Quantum Nose

Why should we be surprised if quantum phenomenon can be applied to biology? Biology is, after all, a kind of applied chemistry and chemistry is a kind of applied physics. Everything at the end must come down to a fundamental level right? After all the Biomolecules such as DNA and enzymes are made up of fundamental particles like protons and electrons whose interactions are governed by quantum mechanics. Quantum biology arises out of recent research works on biological phenomenon such as photosynthesis, migration of birds from southern hemisphere and fishes on coral reefs, the olfactory receptors of humans and animals, DNA mutation and so on.

                                    “A rose by any other name would smell as sweet”

                                                                                    -William Shakespeare

Today we will not be going far away to magnetics poles and southern hemisphere but right at our nose tip! Aromas and scents have occupied a vast place in literature and poetry but it turns out that the fundamental mechanism lies in the quantum realm of molecules.

The conventional mechanism was understood to be as key and lock mechanism where molecules with different shapes gets locked in our receptors and sent a G-protein which sends a message to our brain. This further developed into a theory by Malcolm Dyson that receptors rather detect the vibrational frequency of the bonded molecules than their structures. However, it came with its own deficiencies as limonene and di-pentene were some of the exceptions.

Luca Turin who studied physiology at London was convinced that the vibrational frequency of bonds and their scents could not be a mere coincidence. He went on to proposing that the biomolecules could detect the vibrations of chemical bonds via quantum tunneling of electrons. This was based on inelastic electron tunneling spectroscopy (IETS). In which two plates are held parallel at a potential difference between them. The electrons at the donor side can jump to the acceptor either by losing or gaining a particular amount of energy. The electron can donate the excess of energy to the chemical placed between the plates who vibrates at just right frequency. Thus, making the electron tunnel “inellastically” to the acceptor side. Turin proposed that the olfactory receptors work in similar way –the olfactory receptors taking the place of plates of IETS. If the receptor captures an odorant molecule that possesses a bond tuned to just the right vibrational frequency, then the electron can pop from donor to accepter via tunnelling. Turin proposed that the tunnelled electron, now sitting in the accepter site, causes the release of G protein allowing us to experience scent.

However, it still remains a task to find more about the structure of olfactory receptors and no direct experiment yet has tested weather quantum tunnelling in involved in smell.


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