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State-resolved Spectroscopy of Biomolecules


Sensitive and fully state resolved spectroscopic methods in the terahertz (THz) and ultraviolet (UV) regions are being developed to investigate the structure and dynamics of biomolecules including model systems and their response to and impact on the presence of the ubiquitous solvent, water. The experimental data from these studies are compared with predictions from state-of-the-art classical and quantum chemical methods to elucidate the fundamental physics behind biomolecular structure and function and to expose the strengths and deficiencies inherent in the underlying models.


Terahertz radiation interrogates the lowest frequency vibrational modes of a biomolecule. These modes characterize the incipient motions for large-scale conformational changes responsible for the backbone flexibility of protein, polynucleotide and polysaccharide. Thus, terahertz spectral features provide a sensitive probe of the subtle force constants that influence the collective nuclear motions that extend over a large portion of the biomolecular framework. Experimental data on these biomolecule systems may also be used to validate and improve current force field and biomolecular dynamics models. And, because the energy available at terahertz frequencies is comparable to the thermal energy at room temperature, detailed investigations of the vibrational anharmonicities of the hydrogen bonding networks associated with these large amplitude motions can be made in a direct way.

For examples, see State-resolved terahertz spectroscopy of biomolecules.

Major Accomplishments

  • THz spectra of dipeptide nanotubes have revealed the importance of mode coupling and decoupling on the permeability dynamics of water through hydrophobic pore regions.
  • THz features undergo dramatic change when water binds to hydrophilic sites in peptide crystals.
  • Temperature dependent studies in the THz region provide direct information about the anharmonic character of phonon modes.

Created September 9, 2009, Updated May 9, 2023