ABSTRACT
It would clearly be of highest priority to obtain low-frequency vibrationally resolved spectra for biologic systems in aqueous-phase environments because this condition would most closely mimic their natural environment. However, this scenario has not been immediately feasible for most systems using far-infrared absorption spectroscopy because (1) absorption by the amino acids and most other biomolecules is masked by much stronger water absorption in the 1 to 3 THz spectral region8 and (2) spectral broadening arising from the full accessibility to conformational space and the rapid time scale for interconversion in these environments. Despite this limitation, recent studies of biomolecules in aqueous or high relative humidity environments reviewed in this chapter have revealed detailed information about the dynamics of these systems through careful broadband absorption measurements. Also reviewed here is the work performed to determine whether pure solid samples of organic model systems and protein fragments do indeed show sharp spectral features that are uniquely determined from their individual molecular symmetries and structures. Spectral THz absorption data and spectral modeling methods discussed in this review are the rst of their kind and demonstrate that these expectations are indeed borne out.
