58 DEOXYPENTOSE NUCLEOPROTEINS AND PROSTHETIC GROUPS 



100 



■ Adenine + thymine 

 13 Guanine + cytosine 

 m Guanine + hydroxymethyl cytosine 

 T 1 2 3 4 T 1 2 345 



50 



T 1 2 3456 



50 100 50 100 50 100 50 100 

 Calf thymus Pig liver Human spleen Coliphage 76 



Fig, 7. Composition of fractions (in moles per 100 gram-atoms of phos- 

 phorus) prepared by the fractional dissociation of artificial histone com- 

 plexes with the indicated sodium deoxypentose nucleate preparations. 

 Each block represents a fractionation run; the consecutively numbered 

 bars within each block represent individual fractions, with the NaCl con- 

 centration of the solutions employed for extraction rising from left to 

 right. The first column (T) indicates the average composition of the total 

 deoxypentose nucleic acid preparations. The abscissa indicates the propor- 

 tion of original nucleic acid P recovered in each fraction. (Taken from 



Chargaffi.) 



concentrations of adenine and thymine. What should, however, 

 be stressed is that in all fractions the equimolarity of each pair 

 of constituents and of total purines and pyrimidines is fully main- 

 tained. A selection of such fractionation experiments is shown in 

 Fig. 7. 



These findings, fully discussed in the publications cited above, 

 suggest that the deoxypentose nucleic acid of a given cell is 

 composed of a very large number of differently constituted in- 

 dividuals and that it is possible to achieve the resolution of this 

 entire spectrum of structural gradations into several distinct 

 "bands", in which all the regularities characteristic of the entire 

 nucleic acid are maintained. 



