Journal articles on the topic 'Synthetic ionic channels'
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Negi, Sangeeta, Awadhesh Prasad, and Amita Chandra. "Chaotic Behavior of Ionic Transportation Through Synthetic Ion Channels." International Journal of Bifurcation and Chaos 29, no. 08 (July 2019): 1950107. http://dx.doi.org/10.1142/s0218127419501074.
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Selective ion transportation through synthetic ion channels in polymeric membranes (which mimic natural systems, e.g. excitable cell membranes) is being reported through this article. The synthetic ion channels have been created by swift heavy ion irradiation of polymeric membranes followed by chemical etching. Since, the transportation of sodium and potassium ions of aqueous electrolytes through synthetic ion channels in polyethylene terephthalate depends on the electrophoretic forces present in the electrolyte; these ion channels are referred to as “voltage activated channels”. For a particular range of applied voltage, these channels behave as K-channels while they act as Na-channels in another voltage range. The channels have been found to switch between high and low conduction states referred to as opening and closing of ion channels with applied potential. A mechanism is being proposed to explain the voltage dependent ion selectivity of the channels in both closed and open states. Nonlinear dynamical analysis of ion transportation and current oscillations confirm its chaotic behavior. Their possible applications as ionic switches and ionic flip-flops are discussed.
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Chui, Jonathan K. W., and Thomas M. Fyles. "Ionic conductance of synthetic channels: analysis, lessons, and recommendations." Chem. Soc. Rev. 41, no. 1 (2012): 148–75. http://dx.doi.org/10.1039/c1cs15099e.
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Murrell-Lagnado, R. D., and R. W. Aldrich. "Energetics of Shaker K channels block by inactivation peptides." Journal of General Physiology 102, no. 6 (December 1, 1993): 977–1003. http://dx.doi.org/10.1085/jgp.102.6.977.
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A synthetic peptide of the NH2-terminal inactivation domain of the ShB channel blocks Shaker channels which have an NH2-terminal deletion and mimics many of the characteristics of the intramolecular inactivation reaction. To investigate the role of electrostatic interactions in both peptide block and the inactivation process we measured the kinetics of block of macroscopic currents recorded from the intact ShB channel, and from ShB delta 6-46 channels in the presence of peptides, at different ionic strengths. The rate of inactivation and the association rate constants (k(on)) for the ShB peptides decreased with increasing ionic strength. k(on) for a more positively charged peptide was more steeply dependent on ionic strength consistent with a simple electrostatic mechanism of enhanced diffusion. This suggests that a rate limiting step in the inactivation process is the diffusion of the NH2-terminal domain towards the pore. The dissociation rates (k(off)) were insensitive to ionic strength. The temperature dependence of k(on) for the ShB peptide was very high, (Q10 = 5.0 +/- 0.58), whereas k(off) was relatively temperature insensitive (Q10 approximately 1.1). The results suggest that at higher temperatures the proportion of time either the peptide or channel spends in the correct conformation for binding is increased. There were two components to the time course of recovery from block by the ShB peptide, indicating two distinct blocked states, one of which has similar kinetics and dependence on external K+ concentration as the inactivated state of ShB. The other is voltage-dependent and at -120 mV is very unstable. Increasing the net charge on the peptide did not increase sensitivity to knock-off by external K+. We propose that the free peptide, having fewer constraints than the tethered NH2-terminal domain binds to a similar site on the channel in at least two different conformations.
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Chui, Jonathan K. W., and Thomas M. Fyles. "ChemInform Abstract: Ionic Conductance of Synthetic Channels: Analysis, Lessons, and Recommendations." ChemInform 43, no. 13 (March 1, 2012): no. http://dx.doi.org/10.1002/chin.201213258.
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You, Yi, Abdulghani Ismail, Gwang-Hyeon Nam, Solleti Goutham, Ashok Keerthi, and Boya Radha. "Angstrofluidics: Walking to the Limit." Annual Review of Materials Research 52, no. 1 (July 1, 2022): 189–218. http://dx.doi.org/10.1146/annurev-matsci-081320-032747.
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Angstrom-scale fluidic channels are ubiquitous in nature and play an important role in regulating cellular traffic, signaling, and responding to stimuli. Synthetic angstrom channels are now a reality with the emergence of several cutting-edge bottom-up and top-down fabrication methods. In particular, the use of atomically thin 2D materials and nanotubes as components to build fluidic conduits has pushed the limits of fabrication to the angstrom scale. Here, we provide an overview of recent developments in the fabrication methods for nano- and angstrofluidic channels while categorizing them on the basis of dimensionality (0D pores, 1D tubes, 2D slits), along with the latest advances in measurement techniques. We discuss the ion transport governed by various stimuli in these channels and the variation of ionic mobility, streaming power, and osmotic power with pore size across all the dimensionalities. Finally, we highlight unique future opportunities in the development of smart ionic devices.
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Leibowitz, M. D., J. R. Schwarz, G. Holan, and B. Hille. "Electrophysiological comparison of insecticide and alkaloid agonists of Na channels." Journal of General Physiology 90, no. 1 (July 1, 1987): 75–93. http://dx.doi.org/10.1085/jgp.90.1.75.
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Macroscopic currents in Na channels were recorded from adult frog skeletal muscle under voltage clamp as various toxins were added to the bathing medium. Veratridine, cevadine, and 3-(4-ethoxybenzoyl)-veracevine modified the Na channels in a use-dependent manner during depolarizations and held them open for 3, 2.4, and 1.2 s, respectively, at -90 mV. The three alkaloids modified channels in the same way. Activation gating was shifted about -100 mV by the modification, and reversible closing of the channels by strong hyperpolarizations slowed reversal of the modification. The synthetic insecticides deltamethrin, EDO, GH739, and GH414 also modified channels during depolarizations that opened channels. The modification lasted 3 s with deltamethrin, but only 3-5 ms with the others. Hyperpolarization speeded the shutting off of current in insecticide-modified channels, but no reversible activation gating could be demonstrated. The ionic selectivity, PNa/PNH4, of channels was decreased by all of the toxins. This ratio was 0.11 in normal channels, 0.26 in insecticide-modified channels, and 0.7-1.6 in veratrum-alkaloid-modified channels. During use-dependent modification, the veratrum alkaloids reduced the total Na current markedly, while deltamethrin did not. Thus, alkaloid and insecticide modifications share many features but differ in how much the conducting properties of the pore are changed and whether the channel can close reversibly while the toxin remains bound.
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Brutyan, R. A., and P. McPhie. "On the one-sided action of amphotericin B on lipid bilayer membranes." Journal of General Physiology 107, no. 1 (January 1, 1996): 69–78. http://dx.doi.org/10.1085/jgp.107.1.69.
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The one-sided action of the polyene antibiotic, amphotericin B, on phospholipid bilayer membranes formed from synthetic phosphatidylcholines (DOPC and DPhPC) and sterols (ergosterol and cholesterol), has been investigated. We found formation of well-defined ionic channels for both sterols and not only for ergosterol-containing membranes (Bolard, J., P. Legrand, F. Heitz, and B. Cybulska. 1991. Biochemistry. 30:5707-5715). Characteristics of these channels were studied in the presence of different salts. It was found that the channels have comparable conductances but different lifetimes that are approximately 100-fold less in cholesterol-containing membranes than in ergosterol-containing ones. Channel blocking by tetraethylammonium (TEA) ions shows that TEA blockage of channels in the presence of cholesterol increases their lifetimes in analogy to the lengthening of lifetimes of protein channels blocked by local anesthetics (Neher, E., and J. H. Steinbach. 1978. J. Physiol. 277: 153-176). However, the effect of the blocker on single-channel conductance is very close for both sterols. The data support the classical model of amphotericin B pore formation from complexes initially lying on the membrane surface as nonconducting prepores. We explain the antibiotic's cytotoxic selectivity by differences in the lifetimes of the channels formed with different sterols and suggest that phosphatidylcholine-sterol membranes can be used as a tool for rapid estimation of polyene antibiotic cytotoxicity.
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Montal, M., M. S. Montal, and J. M. Tomich. "Synporins--synthetic proteins that emulate the pore structure of biological ionic channels." Proceedings of the National Academy of Sciences 87, no. 18 (September 1990): 6929–33. http://dx.doi.org/10.1073/pnas.87.18.6929.
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Morzy, Diana, Michael Schaich, and Ulrich F. Keyser. "A Surfactant Enables Efficient Membrane Spanning by Non-Aggregating DNA-Based Ion Channels." Molecules 27, no. 2 (January 17, 2022): 578. http://dx.doi.org/10.3390/molecules27020578.
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DNA nanotechnology makes use of hydrophobically modified constructs to create synthetic membrane protein mimics. However, nucleic acid structures exhibit poor insertion efficiency, leading to a low activity of membrane-spanning DNA protein mimics. It is suggested that non-ionic surfactants improve insertion efficiency, partly by disrupting hydrophobicity-mediated clusters. Here, we employed confocal microscopy and single-molecule transmembrane current measurements to assess the effects of the non-ionic surfactant octylpolyoxyethylene (oPOE) on the clustering behavior and membrane activity of cholesterol-modified DNA nanostructures. Our findings uncover the role of aggregation in preventing bilayer interactions of hydrophobically decorated constructs, and we highlight that premixing DNA structures with the surfactant does not disrupt the cholesterol-mediated aggregates. However, we observed the surfactant’s strong insertion-facilitating effect, particularly when introduced to the sample separately from DNA. Critically, we report a highly efficient membrane-spanning DNA construct from combining a non-aggregating design with the addition of the oPOE surfactant.
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Fertig, Dávid, Eszter Mádai, Mónika Valiskó, and Dezső Boda. "Simulating Ion Transport with the NP+LEMC Method. Applications to Ion Channels and Nanopores." Hungarian Journal of Industry and Chemistry 45, no. 1 (October 1, 2017): 73–84. http://dx.doi.org/10.1515/hjic-2017-0011.
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Abstract We describe a hybrid simulation technique that uses the Nernst-Planck (NP) transport equation to compute steady-state ionic flux in a non-equilibrium system and uses the Local Equilibrium Monte Carlo (LEMC) simulation technique to establish the statistical mechanical relation between the two crucial functions present in the NP equation: the concentration and the electrochemical potential profiles (Boda, D., Gillespie, D., J. Chem. Theor. Comput., 2012 8(3), 824–829). The LEMC method is an adaptation of the Grand Canonical Monte Carlo method to a non-equilibrium situation. We apply the resulting NP+LEMC method to ionic systems, where two reservoirs of electrolytes are separated by a membrane that allows the diffusion of ions through a nanopore. The nanopore can be natural (as the calcium selective Ryanodine Receptor ion channel) or synthetic (as a rectifying bipolar nanopore). We show results for these two systems and demonstrate the effectiveness of the NP+LEMC technique.
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Boda, Dezső, Mónika Valiskó, and Dirk Gillespie. "Modeling the Device Behavior of Biological and Synthetic Nanopores with Reduced Models." Entropy 22, no. 11 (November 5, 2020): 1259. http://dx.doi.org/10.3390/e22111259.
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Biological ion channels and synthetic nanopores are responsible for passive transport of ions through a membrane between two compartments. Modeling these ionic currents is especially amenable to reduced models because the device functions of these pores, the relation of input parameters (e.g., applied voltage, bath concentrations) and output parameters (e.g., current, rectification, selectivity), are well defined. Reduced models focus on the physics that produces the device functions (i.e., the physics of how inputs become outputs) rather than the atomic/molecular-scale physics inside the pore. Here, we propose four rules of thumb for constructing good reduced models of ion channels and nanopores. They are about (1) the importance of the axial concentration profiles, (2) the importance of the pore charges, (3) choosing the right explicit degrees of freedom, and (4) creating the proper response functions. We provide examples for how each rule of thumb helps in creating a reduced model of device behavior.
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Evans, W. Howard, Elke De Vuyst, and Luc Leybaert. "The gap junction cellular internet: connexin hemichannels enter the signalling limelight." Biochemical Journal 397, no. 1 (June 14, 2006): 1–14. http://dx.doi.org/10.1042/bj20060175.
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Cxs (connexins), the protein subunits forming gap junction intercellular communication channels, are transported to the plasma membrane after oligomerizing into hexameric assemblies called connexin hemichannels (CxHcs) or connexons, which dock head-to-head with partner hexameric channels positioned on neighbouring cells. The double membrane channel or gap junction generated directly couples the cytoplasms of interacting cells and underpins the integration and co-ordination of cellular metabolism, signalling and functions, such as secretion or contraction in cell assemblies. In contrast, CxHcs prior to forming gap junctions provide a pathway for the release from cells of ATP, glutamate, NAD+ and prostaglandin E2, which act as paracrine messengers. ATP activates purinergic receptors on neighbouring cells and forms the basis of intercellular Ca2+ signal propagation, complementing that occuring more directly via gap junctions. CxHcs open in response to various types of external changes, including mechanical, shear, ionic and ischaemic stress. In addition, CxHcs are influenced by intracellular signals, such as membrane potential, phosphorylation and redox status, which translate external stresses to CxHc responses. Also, recent studies demonstrate that cytoplasmic Ca2+ changes in the physiological range act to trigger CxHc opening, indicating their involvement under normal non-pathological conditions. CxHcs not only respond to cytoplasmic Ca2+, but also determine cytoplasmic Ca2+, as they are large conductance channels, suggesting a prominent role in cellular Ca2+ homoeostasis and signalling. The functions of gap-junction channels and CxHcs have been difficult to separate, but synthetic peptides that mimic short sequences in the Cx subunit are emerging as promising tools to determine the role of CxHcs in physiology and pathology.
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Oiki, S., W. Danho, and M. Montal. "Channel protein engineering: synthetic 22-mer peptide from the primary structure of the voltage-sensitive sodium channel forms ionic channels in lipid bilayers." Proceedings of the National Academy of Sciences 85, no. 7 (April 1, 1988): 2393–97. http://dx.doi.org/10.1073/pnas.85.7.2393.
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LAPIED, BRUNO, CLAIRE O. MALÉCOT, and MARCEL PELHATE. "Ionic Species Involved in the Electrical Activity of Single Adult Aminergic Neurones Isolated from the Sixth Abdominal Ganglion of the Cockroach Periplaneta Americana." Journal of Experimental Biology 144, no. 1 (July 1, 1989): 535–49. http://dx.doi.org/10.1242/jeb.144.1.535.
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Adult neurones were obtained by dissociation of the dorsal area of the sixth abdominal (A6) ganglion of the cockroach, and electrical properties were studied with the patch-clamp technique. The neurones showed spontaneous fast action potentials, similar to those recorded with microelectrodes in neurones in situ along the dorsal median line of the A6 ganglion. Synthetic saxitoxin (sSTX) at concentrations of 10 × 10−8 to 1.0×10−7mol l−1 suppressed the action potential (AP) and induced a dose-dependent hyperpolarization of the resting potential, suggesting that two types of sSTX-sensitive Na+ channels are present. The resting potential was dependent on the external concentration of both Na+ and K+, with a similar sensitivity to each, yielding a slope of about 43 mV per 10-fold change in concentration. The delayed outward rectification present under control conditions was reduced by tetraethylammonium chloride (TEA-Cl, 1.0×10−2mol l−1). TEA-Cl or Ca2+-free saline abolished the afterhyperpolarization and increased the overshoot and duration of triggered APs, indicating that a calcium-activated potassium conductance contributes to the falling phase of the AP. At 3.0×10−3mol l−1, the Ca2+ channel blockers MnCl2, CoCl2 and NiCl2 lengthened the AP. A blocker-dependent increase in the overshoot and threshold of the AP and reduction of the afterhyperpolarization were observed, probably reflecting the relative potencies of these ions in blocking Ca2+ channels and thus the Ca2+- activated K+ conductance. Increasing MgCl2 concentration by 3.0 × 10−3mol l−1 had no effect on the AP, indicating that the positive shift of the threshold is due to the blockade of Ca2+ channels present at this potential. The results suggest that these isolated neurones are dorsal unpaired median neurones previously studied in a number of insect species.
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Kim, Sung Huhn, Kyunghee X. Kim, Nithya N. Raveendran, Tao Wu, Satyanarayana R. Pondugula, and Daniel C. Marcus. "Regulation of ENaC-mediated sodium transport by glucocorticoids in Reissner's membrane epithelium." American Journal of Physiology-Cell Physiology 296, no. 3 (March 2009): C544—C557. http://dx.doi.org/10.1152/ajpcell.00338.2008.
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Reissner's membrane epithelium forms much of the barrier that produces and sustains the large ionic differences between cochlear endolymph and perilymph. We have reported that Reissner's membrane contributes to normal cochlear function by absorbing Na+ from endolymph via amiloride-sensitive channels in gerbil inner ear. We used mouse Reissner's membrane to 1) identify candidate genes involved in the Na+ transport pathway, 2) determine whether their level of expression was regulated by the synthetic glucocorticoid dexamethasone, and 3) obtain functional evidence for the physiological importance of these genes. Transcripts were present for α-, β-, and γ-subunits of epithelial Na+ channel (ENaC); corticosteroid receptors GR (glucocorticoid receptor) and MR (mineralocorticoid receptor); GR agonist regulator 11β-hydroxysteroid dehydrogenase (HSD) type 1 (11β-HSD1); Na+ transport control components SGK1, Nedd4-2, and WNKs; and K+ channels and Na+-K+-ATPase. Expression of the MR agonist regulator 11β-HSD2 was not detected. Dexamethasone upregulated transcripts for α- and β-subunits of ENaC (∼6- and ∼3-fold), KCNK1 (∼3-fold), 11β-HSD1 (∼2-fold), SGK1 (∼2-fold), and WNK4 (∼3-fold). Transepithelial currents from the apical to the basolateral side of Reissner's membrane were sensitive to amiloride (IC50 ∼0.7 μM) and benzamil (IC50 ∼0.1 μM), but not EIPA (IC50 ∼34 μM); amiloride-blocked transepithelial current was not immediately changed by forskolin/IBMX. Currents were reduced by ouabain, lowered bath Na+ concentration (from 150 to 120 mM), and K+ channel blockers (XE-991, Ba2+, and acidification from pH 7.4 to 6.5). Dexamethasone-stimulated current and gene expression were reduced by mifepristone, but not spironolactone. These molecular, pharmacological, and functional observations are consistent with Na+ absorption by mouse Reissner's membrane, which is mediated by apical ENaC and/or other amiloride-sensitive channels, basolateral Na+-K+-ATPase, and K+-permeable channels and is under the control of glucocorticoids. These results provide an understanding and a molecular definition of an important transport function of Reissner's membrane epithelium in the homeostasis of cochlear endolymph.
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Messersmith, Phillip B., and Samuel I. Stupp. "Synthesis of nanocomposites: Organoceramics." Journal of Materials Research 7, no. 9 (September 1992): 2599–611. http://dx.doi.org/10.1557/jmr.1992.2599.
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We report here on the synthesis of new materials termed organoceramics in which polymers are molecularly dispersed within inorganic crystalline phases. These nanocomposite materials may not only have unique morphologies and physical properties but may also lead to new processing methods for ceramic-based materials. In organoceramics polymer molecules could opportunistically occupy sites such as grain boundaries or other two-dimensional defects, nanopores, lattice channels, or interlamellar spaces. Our synthetic approach to get macromolecules to those sites is to nucleate and grow inorganic crystals from homogeneous solutions containing the polymer chains as co-solutes. The new materials discussed in this manuscript were synthesized by growing calcium aluminate crystals in the presence of water soluble polymers and were characterized by x-ray diffraction, scanning electron microscopy, elemental analysis, and diffuse reflectance infrared spectroscopy. The macromolecules used in organoceramic synthesis included poly(vinyl alcohol), poly(dimethyldiallyl ammonium chloride), and poly(dibutyl ammonium iodide). We found that the chemistry of polymer repeats can impact on the spatial distribution of the dispersed organic chains and also on the morphology of organoceramic powders. In the case of the poly(vinyl alcohol) organoceramic the polymer is intercalated in “flattened” conformations in Ca2Al(OH)6[X] ·nH2O, thus increasing the distance between ionic layers from 7.9 Å to ∊ 18 Å (X is a monovalent or divalent anion). Such a layered nanocomposite can be formed only by intercalating the poly(vinyl alcohol) during growth of the Ca2Al(OH)6[X] · nH2O crystal. The synthetic pathway is therefore able to overcome large entropic barriers and incorporate significant amounts of polymer in the organoceramic product, in some cases up to 38% by weight. The particles of this nanocomposite are spheroidal aggregates of thin plate crystals whereas the use of a polycationic polymer in the synthesis leads to rod-like particles in which organic chains may reside in channels of the inorganic crystal.
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Woerly, S., C. Lavallée, and R. Marchand. "Intracerebral Implantation of Ionic Synthetic Hydrogels: Effect of Polar Substrata on Astrocytosis and Axons." Journal of Neural Transplantation and Plasticity 3, no. 1 (1992): 21–34. http://dx.doi.org/10.1155/np.1992.21.
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In previous studies, hyperporous synthetic hydrogels of poly(glyceryl methacrylate) or p(GMA), containing bioadhesive substrates of collagen, were implanted into rat cerebral tissue in order to provide systems of oriented guidance channels for directing the growth of the scar and axons /28/. In the present study, ionic p(GMA)- collagen hydrogels containing polar chemical groups, either basic amino groups or acidic carboxyl groups, were evaluated for their tolerance and their effects on the brain scarring response and axonal reactivity after long-term implantation in the cerebral cortex. In all animals, the implants were well tolerated. Although both types of gels influenced the astroglial reaction near the bioimplant, hydrogels carrying carboxyl groups had the strongest influence on the elongation, the direction and the organization of astrocytic processes so that a glial matrix could form in regions of the gel. Extracellular material (e.g. reticulin) was also deposited into the gels carrying carboxyl groups. Although cortical nerve fibers .in the surrounding tissue showed a regenerative response, extending onto or into the matrices, this behavior seemed to depend more on the organization of the .astrocytic scar imposed by the gel than on the type of gel. We conclude that matrices carrying negatively charged groups influence favorably the astrocytosis and the deposition of connective tissue, and that this approach represents a new avenue in attempting to modulate the brain scar formation.
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Khosravi, Monireh, Vinuthaa Murthy, and Ian D R Mackinnon. "The Exchange Mechanism of Alkaline and Alkaline-Earth Ions in Zeolite N." Molecules 24, no. 20 (October 10, 2019): 3652. http://dx.doi.org/10.3390/molecules24203652.
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Zeolite N is a synthetic zeolite of the EDI framework family from the more than 200 known zeolite types. Previous experimental laboratory and field data show that zeolite N has a high capacity for exchange of ions. Computational modelling and simulation techniques are effective tools that help explain the atomic-scale behaviour of zeolites under different processing conditions and allow comparison with experiment. In this study, the ion exchange behaviour of synthetic zeolite N in an aqueous environment is investigated by molecular dynamics simulations. The exchange mechanism of K+ extra-framework cations with alkaline and alkaline-earth cations NH4+, Li+, Na+, Rb+, Cs+, Mg2+ and Ca2+ is explored in different crystallographic directions inside the zeolite N structure. Moreover, the effect of different framework partial charges on MD simulation results obtained from different DFT calculations are examined. The results show that the diffusion and exchange of cations in zeolite N are affected by shape and size of channels controlling the ion exchange flow as well as the nature of cation, ionic size and charge density.
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Morel, Jean-Luc, Nathalie Mokrzycki, Guy Lippens, Hervé Drobecq, Pierre Sautière, and Michel Hugues. "Characterization of a Family of Scorpion Toxins Modulating Ca2+-Activated Cl− Current in Vascular Myocytes." Toxins 14, no. 11 (November 10, 2022): 780. http://dx.doi.org/10.3390/toxins14110780.
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The pharmacology of calcium-activated chloride current is not well developed. Peptides from scorpion venom present potent pharmacological actions on ionic conductance used to characterize the function of channels but can also be helpful to develop organic pharmacological tools. Using electrophysiological recording coupled with calcium measurement, we tested the potent effect of peptides extracted from Leuirus quinquestratus quinquestratus venom on the calcium-activated chloride current expressed in smooth muscle cells freshly dissociated from rat portal veins. We identified one peptide which selectively inhibited the chloride conductance without effects on either calcium signaling or calcium and potassium currents expressed in this cell type. The synthetic peptide had the same affinity, but the chemical modification of the amino acid sequence altered the efficiency to inhibit the calcium-activated chloride conductance.
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Grove, Anne, Manfred Mutter, Jean E. Rivier, and Mauricio Montal. "Template-assembled synthetic proteins designed to adopt a globular, four-helix bundle conformation form ionic channels in lipid bilayers." Journal of the American Chemical Society 115, no. 14 (July 1993): 5919–24. http://dx.doi.org/10.1021/ja00067a004.
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Irokawa, Toshiya, Tsukasa Sasaki, Sanae Shimura, Kan Sasamori, Takako Oshiro, Masayuki Nara, Tsutomu Tamada, and Kunio Shirato. "Cholinomimetic action of macrolide antibiotics on airway gland electrolyte secretion." American Journal of Physiology-Lung Cellular and Molecular Physiology 276, no. 6 (June 1, 1999): L951—L957. http://dx.doi.org/10.1152/ajplung.1999.276.6.l951.
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We investigated the acute effects of erythromycin (EM) and its derivatives on ionic currents in airway glands from feline tracheae. Therapeutic concentrations of EM or clarithromycin (CAM) attenuated the whole cell currents evoked by ACh in a competitive manner. The maximally stimulated inward Cl−currents were reduced to 54 and 83% and the outward K+currents to 55 and 84% of control values by EM and CAM, respectively, whereas the responses induced by phenylephrine, norepinephrine, caffeine, or ionomycin were unaffected by EM, CAM, or EM523, a synthetic derivative of EM. K+channels in excised outside-out patches were not influenced by macrolides. Although therapeutic concentrations of macrolides showed no effect on the baseline currents, high concentrations of macrolides alone evoked currents mimicking the ACh response, which were abolished completely by atropine. We concluded that macrolides act as a partial agonist on cholinergic receptors, resulting in a reduction of Cl−secretion at pharmacological doses of the agents, which may exhibit a pronounced effectiveness on hypertrophied and/or cholinergically sensitized submucosal glands in pathological airways.
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Wu, Po-Ming, Hsin-Yen Cho, Chi-Wu Chiang, Tzu-Hsien Chuang, Sheng-Nan Wu, and Yi-Fang Tu. "Characterization in Inhibitory Effectiveness of Carbamazepine in Voltage-Gated Na+ and Erg-Mediated K+ Currents in a Mouse Neural Crest-Derived (Neuro-2a) Cell Line." International Journal of Molecular Sciences 23, no. 14 (July 17, 2022): 7892. http://dx.doi.org/10.3390/ijms23147892.
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Carbamazepine (CBZ, Tegretol®) is an anticonvulsant used in the treatment of epilepsy and neuropathic pain; however, several unwanted effects of this drug have been noticed. Therefore, the regulatory actions of CBZ on ionic currents in electrically excitable cells need to be reappraised, although its efficacy in suppressing voltage-gated Na+ current (INa) has been disclosed. This study was undertaken to explore the modifications produced by CBZ on ionic currents (e.g., INa and erg-mediated K+ current [IK(erg)]) measured from Neuro-2a (N2a) cells. In these cells, we found that this drug differentially suppressed the peak (transient, INa(T)) and sustained (late, INa(L)) components of INa in a concentration-dependent manner with effective IC50 of 56 and 18 μM, respectively. The overall current–voltage relationship of INa(T) with or without the addition of CBZ remained unchanged; however, the strength (i.e., ∆area) in the window component of INa (INa(W)) evoked by the short ascending ramp pulse (Vramp) was overly lessened in the CBZ presence. Tefluthrin (Tef), a synthetic pyrethroid, known to stimulate INa, augmented the strength of the voltage-dependent hysteresis (Hys(V)) of persistent INa (INa(P)) in response to the isosceles-triangular Vramp; moreover, further application of CBZ attenuated Tef-mediated accentuation of INa(P)’s Hys(V). With a two-step voltage protocol, the recovery of INa(T) inactivation seen in Neuro-2a cells became progressively slowed by adding CBZ; however, the cumulative inhibition of INa(T) evoked by pulse train stimulation was enhanced during exposure to this drug. Neuro-2a-cell exposure to CBZ (100 μM), the magnitude of erg-mediated K+ current measured throughout the entire voltage-clamp steps applied was mildly inhibited. The docking results regarding the interaction of CBZ and voltage-gate Na+ (NaV) channel predicted the ability of CBZ to bind to some amino-acid residues in NaV due to the existence of a hydrogen bond or hydrophobic contact. It is conceivable from the current investigations that the INa (INa(T), INa(L), INa(W), and INa(P)) residing in Neuro-2a cells are susceptible to being suppressed by CBZ, and that its block on INa(L) is larger than that on INa(T). Collectively, the magnitude and gating of NaV channels produced by the CBZ presence might have an impact on its anticonvulsant and analgesic effects occurring in vivo.
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Tait, Kimberly T., Frank C. Hawthorne, and Norman M. Halden. "Alluaudite-Group Phosphate and Arsenate Minerals." Canadian Mineralogist 59, no. 1 (January 1, 2021): 243–63. http://dx.doi.org/10.3749/canmin.2000057.
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ABSTRACT A systematic study of alluaudite, hagendorfite, and varulite was done using single-crystal X-ray diffraction, powder diffraction, and electron probe microanalysis of samples from 12 separate localities. The crystal structures of the representative alluaudite and hagendorfite samples were refined to R1 indices of 3.7 and 1.8%, respectively, using a Siemens P4 automated four-circle diffractometer equipped with a graphite monochromator and MoKα X-radiation. These samples and several others were analyzed with an electron microprobe to study variations in chemical composition. For the single-crystal analyses, the resulting unit formulae are (Na0.11□0.89)(Na0.59Mn0.27Ca0.14)Mn1.00(Fe3+1.64Al0.24Mg0.13)(PO4)3 for alluaudite, (Na0.79□0.21)(Na0.81Mn2+0.19)(Mn0.70Fe2+0.30)(Fe2+1.72Mg0.27Al0.01)(PO4)3 for hagendorfite, and (Na0.84□0.16)(Na0.71Ca0.23□0.06)Mn1.00(Fe3+0.89Fe2+0.68Mn0.42Mg0.01)(PO4)3 for varulite. Originally, a nomenclature scheme was proposed for the alluaudite-group minerals that was based on sequentially distributing the cations in the cell according to increasing polyhedron size, matching that size with increasing ionic radii of the cations. For alluaudite, the structural formula was written as X(2)4X(1)4M(1)4M(2)8(PO4)12, with the sites ordered in decreasing size of the discrete polyhedra. Later, the formula [A(2)A(2)'A(2)”2][A(1)A(1)'A(1)”2]M(1)M(2)2(PO4)3 was proposed, which takes into account the distinct crystallographic sites in the channels of the structure. More recently there has been a revision to the nomenclature of the group. The simplified structural formula for the alluaudite-type is now A(2)'A(1)M(1)M(2)2(TO4)3; the new nomenclature scheme has been adopted by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA-CNMNC), based on the contents of the M(1) and M(2) octahedral sites, and the results are reviewed here. Compounds belonging to the alluaudite structural family have been the focus of synthetic mineral studies for decades owing to the open-framework architecture and their unique physical properties. Improvements in synthesis methods have allowed researchers to substitute a wide range of elements into the alluaudite structure.
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Cibelli, Antonio, Eliana Scemes, and David C. Spray. "Activity and Stability of Panx1 Channels in Astrocytes and Neuroblastoma Cells Are Enhanced by Cholesterol Depletion." Cells 11, no. 20 (October 14, 2022): 3219. http://dx.doi.org/10.3390/cells11203219.
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Pannexin1 (Panx1) is expressed in both neurons and glia where it forms ATP-permeable channels that are activated under pathological conditions such as epilepsy, migraine, inflammation, and ischemia. Membrane lipid composition affects proper distribution and function of receptors and ion channels, and defects in cholesterol metabolism are associated with neurological diseases. In order to understand the impact of membrane cholesterol on the distribution and function of Panx1 in neural cells, we used fluorescence recovery after photobleaching (FRAP) to evaluate its mobility and electrophysiology and dye uptake to assess channel function. We observed that cholesterol extraction (using methyl-β-cyclodextrin) and inhibition of its synthesis (lovastatin) decreased the lateral diffusion of Panx1 in the plasma membrane. Panx1 channel activity (dye uptake, ATP release and ionic current) was enhanced in cholesterol-depleted Panx1 transfected cells and in wild-type astrocytes compared to non-depleted or Panx1 null cells. Manipulation of cholesterol levels may, therefore, offer a novel strategy by which Panx1 channel activation might modulate various pathological conditions.
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Partiseti, M., H. Korn, and D. Choquet. "Pattern of potassium channel expression in proliferating B lymphocytes depends upon the mode of activation." Journal of Immunology 151, no. 5 (September 1, 1993): 2462–70. http://dx.doi.org/10.4049/jimmunol.151.5.2462.
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Abstract Ionic channel expression is highly regulated during mitogenesis. But it is not clear whether these regulations only follow intrinsic programs during the course of the cell cycle or if they also depend upon the external factors used to promote cell activation. B lymphocytes express two classes of potassium channels and can be stimulated to enter the cell cycle by distinct pathways. Thus, we have analyzed, with the patch-clamp technique, if the expression of channels varies when the cells are activated by different signals that lead to cell proliferation. We found that stimulation through Ag receptors increases the expression of calcium- and voltage-activated potassium channels, whereas a bacterial mitogen, LPS, only enhances the expression of the latter. Moreover, channel expression can still be modified in proliferating cells because stimulation of LPS-activated cells through Ag receptors induces rapid expression of calcium-activated channels. The use of inhibitors of mRNA synthesis revealed that this process depends upon gene transcription. Thus, differential induction of the expression of potassium channels is not only linked to the entry into the cell cycle but depends also on pathways of stimulation.
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Dong, Bin, Liangying Wang, Shang Zhao, Rile Ge, Xuedan Song, Yu Wang, and Yanan Gao. "Immobilization of ionic liquids to covalent organic frameworks for catalyzing the formylation of amines with CO2 and phenylsilane." Chemical Communications 52, no. 44 (2016): 7082–85. http://dx.doi.org/10.1039/c6cc03058k.
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Storey, Nina, David Latchman, and Stuart Bevan. "Selective internalization of sodium channels in rat dorsal root ganglion neurons infected with herpes simplex virus-1." Journal of Cell Biology 158, no. 7 (September 23, 2002): 1251–62. http://dx.doi.org/10.1083/jcb.200204010.
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The neurotropic virus, herpes simplex type 1 (HSV-1), inhibits the excitability of peripheral mammalian neurons, but the molecular mechanism of this effect has not been identified. Here, we use voltage-clamp measurement of ionic currents and an antibody against sodium channels to show that loss of excitability results from the selective, precipitous, and complete internalization of voltage-activated sodium channel proteins from the plasma membrane of neurons dissociated from rat dorsal root ganglion. The internalization process requires viral protein synthesis but not viral encapsulation, and does not alter the density of voltage-activated calcium or potassium channels. However, internalization is blocked completely when viruses lack the neurovirulence factor, infected cell protein 34.5, or when endocytosis is inhibited with bafilomycin A1 or chloroquine. Although it has been recognized for many years that viruses cause cell pathology by interfering with signal transduction pathways, this is the first example of viral pathology resulting from selective internalization of an integral membrane protein. In studying the HSV-induced redistribution of sodium channels, we have uncovered a previously unknown pathway for the rapid and dynamic control of excitability in sensory neurons by internalization of sodium channels.
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Cui, Xili, Qiwei Yang, Yijun Xiong, Zongbi Bao, Huabin Xing, and Sheng Dai. "Preparation of ordered N-doped mesoporous carbon materials via a polymer–ionic liquid assembly." Chemical Communications 53, no. 36 (2017): 4915–18. http://dx.doi.org/10.1039/c7cc01000a.
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A facile and efficient method for the synthesis of carbon materials with uniform channels and a high-nitrogen-content coating layer was successfully developed through a polymer–ionic liquid assembly strategy.
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Deenadayalu, Viju, Yashoda Puttabyatappa, Alexander T. Liu, John N. Stallone, and Richard E. White. "Testosterone-induced relaxation of coronary arteries: activation of BKCa channels via the cGMP-dependent protein kinase." American Journal of Physiology-Heart and Circulatory Physiology 302, no. 1 (January 2012): H115—H123. http://dx.doi.org/10.1152/ajpheart.00046.2011.
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Androgens are reported to have both beneficial and detrimental effects on human cardiovascular health. The aim of this study was to characterize nongenomic signaling mechanisms in coronary artery smooth muscle (CASM) and define the ionic basis of testosterone (TES) action. TES-induced relaxation of endothelium-denuded porcine coronary arteries was nearly abolished by 20 nM iberiotoxin, a highly specific inhibitor of large-conductance, calcium-activated potassium (BKCa) channels. Molecular patch-clamp studies confirmed that nanomolar concentrations of TES stimulated BKCa channel activity by ∼100-fold and that inhibition of nitric oxide synthase (NOS) activity by NG-monomethyl-l-arginine nearly abolished this effect. Inhibition of nitric oxide (NO) synthesis or guanylyl cyclase activity also attenuated TES-induced coronary artery relaxation but did not alter relaxation due to 8-bromo-cGMP. Furthermore, we detected TES-stimulated NO production in porcine coronary arteries and in human CASM cells via stimulation of the type 1 neuronal NOS isoform. Inhibition of the cGMP-dependent protein kinase (PKG) attenuated TES-stimulated BKCa channel activity, and direct assay determined that TES increased activity of PKG in a concentration-dependent fashion. Last, the stimulatory effect of TES on BKCa channel activity was mimicked by addition of purified PKG to the cytoplasmic surface of a cell-free membrane patch from CASM myocytes (∼100-fold increase). These findings indicate that TES-induced relaxation of endothelium-denuded coronary arteries is mediated, at least in part, by enhanced NO production, leading to cGMP synthesis and PKG activation, which, in turn, opens BKCa channels. These findings provide a molecular mechanism that could help explain why androgens have been reported to relax coronary arteries and relieve angina pectoris.
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Fu, Xiaoqin, Xiaoli Sheng, Yuming Zhou, Zhiwei Fu, Shuo Zhao, Zewu Zhang, and Yiwei Zhang. "One-step synthesis of hierarchical aluminosilicates using alkoxy-functionalized ionic liquid as a novel template." New Journal of Chemistry 40, no. 7 (2016): 6036–45. http://dx.doi.org/10.1039/c5nj02927a.
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Chen, D., J. Lear, and B. Eisenberg. "Permeation through an open channel: Poisson-Nernst-Planck theory of a synthetic ionic channel." Biophysical Journal 72, no. 1 (January 1997): 97–116. http://dx.doi.org/10.1016/s0006-3495(97)78650-8.
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Xing, Yan, Xiaopeng Chen, Yujia Huang, Xiali Zhen, Lujun Wei, Xiqiang Zhong, and Wei Pan. "Facile Synthesis of Two-Dimensional Natural Vermiculite Films for High-Performance Solid-State Electrolytes." Materials 16, no. 2 (January 11, 2023): 729. http://dx.doi.org/10.3390/ma16020729.
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Ceramic electrolytes hold application prospects in all-solid-state lithium batteries (ASSLB). However, the ionic conductivity of ceramic electrolytes is limited by their large thickness and intrinsic resistance. To cope with this challenge, a two-dimensional (2D) vermiculite film has been successfully prepared by self-assembling expanded vermiculite nanosheets. The raw vermiculite mineral is first exfoliated to thin sheets of several atomic layers with about 1.2 nm interlayer channels by a thermal expansion and ionic exchanging treatment. Then, through vacuum filtration, the ion-exchanged expanded vermiculite (IEVMT) sheets can be assembled into thin films with a controllable thickness. Benefiting from the thin thickness and naturally lamellar framework, the as-prepared IEVMT thin film exhibits excellent ionic conductivity of 0.310 S·cm−1 at 600 °C with low excitation energy. In addition, the IEVMT thin film demonstrates good mechanical and thermal stability with a low coefficient of friction of 0.51 and a low thermal conductivity of 3.9 × 10−3 W·m−1·K−1. This reveals that reducing the thickness and utilizing the framework is effective in increasing the ionic conductivity and provides a promising stable and low-cost candidate for high-performance solid electrolytes.
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Zhang, J., Y. J. Wang, and S. Z. Hu. "Synthesis of Ionic Liquid [BMIM]Br in Micro-Channel Reactor." Asian Journal of Chemistry 26, no. 8 (2014): 2369–72. http://dx.doi.org/10.14233/ajchem.2014.16005.
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Rotem, Dvir, Amy Mason, and Hagan Bayley. "Inactivation of the KcsA potassium channel explored with heterotetramers." Journal of General Physiology 135, no. 1 (December 28, 2009): 29–42. http://dx.doi.org/10.1085/jgp.200910305.
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The tetrameric prokaryotic potassium channel KcsA is activated by protons acting on the intracellular aspect of the protein and inactivated through conformational changes in the selectivity filter. Inactivation is modulated by a network of interactions within each protomer between the pore helix and residues at the external entrance of the channel. Inactivation is suppressed by the E71A mutation, which perturbs the stability of this network. Here, cell-free protein synthesis followed by protein purification by sodium dodecyl sulfate–polyacrylamide gel electrophoresis was used to produce heterotetramers of KcsA that contain different combinations of wild-type and E71A subunits. Single-channel recordings from these heterotetramers reveal how the network of interactions in individual protomers affects ionic conduction and channel inactivation, suggesting that the latter is a cooperative process.
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Xu, Hang, Tianlong Yu, and Mei Li. "Zinc Acetate Immobilized on Mesoporous Materials by Acetate Ionic Liquids as Catalysts for Vinyl Acetate Synthesis." Journal of Chemistry 2015 (2015): 1–5. http://dx.doi.org/10.1155/2015/238287.
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Ionic liquid containing active ingredient Zn(CH3COO)2was loaded in mesoporous silica gel to form supported ionic liquids catalyst (SILC) which was used to synthesize vinyl acetate monomer (VAM). SILC was characterized by1HNMR, FT-IR, TGA, BET, and N2adsorption/desorption and the acetylene method was used to evaluate SILC catalytic activity and stability in fixed reactor. The result shows that 1-allyl-3-acetic ether imidazole acetate ionic liquid is successfully fixed within mesoporous channel of silica gel. The average thickness of ionic liquid catalyst layer is about 1.05 nm. When the catalytic temperature is 195°C, the acetic acid (HAc) conversion is 10.9% with 1.1 g vinyl acetate yield and 98% vinyl acetate (VAc) selectivity. The HAc conversion is increased by rise of catalytic temperature and molar ratio of C2H2 : HAc and decreased by mass space velocity (WHSV). The catalyst activity is not significantly reduced within 7 days and VAc selectivity has a slight decrease.
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Moolenaar, W. H., L. H. Defize, and S. W. De Laat. "Ionic signalling by growth factor receptors." Journal of Experimental Biology 124, no. 1 (September 1, 1986): 359–73. http://dx.doi.org/10.1242/jeb.124.1.359.
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The proliferation of cells in vivo and in culture is regulated by polypeptide growth factors, such as epidermal growth factor (EGF) and platelet-derived growth factor (PDGF). Growth factors initiate their action by binding to specific cell surface receptors. Receptor occupancy triggers a cascade of physiological changes in the target cell which ultimately lead to DNA synthesis and cell division. Immediate consequences of receptor activation include tyrosine-specific protein phosphorylations, a sustained increase in cytoplasmic pH (pHi) and a transient rise in free Ca2+. The rise in pHi has a permissive effect on DNA synthesis and is mediated by an otherwise quiescent Na+/H+ exchange mechanism in the plasma membrane, which is turned on by protein kinase C, the cellular receptor for phorbol esters. The rapid Ca2+ signal is due to either release from internal stores (PDGF) or net entry via a voltage-independent channel in the plasma membrane (EGF). Phorbol esters, acting via kinase C, inhibit the growth factor-induced Ca2+ signals without affecting resting Ca2+ levels. Monoclonal antibodies against the human EGF receptor can act as partial agonists in that they activate the tyrosine-specific protein kinase without inducing any of the ionic signals. These antibodies fail to induce DNA synthesis when added to quiescent fibroblasts, indicating that the Ca2+ and pHi signals can be dissociated from tyrosine kinase activity and suggesting that these signals are indispensable for the stimulation of cell proliferation.
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Brent, L. H., J. L. Butler, W. T. Woods, and J. K. Bubien. "Transmembrane ion conductance in human B lymphocyte activation." Journal of Immunology 145, no. 8 (October 15, 1990): 2381–89. http://dx.doi.org/10.4049/jimmunol.145.8.2381.
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Abstract Human B lymphocytes were examined to determine whether transmembrane ion conductance plays a role in cell activation. Mitogens (anti-human IgM F(ab')2 fragment (anti-mu) and PMA) were used to stimulate B lymphocytes. Mitogen-induced DNA synthesis was inhibited by tetraethylammonium-Cl (TEA), 4-aminopyridine (4AP), verapamil, and diltiazem in a dose-dependent manner. This inhibition was not due to reduction in cell viability as determined by trypan blue exclusion. Mitogen-induced increases in RNA synthesis were partially inhibited by TEA and 4AP and were more completely inhibited by verapamil and diltiazem. Mitogen-induced cell volume increases were not affected by TEA or 4AP but were completely inhibited by verapamil and diltiazem. B lymphocytes stimulated with anti-mu expressed G1 phase cell surface antigens in the presence of TEA or 4AP, but failed to do so in the presence of verapamil or diltiazem. Substitution of PMA for anti-mu as the mitogen did not alter the effects of TEA or 4AP. However, verapamil inhibited PMA-induced expression of G1 phase cell surface markers although diltiazem did not. The patch clamp technique was used to directly examine plasma membrane ionic currents in whole-cell, cell-attached, and inside-out patch configurations. Activation of B lymphocytes with either anti-mu or the Ca2+ ionophore, A23187, inhibited opening of one type of channel in cell-attached patches. In inside-out patches, this channel type conducted current when the bath [Ca2+] was low (6 X 10(-8) M) but failed to conduct current when the bath [Ca2+] was increased above 1 X 10(-6) M. The results of these experiments are consistent with the hypothesis that activation of B lymphocytes induces alterations in plasma membrane ion conductance. Single channel studies suggest that activation induced increases in [Ca2+]i may directly inhibit a specific set of plasma membrane ion channels as one mechanism by which transmembrane ion flux is altered.
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Guo, Ya Jie, Yu Ran Wang, Guang Jian Wang, Zhen Xing Yang, and Wen Wen Ji. "Morphological Control Synthesis and Characterization of Hydroxyapatite with Star-Shaped." Advanced Materials Research 152-153 (October 2010): 1603–6. http://dx.doi.org/10.4028/www.scientific.net/amr.152-153.1603.
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The aim of the present work was to study the feasibility of wet synthesizing hydroxyapatite (HAP) with star-like and high specific surface area. HAP was synthesized by one-step self-assembly process in ionic liquid media under microwave irradiation, and treated at 300, 600, 900 , respectively. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analysis revealed that HAP was pure crystal phase. Nitrogen adsorption and desorption isotherms (NADI) with a characteristic hysteresis loop further confirmed the existence of uniform micropores or channels of HAP. The BET surface area, pore volume, and pore size distribution were calculated to be 324m2g-1, 0.39cm3g-1, and 3.28 nm, respectively. Scanning electron microscopy (SEM) results indicated that the HAP was of star-shaped morphology. The formation of HAP could be explained by functional ionic liquid as structure-directing template. Well-ordered mesostructure of HAP with star-like might be therefore used as a potential biomaterial for preparation of bone implant materials.
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Tixier, Eliott, Damiano Lombardi, Blanca Rodriguez, and Jean-Frédéric Gerbeau. "Modelling variability in cardiac electrophysiology: a moment-matching approach." Journal of The Royal Society Interface 14, no. 133 (August 2017): 20170238. http://dx.doi.org/10.1098/rsif.2017.0238.
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The variability observed in action potential (AP) cardiomyocyte measurements is the consequence of many different sources of randomness. Often ignored, this variability may be studied to gain insight into the cell ionic properties. In this paper, we focus on the study of ionic channel conductances and describe a methodology to estimate their probability density function (PDF) from AP recordings. The method relies on the matching of observable statistical moments and on the maximum entropy principle. We present four case studies using synthetic and sets of experimental AP measurements from human and canine cardiomyocytes. In each case, the proposed methodology is applied to infer the PDF of key conductances from the exhibited variability. The estimated PDFs are discussed and, when possible, compared to the true distributions. We conclude that it is possible to extract relevant information from the variability in AP measurements and discuss the limitations and possible implications of the proposed approach.
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Yang, Xuzhao, Yarong Bai, Qing Li, and Jun Wang. "Preparation and Adsorption Properties of MCM-41 with Novel Gemini Ionic Liquid Surfactants as Template." Materials 15, no. 8 (April 10, 2022): 2780. http://dx.doi.org/10.3390/ma15082780.
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A mesoporous molecular sieve was prepared by the hydrothermal synthesis method with symmetric Gemini surfactant 1,3-bis(hexadecyldimethylammonio)-propane dibromide, symmetric Gemini ionic liquid surfactant 1,3-bis(3-hexadecylimidazolium-1-yl) propane dibromide and self-designed asymmetric Gemini ionic liquid surfactant 1-(3-(hexadecyldimethylammonio)prop-1-yl)-3-hexadecylimidazolium dibromide as the template agent. The structure characterization results for mesoporous molecular sieves show that the material possesses a hexagonal pore structure with uniform channels. The mesoporous silica that was synthesized with self-designed asymmetric Gemini ionic liquid surfactant as the template agent possesses the largest surface area and its pore size and specific surface area are, respectively, 3.28 nm and 879.37 m2/g. The adsorption properties of the prepared MCM-41 for crystal violet were investigated, and the adsorption thermodynamics and kinetics were investigated. The results show that adsorption equilibrium can be reached under pH = 9 and 35 °C for 50 min, and the quantity of adsorption can reach up to 464.21 mg/g. The adsorption process belongs to Langmuir isothermal adsorption, conforming to second-order adsorption kinetics, and the adsorption process is an endothermic process.
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Smith, Stephen S., Erich D. Steinle, Mark E. Meyerhoff, and David C. Dawson. "Cystic Fibrosis Transmembrane Conductance Regulator." Journal of General Physiology 114, no. 6 (November 29, 1999): 799–818. http://dx.doi.org/10.1085/jgp.114.6.799.
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The cystic fibrosis transmembrane conductance regulator (CFTR) Cl channel exhibits lyotropic anion selectivity. Anions that are more readily dehydrated than Cl exhibit permeability ratios (PS/PCl) greater than unity and also bind more tightly in the channel. We compared the selectivity of CFTR to that of a synthetic anion-selective membrane [poly(vinyl chloride)–tridodecylmethylammonium chloride; PVC-TDMAC] for which the nature of the physical process that governs the anion-selective response is more readily apparent. The permeability and binding selectivity patterns of CFTR differed only by a multiplicative constant from that of the PVC-TDMAC membrane; and a continuum electrostatic model suggested that both patterns could be understood in terms of the differences in the relative stabilization of anions by water and the polarizable interior of the channel or synthetic membrane. The calculated energies of anion–channel interaction, derived from measurements of either permeability or binding, varied as a linear function of inverse ionic radius (1/r), as expected from a Born-type model of ion charging in a medium characterized by an effective dielectric constant of 19. The model predicts that large anions, like SCN, although they experience weaker interactions (relative to Cl) with water and also with the channel, are more permeant than Cl because anion–water energy is a steeper function of 1/r than is the anion–channel energy. These large anions also bind more tightly for the same reason: the reduced energy of hydration allows the net transfer energy (the well depth) to be more negative. This simple selectivity mechanism that governs permeability and binding acts to optimize the function of CFTR as a Cl filter. Anions that are smaller (more difficult to dehydrate) than Cl are energetically retarded from entering the channel, while the larger (more readily dehydrated) anions are retarded in their passage by “sticking” within the channel.
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RANJALAHY-RASOLOARIJAO, L., R. LAZARO, P. DAUMAS, and F. HEITZ. "Synthesis and ionic channels of a linear gramicidin containing naphthylalanine instead of tryptophan." International Journal of Peptide and Protein Research 33, no. 4 (January 12, 2009): 273–80. http://dx.doi.org/10.1111/j.1399-3011.1989.tb01282.x.
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Cai, Shixuan, Hongyan Shi, Guoqian Li, Qilu Xue, Lei Zhao, Fu Wang, and Bo Hu. "3D-Printed Concentration-Controlled Microfluidic Chip with Diffusion Mixing Pattern for the Synthesis of Alginate Drug Delivery Microgels." Nanomaterials 9, no. 10 (October 12, 2019): 1451. http://dx.doi.org/10.3390/nano9101451.
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Alginate as a good drug delivery vehicle has excellent biocompatibility and biodegradability. In the ionic gelation process between alginate and Ca2+, the violent reaction is the absence of a well-controlled strategy in the synthesizing calcium alginate (CaA) microgels. In this study, a concentration-controlled microfluidic chip with central buffer flow was designed and 3D-printed to well-control the synthesis process of CaA microgels by the diffusion mixing pattern. The diffusion mixing pattern in the microfluidic chip can slow down the ionic gelation process in the central stream. The particle size can be influenced by channel length and flow rate ratio, which can be regulated to 448 nm in length and 235 nm in diameter. The delivery ratio of Doxorubicin (Dox) in CaA microgels are up to 90% based on the central stream strategy. CaA@Dox microgels with pH-dependent release property significantly enhances the cell killing rate against human breast cancer cells (MCF-7). The diffusion mixing pattern gives rise to well-controlled synthesis of CaA microgels, serving as a continuous and controllable production process for advanced drug delivery systems.
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Zhang, Shao Feng, and Ji Wu Shang. "Characterization of Swept Synthetic High Quality Quartz Crystal." Key Engineering Materials 633 (November 2014): 326–29. http://dx.doi.org/10.4028/www.scientific.net/kem.633.326.
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The synthetic quartz crystal is widely utilized in electronic and optical components due to its high frequency and temperature stability, good dielectric properties, low thermal coefficient of linear expansion, and wide range of optical transparency. However, radiation effects due to cosmic rays are responsible for a frequency shift for quartz oscillators in space systems, which impair their performance. Sweeping quartz at high electric field is a well-established method for improving device performance in a radiation environment. The present paper focuses on the voltage current characteristic of swept quartz. First, the sweeping conduction mechanism is ionic conduction. Second, as the voltage increases, the current increases first, then decreases, and then increases. ICP-AES results indicated that the sweeping process make Na+ a oriented locomotion. Third, the etch channel tensity is obviously reduced to less than 3/cm3, which is a very promising result for space applications. Moreover, the radiation resistance properties are improved after electrical sweeping.
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Siddiqui, Kafeel Ahmad, Michael Bolte, and Gopal Krishna Mehrotra. "Triazole based cadmium(II) anionic framework with 2-dimensional helical channels: Ionic liquid induced synthesis." Inorganica Chimica Acta 363, no. 2 (January 2010): 457–63. http://dx.doi.org/10.1016/j.ica.2009.10.024.
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Martini, L., G. Giavaresi, M. Fini, P. Torricelli, V. Borsari, R. Giardino, M. De Pretto, D. Remondini, and G. C. Castellani. "Shock Wave Therapy as an Innovative Technology in Skeletal Disorders: Study on Transmembrane Current in Stimulated Osteoblast-Like Cells." International Journal of Artificial Organs 28, no. 8 (August 2005): 841–47. http://dx.doi.org/10.1177/039139880502800810.
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Extracorporeal shock wave treatment (ESWT) is successfully used in various musculoskeletal disorders and pathologies. Despite the increasing use of this kind of therapy, some aspects of its mechanism of action are still unclear. In vitro bone cell behavior under ESWT were previously investigated by the present author and MG63 osteoblast-like cells showed an enhancement in proliferation and in the osteoblast differentiation after therapy with a low-energy flux density. The aim of the present study was to evaluate the effect of ESWT on the permeabilization of cell membrane. We characterized physiological changes in the MG63 associated with ESWT generated by an ESW device and patch clamp recording was performed to study ion channels. Experiments were carried out using the whole-cell recording configuration of the patch-clamp technique and the ionic current measurements were performed on cell samples of ESW treated and control groups. The patch-clamp technique showed the effect of ESWT on the amplitude of transmembrane currents. The treatment with ESW enhanced the transmembrane current as well the voltage dependence of Ca-activated and K channels that mediate these currents: the differences between treated cells and control at 80mV were over 1000 pA (P<0.05). These modifications of ion channels activity positively influence cell proliferation (MTT test, P<0.0001) without interfering with the normal synthesis activity of stimulated osteoblasts.
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Hui, Wei, Lingfeng Chao, Hui Lu, Fei Xia, Qi Wei, Zhenhuang Su, Tingting Niu, et al. "Stabilizing black-phase formamidinium perovskite formation at room temperature and high humidity." Science 371, no. 6536 (March 25, 2021): 1359–64. http://dx.doi.org/10.1126/science.abf7652.
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The stabilization of black-phase formamidinium lead iodide (α-FAPbI3) perovskite under various environmental conditions is considered necessary for solar cells. However, challenges remain regarding the temperature sensitivity of α-FAPbI3 and the requirements for strict humidity control in its processing. Here we report the synthesis of stable α-FAPbI3, regardless of humidity and temperature, based on a vertically aligned lead iodide thin film grown from an ionic liquid, methylamine formate. The vertically grown structure has numerous nanometer-scale ion channels that facilitate the permeation of formamidinium iodide into the lead iodide thin films for fast and robust transformation to α-FAPbI3. A solar cell with a power-conversion efficiency of 24.1% was achieved. The unencapsulated cells retain 80 and 90% of their initial efficiencies for 500 hours at 85°C and continuous light stress, respectively.
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Liu, Zhantao, Alex Chien, Shuo Wang, Zihao Lin, Jue Liu, Yifei Mo, and Hailong Chen. "Insights into the Crystal Structure of Halide Solid Electrolytes and Li Diffusion." ECS Meeting Abstracts MA2022-02, no. 4 (October 9, 2022): 390. http://dx.doi.org/10.1149/ma2022-024390mtgabs.
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Lithium halides with general formula Li3MX6 (M = metals such as Y, In, Yb or Sc; X = Cl or Br) have attracted significant attention because of their promising room temperature conductivities and high oxidative stability[1]. Li-ion mobility in these halides is strongly affected by the synthesis method and parameters. In Li3YCl6 with a hexagonal-close-packed (hcp) anion framework, the ionic conductivity is commonly observed to decrease with increased crystallinity. While in Li3YBr6 with a face-centered-cubic (fcc) anion framework, the ionic conductivity increases with increased crystallinity. So far there is no clear explanation for such opposite trends in these two otherwise very similar crystal structures. Ab initio molecular dynamics (AIMD) simulation[2] suggested higher ionic conductivity and lower activation energy in Li3YCl6 than inLi3YBr6, which also does not agree well with the experimental observation that Li3YBr6 commonly shows higher conductivity than Li3YCl6. Above-mentioned unexplained observations and inconsistencies imply that likely some critical structural features of these halides that strongly impact ionic diffusion are not yet explored nor taken into consideration. Here, we report our recent findings in the crystal structure of Li3YCl6 and Li3YBr6 and the design, synthesis and electrochemical testing of a few new halide compounds designed based on the new findings. The crystal structures are investigated with using ex situ and in situ synchrotron X-ray diffraction (XRD) and neutron diffraction (ND). Our study[3] demonstrated that the discrepancies between simulated and experimental results in Li3YBr6-type structure is partly caused by the grain boundary. Through PDF data analysis, we provide experimental evidences of cation local ordering in ab plane and stacking fault along c-direction in Li3YBr6-type structure. The lower ionic conductivity in low crystallinity is owing to the blockage of Li diffusion channel along c-direction caused by the stacking fault. Moreover, a new tetrahedral Li-site is identified, which may be critical in understanding the Li diffusion behaviors. Via rationally tuning Li occupancies at the tetrahedral and octahedral sites, low Li diffusion barriers can be achieved, which is in consistence with theoretical calculation results. [1] T. Asano, A. Sakai, S. Ouchi, M. Sakaida, A. Miyazaki, S. Hasegawa, Advanced Materials 2018, 30, 1803075. [2] S. Wang, Q. Bai, A. M. Nolan, Y. Liu, S. Gong, Q. Sun, Y. Mo, Angewandte Chemie International Edition 2019, 58, 8039-8043. [3] Z. Liu, S. Ma, J. Liu, S. Xiong, Y. Ma, H. Chen, ACS Energy Letters 2021, 6, 298-304.
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Wang, Lulan, Aiping Wu, Yao E. Wang, Natalie Quanquin, Chunfeng Li, Jingfeng Wang, Hsiang-Wen Chen, et al. "Functional Genomics Reveals Linkers Critical for Influenza Virus Polymerase." Journal of Virology 90, no. 6 (December 30, 2015): 2938–47. http://dx.doi.org/10.1128/jvi.02400-15.
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ABSTRACTInfluenza virus mRNA synthesis by the RNA-dependent RNA polymerase involves binding and cleavage of capped cellular mRNA by the PB2 and PA subunits, respectively, and extension of viral mRNA by PB1. However, the mechanism for such a dynamic process is unclear. Using high-throughput mutagenesis and sequencing analysis, we have not only generated a comprehensive functional map for the microdomains of individual subunits but also have revealed the PA linker to be critical for polymerase activity. This PA linker binds to PB1 and also forms ionic interactions with the PA C-terminal channel. Nearly all mutants with five-amino-acid insertions in the linker were nonviable. Our model further suggests that the PA linker plays an important role in the conformational changes that occur between stages that favor capped mRNA binding and cleavage and those associated with viral mRNA synthesis.IMPORTANCEThe RNA-dependent RNA polymerase of influenza virus consists of the PB1, PB2, and PA subunits. By combining genome-wide mutagenesis analysis with the recently discovered crystal structure of the influenza polymerase heterotrimer, we generated a comprehensive functional map of the entire influenza polymerase complex. We identified the microdomains of individual subunits, including the catalytic domains, the interaction interfaces between subunits, and nine linkers interconnecting different domains. Interestingly, we found that mutants with five-amino-acid insertions in individual linkers were nonviable, suggesting the critical roles these linkers play in coordinating spatial relationships between the subunits. We further identified an extended PA linker that binds to PB1 and also forms ionic interactions with the PA C-terminal channel.
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Giovannitti, Alexander, Dan-Tiberiu Sbircea, Sahika Inal, Christian B. Nielsen, Enrico Bandiello, David A. Hanifi, Michele Sessolo, George G. Malliaras, Iain McCulloch, and Jonathan Rivnay. "Controlling the mode of operation of organic transistors through side-chain engineering." Proceedings of the National Academy of Sciences 113, no. 43 (October 10, 2016): 12017–22. http://dx.doi.org/10.1073/pnas.1608780113.
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Electrolyte-gated organic transistors offer low bias operation facilitated by direct contact of the transistor channel with an electrolyte. Their operation mode is generally defined by the dimensionality of charge transport, where a field-effect transistor allows for electrostatic charge accumulation at the electrolyte/semiconductor interface, whereas an organic electrochemical transistor (OECT) facilitates penetration of ions into the bulk of the channel, considered a slow process, leading to volumetric doping and electronic transport. Conducting polymer OECTs allow for fast switching and high currents through incorporation of excess, hygroscopic ionic phases, but operate in depletion mode. Here, we show that the use of glycolated side chains on a thiophene backbone can result in accumulation mode OECTs with high currents, transconductance, and sharp subthreshold switching, while maintaining fast switching speeds. Compared with alkylated analogs of the same backbone, the triethylene glycol side chains shift the mode of operation of aqueous electrolyte-gated transistors from interfacial to bulk doping/transport and show complete and reversible electrochromism and high volumetric capacitance at low operating biases. We propose that the glycol side chains facilitate hydration and ion penetration, without compromising electronic mobility, and suggest that this synthetic approach can be used to guide the design of organic mixed conductors.