The rate at which electrons and holes move along DNA is sufficient to prevent strand-cleavage reactions, but too slow to make DNA a useful molecular wire.
Oxidative damage yields isolated electrons and their corresponding "holes" that can migrate along DNA. In the 6 July Nature Lewis et al. determine rate constants of ~5x107 s-1 and 5x106 s-1, respectively, for forward and return hole transport from a single guanine base to a double guanine base across a single adenine (Nature 2000, 406:51-53). These rates mean that electrons do not linger long enough to participate in strand-cleavage reactions. But the electrons move too slowly to avoid charge recombination, so DNA cannot act as a useful molecular wire.
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