Study on the interaction of porphyrin with G-quadruplex DNAs

Interactions of 5,10,15,20-Tetrakis(N-propylpyridinium-4-yl)-21H,23H-porphyrin (TPrPyP4) with dimer hairpin (G4T4G4)2 and parallel four-stranded (TG4T)4 G-quadruplex DNAs in Na+-containing buffer were studied. The results show that two TPrPyP4 molecules bind to both G-quadruplexes by a noncooperative and nonequivalent binding mode, and there are one high affinity site and one low affinity site, the respective binding constants are 8.06 × 108 and 1.13 × 106 M− 1 for (G4T4G4)2-TPrPyP4, 8.04 × 107 and 9.08 × 105M− 1 for (TG4T)4-TPrPyP4. TPrPyP4 presents two lifetimes of about 5.8 and 12.0 ns in the complexes of G-quadruplexes-TPrPyP4. The primary results suggest that two TPrPyP4 molecules bind to both G-quadruplexes by terminal stacking and outside binding mode.