Etiology of Potentially Primordial Biomolecular Structures: From Vitamin B₁₂to the Nucleic Acids and an Inquiry into the Chemistry of Life’s Origin: A Retrospective

Abstract

"We'll never be able to know" is a truism that leads to resignation with respect to any experimental effort to search for the chemistry of life's origin. But such resignation runs radically counter to the challenge imposed upon chemistry as a natural science. Notwithstanding the prognosis according to which the shortest path to understanding the metamorphosis of the chemical into the biological is by way of experimental modeling of "artificial chemical life", the scientific search for the route nature adopted in creating the life we know will arguably never truly end. It is, after all, part of the search for our own origin.

Prebiotic selection and assembly of proteinogenic amino acids and natural nucleotides from complex mixtures

“…[1][2][3][4][5][6][7]13,[15][16][17][18][19][20][21] A separate synthesis of pure glycolaldehyde (2a) and glyceraldehyde (2b) is ostensively implausible, therefore a means of physical separation is better suited to promote the desired selective and sequential delivery of these simple sugars. 6,14,28 Our attention was first drawn to the possible role of 2-aminothiazole (7) in mediating the sequestration, separation and accumulation of glycolaldehyde (2a) and glyceraldehyde (2b) when we observed precipitation of glycolaldehyde (2a) and homochiral D-glyceraldehyde (D-2b) from water as aminals 8a and D-8b.…”

“…[1][2][3][4][5][6][7]12,13,15,19,22,32,33 Previous models have advocated that kinetically controlled, segregated syntheses (under different local geochemical conditions) are required to overcome the incompatibility of distinct reactions. [1][2][3][4][5][6][7] However, these models are necessarily highly contingent upon the rapid exploitation of reagents as and when they form. Accordingly, these models rely upon achieving of a specific and controlled order of synthetic steps under geochemical constraints, and are also incompatible with the accumulation or purification of intermediates.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13] Proteins are built from a highly restricted set of about 20 amino acids according to a universal triplet code of four ribonucleotides. Therefore, it is essential to learn how this specific small constellation of molecules became irrevocably linked at the advent of life.…”

“…Accordingly, it has been recognised that "the chief obstacle to understanding the origin of RNA-based life is identifying a plausible mechanism for overcoming the clutter wrought by prebiotic chemistry". [4][5][6][7] For example, the most-efficient and specific proposed prebiotic pathway to the pyrimidine ribonucleotides requires synthesis of the key intermediate pentose aminooxazoline (1) (Fig. 1a).…”

“…1a). [2][3][4][5][6][22][23][24] However, the plausibility of this proposed prebiotic synthesis of pentose aminooxazoline (1) has been questioned because it is contingent upon the strictly controlled sequential delivery of pure glycolaldehyde (2a) to cyanamide (3) to yield 2-aminooxazole (4), followed by pure glyceraldehyde (2b) to 2-aminooxazole (4) to yield the desired product (Fig. 1a).…”