Proteins are intriguing biomacromolecules for all living systems, not only as essential building blocks of organisms, but also as participants in almost every aspect of cellular activity such as metabolism and gene transcription/expression. Developing chemical biology tools that are capable of labeling/modifying proteins is a powerful method for decoding their detailed structures and functions. However, most current approaches heavily rely on the installation of permanent tags or genetic engineering of unnatural amino acids. There has been slow development in reversible chemical labeling using small organic probes and bioorthogonal transformations to construct site‐selectively modified proteins and conditionally restore their activities or structures. This review summarizes recent advances in the field of chemical regulation of proteins with reversible transformations towards distinct motifs, including amino acid residues, amide backbones and native post‐translational lysine. Finally, current challenges and future perspectives are discussed.

We have developed an efficient fragment splicing method for the construction of multiple nucleobase-terminated monomers. Conformationally fixed rod, trigonal planer and tetrahedral thymine and adenine structures were generated in moderate to good yields, which will serve as inspiring examples for exploration of nucleobases as natural hydrogen-bond components in supramolecular chemistry.