Neu Jens, Nikonow Heinrich, Schmuttenmaer Charles A
Yale University , Department of Chemistry , New Haven , Connecticut 06520 , United States.
Yale University , Energy Science Institute (ESI) , New Haven , Connecticut 06520 , United States.
J Phys Chem A. 2018 Jul 19;122(28):5978-5982. doi: 10.1021/acs.jpca.8b04978. Epub 2018 Jul 5.
We present terahertz (THz) measurements and density functional theory (DFT) calculations of two amino acid crystals: dl-norleucine and dl-methionine. Their molecular structures are very similar and therefore also their crystal structures. We report the absorption spectra for both amino acids, which have a strong resonance at 1.87 THz in dl-norleucine and 1.94 THz in dl-methionine. In addition, we find a higher frequency resonance at 2.49 THz in dl-methionine, which has no corresponding mode in dl-norleucine. The experimental data are supported by DFT calculations, which show that the origin of the two strongest vibrational modes in dl-norleucine and dl-methionine are based on the same underlying vibrational motions, whereas the 2.49 THz resonance in dl-methionine is due to the motion of the sulfur atom, which is not present in dl-norleucine.
我们展示了两种氨基酸晶体（dl-正亮氨酸和dl-蛋氨酸）的太赫兹（THz）测量结果和密度泛函理论（DFT）计算结果。它们的分子结构非常相似，因此晶体结构也相似。我们报告了这两种氨基酸的吸收光谱，dl-正亮氨酸在1.87 THz处有一个强共振峰，dl-蛋氨酸在1.94 THz处有一个强共振峰。此外，我们发现dl-蛋氨酸在2.49 THz处有一个更高频率的共振峰，而dl-正亮氨酸中没有相应的模式。实验数据得到了DFT计算的支持，计算结果表明，dl-正亮氨酸和dl-蛋氨酸中两个最强振动模式的起源基于相同的基本振动运动，而dl-蛋氨酸中2.49 THz的共振是由于硫原子的运动引起的，而dl-正亮氨酸中不存在硫原子。
