Addition Of Neutral Salts Research Articles

Physicochemical behaviour and biological activity of bovine growth hormone in acidic solution

1. 1.|The variation of some physicochemical and biological properties of bovine growth hormone dissolved in various acidic buffers, has been examined. 2. 2.|The hormone preparation used was not contaminated with acid proteases. 3. 3.|Measurements of sedimentation velocities, intrinsic viscosities, half-escape times in analytical dialysis and elution volumes in gel filtration with hormone solutions in glycine-hydrochloric acid buffers, indicate conformation changes of the molecule between pH values 2.2 and 3.6. These changes do not affect the growth-promoting activity of the hormone. 4. 4.|The addition of neutral salts to the acidic glycine buffers promotes an association whose extension is dependent on the concentration of salt and the nature of the anion. The associated hormone has decreased biological activity. 5. 5.|The maximum physicochemical and biological stability of the hormone in acidic solution was found in glycine hydrochloric acid buffer, I 0.010, at pH 3.6. The s 20 1% obtained in this solvent is 2.3 and corresponds to a molecular weight in the neighbourhood at 21 000.

Esterase Activities of Human Carbonic Anhydrases B and C

Abstract Both human carbonic anhydrases B and C act as esterases on o- and p-nitrophenyl acetates. Enzyme C is the more active of the two for the hydrolysis of p-nitrophenyl acetate, and enzyme B for o-nitrophenyl acetate. The pH-activity curves are sigmoid, the esterase activity being very small below pH 6 and rising to a high level around pH 9; the inflection point lies at pH 7.3 for Enzyme B and at 6.8 for Enzyme C. The Km values are nearly independent of pH in all cases; thus the pH dependence curves appear to reflect the catalytic center activity. The reactions follow Michaelis-Menten kinetics over the range of substrate concentrations studied, but this range is limited to values less than the Km values, because of the limited solubility of the esters. Measurements in a stop-flow apparatus, at times from 10 msec to 2 sec, gave the same kinetic constants as those measured under steady state conditions. There was no evidence of an initial burst of release of nitrophenol. When the reactions were studied under the condition (E0) ≅ (S0) << Km, the process followed first order kinetics until hydrolysis was nearly complete. The data thus gave no evidence for the presence of an acyl intermediate; if such an intermediate exists it must be very rapidly hydrolyzed. Both enzymes are inhibited by monovalent anions, by acetazolamide, and by alcohols. Anion inhibition decreases with increasing pH, and so does the acetazolamide inhibition. The alcohol inhibition is not affected by pH. Enzyme B is somewhat more strongly inhibited by anions, but Enzyme C is much more strongly inhibited by alcohols and by acetazolamide. Only one site seems to be involved in the inhibition by either type of inhibitor. Competition for one site has been demonstrated between the anions and the alcohols. The inhibitions are reversible, and noncompetitive with respect to substrate. Since anion inhibition follows the lyotropic series, the binding site is believed not to be the zinc ion. Binding of anions by Enzyme B, and by zinc-free apoenzyme, has been demonstrated by an increase in pH of an isoionic solution caused by the addition of neutral salts. At low salt concentrations solutions of the apoenzyme show a lower change in pH than these of the holoenzyme, but at higher salt concentrations the values are very similar. Thus in 0.1 m KCl both the enzyme and apoenzyme bind approximately 6 chloride ions.

A Source of Error in an AutoAnalyzer Determination of Serum Iron

Abstract An AutoAnalyzer method for serum iron was found to be giving erroneously high values owing to a Donnan equilibrium effect on the rate of dialysis of ferrous ions. The addition of neutral salt to the reagent corrected the deficiency. The validity of other assays on the AutoAnalyzer that measure dialyzable ions in the presence of relatively high concentrations of protein should be verified in view of this finding.

Studies on the Adenosine Triphosphatase Activity of 14 S and 30 S Dynein from Cilia of Tetrahymena

Abstract The axonemal adenosine triphosphatase protein, dynein, consists of 14 S and 30 S fractions. Both forms of dynein require the presence of a divalent cation for activity: Mg++, Ca++, Mn++, Fe++, Co++, and Ni++ can all function as activator, but Be++, Cd++, Sr++, and Zn++ cannot. Specificity for ATP or deoxy-ATP is moderately high; other nucleoside triphosphates are hydrolyzed at only about 10% of the rate of ATP; AMP, pyrophosphate, and p-nitrophenyl phosphate are not hydrolyzed. The two forms of dynein both have a pH optimum at pH 8.5 to 9.0. Addition of neutral salts to the assay medium inhibits the activity of 14 S dynein but enhances that of 30 S dynein. When assayed under standard conditions with Mg++ activation, 14 S and 30 S dynein had maximal velocities of 3.5 and 1.3 µmoles of Pi per (min x mg of protein), respectively, and Michaelis constants of 3.5 x 10-5 and 1.1 x 10-5 m. The general similarity in enzymatic properties is consistent with a monomer-polymer relationship between 14 S and 30 S dynein, with the differences that occur being the results of a configurational change attendant upon polymerization. The possible physiological significance of the partial repression of ATPase activity in 30 S dynein is discussed.

Influence of Concentrated Neutral Salt Solutions on the Corrosion of Metals

The H+ activity of diluted strong acids, such as or , rises by the addition of such neutral salts as , from 10−1 to 10 at constant concentration of the acid. The effect of this increase of activity on the anodic dissolution of Fe, Co, and Ni has been investigated. Fe and Co show the order with respect to the H+ activity, which was found by many other authors with respect to the H+ concentration when stationary measurements were accomplished. In accordance with the Heusler mechanism the order changed to at unstationary measurements. The cathodic process has the order with respect to the H+ concentration and 0.5 with regard to H+ activity changed by addition of neutral salts. The anodic dissolution is influenced by the nature of the cations .On the contrary the order of anodic dissolution of Ni is with regard to H+ concentration as well as to activity both at stationary and unstationary measurements. The cathodic process at Ni has the order with regard to H+ concentration and 0.5 with regard to H+ activity changed by addition of neutral salts. At the hydrogen ion discharge on the mercury electrode the order of reaction with regard to H+ concentration rises from 0.5 to 1 with increasing ionic strength according to the theory of Frumkin. The dependence upon at constant H+ concentration is complicated. The current density at constant potential passes through a maximum with increasing H+ activity and content of neutral salt. Height and position of this maximum with regard to the neutral salt concentration depend on the potential. A qualitative interpretation of the experimental results is proposed.

Taste sensitivity to some chemicals in Rhodnius prolixus Stål and Aedes aegypti L.

Rhodnius prolixus adults were fed through chick skin and Naturalamb membrane on 0·15 M NaCl containing ATP at 10−3 M, adjusted to pH 7. Inhibition of feeding occurs after addition of neutral salts at concentrations in an order mostly inversely related to the ionic mobility.Both Aedes and Rhodnius reject normal alcohols when mixed with the standard acceptable diet. The median rejection thresholds decrease with increase in molecular weight. The stimulating efficiency and the vapour pressure are inversely related. There is an inflexion in the curve relating rejection thresholds to chain length of the alcohols between butanol and pentanol in Aedes and immediately before butanol in Rhodnius. It is suggested that stimulation by alcohols involves a two-phase system as in Phormia regina. No relationship of equal physiological effect at equal thermodynamic activity exists.

The temperature dependence of magnesium chloride interaction with polyacrylic acid

AbstractThe effect of temperature on a modified pH “titration” of polyacrylic acid is reported. The extent of acid ionization was varied by pretitration to various degrees with the strong base of a weak counterion binder, tetra‐n‐propyl ammonium hydroxide. The effect of subsequent additions of magnesium chloride to these pretitrated solutions at 15, 25, and 38°C. is reported. The release of hydrogen ions caused by this neutral salt addition varied with both degree of pretitration and temperature. The displacement caused by temperature on the maxima and minima behavior of hydrogen ions released as a function of degree of preionization can be explained by the effects of temperature on polymer configuration. The increased release of hydrogen ions at higher temperature can be explained by the combined effects of temperature on the polymer configuration and on the binding equilibria. The acid dissociation constants at 15, 25, and 38°C. have been obtained by titration with tetra‐n‐propyl ammonium hydroxide.

A kinetic study of the mild oxidation of wheat starch by sodium hypochlorite in the alkaline pH range

Abstract(1) Some kinetic aspects of mild oxidation of wheat starch by sodium hypochlorite in the pH range 7.5–11.0 were studied. (2) No significant chlorate formation was observed at any time. From this and from other experimental evidence it is concluded that the reaction is most likely to be purely chemical in type and to proceed according to the overall scheme: (3) The reaction appears to be of the first order with respect to starch. (4) The reaction appears to be of the first order with respect to hypochlorite at pH = 8.0. At pH = 9.0 and 10.0, the reaction velocity is still approximately proportional to the concentration of the oxidant present, but the course of the reaction appears to be more complicated. (5) The reaction rate decreases with increasing pH of the oxidizing medium. An approximate empirical equation is proposed adequately representing the interdependence of the first‐order constant and pH in the pH range 7.5–10.0. (6) The activation energy of the reaction is within the range of 21–23 kcal./mole, i.e., that obtained for many homogeneous, truly chemical reactions. (7) The fact that the reaction rate of a starch solution is about 50% higher than the corresponding rate for a starch suspension would seem to indicate that the number of sites available for oxidation in a granule is about two‐thirds of that available when that granule is dissolved. (8) The addition of neutral salts had an accelerating effect on the reaction rate. Under the experimental conditions of the present paper, this effect was negligible, but at much higher salt concentrations it would have to be taken into account.

Light scattering and viscosity of proteins in anhydrous formic acid

AbstractThe use of anhydrous formic acid as a solvent for proteins has been investigated with a view to its application to proteins which are aggregated or insoluble in aqueous media. Five proteins of known molecular weight–bovine serum albumin, ovalbumin, lysozyme, β‐lactoglobulin, and insulin–have been studied in this solvent by light scattering and viscosity techniques. Bovine serum albumin and ovalbumin showed time‐dependent changes in viscosity which complicated the interpretation of viscosity measurements. These changes in viscosity with time were not due to hydrolysis or aggregation of the protein. It was necessary to correct the light scattering data for fluorescence of the protein in formic acid. The molecular weights determined in formic acid and in the presence of neutral salt indicate that β‐lactoglobulin and insulin are largely dissociated to the monomeric form; the other proteins gave slightly higher molecular weights in formic acid than in aqueous solution. In the absence of salt the concentration dependence of both properties measured is typical of highly charged polyelectrolytes. The KC/R90 vs. C plots show a very steep rise from zero concentration and level off at higher concentrations. The ηsp/C vs. C plots for bovine serum albumin, ovalbumin, and β‐lactoglobulin exhibit maxima at protein concentrations between 0.1 and 0.2%. On addition of neutral salt or water to the formic acid, the light scattering and viscosity show a normal dependence on concentration. The difference in polyelectrolyte behavior between the proteins is attributed to differences in molecular weight, varying degrees of intramolecular crosslinking by disulfide bonds, and different distributions of positively charged side‐chains along the polypeptide backbone. The viscosity measurements show that in formic acid the proteins are in a highly swollen state. Optical rotation measurements indicate that the proteins are denatured in formic acid.

Concentrations of Ions at the Surfaces of Clays

Equations based on the theory of the structure of the electrical double layer developed at a charged plane surface are used to calculate the concentrations of ions at the surfaces of clays suspended in various electrolyte solutions. The results indicate that in clays where the surface density of charge is high the conditions close to the surface are independent of the outer electrolyte concentration provided that this is not too high. The treatment is applied to the problem of the conditions present at the surfaces of clays suspended in dilute acid, and the effect of the addition of neutral salts on the acidity at the surface is discussed.

Aggregation of mitochondria, mitochondrial fragments, and microsomes by cytochrome c

Cytochrome c at a concentration of 5·10 −6 M in solutions of low ionic strength at pH 6.5 will complex with mitochondria, mitochondrial fragments, and microsomes, causing these particulate structures to aggregate. This effect can be reversed by the addition of neutral salts to the medium, although the reversal is not strictly a function of ionic strength alone. ATP and ADP are particularly effective in physiological concentrations. This cytochrome c-induced aggregation reaction has been found to have no significant effect on the enzymic activities of these particles.

Polarographic Studies on Heterocyclic Compounds. II. Saponification of Isonicotinic Acid Methyl Ester

Abstract (1) Isonicotinic acid methyl ester gives a single reduction wave and the half-wave potential shifts to more negative potential with increasing pH. (2) Isonicotinic acid methyl ester is saponified in the alkaline medium and the velocity constant of saponification is determined polarographically on the basis of the second order reaction equation. (3) The velocity constant is scarcely influenced by the addition of neutral salts, but increases with rising temperature. The activation energy of saponification is calculated according to the Arrhenius equation.

Observations with the electron microscope on the solvation and reconstitution of collagen.

The course of events in the solvation and reconstitution of collagen obtained from rat tail tendon is described as seen with the electron microscope. Under the influence of 0.01 per cent acetic acid the collagen fibers swell and dissociate into submicroscopic filaments, the smallest of which are probably beyond the resolution of the electron microscope. These filaments can be made to reconstitute into fibers either by the addition of neutral salts to the acid solution or by raising the pH. The structural form of the resulting fibers is influenced by the concentration of the salt and by the pH of the solution employed. Saline-concentrations around 1 per cent and pH's ranging from 4.8 to 6.8 lead to the formation of needle-shaped crystals, or tactoids, showing the striated structure characteristic of collagen. Saline concentrations outside of this range (0.5 per cent and 5.0 per cent) lead to the formation of long fibrils without evidence of striations. pH's on the alkaline side of 6.8 bring about the formation of long slender fibers. Some of the possible reasons for these different fiber forms are discussed. Apparently fibers are formed in vitro by the lateral and longitudinal association of the filaments seen in the original solutions. Some of the fibers thus formed may in turn associate laterally and longitudinally to form the larger fibers. The formation of the needle-shaped crystals appears to be an orderly process since it leads to the formation of a periodicity in the fibers. The striations in the smaller fibers are uniform and regularly spaced at around 210 A. With continued growth of these fibers there is a simultaneous development of a more obvious and precise banding. It is evident that two out of each group of three regularly spaced striae are more prominent. This produces the macroperiod of collagen measuring around 640 A in length.

THE EFFECT OF SOLVENT AND TEMPERATURE ON THE VISCOSITY OF THE POLYSACCHARIDE OF IRISH MOSS AND THE EFFECT OF SOLVENT ON ITS INITIAL GELATION

The viscosity of aqueous extracts of Irish moss (Chondrus crispus) has been found to depend mainly on the concentration of the neutral salts present in the solution. Samples of dialyzed polysaccharide, however, show considerable variation. The relation between the specific viscosity and the concentration in dilute aqueous solutions and formamide is such that ηsp = acv + bcc2, where ηsp is the specific viscosity, cv the concentration, and both a and b are constants. In aqueous solution these constants are decreased by the addition of neutral salts. A rise in temperature causes a decrease in viscosity. This decrease is less rapid for solutions in formamide and aqueous solutions containing neutral salts. The effectiveness of individual salt solutions in promoting a decrease in viscosity coincides with their effect in producing precipitation of the polysaccharide. The order of decreasing effectiveness was: potassium chloride, calcium chloride, sodium chloride. When the concentration of gelose is such that gelation takes place on standing, measurements of viscosity become irregular and are not reproducible. The concentration of gelose at which the regular viscosity measurements are obtained decreases with increasing concentration of neutral salts. The rigidity of the gels so formed also decreases. The firmness of a gel seemingly depends on the concentration and type of neutral salt, as well as on the intrinsic viscosity of the polysaccharide. The intrinsic viscosity is defined as: the limit of the specific viscosity as the concentration approaches zero.

Diameter changes of gelatinized coacervate drops of the complex coacervate gelatine‐gum arabic resulting from a change in the pH of, or from the addition of neutral salts to the surrounding medium. I

Abstract1. A microscopic method is developed for the measurement of diameter changes of gelatinized coacervate drops.2. The influence of the pH and with constant pH (3.7) the influence of neutral salts is investigated on the gelatinized complex coacervate gelatine (positive)‐gum arabic (negative).3. Upon variation of the pH the diameter passes through a minimum lying very close to the pH (3.7) at which, with the given ratio of mixing of gelatine and gum arabic, complex coacervation is optimum (where for example the water content of the coacervate is a minimum).4. In the regions of smaller salt concentrations the diameter changes are reversible, at higher concentrations irreversible.5. The reversible change due to the addition of a salt is a swelling. For this swelling the double valence rule holds:3‐1&gt;2‐1 &gt; 1‐1 and 1‐3 &gt; 1‐2 &gt; 1‐1.6. The position of the minimum of the swelling‐pH curve, the swelling with salts and the thereby prevailing double valence rule are in agreement with the conception that in the gelatinization of the complex coacervate the typical complex relations (electrostatic attraction versus water content) have been retained. The complex gel which results is distinghuised from the complex coacervate only by the coherence of the positively charged gelatine to a gel structure.

Potentiometric studies in the formation and stability of colloidal solutions

1. Potentiometric titrations of acidified and unacidified ferric chloride solutions have been conducted against carbonate-free sodium hydroxide, with and without the addition of neutral salts. 2. The titration curves show that the range of stability of ferric oxide sols is between the pH limits 3·20–4·45, the precipitation of ferric oxide commences in the neighbourhood of pH 4·5, and is complete at pH 6·0. 3. The composition of the precipitate of ferric oxide is found to vary with the neutral salt added. The molar ratio between ferric chloride and sodium hydroxide varies between the limits 1:2·69 to 1:2·85, the theoretical ratio being 1:3·0. The molar ratio at the end point follows the series SO4″ < Cl′ < NO3′ < water. 4. The different stages in the formation of micelles of ferric oxide and their subsequent coagulation have been elucidated. 5. The variations in pH of ferric oxide sols with dilution have been studied, and the results support the view proposed by the author that there is an equilibrium between the ions in the micelle and those in the intermicellary liquid. 6. An explanation has been offered for the development of alkalinity on addition of neutral salts to ferric oxide sols. The liberation of OH− ions on addition of salts has been correlated with the lower molar ratio obtained in the titrations of ferric chloride against alkali.

Some Factors Influencing the Rate of Thermal Destruction of the Tetanus Antitoxin of Antitetanic Horse Plasma at 60° to 66°C.

Summary Data are presented to show the influence of ammonium sulphate, phenol and pH on the heat destruction at 60° to 66°C. of tetanus antitoxin of antitetanic horse plasma. The results may be summarized as follows: Addition of neutral salts increased the rate of destruction of tetanus antitoxin up to an ionic strength of 0.6 to 0.9 where a maximum is reached. With further addition of salt the rate decreased.The pH of maximum stability is at or near neutrality.Phenol increases markedly the rate of destruction of tetanus antitoxin. Its accelerating action is approximately proportional to the square of the phenol concentration.Between 60° and 66°C. an increase in temperature of 1°C. increases the rate of destruction of tetanus antitoxin 1.85 times.

CCCCXXXI.—Neutral salt addition compounds of β-alanine

CCCCXXXI.—Neutral salt addition compounds of β-alanine

Hydrolytic Adsorption at Colloid Surfaces

THE outstanding work on hydrolytic adsorption has been carried out with purified charcoal (see, for example, Bartell and Miller, J. Am. Chem. Soc., 44, 1866; 1922: 45, 1106; 1923), and definite positive results have been obtained. The measure of the hydrolytic effect in the case of the numerous negative hydrophobic (acidoid) sols, such as colloidal mastic, platinum, gold, arsenious suiphide, etc.—all of which are remarkably alike in structure and in reactions—is complicated by the well-established phenomenon of catalytic interchange. For example, in the presence of salts, such as barium chloride, the hydrogen ion at the colloid surface suffers an interchange with the added barium ion, and the corresponding increase in acidity is superimposed upon any change in acidity due to the hydrolytic action at the surface. It has become the general practice to ascribe the whole of the increase in acidity of acidoid sols (on the addition of neutral salts) solely to the cationic replacement, and to neglect any probable hydrolytic effect. That the latter effect is real is evident from the following consideration.

Neutral salt addition compounds of N-methylated glycines: their formulation and that of their hydrates

Neutral salt addition compounds of <i>N</i>-methylated glycines: their formulation and that of their hydrates