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Achieving the removal of pharmaceuticals and personal care products (PPCPs) while selectively rejecting divalent cations like Ca2⁺ and Mg2⁺ without compromising water productivity and recovery remains a challenge for existing commercial nanofiltration (NF) membranes used in drinking water treatment. These challenges stem from the limited pore size and insufficient negatively charged surface density of conventional NF membrane. This study employed a polydopamine-coated nanofibrous membrane, uniformly embedded with in-situ grown ZnO nanoparticles, as a porous support layer. In the interfacial polymerization process, the fabricated substrate regulated the diffusion of aqueous monomers, thereby optimizing the polyamide layer on composite NF membrane with thinner thickness, stronger surface density, crumple structure and appropriate pore size. This resulting membrane demonstrated excellent PPCP rejection while maintaining high permeability to essential minerals. Under optimal conditions, the designed membrane achieved an impressive water flux at about 21 L m⁻2 h⁻1 bar⁻1 and showed significant selectivity for PPCP and divalent cation, with diclofenac sodium rejection exceeding 90 % and Ca2⁺ rejection of below 20 %. The incorporation of ZnO nanoparticles enlarged the active filtration surface and created additional water pathways, resulting in a water permeation rate that was double that of a pristine NF membrane, without compromising PPCP/divalent cation selectivity. This work provides valuable insights and important correlations for developing NF membranes aimed at enhancing water production while preserving selectivity for PPCP/divalent cation. [Display omitted] • Uniformly embedded ZnO nanoparticles induce a crumpled PA structure. • PDA incorporation enhances the bonding interface between PA layer and nanofibers. • The hydrophilic integration of PDA and ZnO/PVDF nanofibers boosts permeability. • The developed NF membrane exhibits high selectivity for PPCP and divalent cation. [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]

Graphical abstract Highlights • SMA polymers SZ300110 and SMA2000 are comparable for protein solubilisation, yield, purity and thermostability. • Sensitivity of SMALPs to Mg2+ is similar for different membrane proteins. • The sensitivity to Mg2+ is independent of the concentration of SMALPs. • SMALPs are even more sensitive to larger divalent cations. Abstract Amphipathic co-polymers such as styrene-maleic acid (SMA) have gained popularity over the last few years due to their ability and ease of use in solubilising and purifying membrane proteins in comparison to conventional methods of extraction such as detergents. SMA2000 is widely used for membrane protein studies and is considered as the optimal polymer for this technique. In this study a side-by-side comparison of SMA2000 with the polymer SZ30010 was carried out as both these polymers have similar styrene:maleic acid ratios and average molecular weights. Ability to solubilise, purify and stabilise membrane proteins was tested using three structurally different membrane proteins. Our results show that both polymers can be used to extract membrane proteins at a comparable efficiency to conventional detergent dodecylmaltoside (DDM). SZ30010 was found to give a similar protein yield and, SMALP disc size as SMA2000, and both polymers offered an increased purity and increased thermostability compared to DDM. Further investigation was conducted to investigate SMALP sensitivity to divalent cations. It was found that the sensitivity is polymer specific and not dependent on the protein encapsulated. Neither is it affected by the concentration of SMALPs. Larger divalent cations such as Co2+ and Zn2+ resulted in an increased sensitivity. [ABSTRACT FROM AUTHOR]

Abstract A simultaneous high rejection of trace organic compounds (TrOCs) and low rejection of divalent cations (Ca2+/Mg2+) would be desirable for nanofiltration (NF) applied for drinking water treatment. The target was however not attainable by using the currently available commercial NF membranes. In this study, 3,5-diaminobenzoic acid (BA) was used as an additional diamine monomer besides piperazine (PIP) to prepare novel thin film composite NF membranes via interfacial polymerization with trimesoyl chloride (TMC). A series of NF membranes were prepared by varying BA to PIP concentration ratios in order to obtain a proper membrane pore size and a sufficiently high negative surface charge density. Membrane characterizations and performance tests showed that the incorporation of BA could increase the pore size, enhance the negative surface charge and change the structural properties of the membrane, which in turn affected the membrane water permeability and separation performance. The optimal membrane prepared with a BA/PIP ratio of 50%:50% exhibited a low rejection of CaCl 2 (25.8%) and MgCl 2 (32.0%) in single salt solutions at 10 mmol/L and a moderate rejection of Ca2+/Mg2+ ions (<60%) in a real tap water, while maintaining a reasonably high water permeability and an effective removal (>80%) for six out of eight selected pharmaceuticals (PhACs). The ATR-FTIR spectra and XPS analysis showed that BA could interfere the polymerization between PIP and TMC in forming the membrane active layer while the cross-linking degree between BA and TMC was relatively low. This implied that the proposed treatment target could also be achieved by using some other acidic diamines with similar functionalities of BA. Graphical abstract fx1 Highlights • 3,5-diaminobenzoic acid (BA) in addition to PIP was used to prepare novel NF membranes. • Addition of BA increased membrane pore size and negative surface charge density. • The optimal membrane exhibited low rejection of Ca2+/Mg2+ and high rejection of TrOCs. • The role of BA in affecting PA layer structure and properties was elucidated. [ABSTRACT FROM AUTHOR]

To assess the relationship between metal ion-mediated microstructures and the macro-performance, Cu- and Zn-doped α-Fe 2 O 3 nanoparticles were prepared via a solvothermal method. The morphologies of the as-synthesized nanoparticles were investigated by scanning electron microscopy and transmission electron microscopy. The results revealed that the sizes and morphologies could be regulated by doping with divalent cations. The structures of the as-synthesized nanoparticles were characterized by X-ray diffraction and Raman spectroscopy, indicating that Cu 2+ and Zn 2+ ions had diffused into the lattice of α-Fe 2 O 3 matrix. The magnetization behaviors of these nanoparticles were measured to analyze the effect of doping on α-Fe 2 O 3 . Furthermore, the catalytic activities of Cu- and Zn-doped α-Fe 2 O 3 nanoparticles demonstrated that the high-temperature decomposition temperature of ammonium perchlorate could be lowered by 115 °C and 107 °C, respectively, compared to that of ammonium perchlorate without catalyst. The enhanced catalytic activity could be attributed to the defect structure induced by doping with divalent cations. [ABSTRACT FROM AUTHOR]

Fate and transport of engineered nanoscale titanium dioxide (nTiO 2 ) have received much attention during the past decade. The aggregation and stability of nTiO 2 in water with complicated components, however, have not been fully examined. The objective of this paper is to determine the individual and synergistic effect of cation valence, humic acid, and clay colloids on nTiO 2 stability and aggregation, and elucidate the related mechanisms. We conducted systematic laboratory experiments to determine nTiO 2 stability and aggregation in NaCl and MgCl 2 solutions, both in the absence and presence of humic acid and illite colloids. Results showed that Mg 2+ , in comparison to Na + , could make the zeta potential of nTiO 2 more positive, and shift the point of zero charge of nTiO 2 (pH pzc,TiO2 ) towards higher pH. We also found that nTiO 2 are destabilized by illite colloids at pH < pH pzc,TiO2 through formation of illite-nTiO 2 hetero-aggregates, but are not interfered by illite colloids at higher pH. HA was found to make nTiO 2 stable via electrostatic and steric effects, both in the absence and presence of illite colloids. Calculated interaction energy based on DLVO theory revealed that instability of the nTiO 2 suspensions is mainly caused by primary minima, and that secondary minima normally do not destabilize the suspension, even though they are found to promote aggregation. [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]

[Display omitted] • EDTA functionalized graphene oxide (EDTA-GO) showed a high aqueous dispersiblity. • Liquid crystalline phase was observed from the suspension of EDTA-GO. • EDTA-GO was strongly cross-linked with divalent cations. • The mechanical properties of EDTA-GO films were enhanced with ionic cross-linking. Graphene oxide is functionalized with ethylenediaminetetraacetic acid groups to investigate the effect of ethylenediaminetetraacetic acid groups on its colloidal, assembly, and ionic cross-linking behaviors. Ethylenediaminetetraacetic acid-functionalized graphene oxide exhibits a high aqueous dispersibility for presenting a nematic liquid-crystalline phase which is an important factor for fabrication of the well-ordered laminated films. Ethylenediaminetetraacetic acid-graphene oxide films show a distinct internal structure from graphene oxide films owing to the heterogeneous surface of ethylenediaminetetraacetic acid-graphene oxide sheets composed of partially reduced and ethylenediaminetetraacetic acid decorated regions. In addition, the mechanical properties of ethylenediaminetetraacetic acid-graphene oxide films are more enhanced by ionic cross-linking with divalent cations, and their degree of mechanical enhancement is also more dependent on the type of cations than graphene oxide films. The interesting behaviors of ethylenediaminetetraacetic acid-graphene oxide suggest the ethylenediaminetetraacetic acid functionalization can greatly improve the potential of graphene oxide derivatives to develop a high-performance structural material. [ABSTRACT FROM AUTHOR]

The effects of water components (nature organic matters and inorganic cations) and pH on the anti-algae efficacy of silver nanoparticles (AgNPs) against Microcystis aeruginosa were studied. Humic acid decreased the antimicrobial toxicity of AgNPs on M. aeruginosa while calcium and magnesium ions enhanced toxicity. The anti-algae efficacy was greater at low pH. The physicochemical properties of AgNPs were studied to determine the role of nanomaterial contact with M. aeruginosa and the effect of silver ions on algaecidal toxicity. A comparison of particle sizes and silver ion changes under different water conditions showed that direct contact of nanoparticles with algae cells and the release of silver ions both contributed to anti-algae ability. The dominating mode of action of the AgNPs may occur through direct contact of AgNPs particles with algae cells rather than through toxicity effects from the silver ion. [ABSTRACT FROM AUTHOR]

Citrate-coated AgNPs (c-AgNPs) have negatively charged surfaces and their surface interactions with heavy metals can affect metal toxicity in aquatic environments. This study used Daphnia magna to compare the acute toxicities and bioaccumulation of As(V), Cd, and Cu when they interact with c-AgNPs. The 24-h acute toxicities of As(V) and Cu were not affected by the addition of c-AgNPs, while bioaccumulation significantly decreased in the presence of c-AgNPs. In contrast, both the 24-h acute toxicity and bioaccumulation of Cd increased in the presence of c-AgNPs. These toxicity and bioaccumulation trends can be attributed to the interactions between the AgNP surface and the heavy metals. As(V) and c-AgNPs compete by negative charge, decreasing As(V) toxicity. Copper adheres readily to c-AgNP citrate, decreasing Cu bioavailability, and thus reducing Cu toxicity and bioaccumulation. Citrate complexes with divalent cations such as Ca and Mg reduce the competition between divalent cations and Cd on biotic ligand, increasing toxicity and bioaccumulation of Cd. This study shows that surface properties determine the effect of c-AgNPs on heavy metal toxicities and bioaccumulations; hence, further studies on the effect of nanoparticle by it surface properties are warranted. [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 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. [ABSTRACT FROM AUTHOR]

Highlights: • Protein isolate possessed the increased gel forming ability, compared with surimi. • Zn2+ increased gel strength of surimi and protein isolates. • Phosphorylation yielded protein isolate with negatively charged side chains. • Phosphorylated protein isolate was better substrate for crosslinking mediated by Zn2+. • Phosphorylated protein isolate had superior gel properties when added with Zn2+. [Copyright &y& Elsevier]

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: Background: Thiamine triphosphate (ThTP) is present in most organisms and might be involved in intracellular signaling. In mammalian cells, the cytosolic ThTP level is controlled by a specific thiamine triphosphatase (ThTPase), belonging to the CYTH superfamily of proteins. CYTH proteins are present in all superkingdoms of life and act on various triphosphorylated substrates. Methods: Using crystallography, mass spectrometry and mutational analysis, we identified the key structural determinants of the high specificity and catalytic efficiency of mammalian ThTPase. Results: Triphosphate binding requires three conserved arginines while the catalytic mechanism relies on an unusual lysine–tyrosine dyad. By docking of the ThTP molecule in the active site, we found that Trp-53 should interact with the thiazole part of the substrate molecule, thus playing a key role in substrate recognition and specificity. Sea anemone and zebrafish CYTH proteins, which retain the corresponding Trp residue, are also specific ThTPases. Surprisingly, the whole chromosome region containing the ThTPase gene is lost in birds. Conclusions: The specificity for ThTP is linked to a stacking interaction between the thiazole heterocycle of thiamine and a tryptophan residue. The latter likely plays a key role in the secondary acquisition of ThTPase activity in early metazoan CYTH enzymes, in the lineage leading from cnidarians to mammals. General significance: We show that ThTPase activity is not restricted to mammals as previously thought but is an acquisition of early metazoans. This, and the identification of critically important residues, allows us to draw an evolutionary perspective of the CYTH family of proteins. [Copyright &y& Elsevier]

Effects of zinc sulphate (ZnSO4) and zinc chloride (ZnCl2) at various levels (0–80µmol/kg) on the properties of gels from yellow stripe trevally (Selaroides leptolepis) surimi were investigated. Both kamaboko (40/90°C) and modori (60/90°C) gels added with ZnSO4 or ZnCl2 up to 60µmol/kg had the increases in breaking force and deformation (P<0.05), compared with the control. The higher breaking force and deformation were generally found in kamaboko gels added with ZnSO4, compared with ZnCl2 (P<0.05). Whiteness of both kamaboko and modori gels increased with increasing levels of zinc salts (P<0.05). Salt bridge and ionic interactions played a major role in cross-linking of proteins. Kamaboko gel had highly interconnected, denser and finer network with smaller voids when zinc salts, especially ZnSO4 at 60µmol/kg, was incorporated. Therefore, ZnSO4 at an appropriate level could improve gel strength and whiteness of surimi from dark fleshed fish. [ABSTRACT FROM AUTHOR]

Abstract: Depolymerization of xylan, a major fraction of lignocellulosic biomass, releases xylose which can be converted into transportation fuels and chemical feedstocks. A requisite enzyme for the breakdown of xylan is β-xylosidase. A gene encoding the 324-amino acid β-xylosidase, RS223-BX, was cloned from an anaerobic mixed microbial culture. This glycoside hydrolase belongs to family 43. Unlike other GH43 enzymes, RS223-BX can be strongly activated by exogenously supplied Ca2+, Co2+, Fe2+, Mg2+, Mn2+ and Ni2+ (e.g., 28-fold by Mg2+) and it is inhibited by Cu2+ or Zn2+. Sedimentation equilibrium centrifugation experiments indicated that the divalent metal cations mediate multimerization of the enzyme from a dimeric to a tetrameric state, which have equal catalytic activity on an active-site basis. Compared to the determined active sites of other GH43 β-xylosidases, the predicted active site of RS223-BX contains two additional amino acids with carboxylated side chains that provide potential sites for divalent metal cations to reside. Thus, the divalent metal cations likely occupy the active site and participate in the catalytic mechanism. RS223-BX accepts as substrate xylobiose, arabinobiose, 4-nitrophenyl-β-d-xylopyranoside, and 4-nitrophenyl-α-l-arabinofuranoside. Additionally, the enzyme has good pH and temperature stabilities and a large K i for d-glucose (1.3M), favorable properties for performance in saccharification reactors. [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: Ca2+ influx through voltage-gated Ca2+ channels is a fundamental signaling event in neurons; however, non-traditional routes, such as non-selective cation channels, also permit Ca2+ entry. The present study examines the Ca2+ permeability of a cation channel that drives an afterdischarge in Aplysia bag cell neurons. The firing of these neurons induces peptide release and reproduction. Single channel-containing inside-out patches excised from cultured bag cell neurons, with the cytoplasmic face bathed in K+-aspartate and the extracellular face bathed in artificial seawater (11 mM Ca2+), had a reversal potential near +50 mV. In keeping with Ca2+ permeability, this was right-shifted to approximately +60 mV in high Ca2+ (substituted for Mg2+) and left-shifted to around +40 mV in zero Ca2+ (replaced with Mg2+). The current showed inward rectification between +30 and +90 mV, and a conductance of 29 pS in normal Ca2+, 30 pS in high Ca2+, 32 pS in Ba2+ (substituted for Ca2+), but only 21 pS in zero Ca2+. Despite a greater conductance in Ba2+, the channel did not display anomalous mol fraction in an equimolar Ca2+–Ba2+ mix. Eliminating internal Mg2+ lowered activity, but did not alter inward rectification, suggesting intracellular Mg2+ is a fast, voltage-independent blocker. Imaging bag cell neurons in Mn2+ saline (substituted for Ca2+) revealed enhanced fura-quench following cation channel activation, consistent with Mn2+ permeating as a Ca2+ surrogate. Finally, triggering the cation channel while tracking capacitance revealed a Ca2+-dependent increase in membrane surface area, consistent with vesicle fusion. Thus, the cation channel not only drives the afterdischarge, but also passes Ca2+ to potentially initiate secretion. In general, this may represent an alternate means by which neurons elicit neuropeptide release. [Copyright &y& Elsevier]

• An increase of PO number will reduce the interfacial tension. • Adding Ca2+ can achieve ultralow value at lower PO number and wider ACN range. • The ability to reduce the IFT of adding Mg2+ is weaker than that of Ca2+. • Surface active substances in the crude oil will adsorb competitively on the interface. Extended surfactants have shown great potential in enhanced oil recovery (EOR). In this paper, the effects of extended surfactant concentration, polypropylene oxide (PO) number, and various counter ions (Na+, Ca2+, and Mg2+) on the oil–water interfacial tension (IFT) of extended surfactant solutions were investigated in detail. The selected extended surfactants were sodium dodecyl polyoxypropylene sulfate (L-C 12 PO m S, m = 5, 10, 15). Based on our experimental results, under NaCl conditions, with an increase in the PO number, the space occupied by the surfactant molecules on the side of the oil phase increases, which matches the size of the anionic head, and the surfactant film becomes tight. An ultralow IFT value appears for L-C 12 PO 15 S at 0.5% NaCl against decane. The addition of bivalent cations can significantly reduce the IFT. As the Ca2+ concentration increases, IFTs of APS solutions against alkanes can achieve ultralow values at lower PO numbers and against alkanes with a wide ACN range. For the MgCl 2 system, the smaller hydration radius of Mg2+ improves the tightness of the anionic head, resulting in a crowded arrangement of the PO chains on the oil phase side. Therefore, the ability of Mg2+ to reduce the IFT against alkanes is weaker than that of Ca2+. Moreover, the surface-active substances in the crude oil adsorb competitively on the interface, resulting in an increase in IFT. By adding Ca2+or Mg2+, a tight adsorption film of surfactant molecules will be formed, and the IFT value reaches ultralow against crude oil. The studies in this paper have important implications for the application of extended surfactant solutions to enhance oil recovery under high salt reservoir conditions. [ABSTRACT FROM AUTHOR]

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: The effects of ferrous cation (Fe2+), copper cation (Cu2+) and calcium cation (Ca2+) on the reduction of hexavalent chromium Cr(VI) by zerovalent iron (Fe0) were investigated. The pseudo-first-order kinetic model was used for describing the reduction of Cr(VI). The experimental results showed that Cu2+ and Fe2+ could improve the reduction of Cr(VI) but Ca2+ might inhibit the reduction of Cr(VI) by Fe0. The improvement of the reduction of Cr(VI) by Cu2+ on Fe0 might be ascribed to Cu2+ acting as a catalyst or the media of charge transfer during the reaction. Different concentration of Cu2+ might lead to the different reduction kinetics of Cr(VI) by Fe0. The X-ray diffraction (XRD) results showed that the reacted iron powder was coated by a small amount of β-FeOOH. The results of scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDS) and Fourier-transform infra-red (FTIR) showed that the Fe–Cr coprecipitate or Fe–Cr–Cu coprecipitate might be formed during the reaction. [Copyright &y& Elsevier]

Abstract: Symbiotic Chlorella F36-ZK isolated from Paramecium bursaria F36 lacks nitrate reductase activity and has constitutive amino acid transport systems. Divalent cations generally accelerate amino acid uptake and Ca2+ affects membrane permeability and H+-ATPase activity. However, Ser uptake by F36-ZK was decreased by divalent cations, especially Ca2+, and the cation had no effect on membrane permeability or H+-ATPase activity. Extracellular Ca2+ contributed to inhibit Ser uptake. The cation selectively inhibited uptake of Ser, Ala and Gln, which are transported via the same system, but not Arg. Based on kinetic analysis of Ser transport, inhibition was noncompetitive, i.e., Ca2+ affected only the V max of Ser uptake. Calcium ions were found in symbiotic Chlorella cells associated with their host by transmission electron microscopy using an oxalate-pyroantimonate method, suggesting the transfer of Ca2+ during symbiosis. From these results obtained in this paper, we discuss the role of divalent cations on amino acid transport in the Paramecium symbiosis. [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]

Abstract: Galactoside-binding lectin was purified from the snake venom of Crotalus ruber by affinity chromatography on a lactose–agarose column, and the complete amino acid sequence was determined. The C. ruber venom lectin (CRL) showed a single band of 28 kDa by SDS-polyacrylamide electrophoresis under non-reducing conditions, but it showed a single band of 15 kDa under reducing conditions, indicating that CRL is a disulfide-linked homodimer of 15 kDa subunit. CRL specifically recognized beta-galactosides such as thiodigalactoside followed by N-acetylgalactosamine when examined with their inhibitory effects on CRL-induced hemagglutination. A CRL subunit was composed of 135 residues containing nine Cys residues and showed a high similarity to other C-type galactoside-binding lectins from snake venoms. C. atrox lectin (CAL) showed almost the same sequence except for eight amino acid residues. Neither CRL nor CAL induced platelet aggregation by itself or inhibited platelet aggregation mediated by von Willebrand factor or fibrinogen with agonists. CRL showed a similar oligomeric form and the sugar specificity as CAL, but it showed different divalent cation sensitivity such as Mn2+ and Ni2+. Homology modeling suggested that the amino acid substitution found in CRL does not affect sugar recognition of the lectin but might alter the conformation and influence the sugar binding pocket induced by the metal–ion binding. [Copyright &y& Elsevier]

Abstract: Recently, Paul Modrich''s group reported the discovery of an intrinsic endonuclease activity for human MutLα. This breakthrough provides a satisfactory answer to the longstanding puzzle of a missing nuclease activity in human mismatch repair and will undoubtedly lead to new investigations of DNA repair and replication. Here, the implications of this exciting new finding are discussed in the context of mismatch repair in Escherichia coli and humans. [Copyright &y& Elsevier]

Abstract: The pilot plant running demonstrated that the flocculating control of SPSC01, a self-flocculating ethanol fermentation yeast strain, is a prerequisite for both yeast cell immobilization through retention during fermentation and yeast floc recovery through sedimentation after fermentation. The impacts of fermentation process parameters including temperature, pH, divalent cations, sugars, and ethanol on the flocculating of SPSC01 were quantitatively investigated using recently established floc size distribution on-line monitoring technology. It was found that the flocculating of SPSC01 was thermo-stable when temperature was below 60°C, but the deflocculating of SPSC01 occurred when temperature was higher than this criterion. The change of pH from 3.5 to 6.0 did not exert significant impact on the flocculating of SPSC01. The roles of divalent cations, Ca2+ and Mg2+, in the flocculating of SPSC01 depended on their concentrations. The optimum concentration of Ca2+ was experimentally measured to be 1mmol/L, almost the same level as that naturally existed in the industrial mash of starch materials, while no optimum concentration for Mg2+ was observed in its concentration range of 0–100mmol/L. Mannose showed deflocculating ability, which indicated that the flocculating of SPSC01 is MS phenotype. Glucose and sucrose showed weak deflocculating ability, which indicates industrial sugar or mash from starch materials for ethanol fermentation is suitable for this self-flocculating yeast strain. Ethanol exerted positive impact on the flocculating of SPSC01 when its concentration was below 15% (v/v), which indicates that better flocculating can be achieved in those rear fermentors in cascade fermentation systems where higher ethanol concentrations present. The negative impact of ethanol on the flocculating of SPSC01 was observed when ethanol concentration was higher than 15% (v/v). [Copyright &y& Elsevier]

Abstract: The present study aimed to investigate the effects of plasticization on the mechanical properties and morphology of poly(ethyl acrylate) ionomers neutralized with either Co2+ or Na+. In experiments, the dynamic mechanical properties of divalent Co2+-neutralized poly(ethyl acrylate) ionomers containing polar and non-polar plasticizers were compared with those of the monovalent Na+-neutralized ionomers. In the case of the ionomers plasticized with non-polar 4-decylaniline (4-DA), residing in non-ionic regions, the matrix and cluster T gs of the ionomer decreased with increasing 4-DA contents. The decreasing rates of the matrix and cluster T gs were found to be similar at 0.8 and 1.0°C/(wt% of 4-DA) for the Co2+ and Na+ ionomers, respectively. The ionic modulus of the Co2+ ionomer changed only slightly with increasing 4-DA contents, but that of the Na+ ionomer decreased noticeably. In the SAXS study, it was observed that the un-plasticized Co2+ ionomer showed a strong small angle upturn and a very broad SAXS peak, indicating that the ionomer phase was compositionally heterogeneous. The plasticization of the Co2+ ionomer with 4-DA, however, induced a well-developed SAXS peak that was comparable to that of the un-plasticized Na+ ionomer. These results suggested that the addition of 4-DA to the Co2+ ionomer made the ionomer have more multiplets at a prevalent distance, leading to more clustering. In the case of the Co2+ ionomers plasticized with polar glycerol (Gly) that acted mainly as multiplet plasticizer, a very weak cluster glass transition, decreasing ionic modulus and only a well-developed small angle upturn were observed. These indicated that the addition of Gly to the Co2+ ionomer disrupted the multiplet formation, resulting in lower clustering. [Copyright &y& Elsevier]

Abstract: During the reaction catalyzed by enolase, a mobile loop, residues 36–45, closes over the active site. In order to probe the role of this loop movement in catalysis, the glycines at positions 37 and 41 of rabbit muscle enolase (ββ) have been mutated to alanines. The mutant forms–G37A and G41A–of enolase are both active, but have altered selectivity for divalent cations. G37A, when assayed with Mg2+, has 12% the activity of the wild type. However, it is twice as active as wild type when assayed with Mn2+, Zn2+, or Co2+. G41A has 4% the activity of the wild type with Mg2+, is more active than wild type with Co2+, and slightly less active than wild type with Mn2+ and Zn2+. The kinetic isotope effect for both mutants is greater than that of the wild type with all 4 divalent cations. These results indicate that the flexibility of this loop has subtle effects on catalytic activity. [Copyright &y& Elsevier]

Abstract: Merulinic acid (heptadecenylresorcinolic acid, resorcinolic acid) is one of the members of resorcinolic lipids, the natural amphiphilic long-chain homologues of orcinol (1,3-dihydroksy-5-methylbenzene). In the present study, membrane properties of merulinic acid were investigated. Merulinic acid exhibits strong haemolytic activity against sheep erythrocytes (EH50 of 5±2 μM) regardless of the form of its application—direct injection into the erythrocyte suspension or injection as merulinic acid-enriched liposomes. The lysis of erythrocytes induced by merulinic acid was inhibited by the presence of divalent cations. The effectivity of the protection of erythrocytes was highest for Zn2+ and weakest for Mn2+. Merulinic acid at low concentrations also exhibits the ability for protection of cells against their lysis in hypoosmotic solutions. This protective effect is significant as, at 10 μM concentration of merulinic acid, the extent of osmotically induced cell lysis is reduced by approximately 40%. Merulinic acid induces increased permeability of liposomal vesicles. This effect was shown to be dependent on the composition of liposomal bilayer and it was stronger when lipid bilayer contained glycolipids (MGDG and DGDG) and sphingomyelin. Changes of TMA-DPH and NBD-PE fluorescence polarization show that the degree of merulinic acid incorporation into liposomal membrane is not very high. The polar “heads” of the molecules of investigated compounds are localized on the level of fatty acid''s ester bonds in phospholipid molecules. Merulinic acid caused the increased fluorescence of the membrane potential fragile probe. This indicated an alteration of the surface charge and a decrease of the local pH at the membrane surface. This effect was visible in both low- and high-ionic strength environment. Merulinic acid causes also a decrease in activity of the membrane-bound enzyme acetylcholinesterase. [Copyright &y& Elsevier]

α7 nicotinic receptors are highly permeable to Ca2+ as well as monovalent cations. We extended the characterization of the Ca2+ permeation of non-desensitizing chick α7 receptors (S240T/L247T α7 nAChRs) expressed in Xenopus oocytes by (1) measuring the concentration dependence of conductance under conditions in which Ca2+ or Ba2+ were the only permeant cations in the extracellular solution, and (2) measuring the concentration dependence of Ca2+ block of K+ currents through the receptors. The first set of experiments yielded an apparent affinity of 0.96 mM Ca2+ activity (2.4 mM concentration) for Ca2+ permeation and an apparent affinity of 0.65 mM Ba2+ activity (1.7 mM concentration) for Ba2+ permeation. The apparent affinity of Ca2+ inhibition of K+ currents was 0.49 mM activity (1.5 mM concentration). The similarity of these apparent affinities in the millimolar range suggests that the pore of α7 receptors has one or more low-affinity Ca2+ binding sites and no high-affinity sites. [Copyright &y& Elsevier]

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]

Voltage-gated calcium channels are exquisitely Ca2+ selective, conferred primarily by four conserved pore-loop glutamate residues contributing to the selectivity filter. There has been little previous work directly measuring whether the trafficking of calcium channels requires their ability to bind Ca2+ in the selectivity filter or to conduct Ca2+. Here, we examine trafficking of neuronal Ca V 2.1 and 2.2 channels with mutations in their selectivity filter and find reduced trafficking to the cell surface in cell lines. Furthermore, in hippocampal neurons, there is reduced trafficking to the somatic plasma membrane, into neurites, and to presynaptic terminals. However, the Ca V 2.2 selectivity filter mutants are still influenced by auxiliary α 2 δ subunits and, albeit to a reduced extent, by β subunits, indicating the channels are not grossly misfolded. Our results indicate that Ca2+ binding in the pore of Ca V 2 channels may promote their correct trafficking, in combination with auxiliary subunits. Furthermore, physiological studies utilizing selectivity filter mutant Ca V channels should be interpreted with caution. • Selectivity filter mutations in Ca V 2 channels block inward Ba2+ currents • Surprisingly, these mutations severely reduce trafficking of the Ca V 2 channels • Pore mutant N-type channels show reduced expression in presynaptic terminals • Pore mutant channels still require β and α 2 δ and thus are not grossly misfolded Meyer et al. examine whether selectivity filtering mutations in Ca V 2 channels, preventing inward Ba2+ currents, would reduce trafficking. Pore-mutant channels show strongly reduced cell-surface expression in cell lines and neurons, but still require β and α 2 δ subunits and thus are not grossly misfolded. [ABSTRACT FROM AUTHOR]