Profiling the N-Glycan Composition of IgG with Lectins and Capillary Nanogel Electrophoresis

Anal Chem. 2019 Jan 15;91(2):1375-1383. doi: 10.1021/acs.analchem.8b03725. Epub 2018 Dec 21.

Abstract

Glycosylated human IgG contains fucosylated biantennary N-glycans with different modifications including N-acetylglucosamine, which bisects the mannose core. Although only a limited number of IgG N-glycan structures are possible, human IgG N-glycans are predominantly biantennary and fucosylated and contain varying levels of α2-6-linked sialic acid, galactose, and bisected N-acetylglucosamine. Monitoring the relative abundance of bisecting N-acetylglucosamine is relevant to physiological processes. A rapid, inexpensive, and automated method is used to successfully profile N-linked IgG glycans and is suitable to distinguish differences in bisection, galactosylation, and sialylation in N-glycans derived from different sources of human IgG. The separation is facilitated with self-assembled nanogels that also contain a single stationary zone of lectin. When the lectin specificity matches the N-glycan, the peak disappears from the electropherogram, identifying the N-glycan structure. The nanogel electrophoresis generates separation efficiencies of 500 000 plates and resolves the positional isomers of monogalactosylated biantennary N-glycan and the monogalactosylated bisected N-glycan. Aleuria aurantia lectin, Erythrina cristagalli lectin (ECL), Sambucus nigra lectin, and Phaseolus vulgaris Erythroagglutinin (PHA-E) are used to identify fucose, galactose, α2-6-linked sialic acid, and bisected N-acetylglucosamine, respectively. Although PHA-E lectin has a strong binding affinity for bisected N-glycans that also contain a terminal galactose on the α1-6-linked mannose branch, this lectin has lower affinity for N-glycans containing terminal galactose and for agalactosylated bisected biantennary N-glycans. The lower affinity to these motifs is observed in the electropherograms as a change in peak width, which when used in conjunction with the results from the ECL lectin authenticates the composition of the agalactosylated bisected biantennary N-glycan. For runs performed at 17 °C, the precision in migration time and peak area was less than or equal to 0.08 and 4% relative standard deviation, respectively. The method is compatible with electrokinetic and hydrodynamic injections, with detection limits of 70 and 300 pM, respectively.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Ascomycota / chemistry
  • Electrophoresis, Capillary / methods*
  • Erythrina / chemistry
  • Humans
  • Immunoglobulin G / chemistry*
  • Lectins / chemistry
  • Nanogels / chemistry*
  • Phaseolus / chemistry
  • Plant Lectins / chemistry*
  • Polysaccharides / analysis*
  • Polysaccharides / chemistry
  • Ribosome Inactivating Proteins / chemistry
  • Sambucus nigra / chemistry

Substances

  • Immunoglobulin G
  • Lectins
  • Nanogels
  • Plant Lectins
  • Polysaccharides
  • Sambucus nigra lectins
  • erythrina lectin
  • lectin, Aleuria aurantia
  • Ribosome Inactivating Proteins