title: Calculation of the HOMO localization of Tetrahymena and Oxytricha telomeric quadruplex DNA.
abstract: Several guanine-rich sequences exist in many important regions, such as telomeres, and these sequences can form quadruplex DNA structures. It was previously reported that 3'-guanines are mainly oxidized in the Tetrahymena and Oxytricha telomeric quadruplex DNA, d(TGGGGT)4, and 5'-guanines are mainly oxidized in the human telomeric quadruplex DNA, d(TAGGGT)4T. We speculated that the differences in site reactivity between d(TGGGGT)4 and d(TAGGGT)4T are induced by the localization of the HOMO. The HOMOs of the possible quadruplex structures were thus determined and the results showed that the HOMOs of d(TGGGGT)4 +3K(+) and d(TAGGGT)4T +2K(+) localized at the 5'-guanine, and that the HOMO shifted from the 5'-guanine to the 3'-guanine by the addition of a 5'-capping cation. Furthermore, we determined the influence of the cation and demonstrated that localization of the HOMO at the G-quartet plane located immediately adjacent to the cation is disfavored. The calculated HOMO localization of d(TGGGGT)4 +4K(+) and d(TAGGGT)4T +2K(+) matched the experimental results and suggest that d(TGGGGT)4 contains a 5'-capping cation in solution.
authors.affiliation: Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, 1314-1 Shido, Sanuki, Kagawa 769-2193, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Morikawa
authors.affiliation: Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, 1314-1 Shido, Sanuki, Kagawa 769-2193, Japan. Electronic address: kkino@kph.bunri-u.ac.jp.
authors.forename: Katsuhito
authors.initials: K
authors.lastname: Kino
authors.affiliation: Faculty of Science, Department of Chemistry, Shizuoka University, 836 Ohya, Suruga, Shizuoka 422-8529, Japan.
authors.forename: Takanori
authors.initials: T
authors.lastname: Oyoshi
authors.affiliation: Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, 1314-1 Shido, Sanuki, Kagawa 769-2193, Japan.
authors.forename: Masayo
authors.initials: M
authors.lastname: Suzuki
authors.affiliation: Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, 1314-1 Shido, Sanuki, Kagawa 769-2193, Japan.
authors.forename: Takanobu
authors.initials: T
authors.lastname: Kobayashi
authors.affiliation: Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, 1314-1 Shido, Sanuki, Kagawa 769-2193, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Miyazawa
mesh_terms: D002412:Cations / Q000737:chemistry; D004247:DNA / Q000737:chemistry* / Q000235:genetics; D054856:G-Quadruplexes; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D010084:Oxidation-Reduction; D016813:Oxytricha / Q000737:chemistry* / Q000235:genetics; D016615:Telomere / Q000737:chemistry* / Q000235:genetics; D013768:Tetrahymena / Q000737:chemistry* / Q000235:genetics
chemical_list: D002412:Cations; D004247:DNA
keywords: DNA damage; G-quadruplexes; Photooxidation