title: 125I-labeled gonadoliberin and high specific activity and immunoreactivity: method of iodination and rapid separation.
abstract: We describe optimum conditions for iodinating gonadoliberin with use of relatively large proportions of Na 125I. Products of the iodination are separated on an anion-exchange resin (Amberlite IRA-400). The 125I-labeled gonadoliberin thus obtained has a high specific activity (1400 to 1590 Ci/g); because of the conditions of iodination, we believe that the predominant species of the labeled decapeptide is the mono-iodinated one. Our separation and purification of the labeled substance on ion-exchange resin is rapid, economical, and less cumbersome than the use of a Biogel P-2 column. There is no adsorption of the labeled hormone onto the resin, as evidenced by analytical recovery studies with tritium-labeled gonadoliberin. Paper-strip chromatoelectrophoresis showed no free Na 125I or radiolabeled damaged peptide fragments after purification on the resin. When antiserum was used at a concentration 32-fold that used in the regular assay procedure, only 4% of the radioactivity remained in the free form, indicating the high immunoreactivity of the labeled hormone.
mesh_terms: D000837:Anion Exchange Resins; D004590:Electrophoresis, Paper; D007987:Gonadotropin-Releasing Hormone / Q000032:analysis*; D006801:Humans; D007457:Iodine Radioisotopes; D011863:Radioimmunoassay
chemical_list: D000837:Anion Exchange Resins; D007457:Iodine Radioisotopes; D007987:Gonadotropin-Releasing Hormone