Effects Of Divalent Cations Research Articles

Calcium Calmodulin Regulates Zinc Mediated Changes in the Structure, Self-Association, and Activity of CaMKII

Ca2+-Calmodulin-dependent protein kinase II (CaMKII) is an interpreter of Ca2+ signaling and has been shown to be a critical component of learning and memory. This dodecameric oligomer also functions in part as a scaffolding molecule, serving to promote the formation of higher order signaling complexes within synapses. We set to study the effect that divalent cations, known to be critically important in neuronal signaling, have on the structure and function CaMKII. First, we computed the electrostatic surface potential of the dodecameric complex as a means to predict possible binding sites for divalent cations. A discrete set of high probability binding sites were identified at the interface between catalytic and association domains of neighboring subunits, far from the Mg2+ binding sites required to coordinate ATP in the catalytic cleft. Next, we experimentally characterized the effects of divalent cations on CaMKII structure using fluorescence, light scattering and electron microscopy. We found that some, but not all, divalent ions including Zn2+ promote the reversible formation of self-assembled CaMKII fibers that can extend for several μm. When associated in fibers, CaMKII activity is compromised; however, Ca2+/CaM activation of the enzyme disassembles fibers and the loss of activity is reversed. Interestingly, fiber assembly does not interfere with the autophosphorylation of CaMKII at T286, an autoregulatory modification, which confers autonomous activity in monodisperse CaMKII. We compile our results with structural and mechanistic data from literature to propose a model of Zn2+-mediated CaMKII fiber formation, where Ca2+/CaM regulates fiber formation through allosteric modification of a divalent ion site identified in our electrostatic map.

Nitrogen recovery from low-strength wastewater by combined membrane capacitive deionization (MCDI) and ion exchange (IE) process

Nitrogen exists in municipal wastewater in the form of ammonia/ammonium which is a recoverable resource. Recovering nitrogen to improve nitrogen-use efficiency should be carefully considered to promote global environmental sustainability. However, ammonia/ammonium is always not well recovered but removed as one of the main pathways for nitrogen release into the environment, which is due to ineffective ammonia capture. In this study, a new method of ion-exchange resin ammonium recovery combined with membrane capacitive deionization (MCDI+IE process) pretreatment is proposed. Selective ion removal by MCDI is demonstrated and ammonium ratio to the total prior ion (K+, Ca2+ and Mg2+) in outflow of MCDI cell is respectively increased from ∼15% to over 30% and 45% after 3 and 5 MCDI cycles. The MCDI+IE process could deal with 2.48 and 3.89 times of inflow, respectively, compared with the single IE process after 3 and 5 MCDI charge–discharge cycles and recover more than 65% of ammonium in a resin regeneration cycle after 3 MCDI cycles. It ascribes to MCDI desalination eliminating the negative effects of divalent cations, such as Ca2+ and Mg2+, on the IE absorb–desorb process.

Divalent Cations Increase DNA Repair Activities of Bacterial (6-4) Photolyases.

The (6-4) photolyases of the FeS-BCP group can be considered as the most ancient type among the large family of cryptochrome and photolyase flavoproteins. In contrast to other photolyases, they contain an Fe-S cluster of unknown function, a DMRL chromophore, an interdomain loop, which could interact with DNA, and a long C-terminal extension. We compared DNA repair and photoreduction of two members of the FeS-BCP family, Agrobacterium fabrum PhrB and Rhodobacter sphaeroides RsCryB, with a eukaryotic (6-4) photolyase from Ostreococcus, OsCPF, and a member of the class III CPD photolyases, PhrA from A.fabrum. We found that the low DNA repair effectivity of FeS-BCP proteins is largely stimulated by Mg2+ and other divalent cations, whereas no effect of divalent cations was observed in OsCPF and PhrA. The (6-4) repair activity in the presence of Mg2+ is comparable with the repair activities of the other two photolyases. The photoreduction, on the other hand, is negatively affected by Mg2+ in PhrB, but stimulated by Mg2+ in PhrA. A clear relationship of Mg2+ dependency on DNA repair with the evolutionary position conflicts with Mg2+ dependency of photoreduction. We discuss the Mg2+ effect in the context of structural data and DNA binding.

Negative effects of divalent mineral cations on the bioaccessibility of carotenoids from plant food matrices and related physical properties of gastro-intestinal fluids.

Carotenoid intake and tissue levels have been frequently associated with reduced risk of chronic diseases. However, their bioavailability is low and influenced by many dietary related parameters. Divalent mineral cations have been suggested to interfere with carotenoid digestion and to hamper micellarization, a prerequisite for their uptake, via complexation of bile salts and precipitation of fatty acids. In the present investigation, we have evaluated the effects of increasing concentrations of magnesium (0-300 mg L-1), calcium (0-1500 mg L-1), zinc (0-200 mg L-1), and sodium (0-1500 mg L-1; control monovalent cation), on carotenoid bioaccessibility from frequently consumed food items rich in carotenoids (tomato juice, carrot juice, apricot nectar, spinach and field salad), following simulated gastro-intestinal digestion. In addition, physicochemical parameters of digesta (macroviscosity, surface tension), micelle size, and zeta-potential were evaluated. All divalent minerals (DM) reduced bioaccessibility of total carotenoids (P < 0.01), as well as of individual carotenoids. Calcium and magnesium led to reductions of up to 100% at the 2 highest concentrations. Curiously, sodium increased (P < 0.01) carotenoid bioaccessiblity of most investigated matrices. The absolute value of the zeta-potential decreased with increasing concentrations of DM, suggesting a decreased stability of the colloidal digesta dispersion. Viscosity decreased, except for apricot nectar samples, while surface tension increased with DM concentration (P < 0.05). Thus, at physiological ranges, calcium and magnesium could negatively impact carotenoid bioavailability, while for zinc, negative effects were only seen at supplemental concentrations. The potential negative effects of DM on carotenoid bioavailability should be further studied in vivo.

Species Difference in Sensitivity of Human and Mouse P2X7 Receptors to Inhibitory Effects of Divalent Metal Cations.

P2X7 receptor (P2X7R), a purinergic receptor, is involved in pathophysiological events such as inflammation and cell death, and thus is an attractive target for therapeutic approaches. It is reported that divalent metal cations (DMCs) inhibit P2X7R activation and that there are species differences in their inhibitory effects. To extrapolate the findings in experimental animals to humans, these species differences have to be clarified, but species differences in the sensitivity of P2X7R to DMCs between man and mouse have not been demonstrated. Here we performed direct comparison of the inhibitory effects of DMCs on human and mouse P2X7R activation. Cell lines constitutively expressing human and mouse P2X7R were used, and their P2X7R activation was evaluated as means of YO-PRO-1 dye uptake. MgCl2, NiCl2, ZnCl2, CuCl2 and CaCl2 dose-dependently decreased agonist-induced YO-PRO-1 uptake via both human and mouse P2X7Rs. Apparent differences in the inhibitory profiles for NiCl2 and CaCl2 between them were found, and the IC50 values of DMCs were in the order of CaCl2>MgCl2>NiCl2≈ZnCl2>CuCl2 for both human and mouse P2X7Rs. In this study, we demonstrate that human P2X7R exhibits different sensitivity to nickel and calcium compared with the case of the mouse one, while there is no species difference in the sensitivity of their P2X7Rs to magnesium, zinc and copper, suggesting that the effects of magnesium, zinc and copper on P2X7R-associated pathophysiological events in humans might be predicted from those in mice.

Ca2+ in Hybridization Solutions for Fluorescence in situ Hybridization Facilitates the Detection of Enterobacteriaceae.

Fluorescence in situ hybridization (FISH) has been employed to identify microorganisms at the single cell level under a microscope. Extensive efforts have been made to improve and extend the FISH technique; however, the development of a widely applicable protocol is a continuing challenge. The present study evaluated the effects of divalent cations in the hybridization solution on the FISH-based detection of various species of bacteria and archaea with rRNA-targeted probes. A flow cytometric analysis after FISH with a standard hybridization buffer detected positive signals from less than 30% of Escherichia coli IAM 1264 cells. However, the number of cells with positive signals increased to more than 90% after the addition of calcium chloride to the hybridization buffer. Mn2+ also had positive effects, whereas Mg2+ did not. The positive effects of Ca2+ were similarly observed for bacteria belonging to Enterobacteriaceae, including Enterobacter sakazakii IAM 12660T, E. aerogenes IAM 12348, Klebsiella planticola IAM 14202, and Salmonella enterica subsp. enterica serovar Typhimurium strain LT2. These results indicate that the supplementation of Ca2+ to the hybridization buffer for FISH contributes to the efficient detection of Enterobacteriaceae cells.

Inhibitory effect of divalent metal cations on zinc uptake via mouse Zrt-/Irt-like protein 8 (ZIP8)

AimsThere is controversy regarding the substrate specificity of ZIP8, a ZIP isoform, involved in regulation of extra- and intracellular zinc levels. Here, we investigated the inhibitory effects of divalent metal cations on zinc uptake via mouse ZIP8 (mZIP8). Main methodsmZIP8 cDNA was transfected into HEK293T cells by a lipofection method, and its functional expression was evaluated by immunocytochemistry, Western blotting and 65Zn (65ZnCl2) uptake measurement. Key findingsTransfection of mZIP8 cDNA into HEK293T cells induced expression of mZIP8 in the cells, and increased zinc uptake. mZIP8-mediated zinc uptake depended on extracellular bicarbonate, and the Michaelis constant for the uptake was estimated to be 8.48±2.46μM. In the inhibition study, iron and cadmium competitively, and cobalt, nickel and copper non-competitively inhibited the mZIP8-mediated zinc uptake, the inhibition constants being calculated to be 3.37, 55.5, 80.6, 198 and 48.3μM, respectively. In contrast, magnesium and manganese at concentrations of up to 1500 and 200μM, respectively, had no inhibitory effect on the zinc uptake via mZIP8. SignificanceIn this study, we reveal that the inhibition profiles of divalent metal cations as to zinc uptake via mZIP8 apparently differ from those for mZIP1, especially in the affinity and inhibition manner of nickel. These findings should contribute to identification of ZIP isoforms involved in total cellular zinc transport.

Effects of Divalent Cations on Outward Potassium Currents in Leech Retzius Nerve Cells

AbstractThe present study examines the effects of divalent metals, cadmium (Cd2+) and manganese (Mn2+), on the outward potassium currents of Retzius cells in the hirudinid leeches Haemopis sanguisuga using conventional two-microelectrode voltageclamp techniques. The outward potassium current is activated by depolarization and plays an important role in determining both the neuronal excitability and action potential duration. A strong inhibition of the fast current and a clear reduction in the late currents of the outward current with 1 mM Cd2+were obtained, which indicated that both components are sensitive to this metal. Complete blockage of the fast and partial reduction of the slow outward currents was observed after adding 1 mM Mn2+to the extracellular fluid. These data show that the outward K+current in leech Retzius nerve cells comprises at least two components: a voltage-dependent K+current and a Ca2+- activated K+current. These observations also indicate that Cd2+is more eff ective than Mn2+in blocking ion fl ow through these channels and that suppressing Ca2+-activated K+outward currents can prolong the action potential in nerve cells.

Reversible changes of canavalin solubility controlled by divalent cation concentration in crude sword bean extract

Canavalin is a vicilin-class (7S) storage protein found in sword bean (Canavalia gladiata). Our previous report indicated that canavalin is precipitated by the addition of 20mMMgCl2 to crude sword bean extract. Here, we examined the solubility changes induced by the addition of Mg2+ and Ca2+ at various concentrations. Canavalin tended to be insolubilized at relatively low concentrations of MgCl2 (<20mM) and solubilized at relatively high concentrations (>20mM). In addition, canavalin was slightly insolubilized in the presence of NaCl. Overall, the results revealed that solubility changes are reversible and depend on the concentration of divalent cations. Therefore, we suggested a reaction scheme that describes the effects of divalent cations on the solubility of canavalin, which would facilitate the study of its physiological function and the application of canavalin in the food processing industry.

The effect of divalent and trivalent cations on aggregation and surface hydrophobicity of selected microorganism

This study investigated the effect of various cations (Ca2+, Mg2+, Al3+, Mn2+, Zn2+) on the autoaggregation (AAg) and surface hydrophobicity (SHb) of three different bacteria (Brevibacillus panacihumi strain (ZB1), Lysinibacillus fusiformis strain (ZB2) and Enterococcus faecalis strain (ZL)) using a 2-level factorial design. The AAg ratio was measured from the changes in the absorbance of the media. Results show that ZB2 had maximum AAg for the three bacteria investigated. A microscopic clustering of cells was observed when Ca2+ was added to ZB2. The AAg was in the range of 62%, 58% and 34% for ZB2, ZB1 and ZL, respectively and correlated to the SHb. The aggregation and SHb of the microbial cells increased with increasing ionic strength due to the repulsive steric or overlap forces between the polymer covered surfaces. Ca2+ demonstrated a more significant effect on aggregation and SHb of microbial cells due to an attractive binding force. Keywords: Aggregation, Biogranules, Cations, Surface hydrophobicity

Modelling low-salinity waterflooding: Effect of divalent cations and capillary pressure

Many laboratory results have proved potential of low salinity water injection (LSWI) for improving oil recovery in sandstone formation. Some one-dimensional models have been developed to describe the low salinity effect and possible driving mechanisms.The objective of this study is to develop two-dimensional model based on two different approaches, linear relationship proposed by Jerauld et al. (2008) and multi-ion exchange (MIE) model of Omekeh et al. (2012), for LSWI in sandstone formation. Furthermore, capillary pressure concept that is usually neglected in calculations is taken into account.The developed model successfully matched the experimental data. The model and experiments matched on a number of criteria such as oil recovery, and pressure drop. Wettability alteration from weakly oil-wet toward mixed-wet can be considered as the probable driving mechanism as a result of cation exchange.In the end, based on each approach's matching quality history, the application range for each method is addressed in this paper. However, the MIE approach is a more realistic representative of low salinity condition.

Characterization and adsorption of Lactobacillus virulent phage P1

Bacteriophage infection of lactic acid bacteria is considered an important problem worldwide in the food fermentation industry, as it may produce low quality or unsafe foods, cause fermentation failure, and result in economic losses. To increase current knowledge on the properties of Lactobacillus virulent phages, we evaluated the effect of divalent cations, temperature, pH, and chloramphenicol on the adsorption ability of Lactobacillus virulent phage P1. Phage P1 was isolated from the abnormal fermentation liquid of Lactobacillus plantarum IMAU10120. The results showed that this phage belonged to the Siphoviridae family. The latent period of this phage was 45min, and the burst time was 90min. Burst size was 132.88±2.37 phage counts expressed per milliliter per infective center. This phage showed good tolerance at different temperatures, but incubation at 50°C only affected its adsorption. Adsorption rate reached a maximum value between 30 and 42°C. A high adsorption value of phage infectivity was obtained from pH 6 to 8. Moreover, calcium ions promoted and increased the adsorption capacity of phage P1, but magnesium ions had negative effects. Chloramphenicol had no effect on phage adsorption. This study increased current knowledge on the characterization and biological aspects of Lactobacillus virulent phages, and may provide some basic information that can be used to design successful antiphage strategies in the food industry.

Influence of Divalent Cations on Deformation and Rupture of Adsorbed Lipid Vesicles.

The fate of adsorbed lipid vesicles on solid supports depends on numerous experimental parameters and typically results in the formation of a supported lipid bilayer (SLB) or an adsorbed vesicle layer. One of the poorly understood questions relates to how divalent cations appear to promote SLB formation in some cases. The complexity arises from the multiple ways in which divalent cations affect vesicle-substrate and vesicle-vesicle interactions as well as vesicle properties. These interactions are reflected, e.g., in the degree of deformation of adsorbed vesicles (if they do not rupture). It is, however, experimentally challenging to measure the extent of vesicle deformation in real-time. Herein, we investigated the effect of divalent cations (Mg(2+), Ca(2+), Sr(2+)) on the adsorption of zwitterionic 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) lipid vesicles onto silicon oxide- and titanium oxide-coated substrates. The vesicle adsorption process was tracked using the quartz crystal microbalance-dissipation (QCM-D) and localized surface plasmon resonance (LSPR) measurement techniques. On silicon oxide, vesicle adsorption led to SLB formation in all cases, while vesicles adsorbed but did not rupture on titanium oxide. It was identified that divalent cations promote increased deformation of adsorbed vesicles on both substrates and enhanced rupture on silicon oxide in the order Ca(2+) > Mg(2+) > Sr(2+). The influence of divalent cations on different factors in these systems is discussed, clarifying experimental observations on both substrates. Taken together, the findings in this work offer insight into how divalent cations modulate the interfacial science of supported membrane systems.

Effects of Porous Medium Geochemical Heterogeneity and Divalent Cations on the Transport of Humic Acid

Effects of Porous Medium Geochemical Heterogeneity and Divalent Cations on the Transport of Humic Acid

Divalent cation shrinks DNA but inhibits its compaction with trivalent cation.

Our observation reveals the effects of divalent and trivalent cations on the higher-order structure of giant DNA (T4 DNA 166 kbp) by fluorescence microscopy. It was found that divalent cations, Mg(2+) and Ca(2+), inhibit DNA compaction induced by a trivalent cation, spermidine (SPD(3+)). On the other hand, in the absence of SPD(3+), divalent cations cause the shrinkage of DNA. As the control experiment, we have confirmed the minimum effect of monovalent cation, Na(+) on the DNA higher-order structure. We interpret the competition between 2+ and 3+ cations in terms of the change in the translational entropy of the counterions. For the compaction with SPD(3+), we consider the increase in translational entropy due to the ion-exchange of the intrinsic monovalent cations condensing on a highly charged polyelectrolyte, double-stranded DNA, by the 3+ cations. In contrast, the presence of 2+ cation decreases the gain of entropy contribution by the ion-exchange between monovalent and 3+ ions.

Effect of Different Divalent Cations on the Kinetics and Fidelity of RB69 DNA Polymerase.

Although Mg(2+) is the cation that functions as the cofactor for the nucleotidyl transfer reaction for almost all DNA polymerases, Mn(2+) can also serve, but when it does, the degree of base discrimination exhibited by most DNA polymerases (pols) is diminished. Metal ions other than Mg(2+) or Mn(2+) can also act as cofactors depending on the specific DNA polymerase. Here, we tested the ability of several divalent metal ions to substitute for Mg(2+) or Mn(2+) with RB69 DNA polymerase (RB69pol), a model B-family pol. Our choice of metal ions was based on previous studies with other DNA pols. Co(2+), and to a lesser extent Ni(2+), were the only cations among those tested besides Mg(2+) and Mn(2+) that could serve as cofactors with RB69pol. The incorporation efficiency of correct dNMPs increased by 5-fold with Co(2+), relative to that of Mg(2+). The incorporation efficiencies of incorrect dNMPs increased by 2-17-fold with Co(2+), relative to that with Mg(2+) depending on the incoming dNTP. Base selectivity was reduced even further with Mn(2+) compared to that observed with Co(2+). Substitution of Mn(2+), Co(2+), or Ni(2+) for Mg(2+) reduced the exonuclease activity of RB69pol by 2-, 6-, and 33-fold, respectively, contributing to the frequency of misincorporation. In addition, Co(2+) and Mn(2+) were better able to extend a primer past a mismatch than Mg(2+). Finally, Co(2+) and Mn(2+) enhanced ground-state binding of both correct and incorrect dNTPs to RB69pol:dideoxy-terminated primer-template complexes.

Comparative functional properties of engineered cationic antimicrobial peptides consisting exclusively of tryptophan and either lysine or arginine.

We previously reported a series of de novo engineered cationic antibiotic peptides (eCAPs) consisting exclusively of arginine and tryptophan (WR) that display potent activity against diverse multidrug-resistant (MDR) bacterial strains. In this study, we sought to examine the influence of arginine compared to lysine on antibacterial properties by direct comparison of the WR peptides (8-18 residues) with a parallel series of engineered peptides containing only lysine and tryptophan. WR and WK series were compared for antibacterial activity by bacterial killing and growth inhibition assays and for mechanism of peptide-bacteria interactions by surface plasmon resonance and flow cytometry. Mammalian cytotoxicity was also assessed by flow cytometry, haemolytic and tetrazolium-based assays. The shortest arginine-containing peptides (8 and 10 mers) displayed a statistically significant increase in activity compared to the analogous lysine-containing peptides. The WR and WK peptides achieved maximum antibacterial activity at the 12-mer peptide (WK12 or WR12). Further examination of antibacterial mechanisms of the optimally active 12-mer peptides using surface plasmon resonance and flow cytometry demonstrates stronger interactions with Pseudomonasaeruginosa, greater membrane permeabilizing activity, and lower inhibitory effects of divalent cations on activity and membrane permeabilization properties of WR12 compared to WK12 (P < 0.05). Importantly, WK12 and WR12 displayed similar negligible haemolytic and cytotoxic effects at peptide concentrations up to ten times the MIC or 20 times the minimum bactericidal concentration. Thus, arginine, compared to lysine, can indeed yield enhanced antibacterial activity to minimize the required length to achieve functional antimicrobial peptides.

Effect of magnesium ion concentration on two-dimensional structure of DNA-functionalized nanoparticles on supported lipid bilayer

The effect of divalent cations on lipid-bilayer-assisted DNA-functionalized nanoparticle (DNA-NP) assembly has been studied. We previously reported the lateral diffusion of DNA-NPs on planar lipid bilayer patches, owing to the mobility of lipid molecules in a supported lipid bilayer (SLB), and the resultant two-dimensional (2D) assembly of DNA-NPs. We here report the structural change of the assembled 2D DNA-NP lattices by magnesium ion concentration control on a successfully formed uniform SLB. In the magnesium-free buffer solution, DNA-NPs on SLB loosely assembled into quasi-hexagonal ordered lattices. In buffer solution containing 1 mM magnesium acetate, the interparticle distance of DNA-NPs decreased and the lattice structure became disordered. In buffer solution containing 5 mM magnesium acetate, the structure of DNA-NP arrays changed markedly and square lattices appeared. It is suggested that magnesium ions affected DNA molecules, which linked nanoparticles, and enabled the control of the structure of DNA-NP 2D arrays.

Understanding the interaction between biomacromolecules and their influence on forward osmosis process

This paper presents studies on the interactions and effects of biomacromolecules compounds on forward osmosis (FO) membrane performance. Individual components and a combination of various organic substances such as bovine serum albumin (BSA), dextran, sodium alginate and xanthan gum were used as model feeds and tested for their influences on FO performance with the active layer of the FO hollow fiber membrane facing the feed solution (AL-FS). The interactions between foulants were examined by using fluorescence spectroscopy, rotational rheometry and laser doppler micro-electrophoresis techniques. For a system containing combined organic foulants, it was found that viscosity was not the dominant factor governing FO membrane fouling as the decrease in viscosity did not always result in less fouling. The effect of divalent cations on the FO fouling behavior was also studied by adding CaCl2. The presence of calcium ions has exacerbated the flux decline, this occurred particularly for any combined organic foulants containing alginate, due to intermolecular bridging among alginate molecules. It is interesting to note that combined BSA+alginate caused moderate flux decline, while BSA and alginate alone did not cause any observable water flux loss. The (BSA+alginate) fouling became more severe with the presence of calcium ions.

Low-Salinity-Surfactant Enhanced Oil Recovery (EOR) with a New Surfactant Blend: Effect of Calcium Cations

Coreflooding experiments on aged Berea sandstone cores were performed to study the effect of divalent cations on the low-salinity-surfactant enhanced oil recovery (EOR). In the experiments where the core samples were aged for 4 weeks, replacement of a small amount of sodium with calcium in the injected low-salinity surfactant did not lead to higher tertiary recovery. However, the effects on wettability alteration and relative permeabilities were substantial. For the experiments with longer aging duration of 7 weeks, addition of calcium to the injected low salinity surfactant led to better oil recovery and the impact on wettability alteration was strong. Further addition of calcium led to lower oil recovery. Results of the injection experiments were discussed based on interfacial tension (IFT), surfactant adsorption, end-point relative permeabilities, and contact angles. A part of discussion was also dedicated to the effect of calcium on the secondary low-salinity water (LSW) injection. Although the oil re...