A Self-Assembled\nPeriodic Nanoporous Framework in\nAqueous Solutions of the DNA Tetramer GCCG

The collective behavior of the shortest DNA oligomers\nin high concentration\naqueous solutions is an unexplored frontier of DNA science and technology.\nHere we broaden the realm of DNA nanoscience by demonstrating that\nsingle-component aqueous solutions of the DNA 4-base oligomer GCCG\ncan spontaneously organize into three-dimensional (3D) periodic mesoscale\nframeworks. This oligomer can form B-type double helices by Watson–Crick\n(WC) pairing into tiled brickwork-like duplex strands, which arrange\ninto mutually parallel arrays and form the nematic and columnar liquid\ncrystal phases, as is typical for long WC chains. However, at DNA\nconcentrations above 400 mg/mL, these solutions nucleate and grow\nan additional mesoscale framework phase, comprising a periodic network\non a three-dimensional body-centered cubic (BCC) lattice. This lattice\nis an array of nodes (valence-8, each formed by a pair of quadruplexes\nof GCCG terminal Gs), connected with a separation of 6.6 nm by struts\n(6-GCCG-long WC duplexes). This 3D-ordered DNA framework is of low\ndensity (DNA volume fraction ∼0.2), but due to its 3D crystal\nstructure, it is osmotically incompressible over its phase range.\nAtomistic simulations confirm the stability of such structures, which\npromise to form the basis of families of simply and inexpensively\nmade nanoscale frameworks for templating and selection applications.