The Nobel Prize in Physiology or Medicine was awarded yesterday to two American researchers, Linda B. Buck of the Fred Hutchinson Cancer Research Center and Richard Axel of Columbia University. The scientists were honored for their work on unraveling the sense of smell.

For years, the principles governing the olfactory system eluded explanation. Then, in 1991, Buck and Axel published a seminal paper describing a family of about a thousand genes in mice (that is, a whopping 3 percent of the total gene count) for odorant receptors that detect inhaled odorant molecules. Humans have a comparable number of these receptors, which make up a subset of the so-called G protein-coupled receptors (GPCR).

Since then Buck and Axel have worked independently of one another and further clarified the workings of the olfactory system. The highly specialized receptors--each of which can detect only a few odorants--sit on olfactory receptor cells (one receptor type to a cell) located in the nose that transmit information to the olfactory bulb and other parts of the brain. Here, the information from the receptors generates a unique pattern, or fingerprint, for each scent, enabling humans to recognize and remember some 10,000 different odors.

Other sensory systems appear to operate according to the same general principles that Buck and Axel discovered for olfaction: pheromones and taste buds both rely on other families of GPCR. --Kate Wong