Abiotic synthesis

The first indication of a possible connection between geological processes occurring at the boundaries between tectonic plates of the mid-oceanic ridges and the biogenesis problem was provided by J. B. Corliss (1981). He considered the hydrothermal conditions to be ideal reactors for abiotic synthesis these ideal conditions were the water temperature gradients, the pH, and the concentrations of solutes in the hot springs. The presence of certain minerals which could act as catalysts, such as montmorillonite, clay minerals, iron oxide, sulphides etc., was also very important. The initial model presented for the hydrothermal synthesis of biomolecules (Corliss, 1981) was modified, particularly by Russell (1989) and Wachtershauser (see Sect. 7.3). 

Shindo H, Huang PM (1985a) The catalytic power of inorganic components in the abiotic synthesis of hydroquinone-derived humic polymers. Appl Clay Sci 1 71-81... 

On the abiotic synthesis of biochemical monomers and the heterotrophic theory on the origin of life... 

Fig. 4.2. The Miller-Urey apparatus for abiotic synthesis of biochemicals from primordial gases is shown. Before each experiment the system was thoroughly evacuated, flushed with interstellar-type gases, and sealed. Water is brought to a boil and vapors rise through an electric discharge chamber and are re-condensed and led back into the boiling water reservoir. It took only a few weeks to produce a color change in the water which indicated an accumulation of organic compounds shown in Table 4.1. On the young earth, of course, this experiment would have been carried on for a few million years.

McCollom T. M. Seewald J. S. Abiotic synthesis of organic compounds in deep-sea hydrothermal environments. Chem. Rev. 2007, 107, 382-401. 

Since HCN and aldehydes were produced directly from the electric discharge in the Miller s experiment [33], the Strecker reaction was very early proposed as a likely pathway for the prebiotic synthesis of amino acids. This reaction discovered in 1850 [34] is the most anciently known abiotic synthesis of a-amino acids, it originally consisted in the formation of an a-aminonitrile 1 from a carbonyl compound (either aldehyde or ketone), ammonia and hydrogen cyanide in moderately alkaline aqueous solution followed by aminonitrile hydrolysis in strong acid. 

Synthesis from Acyclic Precursors Abiotic Synthesis 419... 

Some observations proposed that PolyP may be a catalyst in the abiotic synthesis of peptides (Rabinowitz et al, 1969 Rabinowitz and Hampai, 1984 Chetkauskaite et al, 1988). 

Together with the positive results, however, we must also consider the negatives ones, and of these one of the most important is the fact that the abiotic synthesis of molecules has been relatively easy for... 

Today, replication is firmly based on nucleic acids, but the nucleotides that make up these molecules are much more complex than the amino acids which produce proteins, as can be clearly seen in Figure 5.5. We know, in addition, that the abiotic synthesis of nucleic acids is far more difficult than that of proteins, and it is... 

The basic dilemma of abiotic synthesis is that the organic compounds sought are thermodynamically unstable with respect to the low-T equilibrium forms of C, N,... 

Actually, much of the experimental work on chemical evolution (cf. Lemmon, 19701 utilizes such unstable compoumls, e.g. HCN, HCHO, HC=CCN, H2NCN, etc., on the grounds that they can be made by Miller-Urey reactions. But they can also be made by spontaneous reactions of CO, NH3, and Hj (Anders et al., 1974). Hence this class of reactions provides some common ground between the two main types of abiotic synthesis. 

Once photochemically formed in the early atmosphere via reactions (1), (2), (11), and (12), HhCO, being very water soluble, rained out of the atmosphere. In the early oceans, H2CO accumulated and eventually underwent aqueous solution polymerization reactions leading to the abiotic synthesis of organic molecules of increasing complexity (Pinto et al., 1980). 

The effects of H2, CO2, and solar UV on the vertical distribution of the ratio of CO/CO2 are shown in Figures 18 (H2 = 17 ppmv) and 19 (H2 = 10 ). The value of the ratio of CO/CO2 has recently been identified as a key parameter in laboratory experiments dealing with the abiotic synthesis of complex organic molecules in mildly reducing early atmospheric mixtures of N2, H2O, CO2, and CO (Bar-Nun and Chang, 1983). The calculated ratio of CO/CO2 in the lower atmosphere exhibited a strong dependence on the level of H2. For H2 = 17 ppmv, this ratio was about 10 for various combinations of CO2 and solar UV flux, while for H2 = 10 this ratio was considerably more — about 10 for the same combination of CO2 and solar UV flux. However, for either value of H2, a ratio of CO/CO2 of unity or greater was reached above about 40 km. The surface ratio of CO/CO2 as a function of H2, CO2, and UV levels is summarized in Table 3. 

Yuasa S, Flory D, Basile B, Oro J. Abiotic synthesis of purines and other heterocyclic compounds by the action of electrical discharges. J. Mol. Evol. 1984 21 76-80. 

On the other hand, some studies on shock-induced devolatilization produced results inconsistent wiOt the above conclusion. Mukliin et al. [70J examined tlie effect of laser-pulse heating on meteorite materials and silicates in order to simulate the vaporization that occurs during impacts and to stud the chemical composition of the gases produced. The experimental results showed tliat the residual gas mixture consisted of both oxidized and reduced components CO, CO2, SO2, H2O, H2, N2, H2S, COS, CS2, various hydrocarbons from Ci to Ce, HCN, and CH3CHO. They emphasized that the gas mixtures formed by vaporization of silicates provide favorable conditions for abiotic synthesis of organic materials. 

The story of the evolution of life on Earth is relatively straightforward in comparison to the problem of how it first arose. The abiotic synthesis on Earth of the organic compounds necessary for the creation of life appears to require a reducing atmosphere (see Box 1.5). Early experiments with electrical discharges in mixtures of methane, ammonia and hydrogen sulphide in the presence of water created various organic compounds es-... 

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