胸腺嘧啶分子红外光谱及拉曼光谱的理论研究

发布时间：2018-04-14 16:36

本文选题：胸腺嘧啶 + 密度泛函理论　；参考：《曲阜师范大学》2017年硕士论文

【摘要】：胸腺嘧啶是DNA中A-T碱基对(腺嘌呤-胸腺嘧啶)的组成部分,它们之间彼此配对,通过氢键作用,使DNA双螺旋结构变得更加稳定。胸腺嘧啶是遗传物质的重要构成部分,也是许多抗疾病药物的关键合成成分,无论是在生物遗传学还是在医药学上,都具有十分重要的作用。因此胸腺嘧啶分子的结构特性具有较高的研究价值。本文通过密度泛函理论(DFT)分别对胸腺嘧啶与水分子团簇的基态结构、红外振动光谱,以及胸腺嘧啶在银团簇表面上的表面增强拉曼光谱做了充分的研究。本文共有五个章节:第一部分:讲述了胸腺嘧啶分子的重要性质和广泛的用途,叙述了氢键的作用以及红外光谱的应用,介绍了表面增强拉曼光谱的相关增强机理。第二部分:分别对量子化学的计算方法、Gaussian系列软件、密度泛函的相关理论、AIM软件等进行了介绍,同时也对拉曼散射强度的计算进行了说明。第三部分:主要应用Gaussian09W程序中密度泛函理论(DFT)B3LYP方法,在6-311++G(d,p)基组水平上,研究了C5H6N2O2?(H2O)n(n=1~4)分子团簇的基态结构以及它们的红外光谱。通过对C5H6N2O2?(H2O)n(n=1~4)分子团簇的结构进行优化,获得了团簇最稳定的结构。AIM程序分析表明:分子团簇间形成了氢键,而且电子密度?的强弱也反映了红移和蓝移的大小。之后使用Veda4软件对C5H6N2O2?(H2O)n(n=1~4)分子团簇红外光谱的振动频率进行了分析,并对振动频率进行了比较。最后,通过分析四种最稳定结构的分子团簇的红外光谱,我们发现O H…O和N H…O氢键的形成使得O H和N H原子之间伸缩频率减小,即发生了红移;同样的,O H…N氢键使O H原子之间的弯曲振动频率变大,即发生了蓝移。第四部分:应用DFT的B3LYP方法,在6-311++G(d,p)(C,H,O)/Lan L2DZ(Ag)基组上,优化得到胸腺嘧啶分子与Ag团簇形成的复合物C5H6N2O2-Agn(n=1~6)的最稳定结构。同时计算了C5H6N2O2-Agn(n=2,4,6)三种复合物的表面增强拉曼光谱(SERS)和预共振拉曼光谱(SERRS),其结果与实验值相一致,证明了理论方法的合理性和精确性。复合物的SERS中,大部分振动模式没有明显增强,但其中C=O的弯曲振动和O Ag的伸缩振动有明显的增强,是由复合物结构极化率的改变而引起的,属于静化学增强。进一步采用含时密度泛函理论(TDDFT)方法计算得到了复合物的吸收光谱,分别选择385 nm、417 nm和388 nm作为入射光,计算得到了它们的共振拉曼光谱。在SERRS中,O Ag的伸缩振动增强了104左右,是由电荷转移引起的共振增强,且转移模式都是电子在Ag团簇向胸腺嘧啶分子的π*键轨道转移跃迁。其增强模式属于选择性增强,证明复合物的SERRS是化学增强。第五部分:对全文进行综合性总结与展望。
[Abstract]:Thymidine is a component of A-T base pairs (adenine thymine) in DNA. They pair with each other and make the double helix structure of DNA more stable by hydrogen bonding.Thymine is an important component of genetic material and a key synthetic component of many anti-disease drugs. It plays an important role in both biogenetics and medicine.Therefore, the structural properties of thymidine molecules are of high value.In this paper, the ground state structure, infrared vibrational spectrum and surface-enhanced Raman spectra of thymine and water clusters on the surface of silver clusters have been studied by density functional theory (DFT).There are five chapters in this paper: in the first part, the important properties and wide applications of thymidine are described, the function of hydrogen bond and the application of infrared spectroscopy are described, and the mechanism of surface enhanced Raman spectroscopy is introduced.In the second part, the calculation methods of quantum chemistry are introduced, such as Gaussian series software, density functional theory and AIM software, and the calculation of Raman scattering intensity is also explained.Part three: the ground state structure and infrared spectra of C _ 5H _ 6N _ 2O _ 2 H _ 2O _ N _ 2 O _ 2 H _ 2O _ n _ (1) N _ (1) O _ (4) clusters have been studied by using the density functional Theory (DFT) B3LYP method at the level of 6-311 G ~ (2 +) base set in the Gaussian09W program.By optimizing the structure of C _ 5H _ 6N _ 2O _ 2H _ 2O _ 2 H _ 2O _ N _ N _ N _ 4) clusters, the most stable structure of the clusters is obtained. AIM program shows that hydrogen bonds are formed among the clusters, and the electron density?The magnitude of the red shift and the blue shift is also reflected in the magnitude of the red shift and the blue shift.The frequency of infrared spectra of C _ 5H _ 6N _ 2O _ 2 and H _ 2O _ n _ (1) O _ (4) molecular clusters was analyzed by Veda4 software, and the vibrational frequencies were compared.Finally, by analyzing the IR spectra of the four most stable molecular clusters, we found that O _ (H) 鈥 and N...The formation of O hydrogen bond reduces the stretching frequency between O H and N H atoms, that is, red shift occurs.The N hydrogen bond increases the frequency of the bending vibration between O and H atoms, that is, the blue shift occurs.Part IV: using DFT's B3LYP method, the most stable structure of the complex C _ 5H _ 6N _ 2O _ 2-Agnn ~ (1 /) formed by thymidine and Ag clusters was optimized on the 6-311 G ~ (11) G ~ (-1) B3LYP group.At the same time, the surface-enhanced Raman spectra (SERS) and pre-resonance Raman spectra (SERRSs) of C _ 5H _ 6N _ 2O _ 2-Agnn _ (2) O _ (2) O _ (4)) complexes are calculated. The results are in agreement with the experimental data, which proves the rationality and accuracy of the theoretical method.In the SERS of the composite, most of the vibration modes are not obviously enhanced, but the flexural vibration and the stretching vibration of O-Ag are obviously enhanced, which is caused by the change of the polarizability of the complex structure and belongs to the static and chemical enhancement.Furthermore, the absorption spectra of the complexes were calculated by time-dependent density functional theory (TDDFT) method. 385nm and 388nm were selected as incident light respectively, and their resonance Raman spectra were calculated.In SERRS, the stretching vibration of Ag increases by about 104, which is due to the resonance enhancement caused by charge transfer, and the transfer mode is the transition of electrons from Ag cluster to the 蟺 * bond orbital of thymidine molecule.The enhancement mode is selective enhancement, which proves that the SERRS of the complex is chemically enhanced.Part V: a comprehensive summary and prospect of the full text.
【学位授予单位】：曲阜师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：Q526.1;O657.3

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