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A red-emitting fluorescent probe for selective detection of cysteine was developed based on the conjugated addition/cyclization sequence mechanism. Upon the treatment with cysteine, this probe exhibits a strong fluorescence enhancement (62-fold) and a large Stokes shift (148 nm). The detection limit was calculated to be as low as 6.6 nM based on S/N = 3. Importantly, the practical application of this probe for the selective detection of cysteine was successfully demonstrated in living cells. [ABSTRACT FROM AUTHOR]

A fluorescent probe, 1,4-diethyl-7-(3-pyridin-2-yl-acroyloyl)-1,2,3,4-tetrahydro-5-oxa-1,4-diazaanthracen-6-one (probe 1 ), with an emission in near-infrared region was developed for sensitive and selective detection of biothiols. Probe 1 is essentially non-fluorescent due to the strong intramolecular charge transfer (ICT) from the electron-donating tetrahydroquinoxaline moiety to the electron-withdrawing pyridine group. Upon the treatment with biothiols, the conjugation system was broken via Michael addition reaction between biothiols and α,β-unsaturated ketone, which inhibited the ICT process and resulted in a remarkable fluorescence enhancement with an emission maximum at 660 nm. Moreover, probe 1 was successfully applied to image intracellular thiols in living cells. [ABSTRACT FROM AUTHOR]