Fluorogenic Cyclopropenones for Multicomponent, Real-TimeImaging

Fluorogenic bioorthogonal reactions enable biomolecule visualization in real time. These reactions comprise reportersthat"light up"upon reaction with complementary partners. While the spectrum offluorogenic chemistries is expanding, fewtransformations are compatible with live cells due to cross-reactivities or insufficient signal turn-on. To address the need for moresuitable chemistries for cellular imaging, we developed afluorogenic reaction featuring cyclopropenone reporters and phosphines.The transformation involves regioselective activation and cyclization of cyclopropenones to form coumarin products. With optimalprobes, the reaction provides >1600-fold signal turn-on, one of the highestfluorescence enhancements reported to date. Thebioorthogonal motifs were evaluated in vitro and in cells. The reaction was also found to be compatible with other commonfluorogenic transformations, enabling multicomponent, real-time imaging. Collectively, these data suggest that the cyclopropenone-phosphine reaction will bolster efforts to track biomolecule targets in their native settings.