Chunying Wei

Spectroscopic study on the binding of porphyrins to (G4T4G4)4 parallel G-quadruplex

The binding mode and stoichiometry of the cationic porphyrin TMPyP4 to G-quadruplex structure are still controversial to date, mainly due to the intricate polymorphism of G-rich sequences in the different conditions of solution. Here in the presence of the molecular crowding agent PEG, the binding interaction of TMPyP4 and another porphyrin derivative TPrPyP4 with four-stranded parallel (G(4)T(4)G(4))4 G-quadruplex was studied systematically using circular dichroism, visible absorption titration, and steady-state and time-resolved fluorescence spectroscopies. The results show that each (G(4)T(4)G(4))4 molecule is able to bind four TMPyP4 or TPrPyP4 molecules. Two types of independent and nonequivalent binding sites with the higher and lower binding affinity are confirmed, and the stronger and weaker binding constants are 2.74 x 10(8) and 8.21 x 10(5)M(-1) for (G(4)T(4)G(4))4-TMPyP4, 2.05 x 10(8) and 1.05 x 10(6)M(-1) for (G(4)T(4)G(4))4-TPrPyP4, respectively. The two porphyrin molecules stack on the two ends of G-quadruplex with the higher binding affinity, another two porphyrins bind weakly to the two external grooves.

The structural transition and compaction of human telomeric G-quadruplex induced by excluded volume effect under cation-deficient conditions.

The structure polymorphism of human telomeric G-quadruplex (ht-quadruplex) is currently an important topic but remains controversy. Here, we present study of the ht-quadruplex under the cation-deficient but molecular crowding conditions by circular dichroism (CD), microchip electrophoresis (MCE) and UV-melting experiments. Our results show that with concentration increasing of poly(ethylene glycol) (PEG), the structural transition of ht-quadruplex occurs accompanied by structural compaction and enhanced stabilization, which may be caused by excluded volume effect. This work also demonstrates that ht-quadruplex can be well assembled without cations and the structure of ht-quadruplex is actually very complex in vivo.

Dynamic Insight into the Interaction between Porphyrin and G-quadruplex DNAs: Time-Resolved Fluorescence Anisotropy Study

Understanding the nature of the interaction between small molecules and G-quadruplex DNA is crucial for the development of novel anticancer drugs. In this paper, we present the first data on time-resolved fluorescence anisotropy study on the interaction between a water-soluble cationic porphyrin H(2)TMPyP4 and four distinct G-quadruplex DNAs, that is, AG(3)(T(2)AG(3))(3), thrombin-binding aptamer (TBA), (G(4)T(4)G(4))2, and (TG(4)T)4. The anisotropy decay curves show the monoexponential for free H(2)TMPyP4 and the biexponential upon binding to the excess amount of G-quadruplex DNAs. The biexponential anisotropy decay can be well interpreted using a wobbling-in-the-cone model. The orientational diffusion of the bound H(2)TMPyP4 is initially restricted to a limited cone angle within the G-quadruplex DNAs, and then an overall orientational relaxation of the G-quadruplex DNA-H(2)TMPyP4 complexes occurs in a longer time scale. It was found that the dynamics of the restricted internal rotation of bound H(2)TMPyP4 strongly depends on the ending structures of the G-quadruplex DNAs. According to the order parameter (Q) calculated from the wobbling-in-the-cone model, we deduce that the degree of restriction around the bound H(2)TMPyP4 follows the order of TBA > (TG(4)T)4 > AG(3)(T(2)AG(3))(3) > (G(4)T(4)G(4))2. Especially, based on the maximum order parameter (Q) of bound H(2)TMPyP4 within TBA, a new sandwich-type binding mode for TBA-H(2)TMPyP4 complex was proposed in which both terminal G-quartet and T*T base pair stack on the porphyrin ring through pi-pi interaction. This study thus provides a new insight into the interaction between G-quadruplex DNAs and H(2)TMPyP4.

The binding mode of porphyrins with cation side arms to (TG4T)4 G-quadruplex: Spectroscopic evidence

Interactions of 5,10,15,20-Tetrakis(N-methylpyridinium-4-yl)-21H,23H-porphyrin (TMPyP4) and 5,10,15,20-Tetrakis(N-propylpyridinium-4-yl)-21H,23H-porphyrin (TPrPyP4) with the parallel four-stranded (TG(4)T)4 G-quadruplex DNA in 100 mM K(+)-containing buffer were studied using circular dichroism (CD) spectroscopy, visible absorption titration, and steady and time-resolved fluorescence spectroscopies. The results show that the binding stoichiometric ratios of both TMPyP4 and TPrPyP4 to (TG(4)T)4 are 3:1. Two types of independent and nonequivalent binding sites with the higher and lower binding affinities are confirmed, and the stronger and weaker binding constants are 9.44x10(7) and 6.94x10(5) M(-1) for (TG(4)T)4-TMPyP4 complex, 7.86x10(7) and 6.35x10(5) M(-1) for (TG(4)T)4-TPrPyP4 complex, respectively. For both TMPyP4-(TG(4)T)4 and TPrPyP4-(TG(4)T)4 complexes, one porphyrin molecule stacks on the one end of G-quadruplex with the higher binding affinity, another two porphyrins bind weakly to the two external grooves. The size of cation side arms around porphyrin core almost fails to affect the binding mode, stoichiometry and affinity of porphyrin to (TG(4)T)4 G-quadruplex in 100 mM K(+)-containing buffer.

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 x 10(8) and 1.13 x 10(6) M(-1) for (G4T4G4)2-TPrPyP4, 8.04 x 10(7) and 9.08 x 10(5)M(-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.

Formation and stabilization of G-quadruplex in nanosized water pools

We demonstrate here that G-quadruplex structure can form and exhibits strong stability in nanosized water pools, providing new insight into investigating G-quadruplexes in the cellular environment.

Novel platinum complexes as efficient G-quadruplex DNA binders and telomerase inhibitors

Three 4-(1H-imidazo[4,5-f]-1,10-phenanthrolin-2-yl)phenol derivatives-based platinum (II) complexes have been synthesized, and their G-quadruplex DNAs-binding interactions, telomerase inhibition, antiproliferative activity, and cell cycle arrest were studied. Three complexes show the preference for stabilizing h-telo, c-kit2, and c-myc G-quadruplexes in the presence of 10-fold excess of duplex DNA and the higher binding affinities to G-quadruplexes than to duplex. The complexes 1 and 3 present a high stabilization potential (ΔTm) for h-telo G-quadruplex and thus give a significant inhibition of telomerase activity at 2μM concentration, whereas the complex 2 displays higher antiproliferative activity against HeLa and HepG2 cancer cells by MTT assay with IC50 values of about 10(-5)M. The complexes 2 and 3 arrest both cells in the G0/G1 phase of cell cycle, whereas the complex 1 arrests the cell cycle in the S phase for HeLa cells and the G0/G1 phase for HepG2 cells.