286 ZACHARIAS DISCHE 



tumors, very large discrepancies are encountered between determinations 

 based on phosphorus and those based on other constituents. Recently, 

 several sensitive color reactions for the purine and pyrimidine bases were 

 developed. These reactions have not yet been sufficiently used and tested 

 as to their suitability for the determination of the bases in nucleic acids 

 and tissues. More widely used and better tested are methods using color 

 reactions of the sugars of nucleic acids. Because of the fundamental dif- 

 ference in the nature of the respective sugars in the ribo- and deoxyribo- 

 nucleic acids, the methods based on characteristic color reactions of these 

 sugars do not require any separation of the two types of nucleic acids, and 

 are therefore less tedious and simpler in operation. 



I. Color Reactions of Nucleic Acids and their Constituents 

 Based on Reactions of Their Sugars 



Of the two types of nucleic acid, deoxyribonucleic acid contains in all 

 its nucleotides 2-deoxyribose in the furanoid configuration, while the nucleo- 

 tides of the pentose nucleic acids were shown to be ribofuranosides. [Cf. 

 Chapters 2 and 4.] The color reactions of the two types of nucleic acid 

 based on the sugar components are therefore general reactions of the 2- 

 deoxypentoses or pentoses, respectively. 



1. Color Reactions of Deoxyribonucleic Acid and Its Nucleotides 



Among the color reactions of 2-deoxypentoses so far described three 

 groups can be distinguished. One represents a type of reaction character- 

 istic for aldehydes and is due to the fact that 2-deoxypentose, in contrast to 

 other saccharides, is present in solution largely in its aldehydic form.^ A 

 second group is represented by a type of reaction given with varying in- 

 tensity by various hydroxy and keto aldehydes; and a third by reactions of 

 furan derivatives which are formed from saccharides. It seems noteworthy 

 in this connection that the ring form of 2-deoxypentose can, by simple 

 dehydration, produce furfuryl alcohol, while the straight chain form of the 

 sugar by a simple dismutation between carbon 3 and 4 can be transformed 

 to a highly reactive compound, the w-hydroxylsevulic aldehyde. On the 

 other hand, the transformation of pentoses to the corresponding furan 

 derivatives is probably preceded by an inner rearrangement of the molecule 

 consisting of a dehydration and double bond formation between carbons 2 

 and 3,* and proceeds, therefore, less easily than the formation of furan 

 derivatives of 2-deoxypentose. 



3 N. G. Overend, J. Chem. Soc. 1950, 2769. 



*M. L. Wolfrom, R. D. Schuetz, and L. F. Cavalieri, /. Am. Chem. Soc. 70, 514 

 (1948). 



