5-Ethynyl-2'-deoxyuridine (5-EdU) is a thymidine analog that can be incorporated into replicating DNA for detection of cell proliferation. 5-EdU can be used as a replacement for BrdU (5-Bromo-2'-deoxyuridine) to measure de novo DNA synthesis during the S-phase of the cell cycle through click chemistry. Click chemistry is a method of covalently coupling an azide with an alkyne. 5-EdU has an alkyne handle that can be detected using azide-containing fluorescent probes through a highly efficient click chemistry reaction [1][2]. In contrast to the use of BrdU, the new method does not require sample fixation or DNA denaturation. 5-EdU-labelled cells may be isolated to determine the transcript of cells, from neural cancer or tissues that have undergone division in vitro and in vivo[3].

References：

[1] Zeng C, Pan F, et al. Evaluation of 5-ethynyl-2'-deoxyuridine staining as a sensitive and reliable method for studying cell proliferation in the adult nervous system. Brain Res. 2010 Mar 10;1319:21-32.

[2] Cavanagh BL, Walker T, et al. Thymidine analogues for tracking DNA synthesis. Molecules. 2011 Sep 15;16(9):7980-93.

[3] Endaya BB, Lam PY, et al. Transcriptional profiling of dividing tumor cells detects intratumor heterogeneity linked to cell proliferation in a brain tumor model. Mol Oncol. 2016 Jan;10(1):126-37.