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Receptors and more receptors
"The goal of the hunt was simply to possess everything the world could offer in the way of odors."
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Receptors detect and relay messages
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We sense a smell when a chemical wafts into our nose and contacts a protein called a receptor. That contact turns on, or activates, the receptor protein, so that the receptor can pass a message to the inside of a nerve cell. The nerve cell relays the message to the brain.
The problem, then, is not how a smell is detected, but how one smell is classified as different from all the other smells. A good place to start on this problem is to find receptor proteins, so we can work out how many different receptors there are, and how many different chemicals each one detects.
Senomyx was born in April 1999 soon after Charles Zuker (University of California, San Diego) and Nicholas Ryba (National Institutes of Health, (Bethesda, Maryland) found two receptor proteins not for smell, but for taste. Zuker had originally made his name by deciphering how the fruit fly Drosophila makes a functional eye. But his new receptor proteins were from rats. "Drosophila have even smaller mouths than they have eyes," says Grayson, "so when Charles started working on taste he moved to mammals."
From the initial idea of taste, the company quickly started thinking about the science of smell. The appeal was the lack of regulation ("Phase III clinical trials are basically someone smelling it," says Grayson) and the more developed state of the science.
The molecular era of olfaction (smell) research had started in 1991 with the isolation of olfactory receptor genes by Linda Buck and Richard Axel (then both at Columbia University in New York). At last count there were ~1000 olfactory receptor genes in rats and mice and over 500 in humans (including many non-functional versions called pseudogenes).
Senomyx has intellectual property covering not only many of these olfactory receptors, but also a host of bitter taste receptors discovered by Zuker and Ryba in March 2000, and a method for making large amounts of the receptors. Now the company has to work out what to do with all those receptor proteins.
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Stinky Science 
Biotech Applied Index
