Status of the Vibrational Theory of Olfaction

Abstract

The vibrational theory of olfaction is an attempt to describe a possible mechanism for olfaction which is explanatory and provides researchers with a set of principles which permit predictions allowing for structure-odor relations. Similar theories have occurred several times throughout olfactory science; this theory has again recently come to prominence by Luca Turin, who suggested that inelastic electron tunneling is the method by which vibrations are detected by the olfactory receptors within the hose. This work is intended to convey to the reader an up-to-date account of the vibrational theory of olfaction, both the historical iterations as well as the present iteration. This text is designed to give a chronological account of both theoretical and experimental studies on the topic, while providing context, comments, and background where they were found to be needed.

Gated electron transport in rhodopsin and its relevance to GPCR activation

“…electron transfer from a donor via an odorant to an acceptor, enabled by excita4on of molecular vibra4ons in the odorant 1 . The physics behind this idea was shown to be sound [2][3][4][5][6] , and strong behavioural and perceptual evidence in its favour has come from experiments on insects and humans [7][8][9][10] . However, the idea currently remains controversial [11][12][13] , in part because vertebrate olfactory receptors are members of the G-protein-coupled receptor (GPCR) family: GPCRs are thought to work by a conven4onal lock and key mechanism 14,15 .…”

Quantum Biology: Does quantum physics hold the key to revolutionizing medicine?

“…However, a new and controversial theory of olfaction involves quantum phenomena and suggests that smell originates from the sensing of molecular vibrations by structures in the nasal mucosa; this process is proposed to involve electron tunnelling between the odorant and the receptor to which it binds in the nose [120] . Turin proposed that the inelastic tunnelling of electrons from donor to acceptor molecules is proton assisted [121] . Recently, a model proposed by Brookes presented evidence that this proposed proton assisted electron tunnelling mechanism fits the observed features of smell.…”

Does Archaeology Stink? Detecting Smell in the Past Using Headspace Sampling Techniques

“…Questions abound around how the odor molecules connected with the cilia in the nasal epithelium remain long enough to make an impression on the limbic system. A theory put forward in the 1930s was a vibration theory suggesting that odor molecules vibrated and created the signals in the cilia (Hoehn et al 2018). Amoore's (1952) shape theory defined volatile odor molecules as having shape which worked on a lock and Fig.…”

“…6), triggering and sending electronic signals to the limbic area (Amoore 1971;Engen 1982: 17-34). Turin (1996) combined vibration theory with the lock and key theory, suggesting that an electronic tunneling system by which the vibrational molecules effectively "burrowed" their way through to the cilia where they interlocked in the right place for sending signals to the limbic system (also see Hoehn et al 2018).…”