Facile preparation of nitrogen/titanium-rich porous organic polymers for specific enrichment of N-glycopeptides and phosphopeptides

Abstract

The comprehensive investigation of protein phosphorylation and glycosylation aids in the discovery of novel biomarkers as well as the understanding of the pathophysiology of illness. In this work, a nitrogen/titanium-rich porous organic polymer was developed by copolymerizing carbohydrazide (CH) and 2,3-dihydroxyterephthalaldehyde (2,3-Dha) and modifying with Ti⁴⁺ (CH–Dha–Ti⁴⁺). The adequate nitrogen contributes to the enrichment of glycopeptides via HILIC, while titanium benefits from capturing phosphopeptides through IMAC. The proposed method exhibits excellent selectivity (1 : 1000, both for glycopeptides and phosphopeptides), LOD (for glycopeptides: 0.05 fmol μL⁻¹, for phosphopeptides: 0.2 fmol), loading capacity (for glycopeptides: 100 mg g⁻¹, for phosphopeptides: 125 mg g⁻¹) and size-exclusion effect (1 : 10 000, both for glycopeptides and phosphopeptides). Furthermore, CH–Dha–Ti⁴⁺ was applied to capture glycopeptides and phosphopeptides from human serum; 205 glycopeptides and 45 phosphopeptides were detected in the serum of normal controls; and 294 glycopeptides and 63 phosphopeptides were found in the serum of uremia patients after being analyzed by nano LC-MS/MS. The discovered glycopeptides and phosphopeptides were involved in several molecular biological processes and activities, according to a gene ontology study.