## Abstract

In this paper we present a self-consistent kinetic-quantum mechanical analysis of chemical yield data for hole trapping/detrapping in G^{+}(T-A)_{m}GGG duplexes (with free energy gaps Δ_{t}) and for hole hopping/trapping/detrapping in G^{+}[(T)_{m}G]_{n}(T)_{m}GGG duplexes of DNA. Bridge specificity of hole trapping/detrapping by GGG traps was specified by superexchange electronic contributions, inferred from electronic coupling matrix elements between nearest-neighbor nucleobases and semiempirical energy gaps, and energetic contributions, which determine the nuclear Franck-Condon factors. Unistep hole-trapping yields are accounted for by a weak bridge length dependence for short (N = 1, 2) bridges, due to detrapping. Marked bridge specificity is manifested for short (N = 1, 2) bridges, being distinct for (T)_{N} and for [(A)_{m+1}(T)_{m'}]_{n} (m, m' ≥ 0 and N = n(m + m' + 1)) bridges. For long (N > 2) bridges an exponential bridge size dependence of the trapping yields prevails. Multistep hole transport results in different reaction rates of G^{+} (rate k_{d}) and of (GGG)^{+} (rate k_{dt}) with water, i.e., k_{d}/k_{dt} = 1.6, which, in conjunction with the unistep trapping/detrapping data, results in the free energy gaps for hole trapping of Δ_{t} = 0.096 eV in the G^{+}(T)_{N}GGG duplexes and of Δ_{t} = 0.062 eV in the G^{+}[(A)_{m+1}(T)_{m'}]_{n}GGG duplexes.

Original language | English |
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Pages (from-to) | 10322-10328 |

Number of pages | 7 |

Journal | Journal of Physical Chemistry A |

Volume | 105 |

Issue number | 45 |

DOIs | |

State | Published - 15 Nov 2001 |