Resolving Oligomers from Fully Grown Polymers with IMS−MS

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105

A simple device is described for desolvation of highly charged matrix/analyte clusters produced by laser ablation leading to multiply charged ions that are analyzed by ion mobility spectrometry-mass spectrometry. Thus, for example, highly charged ions of ubiquitin and lysozyme are cleanly separated in the gas phase according to size and mass (shape and molecular weight) as well as charge using Tri-Wave ion mobility technology coupled to mass spectrometry. This contribution confirms the mechanistic argument that desolvation is necessary to produce multiply charged matrix-assisted laser desorption/ionization (MALDI) ions and points to how these ions can be routinely formed on any atmospheric pressure mass spectrometer. (J Am Soc Mass Spectrom 2010, 21, 1260 -1264 -3]. The principle of this ionization method is that the analyte/matrix sample is ablated by the use of a laser operating at atmospheric pressure (AP) and ions are subsequently formed from highly charged matrix/analyte clusters during a desolvation process. The free choice of charge state selection demonstrates the utility of LSI for the analysis of complex mixtures. Singly charged ions similar to those obtained with matrix-assisted laser desorption/ ionization (MALDI) or multiply charged ions similar to those produced by electrospray ionization (ESI) [2] can be selected using LSI. Multiply charged ions are especially beneficial for providing the ability to ionize by laser ablation larger molecules such as proteins and synthetic polymers on high-performance but mass range limited mass spectrometers such as the Orbitrap Exactive [2,3]. Full range mass spectra of bovine insulin were obtained on as little as 40 fmol when applying ion transfer capillary temperatures of ϳ350°C [3].The unique feature of LSI to produce highly charged ions using direct laser ablation of a solid surface enhances fragmentation as was demonstrated by obtaining nearly complete protein sequence coverage of ubiquitin using electron-transfer dissociation (ETD) technology on a LTQ mass spectrometer [3]. Initial laserspray applications demonstrated the ability to produce singly charged lipid ions from mouse brain tissue under ambient conditions [1]. Using transmission geometry the matrix treated tissue sections were passed free-hand through the focused laser beam in front of the mass spectrometer orifice (Orbitrap Exactive) obtaining a spatial resolution of Ͻ100 m [1]. The objective is to observe proteins from tissue.Ion mobility spectrometry (IMS) MS has many advantages compared with even high-resolution mass spectrometers because of its ability to extend the dynamic range and separate isomeric composition [4][5][6][7]. This is possible because ions are separated in the IMS dimension according to charge and cross-section (size and shape) [8][9][10][11]. One key benefit of this solvent-free gas-phase separation by IMS is that when combined with solvent-free sample preparation [12] achieves total solvent-free analysis by MS entirely decoupling ionization, separation, and mass analyses fro...

mentioning

confidence: 99%

Laserspray ionization (LSI) ion mobility spectrometry (IMS) mass spectrometry

Inutan

Trimpin

2010

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105

“…When subjected to laser irradiation (50 laser shots) at 220 nm, doubly charged PMAA oligomers undergo charge reduction followed by elimination of CO 2 . As exemplified for the case of [M 13 -2H] 2-at m/z 559.4 in Figure S1, the oxidation product [M n -2H] -• expected at m/z 1118.8 was hardly observed in EPD spectra and would instead readily decarboxylate to a radical quaternary carbon in the soformed m/z 1074.3 ion. Activated-EPD experiments would thus consist of activating [M -2H -CO 2 ] -• via collisions.…”

Section: Resultsmentioning

confidence: 95%

Efficient Structural Characterization of Poly(Methacrylic Acid) by Activated-Electron Photodetachment Dissociation

Girod

Brunet

Antoine

et al. 2011

Characterization of end-groups in poly(methacrylic acid) (PMAA) was achieved using tandem mass spectrometry after activated-electron photodetachment dissociation (activated-EPD). In this technique, multiply deprotonated PMAA oligomers produced in the negative-ion mode of electrospray ionization were oxidized into radical anions upon electron photodetachment using a 220 nm laser wavelength, and further activated by collision. In contrast to conventional collision induced dissociation of negatively charged PMAA, which mainly consists of multiple dehydration steps, fragmentation of odd-electron species is shown to proceed via a radical-induced decarboxylation, followed by reactions involving backbone bond cleavages, giving rise to product ions containing one or the other oligomer termination. A single radical-induced mechanism accounts for the four main fragment series observed in MS/MS. The relative position of the radical and of the anionic center in distonic precursor ions determines the nature of the reaction products. Experiments performed using PMAA sodium salts allowed us to account for relative abundances of product ions in series obtained from PMAA, revealing that ion stability is ensured by hydrogen bonds within pairs of MAA units.

“…Various attempts to deal with this challenge have been reported. In summary, methods such as charge reduction [13][14][15][16][17][18][19][20][21][22][23], high resolution MS [24,25], and separation of ions with different chargestate with IMS-MS [26,27] have been used. All of these strategies require advanced and/or custom made MS instruments.…”

Section: Introductionmentioning

confidence: 99%

Electrospray Ionization Tandem Mass Spectrometry of Ammonium Cationized Polyethers

Nasioudis

Heeren

Doormalen

et al. 2011

Quaternary ammonium salts (Quats) and amines are known to facilitate the MS analysis of high molar mass polyethers by forming low charge state adduct ions. The formation, stability, and behavior upon collision-induced dissociation (CID) of adduct ions of polyethers with a variety of Quats and amines were studied by electrospray ionization quadrupole time-of-flight, quadrupole ion trap, and linear ion trap tandem mass spectrometry (MS/MS). The linear ion trap instrument was part of an Orbitrap hybrid mass spectrometer that allowed accurate mass MS/MS measurements. The Quats and amines studied were of different degree of substitution, structure, and size. The stability of the adduct ions was related to the structure of the cation, especially the amine's degree of substitution. CID of singly/doubly charged primary and tertiary ammonium cationized polymers resulted in the neutral loss of the amine followed by fragmentation of the protonated product ions. The latter reveals information about the monomer unit, polymer sequence, and endgroup structure. In addition, the detection of product ions retaining the ammonium ion was observed. The predominant process in the CID of singly charged quaternary ammonium cationized polymers was cation detachment, whereas their doubly charged adduct ions provided the same information as the primary and tertiary ammonium cationized adduct ions. This study shows the potential of specific amines as tools for the structural elucidation of high molar mass polyethers.