title: Liquid chromatography/mass spectrometry analysis of branched fructans produced in vitro with 13C-labeled substrates.
abstract: BACKGROUND
  Fructans are carbohydrates predominantly based on fructose which are generally considered to be soluble dietary fibers with health-promoting properties. It is known that the nutritional properties of fructans are affected by their structure. This study focused on structural determination of branched fructans, as the most important dietary fructans are branched graminan-type fructans.
  
  
  METHODS
  Branched fructans were synthesized enzymatically by incubation of a heterologously expressed sucrose:fructan 6-fructosyltransferase (6-SFT) from Pachysandra terminalis with native or (13)C-labeled substrates. Liquid chromatography/mass spectrometry (LC/MS) was used for the structural identification of branched fructans. The MS(2) fragmentation of these compounds is described for the first time. Analytes were charged by electrospray ionization in negative mode and a quadrupole mass analyzer was used for MS(2) analysis.
  
  
  RESULTS
  The MS(2) fragmentation patterns of branched and linear fructans were shown to differ and distinctive ion formation allowed differentiation between all branched fructan isomers formed. P. terminalis 6-SFT preferred extending the existing fructan branch rather than creating a new branch.
  
  
  CONCLUSIONS
  The MS(2) fragmentation patterns described in the current paper now allow rapid screening of large sample sets for the presence of branched, graminan-type fructans. Furthermore, the data enables the characterization of fructan-metabolizing enzymes by identification of the fructan structures produced by in vitro reactions as described here for P. terminalis 6-SFT.
authors.affiliation: Laboratory of Food Chemistry and Biochemistry, Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven, 3001, Leuven, Belgium.
authors.forename: Joran
authors.initials: J
authors.lastname: Verspreet
authors.forename: Anders
authors.initials: A
authors.lastname: Holmgaard Hansen
authors.forename: Emmie
authors.initials: E
authors.lastname: Dornez
authors.forename: Jan A
authors.initials: JA
authors.lastname: Delcour
authors.forename: Scott J
authors.initials: SJ
authors.lastname: Harrison
authors.forename: Christophe M
authors.initials: CM
authors.lastname: Courtin
mesh_terms: D002236:Carbohydrate Conformation; D002247:Carbon Isotopes / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D002853:Chromatography, Liquid / Q000379:methods*; D005630:Fructans / Q000032:analysis* / Q000737:chemistry* / Q000378:metabolism; D006602:Hexosyltransferases / Q000378:metabolism; D008958:Models, Molecular; D031236:Pachysandra / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D002247:Carbon Isotopes; D005630:Fructans; D010940:Plant Proteins; D006602:Hexosyltransferases