23 



of commercial enzymes put in solution), there is present an aggregated unit 

 with a definite biological function. The part that we measure is the part that is 

 concerned with hemagglutination and it seems to differ in its radiobiological 

 sensitivity according to whether it is dried-out-of-gelatin (whatever that does 

 to it) or whether it is dried-out-of-phosphate buffer, (whatever that does to it). 

 We get a tendency to greater sensitivity in the phosphate buffer case than in the 

 gelatin. 



These two phenomena are disquieting, in a sense, but not to me, be- 

 cause they tell me that there is more color and more definite information to be 

 gained from radiation action. Since one of my primary aims is to use radiation 

 action to study structure, the more "color" we can develop, the better I like it. 

 Now I should like to throw this open to discussion. 



KAMEN: What percentage of your dry material is still virus? 



POLLARD: In the case of T-1, between 90 and 100 percent. In the 

 case of influenza, the hemagglutination is intact. The drying does not touch it, 

 but the infectivity is, of course, largely gone. 



KAMEN: There is not enough impurity to talk about the effect any 

 more even in the dry film ? 



POLLARD: No. I would say that in the dry state there could hardly 

 be any indirect effect. 



CHARGAFF: Is there any such thing as a dry protein or a dry nucleic 

 acid? We must have prepared hundreds of samples of nucleic acid. When we 

 recover the material after pumping off the water at 10"^ mm. Hg. , we invari- 

 ably end up with 12 percent water in our "dry" nucleic acid which I have always 

 considered structurally bound. 



Furthermore, as to the evidence from X-ray diffraction, Wilkins and 

 his associates have shown that they get these pretty pictures only at relatively 

 high humidity. I don't doubt that you can pump out all the water if you let it go 

 long enough, but I would hesitate to call that a protein or nucleic acid until I 

 have been shown that it has not been changed. 



You see, the transforming principle is really damaged even by dialysis 

 against an electrolyte-free medium. I think that no one has been able to restore 

 the viscosity of nucleic acid after drying, and that goes even for drying to 12 

 percent moisture. When you go down to I doubt very much that you can really 

 reconstitute the solution so that it has the properties of the original nucleic acid. 



POLLARD: I get this very often. Dr. Chargaff. Let me ask a ques- 

 tion. What does that tell you? 



CHARGAFF: It does not tell me what has happened but it tells me that 

 something has happened, In biology, it is always very easy to recognize degra- 

 dation. It is not easy to recognize the native state. We don't know what the 

 native nucleic acid looks like; but we can recognize the degraded state. 



POLLARD: I quite agree about the degraded state. However, we are 

 considering whether a separate effect due to diffusion of activated molecules is 

 present. Diffusion involves motion through a medium. I claim that in these ex- 

 periments I have removed that medium. That is all. I do not claim that I have 



