Radicals formed by electron transfer from cytosine and 1-methylcytosine to the triplet state of anthraquinone-2,6-disulfonic acid. A Fourier-transform EPR study
Radicals formed by electron transfer from cytosine and 1-methylcytosine to the triplet state of anthraquinone-2,6-disulfonic acid. A Fourier-transform EPR study
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DOI：
10.1039/b004617p
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发表时间：
2000
影响因子：
3.3
通讯作者：
J. Geimer;K. Hildenbrand;S. Naumov;D. Beckert
中科院分区：
文献类型：
--
作者：
J. Geimer;K. Hildenbrand;S. Naumov;D. Beckert
用时间分辨傅立叶变换(FT)EPR方法研究了10℃下，在水和水中由胞嘧啶和1-甲基胞嘧啶电子转移到2，6-二磺酸的激光诱导三重态所产生的自由基，在纳秒时间尺度上观察到的主要产物是碱自由基阳离子的继承者。通过对实验光谱的计算机模拟确定了它们的超精细耦合。通过密度泛函理论(DFT)量子力学计算，对其自由基结构进行了归属。在N1下的胞嘧啶去质子化实验得到了在N1和C5具有高自旋密度的胞嘧啶-1-基自由基1，而对于1-甲基胞嘧啶，在外环氨基上的去质子化得到了氨基自由基2。对于两种母体化合物胞嘧啶和1-甲基胞嘧啶，在纳秒到微秒的时间尺度上检测到另外两个结构未知的长寿命自由基(3和4)。它们的光谱参数与N1取代基无关。
Radicals generated by electron transfer from cytosine and 1-methylcytosine to the laser-induced triplet state of anthraquinone-2,6-disulfonic acid were studied by time-resolved Fourier-transform (FT) EPR in H2O and D2O at 10°C. The main products observed on the nanosecond timescale were successors of the base radical cations. Their hyperfine couplings were determined by computer simulation of the experimental spectra. Assignment of the radical structures was supported by density functional theory (DFT) quantum mechanical calculations. The experiments with cytosine deprotonation at N1 resulted in the cytosin-1-yl radical 1 with high spin density at N1 and C5 whereas, for 1-methylcytosine, deprotonation at the exocyclic amino group yielded the aminyl radical 2. For both parent compounds, cytosine and 1-methylcytosine, two additional long-lived radicals (3 and 4) with unknown structure were detected on the nanosecond to microsecond timescale. Their spectral parameters were independent of the N1 substituent.