Function Of Sodium Chloride Concentration Research Articles

Mechanisms shaping the gypsum stromatolite-like structures in the Salar de Llamara (Atacama Desert, Chile)

The explanation of the origin of microbialites and specifically stromatolitic structures is a problem of high relevance for decoding past sedimentary environments and deciphering the biogenicity of the oldest plausible remnants of life. We have investigated the morphogenesis of gypsum stromatolite-like structures currently growing in shallow ponds (puquíos) in the Salar de Llamara (Atacama Desert, Northern Chile). The crystal size, aspect ratio, and orientation distributions of gypsum crystals within the structures have been quantified and show indications for episodic nucleation and competitive growth of millimetric to centimetric selenite crystals into a radial, branched, and loosely cemented aggregate. The morphogenetical process is explained by the existence of a stable vertical salinity gradient in the ponds. Due to the non-linear dependency of gypsum solubility as a function of sodium chloride concentration, the salinity gradient produces undersaturated solutions, which dissolve gypsum crystals. This dissolution happens at a certain depth, narrowing the lower part of the structures, and producing their stromatolite-like morphology. We have tested this novel mechanism experimentally, simulating the effective dissolution of gypsum crystals in stratified ponds, thus providing a purely abiotic mechanism for these stromatolite-like structures.

Effects of ionic strength on the folding and stability of SAMP1, a ubiquitin-like halophilic protein

Our knowledge of the folding behavior of proteins from extremophiles is limited at this time. These proteins may more closely resemble the primordial proteins selected in early evolution under extreme conditions. The small archaeal modifier protein 1 (SAMP1) studied in this report is an 87-residue protein with a β-grasp fold found in the halophile Haloferax volcanii from the Dead Sea. To gain insight into the effects of salt on the stability and folding mechanism of SAMP1, we conducted equilibrium and kinetic folding experiments as a function of sodium chloride concentration. The results revealed that increasing ionic strength accelerates refolding and slows down unfolding of SAMP1, giving rise to a pronounced salt-induced stabilization. With increasing NaCl concentration, the rate of folding observed via a combination of continuous-flow (0.1–2 ms time range) and stopped-flow measurements (>2 ms) exhibited a >100-fold increase between 0.1 and 1.5 M NaCl and leveled off at higher concentrations. Using the Linderström-Lang smeared charge formalism to model electrostatic interactions in ground and transition states encountered during folding, we showed that the observed salt dependence is dominated by Debye-Hückel screening of electrostatic repulsion among numerous negatively charged residues. Comparisons are also drawn with three well-studied mesophilic members of the β-grasp superfamily: protein G, protein L, and ubiquitin. Interestingly, the folding rate of SAMP1 in 3 M sodium chloride is comparable to that of protein G, ubiquitin, and protein L at lower ionic strength. The results indicate the important role of electrostatic interactions in protein folding and imply that proteins have evolved to minimize unfavorable charge-charge interactions under their specific native conditions.

Hyperproduction of γ-glutamyl transpeptidase from Bacillus licheniformis ER15 in the presence of high salt concentration

ABSTRACTBackground: Microbial γ-glutamyl transpeptidases (GGTs) have been exploited in biotechnological, pharmaceutical, and food sectors for the synthesis of various γ-glutamyl compounds. But, till date, no bacterial GGTs are commercially available in the market because of lower levels of production from various sources. In the current study, production of GGT from Bacillus licheniformis ER15 was investigated to achieve high GGT titers. Results: Hyperproduction of GGT from B. licheniformis ER15 was achieved with 6.4-fold enhancement (7921.2 ± 198.7 U/L) by optimization of culture medium following one-variable-at-a-time strategy and statistical approaches. Medium consisting of Na2HPO4: 0.32% (w/v); KH2PO4: 0.15% (w/v); starch: 0.1% (w/v); soybean meal: 0.5% (w/v); NaCl: 4.0% (w/v), and MgCl2: 5 mM was found to be optimal for maximum GGT titers. Maximum GGT titers were obtained, in the optimized medium at 37°C and 200 rpm, after 40 h. It was noteworthy that GGT production was a linear function of sodium chloride concentration, as observed during response surface methodology. While investigating the role of NaCl on GGT production, it was found that NaCl drastically decreased subtilisin concentration and indirectly increasing GGT recovery. Conclusion: B. licheniformis ER15 is proved to be a potential candidate for large-scale production of GGT enzyme and its commercialization.

Texture Profile Analysis and Functional Properties of Gelatin from the Skin of Three Species of Fresh Water Fish

The texture profile analysis and functional properties of gelatin from fresh water fish (carps) and porcine skin were measured. Texture profile analysis revealed that the porcine gelatin showed significantly higher values for hardness, springiness, cohesiveness, gumminess, and chewiness than carp skin gelatin (p < 0.05). The bloom strength of gelatin from a porcine source was higher (466.40 g) than carp skin. The solubility profile of gelatin from carps and porcine as function of sodium chloride concentration indicated a maximum solubility at 0.3 M. The relationship between emulsion capacity values and concentration of proteins were found to be inversed in all of the gelatin samples.

Estimation of potential barium sulfate (barite) precipitation in oilfield brines using a simple predictive tool

Scale deposition is one of the most important and serious problems that limits and sometimes blocks oil and gas production by plugging the oil producing formation matrix or fractures and perforated intervals. One of the most insoluble substances formed from formation water (brine) and one that is very difficult to remove once formed on equipment, formation matrix or fractures and perforated intervals is barium sulfate. It is so insoluble that quantitative analysis methods for both barium and sulfate are based on the precipitation of barium sulfate. In this work a simple‐to‐use predictive tool is developed to estimate potential barium sulfate (barite) precipitation in oilfield brines that are predominantly sodium chloride solutions as a function of sodium chloride concentration and temperature. Estimations are found to be in excellent agreement with reported data in the literature with average absolute deviation being &lt;1.3%. The tool developed in this study can be of immense practical value for experts and engineers to have a quick check of barium sulfate scale formation at various conditions without opting for any experimental trials. In particular, petroleum and process engineers would find the approach to be user‐friendly with transparent calculations involving no complex expressions. © 2012 American Institute of Chemical Engineers Environ Prog, 32: 860–865, 2013

Selective transport of Cadmium by PVC/Aliquat 336 polymer inclusion membranes (PIMs): the role of membrane composition and solution chemistry

This study investigated the extraction and stripping performance of PIMs consisting of PVC and Aliquat 336. Extraction and stripping of three representative heavy metals - namely <TEX>$Cd^{2+}$</TEX>, <TEX>$Cu^{2+}$</TEX>, and <TEX>$Zn^{2+}$</TEX> - by the synthesized membranes were evaluated as a function of sodium chloride concentration and under different stripping solutions (0.01 M <TEX>$HNO_3$</TEX>, Milli-Q water, 0.01 M HCl and 0.01 M NaOH), respectively. Results reported here indicate that the formation of negatively charged metal chloride complex species was responsible for the extraction of the target metal to PIMs. Experimental results and thermodynamic modeling of the speciation of chloro metal complexes further confirm that the extraction selectivity between <TEX>$Cd^{2+}$</TEX>, <TEX>$Cu^{2+}$</TEX> and <TEX>$Zn^{2+}$</TEX> can be controlled by regulating the chloride concentration of the feed solution. An acidic solution without any chloride was the most effective stripping solution, followed by Milli-Q water, and a diluted hydrochloric acid solution. On the other hand, the stripping of metals from PIMs did not occur when a basic stripping solution was used.

Growth Rate Dispersion in Protein Crystal Growth

Like many small molecule materials, tetragonal lysozyme crystals exhibit growth rate dispersion. To investigate this phenomenon further, the growth rate dispersion of the (110) and (101) crystal faces was determined as a function of sodium chloride concentration, temperature, and solution pH. Under the conditions investigated, the growth rate dispersion follows the constant crystal growth model, in which each individual crystal is assumed to have a unique, constant growth rate. While the growth rate dispersion of the (110) face seems independent of the solution conditions, for the (101) face it was observed to vary systematically with temperature and pH. The greater susceptibility of the (101) face to the causes of growth rate dispersion was interpreted in light of a model proposed to explain the differing growth mechanisms of each face. Overall, the magnitude of crystal growth rate dispersion observed for lysozyme is similar to that reported for some small organic molecules.

Complexation Constants of Procaine with β-Cyclodextrin in NaCl Media

The complexation constants of neutral and protonated procaine (also called novocaine) with β-cyclodextrin have been obtained as a function of sodium chloride concentration, at 25 °C, using the potentiometric technique with a glass electrode. It was found that the formation of the complex with protonated procaine is not altered by the presence of the salt and the logarithm of the formation constant of the neutral complex increases slowly with ionic strength, varing linearly with salt concentration.

Osmotic Second Virial Coefficients and Phase Diagrams for Aqueous Proteins from a Much-Improved Poisson−Boltzmann Equation

A much-improved Poisson - Boltzmann equation for two globular proteins using bispherical coordinates is used to establish the potential of mean force (PMF) between two globular lysozyme particles. Calculations presented here include previously ignored ion-protein nonelectrostatic potentials. The lysozyme - lysozyme PMF is used to calculate osmotic second virial coeffiencients. The theoretical PMF curve as a function of sodium chloride concentration is successfully compared with that from experiment. Our theoretical PMF shows how the second virial coefficient and the phase diagram depends on salt concentration, pH and, most notably, on the choice of salt in the aquous solution. © 2007 American Chemical Society.

Observation of biological samples using a scanning microwave microscope

We present the application of a scanning microwave microscope technique to biological samples. Since dielectric properties of most biological samples originate mainly from the water they contain, we were able to obtain microscope images of biological samples by our scanning microwave microscope technique. As a model system, we have measured the electrical properties of water in the microwave region. The high dielectric constant and the large loss tangent of water were verified. Furthermore, we have measured the properties of water with differing amounts of sodium chloride concentration ranging from de-ionized water to the saturated solution. We have observed a significant change in the resonant frequency and Q value of the resonator as a function of sodium chloride concentration. The concentration dependence of the signals shows that our scanning microwave microscope technique can be useful for investigating the local electric behavior of biological samples with a simple model of ionic conduction.

Chloride ion catalyzed conformational inversion of carbocation intermediates in the hydrolysis of a benzo[a]pyrene 7,8-diol 9,10-epoxide.

A highly efficient procedure for converting 7beta,8alpha-dihydroxy-9alpha,10alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (1) to its trans-9,10-chlorohydrin (5) with excellent yield and purity by the reaction of anhydrous HCl in THF has been developed. The rate of reaction of 5 has been determined as a function of sodium chloride concentration in 1:1 dioxane-water solutions. A large common ion rate depression for the reaction of the chlorohydrin was observed, and the rate data are fit to a mechanism in which all of the tetrol products are formed by the reaction of water with the C-10 carbocation intermediate. Yet, the cis/trans ratio of tetrols from the reaction of the carbocation intermediate from the hydrolysis of chlorohydrin 5 is different than the cis/trans tetrol ratio from the acid-catalyzed hydrolysis of diol epoxide 1, which hydrolyzes via a carbocation with the same connectivity as that formed in the hydrolysis of 5. To rationalize these results, it is proposed that the S(N)1 reaction of chlorohydrin 5 yields a different distribution of carbocation conformations than that formed from the reaction of 1 with H(+). The energy barrier for the inversion of these carbocation conformations must be large relative to the energy barriers for the reaction of each carbocation conformation with water. In solutions containing sufficient concentrations of chloride ion, however, a lower energy pathway via a halohydrin exists for the interconversion of the carbocation conformations. Thus, chloride ion catalyzes the interconversion of these two carbocation conformations.

Flocculation of Weakly Charged Oil−Water Emulsions

This study concerns dodecane-water emulsions stabilized primarily by the nonionic surfactant decyl-β-D-glucoside (C 10 βGlu). The emulsions are stable with respect to coalescence and Ostwald ripening but unstable with respect to flocculation and creaming. Emulsions stabilized by monolayers of pure C 10 βGlu flocculate and show rapid creaming. A sharp transition from a flocculated state to a nonflocculated state can be induced by the addition of small mole fractions of either the anionic sodium octadecylsulfate or the cationic octadecyltrimethylammonium bromide surfactants. The nonflocculated emulsions show slower creaming and the discontinuous change in creaming rate can be used to detect the flocculation transition. We have measured the concentration of ionic surfactant required to induce the flocculation transition as a function of sodium chloride concentration in the continuous aqueous phase. Using a model in which the colloidal interactions between the deformable emulsion drops are taken to consist of electrostatic repulsion, van der Waals attraction, and a short-range repulsion modeled as a hard wall, we show how the flocculation transition can be quantitatively predicted using no adjustable parameters.

Lysozyme solubility in H2O and D2O solutions as a function of sodium chloride concentration

Some spectroscopic methods require solubilization or crystallization of proteins in heavy water because of the large difference in neutron scattering properties between protons and deuterons. In order to quantify the impact of slightly different physical properties of D2O and H2O, lysozyme solubility curves have been measured for these solvents, using 0.2 to 3.0 M sodium chloride in 0.050 M sodium acetate buffer (pH 4.5) at 291 K. After four months of crystallization, solubility data were measured within 9% error and showed that the lysozyme solubility in H2O is 1.3 times that in D2O.

Preferred high-performance liquid chromatographic anion-exchange chromatographic contact region for recombinant rat cytochrome b 5

The HPLC anion-exchange isocratic retention behaviors of site-directed charge mutants of the recombinant soluble core of rat cytochrome b 5 on Mono Q HR 5 5 were investigated as a function of sodium chloride concentration, at a fixed temperature and eluent flow-rate. The retention behavior of the charge mutants was observed to depend on both the net charge of the protein and on the distribution of charged residues on the protein surface. Site-directed mutants of the same net charge differed significantly in retention behavior; differences in retention were observed to increase with decreasing ionic strength. The retention results were interpreted in terms of the stoichiometric displacement model (SDM) to obtain the apparent number of binding sites in the contact region, Z. Elimination of a single negatively charged residue, in an apparent preferred chromatographic contact region, resulted in disproportionately large changes in the retention behavior as compared with elimination of a single negatively charged residue on other areas of the protein surface. The experimentally determined preferred chromatographic contact region compares favorably with the results of batch equilibrium adsorption studies on the same system and with previously reported results of computational molecular electrostatic modeling. The results of this study indicate that the observed protein ion-exchange retention represents the summation of many fractional electrostatic interactions of varying interaction energies. Therefore, protein ion-exchange retention is a function of both the number of contacts and the individual electrostatic interaction energies of the contacts between the protein and the ion-exchange surface.

Pressure dependence of the melting temperature of dA.dT polymers.

The pressure dependence of the helix-to-coil transition temperature (Tm) of poly[d(A-T)], poly(dA).poly(dT), and poly(dA).poly(dT)2 was studied as a function of sodium chloride concentration. The molar volume change of the transition (delta V) was calculated using the Clapeyron equation and calorimetrically determined enthalpies. The delta V of the transition varied linearly with the logarithm of the salt concentration for both double-stranded polymers. The delta V of poly[d(A-T)] changed from +0.36 to +3.86 cm3 mol-1 as the sodium chloride concentration changed from 0.020 to 1.0 M. For poly(dA).poly-(dT), the delta V varied from +2.60 to +4.59 cm3 mol-1 over the range of 0.020-0.20 M NaCl. No pressure dependence of the van't Hoff enthalpy was observed for the double-helical form of either polymer. The delta V for denaturation of the triple-helical species poly(dA).poly(dT)2 was found to be +7.81 and +10.4 cm3 mol-1 at 1.0 and 3.0 M NaCl, respectively. The observed delta V values are interpreted in terms of changes in the hydration of the polymers arising from release of counterions and changes in the stacking of the bases upon denaturation. Counterion release is assumed to make a net negative contribution to the overall delta V, implying that disruption of the stacking interactions must make a positive volume change to the overall delta V. The difference in the delta V values for the two polymers remains constant as the salt concentration is changed, suggesting a difference in the partial molar volume of their single-stranded forms.(ABSTRACT TRUNCATED AT 250 WORDS)

Hydrocarbon biodegradation and hydrocarbonoclastic bacterial communities composition grown in seawater as a function of sodium chloride concentration

Bacterial strains have been enriched and isolated from marine sediment of an oil-contaminated area and grown in a culture medium prepared with synthetic seawater (0.4 M NaCl) and containing crude oil (EH1 community) or an hydrocarbon mixture (EH2 community) as sole energy and carbon source. The strains isolated from crude oil were code named EH1 community; those from the mixture EH2 community. Hydrocarbon biodegradation in enrichment culture was maximum for 0.4 M NaCl and decreased for NaCl concentrations above or below this value. However, the effect of NaCl concentration depended somewhat on the nature of the substrate supplied for growth. With 2 M NaCl, the saturated fraction of crude oil was the only one significantly biodegraded (27%). In contrast, the level of biodegradation remains rather high for the standard hydrocarbon mixture: 80–95% for saturated hydrocarbons, 17–34% for aromatics. Few phenotypic differences were noted between strains growing on crude oil (EH1) and/or mixture of hydro-carbons (EH2). The clustering of the strains isolated after enrichment at various NaCl concentrations (from 0 to 2 M NaCl) demonstrated the presence of ecotypes of similar bacterial species. From initial enrichments most of the strains were Gram-negative, aerobic rods, possessing few exoenzymes and using mostly fatty acids and organic acids as carbon and energy sources.

Studies on polytetrafluoroethylene latices Part 3. Electrophoretic mobility in univalent electrolytes

The electrophoretic mobilities of particles of polytetrafluoroethylene (PTFE), prepared by a dispersion polymerisation technique using a peroxyacid initiator, have been determined using a mass transport technique. Investigations were carried out as a function of sodium chloride concentration at pH 9 and as a function of pH in the presence of various salts, namely, sodium chloride, potassium nitrate and potassium thiocyanate. The particles were found to have a low surface charge density, consistent with the idea that sparsely distributed charged sites originated from initiator fragments leaving the major part of the surface in a hydrophobic condition. Below a pH of ca. 4.5 increases of mobility with decreasing pH were observed with chloride and thiocyanate as the anion. These were attributed to an anion adsorption process, dependent on thepKa of the surface groups, and a model for the process is described.

Effect of added sodium chloride on the molecular environment and photoionization of N,N,N′,N′-tetramethylbenzidine in micellar solutions as studied by electron spin echo and electron spin resonance spectroscopy

The electron spin echo modulation (ESEM) and electron spin resonance (ESR) spectra of the cation radical of N,N,N′,N′-tetramethylbenzidine (TMB) in frozen sodium dodecyl sulfate (SDS) and dodecyltrimethylammonium chloride (DTAC) micelles were studied as a function of sodium chloride concentration. TMB+⋅ was produced by photoionization at 350 nm of the parent compound in the micelles at 77 K. From the ESEM analysis it is found that the cation–water interactions increase with salt addition in both anionic and cationic micelles to a maximum near 0.2 M NaCl and then decrease somewhat. The increase is interpreted in terms of an increase in the water density at the micellar surface due to an increased surface concentration of hydrated counterions. The decrease may be due to TMB moving further from the polar micellar surface with added salt. From ESR spectra the photoionization yields of TMB at 77 K were determined. For DTAC micelles the yields are found to decrease with salt addition as expected from electrostatic considerations. For SDS micelles the photoionization yields increase for salt concentrations up to about 0.15 M and decrease for greater salt concentrations up to 0.5 M. The initial increase in cation yield correlates with electrostatic expectations. The decrease may be due to TMB moving further from the polar micellar surface with added salt. The possible effect of differing TMB protonation equilibria between anionic and cationic micelles on the photoionization yields was found to be unimportant by adjusting the bulk solution pH. An important conclusion is that salt addition can be used to optimize charge separation for photoionized solutes in anionic micelles.

Red blood cell adhesion. I. Determination of the ionic conditions for adhesion to an oil-water interface.

We have examined the adhesion of glutaraldehyde-treated human red blood cells to a clean liquid hydrocarbon interface as a function of sodium chloride concentration. Cells adhere reversibly to the interface over a wide range of concentrations but fail to do so below about 0.1 mM. Adherent cells do not alter the tension of the oil/water interface. These results show that cells can adhere by physical forces in special situations without biochemical interactions. The data provide a basis for calculating the size of the physical forces.

THE LACK OF SPECIFICITY TOWARDS SALTS IN THE ACTIVATION OF CHOLINE ACETYLTRANSFERASE FROM HUMAN PLACENTA

Abstract— The effects of monovalent and divalent anions on the choline acetyltransferase reaction have been determined at high (5.0 mM) and low (0.58 mM) choline. At 0.58 mM‐choline, both monovalent and divalent anions activate the enzyme ±9 fold; however, at 5.0mM‐choline, monovalent anions activate the enzyme ±25 fold, while divalent anions activate ±9 fold. Both monovalent and divalent anions show uncompetitive activation with respect to choline. When either dimethylaminoethanol, N‐(2‐hydroxyethyl)‐N‐methyl piperidinium iodide, or N‐(2‐hydroxyethyl)‐N‐propyl pyrrolidinium iodide was substituted for choline, activation by monovalent or divalent anions was only 2.5‐4 fold. With AcCoA as substrate the ChA reaction can be increased ±20 fold by increased salts; however, with acetyl dephosphoCoA as substrate, the reaction is insensitive to the salt concentration. Similar salt effects on the ChA reaction, as measured in the direction of acetylcholine synthesis, have been demonstrated in the reverse reaction. In addition, inhibition of the forward reaction by acetylcholine has been measured as a function of sodium chloride concentration. Although the K1 for acetylcholine increases with increasing salt, this change in K1, parallels the increase in the Km for choline. These results support the hypothesis that both monovalent and divalent anions activate choline acetyltransferase by the same singular mechanism; which is to increase the rate of dissociation of coenzyme A from the enzyme.