THE rROTETNS OF :\rTrRO -OKfl ANT.SMS 333 



c\*tidylic acid. 



=C.NH, 



CO CH 



I I! 



R.N CH 



and iiridvlic acid, 



XH CO 



I I 



CO CH 



I II 



R.N CH 



The group R is ribose-3-phosphate, 



-CH.CHOH.CH.CH.CHaOH 

 I OH 



I / 



- P = 



\ 



OH 



The animal nucleic acids (often called th\Tiionucleic acids 

 because they were first isolated from the thymus) are 

 built up of desoxyriboguanylic acid, desoxyriboadenylic 

 acid, desoxyribocytidylic acid and desoxyribothjTnosine 



NH— CO 

 phosphoric acid, ^'<^ C.CH3 . Tn these nucleic acids 



R.N CH 







the group R is 2-desoxyribose, — cH.CHa.CHOH.CH.CHgOH, 



carrying a phosphate group whose position of attachment 

 is still unknown. 



If the nucleic acids are subjected to alkaline hydro- 

 lysis the phosphate group is split off and the corresponding 

 nucleosides are formed. The nucleosides are ribosides 

 or desoxyribosides of guanine, adenine, cytosine, uracil 

 or thymine (methyl uracil). It is seen, then, that the 

 nucleic acids consist of phosphoric acid, a pentose, two 

 purine bases, guanine and adenine, and two pyrimidine 



