Fluorogenic Strain-Promoted Alkyne-Diazo Cycloadditions.
Fluorogenic reactions, in which non- or weakly fluorescent reagents produce highly fluorescent products, are attractive for detecting a broad range of compounds in the fields of bioconjugation and material sciences. Herein, we report that a dibenzocyclooctyne derivative modified with a cyclopropenone moiety (Fl-DIBO) can undergo fast strain-promoted cycloaddition reactions under catalyst-free conditions with azides, nitrones, nitrile oxides, as well as mono- and disubstituted diazo-derivatives. Although the reaction with nitrile oxides, nitrones, and disubstituted diazo compounds gave cycloadducts with low quantum yield, monosubstituted diazo reagents produced 1H-pyrazole derivatives that exhibited an approximately 160-fold fluorescence enhancement over Fl-DIBO combined with a greater than 10,000-fold increase in brightness. Concluding from quantum chemical calculations, fluorescence quenching of 3H-pyrazoles, which are formed by reaction with disubstituted diazo-derivatives, is likely due to the presence of energetically low-lying (n,π*) states. The fluorogenic probe Fl-DIBO was successfully employed for the labeling of diazo-tagged proteins without detectable background signal. Diazo-derivatives are emerging as attractive reporters for the labeling of biomolecules, and the studies presented herein demonstrate that Fl-DIBO can be employed for visualizing such biomolecules without the need for probe washout.
Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, GA 30602 (USA), Fax: (+1) 706-542-4412.|Present address: Institut Européen de Chimie et Biologie, Université de Bordeaux, INCIA, CNRS UMR 5287, 2 rue Robert Escarpit, 33607 Pessac (France).
Frédéric
F
Friscourt
School of Chemistry and Biochemistry and Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, 901 Atlantic Drive, Atlanta, GA 30332 (USA).
Christoph J
CJ
Fahrni
Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, GA 30602 (USA), Fax: (+1) 706-542-4412. gjboons@ccrc.uga.edu.
Geert-Jan
GJ
Boons
D000480:Alkynes / Q000737:chemistry*; D001391:Azo Compounds / Q000737:chemistry*; D002384:Catalysis; D061565:Cycloaddition Reaction; D034242:Cyclooctanes / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000737:chemistry*; D011789:Quantum Theory
D000480:Alkynes; D001391:Azo Compounds; D034242:Cyclooctanes; D005456:Fluorescent Dyes
bioorthogonal; click chemistry; cycloaddition; cyclooctyne; fluorogenic probes