ELECTRON SPIN RESONANCE INVESTIGATIONS 61 



signal characteristic of comiiounds containing sulphur. The doublet was 

 observed in proteins that did not contain sulphur, such as, for 

 example, collagen. 



Signals characteristic of irradiated sulphur-containing amino acids, 

 were observed with those irradiated proteins which contain a consider- 

 able amount of sulphur, such as wool, horn, hoof, and nails. 



No other hyperfine structure in sulphur-containing j)roteins was 

 found by Gordy and his collaborators although all these proteins con- 

 tain enough protons and nitrogen nuclei in various positions. It is 

 known that the magnetic moments of such protons and nitrogen 

 nuclei are responsible for the appearance of the hyperfine structure of 

 irradiated amino acids. 



Gordy was quite right in suggesting a possible migration of "injuries" 

 along the protein molecules towards certain more vulnerable points 

 whose properties in this respect, however, were not made clear. Gordy 

 gives no explanation of the "migration of injuries" in his early work. 



In his later work Gordy develops various assumptions of the possible 

 radio-protective role of sulphur-containing compounds. Such studies 

 are justified and to some extent are connected with the numerous 

 radiobiological investigations on the anti-radiation effect of sulphur- 

 containing substances. 



In spite of numerous experimental data and a quite profound 

 theoretical evaluation of these data from the point of view of quantum 

 chemistry and the ESR theory, we think that Gordy's work has some 

 defects. First, no quantitative estimation is given of radical yields for 

 irradiated biological structures of different complexity and in different 

 native states. The second defect, apparently due to the physical rather 

 than biological treatment of the problems being studied, is that Gordy's 

 group often use proteins without clearly defined biological properties. 



So far as radiobiology is concerned some research paj)ers published 

 by the Swedish scientists Lars and Andreas Ehrenberg (1958) together 

 with the noted German radiobiologist Karl Zimmer (Zimmer, 1960; 

 Ehrenberg and Zimmer, 1956) are far more interesting. In these papers 

 ESR spectra of irradiated seeds and sprouts of different water content 

 were investigated. 



The authors gave a quantitative estimation of the radical yield as a 

 function of the radiation dose, and also traced the rate of decay of free 

 radicals after the irradiation as a function of the percentage of water 

 of the samples. 



The main results of the Ehrenbergs' and Zimmer's work are: 



1. A linear de]3endence of the free radical yield on the radiation dose 

 was established. 



