Rapid Folding of DNA into Nanoscale Shapes at Constant Temperature

Speeding Up Nanoscale DNA Assembly An impressive array of three-dimensional (3D) nanoscale objects has been assembled by folding a long, single-stranded DNA scaffold by binding of short DNA staples. However, these processes tend to be slow and inefficient. Sobczak et al. (p. 1458) examined the folding process with an intercalating fluorescence dye to measure the formation of double-stranded DNA in folding processes or single-stranded DNA in unfolding. Reaction conditions were identified that sped up folding by orders of magnitude and increased yields of the 3D nanoscale objects to nearly 100%. Complex DNA nanoscale objects may be assembled within minutes in high yields through a process resembling protein folding. We demonstrate that, at constant temperature, hundreds of DNA strands can cooperatively fold a long template DNA strand within minutes into complex nanoscale objects. Folding occurred out of equilibrium along nucleation-driven pathways at temperatures that could be influenced by the choice of sequences, strand lengths, and chain topology. Unfolding occurred in apparent equilibrium at higher temperatures than those for folding. Folding at optimized constant temperatures enabled the rapid production of three-dimensional DNA objects with yields that approached 100%. The results point to similarities with protein folding in spite of chemical and structural differences. The possibility for rapid and high-yield assembly will enable DNA nanotechnology for practical applications.