title: Analysis of guanine oxidation products in double-stranded DNA and proposed guanine oxidation pathways in single-stranded, double-stranded or quadruplex DNA.
abstract: Guanine is the most easily oxidized among the four DNA bases, and some guanine-rich sequences can form quadruplex structures. In a previous study using 6-mer DNA d(TGGGGT), which is the shortest oligomer capable of forming quadruplex structures, we demonstrated that guanine oxidation products of quadruplex DNA differ from those of single-stranded DNA. Therefore, the hotooxidation products of double-stranded DNA (dsDNA) may also differ from that of quadruplex or single-stranded DNA, with the difference likely explaining the influence of DNA structures on guanine oxidation pathways. In this study, the guanine oxidation products of the dsDNA d(TGGGGT)/d(ACCCCA) were analyzed using HPLC and electrospray ionization-mass spectrometry (ESI-MS). As a result, the oxidation products in this dsDNA were identified as 2,5-diamino-4H-imidazol-4-one (Iz), 8-oxo-7,8-dihydroguanine (8oxoG), dehydroguanidinohydantoin (Ghox), and guanidinohydantoin (Gh). The major oxidation products in dsDNA were consistent with a combination of each major oxidation product observed in single-stranded and quadruplex DNA. We previously reported that the kinds of the oxidation products in single-stranded or quadruplex DNA depend on the ease of deprotonation of the guanine radical cation (G•+) at the N1 proton. Similarly, this mechanism was also involved in dsDNA. Deprotonation in dsDNA is easier than in quadruplex DNA and more difficult in single-stranded DNA, which can explain the formation of the four oxidation products in dsDNA.
authors: Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, 1314-1 Shido, Sanuki, Kagawa 769-2193, Japan. s110702@stu.bunri-u.ac.jp.
authors: Masayuki
authors: M
authors: Morikawa
authors: Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, 1314-1 Shido, Sanuki, Kagawa 769-2193, Japan. kkino@kph.bunri-u.ac.jp.
authors: Katsuhito
authors: K
authors: Kino
authors: Faculty of Science, Department of Chemistry, Shizuoka University, 836 Ohya, Suruga, Shizuoka 422-8529, Japan. stohyos@ipc.shizuoka.ac.jp.
authors: Takanori
authors: T
authors: Oyoshi
authors: Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, 1314-1 Shido, Sanuki, Kagawa 769-2193, Japan. s120002@stu.bunri-u.ac.jp.
authors: Masayo
authors: M
authors: Suzuki
authors: Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, 1314-1 Shido, Sanuki, Kagawa 769-2193, Japan. kobayashit@kph.bunri-u.ac.jp.
authors: Takanobu
authors: T
authors: Kobayashi
authors: Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, 1314-1 Shido, Sanuki, Kagawa 769-2193, Japan. miyazawah@kph.bunri-u.ac.jp.
authors: Hiroshi
authors: H
authors: Miyazawa
mesh_terms: D004247:DNA / Q000737:chemistry*; D004249:DNA Damage / Q000528:radiation effects; D004277:DNA, Single-Stranded / Q000737:chemistry*; D054856:G-Quadruplexes; D006147:Guanine / Q000737:chemistry*; D008027:Light; D010084:Oxidation-Reduction / Q000528:radiation effects
chemical_list: D004277:DNA, Single-Stranded; D006147:Guanine; D004247:DNA