How do HYNIC-conjugated peptides bind technetium? Insights from LC-MS and stability studies

TY - JOUR

T1 - How do HYNIC-conjugated peptides bind technetium? Insights from LC-MS and stability studies

AU - King, R C

AU - Surfraz, M B U

AU - Biagini, S C G

AU - Blower, P J

AU - Mather, S J

PY - 2007

Y1 - 2007

N2 - Hydrazinonicotinamide ( HYNIC) is an established bifunctional complexing agent for technetium-99m ( Tc-99m) but the structure of the technetium coordination sphere remains uncertain. To gain further insight into this, we have prepared conjugates of HYNIC and hydrazinobenzoic acid ( HYBA) with a model peptide, and radiolabelled them with Tc-99m using three well-established co-ligand systems: EDDA, tricine and tricine-nicotinic acid. The labelled peptides were studied by LC-MS and by subjecting them to serum stability and protein binding assays. For each co-ligand system, HYNIC conjugates formed fewer and more stable labelled species than the corresponding HYBA conjugates. LC-MS analysis showed that all conjugates contained one hydrazine moiety bound to Tc, that binding of Tc to HYNIC-peptide and co-ligand occurs with displacement of 5H(+) indicating a Tc formal oxidation state of +5, and that the Tc has no oxo- or halide ligands. LC-MS also shows that complexes formed with the HYNIC conjugate contain fewer coordinating co-ligand molecules than the HYBA conjugate indicating that HYNIC is able to more effectively satisfy the coordination requirement of technetium, perhaps by binding in chelating mode

AB - Hydrazinonicotinamide ( HYNIC) is an established bifunctional complexing agent for technetium-99m ( Tc-99m) but the structure of the technetium coordination sphere remains uncertain. To gain further insight into this, we have prepared conjugates of HYNIC and hydrazinobenzoic acid ( HYBA) with a model peptide, and radiolabelled them with Tc-99m using three well-established co-ligand systems: EDDA, tricine and tricine-nicotinic acid. The labelled peptides were studied by LC-MS and by subjecting them to serum stability and protein binding assays. For each co-ligand system, HYNIC conjugates formed fewer and more stable labelled species than the corresponding HYBA conjugates. LC-MS analysis showed that all conjugates contained one hydrazine moiety bound to Tc, that binding of Tc to HYNIC-peptide and co-ligand occurs with displacement of 5H(+) indicating a Tc formal oxidation state of +5, and that the Tc has no oxo- or halide ligands. LC-MS also shows that complexes formed with the HYNIC conjugate contain fewer coordinating co-ligand molecules than the HYBA conjugate indicating that HYNIC is able to more effectively satisfy the coordination requirement of technetium, perhaps by binding in chelating mode

M3 - Article

SN - 1477-9234

SP - 4998

EP - 5007

JO - DALTON TRANSACTIONS (2003)

JF - DALTON TRANSACTIONS (2003)

IS - 43

ER -