258 



CORNELIUS A. TOBIAS, TOR BRUSTAD^AND THOMAS MANNEY 



Initial work was carried out seven years ago by Birge and Sayeg 

 (1959) and Birge ef al. (1959). Recently Brnstad (1960). Fluke et al. 

 (1961), Manney et al. (1960) and Mortimer and Brustad (1960) have 



> 



o 



a. 



Cl. 



a. 

 O 



Neon 

 2087 MeV 



1 Oxygen 



166-2 MeV 



Carbon 

 24-4 MeV 



A Boron 

 / ^112-5 

 y iMeV - 



1 



Fig. 



70 



Range (mg /cm ) 

 1. — Bragg ionization curves for various accelerated heavy ions. 



been engaged in heavy ion studies at Berkeley and similar work is being 

 carried on at Yale University (Hutchinson, 1960). 



We already know a great deal about the sensitivity of the cell 

 nucleus to the effects of radiation : but we are not yet certain what kind 

 of molecule is the critical species affected and how ionization and excita- 

 tion energy travels within biological material. We suspect that there 

 are chain reactions leading to cell death, yet we have not been able to 

 define these precisely. Until recently it was believed that in the dry 

 state, macromolecules must be aflFected directly by radiation whereas 

 in aqueous systems the existence of indirect mechanisms have been 

 repeatedly demonstrated. The purpose of this investigation is to show 

 that even in dry molecules there is a considerable indirect radiation 

 effect of sufficient magnitude that target theory type calculations may 

 lead to misleading answers. Further we wish to add to the evidence that 

 in aqueous systems even with the heaviest ionizing particles there is 

 still a considerable part of the radiation effect mediated in water. 



IRRADIATION OF ENZYME MOLECULES IN THE DRY STATE 



The technique of mounting dehydrated samples of enzymes, irradi- 

 ating and assaying them has already been described (Fluke et al., 1961) 



