Oxidative damage to DNA is a causative factor in cancer. Guanine can be using the flash quench technique, where a photoexcited intercalator is quenched by an electron acceptor. Here, we compared the guanine radical decay in the presence of two different quenchers. The guanine radical has broad absorption bands near 390 nm and 550 nm. Using nanosecond transient absorption spectroscopy, the decay of the guanine radical is nearly complete within 100 �s with Ru(NH3)63+ as quencher, whereas the signal persists for > one millisecond with Co(NH3)5Cl2+ as quencher. On a longer timescale, excitation produces no detectable transient with Ru(NH3)63+ , but a broad absorption maximum near 380 nm is visible for several seconds after analogous treatment with Co(NH3)5Cl2+. These results can be explained by the lability of the Co(II) complex formed upon reduction, and formation of a guanine radical that decays into another related radical species on a longer timescale.

Decay of guanine radical produced by the flash quench technique: Dependence upon quencher

243rd National Meeting (2012)

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