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Mikrochimica Acta Mar 2022A microfluidic paper-based thermoplastic electrode (TPE) array has been developed for point-of-care detection of Na and K ions using a custom-made portable...
A microfluidic paper-based thermoplastic electrode (TPE) array has been developed for point-of-care detection of Na and K ions using a custom-made portable potentiometer. TPEs were fabricated using polystyrene as the binder and two different types of graphite to compare the electrode performance. The newly designed TPE array embedded in a polymethyl methacrylate chip consists of two working electrodes modified with carbon black nanomaterial and an ion-selective membrane, and an all-solid-state reference electrode modified with Ag/AgCl ink and poly(butyl methacrylate-co-methyl methacrylate) membrane via drop-casting. Ion-selective membrane compositions and conditioning steps were optimized. Under optimized conditions, ion-selective TPEs demonstrated fast response time (4 s) and good stability. The TPE array demonstrated a Nernstian behavior for K with a sensitivity of 59.2 ± 0.2 mV decade and near-Nernstian response for Na with a sensitivity of 54.0 ± 1.1 mV decade in the range 10 - 10 M and 1 - 10 M, respectively. The detection limits were 1 × 10 M and 1 × 10 M for K and Na, respectively. In addition, a K and Na selective microfluidic paper-based analytical device (µPAD) was applied to artificial serum analysis and found in good agreement with average recoveries of 101.3% and 99.7%, respectively, suggesting that the developed ISE array is suitable for detection of sodium and potassium in complex matrix.
Topics: Ion-Selective Electrodes; Ions; Microfluidics; Point-of-Care Systems; Potassium; Sodium
PubMed: 35322308
DOI: 10.1007/s00604-022-05264-y -
Analytical Methods : Advancing Methods... Aug 2021A fast, simple and inexpensive potentiometric method has been developed for the determination of the major ions potassium and nitrate in nutrient solutions, by means of...
A fast, simple and inexpensive potentiometric method has been developed for the determination of the major ions potassium and nitrate in nutrient solutions, by means of ion-selective electrodes (ISEs) based on plasticized polyvinyl membranes containing an ion-exchanger. Tridodecylmethylammonium chloride (TDMACl) and potassium tetrakis(4-chlorophenyl)borate (KTClPB) were used as ion-exchangers for the nitrate and potassium electrodes, respectively. Electrode membranes built with different plasticizers, bis-[2-ethylhexyl]-sebacate (DOS), tricresyl phosphate (TCP) and 2-nitrophenyloctyl ether (NPOE), were tested, and NPOE was selected. The electrodes were calibrated over both wide and narrow concentration ranges and residual analysis was made. Based on the results of these calibrations, the method of standard addition was developed and found to be suitable for the simultaneous determination of potassium and nitrate in nutrient solutions. A large group of samples taken from different stages of hydroponic crops was analysed. Several approaches recommended for statistical comparisons of the results obtained by potentiometric and by reference methods were tested, obtaining satisfactory results. The potentiometric methodology developed is promising for monitoring the concentration of these essential nutrients in nutrient solutions.
Topics: Ion-Selective Electrodes; Nitrates; Nutrients; Potassium; Potentiometry
PubMed: 34269358
DOI: 10.1039/d1ay00956g -
Current Opinion in Nephrology and... Mar 2021This review focuses on recent efforts in identifying with-no-lysine kinase 4 (WNK4) as a physiological intracellular chloride sensor and exploring regulators of... (Review)
Review
PURPOSE OF REVIEW
This review focuses on recent efforts in identifying with-no-lysine kinase 4 (WNK4) as a physiological intracellular chloride sensor and exploring regulators of intracellular chloride concentration ([Cl-]i) in the distal convoluted tubule (DCT).
RECENT FINDINGS
The discovery of WNK1's chloride-binding site provides the mechanistic details of the chloride-sensing regulation of WNK kinases. The subsequent in-vitro studies reveal that the chloride sensitivities of WNK kinases were variable. Because of its highest chloride sensitivity and dominant expression, WNK4 emerges as the leading candidate of the chloride sensor in DCT. The presentation of hypertension and increased sodium-chloride cotransporter (NCC) activity in chloride-insensitive WNK4 mice proved that WNK4 is inhibitable by physiological [Cl-]i in DCT. The chloride-mediated WNK4 regulation is responsible for hypokalemia-induced NCC activation but unnecessary for hyperkalemia-induced NCC deactivation. This chloride-sensing mechanism requires basolateral potassium and chloride channels or cotransporters, including Kir4.1/5.1, ClC-Kb, and possibly KCCs, to modulate [Cl-]i in response to the changes of plasma potassium.
SUMMARY
WNK4 is both a master NCC stimulator and an in-vivo chloride sensor in DCT. The understanding of chloride-mediated regulation of WNK4 explains the inverse relationship between dietary potassium intake and NCC activity.
Topics: Animals; Chlorides; Humans; Kidney Tubules, Distal; Mice; Potassium; Protein Serine-Threonine Kinases; Sodium Chloride Symporters
PubMed: 33394730
DOI: 10.1097/MNH.0000000000000683 -
Progress in Biophysics and Molecular... 2022This retrospective traces the hypothesis of ion channels from an early statement in a 1970 essay in this journal (Hille, B., 1970, Prog. Biophys. Mol. Biol. 21, 1-32) to... (Review)
Review
This retrospective traces the hypothesis of ion channels from an early statement in a 1970 essay in this journal (Hille, B., 1970, Prog. Biophys. Mol. Biol. 21, 1-32) to its realization today in biophysical, molecular, biochemical, and structural terms. The Na and K channels of the action potential have been isolated, reconstituted, cloned, mutated, and expressed. They are conformationally flexible, multi-pass glycosylated membrane proteins. Refined atomic structures of several conformational states are known. The discoveries over this half century history illustrate the growth of a field from initial ideas to a mature discipline of biology, physiology, and biomedical science.
Topics: Ion Channels; Ions; Potassium; Retrospective Studies; Sodium
PubMed: 34856230
DOI: 10.1016/j.pbiomolbio.2021.11.003 -
Analytical Chemistry Oct 2023G-quadruplex (G4) DNA is found in oncogene promoters and human telomeres and is an attractive anticancer target. Stable G4 structures form in guanine-rich sequences in...
G-quadruplex (G4) DNA is found in oncogene promoters and human telomeres and is an attractive anticancer target. Stable G4 structures form in guanine-rich sequences in the presence of metal cations and can stabilize further with specific ligand adduction. To explore the preservation and stability of this secondary structure with mass spectrometry, gas-phase collision-induced dissociation kinetics of G4-like and non-G4-like ion structures were determined in a linear quadrupole ion trap. This study focused on a sequence from the promoter of the oncogene, MycG4, and a mutant non-G4-forming sequence, MycNonG4. At relatively high ion activation energies, the backbone fragmentation patterns of the MycG4 and MycNonG4 are similar, while potassium ion-stabilized G4-folded [MycG4 + 2K-7H] and counterpart [MycG4-5H] ions are essentially indistinguishable, indicating that high-energy fragmentation is not sensitive to the G4 structure. At low energies, the backbone fragmentation patterns of MycG4 and MycNonG4 are significantly different. For MycG4, fragmentation over time differed significantly between the potassium-bound and free structures, reflecting the preservation of the G4 structure in the gas phase. Kinetic measurements revealed the [MycG4 + 2K-7H] ions to fragment two to three times more slowly than the [MycG4-5H]. Results for the control MycNonG4 indicated that the phenomena noted for [MycG4 + 2K-7H] ions are specific to G4-folding. Therefore, our data show that gentle activation conditions can lead to fragmentation behavior that is sensitive to G-quadruplex structure, revealing differences in kinetic stabilities of isomeric structures as well as the regions of the sequence that are directly involved in forming these structures.
Topics: Humans; DNA; G-Quadruplexes; Promoter Regions, Genetic; Ions; Potassium
PubMed: 37774231
DOI: 10.1021/acs.analchem.3c03143 -
International Journal of Molecular... Apr 2018Ion channels activated by reactive oxygen species (ROS) have been found in the plasma membrane of charophyte , dicotyledon , and , and the monocotyledon . Their... (Review)
Review
Ion channels activated by reactive oxygen species (ROS) have been found in the plasma membrane of charophyte , dicotyledon , and , and the monocotyledon . Their activities have been reported in charophyte giant internodes, root trichoblasts and atrichoblasts, pollen tubes, and guard cells. Hydrogen peroxide and hydroxyl radicals are major activating species for these channels. Plant ROS-activated ion channels include inwardly-rectifying, outwardly-rectifying, and voltage-independent groups. The inwardly-rectifying ROS-activated ion channels mediate Ca-influx for growth and development in roots and pollen tubes. The outwardly-rectifying group facilitates K⁺ efflux for the regulation of osmotic pressure in guard cells, induction of programmed cell death, and autophagy in roots. The voltage-independent group mediates both Ca influx and K⁺ efflux. Most studies suggest that ROS-activated channels are non-selective cation channels. Single-channel studies revealed activation of 14.5-pS Ca influx and 16-pS K⁺ efflux unitary conductances in response to ROS. The molecular nature of ROS-activated Ca influx channels remains poorly understood, although annexins and cyclic nucleotide-gated channels have been proposed for this role. The ROS-activated K⁺ channels have recently been identified as products of Stellar K⁺ Outward Rectifier () and Guard cell Outwardly Rectifying K⁺ channel () genes.
Topics: Animals; Calcium Signaling; Humans; Hydroxyl Radical; Plants; Potassium; Reactive Oxygen Species
PubMed: 29690632
DOI: 10.3390/ijms19041263 -
Biophysical Journal Jun 2022Hyperpolarization-activated cyclic-nucleotide gated channels (HCNs) are responsible for the generation of pacemaker currents (I or I) in cardiac and neuronal cells....
Hyperpolarization-activated cyclic-nucleotide gated channels (HCNs) are responsible for the generation of pacemaker currents (I or I) in cardiac and neuronal cells. Despite the overall structural similarity to voltage-gated potassium (Kv) channels, HCNs show much lower selectivity for K over Na ions. This increased permeability to Na is critical to their role in membrane depolarization. HCNs can also select between Na and Li ions. Here, we investigate the unique ion selectivity properties of HCNs using molecular-dynamics simulations. Our simulations suggest that the HCN1 pore is flexible and dilated compared with Kv channels with only one stable ion binding site within the selectivity filter. We also observe that ion coordination and hydration differ within the HCN1 selectivity filter compared with those in Kv and cyclic-nucleotide gated channels. Additionally, the C358T mutation further stabilizes the symmetry of the binding site and provides a more fit space for ion coordination, particularly for Li.
Topics: Cyclic Nucleotide-Gated Cation Channels; Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; Ions; Nucleotides; Potassium; Potassium Channels; Sodium
PubMed: 35474263
DOI: 10.1016/j.bpj.2022.04.024 -
Plant Physiology and Biochemistry : PPB Dec 2021Carbon monoxide (CO), nitric oxide (NO) and hydrogen sulfide (HS) are gasotransmitters known for their roles in plant response to (a)biotic stresses. The crosstalk... (Review)
Review
Carbon monoxide (CO), nitric oxide (NO) and hydrogen sulfide (HS) are gasotransmitters known for their roles in plant response to (a)biotic stresses. The crosstalk between these gasotransmitters and potassium ions (K) has received considerable attention in recent years, particularly due to the dual role of K as an essential mineral nutrient and a promoter of plant tolerance to abiotic stress. This review brings together what it is known about the interplay among NO, CO, HS and K in plants with focus on the response to high salinity. Some findings obtained for plants under water deficit and metal stress are also presented and discussed since both abiotic stresses share similarities with salt stress. The molecular targets of the gasotransmitters NO, CO and HS in root and guard cells that drive plant tolerance to salt stress are highlighted as well.
Topics: Gasotransmitters; Hydrogen Sulfide; Ions; Nitric Oxide; Potassium; Stress, Physiological
PubMed: 34837865
DOI: 10.1016/j.plaphy.2021.11.023 -
Plant Physiology and Biochemistry : PPB Sep 2022Potassium (K) is an integral part of plant nutrition, playing essential roles in plant growth and development. Despite its abundance in soils, the limitedly available... (Review)
Review
Potassium (K) is an integral part of plant nutrition, playing essential roles in plant growth and development. Despite its abundance in soils, the limitedly available form of K ion (K) for plant uptake is a critical factor for agricultural production. Plants have evolved complex transport systems to maintain appropriate K levels in tissues under changing environmental conditions. Adequate stimulation and coordinated actions of multiple K-channels and K-transporters are required for nutrient homeostasis, reproductive growth, cellular signaling and stress adaptation responses in plants. Various contemporary studies revealed that K-homeostasis plays a substantial role in plant responses and tolerance to abiotic stresses. The beneficial effects of K in plant responses to abiotic stresses include its roles in physiological and biochemical mechanisms involved in photosynthesis, osmoprotection, stomatal regulation, water-nutrient absorption, nutrient translocation and enzyme activation. Over the last decade, we have seen considerable breakthroughs in K research, owing to the advances in omics technologies. In this aspect, omics investigations (e.g., transcriptomics, metabolomics, and proteomics) in systems biology manner have broadened our understanding of how K signals are perceived, conveyed, and integrated for improving plant physiological resilience to abiotic stresses. Here, we update on how K-uptake and K-distribution are regulated under various types of abiotic stress. We discuss the effects of K on several physiological functions and the interaction of K with other nutrients to improve plant potential against abiotic stress-induced adverse consequences. Understanding of how K orchestrates physiological mechanisms and contributes to abiotic stress tolerance in plants is essential for practicing sustainable agriculture amidst the climate crisis in global agriculture.
Topics: Adaptation, Physiological; Ions; Plant Development; Plants; Potassium; Stress, Physiological
PubMed: 35932652
DOI: 10.1016/j.plaphy.2022.07.011 -
Biosensors & Bioelectronics Aug 2022Monitoring electrolytes is critical for newborns and babies in the intensive care unit. However, the gold standard methods use a blood draw, which is painful and only...
Monitoring electrolytes is critical for newborns and babies in the intensive care unit. However, the gold standard methods use a blood draw, which is painful and only offers discrete measures. Although salivary-based detection offers promise as an alternative, existing devices are ineffective for real-time, continuous monitoring of electrolytes due to their rigidity, bulky form factors, and lack of salivary accumulation. Here, we introduce a smart, wireless, bioelectronic pacifier for salivary electrolyte monitoring of neonates, which can detect real-time continuous sodium and potassium levels without a blood draw. The miniature system facilitates the seamless integration of the ultralight and low-profile device with a commercial pacifier without additional fixtures or structural modifications. The portable device includes ion-selective sensors, flexible circuits, and microfluidic channels, allowing simplified measurement protocols in non-invasive electrolyte monitoring. The flexible microfluidic channel enables continuous and efficient saliva collection from a mouth. By modifying the surface properties of the channels and the structure of the capillary reservoir, we achieve reliable pumping of the viscous medium for quick calibration and measurement. Embedded sensors in the system show good stability and sensitivity: 52 and 57 mV/decade for the sodium and potassium sensor, respectively. In vivo study with neonates in the intensive care unit captures the device's feasibility and performance in the natural saliva-based detection of the critical electrolytes without induced stimulation.
Topics: Biosensing Techniques; Electrolytes; Humans; Infant, Newborn; Ions; Pacifiers; Potassium; Sodium
PubMed: 35508093
DOI: 10.1016/j.bios.2022.114329