120 AARON BENDICH 



ducible at the dropping mercury cathode, whereas guanine, guanosine, 

 guanyhc acid, cytidine, cytidylic acid, and uracil are not.^^^ This was pro- 

 posed as a method for the quantitative estimation of as httle as one micro- 

 gram of adenine (error ± 2 %) in a hydrolysate of PNA or DNA. (For 

 theoretical and practical aspects of polarography, see Kolthoff and Lin- 

 gane.^^") Pyrimidine, 2-amino-, 6-amino-, 6-hydroxy-, 2,6-diamino-, and 

 4,6-diaminopyrimidine are reduced polarographically whereas derivatives 

 such as thymine, isocytosine, and barbituric acid are not.^^^ From their 

 polarographic behavior, the reducible group of pyrimidines was found to 



involve the • — C^C — C=N — system.^^^ 



KosseP^'"^ found that adenine and hypoxanthine (but not guanine or 

 caffeine) were decomposed upon heating with zinc and HCl, and that the 

 products (the structures of which were not elucidated) turned a ruby-red 

 when made alkahne. This reductive degradation of adenine (and hypoxan- 

 thine) leads to the formation of a diazotizable amine which couples with 

 A''-(l-naphthyl)ethylenediamine to form a red-colored dye^^^-^^^ and is em- 

 ployed for a colorimetric determination of adenine.^^^ Folic acid and ATP 

 are reduced by zinc and HCl and produce a red color, but guanine, cytosine, 

 isocytosine, thymine, and uracil do not.^^^ Hypoxanthine, isoguanine, and 

 xanthine, but not 2 , 6-diaminopurine or uric -acid, are also reduced by zinc 

 and HCl at 100°,^^* and it is quite hkely that the resulting diazotizable 

 amines are 5-substituted-4-aminoimidazoles. 



c. Action of Oxidizing Agents and Ultraviolet Light 



As pointed out above, thymine is oxidized by permanganate to urea, 

 and cytosine to biuret. The KMn04 oxidation to urea^^^-^^^ and to oxaluric 

 acid^^^ has been utilized for the analysis of the isotope content of specific 

 carbon atoms of labeled uracil (see Fairley et aZ.^"). Uracil is also oxidized 

 by ozone in glacial acetic acid, and the products which are obtained are 

 formylglyoxyiurea, oxaluric acid, urea, and oxalic and formic acids.^^^ Hy- 

 drogen peroxide in the presence of charcoal brings about the oxidation of 



3" J. C. Heath, Nature 158, 23 (1946). 



^5" I. M. Kolthoff and J. J. Lingane, "Polarography," 2nd ed., Vols. 1 and 2. Intersci- 



ence, New York, 1952. 

 ^51 L. F. Cavalieri and B. A. Lowy, Arch. Biochem. and Biophys. 35, 83 (1952). 



352 A. J. Glazko and L. M. Wolf, Arch. Biochem. 21, 241 (1949). 



353 D. L. Woodhouse, Arch. Biochem. 25, 347 (1950). 



354 H. G. Koritz and F. Skoog, Arch. Biochem. and Biophys. 38, 15 (1952). 



355 S. Friedman and J. S. Gets, Arch. Biochem. and Biophys. 39, 254 (1952). 

 355 M. R. Heinrich and D. W. Wilson, J. Biol. Chem. 186, 447 (1950). 



357 J. L. Fairley, L. L. Daus, and B. Krueckel, /. Am. Chem. Soc. 75, 3842 (1953). 



358 T. B. Johnson and R. B. Flint, /. Am. Chem. Soc. 53, 1077 (1931). 



