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.