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Electronic and Steric Optimization of Fluorogenic Probes for Biomolecular Imaging

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journal contribution
posted on 27.03.2017, 00:00 authored by Wen Chyan, Henry R. Kilgore, Brian Gold, Ronald T. Raines
Fluorogenic probes are invaluable tools for spatiotemporal investigations within live cells. In common fluorogenic probes, the intrinsic fluorescence of a small-molecule fluorophore is masked by esterification until entry into a cell, where endogenous esterases catalyze the hydrolysis of the masking groups, generating fluorescence. The susceptibility of masking groups to spontaneous hydrolysis is a major limitation of these probes. Previous attempts to address this problem have incorporated auto-immolative linkers at the cost of atom economy and synthetic adversity. Here, we report on a linker-free strategy that employs adventitious electronic and steric interactions in easy-to-synthesize probes. We find that X···CO n→π* interactions and acyl group size are optimized in 2′,7′-dichloro­fluorescein diisobutyrate. This probe is relatively stable to spontaneous hydrolysis but is a highly reactive substrate for esterases both in vitro and in cellulo, yielding a bright, photostable fluorophore with utility in biomolecular imaging.