Simple Method for De Novo Structural Determination of Underivatised Glucose Oligosaccharides

Hsu Chen Hsu,Shang-Ting Tsai,Chia Yen Liew,Shih-Pei Huang,Chi-Kung Ni

doi:10.1038/s41598-018-23903-4

Abstract

Carbohydrates have various functions in biological systems. However, the structural analysis of carbohydrates remains challenging. Most of the commonly used methods involve derivatization of carbohydrates or can only identify part of the structure. Here, we report a de novo method for completely structural identification of underivatised oligosaccharides. This method, which can provide assignments of linkages, anomeric configurations, and branch locations, entails low-energy collision-induced dissociation (CID) of sodium ion adducts that enable the cleavage of selective chemical bonds, a logical procedure to identify structurally decisive fragment ions for subsequent CID, and the specially prepared disaccharide CID spectrum databases. This method was first applied to determine the structures of four underivatised glucose oligosaccharides. Then, high-performance liquid chromatography and a mass spectrometer with a built-in logical procedure were established to demonstrate the capability of the in situ CID spectrum measurement and structural determination of the oligosaccharides in chromatogram. This consolidation provides a simple, rapid, sensitive method for the structural determination of glucose oligosaccharides, and applications to oligosaccharides containing hexoses other than glucose can be made provided the corresponding disaccharide databases are available.

Highlights

The most frequently used carbohydrate analysis techniques are liquid chromatography (LC)[5], capillary electrophoresis (CE)[6,7], nuclear magnetic resonance spectroscopy (NMR)[8], and mass spectrometry (MS)[9]
The ions m/z 509 and 467 indicate that the carbohydrate is a linear trisaccharide with a 1→4 linkage or a branched trisaccharide with 1→4 and 1→6 linkages on the sugar of the reducing end according to the fragmentation patterns shown in Supplementary Table S8
An alternative approach for structural determination involves 527→467(0,2A3)→365(C2/0,2A3)→fragments. This approach shares the same first step of the aforementioned method, i.e., the ions m/z 509 and 467 in the collision-induced dissociation (CID) of 527→fragments [Fig. 4(a)] indicate that the carbohydrate is a linear trisaccharide with a 1→4 linkage or a branched trisaccharide with 1→4 and 1→6 linkages on the reducing sugar according to the fragmentation patterns shown in Supplementary Table S8

Summary

Introduction

The most frequently used carbohydrate analysis techniques are liquid chromatography (LC)[5], capillary electrophoresis (CE)[6,7], nuclear magnetic resonance spectroscopy (NMR)[8], and mass spectrometry (MS)[9]. A disaccharide is generated only from one side (the reducing or nonreducing side) of parent or fragment ions in each step of CID.

Results

Conclusion