Fragmentation of doubly-protonated peptide ion populations labeled by H/D exchange with CD3OD

Abstract

Doubly-protonated bradykinin (RPPGFSPFR) and an angiotensin III analogue (RVYIFPF) were subjected to hydrogen/deuterium (H/D) exchange with CD 3 OD in a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. A bimodal distribution of deuterium incorporation was present for bradykinin after H/D exchange for 90 s at a CD 3 OD pressure of 4 × 10 −7 Torr, indicating the existence of at least two distinct populations. Bradykinin ion populations corresponding to 0-2 and 5-11 deuteriums (i.e., D 0 , D 1 , D 2 , D 5 , D 6 , D 7 , D 8 , D 9 , D 10 , and D 11 ) were each monoisotopically selected and fragmented via sustained off-resonance irradiation (SORI) collision-induced dissociation (CID). The D 0 -D 2 ion populations, which correspond to the slower exchanging population, consistently require lower SORI amplitude to achieve a similar precursor ion survival yield as the faster-reacting (D 5 -D 11 ) populations. These results demonstrate that conformation/ protonation motif has an effect on fragmentation efficiency for bradykinin. Also, the partitioning of the deuterium atoms into fragment ions suggests that the C-terminal arginine residue exchanges more rapidly than the N-terminal arginine. Total deuterium incorporation in the b 1 /y 8 and b 2 /y 7 ion pairs matches very closely the theoretical values for all ion populations studied, indicating that the ions of a complementary pair are likely formed during the same fragmentation event, or that no scrambling occurs upon SORI. Deuterium incorporation into the y 1 /a 8 pseudo-ion pair does not closely match the expected theoretical values. The other peptide, doubly-protonated RVYIFPF, has a trimodal distribution of deuterium incorporation upon H/D exchange with CD 3 OD at a pressure of 1 × 10 −7 Torr for 600 s, indicating at least three distinct ion populations. After 90 s of H/D exchange where at least two distinct populations are detected, the D 0 -D 7 ion populations were monoisotopically selected and fragmented via SORI-CID over a range of SORI amplitudes. The precursor ion survival yield as a function of SORI amplitude falls into two distinct behaviors corresponding to slower-and faster-reacting ion populations. The slower-reacting population requires larger SORI amplitudes to achieve the same precursor ion survival yield as the faster exchanging population. Total deuterium incorporation into the y 2 /b 5 ion pairs matches closely the theoretical values over all ion populations and SORI amplitudes studied. This result indicates the y 2 and b 5 ions are likely formed by the same mechanism over the SORI amplitudes studied.

Separation and identification of structural isomers by quadrupole collision-induced dissociation-hydrogen/deuterium exchange-infrared multiphoton dissociation (QCID-HDX-IRMPD)

“…Because differences in gas-phase structure will allow for different extents and relative rates of HDX, [14] m/z values consisting of multiple isomeric ion structures can be identified by the presence of multiple HDX populations for a given product ion m/z. The use of HDX to separate isomers has been previously demonstrated by other researchers, including Marshall and coworkers [15] for a series of bradykinins, Herrmann et al [16] for bradykinin and angiotensin analogues in combination with SORI, Lifshitz and coworkers [17] for isomers of serine octamers, and very recently by Polfer and coworkers for fragments of poly-glycine peptides [18] as well by Somogyi and Paizs to reveal b 2 ion structures [19]. For additional confirmation of the presence of different structures, IRMPD can be used to fragment ions that have been separated by differences in HDX rates.…”

Detection of oligonucleotide gas-phase conformers: H/D exchange and ion mobility as complementary techniques

“…Working solutions (1.1765 ϫ 10 Ϫ5 M) were obtained by dilution in water. The injection solutions were prepared by adding the appropriate amount of MeOH to obtain a MeOH/H 2 O ratio of 15/85 (vol/ vol) and an oligonucleotide concentration of 1.0000 ϫ 10 Ϫ5 M. For the injection solutions of the RNA hexanucleotide, NH 4 Ac was added to reduce sodium adducts. The NH 4 Ac concentration was equal to 50 mM.…”

“…The rate of gasphase H/D exchange has been shown to be a function of the reagent used for exchange (nature and concentration), the charge state of the biomolecule, the gasphase basicity/acidity of exchangeable sites, and the internal structure of the biomolecular ions [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Probing the number of exchanged hydrogens and the H/D exchange kinetics makes it possible to distinguish ion populations and to elucidate their structural and thermochemical features.…”

Oxazolone versus macrocycle structures for leu-enkephalin b2–b4: Insights from infrared multiple-photon dissociation spectroscopy and gas-phase hydrogen/deuterium exchange

“…In earlier studies, Wysocki and Somogyi had shown that HDX of b ions often displays bimodal distributions, which can be rationalized by the presence of two different chemical structures [27,28]. Recent HDX studies by Solouki and coworkers also show similar trends [29].…”