328 GENERAL DISCUSSION 



also certain guests who are present here to make l)rief comments and 

 to speak, we shall proceed to the discussion. 



I. Study of electron s])in resonance spectra has shown that the free 

 radicals which are formed at the instant of radiation play a large part 

 in radiation damage. Is it possible to investigate the excited states 

 experimentally ? 



PASSYNSKY : In regard to the question of electron spin resonance, I wish 

 only to caution against an excessively wide interpretation of the data. 



It is possible that the measured effect comprises only a small part 

 of the primary changes, and therefore the method must be developed 

 and measm-ements taken at the moment of irradiation. In radiation 

 conditions many excited molecules are produced without any re- 

 arrangement of the spin or without detachment of an electron ; for ex- 

 ample with the absorption of 3 to 5 eV. Such molecules are capable of 

 many new reactions. I have, in the jjast, put forward the concept of 

 the basic role of the excitation of molecules of protein under radiation 

 conditions. Blumenfeld, whose work on ESR I value highly, said in 

 reply to my question that, in his opinion, the total molecular energy 

 levels for the "conductivity channels" are not in general filled in the 

 native molecules of jirotein and DNi\, and can only be used in enzyme 

 catalysis and irradiation. I agree with him in regard to the irradiation 

 (by ionizing radiations or by u.v. rays), but I do not agree with him 

 on the question of enzyme catalysis. The excitation energy of the pro- 

 tein amounts to about 2-5 eV and the energy of excitation of all the 

 enzymatic reactions to approximately 0-4 to 0-7 eV. This question has 

 been specifically examined by Lowryf and his final conclusion is as 

 follows : 



Enzymes work only in the ground electron state. It is evident that 

 in the normal life of the organism, semi-conductor-like chain reactions 

 do not take place. Under the influence of radiation a transition to an 

 excited state is possible, which must be examined without assuming 

 a simple change in ESR spectra. This important method represents 

 merely one of tlie methods of investigation and must be supported by 

 many others. I think that the measurement of the quenching at low 

 temperatures is very important, provided that chemiluminescence, 

 especially of an oxidizing nature, is excluded. 



t III "The Enzymes", Vol. I. (Paul D. Boyer, Henry Lardy and Karl Myrbaek, eds.) 

 2nd edition, 1959. Academic Press, New York and London. 



