Photoinduced reactions, molecular chemical methods

The study of photoinduced electron transfer between molecular donors and acceptors provides a means to assess the electronic coupling provided by the DNA helix. Early applications of this method to DNA-mediated reactions utilized reactants noncovalently bound to DNA [28-30] These studies provided qualitative information concerning the efficiency and distance dependence of electron transfer, but the ambiguity associated with random distributions of reactants along the DNA helix precluded a quantitative analysis. Once chemical methods were developed for the covalent attachment of donors and acceptors to DNA [31], the distance dependence of these reactions, as well as the effects of perturbations within the intervening medium, could be systematically studied. The identification of unnatural DNA bases with appropriate photophysical and redox properties has also helped to define the extent of electronic coupling provided by the base stack [16]. 

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