Squeezing a single polypeptide through a nanopore

We have already seen a decade of single-molecule science involving protein nanopores, and many lessons have been learned from the extensive studies in this exciting realm. Given the promise of the single-molecule nanopore technique for ultra-rapid sequencing of nucleic acids, most of these investigations have been focused on understanding the transit of single-stranded DNA through a protein nanopore. In contrast, the biophysical and biotechnological applications of polypeptide translocation through a protein nanopore have not been pursued as aggressively. However, recent explorations have shown that a mechanistic understanding of polypeptide translocation at unprecedented single-molecule resolution can be achieved using high-resolution, time-resolved single-channel electrical recordings with nanopores and protein design. Moreover, these efforts have begun to unravel the complexity of the protein-pore interactions that involve various thermodynamic forces. Finally, combining recordings of single-channel electrical currents through nanopores with protein engineering proves to be not only a novel single-molecule analytical tool for the detection, examination, and characterization of polypeptides, but also a critical element for prospective high-throughput screening devices in drug design and proteomics.