Interaction of hypericin with guanine-rich DNA: Preferential binding to parallel G-Quadruplexes

• Hypericin was first reported to specifically bind to parallel G-Quadruplexes.
• Hypericin binds to parallel G-Quadruplexes through end-stacking mode.
• Hypericin binding to parallel G-Quadruplexes causes great fluorescence enhancement.

Hypericin (Hyp) is one of the principal active constituents of a traditional folk medicine, Hypericum (Saint John’s wort), and possesses variety biological activities. The interaction of Hyp with DNA may play an important role in biological activity, however only a few investigations were reported on this issue. In this paper, we studied the interaction of Hyp with different DNA forms. Hyp was found to selectively bind parallel DNA G-Quadruplexes (G4) over other DNA forms, such as ss-/ds-DNA, antiparallel G4s and mix-type G4s. Binding studies suggest that Hyp bind on G-quartet surface of G4s through end-stacking interaction. These results provide new information for the investigation of action mechanism of Hyp.

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