82 



MICROSOMAL PARTICLES 



00 



w 



00 



Fig. 5. Sedimentation photographs at UTS (200,0(%) of 80 S particles isolated from 

 cells nitrogen-starved for 72 hours and suspended in phosphate buffer at 4° C. (a) After 

 1 day. (b) After 2 days, (c) After 7 days, (d) After 11 days. 



SUMMARY 



Ultracentrifugal studies of yeast-cell extracts have shown a correlation be- 

 tween the physiological states of the cells and the stability and appearance or 

 disappearance of microsomal particles from the cytoplasm. 



ACKNOWLEDGMENT 



This work was done in the Biophysics group of Donner Laboratory and was 

 supported by contract with the Atomic Energy Commission. I wish to thank 

 Dr. Cornelius A. Tobias for his interest in this work. 



