光谱学与光谱分析, 2020, 40 (7): 2054, 网络出版: 2020-12-04  

苏氨酸不同分子构型太赫兹吸收峰的量子化学指认

Quantum Chemical Identification of Terahertz Absorption Peaks of Threonine with Different Molecular Configurations
作者单位
内蒙古科技大学信息工程学院, 内蒙古 包头 014010
摘要
与红外、 紫外和拉曼光谱相比, 太赫兹光谱能量低, 在待测物质中不会出现有害光致电离现象, 伴随太赫兹技术的不断成熟, 太赫兹波已经成为常用的无损检测用波。 很多生物大分子在高频光波探测下具有指纹性, 太赫兹时域光谱技术是对生物大分子无损检测的最佳手段。 同时, 不同生物分子在太赫兹吸收谱中呈现出各不相同的吸收峰, 获得待测物质的太赫兹吸收谱后, 与标准谱进行对照可以为待测物质做出定性辨识。 在此基础上, 结合最小二乘法、 支持向量机等数据处理技术还可以实现基于太赫兹时域光谱对待测物质的定量分析。 量子化学分析方法应用了量子力学的基本原理和方法, 其中电子分析理论从电子角度出发, 在分析大分子或原子个数众多的体系时近似误差较小, 并且密度泛函理论不依赖实验数据和先验知识的支撑。 通过量子化学计算方法计算氨基酸分子的太赫兹吸收谱, 可以为氨基酸分子的太赫兹吸收峰匹配分子振动模式, 对氨基酸定性分析有一定的参考性, 并为实验获取的样品太赫兹时域光谱提供理论支撑, 在实验获得太赫兹吸收谱的基础上进行量子化学计算, 能验证实验结果的准确性。 首先利用太赫兹时域光谱系统获取进口苏氨酸样品的太赫兹吸收谱, 其次分别构建苏氨酸样品在实物中以两性离子形式存在的单分子、 二聚体和晶胞三种构型, 并利用量子化学计算方法完成了每种构型的结构优化, 最后计算三种苏氨酸分子构型的太赫兹吸收谱。 结果表明, 单分子构型和二聚体构型的太赫兹计算谱与实验谱差异较大, 但在高频段计算谱与实验谱的吸收峰峰位基本吻合, 而较为全面反映分子间氢键及范德华力作用的晶胞构型计算谱与实验谱则较为吻合。 同时表明, 与样品结构较为一致的、 保持苏氨酸物理性质的最小结构为晶胞。
Abstract
Compared with infrared, ultraviolet and Raman spectra, terahertz spectra have low energy and no harmful photoionization phenomena in the substances to be measured. With the maturation of terahertz technology, the terahertz wave has become a common wave for non-destructive testing. Many biological macromolecules have fingerprints under high-frequency light detection. THz time-domain spectroscopy is the best method for nondestructive detection of biological macromolecules. At the same time, different biological molecules show different absorption peaks in Terahertz Absorption spectra. After obtaining Terahertz Absorption Spectra of the substance to be measured, compared with standard spectra, qualitative identification of the substance to be measured can be made. On this basis, combined with data processing techniques such as least squares method and support vector machine, the quantitative analysis of measured substances based on terahertz time-domain spectroscopy can also be realized. The basic principles and methods of quantum mechanics are applied in the quantum chemical analysis method. From the electronic point of view, the approximation error of the electronic analysis theory in the analysis of systems with large molecules or atoms is small, and the density functional theory does not depend on the support of experimental data and prior knowledge. The Terahertz Absorption Spectra of amino acids can be calculated by a quantum chemistry calculation method, which can match the molecular vibration mode of terahertz absorption peaks of amino acids, provide certain reference and directivity for qualitative analysis of amino acids, and provide theoretical support for terahertz time domain spectra of samples obtained from experiments. Quantum chemistry calculation is carried out on the basis of the terahertz absorption spectra obtained from experiments. It can further verify the accuracy of the experimental results. In this paper, the Terahertz Absorption Spectra of imported threonine samples were obtained by the terahertz time domain spectroscopy system. Then, three configurations of threonine samples in the form of zwitterionic ions were constructed, and the structure optimization of each configuration was completed by quantum chemical calculation method. Finally, the Terahertz Absorption Spectra of three threonine molecular configurations were calculated. The results show that the terahertz calculation spectra of the monomer and dimer configurations are quite different from the experimental spectra, but in the high frequency band, the absorption peaks of the calculated spectra are basically in agreement with the experimeotal spectra, while the lattice configuration calculation spectra of the more comprehensive reaction of intermolecular hydrogen bond and van der Waals force are in good agreement with the experimental spectra. At the same time, the smallest structure, which is consistent with the sample structure and keeps the physical properties of threonine is the cell.

李伟, 燕芳, 王志春, 刘成毫. 苏氨酸不同分子构型太赫兹吸收峰的量子化学指认[J]. 光谱学与光谱分析, 2020, 40(7): 2054. LI Wei, YAN Fang, WANG Zhi-chun, LIU Cheng-hao. Quantum Chemical Identification of Terahertz Absorption Peaks of Threonine with Different Molecular Configurations[J]. Spectroscopy and Spectral Analysis, 2020, 40(7): 2054.

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