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Old 03-19-2009, 06:47 AM   #1
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Default Clues To A Secret Of Life Found In Meteorite Dust

"We found more support for the idea that biological molecules, like amino acids, created in space and brought to Earth by meteorite impacts help explain why life is left-handed," said Dr. Daniel Glavin of NASA's Goddard Space Flight Center in Greenbelt, Md. "By that I mean why all known life uses only left-handed versions of amino acids to build proteins." Glavin is lead author of a paper on this research appearing in the Proceedings of the National Academy of Sciences March 16.

Proteins are the workhorse molecules of life, used in everything from structures like hair to enzymes, the catalysts that speed up or regulate chemical reactions. Just as the 26 letters of the alphabet are arranged in limitless combinations to make words, life uses 20 different amino acids in a huge variety of arrangements to build millions of different proteins. Amino acid molecules can be built in two ways that are mirror images of each other, like your hands. Although life based on right-handed amino acids would presumably work fine, "you can't mix them," says Dr. Jason Dworkin of NASA Goddard, co-author of the study. "If you do, life turns to something resembling scrambled eggs -- it's a mess. Since life doesn't work with a mixture of left-handed and right-handed amino acids, the mystery is: how did life decide -- what made life choose left-handed amino acids over right-handed ones?"

Over the last four years, the team carefully analyzed samples of meteorites with an abundance of carbon, called carbonaceous chondrites. The researchers looked for the amino acid isovaline and discovered that three types of carbonaceous meteorites had more of the left-handed version than the right-handed variety – as much as a record 18 percent more in the often-studied Murchison meteorite. "Finding more left-handed isovaline in a variety of meteorites supports the theory that amino acids brought to the early Earth by asteroids and comets contributed to the origin of only left-handed based protein life on Earth," said Glavin.

If the bias toward left-handedness originated in space, it makes the search for extraterrestrial life in our solar system more difficult, while also making its origin a bit more likely, according to the team.

"If we find life anywhere else in our solar system, it will probably be microscopic, since microbes can survive in extreme environments," said Dworkin. "One of the biggest problems in determining if microscopic life is truly extra-terrestrial is making sure the sample wasn't contaminated by microbes brought from Earth. If we find the life is based on right-handed amino acids, then we know for sure it isn't from Earth. However, if the bias toward left-handed amino acids began in space, it likely extends across the solar system, so any life we may find on Mars, for example, will also be left-handed. On the other hand, if there is a mechanism to choose handedness before life emerges, it is one less problem prebiotic chemistry has to solve before making life. If it was solved for Earth, it probably has been solved for the other places in our solar system where the recipe for life might exist, such as beneath the surface of Mars, or in potential oceans under the icy crust of Europa and Enceladus, or on Titan."

The research was funded by the NASA Astrobiology Institute, the NASA Cosmochemistry program, and the NASA Astrobiology: Exobiology, and Evolutionary Biology program.

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Old 03-19-2009, 08:55 AM   #2
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An interesting panspermia tangent.

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Old 03-19-2009, 02:05 PM   #3
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Can you make food out of right handed amino acids?

You could eat as much as you want and not gain weight. (I think)
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Old 03-19-2009, 02:50 PM   #4
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right handed sugar.
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Old 03-20-2009, 03:16 PM   #5
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Originally Posted by Auburn Boy View Post

The history of sugar substitutes is a catalog of strange scientific accidents stretching back more than a century. In 1879, chemists Ira Remsen and Constantine Fahlberg synthesized a derivative of coal tar called orthobenzoyl sulfimide. One day, Fahlberg spilled the substance on his hand, which later that evening he touched to his mouth. It tasted sweet. He filed for a patent and called the substance saccharin. In 1937, a University of Illinois grad student discovered another sweetener when he set his cigarette on a lab bench during an experiment - testing a would-be antifever drug - and then took a drag off the cyclamate-coated end. In 1965, a chemist named Jim Schlatter was working on a compound to treat gastric ulcers. He licked his finger to grab a sheet of paper and tasted aspartame for the first time. Then there was the 1976 discovery of sucralose by a King's College student working with chemically altered sugars. The student - not a native English speaker - mistook his professor's instruction to "test" the material and tasted a mouthful.

I am just thinking what my high school lab professor would do about this violation of lab safety.

Previously, drugs were produced in a mixture of equal parts right-handed and left-handed enantiomers. The problem with such mixtures is that the correct enantiomer might cure a disease, but the wrong one could wreak havoc on the body. Such was the case with thalidomide in the 1960s. One version cured morning sickness during pregnancy; the other caused birth defects. By the late 1980s, researchers had improved methods of synthesizing single enantiomers, which led to a revolution in pharmaceuticals.
Never knew that. I heard they were bringing thalidomide back but names something else. I guess this is why.
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Last edited by Potemkin; 03-20-2009 at 03:43 PM.
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clues, dust, found, life, meteorite, secret

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