LET Dependence of DNA Single-Strand Scission in E. coli Bs-1 by Charged Particles

概要

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Log-phase cells of E. coli B_<S-1> labelled with ^3H-thymidine were bombarded with α-particles, carbonand nitrogen-ions of various energies and the LET dependence of the eificiency of DNA single-strand break production (Esb) was investigated. The amounts of radiation energy required for single-strand break production proportionally increased with increasing LET_∞ in the range greater than about 90 keV・μm^<-1>. The heavier particle gave an LET_∞-E_<sb> curve shifted to the higher LET as compared with that for the lighter particle. The relationship between the restricted LET (LET_<500>) and Esb corrected for δ-rays was represented by the same linear regression curve for the above three kinds of particles. Analysis of the high-LET data in correlation with survival radiosensitivity indicated that the number of particles passed through the DNA strand per D_<37> decreases with increasing LET, approaching to the unity and the number of single-strand breaks per D_<37> produced by the track-core effect decreases toward a value of about 3. The results suggest that the traversal of a heavy charged particle of high LET through the DNA strand may produce a double-strand break, which would be of major importance in cell inactivation at high LET, but single-strand breaks produced mainly by δ-rays is not necessarily lethal.
日本放射線影響学会の論文