DNA nanotech: Expanding the repertoire of DNA for the assembly of nanoscale objects and electrical devices

Much recent interest has focused on DNA as a material for the construction of objects and the templating of other materials on the nanometer to micrometer scale. Such constructions have made use of the recognition of “complementary” nucleotide sequence by single-stranded stretches of DNA in the formation of double helices. The ability of DNA double helices to act as a semi-conductor for electron transfer has opened more opportunities for using DNA in nanoscale devices. This work describes several advancements involving structural and functional aspect of DNA based nanotechnologies.; We have developed a new approach to assemble DNA nanostructures in a cation dependent manner. Association is via the formation of guanine quartets from two G-G mismatch domains within a duplex DNA framework. Association can be regulated by the addition or removal of cation species that promote guanine quartet formation (i.e. K+ or Sr2+). We have also demonstrated that these domains can be ‘programmed’ to be self-specific in mixed solutions by patterning the G·G mismatches into distinct domains.; We have evaluated the process of charge transfer through immobile DNA junctions. This work compares anthraquinone- and rhodium-based methods to induce charge transfer through DNA and identifies some pitfalls in one of the prominently used systems.; We have also demonstrated that the conformational transitions of folded DNA structures, more complex than simple double helical DNA, can be utilized in regulating charge transfer. We have successfully constructed ‘electrical on/off switches’ composed of DNA, which are modulated by the presence or absence of particular compounds in solution. Switches that are modulated by the small molecule adenosine and as well as ones modulated by short oligonucleotides have been assembled. The construction and demonstration of their operation now opens a new window of opportunity for the development of DNA detector systems, which could be directly coupled to microchips. Direct detection of molecules and nucleic acids in this fashion would result in techniques where target molecules can be immediately detected with very high sensitivity and specificity.