440 CHEMICAL DYNAMICS 



is determined by this ratio, the equihbrium of the system would 

 also be a function of the ferment-concentration. The synthesis 

 of paranuclein A through the agency of pepsin affords us an 

 opportunity of determining the influence of the ferment-concen- 

 tration upon the velocity of protein synthesis, since the product 

 is rapidly formed and can readily be determined quantitatively. 

 The following was the experimental procedure: 



The products of the complete peptic hydrolysis of A^/10 

 potassium hydrate neutralized to litmus by casein* were evapo- 

 rated to one-sixth of their volume and filtered. Seventy-five 

 cubic centimeters of the clear, deep yellow filtrate were placed 

 in each of six flasks and to each, respectively 0, 5, 10, 15, 20 and 

 25 cc. of 10 per cent pepsin (puriss. sice. Gruebler's) were added, 

 and the total volume in each flask was made up to 100 cc. by the 

 addition of distilled water. After the addition of toluol, the 

 tightly-stoppered flasks were set aside at 36 degrees for 22 hours. 

 At the end of this time the flasks containing 25 and 20 cc. of 

 10 per cent pepsin, respectively, contained heavy precipitates, 

 while that containing 15 cc. contained a precipitate and those 

 containing 5 and 10 cc. had undergone no change other than a 

 slight increase in opacity. The contents of the flasks were now 

 filtered through rapid-filtering papers and the precipitates were 

 washed with distilled water until colorless filtrates were obtained; 

 in all cases the filtrates gave no precipitates or increase in opal- 

 escence upon the addition of acetic acid. The filters were then 

 washed with 10 cc. of N/10 potassium hydrate and the filtrates 

 were collected in water containing 20 cc. of N/10 acetic acid. 



* Prepared as follows: To 6 Utres of A^/50 sodium or potassium caseinate, 

 neutral or faintly acid to litmus, were added two gram of Gruebler's pepsra 

 puriss. sice, which had previously been dissolved in a little water. This 

 solution, after thorough mixing, was allowed to stand at 36 degrees for 10 

 days, 2 more grams of pepsin being added after the first 4 days (ia the 

 presence of toluol), and was then sterilized by steam at 100 degrees and 

 filtered through hardened filter paper. To the filtrate were then added two 

 more grams of pepsin, dissolved, as in the previous cases, in a little water, 

 toluol introduced, and the solution was again allowed to stand at 36 degrees for 

 7 to 8 days; it was then again sterihzed by steam at 100 degrees and filtered 

 through hardened filter paper. The filtrate thus obtained is of a clear yellow 

 color with Uttle or no opalescence and gives no trace of a precipitate or 

 opalescence upon the addition of acetic acid either before or after neutraUzation 

 with alkali; hence both casein and paranuclein are completely absent from 

 the solution. 



