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.

Comments

Chirality probably didn't come from space

[LeDopore]

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.