title: A simple two-step approach for introducing a protected diaminedithiol chelator during solid-phase assembly of peptides.
abstract: A simple synthetic strategy is described to incorporate a protected diaminedithiol (N(2)S(2)) chelator during Fmoc solid-phase synthesis of short peptides. The resulting constructs could be efficiently labeled with technetium-99m (99mTc). The chelator was assembled at the N-terminus of peptides in a two-step procedure where the deprotected terminal amino group was first reacted with di-Fmoc-diaminopropionic acid (Fmoc-DAP-[Fmoc]-OH). The two protected amino groups were then simultaneously deprotected and subsequently reacted with S-benzoylthiolglycolic acid (TGA) to generate a protected N(2)S(2) chelator. This metal binding site was introduced into di- and tripeptides. Each peptide construct was composed of a C-terminal lysine residue and an N-terminal diaminopropionic moiety modified to create the chelator site. The epsilon-amino group at the C-terminal lysine was further derivatized with a nitroimidazole group to facilitate cellular retention. The resulting constructs were then cleaved from the resin support, purified, and labeled with [99mTc]pertechnetate. Six constructs were prepared differing by a single amino acid inserted between the diaminopropionic acid and lysine residues. Optimal labeling yields of >70% were achieved around neutral pH and heating at 75 degrees C for 10 min. Purified 99mTc-labeled constructs were found to accumulate in Chinese hamster ovary (CHO) cells in vitro as a function of charge and hydrophobicity.
authors: Ontario Cancer Institute, Princess Margaret Hospital, 610 University Avenue, Toronto, Ontario, Canada M5G 2M9. gariepy@uhnres.utoronto.ca
authors: Jean
authors: J
authors: Gariépy
authors: Sandrine
authors: S
authors: Rémy
authors: Xiuguo
authors: X
authors: Zhang
authors: James R
authors: JR
authors: Ballinger
authors: Eleonora
authors: E
authors: Bolewska-Pedyczak
authors: Michael
authors: M
authors: Rauth
authors: Stuart K
authors: SK
authors: Bisland
mesh_terms: D000818:Animals; D016466:CHO Cells / Q000378:metabolism; D002614:Chelating Agents / Q000378:metabolism*; D006224:Cricetinae; D003959:Diamines / Q000737:chemistry*; D015609:Organotechnetium Compounds / Q000737:chemistry*; D010455:Peptides / Q000138:chemical synthesis* / Q000737:chemistry; D014050:Toluene / Q000031:analogs & derivatives* / Q000737:chemistry*
chemical_list: D002614:Chelating Agents; D003959:Diamines; D015609:Organotechnetium Compounds; D010455:Peptides; D014050:Toluene; C004848:dithiol