Different cell inactivation kinetics of γ-rays and 10B-neutron-captured beams on a green alga, Cylindrocystis brebissonii

Cells of Cylindrocystis brebissonii were irradiated with 60Co γ-rays and 10B-neutron-captured beams (BNCB). This organism was found to be the most tolerant to 60Co γ-rays among green algae which had been examined. The values of D37 for 60Co γ-rays and BNCB were estimated as 470 Gy and 48.1 Gy, respectively. The RBE of BNCB was determined to be 9.8 from the ratio of the values of D37. The semi-logarithmic plot of surviving fraction of this organism after BNCB exposure exhibited a prominent initial shoulder which is generally seen in the survival curve obtained from the irradiation of low LET radiations, but hardly or slightly found after the irradiation of high LET radiations. A split dose experiment suggested that this phenomenon is due to the sublethal damage repair mechanism. (author)