title: Photoaffinity crosslinking of etorphine with opioid binding sites in the bovine adrenal medulla.
abstract: The covalent crosslinking of [3H]etorphine with opioid binding sites in the bovine adrenal medulla is reported. Of all the radiolabeled opiates tested (ethylketocyclazocine, etorphine, [D-Ala2, D-Leu5]enkephalin, [D-Ala2, Me-Phe4, Gly5-ol]enkephalin only etorphine could be crosslinked under uv irradiation. In our conditions (black uv lamp, 160 W, peak mean 360 nm, from a distance of 10 cm) maximum covalent binding was observed after a 10-min irradiation. Protein concentration was a crucial factor for the irreversible/total binding ratio. A good ratio (50%) was obtained at protein concentrations of about 1.0 mg/ml. Covalent binding of nonmodified opiates could be of interest for the biochemical characterization of their binding sites.
mesh_terms: D000313:Adrenal Medulla / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism / Q000528:radiation effects; D005048:Etorphine / Q000378:metabolism*; D007700:Kinetics; D009019:Morphinans / Q000378:metabolism*; D011957:Receptors, Opioid / Q000302:isolation & purification / Q000378:metabolism / Q000528:radiation effects*; D012995:Solubility; D014466:Ultraviolet Rays
chemical_list: D009019:Morphinans; D011957:Receptors, Opioid; D005048:Etorphine