Programming the morphology of DNA origami crystals by magnesium ion strength

Harnessing the programmable nature of DNA origami for controlling structural features in crystalline materials affords opportunities to bring crystal engineering to a remarkable level. However, the challenge of crystallizing a single type of DNA origami unit into varied structural outcomes remains, given the requirement for specific DNA designs for each targeted structure. Here, we show that crystals with distinct equilibrium phases and shapes can be realized using a single DNA origami morphology with an allosteric factor to modulate the binding coordination. As a result, origami crystals undergo phase transitions from a simple cubic lattice to a simple hexagonal (SH) lattice and eventually to a face-centered cubic (FCC) lattice. After selectively removing internal nanoparticles from DNA origami building blocks, the body-centered tetragonal and chalcopyrite lattice are derived from the SH and FCC lattices, respectively, revealing another phase transition involving crystal system conversions. The rich phase space was realized through the de novo synthesis of crystals under varying solution environments, followed by the individual characterizations of the resulting products. Such phase transitions can lead to associated transitions in the shape of the resulting products. Hexagonal prism crystals, crystals characterized by triangular facets, and twinned crystals are observed to form from SH and FCC systems, which have not previously been experimentally realized by DNA origami crystallization. These findings open a promising pathway toward accessing a rich phase space with a single type of building block and wielding other instructions as tools to develop crystalline materials with tunable properties.SignificanceDNA origami is a technique that involves folding a bacteriophage DNA into a prescribed nanostructure using short oligonucleotides. This technique has found great utility in crystal engineering, where DNA origami constructs are assembled into crystalline materials via DNA hybridization. However, accessing distinct structural outcomes is difficult without an intricate set of DNA designs. The limited DNA design space over which DNA origami can crystallize hampers achieving this goal. Here, a facile approach is used to tune the crystallization pathways of DNA origami building blocks. Therein, changes in the strength of allosteric factor lead to distinct equilibrium phases and crystals. This approach promises access to engineering a library of crystalline materials with tunable features and properties via environmental variables.