重离子辐照诱导DNA双链断裂的剂量率效应

利用不同剂量率的50MeV/u^12C^6 辐照B16黑色素瘤细胞的脱蛋白DNA，采用脉冲场凝胶电泳技术对DNA双链断裂（DSB）的诱导和片段的分布进行了研究。结果发现，在剂量率分别为3Gy/min和30Gy/min的情况下，DNA片段释放百分比（PR）都随着剂量的增加而增加，并在超过一定剂量之后趋于相似的准阈值；3Gy/min辐照诱导DSB的产额为0.40DSBs(100Mbp.Gy），30Gy/min辐照诱导的DSB产额准确值无法得到；30Gy/min辐照诱导DSB的截面为2.14μm^2，是3Gy/min的3.1掊。所有结果都表明剂量率越高，诱导DSB越有效。另外，3Gy／min辐照诱导DSB片段在－860kbp处有一个片段峰，而30Gy/min没有，说明剂量率可以影响DSB片段的分布。

DOSE-RATE EFFECTS ON THE INDUCTION OF DNA DOUBLE-STRAND BREAKS WITH HEAVY-ION IRRADIATION

The deproteinized DNA samples of melanoma cells (B16) were irradiated by 50MeV/u 12 12C 6+ of different dose rates. And the inverse pulsed-field gel electrophoresis was employed to measure the distribution of DSB fragments. The results show that both of the percentages of DNA released from plug (PR) induced by 3Gy/min and 30Gy/min increase with the rising dose and approach a similar quasi-threshold. The yields of DSB induced with 3Gy/min are 0.40DSBs/(100Mbp.Gy) while those induced with 30Gy/min are not obtained. The cross section of DSB induction with 30Gy/min is 2.14m 2, which is more than three times of that with 3Gy/min. These show that the higher the dose rate is, the more efficiently DSBs are induced. There is a peak about 860kbp of DSB fragments induced with 3Gy/min, which does not exist in the samples treated with 30Gy/min. It is implied that the dose rate has influence on the distribution of DSB fragments.