New Tools for Analysis of Wood and Pulp Components - Application of MALDI-TOF Mass Spectroscopy and Capillary Zone Electrophoresis

Sammanfattning: In the present thesis, capillary zone electrophoresis (CZE),matrix-assisted laser desorption/ionization time-of-flight massspectroscopy (MALDI-MS) and size-exclusion chromatography incombination with off-line MALDI-MS (SEC/MALDI-MS) have beenapplied successfully to the analysis of wood and pulpcomponents.The carbohydrate compositions of pulp and holocellulosesamples, as well as of isolated hemicellulose preparations,were determined employing enzymatic hydrolysis and subsequentanalysis of the saccharides released by CZE.SEC/MALDI-MS was employed to characterize the molar massesand molar mass distributions of isolated hemicelluloses andlignins. The samples were first separated using SEC intofractions each containing components exhibiting a narrow rangeof molar masses and the average molar mass of each suchfraction subsequently determined by MALDI-MS. The molar massparameters for the samples were thencalculated on the basis ofthe SEC distribution curves and MALDI-MS spectra.The distribution of 4-O-methylglucuronic acid residues along thepolysaccharide chains of xylans isolated from various woodspecies was examined employing MALDI-MS analysis of theoligosaccharide mixtures obtained by partial acid hydrolysis.In the case of all softwood xylans examined, the major portionof these residues were distributed regularly along the polymer;whereas the 4-O-methylglucuronic acid residues in the hardwood xylansexamined were found to be distributed irregularly. Furthersupport for these experimental findings was obtained bycomputer-assisted simulation of the distribution patterns ofthe molar masses of oligosaccharides derived frompolysaccharides with the postulated distributions of uronicacid residues.In the case of native, partially acetylated hemicellulosesisolated by aqueous extraction of spruce and aspen wood chipsemploying microwave treatment, the degree of substitution withacetyl groups (DS) could be calculated from the MALDI-MSspectra recorded before and after deacetylation of thesample.Keywords:capillary zone electrophoresis, carbohydratecomposition, degree of acetylation, degree of polymerization,enzymatic hydrolysis, hardwood, hemicellulose, hexenuronicacid, lignin, MALDI-TOF mass spectrometry, molar mass, molarmass distribution, oligosaccharides, pulp, size-exclusionchromatography, softwood, uronic acid