Weak Distance Dependence of Excess Electron Transfer in DNA

Abstract

Reduktive Fernreparatur von Thymin‐Dimeren in einem DNA‐Duplex durch Transfer von Überschusselektronen über eine Entfernung bis zu ca. 24 Å (n=7) lässt sich auf thermisch aktiviertes Elektronen‐„Hüpfen“ zurückführen (siehe Schema). Eine mögliche Konsequenz: Die schädigende Wirkung von UV‐Strahlung als eine Ursache der Entstehung von Hautkrebs könnte durch Verbindungen unterdrückt werden, die an DNA binden und weit reichenden Elektronentransport ermöglichen.

Bioinspired molecular electrets: bottom-up approach to energy materials and applications

“…47,48 That is, multiple short and efficient "electron hopping" steps along arrays of redox moieties allow ET to exceed the 2-nm tunneling limit. [48][49][50][51][52] Deoxyribonucleic acid (DNA) strands represent a class of biopolymers that can mediate CT at distances exceeding 2 nm. [53][54][55][56][57] Short efficient tunneling steps between closely situated bases, with relatively negative reduction potentials of their radical cations, mediate hole hopping.…”

“…(In a case of tunneling, the CT rates, k CT , fall off exponentially with donor-acceptor distance, rðDAÞ, i.e., k CT ∝ ε −βrðDAÞ , while in a case of hopping, they fall off as an inverse of the number of hopping sites, N, i.e., k CT ∝ 1∕N η .) [49][50][51] As an alternative to DNA, peptide nucleic acid (PNA) strands present certain advantages for long-range hole hopping. [58][59][60][61] The smaller helical twist of PNA, in comparison with DNA, improves the electronic coupling between neighboring bases.…”

Excess Electron Transfer in Flavin-Capped DNA-Hairpins

“…Upon single-electron reduction, this dimer will induce a strand break as recently described by us. [12,35] Hairpin 19 is stable as long as the flavin molecule exists in the oxidized state. For the electron injection experiment, we prepared a solution of hairpin 19 in Tris-buffer (10 m Tris, c DNA ϭ 20 µ, pH ϭ 7.4) and added 50 µL of Figure 6.…”

“…[10,11] We are currently investigating how excess electrons as negative charges move through DNA. [12,13] In this context, γ-irradiation studies suggest that excess electrons might hop through DNA as well. [14Ϫ18] Sevilla and co-workers proposed a thermally activated excess electron hopping mechanism at temperatures above Ϫ70°C, while below this temperature superexchange is believed to dominate.…”

“…[12] These studies were possible because a flavin in its reduced and deprotonated redox state could be inserted into DNA, where it functions as a strong electron donor. This unusual donor possesses a very negative reduction potential of at least Ϫ2.6 V, [19,20] which is low enough to achieve efficient single-electron reduction of pyrimidines and cyclobutane pyrimidine dimers.…”