A molecular theory of cell survival

A theory is presented to explain the effect of radiation on cell survival. The theory is based on the assumption that a double strand break in the DXA helix is the critical damage. The theory is derived from the radiation induced molecular bond breaks in the DNA strands and parameters are included to take account of various repair processes which may occur between the radiation event and the biological result. Implications of the theory with respect to RBE, the oxygen effect and radiological protection are mentioned and a fit of the theoretically derived expression to experimental data for 250 kV, X-rays and 15 MeV neutrons is presented. An appendix contains data which show that the enzymatic repair of single strand breaks in DNA is in accordance with the theoretical analysis of protracted irradiations and that a coherent analysis of the variation of radiation sensitivity in the cell cycle is in strong support of the primary assumption that a double strand break in the DNA helix is the critical damage leading to cell reproductive death.