BY JAMES M. PETRIE. 12") 



acid. Maly* and others also obtained oxidation-products of 

 proteins, which were not precipitated by tannic or phospho- 

 tungstic acids, gave no Millon or xanthoproteic test, but a 

 positive biuret. These products, heated with alkali, evolved 

 large amounts of ammonia : after hydrolyses, they yielded 

 amino-acids and ammonia, and gave off nitrogen when acted 

 on by nitrous acid. 



Plants and seeds contain protease and oxidase ferments, 

 and, therefore, it is not improbable that the above oxidation- 

 products are present in the non-protein solution. 



Polype/ptides. — Swirlowskif submitted protein to hydro- 

 lysis with 0-5/ hydrochloric acid, at 37" C for six months. 

 The phosphotungstic filtrate then contained 27% of the nitro- 

 gen, and no amino-acids could be obtained, until hydrolysed 

 by strong acids. These polypeptides gave only the biuret 

 reaction. 



We have now seen that both tannic and phosphotungstic 

 acids may not precipitate the smaller polypeptides. If we 

 assume the presence of these in the Acacia solutions, then (1) 

 we know, from the negative Millon test, that the tyrosin 

 nucleus is not a constituent. (2) It is more difficult to ex- 

 plain the absence of the biuret reaction ; though it is just 

 possible that the biuret-yielding group is absent, it is more 

 likely that, with these particular polypeptides, the reaction 

 is not reliable. (3) By ordinary hydrolysis, only small 

 amounts of ammonia would be set free, certainly not suffi- 

 cient to account for the large amount obtained. On the other 

 hand, if oxidation has also taken place, then, as has already 

 been shown, oxidation-products could be slowly formed, 

 which would provide large amounts of ammonia on distilla- 

 tion. (4) By the severing of imino-linkings in the poly- 

 peptide hydrolysis, amino-groups would certainly appear. 



* Maly— Sitzber. Wien. Akad. 1889; Monatshr. 1889. 

 t Zeit. physiol. Chem. 48, 1906, 252. 



