New Worlds: Why does success smell sweet?

The Weizmann Institute and the University of California have found that the pleasantness of an odor can be predicted from its molecular structure.

September 29, 2007 20:55
4 minute read.
New Worlds: Why does success smell sweet?

smell 88. (photo credit: )


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A rose is a rose is a rose, but what makes some smells alluring and others disgusting? Is there something in a substance's chemistry that can predict how we will like its smell? Now scientists at the Weizmann Institute in Rehovot and the University of California at Berkeley have found that the pleasantness of an odor can indeed be predicted from its molecular structure. Until now, there was no known physical factor that could explain how our brains sense odors. The new study, led by Prof. Noam Sobel of the institute's neurobiology department, constitutes a first step in understanding the physical laws that underlie smell. Their research was published in the Journal of Neuroscience. To identify the general principles by which our sense of smell is organized, the researchers started with a database of 160 odors that had been ranked by 150 perfume experts according to a set of 146 characteristics (such as sweetish, smoky and musty). These data were then analyzed with a statistical program that examined the variances in perception. The scientists found that the data fell along an axis they called the "pleasantness rating" of the odors - running from "sweet" and "flowery" at one end to "rancid" and "sickening" at the other. The same distribution along this axis, they discovered to their surprise, closely describes the variation in chemical and physical properties from one substance to another. The researchers theorized that they could build a model to predict, from the molecular structure of a substance, how its smell would be perceived. To doublecheck, Sobel and his team tested how experimental subjects assessed 50 odors they had never smelled before. They found that the ratings fit closely with the ranking shown by their model. In other words, they were able to predict the level of pleasantness quite well, even for unfamiliar smells. They noted that, although such preferences are commonly supposed to be culturally learned, the responses of Americans, Israeli Jews and and Israeli Arabs all fit the predictions. VIRUS BEHIND BEE BUZZ-OFFS? A virus identified at The Hebrew University Agriculture Faculty in Rehovot is the prime suspect in the death of bees and the dwindling of bee colonies by "colony collapse disorder" in various parts of the world including Israel. Virology Prof. Ilan Sela, who discovered the virus (dubbed the Israeli Acute Paralysis Virus) published his findings in the online edition of Science. Until then, beekeepers had blamed environmental factors such as cellphone transmissions, climate change and genetically modified crops. A drop of 70-90% in the bee population has been reported in parts of the US, Brazil, Central America, Germany, Italy, Poland, Spain and Portugal in the past few years. Deaths of honeybees in the US led to the country importing them from Australia in 2004. However, the virus has been found in some Australian bees as well, even though the collapse of colonies there has not been as massive as in the US. Statistical analyses showed that a colony infected with the virus was 65 times more likely to experience colony collapse disorder than one without it. To try to find whether the virus was the cause, researchers are preparing a new series of tests in which isolated bee colonies would purposely be infected with the virus to see the effects. Even though the connection has not yet been proven, Sela hopes that within a few years, it will be possible to save the bees by developing varieties that are immune to the virus. Ironically, over a month ago a group of Israeli bee experts went to the US to study the reasons for the mysterious reduction in that country's bee population. Yoram Paz, director of an Emek Hefer beehive company, said there were already worrying signs that the problem had begun to reduce honey and fruit production here. Bees are needed not only to make honey but also for pollination of avocado, almond, cherry, apricot, plum, apple, pear and mango trees; without bees, the production of fruit would be severely hampered, Paz said. ISRAELI TEEN BAGS EU PRIZE A 17-year-old Israeli high-school pupil has won second prize in the 19th European Union Contest for Young Scientists, held in Valencia, Spain. Yael Amarilyo won 3,000 euros for her project on "The Molecular Identification and Characterization of Phytoplasma Bacteria in Grapevines," which, she says will enable grape growers to deal with yellow disease caused mainly by phytoplasmas, and thus reduce financial losses. She was also chosen to attend next year's London International Youth Science Forum, where she will meet young scientists from around the world and take part in the annual two-week summer science festival in 2008. Amarilyo, a pupil of the Rishon Lezion Gymnasia, tied for third place in the Intel-Israel Young Scientist Competition held in March at Jerusalem's Bloomfield Science Museum. Teams from Germany, Hungary and Ireland won the three first prizes of 5,000 euros each for their projects, which were selected from among 81 entries by an international jury. Contestants, aged 14 to 20, represented 32 countries, and their projects covered a wide range of disciplines. "If there are two crucial elements of Europe's future, it's our young people and our research ability," said European Science and Research Commissioner Janez Potocnik. "So it's very heartening to see the interest from around the world in this contest for young scientists, as well as the many innovative ideas on display." To enter, the individual or team had to win a national science competition. Several past participants have achieved major breakthroughs, or set up businesses to market ideas developed for the contest.

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