DNA Assembly Templated by Chiral Nanotube Lattices: From Helix to Rings

Controlled assembly of DNA expands its utility in materials science. Most DNA-based architectures rely on Watson-Crick base pairing and stacking. Identifying additional programmable interactions could widen the design space. Single-stranded DNA (ssDNA) is known to adsorb on carbon nanotubes (CNTs) as sequence- and chirality-dependent helices, but direct structural evidence for a nanotube lattice-templating mechanism has been limited. Here we use cryo-electron microscopy to compare the assembly of the ssDNA sequence TTA TAT TAT ATT (ss65) on enantiomeric (6,5) CNTs. On the left-handed (+) (6,5) CNT, ss65 forms stacked, ring-like wraps with an axial repeat of 15.3 Å and with micrometer-scale coherence length. In contrast, on the right-handed (-) (6,5) CNT, ss65 adopts a conventional 1-start helical wrap with a helical pitch of ∼16.4 Å. These results indicate that the handedness of the underlying chiral lattice can bias ssDNA into distinct topologies (helix versus rings) and suggest a strategy for DNA assembly based on CNT lattice recognition, in addition to base pairing and stacking.