Aqueous TMAO solution under high hydrostatic pressure.

Trimethylamine N-oxide (TMAO) is a well known osmolyte in nature, which is used by deep sea fish to stabilize proteins against High Hydrostatic Pressure (HHP). We present a combined ab initio molecular dynamics, force field molecular dynamics, and THz absorption study of TMAO in water up to 12 kbar to decipher its solvation properties upon extreme compression. On the hydrophilic oxygen side of TMAO, AIMD simulations at 1 bar and 10 kbar predict a change of the coordination number from a dominating TMAO·(HO) complex at ambient conditions towards an increased population of a TMAO·(HO) complex at HHP conditions.

Hydrogen-Bonding in Liquid Water at Multikilobar Pressures.

High-precision THz (30 to 360 cm) spectra of bulk liquid water are presented from ambient conditions up to hydrostatic pressures of 10 kbar. In concert with ab initio simulations, this allows us to characterize the molecular-level changes of the H-bond network under solvent stress conditions. Both the experimental and theoretical THz spectra reveal a blue shift in the intermolecular translational mode at 180 cm by 40 cm at 10 kbar and a blue shift together with an intensity increase in the relaxation mode.

Solvation Dynamics of Trimethylamine N-Oxide in Aqueous Solution Probed by Terahertz Spectroscopy.

We have studied the hydration dynamics of trimethylamine N-oxide (TMAO) in aqueous solution using a combination of concentration-dependent terahertz/far-infrared (THz/FIR) and Raman spectroscopic techniques. Terahertz/FIR absorption was measured using narrowband (76-93 cm(-1)) p-Ge laser and broad band (30-400 cm(-1)) Fourier transform spectroscopy. We used principal component analysis in combination with a semi-ideal chemical equilibrium model to dissect the spectra into linear and nonlinear contributions of the solvated solute extinction.