Effect Of Divalent Ions Research Articles

Impact of permanganate with polyaluminium chloride on algae-laden karst water: Behaviors and disinfection by-products control

The removal of algal organic matter (AOM) through water treatment processes is a major approach of reducing the formation of disinfection by-products (DBP). Here, the formation of DBP from AOM in karst water under different combination of potassium permanganate (KMnO4) and polyaluminium chloride (PACl) was investigated. The effect of divalent ions (Ca2+ and Mg2+) on DBP formation was traced by AOM chemistry variations. For DBP formation after KMnO4 preoxidation, total carbonaceous DBPs (C-DBPs) decreased by 12.9% but nitrogen-containing DBPs (N-DBPs) increased by 18.8%. Conversely, the C-DBPs further increased by 3.3% but N-DBPs reduced by 10.7% after the addition of PACl besides KMnO4 preoxidation. The variations of aromatic protein-like, soluble microbial products-like compounds and ultraviolet absorbance at 254 nm (UV254) were highly correlated with the formation of DBPs, which suggest aromatic substances strongly affect DBP behaviors at different treatment conditions. In the presence of divalent ions (Ca2+ = 135.86 mg/L, Mg2+ = 18.51 mg/L), the combination of KMnO4 and PACl was more effective in controlling DBP formation compared to the situation without Ca2+ and Mg2+. Specifically, trichloromethane formation was largely inhibited compared to the other tested DBPs, which may refer to complexation of electron-donating groups via divalent ions. While Ca2+ and Mg2+ may not affect the nature of α-carbon and amine groups, so the variation of haloacetonitriles (HANs) was not obvious. The study enhances the understanding of the DBP formation patterns, transformation of carbon and nitrogen by preoxidation-coagulation (KMnO4-PACl) treatment in algae-laden karst water.

Structural properties and emulsification of myofibrillar proteins from hairtail (Trichiurus haumela) at different salt ions

The structural properties and emulsification of myofibrillar proteins (MPs) are susceptibly affected by salt ions. The effect of different salt ions on the structural properties and emulsification of MPs from hairtail (Trichiurus haumela) remains unclear. Hairtail MPs were analyzed under different ion treatments of Na+, K+, Ca2+ and Mg2+. MPs at K+ and Na+ treatment showed a similar trend on salt effect due to the unfolding of proteins under salt ions. However, the excessive electrostatic effect of divalent ions could enhance protein aggregation, especially at Ca2+ and Mg2+. The β-sheet of MPs at different salt ions interconverted with α-helix and random coil at ionic strengths from 0.1 mol/L to 1.0 mol/L. The surface hydrophobicity and active sulfhydryl content of MPs increased with the improvement of ionic strengths at 0–0.8 mol/L. Under Ca2+ and Mg2+ treatments, the turbidity of MPs was low compared to that under the treatment of Na+ and K+. Additionally, the emulsification of hairtail MPs treated with different ions was improved at an ionic strength of 0.6 mol/L. This study can contribute to using salts in constructing fish protein-based emulsions for manufacturing emulsified surimi products and promoting the development and utilization of hairtail proteins.

Structural insights into ligand recognition and subtype selectivity of the human melanocortin-3 and melanocortin-5 receptors

Members of the melanocortin receptor (MCR) family that recognize different melanocortin peptides mediate a broad spectrum of cellular processes including energy homeostasis, inflammation and skin pigmentation through five MCR subtypes (MC1R–MC5R). The structural basis of subtype selectivity of the endogenous agonist γ-MSH and non-selectivity of agonist α-MSH remains elusive, as the two agonists are highly similar with a conserved HFRW motif. Here, we report three cryo-electron microscopy structures of MC3R–Gs in complex with γ-MSH and MC5R–Gs in the presence of α-MSH or a potent synthetic agonist PG-901. The structures reveal that α-MSH and γ-MSH adopt a “U-shape” conformation, penetrate into the wide-open orthosteric pocket and form massive common contacts with MCRs via the HFRW motif. The C-terminus of γ-MSH occupies an MC3R-specific complementary binding groove likely conferring subtype selectivity, whereas that of α-MSH distances itself from the receptor with neglectable contacts. PG-901 achieves the same potency as α-MSH with a shorter length by rebalancing the recognition site and mimicking the intra-peptide salt bridge in α-MSH by cyclization. Solid density confirmed the calcium ion binding in MC3R and MC5R, and the distinct modulation effects of divalent ions were demonstrated. Our results provide insights into ligand recognition and subtype selectivity among MCRs, and expand the knowledge of signal transduction among MCR family members.

Kinetic analysis of RNA cleavage by coronavirus Nsp15 endonuclease: Evidence for acid–base catalysis and substrate-dependent metal ion activation

Understanding the functional properties of severe acute respiratory syndrome coronavirus 2 nonstructural proteins is essential for defining their roles in the viral life cycle, developing improved therapeutics and diagnostics, and countering future variants. Coronavirus nonstructural protein Nsp15 is a hexameric U-specific endonuclease whose functions, substrate specificity, mechanism, and dynamics are not fully defined. Previous studies report that Nsp15 requires Mn2+ ions for optimal activity; however, the effects of divalent ions on Nsp15 reaction kinetics have not been investigated in detail. Here, we analyzed the single- and multiple-turnover kinetics for model ssRNA substrates. Our data confirm that divalent ions are dispensable for catalysis and show that Mn2+ activates Nsp15 cleavage of two different ssRNA oligonucleotide substrates but not a dinucleotide. Biphasic kinetics of ssRNA substrates demonstrates that Mn2+ stabilizes alternative enzyme states that have faster substrate cleavage on the enzyme. However, we did not detect Mn2+-induced conformational changes using CD and fluorescence spectroscopy. The pH-rate profiles in the presence and absence of Mn2+ reveal active-site ionizable groups with similar pKas of ca. 4.8 to 5.2. An Rp stereoisomer phosphorothioate modification at the scissile phosphate had minimal effect on catalysis supporting a mechanism involving an anionic transition state. However, the Sp stereoisomer is inactive because of weak binding, consistent with models that position the nonbridging phosphoryl oxygen deep in the active site. Together, these data demonstrate that Nsp15 employs a conventional acid-base catalytic mechanism passing through an anionic transition state, and that divalent ion activation is substrate dependent.

An experimental investigation on the impact of divalent ions on the emulsification of oil: Comparison of biodegradable (green) and petroleum-based surfactants

Emulsification of oil with surfactants often yields in complex colloidal systems which require understanding their physicochemical properties prior to their use in industry. This study aims to investigate the effects of divalent ions (calcium and magnesium) on the emulsification performance of biodegradable (green) surfactants of Triton™ CG-110 (alkyl polyglycoside, APG) and GreenZyme (GZ) at two temperature conditions (25 °C and 70 °C). For this purpose, the phase behaviour, interfacial tension (IFT), stability, droplet size distribution and rheological properties of APG and GZ microemulsion were evaluated. The outcomes were then compared with the emulsification performance of petroleum-based (synthetic) surfactants of alpha-olefin sulfonate (AOS) and cetyltrimethylammonium bromide (CTAB). Furthermore, the impacts of alkalis (ethanolamine and sodium carbonate) on microemulsions and the demulsification performance of a zwitterionic demulsifier (cocobetaine) were explored. The results show that only APG and CTAB could produce water in oil (W/O) microemulsions in the presence of divalent ions. The stability of APG and CTAB microemulsions was affected by divalent ions since the water segregation rate (WSR) index of these microemulsions went up from ≈21% to ≈ 85% as salinity increased up to 15 wt%. Also, the average droplet size of these microemulsions went up from 50-64 nm to 220–255 nm as salinity increased to 9 wt%. This is because the negative charge density on the microemulsion droplet surface decreases as the salinity increases, thus the electrostatic repulsive force between the droplets becomes weaker. In addition, APG and CTAB microemulsions showed a shear thinning behaviour, and their viscosity value increased with the increase in salinity. It is speculated that the presence of divalent ions generates more friction between the molecules, which causes an increase in the viscosity of the microemulsions.

Concepts and Misconceptions Concerning the Influence of Divalent Ions on the Performance of Reverse Electrodialysis Using Natural Waters.

Divalent ions have a negative effect on the obtained power and efficiency of the reverse electrodialysis (RED) process when using natural waters. These effects can largely be attributed to the interaction between the various ions and the membranes, resulting in a decreased membrane voltage, an increased membrane resistance, and uphill transport of divalent ions. The aim of this study was to investigate the causes of these differences and, if possible, to find underlying causes. The approach mainly followed that in literature articles that specifically focused on the effect of divalent ions on RED. It transpired that seven publications were useful because the methodology was well described and sufficient data was published. I found two widely shared misconceptions. The first concerns the role of the stack voltage in uphill transport of divalent ions; itis often thought that the open circuit voltage (OCV) must be taken into account, but it is plausible that the voltage under working conditions is the critical factor. The second debatable point concerns the methodology used to make a series of solutions to study the effect of divalent ions. Typically, solutions with a constant number of moles of salt are used; however, it is better to make a series with a constant ratio of equivalents of those salts. Moreover, it is plausible that the decreased voltage can be explained by the inherently lower Donnan potential of multi-charged ions and that increased resistance is caused by the fact that divalent ions-with a lower mobility there than the monovalent ions-occupy relatively much of the available space in the gel phase of the membrane. While both resistance and voltage play a decisive role in RED and probably also in other membrane processes like electrodialysis (ED), it is remarkable that there are so few publications that focus on measurements on individual membranes. The implications of these results is that research on the effect of divalent ions in RED, ED and similar processes needs to be more structured in the future. Relatively simple procedures can be developed for the determination of membrane resistance in solutions of mixtures of mono- and divalent salts. The same applies to determining the membrane potential. The challenge is to arrive at a standard method for equipment, methodology, and the composition of the test solutions.

Experimental investigation of divalent ions and screening in smart water on calcite rock surface

Massive demand for fossil fuel against limited available oil conventional reservoirs worldwide highlights that innovative enhanced oil recovery method. Nowadays, due to the accessibility of seawater and rivers, smart water and low salinity water injection have gained more attention. This paper addresses the mechanisms behind smart water injection and studies a real case from a carbonate oil reservoir. For this purpose, contact angle measurement was employed to screen and find the best smart water composition among different types of water. A core flooding experiment was used to evaluate the performance of the smart water injection in calcite rock. Two different scenarios were implemented in the core displacement experiment to examine the effect of divalent ions. Based on the experimental results, the main mechanism behind the smart water injection is the wettability alteration of the calcite rock surface. Also, as the most central divalent ions, an increase in calcium ions has been effective in increasing the water wetness of the rock surface, resulting in river water with double calcium ion content as the best smart water. [Received: November 8, 2021; Accepted: June 2, 2022]

Microwave dielectric properties of Mg1.8R0.2Al4Si5O18 (R = Mg, Ca, Sr, Ba, Mn, Co, Ni, Cu, Zn) cordierite ceramics and their application for 5G microstrip patch antenna

In this work, the effects of divalent ions on the phase structure, microstructure, and microwave dielectric properties of Mg1.8R0.2Al4Si5O18 (R = Mg, Ca, Sr, Ba, Mn, Co, Ni, Cu, Zn) cordierite ceramics were investigated. Complex chemical bond theory, Raman spectrum and infrared reflectance spectrum were employed to understand the relationship among structural characteristics, vibration modes and microwave dielectric properties for alkaline earth and transitional metal divalent elements doped cordierite ceramics. The optimal microwave dielectric properties were obtained for Mg1.8Ni0.2Al4Si5O18 with εr of 4.53, Q×f of 61,880 GHz and τf of -32 ppm/℃. Finally, a 5G-Sub 6GHz patch antennas with a central frequency of 4.91 GHz was successfully designed and fabricated using a Mg1.8Ni0.2Al4Si5O18 substrate. The antenna exhibited excellent performance with a gain of 5.83 dBi and an efficiency of 76 %, showing promise to be employed in 5 G/6G millimeter-wave communication technology.

Divalent Ion-Induced Switch in DNA Cleavage of KpnI Endonuclease Probed through Surface-Enhanced Raman Spectroscopy.

We demonstrate the remarkable ability of surface-enhanced Raman spectroscopy (SERS) to track the allosteric changes in restriction endonuclease KpnI (R.KpnI) caused by metal ions. R.KpnI binds and promiscuously cleaves DNA upon activation by Mg2+ ions. However, the divalent ion Ca2+ induces high fidelity cleavage, which can be overcome by higher concentrations of Mg2+ ions. In the absence of any 3D crystal structure, for the first time, we have elucidated the structural underpinnings of such a differential effect of divalent ions on the endonuclease activity. A combined SERS and molecular dynamics (MD) approach showed that Ca2+ ion activates an enzymatic switch in the active site, which is responsible for the high fidelity activity of the enzyme. Thus, SERS in combination with MD simulations provides a powerful tool for probing the link between the structure and activity of enzyme molecules that play vital roles in DNA transactions.

The Effect of Divalent Ions on the Structure of Bilayers in the Dimyristoylphosphatidylcholine Vesicles

The Effect of Divalent Ions on the Structure of Bilayers in the Dimyristoylphosphatidylcholine Vesicles

Influence of Additional Doping of Divalent Ions on Emission Intensity of Mn-Doped CaAl12O19

In recent years, phosphor-converted white light-emitting diodes (pc-WLED) have great attention due to long lifetime and low power consumption compared to traditional lighting source. The most popular method to fabricate the pc-WLEDs is a combination of blue LED chips (GaN) and yellow phosphor (Y3Al5O12:Ce3+), which shows high luminescence intensity. However, such pc-WLED does not have high color rendering property due to the lack of red color emission component. In order to solve the problem and obtain warmer colored pc-WLEDs, it is efficient to incorporate a red phosphor in the pc-WLED. It is known that Mn-doped phosphor have been studied because of their broad excitation band in UV-blue region and their deep red emission. Among the oxide basis phosphors, several materials such as Mn-doped CaAl12O19 [1] and Mg2TiO4 [2] were reported with good luminescence property. To increase the emission efficiency, additional doping into such Mn-doped oxide phosphors were examined. The remarkable enhancement of the emission intensity was reported for Mg co-doping in Mn-doped CaAl12O19 [3]. However, the mechanism why such enhancement was achieved by co-doping has not yet been fully understood. In this study, influence of additional doping of divalent ions, such as Mg2+, Zn2+ and Cd2+, on the red-emission intensity of Mn-doped CaAl12O19 is investigated. All the samples were synthesized with conventional solid-state reaction method by changing divalent ions concentration. Crystal structure of the synthesized samples was characterized with the powder X-ray diffraction (XRD) technique. To determine the charge state and the local environment of Mn ions, the Electron Spin Resonance (ESR) spectra were observed.The observed photoluminescence spectra of non-doped and Cd2+, Mg2+, Zn2+ co-doped CaAl12O19:Mn are shown in Fig. 1. In all cases, it is shown that divalent ions dopings could enhance the emission intensity, among which Mg2+ doping shows the largest enhancement. In the observed ESR spectra of non-doped and Cd2+, Mg2+, Zn2+ co-doped CaAl12O19:Mn, six peaks derived from hyper fine structure of Mn4+ could be seen in all the samples. It is noted that Mg and Zn co-doping significantly affects the spectral profiles, whereas only slight change was observed in Cd co-doped one. This indicates that Mg and Zn co-doping influence on local structure of Mn. In order to understand the effect of divalent ions doping on the enhancement of the red emission intensity, the first principles calculations within a density functional theory (DFT) have been also performed. As it is well known that the local environment of Mn ions is quite important on the emission intensity, local environment of Mn ions in CaAl12O19 were examined by substituting Mn ions at five crystallographically independent Al sites using the Vienna Ab initio Simulation Package (VASP)[4]. Using the same method, influence of additional dopings of divalent ions are investigated. In the conventional DFT calculations with local density approximation (LDA) or generalized gradient approximation (GGA) the band gap is always underestimated. As there are some methods developed recently to obtain more accurate band gap, for the electronic structure analysis, the modified Becke-Johnson potential by Tran and Blaha (TB-mBJ) [5] implemented in WIEN2k package [6] was employed here. In addition, Hubbard U correction on the d electron state is adopted to represent the strong correlation between d-electrons on Mn ions, which cannot be fully included in TB-mBJ.AcknowledgementThis work was partially supported by the Joint Research Center for Environmentally Conscious Technologies in Materials Science (project No. 30009, 30012, 31008, and 31017) at ZAIKEN, Waseda University.

Effect of divalent ions on cariogenic biofilm formation

BackgroundDivalent cations are able to interact with exopolysaccharides (EPS) and thus are capable to modify the structure and composition of dental biofilm. At the moment, little is known about the adsorption of metals by cariogenic EPS; thus, the aim of the present study was to evaluate the effect of divalent ions (calcium, magnesium, and zinc) on the growth and biofilm formation of mutans streptococci and on the dissolution of hydroxyapatite as well as to investigate their binding to the bacterial EPS.ResultsS. mutans strains used in this study show the highest tolerance towards calcium of the ions tested. Growth parameters showed no differences to control condition for both strains up to 100 mM; revealing natural tolerance to higher concentration of calcium in the surroundings. Although excessive levels of calcium did not impair the growth parameters, it also did not have a positive effect on biofilm formation or its binding affinity to EPS. Magnesium-saturated environment proved to be counterproductive as strains were able to dissolve more Ca2+ from the tooth surface in the presence of magnesium, therefore releasing excessive amounts of Ca2+ in the environment and leading to the progression of the disease. Thus, this supports the idea of self-regulation, when more Ca2+ is released, more calcium is bound to the biofilm strengthening its structure and however, also less is left for remineralization. Zinc inhibited bacterial adhesion already at low concentrations and had a strong antibacterial effect on the strains as well as on calcium dissolution; leading to less biofilm and less EPS. Additionally, Zn2+ had almost always the lowest affinity to all EPS; thus, the unbound zinc could also still remain in the surrounding environment and keep its antimicrobial properties.ConclusionIt is important to maintain a stable relationship between calcium, magnesium and zinc as excessive concentrations of one can easily destroy the balance between the three in cariogenic environment and lead to progression of the disease.

The Effect of Divalent Metal Ions on the Temperature Stability of Poly(I:C) Duplex

The effect of divalent ions on the thermal stability of the double-stranded polynucleotide polyinosinic:polycytidylic acid (poly(I:C)) in a buffer solution (pH 7) was studied by UV absorption spectroscopy and thermal denaturation by measuring the absorbance at 260 nm. The concentration dependence of the polynucleotide melting temperature (Tm) in the presence of metal ions (2.5 × 10−6–10−2 M) was obtained. It was found that the duplex thermal stability grew gradually upon an increase of Ca2+ and Mn2+ concentration. The thermal stability of the duplex in the presence of Cd2+, Ni2+, and Zn2+ rises up to an ion concentration of about 10−4 M and further falls. In contrast to these ions, the addition of Cu2+ to the solution leads to a sharp decline in Тm of the duplex at a concentration above 10−5 M. The observed difference in the influence of metal ions on the poly(I:C) thermal stability is explained by the different affinity of these ions to both the phosphate groups and the nitrogenous bases of the polynucleotides. Based on the analysis of the Tm concentration dependence, the dominant binding of each ion to the specific polynucleotide components was proposed.

The effect of divalent ions of zinc and strontium substitution on the structural and magnetic properties on the cobalt site in cobalt ferrite

The effect of doping of divalent Sr2+ and Zn2+ ions on the structural and magnetic properties of cobalt ferrite was investigated. For this purpose, the samples with the composition of Co1-x-ySrxZnyFe2O4 (where x = 0.0, 0.01, 0.05, 0.3 and y = 0.0, 0.05, 0.1, 0.4, 0.5, 0.7) were synthesized by using the spontaneous gel auto-combustion (Pechini) technique. The effect of the presence of these dopants on the average of crystallite/grain size, lattice parameter, density, the purity of the formed phase, and morphology of the synthesized nanoparticles was determined. Although formation of spinel ferrite was confirmed in the all samples, the secondary phase of SrFeO2.86 was detected for the samples containing high values of Sr (=0.3). Also, thermal DTA-TG analysis showed that the formation enthalpy of the doped-samples was increased. FE-SEM micrographs showed a semi-spherical morphology, regular and well-distributed nanoparticles in the samples with high values of these dopant elements. According to the FTIR data, simultaneous doping of Sr2+ and Zn2+ ions caused to a slightly shift in spectrum. The magnetic characterization of the synthesized samples revealed that the simultaneous doping of Sr2+ and Zn2+ ions in cobalt ferrite drastically changes the magnetic parameters of cobalt ferrite. For instance, the saturation magnetization and coercivity values were changed from 72 to 4 emu/g and from 1019 to 5 Oe, respectively. Furthermore, the hard magnetic behavior of cobalt ferrite changed to the superparamagnetic behavior in the doped-samples.

Dynamic interaction of fluoroquinolones with magnesium ions monitored using bacterial outer membrane nanopores.

Divalent ions are known to have a severe effect on the translocation of several antibiotic molecules into (pathogenic) bacteria. In the present study we have investigated the effect of divalent ions on the permeability of norfloxacin across the major outer membrane channels from E. coli (OmpF and OmpC) and E. aerogenes (Omp35 and Omp36) at the single channel level. To understand the rate limiting steps in permeation, we reconstituted single porins into planar lipid bilayers and analyzed the ion current fluctuations caused in the presence of norfloxacin. Moreover, to obtain an atomistic view, we complemented the experiments with millisecond-long free energy calculations based on temperature-accelerated Brownian dynamics simulations to identify the most probable permeation pathways of the antibiotics through the respective pores. Both, the experimental analysis and the computational modelling, suggest that norfloxacin is able to permeate through the larger porins, i.e., OmpF, OmpC, and Omp35, whereas it only binds to the slightly narrower porin Omp36. Moreover, divalent ions can bind to negatively charged residues inside the porin, reversing the ion selectivity of the pore. In addition, the divalent ions can chelate with the fluoroquinolone molecules and alter their physicochemical properties. The results suggest that the conjugation with either pores or molecules must break when the antibiotic molecules pass the lumen of the porin, with the conjugation to the antibiotic being more stable than that to the respective pore. In general, the permeation or binding process of fluoroquinolones in porins occurs irrespective of the presence of divalent ions, but the presence of divalent ions can vary the kinetics significantly. Thus, a detailed investigation of the interplay of divalent ions with antibiotics and pores is of key importance in developing new antimicrobial drugs.

Modeling the influence of divalent ions on membrane resistance and electric power in reverse electrodialysis

The prospects and potential of Reverse Electrodialysis (RED) for energy harvesting from natural streams with salinity gradient demand more in-depth studies to understand and overcome the limitations posed by divalent ions. Power performance is greatly influenced by the ionic resistance displayed by the alternating cation and anion exchange membranes (CEMs and AEMs, respectively) housed in RED stacks, which in turn is determined by the type and concentration of ions and counter-ions in the water streams. The effects of divalent ions on power output have been experimentally approached in several works by using real or synthetic water. However, the development of comprehensive models including the effect of divalent ions on membrane resistance and power performance under different scenarios is still very scarce. Thus, this work investigates experimentally the effect of ion species on membrane resistance, providing for the first time mathematical correlations useful to predict power performance in RED stacks under a wide range of compositions of salinity gradient solutions. To this end, electrochemical impedance spectroscopy (EIS) measurements have been performed for CEM and AEM commercial membranes in contact with different concentration of NaCl solutions and including different mixtures of divalent ions (Ca2+, Mg2+, SO42−). These correlations have been implemented in a previously developed model to determine power outputs as function of ion mixture compositions. Scenarios of general interest for RED practical implementation have been addressed; specifically, solutions with a composition representative of seawater or high salinity brines have been studied as high concentration solutions (HCS) and, on the other hand, typical concentrations of wastewater treatment plant effluents, river water or brackish water from desalination plants were used as low concentration solutions (LCS).

Ion-Specific Effects of Divalent Ions on the Structure of Polyelectrolyte Brushes.

Polyelectrolyte brushes consist of charged polymer chains attached on one end to a surface at high densities. They are relevant for many practical applications ranging from biosensors to drug delivery to colloidal stability. Their structure and functionality can be dramatically influenced by multivalent counterions in the solution environment. In this work, the surface forces apparatus (SFA) and atomic force microscopy (AFM) were used to investigate the effects of three alkaline earth divalent cations, Mg2+, Ca2+, and Ba2+, on the structures of polystyrenesulfonate (PSS) brushes tethered to mica and silicon oxide surfaces. While all these ions caused significant shrinkage of the height of the PSS brushes, strong ion-specific effects were observed. Mg2+ and Ca2+ caused homogeneous shrinkage; Ba2+ led to pinned-micelle like inhomogeneous structures. Isothermal titration calorimetry (ITC) demonstrated that this ion specificity was mainly caused by the difference in binding energy between sulfonate groups and the divalent cations. Considering the abundance of divalent cations in industrial processes, natural environments, and biological systems, the understanding of strong ion-specific effects of divalent counterions is of great importance for theoretical studies and various applications involving polyelectrolytes.

Purification and Characterization of α-amylase from a Novel Thermoalkalophilic Strain of Bacillus sonorensis GV2 Isolated from Mushroom Compost

A novel thermoalkalophilic α-amylase producing bacterial strain Bacillus sonorensis GV2 |KJ775811.1| was isolated from mushroom compost. The purification of α-amylase was performed through different chromatography techniques. After purification with SDS-PAGE and Sephadex G-75 gel filtration, the molecular weight of monomeric α-amylase was found to be 45 kDa. The enzyme showed an optimal activity over a wide range of temperature and pH of 35-60oC and 7-11, respectively. The effect of divalent ions i.e. Mg2+ and Ca2+ showed a positive increase in enzyme activity. This enzyme is unique in a sense that it also exhibited a considerable raw corn starch hydrolyzing activity at 55oC. The end products when subjected to TLC which were identified as main maltooligosaccharides, proving the endo action of an enzyme. The Vmax and Km values of Bacillus sonorensis GV2 α-amylase were found to be 1347 μmol/mg/min and 3.46 mMol/ml. The MALDI peptide mass fingerprint analysis of the reduced and carboxymethylated amylase digested with chymotrypsin indicated that this partial amino acid sequence was homologous by a score of 6 with UDP transferalyase. All these findings suggests about the potential role of this α-amylase for raw starch degrading applications in the relevant industry.

Determining and unravelling origins of reduced photoinactivation efficacy of bacteria in milk

Bovine mastitis is an endemic disease of dairy cattle that is considered to be one of the most frequent and costly diseases in veterinary medicine. An increase in the incidence of disease results in the increased use of antibiotics, which in turn increases the potential of bacterial resistance. This study aimed to investigate the effectiveness of antimicrobial photodynamic therapy (aPDT) in the treatment of bovine mastitis, as an alternative to systemic antibiotics. To identify the key factors affecting photoinactivation efficacy, realistic experiments in view of the end-use were conducted in milk samples using two different photosensitizers: methylene blue (MB) and silicon (IV) phthalocyanine derivative (SiPc). We explored the effects of divalent ions and fat content on the aPDT outcome and determined influence of different proteins on aPDT efficacy. Levels of bacterial sensitivity to PSs varied depending on the type of bacteria (Gram-positive vs. Gram-negative) and light exposure time. Critical interrelated factors affecting aPDT in milk were identified and an efficient combination of treatment conditions that can lead to a full photodynamic inactivation of bacteria was determined.

Effect of divalent ions on the dynamics of disjoining pressure induced by salinity modification

Disjoining pressure is defined as the net difference between the pressure in a water film and that of the bulk fluid. It is known that disjoining pressure in water films is one of the thermodynamic aspects that control wettability, and is itself locally determined by short-range and long-range surface forces. Modifying the ionic strength and composition of water films leads to alteration of local electrostatic/electrokinetic forces, which results in the variation of disjoining pressure. This has been of particular interest in industrial applications such as enhanced oil recovery technology. In low salinity waterflooding, the variation of disjoining pressure has been linked to alteration of wettability, however, there are still many unanswered questions in this regard, such as the role of ion valency in the dynamics of disjoining pressure.In this work, we carried out a numerical study of the relation between ionic composition and disjoining pressure in a water film, induced by the reduction of the ionic strength in the bulk fluid. We compared systems composed of electrolytes of different valencies, with the aim of studying the impact of divalent ions and the role of charge symmetry on disjoining pressure.We simulate the initial equilibrium conditions under high ionic strength by solving the Poisson-Boltzmann equation. Then, we reduce the ionic strength at the boundary of the domain and use the Poisson-Nernst-Planck equations to model the transient re-distribution of ions within the film. In order to investigate the impact of ionic composition on the ionic transport and pressure dynamics, all simulations are implemented at the same initial ionic strength, but different ion pairs (1:1, 1:2 and 2:1), and different finite film thicknesses. We discuss the impact of system scaling factors in the total disjoining pressure, such as the ratio between film thickness and Debye length, as well as the relation between the electrostatic and osmotic pressure effects.