Nobel Prize in Medicine for "Noses"

Award for groundbreaking insouciation of the human sense of smell

Nobel Prize winners Richard Axel and Linda Buck HHMI
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Hardly any sensory stimulation awakens such immediate feelings and memories as a smell. But how the sense of smell works has been puzzling for a long time. How and why the human nose perceives more than 10, 000 different fragrances was unclear. Until the American scientists Richard Axel and Linda Buck took on this puzzle more than 13 years ago and discovered by means of a series of pioneering studies that a large, consisting of several thousand different genes gene family responsible for the formation of the various odor receptors.

Now both scientists have been jointly awarded the Nobel Prize for Physiology and Medicine for their "Discovery of the Odor Receptors and the Organization of the Olfactory System". Axel currently works at Columbia University in New York and his colleague Buck at the Howard Hughes Medical Institute in Seattle. Both published their decisive results in 1991 in a joint paper, but since then they have been independently researching each other - but still in the realm of "supernatants".

The sense of smell is the first of our senses that has been decoded using molecular biological methods. Axel and Buck showed that an amazing three percent of our genes - more than any other sense - are needed to encode the various olfactory receptors on our nasal mucosa. Their discovery that every single receptor cell expresses only one of the receptor genes was completely unexpected to researchers as well as to science.

All olfactory receptors are made up of related proteins, but differ in small details. A chain of amino acids anchored in the cell wall and crossing them seven times forms the backbone of an olfactory receptor. This chain creates a specifically shaped "pocket" to which the scent substance binds. When this happens, the shape of the receptor protein changes and a signaling protein is activated that activates the signal chain to the brain.

The two researchers recorded the electrical signals from individual olfactory cells, revealing that each cell not only reacts to a single olfactory substance, but to several related molecules - albeit with different strengths. Most odors consist of a variety of chemical compounds - and each of these compounds can activate multiple receptors. This creates a typical "smell pattern" in the brain - comparable to a complex color pattern in a patchwork blanket. This pattern forms the basis for our ability to recognize odors and to recall fragrances and their associated memories even after many years. display

(Karolinska Institutet, 05.10.2004 - NPO)