Gas Phase Investigation of [(Cu 2+ ,Ni 2+ -Gly-Gly-His)-3H + ] -1 Complex by Electrospray Ionization MS/MS and MS/MS/MS

Mass spectrometry (MS) is a very useful means by which to study the interactions of metal cation-biomolecule complexes in the gas phase. The analysis of the fragmentation patterns of metal cationized peptides produced under electrospray ionization (ESI)-MS can provide complementary information for peptide sequencing when the fragmentation of the protonated peptide is insufficient. The specific interactions in metal ion-peptide systems have been studied to develop practical sensors for the detection and quantification of metal ions. Complexes of transition metal cations and peptides (transition metal--peptide) have been studied by many research groups. However, investigations regarding the [(Metal--peptide) – 3H+]−1 anion complex have not been conducted systematically using MS. The copper and nickel binding peptide Gly-Gly-His has been investigated in aqueous solution because the peptide Gly-Gly-His mimics the form of the specific Cu, Ni-transport active site of human serum albumin. Theoretical studies concerning metal-oligopeptide structure and metal-ligand coordination geometry have also been performed through molecular dynamics simulations and ab initio calculations. Structures, molecular orbital and stabilization energies of metal-oligopeptides are reported by the research groups. In this study, our attention was focused on the interaction between the oligopeptide of three amino acid residues GlyGly-His and metal ions (Cu, Ni) in the gas phase. The interaction between the Gly-Gly-His and metal ions was studied by ESI-MS in negative mode. The fragmentation pattern of the [(Cu, Ni---Gly-Gly-His) – 3H+]−1 anion complex was analyzed by MS/MS and MS/MS/MS spectra.