Nuclear Science and Engineering Directorate, Japan Atomic Energy Agency, Tokai, Naka, Ibaraki, Japan.
Int J Radiat Biol. 2012 Dec;88(12):928-32. doi: 10.3109/09553002.2012.708086. Epub 2012 Jul 18.
To develop a method for simulating the dynamics of the photoelectrons and Auger electrons ejected from DNA molecules irradiated with pulsed monochromatic X-rays.
A 30-base-pair (bp) DNA molecule was used as the target model, and the X-rays were assumed to have a Gaussian-shaped time distribution. Photoionization and Auger decay were considered as the atomic processes. The atoms from which the photoelectrons or Auger electrons were emitted were specified in the DNA molecule (or DNA ion) using the Monte Carlo method, and the trajectory of each electron in the electric field formed around the positively charged DNA molecule was calculated with a Newtonian equation. The kinetics of the electrons produced by irradiation with X-rays at an intensity ranging from 1 × 10(12) to 1 × 10(16) photons/mm(2) and energies of 380 eV (below the carbon K-edge), 435 eV (above the nitrogen K-edge), and 560 eV (above the oxygen K-edge) were evaluated.
It was found that at an X-ray intensity of 1 × 10(14) photons/mm(2) or less, all the produced electrons escaped from the target. However, above an X-ray intensity of 1 × 10(15) photons/mm(2) and an energy of 560 eV, some photoelectrons that were ejected from the oxygen atoms were trapped near the target DNA.
A simulation method for studying the trajectories of electrons ejected from a 30-bp DNA molecule irradiated with pulsed monochromatic X-rays has been developed. The present results show that electron dynamics are strongly dependent on the charged density induced in DNA by pulsed X-ray irradiation.
开发一种模拟单脉冲单色 X 射线辐照 DNA 分子时发射的光电子和俄歇电子动力学的方法。
以 30 个碱基对（bp）的 DNA 分子为靶模型，假设 X 射线具有高斯形状的时间分布。光电离和俄歇衰变被视为原子过程。用蒙特卡罗方法在 DNA 分子（或 DNA 离子）中指定发射光电子或俄歇电子的原子，并用牛顿方程计算围绕带正电荷的 DNA 分子形成的电场中每个电子的轨迹。评估了 X 射线辐照强度从 1×10(12)到 1×10(16)光子/mm(2)、能量为 380 eV（低于碳 K 边）、435 eV（高于氮 K 边）和 560 eV（高于氧 K 边）时产生的电子动力学。
发现 X 射线强度为 1×10(14)光子/mm(2)或更低时，所有产生的电子都从靶中逃逸。然而，当 X 射线强度高于 1×10(15)光子/mm(2)且能量为 560 eV 时，一些从氧原子发射的光电子被捕获在靶 DNA 附近。
已经开发出一种用于研究单脉冲单色 X 射线辐照 30bp DNA 分子时发射的电子轨迹的模拟方法。目前的结果表明，电子动力学强烈依赖于脉冲 X 射线辐照在 DNA 中诱导的电荷密度。
