whereas the present accepted figure is 17,000. We have a number of figures for 

 radiation molecular weights which have not been checked in any other way. As 

 they are gradually being checked, we find that our figures are quite often in the 

 right league. 



A very interesting one is that of DNA, If DNA is assayed as the pneu- 

 mococcus transforming principle, then we come out with a molecular weight of 

 6, 000, 000 and we also require that the molecule be long and thin. The figure 

 given is 45 ^ wide and 3800 % long. When we assay DNA, however, by some- 

 thing quite different -- the capacity to act as a substrate for its enzyme -- we 

 come out with a figure of something like 2100 molecular weight and a crOss-sec- 

 tion of about 500 square ^ . The conclusion is that perhaps 8 nucleotides are 

 sufficient to be specific for digestion by DNA ase. 



CARTER: What are the criteria for the enzymatic activity that you 

 used? 



POLLARD: This was done by Dr. Smith. I think he measured the 

 amount of substrate converted in a fixed time, being certain that the amount of 

 substrate was not the limiting factor. 



CARTER: What was the endpoint? 



POLLARD: No endpoint was measured. 



CARTER: Was this loss of viscosity? 



POLLARD: No. 



CARTER: It would have to be done like everything we do in a Beck- 

 mann apparatus, and this would be measured by the amount of specific changes . 

 in absorption, probably at two wavelengths. 



CHARGAFF: I am not sure that this is a very good criterion. 



POLLARD: I am rather interested that you grabbed on to that as a 

 method of measurement. That was not our point. Our whole point is that there 

 is a completely different response to irradiation. 



CARTER: The other point is that if you inactivated the desoxyribose 

 nucleic acid by three different methods you might come out with three different 

 answers. 



POLLARD: We bombarded the nucleic acid to see whether it could still 

 be used as a substrate. The enzyme was not bombarded in these experiments. 



CARTER: That irradiation can do so many different things to the 

 molecule is the point that we want to establish. 



POLLARD: I would confidently expect that if one actually studied these 

 separately there would be significant differences between them. 



CARTER: There may be significant areas of agreement. 



POLLARD: Yes, quite possibly. 



CHARGAFF: The transforming molecular weight was about 6,000,000, 



