Influence Of Calcium Ions Research Articles

Influence of divalent metal cations on α-lactalbumin fibril formation.

The effect of binding of divalent metal cations (Ca2+, Cu2+, Mg2+, Mn2+, Zn2+) on the kinetics of fibril formation of bovine α-lactalbumin at acidic conditions is considered. The kinetic parameters of the process were determined using a thioflavin T fluorescence assay. The DSC thermograms of bovine α-lactalbumin in the presence and absence of cations were recorded. The duration of the lag period correlates with the changes in the thermal stability of the molten globule of the protein in the presence of cations. The final thioflavin T fluorescence intensity after formation of the mature fibrils decreases under the influence of calcium ions which strongly bind to the monomeric protein, and increases in solutions containing copper and especially zinc. These ions seem to accelerate secondary nucleation processes and change the fibril morphology, which was confirmed by atomic force microscopy imaging.

The influence of cholesterol and calcium ions on the interaction of cryoprotectors with a biological membrane model

In this work, we studied the effects of three cryoprotectors – ethylene glycol, dimethyl sulfoxide and sucrose – on the compression isotherms of egg yolk Langmuir monolayers both in the presence and in the absence of cholesterol in the monolayer. The influence of calcium ions from the subphase affecting the effectiveness of cryoprotection on π-A isotherms is also examined. In addition, the elastic properties of the obtained monolayers are investigated by calculation and comparison the compression modulus of the monolayer. The scientific novelty of the work is in consideration of a complex biosimilar system (an egg yolk monolayer, cholesterol and their mixtures) on the surface of the aqueous solution of the nutrient mixture and obtaining information about the specific interaction of different cryoprotectors with lipid membranes. We found that when calcium ions and cryoprotectors are simultaneously added to the subphase, they block each other's influence on the lipid monolayer and reduce the effectiveness of cryoprotection. Cholesterol in the yolk in a ratio of 1:50 m m−1 changes the properties of the monolayer, which leads to increased action of cryoprotectors. Also, for the first time, the effect of a significant increase in surface pressure (by ∼20 mN m−1) was detected when cryoprotectors were added to the system under consideration. This effect can serve as an indicator of the effectiveness of membrane dehydration by cryoprotectors and can be used to find the most effective and safe cryoprotector compositions. The obtained data can provide important recommendations for the development of cryoprotective media for cell freezing. Since the study of the mechanisms of calcium interaction (the most important signaling cation) with biological membrane and membrane-like systems is important for understanding the various effects caused by medicinal and biologically active drugs at the cellular level, the study is of interest for various fields of biophysics and biomedicine.

The enhanced performance of Chlorococcum sphacosum in rich carbon wastewater treatment under the influence of calcium ion

The performance of microalgae-based wastewater treatment process is probably affected by high concentrations of organic carbon in wastewater, and calcium ions may influence this process. Nevertheless, the phenomena and mechanism involved have not been well explored. Here the performance of Chlorococcum sphacosum in treating wastewater with high concentrations of organic carbon was studied by coupling calcium ion concentration regulation (adding CaCl2 and free Ca2+ chelator EGTA) via physicochemical and transcriptomic analysis. It was found that photosynthesis and nutrients removal were suppressed and lipid accumulation was enhanced as the microalga was used to treat wastewater with high concentrations of organic carbon (more than 1500 mg/L). Simultaneously, antioxidant enzymes (SOD, CAT and POD) activity and calcium signaling-related protein (CaM, CDPK, and Ca2+-ATPase) content rose implying that the microalga was in a state of stress and calcium was involved in stress response. It was found that EGTA treatment further weakened the performance of microalgal photosynthesis and nutrients removal. However, the supplementation of Ca2+ had the opposite effect. Transcriptomic analysis revealed that Ca2+ strengthened the heterotrophic decomposition process of carbon (up-regulating the gene expression related to glycolysis and tricarboxylic acid cycle) and inhibited lipid accumulation (down-regulating lipid synthesis) via Ca2+ signalings transduction. Briefly, Ca2+ alleviated the stress of high concentration of organic carbon and strengthened the performance treating the corresponding wastewater.

Modulation the Synergistic Effect of Chitosan-Sodium Alginate Nanoparticles with Ca2+: Enhancing the Stability of Pickering Emulsion on D-Limonene.

Pickering emulsions (PEs) have been regarded as an effective approach to sustaining and preserving the bioactivities of essential oils. The aim of this research is to prepare a PE stabilized by chitosan/alginate nanoparticles (CS-SA NPs) for the encapsulation and stabilization of D-limonene. In this work, the influence of calcium ions (Ca2+) on the morphology and interaction of nanoparticles was studied, and then the preparation technology of CS-SA/Ca2+ NPs was optimized. The results showed that the presence of Ca2+ reduced the size of the nanoparticles and made them assume a spherical structure. In addition, under the conditions of 0.2 mg/mL CaCl2, 0.6 mg/mL SA, and 0.4 mg/mL CS, the CS-SA/Ca2+ NPs had the smallest size (274 ± 2.51 nm) and high stability (-49 ± 0.69 mV). Secondly, the PE was prepared by emulsifying D-limonene with CS-SA/Ca2+ NPs, and the NP concentrations and homogenization speeds were optimized. The results showed that the small droplet size PE could be prepared with 2 mg/mL NP and a homogenization speed of 20,000 r/min, and it had excellent antibacterial and antioxidant activities. Most importantly, the emulsion showed higher activity, higher resistance to ultraviolet (UV) and a higher temperature than free D-limonene. This research provides a feasible solution for the encapsulation, protection and delivery of essential oils.

Unveiling the effect of CaCl2 on amyloid β aggregation via supercritical angle Raman and fluorescence spectroscopy and microscopy.

Amyloid β aggregation is an important factor in Alzheimer's disease. Since calcium homeostasis plays an important role in amyloid β aggregation, it is crucial to study the interaction between calcium ions and amyloid β directly at the surface of the lipid membrane. With supercritical angle techniques, the signal of interest at the surface is easily separated from the bulk solution, making them a powerful tool for aggregation study. In this work, the influence of calcium ions on amyloid β aggregation over different aggregation time periods is investigated with supercritical angle Raman and fluorescence spectroscopy and microscopy. Note that calcium ions have a larger influence on amyloid β1-42 than on the 40 amino acid variant. We found that a small layer of calcium ions significantly protects the lipid membrane against the protein insertion process.

Insights into the influence of calcium ions on the adsorption behavior of sodium oleate and its response to flotation of quartz: FT-IR, XPS and AMF studies

Assiduous efforts on the high-efficiency flotation of quartz with calcium ion activation have been ongoing, while there is a lack of understanding of its potential mechanism. In this research, insights into the influence of calcium ions on the adsorption behavior of sodium oleate and its response to flotation of quartz were systematically investigated. Micro-flotation experimental results show that addition order of calcium ions influences the quartz flotation. Ca2+/NaOL complexes exhibit higher flotation recovery of quartz (92.18 %) under the recommended conditions. The Zeta potential and Fourier transform infrared spectroscopy results indicate that the adsorption of NaOL onto bare quartz surfaces is extremely difficult, and the addition of Ca2+ promotes the adsorption of NaOL. X-ray photoelectron spectroscopy analysis results confirm that Ca2+/NaOL complexes reinforce the adsorption of NaOL and Ca2+ onto quartz surface by the formation of -Si-O-Ca-OOCR, and the Ca-OOCR content in the total Ca reaches 62.61 %. The adsorption amount results further illustrate that the adsorption amount of Ca2+ and NaOL increase to 18.56 × 10−2 mg/g and 40.83 × 10−2 mg/g, respectively. Additionally, starch slightly decrease the adsorption amount of Ca2+ on quartz surfaces. Atomic force microscope analysis reveal that Ca2+/NaOL components promote the formation of Ca-OOCR colloid precipitates and the transportation of the precipitates to the quartz surface. The main adsorption of Ca-OOCR colloid precipitates contributes to the enveloped bulge image. Notably, the Ca-OOCR colloid precipitates adsorption mechanism exerts more important role in the adsorption of sodium oleate and calcium ion species, as well as its response to flotation of quartz.

Regulation of calcium ions on the interaction between amphotericin B and cholesterol-rich phospholipid monolayer in LE phase and LC phase

Amphotericin B, as a “gold standard”, is used to treat invasive fungal infections. The AmB molecule can bind easily to cholesterol and damage cell membranes, so it produces the toxicity on cell membrane, which limits its clinical dose. However, the interaction between AmB and cholesterol-rich membrane is unclear now. The phase state of the membrane and the metal cation outside cell membrane may affect the interaction between AmB and the membrane. In this work, the effects of amphotericin B on the mean molecular area, elastic modulus and stability of mammalian cell membrane rich in cholesterol in the presence of Ca2+ ions were studied using DPPC/Chol mixed Langmuir monolayer as a model. The Langmuir-Blodgett method and AFM test were used to study the effects of this drug on the morphology and height of cholesterol-rich phospholipid membrane in the presence of Ca2+ ions. The influence of calcium ions on the mean molecular area and the limiting molecular area was similar in LE phase and in LC phase. The calcium ions made the monolayer more condensed. However, calcium ions can weaken the shortening effect of AmB on the relaxation time of the DPPC/Chol mixed monolayer in LE phase but enhance it in LC phase. Interestingly, calcium ions caused a LE-LC coexistence phase to occur in the DPPC/Chol/AmB mixed monolayers at 35mN/m, which was confirmed by atomic force microscopy. The results can help to understand the interaction between amphotericin B and cell membrane rich in cholesterol in the calcium ions environment.

The Influence of Calcium Ions on the Electrotransfer Efficiency of Plasmid DNA and Cell Viability

Gene electrotransfer (GET) is recognized as a promising technique for the development of an efficient tool for gene therapy. Such a therapy would have applications in the treatment of a variety of genetic diseases, including cancer. However, despite its wide applicability, the technique is limited by the lack of understanding of the fundamental mechanism of electroporation as well as other important factors that directly or indirectly influence its success rate. In the current study, we analyzed the impact of low concentrations (0–1 mM) of Ca2+ on the process of DNA electrotransfer using flow cytometry. The results revealed that the presence of a CaCl2 concentration as low as 0.25 mM decreased the efficiency of GET by ~1.5-fold and cell viability decreased by ~2–3-fold. In addition, we determined that the observed phenomenon of the decrease in pDNA electrotransfer due to the influence of Ca2+ was not the consequence of cell death but rather should be attributed to secondary mechanisms. The data presented in this study provide an insight into the importance of Ca2+ in the process of gene electrotransfer that may be directly applicable to in vivo settings.

The influence of calcium ions (Ca2+) on the enzymatic hydrolysis of lipopolysaccharide aggregates to liberate free fatty acids (FFA) in aqueous solution.

The chemical environment in aqueous solutions greatly influences the ability of amphiphilic molecules such as lipopolysaccharides (LPS) to aggregate into different structural phases in aqueous solutions. Understanding the substrate's morphology and conditions of aqueous solution that favor both enzymatic activity and the disruption of LPS aggregates are crucial in developing agents that can counteract the new trend of multidrug resistance by gram-negative bacteria. In this study, we developed two LPS morphologies using LPS from Escherichia coli as a model to study the in vitro hydrolytic response when using a lipase treatment. The hydrolysis was performed using lipase b from Candida antarctica to understand the catalytic effect in removing fatty acids from its lipid A moiety on different LPS aggregates. Physical and chemical characterizations of the products included dynamic light scattering, small angle X-ray scattering, Fourier transform infrared spectroscopy, thin-layer chromatography, and gas chromatography. Our results suggest a trend of prominent hydrolytic response (72% enhancement) upon the addition of calcium ions to induce LPS aggregates into bilayer formations. Moreover, our results revealed the detection of myristic acid (C14:0) as the product of the hydrolysis when using RaLPS in its aggregate forms.

Multigram-scale enzymatic kinetic resolution of trans-2-azidocyclohexyl acetate and chiral reversed-phase HPLC analysis of trans-2-azidocyclohexanol.

Lipase-catalyzed hydrolytic kinetic resolution is a method of obtaining optically pure chiral alcohols and amines, which requires additional tools for determining enantiomerical purity. Herein, we present a study on multigram-scale hydrolytic kinetic resolution of trans-2-azidocyclohexyl acetate using Pseudomonas cepacia lipase immobilized on Immobead support. We investigated several parameters of the preparative-scale process: temperature, organic co-solvent, and the influence of calcium ions. Moreover, we have developed an efficient fluorenylmethyloxycarbonyl chloride (Fmoc-Cl) derivatization protocol for 2-azidocyclohexanol, which enabled chiral reversed-phase high-performance liquid chromatography (RP-HPLC) determination of enantiomeric excess.

Interaction between polyene antifungal drug and saturated phospholipid monolayer regulated by calcium ions at the air-water interface

Amphotericin B (AmB) is a polyene antifungal drug, which could directly form pores on the sterol-free phospholipid monolayers. The interaction between AmB and phospholipid can be affected by calcium ions, but the mechanism is still unclear. DPPC is a saturated phospholipid with -PC group, which is often used to simulate the outer cell membrane leaflet. And DPPC is also the main constituent of pulmonary surfactants. In this work, the DPPC monolayer was used as a model membrane to study the effect of calcium ions on the interaction between AmB and phospholipid. The influence of different concentration of calcium ions on the elastic modulus, mean molecular area increment, excess Gibbs free energy and stability of the AmB/DPPC mixed monolayer has been researched at the surface pressure of 7.5 mN/m, 12.5 mN/m and 22.5 mN/m. The AmB/DPPC monolayers at the air-water interface have been observed in real-time by Brewster angle microscope and the microstructure of the Langmuir-Blodgett monolayer films transferred onto the mica have been researched by scanning electron microscope and atomic force microscope. The results showed that calcium ions had a significant influence on the elastic modulus, mean molecular area increment, excess Gibbs free energy, stability and microstructure of the AmB/DPPC monolayer. It has been indicated that the influence of calcium ions on the interaction between AmB and DPPC molecules mainly depended on the effect of calcium ions on the orientation of AmB molecules. The calcium ions could regulate the effect of AmB to the stability of the DPPC monolayer. This regulatory role changed with the different concentrations of calcium ions and the different phase states of the monolayer. This work provides useful information to further understand the influence mechanism of calcium ions on the interaction between AmB and saturated phospholipid with -PC group, which is helpful to find out the effect mechanism of calcium ion on the interaction between AmB and the outer layer of cell membrane or pulmonary surfactants in different phase states and to understand the toxicity mechanism of AmB on the cell membrane or lungs.

Experimental investigation of influence of calcium ion (Ca2+) and pH on the shear strength of Taipei silty clay

ABSTRACT Electroosmotic chemical treatment is a technique for improving the strength of soft soil. This study examined the effects of injection duration, Ca2+ions concentration, and pH distribution on the shear strength of Taipei silty clay. Experimental tests were conducted by injecting calcium chloride (CaCl2) solution into Taipei silty clay during electroosmosis for various durations. After testing, the water content, pH, Ca2+ ions concentration, injection volume, drainage volume, and cone resistance were measured. The results indicated that the injection volume, drainage volume, Ca2+ ions concentration, and strength of the silty clay were low compared with the same measurements for kaolinite because Taipei silty clay consists mainly of illite, which results in the soil having a lower coefficient of electroosmotic permeability. The treatments of 12–48 h were insufficient for improving soil strength. However, the 120-h 1.5 M C120 injection treatment resulted in a moderate increase in soil strength due to consolidation and Ca2+ ions precipitation. By comparing our results with those of studies on kaolinite, we established a suitable injection procedure, which includes solutions for treatment duration and concentration of CaCl2 solution (i.e. 1.5 M C48, 0.2 M C120, and 0.75 M C120).

Influence of calcium ions on physical chemical characteristics of semiconductor quantum dots encapsulated by amphiphilic polymer and their efficiency of cellular uptake

Here, we studied the effect of calcium ions on the physicochemical properties and cellular uptake of CdSe/ZnS quantum dots encapsulated with poly(maleic anhydride-alt-1-tetradecene), modified to a varying extent by quaternary ammonium groups. It was shown that quantum dots carrying negatively charged carboxyl groups in the polymer shell change their physicochemical and optical characteristics in the presence of Ca2+ and Ba2+ ions. As the negatively charged carboxyl groups in the shell are completely replaced by positively charged quaternary ammonium groups, these effects gradually decrease. A change in the physicochemical properties of nanoparticles leads to a change in their cellular uptake in the presence of calcium ions. Nanoparticles carrying only negatively charged groups in the shell in the presence of Ca2+ agglomerate and form conglomerates of nanoparticles and cells. The positively charged quaternary ammonium groups in the polymer shell of the nanoparticles increase their aggregative stability in the presence of Ca2+ and contribute to their uptake by cells. The mechanisms of uptake depend on nanoparticle’s charge. Nanoparticles with a positive ζ potential are absorbed by calcium-dependent mechanisms, which are suppressed by inhibition of the calcium-dependent enzyme dynamin or in the presence of calcium chelator EGTA. The uptake of nanoparticles with a negative ζ potential, in contrast, is enhanced by the chelation of calcium ions. This indicates the different role of cellular calcium-dependent mechanisms in the uptake of positively and negatively charged nanoparticles.

Influence of Calcium Ions on the Structure and Properties of LaMnO3

Influence of Calcium Ions on the Structure and Properties of LaMnO3

Influence of calcium ions on the stability, microstructure and in vitro digestion fate of zein-propylene glycol alginate-tea saponin ternary complex particles for the delivery of resveratrol

Calcium ions (Ca2+) can alter the molecular structure of proteins and polysaccharides through electrostatically binding to negatively charged groups. In this study, the zein-propylene glycol alginate (PGA)-tea saponin (TS) ternary complex particles induced by different Ca2+ levels (1–10 mM) were fabricated and characterized for the delivery of resveratrol. Fluorescence spectrum and circular dichroism analysis were applied to investigate the effect of Ca2+ on the micro-environment and secondary structure of zein in the complex particles. The hydrogen bonds, hydrophobic effects and electrostatic interactions contributed to the formation of the complex particles. Environmental stability evaluation showed that the stability of the complex particles and retention rate of resveratrol were enhanced by the addition of Ca2+ at the lower concentration (≤4 mM). Besides, the level of Ca2+ could modulate the digestion behavior of the complex particles and achieve the better sustained-release of resveratrol at the Ca2+ level of 2 mM. However, the aggregation of complex particles occurred through bridging flocculation induced by the high level of Ca2+ (>6 mM). These results indicated that Ca2+ induction has a great potential for the fabrication and application of food-grade complex particles loaded with nutraceuticals.

Influence of Calcium Ions on the Fouling of a Thin-film Composite Reverse Osmosis Membrane by Alginate

Influence of Calcium Ions on the Fouling of a Thin-film Composite Reverse Osmosis Membrane by Alginate

Effects of alkyl ether amine and calcium ions on fine quartz flotation and its guidance for upgrading vanadium from stone coal

Great progress has been made in reverse flotation of fine quartz, especially many new reagents were proved their excellent effects. However, the influences of complex flotation system on fine quartz flotation still need to be scrutinized. In this study, alkyl ether amine (Flotigam EDA-C from Clariant) was used as a collector for the flotation of quartz. It shows better collectability for the flotation of quartz at about pH 10.0 (±0.2). The adsorption mechanism of EDA-C on quartz and the influence of calcium ions on the flotation of quartz were investigated by adsorption tests, zeta-potential measurements, FTIR spectra measurements, X-ray photoelectron spectroscopic and atomic force microscopy imaging. Results show that EDA-C adsorbs on the quartz surface in physical adsorption with no new products, changing its zeta potentials and increasing its hydrophobicity. Calcium ion concentration of 20 mg/L, 40 mg/L, 60 mg/L and 1 g/L can inhibit the quartz surface strongly and decrease its recovery sharply. Inhibition action of 2 g/L Ca2+ decreased, even disappeared when the collector concentration increased to 90 mg/L. Calcium ions changed the chemical environment of Si atoms and O1s on the quartz surface. After positively charged CaOH+ adsorbed on quartz surface, the amount of EDA-C adsorbed on quartz surface and the recovery decreased. It was greatly inspired to explore quartz separation application from these results.

Effects of Metal Ions on the Flotation of Apatite, Dolomite and Quartz

The effects of Ca2+, Mg2+, Al3+, and Fe3+ on the flotation behaviors of apatite, dolomite and quartz were investigated through a micro-flotation test, and the influence of calcium ions on the flotation of these minerals was further elucidated by solution chemistry study, zeta potential measurement, and X-ray photoelectron spectroscopy (XPS) analyses. The results indicate that an appropriate amount of Ca2+ and Mg2+ can improve the floatability of apatite but had a negligible effect on the flotation performance of dolomite, whereas Al3+, Fe3+, and excessive amounts of Ca2+ decreased the recovery of apatite and dolomite. The studied metal cations can activate quartz at a particular pH. It can be inferred from solution chemistry and zeta potential measurement that the influence of metal ions on the flotation of different minerals should be attributed to the adsorption of various hydrolysis species on the mineral surfaces. XPS analyses reveal that calcium ions can enhance the adsorption of anionic collector on apatite and quartz surfaces, and there are no apparent changes to be observed on the surface of dolomite in the absence and presence of calcium ions at a concentration of 2.5 × 10−3 M, which was in good agreement with the micro-flotation results.

An Exact Model of Daptomycin Binding to Lipid Bilayers: An Update

Daptomycin is a cyclic lipopeptide of clinical importance in the treatment of multi-drug resistant infections, including those caused by methicillin-resistant S. aureus (MRSA) strains. Similar to other antimicrobial peptides, daptomycin binds with preference to the anionic cytoplasmic membranes typically found in prokaryotes. However, in contrast to most linear, alpha-helical peptides, daptomycin binds to lipid bilayers only in the presence of calcium ions and its activity is absolutely calcium-dependent. We measured the interaction of daptomycin with anionic lipid membranes using kinetic binding experiments and equilibrium titrations. The data were analyzed using an exact model describing the interactions of daptomycin with the lipid bilayer that includes solution and membrane-bound states, and the influence of calcium ions on daptomycin-lipid interactions. A preliminary version of the model was presented at the Biophysical Society Meeting in 2017. Here, we present a more complete analysis.

Influence of calcium ions on subcritical crack growth in granite

Influence of calcium ions on subcritical crack growth in granite