Specific fluorescence labeling of target proteins by using a ligand-4-azidophthalimide conjugate.

We herein propose a simple affinity-labeling method using a ligand-4-azidophthalimide (AzPI) conjugate. As a proof of concept, we show that two different ligand-AzPI conjugates enabled highly specific fluorescence labeling of their individual target proteins even in crude cell lysates. This method was also applied to label endogenous target proteins inside living cells.