3-(4-Carboxybenzoyl)quinoline-2-carboxaldehyde

3-(4-Carboxybenzoyl)quinoline-2-carboxaldehyde (CBQCA) is a fluorogenic amine labeling dye that is not fluorescent itself, but covalently reacts with primary amines to form fluorescent products.^[1] It was first reported in 1991.^[2]

Quick facts Names, Identifiers ...

CBQCA

Names
Preferred IUPAC name 4-(2-Formylquinoline-3-carbonyl)benzoic acid
Other names CBQCA, ATTO-TAG CBQCA
Identifiers
CAS Number	131124-59-9 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:51934
ChemSpider	111618
PubChem CID	125448
CompTox Dashboard (EPA)	DTXSID70156907
InChI InChI=1S/C18H11NO4/c20-10-16-14(9-13-3-1-2-4-15(13)19-16)17(21)11-5-7-12(8-6-11)18(22)23/h1-10H,(H,22,23) Key: MWNLTKCQHFZFHN-UHFFFAOYSA-N
SMILES C1=CC=C2C(=C1)C=C(C(=N2)C=O)C(=O)C3=CC=C(C=C3)C(=O)O
Properties
Chemical formula	C18H11NO4
Molar mass	305.289 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

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CBQCA is largely used in the context of quantifying peptides or proteins. Either cyanide or thiols are required as a co-substrate in the fluorogenic reaction, although thiols also react with and mask the CBQCA aldehyde thereby preventing the fluorogenic reaction against the targeted primary amines.^[1] Once bound to protein the excitation wavelength is 465 nm (blue) and the emission wavelength is ~550 nm (green).^[3]