Structural Analysis of Chromophore-Labeled Disaccharides and Oligosaccharides by HPLC/ESIMS and CE/MS/MS

• Main Authors: Li, Ding-Tzai, 李丁在
• Other Authors: Her Guor-Rong
• Format: Others
• Language: zh-TW
• Published: 1998
• Online Access: http://ndltd.ncl.edu.tw/handle/59698937356441660438

博士 === 國立臺灣大學 === 化學系研究所 === 86 === AbstractDisaccharides and linear oligosaccharides were labeled with p-aminobe nzoic ethyl ester (ABEE) chromophore and analyzed by on-line coupling of high performance liquid chromatography (HPLC)/negative ion electrospray mass spectr ometry (ESIMS). The formation of glycosylamines rather than reductive aminati on in labeling reaction produced many characteristic fragment ions under in-so urce collision-induced dissociation (CID). These ions provided unambiguous as signment of the position of the glycosidic linkages. This approach was extend ed to the analysis of linkages as well as the sequence of the linkages of seve ral linear oligosaccharides. Additionally, anomeric configuration of ABEE-lab eled 1-3, 1-4 and 1-6-linked glucose disaccharides could be differentiated acc ording to the relative abundance of characteristic ions. Semiempirical cacula tions and comformation analysis support the experimental data which suggest th at the terminal sugar of b-form 1-4-linked disaccahrides can be determined by the relative intensity of m/z 263 and m/z 221 ion. Disaccharides tagged with p-aminobenzoic acid (ABA) chromophore were separated by capillary electrophore sis (CE) and successfully on-line detected with negative ion ESI/MS/MS. Two e lectrolyte systems were employed for the separation of the derivatized disacch arides. The best results of analyzing linkage isomers was obtained by using 5 0 mM NH4OAc containing 10 mM a-CD adjusted to pH 5.5, while 10 mM borate at pH 10.0 provided the best result for the analysis of disaccharides with differen t monosaccharide composition and anomeric configuration. In general, the link age-specific ions of the ABA-labeled disaccharides in the MS/MS spectra were s imilar to that of the ABEE-derivatives in-source CID mass spectra. However, u nlike the use of intensity ratio in in-source CID mass spectra of ABEE-labeled disaccharides, anomeric configuration of ABA-labeled 1-4 and 1-6-linked disac charides could be differentiated according to the presence or absence of the p eak at m/z 221 in product ion mass spectra. Deuterium labeling in combination with sequential tandem mass spectrometry were used to explore the mechanism o f fragmentation of the chromophore-labeled disaccharides under CID. The multi ple peaks with different number of deuterium atom suggested that the same m/z fragment ion of nondeuterium-labeled disaccharide could be produced through mu ltiple reaction pathways. Carbonyl migration in combination with retro-aldol fragmentation or charge induced dissociation could rationalize the formation o f the major fragment ions. Other fragmentation paths were also postulated to explain the formation of the minor ions adjacent to the major one.