Detachment of Segments from DNA Double Strands as Detected by Time Resolved Rayleigh Light Scattering

Abstract
Calf thymus DNA was irradiated in O2-saturated 0.01 N NaCl solution with 2 .mu.s pulses of 15 MeV electrons. By monitoring the decrease of light scattering intensity after the pulse, 2 modes of decrease were detected. The fast decrease (.tau.1/2 .apprxeq. 0.8 ms) is ascribed to the separation of DNA fragments produced by double strand breaks at positions directly opposite to each other. The slow decrease (.tau.1/2 .apprxeq. 8 s) is attributed to the detachment of segments generated by single strand breaks at sites on the alternate strands being separated by about 10 nucleotide units.

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