150 THE PROTEIN SUBSTANCES. 



compound passes to the anhydride, which is a hydantoin melting at 

 119 C. By the action of potassium cyanide MAUTHNER l obtained 

 a-amino-/3-suphocyanpropionic acid, CH 2 (SCN).CH(NH 2 )COOH. 



Stone-cystine, according to NEUBERG and MAYER, differs in many respects 

 from the ordinary cystine, among which the following may be mentioned: The 

 optically active stone-cystine crystallizes in needles, the specific rotation is 

 ()D = -206; it melts at 190-192 with marked swelling up. The benzoyl 

 compound melts at 157-159; the phenylcyanate compound melts at 170-172, 

 and it is not changed on boiling with hydrochloric acid, 



In the detection and identification of cystine we make use of the 

 crystalline form, the behavior on heating on platinum-foil, and the sul- 

 phur reaction after boiling with alkali. As to its preparation from protein 

 substances see K. MORNER and FOLIN 2 . In regard to the detection 

 of cystine in the urine see Chapter XIV. 



CH 2 .SH 



Cysteine (a-amino-/3-thiolactic acid), C 3 H 7 NS0 2 =CH(NH2), is formed from 



COOH 



cystine by reduction with tin and hydrochloric acid. It is also produced in the 

 cleavage of protein substances not as EMBDEN believes as a primary formation 

 but according to MORNER and PATTEN 3 as a secondary formation. Cysteine 

 can be easily converted into cystine by oxidation. 



According to V. ARNOLD 4 cysteine occurs as a constituent of the press-juice 

 or extracts of various animal organs. He has found it especially in the hair and 

 he considers it as a primary cell constituent. 



Toward alkalies and lead acetate it acts like cystine. With sodium nitro- 

 prusside and alkali it gives a deep purple-red coloration; with ferric chloride 

 the solution gives an indigo-blue coloration which quickly disappears. 



CH/ 



Thiolactic acid (a-thiolactic acid), C 3 H 6 S0 2 =CH(SH), has been found once 



COOH 



as a cleavage product of ox-horn by BAUMANN and SUTER. MORNER, FRIED- 

 MANN and BAER obtained it from cystine. It has been shown by FRIEDMANN 

 that this acid is a regular cleavage product of keratin substances, and that it 

 can also be obtained from the proteins. FRANKEL 5 obtained the acid from 

 haemoglobin. The pyroracemic acid obtained by MORNER as a decomposition 

 product from several protein substances originates, according to MORNER, only 

 in part from the cystine. 



Taurine (aminoethylsulphonic acid), C 2 H 7 NS03 = TTx , has 



dlovfeUo.vJrl) 



not been obtained as a cleavage product of protein suostances; still its 



1 Zeitschr. f. physiol. Chem., 78. 



2 Morner, Zeitschr. f. physiol. Chem., 34; Folin, Journ. of Biol. Chem., 8. 



3 See foot-note 2, page 80. 



4 Zeitschr. f. physiol. Chem., 70. 



5 Morner, Zeitschr. f. physiol. Chem., 42; Suter, Zeitschr. f. physiol. Chem., 20; 

 Friedmann, Hofmeister's Beitrage, 3; with Baer, ibid., 8; Frankel, Sitzungsber. d. 

 Wien. Akad., 112, II, b, 1903. 



