Collision-Induced Dissociation of Fucose and Identification of Anomericity

Structural determination of carbohydrates using mass
spectrometry
remains challenging, particularly, the differentiation of anomeric
configurations. In this work, we studied the collision-induced dissociation
(CID) mechanisms of sodiated α- and β-l-fucose
using an experimental method and quantum chemistry calculations. The
calculations show that α-l-fucose is more likely to
undergo dehydration due to the fact that O1 and O2 are on the same
side of the sugar ring. In contrast, β-l-fucose is
more prone to the ring-opening reaction because more OH groups are
on the same side of the sugar ring as O1. These differences suggest
a higher preference for the dehydration reaction in sodiated α-l-fucose but a lower preference for ring-opening compared to
that of β-l-fucose. The calculation results, which
are used to assign the CID mass spectra of α- and β-l-fucose separated by high-performance liquid chromatography,
are supported by the fucose produced from the CID of disaccharides
Fuc-β-(1 → 3)-GlcNAc and Fuc-α-(1 → 4)-GlcNAc.
This study demonstrates that the correlation of cis- and trans-configurations
of O1 and O2 to the relative branching ratios of dehydration and cross-ring
dissociation in CID, observed in aldohexose and ketohexose in the
pyranose form, can be extended to deoxyhexoses for anomericity determination.