title: Investigating a quadruplex-ligand interaction by unfolding kinetics.
abstract: We have investigated the interaction of the intramolecular human telomeric DNA G-quadruplex with a hemicyanine-peptide ligand, by studying the rate of quadruplex opening with a complementary DNA oligonucleotide. By employing a minimal kinetic model, the relationship between the observed rate of quadruplex opening and the ligand concentration has enabled estimation of the dissociation constant. A van't Hoff analysis revealed the enthalpy and entropy changes of binding to be -77 +/- 22 kJ mol(-1) and -163 +/- 75 J mol(-1) K(-1), respectively. Arrhenius analyses of the rate constants of opening free and bound quadruplex gave activation energies of 118 +/- 2 and 98 +/- 10 kJ mol(-1), respectively. These results indicate that the presence of the ligand has only a small effect on the activation energy, suggesting that the unbinding of the ligand occurs after the transition state for quadruplex unfolding.
authors.affiliation: Department of Chemistry, University of Cambridge, UK.
authors.forename: Jeremy J
authors.initials: JJ
authors.lastname: Green
authors.forename: Sylvain
authors.initials: S
authors.lastname: Ladame
authors.forename: Liming
authors.initials: L
authors.lastname: Ying
authors.forename: David
authors.initials: D
authors.lastname: Klenerman
authors.forename: Shankar
authors.initials: S
authors.lastname: Balasubramanian
mesh_terms: D004247:DNA / Q000737:chemistry*; D054856:G-Quadruplexes; D006801:Humans; D007700:Kinetics; D008024:Ligands; D008956:Models, Chemical; D015394:Molecular Structure; D010455:Peptides / Q000737:chemistry*; D011485:Protein Binding; D016615:Telomere / Q000737:chemistry
chemical_list: D008024:Ligands; D010455:Peptides; D004247:DNA