PENTOSE NUCLEIC ACIDS 17 



from baker's yeast by Magasanik in this laboratory by procedures 

 similar to those used for the preparation of pentose nucleic acids 

 from animal tissues and had not been dialyzed. It will be seen 

 that the results are quite constant and not very far from the 

 proportions required by the presence of equimolar quantities of 

 all four nitrogenous constituents. 



An entirely different picture, however, was encountered when 

 the composition of pentose nucleic acids from animal cells was 

 investigated. A preliminary summary of the results, in all cases 

 obtained by Procedure 1, is given in Table 8. Here guanylic acid 

 was the preponderating nucleotide followed, in this order, by 

 cytidylic and adenylic acids; uridylic acid definitely was a minor 

 constituent. This was true not only of the ribonucleic acid of 

 pancreas which has been known to be rich in guanine^^-^^, but 

 also of all pentose nucleic acids isolated by us from the livers of 

 three different species (Table 8). 



TABLE 8 



COMPOSITION OF PENTOSE NUCLEIC ACIDS FROM ANIMAL TISSUES 



In the absence of a truly reliable standard method for the 

 isolation of pentose nucleic acid from animal tissue, generali- 

 zations are not yet permitted; but it would appear that pentose 

 nucleic acids from the same organ of different species are more 

 similar to each other, at least in certain respects {e.g., the ratio 

 of guanine to adenine), than are those from different organs of 

 the same species. (Compare the pentose nucleic acids from the 

 liver and the pancreas of pig in Table 8.) 



References p. 23 



