Simultaneous single-molecule discrimination of cysteine and homocysteine with a protein nanopore.

Discrimination between cysteine and homocysteine at the single-molecule level is achieved within a K238Q mutant aerolysin nanopore, which provides a confined space for high spatial resolution to identify the amino acid difference with a 5'-benzaldehyde poly(dA) ₄ probe. Our strategy allows potential detection and characterization of various amino acids and their modifications, and provides a crucial step towards developing nanopore protein sequencing devices.