Sequencing a DNA analog composed of artificial bases

“ALternative Isoinformational ENgineered” (ALIEN) DNA is a biomimetic polymer composed of four entirely anthropogenic nucleotides. These alternative nucleosides form base pairs orthogonal to canonical bases and fold into the familiar B-form DNA double-helix, endowing ALIEN DNA with valuable biotechnological applications. The ability to sequence ALIEN DNA is essential for its continued development. However traditional sequencing approaches rely on chemical recognition of ACGT-DNA and cannot be easily adapted to ALIEN DNA. Here we demonstrate de novo nanopore sequencing of DNA comprised entirely of the four anthropogenic DNA bases. We show direct, label-free, single-molecule sequencing of such nucleic acids without the requirements of fluorescent labels, transliteration, amplification, or enzymatic synthesis. This paves the way for routine, accessible, and high-accuracy sequencing of DNA beyond A, C, G, and T.