BODIPY Catalyzes Proximity‐Dependent Histidine Labelling

The novel function of BODIPY, a widely used fluorescent probe, as a catalyst for the chemical labelling of histidine is revealed. Singlet oxygen (O-1(2)) produced by the photosensitizer property of BODIPY oxidises histidine residues, and the histidine oxidised by O-1(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 O-1(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.