High Concentration Of Chloride Ions Research Articles

Three high-resolution crystal structures of cadmium-substituted carboxypeptidase A provide insight into the enzymatic function

Three high-resolution crystal structures of Cd(II)-substituted carboxypeptidase A (CPA) have been determined by X-ray diffraction from crystals prepared in three different buffer systems to assess the effect of pH and ionic strength on the Cd(II) coordination geometry. All crystallize in the space group P2(1) with identical cell dimensions. Cd-CPA(7.5): Cd(II)-substituted CPA prepared at pH 7.5 with [Cl(-)]=2 mM determined to 1.70 A resolution ( R=17.4% and R(free)=19.8%); Cd-CPA(5.5): Cd(II)-substituted CPA prepared at pH 5.5 with [Cl(-)]=2 mM to 2.00 A resolution ( R=16.1% and R(free)=18.6%); Cd-CPA(7.5)-Cl: Cd(II)-substituted CPA prepared at pH 7.5 with [Cl(-)]=250 mM to 1.76 A resolution ( R=16.7% and R(free)=17.8%). No noticeable structural changes were observed between the three structures. Two water molecules coordinate to Cd(II), in contrast to the single water molecule coordinating to Zn(II) in the Zn-CPA structure. No binding sites for anions could be identified, even in the structure with a high concentration of chloride ions. It is suggested that the anion inhibition is due to weak outer-sphere association of Cl(-) ions at several binding sites, shielding the strong positive charge distribution at the surface of the protein near the active site. Based on structural data and a sequence alignment of 18 non-redundant carboxypeptidases, a more elaborate version of the earlier reaction model is proposed that also addresses the transport of water to and from the active site. Conserved residues whose function was not addressed previously delineate the proposed pathways used in the transport of water during catalysis.

Extraction equilibrium of palladium(II) with 2-methyl-8-quinolinol into supercritical carbon dioxide fluid

The present study is concerned with the extraction behavior and equilibrium of Pd(II) with 2-methyl-8-quinolinol (HMQ) into supercritical fluid CO 2 (SF-CO 2). Pd(II)–HMQ complex extracted from a weakly acidic solution (pH 2–3) into SF-CO 2 was determined to be Pd(MQ) 2 on the basis of a slope analysis. The extraction constant K ex,SF (=[Pd(MQ) 2] SF[H +] 2[Cl −] 4[PdCl 4 2−] −1[HMQ] −2) was determined to be 10 4.3±0.2 at 8.5 MPa, 45 °C and I=0.4 M (H, Na)Cl (1 M=1 mol dm −3). The distribution behavior of HMQ between an aqueous and a SF-CO 2 phase was examined so as to discuss quantitatively the extraction equilibrium. The extraction constant ( K ex,Cy) of Pd(II) with HMQ into cyclohexane with a similar polarity to SF-CO 2 was determined and the K ex,SF was compared with the K ex,Cy. Pd(II) at the concentration range of 10 −5–10 −4 M in the aqueous solution (pH<3) containing relatively high concentration of chloride ion was found to be extracted efficiently by the SF-CO 2 extraction.

The Changes in the Laboratory Values During Administration of Commercially Available Ready-to-use Basal Solutions for Total Parenteral Nutrition

Some differences are seen in the concentrations of glucose and electrolytes between commercially available ready-to-use basal solutions for total parenteral nutrition (R-TPN).In this study, we investigated the effects of the long-term administration of Unicaliq®, which contains relatively higher concentrations of chloride ions than other R-TPNs, on the clinical laboratory values. One hundred and nineteen patients, who received Unicaliq® for more than four weeks at Hiroshima University Hospital, participated in this study. The laboratory values of chloride ion (Cl-) and blood urea nitrogen (BUN) significantly increased after receiving Unicaliq® for 2 weeks, but all levels, except for BUN, returned to the pretreatment levels after 4 weeks of administration. However, these changes were slight and all were within the normal ranges.No changes were observed in other laboratory values during the 4-week administration period.These results suggest that the clinical laboratory values are not affected by the long-term administration of Unicaliq®, at least up until 4 weeks.

Separation of Copper(Ii) and Zinc(Ii) from Chloride Solutions with Alkyl-8-hydroxyquinoline in Various Stages of Extraction: Stripping Process

Separation of zinc(II) from copper(II) from chloride solutions is studied using alkyl-8-hydroxyquinoline (KELEX 100). The separation can be achieved in the stage of extraction, scrubbing with water, or stripping with sulfuric acid. Appropriate conditions for such separation are given and discussed, with selective stripping being the most promising. In such a process, the extraction of both Zn(II) and Cu(II) can be carried out from solutions of high acidity and high concentration of chloride ions. An ammoniacal solution can be used for scrubbing chloride from the organic phase. Zinc(II) can then be selectively stripped from the organic phase with 0.25−0.8 M sulfuric acid at a 1:1 volume ratio. Nearly 3 M sulfuric acid is needed for the stripping of copper.

Complex periodic and chaotic current oscillations related to different states of the localized corrosion of iron in chloride-containing sulfuric acid solutions

Current oscillations generated during pitting of Fe in chloride-containing 0.75 M H 2 SO 4 solutions were monitored and analyzed under potentiostatic conditions in a wide range of chloride ion concentrations. The increase of chloride ion concentration leads to: (i) deviation of the oscillation type from monoperiodicity observed in the chloride-free system and (ii) increase of the current in the passive region up to a limiting value and simultaneously to the disappearance of the passive-to-active transition region in the I – E curve. The current oscillations for relatively low chloride ion concentrations (≤20 mM) are complex periodic or aperiodic depending on the potential. For relatively high chloride ion concentrations (>20 mM) the current oscillations become aperiodic (chaotic). Two limiting cases of the pitting growth process are distinguished on the basis of the type of oscillation observed for low and high chloride ion concentrations. First, the unstable pit growth related to complex periodic oscillations; the oxide passive film is formed but it is destabilized by Cl − ions. Then repeated breakdown and formation of the passive film occurs and the current oscillates between a maximum and a minimum value which represent the active and passive states, respectively, of the specific Fe ∣ 0.75 M H 2 SO 4 + x M Cl − system. The second case of aperiodic (chaotic) oscillations is related to a continued pit growth; the formation of the oxide passive film is prevented and a salt layer is formed resulting in a limiting current region with oscillations. The potential and the Cl − ion concentration in the vicinity of the Fe electrode control the pitting corrosion and the oscillatory phenomena associated with it. Polishing state pitting was found to proceed at more positive potentials and high Cl − ion concentrations.

鉄酸化細菌の塩素イオン阻害に及ぼす珪藻土の効果

This paper describes an inhibition of oxidation and growth of Thiobacillus ferrooxidans by chloride ion and the effect of diatomaceous earth against its inhibition. Ferrous ion oxidation experiment in the absence of nutrient salts was carried out with various amount of chloride ion. The assay solution of this experiment contained only ferrous sulfate and magnesium sulfate (pH 1.5), and no bacteria grew in this condition. The oxidation of ferrous ion was inhibited by the chloride ion, and was subjected to the competitive inhibition from the Lineweaver-Burg plot. The addition of the diatomaceous earth in assay solution had no effect on the bacterial oxidation. The growth of T. ferrooxidans in 9 K medium was also inhibited by the chloride ion. The growth kinetics of this bacterium in the presence of chloride ion were described with the modified Monod type equation including the term of inhibitor concentration. The growth inhibition reduced by the addition of diatomaceous earth in the medium. The oxidation rate in the presence of diatomaceous earth was much faster than that in the absence of it in high concentration of chloride ion. The growth inhibition constant of adsorbed bacteria was about 60 % larger than that of free bacteria, which was the reason the oxidation of ferrous ion in the presence of diatomaceous earth was faster. The adsorption amount of T. ferrooxidans onto the diatomaceous earth was almost constant in this experimental range of the chloride ion.

Optimization of the methylene blue assay for anionic surfactants added to estuarine and marine water.

The existing rapid method for the determination of anionic surfactants in aqueous solutions relies on the association of the cationic methylene blue dye with the anionic surfactant to form an electroneutral complex that is subsequently extracted into chloroform and determined spectrophotometrically. This methylene blue active substance (MBAS) assay suffers from salt interference in estuarine and marine waters due to the high concentration of chloride (Cl-) ions. The interference was shown to arise from the association of Cl- ions with the cationic methylene blue dye, which, although weak, becomes significant at the elevated concentrations of Cl- in marine water. Analysis of the kinetics of the formation and extraction into chloroform of complexes of methylene blue with a typical anionic surfactant (sodium dodecyl sulfate, SDS) and with Cl- ions revealed that the efficacy of the extraction step was critical in yielding reliable data. Based on these results, a modified, simple one-step MBAS method is described that overcomes interference by salt.

Simultaneous determination of nitrate and nitrite ions in seawater by capillary zone electrophoresis using artificial seawater as the carrier solution

We are proposing a novel capillary zone electrophoresis for the simultaneous determination of nitrate and nitrite ions in seawater. An artificial seawater was adopted as the carrier solution to eliminate the interference of high concentrations of chloride ion etc., in seawater. For the purpose of reversing the electroosmotic flow, 3 m M cetyltrimethylammonium chloride was added to the carrier solution. A 100 μm I.D. capillary was used to extend the optical path length. Regardless of the salinity of sample solutions, the peak areas and migration times for nitrate and nitrite ions were within ±3%, while the peak heights for these ions decreased linearly with increasing salinity of sample solutions. The limits of detection for nitrate and nitrite ions were 0.04 and 0.07 mg/l ( S/ N=3, based on three-times the baseline noise), respectively. The values of the relative standard deviation (RSD) of peak areas for these ions were 1.5 and 2.4%. The RSDs of migration time for these ions were 0.85 and 0.78%. The proposed method was applied to the determination of nitrate and nitrite ions in seawater samples taken from the surface and the seabed. The recovery of nitrate and nitrite ions was 97–114%.

Kinetics of formation and stability of {Pt(dien)}2+ complexes with octamer and 14-mer DNA oligonucleotides containing a GG sequence

Reaction of [Pt(dien)Cl]+ (1) with the 14-mer oligonucleotide 5'-d(ATACATGGTACATA) (I) gave rise to two major species which corresponded to the 5'-G and 3'-G platinated monofunctional adducts, and a minor amount of the bis-platinated adduct formed during the later stages of the reaction. The reaction of (1) with the related octamer 5'-d(ATA-CATGG) (II) was also investigated. Kinetic data obtained by HPLC showed that the 5'-G and 3'-G bases of the 14-mer oligonucleotide were platinated at similar rates: the second-order rate constant is 53 x 10(-2) M-1 s-1 at 298 K in 0.1 M NaClO4. However, the platination rate of 5'-G of the octamer (II) (k = 69 x 10(-2) M-1 s-1) was enhanced by a factor of three compared to the rate of platination at 3'-G (k = 22 x 10(-2) M-1 s-1). All the adducts were separated by HPLC and characterized by NMR spectroscopy, enzymatic digestion and MALDITOF mass spectrometry. 1H and 15N NMR shifts suggest that there are distinct conformational differences between 14-mer duplexes platinated at 5'-G (I5' ds) and 3'-G (I3' ds). Molecular mechanics modelling indicates that rotation around the Pt-N7 bond is more restricted in the case of the 5'-G adduct than in that of the 3'-G adduct. The binding of {Pt(dien)}2+ to 5'-GN7 and 3'-GN7 in the monofunctional adducts of (I) was shown to be reversible upon the addition of high concentrations of chloride ions.

Determination of bromide ions in seawater by capillary zone electrophoresis using diluted artificial seawater as the buffer solution

A novel capillary zone electrophoresis method was developed for the determination of bromide ion in seawater. A tenfold-diluted artificial seawater was adopted as the buffer solution, to prevent interference from high concentrations of chloride ion in seawater. No electroosmotic flow reverser was used to shorten the analysis time. It was found that the peak area and migration time for bromide ion were almost constant, despite differences in the salinity of sample solutions; the peak height decreased linearly with an increase in the salinity. The limit of detection for bromide ion was 0.46 mg/l ( S/ N=3). The values of the relative standard deviation for peak area and migration time for bromide ion were 1.4 and 1.5%, respectively. The proposed method was applied to the determination of bromide ion in seawater samples taken from the surface and the sea-bed. The analytical results obtained by the working curve method agreed with those obtained by the standard addition method. The method may be applicable to the determination of other ions, such as nitrite and nitrate ions, in seawater

Impact of anaerobic digestion on inhibition potential of Parthenium solids

Parthenium hysterophorus L. is a widely distributed terrestrial weed. It has been shown to contain parthenin, a sesquiterpene lactone. Parthenin has been reported as a germination and radicle growth inhibitor in a variety of dicot and monocot plants and it enters the soil through the decomposing leaf litter. The methane potential of untreated and NaOH-treated Parthenium in anaerobic, laboratory-scale digesters has been reported in detail earlier. Anaerobic digestion of Parthenium biomass generates an effluent (liquid and sludge). The effluent from the NaOH-treated Parthenium fermenter had high concentrations of Na + and Cl −. This study focuses on the utilisation of the effluents as manure and examines the impact of anaerobic digestion on the inhibition potential of Parthenium. Pearl millet ( Pennisetum glaucum) seeds were used to bioassay the inhibition potential. It was found that the seed germination and radicle growth were inhibited at ≥10 g total solids (TS) l −1 and 15 g TS l −1 Parthenium dried solids (DP) treatment, respectively. There was no inhibition of plumule length in the DP treatment. The untreated Parthenium fermenter effluent (UPFE) significantly ( P<0.05) increased germination. The radicle and plumule lengths were significantly ( P<0.05) higher up to the 30 g TS l −1 UPFE treatment, relative to the control treatment, with de-ionised water. Data for the NaOH-treated Parthenium fermenter effluent (NPFE) showed inhibition of the germination only in the 30 g TS l −1 treatment. Above 15 g TS l −1, there was inhibition of radicle length and inhibition of plumule length occurred only at 30 g TS l −1. The inhibition in the NPFE treatment was related to the high concentration of chloride ion in the NPFE. The results of this study showed that DP is a potential germination and radicle growth inhibitor and anaerobic digestion of DP could have biodegraded the inhibitor as evidenced from the enhanced germination and seedling growth in the UPFE. This study also showed that anaerobic digestion of DP conserved the NPK content and both the effluents could be land applied as organic manure.

Langmuir Study of Octadecyltrimethoxysilane Behavior at the Air−Water Interface

The behavior of octadecyltrimethoxysilane (C18TMS) at the air−water interface for different subphases pH has been studied through surface pressure−area and surface potential−area isotherms combined with Brewster angle microscopy. C18TMS monomolecular behavior has been assigned to the one observed at pH around 8.0. Hydrolysis or hydrolysis followed by condensation occurs when pH is lowered below 5.0. Hydrolysis followed by condensation is also observed when the pH is raised above 10.5. The type of catalysis predominantly influences the product of the reaction. Condensation is performed at low pH under two constraints: steric hindrance between the C18 tail chains and electrostatic repulsion between polar groups, resulting in a very low or nil polymerization degree of the condensation products around the isoelectric point (pH 3.8). Higher concentration of chloride ions gradually inhibits the second constraint, resulting in the formation of a linear polymer. Only steric hindrance has been observed under basi...

Synthesis and characterisation of chromium-selective porous condensate polymers

A series of porous condensate polymers were synthesised by catechol-phenol-paraformaldehyde polycondensation using 1,2-ethanediol as the porosogenic agent. They were thoroughly characterised for moisture content, ion-exchange capacity, solvent uptake, dye uptake, surface area and the uptake of Cr(VI) from an aqueous solution. A selected porous condensate polymer was further studied for the technical volume capacity, Cr(VI) uptake from chromate and dichromate solution and the distribution coefficient for Cr(VI) in the presence of high concentration of Cl − and SO 4 2−. The uptake of Cr(VI) by this selected porous condensate polymer was also studied under dynamic conditions using simulated cooling tower blow-down as the influent. For comparison purpose, a conventional gel-type product and a commercially available porous condensate product Duolite S-761, was also studied. Results obtained reveal that the porous condensate polymer, CPPF-G-Cr 5, has good dimensional stability, higher ion-exchange capacity, porosity, surface area and chromium uptake as compared to the conventional gel-type condensate polymer, CPPF-GEL-Cr 0. The porous condensate polymer shows very high selectivity for Cr(VI) even in the presence of high concentration of sulphate and chloride ion but the uptake is susceptible to the pH range and hence the porous condensate polymer removes Cr(VI) from the simulated cooling tower blow-down which usually has pH 4. It removes chromium from a fairly large volume of simulated cooling tower blown-down and gives out the chromium in the form of a concentrated solution of very small volume.

The role of precipitates enriched with copper on the susceptibility to pitting corrosion of the 2024 aluminium alloy

The susceptibility to pitting corrosion of pure aluminium and 2024 T351 alloy in 0.1 mol l −1 Na 2SO 4 solutions containing chloride ions was investigated by a statistical approach. At high concentrations of chloride ions, the logarithm of the pit germination rate, A, varied linearly with concentration for both materials. The 2024 alloy was less resistant to chloride ion attack than pure aluminium. The influence of the polarization potential on the susceptibility to pitting of the two materials was also determined. For the 2024 alloy, a considerable peak of pitting susceptibility appeared in the low potential range which can be related to the copper content of the alloy. Observations by Scanning Electron Microscopy (SEM) confirmed these results.

Strategies to maximize the microbial leaching of lead from metal-contaminated aquatic sediments

Different strategies designed to increase the removal of Pb were tested during the application of a biological remediation procedure to treat highly-contaminated aquatic sediments. The use of FeCl 2 instead of FeSO 4·7H 2O as a substrate for thiobacilli bacteria did not interfere with the biological solubilization process which occurred in sediments acidified to pH 4 with H 2SO 4. With FeCl 2, twice as much Pb was solubilized (5 mg Pb l −1) compared to the same strain acclimated to FeSO 4·7H 2O. With FeCl 2, the solubilization of other trace metals (Cu,Zn) was similar to that obtained with the strain acclimated to FeSO 4·7H 2O. If the sediments were acidified with HCl, rather than H 2SO 4, then the solubilization of Pb increased to 11 mg Pb l −1: this was five times greater than when a strain acclimated to FeSO 4·7H 2O was used in sediments acidified with H 2SO 4. Theoretical calculations with MINEQL + (chemical equilibrium program) predicted 10.8 mg Pb l −1 under similar conditions. This biological solubilization process was generally poorly adaptable to changes in the source of acidity (i.e. HCl vs H 2SO 4). The solubilization of Cu remained relatively low (solubilization of only 35% after 72 h) since the inadequately low levels of sulphate prevented the Thiobacillus bacteria from properly developing. Finally, the higher concentration of chloride ions gained through an increased level of total solids (7% rather than 3% TS) did not increase the soluble concentration of Pb. The soluble concentration of Pb remained at 11 mg Pb l −1 (46%), whereas theory predicted a concentration of 24.1 (100%) mg Pb l −1. Most of the experimental results seemed to follow the theoretically predicted outcome for Pb solubilization. There is more work to do to optimize the process. However, this work reveals that it seems possible to develop an economical process for the removal of Pb from contaminated sediments.

Specific cleavage of histidine-containing peptides by copper(II).

Copper(II) cleaves with moderate specificity peptides containing Ser-His or Thr-His sequences, at the N-terminal side of the hydroxyaminoacyl residue. The reaction is slow, and is first-order in peptide: CuII complex, with a half-life of several hours at 62 degrees C in sodium bicarbonate buffer, pH 8. Cleavage of other histidine-containing peptides also occurs, at a rate around 10-100-fold less. EDTA completely quenches the cleavage. The reaction is stoichiometric in CuII and is inhibited by amine-containing buffer components; Tris at 19 mM inhibits cleavage by 50%. The reaction has a complex pH-dependence, being very slow below pH 5, and with rates increasing with pH from pH 7 to pH 9.5. Slower degradative side reactions do occur, with destruction of tyrosine residues, particularly in the presence of high concentrations of chloride ion, but the specific cleavage appears to be a hydrolysis, as determined by amino-acid analysis and mass spectrometry of the products. The cleavage is clearly different from the previously described oxidative degradation of proteins catalysed by copper ions. Cleavage of denatured IgG protein occurs with sufficient specificity to reveal distinct bands on SDS-polyacrylamide gel electrophoresis under reducing conditions.

Lysine:N6-Hydroxylase: Cofactor Interactions

Recombinant lysine:N6-hydroxylase (rIucD) requires the cofactors FAD and NADPH for its catalytic function of the conversion ofL-lysine to itsN6-hydroxy derivative. In the presence of high concentration of chloride ions (≥ 600 mM), the protein exists in a reversible inactive conformation. Depending on the oxidation state of its thiol functions, rIucD can bind 2,6-dichlorophenol indophenol (DPIP), either covalently or noncovalently, the former type of interaction occurring with protein preparations possessing unmodified thiol groups. Both covalent and noncovalent complexes of rIucD and DPIP appear to be capable of NADPH oxidation in the presence of exogenous DPIP by a phenomenon of exchange of reducing equivalents between the protein-bound dye and that free in the medium. In the presence of FAD, the latter type of complex has been found to function as a diaphorase. The diminution in the catalytic activity of rIucD observed at high concentrations of the flavin cofactor does not appear to be due to an uncoupling of the processes of NADPH oxidation and lysine:N-hydroxylation caused by an exchange of reducing equivalents between the enzyme-bound FAD and that free in the medium.

Anomalous aggregation behaviour of aluminium oxyhydroxides

The aggregation of alumina suspensions (γ-alumina, boehmite and gibbsite) has been observed by light scattering as a function of the identity and concentration of added electrolyte, and of acidic pH. All the suspensions aggregated rapidly in the presence of less than 1 mM sulfate ion. The gibbsite suspension displayed a critical coagulation concentration of less than 50 mM chloride ion. The other three suspensions displayed anomalous stability in chloride solutions of concentrations greater than 0.1 M and only aggregated at higher chloride ion concentrations. This stability is not related to the pH and electrolyte dependence of the zeta potential.

Morphology and structure of nickel nuclei as a function of the conditions of electrodeposition

A study of nickel nuclei deposited on a vitreous carbon electrode from chloride baths was performed at several pH values (1 < pH < 4.5). The effects of growth rate (affected by the temperature and/or the nickel concentration), bath composition and deposition time (particularly at low overpotentials) on the morphology of nickel nuclei were analysed. Before coalescence and during the early stages of deposition, the morphology of the nuclei was influenced by the bath composition. When solutions with a high concentration of chloride ions were used, a characteristic star-shaped morphology was obtained which was attributed to the adsorption of chloride complexes. This morphology was related to the results obtained from impedance spectroscopy diagrams.

Formation of Cm(III) chloride complexes in CaCl 2 solutions

The chloride complexation of curium(III) in trace amounts at very high chloride ion concentrations was studied by time-resolved laser fluorescence spectroscopy at 25 °C. The chloride ion concentration was varied from 0 to about 20 mol kg −1 H 2O with CaCl 2 at acidic pH. The Cm species Cm 3+, CmCl 2+ and CmCl 2 + were quantified spectroscopically from the fluorescence emission spectra by peak deconvolution and the chloride complexation constants β 1 and β 2 were evaluated at each given CaCl 2 molality. The experiment verifies that at low Cl − concentrations (below 3 mol kg −1 H 2O) the chloride complexation is less important (less than 5% of chloride complexes are formed) and hence it can be neglected in moderately concentrated brines.