The Effect of Temperature on the Titration Curve of Casein

Pertzoff, Vladimir; Carpenter, S. C.

doi:10.1085/jgp.16.2.257

Cited by 8 publications

(2 citation statements)

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“…The well-marked differences in the relative magnitudes of the effects of temperature on the three main parts of the titration curves appear to be as characteristic of proteins as of their constituent aminoacids, as the recalculation of the data of Hoffman and Gortner on casein by Pertzoff and Oarpenter [18,24] and the work of Wyman on horse hemoglobin [36] have shown. They are entirely consistent with the assumption previously made that the carboxyl and amino groups of the uncombined protein are completely ionized.…”

Section: Resultsmentioning

confidence: 99%

“…Since the publication of Bjerrum's paper this criterion has been made use of in the study of proteins as well as of amino-acids by Pertzoff and Carpenter (casein) [24], and by Wyman (hemoglobin) [36]. Changes in temperature were observed to have very small effects on the parts of the titration curves of these proteins which lie on the acid side of neutrality, but the effects on the alkaline side were very considerable.…”

Section: Introductionmentioning

confidence: 99%

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Combination of wool protein with acid and base: The effect of temperature on the titration curve

Steinhardt¹,

Fugitt²,

Harris³

1940

J. RES. NATL. BUR. STAN.

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Equilibrium measurements are reported of the amounts of hydrochloric acid and potassium hydroxide bound by wool, as a function of pH and salt concentration at 0°, 25°, and 50° C. In order to eliminate from the measurements of base combination effects due to decomposition, a study was also m ade of the effect of temperature on the rate of decomposition of the disulfide bonds in wool and on the rate of solution of the fiber in alkaline solutions. The data support the assumption made in accounting for previously reported titration measurements at 0° C, that the carboxyl and amino groups of wool in the uncombined state are completely ionized. Thus changes in the pH coordinates of the titration curves brought about by changes in temperature are small in the pH range in which acid is combined, which indicates that combination with acid is equivalent to backtitration of the carboxyl groups, but are large in the pH range in which base is combined, which indicates that combination with base is equivalent to backtitration of amino groups.The heats of dissociation calculated for the two kinds of groups, approxim at ely 2,500 and 14,000 calories, respectively, are in good agreement with values for these groups in comparable compounds and in soluble proteins. The value obtained in the acid range also agrees with the results of calorimetric measurements on the combination of acid with wool.It is shown that approximately equal parts of the total heat changes in the acid range are associated with the dissociation of hydrogen ions and chloride ions from the fiber. An appreciable part of the total heat effect may be ascribed to a heat of transfer of the ions between the two phases of the heterogeneous titration system. Neither titrimetric nor calorimetric estimations of the heats of dissociation provide evidence for or against the existence of "salt linkages" in wool.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%