THE EFFECT OF BETA RADIATION OX PORPHYRIN COMPOUNDS 



(b) Effect of dose rate 



The result of using a dose of 2000 rad with varying dose rates, is seen in 

 II (Figure 2). A complete conversion to the product substance occurred at 

 the higher dose rates and the effect was essentially the same as in Figure 1 

 (II and III 1. No relationship ])ct\vccn dose rate and effect on protoporphyrin 

 could be oljtaincd. 



In the next irradiation, a dose of 750 rad was used and complete conversion 

 to the product substance did not occur. The degree of conversion, as 

 measured by Soret band strength, thus appears to be a function of dose rate 

 (I, Figure 2). The fluctuation of the points about the straight line was 



10 20 30 40 50 60 70 80 90 100 110 

 Dose rate (rad/min) 



Figure 2. Effect of dose rate. Ordinate : Porphyrin 



concentration, calculated as protoporphyrin and 



expressed as percentaE^e of non-irradiated controls. 



1 : 750 rad dose. II : 2000 rad dose 



probably due to the fact that a period of four days elapsed between the 

 irradiation of plasma and estimation of porphyrins. A line of best fit was 

 therefore calculated statistically. 



Changes in the Porphyrin Molecule 

 (a) Protoporphyrin 



The position and strength of the absorption bands of the irradiated and 

 non-irradiated solutions are given in Table 1. 



Table 1. EfTcct of irradiation on absorption bands of protoporphyrin 



98 



