The mechanism of detection of odorant molecules by olfactory receptors (OR) is not known. The literature reveals two competing models. The first model known as the “Shape Theory of Olfaction, STO” posits that odorants are detected by ORs through a key-lock-like docking mechanism. The second, quantum mechanics-based model known as the “Vibrational Theory of Olfaction, VTO” relates molecules’ scent to their vibrational spectra and postulates that odor recognition involves quantum mechanical inelastic tunneling of electrons through the odorant-bound receptor. However, both theories have remained unproven and controversial.
