In-source CID of guanosine: Gas phase ion-molecule reactions

Abstract

In-source collision induced dissociation was applied to access second generation ions of protonated guanosine. The in-source gas-phase behavior of [BH 2 ] ϩ -NH 3 (m/z 135, C 5 H 3 N 4 O ϩ ) was investigated. Adduct formation and reactions with available solvent molecules (H 2 O and CH 3 OH) were demonstrated. Several addition/elimination sequences were observed for this particular ion and solvent molecules. Dissociation pathways for the newly formed ions were developed using a QqTOF mass spectrometer, permitting the assignment of elemental compositions of all product ions produced. Reaction schemes were suggested arising from the ring-opened intermediate of the protonated base moiety [BH 2 ] ϩ , obtained from fragmentation of guanosine. The mass spectral data revealed that the in-source CH 3 OH-reaction product underwent more complex fragmentations than the comparable ion following reaction with H 2 O. A rearrangement and a parallel radical dissociation pathway were discerned. Apart from the mass spectrometric evidence, the fragmentation schemes are supported by density functional theory calculations, in which the reaction of the ring-opened protonated guanine intermediate with CH 3 OH and a number of subsequent fragmentations were elaborated. uring the last decade, most fragmentation pathways were elaborated on triple quadrupole (QqQ) and particularly quadrupole ion-trap (QIT) instruments. The latter's capabilities of accessing MS n product ions by applying repeated stages of mass selection and fragmentation proved to be very useful [1]. The maturation of the time of flight (TOF) technology and, more importantly, its use in hybrid-arrangements such as the popular orthogonal QqTOF mass spectrometer made accurate mass data of product ions more readily available [2]. In many cases, the elemental compositions of the product ions can unambiguously be assigned when using a QqTOF mass spectrometer. Product ions lower in the genealogical ladder are also accessible by applying relatively high collision energies in the collision cell. Yet disentanglement of different dissociation pathways originating from a communal progenitor is -in general-still confined to QIT set ups, although the interpretation of energy resolved spectra also has proven its usefulness [3].Recently we and others showed [4 -6] that by making optimal use of in-source CID, combined with the inherent tandem MS capabilities of the QqTOF, what is in effect up to MS 5 data can be acquired. Compared to QIT data the QqTOF data obtained is superior in respect of higher mass accuracy. On the other hand QIT-CID experiments, in general, access almost exclusively the dissociation reaction channels of the lowest energy of activation [7]. This energy-dependent information can

Revisiting the Reactivity of Uracil During Collision Induced Dissociation: Tautomerism and Charge-Directed Processes

“…For QIT, we were able to simply select [UR + H] + at m/z 245 in MS 2 in order to obtain [U + H] + at m/z 113 as a precursor in MS 3 . The product-ion spectrum in MS 3 of protonated uracil by QIT-MS is shown in Figure 1A and shows abundant products of the loss of ammonia (-17), water (-18) and isocyanic acid (-HNCO, -43) as well as an ion-neutral reaction with residual water (+18) present as an impurity in the collision gas of our QIT [29].…”

Detection, Identification, and Occurrence of Thiotetronic Acids in Drinking Water from Underground Sources by Electrospray Ionization-High Field Asymmetric Waveform Ion Mobility Spectrometry-Quadrupole Time-of-Flight-Mass Spectrometry

“…Analogous reactions were observed in the CID of protonated guanine where H 2 O addition to a ketene moiety was attributed to reversible opening of the pyrimidine ring. 27,28 The heterolytic thiolactone bond cleavage proceeds through a transition state intermediate ion (Scheme 1) in which the positive charge density at C-2 increases progressively until the bond is broken. Stabilization of the intermediate arises from delocalization of the charge from the C-2 site as a result of interactions with the HS moiety and resonance through the adjacent (−CC−OH) bond system.…”

Solvation in Gas-Phase Reactions of Sulfonic Groups Containing Ionic Liquids in Electrospray Ionization Quadrupole Ion Trap Mass Spectrometry

“…In establishing the fragmentation pathways and associating mass spectral fragmentation with chemical structure, it is assumed that product ions are subunits of their precursor ion. However, during the course of using ion trap-based ESI-MS/MS to characterize natural products, it has been reported earlier [9][10][11][12][13][14][15] that certain fragmentation products react with H 2 o and other commonly used ESI solvent molecules, thereby complicating MS/MS data interpretation.…”