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 (1O2) produced by the photosensitizer property of BODIPY oxidises histidine residues, and the histidine oxidised by 1O2 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 1O2, the reaction was selectively completed in close proximity with BODIPY. Site‐selective functionalization of the target/antibody was successfully achieved using ligand‐conjugated BODIPY. BODIPY, a widely used fluorescent probe, functions as a photosensitizer and a catalyst for the chemical labelling of histidine. The histidine oxidised by 1O2 is trapped by the nucleophile 1‐methyl‐4‐arylurazole (MAUra). The simple chemical structure of BODIPY allows catalysis of protein/peptide‐labelling with higher histidine selectivity.