title: Hole trapping at N6-cyclopropyldeoxyadenosine suggests a direct contribution of adenine bases to hole transport through DNA.
abstract: Recent studies predict that adenine radical cation (A*+) contributes to the hole-trapping process through long A/T sequences and exists as a real chemical intermediate. However, the experimental evidence for the existence of A*+ has not been observed in the DNA-mediated hole transport reaction. To examine the direct contribution of A*+, we have developed a novel hole-trapping nucleobase N6-cyclopropyldeoxyadenosine (dCPA) which possesses a cyclopropyl group as a radical trapping device. One-electron oxidation of dCPA revealed that dCPA radical cation undergoes a rapid cyclopropane ring opening. With the use of the dCPA-containing DNA, we have demonstrated that the migrating hole was trapped at CPA incorporated into a long A/T bridge between two GG sites. The present results indicate that nucleobases possessing ionization potential higher than that of dG, such as dA, are able to participate directly in the multistep hopping mechanism.
authors.affiliation: Department of Synthetic Chemistry and Biological Chemistry, Faculty of Engineering, Kyoto University, SORST, Japan Science and Technology Corporation, Kyoto 606-8501, Japan. cdohno@caltech.edu
authors.forename: Chikara
authors.initials: C
authors.lastname: Dohno
authors.forename: Atsushi
authors.initials: A
authors.lastname: Ogawa
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Nakatani
authors.forename: Isao
authors.initials: I
authors.lastname: Saito
mesh_terms: D000225:Adenine / Q000737:chemistry*; D001345:Autoradiography; D002412:Cations / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D003521:Cyclopropanes / Q000737:chemistry*; D004247:DNA / Q000737:chemistry*; D003839:Deoxyadenosines / Q000737:chemistry*
chemical_list: D002412:Cations; D003521:Cyclopropanes; D003839:Deoxyadenosines; D004247:DNA; D000225:Adenine