A 9 kbp dsDNA scaffold sequence was commercially synthesized as an artificial gene and cloned into an E. coli plasmid for easy in-house amplification (Supplementary Table ). Gene production is facilitated by periodic insertion of purine/pyrimidine mixed regions, but this introduces TFO-incompatible scaffold domains. Fortunately, an intermittent pattern of 60 purines (60R) and 21 mixed bases (21N) consolidates all the spatial organizations discussed in Figs. . The 21N domains function as dsDNA spacers of two helical turns and loops, and incorporate recognition sites for restriction enzymes so that the scaffold length can be customized (Supplementary Table ). The linearized dsDNA scaffold is enzymatically cleaved from the 60R21N-9kbp plasmid. Six different designs were explored and their predicted and experimentally observed shapes are shown in Fig. . The staple sequences and detailed design schematics of all structures depicted henceforth are shown in Supplementary Tables , and Supplementary Figs.