One-Step Universal TUNEL Apoptosis Kits (Fluorescein 594, Red)

During apoptosis, activated intracellular endonucleases cleave genomic DNA between nucleosomes, producing DNA fragments of 180–200 bp, which appear as a characteristic ladder pattern in agarose gel electrophoresis. When genomic DNA is broken (double- or single-stranded), a large number of sticky 3'-OH termini are generated. These termini can be labeled with dUTP under the catalysis of terminal deoxynucleotidyl transferase (TdT) . This allows direct detection of apoptotic cells using fluorescence microscopy or flow cytometry. This method is known as Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) . Since normal or proliferating cells rarely have DNA breaks, 3'-OH termini are almost absent, resulting in minimal background staining. The TUNEL assay enables in situ labeling of intact apoptotic nuclei or apoptotic bodies, accurately reflecting the biochemical and morphological characteristics of apoptosis. It is highly sensitive and capable of detecting even a small number of apoptotic cells, making it widely used in apoptosis research. This kit has a broad range of applications. It can be used to detect apoptosis in frozen or paraffin-embedded tissue sections, as well as in adherent or suspension cell cultures. It selectively labels apoptotic cells, distinguishing them from necrotic cells or cells with DNA strand breaks caused by irradiation or drug treatment. The assay is rapid, requiring only a single staining step followed by washing and detection.