Scheme 1:

Schematic representation of the multi-labelling reaction that highlights multiple damage types on the same DNA sample. First, the oxidative DNA damage is repaired using hOGG1 and Endonuclease IV enzymes followed by ATTO550 dye labelling (represented with blue markers). Then the ATTO550 nucleotides are rendered inactive by an alkaline phosphatase that removes the phosphate groups from the unincorporated nucleotides, followed by heat inactivation. Finally, the photoproducts are repaired using the T4 PDG and Endonuclease IV enzymes followed by ATTO647N dye labelling (represented with red markers).