title: Rates of DNA-mediated electron transfer between metallointercalators.
abstract: Ultrafast emission and absorption spectroscopies were used to measure the kinetics of DNA-mediated electron transfer reactions between metal complexes intercalated into DNA. In the presence of rhodium(III) acceptor, a substantial fraction of photoexcited donor exhibits fast oxidative quenching (>3 x 10(10) per second). Transient-absorption experiments indicate that, for a series of donors, the majority of back electron transfer is also very fast (approximately 10(10) per second). This rate is independent of the loading of acceptors on the helix, but is sensitive to sequence and pi stacking. The cooperative binding of donor and acceptor is considered unlikely on the basis of structural models and DNA photocleavage studies of binding. These data show that the DNA double helix differs significantly from proteins as a bridge for electron transfer.
authors.affiliation: Beckman Institute, California Institute of Technology, Pasadena, CA 91125, USA.
authors.forename: M R
authors.initials: MR
authors.lastname: Arkin
authors.forename: E D
authors.initials: ED
authors.lastname: Stemp
authors.forename: R E
authors.initials: RE
authors.lastname: Holmlin
authors.forename: J K
authors.initials: JK
authors.lastname: Barton
authors.forename: A
authors.initials: A
authors.lastname: Hörmann
authors.forename: E J
authors.initials: EJ
authors.lastname: Olson
authors.forename: P F
authors.initials: PF
authors.lastname: Barbara
mesh_terms: D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004247:DNA / Q000737:chemistry* / Q000378:metabolism*; D004579:Electron Transport; D007364:Intercalating Agents / Q000737:chemistry / Q000378:metabolism*; D008024:Ligands; D009690:Nucleic Acid Conformation; D009942:Organometallic Compounds / Q000737:chemistry / Q000378:metabolism*; D010777:Photochemistry; D012238:Rhodium / Q000378:metabolism; D013057:Spectrum Analysis
chemical_list: D007364:Intercalating Agents; D008024:Ligands; D009942:Organometallic Compounds; D004247:DNA; D012238:Rhodium