Proton magnetic resonance studies on dermorphin and its peptide fragments

Dermorphin (Tyr D ‐AlaPheGlyTyrProSerNH 2 ), a potent natural peptide opioid, its synthetic L‐Ala 2 analog, and all the N fragments from the tripeptide (Tyr D ‐AlaPheNH 2 ) to the parent hexapeptide amide were characterized for the first time by means of proton nmr spectroscopy at 11.74 T. Assignments of most protons of dermorphin were facilitated by the study of the N‐terminal fragments. Comparison of spectroscopic parameters with relative pharmacological activity is proposed as a possible means of studying flexible agonists in solution.