Accelerated Strain-Promoted and Oxidation-Controlled Cyclooctyne-Quinone Cycloaddition for Cell Labeling

We developed an accelerated strain-promoted oxidation-controlled cyclooctyne-1,2-quinone cycloaddition (SPOCQ) for protein modification. Here, dopaquinone was generated using potassium nitrosodisulfonate (PTN) in a reaction that is six orders of magnitude faster than the enzymatic one. The dopaquinone generated then reacts with bicyclononyne (BCN) derivatives in the bioconjugation. The PTN yields a single product with defined stereochemistry and temporally controlled conjugation with BCN. The feasibility of this bioconjugation was demonstrated with different proteins. Cell labeling was explored by conjugating annexin-dibenzocyclooctyne-PEG4- fluor545 through the SPOCQ approach for the detection of apoptosis in HeLa cells.