18 CHEMICAL SPECIFICITY OF NUCLEIC ACIDS 



9. SUGAR COMPONENTS 



It is deplorable that such designations as deoxyribose and ribose 

 nucleic acids continue to be used as if they were generic terms. 

 Even the "thymus nucleic acid of fish sperm" is encountered in 

 the literature. As a matter of fact, only in a few cases have the 

 sugars been identified, namely, J-2-deoxyribose as a constituent 

 of the guanine and thymine nucleosides of the deoxypentose 

 nucleic acid from calf thymus, D-ribose as a constituent of the 

 pentose nucleic acids from yeast, pancreas, and sheep liver. 



Since the quantities of novel nucleic acids usually will be in- 

 sufficient for the direct isolation of their sugar components, we 

 attempted to employ the very sensitive procedure of the filter 

 paper chromatography of sugars^^^^^ for the study of the sugars 

 isolated from minute quantities of nucleic acids. It goes without 

 saying that identifications based on behavior in adsorption or 

 partition are by no means as convincing as the actual isolation, 

 but they will at least permit a tentative classification of new 

 nucleic acids. Thus far the pentose nucleic acids of pig pancreas^^ 

 and of the avian tubercle bacillus^^ have been shown to contain 

 ribose, the deoxypentose nucleic acids of ox spleen^^, yeast and 

 avian tubercle bacilli^^ deoxyribose. It would seem that the free 

 play with respect to the variability of components that nature 

 permits itself is extremely restricted where nucleic acids are con- 

 cerned. 



10. DEPOLYMERIZING ENZYMES 



Enzymes capable of bringing about the depolymerization of both 

 types of nucleic acids have long been knovv'n; but it is only during 

 the last decade that crystalline ribonuclease^^ and deoxyribonu- 

 clease^^ from pancreas have become available thanks to the work 

 of Kunitz. Important work on the latter enzyme was also done 

 by McCartyi^. 



We were, of course, interested in applying the chromato- 

 graphic micromethods for the determination of nucleic acid 



