Centre for DNA Nanotechnology (CDNA) was established in March 2007 by Kjems, Besenbacher and Gothelf in collaboration with the two American researchers Yan and LaBean. In 2011 the centre was extended from 2012 to 2017.
The purpose of the research at CDNA is to explore fundamental aspects of DNA as a programmable tool for directing the assembly of molecules and materials into nanoarchitectures and functional structures. The highlights for CDNA in 2011 are described in the following.
Synthesis of conjugated and potentially electronically conducting organic wires is conventionally done by polymerization or by iterative synthesis where one building block is added in each step. However, the iterative synthesis is tedious and requires many steps whereas in polymerization the length of the wire cannot be precisely controlled and polydisperse material is obtained. One of the long-term goals of CDNA has been to develop new approaches to use DNA to direct the assembly and coupling of building blocks. Many different chemical reactions have been tested for coupling of the wires. In 2011 we reported a superior method to couple short oligo(phenylene ethynylene) modules by the Cu-mediated Glaser-Eglinton reaction. The attached DNA strands direct the formation of 1,3-diyne linkages between the modules to selectively form dimer, trimer and tetramer conjugated wires of up to 8 nm in length (Figure 1). Compared to previous coupling methods a stable C-C bond is formed between the modules, connecting chromophores to make a fully conjugated wire.
Figure 1 DNA-directed assembly and coupling of 2 nm long molecular rods.
The work was published in Angewandte Chemie in 20111 and constitute and important step in our attempts to prepare larger conjugate wires that in turn will be immobilized on larger DNA structures such as DNA origami and ultimately connected to electrodes.
In the second period of CDNA, William Shih’s group at Harvard Medical School has become associated with CDNA. The collaboration has however already started. CDNA PhD student Niels V. Voigt spent half year in William Shih’s group and in the beginning of 2012 the first joint publication appeared in J. Am. Chem. Soc.2
In this work DNA origami has been used for folding of multilayer DNA origami with helices arranged on a close-packed hexagonal lattice (Figire 2). This arrangement yields a higher density of helical packing and therefore higher resolution of spatial addressability than has been shown previously. It was also demonstrated that hybrid multilayer DNA origami could be formed with honeycomb-lattice, square-lattice, and hexagonal-lattice packing of helices all in one design. The availability of hexagonal close-packing of helices extends our ability to build complex structures using DNA nanotechnology.
Figure 2. Multilayer origami in hexagonal lattices and hybrid lattices.
With the purpose of emphasizing DNA nanotechnology as a hot topic in nanoscience, the Wyss Institute at Harvard has recently established a student competition in biomolecular design called BIOMOD. In 2011, the inaugural year, 21 teams from all over the world participated. A team of five bachelor students from CDNA/iNANO called “The Danish Nanoartists” made a joint bachelor project for the competition and it was presented at Harvard in November. It was highly successful and the team was awarded both the prize for the best presentation and the Grand prize.
Figure 3. The Danish Nano Artists (DNAs) and their mentors.
The team presented a novel RNA nanostructure that was build from drug molecules called siRNAs and showed that it functions inside living cells to regulate the expression of specific genes. A future application could be to combat the expression of specific genes related to genetic diseases.
Three of the young groups leaders at CDNA: Victoria Birkedal, Ebbe Andersen and Mingdong Dong have all received prestigious funding awards such as the Sapere Aude DFF research leader (Birkedal 2011, Andersen 2012) and the Young Investigator Award from the Villum Foundation (Dong, 2012).
(1) DNA-programmed Glaser-Eglinton reactions for the synthesis of conjugated molecular wires. Ravnsbæk, J. B.; Jacobsen, M. F.; Rosen, C. B.; Voigt, N. V.; Gothelf, K. V. Angew. Chem. Int. Ed. 2011, 50, 10851–10854.
(2) Multilayer DNA Origami Packed on Hexagonal and Hybrid Lattices. Ke, Y.; Voigt, N. V.; Gothelf, K. V.; Shih, W. M. J. Am. Chem. Soc.134, 1770−1774.