Nov 17, 2009

Imitating prebiotic homochirality on Earth

Origins of Life and Evolution of the Biosphere : the Journal of the International Society for the Study of the Origin of Life
Ronald BreslowZhan-Ling Cheng

Abstract

We show how the amino acids needed on prebiotic earth in their homochiral L form can be produced by a reaction of L-alpha-methyl amino acids-that have been identified in the Murchison meteorite-with alpha-keto acids under credible prebiotic conditions. When they are simply heated together they perform a process of decarboxylative transamination but with almost no chiral transfer, and that in the wrong direction, producing D-amino acids from the L-alpha-methyl amino acids. With copper ion a square planar complex with two of the reaction intermediates is formed, and now there is the desired L to L transformation, producing small enantioexcesses of the normal L-amino acids. We also show how these can be amplified, not by making more of the L form but by increasing its concentration in water solution. The process can start with a miniscule excess and in one step generate water solutions with L/D ratios in the over 90% region. Kinetic processes can exceed the results from equilibria. We have also examined such amplifications with ribonucleosides, and have shown that initial modest excesses of the D-nucleosides can be amplified to afford water solutions with D to L ratios in the high 90's. We have shown that the homochiral compound h...Continue Reading

  • References27
  • Citations10

References

  • References27
  • Citations10

Citations

Mentioned in this Paper

Molecular Stereochemistry
Keto Acids
One Step (dimethicone)
Amino Acids, I.V. solution additive
Ribonucleosides
Prebiotics
One-Step Dentin Bonding System
Evolution, Chemical
Pyridoxal Phosphate
Gene Amplification Technique

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