Journal of the American Chemical Society 2012, 134 Lateral Distribution of Charged Species along a Polyelectrolyte Probed with a Fluorescence Blob Model. Christine Keyes, Manoj Mathew, Jean Duhamel.Electrochemical Methods for the Analysis of Clinically Relevant Biomolecules. This article is cited by 56 publications. These results are quite similar to those previously observed with a covalently tethered rhodium photooxidant and underscore the unique ability of the DNA base stack to facilitate long-range electron transfer so as to effect oxidative damage from a distance. The yield of this electron-transfer reaction is not attenuated with distance equal yields of guanine damage are observed at a proximal (17 Å Et−GG separation) and distal (44 Å Et−GG separation) site. The long-range reaction is entirely consistent with oxidation of guanine by DNA-mediated electron transfer. The short-range reaction involves a covalent modification of guanine by ethidium, based upon HPLC analysis of the nucleoside products and studies with ethidium derivatives. By covalently tethering ethidium to one end of a DNA duplex, we demonstrate the presence of two distinct reactions, one short-range and the other long-range. This reactivity is not consistent with oxidation of guanine by either electron transfer or singlet oxygen as shown by comparison with reactions of a rhodium intercalator and methylene blue, respectively. While no DNA reaction is observed upon excitation into the visible absorption band of ethidium, higher-energy irradiation (313−340 nm) leads both to direct strand cleavage at the 5‘-G of 5‘-GG-3‘ doublets and to piperidine-sensitive lesions at guanine. Short-range and long-range photoreactions between ethidium and DNA have been characterized.
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