Shake or Shape?

The more I learn about perfumery, the more intriguing the shape/vibration argument becomes. Recently I read (in the wrong order) Luca Turin's book about his research process, The Secret of Scent, then Avery Gilbert's What the Nose Knows, then Chandler Burr's The Emperor of Scent, about Luca Turin's quest to identify the mechanism that our bodies use to identify scent.

After following the arguments for and against molecular shape and molecular vibration, I had to come down on the side of vibration. But then I needed to know why the perfume industry, Avery Gilbert and many biologists are so dead set against it, so over the Christmas holidays I downloaded and read Luca Turin's original academic paper: A Spectroscopic Mechanism for Primary Olfactory Reception. It's not exactly poolside reading, but it's not impossible to understand. It's objective, and as well as describing his methods in uncovering a valid mechanism for the human nervous system to detect smells by their vibration, he also gives a new scientific explanation for the anomalies which scuppered the previous vibration theories by Dyson and Wright: how two molecules that have the same vibration (the right hand and left hand versions of the same compound) smell different.

His theory explains why molecules with completely different shapes can smell the same. Turin goes further and shows that two molecules with the same shape can smell different (because they have a two different ions captured inside them). That ought to be good enough to get it a fair hearing, so how come the people on the opposing bench claim that they refuse to read Turin's paper because it's a waste of time? (Read The Emperor of Scent for the whole story and see Avery Gilbert's blog for the way he writes about anyone who explores Turin's theory further.)

The difference between a true scientific theory - not just a good idea, the way we use the word theory in everyday life - is that it should be able to predict the outcome of an experiment.
Turin's vibrational theory basically says this:
If two molecules have a similar vibration, they will have a smiliar smell.

The shape explanation says that each scent molecule corresponds exactly to a receptor which it fits into perfectly. It's known as the lock and key method.

The shape explanation can't predict what something will smell like. Molecules with similar shapes can smell completely different, or not smell at all. It seems pretty obvious to someone coming to this from a scientific background, but from outside the circle of the modern perfumery industry, that the shape theory is rubbish. It doens't work, and it doesn't help to make new scents, but it's the one that the scent chemists have invested in.

I read a lot of books about perfume. Jean-Claude Ellena's little gem, Perfume, the Alchemy of Scent, dances round the round the issue by using phrases artistic rather than scientific. For Ellena, the scent molecule expresses itself to the nervous system. Roja Dove never strays from the industry line: it's the shape that does it. For him, a scent molecule searches for the right receptor them fits into it, the lock and key method.

The lock and key method does exist in nature, in our immune system, but it's not instant. Smell is. Our eyes and ears both use vibrations to explain what we hear and see. You'd have thought it was worth an investigation.

So what's the big problem? As Chandler Burr explains in The Emperor of Scent, and Luca Turin also spells out point by point in The Secret of Scent, the entire multi-million pound perfume industry relies on five (six at the time they were writing) massive companies which pretty much own the world of smell.

They make their multi-millions by creating thousands of new molecules (mostly from oxygen, carbon and hydrogen) aiming to invent and patent one that smells 1) great  and 2) strong and is safe and stable enough to be used in a brand new fragrance. They aim to impress the top perfumers (the noses, creative directors and the marketing teams) and sell this molecule to one of the huge perfume houses that dominate the world's markets. It could be used for luxury perfumery, or for washing powder, room fragrances or soap - anything that smells good.
Of the thousands that they make each year, most don't make the grade. Only about 1% of their research chemists' results will be useful. That's 99% of their work down the plughole. That's the way research goes.
But if they chose to apply Luca Turin's theory, and aimed to create molecules with similar vibrations to sandalwood, jasmine, rose and all the really expensive natural stuff, which was what he recommended, he suggested that they could maybe save 90% of their costs. So why don't they? Why is the vibration theory stamped on so hard whenever it's mentioned? Chandler Burr's explanation is that the people who really do understand Turin's method, CHYPRE (CHaracter PREdiction (he has a sense of humour)), realise that 90% of them would lose their jobs if it were adopted so they denounce it as ridiculous.

Luca Turin appears to be entirely unmotivated by money; he is besotted with scent and he adores pure science. He's also defiantly anti-political, in the sense that he doesn't really care about his career or status in the academic world as long as he has a lab and access to research facilities. He has also crossed scientific discliplines to get to his result, something that hasn't been popular in the last 100 years since science split up into specialisms. He's technically a biophysicist, but he had to delve into chemistry, physics and biology to get the answers he needed. While the chemists say that his chemistry is valid, and likewise with the physicists and biologists, if a scientist sticks his or head up and says "Isn't this worth a further look?" they risk being shot at from all directions.

This isn't a new situation. Even Einstein had one theory that no-one believed until after his death. Centuries ago, scientists who dared to suggest something that disagreed with the powers that be risked burning at the stake. It was obvious that the sun orbited the earth, wasn't it? You could see it happening. Fortunately for Turin, you don't get shoved in the slammer for your theories these days, but the verbal abuse he's had is a wonder to behold.

Now, he's working on scent research for the US military, the organisation that funded the internet. Isn't that a bit of a hint that he might actually be right?