5-Ethynyl-2'-deoxyuridine (EdU) | CAS 61135-33-9

5-Ethynyl-2'-deoxyuridine (EdU) is a thymidine analog designed for bioorthogonal click chemistry, most commonly used in the copper-catalyzed azide–alkyne cycloaddition (CuAAC) workflow. Its ethynyl group provides a reactive handle for post-incubation labeling, enabling sensitive detection of nucleoside incorporation into newly synthesized DNA. Because EdU is structurally compatible with DNA replication processes and is widely adopted in cell biology and molecular imaging, it has become a standard reagent for mapping proliferation-associated DNA synthesis with downstream fluorescent or affinity-tag readouts.

1. DNA Replication Labeling

5-Ethynyl-2'-deoxyuridine (EdU) is routinely used as a nucleoside analog to label newly synthesized DNA in cultured cells and other replicating systems, supporting experimental designs that require temporal resolution of DNA synthesis. Researchers incorporate EdU into replication workflows and then perform a subsequent CuAAC reaction to attach reporter dyes, fluorophores, or affinity tags, allowing visualization by fluorescence microscopy, flow cytometry, or plate-based imaging. This application is especially common in laboratories building standardized proliferation assays, cell-cycle studies, and replication dynamics experiments where robust downstream detection is essential.

2. Fluorescent Imaging Probes

5-Ethynyl-2'-deoxyuridine (EdU) serves as a versatile precursor for generating fluorescent imaging probes through click-based conjugation to azide-functional dyes or imaging reagents. In molecular imaging and microscopy workflows, EdU labeling followed by click attachment of a fluorescent reporter enables spatial mapping of DNA synthesis at the single-cell and subcellular levels. Many imaging-focused users select EdU because the click step can be performed after fixation or permeabilization, integrating smoothly into established staining pipelines for multiplex experiments that combine DNA synthesis readouts with additional cellular markers.

3. Flow Cytometry Readouts

5-Ethynyl-2'-deoxyuridine (EdU) is widely applied in cell analysis workflows where quantitative measurement of DNA synthesis is required, such as flow cytometry-based assays. After EdU incorporation, the CuAAC labeling step with an azide-linked fluorophore produces a stable fluorescent signal that can be measured across large cell populations. This approach is commonly used to compare labeling intensity across experimental conditions, to profile cell-cycle distributions, and to support high-throughput screening formats in research settings that rely on consistent, reproducible signal generation.

4. Educational Molecular Biology Assays

5-Ethynyl-2'-deoxyuridine (EdU) is frequently adopted in teaching and training laboratories that introduce bioorthogonal chemistry and DNA synthesis assays using a straightforward labeling-and-detection workflow. Because EdU provides a clear, visual readout after click conjugation to reporter azides, it is well suited for demonstrating how nucleoside analogs can be used to mark replication-associated DNA and how click chemistry enables selective tagging. Many educators and core facilities also favor EdU for building reproducible demonstration protocols that connect chemical reactivity to measurable biological outcomes in a classroom or workshop environment.

5. Biomolecular Conjugation Standards

5-Ethynyl-2'-deoxyuridine (EdU) is used as a reference labeling reagent in chemical biology and biomaterials research settings that require controllable incorporation of an alkyne handle into nucleic acid contexts. By providing an ethynyl functional group that can be selectively addressed by azide partners, EdU supports the development of assay standards, labeling controls, and method validation experiments for click-based detection strategies. This use case is common in workflows optimizing probe density, signal-to-background behavior, and compatibility with downstream analytical platforms that rely on reliable, orthogonal conjugation chemistry.