Lehrstuhl für Physikalische Chemie II, Ruhr-Universität Bochum, 44780, Bochum, Germany.
Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, 44780, Bochum, Germany.
Angew Chem Int Ed Engl. 2021 Feb 15;60(7):3768-3772. doi: 10.1002/anie.202014133. Epub 2020 Dec 21.
Based upon precise terahertz (THz) measurements of the solvated amino acid glycine and accompanying ab-initio molecular-dynamics simulations, we show that the N-C-C-O open/close mode at 315 cm serves as a sensitive, label-free probe for the local protonation of the amide group. Experimentally, we can show that this holds not only for glycine but also for diglycine and valine. The approach is more general, since the changes due to protonation result in intensity changes which can be probed by THz time domain (0-50 cm ) as well as by precise THz-FT spectroscopy (50-400 cm ). A detailed analysis allows us to directly correlate the titration spectra with pK values. This demonstrates the potential of THz spectroscopy to probe the charge state of a natural amino acid in water in a label-free manner.
基于对溶剂化氨基酸甘氨酸的精确太赫兹（THz）测量和伴随的从头分子动力学模拟，我们表明 315 cm 处的 N-C-C-O 开/合模式可作为酰胺基团局部质子化的灵敏、无标记探针。实验上，我们可以证明这不仅适用于甘氨酸，也适用于二肽和缬氨酸。该方法更具普遍性，因为由于质子化引起的变化会导致强度变化，这些变化可以通过太赫兹时域（0-50 cm）以及精确的太赫兹傅里叶变换光谱（50-400 cm）来探测。详细的分析使我们能够将滴定光谱直接与 pK 值相关联。这证明了太赫兹光谱在无标记的情况下探测水中天然氨基酸电荷状态的潜力。
