PENTOSE NUCLEIC ACIDS 69 



5. DIFFERENCES BETWEEN PENTOSE NUCLEIC ACIDS 



The demonstration of clear-cut analytical differences in pentose 

 nucleic acids has met with greater difficulties than was true of 

 the deoxypentose nucleic acids. This was in part due to their 

 greater lability, which rendered many of the results obtained on 

 highly purified specimens doubtful, but it was also due to the 

 fact that the spread in individual nucleotide proportions is by no 

 means as great in PNA as in DNA. That there existed great dif- 

 ferences between the ribonucleic acids of yeast and those of pan- 

 creas or liver had, however, been recognized early. The entire 

 problem has been reviewed^. I shall limit myself here to quoting 

 a few typical results from a recent paper in which total pentose 

 nucleoprotein fractions were analyzed under conditions that 

 could not have led to fractionation^. These results will be found 

 in Table 19. 



A comparison between pentose nucleic acids from different 



TABLE 19 



NUCLEOXroE RATIOS IN PENTOSE NUCLEIC ACIDS* 



* Taken from Elson and Chargaff^, with the exception of the results on 

 wheat germ PNA which are taken from Lipshitz and Chargaffio. — Ab- 

 breviations: A, adenylic acid; G, guanylic acid; C, cytidylic acid; U, 

 uridylic acid; Pu, purine nucleotides: Py, pyrimidine nucleotides; 6-Am, 

 A + C; 6-K, G + U. 



References p. 75 



