Infrared laser desorptlon/lonlzatlon of oligosaccharides and their naturally occurring derivatives leads to a distinctive fragmentation pattern, which Is useful both for the analysis of functional groups (e.g., the positions of fatty acyl groups In lipid A and other glycollplds) and for distinguishing Isomers of underivatized oligosaccharides with different glycosidic linkages. The predominant mechanism of fragmentation can be understood as a perlcycllc hydrogen rearrangement of the retro-aldol reaction type, leading to fragmentation of the sugar ring. A prerequisite for this process appears to Involve opening of the hemlacetal saccharide ring to the linear saccharide form by rapid heating from the Infrared laser irradiation. Saccharides derlvatlzed at the anomerlc hydroxyl group (l.e., cyclic acetals) normally do not undergo this ring opening and thus do not exhibit ring fragmentation reactions. This fragmentation mechanism can be used to predict and Interpret fragmentation patterns of unknown oligosaccharides, glycosides, lipid A, and other glycoconjugates.
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