The low-wavenumber spectra of CCl4, Milli-Q water and aqueous solution of α-chymotrypsin protein were measured using four-photon coherent spectroscopy in the subterahertz range. Good coincidence of narrow peak positions in the four-photon spectra of liquid CCl4 with the rotational frequencies in the gas phase was observed for the first time. A new sharp (width ∼0.6 cm−1) resonance at ∼3 cm−1 was observed in the aqueous protein solution, in contrast with water. This difference was interpreted as an exhibition of low-wavenumber vibrations of large fragments of the protein molecule. Copyright © 2006 John Wiley & Sons, Ltd.