46 A. G. PASSYNSKY 



indivisible relation between the spatial and temporal organization of 

 metabolic processes. 



The action of radiation on open systems, like that of other extex'nal 

 factors, consists, in general form, in a disturbance of the stationary 

 state of the system which, within a definite range of changes, can be 

 compensated by the open system, while for more extensive changes it 

 becomes impossible to estalilish a ncAv stationary state and the system 

 is degraded. The specific peculiarity of the biological action of I'adia- 

 tions, however, when compared with other jihysical factors, is their 

 ability to induce considerable physiological disturbances or even the 

 death of the organism by small amounts of energy. The lethal dose for 

 mammals (500 to 600 r) is known to correspond to the absorption of 

 energy which, by heat equivalent, would cause a temperature rise of 

 only some 0-002°C. But most of even this small amount of the absorbed 

 energy does not have a lethal effect. For example, with a dose that pro- 

 duces an average of about 1,000 ionizations in each yeast cell, only some 

 10 per cent of the cells perish. It is beyond any doubt that so far as the 

 effect of radiation is concerned the total amount of either chemically or 

 structurally changed polymer molecules — such as proteins, nucleic acids 

 — per cell is many times greater than that of changed molecules which 

 effectively determine radiation damage to the cell. 



By means of trivial physico-chemical methods (viscosity, electro- 

 phoresis, solubility, absorption spectra, etc.) the action of radiation on 

 protein solutions can be detected only with very heavy irradiation 

 doses, (75,000 to 100,000 r and higher). A new, isotopic method for the 

 investigation of protein changes on radiation, has been developed in 

 our laboratory. This is based on the ability of irradiated protein to 

 show an increased binding of some organic substances, including 

 35S-labelled methionine (Passynsky et al. 1955). The high sensitivity 

 of the isotopic procedure has enabled us to lower considerably the 

 threshold of the observed action of radiations. 



In most experiments 30 mg of protein was dissolved in 1 ml of borate 

 buffer (M/15, pH 8-5), and 0-5 ml. of an aqueous solution of 35;^- 

 methionine (about 30,000 to 50,000 counts per min per ml of the 

 mixture) was added to the solution. After irradiation the protein was 

 precipitated with an equal t^ohime of 10 per cent TCA, and the pre- 

 cipitate washed on a filter 50 times with a mixture of equal volumes of 

 10 per cent TCA and borate buffer; the constancy of the specific 

 activity of the precipitate served to control the procedure. Thereafter 

 the precipitate was dried and its activity measiu'ed on an end-window 

 counter (evaluated per 10 mg of dry protein precipitate). It was shown 

 in this way that appreciable molecular changes in protein (in 0-1 per 



