Abstract
DNA is considered to be the critical target for cell killing by ionizing radiation. Therefore it is expected that the photoionization of phosphorus in DNA may cause some specific biological effects. However, at the 45th Annual Meeting of the Japan Radiation Research Society, we reported the similar enhancement of cell lethality of photoionization of phosphorus for both normal and DNA repair deficient cell lines including non-homologous repair deficient or homologous recombination repair deficient cell lines. Here, we will report the γ-H2AX induction by k-shell photoionization of phosphorus in wild type and DNA repaire defficient mammalian cells.
Exponentially growing L5178Y cells (derived from mouse leukemia) and M10 (XRCC4 deficient cells derived from L5178Y) were irradiated by monochromatic X-rays at 2.153 keV (K-shell resonance absorption peak of phosphorus) and 2.146 keV (off peak) at the Beam Line-27A in KEK-PF. For both cell lines, the amount of γ-H2AX per cell after 30 min incubation at 37°C, detected by flowcytometry increased linearly with increasing dose for the both energy of X-rays. The dose enhancement ratio was about 1.3 and was similar to those for cell inactivation.
