ANALYSIS OF FRUCTANS FROM HIGHER-PLANTS BY MATRIX-ASSISTED LASER DESORPTION IONIZATION MASS-SPECTROMETRY/

In this communication both matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) and high-performance anion-exchange chro matography (HPAEC) have been applied to analyze fructans from higher p lants. Size distribution of a commercially available fructan preparati on from Dahlia variabilis L, was determined by MALDI-MS. Molecular mas ses ranged from 2000 up to 6000 Da with a peak value of the distributi on at 2635 Da, Essentially the same pattern was obtained using HPAEC. Low-molecular-weight fructans from onion bulbs (Allium cepa L,) were s tudied in more detail, Tissue extracts were analyzed by MALDI-MS witho ut any analyte purification. Mass spectra of both proteins and oligosa ccharides were obtained. For identification, metastable ion scanning w as performed. Neither deproteinization nor deionization of the samples affected the oligosaccharide pattern. Using HPAEC, a more complex oli gosaccharide pattern was obtained because isomeric glycans were differ entiated. However, the overall size distribution was similar to that o btained by MALDI-MS. In further experiments epidermal or parenchyma ce ll layers of the onion bulb were placed into matrix solution and were then subjected to MALDI-MS and metastable ion scanning as well. By tak ing this approach, analyte desorption was achieved immediately from pl ant tissue. Oligosaccharide mass spectra were essentially the same as those of the extracts. To our knowledge, this is the first time that M ALDI-MS has been applied as a microprobe to plant tissue. Finally MALD I-MS analysis was performed using single-cell extracts from onion tiss ues without any purification of the analyte. (C) 1997 Academic Press.