112 



PLATZMAN: I would tend to bet at the moment on heat. That is, the 

 energy of the initial ionization or excitation would be dissipated as heat inside 

 one of these units, a small enough unit, so that breakage would occur at the 

 weakest point. 



MAZIA: I should think so, since the procedure I have described will 

 alone split the chromosomes. 



CHARGAFF: What would put these particles together? Each of your 

 particles is much smaller and thinner than the chromosome. 



MAZIA: I am postulating these ionic bridges plus the fact that under 

 the conditions of ionic strength, which we believe to exist in the cell, the nucleo- 

 protein is insoluble -- the particles interact and do not separate readily. 



CHARGAFF: The nucleic acid has many primary phosphoric acid dis- 

 sociations, and I think those probably would be taken care of in each of the pro- 

 tein particles. There would not be much ionic force left over -- I don't know 

 how many of these particles go to form a chromosome and to keep it together 

 before it has to split. You see you must have a factor that assures regularity. 



MAZIA: So far as their holding together is concerned, it is a fact that 

 in vitro, at the ionic strength that we consider to be reasonable for the cell, the 

 material is insoluble. 



CHARGAFF: Oh yes, there is no question about that. 



PLATZMAN: Would you complete the picture as to how the small 

 chromosome builds up? 



MAZIA: There is evidence that these two variables are involved. 

 There is no evidence as to where the two kinds of interactions are located. 



PLATZMAN: If we don't speculate, we probably never will get any- 

 where. Do you have a lot of those going up and down and also sideways? Is that 

 what you have in mind? 



MAZIA: Yes. Let's try a picture in which the divalent ions serve as 

 end-to-end bridges for the particles, for the sake of speculation. 



POLLARD: van der Waals' forces will hold things of that size together 

 to some extent. 



bond. 



PLATZMAN: I still think that heat is the thing that finds our weakest 



POLLARD: There is not enough heat in these things. 



PLATZMAN: I am not thinking of general heating. 



I have in mind a high vibrational excitation of the molecule (probably 

 produced via internal conversion of electronic energy), -- you called it pre- 

 partitioned heat last year, I believe. The physical question devolves on whether 

 enough of this energy can find the critical bond before dissipation outside of the 

 molecule has proceeded too far. 



POLLARD: I prefer my moving charge. Still it does not matter. It is 



