Keith Kelsen’s Scent Narrative: Molecules of Scent Part 1 

Molecules are small but mighty. Molecules play a massive role in humanity. They have saved billions of lives (R-C9H11N2O4S Penicillin), been the alchemy of technology (Si Silicon), wreaked environmental havoc (CO2 Carbon Monoxide), and have made the world a happier place (C2H6O Methanol as in Alcoholic Spirits). It’s probable that molecules have changed the course of human history. Now, small scent molecules have been found to have a tremendous impact.

1,000,000,000,000 Human Scents!

We know that humans can discriminate 16 million different colors and almost half a million different audio tones, but the number of scents seems infinite. Recently, during psychophysical tests of “odor mixture discrimination”, it was found that humans can discriminate among more than a trillion different smells. (The tests were drawn from a collection of 128 different scent molecules.1)

This amazing number is far more than previous estimates of distinguishable scents. It demonstrates that the human olfactory system, with its hundreds of different receptors, far outperforms the other senses. All of it based on the molecular dynamics of scent.

Suddenly, Scent Molecules are Important; Here’s Why…

The molecules of scent are being studied by organic chemists worldwide as a clue to the universe. The most amazing realization being that while scent is only molecules, it can have significant emotional, psychological and even physiological impact. Scent (or Odors as it is referred to in scientific journals) attributes are complex and varied. Arranging smells like basic tastes (sweet, sour, salty, and bitter) into distinct classes is not easy. Fortunately, there are various “Tones” that can be arranged into groups.

There are many organic and synthetic molecules that smell nice. We experience these all the time; using a perfume to smell good to others or stopping to put our nose in a rose. To be detectable to our noses, molecules must be dissolved in lipids or fats, small2 and volatile. Fragrant molecules then escape from their fluid into the air. 3

That is where we catch them. Does a rose by any other name smell as sweet? Yes. It does.

The Nose Knows. Here’s how…

The nose is the most important organ to distinguish the scent. The sensory tissue, (olfactory epithelium), is a mucous membrane on the roof of the nasal cavity. Scent reaches this in the air we breathe. For more unnoticeable smells, we just sniff more times, pulling in more air and fragrance. It is then when the molecules dissolve and join to the smell receptors. All in the briefest of moments, the cells send nerve impulses directly to our brain.

In early life, it learns to associate the smell with its origin (like the rose). That stored memory, let’s us recognize it (even when the object is hidden). It also associates it with a memory (the first rose ever smelled was with my grandma, so roses make me remember Grandma’s garden) or classifies it as unknown.

Synthetic Molecules Created the Modern Scent Industry

At the start of the 20th Century, a burst of innovative synthetic chemicals hit the scent market—including ionones, (simulating the scent of violets), and synthetic musk. As with all great innovations, musk was discovered accidentally by a chemist trying to make an explosive. Now available in quantity, these manufactured molecules were readily available. The world of fragrances essentially went from black-and-white to color. This is when the true “Scent Narrative” was born.

“Synthetics are what made modern perfumery possible,” says scent maker Rodrigo Flores-Roux, who has created fragrances for Calvin Klein and Tom Ford. “Historically, it’s been the application of something never used before or an overdose of an ingredient that has made a perfume stand the test of time, and in almost every case, like the famous aldehydes in Chanel No. 5, it was a synthetic material that did this.”  4

The top-secret French labs of leading fragrance makers like Firmenich, International Flavors & Fragrances (IFF) and Givaudan, brilliant scientists disassemble then reassemble the chemical bonds that hold the molecules together. They craft new scents from this and often are surprised by the outcome.

“Columbus left to discover a route to India but ended up in America,” said Anubhav Narula, research director for fragrance ingredients at IFF in a December Elle article last year, “A scientist may design a molecule to make a rose but end up with a jasmine.”

As with all innovation, the discovery path may lead you places you never expect with results that are better than you ever imagined.

You don’t have to Recite a Trillion Scents, Just impress your friends with these…

Synthetic Molecules are undistinguishable from their organic cousins. There are many, but the most prevalent include Flowery (jasmine), Spicy (ginger, pepper), Fruity (ethyl acetate), Resinous (resin smoke), Foul (rotten egg), Burning (tar). Musk (muscone), Camphor, Rancid (isovaleric acid, butyric acid) and Pungent (formic acid, acetic acid) all key basics for scents.

The intensity of combining them can create an almost three-dimensional world in a whiff. It transcends memories and forces the brain to grasp at elements it cannot describe. Theories and hypotheses about these molecules are complicated by the fact that some very differently shaped molecules can have similar smells, whereas similarly shaped molecules can sometimes smell quite different from each other. How do these experts create scents that have no background? There is a reason that people can do the things these perfumers can. They are passionate. Hugely, unabashedly, passionate.

Here’s the Most Amazing Part: Scent Molecules VIBRATE

Scent molecules are made of atoms connected by bonds. The arrangement of bonds and atoms defines the “vibration” of the molecule. British chemist Malcolm Dyson in the 1930s first suggested that our nose detects the vibrations of molecules.

Therefore, Chemists can identify molecules by their vibrations, using a spectroscope to observe the radiation and vibration. Understanding how they vibrate and why is a key to understanding how scent is perceived.

It’s the Vibe! The Secret of Scent Lies in Molecular Vibrations

Dr. Luca Turin led a brilliant group in a breakthrough study that changed the Fragrance industry. Their study revealed “the secret of scent” lies in molecular vibrations. Molecular vibrations, rather than molecular shape, give substances their distinct smell. A Lebanon-born biophysicist fascinated with the mechanisms of smell,

Dr. Turin came up this innovative theory in 1996. It’s not just the molecule’s shape that’s important, according to Dr. Turin, but also how it vibrates once inside the receptor’s binding pocket. If it oscillates in just the right way it encourages an electron to ‘jump’ from one part of the receptor protein to another. This process called “quantum tunneling” sets off a nerve impulse. Turin’s theory can potentially explain the different scents of molecules with the same shape but different atoms.

All of this and more has been proven, according to a new joint study by London Center for Nanotechnology (LCN) and University College London (UCL) scientists. (UCL ranks 7 in the world’s top 10 universities, according to the QS World University Rankings® 2018.) In this study designed to find out how smell is written into a molecule’s structure, scientists tested whether changing how a molecule vibrates on a nanoscale, it changes its smell. Dr. Turin, the author of this study said:

“We can detect and identify tens of thousands of smelly molecules by smell alone. The greatest mystery can be summed up in one question: what makes a molecule smell of rose, lemon or rotten eggs? This work shows that altering molecular vibrations of molecules changes their smell. Receptors in our noses are acting like tiny spectrometers to identify molecules by their vibrations.”

Scent Molecules vibrate and move to be recognized. This “Tiny Dancer5” can create an impact on humans in ways that cause behavior changes. In Part 2, I will discuss how this works and how it may help the world.

Related Posts

Leave a comment