Cool Science: DNA Origami and DNA LEGOs
Researchers have been taking cues from nature since its inception. Building nanostructures and and devices out of DNA is simply another example of this. DNA and RNA is a sophisticated assembly of nucleic acids that encodes genetic information. However, the hydrogen bonds and base pair stacking lead to self-assembly, which is being incorporated in materials science with greater success. Different structures including lattices, ribbons, tubes, tiles, origami, and bricks have been constructed out of DNA to create larger 2D and 3D subunits. Optimism is abundant at the moment with hope that these DNA nanostructures will facilitate research in other areas including protein structure determination, the modulation of biosynthetic and cell-signaling pathways, and the development of bioimaging probes.
One of the first instances of DNA being used to construct a larger nanostructure began with ’tiles’. DNA tiles were able to form 2D lattices, ribbons, tubes, and 3D crystals. However, it is extremely difficult to create specific, complex shapes is from this building material.
DNA origami poses a much better method because the 3D structures can be much more intricate, however the process is slow and yields are low. The origami name comes from the process itself. A long scaffold strand of DNA is folded into a specific shape due to hundreds of interactions with staple strands. Each different origami shape requires a newly designed scaffold and a unique set of synthetic staple strands.
The different methods already have certain advantages and disadvantages. The origami creates a more complex structure, but lacks chemical diversity due to the scaffold being biological material and only the staples are synthetic. The opposite goes for DNA tiles which have greater diversity due to the modular nature of the strands. Pieces are swapped out easily, but the overall 2D and 3D structures are significantly more simple compared to those made by DNA origami.
DNA bricks are the latest hotness in DNA nanostructure building materials, which debuted in Science in November 2012.Their basic structure is a piece of single stranded DNA made of 32 nucleotides (i.e. guanine, adenine, cytosine, and thymine). These strands contain four regions with distinct building abilities resembling LEGOs. For example, the chemical properties of the region determine whether it is likely to form a 90° left-hand turn or a 90º right-hand turn. From these basic blocks larger 3D structures are formed. Similar to DNA tiles and DNA origami, advantages and disadvantages exist. The advantage is that the greater 3D nanostructure can change easily by simply leaving out or including additional basic strands. However, similar to DNA origami yields are still quite low.
The good news is that DNA bricks and DNA origami is compatible. Researchers are hopeful that the combination of both methods will create larger nanostructures with greater yields. These methods are the foundation for creating complex functional 3D nanostructures, just another simple lesson learned from nature.
[Reference: Science, 2012, Vol. 338, 1177.]