Potassium Ion Conductivity Research Articles

Cardanol-Derived Epoxy Resins as Biobased Gel Polymer Electrolytes for Potassium-Ion Conduction.

In this study, biobased gel polymer electrolyte (GPE) membranes were developed via the esterification reaction of a cardanol-based epoxy resin with glutaric anhydride, succinic anhydride, and hexahydro-4-methylphthalic anhydride. Nonisothermal differential scanning calorimetry was used to assess the optimal curing time and temperature of the formulations, evidencing a process activation energy of ∼65–70 kJ mol–1. A rubbery plateau modulus of 0.65–0.78 MPa and a crosslinking density of 2 × 10–4 mol cm–3 were found through dynamic mechanical analysis. Based on these characteristics, such biobased membranes were tested for applicability as GPEs for potassium-ion batteries (KIBs), showing an excellent electrochemical stability toward potassium metal in the −0.2–5 V voltage range and suitable ionic conductivity (10–3 S cm–1) at room temperature. This study demonstrates the practical viability of these biobased materials as efficient GPEs for the fabrication of KIBs, paving the path to increased sustainability in the field of next-generation battery technologies.

Transcriptomic characterization of dying hair cells in the avian cochlea

Sensory hair cells are prone to apoptosis caused by various drugs including aminoglycoside antibiotics. In mammals, this vulnerability results in permanent hearing loss because lost hair cells are not regenerated. Conversely, hair cells regenerate in birds, making the avian inner ear an exquisite model for studying ototoxicity and regeneration. Here, we use single-cell RNA sequencing and trajectory analysis on control and dying hair cells after aminoglycoside treatment. Interestingly, the two major subtypes of avian cochlear hair cells, tall and short hair cells, respond differently. Dying short hair cells show a noticeable transient upregulation of many more genes than tall hair cells. The most prominent gene group identified is associated with potassium ion conductances, suggesting distinct physiological differences. Moreover, the dynamic characterization of >15,000 genes expressed in tall and short avian hair cells during their apoptotic demise comprises a resource for further investigations toward mammalian hair cell protection and hair cell regeneration.

Lithium-, Sodium-, and Potassium-ion Conduction in Polymeric and Discrete Coordination Systems

Abstract Coordination compounds have been increasingly studied as a new class of promising candidates for the matrix of ionic conducting materials because of their designability and high crystallinity. The ionic conduction of light alkali metal ions (Li+ and Na+) has been developed in polymeric coordination systems, which are commonly used under nonaqueous conditions. Recent studies have shown that discrete coordination compounds, as well as hydrated polymeric coordination compounds, can function as excellent ionic conductors even for heavier K+.

Tunable Potassium Ion Conductivity and Magnetism in Substituted Layered Ferrates

AbstractFive substituted oxohydroxoferrates K2–x(Fe,M)4O7–y(OH)y (M=Si, Ge, Ti, Mn, Ir) were synthesized in a potassium hydroxide hydroflux with a molar base‐water ratio q(K) of about 0.9. While the hexagonal prisms of K2–x(Fe,Ti)4O7–y(OH)y crystallize in P63/mcm, all other compounds form hexagonal plates with the trigonal space group P 1 m. The crystal structure of the oxohydroxoferrates resembles ß‐alumina. It consists of honeycomb layers Fe2O6] of edge‐sharing [FeO6] octahedra, where the hexagonal voids are capped by vertex‐sharing [FeO4] tetrahedra pairs. The cavities between the oxoferrate layers host the potassium ions. Depending on M, the substitution affects different iron positions and varies between 5 and 20 %. The magnetic structures of the antiferromagnetic compounds were determined by neutron powder diffraction. The potassium ion conductivity was characterized by electrochemical impedance spectroscopy at room temperature. By storing the oxohydroxoferrates in air or annealing them at 700 °C the ion conductivity was significantly increased, e. g. to 5.0 ⋅ 10−3 S cm−1 for a pressed pellet of the iridium substituted compound.

MEA Preparation for Direct Formate/Formic Acid Fuel Cell-Comparison of Palladium Black and Palladium Supported on Activated Carbon Performance on Power Generation in Passive Fuel Cell.

Membrane electrode assemblies (MEAs) with palladium catalysts were successfully prepared by using a home-made manual pressing system with Nafion glue application that contributed to a decrease of additional energy consumption. The catalyst coated membranes were prepared with supported palladium on activated carbon (PdC) and unsupported palladium black (PdB) for comparison. The performance of passive, air breathing, functioning under ambient conditions and with low concentration (1 M) formate/formic acid fuel cell was evaluated. Based on polarization curves, the best result was obtained with carbon supported catalyst and HCOOK fuel, achieving 21.01 mW/mgPd. Still, constant current discharge with PdC showed an energy generation efficiency of 14% with HCOOH over 3% with HCOOK caused by lower potassium ion conductivity and its permeability through the proton exchange membrane. The faradic efficiency of conversion in the cell is equal to the overall energy efficiency and makes the cell self-sufficient.

Transcriptomic Characterization of Dying Hair Cells in the Avian Cochlea

Highlights: • New in vivo model to study cochlear hair cell death • Cochlear hair cells die rapidly and in synchronous fashion • Single cell RNA-seq reveals two stages of hair cell demise • Major types of dying cochlear hair cells express different sets of genes Summary: Sensory hair cells are prone to apoptosis caused by various drugs including aminoglycoside antibiotics. In mammals, this vulnerability results in permanent hearing loss because lost hair cells are not regenerated. Conversely, hair cells regenerate in birds, making the avian inner ear an exquisite model for studying ototoxicity and regeneration. Here we used single-cell RNAsequencing and trajectory analysis on control and dying hair cells after aminoglycoside treatment. Interestingly, the two major subtypes of avian cochlear hair cells, tall and short hair cells, responded differently. Dying short hair cells showed a noticeable transient upregulation of many more genes than tall hair cells. The most prominent gene group identified was associated with potassium ion conductances, suggesting distinct physiological differences. Moreover, the dynamic characterization of >15,000 genes expressed in tall and short avian hair cells during their apoptotic demise comprises a resource for further investigations towards mammalian hair cell protection and hair cell regeneration.

Renal Tubule Nedd4-2 Deficiency Stimulates Kir4.1/Kir5.1 and Thiazide-Sensitive NaCl Cotransporter in Distal Convoluted Tubule.

The potassium channel Kir4.1 forms the Kir4.1/Kir5.1 heterotetramer in the basolateral membrane of the distal convoluted tubule (DCT) and plays an important role in the regulation of the thiazide-sensitive NaCl cotransporter (NCC). Kidney-specific deletion of the ubiquitin ligase Nedd4-2 increases expression of NCC, and coexpression of Nedd4-2 inhibits Kir4.1/Kir5.1 in vitro. Whether Nedd4-2 regulates NCC expression in part by regulating Kir4.1/Kir5.1 channel activity in the DCT is unknown. We used electrophysiology studies, immunoblotting, immunostaining, and renal clearance to examine Kir4.1/Kir5.1 activity in the DCT and NCC expression/activity in wild-type mice and mice with kidney-specific knockout of Nedd4-2, Kir4.1, or both. Deletion of Nedd4-2 increased the activity/expression of Kir4.1 in the DCT and also, hyperpolarized the DCT membrane. Expression of phosphorylated NCC/total NCC and thiazide-induced natriuresis were significantly increased in the Nedd4-2 knockout mice, but these mice were normokalemic. Double-knockout mice lacking both Kir4.1/Kir5.1 and Nedd4-2 in the kidney exhibited increased expression of the epithelial sodium channel α-subunit, largely abolished basolateral potassium ion conductance (to a degree similar to that of kidney-specific Kir4.1 knockout mice), and depolarization of the DCT membrane. Compared with wild-type mice, the double-knockout mice displayed inhibited expression of phosphorylated NCC and total NCC and had significantly blunted thiazide-induced natriuresis as well as renal potassium wasting and hypokalemia. However, NCC expression/activity was higher in the double-knockout mice than in Kir4.1 knockout mice. Nedd4-2 regulates Kir4.1/Kir5.1 expression/activity in the DCT and modulates NCC expression by Kir4.1-dependent and Kir4.1-independent mechanisms. Basolateral Kir4.1/Kir5.1 activity in the DCT partially accounts for the stimulation of NCC activity/expression induced by deletion of Nedd4-2.

Atomistic basis of opening and conduction in mammalian inward rectifier potassium (Kir2.2) channels.

Potassium ion conduction through open potassium channels is essential to control of membrane potentials in all cells. To elucidate the open conformation and hence the mechanism of K+ ion conduction in the classic inward rectifier Kir2.2, we introduced a negative charge (G178D) at the crossing point of the inner helix bundle, the location of ligand-dependent gating. This "forced open" mutation generated channels that were active even in the complete absence of phosphatidylinositol-4,5-bisphosphate (PIP2), an otherwise essential ligand for Kir channel opening. Crystal structures were obtained at a resolution of 3.6 Å without PIP2 bound, or 2.8 Å in complex with PIP2. The latter revealed a slight widening at the helix bundle crossing (HBC) through backbone movement. MD simulations showed that subsequent spontaneous wetting of the pore through the HBC gate region allowed K+ ion movement across the HBC and conduction through the channel. Further simulations reveal atomistic details of the opening process and highlight the role of pore-lining acidic residues in K+ conduction through Kir2 channels.

Antioxidant and antimicrobial efficacy of a biflavonoid, amentoflavone from Nandina domestica in vitro and in minced chicken meat and apple juice food models

A biflavonoid, amentoflavone isolated from Nandina domestica and characterized by NMR spectral-data analyses was assessed for its antioxidant, and antibacterial potential in vitro and in food-model systems. Amentoflavone exhibited potent antioxidant ability (19.21–75.52%) on scavenging DPPH, ABTS, superoxide, and hydroxyl radicals. Fluorescent images confirmed bacterial membrane depolarization of both the tested pathogens Staphylococcus aureus and Escherichia coli, with a significant reduction in cell viabilities at their respective MIC of 62.5 and 125 µg/mL. Increasing rates of membrane permeability observed in 260 nm-absorbing material, potassium ion, extracellular ATP, and relative electrical conductivity assays confirmed antibacterial mechanistic role of amentoflavone as also evidenced by microscopic studies of SEM and TEM. There was a marked inhibitory effect of amentoflavone with a significant reduction in cell counts of S. aureus and E. coli in minced chicken and apple juice at 4 °C, thus suggesting its nutritional enhancing efficacy as a natural antioxidant and antimicrobial agent.

Vibrational Spectra and Electrophysical Properties of Li0.2K0.8–yMg1–xSc(Lu)1 + x(MoO4)3 (0 ≤ х ≤ 0.5; 0 ≤ y ≤ 0.3) Solid Solutions with a NASICON Structure

The phase relationships in the subsolidus region of the Li2MoO4–K2MoO4–MgMoO4–Sc2(MoO4)3–Lu2(MoO4)3 system have been studied by X-ray crystallography and vibrational spectroscopy. A phase of variable composition Li0.2K0.8–yMg1–xSc(Lu)1 + x(MoO4)3 (0 ≤ х ≤ 0.5; 0 ≤ y ≤ 0.3) with a NASICON structure (space group R $$\bar 3c$$ ) was synthesized by the ceramic route. The phase exhibits high conductivity, which makes it a candidate for use as a solid electrolyte with lithium and potassium ion conductivity. The unit cell parameters were determined, and IR and Raman spectra were interpreted.

Ion Permeation in Potassium Channels Involves Direct Coulomb Knock-On between Ions

Potassium channels are essential elements in almost all cell types. They are, at the same time, highly selective for potassium and conduct potassium ions across membranes with great efficiency. By analyzing more than 1,300 potassium permeation events recorded in Computational Electrophysiology (CompEl) [1] atomistic molecular dynamics simulations under physiological voltages, we observed that Coulomb repulsion between neighboring potassium ions in the selectivity filter is the key to high-efficiency potassium flux. This is in contrast to previous models which assumed that alternate occupancy of the selectivity filter binding sites with potassium and water underpins potassium conduction. The mechanism we observed relies on the formation of ion pairs in the selectivity filter. These ion pairs form over very broad potassium concentration ranges in our simulations from 10-400 mM. Reinvestigation of crystallographic data on several potassium channels showed that the crystal data are consistent with ions occupying adjacent filter binding sites. The rate of potassium throughput across the filter recorded in our simulations depends on the rate with which incoming ions arrive at the filter. Taken together, the mechanism we propose therefore explains the efficiency, diffusion control, and linear concentration dependence of potassium ion conduction across potassium channels in a simple new model.[1] C. Kutzner et al., Biophys. J. 101, 809-817 (2011).

Bombardment induced ion transport—Part II. Experimental potassium ion conductivities in borosilicate glass

A new experimental approach for measuring the ionic conductivity of solid materials is proposed. The experiment is based on bombarding an ion conducting sample with an alkali ion beam. This generates a well defined surface potential which in turn causes ion transport in the material. The ion transport is measured at the back side of the sample. The viability of the concept is demonstrated by measuring the temperature dependence of the potassium ion conductivity of a potassium borosilicate glass. The activation energy for the potassium transport is 1.04 eV ± 0.06 eV. For comparison, conductivity data obtained by impedance spectroscopy are presented, which support the bombardment induced data.

Conduction mechanism in the low-temperature phase of KAlO2

The crystal structure of the low-temperature phase of KAlO2 has been studied by neutron diffraction, and its structural parameters have been refined with FullProf software. The TOPOS software package has been used to construct an ionic conduction map and analyze possible potassium ion migration paths. A geometric analysis in conjunction with a qualitative analysis of migration energies lends support to the assumption that low-temperature KAlO2 has one-dimensional potassium ion conduction.

Ab‐initio Structure Determination of the New Ion Conductor K2Al2O3F2 from Powder Diffraction Data

AbstractThe crystal structure of K2Al2O3F2, prepared at 800 °C by ceramic methods, was determined from conventional laboratory X‐ray powder diffraction data. The compound crystallizes in the monoclinic space group C2/m (No. 12) with a = 11.21675(8), b = 8.16351(6), c = 6.12301(5) Å β = 88.8108(6) ° and Z = 4. Unit cell and space group suggestions were found by using the TOPAS program. Starting positional parameters for potassium and aluminum atoms were obtained from 548 reflections by the methods implemented in the FOX program. Oxygen and fluorine atom positions were determined by structural considerations. The structure was refined using the fundamental parameter approach of TOPAS, which gave the final residuals (%) RBragg = 1.6 and Rwp = 4.6. The crystal structure consists of individual layers of oxygen connected AlO3F tetrahedral groups with the fluorine atoms separating the layers. Empirical energy calculations agree with the crystal structure refinements and suggest no or little oxygen–fluorine exchange. Between and perpendicular to the sheets, the potassium ion can move without steric hindrance. Conductivity measurements from room temperature to 300 °C show decent potassium ion conductivity.

Immunomodulation of voltage-dependent K+ channels in macrophages: molecular and biophysical consequences

Voltage-dependent potassium (Kv) channels play a pivotal role in the modulation of macrophage physiology. Macrophages are professional antigen-presenting cells and produce inflammatory and immunoactive substances that modulate the immune response. Blockage of Kv channels by specific antagonists decreases macrophage cytokine production and inhibits proliferation. Numerous pharmacological agents exert their effects on specific target cells by modifying the activity of their plasma membrane ion channels. Investigation of the mechanisms involved in the regulation of potassium ion conduction is, therefore, essential to the understanding of potassium channel functions in the immune response to infection and inflammation. Here, we demonstrate that the biophysical properties of voltage-dependent K+ currents are modified upon activation or immunosuppression in macrophages. This regulation is in accordance with changes in the molecular characteristics of the heterotetrameric Kv1.3/Kv1.5 channels, which generate the main Kv in macrophages. An increase in K+ current amplitude in lipopolysaccharide-activated macrophages is characterized by a faster C-type inactivation, a greater percentage of cumulative inactivation, and a more effective margatoxin (MgTx) inhibition than control cells. These biophysical parameters are related to an increase in Kv1.3 subunits in the Kv1.3/Kv1.5 hybrid channel. In contrast, dexamethasone decreased the C-type inactivation, the cumulative inactivation, and the sensitivity to MgTx concomitantly with a decrease in Kv1.3 expression. Neither of these treatments apparently altered the expression of Kv1.5. Our results demonstrate that the immunomodulation of macrophages triggers molecular and biophysical consequences in Kv1.3/Kv1.5 hybrid channels by altering the subunit stoichiometry.

Immunomodulation of Voltage-Dependent K+ Channels in Macrophages: Molecular and Biophysical Consequences

Voltage-dependent potassium channels play a pivotal role in the modulation of macrophage physiology. Macrophages are professional antigen-presenting cells and produce inflammatory and immunoactive substances that modulate the immune response. Blockage of Kv channels by specific antagonists decreases macrophage cytokine production and inhibits proliferation. Numerous pharmacological agents exert their effects on specific target cells by modifying the activity of their plasma membrane ion channels. Investigation of the mechanisms involved in the regulation of potassium ion conduction is, therefore, essential to the understanding of potassium channel functions in the immune response to infection and inflammation. Here we demonstrate that the biophysical properties of voltage-dependent K+ currents are modified upon activation or immunosuppression in macrophages. This regulation is in accordance with changes in the molecular characteristics of the heterotetrameric Kv1.3/Kv1.5 channels, which generate the main Kv in macrophages. An increase in K+ current amplitude in LPS-activated macrophages is characterized by a faster C-type inactivation, a greater percentage of cumulative inactivation and a more effective Margatoxin inhibition than control cells. These biophysical parameters are related to an increase in Kv1.3 subunits in the Kv1.3/Kv1.5 hybrid channel. In contrast, DEX decreased the C-type, the cumulative inactivation and the sensitivity to Margatoxin concomitantly with a decrease in Kv1.3 expression. Neither of these treatments apparently altered the expression of Kv1.5. Our results demonstrate that the immunomodulation of macrophages triggers molecular and biophysical consequences in Kv1.3/Kv1.5 hybrid channels by altering the subunit stoichiometry.

Synthesis, Structural Characterization, and Cation Transport of Tripotassium Pentabismuth Arsenate K3Bi5(AsO4)6

During the exploration of the K2O-Bi2O 3 -As2O5 system, single crystals of a new arsenate of trivalent bismuth, K3Bi5(AsO4) 6, were isolated by solid state reaction at 600°C. The title compound crystallizes in the monoclinic system, space group C2/c (N°15) with a = 18.257(2) Å, b = 7.260(1) Å, c = 20.130(4) Å, β = 119.86(1)°, and Z = 4. Its structure consists of a three-dimensional framework made up of AsO4 tetrahedra and BiO6 and BiO7 polyhedra sharing edges and corners, delimiting cavities wherein K+ ions reside. This compound exhibits a potassium ion conductivity but with rather low conductivity value.

K+ ion conducting properties in the R2O3-KNO3 (R: Rare earths) solid solution series

A new type of polycrystalline potassium ion conducting solid electrolyte doped with potassium nitrite as the starting material, was developed. Since cubic rare earth oxides hold reasonably enough interstitial space for bulky K+ ion migration in the crystal lattice, an extraordinary high K+ ion conductivity was successfully achieved by forming a polycrystalline (1 − x)R2O3-xKNO3 solid solution, which was realized by doping KNO2 as the KNO3 state into the interstitial site of cubic rare earth oxide crystal lattice. The potassium ion conductivity of the (1 − x)R2O3-xKNO3 (R: rare earths) solid solution linearly increased with expanding the R2O3 crystal lattice and the highest K+ ion conductivity was obtained for the 0.653Gd2O3-0.347KNO3 solid solution, which is three orders of magnitude higher than that of a well-known polycrystalline K+ ion conducting K2SO4 solid and the value exceeds that in the ab conducting plane of a K+-β ”-Al2O3 single crystal.

Drugs effects on ventricular repolarization: A critical evaluation of the strengths and weaknesses of current methodologies and regulatory practices

A growing number of drugs and drug combinations inhibit cardiac potassium ion conductance and ventricular repolarization, and increase cardiac APD, QT interval, and risk of potentially fatal TdP. The past decade has seen an explosion of research advances into the mechanism of action underpinning these observations, and an unprecedented level of collaboration between academia, industry, and regulatory authorities to define effective strategies for accurate prediction of increased TdP risk (if any) in humans, based upon nonclinical and/or clinical endpoints. Because the incidence of TdP is so very low, even for drugs for which the association is known, the risk can only be assessed based upon surrogate markers (signals) in in vitro and in vivo non-clinical studies as well as in clinical trials. In this article, we review both the strengths and weaknesses of current methodologies and regulatory practices for assessment of TdP risk for pharmaceuticals.

Potassium ion conductivity of KNO 2 mixed oxides

Two types of polycrystalline solids, KNO 2 mixed Gd 2O 3 and KNO 2 mixed Nb 2O 5, were prepared. In the case for KNO 2 mixed Gd 2O 3, a remarkable enhancement in K + ion conductivity was successfully realized by interstitially dissolved KNO 3 formed during the preparation process in the C-type cubic Gd 2O 3 crystal lattice. In contrast, the conductivity of KNO 2 mixed Nb 2O 5 was more than three orders of magnitude below that of the Gd 2O 3–KNO 3 solid solution due to the KNO 3 decomposition during the preparation procedure. The K + ion conductivity of the polycrystalline Gd 2O 3–KNO 3 solid solution is more than three orders of magnitude higher than that of the K + ion conducting K 2SO 4 polycrystal and the value exceeds that of K +-β′′-alumina single crystal in ab plane, realizing the highest ion conductivity among the K + ion conducting solid electrolyte series. The superior ion conducting properties are realized by forming the interstitially KNO 3 dissolved Gd 2O 3 solid solution, without decomposing the mixed salt with K +.