Tyrosine-Specific Chemical Modification with in Situ Hemin-Activated Luminol Derivatives

Tyrosine-specific chemical modification was achieved using in situ hemin-activated luminol derivatives. Tyrosine residues in peptide and protein were modified effectively with N-methylated luminol derivatives under oxidative conditions in the presence of hemin and H2O2. Both single and double modifications of the tyrosine residue occurred in the reaction of angiotensin II with N-methylated luminol derivative 9. Tyrosine-specific chemical modification of the model protein bovine serum albumin (BSA) revealed that the surface-exposed tyrosine residues were selectively modified with 9. We succeeded in the functionalization of several proteins using azide-conjugated compound 18 using alkyne-conjugated probes by copper­(I)-catalyzed azide–alkyne cycloaddition (CuAAC) or dibenzocyclooctyne (DBCO)-mediated copper-free click chemistry. This tyrosine-specific modification was orthogonal to conventional lysine modification by N-hydroxysuccinimide (NHS) ester, and dual functionalization by fluorescence modification of tyrosine residues and PEG modification of lysine residues was achieved without affecting the modification efficiency.