Charge inversion mass spectrometry: dissociation of resonantly neutralized molecules

Abstract

Charge inversion mass spectrometry is an MS/MS method in which the electric charge of the precursor ions is opposite to that of the secondary product ions. Charge inversion mass spectrometry is classified into four types depending on the electric charge and time scale of collisions. Charge inversion mass spectrometry using collisions with gaseous targets in the keV energy collision range has provided insights into the structures and reactions of ions and neutral molecules. The characteristics of charge inversion experiments are presented in terms of the reaction endothermicities and the cross sections and their dependence on the target species. In the case of rare-gas or simple molecular targets, double-electron transfer in one collision is effective to form positive ions from negative ions, while, in the case of alkali metal targets, successive single-electron transfers in two collisions is effective to form negative ions from positive ions. On the basis of the observed target-density dependence of the product ion intensity and thermochemical considerations for internal energy distribution using thermometer molecules, the charge inversion processes using alkali metal targets have been confirmed to occur by electron transfers in successive collisions and the dissociation processes are found to occur in energy-selected neutral species formed from near-resonant neutralization with alkali metal targets. While collisionally activated dissociation (CAD) is due to dissociation of activated ions with broad internal energy distributions, the charge inversion process using alkali metal targets is due to dissociation of energy-selected neutral species with narrow internal energy distributions. The charge inversion/alkali metal spectra provide clear differentiation of the isomeric cations of C(2)H(2), C(3)H(4) and dichlorobenzenes. The CAD spectra of these isomeric cations are similar.

Charge permutation reactions in tandem mass spectrometry

“…24 Most charge inversion experiments have been performed on sector instruments. 25 Albeit early work involved the use of forward geometry sector instruments, most charge inversion experiments have been conducted with reverse geometry sector instruments. Typically, the magnetic sector is set to select the negatively charged precursor ion, which undergoes charge inversion in a collision region between the magnetic and electric sectors to form the oppositely charged product ion.…”

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

“…While relative abundances of the respective c-type and z-type ions by the LE-ETD in Figure 4a, b, and c are not same as those by HE-ETD in Figure 3a, b, and c, spectral features between the LE-ETD and the HE-ETD are similar for the respective precursors. In HE-ETD of the present work, the speed of the doubly charged ion with m/z of 750 u accelerated by 5 kV is 3.6 ϫ 10 4 m/s [23]. By assuming that the interaction region is twice of 6.8 ϫ 10 -10 m of the length at the Landau-Zener potential crossing evaluated for the Cs target [39], the interaction time between the collision partners is estimated to be 3.8 ϫ 10 -14 s. A period for dissociation was estimated from the length of 230 cm between the exit of the target chamber and the entrance of the MS-II is 6.5 s. This period is much shorter than the reaction time in the LE-ETD.…”

“…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…”