| In recent years DNA has become a valuable functional building block and tool in nanotechnology and material science. This is due to the unique nature and properties of DNA in comparison to conventional polymers. The special features of DNA in regard to this proposal are the following: 1) Nowadays solid phase organic synthesis methods allow the preparation of single stranded (ss) DNA with any desired sequence of up to 100 bases. 2) Biosynthetically, DNA is produced in a templated reaction by polymerases with the implication that the sequence of this copolymer consisting of four monomers is controlled very accurately. 3) Hybridization of complementary sequences leads to the formation of a helical double stranded (ds) polymer. 4) Enzymes allow site specific modifications on ss and ds DNA strands. In the herein proposed research, these features of DNA will be combined with those of organic polymers to address, manipulate, improve or evolve a particular function in the field of biology and biotechnology. The topology of these new biological polymeric hybrid structures ranges from linear block type architectures, over star shaped structures to cross-linked networks. A characteristic feature is that the connection between DNA and the organic polymers is always realized by covalent bonds so that bioorganic hybrid materials are formed. The first part of the proposal is dedicated to the synthesis of DNA/polymer conjugates and new nucleopolymer structures, while the second part deals with applications of these materials. The synthesis of DNA block copolymers relies on methods from three different fields: organic chemistry, polymer chemistry and molecular biology. For the preparation of ss DNA diblock copolymers two strategies are already established in our group. DNA is connected to water soluble polymer units in high yields by coupling both segments in solution via their complementary end-groups. In contrast, when a hydrophobic polymer is attached to DNA a ?grafting onto? approach on the solid support is followed. This allows preparation of the amphiphilic bioorganic hybrids in a single process, fully automated applying a DNA synthesizer. Starting from these simple ss diblock structures, ds DNA multiblock copolymers will be prepared that have never been reported so far. The synthetic strategies employed are the polymerase chain reaction (PCR) and enzymatic restriction and ligation of plasmid DNA building blocks. After the realization of linear topologies our synthetic efforts are directed towards nucleopolymers like star-shaped architectures and DNA hydrogels. What are the anticipated applications of these materials? One appealing aspect of combining DNA with synthetic polymers is that the properties of the polymer can be transferred to the nucleic acid unit. In the case of attaching a thermo-responsive polymer, DNA is outfitted with thermo-sensitive features. In this way, a highly efficient method will be elaborated that allows the convenient purification of PCR-products by thermoprecipitation. Similar thermo-responsive hybrids will be employed for the isolation of DNA binding proteins. Finally, such DNA block copolymers will be used as artificial transcription factors that allow control over gene expression by variation of the temperature. |
