We have synthesized psoralen-terminated poly(N-isopropylacrylamide)(1) and poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide)(2), both of which show temperature-responsive properties and DNA-binding ability. These polymers were grafted on plasmid double stranded DNA through a photochemical reaction of their terminal psoralen groups. The double stranded DNA grafted with the vinyl polymers turned out to lose the function as templates for RNA synthesis, while it showed characteristic solution property derived from the vinyl polymers. Ligation reaction between the polymer-grafted DNA and native DNA resulted in the AB-type block conjugate with the polymer-grafted DNA as A-segment and native DNA as B-segment. It was found that the block conjugate which have two different functional domains retains two functions independently; B-domain of the block conjugate worked as a template for RNA synthesis, while A-domain responded to temperature and made the conjugate precipitate. In this way, one can construct tailor-made and precisely-regulated structures with multiple functions at his own will by using recombinant DNA techniques.
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