中文摘要：

为研究不同类型和能量的粒子照射细胞核DNA时导致的DNA损伤等辐射生物效应,建立了DNA、染色质原子模型,并开发了纳剂量蒙特卡罗程序NASIC。该程序可模拟包括光子、电子、质子在内的多种粒子在生物介质中的作用过程,既包括物理和化学径迹结构,也包括后续的生物响应过程。使用NASIC程序模拟了（137）Cs源、Al的K层特征X射线（Al_K）源照射哺乳动物细胞后造成的单链断裂和双链断裂产额。研究结果表明,本文使用的DNA原子模型更加接近真实结构,DNA双链断链产额计算结果与实验值吻合较好。

英文摘要：

In order to study the effect of nuclear DNA damage induced by different ener- gy and types of particles, a DNA and chromosome atomic model was established and nanodosimetry Monte Carlo code NASIC was developed. NASIC can simulate the interaction process of different kinds of particles in biological media, including physical and chemical process and the biological response. The yields of single-strand break and double-strand break after the.mammalian cell irradiated by sources of 1arCs and K shell characteristic X-ray of A1 （A1K） were calculated using NASIC. The DNA atomic model used in this paper is close to the real structure. The calculation results of DNA doublestrand break yield are in good agreement with the experiment results.