Addition Of Neutral Salts Research Articles

Characterization of a new type of ferredoxin from Desulfovibrio africanus

A new ferredoxin designated ferredoxin III has been isolated from Desulfovibrio africanus grown on media high in iron. Native ferredoxin III is a dimer constituted by two identical subunits of approx. 7500. It is distinguished from the two other ferredoxins (I and II) isolated from this microorganism by its amino acid composition, N-terminal sequence, spectral properties and ironsulfur content. The amino acid composition of D. africanus ferredoxin III is typical of ferredoxins with an excess of acidic over basic residues and the absence of histidine and arginine residues. The absorption spectrum of ferredoxin III exhibits two maxima, at 408 nm ( ϵ = 58.5 · 10 3 M −1 · cm −1) and 285 nm ( ϵ = 82 · 10 3 M −1 · cm −1), with a shoulder at 305 nm ( ϵ = 75 · 10 3 M −1 · cm −1). Its A 408/A 285 absorbance ratio is 0.78. Ferredoxin III contains approx. 12–13 atoms each of iron and labile sulfur. This is in agreement with the high value of the extinction coefficient at 408 nm, which is slightly higher than 3-fold that of one [4Fe-4S] cluster. However, the number of cysteine residues of the protein (six residues), which is about the half that of iron atoms, is indicative of the presence of a new type of iron-sulfur cluster in ferredoxin III. The protein is unstable in a low ionic strength environment; the addition of neutral salts stabilizes the protein conformation. The data on the biological activity of ferredoxin III as compared to the two other ferredoxins from D. africanus show that the three iron-sulfur proteins function with equal effectiveness as electron carrier in the phosphoroclastic reaction and the H 2-sulfite reductase system.

Catalytic polarographic pre-waves of Co (II) in presence of thiopyrimidines

4-amino 2-thiopyrimidine, 4-hydroxy 2-thiopyrimidine, 2-thiopyrimidine and 2,4 dithiopyrimidine in borate media cause Co (II) pre-waves to appear. Below a fixed pH (different for each substance) the apparent pre-waves probably include the contribution of processes of catalytic discharge of the hydrogen ion. In the media of pH higher than this value 2,4-dithiopyrimidine yields two true pre-waves, whereas each of the other substances causes a single true pre-wave to appear. These Co (II) pre-waves were studied as a function of mercury height, temperature, composition of the borate medium, thiopyrimidine concentration, Co (II) concentration, addition of neutral salts and addition of surfactants. When a single true pre-wave is obtained, the effects of changes in these parameters were explained and a mechanism for the electrode process was proposed. According to this mechanism it was proved by using the approximate method for the catalytic currents that the catalytic complex is formed between Co(II) and each thiopyrimidine in the ratio 1:1.

Deposition of cationic polymeric pigments on pulp fibers

The potential advantage of using cationic pigments as wet-end additives in papermaking is in their expected ready deposition on anionic pulp fibers. The deposition characteristics of cationic polystyrene latex particles onto pulp fibers in a stirred system provide an information of the general behavior. The deposition proceeds at maximum rate in the pH region where the latex particles and the fibers have electrophoretic mobility of opposite sign. A departure from the expected behavior is observed in the pH region of latex destabilization. The failure of the coagulating latex to deposit indicates that hydrodynamic forces (introduced by mixing) acting on latex aggregates may prevent a deposition. An addition of neutral salt to the stirred system after deposition of latex particles was completed may result in a partial removal of latex particles from the fibers. The explanation for this reversible deposition is sought in an interplay of attractive forces between latex particles and fiber, the distance of their closest approach, and the size of particles upon which the hydrodynamic forces act. The behavior suggests that although the mutual attraction promotes deposition an intimate contact between latex particles and fiber is not established.

Electrolyte effects on the activity of mutant enzymes in vivo and in vitro

All temperature-sensitive histidine auxotrophs of Salmonella typhimurium tested are corrected by addition of neutral salts to their growth medium. The correctability seems to result from direct electrolyte effects on mutant protein stability since several of the mutant proteins are also salt correctable in vitro.

Calcium-activated adenosine triphosphatase activity of pellicles from Paramecium caudatum.

Pellicles were isolated from Paramecium caudatum for a study of the properties of its insoluble ATPase [EC 3.6.1.3] activity. Pellicular ATPase was solubilized by sonication and fractionated by sucrose density gradient centrifugation. The sedimentation coefficient of the ATPase was about 9S. The ATPase required Ca2+ for maximum activation. Addition of neutral salts to the assay medium inhibited the activity. Substrate specificity for ATP was low; other nucleoside triphosphates were hydrolyzed at about the same rate as ATP; AMP, pyrophosphate, and p-nitrophenyl phosphate were not hydrolyzed. The ATPase activity of the pellicle preparation had a pH optimum at pH 6.5, and a Michaelis constant of 9 micrometer. On the other hand, the enzymatic properties of the ATPase were somewhat modified by the procedure of solubilization and fractionation. The pellicular ATPase does not resemble ciliary dynein ATPase or the soluble ATPase of Tetrahymena.

Activation of heavy meromyosin adenosine triphosphatase by various states of actin.

F-actin monomer (F-monomer) is formed upon the addition of neutral salt to G-actin. Since F-monomer has a digestibility similar to that of F-actin and much lower than that of G-actin, it has been proposed that F-monomer has a conformation different from that of G-actin and similar to the conformation of the subunits in F-actin. To examine whether F-monomer will enhance the magnesium-activated myosin adenosine triphosphatase (Mg2+-ATPase) as much as F-actin, the ability of partially polymerized actin populations at equilibrium to activate the Mg2+-ATPase of heavy meromyosin was investigated. Correlations were made between ATPase activities and the polymerization state of actin as determined by measurements of viscosity and digestibility. No significant activation of the heavy meromyosin ATPase was observed under conditions where G-actin or mixtures of G-actin and F-monomer were present. As polymer formation occurred at higher actin concentrations, or with increased KCl concentrations, substantial activation characteristic of F-actin was observed. The data suggest that F-monomer may undergo a further conformational change as it forms nuclei or joins onto polymers. Alternatively, the site of actin which activates the myosin ATPase may involve the crevice between two adjacent actin subunits.

Deposition of cationic styrene and styrene—butadiene latex particles on cellulose fibers

Deposition of cationic latex, stabilized with tertiary amino groups, on anionic pulp fibers in a stirred system shows a distinct difference in the behavior of hard, nonfilming (polystyrene) and soft, film-forming (polystyrene—butadiene) latexes despite their similar surface characteristics. The hard latex deposits as individual particles at a rate that is apparently diffusion controlled. The behavior expected in mutual coagulation of unlike particles is generally observed except that homocoagulating hard latex does not deposit. The deposition of soft latex indicates two concurrent mechanisms. Initial deposition of individual particles is accompanied by aggregation of the depositing latex. The rate is likely affected by the latex's tendency to coagulate and full deposition of the homocoagulating latex is observed. The response of deposited latex to the addition of neutral salt is also different. The hard latex, in apparent contradiction to expectation, is redispersed by a salt addition to the stirred system. The soft latex, after deposition, is not removed and further deposition of unattached latex takes place when enough salt is added to cause its homocoagulation. An explanation is sought in an interplay of attraction forces between latex and fiber, the distance of their closest approach and the hydrodynamic forces acting on deposited latexes. The hard latex is apparently not in intimate contact with the fiber surface and when the attractive double layer interaction is diminished due to the salt effect the attraction is outbalanced by thermal motion and fluid shear. The soft latex can establish a better contact with fibers and the attraction force over a shorter separation distance resists the hydrodynamic forces.

The effect of sodium chloride on the solubilization of decan-1-ol in sodium octanoate solutions and the formation of mesophases

The influence of sodium chloride addition upon the ability of aqueous sodium octanoate solutions to solubilize decan-1-ol has been studied. At low octanoate concentrations an addition of neutral salt increases the solubilizing capacity; this depends on the displacement of cmc toward lower concentrations, thereby causing an increase in the content of micellar matter. At high octanoate concentrations the neutral salt exerts the opposite effect; this is obviously a result of the increased number of counterions bound to the mixed micelles and the earlier formation of mesophases caused thereby. Between the limiting association concentration and the second critical concentration, within which region of the neutral salt-free system water-rich mesophases are formed (water-rich D, B, and C phase), the addition of sodium chloride causes a decrease in the water content of the mesophase. Above the second critical concentration where even in the absence of sodium chloride a water-poor mesophase (D phase) is formed, there will primarily be an increase in the octanoate content of the phase. The composition of the middle phase (E phase) seems to be rather unaffected by sodium chloride addition. At high neutral salt addition the formation of mesophases is replaced by the formation of crystalline sodium octanoate; simultaneously, the aqueous solubility of octanoate markedly decreases.

The influence of neutral salts on the easily polarizable hydrogen bond of H5O2+ groupings in acid solutions

The influence of neutral salts on the easily polarizable hydrogen bond of H5O2+ groupings in aqueous acid solutions is studied, using ir spectroscopy. The absorbance of the ir continuum, caused by the polarizable hydrogen bond in the H5O2+ groupings, usually decreases with increasing neutral salt concentration. This is explained by the polarization of the hydrogen bonds caused by local fields due to the neutral salt ions. The H+ becomes more or less trapped at one of the H2O of the H5O2+. The prominence of this effect increases with increasing cation field, i.e., from Cs+ to Li+, and is more pronounced with bivalent than with monovalent cations. The opposite effect is observed with tetraethylammonium chloride. The symmetry of H5O2+ groups is less strongly disturbed in the presence of neutral salts with ions with very large radii, i.e., small electrical fields, than in pure acid solutions. Considering the torsional vibration of the water molecules, it is finally shown that the hydrate structure network around the H5O2+ becomes disintegrated due to the presence of neutral salts.It is known from electrochemical investigations that the activity coefficient of the excess proton usually increases strongly due to the addition of neutral salts to acid solutions. The opposite is true with the addition of tetraethylammonium salt. Furthermore, the addition of neutral salt decreases the excess proton conductivity. All these observations are discussed on the basis of the ir spectroscopic results.

Aqueous redox polymerization of acrylamide initiated by citric acid/permanganate

AbstractThe homogeneous redox polymerization of acrylamide by the citric acid/permanganate initiating system was investigated at 35±0,2°C under nitrogen. Variation of the activator concentration in the range of 2,5.10−3 to 20,0.10−3 mol/dm3 had no effect on the rate of polymerization. The initial rate increased with the increasing catalyst concentration and a value of nearly unity of the catalyst exponent confirmed a unimolecular chain termination process. The rate varied linearly with the monomer concentration over a wide range (5,0.10−2 to 20,0.10−2mol/dm3). The initial rate increased with the increasing temperature but the maximum conversion showed a decrease as the temperature was raised above 35°C. The energy of activation, in the temperature range of 25 to 45°C, was found to be 55,90kJ/mol (13,36 kcal/mol).The addition of neutral salts, Co(NO3)2, Ni(NO3)2, organic solvents, and complexing agents, all water soluble, reduced the rate and percentage of conversion. The introduction of MnSO4 or of more catalyst (at intermediate stages) into the system increased both the rate and limiting conversion.

Physico-chemical studies of cation exchanging properties of Japanese acid clay in aqueous media (author's transl)

When Japanese acid clay is dispersed in an aqueous medium, pH of the solution deviates to acidic because of dissociation of H+ from clay minerals. Addition of neutral salt to this solution decreases pH values further. The order of electrolytes having common anion, Cl-, to decrease pH of the solution was found to be Na+, K+, and Ba2+, the latter being the most effective. The pH value of final equilibrium, (pH)f, was found to be constant in the range of initial pH of medium, (pH)i, between 3 and 11, which is prepared by adding hydrochloric acid or alkali hydroxide tb the salt solution. It was, therefore, concluded that Japanese acid clay has both buffer function and ion-exchanging property. On the other hand, the amount of alkali adsorbed to this clay increases with the concentration of hydroxide in the medium, and KOH is absorbed more than NaOH. It was, therefore, concluded that ion-exchanging capacity for K+ is larger than that for Na+. The rate of reaction of alkali adsorption was measured at constant pH by using pH-statt. It was concluded from analysis of the amount of adsorbed alkali as a function of time, that there are two ion-exchanging mechanisms which are competitive; the one is on the outer surface and the other in the inner layer of the clay mineral. It was concluded that the capacity of ion-exchange, α1, and the rate constant, k1, of the former is larger than those of the latter.

THE ALKALINITY OF ALKALI SOILS

SummaryThe theoretically derived equation: log Alk–pH = log Pco2–7.82 describes the relation between three easily estimated parameters, viz. the composition (alkalinity), CO, partial pressure and the pH of the soil solution. This equation is also important for understanding the formation of alkaline soils. The concept of residual alkalinity, i.e. the difference between the alkalinity and the total concentration of the divalent cations in the soil solution (on an equivalent basis) is introduced. In a closed basin with excess evaporation over precipitation highly alkaline soils, i.e. soils with a pH above 8 to 8.5, develop if the inflowing water has a positive residual alkalinity. A number of processes, such as weathering, oxidation and reduction, cation exchange, precipitation, addition of neutral salts, evaporation, which may influence the alkalinity and residual alkalinity of natural waters and soils are discussed briefly.

Alkylation of urea-denatured actin with iodoacetate: Functional reorganization of actin

1. 1. Starting with actin alkylated with monoiodoacetate in the presence of 4 M urea, the functional reorganization of actin, namely polymerization, its interaction with myosin, and the binding of nucleotide, was examined. 2. 2. After removal of urea by dialysis, the alkylated actin was in a monomeric state in a low ionic strength solution at neutral pH. Nucleotide was completely removed from the solution. Addition of neutral salt did not cause polymerization of alkylated actin. A polymer of alkylated actin was formed when the protein was precipitated at pH 5.5 and redissolved into a low ionic strength solution of neutral pH. Polymerization occurred without participation of nucleotide. The sedimentation pattern of alkylated actin polymer gave a single peak of 10 S. 3. 3. Both increasing ionic strength and raising temperature (above 20 °C) caused a change in polymer conformation which was reversible. 4. 4. Myosin and heavy meromyosin bound to alkylated actin polymer and the ATPase of heavy meromyosin were activated through the interaction with alkylated actin polymer. Specifically, alkylated actin polymer incubated at pH 6.5 for several days showed a Mg 2+-sensitized ATPase of heavy meromyosin. The extent of the Mg 2+-sensitized ATPase was close to that found with normal F-actin. 5. 5. The monomer of alkylated actin exhibited a specific receptivity to ATP with a dissociation constant of the order of 10 −5 M. 1-Anilinonaphthalene-5-sulfonic acid also bound to alkylated actin competitively with ATP. Fluorescence of the bound 1-anilinonaphthalene 5-sulfonic acid suggested that the binding site forms a hydrophobic cleft.

Analytical application of the cobalt(II) catalytic pre-wave in the presence of thiamine in its disulphide form.

The cobalt catalytic pre-wave in the presence of thiamine in its disulphide form, and in a borate medium, was studied as a function of the thiamine (disulphide form) and cobalt(II) concentrations and of the pH of the solution. The effects of temperature, the addition of neutral salts and the presence of surface-active agents on the pre-wave are described. The effect of thiamine (disulphide form) is shown on the electrocapillary curves. The electrode process involves the formation of complexes between cobalt(II) and thiamine, in its thiolic form, adsorbed on the dropping-mercury electrode, and the electrochemical decomposition of these complexes with liberation of the catalytic ligand. The analytical application of this pre-wave was studied.

Reaction Kinetics of the Redox Decomposition of Hydroxymercurated Propylene in Aqueous Solution Followed by Time-Sequential NMR Spectroscopy

Abstract The redox decomposition process of hydroxymercurated propylene in aqueous solution yielding acetone has been followed by time-sequential NMR spectroscopy in situ. No reaction intermediates and reaction products other than acetone were observed. Stoichiometric relationship holds between the reactant and the product during the reaction, which was verified by NMR spectra. The reaction rate was confirmed to be of first order with respect to mercurial. Although the rate was accelerated at higher acidity in solution, a similar rate enhancement took place by addition of neutral salts. At a certain ionic strength, no close linear correlation between the apparent rate constants and proton concentration was observed. In contrast, excellent linear dependence was obtained by the thermodynamic activities of the added electrolytes including acid. Since the apparent rate constant was independent of the concentration of free mercuric ion, a monomolecular mechanism is proposed. Taking into account the rate dependence upon added electrolytes, the redox decomposition of the hydroxymercurated olefins to give carbonyl compounds seems to proceed only when an aquo ligand is removed from the carbon-bonded mercuric ion.

Kinetics of Silver(I) Ion Catalysed Oxidation of Glycine by Peroxodisulphate Ion

Abstract The kinetics of Ag(I) ion catalysed oxidation of glycine by peroxodisulphate in aqueous medium has been studied. The reaction is found to be first order in peroxodisulphate and Ag(I) ions and almost independent of glycine concentration. The rate constant is found to decrease with the increase in the concentration of peroxodisulphate ion. Addition of neutral salts shows a retarding effect. A suitable mechanism has been proposed and a theoretical rate law has been derived to account for the results.

Physicochemical investigations on buffalo β-lactoglobulin. Studies on sedimentation, diffusion, and hydrogen ion titration

The sedimentation and titration behavior of buffalo β-lactoglobulin have been compared with those of cow β-lactoglobulin B. In sedimentation analysis buffalo β shows homogeneity. Its molecular weight from sedimentation and diffusion data have been found to be close to that of cow β-lactoglobulins in the neutral region. Archibald experiment suggests dissociation of the molecule into subunits at low pH values. Titrations in the pH range 2–10, in formaldehyde and at different temperatures show that buffalo β, possesses the same number of ionizable groups with a pair of carboxyl groups per dimer of anamolous p K′ (p K′ 7.00) as in cow β-B. In both the proteins two of the eight phenolic OH groups titrate slowly above pH 12 after a probable configurational change. Buffalo β and cow β-B have almost the same values of isoionic pH which are lowered nearly to the same extent by the addition of neutral salt. The p K′ values of different classes of groups and also the value of the electrostatic interaction factor ω′ have been found to be very close. Comparison of properties and amino acid composition of buffalo β and cow β-B indicates their striking similarities in structure and solution conformation, similarities not shown by other milk protein constituents of these two species.

Adsorption von Elektrolyten an Kartoffelstärke. Wärmeentwicklung, Sedimentvolumen, Kontraktion

AbstractAdsorption of Electrolytes on Potato Starch. Heat Development, Swelling and Contraction. On addition of electrolyte solutions to moist potato starch an adsorption takes place, accompanied by the development of heat and by swelling. In alkali salts both phenomena proceed rapidly, usually within a few minutes, and reversible.In potassium salts the evolution of heat depends on the anion (in the sequence of the lyotropic series: rhodanid strongly adsorbed with high thermal effect, sulphate weakly adsorbed with hardly any effect). The amount of swelling on the contrary is hardly different in this case, and the amount of contraction is the same. In this respect there is a contrast with earlier research on the adsorption of water in air‐dry starch in which heat development and contraction proved to be proportional.Calcium hydroxyde is adsorbed in much higher quantities than those of the monovalent cations and this adsorption takes a much longer time (up to 50 minutes).The adsorption of hydroxyl ions from monovalent hydroxydes is augmented by the addition of neutral salts. The practical combination NaOH‐Na2SO4 is studied.

Kinetics of arsenite-ferricyanide reaction in an alkaline medium

The kinetics of the oxidation of arsenite to arsenate by ferricyanide has been studied in an alkaline medium. At low alkali concentrations the reaction is very slow and the reaction rates have therefore been determined in highly alkaline media (OH − > 10 −2M). The overall kinetics are first order in ferricyanide, arsenite and hydroxide ions. Addition of neutral salts viz. KCl and K 2SO 4 has a pronounced accelerating effect. Addition of ferrocyanide has no effect while methanol considerably lowers the reaction rate. The temperature coefficient of the reaction has been found to be unusually low. The energy and entropy of activation have been obtained as 8·2 Kcal and −42·8 cal. deg −1 mole −1 respectively. A mechanism has been proposed which involves the primary equilibria between various arsenite species and the hydroxide ions and is followed by the rate determining bimolecular reaction between a tribasic arsenite ion and ferricyanide.

Oxidation of Hydrazine by Alkaline Ferricyanide in Water-methanol Mixtures

Kinetics of the oxidation of hydrazine by ferricyanide was investigated in water-methanol mixtures using several buffer solutions. The reaction showed first order dependence in both hydrazine and ferricyanide. The order with respect to hydroxide ion concentration was zero. Increase in concentration of methanol had a retarding influence on the rate while the addition of neutral salts showed a specific ion effect. The energy and entropy of activation were calculated as 12.3 kcals. mole-1 and -20.8 cals. deg-1 mole-1 respectively. A suitable mechanism has been proposed which suggests the primary rate determining reaction between N2H4 and Fe (CN)6 3⊖. Nitrogen was found to be the product of the reaction.