154 LECTURE VIII. 



belongs. We are indebted to A. Kossel l for its discovery among the 

 cleavage-products of the protamine, sturine. It was for a long time 

 assigned to the di-amino acids, also called hexon bases. Pauly 2 has 

 recently succeeded in throwing some light on its constitution. He gives 

 it the formula of a-amino-/?-imidazol-propionic acid: 



CH^-NH 



II 



CH 2 

 *CH . NH 2 



COOH 



Histidine 



F. Knoop and A. Windaus, 3 through further investigations, have shown 

 this constitution to be correct. The compound is lasvorotary and has an 

 alkaline reaction. 



Only three di-amino acids are, as yet, known. These are lysine, arginine, 

 and di-amino-tri-hydroxydodecoic acid. The constitution of the latter is not 

 yet determined. It was separated from casein by Emil Fischer and Emil 

 Abderhalden. 4 There are many indications that it, or other closely allied 

 substances, occurs in other proteins. 



Drechsel 5 first isolated lysine. He noticed in the decomposition of 

 casein by hydrochloric acid that other substances besides ammonia and 

 mono-amino acids were formed, which possessed a strong basic character. 

 Among these lysine was found. Drechsel concluded that it was probably 

 a di-amino-caproic acid. Ellinger 6 proved that this supposition was 

 correct. He allowed putrefactive bacteria to act on lysine, and after a 

 while obtained pentamethylenediamine (cadaverine). Ladenburg has 

 shown 7 that cadaverine has the following constitution: 



CH 2 . CH 2 . CH 2 . CH 2 . CH 2 



b 



Cadaverine 



A. Kossel: Z. physiol. Chem. 22, 177 (1896-97); Sitzber. Akad. Wiss. Berlin, 1896. 

 H. Pauly: Z. physiol. Chem. 42, 508 (1904). 



F. Knoop and A. Windaus: Hofmeister's Beitr. 7, 144 (1905); 8, 407 (1906). 

 Fischer and Abderhalden: Z. physiol. Chem. 42, 540 (1904). 



E. Drechsel: Ber. 21, 117 (1889); Arch. Anat. Physiol. 1891, 254. E. Schulze and 

 E. Winterstein: Ergebnisse Physiol. (Asher and Spiro), 1, 32 (1902). 



8 A. Ellinger: Z. physiol. Chem. 29, 334 (1902). Cf. Ber. 31, 3183 (1899); 32, 3542 

 (1900). 



7 Ladenburg: ibid. 19, 780 (1886). 



