Monovalent Cation Species Research Articles

Transport coefficients of gel electrolytes: A molecular dynamics simulation study.

The responses of gel electrolytes to stimuli make them useful in applications such as sensors and actuators. However, few studies have explored their transport properties from a molecular viewpoint. We studied the transport coefficients of gel electrolytes based on perfluorinated sulfonic acid using molecular dynamics simulations. The transport coefficients for electric and pressure fields, namely, the ionic conductivity, Darcy permeability, and cross coupling constant, were calculated based on Kubo's linear response theory from the corresponding velocity correlation functions and mean square displacements. The effects of the water content of the gel electrolyte and those of the monovalent cationic species were also analyzed. The calculated transport coefficients qualitatively agree with the reported experimental results. The role of the cross coupling constants in determining the functional efficiency of gel electrolytes as pressure sensors or electroactive actuators is discussed.

Self-assembly of highly ordered DNA origami lattices at solid-liquid interfaces by controlling cation binding and exchange

The surface-assisted hierarchical self-assembly of DNA origami lattices represents a versatile and straightforward method for the organization of functional nanoscale objects such as proteins and nanoparticles. Here, we demonstrate that controlling the binding and exchange of different monovalent and divalent cation species at the DNA-mica interface enables the self-assembly of highly ordered DNA origami lattices on mica surfaces. The development of lattice quality and order is quantified by a detailed topological analysis of high-speed atomic force microscopy (HS-AFM) images. We find that lattice formation and quality strongly depend on the monovalent cation species. Na+ is more effective than Li+ and K+ in facilitating the assembly of high-quality DNA origami lattices, because it is replacing the divalent cations at their binding sites in the DNA backbone more efficiently. With regard to divalent cations, Ca2+ can be displaced more easily from the backbone phosphates than Mg2+ and is thus superior in guiding lattice assembly. By independently adjusting incubation time, DNA origami concentration, and cation species, we thus obtain a highly ordered DNA origami lattice with an unprecedented normalized correlation length of 8.2. Beyond the correlation length, we use computer vision algorithms to compute the time course of different topological observables that, overall, demonstrate that replacing MgCl2 by CaCl2 enables the synthesis of DNA origami lattices with drastically increased lattice order.

Variations in Electroosmotic Flow Outside Glass Nanopores with Species of Monovalent Cation

Nanopores are an important technology in molecular sensing systems. Their behaviour is strongly affected by flow characteristics that are not well understood. Utilising a novel 3 dimensional combination optical tweezers and capillary nanopore measurement system, we have measured flow behaviour outside conical glass nanopores as a function of species of group 1 cation. We present a full 3 dimensional flow field about the nanopore. We use this 3 dimensional measurement system to find the flow force as a function of distance from the pore, allowing us to determine the momentum flux for each salt condition. We find strong salt dependence on the strength of momentum flux from the nanopore. Additionally we find previously reported voltage dependent flow reversal to be dictated by salt species. For a subset of species we observe EOF in the expected direction as predicted by classical electrokinetic theory, while for others the direction of the flow is reversed. We present a model explaining the observed behaviour. These data and corresponding model are key to understanding ion transport, fluid flow and translocation dynamics in voltage driven nanopore systems.

Adsorption characteristics of zeolites for dehydration of ethanol: Evaluation of diffusivity of water in porous structure

The adsorption characteristics of zeolites with different framework structures and different exchanged cation species were examined with a view to using zeolites as adsorbents for the dehydration of ethanol. We measured the adsorption isotherm of water vapor on zeolites, the differential heat of the adsorption of water vapor, the liquid-phase adsorption isotherm of water in ethanol and packed bed breakthrough curves (BTC) for the adsorption of water in ethanol. As a result, we confirmed that an LTA or FAU zeolite exchanged with a monovalent cation species, such as a sodium cation or a potassium cation, showed a strong affinity to water in ethanol. We also found that the Langmuir model explained the liquid-phase adsorption of water in ethanol on the zeolite more accurately than the Freundlich model. Using the constants determined from the Langmuir isotherm, we calculated the BTC for a zeolite packed bed as regards the dehydration of ethanol. The intra-particle diffusion coefficient of water in the zeolite particles was estimated by fitting the calculated BTC to the experimental result.

Characteristics of enzymatically-deesterified pectin gels produced in the presence of monovalent ionic salts

Pectin methylesterases (PMEs) from Valencia orange (p-PME) and Aspergillus aculeatus (f-PME) were used to produce pectin gels in the presence of 0.2 M monovalent ionic salts. At pH 5.0, pectin gels were induced following enzymatic deesterification of high methoxy pectin, with greater deesterification observed using p-PME compared to f-PME. Under these conditions, the deesterification limit of f-PME ended up with a pectin of DE 30.5–31.9 which did not gel at the PME reaction completion, while p-PME reduced the pectin's DE to 16.0–17.2, resulting in gel formation. The pectin gel induced by KCl was significantly stronger than the NaCl-induced gel, but LiCl did not induce pectin gelation. The gel strength was influenced by both DE and species of monovalent cation. The KCl-induced gels released less water than NaCl-induced gels. A synergistic effect on gel strength was observed from the pectin treated with a combination of (p + f)-PMEs, producing even more stable gels. These results indicated that the pectin gelation of our system would be enhanced both by using larger monovalent cation and by lowering the DE value, which would presumably be attributed to the different action patterns recognized for p- and f-PMEs. This pectin gelation system could provide a useful alternative to acid-sugar or calcium cross-linked gels in food and other industrial applications.

Mutual separation of two monovalent metal ions by multistage electrodialysis

A multistage electrodialyzer having an enriching section and a stripping one has been developed to separate monovalent cation species in the aqueous solution. A feed solution containing LiCl and KCl is supplied to the middle stage of the dialyzer, and a solution of HCl is supplied to the cathode stage. Stages from cathode to feed are the enriching section and those from feed to anode are stripping section. Aqueous solution flows from the cathode stage toward the anode stage as a reflux flow. The ratio K + / Li + in the enriching product increased with the increase in reflux flow rate and decreased with the increase in current density, while the ratio Li + / K + in the stripping product increased with the current density and decreased with the reflux flow rate. Simulation by a stage to stage calculation was carried out by use of the operating equation based on mass balance and the relation of permselectivities alternatively. The calculated results were in good agreement with the experimental ones, and indicated that a large yield of product as well as a large concentration ratio can be achieved by increasing stage number.

Monovalent salt-induced gelation of enzymatically deesterified pectin.

Pectin gels were induced by monovalent salts (0.2 M) concurrently with deesterification of high methoxy pectin using a salt-independent orange pectin methylesterase (PME). Constant pH was maintained during deesterification and gelation. If salt or PME was absent, the pectin did not form a gel. The gel strength was influenced by both pH and species of monovalent cation. At pH 5.0, the pectin gel induced by KCl was significantly stronger than the NaCl-induced gel. In contrast, a much stronger gel was produced in the presence of NaCl as compared to KCl at pH 7.0. LiCl did not induce pectin gelation at either pH. Molecular weights of pectins increased from 1.38 x 10(5) to 2.26 x 10(5) during NaCl-induced gelation at pH 7. One proposal to explain these pectin molecular weight changes is a hypothetical PME transacylation mechanism. However, these pectin molecular weight changes can also be explained by metastable aggregation of the enzymatically deesterified low methoxy pectin. We postulate that gelation was induced by a slow deesterification of pectin under conditions that would normally salt out (precipitate) low methoxy pectin in the absence of PME.

Cation Affinities of Cyclohexadepsipeptide: Ab Initio Study

The interactions of cations (Li+, Na+, Be2+, Mg2+) with a cyclohexadepsipeptide composed of glycines and glycolic acids have been investigated using ab initio calculations. The crucial role played by the orientation of the ion−dipolar moiety could possibly explain the binding preference upon complexation with alkali cations since the dipole moment of the amide carbonyl moiety is greater than that of the ester carbonyl moiety. We find that cations prefer to bind amide carbonyl oxygen atoms rather than ester oxygen atoms. This should also explain why the binding affinities of the cyclohexadepsipeptide for cations are larger than those of 18-crown-6 and [16]starand in the gas phase. However, in divalent cationic cases which have twice the charge of the monovalent cationic species, the coordination numbers related to charge−charge interactions tend to be somewhat more important than the ion−dipolar moiety interactions. The self-consistent reaction field (SCRF) results for hexahydrated complexes of Na+ with the cyclohexadepsipeptide indicate that cations prefer to bind amide carbonyl oxygen atoms rather than ester oxygen atoms in solution as well as in the gas phase. The complexation of two cyclohexadepsipeptide molecules with one cation (i.e., 2:1 sandwich-type complexes) in the gas phase has also been discussed to affirm the possible existence of such complexes suggested by Ovchinnikov. In these complexes, a cation binds mainly amide carbonyl oxygen atoms. If glycines and glycolic acids are replaced by other residues, these modified cyclodepsipeptide ionophores could show different selectivities for cations with varying flexibilities.

Ca selectivity of the transduction channels in the hair cells of the frog sacculus

The extracellular receptor currents evoked by step displacements of the otolithic membrane of the isolated saccular macula of Rana esculenta were recorded under transepithelial voltage clamp conditions. With the aim to depolarize the hair cells and increase the fractional resistance of the apical membranes, the basal side of the preparation was bathed in saline with an increased K+ concentration (62 mM). This caused a shift in the non-linear receptor current-voltage relation along the voltage axis of -51 mV +/- 10 mV; (mean +/- SD; n = 32) and a reduction in the transepithelial resistance of 10%. Under these conditions the electrical properties of the macula are assumed to be controlled by the apical membranes. The effects of different concentrations of Ca2+ in the apical solution on the receptor current-voltage relation were examined. Change of the apical Ca2+ concentration (range 3 mM to 70 microM) varied the transepithelial voltage at which the receptor current was zero (Vrev). Fitting a modified constant field equation to the relation between the apical Ca2+ concentration and the change in Vrev gave an estimate of PCa/PK of the transduction channels of 212. Furthermore, a high relative permeability of the transduction channels for other divalent cations (Ba2+, Sr2+) was measured, whereas Mn2+ inhibited the receptor current. The receptor current was inhibited by amiloride (IC50 3.2 microM +/- 1.7 microM) and nifedipine (IC50 1.9 microM +/- 0.6 microM). Reduction of the apical Ca2+ concentration to 90 microM in standard apical solution reduced the size of the receptor current to 67% +/- 30% (n = 17) compared to control but did not affect the shape of the receptor current-voltage relation. Subsequent substitution of K+ by Na+ caused a further reduction of the receptor current to 32% +/- 29% (n = 9), changed the receptor current-voltage relation into a linear relation and diminished the adaptation of the receptor current. These results indicate that the mechano-electrical transduction channels of the frog saccular hair cells are highly selective to Ca2+ and that the conductance of the channels may be influenced by the apical monovalent cation species.

Minimum enzyme unit for Na +/K +-ATPase is the αβ-protomer. Determination by low-angle laser light scattering photometry coupled with high-performance gel chromatography for substantially simultaneous measurement of ATPase activity and molecular weight

The oligomeric state of canine renal Na +/K +-ATPase solubilized by octaethylene glycol n-dodecyl ether (C 12E 8) was studied by means of low-angle laser light scattering photometry coupled with high-performance gel chromatography (HPGC). At around 0°C the solubilized enzyme was separated into the (αβ) 2-diprotomeric and αβ-protomeric protein components with M r values of 302 000 ± 10 000 and 156 000 ± 4000, respectively, in approximately equal quantities. As the temperature of chromatography was increased toward 20°C, the two protein components converged into a single major component. The M r of this component depended on the monovalent cation included in the elution buffer, and was 255 000 or 300 000 in the presence of 0.1 M NaCl or 0.1 M KCl, respectively. A computer simulation technique showed that the solubilized enzyme was in a dissociation-association equilibrium of 2 promoters ⇌ diprotomer at 20°C, and the difference in apparent M r of the solubilized enzyme between the two species of monovalent cation was interpreted by an association constant ( K a) in the presence of 0.1 M KCl that was about 50-fold larger than in the presence of 0.1 M NaCl. In order to measure ATPase activity and M r of the solubilized enzyme simultaneously, a TSKgel G3000SW column had been equilibrated and was eluted with an elution buffer containing 0.30 mg/ml C 12E 8 and 60 μg/ml phosphatidylserine (bovine brain) as well as the ligands necessary for the enzyme to exhibit the activity at pH 7.0 and 20°C. The solubilized enzyme was always eluted as a single protein component irrespective of the amount of the protein applied to the column, ranging between 240 and 10 μg. The M r of the protein component, however, decreased from 214 000 to 158 000 with the decrease of the protein amount. The specific ATPase activity, however, remained constant at a level of 64 ± 4% of that of the membrane-bound enzyme even in the range of protein concentration sufficiently low as to allow the enzyme to exist only in the protomeric form. Thus, the αβ-protomer is concluded to be the minimum functional unit for the ATPase activity. The value of K a obtained from the concentration-dependent dissociation curve was 5 · 10 5 M −1 for the enzyme turning over, and 1.1 · 10 7 M −1 for the enzyme inhibited with ouabain. It was discussed, based on the values of K a obtained, that the enzyme would exist as the diprotomer or the higher oligomer in the membrane.

Monovalent cation dependent phase behaviour of dipalmitoylphosphatidylglycerol

The phase behaviour of dipalmitoylphosphatidylglycerol (DPPG) was studied as a function of [NaCl] using differential scanning calorimetry and the effects of monovalent cations, Na +, K +, Li + and Cs + were compared at 300 mM cation concentration. Main phase transition, pretransition, and subtransition temperatures and enthalpies were found to depend on the concentration of NaCl and the monovalent cation species. Compared to the main phase transition both pretransition and subtransition were more sensitive and also exerted greater specificity with respect to the different cations. Considerable hysteresis ( δT m ) in the main transition temperature ( T m ) upon heating and cooling was evident in the absence of salt. Upon increasing [NaCl], a decrease in δT m was observed. Subtransition and pretransition temperatures and enthalpies increased upon increasing [NaCl] from 50 mM to 1 M. The appearance of subtransition was considerably faster in the presence of high NaCl concentrations. No pretransition was observed in the absence of salt or in the presence of 300 mM LiCl. Pretransition temperatures of DPPG in the presence of 300 mM NaCl, KCl, and CsCl were 34.0, 34.3 and 30.4°C, respectively. The subtransition temperatures after 5 days of incubation at 6°C with 300 mM NaCl, KCl, CsCl were 29.3, 22.6 and 23.6°C, respectively. The highest subtransition temperature of 32.6°C was observed in the presence of 300 mM LiCl but compared to other cations the appearance of subtransition in the presence of Li + required considerably longer incubation times.

Electrical properties of ?-zirconium phosphate and its alkali salts in a humid atmosphere

Humidity dependence of impedance was examined by using the complex impedance analysis for fine crystalline zirconium bis(monohydrogen phosphate) monohydrate and its alkali salts. The value of C0 in Cp(ω)=C0(jω/ω0)−α was hardly dependent on the relative humidity and monovalent cation species. The resistive component and its activation energy decreased with increase in the relative humidity and the former was expressed as R=R* exp (−E/kT*) exp (E/kT) The pre-exponential factor R*, was hardly influenced by the humidity and decreased when the acidic protons were replaced with monovalent alkali cations. The activation energy of conduction was strongly affected by the degree of orientation and particle size of crystal with layered structure in a whole humidity region and increased by replacing the protons by alkali cations.

Uptake and Leakage of Some Ions in Relation to Potassium Uptake Rhythm in <italic>Lemna gibba</italic> G3

The time courses of the uptake of various inorganic ions from the flow medium were compared with the rhythmical potassium uptake in Lemna gibba G3. The duckweeds in the flow medium absorbed 20–40% of magnesium, 30–50% of phosphate, 40–80% potassium and 50–90% of nitrate, the percentage varying rhythmically, but they constantly absorbed about 20% of calcium. The total anion uptake was 1.5 times greater than the total cation uptake. The duckweeds absorbed cesium or rubidium as well as they did potassium. They also absorbed sodium if potassium was absent from the medium. Lithium was not absorbed even in the absence of potassium. Potassium leaked from the duckweed into the potassium-free flow medium, and the rate of leakage changed diurnally under continuous light, with maximum leakage occurring at the same circadian time as when the potassium uptake rhythm in the normal flow medium drops to the minimum point. The pattern of potassium leakage in dim light was influenced by the species of monovalent cation in the medium. In darkness, however, the leakage rhythm ran for 36 hr irrespective of cation species.

Calcium ion binding to lobster nerve membranes

The binding of 45Ca 2+ to membrane material isolated from lobster walking leg nerves was studied using a rapid filtration technique. In solutions of high ionic strength (450 mM), the amount of 45Ca 2+ bound to this membrane material was found to be highly dependent on the monovalent cation used in the incubating solution. The amount of 45Ca 2+ bound was larger when the membranes were incubated in a KCl solution compared to when they were incubated in a NaCl solution. This difference was attributed to the ability of these closed membrane vesicles to accumulate Ca 2+ into the vesicle when incubating in a KCl solution but not in a NaCl solution. This accumulation of Ca 2+ was found to be independent of metabolic energy and depended primarily on the absence of Na + from the incubation medium. At low ionic strength, the membranes formed open fragments and the amount of Ca 2+ bound was no longer sensitive to the monovalent cation species in the incubation solution. The 45Ca 2+ bound under these low ionic strength conditions was considered to be bound to anionic sites on the membranes.

Threshold phenomena in chemoreception and taxis in slime mold Physarum polycephalum.

The plasmodium of Physarum polycephalum reacts to various kinds of chemicals substances and moves towards or away from them. Threshold concentration of recognition of chemicals was examined in terms of membrane potential and of the averaged motive force of tactic movement by using a double-chamber method, i.e., a single plasmodium was placed between two compartments through a narrow ditch, and differences in membrane potential and in pressure between two compartments were measured. Results are summarized as follows: (a) By increasing the concentration of various substances in one compartment, the membrane potential started to change at a certain threshold concentration, C-th, for each chemical. Chemotactic movement of the plasmodium took place at the same threshold concentration. These results held both for attractants (glucose, galactose, phosphates, pyrophosphates, ATP, c-AMP, etc) and for repellents (various inorganic salts, sucrose, fructose, etc.). (b) The threshold concentration, Cth, for inorganic salts decreased remarkably with increase of the valences of cations, zeta, and was proportional to Z-6, I.E., THE Shultze-Hardy rule known in the field of colloid chemistry was found to be applicable. (c) The plasmodium distinguished the species of monovalent cations in the following order: H(Li(K(Na(Rb(Cs(NH-4 Plots of log Cth against the lyotropic number of anion fell on different straight lines for each monovalent cation species. (d) Plots of log Cth, against the reciprocal of the absolute tempe lines were almost the same and gave a value of 12 kcal/mol for the enthalpy change. These results suggest that the recognition of chemical substances appears as the result of a structural change of the membrane at the threshold point, and that the change in membrane structure is transmitted simultaneously to the motile system of the plasmodium.

Electron Paramagnetic Resonance Studies of Manganese(II)-Pyruvate Kinase-Substrate Complexes

Abstract Electron paramagnetic resonance spectra of Mn(II) bound to pyruvate kinase and its substrate and inhibitor complexes are examined in solution. The binary complex of Mn(II) with the enzyme gives a spectrum which indicates that the electronic symmetry of the bound cation is only moderately distorted upon liganding to the protein. The spectrum of the binary enzyme-Mn(II) complex is unaltered upon formation of ternary complexes with either ADP or ATP. However, when ternary complexes are formed with either pyruvate or P-enolpyruvate, there are gross changes in the position and shape of the spectral lines which correlate with changes in the electronic symmetry of the bound Mn(II) and the electron spin relaxation time, respectively. The former changes are indicative of changes in the ligands of the bound metal ion and the latter of the accessibility of the binding site to the bulk solvent. Minor changes are observed in the spectrum of the pyruvate complex upon addition of ATP or enzymatic enolization cofactors such as arsenate or inorganic phosphate. Preliminary studies of Mn(II) complexes with chelating agents have revealed a striking similarity in spectra for the 2:1 complex of iminodiacetic acid and Mn(II) and the ternary complex of manganese-pyruvate kinase and pyruvate. Neither the spectrum of the binary complex nor that of the ternary complex with pyruvate is influenced by the presence or absence of activating monovalent cations such as K+. In contrast, spectra for the ternary complex of P-enolpyruvate are influenced by the species of monovalent cation in solution. In the presence of the nonactivating tetramethylammonium cation, the spectrum for the P-enolpyruvate ternary complex is a superposition of spectra for two distinct species. One species gives a very anisotropic spectrum which resembles that obtained in the presence of K+, whereas the other species gives a much more isotropic spectrum which matches the spectrum for the ternary complex of the inhibitor, α-(dihydroxyphosphinylmethyl) acrylic acid. Higher temperatures favor the species with the anisotropic spectrum. Ternary complexes with the inhibitor, P-glycolate, and the pseudosubstrate, Z-P-enol-3-fluoropyruvate, give spectra which show the presence of two separate species in the presence of tetramethylammonium cations in analogy to the substrate P-enolpyruvate. Another pseudosubstrate, Z-P-enol-α-ketobutyrate, gives only the anisotropic spectrum in the presence of either tetramethylammonium or K+ cations. The presence of only one form of the ternary complex in the presence of tetramethylammonium ion with this weak substrate is attributed to steric restrictions imposed by the methyl group. With the normal substrate, P-enolpyruvate, the fraction of the ternary complex which exists in the anisotropic form for a given monovalent ion appears to be correlated with the activating effect that ion, being greatest for K+ and Rb+, intermediate for Na+ and Li+, and least for tetramethylammonium ion.

Factor IV—ionised calcium—its requirement for glass-contacting of plasma

AFTER prolonged dialysis of citrated platelet-free non-contact plasma against isotonic saline, its behaviour on recalcification alone and in the presence of added platelets, tissue thromboplastin, and long-chain fatty acids was relatively unchanged, but in the presence of a glass surface its behaviour was quite different. Unlike native plasma or citrated plasma, dialysed plasma was insensitive and could be incubated in glass apparatus with little or no contact activation, the amount of change induced being inversely proportional to the duration of the dialysing process. When such dialysed plasma was exposed to glass in the presence of ionised calcium at suitable low concentration, contacting occurred and coagulation on subsequent full recalcification in siliconed apparatus was much accelerated. With calcium citrate the contact activity induced was proportional to the concentration of calcium during the glass-contact stage. The total activity was related to the ionic strength of the electrolytes in the plasma test mixture. The system was sensitive to the monovalent cation species present, sodium being appreciably more active than potassium in promoting coagulation.

Anion-activated 5′-nucleotidase in cell envelopes of a slightly halophilic Vibrio alginolyticus

1. 1. Unique properties of the 5′-nucleotidase (5′-ribonucleotide phosphohydrolase, EC 3.1.3.5) in cell envelopes of a slightly halophilic Vibrio alginolyticus were studied. 2. 2. More than 70% of the 5′-nucleotidase activities were associated with the cell envelopes prepared by the osmotic lysis or by the lysis of penicillin spheroplasts. 3. 3. The activities in the envelopes were increased by storage in a frozen state or by pre-incubation at an alkaline pH in the presence of monovalent cations. The order of effectiveness for the pre-activation was: NH 4 + ⪢ Li + > Na + > K +  Rb +  Cs +. Such pre-activation was not detected with the envelopes prepared in the absence of Mg 2+ and Cl −. 4. 4. Both the unactivated and the activated enzymes hydrolyzed all 5′-ribonucleotides to the corresponding ribonucleosides and P 1. For the hydrolysis of these substrates, both Mg 2+ and an appropriate anion were required for maximal activity. Among monovalent anions, Cl − was the most effective, the order of effectiveness being Cl −  Br − > I − > NO 3 −. Acetate and SO 4 2− showed no effect. No essential requirement for a particular species of monovalent cation was detected. From these results, the activities in the envelopes of V. alginolyticus were identified as a Mg 2+-dependent and anion-activated 5′-nucleotidase. Furthermore, Ca 2+-dependent and anion-activated ribonucleoside 5′-monophosphatase was also found in this envelope. This preparation was unable to hydrolyze UDPG, glucose 1- and 6-phosphates, 2′- and 3′-ribonucleotides, 2′,3′-cyclic ribonucleotides, bis(p- nitrophenyl) phosphate, p- nitrophenyl phosphate or PP i. 5. 5.|The activated enzyme was inhibited by high concentrations of salts such as 1.0 M each of LiCl and NaCl. The unactivated enzyme, however, was unaffected by these salts. 6. 6.|The significance of the Cl − modifications on the enzyme activities isolated from slightly halophilic(marine) bacteria is discussed.