GENERAL DISCUSSION 329 



BLUMENFELD : I entirely agree with Passynsky that the excited electron 

 states do not play any part in the basic, normal biochemical processes. 

 But the fact is that what Me study by the methods of electron spin 

 resonance when enzyme processes are taking place is a ground state 

 and not an excited state. This demands a special discussion, and I will 

 not dwell any longer on this matter. 



In regard to the question of the possibility of utilizing the ESR 

 method in radiobiology, it is necessary to bear in mind that the ESR 

 spectrometer is not an analytical instrument of the spectrophoto- 

 meter type (here a comparison of this kind has been attempted). A 

 correct analysis of the ESR spectra would provide unique information 

 in regard to the places and degrees of localization of the unpaired 

 electrons. The main parameters are the width, form and position of 

 the lines. As an example, let us examine the more detailed work of 

 Alexander and Bacq who have read papers at this symposium. It is 

 impossible to draw any conclusion as to the absence of localization of 

 a free valency in a sulphur atom on the basis of a difference of the 

 external form of the ESR line — of the irradiated serum albumin and of 

 the cysteine. 



The fundamental proof of the localization of an unpaired electron in 

 sulphur lies not in the external shape of the line but in its position, 

 in the magnitude of the gr-factor. 



It is w^ell known from experiment and ESR theory that in the locali- 

 zation of an unpaired electron in the light atoms such as oxygen, 

 nitrogen, carbon and hydrogen, the gf-factor cannot be distinguished 

 from the gr-factor of a free electron by more than several units in the 

 third place. At the same time, in localization in sulphur, the displace- 

 ments of the ^-factor exceed this value more than ten times. Unfor- 

 tunately, the literature quoted does not provide the appropriate data. 

 As far as an alteration in the resolution of the lines at different tem- 

 peratures is concerned, various causes may be responsible for this. 



It is, of course, possible that many injuries to biological macro- 

 molecules caused by ionizing radiation are not connected with the 

 appearance of unpaired electrons. In this case, the ESR method can be 

 of no assistance. The value of the method is determined to a considerable 

 extent by the correctness of the formulation of the problem. We 

 ourselves in our work have used irradiation only as a method of pro- 

 ducing unpaired electrons in the structure and have utilized the valuable 

 information which the ESR method has afforded. 



It is doubtful if one can state today whether the excitation "mi- 

 grates" along the structure and then leads to the disruption of a 

 definite chemical bond or whether the unpaired electron already formed 



