Prebiotic chemical model

From the viewpoint of a model of prebiotic chemical evolution and of the primitive atmosphere of the Earth,174175 photosynthetic reactions of C02 were also examined, and formaldehyde with various nitrogen-containing products was obtained. 

Chessari, S. Thomas, R. Polticelli, F. Luisi, P. L., The production of de novo folded proteins by a stepwise chain elongation A model for prebiotic chemical evolution of macromolecular sequences. Chemistry Biodiversity 2006, 5, 1202-1210. 

The metal-catalyzed amplification of e.e. in small molecules, demonstrated by Soai and coworkers, along with the chiral enrichment of amino arid polymers by sequential polymerization/depolymerization steps, have shown that small enantiomeric excesses in nearly racemic mixtures can be reactively amplified to produce chiral dominance. These real chemical systems, which include plausible prebiotic reactions, experimentally demonstrate the principle of the chiral amplification of a spontaneously broken chiral symmetry in a dynamic and authentic chemical milieu. Therefore amplification to dominance of a small chiral excess of both small and polymeric molecules can be credibly incorporated into an origin-of-life model. 

Prior sequestration of the prebiotic reactions within the micropores of weathered feldspars or other porous rock matrices also avoids many of the other problems of catalysis and dilution encountered by models of chemical biogenesis. That is, this mechanism attains viable evolutionary chemical selection among spatially discrete systems without the need to assume an unlikely capture-and-enclosure event involving a pre-existing lipid membrane. [192] Thus autocatalysis of chiral molecules could evolve before the actual appearance of free-floating lipid vesicles. 

Early theoretical models on the feasibility of stochastic mirror symmetry breaking at prebiotic conditions have been successfully realized under laboratory conditions, particularly in studies in crystal and surface science, asymmetric auto catalysis and polymer chemistry. The first step, common in all these scenarios, is the self-assembly of non-chiral or chiral molecules to form diastereoisomeric supramolecular architectures that display different physico-chemical properties. 

From the methodological point of view the hypercycle model is the most impressive example of the possibility of unifying detailed biochemical examinations and mathematical models of chemical reactions. Both the prebiotic relevance of the model and its mathematical structure were studied, sometimes critically (e.g. King, 1981 Miiller-Herold, 1983 Szathmary, 1984). It was suggested that the hypercyclic evolution is not as effective as conventional autocatalysis, and the model should be defined by multiple time singular perturbation theory. 

Miller s experiment provided a model for much work in the branch of a science now called chemical evolution or prebiotic chemistry, the study of chemical events that may have taken place on earth or elsewhere in the universe leading to the appearance of the first living cell. For additional reading, you can consult Chemical Evolution by Stephen F. Mason, Clarendon Press, Oxford, 1991. 

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