25 



it does not affect the argument. 



CHARGAFF: You may remove 10 percent of the water from all mole- 

 cules or you may remove 100 percent from a part of the molecule and keep the 

 other part hydrated. 



PLATZMAN: But if that hydrated water is different from the semi- 

 liquid water that he removed, it does not matter. 



COHN: If you have this water which is not diffusable and is part of the 

 crystalline structure of the dried nucleic acid or protein, might it not contribute 

 to the sensitive volume? Might it not be connected so intimately with the struc- 

 ture that it obeys all of the things that you are talking about so that you would 

 not be able to distinguish an indirect effect from a direct effect because it would 

 contribute to this molecular volume? 



POLLARD: That is right. I agree. The only thing is, you see, there 

 would still have been ionization taking place within the molecular structure. The 

 water would have been part of the molecular structure. 



PLATZMAN: If one wished to take the water out of ethyl alcohol, he 

 could convert it to pure absolute alcohol. A harsh critic, however, might point 

 out that the formula is still C^H^O, and insist that the true anhydrous form is 

 ethylene. It seems to me that a little of this kind of thinking might be read into 

 Chargaff's objection. 



CHARGAFF: I don't think you can apply the conception of absolute 

 alcohol to extend it to something like an absolute protein. I think there is an es- 

 sential difference. 



PLATZMAN: There is also an essential difference between isolated 

 water molecules bound into a foreign structure, and a liquid drop of water. 



POLLARD: Let me direct a question to either Dr. Zirkle or Dr. 

 Tobias. You have a diffusion theory of radiobiological action, which really is 

 an extention of what I have mentioned here. Don't you feel that you have to have 

 a medium through which the diffusion can take place? 



TOBIAS: When you expose the proteins and virus particles to radia- 

 tion, you take elaborate pains to assure that these materials should be dry, that 

 they should contain as little water as possible. Yet, when you test for the effect 

 after irradiation, you actually place your dry molecules in aqueous medium 

 again. Do you have any evidence at all that the effects, denaturation, inactiva- 

 tion, or change in structure occur immediately after exposure and still in the 

 dry state, or do they occur when you resuspend the molecules in water? 



POLLARD: I am sure the effects occur when we put the preparations 

 into water, for the most part. We have looked for spectroscopic changes. The 

 last case at which we looked was hemoglobin. Appleyard did this work on 

 hemoglobin (8) and expected to find spectroscopic changes in the dry state. He 

 used a quartz slide where everything could be observed. The largest effect does 

 seem to occur when the material is put in water. The only thing I can say is that 

 my whole concept has been that although there is a rejoined bond of some kind, 

 this rejoined bond actually won't produce any change in the over-all ultraviolet 

 absorption spectrum because ninety-nine percent of the usual bonds are still 

 there. However, this 100th bond will affect the biological action. That you can- 

 not see until the material is in water. So water does play a part in the effect. 



