3-Aminoquinoline Acting as Matrix and Derivatizing Agent for MALDI MS Analysis of Oligosaccharides

摘要

Matrix-assisted laser desorption/ionization time-of-flightnmass spectrometry (MALDI-TOF MS) is a widely usednmethod in oligosaccharide analysis. Underivatized oli-ngosaccharides are not well-suited for that purpose due tontheir low ionization efficiency; however, derivatizationnrequires tedious sample purification steps which may leadnto sample losses, thereby decreasing its benefit. On-targetnderivatization performed by the matrix 3-aminoquinolinendoes not require such purification and yields Schiff basesnwhich can be measured in positive and negative ion modenfrom one single spot. In negative ion mode, spectra fromnanionic adducts of the derivatives can be acquired fromn1 fmol of oligosaccharide. Furthermore, postsource decayn(PSD) fragmentation in positive and negative ion mode isnenhanced, providing information on oligosaccharide se-nquence, linkage, and branching. Optimization of reactionnconditions and matrix solution led to a complete andnreproducible derivatization for all tested standard oli-ngosaccharides. Finally, the method was applied to trifu-ncosyllacto-N-hexaose and trifucosyl-para-lacto-N-hexaose,ntwo isomers occurring in human breast milk samples,nwhich were easily identified and distinguished.