184 ASPECTS OF BIOCHEMICAL EFFECTS 



fragments of variable dimensions. It seems to me that there may be a 

 possibiHty of a different interpretation of their experimental results. 

 One would not expect a demonstrable change in the chemical properties 

 of the 3 per cent solution with the dose of x-rays applied. The marked 

 effect, however, of the change in viscosity seems to. point rather to a 

 self-propagating reaction of a physicochemical nature whereby the fric- 

 tional resistance of the dispersed phase is governed by a zeta potential 

 undergoing changes in response to radiation. In that case the viscosity 

 of the nucleic acid particles is a result of the charged water layer, and 

 the change in viscosity would not necessarily be due to a change in the 

 ratio of the longitudinal and transverse axes of the particle; furthermore, 

 the loss of streaming birefringence which was observed could be attrib- 

 uted to the inability of orientation under the influence of changes of 

 charge. In the same direction of a colloidal phenomenon lies the change 

 in the ability to precipitate out of alcohol solutions. In short, the so- 

 lution of nucleic acid would have undergone a change in the direction 

 of becoming more hydrophil. 



This interpretation of these experiments on the viscosity of nucleic 

 acid leads to the consideration of a more physicochemical nature, refer- 

 ring to colloidal systems, surface membranes, and cell structures, all of 

 which may play a vital part from the biochemical point of view. We 

 do not know enough about the state in which enzymes occur within cells, 

 but we do know that certain enzymes are firmly linked to surfaces and 

 cannot be removed, whereas others are easily extracted. We can be 

 pretty certain that some enzymatic reactions proceed on active surfaces, 

 and it seems to me necessary to try to get much more information about 

 the effect of radiation on surface-catalyzed reactions as well as the ef- 

 fect on the surfaces themselves. I would also mention in this respect 

 the well-known hemolytic action of x-radiation on red-blood corpuscles, 

 which obviously means some alteration of their protein-lipoid envelope, 

 and the puzzling investigations by Crowther and Liebmann (15) and 

 Gray, Read, and Liebmann (16) on the effect of radiation on graphite 

 suspensions and colloidal gold solutions. They observed, after irradi- 

 ation with a few roentgens, precipitation followed by alternate zones of 

 suspension and precipitation of the particles when the radiation dose 

 was increased. 



Before I proceed to draw special conclusions on what may happen 

 within the cell, I want to summarize briefly what I have mentioned so 

 far. We have dealt mainly with the results of test-tube experiments 

 on the direct and indirect action on vital substances occurring in cells, 

 such as enzymes, nucleic acids, amino acids, and proteins. We have 

 seen that as a result of irradiation the destruction of the activity of 



