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The effect of neutral salts on protein conformation was first analyzed by Hofmeister in 1888, however, even today this phenomenon is not completely understood. To clarify this effect, we studied changes in the secondary structure of two proteins: human serum albumin with predominantly &alpha, helical structure and porcine pancreas &beta, trypsin with the typical &beta, structural arrangement in aqueous solutions of neutral salts (KSCN, KCl, (NH4)2SO4). The changes in the secondary structure were studied at 23 &deg, C and 80 &deg, C by using the second derivative deconvolution method of the IR spectra. Our results demonstrated that the ability of the salts to stabilize/destabilize these two proteins correlates with the Hofmeister series of ions. At the same time, some exceptions were also observed. The destabilization of the native structures of both &alpha, helical albumin and &beta, structural trypsin upon interaction with neutral salts leads to the formation of intermolecular &beta, sheets typical for amyloid fibrils or amorphous aggregates. Thus, our quantitative FTIR-spectroscopy analysis allowed us to further clarify the mechanisms and complexity of the neutral salt actions on protein structures which may lead to strategies preventing unwelcome misfolding of proteins.

The effects of neutral salt and alkali on the ion distribution were investigated in two alfalfa ( Medicago sativa L.) cultivars, including Zhongmu 1, a high salt-tolerant cultivar, and Algonquin, a low salt-tolerant cultivar. The alkali stress expressed more serious growth inhibition than the neutral salt stress at the same Na+ concentration. Compared with Algonquin, Zhongmu 1 did not exhibit a higher alkali tolerance under the Na 2 CO 3 -NaHCO 3 treatment with the low Na+ concentration (50 mmol L −1 ). The alkali increased the accumulation of Na+, Ca 2+ , and Mg 2+ in the root and changed the Ca 2+ and Mg 2+ balance in the entire alfalfa plant. The salt and alkali stresses decreased the K + and Fe 3+ contents of the roots and leaves, the root Mn 2+ content, and the shoot Zn 2+ content, but they increased the Fe 3+ accumulation of the shoots, the shoot and leaf Cu 2+ contents, and the leaf Zn 2+ content in both alfalfa cultivars. Based on the results obtained under the conditions of this experiment, we found that the salt and alkali stresses reduced the plant growth in both alfalfa cultivars, while the alkali caused a stronger stress than the neutral salt in alfalfa. Thus, we conclude that under hydroponic conditions, the deleterious effects of the alkali on plants are due to the distribution change of some trophic ion balance in the roots, shoots, and leaves of the plants by causing of Na + , CO 3 2− , and/or HCO 3 − stresses.

Soybean proteins have found uses in different nonfood applications due to their interesting properties. We report on the kinetics and extent of adsorption on silica and cellulose surfaces of glycinin and β-conglycinin, the main proteins present in soy. Quartz crystal microgravimetry (QCM) experiments indicate that soy protein adsorption is strongly affected by changes in the physicochemical environment. The affinity of glycinin and the mass adsorbed on silica and cellulose increases (by ca. 13 and 89%, respectively) with solution ionic strength (as it increases from 0 to 100 mM NaCl) due to screening of electrostatic interactions. In contrast, β-conglycinin adsorbs on the same substrates to a lower extent and the addition of electrolyte reduces adsorption (by 25 and 57%, respectively). The addition of 10 mM 2-mercaptoethanol, a denaturing agent, reduces the adsorption of both proteins with a significant effect for glycinin. This observation is explained by the cleavage of disulfide bonds which allows unfolding of the molecules and promotes dissociation into subunits that favors more compact adsorbed layer structures. In addition, adsorption of glycinin onto cellulose decreases with lowering the pH from neutral to pH 3 due to dissociation of the macromolecules, resulting in flatter adsorbed layers. The respective adsorption isotherms fit a Langmuir model and QCM shifts in energy dissipation and frequency reveal multiple-step kinetic processes indicative of changes in adlayer structure.

International audience; Guillaume-François Rouelle is the author of three papers on neutral salts presented at the Académie royale des sciences at the time when the chemistry of saline substances formed an important aspect of the chemical science, which did not necessarily manage to define its exact study field. Rouelle's works concerning this subject spread over ten years during which the chemist adopted two different approaches in order to understand the nature of composed salts. After giving a clear definition of saline substances and suggesting a taxonomy based on crystallographic considerations illustrated by the study of the marine salt crystals formation, Rouelle took a critical step by passing from "history" to neutral salts "chemistry", bringing to light the phenomenon of the acid excess in those substances. A modern interpretation of Rouelle's theory reveals that his work could have marked a step towards the laws of definite and multiple proportions formulated several decades later.; Guillaume-François Rouelle est l'auteur de trois communications sur les sels neutres faites à l'Académie royale des sciences à une époque où la chimie des corps salins représentait un aspect important de la science chimique sans pour autant avoir réussi à bien circonscrire son domaine d'étude. Durant les dix années sur lesquelles s'étalent les travaux de Rouelle sur ce sujet, deux approches différentes ont été adoptées par le chimiste pour saisir la nature des sels composés. Après une définition claire des substances salines et une tentative de taxinomie basée sur des considérations cristallographiques illustrée par l'étude de la formation des cristaux de sel marin, Rouelle franchît le pas qui le fît passer de l'« histoire » à la « chimie » des sels neutres par la mise en évidence du phénomène de surabondance d'acide dans ces êtres. Une interprétation moderne de la théorie de Rouelle fera apparaître la possibilité que son travail ait pu marquer une étape vers les lois de proportions définies et multiples formulées quelques décennies plus tard.

University College of Science. Department of Chemistry, Calcutta-700009 Manuscript received 29 July 1975,accepted 22 September 1975 As protein molecules at a concentration of about 0.2 per cent can cover the surface of particles of glass, quartz etc. so it has been assumed that the surface of a glass electrode, placed in a solution of concentration above 0.7 per cent of bovine serum mercapt-albumin (BSA) at isoionic pH or above it, is almost completely covered by the protein molecules. On the basis of this assumption and the theory of colloidal electrolytes proposed by the author equations have been deduced which can quantitatively account for the rise in pH of isoiouic (BSA) caused by the additon of neutral salts, without assuming anion binding. It has also been shown that the number of proton donors per mole of (BSA) (molecular weight 69,000), dissociating in the pH range 5.1 to about 7 S, is 12.6 and their pK is 6.18.

Department of Nuclear Chemistry, The Institute of Science, Bombay 400 032 Manuscript received 9 August 1977, revised 3 April 1978, accepted 22 June 1978 A rapid spectrophotometric method based on the extraction of Pd(II) with isonitrosobenzoylacetone in benzene and measurements of the colour in the organic phase at 415 om, is described in this paper. The proposed method is free from the interference of other nobel metals and metals which are usually associated with Pd. 56 µg of Pd in 10 ml solution could be determined with an accuracy of 3% at 95% confidence limit. The analysis of a sivler alloy containing 3.89% Pt, Pd and traces of gold gave a value of 0.097±0.003% for Pd compared to the reported value of 0.104± 0.004%.

M. N. College, Visnagar (N.G.) Manuscript received 19 November 1973; revised 10 March 1975 ; accepted 19April 1975 Action of Dinitrogen tetroxide and its Thermal Dissociation Products on Anhydrous Neutral Alkali Salts of Tetrachlorophthallic Acid. &nbsp

University College of Science and Technology, Calcutta-700009 Manuscript received 2 December 1974; revised 17 April 1975; accepted 19 April 1975 The observation of Scatchard, Coleman and Shen that the \(p\)H of isoionic bovine serum mercapt-albumin (BSA) solution rises with increasing concentration of an added neutral salt has been explained on the basis of author's theory without assuming anion binding by BSA. The binding of H+ ions by BSA has been accounted for quantitatively by an equation derived from author's theory on "Colloidal Electrolytes" discussed in previous papers. The dissociation constant of the COOH groups in BSA between \(p\)H 2.0 and 5.0 has been found to be 10-3.18 (i.e., pK= 3.18).

LIMITING EXCHANGE OF ALUMINIUM IONS FROM HYDROGEN CLAYS ON THE ADDITION OF NEUTRAL SALTS.

The jeolin acid behaves like arable acid (already reported) in its interaction with bases, acids and neutral salts, the difference being essentially in the degree in which the effects appear. It is e. monobasic acid, having an equivalent weight of 1200, and dissociatimconstant of the order of 10-4 i.e., of weak character, although its poten­tiometric titration curve is like that of HCl. Total acidity varies with the nature of the cation used for titration. It shows reserve acidity in its interaction with acids and the existence of base-exchange when treated with neutral salts.

REACTION BETWEEN GLUCOSE AND IODINE IN ALKALINE MEDIUM. EFFECT OF NEUTRAL SALTS.

The capacities of different cations to liberate acid from colloidal silicic acid are in the order Ba++ >Ca++ >Na+ >Li+, in agreement with the lyotrope series. The total amount of acid liberated by BaCl2, Ba(CH3COO)2, CaCl2 and Ca(CH3COO)2 is considerably greater than that neutralised at the first inflexion point in the titration curve of silicic acid sol with a dilute base. At low concentrations, alkali metal cations only effect an osmotic displacement of the mobile H+ -ions. The results have been discussed in the light of the theory of electrical double layer and secondary adsorption of ions.

THE INFLUENCE OF STRONG ELECTROLYTES AND MERCURIC CHLORIDE ON THE CONDUCTIVITY OF AQUEOUS BENZOIC ACID

The kinetics of oxidation of lactic acid by quinquevalent vanadium is found to be of first order with respect to both vanadium(v) and lactic acid. The Arrhenius equation is found to be valid for the reaction between 25° and 35°. The values for the energy of activation, entropy of activation, and frequency factor are found to be 164 kcal., -13.70 cal./MA°, and 6.687 X 109 sec—I respectively. These experimental findings are consistent with the postulate that the rate-determining step in the reaction involves the first order disproportionation of a co-ordination complex between lactic acid and vanadium(v), affording products through free-radical formation.

It has been shown that neutral salts, such as Nacl and and Naclo3 and their mixtures, cause an apparent increase in the thermodynamic dissociation constants of weak acids and bases. The pH value of aqueous salt solutions at fixed hydrogen ion concentration decreases linearly with increasing content of neutral salt and represents a linear function of the salt's heat of hydration (12). The hydrogen ion activity coefficient and, hence, the thermodynamic dissociation constants of weak acids and bases apparently follow a corresponding dependence. In solution for the electrolytic chlorate formation, the dissociation constant of hypochlorous acid is thus apparently enlarged by one order of magnitude. As a consequence, in solutions for the electrolytic chlorate production the optimal pH region for the conversion of available chlorine is shifted toward lower values (pH 5.7–6.1), as shown both in theory and practice. The same phenomenon is shown to be of some importance for what happens in the anode diffusion layer, where chlorine hydrolysis may hence be affected.

The kinetics of the reduction of peroxydisulphate by ascorbic acid has been studied in an acidic medium. The rate of reduction has a direct dependence on the concentration of peroxydisulphate and is independent of ascorbic acid concentration. The influence of neutral salts is negligible while that of acidity is slightly retarding. Allyl acetate inhibits strongly and suggests the formation of sulphate (\(SO_4^-\)) radical ions. A chain mechanism, initiated by the decomposition of peroxydisulphate, has been proposed which involves the intermediate formation of hydroxyl and ascorbate free radicals.

Note on the Action of Neutral Salts in Enzymatic Processes. The Effect of Bromides on Salivary Amylase.&nbsp

On the Kinetics of Calcium Exchange from Ca-soil by Ammonium and Potassium Chlorides in Aqueous Solution

Chemical Laboratories, University of Allahabad, Allahabad Manuscript received 4 September 1972; revised 23 December 1972; accepted 5 February 1973 Mechanism of oxidation of cyclopentanone by chloramine-T in alkaline media has been re­ported. A first order dependence in chloramine-T, cyclopentanone and hydroxide ions has been observed. Neutral salts and p-toluene sulphonamide were found to have insignificant effect on the reaction rate while the effect of addition of methanol was negative. A mechanism involving interaction of enol anion of cyclopentanone with chloramine-T to form an intermediate in a slow step and its subsequent reaction with another molecule of chloramine-T in a fast step has been found to explain the data well. Various thermodynamic parameters have been computed Corres­ponding 1,2-diketone has been reported to be the product.

Interaction between Polybasic Acids and Neutral Salts. Part I. ortho-Phosphoric Acid.

The solubility of stearic acid at 35° and at 50° is 1.I7 x 10-5 N and 5.77 x 10-6 N respectively. The dissociation constant of the acid has been found to be 1.7 x 10-6 at 35° and 2.6 x 10-6 at 50°. The pH of the sol at 50° has been found to be less than that at 35° but the total acidity as is to be expected in the case in which the whole acid reacts, remains the same at 50°. The hydrogen ion activity of the sol increases on the addition of neutral salts. The solubility of barium and calcium stearates at 35° has been found to be 9.02 x 10-6 N and 6.15 x 10-6 N and at 50° 2.21 x 10-5 N and 2.33 x 10-5 N respectively.

The hydrolysis and the effect on the hydrolysis of magnesium sulphate in aqueous solution, by the neutral salts—sodium chloride, sodium iodide and potassium iodide have been studied potentiometrically at 25°, using quinhydrone electrode coupled with saturated calomel electrode.