Improving DNA sequencing The cost of genome sequencing limits its conventional use in clinics. Previous studies have found that nucleotides labeled with synthetic oligonucleotide tags can be detected in a nanopore and used in a synthesis-based sequencing platform, a common DNA sequencing method. The tags are removed during DNA synthesis and identified while they pass through a nanopore. This approach requires a protein construct that bridges sequencing to nanopore detection, as well as computational methods to differentiate the tag signals. P. Benjamin Stranges et al. (pp. E6749—E6756) designed a protein construct that couples a single ϕ29 DNA polymerase molecule to a seven-part protein nanopore complex called α-hemolysin. The authors embedded the polymerase–nanopore construct in a lipid bilayer on an electrode array. In the authors’ system, the polymerase feeds the nucleotide tags into the nanopore’s opening, and the electrode array measures resulting current changes in the nanopore. After measuring more than 200 tags for each of the four nucleotide bases, the authors found that a classification algorithm could distinguish between the different tags and background signals. This method identified the correct nucleotide by its tag 79–99% of the time, and identified a background event as a tag less than 1.2% of the time. According to the authors, this approach may provide the foundation for a low-cost, accurate, single-molecule, electronic DNA-sequencing platform.
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