PROTOPLASM 17 



In most, iso-amino-caproic acid, or leucin, is the most 

 abundant, and in disintegrative diseases of the liver, such 

 as acute yellow atrophy, it may appear in the urine, 

 separating out as oily-looking spherules. 



Some of the mon-amino acids split off from the protein 

 molecule attached to the benzene ring, or to the benzene ring 

 linked to a pyrrol ring. In Trsrptophan, amino-propionic 

 acid (Alanin) is linked to such a complex — 



H NH„ 



I Til 



-C-C— C— 0— H 



In tyrosin, alanin is linked to an hydroxy benzene ring. 



H NH 



or/ 



Like leucin, it may appear in the urine in disintegrative 

 diseases of the liver. It takes the form of rosettes of 

 acicular crystals. 



2. Di-amino Acids, — In most proteins, the di-amino acids 

 are less abundant than the mon-amino. But, in a simple 

 form of protein, which occurs linked with nucleic acid in 

 the heads of spermatozoa, called by Kossel protamine, these 

 di-amino acids constitute about 80 per cent, of the molecule. 

 They are — 



Lysin — di-amino-caproic acid. 



Arginin — amino-valerianic acid linked to guanidin 

 (p. 209). 



Histidin — amino-propionic acid linked to the iminazole 

 ring. 



Of these three arginin is the most abundant. 



3. Amides are always present in small amount, linked 

 together as in biuret HgN — CO — NH — CO — NHg, and it is 



