| مستخلص: |
The genotoxic effectsof high-energy ionizing radiation have beenlargely attributed to the ionization of H2O leading tohydroxyl radicals and the ionization of DNA leading mostly to damagethrough base radical cations. However, the contribution of low-energyelectrons (LEEs; ≤ 10 eV), which involves subionization events,has been considered to be less important than that of hydroxyl radicalsand base radical cations. Here, we compare the ability of LEEs andhigh-energy X-ray photons to induce DNA damage using dried thin filmsof TpTpT trinucleotide as a simple and representative model for DNAdamage. The main radiation-induced damage of TpTpT as measured byhigh-performance liquid chromatography (HPLC) with UV detection andHPLC coupled to tandem mass spectrometry analyses included thyminerelease (-Thy), strand breaks (pT, Tp, pTpT, TpTp, and TpT), and theformation of base modifications [5,6-dihydrothymine (5,6-dhT), 5-hydroxymethyluracil(5-hmU), and 5-formyluracil (5-fU)]. The global profile of productswas very similar for both types of radiation indicating convergingpathways of formation. The percent damage of thymine release, fragmentation,and base modification was 20, 19, and 61 for high-energy X-rays, respectively,compared to 35, 13, and 51 for LEEs (10 eV). Base release was significantlylower for X-rays. In both cases, phosphodiester bond cleavage gavemononucleotides (pT and Tp) and dinucleotides (pTpT and TpTp) containinga terminal phosphate as the major fragments. For base modifications,the ratio of reductive (5,6-dhT) to oxidative products (5-hmU plus5-fU) was 0.9 for high-energy X-rays compared to 1.7 for LEEs. Theseresults indicate that LEEs give a similar profile of products comparedto ionizing radiation. [ABSTRACT FROM AUTHOR] |
