Manipulating DNA Conformation Using Intertwined Conducting Polymer Chains

In the field of inherently conducting polymers, polyaniline (Pani) has elicited tremendous interest due to its promising electrical properties and unique redox tunability. Synthetic routes involving the use of polyelectrolytes have significantly improved the processability of polyaniline. Recently, a template guided synthesis catalyzed by an enzyme, horseradish peroxidase (HRP), has provided a means of polymerizing aniline under milder pH conditions (pH 4.3) and subsequently widened the choice of templates to more delicate biological macromolecules. Here we report a strategy that exploits the inherent molecular order as well as the polyelectrolyte behavior of DNA to enzymatically synthesize and biologically assemble conducting polyaniline. This “wrapping” of polyaniline on DNA has been found to induce reversible changes in the secondary structure of DNA, leading to the formation of an over-wound polymorph. The polyaniline synthesized on the DNA also exhibited a template-induced macroasymmetry. This unique polyaniline/DNA intertwined complex has been used to “probe” and control the conformation of the DNA double helix.