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Asymmetric Molecule, Key To Life, Detected In Space For First Time (yahoo.com)
schwit1 quotes a report from Yahoo News: Scientists for the first time have found a complex organic molecule in space that bears the same asymmetric structure as molecules that are key to life on Earth. The researchers said on Tuesday they detected the complex organic molecule called propylene oxide in a giant cloud of gas and dust near the center of the Milky Way galaxy. Akin to a pair of human hands, certain organic molecules including propylene oxide possess mirror-like versions of themselves, a chemical property called chirality. Scientists have long pondered why living things make use of only one version of certain molecules, such as the 'right-handed' form of the sugar ribose, which is the backbone of DNA. The discovery of propylene oxide in space boosts theories that chirality has cosmic origins. The scientists in the new study used radio telescopes to ferret out the chemical details of molecules in the distant, star-forming cloud of gas and dust. As molecules move around in the vacuum of space they emit telltale vibrations that appear as distinctive radio waves. Future studies of how polarized light interacts with the molecules may reveal if one version of propylene oxide dominates in space, the researchers said.
When I first read this, I thought they had found a non-50:50 ratio of enantiomers, but it appears that they have simply detected the presence of propylene oxide in some form, which doesn't seem terribly surprising to me. It would be fascinating if they did discover that one enantiomer was favoured but I'm not sure how this could be done short of collecting the chemical... are there any convenient sources of polarised light in space?
They've found that one of the simplest pair of chiral molecules can be created in space. Not surprising, and both the left and right enantiomers (the left and right handed molecules) are almost certainly present in a 50/50 ratio, so not enantiomerically pure. They have not shown anything at all interesting here.
One of the defining things about chiral chemistry is that to have a pure enantiomeric compound you either have to start with an enantiomerically pure compound as a starting materials (biologically derived materials are the only known natural source) or have it interact with another enantiomericially pure catalyst (biological enzymes being the only known natural source of these) or purification medium. It is pretty much a signature of biology.
What would be interesting is if there was found a chiral molecule in space that was significantly biased to one enantiomer. Depending on the context of what was found this would be proof of either extraterrestrial life, or a cosmic enantiomeric enrichment process that would have huge implications for understanding the origin of life.
The news is interesting not so much for its contents, but for its illumination of a gap in my knowledge. I'm nowhere near astronomy, so I didn't know that in the past we were _not_ aware of the presence of asymmetric molecules in space. If someone asked, I'd have responded, "sure there are probably asymmetric molecules in space, why not" so in some sense, I might have given a more correct answer than someone who knew more about space. The downside is that when you not only learn from a piece of news, but it highlights a gap in your understanding before, then it's quite humbling. It's a bit like waking up in Vegas, and you're told you divorced while you were drunk, yet you aren't aware of getting married in the first place.
One day, the "Most Stupid Comment of the Day!" award will remain non-awarded.
Thanks to you, this won't be the day.
TFA suggests a beautiful idea: that life bears the imprint of handedness derived from cosmic dust. The idea may be beautiful, but it's wrong. It's much more likely that the chirality of biomolecules we see on Earth came from spontaneous symmetry breaking on Earth itself than by space seeding any preferred chirality.
Complex molecules in living beings are assembled from consistent smaller molecules, known as monomers. Some of these monomers have a handedness (they have two enantiomers), and in that case living things will almost always use just one of the enantiomers. The best explanation for why living things tend to use just one enantiomer is the same reason you would hate to have two slightly different kinds of Lego blocks with incompatible pitch: this diversity usually just gets in the way of assembling complex macromolecules without providing any compelling value.
Thus, we know even given no seeding of chirality from space, life would pick one chirality since having just one is usually useful. Add to that the facts that we haven't yet found a non-racemic mixture of anything in space, and that even if we did the fraction of space-derived non-racemic molecules on the Earth's surface would hardly noticeably change the balance of chiralities found in proto-life Earth, and it's pretty clear that the chirality of biomolecules in living things is totally independent of biased enantiomers from space.
Expected time to finish is 1 hour and 60 minutes.
First mover advantage probably has it: since all of the amino acids are made from one another, they're going to match up with whatever they were made from. I would guess that before the last common ancestor there may be have been some other primitive organisms with left handed amino acids, but whichever got slightly bigger faster would have the advantage of a primitive ecology and then swamp out the other after some natural selection feedback loops improved things.
A mirror on vertical plane produces a laterally inverted image. OK. Why it does not produce upside down image? Is it in our brain? A mirror on horizontal plane, like a lake surface, produces an upside down and laterally inverted image. Why?
Richard Feynman explains it best. Watch it here.