Thursday, September 17, 2009

Left-Handed Life: Why are We So Sinister?

"Nanosatellite to Test Life's Handedness in Space" (September 17, 2009)

"Molecules vital to life have been detected in outer space and isolated in meteorites and comets. Some of this material that rained down on Earth may have jump-started biology. If so, these space seeds also may have planted a particular molecular orientation, or 'handedness,' that spread to the world's first creatures. New research is studying how this handedness could arise in space.

"Amino acids, the building blocks of proteins, exist in two so-called 'chiral"' forms that are mirror reflections of each other, like a left and right hand. For some unknown reason, organisms use left-handed amino acids almost exclusively in making proteins (the other mirror image, while rare, is sometimes used in other processes).

" 'Outside of biology the ratio of these chiral forms is 50-50, so we want to understand the starting point of life's preference for left-handed amino acids,' says Orlando Santos of NASA Ames Research Center.

"Santos and his colleagues are designing a small satellite that would carry up biologically relevant molecules to see what effects space has on a sample's handedness, and whether this could explain the origins of homochirality...."

The article does a pretty good job of discussing what the experiment will (they hope) do - and why it's better to do experiments in the field, rather than rely exclusively on mathematical models (a no-brainer, you'd think - but it's a point).

Although word apparently hadn't filtered through to the medical and pharmaceutical industries - at least as of a few years ago - amino acids are very left-handed.

So are chemicals found in meteorites. Many of which formed at temperatures very close to absolute zero.

Why? That's a good question, and we don't have an answer. One possibility, that I ran into decades back and is mentioned in this article, is circularly polarized ultraviolet light. That could be what does it.

Or, maybe something else is the mechanism.

This experiment should narrow down the list of possibilities.

Exciting times, as I've said before.

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