Preparation of Sequence-Controlled Triblock Copolymer-Grafted Silica Microparticles by Sequential-ATRP for Highly Efficient Glycopeptides Enrichment

As one of the most important subproteomes in eukaryote cells, N-glycoproteins play crucial roles in various of biological processes and have long been considered closely correlated with the occurrence, progression, and metastasis of cancer. Comprehensive characterization of protein N-glycosylation and association of their aberrant patterns to the corresponding cancer stage may provide a unique way to discover new diagnostic biomarkers and therapeutic drug targets. However, the extremely complex nature of biological samples and relatively low abundance of N-glycosylated proteins makes the enrichment of glycoprotein/glycopeptide a prerequisite for large scale N-glycosylation identification. In this work, we prepared sequence controlled triblock copolymer grafted silica-microparticles (TCP-SMs) by sequential atom transfer radical polymerization (sequential-ATRP) of monosaccharides and zwitterionic-ion monomers for highly efficient and selective glycopeptides enrichment. The triblock copolymer is composed of sequence defined poly zwitterionic-ion, poly-N-acetylglucosamine and poly mannose blocks. The glycopolymer blocks carrying densely packed pendent sugars are excellent mimics of the natural carbohydrate clusters and may induce multivalent carbohydrate-carbohydrate interaction (CCI) with the target glycopeptides. Therefore, increased retention of glycopeptides can be expected by the combination of CCI and zwitterionic-HILIC interaction. As a result, 1244 glycopeptides were identified after TCP-SMs enrichment from mouse liver, which are 65-120% higher than that obtained by homoglycopolymer or random-copolymer grafted silica microparticles prepared using the conventional free radical polymerization. These results demonstrate the critical role of sequence-defined block copolymer of TCP-SMs for obtaining enhanced affinity toward glycopeptides and the potential of this sequential-ATRP strategy to integrate different affinity moieties into one enrichment material to achieve deeper coverage in protein PTM mapping.