Transitions between Elongated Conformations of Ubiquitin [M+11H]¹¹⁺ Enhance Hydrogen/Deuterium Exchange

Abstract

Hydrogen/deuterium (H/D) exchange reactions between different elongated conformations of [M+11H]11+ ions of ubiquitin and D2O are studied by a combination of ion mobility spectrometry (IMS) and mass spectrometry techniques. Three conformers (B, C, and D), resolved in the IMS separation, each exchange ~27 hydrogens upon exposure to 0.06 torr of D2O vapor for ~35 to 40 ms. However, a region of the IMS spectrum that appears between the C and D states (corresponding to ions that undergo a structural transition during the mobility separation) undergoes substantially more exchanges (~39 total sites, 44% more than the B, C, and D states). Selection and activation of the individual B, C, and D states reveals that the increased H/D exchange occurs during the transition between structures. Overall, these studies suggest a key process in establishing the maximum exchange levels involves structural transitions, which allow protected sites to be exposed for some fraction of the reaction time. Analysis of changes in exchange levels upon structural transitions can provide insight about common regions of structure that exist in the B, C, and D conformations.

Multiple gas-phase conformations of proline-containing peptides: is it always cis/trans isomerization?

“…We interpreted these data as evidence for differential charge location producing two sets of 4+ ion conformations present in both WT 4+ and L7P 4+ IM-MS spectra. Such phenomena has been observed previously for small proteins 44 and large peptides. 45 When a proton is not sequestered by a highly-basic residue, it can be “mobile” and occupy a distribution of protonation sites.…”

Investigation of protonated and sodiated leucine-enkephalin by hydrogen–deuterium exchange and theoretical calculations

“…6,38,39,44 Furthermore, conformational changes can also affect exchange reactions. 2,13,38,39 Intramolecular rearrangement, the surface accessibility of the charged sites and the basic sites and distance between them might be inuenced by the rigid conformation, lowering the associated reactivity.…”

“…Hydrogen-deuterium exchange (HDX) is an important tool for monitoring transitions and conformations of proteins by coupling with mass spectrometry (MS) [1][2][3][4] and ion mobility spectrometry techniques [5][6][7] with the introduction of electrospray ionization (ESI). 8 Moreover, combined with theoretical calculations, it shows great advantages for investigating the intrinsic structure in gas-phase chemistry.…”

Ion Mobility Spectrometry-Hydrogen Deuterium Exchange Mass Spectrometry of Anions: Part 2. Assessing Charge Site Location and Isotope Scrambling

“…Despite these early demonstrations, IMS-HDX-MS studies were not pursued to a significant degree for nearly ten years [8]. This may be attributed to several factors.…”