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BP: Fachverband Biologische Physik

BP 28: Biomedical Applications

BP 28.6: Vortrag

Freitag, 30. März 2007, 12:15–12:30, H44

Analysis of radiation-induced damages of DNA molecules by means of SFM and gel-electrophoresis — •Mihail Brezeanu, Frank Träger, and Frank Hubenthal — Institute of Physics and Center for Interdisciplinary Nanostructure Science and Technology - CINSaT, Universität Kassel, Germany

Studying radiation-induced damages in DNA molecules is important to understand the processes that occur in radiotherapy and DNA repair. The most serious damages of DNA molecules are double-strand breaks (DSB), i.e. the rupture of both DNA strands in the range of a few base pairs and single-strand breaks (SSB), when one of the DNA strands is broken. In this contribution we present our recent analysis of radiation-induced damages in phiX174 plasmids after X-ray and carbon-ion irradiations. The percentages of plasmids with DSBs, SSBs, and multiple strand breaks, i.e. linear fragments (LF), have been determined as a function of radiation dose by means of scanning force microscopy (SFM) and gel-electrophoresis measurements. The results show an increase of the DSBs percentage from initially 0% to 12.5% after X-ray irradiation, while after carbon ion irradiation 19% of DSBs have been found for the same applied dose of 1 kGy. In addition, a detailed SFM analyses revealed that the distribution of LF after irradiation with C-ions contains a significant higher amount of small fragments in the range from 50 nm to 700 nm, compared to the X-rays, while a clear reduction of large fragments has been observed. The results explain, for example, why the DNA repair rate after carbon ion irradiation is much lower that for X-rays at the same dose.