360 



ERWIN CHARGAFF 



TABLE XIII 



Purine and Pyrimidine Contents of Sodium Deoxypentose Nucleate 



Preparations from E. coli Phages T2, T4, and T6 



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



in hydrolysate, corrected for a 100% recovery.* 



• Compare footnotes in Table VII. HMC = 5-hydroxymethylcytosine. 



References 



" G. R. Wyatt and S. S. Cohen, Biochem. J. 55, 774 (1953). 

 *C. F. Crampton et al., J. Biol. Chem. 211, 125 (1954). 



been pointed out in the preceding section. Strictly speaking, the vaUdity 

 of many of the methods of classical organic chemistry ends with the mixed 

 melting point. Beyond, it will often be a matter of preference or utility 

 what to call identical and what different. If a compound is assigned a 

 mainly mechanical function, its composition, let alone the sequence of its 

 constituents, will appear of little importance. The function of a bag is to 

 hold, of a trestle to support; what they are made of is of no consequence. 

 The biochemical literature, especially that dealing with the proteins and 

 polysaccharides, abounds in falsely generic terms which a profounder in- 

 sight will undoubtedly resolve into many different individuals. Our science, 

 so drunk with dynamics, is slowly learning to pay attention to the motions 

 of the immovable. 



For this reason, attention began to be paid to the question of difference 

 only when specific biological functions were assigned to the nucleic acids. 

 In the light of current conceptions, a preparation of deoxypentose nucleic 

 acid, presumably an important component of the genetic material, could be 

 regarded as consisting of many chemically different, though closely related, 

 individuals, the constant composition of the whole being a statistical reflec- 

 tion of the unchanging condition of the cell. That there is, in fact, little 



