The vibrational spectra of trehalose and glucose: terahertz spectroscopy and density functional theory calculations

The THz spectra of α,α-trehalose (α-D-glucopyranosyl α-D-glucopyranoside) and α-D-glucose at high resolution were measured. The low-frequency vibrational absorption bands of those compounds in THz region were assigned by density functional calculations with reliable accuracy. The peaks at 60-80 cm^-1 were assigned to torsion modes of hydroxymethyl groups in the extremely complicated THz spectrum of α,α-trehalose. In addition, several polarization-dependent signals from the motion of water molecules in crystal were found.