Chen Y, Jiang B, Chen Y, Ding X, Liu X, Chen C, Guo X, Yin G
Ion Beam Laboratory, Shanghai Institute of Metallurgy, Chinese Academy of Sciences.
Radiat Environ Biophys. 1998 Jul;37(2):101-6. doi: 10.1007/s004110050101.
Plasmid pGEM 3zf(+) was irradiated by nitrogen ion beam with energies between 20 and 100 keV and the fluence kept as 1x10(12)ions/cm2. The irradiated plasmid was assayed by neutral electrophoresis and quantified by densitometry. The yields of DNA with single-strand and double-strand breaks first increased then decreased with increasing ion energy. There was a maximal yield value in the range of 20-100 keV. The relationship between DNA double-strand breaks (DSB) cross-section and linear energy transfer (LET) also showed a peak-shaped distribution. To understand the physical process during DNA strand breaks, a Monte Carlo calculation code known as TRIM (Transport of Ions in Matter) was used to simulate energy losses due to nuclear stopping and to electronic stopping. It can be assumed that nuclear stopping plays a more important role in DNA strand breaks than electronic stopping in this energy range. The physical mechanisms of DNA strand breaks induced by a low-energy ion beam are also discussed.
用能量在20至100keV之间的氮离子束辐照质粒pGEM 3zf(+)，通量保持为1×10(12)离子/cm2。通过中性电泳对辐照后的质粒进行分析，并通过光密度测定法进行定量。单链和双链断裂的DNA产量随离子能量增加先升高后降低。在20 - 100keV范围内存在一个最大产量值。DNA双链断裂（DSB）截面与线能量转移（LET）之间的关系也呈峰形分布。为了解DNA链断裂过程中的物理过程，使用了一个名为TRIM（物质中离子传输）的蒙特卡罗计算代码来模拟由于核阻止和电子阻止导致的能量损失。可以假定在该能量范围内，核阻止在DNA链断裂中比电子阻止起更重要的作用。还讨论了低能离子束诱导DNA链断裂的物理机制。
