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 and consequently higher fluorescence signal levels. Cells may be loaded with the AM ester forms of these calcium indicators by adding the dissolved indicator directly...

Fluo-4 acetoxymethyl ester (Fluo-4 AM) is a cell-permeable fluorescent calcium indicator. It is cleaved by intracellular esterases to release Fluo-4, which binds to calcium with a Kd value of 345 nM and displays excitation/emission maxima of 490/520 nm, respectively. Fluo-4 AM has been used to measure intracellular...