Proteomics > Which service should I request? > Glycan / Glycoprotein analysis > Characterization of N-linked glycans

Characterization of N-linked glycans



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General description

Glycomics "is the systematic study of all glycan structures of a given cell type or organism" and is a subset of glycobiology. To characterize N-glycans, the protein mixtures would be first extracted from their biological resources. Then, the N-glycans are released by PNGase F or PNGase A depending on the species. To increase the sensitivity of glycans on MS-based detection, glycans would be further permethylated before MS analysis. The MS profile can provide an overview of N-glycome from samples. For advanced structure characterization, tandem mass spectrometry would be applied to confirm the linkage of glycan structures. For O-glycomics, please contact us for further information.

Questions?

Workflow

Based on the biological question and on the type of sample, a typical workflow for processing the samples prior to MS and data analyses consists of:

1. Protein digestion/ glycan release and permethylation

  • Protein digestion: Proteins mixtures extracted from different biological resources, for example, cells or biological fluid, are first digested into peptides.
  • Glycan release: For N-glycomic analysis, samples are treated with PNGase F/A. The released glycans would be purified by a reverse-phase cartridge.
  • Permethylation: Glycans are chemically methylated by methyl iodide.
The principle of permethylation is shown below. In addition, the fragmentation pattern of glycans in MS/MS analysis is shown in the lower panel.

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2. MALDI-MS analysis

At FGCZ, the default data acquisition is operated by Bruker Ultraflextreme MALDI-TOF-TOF. Samples are dissolved in pure acetonitrile and mixed with MADLI matrix, 10 mg/mL of 2,5-dihydroxy-benzoic acid (DHB), and spotted on the MALDI target.

3. Data analysis

The data are processed by Flexanalysis (Bruker). The annotation is done by Glycoworkbench 2.0 and also manual inspection.