Chinese Journal of Physiology

ACID- AND BASE-BINDING POWER OF PROTEINS 13

Effect of coagulation of egg albumin.—Some egg albumin was denatured by heating in acid. After cooling, the albumin was precipitated by neutralization. It was centrifuged and purified once by dissolving in dilute alkali and subsequent reprecipitation by neutralization. The denatured albumin was again dissolved in dilute alkali, giving an apptoximately one per cent solution. Equal portions of the solution were measured into test tubes, and different amounts of acid were added to give pH values from 4 to 6. These tubes were weighed and heated as described above. After heating, the total acid or alkali content of the tubes was equalized before measuring the pH. The results of two experiments are shown in tables 3-4 and fig. 8-!. The point of reference was in table 3 on the acid side of the isoelectric point and in table 4 on the alkaline side.

It will be noted that the coagulated solutions are more acid in acid solution and more alkaline in alkaline solution,

TABLE 3.

Effect of coagulation on acid-binding power of denatured (and flocculated) egg albumin

20 ce of 1 per cent denatured albumin in dilute alkali+graded amounts of N/10

HCl. ee ss ase en ea caer Before heating After heating No. = — | N/10 HCl added | N/10 HCl added pH of suspension pee ce ce 1 0.2 | 0.4 4.04 ~0,10 2 0.3 | 0.8 3.92 —0.22 3 | 0.35 0.25 3.80 —0.34 4 04 0.2 3.81 —0.33 5 0.45 0.15 3.92 —0,22 6 05 | 0.1 402 —0.12 7 0.6 0,0 414 —0,00 Unheated control 0.6 4.14