Vogel Stefanie, Ebel Kenny, Schürmann Robin M, Heck Christian, Meiling Till, Milosavljevic Aleksandar R, Giuliani Alexandre, Bald Ilko
Institute of Chemistry - Physical Chemistry, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476, Potsdam, Germany.
Department 1 - Analytical Chemistry and Reference Materials, BAM Federal Institute of Materials Research and Testing, Richard-Willstätter Str. 11, 12489, Berlin, Germany.
Chemphyschem. 2019 Mar 18;20(6):823-830. doi: 10.1002/cphc.201801152. Epub 2019 Feb 26.
DNA is effectively damaged by radiation, which can on the one hand lead to cancer and is on the other hand directly exploited in the treatment of tumor tissue. DNA strand breaks are already induced by photons having an energy below the ionization energy of DNA. At high photon energies, most of the DNA strand breaks are induced by low-energy secondary electrons. In the present study we quantified photon and electron induced DNA strand breaks in four different 12mer oligonucleotides. They are irradiated directly with 8.44 eV vacuum ultraviolet (VUV) photons and 8.8 eV low energy electrons (LEE). By using Si instead of VUV transparent CaF as a substrate the VUV exposure leads to an additional release of LEEs, which have a maximum energy of 3.6 eV and can significantly enhance strand break cross sections. Atomic force microscopy is used to visualize strand breaks on DNA origami platforms and to determine absolute values for the strand break cross sections. Upon irradiation with 8.44 eV photons all the investigated sequences show very similar strand break cross sections in the range of 1.7-2.3×10 cm . The strand break cross sections for LEE irradiation at 8.8 eV are one to two orders of magnitude larger than the ones for VUV photons, and a slight sequence dependence is observed. The sequence dependence is even more pronounced for LEEs with energies <3.6 eV. The present results help to assess DNA damage by photons and electrons close to the ionization threshold.
辐射会对DNA造成有效损伤，一方面可能导致癌症，另一方面又被直接用于肿瘤组织的治疗。能量低于DNA电离能的光子就能引发DNA链断裂。在高光子能量下，大多数DNA链断裂是由低能二次电子引起的。在本研究中，我们对四种不同的12聚体寡核苷酸中光子和电子诱导的DNA链断裂进行了量化。它们分别直接受到8.44 eV真空紫外线（VUV）光子和8.8 eV低能电子（LEE）的照射。通过使用硅代替对VUV透明的CaF作为基底，VUV照射会导致额外释放出最大能量为3.6 eV的LEE，这些LEE能显著提高链断裂截面。原子力显微镜用于观察DNA折纸平台上的链断裂情况，并确定链断裂截面的绝对值。用8.44 eV光子照射时，所有研究的序列在1.7 - 2.3×10 cm 的范围内都显示出非常相似的链断裂截面。8.8 eV的LEE照射下的链断裂截面比VUV光子照射下的大1到2个数量级，并且观察到有轻微的序列依赖性。对于能量<3.6 eV的LEE，序列依赖性更为明显。本研究结果有助于评估接近电离阈值的光子和电子对DNA的损伤。
