Phenanthrene-derived DNA hairpin mimics

Self-complementary oligodeoxynucleotides containing 3,6-disubstituted phenanthrenes adopt highly stable, hairpin-like structures. The thermodynamic stability of the hairpin mimics depends on the overall length of the phenanthrene building block. Hairpin loops composed of a phenanthrene-3,6-dicarboxamide and ethylene linkers were found to be optimal. The hairpin mimics are more stable than the analogous hairpins containing either a dT(4) or dA(4) tetraloop. Model studies indicate that the thermodynamic stability of the hairpin mimics is primarily due to aromatic stacking of the phenanthrene-3,6-dicarboxamide onto the adjoining base pair of the DNA duplex.