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Sample records for anion exchanger channel

  1. Subtle anion effects on anion exchange and thermolysis: Square supra-channels via array of sinusoidal coordination polymers

    NASA Astrophysics Data System (ADS)

    Moon, So Yun; Park, Min Woo; Noh, Tae Hwan; Jung, Ok-Sang

    2013-12-01

    Self-assembly of AgX (X=ClO4-,BF4-) with a new diethylbis(4-pyridyl)silane (L) ligand basically gives rise to a one-dimensional (1D) sinusoidal structure. Weak C-H⋯π interactions between ethyl and pyridyl groups result in the formation of infinite square supra-channel structures via a molecular array of four sinusoidal chains. The supra-channel size is 10.1-10.7 Å with a void cross-section of 2.1-3.1 Å for [Ag(L)](ClO4) and 9.9-10.5 Å with a void cross-section of 2.0-3.0 Å for [Ag(L)](BF4). The supra-channels are occupied by each counteranion. Anion exchange of [Ag(L)](BF4) with NaClO4 occurs smoothly, whereas the reverse anion exchange of [Ag(L)](ClO4) with NaBF4 does not. Calcination of [Ag(L)](ClO4) crystals at 400 °C produces a circle morphology with evolving burned organics, and, at 600 °C, forms network circles consisting of a silver(0)/silver chloride (chlorargyrite)/silicon(IV) oxide composite with a micro-sized convexo-concave surface. In contrast, calcination of [Ag(L)](BF4) crystals at 600 °C produces silver(0) materials without silicon(IV) oxide.

  2. Anion exchange membrane

    DOEpatents

    Verkade, John G; Wadhwa, Kuldeep; Kong, Xueqian; Schmidt-Rohr, Klaus

    2013-05-07

    An anion exchange membrane and fuel cell incorporating the anion exchange membrane are detailed in which proazaphosphatrane and azaphosphatrane cations are covalently bonded to a sulfonated fluoropolymer support along with anionic counterions. A positive charge is dispersed in the aforementioned cations which are buried in the support to reduce the cation-anion interactions and increase the mobility of hydroxide ions, for example, across the membrane. The anion exchange membrane has the ability to operate at high temperatures and in highly alkaline environments with high conductivity and low resistance.

  3. Anion exchange polymer electrolytes

    SciTech Connect

    Kim, Yu Seung; Kim, Dae Sik

    2015-06-02

    Anion exchange polymer electrolytes that include guanidinium functionalized polymers may be used as membranes and binders for electrocatalysts in preparation of anodes for electrochemical cells such as solid alkaline fuel cells.

  4. Anion exchange polymer electrolytes

    DOEpatents

    Kim, Yu Seung; Kim, Dae Sik; Lee, Kwan-Soo

    2013-07-23

    Solid anion exchange polymer electrolytes and compositions comprising chemical compounds comprising a polymeric core, a spacer A, and a guanidine base, wherein said chemical compound is uniformly dispersed in a suitable solvent and has the structure: ##STR00001## wherein: i) A is a spacer having the structure O, S, SO.sub.2, --NH--, --N(CH.sub.2).sub.n, wherein n=1-10, --(CH.sub.2).sub.n--CH.sub.3--, wherein n=1-10, SO.sub.2-Ph, CO-Ph, ##STR00002## wherein R.sub.5, R.sub.6, R.sub.7 and R.sub.8 each are independently --H, --NH.sub.2, F, Cl, Br, CN, or a C.sub.1-C.sub.6 alkyl group, or any combination of thereof; ii) R.sub.9, R.sub.10, R.sub.11, R.sub.12, or R.sub.13 each independently are --H, --CH.sub.3, --NH.sub.2, --NO, --CH.sub.nCH.sub.3 where n=1-6, HC.dbd.O--, NH.sub.2C.dbd.O--, --CH.sub.nCOOH where n=1-6, --(CH.sub.2).sub.n--C(NH.sub.2)--COOH where n=1-6, --CH--(COOH)--CH.sub.2--COOH, --CH.sub.2--CH(O--CH.sub.2CH.sub.3).sub.2, --(C.dbd.S)--NH.sub.2, --(C.dbd.NH)--N--(CH.sub.2).sub.nCH.sub.3, where n=0-6, --NH--(C.dbd.S)--SH, --CH.sub.2--(C.dbd.O)--O--C(CH.sub.3).sub.3, --O--(CH.sub.2).sub.n--CH--(NH.sub.2)--COOH, where n=1-6, --(CH.sub.2).sub.n--CH.dbd.CH wherein n=1-6, --(CH.sub.2).sub.n--CH--CN wherein n=1-6, an aromatic group such as a phenyl, benzyl, phenoxy, methylbenzyl, nitrogen-substituted benzyl or phenyl groups, a halide, or halide-substituted methyl groups; and iii) wherein the composition is suitable for use in a membrane electrode assembly.

  5. Pu Anion Exchange Process Intensification

    SciTech Connect

    Taylor-Pashow, K.

    2015-10-08

    This project seeks to improve the efficiency of the plutonium anion-exchange process for purifying Pu through the development of alternate ion-exchange media. The objective of the project in FY15 was to develop and test a porous foam monolith material that could serve as a replacement for the current anion-exchange resin, Reillex® HPQ, used at the Savannah River Site (SRS) for purifying Pu. The new material provides advantages in efficiency over the current resin by the elimination of diffusive mass transport through large granular resin beads. By replacing the large resin beads with a porous foam there is much more efficient contact between the Pu solution and the anion-exchange sites present on the material. Several samples of a polystyrene based foam grafted with poly(4-vinylpyridine) were prepared and the Pu sorption was tested in batch contact tests.

  6. Polyethylenimine modified poly(ethylene terephthalate) capillary channeled-polymer fibers for anion exchange chromatography of proteins.

    PubMed

    Jiang, Liuwei; Jin, Yi; Marcus, R Kenneth

    2015-09-01

    Native poly(ethylene terephthalate) (PET) capillary-channeled polymer (C-CP) fibers have been previously studied as stationary phases for reversed phase and affinity protein separations. In this study, surface modified PET C-CP fibers were evaluated for the anion exchange separation of proteins. The native PET C-CP fibers were aminated using polyethylenimine (PEI) followed by a 1,4-butanediol diglycidyl ether (BUDGE) cross-linking step. Subsequent PEI/BUDGE treatments can be employed to further develop the polyamine layer on the fiber surfaces. The PEI densities of the modified fibers were quantified through the ninhydrin reaction, yielding values of 0.43-0.89μmolg(-1). The surface modification impact on column permeability was found to be 0.66×10(-11) to 1.33×10(-11)m(2), depending on the modification time and conditions. The dynamic binding capacities of the modified fiber media were determined to be 1.99-8.54mgmL(-1) bed volume, at linear velocities of 88-438cmmin(-1) using bovine serum albumin as the model protein. It was found that increasing the mobile phase linear velocity (up to 438cmmin(-1)) had no effect on the separation quality for a synthetic protein mixture, reflecting the lack of van Deemter C-term effects for the C-CP fiber phase. The low-cost, easy modification method and the capability of fast protein separation illustrate great potential in the use of PEI/BUDGE-modified PET C-CP fibers for high-throughput protein separation and downstream processing. PMID:26253835

  7. The activation pathway of the volume-sensitive organic osmolyte channel in Xenopus laevis oocytes expressing skate anion exchanger 1 (AE1).

    PubMed

    Koomoa, Dana-Lynn T; Musch, Mark W; Goldstein, Leon

    2005-12-01

    When swollen, skate red blood cells increase permeability and allow efflux of a number of solutes, including taurine. Hypoosmosis-induced taurine permeability appears to involve the red cell anion exchanger. However, three isoforms have been cloned from these cells. Therefore, to determine the ability of the individual isoform skate anion exchanger 1 (skAE1) to mediate hypoosmosis-induced taurine permeability as well as associated regulatory events, skAE1 was expressed in Xenopus oocytes. This study focused on investigating the role of tyrosine kinases and lipid rafts in the regulation of the channel. The results showed that tyrosine kinase inhibitors and lipid raft-disrupting agents inhibited the volume-sensitive organic osmolyte channel while protein tyrosine phosphatase inhibitors activated the channel in oocytes expressing skAE1. To study the role of lipid rafts in the activation of the volume-sensitive organic osmolyte channel, the cellular localization of skAE1 was investigated. Also, the role of tyrosine kinases was investigated by examining the tyrosine phosphorylation state of skAE1. Hypoosmotic stress induced mobilization of skAE1 into light membranes and the cell surface as well as tyrosine phosphorylation of skAE1. These events are involved in the activation of the volume-sensitive organic osmolyte channel in Xenopus oocytes expressing skAE1. PMID:16604471

  8. Ion exchange polymers for anion separations

    DOEpatents

    Jarvinen, Gordon D.; Marsh, S. Fredric; Bartsch, Richard A.

    1997-01-01

    Anion exchange resins including at least two positively charged sites and a ell-defined spacing between the positive sites are provided together with a process of removing anions or anionic metal complexes from aqueous solutions by use of such resins. The resins can be substituted poly(vinylpyridine) and substituted polystyrene.

  9. Ion exchange polymers for anion separations

    DOEpatents

    Jarvinen, G.D.; Marsh, S.F.; Bartsch, R.A.

    1997-09-23

    Anion exchange resins including at least two positively charged sites and a well-defined spacing between the positive sites are provided together with a process of removing anions or anionic metal complexes from aqueous solutions by use of such resins. The resins can be substituted poly(vinylpyridine) and substituted polystyrene.

  10. Molecular physiology of EAAT anion channels.

    PubMed

    Fahlke, Christoph; Kortzak, Daniel; Machtens, Jan-Philipp

    2016-03-01

    Glutamate is the major excitatory neurotransmitter in the mammalian central nervous system. After release from presynaptic nerve terminals, glutamate is quickly removed from the synaptic cleft by a family of five glutamate transporters, the so-called excitatory amino acid transporters (EAAT1-5). EAATs are prototypic members of the growing number of dual-function transport proteins: they are not only glutamate transporters, but also anion channels. Whereas the mechanisms underlying secondary active glutamate transport are well understood at the functional and at the structural level, mechanisms and cellular roles of EAAT anion conduction have remained elusive for many years. Recently, molecular dynamics simulations combined with simulation-guided mutagenesis and experimental analysis identified a novel anion-conducting conformation, which accounts for all experimental data on EAAT anion currents reported so far. We here review recent findings on how EAATs accommodate a transporter and a channel in one single protein. PMID:26687113

  11. Nanoparticle conversion chemistry: Kirkendall effect, galvanic exchange, and anion exchange

    NASA Astrophysics Data System (ADS)

    Anderson, Bryan D.; Tracy, Joseph B.

    2014-10-01

    Conversion chemistry is a rapidly maturing field, where chemical conversion of template nanoparticles (NPs) into new compositions is often accompanied by morphological changes, such as void formation. The principles and examples of three major classes of conversion chemical reactions are reviewed: the Kirkendall effect for metal NPs, galvanic exchange, and anion exchange, each of which can result in void formation in NPs. These reactions can be used to obtain complex structures that may not be attainable by other methods. During each kind of conversion chemical reaction, NPs undergo distinct chemical and morphological changes, and insights into the mechanisms of these reactions will allow for improved fine control and prediction of the structures of intermediates and products. Conversion of metal NPs into oxides, phosphides, sulphides, and selenides often occurs through the Kirkendall effect, where outward diffusion of metal atoms from the core is faster than inward diffusion of reactive species, resulting in void formation. In galvanic exchange reactions, metal NPs react with noble metal salts, where a redox reaction favours reduction and deposition of the noble metal (alloying) and oxidation and dissolution of the template metal (dealloying). In anion exchange reactions, addition of certain kinds of anions to solutions containing metal compound NPs drives anion exchange, which often results in significant morphological changes due to the large size of anions compared to cations. Conversion chemistry thus allows for the formation of NPs with complex compositions and structures, for which numerous applications are anticipated arising from their novel catalytic, electronic, optical, magnetic, and electrochemical properties.

  12. Nanoheterostructure Cation Exchange: Anionic Framework Conservation

    SciTech Connect

    Jain, Prashant K.; Amirav, Lilac; Aloni, Shaul; Alivisatos, A. Paul

    2010-05-11

    In ionic nanocrystals the cationic sub-lattice can be replaced with a different metal ion via a fast, simple, and reversible place-exchange, allowing post-synthetic modification of the composition of the nanocrystal, while preserving its size and shape. Here, we demonstrate for the first time that during such an exchange, the anionic framework of the crystal is preserved. When applied to nanoheterostructures, this phenomenon ensures that compositional interfaces within the heterostructure are conserved throughout the transformation. For instance, a morphology composed of a CdSe nanocrystal embedded in a CdS rod (CdSe/CdS) was exchanged to a PbSe/PbS nanorod via a Cu2Se/Cu2S structure. During every exchange cycle, the seed size and position within the nanorod were preserved, as evident by excitonic features, Z-contrast imaging, and elemental line-scans. Anionic framework conservation extends the domain of cation exchange to the design of more complex and unique nanostructures.

  13. Anion conductance selectivity mechanism of the CFTR chloride channel.

    PubMed

    Linsdell, Paul

    2016-04-01

    All ion channels are able to discriminate between substrate ions to some extent, a process that involves specific interactions between permeant anions and the so-called selectivity filter within the channel pore. In the cystic fibrosis transmembrane conductance regulator (CFTR) anion-selective channel, both anion relative permeability and anion relative conductance are dependent on anion free energy of hydration--anions that are relatively easily dehydrated tend to show both high permeability and low conductance. In the present work, patch clamp recording was used to investigate the relative conductance of different anions in CFTR, and the effect of mutations within the channel pore. In constitutively-active E1371Q-CFTR channels, the anion conductance sequence was Cl(-) > NO3(-) > Br(-) > formate > SCN(-) > I(-). A mutation that disrupts anion binding in the inner vestibule of the pore (K95Q) disrupted anion conductance selectivity, such that anions with different permeabilities showed almost indistinguishable conductances. Conversely, a mutation at the putative narrowest pore region that is known to disrupt anion permeability selectivity (F337A) had minimal effects on anion relative conductance. Ion competition experiments confirmed that relatively tight binding of permeant anions resulted in relatively low conductance. These results suggest that the relative affinity of ion binding in the inner vestibule of the pore controls the relative conductance of different permeant anions in CFTR, and that the pore has two physically distinct anion selectivity filters that act in series to control anion conductance selectivity and anion permeability selectivity respectively. PMID:26779604

  14. An intracellular anion channel critical for pigmentation

    PubMed Central

    Bellono, Nicholas W; Escobar, Iliana E; Lefkovith, Ariel J; Marks, Michael S; Oancea, Elena

    2014-01-01

    Intracellular ion channels are essential regulators of organellar and cellular function, yet the molecular identity and physiological role of many of these channels remains elusive. In particular, no ion channel has been characterized in melanosomes, organelles that produce and store the major mammalian pigment melanin. Defects in melanosome function cause albinism, characterized by vision and pigmentation deficits, impaired retinal development, and increased susceptibility to skin and eye cancers. The most common form of albinism is caused by mutations in oculocutaneous albinism II (OCA2), a melanosome-specific transmembrane protein with unknown function. Here we used direct patch-clamp of skin and eye melanosomes to identify a novel chloride-selective anion conductance mediated by OCA2 and required for melanin production. Expression of OCA2 increases organelle pH, suggesting that the chloride channel might regulate melanin synthesis by modulating melanosome pH. Thus, a melanosomal anion channel that requires OCA2 is essential for skin and eye pigmentation. DOI: http://dx.doi.org/10.7554/eLife.04543.001 PMID:25513726

  15. An intracellular anion channel critical for pigmentation.

    PubMed

    Bellono, Nicholas W; Escobar, Iliana E; Lefkovith, Ariel J; Marks, Michael S; Oancea, Elena

    2014-01-01

    Intracellular ion channels are essential regulators of organellar and cellular function, yet the molecular identity and physiological role of many of these channels remains elusive. In particular, no ion channel has been characterized in melanosomes, organelles that produce and store the major mammalian pigment melanin. Defects in melanosome function cause albinism, characterized by vision and pigmentation deficits, impaired retinal development, and increased susceptibility to skin and eye cancers. The most common form of albinism is caused by mutations in oculocutaneous albinism II (OCA2), a melanosome-specific transmembrane protein with unknown function. Here we used direct patch-clamp of skin and eye melanosomes to identify a novel chloride-selective anion conductance mediated by OCA2 and required for melanin production. Expression of OCA2 increases organelle pH, suggesting that the chloride channel might regulate melanin synthesis by modulating melanosome pH. Thus, a melanosomal anion channel that requires OCA2 is essential for skin and eye pigmentation. PMID:25513726

  16. Advancements in Anion Exchange Membrane Cations

    SciTech Connect

    Sturgeon, Matthew R.; Long, Hai; Park, Andrew M.; Pivovar, Bryan S.

    2015-10-15

    Anion-exchange membrane fuel cells (AME-FCs) are of increasingly popular interest as they enable the use of non-Pt fuel cell catalysts, the primary cost limitation of proton exchange membrane fuel cells. Benzyltrimethyl ammonium (BTMA) is the standard cation that has historically been utilized as the hydroxide conductor in AEMs. Herein we approach AEMs from two directions. First and foremost we study the stability of several different cations in a hydroxide solution at elevated temperatures. We specifically targeted BTMA and methoxy and nitro substituted BTMA. We've also studied the effects of adding an akyl spacer units between the ammonium cation and the phenyl group. In the second approach we use computational studies to predict stable ammonium cations, which are then synthesized and tested for stability. Our unique method to study cation stability in caustic conditions at elevated temperatures utilizes Teflon Parr reactors suitable for use under various temperatures and cation concentrations. NMR analysis was used to determine remaining cation concentrations at specific time points with GCMS analysis verifying product distribution. We then compare the experimental results with calculated modeling stabilities. Our studies show that the electron donating methoxy groups slightly increase stability (compared to that of BTMA), while the electron withdrawing nitro groups greatly decrease stability in base. These results give insight into possible linking strategies to be employed when tethering a BTMA like ammonium cation to a polymeric backbone; thus synthesizing an anion exchange membrane.

  17. Poly(phenylene)-based anion exchange membrane

    DOEpatents

    Hibbs, Michael; Cornelius, Christopher J.; Fujimoto, Cy H.

    2011-02-15

    A poly(phenylene) compound of copolymers that can be prepared with either random or multiblock structures where a first polymer has a repeat unit with a structure of four sequentially connected phenyl rings with a total of 2 pendant phenyl groups and 4 pendant tolyl groups and the second polymer has a repeat unit with a structure of four sequentially connected phenyl rings with a total of 6 pendant phenyl groups. The second polymer has chemical groups attached to some of the pendant phenyl groups selected from CH.sub.3, CH.sub.2Br, and CH.sub.2N(CH.sub.3).sub.3Br groups. When at least one group is CH.sub.2N(CH.sub.3).sub.3Br, the material functions as an anion exchange membrane.

  18. Ionic Block Copolymers for Anion Exchange Membranes

    NASA Astrophysics Data System (ADS)

    Tsai, Tsung-Han; Herbst, Dan; Giffin, Guinevere A.; di Noto, Vito; Witten, Tom; Coughlin, E. Bryan

    2013-03-01

    Anion exchange membrane (AEM) fuel cells have regained interest because it allows the use of non-noble metal catalysts. Until now, most of the studies on AEM were based on random polyelectrolytes. In this work, Poly(vinylbenzyltrimethylammonium bromide)-b- (methylbutylene) ([PVBTMA][Br]-b-PMB) was studied by SAXS, TEM and dielectric spectroscopy to understand the fundamental structure-conductivity relationship of ion transport mechanisms within well-ordered block copolymers. The ionic conductivity and the formation of order structure were dependent on the casting solvent. Higher ion exchange capacity (IEC) of the membranes showed higher conductivity at as IEC values below 1.8mmol/g, as above this, the ionic conductivity decreases due to more water uptake leading to dilution of charge density. The humidity dependence of morphology exhibited the shifting of d-spacing to higher value and the alteration in higher characteristic peak of SAXS plot as the humidity increase from the dry to wet state. This phenomenon can be further explained by a newly developed polymer brush theory. Three ionic conduction pathways with different conduction mechanism within the membranes can be confirmed by broadband electric spectroscopy. US Army MURI (W911NF1010520)

  19. 8. VIEW OF GLOVE BOXES USED IN THE ANION EXCHANGE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    8. VIEW OF GLOVE BOXES USED IN THE ANION EXCHANGE PROCESS. THE ANION EXCHANGE PROCESS PURIFIED AND CONCENTRATED PLUTONIUM-BEARING NITRIC ACID SOLUTIONS TO MAKE THEM ACCEPTABLE AS FEED FOR CONVERSION TO METAL. (6/20/60) - Rocky Flats Plant, Plutonium Recovery & Fabrication Facility, North-central section of plant, Golden, Jefferson County, CO

  20. Anion, cation, and zwitterion selectivity of phospholemman channel molecules.

    PubMed Central

    Kowdley, G C; Ackerman, S J; Chen, Z; Szabo, G; Jones, L R; Moorman, J R

    1997-01-01

    Phospholemman (PLM), a 72-amino acid membrane protein with a single transmembrane domain, forms taurine-selective ion channels in lipid bilayers. Because taurine forms zwitterions, a taurine-selective channel might have binding sites for both anions and cations. Here we show that PLM channels indeed allow fluxes of both cations and anions, making instantaneous and voltage-dependent transitions among conformations with drastically different ion selectivity characteristics. This surprising and novel ion channel behavior offers a molecular explanation for selective taurine flux across cell membranes and may explain why molecules in the phospholemman family can induce cation- or anion-selective conductances when expressed in Xenopus oocytes. PMID:8994599

  1. Purification Or Organic Acids Using Anion Exchange Chromatography.

    DOEpatents

    Ponnampalam; Elankovan

    2001-09-04

    Disclosed is a cost-effective method for purifying and acidifying carboxylic acids, including organic acids and amino acids. The method involves removing impurities by allowing the anionic form of the carboxylic acid to bind to an anion exchange column and washing the column. The carboxylic anion is displaced as carboxylic acid by washing the resin with a strong inorganic anion. This method is effective in removing organic carboxylic acids and amino acids from a variety of industrial sources, including fermentation broths, hydrolysates, and waste streams.

  2. An anion channel in Arabidopsis hypocotyls activated by blue light.

    PubMed Central

    Cho, M H; Spalding, E P

    1996-01-01

    A rapid, transient depolarization of the plasma membrane in seedling stems is one of the earliest effects of blue light detected in plants. It appears to play a role in transducing blue light into inhibition of hypocotyl (stem) elongation, and perhaps other responses. The possibility that activation of a Cl- conductance is part of the depolarization mechanism was raised previously and addressed here. By patch clamping hypocotyl cells isolated from dark-grown (etiolated) Arabidopsis seedlings, blue light was found to activate an anion channel residing at the plasma membrane. An anion-channel blocker commonly known as NPPB 15-nitro-2-(3-phenylpropylamino)-benzoic acid] potently and reversibly blocked this anion channel. NPPB also blocked the blue-light-induced depolarization in vivo and decreased the inhibitory effect of blue light on hypocotyl elongation. These results indicate that activation of this anion channel plays a role in transducing blue light into growth inhibition. PMID:8755616

  3. An anion channel in Arabidopsis hypocotyls activated by blue light

    NASA Technical Reports Server (NTRS)

    Cho, M. H.; Spalding, E. P.; Evans, M. L. (Principal Investigator)

    1996-01-01

    A rapid, transient depolarization of the plasma membrane in seedling stems is one of the earliest effects of blue light detected in plants. It appears to play a role in transducing blue light into inhibition of hypocotyl (stem) elongation, and perhaps other responses. The possibility that activation of a Cl- conductance is part of the depolarization mechanism was raised previously and addressed here. By patch clamping hypocotyl cells isolated from dark-grown (etiolated) Arabidopsis seedlings, blue light was found to activate an anion channel residing at the plasma membrane. An anion-channel blocker commonly known as NPPB 15-nitro-2-(3-phenylpropylamino)-benzoic acid] potently and reversibly blocked this anion channel. NPPB also blocked the blue-light-induced depolarization in vivo and decreased the inhibitory effect of blue light on hypocotyl elongation. These results indicate that activation of this anion channel plays a role in transducing blue light into growth inhibition.

  4. New anion-exchange polymers for improved separations

    SciTech Connect

    Jarvinen, G.D.; Barr, M.E.; Marsh, S.F.

    1997-08-01

    Objective is to improve the understanding of how the structure of a new class of anion-exchange polymers controls the binding of anionic actinide complexes from solution. This is needed to develop practical separation systems that will reduce the cost of actinide processing operations within the DOE complex. In addition anion exchange is widely used in industry. Several new series of bifunctional anion- exchange polymers have been designed, synthesized, and tested for removing Pu(IV), Am(III), and U(VI) from nitric acid. The polymers contain a pyridinium site derived from the host poly(4-vinylpyridine) and a second cationic site attached through a chain of 2 to 6 methylene groups. The new polymers removed Pu four to ten times more efficiently than the best commercial materials.

  5. Nitrate anion exchange in 238Pu aqueous scrap recovery operations

    NASA Astrophysics Data System (ADS)

    Pansoy-Hjelvik, M. E.; Silver, G. L.; Reimus, M. A. H.; Ramsey, K. B.

    1999-01-01

    Strong base, nitrate anion exchange (IX) is crucial to the purification of 238Pu solution feedstocks with gross levels of impurities. This paper discusses the work involved in bench scale experiments to optimize the nitrate anion exchange process. In particular, results are presented of experiments conducted to a) demonstrate that high levels of impurities can be separated from 238Pu solutions via nitrate anion exchange and, b) work out chemical pretreatment methodology to adjust and maintain 238Pu in the IV oxidation state to optimize the Pu(IV)-hexanitrato anionic complex sorption to Reillex-HPQ resin. Additional experiments performed to determine the best chemical treatment methodology to enhance recovery of sorbed Pu from the resin and VIS-NIR absorption studies to determine the steady state equilibrium of Pu(IV), Pu(III), and Pu(VI) in nitric acid are discussed.

  6. A lanthanide complex for metal encapsulations and anion exchanges.

    PubMed

    Sun, Yan-Qiong; Wan, Fang; Li, Xin-Xiong; Lin, Jian; Wu, Tao; Zheng, Shou-Tian; Bu, Xianhui

    2016-08-01

    A cationic lanthanide metalloligand with 3 dangling carboxylate groups on its periphery co-assembles with nitrate into a porous thermochromic solid responsive to both external cations and anions, owing to the presence of exchangeable NO3(-) as well as cation cavities arising from cooperative orientation of free carboxylate groups. An especially interesting feature is the structural memory effect during crystallization exhibited by the metalloligand, even after dissolution and binding to secondary cations (Cu(2+), Cd(2+)…). Moreover, the porous solid can undergo ion-exchange with various anions, leading to tunable thermochromic temperature and color range. PMID:27463609

  7. Understanding and modeling removal of anionic organic contaminants (AOCs) by anion exchange resins.

    PubMed

    Zhang, Huichun; Shields, Anthony J; Jadbabaei, Nastaran; Nelson, Maurice; Pan, Bingjun; Suri, Rominder P S

    2014-07-01

    Ionic organic contaminants (OCs) are a growing concern for water treatment and the environment and are removed inefficiently by many existing technologies. This study examined removal of anionic OCs by anion exchange resins (AXRs) as a promising alternative. Results indicate that two polystyrene AXRs (IRA910 and IRA96) have higher sorption capacities and selectivity than a polyacrylate resin (A860). For the polystyrene resins, selectivity follows: phenolates ≥ aromatic dicarboxylates > aromatic monocarboxylates > benzenesulfonate > aliphatic carboxylates. This trend can be explained based on hydration energy, the number of exchange groups, and aromaticity and hydrophobicity of the nonpolar moiety (NPM) of the anions. For A860, selectivity only varies within a narrow range (0.13-1.64). Despite the importance of the NPM of the anions, neutral solutes were sorbed much less, indicating synergistic combinations of electrostatic and nonelectrostatic interactions in the overall sorption. By conducting multiple linear regression between Abraham's descriptors and nature log of selectivity, induced dipole-related interactions and electrostatic interactions were found to be the most important interaction forces for sorption of the anions, while solute H-bond basicity has a negative effect. A predictive model was then developed for carboxylates and phenolates based on the poly parameter linear free energy relationships established for a diverse range of 16 anions and 5 neutral solutes, and was validated by accurate prediction of sorption of five test solutes within a wide range of equilibrium concentrations and that of benzoate at different pH. PMID:24877792

  8. Hydroxy double salt anion exchange kinetics: effects of precursor structure and anion size.

    PubMed

    Kandare, Everson; Hossenlopp, Jeanne M

    2005-05-01

    (1)H NMR spectroscopy and powder X-ray diffraction have been used to explore the details of anion exchange reactions of two layered hydroxy double salts (HDSs), zinc copper hydroxy acetate (ZCA), nickel zinc hydroxy acetate (NZA), and a related layered material, zinc hydroxy acetate (ZHA), at room temperature (21-22 degrees C). Reactions that followed Avrami-Erofe'ev kinetics with respect to temporal profiles for acetate release, ZCA with butyrate (k = 1.7 x 10(-3) s(-1)), and octanoate (k = 0.79 x 10(-3) s(-1)) anions, as well as ZHA with octanoate (k = 2.6 x 10(-3) s(-1)), demonstrate that rate constants for acetate release are influenced by the exchange anion relative size as well as by the solid precursor structure/composition. The reaction of NZA with octanoate deviated from expected Avrami-Erofe'ev behavior, with evidence for an intermediate species in the solid phase that may influence the rate of acetate release into solution. The reaction of ZCA with formate anions exhibited a unique zeroth-order kinetics release of acetate, providing the possibility of developing tunable nanostructured anion release sources by use of variations in the size of the exchange species. PMID:16851994

  9. Plasmalemmal VDAC controversies and maxi-anion channel puzzle.

    PubMed

    Sabirov, Ravshan Z; Merzlyak, Petr G

    2012-06-01

    The maxi-anion channel has been observed in many cell types from the very beginning of the patch-clamp era. The channel is highly conductive for chloride and thus can modulate the resting membrane potential and play a role in fluid secretion/absorption and cell volume regulation. A wide nanoscopic pore of the maxi-anion channel permits passage of excitatory amino acids and nucleotides. The channel-mediated release of these signaling molecules is associated with kidney tubuloglomerular feedback, cardiac ischemia/hypoxia, as well as brain ischemia/hypoxia and excitotoxic neurodegeneration. Despite the ubiquitous expression and physiological/pathophysiological significance, the molecular identity of the maxi-anion channel is still obscure. VDAC is primarily a mitochondrial protein; however several groups detected it on the cellular surface. VDAC in lipid bilayers reproduced the most important biophysical properties of the maxi-anion channel, such as a wide nano-sized pore, closure in response to moderately high voltages, ATP-block and ATP-permeability. However, these similarities turned out to be superficial, and the hypothesis of plasmalemmal VDAC as the maxi-anion channel did not withstand the test by genetic manipulations of VDAC protein expression. VDAC on the cellular surface could also function as a ferricyanide reductase or a receptor for plasminogen kringle 5 and for neuroactive steroids. These ideas, as well as the very presence of VDAC on plasmalemma, remain to be scrutinized by genetic manipulations of the VDAC protein expression. This article is part of a Special Issue entitled: VDAC structure, function, and regulation of mitochondrial metabolism. PMID:21986486

  10. Removal of Uranium from Plutonium Solutions by Anion Exchange

    SciTech Connect

    Rudisill, T.S.

    2002-03-22

    The anion exchange capacity in the HB-Line Phase II Facility will be used to purify plutonium solutions potentially containing significant quantities of depleted uranium. Following purification, the plutonium will be precipitated as an oxalate and calcined to plutonium oxide (PuO2) for storage until final disposition.

  11. Neptunium Valence Chemistry in Anion Exchange Processing

    SciTech Connect

    KYSER, EDWARD

    2003-02-01

    The current anion resin in use in HB-Line Phase II, Reillex{trademark} HPQ, was tested in the laboratory under expected plant conditions for Np processing and was found to load between 50 and 70 g Np per liter of resin. Losses varied from 0.2 to 15 percent depending on a number of parameters. Hydrazine in the feed at 0.02 to 0.05 M appeared to keep the Np from oxidizing and increasing the losses within four to seven days after the FS addition. Losses of up to three percent were observed five days after FS addition when hydrazine was not used in the feed, compared with 0.3 percent when the feed was loaded immediately after FS addition. Based on these test results the following processing conditions are recommended: (1) Feed conditions: 8 M HNO{sub 3}, 0.02 M hydrazine, 0.05 M excess FS, less than 5 days storage of solution after FS addition. (2) Wash conditions: 100 liters of 8 M HNO{sub 3}, no FS, no hydrazine. (3) Elution conditions: 0.17 M HNO{sub 3}, 0.05 M hydrazine, no FS. (4) Precipitation feed conditions: 0.03 M excess ascorbic acid, no additional hydrazine, no FS, precipitation within three days.

  12. Kinetics and mechanism of exogenous anion exchange in FeFbpA-NTA: significance of periplasmic anion lability and anion binding activity of ferric binding protein A.

    PubMed

    Heymann, Jared J; Gabricević, Mario; Mietzner, Timothy A; Crumbliss, Alvin L

    2010-02-01

    The bacterial transferrin ferric binding protein A (FbpA) requires an exogenous anion to facilitate iron sequestration, and subsequently to shuttle the metal across the periplasm to the cytoplasmic membrane. In the diverse conditions of the periplasm, numerous anions are known to be present. Prior in vitro experiments have demonstrated the ability of multiple anions to fulfill the synergistic iron-binding requirement, and the identity of the bound anion has been shown to modulate important physicochemical properties of iron-bound FbpA (FeFbpA). Here we address the kinetics and mechanism of anion exchange for the FeFbpA-nitrilotriacetate (NTA) assembly with several biologically relevant anions (citrate, oxalate, phosphate, and pyrophosphate), with nonphysiologic NTA serving as a representative synergistic anion/chelator. The kinetic data are consistent with an anion-exchange process that occurs in multiple steps, dependent on the identity of both the entering anion and the leaving anion. The exchange mechanism may proceed either as a direct substitution or through an intermediate FeFbpA-X* assembly based on anion (X) identity. Our kinetic results further develop an understanding of exogenous anion lability in the periplasm, as well as address the final step of the iron-free FbpA (apo-FbpA)/Fe(3+) sequestration mechanism. Our results highlight the kinetic significance of the FbpA anion binding site, demonstrating a correlation between apo-FbpA/anion affinity and the FeFbpA rate of anion exchange, further supporting the requirement of an exogenous anion to complete tight sequestration of iron by FbpA, and developing a mechanism for anion exchange within FeFbpA that is dependent on the identity of both the entering anion and the leaving anion. PMID:19813031

  13. Anion Permeation in Ca2+-Activated Cl− Channels

    PubMed Central

    Qu, Zhiqiang; Hartzell, H. Criss

    2000-01-01

    Ca2+-activated Cl channels (ClCaCs) are an important class of anion channels that are opened by increases in cytosolic [Ca2+]. Here, we examine the mechanisms of anion permeation through ClCaCs from Xenopus oocytes in excised inside-out and outside-out patches. ClCaCs exhibited moderate selectivity for Cl over Na: PNa/PCl = 0.1. The apparent affinity of ClCaCs for Cl was low: Kd = 73 mM. The channel had an estimated pore diameter >0.6 nm. The relative permeabilities measured under bi-ionic conditions by changes in Erev were as follows: C(CN)3 > SCN > N(CN)2 > ClO4 > I > N3 > Br > Cl > formate > HCO3 > acetate = F > gluconate. The conductance sequence was as follows: N3 > Br > Cl > N(CN)2 > I > SCN > COOH > ClO4 > acetate > HCO3 = C(CN)3 > gluconate. Permeant anions block in a voltage-dependent manner with the following affinities: C(CN)3 > SCN = ClO4 > N(CN)2 > I > N3 > Br > HCO3 > Cl > gluconate > formate > acetate. Although these data suggest that anionic selectivity is determined by ionic hydration energy, other factors contribute, because the energy barrier for permeation is exponentially related to anion hydration energy. ClCaCs exhibit weak anomalous mole fraction behavior, implying that the channel may be a multi-ion pore, but that ions interact weakly in the pore. The affinity of the channel for Ca2+ depended on the permeant anion at low [Ca2+] (100–500 nM). Apparently, occupancy of the pore by a permeant anion increased the affinity of the channel for Ca2+. The current was strongly dependent on pH. Increasing pH on the cytoplasmic side decreased the inward current, whereas increasing pH on the external side decreased the outward current. In both cases, the apparent pKa was voltage-dependent with apparent pKa at 0 mV = ∼9.2. The channel may be blocked by OH− ions, or protons may titrate a site in the pore necessary for ion permeation. These data demonstrate that the permeation properties of ClCaCs are different from those of CFTR or ClC-1, and provide

  14. Highly Water Resistant Anion Exchange Membrane for Fuel Cells.

    PubMed

    Yang, Zhengjin; Hou, Jianqiu; Wang, Xinyu; Wu, Liang; Xu, Tongwen

    2015-07-01

    For anion exchange membranes (AEMs), achieving efficient hydroxide conductivity without excessive hydrophilicity presents a challenge. Hence, new strategies for constructing mechanically strengthened and hydroxide conductive (especially at controlled humidity) membranes are critical for developing better AEMs. Macromolecular modification involving ylide chemistry (Wittig reaction) for the fabrication of novel AEMs with an interpenetrating polymer network structure is reported. The macromolecular modification is cost effective, facile, and based on a one-pot synthesis. AEM water uptake is reduced to 3.6 wt% and a high hydroxide conductivity (69.7 mS cm(-1) , 90 °C) is achieved simultaneously. More importantly, the membrane exhibits similar tensile strength (>35 MPa) and comparable flexibility in both dry and wet states. These AEMs could find further applications within anion exchange membrane fuel cells with low humidity or photoelectric assemblies. PMID:25962480

  15. Simple model can explain self-inhibition of red cell anion exchange.

    PubMed Central

    Tanford, C

    1985-01-01

    Ion translocation in red cell anion exchange is assumed to occur by means of an alternating access mechanism, in which a critical binding site for the transported ion alternates between two conformational states, each accessible from only one side of the membrane. If this alternating site is located within the transport protein at some distance from one or both surfaces of the membrane, an access channel is required to connect the alternating site to the adjacent bulk solution. This automatically leads to inhibition of transport at high concentrations of the transported ion because release of the ion from the alternating site can occur only via unoccupied channel sites. PMID:2579684

  16. The sorption of quercetin by high-basicity anion exchangers

    NASA Astrophysics Data System (ADS)

    Udalova, N. A.; Karpov, S. I.; Selemenev, V. F.; Sharmar, I. A.

    2009-06-01

    The sorption of quercetin on anionites with various porosities in the OH- and Cl- forms was studied under static conditions. The equilibrium (distribution coefficients K p) and kinetic (effective diffusion coefficients D eff) parameters of quercetin sorption on AV-17-2P and AV-17-6M anionites in the Cl- and OH- forms were calculated. The mechanism of quercetin interactions with the anion exchangers was studied by electron microscopy and IR spectroscopy.

  17. Alkaline Anion-Exchange Membranes Containing Mobile Ion Shuttles.

    PubMed

    Ge, Xiaolin; He, Yubin; Guiver, Michael D; Wu, Liang; Ran, Jin; Yang, Zhengjin; Xu, Tongwen

    2016-05-01

    A new class of alkaline anion-exchange membranes containing mobile ion shuttles is developed. It is achieved by threading ionic linear guests into poly(crown ether) hosts via host-guest molecular interaction. The thermal- and pH-triggered shuttling of ionic linear guests remarkably increases the solvation-shell fluctuations in inactive hydrated hydroxide ion complexes (OH(-) (H2 O)4 ) and accelerates the OH(-) transport. PMID:26972938

  18. Relationship between anion binding and anion permeability revealed by mutagenesis within the cystic fibrosis transmembrane conductance regulator chloride channel pore

    PubMed Central

    Linsdell, Paul

    2001-01-01

    Anion binding within the pores of wild-type and mutant cystic fibrosis transmembrane conductance regulator (CFTR) Cl− channels, expressed in two different mammalian cell lines, was assayed using patch clamp recording. Specifically, experiments measured both the conductance of different anions and the ability of other permeant anions to block Cl− permeation through the pore. Under symmetrical ionic conditions, wild-type CFTR channels showed the conductance sequence Cl− >NO3− >Br−≥formate >F− >SCN−≈ ClO4−. High SCN− conductance was not observed, nor was there an anomalous mole fraction effect of SCN− on conductance under the conditions used. Iodide currents could not be measured under symmetrical ionic conditions, but under bi-ionic conditions I− conductance appeared low. Chloride currents through CFTR channels were blocked by low concentrations (10 mM) of SCN−, I− and ClO4−, implying relatively tight binding of these anions within the pore. Two mutations in CFTR which alter the anion permeability sequence, F337S and T338A, also altered the anion conductance sequence. Furthermore, block by SCN−, I− and ClO4− were weakened in both mutants. Both these effects are consistent with altered anion binding within the pore. The effects of mutations on anion permeability and relative anion conductance suggested that, for most anions, increased permeability was associated with increased conductance. This indicates that the CFTR channel pore does not achieve its anion selectivity by selective anion binding within the mutated region. Instead, it is suggested that entry of anions into the region around F337 and T338 facilitates their passage through the pore. In wild-type CFTR channels, anion entry into this crucial pore region is probably dominated by anion hydration energies. PMID:11179391

  19. Relationship between anion binding and anion permeability revealed by mutagenesis within the cystic fibrosis transmembrane conductance regulator chloride channel pore.

    PubMed

    Linsdell, P

    2001-02-15

    1. Anion binding within the pores of wild-type and mutant cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channels, expressed in two different mammalian cell lines, was assayed using patch clamp recording. Specifically, experiments measured both the conductance of different anions and the ability of other permeant anions to block Cl- permeation through the pore. 2. Under symmetrical ionic conditions, wild-type CFTR channels showed the conductance sequence Cl- > NO3- > Br- > or = formate > F- > SCN- congruent to ClO4-. 3. High SCN- conductance was not observed, nor was there an anomalous mole fraction effect of SCN- on conductance under the conditions used. Iodide currents could not be measured under symmetrical ionic conditions, but under bi-ionic conditions I- conductance appeared low. 4. Chloride currents through CFTR channels were blocked by low concentrations (10 mM) of SCN-, I- and ClO4-, implying relatively tight binding of these anions within the pore. 5. Two mutations in CFTR which alter the anion permeability sequence, F337S and T338A, also altered the anion conductance sequence. Furthermore, block by SCN-, I- and ClO4- were weakened in both mutants. Both these effects are consistent with altered anion binding within the pore. 6. The effects of mutations on anion permeability and relative anion conductance suggested that, for most anions, increased permeability was associated with increased conductance. This indicates that the CFTR channel pore does not achieve its anion selectivity by selective anion binding within the mutated region. Instead, it is suggested that entry of anions into the region around F337 and T338 facilitates their passage through the pore. In wild-type CFTR channels, anion entry into this crucial pore region is probably dominated by anion hydration energies. PMID:11179391

  20. [Chromatographic separation of plasmid DNA by anion-exchange cryogel].

    PubMed

    Guo, Yantao; Shen, Shaochuan; Yun, Junxian; Yao, Kejian

    2012-08-01

    Plasmid DNA (pDNA) is used as an important vector for gene therapy, and its wide application is restricted by the purity and yield. To obtain high-purity pDNA, a chromatographic method based on anion-exchange supermacroporous cryogel was explored. The anion-exchange cryogel was prepared by grafting diethylaminoethyl-dextran to the epoxide groups of polyacrylamide-based matrix and pUC19 plasmid was used as a target to test the method. The plasmid was transferred into Escherichia coli DH5alpha, cultivated, harvested and lysed. The obtained culture was centrifuged and the supernatant was used as the plasmid feedstock, which was loaded into the anion-exchange cryogel bed for chromatographic separation. By optimizing the pH of running buffer and the elution conditions, high-purity pDNA was obtained by elution with 0.5 mol/L sodium chloride solution at pH 6.6. Compared to the traditional methods for purification of pDNA, animal source enzymes and toxic reagents were not involved in the present separation process, ensuring the safety of both the purification operations and the obtained pDNA. PMID:23185899

  1. ANION EXCHANGE METHOD FOR SEPARATION OF METAL VALUES

    DOEpatents

    Hyde, E.K.; Raby, B.A.

    1959-02-10

    A method is described for selectively separating radium, bismuth, poloniums and lead values from a metallic mixture of thc same. The mixture is dissolved in aqueous hydrochloric acid and the acidity is adjusted to between 1 to 2M in hydrochloric acid to form the anionic polychloro complexes of polonium and bismuth. The solution is contacted with a first anion exchange resin such as strong base quaternary ammonia type to selectively absorb the polonium and bismuth leaving the radium and lead in the effluent. The effluent, after treatment in hydrochloric acid to increase the hydrochloric acid concentration to 6M is contacted with a second anion exchange iesin of the same type as the above to selectively adsorb the lead leaving the radium in the effluent. Radium is separately recovered from the effluent from the second exchange column. Lead is stripped from the loaded resin of the second column by treatment with 3M hydrochloric acid solution. The loaded resin of the first column is washed with 8M hydrochloric acid solution to recover bismuth and then treated with strong nitric acid solution to recover polonium.

  2. Bifunctional anion-exchange resins with improved selectivity and exchange kinetics

    DOEpatents

    Alexandratos, Spiro D.; Brown, Gilbert M.; Bonnesen, Peter V.; Moyer, Bruce A.

    2000-01-01

    Disclosed herein are a class of anion exchange resins containing two different exchange sites with improved selectivity and sorptive capability for chemical species in solution, such as heptavalent technetium (as pertechnetate anion, TcO.sub.4.sup.-). The resins are prepared by first reacting haloalkylated crosslinked copolymer beads with a large tertiary amine in a solvent in which the resin beads can swell, followed by reaction with a second, smaller, tertiary amine to more fully complete the functionalization of the resin. The resins have enhanced selectivity, capacity, and exchange kinetics.

  3. Sorption of tellurium ion from aqueous solutions by anion-exchangers and amphoteric ion-exchangers

    SciTech Connect

    Dreipa, E.F.; Pakholkov, V.S.; Luk'yanov, S.A.

    1981-10-20

    Sorption of tellurium from solutions of telluric acid under dynamic and static conditions by anion-exchangers and amphoteric ion-exchangers containing various ionic groups was studied and the influence of the ion form, pH of the medium, presence of electrolytes, and the H/sub 6/TeO/sub 6/ concentration in the original solutions was determined. The mechanism of sorption of tellurium (VI) by anion-exchangers was deduced from sorption and IR-spectroscopic data. Differences in the behavior of tellurium and selenium were used for separating these elements in 0.05 N H/sub 2/SeO/sub 4/ + 0.05 N H/sub 6/TeO/sub 6/ solution of pH = 1.0 with the aid of EDE-10P anion-exchange resin.

  4. Anion exchangers with branched functional ion exchange layers of different hydrophilicity for ion chromatography.

    PubMed

    Shchukina, O I; Zatirakha, A V; Smolenkov, A D; Nesterenko, P N; Shpigun, O A

    2015-08-21

    Novel polystyrene-divinylbenzene (PS-DVB) based anion exchangers differing from each other in the structure of the branched functional ion exchange layer are prepared to investigate the role of linker and functional site on ion exchange selectivity. The proposed method of synthesis includes the obtaining of aminated PS-DVB particles by means of their acylation with following reductive amination with methylamine. Further modification of the obtained secondary aminogroups is provided by the alkylation with either 1,4-butanediol diglycidyl ether (1,4-BDDGE) or resorcinol diglycidyl ether (RDGE), which form the linkers of different hydrophobicity, and amination of terminal epoxide rings with trimethylamine (TMA), dimethylethanolamine (DMEA), methyldiethanolamine (MDEA) or triethanolamine (TEA). The variation of the structure and hydrophobicity of the linker and terminal quaternary ammonium sites in the functional layer allows the alteration of selectivity and separation efficiency of the obtained adsorbents. The ion exchange selectivity and separation efficiency of the anion exchangers are evaluated using the model mixtures of anions (F(-), HCOO(-), Cl(-), NO2(-), Br(-), NO3(-), HPO4(2-) and SO4(2-)) in potassium hydroxide eluents. The adsorbents show the decrease of selectivity with increasing the hydrophilicity of the terminal functional site. The anion exchangers having more flexible and hydrophilic 1,4-BDDGE linker provide smaller separation factors for most of the analytes as compared with RDGE-containing adsorbents with the same terminal ion exchange sites, but are characterized with higher column efficiencies and better peak symmetry for polarizable anions. In case of 1,4-BDDGE-modified anion exchangers of the particle size of 3.3μm functionalized with DMEA and MDEA the calculated values of column efficiencies for polarizable NO3(-) and Br(-) are up to 49,000 and 53,000N/m, respectively, which is almost twice higher than the values obtained for the RDGE

  5. Anion exchange in Zn-Al layered double hydroxides: In situ X-ray diffraction study

    NASA Astrophysics Data System (ADS)

    Salak, Andrei N.; Tedim, João; Kuznetsova, Alena I.; Zheludkevich, Mikhail L.; Ferreira, Mário G. S.

    2010-07-01

    Anion exchange capacity is a key factor for the application of Zn-Al layered double hydroxides (LDHs) as nano-containers in active corrosion protection. In this work, the nitrate-pyrovanadate anion exchange/re-exchange processes in these LDHs were investigated in situ. We demonstrate that the exchange reactions lead to a decrease of the average crystallite size of LDHs as a result of mechanical fragmentation of the crystallites rather than dissolution/recrystallization. The fragmentation occurs due to fast anion exchange in the initial stage, and can be controlled by changing the ratio of the available substituent anions to the replacement anions and application of a mechanical activation.

  6. Anion Exchange Membranes: Current Status and Moving Forward

    SciTech Connect

    Hickner, MA; Herring, AM; Coughlin, EB

    2013-10-29

    This short review is meant to provide the reader with highlights in anion exchange membrane research, describe current needs in the field, and point out promising directions for future work. Anion exchange membranes (AEMs) provide one possible route to low platinum or platinum-free fuel cells with the potential for facile oxidation of complex fuels beyond hydrogen and methanol. AEMs and related stable cationic polymers also have applications in energy storage and other electrochemical technologies such as water electrolyzers and redox flow batteries. While anion exchange membranes have been known for a long time in water treatment applications, materials for electrochemical technology with robust mechanical properties in thin film format have only recently become more widely available. High hydroxide and bicarbonate anion conductivity have been demonstrated in a range of AEM formats, but intrinsic stability of the polymers and demonstration of long device lifetime remain major roadblocks. Novel approaches to stable materials have focused on new types of cations that employ delocalization and steric shielding of the positive center to mitigate nucleophilic attack by hydroxide. A number of promising polymer backbones and membrane architectures have been identified, but limited device testing and a lack of understanding of the degradation mechanisms in operating devices is slowing progress on engineered systems with alkaline fuel cell technology. Our objective is to spur more research in this area to develop fuel cell systems that approach the costs of inexpensive batteries for large-scale applications. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1727-1735, 2013

  7. The properties, functions, and pathophysiology of maxi-anion channels.

    PubMed

    Sabirov, Ravshan Z; Merzlyak, Petr G; Islam, Md Rafiqul; Okada, Toshiaki; Okada, Yasunobu

    2016-03-01

    The maxi-anion channels (MACs) with a unitary conductance of 200-500 pS are detected in virtually every part of the whole body and found in cells from mammals to amphibia. The channels are normally silent but can be activated by physiologically/pathophysiologically relevant stimuli, such as osmotic, salt, metabolic, oxidative, and mechanical stresses, receptor activation, serum, heat, and intracellular Ca(2+) rise. In some MACs, protein dephosphorylation is associated with channel activation. Among MACs so far studied, around 60 % (designated here as Maxi-Cl) possess, in common, the following phenotypical biophysical properties: (1) unitary conductance of 300-400 pS, (2) a linear current-voltage relationship, (3) high anion-to-cation selectivity with PCl/Pcation of >8, and (4) inactivation at positive and negative potentials over a certain level (usually ±20 mV). The pore configuration of the Maxi-Cl is asymmetrical with extracellular and intracellular radii of ∼1.42 and ∼1.16 nm, respectively, and a medial constriction down to ∼0.55-0.75 nm. The classical function of MACs is control of membrane potential and fluid movement. Permeability to ATP and glutamate turns MACs to signaling channels in purinergic and glutamatergic signal transduction defining them as a perspective target for drug discovery. The molecular identification is an urgent task that would greatly promote the developments in this field. A possible relationship between these channels and some transporters is discussed. PMID:26733413

  8. The CFTR ion channel: gating, regulation, and anion permeation.

    PubMed

    Hwang, Tzyh-Chang; Kirk, Kevin L

    2013-01-01

    Cystic fibrosis transmembrane conductance regulator (CFTR) is an ATP-gated anion channel with two remarkable distinctions. First, it is the only ATP-binding cassette (ABC) transporter that is known to be an ion channel--almost all others function as transport ATPases. Second, CFTR is the only ligand-gated channel that consumes its ligand (ATP) during the gating cycle--a consequence of its enzymatic activity as an ABC transporter. We discuss these special properties of CFTR in the context of its evolutionary history as an ABC transporter. Other topics include the mechanisms by which CFTR gating is regulated by phosphorylation of its unique regulatory domain and our current view of the CFTR permeation pathway (or pore). Understanding these basic operating principles of the CFTR channel is central to defining the mechanisms of action of prospective cystic fibrosis drugs and to the development of new, rational treatment strategies. PMID:23284076

  9. Quaternized agricultural by-products as anion exchange resins.

    PubMed

    Wartelle, Lynda H; Marshall, Wayne E

    2006-01-01

    The objectives of this study were the chemical modification of readily available, low-cost agricultural by-products to anion exchange resins and the selection of the best modified by-product for further use in anion removal. Resins were prepared through the quaternization of a series of 12 agricultural by-products with N-(3-chloro-2-hydroxypropyl) trimethylammonium chloride (CHMAC). Phosphate ion adsorption assays were conducted at pH 7 in order to compare adsorption properties among the by-products. Quaternized corn stover showed the highest phosphorus adsorption at 0.66 mmole/g. Since corn stover exhibited the best uptake of phosphate ion, it was compared to a commercially available, cellulose-based anion exchange resin. Additionally, adsorption capacities of quaternized corn stover for arsenate, chromate, and selenate were evaluated and adsorption efficiencies were determined in simulated wastewater samples. Our results indicate that modified corn stover demonstrates good adsorption uptake for arsenate and selenate and especially for chromate. PMID:16144735

  10. Homologue Structure of the SLAC1 Anion Channel for Closing Stomata in Leaves

    SciTech Connect

    Y Chen; L Hu; M Punta; R Bruni; B Hillerich; B Kloss; B Rost; J Love; S Siegelbaum; W Hendrickson

    2011-12-31

    The plant SLAC1 anion channel controls turgor pressure in the aperture-defining guard cells of plant stomata, thereby regulating the exchange of water vapour and photosynthetic gases in response to environmental signals such as drought or high levels of carbon dioxide. Here we determine the crystal structure of a bacterial homologue (Haemophilus influenzae) of SLAC1 at 1.20 {angstrom} resolution, and use structure-inspired mutagenesis to analyse the conductance properties of SLAC1 channels. SLAC1 is a symmetrical trimer composed from quasi-symmetrical subunits, each having ten transmembrane helices arranged from helical hairpin pairs to form a central five-helix transmembrane pore that is gated by an extremely conserved phenylalanine residue. Conformational features indicate a mechanism for control of gating by kinase activation, and electrostatic features of the pore coupled with electrophysiological characteristics indicate that selectivity among different anions is largely a function of the energetic cost of ion dehydration.

  11. Phosphorylation of the vacuolar anion exchanger AtCLCa is required for the stomatal response to abscisic acid.

    PubMed

    Wege, Stefanie; De Angeli, Alexis; Droillard, Marie-Jo; Kroniewicz, Laetitia; Merlot, Sylvain; Cornu, David; Gambale, Franco; Martinoia, Enrico; Barbier-Brygoo, Hélène; Thomine, Sébastien; Leonhardt, Nathalie; Filleur, Sophie

    2014-01-01

    Eukaryotic anion/proton exchangers of the CLC (chloride channel) family mediate anion fluxes across intracellular membranes. The Arabidopsis thaliana anion/proton exchanger AtCLCa is involved in vacuolar accumulation of nitrate. We investigated the role of AtCLCa in leaf guard cells, a specialized plant epidermal cell that controls gas exchange and water loss through pores called stomata. We showed that AtCLCa not only fulfilled the expected role of accumulating anions in the vacuole during stomatal opening but also mediated anion release during stomatal closure in response to the stress hormone abscisic acid (ABA). We found that this dual role resulted from a phosphorylation-dependent change in the activity of AtCLCa. The protein kinase OST1 (also known as SnRK2.6) is a key signaling player and central regulator in guard cells in response to ABA. Phosphorylation of Thr(38) in the amino-terminal cytoplasmic domain of AtCLCa by OST1 increased the outward anion fluxes across the vacuolar membrane, which are essential for stomatal closure. We provide evidence that bidirectional activities of an intracellular CLC exchanger are physiologically relevant and that phosphorylation regulates the transport mode of this exchanger. PMID:25005229

  12. Specific inhibition of the plasmodial surface anion channel by dantrolene.

    PubMed

    Lisk, Godfrey; Kang, Myungsa; Cohn, Jamieson V; Desai, Sanjay A

    2006-11-01

    The plasmodial surface anion channel (PSAC), induced on human erythrocytes by the malaria parasite Plasmodium falciparum, is an important target for antimalarial drug development because it may contribute to parasite nutrient acquisition. However, known antagonists of this channel are quite nonspecific, inhibiting many other channels and carriers. This lack of specificity not only complicates drug development but also raises doubts about the exact role of PSAC in the well-known parasite-induced permeability changes. We recently identified a family of new PSAC antagonists structurally related to dantrolene, an antagonist of muscle Ca++ release channels. Here, we explored the mechanism of dantrolene's actions on parasite-induced permeability changes. We found that dantrolene inhibits the increased permeabilities of sorbitol, two amino acids, an organic cation, and hypoxanthine, suggesting a common pathway shared by these diverse solutes. It also produced parallel reductions in PSAC single-channel and whole-cell Cl- currents. In contrast to its effect on parasite-induced permeabilities, dantrolene had no measurable effect on five other classes of anion channels, allaying concerns of poor specificity inherent to other known antagonists. Our studies indicate that dantrolene binds PSAC at an extracellular site distinct from the pore, where it inhibits the conformational changes required for channel gating. Its affinity for this site depends on ionic strength, implicating electrostatic interactions in dantrolene binding. In addition to the potential therapeutic applications of its derivatives, dantrolene's specificity and its defined mechanism of action on PSAC make it a useful tool for transport studies of infected erythrocytes. PMID:16950925

  13. Molecular biology of the anion exchanger gene family.

    PubMed

    Kopito, R R

    1990-01-01

    The gene family of anion exchangers consists of at least four or five members, of which three have been characterized at the cDNA level. AE1-3 encode polypeptides that share significant homology with the erythrocyte anion exchanger, band 3 (AE1). Expression of cDNAs encoding these genes in heterologous systems confirms that this sequence similarity is reflected in the capacity to mediate reversible Cl/HCO3 exchange. While the NH2-terminal domain of band 3 is known to interact with several cytoplasmic proteins in erythrocytes, the function of the analogous domains of AE2 and AE3 remains unknown. The AE1 gene is expressed coordinately with other erythroid genes during erythropoiesis in both avian and mammalian erythroid progenitor cells. In addition, AE1 is expressed at the basolateral plasma membrane of the acid-secreting intercalated cells of the kidney. AE2 is expressed in a number of epithelial and nonepithelial cells; it may be expressed in the Golgi apparatus of some of these cells. AE3 is expressed in excitable tissues, including neurons and muscle. It is likely that these proteins play a role in regulation of intracellular pH and chloride in their respective tissue. Understanding of the physiological roles of these proteins, both for ion transport and for plasma membrane organization, remains a central issue. PMID:2289848

  14. The CFTR Ion Channel: Gating, Regulation, and Anion Permeation

    PubMed Central

    Hwang, Tzyh-Chang; Kirk, Kevin L.

    2013-01-01

    Cystic fibrosis transmembrane conductance regulator (CFTR) is an ATP-gated anion channel with two remarkable distinctions. First, it is the only ATP-binding cassette (ABC) transporter that is known to be an ion channel—almost all others function as transport ATPases. Second, CFTR is the only ligand-gated channel that consumes its ligand (ATP) during the gating cycle—a consequence of its enzymatic activity as an ABC transporter. We discuss these special properties of CFTR in the context of its evolutionary history as an ABC transporter. Other topics include the mechanisms by which CFTR gating is regulated by phosphorylation of its unique regulatory domain and our current view of the CFTR permeation pathway (or pore). Understanding these basic operating principles of the CFTR channel is central to defining the mechanisms of action of prospective cystic fibrosis drugs and to the development of new, rational treatment strategies. PMID:23284076

  15. Regeneration of anion exchange resins by catalyzed electrochemical reduction

    DOEpatents

    Gu, Baohua; Brown, Gilbert M.

    2002-01-01

    Anion exchange resins sorbed with perchlorate may be regenerated by a combination of chemical reduction of perchlorate to chloride using a reducing agent and an electrochemical reduction of the oxidized reducing agent. Transitional metals including Ti, Re, and V are preferred chemical reagents for the reduction of perchlorate to chloride. Complexing agents such as oxalate are used to prevent the precipitation of the oxidized Ti(IV) species, and ethyl alcohol may be added to accelerate the reduction kinetics of perchlorate. The regeneration may be performed by continuously recycling the regenerating solution through the resin bed and an electrochemical cell so that the secondary waste generation is minimized.

  16. Determining gold in water by anion-exchange batch extraction

    USGS Publications Warehouse

    McHugh, J.B.

    1986-01-01

    This paper describes a batch procedure for determining gold in natural waters. It is completely adaptable to field operations. The water samples are filtered and acidified before they are equilibrated with an anion-exchange resin by shaking. The gold is then eluted with acetone-nitric acid solution, and the eluate evaporated to dryness. The residue is taken up in hydrobromic acid-bromine solution and the gold is extracted with methyl isobutyl ketone. The extract is electrothermally atomized in an atomic-absorption spectrophotometer. The limit of determination is 1 ng 1. ?? 1986.

  17. The sorption capacity of boron on anionic-exchange resin

    SciTech Connect

    Lou, J.; Foutch, G.L.; Na, J.W.

    1999-11-01

    Boron sorption capacities on anionic-exchange resins vary with temperature, concentration, and resin crosslinkage. A semiempirical correlation, developed from boron solution chemistry, is presented to account for these variations. The relationship, based on boron chemistry and changes in Gibb's energy, can be stated approximately as Q = a{sub 1}C{sub B}{sup a{sub 2}}Z{sup a{sub 3}} exp[{minus}(a{sub 4}T + a{sub 5}T{sup 2} + a{sub 6}Z{sup 0.5})]. Correlation parameters, which vary with resin type, are evaluated experimentally. Parameter values for macroporous resin Diaion PA 300 and for gel-type resins Diaion SA10 and Amberlite IRN 78LC are presented. The resulting expression is used to determine boron sorption and desorption limitations on ion exchangers at various temperatures and concentrations, and to determine the interfacial boron concentration in equilibrium and rate models.

  18. Anion-exchange resin-based desulfurization process

    SciTech Connect

    Sheth, A.C.; Dharmapurikar, R.

    1992-01-01

    Under DOE Grant No. DE-FG22-90PC90309, the University of Tennessee Space Institute (UTSI) is contracted to further develop its anion-exchange, resin-based desulfurization concept to desulfurize alkali metal sulfates. From environmental as well as economic viewpoints, it is necessary to remove soluble sulfates from the wastes created by flue gas desulfurization systems. In order to do this economically, a low-cost desulfurization process for spent sorbents is necessary. UTSI's anion-exchange resin-based desulfurization concept is believed to satisfy these requirements. During the reporting period, October 1, 1992--December 31, 1992, UTSI has completed the batch mode experiments to evaluate the performance enhancement effect caused by organic acids on the resin's exhaustion efficiency. At present, batch mode experiments are being conducted to locate the position of the CO[sub 3]= and SO[sub 4]= ions in the affinity chart, and also reviewing/assessing the ASPEN Code's capabilities for use in the development of the Best Process Schematic and related economics.

  19. A Novel Methodology to Synthesize Highly Conductive Anion Exchange Membranes

    NASA Astrophysics Data System (ADS)

    He, Yubin; Pan, Jiefeng; Wu, Liang; Zhu, Yuan; Ge, Xiaolin; Ran, Jin; Yang, Zhengjin; Xu, Tongwen

    2015-08-01

    Alkaline polyelectrolyte fuel cell now receives growing attention as a promising candidate to serve as the next generation energy-generating device by enabling the use of non-precious metal catalysts (silver, cobalt, nickel et al.). However, the development and application of alkaline polyelectrolyte fuel cell is still blocked by the poor hydroxide conductivity of anion exchange membranes. In order to solve this problem, we demonstrate a methodology for the preparation of highly OH- conductive anion exchange polyelectrolytes with good alkaline tolerance and excellent dimensional stability. Polymer backbones were grafted with flexible aliphatic chains containing two or three quaternized ammonium groups. The highly flexible and hydrophilic multi-functionalized side chains prefer to aggregate together to facilitate the formation of well-defined hydrophilic-hydrophobic microphase separation, which is crucial for the superior OH- conductivity of 69 mS/cm at room temperature. Besides, the as-prepared AEMs also exhibit excellent alkaline tolerance as well as improved dimensional stability due to their carefully designed polymer architecture, which provide new directions to pursue high performance AEMs and are promising to serve as a candidate for fuel cell technology.

  20. A Novel Methodology to Synthesize Highly Conductive Anion Exchange Membranes

    PubMed Central

    He, Yubin; Pan, Jiefeng; Wu, Liang; Zhu, Yuan; Ge, Xiaolin; Ran, Jin; Yang, ZhengJin; Xu, Tongwen

    2015-01-01

    Alkaline polyelectrolyte fuel cell now receives growing attention as a promising candidate to serve as the next generation energy-generating device by enabling the use of non-precious metal catalysts (silver, cobalt, nickel et al.). However, the development and application of alkaline polyelectrolyte fuel cell is still blocked by the poor hydroxide conductivity of anion exchange membranes. In order to solve this problem, we demonstrate a methodology for the preparation of highly OH− conductive anion exchange polyelectrolytes with good alkaline tolerance and excellent dimensional stability. Polymer backbones were grafted with flexible aliphatic chains containing two or three quaternized ammonium groups. The highly flexible and hydrophilic multi-functionalized side chains prefer to aggregate together to facilitate the formation of well-defined hydrophilic-hydrophobic microphase separation, which is crucial for the superior OH− conductivity of 69 mS/cm at room temperature. Besides, the as-prepared AEMs also exhibit excellent alkaline tolerance as well as improved dimensional stability due to their carefully designed polymer architecture, which provide new directions to pursue high performance AEMs and are promising to serve as a candidate for fuel cell technology. PMID:26311616

  1. SLAC1 is required for plant guard cell S-type anion channel function in stomatal signalling

    PubMed Central

    Vahisalu, Triin; Kollist, Hannes; Wang, Yong-Fei; Nishimura, Noriyuki; Chan, Wai-Yin; Valerio, Gabriel; Lamminmäki, Airi; Brosché, Mikael; Moldau, Heino; Desikan, Radhika; Schroeder, Julian I.; Kangasjärvi, Jaakko

    2010-01-01

    Stomatal pores, formed by two surrounding guard cells in the epidermis of plant leaves, allow influx of atmospheric carbon dioxide in exchange for transpirational water loss. Stomata also restrict the entry of ozone—an important air pollutant that has an increasingly negative impact on crop yields, and thus global carbon fixation1 and climate change2. The aperture of stomatal pores is regulated by the transport of osmotically active ions and metabolites across guard cell membranes3,4. Despite the vital role of guard cells in controlling plant water loss3,4, ozone sensitivity1,2 and CO2 supply2,5–7, the genes encoding some of the main regulators of stomatal movements remain unknown. It has been proposed that guard cell anion channels function as important regulators of stomatal closure and are essential in mediating stomatal responses to physiological and stress stimuli3,4,8. However, the genes encoding membrane proteins that mediate guard cell anion efflux have not yet been identified. Here we report the mapping and characterization of an ozone-sensitive Arabidopsis thaliana mutant, slac1. We show that SLAC1 (SLOW ANION CHANNEL-ASSOCIATED 1) is preferentially expressed in guard cells and encodes a distant homologue of fungal and bacterial dicarboxylate/malic acid transport proteins. The plasma membrane protein SLAC1 is essential for stomatal closure in response to CO2, abscisic acid, ozone, light/dark transitions, humidity change, calcium ions, hydrogen peroxide and nitric oxide. Mutations in SLAC1 impair slow (S-type) anion channel currents that are activated by cytosolic Ca2+ and abscisic acid, but do not affect rapid (R-type) anion channel currents or Ca2+ channel function. A low homology of SLAC1 to bacterial and fungal organic acid transport proteins, and the permeability of S-type anion channels to malate9 suggest a vital role for SLAC1 in the function of S-type anion channels. PMID:18305484

  2. Enhanced liquid-liquid anion exchange using macrocyclic anion receptors: effect of receptor structure on sulphate-nitrate exchange selectivity

    SciTech Connect

    Moyer, Bruce A; Sloop Jr, Frederick {Fred} V; Fowler, Christopher J; Haverlock, Tamara; Kang, Hyun Ah; Delmau, Laetitia Helene; Bau, Diadra; Hossain, Alamgir; Bowman-James, Kristin; Shriver, James A.; Gross, Mr. Dustin E.; Bill, Nathan; Marquez, Manuel; Lynch, Vincent M.; Sessler, Jonathan L.

    2010-01-01

    When certain macrocyclic anion receptors are added to a chloroform solution of the nitrate form of a lipophilic quaternary ammonium salt (methyltri-C8,10-ammonium nitrate, Aliquat 336N), the extraction of sulphate from an aqueous sodium nitrate solution via exchange with the organic-phase nitrate is significantly enhanced. Eight macrocycles were surveyed, including two derivatives of a tetraamide macrocycle, five derivatives of calix[4]pyrrole and -decafluorocalix[5]pyrrole. Under the hypothesis that the enhancement originates from sulphate binding by the anion receptors in the chloroform phase, it was possible to obtain reasonable fits to the sulphate distribution survey data based on the formation of 1:1 and 2:1 receptor:sulphate complexes in the chloroform phase. Apparent 1:1 sulphate-binding constants obtained from the model in this system fell in the range . Comparison of the results for the various anion receptors included in this study reveals that sulphate binding is sensitive to the nature of the substituents on the parent macrocycle scaffolds in a way that does not follow straightforwardly from simple chemical expectations, such as electron-withdrawing effects on hydrogen-bond donor strength.

  3. Enhanced DOC removal using anion and cation ion exchange resins.

    PubMed

    Arias-Paic, Miguel; Cawley, Kaelin M; Byg, Steve; Rosario-Ortiz, Fernando L

    2016-01-01

    Hardness and DOC removal in a single ion exchange unit operation allows for less infrastructure, is advantageous for process operation and depending on the water source, could enhance anion exchange resin removal of dissolved organic carbon (DOC). Simultaneous application of cationic (Plus) and anionic (MIEX) ion exchange resin in a single contact vessel was tested at pilot and bench scales, under multiple regeneration cycles. Hardness removal correlated with theoretical predictions; where measured hardness was between 88 and 98% of the predicted value. Comparing bench scale DOC removal of solely treating water with MIEX compared to Plus and MIEX treated water showed an enhanced DOC removal, where removal was increased from 0.5 to 1.25 mg/L for the simultaneous resin application compared to solely applying MIEX resin. A full scale MIEX treatment plant (14.5 MGD) reduced raw water DOC from 13.7 mg/L to 4.90 mg/L in the treated effluent at a bed volume (BV) treatment rate of 800, where a parallel operation of a simultaneous MIEX and Plus resin pilot (10 gpm) measured effluent DOC concentrations of no greater than 3.4 mg/L, even at bed volumes of treatment 37.5% greater than the full scale plant. MIEX effluent compared to simultaneous Plus and MIEX effluent resulted in differences in fluorescence intensity that correlated to decreases in DOC concentration. The simultaneous treatment of Plus and MIEX resin produced water with predominantly microbial character, indicating the enhanced DOC removal was principally due to increased removal of terrestrially derived organic matter. The addition of Plus resin to a process train with MIEX resin allows for one treatment process to remove both DOC and hardness, where a single brine waste stream can be sent to sewer at a full-scale plant, completely removing lime chemical addition and sludge waste disposal for precipitative softening processes. PMID:26624231

  4. Optimized anion exchange membranes for vanadium redox flow batteries.

    PubMed

    Chen, Dongyang; Hickner, Michael A; Agar, Ertan; Kumbur, E Caglan

    2013-08-14

    In order to understand the properties of low vanadium permeability anion exchange membranes for vanadium redox flow batteries (VRFBs), quaternary ammonium functionalized Radel (QA-Radel) membranes with three ion exchange capacities (IECs) from 1.7 to 2.4 mequiv g(-1) were synthesized and 55-60 μm thick membrane samples were evaluated for their transport properties and in-cell battery performance. The ionic conductivity and vanadium permeability of the membranes were investigated and correlated to the battery performance through measurements of Coulombic efficiency, voltage efficiency and energy efficiency in single cell tests, and capacity fade during cycling. Increasing the IEC of the QA-Radel membranes increased both the ionic conductivity and VO(2+) permeability. The 1.7 mequiv g(-1) IEC QA-Radel had the highest Coulombic efficiency and best cycling capacity maintenance in the VRFB, while the cell's voltage efficiency was limited by the membrane's low ionic conductivity. Increasing the IEC resulted in higher voltage efficiency for the 2.0 and 2.4 mequiv g(-1) samples, but the cells with these membranes displayed reduced Coulombic efficiency and faster capacity fade. The QA-Radel with an IEC of 2.0 mequiv g(-1) had the best balance of ionic conductivity and VO(2+) permeability, achieving a maximum power density of 218 mW cm(-2) which was higher than the maximum power density of a VRFB assembled with a Nafion N212 membrane in our system. While anion exchange membranes are under study for a variety of VRFB applications, this work demonstrates that the material parameters must be optimized to obtain the maximum cell performance. PMID:23799776

  5. Evaluation of a new, macroporous polyvinylpyridine resin for processing plutonium using nitrate anion exchange

    SciTech Connect

    Marsh, S.F.

    1989-04-01

    Anion exchange in nitric acid is the major aqueous process used to recover and purify plutonium from impure scrap materials. Most strong-base anion exchange resins incorporate a styrene-divinylbenzene copolymer. A newly available, macroporous anion exchange resin based on a copolymer of 1-methyl-4-vinylpyridine and divinylbenzene has been evaluated. Comparative data for Pu(IV) sorption kinetics and capacity are presented for this new resin and two other commonly used anion exchange resins. The new resin offers high capacity and rapid sorption kinetics for Pu(IV) from nitric acid, as well as greatly stability to chemical and radiolytic degradation. 8 refs., 14 figs.

  6. Relationship of net chloride flow across the human erythrocyte membrane to the anion exchange mechanism

    SciTech Connect

    Knauf, P.A.; Law, F.Y.; Marchant, P.J.

    1983-01-01

    The parallel effects of the anion transport inhibitor DIDS (4,4'-diisothiocyanostilbene-2,2'disulfonate) on net chloride flow and on chloride exchange suggest that a major portion of net chloride flow takes place through the anion exchange system. The ''slippage'' model postulates that the rate of net anion flow is determined by the movement of the unloaded anion transport site across the membrane. Both the halide selectivity of net anion flow and the dependence of net chloride flux on chloride concentration over the range of 75 to 300 mM are inconsistent with the slippage model. Models in which the divalent form of the anion exchange carrier or water pores mediate net anion flow are also inconsistent with the data. The observations that net chloride flux increases with chloride concentration and that the DIDS-sensitive component tends to saturate suggest a model in which net anion flow involves ''transit'' of anions through the diffusion barriers in series with the transport site, without any change in transport site conformation such as normally occurs during the anion exchange process. This model is successful in predicting that the anion exchange inhibitor NAP-taurine, which binds to the modifier site and inhibits the conformational change, has less effect on net chloride flow than on chloride exchange.

  7. Oxalate transport by anion exchange across rabbit ileal brush border.

    PubMed Central

    Knickelbein, R G; Aronson, P S; Dobbins, J W

    1986-01-01

    This study demonstrates the presence of oxalate transporters on the brush border membrane of rabbit ileum. We found that an inside alkaline (pH = 8.5 inside, 6.5 outside) pH gradient stimulated [14C]oxalate uptake 10-fold at 1 min with a fourfold accumulation above equilibrated uptake at 5 min. 1 mM 4,4'-diisothiocyanostilbene-2,2'-disulfonate (disodium salt; DIDS) profoundly inhibited the pH-gradient stimulated oxalate uptake. Using an inwardly directed K+ gradient and valinomycin, we found no evidence for potential sensitive oxalate uptake. In contrast to Cl:HCO3 exchange, HCO3 did not stimulate oxalate uptake more than was seen with a pH gradient in the absence of HCO3. An outwardly directed Cl gradient (50 mM inside, 5 mM outside) stimulated oxalate uptake 10-fold at 1 min with a fivefold accumulation above equilibrated uptake. Cl-stimulated oxalate uptake was largely inhibited by DIDS. Addition of K+ and nigericin only slightly decreased the Cl gradient-stimulated oxalate uptake, which indicates that this stimulation was not primarily due to the Cl gradient generating an inside alkaline pH gradient via Cl:OH exchange. Further, an outwardly directed oxalate gradient stimulated 36Cl uptake. These results suggested that both oxalate:OH and oxalate:Cl exchange occur on the brush border membrane. To determine if one or both of these exchanges were on contaminating basolateral membrane, the vesicle preparation was further fractionated into a brush border and basolateral component using sucrose density gradient centrifugation. Both exchangers localized to the brush border component. A number of organic anions were examined (outwardly directed gradient) to determine if they could stimulate oxalate and Cl uptake. Only formate and oxaloacetate were found to stimulate oxalate and Cl uptake. An inwardly directed Na gradient only slightly stimulated oxalate uptake, which was inhibited by DIDS. PMID:3003149

  8. Single-channel properties of a rat brain endoplasmic reticulum anion channel.

    PubMed Central

    Clark, A G; Murray, D; Ashley, R H

    1997-01-01

    Many intracellular membranes contain ion channels, although their physiological roles are often poorly understood. In this study we incorporated single anion channels colocalized with rat brain endoplasmic reticulum (ER) ryanodine-sensitive Ca(2+)-release channels into planar lipid bilayers. The channels opened in bursts, with more activity at negative (cytoplasm-ER lumen) membrane potentials, and they occupied four open conductance levels with frequencies well described by the binomial equation. The probability of a protomer being open decreased from approximately 0.7 at -40 mV to approximately 0.2 at +40 mV, and the channels selected between different anions in the order PSCN > PNO3 > PBr > PCl > PF. They were also permeant to cations, including the large cation Tris+ (PTris/PCl = 0.16). Their conductance saturated at 170 pS in choline Cl. The channels were inactivated by 15 microM 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) and blocked with low affinity (KD of 1-100 microM) by anthracene-9-carboxylic acid, ethacrynic acid, frusemide (furosemide), HEPES, the indanyloxyacetic acid derivative IAA-94, 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB), and Zn2+. Unlike protein translocation pores, the channels were unaffected by high salt concentrations or puromycin. They may regulate ER Ca2+ release, or be channel components en route to their final cellular destinations. Alternatively, they may contribute to the fusion machinery involved in intracellular membrane trafficking. PMID:9199781

  9. Using solvent extraction to process nitrate anion exchange column effluents

    SciTech Connect

    Yarbro, S.L.

    1987-10-01

    Octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO), a new organophosphorous extractant, and a new centrifugal mixer-settler both recently developed at Argonne were evaluated for their potential use in the recovery of actinides from nitrate anion exchange column effluents. The performance of the extractant was evaluated by measuring the extraction coefficient values as a function of acid and salt concentration. Additional performance parameters include extraction coefficient behavior as a function of the total metal concentration in the organic phase, and comparison of different stripping and organic scrubbing techniques. A simulated effluent stream was used to evaluate the performance of the centrifugal mixer-settlers by comparing experimental and calculated interstage concentration profiles. Both the CMPO extractant and the centrifugal mixer-settlers have potential for processing nitrate column effluents, particularly if the stripping behavior can be improved. Details of the proposed process are presented in the flowsheet and contactor design analyses.

  10. Alkaline direct alcohol fuel cells using an anion exchange membrane

    NASA Astrophysics Data System (ADS)

    Matsuoka, Koji; Iriyama, Yasutoshi; Abe, Takeshi; Matsuoka, Masao; Ogumi, Zempachi

    Alkaline direct alcohol fuel cells using an OH-form anion exchange membrane and polyhydric alcohols were studied. A high open circuit voltage of ca. 800 mV was obtained for a cell using Pt-Ru/C (anode) and Pt/C (cathode) at 323 K, which was about 100-200 mV higher than that for a DMFC using Nafion ®. The maximum power densities were in the order of ethylene glycol > glycerol > methanol > erythritol > xylitol. Silver catalysts were used as a cathode catalyst to fabricate alkaline fuel cells, since silver catalyst is almost inactive in the oxidation of polyhydric alcohols. Alkaline direct ethylene glycol fuel cells using silver as a cathode catalyst gave excellent performance because higher concentrations of fuel could be supplied to the anode.

  11. Distinct pharmacological and molecular properties of the acid-sensitive outwardly rectifying (ASOR) anion channel from those of the volume-sensitive outwardly rectifying (VSOR) anion channel.

    PubMed

    Sato-Numata, Kaori; Numata, Tomohiro; Inoue, Ryuji; Okada, Yasunobu

    2016-05-01

    Expressed by many cell types, acid-sensitive outwardly rectifying (ASOR) anion channels are known to be activated by extracellular acidification and involved in acidotoxic necrotic cell death. In contrast, ubiquitously expressed volume-sensitive outwardly rectifying (VSOR) anion channels are activated by osmotic cell swelling and involved in cell volume regulation and apoptotic cell death. Distinct inhibitors to distinguish ASOR from VSOR anion channels have not been identified. Although leucine-rich repeats containing 8A (LRRC8A) was recently found to be an essential component of VSOR anion channels, the possibility of an LRRC8 family member serving as a component of ASOR anion channels has not been examined. In this study, we explored the effects of 12 known VSOR channel inhibitors and small interfering RNA (siRNA)-mediated knockdown of LRRC8 family members on ASOR and VSOR currents in HeLa cells. Among these inhibitors, eight putative VSOR blockers, including 4-(2-butyl-6,7-dichlor-2-cyclopentylindan-1-on-5-yl) oxobutyric acid (DCPIB) and 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB), were totally ineffective at blocking ASOR channel activity, whereas suramin, R-(+)-[(2-n-butyl-6,7-dichloro-2-cyclopentyl-2,3-dihydro-1-oxo-1H-inden-5-yl)oxy] acetic acid (DIOA), arachidonic acid, and niflumic acid were found to be effective ASOR anion channel antagonists. In addition, gene-silencing studies showed that no LRRC8 family members are essentially involved in ASOR anion channel activity, whereas LRRC8A is involved in VSOR anion channel activity in HeLa cells. PMID:26743872

  12. Selectivity Control in Synergistic Liquid-Liquid Anion Exchange of Univalent Anions via Structure-Specific Cooperativity between Quaternary Ammonium Cations and Anion Receptors

    SciTech Connect

    Borman, Christopher J; Bonnesen, Peter V; Moyer, Bruce A

    2012-01-01

    Two anion receptors enhance liquid-liquid anion exchange when added to quaternary alkylammonium chloride anion exchangers, but with a striking dependence upon the structure of the alkylammonium cation. Two anion receptors were investigated, meso-octamethylcalix[4]pyrrole (C4P) and the bisthiourea tweezer 1,1'-(propane-1,3-diyl)bis(3-(4-sec-butylphenyl)thiourea (BTU). C4P has the unique ability in its cone anion-binding conformation to accept an appropriately sized electropositive species in the resulting cup formed by its four electron-rich pyrrole groups, while BTU is not expected to be predisposed for a specific host-guest interaction with the quaternary ammonium cations. It was therefore hypothesized that synergism between C4P and methyltri(C8,10)alkylammonium chloride (Aliquat 336) would be uniquely pronounced owing to insertion of the methyl group of the Aliquat cation into the C4P cup, and we present herein data supporting this expectation. While synergism is comparatively weak for both exchangers with the BTU receptor, synergism between C4P and Aliquat 336 is indeed so strong that anion exchange prefers chloride over more extractable nitrate and trifluoroacetate, effectively overcoming the ubiquitous Hofmeister bias. A thermochemical analysis of synergistic anion exchange has been provided for the first time, unraveling the observed selectivity behavior and resulting in the estimation of binding constants for C4P with the ion pairs of A336+ with Cl , Br , OAcF3 , NO3 , and I . The uniquely strong positive cooperativity between A336 and C4P underscores the advantage of a supramolecular approach in the design of synergistic anion exchange systems.

  13. Human anion exchanger1 mutations and distal renal tubular acidosis.

    PubMed

    Yenchitsomanus, Pa-thai

    2003-09-01

    The human anion exchanger 1 (AE1 or SLC4A1) gene encodes anion exchanger 1 (or band 3) protein in erythrocytes and in alpha-intercalated cells of the kidney. Thus, AE1 mutations show pleiotrophic effects resulting in two distinct and seemingly unrelated defects, an erythrocyte abnormality and distal renal tubular acidosis (dRTA). Southeast Asian ovalocytosis (SAO), a well-known red blood cell (RBC) defect, which is widespread in Southeast Asian regions, is caused by AE1 mutation due to a deletion of 27 base pairs in codons 400-408 (delta400-408) leading to an in-frame 9 amino-acid loss in the protein. Co-existence of SAO and dRTA is usually not seen in the same individual. However, the two conditions can co-exist as the result of compound heterozygosities between delta400-408 and other mutations. The reported genotypes include delta400-408/G701D, delta400-408/R602H, delta400-408/deltaV850, and delta400-408/A858D. The presence of dRTA, with or without RBC abnormalities, may occur from homozygous or compound heterozygous conditions of recessive AE1 mutations (eg G701D/G701D, V488M/V488M, deltaV850/deltaV850, deltaV850/A858D, G701D/S773P) or heterozygous dominant AE1 mutations (eg R598H, R589C, R589S, S613F, R901X). Codon 589 of this gene seems to be a 'mutational hot-spot' since repeated mutations at this codon occurring in different ethnic groups and at least two de novo (R589H and R589C) mutations have been observed. Therefore, AE1 mutations can result in both recessive and dominant dRTA, possibly depending on the position of the amino acid change in the protein. As several mutant AE1 proteins still maintain a significant anion transport function but are defective in targeting to the cell surface, impaired intracellular trafficking of the mutant AE1 is an important molecular mechanism involved in the pathogenesis of dRTA associated with AE1 mutations. PMID:15115146

  14. 3D Printing of Micropatterned Anion Exchange Membranes.

    PubMed

    Seo, Jiho; Kushner, Douglas I; Hickner, Michael A

    2016-07-01

    Micropatterned anion exchange membranes (AEMs) have been 3D printed via a photoinitiated free radical polymerization and quaternization process. The photocurable formulation, consisting of diurethane dimethacrylate (DUDA), poly(ethylene glycol) diacrylate (PEGDA), dipentaerythritol penta-/hexa- acrylate, and 4-vinylbenzyl chloride (VBC), was directly cured into patterned films using a custom 3D photolithographic printing process similar to stereolithography. Measurements of water uptake, permselectivity, and ionic resistance were conducted on the quaternized poly(DUDA-co-PEGDA-co-VBC) sample series to determine their suitability as ion exchange membranes. The water uptake of the polymers increased as the ion exchange capacity (IEC) increased due to greater quaternized VBC content. Samples with IEC values between 0.98 to 1.63 mequiv/g were synthesized by varying the VBC content from 15 to 25 wt %. The water uptake was sensitive to the PEGDA content in the network resulting in water uptake values ranging from 85 to 410 wt % by varying the PEGDA fractions from 0 to 60 wt %. The permselectivity of the AEM samples decreased from 0.91 (168 wt %, 1.63 mequiv/g) to 0.85 (410 wt %, 1.63 mequiv/g) with increasing water uptake and to 0.88 (162 wt %, 0.98 mequiv/g) with decreasing IEC. Permselectivity results were relatively consistent with the general understanding of the correlation between permselectivity, water uptake, and ion content of the membrane. Lastly, it was revealed that the ionic resistance of patterned membranes was lower than that of flat membranes with the same material volume or equivalent thickness. A parallel resistance model was used to explain the influence of patterning on the overall measured ionic resistance. This model may provide a way to maximize ion exchange membrane performance by optimizing surface patterns without chemical modification to the membrane. PMID:27218137

  15. Transient ion exchange of anion exchange membranes exposed to carbon dioxide

    NASA Astrophysics Data System (ADS)

    Myles, Timothy D.; Grew, Kyle N.; Peracchio, Aldo A.; Chiu, Wilson K. S.

    2015-11-01

    A common issue with anion exchange membranes (AEMs) is carbon dioxide contamination which causes a conversion from the hydroxide form to a mixed carbonate/bicarbonate form. In the mixed ionic form the membrane suffers from lower conductivity due to the larger and heavier ions having a lower mobility. The purpose of this study is to develop a theoretical model of the transient ion exchange process and elucidate the nature of the conversion of the AEM from a hydroxide form to a carbonate/bicarbonate form. Experimental data available from the literature providing the anion concentrations versus time are used for comparison. The prevalent mechanisms are discussed and the governing equations are cast in a dimensionless form. Extensions are then made to conductivity predictions.

  16. Conductance hysteresis in the voltage-dependent anion channel.

    PubMed

    Rappaport, Shay M; Teijido, Oscar; Hoogerheide, David P; Rostovtseva, Tatiana K; Berezhkovskii, Alexander M; Bezrukov, Sergey M

    2015-09-01

    Hysteresis in the conductance of voltage-sensitive ion channels is observed when the transmembrane voltage is periodically varied with time. Although this phenomenon has been used in studies of gating of the voltage-dependent anion channel, VDAC, from the outer mitochondrial membrane for nearly four decades, full hysteresis curves have never been reported, because the focus was solely on the channel opening branches of the hysteresis loops. We studied the hysteretic response of a multichannel VDAC system to a triangular voltage ramp the frequency of which was varied over three orders of magnitude, from 0.5 mHz to 0.2 Hz. We found that in this wide frequency range the area encircled by the hysteresis curves changes by less than a factor of three, suggesting broad distribution of the characteristic times and strongly non-equilibrium behavior. At the same time, quasi-equilibrium two-state behavior is observed for hysteresis branches corresponding to VDAC opening. This enables calculation of the usual equilibrium gating parameters, gating charge and voltage of equipartitioning, which were found to be almost insensitive to the ramp frequency. To rationalize this peculiarity, we hypothesize that during voltage-induced closure and opening the system explores different regions of the complex free energy landscape, and, in the opening branch, follows quasi-equilibrium paths. PMID:26094068

  17. Removal of bromide and natural organic matter by anion exchange.

    PubMed

    Hsu, Susan; Singer, Philip C

    2010-04-01

    Bromide removal by anion exchange was explored for various water qualities, process configurations, and resin characteristics. Simulated natural waters containing different amounts of natural organic matter (NOM), bicarbonate, chloride, and bromide were treated with a polyacrylate-based magnetic ion exchange (MIEX) resin on a batch basis to evaluate the effectiveness of the resin for removal of bromide. While bromide removal was achieved to some degree, alkalinity (bicarbonate), dissolved organic carbon (DOC), and chloride were shown to inhibit bromide removal in waters with bromide concentrations of 100 and 300 microg/L. Water was also treated using a two-stage batch MIEX process. Two-stage treatment resulted in only a slight improvement in bromide removal compared to single-stage treatment, presumably due to competition with the high concentration of chloride which is present along with bromide in natural waters. In view of the relatively poor bromide removal results for the MIEX resin, a limited set of experiments was performed using polystyrene resins. DOC and bromide removal were compared by treating model waters with MIEX and two polystyrene resins, Ionac A-641 and Amberlite IRA910. The two polystyrene resins were seen to be more effective for bromide removal, while the MIEX resin was more effective at removing DOC. PMID:20045170

  18. Hydroxide Solvation and Transport in Anion Exchange Membranes.

    PubMed

    Chen, Chen; Tse, Ying-Lung Steve; Lindberg, Gerrick E; Knight, Chris; Voth, Gregory A

    2016-01-27

    Understanding hydroxide solvation and transport in anion exchange membranes (AEMs) can provide important insight into the design principles of these new membranes. To accurately model hydroxide solvation and transport, we developed a new multiscale reactive molecular dynamics model for hydroxide in aqueous solution, which was then subsequently modified for an AEM material. With this model, we investigated the hydroxide solvation structure and transport mechanism in the membrane. We found that a relatively even separation of the rigid side chains produces a continuous overlapping region for hydroxide transport that is made up of the first hydration shell of the tethered cationic groups. Our results show that hydroxide has a significant preference for this overlapping region, transporting through it and between the AEM side chains with substantial contributions from both vehicular (standard diffusion) and Grotthuss (proton hopping) mechanisms. Comparison of the AEM with common proton exchange membranes (PEMs) showed that the excess charge is less delocalized in the AEM than the PEMs, which is correlated with a higher free energy barrier for proton transfer reactions. The vehicular mechanism also contributes considerably more than the Grotthuss mechanism for hydroxide transport in the AEM, while our previous studies of PEM systems showed a larger contribution from the Grotthuss mechanism than the vehicular mechanism for proton transport. The activation energy barrier for hydroxide diffusion in the AEM is greater than that for proton diffusion in PEMs, implying a more significant enhancement of ion transport in the AEM at elevated temperatures. PMID:26716727

  19. Gamma radiation effect on gas production in anion exchange resins

    NASA Astrophysics Data System (ADS)

    Traboulsi, A.; Labed, V.; Dauvois, V.; Dupuy, N.; Rebufa, C.

    2013-10-01

    Radiation-induced decomposition of Amberlite IRA400 anion exchange resin in hydroxide form by gamma radiolysis has been studied at various doses in different atmospheres (anaerobic, anaerobic with liquid water, and aerobic). The effect of these parameters on the degradation of ion exchange resins is rarely investigated in the literature. We focused on the radiolysis gases produced by resin degradation. When the resin was irradiated under anaerobic conditions with liquid water, the liquid phase over the resin was also analyzed to identify any possible water-soluble products released by degradation of the resin. The main products released are trimethylamine (TMA), molecular hydrogen (H2g) and carbon dioxide (CO2g). TMA and H2g are produced in all the irradiation atmospheres. However, TMA was in gaseous form under anaerobic and aerobic conditions and in aqueous form in presence of liquid water. In the latter conditions, TMAaq was associated with aqueous dimethylamine (DMAaq), monomethylamine (MMAaq) and ammonia (NH). CO2g is formed in the presence of oxygen due to oxidation of organic compounds present in the system, in particular the degradation products such as TMAg.

  20. Hetero-Epitaxial Anion Exchange Yields Single-Crystalline Hollow Nanoparticles

    SciTech Connect

    Park, Jungwon; Zheng, Haimei; Jun, Young-wook; Alivisatos, A. Paul

    2009-08-26

    Anion exchange with S was performed on ZnO colloidal nanoparticles. The resulting hollow ZnS nanoparticles are crystal whose shape is dictated by the initial ZnO. Crystallographic and elemental analyses provide insight into the mechanism of the anion exchange.

  1. Selectivity control in synergistic liquid-liquid anion exchange of univalent anions via structure-specific cooperativity between quaternary ammonium cations and anion receptors.

    PubMed

    Borman, Christopher J; Bonnesen, Peter V; Moyer, Bruce A

    2012-10-01

    Two anion receptors enhance liquid-liquid anion exchange when added to quaternary alkylammonium chloride anion exchangers, but with a striking dependence on the structure of the alkylammonium cation that suggests a supramolecular cooperative effect. Two anion receptors were investigated, meso-octamethylcalix[4]pyrrole (C4P) and the bisthiourea tweezer 1,1'-(propane-1,3-diyl)bis(3-(4-sec-butylphenyl)thiourea (BTU). Whereas synergism is comparatively weak when either methyltri(C(8,10))alkylammonium chloride (Aliquat 336) or tetraheptylammonium chloride is used with the BTU receptor, synergism between C4P and Aliquat 336 is so pronounced that anion exchange prefers chloride over more extractable nitrate and trifluoroacetate, effectively overcoming the ubiquitous Hofmeister bias. A thermochemical analysis of synergistic anion exchange has been provided for the first time, resulting in the estimation of binding constants for C4P with the ion pairs of A336(+) with Cl(-), Br(-), OAc(F3)(-), NO(3)(-), and I(-). PMID:22931168

  2. Removal of Pu238 from Neptunium Solution by Anion Exchange

    SciTech Connect

    KYSER, EDWARD

    2003-12-01

    A new anion flowsheet for use in HB-Line was tested in the lab with Reillex{trademark} HPQ for removal of Pu{sup 238} contamination from Np. Significant rejection of Pu{sup 238} was observed by washing with 6 to 12 bed volumes (BV) of reductive wash containing reduced nitric acid concentration along with both ferrous sulfamate (FS) and hydrazine. A shortened-height column was utilized in these tests to match changes in the plant equipment. Lab experiments scaled to plant batch sizes of 1500 to 2200 g Np were observed with modest losses for up-flow washing. Down-flow washing was observed to have high losses. The following are recommended conditions for removing Pu{sup 238} from Np solutions by anion exchange in HB-Line: (1) Feed conditions: Up-flow 6.4-8 M HNO{sub 3}, 0.02 M hydrazine, 0.05 M excess FS, less than 5 days storage of solution after FS addition. (2) Reductive Wash conditions: Up-flow 6-12 BV of 6.4 M HNO{sub 3}, 0.05 M FS, 0.05 M hydrazine. 1.8 mL/min/cm{sup 2} flowrate. (3) Decontamination Wash conditions: Up-flow 1-2 BV of 6.4-8 M HNO{sub 3}, no FS, no hydrazine. (4) Elution conditions: Down-flow 0.17 M HNO{sub 3}, 0.05 M hydrazine, no FS.

  3. High-capacity anion exchangers based on poly (glycidylmethacrylate-divinylbenzene) microspheres for ion chromatography.

    PubMed

    Liu, Junwei; Wang, Yong; Cheng, Heli; Wang, Nani; Wu, Shuchao; Zhang, Peimin; Zhu, Yan

    2016-10-01

    Poly (glycidylmethacrylate-divinylbenzene) microspheres were prepared by the two-staged swelling and polymerization method and applied to prepare anion exchange stationary phases. Methylamine, dimethylamine, trimethylamine, diethylamine and triethylamine were selected to prepare the quaternary ammonium groups of anion exchangers, respectively. The diameters and surface characteristics of microspheres were measured by scanning electron microscope and nitrogen adsorption-desorption measurements. The anion exchangers were characterized by Fourier transform infrared spectrum, elemental analysis and breakthrough curve methods. The chromatographic performances of anion exchangers were illustrated by separating conventional anions, organic weak acids and carbohydrates. The results indicated that the anion exchange capacities were controllable by changing either the content of glycidylmethacrylate in microspheres or the number of bonded quaternary ammonium layer. Meanwhile, the substituents of quaternary ammonium groups greatly influenced the separation properties of anion exchangers. Finally, the three-layer methylamine-quaternized anion exchanger was successfully applied for the determination of fluoride in tea sample. The content of fluoride was detected to be 0.13mgg(-1) without the interference of acetate and formate. PMID:27474308

  4. Tubulin binding blocks mitochondrial voltage-dependent anion channel and regulates respiration.

    PubMed

    Rostovtseva, Tatiana K; Sheldon, Kely L; Hassanzadeh, Elnaz; Monge, Claire; Saks, Valdur; Bezrukov, Sergey M; Sackett, Dan L

    2008-12-01

    Regulation of mitochondrial outer membrane (MOM) permeability has dual importance: in normal metabolite and energy exchange between mitochondria and cytoplasm and thus in control of respiration, and in apoptosis by release of apoptogenic factors into the cytosol. However, the mechanism of this regulation, dependent on the voltage-dependent anion channel (VDAC), the major channel of MOM, remains controversial. A long-standing puzzle is that in permeabilized cells, adenine nucleotide translocase (ANT) is less accessible to cytosolic ADP than in isolated mitochondria. We solve this puzzle by finding a missing player in the regulation of MOM permeability: the cytoskeletal protein tubulin. We show that nanomolar concentrations of dimeric tubulin induce voltage-sensitive reversible closure of VDAC reconstituted into planar phospholipid membranes. Tubulin strikingly increases VDAC voltage sensitivity and at physiological salt conditions could induce VDAC closure at <10 mV transmembrane potentials. Experiments with isolated mitochondria confirm these findings. Tubulin added to isolated mitochondria decreases ADP availability to ANT, partially restoring the low MOM permeability (high apparent K(m) for ADP) found in permeabilized cells. Our findings suggest a previously unknown mechanism of regulation of mitochondrial energetics, governed by VDAC and tubulin at the mitochondria-cytosol interface. This tubulin-VDAC interaction requires tubulin anionic C-terminal tail (CTT) peptides. The significance of this interaction may be reflected in the evolutionary conservation of length and anionic charge in CTT throughout eukaryotes, despite wide changes in the exact sequence. Additionally, tubulins that have lost significant length or anionic character are only found in cells that do not have mitochondria. PMID:19033201

  5. Molecular determinants of anion selectivity in the cystic fibrosis transmembrane conductance regulator chloride channel pore.

    PubMed Central

    Linsdell, P; Evagelidis, A; Hanrahan, J W

    2000-01-01

    Ionic selectivity in many cation channels is achieved over a short region of the pore known as the selectivity filter, the molecular determinants of which have been identified in Ca(2+), Na(+), and K(+) channels. However, a filter controlling selectivity among different anions has not previously been identified in any Cl(-) channel. In fact, because Cl(-) channels are only weakly selective among small anions, and because their selectivity has proved so resistant to site-directed mutagenesis, the very existence of a discrete anion selectivity filter has been called into question. Here we show that mutation of a putative pore-lining phenylalanine residue, F337, in the sixth membrane-spanning region of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel, dramatically alters the relative permeabilities of different anions in the channel. Specifically, mutations that reduce the size of the amino acid side chain present at this position virtually abolish the relationship between anion permeability and hydration energy, a relationship that characterizes the anion selectivity not only of wild-type CFTR, but of most classes of Cl(-) channels. These results suggest that the pore of CFTR may indeed contain a specialized region, analogous to the selectivity filter of cation channels, at which discrimination between different permeant anions takes place. Because F337 is adjacent to another amino acid residue, T338, which also affects anion selectivity in CFTR, we suggest that selectivity is predominantly determined over a physically discrete region of the pore located near these important residues. PMID:10827976

  6. Molecular determinants of anion selectivity in the cystic fibrosis transmembrane conductance regulator chloride channel pore.

    PubMed

    Linsdell, P; Evagelidis, A; Hanrahan, J W

    2000-06-01

    Ionic selectivity in many cation channels is achieved over a short region of the pore known as the selectivity filter, the molecular determinants of which have been identified in Ca(2+), Na(+), and K(+) channels. However, a filter controlling selectivity among different anions has not previously been identified in any Cl(-) channel. In fact, because Cl(-) channels are only weakly selective among small anions, and because their selectivity has proved so resistant to site-directed mutagenesis, the very existence of a discrete anion selectivity filter has been called into question. Here we show that mutation of a putative pore-lining phenylalanine residue, F337, in the sixth membrane-spanning region of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel, dramatically alters the relative permeabilities of different anions in the channel. Specifically, mutations that reduce the size of the amino acid side chain present at this position virtually abolish the relationship between anion permeability and hydration energy, a relationship that characterizes the anion selectivity not only of wild-type CFTR, but of most classes of Cl(-) channels. These results suggest that the pore of CFTR may indeed contain a specialized region, analogous to the selectivity filter of cation channels, at which discrimination between different permeant anions takes place. Because F337 is adjacent to another amino acid residue, T338, which also affects anion selectivity in CFTR, we suggest that selectivity is predominantly determined over a physically discrete region of the pore located near these important residues. PMID:10827976

  7. Acid-sensing ion channels (ASICs) are differentially modulated by anions dependent on their subunit composition

    PubMed Central

    Kusama, Nobuyoshi; Gautam, Mamta; Harding, Anne Marie S.; Snyder, Peter M.

    2013-01-01

    Acid-sensing ion channels (ASICs) are sodium channels gated by extracellular protons. ASIC1a channels possess intersubunit Cl−-binding sites in the extracellular domain, which are highly conserved between ASIC subunits. We previously found that anions modulate ASIC1a gating via these sites. Here we investigated the effect of anion substitution on native ASICs in rat sensory neurons and heterologously expressed ASIC2a and ASIC3 channels by whole cell patch clamp. Similar to ASIC1a, anions modulated the kinetics of desensitization of other ASIC channels. However, unlike ASIC1a, anions also modulated the pH dependence of activation. Moreover, the order of efficacy of different anions to modulate ASIC2a and -3 was very different from that of ASIC1a. More surprising, mutations of conserved residues that form an intersubunit Cl−-binding site in ASIC1a only partially abrogated the effects of anion modulation of ASIC2a and had no effect on anion modulation of ASIC3. The effects of anions on native ASICs in rat dorsal root ganglion neurons mimicked those in heterologously expressed ASIC1a/3 heteromeric channels. Our data show that anions modulate a variety of ASIC properties and are dependent on the subunit composition, and the mechanism of modulation for ASIC2a and -3 is distinct from that of ASIC1a. We speculate that modulation of ASIC gating by Cl− is a novel mechanism to sense shifts in extracellular fluid composition. PMID:23135698

  8. Effects of arginine on multimodal anion exchange chromatography.

    PubMed

    Hirano, Atsushi; Arakawa, Tsutomu; Kameda, Tomoshi

    2015-12-01

    The effects of arginine on binding and elution properties of a multimodal anion exchanger, Capto adhere, were examined using bovine serum albumin (BSA) and a monoclonal antibody against interleukin-8 (mAb-IL8). Negatively charged BSA was bound to the positively charged Capto adhere and was readily eluted from the column with a stepwise or gradient elution using 1M NaCl at pH 7.0. For heat-treated BSA, small oligomers and remaining monomers were also eluted using a NaCl gradient, whereas larger oligomers required arginine for effective elution. The positively charged mAb-IL8 was bound to Capto adhere at pH 7.0. Arginine was also more effective for elution of the bound mAb-IL8 than was NaCl. The results imply that arginine interacts with the positively charged Capto adhere. The mechanism underlying the interactions of arginine with Capto adhere was examined by calculating the binding free energy between an arginine molecule and a Capto adhere ligand in water through molecular dynamics simulations. The overall affinity of arginine for Capto adhere is attributed to the hydrophobic and π-π interactions between an arginine side chain and the aromatic moiety of the ligand as well as hydrogen bonding between arginine and the ligand hydroxyl group, which may account for the characteristics of protein elution using arginine. PMID:26225914

  9. Anion-exchange resin-based desulfurization process

    SciTech Connect

    Sheth, A.C.; Strevel, S.D.

    1991-01-01

    Under the current grant (FG22-90PC90309), the University of Tennessee Space Institute (UTSI) will carry out the necessary bench scale experiments to further develop it anion-exchange, resin-based desulfurization concept to desulfurize alkali metal sulfates. In particular, it is planned to screen commercially available resins and then carry out process optimization work with three selected resins. Further optimization of the resin regeneration step as well as evaluation of the effect of various performance enhancers will then be carried out with one selected resin. A process schematic, to be developed based on the bench scale results, will be used to estimate the related economics. Some limited scope testing will also be carried out using the spent-seed and sorbent materials obtained from both the coal-fired magnetohydrodynamics (MHD) and the in-duct sorbent injection pilot scale facilities. During this reporting period, 90% of the planned batch mode screening experiments for the eleven samples of candidate resins were completed. Preliminary evaluation of the resulting data is continuing in order to select a smaller number (3--4) of samples for screening in the fixed-bed setup. The installation of the semi-automated fixed-bed setup is about 70% complete and shakedown experiments will be started in 3--4 weeks. Progress made in relation to these activities is presented below. 2 figs., 3 tabs.

  10. Fouling mitigation of anion exchange membrane by zeta potential control.

    PubMed

    Park, Jin-Soo; Lee, Hong-Joo; Choi, Seok-Ju; Geckeler, Kurt E; Cho, Jaeweon; Moon, Seung-Hyeon

    2003-03-15

    The feasibility of fouling mitigation of anion exchange membranes (AEMs) in the presence of humate was studied by adding three different types of water-soluble polymers, i.e., poly(acrylic acid) (PAA), poly(vinyl alcohol) (PVA), and poly(ethylene imine) (PEI), during electrodialysis (ED) desalination. Measurement of zeta potential of the humate used in this study showed highly negative potential (about -30 mV), implying that the humate had a strong fouling potential on the AEMs in ED. Of the three water-soluble polymers, PEI showed a positive zeta potential (about +14 mV) and is able to form an interpolymer complex with the humate. PAA and PVA hardly formed interpolymer complexes with humate due to electrostatic repulsion. The PEI-humate mixture with a volume ratio of 1:20 (PEI:humate) showed zero zeta potential, and a complexed humate with zero surface charge was formed, resulting in no fouling effects on the AEMs. Accordingly, the desalting ED experiments with PEI showed improved ED performance. Further, black colloids formed in the mixture did not cause the cell resistance to increase. PMID:16256509

  11. Highly conductive side chain block copolymer anion exchange membranes.

    PubMed

    Wang, Lizhu; Hickner, Michael A

    2016-06-28

    Block copolymers based on poly(styrene) having pendent trimethyl styrenylbutyl ammonium (with four carbon ring-ionic group alkyl linkers) or benzyltrimethyl ammonium groups with a methylene bridge between the ring and ionic group were synthesized by reversible addition-fragmentation radical (RAFT) polymerization as anion exchange membranes (AEMs). The C4 side chain polymer showed a 17% increase in Cl(-) conductivity of 33.7 mS cm(-1) compared to the benzyltrimethyl ammonium sample (28.9 mS cm(-1)) under the same conditions (IEC = 3.20 meq. g(-1), hydration number, λ = ∼7.0, cast from DMF/1-propanol (v/v = 3 : 1), relative humidity = 95%). As confirmed by small angle X-ray scattering (SAXS), the side chain block copolymers with tethered ammonium cations showed well-defined lamellar morphologies and a significant reduction in interdomain spacing compared to benzyltrimethyl ammonium containing block copolymers. The chemical stabilities of the block copolymers were evaluated under severe, accelerated conditions, and degradation was observed by (1)H NMR. The block copolymer with C4 side chain trimethyl styrenylbutyl ammonium motifs displayed slightly improved stability compared to that of a benzyltrimethyl ammonium-based AEM at 80 °C in 1 M NaOD aqueous solution for 30 days. PMID:27216558

  12. Controlled optical properties of water-soluble CdTe nanocrystals via anion exchange.

    PubMed

    Li, Jing; Jia, Jianguang; Lin, Yuan; Zhou, Xiaowen

    2016-02-01

    We report a study on anion exchange reaction of CdTe nanocrystals with S(2-) in aqueous solution under ambient condition. We found that the optical properties of CdTe nanocrystals can be well tuned by controlling the reaction conditions, in which the reaction temperature is crucially important. At low reaction temperature, the product nanocrystals showed blue-shifts in both absorption and PL spectra, while the photoluminescence quantum yield (PLQY) was significantly enhanced. When anion exchanges were carried out at higher reaction temperature, on the other hand, obvious red shifts in absorption and PL spectra accompanied by a fast increase followed by gradual decrease in PLQY were observed. On variation of S(2-) concentration, it was found that the overall kinetics of Te(2-) for S(2-) exchanges depends also on [S(2-)] when anion exchanges were performed at higher temperature. A possible mechanism for anion exchanges in CdTe NCs was proposed. PMID:26520812

  13. Ionic resistance and permselectivity tradeoffs in anion exchange membranes.

    PubMed

    Geise, Geoffrey M; Hickner, Michael A; Logan, Bruce E

    2013-10-23

    Salinity gradient energy technologies, such as reverse electrodialysis (RED) and capacitive mixing based on Donnan potential (Capmix CDP), could help address the global need for noncarbon-based energy. Anion exchange membranes (AEMs) are a key component in these systems, and improved AEMs are needed in order to optimize and extend salinity gradient energy technologies. We measured ionic resistance and permselectivity properties of quaternary ammonium-functionalized AEMs based on poly(sulfone) and poly(phenylene oxide) polymer backbones and developed structure-property relationships between the transport properties and the water content and fixed charge concentration of the membranes. Ion transport and ion exclusion properties depend on the volume fraction of water in the polymer membrane, and the chemical nature of the polymer itself can influence fine-tuning of the transport properties to obtain membranes with other useful properties, such as chemical and dimensional stability. The ionic resistance of the AEMs considered in this study decreased by more than 3 orders of magnitude (i.e., from 3900 to 1.6 Ω m) and the permselectivity decreased by 6% (i.e., from 0.91 to 0.85) as the volume fraction of water in the polymer was varied by a factor of 3.8 (i.e., from 0.1 to 0.38). Water content was used to rationalize a tradeoff relationship between the permselectivity and ionic resistance of these AEMs whereby polymers with higher water content tend to have lower ionic resistance and lower permselectivity. The correlation of ion transport properties with water volume fraction and fixed charge concentration is discussed with emphasis on the importance of considering water volume fraction when interpreting ion transport data. PMID:24040962

  14. Anion exchange purification of plasmid DNA using expanded bed adsorption.

    PubMed

    Ferreira, G N; Cabral, J M; Prazeres, D M

    2000-01-01

    Recent developments in gene therapy with non-viral vectors and DNA vaccination have increased the demand for large amounts of pharmaceutical-grade plasmid DNA. The high viscosity of process streams is of major concern in the purification of plasmids, since it can cause high back pressures in column operations, thus limiting the throughput. In order to avoid these high back pressures, expanded bed anion exchange chromatography was evaluated as an alternative to fixed bed chromatography. A Streamline 25 column filled with 100 ml of Streamline QXL media, was equilibrated with 0.5 M NaCl in TE (10 mM Tris, 1 mM EDTA, pH = 8.0) buffer at an upward flow of 300 cmh-1, E. coli lysates (obtained from up to 3 liters of fermentation broth) were injected in the column. After washing out the unbound material, the media was allowed to sediment and the plasmid was eluted with 1 M NaCl in TE buffer at a downward flow of 120 cmh-1. Purification factors of 36 +/- 1 fold, 26 +/- 0.4 plasmid purity, and close to 100% yields were obtained when less than one settled column volume of plasmid feed was injected. However, both recovery yield and purity abruptly decreased when larger amounts were processed-values of 35 +/- 2 and 5 +/- 0.7 were obtained for the recovery yield and purity, respectively, when 250 ml of feedstock were processed. In these cases, gel clogging and expansion collapse were observed. The processing of larger volumes, thus larger plasmid quantities, was only possible by performing an isopropanol precipitation step prior to the chromatographic step. This step led to an enhancement of the purification step. PMID:10840595

  15. Analysis of carbohydrates by anion exchange chromatography and mass spectrometry.

    PubMed

    Bruggink, Cees; Maurer, Rolf; Herrmann, Heiko; Cavalli, Silvano; Hoefler, Frank

    2005-08-26

    A versatile liquid chromatographic platform has been developed for analysing underivatized carbohydrates using high performance anion exchange chromatography (HPAEC) followed by an inert PEEK splitter that splits the effluent to the integrated pulsed amperometric detector (IPAD) and to an on-line single quadrupole mass spectrometer (MS). Common eluents for HPAEC such as sodium hydroxide and sodium acetate are beneficial for the amperometric detection but not compatible with electrospray ionisation (ESI). Therefore a membrane-desalting device was installed after the splitter and prior to the ESI interface converting sodium hydroxide into water and sodium acetate into acetic acid. To enhance the sensitivity for the MS detection, 0.5 mmol/l lithium chloride was added after the membrane desalter to form lithium adducts of the carbohydrates. To compare sensitivity of IPAD and MS detection glucose, fructose, and sucrose were used as analytes. A calibration with external standards from 2.5 to 1000 pmole was performed showing a linear range over three orders of magnitude. Minimum detection limits (MDL) with IPAD were determined at 5 pmole levels for glucose to be 0.12 pmole, fructose 0.22 pmole and sucrose 0.11 pmole. With MS detection in the selected ion mode (SIM) the lithium adducts of the carbohydrates were detected obtaining MDL's for glucose of 1.49 pmole, fructose 1.19 pmole, and sucrose 0.36 pmole showing that under these conditions IPAD is 3-10 times more sensitive for those carbohydrates. The applicability of the method was demonstrated analysing carbohydrates in real world samples such as chicory inulin where polyfructans up to a molecular mass of 7000 g/mol were detected as quadrupoly charged lithium adducts. Furthermore mono-, di-, tri-, and oligosaccharides were detected in chicory coffee, honey and beer samples. PMID:16106855

  16. Crystallization and preliminary X-ray crystallographic studies of human voltage-dependent anion channel isoform I (HVDAC1)

    SciTech Connect

    Meins, Thomas; Vonrhein, Clemens; Zeth, Kornelius

    2008-07-01

    The human voltage-dependent anion channel was overproduced in bacteria and refolded with the help of detergents. Extensive screening of crystallization conditions resulted in the first crystals to be obtained of this voltage-dependent anion-channel type. The crystals diffracted to a resolution of 3.6 Å. The major channel by which metabolites can pass through the outer mitochondrial membrane is formed by the voltage-dependent anion-channel (VDAC) family. Functionally, VDAC is involved in the limited exchange of ATP, ADP and small hydrophilic molecules across the outer membrane. Moreover, there is compelling evidence that VDAC isoforms in mammals may act in the cross-talk between mitochondria and the cytoplasm by direct interaction with enzymes involved in energy metabolism and proteins involved in mitochondrial-induced apoptosis. To obtain a high-resolution structure of this channel, human VDAC protein isoform I was overproduced in Escherichia coli. After refolding and testing the correct fold using circular dichroism, a subsequent broad-range screening in different detergents resulted in a variety of crystals which diffracted to 3.5 Å resolution. The crystal lattice belongs to the trigonal space group P321, with unit-cell parameters a = 78.9, c = 165.7 Å and one monomer in the asymmetric unit.

  17. Separation of bivalent anti-T cell immunotoxin from Pichia pastoris glycoproteins by borate anion exchange.

    PubMed

    Woo, Jung Hee; Neville, David M

    2003-08-01

    A major problem encountered in the large-scale purification of the bivalent anti-T cell immunotoxin, A-dmDT390-bisFv(G4S), from Pichia pastoris supernatants was the presence of host glycoproteins exhibiting similar charge, size, and hydrophobicity characteristics. We overcame this problem by employing borate anion exchange chromatography. The borate anion has an affinity for carbohydrates and imparts negative charges to these structures. We found that at a concentration of sodium borate between 50 and 100 mM, the nonglycosylated immunotoxin did not bind to Poros 50 HQ anion exchanger resin, but glycoproteins, including aggregates related to the immunotoxin, did. By using this property of the immunotoxin in the presence of sodium borate, we successfully developed a 3-step purification procedure: (i) Butyl-650M hydrophobic interaction chromatography, (ii) Poros 50 HQ anion exchange chromatography in the presence of borate, and (iii) HiTrap Q anion exchange chromatography. The final preparation exhibited a purity of greater than 98% and a yield of greater than 50% from the supernatant. Previously, boronic acid resins have been used to separate glycoproteins from proteins. However, combining borate anion with conventional anion exchange resins accomplishes the separation of the immunotoxin from glycoproteins and eliminates the need to evaluate nonstandard resins with respect to good manufacturing practice guidelines. PMID:12951782

  18. CATALYTIC PROMOTION OF THE ADSORPTION OF VANADIUM ON AN ANIONIC EXCHANGE RESIN

    DOEpatents

    Bailes, R.H.; Ellis, D.A.

    1958-08-26

    An improvement in the process for the recovery of vanadium from acidic phosphatic solutions is presented. In this process the vanadium is first oxidized to the pentavaleat state, and is then separated by contacting such solutions with an anion exchange resin whereby adsorption of the complexed pentavalent vanadium is effected. The improvement lies in the fact that adsorp tion of the vanadium complex by the anion exchange resin is promoted and improved by providing fiuoride ions in solution to be contacted.

  19. Ion exhange and molecular sorption of oxalic acid with a highly basic anion exchanger

    NASA Astrophysics Data System (ADS)

    Krisilova, E. V.; Oros, G. Yu.; Krisilov, A. V.; Selemenev, V. F.

    2014-04-01

    Ab initio modeling of a matrix fragment of resin and geometry optimization of the molecular structure of oxalic acid were performed. The isotherm of oxalic acid sorption with AV-17-8 anion exchange resin was obtained by the variable concentrations technique. The ion-exchange and molecular components of sorbate fixation with the ion exchanger were determined. The hydration of the highly basic anion exchanger that absorbed different quantities of dicarboxylic acid was evaluated by the centrifuging method. The dependence of the amount of water and sorbate concentration in the resin was linear antibatic.

  20. New Anion-Exchange Resins for Improved Separations of Nuclear Material

    SciTech Connect

    Barr, Mary E.; Bartsch, Richard A.; Jarvinen, Gordon D.

    2000-06-01

    We are developing bifunctional anion-exchange resins that facilitate anion uptake by carefully controlling the structure of the anion receptor site. Our new ion-exchange resins interface the rapidly developing field of ion-specific chelating ligands with robust, commercial ion-exchange technology. The basic scientific issues addressed are actinide complex speciation along with modeling of the metal complex/functional site interactions in order to determine optimal binding site characteristics. Resin materials that actively facilitate the uptake of actinide complexes from solution should display both improved selectivity and kinetic properties. Our implementation of the 'bifunctionality concept' involves N-derivatization of pyridinium units from a base poly(4- vinylpyridine) resin (PVP) with a second cationic site, such that the two anion-exchange sites are linked by 'spacer' arms of varying length and flexibility. The overall objective of our research is to develop a predictive capability that allows the facile design and implementation of multi-functionalized anion-exchange materials to selectively sorb metal complexes of interest from targeted process, waste, and environmental streams. Various Focus Areas and Crosscutting Programs have described needs that would be favorably impacted by the new materials:Tanks, Plutonium; Subsurface Contaminants; Mixed Waste; and Efficient Separations. Sites within the DOE complex which would benefit from the improved anion exchange technology include Hanford, Idaho, Los Alamos, Oak Ridge, and Savannah River.

  1. New Gel-Like Polymers as Selective Weak-Base Anion Exchangers

    PubMed Central

    Gierczyk, Błażej; Cegłowski, Michał; Zalas, Maciej

    2015-01-01

    A group of new anion exchangers, based on polyamine podands and of excellent ion-binding capacity, were synthesized. The materials were obtained in reactions between various poly(ethyleneamines) with glycidyl derivatives of cyclotetrasiloxane. The final polymeric, strongly cross-linked materials form gel-like solids. Their structures and interactions with anions adsorbed were studied by spectroscopic methods (CP-MAS NMR, FR-IR, UV-Vis). The sorption isotherms and kinetic parameters were determined for 29 anions. Materials studied show high ion capacity and selectivity towards some important anions, e.g., selenate(VI) or perrhenate. PMID:25946220

  2. State-dependent access of anions to the cystic fibrosis transmembrane conductance regulator chloride channel pore.

    PubMed

    Fatehi, Mohammad; Linsdell, Paul

    2008-03-01

    The cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel is gated by intracellular factors; however, conformational changes in the channel pore associated with channel activation have not been identified. We have used patch clamp recording to investigate the state-dependent accessibility of substituted cysteine residues in the CFTR channel pore to a range of cysteine-reactive reagents applied to the extracellular side of the membrane. Using functional modification of the channel current-voltage relationship as a marker of modification, we find that several positively charged reagents are able to penetrate deeply into the pore from the outside irrespective of whether or not the channels have been activated. In contrast, access of three anionic cysteine-reactive reagents, the methanesulfonate sodium (2-sulfonatoethyl)methanesulfonate, the organic mercurial p-chloromercuriphenylsulfonic acid, and the permeant anion Au(CN)(2)(-), to several different sites in the pore is strictly limited prior to channel activation. This suggests that in nonactivated channels some ion selectivity mechanism exists to exclude anions yet permit cations into the channel pore from the extracellular solution. We suggest that activation of CFTR channels involves a conformational change in the pore that removes a strong selectivity against anion entry from the extracellular solution. We propose further that this conformational change occurs in advance of channel opening, suggesting that multiple distinct closed pore conformations exist. PMID:18167343

  3. Anion-Exchange Properties of Trifluoroacetate and Triflate Salts of N-Alkylammonium Resorcinarenes.

    PubMed

    Pan, Fangfang; Beyeh, Ngong Kodiah; Bertella, Stefania; Rissanen, Kari

    2016-03-01

    The synthesis of N-benzyl- and N-cyclohexylammonium resorcinarene trifluoroacetate (TFA) and triflate (OTf) salt receptors was investigated. Solid-state analysis by single-crystal X-ray diffraction revealed that the N-alkylammonium resorcinarene salts (NARSs) with different upper substituents had different cavity sizes and different affinities for anions. Anion-exchange experiments by mixing equimolar amounts of N-benzylammonium resorcinarene trifluoroacetate and N-cyclohexylammonium resorcinarene triflate, as well as N-benzylammonium resorcinarene triflate and N-cyclohexylammonium resorcinarene trifluoroacetate showed that the NARS with flexible benzyl groups preferred the larger OTf anion, whereas the rigid cyclohexyl groups preferred the smaller TFA anions. The anion-exchange processes were confirmed in the solid state by single-crystal and powder X-ray diffraction experiments and in the gas phase by electrospray ionization mass spectrometry. PMID:26749383

  4. Proton channels and exchangers in cancer.

    PubMed

    Spugnini, Enrico Pierluigi; Sonveaux, Pierre; Stock, Christian; Perez-Sayans, Mario; De Milito, Angelo; Avnet, Sofia; Garcìa, Abel Garcìa; Harguindey, Salvador; Fais, Stefano

    2015-10-01

    Although cancer is characterized by an intratumoral genetic heterogeneity, a totally deranged pH control is a common feature of most cancer histotypes. Major determinants of aberrant pH gradient in cancer are proton exchangers and transporters, including V-ATPase, Na+/H+ exchanger (NHE), monocarboxylate transporters (MCTs) and carbonic anhydrases (CAs). Thanks to the activity of these proton transporters and exchangers, cancer becomes isolated and/or protected not only from the body reaction against the growing tumor, but also from the vast majority of drugs that when protonated into the acidic tumor microenvironment do not enter into cancer cells. Proton transporters and exchangers represent a key feature tumor cells use to survive in the very hostile microenvironmental conditions that they create and maintain. Detoxifying mechanisms may thus represent both a key survival option and a selection outcome for cells that behave as unicellular microorganisms rather than belonging to an organ, compartment or body. It is, in fact, typical of malignant tumors that, after a clinically measurable yet transient initial response to a therapy, resistant tumor clones emerge and proliferate, thus bursting a more malignant behavior and rapid tumor progression. This review critically presents the background of a novel and efficient approach that aims to fight cancer through blocking or inhibiting well characterized proton exchangers and transporters active in human cancer cells. This article is part of a Special Issue entitled: Membrane channels and transporters in cancers. PMID:25449995

  5. Formation of pseudomorphic nanocages from Cu2O nanocrystals through anion exchange reactions.

    PubMed

    Wu, Hsin-Lun; Sato, Ryota; Yamaguchi, Atsushi; Kimura, Masato; Haruta, Mitsutaka; Kurata, Hiroki; Teranishi, Toshiharu

    2016-03-18

    The crystal structure of ionic nanocrystals (NCs) is usually controlled through reaction temperature, according to their phase diagram. We show that when ionic NCs with different shapes, but identical crystal structures, were subjected to anion exchange reactions under ambient conditions, pseudomorphic products with different crystal systems were obtained. The shape-dependent anionic framework (surface anion sublattice and stacking pattern) of Cu2O NCs determined the crystal system of anion-exchanged products of CuxS nanocages. This method enabled us to convert a body-centered cubic lattice into either a face-centered cubic or a hexagonally close-packed lattice to form crystallographically unusual, multiply twinned structures. Subsequent cation exchange reactions produced CdS nanocages while preserving the multiply-twinned structures. A high-temperature stable phase such as wurtzite ZnS was also obtained with this method at ambient conditions. PMID:26989249

  6. Further analysis of the involvement of the envelope anion channel PIRAC in chloroplast protein import.

    PubMed

    van den Wijngaard, P W; Demmers, J A; Thompson, S J; Wienk, H L; de Kruijff, B; Vredenberg, W J

    2000-06-01

    The ability of preferredoxin to inactivate a 50-pS anion channel of the chloroplast inner membrane in the presence of an energy source was investigated using single-channel recordings. It was found that preferredoxin cannot inactivate the channel when GTP is the only energy source present. From this it is concluded that the precursor has to interact with the, translocon of the inner membrane of chloroplasts (Tic) complex to be able to inactivate the 50-pS anion channel. The ability of two mutants of preferredoxin with deletions in their transit sequence to inactivate the channel was also tested. Both mutants have been shown to have a similar binding affinity for the chloroplast envelope, but only one is able to fully translocate. The mutants were both able to inactivate the channel in a similar manner. From this it is concluded that full translocation is not necessary for the inactivation of the channel. It is also shown that preferredoxin is capable of inactivating the 50-pS anion channel in the chloroplast-attached configuration as was previously found in the inside-out configuration. From this it is concluded that stromal factors do not influence the protein-import-induced inactivation of the 50-pS anion channel of the chloroplast inner membrane. Finally the effect of the anion channel blocker 4, 4'-diisothiocyanostilbene-2,2'-disulfonate (DIDS) on the channel activity and on protein import was investigated. It was found that DIDS blocked the channel. Furthermore the addition of the channel blocker reduces the efficiency of import to 52%. This leads to the conclusion that correct functioning of the channel is important for protein import. PMID:10849000

  7. Anion exchange resins: Structure, formulation, and applications. (Latest citations from the Rubber and Plastics Research Association database). Published Search

    SciTech Connect

    Not Available

    1994-07-01

    The bibliography contains citations concerning the formulation and synthesis of anion exchange resins based on such resins as amides, polyethylenes, and styrenes. Osmotic, sorption, and electrical properties; exchange kinetics behavior; structure studies; and temperature related performance effects on anion exchange resins are considered. Anion exchange chromatography of liquids, and applications in water purification, pollution control, and protein and metallic ion separation are included. (Contains a minimum of 222 citations and includes a subject term index and title list.)

  8. Anion selective membrane. [ion exchange resins and ion exchange membrane electrolytes for electrolytic cells

    NASA Technical Reports Server (NTRS)

    Alexander, S. S.; Geoffroy, R. R.; Hodgdon, R. B.

    1975-01-01

    Experimental anion permselective membranes were prepared and tested for their suitability as cell separators in a chemical redox power storage system being developed at NASA-Lewis Research Center. The goals of long-term (1000 hr) oxidative and thermal stability at 80 C in FeCl3 and CrCl3 electrolytes were met by most of the weak base and strong base amino exchange groups considered in the program. Good stability is exhibited by several of the membrane substrate resins. These are 'styrene' divinylbenzene copolymer and PVC film. At least four membrane systems produce strong flexible films with electrochemical properties (resistivity, cation transfer) superior to those of the 103QZL, the most promising commercial membrane. The physical and chemical properties of the resins are listed.

  9. Mechanism of Polysulfone-Based Anion Exchange Membranes Degradation in Vanadium Flow Battery.

    PubMed

    Yuan, Zhizhang; Li, Xianfeng; Zhao, Yuyue; Zhang, Huamin

    2015-09-01

    The stability of hydrocarbon ion exchange membranes is one of the critical issues for a flow battery. However, the degradation mechanism of ion exchange membranes has been rarely investigated especially for anion exchange membranes. Here, the degradation mechanism of polysulfone based anion exchange membranes, carrying pyridine ion exchange groups, under vanadium flow battery (VFB) medium was investigated in detail. We find that sp(2) hybrid orbital interactions between pyridinic-nitrogen in 4,4'-bipyridine and benzylic carbon disrupt the charge state balance of pristine chloromethylated polysulfone. This difference in electronegativity inversely induces an electrophilic carbon center in the benzene ring, which can be attacked by the lone pair electron on the vanadium(V) oxygen species, further leading to the degradation of polymer backbone, while leaving the 4,4'-bipyridine ion exchange groups stable. This work represents a step toward design and construction of alternative type of chemically stable hydrocarbon ion exchange membranes for VFB. PMID:26284752

  10. Removal of dissolved organic matter by anion exchange: Effect of dissolved organic matter properties

    USGS Publications Warehouse

    Boyer, T.H.; Singer, P.C.; Aiken, G.R.

    2008-01-01

    Ten isolates of aquatic dissolved organic matter (DOM) were evaluated to determine the effect that chemical properties of the DOM, such as charge density, aromaticity, and molecular weight, have on DOM removal by anion exchange. The DOM isolates were characterized asterrestrial, microbial, or intermediate humic substances or transphilic acids. All anion exchange experiments were conducted using a magnetic ion exchange (MIEX) resin. The charge density of the DOM isolates, determined by direct potentiometric titration, was fundamental to quantifying the stoichiometry of the anion exchange mechanism. The results clearly show that all DOM isolates were removed by anion exchange; however, differences among the DOM isolates did influence their removal by MIEX resin. In particular, MIEX resin had the greatest affinity for DOM with high charge density and the least affinity for DOM with low charge density and low aromaticity. This work illustrates that the chemical characteristics of DOM and solution conditions must be considered when evaluating anion exchange treatment for the removal of DOM. ?? 2008 American Chemical Society.

  11. OXIDATIVE STRESS ACTIVATES ANION EXCHANGE PROTEIN 2 AND AP-1 IN AIRWAY EPITHELIAL CELLS

    EPA Science Inventory

    Anion exchange protein 2 (AE2) is a membrane-bound protein that mediates chloride-bicarbonate exchange. In addition to regulating intracellular pH and cell volume, AE2 exports superoxide (O.) to the extracellular matrix in an HCO-dependent process. Given this ability to export O....

  12. ZEOLITE PERFORMANCE AS AN ANION EXCHANGER FOR ARSENIC SEQUESTRATION IN WATER

    EPA Science Inventory

    Zeolites are well known for their use in ion exchange and acid catalysis reactions. The use of zeolites in anion or ligand exchange reactions is less studied. The NH4+ form of zeolite Y (NY6, Faujasite) has been tested in this work to evaluate its performance for arsenic removal...

  13. Americium purification by a combined anion exchange and bidentate organophosphorus solvent extraction process. [Patent application

    SciTech Connect

    Navratil, J.D.; Martella, L.L.

    1981-04-10

    Americium is separated from mixtures containing plutonium, other actinides, and other non-lanthamide impurities, by a combined process of anion exchange resin sorption to remove plutonium, and a bidentate organophosphorus solvent extraction of americium of the anion exchange resin effluent. Dihexyl-N,N-diethylcarbamylmethylenephosphonate is a preferred solvent. The initial mixture may be subjected to a cation exchange operation to remove monovalent impurities. The process is especially effective when aluminum, zinc, lead, and copper are present in significant quantities in the original mixture.

  14. A new anionic exchange stir bar sorptive extraction coating based on monolithic material for the extraction of inorganic anion.

    PubMed

    Huang, Xiaojia; Lin, Jianbing; Yuan, Dongxing

    2010-07-23

    A novel anionic exchange stir bar sorptive extraction (SBSE) coating based on poly(2-(methacryloyloxy)ethyltrimethylammonium chloride-co-divinylbenzene) monolithic material for the extraction of inorganic anion was prepared. The effect of preparation conditions such as ratio of functional monomer to cross-linker, content of porogenic solvent on the extraction efficiencies were investigated in detailed. The monolithic material was characterized by elemental analysis, scanning electron microscopy and infrared spectroscopy. In order to investigate the extraction capacity of the new coating for inorganic anion, the new SBSE was combined with ionic chromatography with conductivity detection, Br-, NO3-, PO4(3-) and SO4(2-) were selected as detected solutes. Several extractive parameters, including pH value and ionic strength in sample matrix, desorption solvent, extraction and desorption time were optimized. The results showed that strongly ionic strength did not favor the extraction of anlaytes. Under the optimum experimental conditions, low detection limits (S/N=3) and quantification limits (S/N=10) of the proposed method for the target anions were achieved within the range of 0.92-2.62 and 3.03-9.25 microg/L, respectively. The method also showed good linearity, simplicity, practicality and low cost for the extraction inorganic anions. Finally, the proposed method was successfully used to detect the two different trademarks of commercial purified water with satisfactory recovery in the range of 70.0-92.6%. To the best of our knowledge, this is the first to use SBSE to enrich inorganic anions. PMID:20576270

  15. Improved recovery and purification of plutonium at Los Alamos using macroporous anion exchange resin

    SciTech Connect

    Marsh, S.F.; Mann, M.J.

    1987-05-01

    For almost 30 years, Los Alamos National Laboratory has used anion exchange in nitric acid as the major aqueous process or the recovery and purification of plutonium. One of the few disadvantages of this system is the particularly slow rate at which the anionic nitrato complex of Pu(IV) equilibrates with the resin. The Nuclear Materials Process Technology Group at Los Alamos recently completed an ion exchange development program that focused on improving the slow sorption kinetics that limits this process. A comprehensive investigation of modern anion exchange resins identified porosity and bead size as the properties that most influence plutonium sorption kinetics. Our study found that small beads of macroporous resin produced a dramatic increase in plutonium process efficiency. The Rocky Flats Plant has already adopted this improved ion exchange technology, and it currently is being evaluated for use in other DOE plutonium-processing facilities.

  16. Sequential Anion and Cation Exchange Reactions for Complete Material Transformations of Nanoparticles with Morphological Retention.

    PubMed

    Hodges, James M; Kletetschka, Karel; Fenton, Julie L; Read, Carlos G; Schaak, Raymond E

    2015-07-20

    Ion exchange reactions of colloidal nanocrystals provide access to complex products that are synthetically challenging using traditional hot-injection methods. However, such reactions typically achieve only partial material transformations by employing either cation or anion exchange processes. It is now shown that anion and cation exchange reactions can be coupled together and applied sequentially in one integrated pathway that leads to complete material transformations of nanocrystal templates. Although the product nanocrystals do not contain any of the original constituent elements, the original morphology is retained, thereby fully decoupling morphology and composition control. The sequential anion/cation exchange process was applied to pseudo-spherical CdO nanocrystals and ZnO tetrapods, producing fully transformed and shape-controlled nanocrystals of copper and silver sulfides and selenides. Furthermore, hollow core-shell tetrapod ZnS@CdS heterostructures were readily accessible. PMID:26110653

  17. Quaternized poly (styrene-co-vinylbenzyl chloride) anion exchange membranes for alkaline water electrolysers

    NASA Astrophysics Data System (ADS)

    Vengatesan, S.; Santhi, S.; Jeevanantham, S.; Sozhan, G.

    2015-06-01

    In this study, poly (ST-co-VBC) based anion exchange membranes with different styrene to VBC ratios (1: 0.16, 1: 0.33 and 1: 1) have been prepared via chloromethylation-free synthetic route using aromatic vinyl monomers. The synthesized co-polymers are identified by FTIR and 1H-NMR analysis. Hydroxide (OH-) ion conductivity of the anion exchange membrane with styrene to VBC ratio of 1: 0.33 is as high as 6.8 × 10-3 S cm-1 in de-ionised water at 25 °C. The membrane also acquires the ion-exchange capacity of 2.14 meq. g-1, and the water uptake of 127%. Membrane-electrode-assembly (MEA) using the anion exchange membrane and Ni - foam catalyst demonstrate the current density of 40 mA cm-2 at 2.3 V in a water electrolyser cell.

  18. Rapid exchange between atmospheric CO2 and carbonate anion intercalated within magnesium rich layered double hydroxide.

    PubMed

    Sahoo, Pathik; Ishihara, Shinsuke; Yamada, Kazuhiko; Deguchi, Kenzo; Ohki, Shinobu; Tansho, Masataka; Shimizu, Tadashi; Eisaku, Nii; Sasai, Ryo; Labuta, Jan; Ishikawa, Daisuke; Hill, Jonathan P; Ariga, Katsuhiko; Bastakoti, Bishnu Prasad; Yamauchi, Yusuke; Iyi, Nobuo

    2014-10-22

    The carbon cycle, by which carbon atoms circulate between atmosphere, oceans, lithosphere, and the biosphere of Earth, is a current hot research topic. The carbon cycle occurring in the lithosphere (e.g., sedimentary carbonates) is based on weathering and metamorphic events so that its processes are considered to occur on the geological time scale (i.e., over millions of years). In contrast, we have recently reported that carbonate anions intercalated within a hydrotalcite (Mg0.75Al0.25(OH)2(CO3)0.125·yH2O), a class of a layered double hydroxide (LDH), are dynamically exchanging on time scale of hours with atmospheric CO2 under ambient conditions. (Ishihara et al., J. Am. Chem. Soc. 2013, 135, 18040-18043). The use of (13)C-labeling enabled monitoring by infrared spectroscopy of the dynamic exchange between the initially intercalated (13)C-labeled carbonate anions and carbonate anions derived from atmospheric CO2. In this article, we report the significant influence of Mg/Al ratio of LDH on the carbonate anion exchange dynamics. Of three LDHs of various Mg/Al ratios of 2, 3, or 4, magnesium-rich LDH (i.e., Mg/Al ratio = 4) underwent extremely rapid exchange of carbonate anions, and most of the initially intercalated carbonate anions were replaced with carbonate anions derived from atmospheric CO2 within 30 min. Detailed investigations by using infrared spectroscopy, scanning electron microscopy, powder X-ray diffraction, elemental analysis, adsorption, thermogravimetric analysis, and solid-state NMR revealed that magnesium rich LDH has chemical and structural features that promote the exchange of carbonate anions. Our results indicate that the unique interactions between LDH and CO2 can be optimized simply by varying the chemical composition of LDH, implying that LDH is a promising material for CO2 storage and/or separation. PMID:25275963

  19. Significance of anion exchange in pentachlorophenol sorption by variable-charge soils.

    PubMed

    Hyun, Seunghun; Lee, Linda S; Rao, P Suresh C

    2003-01-01

    Sorption data and subsequent predictive models for evaluating acidic pesticide behavior on variable-charge soils are needed to improve pesticide management and environmental stewardship. Previous work demonstrated that sorption of pentachlorophenol (PCP), a model organic acid, was adequately modeled by accounting for pH-and pKa-dependent chemical speciation and using two organic carbon-normalized sorption coefficients; one each for the neutral and anionic species. Such models do not account for organic anion interaction to positively charged surface sites, which can be significant for variable-charge minerals present in weathered soils typical of tropical and subtropical regions. The role of anion exchange in sorption of ionizable chemicals by variable-charge soils was assessed by measuring sorption of PCP by several variable-charge soils from aqueous solutions of CaCl2, CaSO4, Ca(H2PO4)2 as a function of pH. Differences in sorption from phosphate and chloride electrolyte solutions were attributed to pentachlorophenolate interactions with anion exchange sites. Suppression of PCP sorption by phosphate ranged from negligible in a soil with essentially no positively charge sites, as measured by negligible anion exchange capacity, to as much as 69% for variable-charge soils. Pentachlorophenolate exchange correlated well with the ratio of pH-dependent anion exchange capacity to net surface charge. Sorption reversibility of PCP by both CaCl2 and Ca(H2PO4)2 solutions was also demonstrated. Results for PCP clearly demonstrate that sorption to anion exchange sites in variable-charge soils should be considered in assessing pesticide mobility and that phosphate fertilizer application may increase the mobility of acidic pesticides. PMID:12809297

  20. Pharmacological characterization of volume-sensitive, taurine permeable anion channels in rat supraoptic glial cells

    PubMed Central

    Brès, Vanessa; Hurbin, Amandine; Duvoid, Anne; Orcel, Hélène; Moos, Françoise C; Rabié, Alain; Hussy, Nicolas

    2000-01-01

    To characterize the volume-sensitive, osmolyte permeable anion channels responsible for the osmodependent release of taurine from supraoptic nucleus (SON) astrocytes, we investigated the pharmacological properties of the [3H]-taurine efflux from acutely isolated SON.Taurine release induced by hypotonic stimulus (250 mosmol l−1) was not antagonized by the taurine transporter blocker guanidinoethyl sulphonate, confirming the lack of implication of the transporter.The osmodependent release of taurine was blocked by a variety of Cl− channel inhibitors with the order of potency: NPPB>niflumic acid>DPC>DIDS>ATP. On the other hand, release of taurine was only weakly affected by other compounds (dideoxyforskolin, 4-bromophenacyl bromide, mibefradil) known to block volume-activated anion channels in other cell preparations, and was completely insensitive to tamoxifen, a broad inhibitor of these channels.Although the molecular identity of volume-sensitive anion channels is not firmly established, a few genes have been postulated as potential candidates to encode such channels. We checked the expression in the SON of three of them, ClC3, phospholemman and VDAC1, and found that the transcripts of these genes are found in SON neurons, but not in astrocytes. Similar observation was previously reported for ClC2.In conclusion, the osmodependent taurine permeable channels of SON astrocytes display a particular pharmacological profile, suggesting the expression of a particular type or subtype of volume-sensitive anion channel, which is likely to be formed by yet unidentified proteins. PMID:10952690

  1. Pharmacological characterization of volume-sensitive, taurine permeable anion channels in rat supraoptic glial cells.

    PubMed

    Brès, V; Hurbin, A; Duvoid, A; Orcel, H; Moos, F C; Rabié, A; Hussy, N

    2000-08-01

    To characterize the volume-sensitive, osmolyte permeable anion channels responsible for the osmodependent release of taurine from supraoptic nucleus (SON) astrocytes, we investigated the pharmacological properties of the [(3)H]-taurine efflux from acutely isolated SON. Taurine release induced by hypotonic stimulus (250 mosmol l(-1)) was not antagonized by the taurine transporter blocker guanidinoethyl sulphonate, confirming the lack of implication of the transporter. The osmodependent release of taurine was blocked by a variety of Cl(-) channel inhibitors with the order of potency: NPPB>niflumic acid>DPC>DIDS>ATP. On the other hand, release of taurine was only weakly affected by other compounds (dideoxyforskolin, 4-bromophenacyl bromide, mibefradil) known to block volume-activated anion channels in other cell preparations, and was completely insensitive to tamoxifen, a broad inhibitor of these channels. Although the molecular identity of volume-sensitive anion channels is not firmly established, a few genes have been postulated as potential candidates to encode such channels. We checked the expression in the SON of three of them, ClC(3), phospholemman and VDAC(1), and found that the transcripts of these genes are found in SON neurons, but not in astrocytes. Similar observation was previously reported for ClC(2). In conclusion, the osmodependent taurine permeable channels of SON astrocytes display a particular pharmacological profile, suggesting the expression of a particular type or subtype of volume-sensitive anion channel, which is likely to be formed by yet unidentified proteins. PMID:10952690

  2. Anion Conductance of Frog Muscle Membranes: One Channel, Two Kinds of pH Dependence

    PubMed Central

    Woodbury, J. W.; Miles, P. R.

    1973-01-01

    Anion conductance and permeability sequences were obtained for frog skeletal muscle membranes from the changes in characteristic resistance and transmembrane potential after the replacement of one anion by another in the bathing solution. Permeability and conductance sequences are the same. The conductance sequence at pH = 7.4 is Cl- Br- > NO3- > I- > trichloroacetate ≥ benzoate > valerate > butyrate > proprionate > formate > acetate ≥ lactate > benzenesulfonate ≥ isethionate > methylsulfonate > glutamate ≥ cysteate. The anions are divided into two classes: (a) Chloride-like anions (Cl- through trichloroacetate) have membrane conductances that decrease as pH decreases. The last six members of the complete sequence are also chloride like. (b) Benzoate-like anions (benzoate through acetate) have conductances that increase as pH decreases. At pH = 6.7 zinc ions block Cl- and benzoate conductances with inhibitory dissociation constants of 0.12 and 0.16 mM, respectively. Chloride-like and benzoate-like anions probably use the same channels. The minimum size of the channel aperture is estimated as 5.5 x 6.5 Å from the dimensions of the largest permeating anions. A simple model of the channel qualitatively explains chloride-like and benzoate-like conductance sequences and their dependence on pH. PMID:4542368

  3. Intracellular Na(+) inhibits volume-regulated anion channel in rat cortical astrocytes.

    PubMed

    Minieri, Laura; Pivonkova, Helena; Harantova, Lenka; Anderova, Miroslava; Ferroni, Stefano

    2015-02-01

    Accumulating evidence indicates that increased intracellular Na(+) concentration ([Na(+) ]i ) in astroglial cells is associated with the development of brain edema under ischemic conditions, but the underlying mechanisms are still elusive. Here, we report that in primary cultured rat cortical astrocytes, elevations of [Na(+) ]i reflecting those achieved during ischemia cause a marked decrease in hypotonicity-evoked current mediated by volume-regulated anion channel (VRAC). Pharmacological manipulations revealed that VRAC inhibition was not due to the reverse mode of the plasma membrane sodium/calcium exchanger. The negative modulation of VRAC was also observed in an astrocytic cell line lacking the predominant astrocyte water channel aquaporin 4, indicating that [Na(+) ]i effect was not mediated by the regulation of aquaporin 4 activity. The inward rectifier Cl(-) current, which is also expressed by cultured astrocytes, was not affected by [Na(+) ]i increase. VRAC depression by high [Na(+) ]i was confirmed in adult astrocytes, suggesting that it was not developmentally regulated. Altogether, these results provide the first evidence that intracellular Na(+) dynamics can modulate astrocytic membrane conductance that controls functional processes linked to cell volume regulation and add further support to the concept that limiting astrocyte intracellular Na(+) accumulation might be a favorable strategy to counteract the development of brain edema. PMID:25279950

  4. Evidence that extracellular anions interact with a site outside the CFTR chloride channel pore to modify channel properties.

    PubMed

    Zhou, Jing-Jun; Linsdell, Paul

    2009-05-01

    Extracellular anions enter into the pore of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel, interacting with binding sites on the pore walls and with other anions inside the pore. There is increasing evidence that extracellular anions may also interact with sites away from the channel pore to influence channel properties. We have used site-directed mutagenesis and patch-clamp recording to identify residues that influence interactions with external anions. Anion interactions were assessed by the ability of extracellular Pt(NO2)42- ions to weaken the pore-blocking effect of intracellular Pt(NO2)42- ions, a long-range ion-ion interaction that does not appear to reflect ion interactions inside the pore. We found that mutations that remove positive charges in the 4th extracellular loop of CFTR (K892Q and R899Q) significantly alter the interaction between extracellular and intracellular Pt(NO2)42- ions. These mutations do not affect unitary Cl- conductance or block of single-channel currents by extracellular Pt(NO2)42- ions, however, suggesting that the mutated residues are not in the channel pore region. These results suggest that extracellular anions can regulate CFTR pore properties by binding to a site outside the pore region, probably by a long-range conformational change. Our findings also point to a novel function of the long 4th extracellular loop of the CFTR protein in sensing and (or) responding to anions in the extracellular solution. PMID:19448737

  5. Regeneration of strong-base anion-exchange resins by sequential chemical displacement

    SciTech Connect

    Brown, Gilbert M.; Gu, Baohua; Moyer, Bruce A.; Bonnesen, Peter V.

    2002-01-01

    A method for regenerating strong-base anion exchange resins utilizing a sequential chemical displacement technique with new regenerant formulation. The new first regenerant solution is composed of a mixture of ferric chloride, a water-miscible organic solvent, hydrochloric acid, and water in which tetrachloroferrate anion is formed and used to displace the target anions on the resin. The second regenerant is composed of a dilute hydrochloric acid and is used to decompose tetrachloroferrate and elute ferric ions, thereby regenerating the resin. Alternative chemical displacement methods include: (1) displacement of target anions with fluoroborate followed by nitrate or salicylate and (2) displacement of target anions with salicylate followed by dilute hydrochloric acid. The methodology offers an improved regeneration efficiency, recovery, and waste minimization over the conventional displacement technique using sodium chloride (or a brine) or alkali metal hydroxide.

  6. Characterization of basolateral K+ channels underlying anion secretion in the human airway cell line Calu-3

    PubMed Central

    Cowley, Elizabeth A; Linsdell, Paul

    2002-01-01

    Transepithelial anion secretion in many tissues depends upon the activity of basolateral channels. Using monolayers of the Calu-3 cell line, a human submucosal serous cell model mounted in an Ussing chamber apparatus, we investigated the nature of the K+ channels involved in basal, cAMP- and Ca2+-stimulated anion secretion, as reflected by the transepithelial short circuit current (Isc). The non-specific K+ channel inhibitor Ba2+ inhibited the basal Isc by either 77 or 16 % when applied directly to the basolateral or apical membranes, respectively, indicating that a basolateral K+ conductance is required for maintenance of basal anion secretion. Using the K+ channel blockers clofilium and clotrimazole, we found basal Isc to be sensitive to clofilium, with a small clotrimazole-sensitive component. By stimulating the cAMP and Ca2+ pathways, we determined that cAMP-stimulated anion secretion was almost entirely abolished by clofilium, but insensitive to clotrimazole. In contrast, the Ca2+-stimulated response was sensitive to both clofilium and clotrimazole. Thus, pharmacologically distinct basolateral K+ channels are differentially involved in the control of anion secretion under different conditions. Isolation of the basolateral K+ conductance in permeabilized monolayers revealed a small basal and forskolin-stimulated Isc. Finally, using the reverse transcriptase-polymerase chain reaction, we found that Calu-3 cells express the K+ channel genes KCNN4 and KCNQ1 and the subunits KCNE2 and KCNE3. We conclude that while KCNN4 contributes to Ca2+-activated anion secretion by Calu-3 cells, basal and cAMP-activated secretion are more critically dependent on other K+ channel types, possibly involving one or more class of KCNQ1-containing channel complexes. PMID:11826162

  7. Molecular Evolution of Slow and Quick Anion Channels (SLACs and QUACs/ALMTs)

    PubMed Central

    Dreyer, Ingo; Gomez-Porras, Judith Lucia; Riaño-Pachón, Diego Mauricio; Hedrich, Rainer; Geiger, Dietmar

    2012-01-01

    Electrophysiological analyses conducted about 25 years ago detected two types of anion channels in the plasma membrane of guard cells. One type of channel responds slowly to changes in membrane voltage while the other responds quickly. Consequently, they were named SLAC, for SLow Anion Channel, and QUAC, for QUick Anion Channel. Recently, genes SLAC1 and QUAC1/ALMT12, underlying the two different anion current components, could be identified in the model plant Arabidopsis thaliana. Expression of the gene products in Xenopus oocytes confirmed the quick and slow current kinetics. In this study we provide an overview on our current knowledge on slow and quick anion channels in plants and analyze the molecular evolution of ALMT/QUAC-like and SLAC-like channels. We discovered fingerprints that allow screening databases for these channel types and were able to identify 192 (177 non-redundant) SLAC-like and 422 (402 non-redundant) ALMT/QUAC-like proteins in the fully sequenced genomes of 32 plant species. Phylogenetic analyses provided new insights into the molecular evolution of these channel types. We also combined sequence alignment and clustering with predictions of protein features, leading to the identification of known conserved phosphorylation sites in SLAC1-like channels along with potential sites that have not been yet experimentally confirmed. Using a similar strategy to analyze the hydropathicity of ALMT/QUAC-like channels, we propose a modified topology with additional transmembrane regions that integrates structure and function of these membrane proteins. Our results suggest that cross-referencing phylogenetic analyses with position-specific protein properties and functional data could be a very powerful tool for genome research approaches in general. PMID:23226151

  8. Spatial Distribution of Maxi-Anion Channel on Cardiomyocytes Detected by Smart-Patch Technique☆

    PubMed Central

    Dutta, Amal K.; Korchev, Yuri E.; Shevchuk, Andrew I.; Hayashi, Seiji; Okada, Yasunobu; Sabirov, Ravshan Z.

    2008-01-01

    Spatial distribution of maxi-anion channels in rat cardiomyocytes were studied by applying the recently developed patch clamp technique under scanning ion conductance microscopy, called the “smart-patch” technique. In primary-cultured neonatal cells, the channel was found to be unevenly distributed over the cell surface with significantly lower channel activity in cellular extensions compared with the other parts. Local ATP release, detected using a PC12 cell-based biosensor technique, also exhibited a similar pattern. The maxi-anion channel activity could not be detected in freshly isolated adult cardiomyocytes by the conventional patch-clamp with 2-MΩ pipettes. However, when fine-tipped 15–20 MΩ pipettes were targeted to only Z-line areas, we observed, for the first time, the maxi-anion events. Smart-patching different regions of the cell surface, we found that the channel activity was maximal at the openings of T-tubules and along Z-lines, but was significantly decreased in the scallop crest area. Thus, it is concluded that maxi-anion channels are concentrated at the openings of T-tubules and along Z-lines in adult cardiomyocytes. This study showed that the smart-patch technique provides a powerful method to detect a unitary event of channels that are localized at some specific site in the narrow region. PMID:18024498

  9. Calcium-dependent anion channel in the water mold, Blastocladiella emersonii.

    PubMed

    Caldwell, J H; Van Brunt, J; Harold, F M

    1986-01-01

    Injection of depolarizing current into vegetative cells of the water mold Blastocladiella emersonii elicits a regenerative response that has the electrical characteristics of an action potential. Once they have been taken past a threshold of about -40 mV, cells abruptly depolarize to +20 mV or above; after an interval ranging from several hundred milliseconds to a few seconds, the cells spontaneously return to their resting potential near -100 mV. When the action potential was analyzed with voltage-clamp recording, it proved to be biphasic. The initial phase reflects an influx of calcium ions through voltage-sensitive channels that also carry Sr2+ ions. The delayed, and more extended, phase of inward current results from the efflux of chloride and other anions. The anion channels are broadly selective, passing chloride, nitrate, phosphate, acetate, succinate and even PIPES. The anion channels open in response to the entry of calcium ions, but do not recognize Sr2+. Calcium channels, anion channels and calcium-specific receptors that link the two channels appear to form an ensemble whose physiological function is not known. Action potentials rarely occur spontaneously but can be elicited by osmotic downshock, suggesting that the ion channels may be involved in the regulation of turgor. PMID:2420994

  10. Nanocomposite membranes based on quaternized polysulfone and functionalized montmorillonite for anion-exchange membranes

    NASA Astrophysics Data System (ADS)

    Liao, Xiaofeng; Ren, Li; Chen, Dongzhi; Liu, Xiaohong; Zhang, Hongwei

    2015-07-01

    In this paper, functionalized montmorillonite is intercalated with cetyl trimethyl ammonium chloride and (3-aminopropyl)triethoxysilane. Quaternized polysulfone/functionalized montmorillonite nanocomposite membranes are fabricated to evaluate their potential in anion-exchange membrane fuel cells. Fourier transform infrared spectroscopy, thermogravimetric analyzer and X-ray diffractometer are used to confirm the success of intercalation. The performances of the composite membranes for the anion-exchange membrane fuel cells in terms of their water uptake, mechanical property and ionic conductivity are investigated. Compared with other anion-exchange membranes, the nanocomposite membrane containing 5% montmorillonite modified by cetyl trimethyl ammonium chloride exhibits lower water uptake, higher ultimate stress and larger ionic conductivity. It exhibits an ionic conductivity of 4.73 × 10-2 S cm-1 at 95 °C.

  11. Anion-exchange extraction of cephapirin, cefotaxime, and cefoxitin from serum for liquid chromatography.

    PubMed Central

    Fasching, C E; Peterson, L R

    1982-01-01

    An anion-exchange column technique for extraction of antibiotics from serum proteins has been developed for use in the assay of cephapirin, cefotaxime, and cefoxitin by high-pressure liquid chromatography. Anion-exchange extraction of cephapirin from serum samples by this technique was compared with protein precipitation methods, using 6% trichloroacetic acid or absolute ethanol. Column extraction gave improved quantitative drug recovery and reduced background serum interferences in the resultant chromatograms when evaluated against protein precipitation. Comparisons of this method with microbiological assay gave statistically equivalent results. Twelve patient samples were assayed for cephapirin, and no interferences were encountered from the 22 systemic agents these subjects were receiving. The anion-exchange technique for antibiotic extraction provides a rapid, precise, and quantitative antibiotic assay when used with liquid chromatography. PMID:6282213

  12. Highly Conductive Anion-Exchange Membranes from Microporous Tröger's Base Polymers.

    PubMed

    Yang, Zhengjin; Guo, Rui; Malpass-Evans, Richard; Carta, Mariolino; McKeown, Neil B; Guiver, Michael D; Wu, Liang; Xu, Tongwen

    2016-09-12

    The development of polymeric anion-exchange membranes (AEMs) combining high ion conductivity and long-term stability is a major challenge for materials chemistry. AEMs with regularly distributed fixed cationic groups, based on the formation of microporous polymers containing the V-shape rigid Tröger's base units, are reported for the first time. Despite their simple preparation, which involves only two synthetic steps using commercially available precursors, the polymers provide AEMs with exceptional hydroxide conductivity at relatively low ion-exchange capacity, as well as a high swelling resistance and chemical stability. An unprecedented hydroxide conductivity of 164.4 mS cm(-1) is obtained at a relatively a low ion-exchange capacity of 0.82 mmol g(-1) under optimal operating conditions. The exceptional anion conductivity appears related to the intrinsic microporosity of the charged polymer matrix, which facilitates rapid anion transport. PMID:27505421

  13. Location of a permeant anion binding site in the cystic fibrosis transmembrane conductance regulator chloride channel pore.

    PubMed

    Rubaiy, Hussein N; Linsdell, Paul

    2015-05-01

    In the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel, lyotropic anions with high permeability also bind relatively tightly within the pore. However, the location of permeant anion binding sites, as well as their relationship to anion permeability, is not known. We have identified lysine residue K95 as a key determinant of permeant anion binding in the CFTR pore. Lyotropic anion binding affinity is related to the number of positively charged amino acids located in the inner vestibule of the pore. However, mutations that change the number of positive charges in this pore region have minimal effects on anion permeability. In contrast, a mutation at the narrow pore region alters permeability with minimal effects on anion binding. Our results suggest that a localized permeant anion binding site exists in the pore; however, anion binding to this site has little influence over anion permeability. Implications of this work for the mechanisms of anion recognition and permeability in CFTR are discussed. PMID:25673337

  14. [Volume regulated anion channel and ischemia/reperfusion injury of myocardium].

    PubMed

    Li, Ping; Sun, Xiaoli

    2008-08-01

    It has been shown that a lot of diseases were related with the change or loss of Cl- channel functions. Among the Cl- channels, volume-regulated anion channel (VRAC) plays important roles in myocardial ischemia/reperfusion injury, cardiac arrhythmia and apoptosis; it may become a new target in the clinical treatment of heart diseases. This paper presents an overview of the physiological characteristics of VRAC and its relations with myocardial ischemia/reperfusion injury. PMID:18788323

  15. Preparation and chromatographic performance of polymer-based anion exchangers for ion chromatography: A review.

    PubMed

    Zatirakha, A V; Smolenkov, A D; Shpigun, O A

    2016-01-21

    In the last decade the developments in the field of ion chromatography (IC) were aimed at increasing the efficiency, sensitivity and rapidity of analysis, as well as on improving separation selectivity. Since selectivity and efficiency to the large extent depend on the surface chemistry of the stationary phase, the development of novel anion exchangers remains one of the priority tasks in modern IC. The exact chemistry of commercially available resins is not known and not many literature data devoted to the procedures of preparing anion exchangers for IC have become available in the last 10-15 years. However, the knowledge about the surface chemistry of anion exchangers can provide understanding of the trends in selectivity and efficiency changes, as well as help with the choice of the stationary phase type suitable for solving a particular analytical task. The current review is devoted to the methods of preparing anion exchangers based on polystyrene-divinylbenzene (PS-DVB) and ethylvinylbenzene-divinylbenzene (EVB-DVB) for IC of inorganic and small organic anions and is aimed at demonstrating the improvement of their performance over the years, which was brought by the development of the new types of stationary phase architecture. PMID:26724761

  16. Measurement of the distribution of anion exchange function in normal human red cells.

    PubMed Central

    Raftos, J E; Bookchin, R M; Lew, V L

    1997-01-01

    1. The aim of the present work was to investigate cell-to-cell variation in anion exchange turnover in normal human red cells. Red cells permeabilized to protons and K+ dehydrate extremely rapidly by processes that are rate-limited by the induced K+ permeability or by anion exchange turnover. Conditions were designed to render dehydration rate-limited by anion exchange turnover. Cell-to-cell variation in anion exchange function could then be measured from the distribution of delay times required for dehydrating cells to attain resistance to haemolysis in a selected hypotonic medium. 2. Red cells were suspended at 10% haematocrit in a low-K+ solution and, after a brief preincubation with 20 microM SITS at 4 degrees C, were warmed to 24 degrees C, and the protonophore CCCP was added (20 microM) followed 2 min later by valinomycin (60 microM). Delay times for cells to become resistant to lysis were measured from the instant of valinomycin addition by sampling suspension aliquots into thirty volumes of 35 mM NaCl. After centrifugation the per cent lysis was estimated by measuring the haemoglobin concentration in the supernatant. Typical median delay times with this standardized method were 4-5 min. 3. The statistical parameters of the delay time distributions report the population spread in the transport function that was limiting to dehydration. In the absence of SITS and CCCP, dehydration was limited by the diffusional Cl- permeability (PCl). Delay time distributions for PCl- and anion exchange-limited dehydration were measured in red cells from three normal donors. For both distributions, the coefficients of variation ranged between 13.0 and 15.2%, indicating a high degree of uniformity in PCl and anion exchange function among individual red cells. PMID:9061637

  17. Relationships of anion-exchange sorption of boron from natural thermal-spring water

    SciTech Connect

    Meichik, N.R.; Leikin, Yu.A.; Antipov, M.A.; Goryacheva, N.V.; Klimenko, I.S.; Medvedev, S.A.; Galitskaya, N.B.

    1988-02-20

    Boric acid is one of the characteristic components of Kamchatka waters. Extraction of boron from thermal waters for production of potable water is closely linked with current problems of multiproduct utilization of resources and protection of the environment. The authors have investigated the possibilities of using ion exchange for extraction of boron from natural waters, and studied the sorption relationships by a dynamic method. They synthesized a macroporous anion-exchanger based on a copolymer of styrene with divinylbenzene, containing N-methylglucamine groups (ANB-11 resin). ANB-11 resin had high sorption capacity for boron anions during sorption from thermal-spring water. The experimental data were described by Elkins equation.

  18. Flickery block of single CFTR chloride channels by intracellular anions and osmolytes.

    PubMed

    Linsdell, P; Hanrahan, J W

    1996-08-01

    Cystic fibrosis transmembrane conductance regulator (CFTR) is a phosphorylation- and nucleotide-dependent chloride channel. Single CFTR currents recorded on cell show slight outward rectification, which has previously been suggested to be due to an asymmetrical chloride ion gradient or to a specific interaction between permeant intracellular anions and the channel. Using a single-channel recording from Chinese hamster ovary cells stably expressing CFTR, we have found that both the sparingly permeant anion glutamate and the impermeant anion gluconate cause a rapid, voltage-dependent block of CFTR channels when applied to the intracellular, but not the extracellular, face of excised patches. Both the affinity and the voltage dependence of block were affected by the extracellular chloride concentration in a manner consistent with chloride ions being able to repel these blocking ions from the pore. These results are discussed in terms of previous models of CFTR current outward rectification, and it is suggested that this rectification may result from a combination of asymmetrical chloride concentrations and voltage-dependent block of the channel by large cytoplasmic anions. In addition, we find that CFTR conductance is decreased by high concentrations of intracellular sucrose, sorbitol, and urea in a manner consistent with a rapid block of the channel by these molecules. PMID:8770004

  19. Void exclusion of antibodies by grafted-ligand porous particle anion exchangers.

    PubMed

    Nian, Rui; Chuah, Cindy; Lee, Jeremy; Gan, Hui Theng; Latiff, Sarah Maria Abdul; Lee, Wan Yee; Vagenende, Vincent; Yang, Yuan-Sheng; Gagnon, Pete

    2013-03-22

    We describe a new variant of anion exchange chromatography in columns packed with porous particles that embody charged low-density polymer zones supported by a higher density polymer skeleton. IgG defies the norms of anion exchange and is excluded to the void volume at pH 3-10 and 0-4M NaCl. Void exclusion also occurs with Fab, F(ab')2, and IgM. Host cell protein contaminants mostly follow the usual norms of anion exchange and bind more strongly with increasing pH and decreasing conductivity. Sample buffer composition has no impact on partitioning so long as applied sample volume does not exceed the interparticle void volume of the column. Void-excluded antibody elutes in equilibration buffer. This seemingly conflicted collection of behaviors is reconciled by a variable size exclusion function mediated through the low-density polymer zones, the charge properties of the antibody species, and the pH and conductivity of the equilibration buffer. Current-generation porous particle anion exchangers that employ grafting techniques to achieve high charge density mediate void exclusion to varying degrees, with the best-suited achieving complete exclusion, and others as little as 65%. Perfusive and non-grafted particle-based exchangers mediate as little as 50% exclusion. Monoliths mediate no exclusion, due to their lack of an interparticle void volume. On qualified exchangers, the technique supports greater than 99% reduction of host proteins, DNA, and endotoxin. Virus is reduced more than 99.9%, and aggregates are reduced to less than 0.05%. The method supports better process control than other anion exchange formats because pH excursions in conjunction with changes in salt concentration do not occur until after the antibody has eluted from the column. PMID:23422893

  20. New selective anion-exchange resins for nitrate removal from contaminated drinking water and studies on analytical anion-exchange chromatography

    SciTech Connect

    Lockridge, J.E.

    1989-01-01

    Phosphonium resins and ammonium resins of composition resin-R{sub 3}P{sup +}A{sup {minus}} where R is varied from methyl to pentyl were evaluated for nitrate/sulfate selectivity, capacity and nitrate decontamination of drinking water. Phosphonium resins were found to be more nitrate selective and have higher capacities than ammonium resins. A mixed bed process, where nitrate removal and water softening is accomplished in a single column, was also evaluated. A small piece of silver wire, coated with an insoluble silver salt, works well as a selective potentiometric detector for halide ions in ion chromatography. A silver-silver chloride electrode was found to be a selective and reproducible detector for chloride, bromide, iodide, thiocyanate and thiosulfate anions separated by ion chromatography. Calibration curves were non-linear and had slopes ranging from 40 to 60 mV/log concentrations. A working range of 0.05 to 2 mM was used. Two methods for the determination of aluminum by anion chromatography are presented. In the first method, a standard excess of fluoride ion is added to the sample. Evidence is given for the formation of a strong complex of neutral aluminum trifluoride which elutes very quickly from an anion exchange column. The excess fluoride is retained and can be determined. The aluminum concentration can then be related to the difference in fluoride peak height between the sample and standard. In a second method, Al(III) is determined directly by anion chromatography when sodium phthalate is used as an eluent. It was found that Al(III)-phthalate complexes thus formed would show some retention on an anion exchange column. The method is uniquely insensitive to the presence of many foreign cations. Al(III) was successfully determined, by this method, in a 40-fold molar excess of iron(III).

  1. Natural light-gated anion channels: A family of microbial rhodopsins for advanced optogenetics

    PubMed Central

    Govorunova, Elena G.; Sineshchekov, Oleg A.; Janz, Roger; Liu, Xiaoqin; Spudich, John L.

    2016-01-01

    Light-gated rhodopsin cation channels from chlorophyte algae have transformed neuroscience research through their use as membrane-depolarizing optogenetic tools for targeted photoactivation of neuron firing. Photosuppression of neuronal action potentials has been limited by the lack of equally efficient tools for membrane hyperpolarization. We describe anion channel rhodopsins (ACRs), a family of light-gated anion channels from cryptophyte algae that provide highly sensitive and efficient membrane hyperpolarization and neuronal silencing through light-gated chloride conduction. ACRs strictly conducted anions, completely excluding protons and larger cations, and hyperpolarized the membrane of cultured animal cells with much faster kinetics at less than one-thousandth of the light intensity required by the most efficient currently available optogenetic proteins. Natural ACRs provide optogenetic inhibition tools with unprecedented light sensitivity and temporal precision. PMID:26113638

  2. NEUROSCIENCE. Natural light-gated anion channels: A family of microbial rhodopsins for advanced optogenetics.

    PubMed

    Govorunova, Elena G; Sineshchekov, Oleg A; Janz, Roger; Liu, Xiaoqin; Spudich, John L

    2015-08-01

    Light-gated rhodopsin cation channels from chlorophyte algae have transformed neuroscience research through their use as membrane-depolarizing optogenetic tools for targeted photoactivation of neuron firing. Photosuppression of neuronal action potentials has been limited by the lack of equally efficient tools for membrane hyperpolarization. We describe anion channel rhodopsins (ACRs), a family of light-gated anion channels from cryptophyte algae that provide highly sensitive and efficient membrane hyperpolarization and neuronal silencing through light-gated chloride conduction. ACRs strictly conducted anions, completely excluding protons and larger cations, and hyperpolarized the membrane of cultured animal cells with much faster kinetics at less than one-thousandth of the light intensity required by the most efficient currently available optogenetic proteins. Natural ACRs provide optogenetic inhibition tools with unprecedented light sensitivity and temporal precision. PMID:26113638

  3. Anion exchange pathways for Cl sup minus transport in rabbit renal microvillus membranes

    SciTech Connect

    Karniski, L.P.; Aronson, P.S. Yale School of Medicine, New Haven, CT )

    1987-09-01

    The authors evaluated the mechanisms of chloride transport in microvillus membrane vesicles isolated from the rabbit renal cortex. The presence of Cl-formate exchange was confirmed. Outward gradients of oxaloacetate, HCO{sub 3}, acetate, lactate, succinate, sulfate, and p-aminohippurate (PAH) stimulated the rate of Cl uptake minimally or not at all. However, an outward gradient of oxalate stimulated Cl uptake by 70%, and an outward Cl gradient induced uphill oxalate uptake, indicting Cl-oxalate exchange. Moreover, an outward formate gradient induced uphill oxalate uptake, indicating formate-oxalate exchange. Studies of inhibitor and substrate specificity indicated the probably operation of at least two separate anion exchangers in mediating Cl transport. The Cl-formate exchanger accepted Cl and formate as substrates, had little or no affinity for oxalate, was sensitive to inhibition by furosemide, and was less sensitive to inhibition by 4,4{prime}-diisothiocyanostilbene-2,2{prime}-disulfonic acid (DIDS). The Cl (formate)-oxalate exchanger also accepted Cl and formate as substrates but had high affinity for oxalate, was highly sensitive to inhibition by DIDS, and was less sensitive to inhibition by furosemide. The Cl-formate exchanger was electroneutral, whereas the Cl (formate)-oxalate exchanger was electrogenic. They conclude that at least separate anion exchangers mediating Cl transport are present on the luminal membrane of the rabbit proximal tubule cell. These exchangers may play important roles in mediating transtubular Cl and oxalate transport in this nephron segment.

  4. Enhanced performance of anion exchange membranes via crosslinking of ion cluster regions for fuel cells

    NASA Astrophysics Data System (ADS)

    Lai, Ao Nan; Guo, Dong; Lin, Chen Xiao; Zhang, Qiu Gen; Zhu, Ai Mei; Ye, Mei Ling; Liu, Qing Lin

    2016-09-01

    Development of anion exchange membranes (AEMs) with high hydroxide conductivity, good dimensional and alkaline stabilities is still a challenge for the practical application of AEM fuel cells. In this study, we report a new strategy to prepare high-performance AEMs with crosslinked ionic regions. A series of phenolphthalein-containing poly(arylene ether sulfone)s crosslinked AEMs was synthesized by grafting ion groups selectively and densely on the phenolphthalein units to form ion clusters that are further crosslinked to generate the hydrophilic ionic regions. The crosslinking reaction not only improved the dimensional stability of the AEMs, but also increased the aggregation of the ion clusters leading to the formation of hydrophilic/hydrophobic phase-separated morphology and ion-conducting channels. As a result, enhancements in both ion conductivity and dimensional stability can be achieved. The crosslinked AEMs showed high hydroxide conductivities in the range of 52.2-143.4 mS cm-1 from 30 to 80 °C and a superb ratio of relative conductivity to relative swelling at 80 °C. Furthermore, the crosslinked AEMs also exhibited good mechanical properties, thermal and alkaline stabilities and desirable single cell performance. This work presents a promising strategy for the synthesis of high-performance AEMs for fuel cells.

  5. Central functions of bicarbonate in S-type anion channel activation and OST1 protein kinase in CO2 signal transduction in guard cell.

    PubMed

    Xue, Shaowu; Hu, Honghong; Ries, Amber; Merilo, Ebe; Kollist, Hannes; Schroeder, Julian I

    2011-04-20

    Plants respond to elevated CO(2) via carbonic anhydrases that mediate stomatal closing, but little is known about the early signalling mechanisms following the initial CO(2) response. It remains unclear whether CO(2), HCO(3)(-) or a combination activates downstream signalling. Here, we demonstrate that bicarbonate functions as a small-molecule activator of SLAC1 anion channels in guard cells. Elevated intracellular [HCO(3)(-)](i) with low [CO(2)] and [H(+)] activated S-type anion currents, whereas low [HCO(3)(-)](i) at high [CO(2)] and [H(+)] did not. Bicarbonate enhanced the intracellular Ca(2+) sensitivity of S-type anion channel activation in wild-type and ht1-2 kinase mutant guard cells. ht1-2 mutant guard cells exhibited enhanced bicarbonate sensitivity of S-type anion channel activation. The OST1 protein kinase has been reported not to affect CO(2) signalling. Unexpectedly, OST1 loss-of-function alleles showed strongly impaired CO(2)-induced stomatal closing and HCO(3)(-) activation of anion channels. Moreover, PYR/RCAR abscisic acid (ABA) receptor mutants slowed but did not abolish CO(2)/HCO(3)(-) signalling, redefining the convergence point of CO(2) and ABA signalling. A new working model of the sequence of CO(2) signalling events in gas exchange regulation is presented. PMID:21423149

  6. New anion-exchange resins for improved separations of nuclear materials. Mid-year progress report

    SciTech Connect

    Barr, M.E.

    1997-06-01

    'The authors are developing multi-functional anion-exchange resins that facilitate anion uptake by carefully controlling the structure of the anion receptor site. The new ion-exchange resins interface the rapidly developing field of ion-specific chelating ligands with robust, commercial ion exchange technology. The overall objective of the research is to develop a predictive capability which allows the facile design and implementation of multi-functionalized anion exchange materials which selectively sorb metal complexes of interest from targeted process, waste, and environmental streams. The basic scientific issues addressed are actinide complex speciation along with modeling of the metal complex/functional site interactions in order to determine optimal binding-site characteristics. Their approach uses a thorough determination of the chemical species both in solution and as bound to the resin to determine the characteristics of resin active sites which can actively facilitate specific metal-complex sorption to the resin. The first year milestones were designed to allow us to build off of their extensive expertise with plutonium in nitrate solutions prior to investigating other, less familiar systems. While the principle investigators have successfully developed actinide chelators and ion-exchange materials in the past, the authors were fully aware that integration of this two fields would be challenging, rewarding and, at times, highly frustrating. Relatively small differences in the substrate (cross-linkage, impurities), the active sites (percent substitution, physical accessibility), the actinide solution (oxidation state changes, purity) and the analytical procedures (low detection limits) can produce inconsistent sorption behavior which is difficult to interpret. The potential paybacks for success, however, are enormous. They feel that they have learned a great deal about how to control these numerous variables to produce consistent, reliable analysis of

  7. Test procedure for anion exchange testing with Argonne 10-L solutions

    SciTech Connect

    Compton, J.A.

    1995-05-17

    Four anion exchange resins will be tested to confirm that they will sorb and release plutonium from/to the appropriate solutions in the presence of other cations. Certain cations need to be removed from the test solutions to minimize adverse behavior in other processing equipment. The ion exchange resins will be tested using old laboratory solutions from Argonne National Laboratory; results will be compared to results from other similar processes for application to all plutonium solutions stored in the Plutonium Finishing Plant.

  8. Enhanced Anion Exchange for Selective Sulfate Extraction: Overcoming the Hofmeister Bias

    SciTech Connect

    Fowler, Christopher J; Haverlock, Tamara; Moyer, Bruce A; Shriver, James A.; Gross, Mr. Dustin E.; Marquez, Manuel; Sessler, Jonathan L.; Hossain, Alamgir; Bowman-James, Kristin

    2008-01-01

    Synergism in liquid-liquid extraction, typified by the combination of a neutral extractant with a cation-exchanger to enhance selectively cation extraction strength, has been used and understood for over five decades.1 Surprisingly, analogous synergism in anion extraction has not yet been developed. In this Communication we present a simple way to achieve non-Hofmeister selectivity in liquid-liquid anion exchange by combining a synthetic hydrogen-bond-donating (HBD) anion receptor with a standard quaternary ammonium type extractant. Specifically, we show that the fluorinated calixpyrroles 1 and 22 and the tetraamide macrocycles 3 5,3 may be used to enhance the solvent extraction of sulfate from nitrate by Aliquat 336-nitrate (A336-nitrate).

  9. Characterization of an anion-permeable channel from sugar beet vacuoles: effect of inhibitors

    PubMed Central

    Hedrich, Rainer; Kurkdjian, Armen

    1988-01-01

    The vacuole occupies 25-95% of the plant cell volume and plays an essential role in maintaining cytoplasmic homeostasis of nutrients and ions. Recent patch-clamp studies identified ion channels and electrogenic pumps as pathways for the movement of ions and metabolites across the vacuolar membrane (tonoplast). At high cytoplasmic Ca2+ (>10-6 M) and negative potentials (inside the vacuole) non-selective channels of the `slow-vacuolar (SV)-type' were activated resulting in anion release or cation influx. In the present study these vacuolar channels were characterized pharmacologically by ion channel inhibitors. The cation-transport inhibitors Ba2+, TEA+ and amiloride caused only partial and reversible block of the `SV-type'channels, whereas anion-transport inhibitors strongly affected the vacuolar channels. Pyridoxalphosphate and the dimethylaminecarboxylate derivates anthracene-9-carboxylic acid and C 144 reversibly blocked the channels up to 70% and Zncl2 up to 95%. DIDS and SITS inhibited this channel irreversibly up to 95%. The block developed under a variety of experimental conditions using solutions containing combinations of permanent cations and anions. The DIDS binding site is located on the cytoplasmic surface of the tonoplast, as intravacuolar DIDS did not block the channels. DIDS concentrations in the micromolar range, efficient in blocking 70—80% of the `SV-type' channels did not significantly affect ATP-induced or pyrophosphate-induced proton-pumps. Stilbene derivatives may therefore be useful tools for studies on the substrate binding site on this vacuolar channel and for channel isolation. PMID:16453861

  10. Investigation of an anion exchange resin for cleanup of a coolant used to machine nuclear materials

    SciTech Connect

    Hinton, E.R. Jr.; Tucker, H.L.; Asbury, W.L.

    1986-01-01

    This article describes the interaction of Dowex SBR-P, which is a strongly basic anion exchange resin, with ions found in a used machining coolant. The coolant is used in machining enriched uranium and contains uranium, chloride, nitrite, borate ions, water, and propylene glycol.

  11. Separation of the rare earths by anion-exchange in the presence of lactic acid

    NASA Technical Reports Server (NTRS)

    Faris, J. P.

    1969-01-01

    Investigation of adsorption of rare earths and a few other elements to an anion-exchange resin from mixed solvents containing lactic acid shows that the lanthanides are absorbed more strongly than from the alpha-hydroxyisobutryric acid system, but with less separation between adjacent members of the series.

  12. Hyper-branched anion exchange membranes with high conductivity and chemical stability.

    PubMed

    Ge, Qianqian; Liu, Yazhi; Yang, Zhengjin; Wu, Bin; Hu, Min; Liu, Xiaohe; Hou, Jianqiu; Xu, Tongwen

    2016-08-01

    In the manuscript, we report the design and preparation of hyper-branched polymer electrolytes intended for alkaline anion exchange membrane fuel cells. The resulting membrane exhibits high conductivity, lower water swelling and shows prolonged chemical stability under alkaline conditions. PMID:27456659

  13. EFFECTS OF PH AND COMPETING ANIONS ON THE SOLUTION SPECIATION OF ARSENIC BY ION EXCHANGE RESINS

    EPA Science Inventory

    Anion-exchange resins (AER) are used to differentiate As(V) and As(III) by retaining As(V) and allowing As(III) to pass through. AERs allow rapid speciation of As in the field which precludes the effects sample preservation on As speciation. Aqueous environmental samples contai...

  14. FINAL REPORT. NEW ANION-EXCHANGE RESINS FOR IMPROVED SEPARATIONS OF NUCLEAR MATERIALS

    EPA Science Inventory

    The overall objective of this project was to develop a predictive capability that would enable us to design and implement new anion-exchange materials that selectively sorb metal complexes. Our approach was to extend the principles applied to optimization of chelating ligands (i....

  15. DEMINERALIZER BUILDING, TRA608. CATION AND ANION EXCHANGERS LINE UP ALONG ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    DEMINERALIZER BUILDING, TRA-608. CATION AND ANION EXCHANGERS LINE UP ALONG NORTH WALL ON CONCRETE PLATFORMS. INL NEGATIVE NO. 2527. Unknown Photographer, 6/12/1951 - Idaho National Engineering Laboratory, Test Reactor Area, Materials & Engineering Test Reactors, Scoville, Butte County, ID

  16. M8L12 cubic cages with all facial Δ or facial Λ configuration: effects of surface anions on the occupancy of the cage and anion exchange.

    PubMed

    Yang, Jing; Chang, Xiao-Yong; Sham, Kiu-Chor; Yiu, Shek-Man; Kwong, Hoi-Lun; Che, Chi-Ming

    2016-05-21

    M8L12 cubic cages (M = Mn(II), Zn(II) or Cd(II)), with all eight metal ions having all facial Δ or facial Λ configurations and having an encapsulated anion, were prepared by the self-assembly of m-xylene-bridged imidazolyl-imine ligands and MX2 (X = PF6(-), SbF6(-), TfO(-)) salts; the encapsulated anion exchange with different anions (SbF6(-), Tf2N(-), NO3(-), TsO(-)) was studied and the results with NO3(-) and TsO(-) indicate that anions on the cage surfaces affect the encapsulated anion exchange and the occupancy of the cage. PMID:27064122

  17. Influence of montmorillonites exchange capacity on the basal spacing of cation–anion organo-montmorillonites

    SciTech Connect

    Sanqin, Wu; Zepeng, Zhang; Yunhua, Wang; Libing, Liao; Jiansheng, Zhang

    2014-11-15

    Graphical abstract: This picture shows the distribution of organic modifier (CTAB and SDS) in Mt interlayer and the basal spacing changes of Mt modified by CTAB and SDS. Organic modifier molecule in Mt interlayer is more and more orderly. The basal spacing of Mt is from 1.5 nm to 5 nm as modifier added. - Highlights: • The d{sub 001} of Ca-Mt, R-Na-Mt, Na-Mt modified by CTAB and SDS can reach 5 nm. • It is easier to get cation–anion OMt with greater d{sub 001} if CEC is lower. • The organic molecules distribution in cation–anion OMt was analyzed. • The influence mechanism of Ca-Mt CEC on the d{sub 001} was discussed. - Abstract: With cationic and anionic surfactants cetyltrimethylammonium bromide (CTAB) and sodium dodecylsulfonate (SDS) as modifiers, Ca-montmorillonites (Ca-Mt), artificial Na-montmorillonites (R-Na-Mt) and natural Na-montmorillonites (Na-Mt) with different cation exchange capacity (CEC) were modified by solution intercalation method, respectively. Then cation–anion organo-montmorillonites (OMt) were prepared. The influence of CEC on the basal spacing of cation–anion OMt and the influence mechanism were discussed by X-ray diffraction (XRD) and zeta potential testing. The results indicate that the basal spacing of cation–anion OMt is related to CEC. For the same type montmorillonites, the basal spacing of cation–anion OMt decreases with the increase of CEC and it is easier to get cation–anion OMt with greater basal spacing when CEC is lower. Moreover, the CEC of Na-Mt has the greatest influence on the basal spacing of cation–anion OMt.

  18. Anion-exchange resin-based desulfurization process. Final report

    SciTech Connect

    Sheth, A C; Dharmapurikar, R; Strevel, S D

    1994-01-01

    The following investigations were performed: (1) batch mode screening of eleven(11) commercially available resins and selection of three candidate resins for further evaluation in a fixed-bed setup. (2) Process variables study using three candidate resins in the fixed-bed setup and selection of the ``best`` resin for process economics development. (3) Exhaustion efficiency and solution concentration were found to be inversely related necessitating a trade-off between the resin cost versus the cost of evaporation/concentration of ensuing effluents. (4) Higher concentration of the HCO{sub 3}{sup {minus}} form of active sites over less active CO{sub 3}{sup 2{minus}} form of sites in the resin was believed to be the main reason for the observed increase in the equilibrium capacity of the resin at an elevated static CO{sub 2}-pressure. This Increase in capacity was found to level off around 80--120 psig range. The increase in CO{sub 2}-pressure, however, did not appear to affect the overall ion-exchange kinetics. (5) In the fixed-bed mode, the solution concentration was found to affect the equilibrium capacity of candidate resins. Their relationship was well satisfied by the Langmuir type non-linear equilibrium isotherm. Alternatively, the effect of solution concentration on overall ion-exchange kinetics varied from resin to resin. (6) Product inhibition effect on the resin was observed as an initial increase followed by a significant decrease in the resin`s equilibrium capacity for SO{sub 4}{sup 2{minus}} as the HCO{sub 3}{sup {minus}}/SO{sub 4}{sup 2{minus}} molar ratio in the solution was increased from 0 to 1.0. This ratio, however, did not affect the overall ion-exchange kinetics.

  19. Multistep Mechanism of Chloride Translocation in a Strongly Anion-Selective Porin Channel

    PubMed Central

    Zachariae, Ulrich; Helms, Volkhard; Engelhardt, Harald

    2003-01-01

    The strongly anion-selective porin channel Omp32 from the bacterium Delftia acidovorans differs from other unspecific porins by its pronounced selectivity for anions and its particularly small channel cross-section. Multinanosecond molecular dynamics simulations of chloride ion movement in this pore protein suggest that translocated anions interact intimately with the charges of a “basic ladder”, whose dynamics lead the anions in a stepwise manner through the constriction zone of the channel. The ladder-steps comprise the central clustered arginine groups and flanking basic residues at its exoplasmic and periplasmic sides. The computed free energy profile of ion movement in and around the constriction zone shows a corresponding succession of free energy minima and barriers. A number of polar atoms from other amino acids contribute to the coordination of Cl− at certain sites and to its temporary immobilization in the channel. A special binding site occurs at the transition of the constriction zone to the periplasmic funnel, binding the chloride ion over significant lengths of time. The results from our MD study offer a possible explanation for the nonlinear conductance properties and unusual salt-dependent characteristics of Omp32 observed earlier in experimental measurements. PMID:12885642

  20. Hydrophilic Strong Anion Exchange (hSAX) Chromatography for Highly Orthogonal Peptide Separation of Complex Proteomes

    PubMed Central

    2013-01-01

    Due to its compatibility and orthogonality to reversed phase (RP) liquid chromatography (LC) separation, ion exchange chromatography, and mainly strong cation exchange (SCX), has often been the first choice in multidimensional LC experiments in proteomics. Here, we have tested the ability of three strong anion exchanger (SAX) columns differing in their hydrophobicity to fractionate RAW264.7 macrophage cell lysate. IonPac AS24, a strong anion exchange material with ultralow hydrophobicity, demonstrated to be superior to other materials by fractionation and separation of tryptic peptides from both a mixture of 6 proteins as well as mouse cell lysate. The chromatography displayed very high orthogonality and high robustness depending on the hydrophilicity of column chemistry, which we termed hydrophilic strong anion exchange (hSAX). Mass spectrometry analysis of 34 SAX fractions from RAW264.7 macrophage cell lysate digest resulted in an identification of 9469 unique proteins and 126318 distinct peptides in one week of instrument time. Moreover, when compared to an optimized high pH/low pH RP separation approach, the method presented here raised the identification of proteins and peptides by 10 and 28%, respectively. This novel hSAX approach provides robust, reproducible, and highly orthogonal separation of complex protein digest samples for deep coverage proteome analysis. PMID:23294059

  1. Tuning the Optical Properties of Cesium Lead Halide Perovskite Nanocrystals by Anion Exchange Reactions

    PubMed Central

    2015-01-01

    We demonstrate that, via controlled anion exchange reactions using a range of different halide precursors, we can finely tune the chemical composition and the optical properties of presynthesized colloidal cesium lead halide perovskite nanocrystals (NCs), from green emitting CsPbBr3 to bright emitters in any other region of the visible spectrum, and back, by displacement of Cl– or I– ions and reinsertion of Br– ions. This approach gives access to perovskite semiconductor NCs with both structural and optical qualities comparable to those of directly synthesized NCs. We also show that anion exchange is a dynamic process that takes place in solution between NCs. Therefore, by mixing solutions containing perovskite NCs emitting in different spectral ranges (due to different halide compositions) their mutual fast exchange dynamics leads to homogenization in their composition, resulting in NCs emitting in a narrow spectral region that is intermediate between those of the parent nanoparticles. PMID:26214734

  2. Tuning the Optical Properties of Cesium Lead Halide Perovskite Nanocrystals by Anion Exchange Reactions.

    PubMed

    Akkerman, Quinten A; D'Innocenzo, Valerio; Accornero, Sara; Scarpellini, Alice; Petrozza, Annamaria; Prato, Mirko; Manna, Liberato

    2015-08-19

    We demonstrate that, via controlled anion exchange reactions using a range of different halide precursors, we can finely tune the chemical composition and the optical properties of presynthesized colloidal cesium lead halide perovskite nanocrystals (NCs), from green emitting CsPbBr3 to bright emitters in any other region of the visible spectrum, and back, by displacement of Cl(-) or I(-) ions and reinsertion of Br(-) ions. This approach gives access to perovskite semiconductor NCs with both structural and optical qualities comparable to those of directly synthesized NCs. We also show that anion exchange is a dynamic process that takes place in solution between NCs. Therefore, by mixing solutions containing perovskite NCs emitting in different spectral ranges (due to different halide compositions) their mutual fast exchange dynamics leads to homogenization in their composition, resulting in NCs emitting in a narrow spectral region that is intermediate between those of the parent nanoparticles. PMID:26214734

  3. Donnan dialysis of transition metal ions using anion exchange membrane modified with Xylenol Orange

    SciTech Connect

    Sawicka, B.; Brajter, K.; Trojanowicz, M.; Kado, B. )

    1991-01-01

    A chelating ion-exchange membrane was obtained by modification of a PTFE-based anion-exchange membrane with Xylenol Orange. Its utility for dialysis of Cu(II), Ni(II), Mn(II), and Zn(II) was investigated by using receiver solutions without and with iminodiacetate. 1,2-diaminocyclohexanetetraacetic acid, and tetraethylenepentamine. In comparison to commercial PTFE cation-exchange membranes, modified chelating membranes exhibit for the metal ions investigated a larger differentiation of retention in the membrane phase and transport-to-receiver solution depending on the modifier used and the composition of the receiver solution.

  4. Anion-exchangeable layered materials based on rare-earth phosphors: unique combination of rare-earth host and exchangeable anions.

    PubMed

    Geng, Fengxia; Ma, Renzhi; Sasaki, Takayoshi

    2010-09-21

    Layered materials, three-dimensional crystals built from stacking two-dimensional components, are attracting intense interest because of their structural anisotropy and the fascinating properties that result. However, the range of such layered materials that can exchange anions is quite small. Continuing efforts have been underway to identify a new class of anion-exchangeable materials. One major goal is the incorporation of rare-earth elements within the host because researchers expect that the marriage of rare-earth skeleton host and the exchangeable species within the interlayer will open up new avenues both for the assembly of layered materials and for the understanding of rare-earth element chemistry. Such lanthanide layered solids have industrial potential. These materials are also of academic importance, serving as an ideal model for studying the cationic size effect on structure stability associated with lanthanide contraction. In this Account, we present the work done by ourselves and others on this novel class of materials. We examine the following four subtopics regarding these layered anionic materials: (1) synthesis strategy and composition diversity, (2) structural features, (3) structure stability with relative humidity, and (4) applications. These materials can be synthesized either by hydrothermal reactions or by homogeneous precipitation, and a variety of anions can be intercalated into the gallery. Although only cations with a suitable size can form the layered structure, the possible range is wide, from early to late lanthanides. We illustrate the effect of lanthanide contraction on properties including morphology, lattice dimensions, and coordination numbers. Because each lanthanide metal ion coordinates water molecules, and the water molecules point directly into the gallery space, this feature plays a critical role in stabilizing the layered structure. In the 9-fold monocapped square antiprism structure, the humidity-triggered transition

  5. Preparation, Characterization and Anion Exchange Properties of Polypyrrole/Carbon Nanotube Nanocomposite

    SciTech Connect

    Cui, Xiaoli; Engelhard, Mark H.; Lin, Yuehe

    2006-02-01

    In this study, polypyrrole (PPy) thin film was electrodeposited on carbon nanotube (CNT) backbones by applying a constant deposition potential in solution with 0.1 M pyrrole with different electrolytes such as NaCl, NaNO3, or NaClO4. The hybrid films were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and cyclic voltammetry. SEM images revealed the nanostructrure of PPy film generated on CNTs surface. The electrochemical and anion exchange properties of PPy-CNT composite film have been investigated. Nanostructured composite thin films of polypyrrole/CNTs were studied by cyclic voltammetry between 0.4 and -0.8 V in aqueous solution to evaluate their cycling stability and capacity for electrically switched anion exchange. It is found that the PPy/CNTs nanocomposites can improve the anion exchange capacity and stability of the PPy-CNTs composite film, which may be attributed to the nanostructure of the polypyrrole film, which offer the high aspect ratio of the film and ease of diffusion of anions in the nanostructured film, and the interaction between CNTs and PPy.

  6. Reactive oxygen species accelerate degradation of anion exchange membranes based on polyphenylene oxide in alkaline environments.

    PubMed

    Parrondo, Javier; Wang, Zhongyang; Jung, Min-Suk J; Ramani, Vijay

    2016-07-20

    Anion exchange membranes (AEM) based on polyphenylene oxide (PPO) suffered quaternary-ammonium-cation-site degradation in alkaline environments. Surprisingly, the degradation rate was considerably faster in the presence of molecular oxygen. We postulated that the AEM cation-site catalyzes the reduction of dioxygen by hydroxide ions to yield the superoxide anion radical and the highly reactive hydroxyl free radical. We substantiated our hypothesis by using a phosphorous-containing spin trap (5-diisopropoxy-phosphoryl-5-methyl-1-pyrroline-N-oxide) to detect the adducts for both free radicals in situ using (31)P-NMR spectroscopy. PMID:27381009

  7. Single-channel analysis of the anion channel-forming protein from the plant pathogenic bacterium Clavibacter michiganense ssp. nebraskense

    PubMed Central

    Schürholz, Theo; Dloczik, Larissa; Neumann, Eberhard

    1993-01-01

    The anion channel protein from Clavibacter michiganense ssp. nebraskense (Schürholz, Th. et al. 1991, J. Membrane Biol. 123: 1-8) was analyzed at different concentrations of KCl and KF. At 0.8 M KCl the conductance G(Vm) increases exponentially from 21 pS at 50 mV up to 53 pS at Vm = 200 mV, 20°C. The concentration dependence of G(Vm) corresponds to a Michaelis-Menten type saturation function at all membrane voltage values applied (0-200 mV). The anion concentration K0.5, where G(Vm) has its half-maximum value, increases from 0.12 M at 50 mV to 0.24 M at 175 mV for channels in a soybean phospholipid bilayer. The voltage dependence of the single channel conductance, which is different for charged and neutral lipid bilayers, can be described either by a two-state flicker (2SF) model and the Nernst-Planck continuum theory, or by a two barrier, one-site (2B1S) model with asymmetric barriers. The increase in the number of open channels after a voltage jump from 50 mV to 150 mV has a time constant of 0.8 s. The changes of the single-channel conductance are much faster (<1 ms). The electric part of the gating process is characterized by the (reversible) molar electrical work ΔGθel = ρZgFVm ≈ -1.3 RT, which corresponds to the movement of one charge of the gating charge number ǀZgǀ = 1 across the fraction ρ = ΔVm/Vm = 0.15 of the membrane voltage Vm = 200 mV. Unlike with chloride, the single channel conductance of fluoride has a maximum at about 150 mV in the presence of the buffer PIPES (≥5 mM, pH 6.8) with K0.5 ≈ 1 M. It is shown that the decrease in conductance is due to a blocking of the channel by the PIPES anion. In summary, the results indicate that the anion transport by the Clavibacter anion channel (CAC) does not require a voltage dependent conformation change of the CAC. PMID:19431871

  8. Guard cell SLAC1-type anion channels mediate flagellin-induced stomatal closure.

    PubMed

    Guzel Deger, Aysin; Scherzer, Sönke; Nuhkat, Maris; Kedzierska, Justyna; Kollist, Hannes; Brosché, Mikael; Unyayar, Serpil; Boudsocq, Marie; Hedrich, Rainer; Roelfsema, M Rob G

    2015-10-01

    During infection plants recognize microbe-associated molecular patterns (MAMPs), and this leads to stomatal closure. This study analyzes the molecular mechanisms underlying this MAMP response and its interrelation with ABA signaling. Stomata in intact Arabidopsis thaliana plants were stimulated with the bacterial MAMP flg22, or the stress hormone ABA, by using the noninvasive nanoinfusion technique. Intracellular double-barreled microelectrodes were applied to measure the activity of plasma membrane ion channels. Flg22 induced rapid stomatal closure and stimulated the SLAC1 and SLAH3 anion channels in guard cells. Loss of both channels resulted in cells that lacked flg22-induced anion channel activity and stomata that did not close in response to flg22 or ABA. Rapid flg22-dependent stomatal closure was impaired in plants that were flagellin receptor (FLS2)-deficient, as well as in the ost1-2 (Open Stomata 1) mutant, which lacks a key ABA-signaling protein kinase. By contrast, stomata of the ABA protein phosphatase mutant abi1-1 (ABscisic acid Insensitive 1) remained flg22-responsive. These data suggest that the initial steps in flg22 and ABA signaling are different, but that the pathways merge at the level of OST1 and lead to activation of SLAC1 and SLAH3 anion channels. PMID:25932909

  9. Integrating tunable anion exchange with reverse osmosis for enhanced recovery during inland brackish water desalination.

    PubMed

    Smith, Ryan C; SenGupta, Arup K

    2015-05-01

    For inland brackish water desalination by reverse osmosis or RO, concentrate or reject disposal poses a major challenge. However, enhanced recovery and consequent reduction in the reject volume using RO processes is limited by the solubility of ions present in the feedwater. One of the most common and stubborn precipitate formed during desalination is calcium sulfate. Reducing or eliminating the presence of sulfate would allow the process to operate at higher recoveries without threat to membrane scaling. In this research, this goal is accomplished by using an appropriate mixture of self-regenerating anion exchange resins that selectively remove and replace sulfate by chloride prior to the RO unit. Most importantly, the mixed bed of anion exchange resins is self-regenerated with the reject brine from the RO process, thus requiring no addition of external chemicals. The current work demonstrates the reversibility of the hybrid ion exchange and RO (HIX-RO) process with 80% recovery for a brackish water composition representative of groundwater in San Joaquin Valley in California containing approximately 5200 mg/L of total dissolved solids or TDS. Consequently, the reject volume can be reduced by 50% without the threat of sulfate scaling and use of antiscaling chemicals can be eliminated altogether. By appropriately designing or tuning the mixed bed of anion exchange resins, the process can be extended to nearly any composition of brackish water for enhanced recovery and consequent reduction in the reject volume. PMID:25839209

  10. Preparation of agricultural residue anion exchangers and its nitrate maximum adsorption capacity.

    PubMed

    Orlando, U S; Baes, A U; Nishijima, W; Okada, M

    2002-09-01

    Anion exchangers were prepared from different agricultural residues (AR) after reaction with epichlorohydrin and dimethylamine in the presence of pyridine and N,N-dimethylformamide (EDM method). Agricultural residues anion exchangers (AR-AE) produced by the EDM method were inexpensive and showed almost the same NO3- removal capacities as Amberlite IRA-900. AR-AE produced from AR with higher hemicelluloses, lignin, ash and extractive contents resulted in the lower yields. Sugarcane bagasse with the highest alpha-cellulose contents of 51.2% had the highest yield (225%) and lowest preparation cost. The highest maximum adsorption capacity (Qmax) for nitrate was obtained from rice hull (1.21 mmol g(-1)) and pine bark natural exchangers (1.06 mmol g(-1)). No correlation was found between Qmax and alpha-cellulose content in the original AR. AR-AE produced from different AR demonstrated comparable Qmax due to the removal of non-active compounds such as extractives, lignin and hemicelluloses from AR during the preparation process. Similar preparation from pure cellulose and pure alkaline lignin demonstrated that the EDM method could not produce anion exchangers from pure lignin due to its solubilization after the reaction with epichlorohydrin. PMID:12227509

  11. TMEM16F (Anoctamin 6), an anion channel of delayed Ca2+ activation

    PubMed Central

    Grubb, Søren; Poulsen, Kristian A.; Juul, Christian Ammitzbøll; Kyed, Tania; Klausen, Thomas K.

    2013-01-01

    Members of the TMEM16 (Anoctamin) family of membrane proteins have been shown to be essential constituents of the Ca2+-activated Cl− channel (CaCC) in many cell types. In this study, we have investigated the electrophysiological properties of mouse TMEM16F. Heterologous expression of TMEM16F in HEK293 cells resulted in plasma membrane localization and an outwardly rectifying ICl,Ca that was activated with a delay of several minutes. Furthermore, a significant Na+ current was activated, and the two permeabilities were correlated according to PNa = 0.3 PCl. The current showed an EC50 of 100 µM intracellular free Ca2+ concentration and an Eisenman type 1 anion selectivity sequence of PSCN > PI > PBr > PCl > PAsp. The mTMEM16F-associated ICl,Ca was abolished in one mutant of the putative pore region (R592E) but retained in two other mutants (K616E and R636E). The mutant K616E had a lower relative permeability to iodide, and the mutant R636E had an altered anion selectivity sequence (PSCN = PI = PBr = PCl > PAsp). Our data provide evidence that TMEM16F constitutes a Ca2+-activated anion channel or a pore-forming subunit of an anion channel with properties distinct from TMEM16A. PMID:23630341

  12. Interactions between permeant and blocking anions inside the CFTR chloride channel pore.

    PubMed

    Linsdell, Paul

    2015-07-01

    Binding of cytoplasmic anionic open channel blockers within the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel is antagonized by extracellular Cl(-). In the present work, patch clamp recording was used to investigate the interaction between extracellular Cl(-) (and other anions) and cytoplasmic Pt(NO2)4(2-) ions inside the CFTR channel pore. In constitutively open (E1371Q-CFTR) channels, these different anions bind to two separate sites, located in the outer and inner vestibules of the pore respectively, in a mutually antagonistic fashion. A mutation in the inner vestibule (I344K) that greatly increased Pt(NO2)4(2-) binding affinity also greatly strengthened antagonistic Cl(-):blocker interactions as well as the voltage-dependence of block. Quantitative analysis of ion binding affinity suggested that the I344K mutation strengthened interactions not only with intracellular Pt(NO2)4(2-) ions but also with extracellular Cl(-), and that altered blocker Cl(-)- and voltage-dependence were due to the introduction of a novel type of antagonistic ion:ion interaction inside the pore that was independent of Cl(-) binding in the outer vestibule. It is proposed that this mutation alters the arrangement of anion binding sites inside the pore, allowing both Cl(-) and Pt(NO2)4(2-) to bind concurrently within the inner vestibule in a strongly mutually antagonistic fashion. However, the I344K mutation does not increase single channel conductance following disruption of Cl(-) binding in the outer vestibule in R334Q channels. Implications for the arrangement of ion binding sites in the pore, and their functional consequences for blocker binding and for rapid Cl(-) permeation, are discussed. PMID:25892339

  13. Ca2+ and nucleotide dependent regulation of voltage dependent anion channels in the plasma membrane of guard cells.

    PubMed Central

    Hedrich, R; Busch, H; Raschke, K

    1990-01-01

    Using the patch-clamp technique we discovered that the voltage dependent anion channels in the plasma membrane of guard cells are activated by a rise in cytoplasmic Ca2+ in the presence of nucleotides. Upon activation, these anion channels catalyse anion currents 10-20 times higher than in the inactivated state, thus shifting the plasma membrane from a K+ conducting state to an anion conducting state. Prolonged stimulation by depolarizing voltages results in the inactivation of the anion current (t1/2 = 10-12 s). We suggest that activation of the anion channel by Ca2+ and nucleotides is a key event in the regulation of salt efflux from guard cells during stomatal closure. PMID:1701140

  14. Investigation of platinum(IV) ions sorption on some anion exchangers by using photoacoustic and DRS methods

    NASA Astrophysics Data System (ADS)

    Wójcik, G.; Pasieczna, S.; Hubicki, Z.; Ryczkowski, J.

    2006-11-01

    The high cost and increasing demand have prompted the recovery of platinum from low-grade ores and spent catalysts. Platinum exist in chloride solutions in the anionic form, therefore anion-exchanging is a better method than cation exchanging for sorption of platinum(IV) ions. Therefore applicability of four anion exchangers Duolite A 30 B, Lewatit MP 62, Lewatit MP 64 and Purolite A 520E were studied. The FT-IR/PAS spectra were recorded by means of a Bio-Rad Excalibur 3000MX spectrometer equipped with photoacoustic detector MTEC300. The DRS (diffuse reflectance spectrometry) spectra of three anion exchangers Lewatit MP 62, Lewatit MP 64 and Purolite A 520E are similar but spectra of anion exchangers Duolite A 30B is different. The differences in spectra can be result from skeletons of anion exchangers. Recorded FT-IR/PAS spectra allow to distinguish the differences between applied anion exchangers before and after sorption of platinum(IV) ions. In all spectra the biggest differences could be noticed in the OH and CH{2} stretching region.

  15. Determinants of Anion Permeation in the Second Transmembrane Domain of the Mouse Bestrophin-2 Chloride Channel

    PubMed Central

    Qu, Zhiqiang; Hartzell, Criss

    2004-01-01

    Bestrophins have been proposed to constitute a new family of Cl channels that are activated by cytosolic Ca. We showed previously that mutation of serine-79 to cysteine in mouse bestrophin-2 (mBest2) altered the relative permeability and conductance to SCN. In this paper, we have overexpressed various mutant constructs of mBest2 in HEK-293 cells to explore the contributions to anion selectivity of serine-79 and other amino acids (V78, F80, G83, F84, V86, and T87) located in the putative second transmembrane domain (TMD2). Residues selected for mutagenesis were distributed throughout TMD2, but mutations at all positions changed the selectivity. The effects on selectivity were rather modest. Replacement of residues 78, 79, 80, 83, 84, 86, or 87 with cysteine had similar effects: the permeability of the channel to SCN relative to Cl (PSCN/PCl) was decreased three- to fourfold and the relative SCN conductance (GSCN/GCl) was increased five- to tenfold. Side chains at positions 78 and 80 appeared to be situated close to the permeant anion, because the electrostatic charge at these positions affected permeation in specific ways. The effects of charged sulfhydryl-reactive MTS reagents were the opposite in the V78C and F80C mutants and the effects were partially mimicked by substitution of F80 with charged amino acids. In S79T, switching from Cl to SCN caused slow changes in GSCN/GCl (τ = 16.6 s), suggesting that SCN binding to the channel altered channel gating as well as conductance. The data in this paper and other data support a model in which TMD2 plays an important role in forming the bestrophin pore. We suggest that the major determinant in anion permeation involves partitioning of the permeant anion into an aqueous pore whose structural features are rather flexible. Furthermore, anion permeation and gating may be linked. PMID:15452198

  16. Ca(2+)-activated anion channels and membrane depolarizations induced by blue light and cold in Arabidopsis seedlings

    NASA Technical Reports Server (NTRS)

    Lewis, B. D.; Karlin-Neumann, G.; Davis, R. W.; Spalding, E. P.; Evans, M. L. (Principal Investigator)

    1997-01-01

    The activation of an anion channel in the plasma membrane of Arabidopsis thaliana hypocotyls by blue light (BL) is believed to be a signal-transducing event leading to growth inhibition. Here we report that the open probability of this particular anion channel depends on cytoplasmic Ca2+ ([Ca2+]cyt) within the concentration range of 1 to 10 microM, raising the possibility that BL activates the anion channel by increasing [Ca2+]cyt. Arabidopsis seedlings cytoplasmically expressing aequorin were generated to test this possibility. Aequorin luminescence did not increase during or after BL, providing evidence that Ca2+ does not play a second-messenger role in the activation of anion channels. However, cold shock simultaneously triggered a large increase in [Ca2+]cyt and a 110-mV transient depolarization of the plasma membrane. A blocker of the anion channel, 5-nitro-2-(3-phenylpropylamino)-benzoic acid, blocked 61% of the cold-induced depolarization without affecting the increase in [Ca2+]cyt. These data led us to propose that cold shock opens Ca2+ channels at the plasma membrane, allowing an inward, depolarizing Ca2+ current. The resulting large increase in [Ca2+]cyt activates the anion channel, which further depolarizes the membrane. Although an increase in [Ca2+]cyt may activate anion channels in response to cold, it appears that BL does so via a Ca(2+)-independent pathway.

  17. Oxyanion sorption and surface anion exchange by surfactant-modified clay minerals

    SciTech Connect

    Li, Z.

    1999-10-01

    In this study the sorption of nitrate (NO{sub 2}{sup {minus}}) and chromate (CrO{sub 4}{sup 2{minus}}) from aqueous solution by surfactant-modified clay minerals was investigated. Both the sorption and desorption of oxyanions were found to follow a Langmuir sorption isotherm. In general, the sorption affinity is higher for chromate than for nitrate, reflecting that the interaction between the divalent anions and the surfactant bilayer is stronger than that between the monovalent anions and the surfactant bilayer. Surfactant-modified kaolinite has a higher sorption capacity for chromate. The sorption capacities for chromate and nitrate are equal for surfactant-modified illite while the sorption capacity for nitrate is higher for surfactant-modified smectite. Desorption by water revealed that chromate sorption was irreversible, while nitrate sorption was slightly reversible. In a mixed solution system, nitrate and chromate compete for the same sorption sites, resulting in a decrease in sorption capacity for each anion. Stoichiometric counterion desorption due to chromate and/or nitrate sorption further confirms that sorption of oxyanions by surfactant-modified clay minerals was due to surface anion exchange. The selectivity coefficients were higher for chromate to replace bromide than for nitrate to replace bromide for surfactant-modified kaolinite, but lower when surfactant-modified illite and smectite were the anion exchangers. The results indicate that surfactant-modified clay minerals are effective sorbents to remove anionic contaminants from water. However, the types of clay minerals should be correctly selected to maximize the contaminant removal efficiency.

  18. Chromatographic evaluation of reversed-phase/anion-exchange/cation-exchange trimodal stationary phases prepared by electrostatically driven self-assembly process.

    PubMed

    Liu, Xiaodong; Pohl, Christopher; Woodruff, Andrew; Chen, Jinhua

    2011-06-01

    This work describes chromatographic properties of reversed-phase/cation-exchange/anion-exchange trimodal stationary phases. These stationary phases were based on high-purity porous spherical silica particles coated with nano-polymer beads using an electrostatically driven self-assembly process. The inner-pore area of the material was modified covalently with an organic layer that provided both reversed-phase and anion-exchange properties while the outer surface was coated with nano-sized polymer beads with strong cation-exchange characteristics. This design ensured spatial separation of the anion-exchange and the cation-exchange regions, and allowed reversed-phase, anion-exchange and cation-exchange retention mechanisms to function simultaneously. Chromatographic evaluation of ions and small molecules suggested that retention of ionic analytes was influenced by the ionic strength, pH, and mobile phase organic solvent content, and governed by both ion-exchange and hydrophobic interactions. Meanwhile, neutral analytes were retained by hydrophobic interaction and was mainly affected by mobile phase organic solvent content. Depending on the specific application, selectivity could be optimized by adjusting the anion-exchange/cation-exchange capacity ratio (selectivity), which was achieved experimentally by using porous silica particles with different surface areas. PMID:21530974

  19. Sensitivity of the plant vacuolar malate channel to pH, Ca2+ and anion-channel blockers.

    PubMed

    Pantoja, O; Smith, J A C

    2002-03-01

    The organic anion malate is accumulated in the central vacuole of most plant cells. Malate has several important roles in plant vacuoles, such as the maintenance of charge balance and pH regulation, as an osmolyte involved in the generation of cell turgor, and as a storage form of CO2. Transport of malate across the vacuolar membrane is important for the regulation of cytoplasmic pH and the control of cellular metabolism, particularly in plants showing crassulacean acid metabolism (CAM), in which large fluxes of malate occur during the day/night cycle. By applying the patch-clamp technique, in the whole-vacuole configuration, to isolated vacuoles from leaf mesophyll cells of the CAM plant Kalanchoë daigremontiana, we studied the regulation of the vacuolar malate channel by pH and Ca2+, as well as its sensitivity to anion-channel blockers. Malate currents were found to be insensitive to Ca2+ on the cytoplasmic side of the membrane over a range from approximately 10(-8) M to 10(-4) M. In contrast, decreasing cytoplasmic pH below 7.5 had a significant modulatory effect on channel activity, reducing malate currents by 40%, whereas increasing cytoplasmic pH above 7.5 resulted in no change in current. Several known Cl?-channel blockers inhibited the vacuolar malate currents: niflumic acid and indanoyloxyacetic acid (IAA-94) proved to be the most effective inhibitors, exerting half-maximal effects at concentrations of approximately 20 mM, suggesting that the plant vacuolar malate channel may share certain similarities with other classes of known anion channels. PMID:11891587

  20. Genetic demonstration that the plasma membrane maxianion channel and voltage-dependent anion channels are unrelated proteins.

    PubMed

    Sabirov, Ravshan Z; Sheiko, Tatiana; Liu, Hongtao; Deng, Defeng; Okada, Yasunobu; Craigen, William J

    2006-01-27

    The maxianion channel is widely expressed in many cell types, where it fulfills a general physiological function as an ATP-conductive gate for cell-to-cell purinergic signaling. Establishing the molecular identity of this channel is crucial to understanding the mechanisms of regulated ATP release. A mitochondrial porin (voltage-dependent anion channel (VDAC)) located in the plasma membrane has long been considered as the molecule underlying the maxianion channel activity, based upon similarities in the biophysical properties of these two channels and the purported presence of VDAC protein in the plasma membrane. We have deleted each of the three genes encoding the VDAC isoforms individually and collectively and demonstrate that maxianion channel (approximately 400 picosiemens) activity in VDAC-deficient mouse fibroblasts is unaltered. The channel activity is similar in VDAC1/VDAC3-double-deficient cells and in double-deficient cells with the VDAC2 protein depleted by RNA interference. VDAC deletion slightly down-regulated, but never abolished, the swelling-induced ATP release. The lack of correlation between VDAC protein expression and maxianion channel activity strongly argues against the long held hypothesis of plasmalemmal VDAC being the maxianion channel. PMID:16291750

  1. Enhanced removal of fluoride by polystyrene anion exchanger supported hydrous zirconium oxide nanoparticles.

    PubMed

    Pan, Bingcai; Xu, Jingsheng; Wu, Bing; Li, Zhigang; Liu, Xitong

    2013-08-20

    Here we fabricated a novel nanocomposite HZO-201, an encapsulated nanosized hydrous zirconium oxide (HZO) within a commercial porous polystyrene anion exchanger D201, for highly efficient defluoridation of water. HZO-201 exhibited much higher preference than activated alumina and D201 toward fluoride removal when competing anions (chloride, sulfate, nitrate, and bicarbonate) coexisted at relatively high levels. Fixed column adsorption indicated that the effective treatable volume of water with HZO-201 was about 7-14 times as much as with D201 irrespective of whether synthetic solution or groundwater was the feeding solution. In addition, HZO-201 could treat >3000 BV of the acidic effluent (around 3.5 mg F(-)/L) per run at pH 3.5, compared to only ∼4 BV with D201. The exhausted HZO-201 could be regenerated by NaOH solution for repeated use without any significant capacity loss. Such attractive performance of HZO-201 resulted from its specific hybrid structure, that is, the host anion exchanger D201 favors the preconcentration of fluoride ions inside the polymer based on the Donnan principle, and the encapsulated nanosized HZO exhibits preferable sequestration of fluoride through specific interaction, as further demonstrated by XPS spectra. The influence of solution pH, competitive anions, and contact time was also examined. The results suggested that HZO-201 has a great potential in efficient defluoridation of groundwater and acidic mine drainage. PMID:23909842

  2. Incorporation of phthalocyanines by cationic and anionic clays via ion exchange and direct synthesis

    SciTech Connect

    Carrado, K.A.; Botto, R.E.; Winans, R.E. ); Forman, J.E. )

    1993-04-01

    Phthalocyanines (Pc) and metallophthalocyanines were incorporated into the galleries of anionic and cationic clays via ion exchange and in situ crystallization of the synthetic clay layers. Intercalation compounds between the layered magnesium silicate clay hectorite and cationic phthalocyanines were directly prepared by refluxing for 2 days aqueous solutions of silica sol, magnesium hydroxide, lithium flouride, and either alcian blue dyes (Cu(II)Pc) or 15-crown-5 tetra-substituted phthalocyanine (15C5Pc). The CuPc dyes are tetrapositively charged through peripheral quaternary ammonium groups, whereas the 15C5Pc is electrically neutral. Anionic clays prepared by hydrolysis of mixed solutions of aluminum nitrate, magnesium nitrate, and copper(II) phthalocyaninetetrasulfonic acid, tetrasodium salt (CuPcTs) in sodium hydroxide resulted in crystallization of an intercalation compound between a layered double hydroxide (LDH) and this anionic Pc. The material prepared by ion exchange of CuPcTs into a wet, freshly prepared LDH was superior in crystallinity. The phthalocyanines are oriented parallel to cationic hectorite clay layers (gallery heights 4.5-6.5[angstrom]) and perpendicular to anionic layered double hydroxide clay layers (gallery height 18,2[angstrom]) in correlation with their hosts' respective layer charge densities. 32 refs., 4 figs., 2 tabs.

  3. Selective chromatographic fractionation of catechol estrogens on anion exchangers in borate form.

    PubMed

    Fotsis, T; Heikkinen, R

    1983-03-01

    The borate form of anion exchangers has been investigated for its utility in the field of estrogen analysis. The borate form of a weak (DEAE-Sephadex A-25) and a strong (QAE-Sephadex A-25) anion exchanger was easily prepared by appropriate washing of the gels, without the need of time consuming immobilization techniques. Estrogens with vicinal cis-hydroxyls were strongly retained in both gels through formation of borate complexes and readily separated from estrogens not possessing such groups. Moreover, borate complex formation with the labile o-dihydroxyphenyl moiety of catechol estrogens fully protected them from decomposition during chromatography. Quantitative recovery of catechol estrogens was thereby obtained without use of antioxidants. The borate form of QAE-Sephadex A-25 was capable, in addition, of separating estrogens not possessing vicinal cis-hydroxyls from the corresponding neutral steroids. PMID:6298506

  4. Preparation of anion-exchangeable polymer vesicles through the self-assembly of hyperbranched polymeric ionic liquids.

    PubMed

    Fan, Yujiao; Zhang, Dapeng; Wang, Jie; Jin, Haibao; Zhou, Yongfeng; Yan, Deyue

    2015-04-28

    This work reports the self-assembly of anion-exchangeable vesicles from an amphiphilic hyperbranched polymeric ionic liquid (HBPIL). By a simple one-step anion exchange with methyl orange, the obtained HBPILs could self-assemble into pH-indicative and colorful vesicles in water with color changes directly visible to the naked eye in response to solution pH. In addition, by another step of anion exchange with bovine serum albumin (BSA), the BSA-coated vesicles could also be readily prepared. PMID:25813408

  5. New anion-exchange resins for improved separations of nuclear materials

    SciTech Connect

    Barr, M.E.; Bartsch, R.A.

    1998-06-01

    'The overall objective of this research is to develop a predictive capability which allows the facile design and implementation of multi-functionalized anion-exchange materials which selectively sorb metal complexes of interest from targeted process, waste, and environmental streams. The basic scientific issues addressed are actinide complex speciation along with modeling of the metal complex/functional-site interactions in order to determine optimal binding-site characteristics. The new ion-exchange resins interface the rapidly developing field of ion-specific chelating ligands with robust, commercial ion-exchange technology. Various Focus Areas and Crosscutting Programs have described needs that would be favorably impacted by the new materials: Efficient Separations and Processing; Plutonium; Plumes; Mixed Waste; High-Level Tank Waste. Sites within the DOE complex which would benefit from the improved anion-exchange technology include Hanford, INEL, Los Alamos, Oak Ridge, and Savannah River. As of April 1998, this report summarizes work after 1.6 years of a 3-year project. The authors technical approach combines empirical testing with theoretical modeling (applied in an iterative mode) in order to determine optimal binding-site characteristics. They determine actinide-complex speciation in specific media, then develop models for the metal complex/functional-site interactions Synthesis and evaluation of multi-functionalized extractants and ion-exchange materials that implement key features of the optimized binding site provide feedback to the modeling and design activities. Resin materials which actively facilitate the uptake of actinide complexes from solution should display both improved selectivity and kinetic properties. The implementation of the bifunctionality concept involves N-derivatization of pyridinium units from a base poly(4-vinylpyridine) resin with a second cationic site such that the two anion-exchange sites are linked by spacer arms of varying

  6. Anion Exchange Capacity As a Mechanism for Deep Soil Carbon Storage in Variable Charge Soils

    NASA Astrophysics Data System (ADS)

    Dietzen, C.; James, J. N.; Ciol, M.; Harrison, R. B.

    2014-12-01

    Soil is the most important long-term sink for carbon (C) in terrestrial ecosystems, containing more C than plant biomass and the atmosphere combined. However, soil has historically been under-represented in C cycling literature, especially in regards to information about subsurface (>1.0 m) layers and processes. Previous research has indicated that Andisols with large quantities of noncrystalline, variable-charge minerals, including allophane, imogolite, and ferrihydrite, contain more C both in total and at depth than other soil types in the Pacific Northwest. The electrostatic charge of variable-charge soils depends on pH and is sometimes net positive, particularly in acid conditions, such as those commonly developed under the coniferous forests of the Pacific Northwest. However, even soils with a net negative charge may contain a mixture of negative and positive exchange sites and can hold some nutrient anions through the anion exchange capacity. To increase our understanding of the effects of variable-charge on soil organic matter stabilization, deep sampling is under way at the Fall River Long-Term Soil Productivity Site in western Washington. This site has a deep, well-drained soil with few rocks, which developed from weathered basalt and is classified as an Andisol of the Boistfort Series. Samples have been taken to a depth of 3 m at eight depth intervals. In addition to analyzing total soil C, these soils will be analyzed to determine functional groups present, cation exchange capacity, anion exchange capacity, and non-crystalline mineral content. These data will be analyzed to determine any correlations that may exist between these mineralogical characteristics, total soil C, and types of functional groups stored at depth. The most abundant organic functional groups, including carboxylic and phenolic groups, are anionic in nature, and soil positive charge may play an important role in binding and stabilizing soil organic matter and sequestering C.

  7. The dynamics of sorption of sulfuric acid by weakly basic polyacrylic anion exchangers

    NASA Astrophysics Data System (ADS)

    Mamchenko, A. V.; Kushnir, T. V.

    2009-05-01

    The nonequilibrium dynamics of sorption of sulfuric acid by free base forms of Amberlite IRA-67 and Lewatite VP.OC.1072 weakly basic anion exchangers is studied. It is established that, in hydrodynamic regimes of filtration, which are typical of OH filters of the first stage of water-desalting plants, the limiting stage of sorption kinetics is inside diffusion. It is concluded that the process is correctly described by an asymptotic solution to the inside-diffusion model of sorption dynamics.

  8. Anion exchange selectivity of surfactant modified clinoptilolite-rich tuff for environmental remediation.

    PubMed

    de Gennaro, Bruno; Catalanotti, Lilia; Bowman, Robert S; Mercurio, Mariano

    2014-09-15

    Lately, the functionalization of industrial minerals with high technological properties, such as natural zeolites, is shaping as a promising approach in environmental sphere. In fact, under the specific conditions, the surface functionalization via adsorption of cationic surfactants reverses the surface charge of the mineral, enabling zeolites to simultaneously interact either with organic contaminants or inorganic anions. This aspect allows zeolites to be used in the remediation of contaminated fluids. The present research shed new light on some still not fully understood aspects concerning exchange kinetics such as anion-exchange mechanisms and selectivity of surface modified minerals. For this purpose the mineralogical characterization and the surface properties evaluation (X Ray Powder Diffraction, chemical analysis, thermal analysis, ECEC and AEC) of a clinoptilolite-rich tuff were performed, and the anion exchange isotherms of the sample, modified with hexadecyltrimethylammonium chloride or bromide (HDTMA-Cl/-Br), were determined. Ion-exchange equilibrium data of uni-uni valent reaction were obtained by solutions containing Br(-), Cl(-), NO3(-) or ClO4(-). Liquid phase was analysed via high performance liquid chromatography. Thermodynamic quantities (Ka and ΔG(0)) were determined and compared with the Hofmeister series. The value of the ECEC, calculated in batch conditions, was about 137 mmol/kg, in good agreement with that evaluated in dynamic conditions, while the AEC data were different for the SMNZ-Br and -Cl samples, amounting to 137 and 106 mmol/kg, respectively, thus indicating a different compactness of the bilayer formed in the two cases. Moreover, the anion isotherm results and the mathematical evaluation of the thermodynamic parameters, demonstrated the good affinity of SMNZ-Br towards chloride, nitrate and perchlorate, and of SMNZ-Cl for nitrate and perchlorate, also endorsing the possibility of using the same thermodynamic approach developed to

  9. Determination of traces of silver in waters by anion exchange and atomic absorption spectrophotometry

    USGS Publications Warehouse

    Chao, T.T.; Fishman, M. J.; Ball, J.W.

    1969-01-01

    A method has been developed for the accurate determination of 0.1-1 ??g of silver per liter of water. The method permits stabilization of silver in water without loss to container walls. Optimum conditions have been established for the complete recovery of silver from water with an anion-exchange column, for quantitative elution of silver from the resin, and for measurement of silver by atomic absorption spectrophotometry after chelation with ammonium pyrrolidine dithiocarbamate and extraction of the chelate with MIBK. Silver in the 1-10 ??g 1 range can be determined by extraction without pre-concentration on an ion-exchange resin. ?? 1969.

  10. Russian studies of the safety of anion exchange in nitric acid

    SciTech Connect

    Hyder, M.L.; Bartenev, S.A.; Lazarev, L.N.

    1997-07-01

    Synthetic ion exchange resins came into use in the Soviet Union in the 1950`s, and domestic anion exchange resins based on quaternary amine groups have long been used in the Russian nuclear industry. These resins are similar to resins used in the West, and include pyridine-based resins, as well as the more conventional aryl polymers with substituted methyl amines. (Slide 1) The sensitivity of these amines to reaction with nitric acid and other oxidants has been a concern in Russia as in the West, and numerous laboratory studies have been conducted on the reactions involved. Several incidents involving pressure or temperature excursions have provided incentives for such studies. (Slide 2) This report briefly summarizes this work. A report by the Russian authors of this paper providing greater detail is to be issued as a U.S. Dept. of Energy document. Additionally, a second report by these authors, describing new studies on anion exchange resin safety, will also be issued as a DOE report. The separation of plutonium, neptunium, etc. from other materials by ion exchange requires rather strong nitric acid (6-8 M). In some systems, such as the processing of {sup 238}Pu, intense ionizing radiation may also be present during ion exchange separation. As a result, it is necessary to consider not only thermal hydrolysis and oxidation and their effects on the resin, but also radiolysis. All of these were investigated in the Russian studies.

  11. Tailor-made anion-exchange membranes for salinity gradient power generation using reverse electrodialysis.

    PubMed

    Guler, Enver; Zhang, Yali; Saakes, Michel; Nijmeijer, Kitty

    2012-11-01

    Reverse electrodialysis (RED) or blue energy is a non-polluting, sustainable technology for generating power from the mixing of solutions with different salinity, that is, seawater and river water. A concentrated salt solution (e.g., seawater) and a diluted salt solution (e.g., river water) are brought into contact through an alternating series of polymeric anion-exchange membranes (AEMs) and cation-exchange membranes (CEMs), which are either selective for anions or cations. Currently available ion-exchange membranes are not optimized for RED, whereas successful RED operation notably depends on the used ion-exchange membranes. We designed such ion-exchange membranes and for the first time we show the performance of tailor-made membranes in RED. More specifically, we focus on the development of AEMs because these are much more complex to prepare. Herein we propose a safe and more environmentally friendly method and use halogenated polyethers, such as polyepichlorohydrin (PECH) as the starting material. A tertiary diamine (1,4-diazabicyclo[2.2.2]octane, DABCO) was used to introduce the ion-exchange groups by amination and for simultaneous cross-linking of the polymer membrane. Area resistances of the series of membranes ranged from 0.82 to 2.05 Ω cm² and permselectivities from 87 to 90 %. For the first time we showed that tailor-made ion-exchange membranes can be applied in RED. Depending on the properties and especially membrane thickness, application of these membranes in RED resulted in a high power density of 1.27 W m⁻², which exceeds the power output obtained with the commercially available AMX membranes. This shows the potential of the design of ion-exchange membranes for a viable blue energy process. PMID:23109486

  12. Retention behavior of C1-C6 aliphatic monoamines on anion-exchange and polymethacrylate resins with heptylamine as eluent.

    PubMed

    Ohta, Kazutoku; Ohashi, Masayoshi; Jin, Ji-Ye; Takeuchi, Toyohide; Fujimoto, Chuzo; Choi, Seong-Ho; Ryoo, Jae Jeong; Lee, Kwang-Pill

    2004-06-11

    Retention behavior of C1-C6, aliphatic monoamines (methylamine, ethylamine, propylamine, butylamine, amylamine and hexylamine) on columns (150 mm x 6 mm i.d.) packed with various anion-exchange resins (styrene-divinylbenzene (PS-DVB) copolymer-based strongly basic anion-exchange resin: TSKgel SAX, polymethacrylate-based strongly basic anion-exchange resin: TSKgel SuperQ-5PW and polymethacrylate-based weakly basic anion-exchange resin: TSKgel DEAE-5PW) and unfunctionized polymethacrylate resins (TSKgel G5000PW and TSKgel G3000PWXL) was investigated with basic solutions (sodium hydroxide and heptylamine) as the eluents. Due to strongly electrostatic repulsion (ion-exclusion effect) between these anion-exchange resins and these amines, peak resolution between these amines on these anion-exchange resin columns was unsatisfactory with both sodium hydroxide and heptylamine as the eluents. In contrast, these polymethacrylate resins were successfully applied as the stationary phases for the separation of these C1-C6 amines with heptylamine as eluent, because of both small hydrophobicity and small cation-exchange ability of these resins. Excellent simultaneous separation, highly sensitive conductimetric detection and symmetrical peaks for these C1-C6 amines were achieved on the TSKgel G3000PWXL column in 35 min with 5 mM heptylamine at pH 11.1 as the eluent. PMID:15250421

  13. CFTR: Ligand Exchange between a Permeant Anion ([Au(CN)2]−) and an Engineered Cysteine (T338C) Blocks the Pore

    PubMed Central

    Serrano, José R.; Liu, Xuehong; Borg, Erik R.; Alexander, Christopher S.; Shaw, C. Frank; Dawson, David C.

    2006-01-01

    Previous attempts to identify residues that line the pore of the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel have utilized cysteine-substituted channels in conjunction with impermeant, thiol-reactive reagents like MTSET+ and MTSES−. We report here that the permeant, pseudohalide anion [Au(CN)2]− can also react with a cysteine engineered into the pore of the CFTR channel. Exposure of Xenopus oocytes expressing the T338C CFTR channel to as little as 100 nM [Au(CN)2]− produced a profound reduction in conductance that was not reversed by washing but was reversed by exposing the oocytes to a competing thiol like DTT (dithiothreitol) and 2-ME (2-mercaptoethanol). In detached, inside out patches single-channel currents were abolished by [Au(CN)2]− and activity was not restored by washing [Au(CN)2]− from the bath. Both single-channel and macroscopic currents were restored, however, by exposing [Au(CN)2]−-blocked channels to excess [CN]−. The results are consistent with the hypothesis that [Au(CN)2]− can participate in a ligand exchange reaction with the cysteine thiolate at 338 such that the mixed-ligand complex, with a charge of −1, blocks the anion conduction pathway. PMID:16766608

  14. New Anion-Exchange Resins for Improved Separations of Nuclear Materials

    SciTech Connect

    Bartsch, Richard A.; Barr, Mary E.

    2001-04-30

    Improved separations of nuclear materials will have a significant impact upon a broad range of DOE activities. DOE-EM Focus Areas and Crosscutting Programs have identified improved methods for the extraction and recovery of radioactive metal ions from process, waste, and environmental waters as critical needs for the coming years. We propose to develop multifunctional anion-exchange resins that facilitate anion uptake by carefully controlling the structure of the anion receptor site. Our new ion-exchange resins interface the field of ion-specific chelating ligands with robust, commercial ion-exchange technology to provide materials which exhibit superior selectivity and kinetics of sorption and desorption. The following Focus Areas and Crosscutting Programs have described needs that would be favorably impacted by the new material: Efficient Separations and Processing - radionuclide removal from aqueous phases; Plutonium - Pu, Am or total alpha removal to meet regulatory requirement s before discharge to the environment; Plumes - U and Tc in groundwater, U, Pu, Am, and Tc in soils; Mixed Waste - radionuclide partitioning; High-Level Tank Waste - actinide and Tc removal from supernatants and/or sludges. The basic scientific issues which need to be addressed are actinide complex speciation along with modeling of metal complex/functional site interactions in order to determine optimal binding-site characteristics. Synthesis of multifunctionalized extractants and ion-exchange materials that implement key features of the optimized binding site, and testing of these materials, will provide feedback to the modeling and design activities. Resin materials which actively facilitate the uptake of actinide complexes from solution should display both improved selectivity and kinetic properties. The long-range implications of this research, however, go far beyond the nuclear complex. This new methodology of ''facilitated uptake'' could revolutionize ion-exchange technology

  15. Mono- and polyprotic buffer systems in anion exchange chromatography of influenza virus particles.

    PubMed

    Vajda, Judith; Weber, Dennis; Stefaniak, Sabine; Hundt, Boris; Rathfelder, Tanja; Müller, Egbert

    2016-05-27

    Different ions typically used in downstream processing of biologicals are evaluated for their potential in anion exchange chromatography of an industrially produced, pandemic influenza H1N1 virus. Capacity, selectivity and recovery are investigated based on single step elution parallel chromatography experiments. The inactivated H1N1 feedstream is produced in Madin-Darby Bovine Kidney cells. Interesting effects are found for sodium phosphate and sodium citrate. Both anions are triprotic kosmotropes. Anion exchange chromatography generally offers high scalability to satisfy sudden demands for vaccines, which may occur in case of an emerging influenza outbreak. Appropriate pH conditions for H1N1 adsorption are determined by Zeta potential measurements. The dynamic binding capacity of a salt tolerant polyamine-type resin is up to 6.4 times greater than the capacity of a grafted Q-type resin. Pseudo-affinity interactions of polyamines with the M2 protein of influenza may contribute to the obtained capacity increase. Both resins achieve greater capacity in sodium phosphate buffer compared to Tris/HCl. A recovery of 67% and DNA clearance close to 100% without DNAse treatment are achieved for the Q-type resin. Recovery of the virus from the salt tolerant resin requires the use of polyprotic acids in the elution buffer. 85% of the DNA and 60% of the proteins can be removed by the salt tolerant resin. The presence of sodium phosphate during anion exchange chromatography seems to support stability of the H1N1 particles in presence of hydrophobic cations. PMID:27130581

  16. Anion channels and the stimulation of anthocyanin accumulation by blue light in Arabidopsis seedlings

    NASA Technical Reports Server (NTRS)

    Noh, B.; Spalding, E. P.; Evans, M. H. (Principal Investigator)

    1998-01-01

    Activation of anion channels by blue light begins within seconds of irradiation in seedlings and is related to the ensuing growth inhibition. 5-Nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB) is a potent, selective, and reversible blocker of these anion channels in Arabidopsis thaliana. Here we show that 20 microM NPPB blocked 72% of the blue-light-induced accumulation of anthocyanin pigments in seedlings. Feeding biosynthetic intermediates to wild-type and tt5 seedlings provided evidence that NPPB prevented blue light from up-regulating one or more steps between and including phenylalanine ammonia lyase and chalcone isomerase. NPPB was found to have no significant effect on the blue-light-induced increase in transcript levels of PAL1, CHS, CHI, or DFR, which are genes that encode anthocyanin-biosynthetic enzymes. Immunoblots revealed that NPPB also did not inhibit the accumulation of the chalcone synthase, chalcone isomerase, or flavanone-3-hydroxylase proteins. This is in contrast to the reduced anthocyanin accumulation displayed by a mutant lacking the HY4 blue-light receptor, as hy4 displayed reduced expression of the above enzymes. Taken together, the data indicate that blue light acting through HY4 leads to an increase in the amount of biosynthetic enzymes but blue light must also act through a separate, anion-channel-dependent system to create a fully functional biosynthetic pathway.

  17. Differential regulation of a CLC anion channel by SPAK kinase ortholog-mediated multisite phosphorylation

    PubMed Central

    Miyazaki, Hiroaki

    2012-01-01

    Shrinkage-induced inhibition of the Caenorhabditis elegans cell volume and cell cycle-dependent CLC anion channel CLH-3b occurs by concomitant phosphorylation of S742 and S747, which are located on a 175 amino acid linker domain between cystathionine-β-synthase 1 (CBS1) and CBS2. Phosphorylation is mediated by the SPAK kinase homolog GCK-3 and is mimicked by substituting serine residues with glutamate. Type 1 serine/threonine protein phosphatases mediate swelling-induced channel dephosphorylation. S742E/S747E double mutant channels are constitutively inactive and cannot be activated by cell swelling. S742E and S747E mutant channels were fully active in the absence of GCK-3 and were inactive when coexpressed with the kinase. Both channels responded to cell volume changes. However, the S747E mutant channel activated and inactivated in response to cell swelling and shrinkage, respectively, much more slowly than either wild-type or S742E mutant channels. Slower activation and inactivation of S747E was not due to altered rates of dephosphorylation or dephosphorylation-dependent conformational changes. GCK-3 binds to the 175 amino acid inter-CBS linker domain. Coexpression of wild-type CLH-3b and GCK-3 with either wild-type or S742E linkers gave rise to similar channel activity and regulation. In contrast, coexpression with the S747E linker greatly enhanced basal channel activity and increased the rate of shrinkage-induced channel inactivation. Our findings suggest the intriguing possibility that the phosphorylation state of S742 in S747E mutant channels modulates GCK-3/channel interaction and hence channel phosphorylation. These results provide a foundation for further detailed studies of the role of multisite phosphorylation in regulating CLH-3b and GCK-3 activity. PMID:22357738

  18. M2 pore mutations convert the glycine receptor channel from being anion- to cation-selective.

    PubMed Central

    Keramidas, A; Moorhouse, A J; French, C R; Schofield, P R; Barry, P H

    2000-01-01

    Three mutations in the M2 transmembrane domains of the chloride-conducting alpha1 homomeric glycine receptor (P250Delta, A251E, and T265V), which normally mediate fast inhibitory neurotransmission, produced a cation-selective channel with P(Cl)/P(Na), = 0.27 (wild-type P(Cl)/P(Na) = 25), a permeability sequence P(Cs) > P(K) > P(Na) > P(Li), an impermeability to Ca(2+), and a reduced glycine sensitivity. Outside-out patch measurements indicated reversed and accentuated rectification with extremely low mean single channel conductances of 3 pS (inward current) and 11 pS (outward current). The three inverse mutations, to those analyzed in this study, have previously been shown to make the alpha7 acetylcholine receptor channel anion-selective, indicating a common location for determinants of charge selectivity of inhibitory and excitatory ligand-gated ion channels. PMID:10866951

  19. Hydration and sorption characteristics of a polyfunctional weak-base anion exchanger after the sorption of vanillin and ethylvanillin

    NASA Astrophysics Data System (ADS)

    Rodionova, D. O.; Voronyuk, I. V.; Eliseeva, T. V.

    2016-07-01

    Features of the sorption of substituted aromatic aldehydes by a weak-base anion exchanger under equilibrium conditions are investigated using vanillin and ethylvanillin as examples. Analysis of the sorption isotherms of carbonyl compounds at different temperatures allows us to calculate the equilibrium characteristics of their sorption and assess the entropy and enthalpy contributions to the energy of the process. Hydration characteristics of the macroporous weak-base anion exchanger before and after the sorption of aromatic aldehydes are compared.

  20. Synthesis and Characterization of Imidazolium Linear Bisphenol Polycarbonate Hydroxides for Anion Exchange Membrane.

    PubMed

    Jang, Hohyoun; Hossain, Md Awlad; Lee, Soonho; Ha, Jaesung; Yoo, Jihoo; Kim, Kyungchul; Kim, Whangi

    2015-11-01

    A novel anion exchange membrane of imidazolium functionalized bisphenol polycarbonate was prepared for application in alkaline fuel cell. Di-imidazolium polycarbonate anionic membrane was synthesized by sequential interfacial polymerization, chloromethylation, substitution with 1-methylimidazole and ion exchange with 1.0 M KOH. Chloromethylation reaction was quantitative to achieve a high content of hydroxide ions. Introduction of conjugated imidazole ring in polymer plays an important role to improve both thermal and chemical stability. Bisphenol polycarbonate is a flexible polymer and shows a good solubility in polar organic solvent. The alkaline imidazolium bisphenol polycarbonate rendered an elevated molecular weight with excellent solubility in polar aprotic solvent. Different levels of substitution and ion exchange were investigated; the resulting membranes showed high ion exchange capacities (IECs) of up to 2.15 mmol g(-1). The imidazolium-functionalized copolymer membranes showed lower water affinity (14.2-42.8% at 30 degrees C) that satisfied an essential criterion for fuel cell application. The chemical structure of the imidazolium functionalized polycarbonate membrane was confirmed by 1H NMR spectroscopy, and also the membrane properties were evaluated by thermogravimetric analysis (TGA) and water uptake (WU), IEC and conductivity assessment. They exhibited hydroxide conductivity above 10(-2) S cm(-1) at room temperature and good chemical stability for up to five days without significant losses of ion conductivity. PMID:26726604

  1. A green approach for preparing anion exchange membrane based on cardo polyetherketone powders

    NASA Astrophysics Data System (ADS)

    Hu, Jue; Zhang, Chengxu; Zhang, Xiaodong; Chen, Longwei; Jiang, Lin; Meng, Yuedong; Wang, Xiangke

    2014-12-01

    Anion exchange membranes (AEMs) have attracted great attention due to their irreplaceable role in platinum-free fuel cell applications. The majority of AEM preparations have been performed in two steps: the grafting of functional groups and quaternization. Here, we adopted a simpler, more eco-friendly approach for the first time to prepare AEMs by atmospheric-pressure plasma-grafting. This approach enables the direct introduction of anion exchange groups (benzyltrimethylammonium groups) into the polymer matrix, overcoming the need for toxic chloromethyl ether and quaternization reagents. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and 1H NMR spectroscopy results demonstrate that benzyltrimethylammonium groups have been successfully grafted into the cardo polyetherketone (PEK-C) matrix. Thermogravimetric analysis reveals that the plasma-grafting technique is a facile and non-destructive method able to improve the thermal stability of the polymer matrix due to the strong preservation of the PEK-C backbone structure and the cross-linking of the grafted side chains. The plasma-grafted PG-NOH membrane, which shows satisfactory alcohol resistance (ethanol permeability of 6.3 × 10-7 cm2 s-1), selectivity (1.2 × 104 S s cm-3), thermal stability (safely used below 130 °C), chemical stability, anion conductivity (7.7 mS cm-1 at 20 °C in deionized water) and mechanical properties is promising for the construction of high-performance fuel cells.

  2. Removal of fluorescent dissolved organic matter in biologically treated textile effluents by NDMP anion exchange process: efficiency and mechanism.

    PubMed

    Li, Wen-Tao; Xu, Zi-Xiao; Shuang, Chen-Dong; Zhou, Qing; Li, Hai-Bo; Li, Ai-Min

    2016-03-01

    The efficiency and mechanism of anion exchange resin Nanda Magnetic Polymer (NDMP) for removal of fluorescent dissolved organic matter in biologically treated textile effluents were studied. The bench-scale experiments showed that as well as activated carbon, anion exchange resin could efficiently remove both aniline-like and humic-like fluorescent components, which can be up to 40 % of dissolved organic matter. The humic-like fluorescent component HS-Em460-Ex3 was more hydrophilic than HS-Em430-Ex2 and contained fewer alkyl chains but more acid groups. As a result, HS-Em460-Ex3 was eliminated more preferentially by NDMP anion exchange. However, compared with adsorption resins, the polarity of fluorescent components had a relatively small effect on the performance of anion exchange resin. The long-term pilot-scale experiments showed that the NDMP anion exchange process could remove approximately 30 % of the chemical oxygen demand and about 90 % of color from the biologically treated textile effluents. Once the issue of waste brine from resin desorption is solved, the NDMP anion exchange process could be a promising alternative for the advanced treatment of textile effluents. PMID:26578375

  3. Molecular physiology and genetics of Na+-independent SLC4 anion exchangers

    PubMed Central

    Alper, Seth L.

    2009-01-01

    Summary Plasmalemmal Cl–/HCO3– exchangers are encoded by the SLC4 and SLC26 gene superfamilies, and function to regulate intracellular pH, [Cl–] and cell volume. The Cl–/HCO3– exchangers of polarized epithelial cells also contribute to transepithelial secretion and reabsorption of acid–base equivalents and Cl–. This review focuses on Na+-independent electroneutral Cl–/HCO3– exchangers of the SLC4 family. Human SLC4A1/AE1 mutations cause the familial erythroid disorders of spherocytic anemia, stomatocytic anemia and ovalocytosis. A largely discrete set of AE1 mutations causes familial distal renal tubular acidosis. The Slc4a2/Ae2–/– mouse dies before weaning with achlorhydria and osteopetrosis. A hypomorphic Ae2–/– mouse survives to exhibit male infertility with defective spermatogenesis and a syndrome resembling primary biliary cirrhosis. A human SLC4A3/AE3 polymorphism is associated with seizure disorder, and the Ae3–/– mouse has increased seizure susceptibility. The transport mechanism of mammalian SLC4/AE polypeptides is that of electroneutral Cl–/anion exchange, but trout erythroid Ae1 also mediates Cl– conductance. Erythroid Ae1 may mediate the DIDS-sensitive Cl– conductance of mammalian erythrocytes, and, with a single missense mutation, can mediate electrogenic SO42–/Cl– exchange. AE1 trafficking in polarized cells is regulated by phosphorylation and by interaction with other proteins. AE2 exhibits isoform-specific patterns of acute inhibition by acidic intracellular pH and independently by acidic extracellular pH. In contrast, AE2 is activated by hypertonicity and, in a pH-independent manner, by ammonium and by hypertonicity. A growing body of structure–function and interaction data, together with emerging information about physiological function and structure, is advancing our understanding of SLC4 anion exchangers. PMID:19448077

  4. Crystallization and preliminary X-ray crystallographic studies of human voltage-dependent anion channel isoform I (HVDAC1)

    PubMed Central

    Meins, Thomas; Vonrhein, Clemens; Zeth, Kornelius

    2008-01-01

    The major channel by which metabolites can pass through the outer mitochondrial membrane is formed by the voltage-dependent anion-channel (VDAC) family. Functionally, VDAC is involved in the limited exchange of ATP, ADP and small hydrophilic molecules across the outer membrane. Moreover, there is compelling evidence that VDAC isoforms in mammals may act in the cross-talk between mitochondria and the cytoplasm by direct interaction with enzymes involved in energy metabolism and proteins involved in mitochondrial-induced apoptosis. To obtain a high-resolution structure of this channel, human VDAC protein isoform I was overproduced in Escherichia coli. After refolding and testing the correct fold using circular dichroism, a subsequent broad-range screening in different detergents resulted in a variety of crystals which diffracted to 3.5 Å resolution. The crystal lattice belongs to the trigonal space group P321, with unit-cell parameters a = 78.9, c = 165.7 Å and one monomer in the asymmetric unit. PMID:18607100

  5. LRRC8 Proteins Form Volume-Regulated Anion Channels that Sense Ionic Strength.

    PubMed

    Syeda, Ruhma; Qiu, Zhaozhu; Dubin, Adrienne E; Murthy, Swetha E; Florendo, Maria N; Mason, Daniel E; Mathur, Jayanti; Cahalan, Stuart M; Peters, Eric C; Montal, Mauricio; Patapoutian, Ardem

    2016-01-28

    The volume-regulated anion channel (VRAC) is activated when a cell swells, and it plays a central role in maintaining cell volume in response to osmotic challenges. SWELL1 (LRRC8A) was recently identified as an essential component of VRAC. However, the identity of the pore-forming subunits of VRAC and how the channel is gated by cell swelling are unknown. Here, we show that SWELL1 and up to four other LRRC8 subunits assemble into heterogeneous complexes of ∼800 kDa. When reconstituted into bilayers, LRRC8 complexes are sufficient to form anion channels activated by osmolality gradients. In bilayers, as well as in cells, the single-channel conductance of the complexes depends on the LRRC8 composition. Finally, low ionic strength (Γ) in the absence of an osmotic gradient activates the complexes in bilayers. These data demonstrate that LRRC8 proteins together constitute the VRAC pore and that hypotonic stress can activate VRAC through a decrease in cytoplasmic Γ. PMID:26824658

  6. Incorporation of multi-walled carbon nanotubes in microspheres used as anion exchange resin via suspension polymerization

    NASA Astrophysics Data System (ADS)

    Fathy, Mahmoud; Abdel Moghny, Th.; Awadallah, Ahmed E.; El-Bellihi, Abdel-Hameed A.-A.

    2014-06-01

    Amination of vinylbenzyl chloride-divinylbenzene (VBC-DVB) copolymers is an effective method for preparation of anion-exchange resins. Conventionally, the starting polymer is produced by chloromethylation of a styrene-divinylbenzene copolymer that utilizes chloromethyl methyl ether, a known carcinogen. An alterative approach is to copolymerize vinylbenzyl chloride with divinylbenzene to generate the necessary VBC-DVB. This method provides precise control over the density of the ion-exchange groups. The regiochemistry of the vinylbenzyl chloride methods was realized using solvent-ion exchange groups. These resulting anion-exchange polymers were characterized by a variety of techniques such as analytical titrations, transform infrared spectroscopy and thermal gravimetric analysis. Testing of these copolymers for breakthrough was performed. The results indicate that these anion exchangers have a meaningful increase in thermal stability over commercial anionic exchange beads. Resins containing MWCNTs achieved anion exchange capacity value of 323.6 meq/100 g over than that of copolymer resins and that useful in water desalination or treatment.

  7. Performance of selected anion exchange resins for the treatment of a high DOC content surface water.

    PubMed

    Humbert, Hugues; Gallard, Hervé; Suty, Hervé; Croué, Jean-Philippe

    2005-05-01

    The objective of this study was first to compare the performance of four strong anion exchange resins (AERs) (MIEX from Orica Pty Ltd, DOWEX-11 and DOWEX-MSA from DOW chemical and IRA-938 from Rohm and Haas) for their application in drinking water treatment (natural organic matter (NOM), mineral anions (nitrate, sulfate and bromide) and pesticide removal) using bench-scale experimental procedures on a high DOC content surface water. The efficiency of MIEX for NOM and mineral anions removal was furthermore evaluated using bench-scale dose-response experiments on raw, clarified and post-ozonated waters. NOM removal was assessed using the measurement of dissolved organic carbon (DOC), UV absorbance at 254 nm (UV254) and the use of high-performance size exclusion chromatography with UV (HPSEC/UV) and fluorescence detection (HPSEC/FLUO). The MIEX and IRA938 anionic resins exhibit a faster removal of NOM and mineral anions compared to the DOWEX11 and MSA AERs. All the resins were found to be very effective with similar performances after 30 to 45 min of contact time. As expected, only limited sorption of atrazine and isoproturon (C0=1 microg/L) occurred with MIEX, DOWEX11 and MSA AERs. MIEX resin proved to be very efficient in eliminating NOM of high-molecular weight but also a large part of the smallest UV absorbing organic compounds which were refractory to coagulation/flocculation treatment. Remaining DOC levels after 30 min of contact with MIEX were found similar in raw water, clarified water and even post-ozonated water implying no DOC benefit can be gained by employing conventional treatment prior to MIEX treatment. Removal of bromide (initial concentration 110 microg/L) was also observed and ranged from 30% to 65% for resin dose increasing from 2 to 8 mL/L. T PMID:15899268

  8. Guanidinium based blend anion exchange membranes for direct methanol alkaline fuel cells (DMAFCs)

    NASA Astrophysics Data System (ADS)

    Sajjad, Syed D.; Liu, Dong; Wei, Zi; Sakri, Shambhavi; Shen, Yi; Hong, Yi; Liu, Fuqiang

    2015-12-01

    Guanidinium based blend anion exchange membranes (AEMs) for direct methanol alkaline fuel cells have been fabricated and studied. The guanidinium prepolymer is first synthesized through a simple polycondensation process with the ion exchange moieties incorporated directly into the polymer backbone, and then is used to make guanidinium - chitosan (Gu-Chi) blend membranes. Besides, a lipophilic guanidinium prepolymer, synthesized by means of a precipitation reaction between sodium stearate and guanidinium salt, is adopted to tune solubility and mechanical properties of the blend AEMs. Results show that both ionic conductivity and methanol permeability of the AEMs can be tuned by blend composition and chemistry of the guanidinium based prepolymer. The selectivity (ratio of ionic conductivity to methanol permeability) of the fabricated membranes is superior to that of commercial membranes. Under fuel cell tests using 3 M methanol, the open circuit voltage (OCV) value for the blend AEM with 72 wt% of the guanidinium polymer (0.69 V) is much higher than that of the commercial Tokuyama A201 (0.47 V) at room temperature, while the blend AEMs with 50 wt% guanidinium content still show comparable values. Overall, the developed membranes demonstrate superior performance and therefore pose great promise for direct methanol anion exchange fuel cell (DMAFC) applications.

  9. Comparison of reversed-phase/cation-exchange/anion-exchange trimodal stationary phases and their use in active pharmaceutical ingredient and counterion determinations.

    PubMed

    Liu, Xiaodong; Pohl, Christopher A

    2012-04-01

    This study involved three commercial reversed-phase (RP)/anion-exchange (AEX)/cation-exchange (CEX) trimodal columns, namely Acclaim Trinity P1 (Thermo Fisher Scientific), Obelisc R (SIELC Technologies) and Scherzo SM-C18 (Imtakt). Their chromatographic properties were compared in details with respect to hydrophobicity, anion-exchange capacity, cation-exchange capacity, and selectivity, by studying retention behavior dependency on organic solvent, buffer concentration and pH. It was found that their remarkably different column chemistries resulted in distinctive chromatography properties. Trinity P1 exhibited strong anion-exchange and cation-exchange interactions but low RP retention while Scherzo SM-C18 showed strong reversed-phase retention with little cation-exchange and anion-exchange capacities. For Obelisc R, its reversed-phase capacity was weaker than Scherzo SM-C18 but slightly higher than Trinity P1, and its ion-exchange retentions were between Trinity P1 and Scherzo SM-C18. In addition, their difference in selectivity was demonstrated by examples of determining the active pharmaceutical ingredient (API) and counterion of drug products. PMID:22209548

  10. TREATMENT FOR IMPROVING THE OPERATION OF STRONG BASE ANION EXCHANGE RESINS

    DOEpatents

    Stevenson, P.C.

    1960-11-29

    A process is offered for improving quaternary ammonium type strongly basic anion exchange resins so that centain zinc and cadmium residues, which normally stick to and "poison" this type of resin, can be removed by elution. Specifically, the resin as obtained commercially is treated with an aqueous solution of sodium hydroxide of about 1 to 4 M concentration by heating therein and periodically adding small amounts of oxidizing agent selected from hydrogen peroxide, sodium peroxide and hypochlorite. Zinc and cadmium values may then be adsorbed onto the resin from a 0.1 to 3 M HCl and thereafter eluted therefrom with very dilute HCl solutions.

  11. Determination of uranium isotopes in environmental samples by anion exchange in sulfuric and hydrochloric acid media.

    PubMed

    Popov, L

    2016-09-01

    Method for determination of uranium isotopes in various environmental samples is presented. The major advantages of the method are the low cost of the analysis, high radiochemical yields and good decontamination factors from the matrix elements, natural and man-made radionuclides. The separation and purification of uranium is attained by adsorption with strong base anion exchange resin in sulfuric and hydrochloric acid media. Uranium is electrodeposited on a stainless steel disk and measured by alpha spectrometry. The analytical method has been applied for the determination of concentrations of uranium isotopes in mineral, spring and tap waters from Bulgaria. The analytical quality was checked by analyzing reference materials. PMID:27451111

  12. Abscisic acid influx into human nucleated cells occurs through the anion exchanger AE2.

    PubMed

    Vigliarolo, Tiziana; Zocchi, Elena; Fresia, Chiara; Booz, Valeria; Guida, Lucrezia

    2016-06-01

    Abscisic acid (ABA) is a hormone conserved from cyanobacteria to higher plants, where it regulates responses to environmental stimuli. ABA also plays a role in mammalian physiology, pointedly in inflammatory responses and in glycemic control. As the animal ABA receptor is on the intracellular side of the plasma membrane, a transporter is required for the hormone's action. Here we demonstrate that ABA transport in human nucleated cells occurs via the anion exchanger AE2. Together with the recent demonstration that ABA influx into human erythrocytes occurs via Band 3, this result identifies the AE family members as the mammalian ABA transporters. PMID:27015766

  13. Solvent Processable Tetraalkylammonium-Functionalized Polyethylene for Use as an Alkaline Anion Exchange Membrane

    SciTech Connect

    Kostalik, IV, Henry A.; Clark, Timothy J.; Robertson, Nicholas J.; Mutolo, Paul F.; Longo, Julie M.; Abruña, Héctor D.; Coates, Geoffrey W.

    2010-08-02

    We report the synthesis of a solvent processable, tetraalkylammonium-functionalized polyethylene for use as an alkaline anion exchange membrane (AAEM). The membranes are insoluble in both pure water and aqueous methanol (50 vol % water) at 50 °C but exhibit excellent solubility in a variety of other aqueous alcohols (e.g., 5 wt % AAEM in aqueous n-propanol, 50 vol % water). These solubility characteristics extend the potential utility of this system for use as both an AAEM and ionomer electrode material from a single polymer composition. The AAEMs generated are mechanically strong and exhibit high hydroxide and carbonate conductivities.

  14. Alkaline degradation studies of anion exchange polymers to enable new membrane designs

    NASA Astrophysics Data System (ADS)

    Nunez, Sean Andrew

    Current performance targets for anion-exchange membrane (AEM) fuel cells call for greater than 95% alkaline stability for 5000 hours at temperatures up to 120 °C. Using this target temperature of 120 °C, an incisive 1H NMR-based alkaline degradation method to identify the degradation products of n-alkyl spacer tetraalkylammonium cations in various AEM polymers and small molecule analogs. Herein, the degradation mechanisms and rates of benzyltrimethylammonium-, n-alkyl interstitial spacer- and n-alkyl terminal pendant-cations are studied on several architectures. These findings demonstrate that benzyltrimethylammonium- and n-alkyl terminal pendant cations are more labile than an n-alkyl interstitial spacer cation and conclude that Hofmann elimination is not the predominant mechanism of alkaline degradation. Additionally, the alkaline stability of an n-alkyl interstitial spacer cation is enhanced when combined with an n-alkyl terminal pendant. Interestingly, at 120 °C, an inverse trend was found in the overall alkaline stability of AEM poly(styrene) and AEM poly(phenylene oxide) samples than was previously shown at 80 °C. Successive small molecule studies suggest that at 120 °C, an anion-induced 1,4-elimination degradation mechanism may be activated on styrenic AEM polymers bearing an acidic alpha-hydrogen. In addition, an ATR-FTIR based method was developed to assess the alkaline stability of solid membranes and any added resistance to degradation that may be due to differential solubilities and phase separation. To increase the stability of anion exchange membranes, Oshima magnesate--halogen exchange was demonstrated as a method for the synthesis of new anion exchange membranes that typically fail in the presence of organolithium or Grignard reagents alone. This new chemistry, applied to non-resinous polymers for the first time, proved effective for the n-akyl interstitial spacer functionalization of poly(phenylene oxide) and poly(styrene- co

  15. Extracellular Cl(-) regulates human SO4 (2-)/anion exchanger SLC26A1 by altering pH sensitivity of anion transport.

    PubMed

    Wu, Meng; Heneghan, John F; Vandorpe, David H; Escobar, Laura I; Wu, Bai-Lin; Alper, Seth L

    2016-08-01

    Genetic deficiency of the SLC26A1 anion exchanger in mice is known to be associated with hyposulfatemia and hyperoxaluria with nephrolithiasis, but many aspects of human SLC26A1 function remain to be explored. We report here the functional characterization of human SLC26A1, a 4,4'-diisothiocyanato-2,2'-stilbenedisulfonic acid (DIDS)-sensitive, electroneutral sodium-independent anion exchanger transporting sulfate, oxalate, bicarbonate, thiosulfate, and (with divergent properties) chloride. Human SLC26A1-mediated anion exchange differs from that of its rodent orthologs in its stimulation by alkaline pHo and inhibition by acidic pHo but not pHi and in its failure to transport glyoxylate. SLC26A1-mediated transport of sulfate and oxalate is highly dependent on allosteric activation by extracellular chloride or non-substrate anions. Extracellular chloride stimulates apparent V max of human SLC26A1-mediated sulfate uptake by conferring a 2-log decrease in sensitivity to inhibition by extracellular protons, without changing transporter affinity for extracellular sulfate. In contrast to SLC26A1-mediated sulfate transport, SLC26A1-associated chloride transport is activated by acid pHo, shows reduced sensitivity to DIDS, and exhibits cation dependence of its DIDS-insensitive component. Human SLC26A1 resembles SLC26 paralogs in its inhibition by phorbol ester activation of protein kinase C (PKC), which differs in its undiminished polypeptide abundance at or near the oocyte surface. Mutation of SLC26A1 residues corresponding to candidate anion binding site-associated residues in avian SLC26A5/prestin altered anion transport in patterns resembling those of prestin. However, rare SLC26A1 polymorphic variants from a patient with renal Fanconi Syndrome and from a patient with nephrolithiasis/calcinosis exhibited no loss-of-function phenotypes consistent with disease pathogenesis. PMID:27125215

  16. Synergistic Malaria Parasite Killing by Two Types of Plasmodial Surface Anion Channel Inhibitors.

    PubMed

    Pain, Margaret; Fuller, Alexandra W; Basore, Katherine; Pillai, Ajay D; Solomon, Tsione; Bokhari, Abdullah A B; Desai, Sanjay A

    2016-01-01

    Malaria parasites increase their host erythrocyte's permeability to a broad range of ions and organic solutes. The plasmodial surface anion channel (PSAC) mediates this uptake and is an established drug target. Development of therapies targeting this channel is limited by several problems including interactions between known inhibitors and permeating solutes that lead to incomplete channel block. Here, we designed and executed a high-throughput screen to identify a novel class of PSAC inhibitors that overcome this solute-inhibitor interaction. These new inhibitors differ from existing blockers and have distinct effects on channel-mediated transport, supporting a model of two separate routes for solute permeation though PSAC. Combinations of inhibitors specific for the two routes had strong synergistic action against in vitro parasite propagation, whereas combinations acting on a single route produced only additive effects. The magnitude of synergism depended on external nutrient concentrations, consistent with an essential role of the channel in parasite nutrient acquisition. The identified inhibitors will enable a better understanding of the channel's structure-function and may be starting points for novel combination therapies that produce synergistic parasite killing. PMID:26866812

  17. Mechanisms of metal ion transfer into room-temperature ionic liquids : the role of anion exchange.

    SciTech Connect

    Jensen, M. P.; Neuefeind, J.; Beitz, J. V.; Skanthakumar, S.; Soderholm, L.; Chemistry

    2003-12-17

    The structure and stoichiometry of the lanthanide(III) (Ln) complexes with the ligand 2-thenoyltrifluoroacetone (Htta) formed in a biphasic aqueous room-temperature ionic liquid system have been studied by complementary physicochemical methods. Equilibrium thermodynamics, optical absorption and luminescence spectroscopies, high-energy X-ray scattering, EXAFS, and molecular dynamics simulations all support the formation of anionic Nd(tta){sub 4}{sup -} or Eu(tta){sub 4}{sup -} complexes with no water coordinated to the metal center in 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide (C{sub 4}mim{sup +}Tf{sub 2}N{sup -}), rather than the hydrated, neutral complexes, M(tta){sub 3}(H{sub 2}O){sub n} (n = 2 or 3), that form in nonpolar molecular solvents, such as xylene or chloroform. The presence of anionic lanthanide complexes in C{sub 4}mim{sup +}Tf{sub 2}N{sup -} is made possible by the exchange of the ionic liquid anions into the aqueous phase for the lanthanide complex. The resulting complexes in the ionic liquid phase should be thought of as weak C{sub 4}mim{sup +}Ln(tta){sub 4}{sup -} ion pairs which exert little influence on the structure of the ionic liquid phase.

  18. Pullulan Production by Aureobasidium pullulans ATCC 201253 Cells Adsorbed onto Cellulose Anion and Cation Exchangers

    PubMed Central

    West, Thomas P.

    2012-01-01

    The anion exchanger phosphocellulose and the cation exchanger triethylaminoethyl cellulose were used to immobilize cells of the fungus Aureobasidium pullulans ATCC 201253 and the adsorbed cells were subsequently investigated for their ability to produce the polysaccharide pullulan using batch fermentation. The cells adsorbed on the triethylaminoethyl cellulose at pH 7.5 produced higher pullulan levels than those cells immobilized on phosphocellulose at pH 4.0 for 2 cycles of 168 h at 30 °C. Relative to the initial cycle of 168 h, pullulan production by the cells immobilized on the triethylaminoethyl cellulose decreased slightly after 168 h of the second production cycle while pullulan production by the phosphocellulose-immobilized cells remained about the same after 168 h of the second production cycle. PMID:23762749

  19. Radiolysis of the AV-17×8 ČS anion-exchange resin

    NASA Astrophysics Data System (ADS)

    Bartoníček, B.; Habersbergerová, A.; Janovský, I.; Kysela, J.; Pejša, R.

    The mixture of the anion exchange resin AV-17×8 čs in borate form and of a deaerated aqueous solution containing H 3BO 3 and NH 3 ( pH = 7) was irradiated with gamma rays in both static and dynamic conditions. A loss of strong-base exchange capacity and an increase of weak-base capacity was observed. In the solution, (CH 3) 3N, (CH 3) 2NH and CH 3NH 2 were found as the radiolytic products, their relative ratio being 15.7 : 3.7 : 1. Further, NH 3 is formed with the concentration of the same order as that of CH 3NH 2. Beside hydrogen, which is the prevailing gaseous product of the radiolysis of the mixture, methane and ethane arise, their ratio in the dynamic irradiation being 2.8 to 6.0. The main features of the radiolysis are outlined.

  20. Thermally Cross-Linked Anion Exchange Membranes from Solvent Processable Isoprene Containing Ionomers

    SciTech Connect

    Tsai, Tsung-Han; Ertem, S. Piril; Maes, Ashley M.; Seifert, Soenke; Herring, Andrew M; Coughlin, E. Bryan

    2015-01-28

    Random copolymers of isoprene and 4-vinylbenzyl chloride (VBCl) with varying compositions were synthesized via nitroxide-mediated polymerization. Subsequent quaternization afforded solvent processable and cross-linkable ionomers with a wide range of ion exchange capacities (IECs). Solution cast membranes were thermally cross-linked to form anion exchange membranes. Cross-linking was achieved by taking advantage of the unsaturations on the polyisoprene backbone, without added cross-linkers. A strong correlation was found between water uptake and ion conductivity of the membranes: conductivities of the membranes with IECs beyond a critical value were found to be constant related to their high water absorption. Environmentally controlled small-angle X-ray scattering experiments revealed a correlation between the average distance between ionic clusters and the ion conductivity, indicating that a well-connected network of ion clusters is necessary for efficient ion conduction and high ion conductivity.

  1. Heterometallic modular metal-organic 3D frameworks assembled via new tris-β-diketonate metalloligands: nanoporous materials for anion exchange and scaffolding of selected anionic guests.

    PubMed

    Carlucci, Lucia; Ciani, Gianfranco; Maggini, Simona; Proserpio, Davide M; Visconti, Marco

    2010-11-01

    -48% of the cell volume and include the anions and many guest solvent molecules. The guest solvent molecules can be reversibly removed by thermal activation with retention of the framework structure, which proved to be stable up to about 270°C, as confirmed by TGA and powder XRD monitoring. The anions could be easily exchanged in single-crystal to single-crystal processes, thereby allowing the insertion of selected anions into the framework channels. PMID:20938934

  2. Crosslinked poly(vinylbenzyl chloride) with a macromolecular crosslinker for anion exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Lu, Wangting; Shao, Zhi-Gang; Zhang, Geng; Zhao, Yun; Yi, Baolian

    2014-02-01

    A new material based on crosslinked poly(vinylbenzyl chloride) (PVBC) with a macromolecular crosslinker is synthesized and employed as the membrane for anion exchange membrane fuel cells (AEMFCs). PVBC is used as the hydroxide conducting polymers, while poly(vinyl acetal) (PVAc) containing dimethylamino groups plays the role as macromolecular crosslinker and the supporting matrix simultaneously. Fourier transform infrared (FT-IR) absorption spectra and X-ray photoelectron (XPS) spectra prove successful crosslinking between PVBC and PVAc. The crosslinked membrane shows hydroxide conductivity larger than 0.01 S cm-1 at room temperature, and the swelling by water at elevated temperature is suppressed. The H2/O2 AEMFC using the crosslinked membrane shows a peak power density (Pmax) of 124.7 mW cm-2 at 40 °C, and the decrease of the open circuit voltage (OCV) of the fuel cell is negligible under continuous OCV conditions for 120 h. All the results indicate that the crosslinking with a macromolecular crosslinker may be a promising strategy to fabricate anion exchange membrane for the application in the AEMFCs.

  3. First Cationic Uranyl-Organic Framework with Anion-Exchange Capabilities.

    PubMed

    Bai, Zhuanling; Wang, Yanlong; Li, Yuxiang; Liu, Wei; Chen, Lanhua; Sheng, Daopeng; Diwu, Juan; Chai, Zhifang; Albrecht-Schmitt, Thomas E; Wang, Shuao

    2016-07-01

    By controlling the extent of hydrolysis during the self-assembly process of a zwitterionic-based ligand with uranyl cations, we observed a structural evolution from the neutral uranyl-organic framework [(UO2)2(TTTPC)(OH)O(COOH)]·1.5DMF·7H2O (SCU-6) to the first cationic uranyl-organic framework with the formula of [(UO2)(HTTTPC)(OH)]Br·1.5DMF·4H2O (SCU-7). The crystal structures of SCU-6 and SCU-7 are layers built with tetranuclear and dinuclear uranyl clusters, respectively. Exchangeable halide anions are present in the interlaminar spaces balancing the positive charge of layers in SCU-7. Therefore, SCU-7 is able to effectively remove perrhenate anions from aqueous solution. Meanwhile, the H2PO4(-)-exchanged SCU-7 material exhibits a moderate proton conductivity of 8.70 × 10(-5) S cm(-1) at 50 °C and 90% relative humidity, representing nearly 80 times enhancement compared to the original material. PMID:27310580

  4. Phosphorus recovery from microbial biofuel residual using microwave peroxide digestion and anion exchange.

    PubMed

    Gifford, McKay; Liu, Jianyong; Rittmann, Bruce E; Vannela, Raveender; Westerhoff, Paul

    2015-03-01

    Sustainable production of microalgae for biofuel requires efficient phosphorus (P) utilization, which is a limited resource and vital for global food security. This research tracks the fate of P through biofuel production and investigates P recovery from the biomass using the cyanobacterium Synechocystis sp. PCC 6803. Our results show that Synechocystis contained 1.4% P dry weight. After crude lipids were extracted (e.g., for biofuel processing), 92% of the intracellular P remained in the residual biomass, indicating phospholipids comprised only a small percentage of cellular P. We estimate a majority of the P is primarily associated with nucleic acids. Advanced oxidation using hydrogen peroxide and microwave heating released 92% of the cellular P into orthophosphate. We then recovered the orthophosphate from the digestion matrix using two different types of anion exchange resins. One resin impregnated with iron nanoparticles adsorbed 98% of the influent P through 20 bed volumes, but only released 23% during regeneration. A strong-base anion exchange resin adsorbed 87% of the influent P through 20 bed volumes and released 50% of it upon regeneration. This recovered P subsequently supported growth of Synechocystis. This proof-of-concept recovery process reduced P demand of biofuel microalgae by 54%. PMID:25528543

  5. Enhanced performance of CdTe quantum dot sensitized solar cell via anion exchanges

    NASA Astrophysics Data System (ADS)

    Shen, Xuehua; Jia, Jianguang; Lin, Yuan; Zhou, Xiaowen

    2015-03-01

    We report on an eco-friendly way to prepare CdTe/CdS quantum dots for quantum dot sensitized solar cell (QDSSC). CdTe/CdS quantum dots are synthesized through an anion exchange between CdTe quantum dots (QDs) and S2- in aqueous solution at low temperature under ambient condition. The resultant QDs are bonded onto TiO2 with the help of thioglycolic acid bifunctional molecule. The uniform distribution of QDs throughout the TiO2 mesoporous film depth is confirmed by the energy dispersive X-ray (EDX) elemental mapping. Absorption, dark current, impedance spectroscopy, and intensity-modulated photocurrent analyses prove that anion exchange can efficiently extend the absorption range, suppress the charge recombination, increase the electron injection as well as accelerate the electron transportation in the cell. In combination with CdS post-treatment, a solar-to-energy conversion efficiency of 2.44% is achieved for CdTe/CdS QDSSC, which is more than 15 times that of the CdTe based cell.

  6. Qualification of Reillex{trademark} HPQ anion exchange resin for use in SRS processes

    SciTech Connect

    Crooks, W.J. III

    2000-05-18

    The Phase 2 portion of the HB-Line facility was built in the early 1980's to process plutonium and neptunium from nitric acid solutions into oxide suitable for storage in a vault. Although the other portions of HB-Line were started up in the mid 1980's and have operated since that time, the anion exchange and precipitation processes in Phase 2 were never started up. As part of the material stabilization efforts, Phase 2 is currently being started up. A new anion exchange resin is needed because the resins that were proposed for use 10 years ago are limited by performance characteristics, disposal requirements, or are no longer commercially available. SRTC is responsible for qualifying all resins prior to their use in Nuclear Materials Stabilization and Storage (NMSS) processes. Qualification consists of both process suitability and thermal stability with nitric acid. This report describes the thermal stability qualification of Reillex{trademark} HPQ, the new resin proposed for processing plutonium and neptunium in the HB Line facility.

  7. A novel self-adaptive microalgae photobioreactor using anion exchange membranes for continuous supply of nutrients.

    PubMed

    Fu, Qian; Chang, Hai-Xing; Huang, Yun; Liao, Qiang; Zhu, Xun; Xia, Ao; Sun, Ya-Hui

    2016-08-01

    A novel self-adaptive microalgae photobioreactor using anion exchange membranes (AEM-PBR) for continuous supply of nutrients was proposed to improve microalgae biomass production. The introduction of anion exchange membranes to the PBR can realize continuous supply of nutrients at desired rates, which is beneficial to the growth of microalgae. The results showed that the maximum biomass concentration obtained in the AEM-PBR under continuous supply of nitrogen at an average rate of 19.0mgN/L/d was 2.98g/L, which was 129.2% higher than that (1.30g/L) in a PBR with all the nitrogen supplied in batch at initial. In addition, the feeding rates of nitrogen and phosphorus were optimized in the AEM-PBR to maximize biomass production. The maximum biomass concentration of 4.38g/L was obtained under synergistic regulation of nitrogen and phosphorus feeding rates at 19.0mgN/L/d and 4.2mgP/L/d. The AEM-PBR demonstrates a promising approach for high-density cultivation of microalgae. PMID:27187567

  8. Isotope Fractionation of chlorine in Aqueous System: One Study on Anion-Exchange Chromatography.

    NASA Astrophysics Data System (ADS)

    Musashi, M.; Oi, T.; Eggenkamp, H.; Van Cappellen, P.

    2001-05-01

    Stable chlorine isotopes such as 37Cl and 35Cl have been paid attention as useful tool identifying the source, and monitoring the transport process and natural fate of chlorinated organic pollutants in air and groundwater. However, it is not established yet whether any isotope effects accompany biodegradation or reductive dehalogenation of the pollutants (Clark and Fritz, 1997). Here we first present an experimental determination of isotope fractionation factor of chlorine in aqueous system by using anion-exchange chromatographic technique. Into the Cl-free anion exchange resin (Muromac, OH- form) packed in a 30 cm long pyrex glass column and controlled temperature at 25 oC, hydrochloric solution was fed with controlling the flow rate constant. Effluent from the column was recovered by an automatic fraction collector and prepared for Cl isotope analysis. The Cl isotope ratio (δ 37Cl vs. SMOC) was measured by IR-MS at the Utrecht University with precision of 0.06 per-mil. Magnitude of the factor obtained was 1.00035 at 25 oC. The result indicates that the lighter isotope (35Cl) was preferably fractionated into the resin phase, while the heavier one (37Cl) was enriched into the aqueous phase. This trend suggests that molecular structure of hydrolysis with Cl in aqueous phase may be more stable than that of Cl ionically bonding with the resin. This result may offer physico-chemical insights into behavior and fate of the pollutants.

  9. Quantitative H-1 NMR Analysis of Chemical Stabilities in Anion-Exchange Membranes

    SciTech Connect

    Nunez, SA; Hickner, MA

    2013-01-01

    We compared the alkaline stability of three classes of anion exchange membranes that are leading candidates for applications in platinum-free fuel cells. A methodology is presented for the study of chemical stability of anion-exchange polymers in alkaline media that provides clear and quantitative H-1 NMR spectroscopic data of dissolved polymers containing benzyltrimethylammonium functionalities. Recent studies have investigated the stabilities of benzimidazolium- and alkylimidazolium-bearing polymers using periodic H-1 NMR sampling. These studies included varying alkaline concentrations, external heating sources, and excessive processing and contained no internal standard for absolute measurements. Key aspects of our time-resolved H-1 NMR method include in situ heating and sampling within the spectrometer, fixed Stoichiometric relationships between the benzyltrimethylammonium functionalities of each polymer and potassium deuteroxide (KOD), and the incorporation of an internal standard for the absolute measurement of the polymer degradation. In addition, our method permits the identification of the degradation products to find the underlying cause of chemical lability. Our results demonstrate that a styrene-based polymer containing benzyltrimethylammonium functional groups is remarkably stable when exposed to 20 equivalents per cation of KOD at 80 degrees C with a half-life (t(1/2)) of 231 h. Under these standard conditions, functionalized poly(phenylene oxide) and poly(arylene ether sulfone) copolymers, both bearing benzyltrimethylammonium functionalities were found to degrade with a half-lives of 57.8 and 2.7 h, respectively.

  10. Wide Nanoscopic Pore of Maxi-Anion Channel Suits its Function as an ATP-Conductive Pathway

    PubMed Central

    Sabirov, Ravshan Z.; Okada, Yasunobu

    2004-01-01

    The newly proposed function of the maxi-anion channel as a conductive pathway for ATP release requires that its pore is sufficiently large to permit passage of a bulky ATP4− anion. We found a linear relationship between relative permeability of organic anions of different size and their relative ionic mobility (measured as the ratio of ionic conductance) with a slope close to 1, suggesting that organic anions tested with radii up to 0.49 nm (lactobionate) move inside the channel by free diffusion. In the second approach, we, for the first time, succeeded in pore sizing by the nonelectrolyte exclusion method in single-channel patch-clamp experiments. The cutoff radii of PEG molecules that could access the channel from intracellular (1.16 nm) and extracellular (1.42 nm) sides indicated an asymmetry of the two entrances to the channel pore. Measurements by symmetrical two-sided application of PEG molecules yielded an average functional pore radius of ∼1.3 nm. These three estimates are considerably larger than the radius of ATP4− (0.57–0.65 nm) and MgATP2− (∼0.60 nm). We therefore conclude that the nanoscopic maxi-anion channel pore provides sufficient room to accommodate ATP and is well suited to its function as a conductive pathway for ATP release in cell-to-cell communication. PMID:15345546

  11. Plasmodium induces swelling-activated ClC-2 anion channels in the host erythrocyte.

    PubMed

    Huber, Stephan M; Duranton, Christophe; Henke, Guido; Van De Sand, Claudia; Heussler, Volker; Shumilina, Ekaterina; Sandu, Ciprian D; Tanneur, Valerie; Brand, Verena; Kasinathan, Ravi S; Lang, Karl S; Kremsner, Peter G; Hübner, Christian A; Rust, Marco B; Dedek, Karin; Jentsch, Thomas J; Lang, Florian

    2004-10-01

    Intraerythrocytic growth of the human malaria parasite Plasmodium falciparum depends on delivery of nutrients. Moreover, infection challenges cell volume constancy of the host erythrocyte requiring enhanced activity of cell volume regulatory mechanisms. Patch clamp recording demonstrated inwardly and outwardly rectifying anion channels in infected but not in control erythrocytes. The molecular identity of those channels remained elusive. We show here for one channel type that voltage dependence, cell volume sensitivity, and activation by oxidation are identical to ClC-2. Moreover, Western blots and FACS analysis showed protein and functional ClC-2 expression in human erythrocytes and erythrocytes from wild type (Clcn2(+/+)) but not from Clcn2(-/-) mice. Finally, patch clamp recording revealed activation of volume-sensitive inwardly rectifying channels in Plasmodium berghei-infected Clcn2(+/+) but not Clcn2(-/-) erythrocytes. Erythrocytes from infected mice of both genotypes differed in cell volume and inhibition of ClC-2 by ZnCl(2) (1 mm) induced an increase of cell volume only in parasitized Clcn2(+/+) erythrocytes. Lack of ClC-2 did not inhibit P. berghei development in vivo nor substantially affect the mortality of infected mice. In conclusion, activation of host ClC-2 channels participates in the altered permeability of Plasmodium-infected erythrocytes but is not required for intraerythrocytic parasite survival. PMID:15272009

  12. Synergistic Malaria Parasite Killing by Two Types of Plasmodial Surface Anion Channel Inhibitors

    PubMed Central

    Pain, Margaret; Fuller, Alexandra W.; Basore, Katherine; Pillai, Ajay D.; Solomon, Tsione; Bokhari, Abdullah A. B.; Desai, Sanjay A.

    2016-01-01

    Malaria parasites increase their host erythrocyte’s permeability to a broad range of ions and organic solutes. The plasmodial surface anion channel (PSAC) mediates this uptake and is an established drug target. Development of therapies targeting this channel is limited by several problems including interactions between known inhibitors and permeating solutes that lead to incomplete channel block. Here, we designed and executed a high-throughput screen to identify a novel class of PSAC inhibitors that overcome this solute-inhibitor interaction. These new inhibitors differ from existing blockers and have distinct effects on channel-mediated transport, supporting a model of two separate routes for solute permeation though PSAC. Combinations of inhibitors specific for the two routes had strong synergistic action against in vitro parasite propagation, whereas combinations acting on a single route produced only additive effects. The magnitude of synergism depended on external nutrient concentrations, consistent with an essential role of the channel in parasite nutrient acquisition. The identified inhibitors will enable a better understanding of the channel’s structure-function and may be starting points for novel combination therapies that produce synergistic parasite killing. PMID:26866812

  13. Analysis of a novel double-barreled anion channel from rat liver rough endoplasmic reticulum.

    PubMed Central

    Morier, N; Sauvé, R

    1994-01-01

    The presence of anionic channels in stripped rough endoplasmic reticulum membranes isolated from rat hepatocytes was investigated by fusing microsomes from these membranes to a planar lipid bilayer. Several types of anion-selective channels were observed including a voltage-gated Cl- channel, the activity of which appeared in bursts characterized by transitions among three distinct conductance levels of 0 pS (0 level), 160 pS (O1 level), and 320 pS (O2 level), respectively, in 450 mM (cis) 50 mM (trans) KCl conditions. A chi 2 analysis on current records where interburst silent periods were omitted showed that the relative probability of current levels 0 (baseline), O1, and O2 followed a binomial statistic. However, measurements of the conditional probabilities W(level 0 at tau/level O2 at 0) and W(level O2 at tau/level 0 at 0) provided clear evidence of direct transitions between the current levels 0 and O2 without any detectable transitions to the intermediate level O1. It was concluded on the basis of these results that the observed channel was controlled by at least two distinct gating processes, namely 1) a voltage-dependent activation mechanism in which the entire system behaves as two independent monomeric channels of 160 pS with each channel characterized by a simple Open-Closed kinetic, and 2) a slow voltage-dependent process that accounts for both the appearance of silent periods between bursts of channel activity and the transitions between the current levels 0 and O2. Finally, an analysis of the relative probability for the system to be in levels 0, O1, and O2 showed that our results are more compatible with a model in which all the states resulting from the superposition of the two independent monomeric channels have access at different rates to a common inactivated state than with a model where a simple Open-Closed main gate either occludes or exposes simultaneously two independent 160-pS monomers. Images FIGURE 2 FIGURE 6 PMID:7524709

  14. A slow anion channel in guard cells, activating at large hyperpolarization, may be principal for stomatal closing.

    PubMed

    Linder, B; Raschke, K

    1992-11-16

    Slowly activating anion channel currents were discovered at micromolar 'cytoplasmic' Ca2+ during patch-clamp measurements on guard-cell protoplasts of Vicia faba and Xanthium strumarium. They activated at potentials as low as -200 mV, with time constants between 5 and 60 s, and no inactivation. The broad voltage dependence exhibited a current maximum near -40 mV. The single-channel open time was in the order of seconds, and the unitary conductance was 33 ps, similar to that of the already described 'quick' anion channel of guard cells. Because of its activity at low potentials, the slow anion channel may be essential for the depolarization of the plasmalemma that is required for salt efflux during stomatal closing. PMID:1385219

  15. A new procedure to produce lignocellulosic anion exchangers from agricultural waste materials.

    PubMed

    Orlando, U S; Baes, A U; Nishijima, W; Okada, M

    2002-07-01

    Two lignocellulosic agricultural waste materials (LCM), sugarcane bagasse (BG) and rice hull (RH), were converted into weak-base anion exchanger and evaluated for their exchanger capacity for nitrate. Pure cellulose (PC) and pure alkaline lignin (PL) were also used as reference materials to elucidate possible reactivity in LCM. Epoxy and amino groups were introduced into BG, RH, PC and PL substrates after the reaction with epichlorohydrin and dimethylamine in the presence of pyridine and an organic solvent N,N-dimethylformamide (DMF). Amino group incorporation into cellulose decreased with the presence of water in the reaction mixture and increased with the reaction time and presence of a catalyst (pyridine). The highest maximum nitrate exchange capacity (Qmax) and yields of the prepared exchangers was obtained from PL (1.8 mmol g(-1) and 412.5%), followed by BG (1.41 mmol g(-1) and 300%), PC (1.34 mmol g(-1) and 166%) and RH (1.32 mmol g(-1) and 180%). The proposed synthetic procedure was effective in modifying PL, PC and LCM chemically resulting in a higher yield and nitrate removal capacity. PMID:12094793

  16. Molecular Plasticity of the Human Voltage-Dependent Anion Channel Embedded Into a Membrane.

    PubMed

    Ge, Lin; Villinger, Saskia; Mari, Stefania A; Giller, Karin; Griesinger, Christian; Becker, Stefan; Müller, Daniel J; Zweckstetter, Markus

    2016-04-01

    The voltage-dependent anion channel (VDAC) regulates the flux of metabolites and ions across the outer mitochondrial membrane. Regulation of ion flow involves conformational transitions in VDAC, but the nature of these changes has not been resolved to date. By combining single-molecule force spectroscopy with nuclear magnetic resonance spectroscopy we show that the β barrel of human VDAC embedded into a membrane is highly flexible. Its mechanical flexibility exceeds by up to one order of magnitude that determined for β strands of other membrane proteins and is largest in the N-terminal part of the β barrel. Interaction with Ca(2+), a key regulator of metabolism and apoptosis, considerably decreases the barrel's conformational variability and kinetic free energy in the membrane. The combined data suggest that physiological VDAC function depends on the molecular plasticity of its channel. PMID:27021164

  17. Primary structure of a sperm cell anion exchanger and its messenger ribonucleic acid expression during spermatogenesis.

    PubMed

    Holappa, K; Mustonen, M; Parvinen, M; Vihko, P; Rajaniemi, H; Kellokumpu, S

    1999-10-01

    Chloride/bicarbonate (Cl-/HCO(3)-) exchangers are a family of proteins (anion exchanger [AE] gene family) that regulate many vital cellular processes such as intracellular pH, cell volume, and Cl- concentration. They may also be involved in the regulation of sperm cell motility and acrosome reaction during fertilization, as these two phenomena are bicarbonate dependent, and we have previously shown that a polypeptide immunologically related to erythrocyte band 3 is expressed in mammalian sperm cells. We have now identified this putative sperm cell anion exchanger as the AE2 isoform of this gene family. First, we determined its complete primary structure from the human testis lambda gt 11 cDNA library. The cloned sequence was found to consist of 3896 base pairs (bp) with an open reading frame of 3726 bp, and to be almost identical to the previously published human genomic AE2 sequence. Only four amino acid disparities were found between these two sequences. Second, our in situ hybridization analyses showed that AE2 mRNA is expressed in developing sperm cells, indicating that the cloned sequence corresponds to the sperm cell AE. Our reverse transcription-polymerase chain reaction analyses suggested further that the expression of AE2 mRNA was variable to some extent during the epithelial cell cycle. Strongest expression was observed at stages VII-XIV except for stage X, i.e., when major structural and morphological changes take place. These results suggest that the full-length AE2 isoform regulates HCO(3)- transport in mature sperm cells and thus their motility in vivo. PMID:10491633

  18. Separation of Oxidized Variants of a Monoclonal Antibody by Anion-Exchange

    PubMed Central

    Teshima, Glen; Li, Ming-Xiang; Danishmand, Rahima; Obi, Chidi; To, Robert; Huang, Carol; Lahidji, Vafa; Freeberg, Joel; Thorner, Lauren; Tomic, Milan

    2010-01-01

    Monoclonal antibodies are subject to a variety of degradation mechanisms, therefore orthogonal techniques are required to demonstrate product quality. In this study, the three individual antibodies comprising a multi-antibody drug product, XOMA 3AB were evaluated by both cation-exchange (CEX) and anion-exchange chromatography (AEX). In contrast to CEX analysis which showed only a single, broad peak for the force-oxidized antibodies, AEX analysis of Ab-A (pI=7.6) revealed two more basic peaks. Ab-B (pI=6.7) bound but exhibited only a single major peak while Ab-C (pI=8.6) flowed through. Peptide mapping LC/MS analysis of the isolated Ab-A fractions demonstrated that the basic peaks resulted from oxidation in a complementary determining region (CDR). Differential scanning calorimetry (DSC) analysis of the oxidized Ab-A species showed a decrease in the Fab melting point for the oxidized species consistent with unfolding of the molecule. Greater/lesser surface exposure of ionic residues resulting from a conformational change provides a likely explanation for the dramatic shift in retention behavior for the Ab-A oxidized variants. Peptide mapping analysis of the Ab-B antibody showed, in contrast to Ab-A, no detectable CDR oxidation. Hence, the lack of separation of oxidized variants in Ab-B can be explained by the absence of CDR oxidation and the associated changes in secondary/tertiary structure which were observed for oxidized AbA. In summary, anion-exchange HPLC shows potential as an orthogonal analytical technique for assessing product quality of monoclonal antibody therapeutics. In the case of the XOMA 3AB drug product, two of the antibodies bound and one, Ab-A, exhibited separation of CDR oxidized variants. PMID:21145555

  19. Characteristics and roles of the volume-sensitive outwardly rectifying (VSOR) anion channel in the central nervous system.

    PubMed

    Akita, T; Okada, Y

    2014-09-01

    Cell volume regulation (CVR) is essential for all types of cells in the central nervous system (CNS) to counteract cell volume changes that may be associated with neuronal activities or diseases and with osmosensing in the hypothalamus, to facilitate morphological changes during cell proliferation, differentiation and migration, and to execute apoptosis of cells. The regulation is attained by regulating the net influx or efflux of solutes and water across the plasma membrane. The volume-sensitive outwardly rectifying (VSOR) anion channel plays a major role in providing a pathway for anion flux during the regulation. The VSOR anion channel is permeable not only to Cl(-) ions but also to amino acids like glutamate and taurine. This property confers a means of intercellular communications through the opening of the channel in the CNS. Thus exploring the roles of VSOR anion channels is crucial to understand the basic principles of cellular functions in the CNS. Here we review biophysical and pharmacological characteristics of the VSOR anion channel in the CNS, discuss its activation mechanisms and roles in the CNS reported so far, and give some perspectives on the next issues to be examined in the near future. PMID:24937753

  20. Separation of phenolic acids from natural plant extracts using molecularly imprinted anion-exchange polymer confined ionic liquids.

    PubMed

    Bi, Wentao; Tian, Minglei; Row, Kyung Ho

    2012-04-01

    Polymer-confined ionic liquids were used for the separation of phenolic acids from natural plant extract by utilizing an anion-exchange mechanism. They were synthesized using molecular imprinting technique to reduce non-directional ion-ion interactions during anion-exchange and other interactions with interference substances that could decrease selectivity. A suitable sorbent for phenolic acid separation could be identified based on the adsorption behaviors of phenolic acids on different polymer-confined ionic liquids. Thus, the developed ionic liquid-based molecularly imprinted anion-exchange polymer (IMAP) achieved high recovery rates by solid-phase extraction of phenolic acids from Salicornia herbacea L. extract: 90.1% for protocatechuic acid, 95.5% for ferulic acid and 96.6% for caffeic acid. Moreover, the phenolic acids were separable from each other by repeated solid phase extraction cycles. The proposed method could be used to separate other phenolic acids or organic acids from complex samples. PMID:21903215

  1. Oligomeric states of the voltage-dependent anion channel and cytochrome c release from mitochondria.

    PubMed

    Zalk, Ran; Israelson, Adrian; Garty, Erez S; Azoulay-Zohar, Heftsi; Shoshan-Barmatz, Varda

    2005-02-15

    The VDAC (voltage-dependent anion channel) plays a central role in apoptosis, participating in the release of apoptogenic factors including cytochrome c. The mechanisms by which VDAC forms a protein-conducting channel for the passage of cytochrome c are not clear. The present study approaches this problem by addressing the oligomeric status of VDAC and its role in the induction of the permeability transition pore and cytochrome c release. Chemical cross-linking of isolated mitochondria or purified VDAC with five different reagents proved that VDAC exists as dimers, trimers or tetramers. Fluorescence resonance energy transfer between fluorescently labelled VDACs supports the concept of dynamic VDAC oligomerization. Mitochondrial cross-linking prevented both permeability transition pore opening and release of cytochrome c, yet had no effect on electron transport or Ca2+ uptake. Bilayer-reconstituted purified cross-linked VDAC showed decreased conductance and voltage-independent channel activity. In the dithiobis(succinimidyl propionate)-cross-linked VDAC, these channel properties could be reverted to those of the native VDAC by cleavage of the cross-linking. Cross-linking of VDAC reconstituted into liposomes inhibited the release of the proteoliposome-encapsulated cytochrome c. Moreover, encapsulated, but not soluble cytochrome c induced oligomerization of liposome-reconstituted VDAC. Thus the results indicate that VDAC exists in a dynamic equilibrium between dimers and tetramers and suggest that oligomeric VDAC may be involved in mitochondria-mediated apoptosis. PMID:15456403

  2. Secondary anionic phospholipid binding site and gating mechanism in Kir2.1 inward rectifier channels

    NASA Astrophysics Data System (ADS)

    Lee, Sun-Joo; Wang, Shizhen; Borschel, William; Heyman, Sarah; Gyore, Jacob; Nichols, Colin G.

    2013-11-01

    Inwardly rectifying potassium (Kir) channels regulate multiple tissues. All Kir channels require interaction of phosphatidyl-4,5-bisphosphate (PIP2) at a crystallographically identified binding site, but an additional nonspecific secondary anionic phospholipid (PL(-)) is required to generate high PIP2 sensitivity of Kir2 channel gating. The PL(-)-binding site and mechanism are yet to be elucidated. Here we report docking simulations that identify a putative PL(-)-binding site, adjacent to the PIP2-binding site, generated by two lysine residues from neighbouring subunits. When either lysine is mutated to cysteine (K64C and K219C), channel activity is significantly decreased in cells and in reconstituted liposomes. Directly tethering K64C to the membrane by modification with decyl-MTS generates high PIP2 sensitivity in liposomes, even in the complete absence of PL(-)s. The results provide a coherent molecular mechanism whereby PL(-) interaction with a discrete binding site results in a conformational change that stabilizes the high-affinity PIP2 activatory site.

  3. Bifunctional Crosslinking Agents Enhance Anion Exchange Membrane Efficacy for Vanadium Redox Flow Batteries.

    PubMed

    Wang, Wenpin; Xu, Min; Wang, Shubo; Xie, Xiaofeng; Lv, Yafei; Ramani, Vijay K

    2014-06-01

    A series of cross-linked fluorinated poly (aryl ether oxadiazole) membranes (FPAEOM) derivatized with imidazolium groups were prepared. Poly (N-vinylimidazole) (PVI) was used as the bifunctional cross-linking agent to: a) lower vanadium permeability, b) enhance dimensional stability, and c) concomitantly provide added ion exchange capacity in the resultant anion exchange membranes. At a molar ratio of PVI to FPAEOM of 1.5, the resultant membrane (FPAEOM-1.5 PVI) had an ion exchange capacity of 2.2 meq g-1, a vanadium permeability of 6.8×10-7 cm2 min-1, a water uptake of 68 wt.%, and an ionic conductivity of 22.0 mS cm-1, all at 25°C. Single cells prepared with the FPAEOM-1.5 PVI membrane exhibited a higher coulombic efficiency (> 92%) and energy efficiency (> 86%) after 40 test cycles in vanadium redox flow battery. The imidazolium cation showed high chemical stability in highly acidic and oxidizing vanadium solution as opposed to poor stability in alkaline solutions. Based on our DFT studies, this was attributed to the lower HOMO energy (-7.265 eV) of the HSO4- ion (compared to the OH- ion; -5.496 eV) and the larger HOMO-LUMO energy gap (6.394 eV) of dimethylimidazolium bisulfate ([DMIM] [HSO4]) as compared to [DMIM] [OH] (5.387 eV). PMID:24884171

  4. Transport activity of chimaeric AE2-AE3 chloride/bicarbonate anion exchange proteins.

    PubMed Central

    Fujinaga, Jocelyne; Loiselle, Frederick B; Casey, Joseph R

    2003-01-01

    Chloride/bicarbonate anion exchangers (AEs), found in the plasma membrane of most mammalian cells, are involved in pH regulation and bicarbonate metabolism. Although AE2 and AE3 are highly similar in sequence, AE2-transport activity was 10-fold higher than AE3 (41 versus 4 mM x min(-1) respectively), when expressed by transient transfection of HEK-293 cells. AE2-AE3 chimaeras were constructed to define the region responsible for differences in transport activity. The level of AE2 expression was approx. 30% higher than that of AE3. Processing to the cell surface, studied by chemical labelling and confocal microscopy, showed that AE2 is processed to the cell surface approx. 8-fold more efficiently than AE3. The efficiency of cell-surface processing was dependent on the cytoplasmic domain, since the AE2 domain conferred efficient processing upon the AE3 membrane domain, with a predominant role for amino acids 322-677 of AE2. AE2 that was expressed in HEK-293 cells was glycosylated, but little of AE3 was. However, AE2 expressed in the presence of the glycosylation inhibitor, tunicamycin, was not glycosylated, yet retained 85 +/- 8% of anion-transport activity. Therefore glycosylation has little, if any, role in the cell-surface processing or activity of AE2 or AE3. We conclude that the low anion-transport activity of AE3 in HEK-293 cells is due to low level processing to the plasma membrane, possibly owing to protein interactions with the AE3 cytoplasmic domain. PMID:12578559

  5. Diels Alder polyphenylene anion exchange membrane for nonaqueous redox flow batteries

    SciTech Connect

    Small, Leo J.; Pratt, III, Harry D.; Fujimoto, Cy H.; Anderson, Travis M.

    2015-10-23

    Here highly conductive, solvent-resistant anionic Diels Alder polyphenylene (DAPP) membranes were synthesized with three different ionic contents and tested in an ionic liquid-based nonaqueous redox flow battery (RFB). These membranes display 3–10× increase in conductivity in propylene carbonate compared to some commercially available (aqueous) anion exchange membranes. The membrane with an ion content of 1.5 meq/g (DAPP1.5) proved too brittle for operation in a RFB, while the membrane with an ion content of 2.5 meq/g (DAPP2.5) allowed excessive movement of solvent and poor electrochemical yields (capacity fade). Despite having lower voltage efficiencies compared to DAPP2.5, the membrane with an intermediate ion content of 2.0 meq/g (DAPP2.0) exhibited higher coulombic efficiencies (96.4% vs. 89.1%) and electrochemical yields (21.6% vs. 10.9%) after 50 cycles. Crossover of the electroactive species was the primary reason for decreased electrochemical yields. Analysis of the anolyte and catholyte revealed degradation of the electroactive species and formation of a film at the membrane-solution interface. Increases in membrane resistance were attributed to mechanical and thermal aging of the membrane; no chemical change was observed. As a result, improvements in the ionic selectivity and ionic conductivity of the membrane will increase the electrochemical yield and voltage efficiency of future nonaqueous redox flow batteries.

  6. Synthesis of Composition Tunable and Highly Luminescent Cesium Lead Halide Nanowires through Anion-Exchange Reactions.

    PubMed

    Zhang, Dandan; Yang, Yiming; Bekenstein, Yehonadav; Yu, Yi; Gibson, Natalie A; Wong, Andrew B; Eaton, Samuel W; Kornienko, Nikolay; Kong, Qiao; Lai, Minliang; Alivisatos, A Paul; Leone, Stephen R; Yang, Peidong

    2016-06-15

    Here, we demonstrate the successful synthesis of brightly emitting colloidal cesium lead halide (CsPbX3, X = Cl, Br, I) nanowires (NWs) with uniform diameters and tunable compositions. By using highly monodisperse CsPbBr3 NWs as templates, the NW composition can be independently controlled through anion-exchange reactions. CsPbX3 alloy NWs with a wide range of alloy compositions can be achieved with well-preserved morphology and crystal structure. The NWs are highly luminescent with photoluminescence quantum yields (PLQY) ranging from 20% to 80%. The bright photoluminescence can be tuned over nearly the entire visible spectrum. The high PLQYs together with charge transport measurements exemplify the efficient alloying of the anionic sublattice in a one-dimensional CsPbX3 system. The wires increased functionality in the form of fast photoresponse rates and the low defect density suggest CsPbX3 NWs as prospective materials for optoelectronic applications. PMID:27213511

  7. Synthesis and Structure-Property Relationships of Poly(sulfone)s for Anion Exchange Membranes

    SciTech Connect

    Yan, JL; Moore, HD; Hibbs, MR; Hickner, MA

    2013-10-05

    Membranes based on cationic polymers that conduct anions are important for enabling alkaline membrane fuel cells and other solid-state electrochemical devices that operate at high pH. Anion exchange membranes with poly(arylene ether sulfone) backbones are demonstrated by two routes: chloromethylation of commercially available poly(sulfone)s or radical bromination of benzylmethyl moieties in poly(sulfone)s containing tetramethylbisphenol A monomer residues. Polymers with tethered trimethylbenzyl ammonium moieties resulted from conversion of the halomethyl groups by quaternization with trimethyl amine. The water uptake of the chloromethylated polymers was dependent on the type of poly(sulfone) backbone for a given IEC. Bisphenol A-based Udel (R) poly(sulfone) membranes swelled in water to a large extent while membranes from biphenol-based Radel (R) poly(sulfone), a stiffer backbone than Udel, only showed moderate water uptake. The water uptake of cationic poly(sulfone)s was further reduced by synthesizing tetramethylbisphenol A and 4,4-biphenol-containing poly(sulfone) copolymers where the ionic groups were clustered on the tetramethylbisphenol A residues. The conductivity of all samples scaled with the bulk water uptake. The hydration number of the membranes could be increased by casting membranes from the ionic form polymers versus converting the halomethyl form cast polymers to ionic form in the solid state. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1790-1798, 2013

  8. Diels Alder polyphenylene anion exchange membrane for nonaqueous redox flow batteries

    DOE PAGESBeta

    Small, Leo J.; Pratt, III, Harry D.; Fujimoto, Cy H.; Anderson, Travis M.

    2015-10-23

    Here highly conductive, solvent-resistant anionic Diels Alder polyphenylene (DAPP) membranes were synthesized with three different ionic contents and tested in an ionic liquid-based nonaqueous redox flow battery (RFB). These membranes display 3–10× increase in conductivity in propylene carbonate compared to some commercially available (aqueous) anion exchange membranes. The membrane with an ion content of 1.5 meq/g (DAPP1.5) proved too brittle for operation in a RFB, while the membrane with an ion content of 2.5 meq/g (DAPP2.5) allowed excessive movement of solvent and poor electrochemical yields (capacity fade). Despite having lower voltage efficiencies compared to DAPP2.5, the membrane with an intermediatemore » ion content of 2.0 meq/g (DAPP2.0) exhibited higher coulombic efficiencies (96.4% vs. 89.1%) and electrochemical yields (21.6% vs. 10.9%) after 50 cycles. Crossover of the electroactive species was the primary reason for decreased electrochemical yields. Analysis of the anolyte and catholyte revealed degradation of the electroactive species and formation of a film at the membrane-solution interface. Increases in membrane resistance were attributed to mechanical and thermal aging of the membrane; no chemical change was observed. As a result, improvements in the ionic selectivity and ionic conductivity of the membrane will increase the electrochemical yield and voltage efficiency of future nonaqueous redox flow batteries.« less

  9. Multigram group separation of actinide and lanthanide elements by LiCl-based anion exchange

    SciTech Connect

    Collins, E.D.; Benker, D.E.; Chattin, F.R.; Orr, P.B.; Ross, R.G.

    1980-01-01

    The laboratory-scale LiCl AIX process has been successfully adapted to the multigram scale and has been used effectively in transuranium element production campaigns to separate the lanthanide fission products from the transplutonium actinides and to partition americium and curium from the heavier elements. Corrosion of the tantalum and glass equipment has been negligible. Although radiolytic gas generation has not caused a problem, radiation exposure of the Dowex 1-X10 anion exchange resin does occur significantly. However, the 1.3-L resin bed can be used successfully to process up to 3 batches, each containing 19 g of /sup 244/Cm (54 W of decay heat). The chromatographic elution process is controlled by use of an alpha detector in the column effluent line and by periodic measurement of the neutron profile of the column. The development and use of feed pretreatment and operating methods has enabled effective and dependable operation.

  10. Development of direct methanol alkaline fuel cells using anion exchange membranes

    NASA Astrophysics Data System (ADS)

    Yu, Eileen Hao; Scott, Keith

    Research into the development of direct methanol alkaline fuel cell (DMAFC) using an anion exchange polymer electrolyte membrane is described. The commercial membrane used had a higher electric resistance, but a lower methanol diffusion coefficient than Nafion ® membranes. Fuel cell tests were performed using carbon supported Pt catalyst, and the effect of temperature, methanol concentration, methanol flow rate, air pressure and Pt loading were investigated. It was found that the cell performance improved drastically with a membrane assembly electrode (MEA) which did not include the gas diffusion layer on the anode, because of lower reactant mass transfer resistance. To give suitable cathode performance, humidification of the air and a subtle balance between the air pressure and water transport is required.

  11. Fouling of anion exchange resin by fluorescence analysis in advanced treatment of municipal wastewaters.

    PubMed

    Li, Haibo; Li, Aimin; Shuang, Chendong; Zhou, Qing; Li, Wentao

    2014-12-01

    The application of anion exchange resins (AERs) has been limited by the critical problem of resin fouling, which increases the volume of the desorption concentrate and decreases treatment efficiency. To date, resin fouling has not been well studied and is poorly understood compared to membrane fouling. To reflect the resin fouling level, a resin fouling index (RFI) was established in this work according to the decrease of DOC removal after regeneration of the resin for the advanced treatment of municipal wastewater. Comparing the linear fitting results between the RFI and the fluorescence intensity indicated that the resin fouling was related to the protein-like substances with fluorescence peak T in the region of excitation wavelength <250 nm and emission wavelength <380 nm. Using their fluorescent characteristics as a label, the protein-like substances causing the fouling were further identified as hydrophilic components with molecular weights greater than 6500 Da. PMID:25218660

  12. Simultaneous Enhancements of Conductivity and Stability for Anion Exchange Membranes (AEMs) through Precise Structure Design

    PubMed Central

    Ran, Jin; Wu, Liang; Wei, Bing; Chen, Yaoyao; Xu, Tongwen

    2014-01-01

    Polymeric materials as anion exchange membranes (AEMs) play an essential role in the field of energy and environment. The achievement of high performance AEMs by the precise manipulation of macromolecular architecture remains a daunting challenge. Herein, we firstly report a novel rod-coil graft copolymer AEM, possessing rigid hydrophobic main chains and soft hydrophilic graft chains. The low graft density, which can alleviate the adverse influences of ioinc graft chains on the main chains, was obtained by using the living polymerization technique. Consequently, the grafted ionic groups which result in the degradation of polymer backbone was decreased to a small degree. Moreover, the relatively long graft chains induced the nanophase separation between the hydrophobic polymer chains and hydrophilic graft chains, which creates a convinient pathway for high hydroxide ion mobility. Such an accurate molecular design simultaneously improves the hydroxide ion conductivity and alkaline stability as well as dimensional stability. PMID:25255843

  13. Anion-exchange separation of Pt and Pd using perchloric and hydrochloric acid solutions

    USGS Publications Warehouse

    Petrie, R.K.; Morgan, J.W.

    1982-01-01

    On Biorad Ag-1X8 anion-exchange resin (200-400 mesh), Pd and Pt may be separated from one another by elution with 0.2M HClO4, and 5M HClO4, respectively. If present, Au may be retained by making the elutriants 0.003M in HCl. Alternatively, reduction by H2SO3 enables elution of Pt2+ with 6M HCl before recovery of Pd2+ with 0.2M HClO4??Ir4+ is reduced to Ir3+ by H2SO3 and may be eluted ahead of Pt2+ by 2M HCl. ?? 1982 Akade??miai Kiado??.

  14. NASA Li/CF(x) cell problem analysis: Anion exchange chromatography analysis

    NASA Technical Reports Server (NTRS)

    Bytella, Joseph

    1991-01-01

    An analysis was made of wiper samples used to wipe down lithium/chlorine fluorine battery components and production equipment. These components and equipment were potentially exposed to thionyl chloride vapors. In the presence of moisture, thionyl chloride decomposes to sulfur dioxide and hydrogen chloride. The wiper samples were analyzed for soluble chlorides and fluorides by anion exchange chromatography. During the examination of the test chromatographs, fluoride contamination was discovered in wiper samples from the test equipment. An analytical method to determine fluoride was developed. The first 3 extracts from the potentially exposed and clean wiper samples were tested, and the total fluoride from both groups determined. A comparison of the results from both groups was made to determine the extent of fluoride contamination.

  15. Structure and Properties of a Semi-crystalline Cationic Polymer for Anion Exchange Membranes

    NASA Astrophysics Data System (ADS)

    Beyer, Frederick; Price, Samuel; Savage, Alice; Ren, Xiaoming; Insane Membranes Collaboration

    Nafion has long been studied in order to understand its combination of good mechanical properties, chemical resistance, and excellent charge transport characteristics. In the past decade, uncertainty regarding the morphological behavior of Nafion has largely been resolved, allowing researchers to mimic and improve on the structure of this material. In this presentation, work to incorporate key characteristics of Nafion into a model cation-containing polymer will be described. In these new materials, semi-crystalline atactic poly(norbornene) is used to introduce good mechanical properties to anion-exchange membranes, analogous to the PTFE crystallites in Nafion. The ether linkages between the charged species and backbone are also utilized to place the cationic species (trimethylamine) in our materials into a mechanically soft environment. The resulting polymer shows some characteristics that are similar to those of Nafion. In this presentation, the synthesis, alkaline stability, mechanical properties, morphological behavior and charge transport properties will all be described.

  16. The direct formate fuel cell with an alkaline anion exchange membrane

    NASA Astrophysics Data System (ADS)

    Bartrom, Amy M.; Haan, John L.

    2012-09-01

    We demonstrate for the first time an operating Direct Formate Fuel Cell employing formate salts as the anode fuel, air or oxygen as the oxidant, a polymer anion exchange membrane, and metal catalysts at the anode and cathode. Operation of the DFFC at 60 °C using 1 M KOOCH and 2 M KOH as the anode fuel and electrolyte and oxygen gas at the cathode produces 144 mW cm-2 of peak power density, 181 mA cm-2 current density at 0.6 V, and an open circuit voltage of 0.931 V. This performance is competitive with alkaline Direct Liquid Fuel Cells (DLFCs) previously reported in the literature and demonstrates that formate fuel is a legitimate contender with alcohol fuels for alkaline DLFCs. A survey of the literature shows that a formate-oxygen fuel cell has a high theoretical potential, and the safe, renewable formate fuel does not poison the anode catalyst.

  17. Enhancement of anion-exchange chromatography of DNA using compaction agents

    NASA Technical Reports Server (NTRS)

    Murphy, Jason C.; Fox, George E.; Willson, Richard C.

    2003-01-01

    The use of adsorptive chromatography for preparative nucleic acid separations is often limited by low capacity. The possibility that the adsorbent surface area sterically accessible to nucleic acid molecules could be increased by reducing their radius of gyration with compaction agents has been investigated. The equilibrium adsorption capacity of Q Sepharose anion-exchange matrix for plasmid DNA at 600 mM NaCl was enhanced by up to ca. 40% in the presence of 2.5 mM spermine. In addition, compaction agent selectivity has been demonstrated. Spermine, for example, enhances the adsorption of both plasmid and genomic DNA, spermidine enhances binding only of plasmid, and hexamine cobalt enhances only the binding of genomic DNA. Compaction may be generally useful for enhancing adsorptive separations of nucleic acids.

  18. Anion channel sensitivity to cytosolic organic acids implicates a central role for oxaloacetate in integrating ion flux with metabolism in stomatal guard cells

    PubMed Central

    Wang, Yizhou; Blatt, Michael R.

    2011-01-01

    Stomatal guard cells play a key role in gas exchange for photosynthesis and in minimizing transpirational water loss from plants by opening and closing the stomatal pore. The bulk of the osmotic content driving stomatal movements depends on ionic fluxes across both the plasma membrane and tonoplast, the metabolism of organic acids, primarily Mal (malate), and its accumulation and loss. Anion channels at the plasma membrane are thought to comprise a major pathway for Mal efflux during stomatal closure, implicating their key role in linking solute flux with metabolism. Nonetheless, little is known of the regulation of anion channel current (ICl) by cytosolic Mal or its immediate metabolite OAA (oxaloacetate). In the present study, we have examined the impact of Mal, OAA and of the monocarboxylic acid anion acetate in guard cells of Vicia faba L. and report that all three organic acids affect ICl, but with markedly different characteristics and sidedness to their activities. Most prominent was a suppression of ICl by OAA within the physiological range of concentrations found in vivo. These findings indicate a capacity for OAA to co-ordinate organic acid metabolism with ICl through the direct effect of organic acid pool size. The findings of the present study also add perspective to in vivo recordings using acetate-based electrolytes. PMID:21745184

  19. Anion channel sensitivity to cytosolic organic acids implicates a central role for oxaloacetate in integrating ion flux with metabolism in stomatal guard cells.

    PubMed

    Wang, Yizhou; Blatt, Michael R

    2011-10-01

    Stomatal guard cells play a key role in gas exchange for photosynthesis and in minimizing transpirational water loss from plants by opening and closing the stomatal pore. The bulk of the osmotic content driving stomatal movements depends on ionic fluxes across both the plasma membrane and tonoplast, the metabolism of organic acids, primarily Mal (malate), and its accumulation and loss. Anion channels at the plasma membrane are thought to comprise a major pathway for Mal efflux during stomatal closure, implicating their key role in linking solute flux with metabolism. Nonetheless, little is known of the regulation of anion channel current (I(Cl)) by cytosolic Mal or its immediate metabolite OAA (oxaloacetate). In the present study, we have examined the impact of Mal, OAA and of the monocarboxylic acid anion acetate in guard cells of Vicia faba L. and report that all three organic acids affect I(Cl), but with markedly different characteristics and sidedness to their activities. Most prominent was a suppression of ICl by OAA within the physiological range of concentrations found in vivo. These findings indicate a capacity for OAA to co-ordinate organic acid metabolism with I(Cl) through the direct effect of organic acid pool size. The findings of the present study also add perspective to in vivo recordings using acetate-based electrolytes. PMID:21745184

  20. Efficient defluoridation of water using reusable nanocrystalline layered double hydroxides impregnated polystyrene anion exchanger.

    PubMed

    Cai, Jianguo; Zhang, Yanyang; Pan, Bingcai; Zhang, Weiming; Lv, Lu; Zhang, Quanxing

    2016-10-01

    Water decontamination from fluoride is still a challenging task of global concern. Recently, Al-based layered double hydroxides (LDHs) have been extensively studied for specific fluoride adsorption from water. Unfortunately, they cannot be readily applied in scaled-up application due to their ultrafine particles as well as the regeneration issues caused by their poor stability at alkaline pHs. Here, we developed a novel (LDH)-based hybrid adsorbent, i.e., LALDH-201, by impregnating nanocrystalline Li/Al LDHs (LADLH) inside a commercial polystyrene anion exchanger D201. TEM image and XRD spectra of the resultant nanocomposite confirmed that the LDHs particles were nanosized inside the pores of D201 of highly crystalline nature and well-ordered layer structure. After impregnation, the chemical and mechanical stability of LALDH were significantly improved against pH variation, facilitating its application at a wide pH range (3.5-12). Fluoride adsorption onto LALDH-201 was compared to D201 and activated alumina, evidencing the preferable removal fluoride of LALDH-201. Fluoride adsorption onto LALDH-201 followed pseudo-second-order model, with the maximum capacity (62.5 mg/g from the Sips model) much higher than the other two adsorbents. Fixed-bed adsorption run indicated the qualified treatable volume of the fluoride contaminated groundwater (4.1 mg/L initially) with LALDH-201 was about 11 times as much as with the anion exchanger D201 when the breakthrough point was set as 1.5 mg/L. The capacity of LALDH-201 could be effectively refreshed for continuous column operation without observable loss by using the mixed solution of 0.01 M NaOH + 1 M NaCl. The above results suggested that the hybrid adsorbent LALDH-201 is very promising for water defluoridation in scaled-up application. PMID:27337346

  1. Topological and segmental phylogenetic analyses of the anion exchanger (band 3) family of transporters.

    PubMed

    Espanol, M J; Saier, M H

    1995-01-01

    Eleven sequenced anion exchanger (AE; band 3) proteins, including five AE1, four AE2 and two AE3 proteins, comprise the anion exchanger family (AEF) of homologous proteins. Eliminating the rat and rabbit proteins that are nearly identical to the corresponding mouse proteins, seven dissimilar members of this family were selected for study, divided into N-terminal, central and C-terminal segments (designated segments 0, 1 and 2, respectively) and analysed separately for sequence similarity and phylogenetic relatedness. Segments 0 are variable in length and sequence, are essentially lacking in some of the members of the AEF, and are not demonstrably homologous in other members of the family. All segments 1 and 2 are homologous, but they exhibit widely differing degrees of sequence divergence. Segments 2 are highly conserved in all AEF proteins. Segments 1 of the AE2 and AE3 proteins are as conserved as are segments 2, but segments 1 of the AE1 proteins have diverged from each other and from the AE2 and AE3 segments 1 much more than have segments 2 of these same proteins. The distributions of various types of amino acid residues in the putative transmembrane helical spanners of the seven dissimilar members of the AEF, based on a modification of the 14-spanner model of Wang et al. (1994) was determined, and this distribution was compared with those of other transmembrane transport proteins of known structure (bacterial rhodopsins, outer membrane porins of Gram-negative bacteria and bacterial photosynthetic reaction centres.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7795710

  2. A novel erythroid anion exchange variant (Gly796Arg) of hereditary stomatocytosis associated with dyserythropoiesis

    PubMed Central

    Iolascon, Achille; De Falco, Luigia; Borgese, Franck; Esposito, Maria Rosaria; Avvisati, Rosa Anna; Izzo, Pietro; Piscopo, Carmelo; Guizouarn, Helene; Biondani, Andrea; Pantaleo, Antonella; De Franceschi, Lucia

    2009-01-01

    Background Stomatocytoses are a group of inherited autosomal dominant hemolytic anemias and include overhydrated hereditary stomatocytosis, dehydrated hereditary stomatocytosis, hereditary cryohydrocytosis and familial pseudohyperkalemia. Design and Methods We report a novel variant of hereditary stomatocytosis due to a de novo band 3 mutation (p. G796R-band3 CEINGE) associated with a dyserythropoietic phenotype. Band 3 genomic analysis, measurement at of hematologic parameters and red cell indices and morphological analysis of bone marrow were carried out. We then evaluated the red cell membrane permeability and ion transport systems by functional studies of the patient’s erythrocytes and Xenopus oocytes transfected with mutated band 3. We analyzed the red cell membrane tyrosine phosphorylation profile and the membrane association of the tyrosine kinases Syk and Lyn from the Src-family-kinase group, since the activity of the membrane cation transport pathways is related to cyclic phosphorylation-dephosphorylation events. Results The patient showed mild hemolytic anemia with circulating stomatocytes together with signs of dyserythropoiesis. Her red cells displayed increased Na+ content with decreased K+content and abnormal membrane cation transport activities. Functional characterization of band 3 CEINGE in Xenopus oocytes showed that the mutated band 3 is converted from being an anion exchanger (Cl−, HCO3−) to being a cation pathway for Na+ and K+. Increased tyrosine phosphorylation of some red cell membrane proteins was observed in diseased erythrocytes. Syk and Lyn membrane association was increased in the patient’s red cells compared to in normal controls, indicating perturbation of phospho-signaling pathways involved in cell volume regulation events. Conclusions Band 3 CEINGE alters function from that of anion exchange to cation transport, affects the membrane tyrosine phosphorylation profile, in particular of band 3 and stomatin, and its presence

  3. Defluoridation of water via electrically controlled anion exchange by polyaniline modified electrode reactor.

    PubMed

    Cui, Hao; Li, Qin; Qian, Yan; Tang, Rong; An, Hao; Zhai, Jianping

    2011-11-01

    A polyaniline (PANI) modified electrode reactor was designed for fluoride removal from aqueous solutions. The innovative concept behind the reactor design is that the uptake and elute of fluoride could be well controlled by modulating the potential of the PANI film. The maximum fluoride removal capacity of PANI is more than 20 mg/g at a positive voltage based on the electrically controlled anion-exchange mechanism. The results of batch tests showed that terminal potential values had a major impact on fluoride removal by this PANI, with optimal removal occurring at 1.5 V. The fluoride removal capacity (q(e)) increased rapidly within 5 min and reached equilibrium within 10 min, which indicated a rapid removal velocity of fluoride by PANI under this condition. The applicability of defluoridation using the PANI reactor to treat fluoride-contaminated tap water was also tested through flow cell breakthrough studies. At initial fluoride concentrations of 5 mg/L and 10 mg/L, the breakthrough capacities were 20.08 mg/g and 19.24 mg/g, respectively. Moreover, during the first half of the period before the breakthrough point, the fluoride concentration of the treated solution was below the WHO's recommended levels (1.5 mg/L). The results of the five consecutive treatment-regeneration studies also showed that the PANI films could be reused. Taken together, these results implied that the electrically controlled anion exchange by the PANI-modified electrode reactor may be an effective technique for the removal of fluoride from water. PMID:21907382

  4. Imidazolium-Based Polymeric Materials as Alkaline Anion-Exchange Fuel Cell Membranes

    NASA Technical Reports Server (NTRS)

    Narayan, Sri R.; Yen, Shiao-Ping S.; Reddy, Prakash V.; Nair, Nanditha

    2012-01-01

    Polymer electrolyte membranes that conduct hydroxide ions have potential use in fuel cells. A variety of polystyrene-based quaternary ammonium hydroxides have been reported as anion exchange fuel cell membranes. However, the hydrolytic stability and conductivity of the commercially available membranes are not adequate to meet the requirements of fuel cell applications. When compared with commercially available membranes, polystyrene-imidazolium alkaline membrane electrolytes are more stable and more highly conducting. At the time of this reporting, this has been the first such usage for imidazolium-based polymeric materials for fuel cells. Imidazolium salts are known to be electrochemically stable over wide potential ranges. By controlling the relative ratio of imidazolium groups in polystyrene-imidazolium salts, their physiochemical properties could be modulated. Alkaline anion exchange membranes based on polystyrene-imidazolium hydroxide materials have been developed. The first step was to synthesize the poly(styrene-co-(1-((4-vinyl)methyl)-3- methylimidazolium) chloride through a free-radical polymerization. Casting of this material followed by in situ treatment of the membranes with sodium hydroxide solutions provided the corresponding hydroxide salts. Various ratios of the monomers 4-chloromoethylvinylbenzine (CMVB) and vinylbenzine (VB) provided various compositions of the polymer. The preferred material, due to the relative ease of casting the film, and its relatively low hygroscopic nature, was a 2:1 ratio of CMVB to VB. Testing confirmed that at room temperature, the new membranes outperformed commercially available membranes by a large margin. With fuel cells now in use at NASA and in transportation, and with defense potential, any improvement to fuel cell efficiency is a significant development.

  5. High Guanidinium Permeability Reveals Dehydration-Dependent Ion Selectivity in the Plasmodial Surface Anion Channel

    PubMed Central

    Bokhari, Abdullah A. B.; Mita-Mendoza, Neida K.; Fuller, Alexandra; Pillai, Ajay D.; Desai, Sanjay A.

    2014-01-01

    Malaria parasites grow within vertebrate erythrocytes and increase host cell permeability to access nutrients from plasma. This increase is mediated by the plasmodial surface anion channel (PSAC), an unusual ion channel linked to the conserved clag gene family. Although PSAC recognizes and transports a broad range of uncharged and charged solutes, it must efficiently exclude the small Na+ ion to maintain infected cell osmotic stability. Here, we examine possible mechanisms for this remarkable solute selectivity. We identify guanidinium as an organic cation with high permeability into human erythrocytes infected with Plasmodium falciparum, but negligible uptake by uninfected cells. Transport characteristics and pharmacology indicate that this uptake is specifically mediated by PSAC. The rank order of organic and inorganic cation permeabilities suggests cation dehydration as the rate-limiting step in transport through the channel. The high guanidinium permeability of infected cells also allows rapid and stringent synchronization of parasite cultures, as required for molecular and cellular studies of this pathogen. These studies provide important insights into how nutrients and ions are transported via PSAC, an established target for antimalarial drug development. PMID:25243175

  6. Current state of theoretical and experimental studies of the voltage-dependent anion channel (VDAC).

    PubMed

    Noskov, Sergei Yu; Rostovtseva, Tatiana K; Chamberlin, Adam C; Teijido, Oscar; Jiang, Wei; Bezrukov, Sergey M

    2016-07-01

    Voltage-dependent anion channel (VDAC), the major channel of the mitochondrial outer membrane provides a controlled pathway for respiratory metabolites in and out of the mitochondria. In spite of the wealth of experimental data from structural, biochemical, and biophysical investigations, the exact mechanisms governing selective ion and metabolite transport, especially the role of titratable charged residues and interactions with soluble cytosolic proteins, remain hotly debated in the field. The computational advances hold a promise to provide a much sought-after solution to many of the scientific disputes around solute and ion transport through VDAC and hence, across the mitochondrial outer membrane. In this review, we examine how Molecular Dynamics, Free Energy, and Brownian Dynamics simulations of the large β-barrel channel, VDAC, advanced our understanding. We will provide a short overview of non-conventional techniques and also discuss examples of how the modeling excursions into VDAC biophysics prospectively aid experimental efforts. This article is part of a Special Issue entitled: Membrane Proteins edited by J.C. Gumbart and Sergei Noskov. PMID:26940625

  7. 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

  8. Calcium-calmodulin does not alter the anion permeability of the mouse TMEM16A calcium-activated chloride channel

    PubMed Central

    Yu, Yawei; Kuan, Ai-Seon

    2014-01-01

    The transmembrane protein TMEM16A forms a Ca2+-activated Cl− channel that is permeable to many anions, including SCN−, I−, Br−, Cl−, and HCO3−, and has been implicated in various physiological functions. Indeed, controlling anion permeation through the TMEM16A channel pore may be critical in regulating the pH of exocrine fluids such as the pancreatic juice. The anion permeability of the TMEM16A channel pore has recently been reported to be modulated by Ca2+-calmodulin (CaCaM), such that the pore of the CaCaM-bound channel shows a reduced ability to discriminate between anions as measured by a shift of the reversal potential under bi-ionic conditions. Here, using a mouse TMEM16A clone that contains the two previously identified putative CaM-binding motifs, we were unable to demonstrate such CaCaM-dependent changes in the bi-ionic potential. We confirmed the activity of CaCaM used in our study by showing CaCaM modulation of the olfactory cyclic nucleotide–gated channel. We suspect that the different bi-ionic potentials that were obtained previously from whole-cell recordings in low and high intracellular [Ca2+] may result from different degrees of bi-ionic potential shift secondary to a series resistance problem, an ion accumulation effect, or both. PMID:24981232

  9. Functional Model of Metabolite Gating by Human Voltage-Dependent Anion Channel 2

    PubMed Central

    2011-01-01

    Voltage-dependent anion channels (VDACs) are critical regulators of outer mitochondrial membrane permeability in eukaryotic cells. VDACs have also been postulated to regulate cell death mechanisms. Erastin, a small molecule quinazolinone that is selectively lethal to tumor cells expressing mutant RAS, has previously been reported as a ligand for hVDAC2. While significant efforts have been made to elucidate the structure and function of hVDAC1, structural and functional characterization of hVDAC2 remains lacking. Here, we present an in vitro system that provides a platform for both functional and structural investigation of hVDAC2 and its small molecule modulator, erastin. Using this system, we found that erastin increases permeability of VDAC2 liposomes to NADH in a manner that requires the amino-terminal region of VDAC2. Furthermore, we confirmed that this VDAC2-lipsome sample is folded using solid-state NMR. PMID:21425834

  10. Functional model of metabolite gating by human voltage-dependent anion channel 2.

    PubMed

    Bauer, Andras J; Gieschler, Simone; Lemberg, Kathryn M; McDermott, Ann E; Stockwell, Brent R

    2011-05-01

    Voltage-dependent anion channels (VDACs) are critical regulators of outer mitochondrial membrane permeability in eukaryotic cells. VDACs have also been postulated to regulate cell death mechanisms. Erastin, a small molecule quinazolinone that is selectively lethal to tumor cells expressing mutant RAS, has previously been reported as a ligand for hVDAC2. While significant efforts have been made to elucidate the structure and function of hVDAC1, structural and functional characterization of hVDAC2 remains lacking. Here, we present an in vitro system that provides a platform for both functional and structural investigation of hVDAC2 and its small molecule modulator, erastin. Using this system, we found that erastin increases permeability of VDAC2 liposomes to NADH in a manner that requires the amino-terminal region of VDAC2. Furthermore, we confirmed that this VDAC2-lipsome sample is folded using solid-state NMR. PMID:21425834

  11. A dication cross-linked composite anion-exchange membrane for all-vanadium flow battery applications.

    PubMed

    Zhang, Fengxiang; Zhang, Huamin; Qu, Chao

    2013-12-01

    We report the fabrication and properties of a high-performance, inexpensive, composite, anion-exchange membrane (AEM) for an all-vanadium flow battery (VFB) application. The AEM was fabricated by dication cross-linking without the involvement of trimethylamine, and shows well-balanced anion conductivity and robustness due to imidazolium and imidazolium-ammonium functionalities, as well as a concomitantly achieved semi-interpenetrating network structure. The VFB single cell yielded a Coulombic efficiency of 99 % and an energy efficiency of 84 % at 80 mA cm(-2) , and operated for over 900 charge/discharge cycles. This work demonstrates the combined use of several favorable AEM design rationales, such as incorporating abundant and efficient anion-exchange groups, constructing a swelling- and oxidation-resistant structure, and facile fabrication; it provides an effective way of developing high-performance, low-cost AEMs for VFB applications. PMID:24124071

  12. Volume-regulated anion channel--a frenemy within the brain.

    PubMed

    Mongin, Alexander A

    2016-03-01

    The volume-regulated anion channel (VRAC) is a ubiquitously expressed yet highly enigmatic member of the superfamily of chloride/anion channels. It is activated by cellular swelling and mediates regulatory cell volume decrease in a majority of vertebrate cells, including those in the central nervous system (CNS). In the brain, besides its crucial role in cellular volume regulation, VRAC is thought to play a part in cell proliferation, apoptosis, migration, and release of physiologically active molecules. Although these roles are not exclusive to the CNS, the relative significance of VRAC in the brain is amplified by several unique aspects of its physiology. One important example is the contribution of VRAC to the release of the excitatory amino acid neurotransmitters glutamate and aspartate. This latter process is thought to have impact on both normal brain functioning (such as astrocyte-neuron signaling) and neuropathology (via promoting the excitotoxic death of neuronal cells in stroke and traumatic brain injury). In spite of much work in the field, the molecular nature of VRAC remained unknown until less than 2 years ago. Two pioneer publications identified VRAC as the heterohexamer formed by the leucine-rich repeat-containing 8 (LRRC8) proteins. These findings galvanized the field and are likely to result in dramatic revisions to our understanding of the place and role of VRAC in the brain, as well as other organs and tissues. The present review briefly recapitulates critical findings in the CNS and focuses on anticipated impact on the LRRC8 discovery on further progress in neuroscience research. PMID:26620797

  13. The effects of anion exchange functional-group variations on the sorption of Pu(IV) from nitric acid

    SciTech Connect

    Marsh, S.F.

    1995-12-01

    A macroporous, polyvinylpyridine anion exchange resin has been used for more than five years at the Los Alamos Plutonium Facility to recover plutonium from nitrate media. This strong-base anion exchanger, Reillex{trademark} HPQ, offers higher capacity, faster kinetics, and significantly higher resistance to chemical and radiation damage than conventional polystyrene-based resins. In this study, we measured the sorption of Pu(IV) on Reillex{trademark} HPQ and on three macroporous, strong-base anion exchange resins that differ from Reillex{trademark} HPQ only in the alkyl group used to quaternize the pyridinium. nitrogen. These four resins, prepared by Reilly Industries, Inc., are copolymers of 1-alkyl-4-vinylpyridine, where the alkyl groups are methyl, butyl, hexyl, and octyl. We compare the trends in Pu(IV) sorption on these four resins to those obtained in our previous study of four polystyrene anion exchange resins having trimethyl, triethyl, tripropyl, and tributyl ammonium functionality. The Pu(IV) sorption was measured from 1 M to 9 M nitric acid in both studies.

  14. ANION EXCHANGE METHOD FOR THE DETERMINATION OF PLUTONIUM IN WATER: SINGLE-LABORATORY EVALUATION AND INTERLABORATORY COLLABORATIVE STUDY

    EPA Science Inventory

    This report gives the results of a single-laboratory evaluation and an interlaboratory collaborative study of a method for determining plutonium in water. The method was written for the analysis of 1-liter samples and involved coprecipitation, acid dissolution, anion exchange, el...

  15. Performance testing of grout-based waste forms for the solidification of anion exchange resins

    SciTech Connect

    Morgan, I.L.; Bostick, W.D.

    1990-10-01

    The solidification of spent ion exchanges resins in a grout matrix as a means of disposing of spent organic resins produced in the nuclear fuel cycle has many advantages in terms of process simplicity and economy, but associated with the process is the potential for water/cement/resins to interact and degrade the integrity of the waste form solidified. Described in this paper is one possible solution to preserving the integrity of these solidified waste forms: the encapsulation of beaded anion exchange resins in grout formulations containing ground granulated blast furnace slag, Type I-II (mixed) portland cement, and additives (clays, amorphous silica, silica fume, and fly ash). The results of the study reported herein show the cured waste form tested has a low leach rate for nitrate ion from the resin (and a low leach rate is inferred for Tc-99) and acceptable durability as assessed by the water immersion and freezing/thawing test protocols. The results also suggest a tested surrogate waste form prepared in vinyl ester styrene binder performs satisfactorily against the wetting/drying criterion, and it should offer additional insight into future work on the solidification of spent organic resins. 26 refs., 4 figs., 5 tabs.

  16. Human kidney anion exchanger 1 interacts with kinesin family member 3B (KIF3B).

    PubMed

    Duangtum, Natapol; Junking, Mutita; Sawasdee, Nunghathai; Cheunsuchon, Boonyarit; Limjindaporn, Thawornchai; Yenchitsomanus, Pa-thai

    2011-09-16

    Impaired trafficking of human kidney anion exchanger 1 (kAE1) to the basolateral membrane of α-intercalated cells of the kidney collecting duct leads to the defect of the Cl(-)/HCO(3)(-) exchange and the failure of proton (H(+)) secretion at the apical membrane of these cells, causing distal renal tubular acidosis (dRTA). In the sorting process, kAE1 interacts with AP-1 mu1A, a subunit of AP-1A adaptor complex. However, it is not known whether kAE1 interacts with motor proteins in its trafficking process to the plasma membrane or not. We report here that kAE1 interacts with kinesin family member 3B (KIF3B) in kidney cells and a dileucine motif at the carboxyl terminus of kAE1 contributes to this interaction. We have also demonstrated that kAE1 co-localizes with KIF3B in human kidney tissues and the suppression of endogenous KIF3B in HEK293T cells by small interfering RNA (siRNA) decreases membrane localization of kAE1 but increases its intracellular accumulation. All results suggest that KIF3B is involved in the trafficking of kAE1 to the plasma membrane of human kidney α-intercalated cells. PMID:21871436

  17. Mechanism of sorption sulpho-derivative organic chelating agents on strong base anion exchanger Amberlite IRA-402 by FT-IR/PAS and DRS methods

    NASA Astrophysics Data System (ADS)

    Wronski, G.; Pasieczna-Patkowska, S.; Hubicki, Z.

    2008-02-01

    In the paper, strong base anion exchanger Amberlite IRA-402 was modified by using sulpho-derivative organic chelating agents as: Brilliant Yellow, Xylenol Orange, Bromophenyl Blue. The investigations exhibited, that anion exchanger Amberlite IRA-402 is modified very simply by organic chelating agents (working capacity 0.25 0.5 g/cm3).

  18. ANIONIC EXCHANGE PROCESS FOR THE RECOVERY OF URANIUM AND VANADIUM FROM CARBONATE SOLUTIONS

    DOEpatents

    Bailes, R.H.; Ellis, D.A.; Long, R.S.

    1958-12-16

    Uranium and vanadium can be economically purified and recovered from non- salt roast carbonate leach liquors by adsorption on a strongly basic anionic exchange resin and subsequent selective elution by one of three alternative methods. Method 1 comprises selectively eluting uranium from the resin with an ammonium sulfate solution followed by eluting vanadium from the resin with either 5 M NaCl, saturated (NH/sub 4/)/sub 2/CO/sub 3/, saturated NaHCO/sub 3/, 1 M NaOH, or saturated S0/sub 2/ solutions. Method II comprises selectively eluting vanadium from the resin with either concentrated NaCl or S0/sub 2/ solutions subsequent to pretreatment of the column with either S0/sub 2/ gas, 1 N HCl, or 0.1 N H/sub 2/8O/sub 4/ followed by eluting uranium from the resin with solutions containing 0.9 M NH/sub 4/Cl or NaCl and 0.1 Cl. Method III comprises flowing the carbonate leac solutlon through a first column of a strongly basic anlonlc exchange resin untll vanadium breakthrough occurs, so that the effluent solution is enriched ln uranium content and the vanadium is chiefly retalned by the resln, absorbing the uranlum from the enriched effluent solution on a second column of a strongly basic anionic exchange resin, pretreating the first column with either 0.1 N HCl, 0.1 H/sub 2/SO/sub 4/, C0/sub 2/ gas, or ammonium sulfate, selectively eluting the vanadlum from the column with saturated S0/sub 2/ solution, pretreatlng the second column with either 0.1 N HCl or S0/sub 2/ gas, selectively eluting residual vanadium from the column with saturated S0/sub 2/ solution, and then eluting the uranium from the column with either 0.1 N HCl and 1 N NaCl orO.l N HCl and 1 N NH/sub 4/Cl.

  19. Grafting glycidyl methacrylate to Sepharose gel for fabricating high-capacity protein anion exchangers.

    PubMed

    Wang, Qianqian; Yu, Linling; Sun, Yan

    2016-04-22

    To develop ion exchangers of high protein adsorption capacity, we have herein introduced atom transfer radical polymerization (ATRP) method to graft glycidyl methacrylate (GMA) onto Sepharose FF gel. GMA-grafted Sepharose FF resins of four grafting densities and different grafting chain lengths were obtained by adjusting reaction conditions. The epoxy groups on the grafted chains were functionalized by modification with diethylamine (DEA), leading to the fabrication of Sepharose-based anion exchangers of 14 different grafting densities and/or grafting chain lengths. The resins were first characterized for the effects of grafting density, chain length and ionic strength on pore sizes by inverse size exclusion chromatography. Then, the resins were evaluated by adsorption equilibria of bovine serum albumin (BSA) as a function of ionic capacity (IC) (chain length) at individual grafting densities. It was observed that at each grafting density there was a specific IC value (chain length) that offered the maximum equilibrium capacity. Of the resins with maximum values at individual grafting densities, the resin of the second grafting density with an IC value of 330 mmol/L (denoted as FF-Br2-pG-D330) showed the highest capacity, 264 mg/mL, about two times higher than that of the traditional ungrafted resin Q Sepharose FF (137 mg/mL). This resin also showed the most favorable uptake kinetics among the resins of similar IC values but different grafting densities, or of the same grafting density but different IC values. Effects of ionic strength showed that the capacities of FF-Br2-pG-D330 were much higher than Q Sepharose FF at a wide range of NaCl concentrations (0-200 mmol/L), and the uptake rates of the two resins were similar in the ionic strength range. Therefore, the dynamic binding capacity values of BSA on FF-Br2-pG-D330 were much higher than Q Sepharose FF as demonstrated at different residence times and ionic strengths. Taken together, the research has proved the

  20. SLAH3-type anion channel expressed in poplar secretory epithelia operates in calcium kinase CPK-autonomous manner.

    PubMed

    Jaborsky, Mario; Maierhofer, Tobias; Olbrich, Andrea; Escalante-Pérez, María; Müller, Heike M; Simon, Judy; Krol, Elzbieta; Cuin, Tracey Ann; Fromm, Jörg; Ache, Peter; Geiger, Dietmar; Hedrich, Rainer

    2016-05-01

    Extrafloral nectaries secrete a sweet sugar cocktail that lures predator insects for protection from foraging herbivores. Apart from sugars and amino acids, the nectar contains the anions chloride and nitrate. Recent studies with Populus have identified a type of nectary covered by apical bipolar epidermal cells, reminiscent of the secretory brush border epithelium in animals. Border epithelia operate transepithelial anion transport, which is required for membrane potential and/or osmotic adjustment of the secretory cells. In search of anion transporters expressed in extrafloral nectaries, we identified PttSLAH3 (Populus tremula × Populus tremuloides SLAC1 Homologue3), an anion channel of the SLAC/SLAH family. When expressed in Xenopus oocytes, PttSLAH3 displayed the features of a voltage-dependent anion channel, permeable to both nitrate and chloride. In contrast to the Arabidopsis SLAC/SLAH family members, the poplar isoform PttSLAH3 is independent of phosphorylation activation by protein kinases. To understand the basis for the autonomous activity of the poplar SLAH3, we generated and expressed chimera between kinase-independent PttSLAH3 and kinase-dependent Arabidopsis AtSLAH3. We identified the N-terminal tail and, to a lesser extent, the C-terminal tail as responsible for PttSLAH3 kinase-(in)dependent action. This feature of PttSLAH3 may provide the secretory cell with a channel probably controlling long-term nectar secretion. PMID:26831448

  1. 47 CFR 22.757 - Channels for basic exchange telephone radio systems.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 2 2010-10-01 2010-10-01 false Channels for basic exchange telephone radio... CARRIER SERVICES PUBLIC MOBILE SERVICES Rural Radiotelephone Service Basic Exchange Telephone Radio Systems § 22.757 Channels for basic exchange telephone radio systems. The channels listed in § 22.725...

  2. 47 CFR 22.757 - Channels for basic exchange telephone radio systems.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 2 2013-10-01 2013-10-01 false Channels for basic exchange telephone radio... CARRIER SERVICES PUBLIC MOBILE SERVICES Rural Radiotelephone Service Basic Exchange Telephone Radio Systems § 22.757 Channels for basic exchange telephone radio systems. The channels listed in § 22.725...

  3. 47 CFR 22.757 - Channels for basic exchange telephone radio systems.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 2 2014-10-01 2014-10-01 false Channels for basic exchange telephone radio... CARRIER SERVICES PUBLIC MOBILE SERVICES Rural Radiotelephone Service Basic Exchange Telephone Radio Systems § 22.757 Channels for basic exchange telephone radio systems. The channels listed in § 22.725...

  4. 47 CFR 22.757 - Channels for basic exchange telephone radio systems.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 2 2011-10-01 2011-10-01 false Channels for basic exchange telephone radio... CARRIER SERVICES PUBLIC MOBILE SERVICES Rural Radiotelephone Service Basic Exchange Telephone Radio Systems § 22.757 Channels for basic exchange telephone radio systems. The channels listed in § 22.725...

  5. 47 CFR 22.757 - Channels for basic exchange telephone radio systems.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 2 2012-10-01 2012-10-01 false Channels for basic exchange telephone radio... CARRIER SERVICES PUBLIC MOBILE SERVICES Rural Radiotelephone Service Basic Exchange Telephone Radio Systems § 22.757 Channels for basic exchange telephone radio systems. The channels listed in § 22.725...

  6. Mutations in the channel domain of a neuronal nicotinic receptor convert ion selectivity from cationic to anionic.

    PubMed

    Galzi, J L; Devillers-Thiéry, A; Hussy, N; Bertrand, S; Changeux, J P; Bertrand, D

    1992-10-01

    Introduction by site-directed mutagenesis of three amino acids from the MII segment of glycine or gamma-aminobutyric acid (GABAA) receptors into the MII segment of alpha 7 nicotinic receptor was sufficient to convert a cation-selective channel into an anion-selective channel gated by acetylcholine. A critical mutation was the insertion of an uncharged residue at the amino-terminal end of MII, stressing the importance of protein geometrical constraints on ion selectivity. PMID:1383829

  7. High-Capacity and Rapid Removal of Refractory NOM Using Nanoscale Anion Exchange Resin.

    PubMed

    Johnson, Billy R; Eldred, Tim B; Nguyen, Andy T; Payne, William M; Schmidt, Emily E; Alansari, Amir Y; Amburgey, James E; Poler, Jordan C

    2016-07-20

    As human health concerns over disinfection byproducts (DBP) in drinking water increase, so does the need to develop new materials that remove them rapidly and at high capacity. Ion exchange (IEX) is an effective method for the removal of natural organic matter (NOM), especially anion exchange resins (AERs) with quaternary ammonium functional groups. However, capacity is limited in existing commercial resin materials because adsorbates can only interact with the outermost surface area, which makes these products inefficient on a mass basis. We have synthesized a novel "NanoResin" exploiting the enhanced NOM removal of the quaternary ammonium resin while utilizing the vast surface area of SWCNTs, which act as scaffolding for the resin. Our nanomaterials show increased adsorption capacity compared to commercially available adsorbents, in a fraction of the time. This NanoResin requires only about 10 s to reach ion-exchange equilibrium. Comparatively, commercial AERs only achieved partial removal after more than 30 min. High capacity adsorption of a low molecular weight (MW) surrogate has been measured. NOM removal was demonstrated in solutions of both low and high specific UV absorbance (SUVA) composition with these nanomaterials. Additionally, the NanoResin showed enhanced removal of a NOM concentrate sample taken from Myrtle Beach, SC, demonstrating NanoResin is an effective method of removal for refractory NOM in a natural aqueous environment. Synthesis and characterization of the polymers and nanomaterials are presented below. Adsorption capacity, adsorption kinetics, and the regeneration and reusability of these new materials for NOM removal are described. The open matrix microstructure precludes any intraparticle diffusion of adsorbates; thus, these nanomaterials act as a "contact resin". PMID:27348616

  8. Anion Exchanger 2 Regulates Dectin-1-Dependent Phagocytosis and Killing of Candida albicans.

    PubMed

    Urso, Katia; Charles, Julia F; Shull, Gary E; Aliprantis, Antonios O; Balestrieri, Barbara

    2016-01-01

    Anion exchanger 2 (Ae2; gene symbol, Slc4a2) is a plasma membrane Cl-/HCO3- exchanger expressed in the gastrointestinal tract, kidney and bone. We have previously shown that Ae2 is required for the function of osteoclasts, bone resorbing cells of the macrophage lineage, to maintain homeostatic cytoplasmic pH and electroneutrality during acid secretion. Macrophages require endosomal acidification for pathogen killing during the process known as phagocytosis. Chloride is thought to be the principal ion responsible for maintaining electroneutrality during organelle acidification, but whether Cl-/HCO3- exchangers such as Ae2 contribute to macrophage function is not known. In this study we investigated the role of Ae2 in primary macrophages during phagocytosis. We find that Ae2 is expressed in macrophages where it regulates intracellular pH and the binding of Zymosan, a fungal cell wall derivative. Surprisingly, the transcription and surface expression of Dectin-1, the major phagocytic receptor for Candida albicans (C. albicans) and Zymosan, is reduced in the absence of Ae2. As a consequence, Zymosan-induced Tnfα expression is also impaired in Ae2-deficient macrophages. Similar to Ae2 deficiency, pharmacological alkalinization of lysosomal pH with bafilomycin A decreases both Dectin-1 mRNA and cell surface expression. Finally, Ae2-deficient macrophages demonstrate defective phagocytosis and killing of the human pathogenic fungus C. albicans. Our results strongly suggest that Ae2 is a critical factor in the innate response to C. albicans. This study represents an important contribution to a better understanding of how Dectin-1 expression and fungal clearance is regulated. PMID:27391897

  9. Anion Exchanger 2 Regulates Dectin-1-Dependent Phagocytosis and Killing of Candida albicans

    PubMed Central

    Urso, Katia; Charles, Julia F.; Shull, Gary E.; Aliprantis, Antonios O.; Balestrieri, Barbara

    2016-01-01

    Anion exchanger 2 (Ae2; gene symbol, Slc4a2) is a plasma membrane Cl-/HCO3- exchanger expressed in the gastrointestinal tract, kidney and bone. We have previously shown that Ae2 is required for the function of osteoclasts, bone resorbing cells of the macrophage lineage, to maintain homeostatic cytoplasmic pH and electroneutrality during acid secretion. Macrophages require endosomal acidification for pathogen killing during the process known as phagocytosis. Chloride is thought to be the principal ion responsible for maintaining electroneutrality during organelle acidification, but whether Cl-/HCO3- exchangers such as Ae2 contribute to macrophage function is not known. In this study we investigated the role of Ae2 in primary macrophages during phagocytosis. We find that Ae2 is expressed in macrophages where it regulates intracellular pH and the binding of Zymosan, a fungal cell wall derivative. Surprisingly, the transcription and surface expression of Dectin-1, the major phagocytic receptor for Candida albicans (C. albicans) and Zymosan, is reduced in the absence of Ae2. As a consequence, Zymosan-induced Tnfα expression is also impaired in Ae2-deficient macrophages. Similar to Ae2 deficiency, pharmacological alkalinization of lysosomal pH with bafilomycin A decreases both Dectin-1 mRNA and cell surface expression. Finally, Ae2-deficient macrophages demonstrate defective phagocytosis and killing of the human pathogenic fungus C. albicans. Our results strongly suggest that Ae2 is a critical factor in the innate response to C. albicans. This study represents an important contribution to a better understanding of how Dectin-1 expression and fungal clearance is regulated. PMID:27391897

  10. Inter-channel effects in monosolvated atomic iodide cluster anion detachment: Correlation of the anisotropy parameter with solvent dipole moment

    NASA Astrophysics Data System (ADS)

    Mbaiwa, Foster; Dao, Diep; Holtgrewe, Nicholas; Lasinski, Joshua; Mabbs, Richard

    2012-03-01

    Photoelectron imaging results are presented for I-.X cluster anions (X = CO2, C4H5N [pyrrole], (CH3)2CO, CH3NO2). The available detachment channels are labeled according to the neutral iodine atom states produced (channel I ≡ 2P3/2 and channel II ≡ 2P1/2). At photon energies in the vicinity of the channel II threshold these data are compared to previously reported results for I-.X (X = CH3CN, CH3Cl, CH3Br, and H2O). In particular, these results show a strong connection between the dipole moment of the solvent molecule and the behavior of the channel I photoelectron angular distributions in this region, which is consistent with an electronic autodetachment process. The evolution of the channel II:channel I branching ratios in this excitation regime supports this contention.

  11. Removing hexavalent chromium from subsurface waters with anion-exchange resin

    SciTech Connect

    Torres, R.A.

    1995-06-01

    Some subsurface waters at Lawrence Livermore National Laboratory (LLNL) are contaminated with volatile organic compounds (VOCs). Hexavalent chromium, Cr(VI), is also present in the ground water; however, the source of the Cr(VI) may be natural. The Cr(VI) still must be treated if brought to the surface because its concentration exceeds discharge standards. We are planning facilities for removing the VOCs and Cr(VI) to a level below the discharge standards. The planned treatment includes the following steps: (1) Pumping the water to the surface facility. (2) Purging the VOCs with air and absorbing them on activated carbon. The VOCs in LLNL`s subsurface waters are primarily chlorinated organic solvents, such as dichloroethylene (DCE), trichloroethylene (TCE), perchloroethylene (PCE), and chloroform (CHCl{sub 3}). Contamination levels range from tens to thousands of parts per billion. (3) Filtering the water. (4) Passing the water through anion-exchange resin to remove the Cr. The Cr in LLNL subsurface waters occurs almost entirely as Cr(VI), which exists as the chromate anion, CrO{sub 4}{sup 2-}, at environmental pH. Cr levels range from tens to hundreds of parts per billion. (5) Discharging the treated water into the local arroyos. The relevant discharge criteria are 5 ppb total VOCs, 11 ppb Cr(VI), and pH between 6.5 and 8.5, inclusive. This report describes laboratory experiments undertaken to learn how the proposed treatment facility can be expected to operate. The laboratory results are expected to supply vendors with the detailed performance specifications needed to prepare bids on the Cr removal portion of the treatment facility. The treatment facility is expected to process 60 gallons per minute (gpm) of water by stripping VOCs with 720 standard cubic feet per minute (scfm) of air and removing Cr(VI) with 60 ft{sup 3} of resin.

  12. Modulation of the voltage-dependent anion channel of mitochondria by elaidic acid.

    PubMed

    Tewari, Debanjan; Bera, Amal Kanti

    2016-08-26

    Dietary trans fatty acids (TFAs) are known to increase the risk of cardiovascular diseases by altering plasma lipid profile and activating various inflammatory signaling pathways. Here we show that elaidic acid (EA), the most abundant TFA in diet, alters the electrophysiological properties of voltage-dependent anion channel (VDAC) of mitochondria. Purified bovine brain VDAC, when incorporated in the planar lipid bilayer (PLB) composed of 1,2-diphytanoyl-sn-glycero-3 phosphatidyl choline (DPhPC) and EA in a 9 to 1 ratio (wt/wt), exhibited complete closing events at different voltages. The closing events were observed at even -10 mV, a voltage at which VDAC usually remains fully open all the time. Additionally, the voltage sensitivity of VDAC was lost in presence of EA; the channel conductance did not decrease with increasing voltages. In identical experimental conditions, membrane containing oleic acid (OA), the cis isomer of EA did not produce any such effect. We propose that EA possibly exerts its adverse effect by modulating VDAC. PMID:27318085

  13. Isolation, characterization, and mapping of two mouse mitochondrial voltage-dependent anion channel isoforms

    SciTech Connect

    Sampson, M.J.; Lovell, R.S.; Craigen, W.J.

    1996-04-15

    Voltage-dependent anion channels (VDACs) are small pore-forming channels found in the mitochondrial outer membrane of all eukaryotes. VDACs conduct adenine nucleotides and are the binding sites for several cytosolic enzymes, including the isoforms of hexokinase and glycerol kinase. VDAC binding is developmentally and metabolically regulated and allows the kinases preferential access to mitochondrial ATP. Two human VDAC cDNAs have recently been identified, and a total four VDAC loci have been mapped. Here, the isolation of two mouse VDAC cDNAs (VDAC5 and VDAC6) is described. By Northern analysis the two mouse VDAC isoforms show nearly identical expression patterns, with high levels of expression detected in heart, kidney, brain, and skeletal muscle and lesser levels of expression in all other tissues examined. The only exception is the lack of expression is highest in this tissue. VDAC6 appears to be encoded by more than one transcript. The mouse VDAC5 gene was mapped using an interspecies DNA mapping panel to the proximal region of chromosome 11, and the mouse VDAC6 gene was mapped using a panel to the proximal region of chromosome 14. 37 refs., 3 figs.

  14. Functional interaction of endothelial nitric oxide synthase with a voltage-dependent anion channel

    PubMed Central

    Sun, Jianxin; Liao, James K.

    2002-01-01

    Endothelium-derived nitric oxide (NO) is an important regulator of vascular function. NO is produced by endothelial NO synthase (eNOS) whose function is modulated, in part, by specific protein interactions. By coimmunoprecipitation experiments followed by MS analyses, we identified a human voltage-dependent anion/cation channel or porin as a binding partner of eNOS. The interaction between porin and eNOS was demonstrated by coimmunoprecipitation studies in nontransfected human endothelial cells and Cos-7 cells transiently transfected with eNOS and porin cDNAs. In vitro binding studies with glutathione S-transferase–porin indicated that porin binds directly to eNOS and that this interaction augmented eNOS activity. The calcium ionophore, A23187, and bradykinin, which are known to activate eNOS, markedly increased porin–eNOS interaction, suggesting a potential role of intracellular Ca2+ in mediating this interaction. Theses results indicate that the interaction between a voltage-dependent membrane channel and eNOS may be important for regulating eNOS activity. PMID:12228731

  15. Structural basis of control of inward rectifier Kir2 channel gating by bulk anionic phospholipids.

    PubMed

    Lee, Sun-Joo; Ren, Feifei; Zangerl-Plessl, Eva-Maria; Heyman, Sarah; Stary-Weinzinger, Anna; Yuan, Peng; Nichols, Colin G

    2016-09-01

    Inward rectifier potassium (Kir) channel activity is controlled by plasma membrane lipids. Phosphatidylinositol-4,5-bisphosphate (PIP2) binding to a primary site is required for opening of classic inward rectifier Kir2.1 and Kir2.2 channels, but interaction of bulk anionic phospholipid (PL(-)) with a distinct second site is required for high PIP2 sensitivity. Here we show that introduction of a lipid-partitioning tryptophan at the second site (K62W) generates high PIP2 sensitivity, even in the absence of PL(-) Furthermore, high-resolution x-ray crystal structures of Kir2.2[K62W], with or without added PIP2 (2.8- and 2.0-Å resolution, respectively), reveal tight tethering of the C-terminal domain (CTD) to the transmembrane domain (TMD) in each condition. Our results suggest a refined model for phospholipid gating in which PL(-) binding at the second site pulls the CTD toward the membrane, inducing the formation of the high-affinity primary PIP2 site and explaining the positive allostery between PL(-) binding and PIP2 sensitivity. PMID:27527100

  16. Removal of perfluorooctane sulfonate from wastewater by anion exchange resins: effects of resin properties and solution chemistry.

    PubMed

    Deng, Shubo; Yu, Qiang; Huang, Jun; Yu, Gang

    2010-10-01

    Perfluorooctane sulfonate (PFOS) is a new persistent organic pollutant of substantial environmental concern, and its removal from industrial wastewater is critical to eliminate its release into water environment. In this paper, six anion exchange resins with different polymer matrix, porosity, and functional group were evaluated for PFOS removal from simulated wastewater. Resin matrix displayed significant effect on the sorption kinetics and capacity of PFOS, and the polyacrylic resins including IRA67 and IRA958 exhibited faster sorption and higher sorption capacity for PFOS than the polystyrene resins due to the hydrophilic matrix. Sorption isotherms illustrated that the sorption capacity of PFOS on IRA67 and IRA958 was up to 4-5 mmol/g, and the amount of PFOS sorbed on the resins was more than chloride released from resins, indicating that other interactions besides anion exchange were involved in the sorption. Solution pH had little impact on the sorption of PFOS on IRA958, but displayed significant effect on IRA67 at pH above 10 due to the deprotonation of amine groups. The coexisting sulfate and hexavalent chromium in wastewater interfered with the sorption of PFOS because of their competitive sorption on the exchange sites. The spent resins were successfully regenerated using the mixture of NaCl and methanol solution. This work provided an understanding of sorption behavior and mechanism of PFOS on different anion exchange resins, and should result in more effective applications of ion exchange for PFOS removal from industrial wastewater. PMID:20605036

  17. Model of a vanadium redox flow battery with an anion exchange membrane and a Larminie-correction

    NASA Astrophysics Data System (ADS)

    Wandschneider, F. T.; Finke, D.; Grosjean, S.; Fischer, P.; Pinkwart, K.; Tübke, J.; Nirschl, H.

    2014-12-01

    Membranes are an important part of vanadium redox flow battery cells. Most cell designs use Nafion®-type membranes which are cation exchange membranes. Anion exchange membranes are reported to improve cell performance. A model for a vanadium redox flow battery with an anion exchange membrane is developed. The model is then used to calculate terminal voltages for open circuit and charge-discharge conditions. The results are compared to measured data from a laboratory test cell with 40 cm2 active membrane area. For higher charge and discharge currents, an empirical correction for the terminal voltage is proposed. The model geometry comprises the porous electrodes and the connected pipes, allowing a study of the flow in the entrance region for different state-of-charges.

  18. Functional characterization of three novel tissue-specific anion exchangers SLC26A7, -A8, and -A9.

    PubMed

    Lohi, Hannes; Kujala, Minna; Makela, Siru; Lehtonen, Eero; Kestila, Marjo; Saarialho-Kere, Ulpu; Markovich, Daniel; Kere, Juha

    2002-04-19

    A second distinct family of anion exchangers, SLC26, in addition to the classical SLC4 (or anion exchanger) family, has recently been delineated. Particular interest in this gene family is stimulated by the fact that the SLC26A2, SLC26A3, and SLC26A4 genes have been recognized as the disease genes mutated in diastrophic dysplasia, congenital chloride diarrhea, and Pendred syndrome, respectively. We report the expansion of the SLC26 gene family by characterizing three novel tissue-specific members, named SLC26A7, SLC26A8, and SLC26A9, on chromosomes 8, 6, and 1, respectively. The SLC26A7-A9 proteins are structurally very similar at the amino acid level to the previous family members and show tissue-specific expression in kidney, testis, and lung, respectively. More detailed characterization by immunohistochemistry and/or in situ hybridization localized SLC26A7 to distal segments of nephrons, SLC26A8 to developing spermatocytes, and SLC26A9 to the lumenal side of the bronchiolar and alveolar epithelium of lung. Expression of SLC26A7-A9 proteins in Xenopus oocytes demonstrated chloride, sulfate, and oxalate transport activity, suggesting that they encode functional anion exchangers. The functional characterization of the novel tissue-specific members may provide new insights to anion transport physiology in different parts of body. PMID:11834742

  19. Effect of Oxalate on the Recycle of Neptunium Filtrate Solution by Anion Exchange

    SciTech Connect

    Kyser, E

    2004-11-18

    A series of laboratory column runs has been performed that demonstrates the recovery of neptunium (Np) containing up to 0.05 M oxalate. Np losses were generally less than one percent to the raffinate for feed solutions that contained 2 to 10 g Np/L. Up to 16 percent Np losses were observed with lower Np feed concentrations, but those losses were attributed to the shortened residence times rather than the higher oxalate to Np ratios. Losses in the plant are expected to be significantly less due to the lower cross-section flowrate possible with existing plant pumps. Elimination of the permanganate treatment of filtrates appears to be reasonable since the amount of Np in those filtrates does not appear to be practical to recover. Combination of untreated filtrates with other actinide rich solutions is not advisable as precipitation problems are likely. If untreated filtrates are kept segregated from other actinide rich streams, the recovery of the remaining Np is probably still possible, but could be limited due to the excessively high oxalate to Np ratio. The persistence of hydrazine/hydrazoic acid in filtrate solutions dictates that the nitrite treatment be retained to eliminate those species from the filtrates prior to transfer to the canyon. Elimination of the permanganate treatment of precipitator flushes and recovery by anion exchange does not appear to be limited by the oxalate effect on anion exchange. Np from solutions with higher oxalate to Np molar ratios than expected in precipitator flushes was recovered with low to modest losses. Solubility problems appear to be unlikely when the moles of oxalate involved are less than the total number of moles of Np due to complexation effects. The presence of significant concentrations of iron (Fe) in the solutions will further decrease the probability of Np oxalate precipitation due the formation of Fe oxalate complexes. Np oxalate solubility data in 8 M HNO{sub 3} with from one to six times as much oxalate as Np have

  20. Fouling of an anion exchange chromatography operation in a monoclonal antibody process: Visualization and kinetic studies

    PubMed Central

    Close, Edward J; Salm, Jeffrey R; Iskra, Timothy; Sørensen, Eva; Bracewell, Daniel G

    2013-01-01

    Fouling of chromatographic resins over their operational lifetimes can be a significant problem for commercial bioseparations. In this article, scanning electron microscopy (SEM), batch uptake experiments, confocal laser scanning microscopy (CLSM) and small-scale column studies were applied to characterize a case study where fouling had been observed during process development. The fouling was found to occur on an anion exchange (AEX) polishing step following a protein A affinity capture step in a process for the purification of a monoclonal antibody. Fouled resin samples analyzed by SEM and batch uptake experiments indicated that after successive batch cycles, significant blockage of the pores at the resin surface occurred, thereby decreasing the protein uptake rate. Further studies were performed using CLSM to allow temporal and spatial measurements of protein adsorption within the resin, for clean, partially fouled and extensively fouled resin samples. These samples were packed within a miniaturized flowcell and challenged with fluorescently labeled albumin that enabled in situ measurements. The results indicated that the foulant has a significant impact on the kinetics of adsorption, severely decreasing the protein uptake rate, but only results in a minimal decrease in saturation capacity. The impact of the foulant on the kinetics of adsorption was further investigated by loading BSA onto fouled resin over an extended range of flow rates. By decreasing the flow rate during BSA loading, the capacity of the resin was recovered. These data support the hypothesis that the foulant is located on the particle surface, only penetrating the particle to a limited degree. The increased understanding into the nature of the fouling can help in the continued process development of this industrial example. Scanning electron microscopy (SEM), batch uptake experiments, confocal laser scanning microscopy (CLSM) and small-scale column experiments were applied to characterize a

  1. Structure and gating of CLC channels and exchangers.

    PubMed

    Accardi, Alessio

    2015-09-15

    Since their serendipitous discovery the CLC family of Cl(-) transporting proteins has been a never ending source of surprises. From their double-barrelled architecture to their complex structure and divergence as channels and transporters, the CLCs never cease to amaze biophysicists, biochemists and physiologists alike. These unusual functional properties allow the CLCs to fill diverse physiological niches, regulating processes that range from muscle contraction to acidification of intracellular organelles, nutrient accumulation and survival of bacteria to environmental stresses. Over the last 15 years, the availability of atomic-level information on the structure of the CLCs, coupled to the discovery that the family is divided into passive channels and secondary active transporters, has revolutionized our understanding of their function. These breakthroughs led to the identification of the key structural elements regulating gating, transport, selectivity and regulation by ligands. Unexpectedly, many lines of evidence indicate that the CLC exchangers function according to a non-conventional transport mechanism that defies the fundamental tenets of the alternating-access paradigm for exchange transport, paving the way for future unexpected insights into the principles underlying active transport and channel gating. PMID:26148215

  2. Chemical modification of membrane proteins in relation to inhibition of anion exchange in human red blood cells.

    PubMed

    Zaki, L; Fasold, H; Schuhmann, B; Passow, H

    1975-12-01

    Mono-, di-, and trisulfonic acids, including 4,4'-diacetamido stilbene-2,2'-disulfonic acid (DAS) and 2-(4'-amino phenyl)-6-methylbenzene thiazol-3',7-disulfonic acid (APMB) produce a reversible inhibition of sulfate equilibrium exchange in human red cells. A study of the sidedness of the action of a number of these sulfonic acids in red cell ghosts revealed that some, like DAS, inhibit only at the outer membrane surface while others, like APMB, inhibit at either surface. This finding suggests that at least two different types of membrane sites are involved in the control of anion permeability. The nature of the anion permeability controlling sites in the outer cell surface was investigated by studying the effects of DAS on the inhibition by dinitrofluorobenzene (DNFB) of anion equilibrium exchange and on the binding of DNFB to the proteins of the red blood cell membrane. After exposure to DNFB in the presence of DAS for a certain period of time, there was a reduction of both the inhibitory effect of DNFB on sulfate exchange and the binding of DNFB to the protein in band 3 of SDS polyacrylamide gel electropherograms (nomenclature of Steck, J. Cell. Biol., 62: 1, '74). Since binding to other membrane proteins was not affected, this observation supports the assumption that the protein in band 3 plays some role in anion transport. In accordance with the absence of an inhibitory effect at the inner membrane surface, internal DAS does not affect DNFB binding to the protein in band 3. DAS protected the anion exchange system not only against inhibition by DNFB but also by m-isothiocyanato benzene sulfonic acid. In contrast to DAS, the equally inhibitory phlorizin does not reduce the rate of dinitrophenylation of the protein in band 3. This suggests that either not all inhibitors of anion exchange exert their action by a combination with sites on the protein in band 3 or that in spite of the described evidence this protein is not involved in the control of anion movements

  3. Adenosine Triphosphate–dependent Asymmetry of Anion Permeation in the Cystic Fibrosis Transmembrane Conductance Regulator Chloride Channel

    PubMed Central

    Linsdell, Paul; Hanrahan, John W.

    1998-01-01

    The cystic fibrosis transmembrane conductance regulator (CFTR) forms a tightly regulated channel that mediates the passive diffusion of Cl− ions. Here we show, using macroscopic current recording from excised membrane patches, that CFTR also shows significant, but highly asymmetrical, permeability to a broad range of large organic anions. Thus, all large organic anions tested were permeant when present in the intracellular solution under biionic conditions (PX/PCl = 0.048–0.25), whereas most were not measurably permeant when present in the extracellular solution. This asymmetry was not observed for smaller anions. ATPase inhibitors that “lock” CFTR channels in the open state (pyrophosphate, 5′-adenylylimidodiphosphate) disrupted the asymmetry of large anion permeation by allowing their influx from the extracellular solution, which suggests that ATP hydrolysis is required to maintain asymmetric permeability. The ability of CFTR to allow efflux of large organic anions represents a novel function of CFTR. Loss of this function may contribute to the pleiotropic symptoms seen in cystic fibrosis. PMID:9524141

  4. Permeability of Wild-Type and Mutant Cystic Fibrosis Transmembrane Conductance Regulator Chloride Channels to Polyatomic Anions

    PubMed Central

    Linsdell, Paul; Tabcharani, Joseph A.; Rommens, Johanna M.; Hou, Yue-Xian; Chang, Xiu-Bao; Tsui, Lap-Chee; Riordan, John R.; Hanrahan, John W.

    1997-01-01

    Permeability of the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel to polyatomic anions of known dimensions was studied in stably transfected Chinese hamster ovary cells by using the patch clamp technique. Biionic reversal potentials measured with external polyatomic anions gave the permeability ratio (PX/PCl) sequence NO3− > Cl− > HCO3− > formate > acetate. The same selectivity sequence but somewhat higher permeability ratios were obtained when anions were tested from the cytoplasmic side. Pyruvate, propanoate, methane sulfonate, ethane sulfonate, and gluconate were not measurably permeant (PX/PCl < 0.06) from either side of the membrane. The relationship between permeability ratios from the outside and ionic diameters suggests a minimum functional pore diameter of ∼5.3 Å. Permeability ratios also followed a lyotropic sequence, suggesting that permeability is dependent on ionic hydration energies. Site-directed mutagenesis of two adjacent threonines in TM6 to smaller, less polar alanines led to a significant (24%) increase in single channel conductance and elevated permeability to several large anions, suggesting that these residues do not strongly bind permeating anions, but may contribute to the narrowest part of the pore. PMID:9379168

  5. Permeability of wild-type and mutant cystic fibrosis transmembrane conductance regulator chloride channels to polyatomic anions.

    PubMed

    Linsdell, P; Tabcharani, J A; Rommens, J M; Hou, Y X; Chang, X B; Tsui, L C; Riordan, J R; Hanrahan, J W

    1997-10-01

    Permeability of the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel to polyatomic anions of known dimensions was studied in stably transfected Chinese hamster ovary cells by using the patch clamp technique. Biionic reversal potentials measured with external polyatomic anions gave the permeability ratio (P/P) sequence NO > Cl > HCO > formate > acetate. The same selectivity sequence but somewhat higher permeability ratios were obtained when anions were tested from the cytoplasmic side. Pyruvate, propanoate, methane sulfonate, ethane sulfonate, and gluconate were not measurably permeant (P/P < 0.06) from either side of the membrane. The relationship between permeability ratios from the outside and ionic diameters suggests a minimum functional pore diameter of approximately 5.3 A. Permeability ratios also followed a lyotropic sequence, suggesting that permeability is dependent on ionic hydration energies. Site-directed mutagenesis of two adjacent threonines in TM6 to smaller, less polar alanines led to a significant (24%) increase in single channel conductance and elevated permeability to several large anions, suggesting that these residues do not strongly bind permeating anions, but may contribute to the narrowest part of the pore. PMID:9379168

  6. Adenosine triphosphate-dependent asymmetry of anion permeation in the cystic fibrosis transmembrane conductance regulator chloride channel.

    PubMed

    Linsdell, P; Hanrahan, J W

    1998-04-01

    The cystic fibrosis transmembrane conductance regulator (CFTR) forms a tightly regulated channel that mediates the passive diffusion of Cl- ions. Here we show, using macroscopic current recording from excised membrane patches, that CFTR also shows significant, but highly asymmetrical, permeability to a broad range of large organic anions. Thus, all large organic anions tested were permeant when present in the intracellular solution under biionic conditions (PX/PCl = 0.048-0.25), whereas most were not measurably permeant when present in the extracellular solution. This asymmetry was not observed for smaller anions. ATPase inhibitors that "lock" CFTR channels in the open state (pyrophosphate, 5'-adenylylimidodiphosphate) disrupted the asymmetry of large anion permeation by allowing their influx from the extracellular solution, which suggests that ATP hydrolysis is required to maintain asymmetric permeability. The ability of CFTR to allow efflux of large organic anions represents a novel function of CFTR. Loss of this function may contribute to the pleiotropic symptoms seen in cystic fibrosis. PMID:9524141

  7. Human kidney anion exchanger 1 interacts with kinesin family member 3B (KIF3B)

    SciTech Connect

    Duangtum, Natapol; Junking, Mutita; Sawasdee, Nunghathai; Cheunsuchon, Boonyarit; Limjindaporn, Thawornchai; Yenchitsomanus, Pa-thai

    2011-09-16

    Highlights: {yields} Impaired trafficking of kAE1 causes distal renal tubular acidosis (dRTA). {yields} The interaction between kAE1 and kinesin family member 3B (KIF3B) is reported. {yields} The co-localization between kAE and KIF3B was detected in human kidney tissues. {yields} A marked reduction of kAE1 on the cell membrane was observed when KIF3B was knockdown. {yields} KFI3B plays an important role in trafficking of kAE1 to the plasma membrane. -- Abstract: Impaired trafficking of human kidney anion exchanger 1 (kAE1) to the basolateral membrane of {alpha}-intercalated cells of the kidney collecting duct leads to the defect of the Cl{sup -}/HCO{sub 3}{sup -} exchange and the failure of proton (H{sup +}) secretion at the apical membrane of these cells, causing distal renal tubular acidosis (dRTA). In the sorting process, kAE1 interacts with AP-1 mu1A, a subunit of AP-1A adaptor complex. However, it is not known whether kAE1 interacts with motor proteins in its trafficking process to the plasma membrane or not. We report here that kAE1 interacts with kinesin family member 3B (KIF3B) in kidney cells and a dileucine motif at the carboxyl terminus of kAE1 contributes to this interaction. We have also demonstrated that kAE1 co-localizes with KIF3B in human kidney tissues and the suppression of endogenous KIF3B in HEK293T cells by small interfering RNA (siRNA) decreases membrane localization of kAE1 but increases its intracellular accumulation. All results suggest that KIF3B is involved in the trafficking of kAE1 to the plasma membrane of human kidney {alpha}-intercalated cells.

  8. Physical and functional links between anion exchanger-1 and sodium pump.

    PubMed

    Su, Ya; Al-Lamki, Rafia S; Blake-Palmer, Katherine G; Best, Alison; Golder, Zoe J; Zhou, Aiwu; Karet Frankl, Fiona E

    2015-02-01

    Anion exchanger-1 (AE1) mediates chloride-bicarbonate exchange across the plasma membranes of erythrocytes and, via a slightly shorter transcript, kidney epithelial cells. On an omnivorous human diet, kidney AE1 is mainly active basolaterally in α-intercalated cells of the collecting duct, where it is functionally coupled with apical proton pumps to maintain normal acid-base homeostasis. The C-terminal tail of AE1 has an important role in its polarized membrane residency. We have identified the β1 subunit of Na(+),K(+)-ATPase (sodium pump) as a binding partner for AE1 in the human kidney. Kidney AE1 and β1 colocalized in renal α-intercalated cells and coimmunoprecipitated (together with the catalytic α1 subunit of the sodium pump) from human kidney membrane fractions. ELISA and fluorescence titration assays confirmed that AE1 and β1 interact directly, with a Kd value of 0.81 μM. GST-AE1 pull-down assays using human kidney membrane proteins showed that the last 11 residues of AE1 are important for β1 binding. siRNA-induced knockdown of β1 in cell culture resulted in a significant reduction in kidney AE1 levels at the cell membrane, whereas overexpression of kidney AE1 increased cell surface sodium pump levels. Notably, membrane staining of β1 was reduced throughout collecting ducts of AE1-null mouse kidney, where increased fractional excretion of sodium has been reported. These data suggest a requirement of β1 for proper kidney AE1 membrane residency, and that activities of AE1 and the sodium pump are coregulated in kidney. PMID:25012180

  9. Oxygen isotope fractionation in phosphates: the role of dissolved complex anions in isotope exchange.

    PubMed

    Zheng, Yong-Fei

    2016-01-01

    Oxygen isotope fractionation factors for phosphates were calculated by means of the increment method. The results suggest that Ag3PO4 and BiPO4 are enriched in (18)O relative to AgPO4, and the three phosphates are consistently depleted in (18)O relative to Ba3[PO4]2; fluorapatite and chlorapatite exhibit a similar behaviour of oxygen isotope fractionation with consistent enrichment of (18)O relative to hydroxyapatite. The valence, radii and coordination of metal cations play a quantitative role in dictating the (18)O/(16)O partitioning in these phosphates of different compositions. The calculated fractionation factors for the Ag3PO4-H2O system are in agreement with experimental determinations derived from enzyme-catalysed isotope exchange between dissolved inorganic phosphate and water at the longest reaction durations at low temperatures. This demonstrates that the precipitated Ag3PO4 has completely captured the oxygen isotope fractionation in the dissolved inorganic phosphate. The calculated fractionation factors for the F/Cl-apatite-water systems are in agreement with the enzyme-catalysed experimental fractionations for the dissolved phosphate-water system at the longest reaction durations but larger than fractionations derived from bacteria-facilitated exchange and inorganic precipitation experiments as well as natural observations. For the experimental calibrations of oxygen isotope fractionation involving the precipitation of dissolved phosphate species from aqueous solutions, the fractionation between precipitate and water is primarily dictated by the isotope equilibration between the dissolved complex anions and water prior to the precipitation. Therefore, the present results provide a quantitative means to interpret the temperature dependence of oxygen isotope fractionation in inorganic and biogenic phosphates. PMID:25587823

  10. Cardiac hypertrophy in anion exchanger 1-null mutant mice with severe hemolytic anemia.

    PubMed

    Alvarez, Bernardo V; Kieller, Dawn M; Quon, Anita L; Robertson, Murray; Casey, Joseph R

    2007-03-01

    Anion exchanger 1 (AE1; SLC4A1), the plasma membrane Cl(-)/HCO(3)(-) exchanger of erythrocytes, is also expressed in heart. The aim of this study was to assess the role of AE1 in heart function through study of AE1-null (AE1(-/-)) mice, which manifest severe hemolytic anemia resulting from erythrocyte fragility. Heart weight-to-body weight ratios were significantly higher in the AE1(-/-) mice than in wild-type (AE1(+/+)) littermates at both 1-3 days postnatal (3.01 +/- 0.38 vs. 1.45 +/- 0.04) and at 7 days postnatal (9.45 +/- 0.53 vs. 4.13 +/- 0.41), indicating that loss of AE1 led to cardiac hypertrophy. Heterozygous (AE1(+/-)) mice had no signs of cardiac hypertrophy. Morphology of the adult AE1(-/-) mutant heart revealed an increased left ventricular mass, accompanied by increased collagen deposition and fibrosis. M-mode echocardiography revealed dysfunction of the AE1(-/-) hearts, including dilated left ventricle end diastole and systole and expanded left ventricular mass compared with AE1(+/+) hearts. Expression of intracellular pH-regulatory mechanisms in the hypertrophic myocardium of neonate AE1(-/-) mutant mice was indistinguishable from AE1(+/-) and AE1(+/+) mice, as assessed by quantitative real-time RT-PCR. Confocal immunofluorescence revealed that, in normal mouse myocardium, AE1 is sarcolemmal, whereas AE3 and slc26a6 are found both at the sarcolemma and in internal membranes (T tubules and sarcoplasmic reticulum). These results indicate that AE1(-/-) mice, which suffer from severe hemolytic anemia and spherocytosis, display cardiac hypertrophy and impaired cardiac function, reminiscent of findings in patients with hereditary abnormalities of red blood cells. No essential role for AE1 in heart function was found. PMID:17056673

  11. High throughput determination of cleaning solutions to prevent the fouling of an anion exchange resin.

    PubMed

    Elich, Thomas; Iskra, Timothy; Daniels, William; Morrison, Christopher J

    2016-06-01

    Effective cleaning of chromatography resin is required to prevent fouling and maximize the number of processing cycles which can be achieved. Optimization of resin cleaning procedures, however, can lead to prohibitive material, labor, and time requirements, even when using milliliter scale chromatography columns. In this work, high throughput (HT) techniques were used to evaluate cleaning agents for a monoclonal antibody (mAb) polishing step utilizing Fractogel(®) EMD TMAE HiCap (M) anion exchange (AEX) resin. For this particular mAb feed stream, the AEX resin could not be fully restored with traditional NaCl and NaOH cleaning solutions, resulting in a loss of impurity capacity with resin cycling. Miniaturized microliter scale chromatography columns and an automated liquid handling system (LHS) were employed to evaluate various experimental cleaning conditions. Cleaning agents were monitored for their ability to maintain resin impurity capacity over multiple processing cycles by analyzing the flowthrough material for turbidity and high molecular weight (HMW) content. HT experiments indicated that a 167 mM acetic acid strip solution followed by a 0.5 M NaOH, 2 M NaCl sanitization provided approximately 90% cleaning improvement over solutions containing solely NaCl and/or NaOH. Results from the microliter scale HT experiments were confirmed in subsequent evaluations at the milliliter scale. These results identify cleaning agents which may restore resin performance for applications involving fouling species in ion exchange systems. In addition, this work demonstrates the use of miniaturized columns operated with an automated LHS for HT evaluation of chromatographic cleaning procedures, effectively decreasing material requirements while simultaneously increasing throughput. Biotechnol. Bioeng. 2016;113: 1251-1259. © 2015 Wiley Periodicals, Inc. PMID:26552005

  12. Molecular determinants and role of an anion binding site in the external mouth of the CFTR chloride channel pore

    PubMed Central

    Gong, Xiandi; Linsdell, Paul

    2003-01-01

    Chloride permeation through the cystic fibrosis transmembrane conductance regulator (CFTR) Cl− channel is blocked by highly lyotropic permeant anions which bind tightly within the pore. Here we show that several different substitutions of a positively charged amino acid residue, arginine R334, in the putative outer mouth of the CFTR pore, greatly reduce the block caused by lyotropic Au(CN)2− ions applied to the intracellular side of the channel. Fixed positive charge at this site appears to play a role in Au(CN)2− binding, as judged by multiple substitutions of differently charged amino acid side chains and also by the pH dependence of block conferred by the R334H mutant. However, non-charge-dependent effects also appear to contribute to Au(CN)2− binding. Mutation of R334 also disrupts the apparent electrostatic interaction between intracellular Au(CN)2− ions and extracellular permeant anions, an interaction which normally acts to relieve channel block. All six mutations studied at R334 significantly weakened this interaction, suggesting that arginine possesses a unique ability to coordinate ion-ion interactions at this site in the pore. Our results suggest that lyotropic anions bind tightly to a site in the outer mouth of the CFTR pore that involves interaction with a fixed positive charge. Binding to this site is also involved in coordination of multiple permeant anions within the pore, suggesting that anion binding in the outer mouth of the pore is an important aspect in the normal anion permeation mechanism. PMID:12679372

  13. Molecular determinants and role of an anion binding site in the external mouth of the CFTR chloride channel pore.

    PubMed

    Gong, Xiandi; Linsdell, Paul

    2003-06-01

    Chloride permeation through the cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel is blocked by highly lyotropic permeant anions which bind tightly within the pore. Here we show that several different substitutions of a positively charged amino acid residue, arginine R334, in the putative outer mouth of the CFTR pore, greatly reduce the block caused by lyotropic Au(CN)2- ions applied to the intracellular side of the channel. Fixed positive charge at this site appears to play a role in Au(CN)2- binding, as judged by multiple substitutions of differently charged amino acid side chains and also by the pH dependence of block conferred by the R334H mutant. However, non-charge-dependent effects also appear to contribute to Au(CN)2- binding. Mutation of R334 also disrupts the apparent electrostatic interaction between intracellular Au(CN)2- ions and extracellular permeant anions, an interaction which normally acts to relieve channel block. All six mutations studied at R334 significantly weakened this interaction, suggesting that arginine possesses a unique ability to coordinate ion-ion interactions at this site in the pore. Our results suggest that lyotropic anions bind tightly to a site in the outer mouth of the CFTR pore that involves interaction with a fixed positive charge. Binding to this site is also involved in coordination of multiple permeant anions within the pore, suggesting that anion binding in the outer mouth of the pore is an important aspect in the normal anion permeation mechanism. PMID:12679372

  14. Water uptake, ionic conductivity and swelling properties of anion-exchange membrane

    SciTech Connect

    Duan, QJ; Ge, SH; Wang, CY

    2013-12-01

    Water uptake, ionic conductivity and dimensional change of the anion-exchange membrane made by Tokuyama Corporation (A201 membrane) are investigated at different temperatures and water activities. Specifically, the amount of water taken up by membranes exposed to water vapor and membranes soaked in liquid water is determined. The water uptake of the A201 membrane increases with water content as well as temperature. In addition, water sorption data shows Schroeder's paradox for the AEMs investigated. The swelling properties of the A201 membrane exhibit improved dimensional stability compared with Nafion membrane. Water sorption of the A201 membrane occurs with a substantial negative excess volume of mixing. The threshold value of hydrophilic fraction in the A201 membrane for ionic conductivity is around 0.34, above which, the conductivity begins to rise quickly. This indicates that a change in the connectivity of the hydrophilic domains occurs when hydrophilic fraction approaches 0.34. (C) 2013 Elsevier B.V. All rights reserved.

  15. Polyphenylene sulfide based anion exchange fiber: synthesis, characterization and adsorption of Cr(VI).

    PubMed

    Huang, Jiajia; Zhang, Xin; Bai, Lingling; Yuan, Siguo

    2012-01-01

    A fibrous strong base anion exchanger (QAPPS) was prepared for the first time via chloromethylation and quaternary amination reaction of polyphenylene sulfide fiber (PPS), and its physical-chemical structure and adsorption behavior for Cr(VI) were characterized by FTIR, Energy Dispersive Spectrometry, TG-DTG, elemental analysis and batch adsorptive technique, respectively. The novel fibrous adsorbent could effectively adsorb Cr(VI) over the pH range 1-12, the maximum adsorption capacity was 166.39 mg/g at pH 3.5, and the adsorption behavior could be described well by Langmuir isotherm equation model. The adsorption kinetics was studied using pseudo first-order and pseudo second-order models, and the t1/2 and equilibrium adsorption time were 5 and 20 min respectively when initial Cr(VI) concentration was 100 mg/L. The saturated fibers could be regenerated rapidly by a mixed solution of 0.5 mol/L NaOH and 0.5 mol/L NaCl, and the adsorption capacity was well maintained after six adsorption-desorption cycles. PMID:23513685

  16. Functional rescue of a kidney anion exchanger 1 trafficking mutant in renal epithelial cells.

    PubMed

    Chu, Carmen Y S; King, Jennifer C; Berrini, Mattia; Alexander, R Todd; Cordat, Emmanuelle

    2013-01-01

    Mutations in the SLC4A1 gene encoding the anion exchanger 1 (AE1) can cause distal renal tubular acidosis (dRTA), a disease often due to mis-trafficking of the mutant protein. In this study, we investigated whether trafficking of a Golgi-retained dRTA mutant, G701D kAE1, or two dRTA mutants retained in the endoplasmic reticulum, C479W and R589H kAE1, could be functionally rescued to the plasma membrane of Madin-Darby Canine Kidney (MDCK) cells. Treatments with DMSO, glycerol, the corrector VX-809, or low temperature incubations restored the basolateral trafficking of G701D kAE1 mutant. These treatments had no significant rescuing effect on trafficking of the mis-folded C479W or R589H kAE1 mutants. DMSO was the only treatment that partially restored G701D kAE1 function in the plasma membrane of MDCK cells. Our experiments show that trafficking of intracellularly retained dRTA kAE1 mutants can be partially restored, and that one chemical treatment rescued both trafficking and function of a dRTA mutant. These studies provide an opportunity to develop alternative therapeutic solutions for dRTA patients. PMID:23460825

  17. Functional Rescue of a Kidney Anion Exchanger 1 Trafficking Mutant in Renal Epithelial Cells

    PubMed Central

    Chu, Carmen Y. S.; King, Jennifer C.; Berrini, Mattia; Alexander, R. Todd; Cordat, Emmanuelle

    2013-01-01

    Mutations in the SLC4A1 gene encoding the anion exchanger 1 (AE1) can cause distal renal tubular acidosis (dRTA), a disease often due to mis-trafficking of the mutant protein. In this study, we investigated whether trafficking of a Golgi-retained dRTA mutant, G701D kAE1, or two dRTA mutants retained in the endoplasmic reticulum, C479W and R589H kAE1, could be functionally rescued to the plasma membrane of Madin-Darby Canine Kidney (MDCK) cells. Treatments with DMSO, glycerol, the corrector VX-809, or low temperature incubations restored the basolateral trafficking of G701D kAE1 mutant. These treatments had no significant rescuing effect on trafficking of the mis-folded C479W or R589H kAE1 mutants. DMSO was the only treatment that partially restored G701D kAE1 function in the plasma membrane of MDCK cells. Our experiments show that trafficking of intracellularly retained dRTA kAE1 mutants can be partially restored, and that one chemical treatment rescued both trafficking and function of a dRTA mutant. These studies provide an opportunity to develop alternative therapeutic solutions for dRTA patients. PMID:23460825

  18. Features of the adsorption of naproxen enantiomers on weak chiral anion-exchangers in nonlinear chromatography

    SciTech Connect

    Asnin, Leonid; Kaczmarski, Krzysztof; Guiochon, Georges A

    2008-01-01

    The retention mechanism of the enantiomers of naproxen on a Pirkle-type chiral stationary phase (CSP) was studied. This CSP is made of a porous silica grafted with quinidine carbamate. It can interact with the weak organic electrolyte naproxen either by adsorbing it or by ion-exchange. Using frontal chromatography, we explored the adsorption equilibrium under such experimental conditions that naproxen dissociates or cannot dissociate. Under conditions preventing ionic dissociation, the adsorption isotherms were measured, the adsorption energy distributions determined, and the chromatographic profiles calculated. Three different types of the adsorption sites were found for both enantiomers. The density and the binding energy of these sites depend on the nature of the organic modifier. Different solute species, anions, neutral molecules, solvent-ion associates, and solute dimers can coexist in solution, giving rise to different forms of adsorption. This study showed the unexpected occurrence of secondary steps in the breakthrough profiles of S-naproxen in the adsorption mode at high concentrations. Being enantioselective, this phenomenon was assumed to result from the association of solute molecules involving a chiral selector moiety. A multisite Langmuir adsorption model was used to calculate band profiles. Although this model accounts excellently for the experimental adsorption isotherms, it does not explain all the features of the breakthrough profiles. A comparison between the calculated and experimental profiles allowed useful conclusions concerning the effects of the adsorbate-adsorbate and adsorbate-solvent interactions on the adsorption mechanism.

  19. The structure and organization of the human erythroid anion exchanger (AE1) gene

    SciTech Connect

    Sahr, K.E.; Taylor, W.M.; Daniels, B.P.

    1994-12-01

    The AE1 (anion exchanger, band 3) protein is expressed in erythrocytes and in the A-type intercalated cells of the kidney distal collecting tubule. In both cell types it mediates the electroneutral transport of chloride and bicarbonate ions across the lipid bilayer, and, in erythrocytes, it also serves as the critical attachment site of the peripheral membrane skeleton. We have characterized the human AE1 gene using overlapping clones isolated from a phage library of human genomic DNA. The gene spans {approximately}20 kb and consists of 20 exons separated by 19 introns. The structure of the human AE1 gene corresponds closely with that of the previously characterized mouse AE1 gene, with a high degree of conservation of exon/intron junctions, as well as exon and intron nucleotide sequences. The putative upstream and internal promoter sequences of the human AE1 gene used in erythroid and kidney cells, respectively, are described. We also report the nucleotide sequence of the entire 3{prime} noncoding region of exon 20, which was lacking in the published cDNA sequences. In addition, we have characterized 9 Alu repeat elements found within the body of the human AE1 gene that are members of 4 related subfamilies that appear to have entered the genome at different times during primate evolution. 59 refs., 5 figs., 2 tabs.

  20. Phosphate recovery using hybrid anion exchange: applications to source-separated urine and combined wastewater streams.

    PubMed

    O'Neal, Jeremy A; Boyer, Treavor H

    2013-09-15

    There is increasing interest in recovering phosphorus (P) from various wastewater streams for beneficial use as fertilizer and to minimize environmental impacts of excess P on receiving waters. One such example is P recovery from human urine, which has a high concentration of phosphate (200-800 mg P/L) and accounts for a small volume (≈ 1%) of total wastewater flow. Accordingly, the goal of this study was to evaluate the potential to recover P from source-separated and combined wastewater streams that included undiluted human urine, urine diluted with tap water, greywater, mixture of urine and greywater, anaerobic digester supernatant, and secondary wastewater effluent. A hybrid anion exchange (HAIX) resin containing hydrous ferric oxide was used to recover P because of its selectivity for phosphate and the option to precipitate P minerals in the waste regeneration solution. The P recovery potential was fresh urine > hydrolyzed urine > greywater > biological wastewater effluent > anaerobic digester supernatant. The maximum loading of P on HAIX resin was fresh urine > hydrolyzed urine > anaerobic digester supernatant ≈ greywater > biological wastewater effluent. Results indicated that the sorption capacity of HAIX resin for phosphate and the total P recovery potential were greater for source-separated urine than the combined wastewater streams of secondary wastewater effluent and anaerobic digester supernatant. Dilution of urine with tap water decreased the phosphate loading on HAIX resin. The results of this work advance the current understanding of nutrient recovery from complex wastewater streams by sorption processes. PMID:23866131

  1. Tunable high performance cross-linked alkaline anion exchange membranes for fuel cell applications.

    PubMed

    Robertson, Nicholas J; Kostalik, Henry A; Clark, Timothy J; Mutolo, Paul F; Abruña, Héctor D; Coates, Geoffrey W

    2010-03-17

    Fuel cells are energy conversion devices that show great potential in numerous applications ranging from automobiles to portable electronics. However, further development of fuel cell components is necessary for them to become commercially viable. One component critical to their performance is the polymer electrolyte membrane, which is an ion conductive medium separating the two electrodes. While proton conducting membranes are well established (e.g., Nafion), hydroxide conducting membranes (alkaline anion exchange membranes, AAEMs) have been relatively unexplored by comparison. Operating under alkaline conditions offers significant efficiency benefits, especially for the oxygen reduction reaction; therefore, effective AAEMs could significantly advance fuel cell technologies. Here we demonstrate the use of ring-opening metathesis polymerization to generate new cross-linked membrane materials exhibiting high hydroxide ion conductivity and good mechanical properties. Cross-linking allows for increased ion incorporation, which, in turn supports high conductivities. This facile synthetic approach enables the preparation of cross-linked materials with the potential to meet the demands of hydrogen-powered fuel cells as well as direct methanol fuel cells. PMID:20178312

  2. Influence of Hydration Level on Polymer and Water Dynamics in Alkaline Anion Exchange Fuel Cell Membranes

    NASA Astrophysics Data System (ADS)

    Tarver, Jacob; Kim, Jenny; Tyagi, Madhu; Soles, Christopher; Tsai, Tsung-Han; Coughlin, Bryan

    2015-03-01

    Triblock copolymers based on poly(chloromethylstyrene)-b-poly(ethylene)-b-poly(chloromethylstyrene) can be quaternized to different extents to yield anion exchange membranes for alkaline fuel cells. In the absence of moisture, these membranes demonstrate bilayer lamellar morphology. Upon high levels of hydration, however, in-situ small angle neutron scattering reveals the emergence of higher-order diffraction peaks. This phenomena has previously been observed in analogous diblock copolymer-based membranes and has been attributed to the induction of a multilayer lamellar morphology in which selective striping of water occurs in the center of the ion-rich domain. By conducting humidity-resolved quasielastic neutron scattering (QENS) measurements using deuterated water, we are able to isolate differences in the pico- to nanosecond timescale dynamics of the hydrogenated membrane upon hydration. QENS measurements in the presence of a hydrogenated water source subsequently permit deconvolution and isolation of the translational and rotational dynamics of water as a function of relative humidity, revealing spatial and temporal changes in polymer and water motion at high levels of hydration.

  3. Tunable High Performance Cross-Linked Alkaline Anion Exchange Membranes for Fuel Cell Applications

    SciTech Connect

    Robertson, Nicholas J.; Kostalik, IV, Henry A.; Clark, Timothy J.; Mutolo, Paul F.; Abruña, Héctor D.; Coates, Geoffrey W.

    2010-02-23

    Fuel cells are energy conversion devices that show great potential in numerous applications ranging from automobiles to portable electronics. However, further development of fuel cell components is necessary for them to become commercially viable. One component critical to their performance is the polymer electrolyte membrane, which is an ion conductive medium separating the two electrodes. While proton conducting membranes are well established (e.g., Nafion), hydroxide conducting membranes (alkaline anion exchange membranes, AAEMs) have been relatively unexplored by comparison. Operating under alkaline conditions offers significant efficiency benefits, especially for the oxygen reduction reaction; therefore, effective AAEMs could significantly advance fuel cell technologies. Here we demonstrate the use of ring-opening metathesis polymerization to generate new cross-linked membrane materials exhibiting high hydroxide ion conductivity and good mechanical properties. Cross-linking allows for increased ion incorporation, which, in turn supports high conductivities. This facile synthetic approach enables the preparation of cross-linked materials with the potential to meet the demands of hydrogen-powered fuel cells as well as direct methanol fuel cells.

  4. PLUTONIUM LOADING CAPACITY OF REILLEX HPQ ANION EXCHANGE COLUMN - AFS-2 PLUTONIUM FLOWSHEET FOR MOX

    SciTech Connect

    Kyser, E.; King, W.; O'Rourke, P.

    2012-07-26

    Radioactive plutonium (Pu) anion exchange column experiments using scaled HB-Line designs were performed to investigate the dependence of column loading performance on the feed composition in the H-Canyon dissolution process for plutonium oxide (PuO{sub 2}) product shipped to the Mixed Oxide (MOX) Fuel Fabrication Facility (MFFF). These loading experiments show that a representative feed solution containing {approx}5 g Pu/L can be loaded onto Reillex{trademark} HPQ resin from solutions containing 8 M total nitrate and 0.1 M KF provided that the F is complexed with Al to an [Al]/[F] molar ratio range of 1.5-2.0. Lower concentrations of total nitrate and [Al]/[F] molar ratios may still have acceptable performance but were not tested in this study. Loading and washing Pu losses should be relatively low (<1%) for resin loading of up to 60 g Pu/L. Loading above 60 g Pu/L resin is possible, but Pu wash losses will increase such that 10-20% of the additional Pu fed may not be retained by the resin as the resin loading approaches 80 g Pu/L resin.

  5. Poly(phenyl sulfone) anion exchange membranes with pyridinium groups for vanadium redox flow battery applications

    NASA Astrophysics Data System (ADS)

    Zhang, Bengui; Zhang, Enlei; Wang, Guosheng; Yu, Ping; Zhao, Qiuxia; Yao, Fangbo

    2015-05-01

    To develop high performance and cost-effective membranes with low permeability of vanadium ions for vanadium redox flow battery (VRFB) application, poly(phenyl sulfone) anion exchange membranes with pyridinium groups (PyPPSU) are prepared and first investigated for VRFB application. PyPPSU membranes show much lower vanadium ions permeability (0.07 × 10-7-0.15 × 10-7 cm2 min-1) than that of Nafion 117 membrane (31.3 × 10-7 cm2 min-1). As a result, the self-discharge duration of the VRFB cell with PyPPSU membrane (418 h) is about four times longer than that of VRFB cell with Nafion 117 membrane (110 h). Furthermore, the VRFB cell with PyPPSU membrane exhibits higher battery efficiency (coulombic efficiency of 97.8% and energy efficiency of 80.2%) compare with that of VRFB cell with Nafion 117 membrane (coulombic efficiency of 96.1% and energy efficiency of 77.2%) at a high current density of 100 mA cm-2. In addition, PyPPSU membrane exhibits stable performance in 100-cycle test. The results indicate that PyPPSU membrane is high performance and low-cost alternative membrane for VRFB application.

  6. Phosphate removal from wastewaters using a weak anion exchanger prepared from a lignocellulosic residue.

    PubMed

    Anirudhan, T S; Noeline, B F; Manohar, D M

    2006-04-15

    Surface modifications of lignocellulosic residues has become increasingly important for improving their applications as adsorbents. In this study a new adsorbent system (BS-DMAHP) containing dimethylaminohydroxypropyl (DMAHP) weak base groups was prepared by the reaction of banana stem (BS), a lignocellulosic residue with epichlorohydrin and dimethylamine followed by treatment of hydrochloric acid. The original BS and BS-DMAHP were characterized with the help of surface area analyzer, infrared spectroscopy (IR) and scanning electron microscopy (SEM). Surface charge density of the samples as a function of pH was investigated using potentiometric titrations. Adsorbent exhibits very high adsorption potential for phosphate and more than 99.0% removal was achieved in the pH range of 5.0-7.0. Adsorption has been found to be concentration dependent and endothermic and follows a reversible second-order kinetics. The Langmuir and Freundlich isotherm models were applied to describe the equilibrium data. Equilibrium data agreed very well with the Langmuir model. Adsorption experiments were conducted using a commercial chloride form Duolite A-7, a weak base anion exchanger. The removal efficiency was tested using fertilizer industry wastewater. Adsorbed phosphate on BS-DMAHP can be recovered by treating with 0.1 M NaOH solution. A stability test operated for four cycles indicate a capacity loss of < 12.0%. PMID:16683617

  7. Development of a modular virus clearance package for anion exchange chromatography operated in weak partitioning mode.

    PubMed

    Iskra, Timothy; Sacramo, Ashley; Gallo, Chris; Godavarti, Ranga; Chen, Shuang; Lute, Scott; Brorson, Kurt

    2015-01-01

    Anion exchange chromatography (AEX) operated under weak partitioning mode has been proven to be a powerful polishing step as well as a robust viral clearance step in Pfizer's monoclonal antibody (mAb) platform purification process. A multivariate design of experiment (DoE) study was conducted to understand the impact of operating parameters and feedstream impurity levels on viral clearance by weak partitioning mode AEX. Bacteriophage was used initially as a surrogate for neutral and acidic isoelectric point mammalian viruses (e.g., retrovirus and parvovirus). Five different mAbs were used in the evaluation of process parameters such as load challenge (both product and impurities), load pH, load conductivity, and contact time (bed height and flow-rate). The operating ranges obtained from phage clearance studies and Pfizer's historical data were used to define an appropriate operating range for a subsequent clearance study with model retrovirus and parvovirus. Both phage and virus clearance evaluations included feedstreams containing different levels of impurities such as high molecular mass species (HMMS), host cell proteins (HCPs), and host cell DNA. For all the conditions tested, over 5 log10 of clearance for both retrovirus and parvovirus was achieved. The results demonstrated that weak partitioning mode AEX chromatography is a robust step for viral clearance and has the potential to be included as part of the modular viral clearance approach. PMID:25826186

  8. Overlapping expression of anion exchangers in the cochlea of a non-human primate suggests functional compensation.

    PubMed

    Hosoya, Makoto; Fujioka, Masato; Kobayashi, Reona; Okano, Hideyuki; Ogawa, Kaoru

    2016-09-01

    Ion homeostasis in the inner ear is essential for proper hearing. Anion exchangers are one of the transporters responsible for the maintenance of homeostasis, but their expression profile in the primate cochlea has not been fully characterized. However, species-specific overlapping expression patterns and functional compensation in other organs, such as the kidney, pancreas and small intestine, have been reported. Here, we determined the expression patterns of the anion exchangers SLC26A4, SLC26A5, SLC26A6, SLC26A7, SLC26A11, SLC4A2 and SLC4A3 in the cochlea of a non-human primate, the common marmoset (Callithrix jacchus). Although the pattern of expression of SLC26A4 and SLC26A5 was similar to that in rodents, SLC26A7, SLC4A2, SLC4A3 exhibited different distributions. Notably, five transporters, SLC26A4, SLC26A6, SLC26A11 SLC4A2 and SLC4A3, were expressed in the cells of the outer sulcus. Our results reveal a species-specific distribution pattern of anion exchangers in the cochlea, particularly in the outer sulcus cells, suggesting functional compensation among these exchangers. This "primate-specific" pattern may be related to the human-specific hearing loss phenotypes of channelopathy disorders, including the SLC26A4-related diseases Pendred syndrome/DFNB4. PMID:27091614

  9. Degradation of imidazolium- and quaternary ammonium-functionalized poly(fluorenyl ether ketone sulfone) anion exchange membranes.

    PubMed

    Chen, Dongyang; Hickner, Michael A

    2012-11-01

    Imidazolium and quaternary ammonium-functionalized poly(fluorenyl ether ketone sulfone)s were synthesized successfully with the same degree of cationic functionalization and identical polymer backbones for a comparative study of anion exchange membranes (AEMs) for solid-state alkaline membrane fuel cells (AMFCs). Both anion exchange membranes were synthesized using a new methyl-containing monomer that avoided the use of toxic chloromethylation reagents. The polymer chemical structures were confirmed by ¹H NMR and FTIR. The derived AEMs were fully characterized by water uptake, anion conductivity, stability under aqueous basic conditions, and thermal stability. Interestingly, both the cationic groups and the polymer backbone were found to be degraded in 1 M NaOH solution at 60 °C over 48 h as measured by changes of ion exchange capacity and intrinsic viscosity. Imidazolium-functionalized poly(fluorenyl ether ketone sulfone)s had similar aqueous alkaline stability to quaternary ammonium-functionalized materials at 60 °C but much lower stability at 80 °C. This work demonstrates that quaternary ammonium and imidazolium cationic groups are not stable on poly(arylene ether sulfone) backbones under relatively mild conditions. Additionally, the poly(arylene ether sulfone) backbone, which is one of the most common polymers used in ion exchange membrane applications, is not stable in the types of molecular configurations analyzed. PMID:23067022

  10. Degradation of Imidazolium- and Quaternary Ammonium-Functionalized Poly(fluorenyl ether ketone sulfone) Anion Exchange Membranes

    SciTech Connect

    Chen, DY; Hickner, MA

    2012-11-01

    Imidazolium and quaternary ammonium-functionalized poly(fluorenyl ether ketone sulfone)s were synthesized successfully with the same degree of cationic functionalization and identical polymer backbones for a comparative study of anion exchange membranes (AEMs) for solid-state alkaline membrane fuel cells (AMFCs). Both anion exchange membranes were synthesized using a new methyl-containing monomer that avoided the use of toxic chloromethylation reagents. The polymer chemical structures were confirmed by H-1 NMR and FTIR. The derived AEMs were fully characterized by water uptake, anion conductivity, stability under aqueous basic conditions, and thermal stability. Interestingly, both the cationic groups and the polymer backbone were found to be degraded in 1 M NaOH solution at 60 degrees C over 48 h as measured by changes of ion exchange capacity and intrinsic viscosity. Imidazolium-functionalized poly(fluorenyl ether ketone sulfone)s had similar aqueous alkaline stability to quaternary ammonium-functionalized materials at 60 degrees C but much lower stability at 80 degrees C. This work demonstrates that quaternary ammonium and imidazolium cationic groups are not stable on poly(arylene ether sulfone) backbones under relatively mild conditions. Additionally, the poly(arylene ether sulfone) backbone, which is one of the most common polymers used in ion exchange membrane applications, is not stable in the types of molecular configurations analyzed.

  11. Role of ATP-conductive anion channel in ATP release from neonatal rat cardiomyocytes in ischaemic or hypoxic conditions

    PubMed Central

    Dutta, Amal K; Sabirov, Ravshan Z; Uramoto, Hiromi; Okada, Yasunobu

    2004-01-01

    It is known that the level of ATP in the interstitial spaces within the heart during ischaemia or hypoxia is elevated due to its release from a number of cell types, including cardiomyocytes. However, the mechanism by which ATP is released from these myocytes is not known. In this study, we examined a possible involvement of the ATP-conductive maxi-anion channel in ATP release from neonatal rat cardiomyocytes in primary culture upon ischaemic, hypoxic or hypotonic stimulation. Using a luciferin–luciferase assay, it was found that ATP was released into the bulk solution when the cells were subjected to chemical ischaemia, hypoxia or hypotonic stress. The swelling-induced ATP release was inhibited by the carboxylate-and stilbene-derivative anion channel blockers, arachidonic acid and Gd3+, but not by glibenclamide. The local concentration of ATP released near the cell surface of a single cardiomyocyte, measured by a biosensor technique, was found to exceed the micromolar level. Patch-clamp studies showed that ischaemia, hypoxia or hypotonic stimulation induced the activation of single-channel events with a large unitary conductance (∼390 pS). The channel was selective to anions and showed significant permeability to ATP4− (PATP/PCl ∼ 0.1) and MgATP2− (PATP/PCl ∼ 0.16). The channel activity exhibited pharmacological properties essentially identical to those of ATP release. These results indicate that neonatal rat cardiomyocytes respond to ischaemia, hypoxia or hypotonic stimulation with ATP release via maxi-anion channels. PMID:15272030

  12. Copper ion-exchanged channel waveguides optimization for optical trapping.

    PubMed

    Reshak, A H; Khor, K N; Shahimin, M M; Murad, S A Z

    2013-08-01

    Optical trapping of particles has become a powerful non-mechanical and non-destructive technique for precise particle positioning. The manipulation of particles in the evanescent field of a channel waveguide potentially allows for sorting and trapping of several particles and cells simultaneously. Channel waveguide designs can be further optimized to increase evanescent field prior to the fabrication process. This is crucial in order to make sure that the surface intensity is sufficient for optical trapping. Simulation configurations are explained in detail with specific simulation flow. Discussion on parameters optimization; physical geometry, optical polarization and wavelength is included in this paper. The effect of physical, optical parameters and beam spot size on evanescent field has been thoroughly discussed. These studies will continue toward the development of a novel copper ion-exchanged waveguide as a method of particle sorting, with biological cell propulsion studies presently underway. PMID:23726859

  13. Silent S-Type Anion Channel Subunit SLAH1 Gates SLAH3 Open for Chloride Root-to-Shoot Translocation.

    PubMed

    Cubero-Font, Paloma; Maierhofer, Tobias; Jaslan, Justyna; Rosales, Miguel A; Espartero, Joaquín; Díaz-Rueda, Pablo; Müller, Heike M; Hürter, Anna-Lena; Al-Rasheid, Khaled A S; Marten, Irene; Hedrich, Rainer; Colmenero-Flores, José M; Geiger, Dietmar

    2016-08-22

    Higher plants take up nutrients via the roots and load them into xylem vessels for translocation to the shoot. After uptake, anions have to be channeled toward the root xylem vessels. Thereby, xylem parenchyma and pericycle cells control the anion composition of the root-shoot xylem sap [1-6]. The fact that salt-tolerant genotypes possess lower xylem-sap Cl(-) contents compared to salt-sensitive genotypes [7-10] indicates that membrane transport proteins at the sites of xylem loading contribute to plant salinity tolerance via selective chloride exclusion. However, the molecular mechanism of xylem loading that lies behind the balance between NO3(-) and Cl(-) loading remains largely unknown. Here we identify two root anion channels in Arabidopsis, SLAH1 and SLAH3, that control the shoot NO3(-)/Cl(-) ratio. The AtSLAH1 gene is expressed in the root xylem-pole pericycle, where it co-localizes with AtSLAH3. Under high soil salinity, AtSLAH1 expression markedly declined and the chloride content of the xylem sap in AtSLAH1 loss-of-function mutants was half of the wild-type level only. SLAH3 anion channels are not active per se but require extracellular nitrate and phosphorylation by calcium-dependent kinases (CPKs) [11-13]. When co-expressed in Xenopus oocytes, however, the electrically silent SLAH1 subunit gates SLAH3 open even in the absence of nitrate- and calcium-dependent kinases. Apparently, SLAH1/SLAH3 heteromerization facilitates SLAH3-mediated chloride efflux from pericycle cells into the root xylem vessels. Our results indicate that under salt stress, plants adjust the distribution of NO3(-) and Cl(-) between root and shoot via differential expression and assembly of SLAH1/SLAH3 anion channel subunits. PMID:27397895

  14. Selective Anion Exchange Resins for the Removal of Perchlorate [(CIO{sub 4}{sup -})] from Groundwater

    SciTech Connect

    Gu, B.

    1999-05-20

    The primary objective of this project was to evaluate a novel bifunctional anion exchange resin for the cost-effective, in situ treatment of groundwater contaminated with perchlorate (ClO{sub 4}{sup -}). Both laboratory and field studies were performed to determine the selectivity and capacity of the bifunctional synthetic resins to sorb ClO{sub 4}{sup -} from simulated or actual contaminated groundwater. A number of synthetic bifunctional resins, including two commercial versions made by Purolite International and three commercially available, mono-functional resins, were tested. Initial laboratory batch and column breakthrough studies determined the best synthetic resins and the optimal conditions for the field experiment. Laboratory results indicated that the bifunctional synthetic resins, D-3696 and RO-02-119 were highly selective toward ClO{sub 4}{sup -} and performed {approx}5 times better than the best commercial nitrate resin (Purolite{reg_sign} A-520E) and more than an order of magnitude better than some nonselective commercial resins (e.g. Amberlite{reg_sign} IRA-900). The bifunctional resins were particularly effective in removing trace quantities of ClO{sub 4}{sup -} in groundwater to below the detection limit ({approx} 3 {micro}g/L). A field trial demonstrated that the bifunctional resin (D-3696) was able to treat {approx} 110,000 bed volumes of groundwater before a 10% breakthrough of ClO{sub 4}{sup -} occurred under the column flow-through conditions (running at {approx} 2 bed volumes per minute). On the other hand, the Purolite{reg_sign} A-520E resin was able to treat {approx} 23,000 bed volumes of groundwater under the same experimental conditions. No pretreatment was needed to remove either dissolved organic matter or other competing anions (such as SO{sub 4}{sup 2-} or NO{sub 3}{sup -}) in the groundwater, and the treatment process did not alter the water quality by removing or adding secondary by-products because of the high selectivity of the

  15. Investigation of the preparation and use of low-capacity anion exchangers in single-column ion chromatography

    SciTech Connect

    Barron, R.E.

    1984-01-01

    The preparation and uses of strong-base anion exchangers of low capacity are reviewed. A new adaptation of known reactions is presented for the reproducible preparation of Type I anion exchangers of low capacity and it is explored in some detail. The resins are based on the macroreticular copolymer known as XAD-1. It is shown that the same reaction scheme may be used on any porous styrene-divinylbenzene copolymer. Procedures are described for the preparation of twelve other strong-base resins with various structural differences in the quaternary ammonium functional group. These resins are then evaluated to determine the effect of chemical structure on selectivity for a number of common monovalent and divalent anions. It is shown that the structure of the quaternary ammonium ion has a definite effect on selectivity. It is also shown that surface modification can affect selectivity. The implications for single-column ion chromatography are discussed and some examples are given where a change in the chemical structure of the functional group is of practical value in the separation of anions. The factors influencing the choice of an eluent acid are outlined and it is shown that some acids are better than others on the basis on their lack of interaction with the copolymer matrix.

  16. Nonsynaptic Communication Through ATP Release from Volume-Activated Anion Channels in Axons

    PubMed Central

    Fields, R. Douglas; Ni, Yingchun

    2016-01-01

    The release of neuronal messengers outside synapses has broad biological implications, particularly with regard to communication between axons and glia. We identify a mechanism for nonsynaptic, nonvesicular release of adenosine triphosphate (ATP) from axons through volume-activated anion channels (VAACs) activated by microscopic axon swelling during action potential firing. We used a combination of single-photon imaging of ATP release, together with imaging for intrinsic optical signals, intracellular calcium ions (Ca2+), time-lapse video, and confocal microscopy, to investigate action potential–induced nonsynaptic release of this neurotransmitter. ATP release from cultured embryonic dorsal root ganglion axons persisted when bafilomycin or botulinum toxin was used to block vesicular release, whereas pharmacological inhibition of VAACs or prevention of action potential–induced axon swelling inhibited ATP release and disrupted activity-dependent signaling between axons and astrocytes. This nonvesicular, nonsynaptic communication could mediate various activity-dependent interactions between axons and nervous system cells in normal conditions, development, and disease. PMID:20923934

  17. Voltage-dependent anion channel (VDAC-1) is required for olfactory sensing in Caenorhabditis elegans.

    PubMed

    Uozumi, Takayuki; Hamakawa, Masayuki; Deno, Yu-Ki; Nakajo, Nobushige; Hirotsu, Takaaki

    2015-10-01

    The Ras-MAP kinase signaling pathway plays important roles for the olfactory reception in olfactory neurons in Caenorhabditis elegans. However, given the absence of phosphorylation targets of MAPK in the olfactory neurons, the mechanism by which this pathway regulates olfactory function is unknown. Here, we used proteomic screening to identify the mitochondrial voltage-dependent anion channel VDAC-1 as a candidate target molecule of MAPK in the olfactory system of C. elegans. We found that Amphid Wing "C" (AWC) olfactory neuron-specific knockdown of vdac-1 caused severe defects in chemotaxis toward AWC-sensed odorants. We generated a new vdac-1 mutant using the CRISPR-Cas9 system, with this mutant also showing decreased chemotaxis toward odorants. This defect was rescued by AWC-specific expression of vdac-1, indicating that functions of VDAC-1 in AWC neurons are essential for normal olfactory reception in C. elegans. We observed that AWC-specific RNAi of vdac-1 reduced AWC calcium responses to odorant stimuli and caused a decrease in the quantity of mitochondria in the sensory cilia. Behavioral abnormalities in vdac-1 knockdown animals might therefore be due to reduction of AWC response, which might be caused by loss of mitochondria in the cilia. Here, we showed that the function of VDAC-1 is regulated by phosphorylation and identified Thr175 as the potential phosphorylation site of MAP kinase. PMID:26223767

  18. Structure and expression of mouse mitochondrial voltage dependent anion channel genes

    SciTech Connect

    Craigen, W.J.; Lovell, R.S.; Sampson, M.J.

    1994-09-01

    Voltage dependent anion channels (VDACs) are small abundant proteins of the outer mitochondrial membrane that interact with the adenine nucleotide translocater and bind glycerol kinase and hexokinase. Kinase binding is developmentally regulated, tissue specific, and increased in various tumor cell lines. VDACs are also components of the peripheral benzodiazepine receptor and GABA{sub A} receptor. Two human VDAC cDNAs have previously been reported, and expression of these isoforms appears ubiquitous. Genomic Southern analysis suggests the presence of other as yet uncharacterised VDAC genes. To study VDAC function in a mammal more amenable to experimental manipulation, we have isolated three mouse VDAC genes by cDNA cloning from a mouse brain cDNA library. DNA sequencing of the cDNAs shows that they share 65-75% amino acid identity. Northern analysis indicates that MVDAC1 is expressed most highly in kidney, heart, and brain. Using an MVDAC3 3{prime} untranslated exon as a probe, three distinct transcripts can be detected. The gene structure for MVDAC3 and MVDAC2 has been completed and suggests that the VDAC isoforms did not arise by gene duplication and divergence. The intron/exon boundaries are not conserved between MVDAC1 and MVDAC3, and MVDAC2 appears to be encoded by a single intronless gene.

  19. Wheat gluten amino acid analysis by high-performance anion-exchange chromatography with integrated pulsed amperometric detection.

    PubMed

    Rombouts, Ine; Lagrain, Bert; Lamberts, Lieve; Celus, Inge; Brijs, Kristof; Delcour, Jan A

    2012-01-01

    This chapter describes an accurate and user-friendly method for determining amino acid composition of wheat gluten proteins and their gliadin and glutenin fractions. The method consists of hydrolysis of the peptide bonds in 6.0 M hydrochloric acid solution at 110°C for 24 h, followed by evaporation of the acid and separation of the free amino acids by high-performance anion-exchange chromatography with integrated pulsed amperometric detection. In contrast to conventional methods, the analysis requires neither pre- or postcolumn derivatization, nor a time-consuming oxidation or derivatization step prior to hydrolysis. Correction factors account for incomplete release of Val and Ile even after hydrolysis for 24 h, and for losses of Ser during evaporation. Gradient conditions including an extra eluent allow multiple sequential sample analyses without risk of Glu accumulation on the anion-exchange column which otherwise would result from high Gln levels in gluten proteins. PMID:22125156

  20. Formation of periodic interfacial misfit dislocation array at the InSb/GaAs interface via surface anion exchange

    NASA Astrophysics Data System (ADS)

    Jia, Bo Wen; Tan, Kian Hua; Loke, Wan Khai; Wicaksono, Satrio; Yoon, Soon Fatt

    2016-07-01

    The relationship between growth temperature and the formation of periodic interfacial misfit (IMF) dislocations via the anion exchange process in InSb/GaAs heteroepitaxy was systematically investigated. The microstructural and electrical properties of the epitaxial layer were characterized using atomic force microscope, high-resolution x-ray diffraction, transmission electron microscopy, and Hall resistance measurement. The formation of interfacial misfit (IMF) dislocation arrays depended on growth temperature. A uniformly distributed IMF array was found in a sample grown at 310 °C, which also exhibited the lowest threading dislocation density. The analysis suggested that an incomplete As-for-Sb anion exchange process impeded the formation of IMF on sample grown above 310 °C. At growth temperature below 310 °C, island coalescence led to the formation of 60° dislocations and the disruption of periodic IMF array. All samples showed higher electron mobility at 300 K than at 77 K.

  1. Anion- or Cation-Exchange Membranes for NaBH4/H2O2 Fuel Cells?

    PubMed

    Sljukić, Biljana; Morais, Ana L; Santos, Diogo M F; Sequeira, César A C

    2012-01-01

    Direct borohydride fuel cells (DBFC), which operate on sodium borohydride (NaBH4) as the fuel, and hydrogen peroxide (H2O2) as the oxidant, are receiving increasing attention. This is due to their promising use as power sources for space and underwater applications, where air is not available and gas storage poses obvious problems. One key factor to improve the performance of DBFCs concerns the type of separator used. Both anion- and cation-exchange membranes may be considered as potential separators for DBFC. In the present paper, the effect of the membrane type on the performance of laboratory NaBH4/H2O2 fuel cells using Pt electrodes is studied at room temperature. Two commercial ion-exchange membranes from Membranes International Inc., an anion-exchange membrane (AMI-7001S) and a cation-exchange membrane (CMI-7000S), are tested as ionic separators for the DBFC. The membranes are compared directly by the observation and analysis of the corresponding DBFC's performance. Cell polarization, power density, stability, and durability tests are used in the membranes' evaluation. Energy densities and specific capacities are estimated. Most tests conducted, clearly indicate a superior performance of the cation-exchange membranes over the anion-exchange membrane. The two membranes are also compared with several other previously tested commercial membranes. For long term cell operation, these membranes seem to outperform the stability of the benchmark Nafion membranes but further studies are still required to improve their instantaneous power load. PMID:24958292

  2. Anion- or Cation-Exchange Membranes for NaBH4/H2O2 Fuel Cells?

    PubMed Central

    Šljukić, Biljana; Morais, Ana L.; Santos, Diogo M. F.; Sequeira, César A. C.

    2012-01-01

    Direct borohydride fuel cells (DBFC), which operate on sodium borohydride (NaBH4) as the fuel, and hydrogen peroxide (H2O2) as the oxidant, are receiving increasing attention. This is due to their promising use as power sources for space and underwater applications, where air is not available and gas storage poses obvious problems. One key factor to improve the performance of DBFCs concerns the type of separator used. Both anion- and cation-exchange membranes may be considered as potential separators for DBFC. In the present paper, the effect of the membrane type on the performance of laboratory NaBH4/H2O2 fuel cells using Pt electrodes is studied at room temperature. Two commercial ion-exchange membranes from Membranes International Inc., an anion-exchange membrane (AMI-7001S) and a cation-exchange membrane (CMI-7000S), are tested as ionic separators for the DBFC. The membranes are compared directly by the observation and analysis of the corresponding DBFC’s performance. Cell polarization, power density, stability, and durability tests are used in the membranes’ evaluation. Energy densities and specific capacities are estimated. Most tests conducted, clearly indicate a superior performance of the cation-exchange membranes over the anion-exchange membrane. The two membranes are also compared with several other previously tested commercial membranes. For long term cell operation, these membranes seem to outperform the stability of the benchmark Nafion membranes but further studies are still required to improve their instantaneous power load. PMID:24958292

  3. Gluconic acid production in bioreactor with immobilized glucose oxidase plus catalase on polymer membrane adjacent to anion-exchange membrane.

    PubMed

    Godjevargova, Tzonka; Dayal, Rajeshwar; Turmanova, Sevdalina

    2004-10-20

    Gluconic acid was obtained in the permeate side of the bioreactor with glucose oxidase (GOD) immobilized onto anion-exchange membrane (AEM) of low-density polyethylene grafted with 4-vinylpiridine. The electric resistance of the anion-exchange membranes was increased after the enzyme immobilization on the membrane. The gluconic acid productions were relatively low with the GOD immobilized by any method on the AEM. To increase the enzyme reaction efficiency, GOD was immobilized on membrane of AN copolymer (PAN) adjacent to an anion-exchange membrane in bioreactor. Uses of anion-exchange membrane led to selective removal of the gluconic acid from the glucose solution and reduce the gluconic acid inhibition. The amount of gluconic acid obtained in the permeate side of the bioreactor with the GOD immobilized on the PAN membrane adjacent to the AEM under electrodialysis was about 30 times higher than that obtained with enzyme directly bound to the AEM. The optimal substrate concentration in the feed side was found to be about 1 g/l. Further experiments were carried out with the co-immobilized GOD plus Catalase (CAT) on the PAN membrane adjacent to the AEM to improve the efficiency of the immobilize system. The yield of this process was at least 95%. The storage stability of the co-immobilized GOD and CAT was studied (lost 20% of initial activity for 90 d). The results obtained clearly showed the higher potential of the dual membrane bioreactor with GOD plus CAT bound to ultrafiltration polymer membrane adjacent to the AEM. Storage stability of GOD activity in GOD plus CAT immobilized on PAN//AEM membranes and on AEM. PMID:15497133

  4. The mechanism of inactivation of a 50-pS envelope anion channel during chloroplast protein import.

    PubMed Central

    van den Wijngaard, P W; Dabney-Smith, C; Bruce, B D; Vredenberg, W J

    1999-01-01

    The mechanism of import-competent precursor protein-induced inactivation of a 50-pS anion channel of the chloroplast envelope is investigated using single-channel recordings. The inactivation by precursor protein is the result of the induction of a long-lived closed state of the channel. The mean duration of this state does not depend on precursor concentration. From this it can be concluded that the protein import related anion channel enters the inactive state less frequently when the precursor concentration is lowered, but that the time spent in this state remains the same. Furthermore, it was found that the presence of precursor protein also decreases the mean durations of preexisting open and closed states of the channel. This decrease is found to be dependent on the precursor concentration. From this it is concluded that there is a direct interaction between the precursor protein and a protein complex of which the channel is a constituent. The mean duration of the precursor-induced long-lived closed state does not depend on the length of the translocation-competent precursor. This suggests that the duration of import is independent of precursor length. PMID:10585937

  5. Thermodynamic study of the interaction between linear plasmid DNA and an anion exchange support under linear and overloaded conditions.

    PubMed

    Aguilar, P A; Twarda, A; Sousa, F; Dias-Cabral, A C

    2014-11-01

    Anion-exchange chromatography has been successfully used in plasmid DNA (pDNA) purification. However, pDNA adsorption mechanism using this method is still not completely understood, and the prediction of the separation behavior is generally unreliable. Flow microcalorimetry (FMC) has proven its ability to provide an improved understanding of the driving forces and mechanisms involved in the adsorption process of biomolecules onto several chromatographic systems. Thus, using FMC, this study aims to understand the adsorption mechanism of linear pDNA (pVAX1-LacZ) onto the anion-exchange support Fast Flow (FF) Q-Sepharose. Static binding capacity studies have shown that the mechanism of pDNA adsorption onto Q-Sepharose follows a Langmuir isotherm. FMC experiments resulted in thermograms that comprised endothermic and exothermic heats. Endothermic heat major contributor was suggested to be the desolvation process. Exothermic heats were related to the interaction between pDNA and Q-Sepharose primary and secondary adsorption. Furthermore, FMC revealed that the overall adsorption process is exothermic, as expected for an anion-exchange interaction. Nevertheless, there are evidences of the presence of nonspecific effects, such as reorientation and electrostatic repulsive forces. PMID:25465014

  6. Dual-channel capillary electrophoresis for simultaneous determination of cations and anions.

    PubMed

    Opekar, František; Tůma, Petr

    2016-05-13

    An original electrophoresis apparatus for simultaneous rapid determination of cations and anions has been designed and tested. The separation part of the apparatus consists of two identical fused-silica capillaries, each with a length of 10.5cm and inner diameter of 25μm. The injection space is formed by the crossing of four channels in a plexiglass cross-piece. The capillaries pass through two opposing channels and their injection ends are located opposite one another at a distance of approx. 0.5mm in the centre of the crossing point. The exit ends of the capillaries are placed in vessels containing the background electrolyte in which are immersed the electrodes of a high-voltage source. Contactless conductivity detectors with semi-cylindrical electrodes are located 2cm from the exit ends of the capillaries. The injection part of the apparatus consists of two piezoelectric micro-pumps bringing the solution through another channel in the cross-piece to the injection ends of the capillary. During the injection, the sample is brought through one of them and is injected electrokinetically for a defined time. Then the sample zone is forced out of the injection space by a stream of background electrolyte from the second micro-pump. The timing of the injection process is computer-controlled. Thus the equipment can be considered to constitute electrophoresis in one capillary with injection into its centre. The use of short capillaries and miniature micro-pumps without other mechanical components enabled the construction of the apparatus on a board with dimensions of 20×25cm. The proposed equipment was used to test simultaneous separation of a mixture of cations and anions, NH4(+), K(+), Ca(2+), Mg(2+), Sr(2+), Ba(2+), Cl(-), NO3(-), SO4(2-), ClO3(-) and F(-), in BGE with composition 500mM HAc+20mM Tris+2mM 18-crown-6 (pH 3.3). Baseline separation of all the components was achieved in time less than 1min. Quantification of the content of nitrate nitrogen (determined as

  7. Gadolinium ions block mechanosensitive channels by altering the packing and lateral pressure of anionic lipids.

    PubMed

    Ermakov, Yury A; Kamaraju, Kishore; Sengupta, Krishnendu; Sukharev, Sergei

    2010-03-17

    Effects of polyvalent ions on the lateral packing of phospholipids have been known for decades, but the physiological consequences have not been systematically studied. Gd(3+) is a relatively nonspecific agent that blocks mechano-gated channels with a variable affinity. In this study, we show that the large mechanosensitive channel MscL of Escherichia coli is effectively blocked by Gd(3+) only when reconstituted with negatively charged phospholipids (e.g., PS). Taking this lead, we studied effects of Gd(3+) on monolayers and unilamellar vesicles made of natural brain PS, DMPS, and its mixtures with DMPC. In monolayer experiments, we found that muM Gd(3+) present in the subphase leads to approximately 8% lateral compaction of brain PS (at 35 mN/m). Gd(3+) more strongly shrinks and rigidifies DMPS films causing a spontaneous liquid expanded-to-compact transition to the limiting 40 A(2)/mol. Pressure-area isotherms of uncharged DMPC were unaffected by Gd(3+), and neutralization of DMPS surface by low pH did not produce strong compaction. Upshifts of surface potential isotherms of DMPS monolayers reflected changes in the diffuse double layer due to neutralization of headgroup charges by Gd(3+), whereas the increased packing density produced up to a 200 mV change in the interfacial dipole potential. The slopes of surface potential versus reciprocal area predicted that Gd(3+) induced a modest ( approximately 18%) increase in the magnitude of the individual lipid dipoles in DMPS. Isothermal titration calorimetry indicated that binding of Gd(3+) to DMPS liposomes in the gel state is endothermic, whereas binding to liquid crystalline liposomes produces heat consistent with the isothermal liquid-to-gel phase transition induced by the ion. Both titration curves suggested a K(b) of approximately 10(6) M(-1). We conclude that anionic phospholipids serve as high-affinity receptors for Gd(3+) ions, and the ion-induced compaction generates a lateral pressure increase estimated as

  8. Anion exchange SPE and liquid chromatography-tandem mass spectrometry in GHB analysis.

    PubMed

    Elian, Albert A; Hackett, Jeffery

    2011-12-01

    In this study, the extraction of γ-hydroxybutyrate (GHB) from urine using solid-phase extraction (SPE) is described. SPE was performed on anion exchange columns after samples of urine had been diluted with de-ionized water. After application of the diluted samples containing GHB-d(6) as an internal standard, the sorbent was washed with deionized water and methanol and dried. The GHB was eluted from the SPE column with a solvent consisting of methanol containing 6% glacial acetic acid. The eluent was collected, evaporated to dryness, and dissolved in mobile phase (100 μL) for analysis by liquid chromatography-tandem mass spectrometry (LC-MS/MS) in negative multiple reaction monitoring (MRM) mode. Liquid chromatography was performed in gradient mode employing a biphenyl column and a mobile phase consisting of acetontitrile (containing 0.1% formic acid) and 0.1% aqueous formic acid. The total run time for each analysis was less than 5 min. The limits of detection/quantification for this method were determined to be 50 and 100 ng/mL, respectively. The method was found to be linear from 500 ng/mL to 10,000 ng/mL (r(2)>0.995). The recovery of GHB was found to be greater than 75%. In this report, results of authentic urine samples analyzed for GHB by this method are presented. GHB concentrations in these samples were found to be range from less than 500 ng/mL to 5110 ng/mL. PMID:22055831

  9. Separation of boric acid in liquid waste with anion exchange membrane contactor

    SciTech Connect

    Park, J.K.; Lee, K.J.

    1995-12-31

    In order to separate boric acid in liquid waste, some possible technologies were investigated and the membrane contactor without dispersion and density differences was selected. The separation experiments on a Celgard 3401{reg_sign} hydrophilic microporous membrane contactor were first performed to obtain the basic data and to determine the properties of the contactor. The experimental conditions were as follows: boric acid concentrations up to 2.0 M, pH 7.0, temperatures of 25 and 55 C, and flow rates of 100, 300, 500, and 800 cm{sup 3}/min. Secondly, an AFN{reg_sign} anion exchange membrane contactor was tested at temperatures of 40 and 55 C and flow rate 400 cm{sup 3}/min. Boric acid solutions were prepared by the same method as that for Celgard 3401{reg_sign} but contained 5.0{times}10{sup {minus}4} M cobalt chloride (CoCl{sub 2}). To simulate membrane contractors, parameters such as the differential diffusion coefficients of boric acid and the mass transfer coefficients in the AFN membrane were measured, and regression models estimating the diffusion coefficient at several conditions were developed. The Celgard 3401{reg_sign} membrane contactor was simulated and compared with experimental data. Simulation results agreed with the experimental data well when a proper correction factor was utilized. The correction factor was independent of the solution temperature and was 8.75 at the flow rates of 300--800 cm{sup 3}/min. This correction factor was also applied to simulate the AFN{reg_sign} resulted in a good agreement with experiment at 40 C, but not 55 C. The retention on cobalt was also better at 40 c than 55 C. The simulating computer program was also applied to a life size contactor designed conceptually.

  10. HB-LINE ANION EXCHANGE PURIFICATION OF AFS-2 PLUTONIUM FOR MOX

    SciTech Connect

    Kyser, E.; King, W.

    2012-04-25

    Non-radioactive cerium (Ce) and radioactive plutonium (Pu) anion exchange column experiments using scaled HB-Line designs were performed to investigate the feasibility of using either gadolinium nitrate (Gd) or boric acid (B as H{sub 3}BO{sub 3}) as a neutron poison in the H-Canyon dissolution process. Expected typical concentrations of probable impurities were tested and the removal of these impurities by a decontamination wash was measured. Impurity concentrations are compared to two specifications - designated as Column A or Column B (most restrictive) - proposed for plutonium oxide (PuO{sub 2}) product shipped to the Mixed Oxide (MOX) Fuel Fabrication Facility (MFFF). Use of Gd as a neutron poison requires a larger volume of wash for the proposed Column A specification. Since boron (B) has a higher proposed specification and is more easily removed by washing, it appears to be the better candidate for use in the H-Canyon dissolution process. Some difficulty was observed in achieving the Column A specification due to the limited effectiveness that the wash step has in removing the residual B after {approx}4 BV's wash. However a combination of the experimental 10 BV's wash results and a calculated DF from the oxalate precipitation process yields an overall DF sufficient to meet the Column A specification. For those impurities (other than B) not removed by 10 BV's of wash, the impurity is either not expected to be present in the feedstock or process, or recommendations have been provided for improvement in the analytical detection/method or validation of calculated results. In summary, boron is recommended as the appropriate neutron poison for H-Canyon dissolution and impurities are expected to meet the Column A specification limits for oxide production in HB-Line.

  11. HB-LINE ANION EXCHANGE PURIFICATION OF AFS-2 PLUTONIUM FOR MOX

    SciTech Connect

    Kyser, E. A.; King, W. D.

    2012-07-31

    Non-radioactive cerium (Ce) and radioactive plutonium (Pu) anion exchange column experiments using scaled HB-Line designs were performed to investigate the feasibility of using either gadolinium nitrate (Gd) or boric acid (B as H{sub 3}BO{sub 3}) as a neutron poison in the H-Canyon dissolution process. Expected typical concentrations of probable impurities were tested and the removal of these impurities by a decontamination wash was measured. Impurity concentrations are compared to two specifications - designated as Column A or Column B (most restrictive) - proposed for plutonium oxide (PuO{sub 2}) product shipped to the Mixed Oxide (MOX) Fuel Fabrication Facility (MFFF). Use of Gd as a neutron poison requires a larger volume of wash for the proposed Column A specification. Since boron (B) has a higher proposed specification and is more easily removed by washing, it appears to be the better candidate for use in the H-Canyon dissolution process. Some difficulty was observed in achieving the Column A specification due to the limited effectiveness that the wash step has in removing the residual B after ~4 BV's wash. However a combination of the experimental 10 BV's wash results and a calculated DF from the oxalate precipitation process yields an overall DF sufficient to meet the Column A specification. For those impurities (other than B) not removed by 10 BV's of wash, the impurity is either not expected to be present in the feedstock or process, or recommendations have been provided for improvement in the analytical detection/method or validation of calculated results. In summary, boron is recommended as the appropriate neutron poison for H-Canyon dissolution and impurities are expected to meet the Column A specification limits for oxide production in HB-Line.

  12. Click Chemistry Finds Its Way in Constructing an Ionic Highway in Anion-Exchange Membrane.

    PubMed

    Ge, Qianqian; Ran, Jin; Miao, Jibin; Yang, Zhengjin; Xu, Tongwen

    2015-12-30

    To find the way to construct an ionic highway in anion-exchange membranes (AEMs), a series of side-chain-type alkaline polymer electrolytes (APEs) based on poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) polymer backbones were synthesized via Cu(I)-catalyzed click chemistry. The resulting triazole groups and quaternary ammonium (QA) groups facilitate the formation of a continuous hydrogen bond network, which will lead to high hydroxide conductivity according to Grotthuss-type mechanism. Microphase separation induced by long alkyl side chains contributes at the same time to further improving the hydroxide conductivity of the resultant AEMs. Hydroxide conductivity as high as 52.8 mS/cm is obtained for membrane TA-14C-1.21 (IEC = 1.21 mmol/g) with the longest pendant chain at 30 °C, and the conductivity can be increased to 140 mS/cm when the temperature was increased to 80 °C. Moreover, the corresponding water uptake is only 8.6 wt % at 30 °C. In the meantime, the membrane properties can be tuned by precisely regulating the hydrophilic/hydrophobic ratio in the cationic head groups. Compared with AEMs containing triazole and quaternized trimethylammonium head groups, enhanced dimensional stability and mechanical properties are obtained by tuning side-chain chemistry. However, the alkaline stability of the membrane is not as stable as anticipated, probably because of the existence of the triazole ring. Further study will be focused on increasing the alkali stability of the membrane. We envisage that the side-chain-type APEs meditated by click chemistry bearing long hydrophobic side chains pendant to the cationic head groups hold promise as a novel AEMs material. PMID:26645427

  13. Chemical separation of Mo and W from terrestrial and extraterrestrial samples via anion exchange chromatography.

    PubMed

    Nagai, Yuichiro; Yokoyama, Tetsuya

    2014-05-20

    A new two-stage chemical separation method was established using an anion exchange resin, Eichrom 1 × 8, to separate Mo and W from four natural rock samples. First, the distribution coefficients of nine elements (Ti, Fe, Zn, Zr, Nb, Mo, Hf, Ta, and W) under various chemical conditions were determined using HCl, HNO3, and HF. On the basis of the obtained distribution coefficients, a new technique for the two-stage chemical separation of Mo and W, along with the group separation of Ti-Zr-Hf, was developed as follows: 0.4 M HCl-0.5 M HF (major elements), 9 M HCl-0.05 M HF (Ti-Zr-Hf), 9 M HCl-1 M HF (W), and 6 M HNO3-3 M HF (Mo). After the chemical procedure, Nb remaining in the W fraction was separated using 9 M HCl-3 M HF. On the other hand, Nb and Zn remaining in the Mo fraction were removed using 2 M HF and 6 M HCl-0.1 M HF. The performance of this technique was evaluated by separating these elements from two terrestrial and two extraterrestrial samples. The recovery yields for Mo, W, Zr, and Hf were nearly 100% for all of the examined samples. The total contents of the Zr, Hf, W, and Mo in the blanks used for the chemical separation procedure were 582, 9, 29, and 396 pg, respectively. Therefore, our new separation technique can be widely used in various fields of geochemistry, cosmochemistry, and environmental sciences and particularly for multi-isotope analysis of these elements from a single sample with significant internal isotope heterogeneities. PMID:24801276

  14. Hexokinase II Detachment from Mitochondria Triggers Apoptosis through the Permeability Transition Pore Independent of Voltage-Dependent Anion Channels

    PubMed Central

    Chiara, Federica; Castellaro, Diego; Marin, Oriano; Petronilli, Valeria; Brusilow, William S.; Juhaszova, Magdalena; Sollott, Steven J.; Forte, Michael; Bernardi, Paolo; Rasola, Andrea

    2008-01-01

    Type II hexokinase is overexpressed in most neoplastic cells, and it mainly localizes on the outer mitochondrial membrane. Hexokinase II dissociation from mitochondria triggers apoptosis. The prevailing model postulates that hexokinase II release from its mitochondrial interactor, the voltage-dependent anion channel, prompts outer mitochondrial membrane permeabilization and the ensuing release of apoptogenic proteins, and that these events are inhibited by growth factor signalling. Here we show that a hexokinase II N-terminal peptide selectively detaches hexokinase II from mitochondria and activates apoptosis. These events are abrogated by inhibiting two established permeability transition pore modulators, the adenine nucleotide translocator or cyclophilin D, or in cyclophilin D knock-out cells. Conversely, insulin stimulation or genetic ablation of the voltage-dependent anion channel do not affect cell death induction by the hexokinase II peptide. Therefore, hexokinase II detachment from mitochondria transduces a permeability transition pore opening signal that results in cell death and does not require the voltage-dependent anion channel. These findings have profound implications for our understanding of the pathways of outer mitochondrial membrane permeabilization and their inactivation in tumors. PMID:18350175

  15. Constraints on -channel leptoquark exchange from LHC contact interaction searches

    NASA Astrophysics Data System (ADS)

    Bessaa, Assia; Davidson, Sacha

    2015-02-01

    The -channel exchange of a first generation leptoquark could contribute to the cross section for . The leptoquark is off-shell, so this process can be sensitive to leptoquarks beyond the mass reach of pair production searches at the LHC (currently GeV). We attempt to analytically translate ATLAS bounds on contact interactions to the various scalar leptoquarks, we but encounter two difficulties: the leptoquark momentum is not negligible, and the leptoquarks do not induce the contact interaction studied by ATLAS, so the interference with the standard model is different. If bounds were quoted on the functional dependence of the cross section on , rather than on particular contact interaction models, these difficulties could be circumvented. We use the results of such a "form factor" fit to CMS plots to obtain bounds on the various leptoquarks' quark-lepton coupling of order TeV).

  16. Investigation of Anion-Exchange and Immunoaffinity Particle-Loaded Membranes for the Isolation of Charged Organic Analytes from Water

    USGS Publications Warehouse

    Dombrowski, T.R.; Wilson, G.S.; Thurman, E.M.

    1998-01-01

    Anion-exchange and immunoaffinity particle loaded membranes (PLMs) were investigated as a mechanism for the isolation of charged organic analytes from water. Kinetic properties determined theoretically included dynamic capacity, pressure drop (??P), residence and diffusion times (Tr, Td), and total membrane porosity (???T). These properties were confirmed through experimental evaluation, and the PLM method showed significant improvement over conventional solid-phase extraction (SPE) and ion-exchange formats. Recoveries of more than 90% were observed for a variety of test compounds at flow rates up to 70 mL/min (equipment-limited maximum flow rate). A fast-flow immunoaffinity column was developed using antibodies (Abs) attached to the PLMs. Reproducible recoveries (88% ?? 4%) were observed at flow rates up to 70 mL/min for the antibody (Ab)-loaded PLMs. Findings indicate increased selectivity over anion-exchange PLMs and conventional SPE or ion-exchange methods and rapid Ab-antigen binding rates given the excellent mass-transfer characteristics of the PLMs.

  17. Mechanism of anion permeation through channels gated by glycine and gamma-aminobutyric acid in mouse cultured spinal neurones.

    PubMed Central

    Bormann, J; Hamill, O P; Sakmann, B

    1987-01-01

    1. The ion-selective and ion transport properties of glycine receptor (GlyR) and gamma-aminobutyric acid receptor (GABAR) channels in the soma membrane of mouse spinal cord neurones were investigated using the whole-cell, cell-attached and outside-out patch versions of the patch-clamp technique. 2. Current-voltage (I-V) relations of transmitter-activated currents obtained from whole-cell measurements with 145 mM-Cl- intracellularly and extracellularly, showed outward rectification. In voltage-jump experiments, the instantaneous I-V relations were linear, and the steady-state I-V relations were rectifying outwardly indicating that the gating of GlyR and GABAR channels is voltage sensitive. 3. The reversal potential of whole-cell currents shifted 56 mV per tenfold change in internal Cl- activity indicating activation of Cl(-)-selective channels. The permeability ratio of K+ to Cl- (PK/PCl) was smaller than 0.05 for both channels. 4. The permeability sequence for large polyatomic anions was formate greater than bicarbonate greater than acetate greater than phosphate greater than propionate for GABAR channels; phosphate and propionate were not measurably permeant in GlyR channels. This indicates that open GlyR and GABAR channels have effective pore diameters of 5.2 and 5.6 A, respectively. The sequence of relative permeabilities for small anions was SCN- greater than I- greater than Br- greater than Cl- greater than F- for both channels. 5. GlyR and GABAR channels are multi-conductance-state channels. In cell-attached patches the single-channel slope conductances close to 0 mV membrane potential were 29, 18 and 10 pS for glycine, and 28, 17 and 10 pS for GABA-activated channels. The most frequently observed (main) conductance states were 29 and 17 pS for the GlyR and GABAR channel, respectively. 6. In outside-out patches with equal extracellular and intracellular concentrations of 145 mM-Cl-, the conductance states were 46, 30, 20 and 12 pS for GlyR channels and 44, 30

  18. Pollen Tube Growth Regulation by Free Anions Depends on the Interaction between the Anion Channel SLAH3 and Calcium-Dependent Protein Kinases CPK2 and CPK20[C][W

    PubMed Central

    Gutermuth, Timo; Lassig, Roman; Portes, Maria-Teresa; Maierhofer, Tobias; Romeis, Tina; Borst, Jan-Willem; Hedrich, Rainer; Feijó, José A.; Konrad, Kai R.

    2013-01-01

    Apical growth in pollen tubes (PTs) is associated with the presence of tip-focused ion gradients and fluxes, implying polar localization or regulation of the underlying transporters. The molecular identity and regulation of anion transporters in PTs is unknown. Here we report a negative gradient of cytosolic anion concentration focused on the tip, in negative correlation with the cytosolic Ca2+ concentration. We hypothesized that a possible link between these two ions is based on the presence of Ca2+-dependent protein kinases (CPKs). We characterized anion channels and CPK transcripts in PTs and analyzed their localization. Yellow fluorescent protein (YFP) tagging of a homolog of SLOW ANION CHANNEL-ASSOCIATED1 (SLAH3:YFP) was widespread along PTs, but, in accordance with the anion efflux, CPK2/CPK20/CPK17/CPK34:YFP fluorescence was strictly localized at the tip plasma membrane. Expression of SLAH3 with either CPK2 or CPK20 (but not CPK17/CPK34) in Xenopus laevis oocytes elicited S-type anion channel currents. Interaction of SLAH3 with CPK2/CPK20 (but not CPK17/CPK34) was confirmed by Förster-resonance energy transfer fluorescence lifetime microscopy in Arabidopsis thaliana mesophyll protoplasts and bimolecular fluorescence complementation in living PTs. Compared with wild-type PTs, slah3-1 and slah3-2 as well as cpk2-1 cpk20-2 PTs had reduced anion currents. Double mutant cpk2-1 cpk20-2 and slah3-1 PTs had reduced extracellular anion fluxes at the tip. Our studies provide evidence for a Ca2+-dependent CPK2/CPK20 regulation of the anion channel SLAH3 to regulate PT growth. PMID:24280384

  19. Understanding ion and solvent transport in anion exchange membranes under humidified conditions

    NASA Astrophysics Data System (ADS)

    Sarode, Himanshu

    Anion exchange membranes (AEM) have been studied for more than a decade for potential applications in low temperature fuel cells and other electrochemical devices. They offer the advantage of faster reaction kinetics under alkaline conditions and ability to perform without costly platinum catalyst. Inherently slow diffusion of hydroxide ions compared to protons is a primary reason for synthesizing and studying the ion transport properties in AEMs. The aim of this thesis is to understand ion transport in novel AEMs using Pulse Gradient stimulated Spin Echo Nuclear Magnetic Resonance technique (PGSE NMR), water uptake, ionic conductivity, Small Angle X-ray Scattering (SAXS) etc. All experiments were performed under humidified conditions (80--95% relative humidity) and fuel cell operating temperatures of 30--90°C. In this work, the NMR tube design was modified for humidifying the entire NMR tube evenly from our previous design. We have developed a new protocol for replacing caustic hydroxide with harmless fluoride or bicarbonate ions for 19F and 13 C NMR diffusion experiments. After performing these NMR experiments, we have obtained in-depth understanding of the morphology linked ion transport in AEMs. We have obtained the highest fluoride self-diffusion coefficient of > 1 x 10-5 cm2/sec ( 55°C) for ETFE-g-PVBTMA membrane which is a result of low tortuosity of 1 obtained for the membrane. This faster fluoride transport combined with low tortuosity of the membrane resulted in > 100mS/cm hydroxide conductivity for the membrane. Polycyclooctene (PCOE) based triblock copolymers are also studied for in-depth understanding of molecular weight, IEC, mechanical and transport properties. Effect of melting temperature of PCOE has favorable effect on increasing ion conductivity and lowering activation energy. Mechanical properties of these types of membranes were studied showing detrimental effect of water plasticization which results in unsuitable mechanical properties

  20. Effects of pH and Competing Anions on the Solution Speciation of Arsenic by Ion Exchange Resins

    SciTech Connect

    Impellitteri, Christopher A.; Ryan, JAmes A.; Al-Abed, Souhail R.; Scheckel, Kirk G.; Randall, Paul M.; Richardson, Collin A.

    2003-03-26

    Anion-exchange resins (AER) are used to differentiate As(V) and As(III) by retaining As(V) and allowing As(III) to pass through. AERs allow rapid speciation of As in the field which precludes the effects of sample preservation on As speciation. Aqueous environmental samples contain anions that may interfere with the speciation of As. This study compares the speciation of As by two commercially available AERs. A silica-based AER was selected for further study. As(V) and As(III) were passed through the AER in the presence of NO3 -, SO4 2-, HPO4 2-, Cl- and HCO3 - at pH 4, 6 and 8. Recoveries of As species in mixed systems range between 90 to 100%. Breakthrough curves for As(V) are presented which allow calculation of loading rates. HPO4 2- has the greatest effect on the speciation of As by AER.

  1. Bordetella pertussis major outer membrane porin protein forms small, anion-selective channels in lipid bilayer membranes.

    PubMed Central

    Armstrong, S K; Parr, T R; Parker, C D; Hancock, R E

    1986-01-01

    The major outer membrane protein of molecular weight 40,000 (the 40K protein) of a virulent isolate of Bordetella pertussis was purified to apparent homogeneity. The purified protein formed an oligomer band (of apparent molecular weight 90,000) on sodium dodecyl sulfate-polyacrylamide gels after solubilization at low temperatures. The porin function of this protein was characterized by the black lipid bilayer method. The 40K protein formed channels smaller than all other constitutive major outer membrane porins studied to date. The average single-channel conductance in 1 M KCl was 0.56 nS. This was less than a third of the conductance previously observed for Escherichia coli porins. Zero-current potential measurements made of the porin to determine its ion selectivity revealed the porin to be more than 100-fold selective for anions over cations. The single-channel conductance was measured as a function of salt concentration. The data could be fitted to a Lineweaver-Burk plot suggesting an anion binding site with a Kd of 1.17 M Cl- and a maximum possible conductance through the channel of 1.28 nS. Images PMID:2420780

  2. Evaluation of anion exchange resins Tulsion A-30 and Indion-930A by application of radioanalytical technique

    NASA Astrophysics Data System (ADS)

    Singare, P. U.

    2014-07-01

    Radioanalytical technique using 131I and 82Br was employed to evaluate organic based anion exchange resins Tulsion A-30 and Indion-930A. The evaluation was based on performance of these resins during iodide and bromide ion-isotopic exchange reactions. It was observed that for iodide ion-isotopic exchange reaction by using Tulsion A-30 resin, the values of specific reaction rate (min-1), amount of iodide ion exchanged (mmol), initial rate of iodide ion exchange (mmol/min) and log K d were 0.238, 0.477, 0.114, and 11.0, respectively, which was higher than 0.155, 0.360, 0.056, and 7.3, respectively as that obtained by using Indion-930A resins under identical experimental conditions of 40.0°C, 1.000 g of ion exchange resins and 0.003 M labeled iodide ion solution. Also at a constant temperature of 40.0°C, as the concentration of labeled iodide ion solution increases 0.001 to 0.004 M, for Tulsion A-30 resins the percentage of iodide ions exchanged increases from 59.0 to 65.1%, and from 46.4 to 48.8% for Indion-930A resins under identical experimental conditions. The identical trend was observed for both the resins during bromide ion-isotopic exchange reactions. The overall results indicate that under identical experimental conditions, Tulsion A-30 show superior performance over Indion-930A resins. The results of present experimental work have demonstrated that the radioanalytical technique used here can be successfully applied for characterization of different ion exchange resins so as to evaluate their performance under various process parameters.

  3. A novel open-framework copper borophosphate containing 1-D borophosphate anion with 10-MR windows and 12-MR channels.

    PubMed

    Feng, Yuquan; Li, Min; Fan, Huitao; Huang, Qunzeng; Qiu, Dongfang; Shi, Hengzhen

    2015-01-21

    A novel open-framework copper borophosphate, Na5KCu3[B9P6O33(OH)3]·H2O (), has been synthesised by a boric acid flux method. Its structure can be viewed as a 3-D open framework constructed by the connection of Cu(II)O6 octahedra and 1-D (4,4)-connected borophosphate anionic structures composed of trigonal-planar BO2(OH) groups, tetrahedral BO4 and PO4 groups. The compound not only features a novel borophosphate anionic partial structure containing 1-D 12-MR channels, but also exhibits ferromagnetic interactions and high catalytic activity for the oxidative degradation of chitosan. PMID:25437261

  4. Improvement of the chromatographic separation performance of an imidazolium ionic liquid functionalized silica column by in situ anion-exchange with dodecyl sulfonate and dodecylbenzene sulfonate anions.

    PubMed

    Sun, Min; Feng, Juanjuan; Chen, Wenjie; Li, Leilei; Duan, Huimin; Luo, Chuannan

    2014-06-01

    The anionic part of ionic liquids can provide additional interactions during chromatographic separations. In this work, the chromatographic separation performance of a silica column functionalized with 1-propyl-3-methylimidazolium chloride ionic liquid was improved by in situ anion-exchange from chloride anions to dodecyl sulfonate anions and dodecylbenzene sulfonate anions. The separation performances of these ionic liquid functionalized phases were investigated and compared with each other using polycyclic aromatic hydrocarbons, phthalates, parabens, and phenols as model compounds. Results indicated that the new columns presented a better chromatographic separation than the original one. This was ascribed retention mechanism from organic anions. The introduction of dodecyl sulfonate anions increased the hydrophobicity of stationary phase. Furthermore, the phenyl groups of dodecylbenzene sulfonate anions could provide an enhanced selectivity to aromatic compounds such as polycyclic aromatic hydrocarbons by π-π interactions. Analysis repeatability of the new columns was satisfactory (RSD of retention time, 0.10-0.40%; RSD of peak area, 0.66-0.84%). PMID:24616155

  5. Influence of preadsorption of organic vapors on the sorption capacity of macroporous anion exchanges for carbon dioxide

    SciTech Connect

    Kats, B.M.; Artyushin, G.A.; Malinovskii, E.K.

    1986-08-01

    This paper examines the influence of preadsorption of vapors of organic compounds (acetic acid, methanol, ethanol, butanol, hexanol, acetone, xylene, benzene, dioxane, toluene, dibutyl phthalate, cyclohexane, butyl acetate, ethylene chlorohydrin) on the equilibrium capacity for carbon dioxide of the weakly basic macroporous anion exchanger AN-511, made by amination, using diethylenetriamine, of the chloromethylated macroporous copolymer of styrene with divinylbenzene (with n-decane as the blowing agent). It is shown that preadsorption of the vapors lowers the sorption capacity of halohydrocarbons for CO/sub 2/.

  6. Boron protected cobalt dicarbollide anions and their use in polymer supported cation exchangers

    SciTech Connect

    Hurlburt, P.K.; Miller, R.L.; Abney, K.D.

    1995-12-01

    The cobalt dicarbollide anion, [CO(C{sub 2}B{sub 9}H{sub 11}){sub 2}]{sup -}, is unique in its ability to separate Cs{sup +} from other cations, an important property in the remediation of nuclear waste. Substitution of B10, in the carborane clusters imparts increased stability in harsh environments. Substitution also provides a handle. which may be useful in attaching this important anion to polymeric structures. Various routes to boron substitution will be discussed along with the possible uses of these boron substituted compounds in polymer synthesis.

  7. "Best Match" Model and Effect of Na+/H+ Exchange on Anion Attachment to Peptides and Stability of Formed Adducts in Negative Ion Electrospray Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Liu, Xiaohua; Cole, Richard B.

    2013-12-01

    The "Best Match" model has been extended to account for the role that Na+/H+ exchange plays on anion attachment in negative ion electrospray. Without any Na+/H+ exchange on (Glu) fibrinopeptide B, the higher basicity anions F- and CH3COO- can hardly form observable adducts; however, after multiple Na+/H+ exchanges, adduct formation is enabled. Moreover, dissociation pathways of CF3COO- adducts with singly deprotonated peptides that have undergone 0 to 3 Na+/H+ exchanges exhibit a shift in CID product ions from losing predominately CF3COOH (case of 0 Na+/H+ exchanges) to losing predominately CF3COO- (case of 3 Na+/H+ exchanges). These phenomena can be rationalized by considering that Na+ cations exchange at, and serve to "block", the most acidic sites, thereby forcing implicated anions to attach to lower acidity protons. In addition to forming ion pairs with carboxylate groups, Na+ also participates in formation of tri-atomic ions of the form ANaA- during adduct dissociation. The fact that low gas-phase basicity (GB) anions preferentially form ANaA- species, even though high GB anions form more stable tri-atomic species, indicates that the monatomic ions were not in close contact in the initial adduct. The propensity for formation of stable anionic adducts is dependent on the degree of matching between anion GBs and GBapp of deprotonated sites on the peptide. The GBapp is raised dramatically as the charge state of the peptide increases via a through-space effect. The presence of Na+ on carboxylate sites substantially decreases the GBapp by neutralizing these sites, while slightly increasing the intrinsic GBs by an inductive effect.

  8. On the origin of asymmetric interactions between permeant anions and the cystic fibrosis transmembrane conductance regulator chloride channel pore.

    PubMed

    Fatehi, Mohammad; St Aubin, Chantal N; Linsdell, Paul

    2007-02-15

    Single channel and macroscopic current recording was used to investigate block of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel pore by the permeant anion Au(CN)2(-). Block was 1-2 orders of magnitude stronger when Au(CN)2(-) was added to the intracellular versus the extracellular solution, depending on membrane potential. A point mutation within the pore, T-338A, strongly decreased the asymmetry of block, by weakening block by intracellular Au(CN)2(-) and at the same time strengthening block by external Au(CN)2(-). Block of T-338A, but not wild-type, was strongest at the current reversal potential and weakened by either depolarization or hyperpolarization. In contrast to these effects, the T-338A mutation had no impact on block by the impermeant Pt(NO2)4(2-) ion. We suggest that the CFTR pore has at least two anion binding sites at which Au(CN)2(-) and Pt(NO2)4(2-) block Cl- permeation. The T-338A mutation decreases a barrier for Au(CN)2(-) movement between different sites, leading to significant changes in its blocking action. Our finding that apparent blocker binding affinity can be altered by mutagenesis of a residue which does not contribute to a blocker binding site has important implications for interpreting the effects of mutagenesis on channel blocker effects. PMID:17142267

  9. 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.

  10. Full cell study of Diels Alder poly(phenylene) anion and cation exchange membranes in vanadium redox flow batteries

    DOE PAGESBeta

    Pezeshki, Alan M.; Fujimoto, Cy; Sun, Che -Nan; Mench, Matthew M.; Zawodzinski, Thomas A.; Tang, Z. J.

    2015-11-14

    In this paper, we report on the performance of Diels Alder poly(phenylene) membranes in vanadium redox flow batteries. The membranes were functionalized with quaternary ammonium groups to form an anion exchange membrane (QDAPP) and with sulfonic acid groups to form a cation exchange membrane (SDAPP). Both membrane classes showed similar conductivities in the battery environment, suggesting that the ion conduction mechanism in the material is not strongly affected by the moieties along the polymer backbone. The resistance to vanadium permeation in QDAPP was not improved relative to SDAPP, further suggesting that the polarity of the functional groups do not playmore » a significant role in the membrane materials tested. Both QDAPP and SDAPP outperformed Nafion membranes in cycling tests, with both achieving voltage efficiencies above 85% while maintaining 95% coulombic efficiency while at a current density of 200 mA/cm2.« less

  11. Full cell study of Diels Alder poly(phenylene) anion and cation exchange membranes in vanadium redox flow batteries

    SciTech Connect

    Pezeshki, Alan M.; Fujimoto, Cy; Sun, Che -Nan; Mench, Matthew M.; Zawodzinski, Thomas A.; Tang, Z. J.

    2015-11-14

    In this paper, we report on the performance of Diels Alder poly(phenylene) membranes in vanadium redox flow batteries. The membranes were functionalized with quaternary ammonium groups to form an anion exchange membrane (QDAPP) and with sulfonic acid groups to form a cation exchange membrane (SDAPP). Both membrane classes showed similar conductivities in the battery environment, suggesting that the ion conduction mechanism in the material is not strongly affected by the moieties along the polymer backbone. The resistance to vanadium permeation in QDAPP was not improved relative to SDAPP, further suggesting that the polarity of the functional groups do not play a significant role in the membrane materials tested. Both QDAPP and SDAPP outperformed Nafion membranes in cycling tests, with both achieving voltage efficiencies above 85% while maintaining 95% coulombic efficiency while at a current density of 200 mA/cm2.

  12. Novel simple process for tocopherols selective recovery from vegetable oils by adsorption and desorption with an anion-exchange resin.

    PubMed

    Hiromori, Kousuke; Shibasaki-Kitakawa, Naomi; Nakashima, Kazunori; Yonemoto, Toshikuni

    2016-03-01

    A novel and simple low-temperature process was used to recover tocopherols from a deodorizer distillate, which is a by-product of edible oil refining. The process consists of three operations: the esterification of free fatty acids with a cation-exchange resin catalyst, the adsorption of tocopherols onto an anion-exchange resin, and tocopherol desorption from the resin. No degradation of tocopherols occurred during these processes. In the tocopherol-rich fraction, no impurities such as sterols or glycerides were present. These impurities are commonly found in the product of the conventional process. This novel process improves the overall recovery ratio and the mass fraction of the product (75.9% and 51.0wt%) compared with those in the conventional process (50% and 35wt%). PMID:26471519

  13. Highly efficient platinum group metal free based membrane-electrode assembly for anion exchange membrane water electrolysis.

    PubMed

    Pavel, Claudiu C; Cecconi, Franco; Emiliani, Chiara; Santiccioli, Serena; Scaffidi, Adriana; Catanorchi, Stefano; Comotti, Massimiliano

    2014-01-27

    Low-temperature electricity-driven water splitting is an established technology for hydrogen production. However, the two main types, namely proton exchange membrane (PEM) and liquid alkaline electrolysis, have limitations. For instance, PEM electrolysis requires a high amount of costly platinum-group-metal (PGM) catalysts, and liquid alkaline electrolysis is not well suited for intermittent operation. Herein we report a highly efficient alkaline polymer electrolysis design, which uses a membrane-electrode assembly (MEA) based on low-cost transition-metal catalysts and an anion exchange membrane (AEM). This system exhibited similar performance to the one achievable with PGM catalysts. Moreover, it is very suitable for intermittent power operation, durable, and able to efficiently operate at differential pressure up to 3 MPa. This system combines the benefits of PEM and liquid alkaline technologies allowing the scalable production of low-cost hydrogen from renewable sources. PMID:24339230

  14. Inhibitors of pendrin anion exchange identified in a small molecule screen increase airway surface liquid volume in cystic fibrosis.

    PubMed

    Haggie, Peter M; Phuan, Puay-Wah; Tan, Joseph-Anthony; Zlock, Lorna; Finkbeiner, Walter E; Verkman, A S

    2016-06-01

    Pendrin (SLC26A4) is a Cl(-)/anion exchanger expressed in the epithelium of inflamed airways where it is thought to facilitate Cl(-) absorption and HCO3 (-) secretion. Studies using pendrin knockout mice and airway epithelial cells from hearing-impaired subjects with pendrin loss of function suggest involvement of pendrin in inflammatory lung diseases, including cystic fibrosis (CF), perhaps by regulation of airway surface liquid (ASL) volume. Here we identified small-molecule pendrin inhibitors and demonstrated their efficacy in increasing ASL volume. A cell-based, functional high-throughput screen of ∼36,000 synthetic small molecules produced 3 chemical classes of inhibitors of human pendrin. After structure-activity studies, tetrahydropyrazolopyridine and pyrazolothiophenesulfonamide compounds reversibly inhibited pendrin-facilitated Cl(-) exchange with SCN(-), I(-), NO3 (-), and HCO3 (-) with drug concentration causing 50% inhibition down to ∼2.5 μM. In well-differentiated primary cultures of human airway epithelial cells from non-CF and CF subjects, treatment with IL-13, which causes inflammation with strong pendrin up-regulation, strongly increased Cl(-)/HCO3 (-) exchange and the increase was blocked by pendrin inhibition. Pendrin inhibition significantly increased ASL depth (by ∼8 μm) in IL-13-treated non-CF and CF cells but not in untreated cells. These studies implicate the involvement of pendrin-facilitated Cl(-)/HCO3 (-) in the regulation of ASL volume and suggest the utility of pendrin inhibitors in inflammatory lung diseases, including CF.-Haggie, P. M., Phuan, P.-W., Tan, J.-A., Zlock, L., Finkbeiner, W. E., Verkman, A. S. Inhibitors of pendrin anion exchange identified in a small molecule screen increase airway surface liquid volume in cystic fibrosis. PMID:26932931

  15. Determination of propofol glucuronide from hair sample by using mixed mode anion exchange cartridge and liquid chromatography tandem mass spectrometry.

    PubMed

    Kwak, Jae-Hwan; Kim, Hye Kyung; Choe, Sanggil; In, Sangwhan; Pyo, Jae Sung

    2016-03-15

    The main objective of this study was to develop and validate a simpler and less time consuming analytical method for determination of propofol glucuronide from hair sample, by using mixed mode anion exchange cartridge and liquid chromatography-tandem mass spectrometry (LC-MS/MS). The study uses propofol glucuronide, a major metabolite of propofol, as a marker for propofol abuse. The hair sample was digested in sodium hydroxide solution and loaded in mixed-mode anion cartridge for solid phase extraction. Water and ethyl acetate were used as washing solvents to remove interfering substances from the hair sample. Consequently, 2% formic acid in ethyl acetate was employed to elute propofol glucuronide from the sorbent of mixed-mode anion cartridge, and analyzed by LC-MS/MS. The method validation parameters such as selectivity, specificity, LOD, LLOQ, accuracy, precision, recovery, and matrix effect were also tested. The linearity of calibration curves showed good correlation, with correlation coefficient 0.998. The LOD and LLOQ of the propofol glucuronide were 0.2 pg/mg and 0.5 pg/mg, respectively. The intra and inter-day precision and accuracy were acceptable within 15%. The mean values of recovery and matrix effect were in the range of 91.7-98.7% and 87.5-90.3%, respectively, signifying that the sample preparation, washing and extraction procedure were efficient, and there was low significant hair matrix effect for the extraction of propofol glucuronide from hair sample on the mixed mode anion cartridge. To evaluate the suitability of method, the hair of propofol administered rat was successfully analyzed with this method. PMID:26946424

  16. Anion-exchange resin-based desulfurization process. Quarterly technical progress report, October 1, 1992--December 31, 1992

    SciTech Connect

    Sheth, A.C.; Dharmapurikar, R.

    1992-12-31

    Under DOE Grant No. DE-FG22-90PC90309, the University of Tennessee Space Institute (UTSI) is contracted to further develop its anion-exchange, resin-based desulfurization concept to desulfurize alkali metal sulfates. From environmental as well as economic viewpoints, it is necessary to remove soluble sulfates from the wastes created by flue gas desulfurization systems. In order to do this economically, a low-cost desulfurization process for spent sorbents is necessary. UTSI`s anion-exchange resin-based desulfurization concept is believed to satisfy these requirements. During the reporting period, October 1, 1992--December 31, 1992, UTSI has completed the batch mode experiments to evaluate the performance enhancement effect caused by organic acids on the resin`s exhaustion efficiency. At present, batch mode experiments are being conducted to locate the position of the CO{sub 3}= and SO{sub 4}= ions in the affinity chart, and also reviewing/assessing the ASPEN Code`s capabilities for use in the development of the Best Process Schematic and related economics.

  17. Boric acid increases the expression levels of human anion exchanger genes SLC4A2 and SLC4A3.

    PubMed

    Akbas, F; Aydin, Z

    2012-01-01

    Boron is an important micronutrient in plants and animals. The role of boron in living systems includes coordinated regulation of gene expression, growth and proliferation of higher plants and animals. There are several well-defined genes associated with boron transportation and tolerance in plants and these genes show close homology with human anion exchanger genes. Mutation of these genes also characterizes some genetic disorders. We investigated the toxic effects of boric acid on HEK293 cells and mRNA expression of anion exchanger (SLC4A1, SLC4A2 and SLC4A3) genes. Cytotoxicity of boric acid at different concentrations was tested by using the methylthiazolyldiphenyl-tetrazolium bromide assay. Gene expression profiles were examined using quantitative real-time PCR. In the HEK293 cells, the nontoxic upper concentration of boric acid was 250 μM; more than 500 μM caused cytotoxicity. The 250 μM boric acid concentration increased gene expression level of SLC4A2 up to 8.6-fold and SLC4A3 up to 2.6-fold, after 36-h incubation. There was no significant effect of boric acid on SLC4A1 mRNA expression levels. PMID:22576912

  18. Direct determination of seleno-amino acids in biological tissues by anion-exchange separation and electrochemical detection.

    PubMed

    Cavalli, S; Cardellicchio, N

    1995-07-01

    Several studies have described the determination of selenium in protein extracts from tissues of marine or terrestrial animals, but have not identified the different chemical forms of selenium that are present. Selenium may be present as seleno-amino acids. Selenocysteine, for example, is a normal component of glutathione peroxidase, an antioxidant enzyme which may behave like other antioxidants, such as vitamin E, protecting tissues against methylmercury toxicity. The present study illustrates a method for the characterization of seleno-amino acids, such as selenocysteine and selenomethionine, in proteins extracted from the liver of marine mammals. The mechanism of detoxification of methylmercury, which involves seleno-compounds, is identified. The analytical determination was carried out using high-performance anion-exchange chromatography coupled with integrated pulsed amperometric detection (HPAEC-IPAD). This method allows the direct determination of underivatized amino acids, eliminating the procedure of pre- or postcolumn derivatization. The chromatographic separation was carried out on an anion-exchange column using a quaternary gradient elution. In order to optimize this method, interferences of amino acids and the influence of pH and ionic strength on the separation and electrochemical detection were studied. The IPAD response for the direct detection of amino acids is optimum at pH > 11. The detection limit (S/N = 3) for selenocysteine was found to be 450 micrograms/l. The application of this method for the identification of seleno-amino acids in protein hydrolysates is also shown. PMID:7640774

  19. Wheat gluten amino acid composition analysis by high-performance anion-exchange chromatography with integrated pulsed amperometric detection.

    PubMed

    Rombouts, Ine; Lamberts, Lieve; Celus, Inge; Lagrain, Bert; Brijs, Kristof; Delcour, Jan A

    2009-07-17

    A simple accurate method for determining amino acid composition of wheat gluten proteins and their gliadin and glutenin fractions using high-performance anion-exchange chromatography with integrated pulsed amperometric detection is described. In contrast to most conventional methods, the analysis requires neither pre- or post-column derivatization, nor oxidation of the sample. It consists of hydrolysis (6.0M hydrochloric acid solution at 110 degrees C for 24h), evaporation of hydrolyzates (110 degrees C), and chromatographic separation of the liberated amino acids. Correction factors (f) accounted for incomplete cleavage of peptide bonds involving Val (f=1.07) and Ile (f=1.13) after hydrolysis for 24h and for Ser (f=1.32) losses during evaporation. Gradient conditions including an extra eluent (0.1M acetic acid solution) allowed multiple sequential sample analyses without risk of Glu contamination on the anion-exchange column. While gluten amino acid compositions by the present method were mostly comparable to those obtained by a conventional method involving oxidation, acid hydrolysis and post-column ninhydrin derivatization, the latter method underestimated Tyr, Val and Ile levels. Results for the other amino acids obtained by the different methods were linearly correlated (r>0.99, slope=1.03). PMID:19523641

  20. Stable and selective scintillating anion-exchange sensors for quantification of 99TcO4- in natural freshwaters.

    PubMed

    Seliman, Ayman F; Helariutta, Kerttuli; Wiktorowicz, Szymon J; Tenhu, Heikki; Harjula, Risto

    2013-12-01

    New dual functionality scintillating anion-exchange resins were developed for selective determination of (99)TcO4(-) in various natural freshwater samples. Stable scintillating particles were formed by preparing the vinyl monomer 2-[4-(4'-vinylbiphenylyl)]-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (vPBD), starting with the commercial organic flour TBut-PBD and its subsequent copolymerization with styrene, divinylbenzene, and p-chloromethylstyrene mixture. To integrate the radiochemical separation and radiometric detection steps within the same bead, the chloromethyl groups of the scintillating resins were subjected to amination reactions with dioctylamine (DOA) and trioctylamine (TOA). On-line quantification of (99)TcO4(-) was achieved by packing the scintillating anion-exchange resin into Teflon tubing for quantification by a flow scintillation analyzer (FSA). The two functionalized resins were selective for pertechnetate over the common anions in natural freshwaters, especially Cl(-) and SO4(2-) with up to 1000 ppm and with up to 10 ppm I(-) and Cr2O7(2-). The uptake efficiency of the TOA sensor decreased from 97.88% to 85.08% in well water and river water, respectively, while the counting efficiency was almost constant (69.50%). The DOA performance showed lower efficiency in the two water types relative to TOA. On the other hand, the DOA sensor could be regenerated by 5 M HNO3 for reuse at least four times without losing its chemical or optical performance. The detection limit was 1.45 Bq which could be achieved by loading 45 mL from well and tap water containing the maximum contaminant level (MCL) of (99)Tc (33 Bq/L). PMID:24012764

  1. Linking stomatal traits and expression of slow anion channel genes HvSLAH1 and HvSLAC1 with grain yield for increasing salinity tolerance in barley

    PubMed Central

    Liu, Xiaohui; Mak, Michelle; Babla, Mohammad; Wang, Feifei; Chen, Guang; Veljanoski, Filip; Wang, Gang; Shabala, Sergey; Zhou, Meixue; Chen, Zhong-Hua

    2014-01-01

    Soil salinity is an environmental and agricultural problem in many parts of the world. One of the keys to breeding barley for adaptation to salinity lies in a better understanding of the genetic control of stomatal regulation. We have employed a range of physiological (stomata assay, gas exchange, phylogenetic analysis, QTL analysis), and molecular techniques (RT-PCR and qPCR) to investigate stomatal behavior and genotypic variation in barley cultivars and a genetic population in four experimental trials. A set of relatively efficient and reliable methods were developed for the characterization of stomatal behavior of a large number of varieties and genetic lines. Furthermore, we found a large genetic variation of gas exchange and stomatal traits in barley in response to salinity stress. Salt-tolerant cultivar CM72 showed significantly larger stomatal aperture under 200 mM NaCl treatment than that of salt-sensitive cultivar Gairdner. Stomatal traits such as aperture width/length were found to significantly correlate with grain yield under salt treatment. Phenotypic characterization and QTL analysis of a segregating double haploid population of the CM72/Gairdner resulted in the identification of significant stomatal traits-related QTLs for salt tolerance. Moreover, expression analysis of the slow anion channel genes HvSLAH1 and HvSLAC1 demonstrated that their up-regulation is linked to higher barley grain yield in the field. PMID:25505473

  2. Triple-channel portable capillary electrophoresis instrument with individual background electrolytes for the concurrent separations of anionic and cationic species.

    PubMed

    Mai, Thanh Duc; Le, Minh Duc; Sáiz, Jorge; Duong, Hong Anh; Koenka, Israel Joel; Pham, Hung Viet; Hauser, Peter C

    2016-03-10

    The portable capillary electrophoresis instrument is automated and features three independent channels with different background electrolytes to allow the concurrent optimized determination of three different categories of charged analytes. The fluidic system is based on a miniature manifold which is based on mechanically milled channels for injection of samples and buffers. The planar manifold pattern was designed to minimize the number of electronic valves required for each channel. The system utilizes pneumatic pressurization to transport solutions at the grounded as well as the high voltage side of the separation capillaries. The instrument has a compact design, with all components arranged in a briefcase with dimensions of 45 (w) × 35 (d) × 15 cm (h) and a weight of about 15 kg. It can operate continuously for 8 h in the battery-powered mode if only one electrophoresis channel is in use, or for about 2.5 h in the case of simultaneous employment of all three channels. The different operations, i.e. capillary flushing, rinsing of the interfaces at both capillary ends, sample injection and electrophoretic separation, are activated automatically with a control program featuring a graphical user interface. For demonstration, the system was employed successfully for the concurrent separation of different inorganic cations and anions, organic preservatives, additives and artificial sweeteners in various beverage and food matrices. PMID:26893094

  3. Effect of Temperature on Nanophase-segregation and Transport in Polysulfone-Based Anion Exchange Membrane Fuel Cell: Molecular Dynamics Simulation Approach

    NASA Astrophysics Data System (ADS)

    Ko, Kwan; Han, Kyung; Choi, Ji; Chang, Ying; Bae, Chulsung; Jang, Seung; Georgia Tech Team; RPI Team

    2013-03-01

    The effect of temperature on hydrated polysulfone-based anion exchange membrane is studied using molecular dynamics. Various temperature conditions such as 313K, 353 K and 393K with two different water contents (10 wt % and 20 wt %) are simulated. From the viewpoint of structure-property relationship, we scrutinize the change in the nanophase-segregated structure of membrane and transport of anionic charge carrier (hydroxide) as a function of temperature. Since it is well known that the anion transport is less than the proton transport, we attempt to pursue a fundamental understanding of the difference between anion transport and proton transport. For this purpose, we simulate the polysulfone-based proton exchange membrane that has the same molecular structure and molecular weight. By analyzing the pair-correlation of charge carriers, we observe the correlation among hydroxides is much stronger than that among hydroniums. The extent of nanophase-segregation is also analyzed using structure factor profile.

  4. Ion-exchange chromatographic separation of anions on hydrated bismuth oxide impregnated papers

    SciTech Connect

    Dabral, S.K.; Muktawat, K.P.S.; Rawat, J.P.

    1988-04-01

    A comparative study of the chromatographic behavior of anions, iodide, sulfide, phosphate, arsenate, arsenite, vanadate, chromate, dichromate, thiosulfate, thiocyanate, ferricyanide and ferrocyanide on papers impregnated with hydrated bismuth oxide and untreated Whatman no.1 paper has been made by employing identical aqueous, non-aqueous and mixed solvent system. Sharp and compact spots were obtained with impregnated papers whereas the opposite applied to plain papers. Various analytically important binary and ternary separations are reported.

  5. Studies of removal of palladium(II) ions from chloride solutions on weakly and strongly basic anion exchangers.

    PubMed

    Hubicki, Z; Wołowicz, A; Leszczyńska, M

    2008-11-30

    Palladium and its compounds find wide application in industry as a catalytic agent in different manufacture processes. Recovery of precious metals from industrial wastes is difficult and time consuming but in spite of these disadvantages it becomes profitable. Palladium(II) ions sorption from various chloride solutions of the composition: 0.1-6.0M HCl-0.00056 M Pd(II), 1.0M ZnCl(2)-0.1M HCl-0.00056 M Pd(II), 1.0M AlCl(3)-0.1M HCl-0.00056 M Pd(II) on the weakly and strongly basic anion exchangers (Varion ATM, Varion ADM and Varion ADAM) was discussed. The sorption research of Pd(II) ions on these resins was carried out by means of static and dynamic methods. The dynamic processes were applied in order to determine the breakthrough curves of Pd(II) ions. Moreover, the working ion-exchange capacities as well as the weight and bed distribution coefficients were determined from the Pd(II) breakthrough curves. The recovery factors of Pd(II) ions (% R) depending on the phase contact time were obtained by means of static methods. The highest ion-exchange capacities for the 0.1-6.0M HCl-0.00056 M Pd(II) systems were obtained for the weakly basic ion-exchange resin Varion ADAM. PMID:18358602

  6. Do TFSA anions slither? Pressure exposes the role of TFSA conformational exchange in self-diffusion

    SciTech Connect

    Suarez, Sophia N.; Wishart, James F.; Rua, Armando; Cuffari, David; Pilar, Kartik; Hatcher, Jasmine L.; Ramati, Sharon

    2015-10-28

    Multi-nuclear (1H, 2H, and 19F) magnetic resonance spectroscopy techniques as functions of temperature and pressure were applied to the study of selectively deuterated 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide (EMIM TFSA) ionic liquid isotopologues and related ionic liquids. For EMIM TFSA, temperature-dependent 2H T1 data indicate stronger electric field gradients in the alkyl chain region compared to the imidazolium ring. Most significantly, the pressure dependences of the EMIM and TFSA self-diffusion coefficients revealed that the displacements of the cations and anions are independent, with diffusion of the TFSA anions being slowed much more by increasing pressure than for the EMIM cations, as shown by their respective activation volumes (28.8 ± 2.5 cm³/mol for TFSA vs. 14.6 ± 1.3 cm³/mol for EMIM). Increasing pressure may lower the mobility of the TFSA anion by hindering its interconversion between trans and cis conformers, a process that is coupled to diffusion according to published molecular dynamics simulations. Measured activation volumes (ΔV) for ion self-diffusion in EMIM bis(fluoromethylsulfonyl)amide and EMIM tetrafluoroborate support this hypothesis.

  7. Do TFSA anions slither? Pressure exposes the role of TFSA conformational exchange in self-diffusion

    DOE PAGESBeta

    Suarez, Sophia N.; Wishart, James F.; Rua, Armando; Cuffari, David; Pilar, Kartik; Hatcher, Jasmine L.; Ramati, Sharon

    2015-10-28

    Multi-nuclear (1H, 2H, and 19F) magnetic resonance spectroscopy techniques as functions of temperature and pressure were applied to the study of selectively deuterated 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide (EMIM TFSA) ionic liquid isotopologues and related ionic liquids. For EMIM TFSA, temperature-dependent 2H T1 data indicate stronger electric field gradients in the alkyl chain region compared to the imidazolium ring. Most significantly, the pressure dependences of the EMIM and TFSA self-diffusion coefficients revealed that the displacements of the cations and anions are independent, with diffusion of the TFSA anions being slowed much more by increasing pressure than for the EMIM cations, as shown bymore » their respective activation volumes (28.8 ± 2.5 cm³/mol for TFSA vs. 14.6 ± 1.3 cm³/mol for EMIM). Increasing pressure may lower the mobility of the TFSA anion by hindering its interconversion between trans and cis conformers, a process that is coupled to diffusion according to published molecular dynamics simulations. Measured activation volumes (ΔV‡) for ion self-diffusion in EMIM bis(fluoromethylsulfonyl)amide and EMIM tetrafluoroborate support this hypothesis.« less

  8. Preparation of high-capacity, weak anion-exchange membranes by surface-initiated atom transfer radical polymerization of poly(glycidyl methacrylate) and subsequent derivatization with diethylamine

    NASA Astrophysics Data System (ADS)

    Qian, Xiaolei; Fan, Hua; Wang, Chaozhan; Wei, Yinmao

    2013-04-01

    Ion-exchange membrane is of importance for the development of membrane chromatography. In this work, a high-capacity anion-exchange membrane was prepared by grafting of glycidyl methacrylate (GMA) onto the surface of regenerated cellulose (RC) membranes via surface-initiated atom transfer radical polymerization (SI-ATRP) and subsequent derivatization with diethylamine. Attenuated total reflectance Fourier-transform infrared (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used to characterize changes in the chemical functionality, surface topography and pore morphology of the modified membranes. The static capacity of the prepared anion-exchange membrane was evaluated with bovine serum albumin (BSA) as a model protein. The results indicated that the anion-exchange membrane which could reach a maximum capacity of 96 mg/mL for static adsorption possesses a higher adsorption capacity, and the adsorption capacity increases with the polymerization time. The effect of pH and salt concentration confirmed that the adsorption of BSA followed ion-exchange mechanism. The established method would have potential application in the preparation of anion-exchange membrane.

  9. Effect of long-term organic removal on ion exchange properties and performance during sewage tertiary treatment by conventional anion exchange resins.

    PubMed

    Sun, Jian; Li, Xiaofeng; Quan, Ying; Yin, Yunjun; Zheng, Shaokui

    2015-10-01

    This study evaluated the long-term dissolved organic matter (DOM), phosphorus and nitrogen removal performance of a commercially available conventional anion exchange resin (AER) from actual secondary effluent (SE) in a sewage treatment plant based on a pilot-scale operation (2.2 m(3) d(-1), 185 cycles, 37,000 bed volume, 1.5 years). Particular emphasis was given to the potential effect of DOM fouling on the ion exchange properties and performance during the long-term operation. Despite the large range of COD (15.6-33.5 mg L(-1)), BOD5 (3.0-5.6 mg L(-1)), DOC (6.5-24.2 mg L(-1)), and UV254 (UV absorption at 254 nm) (0.108-0.229 cm(-1)) levels in the SE, the removal efficiencies of the AER for the aforementioned parameters were 43±12%, 46±15%, 45±9%, and 72±4%, respectively. Based on three-dimensional fluorescence excitation-emission matrix data, i.e., the fluorescence intensities of four regions (peaks A-D), all organic components of the SE were effectively removed (peak A 74%, peak B 48%, peak C 55%, and peak D 45%) following the adsorption. The AER effluent still has considerable polycyclic aromatic hydrocarbons' ecological hazard on freshwater fishes when they were significantly removed from SE. The obvious DOM fouling on the AER, identified by color change, had no significant influence on the long-term removal of the representative inorganic anions (averaging 95±4% phosphate, 100±0% SO4(2-), and 62±17% NO3(-)) and AER properties (including total exchange capacity, moisture content, and true density). The conventional AER can produce high quality reclaimed water from SE at a low operational cost. PMID:25996990

  10. Purification and neutron emission reduction of 238Plutonium oxide by nitrate anion exchange processing

    NASA Astrophysics Data System (ADS)

    Pansoy-Hjelvik, M. E.; Brock, J.; Nixon, J. Z.; Moniz, P.; Silver, G.; Ramsey, K. B.

    2001-02-01

    The use of ion exchange during the aqueous purification of 238Pu oxide results in low levels of uranium, thorium, and americium in the product oxide. Neutron emission rates are also reduced in the product oxide. Fluorine introduced during the dissolution of impure fuel increases the neutron emission rate of the product oxide due to the 238Pu-19F alpha/n reaction. Treating the 238Pu solution with aluminum nitrate prior to ion exchange reduces the neutron emission rate in the product oxide. Data are presented to show that neutron emission rates and concentrations of uranium, thorium, and americium are reduced by ion exchange processing. .

  11. Do TFSA Anions Slither? Pressure Exposes the Role of TFSA Conformational Exchange in Self-Diffusion.

    PubMed

    Suarez, Sophia N; Rúa, Armando; Cuffari, David; Pilar, Kartik; Hatcher, Jasmine L; Ramati, Sharon; Wishart, James F

    2015-11-19

    Multinuclear ((1)H, (2)H, and (19)F) magnetic resonance spectroscopy techniques as functions of temperature and pressure were applied to the study of selectively deuterated 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide (EMIM TFSA) ionic liquid isotopologues and related ionic liquids. For EMIM TFSA, temperature-dependent (2)H T1 data indicate stronger electric field gradients in the alkyl chain region compared to the imidazolium ring. Most significantly, the pressure dependences of the EMIM and TFSA self-diffusion coefficients revealed that the displacements of the cations and anions are independent, with diffusion of the TFSA anions being slowed much more by increasing pressure than for the EMIM cations, as shown by their respective activation volumes (28.8 ± 2.5 cm(3)/mol for TFSA vs 14.6 ± 1.3 cm(3)/mol for EMIM). Increasing pressure may lower the mobility of the TFSA anion by hindering its interconversion between trans and cis conformers, a process that is coupled to diffusion according to published molecular dynamics simulations. Measured activation volumes (ΔV(‡)) for ion self-diffusion in EMIM bis(fluoromethylsulfonyl)amide and EMIM tetrafluoroborate support this hypothesis. In addition, (2)H T1 data suggest increased ordering with increasing pressure, with two T1 regimes observed for the MD3 and D2 isotopologues between 0.1-100 and 100-250 MPa, respectively. The activation volumes for T1 were 21 and 25 cm(3)/mol (0-100 MPa) and 11 and 12 cm(3)/mol (100-250 MPa) for the MD3 and D2 isotopologues, respectively. PMID:26509865

  12. Competition between abstraction and exchange channels in H + HCN reaction: Full-dimensional quantum dynamics

    SciTech Connect

    Jiang, Bin; Guo, Hua

    2013-12-14

    Dynamics of the title reaction is investigated on an ab initio based potential energy surface using a full-dimensional quantum wave packet method within the centrifugal sudden approximation. It is shown that the reaction between H and HCN leads to both the hydrogen exchange and hydrogen abstraction channels. The exchange channel has a lower threshold and larger cross section than the abstraction channel. It also has more oscillations due apparently to quantum resonances. Both channels are affected by long-lived resonances supported by potential wells. Comparison with experimental cross sections indicates underestimation of the abstraction barrier height.

  13. Ion Mobility Spectrometry-Hydrogen Deuterium Exchange Mass Spectrometry of Anions: Part 1. Peptides to Proteins

    NASA Astrophysics Data System (ADS)

    Donohoe, Gregory C.; Khakinejad, Mahdiar; Valentine, Stephen J.

    2015-04-01

    Ion mobility spectrometry (IMS) coupled with hydrogen deuterium exchange (HDX)-mass spectrometry (MS) has been used to study the conformations of negatively-charged peptide and protein ions. Results are presented for ion conformers of angiotensin 1, a synthetic peptide (SP), bovine insulin, ubiquitin, and equine cytochrome c. In general, the SP ion conformers demonstrate a greater level of HDX efficiency as a greater proportion of the sites undergo HDX. Additionally, these ions exhibit the fastest rates of exchange. Comparatively, the angiotensin 1 ions exhibit a lower rate of exchange and HDX level presumably because of decreased accessibility of exchange sites by charge sites. The latter are likely confined to the peptide termini. Insulin ions show dramatically reduced HDX levels and exchange rates, which can be attributed to decreased conformational flexibility resulting from the disulfide bonds. For the larger ubiquitin and protein ions, increased HDX is observed for larger ions of higher charge state. For ubiquitin, a conformational transition from compact to more elongated species (from lower to higher charge states) is reflected by an increase in HDX levels. These results can be explained by a combination of interior site protection by compact conformers as well as decreased access by charge sites. The elongated cytochrome c ions provide the largest HDX levels where higher values correlate with charge state. These results are consistent with increased exchange site accessibility by additional charge sites. The data from these enhanced IMS-HDX experiments are described in terms of charge site location, conformer rigidity, and interior site protection.

  14. Fluorene-based Cu(II)-MOF: a visual colorimetric anion sensor and separator based on an anion-exchange approach.

    PubMed

    Ma, Jian-Ping; Yu, Yang; Dong, Yu-Bin

    2012-03-21

    A new 2D Cu(II)-MOF generated from a fluorene-based ligand and Cu(NO(3))(2) was reported. It is an interesting visual colorimetric anion sensor. In addition, it can completely separate Cl(-)/Br(-), Br(-)/I(-) and SCN(-)/N(3)(-) anions under ambient conditions. PMID:22189967

  15. The Role of Anion Exchanger on Pulmonary Vascular Response to Sustained Alveolar Hypoxia in the Isolated Perfused Rabbit Lung

    PubMed Central

    Ketabchi, Farzaneh; Mansoori, Somayeh; Moosavi, Seyed Mostafa Shid

    2015-01-01

    Background Some respiratory diseases may induce alveolar hypoxia thereby hypoxic pulmonary vasoconstriction (HPV). However, the mechanisms of this physiologic phenomenon are not fully understood. This study was the first to investigate the role of anion exchanger in sustained HPV. Methods Experiments were performed in the isolated perfused rabbit lung. After preparation, the lungs were divided into six groups: two DIDS (4,4-diisothiocyanostilbene 2,2-disulfonic acid, anion exchanger inhibitor)-treated [200 µM (n=5) or 400 µM (n=3)] hypoxic groups, two HCO3- free hypoxic groups, one control hypoxic group (n=7) and one control normoxic group (n=4). DIDS were added to the perfusate at 10 minutes before starting the experiments. In the HCO3- free groups, HEPES (4-(2-Hydroxyethyl)piperazine-1-ethanesulfonic acid) were added to the perfusate instead of bicarbonate. Furthermore, in the HEPES1 (n=4) and HEPES2 (n=4) groups, the lungs were ventilated with hypoxic gas with or without CO2, respectively. Results Ventilation of the lungs with hypoxic gas resulted in biphasic HPV, the acute (0-20 minutes) and sustained (20-60 minutes) phases. No alteration in both phases of HPV was detected by DIDS (200 µM). However, DIDS (400 µM), extended the ascending part of acute HPV until min 24. Both phases of HPV were decreased in the HEPES1 group. However, in the HEPES 2 group, HPV tended to increase during the rising part of the acute phase of HPV. Conclusions Since DIDS (400 µM) extended acute phase of HPV, and HCO3- free perfusate buffer enhanced rising phase of it, therefore it can be suggested that anion exchanger may modulate HPV especially during the acute phase. The abstract of this article was presented as a poster in the congress of European Respiratory Society (ERS) on Monday, 08 September 2014, Munich, Germany and was published in the ERJ September 1, 2014 vol. 44 no. Suppl 58 P2343. PMID:25999626

  16. Sulfate secretion and chloride absorption are mediated by the anion exchanger DRA (Slc26a3) in the mouse cecum.

    PubMed

    Whittamore, Jonathan M; Freel, Robert W; Hatch, Marguerite

    2013-07-15

    Inorganic sulfate (SO₄²⁻) is essential for a multitude of physiological processes. The specific molecular pathway has been identified for uptake from the small intestine but is virtually unknown for the large bowel, although there is evidence for absorption involving Na⁺-independent anion exchange. A leading candidate is the apical chloride/bicarbonate (Cl⁻/HCO₃⁻) exchanger DRA (down-regulated in adenoma; Slc26a3), primarily linked to the Cl⁻ transporting defect in congenital chloride diarrhea. The present study set out to characterize transepithelial ³⁵SO₄²⁻ and ³⁶Cl⁻ fluxes across the isolated, short-circuited cecum from wild-type (WT) and knockout (KO) mice and subsequently to define the contribution of DRA. The cecum demonstrated simultaneous net SO₄²⁻ secretion (-8.39 ± 0.88 nmol·cm⁻²·h⁻¹) and Cl⁻ absorption (10.85 ± 1.41 μmol·cm⁻²·h⁻¹). In DRA-KO mice, SO₄²⁻ secretion was reversed to net absorption via a 60% reduction in serosal to mucosal SO₄²⁻ flux. Similarly, net Cl⁻ absorption was abolished and replaced by secretion, indicating that DRA represents a major pathway for transcellular SO₄²⁻ secretion and Cl⁻ absorption. Further experiments including the application of DIDS (500 μM), bumetanide (100 μM), and substitutions of extracellular Cl⁻ or HCO₃⁻/CO₂ helped to identify specific ion dependencies and driving forces and suggested that additional anion exchangers were operating at both apical and basolateral membranes supporting SO₄²⁻ transport. In conclusion, DRA contributes to SO₄²⁻ secretion via DIDS-sensitive HCO₃⁻/SO₄²⁻ exchange, in addition to being the principal DIDS-resistant Cl⁻/HCO₃⁻ exchanger. With DRA linked to the pathogenesis of other gastrointestinal diseases extending its functional characterization offers a more complete picture of its role in the intestine. PMID:23660504

  17. Tubulin tail sequences and post-translational modifications regulate closure of mitochondrial voltage-dependent anion channel (VDAC).

    PubMed

    Sheldon, Kely L; Gurnev, Philip A; Bezrukov, Sergey M; Sackett, Dan L

    2015-10-30

    It was previously shown that tubulin dimer interaction with the mitochondrial outer membrane protein voltage-dependent anion channel (VDAC) blocks traffic through the channel and reduces oxidative metabolism and that this requires the unstructured anionic C-terminal tail peptides found on both α- and β-tubulin subunits. It was unclear whether the α- and β-tubulin tails contribute equally to VDAC blockade and what effects might be due to sequence variations in these tail peptides or to tubulin post-translational modifications, which mostly occur on the tails. The nature of the contribution of the tubulin body beyond acting as an anchor for the tails had not been clarified either. Here we present peptide-protein chimeras to address these questions. These constructs allow us to easily combine a tail peptide with different proteins or combine different tail peptides with a particular protein. The results show that a single tail grafted to an inert protein is sufficient to produce channel closure similar to that observed with tubulin. We show that the β-tail is more than an order of magnitude more potent than the α-tail and that the lower α-tail activity is largely due to the presence of a terminal tyrosine. Detyrosination activates the α-tail, and activation is reversed by the removal of the glutamic acid penultimate to the tyrosine. Nitration of tyrosine reverses the tyrosine inhibition of binding and even induces prolonged VDAC closures. Our results demonstrate that small changes in sequence or post-translational modification of the unstructured tails of tubulin result in substantial changes in VDAC closure. PMID:26306046

  18. Removal of anionic dyes from aqueous solutions by an ion-exchanger based on pullulan microspheres.

    PubMed

    Constantin, Marieta; Asmarandei, Ionela; Harabagiu, Valeria; Ghimici, Luminita; Ascenzi, Paolo; Fundueanu, Gheorghe

    2013-01-01

    Pullulan-graft-poly(3-acrylamidopropyl trimethylammonium chloride) (P-g-pAPTAC) microspheres were prepared by suspension cross-linking of the pullulan previously grafted with cationic moieties. Adsorption of Azocarmine B by the P-g-pAPTAC microspheres was used as a model to demonstrate the removal of anionic dyes from aqueous solutions. Batch adsorption studies concerning the effect of the contact time, pH, initial dye concentration, temperature, grafting, and the nature of sulfonated anionic dyes on the adsorption kinetics were investigated. Adsorption was shown to be independent of pH. The experimental data best fitted to the pseudo-second order model which provided values of the rate constant k(2) of 1.4×10(-4) g mg(-1) min(-1) for 100 mg L(-1) solution and of 3.7×10(-4) g mg(-1) min(-1) for 500 mg L(-1) solution. From the Langmuir isotherm linear equation, the maximum adsorption capacity determined was 113.63 mg of Azocarmine B per gram of adsorbent; the negative value of the free energy change indicated the spontaneous nature of the adsorption process. PMID:23044107

  19. Synthesis and anion exchange properties of a Zn/Ni double hydroxide salt with a guarinoite structure

    NASA Astrophysics Data System (ADS)

    Delorme, F.; Seron, A.; Licheron, M.; Veron, E.; Giovannelli, F.; Beny, C.; Jean-Prost, V.; Martineau, D.

    2009-09-01

    In this study, the first route to synthesize a compound with the guarinoite structure (Zn,Co,Ni) 6(SO 4)(OH,Cl) 10·5H 2O is reported. Zn/Ni guarinoite is obtained from the reaction of NiSO 4·7H 2O with solid ZnO in aqueous solution. The resulting green Zn/Ni guarinoite ((Zn 3.52Ni 1.63)(SO 4) 1.33(OH 7.64)·4.67H 2O) was characterized by X-ray diffraction, infrared spectrometry, UV-Visible spectrometry and thermal analysis. It is shown that its structure is similar to the one described for the layered Zn sulfate hydroxide hydrate, i.e. brucite layers with {1}/{4} empty octahedra presenting tetrahedrally coordinated divalent atoms above and below the empty octahedra. Ni atoms are located in the octahedra and zinc atoms in tetrahedra and octahedra. In this structure the exchangeable anions are located at the apex of tetrahedra. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations show that the Zn/Ni guarinoite is composed of aggregates of hexagonal plates of several hundreds of nanometers. Due to its interest for industrial or environmental applications, the exchange of sulfate groups by carbonates has been investigated. Results show a limited exchange and a higher affinity of the Zn/Ni guarinoite for sulfates compared to carbonates.

  20. The transfer behavior of different ions across anion and cation exchange membranes under vanadium flow battery medium

    NASA Astrophysics Data System (ADS)

    Sun, Jiawei; Li, Xianfeng; Xi, Xiaoli; Lai, Qinzhi; Liu, Tao; Zhang, Huamin

    2014-12-01

    The transfer behavior of different ions (V2+, V3+, VO2+, VO2+, H+, SO42-) across ion exchange membranes is investigated under vanadium flow battery (VFB) operating condition. VX-20 anion exchange membrane (AEM) and Nafion 115 cation exchange membrane (CEM) are selected to investigate the influence of fixed charged groups on the transfer behavior of different ions. The interaction between different ions and water is discussed in detail aiming to ascertain the variation of different ions in the charge-discharge process. Under the VFB medium, the transfer behavior and function of different ions are very different for the AEM and CEM. V2+ ions at the negative side accumulate when VFB is assembled with Nafion 115, while the VO2+ ions at the positive side accumulate for VX-20. The SO42- ions will transfer across Nafion 115 to balance the charges and the protons can balance the charges of VX-20. Finally the capacity fade mechanism of different membranes is investigated, showing that the capacity decay of VFB assembled with Nafion 115 mainly results from the cross mix of vanadium ions across the membrane, however, for VX-20, the side reactions can be the major reason. This paper provides important information about electrolyte for the application of VFB.

  1. 1,2,3-Triazolium-Based Poly(2,6-Dimethyl Phenylene Oxide) Copolymers as Anion Exchange Membranes.

    PubMed

    Liu, Lei; He, Shuqing; Zhang, Shufang; Zhang, Min; Guiver, Michael D; Li, Nanwen

    2016-02-01

    Anion exchange membranes (AEMs) based on 1,2,3-triazolium (TAM) were prepared from commercial poly(2,6-dimethyl phenylene oxide) (PPO) via "click chemistry" and subsequent N-alkylation. Flexible and tough membranes with various ion exchange capacities (IECs) were obtained by casting the polymers from NMP solutions. Although the resulting TAM-functionalized PPOs (PPO-TAM) membranes exhibited incomplete ion exchange in 1 M NaOH or NaHCO3 for 24 h even at elevated temperature, the highest hydroxide conductivities of the membranes were above 20 mS/cm at room temperature, which is comparable to many reported AEMs. Alkaline stability tests indicate that the PPO-TAM membranes showed a better alkaline stability than that of membranes containing imidazolium groups in 1 M NaOH at 80 °C, but still require further improvements in long-term stability for alkaline fuel cell application. An investigation of alkaline stability of model compounds demonstrated the instability of TAM cations under alkaline conditions could contribute to the deprotonation of benzylic methylene, C4 and C5 position on the triazolium ring. These results suggests that the alkaline stability of 1,2,3-triazolium cation could be improved by the introduction of substituents at the C4, C5 positions and benzylic methylene, and also provide insight and directions for organic cation designs for AEM application by the facile synthetic strategy of "click chemistry". PMID:26820176

  2. The N-Terminal Peptides of the Three Human Isoforms of the Mitochondrial Voltage-Dependent Anion Channel Have Different Helical Propensities.

    PubMed

    Guardiani, Carlo; Scorciapino, Mariano Andrea; Amodeo, Giuseppe Federico; Grdadolnik, Joze; Pappalardo, Giuseppe; De Pinto, Vito; Ceccarelli, Matteo; Casu, Mariano

    2015-09-15

    The voltage-dependent anion channel (VDAC) is the main mitochondrial porin allowing the exchange of ions and metabolites between the cytosol and the mitochondrion. In addition, VDAC was found to actively interact with proteins playing a fundamental role in the regulation of apoptosis and being of central interest in cancer research. VDAC is a large transmembrane β-barrel channel, whose N-terminal helical fragment adheres to the channel interior, partially closing the pore. This fragment is considered to play a key role in protein stability and function as well as in the interaction with apoptosis-related proteins. Three VDAC isoforms are differently expressed in higher eukaryotes, for which distinct and complementary roles are proposed. In this work, the folding propensity of their N-terminal fragments has been compared. By using multiple spectroscopic techniques, and complementing the experimental results with theoretical computer-assisted approaches, we have characterized their conformational equilibrium. Significant differences were found in the intrinsic helical propensity of the three peptides, decreasing in the following order: hVDAC2 > hVDAC3 > hVDAC1. In light of the models proposed in the literature to explain voltage gating, selectivity, and permeability, as well as interactions with functionally related proteins, our results suggest that the different chemicophysical properties of the N-terminal domain are possibly correlated to different functions for the three isoforms. The overall emerging picture is that a similar transmembrane water accessible conduit has been equipped with not identical domains, whose differences can modulate the functional roles of the three VDAC isoforms. PMID:26303511

  3. Cloning and in situ localization of a brain-derived porin that constitutes a large-conductance anion channel in astrocytic plasma membranes.

    PubMed Central

    Dermietzel, R; Hwang, T K; Buettner, R; Hofer, A; Dotzler, E; Kremer, M; Deutzmann, R; Thinnes, F P; Fishman, G I; Spray, D C

    1994-01-01

    We have cloned a protein from bovine brain, brain-derived voltage-dependent anion channel 1 (BR1-VDAC), that is identical to a recently sequenced plasmalemmal-bound porin from human lymphocytes. mRNA hybridization indicates that BR1-VDAC is widely distributed throughout nervous and nonnervous tissues. In situ localization substantiated that the BR1-VDAC is associated with the plasmalemma of astrocytes. A monoclonal antibody that recognizes the N terminus of the BR1-VDAC protein completely blocks an astrocytic high-conductance anion channel that has electrophysiological similarities with the mitochondrial VDAC. Since the high-conductance anion channel in astrocytes has been shown to respond to hypoosmotic solutions, its molecular identification provides the basis for a better understanding of volume regulation in brain tissue. Images Fig. 1 Fig. 3 Fig. 4 PMID:7507248

  4. Results of mathematical modelling the kinetics of gaseous exchange through small channels in micro dischargers

    NASA Astrophysics Data System (ADS)

    Bushin, S. A.

    2016-07-01

    Results obtained using mathematical calculating models for physical processes of gaseous exchange through low-conductivity channels in the sealed envelopes of dischargers for various flow modes of indicative working gas are presented.

  5. A SIM-MOF: three-dimensional organisation of single-ion magnets with anion-exchange capabilities.

    PubMed

    Baldoví, José J; Coronado, Eugenio; Gaita-Ariño, Alejandro; Gamer, Christoph; Giménez-Marqués, Mónica; Mínguez Espallargas, Guillermo

    2014-08-18

    The formation of a metal-organic framework (MOF) with nodes that have single-molecule magnet (SMM) behaviour has been achieved by using mononuclear lanthanoid analogues, also known as single-ion magnets (SIMs), which enormously simplifies the challenging issue of making SMM-MOFs. Here we present a rational design of a family of MOFs, [Ln(bipyNO)4](TfO)3⋅x solvent (Ln=Tb (1); Dy (2); Ho (3); Er (4); TfO=triflate), in which the lanthanoid centres have an square-antiprismatic coordination environment suitable for SIM behaviour. Magnetic measurements confirm the existence of slow magnetic relaxation typical of SMMs, which has been rationalised by means of a radial effective charge model. In addition, we have explored the incorporation of bulky polyoxometalates (POMs) into the cavities of the SIM-MOF by anion exchange, finding that they do not interfere with the slow magnetic relaxation. This demonstrates the robustness of the frameworks and opens the possibility of incorporating non-innocent anions. PMID:24804629

  6. Removal of Cr(VI) and As(V) ions from aqueous solutions by polyacrylate and polystyrene anion exchange resins

    NASA Astrophysics Data System (ADS)

    Jachuła, Justyna; Hubicki, Zbigniew

    2013-09-01

    The sorption of Cr(VI) and As(V) from the aqueous solutions with the polyacrylate anion exchangers of the strong base functional groups Amberlite IRA 458 and Amberlite IRA 958 was studied. The studies were carried out by the static-batch method. The concentration of Cr(VI) and As(V) ions in the aqueous solution was determined by the UV-VIS spectrophotometer. The influence of several parameters was studied with respect to sorption equilibrium. The phase contact time and the concentration affect the sorption process. The equilibrium state was established already after 15 min of phase contact time. Maximum uptake of Cr(VI) and As(V) occurred at pH 5 and 10, respectively. The determined kinetic parameters imply that the sorption process proceeds according to the equation type of pseudo second-order. Sorption equilibrium data were correlated with the Langmuir and Freundlich isotherms. Removal of As(V) ions on macroporous Amberlite IRA 900 decreased about 12 % in presence of other anions (Cl-, NO3 -, SO4 2-) in the solution. The sorption was temperature dependent.

  7. Cell performance of Pd-Sn catalyst in passive direct methanol alkaline fuel cell using anion exchange membrane

    NASA Astrophysics Data System (ADS)

    Kim, Jandee; Momma, Toshiyuki; Osaka, Tetsuya

    Direct methanol alkaline fuel cell (DMAFC) using anion exchange membrane (AEM) was operated in passive condition. Cell with AEM exhibits a higher open circuit voltage (OCV) and superior cell performance than those in cell using Nafion. From the concentration dependences of methanol, KOH in fuel and ionomer in anode catalyst layer, it is found that the key factors are to improve the ionic conductivity at the anode and to form a favorable ion conductive path in catalyst layer in order to enhance the cell performance. In addition, by using home-made Pd-Sn/C catalyst as a cathode catalyst on DMAFC, the membrane electrode assembly (MEA) using Pd-Sn/C catalyst as cathode exhibits the higher performance than the usual commercially available Pt/C catalyst in high methanol concentration. Therefore, the Pd-Sn/C catalyst with high tolerance for methanol is expected as the promising oxygen reduction reaction (ORR) catalyst in DMAFC.

  8. Integrated pulsed amperometric detection of glufosinate, bialaphos and glyphosate at gold electrodes in anion-exchange chromatography.

    PubMed

    Sato, K; Jin, J Y; Takeuchi, T; Miwa, T; Suenami, K; Takekoshi, Y; Kanno, S

    2001-06-15

    A rapid and practical method for direct detection of the herbicides (glufosinate, bialaphos and glyphosate) in anion-exchange chromatography has been developed with integrated pulsed amperometric detection (IPAD). The electrochemical behavior of these herbicides showed catalytic currents based on the oxidation of amines in their structures. Waveform in IPAD was similar to that for amino acids, which exhibited adsorption/desorption catalytic features at gold electrode surface in alkaline solution. Under optimized conditions, detection limits (signal-to-noise ratio of 3) for glufosinate, bialaphos and glyphosate were 20, 65 and 50 ng ml(-1), respectively, with correlation coefficients of 0.995, 0.997 and 0.996 over concentration ranges of 0.1-45, 0.3-32 and 0.1-50 microg ml(-1), respectively. The relative standard deviations (n=5) were 1.7-3.0%. The present method was successfully applied to the determination of glyphosate in urine and serum. PMID:11442037

  9. Immobilized humic substances on an anion exchange resin and their role on the redox biotransformation of contaminants.

    PubMed

    Cervantes, Francisco J; Gonzalez-Estrella, Jorge; Márquez, Arturo; Alvarez, Luis H; Arriaga, Sonia

    2011-01-01

    A novel technique to immobilize humic substances (HS) on an anion exchange resin is presented. Immobilized HS were demonstrated as an effective solid-phase redox mediator (RM) during the reductive biotransformation of carbon tetrachloride (CT) and the azo model compound, Reactive Red 2 (RR2). Immobilized HS increased ∼4-fold the extent of CT reduction to chloroform by a humus-reducing consortium in comparison to incubations lacking HS. Immobilized HS also increased 2-fold the second-order rate constant of decolorization of RR2 as compared with sludge incubations lacking HS. To our knowledge, the present study constitutes the first demonstration of immobilized HS serving as an effective solid-phase RM during the reductive biotransformation of priority contaminants. The immobilizing technique developed could be appropriate for enhancing the redox biotransformation of recalcitrant pollutants in anaerobic wastewater treatment systems. PMID:20801024

  10. Preparation of pure, high titer, pseudoinfectious Flavivirus particles by hollow fiber tangential flow filtration and anion exchange chromatography.

    PubMed

    Mundle, Sophia T; Giel-Moloney, Maryann; Kleanthous, Harry; Pugachev, Konstantin V; Anderson, Stephen F

    2015-08-20

    Purification of enveloped viruses such as live flavivirus vaccine candidates poses a challenge as one must retain viral infectivity to preserve immunogenicity. Here we describe a laboratory-scale purification procedure for two replication defective (single-cycle) flavivirus variants for use in a pre-clinical setting. The two step purification scheme based on hollow fiber tangential flow filtration (TFF) followed by anion exchange chromatography using convective interaction media (CIM(®)) monoliths results in a ∼60% recovery of infectious virus titer and can be used to prepare nearly homogenous, highly purified vaccine viruses with titers as high as 1×10(9) focus forming units per mL. Flavivirus virions prepared by this method are 2 and 3 orders of magnitude more pure with respect to dsDNA and BHK host cell proteins, respectively, as compared to the raw feed stream. PMID:25498209

  11. High performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) for the sensitive determination of hyaluronan oligosaccharides.

    PubMed

    Rothenhöfer, Martin; Grundmann, Marco; Bernhardt, Günther; Matysik, Frank-Michael; Buschauer, Armin

    2015-04-15

    High performance anion exchange chromatography (HPAEC) with pulsed amperometric detection (PAD) was optimized for the analysis of oligosaccharides derived from the extracellular matrix component hyaluronan. Using this sensitive approach, the separation of oligosaccharides consisting of two (molecular weight ca. 0.8 kDa) up to 25-30 (molecular weight: ca. 9.5-11.4 kDa) disaccharide moieties was possible. Standard oligosaccharides (comprising 2-4 repetitive disaccharides) were detectable at very low amounts of 0.2-0.3 pmol (20-30 nM). Including 10 min of column equilibration, a complex mixture of low molecular weight hyaluronan can be analyzed within 40 min. The HPAEC method was successfully applied to the study of the size-dependency of both the action of bovine testicular hyaluronidase (BTH) and the precipitation of hyaluronan by cetyltrimethylammonium bromide (CTAB), a physicochemical reaction often used for the determination of hyaluronan and hyaluronidase activity. PMID:25768984

  12. Inactivation and Anion Selectivity of Volume-regulated Anion Channels (VRACs) Depend on C-terminal Residues of the First Extracellular Loop.

    PubMed

    Ullrich, Florian; Reincke, S Momsen; Voss, Felizia K; Stauber, Tobias; Jentsch, Thomas J

    2016-08-12

    Canonical volume-regulated anion channels (VRACs) are crucial for cell volume regulation and have many other important roles, including tumor drug resistance and release of neurotransmitters. Although VRAC-mediated swelling-activated chloride currents (ICl,vol) have been studied for decades, exploration of the structure-function relationship of VRAC has become possible only after the recent discovery that VRACs are formed by differently composed heteromers of LRRC8 proteins. Inactivation of ICl,vol at positive potentials, a typical hallmark of VRACs, strongly varies between native cell types. Exploiting the large differences in inactivation between different LRRC8 heteromers, we now used chimeras assembled from isoforms LRRC8C and LRRC8E to uncover a highly conserved extracellular region preceding the second LRRC8 transmembrane domain as a major determinant of ICl,vol inactivation. Point mutations identified two amino acids (Lys-98 and Asp-100 in LRRC8A and equivalent residues in LRRC8C and -E), which upon charge reversal strongly altered the kinetics and voltage dependence of inactivation. Importantly, charge reversal at the first position also reduced the iodide > chloride permeability of ICl,vol This change in selectivity was stronger when both the obligatory LRRC8A subunit and the other co-expressed isoform (LRR8C or -E) carried such mutations. Hence, the C-terminal part of the first extracellular loop not only determines VRAC inactivation but might also participate in forming its outer pore. Inactivation of VRACs may involve a closure of the extracellular mouth of the permeation pathway. PMID:27325695

  13. Analytical solution to the equations for parallel-flow four-channel heat exchangers

    SciTech Connect

    Malinowski, L.

    2000-04-01

    Assuming that the thermophysical parameters of the fluids are independent on temperature, the stationary temperature field in a parallel-flow multi-channel heat exchanger can be described by a set of linear differential equations of the first order with constant coefficients. A compact analytical solution to this set is presented for the case of four-channel exchangers and simple eigenvalues of the coefficient matrix of the set.

  14. Anion exchange membranes for electrochemical oxidation-reduction energy storage system

    NASA Technical Reports Server (NTRS)

    Odonnell, P. M.; Sheibley, D. W.; Gahn, R. F.

    1977-01-01

    Oxidation-reduction couples in concentrated solutions separated by appropriate ion selective membranes were considered as an attractive approach to bulk electrical energy storage. A key problem is the development of the membrane. Several promising types of anionic membranes are discussed which were developed and evaluated for redox energy storage systems. The copolymers of ethyleneglycoldimethacrylate with either 2-vinylpyridine or vinylbenzl chloride gave stable resistance values compared to the copolymer of vinylbenzlchloride and divinylbenzene which served as the baseline membrane. A polyvinylchloride film aminated with tetraethylenepentamine had a low resistance but a high ion transfer rate. A slurry coated vinylpyridine had the lowest ion transfer rate. All these membranes functioned well in laboratory cells at ambient temperatures with the acidic chloride oxidant/reductant system, Fe 3, Fe 2/Ti 3, Ti 4.

  15. Anion effects to deliver enhanced iridium catalysts for hydrogen isotope exchange processes.

    PubMed

    Kennedy, Alan R; Kerr, William J; Moir, Rory; Reid, Marc

    2014-10-28

    Synthesis of a series of iridium(I) complexes of the type [(COD)Ir(IMes)(PPh3)]X (X = BF4, OTf, and BArF) has been established. Application of these species in mild hydrogen isotope exchange processes revealed more efficient catalysis and, further, a wider solvent scope when employing larger, more weakly coordinating counterions. PMID:25208265

  16. Helicobacter pylori VacA Toxin/Subunit p34: Targeting of an Anion Channel to the Inner Mitochondrial Membrane

    PubMed Central

    Harsman, Anke; Papatheodorou, Panagiotis; Reljic, Boris; Dian-Lothrop, Elke A.; Galmiche, Antoine; Kepp, Oliver; Becker, Lars; Günnewig, Kathrin; Wagner, Richard; Rassow, Joachim

    2010-01-01

    The vacuolating toxin VacA, released by Helicobacter pylori, is an important virulence factor in the pathogenesis of gastritis and gastroduodenal ulcers. VacA contains two subunits: The p58 subunit mediates entry into target cells, and the p34 subunit mediates targeting to mitochondria and is essential for toxicity. In this study we found that targeting to mitochondria is dependent on a unique signal sequence of 32 uncharged amino acid residues at the p34 N-terminus. Mitochondrial import of p34 is mediated by the import receptor Tom20 and the import channel of the outer membrane TOM complex, leading to insertion of p34 into the mitochondrial inner membrane. p34 assembles in homo-hexamers of extraordinary high stability. CD spectra of the purified protein indicate a content of >40% β-strands, similar to pore-forming β-barrel proteins. p34 forms an anion channel with a conductivity of about 12 pS in 1.5 M KCl buffer. Oligomerization and channel formation are independent both of the 32 uncharged N-terminal residues and of the p58 subunit of the toxin. The conductivity is efficiently blocked by 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB), a reagent known to inhibit VacA-mediated apoptosis. We conclude that p34 essentially acts as a small pore-forming toxin, targeted to the mitochondrial inner membrane by a special hydrophobic N-terminal signal. PMID:20442789

  17. Synthesis, anion exchange, and delamination of Co-Al layered double hydroxide: assembly of the exfoliated nanosheet/polyanion composite films and magneto-optical studies.

    PubMed

    Liu, Zhaoping; Ma, Renzhi; Osada, Minoru; Iyi, Nobuo; Ebina, Yasuo; Takada, Kazunori; Sasaki, Takayoshi

    2006-04-12

    This paper describes a systematic study on the synthesis, anion exchange, and delamination of Co-Al layered double hydroxide (LDH), with the aim of achieving fabrication and clarifying the properties of LDH nanosheet/polyanion composite films. Co-Al-CO3 LDH hexagonal platelets of 4 mum in lateral size were synthesized by the urea method under optimized reaction conditions. The as-prepared CO3(2-)-LDH was converted to Cl- -LDH by treating with a NaCl-HCl mixed solution, retaining its high crystallinity and hexagonal platelike morphology. LDHs intercalated with a variety of anions (such as NO3-, ClO4-, acetate, lactate, dodecyl sulfate, and oleate) were further prepared from Cl- -LDH via an anion-exchange process employing corresponding salts. Exchanged products in various anion forms were found to show different delamination behaviors in formamide. Among them, best results were observed for NO3- -LDH in terms of the exfoliating degree and the quality of the exfoliated nanosheets. The delamination gave a pink transparent suspension containing well-defined nanosheets with lateral sizes of up to 2 microm. The resulting nanosheets were assembled layer-by-layer with an anionic polymer, poly(sodium styrene 4-sulfonate) (PSS), onto quartz glass substrates to produce composite films. Magnetic circular dichroism (MCD) measurements revealed that the assembled multilayer films exhibited an interesting magneto-optical response. PMID:16594724

  18. Paraquat Toxicity Induced by Voltage-dependent Anion Channel 1 Acts as an NADH-dependent Oxidoreductase*

    PubMed Central

    Shimada, Hiroki; Hirai, Kei-Ichi; Simamura, Eriko; Hatta, Toshihisa; Iwakiri, Hiroki; Mizuki, Keiji; Hatta, Taizo; Sawasaki, Tatsuya; Matsunaga, Satoko; Endo, Yaeta; Shimizu, Shigeomi

    2009-01-01

    Paraquat (PQ), a herbicide used worldwide, causes fatal injury to organs upon high dose ingestion. Treatments for PQ poisoning are unreliable, and numerous deaths have been attributed inappropriate usage of the agent. It is generally speculated that a microsomal drug-metabolizing enzyme system is responsible for PQ toxicity. However, recent studies have demonstrated cytotoxicity via mitochondria, and therefore, the cytotoxic mechanism remains controversial. Here, we demonstrated that mitochondrial NADH-dependent PQ reductase containing a voltage-dependent anion channel 1 (VDAC1) is responsible for PQ cytotoxicity. When mitochondria were incubated with NADH and PQ, superoxide anion (O2˙̄) was produced, and the mitochondria ruptured. Outer membrane extract oxidized NADH in a PQ dose-dependent manner, and oxidation was suppressed by VDAC inhibitors. Zymographic analysis revealed the presence of VDAC1 protein in the oxidoreductase, and the direct binding of PQ to VDAC1 was demonstrated using biotinylated PQ. VDAC1-overexpressing cells showed increased O2˙̄ production and cytotoxicity, both of which were suppressed in VDAC1 knockdown cells. These results indicated that a VDAC1-containing mitochondrial system is involved in PQ poisoning. These insights into the mechanism of PQ poisoning not only demonstrated novel physiological functions of VDAC protein, but they may facilitate the development of new therapeutic approaches. PMID:19717555

  19. Resonant indirect exchange via spatially separated two-dimensional channel

    SciTech Connect

    Rozhansky, I. V.; Krainov, I. V.; Averkiev, N. S.; Aronzon, B. A.; Davydov, A. B.; Kugel, K. I.; Tripathi, V.; Lähderanta, E.

    2015-06-22

    We apply the resonant indirect exchange interaction theory to explain the ferromagnetic properties of the hybrid heterostructure consisting of a InGaAs-based quantum well (QW) sandwiched between GaAs barriers with spatially separated Mn δ-layer. The experimentally obtained dependence of the Curie temperature on the QW depth exhibits a peak related to the region of resonant indirect exchange. We suggest the theoretical explanation and a fit to this dependence as a result of the two contributions to ferromagnetism—the intralayer contribution and the resonant exchange contribution provided by the QW.

  20. Fluoride Induces a Volume Reduction in CA1 Hippocampal Slices Via MAP Kinase Pathway Through Volume Regulated Anion Channels.

    PubMed

    Lee, Jaekwang; Han, Young-Eun; Favorov, Oleg; Tommerdahl, Mark; Whitsel, Barry; Lee, C Justin

    2016-04-01

    Regulation of cell volume is an important aspect of cellular homeostasis during neural activity. This volume regulation is thought to be mediated by activation of specific transporters, aquaporin, and volume regulated anion channels (VRAC). In cultured astrocytes, it was reported that swelling-induced mitogen-activated protein (MAP) kinase activation is required to open VRAC, which are thought to be important in regulatory volume decrease and in the response of CNS to trauma and excitotoxicity. It has been also described that sodium fluoride (NaF), a recognized G-protein activator and protein phosphatase inhibitor, leads to a significant MAP kinase activation in endothelial cells. However, NaF's effect in volume regulation in the brain is not known yet. Here, we investigated the mechanism of NaF-induced volume change in rat and mouse hippocampal slices using intrinsic optical signal (IOS) recording, in which we measured relative changes in intracellular and extracellular volume as changes in light transmittance through brain slices. We found that NaF (1~5 mM) application induced a reduction in light transmittance (decreased volume) in CA1 hippocampus, which was completely reversed by MAP kinase inhibitor U0126 (10 µM). We also observed that NaF-induced volume reduction was blocked by anion channel blockers, suggesting that NaF-induced volume reduction could be mediated by VRAC. Overall, our results propose a novel molecular mechanism of NaF-induced volume reduction via MAP kinase signaling pathway by activation of VRAC. PMID:27122993

  1. Fluoride Induces a Volume Reduction in CA1 Hippocampal Slices Via MAP Kinase Pathway Through Volume Regulated Anion Channels

    PubMed Central

    Lee, Jaekwang; Han, Young-Eun; Favorov, Oleg; Tommerdahl, Mark; Whitsel, Barry

    2016-01-01

    Regulation of cell volume is an important aspect of cellular homeostasis during neural activity. This volume regulation is thought to be mediated by activation of specific transporters, aquaporin, and volume regulated anion channels (VRAC). In cultured astrocytes, it was reported that swelling-induced mitogen-activated protein (MAP) kinase activation is required to open VRAC, which are thought to be important in regulatory volume decrease and in the response of CNS to trauma and excitotoxicity. It has been also described that sodium fluoride (NaF), a recognized G-protein activator and protein phosphatase inhibitor, leads to a significant MAP kinase activation in endothelial cells. However, NaF's effect in volume regulation in the brain is not known yet. Here, we investigated the mechanism of NaF-induced volume change in rat and mouse hippocampal slices using intrinsic optical signal (IOS) recording, in which we measured relative changes in intracellular and extracellular volume as changes in light transmittance through brain slices. We found that NaF (1~5 mM) application induced a reduction in light transmittance (decreased volume) in CA1 hippocampus, which was completely reversed by MAP kinase inhibitor U0126 (10 µM). We also observed that NaF-induced volume reduction was blocked by anion channel blockers, suggesting that NaF-induced volume reduction could be mediated by VRAC. Overall, our results propose a novel molecular mechanism of NaF-induced volume reduction via MAP kinase signaling pathway by activation of VRAC. PMID:27122993

  2. Photosynthesis-dependent/independent control of stomatal responses to CO2 in mutant barley with surplus electron transport capacity and reduced SLAH3 anion channel transcript.

    PubMed

    Córdoba, Javier; Molina-Cano, José-Luis; Pérez, Pilar; Morcuende, Rosa; Moralejo, Marian; Savé, Robert; Martínez-Carrasco, Rafael

    2015-10-01

    The mechanisms of stomatal sensitivity to CO2 are yet to be fully understood. The role of photosynthetic and non-photosynthetic factors in stomatal responses to CO2 was investigated in wild-type barley (Hordeum vulgare var. Graphic) and in a mutant (G132) with decreased photochemical and Rubisco capacities. The CO2 and DCMU responses of stomatal conductance (gs), gas exchange, chlorophyll fluorescence and levels of ATP, with a putative transcript for stomatal opening were analysed. G132 had greater gs than the wild-type, despite lower photosynthesis rates and higher intercellular CO2 concentrations (Ci). The mutant had Rubisco-limited photosynthesis at very high CO2 levels, and higher ATP contents than the wild-type. Stomatal sensitivity to CO2 under red light was lower in G132 than in the wild-type, both in photosynthesizing and DCMU-inhibited leaves. Under constant Ci and red light, stomatal sensitivity to DCMU inhibition was higher in G132. The levels of a SLAH3-like slow anion channel transcript, involved in stomatal closure, decreased sharply in G132. The results suggest that stomatal responses to CO2 depend partly on the balance of photosynthetic electron transport to carbon assimilation capacities, but are partially regulated by the CO2 signalling network. High gs can improve the adaptation to climate change in well-watered conditions. PMID:26398787

  3. Increased leaf photosynthesis caused by elevated stomatal conductance in a rice mutant deficient in SLAC1, a guard cell anion channel protein

    PubMed Central

    Kusumi, Kensuke

    2012-01-01

    In rice (Oryza sativa L.), leaf photosynthesis is known to be highly correlated with stomatal conductance; however, it remains unclear whether stomatal conductance dominantly limits the photosynthetic rate. SLAC1 is a stomatal anion channel protein controlling stomatal closure in response to environmental [CO2]. In order to examine stomatal limitations to photosynthesis, a SLAC1-deficient mutant of rice was isolated and characterized. A TILLING screen of N-methyl-N-nitrosourea-derived mutant lines was conducted for the rice SLAC1 orthologue gene Os04g0674700, and four mutant lines containing mutations within the open reading frame were obtained. A second screen using an infrared thermography camera revealed that one of the mutants, named slac1, had a constitutive low leaf temperature phenotype. Measurement of leaf gas exchange showed that slac1 plants grown in the greenhouse had significantly higher stomatal conductance (g s), rates of photosynthesis (A), and ratios of internal [CO2] to ambient [CO2] (C i/C a) compared with wild-type plants, whereas there was no significant difference in the response of photosynthesis to internal [CO2] (A/C i curves). These observations demonstrate that in well-watered conditions, stomatal conductance is a major determinant of photosynthetic rate in rice. PMID:22915747

  4. Removal of chlorophenols from aqueous solution by anion-exchange resins

    SciTech Connect

    Kuen-Chyr Lee; Young Ku

    1996-11-01

    The effects of pH value and chloride ion concentration in the removal of chlorophenols from aqueous solutions by Purolite A-510 resin [macroreticular polystyrene-divinylbenzene resin with R(CH{sub 3}){sub 2}(C{sub 2}H{sub 4}OH)N{sup +} group] are discussed by the species distributions of chlorophenols. Those chlorophenols include phenol, 2-chlorophenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol. The investigations showed that the chlorophenols could be removed effectively at alkaline conditions where the ion-exchange reaction was dominant. Also, the removal of chlorophenols increased with the number of chlorine atoms on the chlorophenols. The removal of chlorophenols via the ion-exchange reaction was hindered by the presence of chloride ions. The effect of chloride ions, however, was diminished in acidic solutions where the adsorption reaction was dominant. The proposed equilibrium model, which considers both adsorption and ion-exchange reactions, adequately describes the sorption behavior of chlorophenols. The partition constants of the protonated chlorophenols can be estimated from the octanol/water partition coefficients of the phenolic compounds.

  5. How pulse modes affect proton-barriers and anion-exchange membrane mineral fouling during consecutive electrodialysis treatments.

    PubMed

    Cifuentes-Araya, Nicolás; Pourcelly, Gérald; Bazinet, Laurent

    2013-02-15

    Mineral fouling of cation-exchange membrane (CEM) was recently reduced by pulsed electric fields (PEFs) during the electrodialysis (ED) of solutions containing high Mg(2+)/Ca(2+) ratios. However, a fouling layer appeared on the diluate side of anion-exchange membrane (AEM) once the pause lapse surpassed certain duration. Recent studies presented a multilayer mineral growth on CEM, but the case of AEM needs yet to be cleared. The current study reveals the mechanisms involved in AEM fouling growth when applying pulse modes of current in comparison with dc current. The results showed that dc current generated steady proton barriers given by water splitting at AEM interfaces that impeded fouling on both membrane sides. The higher frequency of PEF ratio 1 (Ton/Toff=10s/10s) acted removing completely an initial mineral deposit on the concentrate side of AEM, keeping it clean after two and three consecutive runs. Particularly, an undesirable brucite layer was formed on the AEM-diluate side for longer pause lapses as for a PEF ratio 0.3 (Ton/Toff=10s/33.3s) current regime. This structure caused violent water splitting resulting in amorphous magnesium hydroxide formation and consequently in fouling precipitation on the concentrate side during a third run through current exaltation. PMID:23141696

  6. Chitosan Derivatives as Important Biorefinery Intermediates. Quaternary Tetraalkylammonium Chitosan Derivatives Utilized in Anion Exchange Chromatography for Perchlorate Removal

    PubMed Central

    Sayed, Shakeela; Jardine, Anwar

    2015-01-01

    There has recently been great interest in the valorization of biomass waste in the context of the biorefinery. The biopolymer chitosan, derived from chitin, is present in large quantities of crustacean waste. This biomass can be converted into value-added products with applications in energy, fuel, chemicals and materials manufacturing. The many reported applications of this polymer can be attributed to its unique properties, such as biocompatibility, chemical versatility, biodegradability and low toxicity. Cost effective water filters which decontaminate water by removal of specific impurities and microbes are in great demand. To address this need, the development of ion exchange resins using environmentally friendly, renewable materials such as biopolymers as solid supports was evaluated. The identification and remediation of perchlorate contaminated water using an easy, inexpensive method has come under the spotlight recently. Similarly, the use of a low cost perchlorate selective solid phase extraction (SPE) cartridge that can be rapidly employed in the field is desirable. Chitosan based SPE coupled with colorimetric analytical methods showed promise as a renewable anion exchange support for perchlorate analysis or removal. The polymers displayed perchlorate retention comparable to the commercial standard whereby the quaternized iron loaded polymer TMC-Fe(III) displayed the best activity. PMID:25915024

  7. Anion-exchange reactions on a robust phosphonium photopolymer for the controlled deposition of ionic gold nanoclusters.

    PubMed

    Guterman, Ryan; Hesari, Mahdi; Ragogna, Paul J; Workentin, Mark S

    2013-05-28

    UV curing (photopolymerization) is ubiquitous in many facets of industry ranging from the application of paints, pigments, and barrier coatings all the way to fiber optic cable production. To date no reports have focused on polymerizable phosphonium salts under UV irradiation, and despite this dearth of examples, they potentially offer numerous substantial advantages to traditional UV formulation components. We have generated a highly novel coating based on UV-curable trialkylacryloylphosphonium salts that allow for the fast (seconds) and straightforward preparation of ion-exchange surfaces amenable to a roll-to-roll process. We have quantified the surface charges and exploited their accessibility by employing these surfaces in an anion exchange experiment by which [Au25L18](-) (L = SCH2CH2Ph) nanocrystals can be assembled into the solid state. This unprecedented application of such surfaces offers a paradigm shift in the emerging chemistry of Au25 research where the nanocrystals remain single and intact and where the integrity of the cluster and its solution photophysical properties are resilient in the solid state. The specific loading of [Au25L18](-) on the substrates has been determined and the completely reversible loading and unloading of intact nanocrystals to and from the surface has been established. In the solid state, the assembly has an incredible mechanical resiliency, where the surface remains undamaged even when subjected to repeated Scotch tests. PMID:23472738

  8. Cross-linked anion exchange membranes with pendent quaternary pyrrolidonium salts for alkaline polymer electrolyte membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Lan, Chunhua; Fang, Jun; Guan, Yingjie; Zhou, Huili; Zhao, Jinbao

    2015-11-01

    Novel anion-exchange membranes based on two kinds of pyrrolidonium type ionic liquids, N-methyl-N-vinyl-pyrrolidonium (NVMP) and N-ethyl-N-vinyl-pyrrolidonium (NVEP), have been synthesized via polymerization and crosslinking treatment, followed by membrane casting. The covalent cross-linked structures of these membranes are confirmed by FT-IR. The obtained membranes are also characterized in terms of water uptake, ion exchange capacity (IEC), ionic conductivity as well as thermal, dimensional and chemical stability. The membranes display hydroxide conductivity of above 10-2 S cm-1 at 25 °C. Excellent thermal stability with onset degradation temperature above 235 °C, good alkaline stability in 6 mol L-1 NaOH at 60 °C for 168 h and remarkable dimensional stability of the resulting membranes have been proved. H2/air single fuel cells employed membrane M3 and N3 show the open-circuit voltage (OCV) of 0.953 V and 0.933 V, and the maximum power density of 88.90 mW cm-2 and 81.90 mW cm-2 at the current density of 175 mA cm-2 and 200 mA cm-2 at 65 °C, respectively.

  9. Transmembrane protein 139 (TMEM139) interacts with human kidney isoform of anion exchanger 1 (kAE1).

    PubMed

    Nuiplot, Nalin-On; Junking, Mutita; Duangtum, Natapol; Khunchai, Sasiprapa; Sawasdee, Nunghathai; Yenchitsomanus, Pa-Thai; Akkarapatumwong, Varaporn

    2015-08-01

    Human kidney anion exchanger 1 (kAE1) mediates Cl(-)/HCO3(-) exchanges at the basolateral membrane of the acid-secreting α-intercalated cells. Mutations in SLC4A1 gene encoding kAE1 are associated with distal renal tubular acidosis (dRTA). Several studies have shown that impaired trafficking of the mutant kAE1 is an important molecular mechanism underlying the pathogenesis of dRTA. Proteins involved in kAE1 trafficking were identified but the mechanism resulting in dRTA remained unclear. Thus, this study attempted to search for additional proteins interacting with C-terminal of kAE1 (Ct-kAE1) and involved in kAE1 trafficking to cell membrane. Transmembrane protein 139 (TMEM139) was identified as a protein interacting with Ct-kAE1 by yeast two-hybrid screening. The interaction between kAE1 and TMEM139 was confirmed by affinity co-purification, co-immunoprecipitation (co-IP) and yellow fluorescent protein (YFP)-based protein fragment complementation assay (PCA). In addition, flow cytometry results showed that suppression of endogenous TMEM139 by small interfering RNA (siRNA) and over-expression of TMEM139 in HEK293T cells could reduce and increase membrane localization of kAE1, respectively. The presented data demonstrate that TMEM139 interacts with kAE1 and promotes its intracellular trafficking. PMID:26049106

  10. Renal peroxiredoxin 6 interacts with anion exchanger 1 and plays a novel role in pH homeostasis

    PubMed Central

    Johnstone, Duncan B.; Frankl, Fiona E. Karet

    2015-01-01

    Peroxiredoxin 6 (PRDX6) is one of six members of the PRDX family, which have peroxidase and antioxidant activity. PRDX6 is unique, containing only one conserved cysteine residue (C47) rather than the two found in other PRDXs. A yeast two-hybrid screen found PRDX6 to be a potential binding partner of the C-terminal tail of anion exchanger 1 (AE1), a Cl−/HCO3− exchanger basolaterally expressed in renal α-intercalated cells. PRDX6 immunostaining in human kidney was both cytoplasmic and peripheral and co-localized with AE1. Analysis of native protein showed it was largely monomeric, whereas expressed tagged protein was more dimeric. Two methionine oxidation sites were identified. In vitro and ex vivo pulldowns and immunoprecipitation assays confirmed interaction with AE1, but mutation of the conserved cysteine resulted in loss of interaction. Prdx6 knockout mice had a baseline acidosis with a major respiratory component and greater AE1 expression than wild type animals. After an oral acid challenge, PRDX6 expression increased in wild type mice, with preservation of AE1. However, AE1 expression was significantly decreased in knockout animals. Kidneys from acidified mice showed widespread proximal tubular vacuolation in wild type but not knockout animals. Knockdown of PRDX6 by siRNA in mammalian cells reduced both total and cell membrane AE1 levels. Thus, PRDX6-AE1 interaction contributes to maintenance of AE1 during cellular stress such as during metabolic acidosis. PMID:26398495

  11. Assemblies of protective anion exchange membrane on air electrode for its efficient operation in aqueous alkaline electrolyte

    NASA Astrophysics Data System (ADS)

    Bertolotti, Bruno; Chikh, Linda; Vancaeyzeele, Cédric; Alfonsi, Séverine; Fichet, Odile

    2015-01-01

    Aqueous alkaline metal-air batteries represent promising energy storage devices when supplied with atmospheric air. However, under this condition, the air electrode shows a very short life time (i.e. 50 h of operation in 5 M LiOH at -10 mA cm-2), mainly due to the precipitation of carbonates inside the electrode porosity. The air electrode can then be protected by an anion exchange membrane on the electrolyte side. In this paper, we demonstrate that the efficiency of this protective membrane depends on the assembly method on the electrode. When a modified poly(epichlorohydrin) (PECH) network is synthesized directly on the electrode, the polymer seeps inside the electrode porosity, and a suitable interface inducing negligible additional polarization in comparison with classical pressure-assembled membranes is obtained. This protected electrode shows improved stability of up to 160 h of operation in 5 M LiOH. This performance is improved to 350 h by adjusting the conductivity and the ionic exchange capacity. Finally, the interest of interpenetrating polymer network (IPN) architecture compared to a single network is confirmed. Indeed, an electrode protected with a PECH/poly(2-hydroxyethyl methacrylate) (PHEMA) IPN is stable for 650 h in 5 M LiOH. In addition, degradation process becomes reversible since the assembly can be regenerated, which is not possible for the bare electrode.

  12. Forkhead transcription factor FoxA1 regulates sweat secretion through Bestrophin 2 anion channel and Na-K-Cl cotransporter 1

    PubMed Central

    Cui, Chang-Yi; Childress, Victoria; Piao, Yulan; Michel, Marc; Johnson, Adiv A.; Kunisada, Makoto; Ko, Minoru S. H.; Kaestner, Klaus H.; Marmorstein, Alan D.; Schlessinger, David

    2012-01-01

    Body temperature is maintained in a narrow range in mammals, primarily controlled by sweating. In humans, the dynamic thermoregulatory organ, comprised of 2–4 million sweat glands distributed over the body, can secrete up to 4 L of sweat per day, thereby making it possible to withstand high temperatures and endure prolonged physical stress (e.g., long-distance running). The genetic basis for sweat gland function, however, is largely unknown. We find that the forkhead transcription factor, FoxA1, is required to generate mouse sweating capacity. Despite continued sweat gland morphogenesis, ablation of FoxA1 in mice results in absolute anihidrosis (lack of sweating). This inability to sweat is accompanied by down-regulation of the Na-K-Cl cotransporter 1 (Nkcc1) and the Ca2+-activated anion channel Bestrophin 2 (Best2), as well as glycoprotein accumulation in gland lumens and ducts. Furthermore, Best2-deficient mice display comparable anhidrosis and glycoprotein accumulation. These findings link earlier observations that both sodium/potassium/chloride exchange and Ca2+ are required for sweat production. FoxA1 is inferred to regulate two corresponding features of sweat secretion. One feature, via Best2, catalyzes a bicarbonate gradient that could help to drive calcium-associated ionic transport; the other, requiring Nkcc1, facilitates monovalent ion exchange into sweat. These mechanistic components can be pharmaceutical targets to defend against hyperthermia and alleviate defective thermoregulation in the elderly, and may provide a model relevant to more complex secretory processes. PMID:22223659

  13. Cationic Covalent Organic Frameworks: A Simple Platform of Anionic Exchange for Porosity Tuning and Proton Conduction.

    PubMed

    Ma, Heping; Liu, Bailing; Li, Bin; Zhang, Liming; Li, Yang-Guang; Tan, Hua-Qiao; Zang, Hong-Ying; Zhu, Guangshan

    2016-05-11

    Mimicking proton conduction mechanism of Nafion to construct novel proton-conducting materials with low cost and high proton conductivity is of wide interest. Herein, we have designed and synthesized a cationic covalent organic framework with high thermal and chemical stability by combining a cationic monomer, ethidium bromide (EB) (3,8-diamino-5-ethyl-6-phenylphenanthridinium bromide), with 1,3,5-triformylphloroglucinol (TFP) in Schiff base reactions. This is the first time that the stable cationic crystalline frameworks allowed for the fabrication of a series of charged COFs (EB-COF:X, X = F, Cl, Br, I) through ion exchange processes. Exchange of the extra framework ions can finely modulate the COFs' porosity and pore sizes at nanoscale. More importantly, by introducing PW12O40(3-) into this porous cationic framework, we can greatly enhance the proton conductivity of ionic COF-based material. To the best of our knowledge, EB-COF:PW12 shows the best proton conductivity at room temperature among ever reported porous organic materials. PMID:27094048

  14. Anion exchange membrane adsorbers for flow-through polishing steps: Part I. Clearance of minute virus of mice.

    PubMed

    Weaver, Justin; Husson, Scott M; Murphy, Louise; Wickramasinghe, S Ranil

    2013-02-01

    Membrane adsorbers may be a viable alternative to the packed-bed chromatography for clearance of virus, host cell proteins, DNA, and other trace impurities. However, incorporation of membrane adsorbers into manufacturing processes has been slow due to the significant cost associated with obtaining regulatory approval for changes to a manufacturing process. This study has investigated clearance of minute virus of mice (MVM), an 18-22 nm parvovirus recognized by the FDA as a model viral impurity. Virus clearance was obtained using three commercially available anion exchange membrane adsorbers: Sartobind Q®, Mustang Q®, and ChromaSorb®. Unlike earlier studies that have focused on a single or few operating conditions, the aim here was to determine the level of virus clearance under a range of operating conditions that could be encountered in industry. The effects of varying pH, NaCl concentration, flow rate, and other competing anionic species present in the feed were determined. The removal capacity of the Sartobind Q and Mustang Q products, which contain quaternary ammonium based ligands, is sensitive to feed conductivity and pH. At conductivities above about 20 mS/cm, a significant decrease in capacity is observed. The capacity of the ChromaSorb product, which contains primary amine based ligands, is much less affected by ionic strength. However the capacity for binding MVM is significantly reduced in the presence of phosphate ions. These differences may be explained in terms of secondary hydrogen bonding interactions that could occur with primary amine based ligands. PMID:22949170

  15. Antimony(V) removal from water by hydrated ferric oxides supported by calcite sand and polymeric anion exchanger.

    PubMed

    Miao, Yangyang; Han, Feichao; Pan, Bingcai; Niu, Yingjie; Nie, Guangze; Lv, Lu

    2014-02-01

    We fabricated and characterized two hybrid adsorbents originated from hydrated ferric oxides (HFOs) using a polymeric anion exchanger D201 and calcite as host. The resultant adsorbents (denoted as HFO-201 and IOCCS) were employed for Sb(V) removal from water. Increasing solution pH from 3 to 9 apparently weakened Sb(V) removal by both composites, while increasing temperature from 293 to 313 K only improved Sb(V) uptake by IOCCS. HFO-201 exhibited much higher capacity for Sb(V) than for IOCCS in the absence of other anions in solution. Increasing ionic strength from 0.01 to 0.1 mol/L NaNO3 would result in a significant drop of the capacity of HFO-201 in the studied pH ranges; however, negligible effect was observed for IOCCS under similar conditions. Similarly, the competing chloride and sulfate pose more negative effect on Sb(V) adsorption by HFO-201 than by IOCCS, and the presence of silicate greatly decreased their adsorption simultaneously, while calcium ions were found to promote the adsorption of both adsorbents. XPS analysis further demonstrated that preferable Sb(V) adsorption by both hybrids was attributed to the inner sphere complexation of Sb(V) and HFO, and Ca(II) induced adsorption enhancement possibly resulted from the formation of HFO-Ca-Sb complexes. Column adsorption runs proved that Sb(V) in the synthetic water could be effectively removed from 30 microg/L to below 5 microg/L (the drinking water standard regulated by China), and the effective treatable volume of IOCCS was around 6 times as that of HFO-201, implying that HFO coatings onto calcite might be a more effective approach than immobilization inside D201. PMID:25076522

  16. Arsenate Adsorption by Hydrous Ferric Oxide Nanoparticles Embedded in Cross-linked Anion Exchanger: Effect of the Host Pore Structure.

    PubMed

    Li, Hongchao; Shan, Chao; Zhang, Yanyang; Cai, Jianguo; Zhang, Weiming; Pan, Bingcai

    2016-02-10

    Three composite adsorbents were fabricated via confined growth of hydrous ferric oxide (HFO) nanoparticles within cross-linked anion exchangers (NS) of different pore size distributions to investigate the effect of host pore structure on the adsorption of As(V). With the decrease in the average pore size of the NS hosts from 38.7 to 9.2 nm, the mean diameter of the confined HFO nanoparticles was lessened from 31.4 to 11.6 nm as observed by transmission electron microscopy (TEM), while the density of active surface sites was increased due to size-dependent effect proved by potentiometric titration. The adsorption capacity of As(V) yielded by Sips model was elevated from 24.2 to 31.6 mg/g via tailoring the pore size of the NS hosts, and the adsorption kinetics was slightly accelerated with the decrease of pore size in background solution containing 500 mg/L of Cl(-). Furthermore, the enhanced adsorption of As(V) was achieved over a wide pH range from 3 to 10, as well as in the presence of competing anions including Cl(-), SO4(2-), HCO3(-), NO3(-) (up to 800 mg/L), and PO4(3-) (up to 10 mg P/L). In addition, the fixed-bed working capacity increased from 2200 to 2950 bed volumes (BV) owing to the size confinement effect, which did not have adverse effect on the desorption of As(V) as the cumulative desorption efficiency reached 94% with 10 BV of binary solution (5% NaOH + 5% NaCl) for all the three adsorbents. Therefore, this study provided a promising strategy to regulate the reactivity of the nanoparticles via the size confinement effect of the host pore structure. PMID:26765396

  17. Regulation of the cystic fibrosis transmembrane conductance regulator anion channel by tyrosine phosphorylation.

    PubMed

    Billet, Arnaud; Jia, Yanlin; Jensen, Tim; Riordan, John R; Hanrahan, John W

    2015-09-01

    The cystic fibrosis transmembrane conductance regulator (CFTR) channel is activated by PKA phosphorylation of a regulatory domain that interacts dynamically with multiple CFTR domains and with other proteins. The large number of consensus sequences for phosphorylation by PKA has naturally focused most attention on regulation by this kinase. We report here that human CFTR is also phosphorylated by the tyrosine kinases p60c-Src (proto-oncogene tyrosine-protein kinase) and the proline-rich tyrosine kinase 2 (Pyk2), and they can also cause robust activation of quiescent CFTR channels. In excised patch-clamp experiments, CFTR activity during exposure to Src or Pyk2 reached ∼80% of that stimulated by PKA. Exposure to PKA after Src or Pyk2 caused a further increase to the level induced by PKA alone, implying a common limiting step. Channels became spontaneously active when v-Src or the catalytic domain of Pyk2 was coexpressed with CFTR and were further stimulated by the tyrosine phosphatase inhibitor dephostatin. Exogenous Src also activated 15SA-CFTR, a variant that lacks 15 potential PKA sites and has little response to PKA. PKA-independent activation by tyrosine phosphorylation has implications for the mechanism of regulation by the R domain and for the physiologic functions of CFTR. PMID:26062600

  18. Partial flow compensation by transverse bypass configuration in multi-channel cryogenic compact heat exchanger

    NASA Astrophysics Data System (ADS)

    Jung, Jeheon; Hwang, Gyuwan; Baek, Seungwhan; Jeong, Sangkwon; Rowe, Andrew M.

    2012-01-01

    High-performance multi-channel heat exchangers are vulnerable to small defects such as ill-manufacture or contamination in flow channels. Even slight flow mal-distribution may result in drastic reduction of their thermal performance. In order to accommodate such performance reduction in multi-channel heat exchangers, transverse bypass structure among the channels of hot stream or cold stream is proposed. Since transverse bypass structure enables voluntary flow re-distribution among the channels, detrimental effect of flow defects can be partially reduced and flow mal-distribution can be locally relieved. The lower the flow resistance of transverse bypass is, the more substantial the flow re-distribution is and the larger its effect can be. Quantitative analysis and experimental verification on the effect of transverse bypass is carried out, and the results are presented in this paper.

  19. Voltage dependent anion channel is redistributed during Japanese encephalitis virus infection of insect cells.

    PubMed

    Fongsaran, Chanida; Phaonakrop, Narumon; Roytrakul, Sittiruk; Thepparit, Chutima; Kuadkitkan, Atichat; Smith, Duncan R

    2014-01-01

    Despite the availability of an effective vaccine, Japanese encephalitis remains a significant cause of morbidity and mortality in many parts of Asia. Japanese encephalitis is caused by the Japanese encephalitis virus (JEV), a mosquito transmitted flavivirus. Many of the details of the virus replication cycle in mosquito cells remain unknown. This study sought to determine whether GRP78, a well-characterized flavivirus E protein interacting protein, interacted with JEV E protein in insect cells, and whether this interaction was mediated at the cell surface. GRP78 was shown to interact with JEV E protein by coimmunoprecipitation, and was additionally shown to interact with voltage dependent anion protein (VDAC) through the same methodology. Antibody inhibition experiments showed that neither GRP78 nor VDAC played a role in JEV internalization to insect cells. Interestingly, VDAC was shown to be significantly relocalized in response to JEV infection, and significant levels of colocalization between VDAC and GRP78 and VDAC and ribosomal L28 protein were seen in JEV infected but not uninfected cells. This is the first report of relocalization of VDAC in response to JEV infection and suggests that this may be a part of the JEV replication strategy in insect cells. PMID:25126612

  20. Fast Anion-Exchange in Highly Luminescent Nanocrystals of Cesium Lead Halide Perovskites (CsPbX3, X = Cl, Br, I)

    PubMed Central

    2015-01-01

    Postsynthetic chemical transformations of colloidal nanocrystals, such as ion-exchange reactions, provide an avenue to compositional fine-tuning or to otherwise inaccessible materials and morphologies. While cation-exchange is facile and commonplace, anion-exchange reactions have not received substantial deployment. Here we report fast, low-temperature, deliberately partial, or complete anion-exchange in highly luminescent semiconductor nanocrystals of cesium lead halide perovskites (CsPbX3, X = Cl, Br, I). By adjusting the halide ratios in the colloidal nanocrystal solution, the bright photoluminescence can be tuned over the entire visible spectral region (410–700 nm) while maintaining high quantum yields of 20–80% and narrow emission line widths of 10–40 nm (from blue to red). Furthermore, fast internanocrystal anion-exchange is demonstrated, leading to uniform CsPb(Cl/Br)3 or CsPb(Br/I)3 compositions simply by mixing CsPbCl3, CsPbBr3, and CsPbI3 nanocrystals in appropriate ratios. PMID:26207728

  1. Fast Anion-Exchange in Highly Luminescent Nanocrystals of Cesium Lead Halide Perovskites (CsPbX3, X = Cl, Br, I).

    PubMed

    Nedelcu, Georgian; Protesescu, Loredana; Yakunin, Sergii; Bodnarchuk, Maryna I; Grotevent, Matthias J; Kovalenko, Maksym V

    2015-08-12

    Postsynthetic chemical transformations of colloidal nanocrystals, such as ion-exchange reactions, provide an avenue to compositional fine-tuning or to otherwise inaccessible materials and morphologies. While cation-exchange is facile and commonplace, anion-exchange reactions have not received substantial deployment. Here we report fast, low-temperature, deliberately partial, or complete anion-exchange in highly luminescent semiconductor nanocrystals of cesium lead halide perovskites (CsPbX3, X = Cl, Br, I). By adjusting the halide ratios in the colloidal nanocrystal solution, the bright photoluminescence can be tuned over the entire visible spectral region (410-700 nm) while maintaining high quantum yields of 20-80% and narrow emission line widths of 10-40 nm (from blue to red). Furthermore, fast internanocrystal anion-exchange is demonstrated, leading to uniform CsPb(Cl/Br)3 or CsPb(Br/I)3 compositions simply by mixing CsPbCl3, CsPbBr3, and CsPbI3 nanocrystals in appropriate ratios. PMID:26207728

  2. Determination of thorium in geological materials by x-ray fluorescence spectrometry after anion exchange extraction

    SciTech Connect

    Roelandts, I.

    1983-08-01

    The exchange capacity of the resin was determined to be 1 m equiv of Th/g dry resin. Synthetic calibration standards of thorium were prepared over a large concentration range, for use as an independent method of calibration. The advantages and disadvantages of direct x-ray fluorescence analysis are discussed. The lower limit of detection has been calculated according to Currie's convention and was found to be equal to 13 ..mu..g of Th/250 mg of resin, sufficient for the range of concentrations found in Th bearing minerals and ores. Results using Canadian syenite rocks and a suite of South African reference minerals show that the proposed method appears to be relatively precise and accurate for exploration geochemistry. 1 figure, 2 tables.

  3. Diverse Reactivity of an Electrophilic Phosphasilene towards Anionic Nucleophiles: Substitution or Metal-Amino Exchange.

    PubMed

    Willmes, Philipp; Junk, Lukas; Huch, Volker; Yildiz, Cem B; Scheschkewitz, David

    2016-08-26

    The reaction of MesLi (Mes=2,4,6-trimethylphenyl) with the electrophilic phosphasilene R2 (NMe2 )Si-RSi=PNMe2 (2, R=Tip=2,4,6-triisopropylphenyl) cleanly affords R2 (NMe2 )Si-RSi=PMes and thus provides the first example of a substitution reaction at an unperturbed Si=P bond. In toluene, the reaction of 2 with lithium disilenide, R2 Si=Si(R)Li (1), apparently proceeds via an initial nucleophilic substitution step as well (as suggested by DFT calculations), but affords a saturated bicyclo[1.1.0]butane analogue as the final product, which was further characterized as its Fe(CO)4 complex. In contrast, in 1,2-dimethoxyethane the reaction of 1 with 2 results in an unprecedented metal-amino exchange reaction. PMID:27509901

  4. Separation of 'Uncharged' Oligodeoxynucleotide Analogs by Anion-Exchange Chromatography at High pH

    NASA Technical Reports Server (NTRS)

    Schmidt, Jurgen G.; Orgel, Leslie E.; Nielsen, Peter E.

    1996-01-01

    Ion-exchange chromatography is a well-established method for the analysis and purification of phosphodiester-linked oligonucleotides. If elution is carried out under alkaline conditions, the secondary structure of G- and C-rich oligomers is disrupted. Furthermore, elution times become more sensitive to the G and T content of the oligomer, because G and T are deprotonated at pH 10. In recent work on peptide-nucleic acids (PNAs) we noted that mixtures of PNA oligomers G(sub 4), G(sub 6), G(sub 8), and G9(sub 10) are readily separated by elution at pH 12 on an RPC-5 column. Here we show that this separation method is more generally applicable.

  5. Separation of Uncharged Oligodeoxynucleotide Analogs by Anion-Exchange Chromatography at High pH

    NASA Technical Reports Server (NTRS)

    Schmidt, Jurgen G.; Nielsen, Peter E.; Orgel, Leslie

    1996-01-01

    Ion-exchange chromatography is a well-established method for the analysis and purification of phosphodiester-linked oligonucleotides. If elution is carried out under alkaline conditions, the secondary structure of G- and C-rich oligomers is disrupted. Furthermore, elution times become more sensitive to the G and T content of the oligomer, because G and T are deprotonated at pH 10. In recent work on peptide-nucleic acids (PNAs) we noted that mixtures of PNA oligomers G(sub 4), G(Sub 6), G(sub 8), and G(sub 10) are readily separated by elution at pH 12 on an RPC-5 column. Here we show that this separation method is more generally applicable.

  6. Efficiencies and Optimization of Weak Base Anion Ion-Exchange Resin for Groundwater Hexavalent Chromium Removal at Hanford

    SciTech Connect

    Nesham, Dean O.; Ivarson, Kristine A.; Hanson, James P.; Miller, Charles W.; Meyers, P.; Jaschke, Naomi M.

    2014-02-03

    The U.S. Department of Energy’s (DOE’s) contractor, CH2M HILL Plateau Remediation Company, has successfully converted a series of groundwater treatment facilities to use a new treatment resin that is delivering more than $3 million in annual cost savings and efficiency in treating groundwater contamination at the DOE Hanford Site in southeastern Washington State. During the production era, the nuclear reactors at the Hanford Site required a continuous supply of high-quality cooling water during operations. Cooling water consumption ranged from about 151,417 to 378,541 L/min (40,000 to 100,000 gal/min) per reactor, depending on specific operating conditions. Water from the Columbia River was filtered and treated chemically prior to use as cooling water, including the addition of sodium dichromate as a corrosion inhibitor. Hexavalent chromium was the primary component of the sodium dichromate and was introduced into the groundwater at the Hanford Site as a result of planned and unplanned discharges from the reactors starting in 1944. Groundwater contamination by hexavalent chromium and other contaminants related to nuclear reactor operations resulted in the need for groundwater remedial actions within the Hanford Site reactor areas. Beginning in 1995, groundwater treatment methods were evaluated, leading to the use of pump-and-treat facilities with ion exchange using Dowex™ 21K, a regenerable, strong-base anion exchange resin. This required regeneration of the resin, which was performed offsite. In 2008, DOE recognized that regulatory agreements would require significant expansion for the groundwater chromium treatment capacity. As a result, CH2M HILL performed testing at the Hanford Site in 2009 and 2010 to demonstrate resin performance in the specific groundwater chemistry at different waste sites. The testing demonstrated that a weak-base anion, single-use resin, specifically ResinTech SIR-700 ®, was effective at removing chromium, had a significantly

  7. Effect of Fe2+ Oxidation on the Removal of 238Pu from Neptunium Solution by Anion Exchange

    SciTech Connect

    KYSER, EDWARD

    2004-06-01

    The effect of ferrous sulfamate (FS) oxidation and variation in nitric acid concentration on the removal of {sup 238}Pu contamination from Np by the HB-Line anion exchange flowsheet has been tested. Significant rejection of {sup 238}Pu was observed by washing with a reductive wash solution containing 6.0 to 6.8 M nitric acid (HNO{sub 3}) with as little as 30% of the Fe{sup 2+} from the FS remaining in its reduced form. To achieve the desired 30% removal of {sup 238}Pu from the process, conditions should be controlled to maintain the Fe{sup 2+}/Fe{sup 3+} ratio in the reductive wash to be greater than 60%/40% (or 1.5). Since Fe{sup 2+} oxidation is strongly affected by temperature and nitric acid concentration, these parameters (as well as time after FS addition) need to be controlled to ensure predictable results. A shortened-height column was utilized in these tests to match changes in the plant equipment. Lab experiments scaled to plant batch sizes of 2000 g Np were observed with modest losses for ''up-flow'' washing. The following are recommended conditions for removing {sup 238}Pu from Np solutions by anion exchange in HB-Line: (1) Feed conditions: ''Up-flow'' 6.4-8.0 M HNO{sub 3}, 0.02 M hydrazine (N{sub 2}H{sub 4}), 0.05 M excess FS. (2) Reductive Wash conditions: ''Up-flow'' 6 Bed volumes (BV) of 6.4 M HNO{sub 3}, 0.05 M FS (minimum 0.03M Fe{sup 2+} during wash cycle), 0.05 M hydrazine, less than 1.8 mL/min/cm{sup 2} flowrate. (3) Decontamination Wash conditions: ''Up-flow'' 1-2 BV of 6.4-8.0 M HNO{sub 3}, no FS, no hydrazine, less than 1.8 mL/min/cm{sup 2} flowrate. (4) Elution conditions: ''Down-flow'' 0.17 M HNO{sub 3}, 0.05 M hydrazine, no FS.

  8. Evaluation and application of anion exchange resins to measure groundwater uranium flux at a former uranium mill site.

    PubMed

    Stucker, Valerie; Ranville, James; Newman, Mark; Peacock, Aaron; Cho, Jaehyun; Hatfield, Kirk

    2011-10-15

    Laboratory tests and a field validation experiment were performed to evaluate anion exchange resins for uranium sorption and desorption in order to develop a uranium passive flux meter (PFM). The mass of uranium sorbed to the resin and corresponding masses of alcohol tracers eluted over the duration of groundwater installation are then used to determine the groundwater and uranium contaminant fluxes. Laboratory based batch experiments were performed using Purolite A500, Dowex 21K and 21K XLT, Lewatit S6328 A resins and silver impregnated activated carbon to examine uranium sorption and extraction for each material. The Dowex resins had the highest uranium sorption, followed by Lewatit, Purolite and the activated carbon. Recoveries from all ion exchange resins were in the range of 94-99% for aqueous uranium in the environmentally relevant concentration range studied (0.01-200 ppb). Due to the lower price and well-characterized tracer capacity, Lewatit S6328 A was used for field-testing of PFMs at the DOE UMTRA site in Rifle, CO. The effect on the flux measurements of extractant (nitric acid)/resin ratio, and uranium loading were investigated. Higher cumulative uranium fluxes (as seen with concentrations>1 ug U/gram resin) yielded more homogeneous resin samples versus lower cumulative fluxes (<1 ug U/gram resin), which caused the PFM to have areas of localized concentration of uranium. Resin homogenization and larger volume extractions yield reproducible results for all levels of uranium fluxes. Although PFM design can be improved to measure flux and groundwater flow direction, the current methodology can be applied to uranium transport studies. PMID:21798572

  9. Ion Mobility Spectrometry-Hydrogen Deuterium Exchange Mass Spectrometry of Anions: Part 3. Estimating Surface Area Exposure by Deuterium Uptake.

    PubMed

    Khakinejad, Mahdiar; Kondalaji, Samaneh Ghassabi; Donohoe, Gregory C; Valentine, Stephen J

    2016-03-01

    Gas-phase hydrogen deuterium exchange (HDX), collision cross section (CCS) measurement, and molecular dynamics simulation (MDS) techniques were utilized to develop and compare three methods for estimating the relative surface area exposure of separate peptide chains within bovine insulin ions. Electrosprayed [M - 3H](3-) and [M - 5H](5-) insulin ions produced a single conformer type with respective collision cross sections of 528 ± 5 Å(2) and 808 ± 2 Å(2). [M - 4H](4-) ions were comprised of more compact (Ω = 676 ± 3 Å(2)) and diffuse (i.e., more elongated, Ω = 779 ± 3 Å(2)) ion conformer types. Ions were subjected to HDX in the drift tube using D2O as the reagent gas. Collision-induced dissociation was used to fragment mobility-selected, isotopically labeled [M - 4H](4-) and [M - 5H](5-) ions into the protein subchains. Deuterium uptake levels of each chain can be explained by limited inter-chain isotopic scrambling upon collisional activation. Using nominal ion structures from MDS and a hydrogen accessibility model, the deuterium uptake for each chain was correlated to its exposed surface area. In separate experiments, the per-residue deuterium content for the protonated and deprotonated ions of the synthetic peptide KKDDDDDIIKIIK were compared. The differences in deuterium content indicated the regional HDX accessibility for cations versus anions. Using ions of similar conformational type, this comparison highlights the complementary nature of HDX data obtained from positive- and negative-ion analysis. PMID:26620531

  10. Assay for inorganic pyrophosphate in chondrocyte culture using anion-exchange high-performance liquid chromatography and radioactive orthophosphate labeling

    SciTech Connect

    Prins, A.P.; Kiljan, E.; v.d. Stadt, R.J.; v.d. Korst, J.K.

    1986-02-01

    A method is described for determination of inorganic pyrophosphate (PPi) in cell culture medium and in rabbit articular chondrocytes grown in the presence of radioactive orthophosphate (/sup 32/Pi). Intra- and extracellular /sup 32/PPi formed was measured using high-performance liquid chromatographic (HPLC) separation of the PPi from orthophosphate (Pi) and other phosphate-containing compounds. The chromatographic separation on a weak anion-exchange column is based on the extent to which various phosphate compounds form complexes with Mg2+ at low pH and the rate at which such formation occurs. These complexes are eluted more readily than the uncomplexed compounds. Best results were obtained using a simultaneous gradient of Mg2+ ions and ionic strength. In this case separation of small amounts of PPi from a large excess of Pi was possible without prior removal of Pi or extraction of the PPi fraction. The assay is also useful for measurement of inorganic pyrophosphatase activity. The sensitivity of the assay depends on the specific activity of the added /sup 32/Pi and on the culture conditions, but is comparable with the most sensitive of the enzymatic assays. Sample preparation, particularly deproteinization, proved to be of importance. The losses of PPi which occur during procedures of this sort due to hydrolysis and coprecipitation were quantitated.

  11. Two-dimensional NMR spectroscopy reveals cation-triggered backbone degradation in polysulfone-based anion exchange membranes.

    PubMed

    Arges, Christopher G; Ramani, Vijay

    2013-02-12

    Anion exchange membranes (AEMs) find widespread applications as an electrolyte and/or electrode binder in fuel cells, electrodialysis stacks, flow and metal-air batteries, and electrolyzers. AEMs exhibit poor stability in alkaline media; their degradation is induced by the hydroxide ion, a potent nucleophile. We have used 2D NMR techniques to investigate polymer backbone stability (as opposed to cation stability) of the AEM in alkaline media. We report the mechanism behind a peculiar, often-observed phenomenon, wherein a demonstrably stable polysulfone backbone degrades rapidly in alkaline solutions upon derivatization with alkaline stable fixed cation groups. Using COSY and heteronuclear multiple quantum correlation spectroscopy (2D NMR), we unequivocally demonstrate that the added cation group triggers degradation of the polymer backbone in alkaline via quaternary carbon hydrolysis and ether hydrolysis, leading to rapid failure. This finding challenges the existing perception that having a stable cation moiety is sufficient to yield a stable AEM and emphasizes the importance of the often ignored issue of backbone stability. PMID:23335629

  12. Ion Mobility Spectrometry-Hydrogen Deuterium Exchange Mass Spectrometry of Anions: Part 3. Estimating Surface Area Exposure by Deuterium Uptake

    NASA Astrophysics Data System (ADS)

    Khakinejad, Mahdiar; Ghassabi Kondalaji, Samaneh; Donohoe, Gregory C.; Valentine, Stephen J.

    2016-03-01

    Gas-phase hydrogen deuterium exchange (HDX), collision cross section (CCS) measurement, and molecular dynamics simulation (MDS) techniques were utilized to develop and compare three methods for estimating the relative surface area exposure of separate peptide chains within bovine insulin ions. Electrosprayed [M - 3H]3- and [M - 5H]5- insulin ions produced a single conformer type with respective collision cross sections of 528 ± 5 Å2 and 808 ± 2 Å2. [M - 4H]4- ions were comprised of more compact (Ω = 676 ± 3 Å2) and diffuse (i.e., more elongated, Ω = 779 ± 3 Å2) ion conformer types. Ions were subjected to HDX in the drift tube using D2O as the reagent gas. Collision-induced dissociation was used to fragment mobility-selected, isotopically labeled [M - 4H]4- and [M - 5H]5- ions into the protein subchains. Deuterium uptake levels of each chain can be explained by limited inter-chain isotopic scrambling upon collisional activation. Using nominal ion structures from MDS and a hydrogen accessibility model, the deuterium uptake for each chain was correlated to its exposed surface area. In separate experiments, the per-residue deuterium content for the protonated and deprotonated ions of the synthetic peptide KKDDDDDIIKIIK were compared. The differences in deuterium content indicated the regional HDX accessibility for cations versus anions. Using ions of similar conformational type, this comparison highlights the complementary nature of HDX data obtained from positive- and negative-ion analysis.

  13. Improvement of sugar analysis sensitivity using anion-exchange chromatography-electrospray ionization mass spectrometry with sheath liquid interface.

    PubMed

    Xu, Xian-Bing; Liu, Ding-Bo; Guo, Xiao Ming; Yu, Shu-Juan; Yu, Pei

    2014-10-31

    A novel interface that enables high-performance anion-exchange chromatography (HPAEC) to be coupled with electrospray ionization (ESI) mass spectrometry (MS) is reported. A sheath liquid consisting of 50mM NH4Ac in isopropanol with 0.05% acetic acid, infused at a flow rate of 3μL/min at the tip of the electrospray probe, requires less ESI source cleaning and promotes efficient ionization of mono- and di-carbohydrates. The results suggest that use of a sheath liquid interface rather than a T-joint allows volatile ammonium salts to replace non-volatile metal salts as modifiers for improving sugar ESI signals. The efficient ionization of mono- and di-carbohydrates in the ESI source is affected by the sheath liquid properties such as buffer concentration and type of organic solvent. HPAEC-ESI-MS was used for the analysis of monocarbohydrates in pectins, particularly co-eluted sugars, and the performance was evaluated. Addition of a make-up solution through the sheath liquid interface proved to be an efficient tool for enhancing the intensities of sugars analyzed using HPAEC-ESI-MS. PMID:25246101

  14. A pilot-scale evaluation of magnetic ion exchange treatment for removal of natural organic material and inorganic anions.

    PubMed

    Boyer, Treavor H; Singer, Philip C

    2006-08-01

    The objective of this research was to evaluate a magnetic ion exchange process (MIEX) for the removal of natural organic material (NOM) and bromide on a continuous-flow pilot-scale basis under different operating conditions and raw water characteristics. The most important operating variable was the effective resin dose (ERD), which is the product of the steady-state resin concentration in the contactor and the regeneration ratio. The raw water employed in this study had a moderate concentration of ultraviolet (UV)-absorbing substances and dissolved organic carbon (DOC), and a low turbidity, alkalinity, and concentration of competing anionic species. Experiments were conducted using the ambient raw water and raw water spiked with bromide, chloride, and sulfate. Substantial removal of UV-absorbing substances and DOC was achieved at ERDs as low as 0.16mL/L. Moderate bromide removal was achieved, depending on the ERD. Increasing the sulfate concentration resulted in decreased removal of UV-absorbing substances, DOC, and bromide. Consistent results were observed between the continuous-flow pilot plant tests and batch equilibrium studies. PMID:16844182

  15. Dissolved organic matter removal using magnetic anion exchange resin treatment on biological effluent of textile dyeing wastewater.

    PubMed

    Fan, Jun; Li, Haibo; Shuang, Chendong; Li, Wentao; Li, Aimin

    2014-08-01

    This study investigated the removal of dissolved organic matter (DOM) from real dyeing bio-treatment effluents (DBEs) with the use of a novel magnetic anion exchange resin (NDMP). DOMs in two typical DBEs were fractionized using DAX-8/XAD-4 resin and ultrafiltration membranes. The hydrophilic fractions and the low molecular weight (MW) (<3kDa) DOM fractions constituted a major portion (>50%) of DOMs for the two effluents. The hydrophilic and low MW fractions of both effluents were the greatest contributors of specific UV254 absorbance (SUVA254), and the SUVA254 of DOM fractions decreased with hydrophobicity and MW. Two DBEs exhibited acute and chronic biotoxicities. Both acute and chronic toxicities of DOM fractions increased linearly with the increase of SUVA254 value. Kinetics of dissolved organic carbon (DOC) removal via NDMP treatment was performed by comparing it with that of particle active carbon (PAC). Results indicated that the removal of DOC from DBEs via NDMP was 60%, whereas DOC removals by PAC were lower than 15%. Acidic organics could be significantly removed with the use of NDMP. DOM with large MW in DBE could be removed significantly by using the same means. Removal efficiency of NDMP for DOM decreased with the decrease of MW. Compared with PAC, NDMP could significantly reduce the acute and chronic bio-toxicities of DBEs. NaCl/NaOH mixture regenerants, with selected concentrations of 10% NaCl (m/m)/1% NaOH (m/m), could improve desorption efficiency. PMID:25108712

  16. Arsenic(V) removal from aqueous solutions using an anion exchanger derived from coconut coir pith and its recovery.

    PubMed

    Anirudhan, T S; Unnithan, Maya R

    2007-01-01

    The performance of a new anion exchanger (AE) prepared from coconut coir pith (CP), for the removal of arsenic(V) [As(V)] from aqueous solutions was evaluated in this study. The adsorbent (CP-AE) carrying dimethylaminohydroxypropyl weak base functional group was synthesized by the reaction of CP with epichlorohydrin and dimethylamine followed by treatment of hydrochloric acid. IR spectroscopy results confirm the presence of -NH(+)(CH(3))(2)Cl(-) group in the adsorbent. XRD studies confirm the decrease of crystallinity in CP-AE compared to CP, and it favours the protrusion of the functional group into the aqueous medium. Batch experiments were conducted to examine the efficiency of the adsorbent on As(V) removal. Maximum removal of 99.2% was obtained for an initial concentration of 1 mgl(-1) As(V) at pH 7.0 and an adsorbent dose of 2 gl(-1). The kinetics of sorption of As(V) onto CP-AE was described using the pseudo-second-order model. The equilibrium isotherms were determined for different temperatures and the results were analysed using the Langmuir equation. The temperature dependence indicates an exothermic process. Utility of the adsorbent was tested by removing As(V) from simulated groundwater. Regeneration studies were performed using 0.1N HCl. Batch adsorption-desorption studies illustrate that CP-AE could be used to remove As(V) from ground water and other industrial effluents. PMID:16824580

  17. The oxidative degradation of polystyrene resins on the removal of Cr(VI) from wastewater by anion exchange.

    PubMed

    Xiao, Ke; Xu, Fuyuan; Jiang, Linhua; Dan, Zhigang; Duan, Ning

    2016-08-01

    Cr(VI) is a powerful oxidant and is capable of oxidizing most of the organic materials. Therefore, it is possible for Cr(VI) to oxidize the polymeric resins and change the sorption properties of the resins on the removal of Cr(VI) from wastewater by anion exchange. In this study, three polystyrene resins (D201, D202, and D301) with different functional groups (-N(+)(CH3)3, -N(+)(CH3)2(C2H4OH), and N(CH3)2) were assessed on oxidation stability for Cr(VI) removal from wastewater in fixed-bed column experiments. After a 10-cycle operation, due to the oxidation of the resin, the sorption capacity of D201, D202, and D301 resins decreased by 23.5, 29.3, and 17.3%, when approximately 20-34%, 31-50%, and 18-30% of Cr(VI) was reduced to Cr(III) during each cycle respectively. The results of the Fourier transform infrared spectroscopy (FT-IR) showed that both the cleavage of CN and the formation of CO bonds occurred on the polystyrene resins during the Cr(VI) removal process. The resin simulation experiments further validated the oxidation of CC and CN bonds connected with phenethyl groups. Based upon the results from column operations and the resin simulated experiments, the oxidation mechanism of the polystyrene resin was proposed. PMID:27183334

  18. Size exclusion and anion exchange high performance liquid chromatography for characterizing metals bound to marine dissolved organic matter.

    PubMed

    García-Otero, Natalia; Bermejo-Barrera, Pilar; Moreda-Piñeiro, Antonio

    2013-01-14

    Size exclusion chromatography (SEC) followed by anion exchange chromatography (AEC) hyphenated with inductively coupled plasma-mass spectrometry (ICP-MS) was applied for fractionating metals bound to marine dissolved organic matter (DOM). Surface seawater samples (100 L) were subjected to tangential flow ultrafiltration (10,000 Da cut off) for isolating and pre-concentrating dissolved large molecules. The isolated fraction (retentate) consisted of 1L, which was further freeze-dried and re-dissolved to 250 mL with ultrapure water. After HI Trap desalting of the re-dissolved retentate, SEC with UV detection showed marine DOM ranging from 6.5 kDa (lower than the permeable volume of the SEC column) to 16 kDa. A further characterization of this fraction by AEC with UV detection revealed the existence of four groups of macromolecules exhibiting retention times of 2.3, 2.8, 4.5 and 14.0 min. AEC hyphenated with ICP-MS showed the presence of strontium and zinc in the first AE fraction isolated from the SEC fraction; while manganese was found to be bound to the second AE fraction. Cobalt was found to be bound to molecules comprising the third AE fraction. PMID:23265737

  19. Characterization of pore structure of a strong anion-exchange membrane adsorbent under different buffer and salt concentration conditions.

    PubMed

    Tatárová, Ivana; Fáber, René; Denoyel, Renaud; Polakovic, Milan

    2009-02-01

    The quantitative characterization of pore structure of Sartobind Q, a strongly basic membrane anion exchanger that is formed by cross-linked cellulose support and a hydrogel layer on its pore surface, was made combining the results obtained by several experimental techniques: liquid impregnation, batch size-exclusion, inverse size-exclusion chromatography, and permeability. Mercury intrusion and nitrogen sorption porosimetry were carried out for a dry cellulose support membrane in order to get additional information for building a model of the bimodal pore structure. The model incorporated the distribution of the total pore volume between transport and gel-layer pores and the partitioning of solutes of different molecular weights was expressed through the cylindrical pore model for the transport pores and random plane model for the gel layer. The effect of composition of liquid phase on the pore structure was investigated in redistilled water, phosphate and Tris-HCl buffers containing up to 1M NaCl. Evident differences in the bimodal pore structure were observed here when both the specific volume and size of the hydrogel layer pores significantly decreased with the ionic strength of liquid phase. PMID:19117574

  20. Continuous biodiesel production in a fixed bed reactor packed with anion-exchange resin as heterogeneous catalyst.

    PubMed

    Ren, Yanbiao; He, Benqiao; Yan, Feng; Wang, Hong; Cheng, Yu; Lin, Ligang; Feng, Yaohui; Li, Jianxin

    2012-06-01

    A continuous biodiesel production from the transesterification of soybean oil with methanol was investigated in a fixed bed reactor packed with D261 anion-exchange resin as a heterogeneous catalyst. The conversion to biodiesel achieved 95.2% within a residence time 56 min under the conditions: reaction temperature of 323.15K, n-hexane/soybean oil weight rate of 0.5, methanol/soybean oil molar ratio of 9:1 and feed flow rate of 1.2 ml/min. The resin can be regenerated in-situ and restored to the original activity to achieve continuous production after the resin deactivation. The product obtained was mainly composed of methyl esters. No glycerol in the product was detected due to the resin adsorbing glycerol in the fixed bed, which solved the issue of glycerol separation from biodiesel. It is believed that the fixed bed reactor with D261 has a potential commercial application in the transesterification of triglyceride. PMID:22138595

  1. Anion Exchange HPLC Isolation of High-Density Lipoprotein (HDL) and On-Line Estimation of Proinflammatory HDL

    PubMed Central

    Ji, Xiang; Xu, Hao; Zhang, Hao; Hillery, Cheryl A.; Gao, Hai-qing; Pritchard, Kirkwood A.

    2014-01-01

    Proinflammatory high-density lipoprotein (p-HDL) is a biomarker of cardiovascular disease. Sickle cell disease (SCD) is characterized by chronic states of oxidative stress that many consider to play a role in forming p-HDL. To measure p-HDL, apolipoprotein (apo) B containing lipoproteins are precipitated. Supernatant HDL is incubated with an oxidant/LDL or an oxidant alone and rates of HDL oxidation monitored with dichlorofluorescein (DCFH). Although apoB precipitation is convenient for isolating HDL, the resulting supernatant matrix likely influences HDL oxidation. To determine effects of supernatants on p-HDL measurements we purified HDL from plasma from SCD subjects by anion exchange (AE) chromatography, determined its rate of oxidation relative to supernatant HDL. SCD decreased total cholesterol but not triglycerides or HDL and increased cell-free (cf) hemoglobin (Hb) and xanthine oxidase (XO). HDL isolated by AE-HPLC had lower p-HDL levels than HDL in supernatants after apoB precipitation. XO+xanthine (X) and cf Hb accelerated purified HDL oxidation. Although the plate and AE-HPLC assays both showed p-HDL directly correlated with cf-Hb in SCD plasma, the plate assay yielded p-HDL data that was influenced more by cf-Hb than AE-HPLC generated p-HDL data. The AE-HPLC p-HDL assay reduces the influence of the supernatants and shows that SCD increases p-HDL. PMID:24609013

  2. Carbon supported Ag nanoparticles as high performance cathode catalyst for H2/O2 anion exchange membrane fuel cell

    PubMed Central

    Xin, Le; Zhang, Zhiyong; Wang, Zhichao; Qi, Ji; Li, Wenzhen

    2013-01-01

    A solution phase-based nanocapsule method was successfully developed to synthesize non-platinum metal catalyst—carbon supported Ag nanoparticles (Ag/C). XRD patterns and TEM image show Ag nanoparticles with a small average size (5.4 nm) and narrow size distribution (2–9 nm) are uniformly dispersed on the carbon black Vulcan XC-72 support. The intrinsic activity and pathway of oxygen reduction reaction (ORR) on the Ag/C and commercial Pt/C were investigated using rotating ring disk electrode (RRDE) tests at room temperature. The results confirmed that the 4-electron pathway of ORR proceeds on small Ag nanoparticles, and showed comparable ORR activities on the self-prepared Ag/C and a commercial Pt/C. A single H2-O2 anion exchange membrane fuel cell (AEMFC) with the Ag/C cathode catalyst exhibited an open circuit potential of 0.98 V and a peak power density of 190 mW/cm2 at 80°C. PMID:24790944

  3. Comparison of displacement versus gradient mode for separation of a complex protein mixture by anion-exchange chromatography.

    PubMed

    Ahrends, Robert; Lichtner, Björn; Buck, Friedrich; Hildebrand, Diana; Kotasinska, Marta; Kohlbacher, Oliver; Kwiatkowski, Marcel; Wagner, Moritz; Trusch, Maria; Schlüter, Hartmut

    2012-07-15

    Liquid chromatography is often the method of choice for the analysis of proteins in their native state. Nevertheless compared to two-dimensional electrophoresis, the resolution of common chromatographic techniques is low. Liquid chromatography in the displacement mode has previously been shown to offer higher resolution and to elute proteins in the high concentrations. In this study we compared to what extend displacement mode was a suitable alternative to gradient mode for the separation of a complex protein mixture using anion-exchange displacement chromatography and if it is therefore helpful for proteomic investigations. Hence we analyzed the qualitative protein composition of each fraction by tryptic digestion of the proteins, analysis of the tryptic peptides by liquid chromatography coupled to mass spectrometry followed by data base analysis and by measuring the elution profiles of 22 selected proteins with selected reaction monitoring mass spectrometry. In the fractions of displacement mode a significantly higher number of identified proteins (51 versus 16) was yielded in comparison to gradient mode. The resolution of displacement chromatography was slightly lower than of gradient chromatography for many but not for all proteins. The selectivities of displacement mode and gradient mode are very different. In conclusion displacement chromatography is a well suited alternative for top-down proteomic approaches which start with separating intact proteins first prior to mass spectrometric analysis of intact or digested proteins. The significant orthogonality of both modes may be used in the future for combining them in multidimensional fractionation procedures. PMID:22727752

  4. Quantification of genetically modified soya using strong anion exchange chromatography and time-of-flight mass spectrometry.

    PubMed

    Chang, Po-Chih; Reddy, P Muralidhar; Ho, Yen-Peng

    2014-09-01

    Stable-isotope dimethyl labeling was applied to the quantification of genetically modified (GM) soya. The herbicide-resistant gene-related protein 5-enolpyruvylshikimate-3-phosphate synthase (CP4 EPSPS) was labeled using a dimethyl labeling reagent, formaldehyde-H2 or -D2. The identification and quantification of CP4 EPSPS was performed using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The CP4 EPSPS protein was separated from high abundance proteins using strong anion exchange chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Then, the tryptic peptides from the samples and reference were labeled with formaldehyde-H2 and formaldehyde-D2, respectively. The two labeled pools were mixed and analyzed using MALDI-MS. The data showed a good correlation between the peak ratio of the H- and D-labeled peptides and the GM soya percentages at 0.5, 1, 3, and 5 %, with R (2) of 0.99. The labeling reagents are readily available. The labeling experiments and the detection procedures are simple. The approach is useful for the quantification of GM soya at a level as low as 0.5 %. PMID:24969465

  5. Two-dimensional NMR spectroscopy reveals cation-triggered backbone degradation in polysulfone-based anion exchange membranes

    PubMed Central

    Arges, Christopher G.; Ramani, Vijay

    2013-01-01

    Anion exchange membranes (AEMs) find widespread applications as an electrolyte and/or electrode binder in fuel cells, electrodialysis stacks, flow and metal-air batteries, and electrolyzers. AEMs exhibit poor stability in alkaline media; their degradation is induced by the hydroxide ion, a potent nucleophile. We have used 2D NMR techniques to investigate polymer backbone stability (as opposed to cation stability) of the AEM in alkaline media. We report the mechanism behind a peculiar, often-observed phenomenon, wherein a demonstrably stable polysulfone backbone degrades rapidly in alkaline solutions upon derivatization with alkaline stable fixed cation groups. Using COSY and heteronuclear multiple quantum correlation spectroscopy (2D NMR), we unequivocally demonstrate that the added cation group triggers degradation of the polymer backbone in alkaline via quaternary carbon hydrolysis and ether hydrolysis, leading to rapid failure. This finding challenges the existing perception that having a stable cation moiety is sufficient to yield a stable AEM and emphasizes the importance of the often ignored issue of backbone stability. PMID:23335629

  6. Characterization of At- species in simple and biological media by high performance anion exchange chromatography coupled to gamma detector.

    PubMed

    Sabatié-Gogova, A; Champion, J; Huclier, S; Michel, N; Pottier, F; Galland, N; Asfari, Z; Chérel, M; Montavon, G

    2012-04-01

    Astatine is a rare radioelement belonging to the halogen group. Considering the trace amounts of astatine produced in cyclotrons, its chemistry cannot be evaluated by spectroscopic tools. Analytical tools, provided that they are coupled with a radioactive detection system, may be an alternative way to study its chemistry. In this research work, high performance anion exchange chromatography (HPAEC) coupled to a gamma detector (γ) was used to evaluate astatine species under reducing conditions. Also, to strengthen the reliability of the experiments, a quantitative analysis using a reactive transport model has been done. The results confirm the existence of one species bearing one negative charge in the pH range 2-7.5. With respect to the other halogens, its behavior indicates the existence of negative ion, astatide At(-). The methodology was successfully applied to the speciation of the astatine in human serum. Under fixed experimental conditions (pH 7.4-7.5 and redox potential of 250 mV) astatine exists mainly as astatide At(-) and does not interact with the major serum components. Also, the method might be useful for the in vitro stability assessment of (211)At-labeled molecules potentially applicable in nuclear medicine. PMID:22405318

  7. Oxygen evolution reaction characteristics of synthetic nickel-cobalt-oxide electrodes for alkaline anion-exchange membrane water electrolysis

    NASA Astrophysics Data System (ADS)

    Koo, Tae Woo; Park, ChanSu; Kim, Yang Do; Lee, Dooyong; Park, Sungkyun; Lee, Jae Ho; Choi, Sung Mook; Choi, Chul Young

    2015-11-01

    A polymer electrolyte membrane water electrolysis system can produce high-purity hydrogen gases in a highly efficient manner. However, the level of hydrogen gas production is still small. In addition, noble-metal catalysts for the reaction in acidic environments, as well as an additional drying step to remove water contained in the hydrogen, are required. Therefore, water electrolysis system with high efficiency and lower cost, an alkaline anion-exchange membrane system that can produce high-purity hydrogen without a noble-metal catalyst, is needed. Nano-size NiCo2O4 powders were prepared by using a sol-gel method to achieve an efficient and economical water electrolysis system. When the powder was calcined at 450 °C, the crystallinity and the cyclic voltammogram measurement showed the best values. In addition, the 15-wt.% polytetrafluoroethylene mixed NiCo2O4 powders exhibited the largest cyclic voltammetry active area and the highest oxygen evolution reaction activity with the appropriate stability.

  8. Quaternized adamantane-containing poly(aryl ether ketone) anion exchange membranes for vanadium redox flow battery applications

    NASA Astrophysics Data System (ADS)

    Zhang, Bengui; Zhang, Shouhai; Weng, Zhihuan; Wang, Guosheng; Zhang, Enlei; Yu, Ping; Chen, Xiaomeng; Wang, Xinwei

    2016-09-01

    Quaternized adamantane-containing poly(aryl ether ketone) anion exchange membranes (QADMPEK) are prepared and investigated for vanadium redox flow batteries (VRFB) application. The bulky, rigid and highly hydrophobic adamantane segment incorporated into the backbone of membrane material makes QADMPEK membranes have low water uptake and swelling ratio, and the as-prepared membranes display significantly lower permeability of vanadium ions than that of Nafion117 membrane. As a consequence, the VRFB cell with QADMPEK-3 membrane shows higher coulombic efficiency (99.4%) and energy efficiency (84.0%) than those for Nafion117 membrane (95.2% and 80.5%, respectively) at the current density of 80 mA cm-2. Furthermore, at a much higher current density of 140 mA cm-2, QADMPEK membrane still exhibits better coulombic efficiency and energy efficiency than Nafion117 membrane (coulombic efficiency 99.2% vs 96.5% and energy efficiency 76.0% vs 74.0%). Moreover, QADMPEK membranes show high stability in in-situ VRFB cycle test and ex-situ oxidation stability test. These results indicate that QADMPEK membranes are good candidates for VRFB applications.

  9. Rapid isolation of plutonium in environmental solid samples using sequential injection anion exchange chromatography followed by detection with inductively coupled plasma mass spectrometry.

    PubMed

    Qiao, Jixin; Hou, Xiaolin; Roos, Per; Miró, Manuel

    2011-01-31

    This paper reports an automated analytical method for rapid determination of plutonium isotopes ((239)Pu and (240)Pu) in environmental solid extracts. Anion exchange chromatographic columns were incorporated in a sequential injection (SI) system to undertake the automated separation of plutonium from matrix and interfering elements. The analytical results most distinctly demonstrated that the crosslinkage of the anion exchanger is a key parameter controlling the separation efficiency. AG 1-×4 type resin was selected as the most suitable sorbent material for analyte separation. Investigation of column size effect upon the separation efficiency revealed that small-sized (2 mL) columns sufficed to handle up to 50 g of environmental soil samples. Under the optimum conditions, chemical yields of plutonium exceeded 90% and the decontamination factors for uranium, thorium and lead ranged from 10(3) to 10(4). The determination of plutonium isotopes in three standard/certified reference materials (IAEA-375 soil, IAEA-135 sediment and NIST-4359 seaweed) and two reference samples (Irish Sea sediment and Danish soil) revealed a good agreement with reference/certified values. The SI column-separation method is straightforward and less labor intensive as compared with batch-wise anion exchange chromatographic procedures. Besides, the automated method features low consumption of ion-exchanger and reagents for column washing and elution, with the consequent decrease in the generation of acidic waste, thus bearing green chemical credentials. PMID:21168558

  10. Anion Exchange Behavior Of Ti, Zr, Hf, Nb And Ta As Homologues Of Rf And Db In Mixed HF--Acetone Solutions

    SciTech Connect

    Aksenov, N. V.; Bozhikov, G. A.; Starodub, G. Ya.; Dmitriev, S. N.; Filosofov, D. V.; Sun Jin, Jon; Radchenko, V. I.; Lebedev, N. A.; Novgorodov, A. F.

    2010-04-30

    We studied in detail the sorption behavior of Ti, Zr, Hf, Nb and Ta on AG 1 anion exchange resin in HF-acetone mixed solutions as a function of organic cosolvent and acid concentrations. Anion exchange behavior was found to be strongly acetone concentration dependent. The distribution coefficients of Ti, Zr, Hf and Nb increased and those of Ta decreased with increasing content of acetone in HF solutions. With increasing HF concentration anion exchange equilibrium analysis indicated the formation of fluoride complexes of group 4 elements with charge-3 and Ta---2. For Nb the slope of-2 increased up to-5. Optimal conditions for separation of the elements using AIX chromatography were found. Group 4 elements formed MF{sub 7}{sup 3-} (M = Ti, Zr, Hf) complexes whose sorption decreased Ti>Hf>Zr in reverse order of complex stability. This fact is of particular interest for studying ion exchange behavior of Rf compared to Ti. The advantages of studying chemical properties of Rf and Db in aqueous HF solutions mixed with organic solvents are briefly discussed.

  11. Pressure drop characteristics of cryogenic mixed refrigerant at macro and micro channel heat exchangers

    NASA Astrophysics Data System (ADS)

    Baek, Seungwhan; Jeong, Sangkwon; Hwang, Gyuwan

    2012-12-01

    Mixed Refrigerant-Joule Thomson (MR-JT) refrigerators are widely used in various kinds of cryogenic systems these days. The temperature glide effect is one of the major features of using mixed refrigerants since a recuperative heat exchanger in a MR-JT refrigerator is utilized for mostly two-phase flow. Although a pressure drop estimation for a multi-phase and multi-component fluid in the cryogenic temperature range is necessarily required in MR-JT refrigerator heat exchanger designs, it has been rarely discussed so far. In this paper, macro heat exchangers and micro heat exchangers are compared in order to investigate the pressure drop characteristics in the experimental MR-JT refrigerator operation. The tube in tube heat exchanger (TTHE) is a well-known macro-channel heat exchanger in MR-JT refrigeration. Printed Circuit Heat Exchangers (PCHEs) have been developed as a compact heat exchanger with micro size channels. Several two-phase pressure drop correlations are examined to discuss the experimental pressure measurement results. The result of this paper shows that cryogenic mixed refrigerant pressure drop can be estimated with conventional two-phase pressure drop correlations if an appropriate flow pattern is identified.

  12. Non-pore lining amino acid side chains influence anion selectivity of the human CFTR Cl− channel expressed in mammalian cell lines

    PubMed Central

    Linsdell, Paul; Zheng, Shu-Xian; Hanrahan, John W

    1998-01-01

    The effects of individually mutating two adjacent threonine residues in the sixth membrane-spanning region (TM6) of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl− channel on permeation properties were examined using patch clamp recording from mammalian cell lines stably expressing human CFTR.A number of mutations of T338 significantly affected the permeation properties of the channel. Increases and decreases in single channel conductance were observed for different mutants. Anion selectivity was strongly affected, with no two channel variants sharing the same selectivity sequence. Several mutations led to strong inward rectification of the macroscopic current-voltage relationship. The effects of these mutations on permeation properties were correlated with the size of the amino acid side chain substituted, rather than its chemical nature.Most mutations of T339 resulted in a lack of functional channel expression and apparent misprocessing of the protein. One mutant, T339V, was characterized in detail; its permeation properties were significantly altered, although these effects were not as strong as for T338 mutations.These results suggest an important role for T338 in controlling the permeation properties of the CFTR Cl− channel. It is suggested that mutation of this residue alters the interaction between permeating anions and the channel pore via an indirect effect on the orientation of the TM6 helix. PMID:9729613

  13. Non-pore lining amino acid side chains influence anion selectivity of the human CFTR Cl- channel expressed in mammalian cell lines.

    PubMed

    Linsdell, P; Zheng, S X; Hanrahan, J W

    1998-10-01

    1. The effects of individually mutating two adjacent threonine residues in the sixth membrane-spanning region (TM6) of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel on permeation properties were examined using patch clamp recording from mammalian cell lines stably expressing human CFTR. 2. A number of mutations of T338 significantly affected the permeation properties of the channel. Increases and decreases in single channel conductance were observed for different mutants. Anion selectivity was strongly affected, with no two channel variants sharing the same selectivity sequence. Several mutations led to strong inward rectification of the macroscopic current-voltage relationship. The effects of these mutations on permeation properties were correlated with the size of the amino acid side chain substituted, rather than its chemical nature. 3. Most mutations of T339 resulted in a lack of functional channel expression and apparent misprocessing of the protein. One mutant, T339V, was characterized in detail; its permeation properties were significantly altered, although these effects were not as strong as for T338 mutations. 4. These results suggest an important role for T338 in controlling the permeation properties of the CFTR Cl- channel. It is suggested that mutation of this residue alters the interaction between permeating anions and the channel pore via an indirect effect on the orientation of the TM6 helix. PMID:9729613

  14. Characterization of a mini-channel heat exchanger for a heat pump system

    NASA Astrophysics Data System (ADS)

    Arteconi, A.; Giuliani, G.; Tartuferi, M.; Polonara, F.

    2014-04-01

    In this paper a mini-channel aluminum heat exchanger used in a reversible heat pump is presented. Mini-channel finned heat exchangers are getting more and more interest for refrigeration systems, especially when compactness and low refrigerant charge are desired. Purpose of this paper was to characterize the mini-channel heat exchanger used as evaporator in terms of heat transfer performance and to study the refrigerant distribution in the manifold. The heat exchanger characterization was performed experimentally by means of a test rig built up for this purpose. It is composed of an air-to-air heat pump, air channels for the external and internal air circulation arranged in a closed loop, measurement sensors and an acquisition system. The overall heat transfer capacity was assessed. Moreover, in order to characterize the flow field of the refrigerant in the manifold of the heat exchanger, a numerical investigation of the fluid flow by means of CFD was performed. It was meant to evaluate the goodness of the present design and to identify possible solutions for the future improvement of the manifold design.

  15. Exchanges of sediment between the flood plain and channel of the Amazon River in Brazil

    USGS Publications Warehouse

    Dunne, T.; Mertes, L.A.K.; Meade, R.H.; Richey, J.E.; Forsberg, B.R.

    1998-01-01

    Sediment transport through the Brazilian sector of the Amazon River valley, a distance of 2010 km, involves exchanges between the channel and the flood plain that in each direction exceed the annual flux of sediment out of the river at O??bidos (???1200 Mt yr-1). The exchanges occur through bank erosion, bar deposition, settling from diffuse overbank flow, and sedimentation in flood-plain channels. We estimated the magnitude of these exchanges for each of 10 reaches of the valley, and combined them with calculations of sediment transport into and out of the reaches based on sediment sampling and flow records to define a sediment budget for each reach. Residuals in the sediment budget of a reach include errors of estimation and erosion or deposition within the channel. The annual supply of sediment entering the channel from bank erosion was estimated to average 1570 Mt yr-1 (1.3 ?? the O??bidos flux) and the amount transferred from channel transport to the bars (380 Mt yr-1) and the flood plain (460 Mt yr-1 in channelized flow; 1230 Mt yr-1 in diffuse overbank flow) totaled 2070 Mt yr-1 (1.7 ?? the O??bidos flux). Thus, deposition on the bars and flood plain exceeded bank erosion by 500 Mt yr-1 over a 10-16 yr period. Sampling and calculation of sediment loads in the channel indicate a net accumulation in the valley floor of approximately 200 Mt yr-1 over 16 yr, crudely validating the process-based calculations of the sediment budget, which in turn illuminate the physical controls on each exchange process. Another 300-400 Mt yr-1 are deposited in a delta plain downstream of O??bidos. The components of the sediment budget reflect hydrologie characteristics of the valley floor and geomorphic characteristics of the channel and flood plain, which in turn are influenced by tectonic features of the Amazon structural trough.

  16. Direct aqueous determination of glyphosate and related compounds by liquid chromatography/tandem mass spectrometry using reversed-phase and weak anion-exchange mixed-mode column.

    PubMed

    Hao, Chunyan; Morse, David; Morra, Franca; Zhao, Xiaoming; Yang, Paul; Nunn, Brian

    2011-08-19

    Analysis of the broad-spectrum herbicide glyphosate and its related compounds is quite challenging. Tedious and time-consuming derivatization is often required for these substances due to their high polarity, high water solubility, low volatility and molecular structure which lacks either a chromophore or fluorophore. A novel liquid chromatography/tandem mass spectrometry (LC/MS-MS) method has been developed for the determination of glyphosate, aminomethylphosphonic acid (AMPA) and glufosinate using a reversed-phase and weak anion-exchange mixed-mode Acclaim® WAX-1 column. Aqueous environmental samples are directly injected and analyzed in 12 min with no sample concentration or derivatization steps. Two multiple reaction monitoring (MRM) channels are monitored in the method for each target compound to achieve true positive identification, and ¹³C, ¹⁵N-glyphosate is used as an internal standard to carry out isotope dilution mass spectrometric (IDMS) measurement for glyphosate. The instrument detection limits (IDLs) for glyphosate, AMPA and glufosinate are 1, 2 and 0.9 μg/L, respectively. Linearity of the detector response with a minimum coefficient of determination (R² value (R² > 0.995) was demonstrated in the range of ∼10 to 10³ μg/L for each analytes. Spiked drinking water, surface water and groundwater samples were analyzed using this method and the average recoveries of analytes in three matrices ranged from 77.0 to 102%, 62.1 to 101%, 66.1 to 93.7% while relative standard deviation ranged from 6.3 to 10.2%, 2.7 to 14.8%, 2.9 to 10.7%, respectively. Factors that may affect method performance, such as metal ions, sample preservation, and storage time, are also discussed. PMID:21752384

  17. The Voltage-dependent Anion Channel 1 Mediates Amyloid β Toxicity and Represents a Potential Target for Alzheimer Disease Therapy.

    PubMed

    Smilansky, Angela; Dangoor, Liron; Nakdimon, Itay; Ben-Hail, Danya; Mizrachi, Dario; Shoshan-Barmatz, Varda

    2015-12-25

    The voltage-dependent anion channel 1 (VDAC1), found in the mitochondrial outer membrane, forms the main interface between mitochondrial and cellular metabolisms, mediates the passage of a variety of molecules across the mitochondrial outer membrane, and is central to mitochondria-mediated apoptosis. VDAC1 is overexpressed in post-mortem brains of Alzheimer disease (AD) patients. The development and progress of AD are associated with mitochondrial dysfunction resulting from the cytotoxic effects of accumulated amyloid β (Aβ). In this study we demonstrate the involvement of VDAC1 and a VDAC1 N-terminal peptide (VDAC1-N-Ter) in Aβ cell penetration and cell death induction. Aβ directly interacted with VDAC1 and VDAC1-N-Ter, as monitored by VDAC1 channel conductance, surface plasmon resonance, and microscale thermophoresis. Preincubated Aβ interacted with bilayer-reconstituted VDAC1 and increased its conductance ∼ 2-fold. Incubation of cells with Aβ resulted in mitochondria-mediated apoptotic cell death. However, the presence of non-cell-penetrating VDAC1-N-Ter peptide prevented Aβ cellular entry and Aβ-induced mitochondria-mediated apoptosis. Likewise, silencing VDAC1 expression by specific siRNA prevented Aβ entry into the cytosol as well as Aβ-induced toxicity. Finally, the mode of Aβ-mediated action involves detachment of mitochondria-bound hexokinase, induction of VDAC1 oligomerization, and cytochrome c release, a sequence of events leading to apoptosis. As such, we suggest that Aβ-mediated toxicity involves mitochondrial and plasma membrane VDAC1, leading to mitochondrial dysfunction and apoptosis induction. The VDAC1-N-Ter peptide targeting Aβ cytotoxicity is thus a potential new therapeutic strategy for AD treatment. PMID:26542804

  18. In self-defence: hexokinase promotes voltage-dependent anion channel closure and prevents mitochondria-mediated apoptotic cell death.

    PubMed Central

    Azoulay-Zohar, Heftsi; Israelson, Adrian; Abu-Hamad, Salah; Shoshan-Barmatz, Varda

    2004-01-01

    In tumour cells, elevated levels of mitochondria-bound isoforms of hexokinase (HK-I and HK-II) result in the evasion of apoptosis, thereby allowing the cells to continue proliferating. The molecular mechanisms by which bound HK promotes cell survival are not yet fully understood. Our studies relying on the purified mitochondrial outer membrane protein VDAC (voltage-dependent anion channel), isolated mitochondria or cells in culture suggested that the anti-apoptotic activity of HK-I occurs via modulation of the mitochondrial phase of apoptosis. In the present paper, a direct interaction of HK-I with bilayer-reconstituted purified VDAC, inducing channel closure, is demonstrated for the first time. Moreover, HK-I prevented the Ca(2+)-dependent opening of the mitochondrial PTP (permeability transition pore) and release of the pro-apoptotic protein cytochrome c. The effects of HK-I on VDAC activity and PTP opening were prevented by the HK reaction product glucose 6-phosphate, a metabolic intermediate in most biosynthetic pathways. Furthermore, glucose 6-phosphate re-opened both the VDAC and the PTP closed by HK-I. The HK-I-mediated effects on VDAC and PTP were not observed using either yeast HK or HK-I lacking the N-terminal hydrophobic peptide responsible for binding to mitochondria, or in the presence of an antibody specific for the N-terminus of HK-I. Finally, HK-I overexpression in leukaemia-derived U-937 or vascular smooth muscle cells protected against staurosporine-induced apoptosis, with a decrease of up to 70% in cell death. These results offer insight into the mechanisms by which bound HK promotes tumour cell survival, and suggests that its overexpression not only ensures supplies of energy and phosphometabolites, but also reflects an anti-apoptotic defence mechanism. PMID:14561215

  19. The mitochondrial voltage-dependent anion channel 1 in tumor cells.

    PubMed

    Shoshan-Barmatz, Varda; Ben-Hail, Danya; Admoni, Lee; Krelin, Yakov; Tripathi, Shambhoo Sharan

    2015-10-01

    VDAC as critical for deciphering how this channel can perform such a variety of roles, all of which are important for cell life and death. Finally, this review will also provide insight into VDAC function in Ca2+ homeostasis, protection against oxidative stress, regulation of apoptosis and involvement in several diseases, as well as its role in the action of different drugs. We will discuss the use of VDAC1-based strategies to attack the altered metabolism and apoptosis of cancer cells. These strategies include specific siRNA able to impair energy and metabolic homeostasis, leading to arrested cancer cell growth and tumor development, as well VDAC1-based peptides that interact with anti-apoptotic proteins to induce apoptosis, thereby overcoming the resistance of cancer cell to chemotherapy. Finally, small molecules targeting VDAC1 can induce apoptosis. VDAC1 can thus be considered as standing at the crossroads between mitochondrial metabolite transport and apoptosis and hence represents an emerging cancer drug target. This article is part of a Special Issue entitled: Membrane channels and transporters in cancers. PMID:25448878

  20. Clinical implication of voltage-dependent anion channel 1 in uterine cervical cancer and its action on cervical cancer cells

    PubMed Central

    Wu, Chih-Hsien; Lin, Yu-Wen; Wu, Tzu-Fan; Ko, Jiunn-Liang; Wang, Po-Hui

    2016-01-01

    Two-dimensional gel electrophoresis and liquid chromatography-tandem mass spectrometry were performed to investigate the influence of human nonmetastatic clone 23 type 1 (nm23-H1), a metastasis-associated gene on proteomic alterations in cancer cells of the uterine cervix. It was validated by RT-PCR and Western blot analysis. The expression of voltage-dependent anion channel 1 (VDAC1) was increased in nm23-H1 gene silenced SiHa or CaSki cervical cancer cells. The clinical implication was shown that cervical cancer tissues with positive VDAC1 immunoreactivity exhibited deep stromal invasion (>10 mm in depth) and large tumor size (> 4 cm in diameter). Cervical cancer patients with positive VDAC1 immunoreactivity displayed higher recurrence and poorer overall survival than those with negative VDAC1. Silencing of VDAC1 reduced cell proliferation and migratory ability. Mitochondrial membrane potential was decreased and reactive oxygen species generation was increased in the VDAC1 gene-silenced cervical cancer cells. Cell cycle progression and autophagy were not changed in VDAC1 silencing cells. The cytotoxicity of cisplatin was significantly enhanced by knockdown of cellular VDAC1 and the compounds that interfere with hexokinase binding to VDAC. Therapeutic strategies may be offered using VDAC1 as a target to reduce cell growth and migration, enhance the synergistic therapeutic efficacy of cisplatin and reduce cisplatin dose-limiting toxicity. PMID:26716410

  1. Characterization and expression analysis of Paralichthys olivaceus voltage-dependent anion channel (VDAC) gene in response to virus infection.

    PubMed

    Lü, Ai-Jun; Dong, Cai-Wen; Du, Chang-Sheng; Zhang, Qi-Ya

    2007-09-01

    Voltage-dependent anion channel (VDAC, also known as mitochondrial porin) is acknowledged to play an important role in stress-induced mammalian apoptosis. In this study, Paralichthys olivaceus VDAC (PoVDAC) gene was identified as a virally induced gene from Scophthalmus Maximus Rhabdovirus (SMRV)-infected flounder embryonic cells (FEC). The full length of PoVDAC cDNA is 1380 bp with an open reading frame of 852 bp encoding a 283 amino acid protein. The deduced PoVDAC contains one alpha-helix, 13 transmembrane beta-strands and one eukaryotic mitochondrial porin signature motif. Constitutive expression of PoVDAC was confirmed in all tested tissues by real-time PCR. Further expression analysis revealed PoVDAC mRNA was upregulated by viral infection. We prepared fish antiserum against recombinant VDAC proteins and detected the PoVDAC in heart lysates from flounder as a 32 kDa band on western blot. Overexpression of PoVDAC in fish cells induced apoptosis. Immunofluoresence localization indicated that the significant distribution changes of PoVDAC have occurred in virus-induced apoptotic cells. This is the first report on the inductive expression of VDAC by viral infection, suggesting that PoVDAC might be mediated flounder antiviral immune response through induction of apoptosis. PMID:17467295

  2. Recent Advances in Solid Catalysts Obtained by Metalloporphyrins Immobilization on Layered Anionic Exchangers: A Short Review and Some New Catalytic Results.

    PubMed

    Nakagaki, Shirley; Mantovani, Karen Mary; Machado, Guilherme Sippel; Castro, Kelly Aparecida Dias de Freitas; Wypych, Fernando

    2016-01-01

    Layered materials are a very interesting class of compounds obtained by stacking of two-dimensional layers along the basal axis. A remarkable property of these materials is their capacity to interact with a variety of chemical species, irrespective of their charge (neutral, cationic or anionic). These species can be grafted onto the surface of the layered materials or intercalated between the layers, to expand or contract the interlayer distance. Metalloporphyrins, which are typically soluble oxidation catalysts, are examples of molecules that can interact with layered materials. This work presents a short review of the studies involving metalloporphyrin immobilization on two different anionic exchangers, Layered Double Hydroxides (LDHs) and Layered Hydroxide Salts (LHSs), published over the past year. After immobilization of anionic porphyrins, the resulting solids behave as reusable catalysts for heterogeneous oxidation processes. Although a large number of publications involving metalloporphyrin immobilization on LDHs exist, only a few papers have dealt with LHSs as supports, so metalloporphyrins immobilized on LHSs represent a new and promising research field. This work also describes new results on an anionic manganese porphyrin (MnP) immobilized on Mg/Al-LDH solids with different nominal Mg/Al molar ratios (2:1, 3:1 and 4:1) and intercalated with different anions (CO₃(2-) or NO₃(-)). The influence of the support composition on the MnP immobilization rates and the catalytic performance of the resulting solid in cyclooctene oxidation reactions will be reported. PMID:26938518

  3. Corynebacterium jeikeium jk0268 Constitutes for the 40 Amino Acid Long PorACj, Which Forms a Homooligomeric and Anion-Selective Cell Wall Channel

    PubMed Central

    Norouzy, Amir; Schulz, Robert; Nau, Werner M.; Kleinekathöfer, Ulrich; Tauch, Andreas; Benz, Roland

    2013-01-01

    Corynebacterium jeikeium, a resident of human skin, is often associated with multidrug resistant nosocomial infections in immunodepressed patients. C. jeikeium K411 belongs to mycolic acid-containing actinomycetes, the mycolata and contains a channel-forming protein as judged from reconstitution experiments with artificial lipid bilayer experiments. The channel-forming protein was present in detergent treated cell walls and in extracts of whole cells using organic solvents. A gene coding for a 40 amino acid long polypeptide possibly responsible for the pore-forming activity was identified in the known genome of C. jeikeium by its similar chromosomal localization to known porH and porA genes of other Corynebacterium strains. The gene jk0268 was expressed in a porin deficient Corynebacterium glutamicum strain. For purification temporarily histidine-tailed or with a GST-tag at the N-terminus, the homogeneous protein caused channel-forming activity with an average conductance of 1.25 nS in 1M KCl identical to the channels formed by the detergent extracts. Zero-current membrane potential measurements of the voltage dependent channel implied selectivity for anions. This preference is according to single-channel analysis caused by some excess of cationic charges located in the channel lumen formed by oligomeric alpha-helical wheels. The channel has a suggested diameter of 1.4 nm as judged from the permeability of different sized hydrated anions using the Renkin correction factor. Surprisingly, the genome of C. jeikeium contained only one gene coding for a cell wall channel of the PorA/PorH type found in other Corynebacterium species. The possible evolutionary relationship between the heterooligomeric channels formed by certain Corynebacterium strains and the homooligomeric pore of C. jeikeium is discussed. PMID:24116064

  4. Comparative investigations of anion-exchange resins of the AM-3 and amberlite IRA-93 type in relati ion to water Treatment

    SciTech Connect

    Davydova, G.N.; Kulyako, N.I.; Znauenskii, Y.P.; Zorina, A.I.

    1985-10-01

    The typical kinetic curves for sorption of HC1 by the anion-exchangers IRA-93 and AM-3-10 are shown. The principal experimental data on all the samples studied are presented and it follows that all the AM-3 samples are somewhat inferior to the kinetic properties of Amberlite IRA-93. It is suggested that for improvement of the kinetic properties of AM-3 resins it is necessary to alter the structure of the micrograins, increasing their permeability.

  5. Anion-exchange high-performance liquid chromatography with post-column detection for the analysis of phytic acid and other inositol phosphates

    NASA Technical Reports Server (NTRS)

    Rounds, M. A.; Nielsen, S. S.; Mitchell, C. A. (Principal Investigator)

    1993-01-01

    The use of gradient anion-exchange HPLC, with a simple post-column detection system, is described for the separation of myo-inositol phosphates, including "phytic acid" (myo-inositol hexaphosphate). Hexa-, penta-, tetra-, tri- and diphosphate members of this homologous series are clearly resolved within 30 min. This method should facilitate analysis and quantitation of "phytic acid" and other inositol phosphates in plant, food, and soil samples.

  6. Differential inhibition of AE1 and AE2 anion exchangers by oxonol dyes and by novel polyaminosterol analogs of the shark antibiotic squalamine.

    PubMed

    Alper, S L; Chernova, M N; Williams, J; Zasloff, M; Law, F Y; Knauf, P A

    1998-01-01

    Oxonol and polyaminosterol drugs were examined as inhibitors of recombinant mouse AE1 and AE2 anion exchangers expressed in Xenopus laevis oocytes and were compared as inhibitors of AE1-mediated anion flux in red cells and in HL-60 cells that express AE2. The oxonols WW-781, diBA(5)C4, and diBA(3)C4 inhibited HL-60 cell Cl-/Cl- exchange with IC50 values from 1 to 7 microM, 100-1000 times less potent than their IC50 values for red cell Cl-/anion exchange. In Xenopus oocytes, diBA(5)C4 inhibited AE1-mediated Cl- efflux several hundred times more potently than that mediated by AE2. Several novel squalamine-related polyaminosterols were also evaluated as anion exchange inhibitors. In contrast to diBA(5)C4, polyaminosterol 1361 inhibited oocyte-expressed AE2 8-fold more potently than AE1 (IC50 0.6 versus 5.2 microM). The 3-fold less potent desulfo-analog, 1360, showed similar preference for AE2. It was found that 1361 also partially inhibited Cl- efflux from red cells, whereas neither polyaminosterol inhibited Cl efflux from HL60 cells. Thus, the oxonol diBA(5)C4 is >100-fold more potent as an inhibitor of AE1 than of AE2, whereas the polyaminosterols 1360 and 1361 are 8-fold more potent as inhibitors of AE2 than of AE1. Assay conditions and cell type influenced IC50 values for both classes of compounds. PMID:10353714

  7. Groundwater exchanges near a channelized versus unmodified stream mouth discharging to a subalpine lake

    NASA Astrophysics Data System (ADS)

    Constantz, J.; Naranjo, R.; Niswonger, R.; Allander, K.; Neilson, B.; Rosenberry, D.; Smith, D.; Rosecrans, C.; Stonestrom, D.

    2016-03-01

    The terminus of a stream flowing into a larger river, pond, lake, or reservoir is referred to as the stream-mouth reach or simply the stream mouth. The terminus is often characterized by rapidly changing thermal and hydraulic conditions that result in abrupt shifts in surface water/groundwater (sw/gw) exchange patterns, creating the potential for unique biogeochemical processes and ecosystems. Worldwide shoreline development is changing stream-lake interfaces through channelization of stream mouths, i.e., channel straightening and bank stabilization to prevent natural meandering at the shoreline. In the central Sierra Nevada (USA), Lake Tahoe's shoreline has an abundance of both "unmodified" (i.e., not engineered though potentially impacted by broader watershed engineering) and channelized stream mouths. Two representative stream mouths along the lake's north shore, one channelized and one unmodified, were selected to compare and contrast water and heat exchanges. Hydraulic and thermal properties were monitored during separate campaigns in September 2012 and 2013 and sw/gw exchanges were estimated within the stream mouth-shoreline continuum. Heat-flow and water-flow patterns indicated clear differences in the channelized versus the unmodified stream mouth. For the channelized stream mouth, relatively modulated, cool-temperature, low-velocity longitudinal streambed flows discharged offshore beneath warmer buoyant lakeshore water. In contrast, a seasonal barrier bar formed across the unmodified stream mouth, creating higher-velocity subsurface flow paths and higher diurnal temperature variations relative to shoreline water. As a consequence, channelization altered sw/gw exchanges potentially altering biogeochemical processing and ecological systems in and near the stream mouth.

  8. Groundwater exchanges near a channelized versus unmodified stream mouth discharging to a subalpine lake

    USGS Publications Warehouse

    Constantz, James; Naranjo, Ramon C.; Niswonger, Richard; Allander, Kip K.; Neilson, B.; Rosenberry, Donald O.; Smith, David W.; Rosecrans, C.; Stonestrom, David A.

    2016-01-01

    The terminus of a stream flowing into a larger river, pond, lake, or reservoir is referred to as the stream-mouth reach or simply the stream mouth. The terminus is often characterized by rapidly changing thermal and hydraulic conditions that result in abrupt shifts in surface water/groundwater (sw/gw) exchange patterns, creating the potential for unique biogeochemical processes and ecosystems. Worldwide shoreline development is changing stream-lake interfaces through channelization of stream mouths, i.e., channel straightening and bank stabilization to prevent natural meandering at the shoreline. In the central Sierra Nevada (USA), Lake Tahoe's shoreline has an abundance of both “unmodified” (i.e., not engineered though potentially impacted by broader watershed engineering) and channelized stream mouths. Two representative stream mouths along the lake's north shore, one channelized and one unmodified, were selected to compare and contrast water and heat exchanges. Hydraulic and thermal properties were monitored during separate campaigns in September 2012 and 2013 and sw/gw exchanges were estimated within the stream mouth-shoreline continuum. Heat-flow and water-flow patterns indicated clear differences in the channelized versus the unmodified stream mouth. For the channelized stream mouth, relatively modulated, cool-temperature, low-velocity longitudinal streambed flows discharged offshore beneath warmer buoyant lakeshore water. In contrast, a seasonal barrier bar formed across the unmodified stream mouth, creating higher-velocity subsurface flow paths and higher diurnal temperature variations relative to shoreline water. As a consequence, channelization altered sw/gw exchanges potentially altering biogeochemical processing and ecological systems in and near the stream mouth.

  9. On the Origin of Asymmetric Interactions between Permeant Anions and the Cystic Fibrosis Transmembrane Conductance Regulator Chloride Channel Pore

    PubMed Central

    Fatehi, Mohammad; St. Aubin, Chantal N.; Linsdell, Paul

    2007-01-01

    Single channel and macroscopic current recording was used to investigate block of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl− channel pore by the permeant anion \\documentclass[10pt]{article} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{pmc} \\pagestyle{empty} \\oddsidemargin -1.0in \\begin{document} \\begin{equation*}{\\mathrm{Au}}({\\mathrm{CN}})_{2}^{-}\\end{equation*}\\end{document}. Block was 1–2 orders of magnitude stronger when \\documentclass[10pt]{article} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{pmc} \\pagestyle{empty} \\oddsidemargin -1.0in \\begin{document} \\begin{equation*}{\\mathrm{Au}}({\\mathrm{CN}})_{2}^{-}\\end{equation*}\\end{document} was added to the intracellular versus the extracellular solution, depending on membrane potential. A point mutation within the pore, T-338A, strongly decreased the asymmetry of block, by weakening block by intracellular \\documentclass[10pt]{article} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{pmc} \\pagestyle{empty} \\oddsidemargin -1.0in \\begin{document} \\begin{equation*}{\\mathrm{Au}}({\\mathrm{CN}})_{2}^{-}\\end{equation*}\\end{document} and at the same time strengthening block by external \\documentclass[10pt]{article} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{pmc} \\pagestyle{empty} \\oddsidemargin -1.0in \\begin{document} \\begin{equation*}{\\mathrm{Au}}({\\mathrm{CN}})_{2}^{-}\\end{equation*}\\end{document}. Block of T-338A, but not wild-type, was strongest at the current reversal potential and weakened by either depolarization or hyperpolarization. In contrast to these

  10. Electrodialytic Transport Properties of Anion-Exchange Membranes Prepared from Poly(vinyl alcohol) and Poly(vinyl alcohol-co-methacryloyl aminopropyl trimethyl ammonium chloride)

    PubMed Central

    Jikihara, Atsushi; Ohashi, Reina; Kakihana, Yuriko; Higa, Mitsuru; Kobayashi, Kenichi

    2012-01-01

    Random-type anion-exchange membranes (AEMs) have been prepared by blending poly(vinyl alcohol) (PVA) and the random copolymer-type polycation, poly(vinyl alcohol-co-methacryloyl aminopropyl trimethyl ammonium chloride) at various molar percentages of anion-exchange groups to vinyl alcohol groups, Cpc, and by cross-linking the PVA chains with glutaraldehyde (GA) solution at various GA concentrations, CGA. The characteristics of the random-type AEMs were compared with blend-type AEMs prepared in our previous study. At equal molar percentages of the anion exchange groups, the water content of the random-type AEMs was lower than that of the blend-type AEMs. The effective charge density of the random-type AEMs increased with increasing Cpc and reached a maximum value. Further, the maximum value of the effective charge density increased with increasing CGA. The maximum value of the effective charge density, 0.42 mol/dm3, was obtained for the random-type AEM with Cpc = 4.2 mol % and CGA = 0.15 vol %. A comparison of the random-type and blend-type AEMs with almost the same Cpc showed that the random-type AEMs had lower membrane resistance than the blend-type ones. The membrane resistance and dynamic transport number of the random-type AEM with Cpc = 6.0 mol % and CGA = 0.15 vol % were 4.8 Ω cm2 and 0.83, respectively. PMID:24958543

  11. Understanding the Adsorption of PFOA on MIL-101(Cr)-Based Anionic-Exchange Metal-Organic Frameworks: Comparing DFT Calculations with Aqueous Sorption Experiments.

    PubMed

    Liu, Kai; Zhang, Siyu; Hu, Xiyue; Zhang, Kunyang; Roy, Ajay; Yu, Gang

    2015-07-21

    To examine the effects of different functionalization methods on adsorption behavior, anionic-exchange MIL-101(Cr) metal-organic frameworks (MOFs) were synthesized using preassembled modification (PAM) and postsynthetic modification (PSM) methods. Perfluorooctanoic acid (PFOA) adsorption results indicated that the maximum PFOA adsorption capacity was 1.19 and 1.89 mmol g(-1) for anionic-exchange MIL-101(Cr) prepared by PAM and PSM, respectively. The sorption equilibrium was rapidly reached within 60 min. Our results indicated that PSM is a better modification technique for introducing functional groups onto MOFs for adsorptive removal because PAM places functional groups onto the aperture of the nanopore, which hinders the entrance of organic contaminants. Our experimental results and the results of complementary density functional theory calculations revealed that in addition to the anion-exchange mechanism, the major PFOA adsorption mechanism is a combination of Lewis acid/base complexation between PFOA and Cr(III) and electrostatic interaction between PFOA and the protonated carboxyl groups of the bdc (terephthalic acid) linker. PMID:26066631

  12. Strong anion-exchange fast performance liquid chromatography as a versatile tool for preparation and purification of RNA produced by in vitro transcription.

    PubMed

    Koubek, Jiri; Lin, Ku Feng; Chen, Yet Ran; Cheng, Richard Ping; Huang, Joseph Jen Tse

    2013-10-01

    Here we demonstrate the use of strong anion-exchange fast performance liquid chromatography (FPLC) as a simple, fast, and robust method for RNA production by in vitro transcription. With this technique, we have purified different transcription templates from unreacted reagents in large quantities. The same buffer system could be used to readily remove nuclease contamination from the overexpressed pyrophosphatase, the important reagent for in vitro transcription. In addition, the method can be used to monitor in vitro transcription reactions to enable facile optimization of reaction conditions, and we have compared the separation performance between strong and weak anion-exchange FPLC for various transcribed RNAs, including the Diels-Alder ribozyme, the hammerhead ribozyme tRNA, and 4.5S RNA. The functionality of the purified tRNA(Cys) has been confirmed by the aminoacylation assay. Only the purification by strong anion-exchange FPLC has led to the enrichment of the functional tRNA from run-off transcripts as revealed by both enzymatic and electrophoretic analysis. PMID:23929938

  13. Use of a new tandem cation/anion exchange system with clinical-scale generators provides high specific volume solutions of technetium-99m and rhenium-188

    SciTech Connect

    Knapp, F.R. Jr.; Beets, A.L.; Mirzadeh, S.; Guhlke, S. |

    1998-03-01

    In this paper the authors describe the first application of a simple and inexpensive post elution tandem cation-anion exchange column system which is based on generator elution with salts of weak acids such as ammonium acetate instead of saline solution to provide very high specific volume solutions of technetium-99m and rhenium-188 from clinical scale molybdenum-99/technetium-99m generator prepared from low specific activity (n,y) molybdenum-99, and tungsten-188/rhenium-188 generators, respectively. Initial passage of the bolus through a strong cation exchange cartridge converts the ammonium acetate to acetic acid which is essentially not ionized at the acidic pH, allowing specific subsequent amine type (QMA SepPak{trademark}) anion exchange cartridge column trapping of the microscopic levels of the pertechnetate or perrhenate. Subsequent elution of the anion cartridge with a small volume (< 1 mL) of saline then provides high specific volume solutions of technetium-99m by concentration of the high eluant volumes obtained by elution of clinical-scale (1 Ci) generators. This new approach also works very effectively to obtain high specific volume solutions of rhenium-188 (> 500 mCi/mL) from the alumina-based tungsten-188/rhenium-188 generator.

  14. The separation of platinum, palladium and gold from silicate rocks by the anion exchange separation of chloro complexes after a sodium peroxide fusion: an investigation of low recoveries.

    PubMed

    Enzweiler, J; Potts, P J

    1995-10-01

    A series of experiments was undertaken to measure the recovery efficiency of platinum, palladium and gold from silicate rocks using a sodium peroxide fusion followed by anion exchange separation of the analytes as chloro complexes. Results obtained by graphite furnace atomic absorption spectrometric analysis of standard solutions prepared in dilute HCl or HCl-acidified sodium peroxide solution showed that recoveries were near quantitative. However, when standard solutions were added to an alkaline sodium peroxide solution, which was then acidified, low results were obtained for platinum and gold (46% and 76% respectively). Low and variable results were also obtained when standard solutions were added to a peridotite sample that had been dissolved by the state procedure, and in the analysis of the South African Bureau of Standards certified reference material, SARM 7. Various experiments were undertaken to investigate these low recoveries, but the reason proposed here is the formation of hydroxychloro compounds in alkaline solution which are not, on acidification with HCl, converted quantitatively to the chloro complex necessary for quantitative anion exchange separation. It is concluded that a sodium peroxide fusion followed by an anion-exchange separation does not appear to form the basis of a successful technique for the determination of platinum, palladium and gold in silicate rocks. PMID:18966370

  15. Polyelectrolyte functionalized multi-walled carbon nanotubes as strong anion-exchange material for the extraction of acidic degradation products of nerve agents.

    PubMed

    Kanaujia, Pankaj K; Pardasani, Deepak; Purohit, Ajay K; Tak, Vijay; Dubey, D K

    2011-12-30

    Extraction, enrichment and gas chromatography mass spectrometric analysis of degradation products of nerve agents from water is of significant importance for verification of Chemical Weapons Convention (CWC) and gathering forensic evidence of use of nerve agents. Multi-walled carbon nanotubes (MWCNTs) were non-covalently functionalized with poly(diallyldimethylammonium chloride) (PDDA) to afford the cationic functionalized nano-tubes, which were used as solid-phase anionic-exchanger sorbents to extract the acidic degradation products of nerve agents from water. Extraction efficiencies of MWCNTs-PDDA were compared with those of mixed mode anion-exchange (HLB) and silica based strong anion-exchange (Si-SAX) cartridges. Optimized extraction parameters included MWCNTs-PDDA 12 mg, washing solvent 5 mL water and eluting solvent 3 mL of 0.1M aqueous HCl followed by 3 mL methanol. At 1 ng mL(-1) spiking concentration of mono- and di-basic phosphonic acids, MWCNTs-PDDA exhibited higher extraction efficiencies in comparison to Si-SAX and HLB. The limits of detection were achieved down to 0.05 and 0.11 ng mL(-1) in selected ion and full scan monitoring mode respectively; and limits of quantification in selected ion monitoring mode were achieved down to 0.21 ng mL(-1). PMID:22119612