[Calculation of sedimentation curves for single-stranded DNA with induced breaks].

Two alternative models of DNA molecular weight distribution due to induced single strand breaks are considered. Some analytical formulae for molecular weight distribution were deduced and on their basis the sedimentation curves were constructed. The first model declares the subunite structure of DNA. The breaks are induced by chemical or biochemical agents randomly and molecules degrade in points of the subunite connections as well. The other model declares the random of primary induced breaks and breaks of molecular fragments in half if they are longer than any steady size. These latter breaks can occur repeatedly if the sizes of the halves are more than the steady size. The constructed sedimentation curves of the two models were compared with experimental ones. It has been shown that the second model can explain qualitatively some patterns of the sedimentogrammes obtained with high speed centrifugation as the first one.