Differences between collisionally activated and electron‐transfer dissociations found for CH₂X₂(X = Cl, Br, and I) by using alkali‐metal targets

Abstract

High-energy collisionally activated dissociation (HE-CAD) and high-energy electron- transfer dissociation (HE-ETD) on collisions with alkali-metal targets (Cs, K, and Na) were investigated for CH(2)X(2) (+) (X = Cl, Br, and I) ions by tandem mass spectrometry (MS/MS). In the HE-CAD spectra observed, peaks associated with CH(2)X(+) ions formed by a loss of a halogen atom are always predominant regardless of precursor ions and target metals. The observation of the predominant CH(2)X(+) ions is explained by the lowest energy levels of the fragments of CH(2)X(+) + X among the possible fragment energy levels and internal-energy distribution in HE-CAD. In the charge-inversion spectra, relative peak intensities of the negative ions formed by HE-ETD strongly depend on the precursor ions and the target metals. While the CHCl(2) (-) ion was predominant in the spectra of CH(2)Cl(2) (+) regardless of target species, the most intense peaks in those of CH(2)Br(2) (+) and CH(2)I(2) (+) were ascribed to either Br(-) or CH(2)Br(-) and either I(-) or I(2) (-), respectively, depending on the target metals. The dependence of the relative intensities of the fragment ions by HE-ETD on the precursor ions and target species are discussed on the basis of the energy levels of the neutral fragments and the narrow internal-energy distribution resulting from the near-resonant neutralization. It was demonstrated that HE-ETD using the alkali-metal targets provided rich information on the dissociation of the neutral species.

Study of Ion Dynamics by Electron Transfer Dissociation: Alkali Metals as Targets

“…Charge inversion mass spectrometry has also provided information concerning the dissociation pathways of energy-selected neutral species, such as CH n (n=3-5), 44) C 2 H 2 , 45) C 3 H 4 , 46) chlorophenol, 47) and methyl stearate. 48) e dissociation of energy selected neutral of halogen containing simple molecules, such as CH 2 X 2 49,50) and CH 3 X (X=Cl, Br, I) 51) showed a strong dependence on both the target species and halogen in the molecules in charge inversion spectra using alkali metal targets (Cs, K and Na). While the CHCl 2 − ion was predominant in the spectra of CH 2 Cl 2 + regardless of target species, the most intense peaks were CH 2 Br 2 + and CH 2 I 2 + were ascribed to being derived from either Br − or CH 2 Br − and either I − or I 2 − , respectively, depending on the target metal used.…”

High-energy electron transfer dissociation of protonated amino acids

“…Using this technique, unstable neutral intermediates, such as vinylidenes [40,41], CH n (n = 3-5) [42], CH 2 X 2 (X = Cl, Br, and I) [43,44], and CH 3 X (X = Cl, Br, and I) [45], have been studied. Protonated molecules [AB+H] + , which are positive ions formed from stable molecules (AB), are in a singlet state (as are stable molecules) because the proton does not have an electron associated with it.…”

High-energy electron transfer dissociation (HE-ETD) using alkali metal targets for sequence analysis of post-translational peptides

“…Charge inversion mass spectrometry using alkali metal targets [23][24][25][26][27][28][29] for singly protonated peptides and amino acids provided the information of the radical traps in the dissociation mechanism of the charge reduced peptides [28,30,31]. N-C␣ bond cleavages induced by electron-transfer processes of multiply charged peptides upon collision with alkali metals have been reported by Hvelplund and coworkers [32][33][34][35][36][37].…”

“…The charge reduced peptide cation radicals formed by ECD and ETD are known to dissociate at various positions via the low-energy transitionstate for bond cleavage [16 -20]. Differences between ECD and ETD are also reported [15,21,22] .Charge inversion mass spectrometry using alkali metal targets [23][24][25][26][27][28][29] for singly protonated peptides and amino acids provided the information of the radical traps in the dissociation mechanism of the charge …”

“…Charge inversion mass spectrometry using alkali metal targets [23][24][25][26][27][28][29] for singly protonated peptides and amino acids provided the information of the radical traps in the dissociation mechanism of the charge…”