Ultrafast excited-state dynamics and vibrational cooling of 8-oxo-7,8-dihydro-2'-deoxyguanosine in D2O.
Nguyen and Burrows recently demonstrated that UV-B irradiation of 8-oxo-7,8-dihydro-2'-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'-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.
Department of Chemistry and Biochemistry, Montana State University , Bozeman, Montana 59717, United States.
Yuyuan
Y
Zhang
Jordan
J
Dood
Ashley
A
Beckstead
Jinquan
J
Chen
Xi-Bo
XB
Li
Cynthia J
CJ
Burrows
Zhen
Z
Lu
Spiridoula
S
Matsika
Bern
B
Kohler
D000080242:8-Hydroxy-2'-Deoxyguanosine; D003849:Deoxyguanosine / Q000031:analogs & derivatives* / Q000737:chemistry; D017666:Deuterium Oxide / Q000737:chemistry*; D011789:Quantum Theory; D014732:Vibration
D000080242:8-Hydroxy-2'-Deoxyguanosine; D003849:Deoxyguanosine; D017666:Deuterium Oxide