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Ten Amino Acids Thermodynamically Favored

By Richard B. Hoppe

Posted April 14, 2009

One of the "criticisms" (scare quotes to indicate creationist blather) of science is that it doesn't (and, some say, can't) account for the emergence of life on earth. Now a new paper coming out in Astrobiology (pre-pub version online here) shows that 10 of the 20 amino acids in life on earth are thermodynamically favored, and would likely emerge under a variety of conditions.

The implications are profound, as Supernova Condensate notes. Among those implications is that life elsewhere is likely to have some characteristics in common with life on earth at the biochemical level. The abstract of the paper:

Of the twenty amino acids used in proteins, ten were formed in Miller's atmospheric discharge experiments. The two other major proposed sources of prebiotic amino acid synthesis include formation in hydrothermal vents and delivery to Earth via meteorites. We combine observational and experimental data of amino acid frequencies formed by these diverse mechanisms and show that, regardless of the source, these ten early amino acids can be ranked in order of decreasing abundance in prebiotic contexts. This order can be predicted by thermodynamics. The relative abundances of the early amino acids were most likely reflected in the composition of the first proteins at the time the genetic code originated. The remaining amino acids were incorporated into proteins after pathways for their biochemical synthesis evolved. This is consistent with theories of the evolution of the genetic code by stepwise addition of new amino acids. These are hints that key aspects of early biochemistry may be universal.

More discussion at Supernova Condensate, where I found the story.