The Center for Modeling & Simulation Chemistry, Institute of Theoretical Chemistry, Shandong University, Jinan, 250100, PR China.
J Phys Chem B. 2010 Mar 18;114(10):3726-34. doi: 10.1021/jp9117503.
We present the results of a detailed and systematic computational investigation into the excited-state properties of the fluorescent cytosine analogue x-cytosine (xC). Also examined were the influences of hydration, linking to deoxyribose, base pairing with guanine (G), and base stacking on its absorption and emission processes. The calculated excitation and emission energies agree well with the experimentally measured data. It was found that hydration, linking to deoxyribose, and base pairing with G have a hyperchromic effect on the excitation maximum of xC. The linking sugar will red-shift the fluorescence emission of xC by 7 nm, while hydration and base pairing with G, on the contrary, results in a blue-shift of the fluorescence emission by 8 and 9 nm, respectively. In addition, hydration of xCG will further blue-shift the fluorescence emission of xC by about 17 nm. Furthermore, the fluorescence quantum yield of xC would be increased after hydration, linking to deoxyribose, and base pairing with G. When sandwiched by two identical natural bases, a significant decrease of the oscillator strength as well as a red-shift of the dipole-allowed transition with respect to free xC is observed in all cases. The fluorescence quantum yield of xC was expected to be lowered in the stacked complexes due to a static quenching mechanism.
我们呈现了对荧光胞嘧啶类似物 x-胞嘧啶 (xC) 的激发态性质进行详细系统计算研究的结果。还研究了水合作用、与脱氧核糖的连接、与鸟嘌呤 (G) 的碱基配对以及碱基堆积对其吸收和发射过程的影响。计算出的激发和发射能量与实验测量数据吻合良好。结果发现，水合作用、与脱氧核糖的连接以及与 G 的碱基配对对 xC 的激发最大值具有增色效应。连接糖将使 xC 的荧光发射红移 7nm，而水合作用和与 G 的碱基配对则分别使荧光发射蓝移 8nm 和 9nm。此外，xCG 的水合作用将使 xC 的荧光发射进一步蓝移约 17nm。此外，水合作用、与脱氧核糖的连接以及与 G 的碱基配对会增加 xC 的荧光量子产率。在两种相同的天然碱基夹在中间的情况下，在所有情况下，相对于自由 xC，振子强度都会显著降低，偶极允许跃迁也会红移。由于静态猝灭机制，堆叠复合物中 xC 的荧光量子产率预计会降低。
