Experiments on a new phosphine-peptide chelator for labelling of peptides with Tc-99m

A phosphine-containing ligand providing a N-[N-[3-(diphenylphosphino)propionyl]glycyl]-L-S-benzyl-cystein (PNNS) donor atomset for the chelation of 99mTc was studied in labelling experiments with a model peptide (tetragastrin, cholecystokinin-fragment). The peptide was conjugated to the ligand chelator by active ester chemistry either before or after radiolabelling. Both the chelator-conjugate and the preformed chelate approaches resulted in the same radiolabelled isomers of the ligand peptide. Sequence and reaction conditions influence yield and purity.