300 ZACHARIAS DISCHE 



published suggest that the chromogen is more labile than that of the di- 

 phenylamine reaction, and that the presence of even small amounts of 

 proteins makes the determination more laborious. As in this reaction the 

 pyrimidine nucleotides seem to react as well as purine nucleotides, it may 

 prove useful for the detection of breakdown products of DNA. The car- 

 bazole reaction could be used for the same purpose. Although the latter is 

 less specific than the tryptophan reaction and is strongly interfered with by 

 glucose, it is less affected by proteins. The reaction with indole and HCl in 

 Ceriotti's modification appears of interest, as it makes possible quantitative 

 determinations on about 10 times small amounts of material than all the 

 other methods. The use of this method in combination with special micro- 

 techniques like that of Steele et al}^ may make it possible to determine 

 DNA in quantities below 1.6 jug. per. cc. The lesser specificity, however, of 

 this reaction and the lack of sufficient data about its application for the 

 quantitative determination of nucleic acids in tissues and of the effect of 

 proteins on the reaction suggest caution in its use. The availability of sev- 

 eral color reactions of 2-deoxy pentose which differ in their mechanism, 

 specificity, and in the degree of interference from other substances is of 

 particular advantage, as far as detection and identification of DNA and 

 its derivatives in living cells is concerned. The uncertainties inherent in the 

 use of color reactions for this purpose are largely eliminated by checking, 

 on a quantitative basis, the results of one of these reactions by those ob- 

 tained from several other ones.'^* 



2. Reaction of Ribonucleic Acids 



All reactions of ribonucleic acids based on the sugar component, so far 

 published, are general reactions of pentoses. Three such reactions were 

 tested for quantitative determinations of PNA. 



a. Orcinol Reaction 



This reaction was recommended in two different forms — ^one, using FeCls 

 as catalyst, by Bial,^^ and one using CuCl2*^ which was employed for the 

 determinations of ribonucleic acids and its nucleotides by Massart and 

 Hoste.^* The Bial reaction, first used by Embden and Lenhartz'^ for white 

 light colorimetry of free pentose in 1924, was adapted for quantitative 



"» The reaction of DNA with phloroglucinol described by H. v. Euler and L. Hahn 

 (Arch, neerl. physiol. 28, 398, 1946) appears to be 20 times less sensitive than the 

 diphenylamine reaction and does not seem to offer any advantage as compared 

 with other reactions of DNA. 



'2 M. Bial, Deut. med. Wochschr. 29, 253; 29, 477 (1903). 



" H. Barrenscheen and A. Peham, Z. -physiol. Chem. 272, 81 (1942). 



^* L. Massart and J. Hoste, Biochim. et Biophys. Acta 1, 83 (1947). 



36 G. Embden and E. Lenhartz, Z. physiol. Chem. 201, 149 (1931). 



