STRUCTURE OF THE NUCLEIC ACIDS 179 



neutral water under pressure, phosphoric acid may be split off from 

 this substance and Guanosine or the nucleoside of guanine is produced. 

 The /3-Nucleoproteins are, therefore, compounds of protein with a 

 mononucleotid, while the normal or a-Nucleoproteins are compounds 

 of protein with a tetranucleotid. 



Inosinic Acid is prepared from meat-extracts by converting it into 

 the barium salt which is very sparingly soluble in water. On hydrol- 

 ysis with acids it yields phosphoric acid, a-ribose and Hypoxanthine 

 in molecularly equivalent proportions. It will be recollected that 

 hypoxanthine may be derived from adenine by simple deaminization : 



N C N ' )CE + NH 3 



N C r * 



Adenine. Hypoxanthine. 



so that inosinic acid is a derivative of a simple mononucleotid con- 

 taining adenine. The fact that the mononucleotids in animal tissues 

 yield a-ribose on hydrolysis while the tetranucleotid, Thymus Nucleic 

 Acid, which is characteristic of animal tissues yields levulinic acid 

 winch must be derived from a hexose radical, leads us to infer that 

 the mononucleotids which are found in animal tissues are derived 

 from a vegetable source and are possibly not synthesised by animal 

 tissues at all, but formed by partial hydrolysis and subsequent modi- 

 fication of plant nucleic acids received in the food. 



By very careful hydrolysis with acids, interrupting the process 

 before it is complete, it is possible to split off hypoxanthine from 

 inosinic acid, leaving a compound of phosphoric acid and pentose. On 

 the other hand, by neutral hydrolysis under pressure, phosphoric acid 

 is split off leaving the pentose combined with hypoxanthine. It is 

 evident, therefore, that in this mononucleotid the carbohydrate radical 

 occupies a middle position, linking together the phosphoric acid on 

 the one hand and the purine base on the other. This will be clear from 

 the following schema: 



by neutral hydrolysis 

 Phosphoric aci d pentose hypoxanthine 

 by acid hydrolysis 



we shall see that the arrangement of the radical in other mononucleotids 

 is probably of the same type. 



