title: Mixing ratio-dependent energy transfer from DNA-bound 4',6-diamidino-2-phenylindole to [Ru(1,10-phenanthroline)(2)dipyrido[3,2-a:2',3'-c]phenazine](2+).
abstract: The binding mode of Delta- and Lambda-[Ru(1,10-phenanthroline)(2)dipyrido[3,2-a:2',3'-c]phenazine](2+) ([Ru(phen)(2)DPPZ](2+)) to DNA in the presence of 4',6-diamidino-2-phenylindole (DAPI) at a low and high [DAPI]/[DNA base] ratio (0.02 and 0.20, respectively) was investigated using electric absorption and circular dichroism spectroscopy. The spectral properties of both the Delta- and Lambda-[Ru(phen)(2)DPPZ](2+) were not altered in the presence of DAPI disregarding the [DAPI]/[DNA] ratio, suggesting that the presence of DAPI in the minor groove of DNA does not affect the binding mode of the [Ru(phen)(2)DPPZ](2+) complex to DNA. The transferring excited energy of DAPI to both Delta- and Lambda-[Ru(phen)(2)DPPZ](2+) occurs through Förster type resonance when they both spontaneously bound to DNA. At a high [DAPI]/[DNA] ratios, an upward bending curve in the Stern-Volmer plot, and a shortening the DAPI fluorescence decay time with increasing [Ru(phen)(2)DPPZ](2+) concentration were found. These results indicate that the quenching of the DAPI's fluorescence occurs through both the static and dynamic mechanisms. In contrast, the quenching mechanism at a low [DAPI]/[DNA] ratios was found to be purely static. The static quenching constant decreased linearly with respect to the [DAPI]/[DNA] ratio. Decrease in quenching efficiency can be explained by the association constant of [Ru(phen)(2)DPPZ](2+) to DNA while being within a quenchable distance from a DAPI molecule.
authors.affiliation: Department of Chemistry, Yeungnam University, Dae-dong, Gyeongsan City, Gyeong-buk, 712-749, Republic of Korea.
authors.forename: Ji Yeon
authors.initials: JY
authors.lastname: Choi
authors.forename: Jeong-Mi
authors.initials: JM
authors.lastname: Lee
authors.forename: Hyosun
authors.initials: H
authors.lastname: Lee
authors.forename: Maeng Joon
authors.initials: MJ
authors.lastname: Jung
authors.forename: Seog K
authors.initials: SK
authors.lastname: Kim
authors.forename: Jong Moon
authors.initials: JM
authors.lastname: Kim
mesh_terms: D000818:Animals; D020029:Base Pairing; D002417:Cattle; D004247:DNA / Q000737:chemistry*; D004735:Energy Transfer; D007211:Indoles / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D013050:Spectrometry, Fluorescence
chemical_list: C525677:(Ru(1,10-phenanthroline)2dipyrido(3,2-a:2',3'-c)phenazine)2; D007211:Indoles; D009942:Organometallic Compounds; C007293:DAPI; D004247:DNA