The inside cover image, by Keisuke Tominaga et al., is based on the Advanced Review Mixing of intermolecular and intramolecular vibrations in optical phonon modes: terahertz spectroscopy and solid-state density functional theory, DOI: .

Abstract.We have measured spectra of the absorption coefficient and refractive index of hen egg white lysozyme in the wavenumber region from 7 cm −1 to 50 cm −1 by terahertz (THz) time-domain spectroscopy. From comparison with the results of the inelastic neutron scattering experiment it is concluded that analysis of the THz spectra provides information on the vibrational density of states. We studied temperature dependence of the THz spectra as well as hydration effect on them to discuss structural fluctuation of the protein. We observed dynamical transition at around 210 K for lysozyme.

By terahertz (THz) time-domain spectroscopy we have measured low-frequency spectra of amino acid (glycine; Gly), short peptides ((Gly)3and (Gly)4), six globular proteins and bacteriorhodopsin (BR). From the analysis of the THz spectra we defined and obtained the reduced absorption cross sections for these cases, which are proportional to the vibrational density of states. We observed anharmonic behaviors in the low-frequency modes of the short peptides. The globular proteins we investigated show a universal feature in the low-frequency spectra. BR shows the dynamical transition in the temperature dependence of the THz spectrum when the sample is hydrated.