Fura-2 是细胞内钙离子（Ca²⁺）的特异性荧光指示剂，是最常用的检测细胞内钙离子浓度的荧光探针之一。
Fura-2 AM 是一种可以穿透细胞膜的荧光染料。Fura-2 AM 的荧光比较弱，最大激发波长为 369 nm，最大发射波长为 478 nm，并且其荧光不会随钙离子浓度改变而改变。Fura-2 AM 进入细胞后可以被细胞内的酯酶剪切形成 Fura-2，从而被滞留在细胞内。Fura-2 和钙离子结合后，最大激发波长为 335 nm（最大激发波长随离子浓度的不同而有所不同），最大发射波长为 505 nm。实际检测时推荐使用的激发波长为 340 nm，发射波长为 510 nm。如果做双波长检测，则推荐使用的激发波长为 340 nm 和 380 nm。
用于细胞内钙离子检测时，Fura-2 AM 的常用浓度为 0.5-5 μM。通常用含有 0.5-5μM 的 Fura-2 AM 的适当溶液和细胞一起在 4-37℃孵育 15-60 分钟，即可完成荧光探针的装载。
Fura-2 is a specific fluorescent indicator for intracellular calcium ions (Ca²⁺), and it is one of the most commonly used fluorescent probes for detecting intracellular calcium ion concentration.Fura-2 AM is a cell-permeable fluorescent dye. It exhibits weak fluorescence, with a maximum excitation wavelength of 369 nm and a maximum emission wavelength of 478 nm. Notably, its fluorescence intensity does not change with variations in calcium ion concentration. After entering cells, Fura-2 AM can be cleaved by intracellular esterases to form Fura-2, which is then trapped inside the cells. When Fura-2 binds to calcium ions, its maximum excitation wavelength is 335 nm (the maximum excitation wavelength varies with ion concentration), and the maximum emission wavelength is 505 nm. For practical detection, the recommended excitation wavelength is 340 nm and the emission wavelength is 510 nm. For dual-wavelength detection, the recommended excitation wavelengths are 340 nm and 380 nm.
For intracellular calcium ion detection, the commonly used concentration of Fura-2 AM is 0.5–5 μM. Typically, probe loading can be achieved by incubating cells with an appropriate solution containing 0.5–5 μM Fura-2 AM at 4–37 °C for 15–60 minutes.
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