118 



ALLEN: These were experiments in dilute solutions? 



KAMEN: I have forgotten, but I think they were. 



GARRISON: Yes. 



KAMEN: The fact is that they were able to get a variation in the yield de- 

 pending on which radical was dominant. 



ALLEN: That is natural, since he had a different radical. 



KAMEN: But the point is that also in the cell you might have a situation in 

 which the radical population changes from one part of the cell to the next and 

 you could not simply talk about the homogeneous system and use that to speculate 

 about the fate of the ribonucleic molecule. 



There is need for more such studies and they are probably not too difficult 

 to do. 



There is a great need for study of what happens when a simple amino acid 

 is irradiated. What kind of radicals are formed, for instance, and how do they 

 react with the other radicals? 



I brought with me a report on the previous conference held here two years 

 ago and I have looked at it to see what has happened since then with regard to 

 the points that were covered two years ago. At that time there was considerable 

 discussion of the work of Hart (19) on the radical recombination yield for tri- 

 tium betas as compared with alpha rays, and so on . . . The data showed that 

 there seemed to be a variation in total radical yield depending on the ionization 

 density. I understand that has changed now, and the total radical yield does not 

 depend on the ionization density. 



MAZIA: Will you say what this is, Dr. Allen? 



ALLEN: You have no way of telling how many radicals may form and then 

 immediately recombine back to water. Now, the number of radicals that pro- 

 duce any net chemical reaction seems to be about the same for all radiations. 

 However, one would expect that the radicals that go back to water are probably 

 more numerous in the case of densely ionizing radiation than they are in the 

 case of gamma rays. If this is so, you have to say that the total radical yield 

 appears to be larger for the densely ionizing radiations. 



ONSAGER: Could I have a few minutes for elaboration of some most inter- 

 esting ideas about nucleic acid, which Pauling had picked up in England just be- 

 fore he visited us? Pauling told us that the X ray data are compatible with a 

 sort of double coil (See Watson and Crick (20) ). There is purine or pyrimi- 

 dine attached to every sugar. As far as I could make out, Pauling had just two 

 kinds of purines and two kinds offyrimidines. In each layer you would have 

 room for one purine and one matching pyrimidine. Some efforts have been made 

 to check that by analysis and so far the verification is encouraging. 



KAMEN: What nucleic acid is this? 



ONSAGER: I am not quite sure. 



POLLARD: I think this is a preparation of nucleic acid which has been 

 examined by X ray for structure. 



