Description
Annexins are a family of calcium-dependent phospholipid-binding proteins that preferentially bind phosphatidylserine (PS). Under normal physiologic conditions, PS is predominantly located in the inner leaflet of the plasma membrane. Upon initiation of apoptosis, PS loses its asymmetric distribution across the phospholipid bilayer and is translocated to the extracellular membrane leaflet marking cells as targets of phagocytosis. Once on the outer surface of the membrane, PS can be detected by fluorescently labeled Annexin V in a calcium-dependent manner. In early-stage apoptosis, the plasma membrane excludes viability dyes such as propidium iodide (PI), 7-AAD. These cells will stain with Annexin V but not a viability dye, thus distinguishing cells in early apoptosis. However, in late stage apoptosis, the cell membrane loses integrity thereby allowing Annexin V to also access PS in the interior of the cell. A viability dye can be used to resolve these late-stage apoptotic and necrotic cells (Annexin V, viability dye-positive) from the early-stage apoptotic cells (Annexin V positive, viability dye-negative). This kit is suitable for the identification and enumeration of dead cells, such as apoptotic or necrotic cells, by flow cytometry. Kit ContentsA1373480Component20 T50 T100 TStorageQuantity Per TestA1373480A10x Annexin V Binding Buffer5 mL10 mL20 mL2-8℃.200 µL 0.5-1.0x10^5 cellsA1373480BAnnexin V-Biotin450 µL1.5 mL2.5 mL2-8℃, Store in the dark.20 µL 0.5-1.0x10^5 cellsA1373480CPropidium iodide Staining Solution (PI)15 µL30 µL55 µL2-8℃, Store in the dark.0.5 µL 0.5-1.0x10^5 cellsA1373480DStreptavidin protein (FITC) 10 µL15 µL25 µL2-8℃, Store in the dark.0.2 µL 0.5-1.0x10^5 cells Note: The recommended number of cells to stain per test is 0.5-1.0x10^5 cells.Instruction for use1. Before use, dilute the 10x binding buffer with deionized water to 1x (1 mL of 10x buffer plus 9 mL of deionized water);2. After pre-cooling PBS and washing the cells twice, resuspend them in 1x Annexin V binding buffer at a density of 0.5-1.0x10^6 /mL;3. Add 20 µL of fluorescently labeled Annexin V-Biotin and 0.5 µL of PI dye to each 200 µL cell suspension;4. Gently vortex the cells and incubate at room temperature in the dark for 10 minutes;5. Centrifuge at 400g for 5 minutes, remove the supernatant;6. Dilute Streptavidin protein (FITC) with 1x Annexin V binding buffer at a ratio of 1:1000;7. Add 200 µL of the diluted Streptavidin protein (FITC) and gently resuspend the cells;8. Incubate at 4°C in the dark for 30 minutes;9. Centrifuge at 400g for 5 minutes to remove the Streptavidin protein (FITC);10. Add 200 µL of the binding buffer and complete the instrument analysis within 1 hour.Matters needing attention 1. Please try to avoid light when using to slow down the quenching of fluorescence. 2. Propidium Iodide Solution is toxigenic and mutagenic; handle with care. 3. Due to the calcium dependence of the Annexin V:PS interaction, it is critical to avoid buffers containing EDTA or other calcium chelators during Annexin V experiments