| Budget Amount *help |
¥13,300,000 (Direct Cost: ¥13,300,000)
Fiscal Year 2002: ¥5,500,000 (Direct Cost: ¥5,500,000)
Fiscal Year 2001: ¥7,800,000 (Direct Cost: ¥7,800,000)
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| Research Abstract |
While the mechanism of DNA mediated hole transport is a subject of controversy, it is now evident from remote guanine (G) oxidation of duplex DNAs containing a tethered oxidant that G radical cation (hole) migrates distance through DNA _<TT>-stack. Due to lower ionization potentials of GG and GGG than single G, these stacked G sites function as a thermodynamic sink of holes eventually producing, (piperidine labile sites. In principle, hole migration from hole donor to acceptor competes with hole trapping by water and/or oxygen. Therefore, overall efficiency of hole transfer is primarily determined by the rates of hole migration and hole trapping. When the rate of hole trapping is much slower than hole migration rate, equilibration of hole between donor and acceptor can be achieved. While the rate of hole migration can be attenuated by changing the potential energy gap between hole donor and acceptor, the modulation of hole transport efficiency by changing the rate of hole trapping has never been demonstrated. We report a novel hole-trapping nucleoside N2-cyclopropyl2'-deoxyguanosine 1 (dCPG), which possesses a cyclopropyl group on N2 as a radical-trapping device. One electron oxidation of dCPG by photoexcited riboflavine induces homolytic cyclopropane ring opening as evidenced by the formation of N2-(3-hydroxypropanoyl)dG 2. With the use of dCPG -containing duplex, we have demonstrated that dCPG efficiently terminates DNA mediated hole transport at its own site.
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