title: A new electrophoretic method for determining ligand: technetium stoichiometry in carrier free 99mTc-radiopharmaceuticals.
abstract: An electrophoretic procedure is outlined for the determination of the number of ligands bound to technetium-99m radiopharmaceuticals. The approach involves use of ligands that will complex technetium in a similar fashion but that differ in charge. This approach was applied experimentally to dimercapto ligands in which the ligating sulfur atoms are separated by a flexible three-carbon chain (1,3-dimercapto compounds). Two such ligands studied are 1,3-dimercaptopropane (DMP) and dihydrothioctic acid (DHTA). The Tc compound of DHTA migrates much farther on electrophoresis than the Tc complex of DMP. However, when TcO4- is reduced by SnCl2 or NaBH4 in the presence of equimolar quantities of DHTA and DMP, a new compound is formed being twice as abundant as either the TcDMP or the TcDHTA compound and migrating an intermediate distance. The formation of this new complex and the 1:2:1 distribution indicates that two 1,3-dimercapto compounds are attached to the Tc-center in all three compounds.
mesh_terms: D055598:Chemical Phenomena; D002621:Chemistry; D004112:Dimercaprol; D004586:Electrophoresis; D008024:Ligands; D013667:Technetium; D008063:Thioctic Acid / Q000031:analogs & derivatives
chemical_list: D008024:Ligands; D004112:Dimercaprol; D008063:Thioctic Acid; D013667:Technetium; C015144:dihydrolipoic acid