title: Effect of Mg2+ cations on the dynamics and efficiency of hole transport in DNA.
abstract: The effect of Mg(2+) cations on the electronic spectra and dynamics and efficiency of hole transport has been determined by means of femtosecond time-resolved transient absorption spectroscopy for DNA hairpins possessing stilbene electron acceptor and donor chromophores. The results are compared with those obtained previously for the same hairpins in the presence of Na(+) cations and for one hairpin with no added salt. Quantum yields and rate constants for charge separation are smaller in the presence of Mg(2+) than Na(+), the largest differences being observed for the hairpins with the largest number of base pairs. Slower charge separation is attributed to minor groove binding by Mg(2+), which results in a stiffer duplex structure rather than a change in ground state geometry. Reduction in the Na(+) concentration has little effect on either the dynamics or efficiency of hole transport.
authors.affiliation: Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University , Evanston, Illinois 60208, United States.
authors.forename: Arun Kalliat
authors.initials: AK
authors.lastname: Thazhathveetil
authors.forename: Anton
authors.initials: A
authors.lastname: Trifonov
authors.forename: Michael R
authors.initials: MR
authors.lastname: Wasielewski
authors.forename: Frederick D
authors.initials: FD
authors.lastname: Lewis
mesh_terms: D002412:Cations / Q000737:chemistry*; D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry*; D055029:Inverted Repeat Sequences; D008274:Magnesium / Q000737:chemistry*; D015636:Magnesium Chloride / Q000737:chemistry; D009690:Nucleic Acid Conformation; D055668:Photochemical Processes; D012964:Sodium / Q000737:chemistry; D012965:Sodium Chloride / Q000737:chemistry; D013057:Spectrum Analysis; D013267:Stilbenes / Q000737:chemistry; D014466:Ultraviolet Rays
chemical_list: D002412:Cations; D013267:Stilbenes; D015636:Magnesium Chloride; D012965:Sodium Chloride; D004247:DNA; D012964:Sodium; D008274:Magnesium