title: Concentration-dependent conformational changes in GQ-forming ODNs.
abstract: Guanine-rich oligodeoxyribonucleotides (ODNs) can form non-canonical DNA structures known as G-quadruplexes, which are four stranded structures stabilized by sodium or potassium cations. The topologies of G-quadruplexes are highly polymorphic. H-Tel, an ODN with four consecutive repeats of the human telomeric sequence, [d(AGGGTTAGGGTTAGGGTTAGGG)], can assume different monomolecular G-quadruplex topologies depending on the type of cation present in solution. Our previous work demonstrated that at high concentrations of H-Tel, the monomolecular G-quadruplexes formed by H-Tel self-associate to form higher order structures. The aggregates display circular dichroism (CD) spectra similar to that of an all-parallel structure. In the current work, we present data for 19 ODNs for which we have modified the loop sequences of H-Tel in order to learn if concentration-dependent self-aggregation is a general phenomenon and to probe the contribution of the loops to the self-association of these ODNs. Our studies use CD spectroscopy and spectroscopically monitored heat denaturation. Our data show that the concentration-dependent formation of parallel G-quadruplex aggregates is a general phenomenon. We propose that one of the factors that might affect this process is the association of partially unfolded antiparallel structures.
authors.affiliation: Department of Pharmaceutical Sciences, University of Toronto, Canada.
authors.forename: Yang Yun
authors.initials: YY
authors.lastname: Li
authors.affiliation: Department of Pharmaceutical Sciences, University of Toronto, Canada.
authors.forename: Rashid
authors.initials: R
authors.lastname: Abu-Ghazalah
authors.affiliation: Department of Pharmaceutical Sciences, University of Toronto, Canada.
authors.forename: Bita
authors.initials: B
authors.lastname: Zamiri
authors.affiliation: Department of Pharmaceutical Sciences, University of Toronto, Canada. Electronic address: rob.macgregor@utoronto.ca.
authors.forename: Robert B
authors.initials: RB
authors.lastname: Macgregor
mesh_terms: D002942:Circular Dichroism; D054856:G-Quadruplexes; D006147:Guanine / Q000737:chemistry; D006801:Humans; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000737:chemistry*
chemical_list: D009838:Oligodeoxyribonucleotides; D006147:Guanine