Modular caged chlorooximes for cell-selective bioorthogonal labeling

Conventional bioorthogonal reactions label biomolecules indiscriminately across the entire cell or organism, which can produce unwanted background signal that complicates analyses of specific cell types, tissues, or disease states. Activatable bioorthogonal reactions have been developed to address this limitation. These reactions enable selective labeling through activation of one bioorthogonal reaction partner, often by using light. Here, we report a modular, activatable bioorthogonal reaction by caging the reactivity a of chlorooxime. Our results show that caged chlorooximes have enhanced bioorthogonality relative to their uncaged counterparts, remaining unreactive with biological thiols. When activated by uncaging, the chlorooximes react rapidly with popular bioorthogonal dienophiles. Furthermore, the modular design of the caged chlorooxime allows activation by both external (light) and internal (enzymes and metabolites) stimuli. This method enabled cell-selective live-cell imaging, expanding the application repertoire of activatable bioorthogonal reactions.