THz spectroscopy of compatible solutes at HHP conditions probing changes in the hydration water network

本提案的中心目标是详细记录和分析高静水压力（HHP）下溶剂化相容生物分子和辅质的低频频谱。在第一个资助期，我们成功地将HHP金刚石砧细胞植入太赫兹傅立波光谱仪。这种新装置使我们能够在高压条件下（高达13 kbar）记录散装水和溶剂化TMAO的第一个低频谱。我们观察到系统的压力依赖于振动和氢键拉伸模式的变化。结合D. Marx的从头算MD模拟，这些低频HPP谱为水网络动力学变化提供了详细的新见解。在第二个资助期，我们将重点研究HPP在添加相关溶质时对低频氢网络模式的影响。因此，我们将系统地研究溶质尿素/氧化三甲胺混合物对水的压力扰动。HHP条件下溶剂化盐、氨基酸、Ac-Gly-NH2的低频频谱的压力依赖性变化，将对压力诱导的分子内振幅模式、相关和反相关溶质-水网络模式的变化提供新的见解。作为一个高风险的项目，我们将尝试研究超临界条件下的水。实验上，利用太赫兹时域光谱技术将频率范围扩展到50 cm-1以下的频率范围。

The central goal of this proposal is to record and analyze in detail the low frequency spectra of solvated compatible biomolecules and cosolutes under high hydrostatic pressure (HHP). In the first funding period, we were successfully implementing a HHP diamond anvil cell into a THz FT spectrometer. This new set-up allowed us to record the first low frequency spectra of bulk water and solvated TMAO at HHP conditions (up to 13 kbar). We observed systematic pressure dependent changes of the librational and H-bond stretch modes. In combination with ab initio MD simulations of D. Marx these low frequency HPP spectra provide detailed new insights into changes of the water network dynamics.In the second funding period we will focus on the effects of HPP on the low frequency hydrogen network modes when adding relevant solutes. Thus, we will systematically study cosolute urea/TMAO mixtures for the pressure perturbation of water. Pressure dependent changes of the low frequency spectrum of solvated salts, amino acids, Ac-Gly-NH2 under HHP conditions will yield new insights into pressure induced changes of the intramolecular large amplitude modes, and correlated and anticorrelated solute-water network modes. As a high risk project we will try to study water under supercritical conditions. Experimentally, the frequency range will be extended to include the frequency range below 50 cm-1 using THz time domain spectroscopy.