ISOLATION 'OF CYTOPLASMIC PARTICULATES 467 



60 to 200 ni/x, which will include the "microsomes" will be obtained. 

 In the case of liver tissue, the following procedure has been fol- 

 lowed (Claude, 1946) : To the "supernate" obtained when the "large 

 granules" are separated from the liver extract (page 465) , add 0.1 A^ 

 sodium hydroxide to bring the pH to 7.2 to 7.4. Centrifuge for 4 min. 

 at 18,000 times gravity and discard the sediment which contains 

 "large granules" not previously separated. Bring the "supernate" to 

 pH 7.2 to 7.4 if necessary and spin down the "microsomes" by centri- 

 fugation for 1.5 hr. at 18,000 times gravity. Wash the "microsome" 

 fraction which appears as a jellly-like pellet by resuspending in 

 neutral saline soln. and centrifuging for 1.5 hr. at 18,000 times 

 gravity. After a second washing the "microsome" yield on a total 

 solids basis is 10-20% of the original liver extract. 



