AFTER-EFFECTS OF IRRADIATION OF DNA 



Table II. — Effect of X-rays on adenositie-5' -phosphate 



Adenosine-5' -phosphate (initial) 

 Same after 1 0,000 r 

 Same + 16hr standing . . 

 Same after 1 00,000 r in Nj 

 Same -\- 16hr standing 



Same after 1 hr 

 hydrolysis with HgSO^ 



0-34 

 0-48 

 0-48 

 2-04 

 1-92 



phosphate is however comparatively small and of the same order as the 

 amount of phosphate liberated during the irradiation. Similar results 

 have been obtained after treating adenosine-5'-phosphate with photo- 

 chemically generated hydroxyl radicals [Table III). 



Table III. — Effect of photochemically produced OH radicals on adenosine-5' -phosphate 



It can be concluded that treatment with X-rays or OH radicals does pro- 

 duce some phosphate which is more easily hydrolysed by acids, and that 

 this labilization is due either to the removal of the purine or to a partial 

 oxidation of the sugar. In neutral solution the rate of the hydrolysis is 

 rather small. 



IVe are indebted to Mr. E. W. Johns for assistance in some of the analyses, and to Dr. M. 

 Ebert for the irradiations with large doses of X-rays. 



This investigation has been supported by grants to the Chester Beatty Research Institute 

 from the British Empire Cancer Campaign, the Jane Coffin Childs Memorial Fimdfor Medical 

 Research, the Anna Fuller Fimd, and the National Cancer Institute, National Institutes of 

 Health, U.S. Public Health Service. 



REFERENCES 



1 Butler, J. A. V. and Conway, B. E. J. Chem. Soc. 1950, 3418. 



2 Conway, B. E. Brit. J. Radiol. 1954, 27 42 ; Nature, Lond. 1954, 173 579. 



3 ScHOLEs, G. and Weiss, J. Nature, Lond. 1953, 171 920, 1153. 



4 Butler, J. A. V. and Conway, B. E. Proc. Roy. Soc. 1953, 141 562. 



48 



