Terahertz (THz) spectroscopy is regarded as a professional technology to probe collective molecular vibrational modes and intensity of bio–molecules, which is potential to analyze amino acids and short peptides. In this study, THz spectroscopy is utilized to investigate the correlations of glycine (Gly), Serine (Ser), amino acid mixtures of Gly/Ser, and dipeptides (GS and SG) in the frequency range of 0.3–2.5 THz. The results manifest that the collective molecular vibrational intensity of Ser is larger than Gly, implying that the hydroxyl methyl group (–CH₂–OH) on the side chain of Ser exhibits larger motions than that of –H in Gly. Additionally, the THz spectra of amino acid mixtures of Gly/Ser fit the linear addition of the individual amino acid absorption spectrum. Herein, the THz spectra of dipeptide GS and its isomer SG are distinguished according to the different collective molecular vibrations produced by the terminal groups on the carbon skeleton. Compared to physical amino acid mixtures of Gly/Ser, the dipeptides exhibit diverse THz spectra, indicating that the different collective vibrational modes are caused by peptide bonds and terminal groups. These solid evidences confirm that THz spectroscopy can be availably used to analyze the correlations of amino acids, amino acid mixtures, and dipeptides, as well as to identify dipeptide and its isomer from molecular level.

太赫兹（THz）光谱被认为是探测集体分子振动模式和生物分子强度的专业技术，这对于分析氨基酸和短肽具有潜在的作用。在这项研究中，利用THz光谱技术研究了0.3–2.5 THz频率范围内的甘氨酸（Gly），丝氨酸（Ser），Gly / Ser氨基酸混合物和二肽（GS和SG）的相关性。结果表明，Ser的集体分子振动强度大于Gly，这表明羟甲基（–CH ₂Ser侧链上的–OH）的运动比Gly中–H的运动大。另外，Gly / Ser氨基酸混合物的THz光谱适合各个氨基酸吸收光谱的线性加法。在此，根据碳骨架上的端基所产生的不同的集体分子振动来区分二肽GS及其异构体SG的THz光谱。与Gly / Ser的物理氨基酸混合物相比，二肽显示出不同的THz光谱，表明不同的集体振动模式是由肽键和末端基团引起的。这些有力的证据证实，太赫兹光谱可用于分析氨基酸，氨基酸混合物和二肽的相关性，以及从分子水平鉴定二肽及其异构体。