Synthesis and properties of human beta-endorphin-(1-17) and its analogs

Four analogs of human beta-endorphin (beta h-EP) were synthesized by the solid-phase method: beta h-EP-(1-17) (I), [D-Ala2]beta h-EP-(1-17) (II), [Gln8]-beta h-EP-(1-17) (III) and [D-Ala2, Gln8]-beta h-EP-(1-17) (IV). Measurement in a radio-receptor binding assay with use of tritiated beta h-EP as primary ligand gave relative potencies as follows: Met-enkephalin, 100; I, 33; II, 47; III, 889; IV, 123; beta h-endorphin, 2253.