348 GENERAL DISCUSSION 



of the DNA solution amounts to about 50 per cent, whereas for DNP, 

 DNA — CH3NH2 and DNA at pH 2-8. a drop in the viscosity is scarcely 

 observed. DNA with a molecular weight of 10^ or lower is also radio- 

 resistant. The latter were ol)tained by splitting the high polymer DNA 

 by Doty's method. A spectropliotometric investigation of this DNA 

 has shown the absence of differences in the H-bond system in com- 

 parison with the initial DNA with a molecular weight of 6-106. At 

 the same time many reactions, in particular the aj^plication of pH 

 of up to 2-8, do not give rise to any drop in the viscosity of solutions of 

 low molecular weight DNA. Thus, it turned out that in all the cases 

 which were investigated, DNA suitable for "compression'' proves to be 

 mox'e radiosensitive than DNA for which the "compression" occurred 

 before irradiation due to preliminary action. It seems to us that we 

 may draw two conclusions from this: (a) the alteration in the radio- 

 sensitivity of DNP in comparison with DNA is connected with the 

 transition of the DNA under the action of the protein into a configura- 

 tively more stable state, and (b) comjDaratively small doses of radiation 

 produce an alteration in the configuration of the DNA without a marked 

 degradation. The essence of these changes evidently reduces to a natural 

 (peculiar, intrinsic) non-specific "compression" of the DNA macro- 

 molecule. 



As with the complex formation of DNA with protein there will arise 

 not only a configuration change of DNA but also of the protein entering 

 into the complex, the molecule of the protein being somewhat spread 

 out on the surface of the DNA macromolecule. It became of interest 

 to investigate the influence of the DNA on the radiosensitivity of the 

 protein entering into the comj^lex. This problem was studied with the 

 use of artificial complexes of DNA — a-chymotrypsin and in addition 

 it was shown that for doses of 10 to 20 kr for the a-chymotrypsin in the 

 complex with DNA there was a marked inactivation whereas for free a- 

 chymotry psin no fall in the enzyme 's activity is observed. The facts quoted 

 demonstrate that complex formation in some cases reduces and in others 

 increases the radiosensitivity of individual biochemical components. 



kritsky: Tarusov and Mouton in their contributions mention the 

 increase in the autolytic destruction of proteins after X-ray irradiation. 

 An investigation which we carried out on the caterpillars of the bee 

 moth after total X-irradiation by dose of 2 kr shows that autolysis is 

 increased apxDroximately twofold. The ATP content is reduced by 36 

 per cent and the total content of the nucleotides by 33 per cent. Thus 

 the autolysis rate is altered to a greater extent than the concentration 

 of free nucleotides. 



