科研之友
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摘要
Nguyen and Burrows recently demonstrated that UV-B irradiation of 8-oxo-7,8-dihydro-2%26apos;-deoxyguanosine (8-oxodG), a signature product of oxidatively damaged DNA, can repair cyclobutane pyrimidine dimers in double-stranded DNA (J. Am. Chem. Soc. 2011, 133, 14586-14589). In order to test the hypothesis that repair occurs by photoinduced electron transfer, it is critical to determine basic photophysical parameters of 8-oxodG including the excited-state lifetime. Here, femtosecond transient absorption spectroscopy was used to study the ultrafast excited-state dynamics of 8-oxodG with excitation in the UV and probing at visible and mid-IR wavelengths. The excited-state lifetimes of both neutral and basic forms of 8-oxodG in D2O are reported for the first time by monitoring the disappearance of excited-state absorption at 570 nm. The lifetime of the first excited state of the neutral form is 0.9 +/- 0.1 ps, or nearly twice as long as that of 2%26apos;-deoxyguanosine. The basic form of 8-oxodG exhibits a much longer excited-state lifetime of 43 +/- 3 ps. Following ultrafast internal conversion by neutral 8-oxodG, a vibrationally hot ground state is created that dissipates its excess vibrational energy to the solvent on a time scale of 2.4 +/- 0.4 ps. Femtosecond time-resolved IR experiments provide additional insights into excited-state dynamics and the vibrational relaxation of several modes in the fingerprint region.
- 出版日期2013-12-5
