DNA repair processes, starting after the irradiation of cell nuclei, can be made visible by tagging DNA repair proteins (here MDC1) with the green fluorescent protein GFP, so that microscopic accumulations of the repair proteins (foci") at the ion-induced damages (mostly DNA double-strand breaks) can be observed and analyzed "live" under a fluorescence microscope. The aim of this work is to determine the dynamics of the MDC1-foci in the nucleus. Living U2OS osteosarcoma cells were irradiated in a 5x5 µm^2 matrix pattern with one carbon ion (43MeV) per point or 32 protons (20 MeV) respectively at the ion microprobe SNAKE at the Munich 14MV Tandem accelerator. The relative movement (i.e. the distance) of neighboring foci within the living cells was monitored over several hours "online" at the irradiation site at SNAKE. This relative measure is more robust against cell movement than absolute position determination. The distribution of the change of distance dl between two foci in a time interval dt is a measure for the underlying diffusion. The square of its standard deviation sigma^2(dt) is in general described by sigma^2(dt) = G*dt^a, with    «

DNA repair processes, starting after the irradiation of cell nuclei, can be made visible by tagging DNA repair proteins (here MDC1) with the green fluorescent protein GFP, so that microscopic accumulations of the repair proteins (foci") at the ion-induced damages (mostly DNA double-strand breaks) can be observed and analyzed "live" under a fluorescence microscope. The aim of this work is to determine the dynamics of the MDC1-foci in the nucleus. Living U2OS osteosarcoma cells were irradiated in...    »