Primordial synthesis

The fact that the light nuclides, especially H and He, are more abundant by orders of magnitude, compared to all heavier nuclides, is interpreted to distinguish two fundamentally different modes of synthesis. The big bang is postulated responsible for primordial synthesis of the light nuclei and stellar nucleosynthesis (Burbidge et al., 1957) to produce all the heavy nuclides. 

Parker ET, Cleaves FU, Dworkin JP, Glavin DP, Callahan MP, Aubrey A, Lazcano A, Bada R. Primordial synthesis of amines and amino acids in a 1958 Miller H2S-rich spark discharge experiment. Proc Natl Acad Sci USA. 2011 108 5526-31. 

At this stage no nuclear composite objects can be formed yet, since they would instantly disintegrate in collisions with hard electromagnetic quanta. The stabiK2ation occurs for temperatures below 0.1 MeV. Primordial synthesis of light nuclei took place at that cooling stage of the Universe (O Sect. 12.3). 

There seems then to be some agreement that accepted theories of nucleosynthesis can be extended to cover the. superheavy region. Kuchowitz reminds us that primordial synthesis in some galactic core explosion has to be taken into account together with continuous production in supernova explosions, when searches for these elements in nature are attempted. Vdovenko and Sobotovich estimate that (1) primordial superheavy elements in the earth may exist at a concentration of 10 —lO" g/g, and (2) assuming on the contrary that there are no primordial nuclei, but that they are reaching the earth s surface from supernovae at the rate of 0.25 m per day, then the concentration in the earth s crust would be 2 x 10 g/g. 

Helium is the second most abundant element in the universe (76% H, 23% He) as a result of its synthesis from hydrogen (p. 9) but, being too light to be retained by the earth s gravitational field, all primordial helium has been lost and terrestrial helium, like argon, is the result of radioactive decay ( He from a-decay of heavier elements, " °Ar from electron capture by... 

The problems in the nucleoside synthesis arise in the linkage of the 3-N atoms of the pyrimidines and the 9-N atoms of the purines with the l -C atom of ribose, not only without enzyme control, but also under conditions extant on the primordial Earth. How might such reactions occur There have naturally been many attempts... 

As early as 45 years ago, G. Schramm et al. (1962) carried out the synthesis of AMP, ADP and ATP using ethyl metaphosphate as the phosphorylating agent. These successful syntheses led to the formation of longer nucleotide chains however, they by no means correspond to the conditions present on the primordial Earth. Thus, the question as to the source of the phosphates remains paramount. According to Schwartz (1998), the following phosphate sources deserve consideration ... 

G. Wachtershauser formulated his suggestions on the initial metabolic processes on the primeval Earth (as described above) in the form of six postulates and eleven theses (Wachtershauser, 1990b). Laboratory experiments planned to check, and perhaps confirm, these theories have already been attempted. The reductive Krebs cycle (rTCA cycle) has recently been the subject of much discussion. Smith and Morowitz consider that the rTCA cycle is a universal, possibly primordial, core process which could have provided substances for the synthesis of biomolecules on the young Earth (Smith and Morowitz, 2004). 

The pH of the oceans forming the primordial soup is important in controlling the charged nature, or otherwise, of the amino and carboxylic acid species and hence their chemistry. Generating reaction schemes for the prebiotic synthesis of molecules requiring basic conditions will not be relevant if the oceans are acidic. Consider dissolving CO2 into water, simply written as ... 

Although Peebles had himself recently completed a calculation of primordial element synthesis including helium (Peebles 1966). 

Compared with the surprising variety of biochemical compounds that can be readily synthesized in Miller-type one-pot simulation experiments, the suite of organics produced under the conditions proposed by Wachtershauser is quite limited. However, the impressive demonstration that the FeS/H2S combination can reduce nitrogen to ammonia shows that considerable attention should be given to the reducing power of pyrite formation. Primordial life may have not been autotrophic, but should we hesitate to accept the idea that the primitive soup was formed from both extraterrestrial sources and endogenous synthesis in which pyrite production played a role After all, a spicy, thick bouillon is always tastier than a bland, diluted broth. 

Some time after the evolution of this primitive protein-synthesizing system, there was a further development DNA molecules with sequences complementary to the self-replicating RNA molecules took over the function of conserving the genetic information, and RNA molecules evolved to play roles in protein synthesis. (We explain in Chapter 8 why DNA is a more stable molecule than RNA and thus a better repository of inheritable information.) Proteins proved to be versatile catalysts and, over time, took over that function. Lipidlike compounds in the primordial soup formed relatively impermeable layers around self-replicating collections of molecules. The concentration of proteins and nucleic acids within these lipid enclosures favored the molecular interactions required in self-replication. 

Chemistry is the science of matter and of its transformations, and life is its highest expression. It provides structures endowed with properties and develops processes for the synthesis of structures. It plays a primordial role in our understanding of material phenomena, in our capability to act upon them, to modify them, to control them and to invent new expressions of them. 

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.

Extending a previous report of amino acid activation by CO in the presence of colloidal (Ni,Fe)S [195], Wachterhauser and co-workers have recently proposed a primordial peptide cycle in which CO drives peptide synthesis and cleavage in the presence of colloidal (Ni,Fe)S [198]. The reactions were car-... 

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