FRAP measurement of repair proteins bound at damaged DNA.

<p>U2OS cells expressing NBS1-GFP were irradiated with Ti ions (LET ∼270 keV/µm) under a low angle resulting in a streak-shaped foci pattern along the ion trajectory (red arrow). At time 0 s the fluorescence tag of the proteins in a small part of the streak are bleached with a short and intense laser pulse (cyan arrow). Fluorescence recovery in the bleached region represents the protein exchange at the DNA damage. Selected time frames are shown. Time labels correspond to the time after bleaching.