Molecular handedness discovered in space.
A possible clue about why life on Earth chooses only one mirror-image form of certain molecules lies in a gas cloud tens of thousands of light-years away.
For the first time, researchers have detected a chiral molecule, propylene oxide, in interstellar space. Chiral molecules, which come in two mirror-image versions, show up in many of life's building blocks, such as amino acids and sugars. The finding may be a step toward understanding why life prefers one of these versions over the other.
The results were presented June 14 and published in the June 17 Science.
The two forms of a chiral molecule are like opposing hands. Left hands and right hands mirror each other, but no amount of turning will get them to match when overlaid. A chiral molecule's two configurations are labeled as either left-handed or right-handed.
Amino acids and sugars come in both styles of handedness. But life on Earth exclusively uses left-handed amino acids and right-handed sugars. "This is one of the longest-standing mysteries in the origin of life," Caltech chemist Brett McGuire said at a news briefing.
Chiral molecules have shown up in meteorites with a slight preference for one configuration. McGuire and colleagues went looking for chiral molecules in space to see whether some interstellar intervention could preferentially seed a solar system with one handedness. The researchers sifted through radio observations from the Green Bank Telescope In West Virginia of a gas cloud dubbed Sagittarius B2. The nebula sits near the center of the Milky Way and has historically been a rich hunting ground for interstellar molecules.
McGuire and colleagues found that the cloud was loaded with the chiral molecule propylene oxide. The stockpile has a mass equal to about 80 percent of Earth's mass, McGuire said. And if compressed into a liquid blob, it would occupy a volume over five times that of Earth. The observations don't reveal whether the cloud has a preference for one handedness over another; that will have to wait for future observations. But "we're in the best position we could possibly be," he said, to figure out if life's chiral exclusivity has an interstellar origin.
Caption: Propylene oxide, a molecule that comes in mirror-image configurations, fills a gas cloud near the Milky Way's center. Above, white represents hydrogen; gray, carbon; red, oxygen.
Please note: Illustration(s) are not available due to copyright restrictions.
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|Title Annotation:||MEETING NOTES|
|Date:||Jul 9, 2016|
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