132 



MICROSOMAL PARTICLES 



PROLINE 



6000- 



5000- 



4000 



3000 



2000- 



1000- 



15 5 10 15 5 10 I5min 



INCUBATION TIME 



Fig. 8. The effect of a-particle irradiation on proline incorporation. The pool decreases 

 with increasing dose. 



35 



30 



z 

 o 



a so 



in 



CI4 Proline 



TCA Insoluble Fraction 



S35 Methionine 





400 800 1200 



LINEAR ENERGY TRANSFER 



Jl- 



1600 e.v./IOOA 



Fig. 9. Measured cross sections for proline (crosses, dashed line) and methionine (solid 

 circles, solid line) incorporation into the cold-TCA-insoluble fraction as a function of the 

 rate of energy loss (LET). Slopes at the origin are calculated from y-ray experiments as 

 explained in the text. 



by substituting the product of i and V as already found from irradiation with 

 Y rays. Such a relation only applies close to the origin, but can be used to de- 

 termine the initial slope. To a reasonable approximation, i is the energy loss 

 per centimeter, in electron volts, divided by 110. 



