Our OxiSelect™ Cellular UV-Induced DNA Damage Staining Kit measures the formation of 6-4PP structures in DNA by immunofluorescence. Cells are first seeded in a 96-well tissue culture plate. Wells are then UV irradiated to induce DNA damage. After fixation and denaturation, cells containing the DNA lesions are probed with an anti-6-4PP antibody, followed by a FITC conjugated secondary antibody. The unbound secondary antibody is removed during a wash step, and stained cells can then be visualized with a fluorescence microscope.