26 



But many other things can be said. It makes no difference how long 

 you wait before you put it into water. You can heat it after it has been irradi- 

 ated. You can heat it for a considerable time and then put it in the water. We 

 have tried all of these things and they have no effect unless the heating is ex- 

 cessive. 



TOBIAS: A charge from an ion pair does not migrate very far. So it 

 seems to me that the major effect occurs mostly when you put the irradiated 

 molecule in water. Then we should look for a mechanism that can preserve 

 ionization or the excitation for a long time. 



POLLARD: That is why I supposed the wrong bond formation pre- 

 serves it. 



TOBIAS: I would like you to discuss further the assertion that an ion 

 pair causes the effect in large dry molecules. Most of your evidence appears to 

 stem chiefly from the fact that if one assumes a plausible value for the energy 

 necessary to produce an ion pair, this leads to a volume per ion pair, which is 

 close to the correct molecular volume. Can you completely rule out excitation 

 as the cause of the biological effect in dry molecules? 



POLLARD: Well, Hutchinson's experiments with low voltage electrons 

 speak against excitation. Also, the action of ultraviolet light itself is not very 

 great. The quantum yield is low, of the order of 1 in 100. 



TOBIAS; But you could have a wavelength in the far ultraviolet region 

 where the quantum yield is presumably high. 



POLLARD: We have just been looking in the far-off field. 



PLATZMAN: How far off? 



POLLARD: We have gone out to about 1500 now. We have begun to 

 look for absorption, and it is very interesting. 



TOBIAS: I am under the impression that large molecules in the dry 

 state might have considerable charge accumulated on their surface. Do you 

 have any observations available on the net molecular charge? 



POLLARD: I haven't any figures on that. 



KAMEN: Do you know about the recent work of Alexander and Charles- 

 by (18) ? They have studied methacrylate polymers and find a linear relation 

 between radiation dosage and cross-linking. On the other hand, Little (19) 

 thinks that all their data can be explained as straight-forward breakdown of the 

 linear chains. I wanted to ask you whether you knew about this work. 



POLLARD: I don't know much about it. It is in Nature (18), and I have 

 read it as you have. 



ALLEN: I should like to ask one question on this allusion you made to 

 indirect action in the case of the monolayer of catalase, I believe it was. Can 

 you give a figure as to the deduction with regard to the lifetime of the species in 

 water? What was that lifetime? 



POLLARD: The closest I think is 3 microseconds. 



