Dohno Chikara, Stemp Eric D A, Barton Jacqueline K
Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA.
J Am Chem Soc. 2003 Aug 13;125(32):9586-7. doi: 10.1021/ja036397z.
The phenothiazinium dye thionine has a high excited state reduction potential and is quenched by guanine on the femtosecond time scale. Here, we show by gel electrophoresis that irradiation of thionine with 599 nm light in the presence of an oligonucleotide duplex does not produce permanent DNA damage. Upon photoexcitation of thionine weakly associated with guanosine-5'-monophosphate, the reduced protonated thionine radical and neutral guanine radical are detected by transient absorption spectroscopy, indicating that the quenching of thionine by guanine occurs via an electron-transfer mechanism. The observation of radical formation without permanent guanine damage indicates that fast back electron transfer plays a critical role in governing the yield of damage by DNA-binding molecules.
吩噻嗪鎓染料硫堇具有较高的激发态还原电位，并且在飞秒时间尺度上会被鸟嘌呤淬灭。在此，我们通过凝胶电泳表明，在寡核苷酸双链体存在的情况下，用599 nm光照射硫堇不会产生永久性DNA损伤。当与5'-单磷酸鸟苷弱结合的硫堇发生光激发时，通过瞬态吸收光谱检测到还原的质子化硫堇自由基和中性鸟嘌呤自由基，这表明鸟嘌呤对硫堇的淬灭是通过电子转移机制发生的。在没有永久性鸟嘌呤损伤的情况下观察到自由基的形成，表明快速的反向电子转移在控制DNA结合分子造成损伤的产率方面起着关键作用。
