Controlled\nTranslocation of Proteins through a Biological\nNanopore for Single-Protein Fingerprint Identification

After the successful sequencing of nucleic acids, nanopore\ntechnology\nhas now been applied to proteins. Recently, it has been demonstrated\nthat an electro-osmotic flow can be used to induce the transport of\nunraveled polypeptides across nanopores. Polypeptide translocation,\nhowever, is too fast for accurate reading its amino acid compositions.\nHere, we show that the introduction of hydrophobic residues into the\nlumen of the nanopore reduces the protein translocation speed. Importantly,\nthe introduction of a tyrosine at the entry of the nanopore and an\nisoleucine at the entry of the β-barrel of the nanopore reduced\nthe speed of translocation to ∼10 amino acids/millisecond while\nkeeping a relatively large ionic current, a crucial component for\nprotein identification. These nanopores showed unique features within\ntheir current signatures, which may pave the way toward protein fingerprinting\nusing nanopores.