Abstract
A radioligand suitable for crosslinking studies to opoid receptors has been obtained by radioiodination and purification of the monoiodotyrosine-27 derivative of the synthetic human .beta.-endorphin (.beta.h-endorphin) analogue [5-leucine].beta.h-endorphin. The derivative, [27-[125I]monoiodotyrosine, 5-leucine].beta.h-endorphin, was crosslinked to human striatal (caudate and putamen) and NG105-15 neuroblastoma-glioma cell membranes by using disuccinimidyl suberate. Sodium dodecyl sulfate/polyacrylamide gel electrophoresis under reducing conditions revealed four specifically labeled bands at 68, 40, 30, and 25 kDa for both human caudate and putamen, whereas NG108-15 cell membranes gave specifically labeled bands at 92, 56, 38, and 23 kDa.