Terahertz Dielectric Sensitivity to Biomolecular Structure and Function

A review of recent terahertz (THz) dielectric response measurements on large biomolecules is presented. The origin of the dielectric response in this frequency range is discussed. We specifically address the questions of the relative contributions of collective vibrational modes and relaxational contributions. When sample uniformity is controlled and multiple reflection effects included in the analysis, the overall dielectric response of large biomolecules in the THz range is broad and featureless. The response, however, is highly sensitive to hydration, temperature, binding, and conformational change. The origin of these effects is discussed with emphasis on the contribution of surface side chain relaxational loss and how this might be affected by environment, structure, and function.