20 



MICROSOMAL PARTICLES 



hours 



20 hours 



12 min 60,000 RPM 



Fig. 2. Influence of storage at 4° C. The suspending buffers (TSM, left; TS, right) 

 also contained 0.25 M sucrose, although subsequent runs have shown that sucrose has no 

 effect on the pattern of components. 



or not magnesium is included in the original suspending medium, as figure 3 

 demonstrates. In addition, a markedly decreased (<10 per cent) ultraviolet 

 absorption occurs in the 100,000^-1 hour pellets (preparative rotor) when 

 EDTA has been added to the bacterial juices. Figure 4 shows that DNAase 

 (2 ug/ml) has little, if any, effect upon the number and size of the rapidly 

 sedimenting materials, whereas RNAase (approximately 10 ug/ml) removes 

 these components. 



SUMMARY AND CONCLUSIONS 



Pressure cell disruption of E. coli at pH 7.6 in magnesium-containing solu- 

 tions of low ionic strength (e.g., 0.01 M Tris-succinate) releases high-molecu- 

 lar-weight components which range from 20 to 80 S. These components "fall 

 apart," i.e., become elements having sedimentation coefficients less than about 

 20 S, when a chelater, EDTA, or the enzyme ribonuclease is allowed to act 

 upon them. DNAase, sucrose, or cysteine exerts no apparent effect on either 

 the number of components or their relative quantities. Nearly all (>80 per 

 cent) of the ribonucleic acid and about one-seventh of the protein of E. coli 

 can be sedimented in a preparative rotor under optimum conditions (TSM, 

 100,000g, 90 minutes). No RNA and only a trivial amount of protein can be 

 sedimented after EDTA or ribonuclease treatment. Hence, it may be con- 



