FlAsH-EDT2

FlAsH-EDT2
Names
	Other names Fluorescein Arsenical Hairpin Binder; Lumio green
Identifiers
CAS Number	212118-77-9;
3D model (JSmol)	Interactive image; Interactive image;
ChEBI	CHEBI:52107;
ChEMBL	ChEMBL454668;
ChemSpider	2043798;
PubChem CID	2763100;
UNII	Z8CH38Y9L3 ;
CompTox Dashboard (EPA)	DTXSID90431400 ;
	InChI InChI=1S/C24H18As2O5S4/c27-17-7-5-15-19(13-3-1-2-4-14(13)24(29)30)16-6-8-18(28)21(26-34-11-12-35-26)23(16)31-22(15)20(17)25-32-9-10-33-25/h1-8,27H,9-12H2,(H,29,30) Key: KCPRYVGBEBFLIG-UHFFFAOYSA-N;
	SMILES c1ccc(c(c1)c2c3ccc(c(c3oc-4c(c(=O)ccc24)[As]5SCCS5)[As]6SCCS6)O)C(=O)O; OC(=O)C1=C(C=CC=C1)C1=C2C=CC(=O)C([As]3SCCS3)=C2OC2=C([As]3SCCS3)C(O)=CC=C12;
Properties
Chemical formula	C24H18As2O5S4
Molar mass	664.49 g·mol−1
Appearance	Solid
Melting point	169 to 172 °C (336 to 342 °F; 442 to 445 K)
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

FlAsH-EDT₂ is an organoarsenic compound with molecular formula C₂₄H₁₈As₂O₅S₄. Its structure is based around a fluorescein core with two 1,3,2-dithiarsolane substituents. It is used in bioanalytical research as a fluorescent label for visualising proteins in living cells.^[1] FlAsH-EDT₂ is an abbreviation for fluorescin arsenical hairpin binder-ethanedithiol, and is a pale yellow or pinkish fluorogenic solid. It has a semi-structural formula (C₂H₄AsS₂)₂-(C₁₃H₅O₃)-C₆H₄COOH, representing the dithiarsolane substituents bound to the hydroxyxanthone core, attached to an o-substituted molecule of benzoic acid.

FlAsH-EDT₂ is used for site-specific labelling, selectively binding to proteins containing the tetracysteine (TC) motif Cys-Cys-Xxx-Xxx-Cys-Cys and becoming fluorescent when bound. It displays non-specific binding to endogenous cysteine-rich proteins, meaning it binds to sites other than the one of interest (CCXXCC). Further optimization of the TC motif has revealed improved FlAsH binding affinity for a CCPGCC motif,^[2] and higher quantum yield when the tetracysteine motif is flanked with specific residues (HRWCCPGCCKTF or FLNCCPGCCMEP).^[3]

^ Adams, Stephen R.; Tsien, Roger Y. (2008). "Preparation of the membrane-permeant biarsenicals FlAsH-EDT₂ and ReAsH-EDT₂ for fluorescent labeling of tetracysteine-tagged proteins". Nat. Protoc. 3 (9): 1527–1534. doi:10.1038/nprot.2008.144. PMC 2843588. PMID 18772880.
^ Adams, Stephen R.; Campbell, Robert E.; Gross, Larry A.; Martin, Brent R.; Walkup, Grant K.; Yao, Yong; Llopis, Juan; Tsien, Roger Y. (2002). "New biarsenical ligands and tetracysteine motifs for protein labeling in vitro and in vivo: synthesis and biological applications". Journal of the American Chemical Society. 124 (21): 6063–6076. doi:10.1021/ja017687n. PMID 12022841.
^ Martin, Brent R.; Giepmans, Ben N.G.; Adams, Stephen R.; Tsien, Roger Y. (2005). "Mammalian cell–based optimization of the biarsenical-binding tetracysteine motif for improved fluorescence and affinity". Nature Biotechnology. 23 (10): 1308–1314. doi:10.1038/nbt1136. PMID 16155565. S2CID 16456334.

[Synthesis-1] Adams, Stephen R.; Tsien, Roger Y. (2008). "Preparation of the membrane-permeant biarsenicals FlAsH-EDT₂ and ReAsH-EDT₂ for fluorescent labeling of tetracysteine-tagged proteins". Nat. Protoc. 3 (9): 1527–1534. doi:10.1038/nprot.2008.144. PMC 2843588. PMID 18772880.

[Adams-2] Adams, Stephen R.; Campbell, Robert E.; Gross, Larry A.; Martin, Brent R.; Walkup, Grant K.; Yao, Yong; Llopis, Juan; Tsien, Roger Y. (2002). "New biarsenical ligands and tetracysteine motifs for protein labeling in vitro and in vivo: synthesis and biological applications". Journal of the American Chemical Society. 124 (21): 6063–6076. doi:10.1021/ja017687n. PMID 12022841.

[Martin-3] Martin, Brent R.; Giepmans, Ben N.G.; Adams, Stephen R.; Tsien, Roger Y. (2005). "Mammalian cell–based optimization of the biarsenical-binding tetracysteine motif for improved fluorescence and affinity". Nature Biotechnology. 23 (10): 1308–1314. doi:10.1038/nbt1136. PMID 16155565. S2CID 16456334.

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