Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1194264 | International Journal of Mass Spectrometry | 2008 | 9 Pages |
Abstract
The mechanisms of fragmentation of the chlorinated Lewis-type trisaccharides Lewis a and Lewis X were studied by using experimental and theoretical methods. In the fragment ion spectra obtained by ESI-CID-MS, C- and Z-type fragmentations corresponding to 4- and 3-linked glycosyl bond cleavages of the N-acetylglucosamine moiety were observed. The relationships of the relative ion intensities of C- and Z-type fragmentations were ZÂ >Â C in Lewis a and CÂ >Â Z in Lewis X, suggesting that the relationships of the activation energies were CÂ >Â Z in Lewis a and ZÂ >Â C in Lewis X. Anomeric and acetoamide groups were assumed to be included in the mechanisms of C- and Z-type fragmentation; we therefore analyzed 3-fucosyllactose and methylated Lewis-type trisaccharides, which are the derivatives of Lewis-type trisaccharides. These analyses revealed that C-type fragmentation was little influenced by anomeric group and that Z-type fragmentation was influenced by both the anomeric and the acetoamide groups. Fragmentation mechanisms were proposed on the basis of the experimental results and were calculated at the HF/3-21G(d), HF/6-31G(d) levels. From the calculations, C-type fragmentation of the 4-linkage was considered to take place by electron transfer from the acetoamide group, and Z-type fragmentation at the 3-linkage was considered to take place in two steps: (i) elimination of the 3-linked saccharide moiety, and (ii) deprotonation of an anomeric proton by a chloride anion. The activation energies for C- and Z-type fragmentations, as determined by HF calculations, were consistent with the experimentally assumed trends.
Related Topics
Physical Sciences and Engineering
Chemistry
Analytical Chemistry
Authors
Hiroaki Suzuki, Tohru Yamagaki, Kazuo Tachibana, Kazuhiko Fukui,