VII. SYNTHESIS OF RNA AND RIBOSOMES 



323 



component is the proportion of that component. At early times both ^e 

 and cjiT increase as t, </)y increases at t- and <j)ii increases as t\ 



In Fig. 17, <^.v is i)lotted for the two precursor fractions and the 

 product resolved by chromatography, together with theoretical curves 

 calculated from Eqs. (2), (3), and (4) for E = 2.7%, N = 6.8%. (The 

 details of the procedure for deriving values of cj> from the experimental 

 data are described in (McCarthy et ai, 1962). The quantitative analysis 

 thus verifies the assumption that the three components show the kinetic 

 features of two sequential precursors and a stable product. 



The corresponding analysis of the peak resolved by sedimentation is 

 more complicated since there are more components to consider. As a 

 first step the 14S region is compared with other regions of the sedimenta- 

 tion pattern by plotting its radioactivity {<j>e) together with ^r and (}>r' 

 {<{>R' = <l>5o + (}>43 + <j>3o) (Fig. 18). Initially, all of the radioactivity 



SEDIMENTATION ANALYSIS 10"^ Mg"* 



C -Uraci 

 incorporated 

 info RNA 



Fig. 18. The C"-uraoil label incorporated into total RNA (#), the eosome 

 region 8-20S (D), and the ribosome region (O), i-e., material between SOS and 50S 

 including neosome and ribosome. Data from Fig. 16. Tlie label in each component 

 is plotted as <p functions <Pt, <Pe, ^n + r: 



