FREE DEOXYRIBONUCLEOTIDES IN RADIATION DAMAGE 



155 



Table 1. The effects of some fractions of chick-embryo extract on DNA 

 synthesis in bone-marroir suspensions from irradiated guinea-pigs 



Experinieiit 1. Fraction addod 



Relative specific 



activity of DNA- 



pho sphorus : 



No extract 



0-6 X HClOi (acid-soluble) extract 



Acid-soluble extract passed through a cohunn of Dowex 50, 



H"-form, and eluted with water 

 Acid-soluble extract passed through a cokunn of Dowex 2, 



acetate forin, and eluted with water 

 Acid-soluble extract, after adsorption on charcoal and elution 



\\'ith water 



100 

 112 



156 



104 



92 



Experiment 2. Fraction added 



Relative specific 

 activity of DNA- 

 thyinidylate-phos- 

 phorus : 



No extract 



Ringer-solution extract 



Acid-soluble extract 



Acid-soluble extract, passed through a column of Dowex 50, 

 H*-form and eluted with water 



Acid -soluble extract, jDassed through a column of Dowex 2, 

 acetate form and eluted with water 



Acid-soluble extract, bound by a column of Dowex- 2, acetate 

 form, and eluted with 0-5 N HCl, the eluate adsorbed on char- 

 coal and eluted with jayridine, the pyridine distilled off 



100 

 244 

 145 



189 



140 



250 



Experiment 3. Fraction added 



Relative specific 

 activity of DNA- 

 phosphorus : 



No extract 



Ringer-solution-extract 

 Acid-soluble extract 



The acid-soluble extract was passed through a column of 

 Dowex 2, Cl'-form, the fractions were obtained by elution 

 with water and increasing concentrations of chloride 

 (according to Cohn) adsorbed on charcoal, eluted with 

 pyridine and the pyridine was distilled off under reduced 

 pressLU'e : 



Eluted with water 



Eluted with 0-OlN NH4 CI 



Eluted with 0-01 N HCl 



Eluted with 0-OlN HCl + 0-02 N NaCl 



Eluted with 0-01 N HCl + 0-02 N NaCl 



Eluted with 1 N HCl 



100 

 123 

 123 



not tested 

 not tested 

 157 

 119 

 219 

 146 



The fractions were all adjusted to the same volume equal to that of the original 20 per 

 cent chick embryo-extract and each of them was tested by addition of the same volume 

 to the suspension of irradiated bone-marrow, incubated in the presence of 3-P-phosphate. 



