MODIFICATION OF DNA WITH POLY(N-ISOPROPYLACRYLAMIDE) FOR THERMALLY-INDUCED AFFINITY SEPARATION

A semi-synthetic macromolecular conjugate consisting of lambda phage DNA and poly(N-isopropylacrylamide) was prepared by copolymerization of N-isopropylacrylamide (NIPAAM) with a DNA-binding molecule having a vinyl group in the presence of DNA. The polyNIPAAM-modified DNA was found to acquire a thermoresponsive property; the DNA precipitated from aqueous solution when the temperature was raised above 31-degrees-C, due to coil-to-globule transition of polyNIPAAM chains. A preliminary experiment showed that a restriction endonuclease, Hind III, was co-precipitated with the thermoresponsive DNA above the transition temperature. A potential application of this thermosensitive DNA was suggested for an affinity isolation of DNA-binding proteins by temperature changes near physiological conditions.