Discussion 299 



then there are still enough — OH radicals to react with the active mater- 

 ial, and presumably the hydrogen concentration is quite a lot greater 

 still than the number of molecules of protected material. 



Alexander: The two peroxides studied by Latarjet are chemically very 

 different, and a great deal is known about their reaction with proteins. 

 The organic peracid is the type of substance which has enabled Sanger 

 to do his insulin work, i.e. the type of material which reacts very rapidly 

 and very specifically with SH and with -S-S- groups to convert them to 

 sulphonic acid. Cuinene peroxide is quite different: it also reacts with 

 protein and also attacks the SH and -S-S- groups but it does not give 

 sulphonic acid in quantitative yield, it gives largely sulphate. Unlike 

 the peracid it attacks the peptide bond. Chemically these two substances 

 show such different behaviour that one would expect their biological 

 effects to be quite different. 



Latarjet: It is a constant phenomenon. 



Dale: Dr. Latarjet, in your first slide (on pretreatment), how did you 

 protect yourself against the aftereffect ? When you treated your material 

 and then exposed it to ascorbic acid or vice versa, couldn't there have 

 been an aftereffect, or what precautions could you have taken? The 

 time was roughly the same as on your aftereffects slide. 



Latarjet: It was such a slight dose (we had 50 per cent survival) that 

 the aftereffect was not great, and it was the same in both the control 

 and the treated samples. 



Popjak: Dr. Latarjet, with regard to the radiomimetic effect of these 

 peroxides in mice, you said that you gave the substance in oil? 



Latarjet: We first injected cumene hydroperoxide dissolved in oil. 

 Then we had some trouble because the toxicity of the solution increased 

 with time. It seemed that cumene peroxide initiated some peroxidation 

 in the oil itself. Therefore, we turned to the water-soluble persuccinic 

 acid. We are now coming back to cumene, using a new organic solvent 

 which has been synthesized in our laboratory. 



Popjak: I wonder whether the effect might be due to the peroxidating 

 action on the highly unsaturated fatty acids, and that in effect you might 

 be producing the essential fatty acid deficiency in view of the skin 

 lesions. The effect might be of that type. 



