Relationship between Sedimentation Behaviour of DNA–protein Complexes and DNA Single- and Double-strand Breaks after Irradiation with γ-rays, Pulsed Neutrons and ¹²C Ions

Summary

The sedimentation behaviour of DNA—protein complexes was studied following irradiation of Chinese hamster cells (V79-4) and human lymphocytes over a wide dose range of ¹³⁷Cs γ-rays, pulsed neutrons and accelerated ¹²C ions. We have shown that the decrease of relative sedimentation velocity of the complexes at low doses is related to the occurrence of single-strand breaks in DNA. Rejoining of the breaks during a repair period increases the sedimentation velocity. At higher doses of radiation, double-strand breaks lead to an increase of sedimentation velocity of DNA—protein complexes. A new method can be devised on the basis of these results enabling estimation of the yields of single-and double-strand breaks in DNA.