APOPTRAK™

The Science

APOPTRAK™ is a small molecule (442 Da) belonging to the anthraquinone family. It is optimally excited at 633 or 647 nm and emission in the far-red/near infra-red (NIR) peaking at 700 nm.

APOPTRAK™ is a useful dye in flow cytometry applications:

• APOPTRAK™ is a low toxicity dye with similar spectral properties to DRAQ5™ but with a reduced ability to bind to cellular DNA. Being charge neutral APOPTRAK™ is capable of entering viable cells at low but detectable rates to primarily occupy cytoplasmic compartments.
• APOPTRAK™’s far-red florescence signal in ‘intact/live’ cells increases when there is greater dye access upon the disruption of the plasma membrane. Residual DNA binding capacity of APOPTRAK™ permits the detection of the nuclear fragments during cell break-up.

Why APOPTRAK™?

APOPTRAK™ benefits from all the advantageous "far-red" spectral properties of its parent, but differs significantly in its rate of entry into LIVE cells. APOPTRAK™ enters LIVE cells slowly and apoptotic cells rapidly, allowing a positive discrimination between these two populations. Key benefits include:-

• Different rate of entry into LIVE and apoptotic cells, allowing positive discrimination by flow cytometry (with Annexin V-FITC, for example)
• Easy to use - no lyse, no wash, no RNase needed
• Ideal for use with GFP & FITC labels - APOPTRAK™ fluoresces in the far-red region

APOPTRAK™ can bring significant benefits to your application:

• positive discrimination between intact cells, membrane-compromised cells, cellular debris
• validated for use in Annexin V binding assay protocols

Technical Information

APOPTRAK™ enters LIVE cells slowly and leaky (apoptotic) cells rapidly, to give a signal intensity difference of between 5- and 10-fold, depending on the cell type and treatment. This allows a positive discrimination between these two populations as shown in the example data below.

Published data (Wiltshire et al, Cytometry 2000) suggests an ability of APOPTRAK™ to discriminate early and late apoptotic cells when used in combination with Annexin V. The example below shows the uptake of APOPTRAK™ in a B cell lymphoma sample carrying a low burden of apoptotic cells. Cells were co-stained with FITC-Annexin V.

• Exλmax 633 nm
• Emλmax 700.5 nm, with a red-shift of 12 nm upon DNA binding
• Suggested optimal emission filters include Cy5, 695LP, 730/50BP or 780/60BP