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Carbohydrates and glycans are integral to many biological processes, including cell-cell recognition and energy storage. However, carbohydrates are often difficult to analyze due to the high degree of isomerism present. One method being developed to distinguish these isomeric species is hydrogen/deuterium exchange-mass spectrometry (HDX-MS). In HDX-MS, carbohydrates are exposed to a deuterated reagent and the functional groups with labile hydrogen atoms, including hydroxyls and amides, exchange with the 1 amu heavier isotope, deuterium. These labels can then be detected by MS, which monitors the mass increase with the addition of D-labels. The observed rate of exchange is dependent on the exchanging functional group, the accessibility of the exchanging functional group, and the presence of hydrogen bonds. Herein, we discuss how HDX has been applied in the solution-phase, gas-phase, and during MS ionization to label carbohydrates and glycans. Additionally, we compare differences in the conformations that are labeled, the labeling timeframes, and applications of each of these methods. Finally, we comment on future opportunities for development and use of HDX-MS to analyze glycans and glycoconjugates.
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Evidence of H/D Exchange within Metal-Adducted Carbohydrates after Ion/Ion-Dissociation Reactions
Tandem mass spectrometry (MS/MS) using fragmentation has become one of the most effective methods for gaining sequence and structural information of biomolecules. Ion/ion reactions are competitive reactions where either proton transfer (PT) or electron transfer (ET) can occur from interactions between multiply charged cations and singly charged anions. Utilizing ion/ion reactions with fluoranthene has offered a unique method of fragment formation for structural elucidation of biomolecules. Fluoranthene is considered an ideal anion reagent because it selectively causes electron transfer dissociation (ETD) and minimizes PT when interacting with peptides. However, limited investigations have sought to understand how fluoranthene – the primary, commercially available anion reagent – interacts with other biomolecules. Here, we apply deuterium labeling to investigate ion/ion reaction mechanisms between fluoranthene and divalent, metal-adducted carbohydrates (Ca2+, Mg2+, Co2+, and Ni2+). Deuterium labeling of carbohydrates allowed us to observe evidence of hydrogen/deuterium exchange (HDX) occurring after ion/ion dissociation reactions. The extent of deuterium loss is dependent on several factors, including the physical properties of the metal ion and the fragment structure. Based on the deuterium labeling data, we have proposed ETD, PTD, and intermolecular PT – also described as HDX - mechanisms. This research provides a fundamental perspective of ion/ion and ion/molecule reaction mechanisms and illustrates properties that impact ion/ion and ion/molecule reactions for carbohydrates. Together, this could improve the capability to distinguish complex and heterogenous biomolecules, such as carbohydrates.
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- Award ID(s):
- 1945078
- PAR ID:
- 10493382
- Publisher / Repository:
- American Chemical Society
- Date Published:
- Journal Name:
- Journal of the American Chemical Society
- Volume:
- 145
- Issue:
- 44
- ISSN:
- 0002-7863
- Page Range / eLocation ID:
- 23972 to 23985
- Subject(s) / Keyword(s):
- Carbohydrates hydrogen isotopes ions isolation metals
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1021/jacs.3c05793
