The HaloTag® Iodoacetamide (04) Ligand contains a reactive iodoacetamide group connected an alkyl chloride separated by an ethylene glycol repeat (04). The HaloTag® Iodoacetamide (04) Ligand has been designed to rapidly react with sulfhydryl-containing molecules (see figure), whether small organic compounds, peptides or proteins. The ligand with functional group can then be used with the HaloTag® protein for any application of interest.