Fragmentation of protonated dipeptides containing arginine. Effect of activation method

Abstract

The fragmentation reactions of the protonated dipeptides Gly-Arg and Arg-Gly have been studied using collision-induced dissociation (CID) in a quadrupole ion trap, by in-source CID in a single-quadrupole mass spectrometer and by CID in the quadrupole cell of a QqTOF mass spectrometer. In agreement with earlier quadrupole ion trap studies (Farrugia, J. M.; O'Hair, R. A. J., Int. J. Mass Spectrom., 2003, 222, 229), the CID mass spectra obtained with the ion trap for the MH ϩ ions and major fragment ions are very similar for the two isomers indicating rearrangement to a common structure before fragmentation. In contrast, in-source CID of the MH ϩ ions and QqTOF CID of the MH ϩ , [MH Ϫ NH 3 ] ϩ and [MH Ͻ23 HN ϭ C(NH 2 ) 2 ] ϩ ions provide distinctly different spectra for the isomeric dipeptides, indicating that rearrangement to a common structure has not occurred to a significant extent under these conditions even near the threshold for fragmentation in the QqTOF instrument. Clearly, under normal operating conditions significantly different fragmentation behavior is observed in the ion trap and beam-type experiments. This different behavior probably can be attributed to the shorter observation times and concomitant higher excitation energies in the in-source and QqTOF experiments compared to the long observation times and lower excitation energies relevant to the ion trap experiments. Based largely on elemental compositions derived from accurate mass measurements in QqTOF studies fragmentation schemes are proposed for the MH ϩ , [MH Ϫ

Proton Mobility in b2 Ion Formation and Fragmentation Reactions of Histidine-Containing Peptides

“…The fragmentation chemistry of a 2 ions derived from protonated PheHis-OMe and HisPhe-NH 2 , and protonated cyclo-(HisPhe), is a lot more similar than the b 2 ion case. Nevertheless differences in the structures or, more likely, the distribution of structures generated from the preceding collisional activation are apparent at lower collisional energies, consistent with the premise that how the ions are made can have a noticeable effect on the product ion population distributions [59][60][61][62][63][64].…”

Role of Sequence in Salt-Bridge Formation for Alkali Metal Cationized GlyArg and ArgGly Investigated with IRMPD Spectroscopy and Theory

“…b Fragmentation products corresponding to the loss of 60 and 74 Da have been reported in collisionally induced dissociation mass spectra for cationized GlyArg and ArgGly and are discussed elsewhere. 78 above 1700 cm -1 . Instead, much more relative photodissociation is observed for M ) Li, Na, and Cs near 1600 cm -1 and from 1300-1400 cm -1 .…”

Fragmentation reactions of an (n=4–8) ions containing only alanine residues

“…This probably is due to the much shorter time frame of the present experiments. There is increasing evidence [22,26,[34][35][36][37] that the time frame of observation can be an important parameter in determining the structure or mixture of structures observed.…”