Abstract
Sequence determination of permethylated viridopentaoses and their degradation products was performed by chemical ionization mass spectrometry (CIMS) using isobutane and ammonia as reagent gases. The CI mass spectra show MH+ or (M+NH4)+ ions in the molecular ion region. Fragmentation involving carbon-carbon bond fission rarely occurs. As a major fragmentation, the glycosidic linkage is cleaved between the glycosidic oxygen atom and the anomeric carbon atom. Resulting fragment ions in the isobutane spectra can be classified into oxonium and protonated (with methyl or hydrogen transfer) ions, whereas fragment ions in the ammonia spectra can be divided into oxonium (occasionally with attachment of an ammonia molecule) and ammonium adduct (with methyl or hydrogen transfer) ions. These results are shown to be useful for sequencing unknown oligosaccharides.
