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Discussion 



HuLTiN : Did you say that if you treated these particles with spermine then they 

 would swell up ? If you now treat these gels with magnesium, what happens ? 



Siekevitz: Yes, they do swell up. We haven't done what you suggested, but 

 we have incubated them with spermine + magnesium and they looked the same 

 way as with spermine alone. 



Bergeron : Did the aggregates seen in the electron micrographs of the pellets 

 precede fixation or arise in the course of fixation ? 



Siekevitz : This is a visible aggregation during the centrifugation. In the 

 absence of spermine when you centrifuge these particles they form a nice pellet 

 on the bottom. In all these other cases they precipitated on the side of the tubes 

 indicating that they were aggregating during centrifugation, and in the case of the 

 spermine, they aggregated before centrifugation. 



