STABLE STRUCTURAL STATES OF RAT HEART MITOCHONDRL\ lOI 



kinds of systems we are studying. In the more drastic swelling we study, the ampli- 

 tude of the cycle is large. There is a two or three-fold increase in volume. I would 

 like to know whether Dr. Holton can give an estimate of the per cent difference in 

 mitochondrial volume between his two stable states ? 



HoLTON : No, I am afraid that we have no data on which to base such an esti- 

 mate, but perhaps a rough comparison of the magnitudes of the extinction changes 

 we are observing in our respective systems would be helpful. I suspect that you use 

 a lo-mm. cell and a concentration of mitochondria of perhaps 0-5 mg./a ml. of 

 protein. Is that reasonable ? With this arrangement you get changes of about one 

 extinction unit. Our reversible changes would not be discernible at this optical 

 thickness and concentration. We use 0-2 mg./ml. and a 60 mm. cell where the sides 

 are mirrored, and then we observe a total change for reversible swelling of about 

 0-02 extinction units. You see that there are several degrees of magnitude between 

 the amount of extinction change which are seen under your conditions and ours. 



