期刊
JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY
卷 17, 期 6, 页码 844-854出版社
AMER CHEMICAL SOC
DOI: 10.1016/j.jasms.2006.02.022
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资金
- NCRR NIH HHS [P41 RR10888, P41 RR010888-107184, P41 RR010888] Funding Source: Medline
- NHLBI NIH HHS [R01 HL74197, R01 HL074197-03, R01 HL074197] Funding Source: Medline
For the analysis of native glycans using tandem mass spectrometry (MS), it is desirable to choose conditions whereby abundances of cross-ring cleavages indicative of branch positions are maximized. Recently, negative ion tandem mass spectrometry has been shown to produce significantly higher abundances of such ions in glycans compared to the positive ion mode. Much of this prior work has concerned fragmentation patterns in asialo glycans. The present work compares the abundances of critical cross-ring cleavage ions using negative mode tandem mass spectrometry for milk oligosaccharides and N-linked glycans. For comparison, product ion formation was studied for deprotonated and nitrated ions formed from asialo glycans and deprotonated ions from sialylated glycans. Breakdown profiles demonstrate clearly that more energy was required to fragment sialylated compounds to the same extent as either their asialo or nitrate adducted counterparts. The extraction of a proton from a ring hydroxyl group during the ionization process may be viewed, qualitatively, as imparting significantly more energy to the ion than would that from a molecule bearing an acidic group, so that acidic glycans are more stable in the gas phase, as the negative charge resides on the carboxyl group. These results have strong practical implications because a major portion of glycans. released from mammalian proteins will be sialylated.
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