RESEARCH INTERESTS

Terahertz spectroscopy of biomolecules in liquid water

Biomolecules solvated in their natural, liquid water environment exhibit a strong absorption in the terahertz region that contains information on their global and subglobal collective vibrational modes and global dynamical correlations among solvent water molecules and the biomolecule. Measurements in this region, however, are challenging due to the strong water absorption and often severe interference artifacts. In response, we have developed a highly sensitive, frequency domain, high resolution, vector network analyzer-based spectrometer that supports the accurate measurements of both the absorbance and refractive index of aqueous biomolecular solutions over this important spectral region. Using this system we have explored the complex dielectric response of solvated lysozyme protein over range 0.5 GHz to 1.1 THz as a means of probing the protein’s hydration shell and the large-scale dynamics. We make a direct comparison to the existing theoretical calculations and investigate the dependence of the low frequency dynamics on protein concentration and solvent pH. The discoveries shed light on the macromolecular motions in a biologically relevant water environment.

Domain motion due to the lowest frequency modes in
lyzsozyme and the hydration shell around the protein