title: Inverting the G-Tetrad Polarity of a G-Quadruplex by Using Xanthine and 8-Oxoguanine.
abstract: G-quadruplexes are four-stranded nucleic acid structures that are built from consecutively stacked guanine tetrad (G-tetrad) assemblies. The simultaneous incorporation of two guanine base lesions, xanthine (X) and 8-oxoguanine (O), within a single G-tetrad of a G-quadruplex was recently shown to lead to the formation of a stable G⋅G⋅X⋅O tetrad. Herein, a judicious introduction of X and O into a human telomeric G-quadruplex-forming sequence is shown to reverse the hydrogen-bond polarity of the modified G-tetrad while preserving the original folding topology. The control exerted over G-tetrad polarity by joint X⋅O modification will be valuable for the design and programming of G-quadruplex structures and their properties.
authors.affiliation: School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371 (Singapore).
authors.forename: Vee Vee
authors.initials: VV
authors.lastname: Cheong
authors.affiliation: School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371 (Singapore).
authors.forename: Christopher Jacques
authors.initials: CJ
authors.lastname: Lech
authors.affiliation: School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371 (Singapore).
authors.forename: Brahim
authors.initials: B
authors.lastname: Heddi
authors.affiliation: School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371 (Singapore). phantuan@ntu.edu.sg.
authors.forename: Anh Tuân
authors.initials: AT
authors.lastname: Phan
mesh_terms: D054856:G-Quadruplexes; D006147:Guanine / Q000031:analogs & derivatives* / Q000737:chemistry; D006860:Hydrogen Bonding; D008968:Molecular Conformation; D019820:Xanthine / Q000737:chemistry*
chemical_list: D019820:Xanthine; C024829:8-hydroxyguanine; D006147:Guanine
keywords: 8-oxoguanine; DNA structures; G-quadruplexes; NMR spectroscopy; xanthine