358 



ERWIN CHARGAFF 



TABLE XI 



Purine and Pyrimidine Contents of Sodium Deoxypentose Nucleate 



Preparations from Wheat Germ 



Proportions in moles of nitrogenous constituent per 100 g. -atoms of P 



in hydrolysate, corrected for a 100% recovery.* 



* Compare footnotes in Table VII. 



References 



°- G. R. Wyatt. Biochem. J. 48, 584 (1951). 



^ G. Brawerman and E. Chargaff, J. Am. Chem. Soc. 73, 4052 (1951). 

 " S. G. Laland et al., J. Chem. Soc. 1952, 3224. 

 R. O. Hurst et al., J. Biol. Chem. 204, 847 (1953); ion-exchange chromatography of mononucleotides. 



12-16 in Table XII) belong to this type. Even more remarkable, perhaps, 

 is the good agreement in the analytical results on 5 strains of E. coli (Nos. 

 5-9). The composition of the T2, T4, and T6 phages, based on the work of 

 Wyatt and Cohen, '^^ is shown in Table XIII. Attention should also be 

 drawn to a study of the composition of a series of insect viruses in which, 

 again, all three types of deoxypentose nucleic acid appear to have been 

 encountered.^*^ 



It should be mentioned that only in a few cases a statistical interpretation 

 of the significance of the analytical findings has been attempted."' ^'^^- "^' ^^' 

 The conclusions with respect to the mammahan nucleic acids have been 

 mentioned before. In a similar study of the nucleic acids of four different 

 sea urchin genera'"^ (compare also the work on the effect of these prepara- 

 tions on developing sea urchin eggs^*®) it was concluded that the differences 

 in the composition of the preparations from Echinocardium, Psammechinus, 

 and Paracentrotus (Nos. 15-17 in Table X) were not sufficient to permit a 

 distinction, but that the preparations from Arbacia lixula (No. 13) differed 

 significantly from the others. 



VIII. Fractionation of Deoxypentose Nucleic Acids 



1. Gener.\l 



Some of the criteria on which a decision on the difference or identity of 

 macromolecules of an ostensibly identical composition must be based have 



"6 S. Horstadius, I. J. Lorch, and E. ChargafT, Exptl. Cell Research 6, 440 (1954). 



