Electron transfer between physically bound electron donors and acceptors: a fluorescence blob model approach.
The present study reports on the applicability of the fluorescence blob model (FBM) to analyze the complex fluorescence decays obtained with DNA-intercalated ethidium bromide (EB) as it transfers an electron to copper cations bound to the DNA helix. Traditionally, the information retrieved about the electron transfer process taking place between an electron donor intercalated in DNA and an electron acceptor physically and randomly bound to DNA has been limited due to the distribution of distances that quenching can occur over, which leads to a distribution of rate constants resulting in complex fluorescence decays. These complications can be overcome by analyzing the fluorescence data with a fluorescence blob model (FBM) that allows for the study of fluorescence quenching between fluorophores and quenchers randomly spaced along a polymeric backbone. The fluorescence decays obtained for EB intercalated between two DNA base pairs (bp) as it transfers an electron to copper randomly bound to the DNA were well fit with the FBM. In the FBM analysis, electron transfer is characterized by the size of a blob in term of base pairs, N(blob), over which electron transfer occurs, as well as the rate constant of electron transfer inside a blob, k(blob). The present work demonstrates that electron transfer between intercalated EB and randomly bound copper occurs over an average distance that increases with increasing duplex length up to a duplex length of 12 bp, beyond which the distance over which electron transfer occurs remains constant with duplex length and equals 10.8 ± 0.4 bp.
Keyes
Christine
C
Institute for Polymer Research, Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada.
Duhamel
Jean
J
D000818:Animals; D001483:Base Sequence; D002417:Cattle; D003300:Copper / Q000737:chemistry*; D004247:DNA / Q000737:chemistry*; D004579:Electron Transport; D004583:Electrons; D004996:Ethidium / Q000737:chemistry*; D005453:Fluorescence; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D012996:Solutions; D013050:Spectrometry, Fluorescence; D013997:Time Factors
D012996:Solutions; D003300:Copper; D004247:DNA; D004996:Ethidium