Dual-Site Fluorescent Probe for Visualizing the Metabolism of Cys in Living Cells

Fluorescent probes, as noninvasive tools for visualizing the metabolism of biomolecules, hold great potential to explore their physiological and pathological processes. For cysteine (Cys), however, none of the reported fluorescent probes could image the metabolic processes in living cells. To achieve this goal, we developed a coumarin derivative based on rational design of the dual recognition sites for Cys and its metabolite, SO₂. The probe displayed distinct two channels with turn-on fluorescent emission toward Cys and SO₂, which were successfully applied for imaging both A549 cells and zebrafish. Further, with reversible fluorescent responses toward Cys, the probe could image the enzymatic conversion of Cys to SO₂ in living A549 cells in a ratiometric manner. The present work reports the first probe to image the endogenous generated SO₂ without incubation of the SO₂ donors.