ISOLATION AND COMPOSITION OF DEOXYPENTOSE NUCLEIC ACIDS 



363 



TABLE XV 



Fractional Dissociation of Nucleohistone Preparations; 



Composition of DNA Fractions 



Moles per 100 g. -atoms P* 



Molar ratios 



• The total average recovery of moles of nitrogenous constituents per 100 g.-atoms of P is given in the 

 first line. The mean proportions of each constituent have been corrected to a 100% recovery. 



stituents and of total purines and pyrimidines — a characteristic feature of 

 all deoxy pentose nucleic acids, as will be discussed later in this chapter — is 

 fully maintained. (See also Table XV.) 



In later studies these fractionation experiments were extended to many 

 nucleic acid preparations from the tissues of ox, pig, and man, from sea 

 urchin sperm, and from the r"^ strain of coliphage T6.'^^ In these experi- 

 ments, and in subsequent studies with pneumococcal transforming prepara- 

 tions, artificially prepared complexes with histone, or in a few cases with 

 globin, served as the starting material. A selection of such fractionation 

 experiments is shown in Fig. 5. The results are in agreement with those ob- 

 tained with calf thymus nucleohistone. 



Of particular interest is the distribution of the pyrimidine satellite 5- 

 methylcytosine in the fractions thus obtained, as shown in Table XVI. It 

 will be noticed that significant divergences in the concentration of this 



