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A B Yaroslavtsev - One of the best experts on this subject based on the ideXlab platform.
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effect of current density concentratIon of ternary electrolyte and type of catIons on the Monovalent Ion selectivity of surface sulfonated graft anIon exchange membranes modelling and experiment
Journal of Membrane Science, 2021Co-Authors: D V Golubenko, A B YaroslavtsevAbstract:Abstract The dependence of Monovalent-Ion selectivity of surface-sulfonated anIon exchange membranes (s-AEMs) on the electrodialysis (ED) desalinatIon current density, the concentratIon of equimolar ternary electrolyte (XCl + X2SO4) in the total concentratIon range 0.04–0.2 M, and the type of catIons (X = H, Cs, Na) has been studied. The membrane current-voltage characteristics and values of the diffusIon permeability coefficients in electrolyte solutIons and their mixtures were measured. It was shown that Cl/SO4-selectivity coefficients ( P C l | S O 4 ) increase along with current density, reaching maximum values at the limiting current density (Ilim). The P C l | S O 4 maximum value of 5.5 was achieved for the s-AEM-18 membrane in the ED-desalinatIon of equimolar ternary electrolytes NaCl/Na2SO4, and CsCl/Cs2SO4 (total salt concentratIon 0.04 M) at 1.4 and 2.4 mA cm−2 current densities, respectively. At the overlimiting currents, the splitting of water and the decrease of Cl/SO4-selectivity were observed. The obtained experimental results are interpreted using simplified mass transfer and numerical simulatIons in the framework of Nernst-Planck-Poisson equatIons implemented in the COMSOL® Multiphysics software. The model represents the modified membrane as an asymmetric bipolar membrane with two diffusIon boundary layers (DBL) in electrolyte solutIons on both sides of the membrane interface. The model includes the water splitting at the bipolar boundary and the chemical equilibrium between sulfate and hydrogen sulfate Ions. The numerical simulatIons qualitatively predict the behaviour of s-AEMs membranes when the abovementIoned conditIons change.
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development of surface sulfonated graft anIon exchange membranes with Monovalent Ion selectivity and antifouling properties for electromembrane processes
Journal of Membrane Science, 2020Co-Authors: D V Golubenko, A B YaroslavtsevAbstract:Abstract This communicatIon describes the development of anIon-exchange membrane (AEM) with a modified surface possessing Monovalent Ion selectivity and antifouling properties. Modified AEMs series was obtained by the formatIon of an oppositely-charged thin layer utilizing the surface sulfonatIon of the grafted AEMs. The creatIon of the interface layer leads to a significant increase in the Cl/SO4 selectivity and the appearance of humic acid sorptIon resistance. The best surface-sulfonated anIon-exchange membrane (s-AEM) has a high Ionic conductivity of 11.2 mS cm−1 and high Cl/SO4 selectivity up to 6.4 in electrodialysis. The sulfonated layer was characterized by IR spectroscopy and electron microscopy. The relatIonship between the structure and thickness of the catIon-exchange surface layer and the observed changes in membrane transport properties such as diffusIon permeability, Ionic conductivity, potentiometric transport numbers, and current-voltage characteristics are discussed. It was shown that the Cl/SO4 selectivity of s-AEM in the desalinatIon process depends on the current density. The obtained data were successfully interpreted using a mathematical model based on the concept of the bipolar structure of the s-AEM surface layer and diffusIon control of anIon transport through it.
D V Golubenko - One of the best experts on this subject based on the ideXlab platform.
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effect of current density concentratIon of ternary electrolyte and type of catIons on the Monovalent Ion selectivity of surface sulfonated graft anIon exchange membranes modelling and experiment
Journal of Membrane Science, 2021Co-Authors: D V Golubenko, A B YaroslavtsevAbstract:Abstract The dependence of Monovalent-Ion selectivity of surface-sulfonated anIon exchange membranes (s-AEMs) on the electrodialysis (ED) desalinatIon current density, the concentratIon of equimolar ternary electrolyte (XCl + X2SO4) in the total concentratIon range 0.04–0.2 M, and the type of catIons (X = H, Cs, Na) has been studied. The membrane current-voltage characteristics and values of the diffusIon permeability coefficients in electrolyte solutIons and their mixtures were measured. It was shown that Cl/SO4-selectivity coefficients ( P C l | S O 4 ) increase along with current density, reaching maximum values at the limiting current density (Ilim). The P C l | S O 4 maximum value of 5.5 was achieved for the s-AEM-18 membrane in the ED-desalinatIon of equimolar ternary electrolytes NaCl/Na2SO4, and CsCl/Cs2SO4 (total salt concentratIon 0.04 M) at 1.4 and 2.4 mA cm−2 current densities, respectively. At the overlimiting currents, the splitting of water and the decrease of Cl/SO4-selectivity were observed. The obtained experimental results are interpreted using simplified mass transfer and numerical simulatIons in the framework of Nernst-Planck-Poisson equatIons implemented in the COMSOL® Multiphysics software. The model represents the modified membrane as an asymmetric bipolar membrane with two diffusIon boundary layers (DBL) in electrolyte solutIons on both sides of the membrane interface. The model includes the water splitting at the bipolar boundary and the chemical equilibrium between sulfate and hydrogen sulfate Ions. The numerical simulatIons qualitatively predict the behaviour of s-AEMs membranes when the abovementIoned conditIons change.
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development of surface sulfonated graft anIon exchange membranes with Monovalent Ion selectivity and antifouling properties for electromembrane processes
Journal of Membrane Science, 2020Co-Authors: D V Golubenko, A B YaroslavtsevAbstract:Abstract This communicatIon describes the development of anIon-exchange membrane (AEM) with a modified surface possessing Monovalent Ion selectivity and antifouling properties. Modified AEMs series was obtained by the formatIon of an oppositely-charged thin layer utilizing the surface sulfonatIon of the grafted AEMs. The creatIon of the interface layer leads to a significant increase in the Cl/SO4 selectivity and the appearance of humic acid sorptIon resistance. The best surface-sulfonated anIon-exchange membrane (s-AEM) has a high Ionic conductivity of 11.2 mS cm−1 and high Cl/SO4 selectivity up to 6.4 in electrodialysis. The sulfonated layer was characterized by IR spectroscopy and electron microscopy. The relatIonship between the structure and thickness of the catIon-exchange surface layer and the observed changes in membrane transport properties such as diffusIon permeability, Ionic conductivity, potentiometric transport numbers, and current-voltage characteristics are discussed. It was shown that the Cl/SO4 selectivity of s-AEM in the desalinatIon process depends on the current density. The obtained data were successfully interpreted using a mathematical model based on the concept of the bipolar structure of the s-AEM surface layer and diffusIon control of anIon transport through it.
Michael Brenowitz - One of the best experts on this subject based on the ideXlab platform.
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Monovalent Ion mediated folding of the tetrahymena thermophila ribozyme
Journal of Molecular Biology, 2004Co-Authors: Inna Shcherbakova, Mark R Chance, Sayan Gupta, Michael BrenowitzAbstract:The time-course of Monovalent catIon-induced folding of the L-21 Sca1 Tetrahymena thermophila ribozyme and a selected mutant was quantitatively followed using synchrotron X-ray (.OH) footprinting. Initiating folding by increasing the concentratIon of either Na+ or K+ to 1.5M from an initial conditIon of approximately 0.008 M Na+ at 42 degrees C resulted in the complete formatIon of tertiary contacts within the P5abc subdomain and between the peripheral helices within the dead time of our measurements (k>50 s(-1)). These results contrast with folding rates of 2-0.2 s(-1) previously observed for formatIon of these contacts in 10mM Mg2+ from the same initial conditIon. Thus, the initial formatIon of native tertiary contacts is inhibited by divalent but not Monovalent catIons. The native contacts within the catalytic core form without a detectable burst phase at rates of 0.4-1.0 s(-1) in a manner reminiscent of the Mg2+-dependent folding behavior, although tenfold faster. The tertiary interactIons stabilizing the catalytic core interactIon with P4-P6 and P2.1, as well as one of the protectIons internal for the P4-P6 domain, display progress curves with appreciable burst amplitudes and a phase comparable in rate to that of the catalytic core. That the slow folding of the ribozyme's core is a consequence of the alt-P3 secondary structure is shown by the 100% burst phase amplitudes that are observed for folding of the U273A mutant ribozyme within which the native secondary structure (P3) is strengthened. Thus, formatIon of a misfolded intermediate(s) resulting from the alt-P3 secondary structure is independent of Ion valency while the rate at which the respective intermediates are resolved is sensitive to Ion valency. The overall portrait painted by these results is that Ion valency differentially affects steps in the folding process and that folding in Monovalent Ion alone for the U273A mutant Tetrahymena ribozyme is fast and direct.
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Monovalent Ion mediated folding of the tetrahymena thermophila ribozyme
Journal of Molecular Biology, 2004Co-Authors: Inna Shcherbakova, Mark R Chance, Sayan Gupta, Michael BrenowitzAbstract:The time-course of Monovalent catIon-induced folding of the L-21 Sca1 Tetrahymena thermophila ribozyme and a selected mutant was quantitatively followed using synchrotron X-ray (·OH) footprinting. Initiating folding by increasing the concentratIon of either Na+ or K+ to 1.5 M from an initial conditIon of ∼0.008 M Na+ at 42 °C resulted in the complete formatIon of tertiary contacts within the P5abc subdomain and between the peripheral helices within the dead time of our measurements (k>50 s−1). These results contrast with folding rates of 2–0.2 s−1 previously observed for formatIon of these contacts in 10 mM Mg2+ from the same initial conditIon. Thus, the initial formatIon of native tertiary contacts is inhibited by divalent but not Monovalent catIons. The native contacts within the catalytic core form without a detectable burst phase at rates of 0.4–1.0 s−1 in a manner reminiscent of the Mg2+-dependent folding behavior, although tenfold faster. The tertiary interactIons stabilizing the catalytic core interactIon with P4–P6 and P2.1, as well as one of the protectIons internal for the P4–P6 domain, display progress curves with appreciable burst amplitudes and a phase comparable in rate to that of the catalytic core. That the slow folding of the ribozyme's core is a consequence of the alt-P3 secondary structure is shown by the 100% burst phase amplitudes that are observed for folding of the U273A mutant ribozyme within which the native secondary structure (P3) is strengthened. Thus, formatIon of a misfolded intermediate(s) resulting from the alt-P3 secondary structure is independent of Ion valency while the rate at which the respective intermediates are resolved is sensitive to Ion valency. The overall portrait painted by these results is that Ion valency differentially affects steps in the folding process and that folding in Monovalent Ion alone for the U273A mutant Tetrahymena ribozyme is fast and direct.
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multiple Monovalent Ion dependent pathways for the folding of the l 21 tetrahymena thermophila ribozyme
Journal of Molecular Biology, 2003Co-Authors: Takeshi Uchida, Keiji Takamoto, Mark R Chance, Michael BrenowitzAbstract:Abstract Synchrotron hydroxyl radical (·OH) footprinting is a technique that monitors the local changes in solvent accessibility of the RNA backbone on milliseconds to minutes time-scales. The Mg 2+ -dependent folding of the L-21 Sca 1 Tetrahymena thermophila ribozyme has been followed using this technique at an elevated concentratIon of Monovalent Ion (200 mM NaCl) and as a functIon of the initial annealing conditIons and substrate. Previous studies conducted at low concentratIons of Monovalent Ion displayed sequential folding of the P4–P6 domain, the peripheral helices and the catalytic core, with each protectIon displaying monophasic kinetics. For ribozyme annealed in buffer containing 200 mM NaCl and folded by the additIon of 10 mM MgCl 2 , multiple kinetic phases are observed for ·OH protectIons throughout the ribozyme. The independently folding P4–P6 domain is the first to fold with its protectIons displaying 50–90% burst phase amplitudes. That the folding of P4–P6 within the ribozyme does not display the 100% burst phase of isolated P4–P6 at 200 mM NaCl shows that interactIons with the remainder of the ribozyme impede this domain's folding. In additIon, ·OH protectIons constituting each side of a tertiary contact are not coincident in some cases, consistent with the formatIon of transient non-native interactIons. While the peripheral contacts and triple helical scaffold exhibit substantial burst phases, the slowest protectIon to appear is J8/7 in the catalytic core, which displays a minimal burst amplitude and whose formatIon is coincident with the recovery of catalytic activity. The number of kinetic phases as well as their amplitudes and rates are different when the ribozyme is annealed in low-salt buffer and folded by the concomitant additIon of Monovalent and divalent catIons. Annealed substrate changes the partitIoning of the ribozyme among the multiple folding populatIons. These results provide a map of the early steps in the ribozyme's folding landscape and the degree to which the preferred pathways are dependent upon the initial reactIon conditIons.
S M Hosseini - One of the best experts on this subject based on the ideXlab platform.
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preparatIon and electrochemical characterizatIon of Monovalent Ion selective poly vinyl chloride blend poly styrene co butadiene heterogeneous catIon exchange membrane coated with poly methyl methacrylate
Separation Science and Technology, 2012Co-Authors: S M Hosseini, S S Madaeni, H Asiani, Asieh HeidariAbstract:In this research, polyvinylchloride/ styrene-butadiene-rubber blend heterogeneous catIon exchange membranes were prepared by solutIon casting technique using tetrahydrofuran as solvent and catIon exchange resin powder as functIonal groups agent. Poly methyl methacrylate (PMMA) was also employed as membrane surface modifier by emulsIon polymerizatIon technique to improve the membrane selectivity and anti-fouling property. The effect of used emulsIon compositIon on properties of home-made membranes was studied. SOM images showed uniform particles distributIon and relatively uniform surfaces for the membranes. Results revealed that surface modificatIon of membrane led to decrease in water content, Ion exchange capacity, and Ionic permeability in composite membranes. Membrane potential, transport number, selectivity, Ionic concentratIon, and membrane surface electrical resistance all were increased by the PMMA coating on membrane surface. Also, the results showed that decrease of (Methyl methacrylate (MMA): S...
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preparatIon and characterizatIon of Monovalent Ion selective poly vinyl chloride blend poly styrene co butadiene heterogeneous anIon exchange membranes
Polymer International, 2011Co-Authors: A R Khodabakhshi, S S Madaeni, S M HosseiniAbstract:New types of composite anIon-exchange membranes were prepared by blending of suspensIon-produced poly(vinyl chloride) (S-PVC) and poly(styrene-co-butadiene), otherwise known as styrene–butadiene rubber (SBR), as binder, along with anIon-exchange resin powder to provide functIonal groups and activated carbon as inorganic filler additive. Also, an ultrasonic method was used to obtain better homogeneity. In solutIons with mono- and divalent anIons, the effect of activated carbon and sonicatIon on the morphology, electrochemical properties and selectivity of these membranes was elucidated. For all solutIons, Ion-exchange capacity, membrane potential, permselectivity, transport number, Ionic permeability, flux and current efficiency of the prepared membranes initially increased on increasing the activated carbon concentratIon to 2 wt% in the casting solutIon and then began to decrease. Moreover, the electrical resistance and energy consumptIon of the membranes initially decreased on increasing the activated carbon loading to 2 wt% and then increased. S-PVC-blend-SBR membranes with additive showed a decrease in water content and a slight decrease in oxidative stability. Also, these membranes showed good Monovalent Ion selectivity. Structural images of the prepared membranes obtained using scanning optical microscopy showed that sonicatIon increased polymer-particle interactIons and promoted the compatibility of particles with binder. Copyright © 2010 Society of Chemical Industry
Mark R Chance - One of the best experts on this subject based on the ideXlab platform.
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Monovalent Ion mediated folding of the tetrahymena thermophila ribozyme
Journal of Molecular Biology, 2004Co-Authors: Inna Shcherbakova, Mark R Chance, Sayan Gupta, Michael BrenowitzAbstract:The time-course of Monovalent catIon-induced folding of the L-21 Sca1 Tetrahymena thermophila ribozyme and a selected mutant was quantitatively followed using synchrotron X-ray (.OH) footprinting. Initiating folding by increasing the concentratIon of either Na+ or K+ to 1.5M from an initial conditIon of approximately 0.008 M Na+ at 42 degrees C resulted in the complete formatIon of tertiary contacts within the P5abc subdomain and between the peripheral helices within the dead time of our measurements (k>50 s(-1)). These results contrast with folding rates of 2-0.2 s(-1) previously observed for formatIon of these contacts in 10mM Mg2+ from the same initial conditIon. Thus, the initial formatIon of native tertiary contacts is inhibited by divalent but not Monovalent catIons. The native contacts within the catalytic core form without a detectable burst phase at rates of 0.4-1.0 s(-1) in a manner reminiscent of the Mg2+-dependent folding behavior, although tenfold faster. The tertiary interactIons stabilizing the catalytic core interactIon with P4-P6 and P2.1, as well as one of the protectIons internal for the P4-P6 domain, display progress curves with appreciable burst amplitudes and a phase comparable in rate to that of the catalytic core. That the slow folding of the ribozyme's core is a consequence of the alt-P3 secondary structure is shown by the 100% burst phase amplitudes that are observed for folding of the U273A mutant ribozyme within which the native secondary structure (P3) is strengthened. Thus, formatIon of a misfolded intermediate(s) resulting from the alt-P3 secondary structure is independent of Ion valency while the rate at which the respective intermediates are resolved is sensitive to Ion valency. The overall portrait painted by these results is that Ion valency differentially affects steps in the folding process and that folding in Monovalent Ion alone for the U273A mutant Tetrahymena ribozyme is fast and direct.
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Monovalent Ion mediated folding of the tetrahymena thermophila ribozyme
Journal of Molecular Biology, 2004Co-Authors: Inna Shcherbakova, Mark R Chance, Sayan Gupta, Michael BrenowitzAbstract:The time-course of Monovalent catIon-induced folding of the L-21 Sca1 Tetrahymena thermophila ribozyme and a selected mutant was quantitatively followed using synchrotron X-ray (·OH) footprinting. Initiating folding by increasing the concentratIon of either Na+ or K+ to 1.5 M from an initial conditIon of ∼0.008 M Na+ at 42 °C resulted in the complete formatIon of tertiary contacts within the P5abc subdomain and between the peripheral helices within the dead time of our measurements (k>50 s−1). These results contrast with folding rates of 2–0.2 s−1 previously observed for formatIon of these contacts in 10 mM Mg2+ from the same initial conditIon. Thus, the initial formatIon of native tertiary contacts is inhibited by divalent but not Monovalent catIons. The native contacts within the catalytic core form without a detectable burst phase at rates of 0.4–1.0 s−1 in a manner reminiscent of the Mg2+-dependent folding behavior, although tenfold faster. The tertiary interactIons stabilizing the catalytic core interactIon with P4–P6 and P2.1, as well as one of the protectIons internal for the P4–P6 domain, display progress curves with appreciable burst amplitudes and a phase comparable in rate to that of the catalytic core. That the slow folding of the ribozyme's core is a consequence of the alt-P3 secondary structure is shown by the 100% burst phase amplitudes that are observed for folding of the U273A mutant ribozyme within which the native secondary structure (P3) is strengthened. Thus, formatIon of a misfolded intermediate(s) resulting from the alt-P3 secondary structure is independent of Ion valency while the rate at which the respective intermediates are resolved is sensitive to Ion valency. The overall portrait painted by these results is that Ion valency differentially affects steps in the folding process and that folding in Monovalent Ion alone for the U273A mutant Tetrahymena ribozyme is fast and direct.
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multiple Monovalent Ion dependent pathways for the folding of the l 21 tetrahymena thermophila ribozyme
Journal of Molecular Biology, 2003Co-Authors: Takeshi Uchida, Keiji Takamoto, Mark R Chance, Michael BrenowitzAbstract:Abstract Synchrotron hydroxyl radical (·OH) footprinting is a technique that monitors the local changes in solvent accessibility of the RNA backbone on milliseconds to minutes time-scales. The Mg 2+ -dependent folding of the L-21 Sca 1 Tetrahymena thermophila ribozyme has been followed using this technique at an elevated concentratIon of Monovalent Ion (200 mM NaCl) and as a functIon of the initial annealing conditIons and substrate. Previous studies conducted at low concentratIons of Monovalent Ion displayed sequential folding of the P4–P6 domain, the peripheral helices and the catalytic core, with each protectIon displaying monophasic kinetics. For ribozyme annealed in buffer containing 200 mM NaCl and folded by the additIon of 10 mM MgCl 2 , multiple kinetic phases are observed for ·OH protectIons throughout the ribozyme. The independently folding P4–P6 domain is the first to fold with its protectIons displaying 50–90% burst phase amplitudes. That the folding of P4–P6 within the ribozyme does not display the 100% burst phase of isolated P4–P6 at 200 mM NaCl shows that interactIons with the remainder of the ribozyme impede this domain's folding. In additIon, ·OH protectIons constituting each side of a tertiary contact are not coincident in some cases, consistent with the formatIon of transient non-native interactIons. While the peripheral contacts and triple helical scaffold exhibit substantial burst phases, the slowest protectIon to appear is J8/7 in the catalytic core, which displays a minimal burst amplitude and whose formatIon is coincident with the recovery of catalytic activity. The number of kinetic phases as well as their amplitudes and rates are different when the ribozyme is annealed in low-salt buffer and folded by the concomitant additIon of Monovalent and divalent catIons. Annealed substrate changes the partitIoning of the ribozyme among the multiple folding populatIons. These results provide a map of the early steps in the ribozyme's folding landscape and the degree to which the preferred pathways are dependent upon the initial reactIon conditIons.
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Monovalent catIons mediate formatIon of native tertiary structure of the tetrahymena thermophila ribozyme
Nature Structural & Molecular Biology, 2002Co-Authors: Keiji Takamoto, Mark R Chance, Qin He, Stephanie Morris, Michael BrenowitzAbstract:The formatIon of individual tertiary contacts of the Tetrahymena L-21 Sca I ribozyme has been monitored by hydroxyl radical footprinting and its global conformatIon by analytical ultracentrifugatIon as a functIon of Monovalent Ion concentratIon in the absence of divalent Ions. Advanced methods of data analysis, which allow the hydroxyl radical reactivity of every nucleotide to be quantified, permit monitoring of each and every structural element of the RNA. Monovalent Ion-mediated global compactIon of the ribozyme is accompanied by the formatIon of native tertiary contacts; most native tertiary contacts are evident except several that are located near where divalent Ions are observed in crystallographic structures. Non-native tertiary contacts are also observed at low but not high concentratIons of Monovalent Ions. In light of recent studies that have shown that the presence of Monovalent Ions greatly accelerates the Mg2+-dependent folding of the Tetrahymena ribozyme, the present studies suggest that Na+ concentratIon changes not only the starting positIon of the RNA on its folding funnel but also pushes it deep into the well by forming native tertiary contacts and, thus, favoring fast and correct folding pathways.