Structural Determination of Polysaccharides Lichenin Using Logically Derived Sequence Tandem Mass Spectrometry.

A new mass spectrometry method, logically derived sequence (LODES) tandem mass spectrometry (MS n ), was applied to determine the primary structure of polysaccharide lichenin. Conventional polysaccharide structural analysis requires complex processes, including derivation, permethylation, gas chromatography-mass spectrometry, and nuclear magnetic resonance spectrometry. Many of these processes can be replaced by LODES/MS n . In this new method, polysaccharides are hydrolyzed into monosaccharides, disaccharides, and oligosaccharides, and structures of these molecules are determined using LODES/MS n . The application of LODES/MS n for determination of primary structure of polysaccharide lichenin was demonstrated. The repeating unit of lichenin was determined to be A n -B n , where A represents β-Glc-(1 → 4)-β-Glc-(1 → 4)-β-Glc-(1 → 3)-Glc, B represents β-Glc-(1 → 4)-β-Glc-(1 → 4)-β-Glc-(1 → 4)-β-Glc-(1 → 3)-Glc, n is an integral, and n ≥ 2 exists but n = 1 cannot be excluded. LODES/MS n , which substantially reduces the time, effort, and sample quantity necessary for structural determination of oligosaccharides, is a powerful tool for polysaccharide primary structural determination.