Hypericin site specific interactions within polynucleotides used as DNA model compounds

Interactions of the antiretroviral hypericin molecule with polynucleotides, i.e. poly(dG-dC), poly(dA-dT), poly(rG) and poly(rC), have been studied in aqueous solutions by resonance Raman spectroscopy, using an UV excitation wavelength which induces a specific resonance enhancement of spectral band intensities corresponding to proper nucleic base modes of vibration. It is shown that: i) hypericin selectively interacts with the N7 sites of purines, ii) the strength of interaction depends on the polymer structure, and: iii) interaction with guanine is stronger than with adenine molecules.