Immunofluorescence imaging of γH2AX and 53BP1 foci in K562 cells treated with 1 μM 3. (A) 5–60 min post addition 3. Rows (top to bottom): γH2AX (green), 53BP1 (red), DNA (blue), and merge. Columns (left to right): control, 5, 10, 15, 30, and 60 min after addition. (B) 1–24 h post addition 3. Rows (top to bottom): γH2AX (green), 53BP1 (red), DNA (blue), and merge. Columns (left to right): control, 0.5, 1, 2, 4, 8, 16, and 24 h after addition.