Further investigations of the affinities of anions of strong acids for wool protection

Wool immersed in mixtu res of two strong acids, or of one acid and a salt of a second, combines with these acids in uneq ual amounts. The present paper demonstrates that the results obtained wi th mixtures may be predicted with fair approximation from the anion-wool dissociation constants previously assigned to each anion on the basis of titration data. Methods are described for calculating the total acid and the relative proportions of each which are bound. Conversely, it is also shown that approximate values of the dissociation constants may be calculated from the results of experiments with mixtures.

Section: T Ot Al a C Id Boun D I N Mixt U R E S Of Two Acidssupporting

confidence: 51%

Analysis of the selective combination of wool with acids in mixtures

Steinhardt¹

1942

“…Under ordinary conditions, amide and peptide groups are too weakly basIc to combine to any appreciable extent with hydrogen ions at these concentratIOns of acid, but their readiness to combine with hydrogen ions may be greatly increased by acquiring a negative charge by combination with an anion. SImilar effects of charge on the strengths of acids and bases have been discussed by the present authors [8,9] and have been treated theoretically by many others. The fact that much more hydrogen ion than dodecylsulfonate ion must be present to attain the maximum rate of amide hydrolysis mdicates that the proteins com bine with hydrogen ion less readily than with dodecylsulfonate.…”

Section: Mechanism Of the Cat Al Ysismentioning

confidence: 93%

“…Details of the purification of both proteins and, with few exceptions,4 of the reagents used, have been described elsewhere [8,9]. The kinetic procedures were as follows:…”

Section: Experimental Procedures 1 Experimental Conditionsmentioning

confidence: 99%

Catalyzed hydrolysis of amide and peptide bonds in proteins

Steinhardt¹,

Fugitt²

1942

The rates of hydrolysis by dilute acids of both a dissolved protein (egg albumin) and an insoluble protein (wool) are shown to depend not only on the temperature and acidity but also on t he acid used. When hydrolyzed at 65° C by certain strong monobasic acids of high molecular weight, the amide and the peptide bonds are broken over 100 times as fast as when they are hydrolyzed with hydrochloric acid. Even among the common mineral acids, large differences appear. These differences in hydrolytic effectiveness parallel differences in the affinities of the anions of the acids for protein. A further reason for attributing t his effect to the anions is the attainment, with anions of high affinity, of a maximum rate of amide hydrolysis at r elatively low concentrations, stoichiometrically equivalent to the sum of the amino plus the amide groups. A similar limiting anion concentration or maximum rate of hydrolysis of t he much more numerous peptide groups is not observed. On the basis of details of t he dependence of the rate of hydrolysis on concentration of effective anions and hydrogen ions, a m echanism which involves combination of the groups hydrolyzed with hydrogen ions, is proposed.At low concentrations of effective anions, amide hydrolysis is catalyzed more strongly than peptide hydrolysis. By keeping the concentration slightly below stoichiometric equivalence to the sum of the amino plus amide groups the amide groups may be rapidly hydrolyzed without extensive hydrolysis of the peptide bonds in the protein. Practical applications are suggested.

“…The extent of this difference is small, as is made evident elsewhere [7]. Two sets of curves are shown, representing eq 3' Oow affinity) and 4' (high affinity) , respectively.…”

Section: The Calculation Of Affinity With the Modified Equationsmentioning

confidence: 94%

“…Since all the points indicated fall in a region for which the curve representing eq 4' is lower than the curve representing eq 3' , it is obvious that with this ratio eq 4' rather than eq 3' must be used to calculate the affinity for wool of all of the anions represented. 3 In another paper [7] values of K A ' for 33 different acids obtained by the use of eq 4' are tabulated and compared with those previously given.…”

Section: The Calculation Of Affinity With the Modified Equationsmentioning

confidence: 99%

Calculation of protein-anion affinity constants from acid titration data

Steinhardt¹

1942

Self Cite

It has been shown earlier that the titration curves of wool and other proteins obtained with different strong acids differ widely in position with respect to the pH coordinate. By assuming that these differences were due to combination of the protein with anions as well as with hydrogen ions, it was possible to calculate from the pH of the midpoint of each curve numerical values of tbe affinity of each anion for wool. In the present paper modifications of the equations for calculating anion affinity are described. It is shown that the new equations describe the titration curves as a whole instead of merely the positions of their midpoints. The new forms are also shown to describe the effects of the presence of salts on the titration curves at least as adequately as did the earlier ones. CONTENTS Page