296 Raymond Latarjet 



peroxide is sensitized to the toxic effect of a reducing agent 

 such as ascorbic acid. This "part-inactivation" is similar to 

 that produced by X-radiation. Succinic peracid does not 

 part-inactive T4. 



5. Some mutagenicity has been observed for succinic 

 peracid in Esch. coli B, but not all mutations are produced. 



6. Pepsin is slowly inactivated by peroxide after short 

 exposures have slightly enhanced its enzymatic activity. 



7. A TP (DNA) which endows Pneumococcus with resistance 

 to streptomycin, has displayed an extremely high sensitivity 

 to succinic peracid, but remained undamaged after treatment 

 with cumene hydroperoxide. The inactivation curve is broken, 

 as it is in the case of X-ray inactivation, the break being due 

 neither to aggregation of DNA fibres, nor to genetic hetero- 

 geneity. It is postulated that inactivation results from two 

 different mechanisms. A quantitative analysis of the X-ray 

 curve leads to the hypothesis that the particular structure 

 within the DNA fibre actually endowed with the transforming 

 activity is exceedingly small. 



8. X-ray inactivation of several preparations of TP has 

 disclosed two types of aggregation of DNA fibres, which is 

 disrupted by urea. 



9. There is no oxygen effect in the X-ray inactivation of 

 TP, and no protection against the direct effect of radiation by 

 organic solutes. 



10. These results, of prehminary character, stress the radio- 

 mimetic activity of organic peroxides and, therefore, their 

 possible role as intermediates in some actions of radiation 

 in Uving material. They also disclose that the behaviour 

 of a peroxide and of a peracid sometimes displays striking 

 differences. 



Acknowledgements 



I hope that the preceding text has clearly underlined the paramount 

 part played by my collaborators in the present work. It is a great 

 pleasure for me to thank them here : 



Dr. B. Ekert, who performed the peroxide titrations, and, with Dr. R. 

 Royer, synthesized the succinic peroxide; Drs. D. Maxwell, C. C. 



