Profiling of N-linked Glycans from Human Serum with Oxidative Ordered Mesoporous Carbon

Glycosylation is one of the most common forms of post-translational modifications on proteins, and glycoproteins account more than 50% in eukaryotic proteins. Also, glycoproteins play key roles in cell-cell recognition, cancer metastasis, the immune system, and other biological functions1. Because of complicated glycosylation sites and variable glycan structures, the study of glycoproteins is difficult, while the analysis of glycans released from glycoproteins is much easier. Of all the process, purification glycans from the mixtures is the key step. Organic solvent precipitation and chromatographic separation are two main methods now used to extract glycans from proteins. However, it can’t remove proteins absolutely from the mixtures of glycans and proteins. Chromatography, including volume exclusion and hydrophilic, can be used to enrich glycans from proteins with complex procedures. Because of special interaction between oligosacchride and carbon, graphitized was used to enrich glycans released from glycoprotein and salt elimination with proteins removal first in the recent years. So, purification of glycans from the mixtures is still complicated and time-consuming. In this paper, we use oxidative ordered mesoporous carbons (O-OMC) to enrich glycans from the mixtures directly and detected by MALDI-TOF MS, without the removal of proteins firstly. With mild surface oxide, the resulting hydrophilic surface and mesoporous of the particles2 can reduces the absorption of proteins，while the special interaction between carbon and oligosaccharides can lead to selective enrichment of glycans. We select ovalbumin as standard glycoprotein and analyze all of the 24 released glycans, and 15 glycans are successfully detected. 38 of N-linked glycans distribution in human serum and deference between normal and liver cancer are also evaluated. With convenient sample handling and high through detection, this method could be used in disease diagnosis, such as early cancer confirmation. Key words: Glycans, O-OMC, Size exclusion, MALDI-TOF/MS, Human serum