Effects of DNA on driving force dependence of photoinduced electron transfer from the excited state of tris(2,2-bipyridine)ruthenium(II) to intercalators in DNA: Distinction between intra-and inter-DNA pathways

Shunichi Fukuzumi, Makiko Tanaka, Mari Nishimine, Kei Ohkubo

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12 Scopus citations

Abstract

Photoinduced electron transfer (ET) dynamics from the excited state of a ruthenium complex [Ru(bpy)32+ (bpy = 2,2′-bipyridine)] to a series of intercalators in DNA, 9-substituted-10-methylacridinium ions (AcrR+, R = H, CH2Ph, Pri and Ph), 3-substituted-1-methylquinolinium ions (RQuH+, R = H, Me, CN and Br) and 4- and 5-methylphenanthridinium ions (4- and 5-MePhen+), were examined from the emission decay profiles of Ru(bpy)32+ in the absence and presence of DNA in an aqueous solution. Intercalation of AcrH+ to DNA is found to result in inhibition of hydride transfer from an NADH model compound, 1-benzyl-1,4-dihydronicotinamide, to AcrH+. In contrast, the rate constants of photoinduced ET of intercalated molecules to DNA become much larger than those of free intercalators in solution due to the positive shift in the one-electron reduction potentials by the intercalation into DNA. The intramolecular pathway of photoinduced ET from Ru(bpy)32+* bound electrostatically to DNA to intercalators bound to the same DNA molecule has been distinguished from the intermolecular pathway of photoinduced ET of intercalators bound to a different DNA molecule. The occurrence of photoinduced ET is examined by laser flash photolysis experiments which show the transient absorption spectra of the one-electron reduced intercalator when the ET is exergonic. The resulting data were analyzed in light of the Marcus theory of ET to determine reorganization energies of ET in DNA as well as in an aqueous solution.

Original languageEnglish
Pages (from-to)79-88
Number of pages10
JournalJournal of Photochemistry and Photobiology A: Chemistry
Volume175
Issue number2-3
DOIs
StatePublished - 31 Oct 2005

Bibliographical note

Funding Information:
This work was partially supported by Grants-in-Aid for Scientific Research (No. 13440216) from the Ministry of Education, Culture, Sports, Science and Technology, Japan.

Keywords

  • DNA
  • Electron transfer
  • Intercalation
  • Marcus theory
  • Reorganization energy

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