Gas-phase ion chemistry of biomolecules Part 29 - Evaluating the role of the ligand in the fragmentation reactions of platinum(II) complexes of aliphatic dipeptides. Electrospray ionization tandem mass spectrometry of [Pt(L-3)M](2+) and [Pt(L-3)M - H](+) ions [L-3 = (H3N)(3), diethylenetriamine andterpyridine; M = gly-gly, ala-gly and gly-ala]

Incubation of simple aliphatic dipeptides (M) with [Pt(L-3)CI](+) complexes (where L-3 = terpyridine, diethylenetriamine or triamine) results in the f ormation of platinated dipeptides as detected by electrospray ionization ma ss spectrometry, Although the [Pt(L-3)M-H](+) and [Pt(L-3)M](2+) ions repre sent less than 1% of the total-ion current, they can readily be mass select ed and subjected to collision-induced dissociation in an ion trap mass spec trometer, The nature of the coordinating ligands and the charge state have profound effects on the types of fragmentation reactions observed. Thus, th e tridentate ligands terpyridine (terpy) and diethylenetriamine (dien) indu ce dissociation of the peptide bond and the C-terminal OH bond in the [Pt(L -3)M](2+) ions, whereas the complex containing the three unidentate ammonia ligands fragments via neutral and charged ammonia loss. [Pt(terpy)M-H](+) ions fragment via peptide bond cleavage and also through a C-terminal rearr angement reaction for gly-ala and glycyl-N-methylglycine, but not for ala-g ly, In contrast, [Pt(dien)M-H](+) ions fragment via loss of the neutral dip eptide while [Pt(NH3)(3)M - H](+) ions fragment via loss of NH3.