16:7/ Molecular Action of Ionizing Radiations 313 



TABLE I (continued) 



* G value is the number of molecules 

 reacting per 100 ev. All for x 

 irradiation in aerated solutions. 



After E. S. G. Barron, "Effect of Ionizing Radiation on Systems of Biological 

 Importance," Annals of the New York Academy of Sciences 59: 575 (1955). 



7. Summary 



Exposures of proteins and nucleic acids to ionizing radiations have shown 

 that all of these molecules may be altered with sufficient dosages. The 

 similarity between the damages observed in proteins and nucleic acids, 

 and those in synthetic high polymers, has been emphasized. These 

 damages include: direct and indirect effects; crosslinking and scission; elimi- 

 nation of small molecules; and energy transfer. All play an important 

 role in the irradiation of living matter by ionizing particles. 



The data on the irradiation of dried protein films have also contributed 

 to our knowledge of the physical properties of these proteins. However, 

 the net return of knowledge has been very small, being limited to an 

 indication of energy transfer and the relative sensitivity of the proteins to 

 ionizing radiations. In this respect, the methods of X-ray analysis 

 discussed in the previous chapter have been much more rewarding. 

 Similarly, the approaches presented in the following two chapters, while 

 dealing with a quite different aspect of proteins, namely enzymatic 

 activity, have shown far more about the physiological role of proteins 

 than has been discovered in experiments using radiation damage. 



