.148 THE PROTEIN SUBSTANCES. 



been prepared synthetically by NEUBERG and SILBERMANN from diaminosuccinic 

 acid and barium nitrite in sulphuric acid solution. Oxyaminosuberic acid, 

 C 8 Hi 6 N0 6 , has been detected by WOHLGEMUTH 1 in the cleavage products of a 

 liver nucleoprotein. 



Z-Cystine, C6Hi2N2S 2 04 (a-diamino-/3-dithiolactolic acid), the disulphide 



CH 2 S S CH 2 

 of cysteine (a-ammo-|3-thiolactic acid), CH(NH 2 ) CH(NH 2 ), was first 



COOH COOH 



obtained, with certainty, as a cleavage product of protein substances by 

 K. MORNER, and then also by EMBDEN. KULZ 2 obtained it once as a 

 product of tryptic digestion of fibrin. The quantities found by MORNER 

 and BUCHTALA in the various proteins are given in the tables on pages 

 106, 107, 115 and 125. 



According to NEUBERG and MAYER S two kinds of cystine occur in nature, 

 namely, stone-cystine, designated /3-cystine. and protein-cystine, called a-cystine 



CH 2 NH 2 CH 2 NH, 

 Stone-cystine is the disulphide of /3-amino-a-thiolactic acid, CH S S CH 



COOH COOH 



The protein-cystine has been chiefly obtained from the protein substance, 

 but also from calculi, while the stone-cystine has been obtained from urinary 

 calculi only. 



Many objections have been raised from many sides as to the correctness of 

 this assumption. ROTHERA could not find any difference between the stone- 

 cystine and the cystine prepared from hair, and FISCHER and SUZUKI, and recently 

 also ABDERHALDEN, 4 arrived at similar results, which seems to place the exist- 

 ence of stone-cystine in doubt. The occurrence of two structurally isomeric 

 cystines is not improbable, from certain observations of MORNER, but FRIEDMANN 

 and BAER S have shown that these observations do not lead to this assumption 

 and at the present time we cannot admit of the occurrence of two different cystines* 



Cystine probably occurs normally as traces in the urine. In rare 

 cases, in cystinuria, it occurs in larger quantities in the urine, the sediment 

 or in calculi. Traces have also been found in the ox-kidney, in the liver 

 of the horse and dolphin, and in the liver of a drunkard. ABDER- 

 HALDEN 6 has found cystine in the urine and also abundantly in the 

 organs (spleen) in a case of parental cystine diathesis. 



The constitution of cystine has been explained by FRIEDMANN. 7 and 



, Zeitschr. f. physiol. Chem., 42; Neuberg and Silbermann, ibid., 44; 

 Wohlgemuth, ibid., 44. 



2 K. Morner, ibid., 28, 34, and 42; Embden, ibid., 32; Kiilz, Zeitschr. f. Biologie, 

 27. 



8 Zeitschr. f. physiol. Chem., 44. 



4 Rothera, Journ. of Physiol., 32; Fischer and Suzuki, Zeitschr. f. physiol. Chem., 

 45; Abderhalden, ibid., 51. 



5 Friedmann, Hofmeister's Beitrage, 3. With Baer, ibid., 8. 



Zeitschr. f . physiol. Chem., 38. 



7 Hofmeister's Beitrage, 3. 



