Effect Of Potassium Ions Research Articles

Effects of potassium ions and platinum cocatalysts on the photocatalytic performance of Poly(Heptazine Imides)

In the synthesis of highly crystalline carbon nitride, alkali metal halides are used as high-temperature solvents and structural guiding agents, but the effect of alkali metal ions on the catalytic activity of materials is still unclear. In addition, the shape and size of the cocatalyst also significantly affect the catalytic activity of the material. Therefore, we have carried out the density functional theory calculations to reveal the differences in the structure, electronic, and optical properties, as well as the photocatalytic hydrogen evolution performance of one kind of crystalline carbon nitride called potassium poly(heptazine imide) (K-PHI) and its proton-exchanged counterpart (H-PHI) loaded with different sizes of platinum cocatalysts. The results show that potassium ions have the effect of aggregation electrons in K-PHI, and potassium ions have short-range induced dipole effect on nearby Pt atoms, resulting in slightly better photocatalytic hydrogen evolution activity at these reaction sites. Additionally, Pt cocatalyst with larger load size has better photocatalytic hydrogen evolution activity than small size. This work provides a theoretical basis for the rational design of high-performance metal cocatalysts and exploration of the functionality of alkali metal ions in carbon nitrides.

Molecular insights into the vinyl acetate synthesis on Pd/Au (1 1 1) Surface: Effects of potassium ion

The surface structure of bimetallic Pd/Au catalyst, accompanied by the presence of potassium acetate (KOAc) are critical for synthesis of vinyl acetate (VAc). In this study, different configurations of the Pd/Au (111) surface were constructed. The density functional theory (DFT) was used to investigate the adsorption of ethylene and acetate on the Pd/Au (111) surface. The reaction mechanism of VAc formation was studied by following the Samanos pathway. The existence of potassium ion (K+) enhanced the adsorption of ethylene and acetate on the Pd/Au (111) surface, and promoted the dehydrogenation of acetic acid. The Pd/Au (111) surface configuration, with two adjacent palladium atoms embedded on the gold surface, is the most favorable surface structure for VAc synthesis. The introduction of K+ was obstructive to the formation of ethyl acetate-like intermediates, but facilitated β-H elimination during the formation of VAc. This work provides a deeper mechanistic understanding of VAc synthesis on the Pd/Au (111) surface, which could shed some light on the catalysts design and the industrial control of VAc synthesis.

Microdroplet enabled cultivation of single yeast cells correlates with bulk growth and reveals subpopulation phenomena.

Yeast has been engineered for cost-effective organic acid production through metabolic engineering and synthetic biology techniques. However, cell growth assays in these processes were performed in bulk at the population level, thus obscuring the dynamics of rare single cells exhibiting beneficial traits. Here, we introduce the use of monodisperse picolitre droplets as bioreactors to cultivate yeast at the single-cell level. We investigated the effect of acid stress on growth and the effect of potassium ions on propionic acid tolerance for single yeast cells of different species, genotypes, and phenotypes. The results showed that the average growth of single yeast cells in microdroplets experiences the same trend to those of yeast populations grown in bulk, and microdroplet compartments do not significantly affect cell viability. This approach offers the prospect of detecting cell-to-cell variations in growth and physiology and is expected to be applied for the engineering of yeast to produce value-added bioproducts.

Spray pyrolysis deposited K@CdS nanostructured films and their characterizations for optoelectronic and 3rd order nonlinear optical applications

Cadmium Sulfide (CdS) is an excellent semiconductor for photonic devices and its optical and electrical properties are greatly affected by single element doping. In the current manuscript, the effect of potassium ion (K+) doping on linear and nonlinear optical traits of spray pyrolysis deposited CdS films was investigated. The X-ray diffraction (XRD) spectra reveal the increase of defects, decrease of crystallinity and crystallite size also change in growth orientation with K+ doping in CdS films. Moreover, the position of FT-Raman peaks was slightly blue shifted and morphology of films shows clusters of agglomerated CdS nanoparticles along with small size nanoparticles in the background as revealed from SEM images. The bandgap of K+-doped CdS films slightly broaden and shows improved transparency as compare to pure CdS films. The dielectric constants were found to be first decease for 2.5% wt. K+ doping and thereafter slightly increase for 5.0% wt. CdS films whereas optical conductivity decrease for all K+ doping concentrations. The photoluminescence intensity of CdS decreases and slightly blue shifted upon K+ doping, also a new emission band appears at 630 nm, indicating formation of new trap states in the bandgap of semiconductor. The 3rd order nonlinear properties elucidated through Z-scan technique reveals the increase of n2 and χ3 whilst decrease of β with increase of K+ content in CdS thin films.

Guanine Radicals Generated in Telomeric G-Quadruplexes by Direct Absorption of Low-Energy UV Photons: Effect of Potassium Ions.

The study deals with the primary species, ejected electrons, and guanine radicals, leading to oxidative damage, that is generated in four-stranded DNA structures (guanine quadruplexes) following photo-ionization by low-energy UV radiation. Performed by nanosecond transient absorption spectroscopy with 266 nm excitation, it focusses on quadruplexes formed by folding of GGG(TTAGGG)3 single strands in the presence of K+ ions, TEL21/K+. The quantum yield for one-photon ionization (9.4 × 10−3) was found to be twice as high as that reported previously for TEL21/Na+. The overall population of guanine radicals decayed faster, their half times being, respectively, 1.4 and 6.7 ms. Deprotonation of radical cations extended over four orders of magnitude of time; the faster step, concerning 40% of their population, was completed within 500 ns. A reaction intermediate, issued from radicals, whose absorption spectrum peaked around 390 nm, was detected.

Formate and potassium ions affect Escherichia coli proton ATPase activity at low pH during mixed carbon fermentation

Escherichia coli is able to ferment not only single but also mixtures of carbon sources. The formate metabolism and effect of formate on various enzymes have been extensively studied during sole glucose but not mixed carbon sources utilization. It was revealed that in membrane vesicles (MV) of wild type cells grown at pH 7.5 during fermentation of the mixture of glucose (2 g/L), glycerol (10 g/L), and formate (0.68 g/L), in the assays, the addition of formate (10 mM) increased the N,N'-dicyclohexylcarbodiimide (DCCD)-inhibited ATPase activity on ~30% but no effect of potassium ions (100 mM) had been detected. In selC (coding formate dehydrogenases) and fdhF (coding formate dehydrogenase H) single mutants, formate increased DCCD-inhibited ATPase activity on ~40 and ~70%, respectively. At pH 5.5, in wild type cells MV, formate decreased the DCCD-inhibited ATPase activity ~60% but unexpectedly in the presence of potassium ions, it was stimulated ~5.8 fold. The accessible SH or thiol groups number in fdhF mutant was less by 28% compared with wild type. In formate assays, the available SH groups number was less ~10% in wild type but not in fdhF mutant. Taken together, the data suggest that proton ATPase activity depends on externally added formate in the presence of potassium ions at low pH. This effect might be regulated by the changes in the number of redox-active thiol groups via formate dehydrogenase H, which might be directly related to proton ATPase FO subunit.

Effect of Potassium Ions on the Formation of Mixed-Valence Manganese Oxide/Graphene Nanocomposites.

One-pot synthesis of mixed-valence manganese oxide (MnOx)/potassium ion-doped reduced graphene oxide (rGO) composites for efficient electrochemical supercapacitors is introduced. Using manganese nitrate and potassium permanganate as co-precursors for the MnOx and by directly annealing the rGO without tedious purification steps, as described herein, MnOx/rGO composites with a high specific capacitance of 1955.6 F g−1 at a current density of 1 A g−1 are achieved. It is found that the presence of potassium ions helps in the development of mixed-valence MnOx on the surface of the rGO.

Effect of K+ on the performance of Ni/Al2O3 high temperature methanation catalyst

The effects of potassium ions on the properties of co-precipitation Ni/Al2O3 high temperature methanation catalysts were investigated. The catalysts were characterized by low temperature nitrogen adsorption (BET), X-ray diffraction (XRD), and hydrogen programmed reduction (H2-TPR). Activity tests showed that the activity of the catalyst decreased with increasing of potassium ions, but the anti-carbon capacity of the catalyst increased first and then decreased. The activity deactibation is due to the decrease of specific surface aera measured by BET. On this basis, the effect of kaliophilite on the performance of Ni/Al2O3 methanation catalyst was investigated. The results showed that the addition of kaliophilite had little effect on the specific surface area and activity of the catalyst, but could significantly improve the anti-carbon capacity of the catalyst.

The effect of supplementation of a trehalose-based extender with KCl on rainbow trout (Oncorhynchus mykiss) sperm freezability and post-thaw motility

The aim of this study was to test if a cryopreservation procedure using methanol as an internal cryoprotectant and trehalose as an external cryoprotectant could be applied to rainbow trout sperm (Oncorhynchus mykiss). Additionally, the effects of potassium ions and Tris-HCl on post-thaw sperm motility, viability, and fertilizing capacity were analyzed. In this study, we demonstrate for the first time that rainbow trout sperm can be cryopreserved using a trehalose and methanol based extender. Trehalose was found to be effective in rainbow trout sperm cryopreservation at concentrations ranging between 175 and 200mM when supplemented with 10% methanol (v/v). The most effective dilution ratio was 1:11.5, which resulted in a final sperm concentration ranging from 0.8 to 1.6×109 spermatozoa mL−1. A 15-min equilibration period of sperm in the extenders did not influence sperm motility parameters. The highest post-thaw sperm motility was found using extenders containing 175mM trehalose (77.4±10.8) and 175mM trehalose with 40mM KCl (79.3±9.2). The supplementation of the extender with Tris-HCl and the adjustment of the pH to 7.5 and 8.5 resulted in a decrease in post-thaw motility. The post-thaw sperm motility in samples cryopreserved in an extender containing 40mM of KCl did not decrease 60min after thawing. The fertilizing capacity of sperm cryopreserved in 175mM trehalose and 40mM KCl was the highest and did not differ from fresh sperm at a sperm-to-egg ratio of 200,000:1. In conclusion, our results indicate that rainbow trout sperm can be successfully cryopreserved with the application of a trehalose based extender. The supplementation of the cryopreservation extender with 40mM KCl resulted in prolonged post-thaw storage of the sperm, allowing prolonged use of the sperm over time for common fishery practices. Statement of relevanceThis work is related to fish production and conservation.

Effect of potassium ion on the stability and release rate of hydrogen peroxide encapsulated in silica hydrogels

Hydrogen peroxide (H2O2) is encapsulated in silica hydrogels using sol‐gel method and the effects of the K+ : Na+ ion ratio on gelation time, hydrogel structure, stability, and release rate of H2O2 were investigated. As the amount of K+ ions increased relative to the amount of Na+ ions at the same pH, the gel structure became less compact and the pore diameter increased. Hydrogen peroxide retention values up to 90 and 80% were observed at the end of 7 and 20 days, respectively, in the presence of K+ ions at low pH values when the initial H2O2 concentration was 19.9 wt %. Release rate of hydrogen peroxide decreased with decreasing pH for the two K+ : Na+ ion ratios studied. This work presents an environmentally friendly, low cost, and easy to scale up method to increase the stability of high initial concentrations of H2O2 at room temperature and customize the release rate. © 2016 American Institute of Chemical Engineers AIChE J, 63: 409–417, 2017

Proapoptotic Role of Potassium Ions in Liver Cells.

Potassium channels are transmembrane proteins that selectively promote the infiltration of potassium ions. The significance of these channels for tumor biology has become obvious. However, the effects of potassium ions on the tumor or normal cells have seldom been studied. To address this problem, we studied the biological effects of L02 and HepG2 cells with ectogenous potassium ions. Cell proliferation, cell cycle, and apoptosis rate were analyzed. Our results indicated that potassium ions inhibited proliferation of L02 and HepG2 cells and promoted their apoptosis. Potassium ions induced apoptosis through regulating Bcl-2 family members and depolarized the mitochondrial membrane, especially for HepG2 cell. These biological effects were associated with channel protein HERG. By facilitating expression of channel protein HERG, potassium ions may prevent it from being shunted to procancerous pathways by inducing apoptosis. These results demonstrated that potassium ions may be a key regulator of liver cell function. Thus, our findings suggest that potassium ions could inhibit tumorigenesis through inducing apoptosis of hepatoma cells by upregulating potassium ions transport channel proteins HERG and VDAC1.

Effect of in situ acids removal on mixed glucose and xylose fermentation by Clostridium tyrobutyricum

In the present study, the effect of potassium ions and increasing concentrations of glucose and xylose on the growth of a strain of Clostridium tyrobutyricum, adapted to wheat straw hydrolysate, was investigated. Application of continuous fermentation of a mixture of glucose and xylose and in situ acid removal by reverse electro enhanced dialysis (REED) was investigated as a method to alleviate potassium and end-product inhibition and consequently enhance the sugar consumption rates and butyric acid productivity. It was found that glucose and xylose were not inhibitory up to a concentration of 50 and 37 g L−1 respectively, and that they were consumed at comparable rates when fermented alone. However, continuous fermentation of a mixture of glucose and xylose resulted in a significantly decreased xylose consumption rate compared to that of glucose alone, supporting the conclusion that C. tyrobutyricum has a lower affinity for xylose than for glucose. Potassium ions negatively affected the effective maximum growth rate of C. tyrobutyricum at concentrations higher than 5 g L−1 exhibiting a non-competitive type of inhibition. Continuous fermentation of a glucose and xylose mixture with simultaneous acid removal by REED resulted in a two to threefold increase of the glucose consumption rate, while the xylose consumption rate was enhanced sixfold compared to continuous fermentation without in situ acid removal. Similarly, butyric acid productivity was enhanced by a factor of 2–3, while the yield remained unaffected.

Voltage-gated potassium ion channel may play a major role in the settlement of Pacific oyster (Crassostrea gigas) larvae

Abstract While the effects of potassium ion (K + ) on the settlement and metamorphosis of mollusc larvae have been studied in some species, little of this research has focused on the Pacific oyster ( Crassostrea gigas ). It is still unclear which of the potassium channels, the voltage-gated channel or the inward rectifier channel, plays the more important role in the settlement and metamorphosis of mollusc larvae. In this study, the effects of K + and K + channel inhibitors on the settlement and metamorphosis of Pacific oyster larvae were examined. After 24, 48, or 72 h, the highest oyster larval settlement rate was observed at 19 mM K + . The relative metamorphosis rate (number of larvae at metamorphosis ∕ number of larvae at settlement) decreased with increasing K + concentration, however, the highest total metamorphosis rate (number of larvae at metamorphosis ∕ total number of larvae) was observed at 19 mM K + as a result of the very high settlement rate at this concentration. Treatment with tetraethyl-ammonium, the voltage-gated potassium channel inhibitor, resulted in a more obvious suppression of K + -induced oyster larval settlement than Glyburide (Glib), an inhibitor of the inward rectifier potassium channel. These results suggest that the voltage-gated potassium channel may play a more important role than the inward rectifier potassium channel in the settlement of oyster larvae.

Effect of Potassium Ions on the Formation of Crystalline Manganese Oxide Nanorods via Acidic Reduction of Potassium Permanganate

Uniformly grown manganese oxides nanorods are synthesized via a simple and rapid process through an acidic reduction of potassium permanganate followed by heat treatment. The as-produced manganese oxides nanorods are characterized with X-ray diffraction, energy dispersive X-ray analysis, scanning electron microscopy, and transmission electron microscopy. The crystallinity of the nanostructure is found to have a dominant Mn2O3 phase. The compositional and microstructural analyses reveal that the potassium concentration within the as-prepared material has a profound effect on the morphological conversion of manganese oxide nanoparticles to nanorods. Potassium ions are believed to act as a template for the formation of nanorods and the conversion efficiency increases with the increasing content of potassium. Also the morphology of products is found to depend strongly on the annealing time. The mechanism of nanorod growth with respect to different potassium contents and annealing times is discussed.

Effect of Potassium Ions on Protoplast Generation during Yeast Induction from Mucor circinelloides Tieghem.

Mucor circinelloides aerobically exhibits coenocytic thallic growth habit with straight and circinate sporangiophores which culminate in globose or pyriform columellae enclosed within sporangial walls. It undergoes dimorphic switch with its conversion to multipolar budding yeast-like cells or thallic conidia. This paper confirms the induction of plurality of reproductive structures of the pleomorphic microorganism in minimal medium. Furthermore, construction of pH differentials at inflection points in the biphasic profiles during sporangiospore-yeast transformation indicated the intensity of H+ release from intracellular medium of the growing microorganism in a study conducted with K+ levels (0.0, 0.5, 0.7, 0.9, 1.0,1.10 g/L)-mediated broths. Optimum proton release was at 0.00 and 1.0 g/L K+-supplemented broths, but specific growth rate was least in the latter. It also coincided with a preponderance of neoplastic units, protoplasts, and terminal budding yeast cells. On either side of this K+ level, variation in morphologies, including neoplasts, protoplasts, septate hyphae, thallic, holothallic, and holoblastic conidia, was greater, although olive-green septate hyphae with vesicular conidiogenous apparatus occurred at all K+ levels tested. This study suggested that following the establishment of transmembrane pH gradient across protoplast membrane, operation of Mitchellian proton pump was further promoted, thus leading to active transport mechanism, a prelude to yeast morphology induction.

Electrophysiological observations on the effects of potassium ions on the response of intradental nerves to dentinal tubular flow in the cat

Objective To determine the effects of K + on the sensitivity of sensory receptors in teeth to fluid flow through dentine. Methods Evoked discharges were recorded from intradental nerves in anaesthetised cats during the application of 5 s hydrostatic pressure stimuli to exposed dentine through either normal Ringer's or Ringer's containing up to 255 mmol/l K +. The stimuli ranged between −500 and +500 mm Hg. Results The number of impulses evoked by a positive pressure stimulus increased, and the latency of the response decreased, as either the pressure or the K + concentration of the Ringer's was increased. The response to a negative pressure stimulus applied 2 s after a positive pressure pulse of equal but opposite amplitude decreased as either the intensity of the stimulus or the K + concentration of the Ringer's was increased. Conclusions Potassium ions that were transported into the dentine and pulp by bulk flow during the application of positive pressure stimuli increased the sensitivity of the receptors to inward tubular flow but decreased their sensitivity to outward flow.

Selective Na+/K+ Effects on the Formation of α-Cyclodextrin Complexes with Aromatic Carboxylic Acids: Competition for the Guest

We investigated the effects of K(+) and Na(+) ions on the formation of α-cyclodextrin complexes with ionized aromatic carboxylic acids. Using solution calorimetry and (1)H NMR, we performed the thermodynamic and structural investigation of α-cyclodextrin complex formation with benzoic and nicotinic acids in different aqueous solutions containing K(+) and Na(+) ions as well as in pure water. The experiments show that the addition of sodium ions to solution leads to a decrease in the binding constants of the carboxylic acids with α-cyclodextrin as compared to pure water and solutions containing potassium ions. From another side, the effect of potassium ions on the binding constants is insignificant as compared to pure water solution. We suggest that the selectivity of cation pairing with carboxylates is the origin of the difference between the effects of sodium and potassium ions on complex formation. The strong counterion pairing between the sodium cation and the carboxylate group shifts the equilibrium toward dissociation of the binding complexes. In turn, the weak counterion pairing between the potassium cation and the carboxylate group has no effect on the complex formation. We complemented the experiments with molecular modeling, which shows the molecular scale details of the formation of cation pairs with the carboxylate groups of the carboxylic acids. The fully atomistic molecular simulations show that sodium ions mainly form direct contact pairs with the carboxylate group. At the same time, potassium ions practically do not form direct contact pairs with the carboxylate groups and usually stay in the second solvation shell of carboxylate groups. That confirms our hypotheses that the selective formation of ion pairs is the main cause of the difference in the observed effects of sodium and potassium salts on the guest-host complex formation of α-cyclodextrin with aromatic carboxylic acids. We propose a molecular mechanism explaining the effects of salts, based on competition between the cations and α-cyclodextrin for binding with the ionized carboxylic acids.

Epitaxial Growth of Trichosanthin Protein Crystals on Mica Surface

We report the studies of epitaxial growth of trichosanthin (TCS) crystals on a mica substrate. TCS crystals grown on mica surface are found to be aligned well in four orientations, which was induced by the lattice of the mica substrate. The effect of potassium ions both at the mica surface and in solution was investigated by using different cation-modified surfaces and different precipitants. The results indicated that the binding of K+ ions on the mica surface played a critical role in the epitaxial crystal growth of TCS. The high-resolution structures of crystals grown in different precipitants were solved by synchrotron radiation X-ray crystallography, and the K+ binding sites in TCS crystals were identified. A strict lattice match between the TCS crystal and the mica substrate has been demonstrated based on the structural analysis of them. It reveals the mechanism of epitaxial nucleation and growth of TCS crystals. The experimental results provide new insights into the molecular mechanism of epitaxial...

Effect of potassium ion on switching of photoinduced electron transfer in inclusion dyads formed by crown ether-porphyrins and an ammonium cation-fullerene

Reversible switching of electron transfer paths in supramolecular donor-acceptor dyads formed by complexing benzo-18-crown-6 appended porphyrins and fulleropyrrolidine appended with an alkyl ammonium ion is demonstrated. The intra-supramolecular to intermolecular switching is achieved by the addition of K + which dissociates the crown ether-alkyl ammonium complex, while intermolecular to intra-supramolecular switching was achieved by the addition of 18-crown-6 to extract the potassium ions of the porphyrin-crown entity. The employed porphyrin-fullerene donor-acceptor pairs were proved to be especially suitable for the generation of relatively long-lived charge-separated states which allows easy observation of switching and monitoring of such processes. In the absence of K + , the charge-separation takes place within the inclusion complex via the excited singlet state, generating the radical ion pair with the lifetime of 20-60 ns. On addition of K + , the inclusion complexes between the porphyrins and C 60 moieties are dissociated, favoring intermolecular electron transfer via the excited triplet state. Further addition of benzo-18-crown-6 to the solution extracts the K + from the crown-ether appended porphyrin and regenerates the inclusion complex with the functionalized fullerene capable of undergoing intra-complex charge separation. The observed phenomena afford concerted metal ion sensing with photoinduced electron transfer in inclusion complexes.

Emission lifetime study of fluorescence probes based on G-quadruplex oligonucleotides end-labeled with pyrene moieties

Fluorescence lifetime study of two probes abbreviated as Py-Htelom-Py and Py-TBA-Py, carrying pyrene moieties at both termini and sequences of Human telomere and Thrombin Binding Aptamer, respectively are reported. The effect of potassium ion on the photophysical processes was examined in order to elucidate factors that facilitate the production of excimer emission. Emission kinetics data indicated that the relative orientation of pyrene and neighboring nucleobase (guanine, adenine, thymine) plays a crucial role in determining both the rate of electron-transfer quenching of pyrene excited state and the efficiency of excimer emission.