Статті в журналах: "Ionic gating"

1

Tang, Chih-Yung, Francisco Bezanilla, and Diane M. Papazian. "Extracellular Mg2+ Modulates Slow Gating Transitions and the Opening of Drosophila Ether-à-Go-Go Potassium Channels." Journal of General Physiology 115, no. 3 (February 28, 2000): 319–38. http://dx.doi.org/10.1085/jgp.115.3.319.

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We have characterized the effects of prepulse hyperpolarization and extracellular Mg2+ on the ionic and gating currents of the Drosophila ether-à-go-go K+ channel (eag). Hyperpolarizing prepulses significantly slowed channel opening elicited by a subsequent depolarization, revealing rate-limiting transitions for activation of the ionic currents. Extracellular Mg2+ dramatically slowed activation of eag ionic currents evoked with or without prepulse hyperpolarization and regulated the kinetics of channel opening from a nearby closed state(s). These results suggest that Mg2+ modulates voltage-dependent gating and pore opening in eag channels. To investigate the mechanism of this modulation, eag gating currents were recorded using the cut-open oocyte voltage clamp. Prepulse hyperpolarization and extracellular Mg2+ slowed the time course of ON gating currents. These kinetic changes resembled the results at the ionic current level, but were much smaller in magnitude, suggesting that prepulse hyperpolarization and Mg2+ modulate gating transitions that occur slowly and/or move relatively little gating charge. To determine whether quantitatively different effects on ionic and gating currents could be obtained from a sequential activation pathway, computer simulations were performed. Simulations using a sequential model for activation reproduced the key features of eag ionic and gating currents and their modulation by prepulse hyperpolarization and extracellular Mg2+. We have also identified mutations in the S3–S4 loop that modify or eliminate the regulation of eag gating by prepulse hyperpolarization and Mg2+, indicating an important role for this region in the voltage-dependent activation of eag.

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2

Yue, Zengji. "Ionic gating for ion intercalation." Nature Reviews Physics 3, no. 5 (April 1, 2021): 306. http://dx.doi.org/10.1038/s42254-021-00311-8.

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3

Ertel, E. A., M. M. Smith, M. D. Leibowitz, and C. J. Cohen. "Isolation of myocardial L-type calcium channel gating currents with the spider toxin omega-Aga-IIIA." Journal of General Physiology 103, no. 5 (May 1, 1994): 731–53. http://dx.doi.org/10.1085/jgp.103.5.731.

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The peptide omega-agatoxin-IIIA (omega-Aga-IIIA) blocks ionic current through L-type Ca channels in guinea pig atrial cells without affecting the associated gating currents. omega-Aga-IIIA permits the study of L-type Ca channel ionic and gating currents under nearly identical ionic conditions. Under conditions that isolate L-type Ca channel currents, omega-Aga-IIIA blocks all ionic current during a test pulse and after repolarization. This block reveals intramembrane charge movements of equal magnitude and opposite sign at the beginning of the pulse (Q(on)) and after repolarization (Q(off)). Q(on) and Q(off) are suppressed by 1 microM felodipine, saturate with increasing test potential, and are insensitive to Cd. The decay of the transient current associated with Q(on) is composed of fast and slow exponential components. The slow component has a time constant similar to that for activation of L-type Ca channel ionic current, over a broad voltage range. The current associated with Q(off) decays monoexponentially and more slowly than ionic current. Similar charge movements are found in guinea pig tracheal myocytes, which lack Na channels and T-type Ca channels. The kinetic and pharmacological properties of Q(on) and Q(off) indicate that they reflect gating currents associated with L-type Ca channels. omega-Aga-IIIA has no effect on gating currents when ionic current is eliminated by stepping to the reversal potential for Ca or by Cd block. Gating currents constitute a significant component of total current when physiological concentrations of Ca are present and they obscure the activation and deactivation of L-type Ca channels. By using omega-Aga-IIIA, we resolve the entire time course of L-type Ca channel ionic and gating currents. We also show that L- and T-type Ca channel ionic currents can be accurately quantified by tail current analysis once gating currents are taken into account.

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4

Stefani, E., L. Toro, E. Perozo, and F. Bezanilla. "Gating of Shaker K+ channels: I. Ionic and gating currents." Biophysical Journal 66, no. 4 (April 1994): 996–1010. http://dx.doi.org/10.1016/s0006-3495(94)80881-1.

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5

Roux, Michel J., Riccardo Olcese, Ligia Toro, Francisco Bezanilla, and Enrico Stefani. "Fast Inactivation in Shaker K+ Channels." Journal of General Physiology 111, no. 5 (May 1, 1998): 625–38. http://dx.doi.org/10.1085/jgp.111.5.625.

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Fast inactivating Shaker H4 potassium channels and nonconducting pore mutant Shaker H4 W434F channels have been used to correlate the installation and recovery of the fast inactivation of ionic current with changes in the kinetics of gating current known as “charge immobilization” (Armstrong, C.M., and F. Bezanilla. 1977. J. Gen. Physiol. 70:567–590.). Shaker H4 W434F gating currents are very similar to those of the conducting clone recorded in potassium-free solutions. This mutant channel allows the recording of the total gating charge return, even when returning from potentials that would largely inactivate conducting channels. As the depolarizing potential increased, the OFF gating currents decay phase at −90 mV return potential changed from a single fast component to at least two components, the slower requiring ∼200 ms for a full charge return. The charge immobilization onset and the ionic current decay have an identical time course. The recoveries of gating current (Shaker H4 W434F) and ionic current (Shaker H4) in 2 mM external potassium have at least two components. Both recoveries are similar at −120 and −90 mV. In contrast, at higher potentials (−70 and −50 mV), the gating charge recovers significantly more slowly than the ionic current. A model with a single inactivated state cannot account for all our data, which strongly support the existence of “parallel” inactivated states. In this model, a fraction of the charge can be recovered upon repolarization while the channel pore is occupied by the NH2-terminus region.

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6

Misra, Rajiv, Mitchell McCarthy, and Arthur F. Hebard. "Electric field gating with ionic liquids." Applied Physics Letters 90, no. 5 (January 29, 2007): 052905. http://dx.doi.org/10.1063/1.2437663.

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7

Bezanilla, F., and E. Stefani. "Voltage-Dependent Gating of Ionic Channels." Annual Review of Biophysics and Biomolecular Structure 23, no. 1 (June 1994): 819–46. http://dx.doi.org/10.1146/annurev.bb.23.060194.004131.

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8

Bhatnagar-Schöffmann, T., A. Kovàcs, R. Pachat, D. Ourdani, A. Lamperti, M. A. Syskaki, T. da Câmara Santa Clara Gomes, et al. "Controlling interface anisotropy in CoFeB/MgO/HfO₂ using dusting layers and magneto-ionic gating." Applied Physics Letters 122, no. 4 (January 23, 2023): 042402. http://dx.doi.org/10.1063/5.0132870.

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In this work, we present the magneto-ionic response to ionic liquid gating in Ta/CoFeB/MgO/HfO2 stacks, where heavy metal dusting layers of Ta, W, and Pt are inserted at the Ta/CoFeB and CoFeB/MgO interfaces. Dusting layers of W inserted at the Ta/CoFeB interface increase perpendicular magnetic anisotropy (PMA) by more than 50%, while no significant changes are seen for Pt. In these samples, gating cannot break the PMA seeded at the CoFeB/MgO interface, only relatively small changes in the coercivity can be induced, about 20% for Ta and Pt and 6% for W. At the CoFeB/MgO interface, a significant quenching of the magnetization is seen when W and Ta dusting layers are inserted, which remains unchanged after gating, suggesting a critical deterioration of the CoFeB. In contrast, Pt dusting layers result in an in-plane anisotropy that can be reversibly converted to PMA through magneto-ionic gating while preserving the polycrystalline structure of the MgO layer. This shows that dusting layers can be effectively used not only to engineer magnetic properties in multilayers but also to strongly modify their magneto-ionic performance.

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9

Spires, S., and T. Begenisich. "Pharmacological and kinetic analysis of K channel gating currents." Journal of General Physiology 93, no. 2 (February 1, 1989): 263–83. http://dx.doi.org/10.1085/jgp.93.2.263.

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We have measured gating currents from the squid giant axon using solutions that preserve functional K channels and with experimental conditions that minimize Na channel contributions to these currents. Two pharmacological agents were used to identify a component of gating current that is associated with K channels. Low concentrations of internal Zn2+ that considerably slow K channel ionic currents with no effect on Na channel currents altered the component of gating current associated with K channels. At low concentrations (10-50 microM) the small, organic, dipolar molecule phloretin has several reported specific effects on K channels: it reduces K channel conductance, shifts the relationship between channel conductance and membrane voltage (Vm) to more positive potentials, and reduces the voltage dependence of the conductance-Vm relation. The K channel gating charge movements were altered in an analogous manner by 10 microM phloretin. We also measured the dominant time constants of the K channel ionic and gating currents. These time constants were similar over part of the accessible voltage range, but at potentials between -40 and 0 mV the gating current time constants were two to three times faster than the corresponding ionic current values. These features of K channel function can be reproduced by a simple kinetic model in which the channel is considered to consist of two, two-state, nonidentical subunits.

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10

Chen, Senbin, Falk Frenzel, Bin Cui, Fang Gao, Antonella Campanella, Alexander Funtan, Friedrich Kremer, Stuart S. P. Parkin, and Wolfgang H. Binder. "Gating effects of conductive polymeric ionic liquids." Journal of Materials Chemistry C 6, no. 30 (2018): 8242–50. http://dx.doi.org/10.1039/c8tc01936c.

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11

Struyk, Arie F., Vladislav S. Markin, David Francis, and Stephen C. Cannon. "Gating Pore Currents in DIIS4 Mutations of NaV1.4 Associated with Periodic Paralysis: Saturation of Ion Flux and Implications for Disease Pathogenesis." Journal of General Physiology 132, no. 4 (September 29, 2008): 447–64. http://dx.doi.org/10.1085/jgp.200809967.

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S4 voltage–sensor mutations in CaV1.1 and NaV1.4 channels cause the human muscle disorder hypokalemic periodic paralysis (HypoPP). The mechanism whereby these mutations predispose affected sarcolemma to attacks of sustained depolarization and loss of excitability is poorly understood. Recently, three HypoPP mutations in the domain II S4 segment of NaV1.4 were shown to create accessory ionic permeation pathways, presumably extending through the aqueous gating pore in which the S4 segment resides. However, there are several disparities between reported gating pore currents from different investigators, including differences in ionic selectivity and estimates of current amplitude, which in turn have important implications for the pathological relevance of these aberrant currents. To clarify the features of gating pore currents arising from different DIIS4 mutants, we recorded gating pore currents created by HypoPP missense mutations at position R666 in the rat isoform of Nav1.4 (the second arginine from the outside, at R672 in human NaV1.4). Extensive measurements were made for the index mutation, R666G, which created a gating pore that was permeable to K+ and Na+. This current had a markedly shallow slope conductance at hyperpolarized voltages and robust inward rectification, even when the ionic gradient strongly favored outward ionic flow. These characteristics were accounted for by a barrier model incorporating a voltage-gated permeation pathway with a single cation binding site oriented near the external surface of the electrical field. The amplitude of the R666G gating pore current was similar to the amplitude of a previously described proton-selective current flowing through the gating pore in rNaV1.4-R663H mutant channels. Currents with similar amplitude and cation selectivity were also observed in R666S and R666C mutant channels, while a proton-selective current was observed in R666H mutant channels. These results add support to the notion that HypoPP mutations share a common biophysical profile comprised of a low-amplitude inward current at the resting potential that may contribute to the pathological depolarization during attacks of weakness.

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12

Bezanilla, Francisco. "Gating currents." Journal of General Physiology 150, no. 7 (June 25, 2018): 911–32. http://dx.doi.org/10.1085/jgp.201812090.

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Many membrane proteins sense the voltage across the membrane where they are inserted, and their function is affected by voltage changes. The voltage sensor consists of charges or dipoles that move in response to changes in the electric field, and their movement produces an electric current that has been called gating current. In the case of voltage-gated ion channels, the kinetic and steady-state properties of the gating charges provide information of conformational changes between closed states that are not visible when observing ionic currents only. In this Journal of General Physiology Milestone, the basic principles of voltage sensing and gating currents are presented, followed by a historical description of the recording of gating currents. The results of gating current recordings are then discussed in the context of structural changes in voltage-dependent membrane proteins and how these studies have provided new insights on gating mechanisms.

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13

QU, ZhuangZhuang, XingYu JIANG, JianMing LU, QiHong CHEN, and JianTing YE. "Ionic gating in the study of superconductivity." SCIENTIA SINICA Physica, Mechanica & Astronomica 51, no. 4 (March 17, 2021): 047410. http://dx.doi.org/10.1360/sspma-2021-0033.

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14

Rappe, Andrew M. "Ionic gating drives correlated insulator–metal transition." Proceedings of the National Academy of Sciences 115, no. 39 (September 11, 2018): 9655–57. http://dx.doi.org/10.1073/pnas.1812913115.

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15

Kay, Nicola J., Simon J. Higgins, Jan O. Jeppesen, Edmund Leary, Jess Lycoops, Jens Ulstrup, and Richard J. Nichols. "Single-Molecule Electrochemical Gating in Ionic Liquids." Journal of the American Chemical Society 134, no. 40 (September 28, 2012): 16817–26. http://dx.doi.org/10.1021/ja307407e.

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16

Wu, Yang, Chan La-o-vorakiat, Xuepeng Qiu, Jingbo Liu, Praveen Deorani, Karan Banerjee, Jaesung Son, Yuanfu Chen, Elbert E. M. Chia, and Hyunsoo Yang. "Graphene Terahertz Modulators by Ionic Liquid Gating." Advanced Materials 27, no. 11 (February 3, 2015): 1874–79. http://dx.doi.org/10.1002/adma.201405251.

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17

Sharma, Yogesh, Anthony T. Wong, Andreas Herklotz, Dongkyu Lee, Anton V. Ievlev, Liam Collins, Ho Nyung Lee, et al. "Ionic Gating of Ultrathin and Leaky Ferroelectrics." Advanced Materials Interfaces 6, no. 5 (January 16, 2019): 1801723. http://dx.doi.org/10.1002/admi.201801723.

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18

ViolBarbosa, Carlos, Julie Karel, Janos Kiss, Ovidiu-dorin Gordan, Simone G. Altendorf, Yuki Utsumi, Mahesh G. Samant, et al. "Transparent conducting oxide induced by liquid electrolyte gating." Proceedings of the National Academy of Sciences 113, no. 40 (September 19, 2016): 11148–51. http://dx.doi.org/10.1073/pnas.1611745113.

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Optically transparent conducting materials are essential in modern technology. These materials are used as electrodes in displays, photovoltaic cells, and touchscreens; they are also used in energy-conserving windows to reflect the infrared spectrum. The most ubiquitous transparent conducting material is tin-doped indium oxide (ITO), a wide-gap oxide whose conductivity is ascribed to n-type chemical doping. Recently, it has been shown that ionic liquid gating can induce a reversible, nonvolatile metallic phase in initially insulating films of WO3. Here, we use hard X-ray photoelectron spectroscopy and spectroscopic ellipsometry to show that the metallic phase produced by the electrolyte gating does not result from a significant change in the bandgap but rather originates from new in-gap states. These states produce strong absorption below ∼1 eV, outside the visible spectrum, consistent with the formation of a narrow electronic conduction band. Thus WO3 is metallic but remains colorless, unlike other methods to realize tunable electrical conductivity in this material. Core-level photoemission spectra show that the gating reversibly modifies the atomic coordination of W and O atoms without a substantial change of the stoichiometry; we propose a simple model relating these structural changes to the modifications in the electronic structure. Thus we show that ionic liquid gating can tune the conductivity over orders of magnitude while maintaining transparency in the visible range, suggesting the use of ionic liquid gating for many applications.

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19

Perez-Muñoz, Ana M., Pedro Schio, Roberta Poloni, Alejandro Fernandez-Martinez, Alberto Rivera-Calzada, Julio C. Cezar, Eduardo Salas-Colera, et al. "In operando evidence of deoxygenation in ionic liquid gating of YBa2Cu3O7-X." Proceedings of the National Academy of Sciences 114, no. 2 (December 27, 2016): 215–20. http://dx.doi.org/10.1073/pnas.1613006114.

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Field-effect experiments on cuprates using ionic liquids have enabled the exploration of their rich phase diagrams [Leng X, et al. (2011) Phys Rev Lett 107(2):027001]. Conventional understanding of the electrostatic doping is in terms of modifications of the charge density to screen the electric field generated at the double layer. However, it has been recently reported that the suppression of the metal to insulator transition induced in VO2 by ionic liquid gating is due to oxygen vacancy formation rather than to electrostatic doping [Jeong J, et al. (2013) Science 339(6126):1402–1405]. These results underscore the debate on the true nature, electrostatic vs. electrochemical, of the doping of cuprates with ionic liquids. Here, we address the doping mechanism of the high-temperature superconductor YBa2Cu3O7-X (YBCO) by simultaneous ionic liquid gating and X-ray absorption experiments. Pronounced spectral changes are observed at the Cu K-edge concomitant with the superconductor-to-insulator transition, evidencing modification of the Cu coordination resulting from the deoxygenation of the CuO chains, as confirmed by first-principles density functional theory (DFT) simulations. Beyond providing evidence of the importance of chemical doping in electric double-layer (EDL) gating experiments with superconducting cuprates, our work shows that interfacing correlated oxides with ionic liquids enables a delicate control of oxygen content, paving the way to novel electrochemical concepts in future oxide electronics.

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20

White, M. M., and F. Bezanilla. "Activation of squid axon K+ channels. Ionic and gating current studies." Journal of General Physiology 85, no. 4 (April 1, 1985): 539–54. http://dx.doi.org/10.1085/jgp.85.4.539.

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We have used data obtained from measurements of ionic and gating currents to study the process of K+ channel activation in squid giant axons. A marked improvement in the recording of K+ channel gating currents (IKg) was obtained by total replacement of Cl- in the external solution by NO-3, which eliminates approximately 50% of the Na+ channel gating current with no effect on IKg. The midpoint of the steady state charge-voltage (Qrel - V) relationship is approximately 40 mV hyperpolarized to that of the steady state activation (fo - V) curve, which is an indication that the channel has many nonconducting states. Ionic and gating currents have similar time constants for both ON and OFF pulses. This eliminates any Hodgkin-Huxley nx scheme for K+ channel activation. An interrupted pulse paradigm shows that the last step in the activation process is not rate limiting. IKg shows a nonartifactual rising phase, which indicates that the first step is either the slowest step in the activation sequence or is voltage independent. These data are consistent with the following general scheme for K+ channel activation: (formula; see text)

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21

Nishioka, Daiki, Takashi Tsuchiya, Tohru Higuchi, and Kazuya Terabe. "Oxygen-tolerant operation of all-solid-state ionic-gating devices: advantage of all-solid-state structure for ionic-gating." Japanese Journal of Applied Physics 59, SI (March 30, 2020): SIIG09. http://dx.doi.org/10.35848/1347-4065/ab7e12.

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22

Correa, Ana M. "Gating kinetics of ShakerK+ channels are differentially modified by general anesthetics." American Journal of Physiology-Cell Physiology 275, no. 4 (October 1, 1998): C1009—C1021. http://dx.doi.org/10.1152/ajpcell.1998.275.4.c1009.

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The ShakerB K+ channel was used as a model voltage-gated channel to probe the interaction of volatile general anesthetics with gating mechanisms. The effects of three anesthetics, chloroform (CHCl3), isoflurane, and halothane, were studied using recombinant native and mutant Shaker channels expressed in Xenopus oocytes. Gating currents and macroscopic ionic currents were recorded with the cut-open oocyte voltage-clamp technique. The effects of CHCl3 and isoflurane on gating kinetics of noninactivating mutants were opposite, whereas halothane had no effect. The effects on ionic currents were also agent dependent: CHCl3 and halothane produced a reduction of the macroscopic conductance, whereas isoflurane increased it. The results indicate that the gating machinery of the channel is mostly insensitive to the anesthetics during activation until near the open state. The effects on the conductance are mainly due to changes in the transitions in and out of the open state. The data give support to direct protein-anesthetic interactions. The magnitude and nature of the effects invite reconsideration of Shaker-like K+ channels as important sites of action of general anesthetics.

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23

Lieb, Johanna, Valeria Demontis, Domenic Prete, Daniele Ercolani, Valentina Zannier, Lucia Sorba, Shimpei Ono, Fabio Beltram, Benjamin Sacépé, and Francesco Rossella. "Ionic Liquid Gating of Semiconductor Nanostructure-Based Devices." Proceedings 3, no. 1 (September 5, 2018): 5. http://dx.doi.org/10.3390/iocn_2018-1-05499.

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24

Leighton, Chris, Turan Birol, and Jeff Walter. "What controls electrostatic vs electrochemical response in electrolyte-gated materials? A perspective on critical materials factors." APL Materials 10, no. 4 (April 1, 2022): 040901. http://dx.doi.org/10.1063/5.0087396.

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Electrolyte-gate transistors are a powerful platform for control of material properties, spanning semiconducting behavior, insulator-metal transitions, superconductivity, magnetism, optical properties, etc. When applied to magnetic materials, for example, electrolyte-gate devices are promising for magnetoionics, wherein voltage-driven ionic motion enables low-power control of magnetic order and properties. The mechanisms of electrolyte gating with ionic liquids and gels vary from predominantly electrostatic to entirely electrochemical, however, sometimes even in single material families, for reasons that remain unclear. In this Perspective, we compare literature ionic liquid and ion gel gating data on two rather different material classes—perovskite oxides and pyrite-structure sulfides—seeking to understand which material factors dictate the electrostatic vs electrochemical gate response. From these comparisons, we argue that the ambient-temperature anion vacancy diffusion coefficient ( not the vacancy formation energy) is a critical factor controlling electrostatic vs electrochemical mechanisms in electrolyte gating of these materials. We, in fact, suggest that the diffusivity of lowest-formation-energy defects may often dictate the electrostatic vs electrochemical response in electrolyte-gated inorganic materials, thereby advancing a concrete hypothesis for further exploration in a broader range of materials.

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25

Piatti, Erik. "Ionic gating in metallic superconductors: A brief review." Nano Express 2, no. 2 (May 24, 2021): 024003. http://dx.doi.org/10.1088/2632-959x/ac011d.

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26

Saranin, Danila, Artur Ishteev, Alexander B. Cook, Jonathan D. Yuen, Denis Kuznetsov, Marina Orlova, Sergey Didenko, and Anvar Zakhidov. "Tunable organic PV parallel tandem with ionic gating." Journal of Renewable and Sustainable Energy 9, no. 2 (March 2017): 021204. http://dx.doi.org/10.1063/1.4979900.

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27

Kuzmenkin, Alexey, Francisco Bezanilla, and Ana M. Correa. "Gating of the Bacterial Sodium Channel, NaChBac." Journal of General Physiology 124, no. 4 (September 13, 2004): 349–56. http://dx.doi.org/10.1085/jgp.200409139.

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The bacterial sodium channel, NaChBac, from Bacillus halodurans provides an excellent model to study structure–function relationships of voltage-gated ion channels. It can be expressed in mammalian cells for functional studies as well as in bacterial cultures as starting material for protein purification for fine biochemical and biophysical studies. Macroscopic functional properties of NaChBac have been described previously (Ren, D., B. Navarro, H. Xu, L. Yue, Q. Shi, and D.E. Clapham. 2001. Science. 294:2372–2375). In this study, we report gating current properties of NaChBac expressed in COS-1 cells. Upon depolarization of the membrane, gating currents appeared as upward inflections preceding the ionic currents. Gating currents were detectable at −90 mV while holding at −150 mV. Charge–voltage (Q–V) curves showed sigmoidal dependence on voltage with gating charge saturating at −10 mV. Charge movement was shifted by −22 mV relative to the conductance–voltage curve, indicating the presence of more than one closed state. Consistent with this was the Cole-Moore shift of 533 μs observed for a change in preconditioning voltage from −160 to −80 mV. The total gating charge was estimated to be 16 elementary charges per channel. Charge immobilization caused by prolonged depolarization was also observed; Q–V curves were shifted by approximately −60 mV to hyperpolarized potentials when cells were held at 0 mV. The kinetic properties of NaChBac were simulated by simultaneous fit of sodium currents at various voltages to a sequential kinetic model. Gating current kinetics predicted from ionic current experiments resembled the experimental data, indicating that gating currents are coupled to activation of NaChBac and confirming the assertion that this channel undergoes several transitions between closed states before channel opening. The results indicate that NaChBac has several closed states with voltage-dependent transitions between them realized by translocation of gating charge that causes activation of the channel.

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28

Neely, A., R. Olcese, P. Baldelli, X. Wei, L. Birnbaumer, and E. Stefani. "Dual activation of the cardiac Ca2+ channel alpha 1C-subunit and its modulation by the beta-subunit." American Journal of Physiology-Cell Physiology 268, no. 3 (March 1, 1995): C732—C740. http://dx.doi.org/10.1152/ajpcell.1995.268.3.c732.

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Ca2+ channels are heteromultimeric proteins in which the alpha 1-subunit forms the voltage-dependent Ca(2+)-selective ionic channel. We reported recently that coexpression of the beta-subunit with the cardiac alpha 1-subunit (alpha 1C) facilitates channel opening without affecting either the amplitude or the time course of the gating currents (13). Here we present evidence for the existence of two modes of channel opening. Xenopus oocytes expressing the alpha 1C-subunit alone display two modes of activation as indicated by the double-exponential time course of macroscopic ionic currents and the two open-time distributions of single channels. Coexpression of the beta-subunit potentiates Ca2+ currents by a relative increase of the fast-activating component, an acceleration of the slow component, and a larger proportion of long openings. We propose that multiple modes of gating are encoded in the alpha 1-subunit and that the beta-subunit increases Ca2+ channel opening by favoring a willing mode of gating in which the final transitions leading to channel opening are facilitated. In addition, we show that the carboxy terminus of alpha 1C also modulates the channel-gating behavior.

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29

Perez-Flores, Maria C., Jeong H. Lee, Seojin Park, Xiao-Dong Zhang, Choong-Ryoul Sihn, Hannah A. Ledford, Wenying Wang, et al. "Cooperativity of Kv7.4 channels confers ultrafast electromechanical sensitivity and emergent properties in cochlear outer hair cells." Science Advances 6, no. 15 (April 2020): eaba1104. http://dx.doi.org/10.1126/sciadv.aba1104.

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The mammalian cochlea relies on active electromotility of outer hair cells (OHCs) to resolve sound frequencies. OHCs use ionic channels and somatic electromotility to achieve the process. It is unclear, though, how the kinetics of voltage-gated ionic channels operate to overcome extrinsic viscous drag on OHCs at high frequency. Here, we report ultrafast electromechanical gating of clustered Kv7.4 in OHCs. Increases in kinetics and sensitivity resulting from cooperativity among clustered-Kv7.4 were revealed, using optogenetics strategies. Upon clustering, the half-activation voltage shifted negative, and the speed of activation increased relative to solitary channels. Clustering also rendered Kv7.4 channels mechanically sensitive, confirmed in consolidated Kv7.4 channels at the base of OHCs. Kv7.4 clusters provide OHCs with ultrafast electromechanical channel gating, varying in magnitude and speed along the cochlea axis. Ultrafast Kv7.4 gating provides OHCs with a feedback mechanism that enables the cochlea to overcome viscous drag and resolve sounds at auditory frequencies.

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30

Vaquero, Daniel, Vito Clericò, Juan Salvador-Sánchez, Jorge Quereda, Enrique Diez, and Ana M. Pérez-Muñoz. "Ionic-Liquid Gating in Two-Dimensional TMDs: The Operation Principles and Spectroscopic Capabilities." Micromachines 12, no. 12 (December 17, 2021): 1576. http://dx.doi.org/10.3390/mi12121576.

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Ionic-liquid gating (ILG) is able to enhance carrier densities well above the achievable values in traditional field-effect transistors (FETs), revealing it to be a promising technique for exploring the electronic phases of materials in extreme doping regimes. Due to their chemical stability, transition metal dichalcogenides (TMDs) are ideal candidates to produce ionic-liquid-gated FETs. Furthermore, as recently discovered, ILG can be used to obtain the band gap of two-dimensional semiconductors directly from the simple transfer characteristics. In this work, we present an overview of the operation principles of ionic liquid gating in TMD-based transistors, establishing the importance of the reference voltage to obtain hysteresis-free transfer characteristics, and hence, precisely determine the band gap. We produced ILG-based bilayer WSe2 FETs and demonstrated their ambipolar behavior. We estimated the band gap directly from the transfer characteristics, demonstrating the potential of ILG as a spectroscopy technique.

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31

Bangalore, R., G. Mehrke, K. Gingrich, F. Hofmann, and R. S. Kass. "Influence of L-type Ca channel alpha 2/delta-subunit on ionic and gating current in transiently transfected HEK 293 cells." American Journal of Physiology-Heart and Circulatory Physiology 270, no. 5 (May 1, 1996): H1521—H1528. http://dx.doi.org/10.1152/ajpheart.1996.270.5.h1521.

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We have measured ionic and gating currents in human embryonic kidney (HEK 293) cells transiently transfected with cDNAs encoding subunits of the cardiac voltage-gated L-type Ca2+ channel. Robust recombinant ionic current and associated nonlinear charge movement could be measured over a broad voltage range without contamination by endogenous channel activity. Coexpression of the alpha 2/delta-subunit along with alpha 1- and beta 2-subunits speeded activation and deactivation kinetics and significantly increased the maximal conductance of ionic current. Charge movement was measured at voltages negative to the threshold for activation of ionic current, and gating charge could be immobilized at positive holding potentials that did not inactivate ionic current. The ratio of maximal ionic conductance to maximal charge moved remained the same in the absence or presence of the alpha 2/delta-subunit. However, the maximal amount of charge moved was increased about twofold in the presence of the alpha 2/delta-subunit. These results suggest that coexpression of the alpha 2/delta-subunit enhances the expression of functional L-type channels and, in addition, provide evidence that most of the L-type channel-associated nonlinear charge movement is caused by transitions between nonconducting states of the channel protein that precede the open and inactivated states.

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32

Zagotta, W. N., T. Hoshi, J. Dittman, and R. W. Aldrich. "Shaker potassium channel gating. II: Transitions in the activation pathway." Journal of General Physiology 103, no. 2 (February 1, 1994): 279–319. http://dx.doi.org/10.1085/jgp.103.2.279.

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Voltage-dependent gating behavior of Shaker potassium channels without N-type inactivation (ShB delta 6-46) expressed in Xenopus oocytes was studied. The voltage dependence of the steady-state open probability indicated that the activation process involves the movement of the equivalent of 12-16 electronic charges across the membrane. The sigmoidal kinetics of the activation process, which is maintained at depolarized voltages up to at least +100 mV indicate the presence of at least five sequential conformational changes before opening. The voltage dependence of the gating charge movement suggested that each elementary transition involves 3.5 electronic charges. The voltage dependence of the forward opening rate, as estimated by the single-channel first latency distribution, the final phase of the macroscopic ionic current activation, the ionic current reactivation and the ON gating current time course, showed movement of the equivalent of 0.3 to 0.5 electronic charges were associated with a large number of the activation transitions. The equivalent charge movement of 1.1 electronic charges was associated with the closing conformational change. The results were generally consistent with models involving a number of independent and identical transitions with a major exception that the first closing transition is slower than expected as indicated by tail current and OFF gating charge measurements.

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33

Spires, S., and T. Begenisich. "Modification of potassium channel kinetics by amino group reagents." Journal of General Physiology 99, no. 1 (January 1, 1992): 109–29. http://dx.doi.org/10.1085/jgp.99.1.109.

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We have examined the actions of several amino group reagents on delayed rectifier potassium channels in squid giant axons. Three general classes of reagents were used: (1) those that preserved the positive charge of amino groups; (2) those that neutralize the charge; and (3) those that replace the positive with a negative charge. All three types of reagents produced qualitatively similar effects on K channel properties. Trinitrobenzene sulfonic acid (TNBS) neutralizes the peptide terminal amino groups and the epsilon-amino group of lysine groups. TNBS (a) slowed the kinetics of macroscopic ionic currents; (b) increased the size of ionic currents at large positive voltages; (c) shifted the voltage-dependent probability of channel opening to more positive potentials but had no effect on the voltage sensitivity; and (d) altered several properties of K channel gating currents. The actions of TNBS on gating currents suggest the presence of multiple gating current components. These effects are not all coupled, suggesting that several amino groups on the external surface of K channels are important for channel gating. A simple kinetic model that considers the channel to be composed of independent heterologous subunits is consistent with most of the modifications produced by amino group reagents.

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34

Latorre, Ramon, Riccardo Olcese, Claudia Basso, Carlos Gonzalez, Fabian Muñoz, Diego Cosmelli, and Osvaldo Alvarez. "Molecular Coupling between Voltage Sensor and Pore Opening in the Arabidopsis Inward Rectifier K+ Channel KAT1." Journal of General Physiology 122, no. 4 (September 29, 2003): 459–69. http://dx.doi.org/10.1085/jgp.200308818.

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Animal and plant voltage-gated ion channels share a common architecture. They are made up of four subunits and the positive charges on helical S4 segments of the protein in animal K+ channels are the main voltage-sensing elements. The KAT1 channel cloned from Arabidopsis thaliana, despite its structural similarity to animal outward rectifier K+ channels is, however, an inward rectifier. Here we detected KAT1-gating currents due to the existence of an intrinsic voltage sensor in this channel. The measured gating currents evoked in response to hyperpolarizing voltage steps consist of a very fast (τ = 318 ± 34 μs at −180 mV) and a slower component (4.5 ± 0.5 ms at −180 mV) representing charge moved when most channels are closed. The observed gating currents precede in time the ionic currents and they are measurable at voltages (less than or equal to −60) at which the channel open probability is negligible (≈10−4). These two observations, together with the fact that there is a delay in the onset of the ionic currents, indicate that gating charge transits between several closed states before the KAT1 channel opens. To gain insight into the molecular mechanisms that give rise to the gating currents and lead to channel opening, we probed external accessibility of S4 domain residues to methanethiosulfonate-ethyltrimethylammonium (MTSET) in both closed and open cysteine-substituted KAT1 channels. The results demonstrate that the putative voltage–sensing charges of S4 move inward when the KAT1 channels open.

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35

Correa, A. M., and F. Bezanilla. "Gating of the squid sodium channel at positive potentials. I. Macroscopic ionic and gating currents." Biophysical Journal 66, no. 6 (June 1994): 1853–63. http://dx.doi.org/10.1016/s0006-3495(94)80979-8.

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36

Conrad, Linus J., Peter Proks, and Stephen J. Tucker. "Effects of ionic strength on gating and permeation of TREK-2 K2P channels." PLOS ONE 16, no. 10 (October 7, 2021): e0258275. http://dx.doi.org/10.1371/journal.pone.0258275.

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In addition to the classical voltage-dependent behavior mediated by the voltage-sensing-domains (VSD) of ion channels, a growing number of voltage-dependent gating behaviors are being described in channels that lack canonical VSDs. A common thread in their mechanism of action is the contribution of the permeating ion to this voltage sensing process. The polymodal K2P K+ channel, TREK2 responds to membrane voltage through a gating process mediated by the interaction of K+ with its selectivity filter. Recently, we found that this action can be modulated by small molecule agonists (e.g. BL1249) which appear to have an electrostatic influence on K+ binding within the inner cavity and produce an increase in the single-channel conductance of TREK-2 channels. Here, we directly probed this K+-dependent gating process by recording both macroscopic and single-channel currents of TREK-2 in the presence of high concentrations of internal K+. Surprisingly we found TREK-2 is inhibited by high internal K+ concentrations and that this is mediated by the concomitant increase in ionic-strength. However, we were still able to determine that the increase in single channel conductance in the presence of BL1249 was blunted in high ionic-strength, whilst its activatory effect (on channel open probability) persisted. These effects are consistent with an electrostatic mechanism of action of negatively charged activators such as BL1249 on permeation, but also suggest that their influence on channel gating is complex.

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37

Gamal El-Din, Tamer M., Todd Scheuer, and William A. Catterall. "Tracking S4 movement by gating pore currents in the bacterial sodium channel NaChBac." Journal of General Physiology 144, no. 2 (July 28, 2014): 147–57. http://dx.doi.org/10.1085/jgp.201411210.

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Voltage-gated sodium channels mediate the initiation and propagation of action potentials in excitable cells. Transmembrane segment S4 of voltage-gated sodium channels resides in a gating pore where it senses the membrane potential and controls channel gating. Substitution of individual S4 arginine gating charges (R1–R3) with smaller amino acids allows ionic currents to flow through the mutant gating pore, and these gating pore currents are pathogenic in some skeletal muscle periodic paralysis syndromes. The voltage dependence of gating pore currents provides information about the transmembrane position of the gating charges as S4 moves in response to membrane potential. Here we studied gating pore current in mutants of the homotetrameric bacterial sodium channel NaChBac in which individual arginine gating charges were replaced by cysteine. Gating pore current was observed for each mutant channel, but with different voltage-dependent properties. Mutating the first (R1C) or second (R2C) arginine to cysteine resulted in gating pore current at hyperpolarized membrane potentials, where the channels are in resting states, but not at depolarized potentials, where the channels are activated. Conversely, the R3C gating pore is closed at hyperpolarized membrane potentials and opens with channel activation. Negative conditioning pulses revealed time-dependent deactivation of the R3C gating pore at the most hyperpolarized potentials. Our results show sequential voltage dependence of activation of gating pore current from R1 to R3 and support stepwise outward movement of the substituted cysteines through the narrow portion of the gating pore that is sealed by the arginine side chains in the wild-type channel. This pattern of voltage dependence of gating pore current is consistent with a sliding movement of the S4 helix through the gating pore. Through comparison with high-resolution models of the voltage sensor of bacterial sodium channels, these results shed light on the structural basis for pathogenic gating pore currents in periodic paralysis syndromes.

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38

Lotshaw, D. P., and F. Li. "Angiotensin II activation of Ca(2+)-permeant nonselective cation channels in rat adrenal glomerulosa cells." American Journal of Physiology-Cell Physiology 271, no. 5 (November 1, 1996): C1705—C1715. http://dx.doi.org/10.1152/ajpcell.1996.271.5.c1705.

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A Ca(2+)-permeant, nonselective cation channel was observed in cell-attached and inside-out membrane patches from rat adrenal glomerulosa cells maintained in primary cell culture. In cell-attached patches under near physiological ionic conditions, single-channel currents exhibited a reversal potential near -10 mV, inward rectification, a nearly linear slope conductance between 0 and -80 mV of 17.4 pS, and voltage-dependent block at potentials more negative than -80 mV. Channels exhibiting identical conductance and gating properties were observed in inside-out patches; however, channel gating ran down within minutes in this configuation. In the inside-out configuration, channel gating did not require cytosolic Ca2+ (Ca2+ < 10(-9) M), and inward rectification was relieved by removal of intracellular Mg2+. Relative ionic permeability was calculated using reversal potential measurements from inside-out patches under bi-ionic conditions. The channel discriminated poorly among monovalent cations (PLi > PK > PCs > PNa) and was not significantly permeable to anions. The channel was permeable to Ca2+, exhibiting a relative permeability ratio of 0.29 PCa/PNa) when measured with 110 mM Ca2+ on the intracellular face and a permeability ratio of 4.38 (PCa/PNa) with 110 mM Ca2+ on the extracellular face. Channel gating behavior was episodic with open times ranging from milliseconds to tens of seconds and closed times lasting up to several minutes or longer. Channel gating appeared to be relatively voltage independent except that mean channel open time and open probability were reduced by membrane hyperpolarization. In cell-attached patches, bath application of 1 nM angiotensin II (ANG II) increased the channel open probability, primarily affecting channels exhibiting a low open probability, primarily affecting channels exhibiting a low open probability before stimulation. With the use of nystatin perforated-patch current clamp to measure membrane potential, ANG II was observed to induce large transient membrane depolarizations, consistent with activation of an inward current. We hypothesize that this channel is an important component of ANG II-induced membrane depolarization and Ca2+ influx during stimulation of aldosterone secretion.

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39

Fête, A., L. Rossi, A. Augieri, and C. Senatore. "Ionic liquid gating of ultra-thin YBa2Cu3O7−x films." Applied Physics Letters 109, no. 19 (November 7, 2016): 192601. http://dx.doi.org/10.1063/1.4967197.

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40

Ueda, Kenji, Shingo Hirose, and Hidefumi Asano. "Ambipolar transport in Mn2CoAl films by ionic liquid gating." Applied Physics Letters 110, no. 20 (May 15, 2017): 202405. http://dx.doi.org/10.1063/1.4983787.

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41

D'Inzeo, Guglielmo, Stefano Pisa, and Luciano Tarricone. "Ionic channel gating under electromagnetic exposure: a stochastic model." Bioelectrochemistry and Bioenergetics 29, no. 3 (February 1993): 289–304. http://dx.doi.org/10.1016/0302-4598(93)85004-d.

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42

Wu, Yang, Xuepeng Qiu, Hongwei Liu, Jingbo Liu, Yuanfu Chen, Lin Ke, and Hyunsoo Yang. "Tunable terahertz reflection of graphene via ionic liquid gating." Nanotechnology 28, no. 9 (January 26, 2017): 095201. http://dx.doi.org/10.1088/1361-6528/aa57ad.

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43

Franciolini, F., and A. Petris. "Single channel recording and gating function of ionic channels." Experientia 44, no. 3 (March 1988): 183–88. http://dx.doi.org/10.1007/bf01941702.

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44

Yang, Suk, Sukjin Jang, Daehwan Choi, Seok Daniel Namgung, Hyung-Jun Kim, and Jang-Yeon Kwon. "Enhanced Device Stability of Ionic Gating Molybdenum Disulfide Transistors." physica status solidi (RRL) – Rapid Research Letters 13, no. 9 (May 20, 2019): 1900142. http://dx.doi.org/10.1002/pssr.201900142.

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45

Atesci, Hasan, Francesco Coneri, Maarten Leeuwenhoek, Jouri Bommer, James R. T. Seddon, Hans Hilgenkamp, and Jan M. Van Ruitenbeek. "Ionic-Liquid Gating: On the Formation of a Conducting Surface Channel by Ionic-Liquid Gating of an Insulator (Ann. Phys. 10/2018)." Annalen der Physik 530, no. 10 (October 2018): 1870040. http://dx.doi.org/10.1002/andp.201870040.

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46

Jones, Lisa P., Shao-kui Wei та David T. Yue. "Mechanism of Auxiliary Subunit Modulation of Neuronal α1E Calcium Channels". Journal of General Physiology 112, № 2 (1 серпня 1998): 125–43. http://dx.doi.org/10.1085/jgp.112.2.125.

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Voltage-gated calcium channels are composed of a main pore-forming α1 moiety, and one or more auxiliary subunits (β, α2δ) that modulate channel properties. Because modulatory properties may vary greatly with different channels, expression systems, and protocols, it is advantageous to study subunit regulation with a uniform experimental strategy. Here, in HEK 293 cells, we examine the expression and activation gating of α1E calcium channels in combination with a β (β1–β4) and/or the α2δ subunit, exploiting both ionic- and gating-current measurements. Furthermore, to explore whether more than one auxiliary subunit can concomitantly specify gating properties, we investigate the effects of cotransfecting α2δ with β subunits, of transfecting two different β subunits simultaneously, and of COOH-terminal truncation of α1E to remove a second β binding site. The main results are as follows. (a) The α2δ and β subunits modulate α1E in fundamentally different ways. The sole effect of α2δ is to increase current density by elevating channel density. By contrast, though β subunits also increase functional channel number, they also enhance maximum open probability (Gmax/Qmax) and hyperpolarize the voltage dependence of ionic-current activation and gating-charge movement, all without discernible effect on activation kinetics. Different β isoforms produce nearly indistinguishable effects on activation. However, β subunits produced clear, isoform-specific effects on inactivation properties. (b) All the β subunit effects can be explained by a gating model in which subunits act only on weakly voltage-dependent steps near the open state. (c) We find no clear evidence for simultaneous modulation by two different β subunits. (d) The modulatory features found here for α1E do not generalize uniformly to other α1 channel types, as α1C activation gating shows marked β isoform dependence that is absent for α1E. Together, these results help to establish a more comprehensive picture of auxiliary-subunit regulation of α1E calcium channels.

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47

Wang, Xiaoxia, Fanfan Du, Yingmei Zhang, Jie Yang, Xiaoli Li, and Xiaohong Xu. "Manipulating the optical and electronic properties of MoO₃ films through electric-field-induced ion migration." Journal of Materials Chemistry C 10, no. 1 (2022): 135–41. http://dx.doi.org/10.1039/d1tc04659d.

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The intercalation of hydrogen ions and lithium ions in MoO3 films is realized by acidic ionic liquid gating, which modifies the electronic and optical properties of MoO3 films, is promising for designing multifunctional devices.

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48

Silvestri, Antonia, Nicola Di Trani, Giancarlo Canavese, Paolo Motto Ros, Leonardo Iannucci, Sabrina Grassini, Yu Wang, Xuewu Liu, Danilo Demarchi, and Alessandro Grattoni. "Silicon Carbide-Gated Nanofluidic Membrane for Active Control of Electrokinetic Ionic Transport." Membranes 11, no. 7 (July 15, 2021): 535. http://dx.doi.org/10.3390/membranes11070535.

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Manipulation of ions and molecules by external control at the nanoscale is highly relevant to biomedical applications. We report a biocompatible electrode-embedded nanofluidic channel membrane designed for electrofluidic applications such as ionic field-effect transistors for implantable drug-delivery systems. Our nanofluidic membrane includes a polysilicon electrode electrically isolated by amorphous silicon carbide (a-SiC). The nanochannel gating performance was experimentally investigated based on the current-voltage (I-V) characteristics, leakage current, and power consumption in potassium chloride (KCl) electrolyte. We observed significant modulation of ionic diffusive transport of both positively and negatively charged ions under physical confinement of nanochannels, with low power consumption. To study the physical mechanism associated with the gating performance, we performed electrochemical impedance spectroscopy. The results showed that the flat band voltage and density of states were significantly low. In light of its remarkable performance in terms of ionic modulation and low power consumption, this new biocompatible nanofluidic membrane could lead to a new class of silicon implantable nanofluidic systems for tunable drug delivery and personalized medicine.

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49

Schoppa, N. E., and F. J. Sigworth. "Activation of Shaker Potassium Channels." Journal of General Physiology 111, no. 2 (February 1, 1998): 271–94. http://dx.doi.org/10.1085/jgp.111.2.271.

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The conformational changes associated with activation gating in Shaker potassium channels are functionally characterized in patch-clamp recordings made from Xenopus laevis oocytes expressing Shaker channels with fast inactivation removed. Estimates of the forward and backward rates for transitions are obtained by fitting exponentials to macroscopic ionic and gating current relaxations at voltage extremes, where we assume that transitions are unidirectional. The assignment of different rates is facilitated by using voltage protocols that incorporate prepulses to preload channels into different distributions of states, yielding test currents that reflect different subsets of transitions. These data yield direct estimates of the rate constants and partial charges associated with three forward and three backward transitions, as well as estimates of the partial charges associated with other transitions. The partial charges correspond to an average charge movement of 0.5 e0 during each transition in the activation process. This value implies that activation gating involves a large number of transitions to account for the total gating charge displacement of 13 e0. The characterization of the gating transitions here forms the basis for constraining a detailed gating model to be described in a subsequent paper of this series.

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50

Rodríguez, Beatriz M., Daniel Sigg, and Francisco Bezanilla. "Voltage Gating of Shaker K+ Channels." Journal of General Physiology 112, no. 2 (August 1, 1998): 223–42. http://dx.doi.org/10.1085/jgp.112.2.223.

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Ionic (Ii) and gating currents (Ig) from noninactivating Shaker H4 K+ channels were recorded with the cut-open oocyte voltage clamp and macropatch techniques. Steady state and kinetic properties were studied in the temperature range 2–22°C. The time course of Ii elicited by large depolarizations consists of an initial delay followed by an exponential rise with two kinetic components. The main Ii component is highly temperature dependent (Q10 > 4) and mildly voltage dependent, having a valence times the fraction of electric field (z) of 0.2–0.3 eo. The Ig On response obtained between −60 and 20 mV consists of a rising phase followed by a decay with fast and slow kinetic components. The main Ig component of decay is highly temperature dependent (Q10 > 4) and has a z between 1.6 and 2.8 eo in the voltage range from −60 to −10 mV, and ∼0.45 eo at more depolarized potentials. After a pulse to 0 mV, a variable recovery period at −50 mV reactivates the gating charge with a high temperature dependence (Q10 > 4). In contrast, the reactivation occurring between −90 and −50 mV has a Q10 = 1.2. Fluctuation analysis of ionic currents reveals that the open probability decreases 20% between 18 and 8°C and the unitary conductance has a low temperature dependence with a Q10 of 1.44. Plots of conductance and gating charge displacement are displaced to the left along the voltage axis when the temperature is decreased. The temperature data suggests that activation consists of a series of early steps with low enthalpic and negative entropic changes, followed by at least one step with high enthalpic and positive entropic changes, leading to final transition to the open state, which has a negative entropic change.

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