The Contribution of Changes of Intracelluar Potassium Ion Concentration to the Kinetics of Voltage-Dependent Potassium Current

2019 ◽  
Vol 13 (3) ◽  
pp. 233-242
Author(s):  
V. A. Semenov ◽  
D. V. Amakhin ◽  
N. P. Veselkin
Keyword(s):  
Potassium Current ◽  
Potassium Ion ◽  
Ion Concentration ◽  
Voltage Dependent ◽  
Kinetics Of

scholarly journals DNA Aptamer Functionalized Hydrogels for Interferometric Fiber-Optic Based Continuous Monitoring of Potassium Ions

Biosensors ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 266
Author(s):  
Nataša Žuržul ◽  
Bjørn Torger Stokke
Keyword(s):  
Conformational Transition ◽  
Polymer Network ◽  
Potassium Ion ◽  
Ion Concentration ◽  
Dna Aptamer ◽  
Blood Levels ◽  
Label Free ◽  
Practical Applications ◽  
Hydrogel Matrix ◽  
K Concentration

In the present paper, we describe a potassium sensor based on DNA-aptamer functionalized hydrogel, that is capable of continuous label-free potassium ion (K+) monitoring with potential for in situ application. A hydrogel attached to the end of an optical fiber is designed with di-oligonucleotides grafted to the polymer network that may serve as network junctions in addition to the covalent crosslinks. Specific affinity toward K+ is based on exploiting a particular aptamer that exhibits conformational transition from single-stranded DNA to G-quadruplex formed by the di-oligonucleotide in the presence of K+. Integration of this aptamer into the hydrogel transforms the K+ specific conformational transition to a K+ concentration dependent deswelling of the hydrogel. High-resolution interferometry monitors changes in extent of swelling at 1 Hz and 2 nm resolution for the hydrogel matrix of 50 µm. The developed hydrogel-based biosensor displayed high selectivity for K+ ions in the concentration range up to 10 mM, in the presence of physiological concentrations of Na+. Additionally, the concentration dependent and selective K+ detection demonstrated in the artificial blood buffer environment, both at room and physiological temperatures, suggests substantial potential for practical applications such as monitoring of potassium ion concentration in blood levels in intensive care medicine.

Automated Fluoride Ion Determination

1977 ◽  
Vol 14 (1-6) ◽  
pp. 269-274 ◽  
Author(s):  
David C. Cowell
Keyword(s):  
Continuous Flow ◽  
Ion Concentration ◽  
Fluoride Ion ◽  
Selective Electrode ◽  
Automated Method ◽  
Electrode Response ◽  
Kinetics Of ◽  
Fluoride Ion Selective Electrode ◽  
Flow Techniques

An automated method is described, using standard continuous flow techniques, for the determination of urine fluoride ion concentration using a fluoride ion selective electrode. It is shown that the kinetics of the electrode response to changes in fluoride ion can be used for the accurate measurement of fluoride ion concentration in urine, and that equilibration of the electrode response is not a prerequisite for the measurement of fluoride ion. Recovery experiments are in the range 83 to 90%; in-batch precision is between 0·9 and 1·6% and carryover 2·5% or less.

Kinetics of the Variation in the Magnetic Impurity Ion Concentration in Pb1–x–ySn x V y Te Alloys upon Doping

2018 ◽  
Vol 52 (7) ◽  
pp. 828-835
Author(s):  
E. P. Skipetrov ◽  
N. S. Konstantinov ◽  
L. A. Skipetrova ◽  
A. V. Knotko ◽  
V. E. Slynko
Keyword(s):  
Magnetic Impurity ◽  
Ion Concentration ◽  
Impurity Ion ◽  
Kinetics Of

scholarly journals Structure–Function Relations of the First and Fourth Predicted Extracellular Linkers of the Type IIa Na+/Pi Cotransporter

2004 ◽  
Vol 124 (5) ◽  
pp. 475-488 ◽  
Author(s):  
Colin Ehnes ◽  
Ian C. Forster ◽  
Katja Kohler ◽  
Andrea Bacconi ◽  
Gerti Stange ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Reaction Rates ◽  
Transport Pathway ◽  
Extracellular Medium ◽  
Voltage Range ◽  
Substituted Cysteine Accessibility ◽  
Voltage Dependent ◽  
Opposite Behavior ◽  
Rate Limiting ◽  
Kinetics Of

The putative first intracellular and third extracellular linkers are known to play important roles in defining the transport properties of the type IIa Na+-coupled phosphate cotransporter (Kohler, K., I.C. Forster, G. Stange, J. Biber, and H. Murer. 2002b. J. Gen. Physiol. 120:693–705). To investigate whether other stretches that link predicted transmembrane domains are also involved, the substituted cysteine accessibility method (SCAM) was applied to sites in the predicted first and fourth extracellular linkers (ECL-1 and ECL-4). Mutants based on the wild-type (WT) backbone, with substituted novel cysteines, were expressed in Xenopus oocytes, and their function was assayed by isotope uptake and electrophysiology. Functionally important sites were identified in both linkers by exposing cells to membrane permeant and impermeant methanethiosulfonate (MTS) reagents. The cysteine modification reaction rates for sites in ECL-1 were faster than those in ECL-4, which suggested that the latter were less accessible from the extracellular medium. Generally, a finite cotransport activity remained at the end of the modification reaction. The change in activity was due to altered voltage-dependent kinetics of the Pi-dependent current. For example, cys substitution at Gly-134 in ECL-1 resulted in rate-limiting, voltage-independent cotransport activity for V ≤ −80 mV, whereas the WT exhibited a linear voltage dependency. After cys modification, this mutant displayed a supralinear voltage dependency in the same voltage range. The opposite behavior was documented for cys substitution at Met-533 in ECL-4. Modification of cysteines at two other sites in ECL-1 (Ile-136 and Phe-137) also resulted in supralinear voltage dependencies for hyperpolarizing potentials. Taken together, these findings suggest that ECL-1 and ECL-4 may not directly form part of the transport pathway, but specific sites in these linkers can interact directly or indirectly with parts of NaPi-IIa that undergo voltage-dependent conformational changes and thereby influence the voltage dependency of cotransport.

scholarly journals KCNE1 and KCNE3 modulate KCNQ1 channels by affecting different gating transitions

2017 ◽  
Vol 114 (35) ◽  
pp. E7367-E7376 ◽  
Author(s):  
Rene Barro-Soria ◽  
Rosamary Ramentol ◽  
Sara I. Liin ◽  
Marta E. Perez ◽  
Robert S. Kass ◽  
...  
Keyword(s):  
Action Potentials ◽  
Potassium Current ◽  
Voltage Sensor ◽  
Α Subunit ◽  
Voltage Range ◽  
Gate Opening ◽  
Cardiac Action ◽  
Repolarization Phase ◽  
Voltage Dependent ◽  
Salt Secretion

KCNE β-subunits assemble with and modulate the properties of voltage-gated K+ channels. In the heart, KCNE1 associates with the α-subunit KCNQ1 to generate the slowly activating, voltage-dependent potassium current (IKs) in the heart that controls the repolarization phase of cardiac action potentials. By contrast, in epithelial cells from the colon, stomach, and kidney, KCNE3 coassembles with KCNQ1 to form K+ channels that are voltage-independent K+ channels in the physiological voltage range and important for controlling water and salt secretion and absorption. How KCNE1 and KCNE3 subunits modify KCNQ1 channel gating so differently is largely unknown. Here, we use voltage clamp fluorometry to determine how KCNE1 and KCNE3 affect the voltage sensor and the gate of KCNQ1. By separating S4 movement and gate opening by mutations or phosphatidylinositol 4,5-bisphosphate depletion, we show that KCNE1 affects both the S4 movement and the gate, whereas KCNE3 affects the S4 movement and only affects the gate in KCNQ1 if an intact S4-to-gate coupling is present. Further, we show that a triple mutation in the middle of the transmembrane (TM) segment of KCNE3 introduces KCNE1-like effects on the second S4 movement and the gate. In addition, we show that differences in two residues at the external end of the KCNE TM segments underlie differences in the effects of the different KCNEs on the first S4 movement and the voltage sensor-to-gate coupling.

scholarly journals In Vivo Neocortical [K]o Modulation by Targeted Stimulation of Astrocytes

2021 ◽  
Vol 22 (16) ◽  
pp. 8658
Author(s):  
Azin EbrahimAmini ◽  
Shanthini Mylvaganam ◽  
Paolo Bazzigaluppi ◽  
Mohamad Khazaei ◽  
Alexander Velumian ◽  
...  
Keyword(s):  
Nervous System ◽  
Membrane Potential ◽  
Potassium Ion ◽  
Ion Concentration ◽  
Extracellular Potassium ◽  
Spreading Depolarization ◽  
Potential Tool ◽  
Stimulation Of

A normally functioning nervous system requires normal extracellular potassium ion concentration ([K]o). Throughout the nervous system, several processes, including those of an astrocytic nature, are involved in [K]o regulation. In this study we investigated the effect of astrocytic photostimulation on [K]o. We hypothesized that in vivo photostimulation of eNpHR-expressing astrocytes leads to a decreased [K]o. Using optogenetic and electrophysiological techniques we showed that stimulation of eNpHR-expressing astrocytes resulted in a significantly decreased resting [K]o and evoked K responses. The amplitude of the concomitant spreading depolarization-like events also decreased. Our results imply that astrocytic membrane potential modification could be a potential tool for adjusting the [K]o.

scholarly journals PECULIARITIES OF PROCESS KINETICS OF FORMING CATHODE MATERIAL OF COMPOSITION LiХLaYMn1-YO2(C60)n FOR LITHIUM – ION BATTERY

2019 ◽  
Vol 62 (11) ◽  
pp. 99-105
Author(s):  
Ekaterina S. Guseva ◽  
Svetlana S. Popova
Keyword(s):  
Lithium Ion ◽  
Ion Concentration ◽  
Redox Activity ◽  
Solution Temperature ◽  
Stable Phase ◽  
Potential Range ◽  
Unusual Structure ◽  
Kinetics Of ◽  
New Phase ◽  
Mno2 Electrode

The effect of the magnitude of cathodic polarization and the temperature of a solution of lanthanum salicylate on the kinetics of the formation of elecrode LаyMn1-yO2 has been described. It has been established that two phases are formed on the electrode: the phase of the solid solution of the introduced lanthanum in MnO2 at potentials negative -2.5V turns into a new phase LаyMn1-yO2; last on the curve Eб/т-Ек the potential delay characteristic of the process of forming a new phase with an independent crystal lattice corresponds. Thus, to obtain a time-stable phase of the introduction of lanthanum into the structure of the electrode LаyMn1-yO2 the potential range from –2.9 V to –2.5 V can be recommended. The influence of the solution temperature on the kinetic characteristics of the process is ambiguous and is associated with a change in the degree of disorder in the structure of the forming phase at the boundary MnO2 electrode/solution (La3+), which hampers diffusion of ions La3+ into the electrode and leads to a decrease in ion concentration La3+, involved in the act of electrochemical introduction and, accordingly, to a decrease in the value of i (0). At temperatures above 10 °С the structure is stabilized and the characteristics (k, i (0)) increase. The composition of the formed phases is determined LixMnO2, LayMn1-yO2, LixLayMn1-yO2, current-free chronopotentiometry method calculated on the basis of equilibrium potentials Ep of these phases with pulsed galvanostatic polarization mode. Stability formed in the structure of MnO2 electrode chemical compounds of lanthanum was established. The activating effect of fullerene additives С60 composed of modified lanthanum LаyMn1-yO2 electrodes due to the high redox activity and the unusual structure of the molecules С60. Data on the effect of modified MnO2 electrodes on their potentials in an open circuit and during polarization in the working solution are in good agreement in terms of increasing the capacity of lithium with the results of cycling LiхMnO2, LiхLayMn1-yO2, LiхLayMn1-yO2-σ(C60)n in galvanostatic mode. The results of galvanostatic cycling showed that the discharge capacity of the electrodes increases in the series: LixMnO2 > LixLayMn1-yO2 > LiхLayMn1-yO2-σ(C60)n. With the help of cyclic chronovamperometry a good reversibility for LiхLayMn1-yO2-σ(C60)n electrode was established.

scholarly journals Membrane voltage-dependent activation of the flagellar protein export engine

2020 ◽  
Author(s):  
Tohru Minamino ◽  
Yusuke V. Morimoto ◽  
Miki Kinoshita ◽  
Keiichi Namba
Keyword(s):  
Electric Potential ◽  
Cytoplasmic Membrane ◽  
Protein Export ◽  
Ion Concentration ◽  
Activation Mechanism ◽  
Concentration Difference ◽  
Voltage Gated ◽  
Voltage Dependent ◽  
Flagellar Protein ◽  
External Ph

AbstractIon motive force (IMF) consists of the electric potential difference (ΔΨ) and the ion concentration difference (ΔpI) across the cytoplasmic membrane. The flagellar protein export machinery is an ion/protein antiporter utilizing IMF to drive ion-coupled protein export, but it remains unknown how. Here, we report a ΔΨ-dependent activation mechanism of the transmembrane export gate complex. Depletions of both H+ and Na+ gradients nearly diminished flagellar protein export in the absence of the cytoplasmic ATPase complex, but an increase in ΔΨ by an upward shift of external pH from 7.5 to 8.5 dramatically recovered it. An increase in the cytoplasmic level of export substrates and gain-of-function mutations in FlhA enhanced protein export at external pH 7.5 in the absence of Na+ in a similar manner to ΔΨ increase. We propose that the export gate complex has a voltage-gated mechanism to activate the ion/protein antiporter of the flagellar protein export engine.

Extracellular ATP selectively modulates a high-voltage-activated calcium conductance in salivary gland cells of the leech Haementeria ghilianii

1993 ◽  
Vol 181 (1) ◽  
pp. 313-319
Author(s):  
WA Wuttke ◽  
MS Berry
Keyword(s):  
Salivary Gland ◽  
High Voltage ◽  
Cyclic Gmp ◽  
Cyclic Nucleotides ◽  
Extracellular Atp ◽  
Salivary Gland Cells ◽  
Selective Modulation ◽  
Voltage Dependent ◽  
Kinetics Of ◽  
Higher Doses

Extracellular ATP appears to have a widespread role as a neurotransmitter or neuromodulator in mammals (Gordon, 1986; Burnstock, 1990), but little is known about any similar functions in invertebrates. During studies of the effects of cyclic nucleotides on electrically excitable salivary cells of the leech, we found that cyclic GMP produced a rapid (less than 1min) reduction of spike duration, suggesting an extracellular effect (Wuttke and Berry, 1991). We now show that micromolar concentrations of ATP (and higher doses of other nucleotides) also reduce spike duration, and that this is caused by depression of a specific voltage-dependent Ca2+ conductance. Selective modulation of Ca2+ current by external ATP has rarely been found, and the effect is also unusual because it changes the kinetics of inactivation rather than those of activation.

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