trace elements, copper and iron, used in some organisms are in part reproducible by coordination chemists while other features have not been reporduced in models. Poisoning can result from a foreign metal taking part in a reaction irreversibly so that the recognition site or molecule is not released. For major nutrients, sodium, potassium, magnesium and calcium, there are similarities to the trace metals in selective uptake but differences qualitatively and quantitatively in biological activity. Compounds selective for potassium replace all the solvation sphere with a symmetrical arrangement of oxygen atoms; those selective for sodium give an asymmetrical environment with retention of a solvent molecule. Experiments with naturally occurring antibiotics and synthetic model compounds have shown that flexibility is an important feature of selectivity and that for transfer or carrier properties there is an optimum (as opposed to a maximum) metal-ligand stability constant. Thallium is taken up instead of potassium and will activate some enzymes; it is suggested that the poisonous characteristics arise because the thallium ion may bind more strongly than potassium to part of a site and then fail to bind additional atoms as required for the biological activity. Criteria for the design of selective complexing agents are given with indications of those which might transfer more than one metal at once. PMID:1815

  2. Understanding the bioavailability and sequestration of different metal cations in the presence of a biodegradable chelant S,S-EDDS in biological fluids and natural waters.

    PubMed

    Bretti, Clemente; Cigala, Rosalia Maria; De Stefano, Concetta; Lando, Gabriele; Sammartano, Silvio

    2016-05-01

    Ethylenediamine-N,N'-disuccinic acid is a biodegradable alternative to EDTA, therefore its use for the sequestration of Ca(2+), Sn(2+), Cu(2+), Zn(2+) and Fe(3+) is analyzed. New data on its binding ability towards these cations were obtained with potentiometric, voltammetric and calorimetric measurements at different ionic strengths and at T = 298.15 K. Real multi-component fluids, namely fresh water, urine, sea water, saliva and blood plasma were chosen as case studies to evaluate the sequestering ability of EDDS in comparison with EDTA. Speciation diagrams were drawn in selected conditions, considering all interactions among the "natural" components of the fluid and those studied in this work, EDDS and EDTA (cL = 1 mmol dm(-3)) as sequestering agents and the cited metal cations (cM ∼ 10(-5) mol dm(-3)). The comparison of the sequestering ability of EDDS and EDTA is done using pM and pL0.5. In blood plasma the plasma mobilizing index was adopted. It was found that EDDS is a good alternative to EDTA, which tends to bind Ca(2+) and Mg(2+) more than EDDS. In particular, EDTA cannot be used as a sequestrant for Sn(2+) when cCa > cEDTA. EDDS is more efficient than EDTA at pH < 8, particularly in urine, where carbonate is absent. In sea water, the sequestering ability of EDDS towards Fe(3+) is higher than that of EDTA. In blood plasma, the PMI of EDDS towards Cu(2+) is higher than that of EDTA. Thermodynamic information, in terms of ΔH and ΔS, for the protonation and metal complex formation reactions are reported. PMID:26921587

  3. Plant rhamnogalacturonan II complexation of heavy metal cations

    DOEpatents

    O`Neill, M.A.; Pellerin, P.J.M.; Warrenfeltz, D.; Vidal, S.; Darvill, A.G.; Albersheim, P.

    1999-03-02

    The present invention provides rhamnogalacturonan-II (RG-II) and relates to its ability to complex specific multivalent heavy metal cations. In the presence of boric acid, RG-II monomers form dimers that are cross-linked by a borate ester. The yield of such borate ester cross-linked dimers of RG-II is enhanced in the presence of specific heavy metal cations. The present invention further relates to the utility of RG-II in assays for the detection of specific heavy metal contamination; as a reagent useful in the removal of specific heavy metal cations contaminating foods and liquids, for example, fish, wines, etc.; as a pharmaceutical composition useful as an antidote in specific heavy metal cation poisoning; as a treatment for the detoxification of specific heavy metal cations from blood and/or tissues; and in a method of remediation of waters and soils contaminated with specific heavy metal cations. 15 figs.

  4. Plant rhamnogalacturonan II complexation of heavy metal cations

    DOEpatents

    O'Neill, Malcolm A.; Pellerin, Patrice J. M.; Warrenfeltz, Dennis; Vidal, Stephane; Darvill, Alan G.; Albersheim, Peter

    1999-01-01

    The present invention provides rhamnogalacturonan-II (RG-II) and relates to its ability to complex specific multivalent heavy metal cations. In the presence of boric acid, RG-II monomers form dimers that are cross-linked by a borate ester. The yield of such borate ester cross-linked dimers of RG-II is enhanced in the presence of specific heavy metal cations. The present invention further relates to the utility of RG-II in assays for the detection of specific heavy metal contamination; as a reagent useful in the removal of specific heavy metal cations contaminating foods and liquids, for example, fish, wines, etc.; as a pharmaceutical composition useful as an antidote in specific heavy metal cation poisoning; as a treatment for the detoxification of specific heavy metal cations from blood and/or tissues; and in a method of remediation of waters and soils contaminated with specific heavy metal cations.

  5. Cation Selectivity in Biological Cation Channels Using Experimental Structural Information and Statistical Mechanical Simulation.

    PubMed

    Finnerty, Justin John; Peyser, Alexander; Carloni, Paolo

    2015-01-01

    Cation selective channels constitute the gate for ion currents through the cell membrane. Here we present an improved statistical mechanical model based on atomistic structural information, cation hydration state and without tuned parameters that reproduces the selectivity of biological Na+ and Ca2+ ion channels. The importance of the inclusion of step-wise cation hydration in these results confirms the essential role partial dehydration plays in the bacterial Na+ channels. The model, proven reliable against experimental data, could be straightforwardly used for designing Na+ and Ca2+ selective nanopores. PMID:26460827

  6. Cation Selectivity in Biological Cation Channels Using Experimental Structural Information and Statistical Mechanical Simulation

    PubMed Central

    Finnerty, Justin John

    2015-01-01

    Cation selective channels constitute the gate for ion currents through the cell membrane. Here we present an improved statistical mechanical model based on atomistic structural information, cation hydration state and without tuned parameters that reproduces the selectivity of biological Na+ and Ca2+ ion channels. The importance of the inclusion of step-wise cation hydration in these results confirms the essential role partial dehydration plays in the bacterial Na+ channels. The model, proven reliable against experimental data, could be straightforwardly used for designing Na+ and Ca2+ selective nanopores. PMID:26460827

  7. High capacity nickel battery material doped with alkali metal cations

    DOEpatents

    Jackovitz, John F.; Pantier, Earl A.

    1982-05-18

    A high capacity battery material is made, consisting essentially of hydrated Ni(II) hydroxide, and about 5 wt. % to about 40 wt. % of Ni(IV) hydrated oxide interlayer doped with alkali metal cations selected from potassium, sodium and lithium cations.

  8. The Ziegler—Natta olefin insertion reaction for cationic metals

    NASA Astrophysics Data System (ADS)

    Jensen, Vidar R.; Siegban, Per E. M.

    1993-09-01

    The catalytic Ziegler—Natta polymerization reaction has been studied for a set of metal cations, in order to identify the role of the positive charge on this process. Geometry optimizations have been performed for the reactant metal—methyl systems, the π-coordinated olefin systems, the transition states for the olefin insertion and finally for the product metal—propyl systems. All valence electrons are correlated. The cations selected for this study are the transition metals Zr + and Ti +, the non-transition metals Be +, Mg +, Al + and finally also Si +. The transition metal cations are found to have very low barriers for the insertion, but the lowest barrier is actually found for Be +. The results are discussed in terms of the ionization energies and the accessibility to valence p and d orbitals. Comparisons are made to previous theoretical work on cationic model systems.

  9. ABSORPTION METHOD FOR SEPARATING METAL CATIONS

    DOEpatents

    Tompkins, E.R.; Parker, G.W.

    1959-03-10

    An improved method is presented for the chromatographic separation of fission products wherein a substantial reduction in liquid volume is obtained. The process consists in contacting a solution containing fission products with a body of ion-exchange adsorbent to effect adsorption of fission product cations. The loaded exchange resin is then contacted with a small volume of a carboxylic acid eluant, thereby recovering the fission products. The fission product carrying eluate is acidified without increasing its volume to the volume of the original solution, and the acidified eluate is then used as a feed solution for a smaller body of ion-exchange resin effecting readsorption of the fission product cations.

  10. In situ remediation process using divalent metal cations

    DOEpatents

    Brady, Patrick V.; Khandaker, Nadim R.; Krumhansl, James L.; Teter, David M.

    2004-12-14

    An in situ process for treating ambient solid materials (e.g., soils, aquifer solids, sludges) by adding one or more divalent metal cations to the ambient solid material. The added divalent metal cations, such as Cu.sup.2+ or Zn.sup.2+, combine with metal oxide/hydroxides (e.g., ferric oxide/hydroxide or aluminum oxide/hydroxide) already present in the ambient solid material to form an effective sorbent material having a large number of positively-charged surface complexes that binds and immobilizes anionic contaminant species (e.g., arsenic or chromate). Divalent metal cations can be added, for example, by injecting an aqueous solution of CuSO.sub.4 into an aquifer contaminated with arsenic or chromate. Also, sludges can be stabilized against leaching of anionic contaminants through the addition of divalent metal cations. Also, an inexpensive sorbent material can be easily formed by mixing divalent metal cations with soil that has been removed from the ground.

  11. Fluorescent metal ion chemosensors via cation exchange reactions of complexes, quantum dots, and metal-organic frameworks.

    PubMed

    Cheng, Jinghui; Zhou, Xiangge; Xiang, Haifeng

    2015-11-01

    Due to their wide range of applications and biological significance, fluorescent sensors have been an active research area in the past few years. In the present review, recent research developments on fluorescent chemosensors that detect metal ions via cation exchange reactions (transmetalation, metal displacement, or metal exchange reactions) of complexes, quantum dots, and metal-organic frameworks are described. These complex-based chemosensors might have a much better selectivity than the corresponding free ligands/receptors because of the shielding function of the filled-in metal ions. Moreover, not only the chemical structure of the ligands/receptors but also the identity of the central metal ions have a tremendous impact on the sensing performances. Therefore, sensing via cation exchange reactions potentially provides a new, simple, and powerful way to design fluorescent chemosensors. PMID:26375420

  12. Infrared spectroscopy of mass-selected metal carbonyl cations

    NASA Astrophysics Data System (ADS)

    Ricks, A. M.; Reed, Z. E.; Duncan, M. A.

    2011-04-01

    Metal carbonyl cations of the form M(CO)n+ are produced in a molecular beam by laser vaporization in a pulsed nozzle source. These ions, and their corresponding rare gas atom "tagged" analogs, M(CO)n(RG)m+, are studied with mass-selected infrared photodissociation spectroscopy in the carbonyl stretching region and with density functional theory computations. The number of infrared-active bands, their frequency positions, and their relative intensities provide distinctive patterns allowing determination of the geometries and electronic structures of these complexes. Cobalt penta carbonyl and manganese hexacarbonyl cations are compared to isoelectronic iron pentacarbonyl and chromium hexacarbonyl neutrals. Gold and copper provide examples of "non-classical" carbonyls. Seven-coordinate carbonyls are explored for the vanadium group metal cations (V +, Nb + and Ta +), while uranium cations provide an example of an eight-coordinate carbonyl.

  13. Fluorescence quenching of water-soluble conjugated polymer by metal cations and its application in sensor

    NASA Astrophysics Data System (ADS)

    Chen, Yan-Guo; Zhao, Dan; He, Zhi-Ke; Ai, Xin-Ping

    2007-02-01

    The effects of different metal cations on the fluorescence of water-soluble conjugated polymer (CP) and their quenching mechanism have been explored. Most transition metal cations, especially noble metal cations, such as Pd 2+, Ru 3+, and Pt 2+ possessed higher quenching efficiency to CP fluorescence than that of the main group metal cations and other transition metal cations, which have filled or half-full outmost electron layer configurations. Base on this, rapid, sensitive detection of noble metal cations can be realized and a novel quencher-tether-ligand (QTL) probe was developed to detect avidin and streptavidin.

  14. Alkali Metal Cation versus Proton and Methyl Cation Affinities: Structure and Bonding Mechanism

    PubMed Central

    Boughlala, Zakaria; Fonseca Guerra, Célia

    2016-01-01

    Abstract We have analyzed the structure and bonding of gas‐phase Cl−X and [HCl−X]+ complexes for X+= H+, CH3 +, Li+, and Na+, using relativistic density functional theory (DFT). We wish to establish a quantitative trend in affinities of the anionic and neutral Lewis bases Cl− and HCl for the various cations. The Cl−X bond becomes longer and weaker along X+ = H+, CH3 +, Li+, and Na+. Our main purpose is to understand the heterolytic bonding mechanism behind the intrinsic (i.e., in the absence of solvent) alkali metal cation affinities (AMCA) and how this compares with and differs from those of the proton affinity (PA) and methyl cation affinity (MCA). Our analyses are based on Kohn–Sham molecular orbital (KS‐MO) theory in combination with a quantitative energy decomposition analysis (EDA) that pinpoints the importance of the different features in the bonding mechanism. Orbital overlap appears to play an important role in determining the trend in cation affinities. PMID:27551660

  15. Alkali Metal Cation versus Proton and Methyl Cation Affinities: Structure and Bonding Mechanism.

    PubMed

    Boughlala, Zakaria; Fonseca Guerra, Célia; Bickelhaupt, F Matthias

    2016-06-01

    We have analyzed the structure and bonding of gas-phase Cl-X and [HCl-X](+) complexes for X(+)= H(+), CH3 (+), Li(+), and Na(+), using relativistic density functional theory (DFT). We wish to establish a quantitative trend in affinities of the anionic and neutral Lewis bases Cl(-) and HCl for the various cations. The Cl-X bond becomes longer and weaker along X(+) = H(+), CH3 (+), Li(+), and Na(+). Our main purpose is to understand the heterolytic bonding mechanism behind the intrinsic (i.e., in the absence of solvent) alkali metal cation affinities (AMCA) and how this compares with and differs from those of the proton affinity (PA) and methyl cation affinity (MCA). Our analyses are based on Kohn-Sham molecular orbital (KS-MO) theory in combination with a quantitative energy decomposition analysis (EDA) that pinpoints the importance of the different features in the bonding mechanism. Orbital overlap appears to play an important role in determining the trend in cation affinities. PMID:27551660

  16. The role of alkali metal cations in the stabilization of guanine quadruplexes: why K(+) is the best.

    PubMed

    Zaccaria, F; Paragi, G; Fonseca Guerra, C

    2016-08-21

    The alkali metal ion affinity of guanine quadruplexes has been studied using dispersion-corrected density functional theory (DFT-D). We have done computational investigations in aqueous solution that mimics artificial supramolecular conditions where guanine bases assemble into stacked quartets as well as biological environments in which telomeric quadruplexes are formed. In both cases, an alkali metal cation is needed to assist self-assembly. Our quantum chemical computations on these supramolecular systems are able to reproduce the experimental order of affinity of the guanine quadruplexes for the cations Li(+), Na(+), K(+), Rb(+), and Cs(+). The strongest binding is computed between the potassium cation and the quadruplex as it occurs in nature. The desolvation and the size of alkali metal cations are thought to be responsible for the order of affinity. Until now, the relative importance of these two factors has remained unclear and debated. By assessing the quantum chemical 'size' of the cation, determining the amount of deformation of the quadruplex needed to accommodate the cation and through the energy decomposition analysis (EDA) of the interaction energy between the cation and the guanines, we reveal that the desolvation and size of the alkali metal cation are both almost equally responsible for the order of affinity. PMID:27185388

  17. Infrared Photodissociation Spectroscopy of Metal Oxide Carbonyl Cations.

    NASA Astrophysics Data System (ADS)

    Brathwaite, Antonio D.; Duncan, Michael A.

    2013-06-01

    Mass selected metal oxide-carbonyl cations of the form MO_{m}(CO)_{n}^{+} are studied via infrared laser photodissociation spectroscopy, in the 600-2300cm^{1} region. Insight into the structure and bonding of these complexes is obtained from the number of infrared active bands, their relative intensities and their frequency positions. Density functional theory calculations are carried out in support of the experimental data. Insight into the bonding of CO ligands to metal oxides is obtained and the effect of oxidation on the carbonyl stretching frequency is revealed.

  18. Metal-Metal Bonds in Biology

    PubMed Central

    Lindahl, Paul A.

    2011-01-01

    Nickel-containing carbon monoxide dehydrogenases, acetyl-CoA synthases, nickel-iron hydrogenases, and diron hydrogenases are distinct metalloenzymes yet they share a number of important characteristics. All are O2-sensitive, with active-sites composed of iron and/or nickel ions coordinated primarily by sulfur ligands. In each case, two metals are juxtaposed at the “heart” of the active site, within range of forming metal-metal bonds. These active-site clusters exhibit multielectron redox abilities and must be reductively activated for catalysis. Reduction potentials are milder than expected based on formal oxidation state changes. When reductively activated, each cluster attacks an electrophilic substrate via an oxidative addition reaction. This affords a two-electron-reduced substrate bound to one or both metals of an oxidized cluster. M-M bonds have been established in hydrogenases where they serve to initiate the oxidative addition of protons and perhaps stabilize active sites in multiple redox states. The same may be true of the CODH and ACS active sites – Ni-Fe and Ni-Ni bonds in these sites may play critical roles in catalysis, stabilizing low-valence states and initiating oxidative addition of CO2 and methyl group cations, respectively. In this article, the structural and functional commonalities of these metalloenzyme active sites are described, and the case is made for the formation and use of metal-metal bonds in each enzyme mentioned. As a post-script, the importance of Fe-Fe bonds in the nitrogenase FeMoco active site is discussed. PMID:22119810

  19. Selective enrichment of metal-binding proteins based on magnetic core/shell microspheres functionalized with metal cations.

    PubMed

    Fang, Caiyun; Zhang, Lei; Zhang, Xiaoqin; Lu, Haojie

    2015-06-21

    Metal binding proteins play many important roles in a broad range of biological processes. Characterization of metal binding proteins is important for understanding their structure and biological functions, thus leading to a clear understanding of metal associated diseases. The present study is the first to investigate the effectiveness of magnetic microspheres functionalized with metal cations (Ca(2+), Cu(2+), Zn(2+) and Fe(3+)) as the absorbent matrix in IMAC technology to enrich metal containing/binding proteins. The putative metal binding proteins in rat liver were then globally characterized by using this strategy which is very easy to handle and can capture a number of metal binding proteins effectively. In total, 185 putative metal binding proteins were identified from rat liver including some known less abundant and membrane-bound metal binding proteins such as Plcg1, Acsl5, etc. The identified proteins are involved in many important processes including binding, catalytic activity, translation elongation factor activity, electron carrier activity, and so on. PMID:25913209

  20. Molecular modeling of organic corrosion inhibitors: why bare metal cations are not appropriate models of oxidized metal surfaces and solvated metal cations.

    PubMed

    Kokalj, Anton

    2014-01-01

    The applicability of various models of oxidized metal surfaces - bare metal cations, clusters of various size, and extended (periodic) slabs - that are used in the field of quantum-chemical modeling of corrosion inhibitors is examined and discussed. As representative model systems imidazole inhibitor, MgO surface, and solvated Mg(2+) ion are considered by means of density-functional-theory calculations. Although the results of cluster models are prone to cluster size and shape effects, the clusters of moderate size seem useful at least for qualitative purposes. In contrast, the bare metal cations are useless not only as models of oxidized surfaces but also as models of solvated cations, because they bind molecules several times stronger than the more appropriate models. In particular, bare Mg(2+) binds imidazole by 5.9 eV, while the slab model of MgO(001) by only 0.35 eV. Such binding is even stronger for 3+ cations, e.g., bare Al(3+) binds imidazole by 17.9 eV. The reasons for these fantastically strong binding energies are discussed and it is shown that the strong bonding is predominantly due to electron charge transfer from molecule to metal cation, which stems from differences between molecular and metal ionization potentials. PMID:25125117

  1. Coordination of trivalent metal cations to peptides: results from IRMPD spectroscopy and theory.

    PubMed

    Prell, James S; Flick, Tawnya G; Oomens, Jos; Berden, Giel; Williams, Evan R

    2010-01-21

    Structures of trivalent lanthanide metal cations La(3+), Ho(3+), and Eu(3+) with deprotonated Ala(n) (n = 2-5) or Leu-enk (Tyr-Gly-Gly-Phe-Leu) are investigated with infrared multiple photon dissociation (IRMPD) spectroscopy between 900 and 1850 cm(-1) and theory. In all of these complexes, a salt bridge is formed in which the metal cation coordinates to the carboxylate group of the peptide, resulting in a limited conformational space and many sharp IRMPD spectral bands. The IRMPD spectra clearly indicate that all carbonyl groups solvate the metal cation in each of the Ala(n) complexes. Due to strong vibrational coupling between the carbonyl groups, a sharp, high-energy amide I band due to in-phase stretching of all of the amide carbonyl groups bound to the metal cation is observed that is separated by approximately 50 cm(-1) from a strong, lower-energy amide I band. This extent of carbonyl coupling, which is sometimes observed in condensed-phase peptide and protein IR spectroscopy, has not been reported in IRMPD spectroscopy studies of other cationized peptide complexes. Intense bands due to carbonyl groups not associated with the metal cation are observed for Leu-enk complexes, indicating that a side chain group, such as the Tyr or Phe aromatic ring, prevents complete carbonyl coordination of the metal cation. Substitution of smaller lanthanide cations for La(3+) in these peptide complexes results only in minor structural changes consistent with the change in metal cation size. These are the first IRMPD spectra reported for lanthanide metal cationized peptides, and comparison to previously reported protonated and alkali metal or alkaline earth metal cationized peptide complexes reveals many trends consistent with the higher charge state of the lanthanide cations. PMID:19950916

  2. Sensing of biologically important cations such as Na(+), K(+), Ca(2+), Cu(2+), and Fe(3+) using magnetic nanoemulsions.

    PubMed

    Mahendran, V; Philip, John

    2013-04-01

    We report a simple approach to the ultrasensitive detection of biologically important metal ions using a magnetic nanoemulsion. The nanoemulsion used in our study was an oil-in-water emulsion droplet of average size ∼190 nm containing ferrimagnetic iron oxide nanoparticles of average size ∼10 nm. In a static magnetic field, the emulsion droplets self-assemble into a nanoarray with distinct interdroplet spacing. In the presence of cations in the solution, the nanofluid array shows a large blue shift in the diffracted Bragg peak and a visually perceivable color change due to changes in the electrical double layer upon the diffusion of cations. The colloidal force-distance measurements in the presence of cations show large variations at the onset of repulsion in the presence of cations. The sensor shows good selectivity to Na(+), K(+), Ca(2+), Cu(2+), and Fe(3+) ions and offers a rapid response compared to conventional techniques. This approach can be useful for the recognition of biologically important cations. PMID:23477486

  3. Tryptophan fluorescence quenching by alkaline earth metal cations in deionized bacteriorhodopsin.

    PubMed

    Wang, G; Wang, A J; Hu, K S

    2000-12-01

    Tryptophan quenching by the addition of alkaline earth metal cations to deionized bacteriorhodopsin suspensions was determined. The results show that the addition of cation primarily quenches fluorescence from surface tryptophan residues. The quenched intensity exhibits a 1/R dependence, where R is the ionic radius of the corresponding metal ion. This observation results from a stronger energy transfer coupling between the tryptophan and the retinal. The membrane curvature may be involved as a result of cations motion and correlated conformational changes. PMID:11332888

  4. 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.

  5. Observation of Accumulated Metal Cation Distribution in Fish by Novel Stigmatic Imaging Time-of-Flight Mass Spectrometer

    NASA Astrophysics Data System (ADS)

    Aoki, Jun; Ikeda, Shinichiro; Toyoda, Michisato

    2014-02-01

    The accumulation of radioactive substances in biological organisms is a matter of great concern since the incident at the nuclear power plant in Fukushima, Japan. We have developed a novel technique for observing the distribution of accumulated metal cations in fish that employs a new imaging mass spectrometer, MULTUM-IMG2. Distributions of 133Cs and 88Sr in a sliced section of medaka (Oryzias latipes) are obtained with spatial resolution of µm-scale.

  6. The diastereoselective synthesis of octahedral cationic iridium hydride complexes with a stereogenic metal centre.

    PubMed

    Humbert, Nicolas; Mazet, Clément

    2016-08-23

    We report herein the highly diastereoselective synthesis of octahedral cationic Ir(iii) hydride complexes with a stereogenic metal centre following various strategies. The configurational stability of these compounds has also been investigated. PMID:27498763

  7. Low-Temperature Cationic Rearrangement in a Bulk Metal Oxide.

    PubMed

    Li, Man-Rong; Retuerto, Maria; Stephens, Peter W; Croft, Mark; Sheptyakov, Denis; Pomjakushin, Vladimir; Deng, Zheng; Akamatsu, Hirofumi; Gopalan, Venkatraman; Sánchez-Benítez, Javier; Saouma, Felix O; Jang, Joon I; Walker, David; Greenblatt, Martha

    2016-08-16

    Cationic rearrangement is a compelling strategy for producing desirable physical properties by atomic-scale manipulation. However, activating ionic diffusion typically requires high temperature, and in some cases also high pressure in bulk oxide materials. Herein, we present the cationic rearrangement in bulk Mn2 FeMoO6 at unparalleled low temperatures of 150-300 (o) C. The irreversible ionic motion at ambient pressure, as evidenced by real-time powder synchrotron X-ray and neutron diffraction, and second harmonic generation, leads to a transition from a Ni3 TeO6 -type to an ordered-ilmenite structure, and dramatic changes of the electrical and magnetic properties. This work demonstrates a remarkable cationic rearrangement, with corresponding large changes in the physical properties in a bulk oxide at unprecedented low temperatures. PMID:27203790

  8. Biological interactions at metal surfaces

    NASA Astrophysics Data System (ADS)

    Hansen, Douglas C.

    2011-06-01

    Adsorption of biomolecules, whether it is a consequence of a material being put into service in a biological medium such as a biomedical implant device or a heat exchanger tube, are governed by fundamental interactions and surface conditions that are well characterized (and in some cases not so well). This work reviews those fundamental interactions and also describes a study of the adsorption of a naturally occurring biological polymer onto a stainless steel alloy.

  9. Inhibition of iron corrosion in 0.5 M sulphuric acid by metal cations

    NASA Astrophysics Data System (ADS)

    Sathiyanarayanan, S.; Jeyaprabha, C.; Muralidharan, S.; Venkatachari, G.

    2006-09-01

    Corrosion inhibitors are widely used in acid solutions during pickling and descaling. Mostly organic compounds containing N, O, and S groups are employed as inhibitors. In this study, the inhibition performance of metal cations such as Zn 2+, Mn 2+ and Ce 4+ ions in the concentration range 1-10 × 10 -3 M has been found out. The corrosion behaviour of iron in 0.5 M H 2SO 4 in the presence of metal cations is studied using polarization and impedance methods. It is found that the addition of these metal cations inhibits the corrosion markedly. The inhibition effect is in the following order Ce 4+ ≫ Mn 2+ > Zn 2+.

  10. A Bioluminescence Assay System for Imaging Metal Cationic Activities in Urban Aerosols.

    PubMed

    Kim, Sung-Bae; Naganawa, Ryuichi; Murata, Shingo; Nakayama, Takayoshi; Miller, Simon; Senda, Toshiya

    2016-01-01

    A bioluminescence-based assay system was fabricated for an efficient determination of the activities of air pollutants. The following four components were integrated into this assay system: (1) an 8-channel assay platform uniquely designed for simultaneously sensing multiple optical samples, (2) single-chain probes illuminating toxic chemicals or heavy metal cations from air pollutants, (3) a microfluidic system for circulating medium mimicking the human body, and (4) the software manimulating the above system. In the protocol, we briefly introduce how to integrate the components into the system and the application to the illumination of the metal cationic activities in air pollutants. PMID:27424913

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

    PubMed

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

    2015-01-01

    Ciprofloxacin (CIP) can be strongly adsorbed by ferric oxides, but some influencing factors, such as multivalent cations and soil organic matter, have not been evaluated extensively. In this study, the interaction between CIP and four divalent metals (Ca, Cd, Cu, and Pb) was investigated using potentiometric titration and the results indicated that CIP can bind to the divalent metals in the following affinity order: Cu(II) > Pb(II) > Cd(II) > Ca(II). The effects of metals and fulvic acid (FA) on the adsorption behavior of CIP onto goethite surfaces were also examined using batch experiments. It was found that metal cations enhanced the CIP retention on goethite surfaces in the same order as the affinity order with CIP, indicating that metals likely increased CIP retention through cation bridging. FA was found to promote CIP sorption rather than compete with it, and the coexistence of FA and Cu(II) in the system exhibited an addictive effect with CIP sorption, indicating that they might influence the sorption separately under the studied loading condition. Taken together, our results suggested that the coexistence of divalent cations or soil organic matter will enhance CIP sorption on goethite surfaces, hence reducing its mobility and bioavailability in the environment. PMID:25096489

  12. Removal of metal cations from water using zeolites

    SciTech Connect

    Zamzow, M.J.; Murphy, J.E. )

    1992-11-01

    Zeolites from abundant natural deposits were investigated by the Bureau of Mines for efficiently cleaning up mining industry wastewaters. Twenty-four zeolite samples were analyzed by x-ray diffraction and inductively coupled plasma. These included clinoptilolite, mordenite, chabazite, erionite, and phillipsite. Bulk densities of a sized fraction ([minus]40, +65 mesh) varied from 0.48 to 0.93 g/ml. Attrition losses ranged from 1 to 18% during an hour-long shake test. The 24 zeolites and an ion-exchange resin were tested for the uptake of Cd, Cu, and Zn. Of the natural zeolites, phillipsite proved to be the most efficient, while the mordenites had the lowest uptakes. Sodium was the most effective exchangeable ion for exchange of heavy metals. Wastewater from an abandoned copper mine in Nevada was used to test the effectiveness of clinoptilolite for treating a multi-ion wastewater. The metal ions Fe[sup 3+], Cu[sup 2+], and Zn[sup 2+] in the copper mine wastewater were removed to below drinking water standards, but Mn[sup 2+] and Ni[sup 2+] were not. Calcium and NH[sub 4][sup +] interfered with the uptake of heavy metals. Adsorbed heavy metals were eluted from zeolites with a 3% NaCl solution. Heavy metals were concentrated in the eluates up to 30-fold relative to the waste solution. Anions were not adsorbed by the zeolites.

  13. Electrochemical Removal of Metal Cations from Wastewater Monitored by Differential Pulse Polarography

    ERIC Educational Resources Information Center

    Bruce, Delphine; Kuhn, Alexander; Sojic, Neso

    2004-01-01

    Electrodeposition eliminates wastewater pollutants such as electrochemically active metal cations, with different pulse polarography (DPP) scrutinizing the kinetics of the treatment process. These mechanisms produce qualitative and quantitative data about the removal process, while students appreciate the use of electrochemistry in resolving…

  14. Enhancing electrocatalytic hydrogen evolution by nickel salicylaldimine complexes with alkali metal cations in aqueous media.

    PubMed

    Shao, Haiyan; Muduli, Subas K; Tran, Phong D; Soo, Han Sen

    2016-02-18

    New salicylaldimine nickel complexes, comprising only earth-abundant elements, have been developed for electrocatalytic hydrogen evolution in aqueous media. The second-sphere ether functionalities on the periphery of the complexes enhance the electrocatalytic activity in the presence of alkali metal cations. The electrocatalysts demonstrate improved performances especially in the economical and sustainable seawater reaction medium. PMID:26779580

  15. Theoretical study of alpha/beta-alanine and their protonated/alkali metal cationized complexes.

    PubMed

    Abirami, S; Xing, Y M; Tsang, C W; Ma, N L

    2005-01-27

    Density functional theory has been employed to model the structure and the relative stabilities of alpha/beta-alanine conformers and their protonated and alkali metal cationized complexes. In general, we find that the behavior of the beta-alanine (beta-Ala) system is quite similar to that of alpha-alanine (alpha-Ala). However, the presence of the methylene group (-CH2-) at the beta position in beta-Ala leads to a few key differences. First, the intramolecular hydrogen bonding patterns are different between free alpha- and beta-Ala. Second, the stability of zwitterionic species (in either the free ligand or alkali metal cationized complexes) is often enhanced in beta-Ala. Third, the preferred mode of alkali metal cation (M+) binding may also differ in alpha- and beta-Ala. Natural energy decomposition analysis has been applied here to gain further insight into the effects of the ligand, cation size, and mode of binding on the nature of interaction in these M+-Ala complexes. PMID:16833371

  16. Environmental Remediation and Sorption of Metal Cations Using Aluminum Pillared Nano-Bentonite

    NASA Astrophysics Data System (ADS)

    Rifai, Rifai; Abou El Safa, Magda

    2015-04-01

    The release of heavy metal cations into the environment is a potential threat to water and soil quality. Some clay minerals play an important role, as physical and chemical barriers, for the isolation of metal-rich wastes and to adsorb heavy metals as well as to avoid their environmental dispersion. In the present study, the bentonitic clay (southeast El-Hammam City, Egypt) was subjected to pillaring using hydroxyl-aluminum solution. The XRD patterns of the Aluminum Pillared Nano-Bentonite (APNB) showed severe alteration of the crystal structure after pillaring. Poly metal solutions with different metal concentrations of Cu, Co, Ni, Zn, Cd and Pb (0.001, 0.005 and 0.01 moles), and pH (1, 2.5, 5 and 6) were subjected to treatment by the APNB. The removal process is very rapid and spontaneous and the contact time may be short (several minutes) for most adsorption to occur. The criterion for environmental remediation of APNB is less stringent and a short contact time is sufficient. The rate of Cu2+, Zn2+, Co2+, Cd2+, Ni2+ and Pb2+sorption remained higher or equal to the CEC. The sorption of metal ions by APNB are complex and probably involve several mechanisms. In general, APNB can be used to immobilize Cu2+, Zn2+, Co2+, Cd2+, Ni2+ and Pb2+ to any extent. For each metal ion, the most effective immobilization occurs over a particular pH around 5. According to the experimental data obtained, the uptake amount of the studied cations by APNB increased with increasing solution pH, sorbent dose and contact time. The preference of the APNB adsorption for heavy metal ions that are through the cation exchange processes decreases in the order: Cu2+>Zn2+>Co2+>Cd2+ >Ni2+ >Pb2+. Keywords: Bentonitic clay, Egypt, Aluminum Pillared Nano-Bentonite, heavy metal, environmental remediation

  17. Structural fluctuation observed in Z-DNA d(CGCGCG)2 in the absence of divalent metal cations and polyamines

    PubMed Central

    Chatake, Toshiyuki

    2013-01-01

    In the present study, Z-DNA d(CGCGCG)2 was crystallized from a DNA solution in the absence of divalent metal cations and polyamines, and its X-ray structure was determined at 0.98 Å resolution. Comparison of this structure and previously reported Z-DNA structures, containing Mg2+ cations and/or polyamines, demonstrated that Z-DNA can have structural fluctuations with respect to phosphate groups and hydration in the minor groove. At the GpC steps, a two-state structural equilibrium between the ZI and ZII conformations was frequently observed. In contrast, at the CpG steps, the phosphate groups exhibited rotational fluctuation, which could induce distortion of sugar puckering. In addition, alternative positions of water molecules were found in the middle of the minor groove of the Z-DNA. These structural fluctuations were likely observable because of the absence of Mg2+ cations and polyamines. The results related to these phenomena were supported by those of other experimental methods, suggesting the possibility of these fluctuations occurring in biological conditions. PMID:24121329

  18. Cation-pi interactions in aromatics of biological and medicinal interest: electrostatic potential surfaces as a useful qualitative guide.

    PubMed Central

    Mecozzi, S; West, A P; Dougherty, D A

    1996-01-01

    The cation-pi interaction is an important, general force for molecular recognition in biological receptors. Through the sidechains of aromatic amino acids, novel binding sites for cationic ligands such as acetylcholine can be constructed. We report here a number of calculations on prototypical cation-pi systems, emphasizing structures of relevance to biological receptors and prototypical heterocycles of the type often of importance in medicinal chemistry. Trends in the data can be rationalized using a relatively simple model that emphasizes the electrostatic component of the cation-pi interaction. In particular, plots of the electrostatic potential surfaces of the relevant aromatics provide useful guidelines for predicting cation-pi interactions in new systems. Images Fig. 2 Fig. 3 Fig. 4 PMID:8855218

  19. Study on bending behavior of ionic polymer metal composites with various organic solvents and cationic species

    NASA Astrophysics Data System (ADS)

    Nam, Byung K.; Yoo, Youngtai

    2005-05-01

    Ion exchange polymer metal composites (IPMC) are electro-active actuators that show large deformation in the presence of low applied voltage. Perfluorosulfonic acid membrane, Nafion, is one of the most widely studied materials for this purpose. Experimental studies were carried out on the bending behavior of Nafion-based IPMCs containing various solvents and cation species. Various counter cations of sulfonate groups in the membrane were obtained by soaking the composite membrane in aqueous salt solutions. The salts used in ion exchange process include LiOH, NaOH, Cu(NO3)2, Co(NO3)2. Ion-exchange capacity of the IPMC was measured by ICP. In the case of cationic effect the Li-form IPMC demonstrated an immediate and efficient deformation behavior at 1 DC V, while divalent cuprous cation containing IPMC exhibited the larger tip displacement at an elevated electric potential. A threshold electric driving force appears to be required for cations with large hydration and high volume. IPMCs were also prepared by soaking in various transport media. The solutions were prepared by adding 1 mole of NMP, DMF, DMSO, and PEG 200 in water. The feasibility of D2O was also investigated. Addition of organic polar solvents in water decreases the dielectric constant of medium, which subsequently reduces the dissociation of ion pairs. Among the various solutions the heavy water, D2O and DMSO/water (1 Mole/L) mixture demonstrated unusually stable tendency in terms of electrolysis.

  20. Role of encapsulated metal cation in the reactivity and regioselectivity of the C₆₀ Diels-Alder reaction.

    PubMed

    Cui, Cheng-Xing; Liu, Ya-Jun

    2015-03-26

    Endohedral metallofullerene has novel properties because of the interaction between the encapsulated metal atom or cation and fullerene. Experiments have demonstrated that the insertion of Li(+) into C60 can greatly promote the reactivity of the Diels-Alder (DA) cycloaddition of cyclopentadiene (CpH) to C60. However, the reaction is sufficiently fast that its quantitative kinetic data cannot be obtained experimentally. In addition, knowledge regarding the effects of other alkali metal cations and metal cations with more charges on the reactivity and regioselectivity of C60 is almost nonexistent. In the current study, DA cycloadditions of CpH to M(+)@C60 (where M = Li, Na, K, Rb, and Cs) and Ca(2+)@C60 were investigated via density functional theory in the gas phase and in solvent. Via careful discussion and comparison with the results of C60, we concluded the following for the DA reaction of CpH to C60 and, more generally, for DA reactions of other fullerenes: (1) the encapsulated metal cations enhance the reactivity; (2) among alkali metal cations, Na(+) could be the best catalyst; (3) Ca(2+) is more favorable in promoting the reactivity than any alkali metal cation; (4) encapsulated metal cations with more positive charges enhance the reactivity of the 6-5 bond in C60, which is significant when the 6-5 adduct is the target product. PMID:25714730

  1. Bioaccessibility of metal cations in soil is linearly related to its water exchange rate constant.

    PubMed

    Laird, Brian D; Peak, Derek; Siciliano, Steven D

    2011-05-01

    Site-specific risk assessments often incorporate the concepts of bioaccessibility (i.e., contaminant fraction released into gastrointestinal fluids) or bioavailability (i.e., contaminant fraction absorbed into systemic circulation) into the calculation of ingestion exposure. We evaluated total and bioaccessible metal concentrations for 19 soil samples under simulated stomach and duodenal conditions using an in vitro gastrointestinal model. We demonstrated that the median bioaccessibility of 23 metals ranged between <1 and 41% under simulated stomach conditions and < 1 and 63% under simulated duodenal conditions. Notably, these large differences in metal bioaccessibility were independent of equilibrium solubility and stability constants. Instead, the relationship (stomach phase R = 0.927; duodenum phase R = 0.891) between bioaccessibility and water exchange rates of metal cations (k(H₂O)) indicated that desorption kinetics may influence if not control metal bioaccessibility. PMID:21466150

  2. Ultrafine Na-4-mica: uptake of alkali and alkaline earth metal cations by ion exchange.

    PubMed

    Kodama, Tatsuya; Ueda, Masahito; Nakamuro, Yumiko; Shimizu, Ken-ichi; Komarneni, Sridhar

    2004-06-01

    The cation exchange properties of alkali and alkaline earth metal cations at room temperature were investigated on an ultrafine, highly charged Na-4-mica (with the ideal mica composition Na4Mg6Al4Si4O20F4.xH2O). Ultrafine mica crystallites of 200 nm in size led to faster Sr2+ uptake kinetics in comparison to larger mica crystallites. The alkali metal ion (K+, Cs+, and Li+) exchange uptake was rapid, and complete exchange occurred within 30 min. For the alkaline earth metal ions Ba2+, Ca2+, and Mg2+, however, the exchange uptake required lengthy periods from 3 days to 4 weeks to be completed, similar to its Sr uptake, as previously reported. Kinetic models of the modified Freundlich and parabolic diffusion were examined for the experimental data on the Ba2+, Ca2+, and Mg2+ uptakes. The modified Freundlich model described well the Ba2+ ion uptake kinetics as well as that for the Sr2+ ion, while for the Ca2+ and Mg2+ ions the parabolic diffusion model showed better fitting. The alkali and alkaline earth ion exchange isotherms were also determined in comparison to the Sr2+ exchange isotherm. The thermodynamic equilibria for these cations were compared by using Kielland plots evaluated from the isotherms. PMID:15984251

  3. New generation super alloy candidates for medical applications: corrosion behavior, cation release and biological evaluation.

    PubMed

    Reclaru, L; Ziegenhagen, R; Unger, R E; Eschler, P Y; Constantin, F

    2014-12-01

    Three super alloy candidates (X1 CrNiMoMnW 24-22-6-3-2 N, NiCr21 MoNbFe 8-3-5 AlTi, CoNiCr 35-20 Mo 10 BTi) for a prolonged contact with skin are evaluated in comparison with two reference austenitic stainless steels 316L and 904L. Several electrochemical parameters were measured and determined (E(oc), E(corr), i(corr), b(a), b(c), E(b), R(p), E(crev) and coulometric analysis) in order to compare the corrosion behavior. The cation release evaluation and in vitro biological characterization also were performed. In terms of corrosion, the results reveal that the 904L steels presented the best behavior followed by the super austenitic steel X1 CrNiMoMnW 24-22-6-3-2 N. For the other two super alloys (NiCr and CoNiCr types alloys) tested in different conditions (annealed, work hardened and work hardened+age hardened) it was found that their behavior to corrosion was weak and close to the other reference stainless steel, 316L. Regarding the extraction a mixture of cations in relatively high concentrations was noted and therefore a cocktail effect was not excluded. The results obtained in the biological assays WST-1 and TNF-alpha were in correlation with the corrosion and extraction evaluation. PMID:25491846

  4. Synthesis and chemistry of cationic d sup 0 metal alkyl complexes

    SciTech Connect

    Jordan, R.F.

    1990-01-01

    The long term goals of this project are to design and synthesize highly unsaturated, electrophilic metal complexes and to explore their use as catalysts, reagents, and/or model systems for olefin polymerization and C-H activation chemistry. During the 1990 budget year we have focused our attention on (i) the ligand C-H activation chemistry of Cp{sub 2}Zr(CH{sub 3})(THF){sup +} and related cationic, d{sup o} Zr alkyl complexes, and (ii) the synthesis of new classes of group 4 metal alkyl complexes with non-Cp{sub 2}M ligand environments.

  5. A high-performance "sweeper" for toxic cationic herbicides: an anionic metal-organic framework with a tetrapodal cage.

    PubMed

    Jia, Yan-Yuan; Zhang, Ying-Hui; Xu, Jian; Feng, Rui; Zhang, Ming-Shi; Bu, Xian-He

    2015-12-21

    This communication reports a novel metal-organic framework exhibiting an excellent performance in adsorbing small toxic cationic herbicides, i.e. methyl viologen and diquat, with large adsorption capacities and ultratrace residue levels. To the best of our knowledge, this is the first example of high-performance MOFs trapping toxic cationic herbicides. PMID:26468513

  6. Humic Acid Metal Cation Interaction Studied by Spectromicroscopy Techniques in Combination with Quantum Chemical Calculations

    SciTech Connect

    Plaschke, M.; Rothe, J; Armbruster, M; Denecke, M; Naber, A; Geckeis, H

    2010-01-01

    Humic acids (HA) have a high binding capacity towards traces of toxic metal cations, thus affecting their transport in aquatic systems. Eu(III)-HA aggregates are studied by synchrotron-based scanning transmission X-ray microscopy (STXM) at the carbon K-edge and laser scanning luminescence microscopy (LSLM) at the {sup 5}D{sub 0} {yields} {sup 7}F{sub 1,2} fluorescence emission lines. Both methods provide the necessary spatial resolution in the sub-micrometre range to resolve characteristic aggregate morphologies: optically dense zones embedded in a matrix of less dense material in STXM images correspond to areas with increased Eu(III) luminescence yield in the LSLM micrographs. In the C 1s-NEXAFS of metal-loaded polyacrylic acid (PAA), used as a HA model compound, a distinct complexation effect is identified. This effect is similar to trends observed in the dense fraction of HA/metal cation aggregates. The strongest complexation effect is observed for the Zr(IV)-HA/PAA system. This effect is confirmed by quantum chemical calculations performed at the ab initio level for model complexes with different metal centres and complex geometries. Without the high spatial resolution of STXM and LSLM and without the combination of molecular modelling with experimental results, the different zones indicating a 'pseudo'-phase separation into strong complexing domains and weaker complexing domains of HA would never have been identified. This type of strategy can be used to study metal interaction with other organic material.

  7. Interparticle migration of metal cations in stream sediments as a factor in toxics transport

    USGS Publications Warehouse

    Jackman, A.P.; Kennedy, V.C.; Bhatia, N.

    2001-01-01

    Sorption of metal cations by stream sediments is an important process affecting the movement of released contaminants in the environment. The ability of cations to desorb from one sediment particle and subsequently sorb to another can greatly affect metal transport rates but rates for this process have not been reported. The objective of this study was to determine the rate at which sorbed metals can migrate from contaminated sediment particles to uncontaminated sediment particles as a function of the concentration of the contaminating solution and the duration of the contact with the contaminating solution. Samples of small sediment particles were exposed to solutions containing cobalt, after which they were rinsed and combined with larger uncontaminated sediment particles in the presence of stream water. Initial concentrations of the contaminating solution ranged from 1ng/l to 1000mg/l and exposures to the contaminating solution ranged from 6h to 14 days. The rate of the migration increased with increasing concentrations in the contaminating solution and with decreasing times of exposure to the contaminating solution. Under the conditions of these experiments, the time required for the migration to reach equilibrium was on the order of months or longer. In separate experiments, the kinetics of adsorption and desorption of cobalt were measured as a function of concentration of the contaminating solution. The time required to reach adsorption equilibrium increased with increasing concentration in the contaminating solution. Times to sorption equilibrium were on the order of months. Desorption was much slower than adsorption and, together with intraparticle diffusion, probably controls the rate of migration from contaminated to uncontaminated sediment. The results of this study show that interparticle migration of metal cations can proceed at significant rates that are strongly influenced by the length of time that the metal has been in contact with the sediment

  8. Gas-phase activation of methane by ligated transition-metal cations

    PubMed Central

    Schröder, Detlef; Schwarz, Helmut

    2008-01-01

    Motivated by the search for ways of a more efficient usage of the large, unexploited resources of methane, recent progress in the gas-phase activation of methane by ligated transition-metal ions is discussed. Mass spectrometric experiments demonstrate that the ligands can crucially influence both reactivity and selectivity of transition-metal cations in bond-activation processes, and the most reactive species derive from combinations of transition metals with the electronegative elements fluorine, oxygen, and chlorine. Furthermore, the collected knowledge about intramolecular kinetic isotope effects associated with the activation of C–H(D) bonds of methane can be used to distinguish the nature of the bond activation as a mere hydrogen-abstraction, a metal-assisted mechanism or more complex reactions such as formation of insertion intermediates or σ-bond metathesis. PMID:18955709

  9. Highly Tunable Colloidal Perovskite Nanoplatelets through Variable Cation, Metal, and Halide Composition.

    PubMed

    Weidman, Mark C; Seitz, Michael; Stranks, Samuel D; Tisdale, William A

    2016-08-23

    Colloidal perovskite nanoplatelets are a promising class of semiconductor nanomaterials-exhibiting bright luminescence, tunable and spectrally narrow absorption and emission features, strongly confined excitonic states, and facile colloidal synthesis. Here, we demonstrate the high degree of spectral tunability achievable through variation of the cation, metal, and halide composition as well as nanoplatelet thickness. We synthesize nanoplatelets of the form L2[ABX3]n-1BX4, where L is an organic ligand (octylammonium, butylammonium), A is a monovalent metal or organic molecular cation (cesium, methylammonium, formamidinium), B is a divalent metal cation (lead, tin), X is a halide anion (chloride, bromide, iodide), and n-1 is the number of unit cells in thickness. We show that variation of n, B, and X leads to large changes in the absorption and emission energy, while variation of the A cation leads to only subtle changes but can significantly impact the nanoplatelet stability and photoluminescence quantum yield (with values over 20%). Furthermore, mixed halide nanoplatelets exhibit continuous spectral tunability over a 1.5 eV spectral range, from 2.2 to 3.7 eV. The nanoplatelets have relatively large lateral dimensions (100 nm to 1 μm), which promote self-assembly into stacked superlattice structures-the periodicity of which can be adjusted based on the nanoplatelet surface ligand length. These results demonstrate the versatility of colloidal perovskite nanoplatelets as a material platform, with tunability extending from the deep-UV, across the visible, into the near-IR. In particular, the tin-containing nanoplatelets represent a significant addition to the small but increasingly important family of lead- and cadmium-free colloidal semiconductors. PMID:27471862

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

    DOEpatents

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

    2013-08-13

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

  11. Complexation of Trivalent Metal Cations to Mannuronate Type Alginate Models from a Density Functional Study.

    PubMed

    Menakbi, Chemseddine; Quignard, Francoise; Mineva, Tzonka

    2016-04-21

    Complexation of alginate models, built of β-d-mannuronic units (M) linked by a 1-4 glycosidic bridge, to Al(3+), Sc(3+), Cr(3+), Fe(3+), Ga(3+), and La(3+) cations was studied by applying the quantum chemical density functional theory (DFT) based method. The binding modes and energies were obtained for complexes with one, two, and three truncated alginate chain(s). In all the hydrated structures a monodentate binding mode is established to be the energetically most favored with shorter M(3+)···O(COO(-)) bonds than M(3+)···O(OH) bonds. Coordination bond lengths are found to be specific to each cation and to depend very little on the water in the coordination sphere and on the number of saccharide units used to model an alginate chain. The binding energy tendency Fe(3+) ≈ Cr(3+) > Al(3+) ≈ Ga(3+) ≫ Sc(3+) ≥ La(3+) is not affected by the alginate models, the coordination to water molecules, and the number of chains. A significant covalent contribution that arises predominantly from a charge donation from the carboxylate oxygen to the metal cation was established from the orbital population analysis. An exothermic chain-chain association is predicted by the computed enthalpy variations. A comparison between the structural features of alginate complexation to trivalent and divalent cations is provided and discussed. PMID:27010554

  12. Hydrogen-bonded inclusion compounds with reversed polarity: anionic metal-complexes and cationic organic linkers.

    PubMed

    Prakash, M Jaya; Sevov, Slavi C

    2011-12-19

    Synthesized and structurally characterized is a new series of soft-host frameworks assembled by charge-assisted hydrogen bonds between an anionic metal complex (MC) and cationic organic linkers (OL), specifically [Co(en)(ox)(2)](-) and diprotonated 4,4'-bipyridinium (H(2)bpy) or 1,2-bis(4-pyridinium)ethylene (H(2)bpye). While frameworks built of cationic complexes and anionic organic linkers are already well-known, the seven new compounds described here represent the first series of frameworks with reversed polarity, that is, made of anionic complexes and cationic organic linkers. The compounds have a general formula [OL][MC](2)·n(guest), where the guest molecules 4,4'-biphenol (bp), 4-methoxyphenol (mp), 1,4-dimethoxybenzene (dmb), 1,6-dimethoxynaphtalene (dmn), and 4-nitroanisole (na). Structurally the compounds can be described as pillared-layer frameworks with layers constructed of MC anions and linked together by hydrogen-bonded cationic OL pillars. The guest molecules occupy the galleries between the pillars while their steric, electronic, and π-π and hydrogen-bonding capabilities influence the overall structure of the soft frameworks. PMID:22085246

  13. Multi-physical model of cation and water transport in ionic polymer-metal composite sensors

    NASA Astrophysics Data System (ADS)

    Zhu, Zicai; Chang, Longfei; Horiuchi, Tetsuya; Takagi, Kentaro; Aabloo, Alvo; Asaka, Kinji

    2016-03-01

    Ion-migration based electrical potential widely exists not only in natural systems but also in ionic polymer materials. We presented a multi-physical model and investigated the transport process of cation and water of ionic polymer-metal composites based on our thorough understanding on the ionic sensing mechanisms in this paper. The whole transport process was depicted by transport equations concerning convection flux under the total pressure gradient, electrical migration by the built-in electrical field, and the inter-coupling effect between cation and water. With numerical analysis, the influence of critical material parameters, the elastic modulus Ewet, the hydraulic permeability coefficient K, the diffusion coefficient of cation dII and water dWW, and the drag coefficient of water ndW, on the distribution of cation and water was investigated. It was obtained how these parameters correlate to the voltage characteristics (both magnitude and response speed) under a step bending. Additionally, it was found that the effective relative dielectric constant ɛr has little influence on the voltage but is positively correlated to the current. With a series of optimized parameters, the predicted voltage agreed with the experimental results well, which validated our model. Based on our physical model, it was suggested that an ionic polymer sensor can benefit from a higher modulus Ewet, a higher coefficient K and a lower coefficient dII, and a higher constant ɛr.

  14. Investigation of biologically-designed metal-specific chelators for potential metal recovery and waste remediation applications.

    SciTech Connect

    Criscenti, Louise Jacqueline; Ockwig, Nathan W.

    2009-01-01

    Bacteria, algae and plants produce metal-specific chelators to capture required nutrient or toxic trace metals. Biological systems are thought to be very efficient, honed by evolutionary forces over time. Understanding the approaches used by living organisms to select for specific metals in the environment may lead to design of cheaper and more effective approaches for metal recovery and contaminant-metal remediation. In this study, the binding of a common siderophore, desferrioxamine B (DFO-B), to three aqueous metal cations, Fe(II), Fe(III), and UO{sub 2}(VI) was investigated using classical molecular dynamics. DFO-B has three acetohydroxamate groups and a terminal amine group that all deprotonate with increasing pH. For all three metals, complexes with DFO-B (-2) are the most stable and favored under alkaline conditions. Under more acidic conditions, the metal-DFO complexes involve chelation with both acetohydroxamate and acetylamine groups. The approach taken here allows for detailed investigation of metal binding to biologically-designed organic ligands.

  15. The effects of mono- and divalent metal cations on the solution structure of caffeine and theophylline

    NASA Astrophysics Data System (ADS)

    Nafisi, Shohreh; Monajemi, Majid; Ebrahimi, Saeedeh

    2004-11-01

    The interactions of caffeine and theophylline with potassium +, cobalt 2+ and nickel 2+ ions were studied in aqueous solution at physiological pH with constant ligand concentration and various metal ion contents. Fourier Transform infrared spectroscopy and absorption spectra were used to determine the cation binding mode and association constants. Spectroscopic results showed direct and indirect cation interactions for Co 2+, Ni 2+ and K + through O6 and N9 atoms (caffeine) and O6, N9 and N7 atoms (theophylline). The overall binding constants were, K(Co-caffeine)=6.92×10 4 M -1, K(Ni-caffeine)=2.22×10 4 M -1, K(K-caffeine)=5.08×10 3 M -1, K(Co-theophylline)=5.06×10 4 M -1, K(Ni-theophylline)=4.84×10 4 M -1 and K(K-theophylline)=2.13×10 3 M -1. The association constants showed weaker interaction for monovalent cation than divalent metal ions.

  16. Strategies to Suppress Cation Vacancies in Metal Oxide Alloys: Consequences for Solar Energy Conversion

    SciTech Connect

    Toroker, Maytal; Carter, Emily A.

    2015-09-01

    First-row transition metal oxides (TMOs) are promising alternative materials for inexpensive and efficient solar energy conversion. However, their conversion efficiency can be deleteriously affected by material imperfections, such as atomic vacancies. In this work, we provide examples showing that in some iron-containing TMOs, iron cation vacancy formation can be suppressed via alloying. We calculate within density functional theory+U theory the iron vacancy formation energy in binary rock-salt oxide alloys that contain iron, manganese, nickel, zinc, and/or magnesium. We demonstrate that formation of iron vacancies is less favorable if we choose to alloy iron(II) oxide with metals that cannot readily accept vacancy-generated holes, e.g., magnesium, manganese, nickel, or zinc. Since there are less available sites for holes and the holes are forced to reside on iron cations, the driving force for iron vacancy formation decreases. These results are consistent with an experiment observing a sharp drop in cation vacancy concentration upon alloying iron(II) oxide with manganese.

  17. A new efficient forest biowaste as biosorbent for removal of cationic heavy metals.

    PubMed

    Kim, Namgyu; Park, Munsik; Park, Donghee

    2014-10-25

    Among various forest biowastes, chestnut bur had the highest uptake values of Cd(II) and Pb(II), and these values were higher than those of agricultural biowastes used as comparable biosorbents. This study is the first report showing the high potential of chestnut bur as biosorbent for the removal of cationic heavy metals. Pseudo-second-order equation satisfactorily described the biosorption behaviors of both metals. Biosorption rate of Pb(II) was 3.12 times higher than that of Cd(II). Langmuir model could fit the equilibrium isotherm data better than Freundlich model. The maximum uptake capacities of Cd(II) and Pb(II) were determined to be 34.77mg/g and 74.35mg/g, respectively. FTIR study showed that carboxyl group on the biosorbent was involved in biosorbing the cationic metals. In conclusion, abundant and cheap forest biowastes, especially chestnut bur, is a potent candidate for efficient biosorbent capable of removing toxic heavy metals from aqueous solutions. PMID:25467000

  18. Changes in the Vibrational Spectra of Zeolites Due to Sorption of Heavy Metal Cations

    NASA Astrophysics Data System (ADS)

    Król, M.; Mozgawa, W.; Barczyk, K.; Bajda, T.; Kozanecki, M.

    2013-11-01

    This work presents the results of spectroscopic (MIR and Raman) studies of zeolite structures after immobilization of heavy metal cations from aqueous solutions. The sorption of Ag+, Cu2+, Cd2+, Pb2+, Zn2+, and Cr3+ ions has been conducted on zeolites belonging to different structural groups, i.e., sodium forms of natural chabazite, mordenite, ferrierite, and clinoptilolite, as well as on synthetic zeolite Y. Systematic changes in intensities and positions of the bands corresponding to the characteristic ring vibrations have been observed in the measured spectra. The most visible changes are observed in the FT-IR spectra of the samples in the range of 850-450 cm-1, and in the Raman spectra in the range of 600-250 cm-1. Depending on the zeolite structure, the bands, which can be regarded as a kind of indicator of ion exchange, were indentifi ed. For example, in the case of IR spectra, these bands are at 766, 703, 648, 578, and 506 cm-1 for zeolite Y, at 733 and 560 cm-1 for mordenite, at 675 cm-1 for clinoptilolite, etc. The degree of changes depends on both the type of cation and its concentration in the initial solution. This is connected with the way of binding of metal ions to the zeolite aluminosilicate framework, i.e., a proportion of the ion exchange and chemisorption in the process. Cations mainly undergoing ion exchange, such as Cd2+ or Pb2+, have the greatest impact on the character of the spectra. On the other hand, Cr3+ ions practically do not modify the spectra of zeolites. Results of IR and Raman spectroscopic studies have been compared with those obtained by atomic absorption spectroscopy (AAS), from which the proportion of ion exchange to chemisorption in the process and the effective cation exchange capacity of the individual samples have been estimated.

  19. On the real performance of cation exchange resins in wastewater treatment under conditions of cation competition: the case of heavy metal pollution.

    PubMed

    Prelot, Benedicte; Ayed, Imen; Marchandeau, Franck; Zajac, Jerzy

    2014-01-01

    Sorption performance of cation-exchange resins Amberlite® IRN77 and Amberlite™ IRN9652 toward Cs(I) and Sr(II) has been tested in single-component aqueous solutions and simulated waste effluents containing other monovalent (Effluent 1) or divalent (Effluent 2) metal cations, as well as nitrate, borate, or carbonate anions. The individual sorption isotherms of each main component were measured by the solution depletion method. The differential molar enthalpy changes accompanying the ion-exchange between Cs+ or Sr2+ ions and protons at the resin surface from single-component nitrate solutions were measured by isothermal titration calorimetry and they showed a higher specificity of the two resins toward cesium. Compared to the retention limits of both resins under such idealized conditions, an important depression in the maximum adsorption capacity toward each main component was observed in multication systems. The overall effect of ion exchange process appeared to be an unpredictable outcome of the individual sorption capacities of the two resins toward various cations as a function of the cation charge, size, and concentration. The cesium retention capacity of the resins was diminished to about 25% of the "ideal" value in Effluent 1 and 50% in Effluent 2; a further decrease to about 15% was observed upon concomitant strontium addition. The uptake of strontium by the resins was found to be less sensitive to the addition of other metal components: the greatest decrease in the amount adsorbed was 60% of the ideal value in the two effluents for Amberlite® IRN77 and 75% for Amberlite™ IRN9652. It was therefore demonstrated that any performance tests carried out under idealized conditions should be exploited with much caution to predict the real performance of cation exchange resins under conditions of cation competition. PMID:24728575

  20. Plant cation/H(+) exchangers (CAXs): biological functions and genetic manipulations

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Inorganic cations play decisive roles in many cellular and physiological processes and are essential components of plant nutrition. Therefore, the uptake of cations and their redistribution must be precisely controlled. Vacuolar antiporters are important elements in mediating the intracellular seque...

  1. Biologically active compounds of semi-metals.

    PubMed

    Rezanka, Tomás; Sigler, Karel

    2008-02-01

    Semi-metals (boron, silicon, arsenic and selenium) form organo-metal compounds, some of which are found in nature and affect the physiology of living organisms. They include, e.g., the boron-containing antibiotics aplasmomycin, borophycin, boromycin, and tartrolon or the silicon compounds present in "silicate" bacteria, relatives of the genus Bacillus, which release silicon from aluminosilicates through the secretion of organic acids. Arsenic is incorporated into arsenosugars and arsenobetaines by marine algae and invertebrates, and fungi and bacteria can produce volatile methylated arsenic compounds. Some prokaryotes can use arsenate as a terminal electron acceptor while others can utilize arsenite as an electron donor to generate energy. Selenium is incorporated into selenocysteine that is found in some proteins. Biomethylation of selenide produces methylselenide and dimethylselenide. Selenium analogues of amino acids, antitumor, antibacterial, antifungal, antiviral, anti-infective drugs are often used as analogues of important pharmacological sulfur compounds. Other metalloids, i.e. the rare and toxic tellurium and the radioactive short-lived astatine, have no biological significance. PMID:17991498

  2. Resorcarene-based receptor: versatile behavior in its interaction with heavy and soft metal cations.

    PubMed

    Danil de Namor, Angela F; Chaaban, Jinane K; Piro, Oscar E; Castellano, Eduardo E

    2006-02-01

    Standard solution Gibbs energies, DeltasG degrees, of the resorcarene-based receptor 5,11,17,23-ethylthiomethylated calix[4]resorcarene, (characterized by 1H NMR and X-ray diffraction studies) in its monomeric state (established through partition experiments) in various solvents are for the first time reported in the area of resorcarene chemistry. Transfer Gibbs energies of from hexane (reference solvent) to other medium are calculated. Agreement between DeltatG degrees (referred to the pure solvents) and standard partition Gibbs energies, DeltapG degrees (solvent mutually saturated) is found. Cation-ligand interactions were investigated through 1H NMR (CD3CN and CD3OD) and conductometric titrations in acetonitrile and methanol. 1H NMR data revealed the sites of interaction of with the metal cation. The composition of the metal-ion complexes (Ag+ and Pb2+ in acetonitrile and Ag+ and Cu2+ in methanol) was established through conductometric titrations. Thus, complexes of 1:1 stoichiometry were formed between and Ag+ and Pb2+ in acetonitrile and Cu2+ in methanol. However, in moving from acetonitrile to methanol, the composition of the silver complex was altered. Thus, two metal cations are hosted by a unit of the ligand. As far as Cu2+ and in acetonitrile is concerned, conductance data suggest that metalates are formed in which up to four units of Cu2+ are taken up per unit of resorcarene. The contrasting behavior of with Cu2+ in acetonitrile relative to methanol is discussed. As far as mercury (II) is concerned, the unusual jump in conductance observed in the titration of Hg2+ with in acetonitrile and methanol after the formation of a multicharged complex (undefined composition) is attributed to the presence of highly charged smaller units (higher mobility) resulting from the departure of pendant arms from the resorcarene backbone. Isolation of these species followed by X-ray diffraction studies corroborated this statement. The thermodynamic characterization of metal

  3. A Water-Stable Cationic Metal-Organic Framework as a Dual Adsorbent of Oxoanion Pollutants.

    PubMed

    Desai, Aamod V; Manna, Biplab; Karmakar, Avishek; Sahu, Amit; Ghosh, Sujit K

    2016-06-27

    A three-dimensional water-stable cationic metal-organic framework (MOF) pillared by a neutral ligand and with Ni(II)  metal nodes has been synthesized employing a rational design approach. Owing to the ordered arrangement of the uncoordinated tetrahedral sulfate (SO4 (2-) ) ions in the channels, the compound has been employed for aqueous-phase ion-exchange applications. The compound exhibits rapid and colorimetric aqueous-phase capture of environmentally toxic oxoanions (with similar geometries) in a selective manner. This system is the first example of a MOF-based system which absorbs both dichromate (Cr2 O7 (2-) ) and permanganate (MnO4 (-) ) ions, with the latter acting as a model for the radioactive contaminant pertechnetate (TcO4 (-) ). PMID:26855323

  4. Ca(2+) function in photosynthetic oxygen evolution studied by alkali metal cations substitution.

    PubMed

    Ono, T; Rompel, A; Mino, H; Chiba, N

    2001-10-01

    Effects of adding monovalent alkali metal cations to Ca(2+)-depleted photosystem (PS)II membranes on the biochemical and spectroscopic properties of the oxygen-evolving complex were studied. The Ca(2+)-dependent oxygen evolution was competitively inhibited by K(+), Rb(+), and Cs(+), the ionic radii of which are larger than the radius of Ca(2+) but not inhibited significantly by Li(+) and Na(+), the ionic radii of which are smaller than that of Ca(2+). Ca(2+)-depleted membranes without metal cation supplementation showed normal S(2) multiline electron paramagnetic resonance (EPR) signal and an S(2)Q(A)(-) thermoluminescence (TL) band with a normal peak temperature after illumination under conditions for single turnover of PSII. Membranes supplemented with Li(+) or Na(+) showed properties similar to those of the Ca(2+)-depleted membranes, except for a small difference in the TL peak temperatures. The peak temperature of the TL band of membranes supplemented with K(+), Rb(+), or Cs(+) was elevated to approximately 38 degrees C which coincided with that of Y(D)(+)Q(A)(-) TL band, and no S(2) EPR signals were detected. The K(+)-induced high-temperature TL band and the S(2)Q(A)(-) TL band were interconvertible by the addition of K(+) or Ca(2+) in the dark. Both the Ca(2+)-depleted and the K(+)-substituted membranes showed the narrow EPR signal corresponding to the S(2)Y(Z)(+) state at g = 2 by illuminating the membranes under multiple turnover conditions. These results indicate that the ionic radii of the cations occupying Ca(2+)-binding site crucially affect the properties of the manganese cluster. PMID:11566758

  5. Separation of silver from other metal cations using pyridone and triazole macrocycles in liquid membrane systems

    SciTech Connect

    Izatt, R.M.; LindH, G.C.; Bruening, R.L.; Huszthy, P.; McDaniel, C.W.; Bradshaw, J.S.; Christensen, J.J.

    1988-09-01

    Selective transport of Ag/sup +/ over other metal ions in competitive experiments in bulk and emulsion liquid membrane systems has been accomplished by using macrocycles of the proton-ionizable pyridone and triazole types. The transport of Ag/sup +/ by the pyridone macrocycles involves the cotransport of an anion, while transport by the triazole macrocycles can involve either co-anion transport or the counter transport of H/sup +/. In particular, the affinity of Ag/sup +/ for the triazole moiety, the excellent fit of Ag/sup +/ into an 18-crown-6 sized cavity, and the presence of only one proton-ionizable site per macrocycle molecule combine to produce highly selective transport of Ag/sup +/ over Pb/sup 2 +/ and Tl/sup +/ with triazolo-18-crown-6 derivatives in membrane systems containing acid receiving phases. Transport of alkali-, alkaline-earth-, and several transition-metal cations is minimal in similar membrane systems and, hence, selective transport of Ag/sup +/ over these cations is also expected.

  6. Asymmetric partitioning of metals among cluster anions and cations generated via laser ablation of mixed aluminum/Group 6 transition metal targets.

    PubMed

    Waller, Sarah E; Mann, Jennifer E; Jarrold, Caroline Chick

    2013-02-28

    While high-power laser ablation of metal alloys indiscriminately produces gas-phase atomic ions in proportion to the abundance of the various metals in the alloy, gas-phase ions produced by moderate-power laser ablation sources coupled with molecular beams are formed by more complicated mechanisms. A mass spectrometric study that directly compares the mass distributions of cluster anions and cations generated from laser ablation of pure aluminum, an aluminum/molybdenum mixed target, and an aluminum/tungsten mixed target is detailed. Mass spectra of anionic species generated from the mixed targets showed that both tungsten and molybdenum were in higher abundance in the negatively charged species than in the target material. Mass spectra of the cationic species showed primarily Al(+) and aluminum oxide and hydroxide cluster cations. No molybdenum- or tungsten-containing cluster cations were definitively assigned. The asymmetric distribution of aluminum and Group 6 transition metals in cation and anion cluster composition is attributed to the low ionization energy of atomic aluminum and aluminum suboxide clusters. In addition, the propensity of both molybdenum and tungsten to form metal oxide cluster anions under the same conditions that favor metallic aluminum cluster anions is attributed to differences in the optical properties of the surface oxide that is present in the metal powders used to prepare the ablation targets. Mechanisms of mixed metal oxide clusters are considered. PMID:23413829

  7. The complexes of some s-triazine herbicides with metal cations studied by ESI mass spectrometry and theoretical calculations

    NASA Astrophysics Data System (ADS)

    Lyapchenko, Nataliya; Eitner, Krystian; Schroeder, Grzegorz; Brzezinski, Bogumił

    2004-03-01

    The complex formation of s-triazine herbicides (prometon, ametryn, terbutryn and simazin) with monovalent and divalent cations as well as the structure of the complexes was studied by the electrospray ionization mass spectrometry and PM5 semiempirical methods. It is demonstrated that the herbicides studied form stable complexes with monovalent and heavy metal cations, which is of very great importance for agriculture especially in the aspect of the environment protection.

  8. Spectroscopic characterization of the uptake of essential and xenobiotic metal cations in cells of the soil bacterium Azospirillum brasilense.

    PubMed

    Kamnev, A A; Renou-Gonnord, M F; Antonyuk, L P; Colina, M; Chernyshev, A V; Frolov, I; Ignatov, V V

    1997-01-01

    The results of flame (FAAS) or graphite furnace atomic absorption spectrometric (GFAAS) analyses are presented and discussed on the accumulation of essential metals (Mg, Ca, Mn and Fe contained in the cultivation medium) and traces of each one of the conventionally xenobiotic elements from the group V, Co, Ni, Cu, Zn or Pb, added to the medium in concentrations (0.2 mM) which do not essentially suppress growth of the bacterial culture, in cells of the plant root-associated nitrogen-fixing bacterium Azospirillum brasilense. Along with the essential cations assimilated by the bacterium, Zn and Cu were found to effectively accumulate in the biomass from the environment. The uptake of Co and Ni was significantly less pronounced, whereas Pb and V appeared to be present in cells in much lower concentrations than in the cultivation medium evidently showing no tendency to be assimilated by azospirilla. The effect of the above xenobiotics on the uptake level of the four essential elements provided evidence that they may compete for the formation of biologically active complexes with substances of both intracellular and extracellular localization. The analytical data obtained are compared with Fourier transform infrared (FTIR) spectra of intact vacuum-dried bacterial cells grown in a standard medium and under the conditions of an increased metal uptake. PMID:9043641

  9. Modeling sorption of divalent metal cations on hydrous manganese oxide using the diffuse double layer model

    USGS Publications Warehouse

    Tonkin, J.W.; Balistrieri, L.S.; Murray, J.W.

    2004-01-01

    Manganese oxides are important scavengers of trace metals and other contaminants in the environment. The inclusion of Mn oxides in predictive models, however, has been difficult due to the lack of a comprehensive set of sorption reactions consistent with a given surface complexation model (SCM), and the discrepancies between published sorption data and predictions using the available models. The authors have compiled a set of surface complexation reactions for synthetic hydrous Mn oxide (HMO) using a two surface site model and the diffuse double layer SCM which complements databases developed for hydrous Fe (III) oxide, goethite and crystalline Al oxide. This compilation encompasses a range of data observed in the literature for the complex HMO surface and provides an error envelope for predictions not well defined by fitting parameters for single or limited data sets. Data describing surface characteristics and cation sorption were compiled from the literature for the synthetic HMO phases birnessite, vernadite and ??-MnO2. A specific surface area of 746 m2g-1 and a surface site density of 2.1 mmol g-1 were determined from crystallographic data and considered fixed parameters in the model. Potentiometric titration data sets were adjusted to a pH1EP value of 2.2. Two site types (???XOH and ???YOH) were used. The fraction of total sites attributed to ???XOH (??) and pKa2 were optimized for each of 7 published potentiometric titration data sets using the computer program FITEQL3.2. pKa2 values of 2.35??0.077 (???XOH) and 6.06??0.040 (???YOH) were determined at the 95% confidence level. The calculated average ?? value was 0.64, with high and low values ranging from 1.0 to 0.24, respectively. pKa2 and ?? values and published cation sorption data were used subsequently to determine equilibrium surface complexation constants for Ba2+, Ca2+, Cd 2+, Co2+, Cu2+, Mg2+, Mn 2+, Ni2+, Pb2+, Sr2+ and Zn 2+. In addition, average model parameters were used to predict additional

  10. Organometallic Probe for the Electronics of Base-Stabilized Group 11 Metal Cations.

    PubMed

    Braunschweig, Holger; Ewing, William C; Kramer, Thomas; Mattock, James D; Vargas, Alfredo; Werner, Christine

    2015-08-24

    A number of trimetalloborides have been synthesized through the reactions of base-stabilized coinage metal chlorides with a dimanganaborylene lithium salt in the hope of using this organometallic platform to compare and evaluate the electronics of these popular coinage metal fragments. The adducts of Cu(I), Ag(I), and Au(I) ions, stabilized by tricyclohexylphosphine (PCy3), N-1,3-bis(4-methylphenyl)imidazol-2-ylidene (ITol), or 1-(2,6-diisopropylphenyl)-3,3,5,5-tetramethylpyrrolidin-2-ylidene (CAAC), with [{Cp(CO)2Mn}2B](-) were studied spectroscopically, structurally, and computationally. The geometries of the adducts fall into two classes, one symmetric and one asymmetric, each relying on the combined characteristics of both the metal and ligand. The energetic factors proposed as the causes of the structural differences were investigated by ETS-NOCV (extended transition state-natural orbitals for chemical valence) analysis, which showed the final geometry to be controlled by the competition between the tendency of the coinage metal to adopt a higher or lower coordination number and the willingness of the cationic fragment to participate in back-bonding interactions. PMID:26178571

  11. Solution-Membrane Equilibrium at Metal-Deposited Cation-Exchange Membranes: Chronopotentiometric Characterization of Metal-Modified Membranes.

    PubMed

    Shahi; Prakash; Ramachandraiah; Rangarajan; Vasudevan

    1999-08-01

    Copper- and lead-deposited interpolymer cationic membranes have been prepared by electroless plating by an ion-exchange method and characterized by chronopotentiometry and cyclic voltammetry. The parameters such as transition time (tau), Itau1/2, the potential drop (E0) across these membranes immediately after the application of constant current (I), and the height of the potential jump (DeltaE) across the membrane at tau have been measured by chronopotentiometry and compared with those of plain membranes. The approximate percentage of metal coverage and the number of ionic sites masked by the deposited metal in terms of NaCl concentration have been estimated from the differences in Itau1/2 values of plain and metal-deposited membranes. The quantity of metal deposited in a unit area of the membrane surface was measured by differential pulse polarography. The oxidation and reduction peak potentials corresponding to Cu(0)/Cu(II) and Pb(0)/Pb(II) couples were identified by cyclic voltammetry at pH 2.8 and 4.5 of 0.2 M CH3COONa-H2SO4. Copyright 1999 Academic Press. PMID:10395776

  12. Structures of the dehydrogenation products of methane activation by 5d transition metal cations.

    PubMed

    Lapoutre, V J F; Redlich, B; van der Meer, A F G; Oomens, J; Bakker, J M; Sweeney, A; Mookherjee, A; Armentrout, P B

    2013-05-23

    The activation of methane by gas-phase transition metal cations (M(+)) has been studied extensively, both experimentally and using density functional theory (DFT). Methane is exothermically dehydrogenated by several 5d metal ions to form [M,C,2H](+) and H2. However, the structure of the dehydrogenation product has not been established unambiguously. Two types of structures have been considered: a carbene structure where an intact CH2 fragment is bound to the metal (M(+)-CH2) and a carbyne (hydrido-methylidyne) structure with both a CH and a hydrogen bound to the metal separately (H-M(+)-CH). For metal ions with empty d-orbitals, an agostic interaction can occur that could influence the competition between carbene and carbyne structures. In this work, the gas phase [M,C,2H](+) (M = Ta, W, Ir, Pt) products are investigated by infrared multiple-photon dissociation (IR-MPD) spectroscopy using the Free-Electron Laser for IntraCavity Experiments (FELICE). Metal cations are formed in a laser ablation source and react with methane pulsed into a reaction channel downstream. IR-MPD spectra of the [M,C,2H](+) species are measured in the 300-3500 cm(-1) spectral range by monitoring the loss of H (2H in the case of [Ir,C,2H](+)). For each system, the experimental spectrum closely resembles the calculated spectrum of the lowest energy structure calculated using DFT: for Pt, a classic C(2v) carbene structure; for Ta and W, carbene structures that are distorted by agostic interactions; and a carbyne structure for the Ir complex. The Ir carbyne structure was not considered previously. To obtain this agreement, the calculated harmonic frequencies are scaled with a scaling factor of 0.939, which is fairly low and can be attributed to the strong redshift induced by the IR multiple-photon excitation process of these small molecules. These four-atomic species are among the smallest systems studied by IR-FEL based IR-MPD spectroscopy, and their spectra demonstrate the power of IR

  13. The role of multivalent metal cations and organic complexing agents in bitumen-mineral interactions in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Gan, Weibing

    A systematic investigation was carried out to study the interactions between bitumen (or hexadecane) and minerals (quartz, kaolinite and illite) in aqueous solutions containing multivalent metal cations Ca2+, Mg2+ and Fe2+/Fe3+, in the absence and presence of organic complexing agents (oxalic acid, EDTA and citric acid). A range of experimental techniques, including coagulation measurement, visualization of bitumen-mineral attachment, metal ion adsorption measurement, zeta potential measurement, Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopic analyses, were employed in the investigation. Free energy changes of adsorption of metal cations on the minerals and bitumen were evaluated using the James & Healy thermodynamic model. Total interaction energies between the minerals and bitumen were calculated using classical DLVO theory. It was observed that while the tested minerals showed varying degrees of mutual-coagulation with bitumen (or hexadecane), the presence of the multivalent metal cations could prominently increase the mutual coagulation. It was also found that such enhancement of the mutual coagulation was only significant when the metal cations formed first-order hydroxyl complexes (such as CaOH +, MgOH+, etc.) or metal hydroxides (such as Fe(OH) 3, Mg(OH)2, etc.). Therefore, the increase of the bitumen-mineral mutual coagulation by the metal cations was strongly pH dependent. Organic complexing agents (oxalic acid, citric acid and EDTA) used in this study, citric acid in particular, significantly reduced or virtually eliminated the mutual coagulation between bitumen (or hexadecane) and minerals caused by metal cations Ca2+, Mg2+, Fe 2+ and Fe3+. Due to its ability to substantially lower the mutual coagulation between bitumen and mineral particles, citric acid was found the most effective in improving bitumen-mineral liberation in solutions containing the multivalent metal cations at pH 8--10. In small scale flotation experiments

  14. HNS(+) and HSN(+) cations: Electronic states, spin-rovibronic spectroscopy with planetary and biological implications.

    PubMed

    Trabelsi, Tarek; Ben Yaghlane, Saida; Al Mogren, Muneerah Mogren; Francisco, Joseph S; Hochlaf, Majdi

    2016-08-28

    Ab initio methods in conjunction with a large basis set are used to compute the potential energy surfaces of the 12 lowest electronic states of the HNS(+) and HSN(+) isomeric forms. These potentials are used in discussions of the metastability of these cations and plausible mechanisms for the H(+)/H + SN(+)/SN, S/S(+) + NH(+)/NH, N/N(+) + SH(+)/SH ion-molecule reactions. Interestingly, the low rovibrational levels of HSN(+)(1(2)A″) and HNS(+)(1(2)A″) electronically excited ions are predicted to be long-lived. Both ions are suggested to be a suitable candidate for light-sensitive NO(⋅) donor in vivo and as a possible marker for the detection of intermediates in nitrites + H2S reactions at the cellular level. The full spin rovibronic levels of HNS(+) are presented, which may assist in the experimental identification of HNS(+) and HSN(+) ions and in elucidating their roles in astrophysical and biological media. PMID:27586922

  15. BIOLOGICAL MONITORING OF TOXIC TRACE METALS. VOLUME 1. BIOLOGICAL MONITORING AND SURVEILLANCE

    EPA Science Inventory

    The needs and priorities in using biological accumulator organisms for monitoring toxic trace metals in plants and animals are analyzed. The toxic trace metals selected for study are antimony, arsenic, beryllium, boron, cadmium, chromium, cobalt, copper, lead, mercury, nickel, se...

  16. Development and validation of a ReaxFF reactive force field for Cu cation/water interactions and copper metal/metal oxide/metal hydroxide condensed phases.

    PubMed

    van Duin, Adri C T; Bryantsev, Vyacheslav S; Diallo, Mamadou S; Goddard, William A; Rahaman, Obaidur; Doren, Douglas J; Raymand, David; Hermansson, Kersti

    2010-09-01

    To enable large-scale reactive dynamic simulations of copper oxide/water and copper ion/water interactions we have extended the ReaxFF reactive force field framework to Cu/O/H interactions. To this end, we employed a multistage force field development strategy, where the initial training set (containing metal/metal oxide/metal hydroxide condensed phase data and [Cu(H(2)O)(n)](2+) cluster structures and energies) is augmented by single-point quantum mechanices (QM) energies from [Cu(H(2)O)(n)](2+) clusters abstracted from a ReaxFF molecular dynamics simulation. This provides a convenient strategy to both enrich the training set and to validate the final force field. To further validate the force field description we performed molecular dynamics simulations on Cu(2+)/water systems. We found good agreement between our results and earlier experimental and QM-based molecular dynamics work for the average Cu/water coordination, Jahn-Teller distortion, and inversion in [Cu(H(2)O)(6)](2+) clusters and first- and second-shell O-Cu-O angular distributions, indicating that this force field gives a satisfactory description of the Cu-cation/water interactions. We believe that this force field provides a computationally convenient method for studying the solution and surface chemistry of metal cations and metal oxides and, as such, has applications for studying protein/metal cation complexes, pH-dependent crystal growth/dissolution, and surface catalysis. PMID:20707333

  17. Competition between pi and non-pi cation-binding sites in aromatic amino acids: a theoretical study of alkali metal cation (Li+, Na+, K+)-phenylalanine complexes.

    PubMed

    Siu, Fung Ming; Ma, Ngai Ling; Tsang, Chun Wai

    2004-04-19

    To understand the cation-pi interaction in aromatic amino acids and peptides, the binding of M(+) (where M(+) = Li(+), Na(+), and K(+)) to phenylalanine (Phe) is studied at the best level of density functional theory reported so far. The different modes of M(+) binding show the same order of binding affinity (Li(+)>Na(+)>K(+)), in the approximate ratio of 2.2:1.5:1.0. The most stable binding mode is one in which the M(+) is stabilized by a tridentate interaction between the cation and the carbonyl oxygen (O[double bond]C), amino nitrogen (--NH(2)), and aromatic pi ring; the absolute Li(+), Na(+), and K(+) affinities are estimated theoretically to be 275, 201, and 141 kJ mol(-1), respectively. Factors affecting the relative stabilities of various M(+)-Phe binding modes and conformers have been identified, with ion-dipole interaction playing an important role. We found that the trend of pi and non-pi cation bonding distances (Na(+)-pi>Na(+)-N>Na(+)-O and K(+)-pi>K(+)-N>K(+)-O) in our theoretical Na(+)/K(+)-Phe structures are in agreement with the reported X-ray crystal structures of model synthetic receptors (sodium and potassium bound lariat ether complexes), even though the average alkali metal cation-pi distance found in the crystal structures is longer. This difference between the solid and the gas-phase structures can be reconciled by taking the higher coordination number of the cations in the lariat ether complexes into account. PMID:15079836

  18. Dependence of bonding interactions in Layered Double Hydroxides on metal cation chemistry

    NASA Astrophysics Data System (ADS)

    Shamim, Mostofa; Dana, Kausik

    2016-12-01

    The evolution of various Infrared bands of Layered Double Hydroxides (LDH) with variable Zn:Al ratio was analyzed to correlate it with the changes in octahedral metal cation chemistry, interlayer carbonate anion and hydroxyl content of LDH. The synthesized phase-pure LDHs were crystallized as hexagonal 2H polytype with a Manasseite structure. The broad and asymmetric hydroxyl stretching region (2400-4000 cm-1) can be deconvoluted into four different bands. With increase in Zn2+:Al3+ metal ratio, the peak position of stretching frequencies of Al3+sbnd OH and carbonate-bridged hydroxyl (water) decrease almost linearly. Individual band's peak position and area under the curve have been successfully correlated with the carbonate and hydroxyl content of LDH. Due to lowering of symmetry of the carbonate anion, the IR-inactive peak νCsbnd O, symm at 1064 cm-1 becomes IR active. The peak position of metal-oxygen bands and carbonate bending modes are practically unaffected by the Zn2+:Al3+ ratio but the area under the individual M-O bands shows a direct correlation.

  19. Preparation of metallic cation conducting polymers based on sterically hindered phenols containing polymeric systems

    DOEpatents

    Skotheim, T.A.; Okamoto, Yoshiyuki; Lee, H.S.

    1989-11-21

    The present invention relates to ion-conducting solvent-free polymeric systems characterized as being cationic single ion conductors. The solvent-free polymer electrolytes comprise a flexible polymer backbone to which is attached a metal salt, such as a lithium, sodium or potassium salt, of a sterically hindered phenol. The solid polymer electrolyte may be prepared either by (1) attaching the hindered phenol directly to a flexible polymeric backbone, followed by neutralization of the phenolic OH's or (2) reacting the hindered phenol with a polymer precursor which is then polymerized to form a flexible polymer having phenolic OH's which are subsequently neutralized. Preferably the hindered phenol-modified polymeric backbone contains a polyether segment. The ionic conductivity of these solvent-free polymer electrolytes has been measured to be in the range of 10[sup [minus]4] to 10[sup [minus]7] S cm[sup [minus]1] at room temperature.

  20. Preparation of metallic cation conducting polymers based on sterically hindered phenols containing polymeric systems

    DOEpatents

    Skotheim, Terje A.; Okamoto, Yoshiyuki; Lee, Hung S.

    1989-01-01

    The present invention relates to ion-conducting solvent-free polymeric systems characterized as being cationic single ion conductors. The solvent-free polymer electrolytes comprise a flexible polymer backbone to which is attached a metal salt, such as a lithium, sodium or potassium salt, of a sterically hindered phenol. The solid polymer electrolyte may be prepared either by (1) attaching the hindered phenol directly to a flexible polymeric backbone, followed by neutralization of the phenolic OH's or (2) reacting the hindered phenol with a polymer precursor which is then polymerized to form a flexible polymer having phenolic OH's which are subsequently neutralized. Preferably the hindered phenol-modified polymeric backbone contains a polyether segment. The ionic conductivity of these solvent-free polymer electrolytes has been measured to be in the range of 10.sup.-4 to 10.sup.-7 S cm.sup.-1 at room temperature.

  1. Structures of Hydrated Alkali Metal Cations, M+(H2O)nAr (m = Li, Na, K, rb and Cs, n = 3-5), Using Infrared Photodissociation Spectroscopy and Thermodynamic Analysis

    NASA Astrophysics Data System (ADS)

    Ke, Haochen; van der Linde, Christian; Lisy, James M.

    2014-06-01

    Alkali metal cations play vital roles in chemical and biochemical systems. Lithium is widely used in psychiatric treatment of manic states and bipolar disorder; Sodium and potassium are essential elements, having major biological roles as electrolytes, balancing osmotic pressure on body cells and assisting the electroneurographic signal transmission; Rubidium has seen increasing usage as a supplementation for manic depression and depression treatment; Cesium doped compounds are used as essential catalysts in chemical production and organic synthesis. Since hydrated alkali metal cations are ubiquitous and the basic form of the alkali metal cations in chemical and biochemical systems, their structural and thermodynamic properties serve as the foundation for modeling more complex chemical and biochemical processes, such as ion transport and ion size-selectivity of ionophores and protein channels. By combining mass spectrometry and infrared photodissociation spectroscopy, we have characterized the structures and thermodynamic properties of the hydrated alkali metal cations, i.e. M+(H2O)nAr, (M = Li, Na, K, Rb and Cs, n = 3-5). Ab initio calculations and RRKM-EE (evaporative ensemble) calculations were used to assist in the spectral assignments and thermodynamic analysis. Results showed that the structures of hydrated alkali metal cations were determined predominantly by the competition between non-covalent interactions, i.e. the water---water hydrogen bonding interactions and the water---cation electrostatic interactions. This balance, however, is very delicate and small changes, i.e. different cations, different levels of hydration and different effective temperatures clearly impact the balance.

  2. Identification and characterization of a Streptococcus pyogenes ABC transporter with multiple specificity for metal cations.

    PubMed

    Janulczyk, R; Pallon, J; Björck, L

    1999-11-01

    Metal ions are crucial trace elements for bacteria infecting the human host. The LraI (lipoprotein receptor-associated antigen I) transporter in Streptococcus spp. belongs to the superfamily of ABC transporters. The transporter consists of a lipoprotein, an ATP-binding protein and a hydrophobic integral membrane protein. Here, we describe a new member of the LraI family in the important human pathogen Streptococcus pyogenes. The system was identified in silico by analysis of the S. pyogenes Genome Sequencing Project. The S. pyogenes operon exhibits an atypical organization compared with equivalents in other Streptococcus spp. The presence and atypical organization of the operon was verified in a number of S. pyogenes strains of different serotypes. Transcriptional analysis of the LraI operon demonstrates a polycistronic transcription attenuated by a stable stem-loop structure, which allows the lipoprotein to be expressed in larger quantities than the other two components. The localization of the native lipoprotein at the bacterial surface was shown by proteolytic digestion of S. pyogenes bacteria and NH2-terminal sequencing of a released lipoprotein fragment. Recombinant lipoprotein was expressed as a GST fusion protein, and studies of molecular interactions with metal radioisotopes demonstrated that the protein has affinity for Zn(II), Fe(III) and Cu(II). Zn(II) and Cu(II) were found to compete for the same binding site, whereas Fe(III) uses a second site. Also, proton-induced X-ray analysis of lipoprotein samples identified iron, copper and zinc. Finally, a mutant strain lacking a functional mtsABC operon was generated and showed reduced uptake of 55Fe and 65Zn compared with the wild-type strain. The operon encoding this novel ABC transporter with multiple specificity for metal cations is designated mtsABC, for metal transporter of Streptococcus. PMID:10564500

  3. Development of Comparative Toxicity Potentials of 14 cationic metals in freshwater.

    PubMed

    Dong, Yan; Gandhi, Nilima; Hauschild, Michael Z

    2014-10-01

    Site-dependent and site-generic Comparative Toxicity Potentials (CTPs) (also known as Characterization Factors (CFs)) were calculated for 14 cationic metals (Al(III), Ba, Be, Cd, Co, Cr(III), Cs, Cu(II), Fe(II), Fe(III), Mn(II), Ni, Pb, Sr and Zn), to be applied in Life Cycle Impact Assessment. CTPs were calculated for 7 EU-archetypes, taking bioavailability and speciation pattern into account. The resulting site-dependent CTPs showed up to 2.4-6.5 orders of magnitude variation across archetypes for those metals that form stable hydroxyl compounds in slightly alkaline waters (Al(III), Be, Cr(III), Cu(II) and Fe(III)), emphasizing the importance of using site-dependent CTPs for these metals where possible. For the other metals, CTPs stayed within around 0.9 orders of magnitude, making spatial differentiation less important. In acidic waters (pH<6.4), Al(III) and Cu(II) had the highest CTPs, while Cd ranked highest in other waters. Based on the site-dependent CTPs, site-generic CTPs were developed applying different averaging principle. Emission weighted average of 7 EU-archetype CTPs was recommended as site-generic CTP for use in LCA studies, where receiving location is unclear. Compared to previous studies by Gandhi et al. (2010, 2011a), new site-dependent CTPs were similar or slightly higher for Cd, Co, Ni, Pb and Zn, but 1-2 orders of magnitude higher for Cu. Compared to the default site-generic CTPs in the frequently used characterization models USES-LCA and USEtox, new site-generic CTPs were mostly higher or similar, within up to ∼2 orders of magnitude difference. PMID:25048884

  4. Identification of a crucial histidine involved in metal transport activity in the Arabidopsis cation/H(+) exchanger CAX1

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In plants, yeast and bacteria, cation/H(+) exchangers (CAXs), have been shown to translocate Ca(2+) and other metals. The best characterized of these related transporters is the plant vacuolar-localized CAX1. We used site-directed mutagenesis to assess the impact of altering the seven histidine re...

  5. Fast detection of oxygen by the naked eye using a stable metal-organic framework containing methyl viologen cations.

    PubMed

    Gong, Yun-Nan; Lu, Tong-Bu

    2013-09-11

    A stable porous metal-organic framework (MOF) containing methyl viologen cations exhibits reversible photochromic, thermochromic and fluorescence changes via host-guest interactions, and can be used for fast and selective detection of oxygen by naked eye recognition of color change within five seconds. PMID:23877538

  6. Functional analysis of "CAX2" and "CAX2"-like genes, which encode Arabidopsis cation/proton transporters with broad metal specificity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The vacuolar sequestration of metals is an important metal tolerance mechanism in plants. Cation transport into the vacuolar lumen can be mediated by cation/H(+) exchanger (CAX) type transporters. Arabidopsis CAX2 was originally identified as a Ca(2+)/H(+) antiporter, but it can also transport oth...

  7. pH-dependent transport of metal cations in porous media.

    PubMed

    Prigiobbe, Valentina; Bryant, Steven L

    2014-04-01

    We study the effect of pH-dependent adsorption and hydrodynamic dispersion on cation transport through a reactive porous medium with a hydrophilic surface. We investigate how competitive adsorption between a proton and a metal (which in some situations of practical interest may also be a radionuclide) can facilitate the migration of a certain fraction of the latter. We performed laboratory experiments using a chromatographic column filled with silica beads coated with iron oxide and flooded initially with an acidic solution (pH ≈ 3) and then with an alkaline solution (pH > 7) containing either sodium, potassium, lithium, calcium, magnesium, or barium. The composition of each injected solution was chosen to represent one of two possible theoretical predictions, either a retarded shock and a fast pulse, that is, traveling at the interstitial fluid velocity, or only a retarded shock. Highly resolved breakthrough curves measured with inline ion chromatography allowed us to observe in all cases agreement with theoretical predictions, including numerous observations of a fast pulse. The fast pulse is the result of the interaction between pH-dependent adsorption and hydrodynamic dispersion and has previously been observed in systems with strontium. Here, we show the fast pulse arises also in the case of other cations allowing a generalization of the physical mechanism underlying this phenomenon and consideration of it as a new fast transport behavior. A one-dimensional reactive transport model for an incompressible fluid was developed combining surface complexation with mass conservation equations for a solute and the acidity (difference between the total proton and hydroxide concentration). In all cases, the model agrees with the measurements capturing the underlying physics of the overall transport behavior. Our results suggest that the interplay between pH-dependent adsorption and hydrodynamic dispersion can give rise to the rapid migration of metals through reactive

  8. An extended basis set {ital ab} {ital initio} study of alkali metal cation--water clusters

    SciTech Connect

    Feller, D.; Glendening, E.D.; Woon, D.E.; Feyereisen, M.W.

    1995-09-01

    Ionic clusters comprised of a single alkali metal cation and up to eight water molecules were studied at the Hartree--Fock and correlated levels of theory using the correlation consistent sequence of basis sets. Estimates of the degree of convergence in the computed properties with respect to the complete basis set limit were facilitated by the underlying systematic manner in which the correlation consistent sets approach completeness. In favorable cases, improved property values could be obtained by fitting finite basis set results with a simple analytical expression in order to extrapolate to the complete basis set limit. The sensitivity of structures and binding energies were analyzed with regard to the inclusion of valence and core-valence correlation recovery at the MP2, MP4, and CCSD(T) levels of theory. The replacement of metal core electrons and the introduction of relativistic contributions via effective core potentials was compared to corresponding all-electron results. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  9. Synthesis and chemistry of cationic d sup 0 metal alkyl complexes

    SciTech Connect

    Jordan, R.F.

    1991-01-01

    The objective of this project is to develop new types of electrophilic metal alkyl complexes for catalytic C-H activation and olefin polymerization chemistry, and associated fundamental mechanistic studies. We have focused our efforts on four classes of early metal alkyl complexes: (1) cationic group 4 Cp{sub 2}M(R){sup +} complexes (1) which are active species in Cp{sub 2}MX{sub 2}-based Ziegler-Natta olefin polymerization catalyst systems and which catalyze productive C-H activation reactions of heterocycles, (2) neutral (dicarbollide)(Cp*)M(R) complexes (2) which are structurally are electronically very similar to 1, (3) half-sandwich complexes CpM(R){sub 2}(L){sub n}{sup +} which are highly coordinatively and electronically unsaturated, and (4) new group 5 (dicarbollide)(Cp)MR{sub 2} and (dicarbollide){sub 2} MR complexes which are more unsaturated than group 5 Cp{sub 2}M systems due to incorporation of the dicarbollide ligand.

  10. Metal nanoclusters: Protein corona formation and implications for biological applications.

    PubMed

    Shang, Li; Nienhaus, Gerd Ulrich

    2016-06-01

    Metal nanoclusters (NCs) are a new type of nanoprobe with great potential in various biological applications. For biocompatible and efficient utilization of NCs, a thorough understanding of their interactions with biological systems is highly important. Herein, we focus on recent studies addressing interactions between metal NCs and proteins as well as implications for their further biological application. These findings show that protein adsorption not only affects the photophysical properties of NCs, but also influences their subsequent biological behavior, i.e., cellular uptake and cytotoxicity. Moreover, specific protein-NC interactions have also been harnessed to develop novel protein discrimination strategies. PMID:26408503

  11. Imaging metals in biology: balancing sensitivity, selectivity and spatial resolution.

    PubMed

    Hare, Dominic J; New, Elizabeth J; de Jonge, Martin D; McColl, Gawain

    2015-10-01

    Metal biochemistry drives a diverse range of cellular processes associated with development, health and disease. Determining metal distribution, concentration and flux defines our understanding of these fundamental processes. A comprehensive analysis of biological systems requires a balance of analytical techniques that inform on metal quantity (sensitivity), chemical state (selectivity) and location (spatial resolution) with a high degree of certainty. A number of approaches are available for imaging metals from whole tissues down to subcellular organelles, as well as mapping metal turnover, protein association and redox state within these structures. Technological advances in micro- and nano-scale imaging are striving to achieve multi-dimensional and in vivo measures of metals while maintaining the native biochemical environment and physiological state. This Tutorial Review discusses state-of-the-art imaging technology as a guide to obtaining novel insight into the biology of metals, with sensitivity, selectivity and spatial resolution in focus. PMID:26505053

  12. Selectivity of externally facing ion-binding sites in the Na/K pump to alkali metals and organic cations.

    PubMed

    Ratheal, Ian M; Virgin, Gail K; Yu, Haibo; Roux, Benoît; Gatto, Craig; Artigas, Pablo

    2010-10-26

    The Na/K pump is a P-type ATPase that exchanges three intracellular Na(+) ions for two extracellular K(+) ions through the plasmalemma of nearly all animal cells. The mechanisms involved in cation selection by the pump's ion-binding sites (site I and site II bind either Na(+) or K(+); site III binds only Na(+)) are poorly understood. We studied cation selectivity by outward-facing sites (high K(+) affinity) of Na/K pumps expressed in Xenopus oocytes, under voltage clamp. Guanidinium(+), methylguanidinium(+), and aminoguanidinium(+) produced two phenomena possibly reflecting actions at site III: (i) voltage-dependent inhibition (VDI) of outwardly directed pump current at saturating K(+), and (ii) induction of pump-mediated, guanidinium-derivative-carried inward current at negative potentials without Na(+) and K(+). In contrast, formamidinium(+) and acetamidinium(+) induced K(+)-like outward currents. Measurement of ouabain-sensitive ATPase activity and radiolabeled cation uptake confirmed that these cations are external K(+) congeners. Molecular dynamics simulations indicate that bound organic cations induce minor distortion of the binding sites. Among tested metals, only Li(+) induced Na(+)-like VDI, whereas all metals tested except Na(+) induced K(+)-like outward currents. Pump-mediated K(+)-like organic cation transport challenges the concept of rigid structural models in which ion specificity at site I and site II arises from a precise and unique arrangement of coordinating ligands. Furthermore, actions by guanidinium(+) derivatives suggest that Na(+) binds to site III in a hydrated form and that the inward current observed without external Na(+) and K(+) represents cation transport when normal occlusion at sites I and II is impaired. These results provide insights on external ion selectivity at the three binding sites. PMID:20937860

  13. Highly stable noble metal nanoparticles dispersible in biocompatible solvents: synthesis of cationic phosphonium gold nanoparticles in water and DMSO.

    PubMed

    Ju-Nam, Yon; Abdussalam-Mohammed, Wanisa; Ojeda, Jesus J

    2016-04-12

    In this work, we report the synthesis of novel cationic phosphonium gold nanoparticles dispersible in water and dimethyl sulfoxide (DMSO) for their potential use in biomedical applications. All the cationic-functionalising ligands currently reported in the literature are ammonium-based species. Here, the synthesis and characterisation of an alternative system, based on phosphonioalkylthiosulfate zwitterions and phosphonioalkylthioacetate were carried out. We have also demonstrated that our phosphonioalkylthiosulfate zwitterions readily disproportionate into phosphonioalkylthiolates in situ during the synthesis of gold nanoparticles produced by the borohydride reduction of gold(iii) salts. The synthesis of the cationic gold nanoparticles using these phosphonium ligands was carried out in water and DMSO. UV-visible spectroscopic and TEM studies have shown that the phosphonioalkylthiolates bind to the surface of gold nanoparticles which are typically around 10 nm in diameter. The resulting cationic-functionalised gold nanoparticles are dispersible in aqueous media and in DMSO, which is the only organic solvent approved by the U.S. Food and Drug Administration (FDA) for drug carrier tests. This indicates their potential future use in biological applications. This work shows the synthesis of a new family of phosphonium-based ligands, which behave as cationic masked thiolate ligands in the functionalisation of gold nanoparticles. These highly stable colloidal cationic phosphonium gold nanoparticles dispersed in water and DMSO can offer a great opportunity for the design of novel biorecognition and drug delivery systems. PMID:26796782

  14. Roles of Cationic and Elemental Calcium in the Electro-Reduction of Solid Metal Oxides in Molten Calcium Chloride

    NASA Astrophysics Data System (ADS)

    Qiu, Guohong; Jiang, Kai; Ma, Meng; Wang, Dihua; Jin, Xianbo; Chen, George Z.

    2007-06-01

    Previous work, mainly from this research group, is re-visited on electrochemical reduction of solid metal oxides, in the form of compacted powder, in molten CaCl2, aiming at further understanding of the roles of cationic and elemental calcium. The discussion focuses on six aspects: 1.) debate on two mechanisms proposed in the literature, i. e. electro-metallothermic reduction and electro-reduction (or electro-deoxidation), for the electrolytic removal of oxygen from solid metals or metal oxides in molten CaCl2; 2.) novel metallic cavity working electrodes for electrochemical investigations of compacted metal oxide powders in high temperature molten salts assisted by a quartz sealed Ag/AgCl reference electrode (650 ºC- 950 ºC); 3.) influence of elemental calcium on the background current observed during electrolysis of solid metal oxides in molten CaCl2; 4.) electrochemical insertion/ inclusion of cationic calcium into solid metal oxides; 5.) typical features of cyclic voltammetry and chronoamperometry (potentiostatic electrolysis) of metal oxide powders in molten CaCl2; and 6.) some kinetic considerations on the electrolytic removal of oxygen.

  15. Preparation of decarboxylic-functionalized weak cation exchanger and application for simultaneous separation of alkali, alkaline earth and transition metals.

    PubMed

    Peng, Yahui; Gan, Yihui; He, Chengxia; Yang, Bingcheng; Guo, Zhimou; Liang, Xinmiao

    2016-06-01

    A novel weak cation exchanger (WCX) with dicarboxyl groups functionalized has been developed by clicking mercaptosuccinic acid onto silica gel. The simple synthesis starts with modification of silica gel with triethoxyvinylsilane, followed by efficient coupling vinyl-bonded silica with mercaptosuccinic acid via a "thiol-ene" click reaction. The obtained WCX demonstrated good separation and high selectivity towards common metals. Simultaneous separation of 10 alkali, alkaline earth and transition metals was achieved within 12min. Ion exchange and complex mechanism dominates the separation process. Its utility was demonstrated for determination of metals in tap water. PMID:27130093

  16. Ionic polymer-metal composite actuators obtained from radiation-grafted cation- and anion-exchange membranes.

    PubMed

    Park, Jong Hyuk; Han, Man Jae; Song, Dae Seock; Jho, Jae Young

    2014-12-24

    Two series of ionic polymer-metal composites (IPMCs), one cationic and one anionic, are designed and prepared from radiation-grafted ion-exchange membranes. Through examination of the properties of the membranes synthesized from the two grafting monomers and the two base polymers, acrylic acid-grafted poly(vinylidene fluoride-co-hexafluoropropylene) and quarternized 4-vinylpyridine-grafted poly(ethylene-co-tetrafluoroethylene) with the appropriate amount of ionic groups are employed for the fabrication of cation and anion IPMCs, respectively. The bending displacement of the cation IPMC is comparable to Nafion-based IPMC under direct- and alternating-current voltage, but back-relaxation is not observed. The actuation performance of the anion IPMC is highly improved over those reported earlier in the literature for the other anion IPMCs. PMID:25420910

  17. Removal of cationic heavy metal from aqueous solution by activated carbon impregnated with anionic surfactants.

    PubMed

    Ahn, Chi K; Park, Donghee; Woo, Seung H; Park, Jong M

    2009-05-30

    To increase their capacity to adsorb heavy metals, activated carbons were impregnated with the anionic surfactants sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS), or dioctyl sulfosuccinate sodium (DSS). Surfactant-impregnated activated carbons removed Cd(II) at up to 0.198 mmol g(-1), which was more than an order of magnitude better than the Cd(II) removal performance of activated carbon without surfactant (i.e., 0.016 mmol g(-1)) even at optimal pH (i.e., pH 6). The capacity of the activated carbon to adsorb Cd(II) increased in proportion to the quantity of surfactant with which they were impregnated. The kinetics of the adsorption of Cd(II) onto the surfactant-impregnated activated carbon was best described by a pseudo-second-order model, and was described better by the Freundlich adsorption isotherm than by the Langmuir isotherm. The surface charge of activated carbon was negative in all pH ranges tested (2-6). These results indicate that surface modification with anionic surfactant could be used to significantly enhance the capacity of activated carbon to adsorb cations. PMID:19022570

  18. Two anionic metal-organic frameworks with tunable luminescent properties induced by cations

    NASA Astrophysics Data System (ADS)

    Chen, Shu-Mei; Chen, Yan-Fei; Liu, Liyang; Wen, Tian; Zhang, Hua-Bin; Zhang, Jian

    2016-03-01

    Two three-dimensional (3-D) MOFs, [(C2H5)4N)]3[H3O]2[Cd6Br(H2-DHBDC)8(DMF)4] (1; H4-DHBDC=2,5-dihydroxy-1,4-benzenedicarboxylic acid, DMF=N,N-dimethylformamide) and [(CH3)2NH2]2[Cd3(H2-DHBDC)4(DMF)2]·2DMF(2), are prepared from the self-assembly reactions between Cd(CH3COO)2 and H4-DHBDC, respectively. Both anionic frameworks consist of linear trinuclear Cd units (e.g., 1: [Cd3BrO2(CO2)7] and [Cd3O2(CO2)8]; 2: [Cd3O2(CO2)8]) linked by the H2-DHBDC ligands. The photoluminescent properties of compound 1 are tunable through cation-exchange with different metal ions. The results demonstrated an effective ion-exchange approach toward the functional modification of MOF materials.

  19. Overcharging in Biological Systems: Reversal of Electrophoretic Mobility of Aqueous Polyaspartate by Multivalent Cations

    NASA Astrophysics Data System (ADS)

    Kubíčková, Anna; Křížek, Tomáš; Coufal, Pavel; Vazdar, Mario; Wernersson, Erik; Heyda, Jan; Jungwirth, Pavel

    2012-05-01

    Charge reversal as an extreme case of charge compensation is directly observed by capillary electrophoresis for a negatively charged peptide in aqueous solutions of trivalent cations. Atomistic and coarse-grained simulations provide molecular interpretation of this effect showing that it is largely of electrostatic origin with a minor contribution of chemical specificity of the salt ions.

  20. Root development under metal stress in Arabidopsis thaliana requires the H(+)/cation antiporter CAX4

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The Arabidopsis vacuolar CAtion eXchangers (CAXs) play a key role in mediating cation influx into the vacuole. In Arabidopsis, there are six CAX genes. However, some members are yet to be characterized fully. In this study, we show that CAX4 is expressed in the root apex and lateral root primordia, ...

  1. Behavior of Zn2+, Cd2+, Ba2+ and Pb2+ cations in ferromanganese crusts from the Marcus Wake seamount (Pacific Ocean) in aqueous solutions of metal salts

    NASA Astrophysics Data System (ADS)

    Novikov, G. V.; Bogdanova, O. Yu.; Melnikov, M. E.; Lobus, N. V.; Drozdova, A. N.; Shulga, N. A.

    2016-01-01

    The behavior of heavy-metal cations in ore minerals of cobalt-rich ferromanganese crusts from the Marcus Wake seamount in aqueous solutions of metal salts was studied in experiments. The Zn2+ and Cd2+ cations showed high reactivity and Ba2+ and Pb2+ showed low reactivity. It was found that Zn2+ and Cd2+ cations within the ore mineral composition are mainly absorbed (up to 66%) whereas Pb2+ and Ba2+ are chemically bound (up to 70%). Ore minerals in the crusts are characterized by sorption properties and high ionexchange capacity by these cations (1.94-2.62 mg-equiv/g). The capacity values by heavy-metal cations for ore minerals of the crusts from different areas of the Marcus Wake seamount are close to each other.

  2. Gas-Phase Reactions of Doubly Charged Lanthanide Cations with Alkanes and Alkenes. Trends in Metal(2+) Reactivity

    SciTech Connect

    Gibson, John K.; Marcalo, Joaquim; Santos, Marta; Pires de Matos, Antonio; Haire, Richard G.

    2008-12-08

    The gas-phase reactivity of doubly-charged lanthanide cations, Ln2+ (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), with alkanes (methane, ethane, propane, n-butane) and alkenes (ethene, propene, 1-butene) was studied by Fourier transform ion cyclotron resonance mass spectrometry. The reaction products consisted of different combinations of doubly-charged organometallic ions?adducts or species formed via metal-ion-induced hydrogen, dihydrogen, alkyl, or alkane eliminations from the hydrocarbons?and singly-charged ions that resulted from electron, hydride, or methide transfers from the hydrocarbons to the metal ions. The only lanthanide cations capable of activating the hydrocarbons to form doubly-charged organometallic ions were La2+, Ce2+, Gd2+, and Tb2+, which have ground-state or low-lying d1 electronic configurations. Lu2+, with an accessible d1 electronic configuration but a rather high electron affinity, reacted only through transfer channels. The remaining Ln2+ reacted via transfer channels or adduct formation. The different accessibilities of d1 electronic configurations and the range of electron affinities of the Ln2+ cations allowed for a detailed analysis of the trends for metal(2+) reactivity and the conditions for occurrence of bond activation, adduct formation, and electron, hydride, and methide transfers.

  3. The electronic structure of vanadium monochloride cation (VCl(+)): tackling the complexities of transition metal species.

    PubMed

    DeYonker, Nathan J; Halfen, DeWayne T; Allen, Wesley D; Ziurys, Lucy M

    2014-11-28

    Six electronic states (X (4)Σ(-), A (4)Π, B (4)Δ, (2)Φ, (2)Δ, (2)Σ(+)) of the vanadium monochloride cation (VCl(+)) are described using large basis set coupled cluster theory. For the two lowest quartet states (X (4)Σ(-) and A (4)Π), a focal point analysis (FPA) approach was used that conjoined a correlation-consistent family of basis sets up to aug-cc-pwCV5Z-DK with high-order coupled cluster theory through pentuple (CCSDTQP) excitations. FPA adiabatic excitation energies (T0) and spectroscopic constants (re, r0, Be, B0, D¯e, He, ωe, v0, αe, ωexe) were extrapolated to the valence complete basis set Douglas-Kroll (DK) aug-cc-pV∞Z-DK CCSDT level of theory, and additional treatments accounted for higher-order valence electron correlation, core correlation, and spin-orbit coupling. Due to the delicate interplay between dynamical and static electronic correlation, single reference coupled cluster theory is able to provide the correct ground electronic state (X (4)Σ(-)), while multireference configuration interaction theory cannot. Perturbations from the first- and second-order spin orbit coupling of low-lying states with quartet spin multiplicity reveal an immensely complex rotational spectrum relative to the isovalent species VO, VS, and TiCl. Computational data on the doublet manifold suggest that the lowest-lying doublet state ((2)Γ) has a Te of ∼11 200 cm(-1). Overall, this study shows that laboratory and theoretical rotational spectroscopists must work more closely in tandem to better understand the bonding and structure of molecules containing transition metals. PMID:25429937

  4. The electronic structure of vanadium monochloride cation (VCl+): Tackling the complexities of transition metal species

    NASA Astrophysics Data System (ADS)

    DeYonker, Nathan J.; Halfen, DeWayne T.; Allen, Wesley D.; Ziurys, Lucy M.

    2014-11-01

    Six electronic states (X 4Σ-, A 4Π, B 4Δ, 2Φ, 2Δ, 2Σ+) of the vanadium monochloride cation (VCl+) are described using large basis set coupled cluster theory. For the two lowest quartet states (X 4Σ- and A 4Π), a focal point analysis (FPA) approach was used that conjoined a correlation-consistent family of basis sets up to aug-cc-pwCV5Z-DK with high-order coupled cluster theory through pentuple (CCSDTQP) excitations. FPA adiabatic excitation energies (T0) and spectroscopic constants (re, r0, Be, B0, bar De, He, ωe, v0, αe, ωexe) were extrapolated to the valence complete basis set Douglas-Kroll (DK) aug-cc-pV∞Z-DK CCSDT level of theory, and additional treatments accounted for higher-order valence electron correlation, core correlation, and spin-orbit coupling. Due to the delicate interplay between dynamical and static electronic correlation, single reference coupled cluster theory is able to provide the correct ground electronic state (X 4Σ-), while multireference configuration interaction theory cannot. Perturbations from the first- and second-order spin orbit coupling of low-lying states with quartet spin multiplicity reveal an immensely complex rotational spectrum relative to the isovalent species VO, VS, and TiCl. Computational data on the doublet manifold suggest that the lowest-lying doublet state (2Γ) has a Te of ˜11 200 cm-1. Overall, this study shows that laboratory and theoretical rotational spectroscopists must work more closely in tandem to better understand the bonding and structure of molecules containing transition metals.

  5. Nanoscale Transformations in Covellite (CuS) Nanocrystals in the Presence of Divalent Metal Cations in a Mild Reducing Environment

    PubMed Central

    2015-01-01

    We studied the structural and compositional transformations of colloidal covellite (CuS) nanocrystals (and of djurleite (Cu1.94S) nanocrystals as a control) when exposed to divalent cations, as Cd2+ and Hg2+, at room temperature in organic solvents. All the experiments were run in the absence of phosphines, which are a necessary ingredient for cation exchange reactions involving copper chalcogenides, as they strongly bind to the expelled Cu+ ions. Under these experimental conditions, no remarkable reactivity was indeed seen for both CuS and Cu1.94S nanocrystals. On the other hand, in the covellite structure 2/3 of sulfur atoms form covalent S–S bonds. This peculiarity suggests that the combined presence of electron donors and of foreign metal cations can trigger the entry of both electrons and cations in the covellite lattice, causing reorganization of the anion framework due to the rupture of the S–S bonds. In Cu1.94S, which lacks S–S bonds, this mechanism should not be accessible. This hypothesis was proven by the experimental evidence that adding ascorbic acid increased the fraction of metal ions incorporated in the covellite nanocrystals, while it had no noticeable effect on the Cu1.94S ones. Once inside the covellite particles, Cd2+ and Hg2+ cations engaged in exchange reactions, pushing the expelled Cu+ ions toward the not-yet exchanged regions in the same particles, or out to the solution, from where they could be recaptured by other covellite nanoparticles/domains. Because no good solvating agent for Cu ions was present in solution, they essentially remained in the nanocrystals. PMID:26617434

  6. Use of zirconium(IV) arsenophosphate columns for cation exchange separation of metal ions interfering in the spectrophotometric determination of uranium with sodium diethyl dithiocarbamate

    SciTech Connect

    Varshney, K.G.; Agrawal, S.; Anwar, S.; Varshney, K.

    1985-01-01

    A simple cation exchange method has been developed for the quantitative separation of uranium from some metal ions which generally interfere in its spectrophotometric determination using sodium diethyl dithiocarbamate as a reagent. The method requires only a single bed operation and enables a satisfactory (Error + or - separation of uranium (UO/sub 2/ (II)) up to 1080 ..mu..g from ten metal ions on a 2 g column of zirconium (IV) arsenophosphate cation exchanger in H(I) form.

  7. Fragmentation of positively-charged biological ions activated with a beam of high-energy cations.

    PubMed

    Chingin, Konstantin; Makarov, Alexander; Denisov, Eduard; Rebrov, Oleksii; Zubarev, Roman A

    2014-01-01

    First results are reported on the fragmentation of multiply protonated polypeptide ions produced in electrospray ionization mass spectrometry (ESI-MS) with a beam of high-energy cations as a source of activation. The ion beam is generated with a microwave plasma gun installed on a benchtop Q Exactive mass spectrometer. Precursor polypeptide ions are activated when trapped inside the collision cell of the instrument (HCD cell), and product species are detected in the Orbitrap analyzer. Upon exposure to the beam of air plasma cations (∼100 μA, 5 s), model precursor species such as multiply protonated angiotensin I and ubiquitin dissociated across a variety of pathways. Those pathways include the cleavages of C-CO, C-N as well as N-Cα backbone bonds, accordingly manifested as b/y, a, and c/z fragment ion series in tandem mass spectra. The fragmentation pattern observed includes characteristic fragments of collision-induced dissociation (CID) (b/y/a fragments) as well as electron capture/transfer dissociation (ECD, ETD) (c/z fragments), suggesting substantial contribution of both vibrational and electronic excitation in our experiments. Besides backbone cleavages, notable amounts of nondissociated precursor species were observed with reduced net charge, formed via electron or proton transfer between the colliding partners. Peaks corresponding to increased charge states of the precursor ions were also detected, which is the major distinctive feature of ion beam activation. PMID:24236851

  8. Density functional theory study of interaction, bonding and affinity of group IIb transition metal cations with nucleic acid bases

    NASA Astrophysics Data System (ADS)

    Bagchi, Sabyasachi; Mandal, Debasish; Ghosh, Deepanwita; Das, Abhijit K.

    2012-05-01

    The structure, bonding, and energetics of the complexes obtained from the interaction between the most stable tautomeric forms of free DNA and RNA bases and Zn2+, Cd2+ and Hg2+ cations have been studied using density functional B3LYP method. The 6-311+G (2df, 2p) basis set along with LANL2DZ pseudopotentials for the cations are used in the calculations. The tautomerization paths of the nucleobases are investigated and transition states between the tautomeric forms of the free bases are located. The relative stability of the complexes and the tautomers of the free nucleobases are discussed referring to MIA and relative energy values. For uracil, thymine and adenine, interaction of the metal cations with the most stable tautomers form the least stable molecular complexes. For cytosine and guanine, the stability of the metalated complexes differs significantly. The enthalpy (ΔH), entropy (TΔS) and free energy (ΔG) of the complexes at 298 K have also been calculated.

  9. Selective removal of alkali metal cations from multiply-charged ions via gas-phase ion/ion reactions using weakly coordinating anions.

    PubMed

    Luongo, Carl A; Bu, Jiexun; Burke, Nicole L; Gilbert, Joshua D; Prentice, Boone M; Cummings, Steven; Reed, Christopher A; McLuckey, Scott A

    2015-03-01

    Selective removal of alkali metal cations from mixed cation multiply-charged peptide ions is demonstrated here using gas-phase ion/ion reactions with a series of weakly coordinating anions (WCAs), including hexafluorophosphate (PF6 (-)), tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (BARF), tetrakis(pentafluorophenyl)borate (TPPB), and carborane (CHB11Cl11 (-)). In all cases, a long-lived complex is generated by dication/anion condensation followed by ion activation to compare proton transfer with alkali ion transfer from the peptide to the anion. The carborane anion was the only anion studied to undergo dissociation exclusively through loss of the metallated anion, regardless of the studied metal adduct. All other anions studied yield varying abundances of protonated and metallated peptide depending on the peptide sequence and the metal identity. Density functional theory calculations suggest that for the WCAs studied, metal ion transfer is most strongly favored thermodynamically, which is consistent with the experimental results. The carborane anion is demonstrated to be a robust reagent for the selective removal of alkali metal cations from peptide cations with mixtures of excess protons and metal cations. PMID:25560986

  10. Selective Removal of Alkali Metal Cations from Multiply-Charged Ions via Gas-Phase Ion/Ion Reactions Using Weakly Coordinating Anions

    NASA Astrophysics Data System (ADS)

    Luongo, Carl A.; Bu, Jiexun; Burke, Nicole L.; Gilbert, Joshua D.; Prentice, Boone M.; Cummings, Steven; Reed, Christopher A.; McLuckey, Scott A.

    2015-03-01

    Selective removal of alkali metal cations from mixed cation multiply-charged peptide ions is demonstrated here using gas-phase ion/ion reactions with a series of weakly coordinating anions (WCAs), including hexafluorophosphate (PF6 -), tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (BARF), tetrakis(pentafluorophenyl)borate (TPPB), and carborane (CHB11Cl11 -). In all cases, a long-lived complex is generated by dication/anion condensation followed by ion activation to compare proton transfer with alkali ion transfer from the peptide to the anion. The carborane anion was the only anion studied to undergo dissociation exclusively through loss of the metallated anion, regardless of the studied metal adduct. All other anions studied yield varying abundances of protonated and metallated peptide depending on the peptide sequence and the metal identity. Density functional theory calculations suggest that for the WCAs studied, metal ion transfer is most strongly favored thermodynamically, which is consistent with the experimental results. The carborane anion is demonstrated to be a robust reagent for the selective removal of alkali metal cations from peptide cations with mixtures of excess protons and metal cations.

  11. Comparative toxicity of five metals on various biological subjects

    SciTech Connect

    Fargasova, A. )

    1994-08-01

    Environmental contaminants, including metals, can have toxic effects on many different organisms and affect biological processes at cellular, population, community and ecosystem levels of organization. Metals are of particular interest because they may have a positive effect as micronutrients at low concentrations as well as a toxic effect at higher levels. Numerous efforts have been made to correlate and predict metal-ion toxicities on various aquatic and terrestrial species, according to the physical and chemical properties of the metals. The acute and chronic toxicities of metals have been studied on many freshwater organisms and also on plants. The water flea, Daphnia magna, an important freshwater zooplankter, is a useful test species to study sensitivity to environmental toxicants and has been recognized as a general representative for other freshwater animals. As Khangarot described, little information is available on the effects of metals to tubificid worms, which are widely distributed in the aquatic environment and are useful indicators of varying degrees of aquatic pollution. Most recent hazard evaluation programs recommend algal toxicity tests for initial evaluations of chemicals that are expected to reach surface waters and that have suspected or unknown phytotoxic properties. For higher plants, the accumulation of metals, especially cadmium, was tested when plants grew in sewage sludge-amended soils or in soils of cadmium residues form phosphate fertilizers. No reports were available indicating the effects of these metals on seed germination and root growth. This study was conducted to determine the acute toxicological effects of some metals (As, Pb, Cr, Hg, Cd) on four biological subjects (tubificid worms, Daphnia magna sp., Scenedesmus quadricauda, seeds of Sinapis alba) and to compare their sensitivity to individual test metals. 16 refs., 1 tab.

  12. Bonding and singlet-triplet gap of silicon trimer: effects of protonation and attachment of alkali metal cations.

    PubMed

    Tam, Nguyen Minh; Hang, Tran Dieu; Pham, Hung Tan; Nguyen, Huyen Thi; Pham-Ho, My Phuong; Denis, Pablo A; Nguyen, Minh Tho

    2015-04-30

    We revisit the singlet-triplet energy gap (ΔE(ST)) of silicon trimer and evaluate the gaps of its derivatives by attachment of a cation (H(+), Li(+), Na(+), and K(+)) using the wavefunction-based methods including the composite G4, coupled-cluster theory CCSD(T)/CBS, CCSDT and CCSDTQ, and CASSCF/CASPT2 (for Si3) computations. Both (1)A1 and (3)A2' states of Si3 are determined to be degenerate. An intersystem crossing between both states appears to be possible at a point having an apex bond angle of around α = 68 ± 2° which is 16 ± 4 kJ/mol above the ground state. The proton, Li(+) and Na(+) cations tend to favor the low-spin state, whereas the K(+) cation favors the high-spin state. However, they do not modify significantly the ΔE(ST). The proton affinity of silicon trimer is determined as PA(Si3) = 830 ± 4 kJ/mol at 298 K. The metal cation affinities are also predicted to be LiCA(Si3) = 108 ± 8 kJ/mol, NaCA(Si3) = 79 ± 8 kJ/mol and KCA(Si3) = 44 ± 8 kJ/mol. The chemical bonding is probed using the electron localization function, and ring current analyses show that the singlet three-membered ring Si3 is, at most, nonaromatic. Attachment of the proton and Li(+) cation renders it anti-aromatic. PMID:25694392

  13. Short cationic lipopeptides as effective antibacterial agents: Design, physicochemical properties and biological evaluation.

    PubMed

    Azmi, Fazren; Elliott, Alysha G; Marasini, Nirmal; Ramu, Soumya; Ziora, Zyta; Kavanagh, Angela M; Blaskovich, Mark A T; Cooper, Matthew A; Skwarczynski, Mariusz; Toth, Istvan

    2016-05-15

    The spread of drug-resistant bacteria has imparted a sense of urgency in the search for new antibiotics. In an effort to develop a new generation of antibacterial agents, we have designed de novo charged lipopeptides inspired by natural antimicrobial peptides. These short lipopeptides are composed of cationic lysine and hydrophobic lipoamino acids that replicate the amphiphilic properties of natural antimicrobial peptides. The resultant lipopeptides were found to self-assemble into nanoparticles. Some were effective against a variety of Gram-positive bacteria, including strains resistant to methicillin, daptomycin and/or vancomycin. The lipopeptides were not toxic to human kidney and liver cell lines and were highly resistant to tryptic degradation. Transmission electron microscopy analysis of bacteria cells treated with lipopeptide showed membrane-damage and lysis with extrusion of cytosolic contents. With such properties in mind, these lipopeptides have the potential to be developed as new antibacterial agents against drug-resistant Gram-positive bacteria. PMID:27048775

  14. Dynamics of Nucleic Acid/Cationic Polymer Complexation and Disassembly under Biologically Simulated Conditions Using In Situ Atomic Force Microscopy

    PubMed Central

    Shim, Min Suk; Wang, Xi; Ragan, Regina; Kwon, Young Jik

    2010-01-01

    Elucidating dynamic morphological changes of gene-carrying vectors and their nucleic acid release under varying intracellular conditions has been a technical challenge. Atomic force microscopy (AFM) was employed to observe nucleic acid/polymer polyplexes under endosomal and reducible cytosolic conditions. Both ketalized (acid-degradable) and unmodified (non-degradable) polyethylenimine (PEI) in linear and branched forms were used to prepare plasmid DNA- or siRNA-complexing polyplexes. Then, the polyplexes’ complexation and disassembly were observed by in situ AFM in various differentially changing buffers that represent intracellular conditions. Results demonstrated obvious morphological destruction of DNA/ketalized linear PEI (KL-PEI) polyplexes under mildly acidic endosomal conditions, while no morphological changes were observed by DNA/ketalized branched PEI (KB-PEI) under the same conditions. In addition, siRNA was more efficiently dissociated from KL-PEI than KB-PEI under the same conditions. Non-degradable PEI did not show any evidence that DNA or siRNA was released. Anionic biomacromolecules (e.g., heparan sulfate), which was hypothesized to dissociate nucleic acids from cationic polymers, did not successfully disassemble polyplexes but appeared to be adsorbed on cationic polymers. The in situ AFM results combined with in vitro cellular transfection and gene silencing indicated that efficient endosomal escape of plasmid DNA in a compact polyplex form is required for efficient gene expression. On the contrary, rapid dissociation of siRNA from its cationic carrier is crucial for efficient gene silencing. The findings of this study may provide new insightful information for designing stimuli-responsive nonviral gene vectors as well as expanding tools for investigating nonviral vectors in nano scales under biologically inspired conditions. PMID:20803694

  15. Tuning the Magnetic Properties of Metal Oxide Nanocrystal Heterostructures by Cation Exchange

    PubMed Central

    2013-01-01

    For three types of colloidal magnetic nanocrystals, we demonstrate that postsynthetic cation exchange enables tuning of the nanocrystal’s magnetic properties and achieving characteristics not obtainable by conventional synthetic routes. While the cation exchange procedure, performed in solution phase approach, was restricted so far to chalcogenide based semiconductor nanocrystals, here ferrite-based nanocrystals were subjected to a Fe2+ to Co2+ cation exchange procedure. This allows tracing of the compositional modifications by systematic and detailed magnetic characterization. In homogeneous magnetite nanocrystals and in gold/magnetite core shell nanocrystals the cation exchange increases the coercivity field, the remanence magnetization, as well as the superparamagnetic blocking temperature. For core/shell nanoheterostructures a selective doping of either the shell or predominantly of the core with Co2+ is demonstrated. By applying the cation exchange to FeO/CoFe2O4 core/shell nanocrystals the Neél temperature of the core material is increased and exchange-bias effects are enhanced so that vertical shifts of the hysteresis loops are obtained which are superior to those in any other system. PMID:23362940

  16. Rational design of carbonitrile-carboxaldehyde cation receptor models: probing the nature of the heteroatom-metal interaction.

    PubMed

    Rosli, Ahmad Nazmi; Abu Bakar, Maizathul Akmam; Lee, Vannajan Sanghiran; Zain, Sharifuddin Md; Ahmad, Mohd Rais; Abdul Manan, Ninie Suhana; Alias, Yatimah; Woi, Pei Meng

    2014-09-01

    In this work, hybrid functional and G4 methods were employed in the rational design of carbonitrile-carboxaldehyde receptor models for cation recognition. Electron-sharing and ionic interactions between the models and the cations were analyzed utilizing the concepts of overlap population, atomic valence, electrostatic potential, and CHELPG charge in order to elucidate the nature of the heteroatom-metal interaction, the N versus O disparity, and the effect of pH. Receptor fragment models from ionomycin were employed to rationalize the selection of receptor models for discriminating group I cations and enhancing the selectivity for Mg(II) rather than Ca(II), and to examine the effects of keto-enol forms and negatively charged sites. The changes in geometries, overlap population, metal valence, and CHELPG charge upon solvation in heptane medium as compared to the gas phase were negligible. The optimized geometries reveal that the interaction between group II cations and the keto, enol, and enolate forms of 2-cyanoethanal causes 12 % bending of the C-C-N angle from linearity. Overlap populations show that the electron-sharing interaction favors group II cations but that the same mechanism allows Li(I) to compete. The total spin of Li(I) is 17 % greater than that of Ca(II), but the G4 binding energies of the two are separated by more than 50 kcal/mol, favoring group II cations, which may eliminate interference from Li(I). 1,2-Dicyanoethylene, which has only one form, shows similar characteristics. CHELPG analysis shows that Mg(II) transfers 25 and 18 % of its positive charge to 2-cyanoethanal enolate and 1,2-dicyanoethylene, respectively. Hydrogen atoms receive most of the positive charge in both receptors, but the N-termini exhibit strikingly different characteristics. Electrostatic potential contour profiles were found to be in good agreement with the atomic charge distributions. The application of uncharged 1,3-dicarbonyl and 2-cyanocarbonyl receptors and a judicious

  17. Metal release from stainless steel in biological environments: A review.

    PubMed

    Hedberg, Yolanda S; Odnevall Wallinder, Inger

    2016-03-01

    Due to its beneficial corrosion resistance, stainless steel is widely used in, e.g., biomedical applications, as surfaces in food contact, and for products intended to come into skin contact. Low levels of metals can be released from the stainless steel surface into solution, even for these highly corrosion resistant alloys. This needs to be considered in risk assessment and management. This review aims to compile the different metal release mechanisms that are relevant for stainless steel when used in different biological settings. These mechanisms include corrosion-induced metal release, dissolution of the surface oxide, friction-induced metal release, and their combinations. The influence of important physicochemical surface properties, different organic species and proteins in solution, and of biofilm formation on corrosion-induced metal release is discussed. Chemical and electrochemical dissolution mechanisms of the surface oxides of stainless steel are presented with a focus on protonation, complexation/ligand-induced dissolution, and reductive dissolution by applying a perspective on surface adsorption of complexing or reducing ligands and proteins. The influence of alloy composition, microstructure, route of manufacture, and surface finish on the metal release process is furthermore discussed as well as the chemical speciation of released metals. Typical metal release patterns are summarized. PMID:26514345

  18. Oxoferryl porphyrin cation radicals in model systems: Evidence for variable metal-radical spin coupling

    NASA Astrophysics Data System (ADS)

    Bill, E.; Bominaar, E. L.; Ding, X.-Q.; Trautwein, A. X.; Winkler, H.; Mandon, D.; Weiss, R.; Gold, A.; Jayaraj, K.; Toney, G. E.

    1990-07-01

    Magnetic properties of frozen solutions of highly oxidized iron porphyrin complexes were investigated by EPR and Mössbauer spectroscopy. The Mössbauer spectra, recorded at low temperatures in various magnetic fields, were analyzed on the basis of spin Hamiltonian simulations. Spin coupling between ferryl iron (FeIV) and porphyrin cation radical was taken into account explicitly. Hyperfine and spin-coupling parameters are given for several complexes, together with zero-field parameters. One of the complexes exhibits weak spin coupling, it is the first model system exhibiting properties comparable to those of the oxoferryl cation radical enzyme Horse Radish Peroxidase I.

  19. Binding of monovalent metal cations by the p-sulfonatocalix[4]arene: experimental evidence for cation-pi interactions in water.

    PubMed

    Morel, Jean-Pierre; Morel-Desrosiers, Nicole

    2006-02-01

    Gibbs free energies, enthalpies and entropies for the binding of Na+, K+, Rb+, Cs+, Ag+, Tl+ and NH4+ by the p-sulfonatocalix[4]arene in water are determined by microcalorimetry. Whereas no significant heat effect is detected with Na+ or Ag+, suggesting that these cations are not complexed, weak but selective binding is observed with the other cations. The whole set of thermodynamic parameters, which demonstrate that the cations bind inside the cavity of the calixarene, evidence the importance of the cation-pi interactions for these complexes in water. PMID:16446803

  20. Vinyl polymer agglomerate based transition metal cation chelating ion-exchange resin containing the 8-hydroxyquinoline functional group

    SciTech Connect

    Landing, W.M.; Haraldsson, C.; Paxeus, N.

    1986-12-01

    A simple synthetic route has been developed for the immobilization of 8-hydroxyquinoline onto Fractogel TSK, a highly porous, mechanically and chemically stable, hydrophilic organic resin gel. The product exhibits an exchange capacity comparable to the highest values reported for silica-immobilized 8-hydroxyquinoline but is more stable at high pH. The resin's selectivity and efficiency of collection of cationic metal species from freshwater and seawater were investigated. The resin was used in a column sequence to obtain concentration and speciation data for Al, Mn, Fe, Co, Cu, Zn, and Cd in an organic-rich freshwater sample.

  1. Interaction of metal cations with functionalised hydrocarbons in the gas phase: further experimental evidence for solvation of metal ions by the hydrocarbon chain.

    PubMed

    van Huizen, Nick A; Luider, Theo M; Jobst, Karl J; Terlouw, Johan K; Holmes, John L; Burgers, Peter C

    2016-01-01

    Relative affinity measurements of monovalent metal ions (= Li(+), Cu(+) and Ag(+)) towards aliphatic amines, alcohols and methyl alkanoates (P) have been performed using the kinetic method on the dissociation of metal bound dimer ions of the type P(1)-M(+)-P(2). It was found that the cations' affinity towards long chain (≥C(4) chain length) n- and s-alkylamines, n-alkanols and methyl n- alkanoates was unexpectedly enhanced. This is attributed to a bidentate interaction of the metal ion with the amine, alcohol or ester functional group and the aliphatic chain, paralleling earlier observations on metal bound nitriles. Methyl substitution at the functional group (s-alkylamines compared with n-alkylamines) serves to strengthen only the N•••M(+) bond, and this can be rationalized by the larger proton affinities of s-alkylamines compared to n-alkylamines. This substitution, however, has no effect on the metal ion-hydrocarbon bond. In contrast, methyl substitution remote from the functional group, as in iso-pentylamine, does lead to strengthening of the metal ion-hydrocarbon bond. The cuprous ion affinity of hexadecylamine, C(16)H(33)NH(2) was found to be as large as that for ethylenediamine (352 kJ mol(-1)), known to be a strong copper binding agent. It is argued that such a metal ion-hydrocarbon interaction does not occur in the metal bound dimers. PMID:27419899

  2. New Insights into Wear and Biological Effects of Metal-on-Metal Bearings

    PubMed Central

    Catelas, Isabelle; Wimmer, Markus A.

    2011-01-01

    Background: Despite the renewed interest in metal-on-metal implants in the past two decades, the underlying wear mechanisms and biological effects are still not fully understood. Methods: This paper first reviews the tribology of metal-on-metal bearings, bringing new insights into the interaction of wear and corrosion, and putting the characteristics and the potential origin of wear particles in perspective with the proposed wear mechanisms. It then summarizes the current knowledge on the biological effects of particles and metal ions in relation to these wear mechanisms. Results: Tribochemical reactions play an important role in the wear of metal-on-metal joints. The generated tribomaterial, which progressively forms by mechanical mixing of the uppermost nanocrystalline zone of the metal surface with proteins from the synovial fluid, governs the wear rate and influences the corrosive behavior of the bearing. Nanometer-sized wear particles may initially originate from the passivation layer covering the implant surface and then detach from this tribolayer. The inflammatory response observed surrounding metal-on-metal implants appears to be lower than that around metal-on-polyethylene implants. However, metallic byproducts, which can complex with proteins, may lead to a T lymphocyte-mediated hypersensitivity response. Conclusions: The tribolayer appears to have beneficial effects on the wear rate. Much information has been gained on wear particle characteristics, but the exact mechanisms of particle detachment remain to be further elucidated. Excessive wear along with a hypersensitivity response may be at the origin of the early adverse tissue reactions that have been recently reported in some patients with metal-on-metal implants. Clinical Relevance: Future development of new methods to improve the tribolayer retention and optimize the tribocorrosive properties of the implant may minimize the clinical impact of implant wear and immune responses. PMID:21543694

  3. Zinc (II) complex with a cationic Schiff base ligand: Synthesis, characterization, and biological studies

    NASA Astrophysics Data System (ADS)

    Lee, Sze Koon; Tan, Kong Wai; Ng, Seik Weng; Ooi, Kah Kooi; Ang, Kok Pian; Abdah, Md Akim

    2014-03-01

    A cationic Schiff base ligand, TSB (L) and its Zn (II) complex (1) were synthesized and characterized by using CHN, 1H-NMR, FT-IR, UV, LC-MS, and X-ray methods. Their ability to inhibit topoisomerase I, DNA cleavage activities, and cytotoxicity were studied. X-ray diffraction study shows that the mononuclear complex 1 is four coordinated with distorted tetrahedral geometry. The singly deprotonated Schiff base ligand L acts as a bidentate ON-donor ligand. Complexation of L increases the inhibitory strength on topoisomerase I activity. Complex 1 could fully inhibit topoisomerase I activity at 250 μM, while L did not show any inhibitory effect on topoisomerase I activity. In addition, L and complex 1 could cleave pBR322 DNA in a concentration and time dependent profile. Surprisingly, L has better DNA cleavage activity than complex 1. The cleavage of DNA by complex 1 is altered in the presence of hydrogen peroxide. Furthermore, L and complex 1 are mildly cytotoxic towards human ovarian cancer A2780 and hepatocellular carcinoma HepG2.

  4. Understanding the biological responses of nanostructured metals and surfaces

    NASA Astrophysics Data System (ADS)

    Lowe, Terry C.; Reiss, Rebecca A.

    2014-08-01

    Metals produced by Severe Plastic Deformation (SPD) offer distinct advantages for medical applications such as orthopedic devices, in part because of their nanostructured surfaces. We examine the current theoretical foundations and state of knowledge for nanostructured biomaterials surface optimization within the contexts that apply to bulk nanostructured metals, differentiating how their microstructures impact osteogenesis, in particular, for Ultrafine Grained (UFG) titanium. Then we identify key gaps in the research to date, pointing out areas which merit additional focus within the scientific community. For example, we highlight the potential of next-generation DNA sequencing techniques (NGS) to reveal gene and non-coding RNA (ncRNA) expression changes induced by nanostructured metals. While our understanding of bio-nano interactions is in its infancy, nanostructured metals are already being marketed or developed for medical devices such as dental implants, spinal devices, and coronary stents. Our ability to characterize and optimize the biological response of cells to SPD metals will have synergistic effects on advances in materials, biological, and medical science.

  5. Ion-exchange and selectivity behavior of thermally treated and. gamma. -irradiated phases of zirconium(IV) arsenophosphate cation exchanger: separation of Al(III) from some metal ions and removal of cations from water

    SciTech Connect

    Varshney, K.G.; Varshney, K.; Agrawal, S.

    1983-01-01

    Ion-exchange and selectivity behavior of zirconium(IV) arsenophosphate (ZAP) has been studied systematically after thermal and irradiation treatments. As a result, an increase in the ion-exchange capacity and a complete reversal in the selectivity sequence for some common metal ions has been observed on heating. The modified phase of ZAP has been utilized successfully for the quantitative separation of aluminum from numerous metal ions and for the removal of cations from water. 5 figures, 3 tables.

  6. Biologics formulation factors affecting metal leachables from stainless steel.

    PubMed

    Zhou, Shuxia; Schöneich, Christian; Singh, Satish K

    2011-03-01

    An area of increasing concern and scientific scrutiny is the potential contamination of drug products by leachables entering the product during manufacturing and storage. These contaminants may either have a direct safety impact on the patients or act indirectly through the alteration of the physicochemical properties of the product. In the case of biotherapeutics, trace amounts of metal contaminants can arise from various sources, but mainly from contact with stainless steel (ss). The effect of the various factors, buffer species, solution fill volume per unit contact surface area, metal chelators, and pH, on metal leachables from contact with ss over time were investigated individually. Three major metal leachables, iron, chromium, and nickel, were monitored by inductively coupled plasma-mass spectrometry because they are the major components of 316L ss. Iron was primarily used to evaluate the effect of each factor since it is the most abundant. It was observed that each studied factor exhibited its own effect on metal leachables from contact with ss. The effect of buffer species and pH exhibited temperature dependence over the studied temperature range. The metal leachables decreased with the increased fill volume (mL) per unit contact ss surface area (cm(2)) but a plateau was achieved at approximately 3 mL/cm(2). Metal chelators produced the strongest effect in facilitating metal leaching. In order to minimize the metal leachables and optimize biological product stability, each formulation factor must be evaluated for its impact, to balance its risk and benefit in achieving the target drug product shelf life. PMID:21360314

  7. Influence of alkali metal cations on the thermal, mechanical and morphological properties of rectorite/chitosan bio-nanocomposite films.

    PubMed

    Babul Reddy, A; Jayaramudu, J; Siva Mohan Reddy, G; Manjula, B; Sadiku, E R

    2015-05-20

    The main theme of this work is to study the influence of ion-exchangeable alkali metal cations, such as: Li(+), Na(+), K(+), and Cs(+) on the thermal, mechanical and morphological properties. In this regard, a set of rectorite/chitosan (REC-CS) bio-nanocomposite films (BNCFs) was prepared by facile reaction of chitosan with ion-exchanged REC clay. The microstructure and morphology of BNCFs were investigated with XRD, TEM, SEM and AFM. Thermal and tensile properties of BNCFs were also investigated. As revealed from TEM and XRD results, the BNCFs featured a mixed morphology. Some intercalated clay sheets, together with nano-sized clay tactoids were obtained in LiREC/CS, NaREC/CS and KREC/CS of the BNCFs. From fractured surface study, via SEM, it was observed that the dispersion of chitosan polymer attaches to (and covers) the clay platelets. FTIR confirmed strong hydrogen bonds between clay and chitosan polymer. In addition, the thermal stabilities significantly varied when alkali metal cations varied from Li(+) to Cs(+). The BNCFs featured high tensile strengths (up to 84 MPa) and tensile moduli (up to 45 GPa). After evaluating these properties of BNCFs, we came to conclusion that these bio-nano composites can be used for packaging applications. PMID:25817663

  8. Alkali metal cation complexation by 1,3-alternate, mono-ionisable calix[4]arene-benzocrown-6 compounds

    DOE PAGESBeta

    Surowiec, Malgorzata A.; Custelcean, Radu; Surowiec, Kazimierz; Bartsch, Richard A.

    2014-04-23

    Alkali metal cation extraction behavior for two series of 1,3-alternate, mono-ionizable calix[4]arene-benzocrown-6 compounds is examined. In Series 1, the proton-ionizable group is a substituent on the benzo group of the polyether ring that directs it away from the crown ether cavity. In Series 2, the proton-ionizable group is attached to one para position in the calixarene framework, thus positioning it over the crown ether ring. Competitive solvent extraction of alkali metal cations from aqueous solutions into chloroform shows high Cs+ efficiency and selectivity. Single-species extraction pH profiles of Cs+ for Series 1 and 2 ligands with the same proton-ionizable groupmore » are very similar. Thus, association of Cs+ with the calixcrown ring is more important than the the proton-ionizable group’s position in relation to the crown ether cavity. Solid-state structures are presented for two unionized ligands from Series 2, as is a crystal containing two different ionized ligand–Cs+ complexes.« less

  9. Alkali metal cation complexation by 1,3-alternate, mono-ionisable calix[4]arene-benzocrown-6 compounds

    SciTech Connect

    Surowiec, Malgorzata A.; Custelcean, Radu; Surowiec, Kazimierz; Bartsch, Richard A.

    2014-04-23

    Alkali metal cation extraction behavior for two series of 1,3-alternate, mono-ionizable calix[4]arene-benzocrown-6 compounds is examined. In Series 1, the proton-ionizable group is a substituent on the benzo group of the polyether ring that directs it away from the crown ether cavity. In Series 2, the proton-ionizable group is attached to one para position in the calixarene framework, thus positioning it over the crown ether ring. Competitive solvent extraction of alkali metal cations from aqueous solutions into chloroform shows high Cs+ efficiency and selectivity. Single-species extraction pH profiles of Cs+ for Series 1 and 2 ligands with the same proton-ionizable group are very similar. Thus, association of Cs+ with the calixcrown ring is more important than the the proton-ionizable group’s position in relation to the crown ether cavity. Solid-state structures are presented for two unionized ligands from Series 2, as is a crystal containing two different ionized ligand–Cs+ complexes.

  10. Desorption-induced recombination-cationization of metal-adsorbate adducts from sulfur precovered Ru(0001)

    NASA Astrophysics Data System (ADS)

    Cocco, R. A.; Tatarchuk, B. J.

    1990-03-01

    Temperature programmed static secondary ion mass spectrometry (TPSS) studies of pyrrole, furan and water on sulfur precovered Ru(0001) reveal significant increases in the coverage corrected adduct yield when these species desorb from the surface in an autocatalytic fashion. This effect has been attributed to an enhancement in the recombination-cationization rate which occurs when sputtered-ruthenium species contact desorbed organics just after leaving the surface. Adsorbates which do not undergo autocatalytic/explosive desorption do not exhibit this effect.

  11. 1H and 23Na MAS NMR spectroscopy of cationic species in CO2 selective alkaline earth metal porous silicoaluminophosphates prepared via liquid and solid state ion exchange

    NASA Astrophysics Data System (ADS)

    Arévalo-Hidalgo, Ana G.; Dugar, Sneha; Fu, Riqiang; Hernández-Maldonado, Arturo J.

    2012-07-01

    The location of extraframework cations in Sr2+ and Ba2+ ion-exchanged SAPO-34 was estimated by means of 1H and 23Na MAS NMR spectroscopy and spectral deconvolution. Incorporation of the alkaline earth metal cations onto the SAPO framework was achieved via liquid state ion exchange, coupled partial detemplation/solid-state ion exchange, and combination of both techniques. MAS NMR revealed that the level of ion exchange was limited by the presence of protons and sodium cations near hexagonal prisms (site SI), which are relatively difficult to exchange with the alkaline earth metal due to steric and charge repulsion criteria. In addition, the presence of ammonium cations in the supercages facilitated the exchange of otherwise tenacious hydrogen as corroborated by unit cell compositional data as well as enhanced CO2 adsorption at low partial pressures. The extraframework ammonium species were produced from partial detemplation of the structure-directing agent employed for the SAPO-34 synthesis, tetraethylammonium.

  12. Imaging metal oxide nanoparticles in biological structures with CARS microscopy.

    PubMed

    Moger, Julian; Johnston, Blair D; Tyler, Charles R

    2008-03-01

    Metal oxide nanomaterials are being used for an increasing number of commercial applications, such as fillers, opacifiers, catalysts, semiconductors, cosmetics, microelectronics, and as drug delivery vehicles. The effects of these nanoparticles on the physiology of animals and in the environment are largely unknown and their potential associated health risks are currently a topic of hot debate. Information regarding the entry route of nanoparticles into exposed organisms and their subsequent localization within tissues and cells in the body are essential for understanding their biological impact. However, there is currently no imaging modality available that can simultaneously image these nanoparticles and the surrounding tissues without disturbing the biological structure. Due to their large nonlinear optical susceptibilities, which are enhanced by two-photon electronic resonance, metal oxides are efficient sources of coherent anti-Stokes Raman Scattering (CARS). We show that CARS microscopy can provide localization of metal oxide nanoparticles within biological structures at the cellular level. Nanoparticles of 20 - 70 nm in size were imaged within the fish gill; a structure that is a primary site of pollutant uptake into fish from the aquatic environment. PMID:18542432

  13. Tetrathiafulvalene-based azine ligands for anion and metal cation coordination

    PubMed Central

    Ayadi, Awatef; El Alamy, Aziz; Alévêque, Olivier; Allain, Magali; Zouari, Nabil; Bouachrine, Mohammed

    2015-01-01

    Summary The synthesis and full characterization of two tetrathiafulvalene-appended azine ligands, namely 2-([2,2’-bi(1,3-dithiolylidene)]-4-yl)-6-((2,4-dinitrophenyl)hydrazono)methyl)pyridine (L1) and 5-([2,2’-bi(1,3-dithiolylidene)]-4-yl)-2-((2,4-dinitrophenyl)hydrazono)methyl)pyridine (L2) are described. The crystal structure of ligand L1 indicates that the ligand is completely planar with the presence of a strong intramolecular N3–H3···O1 hydrogen bonding. Titration experiments with inorganic anions showed that both ligands are suitable candidates for the sensing of fluoride anions. Ligand L2 was reacted with a Re(I) cation to yield the corresponding rhenium tricarbonyl complex 3. In the crystal structure of the newly prepared electroactive rhenium complex the TTF is neutral and the rhenium cation is hexacoordinated. The electrochemical behavior of the three compounds indicates that they are promising for the construction of crystalline radical cation salts. PMID:26425193

  14. Tetrathiafulvalene-based azine ligands for anion and metal cation coordination.

    PubMed

    Ayadi, Awatef; El Alamy, Aziz; Alévêque, Olivier; Allain, Magali; Zouari, Nabil; Bouachrine, Mohammed; El-Ghayoury, Abdelkrim

    2015-01-01

    The synthesis and full characterization of two tetrathiafulvalene-appended azine ligands, namely 2-([2,2'-bi(1,3-dithiolylidene)]-4-yl)-6-((2,4-dinitrophenyl)hydrazono)methyl)pyridine (L1) and 5-([2,2'-bi(1,3-dithiolylidene)]-4-yl)-2-((2,4-dinitrophenyl)hydrazono)methyl)pyridine (L2) are described. The crystal structure of ligand L1 indicates that the ligand is completely planar with the presence of a strong intramolecular N3-H3···O1 hydrogen bonding. Titration experiments with inorganic anions showed that both ligands are suitable candidates for the sensing of fluoride anions. Ligand L2 was reacted with a Re(I) cation to yield the corresponding rhenium tricarbonyl complex 3. In the crystal structure of the newly prepared electroactive rhenium complex the TTF is neutral and the rhenium cation is hexacoordinated. The electrochemical behavior of the three compounds indicates that they are promising for the construction of crystalline radical cation salts. PMID:26425193

  15. Density Functional Theory of Biologically Relevant Metal Centers

    NASA Astrophysics Data System (ADS)

    Siegbahn, Per E. M.; Blomberg, Margareta R. A.

    1999-10-01

    Recent applications of density functional theory to biologically relevant metal centers are reviewed. The emphasis is on reaction mechanisms, structures, and modeling. The accuracy of different functionals is discussed for standard benchmark tests of first- and second-row molecules and for transition metal systems. Modeling aspects of the protein metal complexes are discussed regarding both the size of the model being treated quantum mechanically and the treatment of the protein surrounding it. To illustrate the effects, structures computed without the effects of the protein are compared with experimental structures from enzymes, and results from simple dielectric models of the protein for electron transfer processes are described. The choice of spin state is discussed for multimetal complexes. Examples of mechanisms studied recently by density functional theory are described, such as O2 and methane activation in methane monooxygenase and O2 formation in photosystem II.

  16. Biotic ligand modeling approach: Synthesis of the effect of major cations on the toxicity of metals to soil and aquatic organisms.

    PubMed

    Ardestani, Masoud M; van Straalen, Nico M; van Gestel, Cornelis A M

    2015-10-01

    The biotic ligand model (BLM) approach is used to assess metal toxicity, taking into account the competition of other cations with the free metal ions for binding to the biotic ligand sites of aquatic and soil organisms. The bioavailable fraction of metals, represented by the free metal ion, is a better measure than the total concentration for assessing their potential risk to the environment. Because BLMs are relating toxicity to the fraction of biotic ligands occupied by the metal, they can be useful for investigating factors affecting metal bioaccumulation and toxicity. In the present review, the effects of major cations on the toxicity of metals to soil and aquatic organisms were comprehensively studied by performing a meta-analysis of BLM literature data. Interactions at the binding sites were shown to be species- and metal-specific. The main factors affecting the relationships between toxicity and conditional binding constants for metal binding at the biotic ligand appeared to be Ca(2+) , Mg(2+) , and protons. Other important characteristics of the exposure medium, such as levels of dissolved organic carbon and concentrations of other cations, should also be considered to obtain a proper assessment of metal toxicity to soil and aquatic organisms. PMID:25953362

  17. CAX-ing a wide net: Cation/H(+) transporters in metal remediation and abiotic stress signalling.

    PubMed

    Pittman, J K; Hirschi, K D

    2016-09-01

    Cation/proton exchangers (CAXs) are a class of secondary energised ion transporter that are being implicated in an increasing range of cellular and physiological functions. CAXs are primarily Ca(2+) efflux transporters that mediate the sequestration of Ca(2+) from the cytosol, usually into the vacuole. Some CAX isoforms have broad substrate specificity, providing the ability to transport trace metal ions such as Mn(2+) and Cd(2+) , as well as Ca(2+) . In recent years, genomic analyses have begun to uncover the expansion of CAXs within the green lineage and their presence within non-plant species. Although there appears to be significant conservation in tertiary structure of CAX proteins, there is diversity in function of CAXs between species and individual isoforms. For example, in halophytic plants, CAXs have been recruited to play a role in salt tolerance, while in metal hyperaccumulator plants CAXs are implicated in cadmium transport and tolerance. CAX proteins are involved in various abiotic stress response pathways, in some cases as a modulator of cytosolic Ca(2+) signalling, but in some situations there is evidence of CAXs acting as a pH regulator. The metal transport and abiotic stress tolerance functions of CAXs make them attractive targets for biotechnology, whether to provide mineral nutrient biofortification or toxic metal bioremediation. The study of non-plant CAXs may also provide insight into both conserved and novel transport mechanisms and functions. PMID:27061644

  18. Influence of soil properties on heavy metal sequestration by biochar amendment: 1. Copper sorption isotherms and the release of cations.

    PubMed

    Uchimiya, Minori; Klasson, K Thomas; Wartelle, Lynda H; Lima, Isabel M

    2011-03-01

    The amendment of carbonaceous materials such as biochars and activated carbons is a promising in situ remediation strategy for both organic and inorganic contaminants in soils and sediments. Mechanistic understandings in sorption of heavy metals on amended soil are necessary for appropriate selection and application of carbonaceous materials for heavy metal sequestration in specific soil types. In this study, copper sorption isotherms were obtained for soils having distinct characteristics: clay-rich, alkaline San Joaquin soil with significant heavy metal sorption capacity, and eroded, acidic Norfolk sandy loam soil having low capacity to retain copper. The amendment of acidic pecan shell-derived activated carbon and basic broiler litter biochar lead to a greater enhancement of copper sorption in Norfolk soil than in San Joaquin soil. In Norfolk soil, the amendment of acidic activated carbon enhanced copper sorption primarily via cation exchange mechanism, i.e., release of proton, calcium, and aluminum, while acid dissolution of aluminum cannot be ruled out. For San Joaquin soil, enhanced copper retention by biochar amendment likely resulted from the following additional mechanisms: electrostatic interactions between copper and negatively charged soil and biochar surfaces, sorption on mineral (ash) components, complexation of copper by surface functional groups and delocalized π electrons of carbonaceous materials, and precipitation. Influence of biochar on the release of additional elements (e.g., Al, Ca) must be carefully considered when used as a soil amendment to sequester heavy metals. PMID:21147495

  19. Metal chalcogenide nanoparticle gel networks: Their formation mechanism and application for novel material generation and heavy metal water remediation via cation exchange reactions

    NASA Astrophysics Data System (ADS)

    Palhares, Leticia F.

    The dissertation research is focused on (1) uncovering the mechanism of metal chalcogenide nanoparticle gel formation; (2) extending the cation exchange reaction protocol to zinc sulfide gel networks, with the goal of accessing new aerogel chemistries and understanding the factors that drive the process; and (3) conducting a quantitative analysis of the ability of ZnS aerogels to remove heavy metal ions from aqueous solutions. The mechanism of metal chalcogenide nanoparticle gel formation was investigated using Raman spectroscopy and X-ray Photoelectron Spectroscopy to probe the chemical changes that occur during the gelation process. These techniques suggest that the bonding between the particles in the CdSe nanoparticle gels is due to the oxidation of surface selenide species, forming covalent Se--Se bonds. Treating the gel networks with a suitable reducing agent, such as a thiol, breaks the covalent bond and disperses the gel network. The addition of sodium borohydride, a "pure" reducing agent, also breaks down the gel network, strengthening the hypothesis that the reducing character of the thiols, not their ligation ability, is responsible for the gel network breakdown. UV-Vis spectroscopy, Transmission Electron Microscopy and Powder X-ray Diffraction were used to analyze the particles after successive gelation-dispersion cycles. The primary particle size decreases after repeated oxidation-reduction cycles, due to nanoparticle surface etching. This trend is observed for CdSe and CdS gel networks, allowing for the proposition that the oxidative-reductive mechanism responsible for the formation-dispersion of the gels is general, applying to other metal chalcogenide nanocrystals as well. The cation exchange reaction previously demonstrated for CdSe gels was extended to ZnS gel networks. The exchange occurs under mild reaction conditions (room temperature, methanol solvent) with exchanging ions of different size, charge and mobility (Ag+, Pb2+, Cd2+ , Cu2+). The

  20. Complexation of Donor-Acceptor Substituted Aza-Crowns with Alkali and Alkaline Earth Metal Cations. Charge Transfer and Recoordination in Excited State.

    PubMed

    Volchkov, Valery V; Gostev, Fedor E; Shelaev, Ivan V; Nadtochenko, Viktor A; Dmitrieva, Svetlana N; Gromov, Sergey P; Alfimov, Mikhail V; Melnikov, Mikhail Ya

    2016-03-01

    Complexation between two aza-15-crown-5 ethers bearing electron donor and acceptor fragments and alkali and alkaline earth perchlorates has been studied using absorption, steady-state fluorescence and femtosecond transient absorption spectroscopy. The spectral-luminescent parameters, the stability and dissociation constants of the complexes were calculated. The intramolecular charge transfer reaction takes place both in the excited state of the crowns and their complexes 1:1; the latter is subjected to photorecoordination resulting in a weakening or a complete disruption of coordination bond between nitrogen atom and metal cation, disposed within a cavity of the crown. The compounds investigated can be viewed as novel optical molecular sensors for alkali and alkaline-earth metal cations. The photoejection of a metal cation into the bulk was not observed. PMID:26670689

  1. Adsorption of heavy metal cations by Na-clinoptilolite: equilibrium and selectivity studies.

    PubMed

    Mihaly-Cozmuta, L; Mihaly-Cozmuta, A; Peter, A; Nicula, C; Tutu, H; Silipas, Dan; Indrea, Emil

    2014-05-01

    This paper summarizes the conclusions of experiments conducted on the adsorption of Cd(2+), Co(2+), Cu(2+), Mn(2+), Ni(2+), Pb(2+) and Zn(2+) onto zeolite. The focus of the experiments was to establish the influence of the initial pH of the contact solution as well as the selectivity of zeolite on the efficiency of the adsorption process. To this end, experimental adsorption isotherms were established for the pH values ranging from 1 to 4 by using the Na-form of clinoptilolite (particle size range 0.5-1 mm) as an adsorbent. Langmuir, Freundlich and Dubinin-Raduschkevich isotherm models were used to validate the experimental data and the Gibbs free energy was calculated based on the distribution coefficient. From the Langmuir model, correlations between the maximum adsorption capacity and selected physical-chemical parameters of the cations studied were established. The results of the experiments suggest that the selectivity of zeolite is strongly influenced by the pH of the contact solution, dehydration energy of cations, diffusion coefficient and the pH at which the precipitation of hydroxides occurs. PMID:24603029

  2. Selective adsorption of cationic dyes from aqueous solution by polyoxometalate-based metal-organic framework composite

    NASA Astrophysics Data System (ADS)

    Liu, Xiaoxia; Gong, Wenpeng; Luo, Jing; Zou, Chentao; Yang, Yun; Yang, Shuijin

    2016-01-01

    A novel environmental friendly adsorbent H6P2W18O62/MOF-5 was synthesized by a simple one-step reaction under solvothermal conditions and characterized by XRD, FTIR, thermogravimetric analyses (TGA) and N2 adsorption-desorption isotherms. The removal rate of H6P2W18O62/MOF-5 was quite greater (85%) than that of MOF-5 (almost zero), showing that the adsorption performance of porous MOF-5 can be improved through the modification of H6P2W18O62. Further study revealed that H6P2W18O62/MOF-5 exhibited a fast adsorption rate and selective adsorption ability towards the cationic dyes in aqueous solution. The removal rate was up to 97% for cationic dyes methylene blue (MB) and 68% for rhodamine B(Rhb) within 10 min. However, anionicdye methyl orange(MO) can only reach to 10%. The influences including initial concentration, contact time, initial solution pH and temperature of MB adsorption onto H6P2W18O62/MOF-5 were investigated in detail. The kinetic study indicated that the adsorption of MB onto H6P2W18O62/MOF-5 followed the pseudo second-order model well. The isotherm obtained from experimental data fitted the Langmuir model, yielding maximum adsorption capacity of 51.81 mg/g. The thermodynamic parameters analysis illustrated that the MB adsorption onto H6P2W18O62 immobilized MOF-5 was spontaneous and endothermic process. Besides, these results implied that designing a novel material polyoxometalate-based metal-organic frameworks is great potential for removing cationic organic pollutants and even extended to improve other specific application.

  3. BIOLOGICAL MONITORING OF TOXIC TRACE METALS. VOLUME 2. TOXIC TRACE METALS IN PLANTS AND ANIMALS OF THE WORLD. PART III

    EPA Science Inventory

    The needs and priorities in using biological accumulator organisms for monitoring toxic trace metals in plants and animals are analyzed. The toxic trace metals selected for study are antimony, arsenic, beryllium, boron, cadmium, chromium, cobalt, copper, lead, mercury, nickel, se...

  4. BIOLOGICAL MONITORING OF TOXIC TRACE METALS. VOLUME 2. TOXIC TRACE METALS IN PLANTS AND ANIMALS OF THE WORLD. PART II

    EPA Science Inventory

    The needs and priorities in using biological accumulator organisms for monitoring toxic trace metals in plants and animals are analyzed. The toxic trace metals selected for study are antimony, arsenic, beryllium, boron, cadmium, chromium, cobalt, copper, lead, mercury, nickel, se...

  5. BIOLOGICAL MONITORING OF TOXIC TRACE METALS. VOLUME 2. TOXIC TRACE METALS IN PLANTS AND ANIMALS OF THE WORLD. PART I

    EPA Science Inventory

    The needs and priorities in using biological accumulator organisms for monitoring toxic trace metals in plants and animals are analyzed. The toxic trace metals selected for study are antimony, arsenic, beryllium, boron, cadmium, chromium, cobalt, copper, lead, mercury, nickel, se...

  6. Conjugation of fatty acids with different lengths modulates the antibacterial and antifungal activity of a cationic biologically inactive peptide.

    PubMed

    Malina, Amir; Shai, Yechiel

    2005-09-15

    Many studies have shown that an amphipathic structure and a threshold of hydrophobicity of the peptidic chain are crucial for the biological function of AMPs (antimicrobial peptides). However, the factors that dictate their cell selectivity are not yet clear. In the present study, we show that the attachment of aliphatic acids with different lengths (10, 12, 14 or 16 carbon atoms) to the N-terminus of a biologically inactive cationic peptide is sufficient to endow the resulting lipopeptides with lytic activity against different cells. Mode-of-action studies were performed with model phospholipid membranes mimicking those of bacterial, mammalian and fungal cells. These include determination of the structure in solution and membranes by using CD and ATR-FTIR (attenuated total reflectance Fourier-transform infrared) spectroscopy, membrane leakage experiments and by visualizing bacterial and fungal damage via transmission electron microscopy. The results obtained reveal that: (i) the short lipopeptides (10 and 12 carbons atoms) are non-haemolytic, active towards both bacteria and fungi and monomeric in solution. (ii) The long lipopeptides (14 and 16 carbons atoms) are highly antifungal, haemolytic only at concentrations above their MIC (minimal inhibitory concentration) values and aggregate in solution. (iii) All the lipopeptides adopt a partial alpha-helical structure in 1% lysophosphatidylcholine and bacterial and mammalian model membranes. However, the two short lipopeptides contain a significant fraction of random coil in fungal membranes, in agreement with their reduced antifungal activity. (iv) All the lipopeptides have a membranolytic effect on all types of cells assayed. Overall, the results reveal that the length of the aliphatic chain is sufficient to control the pathogen specificity of the lipopeptides, most probably by controlling both the overall hydrophobicity and the oligomeric state of the lipopeptides in solution. Besides providing us with basic

  7. The Debaryomyces hansenii NHA1 gene encodes a plasma membrane alkali-metal-cation antiporter with broad substrate specificity.

    PubMed

    Velkova, Klara; Sychrova, Hana

    2006-03-15

    Debaryomyces hansenii is a yeast species often found in salty environments. Its genome sequence is known completely, but the mechanisms behind its halotolerance are poorly understood. In the D. hansenii genome, there is a gene strongly homologous to the Saccharomyces cerevisiae NHA1 gene (encoding a plasma membrane Na+/H+ antiporter). We isolated this DhNHA1 gene from two D. hansenii strains (CBS 767 and CBS 1793) differing in their osmotolerance. Both DhNHA1 alleles were heterologously expressed in a S. cerevisiae strain lacking its own systems for the efflux of alkali metal cations (BW31a, ena1-4delta nha1delta). D. hansenii Na+/H+ antiporters were localized in the plasma membrane of BW31a cells, their presence increased BW31a tolerance to sodium, potassium, lithium and also rubidium. Measurements of Na+ and K+ efflux from S. cerevisiae cells expressing DhNHA1 alleles show that the D. hansenii antiporters efficiently transported both cations out of cells. The sodium and potassium transport activity of Nha1 antiporters from both D. hansenii strains was almost identical, indicating that plasma membrane antiporter activity is not one of the factors determining the different levels of halotolerance in the two strains. PMID:16303259

  8. Electrophysical methods of separation of metal cations in the moving salts solution

    NASA Astrophysics Data System (ADS)

    Gofman, V. N.; Tuksov, I. V.; Timchenko, S. N.; Shamanin, I. V.; Poberezhnikov, A. D.; Kazaryan, M. A.

    2016-07-01

    The results of experiments on the excitation of the phenomenon of selective drift of solvated ions under the influence of an external "asymmetric" electric field to the circulating solution of calcium chloride and magnesium salts in a polar liquid dielectric - water are shown. The purpose of the experiments was to determine the influence of the field frequency and amplitude of the field strength on the excitation phenomenon, and the study of the operating characteristics of the testing apparatus - a dividing cell. The dependences of the separation efficiency of solvated cations from the frequency of the external field and the excitation threshold of the phenomenon from the field strength in the separation cell are defined.

  9. Heavy water reactions with atomic transition-metal and main-group cations: gas phase room-temperature kinetics and periodicities in reactivity.

    PubMed

    Cheng, Ping; Koyanagi, Gregory K; Bohme, Diethard K

    2007-09-01

    Reactions of heavy water, D(2)O, have been measured with 46 atomic metal cations at room temperature in a helium bath gas at 0.35 Torr using an inductively coupled plasma/selected ion flow tube tandem mass spectrometer. The atomic cations were produced at ca. 5500 K in an ICP source and were allowed to decay radiatively and thermalize by collisions with Ar and He atoms prior to reaction. Rate coefficients and product distributions are reported for the reactions of fourth-row atomic cations from K+ to Se+, of fifth-row atomic cations from Rb+ to Te+ (excluding Tc+), and of sixth-row atomic cations from Cs+ to Bi+. Primary reaction channels were observed leading to O-atom transfer, OD transfer, and D2O addition. O-Atom transfer occurs almost exclusively (>or=90%) in the reactions with most early transition-metal cations (Sc+, Ti+, V+, Y+, Zr+, Nb+, Mo+, Hf+, Ta+, and W+) and to a minor extent (10%) with one main-group cation (As+). OD transfer is observed to occur only with three cations (Sr+, Ba+, and La+). Other cations, including most late transition and main-group cations, were observed to react with D2O exclusively and slowly by D2O addition or not at all. O-Atom transfer proceeds with rate coefficients in the range of 8.1 x 10(-13) (As+) to 9.5 x 10(-10) (Y+) cm3 molecule(-1)(s-1) and with efficiencies below 0.1 and even below 0.01 for the fourth-row atomic cations V+ (0.0032) and As+ (0.0036). These low efficiencies can be understood in terms of the change in spin required to proceed from the reactant to the product potential energy surfaces. Higher order reactions are also measured. The primary products, NbO+, TaO+, MoO+, and WO+, are observed to react further with D(2)O by O-atom transfer, and ZrO+ and HfO+ react further through OD group abstraction. Up to five D(2)O molecules were observed to add sequentially to selected M+ and MO+ as well as MO2+ cations and four to MO(2)D+. Equilibrium measurements for sequential D(2)O addition to M+ are also reported

  10. Metal-dithiocarbamate complexes: chemistry and biological activity.

    PubMed

    Hogarth, Graeme

    2012-10-01

    Dithiocarbamates are highly versatile mono-anionic chelating ligands which form stable complexes with all the transition elements and also the majority of main group, lanthanide and actinide elements. They are easily prepared from primary or secondary amines and depending upon the nature of the cation can show good solubility in water or organic solvents. They are related to the thiuram disulfides by a one-electron redox process (followed by dimerisation via sulfur-sulfur bond formation) which is easily carried out upon addition of iodide or ferric salts. Dithiocarbamates are lipophilic and generally bind to metals in a symmetrical chelate fashion but examples of other coordination modes are known, the monodentate and anisobidentate modes being most prevalent. They are planar sterically non-demanding ligands which can be electronically tuned by judicious choice of substituents. They stabilize metals in a wide range of oxidation states, this being attributed to the existence of soft dithiocarbamate and hard thioureide resonance forms, the latter formally resulting from delocalization of the nitrogen lone pair onto the sulfurs, and consequently their complexes tend to have a rich electrochemistry. Tetraethyl thiuramdisulfide (disulfiram or antabuse) has been used as a drug since the 1950s but it is only recently that dithiocarbamate complexes have been explored within the medicinal domain. Over the past two decades anti-cancer activity has been noted for gold and copper complexes, technetium and copper complexes have been used in PET-imaging, dithiocarbamates have been used to treat acute cadmium poisoning and copper complexes also have been investigated as SOD inhibitors. PMID:22931592

  11. Equilibrium analysis for heavy metal cation removal using cement kiln dust.

    PubMed

    El Zayat, Mohamed; Elagroudy, Sherien; El Haggar, Salah

    2014-01-01

    Ion exchange, reverse osmosis, and chemical precipitation have been investigated extensively for heavy metal uptake. However, they are deemed too expensive to meet stringent effluent characteristics. In this study, cement kiln dust (CKD) was examined for the removal of target heavy metals. Adsorption studies in completely mixed batch reactors were used to generate equilibrium pH adsorption edges. Studies showed the ability of CKD to remove the target heavy metals in a pH range below that of precipitation after an equilibrium reaction time of 24 h. A surface titration experiment indicated negative surface charge of the CKD at pH below 10, meaning that electrostatic attraction of the divalent metals can occur below the pH required for precipitation. However, surface complexation was also important due to the substantive metal removal. Accordingly, a surface complexation model approach that utilizes an electrostatic term in the double-layer description was used to estimate equilibrium constants for the protolysis interactions of the CKD surface as well as equilibria between background ions and the sorbent surface. It was concluded that the removal strength of adsorption is in the order: Pb > Cu > Cd. The experiments were also supported by Fourier transform infrared spectroscopy (FTIR). PMID:25259489

  12. Dissolution of metal salts in bis(trifluoromethylsulfonyl)imide-based ionic liquids: studying the affinity of metal cations toward a "weakly coordinating" anion.

    PubMed

    Bortolini, Olga; Chiappe, Cinzia; Ghilardi, Tiziana; Massi, Alessandro; Pomelli, Christian Silvio

    2015-05-28

    Despite the weakly coordinating ability of the bis(trifluoromethylsulfonyl)imide anion ([Tf2N](-)) the corresponding ionic liquids (ILs) are able to dissolve relevant amounts of metal salts having the same anion, M[Tf2N]x. To better understand the metal dissolution process we evaluated the interaction ability of a set of metal cations (Y(III), Al(III), Co(II), Ni(II), Cu(II), Zn(II), Ag(I), Li(I), and Na(I)) toward the [Tf2N](-) anion measuring the relative aptitude to give the corresponding anionic monocharged complex, [M(Tf2N)x+1](-) using the ESI-MS technique. UV-vis and NMR measurements were carried out to verify the consistence between the liquid and the gas phase. Density functional theory calculations have been used to identify the metal-containing species and determine their relative stability. An interesting correlation between interaction ability and chemical properties (Lewis acidity) was found. PMID:25361174

  13. New electrolyte systems for capillary zone electrophoresis of metal cations and non-ionic organic compounds

    SciTech Connect

    Shi, Y.

    1995-06-19

    Excellent separations of metal ions can be obtained very quickly by capillary electrophoresis provided a weak complexing reagent is incorporated into the electrolyte to alter the effective mobilities of the sample ions. Indirect photometric detection is possible by also adding a UV-sensitive ion to the electrolyte. Separations are described using phthalate, tartrate, lactate or hydroxyisobutyrate as the complexing reagent. A separation of twenty-seven metal ions was achieved in only 6 min using a lactate system. A mechanism for the separation of lanthanides is proposed for the hydroxyisobutyrate system.

  14. Alkali Metal Ion Complexes with Phosphates, Nucleotides, Amino Acids, and Related Ligands of Biological Relevance. Their Properties in Solution.

    PubMed

    Crea, Francesco; De Stefano, Concetta; Foti, Claudia; Lando, Gabriele; Milea, Demetrio; Sammartano, Silvio

    2016-01-01

    Alkali metal ions play very important roles in all biological systems, some of them are essential for life. Their concentration depends on several physiological factors and is very variable. For example, sodium concentrations in human fluids vary from quite low (e.g., 8.2 mmol dm(-3) in mature maternal milk) to high values (0.14 mol dm(-3) in blood plasma). While many data on the concentration of Na(+) and K(+) in various fluids are available, the information on other alkali metal cations is scarce. Since many vital functions depend on the network of interactions occurring in various biofluids, this chapter reviews their complex formation with phosphates, nucleotides, amino acids, and related ligands of biological relevance. Literature data on this topic are quite rare if compared to other cations. Generally, the stability of alkali metal ion complexes of organic and inorganic ligands is rather low (usually log K < 2) and depends on the charge of the ligand, owing to the ionic nature of the interactions. At the same time, the size of the cation is an important factor that influences the stability: very often, but not always (e.g., for sulfate), it follows the trend Li(+) > Na(+) > K(+) > Rb(+) > Cs(+). For example, for citrate it is: log K ML = 0.88, 0.80, 0.48, 0.38, and 0.13 at 25 °C and infinite dilution. Some considerations are made on the main aspects related to the difficulties in the determination of weak complexes. The importance of the alkali metal ion complexes was also studied in the light of modelling natural fluids and in the use of these cations as probes for different processes. Some empirical relationships are proposed for the dependence of the stability constants of Na(+) complexes on the ligand charge, as well as for correlations among log K values of NaL, KL or LiL species (L = generic ligand). PMID:26860301

  15. Synthesis and antimicrobial activity of polysaccharide alginate derived cationic surfactant-metal(II) complexes.

    PubMed

    Tawfik, Salah M; Hefni, Hassan H

    2016-01-01

    New natural polysaccharide carbohydrate derivatives of sodium alginate surfactant and its cobalt, copper and zinc complexes were synthesized. Structures of the synthesized compounds are reported using FTIR, (1)H NMR and UV-vis. The critical micelle concentration (CMC) value of the alginate surfactant and its metal complexes in aqueous solution was found out from surface tension measurements. Surface tension data at different temperatures served for the evaluation of the temperature-dependent CMC and the thermodynamics of micellization (ΔGmic, ΔHmic, ΔSmic) and adsorption (ΔGads, ΔGads, ΔSads). The surface activities of the synthesized polymeric surfactant and its metal complexes were influenced by their chemical structures and the type of the transition metals. These compounds were evaluated against Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus), Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) and fungi (Candida albicans and Asperigllus niger). The antibacterial and antifungal screening tests of the alginate surfactant metal complexes have shown good results compared to its precursor alginate surfactant. PMID:26478092

  16. A combined experimental and quantum mechanical investigation on some selected metal complexes of L-serine with first row transition metal cations

    NASA Astrophysics Data System (ADS)

    Mandal, Shilpi; Das, Gunajyoti; Askari, Hassan

    2015-02-01

    In the current study a joint solvent-free synthetic and computational approach has been adopted to explore the coordination properties of L-serine with the doubly charged cations of nickel, copper and zinc. The reaction products were characterized by elemental analyses, molar conductance, EDAX-SEM, TEM, TG/DTA, infrared, electronic absorption and fluorescence spectroscopy. Quantum chemical calculations, carried out in gas and aqueous phase using the BHandHLYP and MP2 methods in conjunction with 6-311++G(d,p) basis set, provide valuable insights concerning the interaction enthalpies and free energies; vibrational and absorption spectra along with various other molecular and electronic properties of the metal complexes. This study reveals that L-serine binds to the metal ions in a bi-dentate manner through its amino and carboxylate groups exhibiting highest binding affinity towards Cu(II) among the three metal ions considered here. As compared to the MP2 method, the spin-delocalized situations of the open-shell Cu(II) complex of L-serine have been better described at the BHandHLYP level. The physical origin of the molecular interactions of L-serine with the metal ions has also been examined by performing energy decomposition analysis (EDA). Effects of the aqueous environment are evident on the structure and stability of the metal complexes. The vibrational spectroscopic data furnished at MP2/6-311++G(d,p) level, which provide a good account of the structural changes inflicted in the molecular geometry of L-serine as a result of metal coordination, are in better agreement with our experimental observations as compared to those produced at the BHandHLYP/6-311++G(d,p) level.

  17. Coordination Chemistry of Alkali and Alkaline-Earth Cations with Macrocyclic Ligands.

    ERIC Educational Resources Information Center

    Dietrich, Bernard

    1985-01-01

    Discusses: (l) alkali and alkaline-earth cations in biology (considering naturally occurring lonophores, their X-ray structures, and physiochemical studies); (2) synthetic complexing agents for groups IA and IIA; and (3) ion transport across membranes (examining neutral macrobicyclic ligands as metal cation carriers, transport by anionic carriers,…

  18. Crystal phase competition by addition of a second metal cation in solid solution metal-organic frameworks.

    PubMed

    Castillo-Blas, C; Snejko, N; de la Peña-O'Shea, V A; Gallardo, J; Gutiérrez-Puebla, E; Monge, M A; Gándara, F

    2016-03-14

    Herein we report a synthetic study focused on the preparation of solid-solution metal-organic frameworks, MOFs, with the use of two kinds of linkers. In particular, we have explored the system composed by zinc, cobalt, 1,2,4-triazole and 4,4′-hexafluoroisopropylidenebisbenzoic acid (H2hfipbb). During this study, four new MOFs have been isolated, denoted TMPF-88 [M3(hfipbb)2(triazole)2(H2O)], TMPF-90 [M2(triazole)3(OCH2CH3)], TMPF-91 [M2(hfipbb)(triazole)2(H2O)] and TMPF-95 [M5(hfipbb)4(triazole)2(H2O)] (TMPF = transition metal polymeric framework, M = Zn, Co, or mixture of them). The study demonstrates that the addition of a second metal element during the MOF synthesis has a major effect in the formation of new phases, even at very high Zn/Co metal ratios. Furthermore, we show that during the MOF formation reaction, there is a competition among different crystal phases, where kinetically favoured phases of various compositions crystallize in short reaction times, precluding the formation of the pure solid-solution phases of other energetically more stable MOFs. PMID:26674593

  19. Ceruloplasmin revisited: structural and functional roles of various metal cation-binding sites

    SciTech Connect

    Bento, Isabel; Peixoto, Cristina; Zaitsev, Vjacheslav N.; Lindley, Peter F.

    2007-02-01

    The three-dimensional molecular structure of human serum ceruloplasmin has been reinvestigated using X-ray synchrotron data collected at 100 K from a crystal frozen to liquid-nitrogen temperature. The three-dimensional molecular structure of human serum ceruloplasmin has been reinvestigated using X-ray synchrotron data collected at 100 K from a crystal frozen to liquid-nitrogen temperature. The resulting model, with an increase in resolution from 3.1 to 2.8 Å, gives an overall improvement of the molecular structure, in particular the side chains. In addition, it enables the clear definition of previously unidentified Ca{sup 2+}-binding and Na{sup +}-binding sites. The Ca{sup 2+} cation is located in domain 1 in a configuration very similar to that found in the activated bovine factor Va. The Na{sup +} sites appear to play a structural role in providing rigidity to the three protuberances on the top surface of the molecule. These features probably help to steer substrates towards the mononuclear copper sites prior to their oxidation and to restrict the size of the approaching substrate. The trinuclear copper centre appears to differ from the room-temperature structure in that a dioxygen moiety is bound in a similar way to that found in the endospore coat protein CotA from Bacillus subtilis.

  20. Influence of both cation and alginate nature on the rheological behavior of transition metal alginate gels.

    PubMed

    Agulhon, Pierre; Robitzer, Mike; Habas, Jean-Pierre; Quignard, Françoise

    2014-11-01

    The rheological properties of several ionotropic alginate hydrogels were investigated according to the nature of the divalent cation (Mn(2+), Co(2+), Cu(2+)) and the guluronic fraction of the alginate (HG and LG for "high G-content" and "low G-content"). Six hydrogels (Mn-LG, Mn-HG, Co-LG, Co-HG, Cu-LG and Cu-HG) were synthesized and studied by spectromechanical analyses. On one hand, Cu-HG, Cu-LG and Co-HG behaved as viscoelastic solids: the elastic contribution was higher than the dissipative component in all the frequency range studied (G'>G"). No flow zone (G">G') was detected even at very low values of the shearing frequency. On the other, Mn-HG, Mn-LG and Co-LG presented a spectromechanical behavior that resembled that observed classically for entangled polymers. Indeed, at high frequency, these latter materials could be compared to a viscoelastic solid but at low frequency, the flow zone was described and the viscous character became prevalent with finite relaxation time. Very good correlations with the microscopic structurations of the network were evidenced (rubbery vs. flow zone and fibrillar vs. complex morphology respectively). PMID:25129777

  1. Novel Organic Membrane-based Thin-film Microsensors for the Determination of Heavy Metal Cations

    PubMed Central

    Arida, Hassan A.; Kloock, Joachim P.; Schöning, Michael J.

    2006-01-01

    A first step towards the fabrication and electrochemical evaluation of thin-film microsensors based on organic PVC membranes for the determination of Hg(II), Cd(II), Pb(II) and Cu(II) ions in solutions has been realised. The membrane-coating mixture used in the preparation of this new type of microsensors is incorporating PVC as supporting matrix, o-nitrophenyloctylether (o-NPOE) as solvent mediator and a recently synthesized Hg[dimethylglyoxime(phene)]2+ and Bis-(4-hydroxyacetophenone)-ethylenediamine as electroactive materials for Hg(II) and Cd(II), respectively. A set of three commercialised ionophores for Cd(II), Pb(II) and Cu(II) has been also used for comparison. Thin-film microsensors based on these membranes showed a Nernstian response of slope (26-30 mV/dec.) for the respective tested cations. The potentiometric response characteristics (linear range, pH range, detection limit and response time) are comparable with those obtained by conventional membranes as well as coated wire electrodes prepared from the same membrane. The realisation of the new organic membrane-based thin-film microsensors overcomes the problem of an insufficient selectivity of solid-state-based thin-film sensors.

  2. Promotion of the halide effect in the formation of shaped metal nanocrystals via a hybrid cationic, polymeric stabilizer: Octahedra, cubes, and anisotropic growth

    NASA Astrophysics Data System (ADS)

    Sneed, Brian T.; Golden, Matthew C.; Liu, Yejing; Lee, Hiang K.; Andoni, Ilektra; Young, Allison P.; McMahon, Greg; Erdman, Natasha; Shibata, Masateru; Ling, Xing Yi; Tsung, Chia-Kuang

    2016-06-01

    To promote the effect of halide ions (Cl-, Br-, and I-) in facet-selective growth of {111} and {100} of shaped metal nanocrystals, we utilize PDADMAC, a hybrid cationic, polymeric stabilizer. SERS and synthesis experiments provide evidence supporting that the higher amount of PDADMA+ at surfaces promotes the local adsorption of halides, allowing the creation of Pd cubes, octahedra, and cuboctopods.

  3. Fluorescence properties of riboflavin-functionalized mesoporous silica SBA-15 and riboflavin solutions in presence of different metal and organic cations

    NASA Astrophysics Data System (ADS)

    Lewandowski, Dawid; Schroeder, Grzegorz; Sawczak, Mirosław; Ossowski, Tadeusz

    2015-10-01

    Riboflavin was covalently linked to mesoporous SBA-15 silica surface via grafting technique. Then fluorescence properties of the system obtained were analyzed in the presence of several metal and organic cations. Both quenching and strengthening of fluorescence as well as significant changes in the maximum fluorescence wavelength were observed. The results were compared with absorption and fluorescence data obtained for riboflavin water solutions.

  4. Knockout of multiple arabidopsis Cation/H+ exchangers suggest isoform-specific roles in metal stress response, germinatin and seed mineral nutrition

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cation/H(+) exchangers encoded by CAX genes play an important role in the vacuolar accumulation of metals including Ca(2+) and Mn(2+). Arabidopsis thaliana CAX1 and CAX3 have been previously shown to differ phylogenetically from CAX2 but the physiological roles of these different transporters are st...

  5. Ammonium-crown ether supramolecular cation-templated assembly of an unprecedented heterobicluster-metal coordination polymer with enhanced NLO properties.

    PubMed

    Zhang, Jinfang; Jia, Ding; Humphrey, Mark G; Meng, Suci; Zaworotko, Michael J; Cifuentes, Marie P; Zhang, Chi

    2016-03-01

    An ammonium-crown ether host-guest supramolecular cation-templated synthetic methodology has been developed to construct a structurally unprecedented heterobicluster-metal coordination polymer (HCM-CP 1) based on tetranuclear clusters [WS4Cu3](+) with different connection environments, pentanuclear clusters [WS4Cu4](2+), and Cu(+) building metal ions. HCM-CP 1 exhibits enhanced NLO properties, which may be ascribed to the incorporation of diverse building cluster components. PMID:26864604

  6. 2013 METALS IN BIOLOGY GORDON RESEARCH CONFERENCE, JANUARY 20-25, 2013

    SciTech Connect

    Rosenzweig, Amy

    2013-01-25

    Typical topics for lectures and posters include: biochemical and biophysical characterization of new metal containing proteins, enzymes, nucleic acids, factors, and chelators from all forms of life; synthesis, detailed characterization, and reaction chemistry of biomimetic compounds; novel crystal and solution structures of biological molecules and synthetic metal-chelates; discussions of the roles that metals play in medicine, maintenance of the environment, and biogeochemical processes; metal homeostasis; application of theory and computations to the structure and mechanism of metal-containing biological systems; and novel applications of spectroscopy to metals in biological systems.

  7. Metal-Free Dihydrogen Oxidation by a Borenium Cation: A Combined Electrochemical/Frustrated Lewis Pair Approach**

    PubMed Central

    Lawrence, Elliot J; Herrington, Thomas J; Ashley, Andrew E; Wildgoose, Gregory G

    2014-01-01

    In order to use H2 as a clean source of electricity, prohibitively rare and expensive precious metal electrocatalysts, such as Pt, are often used to overcome the large oxidative voltage required to convert H2 into 2 H+ and 2 e−. Herein, we report a metal-free approach to catalyze the oxidation of H2 by combining the ability of frustrated Lewis pairs (FLPs) to heterolytically cleave H2 with the in situ electrochemical oxidation of the resulting borohydride. The use of the NHC-stabilized borenium cation [(IiPr2)(BC8H14)]+ (IiPr2=C3H2(NiPr)2, NHC=N-heterocyclic carbene) as the Lewis acidic component of the FLP is shown to decrease the voltage required for H2 oxidation by 910 mV at inexpensive carbon electrodes, a significant energy saving equivalent to 175.6 kJ mol−1. The NHC–borenium Lewis acid also offers improved catalyst recyclability and chemical stability compared to B(C6F5)3, the paradigm Lewis acid originally used to pioneer our combined electrochemical/frustrated Lewis pair approach. PMID:25044562

  8. Synthesis and chemistry of cationic d{sup 0} metal alkyl complexes. Progress report, July 1988--May 1991

    SciTech Connect

    Jordan, R.F.

    1991-12-31

    The objective of this project is to develop new types of electrophilic metal alkyl complexes for catalytic C-H activation and olefin polymerization chemistry, and associated fundamental mechanistic studies. We have focused our efforts on four classes of early metal alkyl complexes: (1) cationic group 4 Cp{sub 2}M(R){sup +} complexes (1) which are active species in Cp{sub 2}MX{sub 2}-based Ziegler-Natta olefin polymerization catalyst systems and which catalyze productive C-H activation reactions of heterocycles, (2) neutral (dicarbollide)(Cp*)M(R) complexes (2) which are structurally are electronically very similar to 1, (3) half-sandwich complexes CpM(R){sub 2}(L){sub n}{sup +} which are highly coordinatively and electronically unsaturated, and (4) new group 5 (dicarbollide)(Cp)MR{sub 2} and (dicarbollide){sub 2} MR complexes which are more unsaturated than group 5 Cp{sub 2}M systems due to incorporation of the dicarbollide ligand.

  9. Optical probes for the detection of protons, and alkali and alkaline earth metal cations.

    PubMed

    Hamilton, Graham R C; Sahoo, Suban K; Kamila, Sukanta; Singh, Narinder; Kaur, Navneet; Hyland, Barry W; Callan, John F

    2015-07-01

    Luminescent sensors and switches continue to play a key role in shaping our understanding of key biochemical processes, assist in the diagnosis of disease and contribute to the design of new drugs and therapies. Similarly, their contribution to the environment cannot be understated as they offer a portable means to undertake field testing for hazardous chemicals and pollutants such as heavy metals. From a physiological perspective, the Group I and II metal ions are among the most important in the periodic table with blood plasma levels of H(+), Na(+) and Ca(2+) being indicators of several possible disease states. In this review, we examine the progress that has been made in the development of luminescent probes for Group I and Group II ions as well as protons. The potential applications of these probes and the mechanism involved in controlling their luminescent response upon analyte binding will also be discussed. PMID:25742963

  10. Experimental and quantum chemical modeling studies of the interactions of L-phenylalanine with divalent transition metal cations.

    PubMed

    Mandal, Shilpi; Das, Gunajyoti; Askari, Hassan

    2014-09-22

    Encoded by the UUU and UUC codons of the genetic code, L-phenylalanine (LPA) serves as an important precursor for tyrosine and various other compounds that are necessary to support life on earth. Here, we report the synthesis (both in solid and solvent phases) and characterization of the Ni(2+), Cu(2+), and Zn(2+) complexes of LPA by several analytical, spectral, thermal, and electrochemical techniques. The results reveal that the products formed by following the two synthetic approaches are the same, and the metal ions bind to the LPA molecules in a 1:2 molar ratio (M(+2)/LPA). Complementary geometries of the metal complexes are modeled involving the most predominant LPA conformers predicted at the MP2/6-311++G(d,p) level. The gaseous and aqueous phase interaction enthalpies and free energies; theoretical IR and UV-vis spectra; HOMO-LUMO energy gaps; dipole moments; Wiberg bond indices as well as the partial atomic charges in LPA and its metallic complexes are calculated and evaluated using B3LYP/6-311++G(d,p) as the main computational method. This study also incorporates analyses on the efficacy of the DFT-D2 level in describing dispersion contributions, performance of the BHandHLYP functional for the open-shell Cu(2+)-LPA system, and relative metal binding affinities of the singlet versus triplet states of the Ni(2+)-LPA complex. Metal-π interactions established via the aromatic side chain of LPA add to the thermodynamic stability of the complexes, whereas metal coordination induces considerable intrinsic structural rearrangements in the molecular geometry of LPA. The LPA binding affinity order of the three Lewis acids investigated emerges as Cu(2+) > Ni(2+) > Zn(2+), paralleling the Irving-Williams series. The illustrative evidence offered by the present work suggests that the B3LYP/6-311++G(d,p) level in combination with an empirical dispersion-correction term performs well in describing the vibrational frequencies and cation-π interactions, which are

  11. Optical Properties and Biological Applications of Electromagnetically Coupled Metal Nanoparticles

    NASA Astrophysics Data System (ADS)

    Sheikholeslami, Sassan Nathan

    The optical properties of metallic particles change dramatically as the size shrinks to the nanoscale. The familiar mirror-like sheen of bulk metals is replaced by the bright, sharp, colorful plasmonic resonances of nanoparticles. The resonances of plasmonic metal nanoparticles are highly tunable throughout the visible spectrum, depending on the size, shape, local dielectric environment, and proximity to other optical resonances. Fundamental and applied research in the nanoscience community in the past few decades has sought to understand and exploit these phenomena for biological applications. In this work, discrete nanoparticle assemblies were produced through biomolecular interactions and studied at the single particle level with darkfield spectroscopy. Pairs of gold nanoparticles tethered by DNA were utilized as molecular rulers to study the dynamics of DNA bending by the restriction enzyme EcoRV. These results substantiated that nanoparticle rulers, deemed "plasmon rulers", could measure the dynamics of single biomolecules with high throughput, long lifetime, and high temporal resolution. To extend these concepts for live cell studies, a plasmon ruler comprised of peptide-linked gold nanoparticle satellites around a core particle was synthesized and utilized to optically follow cell signaling pathways in vivo at the single molecule level. The signal provided by these plasmon rulers allowed continuous observation of caspase-3 activation at the single molecule level in living cells for over 2 hours, unambiguously identifying early stage activation of caspase-3 in apoptotic cells. In the last section of this dissertation, an experimental and theoretical study of electomagnetic coupling in asymmetric metal nanoparticle dimers is presented. A "heterodimer" composed of a silver particle and a gold particle is observed to have a novel coupling between a plasmon mode (free electron oscillations) and an inter-band absorption process (bound electron transitions). The

  12. Cation induced electrochromism in 2,4-dinitrophenylhydrazine (DNPH): Tuning optical properties of aromatic rings

    NASA Astrophysics Data System (ADS)

    Sanader, Željka; Brunet, Claire; Broyer, Michel; Antoine, Rodolphe; Dugourd, Philippe; Mitrić, Roland; Bonačić-Koutecký, Vlasta

    2013-05-01

    We have theoretically investigated the influence of protons and noble metal cations on optical properties of 2,4-dinitrophenylhydrazine (DNPH). We show that optical properties of aromatic rings can be tuned by cation-induced electrochromism in DNPH due to binding to specific NO2 groups. Our findings on cation-induced electrochromism in DNPH may open new routes in two different application areas, due to the fact that DNPH can easily bind to biological molecules and surface materials through carbonyl groups.

  13. Macroscopic and bulk-controlled elastic modes in an interaction of interstitial alcali metal cations within a face-centered cubic crystalline fullerine

    NASA Technical Reports Server (NTRS)

    Tatarenko, Valentine A.; Tsysman, Constantin L.; Oltarzhevskaya, Yelena T.

    1995-01-01

    The calculations in a majority of previous works for the fulleride (AqC-60) crystals were performed within the framework of the rigid-lattice model, neglecting the distortion relaxation of the host fullerene (C-60) crystal caused by the interstitial alkali-metal (A) cations. However, an each cation is a source of a static distortion field, and the resulting field is a superposition of such fields generated by all cations. This is a reason why the host-crystal distortions depend on the A-cations configurations, i.e. on a type of a spatial bulk distribution of interstitial cations. The given paper seeks to find a functional relation between the amplitudes of the doping-induced structure-distortion waves and of static concentration ones. A semiphenomenological model is constructed here within the scope of statistical-thermodynamic treatment and using the lattice-statistics simulation method(*). In this model the effects due to the presence of q solute A cations over available interstices (per unit cell) on the static inherent reorientation and/or displacements of the solvent molecules from the 'average-lattice' sites' as well as on the lattice parameter a of a elastically-anysotropic 'cubic' C-60 crystal are taken into account.

  14. Macroscopic and bulk-controlled elastic modes in an interaction of interstitial alcali metal cations within a face-centered cubic crystalline fullerine

    SciTech Connect

    Tatarenko, V.A.; Tsysman, C.L.; Oltarzhevskaya, Y.T.

    1994-12-31

    The calculations in a majority of previous works for the fulleride (AqC{sub 60}) crystals were performed within the framework of the rigid-lattice model, neglecting the distoration relaxation of the host fullerene (C{sub 60}) crystal caused by the interstitial alkali-metal (A) cations. However, an each cation is a source of a static distoration field, and the resulting field is a superposition of such fields generated by all cations. This is a reason why the host-crystal distortions depend on the A-cations configurations, i.e. on a type of a spatial bulk distribution of interstitial cations. This paper seeks to find a functional relation between the amplitudes of the doping-induced structure-distortion waves and of statistic concentration ones. A semiphenomenological model is constructed here within the scope of statistical-thermodynamic treatment and using the lattice-statistics simulation method. In this model the effects due to the presence of q solute A cations over available interstices (per unit cell) on the statistic inherent reorientation and/or displacements of the solvent molecules from the average-lattice sites as well as on the lattice parameter a of the elastically-anysotropic cubic C{sub 60} crystal are taken into account.

  15. How the spontaneous insertion of amphiphilic imidazolium-based cations changes biological membranes: a molecular simulation study.

    PubMed

    Lim, Geraldine S; Jaenicke, Stephan; Klähn, Marco

    2015-11-21

    The insertion of 1-octyl-3-methylimidazolium cations (OMIM(+)) from a diluted aqueous ionic liquid (IL) solution into a model of a bacterial cell membrane is investigated. Subsequently, the mutual interactions of cations inside the membrane and their combined effect on membrane properties are derived. The ionic liquid solution and the membrane model are simulated using molecular dynamics in combination with empirical force fields. A high propensity of OMIM(+) for membrane insertion is observed, with a cation concentration at equilibrium inside the membrane 47 times larger than in the solvent. Once inserted, cations exhibit a weak effective attraction inside the membrane at a distance of 1.3 nm. At this free energy minimum, negatively charged phosphates of the phospholipids are sandwiched between two OMIM(+) to form energetically favorable OMIM(+)-phosphate-OMIM(+) types of coordination. The cation-cation association free energy is 5.9 kJ mol(-1), whereas the activation barrier for dissociation is 10.1 kJ mol(-1). Subsequently, OMIM(+) are inserted into the leaflet of the membrane bilayer that represents the extracellular side. The cations are evenly distributed with mutual cation distances according to the found optimum distance of 1.3 nm. Because of the short length of the cation alkyl chains compared to lipid fatty acids, voids are generated in the hydrophobic core of the membrane. These voids disorder the fatty acids, because they enable fatty acids to curl into these empty spaces and also cause a thinning of the membrane by 0.6 nm. Additionally, the membrane density increases at its center. The presence of OMIM(+) in the membrane facilitates the permeation of small molecules such as ammonia through the membrane, which is chosen as a model case for small polar solutes. The permeability coefficient of the membrane with respect to ammonia increases substantially by a factor of seven. This increase is caused by a reduction of the involved free energy barriers

  16. Distinct reaction pathway promoted by non-divalent-metal cations in a tertiary stabilized hammerhead ribozyme

    PubMed Central

    Roychowdhury-Saha, Manami; Burke, Donald H.

    2007-01-01

    Divalent ion sensitivity of hammerhead ribozymes is significantly reduced when the RNA structure includes appropriate tertiary stabilization. Therefore, we investigated the activity of the tertiary stabilized “RzB” hammerhead ribozyme in several nondivalent ions. Ribozyme RzB is active in spermidine and Na+ alone, although the cleavage rates are reduced by more than 1,000-fold relative to the rates observed in Mg2+ and in transition metal ions. The trivalent cobalt hexammine (CoHex) ion is often used as an exchange-inert analog of hydrated magnesium ion. Trans-cleavage rates exceeded 8 min−1 in 20 mM CoHex, which promoted cleavage through outersphere interactions. The stimulation of catalysis afforded by the tertiary structural interactions within RzB does not require Mg2+, unlike other extended hammerhead ribozymes. Site-specific interaction with at least one Mg2+ ion is suggested by CoHex competition experiments. In the presence of a constant, low concentration of Mg2+, low concentrations of CoHex decreased the rate by two to three orders of magnitude relative to the rate in Mg2+ alone. Cleavage rates increased as CoHex concentrations were raised further, but the final fraction cleaved was lower than what was observed in CoHex or Mg2+ alone. These observations suggest that Mg2+ and CoHex compete for binding and that they cause misfolded structures when they are together. The results of this study support the existence of an alternate catalytic mechanism used by nondivalent ions (especially CoHex) that is distinct from the one promoted by divalent metal ions, and they imply that divalent metals influence catalysis through a specific nonstructural role. PMID:17456566

  17. Effect of the chelation of metal cation on the antioxidant activity of chondroitin sulfates.

    PubMed

    Ajisaka, Katsumi; Oyanagi, Yutaka; Miyazaki, Tatsuo; Suzuki, Yasuhiro

    2016-06-01

    The antioxidant potencies of chondroitin sulfates (CSs) from shark cartilage, salmon cartilage, bovine trachea, and porcine intestinal mucosa were compared by three representative methods for the measurement of the antioxidant activity; DPPH radical scavenging activity, superoxide radical scavenging activity, and hydroxyl radical scavenging activity. CSs from salmon cartilage and bovine trachea showed higher potency in comparison with CSs from shark cartilage and porcine intestinal mucosa. Next, CS from salmon cartilage chelating with Ca(2+), Mg(2+), Mn(2+), or Zn(2+) were prepared, and their antioxidant potencies were compared. CS chelating with Ca(2+) or Mg(2+) ions showed rather decreased DPPH radical scavenging activity in comparison with CS of H(+) form. In contrast, CS chelating with Ca(2+) or Mg(2+) ion showed remarkably enhanced superoxide radical scavenging activity than CS of H(+) or Na(+) form. Moreover, CS chelating with divalent metal ions, Ca(2+), Mg(2+), Mn(2+), or Zn(2+), showed noticeably higher hydroxyl radical scavenging activity than CS of H(+) or Na(+) form. The present results revealed that the scavenging activities of, at least, superoxide radical and hydroxyl radical were enhanced by the chelation with divalent metal ions. PMID:26856546

  18. Tetrazole-5-carboxylic acid based salts of earth alkali and transition metal cations.

    PubMed

    Hartdegen, Vera; Klapötke, Thomas M; Sproll, Stefan M

    2009-10-01

    The tetrazole-5-carboxylate anion was investigated as ligand for earth alkali metal and transition metal complexes. Therefore, the strontium 4a (*3 H(2)O, *2.75 H(2)O, *2.5 H(2)O), barium 4b (*3 H(2)O), copper 4c (*3.5 H(2)O, *4 H(2)O), manganese 4d (*4 H(2)O, *5 H(2)O), and silver tetrazol-5-carboxylate 4e (*1.56 H(2)O) were synthesized and characterized by vibrational spectroscopy (IR), and the crystal structures of 4a (*2.75 H(2)O, *2.5 H(2)O), 4b*3 H(2)O, 4c*4 H(2)O, and 4d*5 H(2)O were determined using single crystal X-ray diffraction. The thermal stability was investigated by DSC-measurements, and the sensitivity toward impact and friction was determined by BAM-standards. The copper, strontium, and barium tetrazole-5-carboxyate proved to be suitable thermal and physical stable colorants for pyrotechnic compositions. The crystal structure of the tetragonal modification of strontium tetrazole-5-carboxyate possesses channels along the c-axis, leading to a porous material. PMID:19780625

  19. Hetero-metal cation control of CuO nanostructures and their high catalytic performance for CO oxidation

    NASA Astrophysics Data System (ADS)

    Huang, Hongwen; Zhang, Liqiang; Wu, Kewei; Yu, Qing; Chen, Ru; Yang, Hangsheng; Peng, Xinsheng; Ye, Zhizhen

    2012-11-01

    A controllable synthesis of various morphologies of CuO nanostructures with tuning by hetero-metal cations has been developed in aqueous solution at room temperature. The morphologies of CuO can be engineered from nanosheets to nanoparticles with different length ratios of the long axis to the short axis. The formation of many metal-ion complexes plays an important role in slowing the release rate of OH- and affects the reaction kinetics further. We found that the effect of hetero-metal cations on the final morphology of the CuO nanostructures was the same as that of the cooling temperature. A series of temperature-controlled experiments demonstrated this. Furthermore, among all the synthesized CuO nanostructures, the fascinating colloidal mesoporous CuO quasi-monocrystalline nanosheets prepared at 25 °C with a thickness of ca. 10 nm and large specific surface area of 80.32 m2 g-1 is investigated intensively. These CuO nanosheets demonstrate a superior catalytic activity for CO oxidation, with features of high CO conversion efficiency (47.77 mmolCO g-1CuO h-1 at 200 °C), which is close to that reported for previously investigated supported-CuO catalysts, and a low apparent activation energy Ea (53.3 kJ mol-1).A controllable synthesis of various morphologies of CuO nanostructures with tuning by hetero-metal cations has been developed in aqueous solution at room temperature. The morphologies of CuO can be engineered from nanosheets to nanoparticles with different length ratios of the long axis to the short axis. The formation of many metal-ion complexes plays an important role in slowing the release rate of OH- and affects the reaction kinetics further. We found that the effect of hetero-metal cations on the final morphology of the CuO nanostructures was the same as that of the cooling temperature. A series of temperature-controlled experiments demonstrated this. Furthermore, among all the synthesized CuO nanostructures, the fascinating colloidal mesoporous Cu

  20. The biological chemistry of the transition metal "transportome" of Cupriavidus metallidurans.

    PubMed

    Nies, Dietrich H

    2016-05-01

    This review tries to illuminate how the bacterium Cupriavidus metallidurans CH34 is able to allocate essential transition metal cations to their target proteins although these metals have similar charge-to-surface ratios and chemical features, exert toxic effects, compete with each other, and occur in the bacterial environment over a huge range of concentrations and speciations. Central to this ability is the "transportome", the totality of all interacting metal import and export systems, which, as an emergent feature, transforms the environmental metal content and speciation into the cellular metal mélange. In a kinetic flow equilibrium resulting from controlled uptake and efflux reactions, the periplasmic and cytoplasmic metal content is adjusted in a way that minimizes toxic effects. A central core function of the transportome is to shape the metal ion composition using high-rate and low-specificity reactions to avoid time and/or energy-requiring metal discrimination reactions. This core is augmented by metal-specific channels that may even deliver metals all the way from outside of the cell to the cytoplasm. This review begins with a description of the basic chemical features of transition metal cations and the biochemical consequences of these attributes, and which transition metals are available to C. metallidurans. It then illustrates how the environment influences the metal content and speciation, and how the transportome adjusts this metal content. It concludes with an outlook on the fate of metals in the cytoplasm. By generalization, insights coming from C. metallidurans shed light on multiple transition metal homoeostatic mechanisms in all kinds of bacteria including pathogenic species, where the "battle" for metals is an important part of the host-pathogen interaction. PMID:27065183

  1. Effect of Siloxane Ring Strain and Cation Charge Density on the Formation of Coordinately Unsaturated Metal Sites on Silica: Insights from DFT Studies

    SciTech Connect

    Das, Ujjal; Zhang, Guanghui; Hu, Bo; Hock, Adam S.; Redfern, Paul C.; Miller, Jeffrey T.; Curtiss, Larry A.

    2015-12-01

    Amorphous silica (SiO2) is commonly used as a support in heterogeneous catalysis. However, due to the structural disorder and temperature induced change of surface morphology, the structures of silica supported metal catalysts are difficult to determine. Most studies are primarily focused on understanding the interactions of different types of surface hydroxyl groups with metal ions. In comparison, the effect of siloxane ring size on the structure of silica supported metal catalysts and how it affects catalytic activity is poorly understood. Here, we have used density functional theory calculations to understand the effect of siloxane ring strain on structure and activity of different monomeric Lewis acid metal sites on silica. In particular, we have found that large siloxane rings favor strong dative bonding interaction between metal ion and surface hydroxyls, leading to the formation of high-coordinate metal sites. In comparison, metal-silanol interaction is weak in small siloxane rings, resulting in low-coordinate metal sites. The physical origin of this size dependence is associated with siloxane ring strain, and, a correlation between metal-silanol interaction energy and ring strain energy has been observed. In addition to ring strain, the strength of the metal-silanol interaction also depends on the positive charge density of the cations. In fact, a correlation also exists between metal-silanol interaction energy and charge density of several first-row transition and post-transition metals. The theoretical results are compared with the EXAFS data of monomeric Zn(II) and Ga(III) ions grafted on silica. The molecular level insights of how metal ion coordination on silica depends on siloxane ring strain and cation charge density will be useful in the synthesis of new catalysts.

  2. Gas-phase reactions of carbon dioxide with atomic transition-metal and main-group cations: room-temperature kinetics and periodicities in reactivity.

    PubMed

    Koyanagi, Gregory K; Bohme, Diethard K

    2006-02-01

    The chemistry of carbon dioxide has been surveyed systematically with 46 atomic cations at room temperature using an inductively-coupled plasma/selected-ion flow tube (ICP/SIFT) tandem mass spectrometer. The atomic cations were produced at ca. 5500 K in an ICP source and allowed to cool radiatively and to thermalize by collisions with Ar and He atoms prior to reaction downstream in a flow tube in helium buffer gas at 0.35 +/- 0.01 Torr and 295 +/- 2 K. Rate coefficients and products were measured for the reactions of first-row atomic ions from K(+) to Se(+), of second-row atomic ions from Rb(+) to Te(+) (excluding Tc(+)), and of third-row atomic ions from Cs(+) to Bi(+). CO(2) was found to react in a bimolecular fashion by O atom transfer only with 9 early transition-metal cations: the group 3 cations Sc(+), Y(+), and La(+), the group 4 cations Ti(+), Zr(+), and Hf(+), the group 5 cations Nb(+) and Ta(+), and the group 6 cation W(+). Electron spin conservation was observed to control the kinetics of O atom transfer. Addition of CO(2) was observed for the remaining 37 cations. While the rate of addition was not measurable some insight was obtained into the standard free energy change, DeltaG(o), for CO(2) ligation from equilibrium constant measurements. A periodic variation in DeltaG(o) was observed for first row cations that is consistent with previous calculations of bond energies D(0)(M(+)-CO(2)). The observed trends in D(0) and DeltaG(o) are expected from the variation in electrostatic attraction between M(+) and CO(2) which follows the trend in atomic-ion size and the trend in repulsion between the orbitals of the atomic cations and the occupied orbitals of CO(2). Higher-order CO(2) cluster ions with up to four CO(2) ligands also were observed for 24 of the atomic cations while MO(2)(+) dioxide formation by sequential O atom transfer was seen only with Hf(+), Nb(+), Ta(+), and W(+). PMID:16435784

  3. Hydration Structures and Thermodynamic Properties of Cationized Biologically Relevant Molecules, M+(Indole)(H2O)n (M = Na, K; n = 3-6)

    NASA Astrophysics Data System (ADS)

    Ke, Haochen; Lisy, James

    2015-03-01

    The balance between various noncovalent interactions plays a key role in determining the hydration structures and thermodynamic properties of biologically relevant molecules in biological mediums. Such properties of biologically relevant molecules are closely related to their often unique biological functionalities. The indole moiety is a basic functional group of many important neurotransmitters and hormones and has been used as tractable model for more complex biomolecules. The cationized indole water cluster is a perfect system for the quantitative and systematic study of the competition and cooperation of noncovalent interactions, as electrostatic interactions can be adjusted by introducing different monovalent cations and hydrogen bonding interactions can be adjusted by varying the level of hydration. IRPD spectra with isotopic (H/D) analysis helped unravel the overlapping N-H and O-H stretching modes, a major challenge of earlier studies. Thermodynamic analysis using relative Gibbs free energies, for energy ordering, together with spectral analysis provided unambiguous assignment of spectral features and structural configurations. A systematic hydration model with an in-depth account of noncovalent interactions is presented.

  4. Chiral Nanostructures from Helical Copolymer-Metal Complexes: Tunable Cation-π Interactions and Sergeants and Soldiers Effect.

    PubMed

    Arias, Sandra; Bergueiro, Julián; Freire, Félix; Quiñoá, Emilio; Riguera, Ricardo

    2016-01-13

    Poly(phenylacetylene) (PPA) copolymers containing (R)- or (S)-MPA as minor chiral pendant can be forced to selectively adopt the right- o left-handed helix, in the presence of small amounts of Na(+) or Ag(+) ("Sergeants and Soldiers Effect") by addition of a donor cosolvent. The helical sense depends exclusively on the chiral monomer/donor cosolvent ratio, and this allows a perfect on/off tuning of the helicity of the copolymer. When the amount of the donor cosolvent is low, the metal ion complex is stabilized by a cation-π interaction, which is selectively cleaved when the amount of cosolvent is higher. Macroscopically chiral nanospheres and nanotubes composed by helical copolymers with P or M helical sense are also described. Our results demonstrate that it is possible to obtain the two enantiomeric helical structures (P and M helicities) and the corresponding nanospheres and nanotubes from a single helical copolymer, by controlled activation/deactivation of the Sergeant and Soldiers Effect with a donor cosolvent. PMID:26578292

  5. Emission channeling studies on transition-metal doped GaN and ZnO: Cation versus anion substitution

    NASA Astrophysics Data System (ADS)

    Pereira, L. M. C.; Wahl, U.; Correia, J. G.; Amorim, L. M.; Silva, D. J.; Decoster, S.; da Silva, M. R.; Temst, K.; Vantomme, A.

    2014-08-01

    The magnetic and electric properties of impurities in semiconductors are strongly dependent on the lattice sites which they occupy. While the majority site can often be predicted based on chemical similarities with the host elements and is usually simple to confirm experimentally, minority sites are far more complicated to predict, detect and identify. We have carried out extensive β- emission channeling studies on the lattice location of transition metal impurities in wide-gap dilute magnetic semiconductors, namely Co and Mn in GaN and ZnO, making use of radioactive 61Co and 56Mn implanted at the ISOLDE facility at CERN. In addition to the majority occupation of cation (Ga, Zn) sites, we located significant fractions (of the order of 20%) of the Co and Mn impurities in anion (N, O) sites, which are virtually unaffected by thermal annealing up to 900 °C. Here, we present the β- emission channeling experiments on 61Co-implanted GaN. We discuss these results in the context of our recent reports of minority anion substitution in Mn-implanted GaN Pereira et al. (2012) [19] and Mn/Co-implanted ZnO Pereira et al. (2011) [20], particularly in terms of the advantages of the emission channeling technique in such cases of multi-site occupancy.

  6. Reversible, Selective Trapping of Perchlorate from Water in Record Capacity by a Cationic Metal-Organic Framework.

    PubMed

    Colinas, Ian R; Silva, Rachel C; Oliver, Scott R J

    2016-02-16

    We report the capture of ppm-level aqueous perchlorate in record capacity and kinetics via the complete anion exchange of a cationic metal-organic framework. Ambient conditions were used for both the synthesis of silver 4,4'-bipyridine nitrate (SBN) and the exchange, forming silver 4,4'-bipyridine perchlorate (SBP). The exchange was complete within 90 min, and the capacity was 354 mg/g, representing 99% removal. These values are greater than current anion exchangers such as the resins Amberlite IRA-400 (249 mg/g), Purolite A530E (104 mg/g), and layered double hydroxides (28 mg/g). Moreover, unlike resins and layered double hydroxides, SBN is fully reusable and displays 96% regeneration to SBN in nitrate solution, with new crystal formation allowing the indefinite cycling for perchlorate. We show seven cycles as proof of concept. Perchlorate contamination of water represents a serious health threat because it is a thyroid endocrine disruptor. This noncomplexing anionic pollutant is significantly mobile and environmentally persistent. Removal of other anionic pollutants from water such as chromate, pertechnetate, or arsenate may be possible by this methodology. PMID:26765213

  7. Alginate and Algal-Based Beads for the Sorption of Metal Cations: Cu(II) and Pb(II).

    PubMed

    Wang, Shengye; Vincent, Thierry; Faur, Catherine; Guibal, Eric

    2016-01-01

    Alginate and algal-biomass (Laminaria digitata) beads were prepared by homogeneous Ca ionotropic gelation. In addition, glutaraldehyde-crosslinked poly (ethyleneimine) (PEI) was incorporated into algal beads. The three sorbents were characterized by scanning electron microscopy (SEM) coupled with energy dispersive X-ray analysis (EDX): the sorption occurs in the whole mass of the sorbents. Sorption experiments were conducted to evaluate the impact of pH, sorption isotherms, and uptake kinetics. A special attention was paid to the effect of drying (air-drying vs. freeze-drying) on the mass transfer properties. For alginate, freeze drying is required for maintaining the porosity of the hydrogel, while for algal-based sorbents the swelling of the material minimizes the impact of the drying procedure. The maximum sorption capacities observed from experiments were 415, 296 and 218 mg Pb g(-1) and 112, 77 and 67 mg Cu g(-1) for alginate, algal and algal/PEI beads respectively. Though the sorption capacities of algal-beads decreased slightly (compared to alginate beads), the greener and cheaper one-pot synthesis of algal beads makes this sorbent more competitive for environmental applications. PEI in algal beads decreases the sorption properties in the case of the sorption of metal cations under selected experimental conditions. PMID:27598128

  8. Drivers of Tree Species Effects on Phosphorus and Cation Cycling in Plantations at La Selva Biological Station, Costa Rica

    NASA Astrophysics Data System (ADS)

    Russell, A. E.

    2014-12-01

    Fast-growing trees in secondary forests and plantations in the humid tropics play an important role in the atmospheric CO2 balance owing to their high rates of carbon sequestration. Because plants require nutrients to sustain high CO2 uptake, differences among tree species in traits related to nutrient uptake, retention and recycling could influence ecosystem-scale carbon cycling. A better understanding of the relationships among plant traits, nutrient and carbon cycling will thus improve ecosystem- to global scale modeling of effects of vegetation change on carbon cycling. In an experimental setting in which state factors were similar among four species of tropical trees situated on an Oxisol in replicated, 25-yr-old, mono-dominant plantations, I evaluated various drivers of aboveground storage of phosphorus (P) and cations, measuring nutrient fluxes in litterfall and fine-root growth and storage in biomass and soil to 1-m depth. Because fine roots increase the capacity to scavenge nutrients already on exchange sites within the soil environment, I hypothesized that P and cation uptake would be correlated directly with fine-root growth. The four tree species in this experiment, Hieronyma alchorneoides, Pentaclethra macroloba, Virola koschnyi, and Vochysia guatemalensis differed significantly in net cation uptake over the first 25 years of growth (P = 0.013, Ca; P >0.0001, Mg, Mn, K, Al, Fe, and Sr). For all cations, aboveground tree biomass was highly correlated with fine-root ingrowth length, with P values >0.0001 for all cations except Ca (P = 0.013). In contrast for P, differences among species were only marginally significant (P = 0.062). Similarly, P in aboveground tree biomass was marginally correlated with fine-root ingrowth (P = 0.068). Neither cation nor P uptake was correlated with measures of available P and cations, organic or total P in surface soil. For P, the less significant correlation with fine-root growth suggests that some other mechanism, such

  9. Gas sorption and transition-metal cation separation with a thienothiophene based zirconium metal-organic framework

    NASA Astrophysics Data System (ADS)

    SK, Mostakim; Grzywa, Maciej; Volkmer, Dirk; Biswas, Shyam

    2015-12-01

    The modulated synthesis of the thienothiophene based zirconium metal-organic framework (MOF) material having formula [Zr6O4(OH)4(DMTDC)6]·4.8DMF·10H2O (1) (H2DMTDC=3,4-dimethylthieno[2,3-b]thiophene-2,5-dicarboxylic acid; DMF=N,N'-dimethylformamide) was carried out by heating a mixture of ZrCl4, H2DMTDC linker and benzoic acid (used as a modulator) with a molar ratio of 1:1:30 in DMF at 150 °C for 24 h. Systematic investigations have been performed in order to realize the effect of ZrCl4/benzoic acid molar ratio on the crystallinity of the material. The activation (i.e., the removal of the guest solvent molecules from the pores) of as-synthesized compound was achieved by stirring it with methanol and subsequently heating under vacuum. A combination of X-ray diffraction (XRD), Fourier transform infrared (FT-IR), thermogravimetric (TG) and elemental analysis was used to examine the phase purity of the as-synthesized and thermally activated 1. The material displays high thermal stability up to 310 °C in an air atmosphere. As revealed from the XRD measurements, the compound retains its crystallinity when treated with water, acetic acid and 1 M HCl solutions. The N2 and CO2 sorption analyses suggest that the material possesses remarkably high microporosity (SBET=1236 m2 g-1; CO2 uptake=3.5 mmol g-1 at 1 bar and 0 °C). The compound also shows selective adsorption behavior for Cu2+ over Co2+ and Ni2+ ions.

  10. Biological attributes of rehabilitated soils contaminated with heavy metals.

    PubMed

    Valentim Dos Santos, Jessé; Varón-López, Maryeimy; Fonsêca Sousa Soares, Cláudio Roberto; Lopes Leal, Patrícia; Siqueira, José Oswaldo; de Souza Moreira, Fatima Maria

    2016-04-01

    This study aimed to evaluate the effects of two rehabilitation systems in sites contaminated by Zn, Cu, Pb, and Cd on biological soil attributes [microbial biomass carbon (Cmic), basal and induced respiration, enzymatic activities, microorganism plate count, and bacterial and fungal community diversity and structure by denaturing gradient gel electrophoresis (DGGE)]. These systems (S1 and S2) consisted of excavation (trenching) and replacement of contaminated soil by uncontaminated soil in rows with Eucalyptus camaldulensis planting (S1-R and S2-R), free of understory vegetation (S1-BR), or completely covered by Brachiaria decumbens (S2-BR) in between rows. A contaminated, non-rehabilitated (NR) site and two contamination-free sites [Cerrado (C) and pasture (P)] were used as controls. Cmic, densities of bacteria and actinobacteria, and enzymatic activities (β-glucosidase, acid phosphatase, and urease) were significantly higher in the rehabilitated sites of system 2 (S2-R and S2-BR). However, even under high heavy metal contents (S1-R), the rehabilitation with eucalyptus was also effective. DGGE analysis revealed similarity in the diversity and structure of bacteria and fungi communities between rehabilitated sites and C site (uncontaminated). Principal component analysis showed clustering of rehabilitated sites (S2-R and S2-BR) with contamination-free sites, and S1-R was intermediate between the most and least contaminated sites, demonstrating that the soil replacement and revegetation improved the biological condition of the soil. The attributes that most explained these clustering were bacterial density, acid phosphatase, β-glucosidase, fungal and actinobacterial densities, Cmic, and induced respiration. PMID:26662102

  11. Actinide cation-cation complexes

    SciTech Connect

    Stoyer, N.J.; Seaborg, G.T.

    1994-12-01

    The +5 oxidation state of U, Np, Pu, and Am is a linear dioxo cation (AnO{sub 2}{sup +}) with a formal charge of +1. These cations form complexes with a variety of other cations, including actinide cations. Other oxidation states of actinides do not form these cation-cation complexes with any cation other than AnO{sub 2}{sup +}; therefore, cation-cation complexes indicate something unique about AnO{sub 2}{sup +} cations compared to actinide cations in general. The first cation-cation complex, NpO{sub 2}{sup +}{center_dot}UO{sub 2}{sup 2+}, was reported by Sullivan, Hindman, and Zielen in 1961. Of the four actinides that form AnO{sub 2}{sup +} species, the cation-cation complexes of NpO{sub 2}{sup +} have been studied most extensively while the other actinides have not. The only PuO{sub 2}{sup +} cation-cation complexes that have been studied are with Fe{sup 3+} and Cr{sup 3+} and neither one has had its equilibrium constant measured. Actinides have small molar absorptivities and cation-cation complexes have small equilibrium constants; therefore, to overcome these obstacles a sensitive technique is required. Spectroscopic techniques are used most often to study cation-cation complexes. Laser-Induced Photacoustic Spectroscopy equilibrium constants for the complexes NpO{sub 2}{sup +}{center_dot}UO{sub 2}{sup 2+}, NpO{sub 2}{sup +}{center_dot}Th{sup 4+}, PuO{sub 2}{sup +}{center_dot}UO{sub 2}{sup 2+}, and PuO{sub 2}{sup +}{center_dot}Th{sup 4+} at an ionic strength of 6 M using LIPAS are 2.4 {plus_minus} 0.2, 1.8 {plus_minus} 0.9, 2.2 {plus_minus} 1.5, and {approx}0.8 M{sup {minus}1}.

  12. Dynamic chiral-at-metal stability of tetrakis(d/l-hfc)Ln(III) complexes capped with an alkali metal cation in solution.

    PubMed

    Lin, Yiji; Zou, Fang; Wan, Shigang; Ouyang, Jie; Lin, Lirong; Zhang, Hui

    2012-06-14

    Chiral tetrakis(β-diketonate) Ln(III) complexes Δ-[NaLa(d-hfc)(4)(CH(3)CN)] (1) and Λ-[NaLa(l-hfc)(4) (CH(3)CN)] (2) (d/l-hfc(-) = 3-heptafluo-robutylryl-(+)/(-)-camphorate) are a pair of enantiomers and crystallize in the same Sohncke space group (P2(1)2(1)2(1)) with dodecahedral (DD) geometry. Typically positive and negative exciton splitting patterns around 320 nm were observed in the solid-state circular dichroism (CD) spectra of complexes 1 and 2, which indicate that their shell configurational chiralities are Δ and Λ, respectively. The apparent bisignate couplets in the solid-state CD spectra of [CsLn(d-hfc)(4)(H(2)O)] [Ln = La (3), Yb (5)] and [CsLn(l-hfc)(4)(H(2)O)] [Ln = La (4), Yb (6)] show that they are a pair of enantiomers and their absolute configurations are denoted Δ and Λ, respectively. The crystallographic data of 5 reveals that its coordination polyhedron is the square antiprism (SAP) geometry and it undergoes a phase transition from triclinic (α phase, P1) to monoclinic (β phase, C2) upon cooling. The difference between the two phases is brought about by the temperature dependent behaviour of the coordination water molecules, but this did not affect the configurational chirality of the Δ-SAP-[Yb(d-hfc)(4)](-) moiety. Furthermore, time-dependent CD, UV-vis and (19)F NMR were applied to study the solution behavior of these complexes. It was found that the chiral-at-metal stability of the three pairs of complexes is different and affected by both the Ln(3+) and M(+) ion size. The results show that the Cs(+) cation can retain the metal center chirality and stablize the structures of [Ln(d/l-hfc)(4)](-) or the dissociated tris(d/l-hfc)Ln(III) species in solution for a longer time than that of the Na(+) cation, and it is important that the Cs(+) ion successfully lock the configurational chirality around the Yb(3+) center of the complex species in solution. This is reasoned by the short Cs(+)···FC, Cs(+)···O-Yb and Cs(+)···Yb(3

  13. Synthesis of metal-metal oxide catalysts and electrocatalysts using a metal cation adsorption/reduction and adatom replacement by more noble ones

    DOEpatents

    Adzic, Radoslav; Vukmirovic, Miomir; Sasaki, Kotaro

    2010-04-27

    The invention relates to platinum-metal oxide composite particles and their use as electrocatalysts in oxygen-reducing cathodes and fuel cells. The invention particularly relates to methods for preventing the oxidation of the platinum electrocatalyst in the cathodes of fuel cells by use of these platinum-metal oxide composite particles. The invention additionally relates to methods for producing electrical energy by supplying such a fuel cell with an oxidant, such as oxygen, and a fuel source, such as hydrogen. The invention also relates to methods of making the metal-metal oxide composites.

  14. Three Alkali-Metal-Gold-Gallium Systems. Ternary Tunnel Structures and Some Problems with Poorly Ordered Cations

    SciTech Connect

    Smetana, Volodymyr; Miller, Gordon J.; Corbett, John D.

    2012-06-27

    Six new intermetallic compounds have been characterized in the alkali metal (A = Na, Rb, Cs)–gold–gallium systems. Three isostructural compounds with the general composition A0.55Au2Ga2, two others of AAu3Ga2 (A = Rb, Cs), and the related Na13Au41.2Ga30.3 were synthesized via typical high-temperature reactions and their crystal structures determined by single-crystal X-ray diffraction analysis: Na0.56(9)Au2Ga2 (I, I4/mcm, a = 8.718(1) Å, c = 4.857(1) Å, Z = 4), Rb0.56(1)Au2Ga2 (II, I4/mcm, a = 8.950(1) Å, c = 4.829(1) Å, Z = 4), Cs0.54(2)Au2Ga2 (III, I4/mcm, a = 9.077(1) Å, c = 4.815(1) Å, Z = 4), RbAu3Ga2 (IV, Pnma, a = 13.384(3) Å, b = 5.577(1) Å, c = 7.017(1) Å, Z = 4), CsAu3Ga2 (V, Pnma, a = 13.511(3) Å, b = 5.614(2) Å, c = 7.146(1) Å, Z = 4), Na13Au41.2(1)Ga30.3(1) (VI, P6 mmm, a = 19.550(3) Å, c = 8.990(2) Å, Z = 2). The first three compounds (I–III) are isostructural with tetragonal K0.55Au2Ga2 and likewise contain planar eight-member Au/Ga rings that stack along c to generate tunnels and that contain varying degrees of disordered Na–Cs cations. The cation dispositions are much more clearly and reasonably defined by electron density mapping than through least-squares refinements with conventional anisotropic ellipsoids. Orthorhombic AAu3Ga2 (IV, V) are ordered ternary Rb and Cs derivatives of the SrZn5 type structure, demonstrating structural variability within the AAu3Ga2 family. All attempts to prepare an isotypic “NaAu3Ga2” were not successful, but yielded only a similar composition Na13Au41.2Ga30.3 (NaAu3.17Ga2.33) (VI) in a very different structure with two types of cation sites. Crystal orbital Hamilton population (COHP) analysis obtained from tight-binding electronic structure calculations for idealized I–IV via linear muffin-tin-orbital (LMTO) methods emphasized the major contributions of heteroatomic Au–Ga bonding to the structural stability of these compounds. The relative minima (pseudogaps) in the DOS curves for IV

  15. A comparative study of optical absorption and photocatalytic properties of nanocrystalline single-phase anatase and rutile TiO{sub 2} doped with transition metal cations

    SciTech Connect

    Kernazhitsky, L.; Shymanovska, V.; Gavrilko, T.; Naumov, V.; Kshnyakin, V.; Khalyavka, T.

    2013-02-15

    The effect of nanocrystalline TiO{sub 2} doping with transition metal cations (Cu{sup 2+}, Fe{sup 3+}, Co{sup 2+}, Cr{sup 3+}) on their optical absorption and photocatalytic properties was investigated. The obtained metal-doped TiO{sub 2} samples were characterized by X-ray diffraction, scanning electron microscopy, and UV-vis absorption spectroscopy. It is shown that doping effect on anatase (A) and rutile (R) properties is quite different, being much stronger and complicated on A than on R. Contrary to doped R, doped A revealed a significant red shift of the absorption edge along with the band gap narrowing. Photocatalytic activity of anatase increases upon doping in the order: AR/Co>R/Cu>R/Fe>R/Cr, indicating the inhibitory effect of impurity cations. This fact correlates with the decrease in the UV absorption of the doped rutile in the region of the Hg-lamp irradiation at 4.88 eV. - Graphical abstract: A red shift of the absorption edge of nanocrystalline single-phase anatase after doping with transition metal cations. Highlights: Black-Right-Pointing-Pointer Single-phase anatase and rutile powders surface-doped with transition metal cations. Black-Right-Pointing-Pointer Absorption edge and band gap of rutile do not change with surface doping. Black-Right-Pointing-Pointer Band gap of surface-doped anatase reduces being the lowest for A/Fe. Black-Right-Pointing-Pointer The surface-doping improves photocatalytic activity of anatase. Black-Right-Pointing-Pointer The surface-doping inhibits photocatalytic activity of rutile.

  16. The Stabilized Cation Pool Method: Metal- and Oxidant-Free Benzylic C-H/Aromatic C-H Cross-Coupling.

    PubMed

    Hayashi, Ryutaro; Shimizu, Akihiro; Yoshida, Jun-Ichi

    2016-07-13

    Electrochemical oxidation of toluene derivatives in the presence of a sulfilimine gave benzylaminosulfonium ions as stabilized benzyl cation pools, which reacted with subsequently added aromatic nucleophiles to give the corresponding cross-coupling products. The transformation serves as a powerful metal- and chemical-oxidant-free method for benzylic C-H/aromatic C-H cross-coupling. The method has been successfully applied to synthesis of TP27, an inhibitor of PTPase. PMID:27341676

  17. Precipitation of Metallic Cations by the Acidic Exopolysaccharides from Bradyrhizobium japonicum and Bradyrhizobium (Chamaecytisus) Strain BGA-1

    PubMed Central

    Corzo, J.; León-Barrios, M.; Hernando-Rico, V.; Gutierrez-Navarro, A. M.

    1994-01-01

    The interaction between the acidic exopolysaccharides produced by two Bradyrhizobium strains and several metal cations has been studied. Aqueous solutions in the millimolar range of Fe3+ but not of Fe2+ precipitated the exopolysaccharides from Bradyrhizobium (Chamaecytisus) strain BGA-1 and, to a lesser extent, Bradyrhizobium japonicum USDA 110. The precipitation was pH dependent, with a maximum around pH 3. The precipitate was redissolved by changing the pH and by Fe3+ reduction or chelation. Deacetylation of B. japonicum polysaccharide increased its precipitation by Fe3+. At pH near neutrality, the polysaccharide from Bradyrhizobium (Chamaecytisus) strain BGA-1 stabilized Fe3+ solutions, despite the insolubility of Fe(OH)3. Aluminum precipitated Bradyrhizobium (Chamaecytisus) polysaccharide but not the polysaccharide produced by B. japonicum. The precipitation showed a maximum at about pH 4.8, and the precipitate was redissolved after Al3+ chelation with EDTA. Precipitation was inhibited by increases in the ionic strength over 10 mM. Bradyrhizobium (Chamaecytisus) polysaccharide was also precipitated by Th4+, Sn2+, Mn2+, and Co2+. The presence of Fe3+ increased the exopolysaccharide precipitation by aluminum. No precipitation, gelation, or increase in turbidity of polysaccharide solutions occurred when K+, Na+, Ca2+, Mg2+, Cu2+, Cd2+, Pb2+, Zn2+, Hg2+, or U6+ was added at several pH values. The results suggest that the precipitation is based on the interaction between carboxylate groups from different polysaccharide chains and the partially hydrolyzed aquoions of Fe3+, Al3+, Th4+, and Sn2+. PMID:16349466

  18. Biological and Bioelectrochemical Recovery of Critical and Scarce Metals.

    PubMed

    Nancharaiah, Y V; Mohan, S Venkata; Lens, P N L

    2016-02-01

    Metal-bearing solid and liquid wastes are increasingly considered as secondary sources of critical and scarce metals. Undoubtedly, microorganisms are a cost-effective resource for extracting and concentrating diffuse elements from secondary sources. Microbial biotechnology for extracting base metals from ores and treatment of metal-laden wastewaters has already been applied at full scale. By contrast, microbe-metal interactions in the recovery of scarce metals and a few critical metals have received attention, whereas the recovery of many others has been barely explored. Therefore, this article explores and details the potential application of microbial biotechnologies in the recovery of critical and scarce metals. In the past decade bioelectrochemical systems have emerged as a new technology platform for metal recovery coupled to the removal of organic matter. PMID:26763129

  19. Analysis of inorganic cations in biological samples by the combination of micro-electrodialysis and capillary electrophoresis with capacitively coupled contactless conductivity detection.

    PubMed

    Doan, Thi Kieu Oanh; Kubáň, Pavel; Kubáň, Petr; Kiplagat, Isaac K; Boček, Petr

    2011-02-01

    Micro-electrodialysis (μED) and CE were combined for rapid pretreatment and subsequent determination of inorganic cations in biological samples. Combination of μED with CE greatly improved the analytical performance of the latter as the adsorption of high molecular weight compounds present in real samples on the inner capillary wall was eliminated. Fifty microliter of 80-fold diluted human body fluids such as plasma, serum and whole blood was used in the donor compartment of the μED system requiring less than 1 μL of the original body fluid per analysis. Inorganic cations that migrated through a cellulose acetate dialysis membrane with molecular weight cut-off value of 500 Da were collected in the acceptor solution and were then analyzed using CE-C⁴D. Baseline separation of inorganic cations was achieved in a BGE solution consisting of 12.5 mM maleic acid, 15 mM L-arginine and 3 mM 18-crown-6 at pH 5.5. Repeatability of the CE-C⁴D method was better than 0.5% and 2.5% for migration times and peak areas, respectively; limits of detection of all inorganic cations in the presence of 2 mM excess of Na(+) were around 1 μM and calibration curves were linear with correlation coefficients better than 0.998. Repeatability of the sample pretreatment procedure was calculated for six independent electrodialysis runs of artificial and real samples and was better than 11.8%. Recovery values between 96.3 and 110% were achieved for optimized electrodialysis conditions of standard solutions and real samples; lifetime of the dialysis membranes for pretreatment of real samples was estimated to 100 runs. PMID:21298671

  20. Systematically biological prioritizing remediation sites based on datasets of biological investigations and heavy metals in soil

    NASA Astrophysics Data System (ADS)

    Lin, Wei-Chih; Lin, Yu-Pin; Anthony, Johnathen

    2015-04-01

    Heavy metal pollution has adverse effects on not only the focal invertebrate species of this study, such as reduction in pupa weight and increased larval mortality, but also on the higher trophic level organisms which feed on them, either directly or indirectly, through the process of biomagnification. Despite this, few studies regarding remediation prioritization take species distribution or biological conservation priorities into consideration. This study develops a novel approach for delineating sites which are both contaminated by any of 5 readily bioaccumulated heavy metal soil contaminants and are of high ecological importance for the highly mobile, low trophic level focal species. The conservation priority of each site was based on the projected distributions of 6 moth species simulated via the presence-only maximum entropy species distribution model followed by the subsequent application of a systematic conservation tool. In order to increase the number of available samples, we also integrated crowd-sourced data with professionally-collected data via a novel optimization procedure based on a simulated annealing algorithm. This integration procedure was important since while crowd-sourced data can drastically increase the number of data samples available to ecologists, still the quality or reliability of crowd-sourced data can be called into question, adding yet another source of uncertainty in projecting species distributions. The optimization method screens crowd-sourced data in terms of the environmental variables which correspond to professionally-collected data. The sample distribution data was derived from two different sources, including the EnjoyMoths project in Taiwan (crowd-sourced data) and the Global Biodiversity Information Facility (GBIF) ?eld data (professional data). The distributions of heavy metal concentrations were generated via 1000 iterations of a geostatistical co-simulation approach. The uncertainties in distributions of the heavy

  1. Catalytic oxidation of H2 by N2O in the gas phase: O-atom transport with atomic metal cations.

    PubMed

    Blagojevic, Voislav; Bozović, Andrea; Orlova, Galina; Bohme, Diethard K

    2008-10-16

    Twenty-five atomic cations, M (+), that lie within the thermodynamic window for O-atom transport catalysis of the oxidation of hydrogen by nitrous oxide, have been checked for catalytic activity at room temperature with kinetic measurements using an inductively-coupled plasma/selected-ion flow tube (ICP/SIFT) tandem mass spectrometer. Only 4 of these 25 atomic cations were seen to be catalytic: Fe (+), Os (+), Ir (+), and Pt (+). Two of these, Ir (+) and Pt (+), are efficient catalysts, while Fe (+) and Os (+) are not. Eighteen atomic cations (Cr (+), Mn (+), Co (+), Ni (+), Cu (+), Ge (+), Se (+), Mo (+), Ru (+), Rh (+), Sn (+), Te (+), Re (+), Pb (+), Bi (+), Eu (+), Tm (+), and Yb (+)) react too slowly at room temperature either in their oxidation with N 2O to form MO (+) or in the reduction of MO (+) by H 2. Many of these reactions are known to be spin forbidden and a few actually may lie outside the thermodynamic window. Three alkaline-earth metal monoxide cations, CaO (+), SrO (+), and BaO (+), were observed to favor MOH (+) formation in their reactions with H 2. A potential-energy landscape is computed for the oxidation of H 2 with N 2O catalyzed by Fe (+)( (6)D) that vividly illustrates the operation of an ionic catalyst and qualitatively accounts for the relative inefficiency of this catalyst. PMID:18808088

  2. Thiophene complexes of the platinum group metals. 2. Preparation and characterization of cationic thiophene complexes of [(cyclooctadiene)Ir][BF[sub 4

    SciTech Connect

    Polam, J.R.; Porter, L.C. )

    1993-09-01

    Cleavage of chloro-bridged rhodium and iridium dimers, [(NBD)RhCl][sub 2] and [(COD)IrCl][sub 2], in methanol leads to the formation of cationic (COD)[sub 2]Ir[sup +] and (NBD)Rh[sup +] monomers, respectively. Reaction of these cationic species with 2-methylthiophene and 2,5-dimethylthiophene results in the formation of complexes in which the thiophene coordinates in an [eta][sup 5] manner. With benzothiophene and dibenzothiophene, complexes bearing a 1:1 metal:ligand stoichiometry are obtained with the ligand coordinating in an [eta][sup 6] fashion using the six carbon atoms of the arene ring. Good yields of these Rh and Ir products are obtained with the exception of those of reactions involving thiophene, where only small amounts of product were obtained. A crystal structure determination of the cationic (cyclooctadiene)rhodium 2,5-dimethylthiophene complex shows that the thiophene ligand binds to the transition metal center in an [eta][sup 5] manner. The S atom is displaced 0.1888 A from the least-squares plane defined by the four carbon ring atoms and displays C-S bond lengths similar to those found in free thiophene. 17 refs., 2 figs., 3 tabs.

  3. Different Cation Arrangements in Au-In Networks. Syntheses and Structures of Six Intermetallic Compounds in Alkali-Metal-Au-In Systems

    SciTech Connect

    Bin Li; John D. Corbett

    2007-06-20

    Six robust intermetallic compounds with cations in three different tunnel-like structures have been synthesized in alkali-metal-Au-In systems via high-temperature solid-state methods and characterized by X-ray diffraction: AAu{sub 4}-In{sub 6} [A = K (I), Rb (II), F6m2, Z = 1], K{sub 1.76(6)}Au{sub 6}Ln{sub 4} (III,; 4/mcm, Z = 4), and A{sub x}Au{sub 2}In{sub 2} [x{approx} 0.7, A = K (IV), Rb (V), Cs (VI), P4{sub 2}/nmc, Z = 8]. The first type is constructed from a single cage unit: an alkali-metal-centered 21-vertex polyhedron A@AugIn12 with 6-9-6 arrangement of planar rings. The others contain uniaxial arrays of tunnels built of differently puckered eight- and four-member Au/In rings. The largely different cation distributions depend on the tunnel constitutions and cation sizes. Tight-binding electronic structure calculations by linear muffin-tin-orbital (LMTO) methods were performed for I and idealized III in order to help understand their chemical bonding. These also reveal large differences in relativistic effects for Au d orbitals, as well as for different Au sites in each structure.

  4. Different Cation Arrangements in Au-In Networks. Syntheses and Structures of Six Intermetallic compounds in Alkali-Metal-Au-In Systems

    SciTech Connect

    Li, Bin; Corbett, John D.

    2007-06-20

    Six robust intermetallic compounds with cations in three different tunnel-like structures have been synthesized in alkali-metal-Au-In systems via high-temperature solid-state methods and characterized by X-ray diffraction: AAu{sub 4}-In{sub 6} [A = K (I), Rb (II), F6m2, Z = 1], K{sub 1.76(6)}Au{sub 6}Ln{sub 4} (III, /4/mcm, Z = 4), and A{sub x}Au{sub 2}In{sub 2} [x {approx} 0.7, A = K (IV), Rb (V), Cs (VI), P4{sub 2}/nmc, Z = 8]. The first type is constructed from a single cage unit: an alkali-metal-centered 21-vertex polyhedron A{at}AugIn{sub 12} with 6-9-6 arrangement of planar rings. The others contain uniaxial arrays of tunnels built of differently puckered eight- and four-member Au/In rings. The largely different cation distributions depend on the tunnel constitutions and cation sizes. Tight-binding electronic structure calculations by linear muffin-tin-orbital (LMTO) methods were performed for I and idealized III in order to help understand their chemical bonding. These also reveal large differences in relativistic effects for Au d orbitals, as well as for different Au sites in each structure.

  5. Effect of Metal Cations on the Viscosity of a Pectin-Like Capsular Polysaccharide from the Cyanobacterium Microcystis flos-aquae C3-40

    PubMed Central

    Parker, D. L.; Schram, B. R.; Plude, J. L.; Moore, R. E.

    1996-01-01

    The properties of purified capsular polysaccharide from the cyanobacterium Microcystis flos-aquae C3-40 were examined by capillary viscometry. Capsule suspensions exhibited similar viscosities between pH 6 and 10 but were more viscous at pH <=4 than at pH 6 to 11. At pH 7, a biphasic effect of metal ion concentration on capsule viscosity was observed: (i) capsule viscosity increased with increasing metal ion concentration until a maximal viscosity occurred at a specific concentration that was a reproducible characteristic of each metal ion, and (ii) the viscosity decreased with further addition of that ion. Because the latter part of the biphasic curve was complicated by additional factors (especially the precipitation or gelation of capsule by divalent metal ions), the effects of various metal chlorides were compared for the former phase in which capsule viscosity increased in the presence of metal ions. Equivalent increases in capsule viscosity were observed with micromolar concentrations of divalent metal ions but only with 10 to 20 times greater concentrations of Na(sup+). The relative abilities of various metal salts to increase capsule viscosity were as follows: CdCl(inf2), Pb(NO(inf3))(inf2), FeCl(inf2) > MnCl(inf2) > CuCl(inf2), CaCl(inf2) >> NaCl. This pattern of metal efficacy resembles known cation influences on the structural integrity of capsule in naturally occurring and cultured M. flos-aquae colonies. The data are the first direct demonstration of an interaction between metal ions and purified M. flos-aquae capsule, which has previously been proposed to play a role in the environmental cycling of certain multivalent metals, especially manganese. The M. flos-aquae capsule and the plant polysaccharide pectin have similar sugar compositions but differ in their relative responses to various metals, suggesting that capsular polysaccharide could be a preferable alternative to pectin for certain biotechnological applications. PMID:16535287

  6. Quantification of Site-Specific Cation Exchange in Metal-Organic Frameworks Using Multi-Wavelength Anomalous X-ray Dispersion

    SciTech Connect

    Brozek, Carl K.; Cozzolino, Anthony F.; Teat, Simon J.; Chen, Yu-Sheng; Dinc,; #259; Mircea,

    2013-09-23

    We employed multiwavelength anomalous X-ray dispersion to determine the relative cation occupation at two crystallographically distinct metal sites in Fe2+-, Cu2+-, and Zn2+-exchanged versions of the microporous metal–organic framework (MOF) known as MnMnBTT (BTT = 1,3,5-benzenetristetrazolate). By exploiting the dispersive differences between Mn, Fe, Cu, and Zn, the extent and location of cation exchange were determined from single crystal X-ray diffraction data sets collected near the K edges of Mn2+ and of the substituting metal, and at a wavelength remote from either edge as a reference. Comparing the anomalous dispersion between these measurements indicated that the extent of Mn2+ replacement depends on the identity of the substituting metal. We contrasted two unique methods to analyze this data with a conventional approach and evaluated their limitations with emphasis on the general application of this method to other heterometallic MOFs, where site-specific metal identification is fundamental to tuning catalytic and physical properties.

  7. Photochemical reactions of metal nitrosyl complexes. Mechanisms of NO reactions with biologically relevant metal centers

    DOE PAGESBeta

    Ford, Peter C.

    2001-01-01

    Tmore » he discoveries that nitric oxide (a.k.a. nitrogen monoxide) serves important roles in mammalian bioregulation and immunology have stimulated intense interest in the chemistry and biochemistry of NO and derivatives such as metal nitrosyl complexes. Also of interest are strategies to deliver NO to biological targets on demand. One such strategy would be to employ a precursor which displays relatively low thermal reactivity but is photochemically active to release NO.his proposition led us to investigate laser flash and continuous photolysis kinetics of nitrosyl complexes such as the Roussin's iron-sulfur-nitrosyl cluster anions Fe 2 S 2 ( NO ) 4 2 − and Fe 4 S 3 ( NO ) 7 − and several ruthenium salen and porphyrin nitrosyls.hese include studies using metal-nitrosyl photochemistry as a vehicle for delivering NO to hypoxic cell cultures in order to sensitize γ -radiation damage. Also studied were the rates and mechanisms of NO “on” reactions with model water soluble heme compounds, the ferriheme protein met-myoglobin and various ruthenium complexes using ns laser flash photolysis techniques. An overview of these studies is presented.« less

  8. [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. PMID:26350735

  9. Multi-source MBE with high-precision rate control system as a synthesis method sui generis for multi-cation metal oxides

    NASA Astrophysics Data System (ADS)

    Yamamoto, Hideki; Krockenberger, Yoshiharu; Naito, Michio

    2013-09-01

    Molecular beam epitaxy (MBE) has been an excellent tool to design artificial heterostructures in the research field of semiconductors by means of an alternate stacking of existing lattices. This article describes further capabilities of MBE as a synthesis tool sui generis, especially for multi-cation oxides, due to low-temperature reaction and the pseudomorphic stabilization effect by epitaxy. Single-crystalline Sr0.9La0.1CuO2 films exhibiting metallic conduction and superconductivity are successfully prepared by MBE. A new phase, T*-La2CuO4, is also stabilized on a DyScO3 substrate. Methods of high-precision rate control of each constituent element, which is prerequisite for a reproducible growth of the multi-cation oxide films, are also discussed.

  10. An anionic zeolite-like metal-organic framework (AZMOF) with a Moravia network for organic dye absorption through cation-exchange.

    PubMed

    Shen, Yu; Fan, Cong-Cong; Wei, Yu-Zhen; Du, Jie; Zhu, Hai-Bin; Zhao, Yue

    2016-07-01

    An anionic zeolite-like metal-organic framework (AZMOF) with a twisted partially augmented the net, known as the "Moravia" net, [(CH3)2NH2]6[Sr13(O)3()8(OH)2(H2O)16]·xS (, where S represents non-coordinated solvent molecules, and is the abbreviation of benzo-(1,2;3,4;5,6)-tris-(thiophene-2'-carboxylic acid)), has been solvothermally synthesized and characterized, which possesses an anionic framework and nano-sized sodalite cage. Through cation-exchange, is capable of uptaking large organic cationic dyes including Rhodamine B (RB), Basic Red 2 (BR2), Crystal Violet (CV) and Methylene Blue (MB), amongst which the adsorption capability for RB (up to 545 mg g(-1)), and BR2 (up to 675 mg g(-1)) is the highest for reported absorbants to date. PMID:27301344

  11. Recognition of some lanthanides, actinides, and transition- and heavy-metal cations by N-donor ligands: thermodynamic and kinetic aspects.

    PubMed

    Hubscher-Bruder, Véronique; Haddaoui, Jaouad; Bouhroum, Saliha; Arnaud-Neu, Françoise

    2010-02-15

    The remarkable actinide(III) selectivity of the polyaromatic N-donors bis-triazine-pyridines (BTPs), hemi-bis-triazine-pyridines (hemi-BTPs) and bis-triazine-bipyridines (BTBPs) make these ligands the most promising candidates in partitioning and transmutation processes developed so far to better manage nuclear waste. The interactions of n-Pr-BTP, C(5)-hemi-BTP, and the two most extensively investigated BTBPs (C(5)-BTBP and CyMe(4)-BTBP) have been studied with some representative lanthanide(III), uranyl, thorium, and transition- and other heavy-metal cations in methanol. The formation of complexes of different stoichiometries, the stability of which depended on both the ligands and the cations, was shown using UV absorption spectrophotometry. Study of the complexation reactions of La(3+), Eu(3+) and Yb(3+) with these four ligands by stopped-flow spectrophotometry allowed determination of the rate constants and postulation of possible complexation mechanisms. PMID:20055507

  12. The electronic structure of vanadium monochloride cation (VCl{sup +}): Tackling the complexities of transition metal species

    SciTech Connect

    DeYonker, Nathan J.; Halfen, DeWayne T.; Ziurys, Lucy M.; Allen, Wesley D.

    2014-11-28

    Six electronic states (X {sup 4}Σ{sup −}, A {sup 4}Π, B {sup 4}Δ, {sup 2}Φ, {sup 2}Δ, {sup 2}Σ{sup +}) of the vanadium monochloride cation (VCl{sup +}) are described using large basis set coupled cluster theory. For the two lowest quartet states (X {sup 4}Σ{sup −} and A {sup 4}Π), a focal point analysis (FPA) approach was used that conjoined a correlation-consistent family of basis sets up to aug-cc-pwCV5Z-DK with high-order coupled cluster theory through pentuple (CCSDTQP) excitations. FPA adiabatic excitation energies (T{sub 0}) and spectroscopic constants (r{sub e}, r{sub 0}, B{sub e}, B{sub 0}, D{sup ¯}{sub e}, H{sub e}, ω{sub e}, v{sub 0}, α{sub e}, ω{sub e}x{sub e}) were extrapolated to the valence complete basis set Douglas-Kroll (DK) aug-cc-pV∞Z-DK CCSDT level of theory, and additional treatments accounted for higher-order valence electron correlation, core correlation, and spin-orbit coupling. Due to the delicate interplay between dynamical and static electronic correlation, single reference coupled cluster theory is able to provide the correct ground electronic state (X {sup 4}Σ{sup −}), while multireference configuration interaction theory cannot. Perturbations from the first- and second-order spin orbit coupling of low-lying states with quartet spin multiplicity reveal an immensely complex rotational spectrum relative to the isovalent species VO, VS, and TiCl. Computational data on the doublet manifold suggest that the lowest-lying doublet state ({sup 2}Γ) has a T{sub e} of ∼11 200 cm{sup −1}. Overall, this study shows that laboratory and theoretical rotational spectroscopists must work more closely in tandem to better understand the bonding and structure of molecules containing transition metals.

  13. How Cation-Pi Interactions Enhance and Structure the Binding of Metal Ions to Amino Acids and Peptides. Dialanine Probed by Irmpd Spectroscopy as a Prime Example

    NASA Astrophysics Data System (ADS)

    Dunbar, Robert C.; Steill, Jeffrey; Oomens, Jos

    2010-06-01

    Spectroscopic examination of metalated amino acids and model peptides in the infrared region gives incisive conformational information. The role of cation-pi interactions of the metal ions with aromatic amino acids in structuring the complexes and enforcing particular architectures is being clarified by such experiments using IRMPD action spectroscopy as the experimental probe. The presence of multiple aromatic groups as in dialanine gives particularly stringent conformational stabilization. Comparing spectroscopic peak shifts across a range of alkali and alkaline earth metal ions, ranging from lithium to cesium, and from calcium to barium, allows us to view the systematic relations between normal mode frequencies and ion/peptide interactions. The spectra of the ions were acquired by irradiating the cell of the Fourier-transform ion cyclotron resonance mass spectrometer with infrared light from the FELIX free electron laser at wavelengths in the approximate range 500 to 1900 cm-1.

  14. Influence of pH and Metal Cations on Aggregative Growth of Non-Slime-forming Strains of Zoogloea ramigera

    PubMed Central

    Angelbeck, Donald I.; Kirsch, Edwin J.

    1969-01-01

    Aggregative growth of non-slime-forming strains of Zoogloea ramigera was induced by growing the organisms at a depressed pH. Calcium and magnesium ion was found to reverse aggregative growth of the organisms. Conversely, aggregation was stimulated when the available inorganic cation concentration of the growth medium was lowered by the use of a chelating agent. The aggregative effects of pH depression or cation depletion and the dispersal effects of cation supplementation were observed only during cellular growth. The data suggest that aggregate formation of non-slime-forming strains of Z. ramigera may be related to the calcium or magnesium metabolism of the organisms, or both. Images PMID:4976326

  15. Effect of metal cation replacement on the electronic structure of metalorganic halide perovskites: Replacement of lead with alkaline-earth metals

    NASA Astrophysics Data System (ADS)

    Pazoki, Meysam; Jacobsson, T. Jesper; Hagfeldt, Anders; Boschloo, Gerrit; Edvinsson, Tomas

    2016-04-01

    Organic and inorganic lead halogen perovskites, and in particular, C H3N H3Pb I3 , have during the last years emerged as a class of highly efficient solar cell materials. Herein we introduce metalorganic halogen perovskite materials for energy-relevant applications based on alkaline-earth metals. Based on the classical notion of Goldschmidt's rules and quantum mechanical considerations, the three alkaline-earth metals, Ca, Sr, and Ba, are shown to be able to exchange lead in the perovskite structure. The three alkaline-earth perovskites, C H3N H3Ca I3,C H3N H3Sr I3 , and C H3N H3Ba I3 , as well as the reference compound, C H3N H3Pb I3 , are in this paper investigated with density functional theory (DFT) calculations, which predict these compounds to exist as stable perovskite materials, and their electronic properties are explored. A detailed analysis of the projected molecular orbital density of states and electronic band structure from DFT calculations were used for interpretation of the band-gap variations in these materials and for estimation of the effective masses of the electrons and holes. Neglecting spin-orbit effects, the band gap of MACa I3,MASr I3 , and MABa I3 were estimated to be 2.95, 3.6, and 3.3 eV, respectively, showing the relative change expected for metal cation exchange. The shifts in the conduction band (CB) edges for the alkaline-earth perovskites were quantified using scalar relativistic DFT calculations and tight-binding analysis, and were compared to the situation in the more extensively studied lead halide perovskite, C H3N H3Pb I3 , where the change in the work function of the metal is the single most important factor in tuning the CB edge and band gap. The results show that alkaline-earth-based organometallic perovskites will not work as an efficient light absorber in photovoltaic applications but instead could be applicable as charge-selective contact materials. The rather high CB edge and the wide band gap together with the large

  16. Titanates and Titanate-Metal Compounds in Biological Contexts

    PubMed Central

    Chen, Yen-Wei; Drury, Jeanie L.; Chung, Whasun Oh; Hobbs, David T.; Wataha, John C.

    2015-01-01

    Metal ions are notorious environmental contaminants, some causing toxicity at exquisitely low (ppm-level) concentrations. Yet, the redox properties of metal ions make them attractive candidates for bio-therapeutics. Titanates are insoluble particulate compounds of titanium and oxygen with crystalline surfaces that bind metal ions; these compounds offer a means to scavenge metal ions in environmental contexts or deliver them in therapeutic contexts while limiting systemic exposure and toxicity. In either application, the toxicological properties of titanates are crucial. To date, the accurate measurement of the in vitro toxicity of titanates has been complicated by their particulate nature, which interferes with many assays that are optical density (OD)-dependent, and at present, little to no in vivo titanate toxicity data exist. Compatibility data garnered thus far for native titanates in vitro are inconsistent and lacking in mechanistic understanding. These data suggest that native titanates have little toxicity toward several oral and skin bacteria species, but do suppress mammalian cell metabolism in a cells-pecific manner. Titanate compounds bind several types of metal ions, including some common environmental toxins, and enhance delivery to bacteria or cells. Substantial work remains to address the practical applicability of titanates. Nevertheless, titanates have promise to serve as novel vehicles for metal-based therapeutics or as a new class of metal scavengers for environmental applications. PMID:26430701

  17. Incorporation of transition metals into Mg Al layered double hydroxides: Coprecipitation of cations vs. their pre-complexation with an anionic chelator

    NASA Astrophysics Data System (ADS)

    Tsyganok, Andrey; Sayari, Abdelhamid

    2006-06-01

    A comparative study on two different methods for preparing Mg-Al layered double hydroxides (LDH) containing various divalent transition metals M ( M=Co, Ni, Cu) has been carried out. The first (conventional) method involved coprecipitation of divalent metals M(II) with Mg(II) and Al(III) cations using carbonate under basic conditions. The second approach was based on the ability of transition metals to form stable anionic chelates with edta 4- (edta 4-=ethylenediaminetetraacetate) that were synthesized and further introduced into LDH by coprecipitation with Mg and Al. The synthesized LDHs were characterized by X-ray diffraction (XRD) and X-ray fluorescence (XRF) methods, thermogravimetry with mass-selective detection of decomposition products (TG-MSD), Fourier transform infrared (FTIR) and Raman spectroscopy techniques. The results obtained were discussed in terms of efficiency of transition metal incorporation into the LDH structure, thermal stability of materials and the ability of metal chelates to intercalate the interlayer space of Mg-Al LDH. Vibrational spectroscopy studies confirmed that the integrity of the metal chelates was preserved upon incorporation into the LDH.

  18. CAX-ing a wide net: Cation/H(+) transporters in metal remediation and abiotic stress signalling

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cation/proton exchangers (CAXs) are a class of secondary energised ion transporter that are being implicated in an increasing range of cellular and physiological functions. CAXs are primarily Ca(2+) efflux transporters that mediate the sequestration of Ca(2+) from the cytosol, usually into the vacuo...

  19. Specific interactions between alkali metal cations and the KcsA channel studied using ATR-FTIR spectroscopy

    PubMed Central

    Furutani, Yuji; Shimizu, Hirofumi; Asai, Yusuke; Oiki, Shigetoshi; Kandori, Hideki

    2015-01-01

    The X-ray structure of KcsA, a eubacterial potassium channel, displays a selectivity filter composed of four parallel peptide strands. The backbone carbonyl oxygen atoms of these strands solvate multiple K+ ions. KcsA structures show different distributions of ions within the selectivity filter in solutions containing different cations. To assess the interactions of cations with the selectivity filter, we used attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy. Ion-exchange-induced ATR-FTIR difference spectra were obtained by subtracting the spectrum of KcsA soaked in K+ solution from that obtained in Li+, Na+, Rb+, and Cs+ solutions. Large spectral changes in the amide-I and -II regions were observed upon replacing K+ with smaller-sized cations Li+ and Na+ but not with larger-sized cations Rb+ and Cs+. These results strongly suggest that the selectivity filter carbonyls coordinating Rb+ or Cs+ adopt a conformation similar to those coordinating K+ (cage configuration), but those coordinating Li+ or Na+ adopt a conformation (plane configuration) considerably different from those coordinating K+. We have identified a cation-type sensitive amide-I band at 1681 cm−1 and an insensitive amide-I band at 1659 cm−1. The bands at 1650, 1639, and 1627 cm−1 observed for Na+-coordinating carbonyls were almost identical to those observed in Li+ solution, suggesting that KcsA forms a similar filter structure in Li+ and Na+ solutions. Thus, we conclude that the filter structure adopts a collapsed conformation in Li+ solution that is similar to that in Na+ solution but is in clear contrast to the X-ray crystal structure of KcsA with Li+. PMID:27493853

  20. Block of current through T-type calcium channels by trivalent metal cations and nickel in neural rat and human cells.

    PubMed Central

    Mlinar, B; Enyeart, J J

    1993-01-01

    1. The effects of the trivalent cations yttrium (Y3+), lanthanum (La3+), cerium (Ce3+), neodymium (Nd3+), gadolinium (Gd3+), holmium (Ho3+), erbium (Er3+), ytterbium (Yb3+) and the divalent cation nickel (Ni2+) on the T-type voltage gated calcium channel (VGCC) were characterized by the whole-cell patch clamp technique using rat and human thyroid C cell lines. 2. All the metal cations (M3+) studied, blocked current through T-type VGCC (IT) in a concentration-dependent manner. Smaller trivalents were the best T-channel antagonists and potency varied inversely with ionic radii for the larger M3+ ions. Estimation of half-maximal blocking concentrations (IC50s) for IT carried by 10 mM Ca2+ resulted in the following potency sequence: Ho3+ (IC50 = 0.107 microM) approximately Y3+ (0.117) approximately Yb3+ (0.124) > or = Er3+ (0.153) > Gd3+ (0.267) > Nd3+ (0.429) > Ce3+ (0.728) > La3+ (1.015) >> Ni2+ (5.65). 3. Tail current measurements and conditioning protocols were used to study the influence of membrane voltage on the potency of these antagonists. Block of IT by Ni2+, Y3+, La3+ and the lanthanides was voltage independent in the range from -200 to +80 mV. In addition, the antagonists did not affect macroscopic inactivation and deactivation of T-type VGCC. 4. Increasing the extracellular Ca2+ concentration reduced the potency of IT block by Ho3+, indicative of competitive antagonism between this blocker and the permeant ion for a binding site. 5. The results suggest that the mechanism of metal cation block of T-type VGCC is occlusion of the channel pore by the antagonist binding to a Ca2+/M3+ binding site, located out of the membrane electric field. 6. Block of T-type VGCC by Y3+, lanthanides and La3+ differ from the inhibition of high voltage-activated VGCC block in several respects: smaller cations are more potent IT antagonists; block is voltage independent and the antagonists do not permeate T-type channels. These differences suggest corresponding structural

  1. Differential coordination demands in Fe vs Mn water-soluble cationic metalloporphyrins translates into remarkably different aqueous redox chemistry and biology

    PubMed Central

    Tovmasyan, Artak; Weitner, Tin; Sheng, Huaxin; Lu, MiaoMiao; Rajic, Zrinka; Warner, David S.; Spasojevic, Ivan; Reboucas, Julio S.; Benov, Ludmil; Batinic-Haberle, Ines

    2013-01-01

    The different biological behavior of cationic Fe and Mn pyridylporphyrins in Escherichia coli and mouse studies prompted us to revisit and compare their chemistry. For that purpose the series of ortho and meta isomers of Fe(III) meso-tetrakis-N-alkylpyridylporphyrins, alkyl being methyl to n-octyl, were synthesized and characterized by elemental analysis, UV/vis spectroscopy, mass spectrometry, lipophilicity, protonation equilibria of axial waters, metal-centered reduction potential, E1/2 for MIIIP/MIIP redox couple (M = Fe, Mn, P=porphyrin), kcat for the catalysis of O2•− dismutation, stability towards peroxide-driven porphyrin oxidative degradation (produced in the catalysis of ascorbate oxidation by MP), ability to affect growth of SOD-deficient E. coli and toxicity to mice. Electron-deficiency of the metal site is modulated by the porphyrin ligand, which renders Fe(III) porphyrins ≥ 5 orders of magnitude more acidic than the analogous Mn(III) porphyrins, as revealed by the pKa1 of axially coordinated waters. The 5 log units difference in the acidity between the Mn and Fe sites in porphyrin translates into the predominance of tetracationic (OH)(H2O)FeP complexes relative to pentacationic (H2O)2MnP species at pH ~7.8. This is evidenced in large differences in the thermodynamic parameters - pKa of axial waters and E1/2 of MIII/MII redox couple. The presence of hydroxo ligand labilizes trans-axial water which results in higher reactivity of Fe- relative to Mn center. The differences in the catalysis of O2•− dismutation (log kcat) between Fe and Mn porphyrins is modest, 2.5-5-fold, due to predominantly outer-sphere, with partial inner-sphere character of two reaction steps. However, the rate constant for the inner-sphere H2O2-based porphyrin oxidative degradation is 18-fold larger for (OH)(H2O)FeP than for (H2O)2MnP. The in vivo consequences of the differences between the Fe- and Mn porphyrins were best demonstrated in SOD-deficient E. coli growth. Based

  2. General features in the stoichiometry and stability of ionophore A23187-cation complexes in homogeneous solution.

    PubMed

    Chapman, C J; Puri, A K; Taylor, R W; Pfeiffer, D R

    1990-08-15

    Existing literature describing the stoichiometry and stability of complexes between A23187 and divalent cations in solution has been extended to include additional transition series cations, the heavy-metal cations Cd2+ and Pb2+, plus seven lanthanide series trivalent cations. Stability constants of 1:1 complexes between the ionophore and the divalent cations vary by 6.2 orders of magnitude between Cu2+ and Ba2+ which are the strongest and weakest complexes, respectively. Considering alkaline-earth and first-series transition cations together, the pattern of stability constants obeys the extended Irving-Williams series as is seen with many nonionophorous liganding agents. Cd2+ and Pb2+ are bound with an affinity similar to those of Mn2+ and Zn2+, whereas the lanthanides are bound with little selectivity and slightly higher stability. Titration of the ionophore in the 10(-5) M concentration range with di- and trivalent cations gives rise first to complexes of stoichiometry MA2 and subsequently to MA as the metal concentration is increased. The second stepwise stability constants for formation of the MA2 species exceeds the first constant by approximately 10-fold. With lanthanides, heavy metals, and transition-metal cations, OH-, at near physiological concentrations, competes significantly with free ionophore for binding to the 1:1 complexes. This competition is not apparent when Ca2+ or Mg2+ are the central cations. Possible implications of the 1:1 complex selectivity pattern, the ionophore-hydroxide competitive binding equilibria, and potential ternary complexes involving 1:1 ionophore:cation complexes and other anions present in biological systems are discussed with respect to the ionophore's transport selectivity and biological actions. PMID:2116770

  3. Many-body exchange-repulsion in polarizable molecular mechanics. I. Orbital-based approximations and applications to hydrated metal cation complexes.

    PubMed

    Chaudret, Robin; Gresh, Nohad; Parisel, Olivier; Piquemal, Jean-Philip

    2011-11-15

    We have quantified the extent of the nonadditivity of the short-range exchange-repulsion energy, E(exch-rep), in several polycoordinated complexes of alkali, alkaline-earth, transition, and metal cations. This was done by performing ab initio energy decomposition analyses of interaction energies in these complexes. The magnitude of E(exch-rep(n-body, n > 2)) was found to be strongly cation-dependent, ranging from close to zero for some alkali metal complexes to about 6 kcal/mol for the hexahydrated Zn(2+) complex. In all cases, the cation-water molecules, E(exch-rep(three-body)), has been found to be the dominant contribution to many-body exchange-repulsion effects, higher order terms being negligible. As the physical basis of this effect is discussed, a three-center exponential term was introduced in the SIBFA (Sum of Interactions Between Fragments Ab initio computed) polarizable molecular mechanics procedure to model such effects. The three-body correction is added to the two-center (two-body) overlap-like formulation of the short-range repulsion contribution, E(rep), which is grounded on simplified integrals obtained from localized molecular orbital theory. The present term is computed on using mostly precomputed two-body terms and, therefore, does not increase significantly the computational cost of the method. It was shown to match closely E(three-body) in a series of test cases bearing on the complexes of Ca(2+), Zn(2+), and Hg(2+). For example, its introduction enabled to restore the correct tetrahedral versus square planar preference found from quantum chemistry calculations on the tetrahydrate of Hg(2+) and [Hg(H(2)O)(4)](2+). PMID:21793002

  4. 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

  5. [Design and synthesis of imine compound for metal cation logical gates recognition and setup of double-control fluorescent molecule switch].

    PubMed

    Huang, Tao; Zhu, Yu-lian; Dai, Xue-qin; Zhang, Qi; Huang, Yan

    2011-07-01

    The Schiff base's reduced product N,N-bis(4-methoxybenzyl) ethane-1,2-diamine, which was used as a receptor L, was designed and synthesized for the first time in the present article. It was found that Cu2+ and Fe3+ could quench L in fluorescence observably and Zn2+ and Cd2+ could enhance L remarkably. So the two pair metal cation could set up "OR" logical gate relation with the receptor molecule L, then a logical recognition system be formed. The data of resolved ZnL's single crystal indicated that ZnL belonged to monoclinic (CCDC No. 747994). Integrated spectrum instrument was used to characterize the structure of its alike series of complex compound. According to ZnL's excellent fluorescence character and the ability to exchange with contiguous metal cation, ZnZ+/ZnL/Co2+, Zn2+/ZnL/Nit+ fluorescent molecule switch was designed. It is hoped that the work above could be positive for the development of molecule computer, bio-intellectualized inspection technology (therapy) and instrument. PMID:21942034

  6. Effects of nonframework metal cations and phonon scattering mechanisms on the thermal transport properties of polycrystalline zeolite LTA films

    NASA Astrophysics Data System (ADS)

    Greenstein, Abraham; Hudiono, Yeny; Graham, Samuel; Nair, Sankar

    2010-03-01

    We present a systematic study to investigate the effects of nonframework cations and the role of phonon scattering mechanisms on the thermal transport properties of zeolite LTA, via experiment and semiempirical lattice dynamics calculations. Our study is motivated by the increasing interest in accurate measurements and mechanistic understanding of the thermal transport properties of zeolite materials. The presence of a nanostructured pore network, extra-framework cations, and tunable framework structure and composition confer interesting thermophysical properties to these materials, making them a good model system to investigate thermal transport in complex materials. Continuous films of zeolite LTA with different nonframework cations (Na+, K+, and Ca+2) were synthesized and characterized. The thermal conductivity was measured using the three-omega method over a wide range of temperature (150-450 K). These are the first thermal conductivity measurements performed on bulk LTA, so they are more accurate than previous measurements, which involved the use of compacted zeolite powders. Our data showed significant dependence of the thermal conductivity on the extra-framework cations as well the temperature. The thermal conductivities of the zeolite LTA samples were modeled with the relaxation time approximation to the Boltzmann transport equation. The full phonon spectra for each type of LTA zeolite were calculated and used in conjunction with semiempirical relaxation time expressions to calculate the thermal conductivity. The results both validated, and suggested the limitations of, this modeling approach. Optical phonons dominated the thermal conductivity and boundarylike scattering was found to be the strongest phonon scattering mechanism, as also observed in MFI zeolite.

  7. Organochlorines, heavy metals, and the biology of North American accipiters

    USGS Publications Warehouse

    Snyder, N.F.R.; Snyder, H.A.; Lincer, J.L.; Reynolds, R.T.

    1973-01-01

    Analyses of eggs of three species of North American accipitrine hawks for organochlorines and heavy metals indicate that contamination with DDE may be the primary cause of recent population declines of two of the species, Cooper's hawk and sharp-shinned hawk.

  8. A self-cleaving DNA enzyme modified with amines, guanidines and imidazoles operates independently of divalent metal cations (M2+)

    PubMed Central

    Hollenstein, Marcel; Hipolito, Christopher J.; Lam, Curtis H.; Perrin, David M.

    2009-01-01

    The selection of modified DNAzymes represents an important endeavor in expanding the chemical and catalytic properties of catalytic nucleic acids. Few examples of such exist and to date, there is no example where three different modified bases have been simultaneously incorporated for catalytic activity. Herein, dCTP, dATP and dUTP bearing, respectively, a cationic amine, an imidazole and a cationic guanidine, were enzymatically polymerized on a DNA template for the selection of a highly functionalized DNAzyme, called DNAzyme 9-86, that catalyzed (M2+)-independent self-cleavage under physiological conditions at a single ribo(cytosine)phosphodiester linkage with a rate constant of (0.134 ± 0.026) min−1. A pH rate profile analysis revealed pKa's of 7.4 and 8.1, consistent with both general acid and base catalysis. The presence of guanidinium cations permits cleavage at significantly higher temperatures than previously observed for DNAzymes with only amines and imidazoles. Qualitatively, DNAzyme 9-86 presents an unprecedented ensemble of synthetic functionalities while quantitatively it expresses one of the highest reported values for any self-cleaving nucleic acid when investigated under M2+-free conditions at 37°C. PMID:19153138

  9. Biological Aspects of Metal Waste Reclamation With Sewage Sludge

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Smelter waste deposits pose an environmental threat worldwide. Sewage sludges are potentialy useful in reclamation of such sites. Biological aspects of revegetation of Zn and Pb smelter wastelands are discussed in a paper. The goal of the studies was to asses to what extent sludge treatment would...

  10. Chemical and biological extraction of metals present in E waste: A hybrid technology

    SciTech Connect

    Pant, Deepak; Joshi, Deepika; Upreti, Manoj K.; Kotnala, Ravindra K.

    2012-05-15

    Highlights: Black-Right-Pointing-Pointer Hybrid methodology for E waste management. Black-Right-Pointing-Pointer Efficient extraction of metals. Black-Right-Pointing-Pointer Trace metal extraction is possible. - Abstract: Management of metal pollution associated with E-waste is widespread across the globe. Currently used techniques for the extraction of metals from E-waste by using either chemical or biological leaching have their own limitations. Chemical leaching is much rapid and efficient but has its own environmental consequences, even the future prospects of associated nanoremediation are also uncertain. Biological leaching on the other hand is comparatively a cost effective technique but at the same moment it is time consuming and the complete recovery of the metal, alone by biological leaching is not possible in most of the cases. The current review addresses the individual issues related to chemical and biological extraction techniques and proposes a hybrid-methodology which incorporates both, along with safer chemicals and compatible microbes for better and efficient extraction of metals from the E-waste.

  11. In situ fixation of metals in soils using bauxite residue: biological effects.

    PubMed

    Lombi, Enzo; Zhao, Fang-Jie; Wieshammer, Gerlinde; Zhang, Gangya; McGrath, Steve P

    2002-01-01

    Soils polluted with heavy metals can cause phytotoxicity and exhibit impared microbial activities. In this paper we evaluate the responses of different biological endpoints to in situ remediation processes. Three soil amendments (red mud, beringite and lime) were applied to two soils polluted by heavy metals. Oilseed rape, wheat, pea and lettuce were grown successively in pots on the untreated and amended soils and their yield and metal uptake were determined. A suite of microbial tests (lux-marked biosensors, Biolog and soil microbial biomass) were performed to determine the effect of the soil amendments on the functionality and size of the soil microbial community. In both soils all three amendments reduced phytotoxicity of heavy metals, enhanced plant yields and decreased the metal concentrations in plants. The red mud treatment also increased soil microbial biomass significantly. The microbial biosensors responded positively to the remediation treatments in the industrially-contaminated soil used in the experiment. Red mud applied at 2% of soil weight was as effective as beringite applied at 5%. The results also showed that since the biological systems tested respond differently to the alleviation of metal toxicity, a suite of biological assays should be used to assess soil remediation processes. PMID:12009143

  12. Design and synthesis of redox-switched lariat ethers and their application for transport of alkali and alkaline-Earth metal cations across supported liquid membrane.

    PubMed

    Awasthy, Anubhuti; Bhatnagar, Mamta; Tomar, Jyoti; Sharma, Uma

    2006-01-01

    A new class of redox-switched anthraquinone derived lariat ethers 1-(1-anthraquinonyloxy) 3, 6, 9 trioxaundecane 11-ol (M(1)), 1-(1-anthraquinonyloxy) 3, 6 dioxaoctane 9-ol (M(2)), 1-(1-anthraquinonyloxy) 3 oxapentane 5-ol (M(3)), 1-(1-anthraquinonyloxy) 3 oxapentane 5-butane (M(4)), 1-(1-anthraquinonyloxy) 3, 6 dioxaoctane 9-methane (M(5)) and 1-(1-anthraquinonyloxy) 3 oxapentane 5-methane (M(6)) have been synthesized and characterized by spectral analysis. These ionophores were used in liquid membrane carrier facilitated transport of main group metal cations across supported liquid membrane (SLM). Cellulose nitrate membrane was used as membrane support. Effect of various parameters such as variation in concentration of metal as well as ionophore, effect of chain length and end group of ionophore have been studied. The sequence of metal ions transported by ionophore M(1) is Na(+) > Li(+) > K(+) > Ca(2+) > Mg(2+) and the order of metal ions transported by ionophores (M(2)-M(6)) is Li(+) > Na(+) > K(+) > Ca(2+) > Mg(2+). Ionophore M(1) is selective for Na(+), Li(+), and K(+) and ionophores (M(2)-M(6)) are selective for Li(+) and Na(+). PMID:17497021

  13. Interaction of metallic clusters with biologically active curcumin molecules

    NASA Astrophysics Data System (ADS)

    Gupta, Sanjeev K.; He, Haiying; Liu, Chunhui; Dutta, Ranu; Pandey, Ravindra

    2015-09-01

    We have investigated the interaction of subnano metallic Gd and Au clusters with curcumin, an important biomolecule having pharmacological activity. Gd clusters show different site preference to curcumin and much stronger interaction strength, in support of the successful synthesis of highly stable curcumin-coated Gd nanoparticles as reported recently. It can be attributed to significant charge transfer from the Gd cluster to curcumin together with a relatively strong hybridization of the Gd df-orbitals with curcumin p-orbitals. These results suggest that Gd nanoparticles can effectively be used as delivery carriers for curcumin at the cellular level for therapy and medical imaging applications.

  14. Aldimines generated from aza-Wittig reaction between bis(iminophosphoranes) derived from 1,1'-diazidoferrocene and aromatic or heteroaromatic aldehydes: electrochemical and optical behaviour towards metal cations.

    PubMed

    Sola, Antonia; Otón, Francisco; Espinosa, Arturo; Tárraga, Alberto; Molina, Pedro

    2011-12-14

    Aldimine 4 bearing a 2-quinolyl group was prepared by aza-Wittig reaction between the triphenyliminophosphorane derived from the 1,1'-diazidoferrocene and 2-formylquinoline. However, aldimine 5, bearing a pyrene ring, was prepared using the most reactive tributyliminophosphorane derivative and the corresponding 1-formylpyrene. On the other hand, formation of aldimine 8 involves a tandem process, Staudinger reaction/intramolecular aza-Wittig reaction, by using directly 1,1'-diazidoferrocene and 2-(diphenylphosphonyl)benzaldehyde. Aldimine 4 behaves as chemosensor molecule for Ni(2+), Zn(2+), Cd(2+), Hg(2+) and Pb(2+) cations through two different channels: electrochemical (ΔE(1/2) = 222-361 mV) and chromogenic (Δλ = 122-153 nm), which can be used for the "naked eye" detection of these metal cations. Aldimine 5 behaves as a highly selective redox (in CH(3)CN) and fluorescent (in CH(3)Cl-DMF) probe for Hg(2+) metal cations even in the presence of a large excess of the other metal cations tested. Aldimine 8 displays electrochemical affinity (ΔE(1/2) = 60-288 mV) to Li(+), Ca(2+), Mg(2+), Zn(2+) and Pb(2+) metal cations, with the phosphorus oxide functionality as a binding site. From the (1)H NMR titration data as well as DFT calculations, different tentative binding modes have been established, for these structurally related ferrocenyl derivatives. PMID:21989479

  15. {sup 1}H and {sup 23}Na MAS NMR spectroscopy of cationic species in CO{sub 2} selective alkaline earth metal porous silicoaluminophosphates prepared via liquid and solid state ion exchange

    SciTech Connect

    Arevalo-Hidalgo, Ana G.; Dugar, Sneha; Fu, Riqiang; Hernandez-Maldonado, Arturo J.

    2012-07-15

    The location of extraframework cations in Sr{sup 2+} and Ba{sup 2+} ion-exchanged SAPO-34 was estimated by means of {sup 1}H and {sup 23}Na MAS NMR spectroscopy and spectral deconvolution. Incorporation of the alkaline earth metal cations onto the SAPO framework was achieved via liquid state ion exchange, coupled partial detemplation/solid-state ion exchange, and combination of both techniques. MAS NMR revealed that the level of ion exchange was limited by the presence of protons and sodium cations near hexagonal prisms (site SI), which are relatively difficult to exchange with the alkaline earth metal due to steric and charge repulsion criteria. In addition, the presence of ammonium cations in the supercages facilitated the exchange of otherwise tenacious hydrogen as corroborated by unit cell compositional data as well as enhanced CO{sub 2} adsorption at low partial pressures. The extraframework ammonium species were produced from partial detemplation of the structure-directing agent employed for the SAPO-34 synthesis, tetraethylammonium. - Graphical abstract: MAS NMR was used to elucidate the position the cationic species in alkaline earth metal exchanged silicoaluminophosphates. These species played a significant role during the ion exchange process and, therefore, the materials ultimate CO{sub 2} adsorption performance. Highlights: Black-Right-Pointing-Pointer Location of extraframework Sr{sup 2+} or Ba{sup 2+} cations was estimated by means of {sup 1}H and {sup 23}Na MAS NMR. Black-Right-Pointing-Pointer Level of Sr{sup 2+} or Ba{sup 2+} ion exchange was limited by the presence of protons and sodium cations. Black-Right-Pointing-Pointer Presence of ammonium cations in the supercages facilitated the exchange. Black-Right-Pointing-Pointer Sr{sup 2+} and Ba{sup 2+} ion exchanged SAPOs are outstanding CO{sub 2} adsorbents.

  16. Surface coating affects behavior of metallic nanoparticles in a biological environment

    PubMed Central

    Jurašin, Darija Domazet; Ćurlin, Marija; Capjak, Ivona; Crnković, Tea; Lovrić, Marija; Babič, Michal; Horák, Daniel; Gajović, Srećko

    2016-01-01

    Summary Silver (AgNPs) and maghemite, i.e., superparamagnetic iron oxide nanoparticles (SPIONs) are promising candidates for new medical applications, which implies the need for strict information regarding their physicochemical characteristics and behavior in a biological environment. The currently developed AgNPs and SPIONs encompass a myriad of sizes and surface coatings, which affect NPs properties and may improve their biocompatibility. This study is aimed to evaluate the effects of surface coating on colloidal stability and behavior of AgNPs and SPIONs in modelled biological environments using dynamic and electrophoretic light scattering techniques, as well as transmission electron microscopy to visualize the behavior of the NP. Three dispersion media were investigated: ultrapure water (UW), biological cell culture medium without addition of protein (BM), and BM supplemented with common serum protein (BMP). The obtained results showed that different coating agents on AgNPs and SPIONs produced different stabilities in the same biological media. The combination of negative charge and high adsorption strength of coating agents proved to be important for achieving good stability of metallic NPs in electrolyte-rich fluids. Most importantly, the presence of proteins provided colloidal stabilization to metallic NPs in biological fluids regardless of their chemical composition, surface structure and surface charge. In addition, an assessment of AgNP and SPION behavior in real biological fluids, rat whole blood (WhBl) and blood plasma (BlPl), revealed that the composition of a biological medium is crucial for the colloidal stability and type of metallic NP transformation. Our results highlight the importance of physicochemical characterization and stability evaluation of metallic NPs in a variety of biological systems including as many NP properties as possible. PMID:26977382

  17. Surface coating affects behavior of metallic nanoparticles in a biological environment.

    PubMed

    Jurašin, Darija Domazet; Ćurlin, Marija; Capjak, Ivona; Crnković, Tea; Lovrić, Marija; Babič, Michal; Horák, Daniel; Vinković Vrček, Ivana; Gajović, Srećko

    2016-01-01

    Silver (AgNPs) and maghemite, i.e., superparamagnetic iron oxide nanoparticles (SPIONs) are promising candidates for new medical applications, which implies the need for strict information regarding their physicochemical characteristics and behavior in a biological environment. The currently developed AgNPs and SPIONs encompass a myriad of sizes and surface coatings, which affect NPs properties and may improve their biocompatibility. This study is aimed to evaluate the effects of surface coating on colloidal stability and behavior of AgNPs and SPIONs in modelled biological environments using dynamic and electrophoretic light scattering techniques, as well as transmission electron microscopy to visualize the behavior of the NP. Three dispersion media were investigated: ultrapure water (UW), biological cell culture medium without addition of protein (BM), and BM supplemented with common serum protein (BMP). The obtained results showed that different coating agents on AgNPs and SPIONs produced different stabilities in the same biological media. The combination of negative charge and high adsorption strength of coating agents proved to be important for achieving good stability of metallic NPs in electrolyte-rich fluids. Most importantly, the presence of proteins provided colloidal stabilization to metallic NPs in biological fluids regardless of their chemical composition, surface structure and surface charge. In addition, an assessment of AgNP and SPION behavior in real biological fluids, rat whole blood (WhBl) and blood plasma (BlPl), revealed that the composition of a biological medium is crucial for the colloidal stability and type of metallic NP transformation. Our results highlight the importance of physicochemical characterization and stability evaluation of metallic NPs in a variety of biological systems including as many NP properties as possible. PMID:26977382

  18. Metals and the Integrity of a Biological Coating

    PubMed Central

    Holten-Andersen, Niels; Mates, Thomas E.; Toprak, Muhammet S.; Stucky, Galen D.; Zok, Frank W.; Waite, J. Herbert

    2009-01-01

    The cuticle of mussel byssal threads is a robust natural coating that combines high extensibility with high stiffness and hardness. In this study, fluorescence microscopy and elemental analysis were exploited to show that the 3,4-dihydroxyphenyl-l-alanine (dopa) residues of mussel foot protein-1 colocalize with Fe and Ca distributions in the cuticle of Mytilus galloprovincialis mussel byssal threads. Chelated removal of Fe and Ca from the cuticle of intact threads resulted in a 50% reduction in cuticle hardness, and thin sections subjected to the same treatment showed a disruption of cuticle integrity. Dopa-metal complexes may provide significant interactions for the integrity of composite cuticles deformed under tension. PMID:18847291

  19. Cationic Ionic Liquids Organic Ligands Based Metal-Organic Frameworks for Fabrication of Core-Shell Microspheres for Hydrophilic Interaction Liquid Chromatography.

    PubMed

    Dai, Qian; Ma, Junqian; Ma, Siqi; Wang, Shengyu; Li, Lijun; Zhu, Xianghui; Qiao, Xiaoqiang

    2016-08-24

    In this study, new metal-organic frameworks (MOFs) nanocrystals modified SiO2 core-shell microspheres were designed with cationic ionic liquids (ILs) 1,3-bis(4-carboxybutyl)imidazolium bromide (ILI) as organic ligands. By further adjustment the growth cycles, the new ILI-01@SiO2 core-shell stationary phase was facilely fabricated. The developed stationary phase was respectively characterized via element analysis, thermogravimetric analysis, scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectrometry. Because the introduction of cationic imidazolium-based ILs ILI for fabrication of the MOFs nanocrystals shell, the new stationary phase exhibits the retention mechanism of hydrophilic interaction liquid chromatography (HILIC). Many polar samples, such as amides, vitamins, nucleic acid bases, and nucleosides, were utilized to investigate the performance of the prepared ILI-01@SiO2 column. Compared to the conventional aminosilica column, the new ILI-01@SiO2 column displays high separation selectivity in a shorter separation time. Furthermore, the new ILI-01@SiO2 column was also used for detection of illegal melamine addition in the baby formula. All the above results demonstrate the new ILI-01@SiO2 core-shell stationary phase is of good potentials for high-selectivity separation the polar samples. PMID:27483161

  20. Collection of trace metals with cationic surfactant-silica particles followed by flotation with an anionic surfactant for seawater analysis.

    PubMed

    Matsumiya, Hiroaki; Kitakata, Kengo; Hiraide, Masataka

    2012-02-01

    The analysis of seawater for trace metals is important for pollution monitoring and better understanding of marine systems. The present paper describes an efficient preconcentration method for the determination of trace metals in seawater. Trace metals [Ni(II), Cu(II), Ga(III), Cd(II), Pb(II), and Bi(III)] in 1,000 mL of seawater sample were complexed with ammonium pyrrolidinedithiocarbamate and sorbed onto silica particles covered with cetyltrimethylammonium chloride. After the addition of sodium dodecyl sulfate, the particles were floated to the solution surface by bubbling and then collected by suction. The trace metals were desorbed with dilute nitric acid and determined by inductively coupled plasma-mass spectrometry. The rapid 200-fold preconcentration was demonstrated with certified seawater samples. PMID:22159468

  1. Challenge to assess the toxic contribution of metal cation released from nanomaterials for nanotoxicology - the case of ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Xu, Mingsheng; Li, Jie; Hanagata, Nobutaka; Su, Huanxing; Chen, Hongzheng; Fujita, Daisuke

    2013-05-01

    The identification of physicochemical factors that govern toxic effects of nanomaterials (NMs) is important for the safe design and synthesis of NMs. The release of metal cations from NMs in cell culture medium and the role of the metal cations in cytotoxicity are still under dispute. Here, we report that removal of NMs such as ZnO nanoparticles (NPs) by centrifugation, the procedure commonly used for the estimation of released ion concentration in nanotoxicology, was incomplete even at a relative centrifugal force of 150 000 × g. In this sense, the Zn concentration in supernatant measured by inductively coupled plasma-mass spectrometry cannot be regarded as the concentration of free Zn2+ ions which were released from ZnO NPs in cell culture medium. This suggests the urgent need to develop relevant analytical techniques for nanotoxicology. The toxic contribution of released Zn2+ ions to the A549 cell lines was estimated to be only about 10%. We conclude that the cytotoxicity associated with ZnO NPs is not a function of the Zn concentration, suggesting that other factors play an important role in the toxic effect of ZnO NPs.The identification of physicochemical factors that govern toxic effects of nanomaterials (NMs) is important for the safe design and synthesis of NMs. The release of metal cations from NMs in cell culture medium and the role of the metal cations in cytotoxicity are still under dispute. Here, we report that removal of NMs such as ZnO nanoparticles (NPs) by centrifugation, the procedure commonly used for the estimation of released ion concentration in nanotoxicology, was incomplete even at a relative centrifugal force of 150 000 × g. In this sense, the Zn concentration in supernatant measured by inductively coupled plasma-mass spectrometry cannot be regarded as the concentration of free Zn2+ ions which were released from ZnO NPs in cell culture medium. This suggests the urgent need to develop relevant analytical techniques for nanotoxicology. The

  2. CATION EXCHANGER1 Cosegregates with Cadmium Tolerance in the Metal Hyperaccumulator Arabidopsis halleri and Plays a Role in Limiting Oxidative Stress in Arabidopsis Spp.

    PubMed

    Baliardini, Cecilia; Meyer, Claire-Lise; Salis, Pietrino; Saumitou-Laprade, Pierre; Verbruggen, Nathalie

    2015-09-01

    Arabidopsis halleri is a model species for the study of plant adaptation to extreme metallic conditions. In this species, cadmium (Cd) tolerance seems to be constitutive, and the mechanisms underlying the trait are still poorly understood. A previous quantitative trait loci (QTL) analysis performed on A. halleri × Arabidopsis lyrata backcross population1 identified the metal-pump gene Heavy Metal ATPase4 as the major genetic determinant for Cd tolerance. However, although necessary, Heavy Metal ATPase4 alone is not sufficient for determining this trait. After fine mapping, a gene encoding a calcium(2+)/hydrogen(+) antiporter, cation/hydrogen(+) exchanger1 (CAX1), was identified as a candidate gene for the second QTL of Cd tolerance in A. halleri. Backcross population1 individuals displaying the A. halleri allele for the CAX1 locus exhibited significantly higher CAX1 expression levels compared with the ones with the A. lyrata allele, and a positive correlation between CAX1 expression and Cd tolerance was observed. Here, we show that this QTL is conditional and that it is only detectable at low external Ca concentration. CAX1 expression in both roots and shoots was higher in A. halleri than in the close Cd-sensitive relative species A. lyrata and Arabidopsis thaliana. Moreover, CAX1 loss of function in A. thaliana led to higher Cd sensitivity at low concentration of Ca, higher sensitivity to methylviologen, and stronger accumulation of reactive oxygen species after Cd treatment. Overall, this study identifies a unique genetic determinant of Cd tolerance in the metal hyperaccumulator A. halleri and offers a new twist for the function of CAX1 in plants. PMID:26162428

  3. CATION EXCHANGER1 Cosegregates with Cadmium Tolerance in the Metal Hyperaccumulator Arabidopsis halleri and Plays a Role in Limiting Oxidative Stress in Arabidopsis Spp.1[OPEN

    PubMed Central

    Baliardini, Cecilia; Meyer, Claire-Lise; Salis, Pietrino; Saumitou-Laprade, Pierre; Verbruggen, Nathalie

    2015-01-01

    Arabidopsis halleri is a model species for the study of plant adaptation to extreme metallic conditions. In this species, cadmium (Cd) tolerance seems to be constitutive, and the mechanisms underlying the trait are still poorly understood. A previous quantitative trait loci (QTL) analysis performed on A. halleri × Arabidopsis lyrata backcross population1 identified the metal-pump gene Heavy Metal ATPase4 as the major genetic determinant for Cd tolerance. However, although necessary, Heavy Metal ATPase4 alone is not sufficient for determining this trait. After fine mapping, a gene encoding a calcium2+/hydrogen+ antiporter, cation/hydrogen+ exchanger1 (CAX1), was identified as a candidate gene for the second QTL of Cd tolerance in A. halleri. Backcross population1 individuals displaying the A. halleri allele for the CAX1 locus exhibited significantly higher CAX1 expression levels compared with the ones with the A. lyrata allele, and a positive correlation between CAX1 expression and Cd tolerance was observed. Here, we show that this QTL is conditional and that it is only detectable at low external Ca concentration. CAX1 expression in both roots and shoots was higher in A. halleri than in the close Cd-sensitive relative species A. lyrata and Arabidopsis thaliana. Moreover, CAX1 loss of function in A. thaliana led to higher Cd sensitivity at low concentration of Ca, higher sensitivity to methylviologen, and stronger accumulation of reactive oxygen species after Cd treatment. Overall, this study identifies a unique genetic determinant of Cd tolerance in the metal hyperaccumulator A. halleri and offers a new twist for the function of CAX1 in plants. PMID:26162428

  4. Investigation of Metal Bioavailability and Microbial Metal Utilization in Methane Seep Ecosystems through Integration of Geochemical and Biological Datasets

    NASA Astrophysics Data System (ADS)

    Glass, J. B.; Gadh, V.; Steele, J. A.; Adkins, J. F.; Orphan, V. J.

    2012-12-01

    Methane hydrate seeps are important sources of greenhouse gases and host unique microbial communities that couple anaerobic oxidation of methane and sulfate reduction. Microbial enzymes that catalyze the reactions driving these anaerobic metabolisms require transition metals such as Fe, Ni, Co, Zn, and Mo as essential cofactors. These metals are expected to be drawn down to low concentrations by precipitation as sulfide phases in the highly sulfidic porewaters at methane seep ecosystems. However, in situ concentrations of biologically-important metals in sulfidic methane seep pore fluids and the relative importance of different metals for anaerobic methanotrophic archaea (ANME) vs. sulfate reducing bacteria (SRB) are unknown. We are integrating geochemical and metagenomic datasets with nano-scale maps of cellular metal distributions to gain insights into metal bioavailability and utilization in methane seep ecosystems. We have measured porewater profiles of dissolved metals (V, Ni, Cu, Co, Fe, Mn, Zn, Mo and W) from three habitat types at Hydrate Ridge, offshore Oregon: Calyptogena clam beds, microbial mats and sites with low methane flux. Highly sulfidic sediment porewaters beneath microbial mats contained the lowest metal concentrations, suggesting that microbes inhabiting these environments may be limited by metal scarcity. Cobalt occurred at particularly low abundances (≤5 nM in all cores and frequently at sub-nanomolar levels). We also analyzed the taxonomic distribution of ABC (ATP-binding cassette) metal transporters in metagenomes from environmentally-enriched consortia of ANME-2 and SRB from Eel River Basin methane seeps. Our findings suggest that both ANME and SRB possess genes encoding ABC transporters with high affinity for Fe, Ni, Co, Zn and Mo. Combined with our geochemical data, these results imply that ANME-SRB consortia in highly sulfidic environments have specialized mechanisms that allow them to acquire metal micronutrients

  5. Whole Genome Duplication and Enrichment of Metal Cation Transporters Revealed by De Novo Genome Sequencing of Extremely Halotolerant Black Yeast Hortaea werneckii

    PubMed Central

    Jackman, Shaun; Turk, Martina; Sadowski, Ivan; Nislow, Corey; Jones, Steven; Birol, Inanc; Cimerman, Nina Gunde; Plemenitaš, Ana

    2013-01-01

    Hortaea werneckii, ascomycetous yeast from the order Capnodiales, shows an exceptional adaptability to osmotically stressful conditions. To investigate this unusual phenotype we obtained a draft genomic sequence of a H. werneckii strain isolated from hypersaline water of solar saltern. Two of its most striking characteristics that may be associated with a halotolerant lifestyle are the large genetic redundancy and the expansion of genes encoding metal cation transporters. Although no sexual state of H. werneckii has yet been described, a mating locus with characteristics of heterothallic fungi was found. The total assembly size of the genome is 51.6 Mb, larger than most phylogenetically related fungi, coding for almost twice the usual number of predicted genes (23333). The genome appears to have experienced a relatively recent whole genome duplication, and contains two highly identical gene copies of almost every protein. This is consistent with some previous studies that reported increases in genomic DNA content triggered by exposure to salt stress. In hypersaline conditions transmembrane ion transport is of utmost importance. The analysis of predicted metal cation transporters showed that most types of transporters experienced several gene duplications at various points during their evolution. Consequently they are present in much higher numbers than expected. The resulting diversity of transporters presents interesting biotechnological opportunities for improvement of halotolerance of salt-sensitive species. The involvement of plasma P-type H+ ATPases in adaptation to different concentrations of salt was indicated by their salt dependent transcription. This was not the case with vacuolar H+ ATPases, which were transcribed constitutively. The availability of this genomic sequence is expected to promote the research of H. werneckii. Studying its extreme halotolerance will not only contribute to our understanding of life in hypersaline environments, but should also

  6. Whole genome duplication and enrichment of metal cation transporters revealed by de novo genome sequencing of extremely halotolerant black yeast Hortaea werneckii.

    PubMed

    Lenassi, Metka; Gostinčar, Cene; Jackman, Shaun; Turk, Martina; Sadowski, Ivan; Nislow, Corey; Jones, Steven; Birol, Inanc; Cimerman, Nina Gunde; Plemenitaš, Ana

    2013-01-01

    Hortaea werneckii, ascomycetous yeast from the order Capnodiales, shows an exceptional adaptability to osmotically stressful conditions. To investigate this unusual phenotype we obtained a draft genomic sequence of a H. werneckii strain isolated from hypersaline water of solar saltern. Two of its most striking characteristics that may be associated with a halotolerant lifestyle are the large genetic redundancy and the expansion of genes encoding metal cation transporters. Although no sexual state of H. werneckii has yet been described, a mating locus with characteristics of heterothallic fungi was found. The total assembly size of the genome is 51.6 Mb, larger than most phylogenetically related fungi, coding for almost twice the usual number of predicted genes (23333). The genome appears to have experienced a relatively recent whole genome duplication, and contains two highly identical gene copies of almost every protein. This is consistent with some previous studies that reported increases in genomic DNA content triggered by exposure to salt stress. In hypersaline conditions transmembrane ion transport is of utmost importance. The analysis of predicted metal cation transporters showed that most types of transporters experienced several gene duplications at various points during their evolution. Consequently they are present in much higher numbers than expected. The resulting diversity of transporters presents interesting biotechnological opportunities for improvement of halotolerance of salt-sensitive species. The involvement of plasma P-type H⁺ ATPases in adaptation to different concentrations of salt was indicated by their salt dependent transcription. This was not the case with vacuolar H⁺ ATPases, which were transcribed constitutively. The availability of this genomic sequence is expected to promote the research of H. werneckii. Studying its extreme halotolerance will not only contribute to our understanding of life in hypersaline environments, but should

  7. On the mechanisms of cation injection in conducting bridge memories: The case of HfO2 in contact with noble metal anodes (Au, Cu, Ag)

    NASA Astrophysics Data System (ADS)

    Saadi, M.; Gonon, P.; Vallée, C.; Mannequin, C.; Grampeix, H.; Jalaguier, E.; Jomni, F.; Bsiesy, A.

    2016-03-01

    Resistance switching is studied in HfO2 as a function of the anode metal (Au, Cu, and Ag) in view of its application to resistive memories (resistive random access memories, RRAM). Current-voltage (I-V) and current-time (I-t) characteristics are presented. For Au anodes, resistance transition is controlled by oxygen vacancies (oxygen-based resistive random access memory, OxRRAM). For Ag anodes, resistance switching is governed by cation injection (Conducting Bridge random access memory, CBRAM). Cu anodes lead to an intermediate case. I-t experiments are shown to be a valuable tool to distinguish between OxRRAM and CBRAM behaviors. A model is proposed to explain the high-to-low resistance transition in CBRAMs. The model is based on the theory of low-temperature oxidation of metals (Cabrera-Mott theory). Upon electron injection, oxygen vacancies and oxygen ions are generated in the oxide. Oxygen ions are drifted to the anode, and an interfacial oxide is formed at the HfO2/anode interface. If oxygen ion mobility is low in the interfacial oxide, a negative space charge builds-up at the HfO2/oxide interface. This negative space charge is the source of a strong electric field across the interfacial oxide thickness, which pulls out cations from the anode (CBRAM case). Inversely, if oxygen ions migration through the interfacial oxide is important (or if the anode does not oxidize such as Au), bulk oxygen vacancies govern resistance transition (OxRRAM case).

  8. Metal-containing Complexes of Lactams, Imidazoles, and Benzimidazoles and Their Biological Activity

    NASA Astrophysics Data System (ADS)

    Kukalenko, S. S.; Bovykin, B. A.; Shestakova, S. I.; Omel'chenko, A. M.

    1985-07-01

    The results of the latest investigations of the problem of the synthesis of metal-containing complexes of lactams, imidazoles, and benzimidazoles, their structure, and their stability in solutions are surveyed. Some data on their biological activity (pesticide and pharmacological) and the mechanism of their physiological action are presented. The bibliography includes 190 references.

  9. Transition metal associations with primary biological particles in sea spray aerosol generated in a wave channel.

    PubMed

    Guasco, Timothy L; Cuadra-Rodriguez, Luis A; Pedler, Byron E; Ault, Andrew P; Collins, Douglas B; Zhao, Defeng; Kim, Michelle J; Ruppel, Matthew J; Wilson, Scott C; Pomeroy, Robert S; Grassian, Vicki H; Azam, Farooq; Bertram, Timothy H; Prather, Kimberly A

    2014-01-21

    In the ocean, breaking waves generate air bubbles which burst at the surface and eject sea spray aerosol (SSA), consisting of sea salt, biogenic organic species, and primary biological aerosol particles (PBAP). Our overall understanding of atmospheric biological particles of marine origin remains poor. Here, we perform a control experiment, using an aerosol time-of-flight mass spectrometer to measure the mass spectral signatures of individual particles generated by bubbling a salt solution before and after addition of heterotrophic marine bacteria. Upon addition of bacteria, an immediate increase occurs in the fraction of individual particle mass spectra containing magnesium, organic nitrogen, and phosphate marker ions. These biological signatures are consistent with 21% of the supermicrometer SSA particles generated in a previous study using breaking waves in an ocean-atmosphere wave channel. Interestingly, the wave flume mass spectral signatures also contain metal ions including silver, iron, and chromium. The nascent SSA bioparticles produced in the wave channel are hypothesized to be as follows: (1) whole or fragmented bacterial cells which bioaccumulated metals and/or (2) bacteria-derived colloids or biofilms which adhered to the metals. This study highlights the potential for transition metals, in combination with specific biomarkers, to serve as unique indicators for the presence of marine PBAP, especially in metal-impacted coastal regions. PMID:24328130

  10. Inorganic concepts relevant to metal binding, activity, and toxicity in a biological system

    SciTech Connect

    Hoeschele, J.D. . Parke-Davis Pharmaceutical Research Div.); Turner, J.E.; England, M.W. )

    1990-01-01

    The purpose of this paper is to review selected physical and inorganic concepts and factors which might be important in assessing and/or understanding the fact and disposition of a metal system in a biological environment. Hopefully, such inquiries will ultimately permit us to understand, rationalize, and predict differences and trends in biological effects as a function of the basic nature of a metal system and, in optimal cases, serve as input to a system of guidelines for the notion of Chemical Dosimetry.'' The plan of this paper is to first review, in general terms, the basic principles of the Crystal Field Theory (CFT), a unifying theory of bonding in metal complexes. This will provide the necessary theoretical background for the subsequent discussion of selected concepts and factors. 21 refs., 7 figs., 6 tabs.

  11. Biological and chemical characterization of metal bioavailability in sediments from Lake Roosevelt, Columbia River, Washington, USA

    USGS Publications Warehouse

    Besser, J.M.; Brumbaugh, W.G.; Ivey, C.D.; Ingersoll, C.G.; Moran, P.W.

    2008-01-01

    We studied the bioavailability and toxicity of copper, zinc, arsenic, cadmium, and lead in sediments from Lake Roosevelt (LR), a reservoir on the Columbia River in Washington, USA that receives inputs of metals from an upstream smelter facility. We characterized chronic sediment toxicity, metal bioaccumulation, and metal concentrations in sediment and pore water from eight study sites: one site upstream in the Columbia River, six sites in the reservoir, and a reference site in an uncontaminated tributary. Total recoverable metal concentrations in LR sediments generally decreased from upstream to downstream in the study area, but sediments from two sites in the reservoir had metal concentrations much lower than adjacent reservoir sites and similar to the reference site, apparently due to erosion of uncontaminated bank soils. Concentrations of acid-volatile sulfide in LR sediments were too low to provide strong controls on metal bioavailability, and selective sediment extractions indicated that metals in most LR sediments were primarily associated with iron and manganese oxides. Oligochaetes (Lumbriculus variegatus) accumulated greatest concentrations of copper from the river sediment, and greatest concentrations of arsenic, cadmium, and lead from reservoir sediments. Chronic toxic effects on amphipods (Hyalella azteca; reduced survival) and midge larvae (Chironomus dilutus; reduced growth) in whole-sediment exposures were generally consistent with predictions of metal toxicity based on empirical and equilibrium partitioning-based sediment quality guidelines. Elevated metal concentrations in pore waters of some LR sediments suggested that metals released from iron and manganese oxides under anoxic conditions contributed to metal bioaccumulation and toxicity. Results of both chemical and biological assays indicate that metals in sediments from both riverine and reservoir habitats of Lake Roosevelt are available to benthic invertebrates. These findings will be used as

  12. Quantitative investigations of cation complexation of photochromic 8-benzothiazole-substituted benzopyran: towards metal-ion sensors.

    PubMed

    Zakharova, Marianna I; Coudret, Christophe; Pimienta, Véronique; Micheau, Jean Claude; Delbaere, Stéphanie; Vermeersch, Gaston; Metelitsa, Anatoly V; Voloshin, Nikolai; Minkin, Vladimir I

    2010-02-01

    The photochromic, thermochromic and metallochromic behaviour of a series of three spiro[indoline-8-(benzothiazol-2-yl)-benzopyrans] has been investigated. The thermodynamic and kinetic parameters of their thermal equilibrium between the ring-closed (spiro) and ring-opened (merocyanine) isomeric forms have been determined using UV-Vis absorption and (1)H NMR spectroscopies. By adding Co(ii) and Ni(ii) ions in acetonitrile solution, 1 : 1 and 1 : 2 metal : merocyanine complexes are formed simultaneously. Using appropriate numerical methods, the kinetic analysis of the complexation allowed us to determine accurately key thermodynamic and spectroscopic parameters of the metal complexes. Results showed that the complexation strength is very sensitive to the size of the indoline nitrogen substituent. Complexation can be reversed by shining white light on the coloured complexes which regenerates the inactive spiropyran form, and releases the metallic ion; hence, these systems display fully reversible negative photochromism. The Zn(ii) complexes exhibit intense fluorescence in the 600-800 nm wavelength range. All these behaviours make these spiropyrans bearing benzothiazole heterocycles promising building blocks for the future construction of photodynamic chemosensors for transition metal ions. PMID:20126795

  13. Competition effects in cation binding to humic acid: Conditional affinity spectra for fixed total metal concentration conditions

    NASA Astrophysics Data System (ADS)

    David, Calin; Mongin, Sandrine; Rey-Castro, Carlos; Galceran, Josep; Companys, Encarnació; Garcés, José Luis; Salvador, José; Puy, Jaume; Cecilia, Joan; Lodeiro, Pablo; Mas, Francesc

    2010-09-01

    Information on the Pb and Cd binding to a purified Aldrich humic acid (HA) is obtained from the influence of different fixed total metal concentrations on the acid-base titrations of this ligand. NICA (Non-Ideal Competitive Adsorption) isotherm has been used for a global quantitative description of the binding, which has then been interpreted by plotting the Conditional Affinity Spectra of the H + binding at fixed total metal concentrations (CAScTM). This new physicochemical tool, here introduced, allows the interpretation of binding results in terms of distributions of proton binding energies. A large increase in the acidity of the phenolic sites as the total metal concentration increases, especially in presence of Pb, is revealed from the shift of the CAScTM towards lower affinities. The variance of the CAScTM distribution, which can be used as a direct measure of the heterogeneity, also shows a significant dependence on the total metal concentration. A discussion of the factors that influence the heterogeneity of the HA under the conditions of each experiment is provided, so that the smoothed pattern exhibited by the titration curves can be justified.

  14. Distinct roles of beta1 metal ion-dependent adhesion site (MIDAS), adjacent to MIDAS (ADMIDAS), and ligand-associated metal-binding site (LIMBS) cation-binding sites in ligand recognition by integrin alpha2beta1.

    PubMed

    Valdramidou, Dimitra; Humphries, Martin J; Mould, A Paul

    2008-11-21

    Integrin-ligand interactions are regulated in a complex manner by divalent cations, and previous studies have identified ligand-competent, stimulatory, and inhibitory cation-binding sites. In collagen-binding integrins, such as alpha2beta1, ligand recognition takes place exclusively at the alpha subunit I domain. However, activation of the alphaI domain depends on its interaction with a structurally similar domain in the beta subunit known as the I-like or betaI domain. The top face of the betaI domain contains three cation-binding sites: the metal-ion dependent adhesion site (MIDAS), the ADMIDAS (adjacent to MIDAS), and LIMBS (ligand-associated metal-binding site). The role of these sites in controlling ligand binding to the alphaI domain has yet to be elucidated. Mutation of the MIDAS or LIMBS completely blocked collagen binding to alpha2beta1; in contrast mutation of the ADMIDAS reduced ligand recognition but this effect could be overcome by the activating monoclonal antibody TS2/16. Hence, the MIDAS and LIMBS appear to be essential for the interaction between alphaI and betaI, whereas occupancy of the ADMIDAS has an allosteric effect on the conformation of betaI. An activating mutation in the alpha2 I domain partially restored ligand binding to the MIDAS and LIMBS mutants. Analysis of the effects of Ca(2+), Mg(2+), and Mn(2+) on ligand binding to these mutants showed that the MIDAS is a ligand-competent site through which Mn(2+) stimulates ligand binding, whereas the LIMBS is a stimulatory Ca(2+)-binding site, occupancy of which increases the affinity of Mg(2+) for the MIDAS. PMID:18820259

  15. X-ray crystallography and biological metal centers: is seeing believing?

    SciTech Connect

    Sommerhalter, M.; Lieberman, R.L.; Rosenzweig, A.C.

    2010-03-08

    Metalloenzyme crystal structures have a major impact on our understanding of biological metal centers. They are often the starting point for mechanistic and computational studies and inspire synthetic modeling chemistry. The strengths and limitations of X-ray crystallography in determining properties of biological metal centers and their corresponding ligand spheres are explored through examples, including ribonucleotide reductase R2 and particulate methane monooxygenase. Protein crystal structures locate metal ions within a protein fold and reveal the identities and coordination geometries of amino acid ligands. Data collection strategies that exploit the anomalous scattering effect of metal ions can establish metal ion identity. The quality of crystallographic data, particularly the resolution, determines the level of detail that can be extracted from a protein crystal structure. Complementary spectroscopic techniques can provide crucial information regarding the redox state of the metal center as well as the presence, type, and protonation state of exogenous ligands. The final result of the crystallographic characterization of a metalloenzyme is a model based on crystallographic data, supported by information from biophysical and modeling studies, influenced by sample handling, and interpreted carefully by the crystallographer.

  16. History of biological metal utilization inferred through phylogenomic analysis of protein structures

    PubMed Central

    Dupont, Christopher L.; Butcher, Andrew; Valas, Ruben E.; Bourne, Philip E.; Caetano-Anollés, Gustavo

    2010-01-01

    The fundamental chemistry of trace elements dictates the molecular speciation and reactivity both within cells and the environment at large. Using protein structure and comparative genomics, we elucidate several major influences this chemistry has had upon biology. All of life exhibits the same proteome size-dependent scaling for the number of metal-binding proteins within a proteome. This fundamental evolutionary constant shows that the selection of one element occurs at the exclusion of another, with the eschewal of Fe for Zn and Ca being a defining feature of eukaryotic proteomes. Early life lacked both the structures required to control intracellular metal concentrations and the metal-binding proteins that catalyze electron transport and redox transformations. The development of protein structures for metal homeostasis coincided with the emergence of metal-specific structures, which predominantly bound metals abundant in the Archean ocean. Potentially, this promoted the diversification of emerging lineages of Archaea and Bacteria through the establishment of biogeochemical cycles. In contrast, structures binding Cu and Zn evolved much later, providing further evidence that environmental availability influenced the selection of the elements. The late evolving Zn-binding proteins are fundamental to eukaryotic cellular biology, and Zn bioavailability may have been a limiting factor in eukaryotic evolution. The results presented here provide an evolutionary timeline based on genomic characteristics, and key hypotheses can be tested by alternative geochemical methods. PMID:20498051

  17. Specific absorption rate in electrically coupled biological samples between metal plates.

    PubMed

    Joines, W T; Blackman, C F; Spiegel, R J

    1986-01-01

    The specific absorption rate (SAR) in a biological sample irradiated by electromagnetic fields between the metal plates of a transmission line can be altered significantly by the spacing of the metal plates and the distance between neighboring samples. The SAR in spherical biological samples is calculated for a number of neighboring sample arrangements and metal-plate spacings by using the method of images and induced dipole coupling. For a decrease in metal-plate spacing, the derived equations predict an increase in SAR within a sample and a decrease in SAR with a decrease in neighboring-sample spacing. The calculations are compared with measurements made with the aid of an array of 1-in radius metal hemispheres on the lower plate of two parallel plates (thus forming an image system). The hemisphere on which measurements are taken is insulated from the metal plate and is connected via a coaxial center conductor to an HP 3582A spectrum analyzer that measures the voltage and hence the electric field intensity at the hemisphere. Measurements made at a frequency where wavelength is large compared with sample size (48 Hz) are in good agreement with calculations. PMID:3741491

  18. Zeolite-type metal organic frameworks immobilized Eu³⁺ for cation sensing in aqueous environment.

    PubMed

    Liu, Chang; Yan, Bing

    2015-12-01

    A novel luminescent lanthanide metal organic framework (Ln-MOF) is synthesized by in situ encapsulating Eu(3+) ions to partial replace the transition-metal clusters in the channels of CPM-17-Zn nanocrystals. The Eu(3+) functionalized zeolite-type MOF hybrid system shows excellent luminescence property and photo-stability in aqueous environment for the sensitization and protection from the host framework. Subsequently, as a highly selective and sensitive sensor, its nanocrystals can be used to detect Cd(2+) in aqueous solution. In addition, the possible sensing mechanism based on ion exchange is discussed in detail. This work is one of the few cases for detecting Cd(2+) in aqueous solution based on a zeolite-type MOF. The good fluorescence stability, low detection limit and broad linear range in aqueous environment make this probe to be expected to have potential application in intracellular sensing and imaging of Cd(2+) potentially. PMID:26298079

  19. Permeation rate of metal species through supported liquid membranes: diffusional and chemical resistances with cationic and anionic carriers

    SciTech Connect

    Danesi, P.R.; Horwitz, E.P.; Rickert, P.G.

    1983-01-01

    Facilitated transport by means of a mobile carrier in an organic diluent and adsorbed on a polymeric film, through supported liquid membranes (SLM), is a new method for the separation and recovery of metal ions. A permeability coefficient equation for this transport was tested. The facilitated transport of Cu/sup 2 +/ and Fe/sup 3 +/ ions through a SLM was characterized with respect to the membrane resistance. Transport of Am/sup 3 +/ through a SLM was also characterized. (DLC)

  20. Structural, chemical and biological aspects of antioxidants for strategies against metal and metalloid exposure

    PubMed Central

    2009-01-01

    Oxidative stress contributes to the pathophysiology of exposure to heavy metals/metalloid. Beneficial renal effects of some medications, such as chelation therapy depend at least partially on the ability to alleviate oxidative stress. The administration of various natural or synthetic antioxidants has been shown to be of benefit in the prevention and attenuation of metal induced biochemical alterations. These include vitamins, N-acetylcysteine, α-lipoic acid, melatonin, dietary flavonoids and many others. Human studies are limited in this regard. Under certain conditions, surprisingly, the antioxidant supplements may exhibit pro-oxidant properties and even worsen metal induced toxic damage. To date, the evidence is insufficient to recommend antioxidant supplements in subject with exposure to metals. Prospective, controlled clinical trials on safety and effectiveness of different therapeutic antioxidant strategies either individually or in combination with chelating agent are indispensable. The present review focuses on structural, chemical and biological aspects of antioxidants particularly related to their chelating properties. PMID:20716905

  1. S/G-1: an ab initio force-field blending frozen Hermite Gaussian densities and distributed multipoles. Proof of concept and first applications to metal cations.

    PubMed

    Chaudret, Robin; Gresh, Nohad; Narth, Christophe; Lagardère, Louis; Darden, Thomas A; Cisneros, G Andrés; Piquemal, Jean-Philip

    2014-09-01

    response level. This opens up the possibility of embodying explicit scalar relativistic effects in molecular mechanics thanks to the direct transferability of ab initio pseudopotentials. Therefore, incorporating GEM-like electron density for a metal cation enable the introduction of nonambiguous short-range quantum effects within any point-dipole based polarizable force field without the need of an extensive parametrization. PMID:24878003

  2. Cation-Induced Hydration Effects Cause Lower Critical Solution Temperature Behavior in Protein Solutions.

    PubMed

    Matsarskaia, Olga; Braun, Michal K; Roosen-Runge, Felix; Wolf, Marcell; Zhang, Fajun; Roth, Roland; Schreiber, Frank

    2016-08-11

    The phase behavior of protein solutions is important for numerous phenomena in biology and soft matter. We report a lower critical solution temperature (LCST) phase behavior of aqueous solutions of a globular protein induced by multivalent metal ions around physiological temperatures. The LCST behavior manifests itself via a liquid-liquid phase separation of the protein-salt solution upon heating. Isothermal titration calorimetry and zeta-potential measurements indicate that here cation-protein binding is an endothermic, entropy-driven process. We offer a mechanistic explanation of the LCST. First, cations bind to protein surface groups driven by entropy changes of hydration water. Second, the bound cations bridge to other protein molecules, inducing an entropy-driven attraction causing the LCST. Our findings have general implications for condensation, LCST, and hydration behavior of (bio)polymer solutions as well as the understanding of biological effects of (heavy) metal ions and their hydration. PMID:27414502

  3. PIXE characterization of tissues surrounding metallic prostheses coated with biological glasses

    NASA Astrophysics Data System (ADS)

    Barbotteau, Y.; Irigaray, J. L.; Moretto, Ph.

    2004-01-01

    Biological glasses can be used as coatings for metallic prostheses in order to prevent corrosion. According to their composition, these glasses have different properties. We studied, in vivo, two glasses referred to as BVA and BVH. They are used as coatings of Ti6Al4V metallic implant. BVA glass disappears after 3 months of implantation and is replaced by bone. Prostheses initially coated by this glass have a larger osseous contact perimeter compared to the uncoated prostheses. This ensures a better anchoring of the implant and limits the micro-motions which cause wear debris. BVH glass keeps a constant composition during implantation and it is used like a layer which isolates metal implant from biological environment. In order to characterize the bony environment surrounding implants, we have used PIXE and RBS methods. This paper shows results of the behavior of bony tissue under micro-beam, the quality tests of new bone which replaces the BVA glass coating and the evaluation of corrosion effects. Titanium release in bony tissues begins when the metal surface of the prosthesis is exposed to biological fluids. After a few months of implantation, the titanium contamination is stabilized and remains localized within the first tens of micrometers of surrounding bone.

  4. A multinuclear solid-state NMR study of alkali metal ions in tetraphenylborate salts, M[BPh4] (M = Na, K, Rb and Cs): what is the NMR signature of cation-pi interactions?

    PubMed

    Wu, Gang; Terskikh, Victor

    2008-10-16

    We report a multinuclear solid-state ( (23)Na, (39)K, (87)Rb, (133)Cs) NMR study of tetraphenylborate salts, M[BPh 4] (M = Na, K, Rb, Cs). These compounds are isostructural in the solid state with the alkali metal ion surrounded by four phenyl groups resulting in strong cation-pi interactions. From analyses of solid-state NMR spectra obtained under stationary and magic-angle spinning (MAS) conditions at 11.75 and 21.15 T, we have obtained the quadrupole coupling constants, C Q, and the chemical shift tensor parameters for the alkali metal ions in these compounds. We found that the observed quadrupole coupling constant for M (+) in M[BPh 4] is determined by a combination of nuclear quadrupole moment, Sternheimer antishielding factor, and unit cell dimensions. On the basis of a comparison between computed paramagnetic and diamagnetic contributions to the total chemical shielding values for commonly found cation-ligand interactions, we conclude that cation-pi interactions give rise to significantly lower paramagnetic shielding contributions than other cation-ligand interactions. As a result, highly negative chemical shifts are expected to be the NMR signature for cations interacting exclusively with pi systems. PMID:18816043

  5. EDTA-Cross-Linked β-Cyclodextrin: An Environmentally Friendly Bifunctional Adsorbent for Simultaneous Adsorption of Metals and Cationic Dyes.

    PubMed

    Zhao, Feiping; Repo, Eveliina; Yin, Dulin; Meng, Yong; Jafari, Shila; Sillanpää, Mika

    2015-09-01

    The discharge of metals and dyes poses a serious threat to public health and the environment. What is worse, these two hazardous pollutants are often found to coexist in industrial wastewaters, making the treatment more challenging. Herein, we report an EDTA-cross-linked β-cyclodextrin (EDTA-β-CD) bifunctional adsorbent, which was fabricated by an easy and green approach through the polycondensation reaction of β-cyclodextrin with EDTA as a cross-linker, for simultaneous adsorption of metals and dyes. In this setting, cyclodextrin cavities are expected to capture dye molecules through the formation of inclusion complexes and EDTA units as the adsorption sites for metals. The adsorbent was characterized by FT-IR, elemental analysis, SEM, EDX, ζ-potential, and TGA. In a monocomponent system, the adsorption behaviors showed a monolayer adsorption capacity of 1.241 and 1.106 mmol g(-1) for Cu(II) and Cd(II), respectively, and a heterogeneous adsorption capacity of 0.262, 0.169, and 0.280 mmol g(-1) for Methylene Blue, Safranin O, and Crystal Violet, respectively. Interestingly, the Cu(II)-dye binary experiments showed adsorption enhancement of Cu(II), but no significant effect on dyes. The simultaneous adsorption mechanism was further confirmed by FT-IR, thermodynamic study, and elemental mapping. Overall, its facile and green fabrication, efficient sorption performance, and excellent reusability indicate that EDTA-β-CD has potential for practical applications in integrative and efficient treatment of coexistenting toxic pollutants. PMID:26237660

  6. Evaluation of the effectiveness of various amendments on trace metals stabilization by chemical and biological methods.

    PubMed

    Lee, Sang-Hwan; Park, Hyun; Koo, Namin; Hyun, Seunghun; Hwang, Anna

    2011-04-15

    We evaluated the effects of five different kinds of amendments on heavy metals stabilization. The five amendments were: zero valent iron, limestone, acid mine drainage treatment sludge, bone mill, and bottom ash. To determine bioavailability of the heavy metals, different chemical extraction procedures were used such as, extraction with (Ca(NO(3))(2), DTPA; toxic characteristic leaching procedure (TCLP), physiologically based extraction test (PBET) that simulates gastric juice, and sequential extraction test. Bioavailability was also determined by measuring uptake of the heavy metals by lettuce (Lactuca sativa L.) and earthworms (Eisenia fetida). In addition, dehydrogenase activity was measured to determine microbial activity in the soil with the different amendments. The addition of amendments, especially limestone and bottom ash, resulted in a significant reduction in extractable metal contents. Biological assays using lettuce, earthworm, and enzyme activity were found as appropriate indicators of available metal fraction after in situ stabilization of heavy metals. In conclusion, TCLP and sequential extraction test appear to be promising surrogate measure of metal bioavailability in soils for several environment endpoints. PMID:21333442

  7. Single-Site Heterogeneous Catalysts for Olefin Polymerization Enabled by Cation Exchange in a Metal-Organic Framework.

    PubMed

    Comito, Robert J; Fritzsching, Keith J; Sundell, Benjamin J; Schmidt-Rohr, Klaus; Dincă, Mircea

    2016-08-17

    The manufacture of advanced polyolefins has been critically enabled by the development of single-site heterogeneous catalysts. Metal-organic frameworks (MOFs) show great potential as heterogeneous catalysts that may be designed and tuned on the molecular level. In this work, exchange of zinc ions in Zn5Cl4(BTDD)3, H2BTDD = bis(1H-1,2,3-triazolo[4,5-b],[4',5'-i])dibenzo[1,4]dioxin) (MFU-4l) with reactive metals serves to establish a general platform for selective olefin polymerization in a high surface area solid promising for industrial catalysis. Characterization of polyethylene produced by these materials demonstrates both molecular and morphological control. Notably, reactivity approaches single-site catalysis, as evidenced by low polydispersity indices, and good molecular weight control. We further show that these new catalysts copolymerize ethylene and propylene. Uniform growth of the polymer around the catalyst particles provides a mechanism for controlling the polymer morphology, a relevant metric for continuous flow processes. PMID:27443860

  8. Metal-organic frameworks for the storage and delivery of biologically active hydrogen sulfide

    SciTech Connect

    Allan, Phoebe K; Wheatley, Paul S; Aldous, David; Mohideen, M Infas; Tang, Chiu; Hriljac, Joseph A; Megson, Ian L; Chapman, Karena W; De Weireld, Guy; Vaesen, Sebastian; Morris, Russell E

    2012-04-02

    Hydrogen sulfide is an extremely toxic gas that is also of great interest for biological applications when delivered in the correct amount and at the desired rate. Here we show that the highly porous metal-organic frameworks with the CPO-27 structure can bind the hydrogen sulfide relatively strongly, allowing the storage of the gas for at least several months. Delivered gas is biologically active in preliminary vasodilation studies of porcine arteries, and the structure of the hydrogen sulfide molecules inside the framework has been elucidated using a combination of powder X-ray diffraction and pair distribution function analysis.

  9. Biological in vitro and in vivo studies of a series of new asymmetrical cationic [99mTc(N)(DTC-Ln)(PNP)]+ complex (DTC-Ln = alicyclic dithiocarbamate and PNP = diphosphinoamine).

    PubMed

    Bolzati, Cristina; Cavazza-Ceccato, Mario; Agostini, Stefania; Refosco, Fiorenzo; Yamamichi, Yoshihiro; Tokunaga, Shinji; Carta, Davide; Salvarese, Nicola; Bernardini, Daniele; Bandoli, Giuliano

    2010-05-19

    (99m)Tc(N)-DBODC5 is a cationic mixed compound under clinical investigation as potential myocardial imaging agent. In spite of this, analogously to the other cationic (99m)Tc-agents, presents a relatively low first-pass extraction. Thus, modification of (99m)Tc(N)-DBODC(5) direct to increase its first-pass extraction keeping unaltered the favorable imaging properties would be desirable. This work describes the synthesis and biological evaluation of a series of novel cationic (99m)Tc-nitrido complexes, of general formula [(99m)TcN(DTC-Ln)(PNP)](+) (DTC-Ln= alicyclic dithiocarbamates; PNP = diphosphinoamine), as potential radiotracers for myocardial perfusion imaging. The synthesis of cationic (99m)Tc-(N)-complexes were accomplished in two steps. Biodistribution studies were performed in rats and compared with the distribution profiles of (99m)Tc(N)-DBODC5 and (99m)Tc-Sestamibi. The metabolisms of the most promising compounds were evaluated by HPLC methods. Biological studies revealed that most of the complexes have a high initial and persistent heart uptake with rapid clearance from nontarget tissues. Among tested compounds, 2 and 12 showed improved heart uptake with respect to the gold standard (99m)Tc-complexes with favorable heart-to-liver and slightly lower heart-to-lung ratios. Chromatographic profiles of (99m)Tc(N)-radioactivity extracted from tissues and fluids were coincident with the native compound evidencing remarkable in vivo stability of these agents. This study shows that the incorporation of alicyclic dithiocarbamate in the [(99m)Tc(N)(PNP)](+) building block yields to a significant increase of the heart uptake at early injection point suggesting that the first-pass extraction fraction of these novel complexes may be increased with respect to the other cationic (99m)Tc-agents keeping almost unaltered the favorable target/nontarget ratios. PMID:20402465

  10. Metal-phosphate binders

    DOEpatents

    Howe, Beth Ann [Lewistown, IL; Chaps-Cabrera, Jesus Guadalupe [Coahuila, MX

    2009-05-12

    A metal-phosphate binder is provided. The binder may include an aqueous phosphoric acid solution, a metal-cation donor including a metal other than aluminum, an aluminum-cation donor, and a non-carbohydrate electron donor.

  11. Versatile Cellulose-Based Carbon Aerogel for the Removal of Both Cationic and Anionic Metal Contaminants from Water.

    PubMed

    Alatalo, Sara-Maaria; Pileidis, Filoklis; Mäkilä, Ermei; Sevilla, Marta; Repo, Eveliina; Salonen, Jarno; Sillanpää, Mika; Titirici, Maria-Magdalena

    2015-11-25

    Hydrothermal carbonization of cellulose in the presence of the globular protein ovalbumin leads to the formation of nitrogen-doped carbon aerogel with a fibrillar continuous carbon network. The protein plays here a double role: (i) a natural source of nitrogen functionalities (2.1 wt %) and (ii) structural directing agent (S(BET) = 38 m(2)/g). The applicability in wastewater treatment, namely, for heavy metal removal, was examined through adsorption of Cr(VI) and Pb(II) ion solely and in a mixed bicomponent aqueous solutions. This cellulose-based carbogel shows an enhanced ability to remove both Cr(VI) (∼68 mg/g) and Pb(II) (∼240 mg/g) from the targeted solutions in comparison to other carbon materials reported in the literature. The presence of competing ions showed little effect on the adsorption efficiency toward Cr(VI) and Pb(II). PMID:26540557

  12. Synthesis and crystal structure of a new N-(2,6-dichlorobenzoyl)- N', N″-bis(pyrrolidinyl)-phosphoric triamide as a carrier and competitive bulk liquid membrane transport of six metal cations

    NASA Astrophysics Data System (ADS)

    Khoshnood, Razieh Sanavi; Pourayoubi, Mehrdad; Kasraee, Farideh; Toghraee, Maryam; Dušek, M.; Bereciartua, P. J.

    2014-12-01

    The competitive metal ion transport experiments of Co+2, Cd+2, Ag+, Pb+2, Ni+2, and Cu+2 were carried out by N-(2,6-dichlorobenzoyl)- N', N″-bis(pyrrolidinyl)-phosphoric triamide as a carrier in organic membrane phase. 2,6-Cl2C6H3C(O)NHP(O)[NC4H8]2 has been synthesized and characterized by mass spectrometry IR spectroscopy and single crystal X-ray diffraction. The asymmetric unit of title phosphoric triamide contains one symmetrically independent molecule. The source phase contained equimolar concentrations of metal ions at pH 5 and the receiving phase being buffered at pH 3. The following solvents were examined as membrane: chloroform (CHCl3), nitrobenzene (NB), 1,2-dichloroethane (1,2-DCE), dichloromethane (DCM), dichloromethane/1,2-dichloroethane (DCM/1,2-DCE). The obtained results show that the selectivity and efficiency of transport for these heavy metal cations change with the nature of the ligand and also the organic solvents, which were used as liquid membrane in these experiments. A good selectivity was observed for Pb+2 cation by this ligand in all membrane systems. Moreover, the selectivity of metal cations in DCM is higher than other solvents. A non-linear relationship was found between the percent of transport of Pb+2 cation by this ligand and the compositions of DCM/1,2-DCE and binary solution by this ligand. The effect of several factors such as the nature of carboxylic acids (stearic, fumaric and maleic acid) as surfactant in the membrane phase and the time of transport on transport efficiency of Pb+2 cation were investigated.

  13. Chemical and biological properties in the rhizosphere of Lupinus albus alter soil heavy metal fractionation.

    PubMed

    Martínez-Alcalá, I; Walker, D J; Bernal, M P

    2010-05-01

    To understand better the suitability of white lupin (Lupinus albus L.) for phytoremediation of heavy metal-contaminated soils, the effect of its roots on chemical and biological properties of the rhizosphere affecting soil metal fractionation was studied. Plants were cultivated in two similar soils, with high levels of Zn, Cd, Cu and Pb but differing pH values (4.2 and 6.8). In the rhizosphere of both soils, its roots induced increases in water-soluble carbon, which influenced the fractionation of heavy metals and ultimately their uptake by plant roots. In the rhizosphere of the acid soil, the concentrations of 0.1M CaCl(2)-extractable Mn, Zn and Cu were lower than in the bulk soil, possibly due to their increased retention on Fe (III) hydroxides/oxyhydroxides, while in the neutral soil only the Zn concentration was lower. Higher concentrations of heavy metals were found in plants growing on the acid soil, reflecting their greater availability in this soil. The restricted transfer of heavy metals to the shoot confirms the potential role of this species in the initial phytoimmobilisation of heavy metals, particularly in neutral-alkaline soils. PMID:20060590

  14. Functionalized Nanoporous Silica for Removal of Heavy Metals from Biological Systems; Adsorption and Application

    SciTech Connect

    Yantasee, Wassana; Rutledge, Ryan D.; Chouyyok, Wilaiwan; Sukwarotwat, Vichaya; Orr, Galya; Warner, Cynthia L.; Warner, Marvin G.; Fryxell, Glen E.; Wiacek, Robert J.; Timchalk, Charles; Addleman, Raymond S.

    2010-10-01

    Functionalized nanoporous silica, often referred to as self-assembled monolayers on mesoporous supports (SAMMS) have previously demonstrated the ability to serve as very effective heavy metal sorbents in a range of aquatic and environmental systems suggesting they may be advantageously utilized for biomedical applications such as chelation therapy. Herein we evaluate surface chemistries for heavy metal capture from biological fluids, various facets of the materials biocompatibility and the suitability of these materials as potential therapeutics. Of the materials tested, thiol-functionalized SAMMS proved most capable of removing selected heavy metals from biological solutions (i.e. blood, urine, etc.) As a result, thiol SAMMS was further analyzed to assess the material’s performance under a number of different biologically relevant conditions (i.e. variable pH and ionic strength) as well to gauge any potentially negative cellular effects resulting from interaction with the sorbent, such as cellular toxicity or possible chelation of essential minerals. Additionally, cellular uptake studies demonstrated no cell membrane permeation by the silica-based materials generally highlighting their ability to remain cellularly inert and thus non-toxic. As a result, it has been determined that organic ligand-functionalized nanoporous silica materials could be a valuable material for detoxification therapeutics and potentially other biomedical applications as needed.

  15. Functionalized Nanoporous Silica for the Removal of Heavy Metals from Biological Systems: Adsorption and Application

    PubMed Central

    Yantasee, Wassana; Rutledge, Ryan D.; Chouyyok, Wilaiwan; Sukwarotwat, Vichaya; Orr, Galya; Warner, Cynthia L.; Warner, Marvin G.; Fryxell, Glen E.; Wiacek, Robert J.; Timchalk, Charles; Addleman, R. Shane

    2012-01-01

    Surface-functionalized nanoporous silica, often referred to as self-assembled monolayers on mesoporous supports (SAMMS), has previously demonstrated the ability to serve as very effective heavy metal sorbents in a range of aquatic and environmental systems, suggesting that they may be advantageously utilized for biomedical applications such as chelation therapy. Herein we evaluate surface chemistries for heavy metal capture from biological fluids, various facets of the materials’ biocompatibility, and the suitability of these materials as potential therapeutics. Of the materials tested, thiol-functionalized SAMMS proved most capable of removing selected heavy metals from biological solutions (i.e., blood, urine, etc.) Consequentially, thiol-functionalized SAMMS was further analyzed to assess the material’s performance under a number of different biologically relevant conditions (i.e., variable pH and ionic strength) to gauge any potentially negative effects resulting from interaction with the sorbent, such as cellular toxicity or the removal of essential minerals. Additionally, cellular uptake studies demonstrated no cell membrane permeation by the silica-based materials generally highlighting their ability to remain cellularly inert and thus nontoxic. The results show that organic ligand functionalized nanoporous silica could be a valuable material for a range of detoxification therapies and potentially other biomedical applications. PMID:20939537

  16. Thermodynamic Control of the Isotope Composition of Divalent Metal Cations in Aqueous Solutions and in Carbonate Minerals

    NASA Astrophysics Data System (ADS)

    Schott, J.; Mavromatis, V.; Pearce, C. R.; Fujii, T.; Oelkers, E. H.

    2014-12-01

    The very contrasting steric and electronic properties of divalent metals dramatically affect the reactivity and composition of their aqueous species and their partitioning between fluids and minerals. These contrasting properties result also in very distinct kinetic and thermodynamic trends of their isotopic composition in aqueous fluids and carbonate minerals. For example, if alkaline earths in calcite are all enriched in light isotopes, only Mg exhibits a decrease of its isotope fractionation with increasing calcite growth rate. Moreover, the Mg2+ aquo ion is the only alkaline earth ion whose isotopic composition is markedly affected by the presence in solution of inorganic ligands like bicarbonate, carbonate or sulfate. The distinct behavior of Mg stems from the reduced lability of water molecules in its coordination sphere and from the reduction of its aquo ion coordination sphere when it coordinates to HCO3- and CO32-. Ab initio calculations show that the preferred four hydration number of Mg in stable Mg bicarbonate and Mg carbonate monomers results in a strong enrichment in 26Mg of these species compared to Mg(H2O)62+ (i.e. 1000lnβ26/24MgCO3°-1000lnβ26/24Mg2+ = 5.16 ‰; Fujii, personal communication). The analysis of recent experiments on Mg isotope fractionation between carbonate crystals and solution using density functionnal theory estimation of lnβ values from Fujii i) confirm the marked impact of carbonate and bicarbonate ligands on the isotope composition of Mg in calcite and magnesite and ii) allow to reconcile First-principles and experimental estimates of equilibrium Mg isotope fractionation in carbonate crystals. Recent experiments also confirm that the strong affinity of Zn2+ or Cu2+ for RO- ligands results in a marked impact of fluid pH, ΣCO2(aq) and/or carboxylic ligands concentrations on the isotope composition of these metals in carbonate minerals. These observations provide new insights into the parameters controlling the isotope

  17. The Metals in the Biological Periodic System of the Elements: Concepts and Conjectures

    PubMed Central

    Maret, Wolfgang

    2016-01-01

    A significant number of chemical elements are either essential for life with known functions, or present in organisms with poorly defined functional outcomes. We do not know all the essential elements with certainty and we know even less about the functions of apparently non-essential elements. In this article, I discuss a basis for a biological periodic system of the elements and that biochemistry should include the elements that are traditionally part of inorganic chemistry and not only those that are in the purview of organic chemistry. A biological periodic system of the elements needs to specify what “essential” means and to which biological species it refers. It represents a snapshot of our present knowledge and is expected to undergo further modifications in the future. An integrated approach of biometal sciences called metallomics is required to understand the interactions of metal ions, the biological functions that their chemical structures acquire in the biological system, and how their usage is fine-tuned in biological species and in populations of species with genetic variations (the variome). PMID:26742035

  18. The influence of humic acid on the biological effects of selected trace metals

    SciTech Connect

    Stackhouse, R.A.

    1988-01-01

    The influence of humic acid (HA) on the biological effects of cadmium, hexavalent chromium, and two forms of trivalent chromium was assessed using common freshwater invertebrates. The acute toxicity was determined using Daphnia pulex, while D. magna was used in bioaccumulation studies. Final concentrations of HA tested were 0, 0.5, 5, and 50 mg/l. Humic acid was observed to significantly increase, decrease, or not influence both the acute toxicity and bioaccumulation of cadmium depending on HA concentration and time point examined. Additionally, dialysis studies were used to determine the influence of HA on the bioavailability of the metals. As with the biological effects, HA had little influence on the bioavailability of hexavalent chromium, while having a greater influence on cadmium and chromic chloride. There was a HA concentration dependent pattern of binding (a maximal decrease in percent free metal followed by metal release from HA) observed with cadmium and chromic chloride. This metal release from HA may have resulted from an associated time dependent decrease in pH of the surrounding water. Humic acid had little influence on the bioavailability of chrome lignosulfonate.

  19. On the bioavailability of trace metals in surface sediments: a combined geochemical and biological approach.

    PubMed

    Roosa, Stéphanie; Prygiel, Emilie; Lesven, Ludovic; Wattiez, Ruddy; Gillan, David; Ferrari, Benoît J D; Criquet, Justine; Billon, Gabriel

    2016-06-01

    The bioavailability of metals was estimated in three river sediments (Sensée, Scarpe, and Deûle Rivers) impacted by different levels of Cu, Cd, Pb, and Zn (Northern France). For that, a combination of geochemistry and biological responses (bacteria and chironomids) was used. The results obtained illustrate the complexity of the notion of "bioavailability." Indeed, geochemical indexes suggested a low toxicity, even in surface sediments with high concentrations of total metals and a predicted severe effect levels for the organisms. This was also suggested by the abundance of total bacteria as determined by DAPI counts, with high bacterial cell numbers even in contaminated areas. However, a fraction of metals may be bioavailable as it was shown for chironomid larvae which were able to accumulate an important quantity of metals in surface sediments within just a few days.We concluded that (1) the best approach to estimate bioavailability in the selected sediments is a combination of geochemical and biological approaches and that (2) the sediments in the Deûle and Scarpe Rivers are highly contaminated and may impact bacterial populations but also benthic invertebrates. PMID:26884242

  20. Ultrasound-assisted synthesis of nanosized zero-valent iron for metal cations extraction and wastewater treatment applications

    NASA Astrophysics Data System (ADS)

    Mikhailov, I. Yu; Lysov, D. V.; Levina, V. V.; Mazov, I. N.; Gusev, A. A.; Yudintseva, T. I.; Kuznetsov, D. V.

    2016-01-01

    Nanosized zero-valent iron has shown good results in wastewater treatment and activation of physicochemical processes. Its applications in modern industry are complicated by high production costs of nanomaterials produced via existing synthesis routes. Therefore there is a need of cheap and high-productive methods of nanosized zero-valent iron with advanced functional properties. Improvement of oxidative conditions with additions may find its place in extraction of rare-earth metals, where high cost of nanomaterials could be viable. In this paper we studied an effect of ultrasonic irradiation on specific surface area and particle size of nanosized zero-valent iron synthesized by methods of chemical precipitation with high- temperature reduction in hydrogen flow and sodium borohydride reduction. Obtained results showed significant decrease of particle size and differences in particles morphology depending on presence of ultrasonication during synthesis and on chosen method. For ultrasonic-assisted synthesis with 100% amplitude, particle size calculated from specific surface area was 70 nm for sample synthesized by chemical precipitation with high-temperature reduction and 35 nm for borohydide reduction method compared to 63 nm for reference sample without ultrasonication.

  1. Cardiac ryanodine receptor: Selectivity for alkaline earth metal cations points to the EF-hand nature of luminal binding sites.

    PubMed

    Gaburjakova, Jana; Gaburjakova, Marta

    2016-06-01

    A growing body of evidence suggests that the regulation of cardiac ryanodine receptor (RYR2) by luminal Ca(2+) is mediated by luminal binding sites located on the RYR2 channel itself and/or its auxiliary protein, calsequestrin. The localization and structure of RYR2-resident binding sites are not known because of the lack of a high-resolution structure of RYR2 luminal regions. To obtain the first structural insight, we probed the RYR2 luminal face stripped of calsequestrin by alkaline earth metal divalents (M(2+): Mg(2+), Ca(2+), Sr(2+) or Ba(2+)). We show that the RYR2 response to caffeine at the single-channel level is significantly modified by the nature of luminal M(2+). Moreover, we performed competition experiments by varying the concentration of luminal M(2+) (Mg(2+), Sr(2+) or Ba(2+)) from 8mM to 53mM and investigated its ability to compete with 1mM luminal Ca(2+). We demonstrate that all tested M(2+) bind to exactly the same RYR2 luminal binding sites. Their affinities decrease in the order: Ca(2+)>Sr(2+)>Mg(2+)~Ba(2+), showing a strong correlation with the M(2+) affinity of the EF-hand motif. This indicates that the RYR2 luminal binding regions and the EF-hand motif likely share some structural similarities because the structure ties directly to the function. PMID:26849106

  2. Reactions of cationic transition metal acetonitrile complexes [M(CH3CN)n]m+ with GaCp*: novel gallium complexes of iron, cobalt, copper and silver.

    PubMed

    Bollermann, Timo; Puls, Arik; Gemel, Christian; Cadenbach, Thomas; Fischer, Roland A

    2009-02-28

    The reactions of the cationic transition metal acetonitrile complexes [M(CH3CN)n]m+ (m = 2: M = Fe, Co and m = 1: M = Cu, Ag) with GaCp* were investigated. The reaction of [Fe(CH3CN)6][BArF]2 (BAr(F) = [B{C6H3(CF3)2}4) with GaCp* leads to [Cp*Fe(GaCp*)3][BAr(F)] (1) via a redox neutral Cp* transfer and [Ga2Cp*][BAr(F)] as a by-product while the formation of [Cp*Co(GaCp*)3][BAr(F)]2 (2) from [Co(CH3CN)6][BAr(F)]2 is accompanied by oxidation of Co(II) to Co(III) with GaCp* as the oxidant. The reactions of [Cu(CH3CN)4][BAr(F)] and Ag[BPh4] with GaCp* lead to the formation of the homoleptic compounds [Cu(GaCp*)4][BAr(F)] (4) and [Ag(GaCp*)4][BPh4] (5), while treatment of Ag[CF3SO3] with GaCp* leads to the dimeric complex [Ag2(GaCp*)3(micro-GaCp*)2][CF3SO3]2 (6). All compounds were characterized by NMR spectroscopy, single crystal X-ray diffraction and elemental analysis. PMID:19462658

  3. Four homochiral coordination polymers contain N-acetyl-L-tyrosine and different N-donor ligand: Influence of metal cations, ancillary ligands and coordination modes

    NASA Astrophysics Data System (ADS)

    Li, Meng-Li; Song, Hui-Hua

    2013-10-01

    Using the chiral ligand N-acetyl-L-tyrosine (Hacty) and maintaining identical reaction conditions, Zn(II), Co(II), and Cd(II) salts provided four novel homochiral coordination polymers {[Zn(acty)(bipy)2(H2O)2]·NO3·2H2O}n1, {[Co(acty)(bipy)2(H2O)2]·NO3·2H2O}n2, {[Cd(acty)2(bipy)H2O]·H2O}n3, and {[Cd(acty)(bpe)2(Ac)]·6H2O}n4 (bipy=4,4‧-bipyridine; bpe=1,2-di(4-pyridyl)ethane) in the presence of ancillary ligands. Compounds 1 and 2 are isostructural 1D chain structures. The neighboring chains are further linked into a 3D supramolecular structure via π⋯π stacking and hydrogen bond interactions. Compound 3 shows a 2D network and 4 generates 1D infinite chains along the c-axis. Compounds 3 and 4 are further connected into 3D supramolecular network by hydrogen bond interactions. More importantly, coordination in acyl oxygen atoms and ancillary ligands (bpe) as monodentate decorating ligands in 4 are rarely reported. Ancillary ligands and metal cations significantly influence the structure of the complexes. The photoluminescence properties of 1, 3, and 4 were studied at room temperature. Circular dichroism (CD) of the complexes have been investigated.

  4. STRUCTURAL BIOLOGY OF THE SEQUESTRATION & TRANSPORT OF HEAVY METAL TOXINS: NMR STRUCTURE DETERMINATION OF PROTEINS CONTAINING THE CYS-X-Y-CYS-METAL BINDING MOTIFS

    EPA Science Inventory

    There are enormous amounts of heavy metals in the environment, much of it in the form of organometallic compounds resulting from various types of industrial and military waste. Nearly all of these metals and compounds are highly toxic to biological organisms including humans. How...

  5. Halocuprate(I) zigzag chain structures with N-methylated DABCO cations--bright metal-centered luminescence and thermally activated color shifts.

    PubMed

    Maderlehner, Sebastian; Leitl, Markus J; Yersin, Hartmut; Pfitzner, Arno

    2015-11-28

    Two compounds 1,4-dimethyl-1,4-diazoniabicyclo[2.2.2]octane catena-tetra-μ-halo-dicuprate(I) with DABCOMe2 Cu2X4 (1: X = Br, 2: X = I) were synthesized by hydrothermal reaction of copper(I) halides with the corresponding 1,4-diazoniabicyclo[2.2.2]octane (DABCO) dihydrohalides in an acetonitrile/methanol mixture. Both compounds crystallize monoclinically, 1 with a = 9.169(4) Å, b = 10.916(6) Å, c = 15.349(6) Å, β = 93.93(2)°, V = 1533(1) Å(3), Z = 4, space group P2(1)/n (no. 14) and 2 with a = 15.826(9) Å, b = 9.476(5) Å, c = 22.90(2) Å, β = 90.56(5)°, V = 3434(5) Å(3), Z = 8, space group P2(1) (no. 4), respectively (lattice constants refined from powder diffraction data measured at 293 K). The cations in both compounds are formed by in situ N-methylation of DABCOH2(2+) cations by methanol in a S(N)2 reaction. Both compounds contain an anionic copper(I) halide chain structure consisting of trans edge-sharing CuX4 tetrahedra. The chains are strongly kinked at every 2(nd) junction thus forming a zigzag structure. The shortest halide-halide distances are observed between the halide ions of adjacent tetrahedra which are approaching each other due to the kinking. This structure type shows a specific luminescence behavior. Under optical excitation, the compounds exhibit yellow (1) and green (2) emission with photoluminescence quantum yields of Φ(PL) = 52 and 4%, respectively, at ambient temperature. According to DFT and TDDFT calculations, the emission is assigned to be a phosphorescence essentially involving a metal centered transition between the HOMO consisting mainly of copper 3d and halide p orbitals and the LUMO consisting mainly of copper 4s and 4p orbitals. The temperature dependence of the emission spectra, decay times, and quantum yields has been investigated in detail, especially for 1. From the resulting trends it can be concluded that the emission for T≤ 100 K stems from energetically lower lying copper halide segments. Such segments represent

  6. Metal Complexes of Macrocyclic Schiff-Base Ligand: Preparation, Characterisation, and Biological Activity

    PubMed Central

    Ahmed, Riyadh M.; Yousif, Enaam I.; Hasan, Hasan A.; Al-Jeboori, Mohamad J.

    2013-01-01

    A new macrocyclic multidentate Schiff-base ligand Na4L consisting of two submacrocyclic units (10,21-bis-iminomethyl-3,6,14,17-tricyclo[17.3.1.18,12]tetracosa-1(23),2,6,8,10,12(24),13,17,19,21,-decaene-23,24-disodium) and its tetranuclear metal complexes with Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) are reported. Na4L was prepared via a template approach, which is based on the condensation reaction of sodium 2,4,6-triformyl phenolate with ethylenediamine in mole ratios of 2 : 3. The tetranuclear macrocyclic-based complexes were prepared from the reaction of the corresponding metal chloride with the ligand. The mode of bonding and overall geometry of the compounds were determined through physicochemical and spectroscopic methods. These studies revealed tetrahedral geometries about Mn, Co, and Zn atoms. However, square planar geometries have been suggested for NiII and CuII complexes. Biological activity of the ligand and its metal complexes against Gram positive bacterial strain Staphylococcus aureus and Gram negative bacteria Escherichia coli revealed that the metal complexes become more potentially resistive to the microbial activities as compared to the free ligand. However, these metal complexes do not exhibit any effects on the activity of Pseudomonas aeruginosa bacteria. There is therefore no inhibition zone. PMID:23935414

  7. Four homochiral coordination polymers contain N-acetyl-L-tyrosine and different N-donor ligand: Influence of metal cations, ancillary ligands and coordination modes

    SciTech Connect

    Li, Meng-Li; Song, Hui-Hua

    2013-10-15

    Using the chiral ligand N-acetyl-L-tyrosine (Hacty) and maintaining identical reaction conditions, Zn(II), Co(II), and Cd(II) salts provided four novel homochiral coordination polymers ([Zn(acty)(bipy){sub 2}(H{sub 2}O){sub 2}]·NO{sub 3}·2H{sub 2}O){sub n}1, ([Co(acty)(bipy){sub 2}(H{sub 2}O){sub 2}]·NO{sub 3}·2H{sub 2}O){sub n}2, ([Cd(acty){sub 2}(bipy)H{sub 2}O]·H{sub 2}O){sub n}3, and ([Cd(acty)(bpe){sub 2}(Ac)]·6H{sub 2}O){sub n}4 (bipy=4,4′-bipyridine; bpe=1,2-di(4-pyridyl)ethane) in the presence of ancillary ligands. Compounds 1 and 2 are isostructural 1D chain structures. The neighboring chains are further linked into a 3D supramolecular structure via π⋯π stacking and hydrogen bond interactions. Compound 3 shows a 2D network and 4 generates 1D infinite chains along the c-axis. Compounds 3 and 4 are further connected into 3D supramolecular network by hydrogen bond interactions. More importantly, coordination in acyl oxygen atoms and ancillary ligands (bpe) as monodentate decorating ligands in 4 are rarely reported. Ancillary ligands and metal cations significantly influence the structure of the complexes. The photoluminescence properties of 1, 3, and 4 were studied at room temperature. Circular dichroism (CD) of the complexes have been investigated. - Graphical abstract: Four new homochiral coordination polymers were prepared and structurally characterized, which investigate the influence of the ancillary ligands and metal ions on the design and synthesis of coordination polymers. Display Omitted - Highlights: • It is rarely reported that the chiral coordination polymers prepared with N-acetyl-L-tyrosine ligands. • The alkalescent acetyl oxygen atom is difficult to participate in coordination but it is happened in the N-acetyl-L-tyrosine ligands. • The ancillary ligands (4,4′-bipy and bpe) are present in an unusual coordination modes, monodentate decorating ligands in 1, 2 and 4. • Structure comparative analyses results indicate that the

  8. Elucidating the mechanism behind the stabilization of multi-charged metal cations in water: A case study of the electronic states of microhydrated Mg2+, Ca2+ and Al3+”

    SciTech Connect

    Miliordos, Evangelos; Xantheas, Sotiris S.

    2014-04-21

    Metal atoms typically have second and higher ionization potentials (IPs) that are larger than the IP of water, resulting in the Coulombic explosion of the first few [M(H2O)n]+q (q ≥ 2) clusters as the M+ + (H2O)n + or MOH+ + H3O+(H2O)n energy levels are energetically more stable than the M2+ + (H2O)n ones for small n. We present a theoretical analysis of the various electronic states correlating with the above channels that are involved in the sequential hydration of the Ca2+, Mg2+ and Al3+ cations with up to six water molecules that, for the first time, quantifies their relative shift with the degree of solvation accounting for the observed stabilization of those multi-charged metal cations in an aqueous solution. *

  9. [Sediment heavy metals quality criteria for fresh waters based on biological effect database approach].

    PubMed

    Zhang, Ting; Zhong, Wen-Jue; Zeng, Yi; Zhu, Ling-Yan

    2012-09-01

    Heavy metals are the important pollutants in sediments, which can cause serious damage to benthonic organisms and aquatic ecology, while biological effect database approach (BEDA) is a widely used method for assessing sediment quality in developed countries or regions. This paper introduced the concrete steps of this approach, and built the sediment quality criteria of five heavy metals (Cu, Zn, Cd, Pb, and Ni) for fresh waters. The comparability, reliability, and predictability of the criteria were also tested. It was shown that the threshold effect level (TEL) of the Cd, Ni, Pb, Zn, and Cu was 3.0, 31.4, 47.3, 74.9, and 45.5 mg x kg(-1) dry mass, and the probable effect level (PEL) of the Cd, Ni, Pb, Zn, and Cu was 19, 76.9, 204.1, 403.6, and 181.1 mg x kg(-1) dry mass basis, respectively. Except for Zn, the TEL and PEL for the Cu, Cd, Pb, and Ni were consistent with the definitional biological effect of the heavy metals, being accor-dance with the demands of sediment quality criteria for protecting benthic organisms and having high reliability, and thus, could be used as the proposed sediment quality criteria for fresh waters in China. PMID:23286020

  10. Biological Strategies for Improved Osseointegration and Osteoinduction of Porous Metal Orthopedic Implants

    PubMed Central

    Riester, Scott M.; Bonin, Carolina A.; Kremers, Hilal Maradit; Dudakovic, Amel; Kakar, Sanjeev; Cohen, Robert C.; Westendorf, Jennifer J.

    2015-01-01

    The biological interface between an orthopedic implant and the surrounding host tissue may have a dramatic effect upon clinical outcome. Desired effects include bony ingrowth (osseointegration), stimulation of osteogenesis (osteoinduction), increased vascularization, and improved mechanical stability. Implant loosening, fibrous encapsulation, corrosion, infection, and inflammation, as well as physical mismatch may have deleterious clinical effects. This is particularly true of implants used in the reconstruction of load-bearing synovial joints such as the knee, hip, and the shoulder. The surfaces of orthopedic implants have evolved from solid-smooth to roughened-coarse and most recently, to porous in an effort to create a three-dimensional architecture for bone apposition and osseointegration. Total joint surgeries are increasingly performed in younger individuals with a longer life expectancy, and therefore, the postimplantation lifespan of devices must increase commensurately. This review discusses advancements in biomaterials science and cell-based therapies that may further improve orthopedic success rates. We focus on material and biological properties of orthopedic implants fabricated from porous metal and highlight some relevant developments in stem-cell research. We posit that the ideal primary and revision orthopedic load-bearing metal implants are highly porous and may be chemically modified to induce stem cell growth and osteogenic differentiation, while minimizing inflammation and infection. We conclude that integration of new biological, chemical, and mechanical methods is likely to yield more effective strategies to control and modify the implant–bone interface and thereby improve long-term clinical outcomes. PMID:25348836

  11. Features of the complexation of 3,3'-dimethoxy-4,4'-dihydroxy-5,5'-bis(di(n-carboxymethyl)aminomethyl)benzophenone with some cations and oxo cations of metals

    SciTech Connect

    Sinitsyna, T.A.; Ivakin, A.A.

    1988-02-01

    The complexation of 3,3'-dimethoxy-4,4'-dihydroxy-5,5'-bis(di(N-carboxymethyl)amino-methyl)benzophenone with Ca/sup 2 +/, Zn/sup 2 +/, Y/sup 3 +/, VO/sup 2 +/, and VO/sub 2//sup +/ cations has been investigated by the methods of IR and PMR spectroscopy. Hypotheses regarding the coordination capacity of the chelating agent in the complexes studied have been advanced on the basis of the data obtained.

  12. Bivalent transition metal complexes of cetirizine: Spectroscopic, equilibrium studies and biological activity

    NASA Astrophysics Data System (ADS)

    El-Sherif, Ahmed A.; Shoukry, Mohamed M.; Abobakr, Lamis O.

    2013-08-01

    Metal complexes of cetirizineṡ2HCl (CTZ = 2-[2-[4-[(4-chlorophenyl)phenyl methyl]piperazine-1-yl]-ethoxy]acetic acid, dihydrochloride have been prepared and characterized by elemental analyses, IR, solid reflectance, magnetic moment, molar conductance, and UV-Vis spectra. The analytical data of the complexes show the formation of 1:2 [M:L] ratio, where M represents Ni(II), Co(II) and Cu(II) ions, while L represents the deprotonated CTZ ligand. IR spectra show that CTZ is coordinated to the metal ions in a monodentate manner through carboxylate-O atom. Protonation equilibria of CTZ and its metal complexation by some divalent metal ions were determined in aqueous solution at constant ionic strength (0.1 M NaCl) using an automatic potentiometric technique. Thermodynamic parameters for the protonation equilibria of CTZ were calculated and discussed. The stability order of M(II)-CTZ complexes were found to obey Mn2+ < Co2+ < Ni2+ < Cu2+, in accordance with the Irving-Williams order. The concentration distribution of the complexes in solution is evaluated as a function of pH. The CTZ ligand and its metal complexes were screened for their biological activity against bacterial species (Bacillus subtillis RCMB 010067, Staphylococcus aureus RCMB 010028, Pseudomonas aeuroginosa RCMB 010043, and Escherichia coli RCMB 010052) and fungi as (Aspergillus flavus RCMB 02568, Pencicillium italicum RCMB 03924, Candida albicans RCMB 05031 and Geotricum candidum RCMB 05097). The activity data show that the metal complexes have antibacterial and antifungal activity more than the parent CTZ ligand against one or more bacterial or fungi species. MIC was evaluated for the isolated complexes.

  13. Comparison of sediments and organisms in identifying sources of biologically available trace metal contamination

    USGS Publications Warehouse

    Thomson, E.A.; Luoma, S.N.; Johansson, C.E.; Cain, D.J.

    1984-01-01

    Sediments and an indicator organism (Macoma balthica, a deposit-feeding bivalve) were used to assess the relative importance of secondary sewage, urban runoff, a landfill containing metal-enriched ash wastes and a yacht harbor in contributing to Ag, Cu and Zn enrichment in South San Francisco Bay. Spatial gradients in sediments and organisms showed Cu and Ag enrichment originated from sewage discharge, whereas Zn enrichment originated from both sewage and urban runoff. Elevated concentrations of Cu in the sediments of the yacht harbor resulted from a high abundance of fine particles. The biological availability of Cu, Ag and Zn did not coincide with metal enrichment in sediments. The availability of Cu and Ag was greatest nearest the sewage outfall and greater in winter and spring than in summer. The availability of Zn in urban runoff appeared to be lower than the availability of Zn associated with sewage.

  14. Spectroscopic studies and biological activity of some transition metal complexes of unusual Schiff base

    NASA Astrophysics Data System (ADS)

    Abu Al-Nasr, Ahmad K.; Ramadan, Ramadan M.

    2013-03-01

    Unusual Schiff base ligand, 4-ethanimidoyl-6-[(1E)-N-(2-hydroxy-4-methylphenyl)ethanimidoyl]benzene-1,3-diol, L, was synthesized via catalytic process involving the interaction of some metal ions with a macrocyclic Schiff base (MSB). The transition metal derivatives [ML(H2O)4](NO3)3, M = Cr(III) and Fe(III), [NiL(H2O)4](NO3)2, [ML(H2O)2](NO3)2, M = Zn(II) and Cd(II), [Cl2Pd(μ-Cl)2PdL], [PtL(Cl)2] and [PtL(Cl)4] were also synthesized from the corresponding metal species with L. The Schiff bases and complexes were characterized by elemental analysis, mass spectrometry, IR and 1H NMR spectroscopy. The crystal structure of L was determined by X-ray analysis. The spectroscopic studies revealed a variety of structure arrangements for the complexes. The biological activities of L and metal complexes against the Escherchia coli as Gram-negative bacteria and Staphylococcus aureus as Gram-positive bacteria, and the two fungus Aspergillus flavus and Candida albicans were screened. The cytotoxicity of [PtL(Cl)2] complex, a cis-platin analogous, was checked as an antitumor agent on two breast cancer cell lines (MCF7 and T47D) and human liver carcinoma cell line (HepG2).

  15. Synthesis, Characterization and Biological Evaluation of Transition Metal Complexes Derived from N, S Bidentate Ligands

    PubMed Central

    Md Yusof, Enis Nadia; Ravoof, Thahira Begum S. A.; Tiekink, Edward R. T.; Veerakumarasivam, Abhimanyu; Crouse, Karen Anne; Mohamed Tahir, Mohamed Ibrahim; Ahmad, Haslina

    2015-01-01

    Two bidentate NS ligands were synthesized by the condensation reaction of S-2-methylbenzyldithiocarbazate (S2MBDTC) with 2-methoxybenzaldehyde (2MB) and 3-methoxybenzaldehyde (3MB). The ligands were reacted separately with acetates of Cu(II), Ni(II) and Zn(II) yielding 1:2 (metal:ligand) complexes. The metal complexes formed were expected to have a general formula of [M(NS)2] where M = Cu2+, Ni2+, and Zn2+. These compounds were characterized by elemental analysis, molar conductivity, magnetic susceptibility and various spectroscopic techniques. The magnetic susceptibility measurements and spectral results supported the predicted coordination geometry in which the Schiff bases behaved as bidentate NS donor ligands coordinating via the azomethine nitrogen and thiolate sulfur. The molecular structures of the isomeric S2M2MBH (1) and S2M3MBH (2) were established by X-ray crystallography to have very similar l-shaped structures. The Schiff bases and their metal complexes were evaluated for their biological activities against estrogen receptor-positive (MCF-7) and estrogen receptor-negative (MDA-MB-231) breast cancer cell lines. Only the Cu(II) complexes showed marked cytotoxicity against the cancer cell lines. Both Schiff bases and other metal complexes were found to be inactive. In concordance with the cytotoxicity studies, the DNA binding studies indicated that Cu(II) complexes have a strong DNA binding affinity. PMID:25988384

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

    NASA Astrophysics Data System (ADS)

    Hanif, Muhammad; Chohan, Zahid H.

    2013-03-01

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

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

    PubMed

    Hanif, Muhammad; Chohan, Zahid H

    2013-03-01

    A new series of three biologically active triazole derived Schiff base ligands L(1)-L(3) have been synthesized in equimolar reaction of 3-amino-1H-1,2,4-triazole with pyrrol-2-carboxaldehyde, 4-bromo-thiophene-2-carboxaldehyde, and 5-iodo-2-hydroxy benzaldehyde. The prepared Schiff bases were used for further complex formation reaction with different metal elements like Co(II), Ni(II), Cu(II) and Zn(II) as chlorides by using a molar ratio of ligand:metal as 2:1. The structure and bonding nature of all the compounds were identified by their physical, spectral and analytical data. All the metal(II) complexes possessed an octahedral geometry except the Cu(II) complexes which showed a distorted octahedral geometry. All the synthesized compounds, were studied for their in vitro antibacterial, and antifungal activities, against four Gram-negative (Escherichia coli, Shigella sonnei, Pseudomonas aeruginosa and Salmonella typhi) and two Gram-positive (Bacillus subtilis and Staphylococcus aureus) bacterial strains and against six fungal strains (Trichophyton longifusus, Candida albicans, Aspergillus flavus, Microsporum canis, Fusarium solani and Candida glabrata) by using agar-well diffusion method. It has been shown that all the synthesized compounds showed moderate to significant antibacterial activity against one or more bacterial strains. In vitro Brine Shrimp bioassay was also carried out to investigate the cytotoxic properties of these compounds. The data also revealed that the metal complexes showed better activity than the ligands due to chelation/coordination. PMID:23277183

  18. 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

  19. Detection of heavy-metal ions using liquid crystal droplet patterns modulated by interaction between negatively charged carboxylate and heavy-metal cations.

    PubMed

    Han, Gyeo-Re; Jang, Chang-Hyun

    2014-10-01

    Herein, we demonstrated a simple, sensitive, and rapid label-free detection method for heavy-metal (HM) ions using liquid crystal (LC) droplet patterns on a solid surface. Stearic-acid-doped LC droplet patterns were spontaneously generated on an n-octyltrichlorosilane (OTS)-treated glass substrate by evaporating a solution of the nematic LC, 4-cyano-4'-pentylbiphenyl (5CB), dissolved in heptane. The optical appearance of the droplet patterns was a dark crossed texture when in contact with air, which represents the homeotropic orientation of the LC. This was caused by the steric interaction between the LC molecules and the alkyl chains of the OTS-treated surface. The dark crossed appearance of the acid-doped LC patterns was maintained after the addition of phosphate buffered saline (PBS) solution (pH 8.1 at 25°C). The deprotonated stearic-acid molecules self-assembled through the LC/aqueous interface, thereby supporting the homeotropic anchoring of 5CB. However, the optical image of the acid-doped LC droplet patterns incubated with PBS containing HM ions appeared bright, indicating a planar orientation of 5CB at the aqueous/LC droplet interface. This dark to bright transition of the LC patterns was caused by HM ions attached to the deprotonated carboxylate moiety, followed by the sequential interruption of the self-assembly of the stearic acid at the LC/aqueous interface. The results showed that the acid-doped LC pattern system not only enabled the highly sensitive detection of HM ions at a sub-nanomolar concentration but it also facilitated rapid detection (<10 min) with simple procedures. PMID:25059128

  20. Schwertmannite and Fe oxides formed by biological low-pH Fe(II) oxidation versus abiotic neutralization: Impact on trace metal sequestration

    NASA Astrophysics Data System (ADS)

    Burgos, William D.; Borch, Thomas; Troyer, Lyndsay D.; Luan, Fubo; Larson, Lance N.; Brown, Juliana F.; Lambson, Janna; Shimizu, Masayuki

    2012-01-01

    Three low-pH coal mine drainage (CMD) sites in central Pennsylvania were studied to determine similarities in sediment composition, mineralogy, and morphology. Water from one site was used in discontinuous titration/neutralization experiments to produce Fe(III) minerals by abiotic oxidative hydrolysis for comparison with the field precipitates that were produced by biological low-pH Fe(II) oxidation. Even though the hydrology and concentration of dissolved metals of the CMD varied considerably between the three field sites, the mineralogy of the three iron mounds was very similar. Schwertmannite was the predominant mineral precipitated at low-pH (2.5-4.0) along with lesser amounts of goethite. Trace metals such as Zn, Ni and Co were only detected at μmol/g concentrations in the field sediments, and no metals (other than Fe) were removed from the CMD at any of the field sites. Metal cations were not lost from solution in the field because of unfavorable electrostatic attraction to the iron mound minerals. Ferrihydrite was the predominant mineral formed by abiotic neutralization (pH 4.4-8.4, 4 d aging) with lesser amounts of schwertmannite and goethite. In contrast to low-pH precipitation, substantial metal removal occurred in the neutralized CMD. Al was likely removed as hydrobasaluminite and Al(OH) 3, and as a co-precipitate into schwertmannite or ferrihydrite. Zn, Ni and Co were likely removed via adsorption onto and co-precipitation into the freshly formed Fe and Al solids. Mn was likely removed by co-precipitation and, at the highest final pH values, as a Mn oxide. Biological low-pH Fe(II) oxidation can be cost-effectively used to pre-treat CMD and remove Fe and acidity prior to conventional neutralization techniques. A further benefit is that solids formed under these conditions may be of industrial value because they do not contain trace metal or metalloid contaminants.

  1. Biological effects of anionic meso-tetrakis (para-sulfonatophenyl) porphyrins modulated by the metal center. Studies in rat liver mitochondria.

    PubMed

    Pessoto, Felipe Samuel; Inada, Natalia Mayumi; Nepomuceno, Maria de Fátima; Ruggiero, Ana Célia; Nascimento, Otaciro R; Vercesi, Anibal E; Nantes, Iseli L

    2009-10-30

    In this paper, we present a study about the influence of the porphyrin metal center and meso ligands on the biological effects of meso-tetrakis porphyrins. Different from the cationic meso-tetrakis 4-N-methyl pyridinium (Mn(III)TMPyP), the anionic Mn(III) meso-tetrakis (para-sulfonatophenyl) porphyrin (Mn(III)TPPS4) exhibited no protector effect against Fe(citrate)-induced lipid oxidation. Mn(III)TPPS4 did not protect mitochondria against endogenous hydrogen peroxide and only delayed the swelling caused by tert-BuOOH and Ca2+. Fe(III)TPPS4 exacerbated the effect of the tert-BuOOH, and both porphyrins did not significantly affect Fe(II)citrate-induced swelling. Consistently, Fe(III)TPPS4 predominantly promotes the homolytic cleavage of peroxides and exhibits catalytic efficiency ten-fold higher than Mn(III)TPPS4. For Mn(III)TPPS4, the microenvironment of rat liver mitochondria favors the heterolytic cleavage of peroxides and increases the catalytic efficiency of the manganese porphyrin due to the availability of axial ligands for the metal center and reducing agents such as glutathione (GSH) and proteins necessary for Compound II (oxomanganese IV) recycling to the initial Mn(III) form. The use of thiol reducing agents for the recycling of Mn(III)TPPS4 leads to GSH depletion and protein oxidation and consequent damages in the organelle. PMID:19631199

  2. The cation-π interaction.

    PubMed

    Dougherty, Dennis A

    2013-04-16

    The chemistry community now recognizes the cation-π interaction as a major force for molecular recognition, joining the hydrophobic effect, the hydrogen bond, and the ion pair in determining macromolecular structure and drug-receptor interactions. This Account provides the author's perspective on the intellectual origins and fundamental nature of the cation-π interaction. Early studies on cyclophanes established that water-soluble, cationic molecules would forego aqueous solvation to enter a hydrophobic cavity if that cavity was lined with π systems. Important gas phase studies established the fundamental nature of the cation-π interaction. The strength of the cation-π interaction (Li(+) binds to benzene with 38 kcal/mol of binding energy; NH4(+) with 19 kcal/mol) distinguishes it from the weaker polar-π interactions observed in the benzene dimer or water-benzene complexes. In addition to the substantial intrinsic strength of the cation-π interaction in gas phase studies, the cation-π interaction remains energetically significant in aqueous media and under biological conditions. Many studies have shown that cation-π interactions can enhance binding energies by 2-5 kcal/mol, making them competitive with hydrogen bonds and ion pairs in drug-receptor and protein-protein interactions. As with other noncovalent interactions involving aromatic systems, the cation-π interaction includes a substantial electrostatic component. The six (four) C(δ-)-H(δ+) bond dipoles of a molecule like benzene (ethylene) combine to produce a region of negative electrostatic potential on the face of the π system. Simple electrostatics facilitate a natural attraction of cations to the surface. The trend for (gas phase) binding energies is Li(+) > Na(+) > K(+) > Rb(+): as the ion gets larger the charge is dispersed over a larger sphere and binding interactions weaken, a classical electrostatic effect. On other hand, polarizability does not define these interactions. Cyclohexane is

  3. The Cation-π Interaction

    PubMed Central

    DOUGHERTY, DENNIS A.

    2014-01-01

    CONSPECTUS The chemistry community now recognizes the cation-π interaction as a major force for molecular recognition, joining the hydrophobic effect, the hydrogen bond, and the ion pair in determining macromolecular structure and drug-receptor interactions. This Account provides the author’s perspective on the intellectual origins and fundamental nature of the cation-π interaction. Early studies on cyclophanes established that water-soluble, cationic molecules would forgo aqueous solvation to enter a hydrophobic cavity if that cavity was lined with π systems. Important gas phase studies established the fundamental nature of the cation-π interaction. The strength of the cation-π interaction – Li+ binds to benzene with 38 kcal/mol of binding energy; NH4+ with 19 kcal/mol– distinguishes it from the weaker polar-π interactions observed in the benzene dimer or water-benzene complexes. In addition to the substantial intrinsic strength of the cation-π interaction in gas phase studies, the cation-π interaction remains energetically significant in aqueous media and under biological conditions. Many studies have shown that cation-π interactions can enhance binding energies by 2 – 5 kcal/mol, making them competitive with hydrogen bonds and ion pairs in drug-receptor and protein-protein interactions. As with other noncovalent interactions involving aromatic systems, the cation-π interaction includes a substantial electrostatic component. The six (four) Cδ−–Hδ+ bond dipoles of a molecule like benzene (ethylene) combine to produce a region of negative electrostatic potential on the face of the π system. Simple electrostatics facilitate a natural attraction of cations to the surface. The trend for (gas phase) binding energies is Li+>Na+>K+>Rb+: as the ion gets larger the charge is dispersed over a larger sphere and binding interactions weaken, a classical electrostatic effect. On other hand, polarizability does not define these interactions. Cyclohexane

  4. [Bioaccumulation and Biomagnification of Heavy Metals in Three Gorges Reservoir and Effect of Biological Factors].

    PubMed

    Wei, Li-li; Zhou, Qiong; Xie, Cong-xin; Wang, Jun; Li, Jun

    2016-01-15

    Three Gorges Reservoir (TGR) reached the maximum water level (175 m) of impoundment in Oct. 2010. In order to reveal the potential influence of the greatest water-level impoundment on the heavy metal pollution in the typical waters of TGR, the content level of trace metals ( Hg, Cd and Pb) in biota and potential biomagnification along the aquatic food chain were investigated in the main stem of TGR from July 2011 to August 2012, as well as the relationship between the trace metal concentrations of aquatic consumers (fish and aquatic invertebrate) and biological factors. Our study showed that no individual data of the three trace metals in biota exceeded the edible safety criteria of aquatic products in China and FAO. In contrast with those before the impoundment of TGR, Hg showed a little higher, while Cd and Pb exhibited a little lower level after the impoundment. Trace metals in TGR exhibited relatively lower concentrations compared with those in reservoirs in other countries. Significant correlations were found between the Cd concentration and body size (body length and body weight) of Cyprinus carpio, as well as the Hg concentration and body size (body length and body weight) of Erythroculter ilishaeformis. As for feeding habits, there was statistically significant difference between trace metal concentrations in herbivorous, planktonic, omnivorous and carnivorous fish. However, no significant difference was found between the metal concentrations in fish with different habitats (pelagic, mesopelagic and benthic). Even so, the overall trend was that fish living in benthic layer had higher heavy metal concentrations than those in pelagic and mesopelagic zones. The regression slopes of log-Hg concentration versus delta(15)N, served as an indicator of trophic magnification factor (TMF). Significant correlations (P < 0.05) were observed for Hg in the food web of TGR. TMF of Hg in TGR indicated lower level (0.046-0.066) in contrast with those in the reservoirs of

  5. The interaction of biological and noxious transition metals with the zinc probes FluoZin-3 and Newport Green

    PubMed Central

    Zhao, Jinfu; Bertoglio, Bryan A.; Devinney, Michael J.; Dineley, Kirk E.; Kay, Alan R.

    2009-01-01

    Zinc sensitive fluorescent probes have become increasingly important in the investigation of the cellular roles of zinc. There is however little information on how the other transition metals in cells may influence zinc measurements. We have characterized in-vitro the interaction of the nominal zinc indicators, FluoZin-3 and Newport Green with all the cationic transition metals found within cells, Cr, Mn, Fe, Co and Cu, as well as Ni and Cd, by measuring their dissociation constants. In addition, we have shown how FluoZin-3 can be used to quantify the concentration of copper in a cell-free assay and report that the fluorescence of NPG is boosted by both Cu(I) and Fe(II). Furthermore, we have introduced diagnostics for detecting the interference of metals other than zinc with its measurement within cells. PMID:18848515

  6. Determination of polycyclic aromatic compounds and heavy metals in sludges from biological sewage treatment plants.

    PubMed

    Bodzek, D; Janoszka, B; Dobosz, C; Warzecha, L; Bodzek, M

    1997-07-11

    The procedure of the analysis of polycyclic aromatic hydrocarbons (PAHs) and their derivatives in the sludges from biological sewage treatment plants has been worked out. The analysis included isolation of organic matter from sludges, separation of the extract into fractions of similar chemical character, qualitative-quantitative analysis of individual PAHs and their nitrogenated and oxygenated derivatives. Liquid-solid chromatography, solid-phase extraction and semipreparative band thin-layer chromatography techniques were used for the separation. Capillary gas chromatography-mass spectrometry analysis of the separated fractions enabled identification of more than 21 PAHs, including hydrocarbons which contained 2-6 aromatic rings as well as their alkyl derivatives, 10 oxygen derivatives, 9 nitroarenes, aminoarenes and over 20 azaarenes and carbazoles. Using the capillary gas chromatography-flame ionization detection technique the content of 17 dominant PAHs was determined. The content of heavy metals was determined in investigated sludges with the use of atomic absorption spectrometry. The concentrations of the respective metals could be ranked in the order Cd < Co < Ni < Pb < Cr < or = Cu < Mn < Zn < Fe. The sludges were analysed for the first time in Poland in view of their possible utilisation in agriculture and in cultivating dumps of coal mine wastes, taking into consideration the contents of toxic organic pollutants and heavy metals. PMID:9253190

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

    PubMed

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

    2015-09-01

    Synthesis of compounds analogous to natural products from secondary metabolites, such as flavonoids, is a promising source of novel drugs. Rutin (quercetin-3-O-rutinoside) is a natural flavone, which has, in its chemical structure, different sites for coordination with transition metals and the complexation with these metals enhances its biological properties. Rutin-zinc(II), a flavonoid-metal complex, was synthesized and characterized by UV-VIS, FT-IR, elemental analysis and (1)H NMR. The antioxidant and antitumor activities, as well as the cytotoxicity and in vivo toxicity of this complex were evaluated and compared with the free rutin. Rutin-zinc(II) has not shown any cytotoxicity against normal cells (fibroblasts and HUVECs) or toxicity in BALB/c mice, but has shown antioxidant activity in vitro and cytotoxicity against leukemia (KG1, K562 and Jurkat), multiple myeloma (RPMI8226) and melanoma (B16F10 and SK-Mel-28) cell lines in vitro. In Ehrlich ascites carcinoma model, Rutin-zinc(II) modulated the mitochondrial membrane potential and the expression of genes related to cell cycle progression, angiogenesis and apoptosis. PMID:26091902

  8. Spectroscopic Properties of Novel Aromatic Metal Clusters: NaM4 (M=Al, Ga, In) and their Cations and Anions

    SciTech Connect

    Balasubramanian, K; Zhao, C

    2004-03-17

    The ground and several excited states of metal aromatic clusters, namely NaM4 and NaM{sub 4}{sup {+-}} (M=Al, Ga, In) clusters have been investigated by employing complete activespace self-consistent-field (CASSCF) followed by Multi-reference singles and doubles configuration interaction (MRSDCI) computations that included up to 10 million configurations and other methods. The ground states NaM{sub 4}{sup -} of aromatic anions are found to be symmetric C{sub 4v} ({sup 1}A{sub 1}) electronic states with ideal square pyramid geometries. While the ground state of NaIn4 is also predicted to be a symmetric C{sub 4v} ({sup 2}A{sub 1}) square pyramid, the ground state of the NaAl4 cluster is found to have a C{sub 2v} ({sup 2}A{sub 1}) pyramid with a rhombus base and the ground state of NaGa{sub 4} possesses a C{sub 2v} ({sup 2}A{sub 1}) pyramid with a rectangle base. In general these structures exhibit 2 competing geometries, viz., an ideal C{sub 4v} structure and a distorted rhomboidal or rectangular pyramid structure (C{sub 2v}). All of the ground states of the NaM{sub 4}{sup +} (M= Al, Ga, In) cations are computed to be C{sub 2v} ({sup 3}A{sub 2}) pyramids with rhombus bases. The equilibrium geometries, vibrational frequencies, dissociation energies, adiabatic ionization potentials, adiabatic electron affinities for the electronic states of NaM{sub 4} (M=Al, Ga, In) and their ions are computed and compared with experimental results and other theoretical calculations. On the basis of our computed excited states energy separations, we have tentatively suggested assignments to the observed X and A states in the anion photoelectron spectra of Al{sub 4}Na{sup -} reported by Li et al. The X state can be assigned to a C{sub 2v} ({sup 2}A{sub 1}) rhomboidal pyramid. The A state observed in the anion spectrum is assigned to the first excited state ({sup 2}B{sub 1}) of the neutral NaAl{sub 4} with the C{sub 4v} symmetry. The assignments of the excited states are consistent with

  9. Heavy metal accumulations in hair of northern fur seals: Application for biological monitoring

    SciTech Connect

    Noda, K.; Saeki, K.; Tatsukawa, R.; Baba, N.; Kiyota, M.; Nitto, H.; Watabe, M.

    1995-12-31

    Hair of northern fur seals had the highest concentrations of many heavy metals among tissues and organs analyzed. Hair could be used as a sensitive indicator for its higher element levels, and can serve as a noninvasive technique for biological monitoring. Significant positive correlation were found between Hg in muscle, Fe in kidney and Cu in liver and those in hair of 42 fur seals from Off-Sanriku, Japan. Using age as a explanatory co-variables, significant multiple regression equations to estimate metal concentrations in internal organs by those in hair were obtained for Hg, Cd, Fe, Cu, Mn. To monitor the seasonal changes in hair concentrations, from the cervical region of 7 fur seals in the Otaru aquarium, Japan, guard hair were clipped during November, 1993 March, 1994 at 7 weeks intervals. Heavy metal levels in hair from the aquarium were compared with those collected in April, 1990--1991 from Off-Sanriku, Japan and from the Pribilof Islands, Alaska which were collected in July, 1992. The levels of Cu, Zn, Mn and Ni in hair in the captive seals gradually increased and were higher than those from Off-Sanriku. Those changes could be associated with growth of hair. In the hair of the breeding animals collected from the island, concentrations of Mn, Ni and Fe were found to be significantly higher than those from Off-Sanriku. increased concentrations of Mn, Ni and Fe were supposed to be caused by exogenous contaminations derived from soil and blood. Fur seal hair seems to be an useful indicator to estimate the internal accumulations of heavy metals provided the seasonal changes and exogenous contamination are taken into account.

  10. A multimodal imaging workflow to visualize metal mixtures in the human placenta and explore colocalization with biological response markers.

    PubMed

    Niedzwiecki, Megan M; Austin, Christine; Remark, Romain; Merad, Miriam; Gnjatic, Sacha; Estrada-Gutierrez, Guadalupe; Espejel-Nuñez, Aurora; Borboa-Olivares, Hector; Guzman-Huerta, Mario; Wright, Rosalind J; Wright, Robert O; Arora, Manish

    2016-04-01

    Fetal exposure to essential and toxic metals can influence life-long health trajectories. The placenta regulates chemical transmission from maternal circulation to the fetus and itself exhibits a complex response to environmental stressors. The placenta can thus be a useful matrix to monitor metal exposures and stress responses in utero, but strategies to explore the biologic effects of metal mixtures in this organ are not well-developed. In this proof-of-concept study, we used laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) to measure the distributions of multiple metals in placental tissue from a low-birth-weight pregnancy, and we developed an approach to identify the components of metal mixtures that colocalized with biological response markers. Our novel workflow, which includes custom-developed software tools and algorithms for spatial outlier identification and background subtraction in multidimensional elemental image stacks, enables rapid image processing and seamless integration of data from elemental imaging and immunohistochemistry. Using quantitative spatial statistics, we identified distinct patterns of metal accumulation at sites of inflammation. Broadly, our multiplexed approach can be used to explore the mechanisms mediating complex metal exposures and biologic responses within placentae and other tissue types. Our LA-ICP-MS image processing workflow can be accessed through our interactive R Shiny application 'shinyImaging', which is available at or through our laboratory's website, . PMID:26987553

  11. Cationic Noncovalent Interactions: Energetics and Periodic Trends.

    PubMed

    Rodgers, M T; Armentrout, P B

    2016-05-11

    In this review, noncovalent interactions of ions with neutral molecules are discussed. After defining the scope of the article, which excludes anionic and most protonated systems, methods associated with measuring thermodynamic information for such systems are briefly recounted. An extensive set of tables detailing available thermodynamic information for the noncovalent interactions of metal cations with a host of ligands is provided. Ligands include small molecules (H2, NH3, CO, CS, H2O, CH3CN, and others), organic ligands (O- and N-donors, crown ethers and related molecules, MALDI matrix molecules), π-ligands (alkenes, alkynes, benzene, and substituted benzenes), miscellaneous inorganic ligands, and biological systems (amino acids, peptides, sugars, nucleobases, nucleosides, and nucleotides). Hydration of metalated biological systems is also included along with selected proton-based systems: 18-crown-6 polyether with protonated peptides and base-pairing energies of nucleobases. In all cases, the literature thermochemistry is evaluated and, in many cases, reanchored or adjusted to 0 K bond dissociation energies. Trends in these values are discussed and related to a variety of simple molecular concepts. PMID:26953819

  12. Investigation of the soluble metals in tissue as biological response pattern to environmental pollutants (Gammarus fossarum example).

    PubMed

    Filipović Marijić, Vlatka; Dragun, Zrinka; Sertić Perić, Mirela; Matoničkin Kepčija, Renata; Gulin, Vesna; Velki, Mirna; Ečimović, Sandra; Hackenberger, Branimir K; Erk, Marijana

    2016-07-01

    In the present study, Gammarus fossarum was used to investigate the bioaccumulation and toxic effects of aquatic pollutants in the real environmental conditions. The novelty of the study is the evaluation of soluble tissue metal concentrations in gammarids as indicators in early assessment of metal exposure. In the Sutla River, industrially/rurally/agriculturally influenced catchment in North-Western Croatia, physico-chemical water properties pointed to disturbed ecological status, which was reflected on population scale as more than 50 times lower gammarid density compared to the reference location, Črnomerec Stream. Significantly higher levels of soluble toxic metals (Al, As, Cd, Pb, Sb, Sn, Sr) were observed in gammarids from the Sutla River compared to the reference site and reflected the data on higher total dissolved metal levels in the river water at that site. The soluble metal estimates were supplemented with the common multibiomarker approach, which showed significant biological responses for decreased acetylcholinesterase activity and increased total soluble protein concentrations, confirming stressed environmental conditions for biota in the Sutla River. Biomarker of metal exposure, metallothionein, was not induced and therefore, toxic effect of metals was not confirmed on molecular level. Comparable between-site pattern of soluble toxic metals in gammarids and total dissolved metal levels in water suggests that prior to biomarker response and observed toxic impact, soluble metals in tissue might be used as early warning signs of metal impact in the aquatic environment and improve the assessment of water quality. PMID:27060638

  13. Comparative Study of the Effects of Long and Short Term Biological Processes on the Cycling of Colloidal Trace Metals

    NASA Astrophysics Data System (ADS)

    Pinedo, P.; Sanudo-Wilhelmy, S. A.; West, A.

    2013-05-01

    Nanoparticle (or colloids), with sizes operationally defined as ranging from 1nm to 1000nm diameter, are thought to play an important role in metal cycling in the ocean due to their high surface area to volume ratio and abundance in marine systems. In coastal waters, the bulk of marine nanoparticles are organic, so short and long term biological processes are expected to influence the dynamics of these types of particles in marine environments. This is, in turn, expected to influence metal concentrations. Here we selected two different environments to study the influence of long-term biological events (phytoplankton blooms) and short-term biological events (diel cycles of photosynthesis and respiration) on the cycling of colloidal trace metals. We focus on Cu and Fe, both biogeochemically important metals but with differing colloidal behavior. Long term processes (West Neck Bay): A bay (West Neck Bay, Long Island) with predictable natural phytoplankton blooms, but with limited inputs of freshwater, nutrients and metals, was selected to study the partitioning of Cu and Fe between colloidal and soluble pools over the course of a bloom. During the bloom, there was a significant build-up of Cu associated with DOM accumulation and a removal of Fe via particle stripping. Fraction-specific metal concentrations, and metal accumulation and removal rates, were found to be significantly correlated with chlorophyll-a concentration and with dissolved organic matter (DOM). Short term processes (Catalina Island): To identify the cyclical variation in metal speciation during diel (24-hour) cycles of photosynthesis and respiration, we conducted a study off Catalina Island, a pristine environment where trace metal cycling is solely controlled by biological processes and changes in the phytoplankton community are well characterized. The speciation of Fe between soluble and colloidal pools showed that Fe has a high affinity for colloidal material and that the distribution between

  14. Designing, syntheses, characterization, computational study and biological activities of silver-phenothiazine metal complex

    NASA Astrophysics Data System (ADS)

    Kumar, Vijay; Upadhyay, Niraj; Manhas, Anu

    2015-11-01

    A noble biologically active compound Ag(I)-PTZ metal complex (1) with spherical morphology was synthesized first time. Entire characterization tool (spectral, elemental, mass and thermal analysis) was supported a distorted tetrahedral structure, where two water compounds were coordinated with Ag(I) including one phenothiazine and one nitrate group. For the better insight, obtained spectral/structural results were supported by 3D molecular modeling. Compound 1 had shown excellent activities against the Salmonella typhimurium and Aspergillus fumigatus with minimum inhibitory concentration (MIC) value 20 mg/L and 25 mg/L. The observed antioxidant radical scavenging activity (in %) of compound 1 (62.74%) was more than control ascorbic acid (28.58%). The observed protein (BSA) binding constant of 1 was 8.86 × 104 M-1, which is similar to binding constant of salicylic acid with BSA protein. Initial studies have revealed that synthesized compound 1 may act as multipurpose drug analogue in future.

  15. Mapping the Metal Uptake in Plants from Jasper Ridge Biological Preserve - Oral Presentation

    SciTech Connect

    Lo, Allison

    2015-08-24

    Serpentine soil originates in the Earth’s mantle and contains high concentrations of potentially toxic transition metals. Although serpentine soil limits plant growth, endemic and adapted plants at Jasper Ridge Biological Preserve, located behind SLAC National Accelerator Laboratory, can tolerate these conditions. Serpentine soil and seeds belonging to native California and invasive plants were collected at Jasper Ridge. The seeds were grown hydroponically and on serpentine and potting soil to examine the uptake and distribution of ions in the roots and shoots using synchrotron micro-focused X-ray fluorescence spectroscopy. The results were used to determine differences between serpentinetolerant plants. Rye grown on potting soil was enriched in Ni, Fe, Mn, and Cr compared to purple needlegrass grown on serpentine soil. Serpentine vegetation equally suppressed the uptake of Mn, Ni, and Fe in the roots and shoots. The uptake of Ca and Mg affected the uptake of other elements such as K, S, and P.

  16. Sequential metal vapor elution analysis for the determination of Cu and Mn in biological materials and waters.

    PubMed

    Ohta, K; Uegomori, H; Kaneco, S; Mizuno, T

    1999-04-01

    The determination of copper and manganese in biological materials and river waters by sequential metal vapor elution analysis (SMVEA) using an atomic absorption detector (AA) is reported. An improved molybdenum column (open column, i.d. 1.22 mm) with three ring supporters was developed for SMVEA. An optimum flow rate of carrier gas (pure argon) for separation of metal vapors was 4.0 ml min(-1). Copper and manganese peaks separated from Al, Ca, Cd, Fe, K, Mg, Na, Pb, and Zn peaks at a vaporization temperature of 1950 degrees C and a column temperature of 1900 degrees C. The appearing order of these metals was Cd, Zn, Pb, Cu, Na and Mn. It was understood by considering the boiling points of these metals or chlorides. The delay of appearing time is due to an interaction between the metal vapors and inside surface of the column. Under the experimental conditions, the number of theoretical plates was 11.3 for Cd, 89.6 for Cu, 160 for Na, and 258 for Mn in the improved column. Under the optimal experimental conditions, NIST biological standards and river waters were analyzed for copper and manganese. The analytical results agreed well with the certified values and the recoveries were in the range of 94 to 109%. By SMVEA, it was found that copper and manganese in biological materials and waters were determined without interference of matrix elements, after only acid digestion for biological materials and no chemical treatment for river water samples. PMID:18967537

  17. Subcellular compartmentalization of Cd and Zn in two bivalves. I. Significance of metal-sensitive fractions (MSF) and biologically detoxified metal (BDM)

    USGS Publications Warehouse

    Wallace, W.G.; Lee, B.-G.; Luoma, S.N.

    2003-01-01

    Many aspects of metal accumulation in aquatic invertebrates (i.e. toxicity, tolerance and trophic transfer) can be understood by examining the subcellular partitioning of accumulated metal. In this paper, we use a compartmentalization approach to interpret the significance of metal, species and size dependence in the subcellular partitioning of Cd and Zn in the bivalves Macoma balthica and Potamocorbula amurensis. Of special interest is the compartmentalization of metal as metal-sensitive fractions (MSF) (i.e. organelles and heat-sensitive proteins, termed 'enzymes' hereafter) and biologically detoxified metal (BDM) (i.e. metallothioneins [MT] and metal-rich granules [MRG]). Clams from San Francisco Bay, CA, were exposed for 14 d to seawater (20??? salinity) containing 3.5 ??g l-1 Cd and 20.5 ??g l-1 Zn, including 109Cd and 65Zn as radiotracers. Uptake was followed by 21 d of depuration. The subcellular partitioning of metal within clams was examined following exposure and loss. P. amurensis accumulated ???22x more Cd and ???2x more Zn than M. balthica. MT played an important role in the storage of Cd in P. amurensis, while organelles were the major site of Zn accumulation. In M. balthica, Cd and Zn partitioned similarly, although the pathway of detoxification was metal-specific (MRG for Cd; MRG and MT for Zn). Upon loss, M. balthica depurated ???40% of Cd with Zn being retained; P. amurensis retained Cd and depurated Zn (???40%). During efflux, Cd and Zn concentrations in the MSF compartment of both clams declined with metal either being lost from the animal or being transferred to the BDM compartment. Subcellular compartmentalization was also size-dependent, with the importance of BDM increasing with clam size; MSF decreased accordingly. We hypothesized that progressive retention of metal as BDM (i.e. MRG) with age may lead to size dependency of metal concentrations often observed in some populations of M. balthica.

  18. Synthesis, spectroscopic characterization, biological screenings, DNA binding study and POM analyses of transition metal carboxylates

    NASA Astrophysics Data System (ADS)

    Uddin, Noor; Sirajuddin, Muhammad; Uddin, Nizam; Tariq, Muhammad; Ullah, Hameed; Ali, Saqib; Tirmizi, Syed Ahmed; Khan, Abdur Rehman

    2015-04-01

    This article contains the synthesis of a novel carboxylic acid derivative, its transition metal complexes and evaluation of biological applications. Six carboxylate complexes of transition metals, Zn(II) and Hg(II), have been successfully synthesized and characterized by FT-IR and NMR (1H, 13C). The ligand, HL, (4-[(2,6-Diethylphenyl)amino]-4-oxobutanoic acid) was also characterized by single crystal X-ray analysis. The complexation occurs via oxygen atoms of the carboxylate moiety. FT-IR date show the bidentate nature of the carboxylate moiety of the ligand as the Δν value in all complexes is less than that of the free ligand. The ligand and its complexes were screened for antifungal and antileishmanial activities. The results showed that the ligand and its complexes are active with few exceptions. UV-visible spectroscopy and viscometry results reveal that the ligand and its complexes interact with the DNA via intercalative mode of interaction. A new and efficient strategy to identify the pharmacophores and anti-pharmacophores sites in carboxylate derivatives for the antibacterial/antifungal activity using Petra, Osiris and Molinspiration (POM) analyses was also carried out.

  19. Synthesis, spectroscopic characterization, biological screenings, DNA binding study and POM analyses of transition metal carboxylates.

    PubMed

    Uddin, Noor; Sirajuddin, Muhammad; Uddin, Nizam; Tariq, Muhammad; Ullah, Hameed; Ali, Saqib; Tirmizi, Syed Ahmed; Khan, Abdur Rehman

    2015-04-01

    This article contains the synthesis of a novel carboxylic acid derivative, its transition metal complexes and evaluation of biological applications. Six carboxylate complexes of transition metals, Zn(II) and Hg(II), have been successfully synthesized and characterized by FT-IR and NMR (1H, 13C). The ligand, HL, (4-[(2,6-Diethylphenyl)amino]-4-oxobutanoic acid) was also characterized by single crystal X-ray analysis. The complexation occurs via oxygen atoms of the carboxylate moiety. FT-IR date show the bidentate nature of the carboxylate moiety of the ligand as the Δν value in all complexes is less than that of the free ligand. The ligand and its complexes were screened for antifungal and antileishmanial activities. The results showed that the ligand and its complexes are active with few exceptions. UV-visible spectroscopy and viscometry results reveal that the ligand and its complexes interact with the DNA via intercalative mode of interaction. A new and efficient strategy to identify the pharmacophores and anti-pharmacophores sites in carboxylate derivatives for the antibacterial/antifungal activity using Petra, Osiris and Molinspiration (POM) analyses was also carried out. PMID:25646895

  20. Biological nitrogen removal from industrial wastewater discharged from metal recovery processes.

    PubMed

    Hirata, A; Nakamura, Y; Tsuneda, S

    2001-01-01

    The wastewater generated from the processes of recovering precious metals from industrial wastes contains high concentrations of acids and alkalis such as nitric acid and aqueous ammonia, and of salts such as sodium chloride and sodium sulfate. Biological nitrogen removal from this wastewater was attempted by using a circulating bioreactor system equipped with an anaerobic packed bed and an aerobic three-phase fluidized bed. As a result of acclimating microorganisms with change of the hydraulic residence time, this system effectively removed nitrogen from diluted wastewater (T-N: from 2,000 to 4,000 g/m3), such that the total nitrogen concentration in the effluent met the sewage discharge control criteria in Japan (240 g/m3). The removal ratio of total nitrogen was 90% to 98% and that of ammonia was 80% to 92%. In addition, the characteristic equations for biological treatment were applied to this system on the assumption that both reactions of denitrification in the anaerobic reactor and nitrification in the aerobic reactor can be approximated to a first-order reaction. This simplified approach successfully led to a new analytical method for simulating the optimum volume ratio of anaerobic reactor to aerobic reactor for minimizing the total hydraulic residence time. PMID:11547981

  1. Comment on ``An enhanced polarization mechanism for the metal cations modified amorphous TiO2 based electrorheological materials'' by Qing Wu, Bin Yuan Zhao, Chen Fang and Ke Ao Hu

    NASA Astrophysics Data System (ADS)

    Lee, K.-H.; Park, B. J.; Choi, H. J.

    2006-12-01

    Comments on a recent article on an enhanced polarization mechanism for the metal cations modified amorphous TiO2 based electrorheological materials are presented, based upon an examination of the yield stress, which is a function of electric-field strength, of the materials. Using the deduced critical electric-field strengths, we find that the universal yield stress equation proposed collapses the data given by Qing Wu, Bin Yuan Zhao, Chen Fang, Ke Ao Hu, Eur. Phys. J. E 17, 63 (2005), onto a single curve.

  2. Solid State Structures of Alkali Metal Ion Complexes Formed by Low-Molecular-Weight Ligands of Biological Relevance.

    PubMed

    Aoki, Katsuyuki; Murayama, Kazutaka; Hu, Ning-Hai

    2016-01-01

    This chapter provides structural data, mainly metal binding sites/modes, observed in crystal structures of alkali metal ion complexes containing low-molecular-weight ligands of biological relevance, mostly obtained from the Cambridge Structural Database (the CSD version 5.35 updated to February 2014). These ligands include (i) amino acids and small peptides, (ii) nucleic acid constituents (excluding quadruplexes and other oligonucleotides), (iii) simple carbohydrates, and (iv) naturally occurring antibiotic ionophores. For some representative complexes of these ligands, some details on the environment of the metal coordination and structural characteristics are described. PMID:26860299

  3. Hemin/G-quadruplex structure and activity alteration induced by magnesium cations.

    PubMed

    Kosman, J; Juskowiak, B

    2016-04-01

    The influence of metal cations on G-quadruplex structure and peroxidase-mimicking DNAzyme activity was investigated. Experiments revealed a significant role of magnesium ion, which in the presence of potassium cation influenced DNAzyme activity. This ability has been associated with alteration of G-quadruplex topology and consequently affinity to bind hemin molecule. It has been demonstrated that G-quadruplex based on PS2.M sequence under these conditions formed parallel topology, which exhibited lower activity than that observed in standard potassium-containing solution. On the other hand DNAzyme/magnesium ion system based on telomeric sequence, which did not undergo significant structural changes, exhibited higher peroxidase activity upon magnesium ion addition. In both cases, the stabilization effect of magnesium cations on G-quadruplex structure was observed. The mechanism of DNAzyme activity alteration by magnesium ion can be explained by its influence on the pKa value of DNAzyme. Magnesium ion decreased pKa for PS2.M based system but increased it for telomeric DNAzyme. Magnesium cation effect on G-quadruplex structure as well as DNAzyme activity is particularly important since this ion is one of the most common metal cations in biological samples. PMID:26778160

  4. X-ray, spectroscopic and semiempirical investigation of the structure of lasalocid 6-bromohexyl ester and its complexes with alkali metal cations

    NASA Astrophysics Data System (ADS)

    Huczyński, Adam; Ratajczak-Sitarz, Małgorzata; Katrusiak, Andrzej; Brzezinski, Bogumil

    2011-07-01

    The ionophoric antibiotic lasalocid acid has been converted to a novel 6-bromohexyl ester (LASBR) and its structure has been determined in the crystal by X-ray diffraction and in solution by NMR and FT-IR methods. In the crystal two symmetry-independent LASBR molecules are present. The structure of LASBR in solution is slightly different because the strongest intramolecular C(1) dbnd O⋯H sbnd (3)O hydrogen bond in the pseudo-aromatic ring becomes partially broken and a new hydrogen bond between O(4)H and carbonyl group C(13) dbnd O is formed. LASBR forms complexes with Li +, Na + and K + cations of exclusively 1:1 stoichiometry. The structures of complexes have been studied and visualized using semi-empirical calculation based on results of spectrometric and spectroscopic investigation. It is demonstrated that in contrast to lasalocid acid the novel ester forms preferential complexes with Li + cation.

  5. Photocatalytic Reactive Oxygen Species Formation by Semiconductor-Metal Hybrid Nanoparticles. Toward Light-Induced Modulation of Biological Processes.

    PubMed

    Waiskopf, Nir; Ben-Shahar, Yuval; Galchenko, Michael; Carmel, Inbal; Moshitzky, Gilli; Soreq, Hermona; Banin, Uri

    2016-07-13

    Semiconductor-metal hybrid nanoparticles manifest efficient light-induced spatial charge separation at the semiconductor-metal interface, as demonstrated by their use for hydrogen generation via water splitting. Here, we pioneer a study of their functionality as efficient photocatalysts for the formation of reactive oxygen species. We observed enhanced photocatalytic activity forming hydrogen peroxide, superoxide, and hydroxyl radicals upon light excitation, which was significantly larger than that of the semiconductor nanocrystals, attributed to the charge separation and the catalytic function of the metal tip. We used this photocatalytic functionality for modulating the enzymatic activity of horseradish peroxidase as a model system, demonstrating the potential use of hybrid nanoparticles as active agents for controlling biological processes through illumination. The capability to produce reactive oxygen species by illumination on-demand enhances the available peroxidase-based tools for research and opens the path for studying biological processes at high spatiotemporal resolution, laying the foundation for developing novel therapeutic approaches. PMID:27224678

  6. Effects of metal cations present naturally in coal on the fate of coal-bound nitrogen in the fixed-bed pyrolysis of 25 coals with different ranks: correlation between inherent Fe cations and N{sub 2} formation from low-rank coals

    SciTech Connect

    Yasuo Ohtsuka; Zhiheng Wu

    2009-09-15

    The fate of coal-N in the fixed-bed pyrolysis of 25 coals with 62-81 wt % (daf) C has been studied with a quartz reactor at 1000 C under ambient pressure to examine the effects of metal cations present naturally in these coals on the partitioning of coal-N into N{sub 2}, NH{sub 3}, HCN, tar-N, and char-N. Nitrogen mass balances for all runs fall within the reasonable range of 100 {+-} 5%, and N{sub 2} is the predominant product for all of the coals. As the N{sub 2} yield increases, the sum of NH{sub 3}, HCN, and tar-N is unchanged significantly, whereas the char-N yield decreases almost linearly, showing that most of N{sub 2} originates from char-N. When eight kinds of inherent metals, such as Na, Mg, Al, Si, K, Ca, Fe, and Ti, are determined by the conventional method and related with the N{sub 2} yield, there exists a strong, direct correlation between the Fe content and N{sub 2} formation for low-rank coals with less than 75 wt % (daf) C. Transmission electron microscopy coupled with an energy-dispersive analysis of X-rays (TEM-EDAX) measurements after pyrolysis at 1000{sup o}C of a German brown coal, which provides the highest N{sub 2} yield of about 60%, reveal the existence of lamella structures because of graphitized carbon as well as nanoscale Fe particles with different sizes and shapes. The mechanism for conversion reactions of char-N to N{sub 2} is discussed in terms of the catalysis by nanoparticles of metallic Fe formed from inherent Fe cations. 34 refs., 18 figs., 1 tab.

  7. Stability constants and thermodynamic data for complexes of 12-crown-4 with alkali metal and alkaline-earth cations in methanol solutions

    SciTech Connect

    Buschmann, H.

    1987-03-01

    The formation of 1:1- and 2:1-complexes of the crown ether 12C4 with mono- and bivalent cations was studied in methanol solutions by calorimetric, potentiometric and conductometric titrations. It is shown that not all donor atoms of the ligand 12C4 take part in complex formation. The accuracy of the three experimental methods are checked by comparing the results for the complexation of alkali ions with crown ether 18C6.

  8. EFFECT OF NITROGEN AND METAL ADDITIONS ON NITROGEN FIXATION ACTIVITY IN BIOLOGICAL SOIL CRUSTS

    NASA Astrophysics Data System (ADS)

    Alexander, K.; Lui, D.; Anbar, A. D.; Garcia-Pichel, F.; Hartnett, H. E.

    2009-12-01

    Biological soil crusts (BSCs) are diverse consortia of microorganisms that live in intimate association with soils in arid environments. Also called cryptogamic or microbiotic crusts, these communities can include cyanobacteria, algae, heterotrophic bacteria, fungi, lichens, and mosses. Together, these organisms provide many services to their surrounding ecosystems, including reduction of water runoff, promotion of water infiltration, and prevention of soil erosion. The cyanobacteria and algae also provide fixed carbon (C) to the soil through photosynthesis, and because atmospheric deposition of nitrogen (N) in arid environments is low, the major input of biologically available N comes from cyanobacteria capable of converting nitrogen gas (N2) to ammonium (NH4+). Biological soil crusts are easily destroyed by livestock grazing, motor vehicle travel, and many forms of recreational and agricultural land use. Loss of BSC cover can leave the soil vulnerable to intense erosion that can remove the nutrients necessary to sustain plant and animal life, thus accelerating the process of desertification. In order to preserve existing crusts and encourage the development of new crusts, it is crucial to understand the nutrient requirements of metabolism and growth in these microbial communities. This study investigated the affect of nitrogen and metal additions on N2-fixation activity in cyanobacterially-dominated crusts from the Colorado Plateau near Moab, Utah. Although N2-fixation has been studied in this system before, the affect of nutrient additions on N2-fixation activity has not been documented. The goal of this work was to understand how N and metal supplementation affects crust N metabolism. Three experiments were conducted to observe how N2-fixation activity changed with the addition of N, molybdenum (Mo), and vanadium (V). Molybdenum and vanadium were chosen because they are most commonly found at the active site of the enzyme nitrogenase, the molecule responsible

  9. New metal complexes of N3 tridentate ligand: Synthesis, spectral studies and biological activity

    NASA Astrophysics Data System (ADS)

    Al-Hamdani, Abbas Ali Salih; Al Zoubi, Wail

    2015-02-01

    New tridentate ligand 3-amino-4-{1,5-dimethyl-3-[2-(5-methyl-1H-indol-3-yl)-ethylimino]-2phenyl-2,3-dihydro-1H-pyrazol-4-ylazo}-phenol L was synthesized from the reaction of 1,5-dimethyl-3-[2-(5-methyl-1H-indol-3-yl)-ethylimino]-2-phenyl-2,3-dihydro-1H-pyrazol-4-ylamine and 3.4-amino phenol. A complexes of these ligand [Ni(II)(L)(H2O)2 Cl]Cl, [pt(IV)(L)Cl3]Cl and [M(II)(L)Cl]Cl (M = Pd (II), Zn (II), Cd (II) and Hg (II) were synthesized. The complexes were characterized by spectroscopic methods and magnetic moment measurements, elemental analysis, metal content, Chloride containing and conductance. These studies revealed octahedral geometries for the Ni (II), pt (IV) complexes, square planar for Pd (II) complex and tetrahedral for the Zn (II), Cd(II) and Hg (II) complexes. The study of complexes formation via molar ratio and job method in DMF solution has been investigated and results were consistent to those found in the solid complexes with a ratio of (M:L) as (1:1). The thermodynamic parameters, such as ΔE*, ΔH*, ΔS* ΔG* and K are calculated from the TGA curve using Coats-Redfern method. Hyper Chem-8 program has been used to predict structural geometries of compounds in gas phase. The synthesized ligand and its metal complexes were screened for their biological activity against bacterial species, two Gram positive bacteria (Bacillus subtilis and Staphylococcus aureus) and two Gram negative bacteria (Escherichia coli and Pseudomonasaeruginosa).

  10. Method for encapsulating and isolating hazardous cations, medium for encapsulating and isolating hazardous cations

    SciTech Connect

    Wasserman, S.R.; Anderson, K.B.; Song, K.; Yuchs, S.E.; Marshall, C.L.

    1996-12-31

    The problems associated with the disposal of toxic metals in an environmentally acceptable manner continues to plague industry. Such metals as nickel, vanadium, molybdenum, cobalt, iron, and antimony present physiological and ecological challenges that are best addressed through minimization of exposure and dispersion. A method for encapsulating hazardous cations is provided comprising supplying a pretreated substrate containing the cations; contacting the substrate with an organo-silane compound to form a coating on the substrate; and allowing the coating to cure. A medium for containing hazardous cations is also provided, comprising a substrate having ion-exchange capacity and a silane-containing coating on the substrate.

  11. Generation of Scalable, Metallic High-Aspect Ratio Nanocomposites in a Biological Liquid Medium.

    PubMed

    Cotton Kelly, Kinsey; Wasserman, Jessica R; Deodhar, Sneha; Huckaby, Justin; DeCoster, Mark A

    2015-01-01

    The goal of this protocol is to describe the synthesis of two novel biocomposites with high-aspect ratio structures. The biocomposites consist of copper and cystine, with either copper nanoparticles (CNPs) or copper sulfate contributing the metallic component. Synthesis is carried out in liquid under biological conditions (37 °C) and the self-assembled composites form after 24 hr. Once formed, these composites are highly stable in both liquid media and in a dried form. The composites scale from the nano- to micro- range in length, and from a few microns to 25 nm in diameter. Field emission scanning electron microscopy with energy dispersive X-ray spectroscopy (EDX) demonstrated that sulfur was present in the NP-derived linear structures, while it was absent from the starting CNP material, thus confirming cystine as the source of sulfur in the final nanocomposites. During synthesis of these linear nano- and micro-composites, a diverse range of lengths of structures is formed in the synthesis vessel. Sonication of the liquid mixture after synthesis was demonstrated to assist in controlling average size of the structures by diminishing the average length with increased time of sonication. Since the formed structures are highly stable, do not agglomerate, and are formed in liquid phase, centrifugation may also be used to assist in concentrating and segregating formed composites. PMID:26274773

  12. Reactions of HNO with metal porphyrins: underscoring the biological relevance of HNO.

    PubMed

    Doctorovich, Fabio; Bikiel, Damian E; Pellegrino, Juan; Suárez, Sebastián A; Martí, Marcelo A

    2014-10-21

    Azanone ((1)HNO, nitroxyl) shows interesting yet poorly understood chemical and biological effects. HNO has some overlapping properties with nitric oxide (NO), sharing its biological reactivity toward heme proteins, thiols, and oxygen. Despite this similarity, HNO and NO show significantly different pharmacological effects. The high reactivity of HNO means that studies must rely on the use of donor molecules such as trioxodinitrate (Angeli's salt). It has been suggested that azanone could be an intermediate in several reactions and that it may be an enzymatically produced signaling molecule. The inherent difficulty in detecting its presence unequivocally prevents evidence from yielding definite answers. On the other hand, metalloporphyrins are widely used as chemical models of heme proteins, providing us with invaluable tools for the study of the coordination chemistry of small molecules, like NO, CO, and O2. Studies with transition metal porphyrins have shown diverse mechanistic, kinetic, structural, and reactive aspects related to the formation of nitrosyl complexes. Porphyrins are also widely used in technical applications, especially when coupled to a surface, where they can be used as electrochemical gas sensors. Given their versatility, they have not escaped their role as key players in chemical studies involving HNO. This Account presents the research performed during the last 10 years in our group concerning azanone reactions with iron, manganese, and cobalt porphyrins. We begin by describing their HNO trapping capabilities, which result in formation of the corresponding nitrosyl complexes. Kinetic and mechanistic studies of these reactions show two alternative operating mechanisms: reaction of the metal center with HNO or with the donor. Moreover, we have also shown that azanone can be stabilized by coordination to iron porphyrins using electron-attracting substituents attached to the porphyrin ring, which balance the negatively charged NO¯. Second, we

  13. Chemical and biological methods to evaluate the availability of heavy metals in soils of the Siena urban area (Italy).

    PubMed

    Nannoni, Francesco; Protano, Giuseppe

    2016-10-15

    A biogeochemistry field study was conducted in the Siena urban area (Italy) with the main objective of establishing the relationship between available amounts of heavy metals in soil assessed by a chemical method (soil fractionation) and bioavailability assessed by a biological method (bioaccumulation in earthworm tissues). The total content of traffic-related (Cd, Cu, Pb, Sb, Zn) and geogenic (Co, Cr, Ni, U) heavy metals in uncontaminated and contaminated soils and their concentrations in soil fractions and earthworms were used for this purpose. The bioavailability of heavy metals assessed by earthworms did not always match the availability defined by soil fractionation. Earthworms were a good indicator to assess the bioavailability of Pb and Sb in soil, while due to physiological mechanisms of regulation and excretion, Cd, Cu and Zn tissue levels in these invertebrates gave misleading estimates of their bioavailable pool. No relationship was identified between chemical and biological availability for the geogenic heavy metals, characterized by a narrow range of total contents in soil. The study highlighted that chemical and biological methods should be combined to provide more complete information about heavy element bioavailability in soils. PMID:27281550

  14. A new window towards multidimensional sensing of transition metal cations through dual mode sensing ability of N-benzyl-(3-hydoxy-2-naphthalene): Emission enhancement coupled remarkable spectral shift

    NASA Astrophysics Data System (ADS)

    Paul, Bijan Kumar; Mahanta, Subrata; Singh, Rupashree Balia; Guchhait, Nikhil

    2011-06-01

    A structurally simple Schiff base N-benzyl-(3-hydroxy-2-naphthalene) (NBHN32) has been synthesized and characterized by 1H NMR, 13C NMR, and DEPT spectroscopy. The photophysical behaviour of NBHN32 in response to the presence of various transition metal cations has been explored by means of steady-state absorption, emission and time-resolved emission spectroscopy techniques. Efficient through space intramolecular photoinduced electron transfer (PET) between the naphthalene fluorophore and the imine group has been argued for extremely low fluorescence yield of NBHN32 compared to the parent molecule 3-hydroxy-2-naphthaldehyde (HN32) containing the same fluorophore but lacking the receptor moiety. Transition metal ion-induced emission enhancement is thus addressed on the lexicon of perturbation of the PET by the metal ions. Apart from fluorescence enhancement, transition metal ion imparts remarkable shift of the emission maxima of NBHN32, which is another unique aspect on the proposed ability of NBHN32 to function as a fluorescence chemosensor.

  15. Design of Multichannel Osmium-Based Metalloreceptor for Anions and Cations by Taking Profit from Metal-Ligand Interaction and Construction of Molecular Keypad Lock and Memory Device.

    PubMed

    Karmakar, Srikanta; Mardanya, Sourav; Pal, Poulami; Baitalik, Sujoy

    2015-12-21

    A polypyridylimidazole-based bifunctional Os(II) complex of the type [(bpy)2Os(tpy-Hbzim-dipy)](ClO4)2 (1), where tpy-Hbzim-dipy = 4'-[4-(4,5-dipyridin-2-yl-1H-imidazol-2-yl)-phenyl]-2,2';6',2″-terpyridine and bpy = 2,2'-bipyridine, has been synthesized and structurally characterized for the construction of multifunctional logic devices. After coordination of an [Os(bpy)2](2+) unit to one of the two bidentate chelating sites, the complex offers a terpyridine motif for binding with cationic guests and an imidazole moiety for interacting with selective anionic species. Consequently, the anion- and cation-binding aspects of the metallorecptor were examined in solution and in the solid state by different spectroscopic and electrochemical methods. The complex behaves as a bifunctional sensor for F(-), AcO(-), CN(-), Fe(2+), and Cu(2+) ions in acetonitrile, whereas it is a highly selective chromogenic chemosensor for only CN(-) and Fe(2+) ions in water. Based on various output signals with a particular set of anionic and cationic inputs, the complex mimics the functions of two-input INHIBIT, OR, NOR, and XNOR logic gates, as well as three-input NOR logic behavior. More importantly, the complicated functions of a keypad lock and memory device were also nicely demonstrated by the complex. Finally, density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations also provide a rationale for properly understanding and interpreting the experimentally observed results. PMID:26687380

  16. A Study of Different Doped Metal Cations on the Physicochemical Properties and Catalytic Activities of Ce20 M1 Ox (M=Zr, Cr, Mn, Fe, Co, Sn) Composite Oxides for Nitric Oxide Reduction by Carbon Monoxide.

    PubMed

    Deng, Changshun; Li, Min; Qian, Junning; Hu, Qun; Huang, Meina; Lin, Qingjin; Ruan, Yongshun; Dong, Lihui; Li, Bin; Fan, Minguang

    2016-08-01

    This work is mainly focused on investigating the effects of different doped metal cations on the formation of Ce20 M1 Ox (M=Zr, Cr, Mn, Fe, Co, Sn) composite oxides and their physicochemical and catalytic properties for NO reduction by CO as a model reaction. The obtained samples were characterized by using N2 physisorption, X-ray diffraction, laser Raman spectroscopy, UV/Vis diffuse reflectance spectroscopy, inductively coupled plasma atomic emission spectroscopy, X-ray photoelectron spectroscopy, temperature-programmed reduction by hydrogen and by oxygen (H2 -TPR and O2 -TPD), in situ diffuse reflectance infrared Fourier transform spectroscopy, and the NO+CO model reaction. The results imply that the introduction of M(x+) into the lattice of CeO2 increases the specific surface area and pore volume, especially for variable valence metal cations, and enhances the catalytic performance to a great extent. In this regard, increases in the oxygen vacancies, reduction properties, and chemisorbed O2 (-) (and/or O(-) ) species of these Ce20 M1 Ox composite oxides (M refers to variable valence metals) play significant roles in this reaction. Among the samples, Ce20 Cr1 Ox exhibited the best catalytic performance, mainly because it has the best reducibility and more chemisorbed oxygen, and significant reasons for these attributes may be closely related to favorable synergistic interactions of the vacancies and near-surface Ce(3+) and Cr(3+) . Finally, a possible reaction mechanism was tentatively proposed to understand the reactions. PMID:27435470

  17. A metabolomic study on the biological effects of metal pollutions in oysters Crassostrea sikamea.

    PubMed

    Ji, Chenglong; Wang, Qing; Wu, Huifeng; Tan, Qiaoguo; Wang, Wen-Xiong

    2016-01-15

    Metal pollution has become a great threat to organisms in the estuaries in South China. In the present study, the oysters Crassostrea sikamea were collected from one clean (Jiuzhen) and five metal polluted sites (Baijiao, Fugong, Gongqian, Jinshan and Songyu). The tissue metal concentrations in oysters indicated that the five metal sites were polluted by several metals, including Cr, Ni, Co, Cu, Zn, Ag, Cd and Pb with different patterns. Especially, Cu and Zn were the major contaminants in Baijiao, Fugong and Jinshan sites. The metabolic responses in oysters C. sikamea indicated that the metal pollutions in BJ, FG, JS and SY sites induced disturbances in osmotic regulation and energy metabolism via different metabolic pathways. However, the metal pollution in GQ site mainly influenced the osmotic regulation in the oysters C. sikamea. This study demonstrates that NMR-based metabolomics is useful to characterize metabolic responses induced by metal pollution. PMID:26616746

  18. Biosorption of heavy metals in a photo-rotating biological contactor--a batch process study.

    PubMed

    Orandi, Sanaz; Lewis, David M

    2013-06-01

    Metal removal potential of indigenous mining microorganisms from acid mine drainage (AMD) has been well recognised in situ at mine sites. However, their removal capacity requires to be investigated for AMD treatment. In the reported study, the capacity of an indigenous AMD microbial consortium dominated with Klebsormidium sp., immobilised in a photo-rotating biological contactor (PRBC), was investigated for removing various elements from a multi-ion synthetic AMD. The synthetic AMD was composed of major (Cu, Mn, Mg, Zn, Ca, Na, Ni) and trace elements (Fe, Al, Cr, Co, Se, Ag, Mo) at initial concentrations of 2 to 100 mg/L and 0.005 to 1 mg/L, respectively. The PRBC was operated for two 7-day batch periods under pH conditions of 3 and 5. The maximum removal was observed after 3 and 6 days at pH 3 and 5, respectively. Daily water analysis data demonstrated the ability of the algal-microbial biofilm to remove an overall average of 25-40 % of the major elements at pH 3 in the order of Na > Cu > Ca > Mg > Mn > Ni > Zn, whereas a higher removal (35-50 %) was observed at pH 5 in the order of Cu > Mn > Mg > Ca > Ni > Zn > Na. The removal efficiency of the system for trace elements varied extensively between 3 and 80 % at the both pH conditions. The batch data results demonstrated the ability for indigenous AMD algal-microbial biofilm for removing a variety of elements from AMD in a PRBC. The work presents the potential for further development and scale-up to use PBRC inoculated with AMD microorganisms at mine sites for first or secondary AMD treatment. PMID:23011347

  19. Femtosecond pulse laser ablation of metallic, semiconducting, ceramic, and biological materials

    NASA Astrophysics Data System (ADS)

    Kautek, Wolfgang; Krueger, Joerg

    1994-09-01

    Production of holes and grooves of < 30 micrometers diameter with high aspect ratio value is a delicate task either for mechanical tools, or for conventional nanosecond pulse lasers like e.g. pulsed Nd:YAG or excimer lasers. They later tend to cause microcracks extending from an annular melting zone, or substantial disruption, respectively. Experimental results are presented which demonstrate that the development of intense ultrashort pulse laser systems (>> 1012 W cm-2, (tau) < 1 ps) opens up possibilities for materials processing by cold plasma generation and ablation of metals, semiconductors, ceramics, composites, and biological materials. A femtosecond and a nanosecond dye laser with pulse durations of 300 fs (< 200 (mu) J) and 7 ns (< 10 mJ), and center wavelengths at 612 and 600 nm, respectively, both focused on an area of the order of 10-5 cm2, have been applied either to absorbing substrates, like polycrystalline gold, silicon (111), aluminum nitride ceramics, or transparent materials, like synthetic and human dental hydroxyapatite composites, bone material, and human cornea transplants. The fs-laser generates its own absorption in transparent materials by a multiphoton absorption process, and thus forces the absorption of visible radiation. Because the time is too short (< ps) for significant transport of mass and energy, the beam interaction generally results in the formation of a thin plasma layer of approximately solid state density. Only after the end of the subpicosecond laser pulse, it expands rapidly away from the surface without any light absorption and further plasma heating. Therefore, energy transfer (heat and impulse) to the target material, and thermal and mechanical disruption are minimized. In contrast to heat- affected zones (HAZ's) generated by conventional nanosecond pulse lasers of the order of 1 - 10 micrometers , HAZ's of less than 0.02 micrometers were observed.

  20. The relationship between molecular structure and biological activity of alkali metal salts of vanillic acid: Spectroscopic, theoretical and microbiological studies

    NASA Astrophysics Data System (ADS)

    Świsłocka, Renata; Piekut, Jolanta; Lewandowski, Włodzimierz

    In this paper we investigate the relationship between molecular structure of alkali metal vanillate molecules and their antimicrobial activity. To this end FT-IR, FT-Raman, UV absorption and 1H, 13C NMR spectra for lithium, sodium, potassium, rubidium and caesium vanillates in solid state were registered, assigned and analyzed. Microbial activity of studied compounds was tested against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Proteus vulgaris, Bacillus subtilis and Candida albicans. In order to evaluate the dependence between chemical structure and biological activity of alkali metal vanillates the statistical analysis was performed for selected wavenumbers from FT-IR spectra and parameters describing microbial activity of vanillates. The geometrical structures of the compounds studied were optimized and the structural characteristics were determined by density functional theory (DFT) using at B3LYP method with 6-311++G** as basis set. The obtained statistical equations show the existence of correlation between molecular structure of vanillates and their biological properties.

  1. Cadmium accumulation by a Citrobacter sp. immobilized on gel and solid supports: applicability to the treatment of liquid wastes containing heavy metal cations

    SciTech Connect

    Macaskie, L.E.; Wates, J.M.; Dean, A.C.R.

    1987-01-01

    Polyacrylamide gel-immobilized cells of a Citrobacter sp. removed cadmium from flows supplemented with glycerol 2-phosphate, the metal uptake mechanism being mediated by the activity of a cell-bound phosphatase that precipitates liberated inorganic phosphate with heavy metals at the cell surface. The constraints of elevated flow rate and temperature were investigated and the results discussed in terms of the kinetics of immobilized enzymes. Loss in activity with respect to cadmium accumulation but not inorganic phosphate liberation was observed at acid pH and was attributed to the pH-dependent solubility of cadmium phosphate. Similarly high concentrations of chloride ions, and traces of cyanide inhibited cadmium uptake and this was attributed to the ability of these anions to complex heavy metals, especially the ability of CN/sup -/ to form complex anions with Cd/sup 2 +/. The data are discussed in terms of the known chemistry of chloride and cyanide-cadmium complexes and the relevance of these factors in the treatment of metal-containing liquid wastes is discussed. The cells immobilized in polyacrylamide provided a convenient small-scale laboratory model system. It was found that the Citrobacter sp. could be immobilized on glass supports with no chemical treatment or modification necessary. Such cells were also effective in metal accumulation and a prototype system more applicable to the treatment of metal-containing streams on a larger scale is described.

  2. Quantifying restoration success and recovery in a metal-polluted stream: A 17-year assessment of physicochemical and biological responses

    USGS Publications Warehouse

    Clements, W.H.; Vieira, N.K.M.; Church, S.E.

    2010-01-01

    Evaluating the effectiveness of stream restoration is often challenging because of the lack of pre-treatment data, narrow focus on physicochemical measures and insufficient post-restoration monitoring. Even when these fundamental elements are present, quantifying restoration success is difficult because of the challenges associated with distinguishing treatment effects from seasonal variation, episodic events and long-term climatic changes.2. We report results of one of the most comprehensive and continuous records of physical, chemical and biological data available to assess restoration success for a stream ecosystem in North America. Over a 17 year period we measured seasonal and annual changes in metal concentrations, physicochemical characteristics, macroinvertebrate communities, and brown trout Salmo trutta populations in the Arkansas River, a metal-contaminated stream in Colorado, USA.3. Although we observed significant improvements in water quality after treatment, the effectiveness of restoration varied temporally, spatially and among biological response variables. The fastest recovery was observed at stations where restoration eliminated point sources of metal contamination. Recovery of macroinvertebrates was significantly delayed at some stations because of residual sediment contamination and because extreme seasonal and episodic variation in metal concentrations prevented recolonization by sensitive species. Synthesis and applications. Because recovery trajectories after the removal of a stressor are often complex or nonlinear, long-term studies are necessary to assess restoration success within the context of episodic events and changes in regional climate. The observed variation in recovery among chemical and biological endpoints highlights the importance of developing objective criteria to assess restoration success. Although the rapid response of macroinvertebrates to reduced metal concentrations is encouraging, we have previously demonstrated that

  3. Novel biological sources of electrochemiluminescence and potential applications to metals detection

    NASA Astrophysics Data System (ADS)

    Bruno, John G.; Collard, Sneed B.; Kuch, David J.; Cornette, Jimmy C.

    1996-11-01

    Electrochemiluminescence (ECL) is an electrochemical means of generating light from certain organic-metal complexes (e.g., Cr, Os, or Ru with bipyridine) and other types of molecules. Thus, it may be possible to develop an ECL-based metals sensor or biosensor consisting of organic molecules coated onto electrodes which emit light only upon complexation of particular metal ions and application of a small voltage. Toxic metals in water sources are of environmental concern. Some marine invertebrates, such as tunicates (i.e., `sea squirts') and molluscs, are noted for their ability to concentrate toxic metals as much as 100 million-fold over ambient seawater concentrations. In the present work, extracts from a tunicate species, as well as synthetic tunicate blood pigments or `tunichromes', oysters, and other organisms are examined for intrinsic ECL in the presence and absence of various metal ions. Results suggest a promising novel, potentially sensitive, and specific means for metal ion detection based on ECL.

  4. Soil Cation Status in Southern California: Interactions of Vehicular Emissions

    NASA Astrophysics Data System (ADS)

    Rossi, R.; Bain, D. J.; Jenerette, D.; Clarke, L. W.

    2012-12-01

    Roadside soils are often enriched in trace metals due to vehicular deposition. However, less attention is given to base cation pools in roadside soils. Relatively high loadings of nitrate from vehicular exhaust should acidify roadside soils, potentially mobilizing cationic species by displacing them from soil exchange sites. In contrast, weathering of road materials can contribute substantial amounts of these cations to the same soils, potentially replenishing cation pools. Base cations are essential nutrients and these dynamics may alter ecosystem processes in near-road environments. Metal concentrations in park and garden soils collected from Southern California (Los Angeles and Riverside Counties) were examined across gradients of road network intensity, climate and geology. In these samples, base cation concentrations decrease in areas of denser road networks. Base cation concentrations also decrease with distance from the road, with near-road samples relatively depleted in base cation concentrations. In addition, base cation concentrations are associated with traffic flux density, with exchange pools decreasing near heavily trafficked areas. These relationships suggest road activity is mobilizing cations, depleting near-road soils of essential nutrient pools, despite road material weathering. This depletion of soil nutrients from exchange pools in roadside soils likely influences local ecological function in unpredictable ways. This observation lays the groundwork for continued characterization of soil metal processes in the increasingly common roadside environment.

  5. Influence of Nano-Crystal Metals on Texture and Biological Properties of Water Soluble Polysaccharides of Medicinal Plants

    NASA Astrophysics Data System (ADS)

    Churilov, G.; Ivanycheva, J.; Kiryshin, V.

    2015-11-01

    When treating the plants seeds with nano-materials there are some quality and quantity changes of polysaccharides, the molecular mass increase and monosaccharides change that leads to the increase of physiological and pharmacological activity of carbohydrates got from medicinal plants. We have got water soluble polysaccharides and nano-metals combinations containing 0.000165-0.000017 mg/dm3 of the metal. In a case of induced anemia the blood composition has practically restored on the 10th day of the treatment with nanocomposites. The use of pectin polysaccharides (that are attributed to modifiers of biological respond) to get nano-structured materials seems to be actual relative to their physiological activity (radio nuclides persorption, heavy metals ions, bacteria cells and their toxins; lipids metabolism normalization; bowels secreting and motor functions activation and modulation of the endocrine system.

  6. Comparative analysis of cation/proton antiporter superfamily in plants

    SciTech Connect

    Ye, Chuyu; Yang, Xiaohan; Xia, Xinli; Yin, Weilun

    2013-01-01

    The cation/proton antiporter superfamily is associated with the transport of monovalent cations across membranes. This superfamily was annotated in the Arabidopsis genome and some members were functionally characterized. In the present study, a systematic analysis of the cation/proton antiporter genes in diverse plant specieswas reported.We identified 240 cation/proton antiporters in alga, moss, and angiosperm. A phylogenetic tree was constructed showing these 240members are separated into three families, i.e., Na+/H+ exchangers, K+ efflux antiporters, and cation/H+ exchangers. Our analysis revealed that tandem and/or segmental duplications contribute to the expansion of cation/H+ exchangers in the examined angiospermspecies. Sliding windowanalysis of the nonsynonymous/synonymous substitution ratios showed some differences in the evolutionary fate of cation/proton antiporter paralogs. Furthermore, we identified over-represented motifs among these 240 proteins and foundmostmotifs are family specific, demonstrating diverse evolution of the cation/proton antiporters among three families. In addition, we investigated the co-expressed genes of the cation/proton antiporters in Arabidopsis thaliana. The results showed some biological processes are enriched in the co-expressed genes, suggesting the cation/proton antiporters may be involved in these biological processes. Taken together, this study furthers our knowledge on cation/proton antiporters in plants.

  7. The cubyl cation rearrangements.

    PubMed

    Jalife, Said; Mondal, Sukanta; Cabellos, Jose Luis; Martinez-Guajardo, Gerardo; Fernandez-Herrera, Maria A; Merino, Gabriel

    2016-02-25

    Born-Oppenheimer molecular dynamics simulations and high-level ab initio computations predict that the cage-opening rearrangement of the cubyl cation to the 7H(+)-pentalenyl cation is feasible in the gas phase. The rate-determining step is the formation of the cuneyl cation with an activation barrier of 25.3 kcal mol(-1) at the CCSD(T)/def2-TZVP//MP2/def2-TZVP level. Thus, the cubyl cation is kinetically stable enough to be formed and trapped at moderate temperatures, but it may be rearranged at higher temperatures. PMID:26880646

  8. Noble metals on the nanoscale: optical and photothermal properties and some applications in imaging, sensing, biology, and medicine.

    PubMed

    Jain, Prashant K; Huang, Xiaohua; El-Sayed, Ivan H; El-Sayed, Mostafa A

    2008-12-01

    Noble metal nanostructures attract much interest because of their unique properties, including large optical field enhancements resulting in the strong scattering and absorption of light. The enhancement in the optical and photothermal properties of noble metal nanoparticles arises from resonant oscillation of their free electrons in the presence of light, also known as localized surface plasmon resonance (LSPR). The plasmon resonance can either radiate light (Mie scattering), a process that finds great utility in optical and imaging fields, or be rapidly converted to heat (absorption); the latter mechanism of dissipation has opened up applications in several new areas. The ability to integrate metal nanoparticles into biological systems has had greatest impact in biology and biomedicine. In this Account, we discuss the plasmonic properties of gold and silver nanostructures and present examples of how they are being utilized for biodiagnostics, biophysical studies, and medical therapy. For instance, taking advantage of the strong LSPR scattering of gold nanoparticles conjugated with specific targeting molecules allows the molecule-specific imaging and diagnosis of diseases such as cancer. We emphasize in particular how the unique tunability of the plasmon resonance properties of metal nanoparticles through variation of their size, shape, composition, and medium allows chemists to design nanostructures geared for specific bio-applications. We discuss some interesting nanostructure geometries, including nanorods, nanoshells, and nanoparticle pairs, that exhibit dramatically enhanced and tunable plasmon resonances, making them highly suitable for bio-applications. Tuning the nanostructure shape (e.g., nanoprisms, nanorods, or nanoshells) is another means of enhancing the sensitivity of the LSPR to the nanoparticle environment and, thereby, designing effective biosensing agents. Metal nanoparticle pairs or assemblies display distance-dependent plasmon resonances as a

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

    SciTech Connect

    Skomski, Daniel; Tempas, Christopher D.; Bukowski, Gregory S.; Smith, Kevin A.; Tait, Steven L.

    2015-03-14

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

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

    NASA Astrophysics Data System (ADS)

    Skomski, Daniel; Tempas, Christopher D.; Bukowski, Gregory S.; Smith, Kevin A.; Tait, Steven L.

    2015-03-01

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

  11. Biological interaction between transition metals (Ag, Cd and Hg), selenide/sulfide and selenoprotein P.

    PubMed

    Sasakura, C; Suzuki, K T

    1998-09-01

    The interaction between transition metals (Ag+, Cd2+ and Hg2+) and selenium (Se) in the bloodstream was studied in vitro by means of the HPLC--inductively coupled argon plasma-mass spectrometry (ICP MS) method. Transition metal ions and selenide (produced in vitro from selenite in the presence of glutathione) or sulfide (Na2S) formed a (metal-Se/S) complex, which then bound to a plasma protein, selenoprotein P (Sel P), to form a ternary complex, (metal-Se/S)-Sel P. The molar ratios of metals to Se were 1:1 for Hg/Se and Cd/Se, but either 1:1 or 2:1 for Ag/Se, depending on the ratio of their doses. The results indicate that the interaction between transition metals and Se occurs through the general mechanism, i.e., transition metal ions and selenide form the unit complex (metal-Se)n, and then the complex binds to selenoprotein P to form the ternary complex ¿(metal-Se)n¿m--seleno-protein P in the bloodstream. PMID:9833321

  12. Growth of Novel Ceramic Layers on Metals via Chemical and Heat Treatments for Inducing Various Biological Functions.

    PubMed

    Kokubo, Tadashi; Yamaguchi, Seiji

    2015-01-01

    The present authors' systematic studies on growth of novel ceramic layers on Ti metal and its alloys by chemical and heat treatments for inducing bone-bonding bioactivity and some other biological functions are reviewed. Ti metal formed an apatite on its surface in a simulated body fluid, when heat-treated after exposure to strong acid solutions to form rutile surface layer, or to strong alkali solutions to form sodium titanate surface layer. Both types of Ti metal tightly bonded to the living bone. The alkali and heat treatment was applied to the surface Ti metal of an artificial hip joint and successfully used in the clinic since 2007. The acid and heat treatments was applied to porous Ti metal to induce osteoconductivity as well as osteoinductivity. The resulting product was successfully used in clinical trials for spinal fusion devices. For the Ti-based alloys, the alkali and heat treatment was little modified to form calcium titanate surface layer. Bone-growth promoting Mg, Sr, and Zn ions as well as the antibacterial Ag ion were successfully incorporated into the calcium titanate layer. PMID:26579517

  13. Growth of Novel Ceramic Layers on Metals via Chemical and Heat Treatments for Inducing Various Biological Functions

    PubMed Central

    Kokubo, Tadashi; Yamaguchi, Seiji

    2015-01-01

    The present authors’ systematic studies on growth of novel ceramic layers on Ti metal and its alloys by chemical and heat treatments for inducing bone-bonding bioactivity and some other biological functions are reviewed. Ti metal formed an apatite on its surface in a simulated body fluid, when heat-treated after exposure to strong acid solutions to form rutile surface layer, or to strong alkali solutions to form sodium titanate surface layer. Both types of Ti metal tightly bonded to the living bone. The alkali and heat treatment was applied to the surface Ti metal of an artificial hip joint and successfully used in the clinic since 2007. The acid and heat treatments was applied to porous Ti metal to induce osteoconductivity as well as osteoinductivity. The resulting product was successfully used in clinical trials for spinal fusion devices. For the Ti-based alloys, the alkali and heat treatment was little modified to form calcium titanate surface layer. Bone-growth promoting Mg, Sr, and Zn ions as well as the antibacterial Ag ion were successfully incorporated into the calcium titanate layer. PMID:26579517

  14. Assigning Oxidation States to Some Metal Dioxygen Complexes of Biological Interest.

    ERIC Educational Resources Information Center

    Summerville, David A.; And Others

    1979-01-01

    The bonding of dioxygen in metal-dioxygen complexes is discussed, paying particular attention to the problems encountered in assigning conventional oxidation numbers to both the metal center and coordinated dioxygen. Complexes of iron, cobalt, chromium, and manganese are considered. (BB)

  15. SYNTHESIS OF THERMALLY STABLE CARBOXYMETHYL CELLULOSE/METAL BIODEGRADABLE NANOCOMPOSITES FOR POTENTIAL BIOLOGICAL APPLICATIONS

    EPA Science Inventory

    A green approach is described that generates bulk quantities of nanocomposites containing transition metals such as Cu, Ag, In and Fe at room temperature using a biodegradable polymer carboxymethyl cellulose (CMC) by reacting respective metal salts with sodium salt of CMC in aqu...

  16. WATER QUALITY, MERCURY, AND HEAVY METAL DEPOSITION STUDIES IN BIOLOGICAL SPECIMENS AND SEDIMENTS FOR ECOLOGICAL BASELINE DATA IN THE ISLAND PARK WATERWAYS SYSTEM, 1973

    EPA Science Inventory

    The water quality, mercury, and heavy metal deposition in biological specimens from the Island Park waterways (17040202) were measured to establish ecological baseline data. Neutron activation analysis was used to identify quantitatively and qualitatively approximately 20 differ...

  17. Atypical behavior in the electron capture induced dissociation of biologically relevant transition metal ion complexes of the peptide hormone oxytocin

    NASA Astrophysics Data System (ADS)

    Kleinnijenhuis, Anne J.; Mihalca, Romulus; Heeren, Ron M. A.; Heck, Albert J. R.

    2006-07-01

    Doubly protonated ions of the disulfide bond containing nonapeptide hormone oxytocin and oxytocin complexes with different transition metal ions, that have biological relevance under physiological conditions, were subjected to electron capture dissociation (ECD) to probe their structural features in the gas phase. Although, all the ECD spectra were strikingly different, typical ECD behavior was observed for complexes of the nonapeptide hormone oxytocin with Ni2+, Co2+ and Zn2+, i.e., abundant c/z' and a'/y backbone cleavages and ECD characteristic S-S and S-C bond cleavages were observed. We propose that, although in the oxytocin-transition metal ion complexes the metal ions serve as the main initial capture site, the captured electron is transferred to other sites in the complex to form a hydrogen radical, which drives the subsequent typical ECD fragmentations. The complex of oxytocin with Cu2+ displayed noticeably different ECD behavior. The fragment ions were similar to fragment ions typically observed with low-energy collision induced dissociation (CID). We propose that the electrons captured by the oxytocin-Cu2+ complex might be favorably involved in reducing the Cu2+ metal ion to Cu+. Subsequent energy redistribution would explain the observed low-energy CID-type fragmentations. Electron capture resulted also in quite different specific cleavage sites for the complexes of oxytocin with Ni2+, Co2+ and Zn2+. This is an indication for structural differences in these complexes possibly linked to their significantly different biological effects on oxytocin-receptor binding, and suggests that ECD may be used to study subtle structural differences in transition metal ion-peptide complexes.

  18. Structures of Metal-Substituted Human Histone Deacetylase 8 Provide Mechanistic Inferences on Biological Function

    SciTech Connect

    Dowling, Daniel P.; Gattis, Samuel G.; Fierke, Carol A.; Christianson, David W.

    2010-08-23

    The metal-dependent histone deacetylases (HDACs) adopt an {alpha}/{beta} protein fold first identified in rat liver arginase. Despite insignificant overall amino acid sequence identity, these enzymes share a strictly conserved metal binding site with divergent metal specificity and stoichiometry. HDAC8, originally thought to be a Zn{sup 2+}-metallohydrolase, exhibits increased activity with Co{sup 2+} and Fe{sup 2+} cofactors based on k{sub cat}/K{sub M} (Gantt, S. L., Gattis, S. G., and Fierke, C. A. (2006) Biochemistry 45, 6170-6178). Here, we report the first X-ray crystal structures of metallo-substituted HDAC8, Co{sup 2+}-HDAC8, D101L Co{sup 2+}-HDAC8, D101L Mn{sup 2+}-HDAC8, and D101L Fe{sup 2+}-HDAC8, each complexed with the inhibitor M344. Metal content of protein samples in solution is confirmed by inductively coupled plasma mass spectrometry. For the crystalline enzymes, peaks in Bijvoet difference Fourier maps calculated from X-ray diffraction data collected near the respective elemental absorption edges confirm metal substitution. Additional solution studies confirm incorporation of Cu{sup 2+}; Fe{sup 3+} and Ni{sup 2+} do not bind under conditions tested. The metal dependence of the substrate K{sub M} values and the K{sub i} values of hydroxamate inhibitors that chelate the active site metal are consistent with substrate-metal coordination in the precatalytic Michaelis complex that enhances catalysis. Additionally, although HDAC8 binds Zn{sup 2+} nearly 106-fold more tightly than Fe{sup 2+}, the affinities for both metal ions are comparable to the readily exchangeable metal concentrations estimated in living cells, suggesting that HDAC8 could bind either or both Fe{sup 2+} or Zn{sup 2+} in vivo.

  19. Selective trans-membrane transport of alkali and alkaline earth cations through graphene oxide membranes based on cation-π interactions.

    PubMed

    Sun, Pengzhan; Zheng, Feng; Zhu, Miao; Song, Zhigong; Wang, Kunlin; Zhong, Minlin; Wu, Dehai; Little, Reginald B; Xu, Zhiping; Zhu, Hongwei

    2014-01-28

    Graphene and graphene oxide (G-O) have been demonstrated to be excellent filters for various gases and liquids, showing potential applications in areas such as molecular sieving and water desalination. In this paper, the selective trans-membrane transport properties of alkali and alkaline earth cations through a membrane composed of stacked and overlapped G-O sheets ("G-O membrane") are investigated. The thermodynamics of the ion transport process reveal that the competition between the generated thermal motions and the interactions of cations with the G-O sheets results in the different penetration behaviors to temperature variations for the considered cations (K(+), Mg(2+), Ca(2+), and Ba(2+)). The interactions between the studied metal atoms and graphene are quantified by first-principles calculations based on the plane-wave-basis-set density functional theory (DFT) approach. The mechanism of the selective ion trans-membrane transportation is discussed further and found to be consistent with the concept of cation-π interactions involved in biological systems. The balance between cation-π interactions of the cations considered with the sp(2) clusters of G-O membranes and the desolvation effect of the ions is responsible for the selectivity of G-O membranes toward the penetration of different ions. These results help us better understand the ion transport process through G-O membranes, from which the possibility of modeling the ion transport behavior of cellular membrane using G-O can be discussed further. The selectivity toward different ions also makes G-O membrane a promising candidate in areas of membrane separations. PMID:24401025

  20. Changes of toxic metals during biological stabilization and their potential ecological risk assessment.

    PubMed

    Wang, Hou-cheng; Zeng, Zheng-zhong; Zhang, He-fei; Nan, Zhong-ren

    2015-01-01

    With various disadvantages of pollution control technologies for toxic metal-contaminated soil, we mixed contaminated soil with sludge for in situ composting to stabilize toxic metals, so plants are enriched to take up the toxic metals. When simulating the above, we added toxic metal solution into sewage sludge, and then composed it with steel slag to determine inhibition of the availability of toxic metals. When toxic metals were added into sludge, the potential ecological index and geoaccumulation index of Cd became high while Zn was low. Steel slag had an inhibited availability of Cd, and when the adjunction of steel slag was 7%, the availability of Cd was lowest. Steel slag promoted the availability of Zn, and when the adjunction of steel slag was 27%, the availability of Zn was highest. Results showed that during composting, with increasing steel slag, Cd stabilizing time was reached sooner but Zn stabilizing time was slower, and the availability of all metals became lower. In the end, composting inhibited the potential ecological index of Cd, but it promoted the potential ecological index of Zn. Steel slag promoted the stability of Cd and Zn as Fe/Mn oxide-bound and residual species. Therefore, composting sludge and steel slag could be used as an effective inhibitor of Zn and Cd pollution. PMID:26540531

  1. Specific capture of uranyl protein targets by metal affinity chromatography.

    PubMed

    Basset, Christian; Dedieu, Alain; Guérin, Philippe; Quéméneur, Eric; Meyer, Daniel; Vidaud, Claude

    2008-03-28

    To improve general understanding of biochemical mechanisms in the field of uranium toxicology, the identification of protein targets needs to be intensified. Immobilized metal affinity chromatography (IMAC) has been widely developed as a powerful tool for capturing metal binding proteins from biological extracts. However uranyl cations (UO2(2+)) have particular physico-chemical characteristics which prevent them from being immobilized on classical metal chelating supports. We report here on the first development of an immobilized uranyl affinity chromatography method, based on the cation-exchange properties of aminophosphonate groups for uranyl binding. The cation distribution coefficient and loading capacity on the support were determined. Then the stability of the uranyl-bonded phase under our chromatographic conditions was optimized to promote affinity mechanisms. The successful enrichment of uranyl binding proteins from human serum was then proven using proteomic and mass spectral analysis. PMID:18308325

  2. Biological leaching of heavy metals from a contaminated soil by Aspergillus niger.

    PubMed

    Ren, Wan-Xia; Li, Pei-Jun; Geng, Yong; Li, Xiao-Jun

    2009-08-15

    Bioleaching of heavy metals from a contaminated soil in an industrial area using metabolites, mainly weak organic acids, produced by a fungus Aspergillus niger was investigated. Batch experiments were performed to compare the leaching efficiencies of one-step and two-step processes and to determine the transformation of heavy metal chemical forms during the bioleaching process. After the one or two-step processes, the metal removals were compared using analysis of variance (ANOVA) and least-significance difference (LSD). A. niger exhibits a good potential in generating a variety of organic acids effective for metal solubilisation. Results showed that after the one-step process, maximum removals of 56%, 100%, 30% and 19% were achieved for copper, cadmium, lead and zinc, respectively. After the two-step process, highest removals of 97.5% Cu, 88.2% Cd, 26% Pb, and 14.5% Zn were obtained. Results of sequential extraction showed that organic acids produced by A. niger were effective in removing the exchangeable, carbonate, and Fe/Mn oxide fractions of Cu, Cd, Pb and Zn; and after both processes the metals remaining in the soil were mainly bound in stable fractions. Such a treatment procedure indicated that leaching of heavy metals from contaminated soil using A. niger has the potential for use in remediation of contaminated soils. PMID:19232463

  3. The detection of Sr sputtered from metallic and biological matrices by double-resonant photoionization mass spectrometry

    NASA Astrophysics Data System (ADS)

    Vandeweert, Erno; Bastiaansen, Jeroen; Philipsen, Vicky; Lievens, Peter; Silverans, Roger E.; Telle, Helmut H.

    2001-08-01

    Resonance ionization mass spectrometry (RIMS) was used to obtain isotope and state selective information on Sr sputtered from metallic and biological matrices. In exploratory experiments Sr atoms were sputtered from bulk metal upon impact of 15 keV Ar+ ions, and probed by stepwise resonant ionization using two-color schemes. Efficient ionization schemes were selected to excite ground-state originating atoms into autoionizing states. Cross sections for photoionization were found to be up to the order of 10-15 cm2. The Sr content in bone fragments was probed utilizing these schemes. Even with minimal sample preparation, a detection limit of ±50ppm Sr in the hydroxiapatite-matrix of the bone was demonstrated, with isotope specificity. While this is inferior to detection limits normally associated with RIMS, these preliminary experiments were carried out for sputtering from untreated, non-conducting matrix materials.

  4. Synthesis, characterization and biological activity of transition metal complexes with Schiff bases derived from 2-nitrobenzaldehyde with glycine and methionine

    NASA Astrophysics Data System (ADS)

    Singh, Bibhesh K.; Rajour, Hemant K.; Prakash, Anant

    Schiff bases derived from 2-nitrobenzaldehyde with amino acids (glycine, methionine) and their Co(II), Ni(II) and Cu(II) complexes have been synthesized and characterized by various physico-chemical techniques. From spectral studies, it has been concluded that the ligands acts as bidentate molecule, coordinates metal through azomethine nitrogen and carboxylate oxygen. Mass spectrum explains the successive degradation of the molecular species in solution and justifies ML2 complexes. X-ray powder diffraction helps to determine the cell parameters of the complexes. Molecular structure of the complexes has been optimized by MM2 calculations and suggests a square planar geometry. The ligands and their metal complexes have been tested in vitro against Streptococcus, Staph, Staphylococcus aureus and Escherchia coli bacteria in order to assess their antibacterial potential. The results indicate that the biological activity increases on complexation.

  5. [Biological monitoring of exposure to carcinogenic metallic elements and polycyclic aromatic hydrocarbons in four secondary metallurgical sectors].

    PubMed

    De Palma, G; Corsini, A; Gilberti, E; Gabusi, V; Tagliani, G; Tomasi, C; Gandellini, A; Apostoli, P

    2012-01-01

    This cross-sectional study was aimed at evaluating in a large sample of male foundry workers the current exposure levels to carcinogenic compounds, including metallic elements [arsenic (As), beryllium (Be), cadmium (Cd), chromium (Cr), nickel (Ni)] and aromatic polycyclic hydrocarbons (PAH) by a biological monitoring approach, using validated biomarkers of exposure. Workers were recruited from 15 aluminium, copper alloy, electric steel and cast iron foundries and provided an end-of-shift urine sample to determine urinary concentrations of As, Be, Cd, Cr, Ni and 1-hydroxypyrene (1-OHP). Metallic elements were determined either by inductively coupled plasma mass spectrometry (Be, Cd and Cr) or by atomic absorption spectrometry (As, Ni), whereas 1-OHP was determined by high pressure liquid chromatography with fluorimetric detection. Most of the determinations fell within the laboratory's reference values. Age and lifestyle habits (smoking, alcohol, diet) played a significant interfering role. PMID:23405579

  6. Functional characterisation of metal(loid) processes in planta through the integration of synchrotron techniques and plant molecular biology

    PubMed Central

    Donner, Erica; Punshon, Tracy; Guerinot, Mary Lou; Lombi, Enzo

    2013-01-01

    Functional characterisation of the genes regulating metal(loid) homeostasis in plants is a major focus of crop biofortification, phytoremediation, and food security research. This paper focuses on the potential for advancing plant metal(loid) research by combining molecular biology and synchrotron-based techniques. Recent advances in x-ray focussing optics and fluorescence detection have greatly improved the potential of synchrotron techniques for plant science research, allowing metal(loids) to be imaged in vivo in hydrated plant tissues at sub-micron resolution. Laterally resolved metal(loid) speciation can also be determined. By using molecular techniques to probe the location of gene expression and protein localisation and combining it with this synchrotron-derived data, functional information can be effectively and efficiently assigned to specific genes. This paper provides a review of the state of the art in this field, and provides examples as to how synchrotron-based methods can be combined with molecular techniques to facilitate functional characterisation of genes in planta. PMID:22200921

  7. Prospect of detection and recognition of single biological molecules using ultrafast coherent dynamics in quantum dot-metallic nanoparticle systems

    NASA Astrophysics Data System (ADS)

    Sadeghi, S. M.

    2015-08-01

    Conventional plasmonic sensors are based on the intrinsic resonances of metallic nanoparticles. In such sensors wavelength shift of such resonances are used to detect biological molecules. Recently we introduced ultra-sensitive timedomain nanosensors based on the way variations in the environmental conditions influence coherent dynamics of hybrid systems consisting of metallic nanoparticles and quantum dots. Such dynamics are generated via interaction of these systems with a laser field, generating quantum coherence and coherent exciton-plasmon coupling. These sensors are based on impact of variations of the refractive index of the environment on such dynamics, generating time-dependent changes in the emission of the QDs. In this paper we study the impact of material properties of the metallic nanoparticles on this process and demonstrate the key role played by the design of the quantum dots. We show that Ag nanoparticles, even in a simple spherical shape, may allow these sensors to operate at room temperature, owing to the special properties of quantum dot-metallic nanoparticle systems that may allow coherent effects utilized in such sensors happen in the presence of the ultrafast polarization dephasing of quantum dots.

  8. Model for the field effect from layers of biological macromolecules on the gates of metal-oxide-semiconductor transistors

    NASA Astrophysics Data System (ADS)

    Landheer, D.; Aers, G.; McKinnon, W. R.; Deen, M. J.; Ranuarez, J. C.

    2005-08-01

    The potential diagram for field-effect transistors used to detect charged biological macromolecules in an electrolyte is presented for the case where an insulating cover layer is used over a conventional eletrolyte-insulator metal-oxide-semiconductor (EIMOS) structure to tether or bind the biological molecules to a floating gate. The layer of macromolecules is modeled using the Poisson-Boltzmann equation for an ion-permeable membrane. Expressions are derived for the charges and potentials in the EIMOS and electrolyte-insulator-semiconductor structures, including the membrane and electrolyte. Exact solutions for the potentials and charges are calculated using numerical algorithms. Simple expressions for the response are presented for low solution potentials when the Donnan potential is approached in the bulk of the membrane. The implications of the model for the small-signal equivalent circuit and the noise analysis of these structures are discussed.

  9. Innate cation sensitivity in a semiconducting polymer.

    PubMed

    Althagafi, Talal M; Algarni, Saud A; Grell, Martin

    2016-09-01

    Water-gated organic thin film transistors (OTFTs) using the hole transporting semiconducting polymer, poly(2,5-bis(3-hexadecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT), show an innate response of their threshold voltage to the addition of divalent metal cations to the gating water, without deliberately introducing an ion-sensitive component. A similar threshold response is shown for several divalent cations, but is absent for monovalent cations. Response is absent for transistors using the inorganic semiconductor ZnO, or the similar organic semiconductor poly(3-hexylthiophene) (rrP3HT), instead of PBTTT. We assign innate cation sensitivity to residues of the organometallic Pd(0) complex used as catalyst in PBTTT synthesis which bears strong resemblance to typical metal chelating agents. Organometallic Pd(0) residues are absent from ZnO, and also from rrP3HT which is polymerised with a different type of catalyst. However, when Pd(0) complex is deliberately added to rrP3HT casting solutions, resulting OTFTs also display threshold response to a divalent cation. PMID:27343580

  10. Bioavailability of biologically sequestered cadmium and the implications of metal detoxification

    USGS Publications Warehouse

    Wallace, W.G.; Lopez, G.R.

    1997-01-01

    The deposit-feeding oligochaete Limnodrilus hoffmeisteri possesses metallothionein-like proteins and metal-rich granules for storing and detoxifying cadmium (Cd). In this study we investigated the bioavailability of Cd sequestered within this oligochaete by conducting feeding experiments with 109Cd-labeled oligochaetes and the omnivorous grass shrimp Palaemonetes pugio. We also make predictions on Cd trophic transfer based on oligochaete subcellular Cd distributions and absorption efficiencies of Cd by shrimp Cytosol [including metallothionein-like proteins and other proteins) and a debris fraction (including metal-rich granules and tissue fragments) isolated from homogenized 109Cd-labeled oligochaetes were embedded in gelatin and fed to shrimp. The 109Cd absorption efficiencies of shrimp fed these subcellular fractions were 84.8 and 48.6%, respectively, and were significantly different (p < 0.001), indicating that 109Cd bound in these fractions was not equally available to a predator. Mass balance equations demonstrate that shrimp fed whole worms absorb 61.5% of the ingested 109Cd, an absorption efficiency similar to that obtained experimentally (57.1%). Furthermore, the majority of the absorbed 109Cd comes from the fraction containing metallothionein-like proteins (i.e. cytosol). 109Cd absorbed from the debris fraction probably comes from the digestion of tissue fragments, rather than metal-rich granules. The ecological significance of these findings is that prey detoxification mechanisms may mediate the bioreduction or bioaccumulation of toxic metals along fond chains by altering metal bioavailability. Another important finding is that trophic transfer of metal can be predicted based on the subcellular metal distribution of prey.

  11. Activation of X-H and X-D bonds (X = O, N, C) by alkaline-earth metal monoxide cations: experiment and theory.

    PubMed

    Bozović, Andrea; Bohme, Diethard K

    2009-07-28

    Experimental investigations are reported for reactions of MO (+) (M = Ca, Sr, and Ba) with elemental hydrides water, ammonia and methane proceeding in the gas phase at 295 +/- 3 K in helium buffer gas at a pressure of 0.35 +/- 0.01 Torr. Measurements were taken with an inductively-coupled plasma/selected-ion flow tube (ICP/SIFT) tandem mass spectrometer and a novel electrospray ion source/ion selection quadrupole/selected-ion flow tube/triple quadrupole (ESI/qQ/SIFT/QqQ) mass spectrometer. All three alkaline-earth metal oxide ions exclusively abstract a H-atom from the three hydrides with rate coefficients > 1 x 10(-11) cm(3) molecule(-1) s(-1). Formation of metal hydroxide ion was followed by sequential addition of water or ammonia, but not methane. Density functional calculations have provided potential energy surfaces for the X-H bond activations leading to H-atom abstraction as well as those for O-atom transfer and H(2)O elimination (with ammonia and methane). A comparison of experimental and theoretical isotope effects points toward a mechanism involving the direct atom transfer from XH and XD to O in MO (+)via a three-centered transition structure. PMID:19588017

  12. Reduction by monovalent zinc, cadmium, and nickel cations

    NASA Technical Reports Server (NTRS)

    Meyerstein, D.; Mulac, W. A.

    1969-01-01

    Understanding of chemical properties of monovalent transition metal cations in aqueous solutions was obtained by a study of kinetics of reduction of different inorganic substrates by zinc, cadmium, and nickel.

  13. Square-antiprismatic eight-coordinate complexes of divalent first-row transition metal cations: a density functional theory exploration of the electronic-structural landscape.

    PubMed

    Conradie, Jeanet; Patra, Ashis K; Harrop, Todd C; Ghosh, Abhik

    2015-02-16

    Density functional theory (in the form of the PW91, BP86, OLYP, and B3LYP exchange-correlation functionals) has been used to map out the low-energy states of a series of eight-coordinate square-antiprismatic (D2d) first-row transition metal complexes, involving Mn(II), Fe(II), Co(II), Ni(II), and Cu(II), along with a pair of tetradentate N4 ligands. Of the five complexes, the Mn(II) and Fe(II) complexes have been synthesized and characterized structurally and spectroscopically, whereas the other three are as yet unknown. Each N4 ligand consists of a pair of terminal imidazole units linked by an o-phenylenediimine unit. The imidazole units are the strongest ligands in these complexes and dictate the spatial disposition of the metal three-dimensional orbitals. Thus, the dx(2)-y(2) orbital, whose lobes point directly at the coordinating imidazole nitrogens, has the highest orbital energy among the five d orbitals, whereas the dxy orbital has the lowest orbital energy. In general, the following orbital ordering (in order of increasing orbital energy) was found to be operative: dxy < dxz = dyz ≤ dz(2) < dx(2)-y(2). The square-antiprism geometry does not lead to large energy gaps between the d orbitals, which leads to an S = 2 ground state for the Fe(II) complex. Nevertheless, the dxy orbital has significantly lower energy relative to that of the dxz and dyz orbitals. Accordingly, the ground state of the Fe(II) complex corresponds unambiguously to a dxy(2)dxz(1)dyz(1)dz(2)(1)dx(2)-y(2)(1) electronic configuration. Unsurprisingly, the Mn(II) complex has an S = 5/2 ground state and no low-energy d-d excited states within 1.0 eV of the ground state. The Co(II) complex, on the other hand, has both a low-lying S = 1/2 state and multiple low-energy S = 3/2 states. Very long metal-nitrogen bonds are predicted for the Ni(II) and Cu(II) complexes; these bonds may be too fragile to survive in solution or in the solid state, and the complexes may therefore not be isolable

  14. Synthesis, spectral studies and biological evaluation of 2-aminonicotinic acid metal complexes.

    PubMed

    Nawaz, Muhammad; Abbasi, Muhammad Waseem; Hisaindee, Soleiman; Zaki, Muhammad Javed; Abbas, Hira Fatima; Mengting, Hu; Ahmed, M Arif

    2016-05-15

    We synthesized 2-aminonicotinic acid (2-ANA) complexes with metals such as Co(II), Fe(III), Ni(II), Mn(II), Zn(II), Ag(I),Cr(III), Cd(II) and Cu(II) in aqueous media. The complexes were characterized and elucidated using FT-IR, UV-Vis, a fluorescence spectrophotometer and thermo gravimetric analysis (TGA). TGA data showed that the stoichiometry of complexes was 1:2 metal/ligand except for Ag(I) and Mn(II) where the ratio was 1:1. The metal complexes showed varied antibacterial, fungicidal and nematicidal activities. The silver and zinc complexes showed highest activity against Bacillus subtilis and Bacillus licheniformis respectively. Fusarium oxysporum was highly susceptible to nickel and copper complexes whereas Macrophomina phaseolina was completely inert to the complexes. The silver and cadmium complexes were effective against the root-knot nematode Meloidogyne javanica. PMID:26945123

  15. Synthesis, spectral studies and biological evaluation of 2-aminonicotinic acid metal complexes

    NASA Astrophysics Data System (ADS)

    Nawaz, Muhammad; Abbasi, Muhammad Waseem; Hisaindee, Soleiman; Zaki, Muhammad Javed; Abbas, Hira Fatima; Mengting, Hu; Ahmed, M. Arif

    2016-05-01

    We synthesized 2-aminonicotinic acid (2-ANA) complexes with metals such as Co(II), Fe(III), Ni(II), Mn(II), Zn(II), Ag(I),Cr(III), Cd(II) and Cu(II) in aqueous media. The complexes were characterized and elucidated using FT-IR, UV-Vis, a fluorescence spectrophotometer and thermo gravimetric analysis (TGA). TGA data showed that the stoichiometry of complexes was 1:2 metal/ligand except for Ag(I) and Mn(II) where the ratio was 1:1. The metal complexes showed varied antibacterial, fungicidal and nematicidal activities. The silver and zinc complexes showed highest activity against Bacillus subtilis and Bacillus licheniformis respectively. Fusarium oxysporum was highly susceptible to nickel and copper complexes whereas Macrophomina phaseolina was completely inert to the complexes. The silver and cadmium complexes were effective against the root-knot nematode Meloidogyne javanica.

  16. Metal-based biologically active azoles and β-lactams derived from sulfa drugs.

    PubMed

    Ebrahimi, Hossein Pasha; Hadi, Jabbar S; Almayah, Abdulelah A; Bolandnazar, Zeinab; Swadi, Ali G; Ebrahimi, Amirpasha

    2016-03-01

    Metal complexes of Schiff bases derived from sulfamethoxazole (SMZ) and sulfathiazole (STZ), converted to their β-lactam derivatives have been synthesized and experimentally characterized by elemental analysis, spectral (IR, (1)H NMR, (13)C NMR, and EI-mass), molar conductance measurements and thermal analysis techniques. The structural and electronic properties of the studied molecules were investigated theoretically by performing density functional theory (DFT) to access reliable results to the experimental values. The spectral and thermal analysis reveals that the Schiff bases act as bidentate ligands via the coordination of azomethine nitrogen to metal ions as well as the proton displacement from the phenolic group through the metal ions; therefore, Cu complexes can attain the square planner arrangement and Zn complexes have a distorted tetrahedral structure. The thermogravimetric (TG/DTG) analyses confirm high stability for all complexes followed by thermal decomposition in different steps. In addition, the antibacterial activities of synthesized compounds have been screened in vitro against various pathogenic bacterial species. Inspection of the results revealed that all newly synthesized complexes individually exhibit varying degrees of inhibitory effects on the growth of the tested bacterial species, therefore, they may be considered as drug candidates for bacterial pathogens. The free Schiff base ligands (1-2) exhibited a broad spectrum antibacterial activity against Gram negative Escherichia coli, Pseudomonas aeruginosa, and Proteus spp., and Gram positive Staphylococcus aureus bacterial strains. The results also indicated that the β-lactam derivatives (3-4) have high antibacterial activities on Gram positive bacteria as well as the metal complexes (5-8), particularly Zn complexes, have a significant activity against all Gram negative bacterial strains. It has been shown that the metal complexes have significantly higher activity than corresponding

  17. Cationically polymerizable monomers derived from renewable sources

    SciTech Connect

    Crivello, J.V.

    1992-10-01

    The objectives of this project are to design and synthesize novel monomers which orginate from renewable biological sources and to carry out their rapid, efficient, pollution-free and energy efficient cationic polymerization to useful products under the influence of ultraviolet light or heat. A summary of the results of the past year's research on cationically polymerizable monomers derived from renewable sources is presented. Three major areas of investigation corresponding to the different classes of naturally occurring starting materials were investigated; epoxidized terpenes and natural rubber and vinyl ethers from alcohols and carbohydrates.

  18. Harmful metals concentration in sediments and fishes of biologically important estuary, Bay of Bengal

    PubMed Central

    2013-01-01

    Study on the accumulation level of heavy metals was conducted on sediment and fishes from estuaries of Bay of Bengal. Heavy metals were determined by using Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES) and the results were compared to permissible limits of WHO/USEPA. The accumulation patterns of Fe and Cd were found predominantly in all samples tested when correlated with other metals. It was found that the concentration of metals such as Cd (3.90 ± 0.25 μg/g), Cr (0.44 ± 0.05 μg/g), Ni (0.33 ± 0.01 μg/g), and Mn (1.1 ± 0.11 μg/g) were exceeding the permissible limit, whereas Fe, Co, Pb, and Zn were found within the limit of WHO/USEPA at station 1. In station 2, Cd (16.5 ± 0.4 μg/g), Mn (0.67 ± 0.11 μg/g), and Cr (0.80 ± 0.01 μg/g) were exceeding the permissible limit, whereas Fe, Co, Pb, Ni, and Zn were found within the limit. This study emphasizes that Cd and Mn levels in both stations, are far higher than the acceptable values set by WHO/USEPA and may therefore present human health hazards. It is therefore mandatory to carry out extensive research to evaluate the possible environmental risk factors in the vicinity of both estuaries with respect to heavy metals. PMID:24355110

  19. BIOLOGICAL SIGNIFICANCE OF SOME METALS AS AIR POLLUTANTS. PART II. MERCURY

    EPA Science Inventory

    The study was undertaken in order to elucidate the association between low atmospheric mercury levels and changes in some biological parameters likely to react to such exposures. The study covered four populations believed to be exposed to four different levels of atmospheric mer...

  20. Municipal waste incinerators: air and biological monitoring of workers for exposure to particles, metals, and organic compounds

    PubMed Central

    Maitre, A; Collot-Fertey, D; Anzivino, L; Marques, M; Hours, M; Stoklov, M

    2003-01-01

    Aims: To evaluate occupational exposure to toxic pollutants at municipal waste incinerators (MWIs). Methods: Twenty nine male subjects working near the furnaces in two MWIs, and 17 subjects not occupationally exposed to combustion generated pollutants were studied. Individual air samples were taken throughout the shift; urine samples were collected before and after. Stationary air samples were taken near potential sources of emission. Results: Occupational exposure did not result in the infringement of any occupational threshold limit value. Atmospheric exposure levels to particles and metals were 10–100 times higher in MWIs than at the control site. The main sources were cleaning operations for particles, and residue transfer and disposal operations for metals. MWI workers were not exposed to higher levels of polycyclic aromatic hydrocarbons than workers who are routinely in contact with vehicle exhaust. The air concentrations of volatile organic compounds and aldehydes were low and did not appear to pose any significant threat to human health. Only the measurement of chlorinated hydrocarbon levels would seem to be a reliable marker for the combustion of plastics. Urine metal levels were significantly higher at plant 1 than at plant 2 because of high levels of pollutants emanating from one old furnace. Conclusion: While biological monitoring is an easy way of acquiring data on long term personal exposure, air monitoring remains the only method that makes it possible to identify the primary sources of pollutant emission which need to be controlled if occupational exposure and environmental pollution are to be reduced. PMID:12883016

  1. ZnVSe2O7 and Cd6V2Se5O21: new d10 transition-metal selenites with V(IV) or V(V) cations.

    PubMed

    Jiang, Hai-Long; Kong, Fang; Fan, Yang; Mao, Jiang-Gao

    2008-08-18

    Two new metal selenites with a combination of vanadium(IV) or vanadium(V) cations, namely, ZnVSe 2O 7 and Cd 6V 2Se 5O 21, have been synthesized by hydrothermal and high-temperature solid-state reactions, respectively. The structure of ZnVSe 2O 7 features a 3D network of vanadium(IV) selenite with 1D tunnels occupied by zinc(II) ions. The 3D network of vanadium(IV) selenite is formed by corner-sharing V (IV)O 6 octahedral chains bridged by selenite groups. In Cd 6V 2Se 5O 21, the interconnection of cadmium(II) ions by bridging and chelating selenite groups led to a 3D framework with large tunnels along the b axis, and the 1D chains of corner-sharing V (V)O 4 tetrahedra are inserted in the above large tunnels and are bonded to the cadmium selenite framework via Cd-O-V bridges. Both compounds exhibit broad emission bands in the blue-light region. Results of magnetic property measurements show there is significant antiferromagnetic interaction between V (4+) centers in ZnVSe 2O 7. The electronic structure calculations for both compounds have been also performed. PMID:18576595

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  3. Syntheses and characterization of energetic compounds constructed from alkaline earth metal cations (Sr and Ba) and 1,2-bis(tetrazol-5-yl)ethane

    SciTech Connect

    Xia Zhengqiang; Chen Sanping; Wei Qing; Qiao Chengfang

    2011-07-15

    Two new energetic compounds, [M(BTE)(H{sub 2}O){sub 5}]{sub n} (M=Sr(1), Ba(2)) [H{sub 2}BTE=1,2-bis(tetrazol-5-yl)ethane], have been hydrothermally synthesized and structurally characterized. Single-crystal X-ray diffraction analyses reveal that they are isomorphous and exhibit 2D (4,4) net framework, generated by 4-connected Sr{sub 2}(H{sub 2}O){sub 10}/Ba{sub 2}(H{sub 2}O){sub 10} SBUs linked up by two independent binding modes of H{sub 2}BTE, and the resulting 2D structure is interconnected by hydrogen-bond and strong face to face {pi}-{pi} stacking interactions between two tetrazole rings to lead to a 3D supramolecular architecture. DSC measurements show that they have significant catalytic effects on thermal decomposition of ammonium perchlorate. Moreover, the photoluminescence properties, thermogravimetric analyses, and flame colors of the as-prepared compounds are also investigated in this paper. - Graphical abstract: Two novel 2D isomorphous alkaline earth metal complexes were assembled by 4-connected Sr{sub 2}(H{sub 2}O){sub 10}/Ba{sub 2}(H{sub 2}O){sub 10} SBUs and two independent binding modes of H{sub 2}BTE ligands, and the catalytic performances toward thermal decomposition of ammonium perchlorate and photoluminescent properties of them were investigated. Highlights: > Two novel alkaline earth energetic coordination polymers have been prepared.{yields} Both structures are layered based on 4-connected Sr{sub 2}(H{sub 2}O){sub 10}/Ba{sub 2}(H{sub 2}O){sub 10} SBUs and two distinct H{sub 2}BTE coordination modes.{yields} The dehydrated products of the compounds possess good thermostability and significant catalytic effects on thermal decomposition of AP.

  4. Photocatalytic electrochemistry at a biological-membrane metal-colloid interface

    NASA Astrophysics Data System (ADS)

    Greenbaum, Elias

    1987-10-01

    A method for electrically contacting the electron-transport chain of photosynthesis is described. Colloidal platinum was prepared and precipitated directly onto photosynthetic thylakoid membranes from aqueous solution, and entrapped on fiberglass filter paper. This composition of matter was capable of sustained simultaneous photoevolution of hydrogen and oxygen when irradiated at any wavelength in the chlorophyll absorption spectrum. Experimental data support the interpretation that part of the platinum metal catalyst is precipitated adjacent to the photosystem-I reduction site of photosynthesis and the electron-transfer occurs across the interface between photosystem I and the catalyst. Photoactivity of the material was dependent on the nature of the ionic species from which the platinum was precipitated. When contacted with metal electrodes, the thylakoid-platinum combination is capable of generating a sustained flow of current through an external load resistor.

  5. Photocatalytic electrochemistry at a biological-membrane metal-colloid interface

    SciTech Connect

    Greenbaum, E.

    1987-10-18

    A method for electrically contacting the electron-transport chain of photosynthesis is described. Colloidal platinum was prepared and precipitated directly onto photosynthetic thylakoid membranes from aqueous solution, and entrapped on fiberglass filter paper. This composition of matter was capable of sustained simultaneous photoevolution of hydrogen and oxygen when irradiated at any wavelength in the chlorophyll absorption spectrum. Experimental data support the interpretation that part of the platinum metal catalyst is precipitated adjacent to the photosystem-I reduction site of photosynthesis and the electron-transfer occurs across the interface between photosystem I and the catalyst. Photoactivity of the material was dependent on the nature of the ionic species from which the platinum was precipitated. When contacted with metal electrodes, the thylakoid-platinum combination is capable of generating a sustained flow of current through an external load resistor. 3 refs.

  6. Biological activity of ellagitannins: Effects as anti-oxidants, pro-oxidants and metal chelators.

    PubMed

    Moilanen, Johanna; Karonen, Maarit; Tähtinen, Petri; Jacquet, Rémi; Quideau, Stéphane; Salminen, Juha-Pekka

    2016-05-01

    Ellagitannins are a subclass of hydrolysable tannins that have been suggested to function as defensive compounds of plants against herbivores. However, it is known that the conditions in the digestive tracts of different herbivores are variable, so it seems reasonable to anticipate that the reactivities and modes of actions of these ingested defensive compounds would also be different. A previous study on a few ellagitannins has shown that these polyphenolic compounds are highly oxidizable at high pH and that their bioactivity can be attributed to certain structural features. Herein, the activities of 13 ellagitannins using the deoxyribose assay were measured. The results provided information about the anti-oxidant, pro-oxidant and metal chelating properties of ellagitannins. Surprisingly, many of the tested ellagitannins exhibited pro-oxidant activities even at neutral pH and only moderate to low radical scavenging activities, although the metal chelating capacities of all tested ellagitannins were relatively high. PMID:26899362

  7. Molecular modelling, spectroscopic characterization and biological studies of tetraazamacrocyclic metal complexes

    NASA Astrophysics Data System (ADS)

    Rathi, Parveen; Sharma, Kavita; Singh, Dharam Pal

    2014-09-01

    Macrocyclic complexes of the type [MLX]X2; where L is (C30H28N4), a macrocyclic ligand, M = Cr(III) and Fe(III) and X = Cl-, CH3COO- or NO3-, have been synthesized by template condensation reaction of 1,8-diaminonaphthalene and acetylacetone in the presence of trivalent metal salts in a methanolic medium. The complexes have been formulated as [MLX]X2 due to 1:2 electrolytic nature of these complexes. The complexes have been characterized with the help of elemental analyses, molar conductance measurements, magnetic susceptibility measurements, electronic, infrared, far infrared, Mass spectral studies and molecular modelling. Molecular weight of these complexes indicates their monomeric nature. On the basis of all these studies, a five coordinated square pyramidal geometry has been proposed for all these complexes. These metal complexes have also been screened for their in vitro antimicrobial activities.

  8. The NMR study of biologically active metallated alkanol ammoinium ionic liquids

    NASA Astrophysics Data System (ADS)

    Ushakov, I. A.; Voronov, V. K.; Adamovich, S. N.; Mirskov, R. G.; Mirskova, A. N.

    2016-01-01

    The 1H, 13C, 15N, and 111Cd NMR spectra of a series of metallated alkanol ammonium ionic liquids (MAIL) series [n N(CH2CH2OH;)3M]+ · mX-, where M = Cd, Mg, Zn, Fe, Rh; X = Cl, OOCCH3, obtained in a wide range of temperatures of the studied samples, have been analyzed. It is found that, under biomimetic conditions (H2O, 25 °C), the compounds studied exist as mono- bi- and the tricyclic structures, which are in equilibrium. Shift of the equilibrium depends upon nature of a metal and effects all the parameters of the NMR spectra. Peculiarities of ligand exchange, typical for the studied compounds, have been studied in a wide range of temperatures. It is found that the NMR data can be used to control structure of the compounds formed in the course of synthesis.

  9. Metal-mediated modulation of streptococcal cysteine protease activity and its biological implications.

    PubMed

    Chella Krishnan, Karthickeyan; Mukundan, Santhosh; Landero Figueroa, Julio A; Caruso, Joseph A; Kotb, Malak

    2014-07-01

    Streptococcal cysteine protease (SpeB), the major secreted protease produced by group A streptococcus (GAS), cleaves both host and bacterial proteins and contributes importantly to the pathogenesis of invasive GAS infections. Modulation of SpeB expression and/or its activity during invasive GAS infections has been shown to affect bacterial virulence and infection severity. Expression of SpeB is regulated by the GAS CovR-CovS two-component regulatory system, and we demonstrated that bacteria with mutations in the CovR-CovS two-component regulatory system are selected for during localized GAS infections and that these bacteria lack SpeB expression and exhibit a hypervirulent phenotype. Additionally, in a separate study, we showed that expression of SpeB can also be modulated by human transferrin- and/or lactoferrin-mediated iron chelation. Accordingly, the goal of this study was to investigate the possible roles of iron and other metals in modulating SpeB expression and/or activity in a manner that would potentiate bacterial virulence. Here, we report that the divalent metals zinc and copper inhibit SpeB activity at the posttranslational level. Utilizing online metal-binding site prediction servers, we identified two putative metal-binding sites in SpeB, one of which involves the catalytic-dyad residues (47)Cys and (195)His. Based on our findings, we propose that zinc and/or copper availability in the bacterial microenvironment can modulate the proteolytic activity of SpeB in a manner that preserves the integrity of several other virulence factors essential for bacterial survival and dissemination within the host and thereby may exacerbate the severity of invasive GAS infections. PMID:24799625

  10. Metal-Mediated Modulation of Streptococcal Cysteine Protease Activity and Its Biological Implications

    PubMed Central

    Chella Krishnan, Karthickeyan; Mukundan, Santhosh; Landero Figueroa, Julio A.; Caruso, Joseph A.

    2014-01-01

    Streptococcal cysteine protease (SpeB), the major secreted protease produced by group A streptococcus (GAS), cleaves both host and bacterial proteins and contributes importantly to the pathogenesis of invasive GAS infections. Modulation of SpeB expression and/or its activity during invasive GAS infections has been shown to affect bacterial virulence and infection severity. Expression of SpeB is regulated by the GAS CovR-CovS two-component regulatory system, and we demonstrated that bacteria with mutations in the CovR-CovS two-component regulatory system are selected for during localized GAS infections and that these bacteria lack SpeB expression and exhibit a hypervirulent phenotype. Additionally, in a separate study, we showed that expression of SpeB can also be modulated by human transferrin- and/or lactoferrin-mediated iron chelation. Accordingly, the goal of this study was to investigate the possible roles of iron and other metals in modulating SpeB expression and/or activity in a manner that would potentiate bacterial virulence. Here, we report that the divalent metals zinc and copper inhibit SpeB activity at the posttranslational level. Utilizing online metal-binding site prediction servers, we identified two putative metal-binding sites in SpeB, one of which involves the catalytic-dyad residues 47Cys and 195His. Based on our findings, we propose that zinc and/or copper availability in the bacterial microenvironment can modulate the proteolytic activity of SpeB in a manner that preserves the integrity of several other virulence factors essential for bacterial survival and dissemination within the host and thereby may exacerbate the severity of invasive GAS infections. PMID:24799625

  11. Effect of a heavy metal model mixture on biological parameters of rainbow trout Oncorhynchus mykiss.

    PubMed

    Vosyliene, Milda Zita; Kazlauskiene, Nijole; Svecevicius, Gintaras

    2003-01-01

    The effects of a model mixture (HMMM) of seven heavy metals (Cu, Zn, Ni, Cr, Pb, Cd, Mn) on the rainbow trout Oncorhynchus mykiss at all stages of development (embryos, larvae, adults) were investigated based on the annual average concentrations of these metals in cooling waste waters discharging from Ignalina Nuclear Power Plant (Lithuania) into the Drŭksiai lake. According to mortality parameters, the most sensitive to HMMM were larvae, although no significant differences between the sensitivity of embryos and adult fish to HMMM were found. Maximal toxic effect of HMMM was observed during the hatching period. Long-term exposure to sublethal concentrations of HMMM affected embryo development, growth of larvae, their cardio-respiratory and behavioural responses, induced significant changes in morphological, morpho-physiological, physiological and haematological parameters of adult fish. Respiratory responses and growth parameters of fish were found to be the most sensitive to low concentrations of HMMM. Adult fish were capable of detecting and avoiding low, sublethal concentrations of HMMM. Heavy metals in a mixture at low concentrations were more toxic than single ones. According to the background of the damages induced by HMMM, after-effects in a fish organism, as well as in a whole population, can be predicted. PMID:12729042

  12. Spectral, biological screening of metal chelates of chalcone based Schiff bases of N-(3-aminopropyl) imidazole.

    PubMed

    Kalanithi, M; Rajarajan, M; Tharmaraj, P; Sheela, C D

    2012-02-15

    Tridentate chelate complexes of Co(II), Ni(II), Cu(II) and Zn(II) have been synthesized from the chalcone based ligands 2-[1-(3-(1H-imidazol-1-yl)propylimino)-3-(phenylallyl)]phenol(HL(1)), 2-[1-(3-(1H-imidazol-1-yl)propylimino)-3-p-tolylallyl]phenol(HL(2)), 2-[1-(3-(1H-imidazol-1-yl)propylimino)-3-4-nitrophenylallyl]phenol(HL(3)). Microanalytical data, UV-vis spectrophotometric method, magnetic susceptibility measurements, IR, 1H NMR, Mass, and EPR techniques were used to characterize the structure of chelates. The electronic absorption spectra and magnetic susceptibility measurements suggest a distorted square planar geometry for the copper(II) ion. The other metal complexes show distorted tetrahedral geometry. The coordination of the ligands with metal(II) ions was further confirmed by solution fluorescence spectrum. The antimicrobial activity of the ligands and metal(II) complexes against the species Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Candida albigans and Aspergillus niger has been carried out and compared. The electrochemical behavior of copper(II) complex is studied by cyclic voltammetry. PMID:22169028

  13. Metal based isatin-derived sulfonamides: their synthesis, characterization, coordination behavior and biological activity.

    PubMed

    Chohan, Zahid H; Supuran, Claudiu T; Ben Hadda, Taibi; Nasim, Faiz-Ul-Hassan; Khan, Khalid M

    2009-06-01

    Some isatin derived sulfonamides and their transition metal [Co(II), Cu(II), Ni(II), Zn(II)] complexes have been synthesized and characterized. The structure of synthesized compounds and their nature of bonding have been inferred on the basis of their physical (magnetic susceptibility and conductivity measurements), analytical (elemental analyses) and spectral (IR, (1)H NMR and (13)C NMR) properties. An octahedral geometry has been suggested for Co(II), Ni(II) and Zn(II) and square-planar for Cu(II) complexes. In order to assess the antibacterial and antifungal behavior, the ligands and their metal(II) complexes were screened for their in vitro antibacterial activity against four Gram-negative species, Escherichia coli, Shigella flexneri, Pseudomonas aeruginosa and Salmonella typhi and two Gram-positive species, Staphylococcus aureus and Bacillus subtilis and, for in vitro antifungal activity against Trichophyton longifusus, Candida albicans, Aspergillus flavus, Microsporum canis, Fusarium solani and Candida glaberata. In vitro cytotoxic properties of all the compounds were also studied against Artemia salina by brine shrimp bioassay. The results of average antibacterial/antifungal activity showed that zinc(II) complexes were found to be the most active against one or more bacterial/fungal strains as compared to the other metal complexes. PMID:18825557

  14. Biological removal of heavy metals by sulfate reduction using a submerged packed tower

    SciTech Connect

    Neserke, G.; Figueroa, L.; Cook, N.

    1994-12-31

    The Coors Brewing Co. owns and operates two wastewater treatment plants which handle the combined waste of the City of Golden and the Brewery. The discharge permit for Coors contains very strict limits for metals. Silver and mercury are prohibited from discharge at all and copper and zinc are both at low limits. The copper and zinc limits cannot be achieved with the present plant configuration and several programs are underway to reduce the source concentrations to meet the respective limits. Most of the programs are either very expensive or unlikely to produce the needed results soon enough. One possible treatment alternative that has been described in literature is sulfate reduction leading to the generation of hydrogen sulfide. The hydrogen sulfide in turn can precipitate most divalent metals that are available, though there are limits on the precipitation process. The purpose of this research has been to investigate the use of sulfate reduction to remove metals from the effluent of the Coors` Process Waste Treatment Plant (PWTP).

  15. Spectral, biological screening of metal chelates of chalcone based Schiff bases of N-(3-aminopropyl) imidazole

    NASA Astrophysics Data System (ADS)

    Kalanithi, M.; Rajarajan, M.; Tharmaraj, P.; Sheela, C. D.

    2012-02-01

    Tridentate chelate complexes of Co(II), Ni(II), Cu(II) and Zn(II) have been synthesized from the chalcone based ligands 2-[1-(3-(1H-imidazol-1-yl)propylimino)-3-(phenylallyl)]phenol( HL1), 2-[1-(3-(1H-imidazol-1-yl)propylimino)-3-p-tolylallyl]phenol( HL2), 2-[1-(3-(1H-imidazol-1-yl)propylimino)-3-4-nitrophenylallyl]phenol( HL3). Microanalytical data, UV-vis spectrophotometric method, magnetic susceptibility measurements, IR, 1H NMR, Mass, and EPR techniques were used to characterize the structure of chelates. The electronic absorption spectra and magnetic susceptibility measurements suggest a distorted square planar geometry for the copper(II) ion. The other metal complexes show distorted tetrahedral geometry. The coordination of the ligands with metal(II) ions was further confirmed by solution fluorescence spectrum. The antimicrobial activity of the ligands and metal(II) complexes against the species Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Candida albigans and Aspergillus niger has been carried out and compared. The electrochemical behavior of copper(II) complex is studied by cyclic voltammetry.

  16. Exploring the DNA binding mode of transition metal based biologically active compounds

    NASA Astrophysics Data System (ADS)

    Raman, N.; Sobha, S.

    2012-01-01

    Few novel 4-aminoantipyrine derived Schiff bases and their metal complexes were synthesized and characterized. Their structural features and other properties were deduced from the elemental analysis, magnetic susceptibility and molar conductivity as well as from mass, IR, UV-vis, 1H NMR and EPR spectral studies. The binding of the complexes with CT-DNA was analyzed by electronic absorption spectroscopy, viscosity measurement, and cyclic voltammetry. The interaction of the metal complexes with DNA was also studied by molecular modeling with special reference to docking. The experimental and docking results revealed that the complexes have the ability of interaction with DNA of minor groove binding mode. The intrinsic binding constants ( Kb) of the complexes with CT-DNA were found out which show that they are minor groove binders. Gel electrophoresis assay demonstrated the ability of the complexes to cleave the pUC19 DNA in the presence of AH 2 (ascorbic acid). Moreover, the oxidative cleavage studies using distamycin revealed the minor groove binding for the newly synthesized 4-aminoantipyrine derived Schiff bases and their metal complexes. Evaluation of antibacterial activity of the complexes against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus epidermidis, and Klebsiella pneumoniae exhibited that the complexes have potent biocidal activity than the free ligands.

  17. Redox potential tuning by redox-inactive cations in nature's water oxidizing catalyst and synthetic analogues.

    PubMed

    Krewald, Vera; Neese, Frank; Pantazis, Dimitrios A

    2016-04-20

    The redox potential of synthetic oligonuclear transition metal complexes has been shown to correlate with the Lewis acidity of a redox-inactive cation connected to the redox-active transition metals of the cluster via oxo or hydroxo bridges. Such heterometallic clusters are important cofactors in many metalloenzymes, where it is speculated that the redox-inactive constituent ion of the cluster serves to optimize its redox potential for electron transfer or catalysis. A principal example is the oxygen-evolving complex in photosystem II of natural photosynthesis, a Mn4CaO5 cofactor that oxidizes water into dioxygen, protons and electrons. Calcium is critical for catalytic function, but its precise role is not yet established. In analogy to synthetic complexes it has been suggested that Ca(2+) fine-tunes the redox potential of the manganese cluster. Here we evaluate this hypothesis by computing the relative redox potentials of substituted derivatives of the oxygen-evolving complex with the cations Sr(2+), Gd(3+), Cd(2+), Zn(2+), Mg(2+), Sc(3+), Na(+) and Y(3+) for two sequential transitions of its catalytic cycle. The theoretical approach is validated with a series of experimentally well-characterized Mn3AO4 cubane complexes that are structural mimics of the enzymatic cluster. Our results reproduce perfectly the experimentally observed correlation between the redox potential and the Lewis acidities of redox-inactive cations for the synthetic complexes. However, it is conclusively demonstrated that this correlation does not hold for the oxygen evolving complex. In the enzyme the redox potential of the cluster only responds to the charge of the redox-inactive cations and remains otherwise insensitive to their precise identity, precluding redox-tuning of the metal cluster as a primary role for Ca(2+) in biological water oxidation. PMID:26762578

  18. Do fattening process and biological parameters affect the accumulation of metals in Atlantic bluefin tuna?

    PubMed

    Milatou, Niki; Dassenakis, Manos; Megalofonou, Persefoni

    2015-01-01

    The objective of this study was to determine the current levels of heavy metals and trace elements in Atlantic bluefin tuna muscle tissues and how they are influenced by the fattening process and various life history parameters to ascertain whether the concentrations in muscle tissue exceed the maximum levels defined by the European Commission Decision and to evaluate the health risk posed by fish consumption. A total of 20 bluefin tuna reared in sea cages, ranging from 160 to 295 cm in length and from 80 to 540 kg in weight, were sampled from a bluefin tuna farm in the Ionian Sea. The condition factor K of each specimen was calculated and their age was estimated. Heavy metal and trace element (Hg, Zn, Fe and Cu) contents were determined in muscle tissue using cold vapour atomic absorption spectrometry and flame and graphite furnace atomic absorption spectrometry. The total Hg concentrations ranged from 0.28 to 1.28 mg kg(-1) w/w, Zn from 5.81 to 76.37 mg kg(-1) w/w, Fe from 12.14 to 39.58 mg kg(-1) w/w, and Cu from 0.36 to 0.94 mg kg(-1) w/w. Only 5% of the muscle samples of tuna contained Hg above the maximum level laid down by the European Commission Decision. Moreover, 15% of the muscle samples contained Zn above the maximum level, while Fe and Cu concentrations were within the acceptable tolerable guideline values. The reared bluefin tuna had lower concentrations of Hg than the wild ones from the Mediterranean Sea. Hg and Fe concentrations showed a positive relationship with size and age of bluefin tuna, whereas negative relationships were found for the concentrations of Zn and Cu. The estimated dietary intake values of the analysed metals were mostly below the derived guidelines. PMID:25906290

  19. Determination of trace metals in marine biological reference materials by inductively coupled plasma mass spectrometry

    SciTech Connect

    Beauchemin, D.; McLaren, J.W.; Willie, S.N.; Berman, S.S.

    1988-04-01

    Inductively coupled plasma mass spectrometry (ICP-MS) was used for the analysis of two marine biological reference materials (dogfish liver tissue (DOLT-1) and dogfish muscle tissue (DORM-1)). The materials were put into solution by digestion in a nitric acid/hydrogen peroxide mixture. Thirteen elements (Na, Mg, Cr, Fe, Mn, Co, Ni, Cu, Zn, As, Cd, Hg, and Pb) were then determined. Accurate results were obtained by standard additions or isotope dilution techniques for all of these elements in DORM-1 and for all but Cr in DOLT-1.

  20. Metal complexes of the fourth generation quinolone antimicrobial drug gatifloxacin: Synthesis, structure and biological evaluation

    NASA Astrophysics Data System (ADS)

    Sadeek, Sadeek A.; El-Shwiniy, Walaa H.

    2010-08-01

    Three metal complexes of the fourth generation quinolone antimicrobial agent gatifloxacin (GFLX) with Y(ΙΙΙ), Zr(ΙV) and U(VΙ) have been prepared and characterized with physicochemical and spectroscopic techniques. In these complexes, gatifloxacin acts as a bidentate deprotonated ligand bound to the metal through the ketone oxygen and a carboxylato oxygen. The complexes are six-coordinated with distorted octahedral geometry. The kinetic parameters for gatifloxacin and the three prepared complexes have been evaluated from TGA curves by using Coats-Redfern (CR) and Horowitz-Metzeger (HM) methods. The calculated bond length and force constant, F(U dbnd O), for the UO 2 bond in uranyl complex are 1.7522 Å and 639.46 N m -1. The antimicrobial activity of the complexes has been tested against microorganisms, three bacterial species, such as Staphylococcus aureus ( S. aureus), Escherichia coli ( E. coli) and Pseudomonas aeruginosa ( P. aeruginosa) and two fungi species, penicillium ( P. rotatum) and trichoderma ( T. sp.), showing that they exhibit higher activity than free ligand.

  1. Structural and biological evaluation of some metal complexes of vanillin-4N-(2-pyridyl) thiosemicarbazone

    NASA Astrophysics Data System (ADS)

    Yousef, T. A.; Abu El-Reash, G. M.; Al-Jahdali, M.; El-Rakhawy, El-Bastawesy R.

    2013-12-01

    The synthesis and characterization of Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II) and U(VI)O2 complexes of vanillin-4N-(2-pyridyl) thiosemicarbazone (H2PVT) are reported. Theoretical calculations have been performed to obtain IR spectra of ligand and its complexes using AM1, Zindo/1, MM+ and PM3, methods. The Schiff base and its metal complexes have been screened for antibacterial Pseudomonas aeruginosa, Escherichia coli, Bacillus subtilis and Staphylococcus saprophyticus. H2VPT shows no apparent digestion effect on the egg albumin while Mn(II), Hg(II) and Cu(II) complexes exhibited a considerable digestion effect following the order Cu(II) > Mn(II) > Hg(II). Moreover, Ni(II) and Co(II) complexes revealed strong digestion effect. Fe(II), Mn(II), Cu(II), Zn(II) and Ni(II) acted as metal co- SOD enzyme factors, which are located in different compartments of the cell.

  2. Graphene-Based Materials as Solid Phase Extraction Sorbent for Trace Metal Ions, Organic Compounds, and Biological Sample Preparation.

    PubMed

    Ibrahim, Wan Aini Wan; Nodeh, Hamid Rashidi; Sanagi, Mohd Marsin

    2016-07-01

    Graphene is a new carbon-based material that is of interest in separation science. Graphene has extraordinary properties including nano size, high surface area, thermal and chemical stability, and excellent adsorption affinity to pollutants. Its adsorption mechanisms are through non-covalent interactions (π-π stacking, electrostatic interactions, and H-bonding) for organic compounds and covalent interactions for metal ions. These properties have led to graphene-based material becoming a desirable adsorbent in a popular sample preparation technique known as solid phase extraction (SPE). Numerous studies have been published on graphene applications in recent years, but few review papers have focused on its applications in analytical chemistry. This article focuses on recent preconcentration of trace elements, organic compounds, and biological species using SPE-based graphene, graphene oxide, and their modified forms. Solid phase microextraction and micro SPE (µSPE) methods based on graphene are discussed. PMID:26186420

  3. NMR studies of cation transport across membranes

    SciTech Connect

    Shochet, N.R.

    1985-01-01

    /sup 23/Na NMR Studies of cation transport across membranes were conducted both on model and biological membranes. Two ionophores, the carrier monensin and the channel-former gramicidin, were chosen to induce cation transport in large unilamellar phosphatidylcholine vesicles. The distinction between the NMR signals arising from the two sides of the membrane was achieved by the addition of an anionic paramagnetic shift reagent to the outer solution. The kinetics of the cation transport across the membrane was observed simultaneously monitoring the changes in the /sup 23/Na NMR signals of both compartments. Two mathematical models were developed for the estimation of the transport parameters of the monensin- and gramicidin-induced cation transport. The models were able to fit the experimental data very well. A new method for the estimation of the volume trapped inside the vesicles was developed. The method uses the relative areas of the intra- and extravesicular NMR signals arising from a suspension of vesicles bathed in the same medium they contain, as a measure for the relative volumes of these compartments. Sodium transport across biological membranes was studied by /sup 23/ NMR, using suspensions of cultured nerve cells. The sodium influx through voltage-gated channels was studied using the channel modifier batrachotoxin in combination with scorpion toxin.

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

    USGS Publications Warehouse

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

    2016-01-01

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

  5. Synthesis, spectral and thermal studies of some transition metal mixed ligand complexes: Modeling of equilibrium composition and biological activity

    NASA Astrophysics Data System (ADS)

    Neelakantan, M. A.; Sundaram, M.; Nair, M. Sivasankaran

    2011-09-01

    Several mixed ligand Ni(II), Cu(II) and Zn(II) complexes of 2-amino-3-hydroxypyridine (AHP) and imidazoles viz., imidazole (him), benzimidazole (bim), histamine (hist) and L-histidine (his) have been synthesized and characterized by elemental and spectral (vibrational, electronic, 1H NMR and EPR) data as well as by magnetic moment values. On the basis of elemental analysis and molar conductance values, all the complexes can be formulated as [MAB]Cl except histidine complexes as MAB. Thermogravimetric studies reveal the presence of coordinated water molecules in most of the complexes. From the magnetic measurements and electronic spectral data, octahedral structure was proposed for Ni(II) and Cu(II)-AHP-his, tetrahedral for Cu(II)-AHP-him/bim/hist, but square planar for the Cu(II)-AHP complex. The g∥/ A∥ calculated supports tetrahedral environment around the Cu(II) in Cu(II)-AHP-him/bim/hist and distorted octahedral for Cu(II)-AHP-his complexes. The morphology of the reported metal complexes was investigated by scanning electron micrographs (SEM). The potentiometric study has been performed in aqueous solution at 37 °C and I = 0.15 mol dm -3 NaClO 4. MABH, MAB and MAB 2 species has been identified in the present systems. Proton dissociation constants of AHP and stability constants of metal complexes were determined using MINIQUAD-75. The most probable structure of the mixed ligand species is discussed based upon their stability constants. The in vitro biological activity of the complexes was tested against the Gram positive and Gram negative bacteria, fungus and yeast. The oxidative DNA cleavage studies of the complexes were performed using gel electrophoresis method. Cu(II) complexes have been found to promote DNA cleavage in presence of biological reductant such as ascorbate and oxidant like hydrogen peroxide.

  6. Metallic Nanoislands on Graphene as Highly Sensitive Transducers of Mechanical, Biological, and Optical Signals.

    PubMed

    Zaretski, Aliaksandr V; Root, Samuel E; Savchenko, Alex; Molokanova, Elena; Printz, Adam D; Jibril, Liban; Arya, Gaurav; Mercola, Mark; Lipomi, Darren J

    2016-02-10

    This article describes an effect based on the wetting transparency of graphene; the morphology of a metallic film (≤20 nm) when deposited on graphene by evaporation depends strongly on the identity of the substrate supporting the graphene. This control permits the formation of a range of geometries, such as tightly packed nanospheres, nanocrystals, and island-like formations with controllable gaps down to 3 nm. These graphene-supported structures can be transferred to any surface and function as ultrasensitive mechanical signal transducers with high sensitivity and range (at least 4 orders of magnitude of strain) for applications in structural health monitoring, electronic skin, measurement of the contractions of cardiomyocytes, and substrates for surface-enhanced Raman scattering (SERS, including on the tips of optical fibers). These composite films can thus be treated as a platform technology for multimodal sensing. Moreover, they are low profile, mechanically robust, semitransparent and have the potential for reproducible manufacturing over large areas. PMID:26765039

  7. Metallic Nanoislands on Graphene as Highly Sensitive Transducers of Mechanical, Biological, and Optical Signals

    PubMed Central

    2016-01-01

    This article describes an effect based on the wetting transparency of graphene; the morphology of a metallic film (≤20 nm) when deposited on graphene by evaporation depends strongly on the identity of the substrate supporting the graphene. This control permits the formation of a range of geometries, such as tightly packed nanospheres, nanocrystals, and island-like formations with controllable gaps down to 3 nm. These graphene-supported structures can be transferred to any surface and function as ultrasensitive mechanical signal transducers with high sensitivity and range (at least 4 orders of magnitude of strain) for applications in structural health monitoring, electronic skin, measurement of the contractions of cardiomyocytes, and substrates for surface-enhanced Raman scattering (SERS, including on the tips of optical fibers). These composite films can thus be treated as a platform technology for multimodal sensing. Moreover, they are low profile, mechanically robust, semitransparent and have the potential for reproducible manufacturing over large areas. PMID:26765039

  8. Synthesis, characterization and biological activities of ciprofloxacin drug based metal complexes.

    PubMed

    Patel, Mohan N; Dosi, Promise A; Bhatt, Bhupesh S

    2012-09-01

    The interaction of small molecules with DNA has attracted a great deal of attention. Mixed ligand copper(II) complexes of type [Cu(cpf)(Ln)Cl] [cpf = ciprofloxacin, Ln = phenanthroline derivatives] were synthesized and characterized by elemental analysis, reflectance, IR and mass spectra. Viscosity measurements, absorption titration and DNA melting temperature studies were employed to determine the mode of binding of complexes with DNA. DNA cleavage study showed better cleaving ability of the complexes compare to metal salts and standard drug. The SOD mimic study showed IC50 value of complexes in the range of 0.95 to 1.75 µM. Antibacterial activity was assayed against selective Gram(-ve) and Gram(+ve) microorganisms. PMID:24061319

  9. Supramolecular structural, thermal properties and biological activity of 3-(2-methoxyphenoxy)propane-1,2-diol metal complexes

    NASA Astrophysics Data System (ADS)

    Mahmoud, Walaa H.; Mahmoud, Nessma F.; Mohamed, Gehad G.; El-Bindary, Ashraf A.; El-Sonbati, Adel Z.

    2015-04-01

    New bi- and trivalent transition metal complexes of ligand 3-(2-methoxyphenoxy)propane-1,2-diol (GFS) were synthesized. The ligand and complexes were characterized via: melting point, UV/Visible, IR, 1H NMR, mass and diffused reflectance spectroscopy. The molecular structure of the investigated ligand (GFS) is optimized theoretically and the quantum chemical parameters are calculated. In addition, the complexes were characterized based on conductivity measurement, thermal analysis and biological activity. The infrared spectral study of GFS and its complexes, act as monobasic tridentate through the oxygen atom of hydroxyl group and two etheric oxygen atoms. Also, coordination to the unprotonated oxygen is evidenced from the disappearance of the OH signal in the 1H NMR spectra after complexation. The thermogravimetric analysis of the complexes shows metal oxide remaining as the final product. The compounds were tested against four bacterial species; two Gram positive bacteria (Bacillus subtilis and Staphylococcus aureus) and two Gram negative bacteria (Escherichia coli and Pseudomonas aeruginosa) as well as antifungal activity against (Candida albicans). The complexes showed significant activities against Gram positive bacteria than Gram negative bacteria. [Cd(GFS)Cl(H2O)2] complex showed remarkable antifungal activity. However, some complexes showed more chemotherapeutic efficiency than the parent GFS drug. The drug and complexes were also screened for their in vitro anticancer activity against the Breast cell line (MFC7) and the results obtained show that they exhibit a considerable anticancer activity.

  10. Trace Metals in the Early Ocean, Biological Implications, and Evolving Biospheric Redox

    NASA Astrophysics Data System (ADS)

    Lyons, T. W.; Scott, C.; Gill, B. C.; Anbar, A. D.

    2008-12-01

    Dissolved molybdenum abounds in modern, oxygen-rich seawater as the highly soluble molybdate ion. But this trace metal, also a nutrient essential to phytoplankton productivity, was not always so readily available. Several periods of the geologic past are noted for being euxinic (i.e., oxygen-poor and sulfide-rich) at regional or perhaps even global scales. During the Proterozoic in particular, numerous euxinic settings may have persisted in the ocean for a billion years or more following the initial rise of oxygen in the atmosphere. Under such conditions, Mo is sequestered efficiently, and corresponding limitation in the oceanic inventory may have impacted nitrogen fixation by prokaryotes, as well as uptake of fixed nitrogen by early eukaryotes. Mo is essential for nitrogen fixation and nitrate assimilation as a cofactor for nitrogenase and assimilatory nitrate reductase enzymes, respectively. Evidence for analogous limitations is emerging for portions of the Paleozoic and Mesozoic, but the potential impacts have not yet been considered. In each case, the critical arguments hang on our ability (1) to estimate oceanic extents of oxygen-poor, sulfide-rich settings for the time slice of interest and (2) to discriminate Mo drawdown in the global ocean from that occurring locally within individual basins. Traditional and emerging approaches for distinguishing local from global ancient anoxia/euxinia will be highlighted with an eye toward estimating the impact on availability of Mo and other bioessential, redox-sensitive transition metals. The context for this exploration will be the long history of evolving redox in the ocean and atmosphere from the Archean forward. The Phanerozoic examples are also associated with major biotic extinction events, and our understanding of the relationships among the primary drivers of extinction, widespread euxinic conditions, and the impact of micronutrient availability during extinction and recovery remains nascent.

  11. Derivatives of phosphate Schiff base transition metal complexes: synthesis, studies and biological activity

    NASA Astrophysics Data System (ADS)

    El-Wahab, Z. H. Abd; El-Sarrag, M. R.

    2004-01-01

    We report the synthesis and structural characterization of series of tetra- and hexacoordinate metal chelate complexes of phosphate Schiff base ligands having the general composition LMX n·H 2O and L 2MX n (L=phosphate Schiff base ligand; M=Ag +, Mn 2+, Cu 2+, Zn 2+, Cd 2+, Hg 2+, or Fe 3+ and X=NO 3-, Br - or Cl -). The structure of the prepared compounds was investigated using elemental analysis, IR, 1H and 31P NMR, UV-vis, mass spectra, solid reflectance, magnetic susceptibility and conductance measurements as well as conductometric titration. In all the complexes studied, the ligands act as a chelate ligand with coordination involving the phosphateO-atom and the azomethineN-atom. IR, solid reflectance spectra and magnetic moment measurement are used to infer the structure and to illustrate the coordination capacity of ligand. IR spectra show the presence of coordinated nitrate and water molecule, the magnetic moments of all complexes show normal magnetic behavior and the electronic spectra of the metal complexes indicate a tetra- and octahedral structure for Mn 2+, octahedral structure of Fe 3+ and both square-planar and distorted octahedral structure for Cu 2+ complexes. Antimicrobial activity of the ligands and their complexes were tested using the disc diffusion method and the chosen strains include Staphylococcus aureus, Pseudomonas aereuguinosa, Klebsiella penumoniae, Escherichia coli, Microsporum canis, Trichophyton mentagrophyte and Trichophyton rubrum. Some known antibiotics are included for the sake of comparison and the chosen antibiotic are Amikacin, Doxycllin, Augmantin, Sulperazon, Unasyn, Septrin, Cefobid, Ampicillin, Nitrofurantion, Traivid and Erythromycin.

  12. Nuclear microscopy in biomedical analysis with special emphasis on clinical metal biology

    NASA Astrophysics Data System (ADS)

    Lindh, Ulf; Frisk, Peter; Nyström, Joakim; Danersund, Antero; Hudecek, Romuald; Lindvall, Anders; Thunell, Stig

    1997-07-01

    Nuclear microscopy based upon developments in high energy ion beam techniques is by now an accepted technique in many fields of research. The advancements into the biomedical field have, however, been slower than expected. A major factor explaining this tendency is the availability of nuclear microscopy. This paper reviews briefly the biomedical work using nuclear microscopy that has been carried out since the 4 th International Conference on Nuclear Microprobe Technology and Applications held in Shanghai. Nuclear microscopy of isolated individual blood cells from patients adversely affected by metal exposure from dental amalgam has been performed both before and after removal of the metallic fillings. The elemental profile of blood cells was more or less normalised after treatment. Some of these results will be presented to illustrate a medical application. Results from bulk analysis by ICP-MS of erythrocytes and plasma before and after treatment will also be presented to illustrate the difference in information content between these two approaches as well as the need for complementary information in solving biomedical problems. As part of a larger study of acute porphyria, nuclear microscopy of blood cells was included among the 78 laboratory tests. The approach in this study was unbiased in the sense that no hypothesis was formulated as to which laboratory parameters would be the most explanatory for health or disease. Multivariate discriminant analysis was applied to the large amounts of data acquired. This approach led to the hypothesis that oxidative stress increased the synthesis of manganese-dependent superoxide dismutase in the mitochondria of polymorphonuclear leukocytes, explaining the increase of manganese in these cells. Antioxidant therapy was therefore applied to a couple of patients with porphyria, however, without clinical success.

  13. Scanning electron microscopy at macromolecular resolution in low energy mode on biological specimens coated with ultra thin metal films.

    PubMed

    Peters, K R

    1979-01-01

    In this report, conditions for attaining high resolution in scanning electron microscopy with soft biological specimens are described using the currently available high resolution scanning electron microscopes in emission mode of low energy electrons (secondary and charging electrons). Retinal rod outer segments, red blood cells, intestinal mucosa, and ferritin molecules were all used as biological test specimens. From uncoated specimens a new source of signal, referred to as a discharge signal, can provide a high yield of low energy electrons from an excitation area approximately the size of the beam's cross section. Additionally, under these conditions sufficient topographic contrast can be achieved by applying ultra thin metal coatins. A 0.5 nm thick gold film is found sufficient for generating the total signal, whereas increased coating thickness causes additional topographic background signal. However, a 2.0 nm film is needed for imaging surface details with the present instrument. Ultra thin, even, and grainless tantalum films have been found effective in eliminating the charging artifacts caused by external fields, and the decoration artifacts caused by crystal growth as seen in gold films. To improve, in high magnification work on ultra thin coated specimen, signal-to-noise ratio, methods for obtaining saturation of the signal with discharge electrons are shown. The necessity of confirming the information obtained in SEM by independent techniques (TEM of stereo-replicas or ultra thin sections) is discussed. PMID:392703

  14. Molecularly doped metals.

    PubMed

    Avnir, David

    2014-02-18

    The many millions of organic, inorganic, and bioorganic molecules represent a very rich library of chemical, biological, and physical properties that do not show up among the approximately 100 metals. The ability to imbue metals with any of these molecular properties would open up tremendous potential for the development of new materials. In addition to their traditional features and their traditional applications, metals would have new traits, which would merge their classical virtues such as conductivity and catalytic activity with the diverse properties of these molecules. In this Account, we describe a new materials methodology, which enables, for the first time, the incorporation and entrapment of small organic molecules, polymers, and biomolecules within metals. These new materials are denoted dopant@metal. The creation of dopant@metal yields new properties that are more than or different from the sum of the individual properties of the two components. So far we have developed methods for the doping of silver, copper, gold, iron, palladium, platinum, and some of their alloys, as well as Hg-Ag amalgams. We have successfully altered classical metal properties (such as conductivity), induced unorthodox properties (such as rendering a metal acidic or basic), used metals as heterogeneous matrices for homogeneous catalysts, and formed new metallic catalysts such as metals doped with organometallic complexes. In addition, we have created materials that straddle the border between polymers and metals, we have entrapped enzymes to form bioactive metals, we have induced chirality within metals, we have made corrosion-resistant iron, we formed efficient biocidal materials, and we demonstrated a new concept for batteries. We have developed a variety of methods for synthesizing dopant@metals including aqueous homogeneous and heterogeneous reductions of the metal cations, reductions in DMF, electrochemical entrapments, thermal decompositions of zerovalent metal carbonyls

  15. Predicting the toxicity of metal mixtures.

    PubMed

    Balistrieri, Laurie S; Mebane, Christopher A

    2014-01-01

    The toxicity of single and multiple metal (Cd, Cu, Pb, and Zn) solutions to trout is predicted using an approach that combines calculations of: (1) solution speciation; (2) competition and accumulation of cations (H, Ca, Mg, Na, Cd, Cu, Pb, and Zn) on low abundance, high affinity and high abundance, low affinity biotic ligand sites; (3) a toxicity function that accounts for accumulation and potency of individual toxicants; and (4) biological response. The approach is evaluated by examining water composition from single metal toxicity tests of trout at 50% mortality, results of theoretical calculations of metal accumulation on fish gills and associated mortality for single, binary, ternary, and quaternary metal solutions, and predictions for a field site impacted by acid rock drainage. These evaluations indicate that toxicity of metal mixtures depends on the relative affinity and potency of toxicants for a given aquatic organism, suites of metals in the mixture, dissolved metal concentrations and ratios, and background solution composition (temperature, pH, and concentrations of major ions and dissolved organic carbon). A composite function that incorporates solution composition, affinity and competition of cations for two types of biotic ligand sites, and potencies of hydrogen and individual metals is proposed as a tool to evaluate potential toxicity of environmental solutions to trout. PMID:23973545

  16. Hydrogen as an Indicator to Assess Biological Activity During Trace-Metal Bioremediation

    NASA Astrophysics Data System (ADS)

    Jaffe, P. R.; Komlos, J.; Brown, D. G.; Lovley, D. R.

    2002-05-01

    The design and operation of a trace-metal or radionuclide bioremediation scheme requires that specific redox conditions be achieved at given zones of an aquifer for a predetermined duration. Tools are therefore needed to identify and quantify the terminal electron acceptor processes (TEAPs) that are being achieved during bioremediation in an aquifer, and that this is done at a high spatial resolution. Hydrogen holds the promise of being a key parameter that may be used to identify TEAPs. Theoretical analysis have shown that steady-state hydrogen levels in the subsurface are solely dependent upon the physiological parameters of the hydrogen-consuming microorganisms, and that hydrogen concentrations increase as each successive TEAP yields less energy for bacterial growth. The assumptions for this statement may not hold during a bioremediation scheme in which an organic substrate is injected into the subsurface and where organisms may consume hydrogen and carbon simultaneously. The objective of the research is to gain a basic understanding of the hydrogen dynamics in an aquifer during a trace metal/radionuclide bioremediation scheme. For this purpose, a series of batch studies have been conducted during the first year of this project. In these studies the utilization of acetate and hydrogen by geobacter sulfurreducens were studied. In all cases Fe(III) was the electron acceptor. Microcosms were set up to investigate the utilization of hydrogen and acetate when either of them is the sole electron donor and when both are present and utilized simultaneously as electron donor. These experiments were conducted for varying initial conditions of the hydrogen and acetate concentration, and the disappearance of these compounds plus the evolution of Fe(II) as well as biomass was monitored over time. The results of these studies indicate that the biokinetic coefficients describing the rate of hydrogen utilization are not affected by the simultaneous utilization of acetate. While

  17. Fluorescent probes and bioimaging: alkali metals, alkaline earth metals and pH.

    PubMed

    Yin, Jun; Hu, Ying; Yoon, Juyoung

    2015-07-21

    All living species and life forms have an absolute requirement for bio-functional metals and acid-base equilibrium chemistry owing to the critical roles they play in biological processes. Hence, a great need exists for efficient methods to detect and monitor biometals and acids. In the last few years, great attention has been paid to the development of organic molecule based fluorescent chemosensors. The availability of new synthetic fluorescent probes has made fluorescence microscopy an indispensable tool for tracing biologically important molecules and in the area of clinical diagnostics. This review highlights the recent advances that have been made in the design and bioimaging applications of fluorescent probes for alkali metals and alkaline earth metal cations, including lithium, sodium and potassium, magnesium and calcium, and for pH determination within biological systems. PMID:25317749

  18. Hydrogen as an Indicator to Assess Biological Activity During Trace-Metal Bioremediation

    SciTech Connect

    Jaffe, Peter R.; Lovley, Derek; Komlos, John; Brown, Derick

    2004-03-17

    The design and operation of a trace-metal or radionuclide bioremediation scheme requires that specific redox conditions be achieved at given zones of an aquifer for a pre-determined duration. Tools are therefore needed to identify and quantify the terminal electron accepting processes (TEAPs) that are being achieved during bioremediation in an aquifer, and that this be done at a high spatial resolution. Dissolved hydrogen (H{sub 2}) concentrations have been shown to correlate with specific TEAPs during bioremediation in an aquifer (Table 1). Theoretical analysis has shown that these steady-state hydrogen levels are solely dependent upon the physiological parameters of the hydrogen-consuming microorganisms, with hydrogen concentrations increasing as each successive TEAP yields less energy for bacterial growth. The assumptions for this statement may not hold during a bioremediation scheme in which an organic substrate is injected into the subsurface and where organisms may consume hydrogen and carbon simultaneously. This research examines the effects of simultaneous hydrogen and carbon utilization through obtaining kinetic parameters of both hydrogen and carbon consumption under iron reducing conditions in batch experiments. A dual-donor model was formulated and compared to flow-through column experiments.

  19. Microwave Assisted Synthesis, Spectrofluorometric Characterization of Azomethine as Intermediate for Transition Metal Complexes with Biological Application.

    PubMed

    Zayed, Mohie E M; Asiri, Abdullah M; Khan, Salman A

    2016-05-01

    Azomethine (1, 5 - Dimethyl - 2 - phenyl -[(3, 4, 5 -trimethoxybenzylidene) amino] -1, 2 - dihydropyrazol - 3 - one) (DTAD) was synthesized by the reaction of 4-aminophenazone with 3,4,5 trimrthoxybenzaldehyd by microwave irradiation. Physicochemical studies such as electronic absorption, molar absorptivity, oscillator strength, dipole moment, florescent quantum yield were investigated in order to explore the analytical potential of azomethine dye. Azomethine go through the solubilization in different micelles and may be used as a probe or quencher to determine the critical micelle concentration (CMC) of SDS and CTAB. It's coordinate to metal salt through the pyrazol-3-one oxygen and the azomethine nitrogen. The structure of ligand and its meal complexes was elucidated by IR, (1)H, (13)C-NMR, EI-MS spectroscopic methods and elemental analysis. The antibacterial activity of these compounds were first tested in vitro by the disc diffusion assay against two Gram-positive and two Gram-negative bacteria, and then the minimum inhibitory concentration was using chloramphenicol as reference drug. The results showed that compound 1.1 is better inhibitor of both types of tested bacteria as compared to chloramphenicol. PMID:27048225

  20. New biological reference materials - in vivo incorporated toxic metals in water hyacinth tissues

    SciTech Connect

    Austin, J.R.; Simon, S.J.; Williams, L.R.; Beckert, W.F.

    1985-06-01

    The purpose of this study was to demonstrate that high-quality reference materials, containing high levels of multiple toxic elements, can be produced with in vivo incorporation procedures. The approach taken was to produce water hyacinth tissue materials - leaves and stems containing high levels of arsenic, cadmium, lead, and mercury - as follows: apply a hydroponic feeding procedure for the in vivo incorporation of toxic elements into water hyacinths; dry, blend, and homogenize the plant materials and determine the levels of the incorporated elements and the homogeneity of the generated plant material; demonstrate that low-level control materials can be successfully blended with high-level materials to yield a homogeneous material with intermediate toxicant levels; evaluate the precision of the analytical methods used to determine toxic element levels in the materials; and evaluate the stability of the resulting materials. Sufficient quantities of the parent materials were produced so that characterized reference materials can now be made available on request. Levels of the toxic elements incorporated in water hyacinth leaves were 100, 300, 60, and 27 times the levels present in the control leaves for arsenic, cadmium, lead, and mercury, respectively. Overall precision of sampling, subsampling, and digestion, and chemical analysis of the treated materials, ranged from 3 to 10% relative standard deviation and was generally comparable to that of three NBS biological reference materials tested. 3 references, 1 figure, 4 tables.

  1. Coordination modes, spectral, thermal and biological evaluation of hetero-metal copper containing 2-thiouracil complexes

    NASA Astrophysics Data System (ADS)

    Masoud, Mamdouh S.; Soayed, Amina A.; El-Husseiny, Amel F.

    2012-12-01

    Mononuclear copper complex [CuL(NH3)4]Cl2·0.5H2O and three new hetero-metallic complexes: [Cu2Ni(L)2(NH3)2Cl2·6H2O] 2H2O, [Cu3Co(L)4·8H2O]Cl·4·5H2O, and [Cu4Co2Ni(L)3(OH)4(NH3)Cl4·3H2O]4H2O where L is 2-thiouracil, were prepared and characterized by elemental analyses, molar conductance, room-temperature magnetic susceptibility, spectral (IR, UV-Vis and ESR) studies and thermal analyses techniques (TG, DTG and DTA). The molar conductance data revealed that [CuL(NH3)4]Cl2·0.5H2O and [Cu3Co(L)4·8H2O]Cl·4.5H2O are electrolytes, while, [Cu2Ni(L)2(NH3)2Cl2·6H2O]·2H2O and [Cu4Co2Ni(L)3(OH)4(NH3)Cl4·3H2O]4H2O are non-electrolytes. IR spectra showed, that 2-thiouracil ligand behaves as a bidentate or tetradentate ligand. The geometry around the metal atoms is octahedral in all the prepared complexes except in [Cu4Co2Ni(L)3(OH)4(NH3)Cl4·3H2O]4H2O complex where square planar environment around Co(II), Ni(II) and Cu(II) were suggested. Thermal decomposition study of the prepared complexes was monitored by TG, DTG and DTA analyses under N2 atmosphere. The decomposition course and steps were analyzed. The order of chemical reactions (n) was calculated via the peak symmetry method and the activation parameters of the non- isothermal decomposition were computed from the thermal decomposition data. The negative values of ΔS∗ deduced the ordered structures of the prepared complexes compared to their starting reactants. The antimicrobial activity of the prepared complexes were screened in vitro against a Gram positive, a Gram negative bacteria, a filamentous fungi and a yeast. The antimicrobial screening data showed that the studied compounds exhibited a good level of activity against Escherichia coli, Staphylococcus aureus and Candida albicans but have no efficacy against Aspergillus flavus. It was observed that [Cu4Co2Ni(L)3(OH)4(NH3)Cl4·3H2O]4H2O complex showed the most intensive activity against the tested microorganisms. Trials to prepare single crystals from

  2. Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory; preparation procedure for aquatic biological material determined for trace metals

    USGS Publications Warehouse

    Hoffman, Gerald L.

    1996-01-01

    A method for the chemical preparation of tissue samples that are subsequently analyzed for 22 trace metals is described. The tissue-preparation procedure was tested with three National Institute of Standards and Technology biological standard reference materials and two National Water Quality Laboratory homogenized biological materials. A low-temperature (85 degrees Celsius) nitric acid digestion followed by the careful addition of hydrogen peroxide (30-percent solution) is used to decompose the biological material. The solutions are evaporated to incipient dryness, reconstituted with 5 percent nitric acid, and filtered. After filtration the solutions were diluted to a known volume and analyzed by inductively coupled plasma-mass spectrometry (ICP-MS), inductively coupled plasma-atomic emission spectrometry (ICP-AES), and cold vapor-atomic absorption spectrophotometry (CV-AAS). Many of the metals were determined by both ICP-MS and ICP-AES. This report does not provide a detailed description of the instrumental procedures and conditions used with the three types of instrumentation for the quantitation of trace metals determined in this study. Statistical data regarding recovery, accuracy, and precision for individual trace metals determined in the biological material tested are summarized.

  3. Microscopic characteristic of biological iron sulfide composites during the generation process and the association with treatment effect on heavy metal wastewater.

    PubMed

    Yang, Yang; Xie, Yifei; Li, Xudong; Zhou, Jingchao; Liu, Jingwei

    2014-01-01

    Heavy metal pollution is a serious environmental concern worldwide, resulting in both environmental and human harm. Recently, studies have shown that environmental biotechnologies based on sulfate reduction offer a potential for removal of toxic heavy metals. Biological iron sulfide composites are iron sulfide compounds generated in situ by sulfate-reducing bacteria. In this study, microscopic morphological changes during the composites' generation process were studied, and the effect of biological iron sulfide composites in different generation phases on treatment of heavy metal wastewater was investigated to establish the correlation between macro-effect and micro-properties. The results revealed that the generation process of biological iron sulfide composites occurs in three phases: the formation phase, stationary phase, and agglomeration phase. The stationary phase can be divided into a pre-stationary phase and post-stationary phase. It was found that the best treatment time for Cr(6+) is in the pre-stationary phase, while the best treatment time for Cu(2+)and Cd(2+) is in the post-stationary phase. The results of this study further prove the benefits of treatment of heavy metal wastewater using biological sulfide composites and provide theoretical guidance in practical applications. PMID:25325556

  4. Selectivity of the highly preorganized tetradentate ligand 2,9-di(pyrid-2-yl)-1,10-phenanthroline for metal ions in aqueous solution, including lanthanide(III) ions and the uranyl(VI) cation.

    PubMed

    Carolan, Ashley N; Cockrell, Gregory M; Williams, Neil J; Zhang, Gang; VanDerveer, Donald G; Lee, Hee-Seung; Thummel, Randolph P; Hancock, Robert D

    2013-01-01

    Some metal ion complexing properties of DPP (2,9-Di(pyrid-2-yl)-1,10-phenanthroline) are reported with a variety of Ln(III) (Lanthanide(III)) ions and alkali earth metal ions, as well as the uranyl(VI) cation. The intense π-π* transitions in the absorption spectra of aqueous solutions of 10(-5) M DPP were monitored as a function of pH and metal ion concentration to determine formation constants of the alkali-earth metal ions and Ln(III) (Ln = lanthanide) ions. It was found that log K(1)(DPP) for the Ln(III) ions has a peak at Ln(III) = Sm(III) in a plot of log K(1) versus 1/r(+) (r(+) = ionic radius for 8-coordination). For Ln(III) ions larger than Sm(III), there is a steady rise in log K(1) from La(III) to Sm(III), while for Ln(III) ions smaller than Sm(III), log K(1) decreases slightly to the smallest Ln(III) ion, Lu(III). This pattern of variation of log K(1) with varying size of Ln(III) ion was analyzed using MM (molecular mechanics) and DFT (density functional theory) calculations. Values of strain energy (∑U) were calculated for the [Ln(DPP)(H(2)O)(5)](3+) and [Ln(qpy)(H(2)O)(5)](3+) (qpy = quaterpyrdine) complexes of all the Ln(III) ions. The ideal M-N bond lengths used for the Ln(III) ions were the average of those found in the CSD (Cambridge Structural Database) for the complexes of each of the Ln(III) ions with polypyridyl ligands. Similarly, the ideal M-O bond lengths were those for complexes of the Ln(III) ions with coordinated aqua ligands in the CSD. The MM calculations suggested that in a plot of ∑U versus ideal M-N length, a minimum in ∑U occurred at Pm(III), adjacent in the series to Sm(III). The significance of this result is that (1) MM calculations suggest that a similar metal ion size preference will occur for all polypyridyl-type ligands, including those containing triazine groups, that are being developed as solvent extractants in the separation of Am(III) and Ln(III) ions in the treatment of nuclear waste, and (2) Am(III) is very

  5. Regulation of Cation Balance in Saccharomyces cerevisiae

    PubMed Central

    Cyert, Martha S.; Philpott, Caroline C.

    2013-01-01

    All living organisms require nutrient minerals for growth and have developed mechanisms to acquire, utilize, and store nutrient minerals effectively. In the aqueous cellular environment, these elements exist as charged ions that, together with protons and hydroxide ions, facilitate biochemical reactions and establish the electrochemical gradients across membranes that drive cellular processes such as transport and ATP synthesis. Metal ions serve as essential enzyme cofactors and perform both structural and signaling roles within cells. However, because these ions can also be toxic, cells have developed sophisticated homeostatic mechanisms to regulate their levels and avoid toxicity. Studies in Saccharomyces cerevisiae have characterized many of the gene products and processes responsible for acquiring, utilizing, storing, and regulating levels of these ions. Findings in this model organism have often allowed the corresponding machinery in humans to be identified and have provided insights into diseases that result from defects in ion homeostasis. This review summarizes our current understanding of how cation balance is achieved and modulated in baker’s yeast. Control of intracellular pH is discussed, as well as uptake, storage, and efflux mechanisms for the alkali metal cations, Na+ and K+, the divalent cations, Ca2+ and Mg2+, and the trace metal ions, Fe2+, Zn2+, Cu2+, and Mn2+. Signal transduction pathways that are regulated by pH and Ca2+ are reviewed, as well as the mechanisms that allow cells to maintain appropriate intracellular cation concentrations when challenged by extreme conditions, i.e., either limited availability or toxic levels in the environment. PMID:23463800

  6. Influence of biologically-active substances on {sup 137}Cs and heavy metals uptake by Barley plant

    SciTech Connect

    Kruglov, Stanislav; Filipas, Alexander

    2007-07-01

    Available in abstract form only. Full text of publication follows: When solving the problem of contaminated agricultural lands rehabilitation, most of attention is concentrated on the effective means which allow the obtaining of ecologically safe production. The minimization of radionuclides and heavy metals (HM) content in farm products on the basis of their migration characteristics in agro-landscapes and with the regard for different factors influencing contaminants behavior in the soil-plant system is of great significance. Our investigation has shown that the effect of biologically active substances (BAS) using for seeds treatment on {sup 137}Cs transfer to barley grown on Cd contaminated soil was dependent on their properties and dosage, characteristics of soil contamination and biological peculiarities of plants, including stage of plants development. Seeds treatment by plant growth regulator Zircon resulted in a significant increase in {sup 137}Cs activity in harvest (40- 50%), increase in K concentration and significant reduction in Ca concentration. Increased Cd content in soil reduced {sup 137}Cs transfer to barley plants by 30-60% (p<0,05) and Zircon application further reduced its concentration. Ambiol and El also reduced {sup 137}Cs uptake by roots and Cd and Pb phyto-toxicity. The experimental data do not make it possible to link the BAS effect on inhibition of {sup 137}Cs absorption by plants directly with their influence on HM phyto-toxicity. The dependence of Concentration Ratio of {sup 137}Cs on the Ambiol and El dose was not proportional and the most significant decrease in the radionuclide uptake by plants was reported with the use of dose showing the most pronounced stimulating effect on the barley growth and development. The pre-sowing seed treatment with Ambiol increased Pb absorption by 35-50% and, on the contrary, decreased Cd uptake by plants by 30-40%. (authors)

  7. Hydrogen as an Indicator to Assess Biological Activity During Trace-Metal Bioremediation

    SciTech Connect

    Peter R. Jaffe, John Komlos, Derick Brown

    2005-09-27

    Trace-metal and/or radionuclide bioremediation schemes require that specific redox conditions be achieved at given zones of an aquifer. Tools are therefore needed to identify the terminal electron acceptor processes (TEAPs) that are being achieved during bioremediation in an aquifer. Dissolved hydrogen (H2) concentrations have been shown to correlate with specific TEAPs during bioremediation in an aquifer. Theoretical analysis has shown that these steady-state H2 levels are solely dependent upon the physiological parameters of the hydrogen-consuming microorganisms, with H2 concentrations increasing as each successive TEAP yields less energy for bacterial growth. The objective of this research was to determine if H2 can still be used as an indicator of TEAPs during a uranium bioremediation scheme where an organic substrate is injected into the subsurface and organisms may consume H2 and carbon simultaneously. In addition, the effect of iron bioavailability on H2 concentrations during iron reduction was observed. The first phase of research determined the effect of a competing electron donor (acetate) on the kinetics of H2 utilization by Geobacter sulfurreducens in batch cultures under iron reducing conditions. The results indicate that, though the Monod kinetic coefficients describing the rate of H2 utilization under iron-reducing conditions correlate energetically with the coefficients found in previous experiments under methanogenic and sulfate-reducing conditions, conventionally measured growth kinetics do not predict the steady state H2 levels typical for each TEAP. In addition, with acetate and H2 as simultaneous electron donors, there is slight inhibition between the two electron donors for G. sulfurreducens, and this can be modeled through competitive inhibition terms in the classic Monod formulation, resulting in slightly higher H2 concentrations under steady state conditions in the presence of acetate. This dual-donor model indicates that the steady state H

  8. Study of Ion Specific Interactions of Alkali Cations with Dicarboxylate Dianions

    SciTech Connect

    Murdachaew, Garold; Valiev, Marat; Kathmann, Shawn M.; Wang, Xue B.

    2012-02-10

    Alkali metal cations often show pronounced ion specific interactions and selectivity with macromolecules in biological processes, colloids, and interfacial sciences, but a fundamental understanding about the underlying microscopic mechanism is still very limited. Here we report a direct probe of interactions between alkali metal cations (M{sup +}) and dicarboxylate dianions, O{sub 2}C(CH{sub 2})nCO{sub 2} (D{sub n}{sup 2-}) in the gas phase by combined photoelectron spectroscopy (PES) and ab initio electronic structure calculation on nine M{sup +}-D{sub n}{sup 2-} complexes (M = Li, Na, K; n = 2, 4, 6). PES spectra show that the electron binding energy (EBE) decreases from Li{sup +} to Na{sup +} to K{sup +} for complexes of M{sup +}-D{sub 2}{sup 2-}, whereas the order is Li{sup +} cation M{sup +}. The observed variance of EBEs reflects how well a specific dicarboxylate dianion accommodates each M{sup +}. This work demonstrates the delicate interplay among several factors (electrostatic interaction, size matching, and strain energy) that likely play critical roles in determining the structures and energetics of gaseous clusters as well as ion specificity and selectivity in solutions and biological systems.

  9. Photoinduced electron transfer between the cationic complexes Ru(NH3)5pz2+ and trans-RuCl([15]aneN4)NO2+ mediated by phosphate ion: visible light generation of nitric oxide for biological targets.

    PubMed

    da Silva, Roberto S; Marchesi, Mario S P; Khin, Chosu; Lunardi, Claure N; Bendhack, Lusiane M; Ford, Peter C

    2007-06-21

    The photochemical behavior of the tetraazamacrocyclic complex trans-RuCl([15]ane)(NO)2+ (RuNO2+) in a 10 mM phosphate buffer solution, pH 7.4, and in the presence of Ru(NH3)5pz2+ (Rupz2+) is reported. Irradiation (436 nm) of an aqueous solution containing both cationic complexes as PF6- salts labilizes NO from RuNO2+ with a quantum yield (phiNO) dependent on the concentration of Rupz2+ with a maximum value of phiNO (1.03(11)x10(-3) einstein mol-1) found for a solution with equimolar concentrations (5x10(-5) M) of the two complexes in phosphate buffer solution. The quantitative behavior of this system suggests that the two cations undergo preassociation such that photoexcitation of the visible absorbing Rupz2+ is followed by electron or energy transfer to RuNO2+, which does not absorb appreciably at the excitation wavelength, and this leads to NO release from the reduced nitrosyl complex. Notably, the NO release was not seen in the absence of phosphate buffer; thus, it appears that phosphate ions mediate NO generation, perhaps by facilitating formation of a supramolecular complex between the two ruthenium cations. Reexamination of the cyclic voltammetry of Rupz2+ showed that the electrochemical behavior of this species is also affected by the presence of the phosphate buffer. PMID:17439277

  10. Characterization of selective binding of alkali cations with carboxylate by x-ray absorption spectroscopy of liquid microjets

    SciTech Connect

    Saykally, Richard J; Uejio, Janel S.; Schwartz, Craig P.; Duffin, Andrew M.; Drisdell, Walter S.; Cohen, Ronald C.; Saykally, Richard J.

    2008-01-08

    We describe an approach for characterizing selective binding between oppositely charged ionic functional groups under biologically relevant conditions. Relative shifts in K-shell x-ray absorption spectra of aqueous cations and carboxylate anions indicate the corresponding binding strengths via perturbations of carbonyl antibonding orbitals. XAS spectra measured for aqueous formate and acetate solutions containing lithium, sodium, and potassium cations reveal monotonically stronger binding of the lighter metals, supporting recent results from simulations and other experiments. The carbon K-edge spectra of the acetate carbonyl feature centered near 290 eV clearly indicate a preferential interaction of sodium versus potassium, which was less apparent with formate. These results are in accord with the Law of Matching Water Affinities, relating relative hydration strengths of ions to their respective tendencies to form contact ion pairs. Density functional theory calculations of K-shell spectra support the experimental findings.

  11. Bacterio-electric leaching of metals

    DOEpatents

    Lazaroff, Norman; Dugan, Patrick R.

    1992-07-07

    The separation of cationic materials from an ore body is assisted by the application of an electric potential, and resulting current, to the ore body, in association with iron or sulphur oxidizing bacteria. The combined process induces migration of cationic metals to a cathode suspended within the ore body so that the cationic metal can be preferentially separated from the ore body.

  12. Bacterio-electric leaching of metals

    DOEpatents

    Lazaroff, Norman; Dugan, Patrick R.

    1992-01-01

    The separation of cationic materials from an ore body is assisted by the application of an electric potential, and resulting current, to the ore body, in association with iron or sulphur oxidizing bacteria. The combined process induces migration of cationic metals to a cathode suspended within the ore body so that the cationic metal can be preferentially separated from the ore body.

  13. Structural biology of the sequestration and transport of heavy metal toxins: NMR structure determination of proteins containing the -Cys-X-Y-Cys-metal binding motifs. 1997 annual progress report

    SciTech Connect

    Opella, S.J.

    1997-01-01

    'There are enormous amounts of heavy metals in the environment, much of it in the form of organometallic compounds resulting from various types of industrial and military waste. Nearly all of these metals and compounds are highly toxic to biological organisms including humans. However, some bacteria thrive in the presence of high concentrations of heavy metal toxins because they possess efficient mechanisms for the detoxification of these metals and compounds. Heavy metals appear to be universally toxic because of their non-selective chemistry, for example Hg(II) reacts with essentially all exposed sulfhydryl groups on proteins, thus, it may seem surprising that any organism at all can survive these chemical insults much less those that grow in a toxic milieu. However, the prebiotic environment was undoubtedly heavily polluted with heavy metals from geological processes, and the most primitive organisms simply had to evolve mechanisms for dealing with them if they were going to be able to utilize Cys, His, and the other amino acids that contribute to metal binding sites in their proteins. Genes associated with bacterial resistance to Ag, AsO{sub 2}, AsO{sub 4}, Bi, Cd, Co, CrO{sub 4}, Cu, Hg, iNi, TeO{sub 3}, TI, Pb, Zn, and other metals of environmental concern have been described (Silver, 1992; Silver and Walderhaug, 1995).'

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

    NASA Astrophysics Data System (ADS)

    Justin Dhanaraj, Chellaian; Johnson, Jijo

    2014-01-01

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

  15. Synthesis and characterization of norfloxacin-transition metal complexes (group 11, IB): Spectroscopic, thermal, kinetic measurements and biological activity

    NASA Astrophysics Data System (ADS)

    Refat, Moamen S.

    2007-12-01

    The investigation of the new structures of Ag(I), Cu(II) and Au(III) complexes, [Ag 2(Nor) 2](NO 3) 2, [Cu(Nor) 2(H 2O) 2]SO 4·5H 2O and [Au(Nor) 2 (H 2O) 2]Cl 3 (where, Nor = norfloxacin) was done during the reaction of silver(I), copper(II) and gold(III) ions with norfloxacin drug ligand. Elemental analysis of CHN, infrared, electronic, 1H NMR and mass spectra, as well as thermo gravimetric analysis (TG and DTG) and conductivity measurements have been used to characterize the isolated complexes. The powder XRD studies confirm the amorphous nature of the complexes. The norfloxacin ligand is coordinated to Ag(I) and Au(III) ions as a neutral monodentate chelating through the N atom of piperidyl ring, but the copper(II) complex is coordinated through the carbonyl oxygen atom (quinolone group) and the oxygen atom of the carboxylic group. The norfloxacin and their metal complexes have been biologically tested, which resulted in norfloxacin complexes showing moderate activity against the gram positive and gram negative bacteria as well as against fungi.

  16. The effectiveness of spent coffee grounds and its biochar on the amelioration of heavy metals-contaminated water and soil using chemical and biological assessments.

    PubMed

    Kim, Min-Suk; Min, Hyun-Gi; Koo, Namin; Park, Jeongsik; Lee, Sang-Hwan; Bak, Gwan-In; Kim, Jeong-Gyu

    2014-12-15

    Spent coffee grounds (SCG) and charred spent coffee grounds (SCG-char) have been widely used to adsorb or to amend heavy metals that contaminate water or soil and their success is usually assessed by chemical analysis. In this work, the effects of SCG and SCG-char on metal-contaminated water and soil were evaluated using chemical and biological assessments; a phytotoxicity test using bok choy (Brassica campestris L. ssp. chinensis Jusl.) was conducted for the biological assessment. When SCG and SCG-char were applied to acid mine drainage, the heavy metal concentrations were decreased and the pH was increased. However, for SCG, the phytotoxicity increased because a massive amount of dissolved organic carbon was released from SCG. In contrast, SCG-char did not exhibit this phenomenon because any easily released organic matter was removed during pyrolysis. While the bioavailable heavy metal content decreased in soils treated with SCG or SCG-char, the phytotoxicity only rose after SCG treatment. According to our statistical methodology, bioavailable Pb, Cu and As, as well as the electrical conductivity representing an increase in organic content, affected the phytotoxicity of soil. Therefore, applying SCG during environment remediation requires careful biological assessments and evaluations of the efficiency of this remediation technology. PMID:25242543

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

    PubMed

    Sychrovský, Vladimír; Sponer, Jirí; Hobza, Pavel

    2004-01-21

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

  18. Biological availability of traffic-related platinum-group elements (palladium, platinum, and rhodium) and other metals to the zebra mussel (Dreissena polymorpha) in water containing road dust.

    PubMed

    Zimmermann, Sonja; Alt, Friedrich; Messerschmidt, Jürgen; von Bohlen, Alex; Taraschewski, Horst; Sures, Bernd

    2002-12-01

    The uptake and bioaccumulation of 15 road dust metals by the zebra mussel (Dreissena polymorpha) were investigated in laboratory exposure studies with emphasis on the traffic-related platinum-group elements (PGEs) palladium (Pd), platinum (Pt), and rhodium (Rh). The biological availability of the metals may depend on water characteristics, so the mussels were maintained in two types of water: nonchlorinated tap water and humic water of a bog lake, both of which contained dust of a moderately frequented road. After an exposure period of 26 weeks, soft tissues of the mussels were freeze-dried and analyzed for the metals. The metal concentrations in the mussel soft tissue ranged from several hundred micrograms per gram (e.g., for iron [Fe]) to less than 10 ng/g (for PGEs). Metal uptake from the road dust by the mussels was found for the PGEs and silver (Ag), bismuth (Bi), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), Fe, lead (Pb), and antimony (Sb). After maintenance of mussels in road dust-contaminated tap water, bioaccumulation factors (BAF = (C(exposed mussels) - C(control mussels))/C(total metal, water), where c is concentration) decreased in the following order: Cu > Cd > Ag > Pd > Sb > Pb > Fe > Pt > Rh. The biological availability of most metals was enhanced by humic water as compared to tap water. Our results show a hitherto unrecognized high availability of Pd for the mussels. Thus, this metal should be monitored more intensively in the environment to assess its distribution in the biosphere. PMID:12463569

  19. EFFECT OF CATIONS ON ALUMINUM SPECIATION UNDER ALKALINE CONDITIONS

    SciTech Connect

    Taylor-Pashow, K.; Hobbs, D.

    2012-07-31

    A series of experiments were performed to examine the effect of metal cations common to high level waste on the phase of aluminum formed. Experiments were performed at temperature of 150 C, 75 C, and room temperature, either without additional metal cation, or with 0.01-0.2 molar equivalents of either Ni{sup 2+}, Fe{sup 3+}, Mn{sup 2+}, or Cr{sup 3+}. Results showed that temperature has the greatest effect on the phase obtained. At 150 C, boehmite is the only phase obtained, independent of the presence of other metal cations, with only one exception where a small amount of gibbsite was also detected in the product when 0.2 equivalents of Ni{sup 2+} was present. At 75 C, a mixture of phases is obtained, most commonly including bayerite and gibbsite; however, boehmite is also formed under some conditions, including in the absence of additional metal ion. At room temperature, in the absence of additional metal ion, a mixture of bayerite and gibbsite is obtained. The addition of another metal cation suppresses the formation of gibbsite, with a couple of exceptions (0.2 equivalents of Ni{sup 2+} or 0.01 equivalents of Cr{sup 3+}) where both phases are still obtained.

  20. Cation specific binding with protein surface charges.

    PubMed

    Hess, Berk; van der Vegt, Nico F A

    2009-08-11

    Biological organization depends on a sensitive balance of noncovalent interactions, in particular also those involving interactions between ions. Ion-pairing is qualitatively described by the law of "matching water affinities." This law predicts that cations and anions (with equal valence) form stable contact ion pairs if their sizes match. We show that this simple physical model fails to describe the interaction of cations with (molecular) anions of weak carboxylic acids, which are present on the surfaces of many intra- and extracellular proteins. We performed molecular simulations with quantitatively accurate models and observed that the order K(+) < Na(+) < Li(+) of increasing binding affinity with carboxylate ions is caused by a stronger preference for forming weak solvent-shared ion pairs. The relative insignificance of contact pair interactions with protein surfaces indicates that thermodynamic stability and interactions between proteins in alkali salt solutions is governed by interactions mediated through hydration water molecules. PMID:19666545

  1. MLKL forms cation channels

    PubMed Central

    Xia, Bingqing; Fang, Sui; Chen, Xueqin; Hu, Hong; Chen, Peiyuan; Wang, Huayi; Gao, Zhaobing

    2016-01-01

    The mixed lineage kinase domain-like (MLKL) protein is a key factor in tumor necrosis factor-induced necroptosis. Recent studies on necroptosis execution revealed a commitment role of MLKL in membrane disruption. However, our knowledge of how MLKL functions on membrane remains very limited. Here we demonstrate that MLKL forms cation channels that are permeable preferentially to Mg2+ rather than Ca2+ in the presence of Na+ and K+. Moreover, the N-terminal domain containing six helices (H1-H6) is sufficient to form channels. Using the substituted cysteine accessibility method, we further determine that helix H1, H2, H3, H5 and H6 are transmembrane segments, while H4 is located in the cytoplasm. Finally, MLKL-induced membrane depolarization and cell death exhibit a positive correlation to its channel activity. The Mg2+-preferred permeability and five transmembrane segment topology distinguish MLKL from previously identified Mg2+-permeable channels and thus establish MLKL as a novel class of cation channels. PMID:27033670

  2. Chemical and biological processes for multi-metal extraction from waste printed circuit boards of computers and mobile phones.

    PubMed

    Shah, Monal B; Tipre, Devayani R; Dave, Shailesh R

    2014-11-01

    E-waste printed circuit boards (PCB) of computers, mobile-phones, televisions, LX (LongXiang) PCB in LED lights and bulbs, and tube-lights were crushed to ≥250 µm particle size and 16 different metals were analysed. A comparative study has been carried out to evaluate the extraction of Cu-Zn-Ni from computer printed circuit boards (c-PCB) and mobile-phone printed circuit boards (m-PCB) by chemical and biological methods. Chemical process showed the extraction of Cu-Zn-Ni by ferric sulphate was best among the studied chemical lixiviants. Bioleaching experiments were carried out with the iron oxidising consortium, which showed that when E-waste and inoculum were added simultaneously in the medium (one-step process); 60.33% and 87.50% Cu, 75.67% and 85.67% Zn and 71.09% and 81.87% Ni were extracted from 10 g L(-1) of c-PCB and m-PCB, respectively, within 10-15 days of reaction time. Whereas, E-waste added after the complete oxidation of Fe(2+) to Fe(3+) iron containing medium (two-step process) showed 85.26% and 99.99% Cu, 96.75% and 99.49% Zn and 93.23% and 84.21% Ni extraction from c-PCB and m-PCB, respectively, only in 6-8 days. Influence of varying biogenerated Fe(3+) and c-PCB concentrations showed that 16.5 g L(-1) of Fe(3+) iron was optimum up to 100 g L(-1) of c-PCB. Changes in pH, acid consumed and redox potential during the process were also studied. The present study shows the ability of an eco-friendly process for the recovery of multi-metals from E-waste even at 100 g L(-1) printed circuit boards concentration. PMID:25278513

  3. Cationic Bolaamphiphiles for Gene Delivery

    NASA Astrophysics Data System (ADS)

    Tan, Amelia Li Min; Lim, Alisa Xue Ling; Zhu, Yiting; Yang, Yi Yan; Khan, Majad

    2014-05-01

    Advances in medical research have shed light on the genetic cause of many human diseases. Gene therapy is a promising approach which can be used to deliver therapeutic genes to treat genetic diseases at its most fundamental level. In general, nonviral vectors are preferred due to reduced risk of immune response, but they are also commonly associated with low transfection efficiency and high cytotoxicity. In contrast to viral vectors, nonviral vectors do not have a natural mechanism to overcome extra- and intracellular barriers when delivering the therapeutic gene into cell. Hence, its design has been increasingly complex to meet challenges faced in targeting of, penetration of and expression in a specific host cell in achieving more satisfactory transfection efficiency. Flexibility in design of the vector is desirable, to enable a careful and controlled manipulation of its properties and functions. This can be met by the use of bolaamphiphile, a special class of lipid. Unlike conventional lipids, bolaamphiphiles can form asymmetric complexes with the therapeutic gene. The advantage of having an asymmetric complex lies in the different purposes served by the interior and exterior of the complex. More effective gene encapsulation within the interior of the complex can be achieved without triggering greater aggregation of serum proteins with the exterior, potentially overcoming one of the great hurdles faced by conventional single-head cationic lipids. In this review, we will look into the physiochemical considerations as well as the biological aspects of a bolaamphiphile-based gene delivery system.

  4. Relationship between chemical structure and biological activity of alkali metal o-, m- and p-anisates. FT-IR and microbiological studies

    NASA Astrophysics Data System (ADS)

    Kalinowska, M.; Piekut, J.; Lewandowski, W.

    2011-11-01

    In this work we investigated relationship between molecular structure of alkali metal o-, m-, p-anisate molecules and their antimicrobial activity. For this purpose FT-IR spectra for lithium, sodium, potassium, rubidium and caesium anisates in solid state and solution were recorded, assigned and analysed. Microbial activity of studied compounds was tested against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Proteus vulgaris. In order to evaluate the dependency between chemical structure and biological activity of alkali metal anisates the statistical analysis (multidimensional regression and principal component) was performed for selected wavenumbers from FT-IR spectra and parameters that describe microbial activity of anisates. The obtained statistical equations show the existence of correlation between molecular structure of anisates and their biological properties.

  5. Cationic RAFT polymerization using ppm concentrations of organic acid.

    PubMed

    Uchiyama, Mineto; Satoh, Kotaro; Kamigaito, Masami

    2015-02-01

    A metal-free, cationic, reversible addition-fragmentation chain-transfer (RAFT) polymerization was proposed and realized. A series of thiocarbonylthio compounds were used in the presence of a small amount of triflic acid for isobutyl vinyl ether to give polymers with controlled molecular weight of up to 1×10(5) and narrow molecular-weight distributions (Mw /Mn <1.1). This "living" or controlled cationic polymerization is applicable to various electron-rich monomers including vinyl ethers, p-methoxystyrene, and even p-hydroxystyrene that possesses an unprotected phenol group. A transformation from cationic to radical RAFT polymerization enables the synthesis of block copolymers between cationically and radically polymerizable monomers, such as vinyl ether and vinyl acetate or methyl acrylate. PMID:25511364

  6. α-Cationic Arsines: Synthesis, Structure, Reactivity, and Applications.

    PubMed

    Dube, Jonathan W; Zheng, Yiying; Thiel, Walter; Alcarazo, Manuel

    2016-06-01

    A series of structurally differentiated cationic arsines containing imidazolium, cyclopropenium, formamidinium, and pyridinium substituents have been synthesized through short and scalable routes. Evaluation of the donor properties of these compounds by IR spectroscopy and DFT calculations reveals similar σ-electron-releasing abilities for all of them; however, their π-acceptor properties are strongly influenced by the nature of the positively charged group. We describe the coordination chemistry of the newly prepared α-cationic arsines toward different metal centers and their reactivity in the presence of strong oxidants to afford cationic As(V) species. Their unique electronic properties have been exploited in Pt(II) catalysis to develop a new catalyst with remarkable activity in the cycloisomerization of enynes to trisubstituted cyclopropanes. To the best of our knowledge, this is the first report on the use of α-cationic arsine ligands in catalysis. PMID:27214007

  7. Spatial characteristics of sediment trace metals in an eastern boundary upwelling retention area (St. Helena Bay, South Africa): A hydrodynamic biological pump hypothesis

    NASA Astrophysics Data System (ADS)

    Monteiro, Pedro M. S.; Roychoudhury, Alakendra N.

    2005-10-01

    St. Helena Bay, a retention zone located in the southern Benguela upwelling system, is an important fish nursery. However, it suffers from seasonal bottom water hypoxia causing major economic losses. Anoxic conditions are linked to sulfide fluxes from bottom sediments defined by a high sedimentation rate of organic matter. It is proposed that trace metals may play an important role in alleviating part of the ecological stress by forming sulfide complexes in such systems. A spatially intensive data set of sediment biogeochemical characteristics showed that POC and trace metals (Cr, Cu, Zn, Ni, etc.) accumulated in the central zone of the Bay. Furthermore, trace metal concentrations were strongly correlated with both POC and Al. To explain the observed biogeochemical relationships in St. Helena Bay, we propose a hypothesis that links the upwelling retention hydrodynamics, primary productivity and sediment trace metal distribution. Trace metals are incorporated into phytoplankton cells in the euphotic zone but rapidly sediment along with particulate organics, on their senescence. Both, the biological pump and the dispersion of particulates are primarily controlled by the hydrodynamics prevalent within St. Helena Bay, which also govern the retention zone in the shadow of one of the major upwelling cells. The dynamics of entrainment-stratification drives the productivity, while a residual cyclonic gyre concentrates the surface productivity within the bay. Bed-shear stresses spatially constrain the accumulation of biogenic organic matter, which governs the trace metal biogeochemistry of the sediments, along a narrow terrigenous mud belt.

  8. Metals and Breast Cancer

    PubMed Central

    Byrne, Celia; Divekar, Shailaja D.; Storchan, Geoffrey B.; Parodi, Daniela A.; Martin, Mary Beth

    2014-01-01

    Metalloestrogens are metals that activate the estrogen receptor in the absence of estradiol. The metalloestrogens fall into two subclasses: metal/metalloid anions and bivalent cationic metals. The metal/metalloid anions include compounds such as arsenite, nitrite, selenite, and vanadate while the bivalent cations include metals such as cadmium, calcium, cobalt, copper, nickel, chromium, lead, mercury, and tin. The best studied metalloestrogen is cadmium. It is a heavy metal and a prevalent environmental contaminant with no known physiological function. This review addresses our current understanding of the mechanism by which cadmium and the bivalent cationic metals activate estrogen receptor-α. The review also summarizes the in vitro and in vivo evidence that cadmium functions as an estrogen and the potential role of cadmium in breast cancer. PMID:23338949

  9. 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.

  10. 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.

  11. Photophysical study of the Ca 2+-chelator QUIN 2 ligand: effect of divalent and trivalent cations

    NASA Astrophysics Data System (ADS)

    Guardigli, M.; Sabbatini, N.

    1991-05-01

    The photophysical properties of complexes of the Ca 2+-chelator QUIN 2 ligand with divalent and trivalent cations have been studied. The absorption of the ligand is almost independent of the nature of the complexing cations, while the fluorescence emission strongly depends on the electric charge of the cations. Metal emission upon excitation in the ligand has been observed for the Eu 3+ complex, but not for the Tb 3+ complex.

  12. Eaton's reagent-mediated domino π-cationic arylations of aromatic carboxylic acids to Iasi-red polymethoxylated polycyclic aromatic hydrocarbons: products with unprecedented biological activities as tubulin polymerization inhibitors.

    PubMed

    Ghinet, Alina; Gautret, Philippe; Hijfte, Nathalie Van; Ledé, Bertrand; Hénichart, Jean-Pierre; Bîcu, Elena; Darbost, Ulrich; Rigo, Benoît; Daïch, Adam

    2014-08-01

    A rapid domino π-cationic arylation of aromatic carboxylic acids, mediated by Eaton's reagent, has been developed for the synthesis of Iasi-red polymethoxylated polycyclic aromatic hydrocarbons (PAHs). This route is currently the easiest method to obtain such popular PAH compounds, which bear in addition numerous methoxy groups. The domino process was generalized, the structure of the obtained red products and the mechanism of their formations were elucidated, and some of their photophysical properties were determined. Newly synthesized polymethoxylated-PAHs were tested for their interaction with tubulin polymerization as well as for their cytotoxicity on a panel of NCI-60 human cancer cell lines. Interestingly, one of these rubicene derivatives exhibited remarkable cytotoxicity in vitro, including inhibition of leukemia, colon, melanoma, CNS, and ovarian cancer cell lines with GI50 values in the low nanomolar range (GI50 < 10 nM). PMID:25042333

  13. Low cation coordination in oxide melts

    SciTech Connect

    Skinner, Lawrie; Benmore, Chris J; Du, Jincheng; Weber, Richard; Neuefeind, Joerg C; Tumber, Sonia; Parise, John B

    2014-01-01

    The complete set of Faber-Ziman partial pair distribution functions for a rare earth oxide liquid were measured for the first time by combining aerodynamic levitation, neutron diffraction, high energy x-ray diffraction and isomorphic substitution using Y2 O3 and Ho2 O3 melts. The average Y- O coordination is measured to be 5.5(2), which is significantly less than the octahedral coordination of crystalline Y2 O3 (or Ho2 O3 ). Investigation of high temperature La2 O3 , ZrO2 , SiO2 , and Al2 O3 melts by x-ray diffraction and molecular dynamics simulations also show lower-than-crystal cation- oxygen coordination. These measurements suggest a general trend towards lower M-O coordination compared to their crystalline counterparts. It is found that this coordination number drop is larger for lower field strength, larger radius cations and is negligible for high field strength (network forming) cations. These findings have broad implications for predicting the local structure and related physical properties of metal-oxide melts and oxide glasses.

  14. Anion binding in biological systems

    NASA Astrophysics Data System (ADS)

    Feiters, Martin C.; Meyer-Klaucke, Wolfram; Kostenko, Alexander V.; Soldatov, Alexander V.; Leblanc, Catherine; Michel, Gurvan; Potin, Philippe; Küpper, Frithjof C.; Hollenstein, Kaspar; Locher, Kaspar P.; Bevers, Loes E.; Hagedoorn, Peter-Leon; Hagen, Wilfred R.

    2009-11-01

    We compare aspects of biological X-ray absorption spectroscopy (XAS) studies of cations and anions, and report on some examples of anion binding in biological systems. Brown algae such as Laminaria digitata (oarweed) are effective accumulators of I from seawater, with tissue concentrations exceeding 50 mM, and the vanadate-containing enzyme haloperoxidase is implicated in halide accumulation. We have studied the chemical state of iodine and its biological role in Laminaria at the I K edge, and bromoperoxidase from Ascophyllum nodosum (knotted wrack) at the Br K edge. Mo is essential for many forms of life; W only for certain archaea, such as Archaeoglobus fulgidus and the hyperthermophilic archaeon Pyrococcus furiosus, and some bacteria. The metals are bound and transported as their oxo-anions, molybdate and tungstate, which are similar in size. The transport protein WtpA from P. furiosus binds tungstate more strongly than molybdate, and is related in sequence to Archaeoglobus fulgidus ModA, of which a crystal structure is known. We have measured A. fulgidus ModA with tungstate at the W L3 (2p3/2) edge, and compared the results with the refined crystal structure. XAS studies of anion binding are feasible even if only weak interactions are present, are biologically relevant, and give new insights in the spectroscopy.

  15. Cation-halide transport through peptide pores containing aminopicolinic acid.

    PubMed

    Basak, Debajyoti; Sridhar, Sucheta; Bera, Amal K; Madhavan, Nandita

    2016-05-18

    Synthetic pores that selectively transport ions of biological significance through membranes could be potentially used in medical diagnostics or therapeutics. Herein, we report cation-selective octapeptide pores derived from alanine and aminopicolinic acid. The ion transport mechanism through the pores has been established to be a cation-chloride symport. The cation-chloride co-transport is biologically essential for the efficient functioning of the central nervous system and has been implicated in diseases such as epilepsy. The pores formed in synthetic lipid bilayers do not exhibit any closing events. The ease of synthesis as well as infinite lifetimes of these pores provides scope for modifying their transport behaviour to develop sensors. PMID:27137995

  16. A New Sample Substrate for Imaging and Correlating Organic and Trace Metal Composition in Biological Cells and Tissues

    SciTech Connect

    Miller,L.; Wang, Q.; Smith, R.; Zhong, H.; Elliott, D.; Warren, J.

    2007-01-01

    Many disease processes involve alterations in the chemical makeup of tissue. Synchrotron-based infrared (IR) and X-ray fluorescence (XRF) microscopes are becoming increasingly popular tools for imaging the organic and trace metal compositions of biological materials, respectively, without the need for extrinsic labels or stains. Fourier transform infrared microspectroscopy (FTIRM) provides chemical information on the organic components of a material at a diffraction-limited spatial resolution of 2-10 {mu}m in the mid-infrared region. The synchrotron X-ray fluorescence (SXRF) microprobe is a complementary technique used to probe trace element content in the same systems with a similar spatial resolution. However to be most beneficial, it is important to combine the results from both imaging techniques on a single sample, which requires precise overlap of the IR and X-ray images. In this work, we have developed a sample substrate containing a gold grid pattern on its surface, which can be imaged with both the IR and X-ray microscopes. The substrate consists of a low trace element glass slide that has a gold grid patterned on its surface, where the major and minor parts of the grid contain 25 and 12 nm gold, respectively. This grid pattern can be imaged with the IR microscope because the reflectivity of gold differs as a function of thickness. The pattern can also be imaged with the SXRF microprobe because the Au fluorescence intensity changes with gold thickness. The tissue sample is placed on top of the patterned substrate. The grid pattern's IR reflectivity image and the gold SXRF image are used as fiducial markers for spatially overlapping the IR and SXRF images from the tissue. Results show that IR and X-ray images can be correlated precisely, with a spatial resolution of less than one pixel (i.e., 2-3 microns). The development of this new tool will be presented along with applications to paraffin-embedded metalloprotein crystals, Alzheimer's disease, and hair

  17. A cationic gold complex cleaves BArF24.

    PubMed

    Weber, Simone G; Zahner, David; Rominger, Frank; Straub, Bernd F

    2012-11-28

    A sterically shielded cationic NHC gold complex IPr**Au-BArF(24) without solvent coordination has been prepared in situ in CH(2)Cl(2). The monovalent transition metal electrophile, a "soft proton", heterolytically activates the C-B bond of the weakly coordinating counterion tetrakis[3,5-bis(trifluoromethyl)phenyl]borate at room temperature. PMID:23073224

  18. Metal complexes of ONO donor Schiff base ligand as a new class of bioactive compounds; Synthesis, characterization and biological evolution

    NASA Astrophysics Data System (ADS)

    Kumar Naik, K. H.; Selvaraj, S.; Naik, Nagaraja

    2014-10-01

    Present work reviews that, the synthesis of (E)-N";-((7-hydroxy-4-methyl-2-oxo-2H-chromen-8-yl)methylene)benzohydrazide [L] ligand and their metal complexes. The colored complexes were prepared of type [M2+L]X2, where M2+ = Mn, Co, Ni, Cu, Sr and Cd, L = (7-hydroxy-4-methyl-2-oxo-2H-chromen-8-yl)methylene)benzohydrazide, X = Cl-. Ligand derived from the condensation of 8-formyl-7-hydroxy-4-methylcoumarin and benzohydrazide in the molar ratio 1:1 and in the molar ratio 1:2 for metal complexes have been prepared. The chelation of the ligand to metal ions occurs through the both oxygen groups, as well as the nitrogen atoms of the azomethine group of the ligand. Reactions of the Schiff base ligand with Manganese(II), Cobalt(II), Nickel(II), Copper(II), Strontium(II), and Cadmium(II) afforded the corresponding metal complexes. The structures of the obtained ligand and their respective metal complexes were elucidated by infra-red, elemental analysis, Double beam UV-visible spectra, conductometric measurements, magnetic susceptibility measurements and also thermochemical studies. The metal complex exhibits octahedral coordination geometrical arrangement. Schiff base ligand and their metal complexes were tested against antioxidants, antidiabetic and antimicrobial activities have been studied. The Schiff base metal complexes emerges effective α-glucosidase inhibitory activity than free Schiff base ligand.

  19. Benthic macroalgae as biological indicators of heavy metal pollution in the marine environments: a biomonitoring approach for pollution assessment.

    PubMed

    Chakraborty, Sukalyan; Bhattacharya, Tanushree; Singh, Gurmeet; Maity, Jyoti Prakash

    2014-02-01

    Metal pollution in the marine coastline environment is an important topical issue in the context of ecological disturbance and climate change. Heavy metal contaminations (Cd, Cr, Cu, Mn, Ni, Pb and Zn) in seawater and surficial sediments, as well as macroalgal diversity, were determined in six different locations along the coast of the Gulf of Kutch in India. The marine coastline environment was found to be enriched with Cd and Zn in comparison to other metals. Significant (p ≤ 0.05) inter-elemental positive-correlations were observed between Fe-Mn, Fe-Cu, Fe-Cr, Fe-Zn, Cr-Cu, Cu-Mn, and Cd-Zn, as well as negative-correlations between Cd-Pb, Ni-Pb, and Zn-Pb. Though genus specific macroalgal responses to heavy metal accumulation were significant, species specific response was insignificant (p ≤ 0.05). The relative abundance of metals in macroalgae followed the order of Fe>Zn>Mn>Cu>Cd>Cr>Ni>Pb. The high uptake of metals in green algae (Ulva lactuca and Enteromorpha intestinalis) and brown algae (Padina gymnospora and Dictyota bartayresiana) suggested that these algae may be used as potential biomonitors for heavy metal pollution. Three pollution indicators, Contamination Factor (CF), Enrichment Factor (EF) and Geochemical Index (Igeo) were calculated to determine the degree of metal pollution in the marine coastline and the contribution of anthropogenic influence. PMID:24433792

  20. Cation Diffusion Facilitator family: Structure and function.

    PubMed

    Kolaj-Robin, Olga; Russell, David; Hayes, Kevin A; Pembroke, J Tony; Soulimane, Tewfik

    2015-05-22

    The Cation Diffusion Facilitators (CDFs) form a family of membrane-bound proteins capable of transporting zinc and other heavy metal ions. Involved in metal tolerance/resistance by efflux of ions, CDF proteins share a two-modular architecture consisting of a transmembrane domain (TMD) and C-terminal domain (CTD) that protrudes into the cytoplasm. Discovery of a Zn²⁺ and Cd²⁺ CDF transporter from a marine bacterium Maricaulis maris that does not possess the CTD questions current perceptions regarding this family of proteins. This article describes a new, CTD-lacking subfamily of CDFs and our current knowledge about this family of proteins in the view of these findings. PMID:25896018

  1. Synthesis, characterization and biological activities of metal(II) dipicolinate complexes derived from pyridine-2,6-dicarboxylic acid and 2-(piperazin-1-yl)ethanol

    NASA Astrophysics Data System (ADS)

    Büyükkıdan, Nurgün; Yenikaya, Cengiz; İlkimen, Halil; Karahan, Ceyda; Darcan, Cihan; Korkmaz, Tülin; Süzen, Yasemin

    2015-12-01

    The new water-soluble and air stable compounds (H2ppz)[Co(dipic)2]·6H2O (1), (H2ppz)[Ni(dipic)2]·6H2O (2) and (H2ppz)[Zn(dipic)2]·6H2O (3) were prepared by the reaction of corresponding metal(II) acetates and a proton transfer salt, (H2ppz) (Hdipic)2, (4) of pyridine-2,6-dicarboxylic acid (H2dipic) and 2-(piperazin-1-yl)ethanol (ppz). The compounds 1-3 were characterized by elemental, IR, UV-vis. thermal analyses, magnetic measurement and single crystal X-ray diffraction studies. The molecular structures of the title compounds consist of one 1-(2-hydroxyethyl)piperazine-1,4-diium (H2ppz+2) cation, one bis(pyridine-2,6-dicarboxylate)metal(II) [M(dipic)2]2- anion, and six uncoordinated water molecules. In compounds 1-3 the metal ions coordinate to two oxygen and one nitrogen atoms of two pyridine-2,6-dicarboxylate molecules forming an octahedral environment. Antimicrobial activities against Gram (-) wild type (Escherichia coli and Pseudomonas aeruginosa), Gram (+) wild type (Staphylococcus aureus, Staphylococcus epidermidis, Bacillus cereus and Bacillus subtilis) and clinical isolate (Morganella morganii, Proteus vulgaris and Enterobacter aeruginosa) were also studied. The results were reported, discussed and compared with the corresponding starting materials ((H2ppz) (Hdipic)2 (4), H2dipic and ppz). MIC (Minimal Inhibition Concentration) values of the newly synthesized compounds were determined as 4000 μg/ml (except B. subtilis and clinical isolate E. aeruginosa, >4000 μg/ml).

  2. Synthesis, characterization and biological approach of metal chelates of some first row transition metal ions with halogenated bidentate coumarin Schiff bases containing N and O donor atoms.

    PubMed

    Prabhakara, Chetan T; Patil, Sangamesh A; Toragalmath, Shivakumar S; Kinnal, Shivashankar M; Badami, Prema S

    2016-04-01

    The impregnation of halogen atoms in a molecule is an emerging trend in pharmaceutical chemistry. The presence of halogens (Cl, Br, I and F) increases the lipophilic nature of molecule and improves the penetration of lipid membrane. The presence of electronegative halogen atoms increases the bio- activity of core moiety. In the present study, Co(II), Ni(II) and Cu(II) complexes are synthesised using Schiff bases (HL(I) and HL(II)), derived from 8-formyl-7-hydroxy-4-methylcoumarin/3-chloro-8-formyl-7-hydroxy-4-methylcoumarin with 2,4-difluoroaniline/o-toluidine respectively. The synthesized compounds were characterized by spectral (IR, NMR, UV-visible, Mass, ESI-MS, ESR), thermal, fluorescence and molar conductivity studies. All the synthesized metal complexes are completely soluble in DMF and DMSO. The non-electrolytic nature of the metal complexes was confirmed by molar conductance studies. Elemental analysis study suggest [ML2(H2O)2] stoichiometry, here M=Co(II), Ni(II) and Cu(II), L=deprotonated ligand. The obtained IR data supports the binding of metal ion to Schiff base. Thermal study suggests the presence of coordinated water molecules. Electronic spectral results reveal six coordinated geometry for the synthesized metal complexes. The Schiff bases and their metal complexes were evaluated for antibacterial (Pseudomonas aureginosa and Proteus mirabilis), antifungal (Aspergillus niger and Rhizopus oryzae), anthelmintic (Pheretima posthuma) and DNA cleavage (Calf Thymus DNA) activities. PMID:26874303

  3. Development of a Model, Metal-reducing Microbial Community for a System Biology Level Assessment of Desulfovibrio vulgaris as part of a Community

    SciTech Connect

    Elias, Dwayne; Schadt, Christopher; Miller, Lance; Phelps, Tommy; Brown, S. D.; Arkin, Adam; Hazen, Terry; Drake, Megin; Yang, Z.K.; Podar, Mircea

    2010-05-17

    One of the largest experimental gaps is between the simplicity of pure cultures and the complexity of open environmental systems, particularly in metal-contaminated areas. These microbial communities form ecosystem foundations, drive biogeochemical processes, and are relevant for biotechnology and bioremediation. A model, metal-reducing microbial community was constructed as either syntrophic or competitive to study microbial cell to cell interactions, cell signaling and competition for resources. The microbial community was comprised of the metal-reducing Desulfovibrio vulgaris Hildenborough and Geobacter sulfurreducens PCA. Additionally, Methanococcus maripaludis S2 was added to study complete carbon reduction and maintain a low hydrogen partial pressure for syntrophism to occur. Further, considerable work has been published on D. vulgaris and the D. vulgaris/ Mc. maripaludis co-culture both with and without stress. We are extending this work by conducting the same stress conditions on the model community. Additionally, this comprehensive investigation includes physiological and metabolic analyses as well as specially designed mRNA microarrays with the genes for all three organisms on one slide so as to follow gene expression changes in the various cultivation conditions as well as being comparable to the co- and individual cultures. Further, state-of -the-art comprehensive AMT tag proteomics allows for these comparisons at the protein level for a systems biology assessment of a model, metal-reducing microbial community. Preliminary data revealed that lactate oxidation by D. vulgaris was sufficient to support both G. sulfurreducens and M. maripaludis via the excretion of H2 and acetate. Fumarate was utilized by G. sulfurreducens and reduced to succinate since neither of the other two organisms can reduce fumarate. Methane was quantified, suggesting acetate and H2 concentrations were sufficient for M. maripaludis. Steady state community cultivation will allow for

  4. Dissecting the cation-cation interaction between two uranyl units.

    PubMed

    Tecmer, Paweł; Hong, Sung W; Boguslawski, Katharina

    2016-07-21

    We present a state-of-the-art computational study of the uranyl(vi) and uranyl(v) cation-cation interactions (dications) in aqueous solution. Reliable electronic structures of two interacting uranyl(vi) and uranyl(v) subunits as well as those of the uranyl(vi) and uranyl(v) clusters are presented for the first time. Our theoretical study elucidates the impact of cation-cation interactions on changes in the molecular structure as well as changes in vibrational and UV-Vis spectra of the bare uranyl(vi) and uranyl(v) moieties for different total spin-states and total charges of the dications. PMID:27335229

  5. Combined effects of temperature changes and metal contamination at different levels of biological organization in yellow perch.

    PubMed

    Grasset, Julie; Ollivier, Élodie; Bougas, Bérénice; Yannic, Glenn; Campbell, Peter G C; Bernatchez, Louis; Couture, Patrice

    2016-08-01

    In this study, we measured the effects of temperature (9°C, 20°C, and 28°C), metal contamination (cadmium and nickel) and their interaction on yellow perch (Perca flavescens) using liver enzymatic and transcriptomic endpoints and biometric indices. Kidney metal concentrations increased with a rise of temperature. The biometric indices analysed (Fulton condition factor, pyloric cæca, hepatosomatic and gonadosomatic indices) generally decreased with an increase of temperature but not with metal contamination. At the enzymatic level, the activity of superoxide dismutase (SOD), involved in antioxidant response, was affected by both temperature and metal contamination, whereas the activity of glucose-6-phosphate dehydrogenase (G6PDH), involved in energy accumulation but also in antioxidant response, was only affected by metal exposure. The response of perch to the stressors at the transcriptional level differed from the metabolic response. In particular, the transcription level of the cco and g6pdh genes sharply decreased with increasing temperature, while the activities of the corresponding enzymes remained stable. The normal response of the transcription level of the apoptotic gene (diablo) to heat stress was also altered in metal-contaminated fish. The combination of metal and temperature stresses also modified the response of antioxidant metabolism induced by these stressors individually. This study contributes to a better understanding of the influences of natural stressors like temperature on biomarkers commonly used in ecotoxicological studies and will facilitate their interpretation in the context of multiple stressors characteristic of field situations. PMID:27351718

  6. Cationic lipid-mediated nucleic acid delivery: beyond being cationic.

    PubMed

    Rao, N Madhusudhana

    2010-03-01

    Realization of the potential of nucleic acids as drugs is intricately linked to their in vivo delivery. Cationic lipids demonstrated tremendous potential as safe, efficient and scalable in vitro carriers of nucleic acids. For in vivo delivery of nucleic acids, the extant two component liposomal preparations consisting of cationic lipids and nucleic acids have been largely found to be insufficient. Being a soft matter, liposomes readily respond to many physiological variables leading to complex component and morphological changes, thus confounding the efforts in a priori identification of a "competent" formulation. In the recent past many chemical moieties that provide advantage in facing the challenges of barriers in vivo, were incorporated into cationic lipids to improve the transfection efficiency. The cationic lipids, essential for DNA condensation and protection, definitely require additional components to be efficient in vivo. In addition, formulations of cationic lipid carriers with non-lipidic components, mainly peptides, have demonstrated success in in vivo transfection. The present review describes some recent successes of in vivo nucleic acid delivery by cationic lipids. PMID:20060819

  7. Metallic ions as therapeutic agents in tissue engineering scaffolds: an overview of their biological applications and strategies for new developments

    PubMed Central

    Mouriño, Viviana; Cattalini, Juan Pablo; Boccaccini, Aldo R.

    2012-01-01

    This article provides an overview on the application of metallic ions in the fields of regenerative medicine and tissue engineering, focusing on their therapeutic applications and the need to design strategies for controlling the release of loaded ions from biomaterial scaffolds. A detailed summary of relevant metallic ions with potential use in tissue engineering approaches is presented. Remaining challenges in the field and directions for future research efforts with focus on the key variables needed to be taken into account when considering the controlled release of metallic ions in tissue engineering therapeutics are also highlighted. PMID:22158843

  8. Complexation Between Cationic Diblock Copolymers and Plasmid DNA

    NASA Astrophysics Data System (ADS)

    Jung, Seyoung; Reineke, Theresa; Lodge, Timothy

    Deoxyribonucleic acids (DNA), as polyanions, can spontaneously bind with polycations to form polyelectrolyte complexes. When the polycation is a diblock copolymer with one cationic block and one uncharged hydrophilic block, the polyelectrolyte complexes formed with plasmid DNA (pDNA) are often colloidally stable, and show great promise in the field of polymeric gene therapy. While the resulting properties (size, stability, and toxicity to biological systems) of the complexes have been studied for numerous cationic diblocks, the fundamentals of the pDNA-diblock binding process have not been extensively investigated. Herein, we report how the cationic block content of a diblock influences the pDNA-diblock interactions. pDNA with 7164 base pairs and poly(2-deoxy-2-methacrylamido glucopyranose)-block-poly(N-(2-aminoethyl) methacrylamide) (PMAG-b-PAEMA) are used as the model pDNA and cationic diblock, respectively. To vary the cationic block content, two PMAG-b-PAEMA copolymers with similar PMAG block lengths but distinct PAEMA block lengths and a PAEMA homopolymer are utilized. We show that the enthalpy change from pDNA-diblock interactions is dependent on the cationic diblock composition, and is closely associated with both the binding strength and the pDNA tertiary structure.

  9. Structural Biology of The sequestration & Transport of Heavy Metal Toxins: NMR Structure Determination of Proteins Containing the CYS-X-Y-Metal Binding Motif

    SciTech Connect

    Stanley J. Opella

    2004-03-10

    The support from the Department of Energy enabled us to initiate research on several proteins from the bacterial mercury detoxification system; in particular, we were able to determine the structures of MerP and related metal binding sequences. We have also worked on the membrane transport proteins MerF and MerT.

  10. Trace metal concentrations in Posidonia oceanica of North Corsica (northwestern Mediterranean Sea): use as a biological monitor?

    PubMed Central

    Gosselin, Marc; Bouquegneau, Jean-Marie; Lefèbvre, Frédéric; Lepoint, Gilles; Pergent, Gerard; Pergent-Martini, Christine; Gobert, Sylvie

    2006-01-01

    Background Within semi-closed areas like the Mediterranean Sea, anthropic wastes tend to concentrate in the environment. Metals, in particular, are known to persist in the environment and can affect human health due to accumulation in the food chain. The seagrass Posidonia oceanica, widely found in Mediterranean coastal waters, has been chosen as a "sentinel" to quantify the distribution of such pollutants within the marine environment. Using a technique similar to dendrochronology in trees, it can act as an indicator of pollutant levels over a timeframe of several months to years. In the present study, we measured and compared the levels of eight trace metals (Cr, Ni, Cu, Zn, As, Se, Cd, and Pb) in sheaths dated by lepidochronology and in leaves of shoots sampled from P. oceanica meadows collected from six offshore sites in northern Corsica between 1988 and 2004; in the aim to determine 1) the spatial and 2) temporal variations of these metals in these areas and 3) to compared these two types of tissues. Results We found low trace metal concentrations with no increase over the last decade, confirming the potential use of Corsican seagrass beds as reference sites for the Mediterranean Sea. Temporal trends of trace metal concentrations in sheaths were not significant for Cr, Ni, Cu, As or Se, but Zn, Cd, and Pb levels decreased, probably due to the reduced anthropic use of these metals. Similar temporal trends between Cu levels in leaves (living tissue) and in sheaths (dead tissue) demonstrated that lepidochronology linked with Cu monitoring is effective for surveying the temporal variability of this metal. Conclusion Leaves of P. oceanica can give an indication of the metal concentration in the environment over a short time period (months) with good accuracy. On the contrary, sheaths, which gave an indication of changes over long time periods (decades), seem to be less sensitive to variations in the metal concentration in the environment. Changes in human

  11. Synthesis, Spectral Characterization, and Biological Evaluation of Transition Metal Complexes of Bidentate N, O Donor Schiff Bases

    PubMed Central

    Sumrra, Sajjad Hussain; Ambreen, Sabahat; Imran, Muhammad; Danish, Muhammad; Rehmani, Fouzia Sultana

    2014-01-01

    New series of three bidentate N, O donor type Schiff bases (L1)–(L3) were prepared by using ethylene-1,2-diamine with 5-methyl furfural, 2-anisaldehyde, and 2-hydroxybenzaldehyde in an equimolar ratio. These ligands were further complexed with Co(II), Cu(II), Ni(II), and Zn(II) metals to produce their new metal complexes having an octahedral geometry. These compounds were characterized on the basis of their physical, spectral, and analytical data. Elemental analysis and spectral data of the uncomplexed ligands and their metal(II) complexes were found to be in good agreement with their structures, indicating high purity of all the compounds. All ligands and their metal complexes were screened for antimicrobial activity. The results of antimicrobial activity indicated that metal complexes have significantly higher activity than corresponding ligands. This higher activity might be due to chelation process which reduces the polarity of metal ion by coordinating with ligands. PMID:25147493

  12. Structural modulation of molybdenyl iodate architectures by alkali metal cations in AMoO3(IO3) (A = K, Rb, Cs): a facile route to new polar materials with large SHG responses.

    PubMed

    Sykora, Richard E; Ok, Kang Min; Halasyamani, P Shiv; Albrecht-Schmitt, Thomas E

    2002-03-01

    Three new molybdenyl iodates, KMoO3(IO3) (1), RbMoO3(IO3) (2), and CsMoO3(IO3) (3), have been prepared through the hydrothermal reactions of MoO3 with AIO4 (A = K, Rb, or Cs) at 180 C. These compounds are isolated as nearly colorless, air-stable crystals. Single-crystal X-ray diffraction experiments reveal that 1 possesses a corrugated layered structure constructed from molybdenum oxide chains that are bridged by iodate anions. The puckering of the layers is caused by the alignment of bent molybdenyl (MoO2(2+)) groups along one side of the molybdenum oxide chains. The K+ cations separate these layers from one another and serve to balance charge. In contrast, compounds 2 and 3, which are isostructural, form three-dimensional structures with small cavities filled with Rb+ or Cs+ cations. The differences between the structures of 1 and those of 2 and 3 are due to rotation of the molybdenyl units as translation occurs down the molybdenum oxide chains in order to accommodate the increased size of the Rb+ and Cs+ cations. This rotation allows for the iodate anions to bridge the molybdenum oxide chains in an additional dimension, creating a three-dimensional network structure. Furthermore, while 1 crystallizes in a centrosymmetric space group, 2 and 3 crystallize in polar space groups. Second-harmonic generation measurements on 2 and 3 show large responses of 400x alpha-quartz. Differential scanning calorimetry measurements demonstrate that 2 and 3 are thermally stable to 494 and 486 C, respectively. UV-vis diffuse reflectance spectra of these compounds show a high degree of transparency from 1 to 3 eV and a band gap of 3.1 eV. PMID:11866608

  13. Synthesis Characterization and Biological Activity Study of New Schiff and Mannich Bases and Some Metal Complexes Derived from Isatin and Dithiooxamide

    PubMed Central

    Abdulghani, Ahlam J.; Abbas, Nada M.

    2011-01-01

    Two new Schiff and Mannich bases, namely, 1-Morpholinomethyl-3(1′ -N-dithiooxamide)iminoisatin (LIH) and 1-diphenylaminomethyl-3-1′-N-dithiooxamide)iminoisatin (LIIH), were prepared from condensation reaction of new Schiff base 3-(1′-N-dithiooxamide)iminoisatin (SBH) with morpholine or diphenylamine respectively in presence of formaldehyde . The structures were characterized by IR, 1HNMR, mass spectrometry, and CHN analyses. Metal complexes of the two ligands were synthesized, and their structures were characterized by elemental analyses, atomic absorption, IR and UV-visible spectra, molar conductivity, and magnetic moment determination. All complexes showed octahedral geometries except palladium complexes which were square planar. The biological activity of the prepared compounds and some selected metal complexes was tested against three types of bacteria and against cell line of human epidermoid larynx carcinoma (Hep-2). PMID:21949661

  14. Design, spectral characterization, DFT and biological studies of transition metal complexes of Schiff base derived from 2-aminobenzamide, pyrrole and furan aldehyde

    NASA Astrophysics Data System (ADS)

    Tyagi, Prateek; Chandra, Sulekh; Saraswat, B. S.; Sharma, Deepansh

    2015-05-01

    A series of two biologically active Schiff base ligands L1, L2 have been synthesized in equimolar reaction of 2-aminobenzamide with pyrrol-2-carboxaldehyde and furan-2-carboxaldehyde. The synthesized Schiff bases were used for complexation with different metal ions like Co(II), Ni(II) and Cu(II) by using a molar ratio of ligand: metal as 2:1. The characterization of newly formed complexes was done by 1H NMR, UV-Vis, TGA, IR, mass spectrophotometry, EPR and molar conductivity studies. The thermal studies suggested that the complexes are more stable as compared to ligand. In DFT studies the geometries of Schiff bases and metal complexes were fully optimized with respect to the energy using the 6-31+g(d,p) basis set. On the basis of the spectral studies an octahedral geometry has been assigned for Co(II) and Ni(II) complexes and distorted octahedral geometry for Cu(II) complexes. All the synthesized compounds, were studied for their in vitro antimicrobial activities, against four bacterial strains and two fungal strains by using serial dilution method. The data also revealed that the metal complexes showed better activity than the ligands due to chelation/coordination.

  15. Design, spectral characterization, DFT and biological studies of transition metal complexes of Schiff base derived from 2-aminobenzamide, pyrrole and furan aldehyde.

    PubMed

    Tyagi, Prateek; Chandra, Sulekh; Saraswat, B S; Sharma, Deepansh

    2015-05-15

    A series of two biologically active Schiff base ligands L(1), L(2) have been synthesized in equimolar reaction of 2-aminobenzamide with pyrrol-2-carboxaldehyde and furan-2-carboxaldehyde. The synthesized Schiff bases were used for complexation with different metal ions like Co(II), Ni(II) and Cu(II) by using a molar ratio of ligand: metal as 2:1. The characterization of newly formed complexes was done by (1)H NMR, UV-Vis, TGA, IR, mass spectrophotometry, EPR and molar conductivity studies. The thermal studies suggested that the complexes are more stable as compared to ligand. In DFT studies the geometries of Schiff bases and metal complexes were fully optimized with respect to the energy using the 6-31+g(d,p) basis set. On the basis of the spectral studies an octahedral geometry has been assigned for Co(II) and Ni(II) complexes and distorted octahedral geometry for Cu(II) complexes. All the synthesized compounds, were studied for their in vitro antimicrobial activities, against four bacterial strains and two fungal strains by using serial dilution method. The data also revealed that the metal complexes showed better activity than the ligands due to chelation/coordination. PMID:25706679

  16. Cation Defects and Conductivity in Transparent Oxides

    SciTech Connect

    Exarhos, Gregory J.; Windisch, Charles F.; Ferris, Kim F.; Owings, Robert R.

    2007-10-24

    High quality doped zinc oxide and mixed transition metal spinel oxide films have been deposited by means of sputter deposition from metal and metal oxide targets, and by spin casting from aqueous or alcoholic precursor solutions. Deposition conditions and post-deposition processing are found to alter cation oxidation states and their distributions in both oxide materials resulting in marked changes to both optical transmission and electrical response. For ZnO, partial reduction of the neat or doped material by hydrogen treatment of the heated film or by electrochemical processing renders the oxide n-type conducting. Continued reduction was found to diminish conductivity. In contrast, oxidation of the infrared transparent p-type spinel conductors typified by NiCo2O4 was found to increase conductivity. The disparate behavior of these two materials is caused in part by the sign of the charge carrier and by the existence of two different charge transport mechanisms that are identified as free carrier conduction and polaron hopping. While much work has been reported concerning structure/property relationships in the free carrier conducting oxides, there is a significantly smaller body of information on transparent polaron conductors. In this paper, we identify key parameters that promote conductivity in mixed metal spinel oxides and compare their behavior with that of the free carrier TCO’s.

  17. Cationically polymerizable monomers derived from renewable sources. Annual performance report

    SciTech Connect

    Crivello, J.V.

    1992-10-01

    The objectives of this project are to design and synthesize novel monomers which orginate from renewable biological sources and to carry out their rapid, efficient, pollution-free and energy efficient cationic polymerization to useful products under the influence of ultraviolet light or heat. A summary of the results of the past year`s research on cationically polymerizable monomers derived from renewable sources is presented. Three major areas of investigation corresponding to the different classes of naturally occurring starting materials were investigated; epoxidized terpenes and natural rubber and vinyl ethers from alcohols and carbohydrates.

  18. Maleic acid-styrene encapsulated silica cation exchanger in high performance liquid chromatography.

    PubMed

    Yang, R; Jiang, S; Chen, L

    2001-12-24

    The use of poly(maleic acid-styrene)-encapsulated silica for the determination of monovalent and divalent cations is well accepted in ion chromatography. The separation of Mn(2+), alkali and alkaline earth metal cations is obtained under the same chromatographic conditions. The influences of pH and the concentration of eluent on the retention of cations have been studied. The preparation conditions of packings were studied. The metal ions in the boiler water samples from a thermal power plant were quantitatively determined using this column. The results are in agreement with those determined by ICP and Volumetric analysis methods. PMID:18968461

  19. Immobilization of Thiadiazole Derivatives on Magnetite Mesoporous Silica Shell Nanoparticles in Application to Heavy Metal Removal from Biological Samples

    SciTech Connect

    Emadi, Masoomeh; Shams, Esmaeil

    2010-12-02

    In this report magnetite was synthesized by a coprecipitation method, then coated with a layer of silica. Another layer of mesoporous silica was added by a sol-gel method, then 5-amino-1,3,4-thiadiazole-thiol (ATT) was immobilized onto the synthesized nanoparticles with a simple procedure. This was followed by a series of characterizations, including transmission electron microscopy (TEM), FT-IR spectrum, elemental analysis and XRD. Heavy metal uptake of the modified nanoparticles was examined by atomic absorption spectroscopy. For further investigation we chose Cu{sup 2+} as the preferred heavy metal to evaluate the amount of adsorption, as well as the kinetics and mechanism of adsorption. Finally, the capacity of our nanoparticles for the heavy metal removal from blood was shown. We found that the kinetic rate of Cu{sup 2+} adsorption was 0.05 g/mg/min, and the best binding model was the Freundlich isotherm.

  20. Cation Diffusion in Xenotime

    NASA Astrophysics Data System (ADS)

    Cherniak, D. J.

    2004-05-01

    Xenotime is an important mineral in metamorphic paragenesis, and useful in isotopic dating, garnet-xenotime thermometry, and monazite-xenotime thermometry, so diffusion data for xenotime of cations of geochronological and geochemical importance are of some interest. We report here on diffusion of the rare earth elements Sm, Dy and Yb in synthetic xenotime under dry conditions. The synthetic xenotime was grown via a Na2}CO{3}-MoO_{3 flux method. The source of diffusant for the experiments were REE phosphate powders, with experiments run with sources containing a single REE. Experiments were performed by placing source and xenotime in Pt capsules, and annealing capsules in 1 atm furnaces for times ranging from thirty minutes to a month, at temperatures from 1000 to 1400C. The REE distributions in the xenotime were profiled by Rutherford Backscattering Spectrometry (RBS). The following Arrhenius relations are obtained for diffusion in xenotime, normal to (101): DSm = 1.7x10-4 exp(-442 kJ mol-1/RT) m2}sec{-1 DDy = 3.5x10-7 exp(-365 kJ mol-1/RT) m2}sec{-1 DYb = 7.4x10-7 exp(-371 kJ mol-1/RT) m2}sec{-1. Diffusivities of these REE do not differ greatly in xenotime, in contrast to the findings noted for the REE in zircon (Cherniak et al., 1997), where the LREE diffuse more slowly, and with higher activation energies for diffusion, than the heavier rare earths. In zircon, these differences among diffusion of the rare earths are attributed to the relatively large size of the REE with respect to Zr, for which they substitute in the zircon lattice. With the systematic increase in ionic radius from the heavy to lighter REE, this size mismatch becomes more pronounced and diffusivities of the LREE are as consequence slower. Although xenotime is isostructural with zircon, the REE are more closely matched in size to Y, so in xenotime this effect appears much smaller and the REE diffuse at similar rates. In addition, the process of diffusion in xenotime likely involves simple REE+3

  1. Cation Effects on the Layer Structure of Biogenic Mn-Oxides

    SciTech Connect

    Zhu, M.; Ginder-Vogel, M; Parikh, S; Feng, X; Sparks, D

    2010-01-01

    Biologically catalyzed Mn(II) oxidation produces biogenic Mn-oxides (BioMnO{sub x}) and may serve as one of the major formation pathways for layered Mn-oxides in soils and sediments. The structure of Mn octahedral layers in layered Mn-oxides controls its metal sequestration properties, photochemistry, oxidizing ability, and topotactic transformation to tunneled structures. This study investigates the impacts of cations (H{sup +}, Ni(II), Na{sup +}, and Ca{sup 2+}) during biotic Mn(II) oxidation on the structure of Mn octahedral layers of BioMnO{sub x} using solution chemistry and synchrotron X-ray techniques. Results demonstrate that Mn octahedral layer symmetry and composition are sensitive to previous cations during BioMnO{sub x} formation. Specifically, H{sup +} and Ni(II) enhance vacant site formation, whereas Na{sup +} and Ca{sup 2+} favor formation of Mn(III) and its ordered distribution in Mn octahedral layers. This study emphasizes the importance of the abiotic reaction between Mn(II) and BioMnO{sub x} and dependence of the crystal structure of BioMnO{sub x} on solution chemistry.

  2. Patterns of metal composition and biological condition and their association in male common carp across an environmental contaminant gradient in Lake Mead National Recreation Area, Nevada and Arizona, USA.

    PubMed

    Patiño, Reynaldo; Rosen, Michael R; Orsak, Erik L; Goodbred, Steven L; May, Thomas W; Alvarez, David; Echols, Kathy R; Wieser, Carla M; Ruessler, Shane; Torres, Leticia

    2012-02-01

    There is a contaminant gradient in Lake Mead National Recreation Area (LMNRA) that is partly driven by municipal and industrial runoff and wastewater inputs via Las Vegas Wash (LVW). Adult male common carp (Cyprinus carpio; 10 fish/site) were collected from LVW, Las Vegas Bay (receiving LVW flow), Overton Arm (OA, upstream reference), and Willow Beach (WB, downstream) in March 2008. Discriminant function analysis was used to describe differences in metal concentrations and biological condition of fish collected from the four study sites, and canonical correlation analysis was used to evaluate the association between metal and biological traits. Metal concentrations were determined in whole-body extracts. Of 63 metals screened, those initially used in the statistical analysis were Ag, As, Ba, Cd, Co, Fe, Hg, Pb, Se, Zn. Biological variables analyzed included total length (TL), Fulton's condition factor, gonadosomatic index (GSI), hematocrit (Hct), and plasma estradiol-17β and 11-ketotestosterone (11kt) concentrations. Analysis of metal composition and biological condition both yielded strong discrimination of fish by site (respective canonical model, p<0.0001). Compared to OA, pairwise Mahalanobis distances between group means were WBmetal concentrations and LVBbiological traits. Respective primary drivers for these separations were Ag, As, Ba, Hg, Pb, Se and Zn; and TL, GSI, 11kt, and Hct. Canonical correlation analysis using the latter variable sets showed they are significantly associated (p<0.0003); with As, Ba, Hg, and Zn, and TL, 11kt, and Hct being the primary contributors to the association. In conclusion, male carp collected along a contaminant gradient in LMNRA have distinct, collection site-dependent metal and morpho-physiological profiles that are significantly associated with each other. These associations suggest that fish health and reproductive condition (as measured by the biological variables evaluated in this study) are

  3. Patterns of metal composition and biological condition and their association in male common carp across an environmental contaminant gradient in Lake Mead National Recreation Area, Nevada and Arizona, USA

    USGS Publications Warehouse

    Patino, R.; Rosen, Michael R.; Orsak, E.L.; Goodbred, S.L.; May, T.W.; Alvarez, David; Echols, K.R.; Wieser, C.M.; Ruessler, S.; Torres, L.

    2012-01-01

    There is a contaminant gradient in Lake Mead National Recreation Area (LMNRA) that is partly driven by municipal and industrial runoff and wastewater inputs via Las Vegas Wash (LVW). Adult male common carp (Cyprinus carpio; 10 fish/site) were collected from LVW, Las Vegas Bay (receiving LVW flow), Overton Arm (OA, upstream reference), and Willow Beach (WB, downstream) in March 2008. Discriminant function analysis was used to describe differences in metal concentrations and biological condition of fish collected from the four study sites, and canonical correlation analysis was used to evaluate the association between metal and biological traits. Metal concentrations were determined in whole-body extracts. Of 63 metals screened, those initially used in the statistical analysis were Ag, As, Ba, Cd, Co, Fe, Hg, Pb, Se, Zn. Biological variables analyzed included total length (TL), Fulton's condition factor, gonadosomatic index (GSI), hematocrit (Hct), and plasma estradiol-17?? and 11-ketotestosterone (11kt) concentrations. Analysis of metal composition and biological condition both yielded strong discrimination of fish by site (respective canonical model, p< 0.0001). Compared to OA, pairwise Mahalanobis distances between group means were WB < LVB < LVW for metal concentrations and LVB < WB < LVW for biological traits. Respective primary drivers for these separations were Ag, As, Ba, Hg, Pb, Se and Zn; and TL, GSI, 11kt, and Hct. Canonical correlation analysis using the latter variable sets showed they are significantly associated (p<0.0003); with As, Ba, Hg, and Zn, and TL, 11kt, and Hct being the primary contributors to the association. In conclusion, male carp collected along a contaminant gradient in LMNRA have distinct, collection site-dependent metal and morpho-physiological profiles that are significantly associated with each other. These associations suggest that fish health and reproductive condition (as measured by the biological variables evaluated in this

  4. All-inorganic Germanium nanocrystal films by cationic ligand exchange

    DOE PAGESBeta

    Wheeler, Lance M.; Nichols, Asa W.; Chernomordik, Boris D.; Anderson, Nicholas C.; Beard, Matthew C.; Neale, Nathan R.

    2016-01-21

    In this study, we introduce a new paradigm for group IV nanocrystal surface chemistry based on room temperature surface activation that enables ionic ligand exchange. Germanium nanocrystals synthesized in a gas-phase plasma reactor are functionalized with labile, cationic alkylammonium ligands rather than with traditional covalently bound groups. We employ Fourier transform infrared and 1H nuclear magnetic resonance spectroscopies to demonstrate the alkylammonium ligands are freely exchanged on the germanium nanocrystal surface with a variety of cationic ligands, including short inorganic ligands such as ammonium and alkali metal cations. This ionic ligand exchange chemistry is used to demonstrate enhanced transport inmore » germanium nanocrystal films following ligand exchange as well as the first photovoltaic device based on an all-inorganic germanium nanocrystal absorber layer cast from solution. This new ligand chemistry should accelerate progress in utilizing germanium and other group IV nanocrystals for optoelectronic applications.« less

  5. All-Inorganic Germanium Nanocrystal Films by Cationic Ligand Exchange.

    PubMed

    Wheeler, Lance M; Nichols, Asa W; Chernomordik, Boris D; Anderson, Nicholas C; Beard, Matthew C; Neale, Nathan R

    2016-03-01

    We introduce a new paradigm for group IV nanocrystal surface chemistry based on room temperature surface activation that enables ionic ligand exchange. Germanium nanocrystals synthesized in a gas-phase plasma reactor are functionalized with labile, cationic alkylammonium ligands rather than with traditional covalently bound groups. We employ Fourier transform infrared and (1)H nuclear magnetic resonance spectroscopies to demonstrate the alkylammonium ligands are freely exchanged on the germanium nanocrystal surface with a variety of cationic ligands, including short inorganic ligands such as ammonium and alkali metal cations. This ionic ligand exchange chemistry is used to demonstrate enhanced transport in germanium nanocrystal films following ligand exchange as well as the first photovoltaic device based on an all-inorganic germanium nanocrystal absorber layer cast from solution. This new ligand chemistry should accelerate progress in utilizing germanium and other group IV nanocrystals for optoelectronic applications. PMID:26796765

  6. Does cation break the cyano bond? A critical evaluation of nitrile-cation interaction.

    PubMed

    Woi, Pei Meng; Bakar, Maizathul Akmam A; Rosli, Ahmad Nazmi; Lee, Vannajan Sanghiran; Ahmad, Mohd Rais; Zain, Sharifuddin; Alias, Yatimah

    2014-05-01

    DFT and G4 results reveal that cations display the following trends in imparting its positive charge to acrylonitrile; H⁺ > Li⁺ > Na⁺ > K⁺ for group I and Be²⁺ > Mg²⁺ > Ca²⁺ for group II. Solvation by water molecules and interaction with cation make the cyano bond more polarized and exhibits ketene-imine character. Bond order in nitrile-cation complexes has been predicted based on the s character of the covalent bond orbitals. Mulliken, CHELPG, and NPA charges are in good agreement in predicting positive charge buildup and GIAO nuclear deshileding on C1. G4 enthalpies show that Mg²⁺ is more strongly bound to acrylonitrile than to acetonitrile by 3 kcal mol⁻¹, and the proton affinity of the former is higher by 0.8 kcal mol⁻¹. G4 enthalpies of reductions support prior experimental observation that metalated conjugated nitriles show enhanced reactivity toward weak nucleophiles to afford Michael addition products. PMID:24770548

  7. Biologically active and thermally stable polymeric Schiff base and its metal polychelates: Their synthesis and spectral aspects

    NASA Astrophysics Data System (ADS)

    Rasool, Raza; Hasnain, Sumaiya

    2015-09-01

    New metal polychelates of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) obtained by the interaction of metal acetates with polymeric Schiff base containing formaldehyde and piperazine, have been investigated. Structural and spectroscopic properties have been evaluated by elemental analysis, FT-IR and 1H-NMR. Geometry of the chelated polymers was confirmed by magnetic susceptibility measurements, UV-Visible spectroscopy and Electron Spin Resonance. The molecular weight of the polymer was determined by gel permeation chromatography (GPC). Thermogravimetric analysis indicated that metal polychelates were more thermally stable than their corresponding ligand. All compounds were screened for their antimicrobial activities against Escherichia coli, Staphylococcus aureus, Bacillus subtilis, (bacteria) and Candida albicans, Microsporum canis, Cryptococcus neoformans (fungi) by agar well diffusion method. Interestingly, the polymeric Schiff base was found to be antimicrobial in nature but less effective as compared to the metal polychelates. On the basis of thermal and antimicrobial behavior, these polymers hold potential applications as thermally resistant antimicrobial and antifouling coating materials as well as antimicrobial packaging materials.

  8. Preparation, spectral and biological investigation of formaldehyde-based ligand containing piperazine moiety and its various polymer metal complexes

    NASA Astrophysics Data System (ADS)

    Khan, Shamim Ahmad; Nishat, Nahid; Parveen, Shadma; Rasool, Raza

    2011-10-01

    A novel tetradentate salicylic acid-formaldehyde ligand containing piperazine moiety (SFP) was synthesized by condensation of salicylic acid, formaldehyde and piperazine in presence of base catalyst, which was subjected for the preparation of coordination polymers with metal ions like manganese(II), cobalt(II), copper(II), nickel(II) and zinc(II). All the synthesized polymeric compounds were characterized by elemental analysis, IR, 1H NMR and electronic spectral studies. The thermal stability was determined by thermogravimetric analysis and thermal data revealed that all the polymer metal complexes show good thermal stability than their parent ligand. Electronic spectral data and magnetic moment values revealed that polymer metal complexes of Mn(II), Co(II) and Ni(II) show an octahedral geometry while Cu(II) and Zn(II) show distorted octahedral and tetrahedral geometry respectively. The antimicrobial screening of the ligand and coordination polymers was done by using Agar well diffusion method against various bacteria and fungi. It was evident from the data that antibacterial and antifungal activity increased on chelation and all the polymer metal complexes show excellent antimicrobial activity than their parent ligand.

  9. Preparation, spectral and biological investigation of formaldehyde-based ligand containing piperazine moiety and its various polymer metal complexes.

    PubMed

    Khan, Shamim Ahmad; Nishat, Nahid; Parveen, Shadma; Rasool, Raza

    2011-10-15

    A novel tetradentate salicylic acid-formaldehyde ligand containing piperazine moiety (SFP) was synthesized by condensation of salicylic acid, formaldehyde and piperazine in presence of base catalyst, which was subjected for the preparation of coordination polymers with metal ions like manganese(II), cobalt(II), copper(II), nickel(II) and zinc(II). All the synthesized polymeric compounds were characterized by elemental analysis, IR, (1)H NMR and electronic spectral studies. The thermal stability was determined by thermogravimetric analysis and thermal data revealed that all the polymer metal complexes show good thermal stability than their parent ligand. Electronic spectral data and magnetic moment values revealed that polymer metal complexes of Mn(II), Co(II) and Ni(II) show an octahedral geometry while Cu(II) and Zn(II) show distorted octahedral and tetrahedral geometry respectively. The antimicrobial screening of the ligand and coordination polymers was done by using Agar well diffusion method against various bacteria and fungi. It was evident from the data that antibacterial and antifungal activity increased on chelation and all the polymer metal complexes show excellent antimicrobial activity than their parent ligand. PMID:21757398

  10. Biologically active and thermally stable polymeric Schiff base and its metal polychelates: Their synthesis and spectral aspects.

    PubMed

    Rasool, Raza; Hasnain, Sumaiya

    2015-09-01

    New metal polychelates of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) obtained by the interaction of metal acetates with polymeric Schiff base containing formaldehyde and piperazine, have been investigated. Structural and spectroscopic properties have been evaluated by elemental analysis, FT-IR and (1)H-NMR. Geometry of the chelated polymers was confirmed by magnetic susceptibility measurements, UV-Visible spectroscopy and Electron Spin Resonance. The molecular weight of the polymer was determined by gel permeation chromatography (GPC). Thermogravimetric analysis indicated that metal polychelates were more thermally stable than their corresponding ligand. All compounds were screened for their antimicrobial activities against Escherichia coli, Staphylococcus aureus, Bacillus subtilis, (bacteria) and Candida albicans, Microsporum canis, Cryptococcus neoformans (fungi) by agar well diffusion method. Interestingly, the polymeric Schiff base was found to be antimicrobial in nature but less effective as compared to the metal polychelates. On the basis of thermal and antimicrobial behavior, these polymers hold potential applications as thermally resistant antimicrobial and antifouling coating materials as well as antimicrobial packaging materials. PMID:25955762

  11. Metal (II) Complexes Derived from Naphthofuran-2-carbohydrazide and Diacetylmonoxime Schiff Base: Synthesis, Spectroscopic, Electrochemical, and Biological Investigation

    PubMed Central

    Sumathi, R. B.; Halli, M. B.

    2014-01-01

    A new Schiff base and a new series of Co(II), Ni(II), Cu(II), Cd(II), and Hg(II) complexes were synthesized by the condensation of naphthofuran-2-carbohydrazide and diacetylmonoxime. Metal complexes of the Schiff base were prepared from their chloride salts of Co(II), Ni(II), Cu(II), Cd(II), and Hg(II) in ethanol. The ligand along with its metal complexes have been characterized on the basis of analytical data, IR, electronic, mass, 1HNMR, ESR spectral data, thermal studies, magnetic susceptibility, and molar conductance measurements. The nonelectrolytic behaviour of the complexes was assessed from the measured low conductance data. The elemental analysis of the complexes confirm the stoichiometry of the type CuL2Cl2 and MLCl2 where M = Ni(II), Co(II), Cd(II), and Hg(II) and L = Schiff base. The redox property of the Cu(II) complex was investigated by electrochemical method using cyclic voltammetry. In the light of these results, Co(II), Ni(II), and Cu(II) complexes are assigned octahedral geometry, Cd(II), and Hg(II) complexes tetrahedral geometry. In order to evaluate the effect of metal ions upon chelation, both the ligand and its metal complexes were screened for their antibacterial and antifungal activities by minimum inhibitory concentration (MIC) method. The DNA cleaving capacity of all the complexes was analysed by agarose gel electrophoresis method. PMID:24592203

  12. The influence of bacterial-humus preparations on the biological activity of soils polluted with oil products and heavy metals

    NASA Astrophysics Data System (ADS)

    Kozlova, E. N.; Stepanov, A. L.; Lysak, L. V.

    2015-04-01

    The influence of bacterial-humus preparations based on Gumigel ( Agrosintez Company) on the biological activity of soddy-podzolic soil polluted with Pb(CH3COO)2 and gasoline was studied in a model experiment. Some indicators of biological activity are shown to depend on soil pollution to different extents. The process of nitrogen fixation and the activity of dehydrogenase and phosphatase were mostly inhibited by Pb(CH3COO)2 and gasoline. Gasoline compared to Pb(CH3COO)2 inhibited the soil biological activity to a greater extent. The bacterial-humus preparations exerted a significant positive effect on the biological activity of the polluted soils manifested in the increase of the total number of bacteria and of the enzyme activity (1.5-5.0 times), in the intensification of nitrogen fixation and denitrification (3-8 times), as well as in the increase in the biomass of the plants grown (1.5-2.0 times). The application of bacterial suspensions of pure cultures or the microbial complex without the preparations of humic acids did not always give a positive effect.

  13. A Thermodynamic Model of Monovalent Cation Homeostasis in the Yeast Saccharomyces cerevisiae.

    PubMed

    Gerber, Susanne; Fröhlich, Martina; Lichtenberg-Fraté, Hella; Shabala, Sergey; Shabala, Lana; Klipp, Edda

    2016-01-01

    Cationic and heavy metal toxicity is involved in a substantial number of diseases in mammals and crop plants. Therefore, the understanding of tightly regulated transporter activities, as well as conceiving the interplay of regulatory mechanisms, is of substantial interest. A generalized thermodynamic description is developed for the complex interplay of the plasma membrane ion transporters, membrane potential and the consumption of energy for maintaining and restoring specific intracellular cation concentrations. This concept is applied to the homeostasis of cation concentrations in the yeast cells of S. cerevisiae. The thermodynamic approach allows to model passive ion fluxes driven by the electrochemical potential differences, but also primary or secondary active transport processes driven by the inter- play of different ions (symport, antiport) or by ATP consumption (ATPases). The model-confronted with experimental data-reproduces the experimentally observed potassium and proton fluxes induced by the external stimuli KCl and glucose. The estimated phenomenological constants combine kinetic parameters and transport coefficients. These are in good agreement with the biological understanding of the transporters thus providing a better understanding of the control exerted by the coupled fluxes. The model predicts the flux of additional ion species, like e.g. chloride, as a potential candidate for counterbalancing positive charges. Furthermore, the effect of a second KCl stimulus is simulated, predicting a reduced cellular response for cells that were first exposed to a high KCl stimulus compared to cells pretreated with a mild KCl stimulus. By describing the generalized forces that are responsible for a given flow, the model provi