title: Effects of site-specific guanine C8-modifications on an intramolecular DNA G-quadruplex.
abstract: Understanding the fundamentals of G-quadruplex formation is important both for targeting G-quadruplexes formed by natural sequences and for engineering new G-quadruplexes with desired properties. Using a combination of experimental and computational techniques, we have investigated the effects of site-specific substitution of a guanine with C8-modified guanine derivatives, including 8-bromo-guanine, 8-O-methyl-guanine, 8-amino-guanine, and 8-oxo-guanine, within a well-defined (3 + 1) human telomeric G-quadruplex platform. The effects of substitutions on the stability of the G-quadruplex were found to depend on the type and position of the modification among different guanines in the structure. An interesting modification-dependent NMR chemical-shift effect was observed across basepairing within a guanine tetrad. This effect was reproduced by ab initio quantum mechanical computations, which showed that the observed variation in imino proton chemical shift is largely influenced by changes in hydrogen-bond geometry within the guanine tetrad.
authors: School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore.
authors: Christopher Jacques
authors: CJ
authors: Lech
authors: Joefina Kim
authors: JK
authors: Cheow Lim
authors: Jocelyn Mei
authors: JM
authors: Wen Lim
authors: Samir
authors: S
authors: Amrane
authors: Brahim
authors: B
authors: Heddi
authors: Anh Tuân
authors: AT
authors: Phan
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000737:chemistry* / Q000235:genetics; D054856:G-Quadruplexes; D006147:Guanine / Q000737:chemistry*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D011789:Quantum Theory; D013237:Stereoisomerism; D013379:Substrate Specificity; D016615:Telomere / Q000235:genetics; D013696:Temperature
chemical_list: D006147:Guanine; D004247:DNA