Discovery of Dermorphin-Based Affinity Labels with Subnanomolar Affinity for Mu Opioid Receptors+

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