Earth primordial conditions

The ideas of the well-known physiologist from Bonn, Eduard Pfliiger (1829-1910), seem to predate modern theories he assumed that, under the specific conditions of the primordial Earth, fundamental constituents of protoplasma could have developed from cyanide-type compounds or polymers derived from them (Pfliiger, 1875). 

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 ... 

However, the question must always be asked as to whether these processes could have taken place on the primordial Earth in its archaic state. The answer requires considerable fundamental consideration. Strictly speaking, most of the experiments carried out on prebiotic chemistry cannot be carried out under prebiotic conditions , since we do not know exactly what these were. In spite of the large amount of work done, physical parameters such as temperature, composition and pressure of the primeval atmosphere, extent and results of asteroid impacts, the nature of the Earth s surface, the state of the primeval ocean etc. have not so far been established or even extrapolated. It is not even sure that this will be possible in the future. In spite of these difficulties, attempts are being made to define and study the synthetic possibilities, on the basis of the assumed scenario on the primeval Earth. Thus, for example, in the case of the SPREAD process, we can assume that the surface at which the reactions occur could not have been an SH-containing thiosepharose, but a mineral structure of similar activity which could have carried out the necessary functions just as well. The separation of the copy of the matrix could have been driven by a periodic temperature change (e.g., diurnal variation). For his models, H. Kuhn has assumed that similar periodic processes are the driving force for some prebiotic reactions (see Sect. 8.3). 

Illustration showing apparatus used in the lUfller-Urey experiment to duplicate conditions on primordial Earth. Photograph by Francis Leroy, Biocosmos/Sdence Photo Library Photo Researchers, Inc. Reproduced by permission. 

Pyrolysis of ribonucleosides with inorganic phosphate at 160° (conditions which could reasonably have existed on the primordial earth) yielded nucleotide mixtures containing ribonucleoside 2 -, 3 -, and 5 -phosphates and ribonucleoside 2 3 -cyclic phosphates. - ... 

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