Selective Enhancement of the One-Electron Oxidation of Guanine by Base Pairing with Cytosine

Kawai, Kiyohiko; Wata, Yasuharu; Ichinose, Nobuyuki; Majima, Tetsuro

doi:10.1002/1521-3773(20001201)39:23<4327::aid-anie4327>3.0.co;2-6

Cited by 37 publications

(38 citation statements)

References 18 publications

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“…11 The shorter distance between steps in triplex versus duplex DNA (3.3 vs. 3.4 Å) should result in increased mixing. In addition, increased hydrogen bonding in the triplex versus duplex should lower the oxidation potential of adenine in the bridging T:A⋅T triples 12. Both factors could contribute to the decrease in β for triplex versus duplex charge separation.…”

Section: Fluorescence Quantum Yields and Transient Decay Times For Comentioning

confidence: 99%

DNA-Mediated Electron Transfer across Synthetic T:A⋅T Triplex Structures

Lewis

Hayes

et al. 2002

Angew. Chem. Int. Ed.

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Oligonucleotides which contain three sequences capable of triplex formation, and which are connected with appropriate linkers, can fold into intramolecular triplex structures. [1] Both natural and synthetic linkers have been used to assemble intramolecular T:A¥T triplexes in which poly(T:A) forms a normal Watson±Crick duplex and the third strand (polyT) is parallel to the polyA sequence and associated by Hoogsteen hydrogen bonding (Figure 1 a,b). [2±4] The conformation of intermolecular poly(T:A¥T) triplexes is similar to that of duplex B-DNA with a p-stacking distance of 3.3 ä and a helical pitch of 288. We report here the preparation of the donor±acceptor intramolecular triplex DNA structures 1±5 which possess a stilbenedicarboxamide derivative (Sa) as an electron-acceptor linker and a stilbenediether derivative (Sd) as an electron-donor linker (Figure 1 c,d). The two chromophores undergo intramolecular, photoinduced electron transfer across the p-stacked triplets by single-step tunneling (for 1±4) and multistep hopping (for 5) pathways.The conjugates 1±5 were prepared by conventional phosphoramidite methods as previously described for the preparation of Sa-and Sd-linked hairpins. [5,6] The 3'-3' linkages between the Watson±Crick T:A hairpin sequence and the Hoogsteen-bound polyT were formed by 5' solid-phase oligonucleotide synthesis. The absorption spectra of conjugates 1±5 consist of a broad, long wavelength band with a maximum at 340 nm that is attributed to the overlapping absorptions of the Sa and Sd chromophores and a band at 260 nm attributed to absorption of these chromophores and the nucleobases. [7] The thermal dissociation profiles are independent of concentration and display melting transitions at between 60±71 8C, which are attributed to melting of the Sd-capped Sa-linked Watson±Crick duplex, and premelting behavior at lower temperatures, which is attributed to melting of the Hoogsteen base pairs. [8] The fluorescence spectra of the conjugates 1±5 are similar to those of Sa-linked hairpins such as 6. [5] The Sa-linked poly(T:A) hairpins are strongly fluorescent, whereas the Sdlinked hairpins are very weakly fluorescent, as a consequence of quenching of the singlet form of Sd by neighboring thymine. [6] The fluorescence intensity of 1±5 is strongest when excited in the red edge of the 340 nm absorption band, where Sa absorbs more strongly than Sd. The value of F f for conjugates 1±4 decreases as the number of T:A¥T steps separating the Sa and Sd chromophores decreases (Table 1), [7] in accord with an electron-transfer mechanism for fluorescence quenching of Sa by Sd. The free energy of the photochemical electron transfer process can be estimated using Weller©s equation [DG et ¼ À(E S þ E rdn ) þ E ox ], using the Sa singlet excitation energy (E s ¼ 3.35 V) and ground-state reduction potential E rdn ¼ À1.91 V (vs. SCE in DMF solution) and the Sd oxidation potential (E ox ¼ 0.92 V). [5,6] The resulting value of DG et ¼ À0.52 eV shows that this reaction is more exergonic than quenching of Sa by G (DG...

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Section: Fluorescence Quantum Yields and Transient Decay Times For Comentioning

confidence: 99%

DNA-Mediated Electron Transfer across Synthetic T:A⋅T Triplex Structures

Lewis

Hayes

et al. 2002

Angew. Chem. Int. Ed.

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“…The intermediate reaction products O 2 ‐radical anion, H 2 O 2 and the highly reactive OH radical are potent electrophilic oxidants, which react rapidly with cellular DNA 7. In DNA, guanine is the major target for oxidative DNA damage because it has the lowest oxidation potential among the DNA bases 8–12. In the last decade a large number of such guanine derived DNA lesions were characterized 13–23.…”

Section: Introductionmentioning

confidence: 99%

Synthesis, Stability, and Conformation of the Formamidopyrimidine G DNA Lesion

Burgdorf

Carell

2002

Chem. Eur. J.

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The formamidopyrimidine (FapydGua) lesion, derived from the nucleobase guanine, is a major DNA lesion involved in mutagenesis and carcinogenesis. To date, the chemical information available about this main lesion is very limited. Herein, we describe a synthesis and a detailed characterization of the acetyl-protected monomer of the FapydGua lesion. Stability studies in DMSO and in water/acetonitrile show that the N-glycosidic bond, previously thought to be highly labile, is much more stable than anticipated. Decomposition of the FapydGua lesion proceeds with half-life times of 37.8 h for the beta-anomer and 65.2 h for the alpha-anomer in water/acetonitrile. The relaxation time for the anomerization reaction was determined to tau = 6.5 h at room temperature. Most important, it was found that the formamido group, which is critical for the lesion recognition process by repair enzymes, is fixed in the cis-conformation in apolar solvents such as chloroform. This conformation enables the formation of a hydrogen bond between the carbonyl oxygen of the formamide and the NH of the N-glycosidic bond within the framework of a seven-membered ring system. This has consequences for the recognition of the lesion by repair enzymes (hOGG1 and Fpg protein). These enzymes were so far believed to recognize the carbonyl group of the FapydGua lesion. Our investigations show that this carbonyl group is not readily accessible because it is almost buried in the dominating cis-conformation. In agreement with the recent X-ray structure of hOGG1 in complex with 8-oxo-7,8-dihydroguanine-containing DNA, we can conclude that repair enzymes can contact both lesions only via the N(7)-H group, which is a hydrogen-bond acceptor in guanine.

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“…7). In this study, NDI was used as a Sens that can be excited with a first laser at a wavelength of 355 nm [17,19,34,50,51]. First, to assess the feasibility of electron ejection from Sens bound to DNA, a pulse radiolysis-laser flash photolysis of NDI-conjugated ODN (NDI-ODN) was performed ( Fig.…”

Section: Two-color Two-laser Dna Damagementioning

confidence: 99%

Photosensitized one-electron oxidation of DNA

Kawai

Majima

2005

Pure and Applied Chemistry

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Photosensitized one-electron oxidation of DNA has attracted much interest because it causes oxidative damage which leads to mutation, and because it is involved in the basic mechanism of photodynamic therapy. In the present article, we describe the mechanistic study of photosensitized DNA damage, especially addressing the kinetics of hole transfer by adenine(A)-hopping and its effect on the DNA damage. The combination of the transient absorption measurement and DNA damage quantification by high-performance liquid chromatography clearly demonstrate that the yield of the DNA damage correlates well with the lifetime of the charge-separated state caused by A-hopping, showing that hole transfer helps DNA damage. These findings led us to propose a new method to accomplish the efficient DNA damage using a combination of two-color, two-laser irradiation.

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Selective Enhancement of the One-Electron Oxidation of Guanine by Base Pairing with Cytosine

Cited by 37 publications

References 18 publications

DNA-Mediated Electron Transfer across Synthetic T:A⋅T Triplex Structures

DNA-Mediated Electron Transfer across Synthetic T:A⋅T Triplex Structures

Synthesis, Stability, and Conformation of the Formamidopyrimidine G DNA Lesion

Photosensitized one-electron oxidation of DNA

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