Quantum smell: tunneling mechanisms in olfaction

TL;DR

This paper proposes a tunneling-based mechanism for olfaction, highlighting the role of charge transport, electron-phonon interactions, and off-resonant tunneling in odorant recognition, challenging simpler models.

Contribution

It introduces a novel tunneling perspective on olfaction, emphasizing the importance of electronic coupling and vibrational frequencies in odorant detection.

Findings

Odorants act as weak tunneling conductors due to limited electronic coupling.

Electron-phonon interactions influence charge transport in olfaction.

Mechanisms are more complex than previously thought, involving off-resonant tunneling.

Abstract

The mechanism by which odorants are recognized by olfactory receptors remains primarily unresolved. While charge transport is believed to play a significant role, its precise nature is still unclear. Here, we present a novel perspective by exploring the interplay between the intrinsic energy scales of odorant molecules and the gap states that facilitate intermolecular charge transport. We find that odorants act as weak tunneling conductors mainly because of the limited magnitude of electronic coupling. This behavior is further connected to electron-phonon interactions and reorganization energy, suggesting that physically meaningful values for these parameters emerge only in the deep off-resonant tunneling regime. These findings complement the swipe card model of olfaction, in which an odorant needs both the right shape to bind to a receptor and the correct vibrational frequency to trigger signal transduction. Moreover, they reveal that the underlying mechanisms are much more complex than previously assumed.