High Brilliance Synchrotron Radiation as a Tool for Studies of Radiation Damage to DNA and resulting cellular responses

Synchrotron Radiation from accelerators has been used as a radiation source for many studies of radiobiological effects. In 1980s, first generation synchrotron accelerators provided us intense vacuum ultraviolet light photos (1-20 eV) to induce DNA strand breaks via super-excitation states [1]. The energy region was gradually expanded to the X-ray energy region (~30keV) in second generation facilities in 1990s, and high-resolution monochromators for the X-rays realized targeting inner-shell electrons in a particular atom and following Auger effect in DNA molecule [2,3]. These studies provided us many fruitful evidences on Auger enhancement of the biological effects. Development of insertion devices in third generation facilities (so called undulators) in 2000s, the brilliant photon sources have been used not only as a source of irradiation, but also a probe to explore the electric states of DNA and its excitation/ionization states by various methods such as X-ray Absorption Structure (XAS), desorbed ion spectroscopy, electron paramagnetic resonance (EPR), or photoelectron spectroscopy (PES) [3]. Recently, by applying not only its high intensity, but also the other properties of synchrotron radiation, such as circular polarization or coherent fraction, new approaches have also been tested in the quest for non-crystallized protein structures in a solution or visualization of biological samples, which could not be achieved by conventional methods. In the present talk, physicochemical processes of DNA damage induction and cellular responses revealed by the synchrotron applications in radiation biology will be reviewed. [1] Ito T, Ito A. Effects of broad-band vacuum-UV synchrotron radiation on wet yeast cells. Radiat Res. 82:364-373 (1980).[2] Chetioui A, Despiney I, Guiraud L, Adoui L, Sabatier L, Dutrillaux B. Possible role of inner-shell ionization phenomena in cell inactivation by heavy ions. Int J Radiat Biol. 65:511-22 (1994).[3] Yokoya A, Ito T. Photon-induced Auger Effect in Biological Systems: A Review. Int. J. Radiat. Biol. (2017) Epub ahead of print.[4] Yokoya, A., Fujii, K., Shikazono, N. and Ukai, M. Chapter 20. Spectroscopic study of radiation-induced DNA lesions and their susceptibility to enzymatic repair. In: Charged particle and photon interactions with matter-recent advances, applications and interfaces, Eds., Y. Hatano, Y. Katsumura, and A. Mozumder, CRC/Taylor & Francis Group, USA, pp543-574. (2011).第1回QST国際シンポジウム「量子生命科学 -Quantum Life Science-