204 Hydrolysis of the Soluble Protein of Swede Turnips 



The valine solution (1990 c.c.) was treated in exactly the same 

 way as the alanine liquid, and the same difficulties were encountered. 

 Baryta had to be used in the same way as with the alanine. The 

 solution of valine, free from mineral acids and bases, was concentrated 

 on the water bath until the vaUne began to crystallise at the surface. 

 Three volumes of 80 per cent, acetone were then added and the mixture 

 washed, using more 80 per cent, acetone, into a flask. This was stoppered 

 to .prevent evaporation of the acetone and allowed to stand over night 

 while the vahne crystalUsed out. It was then filtered off and washed 

 with 80 per cent, acetone. 6-77 grms. of pure valine were thus obtained. 



0-1150 grm. gave NHg equal to 9-9 c.c. N/10 acid 

 - 0-01386 grm. N 

 = 12-05 per cent, nitrogen. 



Calculated for CgH^NOg = 11-97 per cent. 



The filtrate from the vahne was evaporated to dryness. This con- 

 tained the alanine which had escaped precipitation by the phospho- 

 tungstic acid and the vahne dissolved by the acetone-water mixture. 



The residue obtained weighed 6-31 grms. and contained 12-57 per 

 cent, of nitrogen. This shows that the separation of the alanine and 

 valine had not been complete. A second separation was not considered 

 advisable, however, because about 40 per cent, had been lost during 

 the separation. This separation apphed once indicates the presence 

 of 9-73 grms. of alanine in the protein. Allowing for portions removed 

 for analysis this becomes 10-29 grms. This corresponds to a percentage 

 of 3-58 of alanine in the protein. 



Second separation of leucine and valine. 



The 7-6 grms. of vaUne obtained from the first separation of leucine 

 and vahne was found to contain leucine (see page 200) so a second 

 separation was necessary. To this were added the two first fractions 

 obtained during the recrystalhsation of portions to remove alanine 

 (see page 199). The mixture was thoroughly ground up and mixed in 

 a mortar and carbon and nitrogen determinations made. 



0-1407 grm. gave 0-2750 grm. COg equal to 53-30 per cent, of carbon. 



Assuming that only vahne and leucine were present this indicated 

 the presence of about 45 per cent, of valine and 55 per cent, of leucine 

 isomers in the mixture. 



53-30-51-28 ^.. 2-02 ^.. k. n o/ i • ^r i o/ r 

 5 4-96 - 51-28 ^^ 3^ ^ ^ /° leucmes, 45-1 % vahne. 



