Mechanisms of Formation of DNA Strand Breaks Induced by gamma-Rays.
Dose responses of DNA single- and double-strand breaks (SSB and DSB) of pBR322 irradiated with gamma-rays were measured by gel electrophoresis scanning and the production process of SSB was tested. Results showed that the formation of DSB was related to the free radicals scavenging capacity sigma of mannitol dissolved in DNA solution. The ratio of alphaDSB to betaDSB non-linearly increased with increasing sigma. On the other hand alphaDSB was induced by the single radical transfer mechanism as sigma<10(8)s(-1) it could however be formed by the LMDS mechanism as sigma>2x10(8)s(-1). Moreover the distance for two SSBs forming a DSB in complementary strands was not obviously influenced by the scavenging capacity.
Institute of Plasma Physics the Chinese Academy of Sciences PO Box 1126 Hefei 230031 China. clshao@ipnc1.hfcas.ac.cn
Chun-Lin
CL
Shao
Masahiro
M
Saito
Zeng-Liang
ZL
Yu