title: Specific interactions of leucine with disaccharides by electrospray ionization mass spectrometry: application to rapid differentiation of disaccharide isomers in combination with statistical analysis.
abstract: The identification of carbohydrate isomers, including mono units, linkage positions and anomeric configurations, remains an arduous subject. In this study, the natural amino acid leucine (Leu) was found to specifically interact with cellobiose (Cello) to form a series of potassium adducts as [Cello + Leu + K](+), [Cello + 2Leu + K](+), and [2Cello + Leu + K](+) in the gas phase using mass spectrometry. By using CID-MS/MS, these complexes produced specific fragmentation patterns from the sugar backbone cleavage instead of non-covalent interactions. Moreover, their fragment distributions were dependent on the ratios of Cello-to-Leu in the complexes and the fragmentation pathways of potassium-cationized disaccharides (Dis) were remarkably changed with leucine binding. It should be pointed out that the ternary complex [2Cello + AA + K](+) was unique for leucine among all the twenty natural amino acids. The [2Dis + Leu + K](+) complex produced the most informative fragments by tandem mass spectrometry, which was successfully applied for rapid and efficient discrimination of twelve glucose-containing disaccharide isomers in combination with statistical analyses including PCA and OPLS-DA. The methodology developed here not only provides a novel analytical approach for the differentiation of disaccharide isomers, but also brings new sight towards the interactions of amino acids with disaccharides.
authors.affiliation: Department of Chemical Biology, College of Chemistry and Chemical Engineering, Key Laboratory for Chemical Biology of Fujian Province, Xiamen University, Xiamen, Fujian 361005, China. stacyliu@xmu.edu.cn.
authors.forename: Hang
authors.initials: H
authors.lastname: Yuan
authors.forename: Jianxi
authors.initials: J
authors.lastname: Ying
authors.forename: Peiran
authors.initials: P
authors.lastname: Deng
authors.forename: Peng
authors.initials: P
authors.lastname: Chen
authors.forename: Jinwen
authors.initials: J
authors.lastname: Shi
authors.forename: Yan
authors.initials: Y
authors.lastname: Liu
authors.forename: Xiang
authors.initials: X
authors.lastname: Gao
authors.forename: Yufen
authors.initials: Y
authors.lastname: Zhao
mesh_terms: D002240:Carbohydrate Sequence; D002623:Chemistry Techniques, Analytical / Q000379:methods*; D056831:Coordination Complexes / Q000737:chemistry; D004187:Disaccharides / Q000737:chemistry*; D005740:Gases; D007536:Isomerism; D007930:Leucine / Q000737:chemistry*; D044367:Phase Transition; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D056831:Coordination Complexes; D004187:Disaccharides; D005740:Gases; D007930:Leucine