title: [125I] Tyr27 beta-endorphin: a radio-iodinated derivative of beta-endorphin for the study of opiate receptors.
abstract: Evidence is presented that a new derivative of beta-endorphin, [125I] Tyr27 beta-endorphin, is a suitable ligand for the study of beta-endorphin binding sites in rat brain. The results obtained with this homogeneous mono-iodinated peptide demonstrated high affinity agonist binding sensitive to the presence of sodium and magnesium ion and to guanine nucleotide. Competition experiments using a series of opiates and opioid peptides including shorter forms of beta-endorphin revealed a range of potencies; beta-endorphin 1-31 exhibited the highest affinity. The findings suggest that binding sites that complement the structure of beta-endorphin are present in rat cortex.
mesh_terms: D000818:Animals; D002540:Cerebral Cortex / Q000378:metabolism; D004723:Endorphins / Q000378:metabolism*; D066298:In Vitro Techniques; D007457:Iodine Radioisotopes; D008297:Male; D010446:Peptide Fragments / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000378:metabolism*; D001615:beta-Endorphin
chemical_list: D004723:Endorphins; D007457:Iodine Radioisotopes; D010446:Peptide Fragments; D011957:Receptors, Opioid; D001615:beta-Endorphin; C035581:beta-endorphin (1-27)