Nosing around

The sense of smell is one of the most undervalued of our five senses. When asked which sense is valued the most, the answer is rarely the sense of smell.

‘NRI engineer develops an electronic nose’ was the headline. Vivek Subramanian, an engineer at Berkeley has fabricated an electronic sensor which can sense different smells. Depending on the kind of polymer used in the sensor, the ‘electronic proboscis’ can tell whether wine is fresh or stale or if the harmless shoe box has RDX. The electronic detector is far more efficient than a chemical one which can be used only for a particular kind of smell.

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The sense of smell is surely one of the most undervalued of our five senses. When asked which sense they value the most, the answer is rarely the sense of smell. But clearly, the multi-billion dollar perfume and deodorant tells us otherwise.

Understanding smell is actually very complicated. There are literally thousands of distinct smells that an average person can distinguish. How does the nose know the difference between the smell of rotten eggs and Chanel 5? About 15 years ago, scientists discovered a class of proteins called olfactory receptors which sit on the nerve cells in our snouts. There are about a thousand different kinds of receptors which bind to molecules found in the chemicals that enter through our nose.

But we still don’t know how the nose quite knows. A missing link in the puzzle was, and remains, the question of how a thousand receptors are able to distinguish between so many smells. Some scientists believe that the receptors act like the alphabet of a language which can be combined to form smells. Others believe that the receptors are sensitive to the vibrations of the atoms in the olfactory stimulus. Clearly, the answer to such questions are important. The Nobel Committee recognised this by giving the 2004 Nobel prize to Richard Axel and Linda Buck who proposed that a single receptor can be sensitive to more than one smell at the same time.

Smell invokes strong memories. One such memory is of entering any apartment complex in the US that houses people from the subcontinent. As soon as one enters the foyer, a strong smell of sambhar powder hits. And this is uniform — irrespective of whether there were South Indians in the complex or not.

A friend of mine, pursuing a Ph.D in chemistry couldn’t identify that a gas pipeline in her lab was leaking as she had no sense of smell. That is a tricky disability. Fortunately for her, a colleague entered the lab and discovered the leak in time. But now, maybe she could wear one of Subramanian’s electronic nose around her neck — an essential accessory, much like the ubiquitous cell phone.