Sample records for modulates anionic conduction
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Seal, Rebecca P.; Shigeri, Yasushi; Eliasof, Scott; Leighton, Barbara H.; Amara, Susan G.
2001-01-01
Excitatory amino acid transporters (EAATs) buffer and remove synaptically released l-glutamate and maintain its concentrations below neurotoxic levels. EAATs also mediate a thermodynamically uncoupled substrate-gated anion conductance that may modulate cell excitability. Here, we demonstrate that modification of a cysteine substituted within a C-terminal domain of EAAT1 abolishes transport in both the forward and reverse directions without affecting activation of the anion conductance. EC50s for l-glutamate and sodium are significantly lower after modification, consistent with kinetic models of the transport cycle that link anion channel gating to an early step in substrate translocation. Also, decreasing the pH from 7.5 to 6.5 decreases the EC50 for l-glutamate to activate the anion conductance, without affecting the EC50 for the entire transport cycle. These findings demonstrate for the first time a structural separation of transport and the uncoupled anion flux. Moreover, they shed light on some controversial aspects of the EAAT transport cycle, including the kinetics of proton binding and anion conductance activation. PMID:11752470
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Zhang, Meng; Liu, Yuxue; Zhu, Hancheng; Yan, Duanting; Yang, Jian; Zhang, Xinyang; Liu, Chunguang; Xu, Changshan
2016-07-28
Conductive C12A7:0.1%Gd(3+),y%Sr(2+) powders with different Sr(2+) doping concentrations have been prepared in a H2 atmosphere by a solid state method in combination with subsequent UV-irradiation. The encaged electron concentration could be modulated through tuning Sr(2+) doping and its maximum value reaches 2.3 × 10(19) cm(-3). This is attributed to the competition between enhanced uptake and the release of the encaged anions during their formation and diffusion processes and the suppression of encaged electrons generation due to the increased encaged OH(-) anions and the decreased encaged O(2-) anions. Although there exists encaged electrons and different encaged anions (O(2-), H(-) and OH(-)) in C12A7 conductive powders prepared through the hydrogen route, a dominant local environment around Gd(3+) could be observed using electron spin resonance (ESR) detection. It can be ascribed to the stronger coupling of the encaged OH(-) to the framework of C12A7 than those of the encaged electrons, O(2-) and H(-) anions. In addition, emission of Gd(3+) ions is enhanced under UV or low voltage electron beam excitation and a new local environment around Gd(3+) ions appears through the thermal annealing in air because of the decrease of the encaged OH(-) anions and the increase of the encaged O(2-) anions. Our results suggested that Sr(2+) doping in combination with thermal annealing in air is an effective strategy for increasing the conductive performance and enhancing the emission of rare earth ions doped into C12A7 conductive phosphors for low-voltage field emission displays (FEDs).
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Cystic Fibrosis and the Nervous System.
Reznikov, Leah R
2017-05-01
Cystic fibrosis (CF) is a life-shortening autosomal recessive disorder caused by mutations in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR). CFTR is an anion channel that conducts bicarbonate and chloride across cell membranes. Although defective anion transport across epithelial cells is accepted as the basic defect in CF, many of the features observed in people with CF and organs affected by CF are modulated by the nervous system. This is of interest because CFTR expression has been reported in both the peripheral and central nervous systems, and it is well known that the transport of anions, such as chloride, greatly modulates neuronal excitability. Thus it is predicted that in CF, lack of CFTR in the nervous system affects neuronal function. Consistent with this prediction, several nervous system abnormalities and nervous system disorders have been described in people with CF and in animal models of CF. The goal of this special feature article is to highlight the expression and function of CFTR in the nervous system. Special emphasis is placed on nervous system abnormalities described in people with CF and in animal models of CF. Finally, features of CF that may be modulated by or attributed to faulty nervous system function are discussed. Copyright © 2016 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.
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Jun, Ikhyun; Cheng, Mary Hongying; Sim, Eunji; Jung, Jinsei; Suh, Bong Lim; Kim, Yonjung; Son, Hankil; Park, Kyungsoo; Kim, Chul Hoon; Yoon, Joo‐Heon; Whitcomb, David C.; Bahar, Ivet
2016-01-01
Key points Cellular stimuli can modulate the ion selectivity of some anion channels, such as CFTR, ANO1 and the glycine receptor (GlyR), by changing pore size.Ion selectivity of CFTR, ANO1 and GlyR is critically affected by the electric permittivity and diameter of the channel pore.Pore size change affects the energy barriers of ion dehydration as well as that of size‐exclusion of anion permeation.Pore dilatation increases the bicarbonate permeability (P HC O3/ Cl ) of CFTR, ANO1 and GlyR.Dynamic change in P HC O3/ Cl may mediate many physiological and pathological processes. Abstract Chloride (Cl−) and bicarbonate (HCO3 −) are two major anions and their permeation through anion channels plays essential roles in our body. However, the mechanism of ion selection by the anion channels is largely unknown. Here, we provide evidence that pore dilatation increases the bicarbonate permeability (P HC O3/ Cl ) of anion channels by reducing energy barriers of size‐exclusion and ion dehydration of HCO3 − permeation. Molecular, physiological and computational analyses of major anion channels, such as cystic fibrosis transmembrane conductance regulator (CFTR), anoctamin‐1(ANO1/TMEM16A) and the glycine receptor (GlyR), revealed that the ion selectivity of anion channels is basically determined by the electric permittivity and diameter of the pore. Importantly, cellular stimuli dynamically modulate the anion selectivity of CFTR and ANO1 by changing the pore size. In addition, pore dilatation by a mutation in the pore‐lining region alters the anion selectivity of GlyR. Changes in pore size affected not only the energy barriers of size exclusion but that of ion dehydration by altering the electric permittivity of water‐filled cavity in the pore. The dynamic increase in P HC O3/ Cl by pore dilatation may have many physiological and pathophysiological implications ranging from epithelial HCO3 − secretion to neuronal excitation. PMID:26663196
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Sukumaran, Sunil K.; Margolskee, Robert F.; Bachmanov, Alexander A.
2016-01-01
Responses in the amiloride-insensitive (AI) pathway, one of the two pathways mediating salty taste in mammals, are modulated by the size of the anion of a salt. This “anion effect” has been hypothesized to result from inhibitory transepithelial potentials (TPs) generated across the lingual epithelium as cations permeate through tight junctions and leave their larger and less permeable anions behind (Ye et al., 1991). We tested directly the necessity of TPs for the anion effect by measuring responses to NaCl and Na-gluconate (small and large anion sodium salts, respectively) in isolated taste cells from mouse circumvallate papillae. Using calcium imaging, we identified AI salt-responsive type III taste cells and demonstrated that they compose a subpopulation of acid-responsive taste cells. Even in the absence of TPs, many (66%) AI salt-responsive type III taste cells still exhibited the anion effect, demonstrating that some component of the transduction machinery for salty taste in type III cells is sensitive to anion size. We hypothesized that osmotic responses could explain why a minority of type III cells (34%) had AI salt responses but lacked anion sensitivity. All AI type III cells had osmotic responses to cellobiose, which were significantly modulated by extracellular sodium concentration, suggesting the presence of a sodium-conducting osmotically sensitive ion channel. However, these responses were significantly larger in AI type III cells that did not exhibit the anion effect. These findings indicate that multiple mechanisms could underlie AI salt responses in type III taste cells, one of which may contribute to the anion effect. SIGNIFICANCE STATEMENT Understanding the mechanisms underlying salty taste will help inform strategies to combat the health problems associated with NaCl overconsumption by humans. Of the two pathways underlying salty taste in mammals, the amiloride-insensitive (AI) pathway is the least understood. Using calcium imaging of isolated mouse taste cells, we identify two separate populations of AI salt-responsive type III taste cells distinguished by their sensitivity to anion size and show that these cells compose subpopulations of acid-responsive taste cells. We also find evidence that a sodium-conducting osmotically sensitive mechanism contributes to salt responses in type III taste cells. Our data not only provide new insights into the transduction mechanisms of AI salt taste but also have important implications for general theories of taste encoding. PMID:26865617
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Turner, Mark J.; Saint‐Criq, Vinciane; Patel, Waseema; Ibrahim, Salam H.; Verdon, Bernard; Ward, Christopher; Garnett, James P.; Tarran, Robert; Cann, Martin J.
2015-01-01
Key points Raised arterial blood CO2 (hypercapnia) is a feature of many lung diseases.CO2 has been shown to act as a cell signalling molecule in human cells, notably by influencing the levels of cell signalling second messengers: cAMP and Ca2+.Hypercapnia reduced cAMP‐stimulated cystic fibrosis transmembrane conductance regulator‐dependent anion and fluid transport in Calu‐3 cells and primary human airway epithelia but did not affect cAMP‐regulated HCO3 − transport via pendrin or Na+/HCO3 − cotransporters.These results further support the role of CO2 as a cell signalling molecule and suggests CO2‐induced reductions in airway anion and fluid transport may impair innate defence mechanisms of the lungs. Abstract Hypercapnia is clinically defined as an arterial blood partial pressure of CO2 of above 40 mmHg and is a feature of chronic lung disease. In previous studies we have demonstrated that hypercapnia modulates agonist‐stimulated cAMP levels through effects on transmembrane adenylyl cyclase activity. In the airways, cAMP is known to regulate cystic fibrosis transmembrane conductance regulator (CFTR)‐mediated anion and fluid secretion, which contributes to airway surface liquid homeostasis. The aim of the current work was to investigate if hypercapnia could modulate cAMP‐regulated ion and fluid transport in human airway epithelial cells. We found that acute exposure to hypercapnia significantly reduced forskolin‐stimulated elevations in intracellular cAMP as well as both adenosine‐ and forskolin‐stimulated increases in CFTR‐dependent transepithelial short‐circuit current, in polarised cultures of Calu‐3 human airway cells. This CO2‐induced reduction in anion secretion was not due to a decrease in HCO3 − transport given that neither a change in CFTR‐dependent HCO3 − efflux nor Na+/HCO3 − cotransporter‐dependent HCO3 − influx were CO2‐sensitive. Hypercapnia also reduced the volume of forskolin‐stimulated fluid secretion over 24 h, yet had no effect on the HCO3 − content of the secreted fluid. Our data reveal that hypercapnia reduces CFTR‐dependent, electrogenic Cl− and fluid secretion, but not CFTR‐dependent HCO3 − secretion, which highlights a differential sensitivity of Cl− and HCO3 − transporters to raised CO2 in Calu‐3 cells. Hypercapnia also reduced forskolin‐stimulated CFTR‐dependent anion secretion in primary human airway epithelia. Based on current models of airways biology, a reduction in fluid secretion, associated with hypercapnia, would be predicted to have important consequences for airways hydration and the innate defence mechanisms of the lungs. PMID:26574187
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Colcombet, Jean; Lelièvre, Françoise; Thomine, Sébastien; Barbier-Brygoo, Hélène; Frachisse, Jean-Marie
2005-07-01
Variations in both intracellular and extracellular pH are known to be involved in a wealth of physiological responses. Using the patch-clamp technique on Arabidopsis hypocotyl cells, it is shown that rapid-type and slow-type anion channels at the plasma membrane are both regulated by pH via distinct mechanisms. Modifications of pH modulate the voltage-dependent gating of the rapid channel. While intracellular alkalinization facilitates channel activation by shifting the voltage gate towards negative potentials, extracellular alkalinization shifts the activation threshold to more positive potentials, away from physiological resting membrane potentials. By contrast, pH modulates slow anion channel activity in a voltage-independent manner. Intracellular acidification and extracellular alkalinization increase slow anion channel currents. The possible role of these distinct modulations in physiological processes involving anion efflux and modulation of extracellular and/or intracellular pH, such as elicitor and ABA signalling, are discussed.
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Ion Permeation and Mechanotransduction Mechanisms of Mechanosensitive Piezo Channels.
Zhao, Qiancheng; Wu, Kun; Geng, Jie; Chi, Shaopeng; Wang, Yanfeng; Zhi, Peng; Zhang, Mingmin; Xiao, Bailong
2016-03-16
Piezo proteins have been proposed as the long-sought-after mechanosensitive cation channels in mammals that play critical roles in various mechanotransduction processes. However, the molecular bases that underlie their ion permeation and mechanotransduction have remained functionally undefined. Here we report our finding of the miniature pore-forming module of Piezo1 that resembles the pore architecture of other trimeric channels and encodes the essential pore properties. We further identified specific residues within the pore module that determine unitary conductance, pore blockage and ion selectivity for divalent and monovalent cations and anions. The non-pore-containing region of Piezo1 confers mechanosensitivity to mechano-insensitive trimeric acid-sensing ion channels, demonstrating that Piezo1 channels possess intrinsic mechanotransduction modules separate from their pore modules. In conclusion, this is the first report on the bona fide pore module and mechanotransduction components of Piezo channels, which define their ion-conducting properties and gating by mechanical stimuli, respectively. Copyright © 2016 Elsevier Inc. All rights reserved.
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A pyrophosphate-responsive gadolinium(III) MRI contrast agent.
Surman, Andrew J; Bonnet, Célia S; Lowe, Mark P; Kenny, Gavin D; Bell, Jimmy D; Tóth, Eva; Vilar, Ramon
2011-01-03
This study shows that the relaxivity and optical properties of functionalised lanthanide-DTPA-bis-amide complexes (lanthanide=Gd(3+) and Eu(3+) , DTPA=diethylene triamine pentaacetic acid) can be successfully modulated by addition of specific anions, without direct Ln(3+) /anion coordination. Zinc(II)-dipicolylamine moieties, which are known to bind strongly to phosphates, were introduced in the amide "arms" of these ligands, and the interaction of the resulting Gd-Zn(2) complexes with a range of anions was screened by using indicator displacement assays (IDAs). Considerable selectivity for polyphosphorylated species (such as pyrophosphate and adenosine-5'-triphosphate (ATP)) over a range of other anions (including monophosphorylated anions) was apparent. In addition, we show that pyrophosphate modulates the relaxivity of the gadolinium(III) complex, this modulation being sufficiently large to be observed in imaging experiments. To establish the binding mode of the pyrophosphate and gain insight into the origin of the relaxometric modulation, a series of studies including UV/Vis and emission spectroscopy, luminescence lifetime measurements in H(2) O and D(2) O, (17) O and (31) P NMR spectroscopy and nuclear magnetic resonance dispersion (NMRD) studies were carried out. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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Ion pathways in the taste bud and their significance for transduction.
DeSimone, J A; Ye, Q; Heck, G L
1993-01-01
Taste buds share a topology with ion-transporting epithelial and evidence now indicates that neural responses in rats to Na+ salts of differing anion are mediated by both transcellular and paracellular ion transport. Na+ exerts its effects mainly on the transcellular pathway. Neural responses to Na+ salts are enhanced by negative voltage clamp and suppressed by positive clamp in a manner indicating modulation of the apical membrane potential of receptor cells. Anion effects are mainly paracellular. Under zero current clamp increasing anion size reduces the neural response at constant Na+ concentration. Below about 50 mM this difference is entirely eliminated under voltage clamp. This suggests that paracellular transepithelial potentials normally create an anion difference. At higher concentrations the relatively high permeability of the paracellular shunt to Cl- permits sufficient electroneutral diffusion of NaCl below the tight junctions to stimulate cells that do not make direct contact with the oral cavity. In general, the sensitivity of a response to perturbations in the apical membrane potential indicates that some phase of Na+ salt taste transduction is accompanied by changes in an apical membrane channel conductance.
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Fenoy, Gonzalo E; Giussi, Juan M; von Bilderling, Catalina; Maza, Eliana M; Pietrasanta, Lía I; Knoll, Wolfgang; Marmisollé, Waldemar A; Azzaroni, Omar
2018-05-15
We present the covalent modification of a Pani-like conducting polymer (polyaminobenzylamine, PABA) by grafting of a polyelectrolyte brush (poly [2-(methacryloyloxy)-ethyl-trimethylammonium chloride], PMETAC). As PABA has extra pendant amino moieties, the grafting procedure does not affect the backbone nitrogen atoms that are implicated in the electronic structure of the conducting polymers. Moreover, perchlorate anions interact very strongly with the quaternary ammonium pendant groups of PMETAC through ion pairing. Therefore, the grafting does not only keep the electroactivity of PABA in aqueous solutions but it adds the ion-actuation properties of the PMETAC brush to the modified electrode as demonstrated by contact angle measurements and electrochemical methods. In this way, the conjugation of the electron transfer properties of the conducting polymer with the anion responsiveness of the integrated brush renders perchlorate actuation of the electrochemical response. These results constitute a rational integration of nanometer-sized polymer building blocks that yields synergism of functionalities and illustrate the potentialities of nanoarchitectonics for pushing the limits of soft material science into the nanoworld. Copyright © 2018 Elsevier Inc. All rights reserved.
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Elucidating the correlation between morphology and ion dynamics in polymerized ionic liquids.
NASA Astrophysics Data System (ADS)
Heres, Maximilian; Cosby, Tyler; Iacob, Ciprian; Runt, James; Benson, Roberto; Liu, Hongjun; Paddison, Stephen; Sangoro, Joshua
Charge transport and dynamics are investigated for a series of poly-ammonium and poly-imidazolium-based polymerized ionic liquids (polyIL) with a common bis(trifluoromethylsulfonyl)imide anion using broadband dielectric spectroscopy and temperature modulated differential scanning calorimetry. A significant enhancement of the Tg independent ionic conductivity is observed for ammonium based polyIL with shorter pendant groups, in comparison to imidazolium based systems. These results emphasize the importance of polymer backbone spacing as well as counter-ion size on ionic conductivity in polymerized ionic liquids. NSF DMR 1508394.
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Ion bipolar junction transistors
Tybrandt, Klas; Larsson, Karin C.; Richter-Dahlfors, Agneta; Berggren, Magnus
2010-01-01
Dynamic control of chemical microenvironments is essential for continued development in numerous fields of life sciences. Such control could be achieved with active chemical circuits for delivery of ions and biomolecules. As the basis for such circuitry, we report a solid-state ion bipolar junction transistor (IBJT) based on conducting polymers and thin films of anion- and cation-selective membranes. The IBJT is the ionic analogue to the conventional semiconductor BJT and is manufactured using standard microfabrication techniques. Transistor characteristics along with a model describing the principle of operation, in which an anionic base current amplifies a cationic collector current, are presented. By employing the IBJT as a bioelectronic circuit element for delivery of the neurotransmitter acetylcholine, its efficacy in modulating neuronal cell signaling is demonstrated. PMID:20479274
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Cytosolic Nucleotides Block and Regulate the Arabidopsis Vacuolar Anion Channel AtALMT9*
Zhang, Jingbo; Martinoia, Enrico; De Angeli, Alexis
2014-01-01
The aluminum-activated malate transporters (ALMTs) form a membrane protein family exhibiting different physiological roles in plants, varying from conferring tolerance to environmental Al3+ to the regulation of stomatal movement. The regulation of the anion channels of the ALMT family is largely unknown. Identifying intracellular modulators of the activity of anion channels is fundamental to understanding their physiological functions. In this study we investigated the role of cytosolic nucleotides in regulating the activity of the vacuolar anion channel AtALMT9. We found that cytosolic nucleotides modulate the transport activity of AtALMT9. This modulation was based on a direct block of the pore of the channel at negative membrane potentials (open channel block) by the nucleotide and not by a phosphorylation mechanism. The block by nucleotides of AtALMT9-mediated currents was voltage dependent. The blocking efficiency of intracellular nucleotides increased with the number of phosphate groups and ATP was the most effective cellular blocker. Interestingly, the ATP block induced a marked modification of the current-voltage characteristic of AtALMT9. In addition, increased concentrations of vacuolar anions were able to shift the ATP block threshold to a more negative membrane potential. The block of AtALMT9-mediated anion currents by ATP at negative membrane potentials acts as a gate of the channel and vacuolar anion tune this gating mechanism. Our results suggest that anion transport across the vacuolar membrane in plant cells is controlled by cytosolic nucleotides and the energetic status of the cell. PMID:25028514
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Cytosolic nucleotides block and regulate the Arabidopsis vacuolar anion channel AtALMT9.
Zhang, Jingbo; Martinoia, Enrico; De Angeli, Alexis
2014-09-12
The aluminum-activated malate transporters (ALMTs) form a membrane protein family exhibiting different physiological roles in plants, varying from conferring tolerance to environmental Al(3+) to the regulation of stomatal movement. The regulation of the anion channels of the ALMT family is largely unknown. Identifying intracellular modulators of the activity of anion channels is fundamental to understanding their physiological functions. In this study we investigated the role of cytosolic nucleotides in regulating the activity of the vacuolar anion channel AtALMT9. We found that cytosolic nucleotides modulate the transport activity of AtALMT9. This modulation was based on a direct block of the pore of the channel at negative membrane potentials (open channel block) by the nucleotide and not by a phosphorylation mechanism. The block by nucleotides of AtALMT9-mediated currents was voltage dependent. The blocking efficiency of intracellular nucleotides increased with the number of phosphate groups and ATP was the most effective cellular blocker. Interestingly, the ATP block induced a marked modification of the current-voltage characteristic of AtALMT9. In addition, increased concentrations of vacuolar anions were able to shift the ATP block threshold to a more negative membrane potential. The block of AtALMT9-mediated anion currents by ATP at negative membrane potentials acts as a gate of the channel and vacuolar anion tune this gating mechanism. Our results suggest that anion transport across the vacuolar membrane in plant cells is controlled by cytosolic nucleotides and the energetic status of the cell. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.
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Two dimensional fluid simulation in capacitively coupled silane discharges
NASA Astrophysics Data System (ADS)
Song, Yuan-Hong; Liu, Xiang-Mei; Wang, Yan; Wang, You-Nian
2011-10-01
A two-dimensional (2D) self-consistent fluid model is developed to describe the formation, subsequent growth, transport and charging mechanisms of nanoparticles in a capacitively coupled silane plasma. In this discharge process, large anions are produced by a series of chemical reactions of anions with silane molecules, while the lower limit of the initial nanoparticles are taken as large anions to directly link the coagulation module with the nucleation module. The influences of source parameters on the electron density, electron temperature, nanoparticle uniformity, and deposition rate, are carefully studied. Moreover, the behavior of silicon plasma mixed with SiH4, N2 and O2 in a pulse modulated capacitively coupled plasma has been also investigated. Results showed a strong dependence of the electron density and electron temperature on the duty cycle and the modulated frequency. Supported by NSFC (No.10775025 and No. 10805008), INSTSP (Grant No: 2011ZX02403-001), and PNCETU (NCET-08-0073).
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Wouters, Sam; Wouters, Bert; Jespers, Sander; Desmet, Gert; Eghbali, Hamed; Bruggink, Cees; Eeltink, Sebastiaan
2014-08-15
A microfluidic membrane suppressor has been constructed to suppress ions of alkaline mobile-phases via an acid-base reaction across a sulfonated poly(tetrafluoroethylene)-based membrane and was evaluated for anion-exchange separations using conductivity detection. The membrane was clamped between two chip substrates, accommodating rectangular microchannels for the eluent and regenerant flow, respectively. Additionally, a clamp-on chip holder has been constructed which allows the alignment and stacking of different chip modules. The response and efficacy of the microfluidic chip suppressor was assessed for a wide range of eluent (KOH) concentrations, using 127 and 183μm thick membranes, while optimizing the flow rate and concentration of the regenerant solution (H2SO4). The optimal operating eluent flow rate was determined at 5μL/min, corresponding to the optimal van-Deemter flow velocity of commercially-available column technology, i.e. a 0.4mm i.d.×250mm long column packed with 7.5μm anion-exchange particles. When equilibrated at 10mM KOH, a 99% decrease in conductivity signal could be obtained within 5min when applying 10mM H2SO4 regenerant at 75μL/min. A background signal as low as 1.2μS/cm was obtained, which equals the performance of a commercially-available electrolytic hollow-fiber suppressor. When increasing the temperature of the membrane suppressor from 15 to 20°C, ion suppression was significantly improved allowing the application of 75mM KOH. The applicability of the chip suppressor has been demonstrated with an isocratic baseline separation of a mixture of seven inorganic ions, yielding plate numbers between 5300 and 10,600 and with a gradient separation of a complex ion mixture. Copyright © 2014 Elsevier B.V. All rights reserved.
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Fang, Zhiwei; Peng, Lele; Qian, Yumin; Zhang, Xiao; Xie, Yujun; Cha, Judy J; Yu, Guihua
2018-04-18
Seeking earth-abundant electrocatalysts with high efficiency and durability has become the frontier of energy conversion research. Mixed-transition-metal (MTM)-based electrocatalysts, owing to the desirable electrical conductivity, synergistic effect of bimetal atoms, and structural stability, have recently emerged as new-generation hydrogen evolution reaction (HER) electrocatalysts. However, the correlation between anion species and their intrinsic electrocatalytic properties in MTM-based electrocatalysts is still not well understood. Here we present a novel approach to tuning the anion-dependent electrocatalytic characteristics in MTM-based catalyst for HER, using holey Ni/Co-based phosphides/selenides/oxides (Ni-Co-A, A = P, Se, O) as the model materials. The electrochemical results, combined with the electrical conductivity measurement and DFT calculation, reveal that P substitution could modulate the electron configuration, lower the hydrogen adsorption energy, and facilitate the desorption of hydrogen on the active sites in Ni-Co-A holey nanostructures, resulting in superior HER catalytic activity. Accordingly we fabricate the NCP holey nanosheet electrocatalyst for HER with an ultralow onset overpotential of nearly zero, an overpotential of 58 mV, and long-term durability, along with an applied potential of 1.56 V to boost overall water splitting at 10 mA cm -2 , among the best electrocatalysts reported for non-noble-metal catalysts to date. This work not only presents a deeper understanding of the intrinsic HER electrocatalytic properties for MTM-based electrocatalyst with various anion species but also offers new insights to better design efficient and durable water-splitting electrocatalysts.
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ESI activity of Br⁻, BF₄⁻ , ClO₄⁻ and BPh₄⁻ anions in the presence of Li⁺ and NBu⁴⁺ counter-ions.
Koszinowski, K; Lissy, F
2017-03-01
To improve our understanding of the electrospray ionization (ESI) process, we have subjected equimolar mixtures of salts A + X - (A + = Li + , NBu 4 + ; X - = Br - , ClO 4 - , BF 4 - , BPh 4 - ) in different solvents (CH 3 CN, tetrahydrofuran, CH 3 OH, H 2 O) to negative-ion mode ESI and analyzed the relative ESI activity of the different anionic model analytes. The ESI activity of the large and hydrophobic BPh 4 - ion greatly exceeds that of the smaller and more hydrophilic anions Br - , ClO 4 - and BF 4 - , which we ascribe to its higher surface activity. Moreover, the ESI activity of the anions is modulated by the action of the counter-ions and their different tendency toward ion pairing. The tendency toward ion pairing can be reduced by the addition of the chelating ligands 12-crown-4 and 2.2.1 cryptand and is, although to a smaller degree, further influenced by the variation of the solvent. Complementary electrical conductivity measurements afford additional information on the interactions of the ionic constituents of the sample solutions. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.
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Unni, Sreekuttan M; Bhange, Siddheshwar N; Illathvalappil, Rajith; Mutneja, Nisha; Patil, Kasinath R; Kurungot, Sreekumar
2015-01-21
Nitrogen-doped carbon morphologies have been proven to be better alternatives to Pt in polymer-electrolyte membrane (PEM) fuel cells. However, efficient modulation of the active sites by the simultaneous escalation of the porosity and nitrogen doping, without affecting the intrinsic electrical conductivity, still remains to be solved. Here, a simple strategy is reported to solve this issue by treating single-walled carbon nanohorn (SWCNH) with urea at 800 °C. The resulting nitrogen-doped carbon nanohorn shows a high surface area of 1836 m2 g(-1) along with an increased electron conductivity, which are the pre-requisites of an electrocatalyst. The nitrogen-doped nanohorn annealed at 800 °C (N-800) also shows a high oxygen reduction activity (ORR). Because of the high weight percentage of pyridinic nitrogen coordination in N-800, the present catalyst shows a clear 4-electron reduction pathway at only 50 mV overpotential and 16 mV negative shift in the half-wave potential for ORR compared to Pt/C along with a high fuel selectivity and electrochemical stability. More importantly, a membrane electrode assembly (MEA) based on N-800 provides a maximum power density of 30 mW cm(-2) under anion-exchange membrane fuel cell (AEMFC) testing conditions. Thus, with its remarkable set of physical and electrochemical properties, this material has the potential to perform as an efficient Pt-free electrode for AEMFCs. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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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.
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Song, Lei; Seeger, Achim; Santos-Sacchi, Joseph
2005-01-01
The outer hair cell (OHC) underlies mammalian cochlea amplification, and its lateral membrane motor, prestin, which drives the cell's mechanical activity, is modulated by intracellular chloride ions. We have previously described a native nonselective conductance (GmetL) that influences OHC motor activity via Cl flux across the lateral membrane. Here we further investigate this conductance and use the environmental toxin tributyltin (TBT) to better understand Cl-prestin interactions. Capitalizing on measures of prestin-derived nonlinear capacitance to gauge Cl flux across the lateral membrane, we show that the Cl ionophore TBT, which affects neither the motor nor GmetL directly, is capable of augmenting the native flux of Cl in OHCs. These observations were confirmed using the chloride-sensitive dye MQAE. Furthermore, the compound's potent ability, at nanomolar concentrations, to equilibrate intra- and extracellular Cl concentrations is shown to surpass the effectiveness of GmetL in promoting Cl flux, and secure a quantitative analysis of Cl-prestin interactions in intact OHCs. Using malate as an anion replacement, we quantify chloride effects on the nonlinear charge density and operating voltage range of prestin. Our data additionally suggest that ototoxic effects of organotins can derive from their disruption of OHC Cl homeostasis, ultimately interfering with anionic modulation of the mammalian cochlear amplifier. Notably, this observation identifies a new environmental threat for marine mammals by TBT, which is known to accumulate in the food chain. PMID:15596517
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Yoshizawa, Shunsuke; Arakawa, Tsutomu; Shiraki, Kentaro
2016-10-01
Arginine is widely used in biotechnological application, but mostly with chloride counter ion. Here, we examined the effects of various anions on solubilization of aromatic compounds and reduced lysozyme and on refolding of the lysozyme. All arginine salts tested increased the solubility of propyl gallate with acetate much more effectively than chloride. The effects of arginine salts were compared with those of sodium or guanidine salts, indicating that the ability of anions to modulate the propyl gallate solubility is independent of the cation. Comparison of transfer free energy of propyl gallate between sodium and arginine salts indicates that the interaction of propyl gallate is more favorable with arginine than sodium. On the contrary, the solubility of aromatic amino acids is only slightly modulated by anions, implying that there is specific interaction between acetic acid and propyl gallate. Unlike their effects on the solubility of small aromatic compounds, the solubility of reduced lysozyme was much higher in arginine chloride than in arginine acetate or sulfate. Consistent with high solubility, refolding of reduced lysozyme was most effective in arginine chloride. These results suggest potential broader applications of arginine modulated by different anions. Copyright © 2016 Elsevier B.V. All rights reserved.
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Electrocurtain coating process for coating solar mirrors
Kabagambe, Benjamin; Boyd, Donald W.; Buchanan, Michael J.; Kelly, Patrick; Kutilek, Luke A.; McCamy, James W.; McPheron, Douglas A.; Orosz, Gary R.; Limbacher, Raymond D.
2013-10-15
An electrically conductive protective coating or film is provided over the surface of a reflective coating of a solar mirror by flowing or directing a cation containing liquid and an anion containing liquid onto the conductive surface. The cation and the anion containing liquids are spaced from, and preferably out of contact with one another on the surface of the reflective coating as an electric current is moved through the anion containing liquid, the conductive surface between the liquids and the cation containing liquid to coat the conductive surface with the electrically conductive coating.
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The Anion Paradox in Sodium Taste Reception: Resolution by Voltage-Clamp Studies
NASA Astrophysics Data System (ADS)
Ye, Qing; Heck, Gerard L.; Desimone, John A.
1991-11-01
Sodium salts are potent taste stimuli, but their effectiveness is markedly dependent on the anion, with chloride yielding the greatest response. The cellular mechanisms that mediate this phenomenon are not known. This "anion paradox" has been resolved by considering the field potential that is generated by restricted electrodiffusion of the anion through paracellular shunts between taste-bud cells. Neural responses to sodium chloride, sodium acetate, and sodium gluconate were studied while the field potential was voltage-clamped. Clamping at electronegative values eliminated the anion effect, whereas clamping at electropositive potentials exaggerated it. Thus, field potentials across the lingual epithelium modulate taste reception, indicating that the functional unit of taste reception includes the taste cell and its paracellular microenvironment.
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Hagiwara, S; Takahashi, K
1974-04-01
1. Properties of anion permeation through the membrane of skeletal muscle fibres of the stingray, Taeniura lymma, were studied with intracellular recording and polarization techniques.2. The Cl conductance of the resting membrane in the normal stingray saline at pH 7.7 is 8-10 times greater than the K conductance.3. The Cl conductance decreases with decreasing external pH, with an apparent pK of 5.3, whereas the K conductance is independent of pH between 4 and 9.4. The Q(10) of the Cl conductance is about 2.0, compared with a value of 1.2-1.4 for the K conductance.5. The Cl conductance is proportional to the external Cl concentration when observed after the fibre is equilibrated in the test solution.6. The permeability sequence obtained by potential measurement is SCN > NO(3) > Cl = Br > I > ClO(3) and the permeability ratio is independent of the mole fraction of anions.7. The conductance sequence determined by total replacement of the external Cl with other anion species differs from the permeability sequence and the conductance observed for partial replacement deviates significantly from that expected from the independence principle.8. Possible mechanisms of anion permeation are discussed.
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Hagiwara, Susumu; Takahashi, Kunitaro
1974-01-01
1. Properties of anion permeation through the membrane of skeletal muscle fibres of the stingray, Taeniura lymma, were studied with intracellular recording and polarization techniques. 2. The Cl conductance of the resting membrane in the normal stingray saline at pH 7·7 is 8-10 times greater than the K conductance. 3. The Cl conductance decreases with decreasing external pH, with an apparent pK of 5·3, whereas the K conductance is independent of pH between 4 and 9. 4. The Q10 of the Cl conductance is about 2·0, compared with a value of 1·2-1·4 for the K conductance. 5. The Cl conductance is proportional to the external Cl concentration when observed after the fibre is equilibrated in the test solution. 6. The permeability sequence obtained by potential measurement is SCN > NO3 > Cl = Br > I > ClO3 and the permeability ratio is independent of the mole fraction of anions. 7. The conductance sequence determined by total replacement of the external Cl with other anion species differs from the permeability sequence and the conductance observed for partial replacement deviates significantly from that expected from the independence principle. 8. Possible mechanisms of anion permeation are discussed. PMID:4838800
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Conductive polymeric compositions for lithium batteries
Angell, Charles A [Mesa, AZ; Xu, Wu [Tempe, AZ
2009-03-17
Novel chain polymers comprising weakly basic anionic moieties chemically bound into a polyether backbone at controllable anionic separations are presented. Preferred polymers comprise orthoborate anions capped with dibasic acid residues, preferably oxalato or malonato acid residues. The conductivity of these polymers is found to be high relative to that of most conventional salt-in-polymer electrolytes. The conductivity at high temperatures and wide electrochemical window make these materials especially suitable as electrolytes for rechargeable lithium batteries.
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Cheng, Jiongjia; Goldstein, Rebecca; Stec, Boguslaw; Gershenson, Anne; Roberts, Mary F.
2012-01-01
Staphylococcus aureus phosphatidylinositol-specific phospholipase C (PI-PLC) is a secreted virulence factor for this pathogenic bacterium. A novel crystal structure shows that this PI-PLC can form a dimer via helix B, a structural feature present in all secreted, bacterial PI-PLCs that is important for membrane binding. Despite the small size of this interface, it is critical for optimal enzyme activity. Kinetic evidence, increased enzyme specific activity with increasing enzyme concentration, supports a mechanism where the PI-PLC dimerization is enhanced in membranes containing phosphatidylcholine (PC). Mutagenesis of key residues confirm that the zwitterionic phospholipid acts not by specific binding to the protein, but rather by reducing anionic lipid interactions with a cationic pocket on the surface of the S. aureus enzyme that stabilizes monomeric protein. Despite its structural and sequence similarity to PI-PLCs from other Gram-positive pathogenic bacteria, S. aureus PI-PLC appears to have a unique mechanism where enzyme activity is modulated by competition between binding of soluble anions or anionic lipids to the cationic sensor and transient dimerization on the membrane. PMID:23038258
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Jakusová, Klaudia; Donovalová, Jana; Cigáň, Marek; Gáplovský, Martin; Garaj, Vladimír; Gáplovský, Anton
2014-04-05
The anion induced tautomerism of isatin-3-4-phenyl(semicarbazone) derivatives is studied herein. The interaction of F(-), AcO(-), H2PO4(-), Br(-) or HSO4(-) anions with E and Z isomers of isatin-3-4-phenyl(semicarbazone) and N-methylisatin-3-4-phenyl(semicarbazone) as sensors influences the tautomeric equilibrium of these sensors in the liquid phase. This tautomeric equilibrium is affected by (1) the inter- and intra-molecular interactions' modulation of isatinphenylsemicarbazone molecules due to the anion induced change in the solvation shell of receptor molecules and (2) the sensor-anion interaction with the urea hydrogens. The acid-base properties of anions and the difference in sensor structure influence the equilibrium ratio of the individual tautomeric forms. Here, the tautomeric equilibrium changes were indicated by "naked-eye" experiment, UV-VIS spectral and (1)H NMR titration, resulting in confirmation that appropriate selection of experimental conditions leads to a high degree of sensor selectivity for some investigated anions. Sensors' E and Z isomers differ in sensitivity, selectivity and sensing mechanism. Detection of F(-) or CH3COO(-) anions at high weakly basic anions' excess is possible. Copyright © 2014 Elsevier B.V. All rights reserved.
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Conger, Bryant T.; Zhang, Shaoyan; Skinner, Daniel; Hicks, Stephen B.; Sorscher, Eric J.; Rowe, Steven M.; Woodworth, Bradford A.
2014-01-01
IMPORTANCE Pharmacologic activation of mucociliary clearance (MCC) represents an emerging therapeutic strategy for patients with chronic rhinosinusitis, even in the absence of congenital mutations of the CFTR gene. Drug discovery efforts have identified small molecules that activate the cystic fibrosis transmembrane conductance regulator (CFTR), including potentiators under development for treatment of cystic fibrosis. OBJECTIVE To evaluate the properties of CFTR modulators and their effects on ciliary beat frequency (CBF) in human sinonasal epithelium (HSNE). DESIGN Primary HSNE cultures (wild type and F508del/F508del) were used to compare stimulation of CFTR-mediated Cl− conductance and CBF by the CFTR modulators genistein, VRT-532, and UCCF-152. MAIN OUTCOMES AND MEASURES Increase in CFTR-dependent anion transport and CBF. RESULTS HSNE cultures were analyzed using pharmacologic manipulation of ion transport (change in short-circuit current [ΔISC]) and high-speed digital imaging (CBF). Activation of CFTR-dependent anion transport was significantly different among agonists (P < .001), with genistein exerting the greatest effect (mean [SD] ΔISC, genistein, 23.1 [1.8] µA/cm2 > VRT-532, 8.1 [1.0] µA/cm2 > UCCF-152, 3.4 [1.4] µA/cm2 > control, 0.7 [0.2] µA/cm2; Tukey-Kramer P < .05) in the absence of forskolin. Genistein and UCCF-152 augmented CBF (under submerged conditions) significantly better (Tukey-Kramer P < .05) than cells treated with VRT-532 or dimethyl sulfoxide vehicle control (mean [SD] fold change over baseline, genistein, 1.63 [0.06]; UCCF-152, 1.56 [0.06]; VRT-532, 1.38 [0.08]; control, 1.27 [0.02]). Activation of CBF was blunted in F508del/F508del HSNE cultures. CONCLUSIONS AND RELEVANCE The degree of CBF stimulation was not dependent on the magnitude of Cl− secretion, suggesting that different mechanisms of action may underlie MCC activation by these small molecule potentiators. Agents that activate both CFTR-dependent ISC and CBF are particularly attractive as therapeutics because they may address 2 independent pathways that contribute to deficient MCC in chronic rhinosinusitis. PMID:23949358
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Conger, Bryant T; Zhang, Shaoyan; Skinner, Daniel; Hicks, Stephen B; Sorscher, Eric J; Rowe, Steven M; Woodworth, Bradford A
2013-08-01
Pharmacologic activation of mucociliary clearance (MCC) represents an emerging therapeutic strategy for patients with chronic rhinosinusitis, even in the absence of congenital mutations of the CFTR gene. Drug discovery efforts have identified small molecules that activate the cystic fibrosis transmembrane conductance regulator (CFTR), including potentiators under development for treatment of cystic fibrosis. To evaluate the properties of CFTR modulators and their effects on ciliary beat frequency (CBF) in human sinonasal epithelium (HSNE). Primary HSNE cultures (wild type and F508del/F508del) were used to compare stimulation of CFTR-mediated Cl- conductance and CBF by the CFTR modulators genistein, VRT-532, and UCCF-152. Increase in CFTR-dependent anion transport and CBF. HSNE cultures were analyzed using pharmacologic manipulation of ion transport (change in short-circuit current [∆ISC]) and high-speed digital imaging (CBF). Activation of CFTR-dependent anion transport was significantly different among agonists (P < .001), with genistein exerting the greatest effect (mean [SD] ∆ISC, genistein, 23.1 [1.8] μA/cm2² > VRT-532, 8.1 [1.0] μA/cm² > UCCF-152, 3.4 [1.4] μA/cm² > control, 0.7 [0.2] μA/cm²; Tukey-Kramer P < .05) in the absence of forskolin. Genistein and UCCF-152 augmented CBF (under submerged conditions) significantly better (Tukey-Kramer P < .05) than cells treated with VRT-532 or dimethyl sulfoxide vehicle control (mean [SD] fold change over baseline, genistein, 1.63 [0.06]; UCCF-152, 1.56 [0.06]; VRT-532, 1.38 [0.08]; control, 1.27 [0.02]). Activation of CBF was blunted in F508del/F508del HSNE cultures. The degree of CBF stimulation was not dependent on the magnitude of Cl- secretion, suggesting that different mechanisms of action may underlie MCC activation by these small molecule potentiators. Agents that activate both CFTR-dependent ISC and CBF are particularly attractive as therapeutics because they may address 2 independent pathways that contribute to deficient MCC in chronic rhinosinusitis.
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Horikoshi, Sonoko; Hanamata, Shigeru; Negi, Juntaro; Yagi, Chikako; Kitahata, Nobutaka; Iba, Koh; Kuchitsu, Kazuyuki
2013-01-01
Pharmacological evidence suggests that anion channel-mediated plasma membrane anion effluxes are crucial in early defense signaling to induce immune responses and hypersensitive cell death in plants. However, their molecular bases and regulation remain largely unknown. We overexpressed Arabidopsis SLAC1, an S-type anion channel involved in stomatal closure, in cultured tobacco BY-2 cells and analyzed the effect on cryptogein-induced defense responses including fluxes of Cl− and other ions, production of reactive oxygen species (ROS), gene expression and hypersensitive responses. The SLAC1-GFP fusion protein was localized at the plasma membrane in BY-2 cells. Overexpression of SLAC1 enhanced cryptogein-induced Cl− efflux and extracellular alkalinization as well as rapid/transient and slow/prolonged phases of NADPH oxidase-mediated ROS production, which was suppressed by an anion channel inhibitor, DIDS. The overexpressor also showed enhanced sensitivity to cryptogein to induce downstream immune responses, including the induction of defense marker genes and the hypersensitive cell death. These results suggest that SLAC1 expressed in BY-2 cells mediates cryptogein-induced plasma membrane Cl− efflux to positively modulate the elicitor-triggered activation of other ion fluxes, ROS as well as a wide range of defense signaling pathways. These findings shed light on the possible involvement of the SLAC/SLAH family anion channels in cryptogein signaling to trigger the plasma membrane ion channel cascade in the plant defense signal transduction network. PMID:23950973
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Kurusu, Takamitsu; Saito, Katsunori; Horikoshi, Sonoko; Hanamata, Shigeru; Negi, Juntaro; Yagi, Chikako; Kitahata, Nobutaka; Iba, Koh; Kuchitsu, Kazuyuki
2013-01-01
Pharmacological evidence suggests that anion channel-mediated plasma membrane anion effluxes are crucial in early defense signaling to induce immune responses and hypersensitive cell death in plants. However, their molecular bases and regulation remain largely unknown. We overexpressed Arabidopsis SLAC1, an S-type anion channel involved in stomatal closure, in cultured tobacco BY-2 cells and analyzed the effect on cryptogein-induced defense responses including fluxes of Cl(-) and other ions, production of reactive oxygen species (ROS), gene expression and hypersensitive responses. The SLAC1-GFP fusion protein was localized at the plasma membrane in BY-2 cells. Overexpression of SLAC1 enhanced cryptogein-induced Cl(-) efflux and extracellular alkalinization as well as rapid/transient and slow/prolonged phases of NADPH oxidase-mediated ROS production, which was suppressed by an anion channel inhibitor, DIDS. The overexpressor also showed enhanced sensitivity to cryptogein to induce downstream immune responses, including the induction of defense marker genes and the hypersensitive cell death. These results suggest that SLAC1 expressed in BY-2 cells mediates cryptogein-induced plasma membrane Cl(-) efflux to positively modulate the elicitor-triggered activation of other ion fluxes, ROS as well as a wide range of defense signaling pathways. These findings shed light on the possible involvement of the SLAC/SLAH family anion channels in cryptogein signaling to trigger the plasma membrane ion channel cascade in the plant defense signal transduction network.
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Density functional theory and conductivity studies of boron-based anion receptors
Leung, Kevin; Chaudhari, Mangesh I.; Rempe, Susan B.; ...
2015-07-10
Anion receptors that bind strongly to fluoride anions in organic solvents can help dissolve the lithium fluoride discharge products of primary carbon monofluoride (CFx) batteries, thereby preventing the clogging of cathode surfaces and improving ion conductivity. The receptors are also potentially beneficial to rechargeable lithium ion and lithium air batteries. We apply Density Functional Theory (DFT) to show that an oxalate-based pentafluorophenyl-boron anion receptor binds as strongly, or more strongly, to fluoride anions than many phenyl-boron anion receptors proposed in the literature. Experimental data shows marked improvement in electrolyte conductivity when this oxalate anion receptor is present. The receptor ismore » sufficiently electrophilic that organic solvent molecules compete with F – for boron-site binding, and specific solvent effects must be considered when predicting its F – affinity. To further illustrate the last point, we also perform computational studies on a geometrically constrained boron ester that exhibits much stronger gas-phase affinity for both F – and organic solvent molecules. After accounting for specific solvent effects, however, its net F – affinity is about the same as the simple oxalate-based anion receptor. Lastly, we propose that LiF dissolution in cyclic carbonate organic solvents, in the absence of anion receptors, is due mostly to the formation of ionic aggregates, not isolated F – ions.« less
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ERIC Educational Resources Information Center
D'Arcy, Mitch; Bullough, Florence; Moffat, Chris; Borgomeo, Edoardo; Teh, Micheal; Vilar, Ramon; Weiss, Dominik J.
2014-01-01
Synthesizing and testing bicomposite adsorbents for the removal of environmentally problematic oxy-anions is high on the agenda of research-led universities. Here we present a laboratory module successfully developed at Imperial College London that introduces the advanced undergraduate student in engineering (chemical, civil, earth) and science…
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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.
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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
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Pongjit, Kanittha; Chanvorachote, Pithi
2011-12-01
Caveolin-1 (Cav-1) expression frequently found in lung cancer was linked with disease prognosis and progression. This study reveals for the first time that Cav-1 sensitizes cisplatin-induced lung carcinoma cell death by the mechanism involving oxidative stress modulation. We established stable Cav-1 overexpressed (H460/Cav-1) cells and investigated their cisplatin susceptibility in comparison with control-transfected cells and found that Cav-1 expression significantly enhanced cisplatin-mediated cell death. Results indicated that the different response to cisplatin between these cells was resulted from different level of superoxide anion induced by cisplatin. Inhibitory study revealed that superoxide anion inhibitor MnTBAP could inhibit cisplatin-mediated toxicity only in H460/Cav-1 cells while had no effect on H460 cells. Further, superoxide anion detected by DHE probe indicated that H460/Cav-1 cells generated significantly higher superoxide anion level in response to cisplatin than that of control cells. The role of Cav-1 in regulating cisplatin sensitivity was confirmed in shRNA-mediated Cav-1 down-regulated (H460/shCav-1) cells and the cells exhibited decreased cisplatin susceptibility and superoxide generation. In summary, these findings reveal novel aspects regarding role of Cav-1 in modulating oxidative stress induced by cisplatin, possibly providing new insights for cancer biology and cisplatin-based chemotherapy.
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Method and apparatus for chromatographic quantitative analysis
Fritz, James S.; Gjerde, Douglas T.; Schmuckler, Gabriella
1981-06-09
An improved apparatus and method for the quantitative analysis of a solution containing a plurality of anion species by ion exchange chromatography which utilizes a single eluent and a single ion exchange bed which does not require periodic regeneration. The solution containing the anions is added to an anion exchange resin bed which is a low capacity macroreticular polystyrene-divinylbenzene resin containing quarternary ammonium functional groups, and is eluted therefrom with a dilute solution of a low electrical conductance organic acid salt. As each anion species is eluted from the bed, it is quantitatively sensed by conventional detection means such as a conductivity cell.
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Kerres, Jochen A.; Krieg, Henning M.
2017-01-01
In view of the many possible applications such as fuel cells and electrolysers, recent interest in novel anion exchange membranes (AEMs) has increased significantly. However, their low conductivity and chemical stability limits their current suitability. In this study, the synthesis and characterization of several three- and four-component anion exchange blend membranes (AEBMs) is described, where the compositions have been systematically varied to study the influence of the AEBM’s composition on the anion conductivities as well as chemical and thermal stabilities under strongly alkaline conditions. It was shown that the epoxide-functionalized poly(ethylene glycol)s that were introduced into the four-component AEBMs resulted in increased conductivity as well as a marked improvement in the stability of the AEBMs in an alkaline environment. In addition, the thermal stability of the novel AEBMs was excellent showing the suitability of these membranes for several electrochemical applications. PMID:28621717
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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.
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NASA Astrophysics Data System (ADS)
Watanabe, Mebae; Fujihara, Shinobu
2014-02-01
Inorganic-organic layered rare-earth compounds were synthesized on the basis of a biphasic liquid-liquid system in one pot. Layered yttrium hydroxides (LYHs) were chosen as a host material for the intercalation of hydrophobic organic guest anions such as benzoate, sebacate, or laurate. In a typical synthesis, an organic phase dissolving carboxylic acid was placed in contact with an equal amount of an aqueous phase dissolving yttrium nitrate n-hydrate and urea. At elevated temperatures up to 80 °C, urea was hydrolyzed to release hydroxyl anions which were used to form yttrium hydroxide layers. LYHs were then precipitated with the intercalation of carboxylate anions delivered from the organic phase under the distribution law. The structure and the morphology of the LYHs could be modulated by the intercalated anions. Doped with Eu3+ ions, the LYHs exhibited red photoluminescence which was enhanced by the intercalated anions due to the antenna effect.
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Through-plane conductivities of membranes for nonaqueous redox flow batteries
DOE Office of Scientific and Technical Information (OSTI.GOV)
Anderson, Travis Mark; Small, Leo J.; Pratt, III, Harry D.
In this study, nonaqueous redox flow batteries (RFB) leverage nonaqueous solvents to enable higher operating voltages compared to their aqueous counterparts. Most commercial components for flow batteries, however, are designed for aqueous use. One critical component, the ion-selective membrane, provides ionic conductance between electrodes while preventing crossover of electroactive species. Here we evaluate the area-specific conductances and through-plane conductivities of commercially available microporous separators (Celgard 2400, 2500) and anion exchange membranes (Neosepta AFX, Neosepta AHA, Fumasep FAP-450, Fumasep FAP-PK) soaked in acetonitrile, propylene carbonate, or two imidazolium-based ionic liquids. Fumasep membranes combined with acetonitrile-based electrolyte solutions provided the highest conductancemore » values and conductivities by far. When tested in ionic liquids, all anion exchange membranes displayed conductivities greater than those of the Celgard microporous separators, though the separators’ decreased thickness-enabled conductances on par with the most conductive anion exchange membranes. Ionic conductivity is not the only consideration when choosing an anion exchange membrane; testing of FAP-450 and FAP-PK membranes in a nonaqueous RFB demonstrated that the increased mechanical stability of PEEK-supported FAP-PK minimized swelling, in turn decreasing solvent mediated crossover and enabling greater electrochemical yields (40% vs. 4%) and Coulombic efficiencies (94% vs. 90%) compared to the unsupported, higher conductance FAP-450.« less
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Through-plane conductivities of membranes for nonaqueous redox flow batteries
Anderson, Travis Mark; Small, Leo J.; Pratt, III, Harry D.; ...
2015-08-13
In this study, nonaqueous redox flow batteries (RFB) leverage nonaqueous solvents to enable higher operating voltages compared to their aqueous counterparts. Most commercial components for flow batteries, however, are designed for aqueous use. One critical component, the ion-selective membrane, provides ionic conductance between electrodes while preventing crossover of electroactive species. Here we evaluate the area-specific conductances and through-plane conductivities of commercially available microporous separators (Celgard 2400, 2500) and anion exchange membranes (Neosepta AFX, Neosepta AHA, Fumasep FAP-450, Fumasep FAP-PK) soaked in acetonitrile, propylene carbonate, or two imidazolium-based ionic liquids. Fumasep membranes combined with acetonitrile-based electrolyte solutions provided the highest conductancemore » values and conductivities by far. When tested in ionic liquids, all anion exchange membranes displayed conductivities greater than those of the Celgard microporous separators, though the separators’ decreased thickness-enabled conductances on par with the most conductive anion exchange membranes. Ionic conductivity is not the only consideration when choosing an anion exchange membrane; testing of FAP-450 and FAP-PK membranes in a nonaqueous RFB demonstrated that the increased mechanical stability of PEEK-supported FAP-PK minimized swelling, in turn decreasing solvent mediated crossover and enabling greater electrochemical yields (40% vs. 4%) and Coulombic efficiencies (94% vs. 90%) compared to the unsupported, higher conductance FAP-450.« less
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Ramesh, Sunita A; Tyerman, Stephen D; Xu, Bo; Bose, Jayakumar; Kaur, Satwinder; Conn, Vanessa; Domingos, Patricia; Ullah, Sana; Wege, Stefanie; Shabala, Sergey; Feijó, José A; Ryan, Peter R; Gilliham, Matthew; Gillham, Matthew
2015-07-29
The non-protein amino acid, gamma-aminobutyric acid (GABA) rapidly accumulates in plant tissues in response to biotic and abiotic stress, and regulates plant growth. Until now it was not known whether GABA exerts its effects in plants through the regulation of carbon metabolism or via an unidentified signalling pathway. Here, we demonstrate that anion flux through plant aluminium-activated malate transporter (ALMT) proteins is activated by anions and negatively regulated by GABA. Site-directed mutagenesis of selected amino acids within ALMT proteins abolishes GABA efficacy but does not alter other transport properties. GABA modulation of ALMT activity results in altered root growth and altered root tolerance to alkaline pH, acid pH and aluminium ions. We propose that GABA exerts its multiple physiological effects in plants via ALMT, including the regulation of pollen tube and root growth, and that GABA can finally be considered a legitimate signalling molecule in both the plant and animal kingdoms.
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Ramesh, Sunita A.; Tyerman, Stephen D.; Xu, Bo; Bose, Jayakumar; Kaur, Satwinder; Conn, Vanessa; Domingos, Patricia; Ullah, Sana; Wege, Stefanie; Shabala, Sergey; Feijó, José A.; Ryan, Peter R.; Gillham, Matthew
2015-01-01
The non-protein amino acid, gamma-aminobutyric acid (GABA) rapidly accumulates in plant tissues in response to biotic and abiotic stress, and regulates plant growth. Until now it was not known whether GABA exerts its effects in plants through the regulation of carbon metabolism or via an unidentified signalling pathway. Here, we demonstrate that anion flux through plant aluminium-activated malate transporter (ALMT) proteins is activated by anions and negatively regulated by GABA. Site-directed mutagenesis of selected amino acids within ALMT proteins abolishes GABA efficacy but does not alter other transport properties. GABA modulation of ALMT activity results in altered root growth and altered root tolerance to alkaline pH, acid pH and aluminium ions. We propose that GABA exerts its multiple physiological effects in plants via ALMT, including the regulation of pollen tube and root growth, and that GABA can finally be considered a legitimate signalling molecule in both the plant and animal kingdoms. PMID:26219411
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Contamination of commercial cane sugars by some organic acids and some inorganic anions.
Wojtczak, Maciej; Antczak, Aneta; Lisik, Krystyna
2013-01-01
The aim of the paper was the identification and the quantitative evaluation of the following inorganic anions: chloride, phosphate, nitrate, nitrite, sulphate and the following organic acids: lactic, acetic, formic, malic and citric in commercial "unrefined" brown cane sugars and in cane raw sugars. The determination was carried out by high performance anion exchange chromatography with conductivity detector HPAEC-CD. The conducted analyses have shown that the content of some inorganic anions and organic acids in cane sugars may be an important criterion of the quality of commercial "unrefined" brown cane sugars. Copyright © 2012 Elsevier Ltd. All rights reserved.
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Improved method and apparatus for chromatographic quantitative analysis
Fritz, J.S.; Gjerde, D.T.; Schmuckler, G.
An improved apparatus and method are described for the quantitative analysis of a solution containing a plurality of anion species by ion exchange chromatography which utilizes a single element and a single ion exchange bed which does not require periodic regeneration. The solution containing the anions is added to an anion exchange resin bed which is a low capacity macroreticular polystyrene-divinylbenzene resin containing quarternary ammonium functional groups, and is eluted therefrom with a dilute solution of a low electrical conductance organic acid salt. As each anion species is eluted from the bed, it is quantitatively sensed by conventional detection means such as a conductivity cell.
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A computational study of anion-modulated cation-π interactions.
Carrazana-García, Jorge A; Rodríguez-Otero, Jesús; Cabaleiro-Lago, Enrique M
2012-05-24
The interaction of anions with cation-π complexes formed by the guanidinium cation and benzene was thoroughly studied by means of computational methods. Potential energy surface scans were performed in order to evaluate the effect of the anion coming closer to the cation-π pair. Several structures of guanidinium-benzene complexes and anion approaching directions were examined. Supermolecule calculations were performed on ternary complexes formed by guanidinium, benzene, and one anion and the interaction energy was decomposed into its different two- and three-body contributions. The interaction energies were further dissected into their electrostatic, exchange, repulsion, polarization and dispersion contributions by means of local molecular orbital energy decomposition analysis. The results confirm that, besides the electrostatic cation-anion attraction, the effect of the anion over the cation-π interaction is mainly due to polarization and can be rationalized following the changes in the anion-π and the nonadditive (three-body) terms of the interaction. When the cation and the anion are on the same side of the π system, the three-body interaction is anticooperative, but when the anion and the cation are on opposite sides of the π system, the three-body interaction is cooperative. As far as we know, this is the first study where this kind of analysis is carried out with a structured cation as guanidinium with a significant biological interest.
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Buffering of protons released by mineral formation during amelogenesis in mice.
Bronckers, Antonius L J J; Lyaruu, Don M; Jalali, Rozita; DenBesten, Pamela K
2016-10-01
Regulation of pH by ameloblasts during amelogenesis is critical for enamel mineralization. We examined the effects of reduced bicarbonate secretion and the presence or absence of amelogenins on ameloblast modulation and enamel mineralization. To that end, the composition of fluorotic and non-fluorotic enamel of several different mouse mutants, including enamel of cystic fibrosis transmembrane conductance regulator-deficient (Cftr null), anion exchanger-2-deficient (Ae2a,b null), and amelogenin-deficient (Amelx null) mice, was determined by quantitative X-ray microanalysis. Correlation analysis was carried out to compare the effects of changes in the levels of sulfated-matrix (S) and chlorine (Cl; for bicarbonate secretion) on mineralization and modulation. The chloride (Cl - ) levels in forming enamel determined the ability of ameloblasts to modulate, remove matrix, and mineralize enamel. In general, the lower the Cl - content, the stronger the negative effects. In Amelx-null mice, modulation was essentially normal and the calcium content was reduced least. Retention of amelogenins in enamel of kallikrein-4-deficient (Klk4-null) mice resulted in decreased mineralization and reduced the length of the first acid modulation band without changing the total length of all acidic bands. These data suggest that buffering by bicarbonates is critical for modulation, matrix removal and enamel mineralization. Amelogenins also act as a buffer but are not critical for modulation. © 2016 Eur J Oral Sci.
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Kwon, Hyukin; Jiang, Wei
2015-01-01
Many existing irrigation, industrial and chemical storage sites are currently introducing hazardous anions into groundwater, making the monitoring of such sites a high priority. Detecting and quantifying anions in water samples typically requires complex instrumentation, adding cost and delaying analysis. Here we address these challenges by development of an optical molecular method to detect and discriminate a broad range of anionic contaminants with DNA-based fluorescent sensors. A library of 1296 tetrameric-length oligodeoxyfluorosides (ODFs) composed of metal ligand and fluorescence modulating monomers was constructed with a DNA synthesizer on PEG-polystyrene microbeads. These oligomers on beads were incubated with YIII or ZnII ions to provide affinity and responsiveness to anions. Seventeen anions were screened with the library under an epifluorescence microscope, ultimately yielding eight chemosensors that could discriminate 250 μM solutions of all 17 anions in buffered water using their patterns of response. This sensor set was able to identify two unknown anion samples from ten closely-responding anions and could also function quantitatively, determining unknown concentrations of anions such as cyanide (as low as 1 mM) and selenate (as low as 50 μM). Further studies with calibration curves established detection limits of selected anions including thiocyanate (detection limit ∼300 μM) and arsenate (∼800 μM). The results demonstrate DNA-like fluorescent chemosensors as versatile tools for optically analyzing environmentally hazardous anions in aqueous environments. PMID:26146537
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Pottosin, Igor; Dobrovinskaya, Oxana
2014-05-15
Both in vacuolar and plasma membranes, in addition to truly K(+)-selective channels there is a variety of non-selective channels, which conduct K(+) and other ions with little preference. Many non-selective channels in the plasma membrane are active at depolarized potentials, thus, contributing to K(+) efflux rather than to K(+) uptake. They may play important roles in xylem loading or contribute to a K(+) leak, induced by salt or oxidative stress. Here, three currents, expressed in root cells, are considered: voltage-insensitive cation current, non-selective outwardly rectifying current, and low-selective conductance, activated by reactive oxygen species. The latter two do not only poorly discriminate between different cations (like K(+)vs Na(+)), but also conduct anions. Such solute channels may mediate massive electroneutral transport of salts and might be involved in osmotic adjustment or volume decrease, associated with cell death. In the tonoplast two major currents are mediated by SV (slow) and FV (fast) vacuolar channels, respectively, which are virtually impermeable for anions. SV channels conduct mono- and divalent cations indiscriminately and are activated by high cytosolic Ca(2+) and depolarized voltages. FV channels are inhibited by micromolar cytosolic Ca(2+), Mg(2+), and polyamines, and conduct a variety of monovalent cations, including K(+). Strikingly, both SV and FV channels sense the K(+) content of vacuoles, which modulates their voltage dependence, and in case of SV, also alleviates channel's inhibition by luminal Ca(2+). Therefore, SV and FV channels may operate as K(+)-sensing valves, controlling K(+) distribution between the vacuole and the cytosol. Copyright © 2014 Elsevier GmbH. All rights reserved.
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Fundamental characteristics study of anion-exchange PVDF-SiO(2) membranes.
Zuo, Xingtao; Shi, Wenxin; Yu, Shuili; He, Jiajie
2012-01-01
A new type of poly(vinylidene fluoride)(PVDF)-SiO(2) hybrid anion-exchange membrane was prepared by blending method. The anion-exchange groups were introduced by the reaction of epoxy groups with trimethylamine (TMA). Contact angle between water and the membrane surface was measured to characterize the hydrophilicity change of the membrane surface. The effects of nano-sized SiO(2) particles in the membrane-forming materials on the membrane mechanical properties and conductivity were also investigated. The experimental results indicated that PVDF-SiO(2) anion-exchange membranes exhibited better water content, ion-exchange capacity, conductivity and mechanic properties, and so may find potential applications in alkaline membrane fuel cells and water treatment processes.
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Sun, Liyuan; Morales-Collazo, Oscar; Xia, Han; Brennecke, Joan F
2015-12-03
A series of room temperature ionic liquids (RTILs) based on 1-ethyl-3-methylimidazolium ([emim](+)) with different aprotic heterocyclic anions (AHAs) were synthesized and characterized as potential electrolyte candidates for lithium ion batteries. The density and transport properties of these ILs were measured over the temperature range between 283.15 and 343.15 K at ambient pressure. The temperature dependence of the transport properties (viscosity, ionic conductivity, self-diffusion coefficient, and molar conductivity) is fit well by the Vogel-Fulcher-Tamman (VFT) equation. The best-fit VFT parameters, as well as linear fits to the density, are reported. The ionicity of these ILs was quantified by the ratio of the molar conductivity obtained from the ionic conductivity and molar concentration to that calculated from the self-diffusion coefficients using the Nernst-Einstein equation. The results of this study, which is based on ILs composed of both a planar cation and planar anions, show that many of the [emim][AHA] ILs exhibit very good conductivity for their viscosities and provide insight into the design of ILs with enhanced dynamics that may be suitable for electrolyte applications.
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Szabados, Márton; Varga, Gábor; Kónya, Zoltán; Kukovecz, Ákos; Carlson, Stefan; Sipos, Pál; Pálinkó, István
2018-01-01
An ultrasonically-enhanced mechanochemical method was developed to synthesize CaFe-layered double hydroxides (LDHs) with various interlayer anions (CO 3 2- , NO 3 - , ClO 4 - , N 3 - , F - , Cl - , Br - and I - ). The duration of pre-milling and ultrasonic irradiation and the variation of synthesis temperature in the wet chemical step were investigated to obtain the optimal parameters of preparation. The main method to characterize the products was X-ray diffractometry, but infrared and synchrotron-based X-ray absorption spectroscopies as well as thermogravimetric measurements were also used to learn about fine structural details. The synthesis method afforded successful intercalation of the anions, among others the azide anion, a rarely used counter ion providing a system, which enables safe handling the otherwise highly reactive anion. The X-ray absorption spectroscopic measurements revealed that the quality of the interlayered anions could modulate the spatial arrangement of the calcium ions around the iron(III) ions, but only in the second coordination sphere. Copyright © 2017 Elsevier B.V. All rights reserved.
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Ye, Q; Heck, G L; DeSimone, J A
1993-07-01
1. Voltage-clamp and current-clamp data were obtained from a circumscribed region of the anterior rat lingual epithelium while simultaneously monitoring the afferent, stimulus-evoked, neural response from the same receptive field. 2. Chorda tympani (CT) responses at constant Na(+)-salt concentration were enhanced by submucosa negative voltage clamp and suppressed by positive voltage clamp. The complete CT response profile, including the time course of adaptation, was not uniquely determined by NaCl concentration alone. The response could be reproduced at different NaCl concentrations by applying a compensating voltage. 3. The form of the concentration and voltage dependence of the CT response indicates that the complete stimulus energy is the Na+ electrochemical potential difference across receptor cell apical membranes, and not Na+ concentration alone. This is the underlying principal behind the equivalence of chemical and electric taste for Na+ salts. 4. CT responses to sodium gluconate (25 and 200 mM) and 25 mM NaCl produced amiloride-insensitive components (AIC) of low magnitude. NaCl at 200 mM produced a significantly larger AIC. The AIC was voltage-clamp independent. The relative magnitude of the AIC was positively correlated with the transepithelial conductance of each salt. This suggests that the large AIC for 200 mM NaCl results from its relatively high permeability through the paracellular pathway. 5. Analysis of the CT response under voltage clamp revealed two anion effects on Na(+)-salt taste, both of which act through the paracellular shunt. 1) Anions modify the transepithelial potential (TP) across tight junctions and thereby modulate the cell receptor potential. This anion effect can be eliminated by voltage clamping the TP. 2) Sufficiently mobile anions facilitate electroneutral diffusion of Na+ salts through tight junctions. This effect is observed especially when Cl- is the anion and when the stimulus concentration favors NaCl influx, allowing Na+ to stimulate receptor cells from the submucosal side. Because the submucosal intercellular spaces are nearly isopotential regions, this effect is insensitive to voltage clamp of the TP. The large AIC associated with this anion effect is due to the low permeability of amiloride.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Dimitrievska, Mirjana; Shea, Patrick; Kweon, Kyoung E.
The disordered phases ofLiCB 11H 12 and NaCB 11H 12 possess superb superionic conductivities that make them suitable as solid electrolytes. In these materials, cation diffusion correlates with high orientational mobilities of the CB 11H 12 - anions; however, the precise relationship has yet to be demonstrated. In this work, ab initio molecular dynamics and quasielastic neutron scattering are combined to probe anion reorientations and their mechanistic connection to cation mobility over a range of timescales and temperatures. It is found that anions do not rotate freely, but rather transition rapidly between orientations defined by the cation sublattice symmetry. Themore » symmetry-breaking carbon atom in CB 11H 12 - also plays a critical role by perturbing the energy landscape along the instantaneous orientation of the anion dipole, which couples fluctuations in the cation probability density directly to the anion motion. Anion reorientation rates exceed 3 x 10 10 s -1, suggesting the underlying energy landscape fluctuates dynamically on diffusion-relevant timescales. Furthermore, carbon is found to modify the orientational preferences of the anions and aid rotational mobility, creating additional symmetry incompatibilities that inhibit ordering. The results suggest that synergy between the anion reorientational dynamics and the carbon-modified cation-anion interaction accounts for the higher ionic conductivity in CB 11H 12 - salts compared with B 12H 12 2-.« less
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Dimitrievska, Mirjana; Shea, Patrick; Kweon, Kyoung E.; ...
2018-02-20
The disordered phases ofLiCB 11H 12 and NaCB 11H 12 possess superb superionic conductivities that make them suitable as solid electrolytes. In these materials, cation diffusion correlates with high orientational mobilities of the CB 11H 12 - anions; however, the precise relationship has yet to be demonstrated. In this work, ab initio molecular dynamics and quasielastic neutron scattering are combined to probe anion reorientations and their mechanistic connection to cation mobility over a range of timescales and temperatures. It is found that anions do not rotate freely, but rather transition rapidly between orientations defined by the cation sublattice symmetry. Themore » symmetry-breaking carbon atom in CB 11H 12 - also plays a critical role by perturbing the energy landscape along the instantaneous orientation of the anion dipole, which couples fluctuations in the cation probability density directly to the anion motion. Anion reorientation rates exceed 3 x 10 10 s -1, suggesting the underlying energy landscape fluctuates dynamically on diffusion-relevant timescales. Furthermore, carbon is found to modify the orientational preferences of the anions and aid rotational mobility, creating additional symmetry incompatibilities that inhibit ordering. The results suggest that synergy between the anion reorientational dynamics and the carbon-modified cation-anion interaction accounts for the higher ionic conductivity in CB 11H 12 - salts compared with B 12H 12 2-.« less
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USDA-ARS?s Scientific Manuscript database
Polyamines (PA) involve in the gene regulation by interacting with various anionic macromolecules such as DNA, RNA and proteins and modulating their structure and function. Previous studies have showed that changing in polyamine biosynthesis alters plant response to different abiotic stresses. Here,...
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Reduced DIDS-sensitive chloride conductance in Ae1-/- mouse erythrocytes
Alper, Seth L.; Vandorpe, David H.; Peters, Luanne L.; Brugnara, Carlo
2008-01-01
The resting membrane potential of the human erythrocyte is largely determined by a constitutive Cl- conductance ∼100-fold greater than the resting cation conductance. The 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid (DIDS)-sensitive electroneutral Cl- transport mediated by the human erythroid Cl-/HCO3- exchanger, AE1 (SLC4A1, band 3) is ≥10,000-fold greater than can be accounted for by the Cl- conductance of the red cell. The molecular identities of conductive anion pathways across the red cell membrane remain poorly defined. We have examined red cell Cl- conductance in the Ae1-/- mouse as a genetic test of the hypothesis that Ae1 mediates DIDS-sensitive Cl- conductance in mouse red cells. We report here that wildtype mouse red cell membrane potential resembles that of human red cells in the predominance of its Cl- conductance. We show with four technical approaches that the DIDS-sensitive component of erythroid Cl- conductance is reduced or absent from Ae1-/- red cells. These results are consistent with the hypothesis that the Ae1 anion exchanger polypeptide can operate infrequently in a conductive mode. However, the fragile red cell membrane of the Ae1-/- mouse red cell exhibits reduced abundance or loss of multiple polypeptides. Thus, loss of one or more distinct, DIDS-sensitive anion channel polypeptide(s) from the Ae1-/- red cell membrane cannot be ruled out as an explanation for the reduced DIDS-sensitive anion conductance. PMID:18329299
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Riddell, Imogen A; Smulders, Maarten M J; Clegg, Jack K; Hristova, Yana R; Breiner, Boris; Thoburn, John D; Nitschke, Jonathan R
2012-09-01
Biochemical systems are adaptable, capable of reconstitution at all levels to achieve the functions associated with life. Synthetic chemical systems are more limited in their ability to reorganize to achieve new functions; they can reconfigure to bind an added substrate (template effect) or one binding event may modulate a receptor's affinity for a second substrate (allosteric effect). Here we describe a synthetic chemical system that is capable of structural reconstitution on receipt of one anionic signal (perchlorate) to create a tight binding pocket for another anion (chloride). The complex, barrel-like structure of the chloride receptor is templated by five perchlorate anions. This second-order templation phenomenon allows chemical networks to be envisaged that express more complex responses to chemical signals than is currently feasible.
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Effect of CO2 absorption on ion and water mobility in an anion exchange membrane
NASA Astrophysics Data System (ADS)
Peng, Jing; Roy, Asa L.; Greenbaum, Steve G.; Zawodzinski, Thomas A.
2018-03-01
We report the measured water uptake, density, ionic conductivity and water transport properties in Tokuyama A201 membrane in OH-, HCO3- and Cl- forms. The water uptake of the AEM varies with anion type in the order λ(OH-) > λ(HCO3-) > λ(Cl-) for samples equilibrated with the same water vapor activity (aw). The conductivity of the AEM is reduced by absorption of CO2. Pulsed-field gradient nuclear magnetic resonance (PFG-NMR) measurements were utilized to characterize the diffusivity of water and HCO3- ion. The anion diffusion coefficient and membrane conductivity are used to probe the applicability of the Nernst-Einstein equation in these AEMs.
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Tang, Wan Si; Unemoto, Atsushi; Zhou, Wei; ...
2015-10-08
Solid electrolytes with sufficiently high conductivities and stabilities are the elusive answer to the inherent shortcomings of organic liquid electrolytes prevalent in today's rechargeable batteries. We recently revealed a novel fast-ion-conducting sodium salt, Na 2B 12H 12, which contains large, icosahedral, divalent B 12H 12 2– anions that enable impressive superionic conductivity, albeit only above its 529 K phase transition. Its lithium congener, Li 2B 12H 12, possesses an even more technologically prohibitive transition temperature above 600 K. Here we show that the chemically related LiCB 11H 12 and NaCB 11H 12 salts, which contain icosahedral, monovalent CB 11H 12–more » anions, both exhibit much lower transition temperatures near 400 K and 380 K, respectively, and truly stellar ionic conductivities (>0.1 S cm –1) unmatched by any other known polycrystalline materials at these temperatures. Furthermore with proper modifications, we are confident that room-temperature-stabilized superionic salts incorporating such large polyhedral anion building blocks are attainable, thus enhancing their future prospects as practical electrolyte materials in next-generation, all-solid-state batteries.« less
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Sabirov, R Z; Dutta, A K; Okada, Y
2001-09-01
In mouse mammary C127i cells, during whole-cell clamp, osmotic cell swelling activated an anion channel current, when the phloretin-sensitive, volume-activated outwardly rectifying Cl(-) channel was eliminated. This current exhibited time-dependent inactivation at positive and negative voltages greater than around +/-25 mV. The whole-cell current was selective for anions and sensitive to Gd(3)+. In on-cell patches, single-channel events appeared with a lag period of approximately 15 min after a hypotonic challenge. Under isotonic conditions, cell-attached patches were silent, but patch excision led to activation of currents that consisted of multiple large-conductance unitary steps. The current displayed voltage- and time-dependent inactivation similar to that of whole-cell current. Voltage-dependent activation profile was bell-shaped with the maximum open probability at -20 to 0 mV. The channel in inside-out patches had the unitary conductance of approximately 400 pS, a linear current-voltage relationship, and anion selectivity. The outward (but not inward) single-channel conductance was suppressed by extracellular ATP with an IC(50) of 12.3 mM and an electric distance (delta) of 0.47, whereas the inward (but not outward) conductance was inhibited by intracellular ATP with an IC(50) of 12.9 mM and delta of 0.40. Despite the open channel block by ATP, the channel was ATP-conductive with P(ATP)/P(Cl) of 0.09. The single-channel activity was sensitive to Gd(3)+, SITS, and NPPB, but insensitive to phloretin, niflumic acid, and glibenclamide. The same pharmacological pattern was found in swelling-induced ATP release. Thus, it is concluded that the volume- and voltage-dependent ATP-conductive large-conductance anion channel serves as a conductive pathway for the swelling-induced ATP release in C127i cells.
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Mori, Masanobu; Tanaka, Kazuhiko; Satori, Tatsuya; Ikedo, Mikaru; Hu, Wenzhi; Itabashi, Hideyuki
2006-06-16
Influence of acidic eluent on retention behaviors of common anions and cations by ion-exclusion/cation-exchange chromatography (ion-exclusion/CEC) were investigated on a weakly acidic cation-exchange resin in the H(+)-form with conductivity. Sensitivities of analyte ions, especially weak acid anions (F(-) and HCOO(-)), were affected with degree of background conductivity level with pK(a1) (first dissociation constant) of acid in eluent. The retention behaviors of anions and cations were related to that of elution dip induced after eluting acid to separation column and injecting analyte sample. These results were largely dependent on the natures of acid as eluent. Through this study, succinic acid as the eluent was suitable for simultaneous separation of strong acid anions (SO(4)(2-), Cl(-), NO(3)(-) and I(-)), weak acid anions (F(-), HCOO(-) and CH(3)COO(-)), and cations (Na(+), K(+), NH(4)(+), Mg(2+) and Ca(2+)). The separation was achieved in 20 min under the optimum eluent condition, 20 mM succinic acid/2 mM 18-crown-6. Detection limits at S/N=3 ranged from 0.10 to 0.51 microM for strong acid anions, 0.20 to 5.04 microM for weak acid anions and 0.75 to 1.72 microM for cations. The relative standard deviations of peak areas in the repeated chromatographic runs (n=10) were in the range of 1.1-2.9% for anions and 1.8-4.5% for cations. This method was successfully applied to hot spring water containing strong acid anions, weak acid anions and cations, with satisfactory results.
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Basic Research in Microplasmas
2012-03-29
concentrations of nitrate anions (NO3-) and nitrite anions (NO2-) in sterile water were measured with a high-performance liquid chromatography , HPLC ( Dionex ...ICS-2500 equipped with an ED50 electrochemical detector and a DIONEX ASRS 4-mm suppressor module). 25 μL samples were injected into the system for...the very few of He* atoms were used for the Penning ionization of the N2 molecule(reaction 6), because no N2 + ion (391nm) were detected in side-on
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Young, Anne B.; Snyder, Solomon H.
1974-01-01
The ability of a series of anions to inhibit [3H]strychnine binding to spinal cord synaptic membranes correlates closely with their neurophysiologic capacity to reverse inhibitory postsynaptic potentials in the mammalian spinal cord. Seven neurophysiologically active anions are also effective inhibitors of [3H]strychnine binding with mean effective doses ranging from 160 to 620 mM. Seven other anions that are ineffective neurophysiologically also fail to alter strychnine binding. Chloride inhibits strychnine binding in a noncompetitive fashion. Hill plots of the displacement of [3H]strychnine by chloride give coefficients of 2.3-2.7. The inhibition of strychnine binding by these anions suggests that strychnine binding is closely associated with the ionic conductance mechanism for chloride in the glycine receptor. PMID:4372600
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Mehdi, Hassan; Pang, Hongchang; Gong, Weitao; Dhinakaran, Manivannan Kalavathi; Wajahat, Ali; Kuang, Xiaojun; Ning, Guiling
2016-07-07
A novel smart supramolecular organic gelator G-16 containing anion and metal-coordination ability has been designed and synthesized. It shows excellent and robust gelation capability as a strong blue fluorescent supramolecular organic gel OG in DMF. Addition of Zn(2+) produced Zn(2+)-coordinated supramolecular metallogel OG-Zn. Organic gel OG and organometallic gel OG-Zn exhibited efficient and different sensing behaviors towards fluoride ion due to the variation in self-assembling nature. Supramolecular metallogel OG-Zn displayed specific selectivity for fluoride ion and formed OG-Zn-F with dramatic color change from blue to blue green in solution and gel to gel states. Furthermore after directly addition of fluoride into OG produced fluoride containing organic gel OG-F with drastically modulation in color from blue to greenish yellow fluorescence via strong aggregation-induced emission (AIE) property. A number of experiments were conducted such as FTIR, (1)H NMR, and UV/Vis spectroscopies, XRD, SEM and rheology. These results revealed that the driving forces involved in self-assembly of OG, OG-Zn, OG-Zn-F and OG-F were hydrogen bonding, metal coordination, π-π interactions, and van der Waal forces. In contrast to the most anion responsive gels, particularly fluoride ion responsive gels showed gel-sol state transition on stimulation by anions, the gel state of OG and OG-Zn did not show any gel-to-sol transition during the whole F(-) response process.
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NASA Astrophysics Data System (ADS)
Ouadah, Amina; Xu, Hulin; Luo, Tianwei; Gao, Shuitao; Wang, Xing; Fang, Zhou; Jing, Chaojun; Zhu, Changjin
2017-12-01
A new series of ionic liquid functionalized copolymers for anion exchange membranes (AEM) is prepared. Poly(butylvinylimidazolium)(b-VIB) is copolymerized with para-methyl styrene (p-MS) by the radical polymerization formed block copolymers b-VIB/p-MS, which is crosslinked with poly(diphenylether bibenzimidazole) (DPEBI) providing the desired materials b-VIB/p-MS/DPEBI. Structures are characterized via H1NMR, FTIR spectra and elemental analysis. The b-VIB blocks offer the anion conduction function while DPEBI moieties contribute to enhancing other properties. The prepared membranes display chloride conductivity as high as 19.5 mS/cm at 25 °C and 69.2 mS/cm at 100 °C-higher than that of the commercial membrane tokuyuama A201-. Their hydroxide conductivity reaches 35.7 Scm-1 at 25 °C and 73.1 Scm-1 at 100 °C. The membranes showed a linear Arrhenius behavior in the anion conduction, low activation energies and distinguished nanophase separation of hydrophilic/hydrophobic regions by the transmission electron microscopy (TEM) studies. Thermal investigations using TGA and DSC confirm that the membranes are stable up to 250 °C. Particularly, drastically alkaline stability due to no decrease in the hydroxide conductivity after 168 h of treatment with 2M KOH.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Sarode, Himanshu N.; Yang, Yuan; Motz, Andrew R.
Herein, we report the anion and water transport properties of an anion-exchange membrane (AEM) comprising a block copolymer of polyethylene and poly- (vinylbenzyl trimethylammonium) (PE-b-PVBTMA) with an ion-exchange capacity (IEC) of 1.08 mequiv/g. The conductivity varied little among the anions CO3 2-, HCO3 -, and F-, with a value of Ea ≈ 20 kJ/mol and a maximum fluoride conductivity of 34 mS/cm at 90 °C and 95% relative humidity. The Br- conductivity showed a transition at 60 °C. Pulsed gradient stimulated spin echo nuclear magnetic resonance (PGSE NMR) experiments showed that water diffusion in this AEM is heterogeneous and ismore » affected by the anion present, being fastest in the presence of F-. We determined the methanol self-diffusion in this membrane and observed that it is lower than that in Nafion 117, because of the lower water uptake. This article reports the first measurements of 13C-labeled bicarbonate self-diffusion in an AEM using PGSE NMR spectrometry, which was found to be significantly slower than F- self-diffusion. Back-calculation of the bicarbonate conductivity using the Nernst-Einstein equation gave a value that was significantly lower than the measured value, implying that bicarbonate transport involves OH- in the transport mechanism. Fourier transform infrared spectroscopy, PGSE NMR spectrometry, and small-angle X-ray scattering (SAXS) indicated the presence of different types of waters present in the membrane at different length scales. The SAXS data indicated that there is a water-rich region within the hydrophilic domains of the polymer that has a temperature dependence in intensity at 95% relative humidity (RH).« less
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Boron compounds as anion binding agents for nonaqueous battery electrolytes
Lee, Hung Sui; Yang, Xia-Oing; McBreen, James; Xiang, Caili
2000-02-08
Novel fluorinated boron-based compounds which act as anion receptors in non-aqueous battery electrolytes are provided. When added to non-aqueous battery electrolytes, the fluorinated boron-based compounds of the invention enhance ionic conductivity and cation transference number of non-aqueous electrolytes. The fluorinated boron-based anion receptors include borane and borate compounds bearing different fluorinated alkyl and aryl groups.
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Phenyl boron-based compounds as anion receptors for non-aqueous battery electrolytes
Lee, Hung Sui; Yang, Xiao-Qing; McBreen, James; Sun, Xuehui
2002-01-01
Novel fluorinated boronate-based compounds which act as anion receptors in non-aqueous battery electrolytes are provided. When added to non-aqueous battery electrolytes, the fluorinated boronate-based compounds of the invention enhance ionic conductivity and cation transference number of non-aqueous electrolytes. The fluorinated boronate-based anion receptors include different fluorinated alkyl and aryl groups.
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Design principles for solid-state lithium superionic conductors.
Wang, Yan; Richards, William Davidson; Ong, Shyue Ping; Miara, Lincoln J; Kim, Jae Chul; Mo, Yifei; Ceder, Gerbrand
2015-10-01
Lithium solid electrolytes can potentially address two key limitations of the organic electrolytes used in today's lithium-ion batteries, namely, their flammability and limited electrochemical stability. However, achieving a Li(+) conductivity in the solid state comparable to existing liquid electrolytes (>1 mS cm(-1)) is particularly challenging. In this work, we reveal a fundamental relationship between anion packing and ionic transport in fast Li-conducting materials and expose the desirable structural attributes of good Li-ion conductors. We find that an underlying body-centred cubic-like anion framework, which allows direct Li hops between adjacent tetrahedral sites, is most desirable for achieving high ionic conductivity, and that indeed this anion arrangement is present in several known fast Li-conducting materials and other fast ion conductors. These findings provide important insight towards the understanding of ionic transport in Li-ion conductors and serve as design principles for future discovery and design of improved electrolytes for Li-ion batteries.
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Reddy, Th Dhileep N; Mallik, Bhabani S
2017-04-19
This study is aimed at characterising the structure, dynamics and thermophysical properties of five alkylammonium carboxylate ionic liquids (ILs) from classical molecular dynamics simulations. The structural features of these ILs were characterised by calculating the site-site radial distribution functions, g(r), spatial distribution functions and structure factors. The structural properties demonstrate that ILs show greater interaction between cations and anions when alkyl chain length increases on the cation or anion. In all ILs, spatial distribution functions show that the anion is close to the acidic hydrogen atoms of the ammonium cation. We determined the role of alkyl group functionalization of the charged entities, cations and anions, in the dynamical behavior and the transport coefficients of this family of ionic liquids. The dynamics of ILs are described by studying the mean square displacement (MSD) of the centres of mass of the ions, diffusion coefficients, ionic conductivities and hydrogen bonds as well as residence dynamics. The diffusion coefficients and ionic conductivity decrease with an increase in the size of the cation or anion. The effect of alkyl chain length on ionic conductivity calculated in this article is consistent with the findings of other experimental studies. Hydrogen bond lifetimes and residence times along with structure factors were also calculated, and are related to alkyl chain length.
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Rimmerman, N; Ben-Hail, D; Porat, Z; Juknat, A; Kozela, E; Daniels, M P; Connelly, P S; Leishman, E; Bradshaw, H B; Shoshan-Barmatz, V; Vogel, Z
2013-01-01
Cannabidiol (CBD) is a non-psychoactive plant cannabinoid that inhibits cell proliferation and induces cell death of cancer cells and activated immune cells. It is not an agonist of the classical CB1/CB2 cannabinoid receptors and the mechanism by which it functions is unknown. Here, we studied the effects of CBD on various mitochondrial functions in BV-2 microglial cells. Our findings indicate that CBD treatment leads to a biphasic increase in intracellular calcium levels and to changes in mitochondrial function and morphology leading to cell death. Density gradient fractionation analysis by mass spectrometry and western blotting showed colocalization of CBD with protein markers of mitochondria. Single-channel recordings of the outer-mitochondrial membrane protein, the voltage-dependent anion channel 1 (VDAC1) functioning in cell energy, metabolic homeostasis and apoptosis revealed that CBD markedly decreases channel conductance. Finally, using microscale thermophoresis, we showed a direct interaction between purified fluorescently labeled VDAC1 and CBD. Thus, VDAC1 seems to serve as a novel mitochondrial target for CBD. The inhibition of VDAC1 by CBD may be responsible for the immunosuppressive and anticancer effects of CBD. PMID:24309936
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Duclohier, Hervé
2006-05-01
The primary targets of defense peptides are plasma membranes, and the induced irreversible depolarization is sufficient to exert antimicrobial activity although secondary modes of action might be at work. Channels or pores underlying membrane permeabilization are usually quite large with single-channel conductances two orders of magnitude higher than those exhibited by physiological channels involved, e.g., in excitability. Accordingly, the ion specificity and selectivity are quite low. Whereas, e.g., peptaibols favor cation transport, polycationic or basic peptides tend to form anion-specific pores. With dermaseptin B2, a 33 residue long and mostly alpha-helical peptide isolated from the skin of the South American frog Phyllomedusa bicolor, we found that the ion specificity of its pores induced in bilayers is modulated by phospholipid-charged headgroups. This suggests mixed lipid-peptide pore lining instead of the more classical barrel-stave model. Macroscopic conductance is nearly voltage independent, and concentration dependence suggests that the pores are mainly formed by dermaseptin tetramers. The two most probable single-channel events are well resolved at 200 and 500 pS (in 150 mM NaCl) with occasional other equally spaced higher or lower levels. In contrast to previous molecular dynamics previsions, this study demonstrates that dermaseptins are able to form pores, although a related analog (B6) failed to induce any significant conductance. Finally, the model of the pore we present accounts for phospholipid headgroups intercalated between peptide helices lining the pore and for one of the most probable single-channel conductance.
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Julio-Kalajzić, Francisca; Villanueva, Sandra; Burgos, Johanna; Ojeda, Margarita; Cid, L Pablo; Jentsch, Thomas J; Sepúlveda, Francisco V
2018-02-01
K + channels are important in intestinal epithelium as they ensure the ionic homeostasis and electrical potential of epithelial cells during anion and fluid secretion. Intestinal epithelium cAMP-activated anion secretion depends on the activity of the (also cAMP dependent) KCNQ1-KCNE3 K + channel, but the secretory process survives after genetic inactivation of the K + channel in the mouse. Here we use double mutant mice to investigate which alternative K + channels come into action to compensate for the absence of KCNQ1-KCNE3 K + channels. Our data establish that whilst Ca 2+ -activated K Ca 3.1 channels are not involved, K 2P two-pore domain TASK-2 K + channels are major players providing an alternative conductance to sustain the intestinal secretory process. Work with double mutant mice lacking both TASK-2 and KCNQ1-KCNE3 channels nevertheless points to yet-unidentified K + channels that contribute to the robustness of the cAMP-activated anion secretion process. Anion and fluid secretion across the intestinal epithelium, a process altered in cystic fibrosis and secretory diarrhoea, is mediated by cAMP-activated CFTR Cl - channels and requires the simultaneous activity of basolateral K + channels to maintain cellular ionic homeostasis and membrane potential. This function is fulfilled by the cAMP-activated K + channel formed by the association of pore-forming KCNQ1 with its obligatory KCNE3 β-subunit. Studies using mice show sizeable cAMP-activated intestinal anion secretion in the absence of either KCNQ1 or KCNE3 suggesting that an alternative K + conductance must compensate for the loss of KCNQ1-KCNE3 activity. We used double mutant mouse and pharmacological approaches to identify such a conductance. Ca 2+ -dependent anion secretion can also be supported by Ca 2+ -dependent K Ca 3.1 channels after independent CFTR activation, but cAMP-dependent anion secretion is not further decreased in the combined absence of K Ca 3.1 and KCNQ1-KCNE3 K + channel activity. We show that the K 2P K + channel TASK-2 is expressed in the epithelium of the small and large intestine. Tetrapentylammonium, a TASK-2 inhibitor, abolishes anion secretory current remaining in the absence of KCNQ1-KCNE3 activity. A double mutant mouse lacking both KCNQ1-KCNE3 and TASK-2 showed a much reduced cAMP-mediated anion secretion compared to that observed in the single KCNQ1-KCNE3 deficient mouse. We conclude that KCNQ1-KCNE3 and TASK-2 play major roles in the intestinal anion and fluid secretory phenotype. The persistence of an, admittedly reduced, secretory activity in the absence of these two conductances suggests that further additional K + channel(s) as yet unidentified contribute to the robustness of the intestinal anion secretory process. © 2017 The Authors. The Journal of Physiology © 2017 The Physiological Society.
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Sluchanko, Nikolai N.; Chebotareva, Natalia A.; Gusev, Nikolai B.
2013-01-01
Molecular mechanisms governing selective binding of a huge number of various phosphorylated protein partners to 14-3-3 remain obscure. Phosphate can bind to 14-3-3 and therefore being present at high intracellular concentration, which undergoes significant changes under physiological conditions, phosphate can theoretically regulate interaction of 14-3-3 with phosphorylated targets. In order to check this hypothesis we analyzed effect of phosphate and other natural abundant anions on interaction of 14-3-3 with phosphorylated human small heat shock protein HspB6 (Hsp20) participating in regulation of different intracellular processes. Inorganic phosphate, glycerol-1-phosphate and glycerol-2-phosphate at physiologically relevant concentrations (5-15 mM) significantly destabilized complexes formed by 14-3-3ζ and phosphorylated HspB6 (pHspB6), presumably, via direct interaction with the substrate-binding site of 14-3-3. Phosphate also destabilized complexes between pHspB6 and 14-3-3γ or the monomeric mutant form of 14-3-3ζ. Inorganic sulfate and pyrophosphate were less effective in modulation of 14-3-3 interaction with its target protein. The inhibitory effect of all anions on pHspB6/14-3-3 interaction was concentration-dependent. It is hypothesized that physiological changes in phosphate anions concentration can modulate affinity and specificity of interaction of 14-3-3 with its multiple targets and therefore the actual phosphointeractome of 14-3-3. PMID:23977325
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Sluchanko, Nikolai N; Chebotareva, Natalia A; Gusev, Nikolai B
2013-01-01
Molecular mechanisms governing selective binding of a huge number of various phosphorylated protein partners to 14-3-3 remain obscure. Phosphate can bind to 14-3-3 and therefore being present at high intracellular concentration, which undergoes significant changes under physiological conditions, phosphate can theoretically regulate interaction of 14-3-3 with phosphorylated targets. In order to check this hypothesis we analyzed effect of phosphate and other natural abundant anions on interaction of 14-3-3 with phosphorylated human small heat shock protein HspB6 (Hsp20) participating in regulation of different intracellular processes. Inorganic phosphate, glycerol-1-phosphate and glycerol-2-phosphate at physiologically relevant concentrations (5-15 mM) significantly destabilized complexes formed by 14-3-3ζ and phosphorylated HspB6 (pHspB6), presumably, via direct interaction with the substrate-binding site of 14-3-3. Phosphate also destabilized complexes between pHspB6 and 14-3-3γ or the monomeric mutant form of 14-3-3ζ. Inorganic sulfate and pyrophosphate were less effective in modulation of 14-3-3 interaction with its target protein. The inhibitory effect of all anions on pHspB6/14-3-3 interaction was concentration-dependent. It is hypothesized that physiological changes in phosphate anions concentration can modulate affinity and specificity of interaction of 14-3-3 with its multiple targets and therefore the actual phosphointeractome of 14-3-3.
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Mixed anion materials and compounds for novel proton conducting membranes
Poling, Steven Andrew; Nelson, Carly R.; Martin, Steve W.
2006-09-05
The present invention provides new amorphous or partially crystalline mixed anion chalcogenide compounds for use in proton exchange membranes which are able to operate over a wide variety of temperature ranges, including in the intermediate temperature range of about 100 .degree. C. to 300.degree. C., and new uses for crystalline mixed anion chalcogenide compounds in such proton exchange membranes. In one embodiment, the proton conductivity of the compounds is between about 10.sup.-8 S/cm and 10.sup.-1 S/cm within a temperature range of between about -60 and 300.degree. C. and a relative humidity of less than about 12%..
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NASA Astrophysics Data System (ADS)
Lin, Kan-Ju; Maranas, Janna
2010-03-01
We use molecular dynamics simulation to study ion clustering and dynamics in ion containing polymers. This PEO based single-ion conducting ionomer serves as a model system for understanding cation transport in solid state polymer electrolytes (SPEs). Although small-angle x-ray scattering does not show an ionomer peak, we observer various cation-anion complexes in the simulation, suggesting ionomer backbones are crosslinked through ion complexes. These crosslinks reduce the adjacent PEO mobility resulting in a symmetric mobility gradient along the PEO chain. We vary the cation-anion interaction in the simulation to observe the interplay of cation-anion association, polymer mobility and cation motion. Cation-anion association controls the number of free ions, which is important in ionic conductivity when these materials are used as SPEs. Polymer mobility controls how fast the free ions are able to move through the SPE. High conductivity requires both a high free ion content and fast polymer motion. To understand the connection between the two, we ``tune'' the force field in order to manipulate the free ion content and observe the influence on PEO dynamics.
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NASA Astrophysics Data System (ADS)
Kim, Sojeong; Choi, Soo-Hyung; Lee, Won Bo
Anion exchange membranes(AEMs) have been widely studied due to their various applications, especially for Fuel cells. Previous proton exchange membranes(PEMs), such as Nafions® have better conductivity than AEMs so far. However, technical limitations such as slow electrode kinetics, carbon monoxide (CO) poisoning of metal catalysts, high methanol crossover and high cost of Pt-based catalyst detered further usages. AEMs have advantages to supplement its drawbacks. AEMs are environmentally friendly and cost-efficient. Based on the well-defined block copolymer, self-assembled morphology is expected to have some relationship with its ionic conductivity. Recently AEMs based on various cations, including ammonium, phosphonium, guanidinium, imidazolium, metal cation, and benzimidazolium cations have been developed and extensively studied with the aim to prepare high- performance AEMs. But more fundamental approach, such as relationships between nanostructure and conductivity is needed. We use well-defined block copolymer Poly(styrene-block-isoprene) as a backbone which is synthesized by anionic polymerization. Then we graft various cationic functional groups and analysis the relation between morphology and conductivity. Theoretical and computational soft matter lab.
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Govorunova, Elena G; Sineshchekov, Oleg A; Janz, Roger; Liu, Xiaoqin; Spudich, John L
2015-08-07
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. Copyright © 2015, American Association for the Advancement of Science.
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Order–Disorder Transitions and Superionic Conductivity in the Sodium nido -Undeca(carba)borates
Tang, Wan Si; Dimitrievska, Mirjana; Stavila, Vitalie; ...
2017-11-20
The salt compounds NaB 11H 14, Na-7-CB10H13, Li-7-CB 10H 13, Na-7,8-C 2B 9H 12, and Na-7,9-C 2B 9H 12 all contain geometrically similar, monocharged, nido-undeca(carba)borate anions (i.e., truncated icosohedral-shaped clusters constructed of only 11 instead of 12 {B-H} + {C-H} vertices and an additional number of compensating bridging and/or terminal H atoms). We used first-principles calculations, X-ray powder diffraction, differential scanning calorimetry, neutron vibrational spectroscopy, neutron elastic-scattering fixed-window scans, quasielastic neutron scattering, and electrochemical impedance measurements to investigate their structures, bonding potentials, phase-transition behaviors, anion orientational mobilities, and ionic conductivities compared to those of their closo-poly(carba)borate cousins. All exhibited order-disordermore » phase transitions somewhere between room temperature and 375 K. All disordered phases appear to possess highly reorientationally mobile anions (> ~10 10 jumps s -1 above 300 K) and cation-vacancy-rich, close-packed or body-center-cubic-packed structures [like previously investigated closo-poly(carba)borates]. Moreover, all disordered phases display superionic conductivities but with generally somewhat lower values compared to those for the related sodium and lithium salts with similar monocharged 1-CB 9H 10- and CB 11H 12- closo-carbaborate anions. This study significantly expands the known toolkit of solid-state, poly(carba)borate-based salts capable of superionic conductivities and provides valuable insights into the effect of crystal lattice, unit cell volume, number of carbon atoms incorporated into the anion, and charge polarization on ionic conductivity.« less
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NASA Astrophysics Data System (ADS)
Varley, Joel; Kweon, Kyoung; Mehta, Prateek; Shea, Patrick; Heo, Tae Wook; Stavila, Vitalie; Udovic, Terrence; Wood, Brandon
Polyborane salts based on B12H122- , B10H102- , and their carboborane counterparts CB11H12- and CB9H10- demonstrate extraordinary Li and Na superionic conductivity that make them attractive as electrolytes in all-solid-state batteries. Their rich chemical and structural diversity creates a versatile design space that could be used to optimize materials with even higher conductivity at lower temperatures; however, many mechanistic details remain enigmatic, including reasons why certain modifications lead to improved performance. Here, we use extensive ab initio molecular dynamics simulations to broadly explore the dependence of ionic conductivity on cation/anion pair combinations for Li and Na polyborane salts. Further simulations based on Li2B12H12 as a model system are used to probe the additional influence of local perturbations, including modifications to chemistry, stoichiometry, and composition. Carbon doping, anion alloying, and cation off-stoichiometry are found to be favorable because they introduce intrinsic disorder, which facilitates local deviations from the expected cation population. Anion reorientations are also discovered to be critical for conduction, with benefits associated with lattice expansion traceable to the facilitation of anion rotation at larger volumes. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
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Cloning and functional expression of a plant voltage-dependent chloride channel.
Lurin, C; Geelen, D; Barbier-Brygoo, H; Guern, J; Maurel, C
1996-01-01
Plant cell membrane anion channels participate in basic physiological functions, such as cell volume regulation and signal transduction. However, nothing is known about their molecular structure. Using a polymerase chain reaction strategy, we have cloned a tobacco cDNA (CIC-Nt1) encoding a 780-amino acid protein with several putative transmembrane domains. CIC-Nt1 displays 24 to 32% amino acid identity with members of the animal voltage-dependent chloride channel (CIC) family, whose archetype is CIC-0 from the Torpedo marmorata electric organ. Injection of CIC-Nt1 complementary RNA into Xenopus oocytes elicited slowly activating inward currents upon membrane hyperpolarization more negative than -120 mV. These currents were carried mainly by anions, modulated by extracellular anions, and totally blocked by 10 mM extracellular calcium. The identification of CIC-Nt1 extends the CIC family to higher plants and provides a molecular probe for the study of voltage-dependent anion channels in plants. PMID:8624442
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Anion-conducting polymer, composition, and membrane
Pivovar, Bryan S [Los Alamos, NM; Thorn, David L [Los Alamos, NM
2011-11-22
Anion-conducing polymers and membranes with enhanced stability to aqueous alkali include a polymer backbone with attached sulfonium, phosphazenium, phosphazene, and guanidinium residues. Compositions also with enhanced stability to aqueous alkali include a support embedded with sulfonium, phosphazenium, and guanidinium salts.
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Anion-conducting polymer, composition, and membrane
Pivovar, Bryan S [Los Alamos, NM; Thorn, David L [Los Alamos, NM
2009-09-01
Anion-conducing polymers and membranes with enhanced stability to aqueous alkali include a polymer backbone with attached sulfonium, phosphazenium, phosphazene, and guanidinium residues. Compositions also with enhanced stability to aqueous alkali include a support embedded with sulfonium, phosphazenium, and guanidinium salts.
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Anion-conducting polymer, composition, and membrane
Pivovar, Bryan S.; Thorn, David L.
2010-12-07
Anion-conducing polymers and membranes with enhanced stability to aqueous alkali include a polymer backbone with attached sulfonium, phosphazenium, phosphazene, and guanidinium residues. Compositions also with enhanced stability to aqueous alkali include a support embedded with sulfonium, phosphazenium, and guanidinium salts.
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Anion-Conducting Polymer, Composition, and Membrane
Pivovar, Bryan S.; Thorn, David L.
2008-10-21
Anion-conducing polymers and membranes with enhanced stability to aqueous alkali include a polymer backbone with attached sulfonium, phosphazenium, phosphazene, and guanidinium residues. Compositions also with enhanced stability to aqueous alkali include a support embedded with sulfonium, phosphazenium, and guanidinium salts.
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Thin Robust Anion Exchange Membranes for Fuel Cell Applications
2014-01-01
water diffsuion. Here we use a Polyphenylene Oxide dibock polymer co-polymerized with polyvinyl benzyl trimethyl ammonium blocks ( PPO -b-PVBTMA[F...in PPO -b-PVBTMA[F-] AEM under saturated humidity environment ECS Transactions, 64 (3) 1185-1194 (2014) 1191 Conductivity of this membrane was...makes it a promising material for applications in anion exchange membrane fuel cells. Figure 5: Conductivity of PPO -b-PVBTMA[F-] under 95% Relative
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Tang, Wan Si; Dimitrievska, Mirjana; Stavila, Vitalie
The salt compounds NaB 11H 14, Na-7-CB10H13, Li-7-CB 10H 13, Na-7,8-C 2B 9H 12, and Na-7,9-C 2B 9H 12 all contain geometrically similar, monocharged, nido-undeca(carba)borate anions (i.e., truncated icosohedral-shaped clusters constructed of only 11 instead of 12 {B-H} + {C-H} vertices and an additional number of compensating bridging and/or terminal H atoms). We used first-principles calculations, X-ray powder diffraction, differential scanning calorimetry, neutron vibrational spectroscopy, neutron elastic-scattering fixed-window scans, quasielastic neutron scattering, and electrochemical impedance measurements to investigate their structures, bonding potentials, phase-transition behaviors, anion orientational mobilities, and ionic conductivities compared to those of their closo-poly(carba)borate cousins. All exhibited order-disordermore » phase transitions somewhere between room temperature and 375 K. All disordered phases appear to possess highly reorientationally mobile anions (> ~10 10 jumps s -1 above 300 K) and cation-vacancy-rich, close-packed or body-center-cubic-packed structures [like previously investigated closo-poly(carba)borates]. Moreover, all disordered phases display superionic conductivities but with generally somewhat lower values compared to those for the related sodium and lithium salts with similar monocharged 1-CB 9H 10- and CB 11H 12- closo-carbaborate anions. This study significantly expands the known toolkit of solid-state, poly(carba)borate-based salts capable of superionic conductivities and provides valuable insights into the effect of crystal lattice, unit cell volume, number of carbon atoms incorporated into the anion, and charge polarization on ionic conductivity.« less
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Towards high conductivity in anion-exchange membranes for alkaline fuel cells.
Li, Nanwen; Guiver, Michael D; Binder, Wolfgang H
2013-08-01
Quaternized poly(2,6-dimethylphenylene oxide) materials (PPOs) containing clicked 1,2,3-triazoles were first prepared through Cu(I) -catalyzed "click chemistry" to improve the anion transport in anion-exchange membranes (AEMs). Clicked 1,2,3-triazoles incorporated into AEMs provided more sites to form efficient and continuous hydrogen-bond networks between the water/hydroxide and the triazole for anion transport. Higher water uptake was observed for these triazole membranes. Thus, the membranes showed an impressive enhancement of the hydroxide diffusion coefficient and, therefore, the anion conductivities. The recorded hydroxide conductivity was 27.8-62 mS cm(-1) at 20 °C in water, which was several times higher than that of a typical PPO-based AEM (TMA-20) derived from trimethylamine (5 mS cm(-1) ). Even at reduced relative humidity, the clicked membrane showed superior conductivity to a trimethylamine-based membrane. Moreover, similar alkaline stabilities at 80 °C in 1 M NaOH were observed for the clicked and non-clicked membranes. The performance of a H2 /O2 single cell assembled with a clicked AEM was much improved compared to that of a non-clicked TMA-20 membrane. The peak power density achieved for an alkaline fuel cell with the synthesized membrane 1a(20) was 188.7 mW cm(-2) at 50 °C. These results indicated that clicked AEM could be a viable strategy for improving the performance of alkaline fuel cells. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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Tang, Wan Si; Yoshida, Koji; Soloninin, Alexei V.; ...
2016-09-01
Solid lithium and sodium closo-polyborate-based salts are capable of superionic conductivities surpassing even liquid electrolytes, but often only at above-ambient temperatures where their entropically driven disordered phases become stabilized. Here we show by X-ray diffraction, quasielastic neutron scattering, differential scanning calorimetry, NMR, and AC impedance measurements that by introducing 'geometric frustration' via the mixing of two different closo-polyborate anions, namely, 1-CB 9H 10- and CB 11H 12-, to form solid-solution anion-alloy salts of lithium or sodium, we can successfully suppress the formation of possible ordered phases in favor of disordered, fast-ion-conducting alloy phases over a broad temperature range from subambientmore » to high temperatures. Finally, this result exemplifies an important advancement for further improving on the remarkable conductive properties generally displayed by this class of materials and represents a practical strategy for creating tailored, ambient-temperature, solid, superionic conductors for a variety of upcoming all-solid-state energy devices of the future.« less
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Lithium ion conducting ionic electrolytes
Angell, C.A.; Xu, K.; Liu, C.
1996-01-16
A liquid, predominantly lithium-conducting, ionic electrolyte is described which has exceptionally high conductivity at temperatures of 100 C or lower, including room temperature. It comprises molten lithium salts or salt mixtures in which a small amount of an anionic polymer lithium salt is dissolved to stabilize the liquid against recrystallization. Further, a liquid ionic electrolyte which has been rubberized by addition of an extra proportion of anionic polymer, and which has good chemical and electrochemical stability, is described. This presents an attractive alternative to conventional salt-in-polymer electrolytes which are not cationic conductors. 4 figs.
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Lithium ion conducting ionic electrolytes
Angell, C. Austen; Xu, Kang; Liu, Changle
1996-01-01
A liquid, predominantly lithium-conducting, ionic electrolyte is described which has exceptionally high conductivity at temperatures of 100.degree. C. or lower, including room temperature. It comprises molten lithium salts or salt mixtures in which a small amount of an anionic polymer lithium salt is dissolved to stabilize the liquid against recrystallization. Further, a liquid ionic electrolyte which has been rubberized by addition of an extra proportion of anionic polymer, and which has good chemical and electrochemical stability, is described. This presents an attractive alternative to conventional salt-in-polymer electrolytes which are not cationic conductors.
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Nakatani, Nobutake; Kozaki, Daisuke; Mori, Masanobu; Hasebe, Kiyoshi; Nakagoshi, Nobukazu; Tanaka, Kazuhiko
2011-01-01
Simultaneous determinations of common inorganic anionic species (SO(4)(2-), Cl(-), NO(3)(-), phosphate and silicate) and cations (Na(+), NH(4)(+), K(+), Mg(2+) and Ca(2+)) were conducted using an ion-chromatography system with dual detection of conductivity and spectrophotometry in tandem. The separation of ionic species on a weakly acidic cation-exchange resin was accomplished using a mixture of 100 mM ascorbic acid and 4 mM 18-crown-6 as an acidic eluent (pH 2.6), after which the ions were detected using a conductivity detector. Subsequently, phosphate and silicate were analyzed based on derivatization with molybdate and spectrophotometry at 700 nm. The detection limits at S/N = 3 ranged from 0.11 to 2.9 µM for analyte ionic species. This method was applied to practical river water and wastewater with acceptable criteria for the anion-cation balance and comparisons of the measured and calculated electrical conductivity, demonstrating the usefulness of the present method for water quality monitoring.
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Facile doping of anionic narrow-band-gap conjugated polyelectrolytes during dialysis.
Mai, Cheng-Kang; Zhou, Huiqiong; Zhang, Yuan; Henson, Zachary B; Nguyen, Thuc-Quyen; Heeger, Alan J; Bazan, Guillermo C
2013-12-02
PCPDTBTSO3 K, an anionic, narrow-band-gap conjugated polyelectrolyte, was found to be doped after dialysis. The proposed doping mechanism involves protonation of the polymer backbone, followed by electron transfer from a neutral chain, to generate radical cations, which are stabilized by the pendant sulfonate anions. Formation of polarons is supported by spectroscopy and electrical-conductivity measurements. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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Role of Anions Associated with the Formation and Properties of Silver Clusters.
Wang, Quan-Ming; Lin, Yu-Mei; Liu, Kuan-Guan
2015-06-16
Metal clusters have been very attractive due to their aesthetic structures and fascinating properties. Different from nanoparticles, each cluster of a macroscopic sample has a well-defined structure with identical composition, size, and shape. As the disadvantages of polydispersity are ruled out, informative structure-property relationships of metal clusters can be established. The formation of a high-nuclearity metal cluster involves the organization of metal ions into a complex entity in an ordered way. To achieve controllable preparation of metal clusters, it is helpful to introduce a directing agent in the formation process of a cluster. To this end, anion templates have been used to direct the formation of high nuclearity clusters. In this Account, the role of anions played in the formation of a variety of silver clusters has been reviewed. Silver ions are positively charged, so anionic species could be utilized to control the formation of silver clusters on the basis of electrostatic interactions, and the size and shape of the resulted clusters can be dictated by the templating anions. In addition, since the anion is an integral component in the silver clusters described, the physical properties of the clusters can be modulated by functional anions. The templating effects of simple inorganic anions and polyoxometales are shown in silver alkynyl clusters and silver thiolate clusters. Intercluster compounds are also described regarding the importance of anions in determining the packing of the ion pairs and making contribution to electron communications between the positive and negative counterparts. The role of the anions is threefold: (a) an anion is advantageous in stabilizing a cluster via balancing local positive charges of the metal cations; (b) an anion template could help control the size and shape of a cluster product; (c) an anion can be a key factor in influencing the function of a cluster through bringing in its intrinsic properties. Properties including electron communication, luminescent thermochromism, single-molecule magnet, and intercluster charge transfer associated with anion-directed silver clusters have been discussed. We intend to attract chemists' attention to the role that anions could play in determining the structures and properties of metal complexes, especially clusters. We hope that this Account will stimulate more efforts in exploiting new role of anions in various metal cluster systems. Anions can do much more than counterions for charge balance, and they should be considered in the design and synthesis of cluster-based functional materials.
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Predicting Carbonate Species Ionic Conductivity in Alkaline Anion Exchange Membranes
2012-06-01
This method has been used previously with both PEM and AEM fuel cells and demonstrated its ability to accurately predict ionic conductivity [2,9,24...water. In an AMFC, the mobile species is a hydroxide ion (OH - ) and in a PEM fuel cell , the proton is solvated with a water molecule forming...membrane synthesis techniques have produced polymer electrolyte membranes that are capable of transporting anions in alkaline membrane fuel cells
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Screening for High Conductivity/Low Viscosity Ionic Liquids Using Product Descriptors.
Martin, Shawn; Pratt, Harry D; Anderson, Travis M
2017-07-01
We seek to optimize Ionic liquids (ILs) for application to redox flow batteries. As part of this effort, we have developed a computational method for suggesting ILs with high conductivity and low viscosity. Since ILs consist of cation-anion pairs, we consider a method for treating ILs as pairs using product descriptors for QSPRs, a concept borrowed from the prediction of protein-protein interactions in bioinformatics. We demonstrate the method by predicting electrical conductivity, viscosity, and melting point on a dataset taken from the ILThermo database on June 18 th , 2014. The dataset consists of 4,329 measurements taken from 165 ILs made up of 72 cations and 34 anions. We benchmark our QSPRs on the known values in the dataset then extend our predictions to screen all 2,448 possible cation-anion pairs in the dataset. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
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Screening for High Conductivity/Low Viscosity Ionic Liquids Using Product Descriptors
Martin, Shawn; Pratt, III, Harry D.; Anderson, Travis M.
2017-02-21
We seek to optimize Ionic liquids (ILs) for application to redox flow batteries. As part of this effort, we have developed a computational method for suggesting ILs with high conductivity and low viscosity. Since ILs consist of cation-anion pairs, we consider a method for treating ILs as pairs using product descriptors for QSPRs, a concept borrowed from the prediction of protein-protein interactions in bioinformatics. We demonstrate the method by predicting electrical conductivity, viscosity, and melting point on a dataset taken from the ILThermo database on June 18th, 2014. The dataset consists of 4,329 measurements taken from 165 ILs made upmore » of 72 cations and 34 anions. In conclusion, we benchmark our QSPRs on the known values in the dataset then extend our predictions to screen all 2,448 possible cation-anion pairs in the dataset.« less
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Screening for High Conductivity/Low Viscosity Ionic Liquids Using Product Descriptors
DOE Office of Scientific and Technical Information (OSTI.GOV)
Martin, Shawn; Pratt, III, Harry D.; Anderson, Travis M.
We seek to optimize Ionic liquids (ILs) for application to redox flow batteries. As part of this effort, we have developed a computational method for suggesting ILs with high conductivity and low viscosity. Since ILs consist of cation-anion pairs, we consider a method for treating ILs as pairs using product descriptors for QSPRs, a concept borrowed from the prediction of protein-protein interactions in bioinformatics. We demonstrate the method by predicting electrical conductivity, viscosity, and melting point on a dataset taken from the ILThermo database on June 18th, 2014. The dataset consists of 4,329 measurements taken from 165 ILs made upmore » of 72 cations and 34 anions. In conclusion, we benchmark our QSPRs on the known values in the dataset then extend our predictions to screen all 2,448 possible cation-anion pairs in the dataset.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Li, Jie
1999-04-01
A novel anion-exchange resin containing three amine groups was prepared by reaction of a chloromethylated polystyrene-divinylbenzene (PS-DVB) resin with diethylenetriamine. After being protonated by contact with an aqueous acid, this resin can be used for ion chromatographic separation of anions. The charge on the resins can be varied from +1 to +3 by changing the mobile phase pH. The selectivity of the new ion exchangers for various inorganic anions was quite different from that of conventional anion exchangers. The performance of this new anion exchanger was studied by changing the pH and the concentration of the eluent, and several differentmore » eluents were used with some common anions as testing analytes. Conductivity detection and UV-visible detection were applied to detect the anions after separation. The new resin can also be used for HPLC separation of neutral organic compounds. Alkylphenols and alkylbenzenes were separated with this new polymeric resin, and excellent separations were obtained under simple conditions. This report contains Chapter 1: General introduction and Chapter 6: General conclusions.« less
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Cation and anion sequences in dark-adapted Balanus photoreceptor
1977-01-01
Anion and cation permeabilities in dark-adapted Balanus photoreceptors were determined by comparing changes in the membrane potential in response to replacement of the dominant anion (Cl-) or cation (Na+) by test anions or cations in the superfusing solution. The anion permeability sequence obtained was PI greater than PSO4 greater than PBr greater than PCl greater than Pisethionate greater than Pmethanesulfonate. Gluconate, glucuronate, and glutamate generally appeared more permeable and propionate less permeable than Cl-. The alkali-metal cation permeability sequence obtained was PK greater than PRb greater than PCx greater than PNa approximately PLi. This corresponds to Eisenman's IV which is the same sequencethat has been obtained for other classes of nerve cells in the resting state. The values obtained for the permeability ratios of the alkali-metal cations are considered to be minimal. The membrane conductance measured by passing inward current pulses in the different test cations followed the sequence, GK greater than GRb greater than GCs greater than GNa greater than GLi. The conductance ratios obtained for a full substitution of the test cation agreed quite well with permeability ratios for all the alkali-metal cations except K+ which was generally higher. PMID:199688
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NASA Astrophysics Data System (ADS)
Nykaza, Jacob Richard
In this study, polymerized ionic liquid (PIL) diblock copolymers were explored as solid-state polymer separators as an anion exchange membrane (AEM) for alkaline fuel cells AFCs and as a solid polymer electrolyte (SPE) for lithium-ion batteries. Polymerized ionic liquid (PIL) block copolymers are a distinct set of block copolymers that combine the properties of both ionic liquids (e.g., high conductivity, high electrochemical stability) and block copolymers (e.g., self-assembly into various nanostructures), which provides the opportunity to design highly conductive robust solid-state electrolytes that can be tuned for various applications including AFCs and lithium-ion batteries via simple anion exchange. A series of bromide conducting PIL diblock copolymers with an undecyl alkyl side chain between the polymer backbone and the imidazolium moiety were first synthesized at various compositions comprising of a PIL component and a non-ionic component. Synthesis was achieved by post-functionalization from its non-ionic precursor PIL diblock copolymer, which was synthesized via the reverse addition fragmentation chain transfer (RAFT) technique. This PIL diblock copolymer with long alkyl side chains resulted in flexible, transparent films with high mechanical strength and high bromide ion conductivity. The conductivity of the PIL diblock copolymer was three times higher than its analogous PIL homopolymer and an order of magnitude higher than a similar PIL diblock copolymer with shorter alkyl side chain length, which was due to the microphase separated morphology, more specifically, water/ion clusters within the PIL microdomains in the hydrated state. Due to the high conductivity and mechanical robustness of this novel PIL block copolymer, its application as both the ionomer and AEM in an AFC was investigated via anion exchange to hydroxide (OH-), where a maximum power density of 29.3 mW cm-1 (60 °C with H2/O2 at 25 psig (172 kPa) backpressure) was achieved. Rotating disk electrode (RDE) experiments determined the interfacial resistance imposed during cell assembly between the AEM, catalyst, and ionomer was a factor in fuel cell performance. Further RDE studies investigated the electrochemical stability of the PIL block copolymer ionomer under applied potentials, where it was determined that potential cycling increased the degradation compared to constant voltage or open circuit voltage studies. The PIL diblock copolymer was then anion exchanged to the bis(trifluoromethane)sulfonamide (TFSI-) anion form and imbibed with a lithium salt and ionic liquid solution for use as a SPE in lithium-ion batteries resulting in a maximum discharge capacity of 112 mAh g-1 at 0.1 C with a Coulombic efficiency greater than 94% over 100 cycles. PIL block copolymers have promising mechanical properties and transport properties (i.e., ion conductivity) in both the hydrated (hydrophilic anions; Br-, OH-) and dry (hydrophobic anions; TFSI-) states resulting in highly conductive, chemically/thermally stable, and mechanically robust solid-state polymer separators for use as AEMs in AFCs and as SPEs in lithium-ion batteries.
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Iseda, Kazuya; Kokado, Kenta; Sada, Kazuki
2018-03-01
In this study, we performed conductometry in various organic solvents to directly detect the transformation from tetrabutylammonium chloride ( TBACl ) ion-pair salt to the free ions through complexation with meso -octamethylcalix[4]pyrrole ( CP ), which is a well-known receptor for chloride anions. In the presence of CP , the conductivity of TBACl increases in various non-polar solvents, indicating that complexation with CP enhances the ionic dissociation of TBACl in such non-polar solvents. In other words, CP recognizes chloride as an ion-paired salt as well as a free anion in non-polar solvents. Additionally, the TBA(CP - Cl ) complex exhibited a considerably lower ion-pairing constant ( K ip ) than TBACl in non-polar solvents, resulting in enhanced conductivity. Based on these findings, we can conclude that complexation of an anion with a hydrophobic anion receptor will be useful for creating functional and stimuli-responsive soft materials in organic solvents using coulombic forces.
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Iseda, Kazuya
2018-01-01
Abstract In this study, we performed conductometry in various organic solvents to directly detect the transformation from tetrabutylammonium chloride (TBACl) ion‐pair salt to the free ions through complexation with meso‐octamethylcalix[4]pyrrole (CP), which is a well‐known receptor for chloride anions. In the presence of CP, the conductivity of TBACl increases in various non‐polar solvents, indicating that complexation with CP enhances the ionic dissociation of TBACl in such non‐polar solvents. In other words, CP recognizes chloride as an ion‐paired salt as well as a free anion in non‐polar solvents. Additionally, the TBA(CP–Cl) complex exhibited a considerably lower ion‐pairing constant (K ip) than TBACl in non‐polar solvents, resulting in enhanced conductivity. Based on these findings, we can conclude that complexation of an anion with a hydrophobic anion receptor will be useful for creating functional and stimuli‐responsive soft materials in organic solvents using coulombic forces. PMID:29610717
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Wang, Shih-Hong; Lin, Yong-Yi; Teng, Chiao-Yi; Chen, Yen-Ming; Kuo, Ping-Lin; Lee, Yuh-Lang; Hsieh, Chien-Te; Teng, Hsisheng
2016-06-15
This study reports on a high ionic-conductivity gel polymer electrolyte (GPE), which is supported by a TiO2 nanoparticle-decorated polymer framework comprising poly(acrylonitrile-co-vinyl acetate) blended with poly(methyl methacrylate), i.e. , PAVM: TiO2. High conductivity TiO2 is achieved by causing the PAVM:TiO2 polymer framework to swell in 1 M LiPF6 in carbonate solvent. Raman analysis results demonstrate that the poly(acrylonitrile) (PAN) segments and TiO2 nanoparticles strongly adsorb PF6(-) anions, thereby generating 3D percolative space-charge pathways surrounding the polymer framework for Li(+)-ion transport. The ionic conductivity of TiO2 is nearly 1 order of magnitude higher than that of commercial separator-supported liquid electrolyte (SLE). TiO2 has a high Li(+) transference number (0.7), indicating that most of the PF6(-) anions are stationary, which suppresses PF6(-) decomposition and substantially enlarges the voltage that can be applied to TiO2 (to 6.5 V vs Li/Li(+)). Immobilization of PF6(-) anions also leads to the formation of stable solid-electrolyte interface (SEI) layers in a full-cell graphite|electrolyte|LiFePO4 battery, which exhibits low SEI and overall resistances. The graphite|electrolyte|LiFePO4 battery delivers high capacity of 84 mAh g(-1) even at 20 C and presents 90% and 71% capacity retention after 100 and 1000 charge-discharge cycles, respectively. This study demonstrates a GPE architecture comprising 3D space charge pathways for Li(+) ions and suppresses anion decomposition to improve the stability and lifespan of the resulting LIBs.
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The Al(I) molecule, Ph2COAl and its anion
NASA Astrophysics Data System (ADS)
Zhang, Xinxing; Eichhorn, Bryan; Schnöckel, Hansgeorg; Bowen, Kit
2016-08-01
We have formed the Al(I)-containing molecule, benzophenone-aluminum, i.e., Ph2COAl, and studied it by conducting density functional theory calculations on both its neutral and anionic forms and by measuring the photoelectron spectrum of its anion. Our calculations identified two nearly iso-energetic anion isomers, (Ph2COAl)-, the vertical detachment energies (VDE) of which are in excellent agreement with our photoelectron spectrum. Natural population analysis (NPA) of Ph2COAl found the Al moiety to be positively charged by +0.81 e, indicating a strongly ionic bond between Al and Ph2CO, i.e., Ph2CO-Al+.
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A Rutile Chevron Modulation in Delafossite-Like Ga 3–x In 3 Ti x O 9+x/2
DOE Office of Scientific and Technical Information (OSTI.GOV)
Rickert, Karl; Boullay, Philippe; Malo, Sylvie
2016-05-02
The structure solution of the modulated, delafossite-related, orthorhombic Ga 3–xIn 3Ti xO 9+x/2 for x = 1.5 is reported here in conjunction with a model describing the modulation as a function of x for the entire system. Previously reported structures in the related A 3–xIn 3Ti xO 9+x/2 (A = Al, Cr, or Fe) systems use X-ray diffraction to determine that the anion lattice is the source of modulation. Neutron diffraction, with its enhanced sensitivity to light atoms, offers a route to solving the modulation and is used here, in combination with precession electron diffraction tomography (PEDT), to solve themore » structure of Ga 1.5In 3Ti 1.5O 9.75. We construct a model that describes the anion modulation through the formation of rutile chevrons as a function of x. This model accommodates the orthorhombic phase (1.5 ≤ x ≤ 2.1) in the Ga 3-xIn 3Ti xO 9+x/2 system, which transitions to a biphasic mixture (2.2 ≤ x ≤ 2.3) with a monoclinic, delafossite-related phase (2.4 ≤ x ≤ 2.5). The optical band gaps of this system are determined, and are stable at ~3.4 eV before a ~0.4 eV decrease between x = 1.9 and 2.0. After this decrease, stability resumes at ~3.0 eV. Resistance to oxidation and reduction is also presented.« less
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Avaritt, Brittany R; Swaan, Peter W
2014-09-01
Poly(amidoamine) (PAMAM) dendrimers show great promise for utilization as oral drug delivery vehicles. These polymers are capable of traversing epithelial barriers, and have been shown to translocate by both transcellular and paracellular routes. While many proof-of-concept studies have shown that PAMAM dendrimers improve intestinal transport, little information exists on the mechanisms of paracellular transport, specifically dendrimer-induced tight junction modulation. Using anionic G3.5 and cationic G4 PAMAM dendrimers with known absorption enhancers, we investigated tight junction modulation in Caco-2 monolayers by visualization and mannitol permeability and compared dendrimer-mediated tight junction modulation to that of established permeation enhancers. [(14)C]-Mannitol permeability in the presence and absence of phospholipase C-dependent signaling pathway inhibitors was also examined and indicated that this pathway may mediate dendrimer-induced changes in permeability. Differences between G3.5 and G4 in tight junction protein staining and permeability with inhibitors were evident, suggesting divergent mechanisms were responsible for tight junction modulation. These dissimilarities are further intimated by the intracellular calcium release caused by G4 but not G3.5. Based on our results, it is apparent that the underlying mechanisms of dendrimer permeability are complex, and the complexities are likely a result of the density and sign of the surface charges of PAMAM dendrimers. The results of this study will have implications on the future use of PAMAM dendrimers for oral drug delivery.
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Ion-water wires in imidazolium-based ionic liquid/water solutions induce unique trends in density.
Ghoshdastidar, Debostuti; Senapati, Sanjib
2016-03-28
Ionic liquid/water binary mixtures are rapidly gaining popularity as solvents for dissolution of cellulose, nucleobases, and other poorly water-soluble biomolecules. Hence, several studies have focused on measuring the thermophysical properties of these versatile mixtures. Among these, 1-ethyl-3-methylimidazolium ([emim]) cation-based ILs containing different anions exhibit unique density behaviours upon addition of water. While [emim][acetate]/water binary mixtures display an unusual rise in density with the addition of low-to-moderate amounts of water, those containing the [trifluoroacetate] ([Tfa]) anion display a sluggish decrease in density. The density of [emim][tetrafluoroborate] ([emim][BF4])/water mixtures, on the other hand, declines rapidly in close accordance with the experimental reports. Here, we unravel the structural basis underlying this unique density behavior of [emim]-based IL/water mixtures using all-atom molecular dynamics (MD) simulations. The results revealed that the distinct nature of anion-water hydrogen bonded networks in the three systems was a key in modulating the observed unique density behaviour. Vast expanses of uninterrupted anion-water-anion H-bonded stretches, denoted here as anion-water wires, induced significant structuring in [emim][Ac]/water mixtures that resulted in the density rise. Conversely, the presence of intermittent large water clusters disintegrated the anion-water wires in [emim][Tfa]/water and [emim][BF4]/water mixtures to cause a monotonic density decrease. The differential nanostructuring affected the dynamics of the solutions proportionately, with the H-bond making and breaking dynamics found to be greatly retarded in [emim][Ac]/water mixtures, while it exhibited a faster relaxation in the other two binary solutions.
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Zhong, Hong; Su, Yanqing; Chen, Xingwei; Li, Xiaoju; Wang, Ruihu
2017-12-22
CO 2 adsorption and concomitant catalytic conversion into useful chemicals are promising approaches to alleviate the energy crisis and effects of global warming. This is highly desirable for developing new types of heterogeneous catalytic materials containing CO 2 -philic groups and catalytic active sites for CO 2 chemical transformation. Here, we present an imidazolium- and triazine-based porous organic polymer with counter chloride anion (IT-POP-1). The porosity and CO 2 affinity of IT-POP-1 may be modulated at the molecular level through a facile anion-exchange strategy. Compared with the post-modified polymers with iodide and hexafluorophosphate anions, IT-POP-1 possesses the highest surface area and the best CO 2 uptake capacity with excellent adsorption selectivity over N 2 . The roles of the task-specific components such as triazine, imidazolium, hydroxyl, and counter anions in CO 2 absorption and catalytic performance were illustrated. IT-POP-1 exhibits the highest catalytic activity and excellent recyclability in solvent- and additive-free cycloaddition reaction of CO 2 with epoxides. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
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Sweet, Deborah M; Kolhatkar, Rohit B; Ray, Abhijit; Swaan, Peter; Ghandehari, Hamidreza
2009-08-19
The purpose of this work was to assess the impact of PEGylation on transepithelial transport of anionic poly(amidoamine) dendrimers. Cytotoxicity, uptake and transport across Caco-2 cells of PEGylated G3.5 and G4.5 PAMAM dendrimers were studied. Methoxy polyethylene glycol (750 Da) was conjugated to carboxylic acid-terminated PAMAM dendrimers at feed ratios of 1, 2 and 4 PEG per dendrimer. Compared to the control, PEGylation of anionic dendrimers did not significantly alter cytotoxicity up to a concentration of 0.1 mM. PEGylation of G3.5 dendrimers significantly decreased cellular uptake and transepithelial transport while PEGylation of G4.5 dendrimers led to a significant increase in uptake, but also a significant decrease in transport. Dendrimer PEGylation reduced the opening of tight junctions as evidenced by confocal microscopy techniques. Modulation of the tight junctional complex correlated well with changes in PEGylated dendrimer transport and suggests that anionic dendrimers are transported primarily through the paracellular route. PEGylated dendrimers show promise in oral delivery applications where increased functionality for drug conjugation and release is desired.
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Sweet, Deborah M.; Kolhatkar, Rohit B.; Ray, Abhijit; Swaan, Peter; Ghandehari, Hamidreza
2009-01-01
The purpose of this work was to assess the impact of PEGylation on transepithelial transport of anionic poly(amidoamine) dendrimers. Cytotoxicity, uptake and transport across Caco-2 cells of PEGylated G3.5 and G4.5 PAMAM dendrimers were studied. Methoxy polyethylene glycol (750 Da) was conjugated to carboxylic acid-terminated PAMAM dendrimers at feed ratios of 1, 2 and 4 PEG per dendrimer. Compared to the control, PEGylation of anionic dendrimers did not significantly alter cytotoxicity up to a concentration of 0.1 mM. PEGylation of G3.5 dendrimers significantly decreased cellular uptake and transepithelial transport while PEGylation of G4.5 dendrimers led to a significant increase in uptake, but also a significant decrease in transport. Dendrimer PEGylation reduced the opening of tight junctions as evidenced by confocal microscopy techniques. Modulation of the tight junctional complex correlated well with changes in PEGylated dendrimer transport and suggests that anionic dendrimers are transported primarily through the paracellular route. PEGylated dendrimers show promise in oral delivery applications where increased functionality for drug conjugation and release is desired. PMID:19393702
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Pedò, Massimo; Löhr, Frank; D'Onofrio, Mariapina; Assfalg, Michael; Dötsch, Volker; Molinari, Henriette
2009-12-18
Bile acid molecules are transferred vectorially between basolateral and apical membranes of hepatocytes and enterocytes in the context of the enterohepatic circulation, a process regulating whole body lipid homeostasis. This work addresses the role of the cytosolic lipid binding proteins in the intracellular transfer of bile acids between different membrane compartments. We present nuclear magnetic resonance (NMR) data describing the ternary system composed of the bile acid binding protein, bile acids, and membrane mimetic systems, such as anionic liposomes. This work provides evidence that the investigated liver bile acid binding protein undergoes association with the anionic membrane and binding-induced partial unfolding. The addition of the physiological ligand to the protein-liposome mixture is capable of modulating this interaction, shifting the equilibrium towards the free folded holo protein. An ensemble of NMR titration experiments, based on nitrogen-15 protein and ligand observation, confirm that the membrane and the ligand establish competing binding equilibria, modulating the cytoplasmic permeability of bile acids. These results support a mechanism of ligand binding and release controlled by the onset of a bile salt concentration gradient within the polarized cell. The location of a specific protein region interacting with liposomes is highlighted.
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Pierucci-Alves, Fernando; Schultz, Bruce D
2008-09-01
Epithelia lining the male reproductive duct modulate fertility by altering the luminal environment to which sperm are exposed. Although vas deferens epithelial cells reportedly express high levels of cyclooxygenases (Ptgs), and activation of bradykinin (BK) receptors can lead to upregulation of PTGS activity in epididymal epithelia, it remains unknown whether BKs and/or PTGSs have any role in modulating epithelial ion transport across vas deferens epithelia. Porcine and human vas deferens epithelial cell primary cultures and the PVD9902 cell line responded to lysylbradykinin with an increase in short circuit current (I SC; indicating net anion secretion), an effect that was 60%-93% reduced by indomethacin. The BK effect was inhibited by the B2 receptor subtype (BDKRB2) antagonist HOE140, whereas the B1 receptor subtype agonist des-Arg9-BK had no effect. BDKRB2 immunoreactivity was documented in most epithelial cells composing the native epithelium and on Western blots derived from cultured cells. Gene expression analysis revealed that the PTGS2 transcript is 20 times more abundant than its PTGS1 counterpart in cultured porcine vas deferens epithelia and that BDKRB2 mRNA is likewise highly expressed. Subsequent experiments revealed that prostaglandin E2, 1-OH prostaglandin E1 (prostaglandin E receptor 4 [PTGER4] agonist) and butaprost (PTGER2 agonist) increase I SC in a concentration-dependent manner, whereas sulprostone (mixed PTGER1 and PTGER3 agonist) produced no change in I SC. These results demonstrate that autacoids can affect epithelial cells to acutely modulate the luminal environment to which sperm are exposed in the vas deferens by enhancing PTGS activity, leading to the production of prostaglandins that act at PTGER4 and/or PTGER2 to induce or enhance anion secretion.
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Pierucci-Alves, Fernando; Schultz, Bruce D.
2008-01-01
Epithelia lining the male reproductive duct modulate fertility by altering the luminal environment to which sperm are exposed. Although vas deferens epithelial cells reportedly express high levels of cyclooxygenases (Ptgs), and activation of bradykinin (BK) receptors can lead to upregulation of PTGS activity in epididymal epithelia, it remains unknown whether BKs and/or PTGSs have any role in modulating epithelial ion transport across vas deferens epithelia. Porcine and human vas deferens epithelial cell primary cultures and the PVD9902 cell line responded to lysylbradykinin with an increase in short circuit current (ISC; indicating net anion secretion), an effect that was 60%–93% reduced by indomethacin. The BK effect was inhibited by the B2 receptor subtype (BDKRB2) antagonist HOE140, whereas the B1 receptor subtype agonist des-Arg9-BK had no effect. BDKRB2 immunoreactivity was documented in most epithelial cells composing the native epithelium and on Western blots derived from cultured cells. Gene expression analysis revealed that the PTGS2 transcript is 20 times more abundant than its PTGS1 counterpart in cultured porcine vas deferens epithelia and that BDKRB2 mRNA is likewise highly expressed. Subsequent experiments revealed that prostaglandin E2, 1-OH prostaglandin E1 (prostaglandin E receptor 4 [PTGER4] agonist) and butaprost (PTGER2 agonist) increase ISC in a concentration-dependent manner, whereas sulprostone (mixed PTGER1 and PTGER3 agonist) produced no change in ISC. These results demonstrate that autacoids can affect epithelial cells to acutely modulate the luminal environment to which sperm are exposed in the vas deferens by enhancing PTGS activity, leading to the production of prostaglandins that act at PTGER4 and/or PTGER2 to induce or enhance anion secretion. PMID:18480467
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Jin, Hui; O'Hare, Bernie; Dong, Jing; Arzhantsev, Sergei; Baker, Gary A; Wishart, James F; Benesi, Alan J; Maroncelli, Mark
2008-01-10
Physical properties of 4 room-temperature ionic liquids consisting of the 1-butyl-3-methylimidazolium cation with various perfluorinated anions and the bis(trifluoromethylsulfonyl)imide (Tf2N-) anion with 12 pyrrolidinium-, ammonium-, and hydroxyl-containing cations are reported. Electronic structure methods are used to calculate properties related to the size, shape, and dipole moment of individual ions. Experimental measurements of phase-transition temperatures, densities, refractive indices, surface tensions, solvatochromic polarities based on absorption of Nile Red, 19F chemical shifts of the Tf2N- anion, temperature-dependent viscosities, conductivities, and cation diffusion coefficients are reported. Correlations among the measured quantities as well as the use of surface tension and molar volume for estimating Hildebrand solubility parameters of ionic liquids are also discussed.
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Anion Recognition in Water: Recent Advances from a Supramolecular and Macromolecular Perspective
Langton, Matthew J.
2015-01-01
Abstract The recognition of anions in water remains a key challenge in modern supramolecular chemistry, and is essential if proposed applications in biological, medical, and environmental arenas that typically require aqueous conditions are to be achieved. However, synthetic anion receptors that operate in water have, in general, been the exception rather than the norm to date. Nevertheless, a significant step change towards routinely conducting anion recognition in water has been achieved in the past few years, and this Review highlights these approaches, with particular focus on controlling and using the hydrophobic effect, as well as more exotic interactions such as C−H hydrogen bonding and halogen bonding. We also look beyond the field of small‐molecule recognition into the macromolecular domain, covering recent advances in anion recognition based on biomolecules, polymers, and nanoparticles. PMID:26612067
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Michalski, Rajmund; Lyko, Aleksandra; Kurzyca, Iwona
2012-07-01
Ion chromatography is the most popular instrumental analytical method used for the determination of anions and cations in water and wastewater. Isocratic ion chromatography with suppressed conductivity detection is frequently used in laboratories carrying out routine analyses of inorganic anions. The paper presents the results of the research into the influence of selected inorganic anions dominant in environmental samples (Cl(-), NO(3)(-), SO(4)(2-)) on the possibility of simultaneous determination of F(-), Cl(-), NO(2)(-), NO(3)(-), PO(4)(3-) and SO(4)(2-) with the application of this most popular ion chromatography type in standard separation conditions. Four Dionex and four Metrohm anion-exchange columns were tested in standard separation conditions recommended by their manufacturers with both standard solutions and environmental samples with complex matrix.
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Cao, Lidong; Li, Xiuhuan; Fan, Li; Zheng, Li; Wu, Miaomiao; Zhang, Shanxue; Huang, Qiliang
2017-02-22
Chitooligosaccharides (COSs) are a promising drug candidate and food ingredient because they are innately biocompatible, non-toxic, and non-allergenic to living tissues. Therefore, the impurities in COSs must be clearly elucidated and precisely determined. As for COSs, most analytical methods focus on the determination of the average degrees of polymerization (DPs) and deacetylation (DD), as well as separation and analysis of the single COSs with different DPs. However, little is known about the concentrations of inorganic cations and anions in COSs. In the present study, an efficient and sensitive ion chromatography coupled with conductivity detection (IC-CD) for the determination of inorganic cations Na⁺, NH₄⁺, K⁺, Mg 2+ , Ca 2+ , and chloride, acetate and lactate anions was developed. Detection limits were 0.01-0.05 μM for cations and 0.5-0.6 μM for anions. The linear range was 0.001-0.8 mM. The optimized analysis was carried out on IonPac CS12A and IonPac AS12A analytical column for cations and anions, respectively, using isocratic elution with 20 mM methanesulfonic acid and 4 mM sodium hydroxide aqueous solution as the mobile phase at a 1.0 mL/min flow rate. Quality parameters, including precision and accuracy, were fully validated and found to be satisfactory. The fully validated IC-CD method was readily applied for the quantification of various cations and anions in commercial COS technical concentrate.
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Cao, Lidong; Li, Xiuhuan; Fan, Li; Zheng, Li; Wu, Miaomiao; Zhang, Shanxue; Huang, Qiliang
2017-01-01
Chitooligosaccharides (COSs) are a promising drug candidate and food ingredient because they are innately biocompatible, non-toxic, and non-allergenic to living tissues. Therefore, the impurities in COSs must be clearly elucidated and precisely determined. As for COSs, most analytical methods focus on the determination of the average degrees of polymerization (DPs) and deacetylation (DD), as well as separation and analysis of the single COSs with different DPs. However, little is known about the concentrations of inorganic cations and anions in COSs. In the present study, an efficient and sensitive ion chromatography coupled with conductivity detection (IC-CD) for the determination of inorganic cations Na+, NH4+, K+, Mg2+, Ca2+, and chloride, acetate and lactate anions was developed. Detection limits were 0.01–0.05 μM for cations and 0.5–0.6 μM for anions. The linear range was 0.001–0.8 mM. The optimized analysis was carried out on IonPac CS12A and IonPac AS12A analytical column for cations and anions, respectively, using isocratic elution with 20 mM methanesulfonic acid and 4 mM sodium hydroxide aqueous solution as the mobile phase at a 1.0 mL/min flow rate. Quality parameters, including precision and accuracy, were fully validated and found to be satisfactory. The fully validated IC-CD method was readily applied for the quantification of various cations and anions in commercial COS technical concentrate. PMID:28241416
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Removal of dissolved organic matter by anion exchange: Effect of dissolved organic matter properties
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.
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Razaq, Aamir; Mihranyan, Albert; Welch, Ken; Nyholm, Leif; Strømme, Maria
2009-01-15
The electrochemically controlled anion absorption properties of a novel large surface area composite paper material composed of polypyrrole (PPy) and cellulose derived from Cladophora sp. algae, synthesized with two oxidizing agents, iron(III) chloride and phosphomolybdic acid (PMo), were analyzed in four different electrolytes containing anions (i.e., chloride, aspartate, glutamate, and p-toluenesulfonate) of varying size.The composites were characterized with scanning and transmission electron microscopy, N2 gas adsorption,and conductivity measurements. The potential-controlled ion exchange properties of the materials were studied by cyclic voltammetry and chronoamperometry at varying potentials. The surface area and conductivity of the iron(III) chloride synthesized sample were 58.8 m2/g and 0.65 S/cm, respectively, while the corresponding values for the PMo synthesized sample were 31.3 m2/g and 0.12 S/cm. The number of absorbed ions per sample mass was found to be larger for the iron(III) chloride synthesized sample than for the PMo synthesized one in all four electrolytes. Although the largest extraction yields were obtained in the presence of the smallest anion (i.e., chloride) for both samples, the relative degree of extraction for the largest ions (i.e., glutamate and p-toluenesulfonate) was higher for the PMo sample. This clearly shows that it is possible to increase the extraction yield of large anions by carrying out the PPy polymerization in the presence of large anions. The results likewise show that high ion exchange capacities, as well as extraction and desorption rates, can be obtained for large anions with high surface area composites coated with relatively thin layers of PPy.
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Removal of copper ions from aqueous solutions by means of micellar-enhanced ultrafiltration
NASA Astrophysics Data System (ADS)
Kowalska, Izabela; Klimonda, Aleksandra
2017-11-01
The aim of the study was to assess the usefulness of micellar-enhanced ultrafiltration (MEUF) for removal of copper ions from water solutions in comparison with classic ultrafiltration process. The tests were conducted in a semi-pilot membrane installation with the use of ultrafiltration module KOCH/ROMICON® at a transmembrane pressure of 0.05 MPa. The effect of concentration of copper ions on ultrafiltration process efficiency was investigated. The second part of the tests concerned the removal of copper ions by MEUF under wide range of anionic surfactant concentration (0.25, 1, and 5 CMC (critical micelle concentration)). Concentration of copper ions in model solutions was equal to 5, 20, and 50 mg Cu/L. Furthermore, the effect of surfactant leakage to the permeate side during filtration was evaluated. Conducted experiments confirmed effectiveness of MEUF in copper ions removal. For the highest copper concentration in the feed (i.e. 50 mg/L), the average concentration of copper ions in the permeate ranged from 1.2-4.7 mg Cu/L depending on surfactant concentration. During filtration experiments, UF module exhibited stable transport properties for model solutions containing copper. For the highest concentration of metal, the decrease of permeate flux did not exceed 11% after 60 minutes of filtration. In the presence of the surfactant, a slight deterioration of transport properties was observed.
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Ion Channel Modulators in Cystic Fibrosis.
Gentzsch, Martina; Mall, Marcus A
2018-05-08
Cystic fibrosis (CF) is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene and remains one of the most common life-shortening genetic diseases affecting the lung and other organs. CFTR functions as a cAMP-dependent anion channel that transports chloride and bicarbonate across epithelial surfaces and disruption of these ion transport processes plays a central role in the pathogenesis of CF. These findings provided the rationale for pharmacological modulation of ion transport, either by targeting mutant CFTR or alternative ion channels that can compensate for CFTR dysfunction, as a promising therapeutic approach. High throughput screening has supported the development of CFTR modulator compounds. CFTR correctors are designed to improve defective protein processing, trafficking and cell surface expression, whereas potentiators increase the activity of mutant CFTR at the cell surface. The approval of the first potentiator ivacaftor for the treatment of patients with specific CFTR mutations and, more recently the corrector lumacaftor in combination with ivacaftor for patients homozygous for the common F508del mutation, were major breakthroughs on the path to causal therapies for all patients with CF. In this review, we focus on recent developments and remaining challenges of CFTR-directed therapies, as well as modulators of other ion channels such as alternative chloride channels and the epithelial sodium channel (ENaC) as additional targets in CF lung disease. Further, we discuss how patient-derived precision medicine models may aid the translation of emerging next generation ion channel modulators from the laboratory to the clinic and tailor their use for optimal therapeutic benefits in individual patients with CF. Copyright © 2018. Published by Elsevier Inc.
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Zheng, Haiyan; Wang, Lijuan; Li, Kuo; Yang, Youyou; Wang, Yajie; Wu, Jiajia; Dong, Xiao; Wang, Chun-Hai; Tulk, Christopher A; Molaison, Jamie J; Ivanov, Ilia N; Feygenson, Mikhail; Yang, Wenge; Guthrie, Malcolm; Zhao, Yusheng; Mao, Ho-Kwang; Jin, Changqing
2017-01-01
Transformation between different types of carbon-carbon bonding in carbides often results in a dramatic change of physical and chemical properties. Under external pressure, unsaturated carbon atoms form new covalent bonds regardless of the electrostatic repulsion. It was predicted that calcium acetylide (also known as calcium carbide, CaC 2 ) polymerizes to form calcium polyacetylide, calcium polyacenide and calcium graphenide under high pressure. In this work, the phase transitions of CaC 2 under external pressure were systematically investigated, and the amorphous phase was studied in detail for the first time. Polycarbide anions like C 6 6- are identified with gas chromatography-mass spectrometry and several other techniques, which evidences the pressure induced polymerization of the acetylide anions and suggests the existence of the polyacenide fragment. Additionally, the process of polymerization is accompanied with a 10 7 fold enhancement of the electrical conductivity. The polymerization of acetylide anions demonstrates that high pressure compression is a viable route to synthesize novel metal polycarbides and materials with extended carbon networks, while shedding light on the synthesis of more complicated metal organics.
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Effect of phloretin on the permeability of thin lipid membranes
1976-01-01
Phloretin dramatically increases cation conductances and decreases anion conductances of membranes treated with ion carriers (nonactin, valinomycin, carbonyl-cyanide-m-chlorophenylhydrazone [CCCP], and Hg(C6F5)2) or lipophilic ions (tetraphenylarsonium [tphAs+] and tetraphenylborate [TPhB-]). For example, on phosphatidylethanolamine membranes, 10(-4) M phloretin increases K+ -nonactin and TPhAs+ conductances and decreases CCCP- and TPhB- conductances 10(3)-fold; on lecithin: cholesterol membranes, it increases K+-nonactin conductance 10(5)-fold and decreases CCCP- conductance 10(3)-fold. Similar effects are obtained with p- and m-nitrophenol at 10(-2) M. These effects are produced by the un-ionized form of phloretin and the nitrophenols. We believe that phloretin, which possesses a large dipole moment, adsorbs and orients at the membrane surface to introduce a dipole potential of opposite polarity to the preexisting positive one, thus increasing the partition coefficient of cations into the membrane interior and decreasing the partition coefficient of anions. (Phloretin may also increase the fluidity of cholesterol-containing membranes; this is manifested by its two- to three-fold increase in nonelectrolyte permeability and its asymmetrical effect on cation and anion conductances in cholesterol-containing membranes.) It is possible that pholoretin's inhibition of chloride, urea, and glucose transport in biological membranes results from the effects of these intense intrafacial dipole fields on the translocator(s) of these molecules. PMID:946975
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Sultatos, L.G.; Kaushik, R.
2008-08-01
The peripheral anionic site of acetylcholinesterase, when occupied by a ligand, is known to modulate reaction rates at the active site of this important enzyme. The current report utilized the peripheral anionic site specific fluorogenic probe thioflavin t to determine if the organophosphates chlorpyrifos oxon and dichlorvos bind to the peripheral anionic site of human recombinant acetylcholinesterase, since certain organophosphates display concentration-dependent kinetics when inhibiting this enzyme. Incubation of 3 nM acetylcholinesterase active sites with 50 nM or 2000 nM inhibitor altered both the B{sub max} and K{sub d} for thioflavin t binding to the peripheral anionic site. However, thesemore » changes resulted from phosphorylation of Ser203 since increasing either inhibitor from 50 nM to 2000 nM did not alter further thioflavin t binding kinetics. Moreover, the organophosphate-induced decrease in B{sub max} did not represent an actual reduction in binding sites, but instead likely resulted from conformational interactions between the acylation and peripheral anionic sites that led to a decrease in the rigidity of bound thioflavin t. A drop in fluorescence quantum yield, leading to an apparent decrease in B{sub max}, would accompany the decreased rigidity of bound thioflavin t molecules. The organophosphate-induced alterations in K{sub d} represented changes in binding affinity of thioflavin t, with diethylphosphorylation of Ser203 increasing K{sub d}, and dimethylphosphorylation of Ser203 decreasing K{sub d}. These results indicate that chlorpyrifos oxon and dichlorvos do not bind directly to the peripheral anionic site of acetylcholinesterase, but can affect binding to that site through phosphorylation of Ser203.« less
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Purification and Characterization of Two Voltage-Dependent Anion Channel Isoforms from Plant Seeds1
Abrecht, Helge; Wattiez, Ruddy; Ruysschaert, Jean-Marie; Homblé, Fabrice
2000-01-01
Mitochondria were isolated from imbibed seeds of lentil (Lens culinaris) and Phaseolus vulgaris. We copurified two voltage-dependent anion channel from detergent solubilized mitochondria in a single purification step using hydroxyapatite. The two isoforms from P. vulgaris were separated by chromatofocusing chromatography in 4 m urea without any loss of channel activity. Channel activity of each isoform was characterized upon reconstitution into diphytanoyl phosphatidylcholine planar lipid bilayers. Both isoforms form large conductance channels that are slightly anion selective and display cation selective substates. PMID:11080295
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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.
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Qiu, Hongdeng; Zhang, Qinghua; Chen, Limei; Liu, Xia; Jiang, Shengxiang
2008-08-01
Separations of common inorganic anions were carried out on ODS columns coated with two long-chain alkylimidazolium ionic liquids ([C(12)MIm]Br and [C(14)MIm]Br) as new cationic surfactants for ion chromatography. With phthalate buffer solution as the mobile phases and non-suppressed conductivity detection, high column efficiencies and excellent selectivity were obtained in the separation of inorganic anions. Chromatographic parameters are calculated and the results show that the coated column possesses significant potential for the analysis of some inorganic anions such as CH(3)COO(-), IO(3)(-), Cl(-), BrO(3)(-), NO(2)(-), Br(-), NO(3)(-), SO(4)(2-), I(-), BF(4)(-), and SCN(-). The effect of eluent pH values on the separation of anions has been studied on the column coated with [C(12)MIm]Br. The stability of the coated columns was also examined.
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NASA Astrophysics Data System (ADS)
Sharma, Raj Pal; Saini, Anju; Kumar, Santosh; Kumar, Jitendra; Sathishkumar, Ranganathan; Venugopalan, Paloth
2017-01-01
A new anionic copper(II) complex, (MeImH)2 [Cu(pfbz)4] (1) where, MeImH = 2-methylimidazolium and pfbz = pentafluorobenzoate has been isolated by reacting copper(II) sulfate pentahydrate, pentafluorobenzoic acid and 2-methylimidazole in ethanol: water mixture in 1:2:2 molar ratio. This complex 1 has been characterized by elemental analysis, thermogravimetric analysis, spectroscopic techniques (UV-Vis, FT-IR) and conductance measurements. The complex salt crystallizes in monoclinic crystal system with space group C2/c. Single crystal X-ray structure determination revealed the presence of discrete ions: [Cu(pfbz)4]2- anion and two 2-methylimidazolium cation (C4H7N2)+. The crystal lattice is stabilized by strong hydrogen bonding and F⋯F interactions between cationic-anionic and the anionic-anionic moieties respectively, besides π-π interactions.
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Local Bonding Influence on the Band Edge and Band Gap Formation in Quaternary Chalcopyrites.
Miglio, Anna; Heinrich, Christophe P; Tremel, Wolfgang; Hautier, Geoffroy; Zeier, Wolfgang G
2017-09-01
Quaternary chalcopyrites have shown to exhibit tunable band gaps with changing anion composition. Inspired by these observations, the underlying structural and electronic considerations are investigated using a combination of experimentally obtained structural data, molecular orbital considerations, and density functional theory. Within the solid solution Cu 2 ZnGeS 4- x Se x , the anion bond alteration parameter changes, showing larger bond lengths for metal-selenium than for metal-sulfur bonds. The changing bonding interaction directly influences the valence and conduction band edges, which result from antibonding Cu-anion and Ge-anion interactions, respectively. The knowledge of the underlying bonding interactions at the band edges can help design properties of these quaternary chalcopyrites for photovoltaic and thermoelectric applications.
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Single lithium-ion conducting solid polymer electrolytes: advances and perspectives.
Zhang, Heng; Li, Chunmei; Piszcz, Michal; Coya, Estibaliz; Rojo, Teofilo; Rodriguez-Martinez, Lide M; Armand, Michel; Zhou, Zhibin
2017-02-06
Electrochemical energy storage is one of the main societal challenges to humankind in this century. The performances of classical Li-ion batteries (LIBs) with non-aqueous liquid electrolytes have made great advances in the past two decades, but the intrinsic instability of liquid electrolytes results in safety issues, and the energy density of the state-of-the-art LIBs cannot satisfy the practical requirement. Therefore, rechargeable lithium metal batteries (LMBs) have been intensively investigated considering the high theoretical capacity of lithium metal and its low negative potential. However, the progress in the field of non-aqueous liquid electrolytes for LMBs has been sluggish, with several seemingly insurmountable barriers, including dendritic Li growth and rapid capacity fading. Solid polymer electrolytes (SPEs) offer a perfect solution to these safety concerns and to the enhancement of energy density. Traditional SPEs are dual-ion conductors, in which both cations and anions are mobile and will cause a concentration polarization thus leading to poor performances of both LIBs and LMBs. Single lithium-ion (Li-ion) conducting solid polymer electrolytes (SLIC-SPEs), which have anions covalently bonded to the polymer, inorganic backbone, or immobilized by anion acceptors, are generally accepted to have advantages over conventional dual-ion conducting SPEs for application in LMBs. A high Li-ion transference number (LTN), the absence of the detrimental effect of anion polarization, and the low rate of Li dendrite growth are examples of benefits of SLIC-SPEs. To date, many types of SLIC-SPEs have been reported, including those based on organic polymers, organic-inorganic hybrid polymers and anion acceptors. In this review, a brief overview of synthetic strategies on how to realize SLIC-SPEs is given. The fundamental physical and electrochemical properties of SLIC-SPEs prepared by different methods are discussed in detail. In particular, special attention is paid to the SLIC-SPEs with high ionic conductivity and high LTN. Finally, perspectives on the main challenges and focus on the future research are also presented.
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Structure of cyano-anion ionic liquids: X-ray scattering and simulations.
Dhungana, Kamal B; Faria, Luiz F O; Wu, Boning; Liang, Min; Ribeiro, Mauro C C; Margulis, Claudio J; Castner, Edward W
2016-07-14
Ionic liquids with cyano anions have long been used because of their unique combination of low-melting temperatures, reduced viscosities, and increased conductivities. Recently we have shown that cyano anions in ionic liquids are particularly interesting for their potential use as electron donors to excited state photo-acceptors [B. Wu et al., J. Phys. Chem. B 119, 14790-14799 (2015)]. Here we report on bulk structural and quantum mechanical results for a series of ionic liquids based on the 1-ethyl-3-methylimidazolium cation, paired with the following five cyano anions: SeCN(-), SCN(-), N(CN)2 (-), C(CN)3 (-), and B(CN)4 (-). By combining molecular dynamics simulations, high-energy X-ray scattering measurements, and periodic boundary condition DFT calculations, we are able to obtain a comprehensive description of the liquid landscape as well as the nature of the HOMO-LUMO states for these ionic liquids in the condensed phase. Features in the structure functions for these ionic liquids are somewhat different than the commonly observed adjacency, charge-charge, and polarity peaks, especially for the bulkiest B(CN)4 (-) anion. While the other four cyano-anion ionic liquids present an anionic HOMO, the one for Im2,1 (+)/B(CN)4 (-) is cationic.
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Aza compounds as anion receptors
Lee, H.S.; Yang, X.Q.; McBreen, J.
1998-01-06
A family of aza-ether based compounds including linear, multi-branched and aza-crown ethers is provided. When added to non-aqueous battery electrolytes, the family of aza-ether based compounds acts as neutral receptors to complex the anion moiety of the electrolyte salt thereby increasing the conductivity and the transference number of Li{sup +} ion in alkali metal batteries. 3 figs.
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Aza compounds as anion receptors
Lee, Hung Sui; Yang, Xiao-Qing; McBreen, James
1998-01-06
A family of aza-ether based compounds including linear, multi-branched and aza-crown ethers is provided. When added to non-aqueous battery electrolytes, the family of aza-ether based compounds acts as neutral receptors to complex the anion moiety of the electrolyte salt thereby increasing the conductivity and the transference number of Li.sup.+ ion in alkali metal batteries.
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Moslehi, Maryam; Yazdanparast, Razieh
2013-07-01
Oxidative stress plays a vital role in the pathogenesis of neurodegenerative diseases. Nerve cells are incessantly exposed to environmental stresses leading to overproduction of some harmful species like reactive oxygen species (ROS). ROS including hydrogen peroxide and superoxide anion are potent inducers of various signaling pathways encompassing MAPKs and JAK-STAT pathways. In the current study, we scrutinized the effects of hydrogen peroxide and/or menadione (superoxide anion generator) on JNK/p38-MAPKs and JAK2-STAT3 pathways to elucidate the mechanism(s) by which each oxidant modulated the above-mentioned pathways leading to SK-N-MC cell death. Our results delineated that hydrogen peroxide and superoxide anion radical induced distinct responses as we showed that STAT3 and p38 were activated in response to hydrogen peroxide, but not superoxide anion radicals indicating the specificity in ROS-induced signaling pathways activations and behaviors. We also observed that menadione induced JNK-dependent p53 expression and apoptotic death in SK-N-MC cells while H2O2-induced JNK activation was p53 independent. Thus, we declare that ROS type has a key role in selective instigation of JNK/p38-MAPKs and JAK2-STAT3 pathways in SK-N-MC cells. Identifying these differential behaviors and mechanisms of hydrogen peroxide and superoxide anion functions illuminates the possible therapeutic targets in the prevention or treatment of ROS-induced neurodegenerative diseases such as Alzheimer's disease.
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Hutchinson, Joseph P; Johns, Cameron; Breadmore, Michael C; Hilder, Emily F; Guijt, Rosanne M; Lennard, Chris; Dicinoski, Greg; Haddad, Paul R
2008-11-01
Novel CE methods have been developed on portable instrumentation adapted to accommodate a capacitively coupled contactless conductivity detector for the separation and sensitive detection of inorganic anions and cations in post-blast explosive residues from homemade inorganic explosive devices. The methods presented combine sensitivity and speed of analysis for the wide range of inorganic ions used in this study. Separate methods were employed for the separation of anions and cations. The anion separation method utilised a low conductivity 70 mM Tris/70 mM CHES aqueous electrolyte (pH 8.6) with a 90 cm capillary coated with hexadimethrine bromide to reverse the EOF. Fifteen anions could be baseline separated in 7 min with detection limits in the range 27-240 microg/L. A selection of ten anions deemed most important in this application could be separated in 45 s on a shorter capillary (30.6 cm) using the same electrolyte. The cation separation method was performed on a 73 cm length of fused-silica capillary using an electrolyte system composed of 10 mM histidine and 50 mM acetic acid, at pH 4.2. The addition of the complexants, 1 mM hydroxyisobutyric acid and 0.7 mM 18-crown-6 ether, enhanced selectivity and allowed the separation of eleven inorganic cations in under 7 min with detection limits in the range 31-240 microg/L. The developed methods were successfully field tested on post-blast residues obtained from the controlled detonation of homemade explosive devices. Results were verified using ion chromatographic analyses of the same samples.
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Wang, Jianguo; Gu, Xinggui; Zhang, Pengfei; Huang, Xiaobo; Zheng, Xiaoyan; Chen, Ming; Feng, Haitao; Kwok, Ryan T K; Lam, Jacky W Y; Tang, Ben Zhong
2017-11-22
Recent years have witnessed the significant role of anion-π + interactions in many areas, which potentially brings the opportunity for the development of aggregation-induced emission (AIE) systems. Here, a new strategy that utilized anion-π + interactions to block detrimental π-π stacking was first proposed to develop inherent-charged AIE systems. Two AIE-active luminogens, namely, 1,2,3,4-tetraphenyloxazolium (TPO-P) and 2,3,5-triphenyloxazolium (TriPO-PN), were successfully synthesized. Comprehensive techniques such as single-crystal analysis, theoretical calculation, and conductivity measurement were used to illustrate the effects of anion-π + interactions on the AIE feature. Their analogues tetraphenylfuran (TPF) and 2,4,5-triphenyloxazole (TriPO-C) without anion-π + interactions suffered from the aggregation-caused emission quenching in the aggregate state, demonstrating the important role of anion-π + interactions in suppressing π-π stacking. TriPO-PN was biocompatible and could specifically target lysosome in fluorescence turn-on and wash-free manners. This suggested that it was a promising contrast agent for bioimaging.
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Preparation and characterization of novel anion phase change heat storage materials.
Hong, Wei; Lil, Qingshan; Sun, Jing; Di, Youbo; Zhao, Zhou; Yu, Wei'an; Qu, Yuan; Jiao, TiFeng; Wang, Guowei; Xing, Guangzhong
2013-10-01
In this paper, polyurethane phase change material was successfully prepared with TDI with BDO for hard segments and PEG for soft segments. Moreover, based on this the solid-solid phase change material, A-PCM1030 which can release anions was prepared with the successful addition of anion additives A1030 for the first time. Then the test of the above material was conducted utilizing FT-IR, DSC, TEM, WAXD and Air Ion Detector. The Results indicated that the polyurethane phase change material possesses excellent thermal stability since there was no appearance of liquid leakage and phase separation after 50 times warming-cooling thermal cycles. It also presented reversibility on absorbing and releasing heat. In addition, adding a little A1030 can increase the thermal stability and reduce phase transition temperatures, as well as reduce the undercooling of the polyurethane phase change material. In addition, the anion test results suggested that the supreme amount of anion released by A-PCM1030 could reach 2510 anions/cm3 under dynamic conditions, which is beneficial for human health.
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Varcoe, John R
2007-03-28
This article presents the first systematic study of the effect of Relative Humidity (RH) on the water content and hydroxide ion conductivity of quaternary ammonium-based Alkaline Anion-Exchange Membranes (AAEMs). These AAEMs have been developed specifically for application in alkaline membrane fuel cells, where conductivities of >0.01 S cm(-1) are mandatory. When fully hydrated, an ETFE-based radiation-grafted AAEM exhibited a hydroxide ion conductivity of 0.030 +/- 0.005 S cm(-1) at 30 degrees C without additional incorporation of metal hydroxide salts; this is contrary to the previous wisdom that anion-exchange membranes are very low in ionic conductivity and represents a significant breakthrough for metal-cation-free alkaline ionomers. Desirably, this AAEM also showed increased dimensional stability on full hydration compared to a Nafion-115 proton-exchange membrane; this dimensional stability is further improved (with no concomitant reduction in ionic conductivity) with a commercial AAEM of similar density but containing additional cross-linking. However, all of the AAEMs evaluated in this study demonstrated unacceptably low conductivities when the humidity of the surrounding static atmospheres was reduced (RH = 33-91%); this highlights the requirement for continued AAEM development for operation in H(2)/air fuel cells with low humidity gas supplies. Preliminary investigations indicate that the activation energies for OH(-) conduction in these quaternary ammonium-based solid polymer electrolytes are typically 2-3 times higher than for H(+) conduction in acidic Nafion-115 at all humidities.
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Zuo, Kuichang; Yuan, Lulu; Wei, Jincheng; Liang, Peng; Huang, Xia
2013-10-01
Mixed ion-exchange resins packed microbial desalination cell (R-MDC) could stabilize the internal resistance, however, the impacts of multiple ions on R-MDC performance was unclear. This study investigated the desalination performance, multiple ions migration behaviors and their impacts on R-MDCs fed with salt solution containing multiple anions and cations. Results showed that R-MDC removed multiple anions better than multiple cations with desalination efficiency of 99% (effluent conductivity <0.05 ms/cm) at hydraulic retention time of 50 h. Competitive migration order was SO4(2-)>NO3(-)>Cl(-) for anions and Ca(2+)≈Mg(2+)>NH4(+)>Na(+) for cations, jointly affected by both their molar conductivity and exchange selectivity on resins. After long-term operation, the existence of higher concentration Ca(2+) and Mg(2+) caused the electric conductivity of mixed resins decrease and scaling on the surface of cation-exchange membrane adjoined with cathode chamber, suggesting that R-MDC would be more suitable for desalination of water with lower hardness. Copyright © 2013 Elsevier Ltd. All rights reserved.
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Bauer, Georg
2015-01-01
Tumor cells generate extracellular superoxide anions and are protected against intercellular apoptosis-inducing HOCl- and NO/peroxynitrite signaling through the expression of membrane-associated catalase. This enzyme decomposes H2O2 and thus prevents HOCl synthesis. It efficiently interferes with NO/peroxynitrite signaling through oxidation of NO and decomposition of peroxynitrite. The regulatory potential of catalase at the crosspoint of ROS and RNS chemical biology, as well as its high local concentration on the outside of the cell membrane of tumor cells, establish tight control of intercellular signaling and thus prevent tumor cell apoptosis. Therefore, inhibition of catalase or its inactivation by singlet oxygen reactivate intercellular apoptosis-inducing signaling. Nitric oxide and peroxynitrite are connected with catalase in multiple and meaningful ways, as (i) NO can be oxidated by compound I of catalase, (ii) NO can reversibly inhibit catalase, (iii) peroxynitrite can be decomposed by catalase and (iv) the interaction between peroxynitrite and H2O2 leads to the generation of singlet oxygen that inactivates catalase. Therefore, modulation of the concentration of free NO through addition of arginine, inhibition of arginase, induction of NOS expression or inhibition of NO dioxygenase triggers an autoamplificatory biochemical cascade that is based on initial formation of singlet oxygen, amplification of superoxide anion/H2O2 and NO generation through singlet oxygen dependent stimulation of the FAS receptor and caspase-8. Finally, singlet oxygen is generated at sufficiently high concentration to inactivate protective catalase and to reactivate intercellular apoptosis-inducing ROS signaling. This regulatory network allows to establish several pathways for synergistic interactions, like the combination of modulators of NO metabolism with enhancers of superoxide anion generation, modulators of NO metabolism that act at different targets and between modulators of NO metabolism and direct catalase inhibitors. The latter aspect is explicitely studied for the interaction between catalase inhibiting acetylsalicylic acid and an NO donor. It is also shown that hybrid molecules like NO-aspirin utilize this synergistic potential. Our data open novel approaches for rational tumor therapy based on specific ROS signaling and its control in tumor cells. PMID:26342455
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Kawano, Tomonori; Kagenishi, Tomoko; Kadono, Takashi; Bouteau, François; Hiramatsu, Takuya; Lin, Cun; Tanaka, Kenichiro; Tanaka, Licca; Mancuso, Stefano; Uezu, Kazuya; Okobira, Tadashi; Furukawa, Hiroka; Iwase, Junichiro; Inokuchi, Reina; Baluška, Frantisek; Yokawa, Ken
2015-01-01
Generation of reactive oxygen species is useful for various medical, engineering and agricultural purposes. These include clinical modulation of immunological mechanism, enhanced degradation of organic compounds released to the environments, removal of microorganisms for the hygienic purpose, and agricultural pest control; both directly acting against pathogenic microorganisms and indirectly via stimulation of plant defense mechanism represented by systemic acquired resistance and hypersensitive response. By aiming to develop a novel classes of artificial redox-active biocatalysts involved in production and/or removal of superoxide anion radicals, recent attempts for understanding and modification of natural catalytic proteins and functional DNA sequences of mammalian and plant origins are covered in this review article. PMID:27066179
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Understanding Anion Transport in an Aminated Trimethyl Polyphenylene with High Anionic Conductivity
2012-01-01
published online DOI: 10.1002/polb.23164 ABSTRACT: An alkaline exchange membrane (AEM) based on an aminated trimethyl poly(phenylene) is studied in...3874–3882. 23 Cotts, R. M.; Hoch, M. J. R.; Sun, T.; Markert , J. T. J. Magn. Reson. (1969) 1989, 83, 252–266. 24 Tanner, J. E. J. Chem. Phys. 1970
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Anion receptor compounds for non-aqueous electrolytes
Lee, Hung Sui; Yang, Xiao-Oing; McBreen, James
2000-09-19
A new family of aza-ether based compounds including linear, multi-branched and aza-crown ethers is provided. When added to non-aqueous battery electrolytes, the new family of aza-ether based compounds acts as neutral receptors to complex the anion moiety of the electrolyte salt thereby increasing the conductivity and the transference number of LI.sup.+ ion in alkali metal batteries.
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Aza crown ether compounds as anion receptors
Lee, Hung Sui; Yang, Xiao-Oing; McBreen, James
1998-08-04
A family of aza-ether based compounds including linear, multi-branched and aza-crown ethers is provided. When added to non-aqueous battery electrolytes, the new family of aza-ether based compounds acts as neutral receptors to complex the anion moiety of the electrolyte salt thereby increasing the conductivity and the transference number of LI.sup.+ ion in alkali metal batteries.
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Aza crown ether compounds as anion receptors
Lee, H.S.; Yang, X.O.; McBreen, J.
1998-08-04
A family of aza-ether based compounds including linear, multi-branched and aza-crown ethers is provided. When added to non-aqueous battery electrolytes, the new family of aza-ether based compounds acts as neutral receptors to complex the anion moiety of the electrolyte salt thereby increasing the conductivity and the transference number of LI{sup +} ion in alkali metal batteries. 3 figs.
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Zheng, Haiyan; Wang, Lijuan; Li, Kuo; ...
2016-08-17
Transformation between different types of carbon–carbon bonding in carbides often results in a dramatic change of physical and chemical properties. Under external pressure, unsaturated carbon atoms form new covalent bonds regardless of the electrostatic repulsion. It was predicted that calcium acetylide (also known as calcium carbide, CaC 2) polymerizes to form calcium polyacetylide, calcium polyacenide and calcium graphenide under high pressure. In this work, the phase transitions of CaC 2 under external pressure were systematically investigated, and the amorphous phase was studied in detail for the first time. Polycarbide anions like C 6 6– are identified with gas chromatography-mass spectrometrymore » and several other techniques, which evidences the pressure induced polymerization of the acetylide anions and suggests the existence of the polyacenide fragment. Additionally, the process of polymerization is accompanied with a 10 7 fold enhancement of the electrical conductivity. As a result, the polymerization of acetylide anions demonstrates that high pressure compression is a viable route to synthesize novel metal polycarbides and materials with extended carbon networks, while shedding light on the synthesis of more complicated metal organics.« less
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Complexes of carboxyl-containing polymer and monosubstituted bipyridinium salts
NASA Astrophysics Data System (ADS)
Merekalova, N. D.; Bondarenko, G. N.; Krylsky, D. W.; Zakirov, M. I.; Talroze, R. V.
2013-09-01
Semi-empirical PM3 method for the quantum calculations of molecular electronic structure based on NDDO integral approximation is used to investigate the complex formation of monosubstituted 4,4‧-bipyridinium salts BpyR (Hal) containing a halide anion interacting with the quaternary nitrogen atom and carboxylic group of the two-units construct. Significant effect of the BpyR (Hal) electronic structure is unveiled that contributes in two different structures of these salts, namely, partial charge transfer complex and ion pair structure, both having stable energy minima. We demonstrate that (i) the structure of the N-substituent modulates the energy and electronic characteristics of monosubstituted salts BpyR with chlorine and bromine anions and (ii) the coulomb interactions between quaternary N-atom, halogen anion, and the proton of carboxylic group stimulate the transformation of the charge transfer complex into the ion pair structure. Results of calculations are compared with the experimental FTIR spectra of blends of BpyR(Hal) with Eudragit copolymer.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Tsai, Tsung-Han; Ertem, S. Piril; Maes, Ashley M.
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 scatteringmore » 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.« less
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Enhancing Cation Diffusion and Suppressing Anion Diffusion via Lewis-Acidic Polymer Electrolytes.
Savoie, Brett M; Webb, Michael A; Miller, Thomas F
2017-02-02
Solid polymer electrolytes (SPEs) have the potential to increase both the energy density and stability of lithium-based batteries, but low Li + conductivity remains a barrier to technological viability. SPEs are designed to maximize Li + diffusivity relative to the anion while maintaining sufficient salt solubility. It is thus remarkable that poly(ethylene oxide) (PEO), the most widely used SPE, exhibits Li + diffusivity that is an order of magnitude smaller than that of typical counterions at moderate salt concentrations. We show that Lewis-basic polymers like PEO favor slow cation and rapid anion diffusion, while this relationship can be reversed in Lewis-acidic polymers. Using molecular dynamics, polyboranes are identified that achieve up to 10-fold increases in Li + diffusivities and significant decreases in anion diffusivities, relative to PEO in the dilute-ion regime. These results illustrate a general principle for increasing Li + diffusivity and transference number with chemistries that exhibit weaker cation and stronger anion coordination.
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Stone, Melani C.; Borman, Jon; Ferreira, Gisela
2017-01-01
Flowthrough anion exchange chromatography is commonly used as a polishing step in downstream processing of monoclonal antibodies and other therapeutic proteins to remove process‐related impurities and contaminants such as host cell DNA, host cell proteins, endotoxin, and viruses. DNA with a wide range of molecular weight distributions derived from Chinese Hamster Ovary cells was used to advance the understanding of DNA binding behavior in selected anion exchange media using the resin (Toyopearl SuperQ‐650M) and membranes (Mustang® Q and Sartobind® Q) through DNA spiking studies. The impacts of the process parameters pH (6–8), conductivity (2–15 mS/cm), and the potential binding competition between host cell proteins and host cell DNA were studied. Studies were conducted at the least and most favorable experimental conditions for DNA binding based on the anticipated electrostatic interactions between the host cell DNA and the resin ligand. The resin showed 50% higher DNA binding capacity compared to the membrane media. Spiking host cell proteins in the load material showed no impact on the DNA clearance capability of the anion exchange media. DNA size distributions were characterized based on a “size exclusion qPCR assay.” Results showed preferential binding of larger DNA fragments (>409 base pairs). © 2017 The Authors Biotechnology Progress published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers Biotechnol. Prog., 34:141–149, 2018 PMID:28884511
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NASA Astrophysics Data System (ADS)
Hu, Yuanfang; Wang, Bingxi; Li, Xiao; Chen, Dongyang; Zhang, Weiying
2018-05-01
To develop high performance anion exchange membranes (AEMs), a novel bisphenol monomer bearing eight benzylmethyl groups at the outer edge of the molecule was synthesized, which after condensation polymerization with various amounts of 4,4‧-dihydroxydiphenylsulfone and 4,4‧-difluorobenzophenone yielded novel poly(arylene ether)s with densely located benzylmethyl groups. These benzylmethyl groups were then converted to quaternary ammonium groups by radical-initiated bromination and quaternization in tandem, leading to the emergence of densely quaternized poly(arylene ether sulfone)s (QA-PAEs) with controlled ion exchange capacities (IECs) ranging from 1.61 to 2.32 mmol g-1. Both small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) studies revealed distinct phase separation in the QA-PAEs. The QA-PAE-40 with an IEC of 2.32 mmol g-1 exhibited a Br- conductivity of 9.2 mS cm-1 and a SO42- conductivity of 14.0 mS cm-1 at room temperature, much higher than those of a control membrane with a similar IEC but without obvious phase separation. Therefore, phase separation of AEMs was validated to be advantageous for the efficient conducting of anions. The experimental results also showed that the QA-PAEs were promising AEM materials, especially for non-alkaline applications.
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Silva, Micael; Figueiredo, Angelo Miguel; Cabrita, Eurico J
2014-11-14
We investigated imidazolium-based ionic liquid (IL) interactions with human serum albumin (HSA) to discern the level of cation interactions towards protein stability. STD-NMR spectroscopy was used to observe the imidazolium IL protons involved in direct binding and to identify the interactions responsible for changes in Tm as accessed by differential scanning calorimetry (DSC). Cations influence protein stability less than anions but still significantly. It was found that longer alkyl side chains of imidazolium-based ILs (more hydrophobic) are associated with a higher destabilisation effect on HSA than short-alkyl groups (less hydrophobic). The reason for such destabilisation lies on the increased surface contact area of the cation with the protein, particularly on the hydrophobic contacts promoted by the terminus of the alkyl chain. The relevance of the hydrophobic contacts is clearly demonstrated by the introduction of a polar moiety in the alkyl chain: a methoxy or alcohol group. Such structural modification reduces the degree of hydrophobic contacts with HSA explaining the lesser extent of protein destabilisation when compared to longer alkyl side chain groups: above [C2mim](+). Competition STD-NMR experiments using [C2mim](+), [C4mim](+) and [C2OHmim](+) also validate the importance of the hydrophobic interactions. The combined effect of cation and anion interactions was explored using (35)Cl NMR. Such experiments show that the nature of the cation has no influence on the anion-protein contacts, still the nature of the anion modulates the cation-protein interaction. Herein we propose that more destabilising anions are likely to be a result of a partial contribution from the cation as a direct consequence of the different levels of interaction (cation-anion pair and cation-protein).
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NASA Astrophysics Data System (ADS)
Chen, Hui; Han, Shu-Yan; Liu, Rui-Heng; Chen, Teng-Fei; Bi, Kai-Lun; Liang, Jian-Bo; Deng, Yu-Heng; Wan, Chong-Qing
2018-02-01
Incorporating ionic liquids (abbreviated as ILs) into porous metal-organic framework (MOF) to obtain ILs@MOF nanocomposites is documented as a feasible method to achieve new type of anhydrous proton conductor with high performance. We newly synthesized a series of ILs with different acid counter anions (R-SO3-) and their ILs@MOF hybrid materials, i.e. SA-EIMS@MIL-101, MSA-EIMS@MIL-101 and PTSA-EIMS@MIL-101 (SA = sulfate acid, MSA = methanesulfonate acid, PTSA = p-toluenesulfonate acid, EIMS = 1-(1-ethyl-3-imidazolium)propane-3-sulfonate). Such hybrid materials displayed as anhydrous proton conduction with long-term durability even heated at 150 °C open to air. σ value of SA-EIMS@MIL-101 is up to 1.89 × 10-3 S cm-1, being in the range of the most conductive MOF-based materials. MOF support exhibited favorable proton transport and long-term retention for ILs. Anion volumes of R-SO3- displayed significant effects on the proton conductivity of such hybrid ILs@MOF materials. The smaller the van der Waals volume of R-SO3- is, the higher the conductivity of ILs@MOF is. This work suggests that the combination of a variety of the incorporated ILs and a MOF framework would afford high proton transport and gives an idea to explore the safe, anhydrous, solid-state electrolyte for high temperature proton exchange membrane fuel cell.
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Application of Novel Anion-Exchange Blend Membranes (AEBMs) to Vanadium Redox Flow Batteries.
Cho, Hyeongrae; Krieg, Henning M; Kerres, Jochen A
2018-06-19
Both cation-exchange membranes and anion-exchange membranes are used as ion conducting membranes in vanadium redox flow batteries (VRFBs). Anion-exchange membranes (AEMs) are applied in vanadium redox flow batteries due to the high blocking property of vanadium ions via the Donnan exclusion effect. In this study, novel anion-exchange blend membranes (AEBMs) were prepared, characterized, and applied in VRFBs. Bromomethylated poly(2,6-dimethyl-1,4-phenylene oxide), poly[(1-(4,4′-diphenylether)-5-oxybenzimidazole)-benzimidazole] (PBI-OO) and sulfonated polyether sulfone polymer were combined to prepare 3-component AEBMs with 1,2,4,5-tetramethylimidazole (TMIm) for quaternization. 3-component AEBMs showed significantly enhanced chemical and mechanical properties compared with those of 2-component AEBMs, resulting in an improved performance in VRFBs. The compositions of the anion-exchange polymers in 3-component AEBMs were systematically varied to optimize the AEBMs for the redox-flow battery application. While the 3-component AEBMs showed comparable efficiencies with Nafion ® 212 membranes, they displayed improved vanadium ions cross-over as was confirmed by open circuit voltage tests and capacity fade tests conducted in VRFBs. In addition, one of the synthesized 3-component AEBM had a superior coulombic efficiency and capacity retention in a charging⁻discharging test over 300 cycles at a current density of 40 mA/cm². It can thus be concluded that 3-component AEBMs are promising candidates for long-term operation in VRFBs.
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Monovalent Cation Permeation through the Connexin40 Gap Junction Channel
Beblo, Dolores A.; Veenstra, Richard D.
1997-01-01
The unitary conductances and permeability sequences of the rat connexin40 (rCx40) gap junction channels to seven monovalent cations and anions were studied in rCx40-transfected neuroblastoma 2A (N2A) cell pairs using the dual whole cell recording technique. Chloride salt cation substitutions (115 mM principal salt) resulted in the following junctional maximal single channel current-voltage relationship slope conductances (γj in pS): CsCl (153), RbCl (148), KCl (142), NaCl (115), LiCl (86), TMACl (71), TEACl (63). Reversible block of the rCx40 channel was observed with TBA. Potassium anion salt γj are: Kglutamate (160), Kacetate (160), Kaspartate (158), KNO3 (157), KF (148), KCl (142), and KBr (132). Ion selectivity was verified by measuring reversal potentials for current in rCx40 gap junction channels with asymmetric salt solutions in the two electrodes and using the Goldman-Hodgkin-Katz equation to calculate relative permeabilities. The permeabilities relative to Li+ are: Cs+ (1.38), Rb+ (1.32), K+ (1.31), Na+ (1.16), TMA+ (0.53), TEA+ (0.45), TBA+ (0.03), Cl− (0.19), glutamate− (0.04), and NO3− (0.14), assuming that the monovalent anions permeate the channel by forming ion pairs with permeant monovalent cations within the pore thereby causing proportionate decreases in the channel conductance. This hypothesis can account for why the predicted increasing conductances with increasing ion mobilities in an essentially aqueous channel were not observed for anions in the rCx40 channel. The rCx40 effective channel radius is estimated to be 6.6 Å from a theoretical fit of the relationship of relative permeability and cation radius. PMID:9101408
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Lee, Byeol-Nim; Son, Tae Yang; Park, Chi Hoon; Kim, Tae Hyun; Nam, Sang Yong
2018-09-01
In this study, various poly(ether ether ketone) were synthesized using three different monomers and the imidazolium group was introduced into synthesized poly(ether ether ketone)s by using substitution reaction. Synthesized polymers were used to prepare anion exchange membranes and to evaluate its properties. Thermal, chemical and structural properties were carried out using thermogravimetric analysis, nuclear magnetic resonance. The anion exchange membranes with different imidazolium moieties were characterized by several different analytical techniques such as water up take, ion exchange capacity, hydroxide conductivity for checking the possibility to apply the anion exchange membrane fuel cell. Consequently, results of characterization were studied to understand the correlation between stabilities of the membrane and functional group and polymer backbone structures. And we confirm membrane performance was improved by increasing imidazolium cation groups.
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NASA Astrophysics Data System (ADS)
Jiang, F. D.; Feng, J. Y.
2008-02-01
Using first principles calculation, we systematically investigate the electronic modification of Cu-based chalcopyrite semiconductors induced by lattice deformation and composition alchemy. It is shown that the optical band gap Eg is remarkably sensitive to the anion displacement μ, resulting from the opposite shifts of conduction band minimum and valence band maximum. Meanwhile, the dependence of structural parameters of alloyed compounds on alloy composition x is demonstrated for both cation and anion alloying. The d orbitals of group-III cations are found to be of great importance in the calculation. Abnormal changes in the optical band gap Eg induced by anion alloying are addressed.
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Electron induced dissociation in condensed-phase nitromethane I: desorption of ionic fragments.
Bazin, Marc; Ptasińska, Sylwia; Bass, Andrew D; Sanche, Léon
2009-03-14
Low energy electron induced dissociation of condensed nitromethane was investigated by measuring the electron stimulated desorption of anions and cations from multilayer films of CH(3)NO(2) and CD(3)NO(2), using a recently constructed, high sensitivity time of flight mass spectrometer. The desorbed yields were measured as a function of incident electron energy in the range between 1 to 20 eV and as function of coverage on Pt and Xe substrates. In anion desorption experiments, the following ions were observed: H(-) (D(-)), O(-), OH(-) (OD(-)), CN(-), NCO(-), NO(2)(-), CHNO(2)(-) (CDNO(2)(-)), CH(2)NO(2)(-) (CD(2)NO(2)(-)). Resonant structure seen in all anion yield functions, is attributed to dissociative electron attachment (DEA), though certain anion signals [e.g., OH(-) (OD(-)) and CH(2)NO(2)(-) (CD(2)NO(2)(-))] are likely the result of reactive scattering by O(-) ions. The dominant desorbed cation signals are CD(3)(+) and NO(+), and the appearance potentials of these species were measured to be 12.2 and 11.5 eV, respectively. The present measurements provide information on how the electron-induced dissociation processes of this proto-typical explosive molecule are modulated by the condensed environment and on how initial dissociation events occurring on a particular molecule, may induce further dissociation.
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Grotthuss Transport of Iodide in EMIM/I3 Ionic Crystal.
McDaniel, Jesse G; Yethiraj, Arun
2018-01-11
Highly ionic environments can mediate unusual chemical reactions that would otherwise be considered impossible based on chemical intuition. For example, the formation of a chemical bond between two iodide anions to form a divalent polyiodide anion is seemingly prohibited due to Coulombic repulsion. Using ab initio molecular dynamics simulations, we show that in the 1-ethyl-3-methylimidazolium (EMIM)/I 3 ionic crystal, the reactive formation of divalent and even trivalent polyiodide anions occurs with extremely small energetic barriers, due to the electrostatic field of the ionic lattice. A practical consequence of this anomalous reactivity is that iodide anions are efficiently transported within the crystal through a "Grotthuss-exchange" mechanism involving bond-breaking and forming events. We characterize two distinct transport pathways, involving both I 4 2- and I 7 3- intermediates, with fast transport of iodide resulting from the release of an I - anion on the opposite side of the intermediate species from the initial bond formation. The ordered cation arrangement in the crystal provides the necessary electrostatic screening for close approach of anions, suggesting a new counterintuitive approach to obtain high ionic conductivity. This new design principle could be used to develop better solid-state electrolytes for batteries, fuel cells, and supercapacitors.
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Hole localization, migration, and the formation of peroxide anion in perovskite SrTiO3
NASA Astrophysics Data System (ADS)
Chen, Hungru; Umezawa, Naoto
2014-07-01
Hybrid density functional calculations are carried out to investigate the behavior of holes in SrTiO3. As in many other oxides, it is shown that a hole tend to localize on one oxygen forming an O- anion with a concomitant lattice distortion; therefore a hole polaron. The calculated emission energy from the recombination of the localized hole and a conduction-band electron is about 2.5 eV, in good agreement with experiments. Therefore the localization of the hole or self-trapping is likely to be responsible for the green photoluminescence at low temperature, which was previously attributed to an unknown defect state. Compared to an electron, the calculated hole polaron mobility is three orders of magnitude lower at room temperature. In addition, two O- anions can bind strongly to form an O22- peroxide anion. No electronic states associated with the O22- peroxide anion are located inside the band gap or close to the band edges, indicating that it is electronically inactive. We suggest that in addition to the oxygen vacancy, the formation of the O22- peroxide anion can be an alternative to compensate acceptor doping in SrTiO3.
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NASA Astrophysics Data System (ADS)
Dekel, Dario R.; Willdorf, Sapir; Ash, Uri; Amar, Michal; Pusara, Srdjan; Dhara, Shubhendu; Srebnik, Simcha; Diesendruck, Charles E.
2018-01-01
Anion exchange membrane fuel cells can potentially revolutionize energy storage and delivery; however, their commercial development is hampered by a significant technological impedance: the chemical decomposition of the anion exchange membranes during operation. The hydroxide anions, while transported from the cathode to the anode, attack the positively charged functional groups in the polymer membrane, neutralizing it and suppressing its anion-conducting capability. In recent years, several new quaternary ammonium salts have been proposed to address this challenge, but while they perform well in ex-situ chemical studies, their performance is very limited in real fuel cell studies. Here, we use experimental work, corroborated by molecular dynamics modeling to show that water concentration in the environment of the hydroxide anion, as well as temperature, significantly impact its reactivity. We compare different quaternary ammonium salts that have been previously studied and test their stabilities in the presence of relatively low hydroxide concentration in the presence of different amounts of solvating water molecules, as well as different temperatures. Remarkably, with the right amount of water and at low enough temperatures, even quaternary ammonium salts which are considered "unstable", present significantly improved lifetime.
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Determination of glycerophosphate and other anions in dentifrices by ion chromatography.
Chen, Yongxin; Ye, Mingli; Cui, Hairong; Wu, Feiyan; Zhu, Yan; Fritz, James S
2006-06-16
Simple, reliable and sensitive analytical methods to determine the anions, such as fluoride, monofluorophaosphate, glycerophosphate related to anticaries are necessary for basic investigations of anticaries and quality control of dentifrices. A method for the simultaneous determination of organic acids, organic anions and inorganic anions in the sample of commercial toothpaste is proposed. Nine anions (fluoride, chloride, nitrite, nitrate, sulfate, phosphate, monofluorophaosphate, glycerophosphate and oxalic acid) were analyzed by means of ion chromatography using a gradient elution with KOH as mobile phase, IonPac AS18 as the separation column and suppressed conductivity detection. Optimized analytical conditions were further validated in terms of accuracy, precision and total uncertainty and the results showed the reliability of the IC method. The relative standard deviations (RSD) of the retention time and peak area of all species were less than 0.170 and 1.800%, respectively. The correlation coefficients for target analytes ranged from 0.9985 to 0.9996. The detection limit (signal to noise ratio of 3:1) of this method was at low ppb level (<15 ppb). The spiked recoveries for the anions were 96-103%. The method was applied to toothpaste without interferences.
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Studies of anions sorption on natural zeolites.
Barczyk, K; Mozgawa, W; Król, M
2014-12-10
This work presents results of FT-IR spectroscopic studies of anions-chromate, phosphate and arsenate - sorbed from aqueous solutions (different concentrations of anions) on zeolites. The sorption has been conducted on natural zeolites from different structural groups, i.e. chabazite, mordenite, ferrierite and clinoptilolite. The Na-forms of sorbents were exchanged with hexadecyltrimethylammonium cations (HDTMA(+)) and organo-zeolites were obtained. External cation exchange capacities (ECEC) of organo-zeolites were measured. Their values are 17mmol/100g for chabazite, 4mmol/100g for mordenite and ferrierite and 10mmol/100g for clinoptilolite. The used initial inputs of HDTMA correspond to 100% and 200% ECEC of the minerals. Organo-modificated sorbents were subsequently used for immobilization of mentioned anions. It was proven that aforementioned anions' sorption causes changes in IR spectra of the HDTMA-zeolites. These alterations are dependent on the kind of anions that were sorbed. In all cases, variations are due to bands corresponding to the characteristic Si-O(Si,Al) vibrations (occurring in alumino- and silicooxygen tetrahedra building spatial framework of zeolites). Alkylammonium surfactant vibrations have also been observed. Systematic changes in the spectra connected with the anion concentration in the initial solution have been revealed. The amounts of sorbed CrO4(2-), AsO4(3-) and PO4(3-) ions were calculated from the difference between their concentrations in solutions before (initial concentration) and after (equilibrium concentration) sorption experiments. Concentrations of anions were determined by spectrophotometric method. Copyright © 2014 Elsevier B.V. All rights reserved.
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Aoyagi, Wataru; Omiya, Masaki
2016-01-01
An ionic polymer-metal composite (IPMC) actuator composed of a thin perfluorinated ionomer membrane with electrodes plated on both surfaces undergoes a large bending motion when a low electric field is applied across its thickness. Such actuators are soft, lightweight, and able to operate in solutions and thus show promise with regard to a wide range of applications, including MEMS sensors, artificial muscles, biomimetic systems, and medical devices. However, the variations induced by changing the type of anion on the device deformation properties are not well understood; therefore, the present study investigated the effects of different anions on the ion exchange process and the deformation behavior of IPMC actuators with palladium electrodes. Ion exchange was carried out in solutions incorporating various anions and the actuator tip displacement in deionized water was subsequently measured while applying a step voltage. In the step voltage response measurements, larger anions such as nitrate or sulfate led to a more pronounced tip displacement compared to that obtained with smaller anions such as hydroxide or chloride. In AC impedance measurements, larger anions generated greater ion conductivity and a larger double-layer capacitance at the cathode. Based on these mechanical and electrochemical measurements, it is concluded that the presence of larger anions in the ion exchange solution induces a greater degree of double-layer capacitance at the cathode and results in enhanced tip deformation of the IPMC actuators. PMID:28773599
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Wang, Xia; Wang, Yanlong; Silver, Mark A.
An ultrahigh proton conductivity of 2.91 × 10 −2 S cm −1 and an ultralow activation energy of 0.10 eV were observed in an anionic lanthanide-organic framework. Both values approach the records for proton-conducting MOF materials.
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Correlating morphology to dc conductivity in polymerized ionic liquids
NASA Astrophysics Data System (ADS)
Iacob, Ciprian; Matusmoto, Atsushi; Inoue, Tadashi; Runt, James
Polymerized ionic liquids (PILs) combine the attractive mechanical characteristics of polymers and unique physico-chemical properties of low molecular weight ionic liquids in the same material. PILs have shown remarkable advantages when employed in electrochemical devices such as dye-sensitized solar cells and lithium batteries, among others. Understanding their ionic transport mechanism is the key for designing highly conductive PILs. In the current study, the correlation between morphology and charge transport in two homologous series of PILs with systematic variation of the alkyl chain length and anions is investigated using broadband dielectric spectroscopy, rheology, differential scanning calorimetry and X-ray scattering. As the alkyl chain length increases, the backbone-to-backbone separation increases, and dc-conductivity consequently decreases. The cations dominate structural dynamics since they are attached to the polymer chains, while the anions are smaller and more mobile ionic species thereby controlling the ionic conductivity. Further interpretation of decoupling of dc conductivity from the segmental relaxation enabled the correlation between polymer morphology and dc conductivity. Supported by the National Science Foundation, Polymers Program.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Yao, Kaisheng; Henan Normal University, School of Chemistry and Environmental Science, Key Laboratory of Green Chemical Media and Reactions, Xin xiang, Henan 453007; Lu, Weiwei
A novel method was proposed for successful fabrication of CuS nanostructures with various morphologies. At the ionic liquids (ILs)-modulated CHCl{sub 3}-H{sub 2}O interface, copper cupferronate [Cu(cup){sub 2}] in CHCl{sub 3} reacted with thiourea in water to generate CuS nanostructures via a solvothermal reaction process. The effects of alkyl chain length of imidazolium cations and nature of anions of the ILs, molar ratio of Cu(cup){sub 2} to thiourea, the reaction temperature and time on the morphology of the products were studied systematically. It was shown that by changing alkyl chain length of imidazolium cations and nature of anions of the ILs,more » CuS nanostructures with various morphologies, including flowers, urchins, large nanodisks and nanoparticles, could be obtained at the liquid-liquid interface, and the ILs played important template roles in directing the formation of CuS nanostructures. Furthermore, the as-prepared CuS samples exhibited high catalytic activity for photodegradation of methyl orange and thermal decomposition of ammonium perchlorate. - Graphical abstract: At the ionic liquids-modulated CHCl{sub 3}-H{sub 2}O interface, the CuS nanostructures with the various morphologies of flowers, urchins, large nanodisks and nanoparticles have been successfully prepared via a solvothermal reaction process. Highlights: Black-Right-Pointing-Pointer The properties of oil-H{sub 2}O interface can be modulated by employing different ILs. Black-Right-Pointing-Pointer The modulated interface has been used to prepare CuS nanostructures with various morphologies. Black-Right-Pointing-Pointer The CuS samples exhibited high catalytic activity for the photodegradation of methyl orange.« less
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NASA Technical Reports Server (NTRS)
Haskins, Justin B.; Bennett, William R.; Wu, James J.; Hernandez, Dionne M.; Borodin, Oleg; Monk, Joshua D.; Bauschlicher, Charles W.; Lawson, John W.
2014-01-01
We employ molecular dynamics (MD) simulation and experiment to investigate the structure, thermodynamics, and transport of N-methyl-N-butylpyrrolidinium bis(trifluoromethylsufonyl)imide ([pyr14][TFSI]), N -methyl-N-propylpyrrolidinium bis(fluorosufonyl)imide ([pyr13][FSI]), and 1-ethyl-3-methylimidazolium boron tetrafluoride ([EMIM][BF4]), as a function of Li-salt mole fraction (0.05 xLi+ 0.33) and temperature (298 K T 393 K). Structurally, Li+ is shown to be solvated by three anion neigh- bors in [pyr14][TFSI] and four anion neighbors in both [pyr13][FSI] and [EMIM][BF4], and at all levels of xLi+ we find the presence of lithium aggregates. Pulsed field gradient spin-echo NMR measurements of diffusion and electrochemical impedance spectroscopy measurements of ionic conductivity are made for the neat ionic liquids as well as 0.5 molal solutions of Li-salt in the ionic liquids. Bulk ionic liquid properties (density, diffusion, viscosity, and ionic conductivity) are obtained with MD and show excellent agreement with experiment. While the diffusion exhibits a systematic decrease with increasing xLi+, the contribution of Li+ to ionic conductivity increases until reach- ing a saturation doping level of xLi+ 0.10. Comparatively, the Li+ conductivity of [pyr14][TFSI] is an order of magnitude lower than that of the other liquids, which range between 0.1-0.3 mScm. Our transport results also demonstrate the necessity of long MD simulation runs ( 200 ns) required to converge transport properties at room T. The differences in Li+ transport are reflected in the residence times of Li+ with the anions (Li), which are revealed to be much larger for [pyr14][TFSI] (up to 100 ns at the highest doping levels) than in either [EMIM][BF4] or [pyr13][FSI]. Finally, to comment on the relative kinetics of Li+ transport in each liquid, we find that while the net motion of Li+ with its solvation shell (vehicular) significantly contributes to net diffusion in all liquids, the importance of transport through anion exchange (hopping) increases at high xLi+ and in liquids with large anions.
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Chattoraj, Joyjit; Knappe, Marisa; Heuer, Andreas
2015-06-04
It is known from experiments that in the polymer electrolyte system, which contains poly(ethylene oxide) chains (PEO), lithium-cations (Li(+)), and bis(trifluoromethanesulfonyl)imide-anions (TFSI(-)), the cation and the anion diffusion and the ionic conductivity exhibit a similar chain-length dependence: with increasing chain length, they start dropping steadily, and later, they saturate to constant values. These results are surprising because Li-cations are strongly correlated with the polymer chains, whereas TFSI-anions do not have such bonding. To understand this phenomenon, we perform molecular dynamics simulations of this system for four different polymer chain lengths. The diffusion results obtained from our simulations display excellent agreement with the experimental data. The cation transport model based on the Rouse dynamics can successfully quantify the Li-diffusion results, which correlates Li diffusion with the polymer center-of-mass motion and the polymer segmental motion. The ionic conductivity as a function of the chain length is then estimated based on the chain-length-dependent ion diffusion, which shows a temperature-dependent deviation for short chain lengths. We argue that in the first regime, counterion correlations modify the conductivity, whereas for the long chains, the system behaves as a strong electrolyte.
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Alemany, Pere; Llunell, Miquel; Canadell, Enric
2008-10-01
A first-principles Density Functional Theory study of several layered solids structurally related to rhombohedral arsenic has been carried out. The electronic structures of rhombohedral arsenic, CaSi(2), CaAl(2)Si(2), KSnSb, and SrSn(2)As(2) are discussed in detail, emphasizing on the origins of their metallic or nonmetallic behaviours. It is found that all of these systems are metallic except KSnSb. Electronegativity differences between the elements in the anionic sublattice and/or direct interlayer interactions play the main role in controlling the conductivity behavior. CaSi(2) exhibits a peculiar feature since the cation directly influences the conductivity but is not essential for its appearance. Cation-anion interactions are shown to have an important covalent contribution, but despite this fact and the metallic character found for most of these phases, the Zintl approach still provides a valid approximation to their electronic structure. (c) 2008 Wiley Periodicals, Inc.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Choi, Daiwon; Zhu, Chengzhou; Fu, Shaofang
2016-09-15
The electrochemically controlled ion-exchange properties of multi-wall carbon nanotube (MWNT)/electronically conductive polypyrrole (PPy) polymer composite in the various electrolyte solutions have been investigated. The ion-exchange behavior, rate and capacity of the electrochemically deposited polypyrrole with and without carbon nanotube (CNT) were compared and characterized using cyclic voltammetry (CV), chronoamperometry (CA), electrochemical quartz crystal microbalance (EQCM), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). It has been found that the presence of carbon nanotube backbone resulted in improvement in ion-exchange rate, stability of polypyrrole, and higher anion loading capacity per PPy due to higher surface area, electronic conductivity, porous structuremore » of thin film, and thinner film thickness providing shorter diffusion path. Chronoamperometric studies show that electrically switched anion exchange could be completed more than 10 times faster than pure PPy thin film. The anion selectivity of CNT/PPy film is demonstrated using X-ray photoelectron spectroscopy (XPS).« less
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Photo-Cross-Linked Anion Exchange Membranes with Improved Water Management and Conductivity
DOE Office of Scientific and Technical Information (OSTI.GOV)
Ertem, S. Piril; Tsai, Tsung-Han; Donahue, Melissa M.
Robust, cross-linked anion exchange membranes (AEMs) were prepared from solvent-processable polyisoprene- ran -poly(vinylbenzyltrimethylammonium chloride) (PI- ran -P- [VBTMA][Cl]) ionomers via photoinitiated thiol - ene chem- istry. Two series of membranes were prepared choosing two dithiol cross-linkers, 1,10-decanedithiol and 2,2 ' - (ethylenedioxy)diethanethiol, selected for their di ff erent hydro- phobicities. A strong correlation was found between the choice of dithiol cross-linker, water uptake, morphology, and the ion conductivity of the membranes. Results were compared with previous fi ndings of thermally cross-linked AEMs from analogous random copolymers. Comparably high chloride ion conductivities were obtained at low to moderate ion exchange capacitiesmore » (IECs) with signi fi cantly low water uptake values. It was shown that by choosing a hydrophilic cross-linker ion cluster formation may be suppressed and ion conduction improved. This study highlights that it is possible to promote ion conductivities for low IEC membranes (<1 mmol/g) by forming well- connected, ion conducting network morphology. This observation paves the way for mechanically robust ion conducting membranes with enhanced conductivities and better water management.« less
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High cation transport polymer electrolyte
Gerald, II, Rex E.; Rathke, Jerome W [Homer Glen, IL; Klingler, Robert J [Westmont, IL
2007-06-05
A solid state ion conducting electrolyte and a battery incorporating same. The electrolyte includes a polymer matrix with an alkali metal salt dissolved therein, the salt having an anion with a long or branched chain having not less than 5 carbon or silicon atoms therein. The polymer is preferably a polyether and the salt anion is preferably an alkyl or silyl moiety of from 5 to about 150 carbon/silicon atoms.
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NASA Astrophysics Data System (ADS)
Montazami, Reza; Liu, Sheng; Liu, Yang; Wang, Dong; Zhang, Qiming; Heflin, James R.
2011-05-01
Ionic electroactive polymer (IEAP) actuators containing porous conductive network composites (CNCs) and ionic liquids can result in high strain and fast response times. Incorporation of spherical gold nanoparticles in the CNC enhances conductivity and porosity, while maintaining relatively small thickness. This leads to improved mechanical strain and bending curvature of the actuators. We have employed the layer-by-layer self-assembly technique to fabricate a CNC with enhanced curvature (0.43 mm-1) and large net intrinsic strain (6.1%). The results demonstrate that curvature and net strain of IEAP actuators due to motion of the anions increase linearly with the thickness of the CNC as a result of the increased volume in which the anions can be stored. In addition, after subtracting the curvature of a bare Nafion actuator without a CNC, it is found that the net intrinsic strain of the CNC layer is independent of thickness for the range of 20-80 nm, indicating that the entire CNC volume contributes equivalently to the actuator motion. Furthermore, the response time of the actuator due to anion motion is independent of CNC thickness, suggesting that traversal through the Nafion membrane is the limiting factor in the anion motion.
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Zhang, Meng; Liu, Yuxue; Yang, Jian; Zhu, Hancheng; Yan, Duanting; Zhang, Xinyang; Liu, Chunguang; Xu, Changshan; Zhang, Hong
2017-05-24
Encaged-OH - -free Ca 12(1-x) Sr 12x Al 14 O 33 :0.1%Gd 3+ conductive phosphors were prepared through a melt-solidification process in combination with a subsequent heat treatment. Absorption spectra showed that the maximum encaged-electron concentration was increased to 1.08 × 10 21 cm -3 through optimizing the doping amount of Sr 2+ (x = 0.005). Meanwhile, FTIR and Raman spectra indicated that pure Ca 11.94 Sr 0.06 Al 14 O 33 :0.1%Gd 3+ conductive phosphor without encaged OH - and C 2 2- anions was acquired. For the conductive powders heat-treated in air for different times, the encaged-electron concentrations were tuned from 1.02 × 10 21 to 8.3 × 10 20 cm -3 . ESR, photoluminescence, and luminescence kinetics analyses indicated that the emission at 312 nm mainly originated from Gd 3+ ions surrounded by encaged O 2- anions, while Gd 3+ ions surrounded by encaged electrons had a negative contribution to the UV emission due to the existence of an energy transfer process. Under low-voltage electron-beam excitation (3 kV), enhanced cathodoluminescence (CL) of the conductive phosphors could be achieved by tuning the encaged-electron concentrations. In particular, for the encaged-OH - -free conductive phosphor, the emission intensity of the CL was about one order of magnitude higher than that of the conductive phosphor containing encaged OH - anions. Our results suggested that the encaged-OH - -free conductive phosphors have potential application in low-voltage FEDs.
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Ion-Gated Gas Separation through Porous Graphene
DOE Office of Scientific and Technical Information (OSTI.GOV)
Tian, Ziqi; Mahurin, Shannon M.; Dai, Sheng
Porous graphene holds great promise as an atom-thin, high-permeance membrane for gas separation, but to precisely control the pore size at three to five angstroms proves challenging. Here we propose an ion-gated graphene membrane comprising a monolayer of ionic liquid coated porous graphene to dynamically modulate the pore size to achieve selective gas separation. This approach enables the otherwise non-selective large pores on the order of 1 nm in size to be selective for gases whose diameters range from three to four angstroms. We show from molecular dynamics simulations that CO 2, N 2 and CH 4 all can permeatemore » through a 1-nm pore in graphene without any selectivity. But when a monolayer of [emim][BF 4] is deposited on the porous graphene, CO 2 has much higher permeance than the other two gases. We find that the anion dynamically modulates the pore size by hovering above the pore and provides affinity for CO 2 while the larger cation (which cannot go through the pore) holds the anion in place via electrostatic attraction. This composite membrane is especially promising for CO 2/CH 4 separation, with a CO 2/CH 4 selectivity of about 42 and CO 2 permeance ~105 GPU (gas permeation unit). We further demonstrate that selectivity and permeance can be tuned by the anion size. The present work points toward a promising direction of using the atom-thin ionic-liquid/porous-graphene hybrid membrane for high-permeance, selective gas separation that allows a greater flexibility in substrate pore size control.« less
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Protein unfolding in detergents: effect of micelle structure, ionic strength, pH, and temperature.
Otzen, Daniel E
2002-01-01
The 101-residue monomeric protein S6 unfolds in the anionic detergent sodium dodecyl sulfate (SDS) above the critical micelle concentration, with unfolding rates varying according to two different modes. Our group has proposed that spherical micelles lead to saturation kinetics in unfolding (mode 1), while cylindrical micelles prevalent at higher SDS concentrations induce a power-law dependent increase in the unfolding rate (mode 2). Here I investigate in more detail how micellar properties affect protein unfolding. High NaCl concentrations, which induce cylindrical micelles, favor mode 2. This is consistent with our model, though other effects such as electrostatic screening cannot be discounted. Furthermore, unfolding does not occur in mode 2 in the cationic detergent LTAB, which is unable to form cylindrical micelles. A strong retardation of unfolding occurs at higher LTAB concentrations, possibly due to the formation of dead-end protein-detergent complexes. A similar, albeit much weaker, effect is seen in SDS in the absence of salt. Chymotrypsin inhibitor 2 exhibits the same modes of unfolding in SDS as S6, indicating that this type of protein unfolding is not specific for S6. The unfolding process in mode 1 has an activation barrier similar in magnitude to that in water, while the activation barrier in mode 2 is strongly concentration-dependent. The strong pH-dependence of unfolding in SDS and LTAB suggests that the rate of unfolding in anionic detergent is modulated by repulsion between detergent headgroups and anionic side chains, while cationic side chains modulate unfolding rates in cationic detergents. PMID:12324439
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Spectroelectrochemical Sensors: New Polymer Films for Improved Sensitivity
DOE Office of Scientific and Technical Information (OSTI.GOV)
Morris, Laura K.; Seliskar, Carl J.; Bryan, Samuel A.
2014-10-31
The selectivity of an optical sensor can be improved by combining optical detection with electrochemical oxidation or reduction of the target analyte to change its spectral properties. The changing signal can distinguish the analyte from interferences with similar spectral properties that would otherwise interfere. The analyte is detected by measuring the intensity of the electrochemically modulated signal. In one form this spectroelectrochemical sensor consists of an optically transparent electrode (OTE) coated with a film that preconcentrates the target analyte. The OTE functions as an optical waveguide for attenuated total reflectance (ATR) spectroscopy, which detects the analyte by absorption. Sensitivity reliesmore » in part on a large change in molar absorptivity between the two oxidation states used for electrochemical modulation of the optical signal. A critical part of the sensor is the ion selective film. It should preconcentrate the analyte and exclude some interferences. At the same time the film must not interfere with the electrochemistry or the optical detection. Therefore, since the debut of the sensor’s concept one major focus of our group has been developing appropriate films for different analytes. Here we report the development of a series of quaternized poly(vinylpyridine)-co-styrene (QPVP-co-S) anion exchange films for use in spectroelectrochemical sensors to enable sensitive detection of target anionic analytes in complex samples. The films were either 10% or 20% styrene and were prepared with varying degrees of quaternized pyridine groups, up to 70%. Films were characterized with respect to thickness with spectroscopic ellipsometry, degree of quaternization with FTIR, and electrochemically and spectroelectrochemically using the anions ferrocyanide and pertechnetate.« less
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Ion-Gated Gas Separation through Porous Graphene
Tian, Ziqi; Mahurin, Shannon M.; Dai, Sheng; ...
2017-02-10
Porous graphene holds great promise as an atom-thin, high-permeance membrane for gas separation, but to precisely control the pore size at three to five angstroms proves challenging. Here we propose an ion-gated graphene membrane comprising a monolayer of ionic liquid coated porous graphene to dynamically modulate the pore size to achieve selective gas separation. This approach enables the otherwise non-selective large pores on the order of 1 nm in size to be selective for gases whose diameters range from three to four angstroms. We show from molecular dynamics simulations that CO 2, N 2 and CH 4 all can permeatemore » through a 1-nm pore in graphene without any selectivity. But when a monolayer of [emim][BF 4] is deposited on the porous graphene, CO 2 has much higher permeance than the other two gases. We find that the anion dynamically modulates the pore size by hovering above the pore and provides affinity for CO 2 while the larger cation (which cannot go through the pore) holds the anion in place via electrostatic attraction. This composite membrane is especially promising for CO 2/CH 4 separation, with a CO 2/CH 4 selectivity of about 42 and CO 2 permeance ~105 GPU (gas permeation unit). We further demonstrate that selectivity and permeance can be tuned by the anion size. The present work points toward a promising direction of using the atom-thin ionic-liquid/porous-graphene hybrid membrane for high-permeance, selective gas separation that allows a greater flexibility in substrate pore size control.« less
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NASA Technical Reports Server (NTRS)
Levine, L. H.; Judkins, J. E.; Garland, J. L.; Sager, J. C. (Principal Investigator)
2000-01-01
A direct approach utilizing ion pairing reversed-phase chromatography coupled with suppressed conductivity detection was developed to monitor biodegradation of anionic surfactants during wastewater recycling through hydroponic plant growth systems and fixed-film bioreactors. Samples of hydroponic nutrient solution and bioreactor effluent with high concentrations (up to 120 mS electrical conductance) of inorganic ions can be analyzed without pretreatment or interference. The presence of non-ionic surfactants did not significantly affect the analysis. Dynamic linear ranges for tested surfactants [Igepon TC-42, ammonium lauryl sulfate, sodium laureth sulfate and sodium alkyl (C10-C16) ether sulfate] were 2 to approximately 500, 1 to approximately 500, 2.5 to approximately 550 and 3.0 to approximately 630 microg/ml, respectively.
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Structure of cyano-anion ionic liquids: X-ray scattering and simulations
DOE Office of Scientific and Technical Information (OSTI.GOV)
Dhungana, Kamal B.; Faria, Luiz F. O.; Wu, Boning
2016-07-14
Ionic liquids with cyano anions have long been used because of their unique combination of low-melting temperatures, reduced viscosities, and increased conductivities. Recently we have shown that cyano anions in ionic liquids are particularly interesting for their potential use as electron donors to excited state photo-acceptors [B. Wu et al., J. Phys. Chem. B 119, 14790–14799 (2015)]. Here we report on bulk structural and quantum mechanical results for a series of ionic liquids based on the 1-ethyl-3-methylimidazolium cation, paired with the following five cyano anions: SeCN-, SCN-, N(CN)-2N(CN)2-, C(CN)-3C(CN)3-, and B(CN)-4B(CN)4-. By combining molecular dynamics simulations, high-energy X-ray scattering measurements,more » and periodic boundary condition DFT calculations, we are able to obtain a comprehensive description of the liquid landscape as well as the nature of the HOMO-LUMO states for these ionic liquids in the condensed phase. Features in the structure functions for these ionic liquids are somewhat different than the commonly observed adjacency, charge-charge, and polarity peaks, especially for the bulkiest B(CN)-4B(CN)4- anion. While the other four cyano-anion ionic liquids present an anionic HOMO, the one for Im+2,1Im2,1+/B(CN)-4B(CN)4- is cationic.« less
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Song, Yingcai; Zhang, Bing; Guo, Fei; Yang, Maojun; Li, Yang; Liu, Zhi-Qiang
2017-01-01
The mechanosensitive channel of small conductance (MscS) is a bacterial membrane pore that senses membrane tension and protects cells from lysis by releasing osmolytes. MscS is a homoheptameric channel with a cytoplasmic domain with seven portals and a β-barrel opening to the cytoplasm. TtMscS, an MscS channel from Thermoanaerobacter tengcongensis, is an anion-selective channel. A previous study from our laboratory has defined the crucial role of β-barrel in the anion selectivity of TtMscS (Zhang et al., 2012). However, the mechanistic details by which the β-barrel determines anion selectivity remain unclear. Here, using mutagenesis and patch-clamp recordings, we investigated the function and structural correlations between β-barrels and the anion selectivity of TtMscS at the atomic level. Our results indicated that mutation of V274, a residue at the center of the inner wall of the β-barrel in TtMscS, caused the anion selectivity of TtMscS reverse to cation selectivity. Moreover, the electrostatic potential (T272) and physical size (L276) of residues in the inner wall of β-barrel also determine the anion selectivity of TtMscS. In summary, the present study confirmed that the β-barrel region of TtMscS acts as a “selective filter” that renders TtMscS anion selectivity. PMID:29118717
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Céspedes, V; Pallarés, S; Arribas, P; Millán, A; Velasco, J
2013-10-01
Water salinity and ionic composition are among the main environmental variables that constrain the fundamental niches of aquatic species, and accordingly, physiological tolerance to these factors constitutes a crucial part of the evolution, ecology, and biogeography of these organisms. The present study experimentally estimated the fundamental saline and anionic niches of adults of two pairs of congeneric saline beetle species that differ in habitat preference (lotic and lentic) in order to test the habitat constraint hypothesis. Osmotic and anionic realised niches were also estimated based on the field occurrences of adult beetle species using Outlying Mean Index analysis and their relationship with experimental tolerances. In the laboratory, all of the studied species showed a threshold response to increased salinity, displaying high survival times when exposed to low and intermediate conductivity levels. These results suggest that these species are not strictly halophilic, but that they are able to regulate both hyperosmotically and hypoosmotically. Anionic water composition had a significant effect on salinity tolerance at conductivity levels near their upper tolerance limits, with decreased species survival at elevated sulphate concentrations. Species occupying lentic habitats demonstrated higher salinity tolerance than their lotic congeners in agreement with the habitat constraint hypothesis. As expected, realised salinity niches were narrower than fundamental niches and corresponded to conditions near the upper tolerance limits of the species. These species are uncommon on freshwater-low conductivity habitats despite the fact that these conditions might be physiologically suitable for the adult life stage. Other factors, such as biotic interactions, could prevent their establishment at low salinities. Differences in the realised anionic niches of congeneric species could be partially explained by the varying habitat availability in the study area. Combining the experimental estimation of fundamental niches with realised field data niche estimates is a powerful method for understanding the main factors constraining species' distribution at multiple scales, which is a key issue when predicting species' ability to cope with global change. Copyright © 2013 Elsevier Ltd. All rights reserved.
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Water uptake, ionic conductivity and swelling properties of anion-exchange membrane
NASA Astrophysics Data System (ADS)
Duan, Qiongjuan; Ge, Shanhai; Wang, Chao-Yang
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.
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Atomic Structure of the Cystic Fibrosis Transmembrane Conductance Regulator.
Zhang, Zhe; Chen, Jue
2016-12-01
The cystic fibrosis transmembrane conductance regulator (CFTR) is an anion channel evolved from the ATP-binding cassette (ABC) transporter family. In this study, we determined the structure of zebrafish CFTR in the absence of ATP by electron cryo-microscopy to 3.7 Šresolution. Human and zebrafish CFTR share 55% sequence identity, and 42 of the 46 cystic-fibrosis-causing missense mutational sites are identical. In CFTR, we observe a large anion conduction pathway lined by numerous positively charged residues. A single gate near the extracellular surface closes the channel. The regulatory domain, dephosphorylated, is located in the intracellular opening between the two nucleotide-binding domains (NBDs), preventing NBD dimerization and channel opening. The structure also reveals why many cystic-fibrosis-causing mutations would lead to defects either in folding, ion conduction, or gating and suggests new avenues for therapeutic intervention. Copyright © 2016 Elsevier Inc. All rights reserved.
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NASA Astrophysics Data System (ADS)
Maes, Ashley M.
Anion exchange membranes (AEMs) are of considerable interest to developers and researchers of electrochemical conversion and storage devices such as anion exchange membrane fuel cells (AAEMFCs), alkaline polymer electrolyte electrolysers, redox flow batteries and bioelectrochemical devices. AEMs are generally in competition with more established proton exchange membranes (PEMs), but offer the potential for reduction of materials costs and greater fuel flexibility across these applications. This work includes an introduction to AEMs in the context of fuel cell technologies and some key techniques for AEM characterization. There are many synthetic strategies to incorporate cationic functional groups, which promote anion transport, into a polymer matrix. Two membrane chemistries are investigated in the following chapters. The first is based on a simple synthesis procedure that produced a membrane consisting of random, crosslinked polypropylene- ran-polyethyleneimine with quaternary ammonium functional groups. This membrane had moderate chloride ionic conductivity of 0.03 S cm -1 at 95 °C and high water uptake with minimal dimensional swelling. However, the lack of control of crosslink location and density during synthesis produced a material with a very random nature, making it a poor candidate for more fundamental transport studies. The second membrane chemistry is a block copolymer with a hydrophobic and hydrophilic block. The hydrophobic block was selected to provide favorable mechanical and barrier characteristics while a hydrophilic block was selected to provide water uptake and anion conducting functionalities. Poly(vinyl benzyl trimethyl ammonium bromide)-b-poly(methylbutylene) ([PVBTMA][Br]- b-PMB) was synthesized by partners at the University of Massachusetts-Amherst with varied degrees of functionalization (DF) along the hydrophilic block, resulting in ion exchange capacities ranging from 0.77 to 2.20 mmol g -1. Water uptake, in-plane ionic conductivity and membrane morphology were measured across a series of membranes with the original bromide (Br -) counter-ion. These bulk materials characterization experiments demonstrated that this polymer structure produces well-ordered lamellar morphology with moderate water uptake and competitive ionic conductivity (ca. 40 mS cm-1 at 90 °C and 95% relative humidity). These characteristics make it an appropriate candidate for the following more fundamental investigations of ionic conductivity mechanisms. Broadband electrical spectroscopy (BES) was conducted on one [PVBTMA][Br]- b-PMB sample in the Br- form and analyzed in conjunction with thermal stability and relaxation experiments in Chapter 4. We were able to propose two separate ionic conductivity mechanisms and relate each to physical attributes of the polymer structure. A significant thermal transition was observed at Tdelta , which resulted in a dramatic drop in conductivity. In a continued effort to characterize the ionic conductivity of these block-copolymer membranes, another BES study was conducted on three samples with varying DFs. Samples were converted to hydroxide (OH- ) form so we could contrast the Br- conductivity mechanisms to those in a more relevant counter-ion form. After analysis of the electric response of the material, combined with the thermal analysis by TGA, MDSC and DMA, conductivity mechanisms were described. As in the Br- study, conductivity involves two distinct conduction pathways, sigmaEP and sigmaIP,1. Importantly, we again observed a drop in conductivity at Tdelta in each of these samples, with Tdelta decreasing as the density of functional groups along the hydrophilic block increased. It is undesirable for this transition to occur during operation in a fuel cell or other electrochemical device, so future work to investigate strategies for inhibition are recommended.
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Verification of the sputter-generated 32SFn- (n = 1-6) anions by accelerator mass spectrometry
NASA Astrophysics Data System (ADS)
Mane, R. G.; Surendran, P.; Kumar, Sanjay; Nair, J. P.; Yadav, M. L.; Hemalatha, M.; Thomas, R. G.; Mahata, K.; Kailas, S.; Gupta, A. K.
2016-01-01
Recently, we have performed systematic Secondary Ion Mass Spectrometry (SIMS) measurements at our ion source test set up and have demonstrated that gas phase 32SFn- (n = 1-6) anions for all size 'n' can be readily generated from a variety of surfaces undergoing Cs+ ion sputtering in the presence of high purity SF6 gas by employing the gas spray-cesium sputter technique. In our SIMS measurements, the isotopic yield ratio 34SFn-/32SFn- (n = 1-6) was found to be close to its natural abundance but not for all size 'n'. In order to gain further insight into the constituents of these molecular anions, ultra sensitive Accelerator Mass Spectrometry (AMS) measurements were conducted with the most abundant 32SFn- (n = 1-6) anions, at BARC-TIFR 14 UD Pelletron accelerator. The results from these measurements are discussed in this paper.
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Borodin, Oleg
2009-09-10
A number of correlations between heat of vaporization (H(vap)), cation-anion binding energy (E(+/-)), molar volume (V(m)), self-diffusion coefficient (D), and ionic conductivity for 29 ionic liquids have been investigated using molecular dynamics (MD) simulations that employed accurate and validated many-body polarizable force fields. A significant correlation between D and H(vap) has been found, while the best correlation was found for -log(DV(m)) vs H(vap) + 0.28E(+/-). A combination of enthalpy of vaporization and a fraction of the cation-anion binding energy was suggested as a measure of the effective cohesive energy for ionic liquids. A deviation of some ILs from the reported master curve is explained based upon ion packing and proposed diffusion pathways. No general correlations were found between the ion diffusion coefficient and molecular volume or the diffusion coefficient and cation/anion binding energy.
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Interactions between water and 1-butyl-1-methylpyrrolidinium ionic liquids
DOE Office of Scientific and Technical Information (OSTI.GOV)
Fadeeva, Tatiana A.; DeVine, Jessalyn A.; Castner, Edward W., E-mail: ed.castner@rutgers.edu
2015-08-14
We report experimental results on the diffusivity of water in two ionic liquids obtained using the pulsed-gradient spin-echo NMR method. Both ionic liquids have the same cation, 1-butyl-1-methylpyrrolidinium, but different trifluoromethyl-containing anions. One has a strongly hydrophobic anion, bis(trifluoromethylsulfonyl)amide, while the second has a hydrophilic anion, trifluoromethylsulfonate. Transport of water in these ionic liquids is much faster than would be predicted from hydrodynamic laws, indicating that the neutral water molecules experience a very different friction than the anions and cations at the molecular level. Temperature-dependent viscosities, conductivities, and densities are reported as a function of water concentration to further analyzemore » the properties of the ionic liquid-water mixtures. These results on the properties of water in ionic liquids should be of interest to researchers in diverse areas ranging from separations, solubilizing biomass and energy technologies.« less
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Perpendicularly Aligned, Anion Conducting Nanochannels in Block Copolymer Electrolyte Films
DOE Office of Scientific and Technical Information (OSTI.GOV)
Arges, Christopher G.; Kambe, Yu; Suh, Hyo Seon
Connecting structure and morphology to bulk transport properties, such as ionic conductivity, in nanostructured polymer electrolyte materials is a difficult proposition because of the challenge to precisely and accurately control order and the orientation of the ionic domains in such polymeric films. In this work, poly(styrene-block-2-vinylpyridine) (PSbP2VP) block copolymers were assembled perpendicularly to a substrate surface over large areas through chemical surface modification at the substrate and utilizing a versatile solvent vapor annealing (SVA) technique. After block copolymer assembly, a novel chemical vapor infiltration reaction (CVIR) technique selectively converted the 2-vinylpyridine block to 2-vinyl n-methylpyridinium (NMP+ X-) groups, which aremore » anion charge carriers. The prepared block copolymer electrolytes maintained their orientation and ordered nanostructure upon the selective introduction of ion moieties into the P2VP block and post ion-exchange to other counterion forms (X- = chloride, hydroxide, etc.). The prepared block copolymer electrolyte films demonstrated high chloride ion conductivities, 45 mS cm(-1) at 20 degrees C in deionized water, the highest chloride ion conductivity for anion conducting polymer electrolyte films. Additionally, straight-line lamellae of block copolymer electrolytes were realized using chemoepitaxy and density multiplication. The devised scheme allowed for precise and accurate control of orientation of ionic domains in nanostructured polymer electrolyte films and enables a platform for future studies that examines the relationship between polymer electrolyte structure and ion transport.« less
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Cass, Albert; Finkelstein, Alan; Krespi, Vivian
1970-01-01
Characteristics of nystatin and amphotericin B action on thin (<100 A) lipid membranes are: (a) micromolar amounts increase membrane conductance from 10-8 to over 10-2 Ω-1 cm-2; (b) such membranes are (non-ideally) anion selective and discriminate among anions on the basis of size; (c) membrane sterol is required for action; (d) antibiotic presence on both sides of membrane strongly favors action; (e) conductance is proportional to a large power of antibiotic concentration; (f) conductance decreases ∼104 times for a 10°C temperature rise; (g) kinetics of antibiotic action are also very temperature sensitive; (h) ion selectivity is pH independent between 3 and 10, but (i) activity is reversibly lost at high pH; (j) methyl ester derivatives are fully active; N-acetyl and N-succinyl derivatives are inactive; (k) current-voltage characteristic is nonlinear when membrane separates nonidentical salt solutions. These characteristics are contrasted with those of valinomycin. Observations (a)–(g) suggest that aggregates of polyene and sterol from opposite sides of the membrane interact to create aqueous pores; these pores are not static, but break up (melt) and reform continuously. Mechanism of anion selectivity is obscure. Observations (h)–(j) suggest—NH3 + is important for activity; it is probably not responsible for selectivity, particularly since four polyene antibiotics, each containing two—NH3 + groups, induce ideal cation selectivity. Possibly the many hydroxyl groups in nystatin and amphotericin B are responsible for anion selectivity. The effects of polyene antibiotics on thin lipid membranes are consistent with their action on biological membranes. PMID:5514157
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Structural and electronic features of binary Li₂S-P₂S₅ glasses.
Ohara, Koji; Mitsui, Akio; Mori, Masahiro; Onodera, Yohei; Shiotani, Shinya; Koyama, Yukinori; Orikasa, Yuki; Murakami, Miwa; Shimoda, Keiji; Mori, Kazuhiro; Fukunaga, Toshiharu; Arai, Hajime; Uchimoto, Yoshiharu; Ogumi, Zempachi
2016-02-19
The atomic and electronic structures of binary Li2S-P2S5 glasses used as solid electrolytes are modeled by a combination of density functional theory (DFT) and reverse Monte Carlo (RMC) simulation using synchrotron X-ray diffraction, neutron diffraction, and Raman spectroscopy data. The ratio of PSx polyhedral anions based on the Raman spectroscopic results is reflected in the glassy structures of the 67Li2S-33P2S5, 70Li2S-30P2S5, and 75Li2S-25P2S5 glasses, and the plausible structures represent the lithium ion distributions around them. It is found that the edge sharing between PSx and LiSy polyhedra increases at a high Li2S content, and the free volume around PSx polyhedra decreases. It is conjectured that Li(+) ions around the face of PSx polyhedra are clearly affected by the polarization of anions. The electronic structure of the DFT/RMC model suggests that the electron transfer between the P ion and the bridging sulfur (BS) ion weakens the positive charge of the P ion in the P2S7 anions. The P2S7 anions of the weak electrostatic repulsion would causes it to more strongly attract Li(+) ions than the PS4 and P2S6 anions, and suppress the lithium ionic conduction. Thus, the control of the edge sharing between PSx and LiSy polyhedra without the electron transfer between the P ion and the BS ion is expected to facilitate lithium ionic conduction in the above solid electrolytes.
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Wang, Xia; Wang, Yanlong; Silver, Mark A.; ...
2018-01-01
An ultrahigh proton conductivity of 2.91 × 10 −2 S cm −1 and an ultralow activation energy of 0.10 eV were observed in an anionic lanthanide-organic framework. Both values approach the records for proton-conducting MOF materials.
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Selection Rule of Preferred Doping Site for n-Type Oxides
DOE Office of Scientific and Technical Information (OSTI.GOV)
Li, C.; Li, J.; Li, S. S.
2012-06-25
Using first-principles calculations and analysis, we show that to create shallow n-type dopants in oxides, anion site doping is preferred for more covalent oxides such as SnO{sub 2} and cation site doping is preferred for more ionic oxides such as ZnO. This is because for more ionic oxides, the conduction band minimum (CBM) state actually contains a considerable amount of O 3s orbitals, thus anion site doping can cause large perturbation on the CBM and consequently produces deeper donor levels. We also show that whether it is cation site doping or anion site doping, the oxygen-poor condition should always bemore » used.« less
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Separation of thorium and uranium in nitric acid solution using silica based anion exchange resin.
Chen, Yanliang; Wei, Yuezhou; He, Linfeng; Tang, Fangdong
2016-09-30
To separate thorium and uranium in nitric acid solution using anion exchange process, a strong base silica-based anion exchange resin (SiPyR-N4) was synthesized. Batch experiments were conducted and the separation factor of thorium and uranium in 9M nitric acid was about 10. Ion exchange chromatography was applied to separate thorium and uranium in different ratios. Uranium could be eluted by 9M nitric acid and thorium was eluted by 0.1M nitric acid. It was proved that thorium and uranium can be separated and recovered successfully by this method. Copyright © 2016 Elsevier B.V. All rights reserved.
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Barbiturates Block Sodium and Potassium Conductance Increases in Voltage-Clamped Lobster Axons
Blaustein, M. P.
1968-01-01
Sodium pentobarbital and sodium thiopental decrease both the peak initial (Na) and late steady-state (K) currents and reduce the maximum sodium and potassium conductance increases in voltage-clamped lobster giant axons. These barbiturates also slow the rate at which the sodium conductance turns on, and shift the normalized sodium conductance vs. voltage curves in the direction of depolarization along the voltage axis. Since pentobarbital (pKa = 8.0) blocks the action potential more effectively at pH 8.5 than at pH 6.7, the anionic form of the drug appears to be active. The data suggest that these drugs affect the axon membrane directly, rather than secondarily through effects on intermediary metabolism. It is suggested that penetration of the lipid layer of the membrane by the nonpolar portion of the barbiturate molecules may cause the decrease in membrane conductances, while electrostatic interactions involving the anionic group on the barbiturate, divalent cations, and "fixed charges" in the membrane could account for the slowing of the rate of sodium conductance turn-on and the shift of the normalized conductance curves along the voltage axis. PMID:5648829
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Petrowsky, Matt; Fleshman, Allison; Bopege, Dharshani N; Frech, Roger
2012-08-09
Temperature-dependent ionic conductivities and cation/anion self-diffusion coefficients are measured for four electrolyte families: TbaTf-linear primary alcohols, LiTf-linear primary alcohols, TbaTf-n-alkyl acetates, and LiTf-n-alkyl acetates. The Nernst-Einstein equation does not adequately describe the data. Instead, the compensated Arrhenius formalism is applied to both conductivity and diffusion data. General trends based on temperature and alkyl chain length are observed when conductivity is plotted against cation or anion diffusion coefficient, but there is no clear pattern to the data. However, plotting conductivity exponential prefactors against those for diffusion results in four distinct curves, one each for the alcohol and acetate families described above. Furthermore, the TbaTf-alcohol and TbaTf-acetate data are "in line" with each other. The conductivity prefactors for the LiTf-alcohol data are smaller than those for the TbaTf data. The LiTf-acetate data have the lowest conductivity prefactors. This trend in prefactors mirrors the observed trend in degree of ionic association for these electrolytes.
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Controlling ion aggregation and conduction in PEO-based ionomers.
NASA Astrophysics Data System (ADS)
Caldwell, David, II; Maranas, Janna
2015-03-01
PEO-based ionomers are ideal for reducing concentration polarization found in typical solid polymer electrolytes. This is achieved by binding the anion to the polymer backbone, significantly reducing the anions mobility. Ion aggregation is prevalent in these systems, but their influence on SPE performance is difficult to study experimentally. We present results of molecular dynamics simulations that explore the relationship between ion content and temperature on ion aggregation, polymer motion, and ion conduction. An unforeseen result of ionomers is the creation of string like aggregates that form conduction pathways in the amorphous region. These conduction pathways allow for a partial decoupling of ion conduction with polymer dynamics. The improvement in conductivity through the use of ion aggregates can be quantified by calculating the inverse of the Haven Ratio, dubbed f-value. Typical SPEs have an f-value less than 0.2, while the ionomers of study exhibit f-values near unity or higher. Understanding what properties influence the development and use of these conduction pathways will provide insight for further development of solid polymer electrolytes.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Song, Peng-Yuan; Xu, Ming; Zhang, Wei-De, E-mail: zhangwd@scut.edu.cn
Highlights: • Heterostructured Bi{sub 2}O{sub 2}CO{sub 3}/BiOI microspheres were prepared via anion exchange. • Sodium citrate-assisted anion exchange for construction of composite photocatalysts. • Bi{sub 2}O{sub 2}CO{sub 3}/BiOI composites show high visible light photocatalytic activity. - Abstract: Bi{sub 2}O{sub 2}CO{sub 3}/BiOI heterojuncted photocatalysts were constructed through a facile partial anion exchange strategy starting from BiOI microspheres and urea with the assistance of sodium citrate. The content of Bi{sub 2}O{sub 2}CO{sub 3} in the catalysts was regulated by modulating the amount of urea as a precursor, which was decomposed to generate CO{sub 3}{sup 2−} in the hydrothermal process. Citrate anion playsmore » a key role in controlling the morphology and composition of the products. The Bi{sub 2}O{sub 2}CO{sub 3}/BiOI catalysts display much higher photocatalytic activity than pure BiOI and Bi{sub 2}O{sub 2}CO{sub 3} towards the degradation of rhodamine B (RhB) and bisphenol A (BPA). The enhancement of photocatalytic activity of the heterojuncted catalysts is attributed to the formation of p–n junction between p-BiOI and n-Bi{sub 2}O{sub 2}CO{sub 3}, which is favorable for retarding the recombination of photoinduced electron-hole pairs. Moreover, the holes are demonstrated to be the main active species for the degradation of RhB and BPA.« less
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Dissociative Electron Attachment in the condensed phase: sample morphology and bio-molecules
NASA Astrophysics Data System (ADS)
Bass, A. D.
2001-10-01
Recent electron impact experiments on condensed plasmid DNA have shown low energy electrons to be remarkably effective in causing damage and reveal that electron-scattering phenomena, such as transient anion formation and their decay via dissociative electron attachment, play a central role in this process. Such experiments may prompt a revision of our understanding of the mutagenic effects of radiation and have significant implications for both radiotherapy and radio-protection. These results can be better understood by investigating electron scattering with the various functional constituents of DNA in condensed environments. Recent work, to be presented here, has focused on electron attachment processes in condensed DNA bases and sugar-like analogues of the DNA backbone, as evidenced by the desorption of fragment anions. Despite this progress, a complete understanding of these processes requires parallel study of simpler `model' systems, which allow the characteristic condensed-phase phenomena modulating electron-scattering to be identified. Factors affecting anion formation and DEA can been classed as either intrinsic (affecting the properties of the resonance) or extrinsic (modifying the energy of electrons before attachment and/or the reactions of fragments, post-dissociation). In this talk we will present new results in which the extrinsic factors of porosity and phase of a sample are probed via the desorption of anionic fragments from either the pure film or from probe molecules condensed upon its surface. We show that anion desorption and hence our ability to observe DEA process, is highly sensitive to sample morphology and phase, a property which can be exploited to study the morphology of the film itself.
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Zhang, Le; Zhang, Jifeng
2012-09-04
The perturbation of salt ions on the solubility of a monoclonal antibody was systematically studied at various pHs in Na(2)SO(4), NaNO(3), NaCl, NaF, MgSO(4), Mg(NO(3))(2) and MgCl(2) solutions below 350 mM. At pH 7.1, close to the pI, all of the salts increased the solubility of the antibody, following the order of SO(4)(2-) > NO(3)(-) > Cl(-) > F(-) for anions and Mg(2+) > Na(+) for cations. At pH 5.3 where the antibody had a net positive charge, the anions initially followed the order of SO(4)(2-) > NO(3)(-) > Cl(-) > F(-) for effectiveness in reducing the solubility and then switched to increasing the solubility retaining the same order. Furthermore, the antibody was more soluble in the Mg(2+) salt solutions than in the corresponding Na(+) salt solutions with the same anion. At pH 9.0 where the antibody had a net negative charge, an initial decrease in the protein solubility was observed in the solutions of the Mg(2+) salts and NaF, but not in the rest of the Na(+) salt solutions. Then, the solubility of the antibody was increased by the anions in the order of SO(4)(2-) > NO(3)(-) > Cl(-) > F(-). The above complex behavior is explained based on the ability of both cation and anion from a salt to modulate protein-protein interactions through their specific binding to the protein surface.
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Single-layer nanosheets with exceptionally high and anisotropic hydroxyl ion conductivity
Sun, Pengzhan; Ma, Renzhi; Bai, Xueyin; Wang, Kunlin; Zhu, Hongwei; Sasaki, Takayoshi
2017-01-01
When the dimensionality of layered materials is reduced to the physical limit, an ultimate two-dimensional (2D) anisotropy and/or confinement effect may bring about extraordinary physical and chemical properties. Layered double hydroxides (LDHs), bearing abundant hydroxyl groups covalently bonded within 2D host layers, have been proposed as inorganic anion conductors. However, typical hydroxyl ion conductivities for bulk or lamellar LDHs, generally up to 10−3 S cm−1, are considered not high enough for practical applications. We show that single-layer LDH nanosheets exhibited exceptionally high in-plane conductivities approaching 10−1 S cm−1, which were the highest among anion conductors and comparable to proton conductivities in commercial proton exchange membranes (for example, Nafion). The in-plane conductivities were four to five orders of magnitude higher than the cross-plane or cross-membrane values of restacked LDH nanosheets. This 2D superionic transport characteristic might have great promises in a variety of applications including alkaline fuel cells and water electrolysis. PMID:28439551
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ERIC Educational Resources Information Center
Nyasulu, Frazier; Stevanov, Kelly; Barlag, Rebecca
2010-01-01
Using a conductivity sensor, a temperature sensor, and a datalogger, fundamental factors that affect conductivity are explored. These factors are (i) concentration, (ii) temperature, (iii) ion charge, and (iv) size and or mass of anion. In addition, the conductivities of a number of other solutions are measured. This lab has been designed to…
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Bauer, Georg
2015-12-01
Tumor cells generate extracellular superoxide anions and are protected against intercellular apoptosis-inducing HOCl- and NO/peroxynitrite signaling through the expression of membrane-associated catalase. This enzyme decomposes H2O2 and thus prevents HOCl synthesis. It efficiently interferes with NO/peroxynitrite signaling through oxidation of NO and decomposition of peroxynitrite. The regulatory potential of catalase at the crosspoint of ROS and RNS chemical biology, as well as its high local concentration on the outside of the cell membrane of tumor cells, establish tight control of intercellular signaling and thus prevent tumor cell apoptosis. Therefore, inhibition of catalase or its inactivation by singlet oxygen reactivate intercellular apoptosis-inducing signaling. Nitric oxide and peroxynitrite are connected with catalase in multiple and meaningful ways, as (i) NO can be oxidated by compound I of catalase, (ii) NO can reversibly inhibit catalase, (iii) peroxynitrite can be decomposed by catalase and (iv) the interaction between peroxynitrite and H2O2 leads to the generation of singlet oxygen that inactivates catalase. Therefore, modulation of the concentration of free NO through addition of arginine, inhibition of arginase, induction of NOS expression or inhibition of NO dioxygenase triggers an autoamplificatory biochemical cascade that is based on initial formation of singlet oxygen, amplification of superoxide anion/H2O2 and NO generation through singlet oxygen dependent stimulation of the FAS receptor and caspase-8. Finally, singlet oxygen is generated at sufficiently high concentration to inactivate protective catalase and to reactivate intercellular apoptosis-inducing ROS signaling. This regulatory network allows to establish several pathways for synergistic interactions, like the combination of modulators of NO metabolism with enhancers of superoxide anion generation, modulators of NO metabolism that act at different targets and between modulators of NO metabolism and direct catalase inhibitors. The latter aspect is explicitely studied for the interaction between catalase inhibiting acetylsalicylic acid and an NO donor. It is also shown that hybrid molecules like NO-aspirin utilize this synergistic potential. Our data open novel approaches for rational tumor therapy based on specific ROS signaling and its control in tumor cells. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.
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γ-Aminobutyric acid (GABA) signalling in plants.
Ramesh, Sunita A; Tyerman, Stephen D; Gilliham, Matthew; Xu, Bo
2017-05-01
The role of γ-aminobutyric acid (GABA) as a signal in animals has been documented for over 60 years. In contrast, evidence that GABA is a signal in plants has only emerged in the last 15 years, and it was not until last year that a mechanism by which this could occur was identified-a plant 'GABA receptor' that inhibits anion passage through the aluminium-activated malate transporter family of proteins (ALMTs). ALMTs are multigenic, expressed in different organs and present on different membranes. We propose GABA regulation of ALMT activity could function as a signal that modulates plant growth, development, and stress response. In this review, we compare and contrast the plant 'GABA receptor' with mammalian GABA A receptors in terms of their molecular identity, predicted topology, mode of action, and signalling roles. We also explore the implications of the discovery that GABA modulates anion flux in plants, its role in signal transduction for the regulation of plant physiology, and predict the possibility that there are other GABA interaction sites in the N termini of ALMT proteins through in silico evolutionary coupling analysis; we also explore the potential interactions between GABA and other signalling molecules.
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Cheung, Min; Akabas, Myles H.
1997-01-01
The cystic fibrosis transmembrane conductance regulator forms an anion-selective channel; the site and mechanism of charge selectivity is unknown. We previously reported that cysteines substituted, one at a time, for Ile331, Leu333, Arg334, Lys335, Phe337, Ser341, Ile344, Arg347, Thr351, Arg352, and Gln353, in and flanking the sixth membrane-spanning segment (M6), reacted with charged, sulfhydryl-specific, methanethiosulfonate (MTS) reagents. We inferred that these residues are on the water-accessible surface of the protein and may line the ion channel. We have now measured the voltage-dependence of the reaction rates of the MTS reagents with the accessible, engineered cysteines. By comparing the reaction rates of negatively and positively charged MTS reagents with these cysteines, we measured the extent of anion selectivity from the extracellular end of the channel to eight of the accessible residues. We show that the major site determining anion vs. cation selectivity is near the cytoplasmic end of the channel; it favors anions by ∼25-fold and may involve the residues Arg347 and Arg352. From the voltage dependence of the reaction rates, we calculated the electrical distance to the accessible residues. For the residues from Leu333 to Ser341 the electrical distance is not significantly different than zero; it is significantly different than zero for the residues Thr351 to Gln353. The maximum electrical distance measured was 0.6 suggesting that the channel extends more cytoplasmically and may include residues flanking the cytoplasmic end of the M6 segment. Furthermore, the electrical distance calculations indicate that R352C is closer to the extracellular end of the channel than either of the adjacent residues. We speculate that the cytoplasmic end of the M6 segment may loop back into the channel narrowing the lumen and thereby forming both the major resistance to current flow and the anion-selectivity filter. PMID:9089437
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Boulanouar, Omar; Fromm, Michel; Mavon, Christophe; Cloutier, Pierre; Sanche, Léon
2013-01-01
We measure the desorption of anions stimulated by the impact of 0–20 eV electrons on highly uniform thin films of plasmid DNA-diaminopropane. The results are accurately correlated with film thickness and composition by AFM and XPS measurements, respectively. Resonant structures in the H−, O−, and OH− yield functions are attributed to the decay of transient anions into the dissociative electron attachment (DEA) channel. The diamine induces ammonium-phosphate bridges along the DNA backbone, which suppresses the DEA O− channel and in counter-part increases considerably the desorption of OH−. The close environment of the phosphate groups may therefore play an important role in modulating the rate and type of DNA damages induced by low energy electrons. PMID:23927286
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A Measurement and Modeling Study of Hair Partition of Neutral, Cationic, and Anionic Chemicals.
Li, Lingyi; Yang, Senpei; Chen, Tao; Han, Lujia; Lian, Guoping
2018-04-01
Various neutral, cationic, and anionic chemicals contained in hair care products can be absorbed into hair fiber to modulate physicochemical properties such as color, strength, style, and volume. For environmental safety, there is also an interest in understanding hair absorption to wide chemical pollutants. There have been very limited studies on the absorption properties of chemicals into hair. Here, an experimental and modeling study has been carried out for the hair-water partition of a range of neutral, cationic, and anionic chemicals at different pH. The data showed that hair-water partition not only depends on the hydrophobicity of the chemical but also the pH. The partition of cationic chemicals to hair increased with pH, and this is due to their electrostatic interaction with hair increased from repulsion to attraction. For anionic chemicals, their hair-water partition coefficients decreased with increasing pH due to their electrostatic interaction with hair decreased from attraction to repulsion. Increase in pH did not change the partition of neutral chemicals significantly. Based on the new physicochemical insight of the pH effect on hair-water partition, a new quantitative structure property relationship model has been proposed, taking into account of both the hydrophobic interaction and electrostatic interaction of chemical with hair fiber. Copyright © 2018 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.
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Organic anion transporting polypeptide 1B transporters modulate hydroxyurea pharmacokinetics.
Walker, Aisha L; Lancaster, Cynthia S; Finkelstein, David; Ware, Russell E; Sparreboom, Alex
2013-12-15
Hydroxyurea is currently the only FDA-approved drug that ameliorates the pathophysiology of sickle cell anemia. Unfortunately, substantial interpatient variability in the pharmacokinetics (PK) of hydroxyurea may result in variation of the drug's efficacy. However, little is known about mechanisms that modulate hydroxyurea PK. Recent in vitro studies identifying hydroxyurea as a substrate for organic anion transporting polypeptide (OATP1B) transporters prompted the current investigation assessing the role of OATP1B transporters in modulating hydroxyurea PK. Using wild-type and Oatp1b knockout (Oatp1b(-/-)) mice, hydroxyurea PK was analyzed in vivo by measuring [(14)C]hydroxyurea distribution in plasma, kidney, liver, urine, or the exhaled (14)CO2 metabolite. Plasma levels were significantly reduced by 20% in Oatp1b(-/-) mice compared with wild-type (area under the curve of 38.64 or 48.45 μg·h(-1)·ml(-1), respectively) after oral administration, whereas no difference was observed between groups following intravenous administration. Accumulation in the kidney was significantly decreased by twofold in Oatp1b(-/-) mice (356.9 vs. 748.1 pmol/g), which correlated with a significant decrease in urinary excretion. Hydroxyurea accumulation in the liver was also decreased (136.6 vs. 107.3 pmol/g in wild-type or Oatp1b(-/-) mice, respectively) correlating with a decrease in exhaled (14)CO2. These findings illustrate that deficiency of Oatp1b transporters alters the absorption, distribution, and elimination of hydroxyurea thus providing the first in vivo evidence that cell membrane transporters may play a significant role in modulating hydroxyurea PK. Future studies to investigate other transporters and their role in hydroxyurea disposition are warranted for understanding the sources of variation in hydroxyurea's PK.
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Organic anion transporting polypeptide 1B transporters modulate hydroxyurea pharmacokinetics
Lancaster, Cynthia S.; Finkelstein, David; Ware, Russell E.; Sparreboom, Alex
2013-01-01
Hydroxyurea is currently the only FDA-approved drug that ameliorates the pathophysiology of sickle cell anemia. Unfortunately, substantial interpatient variability in the pharmacokinetics (PK) of hydroxyurea may result in variation of the drug's efficacy. However, little is known about mechanisms that modulate hydroxyurea PK. Recent in vitro studies identifying hydroxyurea as a substrate for organic anion transporting polypeptide (OATP1B) transporters prompted the current investigation assessing the role of OATP1B transporters in modulating hydroxyurea PK. Using wild-type and Oatp1b knockout (Oatp1b−/−) mice, hydroxyurea PK was analyzed in vivo by measuring [14C]hydroxyurea distribution in plasma, kidney, liver, urine, or the exhaled 14CO2 metabolite. Plasma levels were significantly reduced by 20% in Oatp1b−/− mice compared with wild-type (area under the curve of 38.64 or 48.45 μg·h−1·ml−1, respectively) after oral administration, whereas no difference was observed between groups following intravenous administration. Accumulation in the kidney was significantly decreased by twofold in Oatp1b−/− mice (356.9 vs. 748.1 pmol/g), which correlated with a significant decrease in urinary excretion. Hydroxyurea accumulation in the liver was also decreased (136.6 vs. 107.3 pmol/g in wild-type or Oatp1b−/− mice, respectively) correlating with a decrease in exhaled 14CO2. These findings illustrate that deficiency of Oatp1b transporters alters the absorption, distribution, and elimination of hydroxyurea thus providing the first in vivo evidence that cell membrane transporters may play a significant role in modulating hydroxyurea PK. Future studies to investigate other transporters and their role in hydroxyurea disposition are warranted for understanding the sources of variation in hydroxyurea's PK. PMID:23986199
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Anion-Cation Permeability Correlates with Hydrated Counterion Size in Glycine Receptor Channels
Sugiharto, Silas; Lewis, Trevor M.; Moorhouse, Andrew J.; Schofield, Peter R.; Barry, Peter H.
2008-01-01
The functional role of ligand-gated ion channels depends critically on whether they are predominantly permeable to cations or anions. However, these, and other ion channels, are not perfectly selective, allowing some counterions to also permeate. To address the mechanisms by which such counterion permeation occurs, we measured the anion-cation permeabilities of different alkali cations, Li+ Na+, and Cs+, relative to either Cl− or \\documentclass[10pt]{article} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{pmc} \\usepackage[Euler]{upgreek} \\pagestyle{empty} \\oddsidemargin -1.0in \\begin{document} \\begin{equation*}{\\mathrm{NO}}_{3}^{-}\\end{equation*}\\end{document} anions in both a wild-type glycine receptor channel (GlyR) and a mutant GlyR with a wider pore diameter. We hypothesized and showed that counterion permeation in anionic channels correlated inversely with an equivalent or effective hydrated size of the cation relative to the channel pore radius, with larger counterion permeabilities being observed in the wider pore channel. We also showed that the anion component of conductance was independent of the nature of the cation. We suggest that anions and counterion cations can permeate through the pore as neutral ion pairs, to allow the cations to overcome the large energy barriers resulting from the positively charged selectivity filter in small GlyR channels, with the permeability of such ion pairs being dependent on the effective hydrated diameter of the ion pair relative to the pore diameter. PMID:18708455
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Modulation of Molecular Flux Using a Graphene Nanopore Capacitor.
Shankla, Manish; Aksimentiev, Aleksei
2017-04-20
Modulation of ionic current flowing through nanoscale pores is one of the fundamental biological processes. Inspired by nature, nanopores in synthetic solid-state membranes are being developed to enable rapid analysis of biological macromolecules and to serve as elements of nanofludic circuits. Here, we theoretically investigate ion and water transport through a graphene-insulator-graphene membrane containing a single, electrolyte-filled nanopore. By means of all-atom molecular dynamics simulations, we show that the charge state of such a graphene nanopore capacitor can regulate both the selectivity and the magnitude of the nanopore ionic current. At a fixed transmembrane bias, the ionic current can be switched from being carried by an equal mixture of cations and anions to being carried almost exclusively by either cationic or anionic species, depending on the sign of the charge assigned to both plates of the capacitor. Assigning the plates of the capacitor opposite sign charges can either increase the nanopore current or reduce it substantially, depending on the polarity of the bias driving the transmembrane current. Facilitated by the changes of the nanopore surface charge, such ionic current modulations are found to occur despite the physical dimensions of the nanopore being an order of magnitude larger than the screening length of the electrolyte. The ionic current rectification is accompanied by a pronounced electro-osmotic effect that can transport neutral molecules such as proteins and drugs across the solid-state membrane and thereby serve as an interface between electronic and chemical signals.
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Shimonaka, Atsushi; Koga, Jinichiro; Baba, Yuko; Nishimura, Tomoko; Murashima, Koichiro; Kubota, Hidetoshi; Kono, Toshiaki
2006-04-01
We examined the characteristics of family 45 endoglucanases (glycoside hydrolases family 45; GH45) from Mucorales belonging to Zygomycota in the use of textiles and laundry. The defibrillation activities on lyocell fabric of family 45 endoglucanases from Mucorales, such as RCE1 and RCE2 from Rhizopus oryzae, MCE1 and MCE2 from Mucor circinelloides, and PCE1 from Phycomyces nitens, were much higher than those of the other family 45 endoglucanases. By contrast, family 45 endoglucanases from Mucorales were less resistant to anionic surfactant and oxidizing agent, main components in detergents, than the other family 45 endoglucanases. RCE1 consists of two distinct modules, a catalytic module and a carbohydrate-binding module family 1 (CBM1), and these common specific characteristics were considered to due to the catalytic module, but not to the CBM1.
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Seth, P; Ganapathy, M E; Conway, S J; Bridges, C D; Smith, S B; Casellas, P; Ganapathy, V
2001-07-25
The type 1 sigma receptor (sigmaR1) has been shown to participate in a variety of functions in the central nervous system. To identify the specific regions of the brain that are involved in sigmaR1 function, we analyzed the expression pattern of the receptor mRNA in the mouse brain by in situ hybridization. SigmaR1 mRNA was detectable primarily in the cerebral cortex, hippocampus, and Purkinje cells of cerebellum. To identify the critical anionic amino acid residues in the ligand-binding domain of sigmaR1, we employed two different approaches: chemical modification of anionic amino acid residues and site-directed mutagenesis. Chemical modification of anionic amino acids in sigmaR1 with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide reduced the ligand-binding activity markedly. Since it is known that a splice variant of this receptor which lacks exon 3 does not have the ability to bind sigma ligands, the ligand-binding domain with its critical anionic amino acid residues is likely to be present in or around the region coded by exon 3. Therefore, each of the anionic amino acids in this region was mutated individually and the influence of each mutation on ligand binding was assessed. These studies have identified two anionic amino acids, D126 and E172, that are obligatory for ligand binding. Even though the ligand-binding function was abolished by these two mutations, the expression of these mutants was normal at the protein level. These results show that sigmaR1 is expressed at high levels in specific areas of the brain that are involved in memory, emotion and motor functions. The results also provide important information on the chemical nature of the ligand-binding site of sigmaR1 that may be of use in the design of sigmaR1-specific ligands with potential for modulation of sigmaR1-related brain functions.
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Structural and electronic features of binary Li2S-P2S5 glasses
Ohara, Koji; Mitsui, Akio; Mori, Masahiro; Onodera, Yohei; Shiotani, Shinya; Koyama, Yukinori; Orikasa, Yuki; Murakami, Miwa; Shimoda, Keiji; Mori, Kazuhiro; Fukunaga, Toshiharu; Arai, Hajime; Uchimoto, Yoshiharu; Ogumi, Zempachi
2016-01-01
The atomic and electronic structures of binary Li2S-P2S5 glasses used as solid electrolytes are modeled by a combination of density functional theory (DFT) and reverse Monte Carlo (RMC) simulation using synchrotron X-ray diffraction, neutron diffraction, and Raman spectroscopy data. The ratio of PSx polyhedral anions based on the Raman spectroscopic results is reflected in the glassy structures of the 67Li2S-33P2S5, 70Li2S-30P2S5, and 75Li2S-25P2S5 glasses, and the plausible structures represent the lithium ion distributions around them. It is found that the edge sharing between PSx and LiSy polyhedra increases at a high Li2S content, and the free volume around PSx polyhedra decreases. It is conjectured that Li+ ions around the face of PSx polyhedra are clearly affected by the polarization of anions. The electronic structure of the DFT/RMC model suggests that the electron transfer between the P ion and the bridging sulfur (BS) ion weakens the positive charge of the P ion in the P2S7 anions. The P2S7 anions of the weak electrostatic repulsion would causes it to more strongly attract Li+ ions than the PS4 and P2S6 anions, and suppress the lithium ionic conduction. Thus, the control of the edge sharing between PSx and LiSy polyhedra without the electron transfer between the P ion and the BS ion is expected to facilitate lithium ionic conduction in the above solid electrolytes. PMID:26892385
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NASA Astrophysics Data System (ADS)
Esmaeilzadeh, Pouriya; Bahramian, Alireza; Fakhroueian, Zahra
The adsorption of surfactants at the solid-water interface is important for the control of wetting, lubrication, detergency and in mineral flotation.We have studied the adsorptions of different types of surfactants, cationic (Dodecyl trimethylammonium bromide, DTAB), anionic (sodium dodecyl sulfate, SDS) and non-anionic (lauryl alcohol-7 mole ethoxylate, LA7) on carbonate rock in presence of zirconium oxide spherical nanoparticles (17-19 nm). ZrO2 nanoparticles with tetrahedral structure have significant effect on adsorption of surfactants on the carbonate rock. We have used the measured conductivities to determine the rate of adsorption of surfactants at rock-water interfaces. The conductivity of DTAB in aqueous solutions containing calcite powder decreases more than the other surfactants in contact with ZrO2 nanoparticles. We have also investigated the adsorption of surfactants at the air-water interface. The presence of nanoparticles, as demonstrated by our experiments, enhances the surface activity and surface adsorption of the surfactants through electrostatic forces or formation of nanostructures. Dynamic light structuring data shows similar aggregation number of nanoparticles in presence of nanoparticles.
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Preparation and performance evaluation of novel alkaline stable anion exchange membranes
NASA Astrophysics Data System (ADS)
Irfan, Muhammad; Bakangura, Erigene; Afsar, Noor Ul; Hossain, Md. Masem; Ran, Jin; Xu, Tongwen
2017-07-01
Novel alkaline stable anion exchange membranes are prepared from various amounts of N-methyl dipicolylamine (MDPA) and brominated poly (2,6-dimethyl-1,4-phenylene oxide) (BPPO). The dipicolylamine and MDPA are synthesized through condensation reaction and confirmed by 1H NMR spectroscopy. The morphologies of prepared membranes are investigated by atomic force microscopy (AFM), fourier transform infrared spectroscopy (FTIR), 1H NMR spectroscopy and scanning electron microscopy (SEM). The electrochemical and physical properties of AEMs are tested comprising water uptake (WU), ion exchange capacity (IEC), alkaline stability, linear expansion ratio (LER), thermal stability and mechanical stability. The obtained hydroxide conductivity of MDPA-4 is 66.5 mS/cm at 80 °C. The MDPA-4 membrane shows good alkaline stability, high hydroxide conductivity, low methanol permeability (3.43 × 10-7 cm2/s), higher selectivity (8.26 × 107 mS s/cm3), less water uptake (41.1%) and lower linear expansion (11.1%) despite of high IEC value (1.62 mmol/g). The results prove that MDPA membranes have great potential application in anion exchange membrane fuel cell.
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Review of cell performance in anion exchange membrane fuel cells
NASA Astrophysics Data System (ADS)
Dekel, Dario R.
2018-01-01
Anion exchange membrane fuel cells (AEMFCs) have recently received increasing attention since in principle they allow for the use of non-precious metal catalysts, which dramatically reduces the cost per kilowatt of power in fuel cell devices. Until not long ago, the main barrier in the development of AEMFCs was the availability of highly conductive anion exchange membranes (AEMs); however, improvements on this front in the past decade show that newly developed AEMs have already reached high levels of conductivity, leading to satisfactory cell performance. In recent years, a growing number of research studies have reported AEMFC performance results. In the last three years, new records in performance were achieved. Most of the literature reporting cell performance is based on hydrogen-AEMFCs, although an increasing number of studies have also reported the use of fuels others than hydrogen - such as alcohols, non-alcohol C-based fuels, as well as N-based fuels. This article reviews the cell performance and performance stability achieved in AEMFCs through the years since the first reports in the early 2000s.
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Role of Dynamically Frustrated Bond Disorder in a Li + Superionic Solid Electrolyte
Adelstein, Nicole; Wood, Brandon C.
2016-09-16
Inorganic lithium solid electrolytes are critical components in next-generation solid-state batteries, yet the fundamental nature of the cation-anion interactions and their relevance for ionic conductivity in these materials remains enigmatic. Here, we employ first-principles molecular dynamics simulations to explore the interplay between chemistry, structure, and functionality of a highly conductive Li + solid electrolyte, Li3InBr6. Using local-orbital projections to dynamically track the evolution of the electronic charge density, the simulations reveal rapid, correlated fluctuations between cation-anion interactions with different degrees of directional covalent character. These chemical bond dynamics are shown to correlate with Li + mobility, and are enabled thermallymore » by intrinsic frustration between the preferred geometries of chemical bonding and lattice symmetry. We suggest that the fluctuating chemical environment from the polarizable anions functions similar to a solvent, contributing to the superionic behavior of Li 3InBr 6 by temporarily stabilizing configurations favorable for migrating Li +. The generality of these conclusions for understanding solid electrolytes and key factors governing the superionic phase transition is discussed.« less
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Soloninin, Alexei V.; Dimitrievska, Mirjana; Skoryunov, Roman V.; ...
2016-12-13
The disordered phases of the 1-carba-closo-decaborates LiCB9H10 and NaCB9H10 exhibit the best solid-state ionic conductivities to date among all known polycrystalline competitors, likely facilitated in part by the highly orientationally mobile CB9H10- anions. We have undertaken both NMR and quasielastic neutron scattering (QENS) measurements to help characterize the monovalent anion reorientational mobilities and mechanisms associated with these two compounds and to compare their anion reorientational behaviors with those for the divalent B10H102- anions in the related Li2B10H10 and Na2B10H10 compounds. NMR data show that the transition from the low-T ordered to the high-T disordered phase for both LiCB9H10 and NaCB9H10more » is accompanied by a nearly two-orders-of-magnitude increase in the reorientational jump rate of CB9H10- anions. QENS measurements of the various disordered compounds indicate anion jump correlation frequencies on the order of 1010-1011 s-1 and confirm that NaCB9H10 displays jump frequencies about 60% to 120% higher than those for LiCB9H10 and Na2B10H10 at comparable temperatures. The Q-dependent quasielastic scattering suggests similar small-angular-jump reorientational mechanisms for the different disordered anions, changing from more uniaxial in character at lower temperatures to more multidimensional at higher temperatures, although still falling short of full three-dimensional rotational diffusion below 500 K within the nanosecond neutron window.« less
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Haskins, Justin B; Bennett, William R; Wu, James J; Hernández, Dionne M; Borodin, Oleg; Monk, Joshua D; Bauschlicher, Charles W; Lawson, John W
2014-09-25
We employ molecular dynamics (MD) simulation and experiment to investigate the structure, thermodynamics, and transport of N-methyl-N-butylpyrrolidinium bis(trifluoromethylsufonyl)imide ([pyr14][TFSI]), N-methyl-N-propylpyrrolidinium bis(fluorosufonyl)imide ([pyr13][FSI]), and 1-ethyl-3-methylimidazolium boron tetrafluoride ([EMIM][BF4]), as a function of Li-salt mole fraction (0.05 ≤ xLi(+) ≤ 0.33) and temperature (298 K ≤ T ≤ 393 K). Structurally, Li(+) is shown to be solvated by three anion neighbors in [pyr14][TFSI] and four anion neighbors in both [pyr13][FSI] and [EMIM][BF4], and at all levels of xLi(+) we find the presence of lithium aggregates. Pulsed field gradient spin-echo NMR measurements of diffusion and electrochemical impedance spectroscopy measurements of ionic conductivity are made for the neat ionic liquids as well as 0.5 molal solutions of Li-salt in the ionic liquids. Bulk ionic liquid properties (density, diffusion, viscosity, and ionic conductivity) are obtained with MD simulations and show excellent agreement with experiment. While the diffusion exhibits a systematic decrease with increasing xLi(+), the contribution of Li(+) to ionic conductivity increases until reaching a saturation doping level of xLi(+) = 0.10. Comparatively, the Li(+) conductivity of [pyr14][TFSI] is an order of magnitude lower than that of the other liquids, which range between 0.1 and 0.3 mS/cm. Our transport results also demonstrate the necessity of long MD simulation runs (∼200 ns) to converge transport properties at room temperature. The differences in Li(+) transport are reflected in the residence times of Li(+) with the anions (τ(Li/-)), which are revealed to be much larger for [pyr14][TFSI] (up to 100 ns at the highest doping levels) than in either [EMIM][BF4] or [pyr13][FSI]. Finally, to comment on the relative kinetics of Li(+) transport in each liquid, we find that while the net motion of Li(+) with its solvation shell (vehicular) significantly contributes to net diffusion in all liquids, the importance of transport through anion exchange increases at high xLi(+) and in liquids with large anions.
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Effect of Detergent on Electrical Properties of Squid Axon Membrane
Kishimoto, Uichiro; Adelman, William J.
1964-01-01
The effects of detergents on squid giant axon action and resting potentials as well as membrane conductances in the voltage clamp have been studied. Anionic detergents (sodium lauryl sulfate, 0.1 to 1.0 mM; dimethyl benzene sulfonate, 1 to 20 mM, pH 7.6) cause a temporary increase and a later decrease of action potential height and the value of the resting potential. Cationic detergent (cetyl trimethyl ammonium chloride, 6 x 10-5 M or more, pH 7.6) generally brings about immediate and irreversible decreases in the action and resting potentials. Non-ionic detergent (tween 80, 0.1 M, pH 7.6) causes a slight reversible reduction of action potential height without affecting the value of the resting potential. Both anionic and cationic detergents generally decrease the sodium and potassium conductances irreversibly. The effect of non-ionic detergent is to decrease the sodium conductance reversibly, leaving the potassium conductance almost unchanged. PMID:14158665
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An electroactive conducting polymer actuator based on NBR/RTIL solid polymer electrolyte
NASA Astrophysics Data System (ADS)
Cho, M. S.; Seo, H. J.; Nam, J. D.; Choi, H. R.; Koo, J. C.; Lee, Y.
2007-04-01
This paper reports the fabrication of a dry-type conducting polymer actuator using nitrile rubber (NBR) as the base material in a solid polymer electrolyte. The conducting polymer, poly(3,4-ethylenedioxythiophene) (PEDOT), was synthesized on the surface of the NBR layer by using a chemical oxidation polymerization technique. Room-temperature ionic liquids (RTIL) based on imidazolium salts, e.g. 1-butyl-3-methyl imidazolium X (where X = BF4-, PF6-, (CF3SO2)2N-), were absorbed into the composite film. The compatibility between the ionic liquids and the NBR polymer was confirmed by DMA. The effect of the anion size of the ionic liquids on the displacement of the actuator was examined. The displacement increased with increasing anion size of the ionic liquids. The cyclic voltammetry responses and the redox switching dynamics of the actuators were examined in different ionic liquids.
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Synthesis of new solid polymer electrolyte and actuator based on PEDOT/NBR/ionic liquid
NASA Astrophysics Data System (ADS)
Cho, M. S.; Seo, H. J.; Nam, J. D.; Choi, H. R.; Koo, J. C.; Lee, Y.
2006-03-01
The conducting polymer actuator was presented. The solid polymer electrolyte based on nitrile rubber (NBR) activated with different ionic liquids was prepared. The three different grades of NBR films were synthesized by emulsion polymerization with different amount of acrylonitrile, 23, 35, and 40 mol. %, respectively. The effect of acrylonitrile content on the ionic conductivity and dielectric constant of solid polymer electrolytes was characterized. A conducting polymer, poly(3,4-ethylenedioxythiophene) (PEDOT), was synthesized on the surface of the NBR layer by using a chemical oxidation polymerization technique, and room temperature ionic liquids (RTIL) based on imidazolium salts, e.g. 1-butyl-3-methyl imidazolium X [where X= BF 4 -, PF 6 -, (CF 3SO II) IIN -], were absorbed into the composite film. The effects of the anion size of the ionic liquids on the displacement of the actuator were examined. The displacement increased with increasing the anion-size of the ionic liquids.
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Polymerized Paired Ions as Polymeric Ionic Liquid-Proton Conductivity.
Gu, Hong; Yan, Feng; Texter, John
2016-07-01
A new polymerized ionic liquid has been derived by photopolymerization of a stimuli-responsive ionic liquid surfactant, ILAMPS, which is composed of polymerizable, paired ions. The cation is 1-methyl-3-[11-(acryloyloxy)undecyl] imidazolium (IL), and the anion is 2-acrylamido-2-methyl-1-propanesulfonate (AMPS). This ion combination is a new ionic liquid. The resulting hygroscopic resins are highly polarizable, suitable for sensor design and for ultracapacitor fabrication and proton conducting. Interactions of imidazolium with anions provide basis for stimuli-responsiveness, and are used to promote proton transport. Doping with one equivalent of HPF6 at 0% relative humidity produces a 100-fold increase in proton conductivity at 100-125 °C and activation energies for proton transport lower than those of Nafion at water loadings less than 5 per sulfonate. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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Aaronson, Barak D B; Wigmore, David; Johns, Marcus A; Scott, Janet L; Polikarpov, Igor; Marken, Frank
2017-09-25
Cellulose films as well as chitosan-modified cellulose films of approximately 5 μm thickness, reconstituted from ionic liquid media onto a poly(ethylene-terephthalate) (PET, 6 μm thickness) film with a 5, 10, 20, or 40 μm diameter laser-drilled microhole, show significant current rectification in aqueous NaCl. Reconstituted α-cellulose films provide "cationic diodes" (due to predominant cation conductivity) whereas chitosan-doped cellulose shows "anionic diode" effects (due to predominant anion conductivity). The current rectification, or "ionic diode" behaviour, is investigated as a function of NaCl concentration, pH, microhole diameter, and molecular weight of the chitosan dopant. Future applications are envisaged exploiting the surface charge induced switching of diode currents for signal amplification in sensing.
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Lee, Woo-Hyung; Park, Eun Joo; Han, Junyoung; ...
2017-05-05
A new design concept for ion-conducting polymers in anion exchange membranes (AEMs) fuel cells is proposed based on structural studies and conformational analysis of polymers and their effect on the properties of AEMs. Thermally, chemically, and mechanically stable terphenyl-based polymers with pendant quaternary ammonium alkyl groups were synthesized to investigate the effect of varying the arrangement of the polymer backbone and cation-tethered alkyl chains. The results demonstrate that the microstructure and morphology of these polymeric membranes significantly influence ion conductivity and fuel cell performance. Finally, the results of this study provide new insights that will guide the molecular design ofmore » polymer electrolyte materials to improve fuel cell performance.« less
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Highly Conductive Anion Exchange Block Copolymers
We are developing a comprehensive fundamental understanding of the interplay between transport and morphology in newly synthesized hydroxide...conducting block copolymers. We are synthesizing hydroxide conducting block copolymers of various (1) morphology types, (2) ionic concentrations, and (3...ionic domain sizes. We are carefully characterizing the morphology and transport properties using both conventional and new advanced in situ techniques
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Self-doped microphase separated block copolymer electrolyte
Mayes, Anne M.; Sadoway, Donald R.; Banerjee, Pallab; Soo, Philip; Huang, Biying
2002-01-01
A polymer electrolyte includes a self-doped microphase separated block copolymer including at least one ionically conductive block and at least one second block that is immiscible in the ionically conductive block, an anion immobilized on the polymer electrolyte and a cationic species. The ionically conductive block provides a continuous ionically conductive pathway through the electrolyte. The electrolyte may be used as an electrolyte in an electrochemical cell.
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Soto-Cerrato, Vanessa; Manuel-Manresa, Pilar; Hernando, Elsa; Calabuig-Fariñas, Silvia; Martínez-Romero, Alicia; Fernández-Dueñas, Víctor; Sahlholm, Kristoffer; Knöpfel, Thomas; García-Valverde, María; Rodilla, Ananda M; Jantus-Lewintre, Eloisa; Farràs, Rosa; Ciruela, Francisco; Pérez-Tomás, Ricardo; Quesada, Roberto
2015-12-23
Facilitated anion transport potentially represents a powerful tool to modulate various cellular functions. However, research into the biological effects of small molecule anionophores is still at an early stage. Here we have used two potent anionophore molecules inspired in the structure of marine metabolites tambjamines to gain insight into the effect induced by these compounds at the cellular level. We show how active anionophores, capable of facilitating the transmembrane transport of chloride and bicarbonate in model phospholipid liposomes, induce acidification of the cytosol and hyperpolarization of plasma cell membranes. We demonstrate how this combined effect can be used against cancer stem cells (CSCs). Hyperpolarization of cell membrane induces cell differentiation and loss of stemness of CSCs leading to effective elimination of this cancer cell subpopulation.
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Nonaqueous polypyrrole colloids
Armes, Steven P.; Aldissi, Mahmoud
1991-01-01
Processable conductive polymers including an oxidized, polymerized aromatic heterocyclic monomer, e.g., pyrrole, an stabilizing effective amount of a poly(vinyl acetate) and dopant anions, and a process of preparing said processable conductive polymers directly in a nonaqueous medium such as methyl acetate, methyl formate, ethyl formate, and propyl formate are disclosed.
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Inorganic Nitrite Therapy: Historical perspective and future directions
Kevil, Christopher G.; Kolluru, Gopi K.; Pattillo, Christopher B.; Giordano, Tony
2015-01-01
Over the past several years, investigators studying nitric oxide (NO) biology and metabolism have come to learn that the one electron oxidation product of NO, nitrite anion, serves as a unique player in modulating tissue NO bioavailability. Numerous studies have examined how this oxidized metabolite of NO can act as a salvage pathway for maintaining NO equivalents through multiple reduction mechanisms in permissive tissue environments. Moreover, it is now clear that nitrite anion production and distribution throughout the body can act in an endocrine manner to augment NO bioavailability that is important for physiological and pathological processes. These discoveries have led to renewed hope and efforts for an effective NO based therapeutic agent through the unique action of sodium nitrite as an NO pro-drug. More recent studies also indicate that sodium nitrate may also increase plasma nitrite levels via the enterosalivary circulatory system resulting in nitrate reduction to nitrite by microorganisms found within the oral cavity. In this review, we discuss the importance of nitrite anion in several disease models along with an appraisal of sodium nitrite therapy in the clinic, potential caveats of such clinical uses, and future possibilities of nitrite based therapies. PMID:21619929
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Li, A.S.W.; Kevan, L.
1983-09-07
The photoionization of N,N,N',N'-tetramethylbenzidine (TMB) in dihexadecylphosphate anionic vesicles and in dioctadecyldimethylammonium chloride cationic vesicles has been studied by optical absorption and electron spin resonance in liquid and frozen solutions. The TMB cation has been observed to be stabilized in both types of vesicles. The photoionization efficiency is about twofold greater in the cationic vesicles compared to the anionic vesicles. Shifts in the optical absorption maximum between micellar and vesicle solutions indicate that TMB is in a less polar environment in the vesicle systems. Electron spin echo modulation spectrometry has been used to detect TMB cation-water interactions that are foundmore » to be weaker than in previously studied micellar solutions. This is consistent with the optical absorption results and with an asymmetric solubilization site for TMB and TMB/sup +/ within the vesicular structure. A new absorption in the photoionized vesicles is assigned to a nonparamagnetic diamine-diimine charge-transfer complex between two TMB cations in the same vesicle. This complex is not formed in micellar systems. 5 figures.« less
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Regnier, Elodie; Grange, Philippe A; Ollagnier, Guillaume; Crickx, Etienne; Elie, Laetitia; Chouzenoux, Sandrine; Weill, Bernard; Plainvert, Céline; Poyart, Claire; Batteux, Frédéric; Dupin, Nicolas
2016-02-01
Gram-positive Streptococcus pyogenes (group A Streptococcus or GAS) is a major skin pathogen and interacts with keratinocytes in cutaneous tissues. GAS can cause diverse suppurative and inflammatory infections, such as cellulitis, a common acute bacterial dermo-hypodermitis with a high morbidity. Bacterial isolation yields from the lesions are low despite the strong local inflammation observed, raising numerous questions about the pathogenesis of the infection. Using an in vitro model of GAS-infected keratinocytes, we show that the major ROS produced is the superoxide anion ([Formula: see text]), and that its production is time- and dose-dependent. Using specific modulators of ROS production, we show that [Formula: see text] is mainly synthesized by the cytoplasmic NADPH oxidase. Superoxide anion production leads to keratinocyte necrosis but incomplete inhibition of GAS growth, suggesting that GAS may be partially resistant to the oxidative burst. In conclusion, GAS-stimulated keratinocytes are able to develop an innate immune response based on the production of ROS. This local immune response limits GAS development and induces keratinocyte cell death, resulting in the skin lesions observed in patients with cellulitis. © The Author(s) 2015.
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Gunner, M. R.; Madeo, Jennifer; Zhu, Zhenyu
2009-01-01
Quinones such as ubiquinone are the lipid soluble electron and proton carriers in the membranes of mitochondria, chloroplasts and oxygenic bacteria. Quinones undergo controlled redox reactions bound to specific sites in integral membrane proteins such as the cytochrome bc1 oxidoreductase. The quinone reactions in bacterial photosynthesis are amongst the best characterized, presenting a model to understand how proteins modulate cofactor chemistry. The free energy of ubiquinone redox reactions in aqueous solution and in the QA and QB sites of the bacterial photosynthetic reaction centers (RCs) are compared. In the primary QA site ubiquinone is reduced only to the anionic semiquinone (Q•−) while in the secondary QB site the product is the doubly reduced, doubly protonated quinol (QH2). The ways in which the protein modifies the relative energy of each reduced and protonated intermediate are described. For example, the protein stabilizes Q•− while destabilizing Q= relative to aqueous solution through electrostatic interactions. In addition, kinetic and thermodynamic mechanisms for stabilizing the intermediate semiquinones are compared. Evidence for the protein sequestering anionic compounds by slowing both on and off rates as well as by binding the anion more tightly is reviewed. PMID:18979192
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Ben-Tabou De-Leon, Shlomo; Blotnick, Edna; Nussinovitch, Itzhak
2003-10-01
Decrease in extracellular osmolarity ([Os]e) results in stimulation of hormone secretion from pituitary cells. Different mechanisms can account for this stimulation of hormone secretion. In this study we examined the possibility that hyposmolarity directly modulates voltage-gated calcium influx in pituitary cells. The effects of hyposmolarity on L-type (IL) and T-type (IT) calcium currents in pituitary cells were investigated by using two hyposmotic stimuli, moderate (18-22% decrease in [Os]e) and strong (31-32% decrease in [Os]e). Exposure to moderate hyposmotic stimuli resulted in three response types in IL (a decrease, a biphasic effect, and an increase in IL) and in increase in IT. Exposure to strong hyposmotic stimuli resulted only in increases in both IL and IT. Similarly, in intact pituitary cells (perforated patch method), exposure to either moderate or strong hyposmotic stimuli resulted only in increases in both IL and IT. Thus it appears that the main effect of decrease in [Os]e is increase in calcium channel currents. This increase was differential (IL were more sensitive than IT) and voltage independent. In addition, we show that these hyposmotic effects cannot be explained by activation of an anionic conductance or by an increase in cell membrane surface area. In conclusion, this study shows that hyposmotic swelling of pituitary cells can directly modulate voltage-gated calcium influx. This hyposmotic modulation of IL and IT may contribute to the previously reported hyposmotic stimulation of hormone secretion. The mechanisms underlying these hyposmotic effects and their possible physiological relevance are discussed.
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Méndez-Morales, Trinidad; Carrete, Jesús; Bouzón-Capelo, Silvia; Pérez-Rodríguez, Martín; Cabeza, Óscar; Gallego, Luis J; Varela, Luis M
2013-03-21
Structural and dynamical properties of room-temperature ionic liquids containing the cation 1-butyl-3-methylimidazolium ([BMIM](+)) and three different anions (hexafluorophosphate, [PF6](-), tetrafluoroborate, [BF4](-), and bis(trifluoromethylsulfonyl)imide, [NTf2](-)) doped with several molar fractions of lithium salts with a common anion at 298.15 K and 1 atm were investigated by means of molecular dynamics simulations. The effect of the size of the salt cation was also analyzed by comparing these results with those for mixtures of [BMIM][PF6] with NaPF6. Lithium/sodium solvation and ionic mobilities were analyzed via the study of radial distribution functions, coordination numbers, cage autocorrelation functions, mean-square displacements (including the analysis of both ballistic and diffusive regimes), self-diffusion coefficients of all the ionic species, velocity and current autocorrelation functions, and ionic conductivity in all the ionic liquid/salt systems. We found that lithium and sodium cations are strongly coordinated in two different positions with the anion present in the mixture. Moreover, [Li](+) and [Na](+) cations were found to form bonded-like, long-lived aggregates with the anions in their first solvation shell, which act as very stable kinetic entities within which a marked rattling motion of salt ions takes place. With very long MD simulation runs, this phenomenon is proved to be on the basis of the decrease of self-diffusion coefficients and ionic conductivities previously reported in experimental and computational results.
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NASA Astrophysics Data System (ADS)
Kimura, Taro; Akiyama, Ryo; Miyatake, Kenji; Inukai, Junji
2018-01-01
For higher performances of anion exchange membrane (AEM) fuel cells, understanding the phase-separated structures inside AEMs is essential, as well as those at the catalyst layer/membrane interfaces. The AEMs based on quaternized aromatic semi-block copolymers with different ion exchange capacities (IECs) were systematically investigated. With IECs of 1.23 and 1.95 mequiv g-1, the water uptakes at room temperature were 37% and 98%, and the anion conductivities 23.6 and 71.4 mS cm-1, respectively. The increases were not proportional to the IEC. Images obtained by transmission electron microscopy in vacuum were similar with both IEC values, but the development of a clear phase separation in humidified nitrogen was observed in the profiles only with 1.95 mequiv g-1obtained by small-angle X-ray scattering. At the temperature of 40 °C and the relative humidity (RH) of 30%, the average currents observed at the tip apex by current-sensing atomic force microscopy were <0.5 and 10 pA with 1.23 and 1.95 mequiv g-1, respectively, and those at 70% RH were 10 and 15 pA, respectively. The humidity gave a larger influence on the bulk structure with 1.95 mequiv g-1, whereas a larger influence on the surface conductivity with 1.23 mequiv g-1.
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Diels Alder polyphenylene anion exchange membrane for nonaqueous redox flow batteries
Small, Leo J.; Pratt, III, Harry D.; Fujimoto, Cy H.; ...
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
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Thongnak, Laongdao; Pongchaidecha, Anchalee; Jaikumkao, Krit; Chatsudthipong, Varanuj; Chattipakorn, Nipon; Lungkaphin, Anusorn
2017-10-19
Hyperglycemia-induced oxidative stress is usually found in diabetic condition. 3-hydroxy-3-methylglutaryl coenzyme-A (HMG-CoA) reductase inhibitors, statins, are widely used as cholesterol-lowering medication with several "pleiotropic" effects in diabetic patients. This study aims to evaluate whether the protective effects of atorvastatin and insulin on renal function and renal organic anion transporter 3 (Oat3) function involve the modulation of oxidative stress and pancreatic function in type 1 diabetic rats. Type 1 diabetes was induced by intraperitoneal injection of streptozotocin (50 mg/kg BW). Atorvastatin and insulin as single or combined treatment were given for 4 weeks after diabetic condition had been confirmed. Diabetic rats demonstrated renal function and renal Oat3 function impairment with an increased MDA level and decreased SOD protein expression concomitant with stimulation of renal Nrf2 and HO-1 protein expression. Insulin plus atorvastatin (combined) treatment effectively restored renal function as well as renal Oat3 function which correlated with the decrease in hyperglycemia and oxidative stress. Moreover, pancreatic inflammation and apoptosis in diabetic rats were ameliorated by the combined drugs treatment. Therefore, atorvastatin plus insulin seems to exert the additive effect in improving renal functionby alleviating hyperglycemiaand the modulation of oxidative stress, inflammation and apoptosis.
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Development of Ion Chemosensors Based on Porphyrin Analogues.
Ding, Yubin; Zhu, Wei-Hong; Xie, Yongshu
2017-02-22
Sensing of metal ions and anions is of great importance because of their widespread distribution in environmental systems and biological processes. Colorimetric and fluorescent chemosensors based on organic molecular species have been demonstrated to be effective for the detection of various ions and possess the significant advantages of low cost, high sensitivity, and convenient implementation. Of the available classes of organic molecules, porphyrin analogues possess inherently many advantageous features, making them suitable for the design of ion chemosensors, with the targeted sensing behavior achieved and easily modulated based on their following characteristics: (1) NH moieties properly disposed for binding of anions through cooperative hydrogen-bonding interactions; (2) multiple pyrrolic N atoms or other heteroatoms for selectively chelating metal ions; (3) variability of macrocycle size and peripheral substitution for modulation of ion selectivity and sensitivity; and (4) tunable near-infrared emission and good biocompatibility. In this Review, design strategies, sensing mechanisms, and sensing performance of ion chemosensors based on porphyrin analogues are described by use of extensive examples. Ion chemosensors based on normal porphyrins and linear oligopyrroles are also briefly described. This Review provides valuable information for researchers of related areas and thus may inspire the development of more practical and effective approaches for designing high-performance ion chemosensors based on porphyrin analogues and other relevant compounds.
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Neuroactive Steroids: Receptor Interactions and Responses
Tuem, Kald Beshir; Atey, Tesfay Mehari
2017-01-01
Neuroactive steroids (NASs) are naturally occurring steroids, which are synthesized centrally as de novo from cholesterol and are classified as pregnane, androstane, and sulfated neurosteroids (NSs). NASs modulate many processes via interacting with gamma-aminobutyric acid (GABA), N-methyl-d-aspartate, serotonin, voltage-gated calcium channels, voltage-dependent anion channels, α-adrenoreceptors, X-receptors of the liver, transient receptor potential channels, microtubule-associated protein 2, neurotrophin nerve growth factor, and σ1 receptors. Among these, NSs (especially allopregnanolone) have high potency and extensive GABA-A receptors and hence demonstrate anticonvulsant, anesthetic, central cytoprotectant, and baroreflex inhibitory effects. NSs are also involved in mood and learning via serotonin and anti-nociceptive activity via T-type voltage-gated Ca2+ channels. Moreover, they are modulators of mitochondrial function, synaptic plasticity, or regulators of apoptosis, which have a role in neuroprotective via voltage-dependent anion channels receptors. For proper functioning, NASs need to be in their normal level, whereas excess and deficiency may lead to abnormalities. When they are below the normal, NSs could have a part in development of depression, neuro-inflammation, multiple sclerosis, experimental autoimmune encephalitis, epilepsy, and schizophrenia. On the other hand, stress and attention deficit disorder could occur during excessive level. Overall, NASs are very important molecules with major neuropsychiatric activity. PMID:28894435
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Fan, Shujun; Harfoot, Natalie; Bartolo, Ray C; Butt, A Grant
2012-04-01
The cystic fibrosis transmembrane conductance regulator (CFTR) is central to anion secretion in both the possum and eutherian small intestine. Here, we investigated its role in the possum proximal colon, which has novel transport properties compared with the eutherian proximal colon. Despite considerable CFTR expression, high doses of the CFTR activator forskolin (EC(50)≈10 μmol l(-1)) were required for a modest, CFTR-dependent increase in short-circuit current (I(sc)) in the proximal colon. Presumably, this is because CFTR is restricted to the apical membrane of a small population of CFTR high expresser (CHE) cells in the surface and upper crypt epithelium. Furthermore, although the forskolin-stimulated I(sc) was dependent on serosal Na(+), Cl(-) and HCO(3)(-), consistent with anion secretion, inhibition of the basolateral Na-K-2Cl(-) (NKCC1) or Na-HCO(3) (pNBCe1) cotransporters did not prevent it. Therefore, although NKCC1 and pNBCe1 are expressed in the colonic epithelium they do not appear to be expressed in CHE cells. At low doses (IC(50)≈1 μmol l(-1)), forskolin also decreased the transepithelial conductance (G(T)) of the colon through inhibition of a 4,4'-diisothiocyano-2,2'-stilbenedisulphonic acid-sensitive anion conductance in the basolateral membrane of the CHE cells. This conductance is arranged in series with CFTR in the CHE cells and, therefore, the CHE cells provide a transepithelial Cl(-) conductance for passive Cl(-) absorption across the epithelium. Inhibition of the basolateral Cl(-) conductance of the CHE cells by forskolin will inhibit Na(+) absorption by restricting the movement of its counter-ion Cl(-), assisting in the conversion of the tissue from an absorptive to a secretory state.
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Solid polymeric electrolytes for lithium batteries
Angell, Charles A.; Xu, Wu; Sun, Xiaoguang
2006-03-14
Novel conductive polyanionic polymers and methods for their preparion are provided. The polyanionic polymers comprise repeating units of weakly-coordinating anionic groups chemically linked to polymer chains. The polymer chains in turn comprise repeating spacer groups. Spacer groups can be chosen to be of length and structure to impart desired electrochemical and physical properties to the polymers. Preferred embodiments are prepared from precursor polymers comprising the Lewis acid borate tri-coordinated to a selected ligand and repeating spacer groups to form repeating polymer chain units. These precursor polymers are reacted with a chosen Lewis base to form a polyanionic polymer comprising weakly coordinating anionic groups spaced at chosen intervals along the polymer chain. The polyanionic polymers exhibit high conductivity and physical properties which make them suitable as solid polymeric electrolytes in lithium batteries, especially secondary lithium batteries.
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Conductive Hybrid Crystal Composed from Polyoxomolybdate and Deprotonatable Ionic-Liquid Surfactant
Kobayashi, Jun; Kawahara, Ryosuke; Uchida, Sayaka; Koguchi, Shinichi; Ito, Takeru
2016-01-01
A polyoxomolybdate inorganic-organic hybrid crystal was synthesized with deprotonatable ionic-liquid surfactant. 1-dodecylimidazolium cation was employed for its synthesis. The hybrid crystal contained δ-type octamolybdate (Mo8) isomer, and possessed alternate stacking of Mo8 monolayers and interdigitated surfactant bilayers. The crystal structure was compared with polyoxomolybdate hybrid crystals comprising 1-dodecyl-3-methylimidazolium surfactant, which preferred β-type Mo8 isomer. The less bulky hydrophilic moiety of the 1-dodecylimidazolium interacted with the δ-Mo8 anion by N–H···O hydrogen bonds, which presumably induced the formation of the δ-Mo8 anion. Anhydrous conductivity of the hybrid crystal was estimated to be 5.5 × 10−6 S·cm−1 at 443 K by alternating current (AC) impedance spectroscopy. PMID:27347926
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Wang, Lai-Sheng, E-mail: Lai-Sheng-Wang@brown.edu
2015-07-28
Electrospray ionization (ESI) has become an essential tool in chemical physics and physical chemistry for the production of novel molecular ions from solution samples for a variety of spectroscopic experiments. ESI was used to produce free multiply-charged anions (MCAs) for photoelectron spectroscopy (PES) in the late 1990 s, allowing many interesting properties of this class of exotic species to be investigated. Free MCAs are characterized by strong intramolecular Coulomb repulsions, which create a repulsive Coulomb barrier (RCB) for electron emission. The RCB endows many fascinating properties to MCAs, giving rise to meta-stable anions with negative electron binding energies. Recent developmentmore » in the PES of MCAs includes photoelectron imaging to examine the influence of the RCB on the electron emission dynamics, pump-probe experiments to examine electron tunneling through the RCB, and isomer-specific experiments by coupling PES with ion mobility for biological MCAs. The development of a cryogenically cooled Paul trap has led to much better resolved PE spectra for MCAs by creating vibrationally cold anions from the room temperature ESI source. Recent advances in coupling the cryogenic Paul trap with PE imaging have allowed high-resolution PE spectra to be obtained for singly charged anions produced by ESI. In particular, the observation of dipole-bound excited states has made it possible to conduct vibrational autodetachment spectroscopy and resonant PES, which yield much richer vibrational spectroscopic information for dipolar free radicals than traditional PES.« less
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Shimamura, Akihiro; Jones, Mark I; Metson, James B
2013-12-01
Desorption of interlayer hydrogen phosphate (HPO4) from hydrogen phosphate intercalated Mg/Al-layered double hydroxide (LDH-HPO4) by anion exchange with surfactant anions has been investigated under controlled conditions. Three types of surfactant, Dodecylbenzenesulphonate (DBS), Dodecylsulphate (DS) and 1-Octanesulphonate (OS), anions were used for intercalation experiments over a range of concentrations, and for all solutions, it was shown that the desorption of hydrogen phosphate is enhanced at concentrations close to the critical micelle concentration (CMC). Intercalation of the surfactant anions into LDH-HPO4 was confirmed by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR) and Scanning electron microscopy (SEM). More than 90% removal of the hydrogen phosphate was achieved at CMC. Repeat adsorption tests to investigate recyclability showed that desorption with 0.005 M DBS improved subsequent phosphate re-adsorption, allowing around 90% of the original adsorption over three cycles. This is much higher than when desorption was conducted using either Na2CO3 or NaCl-NaOH solutions, even at much higher concentrations. This study suggests potential economic and environmental advantages in using these surfactants in improving the cycling performance of LDH materials as absorbents for clean-up of water systems. Copyright © 2013 Elsevier Inc. All rights reserved.
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Cognigni, Alice; Gaertner, Peter; Zirbs, Ronald; Peterlik, Herwig; Prochazka, Katharina; Schröder, Christian
2016-01-01
A series of surface-active ionic liquids based on the 1-dodecyl-3-methylimidazolium cation and different anions such as halides and alkylsulfates was synthesized. The aggregation behavior of these ionic liquids in water was characterized by surface tension, conductivity measurements and UV-Vis spectroscopy in order to determine the critical micelle concentration (CMC) and to provide aggregation parameters. The determination of surface activity and aggregation properties of amphiphilic ionic liquids was accompanied by SAXS studies on selected surface-active ionic liquids. The application of these surface-active ionic liquids with different anions was tested in nucleophilic substitution reactions for the degradation of organophosphorus compounds. Kinetic studies via UV-Vis spectrophotometry showed a strong acceleration of the reaction in the micellar system compared to pure water. In addition, an influence of the anion was observed, resulting in a correlation between the anion binding to the micelle and the reaction rate constants, indicating that the careful choice of the surface-active ionic liquid can considerably affect the outcome of reactions. PMID:27121134
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Optimized anion exchange membranes for vanadium redox flow batteries.
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.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Kweon, Kyoung E.; Varley, Joel B.; Shea, Patrick
Li 2B 12H 12, Na 2B 12H 12, and their closo-borate relatives exhibit unusually high ionic conductivity, making them attractive as a new class of candidate electrolytes in solid-state Li- and Na-ion batteries. However, further optimization of these materials requires a deeper understanding of the fundamental mechanisms underlying ultrafast ion conduction. To this end, we use ab initio molecular dynamics simulations and density-functional calculations to explore the motivations for cation diffusion. We find that superionic behavior in Li 2B 12H 12 and Na 2B 12H 12 results from a combination of key structural, chemical, and dynamical factors that introduce intrinsicmore » frustration and disorder. A statistical metric is used to show that the structures exhibit a high density of accessible interstitial sites and site types, which correlates with the flatness of the energy landscape and the observed cation mobility. Furthermore, cations are found to dock to specific anion sites, leading to a competition between the geometric symmetry of the anion and the symmetry of the lattice itself, which can facilitate cation hopping. Finally, facile anion reorientations and other low-frequency thermal vibrations lead to fluctuations in the local potential that enhance cation mobility by creating a local driving force for hopping. In conclusion, we discuss the relevance of each factor for developing new ionic conductivity descriptors that can be used for discovery and optimization of closo-borate solid electrolytes, as well as superionic conductors more generally.« less
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Kweon, Kyoung E.; Varley, Joel B.; Shea, Patrick; ...
2017-10-11
Li 2B 12H 12, Na 2B 12H 12, and their closo-borate relatives exhibit unusually high ionic conductivity, making them attractive as a new class of candidate electrolytes in solid-state Li- and Na-ion batteries. However, further optimization of these materials requires a deeper understanding of the fundamental mechanisms underlying ultrafast ion conduction. To this end, we use ab initio molecular dynamics simulations and density-functional calculations to explore the motivations for cation diffusion. We find that superionic behavior in Li 2B 12H 12 and Na 2B 12H 12 results from a combination of key structural, chemical, and dynamical factors that introduce intrinsicmore » frustration and disorder. A statistical metric is used to show that the structures exhibit a high density of accessible interstitial sites and site types, which correlates with the flatness of the energy landscape and the observed cation mobility. Furthermore, cations are found to dock to specific anion sites, leading to a competition between the geometric symmetry of the anion and the symmetry of the lattice itself, which can facilitate cation hopping. Finally, facile anion reorientations and other low-frequency thermal vibrations lead to fluctuations in the local potential that enhance cation mobility by creating a local driving force for hopping. In conclusion, we discuss the relevance of each factor for developing new ionic conductivity descriptors that can be used for discovery and optimization of closo-borate solid electrolytes, as well as superionic conductors more generally.« less
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Novel fluoropolymer anion exchange membranes for alkaline direct methanol fuel cells.
Zhang, Yanmei; Fang, Jun; Wu, Yongbin; Xu, Hankun; Chi, Xianjun; Li, Wei; Yang, Yixu; Yan, Ge; Zhuang, Yongze
2012-09-01
A series of novel fluoropolymer anion exchange membranes based on the copolymer of vinylbenzyl chloride, butyl methacrylate, and hexafluorobutyl methacrylate has been prepared. Fourier transform infrared (FT-IR) spectroscopy and elemental analysis techniques are used to study the chemical structure and chemical composition of the membranes. The water uptake, ion-exchange capacity (IEC), conductivity, methanol permeability, and chemical stability of the membranes are also determined. The membranes exhibit high anionic conductivity in deionized water at 65 °C ranging from 3.86×10(-2) S cm(-1) to 4.36×10(-2) S cm(-1). The methanol permeability coefficients of the membranes are in the range of 4.21-5.80×10(-8) cm(2) s(-1) at 65 °C. The novel membranes also show good chemical and thermal stability. An open-circuit voltage of 0.7 V and a maximum power density of 53.2 mW cm(-2) of alkaline direct methanol fuel cell (ADMFC) with the membrane C, 1 M methanol, 1 M NaOH, and humidified oxygen are achieved at 65 °C. Therefore, these membranes have great potential for applications in fuel cell systems. Copyright © 2012 Elsevier Inc. All rights reserved.
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NASA Astrophysics Data System (ADS)
Elumalai, Vijayakumar; Sangeetha, Dharmalingam
2018-01-01
A series of novel composite anion exchange membranes were prepared via simple solution casting method using synthesized quaternary ammonium functionalized Polyhedral Oligomeric Silsesquioxane (QA-POSS) with Quaternary polysulfone (QPSU). QA-POSS was synthesized from prepared Cl-POSS and well characterized by FT-IR, NMR, SEM and TEM analyses to confirm the chemical modifications and cubic morphologies. The QA-POSS nano particles have dual role in the membrane providing additional ion conducting groups and reinforcing the membrane in molecular level for the overall improvement of composite membrane. Additionally, the composite membranes were characterized by XRD, SEM, Ion exchange capacity (IEC), water uptake and conductivity to ensure the suitability of its use as an electrolyte in alkaline fuel cell. Finally, membrane electrode assembly (MEA) was fabricated using Pt anode (0.25 mg/cm2), Ag cathode (0.375 mg/cm2) and various synthesized composite membranes, and then it was tested in real time fuel cell setup. The membrane with 15% QA-POSS showed the maximum power density of 321 mW/cm2. The results showed that QA-POSS possess the ability to enhance the performance of the anion exchange membrane significantly.
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Guo, Lin; Wang, Yu; Zheng, Yiliang; Huang, Zhipeng; Cheng, Yiyuan; Ye, Jiannong; Chu, Qingcui; Huang, Dongping
2016-03-01
A capillary electrophoresis approach with capacitively coupled contactless conductivity detection method has been developed for the determination of inorganic metabolites (thiocyanate, nitrite and nitrate) in human saliva. Field amplified sample injection, as a simple sample stacking technique, was used in conjunction for online preconcentration of above inorganic anions. A selective separation for the target anions from other coexisting constituents present in saliva could be obtained within 14min in a 10mmol/L His-90mmol/L HAc buffer (pH 3.70) at the separation voltage of -18kV. The limits of detection and limits of quantification of the three analytes were within the range of 3.1-4.9ng/mL (S/N=3) and 10-16ng/mL (S/N=10), respectively. The average recovery data were in the range of 81-108% at three different concentrations. This method provides a simple, rapid and direct approach for metabolite analyses of nitric oxide and cyanide based on noninvasive saliva sample, which presents a potential fast screening tool for clinical test. Copyright © 2016 Elsevier B.V. All rights reserved.
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NASA Astrophysics Data System (ADS)
Pathak, Arup Kumar
2014-12-01
An explicit analytical expression has been obtained for vertical detachment energy (VDE) that can be used to calculate the same over a wide range (both stable and unstable regions) of cluster sizes including the bulk from the knowledge of VDE for a finite number of stable clusters (n = 16-23). The calculated VDE for the bulk is found to be very good in agreement (within 1%) with the available experimental result and the domain of instability lies between n = 0 and n = 15 for the hydrated clusters, PO3 -4 . nH2O. The minimum number (n0) of water molecules needed to stabilise the phosphate anion is 16. We are able to explain the origin of solvent-berg model and anomalous conductivity from the knowledge of first stable cluster. We have also provided a scheme to calculate the radius of the solvent-berg for phosphate anion. The calculated conductivity using Stokes-Einstein relation and the radius of solvent-berg is found to be very good in agreement (within 4%) with the available experimental results.
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[Oxygen and the superoxide anion. Modulation of NADPH oxidase?].
Delbosc, S; Cristol, J P; Descomps, B; Chénard, J; Sirois, P
2001-01-01
Oxidative stress which results from an imbalance between oxidant production and antioxidant defense mechanisms can promote modifications of lipids, proteins and nucleic acids. This review focuses on the different pathways leading to Reactive Oxygen Species (ROS) production in particular on NADPH oxidase activation. This enzyme is localized in numerous cells including phagocytes and vascular cells and composed of membrane and cytosolic sub-units. The activation of the NADPH oxidase is largely involved in inflammation associated diseases such as asthma, Systemic Inflammatory Response Syndrome and aging associated diseases such as atherosclerosis and neurodeneratives diseases. The modulation of NADPH oxidase could be a way to limit or prevent the development of these diseases.
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NASA Astrophysics Data System (ADS)
Sampora, Yulianti; Juwono, Ariadne L.; Haryono, Agus; Irawan, Yan
2017-11-01
Mechanical Enhanced Oil Recovery (EOR) through chemical injection is using an anionic surfactant to improve the recovery of oil residues, particularly in a reservoir area that has certain characteristics. This case led the authors to conduct research on the synthesis of an anionic surfactant based on oleic acid and polyethylene glycol 400 that could be applied as a chemical injection. In this work, we investigate the sulfonation of Polyethylene glycol oleate (PDO) in a sulfuric acid agent. PDO in this experiment was derived from Indonesian palm oil. Variation of mole reactant and reaction time have been studied. The surfactant has been characterized by measuring the interfacial tension, acid value, ester value, saponification value, iodine value, Fourier Transform Infrared (FTIR), and particle size analyzer. There is a new peak at 1170-1178 cm-1 indicating that S=O bond has formed. PDO sulfonate exhibits good surface activity due to interfacial tension of 0,003 mN/m. Thus, polyethylene glycol oleate sulfonate was successfully synthesized and it could be useful as a novel an anionic surfactant.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Boulanouar, Omar; Fromm, Michel; Mavon, Christophe
We measure the desorption of anions stimulated by the impact of 0–20 eV electrons on highly uniform thin films of plasmid DNA-diaminopropane. The results are accurately correlated with film thickness and composition by AFM and XPS measurements, respectively. Resonant structures in the H{sup −}, O{sup −}, and OH{sup −} yield functions are attributed to the decay of transient anions into the dissociative electron attachment (DEA) channel. The diamine induces ammonium-phosphate bridges along the DNA backbone, which suppresses the DEA O{sup −} channel and in counter-part increases considerably the desorption of OH{sup −}. The close environment of the phosphate groups maymore » therefore play an important role in modulating the rate and type of DNA damages induced by low energy electrons.« less
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ERIC Educational Resources Information Center
Gilbert, George L., Ed.
1987-01-01
Provides instructions on conducting four demonstrations for the chemistry classroom. Outlines procedures for demonstrations dealing with coupled oscillations, the evaporation of liquids, thioxanthone sulfone radical anion, and the control of variables and conservation of matter. (TW)
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The goal of this research is to develop a USEPA method for the determination of sub-ppb concentrations of the perchlorate anion in ground and surface drinking waters. To date, ion chromatography using a KOH mobile phase, electrolytic conductivity suppression and electrospray ion...
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Tibbits, Andrew C; Yan, Yushan S; Kloxin, Christopher J
2017-07-01
Ene-functionalized ionic liquids with a range of different cationic groups and counteranions react stoichiometrically within a tetrathiol-divinyl ether formulation within 20 minutes to form thiol-ene polymers with measurable ionic conductivities via a photoinitiated polymerization and crosslinking reaction. Dynamic mechanical analysis indicates that these networks are more spatially heterogeneous and possess higher glass transition temperatures (T g ) compared with thiol-ene formulations without charge. While tuning the molar content of ionic liquid monomer is one method for adjusting the crosslink and charge densities of the thiol-ene polymeric ionic liquid networks, the presence of cation-anion interactions also plays a critical role in dictating the thermomechanical and conductive properties. Particularly, while cationic structure effects are not significant on the polymer properties, the use of a weakly coordinating hydrophobic anion (bistriflimide) instead of bromide-based networks results in an apparent decrease in hydrated ion conductivity (7.4 to 1.5 mS cm -1 ) and T g (-9.6 to -17.8 °C). © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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Locations of Halide Ions in Tetragonal Lysozyme Crystals
NASA Technical Reports Server (NTRS)
Lim, Kap; Adimurthy, Ganapathi; Nadarajah, Arunan; Forsythe, Elizabeth L.; Pusey, Marc L.
1998-01-01
Anions play an important role in the crystallization of lysozyme, and are known to bind to the crystalline protein. Previous studies employing X-ray crystallography had found one chloride ion binding site in the tetragonal crystal form of the protein and four nitrate ion binding sites in the monoclinic form. Studies using other approaches have reported more chloride ion binding sites, but their locations were not known. Knowing the precise location of these anions is also useful in determining the correct electrostatic fields surrounding the protein. In the first part of this study the anion positions in the tetragonal form were determined from the difference Fourier map obtained from the lysozyme crystals grown in bromide and chloride solutions under identical conditions. The anion locations were then obtained from standard crystallographic methods and five possible anion binding sites were found in this manner. The sole chloride ion binding site found in previous studies was confirmed. The remaining four sites were new ones for tetragonal lysozyme crystals. However, three of these new sites and the previously found one corresponded to the four unique binding sites found for nitrate ions in monoclinic crystals. This suggests that most of the anion binding sites in lysozyme remain unchanged, even when different anions and different crystal forms of lysozyme are employed. It is unlikely that there are many more anions in the tetragonal lysozyme crystal structure. Assuming osmotic equilibrium it can be shown that there are at most three more anions in the crystal channels. Some of the new anion binding sites found in this study were, as expected, in pockets containing basic residues. However, some of them were near neutral, but polar, residues. Thus, the study also showed the importance of uncharged, but polar groups, on the protein surface in determining its electrostatic field. This was important for the second part of this study where the electrostatic field surrounding the protein was accurately determined. This was achieved by solving the linearized version of the Poisson-Boltzmann equation for the protein in solution. The solution was computed employing the commercial code Delphi which uses a finite difference technique. This has recently become available as a module in the general protein visualization code Insight II. Partial charges were assigned to the polar groups of lysozyme for the calculations done here. The calculations showed the complexity of the electrostatic field surrounding the protein. Although most of the region near the protein surface had a positive field strength, the active site cleft was negatively charged and this was projected a considerable distance. This might explain the occurrence of "head-to-side" interactions in the formation of lysozyme aggregates in solution. Pockets of high positive field strength were also found in the vicinity of the anion locations obtained from the crystallographic part of this study, confirming the validity of these calculations. This study clearly shows not only the importance of determining the counterion locations in protein crystals and the electrostatic fields surrounding the protein, but also the advantage of performing them together.
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Gameiro, Armanda; Braams, Simona; Rauen, Thomas; Grewer, Christof
2011-06-08
Excitatory amino acid transporters (EAATs) control the glutamate concentration in the synaptic cleft by glial and neuronal glutamate uptake. Uphill glutamate transport is achieved by the co-/countertransport of Na(+) and other ions down their concentration gradients. Glutamate transporters also display an anion conductance that is activated by the binding of Na(+) and glutamate but is not thermodynamically coupled to the transport process. Of the five known glutamate transporter subtypes, the retina-specific subtype EAAT5 has the largest conductance relative to glutamate uptake activity. Our results suggest that EAAT5 behaves as a slow-gated anion channel with little glutamate transport activity. At steady state, EAAT5 was activated by glutamate, with a K(m)= 61 ± 11 μM. Binding of Na(+) to the empty transporter is associated with a K(m) = 229 ± 37 mM, and binding to the glutamate-bound form is associated with a K(m) = 76 ± 40 mM. Using laser-pulse photolysis of caged glutamate, we determined the pre-steady-state kinetics of the glutamate-induced anion current of EAAT5. This was characterized by two exponential components with time constants of 30 ± 1 ms and 200 ± 15 ms, which is an order of magnitude slower than those observed in other glutamate transporters. A voltage-jump analysis of the anion currents indicates that the slow activation behavior is caused by two slow, rate-limiting steps in the transport cycle, Na(+) binding to the empty transporter, and translocation of the fully loaded transporter. We propose a kinetic transport scheme that includes these two slow steps and can account for the experimentally observed data. Overall, our results suggest that EAAT5 may not act as a classical high-capacity glutamate transporter in the retina; rather, it may function as a slow-gated glutamate receptor and/or glutamate buffering system. Copyright © 2011 Biophysical Society. Published by Elsevier Inc. All rights reserved.
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Structure and size of ions electrochemically doped in conducting polymer
NASA Astrophysics Data System (ADS)
Kaneto, Keiichi; Hata, Fumito; Uto, Sadahito
2018-05-01
Among electroactive polymers (EAPs) for softactuators, conducting polymers have been intensively studied because of the large strain and stress caused by a low voltage operation. A larger deformation is desirable to extend their cycle life by reducing the operation voltage, and this is advantageous for their potential use in wider applications. The deformation is generated by the insertion of ions by electrochemical oxidation; hence, the magnitude of the strain depends on the bulkiness of the ions in the electrolytes. It is important, therefore, to clarify the structure and size of the ions during the electrochemical cycle, in order to achieve better performance of actuation. Anion and cation sizes (radii) in polypyrrole (PPy) film have been estimated using the precise measurement of strain against the amount of charge injected during the electrochemical cycles, assuming isotropic deformation of the film. The anion size was estimated using an anion-drive film, which was electrodeposited in TBABF4/methyl benzoate. The film was electrochemically cycled in sodium electrolytes, and the strain was measured simultaneously using a laser displacement meter. The cation size was obtained using a cation-drive film, being electropolymerized in aqueous dodecylbenzene sulfonic (DBS) acid. The cation-drive film was cycled in chloride electrolytes and measured the strain. The Cl-, Br-, NO3- , BF4- , and ClO4- radii were found to be approximately 235, 245, 250, 270 and 290 pm, respectively. The radii of K+, Na+ and Li+ were approximately 230, 237 and 274 pm, respectively. The results were discussed and took the crystalline ion radius and hydrated ion radius (Stokes radius) into consideration. It was found that the structure and size of the anions were slightly larger than the crystalline ion radius. Contrary to the anions, the cation radii were close to the hydrated ion radius, being larger than the crystalline ion radius.
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NASA Technical Reports Server (NTRS)
Haskins, Justin Bradley; Bennett, William Raymond; Wu, James J.; Hernandez, Dionne M.; Borodin, Oleg; Monk, Joshua D.; Bauschlicher, Charles W., Jr.; Watson, John W.
2014-01-01
Ionic liquid electrolytes have been proposed as a means of improving the safety and cycling behavior of advanced lithium batteries; however, the properties of these electrolytes under high lithium doping are poorly understood. Here, we employ both polarizable molecular dynamics simulation and experiment to investigate the structure, thermodynamics and transport of three potential electrolytes, N-methyl-N-butylpyrrolidinium bis(trifluoromethylsufonyl)imide ([pyr14][TFSI]), N- methyl-N-propylpyrrolidinium bis(fluorosufonyl)imide ([pyr13][FSI]), and 1-ethyl-3-- methylimidazolium boron tetrafluoride ([EMIM][BF4]), as a function of Li (-) salt concentration and temperature. Structurally, Li(+) is shown to be solvated by three anion neighbors in [pyr14][TFSI] and four anion neighbors in both [pyr13][FSI] and [EMIM][BF4], and at all levels of xLi we find the presence of lithium aggregates. Furthermore, the computed density, diffusion, viscosity, and ionic conductivity show excellent agreement with experimental data. While the diffusion and viscosity exhibit a systematic decrease and increase, respectively, with increasing xLi, the contribution of Li(+) to ionic conductivity increases until reaching a saturation doping level of xLi 0.10. Comparatively, the Li(+) conductivity of [pyr14][TFSI] is an order of magnitude lower than that of the other liquids, which range between 0.1-0.3 mScm. The differences in Li(+) transport are reflected in the residence times of Li(+) with the anions, which are revealed to be much larger for [pyr14][TFSI] (up to 100 ns at the highest doping levels) than in either [EMIM][BF4] or [pyr13][FSI]. Finally, we comment on the relative kinetics of Li(+) transport in each liquid and we present strong evidence for transport through anion exchange (hopping) as opposed to the net motion of Li(+) with its solvation shell (vehicular).
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NASA Technical Reports Server (NTRS)
Haskins, Justin B.; Bennett, William R.; Hernandez-Lugo, Dione M.; Wu, James; Borodin, Oleg; Monk, Joshua D.; Bauschlicher, Charles W.; Lawson, John W.
2014-01-01
Ionic liquid electrolytes have been proposed as a means of improving the safety and cycling behavior of advanced lithium batteries; however, the properties of these electrolytes under high lithium doping are poorly understood. Here, we employ both polarizable molecular dynamics simulation and experiment to investigate the structure, thermodynamics and transport of three potential electrolytes, N-methyl-Nbutylpyrrolidinium bis(trifluoromethylsufonyl)imide ([pyr14][TFSI]), N- methyl-Npropylpyrrolidinium bis(fluorosufonyl)imide ([pyr13][FSI]), and 1-ethyl-3-- methylimidazolium boron tetrafluoride ([EMIM][BF4]), as a function of Li-salt concentration and temperature. Structurally, Li(+) is shown to be solvated by three anion neighbors in [pyr14][TFSI] and four anion neighbors in both [pyr13][FSI] and [EMIM][BF4], and at all levels of x(sub Li) we find the presence of lithium aggregates. Furthermore, the computed density, diffusion, viscosity, and ionic conductivity show excellent agreement with experimental data. While the diffusion and viscosity exhibit a systematic decrease and increase, respectively, with increasing x(sub Li), the contribution of Li(+) to ionic conductivity increases until reaching a saturation doping level of x(sub Li) is approximately 0.10. Comparatively, the Li(+) conductivity of [pyr14][TFSI] is an order of magnitude lower than that of the other liquids, which range between 0.1 - 0.3 mS/cm. The differences in Li(+) transport are reflected in the residence times of Li(+) with the anions, which are revealed to be much larger for [pyr14][TFSI] (up to 100 ns at the highest doping levels) than in either [EMIM][BF4] or [pyr13][FSI]. Finally, we comment on the relative kinetics of Li(+) transport in each liquid and we present strong evidence for transport through anion exchange (hopping) as opposed to the net motion of Li(+) with its solvation shell (vehicular).
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Croce, F.; D`Aprano, A.; Nanjundiah, C.
1996-01-01
In order to determine the solution properties of lithium tris(trifluoromethanesulfonyl) methide (LiMe) in water and the aprotic solvents acetonitrile (AN), propylene carbonate (PC), N,N-dimethylformamide (DMF), and nitromethane (MeNO{sub 2}), conductance measurements have been carried out at 25 C. Molar conductivities at infinite dilution ({Lambda}{degree}) and ion pair association constants (K{sub a}) were obtained analyzing the experimental data with the Fuoss-Hsia conductance equation using the expansion of Fernandez-Prini and Justice with and without inclusion of the Chen effect. The results show that according to the ability of the solvents to solvate lithium ion, ion-pair formation is small or nonexistent in solventsmore » with high donor number (water, PC, DMF, and AN) but fairly moderate in nitromethane. Single-ion molar conductivities at infinite dilution for ClO{sub 4}{sup {minus}}, AsF{sub 6}{sup {minus}}, PF{sub 6}{sup {minus}} CF{sub 3}SO{sub 3}{sup {minus}}, N(CF{sub 3}SO{sub 2}){sub 2}{sup {minus}}, and C(CF{sub 3}SO{sub 2}){sub 3}{sup {minus}} anions, obtained by combining these results with literature data, decrease as expected as the ionic radius increases, and with one exception are always greater than that of the lithium ion. This general trend does not, however, apply in water where the limiting ionic conductance of the lithium cation is greater than that of the methide anion. This anomalous behavior is attributed to significant solvation of the methide ion in water. Voltammetric measurements indicate high electrochemical stability of methide anion. Such anodic stability and the increase in the transference number of lithium ion in LiMe solutions strongly support the use of this electrolyte in high energy, high voltage lithium batteries.« less
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Bolintineanu, Dan S.; Sayyed-Ahmad, Abdallah; Davis, H. Ted; Kaznessis, Yiannis N.
2009-01-01
Protegrin peptides are potent antimicrobial agents believed to act against a variety of pathogens by forming nonselective transmembrane pores in the bacterial cell membrane. We have employed 3D Poisson-Nernst-Planck (PNP) calculations to determine the steady-state ion conduction characteristics of such pores at applied voltages in the range of −100 to +100 mV in 0.1 M KCl bath solutions. We have tested a variety of pore structures extracted from molecular dynamics (MD) simulations based on an experimentally proposed octomeric pore structure. The computed single-channel conductance values were in the range of 290–680 pS. Better agreement with the experimental range of 40–360 pS was obtained using structures from the last 40 ns of the MD simulation, where conductance values range from 280 to 430 pS. We observed no significant variation of the conductance with applied voltage in any of the structures that we tested, suggesting that the voltage dependence observed experimentally is a result of voltage-dependent channel formation rather than an inherent feature of the open pore structure. We have found the pore to be highly selective for anions, with anionic to cationic current ratios (ICl−/IK+) on the order of 103. This is consistent with the highly cationic nature of the pore but surprisingly in disagreement with the experimental finding of only slight anionic selectivity. We have additionally tested the sensitivity of our PNP model to several parameters and found the ion diffusion coefficients to have a significant influence on conductance characteristics. The best agreement with experimental data was obtained using a diffusion coefficient for each ion set to 10% of the bulk literature value everywhere inside the channel, a scaling used by several other studies employing PNP calculations. Overall, this work presents a useful link between previous work focused on the structure of protegrin pores and experimental efforts aimed at investigating their conductance characteristics. PMID:19180178
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Castañeda-Bueno, María; Cervantes-Perez, Luz Graciela; Rojas-Vega, Lorena; Arroyo-Garza, Isidora; Vázquez, Norma; Moreno, Erika; Gamba, Gerardo
2014-06-15
Modulation of Na(+)-Cl(-) cotransporter (NCC) activity is essential to adjust K(+) excretion in the face of changes in dietary K(+) intake. We used previously characterized genetic mouse models to assess the role of Ste20-related proline-alanine-rich kinase (SPAK) and with-no-lysine kinase (WNK)4 in the modulation of NCC by K(+) diets. SPAK knockin and WNK4 knockout mice were placed on normal-, low-, or high-K(+)-citrate diets for 4 days. The low-K(+) diet decreased and high-K(+) diet increased plasma aldosterone levels, but both diets were associated with increased phosphorylation of NCC (phospho-NCC, Thr(44)/Thr(48)/Thr(53)) and phosphorylation of SPAK/oxidative stress responsive kinase 1 (phospho-SPAK/OSR1, Ser(383)/Ser(325)). The effect of the low-K(+) diet on SPAK phosphorylation persisted in WNK4 knockout and SPAK knockin mice, whereas the effects of ANG II on NCC and SPAK were lost in both mouse colonies. This suggests that for NCC activation by ANG II, integrity of the WNK4/SPAK pathway is required, whereas for the low-K(+) diet, SPAK phosphorylation occurred despite the absence of WNK4, suggesting the involvement of another WNK (WNK1 or WNK3). Additionally, because NCC activation also occurred in SPAK knockin mice, it is possible that loss of SPAK was compensated by OSR1. The positive effect of the high-K(+) diet was observed when the accompanying anion was citrate, whereas the high-KCl diet reduced NCC phosphorylation. However, the effect of the high-K(+)-citrate diet was aldosterone dependent, and neither metabolic alkalosis induced by bicarbonate, nor citrate administration in the absence of K(+) increased NCC phosphorylation, suggesting that it was not due to citrate-induced metabolic alkalosis. Thus, the accompanying anion might modulate the NCC response to the high-K(+) diet. Copyright © 2014 the American Physiological Society.
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Modulation of NCC activity by low and high K+ intake: insights into the signaling pathways involved
Castañeda-Bueno, María; Cervantes-Perez, Luz Graciela; Rojas-Vega, Lorena; Arroyo-Garza, Isidora; Vázquez, Norma; Moreno, Erika
2014-01-01
Modulation of Na+-Cl− cotransporter (NCC) activity is essential to adjust K+ excretion in the face of changes in dietary K+ intake. We used previously characterized genetic mouse models to assess the role of Ste20-related proline-alanine-rich kinase (SPAK) and with-no-lysine kinase (WNK)4 in the modulation of NCC by K+ diets. SPAK knockin and WNK4 knockout mice were placed on normal-, low-, or high-K+-citrate diets for 4 days. The low-K+ diet decreased and high-K+ diet increased plasma aldosterone levels, but both diets were associated with increased phosphorylation of NCC (phospho-NCC, Thr44/Thr48/Thr53) and phosphorylation of SPAK/oxidative stress responsive kinase 1 (phospho-SPAK/OSR1, Ser383/Ser325). The effect of the low-K+ diet on SPAK phosphorylation persisted in WNK4 knockout and SPAK knockin mice, whereas the effects of ANG II on NCC and SPAK were lost in both mouse colonies. This suggests that for NCC activation by ANG II, integrity of the WNK4/SPAK pathway is required, whereas for the low-K+ diet, SPAK phosphorylation occurred despite the absence of WNK4, suggesting the involvement of another WNK (WNK1 or WNK3). Additionally, because NCC activation also occurred in SPAK knockin mice, it is possible that loss of SPAK was compensated by OSR1. The positive effect of the high-K+ diet was observed when the accompanying anion was citrate, whereas the high-KCl diet reduced NCC phosphorylation. However, the effect of the high-K+-citrate diet was aldosterone dependent, and neither metabolic alkalosis induced by bicarbonate, nor citrate administration in the absence of K+ increased NCC phosphorylation, suggesting that it was not due to citrate-induced metabolic alkalosis. Thus, the accompanying anion might modulate the NCC response to the high-K+ diet. PMID:24761002
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Liu, Wan; Liang, Na; Peng, Pai
2017-02-15
Layered double hydroxides (LDH) are prepared by controlling urea assisted homogeneous precipitation conditions. Morphology and crystallinity of LDHs are confirmed by X-ray diffraction and scanning electron microscope. After LDHs are incorporated into quaternized polysulfone membranes, transmission electron microscope is used to observe the exfoliated morphology of LDH sheets in the membranes. The properties of the nanocomposite membranes, including water uptake, swelling ratio, mechanical property and ionic conductivity are investigated. The nanocomposite membrane containing 5% LDH sheets shows more balanced performances, exhibiting an ionic conductivity of 2.36×10{sup −2} S cm{sup −1} at 60 °C. - Graphical abstract: Anion-exchange membrane based onmore » quaternized polysulfone and exfoliated layered double hydroxide is optically transparent and has good ionic properties.« less
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Achieving Continuous Anion Transport Domains Using Block Copolymers Containing Phosphonium Cations
Zhang, Wenxu; Liu, Ye; Jackson, Aaron C.; ...
2016-06-22
Triblock and diblock copolymers based on isoprene (Ip) and chloromethylstyrene (CMS) were synthesized in this paper by sequential polymerization using reversible addition–fragmentation chain transfer radical polymerization (RAFT). The block copolymers were quaternized with tris(2,4,6-trimethoxyphenyl)phosphine (Ar 3P) to prepare soluble ionomers. The ionomers were cast from chloroform to form anion exchange membranes (AEMs) with highly ordered morphologies. At low volume fractions of ionic blocks, the ionomers formed lamellar morphologies, while at moderate volume fractions (≥30% for triblock and ≥22% for diblock copolymers) hexagonal phases with an ionic matrix were observed. Ion conductivities were higher through the hexagonal phase matrix than inmore » the lamellar phases. Finally, promising chloride conductivities (20 mS/cm) were achieved at elevated temperatures and humidified conditions.« less
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Zhao, Yue; Yoshimura, Kimio; Shishitani, Hideyuki; Yamaguchi, Susumu; Tanaka, Hirohisa; Koizumi, Satoshi; Szekely, Noemi; Radulescu, Aurel; Richter, Dieter; Maekawa, Yasunari
2016-02-07
We investigated the morphology and swelling behavior of a new graft-type of anion exchange membrane (AEM) containing 2-methylimidazolium groups by using a contrast variation small angle neutron scattering (SANS) technique. These AEMs were prepared by radiation-induced grafting of 2-methyl-1-vinylimidazole and styrene into poly(ethylene-co-tetrafluoroethylene) (ETFE) films and subsequent N-alkylation with methyliodide, and possessed both high alkaline durability and high conductivity. Our results showed that the crystalline lamellar and crystallite structures originating from the pristine ETFE films were more or less conserved in these AEMs, but the lamellar d-spacing in both dry and wet membranes was enlarged, indicating an expansion of the amorphous lamellae due to the graft chains introduced in the grafting process and the water incorporated in the swelling process. For the first time, the swelling behavior of the AEMs was studied quantitatively in various water mixtures of water and deuterated water with different volume ratios (contrast variation method), and the morphology of these membranes was elucidated by three phases: phase (1) crystalline ETFE domains, which offer good mechanical properties; phase (2) hydrophobic amorphous domains, which are made up of amorphous ETFE chains and offer a matrix to create conducting regions; phase (3) interconnected hydrated domains, which are composed of the entire graft chains and water and play a key role in promoting the conductivity.
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Harvesting polysulfides by sealing the sulfur electrode in a composite ion-selective net
NASA Astrophysics Data System (ADS)
Chen, Yazhou; Li, Zhong; Li, Xuekui; Zeng, Danli; Xu, Guodong; Zhang, Yunfeng; Sun, Yubao; Ke, Hanzhong; Cheng, Hansong
2017-11-01
A cathode was prepared by sealing a carbon supported sulfur electrode inside a composite ion-selective net made of carbon, binder and lithiated ionomer to restrict shuttling of polysulfide anionic species. As a result, the soluble polysulfide anions become unable to escape from the composite ion-selective films due to the electrostatic repulsion between the immobilized single ion conducting ionomers and the polysulfides with no dead angles. Experimentally, lithiated 4,4‧-difluoro bis(benzene sulfonyl)imide and PEG200 were copolymerized to form a polyether based single ion conducting polymer. The ionic conductivity of the blend film made of ionomer and poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) at a mass ratio of 1:1 is 0.57 mS cm-1 at room temperature. The battery capacity with the sealed sulfur electrode is 1412 mAh g-1 at 0.5 C, 1041 mAh g-1 at 1.0 C, 873 mAh g-1 at 2.0 C and 614 mAh g-1 at 5.0 C, significantly better than the results with lithiated Nafion especially at high C rates. In addition, a long cycling test at 2 C for 500 cycles gives rise to a stable capacity of 800 mAh g-1. The intrinsic electrostatic repulsion between polysulfide anions and the negatively charged electrolyte film, together with the overall sealed electrode configuration, is responsible for blocking the shuttling of polysulfides effectively.
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A bioartificial kidney device with polarized secretion of immune modulators.
Chevtchik, N V; Mihajlovic, M; Fedecostante, M; Bolhuis-Versteeg, L; Sastre Toraño, J; Masereeuw, R; Stamatialis, D
2018-05-15
The accumulation of protein-bound toxins in dialyzed patients is strongly associated with their high morbidity and mortality. The bioartificial kidney device (BAK), containing proximal tubule epithelial cells (PTEC) seeded on functionalized synthetic hollow fiber membranes (HFM), may be a powerful solution for the active removal of those metabolites. In an earlier study, we developed an upscaled BAK containing conditionally immortalized human PTEC (ciPTEC) with functional organic cationic transporter 2 (OCT2). Here, we first extended this development to a BAK device having cells with the organic anionic transporter 1 (OAT1), capable of removing anionic uremic wastes. We confirmed the quality of the ciPTEC monolayer by confocal microscopy and paracellular inulin-FITC leakage, as well as, by the active transport of anionic toxin, indoxyl sulfate (IS). Furthermore, we assessed the immune-safety of our system by measuring the production of relevant cytokines by the cells after lipopolysaccharide (LPS) stimulation. Upon LPS treatment, we observed a polarized secretion of pro-inflammatory cytokines by the cells: 10-fold higher in the extraluminal space, corresponding to the urine compartment, as compared to the intraluminal space, corresponding to the blood compartment. To the best of our knowledge, our work is the first to show this favorable cell polarization in a BAK upscaled device. This article is protected by copyright. All rights reserved.
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NASA Astrophysics Data System (ADS)
Wang, Wenxia; Huang, Guohe; An, Chunjiang; Xin, Xiaying; Zhang, Yan; Liu, Xia
2017-05-01
From the viewpoint of sustainability, biomass adsorbent has a high potential in pollution control and there is an emerging interest to investigate the behaviors of pollutants at the interface between biomass adsorbent and solution. This study investigated the performance of cetyltrimethylammonium bromide surfactant-modified flax shives (MFS) for removal of anionic azo dyes from aqueous solution. The equilibrium and kinetic analysis for the adsorption of Acid Orange 7 (AO-7), Acid Red 18 (AR-18) and Acid Black 1 (AB-1) on MFS were conducted. The surface of MFS was characterized by synchrotron infrared and SEM analysis. The absorbed amount of three anionic azo dyes varied with the change of adsorbent dosage, pH and ionic strength. The adsorption isotherm data well fit to the Langmuir model. The adsorption process followed the pseudo-second-order kinetics and the liquid film diffusion models. Thermodynamic studies indicated that the adsorption of three anionic azo dyes was spontaneous. The adsorption of AR-18 and AB-1 onto MFS was endothermic while the adsorption of AO-7 was exothermic. The results can help better understand the behaviors of organic pollutants at biomass adsorbent-water interface. They also present the potential of using MFS as a suitable adsorbent for the removal of anionic azo dyes from wastewater.
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Imoto, Yurika; Nishiyama, Hiroka; Nakamura, Yukihide; Ohira, Shin-Ichi; Toda, Kei
2018-05-01
A method to introduce target analytes to a chromatograph from a single drop of whole blood was investigated for minimally invasive monitoring of anionic pharmaceuticals. In this work, salicylate and loxoprofen were examined as organic anions. A micro ion extractor (MIE) has been developed for extraction of inorganic trace anions from whole blood, but this device is not suitable for extraction of pharmaceuticals. In the present study, we improved and optimized the MIE device for organic anion extraction. Various supported liquid membranes were evaluated for use as the ion transfer membrane, with each membrane placed between a droplet sample (donor) and an acceptor solution. A supported liquid membrane of porous polypropylene impregnated with 1-butanol was selected. In addition, the methods for electric field creation and electrode contact were examined to improve the characteristics of the MIE device. The current and extraction time were also optimized. With the optimized method, salicylate and loxoprofen were successfully extracted from a single drop of whole blood. Changes in the concentrations of these pharmaceuticals in blood over time were monitored after administration. As only 25μL of whole blood was required for analysis, repeat measurements could be conducted to monitor changes in the concentrations. This MIE will be useful for monitoring pharmaceutical concentrations in blood. Copyright © 2018 Elsevier B.V. All rights reserved.
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Fabrication of catalyzed ion transport membrane systems
Carolan, Michael Francis; Kibby, Charles Leonard
2013-06-04
Process for fabricating a catalyzed ion transport membrane (ITM). In one embodiment, an uncatalyzed ITM is (a) contacted with a non-reducing gaseous stream while heating to a temperature and for a time period sufficient to provide an ITM possessing anion mobility; (b) contacted with a reducing gaseous stream for a time period sufficient to provide an ITM having anion mobility and essentially constant oxygen stoichiometry; (c) cooled while contacting the ITM with the reducing gaseous stream to provide an ITM having essentially constant oxygen stoichiometry and no anion mobility; and (d) treated by applying catalyst to at least one of (1) a porous mixed conducting multicomponent metallic oxide (MCMO) layer contiguous with a first side of a dense layer of MCMO and (2) a second side of the dense MCMO layer. In another embodiment, these steps are carried out in the alternative order of (a), (d), (b), and (c).
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NASA Astrophysics Data System (ADS)
Li, Yun; Sniekers, Jeroen; Malaquias, João C.; Van Goethem, Cedric; Binnemans, Koen; Fransaer, Jan; Vankelecom, Ivo F. J.
2018-02-01
A stable and eco-friendly anion-exchange membrane (AEM) was prepared and applied in a non-aqueous all-copper redox flow battery (RFB). The AEM was prepared via a simple procedure, leading to a cross-linked structure containing quaternary ammonium groups without involvement of harmful trimethylamine. A network was thus constructed which ensured both ion transport and solvent resistance. The ion exchange capacity (IEC) of the membrane was tuned from 0.49 to 1.03 meq g-1 by varying the content of the 4, 4‧-bipyridine crosslinking agent. The membrane showed a good anion conductivity and retention of copper ions. As a proof of principle, a RFB single cell with this crosslinked membrane yielded a coulombic efficiency of 89%, a voltage efficiency of 61% and an energy efficiency of 54% at 7.5 mA cm-2.
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Goswami, Sathi; Sanyal, Sulagna; Chakraborty, Payal; Das, Chandrima; Sarkar, Munna
2017-08-01
NSAIDs are the most common class of painkillers and anti-inflammatory agents. They also show other functions like chemoprevention and chemosuppression for which they act at the protein but not at the genome level since they are mostly anions at physiological pH, which prohibit their approach to the poly-anionic DNA. Complexing the drugs with bioactive metal obliterate their negative charge and allow them to bind to the DNA, thereby, opening the possibility of genome level interaction. To test this hypothesis, we present the interaction of a traditional NSAID, Piroxicam and its copper complex with core histone and chromatin. Spectroscopy, DLS, and SEM studies were applied to see the effect of the interaction on the structure of histone/chromatin. This was coupled with MTT assay, immunoblot analysis, confocal microscopy, micro array analysis and qRT-PCR. The interaction of Piroxicam and its copper complex with histone/chromatin results in structural alterations. Such structural alterations can have different biological manifestations, but to test our hypothesis, we have focused only on the accompanied modulations at the epigenomic/genomic level. The complex, showed alteration of key epigenetic signatures implicated in transcription in the global context, although Piroxicam caused no significant changes. We have correlated such alterations caused by the complex with the changes in global gene expression and validated the candidate gene expression alterations. Our results provide the proof of concept that DNA binding ability of the copper complexes of a traditional NSAID, opens up the possibility of modulations at the epigenomic/genomic level. Copyright © 2017 Elsevier B.V. All rights reserved.
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Photoinduced Miyaura Borylation by a Rare Earth Photoreductant: the Hexachlorocerate(III) Anion.
Qiao, Yusen; Yang, Qiaomu; Schelter, Eric
2018-05-12
The first photoinduced sp2 carbon-heteroatom bond forming reaction by a rare earth photoreductant, a Miyaura borylation, has been achieved. This simple, scalable, and novel borylation method that makes use of the hexachlorocerate(III) anion, [CeIIICl6]3-, has a broad substrate scope and functional group tolerance and can be conducted at room temperature. Combined with Suzuki-Miyaura cross-coupling, the methodology is applicable to the synthesis of various biaryl products, including through the use of aryl chloride substrates. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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Plog, Stephanie; Klymiuk, Nikolai; Binder, Stefanie; Van Hook, Matthew J.; Thoreson, Wallace B.; Gruber, Achim D.; Mundhenk, Lars
2015-01-01
The human CLCA4 (chloride channel regulator, calcium-activated) modulates the intestinal phenotype of cystic fibrosis (CF) patients via an as yet unknown pathway. With the generation of new porcine CF models, species-specific differences between human modifiers of CF and their porcine orthologs are considered critical for the translation of experimental data. Specifically, the porcine ortholog to the human CF modulator gene CLCA4 has recently been shown to be duplicated into two separate genes, CLCA4a and CLCA4b. Here, we characterize the duplication product, CLCA4b, in terms of its genomic structure, tissue and cellular expression patterns as well as its in vitro electrophysiological properties. The CLCA4b gene is a pig-specific duplication product of the CLCA4 ancestor and its protein is exclusively expressed in small and large intestinal crypt epithelial cells, a niche specifically occupied by no other porcine CLCA family member. Surprisingly, a unique deleterious mutation of the CLCA4b gene is spread among modern and ancient breeds in the pig population, but this mutation did not result in an apparent phenotype in homozygously affected animals. Electrophysiologically, neither the products of the wild type nor of the mutated CLCA4b genes were able to evoke a calcium-activated anion conductance, a consensus feature of other CLCA proteins. The apparently pig-specific duplication of the CLCA4 gene with unique expression of the CLCA4b protein variant in intestinal crypt epithelial cells where the porcine CFTR is also present raises the question of whether it may modulate the porcine CF phenotype. Moreover, the naturally occurring null variant of CLCA4b will be valuable for the understanding of CLCA protein function and their relevance in modulating the CF phenotype. PMID:26474299
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NASA Astrophysics Data System (ADS)
Belin, Renaud; Aldon, Laurent; Zerouale, Abdel; Belin, Claude; Ribes, Michel
2001-03-01
Single crystals of the Ag 6.69GeSe 5I 0.69 phase have been obtained by iodine transport of the iodine-partially substituted stoichiometric argyrodite compound Ag 7GeSe 5I. This phase crystallizes in the cubic space group F4¯3 m (argyrodite γ-phase, a=10.921(2) Å at -100°C, a=10.972(3) Å at 25°C, Z=4). It is highly disordered both at anion and cation sites. Crystal structure refinements were completed by an anharmonic Gram-Charlier development of the atomic displacement factors of iodine and silver atoms. The structure of Ag 6.69GeSe 5I 0.69 was determined at -100°C and +25°C and was refined to R( F) values of 5.80 and 6.51%, respectively. Both iodine and selenium (Se1) anions have been found disordered and iodine is slightly defective on its crystallographic site. This is correlated to the disorder observed for the two Ag1 and Ag2 cations that provides this material with superionic conducting properties. Analysis of the joint probability density function allowed the visualization of the Ag + diffusion paths within the anionic framework.
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Copper complexes of anionic nitrogen ligands in the amidation and imidation of aryl halides.
Tye, Jesse W; Weng, Zhiqiang; Johns, Adam M; Incarvito, Christopher D; Hartwig, John F
2008-07-30
Copper(I) imidate and amidate complexes of chelating N,N-donor ligands, which are proposed intermediates in copper-catalyzed amidations of aryl halides, have been synthesized and characterized by X-ray diffraction and detailed solution-phase methods. In some cases, the complexes adopt neutral, three-coordinate trigonal planar structures in the solid state, but in other cases they adopt an ionic form consisting of an L 2Cu (+) cation and a CuX 2 (-) anion. A tetraalkylammonium salt of the CuX 2 (-) anion in which X = phthalimidate was also isolated. Conductivity measurements and (1)H NMR spectra of mixtures of two complexes all indicate that the complexes exist predominantly in the ionic form in DMSO and DMF solutions. One complex was sufficiently soluble for conductance measurements in less polar solvents and was shown to adopt some degree of the ionic form in THF and predominantly the neutral form in benzene. The complexes containing dative nitrogen ligands reacted with iodoarenes and bromoarenes to form products from C-N coupling, but the ammonium salt of [Cu(phth) 2] (-) did not. Similar selectivities for stoichiometric and catalytic reactions with two different iodoarenes and faster rates for the stoichiometric reactions implied that the isolated amidate and imidate complexes are intermediates in the reactions of amides and imides with haloarenes catalyzed by copper complexes containing dative N,N ligands. These amidates and imidates reacted much more slowly with chloroarenes, including chloroarenes that possess more favorable reduction potentials than some bromoarenes and that are known to undergo fast dissociation of chloride from the chloroarene radical anion. The reaction of o-(allyloxy)iodobenzene with [(phen) 2Cu][Cu(pyrr) 2] results in formation of the C-N coupled product in high yield and no detectable amount of the 3-methyl-2,3-dihydrobenzofuran or 3-methylene-2,3-dihydrobenzofuran products that would be expected from a reaction that generated free radicals. These data and computed reaction barriers argue against mechanisms in which the haloarene reacts with a two-coordinate anionic copper species and mechanisms that start with electron transfer to generate a free iodoarene radical anion. Instead, these data are more consistent with mechanisms involving cleavage of the carbon-halogen bond within the coordination sphere of the metal.
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Synthesis and Properties of a Clean and Sustainable Deicing Additive for Asphalt Mixture
Peng, Chao; Yu, Jianying; Zhao, Zhijie; Dai, Jing; Fu, Jingyi; Zhao, Meiling; Wang, Wei
2015-01-01
A clean and sustainable deicing additive was prepared via the adsorption of acetate anions (Ac-) by magnesium (Mg) and aluminum (Al) calcined layered double hydroxide (Mg/Al-CLDH). Fourier transform infrared spectroscopy spectrums proved that Ac- had intercalated into LDH structure. X-ray diffraction patterns, scanning electron microscopy and transmission electron microscopy images showed that the intercalation spacing and platelet thickness of Mg and Al layered double hydroxide containing Ac- anions (Mg/Al-Ac- LDH) had been enlarged due to substitution of divalent CO3 2- anions by a larger quantity of monovalent Ac– anions. Differential scanning calorimetry tests testified that the insoluble Mg2/Al-Ac- LDH evidently decreased the freeze point (FP) of water to -10.68°C. X-ray photoelectron spectroscopy analyses confirmed that the Ac- were strongly confined by the metal layers of LDHs. FP test of asphalt mixtures confirmed that Mg/Al-Ac- LDHs reduced FP to -5.5°C. Immersion test results indicated that Mg/Al-Ac- LDH had a good deicing durability and Ac- did not released from asphalt mixture. Snow melting observation was conducted further testified that Mg/Al-Ac- LDH melted snow or ice sustainably. PMID:25625279
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Synthesis and properties of a clean and sustainable deicing additive for asphalt mixture.
Peng, Chao; Yu, Jianying; Zhao, Zhijie; Dai, Jing; Fu, Jingyi; Zhao, Meiling; Wang, Wei
2015-01-01
A clean and sustainable deicing additive was prepared via the adsorption of acetate anions (Ac-) by magnesium (Mg) and aluminum (Al) calcined layered double hydroxide (Mg/Al-CLDH). Fourier transform infrared spectroscopy spectrums proved that Ac- had intercalated into LDH structure. X-ray diffraction patterns, scanning electron microscopy and transmission electron microscopy images showed that the intercalation spacing and platelet thickness of Mg and Al layered double hydroxide containing Ac- anions (Mg/Al-Ac- LDH) had been enlarged due to substitution of divalent CO32- anions by a larger quantity of monovalent Ac- anions. Differential scanning calorimetry tests testified that the insoluble Mg2/Al-Ac- LDH evidently decreased the freeze point (FP) of water to -10.68°C. X-ray photoelectron spectroscopy analyses confirmed that the Ac- were strongly confined by the metal layers of LDHs. FP test of asphalt mixtures confirmed that Mg/Al-Ac- LDHs reduced FP to -5.5°C. Immersion test results indicated that Mg/Al-Ac- LDH had a good deicing durability and Ac- did not released from asphalt mixture. Snow melting observation was conducted further testified that Mg/Al-Ac- LDH melted snow or ice sustainably.
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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
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NASA Astrophysics Data System (ADS)
Saba, H.; Yumei, Z.; Huaping, W.
2015-12-01
Densities, refractive indices, conductivities and viscosities of binary mixtures of 1-ethyl-3-methylimidazolium-based ionic liquids (ILs) with dimethyl sulfoxide at 298.15 K are reported. Excess molar volumes have been calculated from experimental data and were fitted with Redlich-Kister equation. The density and refractive index were found to increase with increasing concentration in all cases except [EMIM]COOH. The free mobility of ions has found to enhance conductivity and decrease viscosity to varying extent in all mixtures being studied. It has been observed that solubility parameters, dielectric constants and nature of anions of ILs being used play a vital role in determining the subsequent characteristics. As DMSO has high dielectric constant therefore, it was able to form interactions with most of ILs except with [EMIM]COOH due to anomalous nature of anion.
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NASA Astrophysics Data System (ADS)
Kizewski, Jamie Peter; Mudri, Nurul H.; Varcoe, John R.
2013-08-01
The application of alkaline anion-exchange membranes (AAEM) in solid alkaline fuel cells is growing in prominence mainly due to enhanced tolerance to carbon dioxide, compared to alkaline fuel cells containing aqueous electrolytes, and the potential for using non precious metal catalysts. Radiation grafting is a common methodology for the production of functional polymers and membranes. This statistical study examines the synthesis of radiation grafted AAEMs that are formed from electron beam irradiated poly(ethylene-co-tetrafluoroethylene), EB-ETFE. It is shown that EB-ETFE can be cold stored for at least 16 months and still be used to produce ionically conductive AAEMs. The limitations of routine measurements of properties, such as dimensional increases, ion-exchange capacity, water uptakes and ionic conductivities, are also highlighted.
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Kobrin, Eeva-Gerda; Lees, Heidi; Fomitšenko, Maria; Kubáň, Petr; Kaljurand, Mihkel
2014-04-01
A portable capillary electrophoretic system with contactless conductivity detection was used for fingerprint analysis of postblast explosive residues from commercial organic and improvised inorganic explosives on various surfaces (sand, concrete, metal witness plates). Simple extraction methods were developed for each of the surfaces for subsequent simultaneous capillary electrophoretic analysis of anions and cations. Dual-opposite end injection principle was used for fast (<4 min) separation of 10 common anions and cations from postblast residues using an optimized separation electrolyte composed of 20 mM MES, 20 mM l-histidine, 30 μM CTAB and 2 mM 18-crown-6. The concentrations of all ions obtained from the electropherograms were subjected to principal component analysis to classify the tested explosives on all tested surfaces, resulting in distinct cluster formations that could be used to verify (each) type of the explosive. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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Bitner-Michalska, Anna; Nolis, Gene M.; Żukowska, Grażyna; Zalewska, Aldona; Poterała, Marcin; Trzeciak, Tomasz; Dranka, Maciej; Kalita, Michał; Jankowski, Piotr; Niedzicki, Leszek; Zachara, Janusz; Marcinek, Marek; Wieczorek, Władysław
2017-01-01
A new family of fluorine-free solid-polymer electrolytes, for use in sodium-ion battery applications, is presented. Three novel sodium salts withdiffuse negative charges: sodium pentacyanopropenide (NaPCPI), sodium 2,3,4,5-tetracyanopirolate (NaTCP) and sodium 2,4,5-tricyanoimidazolate (NaTIM) were designed andtested in a poly(ethylene oxide) (PEO) matrix as polymer electrolytes for anall-solid sodium-ion battery. Due to unique, non-covalent structural configurations of anions, improved ionic conductivities were observed. As an example, “liquid-like” high conductivities (>1 mS cm−1) were obtained above 70 °C for solid-polymer electrolyte with a PEO to NaTCP molar ratio of 16:1. All presented salts showed high thermal stability and suitable windows of electrochemical stability between 3 and 5 V. These new anions open a new class of compounds with non-covalent structure for electrolytes system applications. PMID:28067301
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NASA Astrophysics Data System (ADS)
Bitner-Michalska, Anna; Nolis, Gene M.; Żukowska, Grażyna; Zalewska, Aldona; Poterała, Marcin; Trzeciak, Tomasz; Dranka, Maciej; Kalita, Michał; Jankowski, Piotr; Niedzicki, Leszek; Zachara, Janusz; Marcinek, Marek; Wieczorek, Władysław
2017-01-01
A new family of fluorine-free solid-polymer electrolytes, for use in sodium-ion battery applications, is presented. Three novel sodium salts withdiffuse negative charges: sodium pentacyanopropenide (NaPCPI), sodium 2,3,4,5-tetracyanopirolate (NaTCP) and sodium 2,4,5-tricyanoimidazolate (NaTIM) were designed andtested in a poly(ethylene oxide) (PEO) matrix as polymer electrolytes for anall-solid sodium-ion battery. Due to unique, non-covalent structural configurations of anions, improved ionic conductivities were observed. As an example, “liquid-like” high conductivities (>1 mS cm-1) were obtained above 70 °C for solid-polymer electrolyte with a PEO to NaTCP molar ratio of 16:1. All presented salts showed high thermal stability and suitable windows of electrochemical stability between 3 and 5 V. These new anions open a new class of compounds with non-covalent structure for electrolytes system applications.
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Pezeshki, Alan M.; Fujimoto, Cy; Sun, Che -Nan; ...
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/cm 2.« less
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NASA Astrophysics Data System (ADS)
Ran, Jin; Wu, Liang; Wei, Bing; Chen, Yaoyao; Xu, Tongwen
2014-09-01
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.
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NASA Astrophysics Data System (ADS)
Mokhtaruddin, Nur Shuhada Mohd; Yusof, Enis Nadia Md; Ravoof, Thahira B. S. A.; Tiekink, Edward R. T.; Veerakumarasivam, Abhi; Tahir, Mohamed Ibrahim Mohamed
2017-07-01
Three tridentate Schiff bases containing N and S donor atoms were synthesized via the condensation reaction between S-2-methylbenzyldithiocarbazate with 2-acetyl-4-methylpyridine (S2APH); 4-methyl-3-thiosemicarbazide with 2-acetylpyridine (MT2APH) and 4-ethyl-3-thiosemicarbazide with 2-acetylpyridine (ET2APH). Three new, binuclear and mixed-ligand copper(II) complexes with the general formula, [Cu(sac)(L)]2 (sac = saccharinate anion; L = anion of the Schiff base) were then synthesized, and subsequently characterized by IR and UV/Vis spectroscopy as well as by molar conductivity and magnetic susceptibility measurements. The Schiff bases were also spectroscopically characterized using NMR and MS to further confirm their structures. The spectroscopic data indicated that the Schiff bases behaved as a tridentate NNS donor ligands coordinating via the pyridyl-nitrogen, azomethine-nitrogen and thiolate-sulphur atoms. Magnetic data indicated a square pyramidal environment for the complexes and the conductivity values showed that the complexes were essentially non-electrolytes in DMSO. The X-ray crystallographic analysis of one complex, [Cu(sac)(S2AP)]2 showed that the Cu(II) atom was coordinated to the thiolate-S, azomethine-N and pyridyl-N donors of the S2AP Schiff base and to the saccharinate-N from one anion, as well as to the carbonyl-O atom from a symmetry related saccharinate anion yielding a centrosymmetric binuclear complex with a penta-coordinate, square pyramidal geometry. All the copper(II) saccharinate complexes were found to display strong cytotoxic activity against the MCF-7 and MDA-MB-231 human breast cancer cell lines.
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NASA Astrophysics Data System (ADS)
Satsukawa, Hidetaka; Yajima, Akio; Hiraki, Ko-ichi; Takahashi, Toshihiro; Kang, Haeyong; Jo, Younjung; Kang, Woun; Chung, Ok-Hee
2016-12-01
We performed 77Se- and 19F-NMR measurements on single crystals of (TMTSF)2FSO3 to characterize the electronic structures of different phases in the temperature-pressure phase diagram, determined by precise transport measurements [Jo et al.,
Phys. Rev. B 67, 014516 (2003) ]. We claim that such varieties of electronic states in the refined phase diagram are caused by strong couplings of the conduction electrons with FSO3 anions, especially with the permanent electric dipoles on the anions. We suggest that as temperature decreases, the FSO3 anions form orientational ordering through two steps; first, only the tetrahedrons form an orientational order leaving the orientations of the electronic dipoles in random (transition I); then the dipoles form a perfect orientational order at a lower temperature (transition II). In the intermediate temperature range between transitions I and II, we found an appreciable enhancement of homogeneous and inhomogeneous widths of the 77Se-NMR spectrum. From the analysis of the angular dependence of the linewidth, we attributed these anomalies to the intramolecular charge disproportionation or imbalance and its slow dynamics caused by the coupling with the permanent electric dipole of the anion. Results of 19F-NMR relaxation and lineshape measurements support this picture very well. Electronic structures at higher pressures up to 1.25 GPa are discussed on the basis of the results of the 77Se- and 19F-NMR measurements. -
Tamilvanan, Shunmugaperumal; Khanum, Ramona; Senthilkumar, Sudalimuthu Ramachandran; Muthuraman, Marimuthu; Rajasekharan, Thenrajan
2013-10-01
Ocular and parenteral application potentials of azithromycin-containing, non-phospholipid-based cationic nanosized emulsion in comparison to the phospholipid-based anionic and neutral-charged nanosized emulsions were investigated. Various physical, chemical, nonclinical toxicity and antimicrobial activity studies (mean droplet diameter, surface charge, creaming index, entrapment efficiency, accelerated, long-term and freeze-thaw cycling stabilities, TLC study, modified hen's egg chorioallantoic membrane (HET-CAM) test, in vitro hemolysis test, in vitro and in vivo myotoxicity, and in vitro antimicrobial activity) were conducted for assessing the potentials of these three types of emulsions. Following autoclave sterilization, all of these emulsions exhibited a nanometer range mean particle diameter (200 ± 29 to 434 ± 13 nm). While the anionic and cationic emulsions did show high negative (-34.2 ± 1.23 mV) and positive zeta potential (42.6 ± 1.45 mV) values, the neutral-charged emulsion did not. Even with 5 freeze-thaw cycles, the cationic emulsion remained stable whereas other two emulsions underwent phase-separation. The hen's egg chorioallantoic membrane test revealed an irritation score value that was higher for the anionic emulsion than for cationic or neutral-charged emulsion. A significantly higher % hemolysis value was also noticed for the anionic emulsion when compared to the % hemolysis value of cationic emulsion (ANOVA, P ‹ 0.05). However, all of the emulsions showed a lesser intracellular creatine kinase (CK) release/plasma CK level in comparison to the positive control (phenytoin) indicating their lesser myotoxicity at the injection site . When compared to anionic and neutral-charged emulsions, the possible controlled drug release from cationic emulsion delayed the in vitro antimicrobial action against H.influenzae and S.pneumoniae.
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Molecular Evolution of Slow and Quick Anion Channels (SLACs and QUACs/ALMTs)
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
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Molecular Evolution of Slow and Quick Anion Channels (SLACs and QUACs/ALMTs).
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.
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NASA Astrophysics Data System (ADS)
Lambert, Jason; Chen, Jing; Buonaugurio, Angela; Bowen, Kit H.; Do-Thanh, Chi-Linh; Wang, Yilin; Best, Michael D.; Compton, R. N.; Sommerfeld, Thomas
2013-12-01
After synthesizing the compounds N-paranitrophenylsulfonylalanine (NPNPSA) and N-paranitrophenylalanine (NPNPA), the photoelectron spectrum of the valence anion of N-paranitrophenylsulfonylalanine (NPNPSA)-, was measured and the collision-induced dissociation (CID) pathways of deprotonated N-paranitrophenylsulfonylalanine (NPNPSA-H)- and deprotonated N-paranitrophenylalanine (NPNPA-H)- were determined. Pertinent calculations were conducted to analyze both sets of experimental data. From the valence anion photoelectron spectrum of (NPNPSA)-, the adiabatic electron affinity (AEA) of NPNPSA was determined to be 1.7 ± 0.1 eV, while the vertical detachment energy (VDE) of (NPNPSA)- was found to be 2.3 ± 0.1 eV. Calculations for four low lying conformers of (NPNPSA)- gave AEA values in the range of 1.6-2.1 eV and VDE values in the range of 2.0-2.4 eV. These calculations are in very good agreement with the experimental values. While the NPNPA anion (NPNPSA)- was not observed experimentally it was studied computationally. The six low lying (NPNPSA)- conformers were identified and calculated to have AEA values in the range of 0.7-1.2 eV and VDE values in the range of 0.9-1.6 eV. CID was used to study the fragmentation patterns of deprotonated NPNPA and deprotonated NPNPSA. Based on the CID data and calculations, the excess charge was located on the delocalized π-orbitals of the nitrobenzene moiety. This is made evident by the fact that the dominant fragments all contained the nitrobenzene moiety even though the parent anions used for the CID study were formed via deprotonation of the carboxylic acid. The dipole-bound anions of both molecules are studied theoretically using the results of previous studies on nitrobenzene as a reference.
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Lambert, Jason; Chen, Jing; Buonaugurio, Angela; Bowen, Kit H; Do-Thanh, Chi-Linh; Wang, Yilin; Best, Michael D; Compton, R N; Sommerfeld, Thomas
2013-12-14
After synthesizing the compounds N-paranitrophenylsulfonylalanine (NPNPSA) and N-paranitrophenylalanine (NPNPA), the photoelectron spectrum of the valence anion of N-paranitrophenylsulfonylalanine (NPNPSA)(-), was measured and the collision-induced dissociation (CID) pathways of deprotonated N-paranitrophenylsulfonylalanine (NPNPSA-H)(-) and deprotonated N-paranitrophenylalanine (NPNPA-H)(-) were determined. Pertinent calculations were conducted to analyze both sets of experimental data. From the valence anion photoelectron spectrum of (NPNPSA)(-), the adiabatic electron affinity (AEA) of NPNPSA was determined to be 1.7 ± 0.1 eV, while the vertical detachment energy (VDE) of (NPNPSA)(-) was found to be 2.3 ± 0.1 eV. Calculations for four low lying conformers of (NPNPSA)(-) gave AEA values in the range of 1.6-2.1 eV and VDE values in the range of 2.0-2.4 eV. These calculations are in very good agreement with the experimental values. While the NPNPA anion (NPNPSA)(-) was not observed experimentally it was studied computationally. The six low lying (NPNPSA)(-) conformers were identified and calculated to have AEA values in the range of 0.7-1.2 eV and VDE values in the range of 0.9-1.6 eV. CID was used to study the fragmentation patterns of deprotonated NPNPA and deprotonated NPNPSA. Based on the CID data and calculations, the excess charge was located on the delocalized π-orbitals of the nitrobenzene moiety. This is made evident by the fact that the dominant fragments all contained the nitrobenzene moiety even though the parent anions used for the CID study were formed via deprotonation of the carboxylic acid. The dipole-bound anions of both molecules are studied theoretically using the results of previous studies on nitrobenzene as a reference.
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NASA Astrophysics Data System (ADS)
Tiruye, Girum Ayalneh; Muñoz-Torrero, David; Palma, Jesus; Anderson, Marc; Marcilla, Rebeca
2016-09-01
Four Ionic Liquid based Polymer Electrolytes (IL-b-PE) were prepared by blending a Polymeric Ionic Liquid, Poly(diallyldimethylammonium) bis(trifluoromethanesulfonyl)imide (PILTFSI), with four different ionic liquids: 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14TFSI) (IL-b-PE1), 1-butyl-1-methylpyrrolidinium bis(fluorosulfonyl)imide (PYR14FSI) (IL-b-PE2), 1-(2-hydroxy ethyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (HEMimTFSI) (IL-b-PE3), and 1-Butyl-1-methylpyrrolidinium dicyanamide, (PYR14DCA) (IL-b-PE4). Physicochemical properties of IL-b-PE such as ionic conductivity, thermal and electrochemical stability were found to be dependent on the IL properties. For instance, ionic conductivity was significantly higher for IL-b-PE2 and IL-b-PE4 containing IL with small size anions (FSI and DCA) than IL-b-PE1 and IL-b-PE3 bearing IL with bigger anion (TFSI). On the other hand, wider electrochemical stability window (ESW) was found for IL-b-PE1 and IL-b-PE2 having ILs with electrochemically stable pyrrolidinium cation and FSI and TFSI anions. Solid state Supercapacitors (SCs) were assembled with activated carbon electrodes and their electrochemical performance was correlated with the polymer electrolyte properties. Best performance was obtained with SC having IL-b-PE2 that exhibited a good compromise between ionic conductivity and electrochemical window. Specific capacitance (Cam), real energy (Ereal) & real power densities (Preal) as high as 150 F g-1, 36 Wh kg-1 & 1170 W kg-1 were found at operating voltage of 3.5 V.
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Benzoate-Induced High-Nuclearity Silver Thiolate Clusters.
Su, Yan-Min; Liu, Wei; Wang, Zhi; Wang, Shu-Ao; Li, Yan-An; Yu, Fei; Zhao, Quan-Qin; Wang, Xing-Po; Tung, Chen-Ho; Sun, Di
2018-04-03
Compared with the well-known anion-templated effects in shaping silver thiolate clusters, the influence from the organic ligands in the outer shell is still poorly understood. Herein, three new benzoate-functionalized high-nuclearity silver(I) thiolate clusters are isolated and characterized for the first time in the presence of diverse anion templates such as S 2- , α-[Mo 5 O 18 ] 6- , and MoO 4 2- . Single-crystal X-ray analysis reveals that the nuclearities of the three silver clusters (SD/Ag28, SD/Ag29, SD/Ag30) vary from 32 to 38 to 78 with co-capped tBuS - and benzoate ligands on the surface. SD/Ag28 is a turtle-like cluster comprising a Ag 29 shell caging a Ag 3 S 3 trigon in the center, whereas SD/Ag29 is a prolate Ag 38 sphere templated by the α-[Mo 5 O 18 ] 6- anion. Upon changing from benzoate to methoxyl-substituted benzoate, SD/Ag30 is isolated as a very complicated core-shell spherical cluster composed of a Ag 57 shell and a vase-like Ag 21 S 13 core. Four MoO 4 2- anions are arranged in a supertetrahedron and located in the interstice between the core and shell. Introduction of the bulky benzoate changes elaborately the nuclearity and arrangements of silver polygons on the shell of silver clusters, which is exemplified by comparing SD/Ag28 and a known similar silver thiolate cluster. The three new clusters emit luminescence in the near-infrared (NIR) region and show different thermochromic luminescence properties. This work presents a flexible approach to synthetic studies of high-nuclearity silver clusters decorated by different benzoates, and structural modulations are also achieved. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
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Restaino, Odile Francesca; Finamore, Rosario; Diana, Paola; Marseglia, Mariacarmela; Vitiello, Mario; Casillo, Angela; Bedini, Emiliano; Parrilli, Michelangelo; Corsaro, Maria Michela; Trifuoggi, Marco; De Rosa, Mario; Schiraldi, Chiara
2017-03-15
Chondroitin sulfate is a glycosaminoglycan widely used as active principle of anti-osteoarthritis drugs and nutraceuticals, manufactured by extraction from animal cartilaginous tissues. During the manufacturing procedures, another glycosaminoglycan, the keratan sulfate, might be contemporarily withdrawn, thus eventually constituting a contaminant difficult to be determined because of its structural similarity. Considering the strict regulatory rules on the pureness of pharmaceutical grade chondrotin sulfate there is an urgent need and interest to determine the residual keratan sulfate with specific, sensitive and reliable methods. To pursue this aim, in this paper, for the first time, we set up a multi-analytical and preparative approach based on: i) a newly developed method by high performance anion-exchange chromatography with pulsed amperometric detection, ii) gas chromatography-mass spectrometry analyses, iii) size exclusion chromatography analyses coupled with triple detector array module and on iv) strong anion exchange chromatography separation. Varied KS percentages, in the range from 0.1 to 19.0% (w/w), were determined in seven pharmacopeia and commercial standards and nine commercial samples of different animal origin and manufacturers. Strong anion exchange chromatography profiles of the samples showed three or four different peaks. These peaks analyzed by high performance anion-exchange with pulsed amperometric detection and size exclusion chromatography with triple detector array, ion chromatography and by mono- or two-dimensional nuclear magnetic resonance revealed a heterogeneous composition of both glycosaminoglycans in terms of sulfation grade and molecular weight. High molecular weight species (>100 KDa) were also present in the samples that counted for chains still partially linked to a proteoglycan core. Copyright © 2016 The Author(s). Published by Elsevier B.V. All rights reserved.
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Protein destabilisation in ionic liquids: the role of preferential interactions in denaturation.
Figueiredo, Angelo Miguel; Sardinha, Joao; Moore, Geoffrey R; Cabrita, Eurico J
2013-12-07
The preferential binding of anions and cations in aqueous solutions of the ionic liquids (ILs) 1-butyl-3-methylimidazolium ([C4mim](+)) and 1-ethyl-3-methylimidazolium ([C2mim](+)) chloride and dicyanamide (dca(-)) with the small alpha-helical protein Im7 was investigated using a combination of differential scanning calorimetry, NMR spectroscopy and molecular dynamics (MD) simulations. Our results show that direct ion interactions are crucial to understand the effects of ILs on the stability of proteins and that an anion effect is dominant. We show that the binding of weakly hydrated anions to positively charged or polar residues leads to the partial dehydration of the backbone groups, and is critical to control stability, explaining why dca(-) is more denaturing than Cl(-). Direct cation-protein interactions also mediate stability; cation size and hydrophobicity are relevant to account for destabilisation as shown by the effect of [C4mim](+) compared to [C2mim](+). The specificity in the interaction of IL ions with protein residues established by weak favourable interactions is confirmed by NMR chemical shift perturbation, amide hydrogen exchange data and MD simulations. Differences in specificity are due to the balance of interaction established between ion pairs and ion-solvent that determine the type of residues affected. When the interaction of both cation and anion with the protein is strong the net result is similar to a non-specific interaction, leading ultimately to unfolding. Since the nature of the ions is a determinant of the level of interaction with the protein towards denaturation or stabilisation, ILs offer a unique possibility to modulate protein stabilisation or even folding events.
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Transition Metal-Involved Photon Upconversion.
Ye, Shi; Song, En-Hai; Zhang, Qin-Yuan
2016-12-01
Upconversion (UC) luminescence of lanthanide ions (Ln 3+ ) has been extensively investigated for several decades and is a constant research hotspot owing to its fundamental significance and widespread applications. In contrast to the multiple and fixed UC emissions of Ln 3+ , transition metal (TM) ions, e.g., Mn 2+ , usually possess a single broadband emission due to its 3 d 5 electronic configuration. Wavelength-tuneable single UC emission can be achieved in some TM ion-activated systems ascribed to the susceptibility of d electrons to the chemical environment, which is appealing in molecular sensing and lighting. Moreover, the UC emissions of Ln 3+ can be modulated by TM ions (specifically d -block element ions with unfilled d orbitals), which benefits from the specific metastable energy levels of Ln 3+ owing to the well-shielded 4 f electrons and tuneable energy levels of the TM ions. The electric versatility of d 0 ion-containing hosts ( d 0 normally viewed as charged anion groups, such as MoO 6 6- and TiO 4 4- ) may also have a strong influence on the electric dipole transition of Ln 3+ , resulting in multifunctional properties of modulated UC emission and electrical behaviour, such as ferroelectricity and oxide-ion conductivity. This review focuses on recent advances in the room temperature (RT) UC of TM ions, the UC of Ln 3+ tuned by TM or d 0 ions, and the UC of d 0 ion-centred groups, as well as their potential applications in bioimaging, solar cells and multifunctional devices.
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Transition Metal‐Involved Photon Upconversion
Song, En‐Hai
2016-01-01
Upconversion (UC) luminescence of lanthanide ions (Ln3+) has been extensively investigated for several decades and is a constant research hotspot owing to its fundamental significance and widespread applications. In contrast to the multiple and fixed UC emissions of Ln3+, transition metal (TM) ions, e.g., Mn2+, usually possess a single broadband emission due to its 3d 5 electronic configuration. Wavelength‐tuneable single UC emission can be achieved in some TM ion‐activated systems ascribed to the susceptibility of d electrons to the chemical environment, which is appealing in molecular sensing and lighting. Moreover, the UC emissions of Ln3+ can be modulated by TM ions (specifically d‐block element ions with unfilled d orbitals), which benefits from the specific metastable energy levels of Ln3+ owing to the well‐shielded 4f electrons and tuneable energy levels of the TM ions. The electric versatility of d 0 ion‐containing hosts (d 0 normally viewed as charged anion groups, such as MoO6 6‐ and TiO4 4‐) may also have a strong influence on the electric dipole transition of Ln3+, resulting in multifunctional properties of modulated UC emission and electrical behaviour, such as ferroelectricity and oxide‐ion conductivity. This review focuses on recent advances in the room temperature (RT) UC of TM ions, the UC of Ln3+ tuned by TM or d 0 ions, and the UC of d 0 ion‐centred groups, as well as their potential applications in bioimaging, solar cells and multifunctional devices. PMID:27981015
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Seo, S; DeSilva, MA; Brennecke, JF
2014-12-25
Ionic liquids (ILs) with aprotic heterocyclic anions (AHA) are attractive candidates for CO2 capture technologies. In this study, a series of AHA ILs with 1-ethyl-3-methylimidazolium ([emim](+)) cations were synthesized, and their physical properties (density, viscosity, and ionic conductivity) were measured. In addition, CO2 solubility in each IL was determined at room temperature using a volumetric method at pressures between 0 and 1 bar. The AHAs are basic anions that are capable of reacting stoichiometrically with CO2 to form carbamate species. An interesting CO2 uptake isotherm behavior was observed, and this may be attributed to a parallel, equilibrium proton exchange processmore » between the imidazolium cation and the basic AHA in the presence of CO2, followed by the formation of "transient" carbene species that react rapidly with CO2. The presence of the imidazolium-carboxylate species and carbamate anion species was verified using H-1 and C-13 NMR spectroscopy. While the reaction between CO2 and the proposed transient carbene resulted in cation-CO2 binding that is stronger than the anion-CO2 reaction, the reactions of the imidazolium AHA ILs were fully reversible upon regeneration at 80 degrees C with nitrogen purging. The presence of water decreased the CO2 uptake due to the inhibiting effect of the neutral species (protonated form of AHA) that is formed.« less
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NASA Astrophysics Data System (ADS)
Kwon, Sohyun; Rao, Anil H. N.; Kim, Tae-Hyun
2018-01-01
Azide-assisted terminal crosslinking of methyl morpholinium-functionalized poly(arylene ether sulfone) block copolymers yields products (xMM-PESs) suitable for use as anion exchange membranes. By combining the advantages of bulky morpholinium conductors and our unique polymer network crosslinked only at the termini of the polymer chains, we can produce AEMs that after the crosslinking show minimal loss in conductivity, yet with dramatically reduced water uptake. Terminal crosslinking also significantly increases the thermal, mechanical and chemical stability levels of the membranes. A high ion conductivity of 73.4 mS cm-1 and low water uptake of 26.1% at 80 °C are obtained for the crosslinked membrane with higher amount of hydrophilic composition, denoted as xMM-PES-1.5-1. In addition, the conductivity of the crosslinked xMM-PES-1.5-1 membrane exceeds that of its non-crosslinked counterpart (denoted as MM-PES-1.5-1) above 60 °C at 95% relative humidity because of its enhanced water retention capacity caused by the terminally-crosslinked structure.
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Tang, Wan Si; Matsuo, Motoaki; Wu, Hui; ...
2016-02-05
Both LiCB 9H 10 and NaCB 9H 10 exhibit liquid-like cationic conductivities (≥0.03 S cm –1) in their disordered hexagonal phases near or at room temperature. Furthermore, these unprecedented conductivities and favorable stabilities enabled by the large pseudoaromatic polyhedral anions render these materials in their pristine or further modified forms as promising solid electrolytes in next-generation, power devices.
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Sun, Liyuan; Morales-Collazo, Oscar; Xia, Han; Brennecke, Joan F
2016-06-30
A series of room-temperature ionic liquids (ILs) composed of triethyl(alkyl)phosphonium cations paired with three different aprotic heterocyclic anions (AHAs) (alkyl = butyl ([P2224](+)) and octyl ([P2228](+))) were prepared to investigate the effect of cationic alkyl chain length on transport properties. The transport properties and density of these ILs were measured from 283.15 to 343.15 K at ambient pressure. The dependence of the transport properties (viscosity, ionic conductivity, diffusivity, and molar conductivity) on temperature can be described by the Vogel-Fulcher-Tamman (VFT) equation. The ratio of the molar conductivity obtained from the molar concentration and ionic conductivity measurements to that calculated from self-diffusion coefficients (measured by pulsed gradient spin-echo nuclear magnetic resonance spectroscopy) using the Nernst-Einstein equation was used to quantify the ionicity of these ILs. The molar conductivity ratio decreases with increasing number of carbon atoms in the alkyl chain, indicating that the reduced Coulombic interactions resulting from lower density are more than balanced by the increased van der Waals interactions between the alkyl chains. The results of this study may provide insight into the design of ILs with enhanced dynamics that may be suitable as electrolytes in lithium ion batteries and other electrochemical applications.
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McDonough, Kathleen; Casteel, Kenneth; Itrich, Nina; Menzies, Jennifer; Belanger, Scott; Wehmeyer, Kenneth; Federle, Thomas
2016-12-01
Alcohol sulfates (AS), alcohol ethoxysulfates (AES), linear alkyl benzenesulfonates (LAS) and methyl ester sulfonates (MES) are anionic surfactants that are widely used in household detergents and consumer products resulting in over 1 million tons being disposed of down the drain annually in the US. A monitoring campaign was conducted which collected grab effluent samples from 44 wastewater treatment plants (WWTPs) across the US to generate statistical distributions of effluent concentrations for anionic surfactants. The mean concentrations for AS, AES, LAS and MES were 5.03±4.5, 1.95±0.7, 15.3±19, and 0.35±0.13μg/L respectively. Since each of these surfactants consist of multiple homologues that differ in their toxicity, the concentration of each homologue measured in an effluent sample was converted into a toxic unit (TU) by normalizing to the predicted no effect concentration (PNEC) derived from high tier effects data (mesocosm studies). The statistical distributions of the combined TUs in the effluents were used in combination with distributions of dilution factors for WWTP mixing zones to conduct a US-wide probabilistic risk assessment for the aquatic environment for each of the surfactants. The 90th percentile level of TUs for AS, AES, LAS and MES in mixing zones were 1.89×10 -2 , 2.73×10 -3 , 2.72×10 -2 , and 3.65×10 -5 under 7Q10 (lowest river flow occurring over a 7day period every 10years) low flow conditions. Because these surfactants have the same toxicological mode of action, the TUs were summed and the aquatic safety for anionic surfactants as a whole was assessed. At the 90th percentile level under the conservative 7Q10 low flow conditions the forecasted TUs were 4.21×10 -2 which indicates that there is a significant margin of safety for the class of anionic surfactants in US aquatic environments. Copyright © 2016 Elsevier B.V. All rights reserved.
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Liao, Benjamin S; Sram, Jacqueline C; Files, Darin J
2013-01-01
A simple and effective anion ion chromatography (IC) method with anion exchange column and conductivity detector has been developed to determine free sulfites (SO3-2) in dried fruits processed with sulfur dioxide. No oxidation agent, such as hydrogen peroxide, is used to convert sulfites to sulfates for IC analysis. In addition, no stabilizing agent, such as formaldehyde, fructose or EDTA, is required during the sample extraction. This method uses aqueous 0.2 N NaOH as the solvent for standard preparation and sample extraction. The sulfites, either prepared from standard sodium sulfite powder or extracted from food samples, are presumed to be unbound SO3-2 in aqueous 0.2 N NaOH (pH > 13), because the bound sulfites in the sample matrix are released at pH > 10. In this study, sulfites in the standard solutions were stable at room temperature (i.e., 15-25 degrees C) for up to 12 days. The lowest standard of the linear calibration curve is set at 1.59 microg/mL SO3-2 (equivalent to 6.36 microg/g sample with no dilution) for analysis of processed dried fruits that would contain high levels (>1000 microg/g) of sulfites. As a consequence, this method typically requires significant dilution of the sample extract. Samples are prepared with a simple procedure of sample compositing, extraction with aqueous 0.2 N NaOH, centrifugation, dilution as needed, and filtration prior to IC. The sulfites in these sample extracts are stable at room temperature for up to 20 h. Using anion IC, the sulfites are eluted under isocratic conditions with 10 mM aqueous sodium carbonate solution as the mobile phase passing through an anion exchange column. The sulfites are easily separated, with an analysis run time of 18 min, regardless of the dried fruit matrix. Recoveries from samples spiked with sodium sulfites were demonstrated to be between 81 and 105% for five different fruit matrixes (apricot, golden grape, white peach, fig, and mango). Overall, this method is simple to perform and effective for the determination of high levels of sulfites in dried fruits.
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Vecchiarelli, Anthony G.; Li, Min; Mizuuchi, Michiyo; Mizuuchi, Kiyoshi
2014-01-01
The E. coli Min system forms a cell-pole-to-cell-pole oscillator that positions the divisome at mid-cell. The MinD ATPase binds the membrane and recruits the cell division inhibitor MinC. MinE interacts with and releases MinD (and MinC) from the membrane. The chase of MinD by MinE creates the in vivo oscillator that maintains a low level of the division inhibitor at mid-cell. In vitro reconstitution and visualization of Min proteins on a supported lipid bilayer has provided significant advances in understanding Min patterns in vivo. Here we studied the effects of flow, lipid composition, and salt concentration on Min patterning. Flow and no-flow conditions both supported Min protein patterns with somewhat different characteristics. Without flow, MinD and MinE formed spiraling waves. MinD and, to a greater extent MinE, have stronger affinities for anionic phospholipid. MinD-independent binding of MinE to anionic lipid resulted in slower and narrower waves. MinE binding to the bilayer was also more susceptible to changes in ionic strength than MinD. We find that modulating protein diffusion with flow, or membrane binding affinities with changes in lipid composition or salt concentration, can differentially affect the retention time of MinD and MinE, leading to spatiotemporal changes in Min patterning. PMID:24930948
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Negative ion kinetics in RF glow discharges
DOE Office of Scientific and Technical Information (OSTI.GOV)
Gottscho, R.A.; Gacbe, C.E.
1986-04-01
Using temporally and spatially resolved laser spectroscopy, the authors have determined the identities, approximate concentrations, effects on the local field, and kinetics of formation and loss of negative ions in RF discharges. CI/sup -/ and BCI/sub 3//sup -/ are the dominant negative ions found in low-frequency discharges through CI/sub 2/ and BCI/sub 3/, respectively. The electron affinity for CI is measured to be 3.6118 +- 0.0005 eV. Negative ion kinetics are strongly affected by application of the RF field. Formation of negative ions by attachment of slow electrons in RF discharges is governed by the extent and duration of electronmore » energy relaxation. Similarly, destruction of negative ions by collisional detachment and field extraction is dependent upon ion energy modulation. Thus, at low frequency, the anion density peaks at the beginning of the anodic and cathodic half-cycles after electrons have attached but before detachment and extraction have had time to occur. At higher frequencies, electrons have insufficient time to attach before they are reheated and the instantaneous anion density in the sheath is greatly reduced. When the negative ion density is comparable to the positive ion density, the plasma potential is observed to lie below the anode potential, double layers form between sheath and plasma, and anions and electrons are accelerated by large sheath fields to electrode surfaces.« less
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Pyrrole-Based Conductive Polymers For Capacitors
NASA Technical Reports Server (NTRS)
Nagasubramanian, Ganesan; Di Stefano, Salvador
1994-01-01
Polypyrrole films containing various dopant anions exhibit superior capacitance characteristics. Used with nonaqueous electrolytes. Candidate for use in advanced electrochemical double-layer capacitors capable of storing electrical energy at high densities. Capacitors made of these films used in automobiles and pulsed power supplies.
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Armes, Steven P.; Aldissi, Mahmoud
1990-01-01
Processable electrically conductive latex polymer compositions including colloidal particles of an oxidized, polymerized amino-substituted aromatic monomer, a stabilizing effective amount of a random copolymer containing amino-benzene type moieties as side chain constituents, and dopant anions, and a method of preparing such polymer compositions are provided.
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ANALYSIS OF HYDROPONIC FERTILIZER MATRIXES FOR PERCHLORATE: COMPARISON OF ANALYTICAL TECHNIQUES
Seven retail hydroponic nitrate fertilizer products, two liquid and five solid, were comparatively analyzed for the perchlorate anion (ClO4-) by ion chromatography (IC) with suppressed conductivity detection, complexation electrospray ionization mass spectrometry (cESI-MS), norma...
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Conductivity Enhancement of PEDOT:PSS Films Through the Surface Treatment with Organic Solvent.
Lee, Sungkoo
2016-03-01
The improvement of conductivity is a key factor in application of conducting polymer to elec- tronic devices. The conductivity enhancement of PSS films were observed after dipping in polar organic solvents, including DMSO, ethylene glycol, glycerol and IPA. The conductivity of PSS films increased from 0.5 S/cm to over 800 S/cm, that is, by a factor of more than 1,600. The conductivity enhancement was dependent on the type of organic solvents and dipping time of PSS into solvent. The enhancement of conductivity may be caused by the phase separation between PEDOT chains and PSS counter anions.
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Lin, YuPo J [Naperville, IL; Henry, Michael P [Batavia, IL; Snyder, Seth W [Lincolnwood, IL
2011-07-12
An electrically and ionically conductive porous material including a thermoplastic binder and one or more of anion exchange moieties or cation exchange moieties or mixtures thereof and/or one or more of a protein capture resin and an electrically conductive material. The thermoplastic binder immobilizes the moieties with respect to each other but does not substantially coat the moieties and forms the electrically conductive porous material. A wafer of the material and a method of making the material and wafer are disclosed.
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Ultrasteep Voltage Dependence in a Membrane Channel
NASA Astrophysics Data System (ADS)
Mangan, Patrick S.; Colombini, Marco
1987-07-01
A mechanism for regulating voltage-gated channels is presented. The treatment amplifies the effect of the applied membrane potential resulting in a dramatic increase in the channel's voltage dependence. Addition of a large polyvalent anion to the medium bathing a phospholipid bilayer containing the voltage-dependent channel from the mitochondrial outer membrane, VDAC, induced up to a 12-fold increase in the channel's voltage sensitivity. The highest polyvalent anion concentration tested resulted in an e-fold conductance change for a 0.36-mV change in membrane potential. On the low end, a concentration of 2 μ M resulted in a 50% increase in VDAC voltage dependence. A mechanism based on polyvalent anion accumulation in the access resistance region at the mouth of the pore is consistent with all findings. Perhaps the voltage dependence of voltage-gated channels is amplified in vivo by polyvalent ions. If so, the control of excitable phenomena may be under much finer regulation than that provided by membrane potential alone.
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NASA Astrophysics Data System (ADS)
Cha, Min Suc; Jeong, Hwan Yeop; Shin, Hee Young; Hong, Soo Hyun; Kim, Tae-Ho; Oh, Seong-Geun; Lee, Jang Yong; Hong, Young Taik
2017-09-01
A series of polysulfone-based crosslinked anion exchange membranes (AEMs) with primary diamine-based crosslinkers has been prepared via simple a crosslinking process as low-cost and durable membranes for vanadium redox flow batteries (VRFBs). Chloromethylated polysulfone is used as a precursor polymer for crosslinked AEMs (CAPSU-x) with different degrees of crosslinking. Among the developed AEMs, CAPSU-2.5 shows outstanding dimensional stability and anion (Cl-, SO42-, and OH-) conductivity. Moreover, CAPSU-2.5 exhibits much lower vanadium ion permeability (2.72 × 10-8 cm2 min-1) than Nafion 115 (2.88 × 10-6 cm2 min-1), which results in an excellent coulombic efficiency of 100%. The chemical and operational stabilities of the membranes have been investigated via ex situ soaking tests in 0.1 M VO2+ solution and in situ operation tests for 100 cycles, respectively. The excellent chemical, physical, and electrochemical properties of the CAPSU-2.5 membrane make it suitable for use in VRFBs.
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Improved Performance of Ionic Liquid Supercapacitors by using Tetracyanoborate Anions.
Martins, Vitor L; Rennie, Anthony J R; Sanchez-Ramirez, Nedher; Torresi, Roberto M; Hall, Peter J
2018-02-01
Supercapacitors are energy storage devices designed to operate at higher power densities than conventional batteries, but their energy density is still too low for many applications. Efforts are made to design new electrolytes with wider electrochemical windows than aqueous or conventional organic electrolytes in order to increase energy density. Ionic liquids (ILs) with wide electrochemical stability windows are excellent candidates to be employed as supercapacitor electrolytes. ILs containing tetracyanoborate anions [B(CN) 4 ] offer wider electrochemical stability than conventional electrolytes and maintain a high ionic conductivity (6.9 mS cm -1 ). Herein, we report the use of ILs containing the [B(CN) 4 ] anion for such an application. They presented a high maximum operating voltage of 3.7 V, and two-electrode devices demonstrate high specific capacitances even when operating at relatively high rates (ca. 20 F g -1 @ 15 A g -1 ). This supercapacitor stored more energy and operated at a higher power at all rates studied when compared with cells using a commonly studied ILs.
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Protic ionic liquids based on the dimeric and oligomeric anions: [(AcO)xH(x-1)]-.
Johansson, K M; Izgorodina, E I; Forsyth, M; MacFarlane, D R; Seddon, K R
2008-05-28
We describe a fluidity and conductivity study as a function of composition in N-methylpyrrolidine-acetic acid mixtures. The simple 1 : 1 acid-base mixture appears to form an ionic liquid, but its degree of ionicity is quite low and such liquids are better thought of as poorly dissociated mixtures of acid and base. The composition consisting of 3 moles acetic acid and 1 mole N-methylpyrrolidine is shown to form the highest ionicity mixture in this binary due to the presence of oligomeric anionic species [(AcO)(x)H(x-1)](-) stabilised by hydrogen bonds. These oligomeric species, being weaker bases than the acetate anion, shift the proton transfer equilibrium towards formation of ionic species, thus generating a higher degree of ionicity than is present at the 1 : 1 composition. A Walden plot analysis, thermogravimetric behaviour and proton NMR data, as well as ab initio calculations of the oligomeric species, all support this conclusion.
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Compatibility of Surfactants and Thermally Activated Persulfate for Enhanced Subsurface Remediation.
Wang, Li; Peng, Libin; Xie, Liling; Deng, Peiyan; Deng, Dayi
2017-06-20
Limited aqueous availability of hydrophobic organic contaminants and nonaqueous phase liquids in subsurface environment may seriously impair the effectiveness of traditional in situ chemical oxidation (ISCO). To tackle the issue, a combination of surfactants and thermally activated persulfate was proposed to enhance the aqueous availability and consequent oxidation of organic contaminants. The compatibility of eight representative nonionic, monovalent anionic, and divalent anionic surfactants with persulfate at various temperatures was first studied, to identify suitable surfactants that have high aqueous stability and low oxidant demands to couple with thermally activated persulfate. C 12 -MADS (sodium dodecyl diphenyl ether disulfonate, a representative divalent anionic surfactant) stands out as the most compatible surfactant. Batch treatability study with coal tar, an example of challenging scenarios for traditional ISCO, was then conducted. The results show that C 12 -MADS can significantly enhance not only the oxidation of polyaromatic hydrocarbons contained in coal tar but also oxidant utilization efficiency, indicating the potential of the proposed coupling process for the treatment of organic contaminants with low aqueous availability.
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Homologue Structure of the SLAC1 Anion Channel for Closing Stomata in Leaves
DOE Office of Scientific and Technical Information (OSTI.GOV)
Y Chen; L Hu; M Punta
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 bymore » 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.« less
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Jaafar, Shoffian Amin; Latif, Mohd Talib; Chian, Chong Woan; Han, Wong Sook; Wahid, Nurul Bahiyah Abd; Razak, Intan Suraya; Khan, Md Firoz; Tahir, Norhayati Mohd
2014-07-15
This study was conducted to determine the composition of surfactants in the sea-surface microlayer (SML) and atmospheric aerosol around the southern region of the Peninsular Malaysia. Surfactants in samples taken from the SML and atmospheric aerosol were determined using a colorimetric method, as either methylene blue active substances (MBAS) or disulphine blue active substances (DBAS). Principal component analysis with multiple linear regressions (PCA-MLR), using the anion and major element composition of the aerosol samples, was used to determine possible sources of surfactants in atmospheric aerosol. The results showed that the concentrations of surfactants in the SML and atmospheric aerosol were dominated by anionic surfactants and that surfactants in aerosol were not directly correlated (p>0.05) with surfactants in the SML. Further PCA-MLR from anion and major element concentrations showed that combustion of fossil fuel and sea spray were the major contributors to surfactants in aerosol in the study area. Copyright © 2014 Elsevier Ltd. All rights reserved.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Zheng, Haiyan; Wang, Lijuan; Li, Kuo
Transformation between different types of carbon–carbon bonding in carbides often results in a dramatic change of physical and chemical properties. Under external pressure, unsaturated carbon atoms form new covalent bonds regardless of the electrostatic repulsion. It was predicted that calcium acetylide (also known as calcium carbide, CaC2) polymerizes to form calcium polyacetylide, calcium polyacenide and calcium graphenide under high pressure. In this work, the phase transitions of CaC2 under external pressure were systematically investigated, and the amorphous phase was studied in detail for the first time. Polycarbide anions like C 6 6- are identified with gas chromatography-mass spectrometry and severalmore » other techniques, which evidences the pressure induced polymerization of the acetylide anions and suggests the existence of the polyacenide fragment. Additionally, the process of polymerization is accompanied with a 107 fold enhancement of the electrical conductivity. The polymerization of acetylide anions demonstrates that high pressure compression is a viable route to synthesize novel metal polycarbides and materials with extended carbon networks, while shedding light on the synthesis of more complicated metal organics.« less
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First Cationic Uranyl-Organic Framework with Anion-Exchange Capabilities.
Bai, Zhuanling; Wang, Yanlong; Li, Yuxiang; Liu, Wei; Chen, Lanhua; Sheng, Daopeng; Diwu, Juan; Chai, Zhifang; Albrecht-Schmitt, Thomas E; Wang, Shuao
2016-07-05
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.
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Highly Stable, Anion Conductive, Comb-Shaped Copolymers for Alkaline Fuel Cells
DOE Office of Scientific and Technical Information (OSTI.GOV)
Li, NW; Leng, YJ; Hickner, MA
2013-07-10
To produce an anion-conductive and durable polymer electrolyte for alkaline fuel cell applications, a series of quaternized poly(2,6-dimethyl phenylene oxide)s containing long alkyl side chains pendant to the nitrogen-centered cation were synthesized using a Menshutkin reaction to form comb-shaped structures. The pendant alkyl chains were responsible for the development of highly conductive ionic domains, as confirmed by small-angle X-ray scattering (SAXS). The comb-shaped polymers having one alkyl side chain showed higher hydroxide conductivities than those with benzyltrimethyl ammonium moieties or structures with more than one alkyl side chain per cationic site. The highest conductivity was observed for comb-shaped polymers withmore » benzyldimethylhexadecyl ammonium cations. The chemical stabilities of the comb-shaped membranes were evaluated under severe, accelerated-aging conditions, and degradation was observed by measuring IEC and ion conductivity changes during aging. The comb-shaped membranes retained their high ion conductivity in 1 M NaOH at 80 degrees C for 2000 h. These cationic polymers were employed as ionomers in catalyst layers for alkaline fuel cells. The results indicated that the C-16 alkyl side chain ionomer had a slightly better initial performance, despite its low IEC value, but very poor durability in the fuel cell. In contrast, 90% of the initial performance was retained for the alkaline fuel cell with electrodes containing the C-6 side chain after 60 h of fuel cell operation.« less
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Linsdell, Paul
2017-01-01
Cystic fibrosis is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR), an epithelial cell anion channel. Potentiator drugs used in the treatment of cystic fibrosis act on the channel to increase overall channel function, by increasing the stability of its open state and/or decreasing the stability of its closed state. The structure of the channel in either the open state or the closed state is not currently known. However, changes in the conformation of the protein as it transitions between these two states have been studied using functional investigation and molecular modeling techniques. This review summarizes our current understanding of the architecture of the transmembrane channel pore that controls the movement of chloride and other small anions, both in the open state and in the closed state. Evidence for different kinds of changes in the conformation of the pore as it transitions between open and closed states is described, as well as the mechanisms by which these conformational changes might be controlled to regulate normal channel gating. The ways that key conformational changes might be targeted by small compounds to influence overall CFTR activity are also discussed. Understanding the changes in pore structure that might be manipulated by such small compounds is key to the development of novel therapeutic strategies for the treatment of cystic fibrosis.
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Angell, C Austen [Mesa, AZ; Xu, Wu [Broadview Heights, OH; Belieres, Jean-Philippe [Chandler, AZ; Yoshizawa, Masahiro [Tokyo, JP
2011-01-11
Disclosed are developments in high temperature fuel cells including ionic liquids with high temperature stability and the storage of inorganic acids as di-anion salts of low volatility. The formation of ionically conducting liquids of this type having conductivities of unprecedented magnitude for non-aqueous systems is described. The stability of the di-anion configuration is shown to play a role in the high performance of the non-corrosive proton-transfer ionic liquids as high temperature fuel cell electrolytes. Performance of simple H.sub.2(g) electrolyte/O.sub.2(g) fuel cells with the new electrolytes is described. Superior performance both at ambient temperature and temperatures up to and above 200.degree. C. are achieved. Both neutral proton transfer salts and the acid salts with HSO.sup.-.sub.4 anions, give good results, the bisulphate case being particularly good at low temperatures and very high temperatures. The performance of all electrolytes is improved by the addition of a small amount of involatile base of pK.sub.a value intermediate between those of the acid and base that make the bulk electrolyte. The preferred case is the imidazole-doped ethylammonium hydrogensulfate which yields behavior superior in all respects to that of the industry standard phosphoric acid electrolyte.
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Nagarajan, Yagnesh; Rongala, Jay; Luang, Sukanya; Shadiac, Nadim; Sutton, Tim; Tyerman, Stephen D.; McPhee, Gordon; Voelcker, Nicolas H.; Lee, Jung-Goo
2016-01-01
Plant growth and survival depend upon the activity of membrane transporters that control the movement and distribution of solutes into, around, and out of plants. Although many plant transporters are known, their intrinsic properties make them difficult to study. In barley (Hordeum vulgare), the root anion-permeable transporter Bot1 plays a key role in tolerance to high soil boron, facilitating the efflux of borate from cells. However, its three-dimensional structure is unavailable and the molecular basis of its permeation function is unknown. Using an integrative platform of computational, biophysical, and biochemical tools as well as molecular biology, electrophysiology, and bioinformatics, we provide insight into the origin of transport function of Bot1. An atomistic model, supported by atomic force microscopy measurements, reveals that the protein folds into 13 transmembrane-spanning and five cytoplasmic α-helices. We predict a trimeric assembly of Bot1 and the presence of a Na+ ion binding site, located in the proximity of a pore that conducts anions. Patch-clamp electrophysiology of Bot1 detects Na+-dependent polyvalent anion transport in a Nernstian manner with channel-like characteristics. Using alanine scanning, molecular dynamics simulations, and transport measurements, we show that conductance by Bot1 is abolished by removal of the Na+ ion binding site. Our data enhance the understanding of the permeation functions of Bot1. PMID:26672067
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Interactions between selected bile salts and Triton X-100 or sodium lauryl ether sulfate.
Cirin, Dejan M; Poša, Mihalj M; Krstonošić, Veljko S
2011-12-29
In order to develop colloidal drug carriers with desired properties, it is important to determine physico-chemical characteristics of these systems. Bile salt mixed micelles are extensively studied as novel drug delivery systems. The objective of the present investigation is to develop and characterize mixed micelles of nonionic (Triton X-100) or anionic (sodium lauryl ether sulfate) surfactant having oxyethylene groups in the polar head and following bile salts: cholate, deoxycholate and 7-oxodeoxycholate. The micellization behaviour of binary anionic-nonionic and anionic-anionic surfactant mixtures was investigated by conductivity and surface tension measurements. The results of the study have been analyzed using Clint's, Rubingh's, and Motomura's theories for mixed binary systems. The negative values of the interaction parameter indicate synergism between micelle building units. It was noticed that Triton X-100 and sodium lauryl ether sulfate generate the weakest synergistic interactions with sodium deoxycholate, while 7-oxodeoxycholate creates the strongest attractive interaction with investigated co-surfactants. It was concluded that increased synergistic interactions can be attributed to the larger number of hydrophilic groups at α side of the bile salts. Additionally, 7-oxo group of 7-oxodeoxycholate enhance attractive interactions with selected co-surfactants more than 7-hydroxyl group of sodium cholate.
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Interactions between selected bile salts and Triton X-100 or sodium lauryl ether sulfate
2011-01-01
Background In order to develop colloidal drug carriers with desired properties, it is important to determine physico-chemical characteristics of these systems. Bile salt mixed micelles are extensively studied as novel drug delivery systems. The objective of the present investigation is to develop and characterize mixed micelles of nonionic (Triton X-100) or anionic (sodium lauryl ether sulfate) surfactant having oxyethylene groups in the polar head and following bile salts: cholate, deoxycholate and 7-oxodeoxycholate. Results The micellization behaviour of binary anionic-nonionic and anionic-anionic surfactant mixtures was investigated by conductivity and surface tension measurements. The results of the study have been analyzed using Clint's, Rubingh's, and Motomura's theories for mixed binary systems. The negative values of the interaction parameter indicate synergism between micelle building units. It was noticed that Triton X-100 and sodium lauryl ether sulfate generate the weakest synergistic interactions with sodium deoxycholate, while 7-oxodeoxycholate creates the strongest attractive interaction with investigated co-surfactants. Conclusion It was concluded that increased synergistic interactions can be attributed to the larger number of hydrophilic groups at α side of the bile salts. Additionally, 7-oxo group of 7-oxodeoxycholate enhance attractive interactions with selected co-surfactants more than 7-hydroxyl group of sodium cholate. PMID:22206681
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Shi, Minjie; Kou, Shengzhong; Yan, Xingbin
2014-11-01
Graphene sheet (GS)-ionic liquid (IL) supercapacitors are receiving intense interest because their specific energy density far exceeds that of GS-aqueous electrolytes supercapacitors. The electrochemical properties of ILs mainly depend on their diverse ions, especially anions. Therefore, identifying suitable IL electrolytes for GSs is currently one of the most important tasks. The electrochemical behavior of GSs in a series of ILs composed of 1-ethyl-3-methylimidazolium cation (EMIM(+)) with different anions is systematically studied. Combined with the formula derivation and building models, it is shown that the viscosity, ion size, and molecular weight of ILs affect the electrical conductivity of ILs, and thus, determine the electrochemical performances of GSs. Because the EMIM-dicyanamide IL has the lowest viscosity, ion size, and molecular weight, GSs in it exhibit the highest specific capacitance, smallest resistance, and best rate capability. In addition, because the tetrafluoroborate anion (BF4(-)) has the best electrochemical stability, the GS-[EMIM][BF4] supercapacitor has the widest potential window, and thus, displays the largest energy density. These results may provide valuable information for selecting appropriate ILs and designing high-performance GS-IL supercapacitors to meet different needs. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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Park, Jozeph; Kim, Yang Soo; Ok, Kyung-Chul; Park, Yun Chang; Kim, Hyun You; Park, Jin-Seong; Kim, Hyun-Suk
2016-01-01
High-mobility zinc oxynitride (ZnON) semiconductors were grown by RF sputtering using a Zn metal target in a plasma mixture of Ar, N2, and O2 gas. The RF power and the O2 to N2 gas flow rates were systematically adjusted to prepare a set of ZnON films with different relative anion contents. The carrier density was found to be greatly affected by the anion composition, while the electron mobility is determined by a fairly complex mechanism. First-principles calculations indicate that excess vacant nitrogen sites (VN) in N-rich ZnON disrupt the local electron conduction paths, which may be restored by having oxygen anions inserted therein. The latter are anticipated to enhance the electron mobility, and the exact process parameters that induce such a phenomenon can only be found experimentally. Contour plots of the Hall mobility and carrier density with respect to the RF power and O2 to N2 gas flow rate ratio indicate the existence of an optimum region where maximum electron mobility is obtained. Using ZnON films grown under the optimum conditions, the fabrication of high-performance devices with field-effect mobility values exceeding 120 cm2/Vs is demonstrated based on simple reactive RF sputtering methods. PMID:27098656
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Understanding SO2 Capture by Ionic Liquids.
Mondal, Anirban; Balasubramanian, Sundaram
2016-05-19
Ionic liquids have generated interest for efficient SO2 absorption due to their low vapor pressure and versatility. In this work, a systematic investigation of the structure, thermodynamics, and dynamics of SO2 absorption by ionic liquids has been carried out through quantum chemical calculations and molecular dynamics (MD) simulations. MP2 level calculations of several ion pairs complexed with SO2 reveal its preferential interaction with the anion. Results of condensed phase MD simulations of SO2-IL mixtures manifested the essential role of both cations and anions in the solvation of SO2, where the solute is surrounded by the "cage" formed by the cations (primarily its alkyl tail) through dispersion interactions. These structural effects of gas absorption are substantiated by calculated Gibbs free energy of solvation; the dissolution is demonstrated to be enthalpy driven. The entropic loss of SO2 absorption in ionic liquids with a larger anion such as [NTf2](-) has been quantified and has been attributed to the conformational restriction of the anion imposed by its interaction with SO2. SO2 loading IL decreases its shear viscosity and enhances the electrical conductivity. This systematic study provides a molecular level understanding which can aid the design of task-specific ILs as electrolytes for efficient SO2 absorption.
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Dai, Sheng [Knoxville, TN; Luo, Huimin [Knoxville, TN
2008-09-09
Ionic compounds which are liquids at room temperature are formed by the method of mixing a neutral organic liqand with the salt of a metal cation and its conjugate anion. The liquids are hydrophobic, conductive and stable and have uses as solvents and in electrochemical devices.
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Dai, Sheng [Knoxville, TN; Luo, Huimin [Knoxville, TN
2011-11-01
Ionic compounds which are liquids at room temperature are formed by the method of mixing a neutral organic ligand with the salt of a metal cation and its conjugate anion. The liquids are hydrophobic, conductive and stable and have uses as solvents and in electrochemical devices.
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Urban Effects on Microbial Processes and Food Webs in Coastal Watershed Streams
We conducted a stream survey in the Narragansett Bay Watershed that targeted a gradient of development intensity and examined how associated changes in nutrients, carbon, and stressors affected periphyton and macroinvertebrates. Concentrations of nutrients, cations, and anions we...
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; Journal of Solar Energy Engineering-Transactions of the Asme 128(1): 54-57. Clark, J., et al. (2015 inorganic anions by ion chromatography with suppressed conductivity detection." Journal of vapors produced from Nordic feedstocks in cyclone pyrolysis." Journal of Analytical and Applied
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Flores-Alsina, Xavier; Kazadi Mbamba, Christian; Solon, Kimberly; Vrecko, Darko; Tait, Stephan; Batstone, Damien J; Jeppsson, Ulf; Gernaey, Krist V
2015-11-15
There is a growing interest within the Wastewater Treatment Plant (WWTP) modelling community to correctly describe physico-chemical processes after many years of mainly focusing on biokinetics. Indeed, future modelling needs, such as a plant-wide phosphorus (P) description, require a major, but unavoidable, additional degree of complexity when representing cationic/anionic behaviour in Activated Sludge (AS)/Anaerobic Digestion (AD) systems. In this paper, a plant-wide aqueous phase chemistry module describing pH variations plus ion speciation/pairing is presented and interfaced with industry standard models. The module accounts for extensive consideration of non-ideality, including ion activities instead of molar concentrations and complex ion pairing. The general equilibria are formulated as a set of Differential Algebraic Equations (DAEs) instead of Ordinary Differential Equations (ODEs) in order to reduce the overall stiffness of the system, thereby enhancing simulation speed. Additionally, a multi-dimensional version of the Newton-Raphson algorithm is applied to handle the existing multiple algebraic inter-dependencies. The latter is reinforced with the Simulated Annealing method to increase the robustness of the solver making the system not so dependent of the initial conditions. Simulation results show pH predictions when describing Biological Nutrient Removal (BNR) by the activated sludge models (ASM) 1, 2d and 3 comparing the performance of a nitrogen removal (WWTP1) and a combined nitrogen and phosphorus removal (WWTP2) treatment plant configuration under different anaerobic/anoxic/aerobic conditions. The same framework is implemented in the Benchmark Simulation Model No. 2 (BSM2) version of the Anaerobic Digestion Model No. 1 (ADM1) (WWTP3) as well, predicting pH values at different cationic/anionic loads. In this way, the general applicability/flexibility of the proposed approach is demonstrated, by implementing the aqueous phase chemistry module in some of the most frequently used WWTP process simulation models. Finally, it is shown how traditional wastewater modelling studies can be complemented with a rigorous description of aqueous phase and ion chemistry (pH, speciation, complexation). Copyright © 2015 Elsevier Ltd. All rights reserved.
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NASA Astrophysics Data System (ADS)
Mourad, Carole Issa
2000-10-01
Growth of high quality mixed anion alloys such as InGaAsSb and AlGaAsSb are critical to laser heterostructures designed for 2--4 micron emission. However, run-to-run reproducibility as well as the ability to reproducibly change alloy compositions within a heterostructure tend to be poor. This is because the competition for incorporation between the two anions (As and Sb) is extremely sensitive to a large number of growth parameters such as temperature, incident fluxes, and growth rate, which may drift during the course of deposition, or are difficult to reset during growth. With the intent of improving reproducibility, we have grown and characterized InGaAsSb and AlGaAsSb "digital alloys" deposited using modulated incident As2 and Sb2 incident fluxes. In0.1Ga 0.9AsySb1-y alloy layers were grown by alternately exposing the film surface to As2 and Sb2 fluxes with a periodicity ranging from ˜9 to ˜22 A. Average alloy composition is determined by the duty-cycle of the anion-oven shutters. Structural characterization using high-resolution x-ray diffraction (HRXRD) shows clear satellite peaks indicating that the digital alloys retain the compositional modulation. Optical characterization using photoluminescence indicate that the digital alloys can successfully replace the conventionally grown quaternary alloys with the same average composition. In addition we have characterized digitally grown InGaAsSb layers using HRXRD and measured the sensitivity of the resulting average composition to the growth temperature. We find that the composition of In0.1Ga0.9AsySb1-y alloy layers grown digitally on GaSb substrates is nearly three times less sensitive to the growth temperature as conventional growth. Digital growth of InGaAsSb and AlGaAsSb layers has enabled the growth of heterostructures containing multiple alloy compositions by toggling between shutter duty-cycles during growth, without necessitating changes to the oven temperatures throughout deposition. We have grown and characterized optically pumped ˜2mum laser structures with InGaAsSb quantum wells and AlGaAsSb barriers both grown using the digital alloy technique. Room temperature operation, a low threshold current density of 104 W/cm2 (at 80K with 808nm pump), and a characteristic temperature (To) of 104 K show the feasibility of applying digital alloying techniques to mid-infrared optical devices.
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Bagchi, D; Bagchi, M; Stohs, S J
2001-06-01
Chromium (VI) is a widely used industrial chemical, extensively used in paints, metal finishes, steel including stainless steel manufacturing, alloy cast irons, chrome, and wood treatment. On the contrary, chromium (III) salts such as chromium polynicotinate, chromium chloride and chromium picolinate, are used as micronutrients and nutritional supplements, and have been demonstrated to exhibit a significant number of health benefits in rodents and humans. However, the cause for the hexavalent chromium to induce cytotoxicity is not entirely understood. A series of in vitro and in vivo studies have demonstrated that chromium (VI) induces an oxidative stress through enhanced production of reactive oxygen species (ROS) leading to genomic DNA damage and oxidative deterioration of lipids and proteins. A cascade of cellular events occur following chromium (VI)-induced oxidative stress including enhanced production of superoxide anion and hydroxyl radicals, increased lipid peroxidation and genomic DNA fragmentation, modulation of intracellular oxidized states, activation of protein kinase C, apoptotic cell death and altered gene expression. In this paper, we have demonstrated concentration- and time-dependent effects of sodium dichromate (chromium (VI) or Cr (VI)) on enhanced production of superoxide anion and hydroxyl radicals, changes in intracellular oxidized states as determined by laser scanning confocal microscopy, DNA fragmentation and apoptotic cell death (by flow cytometry) in human peripheral blood mononuclear cells. These results were compared with the concentration-dependent effects of chromium (VI) on chronic myelogenous leukemic K562 cells and J774A.1 murine macrophage cells. Chromium (VI)-induced enhanced production of ROS, as well as oxidative tissue and DNA damage were observed in these cells. More pronounced effect was observed on chronic myelogenous leukemic K562 cells and J774A.1 murine macrophage cells. Furthermore, we have assessed the effect of a single oral LD50 dose of chromium (VI) on female C57BL/6Ntac and p53-deficient C57BL/6TSG p53 mice on enhanced production of superoxide anion, lipid peroxidation and DNA fragmentation in the hepatic and brain tissues. Chromium (VI)-induced more pronounced oxidative damage in p53 deficient mice. This in vivo study highlighted that apoptotic regulatory protein p53 may play a major role in chromium (VI)-induced oxidative stress and toxicity. Taken together, oxidative stress and oxidative tissue damage, and a cascade of cellular events including modulation of apoptotic regulatory gene p53 are involved in chromium (VI)-induced toxicity and carcinogenesis.
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Mayer, Alejandro MS; Hall, Mary L; Lynch, Sean M; Gunasekera, Sarath P; Sennett, Susan H; Pomponi, Shirley A
2005-01-01
Background Thromboxane B2 (TXB2) and superoxide anion (O2-) are neuroinflammatory mediators that appear to be involved in the pathogenesis of several neurodegenerative diseases. Because activated-microglia are the main source of TXB2 and O2- in these disorders, modulation of their synthesis has been hypothesized as a potential therapeutic approach for neuroinflammatory disorders. Marine natural products have become a source of novel agents that modulate eicosanoids and O2- generation from activated murine and human leukocytes. With the exception of manzamine C, all other manzamines tested are characterized by a complex pentacyclic diamine linked to C-1 of the β-carboline moiety. These marine-derived alkaloids have been reported to possess a diverse range of bioactivities including anticancer, immunostimulatory, insecticidal, antibacterial, antimalarial and antituberculosis activities. The purpose of this investigation was to conduct a structure-activity relationship study with manzamines (MZ) A, B, C, D, E and F on agonist-stimulated release of TXB2 and O2- from E. coli LPS-activated rat neonatal microglia in vitro. Results The manzamines differentially attenuated PMA (phorbol 12-myristate 13-acetate)-stimulated TXB2 generation in the following order of decreasing potency: MZA (IC50 <0.016 μM) >MZD (IC50 = 0.23 μM) >MZB (IC50 = 1.6 μM) >MZC (IC50 = 2.98 μM) >MZE and F (IC50 >10 μM). In contrast, there was less effect on OPZ (opsonized zymosan)-stimulated TXB2 generation: MZB (IC50 = 1.44 μM) >MZA (IC50 = 3.16 μM) >MZC (IC50 = 3.34 μM) >MZD, MZE and MZF (IC50 >10 μM). Similarly, PMA-stimulated O2- generation was affected differentially as follows: MZD (apparent IC50<0.1 μM) >MZA (IC50 = 0.1 μM) >MZB (IC50 = 3.16 μM) >MZC (IC50 = 3.43 μM) >MZE and MZF (IC50 >10 μM). In contrast, OPZ-stimulated O2- generation was minimally affected: MZB (IC50 = 4.17 μM) >MZC (IC50 = 9.3 μM) >MZA, MZD, MZE and MZF (IC50 > 10 μM). From the structure-activity relationship perspective, contributing factors to the observed differential bioactivity on TXB2 and O2- generation are the solubility or ionic forms of MZA and D as well as changes such as saturation or oxidation of the β carboline or 8-membered amine ring. In contrast, the fused 13-membered macrocyclic and isoquinoline ring system, and any substitutions in these rings would not appear to be factors contributing to bioactivity. Conclusion To our knowledge, this is the first experimental study that demonstrates that MZA, at in vitro concentrations that are non toxic to E. coli LPS-activated rat neonatal microglia, potently modulates PMA-stimulated TXB2 and O2- generation. MZA may thus be a lead candidate for the development of novel therapeutic agents for the modulation of TXB2 and O2- release in neuroinflammatory diseases. Marine natural products provide a novel and rich source of chemical diversity that can contribute to the design and development of new and potentially useful anti-inflammatory agents to treat neurodegenerative diseases. PMID:15762999
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Llave, F.; Gall, B.; Gao, H., Scott, L., Cook, I.
Selected surfactant systems containing a series of ethoxylated nonionic surfactants in combination with an anionic surfactant system have been studied to evaluate phase behavior as well as oil recovery potential. These experiments were conducted to evaluate possible improved phase behavior and overall oil recovery potential of mixed surfactant systems over a broad range of conditions. Both polyacrylamide polymers and Xanthan biopolymers were evaluated. Studies were initiated to use a chemical flooding simulation program, UTCHEM, to simulate oil recovery for laboratory and field applications and evaluate its use to simulate oil saturation distributions obtained in CT-monitoring of oil recovery experiments. Themore » phase behavior studies focused on evaluating the effect of anionic-nonionic surfactant proportion on overall phase behavior. Two distinct transition behaviors were observed, depending on the dominant surfactant in the overall system. The first type of transition corresponded to more conventional behavior attributed to nonionic-dominant surfactant systems. This behavior is manifested by an oil-water-surfactant system that inverts from a water-external (highly conducting) microemulsion to an oil-external (nonconducting) one, as a function of temperature. The latter type which inverts in an opposite manner can be attributed to the separation of the anionic-nonionic mixtures into water- and oil-soluble surfactants. Both types of transition behavior can still be used to identify relative proximity to optimal areas. Determining these transition ranges provided more insight on how the behavior of these surfactant mixtures was affected by altering component proportions. Efforts to optimize the chemical system for oil displacement experiments were also undertaken. Phase behavior studies with systems formulated with biopolymer in solution were conducted.« less
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Atzori, Matteo; Pop, Flavia; Auban-Senzier, Pascale; Clérac, Rodolphe; Canadell, Enric; Mercuri, Maria Laura; Avarvari, Narcis
2015-04-06
Electrocrystallization of enantiopure (S,S,S,S)- and (R,R,R,R)-tetramethyl-bis(ethylenedithio)-tetrathiafulvalene (TM-BEDT-TTF) donors, as well as the racemic mixture, in the presence of potassium cations and the tris(chloranilato)ferrate(III) [Fe(Cl2An)3](3-) paramagnetic anion afforded a complete series of chiral magnetic molecular conductors formulated as β-[(S,S,S,S)-TM-BEDT-TTF]3PPh4[K(I)Fe(III)(Cl2An)3]·3H2O (1), β-[(R,R,R,R)-TM-BEDT-TTF]3PPh4[K(I)Fe(III)(Cl2An)3]·3H2O (2), and β-[(rac)-TM-BEDT-TTF]3PPh4[K(I)Fe(III)(Cl2An)3]·3H2O (3). Compounds 1-3 are isostructural and crystallize in triclinic space groups (P1 for 1 and 2, P-1 for 3) showing a segregated organic-inorganic crystal structure, where anionic honeycomb layers obtained by self-assembling of the Λ and Δ enantiomers of the paramagnetic complex with potassium cations alternate with organic layers where the chiral donors are arranged in the β packing motif. Compounds 1-3 show a molecular packing strongly influenced by the topology of the inorganic layers and behave as molecular semiconductors with room-temperature conductivity values of ca. 3 × 10(-4) S cm(-1). The magnetic properties are dominated by the paramagnetic S = 5/2 [Fe(Cl2An)3](3-) anions whose high-spin character is confirmed by magnetic susceptibility measurements. The correlation between crystal structure and conducting behavior has been studied by means of tight-binding band structure calculations which support the observed conducting properties.
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The electrostatics of VDAC: implications for selectivity and gating.
Choudhary, Om P; Ujwal, Rachna; Kowallis, William; Coalson, Rob; Abramson, Jeff; Grabe, Michael
2010-02-26
The voltage-dependent anion channel (VDAC) is the major pathway mediating the transfer of metabolites and ions across the mitochondrial outer membrane. Two hallmarks of the channel in the open state are high metabolite flux and anion selectivity, while the partially closed state blocks metabolites and is cation selective. Here we report the results from electrostatics calculations carried out on the recently determined high-resolution structure of murine VDAC1 (mVDAC1). Poisson-Boltzmann calculations show that the ion transfer free energy through the channel is favorable for anions, suggesting that mVDAC1 represents the open state. This claim is buttressed by Poisson-Nernst-Planck calculations that predict a high single-channel conductance indicative of the open state and an anion selectivity of 1.75--nearly a twofold selectivity for anions over cations. These calculations were repeated on mutant channels and gave selectivity changes in accord with experimental observations. We were then able to engineer an in silico mutant channel with three point mutations that converted mVDAC1 into a channel with a preference for cations. Finally, we investigated two proposals for how the channel gates between the open and the closed state. Both models involve the movement of the N-terminal helix, but neither motion produced the observed voltage sensitivity, nor did either model result in a cation-selective channel, which is observed experimentally. Thus, we were able to rule out certain models for channel gating, but the true motion has yet to be determined. Copyright (c) 2009. Elsevier Ltd. All rights reserved.
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NASA Astrophysics Data System (ADS)
Schampera, Birgit; Dultz, Stefan
2013-04-01
The low permeability, high cation exchange capacity (CEC) and plasticity of bentonites favor their use in multibarrier systems of waste deposits [1]. Bentonites have a high CEC but their ability to sorb anions is very low. There is, however, need for retardation of anions and organic pollutants in many applications. Bentonites, modified with certain organic cations, have the capacity to sorb anions and non-polar organic compounds in addition to cations. Investigations on organically modified clays address a wide variety of applications including immobilization of pollutants in contaminated soils, waste water treatment and in situ placement for the protection of ground water [2]. Many experiments on anion and cation sorption of organo-clays were conducted in the batch mode which does not reflect solid-liquid ratios and material densities in barrier systems. Diffusion experiments on compacted clays allow the evaluation of transport processes and sorption of pollutants at conditions relevant for repositories. For organo-clays only few diffusion studies are published e.g. [3] measured the diffusion of tritium and [4] the diffusion of H2O in bentonite and organo-bentonites. The organic cation hexadecylpyridinium (HDPy) was added to Wyoming bentonite (MX-80) in amounts corresponding to 2-400 % of the CEC. The uptake of organic cations was determined by the C-content, XRD and IR-spectroscopy. Wettability was analyzed by the contact angle. Physical, chemical and mineralogical properties of clays were characterized. Diffusion experiments were carried out in situ in a cell attached to the ATR-unit of a FTIR-spectrometer. For H2O-diffusion the compacted organo-clays are saturated first with D2O, afterwards H2O is supplied to the surface at the top of the clay platelet. Anion-diffusion was conducted with NO3--solution instead of H2O only having characteristic IR band positions at 1350 cm-1. Three different concentrations (0.25M, 0.5M and 1M) were used. Additional batch experiments with NO3- will support the understanding of sorption behavior of the anions. All hydrophilic samples have a higher retardation capacity, indicated by diffusion coefficients of 2.44 x 10-11 m/s2 for original bentonite and ˜2.1 x 10-11m/s2 for hydrophilic organo-clays. For hydrophobic organo-clays the H2O diffusion can be higher and is increased at high bulk density (1-1.5 g/m3) up to 2.76 x 10-10m2/s. Experiments with NO3- at bulk density of 1.5 g/m3 reveal that the apparent diffusion coefficients of nitrate are with results up to 5.61 x 1012 m2/s distinctively lower than free diffusion of nitrate in pure water (6.46 x 1010 m2/s at experimental conditions) and nitrate diffusion in natural bentonite (2.63 x 1011 m2/s). The measurements allow the interpretation of the different sorption mechanisms, retardation capacity and diffusion behavior of the analyzed clays at different anion concentrations. Ongoing molecular dynamic simulations will contribute understanding of diffusion processes in organo-clays including the conditions at the interface of the clay minerals and in solution. References: [1] Shackelford, C.D., Moore S.M. (2013) Fickian diffusion of radionuclides for engineered containment barriers: Diffusion coefficients, porosities, and complicating issues. Engineering Geology, 152, 133-147. [2] Rytwo, G., Nir, S., Shuali, U. (2012) Clay and water treatment. Applied Clay Science, 67-68, 117-118. [3] Lorenzetti, R.L., Bartelt-Hunt, S.L., Burns, S.E., Smith, J.A. (2005) Hydraulic conductivities and effective diffusion coefficients of geosynthetic clay liners with organobentonite amendments. Geotextiles and Geomembranes, 23, 385-400. [4] Schampera, B., Dultz, S. (2011) H2O self-diffusion in compacted clays as influenced by surface charge and wettability - obstruction effects of bound H2O layers. Clay and Clay Minerals,59, 42-57.
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Faridbod, Farnoush; Ganjali, Mohammad Reza; Dinarvand, Rassoul; Norouzi, Parviz
2008-01-01
Many research studies have been conducted on the use of conjugated polymers in the construction of chemical sensors including potentiometric, conductometric and amperometric sensors or biosensors over the last decade. The induction of conductivity on conjugated polymers by treating them with suitable oxidizing agents won Heeger, MacDiarmid and Shirakawa the 2000 Nobel Prize in Chemistry. Common conjugated polymers are poly(acetylene)s, poly(pyrrole)s, poly(thiophene)s, poly(terthiophene)s, poly(aniline)s, poly(fluorine)s, poly(3-alkylthiophene)s, polytetrathiafulvalenes, poly-napthalenes, poly(p-phenylene sulfide), poly(p-phenylenevinylene)s, poly(3,4-ethylene-dioxythiophene), polyparaphenylene, polyazulene, polyparaphenylene sulfide, poly-carbazole and polydiaminonaphthalene. More than 60 sensors for inorganic cations and anions with different characteristics based on conducting polymers have been reported. There have also been reports on the application of non-conducting polymers (nCPs), i.e. PVC, in the construction of potentiometric membrane sensors for determination of more than 60 inorganic cations and anions. However, the leakage of ionophores from the membranes based on these polymers leads to relatively lower life times. In this article, we try to give an overview of Solid-Contact ISE (SCISE), Single-Piece ISE (SPISE), Conducting Polymer (CP)-Based, and also non-conducting polymer PVC-based ISEs for various ions which their difference is in the way of the polymer used with selective\\ membrane. In SCISEs and SPISEs, the plasticized PVC containing the ionophore and ionic additives govern the selectivity behavior of the electrode and the conducting polymer is responsible of ion-to-electron transducer. However, in CPISEs, the conducting polymer layer is doped with a suitable ionophore which enhances the ion selectivity of the CP while its redox response has to be suppressed. PMID:27879825
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Apparatus and Method for Generating Thrust Using a Two Dimensional, Asymmetrical Capacitor Module
NASA Technical Reports Server (NTRS)
Campbell, Jonathan W. (Inventor)
2001-01-01
A capacitor module system is provided for creating a thrust force. The system includes a capacitor module provided with a first conductive element having a cylindrical geometry. The first conductive element can be a hollow cylinder or a solid cylinder. The capacitor module also includes a second conductive element axially spaced from the first conductive element and of smaller axial extent. The second conductive element can be a flat disk, a dome, or a conductive tip at the end of a dielectric rod. A dielectric element is disposed between the first conductive element and the second conductive element. The system also includes a high voltage source having first and second terminals connected respectively to the first and second conductive elements. The high voltage source applies a high voltage to the conductive elements of sufficient value to create a thrust force on the module inducing movement thereof.
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Block copolymers for alkaline fuel cell membrane materials
NASA Astrophysics Data System (ADS)
Li, Yifan
Alkaline fuel cells (AFCs) using anion exchange membranes (AEMs) as electrolyte have recently received considerable attention. AFCs offer some advantages over proton exchange membrane fuel cells, including the potential of non-noble metal (e.g. nickel, silver) catalyst on the cathode, which can dramatically lower the fuel cell cost. The main drawback of traditional AFCs is the use of liquid electrolyte (e.g. aqueous potassium hydroxide), which can result in the formation of carbonate precipitates by reaction with carbon dioxide. AEMs with tethered cations can overcome the precipitates formed in traditional AFCs. Our current research focuses on developing different polymer systems (blend, block, grafted, and crosslinked polymers) in order to understand alkaline fuel cell membrane in many aspects and design optimized anion exchange membranes with better alkaline stability, mechanical integrity and ionic conductivity. A number of distinct materials have been produced and characterized. A polymer blend system comprised of poly(vinylbenzyl chloride)-b-polystyrene (PVBC-b-PS) diblock copolymer, prepared by nitroxide mediated polymerization (NMP), with poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) or brominated PPO was studied for conversion into a blend membrane for AEM. The formation of a miscible blend matrix improved mechanical properties while maintaining high ionic conductivity through formation of phase separated ionic domains. Using anionic polymerization, a polyethylene based block copolymer was designed where the polyethylene-based block copolymer formed bicontinuous morphological structures to enhance the hydroxide conductivity (up to 94 mS/cm at 80 °C) while excellent mechanical properties (strain up to 205%) of the polyethylene block copolymer membrane was observed. A polymer system was designed and characterized with monomethoxy polyethylene glycol (mPEG) as a hydrophilic polymer grafted through substitution of pendent benzyl chloride groups of a PVBC-b-PS. The incorporation of the hydrophilic polymer allows for an investigation of the effect of hydration on ionic conductivity, resulting in the increase in membrane water affinity, enhancement of conductivity and reduced dependence of conductivity on relative humidity. A study of crosslinking of block copolymers was done wherein the crosslinking occurs in the non-matrix phase in order to maintain mechanical properties. The formation of a cationic crosslinked structure improves the mechanical integrity of the membrane in water while showing little deleterious effect on ionic conductivity and mechanical properties.
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On the adsorption of phloretin onto a black lipid membrane.
de Levie, R; Rangarajan, S K; Seelig, P F; Andersen, O S
1979-01-01
The effect of uncharged, dipolar phloretin on anion and cation conductance through a black lipid membrane can be used to study its adsorption behavior. The adsorption of phloretin can be described by a Langmuir isotherm with weak dipole-dipole interaction. PMID:262390
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Modeling of Mutual Anion-Cation Neutralization Processes
2011-07-01
Chemical Kinetics, Plasma Chemistry 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT SAR 18, NUMBER OF PAGES 9 19a. NAME OF...understanding of elementary processes in plasma chemistry , conducted jointly with the research group of Dr. A. A. Viggiano at the AFRL and supported by
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Rezende, Kariolanda C A; Moreira, Roger Cardoso; Logrado, Lucio Paulo Lima; Talhavini, Márcio; Coltro, Wendell K T
2016-10-01
This report describes for the first time the use of microchip electrophoresis (ME) devices integrated with capacitively coupled contactless conductivity detection (C 4 D) to investigate the authenticity of seized whiskey samples, which were probably adulterated by simple dilution with tap water. The proposed microfluidic platform was explored for the monitoring of anionic species (Cl - and F - ) in both original and tampered samples. The best separations were achieved within 70 s using a running buffer composed of lactic acid and histidine (pH = 5.9). ME-C 4 D devices were used to analyze samples from three different brands (five samples each). Based on the presence of inorganic anions like Cl - , F - , SO 4 2- and NO 2 - in different amounts, the authenticity of seized whiskeys was compared to original samples. According to the reported data, the proposed microfluidic platform can be useful to help regulatory authorities in the investigation and monitoring of authenticity of commercialized whiskey beverages. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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Górski, Łukasz; Matusevich, Alexey; Pietrzak, Mariusz; Wang, Lin; Meyerhoff, Mark E.; Malinowska, Elżbieta
2010-01-01
The performance of solid-contact/coated wire type electrodes with plasticized PVC membranes containing metalloporphyrins as anion selective ionophores is reported. The membranes are deposited on transducers based on graphite pastes and graphite rods. The hydrophobicity of the underlying conductive transducer surface is found to be a key factor that influences the formation of an aqueous layer beneath the polymer film. Elimination of this ill-defined water layer greatly improves the electrochemical properties of the ion-sensors, such as EMF stability and life-time. Only highly lipophilic electrode substrates, namely graphite paste with mineral oil, were shown to prevent the formation of aqueous layer underneath the ion-sensing membrane. The possibility of employing Co(III)-tetraphenylporphyrin both as NO2− selective ionophore and as electron/ion conducting species to ensure ion-to-electron translation was also discussed based on the results of preliminary experiments. PMID:20357903
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On the origin of blue emission from ZnO quantum dots synthesized by a sol-gel route
NASA Astrophysics Data System (ADS)
Han, Li-Li; Cui, Lan; Wang, Wei-Hua; Wang, Jiang-Long; Du, Xi-Wen
2012-06-01
ZnO quantum dots (QDs) with blue emission were synthesized by a sol-gel method. A series of control experiments were conducted to explore the origin of the blue emission. It is found that the blue emission arises from neither the quantum confinement nor intermediate products, and it can be achieved only in the presence of Li+ cations and excessive OH- anions. Moreover, the long decay time of the blue emission suggests a defect-related de-excitation process. On the basis of the experimental and calculation results, possible de-excitation paths for light emission were discussed, and the origin of the blue emission was determined as the electron transition from the conduction band to interstitial oxygen defects. Excessive OH- anions are responsible for the formation of interstitial oxygen defects, and Li+ ions can stabilize the defects by substituting for Zn atoms. Besides, Li+ ions can block the growth of ZnO QDs, broaden their band gap and cause a blue shift of the blue emission.
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Liao, Hsiang-Ruei; Chen, Ih-Sheng; Liu, Fu-Chao; Lin, Shinn-Zhi; Tseng, Ching-Ping
2018-06-15
This study investigates the effect and the underlying mechanism of 2',3-dihydroxy-5-methoxybiphenyl (RIR-2), a lignan extracted from the roots of Rhaphiolepis indica (L.) Lindl. ex Ker var. tashiroi Hayata ex Matsum. & Hayata (Rosaceae), on N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP)-induced respiratory burst and cathepsin G in human neutrophils. Signaling pathways regulated by RIR-2 which modulated fMLP-induced respiratory burst were evaluated by an interaction between β subunit of G-protein (Gβ) with downstream signaling induced by fMLP and by immunoblotting analysis of the downstream targets of Gβ-protein. RIR-2 inhibited fMLP-induced superoxide anion production (IC 50 :2.57 ± 0.22 μM), cathepsin G release (IC 50 :18.72 ± 3.76 μM) and migration in a concentration dependent manner. RIR-2 specifically suppresses fMLP-induced Src family kinases phosphorylation by inhibiting the interaction between Gβ-protein with Src kinases without inhibiting Src kinases activities, therefore, RIR-2 attenuated the downstream targets of Src kinase, such as phosphorylation of Raf/ERK, AKT, P38, PLCγ2, PKC and translocation Tec, p47 ph ° x and P40 ph ° x from the cytosol to the inner leaflet of the plasma membrane. Furthermore, RIR-2 attenuated fMLP-induced intracellular calcium mobilization by inhibiting the interaction between Gβ-protein with PLCβ2. RIR-2 was not a competitive or allosteric antagonist of fMLP. On the contrary, phorbol 12-myristate 13-acetate (PMA)-induced phosphorylation of Src, AKT, P38, PKC and membrane localization of p47 ph ° x and P40 ph ° x remained unaffected. RIR-2 specifically modulates fMLP-mediated neutrophil superoxide anion production and cathepsin G release by inhibiting the interaction between Gβ-protein with downstream signaling which subsequently interferes with the activation of intracellular calcium, PLCγ2, AKT, p38, PKC, ERK, p47 ph ° x and p40 phox . Copyright © 2018 Elsevier B.V. All rights reserved.
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Bekar, L K; Loewen, M E; Forsyth, G W; Walz, W
2005-09-30
Chloride concentration has been shown to have a dramatic impact on protein folding and subsequent tertiary conformation [K.D. Collins, Ions from the Hofmeister series and osmolytes: effects on proteins in solution and in the crystallization process, Methods 34 (2004) 300-311; I. Jelesarov, E. Durr, R.M. Thomas, H.R. Bosshard, Salt effects on hydrophobic interaction and charge screening in the folding of a negatively charged peptide to a coiled coil (leucine zipper), Biochemistry 37 (1998) 7539-7550]. As it is known that Kv channel gating is linked to the stability of the cytoplasmic T1 multimerization domain conformation [D.L. Minor, Y.F. Lin, B.C. Mobley, A. Avelar, Y.N. Jan, L.Y. Jan, J.M. Berger, The polar T1 interface is linked to conformational changes that open the voltage-gated potassium channel, Cell 102 (2000) 657-670; B.A. Yi, D.L. Minor Jr., Y.F. Lin, Y.N. Jan, L.Y. Jan, Controlling potassium channel activities: interplay between the membrane and intracellular factors, Proc. Natl. Acad. Sci. U.S.A. 98 (2001) 11016-11023] and that intracellular chloride concentration has been linked to Kv channel kinetics [L.K. Bekar, W. Walz, Intracellular chloride modulates A-type potassium currents in astrocytes, Glia 39 (2002) 207-216; W.B. Thoreson, S.L. Stella, Anion modulation of calcium current voltage dependence and amplitude in salamander rods, Biochim. Biophys. Acta 1464 (2000) 142-150], the objective of the present study was to address how chloride concentration changes affect Kv channel kinetics more closely in an isolated expression system. Initially, no significant chloride concentration-dependent effects on channel steady-state gating kinetics were observed. Only after disruption of the cytoskeleton with cytochalasin-D did we see significant chloride concentration-dependent shifts in gating kinetics. This suggests that the shift in gating kinetics is mediated through effects of intracellular chloride concentration on cytoplasmic domain tertiary conformation as cytoskeletal interaction appears to mask the effect. Furthermore, as cytoskeletal disruption only impacts channel gating kinetics at low physiological intracellular chloride concentrations, these studies highlight the importance of paying close attention to anion concentrations used under experimental conditions.
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Frequency Dependence of Electron Spin-lattice Relaxation for Semiquinones in Alcohol Solutions
Elajaili, Hanan B.; Biller, Joshua R.; Eaton, Sandra S.; Eaton, Gareth R.
2014-01-01
The spin-lattice relaxation rates at 293 K for three anionic semiquinones (2,5-di-t-butyl-1,4-benzosemiquinone, 2,6-di-t-butyl-1,4-benzosemiquinone, and 2,3,5,6-tetramethoxy-1,4-benzosemiquinone) were studied at up to 8 frequencies between 250 MHz and 34 GHz in ethanol or methanol solution containing high concentrations of OH-. The relaxation rates are about a factor of 2 faster at lower frequencies than at 9 or 34 GHz. However, in perdeuterated alcohols the relaxation rates exhibit little frequency dependence, which demonstrates that the dominant frequency-dependent contribution to relaxation is modulation of dipolar interactions with solvent nuclei. The relaxation rates were modeled as the sum of two frequency-independent contributions (spin rotation and a local mode) and two frequency-dependent contributions (modulation of dipolar interaction with solvent nuclei and a much smaller contribution from modulation of g anisotropy). The correlation time for modulation of the interaction with solvent nuclei is longer than the tumbling correlation time of the semiquinone and is consistent with hydrogen bonding of the alcohol to the oxygen atoms of the semiquinones. PMID:25261741
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NASA Astrophysics Data System (ADS)
Gubanov, V. A.; Pentaleri, E. A.; Boekema, C.; Fong, C. Y.; Klein, B. M.
1997-03-01
We have investigated clusterization of nitrogen vacancies and Si and Mg doping impurities in zinc-blende aluminum nitride (c-AlN) and gallium nitride (c-GaN) by the tight-binding LMTO technique. The calculations used 128-site supercells. Si and Mg atoms replacing ions in both the cation and anion sublattices of the host lattices of the host crystals have been considered. The Mg impurity at cation sites is found to form partially occupied states at the valence-band edge, and may result in p-type conductivity. When Si substitutes for Ga, the impurity band is formed at the conduction-band edge, resulting in n-type conductivity. Si impurities at cation sites, and Mg impurity at anion sites are able to form resonance states in the gap. The influence of impurity clusterization in the host lattice and interstitial sites on electronic properties of c-AlN and c-GaN crystals are modeled. The changes in vacancy- and impurity-state energies, bonding type, localization, density of states at the Fermi level in different host lattices, their dependence on impurity/vacancy concentration are analyzed and compared with the experimental data.
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Mechanistic insights related to the design and construction of lithium single ion conductors
NASA Astrophysics Data System (ADS)
Spahlinger, Gregory
Lithium single ion conductors are a class of electrolytes, typically designed for lithium ion batteries, with the potential to improve the performance of these batteries. The benefits of single ion conductors arise out of the fact that their immobile anions are not capable of concentrating near the anode of the battery, causing an increase in resistance as the battery is discharged. Unfortunately lithium single ion conductors suffer severe drawbacks in their conductivity which have been attributed to diverse causes. Because of the low success rate of single ion conductors in the literature and previous work in the Baker group, I have chosen to investigate mechanistic questions related to the design and construction of these materials, without engineering new materials. An attractive design strategy for the screening of immobile anion moieties for single ion conductors would be the use of the copper catalyzed alkyne azide (CUAAC) "click" reaction in order to efficiently introduce anions onto a polymer or nanoparticle support in a way that is efficient and tunable. A variable added by this strategy would be the presence of a 1,2,3-triazole moiety which is without any significant precedent in the lithium ion electrolyte literature. In order to assess the impact of the triazole in on the conductivity of an electrolyte a series of model compounds were synthesized containing a variable number of triazoles in an otherwise poly(ethylene glycol) like oligomer chain. The model compounds were subjected to differential scanning calorimetry, electrochemical impedance spectroscopy, and in one case single crystal X-ray diffraction, and solvent shells were modeled for lithium with and without triazoles using ab initio quantum chemistry calculations. It was concluded that the triazole is not significantly stronger than an ether oxygen as a ligand in the electrolytes, however the triazole has a substantial dipole which exerts some deleterious effects on the conductivity, leading to an increase in the Arrhenius activation energy for the process. These effects are balanced by an increase in the pre-exponential factor which leads to "compensation behavior" due to the dependence of that quantity on the dipole density in the material. The observed effect is one of a lower conductivity for the model compounds relative to poly(ethylene glycol)dimethyl ether 500 at room temperature, which converges to roughly the same conductivity around 80 °C. In synthetic studies, attempts were made to synthesize N-triflylpropanesultam (TPS) a five membered heterocycle whose nucleophilic ring opening would yield a desirable anion for use in single ion conductors. TPS proved to be significantly more difficult to open than expected, which prompted a computational study. In order to study the nucleofugality of polyatomic anionic leaving groups derived from oxygen and nitrogen, a contingent of 19 methylating agents consisting of amines or alcohols activated with carbonyl or sulfonyl substituents has been examined via ab initio calculations. Gas phase activation energies for alkylation of ammonia, and gas phase methyl cation affinitys were calculated. It was found that polyatomic anionic leaving groups derived from nitrogen will have higher activation energies for Menshutkin (SN2) alkylation even when they have similar methyl cation affinities. This inherent deficit in the nucleofugality of nitrogen derived leaving groups appears to be a result of the way bond cleavage is synchronized with bond formation to the incoming ammonia nucleophile. Additionally the second sulfonyl group present in a sulfonimide appears to be less effective at activating nitrogen due to a preference for tetrahedral geometries at nitrogen in the transition states of sulfonamide groups. Optimal delocalization of electron density is therefore frustrated due to the symmetry of the leaving group.
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Adjei, Isaac M; Sharma, Blanka; Peetla, Chiranjeevi; Labhasetwar, Vinod
2016-06-28
Advanced-stage prostate cancer usually metastasizes to bone and is untreatable due to poor biodistribution of intravenously administered anticancer drugs to bone. In this study, we modulated the surface charge/composition of biodegradable nanoparticles (NPs) to sustain their blood circulation time and made them small enough to extravasate through the openings of the bone's sinusoidal capillaries and thus localize into marrow. NPs with a neutral surface charge, achieved by modulating the NP surface-associated emulsifier composition, were more effective at localizing to bone marrow than NPs with a cationic or anionic surface charge. These small neutral NPs (~150nm vs. the more usual ~320nm) were also ~7-fold more effective in localizing in bone marrow than large NPs. We hypothesized that NPs that effectively localize to marrow could improve NP-mediated anticancer drug delivery to sites of bone metastasis, thereby inhibiting cancer progression and preventing bone loss. In a PC-3M-luc cell-induced osteolytic intraosseous model of prostate cancer, these small neutral NPs demonstrated greater accumulation in bone within metastatic sites than in normal contralateral bone as well as co-localization with the tumor mass in marrow. Significantly, a single-dose intravenous administration of these small neutral NPs loaded with paclitaxel (PTX-NPs), but not anionic PTX-NPs, slowed the progression of bone metastasis. In addition, neutral PTX-NPs prevented bone loss, whereas animals treated with the rapid-release drug formulation Cremophor EL (PTX-CrEL) or saline (control) showed >50% bone loss. Neutral PTX-NPs did not cause acute toxicity, whereas animals treated with PTX-CrEL experienced weight loss. These results indicate that NPs with appropriate physical and sustained drug-release characteristics could be explored to treat bone metastasis, a significant clinical issue in prostate and other cancers. Copyright © 2016 Elsevier B.V. All rights reserved.
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IONIC LIQUID-CATALYZED ALKYLATION OF ISOBUTANE WITH 2-BUTENE
A detailed study of the alkylation of isobutane with 2-butene in ionic liquid media has been conducted using 1-alkyl-3-methylimidazolium halides?aluminum chloride encompassing various alkyl groups (butyl-, hexyl-, and octyl-) and halides (Cl, Br, and I) on its cations and anions,...
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Processing α-mercuric iodide by zone refining
NASA Astrophysics Data System (ADS)
Burger, A.; Morgan, S. H.; Henderson, D. O.; Biao, Y.; Zhang, K.; Silberman, E.; Nason, D.; van den Berg, L.; Ortale-Baccash, C.; Cross, E.
1993-03-01
An investigation is being conducted on zone refining α-mercuric iodide. Analytical studies using differential scanning calorimetry and anion chromatography indicate that impurities are accumulated mainly at the end where zone travel terminates. Early results indicate that single crystals can be readily grown from zone-refined material.
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Cl- channels of the gastric parietal cell that are active at low pH.
Cuppoletti, J; Baker, A M; Malinowska, D H
1993-06-01
HCl secretion across mammalian gastric parietal cell apical membrane may involve Cl- channels. H(+)-K(+)-ATPase-containing membranes isolated from gastric mucosa of histamine-stimulated rabbits were fused to planar lipid bilayers. Channels were recorded with symmetric 800 mM CsCl solutions, pH 7.4. A linear current-voltage (I-V) relationship was obtained, and conductance was 28 +/- 1 pS at 800 mM CsCl. Conductance was 6.9 +/- 2 pS at 150 mM CsCl. Reversal potential was +22 mV with a fivefold cis-trans CsCl concentration gradient, indicating that the channel was anion selective with a discrimination ratio of 6:1 for Cl- over Cs+. Anion selectivity of the channel was I- > Cl- > or = Br- > NO3-, and gluconate was impermeant. Channels obtained at pH 7.4 persisted when pH of medium bathing the trans side of the bilayer (pHtrans) was reduced to pH 3, without a change in conductance, linearity of I-V relationship, or ion selectivity. In contrast, asymmetric reduction of pH of medium bathing the cis side of the bilayer from 7.4 to 3 always resulted in loss of channel activity. At pH 7.4, open probability (Po) of the channel was voltage dependent, i.e., predominantly open at +80 mV but mainly closed at -80 mV. In contrast, with low pHtrans, channel Po at -80 mV was increased 3.5-fold. The Cl- channel was Ca2+ indifferent. In absence of ionophores, ion selectivity for support of H(+)-K(+)-ATPase activity and H+ transport was consistent with that exhibited by the channel and could be limited by substitution with NO3-, whereas maximal H(+)-K(+)-ATPase activity was indifferent to anion present, demonstrating that anion transport can be rate limiting. Cl- channels with similar characteristics (conductance, linear I-V relationship, and ion selectivity) were also present in H(+)-K(+)-ATPase-containing vesicles isolated from resting (cimetidine-treated) gastric mucosa, exhibiting at -80 mV a pH-independent approximately 3.5-fold lower Po than stimulated vesicle channels. At -80 mV, reduction of pHtrans increased Po of both resting and stimulated Cl- channels by five- to sixfold. Changing membrane potential from 0 to -80 mV across stimulated vesicles increased Cl- channel activity an additional 10-fold.(ABSTRACT TRUNCATED AT 400 WORDS)
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Enomoto, Takeshi; Matsumoto, Kazuhiko; Hagiwara, Rika
2011-12-14
A room temperature ionic liquid (IL) based on the fluorosulfate anion (SO(3)F(-)) has been synthesized by the reaction of 1-ethyl-3-methylimidazolium (EMIm(+)) chloride and fluorosulfuric acid (HOSO(2)F). The viscosity, ionic conductivity, and electrochemical window of EMImSO(3)F at 25 °C are 46.6 mPa s, 10.8 mS cm(-1), and 4.3 V, respectively. According to a solvatochromic measurement using ILs, there is a trend in the donor ability of fluoro- and oxofluoroanions, PF(6)(-) < BF(4)(-) < N(SO(2)CF(3))(2)(-) < SO(3)CF(3)(-) < SO(3)F(-) < PO(2)F(2)(-), which is explained by the atomic charges obtained from quantum mechanical calculations. The 1 : 2 and 1 : 3 stoichiometric reactions of EMImCl and HOSO(2)F give EMIm(FO(2)SOH)OSO(2)F and EMIm(FO(2)SOH)(2)O(2)SOF, respectively. Both the salts are liquid at room temperature without a HOSO(2)F dissociation pressure (< 1 Pa) and have low viscosity and high ionic conductivity (9.2 mPa s and 30.8 mS cm(-1) for EMIm(FO(2)SOH)OSO(2)F and 5.1 mPa s and 43.2 mS cm(-1) for EMIm(FO(2)SOH)(2)O(2)SOF). The vibrational modes and bonding properties of these anionic species are discussed with the aid of quantum mechanical calculations. The (FO(2)SOH)OSO(2)F(-) anion in EMIm(FO(2)SOH)OSO(2)F does not have an inversion centre, which stands in contrast to the one with an inversion centre (e.g. observed in solid Cs(FO(2)SOH)OSO(2)F). The (FO(2)SOH)(2)O(2)SOF(-) anion in EMIm(FO(2)SOH)(2)O(2)SOF is characterized by vibrational spectroscopy under C(s) symmetry.
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Liu, Ying; Wang, Guoyuan; Yang, Mingguang; Chen, Haining; zhao, Yan; Yang, Shucai; Sun, Changhao
2015-12-25
Arctigenin is a bioactive constituent from dried seeds of Arctium lappa L., which was traditionally used as medicine. Arctigenin exhibits various bioactivities, but its effects on blood pressure regulation are still not widely studied. In this study, we investigated antihypertensive effects of arctigenin by long-term treatment in spontaneously hypertensive rats (SHRs). Arctigenin (50 mg/kg) or vehicle was administered to SHRs or Wistar rats as negative control by oral gavage once a day for total 8 weeks. Nifedipine (3 mg/kg) was used as a positive drug control. After treatment, hemodynamic and physical parameters, vascular reactivity in aorta, the concentration of plasma arctigenin and serum thromboxane B2, NO release and vascular p-eNOS, p-Akt, caveolin-1 protein expression, and vascular superoxide anion generation and p47phox protein expression were detected and analyzed. The results showed that arctigenin significantly reduced systolic blood pressure and ameliorated endothelial dysfunction of SHRs. Arctigenin reduced the levels of thromboxane B2 in plasma and superoxide anion in thoracic aorta of SHRs. Furthermore, arctigenin increased the NO production by enhancing the phosphorylation of Akt and eNOS (Ser 1177), and inhibiting the expression of NADPH oxidase in thoracic aorta of SHRs. Our data suggested that antihypertensive mechanisms of arctigenin were associated with enhanced eNOS phosphorylation and decreased NADPH oxidase-mediated superoxide anion generation. Copyright © 2015 Elsevier Inc. All rights reserved.
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Microsiemens or Milligrams: Measures of Ionic Mixtures ...
In December of 2016, EPA released the Draft Field-Based Methods for Developing Aquatic Life Criteria for Specific Conductivity for public comment. Once final, states and authorized tribes may use these methods to derive field-based ecoregional ambient Aquatic Life Ambient Water Quality Criteria (AWQC) for specific conductivity (SC) in flowing waters. The methods provide flexible approaches for developing science-based SC criteria that reflect ecoregional or state specific factors. The concentration of a dissolved salt mixture can be measured in a number of ways including measurement of total dissolved solids, freezing point depression, refractive index, density, or the sum of the concentrations of individually measured ions. For the draft method, SC was selected as the measure because SC is a measure of all ions in the mixture; the measurement technology is fast, inexpensive, and accurate, and it measures only dissolved ions. When developing water quality criteria for major ions, some stakeholders may prefer to identify the ionic constituents as a measure of exposure instead of SC. A field-based method was used to derive example chronic and acute water quality criteria for SC and two anions a common mixture of ions (bicarbonate plus sulfate, [HCO3−] + [SO42−] in mg/L) that represent common mixtures in streams. These two anions are sufficient to model the ion mixture and SC (R2 = 0.94). Using [HCO3−] + [SO42−] does not imply that these two anions are the
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Weiber, E Annika; Jannasch, Patric
2014-09-01
A series of copoly(arylene ether sulfone)s that have precisely two, three, or four quaternary ammonium (QA) groups clustered directly on single phenylene rings along the backbone are studied as anion-exchange membranes. The copolymers are synthesized by condensation polymerizations that involve either di-, tri-, or tetramethylhydroquinone followed by virtually complete benzylic bromination using N-bromosuccinimide and quaternization with trimethylamine. This synthetic strategy allows excellent control and systematic variation of the local density and distribution of QA groups along the backbone. Small-angle X-ray scattering of these copolymers shows extensive ionic clustering, promoted by an increasing density of QA on the single phenylene rings. At an ion-exchange capacity (IEC) of 2.1 meq g(-1), the water uptake decreases with the increasing local density of QA groups. Moreover, at moderate IECs at 20 °C, the Br(-) conductivity of the densely functionalized copolymers is higher than a corresponding randomly functionalized polymer, despite the significantly higher water uptake of the latter. Thus, the location of multiple cations on single aromatic rings in the polymers facilitates the formation of a distinct percolating hydrophilic phase domain with a high ionic concentration to promote efficient anion transport, despite probable limitations by reduced ion dissociation. These findings imply a viable strategy to improve the performance of alkaline membrane fuel cells. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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Walch, Nicole; Jungbauer, Alois
2017-06-01
Truly continuous biomanufacturing processes enable an uninterrupted feed stream throughout the whole production without the need for holding tanks. We have utilized microporous anion and cation exchangers into which only salts, but not proteins, can penetrate into the pores for desalting of protein solutions, while diafiltration or dilution is usually employed for feed adjustments. Anion exchange and cation exchange chromatography columns were connected in series to remove both anions and cations. To increase operation performance, a continuous process was developed comprised of four columns. Continuous mode was achieved by staggered cycle operation, where one set of columns, consisting of one anion exchange and one cation exchange column, was loaded during the regeneration of the second set. Refolding, desalting and subsequent ion exchange capturing with a scFv as the model protein was demonstrated. The refolding solution was successfully desalted resulting in a consistent conductivity below 0.5 mS/cm from initial values of 10 to 11 mS/cm. With continuous operation process time could be reduced by 39% while productivity was increased to 163% compared to batch operation. Desalting of the protein solution resulted in up to 7-fold higher binding capacities in the subsequent ion exchange capture step with conventional protein binding resins. © 2017 The Authors. Biotechnology Journal published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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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.
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The influence of reagent type on the kinetics of ultrafine coal flotation
Read, R.B.; Camp, L.R.; Summers, M.S.; Rapp, D.M.
1989-01-01
A kinetic study has been conducted to determine the influence of reagent type on flotation rates of ultrafine coal. Two ultrafine coal samples, the Illinois No. 5 (Springfield) and Pittsburgh No. 8, have been evaluated with various reagent types in order to derive the rate constants for coal (kc), ash (ka), and pyrite (kc). The reagents used in the study include anionic surfactants, anionic surfactant-alcohol mixtures, and frothing alcohols. In general, the surfactant-alcohol mixtures tend to float ultrafine coal at a rate three to four times faster than either pure alcohols or pure anionic surfactants. Pine oil, a mixture of terpene alcohols and hydrocarbons, was an exception to this finding; it exhibited higher rate constants than the pure aliphatic alcohols or other pure anionic surfactants studied; this may be explained by the fact that the sample of pine oil used (70% alpha-terpineol) acted as a frother/collector system similar to alcohol/kerosene. The separation efficiencies of ash and pyrite from coal, as evidenced by the ratios of kc/ka or kc/kp, tend to indicate, however, that commercially available surfactant-alcohol mixtures are not as selective as pure alcohols such as 2-ethyl-1-hexanol or methylisobutylcarbinol. Some distinct differences in various rate constants, or their ratios, were noted between the two coals studied, and are possibly attributable to surface chemistry effects. ?? 1989.
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The voltage-dependent anion channel as a biological transistor: theoretical considerations.
Lemeshko, V V; Lemeshko, S V
2004-07-01
The voltage-dependent anion channel (VDAC) is a porin of the mitochondrial outer membrane with a bell-shaped permeability-voltage characteristic. This porin restricts the flow of negatively charged metabolites at certain non-zero voltages, and thus might regulate their flux across the mitochondrial outer membrane. Here, we have developed a mathematical model illustrating the possibility of interaction between two steady-state fluxes of negatively charged metabolites circulating across the VDAC in a membrane. The fluxes interact by contributing to generation of the membrane electrical potential with subsequent closure of the VDAC. The model predicts that the VDAC might function as a single-molecule biological transistor and amplifier, because according to the obtained calculations a small change in the flux of one pair of different negatively charged metabolites causes a significant modulation of a more powerful flux of another pair of negatively charged metabolites circulating across the same membrane with the VDAC. Such transistor-like behavior of the VDAC in the mitochondrial outer membrane might be an important principle of the cell energy metabolism regulation under some physiological conditions.
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Cammarota, Ryan C; Vollmer, Matthew V; Xie, Jing; Ye, Jingyun; Linehan, John C; Burgess, Samantha A; Appel, Aaron M; Gagliardi, Laura; Lu, Connie C
2017-10-11
Large-scale CO 2 hydrogenation could offer a renewable stream of industrially important C 1 chemicals while reducing CO 2 emissions. Critical to this opportunity is the requirement for inexpensive catalysts based on earth-abundant metals instead of precious metals. We report a nickel-gallium complex featuring a Ni(0)→Ga(III) bond that shows remarkable catalytic activity for hydrogenating CO 2 to formate at ambient temperature (3150 turnovers, turnover frequency = 9700 h -1 ), compared with prior homogeneous Ni-centered catalysts. The Lewis acidic Ga(III) ion plays a pivotal role in stabilizing catalytic intermediates, including a rare anionic d 10 Ni hydride. Structural and in situ characterization of this reactive intermediate support a terminal Ni-H moiety, for which the thermodynamic hydride donor strength rivals those of precious metal hydrides. Collectively, our experimental and computational results demonstrate that modulating a transition metal center via a direct interaction with a Lewis acidic support can be a powerful strategy for promoting new reactivity paradigms in base-metal catalysis.
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Metabolomic and Genome-wide Association Studies Reveal Potential Endogenous Biomarkers for OATP1B1.
Yee, S W; Giacomini, M M; Hsueh, C-H; Weitz, D; Liang, X; Goswami, S; Kinchen, J M; Coelho, A; Zur, A A; Mertsch, K; Brian, W; Kroetz, D L; Giacomini, K M
2016-11-01
Transporter-mediated drug-drug interactions (DDIs) are a major cause of drug toxicities. Using published genome-wide association studies (GWAS) of the human metabolome, we identified 20 metabolites associated with genetic variants in organic anion transporter, OATP1B1 (P < 5 × 10 -8 ). Of these, 12 metabolites were significantly higher in plasma samples from volunteers dosed with the OATP1B1 inhibitor, cyclosporine (CSA) vs. placebo (q-value < 0.2). Conjugated bile acids and fatty acid dicarboxylates were among the metabolites discovered using both GWAS and CSA administration. In vitro studies confirmed tetradecanedioate (TDA) and hexadecanedioate (HDA) were novel substrates of OATP1B1 as well as OAT1 and OAT3. This study highlights the use of multiple datasets for the discovery of endogenous metabolites that represent potential in vivo biomarkers for transporter-mediated DDIs. Future studies are needed to determine whether these metabolites can serve as qualified biomarkers for organic anion transporters. Quantitative relationships between metabolite levels and modulation of transporters should be established. © 2016 American Society for Clinical Pharmacology and Therapeutics.
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Curcumin modulates free radical quenching in myocardial ischaemia in rats.
Manikandan, Panchatcharam; Sumitra, Miriyala; Aishwarya, Srinivasan; Manohar, Bhakthavatsalam Murali; Lokanadam, Beema; Puvanakrishnan, Rengarajulu
2004-10-01
This study was designed to investigate the protective effect of curcumin (CUR) against isoprenaline induced myocardial ischaemia in rat myocardium. The effect of single oral dose of curcumin (15 mg kg(-1)), administered 30 min before and/or after the onset of ischaemia, was investigated by assessing oxidative stress related biochemical parameters in rat myocardium. Curcumin pre and post-treatment (PPT) was shown to decrease the levels of xanthine oxidase, superoxide anion, lipid peroxides (LPs) and myeloperoxidase while the levels of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione-S-transferase (GST) activities were significantly increased after curcumin PPT. Histopathological and transmission electron microscopical studies also confirmed the severe myocardial damage occurring as a consequence of isoprenaline induced ischaemia and they also showed the significant improvement effected by curcumin PPT. These findings provided evidence that curcumin was found to protect rat myocardium against ischaemic insult and the protective effect could be attributed to its antioxidant properties as well as its inhibitory effects on xanthine dehydrogenase/xanthine oxidase (XD/XO) conversion and resultant superoxide anion production.
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Wan, Meng; Li, Jiang; Li, Tao; Zhu, Han; Wu, Weiwei; Du, Mingliang
2018-06-28
A facile method to prepared nitrogen anion-decorated cobalt tungsten disulfides solid solutions retaining ultra-thin WS2-like nanosheet structures (The N-CoxW1-xS2) anchored on carbon nanofibers is developed. The synergistic effect of the WS2 nanosheets provides a secure framework for stabilizing the amorphous Co-S clusters, carbon nanofibers (CNFs) substrate and nitrogen anion-decoration significantly enhances the inherent conductivity of the catalyst, resulting in a significantly promoted hydrogen evolution reaction (HER) activity and stable performance compared to pure Co9S8 nanoparticles or ultra-thin WS2 nanosheets. The N-CoxW1-xS2 electrode demonstrates the excellent electrocatalytic performance, with current density of 10 mA cm-2 at a low overpotential of 93 mV and Tafel slope of 85 mV dec-1, as well as the long-term stability in acid electrolyte. The present investigation may provide a feasible strategy for incorporating other heteroatoms into transitional metal disulfides (TMDs) materials to design catalysts with highly active and stable performance for water splitting. © 2018 IOP Publishing Ltd.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Zheng, Haiyan; Wang, Lijuan; Li, Kuo
Transformation between different types of carbon–carbon bonding in carbides often results in a dramatic change of physical and chemical properties. Under external pressure, unsaturated carbon atoms form new covalent bonds regardless of the electrostatic repulsion. It was predicted that calcium acetylide (also known as calcium carbide, CaC 2) polymerizes to form calcium polyacetylide, calcium polyacenide and calcium graphenide under high pressure. In this work, the phase transitions of CaC 2 under external pressure were systematically investigated, and the amorphous phase was studied in detail for the first time. Polycarbide anions like C 6 6– are identified with gas chromatography-mass spectrometrymore » and several other techniques, which evidences the pressure induced polymerization of the acetylide anions and suggests the existence of the polyacenide fragment. Additionally, the process of polymerization is accompanied with a 10 7 fold enhancement of the electrical conductivity. As a result, the polymerization of acetylide anions demonstrates that high pressure compression is a viable route to synthesize novel metal polycarbides and materials with extended carbon networks, while shedding light on the synthesis of more complicated metal organics.« less
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Improved Performance of Ionic Liquid Supercapacitors by using Tetracyanoborate Anions
Martins, Vitor L.; Rennie, Anthony J. R.; Sanchez‐Ramirez, Nedher; Torresi, Roberto M.; Hall, Peter J.
2018-01-01
Abstract Supercapacitors are energy storage devices designed to operate at higher power densities than conventional batteries, but their energy density is still too low for many applications. Efforts are made to design new electrolytes with wider electrochemical windows than aqueous or conventional organic electrolytes in order to increase energy density. Ionic liquids (ILs) with wide electrochemical stability windows are excellent candidates to be employed as supercapacitor electrolytes. ILs containing tetracyanoborate anions [B(CN)4] offer wider electrochemical stability than conventional electrolytes and maintain a high ionic conductivity (6.9 mS cm−1). Herein, we report the use of ILs containing the [B(CN)4] anion for such an application. They presented a high maximum operating voltage of 3.7 V, and two‐electrode devices demonstrate high specific capacitances even when operating at relatively high rates (ca. 20 F g−1 @ 15 A g−1). This supercapacitor stored more energy and operated at a higher power at all rates studied when compared with cells using a commonly studied ILs. PMID:29577008
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Epinephrine stimulation of anion secretion in the Calu-3 serous cell model
Banga, Amiraj; Flaig, Stephanie; Lewis, Shanta; Winfree, Seth
2014-01-01
Calu-3 is a well-differentiated human bronchial cell line with the characteristics of the serous cells of airway submucosal glands. The submucosal glands play a major role in mucociliary clearance because they secrete electrolytes that facilitate airway hydration. Given the significance of both long- and short-term β-adrenergic receptor agonists in the treatment of respiratory diseases, it is important to determine the role of these receptors and their ligands in normal physiological function. The present studies were designed to characterize the effect of epinephrine, the naturally occurring β-adrenergic receptor agonist, on electrolyte transport of the airway serous cells. Interestingly, epinephrine stimulated two anion secretory channels, the cystic fibrosis transmembrane conductance regulator and a Ca2+-activated Cl− channel, with the characteristics of transmembrane protein 16A, thereby potentially altering mucociliary clearance via multiple channels. Consistent with the dual channel activation, epinephrine treatment resulted in increases in both intracellular cAMP and Ca2+. Furthermore, the present results extend previous reports indicating that the two anion channels are functionally linked. PMID:24705724
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Real-time monitoring of ischemia inside stomach.
Tahirbegi, Islam Bogachan; Mir, Mònica; Samitier, Josep
2013-02-15
The low pH in the gastric juice of the stomach makes it difficult to fabricate stable and functional all-solid-state pH ISE sensors to sense ischemia, mainly because of anion interference and adhesion problem between the ISE membrane and the electrode surface. In this work, the adhesion of ISE membrane on solid surface at low pH was improved by modifying the surface with a conductive substrate containing hydrophilic and hydrophobic groups. This creates a stable and robust candidate for low pH applications. Moreover, anion interference problem at low pH was solved by integration of all-solid-state ISE and internal reference electrodes on an array. So, the same tendencies of anion interferences for all-solid-state ISE and all-solid-state reference electrodes cancel each other in differential potentiometric detection. The developed sensor presents a novel all-solid-state potentiometric, miniaturized and mass producible pH ISE sensor for detecting ischemia on the stomach tissue on an array designed for endoscopic applications. Copyright © 2012 Elsevier B.V. All rights reserved.
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Li, Zhiyong; Yuan, Xiaoqing; Feng, Ying; Chen, Yongkui; Zhao, Yuling; Wang, Huiyong; Xu, Qingli; Wang, Jianji
2018-05-09
Photo-induced conductivity modulation of stimuli-responsive materials is of great importance from the viewpoint of fundamental research and technology. In this work, 5 new kinds of azobenzene-based photo-responsive ionic liquids were synthesized and characterized, and UV/vis light modulation of their conductivity was investigated in an aqueous solution. The factors affecting the conductivity modulation of the photo-responsive fluids, such as photo-isomerization efficiency, photo-regulation aggregation, concentration and chemical structure of the ionic liquids, were examined systematically. It was found that the conductivity of the ionic liquids in water exhibited a significant increase upon UV light irradiation and the ionic liquids with a shorter alkyl spacer in the cation showed a more remarkable photo-induced conductivity enhancement with a maximum increase of 150%. In addition, the solution conductivity was restored (or very close) to the initial value upon an alternative irradiation with visible light. Thus, the solution conductivity can be modulated using alternative irradiation with UV and visible light. Although the reversible photo-isomerization of the azobenzene group under UV/vis irradiation is the origin of the conductivity modulation, the photo-regulated aggregation of the ionic liquid in water is indispensable for the maximum degree of conductivity modulation because UV irradiation can weaken, even break the aggregated cis-isomers of the ionic liquids in an aqueous solution.
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Jia, Hanzhong; Gu, Cheng; Li, Hui; Fan, Xiaoyun; Li, Shouzhu; Wang, Chuanyi
2012-09-01
Zero-valent iron holds great promise in treating groundwater, and its reactivity and efficacy depend on many surrounding factors. In the present work, the effects of solution chemistry such as pH, humic acid (HA), and inorganic ions on pentachlorophenol (PCP) dechlorination by smectite-templated Pd(0)/Fe(0) were systematically studied. Smectite-templated Pd(0)/Fe(0) was prepared by saturating the negatively charged sites of smectite clay with Fe(III) and a small amount of Pd(II), followed by borohydride reduction to convert Fe(III) and Pd(II) into zero-valent metal clusters. Batch experiments were conducted to investigate the effects of water chemistry on PCP remediation. The PCP dechlorination rate critically depends on the reaction pH over the range 6.0~10.0; the rate constant (k (obs)) increases with decreasing the reaction pH value. Also, the PCP remediation is inhibited by HA, which can be attributed to the electron competition of HA with H(+). In addition, the reduction of PCP can be accelerated by various anions, following the order: Cl(-) > HCO (3) (-) > SO (4) (2-) ~no anion. In the case of cations, Ca(2+) and Mg(2+) (10 mM) decrease the dechlorination rate to 0.7959 and 0.7798 from 1.315 h(-1), respectively. After introducing HA into the reaction systems with cations or/and anions, the dechlorination rates are similar to that containing HA alone. This study reveals that low pH and the presence of some anions such as Cl(-) facilitate the PCP dechlorination and induce the rapid consumption of nanosized zero-valent iron simultaneously. However, the dechlorination rate is no longer correlated to the inhibitory or accelerating effects by cations and anions in the presence of 10 mg/L HA.
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Dielectric Properties of Aligned Conducting Polymers
1991-10-01
is the "standard" dopant anion for PPy and imparts some of the highest film Lonductivities. Using the rotating cylinder anode at - 2006 rpm... Araya ,, K. Mukoh, and T. Narahara, Syn. Met. 17, 241 (1987). 14. M. Aldissi, US Pat., 4880508, assigned to USDE (1989). 15. T. Nagai, Jpn Kokai Tokkyo
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Pomari, Elena; Dalla Valle, Luisa; Pertile, Paolo; Colombo, Lorenzo; Thornton, M Julie
2015-02-01
Peripheral intracrine sex steroid synthesis from adrenal precursors dehydroepiandrosterone (DHEA) and DHEA-sulfate has evolved in humans. We sought to establish if there are differences in intracrine, paracrine, and endocrine regulation of sex steroids by primary cultures of human skin epidermal keratinocytes and dermal fibroblasts. Microarray analysis identified multifunctional genes modulated by steroids, quantitative RT-PCR (qRT-PCR) mRNA expression, enzymatic assay aromatase activity, scratch assay cell migration, immunocytochemistry α-smooth muscle actin (α-SMA), and collagen gel fibroblast contraction. All steroidogenic components were present, although only keratinocytes expressed the organic anion organic anion transporter protein (OATP) 2B1 transporter. Both expressed the G-protein-coupled estrogen receptor (GPER1). Steroids modulated multifunctional genes, up-regulating genes important in repair and aging [angiopoietin-like 4 (ANGPTL4), chemokine (C-X-C motif) ligand 1 (CXCL1), lamin B1 (LMNB1), and thioredoxin interacting protein (TXNIP)]. DHEA-sulfate (DHEA-S), DHEA, and 17β-estradiol stimulated keratinocyte and fibroblast migration at early (4 h) and late (24-48 h) time points, suggesting involvement of genomic and nongenomic signaling. Migration was blocked by aromatase and steroid sulfatase (STS) inhibitors confirming intracrine synthesis to estrogen. Testosterone had little effect, implying it is not an intermediate. Steroids stimulated fibroblast contraction but not α-SMA expression. Mechanical wounding reduced fibroblast aromatase activity but increased keratinocyte activity, amplifying the bioavailability of intracellular estrogen. Cultured fibroblasts and keratinocytes provide a biologically relevant model system to investigate the complex pathways of sex steroid intracrinology in human skin. © FASEB.
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Tuo, Biguang; Wen, Guorong; Seidler, Ursula
2009-01-01
Background and purpose: Many cystic fibrosis (CF)-associated mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) anion channels affect CFTR-activated HCO3− transport more than Cl− transport. Targeting the CFTR HCO3− conductance, if possible, may therefore be of major therapeutic benefit. In the present study, we examined the effects of genistein and forskolin on duodenal mucosal HCO3− and Cl− secretion. Experimental approach: Murine duodenal mucosal HCO3− and Cl− secretions were examined in vitro in Ussing chambers by the pH stat and short circuit current (Isc) techniques. Key results: Genistein markedly stimulated duodenal HCO3− secretion and Isc in a dose-dependent manner in CFTR wild-type mice, but not in CFTR null mice. CFTRinh-172, a highly specific CFTR inhibitor, inhibited genistein-stimulated duodenal HCO3− secretion and Isc in wild-type mice. Genistein induced 59% net HCO3− increase and 123% net Isc increase over basal value, whereas forskolin, an activator of adenylate cyclase, induced 94% net HCO3− increase and 507% net Isc increase, indicating that, compared with forskolin, genistein induced a relatively high HCO3−/Isc ratio. Further data showed that CFTR HCO3−/Cl− conductance ratio was 1.05 after genistein stimulation, whereas after forskolin stimulation, the CFTR HCO3−/Cl− conductance ratio was 0.27. Conclusions and implications: Genistein stimulates duodenal HCO3− and Cl− secretion through CFTR, and has a relatively high selectivity for the CFTR HCO3− conductance, compared with forskolin. This may indicate the feasibility of selective targeting of the HCO3− conductance of the CFTR channels. PMID:19788494
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Zianni, Xanthippi; Jean, Valentin; Termentzidis, Konstantinos; Lacroix, David
2014-11-21
We report on scaling behavior of the thermal conductivity of width-modulated nanowires and nanofilms that have been studied with the phonon Monte Carlo technique. It has been found that the reduction of the thermal conductivity scales with the nanostructure transmissivity, a property entirely determined by the modulation geometry, irrespectively of the material choice. Tuning of the thermal conductivity is possible by the nanostructure width-modulation without strict limitations for the modulation profile. In addition, a very significant constriction thermal resistance due to width-discontinuity has been identified, in analogy to the contact thermal resistance between two dissimilar materials. The constriction thermal resistance also scales with the modulated nanostructure transmissivity. Our conclusions are generic indicating that a wide range of materials can be used for the modulated nanostructures. Direct heat flow control can be provided by designing the nanostructure width-modulation.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Vermeul, Vince R.; Szecsody, Jim E.; Truex, Michael J.
This treatability study was conducted by Pacific Northwest National Laboratory (PNNL), at the request of the U. S. Environmental Protection Agency (EPA) Region 2, to evaluate the feasibility of using in situ treatment technologies for chromate reduction and immobilization at the Puchack Well Field Superfund Site in Pennsauken Township, New Jersey. In addition to in situ reductive treatments, which included the evaluation of both abiotic and biotic reduction of Puchack aquifer sediments, natural attenuation mechanisms were evaluated (i.e., chromate adsorption and reduction). Chromate exhibited typical anionic adsorption behavior, with greater adsorption at lower pH, at lower chromate concentration, and atmore » lower concentrations of other competing anions. In particular, sulfate (at 50 mg/L) suppressed chromate adsorption by up to 50%. Chromate adsorption was not influenced by inorganic colloids.« less
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Snake Cytotoxins Bind to Membranes via Interactions with Phosphatidylserine Head Groups of Lipids
Konshina, Anastasia G.; Boldyrev, Ivan A.; Utkin, Yuri N.; Omel'kov, Anton V.; Efremov, Roman G.
2011-01-01
The major representatives of Elapidae snake venom, cytotoxins (CTs), share similar three-fingered fold and exert diverse range of biological activities against various cell types. CT-induced cell death starts from the membrane recognition process, whose molecular details remain unclear. It is known, however, that the presence of anionic lipids in cell membranes is one of the important factors determining CT-membrane binding. In this work, we therefore investigated specific interactions between one of the most abundant of such lipids, phosphatidylserine (PS), and CT 4 of Naja kaouthia using a combined, experimental and modeling, approach. It was shown that incorporation of PS into zwitterionic liposomes greatly increased the membrane-damaging activity of CT 4 measured by the release of the liposome-entrapped calcein fluorescent dye. The CT-induced leakage rate depends on the PS concentration with a maximum at approximately 20% PS. Interestingly, the effects observed for PS were much more pronounced than those measured for another anionic lipid, sulfatide. To delineate the potential PS binding sites on CT 4 and estimate their relative affinities, a series of computer simulations was performed for the systems containing the head group of PS and different spatial models of CT 4 in aqueous solution and in an implicit membrane. This was done using an original hybrid computational protocol implementing docking, Monte Carlo and molecular dynamics simulations. As a result, at least three putative PS-binding sites with different affinities to PS molecule were delineated. Being located in different parts of the CT molecule, these anion-binding sites can potentially facilitate and modulate the multi-step process of the toxin insertion into lipid bilayers. This feature together with the diverse binding affinities of the sites to a wide variety of anionic targets on the membrane surface appears to be functionally meaningful and may adjust CT action against different types of cells. PMID:21559494
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Kowsari, Mohammad H; Ebrahimi, Soraya
2018-05-16
Comprehensive molecular dynamics simulations are performed to study the average single-particle dynamics and the transport properties of 1-butyl-3-methylimidazolium hexafluorophosphate, [bmim][PF6], and 1-butyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate, [bmim][FAP], ionic liquids (ILs) at 400 K. We applied one of the most widely used nonpolarizable all-atom force fields for ILs, both with the original unit (±1) charges on each ion and with the partial charges uniformly scaled to 80-85%, taking into account the average polarizability and tracing the experimentally compatible transport properties. In all simulations, [bmim]+ was considered to be flexible, while the effect of a flexible vs. rigid structure of the anions and the effect of two applied charge sets on the calculated properties were separately investigated in detail. The simulation results showed that replacing [PF6]- with [FAP]-, considering anion flexibility, and applying the charge-scaled model significantly enhanced the ionic self-diffusion, ionic conductivity, inverse viscosity, and hyper anion preference (HAP). Both of the calculated self-diffusion coefficients from the long-time linear slope of the mean-square displacement (MSD) and from the integration of the velocity autocorrelation function (VACF) for the centers of mass of the ions were used for evaluation of the ionic transference number, HAP, ideal Nernst-Einstein ionic conductivity (σNE), and the Stokes-Einstein viscosity. In addition, for quantification of the degree of complicated ionic association (known as the Nernst-Einstein deviation parameter, Δ) and ionicity phenomena in the two studied ILs, the ionic conductivity was determined more rigorously by the Green-Kubo integral of the electric-current autocorrelation function (ECACF), and then the σGK/σNE ratio was evaluated. It was found that the correlated motion of the (cationanion) neighbors in [bmim][FAP] is smaller than in [bmim][PF6]. The relaxation times of the normalized reorientational autocorrelation functions were computed to gain a deep, molecular-level insight into the rotational motion of the ions. The geometric shape of the ion is a key factor in determining its reorientational dynamics. [bmim]+ shows faster translational and slower rotational dynamics in contrast to [PF6]-.
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Ion Transport by Ameloblasts during Amelogenesis.
Bronckers, A L J J
2017-03-01
Hypomineralization of developing enamel is associated with changes in ameloblast modulation during the maturation stage. Modulation (or pH cycling) involves the cyclic transformation of ruffle-ended (RE) ameloblasts facing slightly acidic enamel into smooth-ended (SE) ameloblasts near pH-neutral enamel. The mechanism of ameloblast modulation is not clear. Failure of ameloblasts of Cftr-null and anion exchanger 2 ( Ae2)-null mice to transport Cl - into enamel acidifies enamel, prevents modulation, and reduces mineralization. It suggests that pH regulation is critical for modulation and for completion of enamel mineralization. This report presents a review of the major types of transmembrane molecules that ameloblasts express to transport calcium to form crystals and bicarbonates to regulate pH. The type of transporter depends on the developmental stage. Modulation is proposed to be driven by the pH of enamel fluid and the compositional and/or physicochemical changes that result from increased acidity, which may turn RE ameloblasts into SE mode. Amelogenins delay outgrowth of crystals and keep the intercrystalline space open for diffusion of mineral ions into complete depth of enamel. Modulation enables stepwise removal of amelogenins from the crystal surface, their degradation, and removal from the enamel. Removal of matrix allows slow expansion of crystals. Modulation also reduces the stress that ameloblasts experience when exposed to high acid levels generated by mineral formation or by increased intracellular Ca 2+ . By cyclically interrupting Ca 2+ transport by RE ameloblasts and their transformation into SE ameloblasts, proton production ceases shortly and enables the ameloblasts to recover. Modulation also improves enamel crystal quality by selectively dissolving immature Ca 2+ -poor crystals, removing impurities as Mg 2+ and carbonates, and recrystallizing into more acid-resistant crystals.
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Lu, Hang; Lu, Zhiqiang; Li, Xue; Li, Gentao; Qiao, Yilin
2017-01-01
Background Herb-drug interactions (HDIs) resulting from concomitant use of herbal products with clinical drugs may cause adverse reactions. Organic anion transporter 1 (OAT1) and 3 (OAT3) are highly expressed in the kidney and play a key role in the renal elimination of substrate drugs. So far, little is known about the herbal extracts that could modulate OAT1 and OAT3 activities. Methods HEK293 cells stably expressing human OAT1 (HEK-OAT1) and OAT3 (HEK-OAT3) were established and characterized. One hundred seventy-two extracts from 37 medicinal and economic plants were prepared. An initial concentration of 5 µg/ml for each extract was used to evaluate their effects on 6-carboxylfluorescein (6-CF) uptake in HEK-OAT1 and HEK-OAT3 cells. Concentration-dependent inhibition studies were conducted for those extracts with more than 50% inhibition to OAT1 and OAT3. The extract of Juncus effusus, a well-known traditional Chinese medicine, was assessed for its effect on the in vivo pharmacokinetic parameters of furosemide, a diuretic drug which is a known substrate of both OAT1 and OAT3. Results More than 30% of the plant extracts at the concentration of 5 µg/ml showed strong inhibitory effect on the 6-CF uptake mediated by OAT1 (61 extracts) and OAT3 (55 extracts). Among them, three extracts for OAT1 and fourteen extracts for OAT3 were identified as strong inhibitors with IC50 values being <5 µg/ml. Juncus effusus showed a strong inhibition to OAT3 in vitro, and markedly altered the in vivo pharmacokinetic parameters of furosemide in rats. Conclusion The present study identified the potential interactions of medicinal and economic plants with human OAT1 and OAT3, which is helpful to predict and to avoid potential OAT1- and OAT3-mediated HDIs. PMID:28560096
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Bailey, D G; Dresser, G K; Leake, B F; Kim, R B
2007-04-01
We showed previously that grapefruit and orange juices inhibited human enteric organic anion-transporting polypeptide (OATP)1A2 in vitro and lowered oral fexofenadine bioavailability clinically. Inhibition of OATP1A2 transport by flavonoids in grapefruit (naringin) and orange (hesperidin) was conducted in vitro. Two randomized, crossover, pharmacokinetic studies were performed clinically. In one study, 120 mg of fexofenadine was ingested with 300 ml grapefruit juice, an aqueous solution of naringin at the same juice concentration (1,200 microM), or water. In the other study, fexofenadine was administered with grapefruit juice, with or 2 h before aqueous suspension of the particulate fraction of juice containing known clinical inhibitors of enteric CYP3A4, but relatively low naringin concentration (34 microM), or with water. Naringin and hesperidin's half-maximal inhibitions were 3.6 and 2.7 microM, respectively. Fexofenadine area under the plasma drug concentration-time curves (AUCs) with grapefruit juice and naringin solution were 55% (P<0.001) and 75% (P<0.05) of that with water, respectively. Fexofenadine AUCs with grapefruit juice and particulate fractions were 57% (P<0.001), 96% (not significant (NS)), and 97% (NS) of that with water, respectively. Individuals tested in both studies (n=9 of 12) had highly reproducible fexofenadine AUC with water (r(2)=0.85, P<0.001) and extent of reduction of it with grapefruit juice (r(2)=0.72, P<0.01). Naringin most probably directly inhibited enteric OATP1A2 to decrease oral fexofenadine bioavailability. Inactivation of enteric CYP3A4 was probably not involved. Naringin appears to have sufficient safety, specificity, and sensitivity to be a clinical OATP1A2 inhibitor probe. Inherent OATP1A2 activity may be influenced by genetic factors. This appears to be the first report of a single dietary constituent clinically modulating drug transport.
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Campbell, Jeremy B [Torrance, CA; Newson, Steve [Redondo Beach, CA
2011-11-15
A power module assembly of the type suitable for deployment in a vehicular power inverter, wherein the power inverter has a grounded chassis, is provided. The power module assembly comprises a conductive base layer electrically coupled to the chassis, an insulating layer disposed on the conductive base layer, a first conductive node disposed on the insulating layer, a second conductive node disposed on the insulating layer, wherein the first and second conductive nodes are electrically isolated from each other. The power module assembly also comprises a first capacitor having a first electrode electrically connected to the conductive base layer, and a second electrode electrically connected to the first conductive node, and further comprises a second capacitor having a first electrode electrically connected to the conductive base layer, and a second electrode electrically connected to the second conductive node.
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Zhu, Jiang; Rebecchi, Mario J; Glass, Peter S A; Brink, Peter R; Liu, Lixin
2013-04-01
Anesthetic preconditioning (APC) and ischemic preconditioning (IPC) are lost with normal aging. Here, we investigated age-related difference between phosphoglycogen synthase kinase-3beta (pGSK-3β) and pGSK-3β with modulators of mitochondrial permeability transition pore, including adenine nucleotide translocase (ANT), cyclophilin-D, or voltage-dependent anion channel. APC or IPC significantly increased pGSK-3β in the young groups in both the cytosol and the mitochondria and also significantly increased pGSK-3β in co-immunoprecipitates with ANT. Importantly, the level of cyclophilin-D in co-immunoprecipitates with ANT was significantly decreased in the young APC and IPC groups, but not in old rats. We also found that APC or IPC significantly prolonged mitochondrial permeability transition pore opening time in the young cardiomyocytes under oxidative stress, but not in the elderly. Attenuation of APC or IPC protection in the aging heart is associated with failure to reduce ANT-cyclophilin-D interactions and to decreased pGSK-3β responsiveness of ANT, critical modulators of mitochondrial permeability transition pore.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Pandey, Tara P.; Maes, Ashley M.; Sarode, Himanshu N.
We demonstrate that the true hydroxide conductivity in an e-beam grafted poly(ethylene-co-tetrafluoroethylene) [ETFE] anion exchange membrane (AEM) is as high as 132 mS cm -1 at 80 °C and 95% RH, comparable to a proton exchange membrane, but with very much less water present in the film. To understand this behaviour we studied ion transport of hydroxide, carbonate, bicarbonate and chloride, as well as water uptake and distribution. Water uptake of the AEM in water vapor is an order of magnitude lower than when submerged in liquid water. In addition 19F pulse field gradient spin echo NMR indicates that theremore » is little tortuosity in the ionic pathways through the film. A complete analysis of the IR spectrum of the AEM and the analyses of water absorption using FT-IR led to conclusion that the fluorinated backbone chains do not interact with water and that two types of water domains exist within the membrane. The reduction in conductivity was measured during exposure of the OH - form of the AEM to air at 95% RH and was seen to be much slower than the reaction of CO 2 with OH - as the amount of water in the film determines its ionic conductivity and at relative wet RHs its re-organization is slow.« less
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Control of thermal conductivity with species mass in transition-metal dichalcogenides
NASA Astrophysics Data System (ADS)
Thomas, Iorwerth O.; Srivastava, G. P.
2018-04-01
In this paper, we examine how the behaviour of the thermal conductivity of bulk and monolayer transition-metal dichalcogenides XY2 in their 2-H form can be controlled with different choices of cation and anion masses. We employ a semi-ab-initio approach, which combines first-principles phonon eigensolutions, the elastic anharmonic Hamiltonian for phonon-phonon interactions, a quasi-harmonic scheme for the temperature-dependent Grüneisen's constant, and a relaxation-time solution of the Boltzmann transport equation. Our results confirm an earlier finding [Gu and Yang, Appl. Phys. Lett. 105, 131903 (2014)] that the thermal conductivity of 2-H MoS2 is lower than that of 2-H WS2 contrary to what would be expected from the relative masses of Mo and W and the relative stiffnesses of both compounds. In addition to confirming this anomaly as a result of the larger acoustic optical gap of WS2 relative to that of MoS2, it is found that where one constituent species is fixed, more profound changes on the thermal conductivity occur for different anion masses than for different cation masses. We explain how these behaviours arise from the dispersion relations of each compound and the anharmonic interactions of phonon modes, and its connection with the relative masses of the constituent species. This finding provides useful insight into which 2-H dichalcogenides might be suitable for which thermal applications.
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Pandey, Tara P; Maes, Ashley M; Sarode, Himanshu N; Peters, Bethanne D; Lavina, Sandra; Vezzù, Keti; Yang, Yuan; Poynton, Simon D; Varcoe, John R; Seifert, Soenke; Liberatore, Matthew W; Di Noto, Vito; Herring, Andrew M
2015-02-14
We demonstrate that the true hydroxide conductivity in an e-beam grafted poly(ethylene-co-tetrafluoroethylene) [ETFE] anion exchange membrane (AEM) is as high as 132 mS cm(-1) at 80 °C and 95% RH, comparable to a proton exchange membrane, but with very much less water present in the film. To understand this behaviour we studied ion transport of hydroxide, carbonate, bicarbonate and chloride, as well as water uptake and distribution. Water uptake of the AEM in water vapor is an order of magnitude lower than when submerged in liquid water. In addition (19)F pulse field gradient spin echo NMR indicates that there is little tortuosity in the ionic pathways through the film. A complete analysis of the IR spectrum of the AEM and the analyses of water absorption using FT-IR led to conclusion that the fluorinated backbone chains do not interact with water and that two types of water domains exist within the membrane. The reduction in conductivity was measured during exposure of the OH(-) form of the AEM to air at 95% RH and was seen to be much slower than the reaction of CO2 with OH(-) as the amount of water in the film determines its ionic conductivity and at relative wet RHs its re-organization is slow.
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Pandey, Tara P.; Maes, Ashley M.; Sarode, Himanshu N.; ...
2014-12-23
We demonstrate that the true hydroxide conductivity in an e-beam grafted poly(ethylene-co-tetrafluoroethylene) [ETFE] anion exchange membrane (AEM) is as high as 132 mS cm -1 at 80 °C and 95% RH, comparable to a proton exchange membrane, but with very much less water present in the film. To understand this behaviour we studied ion transport of hydroxide, carbonate, bicarbonate and chloride, as well as water uptake and distribution. Water uptake of the AEM in water vapor is an order of magnitude lower than when submerged in liquid water. In addition 19F pulse field gradient spin echo NMR indicates that theremore » is little tortuosity in the ionic pathways through the film. A complete analysis of the IR spectrum of the AEM and the analyses of water absorption using FT-IR led to conclusion that the fluorinated backbone chains do not interact with water and that two types of water domains exist within the membrane. The reduction in conductivity was measured during exposure of the OH - form of the AEM to air at 95% RH and was seen to be much slower than the reaction of CO 2 with OH - as the amount of water in the film determines its ionic conductivity and at relative wet RHs its re-organization is slow.« less
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Kang, Ha Ram; da Costa Fernandes, Célio Junior; da Silva, Rodrigo Augusto; Constantino, Vera Regina Leopoldo; Koh, Ivan Hong Jun; Zambuzzi, Willian F
2018-02-01
The effect of LDH samples comprised of chloride anions intercalated between positive layers of magnesium/aluminum (Mg-Al LDH) or zinc/aluminum (Zn-Al LDH) chemical composition on pre-osteoblast performance is investigated. Non-cytotoxic concentrations of both LDHs modulated pre-osteoblast adhesion by triggering cytoskeleton rearrangement dependent on recruiting of Cofilin, which is modulated by the inhibition of the Protein Phosphatase 2A (PP2A), culminating in osteoblast differentiation with a significant increase of osteogenic marker genes. The alkaline phosphatase (ALP) and bone sialoprotein (BSP) are significantly up-modulated by both LDHs; however, Mg-Al LDH nanomaterial promoted even more significance than both experimental controls, while the phosphorylations of mitogen-activated protein kinase (MAPKs)- extracellular signal-regulated kinases (ERK) and c-Jun N-terminal kinase (JNK) significantly increased. MAPK signaling is necessary to activate Runt-related transcription factor 2 (RUNX2) gene. Concomitantly, it is also investigated whether challenged osteoblasts are able to modulate osteoclastogenesis by investigating both osteoprotegerin (OPG) and Receptor activator of nuclear factor kappa-ligand (RANKL) in this model; a dynamic reprogramming of both these genes is found, suggesting LDHs in modulating osteoclastogenesis. These results suggest that LDHs interfere in bone remodeling, and they can be considered as nanomaterials in graft-based bone healing or drug-delivery materials for bone disorders. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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NASA Astrophysics Data System (ADS)
Cheng, Zhe; Ding, Chunmei; Liu, Huan; Zhu, Ying; Jiang, Lei
2013-12-01
By taking advantage of bacterial extracellular electron transfer behavior, a facile method was developed to fabricate oriented polypyrrole micro-pillars (PPy-MP) with nanoscale surface roughness. Microbes acted as a living conductive template on which PPy was in situ polymerized. The as-prepared PPy-MP exhibit the distinctive underwater low adhesive superoleophobicity which is attributable to the unique hierarchical micro/nano-structures and the high surface energy by doping with inorganic small anions.By taking advantage of bacterial extracellular electron transfer behavior, a facile method was developed to fabricate oriented polypyrrole micro-pillars (PPy-MP) with nanoscale surface roughness. Microbes acted as a living conductive template on which PPy was in situ polymerized. The as-prepared PPy-MP exhibit the distinctive underwater low adhesive superoleophobicity which is attributable to the unique hierarchical micro/nano-structures and the high surface energy by doping with inorganic small anions. Electronic supplementary information (ESI) available: The shape of a water drop on PPy-MPA and cauliflower-like PPy film in air. See DOI: 10.1039/c3nr03788f
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Zhang, Yiming; Zhang, Wei; Cházaro-Ruiz, Luis F
2018-05-01
In this work, polyvinylidene fluoride (PVDF)/polyaniline (PANI) heterogeneous anion-exchange membranes filled with pore-forming agents polyvinylpyrrolidone (PVP) and lithium chloride were prepared by the solution-casting technique using the solvent 1-methyl-2-pyrrolidone (NMP) and a two-step phase inversion procedure. Key properties of the as-prepared membranes, such as hydrophilicity, water content, ion exchange capacity, fixed ion concentration, conductivity and transport number were examined and compared between membranes in different conditions. The pore-forming hydrophilic additives PVP and lithium chloride to the casting solution appeared to improve the ion-exchange membranes (IEMs) by increasing the conductivity, transport number and hydrophilicity. The effects of increasing membrane drying time on the porosity of the as-prepared membranes were found to lower membrane porosity by reducing membrane water content. However, pore-forming agents were found to be able to stabilise membrane transport number with different drying times. As-prepared PVDF/PANI anion-exchange membrane with pore-forming agent is demonstrated to be a more efficient candidate for water purification (e.g. desalination) and other industrial applications.
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Spectroscopic Study of Local Interactions of Platinum in Small [CexOy]Ptx' - Clusters
NASA Astrophysics Data System (ADS)
Ray, Manisha; Kafader, Jared O.; Chick Jarrold, Caroline
2016-06-01
Cerium oxide is a good ionic conductor, and the conductivity can be enhanced with oxygen vacancies and doping. This conductivity may play an important role in the enhancement of noble or coinage metal toward the water-gas shift reaction when supported by cerium oxide. The ceria-supported platinum catalyst in particular has received much attention because of higher activity at lower temperatures (LT) compared to the most common commercial LT-WGS catalyst. We have used a combination of anion photoelectron spectroscopy and density functional theory calculations to study the interesting molecular and electronic structures and properties of cluster models of ceria-supported platinum. [CexOy]Ptx' - (x,x'=1,2 ; y≤2x') clusters exhibit evidence of ionic bonding possible because of the high electron affinity of Pt and the low ionization potential of cerium oxide clusters. In addition, Pt- is a common daughter ion resulting from photodissociation of [CexOy]Ptx' - clusters. Finally, several of the anion and neutral clusters have profoundly different structures. These features may play a role in the enhancement of catalytic activity toward the water-gas shift reaction.
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NASA Astrophysics Data System (ADS)
Ghatee, Mohammad Hadi; Bahrami, Maryam
2017-06-01
We investigate to contrasting structure, dynamic and thermophysical properties of quaternary ammonium and phosphonium ionic liquids (ILs) based on triethylalkylammonium [N222n]+ and triethylalkylphosphonium [P222n]+ cations (n = 5, 8, 12) and (bis(trifluoromethylsulfonyl)imide) anion [NTf2]- by quantum chemical calculations (QCC) and molecular dynamics (MD) simulations. QCCs conform to previous studies, showing that phosphonium cation alkyl chain rotational-energy-barrier is lower than ammonium cation. These molecular nature leads to no appreciable differences in their liquid density. However, their simulated transport properties (self-diffusion, conductivity, etc) are appreciably different. In particular, viscosity of phosphoniums are much lower than ammoniums. Ammoniums make nano-scale structural domains larger than phosphoniums. Employed analysis, vector re-orientational dynamics, ion-pair lifetime and nanostructure domain are in favor of faster dynamic for phosphoniums than ammoniums. [NTf2]- anion features a long lived pairing with ammoniums than phosphoniums. Overall, phosphoniums possess higher transference number, higher conductivity, and appreciably lower viscosity favorable for higher electrochemical performances.
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Ionic liquid compatibility in polyethylene oxide/siloxane ion gel membranes
Kusuma, Victor A.; Macala, Megan K.; Liu, Jian; ...
2018-10-02
Ion gel films were prepared by incorporating eight commercially available ionic liquids in two different cross-linked polymer matrices to evaluate their phase miscibility, gas permeability and ionic conductivity for potential applications as gas separation membranes and solid electrolyte materials. The ionic liquids cations were 1-ethyl-3-methylimidazolium, 1-ethyl-3-methylpyridinium, 1-butyl-1-methylpyrrolidinium, tributylmethylphosphonium, and butyltrimethylammonium with a common anion (bis(trifluoromethylsulfonyl)imide). In addition, ionic liquids with 1-ethyl-3-methylimidazolium cation with acetate, dicyanamide and tetrafluoroborate counterions were evaluated. The two polymers were cross-linked poly(ethylene oxide) and cross-linked poly(ethylene oxide)/siloxane copolymer. Differential scanning calorimetry, X-ray diffractometry and visual observations were performed to evaluate the ion gels’ miscibility, thermal stabilitymore » and homogeneity. Ionic liquids with the least basic anion (bis(trifluoromethylsulfonyl)imide) and aromatic cations containing acidic proton (e.g. imidazolium and pyridinium) gave the most stable and miscible ion gels. Phase stability was shown to be a function of both ionic liquid content and temperature, with phase separation observed at elevated temperatures. In conclusion, gas permeability testing with carbon dioxide and nitrogen and ionic conductivity measurements confirmed that these ionic liquids increased the gas permeability and ionic conductivity of the polymers.« less
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Ionic liquid compatibility in polyethylene oxide/siloxane ion gel membranes
DOE Office of Scientific and Technical Information (OSTI.GOV)
Kusuma, Victor A.; Macala, Megan K.; Liu, Jian
Ion gel films were prepared by incorporating eight commercially available ionic liquids in two different cross-linked polymer matrices to evaluate their phase miscibility, gas permeability and ionic conductivity for potential applications as gas separation membranes and solid electrolyte materials. The ionic liquids cations were 1-ethyl-3-methylimidazolium, 1-ethyl-3-methylpyridinium, 1-butyl-1-methylpyrrolidinium, tributylmethylphosphonium, and butyltrimethylammonium with a common anion (bis(trifluoromethylsulfonyl)imide). In addition, ionic liquids with 1-ethyl-3-methylimidazolium cation with acetate, dicyanamide and tetrafluoroborate counterions were evaluated. The two polymers were cross-linked poly(ethylene oxide) and cross-linked poly(ethylene oxide)/siloxane copolymer. Differential scanning calorimetry, X-ray diffractometry and visual observations were performed to evaluate the ion gels’ miscibility, thermal stabilitymore » and homogeneity. Ionic liquids with the least basic anion (bis(trifluoromethylsulfonyl)imide) and aromatic cations containing acidic proton (e.g. imidazolium and pyridinium) gave the most stable and miscible ion gels. Phase stability was shown to be a function of both ionic liquid content and temperature, with phase separation observed at elevated temperatures. In conclusion, gas permeability testing with carbon dioxide and nitrogen and ionic conductivity measurements confirmed that these ionic liquids increased the gas permeability and ionic conductivity of the polymers.« less
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ANO1 contributes to angiotensin-II-activated Ca2+-dependent Cl- current in human atrial fibroblasts.
El Chemaly, Antoun; Norez, Caroline; Magaud, Christophe; Bescond, Jocelyn; Chatelier, Aurelien; Fares, Nassim; Findlay, Ian; Jayle, Christophe; Becq, Frederic; Faivre, Jean-François; Bois, Patrick
2014-03-01
Cardiac fibroblasts are an integral part of the myocardial tissue and contribute to its remodelling. This study characterises for the first time the calcium-dependent chloride channels (CaCC) in the plasma membrane of primary human atrial cardiac fibroblasts by means of the iodide efflux and the patch clamp methods. The calcium ionophore A23187 and Angiotensin II (Ang II) activate a chloride conductance in cardiac fibroblasts that shares pharmacological similarities with calcium-dependent chloride channels. This chloride conductance is depressed by RNAi-mediated selective Anoctamine 1 (ANO1) but not by Anoctamine 2 (ANO2) which has been revealed as CaCC and is inhibited by the selective ANO1 inhibitor, T16inh-A01. The effect of Ang II on anion efflux is mediated through AT1 receptors (with an EC50 = 13.8 ± 1.3 nM). The decrease of anion efflux by calphostin C and bisindolylmaleimide I (BIM I) suggests that chloride conductance activation is dependent on PKC. We conclude that ANO1 contributes to CaCC current in human cardiac fibroblasts and that this is regulated by Ang II acting via the AT1 receptor pathway. Copyright © 2014 Elsevier Ltd. All rights reserved.
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Hard X-ray photoemission study of the Fabre salts (TMTTF)2X (X = SbF6 and PF6)
NASA Astrophysics Data System (ADS)
Medjanik, Katerina; de Souza, Mariano; Kutnyakhov, Dmytro; Gloskovskii, Andrei; Müller, Jens; Lang, Michael; Pouget, Jean-Paul; Foury-Leylekian, Pascale; Moradpour, Alec; Elmers, Hans-Joachim; Schönhense, Gerd
2014-11-01
Core-level photoemission spectra of the Fabre salts with X = SbF6 and PF6 were taken using hard X-rays from PETRA III, Hamburg. In these salts TMTTF layers show a significant stack dimerization with a charge transfer of 1 e per dimer to the anion SbF6 or PF6. At room temperature and slightly below the core-level spectra exhibit single lines, characteristic for a well-screened metallic state. At reduced temperatures progressive charge localization sets in, followed by a 2nd order phase transition into a charge-ordered ground state. In both salts groups of new core-level signals occur, shifted towards lower kinetic energies. This is indicative of a reduced transverse-conductivity across the anion layers, visible as layer-dependent charge depletion for both samples. The surface potential was traced via shifts of core-level signals of an adsorbate. A well-defined potential could be established by a conducting cap layer of 5 nm aluminum which appears "transparent" due to the large probing depth of HAXPES (8-10 nm). At the transition into the charge-ordered phase the fluorine 1 s line of (TMTTF)2SbF6 shifts by 2.8 eV to higher binding energy. This is a spectroscopic fingerprint of the loss of inversion symmetry accompanied by a cooperative shift of the SbF6 anions towards the more positively charged TMTTF donors. This shift does not occur for the X = PF6 compound, most likely due to smaller charge disproportion or due to the presence of charge disorder.
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Anion- or Cation-Exchange Membranes for NaBH4/H2O2 Fuel Cells?
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
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Anion- or Cation-Exchange Membranes for NaBH4/H2O2 Fuel Cells?
Sljukić, Biljana; Morais, Ana L; Santos, Diogo M F; Sequeira, César A C
2012-07-19
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.
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Billing, Beant Kaur; Mayank; Agnihotri, Prabhat K; Singh, Narinder
2018-06-08
Non-covalent bonding via π-π stacking is in demand these days because it does not affect the structure of the carbon nanotube (CNT). Herein, a hybrid material was fabricated via π-π stacking between the aromatic rings of carbon nanotubes and a dihydropyrimidone-based pyrene derivative. The developed CNT@pyrene hybrid material was fully characterized using SEM, EDX, TEM, XRD, and FTIR techniques. The hybrid was developed to improve the heat transport in the hybrid solution by anion addition. The emission profile of the developed hybrid was screened against TBA salts of different anions in EtOH-H2O (10-90% v/v) solvent system to identify the anion that can interact with the hybrid. The hybrid exhibited high sensitivity and selectivity towards NO3- ions with 1.5-fold enhancement in fluorescence intensity, while other anions neither showed significant responses nor interfered in the sensor's response. The limit of NO3- ions detection was found to be 8.1 nM, calculated using the 3-sigma method. It was observed that the proposed hybrid sensor showed stable response at different pH and diverse salt concentrations. The binding mechanism was elucidated by DFT-based theoretical calculations. Real sample analysis was performed for the detection of NO3- concentrations in local water bodies with accuracy as high as 95%. Viscosity and thermal conductivity experiments were performed to measure the effect of concentration, temperature, and pH on the NO3- response.
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Lepsy, Christopher S.; Guttendorf, Robert J.; Kugler, Alan R.; Smith, David E.
2003-01-01
Cefdinir (Omnicef; Abbott Laboratories) is a cephalosporin antibiotic primarily eliminated by the kidney. Nonlinear renal elimination of cefdinir has been previously reported. Cefdinir renal transport mechanisms were studied in the erythrocyte-free isolated perfused rat kidney. Studies were performed with drug-free perfusate and perfusate containing cefdinir alone to establish the baseline physiology and investigate cefdinir renal elimination characteristics. To investigate cefdinir renal transport mechanisms, inhibition studies were conducted by coperfusing cefdinir with inhibitors of the renal organic anion (probenecid), organic cation (tetraethylammonium), or dipeptide (glycylsarcosine) transport system. Cefdinir concentrations in biological samples were determined using reversed-phase high-performance liquid chromatography. Differences between treatments and controls were evaluated using analysis of variance and Dunnett's test. The excretion ratio (ER; the renal clearance corrected for the fraction unbound and glomerular filtration rate) for cefdinir was 5.94, a value indicating net renal tubular secretion. Anionic, cationic, and dipeptide transport inhibitors all significantly affected the cefdinir ER. With probenecid, the ER was reduced to 0.59, clearly demonstrating a significant reabsorptive component to cefdinir renal disposition. This finding was confirmed by glycylsarcosine studies, in which the ER was elevated to 7.95, indicating that reabsorption was mediated, at least in part, by the dipeptide transporter system. The effects of the organic cation tetraethylammonium, in which the ER was elevated to 7.53, were likely secondary in nature. The anionic secretory pathway was found to be the predominant mechanism for cefdinir renal excretion. PMID:12543679
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Palmberger, Thomas F; Laffleur, Flavia; Greindl, Melanie; Bernkop-Schnürch, Andreas
2015-08-01
Recently, the cationic polymer thiolated chitosan has been reported to modulate drug absorption by inhibition of intestinal efflux pumps. The objective of this study was to evaluate in vitro and in vivo whether thiolated anionic biopolymers also show an efflux pump inhibitory effect in order to improve intestinal transcellular drug uptake. Therefore, three thiomers have been synthesized due covalent attachment of cysteine to various polymer backbones: pectin-cysteine (pect-cys), carboxymethylcellulose-cysteine (CMC-cys) and alginate-cysteine (alg-cys). In vitro, the permeation enhancing properties of these thiomers and their corresponding unmodified polymers have been evaluated on rat small intestine in Ussing-type chambers, using sulforhodamine 101 (SR-101) as MRP2 model substrate. In comparison to buffer only, SR-101 transport in presence of pect-cys, CMC-cys and alg-cys was improved 1.5-fold, 1.8-fold and 3.0-fold, respectively. Due to the comparatively best in vitro performance of thiolated alginate, it has been chosen for in vivo studies: a SR-101 solution containing 4% (w/v) alg-cys led to an AUC0 ≥ 12 of SR-101 of 109 ng ml(-1)h in rats representing a 3.8-fold improvement in comparison to a SR-101 buffer solution. Unmodified alginate improved the AUC0 ≥ 12 of SR-101 by a factor of 1.9. These findings suggest thiolated alginate as promising auxiliary agent for drugs being anionic efflux pump substrates, since the oral bioavailability of a MRP2 substrate could be significantly improved. Copyright © 2015 Elsevier B.V. All rights reserved.
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Frahm, Grant E; Cameron, Brooke E; Smith, Jeffrey C; Johnston, Michael J W
2013-06-01
At elevated temperatures, studies have shown that serum albumin undergoes irreversible changes to its secondary structure. Anionic fatty acids and/or anionic surfactants have been shown to stabilize human serum albumin (HSA) against thermal denaturation through bridging hydrophobic domains and cationic amino acids residues of the protein. As albumin can readily interact with a variety of liposomes, this study proposes that cardiolipin delivered via 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) liposomes can improve the thermal stability of recombinant HSA produced in Saccharomyces cerevisiae (ScrHSA) in a similar manner to anionic fatty acids. Thermal stability and structure of ScrHSA in the absence and presence of DPPC/cardiolipin liposomes was assessed with U/V circular dichroism spectropolarimetry and protein thermal stability was confirmed with differential scanning calorimetry. Although freshly prepared DPPC/cardiolipin liposomes did not improve the stability of ScrHSA, DPPC/cardiolipin liposomes incubated at room temperature for 7 d (7dRT) dramatically improved the thermal stability of the protein. Mass spectrometry analysis identified the presence of fatty acids in the 7dRT liposomes, not identified in freshly prepared liposomes, to which the improved stability was attributed. The generation of fatty acids is attributed to either the chemical hydrolysis or oxidative cleavage of the unsaturated acyl chains of cardiolipin. By modulating the lipid composition through the introduction of lipids with higher acyl chain unsaturation, it may be possible to generate the stabilizing fatty acids in a more rapid manner.
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Investigations into the Membrane Interactions of m-Calpain Domain V
Dennison, Sarah R.; Dante, Silvia; Hauß, Thomas; Brandenburg, Klaus; Harris, Frederick; Phoenix, David A.
2005-01-01
m-Calpain is a calcium-dependent heterodimeric protease implicated in a number of pathological conditions. The activation of m-calpain appears to be modulated by membrane interaction, which has been predicted to involve oblique-orientated α-helix formation by a GTAMRILGGVI segment located in domain V of the protein's small subunit. Here, we have investigated this prediction. Fourier transform infrared conformational analysis showed that VP1, a peptide homolog of this segment, exhibited α-helicity of ∼45% in the presence of dimyristoylphosphatidylcholine/dimyristoylphosphatidylserine (DMPS) vesicles. The level of helicity was unaffected over a 1- to 8-mM concentration range and did not alter when the anionic lipid composition of these vesicles was varied between 1% and 10% DMPS. Similar levels of α-helicity were observed in trifluoroethanol and the peptide appeared to adopt α-helical structure at an air/water interface with a molecular area of 164 Å2 at the monolayer collapse pressure. VP1 was found to penetrate dimyristoylphosphatidylcholine/DMPS monolayers, and at an initial surface pressure of 30 mN m−1, the peptide induced surface pressure changes in these monolayers that correlated strongly with their anionic lipid content (maximal at 4 mN m−1 in the presence of 10% DMPS). Neutron diffraction studies showed VP1 to be localized at the hydrophobic core of model palmitoyloleylphosphatidylcholine/palmitoyloleylphosphatidylserine (10:1 molar ratio) bilayer structures and, in combination, these results are consistent with the oblique membrane penetration predicted for the peptide. It would also appear that although not needed for structural stabilization anionic lipid was required for membrane penetration. PMID:15653743
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A new method of calculating electrical conductivity with applications to natural waters
McCleskey, R. Blaine; Nordstrom, D. Kirk; Ryan, Joseph N.; Ball, James W.
2012-01-01
A new method is presented for calculating the electrical conductivity of natural waters that is accurate over a large range of effective ionic strength (0.0004–0.7 mol kg-1), temperature (0–95 °C), pH (1–10), and conductivity (30–70,000 μS cm-1). The method incorporates a reliable set of equations to calculate the ionic molal conductivities of cations and anions (H+, Li+, Na+, K+, Cs+, NH4+, Mg2+, Ca2+, Sr2+, Ba2+, F-, Cl-, Br-, SO42-, HCO3-, CO32-, NO3-, and OH-), environmentally important trace metals (Al3+, Cu2+, Fe2+, Fe3+, Mn2+, and Zn2+), and ion pairs (HSO4-, NaSO4-, NaCO3-, and KSO4-). These equations are based on new electrical conductivity measurements for electrolytes found in a wide range of natural waters. In addition, the method is coupled to a geochemical speciation model that is used to calculate the speciated concentrations required for accurate conductivity calculations. The method was thoroughly tested by calculating the conductivities of 1593 natural water samples and the mean difference between the calculated and measured conductivities was -0.7 ± 5%. Many of the samples tested were selected to determine the limits of the method and include acid mine waters, geothermal waters, seawater, dilute mountain waters, and river water impacted by municipal waste water. Transport numbers were calculated and H+, Na+, Ca2+, Mg2+, NH4+, K+, Cl-, SO42-, HCO3-, CO32-, F-, Al3+, Fe2+, NO3-, and HSO4- substantially contributed (>10%) to the conductivity of at least one of the samples. Conductivity imbalance in conjunction with charge imbalance can be used to identify whether a cation or an anion measurement is likely in error, thereby providing an additional quality assurance/quality control constraint on water analyses.
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A new method of calculating electrical conductivity with applications to natural waters
NASA Astrophysics Data System (ADS)
McCleskey, R. Blaine; Nordstrom, D. Kirk; Ryan, Joseph N.; Ball, James W.
2012-01-01
A new method is presented for calculating the electrical conductivity of natural waters that is accurate over a large range of effective ionic strength (0.0004-0.7 mol kg-1), temperature (0-95 °C), pH (1-10), and conductivity (30-70,000 μS cm-1). The method incorporates a reliable set of equations to calculate the ionic molal conductivities of cations and anions (H+, Li+, Na+, K+, Cs+, NH4+, Mg2+, Ca2+, Sr2+, Ba2+, F-, Cl-, Br-, SO42-, HCO3-, CO32-, NO3-, and OH-), environmentally important trace metals (Al3+, Cu2+, Fe2+, Fe3+, Mn2+, and Zn2+), and ion pairs (HSO4-, NaSO4-, NaCO3-, and KSO4-). These equations are based on new electrical conductivity measurements for electrolytes found in a wide range of natural waters. In addition, the method is coupled to a geochemical speciation model that is used to calculate the speciated concentrations required for accurate conductivity calculations. The method was thoroughly tested by calculating the conductivities of 1593 natural water samples and the mean difference between the calculated and measured conductivities was -0.7 ± 5%. Many of the samples tested were selected to determine the limits of the method and include acid mine waters, geothermal waters, seawater, dilute mountain waters, and river water impacted by municipal waste water. Transport numbers were calculated and H+, Na+, Ca2+, Mg2+, NH4+, K+, Cl-, SO42-, HCO3-, CO32-, F-, Al3+, Fe2+, NO3-, and HSO4-substantially contributed (>10%) to the conductivity of at least one of the samples. Conductivity imbalance in conjunction with charge imbalance can be used to identify whether a cation or an anion measurement is likely in error, thereby providing an additional quality assurance/quality control constraint on water analyses.
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Highly Dynamic Anion-Quadrupole Networks in Proteins.
Kapoor, Karan; Duff, Michael R; Upadhyay, Amit; Bucci, Joel C; Saxton, Arnold M; Hinde, Robert J; Howell, Elizabeth E; Baudry, Jerome
2016-11-01
The dynamics of anion-quadrupole (or anion-π) interactions formed between negatively charged (Asp/Glu) and aromatic (Phe) side chains are for the first time computationally characterized in RmlC (Protein Data Bank entry 1EP0 ), a homodimeric epimerase. Empirical force field-based molecular dynamics simulations predict anion-quadrupole pairs and triplets (anion-anion-π and anion-π-π) are formed by the protein during the simulated trajectory, which suggests that the anion-quadrupole interactions may provide a significant contribution to the overall stability of the protein, with an average of -1.6 kcal/mol per pair. Some anion-π interactions are predicted to form during the trajectory, extending the number of anion-quadrupole interactions beyond those predicted from crystal structure analysis. At the same time, some anion-π pairs observed in the crystal structure exhibit marginal stability. Overall, most anion-π interactions alternate between an "on" state, with significantly stabilizing energies, and an "off" state, with marginal or null stabilizing energies. The way proteins possibly compensate for transient loss of anion-quadrupole interactions is characterized in the RmlC aspartate 84-phenylalanine 112 anion-quadrupole pair observed in the crystal structure. A double-mutant cycle analysis of the thermal stability suggests a possible loss of anion-π interactions compensated by variations of hydration of the residues and formation of compensating electrostatic interactions. These results suggest that near-planar anion-quadrupole pairs can exist, sometimes transiently, which may play a role in maintaining the structural stability and function of the protein, in an otherwise very dynamic interplay of a nonbonded interaction network as well as solvent effects.
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NASA Technical Reports Server (NTRS)
Alexander, S. S.; Hodgdon, R. B.; Waite, W. A.
1979-01-01
Experimental composite membranes were synthesized on a lab scale consisting of a thin layer of anion permselective resin supported by and bonded to a porous physically strong and conductive substrate film. These showed good selectivity and also substantially lower electrical resistivities than the homogenous candidate membranes optimized in the previous contract. A wide range of resin porosities were examined for three candidate membrane systems, CDIL, CP4L, and A3L to identify the formulation giving the best overall redox cell performance. Candidate anion membranes showed large increases in resistivity after a short time of immersion in concentrated FeCl/HCl solution. Largely on the basis of resistance stability the CDIL formulation was selected as prime candidate and about thirty-five membranes (one foot square) were produced for experimental static and dynamic evaluation.
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Anionic Palladium(0) and Palladium(II) Ate Complexes.
Kolter, Marlene; Böck, Katharina; Karaghiosoff, Konstantin; Koszinowski, Konrad
2017-10-16
Palladium ate complexes are frequently invoked as important intermediates in Heck and cross-coupling reactions, but so far have largely eluded characterization at the molecular level. Here, we use electrospray-ionization mass spectrometry, electrical conductivity measurements, and NMR spectroscopy to show that the electron-poor catalyst [L 3 Pd] (L=tris[3,5-bis(trifluoromethyl)phenyl]phosphine) readily reacts with Br - ions to afford the anionic, zero-valent ate complex [L 3 PdBr] - . In contrast, more-electron-rich Pd catalysts display lower tendencies toward the formation of ate complexes. Combining [L 3 Pd] with LiI and an aryl iodide substrate (ArI) results in the observation of the Pd II ate complex [L 2 Pd(Ar)I 2 ] - . © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
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Ultrahigh Ionic Conduction in Water-Stable Close-Packed Metal-Carbonate Frameworks.
Manna, Biplab; Desai, Aamod V; Illathvalappil, Rajith; Gupta, Kriti; Sen, Arunabha; Kurungot, Sreekumar; Ghosh, Sujit K
2017-08-21
Utilization of the robust metal-carbonate backbone in a series of water-stable, anionic frameworks has been harnessed for the function of highly efficient solid-state ion-conduction. The compact organization of hydrophilic guest ions facilitates water-assisted ion-conduction in all the compounds. The dense packing of the compounds imparts high ion-conducting ability and minimizes the possibility of fuel crossover, making this approach promising for design and development of compounds as potential components of energy devices. This work presents the first report of evaluating ion-conduction in a purely metal-carbonate framework, which exhibits high ion-conductivity on the order of 10 -2 S cm -1 along with very low activation energy, which is comparable to highly conducting well-known crystalline coordination polymers or commercialized organic polymers like Nafion.
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RF transmission line and drill/pipe string switching technology for down-hole telemetry
Clark, David D [Santa Fe, NM; Coates, Don M [Santa Fe, NM
2007-08-14
A modulated reflectance well telemetry apparatus having an electrically conductive pipe extending from above a surface to a point below the surface inside a casing. An electrical conductor is located at a position a distance from the electrically conductive pipe and extending from above the surface to a point below the surface. Modulated reflectance apparatus is located below the surface for modulating well data into a RF carrier transmitted from the surface and reflecting the modulated carrier back to the surface. A RF transceiver is located at the surface and is connected between the electrically conductive pipe and the electrical conductor for transmitting a RF signal that is confined between the electrically conductive well pipe and the electrical conductor to the modulated reflectance apparatus, and for receiving reflected data on the well from the modulated reflectance apparatus.
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Anion transport and supramolecular medicinal chemistry
Gale, Philip A.; Davis, Jeffery T.; Quesada, Roberto
2017-04-05
New approaches to the transmembrane transport of anions are discussed in this review. Advances in the design of small molecule anion carriers are reviewed in addition to advances in the design of synthetic anion channels. The application of anion transporters to the potential future treatment of disease is discussed in the context of recent findings on the selectivity of anion transporters.
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Anion transport and supramolecular medicinal chemistry
DOE Office of Scientific and Technical Information (OSTI.GOV)
Gale, Philip A.; Davis, Jeffery T.; Quesada, Roberto
New approaches to the transmembrane transport of anions are discussed in this review. Advances in the design of small molecule anion carriers are reviewed in addition to advances in the design of synthetic anion channels. The application of anion transporters to the potential future treatment of disease is discussed in the context of recent findings on the selectivity of anion transporters.
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NASA Technical Reports Server (NTRS)
Mon, G. R.
1985-01-01
A general research approach was outlined toward understanding water-module interactions and the influence of temperature involving the need to: quantify module performance loss versus level of accumulated degradation, establish the dependence of the degradation reaction rate on module moisture and temperature levels, and determine module moisture and temperature levels in field environments. These elements were illustrated with examples drawn from studies of the now relatively well understood module electrochemical degradation process. Research data presented include temperature and humidity-dependent equilibrium leakage current values for multiparameter module material and design configurations. The contributions of surface, volume, and interfacial conductivities was demonstrated. Research directions were suggested to more fully understand the contributions to overall module conductivity of surface, volume, and interfacial conductivities over ranges of temperature and relative humidity characteristic of field environments.
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Zhong, Hai; Wang, Chunhua; Xu, Zhibin; Ding, Fei; Liu, Xinjiang
2016-01-01
Polymer solid state electrolytes are actively sought for their potential application in energy storage devices, particularly lithium metal rechargeable batteries. Herein, we report a polymer with high concentration salts as a quasi-solid state electrolyte used for lithium-sulfur cells, which shows an ionic conductivity of 1.6 mS cm−1 at room temperature. The cycling performance of Li-S battery with this electrolyte shows a long cycle life (300 cycles) and high coulombic efficiency (>98%), without any consuming additives in the electrolyte. Moreover, it also shows a remarkably decreased self-discharge (only 0.2%) after storage for two weeks at room temperature. The reason can be attributed to that the electrolyte can suppress polysulfide anions diffusion, due to the high ratio oxygen atoms with negative charges which induce an electrical repulsion to the polysulfide anions, and their relatively long chains which can provide additional steric hindrance. Thus, the polysulfide anions can be located around carbon particles, which result in remarkably improved overall electrochemical performance, and also the electrolyte have a function of suppress the formation of lithium dendrites on the lithium anode surface. PMID:27146645
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NASA Astrophysics Data System (ADS)
Zeng, L.; Zhao, T. S.; An, L.; Zhao, G.; Yan, X. H.; Jung, C. Y.
2015-02-01
In this work, we have synthesized an ionomer-coated graphene-supported platinum catalyst for anion exchange membrane fuel cells. Unlike the common surfactant stabilized colloidal method, we employ a home-made anion exchange ionomer (AEI), namely quaternary ammonia poly (2, 6-dimethyl-1, 4-phenylene oxide) (QAPPO), as the surfactant. The AEI coated on reduced graphene oxide (rGO) surfaces serves as a stabilizer to anchor the platinum precursor on rGO surfaces due to electrostatic interactions. As a result, platinum nanoparticles (Pt NPs) can be easily deposited onto rGO surfaces with a uniform distribution. The remarkable feature of the present synthesis method is that the surfactant, the coated AEI, does not need to be removed from the catalyst, but serves as hydroxide-conductive paths in the catalyst layer, leading to enhanced triple phase boundaries. It is demonstrated that the use of the catalyst obtained with the present method enables a H2/O2 AEMFC to yield a peak power density of 264.8 mW cm-2 at 60 °C, which is 30% higher than that produced from the same fuel cell but with the use of the catalyst synthesized by the conventional synthesis method.
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Martínez, Ana M; Benito, Marta; Pérez, Elena; María Teijón, José; Dolores Blanco, María
2016-01-01
Cancer has become one of the main causes of death in developed countries, and it is expected to be declared as the disease with the highest worldwide morbidity and mortality indexes in the coming decades. Nanomedicine aims to overcome some problems related to this prevalent disease, particularly the lack of efficient diagnostic and therapeutic tools. The most recent scientific advances, which have conducted to a more personalized medicine, were focused on the production of nanocarriers involved into the transport and the delivery of drugs to targeted cells. A wide variety of nanocarriers composed by different materials have been designed for their use as drug delivery systems. Polysaccharides have emerged as very useful biopolymers among all raw materials used in the preparation of these nanoplatforms. They are highly stable, non-toxic and biodegradable molecules, and also present some chemical properties which are very difficult to reproduce using artificial polymers. Anionic polymers, such as hyaluronic acid, heparin or alginate, present some structural and chemical characteristics which make them ideal polymers to prepare nanosystems with anticancer applications. This review will focus on the description of some anionic polysaccharides and the possibilities they offer towards the preparation of nanosystems with applications in cancer treatment and diagnostics.
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Chen, Jiao; Chen, Zhaoqiong; Ai, Yingwei; Xiao, Jingyao; Pan, Dandan; Li, Wei; Huang, Zhiyu; Wang, Yumei
2015-10-09
Taking the slope of Suiyu Railway to study, the research separately studied soil resistivity, soil electrochemistry (corrosion potential, oxidization reduction potential, electric potential gradient and pH), soil anions (total soluble salt, Cl(-), SO4(2-) and ), and soil nutrition (moisture content, organic matter, total nitrogen, alkali-hydrolysable nitrogen, available phosphorus, and available potassium) at different slope levels, and conducted corrosion grade evaluation on artificial soil according to its single index and comprehensive indexes. Compared with other factors, water has the biggest impact on the corrosion of slope protection net, followed by anion content. Total soluble salt has the moderate impact on the corrosion of slope protection net, and stray current has the moderate impact on the corrosion of mid-slope protection net. Comprehensive evaluation on the corrosive degree of soil samples indicates that the corrosion of upper slope is moderate, and the corrosion of mid-slope and lower slope is strong. Organic matter in soil is remarkably relevant to electric potential gradient. Available nitrogen, available potassium and available phosphorus are remarkably relevant to anions. The distribution of soil nutrient is indirectly relevant to slope type.
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Chen, Jiao; Chen, Zhaoqiong; Ai, Yingwei; Xiao, Jingyao; Pan, Dandan; Li, Wei; Huang, Zhiyu; Wang, Yumei
2015-01-01
Taking the slope of Suiyu Railway to study, the research separately studied soil resistivity, soil electrochemistry (corrosion potential, oxidization reduction potential, electric potential gradient and pH), soil anions (total soluble salt, Cl−, SO42− and ), and soil nutrition (moisture content, organic matter, total nitrogen, alkali-hydrolysable nitrogen, available phosphorus, and available potassium) at different slope levels, and conducted corrosion grade evaluation on artificial soil according to its single index and comprehensive indexes. Compared with other factors, water has the biggest impact on the corrosion of slope protection net, followed by anion content. Total soluble salt has the moderate impact on the corrosion of slope protection net, and stray current has the moderate impact on the corrosion of mid-slope protection net. Comprehensive evaluation on the corrosive degree of soil samples indicates that the corrosion of upper slope is moderate, and the corrosion of mid-slope and lower slope is strong. Organic matter in soil is remarkably relevant to electric potential gradient. Available nitrogen, available potassium and available phosphorus are remarkably relevant to anions. The distribution of soil nutrient is indirectly relevant to slope type. PMID:26450811
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Vandiver, Melissa A.; Caire, Benjamin R.; Pandey, Tara P.
Anion exchange m em branes (AEM )are prom ising solid polym er electrolytes utilized in alkalifuelcells and electrochem icalenergy conversion devices.AEM s m ust ef ciently conductions w hile m aintaining chem icaland m echanicalstability undera range ofoperating conditions.The ionicnature ofAEM sleads to stiffand brittle m em branesunderdry conditions w hile athigher hydrations,w ater sorption causes signi cant softening and w eakening of the m em brane.In this w ork,a new polyethylene-b-poly(vinylbenzyltrim ethylam m onium ) polym er (70 kg/m ol) w as cast into large (300 cm 2),thin (127 3 m ) m em branes.These m em branes exhibitedmore » im proved elasticity over previously tested AEM s,m inim aldim ensional sw elling,and m oderate ionic conductivity (57 2 m S/cm at 50 °C,95% RH in the brom ide form ).Extensional testing indicated a 95% reduction in Young's m odulus betw een dry and hydrated states.Furtherinvestigation ofthe com plex m odulusasa function ofhydration,by dynam ic m echanical analysis,revealed a sharp decrease in m odulusbetw een dry and hydrated states.M echanicalsoftening w as reversible,but the location ofthe transition displayed hysteresis betw een hum idi cation and dehum idi cation.Conductivity increased after m em brane softening;suggesting bulk m echanicalpropertiescan identify thehydration levelrequired forim proved ion transport.Understanding the relationship betw een ion conduction and m echanical properties w illhelp guide AEM developm ent and identify operating conditions for sustained perform ance.« less
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The signaling role for chloride in the bidirectional communication between neurons and astrocytes.
Wilson, Corinne S; Mongin, Alexander A
2018-01-09
It is well known that the electrical signaling in neuronal networks is modulated by chloride (Cl - ) fluxes via the inhibitory GABA A and glycine receptors. Here, we discuss the putative contribution of Cl - fluxes and intracellular Cl - to other forms of information transfer in the CNS, namely the bidirectional communication between neurons and astrocytes. The manuscript (i) summarizes the generic functions of Cl - in cellular physiology, (ii) recaps molecular identities and properties of Cl - transporters and channels in neurons and astrocytes, and (iii) analyzes emerging studies implicating Cl - in the modulation of neuroglial communication. The existing literature suggests that neurons can alter astrocytic Cl - levels in a number of ways; via (a) the release of neurotransmitters and activation of glial transporters that have intrinsic Cl - conductance, (b) the metabotropic receptor-driven changes in activity of the electroneutral cation-Cl - cotransporter NKCC1, and (c) the transient, activity-dependent changes in glial cell volume which open the volume-regulated Cl - /anion channel VRAC. Reciprocally, astrocytes are thought to alter neuronal [Cl - ] i through either (a) VRAC-mediated release of the inhibitory gliotransmitters, GABA and taurine, which open neuronal GABA A and glycine receptor/Cl - channels, or (b) the gliotransmitter-driven stimulation of NKCC1. The most important recent developments in this area are the identification of the molecular composition and functional heterogeneity of brain VRAC channels, and the discovery of a new cytosolic [Cl - ] sensor - the Wnk family protein kinases. With new work in the field, our understanding of the role of Cl - in information processing within the CNS is expected to be significantly updated. Copyright © 2018 Elsevier B.V. All rights reserved.
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Concepcion, Axel R; Salas, January T; Sarvide, Sarai; Sáez, Elena; Ferrer, Alex; López, María; Portu, Ainhoa; Banales, Jesús M; Hervás-Stubbs, Sandra; Oude Elferink, Ronald P J; Prieto, Jesús; Medina, Juan F
2014-05-01
Mitogenic stimulation of lymphocytes involves alkalinization of intracellular pH (pHi ). Subsequent pHi regulation may involve HCO3 (-) extrusion through Cl(-) /HCO3 (-) exchangers and/or Na(+) -HCO3 (-) co-transporters with acid-loading capability. Abnormalities in these mechanisms could result in immune dysfunctions, as suggested by the CD8(+) T-cell expansion encountered in mice lacking Ae2 (a widely expressed acid loader with electroneutral and Na(+) -independent Cl(-) /HCO3 (-) anion-exchange activity). Here we report that CD8(+) T cells but not CD4(+) T cells or other lymphocyte populations, are crucially dependent on Ae2 for pHi regulation. While total lymphocytes (including isolated CD4(+) T cells) exhibit Ae1 expression and Na(+) -HCO3 (-) co-transport with acidifying potential, CD8(+) T cells lack these acid-loading mechanisms. In Ae2-KO mice, CD4(+) but not CD8(+) T cells upregulate these potential Ae2 surrogates. As a consequence, Ae2-KO CD8(+) T cells exhibit alkalinized pHi , and dramatically increase their pHi upon CD3 stimulation. Moreover, stimulated Ae2-deficient CD8(+) T cells show enhanced intracellular production of IL-2 and membrane expression of its receptor IL-2Rα, together with increased cell proliferation and activation. These findings demonstrate that CD8(+) T cells are critically dependent on Ae2 for pHi homeostasis and tuning of cell proliferation and activation. Ae2 thus constitutes a novel target to modulate CD8(+) T-cell responses. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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Einfinger, Katrin; Badrnya, Sigrun; Furtmüller, Margareta; Handschuh, Daniela; Lindner, Herbert; Geiger, Margarethe
2015-01-01
Protein C inhibitor is a secreted, non-specific serine protease inhibitor with broad protease reactivity. It binds glycosaminoglycans and anionic phospholipids, which can modulate its activity. Anionic phospholipids, such as phosphatidylserine are normally localized to the inner leaflet of the plasma membrane, but are exposed on activated and apoptotic cells and on plasma membrane-derived microparticles. In this report we show by flow cytometry that microparticles derived from cultured cells and activated platelets incorporated protein C inhibitor during membrane blebbing. Moreover, protein C inhibitor is present in/on microparticles circulating in normal human plasma as judged from Western blots, ELISAs, flow cytometry, and mass spectrometry. These plasma microparticles are mainly derived from megakaryocytes. They seem to be saturated with protein C inhibitor, since they do not bind added fluorescence-labeled protein C inhibitor. Heparin partially removed microparticle-bound protein C inhibitor, supporting our assumption that protein C inhibitor is bound via phospholipids. To assess the biological role of microparticle-bound protein C inhibitor we performed protease inhibition assays and co-precipitated putative binding partners on microparticles with anti-protein C inhibitor IgG. As judged from amidolytic assays microparticle-bound protein C inhibitor did not inhibit activated protein C or thrombin, nor did microparticles modulate the activity of exogenous protein C inhibitor. Among the proteins co-precipitating with protein C inhibitor, complement factors, especially complement factor 3, were most striking. Taken together, our data do not support a major role of microparticle-associated protein C inhibitor in coagulation, but rather suggest an interaction with proteins of the complement system present on these phospholipid vesicles. PMID:26580551
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Imahashi, Kenichi; Schneider, Michael D; Steenbergen, Charles; Murphy, Elizabeth
2004-10-01
The antiapoptotic protein Bcl-2 is targeted to the mitochondria, but it is uncertain whether Bcl-2 affects only myocyte survival after ischemia, or whether it also affects metabolic functions of mitochondria during ischemia. Hearts from mice overexpressing human Bcl-2 and from their wild-type littermates (WT) were subjected to 24 minutes of global ischemia followed by reperfusion. During ischemia, the decrease in pH(i) and the initial rate of decline in ATP were significantly reduced in Bcl-2 hearts compared with WT hearts (P<0.05). The reduced acidification during ischemia was dependent on the activity of mitochondrial F1F0-ATPase. In the presence of oligomycin (Oligo), an F1F0-ATPase inhibitor, the decrease in pH(i) was attenuated in WT hearts, but in Bcl-2 hearts, Oligo had no additional effect on pH(i) during ischemia. Likewise, addition of Oligo to WT hearts slowed the rate of decline in ATP during ischemia to a level similar to that observed in Bcl-2 hearts, but addition of Oligo had no significant effect on the rate of decline in ATP in Bcl-2 hearts during ischemia. These data are consistent with Bcl-2-mediated inhibition of consumption of glycolytic ATP. Furthermore, mitochondria from Bcl-2 hearts have a reduced rate of consumption of ATP on uncoupler addition. This could be accomplished by limiting ATP entry into the mitochondria through the voltage-dependent anion channel, and/or the adenine nucleotide transporter, or by direct inhibition of the F1F0-ATPase. Immunoprecipitation showed greater interaction between Bcl-2 and voltage-dependent anion channel during ischemia. These data indicate that Bcl-2 modulation of metabolism contributes to cardioprotection.
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Liu, Xuehong; Dawson, David C
2011-11-29
Cysteine scanning has been widely used to identify pore-lining residues in mammalian ion channels, including the cystic fibrosis transmembrane conductance regulator (CFTR). These studies, however, have been typically conducted at room temperature rather than human body temperature. Reports of substantial effects of temperature on gating and anion conduction in CFTR channels as well as an unexpected pattern of cysteine reactivity in the sixth transmembrane segment (TM6) prompted us to investigate the effect of temperature on the reactivity of cysteines engineered into TM6 of CFTR. We compared reaction rates at temperatures ranging from 22 to 37 °C for cysteines placed on either side of an apparent size-selective accessibility barrier previously defined by comparing reactivity toward channel-permeant and channel-impermeant, thiol-directed reagents. The results indicate that the reactivity of cysteines at three positions extracellular to the position of the accessibility barrier, 334, 336, and 337, is highly temperature-dependent. At 37 °C, cysteines at these positions were highly reactive toward MTSES(-), whereas at 22 °C, the reaction rates were 2-6-fold slower to undetectable. An activation energy of 157 kJ/mol for the reaction at position 337 is consistent with the hypothesis that, at physiological temperature, the extracellular portion of the CFTR pore can adopt conformations that differ significantly from those that can be accessed at room temperature. However, the position of the accessibility barrier defined empirically by applying channel-permeant and channel-impermeant reagents to the extracellular aspect of the pore is not altered. The results illuminate previous scanning results and indicate that the assay temperature is a critical variable in studies designed to use chemical modification to test structural models for the CFTR anion conduction pathway.
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NASA Astrophysics Data System (ADS)
Yu, L. H.; Yao, K. L.; Liu, Z. L.
2004-12-01
The band structures of the filled tetrahedral semiconductors LiMgN and LiZnN, viewed as the zinc-blende (MgN) - and (ZnN) - lattices partially filled with He-like Li + ion interstitials, were studied using the full-potential linearized augmented plane wave method (FP-LAPW) within density functional theory. The conduction band distortions of LiMgN and LiZnN, compared to their “parent” zinc-blende analog AlN and GaN, are discussed. It was found that the insertion of Li + ions at the interstitial sites near the cation or anion pushes the conduction band minimum of the X point in the Brillouin zone upward, relative to that of the Γ point, for both (MgN) - and (ZnN) - lattices (the valence band maximum is at Γ for AlN, GaN, LiMgN, and LiZnN), which provides a method to convert a zinc-blende indirect gap semiconductor into a direct gap material, but the conduction band distortion of the β phase (Li + near the cation) is quite stronger than that of the α phase (Li + near the anion). The total energy calculations show the α phase to be more stable than the β phase for both LiMgN and LiZnN. The Li-N and Mg-N bonds exhibit a strong ionic character, whereas the Zn-N bond has a strong covalent character in LiMgN and LiZnN.
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Impact of segregation energetics on oxygen conductivity at ionic grain boundaries
DOE Office of Scientific and Technical Information (OSTI.GOV)
Aidhy, Dilpuneet S; Zhang, Yanwen; Weber, William J
2014-01-01
In pursuit of whether nanocrystallinity could lead to higher anion conductivity, research has revealed contradicting results exposing the limited understanding of point defect energetics at grain boundaries (GBs)/interfaces. By disentangling and addressing key GB energetics issues, i.e., segregation, migration and binding energies of oxygen vacancies in the presence and absence of dopants at the GBs, and the segregation energetics of dopants, we elucidate, using atomic simulations of doped ceria, that dopant segregation is the key factor leading to degradation of oxygen conductivity in nanocrystalline materials. A framework for designing enhanced conducting nanocrystalline materials is proposed where the focus of dopingmore » strategies shifts from bulk to segregation at GBs.« less
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Diclofenac removal in urine using strong-base anion exchange polymer resins.
Landry, Kelly A; Boyer, Treavor H
2013-11-01
One of the major sources of pharmaceuticals in the environment is wastewater effluent of which human urine contributes the majority of pharmaceuticals. Urine source separation has the potential to isolate pharmaceuticals at a higher concentration for efficient removal as well as produce a nutrient byproduct. This research investigated the efficacy of using strong-base anion exchange polymer resins to remove the widely detected and abundant pharmaceutical, diclofenac, from synthetic human urine under fresh and ureolyzed conditions. The majority of experiments were conducted using a strong-base, macroporous, polystyrene resin (Purolite A520E). Ion-exchange followed a two-step removal rate with rapid removal in 1 h and equilibrium removal in 24 h. Diclofenac removal was >90% at a resin dose of 8 mL/L in both fresh and ureolyzed urine. Sorption of diclofenac onto A520E resin was concurrent with desorption of an equivalent amount of chloride, which indicates the ion-exchange mechanism is occurring. The presence of competing ions such as phosphate and citrate did not significantly impact diclofenac removal. Comparisons of three polystyrene resins (A520E, Dowex 22, Dowex Marathon 11) as well as one polyacrylic resin (IRA958) were conducted to determine the major interactions between anion exchange resin and diclofenac. The results showed that polystyrene resins provide the highest level of diclofenac removal due to electrostatic interactions between quaternary ammonium functional groups of resin and carboxylic acid of diclofenac and non-electrostatic interactions between resin matrix and benzene rings of diclofenac. Diclofenac was effectively desorbed from A520E resin using a regeneration solution that contained 4.5% (m/m) NaCl in an equal-volume mixture of methanol and water. The greater regeneration efficiency of the NaCl/methanol-water mixture over the aqueous NaCl solution supports the importance of non-electrostatic interactions between resin matrix and benzene rings of diclofenac. Experiments with ketoprofen, in addition to diclofenac, suggest that polystyrene anion exchange resins can be used to selectively remove other acidic pharmaceuticals from urine. Copyright © 2013 Elsevier Ltd. All rights reserved.
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A method for the determination of the anionic Steol CS-330 surfactant is described. CS-330 is a complex mixture of oligomers due to the various sizes of fatty alcohols and the number of moles of the ethoxylation. The main component of CS-330 is sodium lauryl ether sulfate (SLES)....
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The Seebeck coefficient of superionic conductors
DOE Office of Scientific and Technical Information (OSTI.GOV)
Mahan, G. D.
2015-01-28
We present a theory of the anomalous Seebeck coefficient found in the superionic conductor Cu{sub 2}Se. It has a phase transition at T = 400 K where the cations disorder but the anions do not. This disorder gives a temperature-dependent width to the electronic states in the conduction band. This width provides the anomalous Seebeck contribution.
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“Lichens Lite?” chemical analysis of lichens for tracking 26 pollutants
Sarah Jovan; Susan Will-Wolf; Michael Amacher
2015-01-01
Lichen chemistry can be used to estimate concentrations of environmental contaminants, ranging from heavy metals and fertilizers to polycyclic aromatic hydrocarbons, dioxins, pesticides, herbicides, and flame retardants. We conducted a pilot looking at 26 metals and nutrient anions in 5 widespread lichen species across the upper Midwest, including: As, Al, Ba, Ca, Cd,...
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Tissue-transglutaminase contributes to neutrophil granulocyte differentiation and functions.
Balajthy, Zoltán; Csomós, Krisztián; Vámosi, György; Szántó, Attila; Lanotte, Michel; Fésüs, László
2006-09-15
Promyelocytic NB4 leukemia cells undergo differentiation to granulocytes following retinoic acid treatment. Here we report that tissue transglutaminase (TG2), a protein cross-linking enzyme, was induced, then partially translocated into the nucleus, and became strongly associated with the chromatin during the differentiation process. The transglutaminase-catalyzed cross-link content of both the cytosolic and the nuclear protein fractions increased while NB4 cells underwent cellular maturation. Inhibition of cross-linking activity of TG2 by monodansylcadaverin in these cells led to diminished nitroblue tetrazolium (NBT) positivity, production of less superoxide anion, and decreased expression of GP91PHOX, the membrane-associated subunit of NADPH oxidase. Neutrophils isolated from TG2(-/-) mice showed diminished NBT reduction capacity, reduced superoxide anion formation, and down-regulation of the gp91phox subunit of NADPH oxidase, compared with wild-type cells. It was also observed that TG2(-/-) mice exhibited increased neutrophil phagocytic activity, but had attenuated neutrophil chemotaxis and impaired neutrophil extravasation with higher neutrophil counts in their circulation during yeast extract-induced peritonitis. These results clearly suggest that TG2 may modulate the expression of genes related to neutrophil functions and is involved in several intracellular and extracellular functions of extravasating neutrophil.
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Mechanistic insights into the dehalogenation reaction of fluoroacetate/fluoroacetic acid
NASA Astrophysics Data System (ADS)
Miranda-Rojas, Sebastián; Toro-Labbé, Alejandro
2015-05-01
Fluoroacetate is a toxic compound whose environmental accumulation may represent an important contamination problem, its elimination is therefore a challenging issue. Fluoroacetate dehalogenase catalyzes its degradation through a two step process initiated by an SN2 reaction in which the aspartate residue performs a nucleophilic attack on the carbon bonded to the fluorine; the second step is hydrolysis that releases the product as glycolate. In this paper, we present a study based on density functional theory calculations of the SN2 initiation reaction modeled through the interaction between the substrate and the propionate anion as the nucleophile. Results are analyzed within the framework of the reaction force and using the reaction electronic flux to identify and characterize the electronic activity that drives the reaction. Our results reveal that the selective protonation of the substrate catalyzes the reaction by decreasing the resistance of the structural and electronic reorganization needed to reach the transition state. Finally, the reaction energy is modulated by the degree of stabilization of the fluoride anion formed after the SN2 reaction. In this way, a site-induced partial protonation acts as a chemical switch in a key process that determines the output of the reaction.
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Laucirica, Gregorio; Marmisollé, Waldemar A; Azzaroni, Omar
2017-03-22
Although not always considered a preponderant interaction, amine-phosphate interactions are omnipresent in multiple chemical and biological systems. This study aims to answer questions that are still pending about their nature and consequences. We focus on the description of the charge state as surface charges constitute directing agents of the interaction of amine groups with either natural or synthetic counterparts. Our results allow us to quantitatively determine the relative affinities of HPO 4 2- and H 2 PO 4 - from the analysis of the influence of phosphates on the zeta-potential of amino-functionalized surfaces in a broad pH range. We show that phosphate anions enhance the protonation of amino groups and, conversely, charged amines induce further proton dissociation of phosphates, yielding a complex dependence of the surface effective charge on the pH and phosphate concentration. We also demonstrate that phosphate-amine interaction is specific and the modulation of surface charge occurs in the physiological phosphate concentration range, emphasizing its biochemical and biotechnological relevance and the importance of considering this veiled association in both in vivo and in vitro studies.
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NASA Astrophysics Data System (ADS)
Tan, Jie; Li, Fenghui; Sun, Huiling; Gao, Fei; Yan, Jingping; Gai, Chunlei; Chen, Aihua; Wang, Qingyin
2015-04-01
Grading procedure in routine sea cucumber hatchery production is thought to affect juvenile sea cucumber immunological response. The present study investigated the impact of a 3-min mechanical perturbation mimicking the grading procedure on neuroendocrine and immune parameters of the sea cucumber Apostichopus japonicus. During the application of stress, concentrations of noradrenaline and dopamine in coelomic fluid increased significantly, indicating that the mechanical perturbation resulted in a transient state of stress in sea cucumbers. Coelomocytes concentration in coelomic fluid increased transiently after the beginning of stressing, and reached the maximum in 1 h. Whereas, coelomocytes phagocytosis at 3 min, superoxide anion production from 3 min to 0.5 h, acid phosphatase activity at 0.5 h, and phenoloxidase activity from 3 min to 0.5 h were all significantly down-regulated. All of the immune parameters recovered to baseline levels after the experiment was conducted for 8 h, and an immunostimulation occurred after the stress considering the phagocytosis and acid phosphatase activity. The results suggested that, as in other marine invertebrates, neuroendocrine/immune connections exist in sea cucumber A. japonicus. Mechanical stress can elicit a profound influence on sea cucumber neuroendocrine system. Neuroendocrine messengers act in turn to modulate the immunity functions. Therefore, these effects should be considered for developing better husbandry procedures.
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Aza-Bambusurils En Route to Anion Transporters.
Singh, Mandeep; Solel, Ephrath; Keinan, Ehud; Reany, Ofer
2016-06-20
Previous calculations of anion binding with various bambusuril analogs predicted that the replacement of oxygen by nitrogen atoms to produce semiaza-bambus[6]urils would award these new cavitands with multiple anion binding properties. This study validates the hypothesis by efficient synthesis, crystallography, thermogravimetric analysis and calorimetry. These unique host molecules are easily accessible from the corresponding semithio-bambusurils in a one-pot reaction, which converts a single anion receptor into a potential anion channel. Solid-state structures exhibit simultaneous accommodation of three anions, linearly positioned within the cavity along the main symmetry axis. The ability to hold anions at a short distance of about 4 Å is reminiscent of natural chloride channels in E. coli, which exhibit similar distances between their adjacent anion binding sites. The calculated transition-state energy for double-anion movement through the channel suggests that although these host-guest complexes are thermodynamically stable they enjoy high kinetic flexibility to render them efficient anion channels. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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Supramolecular Chemistry of Selective Anion Recognition for Anions of Environmental Relevance
DOE Office of Scientific and Technical Information (OSTI.GOV)
Bowman-James, Kristen
2004-12-01
This project have focuses on the basic chemical aspects of anion receptor design of functional pH independent systems, with the ultimate goal of targeting the selective binding of sulfate, as well as design of separations strategies for selective and efficient removal of targeted anions. Key findings include: (1) the first synthetic sulfate-selective anion-binding agents; (2) simple, structure-based methods for modifying the intrinsic anion selectivity of a given class of anion receptors; and (3) the first system capable of extracting sulfate anion from acidic, nitrate-containing aqueous media. Areas probed during the last funding period include: the design, synthesis, and physical andmore » structural characterization of receptors and investigation of anion and dual ion pair extraction using lipophilic amide receptors for anion binding. A new collaboration has been added to the project in addition to the one with Dr. Bruce Moyer at Oak Ridge National Laboratory, with Professor Jonathan Sessler at the University of Texas at Austin.« less
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NASA Astrophysics Data System (ADS)
Zianni, Xanthippi
2018-03-01
Width-modulated nanowires have been proposed as efficient thermoelectric materials. Here, the electron and phonon transport properties and the thermoelectric efficiency are discussed for dimensions above the quantum confinement regime. The thermal conductivity decreases dramatically in the presence of thin constrictions due to their ballistic thermal resistance. It shows a scaling behavior upon the width-modulation rate that allows for thermal conductivity engineering. The electron conductivity also decreases due to enhanced boundary scattering by the constrictions. The effect of boundary scattering is weaker for electrons than for phonons and the overall thermoelectric efficiency is enhanced. A ZT enhancement by a factor of 20-30 is predicted for width-modulated nanowires compared to bulk silicon. Our findings indicate that width-modulated nanostructures are promising for developing silicon nanostructures with high thermoelectric efficiency.
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Wang, Yujuan; Lin, Hui; Jin, Fangyuan; Niu, Junfeng; Zhao, Jinbo; Bi, Ying; Li, Ying
2016-07-01
Batch experiments were conducted to investigate the effects of cathode materials and anions (Cl(-), SO4(2-), NO3(-), and CO3(2-)/HCO3(-)) on perfluorooctanoate (PFOA) removal in electrocoagulation process using zinc anode. The results indicated that the hydroxide flocs generated in-situ in the electrocoagulation process using the stainless steel rod as cathode were more effective than those using aluminum rod as cathode for the removal of PFOA after 20min of electrocoagulation at a current density of 0.5mAcm(-2). Hydroxide flocs generated in-situ in the electrocoagulation in the presence of Cl(-)/NO3(-) could effectively remove PFOA from aqueous solution with the removal ratios of 99.7%/98.1% and 98.9%/97.3% using stainless steel rod and aluminum rod as cathode, respectively. However, the PFOA removal ratios were 96.2%/4.1% and 7.4%/4.6% using stainless steel rod and aluminum rod as cathode, respectively, in the presence of SO4(2-) and CO3(2-)/HCO3(-). The different removal ratios of PFOA during the electrocoagulation process were primarily due to the fact that the hydroxide flocs generated in-situ were different in the presence of diverse cathodes and anions. We firstly demonstrated that Zn0.70Al0.30(OH)2(CO3)0.15·xH2O and ZnO generated in-situ in the electrocoagulation process (except for CO3(2-)/HCO3(-)) using zinc anode and aluminum/stainless steel rod cathode governed the sorption of PFOA. The adsorbent hydroxide flocs in-situ generated in the presence of Cl(-) could effectively remove PFOA from aqueous solution containing CO3(2-)/HCO3(-) anion at the initial hydroxide flocs concentration of 2000mgL(-1). These results provided an effective and alternative method to remove PFOA from aqueous solution containing CO3(2-)/HCO3(-) anion. Copyright © 2016 Elsevier B.V. All rights reserved.
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Johns, Cameron; Shellie, Robert A; Potter, Oscar G; O'Reilly, John W; Hutchinson, Joseph P; Guijt, Rosanne M; Breadmore, Michael C; Hilder, Emily F; Dicinoski, Greg W; Haddad, Paul R
2008-02-29
Anions and cations of interest for the post-blast identification of homemade inorganic explosives were separated and detected by ion chromatographic (IC) methods. The ionic analytes used for identification of explosives in this study comprised 18 anions (acetate, benzoate, bromate, carbonate, chlorate, chloride, chlorite, chromate, cyanate, fluoride, formate, nitrate, nitrite, perchlorate, phosphate, sulfate, thiocyanate and thiosulfate) and 12 cations (ammonium, barium(II), calcium(II), chromium(III), ethylammonium, magnesium(II), manganese(II), methylammonium, potassium(I), sodium(I), strontium(II), and zinc(II)). Two IC separations are presented, using suppressed IC on a Dionex AS20 column with potassium hydroxide as eluent for anions, and non-suppressed IC for cations using a Dionex SCS 1 column with oxalic acid/acetonitrile as eluent. Conductivity detection was used in both cases. Detection limits for anions were in the range 2-27.4ppb, and for cations were in the range 13-115ppb. These methods allowed the explosive residue ions to be identified and separated from background ions likely to be present in the environment. Linearity (over a calibration range of 0.05-50ppm) was evaluated for both methods, with r(2) values ranging from 0.9889 to 1.000. Reproducibility over 10 consecutive injections of a 5ppm standard ranged from 0.01 to 0.22% relative standard deviation (RSD) for retention time and 0.29 to 2.16%RSD for peak area. The anion and cation separations were performed simultaneously by using two Dionex ICS-2000 chromatographs served by a single autoinjector. The efficacy of the developed methods was demonstrated by analysis of residue samples taken from witness plates and soils collected following the controlled detonation of a series of different inorganic homemade explosives. The results obtained were also confirmed by parallel analysis of the same samples by capillary electrophoresis (CE) with excellent agreement being obtained.
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Controlled Neutralization of Anions in Cryogenic Matrices by Near-Threshold Photodetachment
NASA Astrophysics Data System (ADS)
Ludwig, Ryan M.; Moore, David T.
2014-06-01
Using matrix isolation FTIR, we have observed the formation of anionic copper carbonyl complexes [Cu(CO)n]- (n=1-3) following co-deposition of Cu- and counter-cations (Ar+ or Kr+) into argon matrices doped with CO. The infrared bands have been previously assigned in argon matrix studies employing laser ablation, however they were quite weak compared to the bands for the corresponding neutral species. In the current study, when the deposition is carried out in fully darkened conditions at 10 K with high CO concentrations (1-2%), only the bands for the anionic complexes are observed initially via FTIR. However, upon mild irradiation with broadband visible light, the anionic bands are rapidly depleted, with concomitant appearance of bands corresponding to neutral copper carbonyl complexes. This photo-triggered neutralization is attributed to photodetachment of electrons from the anions, which then "flow" through the solid argon matrix to recombine in the matrix with non-adjacent trapping sites. This mechanism is supported by the appearance of a new band near 1515 wn, assigned to the (CO)2- species in argon. The wavelength dependence of the photodetachment will be discussed in detail, although preliminary indications are that the thresholds for the copper carbonyls, which are normally in the infrared, are shifted into the visible region of the spectrum in argon matrices. This likely occurs because the conduction band of solid argon is known to lie about 1 eV above the vacuum level, and thus the electron must have at least this much energy in order to escape into the matrix and find a trapping site. Funding support from NSF CAREER Award CHE-0955637 is gratefully acknowledged Ryan M. Ludwig and David T. Moore, J. Chem. Phys. 139, 244202 (2013) Zhou, M.; Andrews, L., J. Chem. Phys. 111, 4548 (1999). Thompson, W.E.; Jacox, M.E.; J. Chem. Phys. 91, 735 (1991). Stanzel, J. et al.; Collect. Czech. Chem. Comm. 72, 1 (2007). Harbich, W. et al.; Phys. Rev. B. 76, 104306 (2007).
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CFTR modulates RPS27 gene expression using chloride anion as signaling effector.
Valdivieso, Ángel G; Mori, Consuelo; Clauzure, Mariángeles; Massip-Copiz, Macarena; Santa-Coloma, Tomás A
2017-11-01
In Cystic Fibrosis (CF), the impairment of the CFTR channel activity leads to a variety of alterations, including differential gene expression. However, the CFTR signaling mechanisms remain unclear. Recently, culturing IB3-1 CF cells under different intracellular Cl - concentrations ([Cl - ] i ), we observed several Cl - -dependent genes and further characterized one of them as RPS27. Thus, we hypothesized that Cl - might act as a signaling effector for CFTR signaling. Here, to test this idea, we study RPS27 expression in T84 cells modulating the CFTR activity by using CFTR inhibitors. First, we observed that incubation of T84 cells with increasing concentrations of the CFTR inhibitors CFTR(inh)-172 or GlyH-101 determined a progressive increase in the relative [Cl - ] i (using the Cl - fluorescent probe SPQ). The [Cl - ] i rise was concomitant with a dose-dependent down-regulation of RPS27. These results imply that CFTR inhibition produce Cl - accumulation and that RPS27 expression can be modulated by CFTR inhibition. Therefore, Cl - behaves as a signaling effector for CFTR in the modulation of RPS27 expression. In addition, the IL-1β receptor antagonist IL1RN or the JNK inhibitor SP600125, both restored the down-regulation of RPS27 induced by CFTRinh-172, implying a role of autocrine IL-1β and JNK signaling downstream of Cl - in RPS27 modulation. Copyright © 2017 Elsevier Inc. All rights reserved.
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Segmented saddle-shaped passive stabilization conductors for toroidal plasmas
Leuer, James A.
1990-05-01
A large toroidal vacuum chamber for plasma generation and confinement is lined with a toroidal blanket for shielding using modules segmented in the toroidal direction. To provide passive stabilization in the same manner as a conductive vacuum chamber wall, saddle-shaped conductor loops are provided on blanket modules centered on a midplane of the toroidal chamber with horizontal conductive bars above and below the midplane, and vertical conductive legs on opposite sides of each module to provide return current paths between the upper and lower horizontal conductive bars. The close proximity of the vertical legs provided on adjacent modules without making physical contact cancel the electromagnetic field of adjacent vertical legs. The conductive bars spaced equally above and below the midplane simulate toroidal conductive loops or hoops that are continuous, for vertical stabilization of the plasma even though they are actually segmented.
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The incommensurately modulated(1 - x)Ta 2O 5· xWO 3, 0 ≤ x ≤ 0.267 solid solution
NASA Astrophysics Data System (ADS)
Schmid, Siegbert; Withers, Ray L.; Thompson, John G.
1992-08-01
The phase(1 - x)Ta 2O 5 · WO 3, 0 ≤ x ≤ 0.267 has been studied by X-ray powder diffraction and transmission electron microscopy. It was previously described as an infinite series of anion-deficient, α-UO 3-type "line phases," with compositions resulting from intergrowths of different blocks made up by small numbers of α-UO 3-type cells. More correctly(1 - x)Ta 2O 5· xWO 3, 0 ≤ x ≤ 0.267 is described as an incommensurately modulated structure with a linearly composition-dependent primary modulation wave-vector qprim. = qb*. The underlying orthorhombically distorted α-UO 3-type parent structure has space group symmetry Cmmm ( a ≈ 6.20-6.14, b ≈ 3.66, c ≈ 3.89-3.85Å). Characteristic extinction conditions imply a superspace group symmetry of P : Cmmmm : s, -1,1. The four previously reported crystal structures in the solid solution field are examined by means of apparent valence calculations. Crystal chemical reasons are proposed for the width of the composition range,0 ≤ x ≤ 0.267, observed for the title phase.
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Targeted modulation of reactive oxygen species in the vascular endothelium.
Shuvaev, Vladimir V; Muzykantov, Vladimir R
2011-07-15
'Endothelial cells lining vascular luminal surface represent an important site of signaling and injurious effects of reactive oxygen species (ROS) produced by other cells and endothelium itself in ischemia, inflammation and other pathological conditions. Targeted delivery of ROS modulating enzymes conjugated with antibodies to endothelial surface molecules (vascular immunotargeting) provides site-specific interventions in the endothelial ROS, unattainable by other formulations including PEG-modified enzymes. Targeting of ROS generating enzymes (e.g., glucose oxidase) provides ROS- and site-specific models of endothelial oxidative stress, whereas targeting of antioxidant enzymes SOD and catalase offers site-specific quenching of superoxide anion and H(2)O(2). These targeted antioxidant interventions help to clarify specific role of endothelial ROS in vascular and pulmonary pathologies and provide basis for design of targeted therapeutics for treatment of these pathologies. In particular, antibody/catalase conjugates alleviate acute lung ischemia/reperfusion injury, whereas antibody/SOD conjugates inhibit ROS-mediated vasoconstriction and inflammatory endothelial signaling. Encapsulation in protease-resistant, ROS-permeable carriers targeted to endothelium prolongs protective effects of antioxidant enzymes, further diversifying the means for targeted modulation of endothelial ROS. Copyright © 2011 Elsevier B.V. All rights reserved.
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Picosecond dynamics from lanthanide chloride melts
NASA Astrophysics Data System (ADS)
Kalampounias, Angelos G.
2012-12-01
The picosecond dynamics of molten lanthanide chlorides is studied by means of vibrational spectroscopy. Polarized Raman spectra of molten LaCl3, NdCl3, GdCl3, DyCl3, HoCl3 and YCl3 are fitted to a model enabling to obtain the times of vibrational dephasing, tν and vibrational frequency modulation tω. Our aim is to find possible sensitive indicators of short-time dynamics. It has been found that all lanthanide chlorides exhibit qualitative similarities in the vibrational relaxation and frequency modulation times in the molten state. It appears that the vibrational correlation functions of all melts comply with the Rothschild approach assuming that the environmental modulation is described by a stretched exponential decay. The evolution of the dispersion parameter α indicates the deviation of the melts from the model simple liquid and the similar local environment in which the oscillator is placed and with which it is coupled. The "packing" of the anions around central La3+ cation seems to be the key factor for the structure and the dynamics of the melts. The results are discussed in the framework of the current phenomenological status of the field.
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ZnO nanoparticles modulate the ionic transport and voltage regulation of lysenin nanochannels.
Bryant, Sheenah L; Eixenberger, Josh E; Rossland, Steven; Apsley, Holly; Hoffmann, Connor; Shrestha, Nisha; McHugh, Michael; Punnoose, Alex; Fologea, Daniel
2017-12-16
The insufficient understanding of unintended biological impacts from nanomaterials (NMs) represents a serious impediment to their use for scientific, technological, and medical applications. While previous studies have focused on understanding nanotoxicity effects mostly resulting from cellular internalization, recent work indicates that NMs may interfere with transmembrane transport mechanisms, hence enabling contributions to nanotoxicity by affecting key biological activities dependent on transmembrane transport. In this line of inquiry, we investigated the effects of charged nanoparticles (NPs) on the transport properties of lysenin, a pore-forming toxin that shares fundamental features with ion channels such as regulation and high transport rate. The macroscopic conductance of lysenin channels greatly diminished in the presence of cationic ZnO NPs. The inhibitory effects were asymmetrical relative to the direction of the electric field and addition site, suggesting electrostatic interactions between ZnO NPs and a binding site. Similar changes in the macroscopic conductance were observed when lysenin channels were reconstituted in neutral lipid membranes, implicating protein-NP interactions as the major contributor to the reduced transport capabilities. In contrast, no inhibitory effects were observed in the presence of anionic SnO 2 NPs. Additionally, we demonstrate that inhibition of ion transport is not due to the dissolution of ZnO NPs and subsequent interactions of zinc ions with lysenin channels. We conclude that electrostatic interactions between positively charged ZnO NPs and negative charges within the lysenin channels are responsible for the inhibitory effects on the transport of ions. These interactions point to a potential mechanism of cytotoxicity, which may not require NP internalization.
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The development of form two mathematics i-Think module (Mi-T2)
NASA Astrophysics Data System (ADS)
Yao, Foo Jing; Abdullah, Mohd Faizal Nizam Lee; Tien, Lee Tien
2017-05-01
This study aims to develop a training module i-THINK Mathematics Form Two (Mi-T2) to increase the higher-order thinking skills of students. The Mi-T2 training module was built based on the Sidek Module Development Model (2001). Constructivist learning theory, cognitive learning theory, i-THINK map and higher order thinking skills were the building blocks of the module development. In this study, researcher determined the validity and reliability of Mi-T2 module. The design being used in this study was descriptive study. To determine the needs of Mi-T2 module, questionnaires and literature review were used to collect data. When the need of the module was determined, the module was built and a pilot study was conducted to test the reliability of the Mi-T2 module. The pilot study was conducted at a secondary school in North Kinta, Perak. A Form Two class was selected to be the sample study through clustered random sampling. The pilot study was conducted for two months and one topic had been studied. The Mi-T2 module was evaluated by five expert panels to determine the content validity of the module. The instruments being used in the study were questionnaires about the necessity of the Mi-T2 module for guidance, questionnaires about the validity of the module and questionnaires concerning the reliability of the module. Statistical analysis was conducted to determine the validity and reliability coefficients of the Mi-T2 module. The content validity of Mi-T2 module was determined by Cohen's Kappa's (1968) agreement coefficient and the reliability of Mi-T2 module was determined by Cronbach Alpha's value scale. The content validity of Mi-T2 module was 0.89 and the Cronbach Alpha's value of Mi-T2 module was 0.911.
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NASA Astrophysics Data System (ADS)
Barhoumi, Z.; Saini, M.; Amdouni, N.; Pal, A.
2016-09-01
The micellization of an aqueous solution of the surface active ionic liquid (SAIL), 1-butyl-3-methylimidazolium octylsufate (C4mim)(C8OSO3) and its interaction with an anionic polymer sodium polystyrene sulfonate, (NaPSS) were studied using conductimetry, tensiometry and fluorimetry. Surface tension profile shows a more dramatic increase in the value of surface tension of aqueous (C4mim)(C8OSO3) before the critical micelle concentration (cmc) of IL. The critical micelle concentration (cmc) value of this surfactant was found out from conductance measurements. The thermodynamic parameters, i.e., Gibb's free energy, enthalpy, and entropy of micellization of the IL in aqueous solution have been calculated. Behavior of fluorescence probe confirms the binding interactions between SAIL and the polyelectrolyte.
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Radiolytic preparation of ETFE and PFA based anion exchange membranes for alkaline fuel cell
NASA Astrophysics Data System (ADS)
Ko, Beom-Seok; Sohn, Joon-Yong; Nho, Young-Chang; Shin, Junhwa
2011-11-01
In this study, a versatile monomer, vinylbenzyl chloride (VBC) was radiolytically grafted onto a partially fluorinated ETFE and perfluorinated polymer PFA films. The VBC grafted films were treated with trimethylamine to prepare the alkaline anion exchange membranes (AAEMs). No significant differences in the ion exchange capacities and water uptakes were observed between the ETFE and PFA based AAEMs with similar degree of grafting (DOG). However, the distribution patterns of the graft chains over the cross-section of the ETFE and PFA based AAEMs were found to be quite different; the even distribution was observed from the ETFE based AAEMs while the uneven distribution was observed from the PFA based AAEMs. It was also found that the PFA based AAEMs have the higher ionic conductivity and chemical stability, compared to the ETFE based AAEMs.
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Reciprocal Modulation of IK1–INa Extends Excitability in Cardiac Ventricular Cells
Varghese, Anthony
2016-01-01
The inwardly rectifying potassium current (IK1) and the fast inward sodium current (INa) are reciprocally modulated in mammalian ventricular myocytes. An increase in the expression of channels responsible for one of these two currents results in a corresponding increase in expression of the other. These currents are critical in the propagation of action potentials (AP) during the normal functioning of the heart. This study identifies a physiological role for IK1–INa reciprocal modulation in ventricular fiber activation thresholds and conduction. Simulations of action potentials in single cells and propagating APs in cardiac fibers were carried out using an existing model of electrical activity in cardiac ventricular myocytes. The conductances, GK1, of the inwardly rectifying potassium current, and GNa, of the fast inward sodium current were modified independently and in tandem to simulate reciprocal modulation. In single cells, independent modulation of GK1 alone resulted in changes in activation thresholds that were qualitatively similar to those for reciprocal GK1–GNa modulation and unlike those due to independent modulation of GNa alone, indicating that GK1 determines the cellular activation threshold. On the other hand, the variations in conduction velocity in cardiac cell fibers were similar for independent GNa modulation and for tandem changes in GK1–GNa, suggesting that GNa is primarily responsible for setting tissue AP conduction velocity. Conduction velocity dependence on GK1–GNa is significantly affected by the intercellular gap junction conductance. While the effects on the passive fiber space constant due to changes in both GK1 and the intercellular gap junction conductance, Ggj, were in line with linear cable theory predictions, both conductances had surprisingly large effects on fiber activation thresholds. Independent modulation of GK1 rendered cardiac fibers inexcitable at higher levels of GK1 whereas tandem GK1–GNa changes allowed fibers to remain excitable at high GK1 values. Reciprocal modulation of the inwardly rectifying potassium current and the fast inward sodium current may have a functional role in allowing cardiac tissue to remain excitable when IK1 is upregulated. PMID:27895596
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Chelating ionic liquids for reversible zinc electrochemistry.
Kar, Mega; Winther-Jensen, Bjorn; Forsyth, Maria; MacFarlane, Douglas R
2013-05-21
Advanced, high energy-density, metal-air rechargeable batteries, such as zinc-air, are of intense international interest due to their important role in energy storage applications such as electric and hybrid vehicles, and to their ability to deal with the intermittency of renewable energy sources such as solar and wind. Ionic liquids offer a number of ideal thermal and physical properties as potential electrolytes in such large-scale energy storage applications. We describe here the synthesis and characterisation of a family of novel "chelating" ILs designed to chelate and solubilize the zinc ions to create electrolytes for this type of battery. These are based on quaternary alkoxy alkyl ammonium cations of varying oligo-ether side chains and anions such as p-toluene sulfonate, bis(trifluoromethylsulfonyl)amide and dicyanoamides. This work shows that increasing the ether chain length in the cation from two to four oxygens can increase the ionic conductivity and reduce the melting point from 67 °C to 15 °C for the tosylate system. Changing the anion also plays a significant role in the nature of the zinc deposition electrochemistry. We show that zinc can be reversibly deposited from [N(222(20201))][NTf2] and [N(222(202020201))][NTf2] beginning at -1.4 V and -1.7 V vs. SHE, respectively, but not in the case of tosylate based ILs. This indicates that the [NTf2] is a weaker coordinating anion with the zinc cation, compared to the tosylate anion, allowing the coordination of the ether chain to dominate the behavior of the deposition and stripping of zinc ions.
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Gujt, Jure; Podlipnik, Črtomir; Bešter-Rogač, Marija; Spohr, Eckhard
2014-09-28
The relative position of the hydroxylic and the carboxylic group in the isomeric hydroxybenzoate (HB) anions is known to have a large impact on transport properties of this species. It also influences crucially the self-organisation of cationic surfactants. In this article a systematic investigation of aqueous solutions of the ortho, meta, and para isomers of the HB anion is presented. Molecular dynamics simulations of all three HB isomers were conducted for two different concentrations at 298.15 K and using two separate water models. From the resulting trajectories we calculated the self-diffusion coefficient of each isomer. According to the calculated self-diffusion coefficients, isomers were ranked in the order o-HB > m-HB > p-HB at both concentrations for both the used SPC and SPC/E water models, which agrees very well with the experiment. The structural analysis revealed that at lower concentration, where the tendency for dimerisation or cluster formation is low, hydrogen bonding with water determines the mobility of the HB anion. o-HB forms the least hydrogen bonds and is therefore the most mobile, and p-HB, which forms the most hydrogen bonds with water, is the least mobile isomer. At higher concentration the formation of clusters also needs to be considered. The ortho isomer predominantly forms dimers with 2 hydrogen bonds per dimer between one OH and one carboxylate group of each anion. m-HB mostly forms clusters of sizes around 5 and p-HB forms clusters of sizes even larger than 10, which can be either rings or chains.
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Hybrid MD-Nernst Planck Model of Alpha-hemolysin Conductance Properties
NASA Technical Reports Server (NTRS)
Cozmuta, Ioana; O'Keefer, James T.; Bose, Deepak; Stolc, Viktor
2006-01-01
Motivated by experiments in which an applied electric field translocates polynucleotides through an alpha-hemolysin protein channel causing ionic current transient blockade, a hybrid simulation model is proposed to predict the conductance properties of the open channel. Time scales corresponding to ion permeation processes are reached using the Poisson-Nemst-Planck (PNP) electro-diffusion model in which both solvent and local ion concentrations are represented as a continuum. The diffusion coefficients of the ions (K(+) and Cl(-)) input in the PNP model are, however, calculated from all-atom molecular dynamics (MD). In the MD simulations, a reduced representation of the channel is used. The channel is solvated in a 1 M KCI solution, and an external electric field is applied. The pore specific diffusion coefficients for both ionic species are reduced 5-7 times in comparison to bulk values. Significant statistical variations (17-45%) of the pore-ions diffusivities are observed. Within the statistics, the ionic diffusivities remain invariable for a range of external applied voltages between 30 and 240mV. In the 2D-PNP calculations, the pore stem is approximated by a smooth cylinder of radius approx. 9A with two constriction blocks where the radius is reduced to approx. 6A. The electrostatic potential includes the contribution from the atomistic charges. The MD-PNP model shows that the atomic charges are responsible for the rectifying behaviour and for the slight anion selectivity of the a-hemolysin pore. Independent of the hierarchy between the anion and cation diffusivities, the anionic contribution to the total ionic current will dominate. The predictions of the MD-PNP model are in good agreement with experimental data and give confidence in the present approach of bridging time scales by combining a microscopic and macroscopic model.
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Ache, Peter; Bauer, Hubert; Kollist, Hannes; Al-Rasheid, Khaled A S; Lautner, Silke; Hartung, Wolfram; Hedrich, Rainer
2010-06-01
Uptake of CO(2) by the leaf is associated with loss of water. Control of stomatal aperture by volume changes of guard cell pairs optimizes the efficiency of water use. Under water stress, the protein kinase OPEN STOMATA 1 (OST1) activates the guard-cell anion release channel SLOW ANION CHANNEL-ASSOCIATED 1 (SLAC1), and thereby triggers stomatal closure. Plants with mutated OST1 and SLAC1 are defective in guard-cell turgor regulation. To study the effect of stomatal movement on leaf turgor using intact leaves of Arabidopsis, we used a new pressure probe to monitor transpiration and turgor pressure simultaneously and non-invasively. This probe permits routine easy access to parameters related to water status and stomatal conductance under physiological conditions using the model plant Arabidopsis thaliana. Long-term leaf turgor pressure recordings over several weeks showed a drop in turgor during the day and recovery at night. Thus pressure changes directly correlated with the degree of plant transpiration. Leaf turgor of wild-type plants responded to CO(2), light, humidity, ozone and abscisic acid (ABA) in a guard cell-specific manner. Pressure probe measurements of mutants lacking OST1 and SLAC1 function indicated impairment in stomatal responses to light and humidity. In contrast to wild-type plants, leaves from well-watered ost1 plants exposed to a dry atmosphere wilted after light-induced stomatal opening. Experiments with open stomata mutants indicated that the hydraulic conductance of leaf stomata is higher than that of the root-shoot continuum. Thus leaf turgor appears to rely to a large extent on the anion channel activity of autonomously regulated stomatal guard cells.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Berastegui, P.; Hull, S., E-mail: stephen.hull@stfc.ac.u; Eriksson, S.G.
The compound CsSn{sub 2}F{sub 5} has been investigated over the temperature range from ambient to 545 K using differential scanning calorimetry, impedance spectroscopy and neutron powder diffraction methods. A first-order phase transition is observed from DSC measurements at 510(2) K, to a phase possessing a high ionic conductivity ({sigma}{approx}2.5x10{sup -2} {Omega}{sup -1} cm{sup -1} at 520 K). The crystal structure of the high temperature superionic phase (labelled {alpha}) has been determined to be tetragonal (space group I4/mmm, a=4.2606(10) A, c=19.739(5) A and Z=2) in which the cations form layers perpendicular to the [001] direction, with a stacking sequence CsSnSnCsSnSn... Allmore » the anions are located in two partially occupied sites in the gap between the Cs and Sn layers, whilst the space between the Sn cations is empty, due to the orientation of the lone-pair electrons associated with the Sn{sup 2+}. The structure of {alpha}-CsSn{sub 2}F{sub 5} is discussed in relation to two other layered F{sup -} conducting superionic phases containing Sn{sup 2+} cations, {alpha}-RbSn{sub 2}F{sub 5} and {alpha}-PbSnF{sub 4} and, to facilitate this comparison, an improved structural characterisation of the former is also presented. The wider issue of the role of lone-pair cations such as Sn{sup 2+} in promoting dynamic disorder within an anion substructure is also briefly addressed. - Graphical abstract: CsSn{sub 2}F{sub 5} is shown to undergo a first order phase transition at 510(2) K to a superionic phase in which the specific electronic configuration of the Sn{sup 2+} plays a key role in promoting extensive disorder of the anions.« less
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Bijvelds, Marcel J C; Loos, Michaela; Bronsveld, Inez; Hellemans, Ann; Bongartz, Jean-Pierre; Ver Donck, Luc; Cox, Eric; de Jonge, Hugo R; Schuurkes, Jan A J; De Maeyer, Joris H
2015-12-01
Many enterotoxigenic Escherichia coli strains produce the heat-stable toxin, STa, which, by activation of the intestinal receptor-enzyme guanylyl cyclase (GC) C, triggers an acute, watery diarrhea. We set out to identify GCC inhibitors that may be of benefit for the treatment of infectious diarrheal disease. Compounds that inhibit STa-induced cyclic guanosine 3',5'-monophosphate (cGMP) production were selected by performing cyclase assays on cells and membranes containing GCC, or the related GCA. The effect of leads on STa/GCC-dependent activation of the cystic fibrosis transmembrane conductance regulator anion channel was investigated in T84 cells, and in porcine and human intestinal tissue. Their effect on STa-provoked fluid transport was assessed in ligated intestinal loops in piglets. Four N-2-(propylamino)-6-phenylpyrimidin-4-one-substituted piperidines were shown to inhibit GCC-mediated cellular cGMP production. The half maximal inhibitory concentrations were ≤ 5 × 10(-7) mol/L, whereas they were >10 times higher for GCA. In T84 monolayers, these leads blocked STa/GCC-dependent, but not forskolin/adenylyl cyclase-dependent, cystic fibrosis transmembrane conductance regulator activity. GCC inhibition reduced STa-provoked anion secretion in pig jejunal tissue, and fluid retention and cGMP levels in STa-exposed loops. These GCC inhibitors blocked STa-provoked anion secretion in rectal biopsy specimens. We have identified a novel class of GCC inhibitors that may form the basis for development of future therapeutics for (infectious) diarrheal disease. © The Author 2015. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.
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Effect of salt solutions on radiosensitivity of mammalian cells. I. Specific ion effects.
Raaphorst, G P; Kruuv, J
1977-07-01
The radiation isodose survival curve of cells subjected to a wide concentration range of sucrose solutions has two maxima separated by a minimum. Both cations and anions can alter the cellular radiosensitivity above and beyond the osmotic effect observed for cells treated with sucrose solutions. The basic shape of the isodose curve can also be modulated by changes in temperature and solution exposure times. Some of these alterations in radiosensitivity may be related to changes in the amount and structure of cellular water or macromolecular conformation or to the direct effect of the ions, expecially at high solute concentrations.
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NASA Astrophysics Data System (ADS)
Aziz, Shujahadeen B.; Abdullah, Omed Gh.; Hussein, Sarkawt A.
2018-03-01
The influence of anion type on silver ion reduction and drop in direct current (DC) conductivity was investigated experimentally. The structural, optical, morphological and electrical properties of the samples were investigated using x-ray diffraction (XRD), ultraviolet-visible (UV-Vis), optical micrographs (OM) and impedance spectroscopy. The XRD results reveal significant disruption in the crystalline structure of chitosan (CS) for different concentrations of silver nitrate (AgNt) salt. The localized surface resonance plasmonic (LSRP) peaks that were observed for CS:AgNt samples, along with the white silver specs detected by OM technique confirm the formation of Ag nanoparticles. The appearance of obvious dark regions in the CS:AgNt system reveals the existence of a large percentage of amorphous domains. The nonexistence of spherulitic texture confirms the amorphous nature of the samples. The second semicircle in an impedance plot can be attributed to an Ag nanoparticle grain boundary. The established relationships between dielectric constant and carrier concentration and the behavior of dielectric constant versus salt concentration were used to explain the phenomenon of ion-ion association. The continuous increase of DC conductivity was noticed at high temperatures, which was then explained on the basis of lattice energy of silver salts. The influences of anion size on the rate of silver ion reductions are also interpreted.
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Fluctuation-enhanced electric conductivity in electrolyte solutions.
Péraud, Jean-Philippe; Nonaka, Andrew J; Bell, John B; Donev, Aleksandar; Garcia, Alejandro L
2017-10-10
We analyze the effects of an externally applied electric field on thermal fluctuations for a binary electrolyte fluid. We show that the fluctuating Poisson-Nernst-Planck (PNP) equations for charged multispecies diffusion coupled with the fluctuating fluid momentum equation result in enhanced charge transport via a mechanism distinct from the well-known enhancement of mass transport that accompanies giant fluctuations. Although the mass and charge transport occurs by advection by thermal velocity fluctuations, it can macroscopically be represented as electrodiffusion with renormalized electric conductivity and a nonzero cation-anion diffusion coefficient. Specifically, we predict a nonzero cation-anion Maxwell-Stefan coefficient proportional to the square root of the salt concentration, a prediction that agrees quantitatively with experimental measurements. The renormalized or effective macroscopic equations are different from the starting PNP equations, which contain no cross-diffusion terms, even for rather dilute binary electrolytes. At the same time, for infinitely dilute solutions the renormalized electric conductivity and renormalized diffusion coefficients are consistent and the classical PNP equations with renormalized coefficients are recovered, demonstrating the self-consistency of the fluctuating hydrodynamics equations. Our calculations show that the fluctuating hydrodynamics approach recovers the electrophoretic and relaxation corrections obtained by Debye-Huckel-Onsager theory, while elucidating the physical origins of these corrections and generalizing straightforwardly to more complex multispecies electrolytes. Finally, we show that strong applied electric fields result in anisotropically enhanced "giant" velocity fluctuations and reduced fluctuations of salt concentration.
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Fluctuation-enhanced electric conductivity in electrolyte solutions
Péraud, Jean-Philippe; Nonaka, Andrew J.; Bell, John B.; Donev, Aleksandar; Garcia, Alejandro L.
2017-01-01
We analyze the effects of an externally applied electric field on thermal fluctuations for a binary electrolyte fluid. We show that the fluctuating Poisson–Nernst–Planck (PNP) equations for charged multispecies diffusion coupled with the fluctuating fluid momentum equation result in enhanced charge transport via a mechanism distinct from the well-known enhancement of mass transport that accompanies giant fluctuations. Although the mass and charge transport occurs by advection by thermal velocity fluctuations, it can macroscopically be represented as electrodiffusion with renormalized electric conductivity and a nonzero cation–anion diffusion coefficient. Specifically, we predict a nonzero cation–anion Maxwell–Stefan coefficient proportional to the square root of the salt concentration, a prediction that agrees quantitatively with experimental measurements. The renormalized or effective macroscopic equations are different from the starting PNP equations, which contain no cross-diffusion terms, even for rather dilute binary electrolytes. At the same time, for infinitely dilute solutions the renormalized electric conductivity and renormalized diffusion coefficients are consistent and the classical PNP equations with renormalized coefficients are recovered, demonstrating the self-consistency of the fluctuating hydrodynamics equations. Our calculations show that the fluctuating hydrodynamics approach recovers the electrophoretic and relaxation corrections obtained by Debye–Huckel–Onsager theory, while elucidating the physical origins of these corrections and generalizing straightforwardly to more complex multispecies electrolytes. Finally, we show that strong applied electric fields result in anisotropically enhanced “giant” velocity fluctuations and reduced fluctuations of salt concentration. PMID:28973890
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Anion exchange membrane crosslinked in the easiest way stands out for fuel cells
NASA Astrophysics Data System (ADS)
Hossain, Md. Masem; Wu, Liang; Liang, Xian; Yang, Zhengjin; Hou, Jianqiu; Xu, Tongwen
2018-06-01
Covalent crosslinking is an effective method to stabilize anion exchange membranes (AEMs) against water swelling and high alkaline environment, yet complicated process is required. We report herein a straightforward approach to prepare highly crosslinked, transparent and flexible AEM by simply immersing a halo-alkylated polymer (e.g., brominated poly-(2,6-dimethyl-phenylene oxide)) based membrane in aqueous dimethylamine solution at room temperature and the following methylation. During this crosslinking process, a robust self-crosslinking network is formed which shows a gel fraction in N-methyl-2-pyrrolidone of (up to) 94%. Self-crosslinked membranes show low water uptakes (20-42%) and dimensional swelling (9-16%) compared to non-crosslinked membrane but good hydroxide conductivities (up to 26 mS cm-1) at room temperature. Besides, the resulting membranes show some interesting features: the membranes do not immensely change its room temperature water swelling properties at high temperature but exhibits good hydroxide conductivities (up to 60 mS cm-1 at 80 °C). Noting that, the self-crosslinked AEM reported here has no β-hydrogens, exhibiting extremely high alkaline stability (no decline in hydroxide conductivity in 1 M KOH at 60 °C for 360h). Membrane electrode assembly consists of fabricated membrane shows moderate fuel cell performance reaching peak power density 31 mW cm-2 at 60 °C in a H2/O2 alkaline fuel cell.
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NASA Astrophysics Data System (ADS)
Borodin, Oleg
2010-03-01
Molecular dynamics simulations are well suited for exploring electrolyte structure and ion transport mechanisms on the nanometer length scale and the nanosecond time scales. In this presentation we will describe how MD simulations assist in answering fundamental questions about the lithium transport mechanisms in polymeric electrolytes and ionic liquids. In particular, in the first part of the presentation the extent of ion aggregation, the structure of ion aggregates and the lithium cation diffusion in binary polymeric electrolytes will be compared with that of single-ion conducting polymers. In the second part of the talk, the lithium transport in polymeric electrolytes will be compared with that of three ionic liquids ( [emim][FSI] doped with LiFSI , [pyr13][FSI] doped with LiFSI, [emim][BF4] doped with LiBF4). The relation between ionic liquid self-diffusion, conductivity and thermodynamic properties will be discussed in details. A number of correlations between heat of vaporization Hvap, cation-anion binding energy (E+/-), molar volume (Vm), self-diffusion coefficient (D) and ionic conductivity for 29 ionic liquids have been investigated using MD simulations. A significant correlation between D and Hvap has been found, while best correlation was found for -log((D Vm)) vs. Hvap+0.28E+/-. A combination of enthalpy of vaporization and a fraction of the cation-anion binding energy was suggested as a measure of the effective cohesive energy for ionic liquids.
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Vera-Jimenez, N I; Pietretti, D; Wiegertjes, G F; Nielsen, M E
2013-05-01
The respiratory burst is an important feature of the immune system. The increase in cellular oxygen uptake that marks the initiation of the respiratory burst is followed by the production of reactive oxygen species (ROS) such as superoxide anion and hydrogen peroxide which plays a role in the clearance of pathogens and tissue regeneration processes. Therefore, the respiratory burst and associated ROS constitute important indicators of fish health status. This paper compares two methods for quantitation of ROS produced during the respiratory burst in common carp: the widely used, single-point measurement based on the intracellular reduction of nitroblue tetrazolium (NBT) and a real-time luminol-enhanced assay based on the detection of native chemiluminescence. Both assays allowed for detection of dose-dependent changes in magnitude of the respiratory burst response induced by β-glucans in head kidney cells of carp. However, whereas the NBT assay was shown to detect the production of only superoxide anions, the real-time luminol-enhanced assay could detect the production of both superoxide anions and hydrogen peroxide. Only the chemiluminescence assay could reliably record the production of ROS on a real-time scale at frequent and continual time intervals for time course experiments, providing more detailed information on the respiratory burst response. The real-time chemiluminescence assay was used to measure respiratory burst activity in macrophage and neutrophilic granulocyte-enriched head kidney cell fractions and total head kidney cell suspensions and proved to be a fast, reliable, automated multiwell microplate assay to quantitate fish health status modulated by β-glucans. Copyright © 2013 Elsevier Ltd. All rights reserved.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Maldonado, R.; Kevan, L.; Szajdzinska-Pietek, E.
1984-11-01
The electron spin echo modulation (ESEM) and electron spin resonance (ESR) spectra of the cation radical of N,N,N',N'-tetramethylbenzidine (TMB) in frozen sodium dodecyl sulfate (SDS)= and dodecyltrimethylammonium chloride (DTAC) micelles were studied as a function of sodium chloride concentration. TMB/sup +center-dot/ was produced by photoionization at 350 nm of the parent compound in the micelles at 77 K. From the ESEM analysis it is found that the cation--water interactions increase with salt addition in both anionic and cationic micelles to a maximum near 0.2 M NaCl and then decrease somewhat. The increase is interpreted in terms of an increase inmore » the water density at the micellar surface due to an increased surface concentration of hydrated counterions. The decrease may be due to TMB moving further from the polar micellar surface with added salt. From ESR spectra the photoionization yields of TMB at 77 K were determined. For DTAC micelles the yields are found to decrease with salt addition as expected from electrostatic considerations. For SDS micelles the photoionization yields increase for salt concentrations up to about 0.15 M and decrease for greater salt concentrations up to 0.5 M. The initial increase in cation yield correlates with electrostatic expectations. The decrease may be due to TMB moving further from the polar micellar surface with added salt. The possible effect of differing TMB protonation equilibria between anionic and cationic micelles on the photoionization yields was found to be unimportant by adjusting the bulk solution pH. An important conclusion is that salt addition can be used to optimize charge separation for photoionized solutes in anionic micelles.« less
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Flavonoids Are Inhibitors of Human Organic Anion Transporter 1 (OAT1)–Mediated Transport
An, Guohua; Wang, Xiaodong
2014-01-01
Organic anion transporter 1 (OAT1) has been reported to be involved in the nephrotoxicity of many anionic xenobiotics. As current clinically used OAT1 inhibitors are often associated with safety issues, identifying potent OAT1 inhibitors with little toxicity is of great value in reducing OAT1-mediated drug nephrotoxicity. Flavonoids are a class of polyphenolic compounds with exceptional safety records. Our objective was to evaluate the effects of 18 naturally occurring flavonoids, and some of their glycosides, on the uptake of para-aminohippuric acid (PAH) in both OAT1-expressing and OAT1-negative LLC-PK1 cells. Most flavonoid aglycones produced substantial decreases in PAH uptake in OAT1-expressing cells. Among the flavonoids screened, fisetin, luteolin, morin, and quercetin exhibited the strongest effect and produced complete inhibition of OAT1-mediated PAH uptake at a concentration of 50 μM. Further concentration-dependent studies revealed that both morin and luteolin are potent OAT1 inhibitors, with IC50 values of <0.3 and 0.47 μM, respectively. In contrast to the tested flavonoid aglycones, all flavonoid glycosides had negligible or small effects on OAT1. In addition, the role of OAT1 in the uptake of fisetin, luteolin, morin, and quercetin was investigated and fisetin was found to be a substrate of OAT1. Taken together, our results indicate that flavonoids are a novel class of OAT1 modulators. Considering the high consumption of flavonoids in the diet and in herbal products, OAT1-mediated flavonoid-drug interactions may be clinically relevant. Further investigation is warranted to evaluate the nephroprotective role of flavonoids in relation to drug-induced nephrotoxicity mediated by the OAT1 pathway. PMID:25002746
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Fuel Cell System Contaminants Material Screening Data: Text Version |
explore the results of fuel cell system contaminants studies. Total Anions [IC] and Total Concentration of Elements [ICP] in Leachate Solutions Material Class Manufacturer Trade Name and Use Grade ICP Total (ppm ) IC Total (ppm) Total Organic Carbon (ppm) Solution Conductivity (µS/cm) Adhesives LORD 2-part
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Raman and Brillouin scattering of LiClO4 complexed in poly(propylene-glycol)
NASA Astrophysics Data System (ADS)
Schantz, S.; Torell, L. M.; Stevens, J. R.
1988-08-01
Raman spectra of LiClO4 complexed in poly(propylene-glycol) (PPG) have been obtained for concentrations of the monomer to salt ratio (ether oxygen):Li in the range 30:1-5:1. Splitting of the symmetric stretching mode of the ClO4- anion was observed with an intensity profile that varied with salt concentration. This phenomenon indicates a changing environment about the anion. A two-component band analysis leads to the identification of dissociated ions on one hand and solvent-separated ion pairs on the other. The concentration of ion pairs is relatively low compared to that of the dissociated ions, which are predominant for all concentrations. Despite the observed increase in the absolute number of dissociated ions at higher salt concentration, the electrical conductivity is reported to decrease in the same range. This indicates that the number of ``free'' charge carriers is of less importance for the conductivity than the mobility, which is damped in this concentration range. Frequency shifts of the disordered longitudinal-acoustic mode and increased hypersonic velocities, measured with Raman and Brillouin scattering techniques, respectively, indicate increased stiffness of the polymer matrix for increasing salt concentration, which probably results in decreased ion mobility.
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CNT/conductive polymer composites for low-voltage driven EAP actuators
NASA Astrophysics Data System (ADS)
Sugino, Takushi; Shibata, Yoshiyuki; Kiyohara, Kenji; Asaka, Kinji
2012-04-01
We investigated the effects of additives incorporated into the electrode layer in order to improve the actuation performance of dry-type carbon nanotube (CNT) actuators. Especially, the addition of conductive nano-particles such as polyaniline (PANI) and polypyrrole (PPy) improves actuation performance very much rather than the addition of nonconductive nano-particles such as mesoprous silica (MCM-41 type). In this paper, we studied on the influences of applied voltage, species of ionic liquid (IL), amounts of IL, thickness of actuator to optimize actuation performance. Imidazolium type ionic liquids with three different anions, that is, 1-ethyl-3-methylimidazolium (EMI) as a cation and tetrafluoroborate (BF4), trifluoromethanesulfonate (OTf), and bis(trifluoromethanesulfonyl)imide (TFSI) as anions were chosen in this study. EMIBF4 is the most suitable IL for our CNT actuator including PANI in the electrode layer. We tuned the amount of IL and the thickness of actuator. As a result, the strain was improved to be 2.2% at 0.1 Hz by applying the voltage of 2.5 V. This improved value is almost 2 times larger than our previous results. We also show the potential of improved CNT actuators for a thin and light Braille display.
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Origin of negative resistance in anion migration controlled resistive memory
NASA Astrophysics Data System (ADS)
Banerjee, Writam; Wu, Facai; Hu, Yuan; Wu, Quantan; Wu, Zuheng; Liu, Qi; Liu, Ming
2018-03-01
Resistive random access memory (RRAM) is one of the most promising emerging nonvolatile technologies for the futuristic memory devices. Resistive switching behavior often shows negative resistance (NR), either voltage controlled or current controlled. In this work, the origin of a current compliance dependent voltage controlled NR effect during the resetting of anion migration based RRAM devices is discussed. The N-type voltage controlled NR is a high field driven phenomena. The current conduction within the range of a certain negative voltage is mostly dominated by space charge limited current. But with the higher negative voltage, a field induced tunneling effect is generated in the NR region. The voltage controlled NR is strongly dependent on the compliance current. The area independent behavior indicates the filamentary switching. The peak to valley ratio (PVR) is > 5. The variation of PVR as a function of the conduction band offset is achieved. Compared to other reported works, based on the PVR, it is possible to distinguish the RRAM types. Generally, due to the higher electric field effect on the metallic bridge during RESET, the electrochemical metallization type RRAM shows much higher PVR than the valance change type RRAM.
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Biophysical characterization of OprB, a glucose-inducible porin of Pseudomonas aeruginosa.
Wylie, J L; Bernegger-Egli, C; O'Neil, J D; Worobec, E A
1993-10-01
OprB, a glucose-inducible porin of P. aeruginosa, was characterized by black lipid bilayer analysis and circular dichroism spectroscopy. Black lipid bilayer analysis of OprB revealed a single-channel conductance of 25 pS, the presence of a glucose binding site with a Ks for glucose of 380 +/- 40 mM, and the formation of channels with a strong selection for anions. Analysis of P. aeruginosa OprB circular dichroism spectra revealed a high beta sheet content (40%) which is within the range of that determined for other porins. Values obtained from black lipid bilayer analysis were compared to those previously obtained for OprB of P. putida [Saravolac et al. (1991). J. Bacteriol. 173, 4970-4976] and indicated extensive similarities in the single-channel conductance and glucose-binding properties of these two porins. Immunological and amino terminal sequence analysis revealed a high degree of homology. Of the first 14 amino terminal residues, 12 were identical. A major difference between the two porins was found in their ion selectivity. Whereas P. aeruginosa OprB is anion selective, P. putida OprB and other carbohydrate selective porins are known to be cation selective.
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Highly conductive side chain block copolymer anion exchange membranes.
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.
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Dielectric response and transport properties of alkylammonium formate ionic liquids
NASA Astrophysics Data System (ADS)
Nazet, Andreas; Buchner, Richard
2018-05-01
Dielectric relaxation spectra of three members of the alkylammonium formate family of protic ionic liquids (PILs), namely, ethylammonium formate (EAF), n-butylammonium formate (BuAF), and n-pentylammonium formate (PeAF), as well as the pseudo-PIL triethylamine + formic acid (molar ratio 1:2; TEAF) have been studied over a wide frequency (50 MHz to 89 GHz) and temperature range (5-65 °C), complemented by measurements of their density, viscosity, and conductivity. It turned out that the dominating relaxation of EAF, BuAF, and PeAF arises from both cation and anion reorientations which are synchronized in their dynamics due to hydrogen bonding. Amplitudes and relaxation times of this mode reflect the—compared to nitrate—different nature of H bonding between the formate anion and ethylammonium cation, as well as increasing segregation of the PIL structure into polar and non-polar domains. The TEAF data suggest that its dominating relaxation is due to the rotation of the complex triethylamineṡ(formic acid)2 in which no significant proton transfer to an ion pair occurred. Weak dissociation of this complex into ions was postulated to account for the high conductivity of TEAF.
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Segmented saddle-shaped passive stabilization conductors for toroidal plasmas
Leuer, J.A.
1990-05-01
A large toroidal vacuum chamber for plasma generation and confinement is lined with a toroidal blanket for shielding using modules segmented in the toroidal direction. To provide passive stabilization in the same manner as a conductive vacuum chamber wall, saddle-shaped conductor loops are provided on blanket modules centered on a midplane of the toroidal chamber with horizontal conductive bars above and below the midplane, and vertical conductive legs on opposite sides of each module to provide return current paths between the upper and lower horizontal conductive bars. The close proximity of the vertical legs provided on adjacent modules without making physical contact cancel the electromagnetic field of adjacent vertical legs. The conductive bars spaced equally above and below the midplane simulate toroidal conductive loops or hoops that are continuous, for vertical stabilization of the plasma even though they are actually segmented. 5 figs.
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Sub-micrometer epsilon-near-zero electroabsorption modulators enabled by high-mobility cadmium oxide
DOE Office of Scientific and Technical Information (OSTI.GOV)
Campione, Salvatore; Wood, Michael; Serkland, Darwin K.
Here, epsilon-near-zero materials provide a new path for tailoring light-matter interactions at the nanoscale. In this paper, we analyze a compact electroabsorption modulator based on epsilon-near-zero confinement in transparent conducting oxide films. The non-resonant modulator operates through field-effect carrier density tuning. We compare the performance of modulators composed of two different conducting oxides, namely indium oxide (In2O3) and cadmium oxide (CdO), and show that better modulation performance is achieved when using high-mobility (i.e. low-loss) epsilon-near-zero materials such as CdO. In particular, we show that non-resonant electroabsorption modulators with sub-micron lengths and greater than 5 dB extinction ratios may be achievedmore » through the proper selection of high-mobility transparent conducting oxides, opening a path for device miniaturization and increased modulation depth.« less
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Sub-micrometer epsilon-near-zero electroabsorption modulators enabled by high-mobility cadmium oxide
Campione, Salvatore; Wood, Michael; Serkland, Darwin K.; ...
2017-07-06
Here, epsilon-near-zero materials provide a new path for tailoring light-matter interactions at the nanoscale. In this paper, we analyze a compact electroabsorption modulator based on epsilon-near-zero confinement in transparent conducting oxide films. The non-resonant modulator operates through field-effect carrier density tuning. We compare the performance of modulators composed of two different conducting oxides, namely indium oxide (In2O3) and cadmium oxide (CdO), and show that better modulation performance is achieved when using high-mobility (i.e. low-loss) epsilon-near-zero materials such as CdO. In particular, we show that non-resonant electroabsorption modulators with sub-micron lengths and greater than 5 dB extinction ratios may be achievedmore » through the proper selection of high-mobility transparent conducting oxides, opening a path for device miniaturization and increased modulation depth.« less
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Failure of the Cystic Fibrosis Transmembrane Conductance Regulator to Conduct ATP
NASA Astrophysics Data System (ADS)
Reddy, M. M.; Quinton, P. M.; Haws, C.; Wine, J. J.; Grygorczyk, R.; Tabcharani, J. A.; Hanrahan, J. W.; Gunderson, K. L.; Kopito, R. R.
1996-03-01
The cystic fibrosis transmembrane conductance regulator (CFTR) is chloride ion channel regulated by protein kinase A and adenosine triphosphate (ATP). Loss of CFTR-mediated chloride ion conductance from the apical plasma membrane of epithelial cells is a primary physiological lesion in cystic fibrosis. CFTR has also been suggested to function as an ATP channel, although the size of the ATP anion is much larger than the estimated size of the CFTR pore. ATP was not conducted through CFTR in intact organs, polarized human lung cell lines, stably transfected mammalian cell lines, or planar lipid bilayers reconstituted with CFTR protein. These findings suggest that ATP permeation through the CFTR is unlikely to contribute to the normal function of CFTR or to the pathogenesis of cystic fibrosis.
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Growth of electronically distinct manganite thin films by modulating cation stoichiometry
DOE Office of Scientific and Technical Information (OSTI.GOV)
Ryu, Sangkyun; Lee, Joonhyuk; Ahn, Eunyoung
Nd 1-xSr xMnO 3 (NSMO) is a well-known manganite due to close connection between structure, transport, magnetism, and chemistry. Thus, it would be an ideal system to study modification of physical properties by external stimuli including control of stoichiometry in growth. In this work, we show that abrupt change of electronic and magnetic properties can be achieved by subtle change of oxygen partial pressure in pulsed laser deposition. Interestingly, the pressure indeed modulates cation stoichiometry. We clearly observed that the films grown at 150 mTorr and higher showed clear insulator to metal transition and stronger magnetism, commonly found in lessmore » hole doping, while the films grown at 130 mTorr and lower showed insulating behavior and weak magnetism. From soft x-ray spectroscopic methods, we clearly observed the compositional difference in those thin films. This result is further supported by scattering of lighter elements in high oxygen partial pressure but not by anion deficiency in growth.« less
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Growth of electronically distinct manganite thin films by modulating cation stoichiometry
Ryu, Sangkyun; Lee, Joonhyuk; Ahn, Eunyoung; ...
2017-06-26
Nd 1-xSr xMnO 3 (NSMO) is a well-known manganite due to close connection between structure, transport, magnetism, and chemistry. Thus, it would be an ideal system to study modification of physical properties by external stimuli including control of stoichiometry in growth. In this work, we show that abrupt change of electronic and magnetic properties can be achieved by subtle change of oxygen partial pressure in pulsed laser deposition. Interestingly, the pressure indeed modulates cation stoichiometry. We clearly observed that the films grown at 150 mTorr and higher showed clear insulator to metal transition and stronger magnetism, commonly found in lessmore » hole doping, while the films grown at 130 mTorr and lower showed insulating behavior and weak magnetism. From soft x-ray spectroscopic methods, we clearly observed the compositional difference in those thin films. This result is further supported by scattering of lighter elements in high oxygen partial pressure but not by anion deficiency in growth.« less