Fragmentation behavior of disaccharides during desorption–ionization

Abstract

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 H,O, a loss of a monosaccharide unit and a combination of both losses. The oxygen of the lost H,O 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.

Application of Fourier transform ion cyclotron resonance mass spectrometry to oligosaccharides

“…Fragmentation was more extensive in the cation mode, but in the anion mode we observed significant cross-ring cleavages that yielded linkage information (Carroll & Lebrilla, 1992;Carroll et al, 1993;Carroll, Willard, & Lebrilla, 1995). Significant effort was placed on increasing sensitivity and ion yield but the best detection limit that could be obtained remained in the microgram and sometimes submicrogram range.…”

“…Each cycle reveals a new reducing ring so that MALDI and MALDI-CID fragmentation can be employed to produce crossring cleavages at the nascent reducing end. Furthermore, because the quasimolecular ions are sodium coordinated, cross-ring cleavages are produced to yield the specific linkages (Coates & Wilkins, 1985;Garozzo et al, 1990;Spengler, Dolce, & Cotter, 1990;Carroll & Lebrilla, 1992;Carroll, Willard, & Lebrilla, 1995). Both linkage and sequence information are obtained with less than 100 pmol.…”

Fragmentation Reactions in the Mass Spectrometry Analysis of Neutral Oligosaccharides

“…For a 1−6-linked oligosaccharide such as isomaltotetraose, three cross-ring cleavage products are typically observed: loss of 60, 90, and 120 u. , For a 1−4-linked oligosaccharide such as maltotetraose, two cross-ring products are observed: loss of 60 and 120 u. The different cross-ring products do not have similar MCDTs.…”

“…Alkali metal ion coordinated oligosaccharides produce glycosidic bond cleavages that are analogous to those observed with protonated species. Unlike protonated oligosaccharides, alkali metal ion coordinated species produce cross-ring cleavages that are highly specific to their linkages. − Cross-ring cleavages are useful for determining linkages between component monosaccharides and the branching arrangements. Cross-ring cleavages are generally not observed with protonated oligosaccharides.…”