BODIPY Catalyzes Proximity‐Dependent Histidine Labelling

Abstract The novel function of BODIPY, a widely used fluorescent probe, as a catalyst for the chemical labelling of histidine is revealed. Singlet oxygen ( 1 O 2 ) produced by the photosensitizer property of BODIPY oxidises histidine residues, and the histidine oxidised by 1 O 2 is trapped by the nucleophile 1‐methyl‐4‐arylurazole (MAUra). The simple chemical structure of BODIPY facilitates easier modification compared to other photosensitizer molecules and allows catalysis of protein/peptide‐labelling with higher histidine selectivity compared to the ruthenium complex. Owing to the short life of 1 O 2 , the reaction was selectively completed in close proximity with BODIPY. Site‐selective functionalization of the target/antibody was successfully achieved using ligand‐conjugated BODIPY.