306 



R. H. Ror?KRTS, R. J. HRITTKX. AND I!. .1. MCrAUrin- 



'IWIiLi: II 

 Nucleotide Composition of Various RNA's 



constant. The increased accuracy obtained by use of the isoto])e dilution 

 technique shows a slight difference in composition between the RNA's 

 derived from 308 and oOS ribosomes. 



E. STRUCTURE OF RIBOSOMES 



Table III lists the values of the physical constant of purified E. coli 

 ribosomes as measured by Tissieres et al. Molecular weights of 0.9 X 10*^ 

 and 1.8 X lO'' for the 30S and 50S particles are consistent with the 

 molecular weights of 0.55 X lO'' and 1.1 X 10'^ found for the RNA, 

 assuming an RNA content of 63%. 



