NDLI: Imitating prebiotic homochirality on Earth.

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On the emergence of biochemical homochirality: an elusive beginning.

Stereoselective syntheses of pentose sugars under realistic prebiotic conditions.

Dual role of hydrophobic racemic thioesters of alpha-amino acids in the generation of isotactic peptides and co-peptides in water; implications for the origin of homochirality.

Amplification of chirality at solid surfaces.

Asymmetric autocatalysis induced by chiral crystals of achiral tetraphenylethylenes.

Homochirality and the need for energy.

Homochirality in life: two equal runners, one tripped.

Imitating prebiotic homochirality on Earth.

Spontaneous mirror symmetry breaking in the aldol reaction and its potential relevance in prebiotic chemistry.

Chiral biases in solids by effect of shear gradients: a speculation on the deterministic origin of biological homochirality.

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Imitating prebiotic homochirality on Earth.

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	Breslow, Ronald Levine, Mindy Cheng, Zhan-Ling
Description	Country affiliation: United States Author Affiliation: Breslow R ( Department of Chemistry, Columbia University, New York, NY 10027, USA. rb33@columbia.edu)
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 has two effects on the solubility of the racemate. On one hand it decreases the solubility of the racemate by its role in the solubility product, as a theoretical equation predicts. On the other hand, it increases the solubility of the racemate by changing the nature of the solvent, acting as a cosolvent with the water. This explains why the amplification, while large, is not as large as the simple theoretical equation predicts. Thus when credible examples are produced where small enantioexcesses of D-ribose are created under credible prebiotic conditions, the prerequisites for the RNA world will have been exemplified.
File Format	HTM / HTML
ISSN	01696149
Issue Number	1
Volume Number	40
e-ISSN	15730875
Journal	Origins of Life and Evolution of Biospheres
Language	English
Publisher	Springer
Publisher Date	2010-02-01
Publisher Place	Netherlands
Access Restriction	Subscribed
Subject Keyword	Discipline Molecular Biology Discipline Biology Evolution, Chemical Origin Of Life Stereoisomerism Amino Acids Chemical Synthesis Chemistry Extraterrestrial Environment Meteoroids Molecular Structure Nucleosides Pyridoxal Phosphate Pyridoxamine Ribose Water Journal Article Research Support, Non-u.s. Gov't Research Support, U.s. Gov't, Non-p.h.s.
Content Type	Text
Resource Type	Article
Subject	Medicine Ecology, Evolution, Behavior and Systematics Space and Planetary Science

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