β‐ENDORPHIN: SYNTHESIS AND RADIORECEPTOR BINDING ACTIVITY OF βh‐ENDORPHIN‐(1–27) AND ITS ANALOGS

Abstract
βh‐Endorphin‐(1–27) (I), [Ac‐Tyr1]‐βh‐endorphin‐(1–27) (II), [Gln8]‐βh‐endor‐phin‐(1–27) (III), and [Ac‐Tyr1, Gln8]‐βh‐endorphin‐(1–27) (IV) were synthe sized by the solid‐phase method. The binding potency of I‐IV to rat brain membrane preparations was measured by radioreceptor binding assay. The relative potencies were: βh‐endorphin, 100; I, 30; II, 0.04; III, 90; IV, 0.07.