The Contribution of the Nuclear Reaction1H(n, γ)2D to the Yield of DNA Single Strand Breaks in Cultured Mammalian Cells Irradiated by Thermal Neutrons

Abstract

The yield of single strand breaks (ssb) in DNA of the HeLa S-3 cells after thermal neutron irradiation was examined using the alkaline sucrose gradient method. The contribution of the 1H(n, gamma)2D reaction to the yield of ssb was determined by substituting D2O for H2O in the irradiated medium. Calculation shows that when cells are irradiated in the H2O medium, the per cent contribution of the contaminating gamma-rays, the nuclear reaction 1H(n, gamma)2D and the other nuclear reactions is 31, 44 and 25 per cent respectively assuming additivity of effects. The estimated number of ssb induced by the nuclear reaction 1H(n, gamma)2D was at least 4.4 times greater than that by 60Co gamma-rays at the same absorbed dose. Two possible interpretations are discussed to explain the high efficiency of the 1H(n, gamma)2D reaction for ssb induction.