62 L. A. BLUMENFELD AND A. E. KALMANSON 



2. A protective action of water was discovered; the yield of radicals 

 was halved as the water content of the irradiated seeds increased from 3 

 per cent to 10 per cent. This protective action, accoixling to the anthors, 

 is connected with the greater possibility of recombination between free 

 radicals as the water content in the samples is increased. 



3. Some protective action of water was also observed by the anthors 

 in expei'iments on the germination of irradiated seeds of diffei^ent 

 hnmidity. In these experiments seeds of lower water content perished 

 if iiTadiated by smaller doses. 



4. ESR studies of the rate of decay of free radicals in samples of 

 different water content showed an exponential decrease, the coefficient 

 before the exponential factor being larger for samples of higher water 

 content. 



The work of the Ehrenbergs and Zimmer successfully combines the 

 possibilities of new physical methods and ordinary radiobiological 

 experiments, and thus help to approach one of the most debatable 

 problems of radiobiology — the problem of the direct and indirect (with 

 water px'esent) action of irradiation. 



Any theory that takes into account the participation of the low mole- 

 cular products of water radiolysis must consider the extremely high 

 reactivity and short life-time of these products at the temperature of 

 living cells. It would be right to mention, that according to the ESR 

 data atomic hydrogen can be observed in irradiated ice only at liquid 

 helium tempei'atures, and the free OH radical only at liquid nitrogen 

 temperatures. 



We shall now proceed to give an account of our own exj^eriments and 

 of some general conclusions which we believe can be drawn from them. 

 First of all it must be pointed out that we used ionizing radiation just 

 to obtain and accumulate unpaired electrons in biological structures of 

 increasing complexity and different native states and not at all for the 

 investigation of the initial radiochemical aspects of radiobiological 

 problems. We hoped that the investigation of ESR spectra in such a 

 system would help us to find out what structural peculiarities give rise 

 to the surprising activity of biological structures. 



We proceeded from the general hypothesis that the important role of 

 free electrons in a number of most important biological processes is 

 connected with energy migration within the biological structures. 

 Initially we supposed that enzyme action and muscle contraction be- 

 longed to such phenomena. It is quite clear, however, that all our results 

 are also closely related to the nature of initial radiation-induced effects. 



Having these general considerations in mind in 1955-1957 we 

 systematically investigated a wide range of iri'adiated biological objects : 



