VII. SYNTHESIS OF RNA AND RIBOSOMES 



309 



decreased the ribosomes lose protein and elute at higher salt concentra- 

 tions, as shown in Fig. 9. 



The use of the DEAE column to separate ribosomes and their pre- 

 cursors for kinetic analysis was first reported in 1957 (Roberts et al., 

 1958). Recent examples of this technique are given in Section V,A. 

 Separation is achieved because of the different protein content of the 

 ribosome and precursors. 



B. SEDIMENTATION ANALYSIS 



The separation of ribosomes of different sedimentation coefficients 

 can be carried out by sedimenting a layer of ribosome suspension through 

 a solution stabilized by a density piadient (Brakke, 1953; Britten and 



Fig. 10. Analytical centrifuge pattern of SOS ribosomes purified by centrifugation 

 through a sucrose density gradient. 



