Low energy collisionally activated dissociation of Cu2+(glycine)(H2O), Cu2+(glycine)(H2O)(2), Cu2+(glycine)(2), and Cu2+(glycylglycine)(2)

Doubly charged complex ions of Cu(II) have been formed in an electrospray s ource from dilute aqueous solutions containing copper sulfate and glycine ( G) or glycylglycine (glygly). The most prominent ions, Cu(2+)GW, Cu(2+)GW(2 ), Cu(2+)G(2), and Cu2+(glygly)(2) (W = water) were studied by low energy, collisionally activated dissociation (CAD) in a triple quadrupole instrumen t. At very low collision energy, background water adds to all ions, except Cu2+(glygly)(2), with no charge reduction. Loss of the elements of water fr om Cu(2+)G(2) and Cu2+(glygly)(2) without loss of charge suggests the occur rence of intracomplex peptide bond formation. In charge reduction reactions , the two ions containing water as a ligand produce (+H3NCH2.) as the only significant organic product ion, together with several singly charged coppe r containing ions. By contrast, Cu2+(glygly), produces CH2NH2+ and (glygly) H+, and Cu(2+)G(2) produces GH(+), G(+), CH2NH2+, and (+H3NCH2.) the latter two becoming more important at high collision energy. The major product fr om both Cu(2+)GW and Cu(2+)GW(2) is [Cu,H2O](+), which is suggested to be [ Cu(H)OH](+) rather than [Cu(H2O)](+). From the same two parent ions a strip ping reaction at centre of mass collision energies above similar to 3 eV le ads to loss of water, but no charge reduction, in the formation of Cu(2+)G. In all CAD spectra there is a large imbalance at low collision energy betw een the relative amounts of the singly charged copper-containing product io ns and the expected organic ions originating from the ligands. It is sugges ted that the latter are discriminated against because of inefficient contai nment following coulomb explosion. (C) 1999 Elsevier Science B.V.