Synthetic RNA nanostructures are typically composed of four nucleotides (A, U, G, and C) following a canonical base pairing rule (A-U/G-C). G·U wobble pairs are commonly employed in many RNA nanostructures, but other non-canonical base pairing remains underexplored. In this work, we design RNA nanostructures with only three nucleotides instead of four. Besides Watson–Crick G-C base pairs, we incorporate A·C non-canonical base pairs into this three-letter coding scheme and allow selective nanostructure assembly from mixed DNA templates. With the new paradigm, we produce a variety of RNA nanostructures, further expanding the possibilities of rational molecular design.
