Probing protein function by chemical modification.

Labeling proteins with synthetic probes, such as fluorophores, affinity tags, and other functional labels is enormously useful for characterizing protein function in vitro, in live cells, or in whole organisms. Recent advancements of chemical methods have substantially expanded the tools that are applicable to modify proteins. In this review, we discuss some important chemical methods for site-specific protein modification and highlight the application of established techniques to tackle biological questions.