Fig. 7. RP-A and XKu86 foci form on linear duplex DNA linked to magnetic beads after incubation with HSS. Immunofluorescence with affinity purified anti-RP-A70 (RP-A) and anti-XKu86 antibodies (XKu86) on DNA bound to magnetic beads and incubated with HSS (in DNA amounts equivalent to 5000 sperm heads) for 1 hour at 23°C. The beads were extensively washed and fixed with 2% paraformaldehyde. The DNA bound to the beads was stained with DAPI. Both RP-A and XKu86 form foci all around the beads, whereas the DNA staining appears as a smoother rim. A control immunocytochemical experiment (IC) of naked beads incubated just with the extract and labeled with anti-RP-A70 antibody is shown together with the phase contrast (PC) image. An identical control image was obtained with anti-XKu86 antibodies. Bars, 5 µm.