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The Stabilization and Physical Characteristics of 

 Purified Bacterial Ribonucleoprotein Particles 



JACK WAGMAN WESTON R. TRAWICK 



U. S. Army Chemical Corps, Fort Detric\, Frederick., Maryland 



Principally through electron-microscope studies on thin sections of various 

 species [1] it has been possible to show that a major part of the bacterial cyto- 

 plasm consists of widely dispersed granules 100 to 200 A in diameter. In ultra- 

 centrifugal analysis of aqueous extracts from disrupted bacteria, Schachman, 

 Pardee, and Stanier [2] found one of the major components, with j 2 o,w = 40 S, 

 to consist of roughly spherical particles, about 150 A in diameter, which con- 

 tain much of the cytoplasmic ribonucleic acid (RNA). A variety of enzymatic 

 functions have since been attributed to these particles [3], including the systems 

 for electron transport, for oxidative phosphorylation, and for some of the re- 

 actions of the tricarboxylic acid cycle. 



The present paper reports attempts to isolate the 40 S component, by suc- 

 cessive differential centrifugation of extracts from Escherichia coli, and physi- 

 cal measurements obtained with purified material. Particular attention is drawn 

 to the observation that the stability of these particles is dependent upon a 

 dialyzable substance in cell extracts which apparently inhibits decomposition. 



MATERIALS AND METHODS 



The extracts used were prepared from E. coli (ATCC 4157) grown 24 hours 

 on nutrient agar at 37° C. After washing by alternate centrifugation and re- 

 suspension, cells were disrupted by shaking with glass beads in a Mickle dis- 

 integrator. The procedure consisted of shaking 6-ml volumes of suspensions 

 (about 7xl0 10 cells/ml) with 5 g of beads (type 114 Minnesota Mining and 

 Manufacturing Company) for 5-minute periods at 1700 cycles per minute. The 

 extracts were then cleared of unbroken cells and debris by low-speed centrifu- 



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