@misc{oai:repo.qst.go.jp:00084060,
 author = {Daisuke, Ohsawa and Teruaki, Konishi and Masakazu, Oikawa and Daisuke, Ohsawa and Teruaki, Konishi and Masakazu, Oikawa},
 month = {Dec},
 note = {Unlike X- and γ-rays, swift ions with comparatively high linear energy transfer (LET) induce more complex DNA damage, called double strand break (DSB) or clustered DNA lesions. These complexities make the DNA repair process more difficult, leading to increased chromosome aberrations and cell inactivation. However, molecular mechanisms underlying damage and repair of DNA has not been well understood. Taking advantage of SPICE-QST microbeam, we focus on the localized dose distribution in the targeted cell nucleus irradiated with a defined number of protons and its correlation with fluorescent intensity and area of the DNA DSBs region, visualized by immunostaining against γ-H2AX. Finally, the γ-H2AX spot intensity increased linearly with increasing protons from 50 up to 300p/pos, while it showed a saturation tendency at 500p/pos, implying that the histone protein H2AX was exhausted for a large number of protons per position due to densely ionizing protons. In addition, super-linear dependence of the γ-H2AX spot area to the microbeam area was interestingly observed for more than 50p/pos, indicating that the DSBs induction in the targeted cell nucleus was enhanced beyond the microbeam area for a large number of protons per position. A comparison of dose profiles with beam profiles gives further insight into the super-linear dependence, suggesting that the penumbra dose fraction in the localized dose distribution significantly contributed to the DSBs induction. This study was supported in part by a Japan Society for the Promotion of Science (JSPS) KAKENHI Grant-in-Aid for Scientific Research(B) (20H03634)., 日本マイクロビーム生物研究会2021年度シンポジウム},
 title = {Spatial distribution of DNA double strand breaks in microbeam targeted human cells},
 year = {2021}
}