Cryogenic Infrared Spectroscopy Unmasks Gas-Phase Charge Migration in Mucin-Type O-Glycans.

Area of Science:

• Glycobiology
• Analytical Chemistry
• Physical Chemistry

Background:

• O-glycosylation is a crucial post-translational modification impacting immunity, lubrication, and cell communication.
• Mass spectrometry struggles with detailed O-glycan structure assignment due to complexity and lack of diagnostic fragments.
• Current methods for O-glycan characterization are often laborious and incomplete.

Purpose of the Study:

• To introduce cryogenic gas-phase infrared spectroscopy for enhanced O-glycan characterization.
• To demonstrate the utility of IR spectroscopy in distinguishing isomeric O-glycan core structures.
• To investigate the gas-phase structures and dynamics of deprotonated O-glycans using spectroscopy and computational methods.

Main Methods:

• Utilized cryogenic gas-phase infrared spectroscopy for O-glycan analysis.
• Performed ab initio calculations to model gas-phase structures of deprotonated O-glycans.
• Compared cryogenic IR spectroscopy with ambient temperature ion mobility spectrometry.

Main Results:

• O-glycans exhibit highly diagnostic IR fingerprints, enabling easy differentiation of isomeric core structures.
• Experimental spectra indicate distinct ensembles of deprotomers and conformers at cryogenic temperatures.
• Rapid charge migration, similar to the Grotthuss mechanism, facilitates deprotomer interconversion at ambient temperatures due to flexible hydrogen-bond networks.

Conclusions:

• Cryogenic gas-phase IR spectroscopy is a powerful tool for detailed O-glycan structural characterization.
• The study reveals insights into the structural diversity and dynamic behavior of O-glycans in the gas phase.
• Understanding O-glycan structure and dynamics is vital for elucidating their roles in biological processes.