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• Annexin V-AF 647 Apoptosis Detection Kit, with Propidium Iodide

Annexin V-AF 647 Apoptosis Detection Kit, with Propidium Iodide

Annexin V (or Annexin A5) is a member of the phospholipid-binding annexin family of intracellular proteins. In flow cytometry and fluorescent microscopy, Annexin V is commonly used to detect apoptotic cells by its ability to specifically bind to phosphatidylserine (PS) in a calcium-dependent manner. The method was first reported by Koopman et al. (1994) [1].

In healthy cells, PS is normally retained in the inner leaflet of the plasma membrane. The early stage of apoptosis is accompanied by a loss of membrane phospholipid asymmetry, resulting in the exposure of PS at the cell's surface. In conjunction with vital dyes such as propidium iodide (PI), fluorochrome-labeled Annexin V can distinguish between healthy (Annexin⁻PI⁻), apoptotic (Annexin⁺PI⁻), and necrotic (Annexin⁺PI⁺) cells [2].

The ready-to-use kit contains all necessary reagents to label apoptotic cells with Annexin V-AF 647 conjugate and PI.

AF 647 is a bright, far-red-emitting fluorescent dye with high fluorescence quantum yield and photostability. The spectrum of AF 647 is far from the green-yellow wavelengths, which makes it indispensable for labeling cells with high autofluorescence. The absorption and emission maxima of AF 647 are at 655 and 680 nm, respectively.

PI is a membrane-impermeable DNA stain, making it useful for differentiating necrotic, apoptotic, and healthy cells based on membrane integrity. After DNA binding, the dye emits in the orange-red channel. Its absorption max. is at 535 nm, the emission max. is at 617 nm.

[1] Koopman G. et al. Annexin V for flow cytometric detection of phosphatidylserine expression on B cells undergoing apoptosis. Blood. 1994. 84(5). P.1415-1420.

[2] Martin S.J. et al. Early redistribution of plasma membrane phosphatidylserine is a general feature of apoptosis regardless of the initiating stimulus: inhibition by overexpression of Bcl-2 and Abl. J Exp Med. 1995. 182(5). P.1545-1556.