{{Short description|Fluorogenic amine labelling dye}} {{chembox | Name = CBQCA | Watchedfields = | verifiedrevid = | Reference = | ImageFile = CBQCA_Chemical_structure.svg | ImageSize = 150px | PIN = 4-(2-Formylquinoline-3-carbonyl)benzoic acid | OtherNames = CBQCA, ATTO-TAG CBQCA |Section1={{Chembox Identifiers | CASNo_Ref = {{cascite|correct|cas}} | CASNo = 131124-59-9 | ChEBI = 51934 | ChemSpiderID = 111618 | EC_number = | PubChem = 125448 | SMILES = C1=CC=C2C(=C1)C=C(C(=N2)C=O)C(=O)C3=CC=C(C=C3)C(=O)O | 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) | InChIKey = MWNLTKCQHFZFHN-UHFFFAOYSA-N }} |Section2={{Chembox Properties | C=18 | H=11 | N=1 | O=4 | Appearance = | Density = | MeltingPtC = | MeltingPt_notes = | BoilingPt = | Solubility = }} |Section3={{Chembox Hazards | MainHazards = | FlashPt = | AutoignitionPt = }} }}
'''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.<ref name="You1997">{{cite journal | last1=You | first1=Wendy W. | last2=Haugland | first2=Rosaria P. | last3=Ryan | first3=Diane K. | last4=Haugland | first4=Richard P. | title=3-(4-Carboxybenzoyl)quinoline-2-carboxaldehyde, a Reagent with Broad Dynamic Range for the Assay of Proteins and Lipoproteins in Solution | journal=Analytical Biochemistry | publisher=Elsevier BV | volume=244 | issue=2 | year=1997 | issn=0003-2697 | doi=10.1006/abio.1996.9920 | pages=277–282| pmid=9025944 }}</ref> It was first reported in 1991.<ref name="Liu Hsieh Wiesler Novotny 1991 pp. 408–412">{{cite journal | last1=Liu | first1=Jinping. | last2=Hsieh | first2=You Zoung. | last3=Wiesler | first3=Donald. | last4=Novotny | first4=Milos. | title=Design of 3-(4-carboxybenzoyl)-2-quinolinecarboxaldehyde as a reagent for ultrasensitive determination of primary amines by capillary electrophoresis using laser fluorescence detection | journal=Analytical Chemistry | publisher=American Chemical Society (ACS) | volume=63 | issue=5 | date=1991-03-01 | issn=0003-2700 | doi=10.1021/ac00005a004 | pages=408–412| pmid=2064006 }}</ref>
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.<ref name="You1997"></ref> Once bound to protein the excitation wavelength is 465 nm (blue) and the emission wavelength is ~550 nm (green).<ref>{{cite web |last1=Fisher Scientific |first1=Thermo |title=CBQCA Protein Quantitation Kit - Product Information |url=https://assets.thermofisher.com/TFS-Assets/LSG/manuals/mp06667.pdf |access-date=7 April 2023}}</ref>
==Reaction== CBQCA, which is non-fluorescent, reacts with primary amines in the presence of cyanide to form fluorescent products: :File:CBQCA reaction scheme.svg
==See also== * 3-(2-Furoyl)quinoline-2-carboxaldehyde (FQ)
==References== {{reflist}}
{{DEFAULTSORT:Carboxybenzoyl)quinoline-2-carboxaldehyde, 3-(4-}} Category:Dyes Category:Quinolines Category:Aldehydes Category:Benzoic acids Category:Aromatic ketones