Michalik V, Frankenberg D
Nuclear Physics Institute, Radiation Dosimetry Department, Praha, Czech Republic.
Radiat Environ Biophys. 1996 Aug;35(3):163-9. doi: 10.1007/s004110050026.
Yields of DNA double-strand breaks (dsb), i.e. the average number of dsb, N, per relative molar mass, M(r), and dose, D, produced by electrons and photons in the energy range 50 eV-1 MeV were calculated. The experimental data of dsb induction by ultrasoft x-rays and by photons agree well with the calculated yields of dsb as a function of photon energy. The dsb are classified into simple and complex ones. Energy transfers of less than about 200 eV producing at least two ionizations generate mainly simple dsb, while low-energy electrons with an initial energy between 200 and 500 eV induce preferentially complex dsb. Assuming that dsb is the main DNA lesion leading to exchange-type chromosome aberrations (etca), three different mechanisms have to be considered: 1) complex dsb on its own; 2) interaction between two dsb induced by the same primary particle; and 3) interaction between two dsb induced by different primary particles. Mechanisms 1) and 2) produce a linear term, whereas mechanism 3) leads to a quadratic term for the yield of etca. The sum of contributions 1) and 2) to the yield of dicentrics describes fairly well the non-trivial structure of the experimental data. The results suggest that interaction between complex dsb does not contribute significantly to the formation of dicentrics via mechanism 3).
计算了能量范围在50电子伏特至1兆电子伏特的电子和光子产生的DNA双链断裂（dsb）产率，即每相对摩尔质量M(r)和剂量D产生的dsb平均数量N。极软X射线和光子诱导dsb的实验数据与计算得出的作为光子能量函数的dsb产率吻合良好。dsb分为简单型和复杂型。能量转移小于约200电子伏特且产生至少两次电离主要产生简单dsb，而初始能量在200至500电子伏特之间的低能电子优先诱导复杂dsb。假设dsb是导致交换型染色体畸变（etca）的主要DNA损伤，则必须考虑三种不同机制：1）复杂dsb自身；2）由同一初级粒子诱导的两个dsb之间的相互作用；3）由不同初级粒子诱导的两个dsb之间的相互作用。机制1）和2）产生一个线性项，而机制3）导致etca产率出现一个二次项。对双着丝粒产率的贡献1）和2）之和相当好地描述了实验数据的非平凡结构。结果表明，复杂dsb之间的相互作用通过机制3）对双着丝粒形成的贡献不显著。
