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Browsing by Subject "metylointi"

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  • Arabinoksylaanista eristettyjen oligosakkaridien rakenteen selvittäminen moniulotteisella massaspektrometrisella menetelmällä 
    Kotiranta, Markus (2014)
    The literature review deals with the structure of arabinoxylan and the principles of mass spectrometric methods used in analyzing them. The fragmentation of carbohydrate structures, the structural information gained from it, and naming of the resulting neutral fragments and product ions was also discussed. The aim of the experimental work was to analyze linear xylo-oligosaccharides and branched or linear arabinoxylans with known structures using tandem mass spectrometry. Of the arabinoxylo-oligosaccharides analyzed, three were branched while the others had an arabinose substituent at terminal xylose. The oligosaccharides were analyzed as underivatized, alditols, and methylated alditols with both positive and negative ionization. Derivatization was done in order to produce different product ions and to gain information about the effect of reduction and methylation on fragmentation mechanisms. Underivatized oligosaccharides provided most information with negative mode ionization. Low intensity of C-type fragment ions prevented their isolation in MS3-step when reduced oligosaccharides were analyzed. Methylation changed the weights of fragmentation products, which made it possible to detect branching in the oligosaccharide structure. Methylation also changed the fragmentation mechanism which caused differences in the product ion spectra compared to underivatized oligosaccharides. B-ions were fragmented to gain information about linkage positions when analyzing methylated alditols. The mechanism of B-ion fragmentation differs from that of C-ions, and produced information rich neutral fragments. However, low signal intensity made branch site analysis difficult, especially when arabinose substituent was located at terminal xylose.
  • Metylointianalyysit polysakkaridien rakenteen määrittämisessä 
    Pynnönen, Henna (2009)
    Methylation analysis by Ciucanu and Kerek (1984) and Hakomori (1964) and the meaning of circumstances in the reaction, reaction parameters and structure of the sample were reviewed in this study. The experimental work consisted of methylation analysis of glucose, cellobiose, isomaltose, pullulan, commercial dextran and dextrans produced by lactic acid bacteria Weissella confusa and Leuconostoc citreum. The success of the methylation was controlled using the IR-method. Methylated samples were treated by methanolysis and acid hydrolysis. The structure analyses were carried out with GC-MSspectra. Two different columns: DB-1 and HP-5 were compared in the GC-analysis. Two hours methylation in the ultrasonic bath gave good methylation results. It was easy to control the methylation by IR-method. OH-peak (3400 cm-1) was absent and CH3- peaks (2900 and 2800 cm-1) were high after successful methylation. IR-spectroscopy is a valuable tool to check if methylation has been successful. Samples could be remethylated before hydrolysis and derivation if necessary. After methanolysis there were ?- and ?-pyranose forms from each methylated monosaccharides. Due to reduction after the acid hydrolysis method, there was only one methylated form from each product. The structures of glucose, cellobiose, isomaltose and pullulan were solved by both hydrolysis methods. Recovery of these samples was good but the deviation was large. The structure of commercial dextran and dextran produced by W. confusa were solved by methanolysis method and partly by acid hydrolysis method. Recovery of these samples was poor. The methylation succeeded only in one of the dextran samples produced by L. citreum. The methylation analysis of dextrans could be developed in the future by increasing the temperature and the time of mixing and by adding some glycerol.

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