Contrary to other reports, iodinated .beta.-melanocyte stimulating hormone (.beta.-MSH) is without biological activity as measured by frog skin bioassay, melanoma (mouse S-91) adenylate cyclase assay, or melanoma tyro...
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Contrary to other reports, iodinated .beta.-melanocyte stimulating hormone (.beta.-MSH) is without biological activity as measured by frog skin bioassay, melanoma (mouse S-91) adenylate cyclase assay, or melanoma tyrosinase assay. Inactivation results in part from oxidation of the Met residue by the chloramine T and sodium metabisulfite used in the iodination reaction. Replacement of the Met of .beta.-MSH with norleucine by solid phase synthesis results in an analog which is more resistant, but not completely resistant, to inactivation. To obtain a biologically active radioligand for radioreceptor studies, further tailoring of the hormone and/or modification of the iodination procedure will be needed.
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