EdU assay differs from BrdU assay because it:
EdU, 5-ethynyl-2'-deoxyuridine, retains Watson-Crick pairing but bears terminal alkyne at 5 position instead of bromine. Detection utilizes bioorthogonal click chemistry specifically copper(I)-catalyzed azide-alkyne cycloaddition first described by Sharpless. In this reaction, alkyne on EdU incorporated into DNA reacts with fluorescent azide forming stable 1,2,3-triazole covalent linkage, catalyzed by CuSO4 reduced to Cu(I) by sodium ascorbate, proceeding rapidly in aqueous buffer at room temperature with exquisite specificity. Because fluorescent azide small molecule penetrates duplex DNA, ha
Ref: Salic A & Mitchison TJ PNAS 2008 EdU click chemistry; Kolb et al Click chemistry concept Nobel Prize 2022 CuAAC azide-alkyne.
