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. Author manuscript; available in PMC: 2011 Mar 10.
Published in final edited form as: Chem Rev. 2010 Mar 10;110(3):1642–1662. doi: 10.1021/cr900228f

Figure 5.

Figure 5

(A) The rate of coherent deazaguanine (ZG) oxidation by ethidium bromide is the same over short distances for both the flexible linkage (Et1, black, both CT rates shown) and the rigid linkage (Et2, gray).27 For two intervening nucleotides, a sharp drop in rate is observed for the rigid Et+, but the rate is unaffected for the flexible Et+. (B) This steep drop in rate over short distances is consistent with that observed for oxidation of guanine by a photoinduced sugar radical (circles),207 and CT between hairpin capping stilbenes (squares, photooxidation of Sd by Sa),125 and has been attributed to a crossover between coherent superexchange and incoherent hopping. In the latter case, comparison of injection and hole arrival rates supports superexchange for one or two intervening base pairs, and hopping for three or more base pairs between the stilbenes.