Origin of Life - Ancestral Routes to Biomolecules

Reconstructing the Ancestral Routes to
Nucleobases, D-Sugars, RNAs,
L-alpha-Amino Acids, and Lipids

Sylvain L. Smadja
December 30, 2008

Abstract
     After decades of investigation, many challenges remain to the understanding of Life’s emergence from prebiotic chemicals. Adequate models are needed to explain very early pathways that produced the relevant nucleobases, D-sugars, L-alpha-amino acids, straight-chain fatty acids, and branched-chain isoprenoid compounds. It was the enigma of biological homochirality that first intrigued the author. But the scope of his model grew as his investigations led to insights about the origin of biomolecular building block units. By searching modern biology for molecular fossils, using retro-synthetic analysis, and finding support in experimental data, the author ended up constructing a full-picture model of possible prebiotic pathways to relevant biomolecules.

     The author proposes that within a local sheltered-microenvironment of early Earth, an asymmetric amplification process that propagated from a tiny initial imbalance gave rise to a chiral three-carbon cyanohydrin following a reaction between cyanide ions and glycoaldehyde phosphate entities. Starting with this chiral cyanohydrin acting as the ‘Premier Precursor,’ the author suggests sequences of cascading chemical steps that yield nucleobases, D-sugars, L-alpha-amino acids, and lipids.

     This model holds that biological homochirality was established as a consequence of just a single, fortuitous symmetry-breaking event. It also holds that the proposed early chemical events took place as a 'one-pot’ reaction system that yielded all the necessary biomolecules to usher in the RNA/Protein/Lipid World.

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