Influence of Oxygen on Radiation Effects 115 



nitrogen, decreased only slightly the inactivation which the 

 addition of glucose induces in air. 



It may be legitimate to conclude that in this particular 

 case the enzyme seems most likely to be radiosensitive when 

 it is in the form of a semiquinone (Kuhn and Wagner- Jauregg, 

 1934; Michaehs, Schubert and Smythe, 1936; Haas, 1937)! 

 These data offer further support to the more general conclusion 

 that (1) the oxygen effect, as already pointed out above, is 

 related to enzymic activity during the actual irradiation; 

 (2) the points of attack within the cell or on an enzyme mole- 

 cule, as well as the damaging agents, differ widely depending on 

 the presence or absence of oxygen. The result will therefore 

 depend on the relative role which the affected group plays 

 in the economy of the cell. 



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