A pH-responsive soluble polymer-based homogeneous system for fast and highly efficient N-glycoprotein/glycopeptide...

Liquid phase homogeneous reactions using soluble polymer supports have found numerous applications in homogeneous catalysis and organic synthesis because of their advantages of no interface mass transfer limitation and a high conversion rate. However, their application in analytical separation is limited by the inefficient/inconvenient recovery of the target molecules from the extremely complex biological samples. Here, we report a stimuli-responsive polymer system for facile and efficient enrichment of trace amounts of biomolecules from complex biological samples. The soluble polymer supports provide a homogeneous reaction system with fast mass transfer and facilitate interactions between the supports and the target molecules. More importantly, the stimuli-responsive polymers exhibit reversible self-assembly and phase separation under pH variations, which leads to facial sample recovery with a high yield of the target biomolecules. The stimuli-responsive polymer is successfully applied to the enrichment of low abundant N-glycoproteins/glycopeptides, which play crucial roles in various key biological processes in mammals and are closely correlated with the occurrence, progression and metastasis of cancer. N-Glycoprotein is coupled to the stimuli-responsive polymer using the reported hydrazide chemistry with pre-oxidation of the oligosaccharide structure. Highly efficient enrichment of N-glycoproteins/N-glycopeptides with >95% conversion rate is achieved within 1 h, which is eight times faster than using solid/insoluble hydrazide enrichment materials. Mass spectrometry analysis achieves low femtomolar identification sensitivity and obtained 1317 N-glycopeptides corresponding to 458 N-glycoproteins in mouse brain, which is more than twice the amount obtained after enrichment using commercial solid/insoluble materials. These results demonstrate the capability of this "smart" polymer system to combine stimuli-responsive and target-enrichment moieties to achieve improved identification of key biological and disease related biomolecules.