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iClick™ TUNEL Andy Fluor™ 555 Imaging Assay


Internucleosomal cleavage of DNA is a hallmark of apoptosis. DNA cleavage in apoptotic cells can be detected in situ in fixed cells or tissue sections using the terminal deoxynucleotidyl transferase (TdT) mediated dUTP nick-end labeling (TUNEL) method. TUNEL is highly selective for the detection of apoptotic cells but not necrotic cells or cells with DNA strand breaks resulting from irradiation or drug treatment.

In the TUNEL assay, TdT enzyme catalyzes the addition of modified dUTP to the 3’-OH ends of fragmented DNA. The modifications are fluorophores or haptens, including biotin or bromine which can be detected directly in the case of a fluorescently-modified nucleotide, or indirectly with streptavidin or antibodies, if biotin-dUTP or BrdUTP are used, respectively.

The new iClick™ TUNEL Andy Fluor™ 555 Imaging Assay utilize a dUTP modified with an alkyne, a small, bio-orthogonal functional group that enables the nucleotide to be more readily incorporated by TdT than other modified nucleotides such as biotin-dUTP and fluorescein-dUTP. Detection is based on a click reaction, a copper (I) catalyzed reaction between an azide and alkyne (Figure 1). The small size of the Andy Fluor™ azide (MW ∼1,000) compared to that of an antibody (MW ∼150,000) enables effortless penetration of complex samples with only mild fixation and permeabilization required. As a result, when compared to assays using other modified nucleotides, the iClick™ TUNEL Imaging Assay is fast (complete within 2 hours) and is able to detect a higher percentage of apoptotic cells under identical conditions.


  • Broad application: Suitable for FFPE tissue, frozen tissue and cells.
  • High sensitivity: Can detect a higher percentage of apoptotic cells.
  • Bright apoptotic signal: Uses Andy Fluor dyes, resulting in a stable, non-photobleaching fluorescent signal.

Figure 1. Detection of apoptosis with the iClick™ TUNEL Imaging Assay.


Platform: Fluorescence Microscopy
Detection Method: Fluorescent
Ex/Em: 555/575 nm
Product Size: 50 assays
Storage Conditions: -20 ℃, protect from light
Shipping Condition: Dry ice


Figure 2. Detection of apoptotic cells in mouse tissue using  iClick TUNEL Andy Fluor™ 555 Imaging Assay.

To order

Buy Cat.No. Product Name Ex/Em Unit Price
A061 iClick™ TUNEL Andy Fluor™ 555 Imaging Assay 555/575 50 assay $420




Protocol (PDF): A061  
MSDS (PDF):   

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