MODE OF ACTION OF IONIZING RADIATIONS 



179 



10 



10 



10 



10° 



10" 10 



Glycine concentration, yug/ml 



Fig. 1. Ionic and absolute NH3 yield from irradiation of glycine by 166,000 r. 

 Points are experimental; curve is theoretical. Arrow represents ionic yield of dry 



glycine. 



by the physical chemist. Since water is so preponderant in the com- 

 position of hving matter, it is reasonable to assume that the indirect 

 mode of action of radiation is of importance, and in fact the majority 

 of experiments have been carried out with solutions. 



It will facilitate the later discussions to recall the main features of 

 the indirect action. They consist of the following characteristics. At 

 very high dilutions the ionic yield D/C is smaller than for moderate 

 concentrations, probably because of competitive recombination of radi- 

 cals (Fig. 2). At moderate concentrations up to about 15 per cent so- 



10 



10 



10 10 10 10' 10 



Enzyme concentration, gm/ml 



Fig. 2. Relative ionic yield for different concentrations of carboxy-peptidase irradi- 

 ated by x-rays. 



