Operation of a quadrupole ion trap mass spectrometer to achieve high mass/charge ratios

Abstract. Non-dissociative charge reduction, typically considered to be an unwanted side reaction in electron transfer dissociation (ETD) experiments, can be enhanced significantly in order to reduce the charge state of intact protein complexes to as low as 1+ on a commercially available Q-IM-TOF instrument. This allows for the detection of large complexes beyond 100,000 m/z, while at the same time generating top-down ETD fragments, which provide sequence information from surface-exposed parts of the folded structure. Optimization of the supplemental activation has proven to be crucial in these experiments and the charge-reduced species are most likely the product of both proton transfer (PTR) and non-dissociative electron transfer (ETnoD) reactions that occur prior to the ion mobility cell. Applications of this approach range from deconvolution of complex spectra to the manipulation of charge states of gas-phase ions.

Section: Introductionmentioning

confidence: 99%

Extensive Charge Reduction and Dissociation of Intact Protein Complexes Following Electron Transfer on a Quadrupole-Ion Mobility-Time-of-Flight MS

Lermyte

Williams

Brown

et al. 2015

“…Isolation of ions of interest was effected via the application of resonance ejection voltages to the end caps of the ion trap at the appropriate frequencies while the RF trapping voltage amplitude was scanned [36]. Mass analysis was also performed via resonance ejection during an RF amplitude scan, at a frequency selected to give the desired mass range extension [37]. Figure 1 is a diagram (not to scale) of the new instrument arrangement.…”

Section: Methodsmentioning

confidence: 99%

“Dueling” ESI: Instrumentation to study ion/ion reactions of electrospray-generated cations and anions

Wells

Chrisman

McLuckey

2002

Novel instrumentation has been developed which allows for the sequential injection and subsequent reaction of oppositely-charged ions generated via electrospray ionization (ESI) in a quadrupole ion trap mass spectrometer. The instrument uses a DC turning quadrupole to sequentially direct the two ion polarities into the ion trap from ESI sources which are situated 90°from the axial (z) dimension of the trap, and 180°from one another. This arrangement significantly expands the range of ionic reactants amenable to study over previously-used instrumentation. For example, ion/ion reactions of multiply-charged positive ions with multiply-charged negative ions can be studied. Also, reactions of multiply-charged ions with singly-charged ions of opposite polarity that could not be generated by previously used ionization methods, or that could not be efficiently injected through the ion trap ring electrode, can be studied with the new instrument. This capability allows, for example, the charge state manipulation of negatively-charged precursor and product ions derived from proteins and oligonucleotides via proton transfer reactions with singly-charged cations generated by ESI. (J Am Soc Mass Spectrom 2002, 13, 614 -622) © 2002 American Society for Mass Spectrometry G as-phase ion chemistry has come to play important roles in both the chemical and, increasingly, the biological sciences. Tandem mass spectrometry utilizing unimolecular dissociation of gas-phase ions is a primary method for identifying unknown species in complex mixtures [1]; a recent example which is rapidly increasing in significance is the use of gasphase dissociation of proteolytic peptides to identify individual proteins in protein mixtures [2,3]. Ion/ molecule chemistry provides a means to study novel chemical species that may be impossible to generate in solution, and is the primary method by which intrinsic (i.e., free of solvation effects) thermochemical information is obtained [4 -7]. Ion/molecule reactions that have been applied to large, biologically-derived ions such as proteins include hydrogen/deuterium exchange [8 -11] and hydroiodic acid attachment [12][13][14], which can both be used as probes of gas-phase conformation. Ion/ molecule reactions between multiply-protonated ions and strong neutral bases have been studied as a means for reducing ion charge state [15][16][17][18][19][20]. Modification of gas-phase oligonucleotide ions via nucleophilic substitution has also been demonstrated [21]. Less attention has been given to reactions of multiply-charged gasphase ions with ions of opposite polarity, largely because the instrumentation needed to carry out such ion/ion reactions is not readily available. However, it has recently been shown that ion/ion reactions of multiply-charged ions with singly-charged ions of opposite polarity may have important analytical utility. For example, ion/ion proton transfer reactions can be used to simplify ESI mass spectra of complex mixtures by reducing the charge states of the mixture components, thereby mi...

“…Both protontransfer [26,47] and electron-transfer [48] ion/ion reactions involving multiply charged biopolymer anions were studied with this instrument. The typical experimental sequence involved introduction of multiply charged negative ions (analytes) via an end-cap electrode, ion isolation, in situ formation of singly charged positive ions by gating on the filament to introduce electrons into the ion trap, mutual storage for reaction, and mass analysis using resonance ejection [49]. This combination of ionization approaches was best suited for the study of multiply charged anions with singly charged cations.…”

Section: Ionization Approaches With 3d Ion Trapsmentioning

confidence: 99%

Evolution of instrumentation for the study of gas-phase ion/ion chemistry via mass spectrometry

Xia

McLuckey

2008

The scope of gas-phase ion/ion chemistry accessible to mass spectrometry is largely defined by the available tools. Due to the development of novel instrumentation, a wide range of reaction phenomenologies has been noted, many of which have been studied extensively and exploited for analytical applications. This perspective presents the development of mass spectrometry-based instrumentation for the study of the gas-phase ion/ion chemistry in which at least one of the reactants is multiply charged. The instrument evolution is presented within the context of three essential elements required for any ion/ion reaction study: the ionization source(s), the reaction vessel or environment, and the mass analyzer. Ionization source arrangements have included source combinations that allow for reactions between multiply charged ions of one polarity and singly charged ions of opposite polarity, arrangements that enable the study of reactions of multiply charged ions of opposite polarity and, most recently, arrangements that allow for ion formation from more than two ion sources. Gas-phase ion/ion reaction studies have been performed at near atmospheric pressure in flow reactor designs and within electrodynamic ion traps operated in the mTorr range. With ion trap as a reaction vessel, ionization and reaction processes can be independently optimized and ion/ion reactions can be implemented within the context of MS n experiments. Spatial separation of the reaction vessel from the mass analyzer allows for the use of any form of mass analysis in conjunction with ion/ion reactions. Time-of-flight mass analysis, for example, has provided significant improvements in mass analysis figures of merit relative to mass filters and ion traps. The development and evaluation of new tools has clearly been a central activity and contributor to the dramatic advances in the capabilities of mass spectrometry over the past several decades. In this perspective, we relate the evolution of instrumentation for research activities focused on the study and use of ion/ion reactions and offer it as one example of many where progress in an area of science is intimately related to and dependent on the development of instrumentation. It is provided in appreciation for the inspirational example of creativity in instrumentation development [1] provided by Cooks over the years. Electrospray ionization (ESI) [2], among its many contributions, enabled the development of macro-molecule ion/ ion chemistry as a research area. The multiple-charging phenomenon associated with electrospray makes possible the generation of multiply charged reactant ions. This capability leads to the possibility that at least one ion/ion reaction product can retain charge, which makes such a product directly amenable to study with mass spectrometry. In the past two decades, significant progress has been made in understanding and exploring the gas-phase ion/ion chemistry of high mass multiply charged ions. A variety of potential analytical applications have been developed accordingly. Co...