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Fluo-4 AM Ester

Membrane-permeant form of Fluo-4 calcium indicator.

Product Attributes

CAS number



Calcium indicators

Cell permeability

Membrane permeant

Indicator type



494/516 nm (after hydrolysis)

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10 x 50 ug
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Product Description

Membrane-permeant AM ester form of Fluo-4 that can enter into into cells via incubation. Fluo-4 AM ester itself does not bind Ca2+, but it is readily hydrolyzed to Fluo-4 by endogenous esterases once inside cells. Fluo-4 AM ester is often used to measure intracellular calcium in high throughput drug screening.

Fluo-4 is an analog of Fluo-3 with the two chlorine substituents replaced by fluorines, which results in increased fluorescence excitation at 488 nm that gives higher fluorescence signal. Fluo-4 has its absorption maximum at 494 nm, thus making it excitable by the argon-ion laser. Fluo-4 is essentially nonfluorescent without Ca2 present, but the fluorescence increases at least 100 times on Ca2+ binding. Also, because Fluo-4 binds Ca2+ more weakly (higher Kd) than do fura-2 and indo-1, it is more useful for measuring high transient Ca2+ concentration during Ca2+ spikes.

Fluo-4 AM ester can be used to detect intracellular free calcium by fluorescence microscopy, flow cytometry, or fluorescence microplate reader.

We also offer Fluo-4 as a membrane-impermeant pentapotassium salt version, Cat # 50019.

  • Orange red solid soluble in DMSO
  • Store -20°C and protect from light, especially when in solution
  • λExEm (with Ca2+): 494/506 nm (after hydrolysis)
  • Kd for Ca2+ in buffer: ~335 nM (after hydrolysis)
  • C51H50F2N2O23
  • MW: 1096.95
  • [273221-67-3]



  1. Cell Calcium (2000), doi: 10.1054/ceca.1999.0095

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