PRODU( rS OP HYDROLYSIS OF PROTEINS. 20 



Four purine bases are obtained in which substitution occurs only in 

 pyrimidine ring ; thee arc — 



Hypo-xauthine, .... 6-oxy-puTme. 



Xanthine, . . . 2-ti-dioxy-i)urinc. 



Adenine, .... 6-amino-purine. 



Guanine, . . . 2-amino-ti-oxypurine. 



The nucleic acids are derivatives of purine bases, being compounds in 

 which a phosphoric acid radicle is condensed in the 8 position. 



Uric acid, which is excreted by the kidneys, has the composition of 

 8-oxy-xanthinr. 



*M. Pyrimidine derivatives. 

 Three pyrimidine derivatives are obtained from the nuclco-protems ; — 



Uracil, . . . 2-ii-dioxy-pyrimidine. 



Cytosin, . . 2-oxy-O-amino-pyrimidine. 



Thyniin, . 2-ij-dioxy-.5-methyl-pyrimidine. 



N. ( Uucosamino. 



H H OH H 



I I I 1 



OH.,(()H) — C — C — C — C — CDH 



1 I I I 



i)H OH H NH, 



is obtained from the gluco-pnilein.s. 



(ilyeiue. Monoclinic crystals, soluble in 4'3 piirts cold water. 

 Nearly iusdluble in alcohol. M.P., i'i± to 2:3(i C, wjtli dark 

 purple colour. Best obtained by the action of ammonia on 

 mono-chlor-acetic acid, or by the hydrolysis of i^lue. 



Alanine. Xccdlos. Soluble in I'G jiarts cold water. Nearly 

 insoluble in alcohol. ^lay be prepared from 2 parts aldehyde- 

 ammonia and 1 part hydrocyanic acid with excess of HL'l. 



Leucine. Volatilises at 210" to 22o C. without melting', or 

 melts in a closed tube at 27t)" C. Moderately soluble in water, 

 and crystallises in soft nacreous scales consistinu of concentrically 

 j;i-ouped rhombic prisms. 



Serine. Bunches of monocliuic crystals soluble in 32 parts 

 water at 10" and 24 at 20" C. Insoluble in alcohol. Active 

 form polarises + 6, and the Ifevo-form occurs in proteins. 



Asi)artic acid. Prepared by the hydrolysis of asparagiu, or 

 it may be separated from beet molasses. Polarises to the left 

 in water, and to the right in stron>> acids. Very soluble in hot 

 water, and little so in cold. 



Glutamic acid. Khombic-spheroidal-hemihedric crystals, melts 

 with decomposition at 2U2 to 2025 (.'. One part soluble in KX) 

 parts water at 16" C. ; less soluble in alcohol. May be prepared 

 by heatinu casein with HCl and ZnCL. 



* It is not cert.iin whether purine or pyrimidine derivatives occur in 

 milk proteiTi':. 



