ELECTRON SPIN RESONANCE INVESTIGATIONS 67 



DISCUSSION 



BACQ: You have worked witli absolutely dry proteins. Can you give us the exact 

 temperature and oxygen pressure during the irradiation. 



BLUMENFELD : Irradiation was carried out at room temperature. Oxygen pressure 

 during irradiation was about 10"^ mm Hg. Our samples were freeze-dried at a 

 temperature of — 50°C, ESR spectra were studied both at room temperature and 

 at lower temperatures, down to liquid nitrogen temperature. I did not dwell here 

 on ESK siiectrum changes in irradiated amino acids associated with temperature 

 decrease: it could be the subject of a special report. As for an oxygen effect, it 

 was j)ractically non-existent as far as amino acids and low molecular weight 

 compounds were concerned, but oxygen affected considerably the high molecvilar 

 weight comi^ounds, particularly proteins : the intensity of the ESR signals de- 

 creased considerably on admission of air. 



As to the form of the ESR signals, since we did not perform experiments with 

 irradiation at low temperatures but applied irradiation at a sufficiently high 

 room temperature, we did not observe any changes in the form of the ESR signals. 



ALEXANDER : In our experiments we have observed that when DNA from sperm 

 heads is irradiated at a low temperature, a high yield of radicals occurs. After 

 irradiation at room temperature there is a drop in the radical yield. Our explana- 

 tion was that at high temperatures a recombination of radicals is possible dvie to 

 molecular movements. Could your theory account for this phenomenon? 



blumenfeld: Your observation that during irradiation the radical yield in- 

 creases with the lowering of temperature, is a very interesting one. I believe that 

 it fits in well with our conceptions. For uncoupled electrons to migrate through 

 formed structures, it is necessary that some quite definite structural conditions 

 be fulfilled, which, generally speaking, could be unfulfilled (not realized) in the 

 structure of the proteins and nucleic acids. In order for uncoupled electrons 

 (which are 2p electrons), to migrate through the hydrogen bond system, it is 

 necessary that on all the centres through which they migrate their wave fimctions 

 be parallel. 



This condition may be unfulfilled in molecules of the nucleic acids and proteins 

 at equilibrium configuration. 

 ALEXANDER: May the signal be more intense at low temperatiu'es? 



BLUMENFELD : In Order that semiconductivity properties become manifest, an 

 orderly structure of the hydrogen bonds in protein and nucleic acid molecules is 

 necessary. It is necessary that in proteins all the peptide groups by which migra- 

 tion occurs, should lie in the same plane. If they are oriented at right angles 

 migration is impossible. If they are oriented at different angles, the probability 

 of the migration is proportional to the cosine of the angle. At liquid nitrogen 

 temperatures these conditions may be unfulfilled under equilibrium conditions 

 for all the structm-e. At room temperature owing to vibrational and rotatory 

 movements there always would be moments when different peptide grou]3s are 

 in the same plane and migration may occur. 



passynsky: What is the significance of the g^-factor in all the systems studied? 

 Is it possible to relate the observed intensity of the signals only to the number of 

 the uncoupled electrons, without taking into account their interaction? 



blumenfeld: In all the cases for all the ESR signals in proteins and nucleic 

 acids elicited by the ionizing radiation — I emphasize it — the g^-factor of the 



