“…The vibrational and rotational energy levels of large molecules, especially biological macromolecules mostly lie in the THz wave band [15,16]. Biological molecular vibrations and rotations involve intra/inter molecular weak hydrogen bonds, van der Waals forces, conformational changes, non-bonded hydrophobic and hydrophilic interactions [17,18]. Moreover, THz radiation excites the aforementioned vibrations and rotations that can be revealed by refractive index spectrum and absorption (or transmission) spectrum of biological molecules by their individual symmetries and structures in the THz frequency range [19,20].…”