136 THE PROTEIN SUBSTANCES. 



In another manner, namely by fractional precipitation with metallic 

 salts, especially with mercuric-potassium iodide and the preparation 

 of phenylisocyanate compounds, HOFMEISTER and his pupils STOOKEY, 

 RAPER and ROGOZINSKI l have isolated peptones or polypeptide-like 

 bodies from blood proteid. One of these, called arginine-histidine 

 peptone, yielded arginine and histidine as basic hydrolytic products 

 while another yielded chiefly lysine as basic product and hence was 

 called lysine-peptone. 



From glutin-peptone, SIEGFRIED, on warming with hydrochloric 

 acid, obtained a base, C2iH 39 NgO8, which can also be directly obtained 

 from gelatin. This he calls a kyrin, because it is to be considered as a 

 basic protein nucleus, and he calls this special one glutokyrin. The 

 glutokyrin gives the biuret reaction and is considered as a basic peptone. 

 On complete hydrolytic cleavage it yields arginine, lysine, glutamic 

 acid, and glycocoll. Of the total nitrogen two-thirds belongs to the 

 bases and one-third to the amino-acids. 



Recently he with O. PILZ on further hydrolysis has prepared a 

 ^-glutokyrin, which only yielded arginine, lysine and glutamic acid. 

 Similar basic nuclei, protokyrins, have recently been obtained by SIEG- 

 FRIED 2 from fibrin and casein, using the same method. Caseinokyrin 

 gives a non-crystalline sulphate, but a crystalline phosphotungstate. 

 The free caseinokyrin has an alkaline reaction, gives the biuret test, 

 and its composition corresponds to the formula C23H 47 N908. It yields 

 arginine, lysine, and glutamic acid on cleavage. The basic nitrogen 

 amounts to about 85 per cent of the total nitrogen, and caseinokyrin, 

 whose unit nature is defended by SIEGFRIED 3 against the opinions of 

 SKRATJP, ZWERGER and Wiir, 4 behaves in this respect like a protamine. 



Among the known cleavage products of proteins, arginine is the only 

 one which, up to the present, is never absent, and for this reason we desig- 

 nate as proteins only those atomic complexes which contain, besides 

 chained monamino-acids, also arginine, or, more simply, show the pre- 

 viously mentioned imide bindings. Hence caseinokyrin, which yields 

 only arginine, lysine and glutamic acid, and scombrin (see below), which 

 yields only arginine, proline, and alanine, are the simplest known proteins. 



Scombrin belongs to the previously mentioned group of prot amines 

 which, according to KOSSEL, S are formed by a successive cleavage of the 

 typical protein. The occurrence of basic protokyrins in the hydrolytic 



1 Hofmeister's Beitrage, 7, 9, and 11. 



2 Kgl. Sachs. Ges. d. Wiss., Math.-Phys. Klasse, 1903, and Zeitschr. f. physiol. 

 Chein., 43, with Pilz., ibid., 58. 



3 Zeitschr. f. physiol. Chem., 48 and 50. 



4 Monatash. f. Chem., 26 and 27. 



5 Zeitschr. f. physiol. Chem., 44. 



