title: Characterisation of 3-aminoquinoline-derivatised isomeric oligogalacturonic acid by travelling-wave ion mobility mass spectrometry.
abstract: BACKGROUND
  Mass spectrometry has become a useful technique for elucidating the chemical structures of oligosaccharides. The combined use of chromatography and mass spectrometry for the separation and identification of oligosaccharides has shown much progress in recent years. However, no powerful method has yet been developed to quickly identify isomeric oligosaccharides in complex mixtures.
  
  
  METHODS
  A rapid travelling-wave ion mobility mass spectrometry (TWIMS-MS) method was developed for the identification of various isomeric oligogalacturonic acids in mixtures and determined their structures, using 3-aminoquinoline (3-AQ) as a labelling agent.
  
  
  RESULTS
  TWIMS successfully distinguished isomeric oligogalacturonic acids of various degrees of polymerisation (DPs) and levels of methyl-esterification. After derivatisation by 3-AQ, isomeric oligosaccharides of galacturonic acid, with the DP ranging from 2 to 9 and the number of methyl esters ranging from 1 to 5, were identified by 3-AQ-TWIMS-MS. The isomeric oligosaccharides with varying sites of methyl ester substitution were identified by the post-fragmentation mode of TWIMS using 3-AQ labelling to obtain simplified mass spectra.
  
  
  CONCLUSIONS
  Using the 3-AQ-TWIMS-MS method, the precise distribution of methyl esters within the pectin molecule and isomeric oligogalacturonic acids after enzyme degradation was determined. Simplified product ion mass spectra and precise analysis of the isomers were achieved by labelling 3-AQ at the reducing end of the oligosaccharides. Series of methyl-esterified galacturonic acid oligomers have predictable drift times, depending on the precise position of the methyl ester.
authors.affiliation: Laboratory of Food Chemistry, Wageningen University, P.O. Box 17, 6700 AA, Wageningen, The Netherlands.
authors.forename: Jie-Hong
authors.initials: JH
authors.lastname: Huang
authors.forename: Edwin J
authors.initials: EJ
authors.lastname: Bakx
authors.forename: Harry
authors.initials: H
authors.lastname: Gruppen
authors.forename: Henk A
authors.initials: HA
authors.lastname: Schols
mesh_terms: D007536:Isomerism; D013058:Mass Spectrometry / Q000379:methods*; D009844:Oligosaccharides / Q000737:chemistry*; D015363:Quinolones / Q000737:chemistry*
chemical_list: D009844:Oligosaccharides; D015363:Quinolones; C412763:oligogalacturonic acid