Departamento de Física Aplicada, Instituto de Física "Gleb Wataghin", UNICAMP, Campinas, Brazil.
University of Bordeaux, CENBG, UMR 5797, F-33170 Gradignan, France.
Phys Med. 2018 Jul;51:108-116. doi: 10.1016/j.ejmp.2018.06.006. Epub 2018 Jun 19.
The use of Monte Carlo (MC) simulations remains a powerful tool to study the biological effects induced by ionizing radiation on living beings. Several MC codes are commonly used in research fields such as nanodosimetry, radiotherapy, radiation protection, and space radiation. This work presents an enhancement of an existing model [1] for radiobiological purposes, to account for the indirect DNA damage induced by ionizing particles. The Geant4-DNA simulation toolkit was used to simulate the physical, pre-chemical, and chemical stages of early DNA damage induced by protons and α-particles. Liquid water was used as the medium for simulations. Two phase-space files were generated, one containing the energy deposition events and another with the position of chemical species produced by water radiolysis from 0.1 ps up to 1 ns. These files were used as input in the radiobiological code that contains the genetic material model with atomic resolution, consisting of several copies of 30 nm chromatin fibers. The B-DNA configuration was used. This work focused on the indirect damage produced by the hydroxyl radical (OH) attack on the sugar-phosphate group. The approach followed to account for the indirect DNA damage was the same as those used by other radiobiological codes [2,3]. The critical parameter considered here was the reaction radius, which was calculated from the Smoluchowski's diffusion equation. Single, double, and total strand break yields produced by direct, indirect, and mixed mechanisms are reported. The obtained results are consistent with experimental and calculation data sets published in the literature.
蒙特卡罗 (MC) 模拟的应用仍然是研究电离辐射对生物体产生的生物效应的有力工具。在纳米剂量学、放射治疗、辐射防护和空间辐射等研究领域，通常使用几种 MC 代码。本工作针对放射生物学目的，对现有的模型[1]进行了增强，以考虑电离粒子引起的间接 DNA 损伤。使用 Geant4-DNA 模拟工具包来模拟质子和α粒子诱导的早期 DNA 损伤的物理、预化学和化学阶段。液体水被用作模拟的介质。生成了两个相空间文件，一个包含能量沉积事件，另一个包含水辐射分解产生的化学物质的位置，从 0.1 ps 到 1 ns。这些文件被用作包含具有原子分辨率的遗传物质模型的放射生物学代码的输入，该模型由几个 30nm 染色质纤维的副本组成。使用 B-DNA 构象。本工作重点研究了羟基自由基 (OH) 对糖磷酸基团的攻击产生的间接损伤。为了考虑间接 DNA 损伤，采用了与其他放射生物学代码[2,3]相同的方法。这里考虑的关键参数是反应半径，它是根据 Smoluchowski 的扩散方程计算出来的。报告了由直接、间接和混合机制产生的单链、双链和总链断裂产额。得到的结果与文献中发表的实验和计算数据集一致。
