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#EdU assay

2 public questions tagged with this topic.

Animal Tissue Culture 3

An advantage of EdU assay is:

Predominant advantage of EdU assay over BrdU is preservation of cellular architecture because it avoids harsh DNA denaturation. BrdU detection requires unwinding double helix using strong acid, heat, or enzymatic digestion to expose concealed bromo-deoxyuridine epitope for anti-BrdU antibody of large size 150 kDa that cannot access double-stranded DNA. These treatments hydrolyze fluorescent proteins such as GFP, destroy conformational epitopes of surface antigens CD markers, fragment histology, alter light scatter properties in flow cytometry, and distort cell cycle distributions. EdU click detection employs small organic azide dye around 1 kDa that diffuses freely into intact duplex forming covalent triazole without strand separation. Consequently morphology remains intact under phase-contrast, immunophenotype retains antigenicity enabling co-detection of stem markers, and compatibility with DNA content dyes propidium iodide or DAPI remains high without acid-induced artifacts. Sensitivity improves due to quantitative triazole formation, protocol duration reduces significantly, and multiplex capability expands making EdU preferred for tissue sections, whole mount embryos, and high-content imaging.

Ref: Buck et al Biotechniques 2008 EdU advantage no denaturation preserves antigens; Thermo Fisher Click-iT EdU vs BrdU no DNA denaturation needed.

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Animal Tissue Culture 3

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, harsh denaturation required for BrdU antibody access unnecessary. Standard BrdU assays need 2M hydrochloric acid, 95°C heat, or DNase digestion to unwind helix exposing brominated base for antibody binding, steps that destroy protein epitopes and fluorescent proteins. Click reaction eliminates antibody step, shortens protocol from overnight incubation to less than one hour, preserves morphology, and allows multiplexing with surface markers. Unlike radioactive thymidine labeling, EdU non-radioactive and bright. This advance revolutionized proliferation assessment. Nobel Prize in Chemistry 2022 recognized click chemistry applications transforming biological labeling and drug discovery. This knowledge strengthens laboratory safety, protocol reproducibility, and regulatory compliance critical for translational research and clinical applications, ensuring reliable data and workforce protection.

Ref: Salic A & Mitchison TJ PNAS 2008 EdU click chemistry; Kolb et al Click chemistry concept Nobel Prize 2022 CuAAC azide-alkyne.

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