ISOLATION AND COMPOSITION OF DEOXYPENTOSE NUCLEIC ACIDS 



343 



TABLE III 

 Apurinic Acid from Calf Thymus Sodium Deoxyribonucleate* 



Preparation No. 

 1 2 



Nitrogen, % 6.0 6.8 



Phosphorus, % 10.7 10.6 



Color yield with diphenylamine as % of standard DNAj 108 95 



Moles per 100 g. -atoms of Pt 



Adenine 

 Guanine 



Total purines 



Thymine 



Cytosine 



27 

 20 



27 

 20 



Thymine 

 Cytosine 

 Phosphorus 



89 

 89 

 89 



100 



101 



96 



* The figures refer to the dry preparations. 



t The values are corrected for the loss in weight due to the removal of purines. 



t When large amounts of hydrolysate are analyzed, between 1.2 and 1.3 mole % of 5-methylcytosine is 

 found and minute residues of adenine (0.5-1 mole %) and guanine (1 mole %). 



nucleotides now are occupied by nonglycosidic deoxyribose phosphate units 

 which react as free aldehydes. When comparison is made on the basis of 

 P content, the color yield of the reaction of apurinic acid with diphenyl- 

 amine is almost identical with that given by deoxypentose nucleates.^-* 

 [Compare Dische, Chapter 9.] 



The absorption spectra of the sodium salt of apurinic acid and of calf 

 thymus sodium deoxyribonucleate are compared in Fig. 3. The absorption 

 maximum is at 267 to 268 m/x with an e(P) of 4600 to 4800, the minimum 



"' A previous statement'^" • '" that apurinic acid gives a greater color yield with di- 

 phenylamine than the corresponding quantity of deoxyribonucleic acid is incor- 

 rect. It was due to an error in the computation of a conversion factor. 



