During apoptosis, cells activate specific DNA endonucleases that cleave genomic DNA between nucleosomes. When DNA is extracted from apoptotic cells and analyzed by gel electrophoresis, a characteristic DNA ladder consisting of fragments in multiples of 180–200 bp can be observed.

The TUNEL (TdT-mediated dUTP Nick-End Labeling) Apoptosis Detection Kit (YSFluor™ 640) is designed to detect DNA fragmentation in the nuclei of cells during late-stage apoptosis. The assay is based on the enzymatic activity of Terminal Deoxynucleotidyl Transferase (TdT), which catalyzes the incorporation of YSFluor™ 640-12-dUTP into the 3′-hydroxyl (3′-OH) ends exposed at DNA strand breaks. The labeled DNA can then be detected using a fluorescence microscope or flow cytometer.

YSFluor™ 640 is a bright, photostable red-fluorescent dye that provides high signal intensity and excellent resistance to photobleaching.

This kit is broadly applicable and can be used to detect apoptosis in:

Formalin-fixed paraffin-embedded (FFPE) tissue sections

Frozen tissue sections

Cultured adherent or suspension cells

Features

Rapid and Convenient Detection – Simple workflow enables fast assessment of apoptosis in cultured cells without complex procedures.

High Accuracy – Dual staining with Annexin V-YSFluor™ 647 and Propidium Iodide (PI) allows precise discrimination between early apoptotic, late apoptotic, necrotic, and live cells.

Sensitive and Reliable – Optimized fluorophore conjugation and buffer formulation ensure strong signal with minimal background, suitable for flow cytometry and fluorescence microscopy.

Versatile – Compatible with a wide range of cell types, including adherent and suspension cells.

Components