Deciphering Branched Galactomannan Structures via Multistage Ion Mobility MS and MSⁿ Fragmentation (Multistage IMSⁿ)

Area of Science:

• Carbohydrate Chemistry
• Biochemistry
• Analytical Chemistry

Background:

• Hemicelluloses are vital plant cell wall components with complex structures influencing their function.
• Galactomannans, a type of hemicellulose, present significant structural variability (branching, isomerism) complicating their characterization.
• Establishing structure-function relationships in hemicelluloses is crucial for understanding their biological roles.

Purpose of the Study:

• To adapt and validate a multistage ion mobility spectrometry (IMS) sequencing approach for the detailed structural elucidation of hetero-branched hemicelluloses, specifically galactomannans.
• To demonstrate the capability of IMS combined with mass spectrometry (MS) and porous graphitic carbon (PGC) chromatography for characterizing complex carbohydrate structures.
• To establish a robust method for analyzing the structural diversity and isomerism within galactomannan samples.

Main Methods:

• Development of a database (DB) library containing high-resolution IMS (HR-IMS) profiles of disaccharidic and trisaccharidic fragments.
• Application of multistage IMS (IMS^n) sequencing, previously validated for simpler oligosaccharides, to complex galactomannan structures.
• Retrieval of oligosaccharide sequences by comparing experimental HR-IMS profiles of fragments with the established DB library.

Main Results:

• Successful application of the IMS^n approach to galactomannans, revealing arrival time distribution (ATD) profiles consistent with known structures and confirming the presence of multiple isomers.
• Demonstrated improvement of the method by incorporating trisaccharidic fragments into the DB library, enhancing the characterization of higher degree of polymerization (DP) structures (up to DP4).
• Validation of IMS^n as a powerful tool for detailed structural elucidation of complex, branched hemicelluloses.

Conclusions:

• The developed IMS^n sequencing approach is effective for characterizing complex oligosaccharides, including branched hemicelluloses like galactomannans.
• This methodology provides a pathway for the detailed structural analysis of challenging carbohydrate structures.
• The findings support the potential use of characterized oligosaccharides in the development of novel bio-based materials.