FRAGMENTATION BEHAVIOR OF DISACCHARIDES DURING DESORPTION IONIZATION

The fragmentation behavior of native and singly derivatized protonated disaccharides were examined by fast ion bombardment Fourier transform mass spectrometry to determine the origin of various fragment ions produced during desorption-ionization. The lack of interfering matrix ions in this technique allowed the investigation of model disaccharides. Three major product ions were observed, corresponding in mass to a loss of H2O, a loss of a monosaccharide unit and a combination of both losses. The oxygen of the lost H2O molecule originates from an oxygen attached to the anomeric carbon. The other two product ions come from two different monosaccharide units and are due to competing processes. The relative ion intensities of these two fragment ions are governed by the basicities of the fragments. The basicity of the reducing end increases when the hemiacetal is converted into the methyl glycoside. This increase in basicity is due to the increased size of the alkyl group and the ability of the alkyl group to prevent the opening of the reducing glycosidic ring.