Identification of GOS Disaccharide Isomers Using cIMS-MS/MS

Area of Science:

• Analytical Chemistry
• Carbohydrate Chemistry
• Mass Spectrometry

Background:

• Characterizing isomeric oligosaccharides like galactooligosaccharides (GOS) in complex mixtures presents a significant analytical challenge due to the vast number of possible structures.
• The exponential increase in structural possibilities with higher degrees of polymerization (DP) makes obtaining a complete set of analytical standards difficult.

Purpose of the Study:

• To investigate the combined capabilities of cyclic ion mobility mass spectrometry (cIMS) and collision-induced dissociation (CID) fragmentation for the identification of isomeric disaccharides.
• To evaluate the performance of different metal adducts (lithium, sodium, potassium, rubidium, cesium) in cIMS separation and CID fragmentation of galactose and glucose-based disaccharides.

Main Methods:

• Studied the separation and fragmentation of isomeric disaccharides using combined cIMS and CID.
• Compared the drift time selectivity and fragment yields of lithium, sodium, potassium, rubidium, and cesium adducts.
• Analyzed how cIMS drift times and CID fragmentation patterns correlate with disaccharide composition and linkage types.

Main Results:

• Lithium adducts demonstrated superior performance in cIMS, offering good resolution and significantly higher fragment yields compared to other metal ions.
• cIMS drift times were primarily influenced by disaccharide composition, consistently showing an order of Gal-Gal < Gal-Glc < Glc-Glc for identical linkage types.
• CID cross-ring fragmentation patterns proved to be specific to linkage types, with minimal dependence on composition or anomeric configuration.

Conclusions:

• The developed cIMS-MS/MS approach enables straightforward identification of unknown disaccharides by determining monosaccharide composition from drift times and linkage type from CID fragmentation.
• This method reduces the need for higher DP oligosaccharide standards, offering a pathway for analyzing complex oligosaccharide mixtures.
• These findings represent a crucial advancement for the identification of larger oligosaccharides using cIMS-MS-based techniques.