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

The THz spectra of /spl alpha/,/spl alpha/-trehalose (/spl alpha/-D-glucopyranosyl /spl alpha/-D-glucopyranoside) and /spl alpha/-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/sup -1/ were assigned to torsion modes of hydroxymethyl groups in the extremely complicated THz spectrum of /spl alpha/,/spl alpha/-trehalose. In addition, several polarization-dependent signals from the motion of water molecules in crystal were found.