Label-free relative quantification method for low-abundance glycoproteins in human serum by micrOTOF-Q.

In this study, a label-free relative quantification strategy was developed for quantifying low-abundance glycoproteins in human serum. It included three steps: (1) immunodepletion of 12 high-abundance proteins, (2) enrichment of low-abundance glycoproteins by multi-lectin column, (3) relative quantification of them between different samples by micrOTOF-Q. We also evaluated the specificity and efficiency of immunodepletion, the accuracy of protein quantification and the possible influence of immunodepletion, glycoprotein enrichment, trypsin digestion and peptide ionization on quantification. In conclusion, the relative quantification method can be effectively applied to the screening of low-abundance biomarkers.