Manipulating DNA Conformation Using Intertwined Conducting Polymer Chains

Abstract

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.

Self‐Assembly of DNA‐Templated Polypyrrole Nanowires: Spontaneous Formation of Conductive Nanoropes

“…However, the nanowires formed at short times can assemble non-covalently because of the compensation of the charge on the phosphate backbone of DNA. [32][33][34] A close examination of the end of the bundle presented in Figure 2b shows that individual nanowires have a thickness similar to that obtained of the nanowires formed after a short reaction time (1-2 nm). Data for the evolution of the nanowires and ropes are summarised in Table 1.…”

“…[19] Because of the resemblance of their ends to the frayed end of a rope, we refer to these structures as nanoropes. We propose that the driving force for this process is similar to the condensation of DNA by multivalent cations [26,27] and cationic polymers, [28][29][30][31][32][33][34] although the structures formed by PPy-DNA appear rather different owing to the stiffness of PPy. Some similar bundles have been reported in the Zn 2þ / DNA system known as M-DNA.…”

Enzyme Initiated Radical Polymerizations

“…Other negatively charged polymers [80] such as poly(vinylphosphonic acid) [81]or DNA [82][83][84] have been reported as templates. The templates promote the formation of the electrically conducting emeraldine form of poly(aniline) and significant branching (as in case of in the absence of the templating agent) does not occur.…”

Electrochemical preparation of polyaniline microspheres incorporated with DNA

“…Deoxyribonucleic acids (DNAs) have been employed as one of the most attractive templates because of their helical molecular structures with negatively charged sites, and several successful examples have been reported [15][16][17][18][19][20]. In the present study, however, we attempted to employ DNA not as a template, but as an incorporating component with the PANI molecules.…”