太赫兹时域光谱技术探测亮氨酸和异亮氨酸的低频集体吸收谱

Analysis of Leucine and Isoleucine for Low-Frequency Collective Absorption Spectrum Using Terahertz Time-Domain Spectroscopy

氨基酸同分异构体的检测对食品安全和药品药性控制有重要意义。亮氨酸与异亮氨酸是同系的同分异构体,它们具有相似的化学结构,但物理化学性质有很大的差别。区分氨基酸同分异构体的常见的检测方法常用气相色谱、液相色谱、毛细管电泳、液质联用、色质联用等。但上述方法样品需要进行衍生化处理,很难快速、高效、无损的检测检测氨基酸的同分异构体。太赫兹(Terahertz,THz)波是指频率在0.1~10THz频段的电磁辐射,该技术可以反映物质的结构和构型。生物大分子的太赫兹吸收与其分子间氢键的振动和转动能级有关的偶极跃迁相关,可以利用分子偶极跃迁进行指纹识别。本文研究了太赫兹时域光谱技术在室温条件下的亮氨酸和异亮氨酸样品的光谱特征。结果表明亮氨酸和异亮氨酸样品在这个波段存在不同的光谱响应,可以用来探测分子的结构和振动情况从而区分结构差异小的同分异构体。本文还利用B3LYP杂化密度泛函的自洽场晶体轨道法对亮氨酸和异亮氨酸周期性结构进行了理论研究和光谱计算。通过比较实验和理论结果,并对获得的频谱进行了解析,计算得到的峰位与实验结果能够互相印证。

Amino acid isomers detection is useful for the quality control of food and pharmaceutical potency.Leucine and isoleucine are homologous isomers.They have similar chemical structures,but different chemical and physical properties.To distinguish different amino acid isomers,researchers commonly use gas chromatography,liquid chromatography,capillary electrophoresis,LC-MS,GC-MS etc.The above methods need sample prepreparation,which is time consuming and destructive.THz terahertz(THz,1=1012 Hz)wave refers to the frequency in the 0.1~10THz spectra of electromagnetic radiation and its wavelength is between 0.03 to 3mm.THz time domain spectroscopy(THz-TDS)can reflect the structure of thematerial and configuration.Biological macromolecular terahertz absorption is related with intermolecular hydrogen bond vibration and rotational level about the dipole transition,and it can be used for fingerprint identification of molecular dipole transition.The THz spectral characteristics of leucine and isoleucine were studied at room temperature.Results showed that the samples of leucine and isoleucine have different spectral responses,which can be used to detect the molecular structure and the vibration of structural differences of the isomers.The periodic structure of leucine and isoleucine was investigated using a self-consistent field crystal orbital method based on the B3 LYP hybrid density function.The theoretical results coincide well with the experimental results.