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Enhanced detection and identification of glycopeptides in negative ion mode mass spectrometry.

ABSTRACT: A combined mass spectrometry (MS) and tandem mass spectrometry (MS/MS) approach implemented with matrix-assisted laser desorption ionization Fourier transform ion cyclotron resonance mass spectrometry (MALDI FTICR MS) in the negative ion mode is described for enhanced glycopeptide detection and MS/MS analysis. Positive ion mode MS analysis is widely used for glycopeptide characterization, but the analyses are hampered by potential charge-induced fragmentation of the glycopeptides and poor detection of the glycopeptides harboring sialic acids. Furthermore, tandem MS analysis (MS/MS) via collision-induced dissociation (CID) of glycopeptides in the positive ion mode predominantly yields glycan fragmentation with minimal information to verify the connecting peptide moiety. In this study, glycoproteins such as, bovine lactoferrin (b-LF) for N-glycosylation and kappa casein (k-CN) for O-glycosylation were analyzed in both the positive- and negative ion modes after digestion with bead-immobilized Pronase. For the b-LF analysis, 44 potential N-linked glycopeptides were detected in the positive ion mode while 61 potential N-linked glycopeptides were detected in the negative ion mode. By the same token, more O-linked glycopeptides mainly harboring sialic acids from k-CN were detected in the negative ion mode. The enhanced glycopeptide detection allowed improved site-specific analysis of protein glycosylation and superior to positive ion mode detection. Overall, the negative ion mode approach is aimed toward enhanced N- and O-linked glycopeptide detection and to serve as a complementary tool to positive ion mode MS/MS analysis.

SUBMITTER: Nwosu CC

PROVIDER: S-EPMC2995828 | biostudies-literature | 2010 Dec

REPOSITORIES: biostudies-literature

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Enhanced detection and identification of glycopeptides in negative ion mode mass spectrometry.

Nwosu Charles C CC Strum John S JS An Hyun Joo HJ Lebrilla Carlito B CB

Analytical chemistry 20101104 23

A combined mass spectrometry (MS) and tandem mass spectrometry (MS/MS) approach implemented with matrix-assisted laser desorption ionization Fourier transform ion cyclotron resonance mass spectrometry (MALDI FTICR MS) in the negative ion mode is described for enhanced glycopeptide detection and MS/MS analysis. Positive ion mode MS analysis is widely used for glycopeptide characterization, but the analyses are hampered by potential charge-induced fragmentation of the glycopeptides and poor detect ...[more]

PMID: 21049935

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Project description:Bile acids (BAs) are cholesterol metabolites with important biological functions. They undergo extensive host-gut microbial co-metabolisms during the enterohepatic circulation, creating a vast structural diversity and resulting in great challenges to separate and detect them. Based on the bioanalytical reports in the past decade, this work developed three chromatographic gradient methods to separate a total of 48 BA standards on an ethylene-bridged hybrid (BEH) C18 column and high-strength silica (HSS) T3 column and accordingly unraveled the factors affecting the separation and detection of them by liquid chromatography coupled with mass spectrometry (LC-MS). It was shown that both the acidity and ammonium levels in mobile phases reduced the electrospray ionization (ESI) of BAs as anions of [M-H]-, especially for those unconjugated ones without 12-hydroxylation. It was also found that the retention of taurine conjugates on the BEH C18 column was sensitive to the strength of formic acid and ammonium in mobile phases. By using the volatile buffers with an equivalent ammonium level as mobile phases, we comprehensively demonstrated the effects of the elution pH value on the retention behaviors of BAs on both the BEH C18 column and HSS T3 column. Based on the retention data acquired on a C18 column, we presented the ionization constants (pK a) of various BAs with the widest coverage beyond those of previous reports. When we made attempts to establish the structure-retention relationships (SRRs) of BAs, the lack of discriminative structural descriptors for BA stereoisomers emerged as the bottleneck problem. The methods and results presented in this work are especially useful for the development of reliable, sensitive, high-throughput, and robust LC-MS bioanalytical protocols for the quantitative metabolomic studies. Graphical Abstract Nonlinear curve fitting of capacity factors and elution pH value for the separation of common unconjugated bile acids.

Dataset Information

Enhanced detection and identification of glycopeptides in negative ion mode mass spectrometry.

Publications

Enhanced detection and identification of glycopeptides in negative ion mode mass spectrometry.

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