Still stewing over life’s preference for left-handed amino acids
|July 30, 2012||Posted by News under News, Origin Of Life|
In “Left-Handed Amino Acid Puzzle Remains” (July 28, 2012), Creation-Evolution Headlines notes,
A NASA Goddard press release reported that amino acids found in the Tagish Lake meteorite (British Columbia, 2000) showed some preference for left-handed aspartic acid, but less excess for alanine. As usual, the science news media (e.g., Astrobiology Magazine, Science Daily, PhysOrg) and blogs (e.g., Darwiniana) all echoed the press release uncritically, graphics and all, so Creation-Evolution Headlines will have to do the job they should have done: evaluate the significance of the claim and see whether it solves the long-standing homochirality problem in biology:
Here are problems admitted by the press release:
Only 2 of the 20 amino acids used by life were mentioned.
The excess of one hand was 4x for aspartic acid, but only 8% for alanine.
The scientists do not know what process created the excess, but it was not polarized light, because it must have occurred inside the meteorite. “Perhaps” it was due to properties of crystallization.
The meteorite amino acids were enriched in carbon-13, not the carbon-12 common in life.
An astrobiologist admitted, ” “Synthetic proteins created using a mix of left– and right-handed amino acids just don’t work.”
Left-handed amino acids and right-handed sugars were noted as “a prerequisite for life.”
All ordinary methods of synthetically creating amino acids result in equal mixtures of left– and right-handed amino acids.
The finding complicates searches for extraterrestrial life, because it means finding one-handed molecules may not be a biomarker.
Here are more problems not mentioned in the press release: More.
The problems the press release doesn’t mention are usually far more interesting.
They usually only mention the problems for which they have thunk up distracting talking points.
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