Prebiotic organic synthesis

Chang, S., Desmarias, D., Mack, R., Miller, S. L., and Strathem, G. E. (1983). Prebiotic organic synthesis and the origin of life. In "Earth s Earliest Biosphere, Its Origin and Evolution" (J. W. Schopf, ed.), pp. 53-88. Princeton University Press, Princeton, New Jersey. 

Simoneit BRT. Prebiotic organic synthesis under hydrothermal conditions an overview. Adv. Space. Res. 2004 33 88-94. 

These researchers added carbonate. .. H. J. Cleaves et al. Prebiotic organic synthesis in neutral planetary atmospheres, in Chemical Evolution across Space and Time From the Big Bang to Prebiotic Chemistry, ed. by Zaikowski and Friedrich. 2008, American Chemical Society. Volume 981, Chapter 15, p. 282. DOl 10.1021/ bk-2008-0981.ch015. 

Cleaves H J, Chalmers JH, Lazcano A, Miller SL, Bada JL (2008) A reassessment of prebiotic organic synthesis in neutral planetary atmospheres. Orig Life Evol Biosph 38 105-115... 

The variety of prebiotic organic reactions seems to be almost unlimited. Strasdeit et al. (2002) from the University of Hohenheim (Germany) reported the synthesis of zinc and calcium complexes of the amino acids valine and isovaline. They assume that these could have had a certain significance on the mineral-rich primeval Earth on heating to 593 K under nitrogen, valine was converted to the corresponding cyclic dipeptide. 

Endogenous organic synthesis Urey-Miller experiments as a source of prebiotic molecules via the Strecker synthesis for amino acids, HCN polymerisation for purines and pyrimidines and the formose reaction for sugars... 

Electricity has generally been recognized as a probable promoter of organic synthesis going back billions of years. A report by Sutherland and Whitfield summarizes some of the evidence for this.82 Thus, electrical spark discharges in the presence of simple molecules believed to be present in the planet s prebiotic atmosphere have been shown to produce a few of the building blocks needed for the creation of life. The sun also provided other forms of energy (e.g., infrared and ultraviolet radiation, inter alia). Some of the processes proved by laboratory experiments are ... 

More complex, but still feasible, is the synthesis of pyrimidine bases from simple prebiotic substrates, although the reported yields of these reactions are relatively low. In this context, two main prebiotic precursors have been identified cyanoethine and a primary product of its hydrolysis, cyanoacetaldehyde. These compounds contain a preformed C-C bond which is incorporated in the C5-C6 position of the pyrimidine ring. In 1968 Ferris and co-workers reported that the reaction of cyanoethine with cyanate at 30 °C yields cytosine and, after its hydrolysis, uracil in acceptable yield [27]. trans-Cyanovinylurea was recovered as a key intermediate for this transformation. However, this reaction requires relatively high concentrations of cyanate (>0.1 mol/1), unlikely to occur in aqueous media due to its rapid degradation to carbon dioxide and ammonia. Cyanoethine also reacts with cyanate and yields cytosine and uracil at elevated temperatures. In this reaction urea or guanidine (also considered as prebiotic organic compounds) can easily replace cyanate (Figure 8.8) [26]. 

Nowadays, activities of nucleic acids are controlled by interactions of Mg, Ca or Zn, but also by heavy-metal ions or electrophilic agents with certain specific sequences (e.g. in induction of metallothionein). Though this does imply NAs to act as ligands in physiological conditions, it need not imply that they could achieve the above sequence of steps, let alone the problem that up to now not even a hint of a prebiotic NA synthesis pathway was demonstrated, not even when using polyphosphoric acid in organic solvents. The E (L) values for NAs, nucleoside triphosphates or simpler species such as glycerinaldehyde-2,3-diphosphate are way too low to permit the sequence of events on their own. 

Particularly important here is the role of transition metal sulfides. In 1988 Wachtershauser proposed that pyrite, abundant in hydrothermal vent systems, provided an energy source for the first life. He suggested that pyrite provided the catalyst necessary to drive a number of essential chemical reactions which are important precursors to life. More recent studies have confirmed this view and have shown that the sulfides of Fe, Ni, Co, and Zn can play an important role in the fixation of carbon in a prebiotic world (Cody et al., 2004). Transition metal sulfides also play a role in more advance organic synthesis, and Huber and Wachtershauser (1998) showed how amino acids were converted into their peptides using a (NiFe)S catalyst. 

Kofoed J, Reymond JL, Darbre T Prebiotic carbohydrate synthesis zinc-proline catalyzes direct aqueous aldol reactions of alpha-hydroxy aldehydes and ketones. Organic Biomolecular Chemistry 2005, 3(10) 1850-1855. 

The aldol reaction is one of the most important ways to construct carbon-carbon bonds in organic synthesis. Nature itself seems to prefer this reaction in its biosynthetic processes, for example, in the prebiotic formation of saccharides [1]. Strictly speaking, the aldol reaction is the self-coupling of an aldehyde, having at least one active hydrogen in the a-position, to give a p-hydroxyaldehyde called an aldol (aldol addition), which sometimes dehydrates (aldol condensation). 

The abundant synthesis of varied prebiotic organic molecttles was a prerequisite for life, and it is satisfying that so many plausible mechanisms for their formation have been demonstrated ejqrerimentally. However, this profligate production raises another question how were the essential molecules of life selected, concentrated and organized from the messy prebiotic soup. The authors of this volume demonstrate a range of possibilities. 

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