Abstract
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 .gamma.-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.

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