Ultrafast 4-Azidopyridinium-Based Staudinger (UApS) Ligation for Bioorthogonal Labeling and Imaging.
An ultrafast 4-azidopyridinium-based Staudinger (UApS) ligation is reported that proceeds with large bimolecular reaction rate constants (103-104 M-1s-1) under catalyst-free, physiologically relevant conditions and should extend fast click chemical space, providing a new addition to the bioconjugation toolkit.