植物激素脱落酸分子的光谱与结构研究：理论与实验

植物激素脱落酸(ABA)是植物通过自身代谢产生的有机信号小分子，在极低浓度下可对植物自身产生明显的生理效应，是植物体内五大内源激素之一，因能促进植物叶片的脱落而得名，主要存在于植物干枯的叶子，根茎、种子等部位。由于对植物生长的调节能力，ABA在农业工程领域有着极大的应用前景。然而，ABA在植物体内的浓度很低，实现超低浓度检测是ABA应用的关键。关于ABA的检测，文献中已经报道的方法有很多，但是利用拉曼光谱技术对ABA的理论和实验研究还未见报道，拉曼光谱技术有着样品前处理简单、分析速度快、对于检测人员要求低，更适合于原位和现场检测等特点，因此对ABA拉曼光谱的机理和实验研究可为在植物激素检测及鉴定中提供可靠的依据。利用软件Gaussian09和GaussView5.0构建优化ABA的分子结构，计算了ABA的分子能级、前线轨道、拉曼光谱（Raman）、红外光谱（IR）及核磁共振谱（NMR）。为了验证理论计算的准确性，检测了ABA分子的IR、Raman、表面增强拉曼光谱（SERS）和NMR谱。结果表明：ABA的拉曼特征峰理论计算值位于616，1 056，1 272和1 689 cm-1处，实验测得的拉曼特征峰位于612，1 048，1 272和1 635 cm-1处，SERS实验获得的特征峰位于598，1 032，1 268和1 625 cm-1处，理论计算和实验结果吻合较好；同时对ABA在400～4 000 cm-1波长区间的IR和Raman特征峰进行了指认，指出了其在相应的峰位置上较强拉曼光谱的分子振荡模式，其中拉曼最强峰1 635 cm-1主要来自于ABA分子碳碳双键和碳碳单键的伸缩振动，其中碳碳双键的伸缩振动引起的拉曼散射最强。最后，对比ABA的计算和实验核磁共振谱，并进行原子归属指认和原子相对位移分析，进一步研究了ABA的分子结构，为ABA的痕量检测提供了一定的实验参考和理论依据。

Spectroscopic and Structure Study of Plant Hormone Abscisic Acid: Theory and Experiments

Plant hormone Abscisic Acid (ABA) is a small molecule of an organic signal produced by the plant’s own metabolism and can produce an obvious physiological effect to the plant itself in very low concentrations. ABA is one of the five endogenous hormones in plants, named for its ability to promote leaf shedding and mainly exists in the plant’s withered leaves, roots, seeds etc. Because of its ability to regulate plant growth, ABA has a great prospect of agricultural engineering. However, the concentration of ABA in plants is deficient, so the detection of ultra-low concentration is the key to the application of ABA. As for the detection of ABA, there are many detection methods reported in the literature, but as far as we know, the theoretical and experimental studies on ABA by Raman spectroscopy have not been reported. Raman spectral technology has the advantages of simple sample pretreatment, fast analysis speed, low requirements for the detection personnel, and more suitable for in-situ and in-situ detection. Therefore, the experimental and mechanistic study of ABA Raman spectroscopy can provide a reliable basis for detecting and identifying plant hormones. In this paper, the molecular structure of ABA was optimized by software Gaussian09 and GaussView5. 0, and the molecular energy level, Front orbit, Raman spectrum, Infrared spectrum and Nuclear magnetic resonance spectrum of ABA were calculated. In order to verify the accuracy of theoretical calculation, the IR, Raman, SERS and NMR spectra of ABA molecules were tested. The results show that: ABA Raman characteristic peak theory calculated value at 616, 1 056, 1 272 and 1 689 cm-1, experimental measured Raman characteristic peak in 612, 1 048, 1 272, 1 635 cm-1, SERS experiment to obtain the characteristics peak is located at 598, 1 032, 1 268, 1 625 cm-1, the theoretical calculation and experimental results are in good agreement. At the same time, the infrared and Raman peaks of ABA were identified in the range of 400～4 000 cm-1, and the molecular oscillation modes of the ABA producing Raman spectrum at the corresponding Raman frequency shift were pointed out. The most substantial Raman peak of 1 635 cm-1 was mainly caused by the stretching motion of the C═C bond and the C-C bond of ABA molecules, among which the stretching vibration of the C═C bond caused the most intense Raman scattering. Finally, atomic attribution and relative atomic displacement were analyzed, and the molecular structure of ABA was further studied according to comparing the calculation with the experimental nuclear magnetic resonance spectrum of ABA. What had done in the paper provided some experimental reference and theoretical basis for the trace detection of ABA.