Phase-modulated stored waveform inverse Fourier transform excitation for trapped ion mass spectrometry

Abstract. Two-dimensional Fourier transform ion cyclotron resonance mass spectrometry is a data-independent analytical method that records the fragmentation patterns of all the compounds in a sample. This study shows the implementation of atmospheric pressure photoionization with two-dimensional (2D) Fourier transform ion cyclotron resonance mass spectrometry. In the resulting 2D mass spectrum, the fragmentation patterns of the radical and protonated species from cholesterol are differentiated. This study shows the use of fragment ion lines, precursor ion lines, and neutral loss lines in the 2D mass spectrum to determine fragmentation mechanisms of known compounds and to gain information on unknown ion species in the spectrum. In concert with high resolution mass spectrometry, 2D Fourier transform ion cyclotron resonance mass spectrometry can be a useful tool for the structural analysis of small molecules.

Section: Resultsmentioning

confidence: 99%

Differentiating Fragmentation Pathways of Cholesterol by Two-Dimensional Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Agthoven

Barrow

Chiron³

et al. 2015

“…The laser output was focused to a spherical spot of ϳ200 m 2 using standard fused silica lens. Arginine or arginine-containing peptide [M ϩ H] ϩ ions generated by MALDI were isolated using standard SWIFT excitation pulses [38], and the mass-selected ions were then transferred to the analyzer cell and allowed to react with ND 3 for times ranging from 5 ms to 15 min at 1 ϫ 10 Ϫ8 to 2 ϫ 10 Ϫ7 torr, followed by product ion excitation and detection. The ion temporal profiles were used to determine the kinetics of H/D exchange.…”

Section: Methodsmentioning

confidence: 99%

A mechanistic study of the H/D exchange reactions of protonated arginine and arginine-containing Di- and tripeptides

Huang

Marini

McLean

et al. 2009

The gas-phase H/D exchange reactions of arginine (R) and arginine-containing di-and tri-peptide (gly-arg (GR), arg-gly (RG), gly-gly-arg (GGR), gly-arg-gly (GRG) and arg-gly-gly (RGG)) [M ϩ H] ϩ ions with deuterated ammonia (ND 3 ) were investigated by using Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR), ion mobility-mass spectrometry (IM-MS), ab initio and density functional theory-based molecular orbital calculations and molecular modeling. Three exchanges are observed for arginine and argininecontaining tri-peptide [M ϩ H] [15]. Valentine and Clemmer used ion mobility-mass spectrometry to examine the conformation dependence of H/D exchange reactions, and suggested that ion conformation has a significant effect on H/D exchange [16,17].Compared with the intensive investigations carried out on the conformational characterization of peptides and proteins using solution-phase H/D exchange reaction chemistry, the corresponding gas-phase studies are much less comprehensive. The key question regarding gas-phase H/D exchange is: does the "solvent molecule," i.e., H/D exchange reagent, sample the entire "available surface area" of the peptide/protein ion, or is H/D exchange limited by other factors? For example, are all solution phase labile hydrogen atoms exchangeable in the gas phase and are the reactivities of all exchangeable hydrogen atoms similar? Dookeran and Harrison studied the H/D exchange reactions of 18 naturally occurring amino acids and selected di-and tripeptides with ND 3 , and reported that amino acid [M ϩ H] ϩ ions containing hydroxyl, carboxyl, and amine side chains exchange all labile hydrogen atoms, whereas the side-chain hydrogen atoms of glutamine, asparagine, and histidine [M ϩ H] ϩ ions exchange less readily, and tyrosine and arginine [M ϩ H] ϩ ions do not undergo significant exchange [18]. In a separate study, Lebrilla et al. found that the carboxylic acid group of glycine and aliphatic amino acid [M ϩ H] ϩ ions (alanine, valine, leucine, isoleucine, and proline) undergo H/D exchange three to 10 times faster than the NAddress reprint requests to Dr.

“…The ions were accelerated by continuously exciting them for one second at a frequency 1 kHz higher than their cyclotron frequency, and activated via collisions with argon. The (bi)radicals were then isolated by applying a series of stored-waveform inverse Fourier-transform [15] (SWIFT) excitation pulses to the plates of the cell to eject unwanted ions from the cell.…”

Section: Methodsmentioning

confidence: 99%

Reactivity of aromatic σ,σ-biradicals toward riboses

Adeuya

Yang

Amegayibor

et al. 2006

The gas-phase reactions of sugars with aromatic, carbon-centered ,-biradicals with varying polarities [as reflected by their calculated electron affinities (EA)] and extent of spin-spin coupling [as reflected by their calculated singlet-triplet (S-T) gaps] have been studied. The biradicals are positively charged, which allows them to be manipulated and their reactions to be studied in a Fourier-transform ion cyclotron resonance mass spectrometer. Hydrogen atom abstraction from sugars was found to be the dominant reaction for the biradicals with large EA values, while the biradicals with large S-T gaps tend to form addition/elimination products instead. Hence, not all ,-biradicals may be able to damage DNA by hydrogen atom abstraction. The overall reaction efficiencies of the biradicals towards a given substrate were found to be directly related to the magnitude of their EA values, and inversely related to their S-T gaps. The EA of a biradical appears to be a very important rate-controlling factor, and it may even counterbalance the reduced radical reactivity characteristic of singlet biradicals that have large S-T gaps. . These intermediates are believed to irreversibly damage double-stranded DNA via hydrogen atom abstraction from a sugar moiety in each strand [2]. Therefore, a better understanding of the factors controlling the reactivity of these biradicals toward sugars is important.Solution [3] and gas-phase [4] studies on the reactivity of neutral and charged phenyl radicals have confirmed that these monoradicals can abstract hydrogen atoms from sugars as well as from the sugar moiety in nucleosides and dinucleoside phosphates. Polar effects (i.e., polarization of the transition state) play a major role in controlling these reactions [5][6][7]. However, no such studies have been reported for the analogous biradicals.The magnitude of the singlet-triplet (S-T) gap has been proposed earlier [8] as the major reaction rate controlling factor for aromatic ,-biradicals with singlet ground states. As the magnitude of the S-T gap increases, the reaction efficiency for hydrogen atom abstraction from simple substrates has been observed to decrease, presumably because of the energetically high cost of uncoupling the biradical's electrons in the transition state [8,9]. Biradicals with large S-T gaps appear to avoid this penalty by undergoing nucleophilic or electrophilic (nonradical) addition reactions [10]. Recent gas-phase studies have shown that in addition to S-T gap effects [9], reactions of biradicals with simple organic substrates are also sensitive to polar effects (which is reflected by the biradical's calculated vertical electron affinity, EA) [11]. Here, we report an examination of the reactivity of several ,-biradicals (Scheme 1) toward various sugars, and show that these reactions are also affected by the S-T gap and the EA of the biradical.