:Fluo-3

{{Chembox

| ImageFile = Fluo-3.svg

| ImageSize = 200px

| PIN = 2,2′-{[2-(2-{2-[Bis(carboxymethyl)amino]-5-(2,7-dichloro-6-hydroxy-3-oxo-3H-xanthen-9-yl)phenoxy}ethoxy)-4-methylphenyl]azanediyl}diacetic acid

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|Section1={{Chembox Identifiers

| CASNo = 123632-39-3

| CASNo_Ref = {{cascite|correct|CAS}}

| UNII_Ref = {{fdacite|correct|FDA}}

| UNII = 23D4W0B50Y

| PubChem = 104978

| ChemSpiderID = 94730

| ChEMBL = 509919

| SMILES = O=C(O)CN(c5ccc(cc5OCCOc4c(N(CC(=O)O)CC(=O)O)ccc(C=1c3c(OC=2C=1\C=C(\Cl)C(=O)C=2)cc(O)c(Cl)c3)c4)C)CC(=O)O

| InChI = 1/C36H30Cl2N2O13/c1-18-2-4-24(39(14-32(43)44)15-33(45)46)30(8-18)51-6-7-52-31-9-19(3-5-25(31)40(16-34(47)48)17-35(49)50)36-20-10-22(37)26(41)12-28(20)53-29-13-27(42)23(38)11-21(29)36/h2-5,8-13,41H,6-7,14-17H2,1H3,(H,43,44)(H,45,46)(H,47,48)(H,49,50)

| InChIKey = OZLGRUXZXMRXGP-UHFFFAOYAI

| StdInChI = 1S/C36H30Cl2N2O13/c1-18-2-4-24(39(14-32(43)44)15-33(45)46)30(8-18)51-6-7-52-31-9-19(3-5-25(31)40(16-34(47)48)17-35(49)50)36-20-10-22(37)26(41)12-28(20)53-29-13-27(42)23(38)11-21(29)36/h2-5,8-13,41H,6-7,14-17H2,1H3,(H,43,44)(H,45,46)(H,47,48)(H,49,50)

| StdInChIKey = OZLGRUXZXMRXGP-UHFFFAOYSA-N

}}

|Section2={{Chembox Properties

| C=36 | H=30 | Cl=2 | N=2 | O=13

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|Section3={{Chembox Hazards

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Fluo-3 is a fluorescence indicator of intracellular calcium (Ca²⁺), developed by Roger Y. Tsien.{{cite journal | last1 = Tsien | first1 = R.Y. | year = 1980 | title = New calcium indicators and buffers with high selectivity against magnesium and protons: design, synthesis, and properties of prototype structures | journal = Biochemistry | volume = 19 | issue = 11 | pages = 2396–2404 | doi = 10.1021/bi00552a018| pmid = 6770893 }} It is used to measure Ca²⁺ inside living cells in flow cytometry, and confocal laser scanning microscopy using visible light excitation (compatible with argon laser sources operating at 488 nm). Fluo-3 and derivatives (Fluo-4, Fluo-5 etc) have also been widely used with two-photon excitation microscopy. Fluo-3 is an essentially nonfluorescent compound, but upon binding of Ca²⁺ its fluorescence increases sharply with an emission maximum at 525 nm suitable for conventionally used detectors designed for fluorescein isothiocyanate (FITC) measurements. This large change in fluorescence coupled with a good yield of photons provides very high contrast which allowed the detection of microscopic Ca²⁺ release events inside cells called "Calcium sparks".{{cite journal | last1 = Cheng | first1 = H. | last2 = Lederer | first2 = W.J. | last3 = Cannell | first3 = M.B. | year = 1993 | title = Calcium Sparks - Elementary Events Underlying Excitation-Contraction Coupling in Heart-Muscle | journal = Science | volume = 262 | issue = 5134| pages = 740–744 | pmid = 8235594 | doi=10.1126/science.8235594| bibcode = 1993Sci...262..740C }} Whereas the salts of fluo-3 are unable to penetrate cells, loading can be achieved using its acetoxymethyl (AM) ester derivative. Once inside the cell, unspecific esterases cleave the ester effectively trapping fluo-3.Haugland, RP. Handbook of Fluorescent Probes and Research Products. Molecular Probes, 2010

As calcium is a key second messenger within cells, the specific properties of fluo-3 enable researchers to investigate the time-resolved dynamics of intracellular signal transduction in a diverse range of cells.Gamsjäger, T. Flow Cytometry of Intracellular Calcium in Platelets. Grin, 2012Lambert, DG. Calcium Signaling Protocols. Humana Press, 2006