2D DNA lattices assembled from DX-coupled tiles

Hypothesis: Formation of coupled double crossovers (DXs) in a circular 106-mer oligonucleotide (c106nt) could generate stable tiles with the tile core span of 10 half turns. The large-span tiles with complicated curvatures and mechanics could assemble 2D lattices under different environments. Hence, 2D DNA lattice structures based on tile types and sequences, tile packing modes of corrugation and non-corrugation, and assembly media of solution and the substrate-solution interface are yet to be explored. Experiments: Two c106nt scaffold strands with different sequences were synthesized. Four types of tiles, two rectilinear and two triangular tiles, were designed and their 2D assemblies were examined by atomic force microscopy (AFM). Findings: The DX-coupled tiles provided fair strength and rigidity to assemble 2D lattices. Due to the complicated curvature and mechanics of tiles, the two-tile assemblies in solution displayed a few ripe lattices of ribbons, tubes, or polycrystalline aggregates as the minor products and tile oligomers as the major products; whereas the one-tile assemblies via substrate mediation exhibited well-organized monolayer lattices covering the whole mica disk. The herringbone packing patterns were first observed in DNA nanostructures. Based on the lattice constants and the surface coverages of lattices, we estimated the lattice yields for the substrate-mediated assemblies.