title: Direct measurement of the dynamics of hole hopping in extended DNA G-tracts. An unbiased random walk.
abstract: We report the measurement of distance- and temperature-dependent rate constants for charge separation in capped hairpins in which a stilbene hole acceptor and hole donor are separated by A(3)G(n) diblock polypurine sequences consisting of 3 adenines and 1-19 guanines. The longer diblock systems obey the simplest model for an unbiased random walk, providing a direct measurement of k(hop) = 4.3 × 10(9) s(-1) for a single reversible G-to-G hole hopping step, somewhat faster than the value of 1.2 × 10(9) s(-1) calculated for A-tract hole hopping. The temperature dependence for hopping in A(3)G(13) provides values of E(act) = 2.8 kcal/mol and A = 7 × 10(9) s(-1), consistent with a weakly activated, conformationally gated process.
authors.affiliation: Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208, USA.
authors.forename: Sarah M Mickley
authors.initials: SM
authors.lastname: Conron
authors.forename: Arun K
authors.initials: AK
authors.lastname: Thazhathveetil
authors.forename: Michael R
authors.initials: MR
authors.lastname: Wasielewski
authors.forename: Alexander L
authors.initials: AL
authors.lastname: Burin
authors.forename: Frederick D
authors.initials: FD
authors.lastname: Lewis
mesh_terms: D004247:DNA / Q000737:chemistry*; D006147:Guanine / Q000737:chemistry*; D007700:Kinetics; D013057:Spectrum Analysis; D013696:Temperature
chemical_list: D006147:Guanine; D004247:DNA