Fast, Cell‐Compatible Click Chemistry with Copper‐Chelating Azides for Biomolecular Labeling

Bring your own copper: Copper-chelating azides undergo much faster click reactions (CuAAC) than nonchelating azides under a variety of biocompatible conditions. This kinetic enhancement allows site-specific protein labeling to be performed on the surface of living cells with only 10–40 μM CuI/CuII (see scheme). Detection sensitivity was also increased for CuAAC detection of alkyne-modified proteins and RNA.