Observation of Hole Transfer through DNA by Monitoring the Transient Absorption of Pyrene Radical Cation

Kawai, Kiyoshi; Takada, Tadao; Tojo, Sachiko; Ichinose, Nobuyuki; Majima, Tetsuro

doi:10.1021/ja0158152

Cited by 79 publications

(85 citation statements)

References 21 publications

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“…Gel electrophoretic analysis clearly demonstrated that the hole can migrate over 100 Å, whereas time-resolved transient absorption measurement was limited to the kinetics of the single-step (26) or short-distance (29,30) hole transfer. To our knowledge, there is no reliable report for the kinetics of the multistep long-distance hole transfer because of the difficulty of efficiently generating a hole in DNA, and therefore, the kinetics of the long-distance hole transfer still remains unclear.…”

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Direct observation of hole transfer through double-helical DNA over 100 Å

Takada

Kawai

Fujitsuka

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

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162

177

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Mechanism of photo-induced electron transfer and the subsequent hole transfer in DNA has been studied extensively, but so far we are not aware of any reliable report of the observation of the long-distance hole-transfer process. In this article, we demonstrate the results of direct observation for the long-distance hole transfer in double-helical DNA over 100 Å with time-resolved transient absorption measurements. DNA conjugated with naphthalimide (NI) and phenothiazine (PTZ) (which worked as electron-acceptor and donor molecules, respectively) at both 5 ends was synthesized to observe the hole-transfer process. Site-selective charge injection into G by means of the adenine-hopping process was accomplished by excitation of NI with a 355-nm laser flash. Transient absorption around 400 nm, which was assigned to the NI radical anion, was observed immediately after the irradiation of a laser flash, indicating that the charge separation between NI and the nearest G occurred. Then, the transient absorption of the PTZ radical cation (PTZ •؉ ) at 520 nm was emerged, which was attributed to the hole transfer through DNA to the PTZ site. By monitoring the time profiles of the transient absorption of PTZ •؉ for NI-A6-(GA)n-PTZ and NI-A6-(GT)n-PTZ (n ‫؍‬ 2, 3, 4, 6, 8, 12) (base sequences correspond to those for DNA modified with NI), the long-distance hole-transfer process from G to PTZ, which occurred in the time scale of microsecond to millisecond, was observed directly. By assuming an average distance of 3.4 Å between base-pairs, total distance reaches 100 Å for n ‫؍‬ 12 sequences. Our results clearly show the direct observation of the long-distance hole transfer over 100 Å.D ouble-helical DNA, which has unique structural properties, is a promising candidate for molecular electronic devices and a scaffold for two-and three-dimensional nanostructures (1, 2). Mechanistic studies of charge transfer in DNA have attracted considerable attention because of their relevance to the development of DNA molecular wires (3) and the involvement in DNA oxidative lesion and strand cleavage (4, 5). There are many mechanistic studies for the ''one-dimensional'' conductivity in the double helix (6-8). Factors controlling charge-transfer properties in DNA (such as electronic coupling between donor and acceptor, structural dynamics, reorganization energy, etc.) have been discussed (9-14), and the mechanism for charge transfer, especially hole transfer over long distances in DNA, is the subject of experimental and theoretical studies.Generally, experimental studies of charge transfer in DNA have been performed by time-resolved measurements and electrophoresis analysis (15)(16)(17)(18)(19). A model of a multistep holehopping mechanism, which was proposed by Giese and coworkers (20), is the most widely adopted. An alternative mechanism in which delocalized hole migrates by means of a polaron-like mechanism was proposed by Schuster and coworkers (18). Strand-cleavage studies using PAGE analysis have provided valuable information about the seque...

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confidence: 99%

Direct observation of hole transfer through double-helical DNA over 100 Å

Takada

Kawai

Fujitsuka

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

162

177

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“…A linear correlation between ln k cr and ∆r was obtained to provide the β-value of 0.4 Å -1 which is a little smaller than that for the duplex DNA (Fig. 4) [11][12][13]25]. This might be attributed to the difference in the tunneling energy between the donor or acceptor and bridge states [26,27], or to the structure of the hairpin ODN containing the consecutive A sequence.…”

Section: K Kawai and T Majimamentioning

confidence: 88%

“…The efficiency of the photoinduced one-electron oxidation of DNA is seemingly low since the charge recombination rate is usually much faster than the process leading to the DNA strand cleavage, such as the reaction of G ؒ+ with water [10,13,30]. Hole transfer by G-hopping is also too slow to compete with charge recombination.…”

Section: Lifetime Of Charge-separated State and Photosensitized Dna Dmentioning

confidence: 99%

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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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“…However, the efficiency of producing photosensitized DNA damage is low because the charge recombination rate is usually much faster than the process leading to DNA damage, such as the reaction of GC + with water. [5][6][7][8] Thus, the absorption of a photon by Sens occasionally leads to DNA damage, but only with the aid of hole transfer, which provides time for DNAC + and SensC À to react with water or O 2 . [9][10][11][12][13][14] Herein, we report the first study of nanosecond-laser DNA damaging in which a combination of two-color pulses is used as a promising new strategy to reach a high DNA-damaging efficiency.…”

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confidence: 99%