title: Femtosecond dynamics of the DNA intercalator ethidium and electron transfer with mononucleotides in water.
abstract: Ethidium (E) is a powerful probe of DNA dynamics and DNA-mediated electron transfer (ET). Molecular dynamical processes, such as solvation and orientation, are important on the time scale of ET. Here, we report studies of the femtosecond and picosecond time-resolved dynamics of E, E with 2'deoxyguanosine triphosphate (GTP) in water, and E with 7-deaza-2'-deoxyguanosine triphosphate (ZTP) in water; E undergoes ET with ZTP but not GTP. These studies elucidate the critical role of relative orientational motions of the donor-acceptor complex on ET processes in solution. For ET from ZTP to E, such motions are in fact the rate-determining step. Our results indicate that these complexes reorient before ET. The time scale for the solvation of E in water is 1 ps, and the orientational relaxation time of E is 70 ps. The impact of orientational and solvation effects on ET between E and mononucleotides must be considered in the application of E as a probe of DNA ET.
authors.affiliation: Laboratory for Molecular Science, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, CA 91125, USA.
authors.forename: T
authors.initials: T
authors.lastname: Fiebig
authors.forename: C
authors.initials: C
authors.lastname: Wan
authors.forename: S O
authors.initials: SO
authors.lastname: Kelley
authors.forename: J K
authors.initials: JK
authors.lastname: Barton
authors.forename: A H
authors.initials: AH
authors.lastname: Zewail
mesh_terms: D004247:DNA; D003848:Deoxyguanine Nucleotides / Q000737:chemistry; D004583:Electrons; D004996:Ethidium / Q000737:chemistry*; D005454:Fluorescence Polarization; D006160:Guanosine Triphosphate / Q000737:chemistry; D007364:Intercalating Agents / Q000737:chemistry*; D007700:Kinetics; D008958:Models, Molecular; D008968:Molecular Conformation; D013050:Spectrometry, Fluorescence / Q000295:instrumentation / Q000379:methods