Characterization of carbohydrates using gas chromatography/mass spectrometry (GC/MS)

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Asres, Daniel Derbie
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Methylation analysis has been widely used for determination of carbohydrate structures by mass spectrometry. Permethylation of monosaccharides yields mixtures of anomeric pyranosides and furanosides. One part of this thesis discusses the influence of some of the permethylation reaction parameters on the proportions of isomeric products obtained. The ratios of three, five- and six-membered ring products obtained from two permethylated monosaccharides, D-galactose and L-fucose, have been determined as a function of reaction parameters. The method of Ciucanu and Kerek (methyl iodide in dimethyl sulfoxide (DMSO) in the presence of sodium hydroxide (NaOH)) was used as a starting point. We have investigated the effect of mixing DMSO, substrate, and NaOH for various times prior the addition of methyl iodide on the proportion of products obtained. In summary, higher temperatures and longer reaction times favored the main pyranoside product. Another part of this thesis describes methods of preparing, isolating characterizing permethylated pyranoside and furanoside species of D-(+)-galactose and L-($-$)-fucose. In the third portion of this thesis, two different sets of methods that involve methanolysis, permethylation and acetylation, were developed to identify the components of GM$\sb1$, a glycosphingolipid. (Abstract shortened by UMI.)