VIL ISOLATION OF OTHER PARTICULATES 



FROM CELLS 



In addition to those already considered, a wide variety of particu- 

 lates from different types of cells has been isolated by differential 

 centrifugation. Without going into the details in each case, a number 

 of the particulates will be mentioned. 



Sevag, Smollens, and Stern (1941) isolated a green particle from 

 Streptococcus pyogenes by first disrupting the organisms by sonic 

 vibrations or grinding in a ball mill, precipitating the particles by 

 66% saturated ammonium sulfate, and finally subjecting the resus- 

 pended particles to repeated low- and high-speed centrifugations. 

 The green particulate is sedimented in a gravitational field of 

 60,000-90,000 times gravity in 1 hr. The final yield amounted to 

 0.43%. 



The iron protein, ferritin, was isolated from horse liver by Stern 

 and Wyckoff (1938a, 1938b). Several hours' centrifuging at about 

 70,000 times gravity is required to bring the ferritin down. This 

 particulate is unique in having an extremely high sedimentation 

 constant, and an iron content of about 20%. The average particle 

 size is 10 mfx. 



The association of cytochrome oxidase activity with macro- 

 molecular particles separated from heart muscle was described in 

 a review by Stern (1943) ; Stern also included a description of the 

 centrifugal segregation of particles bearing the activity of Rous sar- 

 coma agent, fowl leukemia virus, and dysentery bacteriophage. 



Sonic vibrations, produced by the instrument of Chambers and 

 Flosdorf (1936), were successfully employed by Henle et al. (1938) 

 and Zittle and O'Dell (1941) for the disruption of spermatozoa into 

 heads, midpieces, and tails, which could then be separated by differ- 

 ential centrifugation. Henle's group found that 7 min. of vibration 

 at 9000 cycles per second of an intensity that promotes vigorous 

 cavitation in the fluid was sufficient to break up the sperm of bull, 

 dog, and rabbit; 15 min. was required for guinea pig sperm and 20 

 min. for human. The temperature was kept below 20° by water cool- 



471 



