R. TIRRELL 



Irradiated and non-irradiated solutions, prepared as above*, were ex- 

 amined in a Gary Recording Spectrophotometer and the position and 

 strength of the absorption bands measured from the tracing. 



RESULTS 



Protoporphyrin in Plasma 

 (a) General effect 



During the initial period of irradiation, there was a drop in Soret band 

 strength, as indicated in Figure 1 (I and II). The drop was much sharper 

 in the second experiment than in the first and this is discussed in relation to 

 dose rate, in the next section. 



.11 



.111 



123A56789l0n 



Dose (rad xlO ) 



Figure 1. Irradiation of protoporphyrin under 

 various conditions. Ordinate: Soret band readings 

 expressed as percentage of non-irradiated controls. 

 I and II : irradiated in plasma. Ill: irradiated in 

 alkaline solution. Dose rates: I: 41-7 rad/min. 

 II: 72-4 rad/min. Ill: 41 -7 rad/min. 



In the second experiment (II, Figure 1), the decrease continued until the 

 Soret band strength was 90 per cent that of the non-irradiated control. 

 After this there was no further decrease. It will be seen that this curve is 

 similar to that obtained by irradiating protoporphyrin in alkaline solution. 

 This is shown in III (Figure 1), which is from an earlier investigation* and 

 is included for comparison. 



Comparing now I and III {Figure 1) which have the same dose rate, it 

 may be seen that the effect of irradiation on protoporphyrin in alkaline 

 solution is greater than in plasma. This, of course, is a percentage decrease. 

 But as the concentration of protoporphyrin in III was greater than in I, 

 the absolute rate of decrease (as well as the percentage decrease) is greater 

 for alkaline solution than for plasma. 



* The name pyridine ferroprotoporphyrin will be used for this particular solution; the 

 name hemochrome will be used to describe the general type of solution (as tabulated by 

 Lemberg and Legge, reference 5, p. 164). 



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