In our bodies, proteins are often modified after translation (post-translational modifications). In many cases, this involves glycosylation: proteins/peptides are given one or more sugar molecules in their structure, which help, for example, with their folding, stability and transport. In many diseases, proteins are also modified with sugars, which means that these modifications could be used as biomarkers for a particular disease. Researchers at Radboud University Medical Centre and Bruker’s French-German division therefore developed an analytical method - glycoproteomics - to profile glycopeptides in plasma to see if they could use it for diagnostics.

The analyses resulted in a map of the glycan and peptide fragments that were identified.

The researchers had access to plasma samples from patients and healthy individuals. They first cut the plasma proteins into smaller pieces using trypsin treatment and enriched the glycopeptides to prepare everything for the next step. They charged the glycopeptides using electrospray ionisation and then analysed them using a Bruker mass spectrometer combined with column chromatography (LC-MS/MS).

Boost

They used the data from these analyses to generate a map of the identified glycan and peptide fragments using existing and custom software (ProteinScape, OpenMS and Matlab). After further processing, 58 unique peptide sequences remained, belonging to 34 proteins. Each of these proteins has a glycoform, a variant with a sugar molecule associated with a disease, which is also found in blood plasma. An additional boost for the new method was that it gave almost identical results to previous clinical trials using a different method (glycomics). This gave the researchers the confidence to delve deeper into the analyses and expand glycomics knowledge with the new glycoproteomics method.

The researchers conclude that their work “illustrates the potential of plasma glycoproteomics to significantly increase the specificity of glycoprotein biomarkers and to provide direct insights into site-specific glycosylation changes to better understand the glycobiological mechanisms underlying human diseases.

Wessels, H.J.C.T. et al. (2023) Journal of Advanced Research, DOI: 10.1016/j.jare.2023.09.002