A New Sulphur-containing Amino Acid. 



161 



75 (1822) 



A new sulphur-containing amino acid isolated from casein. 



By J. HOWARD MUELLER. 



[From the Department of Bacteriology, College oj Physicians and 

 Surgeons, Columbia University, New York City.} 



In a report on a study of the cultural requirements of strep- 

 tococci made last year before this society, the writer stated that a 

 compound containing sulphur had been isolated from casein, which 

 was apparently not related to cystine, and which seemed to be 

 required for the growth of the test organisms. Although subse- 

 quent work has shown that this sulphur compound, when pure, is 

 apparently not concerned in the growth of streptococci, it seemed 

 desirable to make a study of the substance, both because of the 

 uncertainty of the nature of non-cystine protein sulphur, and also 

 in order to be able to effect a separation of this compound from the 

 bacterial growth inducing factor in the amino acid fraction under 

 investigation. While there are still many points to be cleared up 

 in connection with the substance, perhaps enough information has 

 been obtained to warrant a preliminary report. 



There have been a number of difficulties met with in the work. 

 The yield is very small, and probably not by any means quantita- 

 tive, and further, no insoluble compounds suitable for separation 

 have so far been found, so that purification has consisted largely 

 in methods for the removal of impurities. 



In order to obtain sufficient material for analyses, thirty pounds 

 of commercial Argentine casein were used. Briefly, the method 

 consists in hydrolysis with sulphuric acid, neutralization with 

 sodium carbonate, and piecipitation with mercuric sulphate solu- 

 tion. From the washed precipitate, freed from electrolytes, a 

 considerable quantity of other material is removed by a second 

 precipitation with mercuric sulphate, the sulphur compound this 

 time remaining in the filtrate. Further purification is effected by 

 precipitation of the filtrate, after removing electrolytes, by silver 

 sulphate and barium hydroxide, and the compound itself is ob- 

 tained from the silver filtrate, freed, of course, from Ag and Ba, 

 by fractional crystallization, finally from dilute acetone. The 

 yield from thirty pounds was about 10 grams. 



