{{Chembox | ImageFile = Fluo-3.svg | ImageSize = 200px | PIN = 2,2′-<nowiki/>{[2-(2-<nowiki/>{2-[Bis(carboxymethyl)amino]-5-(2,7-dichloro-6-hydroxy-3-oxo-3''H''-xanthen-9-yl)phenoxy}ethoxy)-4-methylphenyl]azanediyl}diacetic acid | OtherNames = |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 | Appearance = | Density = | MeltingPt = | BoilingPt = | Solubility = }} |Section3={{Chembox Hazards | MainHazards = | FlashPt = | AutoignitionPt = }} }}
'''Fluo-3''' is a fluorescence indicator of intracellular calcium (Ca<sup>2+</sup>), developed by Roger Y. Tsien.<ref>{{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 }}</ref> It is used to measure Ca<sup>2+</sup> 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 Ca<sup>2+</sup> 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 Ca<sup>2+</sup> release events inside cells called "Calcium sparks".<ref>{{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 }}</ref> 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.<ref>Haugland, RP. ''Handbook of Fluorescent Probes and Research Products''. Molecular Probes, 2010</ref>
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.<ref>Gamsjäger, T. ''Flow Cytometry of Intracellular Calcium in Platelets''. Grin, 2012</ref><ref>Lambert, DG. ''Calcium Signaling Protocols''. Humana Press, 2006</ref>
==References== {{Reflist}}
Category:9-phenylfluorone dyes Category:Cell imaging Category:Acetic acids Category:Anilines Category:Phenol ethers Category:Chloroarenes Category:Phenylogous carboxylic acids Category:Xanthenes Category:Glycol ethers