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Abstract: Of the twenty amino acids used in proteins, ten were formed in Miller-satmospheric discharge experiments. The two other major proposed sources ofprebiotic amino acid synthesis include formation in hydrothermal vents anddelivery to Earth via meteorites. We combine observational and experimentaldata of amino acid frequencies formed by these diverse mechanisms and showthat, regardless of the source, these ten early amino acids can be ranked inorder of decreasing abundance in prebiotic contexts. This order can bepredicted by thermodynamics. The relative abundances of the early amino acidswere most likely reflected in the composition of the first proteins at the timethe genetic code originated. The remaining amino acids were incorporated intoproteins after pathways for their biochemical synthesis evolved. This isconsistent with theories of the evolution of the genetic code by stepwiseaddition of new amino acids. These are hints that key aspects of earlybiochemistry may be universal.



Autor: Paul G. Higgs, Ralph E. Pudritz

Fuente: https://arxiv.org/



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