Michael B D, Prise K M, Folkard M, Vojnovic B, Brocklehurst B, Munro I H, Hopkirk A
Cancer Research Campaign Gray Laboratory, Mount Vernon Hospital, Northwood, UK.
Int J Radiat Biol. 1994 Nov;66(5):569-72. doi: 10.1080/09553009414551641.
Ionizing radiations deposit a wide range of energies in and around DNA and this leads to a corresponding spectrum of complexity of the lesions induced. The relationships between the amount of energy deposited and the yields and types of damage induced are important in modelling the physical and chemical stages of radiation effect and linking them to biological outcome. To study these relationships experimentally, plasmids were mounted as a monolayer and exposed in vacuum to near-monoenergetic photons from the Daresbury Synchrotron. After irradiation, the DNA was washed off and assayed for single-(ssb) and double-strand breaks (dsb) using agarose gel electrophoresis. Dose-effect relationships for ssb and dsb induction were obtained at various energies in the range 8-25 eV. The initial responses in the low-dose region allowed damage yields to be estimated. However, a common feature is that the responses showed energy-dependent plateaus at higher doses as if a fraction of the DNA were shielded. Various measures were taken both to minimize and to correct for this effect. The data appear to show that the yields of ssb and dsb increase only slowly with photon energies > 10 eV, with a suggestion of similar threshold energies for both lesions. In the energy range covered, the yield of ssb is 12-20-fold greater than that of dsb. The data indicate that ssb and dsb may have a common precursor in this system. Earlier work with low-energy electrons showed that at 25 eV ssb were induced but no dsb were detected.
电离辐射在DNA及其周围沉积多种能量，这导致了相应一系列复杂的诱导损伤。沉积能量的量与诱导损伤的产额和类型之间的关系，对于模拟辐射效应的物理和化学阶段并将它们与生物学结果联系起来很重要。为了通过实验研究这些关系，将质粒铺成单层，并在真空中暴露于来自达雷斯伯里同步加速器的近单能光子。辐照后，洗去DNA，并用琼脂糖凝胶电泳分析单链断裂（ssb）和双链断裂（dsb）。在8 - 25 eV范围内的各种能量下获得了ssb和dsb诱导的剂量效应关系。低剂量区域的初始反应使得能够估计损伤产额。然而，一个共同特征是反应在较高剂量下呈现能量依赖性平台期，就好像一部分DNA受到了屏蔽。采取了各种措施来最小化并校正这种效应。数据似乎表明，当光子能量> 10 eV时，ssb和dsb的产额仅缓慢增加，两种损伤似乎具有相似的阈值能量。在所涵盖的能量范围内，ssb的产额比dsb大12 - 20倍。数据表明在这个系统中ssb和dsb可能有一个共同的前体。早期对低能电子的研究表明，在25 eV时诱导了ssb，但未检测到dsb。
