Schematic representation of the irradiation set-up.

<p>Schematic representation of the microcollimator irradiation and DNA damage foci on 3D skin cultures (A). The cultures were either half shielded or exposed to microcollimated low LET irradiation from the apical side. For DNA damage foci cultures were 4% paraformaldehyde fixed and paraffin embedded, then sectioned as on (A) for immunofluorescence. For western blot experiments, cultures were cut in halves and lysed immediately as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0086092#s2" target="_blank">Materials and methods</a>. On the bottom panels stained for 53 BP1 sections (green, 53BP1, blue – DAPI nuclear staining). Dose profile of the lines of irradiation as detected on gafchromic film after 30 kVp, 45 mA, 1 µm microcollimator exposure (B). Scale bar 20 µm.