Technetium-binding in labelled HYNIC-peptide conjugates: Role of coordinating amino acids

TY - JOUR

T1 - Technetium-binding in labelled HYNIC-peptide conjugates: Role of coordinating amino acids

AU - Surfraz, M. Bashir-Uddin

AU - King, Robert

AU - Mather, Stephen J.

AU - Biagini, Stefano

AU - Blower, Philip J.

PY - 2009/7

Y1 - 2009/7

N2 - Electrospray mass spectrometry (ESMS) of certain peptides labelled with Tc-99m via hydrazinonicotinamide (HYNIC) with tricine as co-ligand shows one Tc-bound tricine, whereas typically two are observed. We speculated that this was due to coordination of a neighbouring histidine (His) or glutamate (Glu). To investigate this possibility, several short peptides incorporating lysine (HYNIC), with and without His and Glu at different positions in the sequence, were radiolabelled with Tc-99m, using tricine, ethylenediaminediacetic acid (EDDA) and nicotinic acid as co-ligands. The products were examined by HPLC-ESMS, cysteine challenge and bovine serum albumin (BSA) challenge. Peptides with His nearby on either side of lysine (HYNIC) contained only one tricine and showed markedly enhanced structural homogeneity and stability to cysteine challenge and BSA binding, except those with His located at the N-terminus. Peptides without His, or with neighbouring N-terminal His, contained two tricines and were less stable to cysteine challenge and BSA binding. Glu participated in Tc-binding but did not enhance stability. We conclude that neighbouring His or Glu side chains coordinate to Tc and this could alter peptide or protein conformation. Inclusion of His in a neighbouring position to lysine (HYNIC) enhances stability. improves homogeneity and reduces the demand of the metal center for binding to additional co-ligands. (C) 2009 Elsevier Inc. All rights reserved.

AB - Electrospray mass spectrometry (ESMS) of certain peptides labelled with Tc-99m via hydrazinonicotinamide (HYNIC) with tricine as co-ligand shows one Tc-bound tricine, whereas typically two are observed. We speculated that this was due to coordination of a neighbouring histidine (His) or glutamate (Glu). To investigate this possibility, several short peptides incorporating lysine (HYNIC), with and without His and Glu at different positions in the sequence, were radiolabelled with Tc-99m, using tricine, ethylenediaminediacetic acid (EDDA) and nicotinic acid as co-ligands. The products were examined by HPLC-ESMS, cysteine challenge and bovine serum albumin (BSA) challenge. Peptides with His nearby on either side of lysine (HYNIC) contained only one tricine and showed markedly enhanced structural homogeneity and stability to cysteine challenge and BSA binding, except those with His located at the N-terminus. Peptides without His, or with neighbouring N-terminal His, contained two tricines and were less stable to cysteine challenge and BSA binding. Glu participated in Tc-binding but did not enhance stability. We conclude that neighbouring His or Glu side chains coordinate to Tc and this could alter peptide or protein conformation. Inclusion of His in a neighbouring position to lysine (HYNIC) enhances stability. improves homogeneity and reduces the demand of the metal center for binding to additional co-ligands. (C) 2009 Elsevier Inc. All rights reserved.

U2 - 10.1016/j.jinorgbio.2009.04.007

DO - 10.1016/j.jinorgbio.2009.04.007

M3 - Article

VL - 103

SP - 971

EP - 977

JO - Journal of Inorganic Biochemistry

JF - Journal of Inorganic Biochemistry

IS - 7

ER -