We reported a classical two-tile system of DAE-O (doublecrossover, antiparallel, and even half-turns tiles with odd half-turns connection) to construct regular single crystalline 2D (two dimensional) DNA lattices, using pre-circularised oligonucleotides of 42-, 64-, and 84-nt (nucleotides) as the central looped strands in DAE tiles respectively. DAE tiles with 42- and 64-nt as central strands, either in circular form or in linear form, grew regular single crystalline lattices well. However DAE tiles including a circular 84-nt as the central strand grew single crystalline lattices, those including a linear 84-nt as the central strand grew polycrystalline 2D lattices. A subtle difference in the lateral rigidity of DAE tiles with regard to the duplex axis was suggested to be the cause of the morphological difference.

Molecular self-assembly using DNA as astructural buildingb lock has proven to be an efficient route to the construction of nanoscale objectsa nd arrays. Using the pre-circularised DNA as the core strand of DNA motifs provides new components for the assembly of one-, two-, and three-dimensional (1D, 2D, 3D) nanostructures. We report here honeycomb-like and grid-like framework nanostructures constructed from 3-arm trianglea nd 4-arm square tiles with pivotalt hree-way junctionso ns mallc ircular oligonucleotides of 32-nt and 42-nt, respectively. However the flexible three-way junction,the crowded spatial environmento ft he small circular DNA motifs, and the lack of rigidity in the double helix connection may reduce the possibility to grow large single crystallineD NA lattices.DNA molecules are functional materials for storing genetic informationi nn ature with Watson-Crick base-pairing interactions. In the field of DNA nanotechnology,n ucleic acids are used as biopolymer engineering materials forn anotechnology rather than as the carriers of genetic information in living cells. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] Researchers in the field have createdi mmobile structures such as one-, two-, and three-dimensional (1D, 2D, 3D) single crystalline lattices, including nanotubes, polyhedra,a rbitrary shapes,a nd dynamic devices such as molecular machines and DNA computers. [15][16][17][18][19][20] Among DNA operations in nature, DNA looping, causingt wisting, bending, torsion, curving, kinking, stressing,a nd disruptiono fD NA molecules, has very important physiological functions, such as regulating transcription or facilitating protein-DNA assembly during replication, recombination,c ondensation, etc. [21,22] Instead of using the most common linear strands as the beginning molecules to self-assemble 1D, 2D, and 3D nanostructures, recently we applied pre-circularised oligonucleotides to successfullyb uild homogeneous nanotubes by stacking lateral duplex rings and to construct 2D latticesi nt he longitudinal direction of doubleh elices, suggestingt he good stabilitya nd rigidity of motifs involving at least one pre-circularised DNA strand. [23][24][25][26] Seeman and his colleaguesi nvestigated the three-way junction and four-wayj unction (Holliday Junction) structures in the early years. They indicated that the three-way DNA junction structures are conformationally flexible, while the double crossover structuresa re more rigid components that are needed to assemblel arge and shapable periodic lattices. [27][28][29] Ag eneral belief is that the DNA junction series of flexibility from high to low are two-way (sticky end cohesion region), three-way,a nd four-way. As we know until now,t here are few reports of applying the three-way junction tiles to assemble DNA nanostructures. What is the boundary of using the three-way junctions for DNA nanostructures?I nt his Communication, we applied the smallest circular oligonucleotides of 32 and 42-nti n size by ligation, which have integerp itches of 3a nd 4i n...