Supramolecular chemistry-based strategies such as metal-anion interactions, macrocyclic self-assembly, and ligand-directed affinity labeling can promote proximity-induced reactivities for protein bioconjugation (Scheme 16A). Supramolecular chemistry pertains to molecular assembly through a range of non-covalent interactions. The process can be viewed as host-guest chemistry that causes a covalent bond-forming reaction between a substrate and reagent through supramolecular forces including hydrophobic interaction, hydrogen bond, van der Waals force, ππ stacking, and ion-dipole effect. Enzymatic systems make use of a number of types of supramolecular chemistry to achieve site-selective modification. For example, a transpeptidase sortase utilizes its domain called β6/β7 loop that recognizes an LPXTG (X = D, E, A, N, Q, or K) motif of a target peptide/proteins for siteselective modification of their C-terminal positions. Supramolecular chemistry has been used for non-catalytic bioconjugation reactions including metal-anion ionic interactions by His6-tag/Ni system and DNA/RNA hybridization through base pairings, as such non-catalytic supramolecular bioconjugation reactions have been reviewed in a recent article. As described below, artificial host molecules such as gallium cluster and cucurbituril as well as ligand-directed affinity labeling strategy (see the organocatalyst section) were used as catalytic protein labeling strategies.