Nanostructured self-assembly of double-stranded DNA/poly(o-methoxyaniline) hybrid

Abstract

Biomolecular hybrids of poly(o-methoxyaniline) (POMA) and deoxyribonucleic acid (DNA) are prepared by reacting protonated and sodium salt forms of DNA with emeraldine base (EB) and emeraldine salt (ES) forms of POMA, respectively. Wide-angle X-ray scattering (WAXS) studies indicate that the DNA double-helical structure remains unaltered in the hybrid. Fourier transform infrared (FTIR) and UV-vis studies indicate that there is specific interaction between the radical cation of POMA produced due to doping and the DNA anion. Transmission electron micrographs (TEM) of the Na-DNA/POMA-ES system show a fibrillar network structure of invariant fibrillar diameter for different hybrid compositions. In contrast, the protonated-DNA/POMA-EB system exhibits a fibrillar network structure where fibrillar diameter does vary with hybrid composition. The doping level and concentration of POMA-EB are attributed for the difference in fibrillar diameter with composition in protonated-DNA/POMA-EB hybrids. In the Na-DNA/POMA-ES system, the cross section of each DNA strand immobilizes approximately 30 POMA chains irrespective of the composition of the hybrid, and this has been attributed to the constant doping level ([Cl]/[N] = 0.52) of POMA-ES. The combination of 19 such units approximately produces the fibril of the Na-DNA/POMA-ES system. Thus the TEM micrographs present firm evidence of wrapping of double-stranded DNA by POMA chains. An approximate model of the Na-DNA/POMA-ES system (doping level of 0.52) indicates nanostructured self-organized assembly of the components in the hybrid.