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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Ultrafast Excited-State Dynamics and Vibrational Cooling of 8?Oxo- 7,8-dihydro-2′-deoxyguanosine in D_2O
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Ultrafast Excited-State Dynamics and Vibrational Cooling of 8?Oxo- 7,8-dihydro-2′-deoxyguanosine in D_2O

机译：D_2O中8？Oxo- 7,8-dihydro-2'-deoxyguanosine的超快激发态动力学和振动冷却

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摘要

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 D_2O are reported for the first time by monitoring the disappearance of excitedstate 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 excitedstate dynamics and the vibrational relaxation of several modes in the fingerprint region.
机译：Nguyen和Burrows最近证明，UV-B辐射可氧化修复DNA的标志性产物8-oxo-7,8-dihydro-2'-deoxyguanosine（8-oxodG），可修复双链DNA中的环丁烷嘧啶二聚体（ J. Am。Chem。Soc。2011，133，14586？14589）。为了检验由光诱导的电子转移进行修复的假说，确定8-oxodG的基本光物理参数（包括激发态寿命）至关重要。在这里，飞秒瞬态吸收光谱用于研究8-oxodG在紫外光下的超快激发态动力学，并在可见光和中红外波长处进行探测。通过监测570 nm处激发态吸收的消失，首次报道了D_2O中中性和碱性形式的8-oxodG的激发态寿命。中性形式的第一激发态的寿命为0.9±0.1 ps，或几乎是2'-脱氧鸟苷的两倍。 8-oxodG的基本形式具有43±3 ps的更长的激发态寿命。在通过中性的8-oxodG进行超快内部转换之后，便产生了一个振动热基态，该状态将其多余的振动能量以2.4±0.4 ps的时间尺度消散到溶剂中。飞秒时间分辨的IR实验提供了有关激发态动力学和指纹区域中几种模式的振动弛豫的更多见解。

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