Role Of Potassium Research Articles

The role of potassium in the activation of oxygen to promote nitric oxide oxidation on honeycomb-like h-BN(001) surfaces.

Two-dimensional materials have developed rapidly in the field of catalysis, which has made honeycomb-like 2D hexagonal boron nitride (h-BN) considered to be a promising material in the application of catalysis. In this study, potassium (K) modified h-BN(001) surfaces are designed for the first time for the purpose of removal of nitric oxide (NO) via dispersion corrected density functional theory (DFT) computations. The role of K in changing the electronic properties and processes of NO oxidation is investigated in detail. The introduction of K effectively narrows the band gap of h-BN and acts as the surface electron donor on the surface. Importantly, the energy barrier is decreased by 3.45 eV at most along the whole NO oxidation path on K-doped h-BN(001), which is directly ascribed to the spontaneous dissociation of O2 induced by K and efficient charge transfer across the interface. The activation of O2 may be beneficial to other analogous oxidation reactions. With the introduction of K, the energy barrier of NO2 conversion to NO3- is significantly decreased and the desorption of NO2 is inhibited. Hence, NO3- instead of NO2 becomes the main oxidation product on K-modified h-BN. This work may provide new insights into the role of alkali metals in the activation of O2 to facilitate oxidation reactions on 2D materials.

ExomeChip-Wide Analysis of 95 626 Individuals Identifies 10 Novel Loci Associated With QT and JT Intervals.

QT interval, measured through a standard ECG, captures the time it takes for the cardiac ventricles to depolarize and repolarize. JT interval is the component of the QT interval that reflects ventricular repolarization alone. Prolonged QT interval has been linked to higher risk of sudden cardiac arrest. We performed an ExomeChip-wide analysis for both QT and JT intervals, including 209 449 variants, both common and rare, in 17 341 genes from the Illumina Infinium HumanExome BeadChip. We identified 10 loci that modulate QT and JT interval duration that have not been previously reported in the literature using single-variant statistical models in a meta-analysis of 95 626 individuals from 23 cohorts (comprised 83 884 European ancestry individuals, 9610 blacks, 1382 Hispanics, and 750 Asians). This brings the total number of ventricular repolarization associated loci to 45. In addition, our approach of using coding variants has highlighted the role of 17 specific genes for involvement in ventricular repolarization, 7 of which are in novel loci. Our analyses show a role for myocyte internal structure and interconnections in modulating QT interval duration, adding to previous known roles of potassium, sodium, and calcium ion regulation, as well as autonomic control. We anticipate that these discoveries will open new paths to the goal of making novel remedies for the prevention of lethal ventricular arrhythmias and sudden cardiac arrest.

Understanding the “seesaw effect” of interlayered K+ with different structure in manganese oxides for the enhanced formaldehyde oxidation

Although the potassium-promoted catalysts exhibit improved catalytic activities, the role of potassium with different structural sites still needs to be studied by more experiments and theory calculation. Herein, potassium (K+) formed via different binding sites (isolated and localized) over layered MnO2 was investigated. The isolated K+ dissociated between layers via weak chemical bond while localized K+ coordinated with oxygen atoms at vacancy site. K+ with localized type (L-MnO2) exhibited the higher activity and the lower Ea (45.2 kJ/mol), compared with isolated one (58.1kJ/mol) under 200ppm HCHO, 120,000mL/gh GHSV and ∼45% relative humidity. Evidenced by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), hydrogen temperature programmed reduction (H2-TPR) and density functional theory (DFT) simulation, the isolated K+ in interlayer are energetically favourable for dissociation of O2 as well as H2O by charge transfer from potassium to oxygen. As a result, the desorption of H2O was inhibited, thus, became the kinetic barriers during the whole reaction process. K+ with localized form possessed suitable ability for O2 activation and weak adsorption of H2O, exhibiting enhanced catalytic activity. Inspired by the seesaw effect, a clear understanding of K+ effect on layered MnO2 towards O2 adsorption and H2O desorption was illustrated.

Development of Diabetes: Possible Role of Potassium

Development of Diabetes: Possible Role of Potassium

Role of Potassium and Calcium on the Combustion Characteristics of Biomass Obtained from Thermogravimetric Experiments

This work focuses on the combustion behavior of raw and demineralized grape pomace and grape pomace doped with 0.1, 0.5, 0.82 (equal to the K concentration in the raw biomass), 3, and 6 wt % K and 0.1, 0.5, 1.08 (equal to the Ca concentration in the raw biomass), 3, and 6 wt % Ca. To identify the individual role of calcium and potassium, the biomass samples were either pyrolyzed in a N2 atmosphere or oxidized in air in a thermogravimetric analyzer (TGA) during non-isothermal runs at 10 K/min from room temperature to a maximum temperature of 1275 K. In all of the cases, the biomass pyrolysis process shows one main stage associated with the volatile matter release. This process is not significantly affected by the mineral content of biomass nor the presence of high K and Ca contents. During combustion in air, the biomass samples show two main distinct stages that are associated with the volatile matter release and the char oxidation. Whereas the main devolatilization stage is not significantly affected by t...

カリウム施用がコムギ、水稲の収量およびカリウム吸収に及ぼす影響 : 黒ボク土長期肥料連用試験における解析

カリウム施用がコムギ、水稲の収量およびカリウム吸収に及ぼす影響 : 黒ボク土長期肥料連用試験における解析

Physiological Responses and Gene Co-Expression Network of Mycorrhizal Roots under K+ Deprivation.

Arbuscular mycorrhizal (AM) associations enhance the phosphorous and nitrogen nutrition of host plants, but little is known about their role in potassium (K+) nutrition. Medicago truncatula plants were cocultured with the AM fungus Rhizophagus irregularis under high and low K+ regimes for 6 weeks. We determined how K+ deprivation affects plant development and mineral acquisition and how these negative effects are tempered by the AM colonization. The transcriptional response of AM roots under K+ deficiency was analyzed by whole-genome RNA sequencing. K+ deprivation decreased root biomass and external K+ uptake and modulated oxidative stress gene expression in M. truncatula roots. AM colonization induced specific transcriptional responses to K+ deprivation that seem to temper these negative effects. A gene network analysis revealed putative key regulators of these responses. This study confirmed that AM associations provide some tolerance to K+ deprivation to host plants, revealed that AM symbiosis modulates the expression of specific root genes to cope with this nutrient stress, and identified putative regulators participating in these tolerance mechanisms.

The Role of Potassium in Plants under Drought Stress: Mini Review

Drought stress is a major catastrophe to plant productivity. Drought stress significantly reduces the crop yield and quality, and probably exceeds losses from all other stresses. Potassium (K+) is an essential nutrient and affects the growth and development, and it also contribute significantly towards plants survival under drought stress. In this mini review we discussed the physiological, biochemical, and molecular mechanisms underlying K induced alleviation of drought stress.

Monitoring zeolite NaY formation from potassium-rich Nigerian kaolinite clay

This work focuses on the successful synthesis of NaY zeolite from highly contaminated kaolinite clay, while investigating the effect of metakaolinization temperature and aging on role of potassium in zeolitization. The presence of potassium was observed to be responsible for formation of microcline, kalsite, and nepheline, which were found to depend on metakaolinization temperature and Si/Al ratio. The desirability function approach of the Response Surface Methodological (RSM) was used to optimized the favorable maximal and minimal conditions for metakaolinization and potassium based mineral removal. The intensity of microcline was employed as response, which gave optimal calcination temperature and time of 900 °C and 6 h, respectively. Synthesis of zeolite Y was observed to be favored at higher Na/Na + K ratio, adequate aging, low Si/Al ratio, even in the presence of some trace potassium. The optimal condition for zeolite Y formation was determined to be calcinations at 900 °C at holding time of 6 h, aged for 8 days and synthesized at 95 °C for 72 h. The zeolite NaY had cubicoshape with relative diameter of 15 μm, ion exchange capacity of 4.72–4.94 meq/g and specific surface area of 672 m2/g. Reproducibility study conducted on Elefun kaolinite clay gave a good crystalline phase of NaY type zeolite after 7 days of aging. The starting materials, intermediate and final products were characterized using X-ray florescence (XRF), X-ray diffractograph (XRD), scanning electron microscopy (SEM) and Branner-Emmet-Teller (BET) analyses.

Role of potassium on insect pests and diseases of puddled transplanted rice cv. Lalat in Odisha

Potassium (K) is one of the most important essential nutrients for rice crop. The role of K in enhancing rice productivity is well established. It also imparts resistance against diseases and insect-pests. A field study was conducted to evaluate the effect of different levels of K application on the disease and insect pest incidence of puddled transplanted rice during dry season (DS) 2013–14 and wet season (WS) 2014 involving 9 potash management options in 3 replications. The experimental soil was highly deficient in exchangeable K (25.85 mg/kg). Increase in K dose from recommended 40 kg/ha to 80 kg/ha significantly reduced all insect pest and disease incidence. Recommended dose of K 40 kg/ha along with one foliar spray of 1% KNO 3 at flowering was also effective than other treatments. Reducing fertiliser K to 50% and adding straw (3 t/ha) was not as effective as full dose of K, but had moderate effect on pest incidence. Both blast and brown spot incidence correlated negatively with K content in leaf at maximum tillering (MT) and panicle initiation (PI) stages with more correlation at MT stage (r= -0.59, -0.69) than PI stage (r= -0.48, -0.37) in dry season and PI stage (r=-0.51, -0.73*) than MT stage (r= -0.48, -0.37) in wet season. Insect attack in both dry and wet seasons negatively correlated with K content in leaf at MT and PI stages with wet season having stronger correlation than dry season for all the major insects. From the study, it is also evident that not only the leaf K content, but K-N balance is also important for making the plant resistant to insect pest and disease attack. Thus, K nutrition is important for control of most common insect pests (stem borer, leaf folder, whorl maggot and Gundhi bug) and diseases (blast and brown spot) in rice.

Role of potassium and arbuscular mycorrhizal fungi in alleviation of water stress on Vigna mungo

Role of potassium and arbuscular mycorrhizal fungi in alleviation of water stress on Vigna mungo

Role of potassium and pH on the initiation of sperm motility in the European eel

The role of potassium from the seminal plasma and/or the activation media was examined by selectively removing K+ from this media, and by testing the use of K+ channel inhibitors and a K-ionophore. Sperm motility was measured using a CASA system, intracellular K+ and pH were measured by flow cytometry, and sperm head area was measured by ASMA: Automated Sperm Morphometry Analyses. Sperm motility was notably inhibited by the removal of K+ from the seminal plasma and by treatment with the K+ ionophore valinomycin. This therefore indicates that a reduction of K+ levels in the quiescent stage inhibits further motility. The normal decrease in sperm head area induced by seawater activation was altered by the removal of K+ from the seminal plasma, and an increase in the pHi in the quiescent stage was also induced. Intracellular pH (pHi) was quantitatively measured for the first time in European eel spermatozoa, being 7.2 in the quiescent stage and 7.1 post-activation. Intracellular and external pH levels influenced sperm motility both in the quiescent stage and at activation. The alkalinization of the pHi (by NH4Cl) inhibited sperm motility activation, while acidification (by Na-acetate) did not have any effect. Our results indicate that a pH gradient between the sperm cell and the seminal plasma is necessary for sperm motility activation. The presence of the ion K+ in the seminal plasma (or in the extender medium) is necessary in order to maintain sperm volume, intracellular pH and sperm motility.

The role of potassium and magnesium in complex therapy of hypertension

The role of potassium and magnesium in complex therapy of hypertension

Abstract 1463: Ionic immune suppression within the tumor microenvironment limits T cell effector function

Abstract Tumors progress in immunocompetent hosts despite the local infiltration of tumor-specific effector T cells. Recent advances have identified ion transport as important for T cell activation and function. We report that the concentration of potassium is markedly elevated within murine and human tumors in comparison to other tissues while other ions are minimally perturbed. Additionally, ex vivo stimulation of effector T cells in hyperkalemic conditions led to profound suppression of T cell activation, cytokine production, and glycolytic metabolism without affecting viability - suggesting a role for potassium in tumor immune evasion. Characterization of this phenomenon with whole-transcriptome RNA-Sequencing revealed that elevated potassium specifically repressed TCR induced transcripts with the effector cytokine interferon gamma (IFNγ) being among the most depressed. Moreover, hyperkalemia limited TCR induced glucose uptake and consumption, metabolic changes required for full effector function. Prior investigations into the role of potassium transport in cellular physiology have centered on the presumption that the ion's sole function is to maintain cellular membrane potential and calcium influx. However, we find that elevated potassium had no effect on TCR induced calcium signaling. Although hyperkalemia increased the cytoplasmic membrane potential of effector T cells as expected, other methods to similarly depolarize the cell without the addition of extracellular potassium did not produce the inhibitory phenomenon. Therefore, we conclude that the immunosuppressive effect induced by hyperkalemia is independent of potassium's previously understood role in the regulation of cytoplasmic membrane potential and calcium signaling. Causatively, elevated potassium led to blunted serine/threonine phosphorylation within the Akt/mTOR signaling cascade following TCR ligation, while pharmacologic or genetic means to restore Akt signaling rescued effector function. Mechanistically, the suppressive effect of elevated extracellular potassium was directly related to an increase in intracellular levels, and depletion of intracellular potassium restored full T cell activation and cytokine production. T cells genetically reprogrammed to express the potassium efflux channel Kcna3 were resistant to potassium mediated suppression - displaying lower intracellular potassium levels and increased cytokine production. Finally, tumor-specific Kcna3 expressing cells exhibited augmented in vivo intratumoral IFNγ production, Akt/mTOR signaling, and enhanced anti-tumor activity against established melanoma in tumor bearing mice. These results uncover a novel axis of tumor-induced immune suppression via an ‘ionic’ checkpoint. The manipulation of cellular ion transport represents an entirely new approach for cancer immunotherapy. Citation Format: Robert L. Eil, Rahul Roychoudhuri, Madhu Sukumar, David Clever, Jenny H. Pan, Shashank Patel, Douglas C. Palmer, Nicholas P. Restifo. Ionic immune suppression within the tumor microenvironment limits T cell effector function. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1463.

Salt stress manifestation on plants, mechanism of salt tolerance and potassium role in alleviating it: a review

Salt stress manifestation on plants, mechanism of salt tolerance and potassium role in alleviating it: a review

The role of potassium and magnesium in the treatment of cardiovascular diseases

The role of potassium and magnesium in the treatment of cardiovascular diseases

Insight on trans-plasma membrane behavior of virus-infected plant cells

Little is known about the ion fluxes generated during plant-virus interactions, despite significant losses caused by viruses to agricultural crops. Changes in average ion currents were identifying an early event in the signal transduction pathway related to virus/host interaction. While significant decrease in the average inward currents, mainly due to Ca2+ moving into the cell was observed, the role of potassium may be significant. Host specific K+ efflux with a concomitant decrease in the intracellular K+ was observed in tobacco plants during the early minutes after infection, suggesting many hypothesis about the role of potassium in host-virus interaction. In the last years, trans-plasma membrane potential was evaluated for some viruses, observing as effect on membrane was different in relation to virus infection and host. Conversely, settle virus infection generally lead to an increase of activity in trans-plasma membrane electron transport.

Role of Potassium and Phosphorus in Catalytic Partial Oxidation in Short Contact Time Reactors

Potassium and phosphorus represent inorganics commonly found in biomass and can significantly affect catalytic gasification of biomass. The alkaline and acidic nature of potassium and phosphorus, respectively, can introduce different reaction chemistries. In this paper, the effects of potassium and phosphorus on Rh catalysts for catalytic gasification have been studied at different fuel/oxygen ratios and temperatures. Catalytic partial oxidation (CPO) of ethanol, a biomass surrogate, was carried out over potassium, phosphorus, and monobasic potassium-phosphate-doped catalysts at loadings of 0.1, 1, 10, and 100% of Rh atoms over a range of fuel/oxygen ratios. In addition, time-on-stream studies were also carried out with methane by predosing inorganics on the catalyst (10% loading) and ethanol by introducing inorganics in the feed (0.05 mol %) to understand their effects on the stability of autothermal operation. With ethanol CPO, synthesis gas selectivities did not change significantly with potassium-doped catalysts, whereas they decreased with phosphorus-doped catalysts. Monobasic potassium phosphate showed synergistic effects of potassium and phosphorus; however, at higher temperatures, the effect of phosphorus was predominantly observed as a result of volatilization of potassium. Similarly, with time-on-stream studies with methane CPO, potassium volatilized at higher temperatures, while phosphorus retained its catalytic activity at higher temperatures. With the introduction of potassium and phosphorus in ethanol feed, steady-state autothermal operation was possible without any deactivation of the catalyst. In all experiments, phosphorus exhibited a stronger poisoning effect on rhodium for catalytic partial oxidation than potassium at similar concentrations.

Role of potassium in deposit formation during wood pellets combustion

Biomass boiler issues regarding slagging, fouling and corrosion are related to alkali species present in fuels. These alkali species are released as gaseous alkali chlorides, hydroxides and/or sulfates during combustion. Alkali chlorides/sulfates later condense on cold boiler surfaces enhancing fouling and corrosion. Subsequent deposition of silica-rich ashes leads to the formation of low temperature melting eutectics, especially alkali/earth alkali-silicates (K/Ca-Si), and creates compact and strong deposits. Condensing chlorides/sulfates and low melting eutectics both reduce boiler performance and its availability.Two different woody biomass fuels and their mixture with two different kinds of aluminosilicate base additives were combusted during this study. Deposits were sampled using two different kinds of probes; cooled deposit probe and un-cooled deposit probe. The macroscopic and microscopic observations and chemical composition of deposit samples are compared using electron microscopic image analysis (EMPA) for both deposit samples. The additive significantly changes the morphology and composition of the deposit samples. The difference in morphology and composition can be explained by the change in potassium chemistry between two cases.

K(+) regulates Ca(2+) to drive inflammasome signaling: dynamic visualization of ion flux in live cells.

P2X7 purinergic receptor engagement with extracellular ATP induces transmembrane potassium and calcium flux resulting in assembly of the NLRP3 inflammasome in LPS-primed macrophages. The role of potassium and calcium in inflammasome regulation is not well understood, largely due to limitations in existing methods for interrogating potassium in real time. The use of KS6, a novel sensor for selective and sensitive dynamic visualization of intracellular potassium flux in live cells, multiplexed with the intracellular calcium sensor Fluo-4, revealed a coordinated relationship between potassium and calcium. Interestingly, the mitochondrial potassium pool was mobilized in a P2X7 signaling, and ATP dose-dependent manner, suggesting a role for mitochondrial sensing of cytosolic ion perturbation. Through treatment with extracellular potassium we found that potassium efflux was necessary to permit sustained calcium entry, but not transient calcium flux from intracellular stores. Further, intracellular calcium chelation with BAPTA-AM indicated that P2X7-induced potassium depletion was independent of calcium mobilization. This evidence suggests that both potassium efflux and calcium influx are necessary for mitochondrial reactive oxygen generation upstream of NLRP3 inflammasome assembly and pyroptotic cell death. We propose a model wherein potassium efflux is necessary for calcium influx, resulting in mitochondrial reactive oxygen generation to trigger the NLRP3 inflammasome.