Oxidative damage to DNA is a causative factor in disease and guanine can be readily oxidized by the flash quench technique. Here, we compared the guanine radical decay in DNA, with the quenchers Ru(NH3)63+ and Co(NH3)5Cl2+. Using nanosecond transient absorption spectroscopy at 373 nm, the guanine radical decays within 100 �s with Ru(NH3)63+ as quencher, but persists for milliseconds with Co(NH3)5Cl2+. On a longer timescale, excitation with a camera flash produces a detectable transient species with an absorbance maximum of ~390 nm. In related studies using guanosine-5'-monophosphate, flash quench with the cobalt quencher produces a broad absorption between 300 nm and 380 nm that decays on the seconds time scale; in contrast, Ru(NH3)63+ gives no signal. 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

245th National Meeting (2013)

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