Bioinspired Saccharide–Saccharide Interaction and Smart Polymer for Specific Enrichment of Sialylated Glycopeptides

Abnormal sialylation
of proteins is highly associated with many
major diseases, such as cancers and neurodegenerative diseases. However,
this study is challenging owing to the difficulty in enriching trace
sialylated glycopeptides (SGs) from highly complex biosamples. The
key to solving this problem relies strongly on the design of novel
SG receptors to capture the sialic acid (SA) moieties in a specific
and tunable manner. Inspired by the saccharide–saccharide interactions
in life systems, here we introduce saccharide-based SG receptors into
this study. Allose (a monosaccharide) displays specific and pH-sensitive
binding toward SAs. Integrating allose units into a polyacrylamide
chain generates a saccharide-responsive smart copolymer (SRSC). Such
design significantly improves the selectivity of SA binding; meanwhile,
this binding can be intelligently triggered in a large extent by solution
polarity and pH. As a result, SRSC exhibits high-performance enrichment
capacity toward SGs, even under 500-fold interference of bovine serum
albumins digests, which is notably higher than conventional materials.
In real biosamples of HeLa cell lysates, 180 sialylated glycosylation
sites (SGSs) have been identified using SRSC. This is apparently superior
to those obtained by SA-binding lectins including WGA (18 SGSs) and
SNA (22 SGSs). Furthermore, lactose displays good chemoselectivity
toward diverse disaccharides, which indicated the good potential of
lactose-based material in glycan discrimination. Subsequently, the
lactose-based SRSC facilitates the stepwise isolation of O-linked
or N-linked SGs with the same peptide sequence but varied glycans
by CH3CN/H2O gradients. This study opens a new
avenue for next generation of glycopeptide enrichment materials.