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荧光核酸碱基类似物的设计合成是众多研究领域的热点课题.本文利用密度泛函理论(DFT)和含时密度泛函理论(TDDFT)考察了新型鸟嘌呤类似物y-鸟嘌呤(y G-t1)及其五个异构体(y G-t2到y G-t6)的结构性质、电子性质和光谱性质,同时考察了甲醇溶剂和碱基配对对其光谱性质的影响.研究表明,气相中y-鸟嘌呤的标准结构并不是最稳定的结构,其具有三个能量相近的异构体,y-鸟嘌呤最有可能以这三种形式存在.光谱性质研究表明y-鸟嘌呤的最大吸收波长比天然鸟嘌呤大得多,人们可以对其进行选择性激发.y-鸟嘌呤的标准结构与其异构体显示出不同的光谱特性,因此可以利用其电子光谱指纹对它们进行区分.研究发现甲醇溶剂将使y-鸟嘌呤标准结构的最大吸收波长和荧光发生蓝移,而使其他异构体相应值发生红移;与胞嘧啶配对将使y G-t1,y G-t2,y G-t5和y G-t6的最大吸收波长和荧光波长发生蓝移,表明y-鸟嘌呤的电子光谱性质受环境影响较大.
The design and synthesis of fluorescent nucleic acid base analogs are hot topics in many fields of study.In this paper, the new guanine analogue y-guanine (y G -t1) and its five isomers (y G-t2 to y G-t6) were investigated. The effects of methanol solvent and base pair on their spectral properties were also investigated. The standard structure of y-guanine in the gas phase is not the most stable structure with three isomers of similar energy, and y-guanine is most likely to exist in these three forms. Spectroscopic characterization studies have shown that y-guanine The maximum absorption wavelength is much greater than that of natural guanine and one can selectively excite it. The standard structure of y-guanine shows different spectral properties with its isomers so they can be distinguished by their electronic spectral fingerprints. The results showed that the methanol solvent will make the maximum absorption wavelength and fluorescence of y-guanine standard structure blue-shift, leaving the corresponding value of the other isomers redshift; pairing with cytosine will make y G-t1, y G-t2, y G-t5 and y G-t6 maximum absorption wavelength and fluorescence wave Long blue shift occurred, indicating that the electronic spectral properties of y-guanine are greatly affected by the environment.