Beta-Endorphin: synthesis and radioreceptor binding activity of Beta h-endorphin-(1-27) and its analogs

Beta h-Endorphin-(1-27) (I), [Ac-Tyr1]-beta h-endorphin-(1-27) (II), [Gln8]-beta h-endorphin-(1-27) (III), and [Ac-Tyr1, Gln8]-beta h-endorphin-(1-27) (IV) were synthesized 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: beta h-endorphin, 100; I, 30; II, 0.04; III, 90; IV, 0.07.