61 



150 — 



75 



NONIRRADIATED 



1 60.000 r 

 HH lOO.OOOf 



TOTAL P32 INORGANIC META P TOTAL 



ACTIVITY ORTHO P ACID SOLUBLE 



IN CELLS P 



AVERAGE VALUES 



Figure 3. Comparison of the specific ac- 

 tivity of various fractions from X- irradi- 

 ated and nonir radiated yeast ( T utilis ). 

 Inorganic orthophosphate, cts./min ./^g- 

 P relative to control; metaphosphate and 

 total acid soluble phosphate, cts./min./ 

 ^g M-P or TAS-Pdivided by cts./min./[j.g. 

 inorganic P relative to control. 



I I NONIRRADIATED 



■ eo.ooor 



lOO.OOOr 



CYTIDYLIC ADENYLIC GUANYLIC URIDYLIC 

 ACID ACID ACID ACID 



Figure 4. The relative specific activity 

 of RNA mononucleotides from irradiated 

 and nonirradiated yeast. (cts./4nin./|ig. 

 RNA-tideP/cts.^nin./|J.g. inorg. O-P). 



of concentrations of ammonium sulfate 

 that were nonlimiting for growth. Our 

 interpretation was in terms of the rela- 

 tive amount of irreparable damage to 

 the fermentation enzymes. 



More recently, we have been 

 looking at the effect of irradiation on the 

 phosphorus metabolism (17). This has 

 been done by incubating the cells after 

 irradiation with inorganic p32 for peri- 

 ods of about an hour. In these experi- 

 ments, the cells are put into a medium 

 that will allow them to divide. Howev- 

 er, an appreciable number of new cells 

 does not form in an hour at this incuba- 

 tion temperature. Nonirradiated cells 

 begin to form buds, but bud formation is 

 not apparent in the irradiated cells. In 

 Figure 3, the activity of various frac- 

 tions is compared in irradiated and non- 

 irradiated cells. There is a marked in- 

 crease in the total uptake of phosphorus 

 by the irradiated cells. However, there 

 is little difference in the specific activi- 

 ty of inorganic orthophosphate or of to- 

 tal acid soluble phosphate. The meta- 

 phosphate picture isn't as clear. In 

 some of the 100,000 r experiments, the 

 metaphosphate values for irradiated 

 cells are fairly near those for nonirra- 

 diated cells; in other experiments, 

 they are considerably depressed. 



BENNETT: What fraction ac- 

 counts for the increase then? 



SHERMAN: That isn't shown in 

 this figure. The increase in activity is 

 apparently in the RNA fraction. 



BENNETT: This could repre- 

 sent just a difference in the phosphorus 

 percentage in the cells. 



SHERMAN: Perhaps, but the 

 amount of p31 in each of these frac- 

 tions is the same. The ribonucleic 

 fraction from irradiated cells has a 

 much higher activity than RNA from 

 control cells. This is shown for the 

 mononucleotides of RNA in Figure 4. 



CHARGAFF: Does this include 

 all the mononucleotides? 



SHERMAN: This does not in- 



