Journal Article Ultrafast Dynamics of a Nucleobase Analogue Illuminated by a Short Intense X-ray Free Electron Laser Pulse

Nagaya, K.  ,  Motomura, K.  ,  Kukk, E.  ,  Fukuzawa, H.  ,  Wada, S.  ,  Tachibana, T.  ,  Ito, Y.  ,  Mondal, S.  ,  Sakai, T.  ,  Matsunami, K.  ,  Koga, R.  ,  Ohmura, S.  ,  Takahashi, Y.  ,  Kanno, M.  ,  Rudenko, A.  ,  Nicolas, C.  ,  Liu, X.-J.  ,  Zhang, Y.  ,  Chen, J.  ,  Anand, M.  ,  Jiang, Y. H.  ,  Kim, D.-E.  ,  Tono, K.  ,  Yabashi, M.  ,  Kono, H.  ,  Miron, C.  ,  Yao, M.  ,  Ueda, K.

6 ( 2 ) 2016-06-16 , American Physical Society
X線自由電子レーザーの超短パルスでリボ核酸塩基分子中の電荷と原子の動きを可視化-ヨウ化ウラシルによる放射線増感効果の機構解明. 京都大学プレスリリース. 2016-07-04.
Understanding x-ray radiation damage is a crucial issue for both medical applications of x rays and x-ray free-electron-laser (XFEL) science aimed at molecular imaging. Decrypting the charge and fragmentation dynamics of nucleobases, the smallest units of a macro-biomolecule, contributes to a bottom-up understanding of the damage via cascades of phenomena following x-ray exposure. We investigate experimentally and by numerical simulations the ultrafast radiation damage induced on a nucleobase analogue (5-iodouracil) by an ultrashort (10 fs) high-intensity radiation pulse generated by XFEL at SPring-8 Angstrom Compact free electron Laser (SACLA). The present study elucidates a plausible underlying radiosensitizing mechanism of 5-iodouracil. This mechanism is independent of the exact composition of 5-iodouracil and thus relevant to other such radiosensitizers. Furthermore, we found that despite a rapid increase of the net molecular charge in the presence of iodine, and of the ultrafast release of hydrogen, the other atoms are almost frozen within the 10-fs duration of the exposure. This validates single-shot molecular imaging as a consistent approach, provided the radiation pulse used is brief enough.

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