Isomerization of DNA-bound distilbazolium ligand induced by electron transfer from photoexcited tris(1,10-phenanthroline)Ru(II).
The ability of the DNA duplex to behave as an efficient organized medium for cis-trans isomerization induced by electron transfer (ET) has been explored. Isomerization studies, luminescence quenching and DNA photocleavage assays show that photoexcited Ru(1,10-phenanthroline [phen])3(2+) transfers an electron to E,Z1,4-bis[2-(1-methylpyridinium-4-yl)vinyl]benzene (E,Z pMPVB), which subsequently undergoes one-way isomerization to E,E pMPVB. The unusual feature of the system is manifested by the lack of friction that is usually imposed on the photoisomerizable ligand by highly organized media. The apparent rate of ET in DNA increases when compared with the homogeneous solution. However, after correction for the local concentration of the reagents onto the biopolymer, the rate constant becomes independent of the DNA concentration and is at least 4 x 10(2) times smaller than that in the homogeneous aqueous solution. Using the photoinduced isomerization system, a large enhancement in the efficiency of single-strand break formation was found in plasmid DNA over that for Ru(phen)3(+2) alone using irradiation at lambda > 480 nm.
Juskowiak
B
B
Department of Analytical Chemistry, Faculty of Chemistry, A. Mickiewicz University, 60-780 Poznan, Grunwaldzka 6, Poland. juskowia@main.amu.edu.pl
Dominiak
A
A
Takenaka
S
S
Takagi
M
M
D004247:DNA / Q000737:chemistry* / Q000528:radiation effects*; D004579:Electron Transport; D007536:Isomerism; D008024:Ligands; D009942:Organometallic Compounds; D010618:Phenanthrolines; D010777:Photochemistry; D012428:Ruthenium
D008024:Ligands; D009942:Organometallic Compounds; D010618:Phenanthrolines; C034282:tris-(1,10-phenanthroline)ruthenium; D012428:Ruthenium; D004247:DNA; C025205:1,10-phenanthroline