Abstract
A series of potent electrophilic affinity labels (IC50= 0.1-5 nM) containing either a bromoacetamide or isothiocyanate based on the μ opioid receptor (MOR) selective peptide dermorphin were prepared. All four analogues exhibited wash resistant inhibition of [3H]DAMGO binding at subnanomolar to nanomolar concentrations, suggesting that these analogues bind covalently to MOR. To our knowledge, these peptides are the highest affinity peptide-based affinity labels for MOR reported to date.