Spectroscopic detection of Z-DNA in short oligonucleotides

The structure of right-handed double helical DNA was discovered in 1953 by James D. Watson and Francis Crick. DNA is known to exist in many possible conformations that include A-DNA, B-DNA, C-DNA, D-DNA and Z-DNA. The right-handed B-DNA is the predominant form in biological systems. The B-to-Z-DNA conformation transition is well studied process by which the right-handed duplex turns into a left handed helix known as Z-DNA (zig-zag DNA). Z-DNA exists as a higher energy state of the canonical B-DNA. Recent studies suggest that Z-DNA plays a role in replication and transcription processes. Our research explored the potential of charged porphyrins as bimolecular recognition tools of short Z-DNA oligonucleotides. We used a short self-complementary oligonucleotide 5'-(dCdG)12-3' for our studies. Selected concentrations of NiCl2 and MgCl2 were used to induce the left-handed Z-DNA form. Following induction, anionic water-soluble tetrasulfonated metalloporphyrins, namely NiTPPS, ZnTPPS, CuTPPS and MnTPPS were used in UV-vis and circular dichroism binding experiments. We will present the spectroscopic recognition of the Z-DNA using the nickel(II) porphyrin.