Novel chemical methods to improve detection efficiency of saccharides in mass spectrometry
Date Issued
2009
Date
2009
Author(s)
Chang, Yu-Ling
Abstract
Matrix-assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI) were successfully developed as the soft ionization techniques for biomolecules, such as proteins and nucleotides. The benefit of MALDI-mass spectrometry (MS) for analysis of polymers is predominantly from the formation of singly charged molecular ions that lead to simple mass spectra for polymer distribution analysis. In view of the increasing biological importance of saccharides associated with cell-cell recognition, protein targeting and metabolic diseases, oligosaccharides and their glycoconjugate research attracted more attention lately. But the ionization efficiency of saccharides is low compared with other biomolecules due to the low proton affinity of carbohydrates. In order to detect oligosaccharides, we utilized the reductive amination processes to produce glycopeptides (DP7-BK) and derivatives of oligosaccharides with 2-amino-1-naphthalensulfonic acid (DP7-ANS) or 7-amino-1, 3-naphthalendisulfonic acid (DP7-A13S). In our study, modifications were found to improve the detection limit of MALDI mass spectrometry. In MALDI-MS, the detection limit of DP7-BK 1~9 is 1.2±0.6 fmol which is better than 54.6±14.9 fmol of DP7. The detection limits of DP7-ANS and DP7-A13S are 3.9±1.6 fmol and 2.7±0.9 fmol in negative ion mode. In ESI-MS, the signal intensity of DP7-BK 1~9 is 8 times higher than that of DP7 and the signal intensities of DP7-ANS and DP7-A13S in negative ion mode are 9 times and 13 times higher than that of DP7, respectively. Ionic liquid (IL) has been used as the matrix to increase ionization efficiency of polysaccharides in MALDI-MS. In this work, we applied IL in ESI-MS. The ionic liquid used are 2, 5-dihydroxybenzoic acid butylamine (DHBB) and α-cyano-4-hydroxycinnamic acids butylamine (CHCA-B). The signal to noise ratios (S / N) of polysaccharides PL6K / 10K are better in positive ion mode. Ion attachments from ionic liquid to polysaccharides are observed. This is the first time that addition of ionic compounds allows us to predict ionic adducts in ESI-MS.
Subjects
MALDI-MS
ESI-MS
ionic liquid (IL)
detection limit of oligosaccharides
glycopeptides
2-amino-1-naphthalensulfonic acid
7-amino-1,3-naphthalendisulfonic acid
Type
thesis
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