Presence Of Calcium Cations Research Articles

Influence of pH on the emulsifying property of high methyl-esterified citrus pectin in the presence of calcium cations

High methyl-esterified citrus pectin (HMCP) is often used as a thickness in food products and is considered a poor emulsifier, especially in neutral pH solutions. Our previous findings show that the emulsifying capacity of HMCP could be significantly enhanced by calcium cations. Besides, the pH of the solution decreased in the presence of calcium cations. However, the impact of solution pH on HMCP emulsifying capacity in the presence of calcium cations is unclear. In this study, the pH of the HMCP solution was adjusted from 3.00 to 8.00 before adding calcium cations. The solution properties and emulsifying properties were analyzed in light of the existence of calcium cations. The results showed that the pH of the HMCP solutions decreased after bringing calcium cations into them. Calcium cations could change the solution rheological properties, particle size distributions and morphologies, and the particle microenvironmental hydrophobic areas in HMCP solutions while increasing the pH of HMCP solutions, contributing to improving the emulsifying capacity of HMCP. HMCP had the best emulsifying ability when the pH of the HMCP solutions was kept at a neutral level. This research gives us new ideas to adjust the emulsifying property of HMCP.

Analysis of the Emulsifying Capacity of Low Methyl-Esterified Citrus Pectin in the Presence of Calcium Cations from Its Aggregates: Micelles

In this study, pectin was considered a soft matter, and the emulsification of low methyl-esterified citrus pectin (LMCP) was analyzed in the presence of calcium cations (Ca2+). The formulation of LMCP aggregates was called micelles, and they could be regarded as granular emulsifiers. The size and morphology of LMCP micelles were affected by the concentration of Ca2+, and this changed the emulsifying properties of LMCP. The particle size distribution range in LMCP solutions was first decreased and then increased with increasing Ca2+ concentrations from 0.00 to 10.00 mM. The concentration of Ca2+ affected the creaming index (CI) of emulsions and the size distribution of the emulsion droplets significantly. Tiny particles and cavities being detected on the oil droplet surface in cryo-scanning electron microscopy (SEM) micrographs illustrated that the stable emulsion could be considered a Pickering emulsion when different concentrations of Ca2+ were brought into the LMCP solution for the preparation of the emulsion.

Development of a novel reinforced scaffold based on chitosan/cellulose nanocrystals/halloysite nanotubes for curcumin delivery

Chitosan, cellulose nanocrystals, and halloysite nanotubes in the presence of calcium cations were used to fabricate a three-dimensional nanocomposite scaffold. The FTIR and XRD analyses revealed that formation of the network and incorporation of halloysite nanotubes into it were successful. FESEM images showed that the addition of higher amounts of halloysite nanotubes into the scaffold's matrix leads to more and smaller pores. The addition of halloysite nanotubes enhanced the thermal stability, mechanical characteristics, water uptake, and degradation rate of the nanocomposite scaffold. The nanocomposite scaffold represented good biomineralization, great cell proliferation, and acceptable cell attachment. Furthermore, the capability of the nanocomposite scaffold for curcumin delivery was approved through cell proliferation, cumulative release, and antibacterial studies. Cell proliferation of the nanocomposite with 10 wt% curcumin-loaded halloysite nanotubes reached around 175% after 72 h. Considering the results, the prepared nanocomposite scaffold holds great potential for being used in bone tissue engineering applications.

Endonuclease from Gram-Negative Bacteria Serratia marcescens Is as Effective as Pulmozyme in the Hydrolysis of DNA in Sputum.

One of the approaches to effective airway cleansing is the degradation of DNA into smaller fragments. For this purpose Pulmozyme® is used with high efficacy because it contains recombinant DNase I as its active component. The aim of the study was to comparatively analyze DNase activity of Pulmozyme® and the nuclease from gram-negative bacteria Serratia marcescens, because at optimal conditions the catalytic efficiency of the nuclease is much higher than the efficiency of DNase I. Highly polymerized DNA and purulent-mucous sputum were used as substrates. The examination showed that both S. marcescens nuclease and Pulmozyme® hydrolyzed DNA in sputum. Also S. marcescens nuclease was found capable of hydrolyzing DNA in conditions that are standard for Pulmozyme® and suitable for its therapeutic application. For manifesting the similar hydrolytic activity the nuclease amount in the assay mixture containing highly polymerized DNA or the sonicated sputum and NaCl together with calcium- or magnesium- cations can be about 10- time lower than that of the recombinant DNase I. In the presence of magnesium cations the DNase activity of both S. marcescens nuclease and Pulmozyme® was higher than in the presence of calcium cations.

Study of structural short order and surface changes of SiO2 compounds

In this work dependence between structure, surface and reactivity of SiO2 is investigated. Different samples are prepared with and without the presence of calcium cations and are characterized by different techniques. The FTIR frequency shifting of the bridging oxygen stretching vibration Si–O–Si and the binding energy shiftingof the Si2p and O1s photoelectron peaks have been observed and discussed. Results show the effect of presence of calcium on the structural change, surface and reactivity of SiO2 aggregate. After reaction, a structural and SiO2 surface changes occur, as the FTIR spectra illustrate depending on the presence of the calcium cations.

Study of structural short order and surface changes of SiO2 compounds

In this work dependence between structure, surface and reactivity of SiO2 is investigated. Different samples are prepared with and without the presence of calcium cations and are characterized by different techniques. The FTIR frequency shifting of the bridging oxygen stretching vibration Si–O–Si and the binding energy shiftingof the Si2p and O1s photoelectron peaks have been observed and discussed. Results show the effect of presence of calcium on the structural change, surface and reactivity of SiO2 aggregate. After reaction, a structural and SiO2 surface changes occur, as the FTIR spectra illustrate depending on the presence of the calcium cations.

Innovative thermal and acoustic insulation foam from recycled waste glass powder

An innovative powder-foaming process able to produce thermal and acoustic insulating foams obtained by sol-gel and a subsequent freeze-drying process was developed.Gel containing glass powder was formed using alginate, a polysaccharide composed of 1-4linked α-L-guluronic acid and β-D-mannuronic acid, capable to form stable gels in presence of calcium cations. In order to obtain a porous foam, gels were frozen and then freeze-dried. Foam properties strongly depend on production parameters, particle dimension and different binder concentrations, their influence was investigated. The resulting glass foams were characterized in order to evaluate structure, density, mechanical and acoustic properties. The results pointed out an improved acoustic insulating performance respect to rock wool.Foams were also subjected to a thermal process to better fix powders into the final glass structure.

Block copolymer-templated mineralization for pH-responsive robust nanocarriers of 5-fluorouracil

We describe a novel synthetic method to prepare calcium carbonate (CaCO3)-mineralized nanoparticles for the intracellular delivery of an anticancer drug, 5-fluorouracil (5-FU). The 5-FU-loaded mineralized nanoparticles (FU-CaCO3-MNPs) were prepared by block copolymer (poly(ethylene glycol)-b-poly(L-aspartic acid) (PEG-PAsp))-templated mineralization in the presence of calcium cations (Ca2+), carbonate anions (CO32−), and negatively charged 5-FU. The mineralization produced hybrid nanoparticles consisting of 5-FU-loaded CaCO3 cores and PEG shells. The mineralized CaCO3 cores of the nanoparticles could stably hold loaded 5-FU by maintaining the structural robustness, and the outer corona of PEG provided colloidal stability to the nanoparticles in serum solutions. The 5-FU release from the FU-CaCO3-MNPs at physiological pH (pH 7.4) was efficiently inhibited, whereas at an endosomal pH (pH 5.0), the 5-FU release was facilitated. Fluorescence microscopic analysis showed that FU-CaCO3-MNPs were taken up by the MCF-7 breast cancer cells, and transferred into acidic endosomes to dissolve the CaCO3 core. Finally, the 5-FU release was facilitated to inhibit the proliferation of cancer cells. These mineralized hybrid nanoparticles may serve as a useful candidate for enhanced intracellular delivery of many ionic anticancer drugs.

Immobilization of lipase with alginate hydrogel beads and the lipase‐catalyzed kinetic resolution of α‐phenyl ethanol

ABSTRACTThe immobilization of enzymes is one of the key issues in both the field of enzymatic research and industrialization. In this article, we report a facile method for immobilizing Candida antarctica lipase B in an alginate carrier. In the presence of calcium cations, an enzyme–alginate suspension was crosslinked to form beads with a porous structure at room temperature, and the enzymes were well dispersed in the beads. The chiral resolution of α‐phenyl ethanol in the organic phase was tested by the enzyme–alginate beads. The effects of the reaction parameters, such as the enzyme concentration, temperature, and molar ratio of the substrate to the solvent, on the resolution behavior are discussed. Reuse cycle experiments for the chiral resolution of α‐phenyl ethanol demonstrated that the activity of the enzyme–alginate beads was maintained without marked deactivation up to five repeated cycles. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40178.

Immobilization of Lipase using Alginate Hydrogel Beads and Enzymatic Evaluation in Hydrolysis of p-Nitrophenol Butyrate

The immobilization of enzyme is one of the key issues both in the field of enzymatic research and industrialization. In this work, we reported a facile method to immobilize Candida Antarctica lipase B (CALB) in alginate carrier. In the presence of calcium cation, the enzyme-alginate suspension could be cross-linked to form beads with porous structure at room temperature, and the enzyme CALB was dispersed in the beads. Activity of the enzyme-alginate composite was verified by enzymatic hydrolysis reaction of p-nitrophenol butyrate in aqueous phase. The effects of reaction parameters such as temperature, pH, embedding and lyophilized time on the reactive behavior were discussed. Reuse cycle experiments for the hydrolysis of p-nitrophenol butyrate demonstrated that activity of the enzyme-alginate composite was maintained without marked deactivation up to 6 repeated cycles.

Influence of exopolysaccharides on the electrophoretic properties of the model cyanobacterium Synechocystis

The influence of extracellular polymeric substances (EPS) on cell electrokinetics was investigated in the model cyanobacterium Synechocystis, in wild-type strains and in ten EPS-depleted mutants. The charge density and the softness of the EPS polyelectrolyte layer were calculated from the dependence of the electrophoretic mobility values of the cells with the ionic strength of the surrounding fluid. Electrophoretic mobility data showed that the eleven Synechocystis strains investigated behave as soft particles and cannot be adequately described by classical electrokinetic models of rigid particles. EPS surrounding the cells, especially those released in the growth medium, significantly increased the softness of the cell surface. Furthermore, the anionic nature of EPS resulted in negative surface charge densities, which appeared to be strongly dependent on the composition of the suspending fluid, as documented by a strong reduction of their absolute values in the presence of calcium cations. These finding stresses the importance of the physicochemical properties of EPS and cell surfaces of cyanobacteria, for both cell-to-medium and cell-to-cell communications. In turn, these results emphasize that, whenever possible, natural waters should be used for meaningful ecotoxicological analyses of potential toxics.

Extracellular Polymeric Substances (EPS) in a Hybrid Growth Membrane Bioreactor (HG-MBR): Viscoelastic and Adherence Characteristics

Extracellular polymeric substances (EPS) comprising the microbial biofilms in membrane bioreactor (MBR) systems are considered the most significant factor affecting sludge viscoelastic properties as well as membrane fouling. Understanding the water chemistry effects on EPS viscoelastic, conformational, and adherence properties are critical for defining the microbial biofilm's propensity of fouling the membrane surface. In this study, EPS extracted from a hybrid growth membrane bioreactor (HG-MBR) were analyzed for their adherence, viscoelastic properties and size distribution using quartz crystal microbalance with dissipation monitoring (QCM-D) and dynamic light scattering (DLS), respectively. Also, adsorption characteristics of EPS extracted from different locations in the HG-MBR (bioreactor liquor, fluidized carriers, and membrane surface) were defined and linked to the extent of the total polysaccharide content in the EPS. In accordance with the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, more EPS were adsorbed at higher ionic strength, lower pH and in the presence of calcium cations. Based on the QCM-D results, the calculated thickness of the EPS adsorbed layer was increased at lower ionic strength, higher pH, and only had a minor increase in the presence of calcium cations. The calculated shear modules and shear viscosity suggest that at lower pH and in the presence of calcium, EPS becomes more viscous and elastic, respectively. DLS analysis correlated to the QCM-D results: A decrease in the hydrodynamic radius of the EPS colloids was observed at lower pH, and in the presence of calcium, most likely attributed to intermolecular attraction forces. Based on this study, low pH and presence of calcium may induce flocs' stability that resist erosion in the MBRs, while on the other hand, these conditions may induce the formation of an elastic and viscous EPS layer fouling the ultrafiltration (UF) membrane.

Aggregation of ε-caprolactone polymers containing at one chain end different number of carboxyl groups in the presence of calcium cations

The aggregation of poly(ε-caprolactone) containing different number of carboxyl groups at one chain end in the presence of Ca2+ cations was investigated by viscosity measurements. With increasing number of carboxyl groups, aggregation is strongly enhanced as evidenced by the viscosity-time profiles. The formation of long cylindrical structures was observed by scanning electron microscopy.

Influence of the composition and structure of α-alkyldicarboxylic acids on the mineral surface hydrophobization under flotation conditions

The hydrophobization effect of α-alkyldicarboxylic acids in microflotation of pure apatite variety was examined in relation to the alkyl radical length, the total length of the hydrocarbon chain and the positional relationships of the carboxy groups in the molecule, and the presence of calcium cations in the liquid phase of suspension. These findings were compared with the analogous data for saturated monocarboxylic acids and unsaturated oleic acid.

Target Peptide Recognition by S100P Protein and Role of Central Linker Region and Dimer Interface

Interaction between S100P and its target protein is an essential step in several cellular functions. The amphipathic mellitin peptide binds tightly to S100P protein in the presence of calcium cation. Since little is known about the recognition sequence, mellitin interaction form a model for S100P. Interaction between mellitin and protein examined to identify key regions required for the protein-protein interaction.

The influence of some metallic cations on deinking flotation

Abstract This paper presents some aspects of the fundamentals of ink flotation with sodium stearate, oleic acid and sodium dodecyl sulphate collectors as well as the influence of metallic cations such as Ca2+, Mg2+ and Al3+ on floatability. Zeta potential studies showed that the isoelectric point (IEP) of ink reached a pH of about 2.3. The presence of calcium, magnesium and aluminum cations modified the zeta potential curves of ink particles in relation to the indifferent electrolyte. The results of microflotation tests indicated that, with sodium stearate, an increase in floatability was probably associated with the precipitation of stearate species on the ink surface. It was suggested that a non-specific adsorption mechanism had occurred with sodium dodecyl sulphate, whilst a specific adsorption mechanism was associated with oleic acid. In the presence of calcium cation, an increase in floatability at pH 8.0 was verified, probably due to calcium/collector salt precipitation on the ink particle surface. In the presence of magnesium and aluminum species, an increase in floatability was noted for pH ranges related to the maximum concentration of their hydroxy complexes and to the predominance of metallic hydroxides at pH values below their IEPs. Scanning electron microscope studies suggested that ink particles formed aggregates with a rough surface in the absence of metallic cations. In contrast, aggregates had a more homogeneous surface in the presence of metallic cations.

Studies on the intermolecular distribution of industrial pectins by means of preparative size exclusion chromatography

Three industrial high methoxyl pectins have been fractionated by size exclusion chromatography (SEC) on a preparative scale and the chemical composition, viscosity and light scattering behaviour of the fractions have been investigated. Chemical analysis revealed that the composition varies greatly from one SEC fraction to another. In all three pectin samples, the fractions of low molecular size contain most of the free neutral polysaccharides as well as some free pectin ‘hairy regions’. In addition, the lemon pectin samples contain some pectin molecules of large size which are rich in neutral sugars. Phenolic and proteinaceous compounds coelute with neutral sugar-rich fractions. However, in the apple pectin, phenolics and proteins occur predominantly in the fractions of low molecular size. Lemon pectin molecules, especially that of the lemon A sample, are prone to aggregation in the presence of calcium cations. The aggregate fraction can be disrupted by shear forces, heating or the presence of a chelating agent. The formation of such calcium-pectinate aggregates seems to be due to the presence of some molecules with low degrees of methoxylation. Light scattering measurements also suggest that even very narrow SEC fractions remain highly heterogeneous on the basis of their molecular weight, thus indicating large differences in molecular conformation.

Protein Precipitation by Acetone for the Analysis of Polyethylene Glycol in Intestinal Perfusion Fluid

Canine ileal segments were luminally perfused with known amounts of polyethylene glycol (PEG), and samples obtained were freed of protein by a cold acetone (CA) method and assayed for PEG by trichloroacetic acid in the presence of calcium cations. This procedure was compared to the Barium salt (BaS) protein precipitation method of Hyden (Ann R Agric Coll Sweden 22:411-424, 1955). The CA method saved specimen volume and time in handling, whereas its stability, linearity, and reproducibility were equivalent to the more complex BaS method. In vitro studies disclosed no appreciable differences when PEG specimens were bile stained or dissolved in various solvents. A small modification of the CA method improved accuracy in measurement of small PEG concentrations.