Attachment of metal trications to peptides

Gas-phase complexes of triply charged metal ions with peptides may be readily produced using electrospray ionization, including for small peptides such as bradykinin and peptides with no basic residues such as insulin chain A. Attachment without charge-reduction is demonstrated for all trications studied: La(3+), Al(3+), Ga(3+), Fe(3+), V(3+), and Cr(3+). The intensities of adducts are often comparable to, or even exceed, those of protonated analogs in any charge state.