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Title: Direct measurement of the dynamics of hole hopping in extended DNA G-tracts. An unbiased random walk. Author: Conron SM, Thazhathveetil AK, Wasielewski MR, Burin AL, Lewis FD. Journal: J Am Chem Soc; 2010 Oct 20; 132(41):14388-90. PubMed ID: 20863110. 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.[Abstract] [Full Text] [Related] [New Search]