Effect of Tween 80 on Strand Breaks of Escherichia coli DNA Irradiated in situ

概要

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The radioprotective action of Tween 80 against strand breaks in the DNA of E. coli irradiated in situ with ^<60>Co γ-rays was investigated using an alkaline sucrose sedimentation technique. Tween 80 (0.1 M) caused the number of breaks to be decreased by a factor of 1.3, a value very close to DRF for E. coli B_<S-1> obtained from the survival studies. On the other hand, this DRE value was considerably lower than that expected from the DRF for E. coli B/r obtained from survival studies. When ^3H-TdR labelled E. coli B/r was irradiated with 15 kR, ^3H-release during post-irradiation incubation was 20%; while the presence of 0.1 M Tween 80 during the irradiation decreased the ^3H-release to 15%, even after as much as 30 kR irradiation. These facts suggest that the action of Tween 80 is not only to diminish the number of breaks of DNA but to cause some change in structural nature of the breaks so that they can be repaired in a short time without any excision of DNA fragments.