不同LET辐射致DNA集簇性损伤的研究

Comparative Studies on Clustered DNA Damage Induced by Different LET Ionizing Radiation

利用辐照质粒DNA构象变化的分子模型,以DNA糖苷酶Fpg和AP核酸内切酶EndoIII识别并切割辐射所致DNA碱基损伤,将其转换为DNA断裂损伤,通过电泳分析DNA分子构象变化,研究比较γ射线、质子和7Li离子诱发DNA集簇性损伤。50Gy以上高剂量γ辐射对质粒DNA的损伤主要表现为单链断裂(SSB)和很少比例的双链断裂(DSB),并能产生一定水平的集簇性损伤。相比之下,高能质子束和高LET的7Li离子直接所致DNA的断裂损伤以及所产生的集簇性碱基损伤比γ射线的要严重,质子10Gy照射就可诱发明显的集簇损伤。

Based on the molecular model of conformation changes of plasmid DNA,the DNA damages induced by γ-rays,proton and 7Li ion were studied and compared.In order to detect the clustered DNA damage,the irradiated plasmid DNA was digested with E Coli formamidopyrimidine DNA glycosylase（Fpg）and AP endonuclease III（Endo III）which convert the damaged bases and AP sites into single-strand breaks（SSB）,and then subjected to agarose gel electrophoresis.The results indicated that SSB,a certain level of clustered bases lesions and a tiny of double-strand breaks（DSB）were induced by the observed 50—200 Gy of γ-rays.The DNA breakage and clustered bases lesions induced by high LET proton and 7Li ion were much higher as compared with that induced by γ-rays.Our data also showed that an obvious clustered DNA damage was induced by proton even at 10 Gy dose,and the effectiveness of DNA damage induction by proton was higher than that of 7↑Li ion.