Abstract: Endomorphin-1(EM-1) and its six analogs which were designed by rationally replacing the 2-/3-amino acid(Aa) of EM-1 were synthesized by using liquid phase peptides synthesis method to study their action of opiate receptor binding(AORB). The order of their affinity intensity for μ opiate receptor(MOR) was  EM-1 >[ D-Ala²]EM-1 >[ D-Pro²]EM-1 > EM-1 >[ L-Tyr³]EM >[ L-Pro ³]EM >EM The sequence of their selectivity for MORis  EM-1 >[ D-Pro²]EM-1 =[ L-Tyr³]EM >[ D-Ala²]EM-1 =[ L-Pro³]EM >EM The results showed that, comparatively speaking, the 2-Aa was more closely related to the selectivity of EM-1 while the 3-Aa to their affinity, though the different replacement changed the AORBof EM-1 dissimilarly.

Key words: Endomorphin-1, Liquid phase peptides synthesis, Action of opiate receptor binding