The low protein concentration study in an extended THz frequency range

To reliably measure protein solutions spectra at low concentrations we optimized dynamic range of two time-domain spectrometers to low and to high frequencies. The transmission and the attenuated total internal reflection geometries data have been combined for precise analyzing of bovine serum albumin (BSA) aqueous solutions spectra at 0.05-3.2 THz. We compare BSA response in three spectral subregions, around 0.1, 1 and 3 THz, and confirmed that slow relaxation is the only process sensitive to biomolecules concentration in water.