Multiply charged ions

Abstract

Formation, characteristics of, and applications using doubly and multiply charged ions are reviewed in the present article. The main emphasis is on medium‐ to large‐sized molecules, from the point‐of‐view of organic, physico‐organic, and bio‐organic mass spectrometry. Multiply charged species can be studied by all conventional mass spectrometric techniques. Those techniques and reaction types that are particularly relevant to multiply charged ions are discussed in some detail in Section III. Studies on small‐ to medium‐sized molecules are discussed in Section IV. A particularly interesting aspect, the distinction of doubly charged isomeric ions, is also treated here. Multiply charged ions of large (bio‐)molecules are discussed in Section V. This area is fast expanding, mainly due to the spread of electrospray ionization. Fragmentation and conformation of multiply protonated peptides is discussed in detail. © 1996 John Wiley & Sons, Inc.

Electron capture dissociation of substance P using a commercially available Fourier transform ion cyclotron resonance mass spectrometer

“…1(a), for Substance P [H-Arg-Pro-Lys-Pro-Gln-GlnPhe-Phe-Gly-Leu-Met-NH 2 ], all c-fragments were observed (Fig. 3), 4 5). An extra H is indicated for all the otherwise neutral products.…”

Charge permutation reactions in tandem mass spectrometry

“…Therefore, this product can be clearly distinguished from the often more abundant product ions formed via neutral loss. 85 Typically, charge separation is accompanied by a large amount of kinetic energy release (KER), thereby yielding very broad peaks when the products are analyzed on the basis of kinetic energy-to-charge ratio. KER carries valuable information concerning both the structures of the species involved and the energetics and dynamics of the reaction.…”

“…It has been demonstrated for macro-ions derived from proteins or peptides that the critical energy usually decreases as the charge state increases, as reflected in the dependence of fragmentation rates on the charge states of the ions. 85,175 A variety of dissociation methods, with activation times ranging from 10 15 to 10 3 s, 152,176 have been applied to multiply charged ions. Slow activation methods such as IRMPD, BIRD and ion trap collisional activation that involve stepwise excitation are generally restricted to ion trapping instruments.…”

“…Methods to better separate peaks from the two sources have been developed, such as floating the collision cell, varying the accelerating voltage and changing the collision gas. 85 A forward geometry double-focusing mass spectrometer 114 and timeof-flight mass spectrometers 115 have also been used to study this process.…”

Ion/ion chemistry of high-mass multiply charged ions

“…By far, most attention has been, and continues to be devoted to the unimolecular (dissociation) chemistry of multiply charged ions derived from biopolymers, where dissociation is used principally to obtain primary structural information. (For a sampling of the large and growing literature on the dissociations of gaseous multiply charged biopolymers see Vékey, 1995 Although unimolecular and bimolecular ion/molecule chemistries of high-mass multiply charged ions will continue to play central and expanding roles in electrospray ionization research and applications, ion/ion chemistry that involves multiply charged high-mass ions with either singly charged or multiply charged ions of opposite polarity shows interesting promise as an area for development. Unlike ion/ion reactions involving two singly charged reactants, wherein all reaction products are neutral species, multiply charged ion/ ion reactions can yield charged products.…”