电离辐射诱导体外DNA链断裂机理研究进展

Progress in the mechanism Study on DNA strand breaks in vitro induced by ionizing radiation

概述了电离辐射诱导体外ＤＮＡ单链断裂（ＳＳＢ）和双链断裂（ＤＳＢ）的形成机理。研究结果 表明， ＤＮＡ链断裂产 额与ＤＮＡ浓度和自由基清除剂的清除力有关，并受ＤＮＡ超螺旋度的影 响； ＤＮＡ α ＤＳＢ除可由直接作用形成外，还可分别由单自由基传递机制和ＬＭＤＳ机制产生；对 高ＬＥＴ辐射， α ＤＳＢ主要由ＬＭＤＳ机制产生。而硫醇类化合物对ＤＮＡ的辐射保护作用则随其 电荷态的增加而增加；由于次级自由基效应，体外ＤＮＡ链断裂具有反向氧效应；非均一动力学 的柱模型被广泛地应用于’ＯＨ等自由基与ＤＮＡ反应的理论研究。

Progress in the mechanism research of irradiation-induced DNA single- and double-strand break are reviewed. Researches in recent years show that the yields of DNA strand breaks are related to DNA concentration and scavenging--capacity and are also influenced by DNA structure. a DSBs, induced by the one-hit event of radiation energy deposition, can be formed from both the single free radical transfer mechanism and the LMDS mechanism besides by the direct effect of radiation. For high LET radiation, αDSBs are mainly induced by the LMDS mechanism. In addition, thiol compounds have charges-related radiation protection effects on DNA. Due to the effects of the secondary free radicals of scavengers, the reverse oxygen effect can be observed for DNA strand break. Furthermore, the cylinder model of non-homogeneous kinetics is widely applied to analyze the reaction of 'OH with DNA theoretically.