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Poster PresentationRatiometric fluorescent sensors of cysteine sulfenylationSteven BoggessChris Tom, Aaron Konopko, and Matt Stone, Dept. of Chemistry, University of MichiganAdvisor: Brent Martin, Dept. of Chemistry, University of MichiganOxidation of cysteine is an important post-translational modification that regulates manyimportant signaling pathways in cells by blocking the activity of protein phosphatases andenhancing growth factor receptor activation. Upon epidermal growth factor stimulation, NADPHoxidase is stimulated to produce hydrogen peroxide (H2O2), which acts as a second messengerby oxidizing reactive cysteines to the sulfenic acids. Recently, functionalized derivatives of theactive methylene compound dimedone have been used to capture sites of sulfenylation forbiochemical and proteomic analysis. Dimedone exists in its enolate form at physiological pH(pKa 4.3), where the α-carbon reactivity is tuned to selectively react with weakly electrophilicsulfenic acids. While these probes are valuable for biochemical studies, fluorophore conjugatesare useless for live cell imaging. In order to overcome this limitation, we present the synthesisand activity of a family of small-molecule probes that combines dimedone with a fluorescentnaphthalene, linking the fluorescent properties to the reactive α-carbon.. These DiNaps(Dimedone Napthalene) retain the reactivity and selectivity of dimedone, and conjugate tonumerous known sulfenylated proteins. In order to induce a fluorescence change, we substituteda single α-proton with a methyl or fluorine blocking group. Blocking the α-position prevents asecond deprotonation of the dimedone upon conjugation to protein which locks it into itsdiketone form, thereby changing the electronics of the ring in order to provide a change in theexcitation spectrum of the probe. Ratiometric imaging of H2O2 stimulated immature B-cellsdemonstrates the first presentation of dynamic sulfenylation in live cells.27