THz-TDS studies on proteins and molecular complexes in solutions

We have investigated low-frequency spectra of various systems in condensed phases by terahertz time-domain spectroscopy (THz-TDS). Low-frequency dynamics of bacteriorhodopsin is studied by changing the amount of hydration and temperature. A hydrated sample shows a sudden change in the THz spectrum at -40degC, although a dried sample does not show any change during the temperature change. For the solute/solvent systems we measured solutions of polar solutes in non-polar solvents to extract microscopic information on the interaction between the solute and solvent.