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The effects of bile salts (sodium cholate and sodium deoxycholate, 0-20 mmol/L), divalent cations (Ca(2+), Mg(2+), Cu(2+) and Zn(2+), 0-20 mmol/L) or pH (3.0-10.0) on the adsorption of norfloxacin by three selected soils (Paddy_H, Paddy_G and Red_J) were systematically studied. Soil adsorption of norfloxacin follows a pseudo second-order kinetics model, and the maximum adsorption capacity has been determined from the nonlinear fit of the Langmuir isotherm model to be 88.8, 88.1 and 63.0 μmol/g for the adsorption onto Paddy_H, Paddy_G and Red_J, respectively. The results indicate that norfloxacin has a high adsorption affinity for the agricultural soils tested and that the organic content of these soils have at least a slight influence on this adsorption. The adsorption of norfloxacin to soils was strongly dependent on pH and exhibited a maximum at approximately pH 6. The presence of divalent cations prominently suppressed the adsorption of norfloxacin by paddy soils, which followed an order of Cu(2+) > Mg(2+) > Ca(2+) > Zn(2+), and by red soil, which followed an order of Cu(2+) > Zn(2+) > Ca(2+) > Mg(2+). The adsorption of norfloxacin (by the soils studied) sharply decreased as the amount of bile salts was increased. For uncharged norfloxacin at environmentally relevant pH values, such factors as soil type, exogenous divalent cations and macromolecules significantly altered the environmental fate and transport of norfloxacin between aquatic and soil interfaces., (Copyright © 2014 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.)

Substitution of ionic either anion or cation in a controlled amount into carbonated hydroxyapatite (CHA) structure is one of the efficient and safest ways in enhancing the properties of the materials. However, most of the works studied only focused on the physical and mechanical properties of single ionic substitution. For the first time, the influence of simultaneous ternary substitutions of divalent cations into porous CHA scaffolds on the physicochemical, mechanical, degradative, and in vitro biological properties is investigated in the present study. Three different compositions of porous scaffolds with binary and ternary divalent cations, namely, pure CHA (S11), CoSr CHA (S21), and MgCoSr CHA (S31) were fabricated using a polyurethane (PU) foam replication technique. Despite a small amount of Mg2+, Co2+, and Sr2+ being added, these divalent cations had successfully substituted into the Ca2+ site and remained as single-phase B-type CHA. The produced scaffolds demonstrated open, interconnected, and uniform pores. Interestingly, simultaneous ternary divalent cation substitution into CHA structure had successfully enhanced the compressive strength of the sintered scaffolds and also promoted better cell attachment and activities than the binary doped- and pure CHA scaffolds. It is important to note that choosing the right divalent cation can be the determining factor in tuning the physicochemical, mechanical, and biological properties of CHA scaffolds. [ABSTRACT FROM AUTHOR]

Divalent ion-conducting solid electrolytes with NASICON-type three-dimensional network structures (MxHf1−x)4/(4−2x)Nb(PO4)3 (M = Ni, Mg, Ca, Sr) were successfully developed by introducing M2+ cations into HfNb(PO4)3 solids. The presence of high-valence cations such as Hf4+, Nb5+, and P5+ in the structures effectively reduced the electrostatic interaction between the conducting M2+ cations and the surrounding oxide anions, enabling the M2+ cations to migrate smoothly in the rigid crystal lattice. The relationship between the cation conductivity in NASICON-type solids and the ionic radius of the migrating divalent cation species was also clarified by taking into account the relative sizes of the conduction pathways in the structures. [ABSTRACT FROM AUTHOR]

Abstract Quantum-mechanical calculations using density functional theory were employed to calculate the incorporation energies of divalent cations (e.g., Mg2+, Ca2+, Sr2+, and Ba2+) in uranium dioxide (UO 2). Divalent cations are known to incorporate into the uranium dioxide system, albeit the incorporation mechanism remains unclear. In this work, three charge-balancing mechanisms were evaluated to achieve a net neutral system, including the substitution of (1) a divalent cation for a tetravalent uranium atom and oxygen atom; (2) two divalent cations for a tetravalent uranium atom; and (3) a divalent cation for a tetravalent uranium atom and associated oxidation of two additional tetravalent uranium atoms. Multiple incorporation scenarios were considered for each charge-balancing mechanism to determine the lowest energy case. For the energetically favorable incorporation mechanisms, Sr2+ incorporation is favored over Mg2+, Ca2+, and Ba2+ incorporation by 0.11 eV–0.97 eV. The coupled substitution of two divalent cations for one uranium cation is unfavorable. The mechanism where the substitution of a divalent cation for a U4+ atom is accompanied with the oxidation of two U4+ to U5+ (e.g. , ΔE incorp (Sr2+) = −3.63 eV), is the most favorable incorporation mechanism compared to the other mechanisms investigated in this paper. In general, the most favorable case is where the oxidized uranium atoms are located at a first nearest neighbor distance (3.914 Å) from the substituted divalent cation and are minimally separated (U5+-U5+ distance = 3.936 Å). Graphical abstract Image 1 Highlights • Divalent cations incorporate in V U '''' in UO 2 requiring charge balancing mechanisms. • Energetically favorable charge balanced mechanisms include an V O ⋅ ⋅ or U U ⋅ . • Most favorable incorporation mechanism occurs with U U ⋅ . • The change in volume corresponds to the size of atomic radii of dopant. [ABSTRACT FROM AUTHOR]

[Display omitted] • Dually charged membranes were prepared by loading UiO-66-(NH 2) 2 into polyamide layer. • The amino-rich nanochannels could be regulated by ligand replacement strategy. • Satisfactory rejection for both CaCl 2 and Na 2 SO 4 could achieved with high permeance. • UiO-66-(NH 2) 2 played a crucial role in the enhanced rejection of divalent cations. • Migration energy barrier across UiO-66-(NH 2) 2 was an order of magnitude higher. Traditional polyamide nanofiltration membranes suffer from permeability-selectivity trade-off limitation and unsatisfactory rejection for divalent cations. Herein, a novel dually charged membrane was constructed by incorporating positively charged UiO-66-(NH 2) 2 into the negatively charged polyamide layer. Thanks to the customizable nanochannels of metal-organic frameworks, the amino-rich nanochannels of UiO-66-(NH 2) 2 could be fabricated through a ligand replacement strategy. UiO-66-(NH 2) 2 played a crucial role in the enhanced rejection of divalent cations, meanwhile negatively charged polyamide surface guaranteed the efficient Na 2 SO 4 rejection. Satisfactory rejections of CaCl 2 (96.07 %) and Na 2 SO 4 (90.62 %) were achieved simultaneously by optimal TFN-D5. Meanwhile, TFN-D5 owned the greatly-improved water permeance of 19.44 LMH/bar, which was about 1.5 times better than that of the TFC-control. Calculations based on density functional theory further confirmed UiO-66-(NH 2) 2 rejected Ca2+ efficiently since the migration energy barrier across UiO-66-(NH 2) 2 was an order of magnitude higher than that of UiO-66-NH 2 and UiO-66. Moreover, the desirable rejections were beyond 94 % towards many divalent cation salts including MgCl 2 , NiCl 2 , PbCl 2 , MnCl 2 , CdCl 2 and ZnCl 2. Thus, this work provided an efficient way to realize the synergistic removal of both divalent cations and anions. [ABSTRACT FROM AUTHOR]

Prior to 2008, all previously studied conventional bacterial flagellar motors appeared to utilize either H or Na as coupling ions. Membrane-embedded stator complexes support conversion of energy using transmembrane electrochemical ion gradients. The main H-coupled stators, known as MotAB, differ from Na-coupled stators, PomAB of marine bacteria, and MotPS of alkaliphilic Bacillus. However, in 2008, a MotAB-type flagellar motor of alkaliphilic Bacillus clausii KSM-K16 was revealed as an exception with the first dual-function motor. This bacterium was identified as the first bacterium with a single stator-rotor that can utilize both H and Na for ion-coupling at different pH ranges. Subsequently, another exception, a MotPS-type flagellar motor of alkaliphilic Bacillus alcalophilus AV1934, was reported to utilize Na plus K and Rb as coupling ions for flagellar rotation. In addition, the alkaline-tolerant bacterium Paenibacillus sp. TCA20, which can utilize divalent cations such as Ca, Mg, and Sr, was recently isolated from a hot spring in Japan, which contains a high Ca concentration. These findings show that bacterial flagellar motors isolated from unique environments utilize unexpected coupling ions. This suggests that bacteria that grow in different extreme environments adapt to local conditions and evolve their motility machinery. [ABSTRACT FROM AUTHOR]

Na-4-mica, a highly charged swelling mica, has suffered from insufficient understanding of some fundamental features such as partial layer collapse and rearrangement of interlayered cations and layers during exchange reaction. This study focuses on elucidating the changes in chemical environments of divalent cations and in layered structure during the exchange reaction with divalent cations. Cation exchange reaction with a series of alkali earth cations led to significant changes in both XRD pattern and IR spectra. The extent of cation exchange reaction depended highly and systematically on cation size and hydration energy. Exchange reaction with Mg 2 + and Ca 2 + led to highly hydrated phases whereas that with Sr 2 + to anhydrous phase and that with Ba 2 + to remarkable degradation of layered structure. The hydrated divalent cations could be quickly stabilized in interlayer space in spite of localized incompatibility of both lattice and charge through formation of interstratified phases having various ratios of Na + /M 2 + and Na + /H 3 O + . Therefore, divalent cations could be stably accommodated either in hydrated or anhydrous state within the cavities, preferably around crystal edges to obstruct their further uptake. [ABSTRACT FROM AUTHOR]

The gating of Ca 2+-activated Cl − channels is controlled by a complex interplay among [Ca 2+] i, membrane potential and permeant anions. Besides Ca 2+, Ba 2+ also can activate both TMEM16A and TMEM16B. This study reports the effects of several divalent cations as regulators of TMEM16A channels stably expressed in HEK293T cells. Among the divalent cations that activate TMEM16A, Ca 2+ is most effective, followed by Sr 2+ and Ni 2+, which have similar affinity, while Mg 2+ is ineffective. Zn 2+ does not activate TMEM16A but inhibits the Ca 2+-activated chloride currents. Maximally effective concentrations of Sr 2+ and Ni 2+ occluded activation of the TMEM16A current by Ca 2+, which suggests that Ca 2+, Sr 2+ and Ni 2+ all regulate the channel by the same mechanism. [ABSTRACT FROM AUTHOR]

Abstract: Separation mechanisms for the three model divalent cations with very similar atomic weights (Cu, 63.5Da; Co, 58.9Da and Ni, 58.7Da) by two nanofiltration (NF) membranes (Nitto Denko ESNA and GE Osmonics DK) were studied in a cross flow module from pHs3 to 5. The results show that the rejection order for the two selected membranes was Ni2+ >Cu2+ >Co2+ from the conducted experiments, and the removal efficiency was increased as pH was decreased for all three metals. It was found that enthalpy of hydration and concentration polarization exerted the controlling effect on the membrane selective transport rather than atomic weight, Stokes radius and hydrated radius. Besides, the counterion of sulfate enhanced the removal efficiencies, but an increase of sulfate more than 0.01M reduced the removal efficiencies. Moreover, the removal efficiency of DK membrane was better than that of the ESNA membrane due to the positive charge of DK membrane at low pH. [Copyright &y& Elsevier]

Abstract: Divalent cations have been reported to develop bridges between anionic polyelectrolytes and negatively-charged colloidal particles, thereby enhancing particle flocculation. However, results from this study of kaolinite suspensions dosed with various anionic polyacrylamides (PAMs) reveal that Ca2+ and Mg2+ can lead to colloid stabilization under some conditions. To explain the opposite but coexisting processes of flocculation and stabilization with divalent cations, a conceptual flocculation model with (1) particle-binding divalent cationic bridges between PAM molecules and kaolinite particles and (2) polymer-binding divalent cationic bridges between PAM molecules is proposed. The particle-binding bridges enhanced flocculation and aggregated kaolinite particles in large, easily-settleable flocs whereas the polymer-binding bridges increased steric stabilization by developing polymer layers covering the kaolinite surface. Both the particle-binding and polymer-binding divalent cationic bridges coexist in anionic PAM- and kaolinite-containing suspensions and thus induce the counteracting processes of particle flocculation and stabilization. Therefore, anionic polyelectrolytes in divalent cation-enriched aqueous solutions can sometimes lead to the stabilization of colloidal particles due to the polymer-binding divalent cationic bridges. [Copyright &y& Elsevier]

Abstract: Interactions in aqueous solutions between a tetrameric naphthenic acid in sodium salt (BP10Na4) and divalent Mg2+ and Ca2+ cations were investigated by isothermal titration calorimetry (ITC) and dynamic light scattering (DLS). Colloidal aggregation of the tetrameric sodium naphthenates to vesicles and micelles enhances its binding with divalent cations. In vesicle systems, Ca2+ was found to bind first with carboxylate groups located at the external water/lipid interface of vesicles. The cations then diffuse through the membrane to interact with the inner carboxylate groups. Higher Ca2+ concentration and higher salinity gradients enhance cation diffusion. Under solution chemistry conditions where micelle dominates, Ca2+ reacts only with outer carboxylate groups of BP10Na4 without any significant cation diffusion through the aggregates. The binding of calcium with sodium naphthenate is an entropy-driven process where entropy gain comes from the dehydration of both cations and carboxylate groups of BP10Na4. The affinity of Mg2+ to BP10Na4 is much weaker than Ca2+ due to its stronger hydration and hence larger size of hydrated magnesium ions than hydrated calcium ions. [Copyright &y& Elsevier]

Abstract: It was reported that the circulating blood cells, including neutrophils, were more likely adherent to the curved micro-vessels than the straight ones. Our previous work indicated that the vessel curvature, cell-cell interaction, and wall shear stress variation would greatly affect this preferential adhesion. It was also found that the affinity state of integrins would be influenced by different divalent cations, which provides an opportunity to explore the particular importance of integrins activation in neutrophils adhesion. In this study, we aim at numerically investigating the effects of divalent cations, i.e. Mn2+, Mg2+ plus EGTA, and Ca2+, on VLA-4/VCAM-1 adhesion under flow condition. The blood dynamics was carried out by the lattice Boltzmann method (LBM), the neutrophil dynamics was governed by the Newton''s law of translation and rotation, and a refined neutrophil adhesive dynamics model that taken into account the effect of wall shear stress gradient on receptor-ligand bonds was applied to solve the VLA-4/VCAM-1 adhesion. The simulation results indicated that the divalent cations significantly influenced neutrophils adhesion under hydrodynamic condition. It was found that the capability of stimulating affinity state of VLA-4 to VCAM-1 was larger in Mg2+ plus EGTA than in Ca2+, and largest in the presence of Mn2+. Our results would be helpful to understand the β1-integrin-mediated neutrophils adhesion in real physiological situations. [Copyright &y& Elsevier]

Abstract: Serum albumin is an abundant protein in blood plasma, that is well-known for its ability to transport hydrophobic biomolecules and drugs. Recent hypotheses propose that serum albumin plays a role in the regulation of lipid metabolism in addition to its lipid transport properties. The present work explores the capacity of bovine serum albumin (BSA) to extract diacylglycerols (DAG) from phospholipid bilayers, and the inhibition of such interaction by divalent cations. Quantitative measurements using radioactive DAG and morphological evidence derived from giant unilamellar vesicles examined by confocal microscopy provide concurrent results. BSA extracts DAG from vesicles consisting of phosphatidylinositol/DAG. Long, saturated DAG species are incorporated more readily than the shorter-chain or unsaturated ones. Divalent cations hinder DAG uptake by BSA. For Ca2+, the concentration causing half-maximal inhibition is ≈10 μM; 90% inhibition is caused by 100 μM Ca2+. Sr2+ requires concentrations one order of magnitude higher, while Mg2+ has virtually no effect. As an example on how DAG uptake by BSA, and its inhibition by Ca2+, could play a regulating role in lipid metabolism, a PI-specific phospholipase C has been assayed in the presence of BSA and/or Ca2+. BSA activates the enzyme by removing the end-product DAG, but the activation is reverted by Ca2+ that inhibits DAG uptake. [Copyright &y& Elsevier]

Abstract: Compounds of the Na1.5(Mn1− xMx 2+)1.5Fe1.5(PO4)3 (M 2+=Cd2+, Zn2+) alluaudite-type solid solutions were synthesized by solid-state reactions in air, between 800 and 900°C, and were investigated by X-ray powder diffraction and infrared spectroscopy. The site occupancy factors of the Na1.5(Mn1− x Cd x 2+)1.5Fe1.5(PO4)3 compounds, obtained from the Rietveld refinements of the X-ray powder patterns, indicate that the replacement of Mn2+ by Cd2+ takes place on the M(1) site for x=0.25 and 0.50, and then on the M(1) and M(2) sites for x=0.75 and 1.00. Small amounts of Cd2+ were also detected on the A(1) site, compensated by small amounts of Na+ occurring on M(1). This partially disordered distribution is probably due to the similar effective ionic radii of Cd2+ and Na+. The cationic distributions in the Na1.5(Mn1− x Zn x 2+)1.5Fe1.5(PO4)3 solid solution indicate that Zn2+ was first introduced in the M(2) site, before to replace Mn2+ in the M(1) site. The unit-cell parameters show a significant increase when Mn2+ is replaced by Cd2+, and a significant decrease when it is replaced by Zn2+. The variations of the β angle were also correlated with the M(1)–M(2) distances. The infrared spectra show the displacement of an absorption band at ca. 400–425cm−1, which is assigned to the vibrations of the M 2+ cations localized on the M(1) site. This assignment is confirmed by the excellent correlations between the M(1)–O bond distances and the energy of the absorption band. [Copyright &y& Elsevier]

The thermal stability of carp G-actin was investigated by monitoring loss of actin polymerization ability. To determine the amount of native actin remaining after heat treatment, actin was labeled with a fluorescence reagent, N-(1-pyrene)iodoacetamide. The loss of polymerization ability of carp actin during heat treatment, at between 45 and 55°C, occurred faster than that of chicken actin. The inactivation rate was influenced by concentrations of ATP and Ca2+ in solution. With the increase of Ca2+ concentration, the inactivation of carp actin was markedly suppressed. Furthermore, the activation energy of the inactivation of carp actin obtained from an Arrhenius plot was similar to that of chicken actin. These results indicated that the thermal instability of carp G-actin was due to the low affinites of ATP and Ca2+ for carp actin described in a previous report. [ABSTRACT FROM AUTHOR]

Abstract: While Dicer alone has been shown to form stable complexes with double-stranded RNAs and short interfering RNAs, its interactions with single-stranded RNAs (ssRNAs) have not been characterized. Here, we show that recombinant human Dicer alone can bind 21-nt ssRNAs in vitro, independent of their sequence and structure. We also demonstrate that Dicer binds ssRNAs having a 5′-phosphate with greater affinity versus those with a 5′-hydroxyl. In addition, 3′-biotinylated ssRNAs are bound by Dicer with lower affinity than 3′-hydroxyl ssRNAs. The stability of ssRNA–Dicer complexes was found to depend on divalent cations. Together, our results suggest a role for the PAZ domain of Dicer in binding ssRNAs and may indicate roles for Dicer in cellular function beyond those currently known. [Copyright &y& Elsevier]

Ca2+ was found to be essential for initiating Halobacterium salinarum CCM 2090 cell aggregation. The floc formed from such aggregation could easily be dissociated without cellular lysis by sodium citrate. Cr2+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+, and Zn2+ could replace Ca2+. However, Mg2+, Sr2+, Mo2+, Cd2+, Sn2+, Hg2+, and Pb2+ induced no flocculation of cells of this halophilic archaeon. Mg2+ acted antagonistically against Ca2+-induced aggregation. Such aggregation might be directly caused by the interaction of Ca2+ and aggregation factors from 55°C-treated cell extract. [Copyright &y& Elsevier]

The stability or interracial naphthenate films of three synthetic naphthenic acids and four different divalent cations is measured by means of the Langmuir technique with a trough for liquid-liquid systems. The chloride salts of Ca2+, Mg2+, Sr2+, and Ba2+ were dissolved in water at two different pH levels: ultrapure water (pH 5.6) and buffered uttrapure water at pH 8.0. The water phase was covered by the oil phase consisting of n-decane and dissolved naphthenic acid. The systems were then equilibrated for 45 minutes before the compression of the interfacial films was initiated. The results, plotted as interfacial pressure (IP) versus compression area, showed clear distinctions depending on acid structure, type of metal salt, and pH of the aqueous phase. The differences in film stability by introducing various salts are assumed to be a result of different degrees of hydration of metal cations, which according to the theory increases with decreasing cationic size. Raising the pH from 5.6 to 8.0 generally caused decreasing Him stability due a higher ionization of the interfacial layer and a higher water solubility. Furthermore, introducing naphthenic acids with bulky structures increases the molecular distance, which in turn may hinder the monomers to be bound in 2: 1 ratio with the divalent cations. [ABSTRACT FROM AUTHOR]

Connexins oligomerize to form intercellular channels that gate in response to voltage and chemical agents such as divalent cations. Historically, these are believed to be two independent processes. Here, data for human connexin37 (hCx37) hemichannels indicate that voltage gating can be explained as block/unblock without the necessity for an independent voltage gate. hCx37 hemichannels closed at negative potentials and opened in a time-dependent fashion at positive potentials. In the absence of polyvalent cations, however; the channels were open at relatively negative potentials, passing current linearly with respect to voltage. Current at negative potentials could be inhibited in a concentration-dependent manner by the addition of polyvalent cations to the bathing solution. Inhibition could be explained as voltage-dependent block of hCx37, with the field acting directly on polyvalent cations, driving them through the pore to an intracellular site. At positive potentials, in the presence of polyvalent cations, the field favored polyvalent efflux from the intracellular blocking site, allowing current flow. The rate of appearance of current depended on the species and valence of the polyvalent cation in the bathing solution. The rate of current decay upon repolarization depended on the concentration of polyvalent cations in the bathing solution, consistent with deactivation by polyvalent block, and was rapid (time constants of tens of milliseconds), implying a high local concentration of polyvalents in or near the channel pore. Sustained depolarization slowed deactivation in a flux-dependent, voltage- and time-independent fashion. The model for hCx37 voltage gating as polyvalent block/unblock can be expanded to account for observations in the literature regarding hCx37 gap junction channel behavior. [ABSTRACT FROM AUTHOR]

Dynamic interfacial tension (JET) measurements were used to investigate the interactions between a dissociated model naphthenic acid (p-(n-dodecyl) benzoic acid) and various divalent metallic cations (Mg2+, Ca2+, Sr2+, and Ba2+) across a toluene/hexadecane-water interface. The measurements were performed by using the pendant drop technique. The results obtained, plotted as IFT vs. time gave curves with similar shapes but different slopes and levels of the equilibrium IFT, depending upon the acid and salt concentrations and the type of cation added. Due to differences in degree of hydration of the various cations, the products of the reaction between dissociated acid monomers and the cations showed differences in solubility, which, in turn, affected the IFT. Based on the shapes of the curves, the mechanisms of the reactions involved in the process are discussed. [ABSTRACT FROM AUTHOR]

DNA oligonucleotides can form multi-stranded structures such as a duplex, triplex, and quadruplex, while the double helical structure is generally considered as the canonical structure of DNA oligonucleotides. Guanine-rich or cytosine-rich oligonucleotides, which are observed in telomere, centromere, and other biologically important sequences in vivo, can form four-stranded G-quadruplex and I-motif structures in vitro. In this study, we have investigated the effects of pH and cation on the structures and their stabilities of d(G4T4G4) and d(C4A4C4). The CD spectra and thermal melting curves of DNAs at various pHs demonstrated that acidic conditions induced a stable I-motif structure of d(C4A4C4), while the pH value did not affect the G-quadruplex structure and stability of d(G4T4G4). The CD spectra of the 1 : 1 mixture of d(G4T4G4) and d(C4A4C4) indicated that the acidic conditions inhibit the duplex formation between d(G4T4G4) and d(C4A4C4). Isothermal titration calorimetry measurements of the duplex formation at various pHs also quantitatively indicated that the acidic conditions inhibit the duplex formation. On the other hand, the CD spectra and thermal melting curves of DNAs in the absence and presence of Ca2+ indicated that Ca2+ induces a parallel G-quadruplex sructure of d(G4T4G4) and then inhibits the duplex formation. These results lead to the conclusion that both the pH and coexisting cation can induce and regulate the structural polymorphisms the oligonucleotides in which they form the G-quadruplex, I-motif, and duplex depending on the conditions. Thus, the results reported here indicate pivotal roles of pH and coexisting cations in biological processes by regulating the conformational switching between the duplex and quadruplexes structures of the guanine-rich or cytosine-rich oligonucleotides in vivo. [ABSTRACT FROM AUTHOR]

The ripening of discs cut from the pericarp of green tomato (Lycopersicon esculentum Mill.) fruits is inhibited by treatments with GA3 and several divalent cations, including calcium. Normal ripening is marked by an increase in the solubility of wall pectins. Calcium and GA3 alter the pattern of pectin solubility changes. In part this may be because polygalacturonase synthesis and/or secretion to the apoplast is reduced. The impact of divalent cations on ripening-related tissue softening appears to have a nonmetabolic component. Ripening-inhibiting ions rapidly reduce tissue softening, pectin solubilization and the normal ripening-related decrease in cellular turgor. [ABSTRACT FROM AUTHOR]

In the geological disposal system of high-level radioactive and transuranic wastes, an increase in Ca concentration (arising from the alteration of cementitious materials) could affect the retention of other radionuclides due to competitive sorption. Batch sorption experiments were performed to investigate the sorption behavior of Ca and its competition with other divalent cations (Sr and Ni) on the edge sites of Kunipia F montmorillonite under alkaline conditions. Ca sorption increased with pH (when pH > 8) and it was more pronounced under high ionic strength conditions, indicating that Ca formed a surface complexation with the edge sites. The sorption behavior of Sr was similar to that of Ca. Meanwhile, the Ni sorption increased with pH, when this was >6 (for lower pH values than in the case of Ca and Sr), Ni tends to form surface complexes more readily than Ca and Sr. The results of a fitting analysis conducted based on the 2-site protolysis non-electrostatic surface complexation and cation exchange (2SPNE SC/CE) model indicate that Ca and Sr sorb onto the ≡SW2OH sites and Ni sorbs onto the ≡SSOH sites. Additionally, the sorption of the CaOH+ and SrOH+ ionic pair species by cation exchange was implied at pH ~ 12. Competitive sorption experiments were also carried out to evaluate the effect of Ca on the sorption of Sr and Ni. Sr sorption decreased with Ca concentration in the alkaline pH region, whereas Ni sorption was not affected by Ca concentration. Overall, these results indicate that Ca and Sr sorb onto the same sites, while Ca and Ni sorb onto different sites; additionally, the competitive sorption seemed to depend on chemical similarities (e.g., hydrolysis behavior). The sorption model parameters obtained from the single-element batch sorption experiments successfully reproduced the results of the competitive sorption experiments. • Ca sorption and its effects on Sr and Ni sorption on montmorillonite under alkaline conditions were investigated. • Ca and Sr form surface complexation with the edge sites of montmorillonite. • Ca and Sr compete with each other under alkaline conditions, whereas Ca and Ni do not. • The 2SPNE SC/CE model reproduced the results of the competitive sorption experiments. [ABSTRACT FROM AUTHOR]

• H 2 O 2 was used to enhance cation-exchange treatment for Cs+ desorption from clay mineral. • Hydrobiotite (HBT) exhibited the most favorable H 2 O 2 activation because of its high Fe content. • H 2 O 2 treatment with solvated Mg2+ enhanced Cs+ desorption from HBT by expansion of interlayer region. • ∼99% removal of radioactive Cs+ from HBT was achieved by three cycles of H 2 O 2 treatment. In this study, hydrogen peroxide (H 2 O 2) was used to enhance the cation-exchange treatment for Cs+ desorption from clay minerals. Among various investigated clay minerals, hydrobiotite (HBT), which has interstratified layers of vermiculite and biotite, exhibited the highest Cs+ sorption capacity and the most favorable H 2 O 2 activation because of its high Fe content. In X-ray diffraction analysis, HBT treated with H 2 O 2 and 0.1 M Mg2+ showed substantial changes in its basal spacing, indicating expansion of the interlayer region induced by treatment of H 2 O 2 and strongly hydrated divalent cations. In addition, more than 80% of the Cs+ was readily desorbed from HBT with 35% H 2 O 2 solution and 0.1 M Mg2+ at room temperature. After three cycles under the same treatment conditions (35% H 2 O 2 solution and 0.1 M Mg2+), approximately 99% removal of radioactive Cs+ was achieved. These results suggested that H 2 O 2 treatment with solvated Mg2+ enhanced Cs+ desorption from HBT by altering the interlayer region through intercalation of hydrated divalent cations in conjunction with the H 2 O 2 decomposition reaction. [ABSTRACT FROM AUTHOR]

• Novel monoamines-incorporated polyamide NF membranes were developed. • Carboxyl or sulfo group of the monoamines resulted in larger negative charges. • The incorporation of the monoamines also resulted in larger MWCOs. • The membranes enabled efficient separations of sulfate ions from magnesium ions. • The membranes could be used for recovery of magnesium in desalinated seawater. For the purpose of efficient separation of sulfate ions from magnesium ions, novel negatively-charged nanofiltration membranes were developed by incorporating the monoamines 4-aminobenozic acid, aniline-2,5-disulfonic acid monosodium salt, and iminodiacetic acid (IDA) during interfacial polymerization of piperazine (PIP) and trimesoyl chloride. PIP–amide membranes without these monomers tended to reject magnesium ions as well as sulfate ions. In contrast, incorporation of the monoamines resulted in large molecular weight cut-offs and large negative charge densities thanks to carboxyl or sulfo terminal groups of the monoamines, which enabled preferential permeation of magnesium ions while maintaining high rejection of sulfate ions. In particular, the IDA-incorporated nanofiltration membrane with an IDA to PIP + IDA mass ratio of 0.40 showed high rejection of sulfate ions with low rejection of magnesium ions even when the concentration of sodium chloride was much higher than that of magnesium sulfate. This result indicates the feasibility of the developed membrane for magnesium recovery from desalinated seawater in the electrodialysis process for table salt production. [ABSTRACT FROM AUTHOR]