A spin column-free approach to sodium hydroxide-based glycan permethylation

Area of Science:

• Glycomics
• Analytical Chemistry
• Biochemistry

Background:

• Glycan permethylation, a technique established in 1903, is crucial for studying glycans.
• Existing permethylation methods often require laborious sample preparation or inefficient spin columns, limiting their applicability for small samples.
• There is a need for improved, cost-effective, and efficient glycan permethylation procedures.

Purpose of the Study:

• To develop and validate a novel spin column-free (SCF) glycan permethylation procedure.
• To assess the efficiency and applicability of the SCF method for both O- and N-linked glycans.
• To evaluate the SCF procedure's performance in intact glycan analysis and glycan linkage analysis using mass spectrometry and gas chromatography-mass spectrometry.

Main Methods:

• A spin column-free (SCF) glycan permethylation procedure was developed, involving neutralization of NaOH beads with acidified phosphate buffer.
• The SCF method was optimized for high permethylation efficiency of hexose and HexNAc residues.
• Intact glycan yields were compared between the SCF and a spin column-based method using light vs. heavy labeling.
• The SCF procedure was applied upstream to hydrolysis, reduction, and acetylation for glycan linkage analysis of blood plasma glycans.
• The SCF method was used to analyze glycan distributions in blood plasma from breast cancer patients and age-matched controls.

Main Results:

• The SCF procedure achieved high permethylation efficiency for hexose (>98%) and HexNAc (>99%) residues, comparable to or better than spin column-based methods.
• Recovery of intact N-glycans was significantly higher with the SCF procedure (p < 0.05), while O-glycan yields were similar or slightly reduced.
• Analytical reproducibility for glycan linkage analysis of blood plasma using the SCF method was comparable to previous spin column-based approaches.
• The SCF procedure enabled the identification of three glycan nodes with significantly different distributions between breast cancer patients and controls (ROC c-statistics > 0.75; p < 0.01).

Conclusions:

• The developed spin column-free (SCF) glycan permethylation procedure is efficient, economical, and applicable to both O- and N-linked glycans.
• The SCF method simplifies glycan analysis, reduces costs, and improves intact glycan recovery, particularly for N-glycans.
• This streamlined approach facilitates both intact glycan analysis and glycan linkage analysis from complex biological specimens, showing potential for biomarker discovery in diseases like breast cancer.