EdU Flow Cytometry Assay Kits (488) provides a novel method based on click chemistry specifically CuAAC (copper-catalyzed azide-alkyne cycloaddition) enabling direct measurement of DNA synthesis during the S-phase of the cell cycle The thymidine analog EdU (5-ethynyl-2 -deoxyuridine) can be incorporated directly into DNA strands during DNA synthesis The alkyne group on EdU a biologically inert moiety undergoes highly selective reaction with azide-functionalized dyes via the CuAAC reaction forming a stable 1 2 3-triazole product The unique biological groups on EdU and 6-FAM Azide allow fluorescent labeling of proliferating cell DNA after conjugation enabling imaging with low background and high detection sensitivity The EdU Flow Cytometry Assay Kits (488) use 6-FAM azide to label the DNA of proliferating cells following its reaction with EdU Samples labeled in this manner can be analyzed via flow cytometry (EXC/EMI 496/516 nm)) with green fluorescence