HUMAN β-ENDORPHIN Immunoreactivity of Synthetic Analogs with Various Chain Lengths

Immunoreactivity of synthetic human β‐endorphin analogs with various chain lengths has been examined using a specific radioimmunoassay. It was found that β‐endorphin‐(1–21) and analogs of shortened chain exhibit no immunoreactivity, whereas β‐endorphin‐(1–15) possesses significant in vitro opiate activity. It appears that immunoreactivity of β‐endorphin resides in the COOH‐terminal segment of residues (22–31). The data also show the lack of correlation between opiate and immunological activities of β‐endorphin.