A photoreactive G-quadruplex ligand triggered by green light.

A photoreactive molecular dye targeting the G-quadruplex nucleic acid (G4) of the human telomeric sequence Tel22, and several mutated analogues, was activated by green light (λ=532 nm). Highly selective covalent modification of G4 versus single-stranded and double-stranded DNA was achieved with efficiency up to 64%. The phenoxyl radical was generated and detected by laser-flash photolysis as a reactive intermediate that targeted loop thymine residues. These insights may suggest a non-invasive tool for selective nucleic acid tagging and "pull-down" cellular applications.