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Functional Nanochannels for Sensing Tyrosine Phosphorylation.

Tyrosine phosphorylation (pTyr), many of which occurred on localized multiple sites, initiates cellular signaling, governs cellular functions, and its dysregulation is implicated in many diseases, especially cancers. pTyr-specific sensing is of great significance for understanding disease states and developing targeted anti-cancer drugs, however, is very challenging due to the slight difference from serine (pSer) or threonine phosphorylation (pThr). Here we present a polyethyleneimine-g-phenylguanidine (PEI-PG)-modified nanochannels that can address the challenge. Rich guanidinium groups enabled PEI-PG to form multiple interactions with phosphorylated residues, especially pTyr residue, which triggered the conformational change of PEI-PG. By taking advantage of "OFF-ON" change of ion flux arising from conformational shrinkage of the grafted PEI-PG, the nanochannels could distinguish phosphorylated peptide (PP) from non-modified peptide, recognize PPs with pSer, pThr or pTyr residue and PPs with different number of identical residues, and importantly could sense pTyr peptides in a bio-sample. Benefiting from the strong interaction between guanidinium group and pTyr side-chain, the specific sensing of pTyr peptide was achieved by performing simple logic operation based on PEI-PG-modified nanochannels when Ca2+ was introduced as an interferent. The excellent pTyr sensing capacity make the nanochannels available for real-time monitoring of pTyr process by c-Abl kinase on a peptide substrate, even in a complicated condition, and the proof-of-concept study of monitoring kinase activity demonstrates its potential in kinase inhibitor screening.