STRUCTURES OF CAULERPA CELL-WALL MICROFIBRIL XYLAN WITH DETECTION OF BETA-1,3-XYLOOLIGOSACCHARIDES AS REVEALED BY MATRIX-ASSISTED LASER-DESORPTION IONIZATION TIME-OF-FLIGHT MASS-SPECTROMETRY

Since the cell wall microfibril xylans from Caulerpa sp, were not assu med to be constituted from beta-1,3-straight chains of homoxylan like Bryopsis maxima but were heteropolysaccharides as glucoxylan or branch ed structures, identification of its fine structures was desired. Alth ough the results for the linkage analysis were discovered from chemica l methods, complementary confirmations were attempted by detection of a series of the beta-1,3-xylooligosaccharides prepared as partial acid hydrolysates. Complete separation of the higher oligosaccharide in ea ch was difficult through high performance liquid gel permeation chroma tography (GPC), so the composition of oligosaccharides in roughly sub- fractionated samples was detected using matrix-assisted laser desorpti on ionization/time of flight/mass spectrometry (TOF-MS). By these proc edures, it was obvious that cell wall xylan from Caulerpa brachypus wa s constituted from at least 25 xylose residues of linear oligosacchari des with beta-1,3-linkages. Thus the successive methods of repeating G PC procedures and TOF-MS spectrometric detection were powerful techniq ues for the identification of incompletely separated oligosaccharides and it was available to obtain a series of purified beta-1,3-oligomers from cell wall xylan.