FITC膜联蛋白V染色先于膜完整性的丧失,伴随着由凋亡或坏死过程引起的细胞死亡阶段。因此,FITC膜联蛋白V的染色通常与重要染料(如碘化丙啶(PI)或7-氨基放线菌素(7-AAD))结合使用,以使研究人员能够鉴定早期凋亡细胞(PI阴性,FITC膜联蛋白V正)。具有完整膜的活细胞排除PI,使死亡和受损细胞的膜可透过PI。FITC膜联蛋白V细胞凋亡检测试剂盒(BD Pharmingen)
更新时间:2017-10-11
FITC膜联蛋白V染色先于膜完整性的丧失,伴随着由凋亡或坏死过程引起的细胞死亡阶段。因此,FITC膜联蛋白V的染色通常与重要染料(如碘化丙啶(PI)或7-氨基放线菌素(7-AAD))结合使用,以使研究人员能够鉴定早期凋亡细胞(PI阴性,FITC膜联蛋白V正)。具有完整膜的活细胞排除PI,使死亡和受损细胞的膜可透过PI。例如,认为可行的细胞是FITC膜联蛋白V和PI阴性; 早期凋亡细胞是FITC Annexin V阳性和PI阴性; 细胞凋亡或已经死亡的细胞都是FITC膜联蛋白V和PI阳性。该测定不区分已经经历凋亡死亡的细胞与由于坏死性途径死亡的细胞,因为在任一情况下,死细胞都会用FITC Annexin V和PI染色。然而,随着时间的推移,当细胞凋亡被测量时,细胞可以经常从FITC膜联蛋白V和PI阴性(可行或无可测量的凋亡)追溯到FITC膜联蛋白V阳性和PI阴性(早期凋亡,膜完整性存在),zui后到FITC膜联蛋白V和PI阳性(末期凋亡和死亡)。细胞通过这三个阶段的运动表明细胞凋亡。相比之下,一个单一的观察结果表明,细胞都是FITC膜联蛋白V和PI阳性,本身就显示出关于细胞进行死亡的过程的信息较少。
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Apoptosis is a normal physiologic process which occurs during embryonic development as well as in maintenence of tissue homeostasis. The apoptotic program is characterized by certain morphologic features, including loss of plasma membrane asymmetry and attachment, condensation of the cytoplasm and nucleus, and internucleosomal cleavage of DNA. Loss of plasma membrane is one of the earliest features. In apoptotic cells, the membrane phospholipid phosphatidylserine (PS) is translocated from the inner to the outer leaflet of the plasma membrane, thereby exposing PS to the external cellular environment. Annexin V is a 35-36 kDa Ca2+ dependent phospholipid-binding protein that has a high affinity for PS, and binds to cells with exposed PS. Annexin V may be conjugated to fluorochromes including FITC. This format retains its high affinity for PS and thus serves as a sensitive probe for flow cytometric analysis of cells that are undergoing apoptosis. Since externalization of PS occurs in the earlier stages of apoptosis, FITC Annexin V staining can identify apoptosis at an earlier stage than assays based on nuclear changes such as DNA fragmentation.
FITC Annexin V staining precedes the loss of membrane integrity which accompanies the latest stages of cell death resulting from either apoptotic or necrotic processes. Therefore, staining with FITC Annexin V is typically used in conjunction with a vital dye such as propidium iodide (PI) or 7-Amino-Actinomycin (7-AAD) to allow the investigator to identify early apoptotic cells (PI negative, FITC Annexin V positive). Viable cells with intact membranes exclude PI, wheras the membranes of dead and damaged cells are permeable to PI. For example, cells that are considered viable are FITC Annexin V and PI negative; cells that are in early apoptosis are FITC Annexin V positive and PI negative; and cells that are in late apoptosis or already dead are are both FITC Annexin V and PI positive. This assay does not distinguish between cells that have undergone apoptotic death versus those that have died as a result of a necrotic pathway because in either case, the dead cells will stain with both FITC Annexin V and PI. However, when apoptosis is measured over time, cells can be often tracked from FITC Annexin V and PI negative (viable, or no measurable apoptosis), to FITC Annexin V positive and PI negative (early apoptosis, membrane integrity is present) and finally to FITC Annexin V and PI positive (end stage apoptosis and death). The movement of cells through these three stages suggests apoptosis. In contrast, a single observation indicating that cells are both FITC Annexin V and PI positive, in of itself, reveals less information about the process by which the cells underwent their demise.
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