Native Chemical Ligation-Based Fluorescent Probes for Cysteine and Aminopeptidase N Using meso-thioester-BODIPY

meso-Carboxyl-BODIPY responds to small electronic changes resulting from acyl substitution reactions with a marked change in fluorescence. Herein, the minute changes that accompany the thioester to amide conversion encountered in native chemical ligation (NCL) are exploited in the construction of fluorescent turn-on probes. Two fluorogenic probes, 1 a and 4, derived from a meso-thioester-BODIPY scaffold, were designed for the selective detection of cysteine (1 a) and aminopeptidase N (4), respectively. The aromatic (1 a) and aliphatic (4) thioesters of meso-carboxyl-BODIPY are nonfluorescent. However, specific analyte-induced conversion to the meso-amide derivative caused significant spectral changes and a dramatic fluorescence enhancement. Probe 1 a exhibited a large fluorescence turn-on response with high selectivity toward cysteine via a tandem NCL reaction. Probe 4 was successfully applied to the monitoring and imaging of endogenous aminopeptidase N in live cancer cells.

Automated summary

meso-Carboxyl-BODIPY exhibits significant changes in fluorescence in response to small electronic changes during acyl substitution reactions, making it useful for constructing fluorescent probes for specific detection of cysteine and aminopeptidase N in live cancer cells.