Characterization of Hemicelluloses from Wood Employing Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry

摘要

This chapter describes some analytical procedures employing Matrix-Assisted-Laser-Desorption/Ionization Time-Of-Flight (MALDI-TOF) mass spectrornetry for the characterization of hemicelluloses. The molar mass parameters for glucuronoxylans, hexenuronoxylans and glucomannans were determined by using an analytical procedure involving size exclusion chromatography followed by off-line MALDI-MS analysis. In the case of 0-acetylated glucuronoxylans and glucomannans, the degree of substitution with acetyl moieties was determined on the basis of the MALDI spectra obtained prior to and following deacetylation. By using this MALDI-MS procedure 0-acetyl residues were found to be present in hardwood glucomannans. The distribution of 4-0-methyl-glucuronic acid residues along the polysaccharide chains of hardwood and softwood xylans was studied employing MALDI-MS analysis. In the case of softwood xylans, the 4-0-methylglucuronic acid residues were distributed regularly within the polysaccharide. In contrast, the corresponding uronic acid residues in hardwood xylans were found to be distributed irregularly along the polysaccharide chains.