Chemoselective Histidine Bioconjugation Using Thiophosphorodichloridate Reagents

Chemoselective bioconjugation techniques are essential tools for precise modification and functional analysis of proteins. Here, we describe a detailed protocol for histidine-specific labeling using thiophosphorodichloridate reagents, forming stable thiophosphoramidate linkages. The procedure includes synthesis of the labeling reagents, protein modification, purification by ion-exchange chromatography, and subsequent copper-catalyzed azide-alkyne cycloaddition (CuAAC) for further conjugation.