Scientists Design Self-Replicating DNA Nanostructures By Darlene Tverdohleb | Aug 26, 2015 12:30 AM EDT According to South Korean and Japanese scientists from the Sungkyunkwan University and Tohoku University, it possible to engineer self-replicating nanomaterials and nanostructures. They compare the process with borrowing nature's building blocks. Scientists explain that DNA is a self-replicating molecule. Its component parts called nucleotides have specific chemical interactions that allow them to design self-assembled structures. According to scientists, DNA replicates with the aid of proteins in biological systems. The team of researchers composed by Junghoon Kim, Junwye Lee, Shogo Hamada,Satoshi Murata, and Sung Ha Park of Sungkyunkwan University and Tohoku University have developed a controllable self-replicating system that does not even require proteins. The research team has published their research paper in Nature Nanotechnology. According to the Korean and Japanese research team, it is important to know the different component parts in order to understand how the self-replicating process works. Kim and his colleagues designed two DNA T-motifs, r1 and r2. They are double-stranded DNA comprised of "sticky" ends as connection points and functional domains that are labeled alpha and beta. The scientists also designed an extension motif that is comprised of twelve units of the r1 motif self-assemble into a small ring called R1, twelve units of r2 plus twelve extension motifs self-assemble into a larger ring, called R2. All these components, according to the research team can be in two different states called "fertilized" and "unfertilized". The difference between them is that the fertilized structures contain some features necessary for replication. Replication or fertilization happens when a single-stranded alpha or beta domain of an r1 or r2 motif will bind with a strand featuring a complimentary alpha or beta domain. This creates a single-strand protrusion called toehold, which extends from the original motif or from the ring. According to researchers, the toeholds indicate that the motif of ring is fertilized. The toeholds that extend from the DNA ring will bind to complementary invader strands. The hybridized structure formed of the toehold and the invading strand will break off of the initial ring and eventually self-assemble into another ring. This process can continue through two replication pathways. The first pathway grows exponentially and the second grows according to Fibonacci's sequence. Which particular pathway is taken depends on the invading strands added. The authors of the research verified with absorbance and AFM studies that the DNA ring populations grew through this toehold-mediated process. Kim and his colleagues demonstrated that the self-assembly abilities of DNA motifs and the thermodynamic properties of toehold-mediated strand displacement can be used for nanoscale self-replication. The researchers presented in their study synthetic DNA T-motifs self-assembling into structures allowing for sequential reactions. Their research demonstrates the possibility of developing functionally programmable self-replicating nanostructures.