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Skeletal formula of tetradeprotonated fluo-4
IUPAC name
Systematic IUPAC name
2,2'-((2-(2-(2-(bis(carboxymethyl)amino)-5-(2,7-difluoro-6-hydroxy-3-oxo-3H-xanthen-9-yl)phenoxy)ethoxy)-4-methylphenyl)azanediyl)diacetic acid
3D model (JSmol)
MeSH Fluo-4
Molar mass 736.63 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Fluo-4 is used to measure calcium (Ca2+) concentrations inside living cells, and is often used for high-throughput screening of receptor ligands and calcium permeable ion channels.

The green-fluorescent calcium indicator, Fluo-4, is an improved version of the calcium indicator, Fluo-3. It is commonly used as the non-fluorescent acetoxymethyl ester (Fluo-4 AM) which is cleaved inside the cell to give the free, fluorescent Fluo-4. It loads faster, is brighter at equivalent concentrations and is well-excited by the 488 nm line of the argon-ion laser which is often used in biological research laboratories.[1] Fluo-4 and its cell-permeable AM ester are available from a few commercial vendors.


  1. ^ Gee KR, Brown KA, Chen WN, Bishop-Stewart J, Gray D, Johnson I (February 2000). "Chemical and physiological characterization of fluo-4 Ca(2+)-indicator dyes". Cell Calcium. 27 (2): 97–106. doi:10.1054/ceca.1999.0095. PMID 10756976.