| Autor: |
Hirato, Misaki, Onizawa, Misato, Baba, Yuji, Haga, Yoshinori, Fujii, Kentaro, Shin-ichi, Wada, Yokoya, Akinari, Misaki, Hirato, Misato, Onizawa, Yuji, Baba, Kentaro, Fujii, Akinari, Yokoya |
| Jazyk: |
angličtina |
| Rok vydání: |
2020 |
| Zdroj: |
International Journal of Radiation Biology. |
| Popis: |
Purpose: Cells are highly radiosensitized when their genomic DNA incorporates Br atoms. This strong radiosensitization can mask the Auger effect externally induced by monochromatic X-rays. We clarified the radiosensitization mechanism by investigating the electronic properties of DNA-related molecules containing Br by X-ray microscopy and specific heat. Materials and Methods: X-ray absorption near-edge structure and X-ray photoemission spectroscopy were used to measure the electronic properties of the nucleotide 5-bromo-2′-deoxyuridine-5′-monophosphate, with thymidine-5′-monophosphate as a reference. We determined the specific heat of 5-bromouracil (BrU) crystals with thymine as a reference molecule at low temperatures of 348 K to calculate the microscopic state numbers. Results: The X-ray absorption near-edge structure spectra around the C, N, O, and P K-edges showed that, contrary to our expectation, the lowest unoccupied molecular orbital levels were the same regardless of Br incorporation. The X-ray photoemission spectroscopy spectra indicated that the core levels were not affected by the Br atom. The state numbers were calculated from the heat capacities obtained around 25 K. The state number of BrU was about 1.5 times larger than that for T below 20 K, although the numbers were almost the same for T below 5 K. Discussion: Our results suggest that the Br atom may not contribute substantially to the core-level electronic states of the molecule, but rather to the microscopic states related to the excitation of lattice vibrations (oscillation and rotation in the molecule), which may be involved in valence electronic states. The phonon (or valence) excitation by secondary low-energy electrons generated around brominated bases in genomic DNA may be important in DNA damage induction. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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